- A Ru(II)-Mn(I) Supramolecular Photocatalyst for CO2 Reduction
-
Supramolecular photocatalysts for CO2 reduction, constituted of redox photosensitizer, catalyst, and bridging ligand, play crucial roles in constructing hybrid systems with solid materials and photoelectrochemical cells for artificial photosynthesis. We report the first supramolecular photocatalysts with a Mn(I) catalyst [MnBr(CO)3(BL)] and photosensitizer unit(s) [Ru(dmb)2(BL)]2+ (dmb = 4,4′-dimethyl-2,2′-bipyridine, BL = bridging ligand). A 1:1 ratio between the redox photosensitizer and catalyst units showed higher activity for HCOOH formation in comparison to the corresponding mixed system of mononuclear complexes.
- Fabry, David C.,Koizumi, Hiroki,Ghosh, Debashis,Yamazaki, Yasuomi,Takeda, Hiroyuki,Tamaki, Yusuke,Ishitani, Osamu
-
-
Read Online
- Atmospheric sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate: Temperature dependent rate coefficients, product distribution of their reactions with Cl atoms and CF2ClC(O)OH formation
-
Rate coefficients as a function of temperature have been measured for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique. The experiments were carried out in a 1080 L photoreactor over the temperature range 287-313 K at a total pressure of 1000 ± 10 mbar of synthetic air using in situ FTIR spectroscopy to monitor reactants and products. The following Arrhenius expressions were obtained: k(MCDFA+Cl) = (9.6 ± 5.1) × 10-12exp[-(1363 ± 79)/T] and k(ECDFA+Cl) = (64.4 ± 29.7) × 10-12exp[-(1110 ± 68)/T]. The kinetic results are compared with previous experimental and theoretical studies. In addition, a product study of the reactions of Cl with methyl chlorodifluoracetate and ethyl chlorodifluoroacetate is reported. The results indicate that in the absence of NOx the main fate of the alkoxy radicals formed after H-atom abstraction by Cl from the -CH3 group in methyl chlorodifluoroacetate is reaction of the radical with O2 to form the mixed anhydride CF2ClC(O)OC(O)H. In the case of ethyl chlorodifluoroacetate the main fate of the alkoxy formed via H-atom abstraction by Cl from the -CH2- entity in the ethyl group is α-ester rearrangement to produce chlorodifluoroacetic acid and the corresponding radical. The yields of chlorofluoracetic acid (CF2ClC(O)OH) obtained were as follows: (34 ± 5)% and (86 ± 8)% for the reactions of Cl with CF2ClC(O)OCH3 and CF2ClC(O)OCH2CH3, respectively. The measured yields are rationalized in terms of mechanisms consisting of competitive reaction channels for the formed products in the oxidation, i.e. reaction with O2, α-ester rearrangement and a decomposition pathway. Atmospheric implications are discussed according to the rate coefficients obtained as a function of temperature and altitude, and regarding the formation of chlorofluorocarboxylic acid.
- Blanco, María B.,Barnes, Ian,Wiesen, Peter,Teruel, Mariano A.
-
-
Read Online
- Investigation of the thermal decomposition of ketene and of the reaction CH2 + H2 ? CH3 + H
-
Using frequency modulation (FM) spectroscopy singlet methylene radicals have been detected for the first time behind shock waves. The thermal decomposition of ketene served as source for metylene radicals at temperatures from 1905 to 2780 K and pressures around 450 mbar. For the unimolecular decomposition reaction, (1) CH2CO+M → CH2 +CO+M, the rate constants obtained are: k1 = (9.5±5.7) · 1015 · exp[(-244±25) kJ mol-1/RT] cm3mol-1 s-1. As a first study of a methylene reaction at high temperatures by diretly tracing methylene the reaction of methylene with hydrogen, (8+9) 1.3CH2 + H2 → CH3 + H, was investigated at temperatures from 1930 to 2455 K and pressures around 500 mbar. For the total rate constant of the singlet and triplet methylene reaction a temperature independent value was obtained: log(kg+9/(cm3mol-1s-1)) = 13.89±0.26. A comparison with low temperature literature data and the systematics of activation energies of triplet methylene reactions allowed a consistent description of singlet and triplet contributions and of the forward and reverse reaction. by Oldenbourg Wissenschaftsverlag, Muenchen.
- Friedrichs, Gernot,Wagner, Heinz Gg.
-
-
Read Online
- Phenyl-grafted carbon nitride semiconductor for photocatalytic CO2-reduction and rapid degradation of organic dyes
-
Molecular engineering of graphitic carbon nitride (g-C3N4) is achieved by the copolymerization of π-conjugated phenyl urea, melamine, and urea. Integration of aromatic phenyl rings into the heptazine network of g-C3N4 alters its structural, optical and electronic properties. The fusion of the polymeric g-C3N4 core with aromatic phenyl groups induces band gap tuning, which greatly improves the separation and lifetime of charge-carriers. As a result, CO2 photoreduction experiments conducted by using phenyl-grafted g-C3N4 afford methane and formic acid in high yields. Furthermore, a selective model organic pollutant rhodamine B dye is rapidly decomposed under visible-light irradiation. This work suggests that pyrolysis of a suitable aromatic π-deficient molecular dopant such as phenyl urea can drastically alter the photo-response of the carbon nitride photocatalyst and may enhance its photocatalytic activity. Hence, the present work is expected to be of significant value in sustainable energy production and environmental remediation.
- Vidyasagar, Devthade,Manwar, Nilesh,Gupta, Akanksha,Ghugal, Sachin G.,Umare, Suresh S.,Boukherroub, Rabah
-
-
Read Online
- Photoactivity of mono- and dicarbonyl complexes of ruthenium(II) bearing an N,N,S-donor ligand: Role of ancillary ligands on the capacity of CO photorelease
-
One monocarbonyl and one dicarbonyl complex of ruthenium(II), namely, [Ru(Cl)(CO)(qmtpm)(PPh3)]BF4 (2) and [Ru(Cl)(CO) 2(qmtpm)]ClO4 (3), derived from the tridentate ligand 2-quinoline-N-(2′-methylthiophenyl)methyleneimine (qmtpm) have been synthesized and structurally characterized. The qmtpm ligand binds in a meridional fashion in these carbonyl complexes, and in 3, the two carbon monoxide (CO) ligands are cis to each other. Solutions of 2 in ethanol, chloroform, or acetonitrile rapidly release CO upon illumination with low-power (3-15 mW) light in the 300-450 nm range. Loss of CO from 2 brings about a dramatic color change from yellow to magenta because of the formation of [Ru(Cl)(MeCN)(qmtpm)(PPh3)]BF4 (4). In acetonitrile, photorelease of CO from 3 under 360 nm light occurs in two steps, and the violet photoproduct [Ru(Cl)(MeCN)2(qmtpm)]+ upon reaction with Ag+ and PPh3 affords red [Ru(MeCN)2(qmtpm) (PPh3)](ClO4)2 (5). The structure of 5 has also been determined by X-ray crystallography. Reduced myoglobin assay confirms that 2 and 3 act as photoactive CO-releasing molecules (photoCORMs) that deliver 1 and 2 equiv of CO, respectively. The results of density functional theory (DFT) and time-dependent DFT studies confirm that electronic transitions from molecular orbitals with predominantly Ru-CO character to ligand-based π* orbitals facilitate CO release from these two photoCORMs. Complexes 2-5 have provided an additional opportunity to analyze the roles of the ancillary ligands, namely, PPh3, Cl-, and MeCN, in shifting the positions of the metal-to-ligand charge-transfer bands and the associated sensitivity of the two photoCORMs to different wavelengths of light. Collectively, the results provide helpful hints toward the future design of photoCORMs that release CO upon exposure to visible light.
- Gonzalez, Margarita A.,Carrington, Samantha J.,Chakraborty, Indranil,Olmstead, Marilyn M.,Mascharak, Pradip K.
-
-
Read Online
- The p-Orbital Delocalization of Main-Group Metals to Boost CO2 Electroreduction
-
Enhancing the p-orbital delocalization of a Bi catalyst (termed as POD-Bi) via layer coupling of the short inter-layer Bi?Bi bond facilitates the adsorption of intermediate *OCHO of CO2 and thus boosts the CO2 reduction reaction (CO2RR) rate to formate. X-ray absorption fine spectroscopy shows that the POD-Bi catalyst has a shortened inter-layer bond after the catalysts are electrochemically reduced in situ from original BiOCl nanosheets. The catalyst on a glassy carbon electrode exhibits a record current density of 57 mA cm?2 (twice the state-of-the-art catalyst) at ?1.16 V vs. RHE with an excellent formate Faradic efficiency (FE) of 95 %. The catalyst has a record half-cell formate power conversion efficiency of 79 % at a current density of 100 mA cm?2 with 93 % formate FE when applied in a flow-cell system. The highest rate of the CO2RR production reported (391 mg h?1 cm2) was achieved at a current density of 500 mA cm?2 with formate FE of 91 % at high CO2 pressure.
- He, Sisi,Ni, Fenglou,Ji, Yujin,Wang, Lie,Wen, Yunzhou,Bai, Haipeng,Liu, Gejun,Zhang, Ye,Li, Youyong,Zhang, Bo,Peng, Huisheng
-
-
Read Online
- CO2 hydrogenation to methanol on Ga2O3-Pd/SiO2 catalysts: Dual oxide-metal sites or (bi)metallic surface sites?
-
A series of palladium (2 wt.%) catalysts supported on silica (301 m2/g) and loaded with increasing amount of gallium – ratio of Ga/Pd = 2, 4 and 8 atom/atom – were investigated for CO2 hydrogenation to methanol. The turnover frequency to methanol (H2/CO2 = 3; 523 K, 3 MPa), based on surface palladium, showed a 200-fold enhancement as compared to the monometallic Pd/SiO2 catalyst. Additionally, the apparent activation energy for methanol synthesis decreased from 60 kJ/mol on Pd/SiO2 to ~40 kJ/mol on the supported Ga-Pd catalysts. Characterization of the Pd-Ga catalyst series by X-ray absorption spectroscopy and high resolution transmission electron microscopy indicates the formation of Pd2Ga bimetallic nanoparticles partially covered by a thin layer of Ga2O3 on the silica surface. In situ infrared spectroscopy was employed to examine the reaction mechanism during the CO2 adsorption and hydrogenation at 0.7 MPa. It is proposed a bifunctional pathway where the carbonaceous species bound to the gallium oxide surface are hydrogenated, stepwise, to formate and methoxy groups by atomic hydrogen, which spillovers from the Pd-Ga bimetallic nanoparticles.
- Collins, Sebastián E.,Baltanás, Miguel A.,Delgado, Juan José,Borgna, Armando,Bonivardi, Adrian L.
-
-
Read Online
- Dynamic Changes in the Structure, Chemical State and Catalytic Selectivity of Cu Nanocubes during CO2 Electroreduction: Size and Support Effects
-
In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size- and shape-controlled ligand-free Cu nanocubes during CO2 electroreduction (
- Grosse, Philipp,Gao, Dunfeng,Scholten, Fabian,Sinev, Ilya,Mistry, Hemma,Roldan Cuenya, Beatriz
-
-
Read Online
- Click and Release: A Chemical Strategy toward Developing Gasotransmitter Prodrugs by Using an Intramolecular Diels–Alder Reaction
-
Prodrug strategies have been proven to be a very effective way of addressing delivery problems. Much of the chemistry in prodrug development relies on the ability to mask an appropriate functional group, which can be removed under appropriate conditions. However, developing organic prodrugs of gasotransmitters represent unique challenges. This is especially true with carbon monoxide, which does not have an easy “handle” for bioreversible derivatization. By taking advantage of an intramolecular Diels–Alder reaction, we have developed a prodrug strategy for preparations of organic CO prodrugs that are stable during synthesis and storage, and yet readily release CO with tunable release rates under near physiological conditions. The effectiveness of the CO prodrug system in delivering a sufficient quantity of CO for possible therapeutic applications has been studied using a cell culture anti-inflammatory assay and a colitis animal model. These studies fully demonstrate the proof of concept, and lay a strong foundation for further medicinal chemistry work in developing organic CO prodrugs.
- Ji, Xingyue,Zhou, Cheng,Ji, Kaili,Aghoghovbia, Robert E.,Pan, Zhixiang,Chittavong, Vayou,Ke, Bowen,Wang, Binghe
-
-
Read Online
- Changing the Product Selectivity for Electrocatalysis of CO2 Reduction Reaction on Plated Cu Electrodes
-
Electrochemical reduction of carbon dioxide (CO2RR) on various types of Cu electrodes to useful chemicals and fuels has attracted much attention. Herein, we comparatively investigate the distributions of CO2RR products over electroplated Cu, chemically plated boron-doped Cu (Cu?B) and electroplated phosphorus-doped Cu (Cu?P) electrodes. A global Faradaic efficiency of more than 50 % can be reached for the C2+ (ethylene, ethanol and n-propanol) products on both plated Cu?B and Cu?P electrodes at ~?1.15 V vs. RHE in 0.1 M KHCO3 electrolyte. Moreover, in situ surface enhanced infrared spectroscopy results together with quantitative analysis of the CO2RR products reveal a more facile conversion/depletion of the *CO intermediate after B- and P-doping, for which Cu?B promotes the C2+ products while Cu?P enhances both C2+ generation and CH4 evolution at faster *CO consumption. The present work suggests the vital role of *CO in the step of C?C bonding formation and highlights that the metalloid doping may alter the reactivity and selectivity of the intermediate.
- Li, Hong,Qin, Xianxian,Jiang, Tianwen,Ma, Xian-Yin,Jiang, Kun,Cai, Wen-Bin
-
-
Read Online
- HEI PHOTOELECTRON SPECTRA OF UNSTABLE MOLECULES: MONO- AND DIHALOGENOKETENES
-
HeI Photoelectron spectra are reported for the mono- and di-chloro-and-bromo-ketenes (XHC=C=O and X2C=C=O, X=Cl,Br) generated in high yield as unstable molecules from thermolysis of acid halides.The spectra are discussed and assigned by reference to the parent ketene molecule, orbital trends, and comparison with theoretical calculations.
- Colbourne, David,Westwood, Nicholas P. C.
-
-
Read Online
- High-performance and long-lived Cu/SiO2 nanocatalyst for CO2 hydrogenation
-
Cu-based nanocatalysts have been widely used for CO2 hydrogenation, but their poor stability is the bottleneck for further industrial applications. A high-performance and long-lived Cu/SiO2 nanocatalyst was synthesized by an ammonia-evaporation method for CO2 hydrogenation. The conversion of CO2 reaches up to 28%, which is close to the equilibrium conversion of CO2 (30%), and the selectivity to methanol is 21.3%, which is much higher than the equilibrium selectivity (6.6%) at 320 °C and 3.0 MPa. Furthermore, after 120 h of evaluation, the conversion can be still maintained at a high value (27%), which is much better than a Cu/SiO2 catalyst prepared by traditional impregnation. The Cu+ species has been demonstrated to be the active component for the activation and conversion of CO2. The higher ratio of Cu+/(Cu0 + Cu+) and interaction between the metal and support deriving from copper phyllosilicate are mainly responsible for the high catalytic activity and excellent stability, respectively.
- Wang, Zhi-Qiao,Xu, Zhong-Ning,Peng, Si-Yan,Zhang, Ming-Jian,Lu, Gang,Chen, Qing-Song,Chen, Yumin,Guo, Guo-Cong
-
-
Read Online
- Morphology Modulation-Engineered Flowerlike In2S3 via Ionothermal Method for Efficient CO2 Electroreduction
-
Electroreduction of carbon dioxide (CO2) to chemicals is a promising route to convert and utilize CO2 under atmospheric conditions. However, the relative poor reaction efficiency seriously hinders the practical applications of this route. In this work, flowerlike In2S3 assembled by nanoflakes was synthesized via ionothermal method and exhibited a high Faradaic efficiency (FE) of 86 % with excellent formate formation rate of 478 μmol h?1 cm?2 in ionic liquid (IL) electrolyte. Flowerlike structure can provide large electrochemically active surface area and enhance mass transfer rate. Additionally, density functional theory (DFT) calculations reveal that the origin of the improved performance can be attributed to the large adsorption energy of CO2 * and OCHO* intermediate on the (440) facet which is the main exposed crystal facet of flowerlike In2S3.[f1].
- Feng, Jiaqi,Gao, Hongshuai,Feng, Jianpeng,Liu, Lei,Zeng, Shaojuan,Dong, Haifeng,Bai, Yinge,Liu, Licheng,Zhang, Xiangping
-
-
Read Online
- Low Temperature Oxidative Coupling of Methane by Perovskite Oxide
-
Perovskite oxides, SrTiO3 which was dopped with MgO and contained oxygen defects, oxidized methane to C2 coupled hydrocarbons at 425 deg C, with the selectivity over 90percent.The used oxides could be regenerated by being treated in air at 425 deg C.Adsorbed oxide ion on the defect seemed to be responsible for their oxidation activity.
- Li, Xiao-Hong,Fujimoto, Kaoru
-
-
Read Online
- Reaction volume and enthalpy changes in photochemical reaction detected by the transient grating method; photodissociation of diphenylcyclopropenone
-
A method for the measurement of reaction volume (ΔV) and enthalpy (ΔH) changes of a photochemical reaction is presented based on the transient grating technique.Since ΔV and ΔV contributions are detected separately by the time-resolved manner, this new me
- Terazima, Masahide,Hara, Takashi,Hirota, Noboru
-
-
Read Online
- Diffuse Reflectance Infrared Fourier Transform Spectroscopic Investigation of the Decomposition
-
The thermal decomposition of Fe3(CO)12 has been studied for the first time by dispersing this cluster on an oxygen-free carbon surface and monitoring its behavior by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).The Fe3(CO)12 cluste
- Venter, Jeremy J.,Vannice, M. Albert
-
-
Read Online
- Fuel composition and diluent effect on gas transport and performance of anode-supported SOFCs
-
Anode-supported solid oxide fuel cells (SOFCs) with Ni+yttria-stabilized zirconia (YSZ) anode, YSZ-samaria-doped ceria (SDC) bilayer electrolyte, and Sr-doped LaCoO3 (LSC)+SDC cathode were fabricated. Fuel used consisted of H2 diluted with He, N2, H2O, or CO2, mixtures of H2 and CO, and mixtures of CO and CO2. Cell performance was measured at 800°C with the above-mentioned fuel gas mixtures and air as oxidant. For a given concentration of the diluent, cell performance was higher with He as the diluent than with N2 as the diluent. Mass transport through porous Ni-YSZ anode for H2-H2O, CO-CO2 binary systems, and H2-H2O-diluent gas ternary systems was analyzed using multicomponent gas diffusion theory. At high concentrations of diluent, the maximum achievable current density was limited by the anodic concentration polarization. From this measured limiting current density, the corresponding effective gas diffusivity was estimated. Highest effective diffusivity was estimated for fuel gas mixtures containing H2-H2O-He mixtures (~0.55 cm2/s), and the lowest for CO-CO2 mixtures (~0.07 cm2/s). The lowest performance was observed with CO-CO2 mixture as a fuel, which in part was attributed to the lowest effective diffusivity of the fuels tested and higher activation polarization.
- Jiang, Yi,Virkar, Anil V.
-
-
Read Online
- Novel photocatalytic activity of Cu@V co-doped TiO2/PU for CO2 reduction with H2O vapor to produce solar fuels under visible light
-
In this study, Cu and V co-doped TiO2 deposited on polyurethane (Cu@V-TiO2/PU) was synthesized as a catalyst for the reduction of CO2 with H2O vapor to preferentially produce CH4 as a valuable solar fuel under visible light. The Cu and V dopants defected into the TiO2 lattice, leading to the formation of Ti3+ and oxygen vacancies in the lattice. The Ti3+ formed in the doped TiO2 lattice created an intermediate band between the valence band and the conduction band of TiO2, leading to an increase in the electron–hole pair separation efficiency of TiO2. The oxygen vacancies existing on the surface of the photocatalyst could induce new adsorption sites to adsorb CO2. The generated electrons and holes reacted with the adsorbed CO2 and with H2O vapor to produce CO and primarily CH4. Therefore, the Cu@V-TiO2/PU photocatalysts successfully utilized visible light as the energy source and H2O vapor as a reductant to reduce CO2 to CO and CH4. The Cu@V-TiO2/PU photocatalysts also supplied sufficient electrons and holes for the selective reduction of CO2 to CH4 rather than CO. The 2Cu@4V-TiO2/PU photocatalyst, with Cu/TiO2 and V/TiO2 ratios of 2 and 4?wt.%, respectively, exhibited the highest photocatalytic activity for CO2 conversion into solar fuels. The production rates of CH4 and CO produced from the CO2 reduction by the 2Cu@4V-TiO2/PU photocatalyst under visible light were 933 and 588?μmol?g?1?cat.?h?1, respectively.
- Pham, Thanh-Dong,Lee, Byeong-Kyu
-
-
Read Online
- Laser-Induced Activation of Methane at Oxide Surfaces: A Probe of Radical-Surface Interactions
-
C-H bond activation was studied via pulsed laser irradiation of oxides in a methane atmosphere.Carbon monoxide was the major product observed at low power densities and room temperature.Significant amounts of C2 products, ethane, ethylene, and acetylene were formed.CO, C2H6, C2H4, and C2H2 are assigned as primary products of the reaction.Laser-induced methane activation produces *CH3 and :CH2 radical species in the gas phase via a plasma mechanism and is utilized as a tool to study radical-oxide surface interactions.These reactions are surface sensitive as evidenced by the changes in conversion and product selectivity as a function of oxide pretreatment and oxides used.
- Sayyed, Basseera A.,Stair, Peter C.
-
-
Read Online
- Effect of Vapor-phase-treatment to CuZnZr Catalyst on the Reaction Behaviors in CO2 Hydrogenation into Methanol
-
CuZnZr catalysts prepared by co-precipitation method were treated by vapor-phase-treatment (VPT) method, and used for the synthesis of methanol for CO2 hydrogenation. Compared with conventional co-precipitation method, this VPT with TPABr (TPABr: tetrapropylammonium bromide) induces obvious increases in the particles size of CuO, ZnO and ZrO2, promotes the formation of the rod-like structure, Zn and Zr enrichments on surface and the presence of more concentration of oxygen vacancies. Due to the increases of particle size especially for CuO particles, the activity of the catalyst for CO2 hydrogenation to CO (RWGS reaction) is furthest suppressed, leading to dramatical decrease in conversion of CO2. However, methanol productivity is affected relatively modestly due to the enrichments of Zn and Zr as another active species on the catalyst surface. In addition, catalyst properties and methanol selectivity can be regulated through adjusting the processing time. The catalyst with the processing time of 3 day (CuZnZr-TPABr-3d catalyst) shows a methanol selectivity above 90 % and no obvious deactivation appeared in a period of 100 h reaction.
- Chen, Shuyao,Zhang, Junfeng,Wang, Peng,Wang, Xiaoxing,Song, Faen,Bai, Yunxing,Zhang, Meng,Wu, Yingquan,Xie, Hongjuan,Tan, Yisheng
-
-
Read Online
- Sn(101) Derived from Metal-Organic Frameworks for Efficient Electrocatalytic Reduction of CO2
-
The synthesis of a specific Sn plane as an efficient electrocatalyst for CO2 electrochemical reduction to generate fuels and chemicals is still a huge challenge. Density functional theory (DFT) calculations first reveal that the Sn(101) crystal plane is more advantageous for CO2 electroreduction. A metal-organic framework (MOF) precursor Sn-MOF has been carbonized and then etched to successfully fabricate Sn(101)/SnO2/C composites with good control of the carbonization time and the concentration of hydrochloric acid. The Sn(101) crystal plane of the catalyst could enhance the faradaic efficiency of formate to as high as 93.3% and catalytic stability up to 20 h. The promotion of the selectivity and activity by Sn(101) advances new possibilities for the rational design of high-activity Sn catalysts derived from MOFs.
- Wu, Jian-Xiang,Zhu, Xiao-Rong,Liang, Ting,Zhang, Xiang-Da,Hou, Shu-Zhen,Xu, Ming,Li, Ya-Fei,Gu, Zhi-Yuan
-
-
Read Online
- Room-Temperature Activation of H2 by a Surface Frustrated Lewis Pair
-
Surface frustrated Lewis pairs (SFLPs) have been implicated in the gas-phase heterogeneous (photo)catalytic hydrogenation of CO2 to CO and CH3OH by In2O3?x(OH)y. A key step in the reaction pathway is envisioned to be the heterolysis of H2 on a proximal Lewis acid–Lewis base pair, the SFLP, the chemistry of which is described as In???In-OH + H2 → In-OH2+???In-H?. The product of the heterolysis, thought to be a protonated hydroxide Lewis base In-OH2+ and a hydride coordinated Lewis acid In-H?, can react with CO2 to form either CO or CH3OH. While the experimental and theoretical evidence is compelling for heterolysis of H2 on the SFLP, all conclusions derive from indirect proof, and direct observation remains lacking. Unexpectedly, we have discovered rhombohedral In2O3?x(OH)y can enable dissociation of H2 at room temperature, which allows its direct observation by several analytical techniques. The collected analytical results lean towards the heterolysis rather than the homolysis reaction pathway.
- Wang, Lu,Yan, Tingjiang,Song, Rui,Sun, Wei,Dong, Yuchan,Guo, Jiuli,Zhang, Zizhong,Wang, Xuxu,Ozin, Geoffrey A.
-
-
Read Online
- Electrocatalytic Reduction of CO2 to Ethylene by Molecular Cu-Complex Immobilized on Graphitized Mesoporous Carbon
-
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions.
- Balamurugan, Mani,Choutipalli, Venkata Surya Kumar,Hong, Jung Sug,Im, Sang Won,Jang, Jun Ho,Jeong, Hui-Yun,Kim, Sun Hee,Lee, Kang-Gyu,Lee, Yoon Ho,Nam, Ki Tae,Saravanan, Natarajan,Seo, Hongmin,Subramanian, Venkatesan
-
-
Read Online
- Catalytic behavior and surface species investigation over γ-Al 2O3 in dimethyl ether hydrolysis
-
The catalytic behavior and surface species over γ-Al 2O3 in hydrolysis of dimethyl ether (DME) was examined by experimental and theoretical studies. It was experimentally observed that γ-Al2O3 substantially catalyzed DME hydrolysis producing methanol at 250-350 C with high stability at this temperature range with respect to carbon formation. Other carbon-containing species yielded from side reactions were present in trace amounts at temperatures below 375 C. The Density Functional Theory calculations results suggested that DME hydrolysis is thermodynamically favorable on the hydroxylated γ-Al2O 3(1 1 0) but it is not favorable on (1 0 0) surfaces at this reaction temperature range. The DME hydrolysis on γ-Al2O3 is more likely to occur at a hydroxyl surface group which has relatively high acidity.
- Hirunsit, Pussana,Faungnawakij, Kajornsak,Namuangruk, Supawadee,Luadthong, Chuleeporn
-
-
Read Online
- Carbon Dioxide Hydrogenation over Au/ZrO2 Catalysts from Amorphous Precursors: Catalytic Reaction Mechanism
-
An active catalyst for carbon dioxide hydrogenation is obtained by exposing an amorphous Au25Zr75 alloy to CO2 hydrogenation conditions.During this in situ activation, metallic gold particles of 8.5 nm mean size are formed, and the zirconium component of the catalyst is oxidized to ZrO2.For comparison, a further Au/ZrO2 catalyst was synthesized by coprecipitation, followed by calcination of the amorphous precipitate.The calcination step strongly enhances the activity of the catalyst; gold segregation and zirconia crystallization are found to occur in this process.The structural and chemical changes are characterized by gas adsorption, X-ray diffraction and thermal analysis. The main products of CO2 hydrogenation over these catalysts, as identified by gas chromatography, are methanol and CO.To investigate the reaction mechanism, diffuse reflectance FTIR spectroscopy has been used.Observed surface species are correlated with the formation of gas-phase products.Adsorption of CO2-H2 results in rapid formation of formate as the primary surface intermediate; two types of formate species are clearly detected on the coprecipitated catalyst, and are assigned by means of formic acid adsorption experiments.CO formation from CO2 appears to proceed via surface carbonate, in a surface reaction that corresponds to a 'basic variant' of the reverse water-gas-shift reaction.The CO formed in this process is, in turn, the starting point for a series of surface hydrogenation steps that yield ?-bonded formaldehyde, surface-bound methylate and finally methanol.This sequence of reactions is confirmed by separate CO-H2 adsorption experiments.
- Koeppel, Rene A.,Baiker, Alfons,Schild, Christoph,Wokaun, Alexander
-
-
Read Online
- Matrix photochemistry of the complexes (CO)5M = C(OMe)Ph (M = Cr, W) having close-lying reactive MLCT and LF states
-
This article describes the photochemistry of (CO)5M=C(OMe)Ph (M = Cr, W) in inert gas matrices as 10 K at different irradiation wavelengths.The reactions were studied by following the IR spectral changes in the carbonyl and carbene stretching region.Irradiation with visible light into the low-energy MLCT band resulted in complete conversion of the complexes from anti- into syn-configurations.A similar isomerization reaction occurred as the primary photoprocess upon irradiation into the LF band at ca. 350 nm but this reaction was followed by release of CO as a secondary photoprocess, and in the case of the W-complex a subsequent third photochemical reaction was also observed.The photoproduct of this last reaction appeared to be coordinatively saturated, although it still contained a W(CO)4-moiety.In agreement with an earlier proposal based on flash-photolysis data, it is suggested that a C-H bond of the carbene methoxy group interacts with W via a two-electron, three-centre bond, thus occupying the open site at the metal.Conclusions are drawn about the reactivity of the MLCT and LF states of the isomers.
- Servaas, Peter C.,Stufkens, Derk J.,Oskam, Ad
-
-
Read Online
- Preparation, characterization and crystal structure of lead(II) tricyanomethanide
-
The so far unknown lead tricyanomethanide, Pb[C(CN)3] 2, was obtained from a saturated aqueous solution of PbCl2 and solid AgC(CN)3. Its IR spectrum and thermal behaviour are described. The crystal structure was determined by single-crystal X-ray diffraction (trigonal, P31m, Z = 3, a = 1414.4(5), c = 409.02(6) pm, R 1 = 0.0249, wR2 = 0.0527). Two crystallographically independent ninefold coordinated Pb atoms are connected by planar tricyanomethanide ions in two distinct bridging coordination modes. The Pb-N distances range between 254 and 293 pm.
- Deflon, Victor M.,De Sousa Lopes, Cassia C.,Bessler, Karl E.,Romualdo, Lincoln L.,Niquet, Elke
-
-
Read Online
- Self-Cleaning Catalyst Electrodes for Stabilized CO2 Reduction to Hydrocarbons
-
A surface-restructuring strategy is presented that involves self-cleaning Cu catalyst electrodes with unprecedented catalytic stability toward CO2 reduction. Under the working conditions, the Pd atoms pre-deposited on Cu surface induce continuous morphological and compositional restructuring of the Cu surface, which constantly refreshes the catalyst surface and thus maintains the catalytic properties for CO2 reduction to hydrocarbons. The Pd-decorated Cu electrode can catalyze CO2 reduction with relatively stable selectivity and current density for up to 16 h, which is one of the best catalytic durability performances among all Cu electrocatalysts for effective CO2 conversion to hydrocarbons. The generality of this approach of utilizing foreign metal atoms to induce surface restructuring toward stabilizing Cu catalyst electrodes against deactivation by carbonaceous species accumulation in CO2 reduction is further demonstrated by replacing Pd with Rh.
- Weng, Zhe,Zhang, Xing,Wu, Yueshen,Huo, Shengjuan,Jiang, Jianbing,Liu, Wen,He, Guanjie,Liang, Yongye,Wang, Hailiang
-
-
Read Online
- The difference of roles of alkaline-earth metal oxides on silica-supported nickel catalysts for CO2 methanation
-
The roles of alkaline-earth metal oxides on CO2 methanation over modified Ni/SiO2 catalysts were investigated. Ni/MO/SiO2 catalysts with variable elements (M = Mg, Ca, Sr and Ba) were prepared by the sequential impregnatio
- Guo, Meng,Lu, Gongxuan
-
-
Read Online
- 1D SnO2 with Wire-in-Tube Architectures for Highly Selective Electrochemical Reduction of CO2 to C1 Products
-
Electrochemical reduction of CO2 (ERC) into useful products, such as formic acid and carbon monoxide, is a fascinating approach for CO2 fixation as well as energy storage. Sn-based materials are attractive catalysts for highly selective ERC into C1 products (including HCOOH and CO), but still suffer from high overpotential, low current density, and poor stability. Here, One-dimensional (1D) SnO2 with wire-in-tube (WIT) structure is synthesized and shows superior selectivity for C1 products. Using the WIT SnO2 as the ERC catalyst, very high Faradaic efficiency of C1 products (>90%) can be achieved at a wide potential range from ?0.89 to ?1.29?V versus RHE, thus substantially suppressing the hydrogen evolution reaction. The electrocatalyst also exhibits excellent long-term stability. The improved catalytic activity of the WIT SnO2 over the commercial SnO2 nanoparticle indicates that higher surface area and large number of grain boundaries can effectively enhance the ERC activity. Synthesized via a facile and low-cost electrospinning technology, the reduced WIT SnO2 can serve as a promising electrocatalyst for efficient CO2 to C1 products conversion.
- Fan, Lei,Xia, Zheng,Xu, Meijia,Lu, Yingying,Li, Zhongjian
-
-
Read Online
- Selective Hydrogenation of Carbon Dioxide to Methanol on Cu-ZnO/SiO2 Catalysts Prepared by Alkoxide Method
-
Hydrogenation of CO2 to methanol was carried out on Cu-ZnO/SiO2 catalysts at 493 K and 3 MPa with a flow rate of 100 cm3min-1 (H2/CO2=2).Higher selectivity (>90percent) was observed on the catalysts prepared by the alkoxide method than on a conventional catalyst prepared by the impregnation method.The selectivity was higher on the catalysts pretreated with H2 at a higher temperature, except at 873 K.The activity of the catalyst pretreated at 873 K was extremely low, probably because of alloy formation.The results of XRD, XPS, and EXAFS demonstrate that the active species for methanol formation is a large metallic Cu particle covered with a partially oxidized layer interacting with highly dispersed ZnO.
- Okabe, Kiyomi,Sayama, Kazuhiro,Matsubayashi, Nobuyuki,Shimomura, Kin'ya,Arakawa, Hironori
-
-
Read Online
- Synthesis of formaldehyde from dimethyl ether on alumina-supported molybdenum oxide catalyst
-
The selective oxidation of DME to formaldehyde over alumina-supported MoOx catalyst (prepared by dry impregnation) is studied in this work. The activity and stability of the catalyst were evaluated in a fixed-bed continuous reactor at different temperatures and reactant concentrations. The influence of the main operating conditions, (DME, O2, CO2 and CO feed concentrations; reaction temperature) on reaction rate and product selectivity was experimentally determined. Thus, DME conversion decreases on increasing DME feed concentration and increases on increasing O2 feed concentration. Formaldehyde selectivity remained almost unaffected. A reaction mechanism, based on a Mars-van-Krevelen redox cycle representing DME oxidation to formaldehyde was used as a basis to develop a kinetic model for the reaction. The resulting simplified model suggests power law dependences for the reaction rate of 0.2 for the O2 and 0.5 for the DME.
- Peláez, Raquel,Marín, Pablo,Ordó?ez, Salvador
-
-
Read Online
- Photosensitive iron(II)-based CO-releasing molecules (CORMs) with vicinal amino and diphenylphosphino substituted chelating ligands
-
The reactions of [Fe(H2O)6] [BF4] 2 with aminoethyl-diphenylphosphane and 2-(diphenylphosphino)aniline lead to the formation of trans-[Fe(NC-Me)2(H2NCH 2CH2PPh2)2] [BF4] 2 (1a) and trans-[Fe(NC-Me)2(H2NC 6H4-2-PPh2)2] [BF4] 2 (1b), respectively. One acetonitrile ligand can be substituted by CO yielding [Fe(CO)(NC-Me)(H2NCH2CH2PPh 2)2] [BF4]2 (2a, CORM-P1) and [Fe(CO)(NC-Me)(H2NC6H4-2-PPh2) 2] [BF4]2 (2b, CORM-P2). Upon irradiation with visible light, CO is liberated making especially 2a a promising photo-CORM whereas for 2b a slow and incomplete CO release is observed.
- Jazzazi, Taghreed M.A.,G?rls, Helmar,Gessner, Guido,Heinemann, Stefan H.,Westerhausen
-
-
Read Online
- Atmospheric chemistry of CF3CF2CHO: Absorption cross sections in the UV and IR regions, photolysis at 308 nm, and gas-phase reaction with OH radicals (T = 263-358 K)
-
The relative importance in the atmosphere of UV photolysis of perfluoropropionaldehyde, CF3CF2CHO, and reaction with hydroxyl (OH) radicals has been investigated in this work. First, the forbidden n → π* transition of the carbonyl chromophore was characterized between 230 and 380 nm as a function of temperature (269-298 K) and UV absorption cross sections, σλ, were determined in those ranges. In addition, IR absorption cross sections were determined between 4000 and 500 cm-1. Pulsed laser photolysis (PLP) of CF3CF 2CHO coupled to Fourier transform infrared (FTIR) was employed to determine the overall photolysis quantum yield, Φλ, at 308 nm and 298 K. Φλ=308 nm was pressure dependent, ranging from (0.94 ± 0.14) at 75 Torr to (0.30 ± 0.01) at 760 Torr. This dependence is characterized by the Stern-Volmer parameters Φλ=308 nm0 = (1.19 ± 0.34) and KSV = (1.22 ± 0.52) × 10-19 cm3 molecule-1. End products of the photodissociation of CF3CF2CHO were measured and quantified by FTIR spectroscopy. Furthermore, the rate coefficients for the OH + CF3CF2CHO reaction, k1, were determined as a function of temperature (T = 263-358 K) by PLP-LIF. At room temperature the rate coefficient is k1(T = 298 K) = (5.57 ± 0.07) × 10 -13 cm3 molecule-1 s-1, whereas the temperature dependence is described by k1(T) = (2.56 ± 0.32) × 10-12 exp{-(458 ± 36)/T} cm3 molecule -1 s-1. On the basis of our results, photolysis of CF 3CF2CHO in the actinic region could be an important removal process for CF3CF2CHO in the atmosphere. The formation of the primary products in the UV photolysis of CF3CF 2CHO is also discussed.
- Antinolo, Maria,Jimenez, Elena,Gonzalez, Sergio,Albaladejo, Jose
-
-
Read Online
- Novel TiO2/C3N4 Photocatalysts for Photocatalytic Reduction of CO2 and for Photocatalytic Decomposition of N2O
-
TiO2/g-C3N4 photocatalysts with the ratio of TiO2 to g-C3N4 ranging from 0.3/1 to 2/1 were prepared by simple mechanical mixing of pure g-C3N4 and commercial TiO2
- Reli, Martin,Huo, Pengwei,?ihor, Marcel,Ambro?ová, Nela,Troppová, Ivana,Matějová, Lenka,Lang, Jaroslav,Svoboda, Ladislav,Ku?trowski, Piotr,Ritz, Michal,Praus, Petr,Ko?í, Kamila
-
-
Read Online
- Epoxidation of Ethylene with Products of Thermal Gas-Phase Oxidation of n-Butane
-
Abstract: Epoxidation of ethylene with the reactive products formed during thermal gas-phase oxidation of n-butane has been carried out under flow conditions with the separation of the zones of generation of radicals and their interaction with ethylene. Butane is oxidized in the first section of a two-section reactor, and ethylene is fed to the second section. It has been found that increasing the residence time of a butane–oxygen mixture in the first section of the reactor from 7 to 13 s increases the ethylene oxide accumulation rate. A further increase in the contact time leads to a decrease in the rate. Similarly, increasing the C4H10/O2 ratio in the range of 0.05–0.25 leads to an increase in the rate of accumulation of ethylene oxide. A further increase in this ratio decreases the rate of epoxidation. It has also been found that the temperature dependences of the ethylene oxide accumulation rate in both sections of the reactor pass through a maximum. The obtained data give evidence for the occurrence of the ethylene epoxidation reaction initiated by the n-butane oxidation products under the conditions when ethylene itself is slightly oxidized.
- Arsentev, S. D.,Grigoryan, R. R.
-
-
Read Online
- Hydrogenation of CO2to LPG over CuZnZr/MeSAPO-34 catalysts
-
The utilization of CO2to synthesize environmentally benign liquid fuels offers a solution to replacing depleting petroleum resources. Herein, a ternary CuZnZr (CZZ) metal oxide catalyst and a SAPO-34 zeolite were synthesized by co-precipitation and hydrothermal synthesis, respectively. Different metals were impregnated into the latter to obtain MeSAPO-34 (Me = Mn, Zn and Zr). A granule mixture of CZZ and MeSAPO-34 components (CZZ/MeSAPO-34 catalyst) was then effectively utilized in a tandem catalytic process for one-step CO2hydrogenation to liquefied petroleum gas (LPG). The CZZ/MeSAPO-34 catalysts were characterized by using XRD, H2-TPR, BET, SEM-EDS and NH3-TPD techniques. SEM-EDS and XRD results indicated that an appropriate amount of Zr metal loading induced minimum zeolite framework collapse compared to a similar amount of Mn and Zn, which was more favorable for higher activity. In addition, NH3-TPD results revealed that the acidity of SAPO-34 could be altered after impregnation with different metals in different quantities. Tuning the acid density and strength, together with adjusting the CZZ to MeSAPO-34 weight ratio, had a collectively critical effect on LPG selectivity. An effective hydrogenation microenvironment which favors lower alkane formation (C3-C4) was enhanced after the acidity of the molecular sieve was tuned. LPG selectivity could reach 86% over the CZZ/5% ZrSAPO-34 catalyst at 2 MPa, 350 °C, a W/F ratio of 6, a H2/CO2ratio of 3 and a weight ratio of 1.
- Du, Ce,Gapu Chizema, Linet,Hondo, Emmerson,Lu, Chengxue,Lu, Peng,Ma, Qingxiang,Mo, Shuting,Tong, Mingliang,Tsubaki, Noritatsu
-
-
Read Online
- Laser photofragmentation time-of-flight mass spectrometric study of acetophenone at 193 and 248 nm
-
The photodissociation of acetophenone (C6H5COCH3) at 193 and 248 nm is studied using the time-of-flight mass spectrometric technique. It is found that the dissociation is dominated by processes (1) and (2): C6H5COCH3+hν→C6H5CO+CH3 (1), C6H5+CH3CO (2) and, C6H5CH3+CO. At 193 nm, processes (1) and (2) occur with comparable cross sections. The cross section for process (3) at 193 nm is estimated to be 3CO and C6H5CO radicals initially formed at 193 nm by processes (1) and (2) are found to undergo further dissociation according to processes (6) and (8). At 248 nm, process (1) is overwhelmingly the dominant channel. The branching ratios for process (1) : process (2) : process (3) are estimated as 1.0:0.01:0.0008. The energy releases for these dissociation processes are also determined.
- Zhao,Cheung,Liao,Liao,Ng
-
-
Read Online
- A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane
-
A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorpt
- Wang, Yichen,Fan, Shizhao,AlOtaibi, Bandar,Wang, Yongjie,Li, Lu,Mi, Zetian
-
-
Read Online
- Comparative study of CO2 hydrogenation to methanol on cubic bixbyite-type and rhombohedral corundum-type indium oxide
-
Hydrogenation of CO2 to value-added chemicals has attracted much attention all through the world. In2O3 with cubic bixbyite-type (denoted as c-In2O3) is well known for its high CO2 hydrogenation activity and CH3OH selectivity at high temperature. However, the other structure of In2O3 with rhombohedral corundum-type (denoted as rh-In2O3) rarely been investigated as catalyst. Herein, c-In2O3 and rh-In2O3 were prepared and comparatively studied for CO2 hydrogenation. The results indicated that c-In2O3 showed higher CO2 conversion activity than rh-In2O3 due to the impressive reducibility and reactivity. Whereas rh-In2O3 had higher CH3OH selectivity due to weaker CH3OH and stronger CO adsorption on rh-In2O3. Although c-In2O3 and rh-In2O3 catalysts showed different CO2 hydrogenation performance, in-situ diffuse reflectance infrared Fourier transform spectroscopy showed CO2 can be reduced to CO through redox cycling and hydrogenation to CH3OH through formate path.
- Yang, Bin,Li, Longtai,Jia, Ziye,Liu, Xiping,Zhang, Chunjie,Guo, Limin
-
-
Read Online
- Joint experimental and DFT study of the gas-phase unimolecular elimination kinetic of methyl trifluoropyruvate
-
The elimination kinetics of methyl trifluoropyruvate in the gas phase was determined in a static system, where the reaction vessel was always deactivated with allyl bromide, and in the presence of at least a 3-fold excess of the free-radical chain inhibitor toluene. The working temperature range was 388.5-430.1 °C, and the pressure range was 38.6-65.8 Torr. The reaction was found to be homogeneous and unimolecular and to obey a first-order rate law. The products of the reaction are methyl trifluoroacetate and CO gas. The Arrhenius equation of this elimination was found to be as follows: log k1 (s-1) = (12.48 ± 0.32) - (204.2 ± 4.2) kJ mol -1(2.303RT)-1 (r = 0.9994). The theoretical calculation of the kinetic and thermodynamic parameters and the mechanism of this reaction were carried out at the B3LYP/6-31G(d,p), B3LYP/6-31++G(d,p), MPW1PW91/6-31G(d,p), MPW1PW91/6-31++G(d,p), PBEPBE/6-31G(d,p), and PBEPBE/6-31G++(d,p) levels of theory. The theoretical study showed that the preferred reaction channel is a 1,2-migration of OCH3 involving a three-membered cyclic transition state in the rate-determining step.
- Tosta, Maria M.,Mora, Jose R.,Cordova, Tania,Chuchani, Gabriel
-
-
Read Online
- Lewis Acid Strength of Interfacial Metal Sites Drives CH3OH Selectivity and Formation Rates on Cu-Based CO2 Hydrogenation Catalysts
-
CH3OH formation rates in CO2 hydrogenation on Cu-based catalysts sensitively depend on the nature of the support and the presence of promoters. In this context, Cu nanoparticles supported on tailored supports (highly dispersed M on SiO2; M=Ti, Zr, Hf, Nb, Ta) were prepared via surface organometallic chemistry, and their catalytic performance was systematically investigated for CO2 hydrogenation to CH3OH. The presence of Lewis acid sites enhances CH3OH formation rate, likely originating from stabilization of formate and methoxy surface intermediates at the periphery of Cu nanoparticles, as evidenced by metrics of Lewis acid strength and detection of surface intermediates. The stabilization of surface intermediates depends on the strength of Lewis acid M sites, described by pyridine adsorption enthalpies and 13C chemical shifts of -OCH3 coordinated to M; these chemical shifts are demonstrated here to be a molecular descriptor for Lewis acid strength and reactivity in CO2 hydrogenation.
- Noh, Gina,Lam, Erwin,Bregante, Daniel T.,Meyet, Jordan,?ot, Petr,Flaherty, David W.,Copéret, Christophe
-
-
Read Online
- Photocatalytic C-C coupling from carbon dioxide reduction on copper oxide with mixed-valence copper(I)/copper(II)
-
To realize the evolution of C2+ hydrocarbons like C2H4 from CO2 reduction in photocatalytic systems remains a great challenge, owing to the gap between the relatively lower efficiency of multielectron transfer in photocatalysis and the sluggish kinetics of C-C coupling. Herein, with Cu-doped zeolitic imidazolate framework-8 (ZIF-8) as a precursor, a hybrid photocatalyst (CuOX@p-ZnO) with CuOX uniformly dispersed among polycrystalline ZnO was synthesized. Upon illumination, the catalyst exhibited the ability to reduce CO2 to C2H4 with a 32.9% selectivity, and the evolution rate was 2.7 μmol·g-1·h-1 with water as a hole scavenger and as high as 22.3 μmol·g-1·h-1 in the presence of triethylamine as a sacrificial agent, all of which have rarely been achieved in photocatalytic systems. The X-ray absorption fine structure spectra coupled with in situ FT-IR studies reveal that, in the original catalyst, Cu mainly existed in the form of CuO, while a unique Cu+ surface layer upon the CuO matrix was formed during the photocatalytic reaction, and this surface Cu+ site is the active site to anchor the in situ generated CO and further perform C-C coupling to form C2H4. The C-C coupling intermediate *OC-COH was experimentally identified by in situ FT-IR studies for the first time during photocatalytic CO2 reduction. Moreover, theoretical calculations further showed the critical role of such Cu+ sites in strengthening the binding of *CO and stabilizing the C-C coupling intermediate. This work uncovers a new paradigm to achieve the reduction of CO2 to C2+ hydrocarbons in a photocatalytic system.
- Wang, Wei,Deng, Chaoyuan,Xie, Shijie,Li, Yangfan,Zhang, Wanyi,Sheng, Hua,Chen, Chuncheng,Zhao, Jincai
-
-
Read Online
- UV photodissociation of oxalyl chloride yields four fragments from one photon absorption
-
The photodissociation of oxalyl chloride, (ClCO)2, has been studied near 235 nm using the photofragment imaging technique. Observed products include both ground state Cl (2P3/2) and spin-orbit excited Cl*(2P1/2) chlorine atoms and ground electronic state CO molecules. The rotational distribution obtained for the CO v=0 product is peaked at about J=30 and extends beyond J=50. Photofragment images were recorded for both chlorine atom fine structure components as well as many rotational levels of the CO v=0, yielding state-resolved angular and translational energy distributions. The recoil speed distribution for the Cl* exhibits a dominant fast component, with a translational energy distribution peaking at about 48 kJ/mol. The ground state chlorine atom showed two components in its speed distribution, with the slow component dominant. The corresponding translational energy distribution peaked at 10 kJ/mol but extended to 80 kJ/mol. The total average translational energy release into the Cl product is 34 kJ/mol. Similarly, the low rotational levels of the CO showed only a slow component, the intermediate rotational levels showed a bimodal speed distribution, and the highest rotational levels showed only the fast component. The fast components of both chlorine atom product and the higher rotational levels of the CO show an anisotropic angular distribution, while all slow fragments show a nearly isotropic angular distribution. These observations suggest a novel dissociation mechanism in which the first step is an impulsive three-body dissociation yielding predominantly Cl*, rotationally excited CO and chloroformyl radical ClCO, with only modest momentum transfer to the latter species. Most of the remaining ClCO undergoes subsequent dissociation yielding low rotational levels of CO and little translational energy release.
- Ahmed, Musahid,Blunt, David,Chen, Daniel,Suits, Arthur G.
-
-
Read Online
- Oxidation of Allyl Radicals: Kinetic Parameters for the Reactions of Allyl Radicals with HO2 and O2 between 400 and 480 deg C
-
The decomposition of 4,4-dimethylpent-1-ene (DMP) in the presence of O2 has been used as a source of allyl and HO2 radicals between 400 and 480 deg C.Propene was added to the mixtures of DMP and O2 in order to monitor from the yields of propene oxide by use of the known value of k14.HO2 + C3H6 -> C3H6O + OH (14).From measurements of the initial yields of CO, hexa-1,5-diene and propene oxide over a range of mixture composition, rate constants have been obtained for reaction (9) and (10). CH2CHCH2 + HO2 -> CO + product (9); CH2CHCH2 + HO2 -> C3H6 + HO2 (10).At 400 deg C, k9 = 3.95 x 109 and k10 = 1.42 x 109 dm3 mol-1 s-1 and both show a slight increase (within experimental error) with temperature, 15percent and 30percent, repectively, at 480 deg C.Strong evidence is obtained for the formation of CO in the reaction between allyl radicals and O2 and values of A15 = 109.4 +/- 0.6 dm3 mol-1 s-1 and E15 = 79 +/- 8 kJ mol-1 are obtained. CH2CHCH2 + O2 -> CO + products (15).The mechanism of reactions (10) and (15) are discussed.Based on current thermochemistry it is shown by calculation that reaction (10) probably occurs only to a minor extent through a direct H-atom abstraction route which is reverse of the chain initiation reaction (16).C3H6 + O2 -> CH2CHCH2 + HO2 (16).The available kinetic data for the reaction between allyl radicals and O2 are summarised.
- Lodhi, Zulfiqar H.,Walker, Raymond W.
-
-
Read Online
- Self-growth-templating synthesis of 3D N,P,Co-doped mesoporous carbon frameworks for efficient bifunctional oxygen and carbon dioxide electroreduction
-
Although mesopore designs are expected to play a key role in exploring electrocatalytic properties of carbons, facile preparation of mesoporous carbons (MPCs) with efficient dopants to enable high performance remains a great challenge. Herein, we for the
- Pan, Fuping,Liang, Aimin,Duan, Youxin,Liu, Qiao,Zhang, Junyan,Li, Ying
-
-
Read Online
- Effect of active and inert oxide on catalytic partial oxidation (CPO) of methane over supported Ni catalysts
-
The effects of preparation method, types of carrier and different catalyst and support structures on the CH4 catalytic partial oxidation (CPO) activity of supported Ni catalysts are reviewed with respect to selected results obtained by this research group during the last five years. In particular, different preparation methods and structural effect of Ni supported on La2O3, on CeO2 and on mixed CeO2-La2O3 are discussed. The effects of the peculiarity of an active (redox) and of an inert oxide carrier, influencing the metal dispersion, the metal reducibility and the carbon formation, are considered by comparing the catalytic performance of nickel catalysts supported on CeO2 and on SiO2. Ni supported over a high surface area silica will be compared with a corresponding ceria-doped nickel catalyst. The results of a detailed material characterization attained by several techniques as XPS, XRD, TPR/TPO are described, aiming to elucidate the structure - activity relationship. The reviewing of the different case studies illustrates the importance of the interaction between support and active metals ultimately determining the surface distribution of the active sites and their final catalytic activity.
- LaParola, V.,Pantaleo, G.,Venezia, Anna
-
-
- Rapid alloying of Au–Pd nanospheres by a facile pulsed laser technique: Insights into a molar-dependent electrocatalytic methanol oxidation reaction
-
Direct methanol fuel cells have attracted extensive research interest because of their relatively high energy density and portability. It is important to rationally design the composition and surface atomic structure by efficient synthesis protocols to boost cell efficiency. In this study, we employed cohesive pulsed laser irradiation and ultrasonochemical techniques to synthesize and tune the molar ratio of an Au–Pd alloy for the methanol oxidation reaction (MOR). The effective implementation of extremely rapid photoinduced reduction and reaction conditions resulted in the formation of well-dispersed and homogenous nanospheres of the Au–Pd alloy with uniform particle size. Moreover, the composition-tuned Au–Pd alloy exhibited an improved electrocatalytic activity, which might be due to its improved electrical conductivity and higher CO tolerance. The alloy achieved relatively high mass and specific activities of 0.50 A/mgPd and 1.36 mA/cmPd2, respectively. Additionally, we studied the effect of the Au–Pd composition on the MOR activity and analyzed the reaction kinetics in depth. This work provides the foundation for implementing a laser-based technique to synthesize Pd-based alloy electrocatalysts for MOR application.
- Chinnadurai, Deviprasath,Choi, Myong Yong,Lee, Seung Jun,Lee, Young Wook,Yeon, Sanghun,Yu, Yiseul
-
-
- Oxygen-vacancy generation in MgFe2O4 by high temperature calcination and its improved photocatalytic activity for CO2 reduction
-
MgFe2O4 spinel with abundant oxygen vacancy was synthesized by a simple precipitation method, and tested in photocatalytic reduction of CO2 with water vapor as reductant. A series of characterization including XRD, XPS, EPR, PL spectrum, UV–vis DRS and TPD-CO2 were performed to investigate the influence of calcination temperature on morphology, optical and electronic properties of MgFe2O4 spinel. The results demonstrated that the oxygen vacancy concentration increases first and then decreases with the increase of calcination temperature. By introducing oxygen vacancies, the recombination of photogenerated electron-hole pairs was significantly suppressed, visible light absorption and chemisorption capacity of CO2 were dramatically boosted. Mg-Fe-750 with the richest oxygen vacancies exhibits the highest photocatalytic activity, for which the production rate of CO and H2 was 24.4 and 34.3 μmol/gcat/h, respectively.
- Chen, Haowen,Fu, Liming,Wang, Kang,Wang, Xitao
-
-
- Ethanol Steam Reforming by Ni Catalysts for H2 Production: Evaluation of Gd Effect in CeO2 Support
-
Abstract: Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the role of gadolinium on ethanol conversion, H2 selectivity, and carbon formation on ethanol steam reforming reaction. For this, catalysts containing 5 wt% of Ni impregnated on supports of ceria modified with different amounts of Gd (1, 5, and 10 wt%) were used. Ex-situ studies of XRPD suggest an increase of the lattice parameters, indicating a solid solution formation between Gd and Ce. Results of TPR showed an increase in metal-support interactions as the content of Gd increased. In situ XRPD studies indicated the formation of a GdNiO ternary phase for the catalysts containing Gd, which is in agreement with the results obtained by XANES. The catalysts were tested at three temperatures: 400?°C, 500?°C, and 600?°C. The conversion and productivity showed dependence with the Gd content and also with the temperature of the reaction. After the catalytic tests, catalysts containing Gd presented filamentous carbon possible due to a change in the reaction pathway. The highest ethanol conversion and H2 productivity were obtained at 600?°C for all catalysts and the best catalyst at this temperature was 5Ni_5GdCeO2. The promising performance of this catalyst may be associate with the lowest formation of GdNiO ternary phase, among the catalysts containing Gd, which means more Ni0 active species available to convert ethanol. Graphical Abstract: [Figure not available: see fulltext.]
- Assaf, Elisabete M.,Ferreira, Gabriella R.,Lucrédio, Alessandra F.,Nogueira, Francisco G. E.
-
-
- Rational Design of Zinc/Zeolite Catalyst: Selective Formation of p-Xylene from Methanol to Aromatics Reaction
-
The production of p-xylene from the methanol to aromatics (MTA) reaction is challenging. The catalytic stability, which is inversely proportional to the particle size of the zeolite, is not always compatible with p-xylene selectivity, which is inversely proportional to the external acid sites. In this study, based on a nano-sized zeolite, we designed hollow triple-shelled Zn/MFI single crystals using the ultra-dilute liquid-phase growth technique. The obtained composites possessed one ZSM-5 layer (≈30 nm) in the middle and two silicalite-1 layers (≈20 nm) epitaxially grown on two sides of ZSM-5, which exhibited a considerably long lifetime (100 % methanol conversion >40 h) as well as an enhanced shape selectivity of p-xylene (>35 %) with a p-xylene/xylene ratio of ≈90 %. Importantly, using this sandwich-like zeolite structure, we directly imaged the Zn species in the micropores of only the ZSM-5 layer and further determined the specific structure and anchor location of the Zn species.
- Chen, Biaohua,Chen, Congmei,Chen, Xiao,Hou, Yilin,Hu, Xiaomin,Li, Jing,Qian, Weizhong,Sun, Wenjing,Wang, Ning,Yang, Yifeng,Zhang, Lan
-
supporting information
(2022/02/16)
-
- Nanoconfinement Engineering over Hollow Multi-Shell Structured Copper towards Efficient Electrocatalytical C?C coupling
-
Nanoconfinement provides a promising solution to promote electrocatalytic C?C coupling, by dramatically altering the diffusion kinetics to ensure a high local concentration of C1 intermediates for carbon dimerization. Herein, under the guidance of finite-element method simulations results, a series of Cu2O hollow multi-shell structures (HoMSs) with tunable shell numbers were synthesized via Ostwald ripening. When applied in CO2 electroreduction (CO2RR), the in situ formed Cu HoMSs showed a positive correlation between shell numbers and selectivity for C2+ products, reaching a maximum C2+ Faradaic efficiency of 77.0±0.3 % at a conversion rate of 513.7±0.7 mA cm?2 in a neutral electrolyte. Mechanistic studies clarified the confinement effect of HoMSs that superposition of Cu shells leads to a higher coverage of localized CO adsorbate inside the cavity for enhanced dimerization. This work provides valuable insights for the delicate design of efficient C?C coupling catalysts.
- Li, Jiawei,Liu, Chunxiao,Xia, Chuan,Xue, Weiqing,Zeng, Jie,Zhang, Menglu,Zheng, Tingting
-
supporting information
(2021/12/06)
-
- Synthesis, thermal behavior in oxidative and pyrolysis conditions, spectroscopic and DFT studies of some alkaline earth metals p-aminobenzoate complexes using TG-DTA, DSC, PXRD and EGA (TG-FTIR) techniques
-
p-aminobenzoic acid is a substance widely used in several areas, such as catalysis, biomarkers, magnetic materials, luminescent materials and biological applications. p-aminobenzoate complexes with alkaline earth metal were synthesized and the thermal and pyrolysis behavior was studied using thermoanalytical and spectroscopic techniques. Based on TG/DTG-DTA and EGA results, the thermal decomposition mechanisms of the compounds were proposed under both atmospheres studied. The main gaseous products identified by EGA in both study conditions were H2O, Aniline, CO and CO2. From DSC analysis, it was possible to measure the enthalpies of dehydration and evaluate the phase transitions of the magnesium complex. FTIR data suggest that metal-ligand coordination occurs through carboxylate group by different ways. The coordination modes suggested by experimental FTIR data were supported by DFT study. The X-ray diffraction powder patterns show that the barium compound was obtained in amorphous state, while the other compounds have a crystalline structure.
- Caires, Flávio J.,Fernandes, Richard P.,Gaspari, Ana P. S.,Ionashiro, Massao,Isquibola, Guilherme,Machado, Antonio E. H.,Teixeira, José Augusto
-
-
- Insights into the Nonthermal Effects of Light in Dry Reforming of Methane to Enhance the H2/CO Ratio near Unity over Ni/Ga2O3
-
Photothermal catalysis, which couples both solar and thermal energies, has burgeoned as a promising approach to drive catalytic reactions. However, the utilization of light irradiation to tune the reaction paths to obtain ideal product distribution in pho
- Rao, Zhiqiang,Cao, Yuehan,Huang, Zeai,Yin, Zihang,Wan, Wenchao,Ma, Minzhi,Wu, Yanxin,Wang, Junbu,Yang, Guidong,Cui, Yi,Gong, Zhongmiao,Zhou, Ying
-
p. 4730 - 4738
(2021/05/04)
-
- Carbon monoxide as an intermediate product in the photocatalytic steam reforming of methane with lanthanum-doped sodium tantalate
-
Photocatalytic steam reforming of methane (PSRM) has been studied as an attractive method to produce hydrogen by utilizing photoenergy like solar energy at around room temperature with metal-loaded photocatalysts, where methane and water are selectively converted to carbon dioxide and hydrogen. In the present study, we used a PSRM system using a flow reactor at around room temperature to yield the partially oxidized product, carbon monoxide (CO). It was found that some La-doped NaTaO3 samples can produce carbon monoxide constantly in addition to hydrogen and carbon dioxide. Among the prepared samples, a La(2 mol%)-doped NaTaO3 photocatalyst without any cocatalyst exhibited the highest photocatalytic activity and the highest CO selectivity of 24%. The CO yield depended on the photocatalysts and the reaction conditions. Suitable reaction conditions for CO yield were high light intensity, a higher flow rate, and a moderately high methane/water ratio. Some additional reaction tests revealed that water gas shift (WGS) can take place as an undesirable successive reaction, i.e., the produced carbon monoxide can successively react with water to form carbon dioxide, which would restrict the CO yield significantly.
- Anzai, Akihiko,Sarwana, Wirya,Takami, Daichi,Yamamoto, Akira,Yoshida, Hisao
-
p. 5534 - 5542
(2021/08/24)
-
- Single-Phase Formation of Rh2O3 Nanoparticles on h-BN Support for Highly Controlled Methane Partial Oxidation to Syngas
-
Single-phase formation of active metal oxides on supports has been vigorously pursued in many catalytic applications to suppress undesired reactions and to determine direct structure-property relationships. However, this is difficult to achieve in nanoscale range because the effect of non-uniform metal-support interfaces becomes dominant in the overall catalyst growth, leading to the nucleation of various metastable oxides. Herein, we develop a supported single-phase corundum-Rh2O3(I) nanocatalyst by utilizing controlled interaction between metal oxide and h-BN support. Atomic-resolution electron microscopy and first-principle calculation reveal that single-phase formation occurs via uniform and preferential attachment of Rh2O3(I) (110) seed planes on well-defined h-BN surface after decomposition of rhodium precursor. By utilizing the Rh/h-BN catalyst in methane partial oxidation, syngas is successfully produced solely following the direct route with keeping a H2/CO ratio of 2, which makes it ideal for most downstream chemical processes.
- Kang, Dohun,Kang, Sungsu,Kim, Ji Soo,Kim, Younhwa,Lee, Hyunjoo,Lee, Kyung Rok,Park, Jungwon,Song, Chyan Kyung,Sung, Jongbaek,Yi, Jongheop
-
supporting information
p. 25411 - 25418
(2021/10/25)
-
- Morphology Effects of Nanoscale Er2O3 and Sr-Er2O3 Catalysts for Oxidative Coupling of Methane
-
Abstract: Er2O3 nanorods were prepared by a hydrothermal method, and Sr-modified Er2O3 nanorods (Sr-Er2O3) were synthesized using an impregnation method. Their catalytic performance for oxidative coupling of methane was investigated. The catalysts were characterized by several techniques such as XRD, N2 adsorption, TEM, XPS, O2-TPD and CO2-TPD. Compared with Er2O3 and Sr-Er2O3 nanoparticles, Er2O3 and Sr-Er2O3 nanorods exhibit higher CH4 conversion and C2–C3 selectivity. This is caused by higher (O? + O2?)/O2? ratio, a higher number of chemisorbed oxygen species and moderate basic sites achieved on the nanorods catalysts. The Sr-Er2O3 nanorods afford a 23.2% conversion of CH4 with 50.3% selectivity to C2–C3 at 650?°C. Graphic Abstract: [Figure not available: see fulltext.]
- Fan, Yuqiao,Sun, Mingxing,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
-
p. 2197 - 2206
(2021/01/04)
-
- New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na2WO4/SiO2 Catalysts
-
The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na2WO4/SiO2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H2-TPR, TAP and steady-state kinetics) experiments, that the long speculated crystalline Na2WO4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na-WOx sites. Kinetic analysis via temporal analysis of products (TAP) and steady-state OCM reaction studies demonstrate that (i) surface Na-WOx sites are responsible for selectively activating CH4 to C2Hx and over-oxidizing CHy to CO and (ii) molten Na2WO4 phase is mainly responsible for over-oxidation of CH4 to CO2 and also assists in oxidative dehydrogenation of C2H6 to C2H4. These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na2WO4/SiO2 catalysts.
- Baltrusaitis, Jonas,Fushimi, Rebecca R.,Kiani, Daniyal,Sourav, Sagar,Wachs, Israel E.,Wang, Yixiao
-
p. 21502 - 21511
(2021/08/25)
-
- THERMAL OXIDATIVE COUPLING OF METHANE PROCESS USING RENEWABLE ENERGY WITH POSSIBLE CO-PRODUCTION OF HYDROGEN
-
The disclosure relates in its first aspect to a process for converting methane into chemicals. The process comprises the steps of (a) providing a first stream (1; 7) comprising methane; (b) providing a second stream (13) which is an oxygen-rich stream; (c) contacting said first stream (1; 7) with said second stream (13) under oxidation reaction conditions to obtain a third stream (15) comprising chemicals and water; (d) performing at least one separation step on said third stream (15) to recover a water stream (21) and a fourth stream (39) comprising chemicals; (e) subjecting said water stream (21) to an oxidation reaction under first reaction conditions to produce at least an oxygen stream (29), wherein the oxygen stream (29) is recycled into the second stream (13). In its second aspect, the disclosure relates to an installation for working the process of the first aspect.
- -
-
Page/Page column 19
(2021/12/30)
-
- Study on the selective oxidation of methane over highly dispersed molybdenum-incorporated KIT-6 catalysts
-
A series of molybdenum-incorporated mesoporous silica (Mo-KIT-6) catalysts were successfully synthesized by a one-pot hydrothermal synthesis method, and were applied in the selective oxidation of methane to formaldehyde using oxygen as an oxidizing agent under atmospheric pressure. Comparatively, the corresponding supported catalysts (Mo/KIT-6) were prepared by incipient-wetness-impregnation method. The results of the small angle XRD, nitrogen adsorption/desorption isotherms, UV-vis, H2-TPR and UV-Raman spectroscopy characterization combined with the catalytic activity tests demonstrated that molybdenum atoms were inserted into the framework of the mesoporous materials for the Mo-KIT-6 catalysts and the highly dispersed MoO bonds dominantly existed, which were responsible for the efficient selective formation of formaldehyde. However, for Mo/KIT-6 catalysts, the molybdenum oxide species were mainly loaded on the surface or inside the outer pore channels of the support and abundant emergence of the Mo-O-Mo bond played a major role in the activation of methane to COx. Furthermore, with equivalent molybdenum content, the methane selective oxidation performance of 8Mo-KIT-6 was obviously better than that of 4.6Mo/KIT-6, and the formaldehyde yield (2.1%) of 8Mo-KIT-6 was 2.3 times as much as that (0.9%) of 4.6Mo/KIT-6.In situandoperandoUV-Raman results demonstrated that the structures of the MoOxactive sites have a strong effect on the formation and elimination of carbon deposition during the separated redox reaction with methane and O2, respectively. The polymerized MoOxactive sites are favorable for the formation of graphitic carbon (G), which is called ordered carbon, while the isolated MoOxactive sites are favorable for the formation of disordered carbon (D). The reduced highly dispersed MoOxactive sites incorporated in the framework of silica are more easily reoxidized than those on the supported catalysts.
- Chen, Pei,Fan, Xiaoqiang,Kong, Lian,Li, Jianmei,Liu, Baijun,Liu, Bonan,Xiao, Xia,Xie, Zean,Zhao, Zhen
-
p. 4083 - 4097
(2021/06/30)
-
- Iron phosphate nanoparticle catalyst for direct oxidation of methane into formaldehyde: Effect of surface redox and acid-base properties
-
The effect of various iron phosphate and oxide catalysts on the direct oxidation of methane (CH4) to formaldehyde (HCHO) with molecular oxygen (O2) as the sole oxidant was studied using a fixed-bed flow reactor. Five crystalline iron-containing catalysts (FePO4, Fe3O3(PO4), Fe4(P2O7)3, Fe2P2O7, and α-Fe2O3) with different iron coordination geometries, iron oxidation states, and Fe/P ratios were synthesized by the sol-gel method using malic acid or aspartic acid. The Fe/P molar ratio had a significant effect on the oxidation catalysis; CH4 conversion increased with the Fe/P molar ratio, although the selectivity to HCHO decreased. Trigonal FePO4 nanoparticles synthesized by the malic acid-aided method with an Fe/P molar ratio of 1/1 exhibited the highest activity for the selective formation of HCHO among the catalysts tested, including FePO4 synthesized by a conventional method. Despite the much higher oxidizing ability of Fe2O3 than FePO4, the oxidation of CH4 using Fe2O3 resulted in the formation of only CO2. In contrast, the temperature-programmed reaction of FePO4 with CH4 gave Fe2P2O7 with the formation of HCHO as a primary product, and Fe2P2O7 reacted with O2 to regenerate FePO4. Based on mechanistic studies including the catalyst effect, kinetics, pulse-reaction experiments, and IR spectroscopy, the bulk structural change between FePO4 and Fe2P2O7 is not involved during the catalysis and the surface redox and acid-base properties of FePO4 are considered to play an important role in CH4 oxidation with the structure preservation of bulk FePO4. The combination of redox-active Lewis acidic iron sites and weakly-basic phosphate units likely contributes to the C-H activation of CH4 and the suppression of complete oxidation to CO2, respectively.
- Hara, Michikazu,Kamata, Keigo,Matsuda, Aoi,Tateno, Haruka
-
p. 6987 - 6998
(2021/11/13)
-
- Fundamental insight into electrochemical oxidation of methane towards methanol on transition metal oxides
-
Electrochemical oxidation of CH4 is known to be inefficient in aqueous electrolytes. The lower activity of methane oxidation reaction (MOR) is primarily attributed to the dominant oxygen evolution reaction (OER) and the higher barrier for CH4 activation on transition metal oxides (TMOs). However, a satisfactory explanation for the origins of such lower activity of MOR on TMOs, along with the enabling strategies to partially oxidize CH4 to CH3OH, have not been developed yet. We report here the activation of CH4 is governed by a previously unrecognized consequence of electrostatic (or Madelung) potential of metal atom in TMOs. The measured binding energies of CH4 on 12 different TMOs scale linearly with the Madelung potentials of the metal in the TMOs. The MOR active TMOs are the ones with higher CH4 binding energy and lower Madelung potential. Out of 12 TMOs studied here, only TiO2, IrO2, PbO2, and PtO2 are active for MOR, where the stable active site is the O on top of the metal in TMOs. The reaction pathway for MOR proceeds primarily through *CHx intermediates at lower potentials and through *CH3OH intermediates at higher potentials. The key MOR intermediate *CH3OH is identified on TiO2 under operando conditions at higher potential using transient open-circuit potential measurement. To minimize the overoxidation of *CH3OH, a bimetallic Cu2O3 on TiO2 catalysts is developed, in which Cu reduces the barrier for the reaction of *CH3 and *OH and facilitates the desorption of *CH3OH. The highest faradaic efficiency of 6% is obtained using Cu-Ti bimetallic TMO.
- Prajapati, Aditya,Collins, Brianna A.,Goodpaster, Jason D.,Singh, Meenesh R.
-
-
- Enhancement and limits of the selective oxidation of methane to formaldehyde over V-SBA-15: Influence of water cofeed and product decomposition
-
The possibility of a selective catalytic oxidation of methane to formaldehyde has been known for decades, and positive influences of water added to the reaction mixture and ultra-short contact times have been reported. In the present work, the complexity of interdependencies has been revealed. Specific parameter variations can increase conversion and selectivity of the target product. Surprisingly, formaldehyde formation over VOx species and its decomposition in gas phase were equally dependent on the partial pressure of the added water, so that the sweet spot can only be found by varying the residence time.
- Kunkel, Benny,Wohlrab, Sebastian
-
-
- Microwave-assisted hydrothermal synthesis, characterization and catalytic performance of Fe2(MoO4)3 in the selective oxidation of propene
-
A method for the simple and efficient microwave radiation-assisted hydrothermal synthesis of Fe2(MoO4)3 has been developed. Several factors such as pH, addition rate, molybdenum precursor, type of solvent and various other microwave synthesis parameters are studied. The catalysts were characterized using X-ray diffraction, scanning electron microscopy, M?ssbauer spectroscopy and specific surface area measurements. The results show that different morphologies can be obtained, depending on the conditions under which the iron molybdate is prepared. Nevertheless, in all cases the solid particles appear to be covered by an amorphous oxide layer, which is less rich in iron than in the case of a crystallized oxide layer. The presence of this amorphous layer was revealed on all facets of the molybdate, with approximately the same composition and thickness. In an effort to evaluate the relationship between the morphology of iron molybdate particles and their catalytic properties, several samples exhibiting different morphology were tested for the oxidation of propene to acrolein. These samples were tested for the oxidation of propene to acrolein. The catalysts with platelets morphology and exhibiting larger surface of (100) planes appeared more active. This was attributed to a faster re-oxidation due to the preferential diffusion of oxygen anions in the bulk structure channels perpendicular to these planes.
- Hidalgo,Tonelli,Burel,Aouine,Millet
-
-
- Unveiling the importance of reactant mass transfer in environmental catalysis: Taking catalytic chlorobenzene oxidation as an example
-
To date, investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis. Herein, we demonstrated that by rationally designing the adsorption sites of multi-reactants, the pollutant destruction efficiency, product selectivity, reaction stability and secondary pollution have been all affected in the catalytic chlorobenzene oxidation (CBCO). Experimental results revealed that the co-adsorption of chlorobenzene (CB) and gaseous O2 at the oxygen vacancies of CeO2 led to remarkably high CO2 generation, owning to their short mass transfer distance on the catalyst surface, while their separated adsorptions at Br?nsted HZSM-5 and CeO2 vacancies resulted in a much lower CO2 generation, and produced significant polychlorinated byproducts in the off-gas. However, this separated adsorption model yielded superior long-term stability for the CeO2/HZSM-5 catalyst, owning to the protection of CeO2 oxygen vacancies from Cl poisoning by the preferential adsorption of CB on the Br?nsted acidic sites. This work unveils that design of environmental catalysts needs to consider both of the catalyst intrinsic property and reactant mass transfer; investigations of the latter could pave a new way for the development of highly efficient catalysts towards environmental pollution control.
- Cao, Kexin,Dai, Xiaoxia,Wu, Zhongbiao,Weng, Xiaole
-
supporting information
p. 1206 - 1209
(2020/10/19)
-
- Nb?V Mixed Oxide with a Random Assembly of Pentagonal Units: A Catalyst for Oxidative Dehydrogenation of Ethane and Propane
-
High-dimensionally structured (HDS) mixed oxides of vanadium with metals (M) (e. g., Nb, Mo, and W; denoted as HDS-MVO) were constructed by {M6O21}12? pentagonal units and {MO6} (M=Nb, Mo, W, or V) octahedra as linkers. The materials were synthesized using a hydrothermal method and rod-shaped solids. The random assembly of the pentagonal units and octahedra in the cross-sectional plane of the rods facilitated the formation of micropore channels along the long axis of the rods. Micropore formation was directly observed in the cross-section by HAADF-STEM. These structural features are common to HDS-NbVO, HDS-MoVO, and HDS-WVO. The catalytic activity of these three HDS-MVOs with V/Mo ratios in the range 0.35–0.39 was tested for the oxidative dehydrogenation of ethane and propane. The reaction rates per surface area for ethane oxidation and propane oxidation over the HDS-MoVO and HDS-WVO catalysts were comparable, whereas the HDS-NbVO catalyst showed an appreciable difference between the two reaction rates. Both HDS-MoVO and HDS-WVO exhibited higher selectivity for olefin formation during ethane oxidation than propane oxidation. Interestingly, the olefin selectivity over the HDS-NbVO catalyst was found to be almost independent of the alkane substrate. These catalytic features were discussed on the basis of V?O?V or V?O?Mo redox coupling and pore structure effects in HDS-MoVO and HDS-WVO and also of isolated and valence stable surface V in HDS-NbVO.
- Shimoda, Kosuke,Ishikawa, Satoshi,Matsumoto, Katsuya,Miyasawa, Mai,Takebe, Marino,Matsumoto, Riku,Lee, Syutoku,Ueda, Wataru
-
p. 3132 - 3139
(2021/05/29)
-
- Quantification of Redox Sites during Catalytic Propane Oxychlorination by Operando EPR Spectroscopy
-
Identification and quantification of redox-active centers at relevant conditions for catalysis is pivotal to understand reaction mechanisms and requires development of advanced operando methods. Herein, we demonstrate operando EPR spectroscopy as an important technique to quantify the oxidation state of representative CrPO4 and EuOCl catalysts during propane oxychlorination, an attractive route for propylene production. In particular, we show that the space-time-yield of C3H6 correlates with the amount of Cr2+ and Eu2+ ions generated over the catalysts during reaction. These results provide a powerful strategy to gather quantitative understanding of selective alkane oxidation, which could potentially be extrapolated to other functionalization approaches and operating conditions.
- Zichittella, Guido,Polyhach, Yevhen,Tschaggelar, René,Jeschke, Gunnar,Pérez-Ramírez, Javier
-
p. 3596 - 3602
(2020/12/17)
-
- Understanding the origin of selective oxidative dehydrogenation of propane on boron-based catalysts
-
Boron-based catalysts have been reported to exhibit high selectivity to olefins in oxidative dehydrogenation of propane (ODHP). However, the origin of their superior ODHP selectivity to conventional vanadium-based catalysts is still under debate. In this work, we proposed that oxidized boron species is the active site for highly selective olefin formation in ODHP on boron-based catalysts. Combined isotopic and kinetic experiments suggested that O2 weakly bonds to the electron-deficient B center to form non-dissociative >B–O-O–BB–O-O–B sites. These findings offer in-depth knowledge of ODHP on boron-based catalysts.
- Li, Jiwei,Lin, Jingdong,Qian, Shuya,Tian, Jinshu,Wan, Shaolong,Wang, Shuai,Wang, Yong,Zhang, Zhaoxia
-
-
- Electro- and Photochemical Reduction of CO2 by Molecular Manganese Catalysts: Exploring the Positional Effect of Second-Sphere Hydrogen-Bond Donors
-
A series of molecular Mn catalysts featuring aniline groups in the second-coordination sphere has been developed for electrochemical and photochemical CO2 reduction. The arylamine moieties were installed at the 6 position of 2,2’-bipyridine (bpy) to generate a family of isomers in which the primary amine is located at the ortho- (1-Mn), meta- (2-Mn), or para-site (3-Mn) of the aniline ring. The proximity of the second-sphere functionality to the active site is a critical factor in determining catalytic performance. Catalyst 1-Mn, possessing the shortest distance between the amine and the active site, significantly outperformed the rest of the series and exhibited a 9-fold improvement in turnover frequency relative to parent catalyst Mn(bpy)(CO)3Br (901 vs. 102 s?1, respectively) at 150 mV lower overpotential. The electrocatalysts operated with high faradaic efficiencies (≥70 %) for CO evolution using trifluoroethanol as a proton source. Notably, under photocatalytic conditions, a concentration-dependent shift in product selectivity from CO (at high [catalyst]) to HCO2H (at low [catalyst]) was observed with turnover numbers up to 4760 for formic acid and high selectivities for reduced carbon products.
- Roy, Sayontani Sinha,Talukdar, Kallol,Jurss, Jonah W.
-
p. 662 - 670
(2020/11/30)
-
- Investigation of Cyclam Based Re-Complexes as Potential Electrocatalysts for the CO2 Reduction Reaction
-
Among the various homogenous electrocatalysts, especially Re(bpy)(CO)3Cl and [Ni(cyclam)]2+ were shown to be highly efficient for the selective conversion of CO2 to CO at moderate potentials. However, a purposeful combination of a ReI tricarbonyl unit with a cyclam ligand hitherto received no attention. Herein, we report on a series of cyclam based Re complexes comprising the original {N4} as well as heteroatom-altered ligand frameworks, describe their synthesis, reveal their coordination behavior and furthermore investigate their performance towards the electrochemical CO2 reduction.
- Gerschel, Philipp,Cordes, Anna L.,Bimmermann, Sarah,Siegmund, Daniel,Metzler-Nolte, Nils,Apfel, Ulf-Peter
-
p. 968 - 977
(2021/04/09)
-
- Engineering Bismuth–Tin Interface in Bimetallic Aerogel with a 3D Porous Structure for Highly Selective Electrocatalytic CO2 Reduction to HCOOH
-
Electrochemical reduction of CO2 (CO2RR) into valuable hydrocarbons is appealing in alleviating the excessive CO2 level. We present the very first utilization of metallic bismuth–tin (Bi-Sn) aerogel for CO2RR with selective HCOOH production. A non-precious bimetallic aerogel of Bi-Sn is readily prepared at ambient temperature, which exhibits 3D morphology with interconnected channels, abundant interfaces and a hydrophilic surface. Superior to Bi and Sn, the Bi-Sn aerogel exposes more active sites and it has favorable mass transfer properties, which endow it with a high FEHCOOH of 93.9 %. Moreover, the Bi-Sn aerogel achieves a FEHCOOH of ca. 90 % that was maintained for 10 h in a flow battery. In situ ATR-FTIR measurements confirmed that the formation of *HCOO is the rate-determining step toward formic acid generation. DFT demonstrated the coexistence of Bi and Sn optimized the energy barrier for the production of HCOOH, thereby improving the catalytic activity.
- Wu, Zexing,Wu, Hengbo,Cai, Weiquan,Wen, Zhenhai,Jia, Baohua,Wang, Lei,Jin, Wei,Ma, Tianyi
-
supporting information
p. 12554 - 12559
(2021/04/30)
-
- Transition-Metal-Modified Vanadoborate Clusters as Stable and Efficient Photocatalysts for CO2Reduction
-
Photocatalytic carbon dioxide reduction (CO2RR) is considered to be a promising sustainable and clean approach to solve environmental issues. Polyoxometalates (POMs), with advantages in fast, reversible, and stepwise multiple-electron transfer without changing their structures, have been promising catalysts in various redox reactions. However, their performance is often restricted by poor thermal or chemical stability. In this work, two transition-metal-modified vanadoborate clusters, [Co(en)2]6[V12B18O54(OH)6]·17H2O (V12B18-Co) and [Ni(en)2]6[V12B18O54(OH)6]·17H2O (V12B18-Ni), are reported for photocatalytic CO2 reduction. V12B18-Co and V12B18-Ni can preserve their structures to 200 and 250 °C, respectively, and remain stable in polar organic solvents and a wide range of pH solutions. Under visible-light irradiation, CO2 can be converted into syngas and HCOO- with V12B18-Co or V12B18-Ni as catalysts. The total amount of gaseous products and liquid products for V12B18-Co is up to 9.5 and 0.168 mmol g-1 h-1. Comparing with V12B18-Co, the yield of CO for V12B18-Ni declines by 1.8-fold, while that of HCOO- increases by 35%. The AQY of V12B18-Co and V12B18-Ni is 1.1% and 0.93%, respectively. These values are higher than most of the reported POM materials under similar conditions. The density functional theory (DFT) calculations illuminate the active site of CO2RR and the reduction mechanism. This work provides new insights into the design of stable, high-performance, and low-cost photocatalysts for CO2 reduction.
- Yu, Xiang,Zhao, Cong-Cong,Gu, Jian-Xia,Sun, Chun-Yi,Zheng, Hai-Yan,Yan, Li-Kai,Sun, Min,Wang, Xin-Long,Su, Zhong-Min
-
supporting information
p. 7364 - 7371
(2021/05/31)
-
- Enhanced Ethylene Formation from Carbon Dioxide Reduction through Sequential Catalysis on Au Decorated Cubic Cu2O Electrocatalyst
-
Electrochemical reduction of carbon dioxide to fuels has been recognized as a perspective way to address the environmental and energy issues. Herein, the novel Au decorated Cu2O electrocatalysts were synthesized via the galvanic replacement reaction and the successive pre-reduction by linear voltammetry (LSV) method. In contrast to Cu2O, CO formation became dominant over HCOOH and H2 on AuxCu2O, and a remarkably enhanced selectivity of C2H4 was obtained beyond ?1.1 V vs. RHE. Among them, Au0.02Cu2O exhibited the highest Faraday efficiency (FE) of C2H4 of 24.4 % at ?1.3 V vs. RHE, which was as high as 2~2.5 and 5 times of those on other two AuxCu2O and bare Cu2O, respectively. Meanwhile, it is demonstrated that the optimal ratio of Au/Cu was essential for effective sequential catalysis between Au and Cu2O to enhance C?C coupling. Furthermore, the effect of copper states resulting from different pre-reduction methods on the selectivity of C2H4 was explored. A half decrease of C2H4 FE was observed on HPR-Au0.02Cu2O (high potential reduced) relative to the LSV reduced Au0.02Cu2O, which was ascribed to the different content of Cu0 and residual Cu+ in two catalysts. Our results demonstrate an effective approach to construct Cu2O based bimetallic catalysts for ethylene formation from CO2.
- Cao, Xuerui,Cao, Guangwei,Li, Mei,Zhu, Xinli,Han, Jinyu,Ge, Qingfeng,Wang, Hua
-
p. 2353 - 2364
(2021/06/17)
-
- Machine-Learning-Guided Discovery and Optimization of Additives in Preparing Cu Catalysts for CO2Reduction
-
Discovery and optimization of new catalysts can be potentially accelerated by efficient data analysis using machine-learning (ML). In this paper, we record the process of searching for additives in the electrochemical deposition of Cu catalysts for CO2 reduction (CO2RR) using ML, which includes three iterative cycles: "experimental test; ML analysis; prediction and redesign". Cu catalysts are known for CO2RR to obtain a range of products including C1 (CO, HCOOH, CH4, CH3OH) and C2+ (C2H4, C2H6, C2H5OH, C3H7OH). Subtle changes in morphology and surface structure of the catalysts caused by additives in catalyst preparation can lead to dramatic shifts in CO2RR selectivity. After several ML cycles, we obtained catalysts selective for CO, HCOOH, and C2+ products. This catalyst discovery process highlights the potential of ML to accelerate material development by efficiently extracting information from a limited number of experimental data.
- Guo, Ying,He, Xinru,Su, Yuming,Dai, Yiheng,Xie, Mingcan,Yang, Shuangli,Chen, Jiawei,Wang, Kun,Zhou, Da,Wang, Cheng
-
supporting information
p. 5755 - 5762
(2021/05/07)
-
- (1,2-Azole)bis(bipyridyl)ruthenium(II) Complexes: Electrochemistry, Luminescent Properties, and Electro- And Photocatalysts for CO2Reduction
-
New cis-(1,2-azole)-aquo bis(2,2′-bipyridyl)ruthenium(II) (1,2-azole (az*H) = pzH (pyrazole), dmpzH (3,5-dimethylpyrazole), and indzH (indazole)) complexes are synthesized via chlorido abstraction from cis-[Ru(bipy)2Cl(az*H)]OTf. The latter are obtained from cis-[Ru(bipy)2Cl2] after the subsequent coordination of the 1,2-azole. All the compounds are characterized by 1H, 13C, 15N NMR spectroscopy as well as IR spectroscopy. Two chlorido complexes (pzH and indzH) and two aquo complexes (indzH and dmpzH) are also characterized by X-ray diffraction. Photophysical and electrochemical studies were carried out on all the complexes. The photophysical data support the phosphorescence of the complexes. The electrochemical behavior of all the complexes in an Ar atmosphere indicate that the oxidation processes assigned to Ru(II) → Ru(III) occurs at higher potentials in the aquo complexes. The reduction processes under Ar lead to several waves, indicating that the complexes undergo successive electron-transfer reductions that are centered in the bipy ligands. The first electron reduction is reversible. The electrochemical behavior in CO2 media is consistent with CO2 electrocatalyzed reduction, where the values of the catalytic activity [icat(CO2)/ip(Ar)] ranged from 2.9 to 10.8. Controlled potential electrolysis of the chlorido and aquo complexes affords CO and formic acid, with the latter as the major product after 2 h. Photocatalytic experiments in MeCN with [Ru(bipy)3]Cl2 as the photosensitizer and TEOA as the electron donor, which were irradiated with >300 nm light for 24 h, led to CO and HCOOH as the main reduction products, achieving a combined turnover number (TONCO+HCOO-) as high as 107 for 2c after 24 h of irradiation.
- Angeles-Boza, Alfredo M.,Cuéllar, Elena,Diez-Varga, Alberto,García-Herbosa, Gabriel,Martín-Alvarez, Jose M.,Miguel, Daniel,Nganga, John,Pastor, Laura,Torroba, Tomás,Villafa?e, Fernando
-
p. 692 - 704
(2021/01/13)
-
- Defect evolution of hierarchical SnO2aggregates for boosting CO2electrocatalytic reduction
-
To efficiently convert CO2into high-value added productsviathe electrocatalytic reduction, the rational regulation of surface defects (e.g., oxygen vacancies) and the interfacial structure of electrocatalysts are crucial but still challenging. Herein, a feasible strategy is presented to manipulate oxygen vacancies and interfacial boundaries on hierarchical tin oxide aggregatesviaa thermal reduction process. The optimized Sn/SnO2-2h electrocatalyst exhibited the maximum faradaic efficiencies (FEs) of 92.5 and 96.4% for C1 products (FEC1) in the H-type cell and the flow cell, respectively. Online differential electrochemical mass spectrometry confirmed the lower onset potential for the electrocatalytic CO2reduction reaction (ECRR) in comparison with the pristine SnO2. With the defect evolution from oxygen vacancies (Ovacs), the formation of Sn/SnO2with favorable interfacial features is crucial to achieve an enhanced performance. More importantly, thein situcharacterization studies and density functional theory (DFT) calculations revealed that the synergistic effect of both residual Ovacsand the interfacial structure is responsible for the energy favorable reduction of carbon dioxideviaproton-coupled electron transfer, thus improving the selectivity for formate generation. This facile strategy for modulating surface defects provides an ideal approach to guide the future designs of ECRR catalysts.
- Cao, Xueying,Tan, Dongxing,Wulan, Bari,Zhang, Baohua,Zhang, Jintao
-
supporting information
p. 14741 - 14751
(2021/07/12)
-
- Binuclear rhenium complex taking dipyridyl xanthene as ligand as well as synthesis method and application of binuclear rhenium complex
-
The invention discloses a binuclear rhenium complex taking dipyridyl xanthene as a ligand as well as a synthesis method and application of the binuclear rhenium complex. The invention aims to provide a catalyst which has good catalytic activity on photocatalytic carbon dioxide reduction under the conditions of normal temperature and normal pressure in an air atmosphere. According to the technical scheme, the preparation method comprises the following steps: putting a 4-bibpy ligand and a pentacarbonyl chloride rhenium solid in a Schracker bottle according to a substance amount ratio of 1: 1.5-2.5, vacuumizing and filling argon for three times; bubbling by using an inert gas for 15-25 minutes, injecting into a bottle, sealing, stirring and heating to 70-90 DEG C under the inert gas component, carrying out condensation reflux reaction for 10-16 hours, and washing the obtained yellow precipitate solid by using a detergent for multiple times; and carrying out alumina column chromatography purification analysis to obtain a trans product of the binuclear rhenium complex trans-bibpyRe2 (CO) 6Cl2 and a cis product of the binuclear rhenium complex cis-bibpyRe2 (CO) 6Cl2. The method belongs to the technical field of catalysts.
- -
-
Paragraph 0038-0039; 0043-0044; 0048-0049
(2021/07/21)
-
- Selectivity Switching of CO2Hydrogenation from HCOOH to CO with an in Situ Formed Ru-Li Complex
-
Herein, we report the role of alkali halide salt in regulating the pathway of CO2 hydrogenation in the presence of Shvo's complex. Particularly, the collaboration of Shvo's complex with LiCl exhibited as a highly efficient catalyst for CO2 hydrogenation to CO instead of the kinetically favorable product HCOOH under mild conditions. The reaction can be initiated at 45 °C with CO as the dominant product, and the rate of CO formation was almost 80 times to that in the absence of LiCl at 60 °C. Under optimized conditions, the TONCO could reach 1555 at 160 °C, much higher than the reported results of the most efficient Ru-based homogeneous catalyst. Density functional theory calculations demonstrated that the cooperation of the alkali cation and chloride anion contributed to reducing the energy barrier of CO2 activation to form the key Ru-CO2H intermediate. An in situ formed mixed Ru-Li complex (5) has been characterized by X-ray crystallography, highlighting the indispensability of electrostatic interactions between LiCl and Shvo's complex for enhanced reactivity and altered selectivity.
- Chen, Qiongyao,Shen, Chaoren,Zhu, Gangli,Zhang, Xuehua,Lv, Chun-Lin,Zeng, Bo,Wang, Sen,Li, Junfen,Fan, Weibin,He, Lin
-
p. 9390 - 9396
(2021/07/31)
-
- Homogeneous electrocatalytic CO2 reduction by hexacarbonyl diiron dithiolate complex bearing hydroquinone
-
Recently, the hexacarbonyl diiron dithiolate complex ((bdt)Fe2(CO)6, bdt = benzene-1,2-dithiolate) was reported for electrochemical CO2 reduction in CH3OH/CH3CN solution. To further simulate the [NiFe] carbon monoxide dehydrogenase (CODH) active center, another diiron dithiolate complex (1) with phenolic hydroxyl as second coordination sphere group was introduced to catalyze CO2 reduction electrochemically. Cyclic voltammetry measurements revealed that the phenolic hydroxyl group of 1 could lower the onset potential of electrochemical CO2 reduction. Under the best conditions, the maximum turnover frequency (TOFmax) of about 35 s?1 and an almost equal amount of HCOOH, CO, and H2 were obtained. Fourier transform infrared reflectance spectroelectrochemistry (IR-SEC) experiments illuminated the intermediate with terminal coordinated –COOH and the changes of intermolecular hydrogen bonds during the catalytic cycle.
- Cheng, Minglun,Fan, Fenglan,Liu, Jinyu,Wang, Lingjuan
-
-
- CO2 hydrogenation to methanol over Rh/In2O3 catalyst
-
CO2 hydrogenation to methanol is of great significance for the emission control and utilization of CO2. In this work, the Rh/In2O3 catalyst with high Rh dispersion was prepared by deposition-precipitation method. The catalyst characterization demonstrates that the highly dispersed Rh species promotes the dissociative adsorption and spillover of hydrogen, which further enhances not only the formation of surface oxygen vacancy of In2O3 but also CO2 adsorption and activation. Enhanced activity was thereby achieved for selective hydrogenation of CO2 to methanol. A CO2 conversion of 17.1 % with methanol selectivity of 56.1 %, corresponding to a methanol space time yield (STY) up to 0.5448 gMeOH h?1 gcat?1, has been obtained under 300 °C, 5 MPa, 76/19/5 of H2/CO2/N2 (molar ratio) and 21,000 cm3 h?1 g?1 of gas hourly space velocity. Under the same reaction condition, the CO2 conversion is only 9.4 % with a methanol STY of 0.3402 gMeOH h?1 gcat?1 over In2O3. The methanol selectivity can be even higher than 70 % at the reaction temperatures below 275 °C for Rh/In2O3 catalyst.
- Wang, Jing,Sun, Kaihang,Jia, Xinyu,Liu, Chang-jun
-
p. 341 - 347
(2020/05/18)
-
- Design of highly stable MgO promoted Cu/ZnO catalyst for clean methanol production through selective hydrogenation of CO2
-
The synergistic interaction between small Cu particles and MgO/ZnO-supported catalysts, synthesized by the hydrothermal method, show a very high methanol production rate (0.0063 mol gCu?1 h?1). High Cu dispersion and large Cu surface area in the hydrothermal synthesized Cu/MgO/ZnO catalyst postulated to be the reason for high activity. The formation of defected ZnO crystals with Mg atoms provided a better adsorption site for CO2 (near Mg atom), whereas Cu-ZnO interface sites are responsible for the activation of CO2. 20 wt% loaded MgO catalyst showed preference to selective CO2 hydrogenation pathway producing clean methanol with > 99 % selectivity. In addition, Density Functional Theory (DFT) studies revealed that the basic nature of the MgO support can be the probable reason for the higher CO2 adsorption at the Cu-MgO interface compared to the Cu-ZnO interface. Cu13/MgO/ZnO (100) surface model is studied to understand the promoting effect of MgO on CO2 adsorption.
- Bal, Rajaram,Bordoloi, Ankur,Gupta, Shelaka,Khan, Tuhin Suvra,Paul, Bappi,Poddar, Mukesh Kumar,Samanta, Chanchal,Sasaki, Takehiko,Sharma, Sachin Kumar,Singha, Rajib Kumar
-
-
- Understanding the Origin of Structure Sensitivity in Nano Crystalline Mixed Cu/Mg?Al Oxides Catalyst for Low-Pressure Methanol Synthesis
-
Cu nanoparticles of size 5–10 nm supported on Mg?Al mixed oxide were prepared by the sol-gel method. Cu loading was varied from 2.5 to 10 wt % on the support to investigate the effect on particle size and activity/selectivity of the catalyst. The Cu/Mg?Al catalysts containing small copper nanoparticles favor high selectivity of methanol, while the rate of CO formation was higher for larger copper particles. The high methanol selectivity (~99 %) and methanol formation rate (0.016 mol gCu?1 h?1) over the 4.8Cu/Mg?Al catalyst was due to the combined effect of the presence of high Cu dispersion, Cu surface area, and strong interaction between small Cu particles with Mg?Al support. The high stability of the catalyst was attributed to the strong binding of the Cu cluster (?179.7 kJ/mol) to the MgO/γ-Al2O3 support, as shown by the DFT study. Additionally, the adsorption energy calculated using DFT showed preferential adsorption of CO2 and H2 at the Cu/MgO(100) active site (?120.9 kJ/mol, ?130.4 kJ/mol) compared to the Cu/γ-Al2O3(100) (?64.2 kJ/mol, ?85.7 kJ/mol)active site. The high selectivity of the catalyst towards methanol can be attributed to the higher stability of the formate (HCOO) intermediate (?257.2 kJ/mol) compared to the carboxylate (COOH) intermediate (?131.0 kJ/mol).
- Sharma, Sachin Kumar,Paul, Bappi,Bhanja, Piyali,Poddar, Mukesh Kumar,Samanta, Chanchal,Khan, Tuhin Suvra,Haider, M. Ali,Bal, Rajaram
-
p. 3290 - 3302
(2021/06/14)
-
- Promotion effect of iron addition on the structure and CO2 hydrogenation performance of Attapulgite/Ce0.75Zr0.25O2 nanocomposite supported Cu-ZnO based catalyst
-
A series of CZFxK/ATP-CZO catalysts (x= 0, 0.3, 0.5, 1.0, 1.5 and 2.0) are applied to clarify the effects of the iron addition on the catalytic performance of CO2 hydrogenation to CH3OH. The physicochemical properties and catalytic mechanism were investigated by N2 adsorption/desorption, XRD, TEM, N2O chemisorption, XPS, H2-TPR, CO2-TPD and in-situ DRIFT techniques. The best catalytic performance is achieved over CZF0.5K/ATP-CZO catalyst, exhibiting XCO2 = 17.5%, STYCH3OH = 0.108 g/gcat.?h and STYCO = 0.146 g/gcat.?h (T = 320°C, P = 6 MPa). The formation of dispersed surface metallic Cu species and larger number of surface adsorbed and lattcie oxygen species and ZnO-CZO interfaces are detected over CZF0.5K/ATP-CZO due to stronger interaction between dispersed metallic Cu particles on ZnO-Fe nano-cluster and ATP-CZO composite, resulting in the superior activation ability for H2 and CO2 respectively. Additionally, the evidence is provided by in-situ DRIFTS under the activity test temperature (320°C) that HCOO? and CO* species are preferable for accumulating over CZK/ATP-CZO catalyst without Fe addition while medium Fe-modified CZFxK/ATP-CZO catalysts (CZF0.3K/ATP-CZO, CZF0.5K/ATP-CZO) catalysts are benefitial to promote the transformation of HCOO? species to CH3OH. These excessive Fe-modified CZFxK/ATP-CZO catalysts (CZF1.0K/ATP-CZO, CZF2.0K/ATP-CZO) are more easily to produce CH4 via formate pathway (CO2* → HCOO* → HCO* → CH* → CH4*). The abundant population and high transformation activity of formate intermediate species over CZF0.5K/ATP-CZO give a strong positive effect on the CO2 hydrogenation to methanol performance.
- Chen, Xinde,Ding, Shuai,Guo, Haijun,Peng, Fen,Wang, Can,Xiong, Lian,Yao, Shimiao,Zhang, Hairong
-
-
- Engineering the Cu/Mo2CTx (MXene) interface to drive CO2 hydrogenation to methanol
-
Development of efficient catalysts for the direct hydrogenation of CO2 to methanol is essential for the valorization of this abundant feedstock. Here we show that a silica-supported Cu/Mo2CTx (MXene) catalyst achieves a higher intrinsic methanol formation rate per mass Cu than the reference Cu/SiO2 catalyst with a similar Cu loading. The Cu/Mo2CTx interface can be engineered due to the higher affinity of Cu for the partially reduced MXene surface (in preference to the SiO2 surface) and the mobility of Cu under H2 at 500 °C. With increasing reduction time, the Cu/Mo2CTx interface becomes more Lewis acidic due to the higher amount of Cu+ sites dispersed onto the reduced Mo2CTx and this correlates with an increased rate of CO2 hydrogenation to methanol. The critical role of the interface between Cu and Mo2CTx is further highlighted by density functional theory calculations that identify formate and methoxy species as stable reaction intermediates. [Figure not available: see fulltext.]
- Abdala, Paula M.,Chen, Zixuan,Comas-Vives, Aleix,Copéret, Christophe,Donat, Felix,Fedorov, Alexey,Kierzkowska, Agnieszka,Kuznetsov, Denis A.,López, Anna Vidal,López, Estefanía Díaz,Lam, Erwin,Müller, Christoph R.,Mance, Deni,Tsoukalou, Athanasia,Willinger, Elena,Zhou, Hui
-
p. 860 - 871
(2021/10/27)
-
- Visualizing Element Migration over Bifunctional Metal-Zeolite Catalysts and its Impact on Catalysis
-
The catalytic performance of composite catalysts is not only affected by the physicochemical properties of each component, but also the proximity and interaction between them. Herein, we employ four representative oxides (In2O3, ZnO, Cr2O3, and ZrO2) to combine with H-ZSM-5 for the hydrogenation of CO2 to hydrocarbons directed by methanol intermediate and clarify the correlation between metal migration and the catalytic performance. The migration of metals to zeolite driven by the harsh reaction conditions can be visualized by electron microscopy, meanwhile, the change of zeolite acidity is also carefully characterized. The protonic sites of H-ZSM-5 are neutralized by mobile indium and zinc species via a solid ion-exchange mechanism, resulting in a drastic decrease of C2+ hydrocarbon products over In2O3/H-ZSM-5 and ZnO/H-ZSM-5. While, the thermomigration ability of chromium and zirconium species is not significant, endowing Cr2O3/H-ZSM-5 and ZrO2/H-ZSM-5 catalysts with high selectivity of C2+ hydrocarbons.
- Cheng, Kang,Wang, Genyuan,Wang, Ye,Wang, Yuhao,Zhang, Qinghong,de Jong, Krijn P.,van der Wal, Lars I.
-
supporting information
p. 17735 - 17743
(2021/07/02)
-
- In situ Irradiated XPS Investigation on S-Scheme TiO2@ZnIn2S4 Photocatalyst for Efficient Photocatalytic CO2 Reduction
-
Reasonable design of efficient hierarchical photocatalysts has gained significant attention. Herein, a step-scheme (S-scheme) core-shell TiO2@ZnIn2S4 heterojunction is designed for photocatalytic CO2 reduction. The optimized sample exhibits much higher CO2 photoreduction conversion rates (the sum yield of CO, CH3OH, and CH4) than the blank control, i.e., ZnIn2S4 and TiO2. The improved photocatalytic performance can be attributed to the inhibited recombination of photogenerated charge carriers induced by S-scheme heterojunction. The improvement is also attributed to the large specific surface areas and abundant active sites. Meanwhile, S-scheme photogenerated charge transfer mechanism is testified by in situ irradiated X-ray photoelectron spectroscopy, work function calculation, and electron paramagnetic resonance measurements. This work provides an effective strategy for designing highly efficient heterojunction photocatalysts for conversion of solar fuels.
- Wang, Libo,Cheng, Bei,Zhang, Liuyang,Yu, Jiaguo
-
-
- Mo–V–O nanocrystals synthesized in the confined space of a mesoporous carbon
-
Ternary Mo–V oxide nanocrystals (Nano-MoVO) were hydrothermally synthesized in the confined space of a mesoporous carbon template and tested in the oxidative dehydrogenation (ODH) of ethane and propane. The synthesized nanocrystals are approximately 60 nm in length, 20 nm in diameter on average, and possess a structure resembling orthorhombic MoVO (Orth-MoVO) as indicated by spectroscopic and microscopy characterization. The Nano-MoVO catalyst has a 5-fold higher mesopore volume and a 4-fold larger external surface area than an Orth-MoVO synthesized by a conventional method (Orth-MoVO) as characterized through N2 adsorption analysis. Nano-MoVO shows similar activation energy in the ODH of ethane compared with other conventional MoVO catalysts. However, Nano-MoVO exhibits significantly higher propane/ethane activation rate ratio and higher propene selectivity even in the absence of elements such as Te and Nb that suppress overoxidation of propane-derived species to COx. The results suggest the benefits of the nanocrystalline morphology to limit overoxidation.
- Mukai, Shin R.,Obunai, Ryo,Ogino, Isao,Tamura, Keisuke,Ueda, Wataru
-
-
- CuAg nanoparticle/carbon aerogel for electrochemical CO2reduction
-
The electrochemical carbon dioxide reduction reaction (eCO2RR) is a promising technology that uses electrical energy to catalytically reduce greenhouse gas-CO2, converting CO2into high value-added products such as hydrocarbons and alcohols. However, due to the complexity of the eCO2RR, the activity and selectivity of the eCO2RR is highly dependent on the intrinsic catalytic activity of a catalyst with mass transportation-favorable morphology. Herein, silk fibroin-derived carbon aerogels (CAs) loaded with small amounts of Cu and Ag nanoparticles were synthesized. Based on the molar content of Cu, the catalysts were labeled SF-CuAg/CA-N(N= 20%, 40%, 60%, 80%). Among them, SF-CuAg/CA-40% showed a good FECOof 71% at ?1.26 Vvs.a reversible hydrogen electrode (RHE), and a significant current density of ?15.77 mA cm?2towards CO at ?1.06 Vvs.RHE, which is close to 2.6, 2.53 and 2.71 times those of SF-CuAg/CA-20% (?6.02 mA cm?2), SF-CuAg/CA-60% (?6.24 mA cm?2) and SF-CuAg/CA-80% (?5.82 mA cm?2). The SF-CuAg/CA-Ncomposite materials prepared in this study provide new ideas for the design of highly efficient electrocatalysts for the eCO2RR.
- Gong, Shanhe,Liu, Bin,Lu, Runqing,Lv, Xiaomeng,Sam, Daniel Kobina,Wang, Wenbo,Xiao, Xinxin
-
p. 18290 - 18295
(2021/10/19)
-
- Steam reforming for syngas production over Ni and Ni-promoted catalysts
-
In this article, nanocrystalline γ-alumina with high surface area (309 m2 g?1) and mesoporous structure with an average pore size of 4.3?nm was synthesized and employed as a carrier for the synthesis of Ni catalysts in steam reformin
- Andache, Mahmood,Rezaei, Mehran,Taherkhani, Zohre
-
p. 3661 - 3672
(2021/06/02)
-
- One-pot synthesis of a highly mesoporous Ni/MgAl2O4spinel catalyst for efficient steam methane reforming: influence of inert annealing
-
A highly mesoporous Ni/MgAl2O4spinel catalyst was facilely synthesized by a scalable one-pot strategy and employed in the steam methane reforming (SMR) reaction. The influence of annealing the catalyst in a N2atmosphere on
- Eissa, Ahmed Al-Shahat,Kim, Hyunjoung,Kim, Seung Bo,Kim, Woohyun,Lee, Hongjin,Lee, Kyubock,Seo, Dong Joo,Yoon, Wang Lai
-
p. 4447 - 4458
(2021/07/12)
-
- Surface Sulfate Ion on CdS Catalyst Enhances Syngas Generation from Biopolyols
-
Photocatalytic biomass conversion represents an ideal way of generating syngas because of the sustainable use of biomass carbon and solar energy. However, the lack of efficient electron-proton transfer limits its efficiency. We here report an unprecedente
- Wang, Feng,Wang, Min,Zhang, Zhe,Zhou, Hongru
-
p. 6533 - 6541
(2021/05/29)
-
- The highly efficient removal of HCN over Cu8Mn2/CeO2catalytic material
-
In this work, porous CeO2flower-like spheres loaded with bimetal oxides were prepared to achieve effective removal of HCN in the lower temperature region of 30-150 °C. Among all samples, the CeO2loaded with copper and manganese oxide
- Yi, Zhihao,Sun, Jie,Li, Jigang,Yang, Yulin,Zhou, Tian,Wei, Shouping,Zhu, Anna
-
p. 8886 - 8896
(2021/03/06)
-
- Selectivity in UV photocatalytic CO2 conversion over bare and silver-decorated niobium-tantalum perovskites
-
The hydrothermal synthesis of the perovskites NaNbO3, NaTaO3 and the intermediate composition NaNb0.5Ta0.5O3, as CO2 conversion photocatalysts is reported. Among them, the niobate shows the most promising performance under UV irradiation not only in terms of conversion and light utilization ability, but also regarding the selectivity towards CO2 reduction against hydrogen evolution from water protons. Further modification of NaNbO3 with silver as co-catalyst results in an increase of the selectivity towards highly reduced products, primarily methanol, against the carbon monoxide production mainly observed with the bare semiconductor. A thorough structural, electronic, electrochemical characterization, together with in-situ surface analysis by APXPS, was undertaken to gain deeper insight into the reasons that account for such changes. On the one hand, for the bare semiconductors, increased light absorption and the sole presence of Nb in +4 state at the surface seem to drive the superior activity of NaNbO3. On the other hand, electronic and surface chemistry modifications induced by 0.1 wt.% silver deposition are proposed to govern the higher selectivity towards methanol. Excessive metal loading, in turn, enhances the selectivity effect but at the expense of conversion, in such a way that light utilization becomes poorer than with the bare niobate.
- Fresno, Fernando,Galdón, Sandra,Barawi, Mariam,Alfonso-González, Elena,Escudero, Carlos,Pérez-Dieste, Virginia,Huck-Iriart, Cristián,de la Pe?a O'Shea, Víctor A.
-
-