- Hybrid carbon@TiO2 hollow spheres with enhanced photocatalytic CO2 reduction activity
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Photocatalytic conversion of carbon dioxide (CO2) into solar fuels is an attractive strategy for solving the increasing energy crisis and greenhouse effect. This work reports the synthesis of hybrid carbon@TiO2 hollow spheres by a facile and green method using a carbon nanosphere template. The carbon content of the carbon@TiO2 composites was adjusted by changing the duration of the final calcination step, and was shown to significantly affect the physicochemical properties and photocatalytic activity of the composites. The optimized carbon@TiO2 composites exhibited enhanced photocatalytic activity for CO2 reduction compared with commercial TiO2 (P25): the photocatalytic CH4 production rate (4.2 μmol g?1 h?1) was twice that of TiO2; moreover, a large amount of CH3OH was produced (at a rate of 9.1 μmol g?1 h?1). The significantly improved photocatalytic activity was not only due to the increased specific surface area (110 m2 g?1) and CO2 uptake (0.64 mmol g?1), but also due to a local photothermal effect around the photocatalyst caused by the carbon. More importantly, UV-vis diffuse reflectance spectra (DRS) showed a remarkable enhancement of light absorption owing to the incorporation of the visible-light-active carbon core with the UV light-responsive TiO2 shell for increased solar energy utilization. Furthermore, electrochemical impedance spectra (EIS) revealed that the carbon content can influence the charge transfer efficiency of the carbon@TiO2 composites. This study can bring new insights into designing carbon@semiconductor nanostructures for applications such as solar energy conversion and storage.
- Wang, Weikang,Xu, Difa,Cheng, Bei,Yu, Jiaguo,Jiang, Chuanjia
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- The solvent-driven formation of multi-morphological Ag-CeO2 plasmonic photocatalysts with enhanced visible-light photocatalytic reduction of CO2
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Ag-CeO2 plasmonic photocatalysts with multiple morphologies were synthesized via a simple solvent-driven method. The phase compositions, morphologies and optical properties of the samples were systematically investigated. A combination of noble metal Ag and semiconductor CeO2 in certain solvents (such as methanol and ethylene glycol) enhanced surface plasmon resonance (SPR), which was attributed to the good dispersion of Ag particles on CeO2 and high Ag0 ratios on the surface. The enhanced SPR effect boosted absorption of incident light and facilitated charge carrier separation and transport efficiency caused by the formation of Schottky barriers, thus promoting VLPCR performance. The optimum ACG sample (ethylene glycol was adopted as the solvent) exhibited the maximum VLPCR activity, achieving a CH4 yield of 100 μmol and a CH3OH yield of 35 μmol per gram of catalyst per hour during 6 h visible-light irradiation.
- Cai, Wei,Shi, Yunpeng,Zhao, Yunxia,Chen, Mindong,Zhong, Qin,Bu, Yunfei
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- Vanadium olefin polymerization catalysts: NMR spectroscopic characterization of V(III) intermediates
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Vanadium(III) species formed upon reacting α-diimine (1) and bis(imino)pyridine (5) vananadium(III) pre-catalysts with MAO, AlMe2Cl, AlMe2Cl/[Ph3C][B(C6F5)4], and AlMe3/[Ph3C][B(C6F5)4] have been characterized in detail by 1H, 2H, and 19F NMR spectroscopy; the VIII-CH3 moiety has been observed by 1H and 2H NMR spectroscopy. For complex 1, zwitterion-like species [L′VIIIR2+···MeMAO?] and ion pairs [L′VIIIR2(THF)2]+[A]- (L′ = 1,4-bis-3,5-dimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene; [A]? = [MeMAO]? or [B(C6F5)4]?) have been identified. The outer-sphere ion pairs of the type [L(Cl)VIII(μ-Cl)2AlMe2]+[A]?, [L(Me)VIII(μ-Cl)2AlMe2]+[A]?, [LVIIICl2(THF)]+[A]? and [LVIII(Cl)Me(THF)]+[A]? (L = 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine; [A]? = [AlMe3Cl]? or [B(C6F5)4]?) have been found in the systems based on the complex 5. The nature of the vanadium species active in ethylene polymerization and the catalyst deactivation pathways are discussed.
- Soshnikov, Igor E.,Semikolenova, Nina V.,Bryliakov, Konstantin P.,Zakharov, Vladimir A.,Talsi, Evgenii P.
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- CO and CO2 methanation over Ni/Al@Al2O3 core–shell catalyst
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Core–shell Al@Al2O3, which was obtained by hydrothermal surface oxidation of Al metal particles, was used as the support in supported Ni catalysts for CO and CO2 methanation. The core–shell micro-structured support (Al@Al2O3) helped develop a highly efficient Ni-based catalyst compared with conventional γ-Al2O3 for these reactions. Moreover, the deposition–precipitation method was shown to outperform the wet impregnation method in the preparation of the active supported Ni catalysts. The catalysts were characterized using various techniques, namely, N2 physisorption, H2 chemisorption, CO2 chemisorption, temperature-programmed reduction with H2, temperature-programmed desorption after CO2 adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, high-resolution transmission electron microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Higher Ni dispersion when using Al@Al2O3 as the support and the deposition–precipitation method resulted in better catalytic performance for CO methanation. Furthermore, the higher density of medium basic sites and enhanced CO2 adsorption capacity observed for Ni/Al@Al2O3 helped increase catalytic activity for CO2 methanation.
- Le, Thien An,Kim, Jieun,Kang, Jong Kyu,Park, Eun Duck
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- Hydrogenolysis and Hydrogenation of Hydrocarbons on Supported Rh-Ir Bimetallic Catalysts
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A study of the characteristics and catalytic behaviour of silica-supported Rh-Ir catalysts has been carried out.Catalysts spanning the spectrum of possible metal compositions were used.Both chemisorption and X.p.s. results suggest a modest Rh enrichment of the surface relative to bulk composition.Hydrogenation activity was characterized by cyclopropane hydrogenation and pure Rh shows activity orders-of-magnitude greater than that of pure Ir.The hydrogenation turnover frequency (normalized by assuming a hydrogen-to-metal surface atom ratio of one) shows a slight maximum on the Rh-rich catalysts which may reflect an electronic effect or be result of selective chemisorption.The hydrogenolysis reactions are most rapid on Rh and the turnover frequencies decrease in a non-linear manner from Rh to Ir.Even though the absolute rates are different, both hydrogenation and hydrogenolyis reactions have reactivity patterns qualitatively similar to the Ni-Cu system.The results for both systems can be interpreted on the basis of different numbers of atoms in the ensembles which constitute the site, larger ensembles being requied for the hydrogenolysis reaction.The relative rate of H-D exchange of methane and the pattern of the rates as a function of catalyst composition indicate that methane desorption is not the rate-limiting step in ethane hydrogenolysis.
- Wong, Teik Chen,Brown, Lee F.,Haller, Gary L.,Kemball, Charles
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- Electrophilic alkylation of an acylmetalate complex at the metal center leading to a stable methylacetylrhenium complex. Photochemical decomposition to give 2,3-butanedione via a mechanism involving carbonylation of free methyl radicals
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Alkylation of the rhenium metalate Li[CpRe-(CO)2(COCH3)] (1) can be controlled to give either the Fischer carbene complex Cp(CO)2Re=C(OCH3)(CH3) or the new alkyl aryl complex Cp(CO)2Re(COCH3)(CH3) (2). Photochemical decomposition of 2 under 20 atm of CO leads to 2,3-butanedione; evidence is presented that the diketone is produced by formation and carbonylation of free methyl radicals.
- Goldberg, Karen I.,Bergman, Robert G.
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- Reactions of NH Radicals. III. Photolysis of HN3 in the Presence of C2H4 at 313 nm
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Photolysis of HN3 vapor in the presence of C2H4 was studied at 313 nm and 30 deg C.The main products were N2, H2, CH4, C2H6, NH4N3, C2H5N * HN3 (salt of C2H5N (azomethines) with HN3), HCN, CH3CN, CH3N3, and C2H5N3.The quantum yields of these products were measured as a function of the light intensity and pressures of HN3 and C2H4.The following mechanism for the main reactions was infered: HN3 + hv(313 nm) -> NH(a1Δ) + N2; NH(a1Δ) + HN3 -> 2N2 + 2H (2a); NH(a1Δ) + HN3 -> NH2 + N3 (2b); NH(a1Δ) + HN3 -> N2 + N2H2* (2c); NH(a1Δ) + C2H4 -> C2H5N* (aziridine and vinylamine) (3); C2H5N* -> CH3 + CH2N (4); C2H5N* -> H2 + CH3CN (5); C2H5N* -> H + C2H4N (6); C2H5N* -> C2H3 + NH2 (7).The rate constant ratios at 30 deg C are: k3/k2 = 1.64; k5/k4 = 0.102; k6/k4 = 0.564; k7/k4 = 0.734.The collisional deactivation from NH(a1Δ) to NH(X3Σ-) by C2H4 was not found.The lifetime of C2H5N* is much shorter than 6.8 * 10-11 s for C2H5NH2*(1Δ) + C2H6)).The relative and absolute rates for the reactions of NH(a1Δ) with HN3, Xe, C2H6, and C2H4 are discussed.
- Kodama, Sukeya
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- Hierarchical Porous O-Doped g-C3N4 with Enhanced Photocatalytic CO2 Reduction Activity
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Artificial photosynthesis of hydrocarbon fuels by utilizing solar energy and CO2 is considered as a potential route for solving ever-increasing energy crisis and greenhouse effect. Herein, hierarchical porous O-doped graphitic carbon nitride (g-C3N4) nanotubes (OCN-Tube) are prepared via successive thermal oxidation exfoliation and curling-condensation of bulk g-C3N4. The as-prepared OCN-Tube exhibits hierarchically porous structures, which consist of interconnected multiwalled nanotubes with uniform diameters of 20–30 nm. The hierarchical OCN-Tube shows excellent photocatalytic CO2 reduction performance under visible light, with methanol evolution rate of 0.88 μmol g?1 h?1, which is five times higher than bulk g-C3N4 (0.17 μmol g?1 h?1). The enhanced photocatalytic activity of OCN-Tube is ascribed to the hierarchical nanotube structure and O-doping effect. The hierarchical nanotube structure endows OCN-Tube with higher specific surface area, greater light utilization efficiency, and improved molecular diffusion kinetics, due to the more exposed active edges and multiple light reflection/scattering channels. The O-doping optimizes the band structure of g-C3N4, resulting in narrower bandgap, greater CO2 affinity, and uptake capacity as well as higher separation efficiency of photogenerated charge carriers. This work provides a novel strategy to design hierarchical g-C3N4 nanostructures, which can be used as promising photocatalyst for solar energy conversion.
- Fu, Junwei,Zhu, Bicheng,Jiang, Chuanjia,Cheng, Bei,You, Wei,Yu, Jiaguo
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- Hydrogenation of CO2 to alcohol species over Co?Co3O4/C-N catalysts
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Co/C-N materials were synthesized with calcination of ZIF-67 at a N2 atmosphere. Co?Co3O4/C-N catalysts were prepared by partially oxidized of Co/C-N in air under different conditions. The catalysts were characterized with XRD, BET, TEM, TGA, H2-TPD, ESR and XPS. The metallic Co in Co/C-N was the main activity site for the CO2 hydrogenation as it supplied dissociative hydrogen on the surface. Partial oxidation of Co/C-N decreased the content of metallic Co, decreasing the amount of dissociative H2 and thus the CO2 conversion, while increasing the methanol selectivity. Oxygen defects in Co?Co3O4/C-N improved the dissociation of CO2 and helped to produce desired alcohol species. The highest yield of MeOH, 2.0 mmol g?1 h?1, was obtained over Co?Co3O4/C-N (250, 2 h) at 220 °C.
- Lian, Yun,Fang, Tingfeng,Zhang, Yuhua,Liu, Bing,Li, jinlin
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- Kinetic isotope effects in the reduction of methyl iodide
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α-Deuterium (α-D) kinetic isotope effects (KIEs) have been determined for the reaction of methyl iodide with a series of reducing agents. Reagents which transfer hydride ion in an SN2 reaction show small inverse or small normal KIEs. Reagents which transfer an electron to methyl iodide to produce methyl radical show large normal KIEs up to 20% per α-D. Large KIEs were found for the reaction of methyl iodide with sodium, for Pd-catalyzed reaction of methyl iodide with hydrogen, for electron transfer (ET) at a platinum cathode, for ET from benzophenone ketyl or from sodium naphthalenide, for iron-catalyzed ET from a Grignard reagent to methyl iodide, and for reduction of methyl iodide with tributyltin hydride or with gaseous hydrogen iodide. Very small KIEs were found for electron transfer to methyl iodide from magnesium in ether or from sodium in ammonia. The reason may be that these reactions are transport or diffusion controlled.
- Holm, Torkil
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- Highly-active direct Z-scheme Si/TiO2 photocatalyst for boosted CO2 reduction into value-added methanol
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In the present study, direct Z-scheme Si/TiO2 photocatalyst was synthesized via a facile hydrothermal reaction using tetrabutyl titanate and Si powder prepared from magnesiothermic reduction of SiO2 nanospheres. The Si/TiO2 nanospheres were composed of porous Si nanospheres with a diameter of ~300 nm and TiO2 nanosheets with a diameter of 50 nm and thickness of 10 nm, and demonstrated superior visible light harvesting ability to either Si nanospheres or TiO2 nanosheets. CO2 photocatalytic reduction proved that Si/TiO2 nanocomposites exhibit high activity in conversion of CO2 to methanol with the maximum photonic efficiency of 18.1%, while pure Si and TiO2 catalyst are almost inactive, which can be ascribed to the integrated suitable band composition in the Si/TiO2 Z-scheme system for CO2 reduction. The enhanced photocatalytic property of Z-scheme Si/TiO2 nanospheres was ascribed to the formation of Si/TiO2 Z-scheme system, which improved the separation efficiency of the photogenerated carriers, prolonged their longevity, and therefore boosted their photocatalytic activity.
- Liu, Yousong,Ji, Guangbin,Dastageer, Mohammed Abdulkader,Zhu, Lei,Wang, Junyi,Zhang, Bin,Chang, Xiaofeng,Gondal, Mohammed Ashraf
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- 1,2-Pentadiene decomposition
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1,2-Pentadiene was decomposed in single pulse shock tube experiments. There appear to be a large number of parallel decomposition and isomerization channels. It was shown that the resonance energy of the 1,3-butadiene-2-yl radical is smaller than that of allyl radical by an amount equal to the π bond conjugation energy of butadiene.
- Herzler, Juergen,Manion, Jeffrey A.,Tsang, Wing
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- Turning the activity of Cr–Ce mixed oxide towards thermocatalytic NO oxidation and photocatalytic CO2 reduction via the formation of yolk shell structure hollow microspheres
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Cr–Ce mixed oxides microspheres will have considerable potential in thermocatalytic NO oxidation and photocatalytic CO2 reduction reaction (CO2RR) if their low porosity and expensive synthetic expenditure can be overcome. To avoid these obstacles, a facile and economical strategy was adopted to synthesize double-shelled hollow Cr–Ce mixed oxide microspheres. The highly active multipurpose catalyst achieved an ultrahigh thermocatalytic NO oxidation efficiency at low temperatures, and provided high yields of CH4 and CH3OH during the photocatalytic CO2RR. For NO oxidation, the optimized catalyst provided over 40% NO removal at 150 °C, which was ascribed to the reduced aggregation of the active subunits and the increased active species availability. Further, the exposed surface could generate an increased content of Cr6+ and Oβ, which played the key role in NO oxidation. For CO2 photocatalytic reduction, the superior behavior originated from the reduced band gap and the effective separation of photoinduced charge carriers. This study opens up new possibilities of using Cr–Ce mixed oxides for application in catalysis.
- Zhao, Yunxia,Cai, Wei,Chen, Mindong,Bu, Yunfei
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- Evaluation of the Catalytic Relevance of the CO-Bound States of V-Nitrogenase
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Binding and activation of CO by nitrogenase is a topic of interest because CO is isoelectronic to N2, the physiological substrate of this enzyme. The catalytic relevance of one- and multi-CO-bound states (the lo-CO and hi-CO states) of V-nitrogenase to C?C coupling and N2 reduction was examined. Enzymatic and spectroscopic studies demonstrate that the multiple CO moieties in the hi-CO state cannot be coupled as they are, suggesting that C?C coupling requires further activation and/or reduction of the bound CO entity. Moreover, these studies reveal an interesting correlation between decreased activity of N2 reduction and increased population of the lo-CO state, pointing to the catalytic relevance of the belt Fe atoms that are bridged by the single CO moiety in the lo-CO state. Together, these results provide a useful framework for gaining insights into the nitrogenase-catalyzed reaction via further exploration of the utility of the lo-CO conformation of V-nitrogenase.
- Lee, Chi Chung,Wilcoxen, Jarett,Hiller, Caleb J.,Britt, R. David,Hu, Yilin
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- Thermal reaction of 2-methyl-2-butene in the presence of azomethane: enthalpy of formation of the radicals (CH3)2CCH(CH3)2 and tert-C4H9
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The reaction of CH3 and 2-methyl-2-butene (2MB2) was investigated in the temperature range 540-610 K. Azomethane was used as the source of CH3. The addition of CH3 to 2MB2 was concluded to be an equilibrium process: . The equilibrium constant of
- Kiraly, Zoltan,Koertvelyesi, Tamas,Seres, Laszlo
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- Adsorption and Catalytic Decomposition of Dimethyl Sulphide and Dimethyl Disulphide on Metal Films of Iron, Palladium, Nickel, Aluminium and Copper
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The interaction of dimethyl sulphide (Me2S) and dimethyl disulphide (Me2S2) has been studied with metal films of Fe, Pd, Ni, Al and Cu over the temperature ranges 193-500 K with Me2S and 223-600 K in the case of Me2S2.At 193 K mainly molecular chemisorption of Me2S occured on the films.With Me2S2, multilayer adsorption, involving both chemisorption and van der Waals adsorption took place on the films at 223 K.Dissociative chemisorption of Me2S or Me2S2 began above 300 K and was accompained by the evolution of gaesous products.The latter involved H2, CH4 and C2H6 gases with Me2S and H2, CH4, C2H6, MeSH and Me2S subsequent to the dissociation of Me2S2.Additional gaseous products throughout the decomposition on the oxidized films were CO, H2O and C2H4.The rate of Me2S or Me2S2 chemisorption depended on the pressure of the reacting gas, and the kinetic data indicated the operation of a compensation effect throughout the interaction of Me2S or Me2S2 with the films.On the basis of kinetic data it was possible to arrange the metal films in the order of decreasing activity toward Me2S or Me2S2 adsorption.The transition-metal films showed greater activity than Al and Cu, and among the former films Fe showed the greatest activity, for chemisorption of Me2S and Me2S2.All the metals have higher tendencies for Me2S adsorption than for Me2S2.
- Al-Haidary, Yousif Kadim,Saleh, Jalal Mohammed
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- Homogeneous Hydrogenation of Carbon Dioxide to Methanol Catalyzed by Ruthenium Cluster Anions in the Presence of Halide Anions
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Methanol, together with methane, is formed for the first time by homogeneous hydrogenation of CO2 using a catalytic system consisting of Ru3(CO)12 and alkaline iodides in N-methylpyrrolidone (NMP) solution at 240 deg C.The time course of the reaction indicates the successive formation of CO, methanol, and then methane.The FT-IR analysis of the resulting reaction solutions reveals the formation of several species of ruthenium carbonyl anion and their mutual interchanges during the reaction.A mechanism for the overall reaction is proposed, based on these results.
- Tominaga, Ken-ichi,Sasaki, Yoshiyuki,Watanabe, Taiki,Saito, Masahiro
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- Efficiently Converting CO2 into C2H4 using a Porphyrin-Graphene Composite Photocatalyst
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In this work, a photocatalyst consisting of porphyrin and graphene was designed to reduce CO2 to hydrocarbons under visible light. This catalyst can (1) effectively reduce CO2 to hydrocarbons, particularly to C2H4; (2) selectively control the photogenerated electrons transfer path due to the physico-chemical properties of porphyrin and graphene; and (3) reduce the complexity of investigating this photocatalytic process because the photocatalyst has fewer defects, thus preventing the introduction of interference factors.
- Piao, Meihua,Liu, Nan,Wang, Yanshu,Feng, Chunsheng
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- One-Pass Conversion of Benzene and Syngas to Alkylbenzenes by Cu–ZnO–Al2O3 and ZSM-5 Relay
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Alkylbenzenes have a wide range of uses and are the most demanded aromatic chemicals. The finite petroleum resources compels the development of production of alkylbenzenes by non-petroleum routes. One-pass selective conversion of benzene and syngas to alkylbenzenes is a promising alternative coal chemical engineering route, yet it still faces challenge to industrialized applications owing to low conversion of benzene and syngas. Here we presented a Cu–ZnO–Al2O3/ZSM-5 bifunctional catalyst which realizes one-pass conversion of benzene and syngas to alkylbenzenes with high efficiency. This bifunctional catalyst exhibited high benzene conversion (benzene conversion of 50.7%), CO conversion (CO conversion of 55.0%) and C7&C8 aromatics total yield (C7&C8 total yield of 45.0%). Characterizations and catalytic performance evaluations revealed that ZSM-5 with well-regulated acidity, as a vital part of this Cu–ZnO–Al2O3/ZSM-5 bifunctional catalyst, substantially contributed to its performance for the alkylbenzenes one-pass synthesis from benzene and syngas due to depress methanol-to-olefins (MTO) reaction. Furthermore, matching of the mass ratio of two active components in the dual-function catalyst and the temperature of methanol synthesis with benzene alkylation reactions can effectively depress the formation of unwanted by-products and guarantee the high performance of tandem reactions. Graphic Abstract: [Figure not available: see fulltext.]
- Han, Tengfei,Xu, Hong,Liu, Jianchao,Zhou, Ligong,Li, Xuekuan,Dong, Jinxiang,Ge, Hui
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p. 467 - 479
(2021/05/21)
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- Ethanol Steam Reforming by Ni Catalysts for H2 Production: Evaluation of Gd Effect in CeO2 Support
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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.
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- Investigation on the Thermal Cracking and Interaction of Binary Mixture of N-Decane and Cyclohexane
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Abstract: The investigation about the thermal cracking performance and interaction of different components in hydrocarbon fuels is of great significance for optimizing the formulation of high-performance hydrocarbon fuels. In this work, thermal cracking of n-decane, cyclohexane and their binary mixture were studied in a tubular reactor under different temperatures and pressures. The gas and liquid products were analyzed in detail with different gas chromatography. The main gas products of pure n-decane and cyclohexane are similar, and there is a certain difference in the main liquid products. For binary mixture, the overall conversion rate and gas yield are lower than their theoretical value. The cracking conversion rate of n-decane in binary mixture is lower than that in pure n-decane, but the opposite change occurs for cyclohexane, and the effect become more obvious as the increase of the reaction pressure. These experimental phenomena can be explained by bond dissociation energy and free radical reaction mechanism. The pressure affects the free radical reaction path, and high pressure is more conducive to bimolecular hydrogen abstraction reaction, which will lead to different product content. A law of interaction between the n-decane and cyclohexane was observed according to the experimental results. [Figure not available: see fulltext.]
- Chen, Xuejiao,Pang, Weiqiang,Wang, Bo,Zhang, Ziduan,Zhou, Lingxiao,Zhu, Quan
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- Nanoconfinement Engineering over Hollow Multi-Shell Structured Copper towards Efficient Electrocatalytical C?C coupling
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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
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supporting information
(2021/12/06)
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- Impact of oxygen vacancies in Ni supported mixed oxide catalysts on anisole hydrodeoxygenation
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The hydrodeoxygenation (HDO) activity of anisole has been investigated over Ni catalysts on mixed metal oxide supports containing Nb–Zr and Ti–Zr in 1:1 and 1:4 ratios. XRD patterns indicate the incorporation of Ti (or Nb) into the ZrO2 framewo
- Ali, Hadi,Kansal, Sushil Kumar,Lauwaert, Jeroen,Saravanamurugan, Shunmugavel,Thybaut, Joris W.,Vandevyvere, Tom
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- Electrochemical Formation and Activation of Hydrogen Peroxide from Water on Fluorinated Tin Oxide for Baeyer-Villiger Oxidation Reactions
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The two-electron oxidation of water (2e-WOR) has been studied in the past as a possible method for the alternative preparation of hydrogen peroxide. Often, fluorinated tin oxide (FTO) is used as an anode and FTO itself was found also to be active for 2e-WOR. Because one use of H2O2is as an oxygen donor for Baeyer-Villiger oxidation of ketones catalyzed by tin compounds and materials, presently we were interested in studying the use of in situ formed H2O2for these reactions. First, the formation of H2O2was verified in an acetonitrile/water solvent in a 2e-WOR reaction, which is more efficient than a comparable reaction in water in terms of the H2O2concentration attained and faradaic efficiency at comparable potentials, that is, ~3 V vs SHE. Second, initial studies on oxygenation of reactive substrates such as sulfides showed normalized reaction rates (NRRs) for two-electron oxidation reactions that were about 3 times higher than the NRR for H2O2formation, indicating the formation of an active oxygen-donating or oxidizing species on the electrode surface prior to the formation and release of H2O2into solution. Third, the Baeyer-Villiger oxygenation of 2-adamantanone at 2.1 V versus SHE in acetonitrile/water showed both the formation of the expected lactone product and hydroxylation at both tertiary and secondary C-H bonds. Hydroxylation is most easily explained by the presence of hydroxyl radical species as supported by the formation of a spin adduct and its identification by electron paramagnetic resonance. However, the potential used, 2.1 V versus SHE, is an underpotential for the formation of a solvated hydroxyl radical in solution, thereby leading to the conclusion that surface-bound hydroxyl species, OH*, are those that are reactive for the apparent one-electron water oxygenation reaction. Fourth, it was shown that although H2O2can be thermally activated on FTO as a catalyst to a minor degree, electrochemical activation is by far more significant, leading to the use of FTO as an electrochemical catalyst for activation of H2O2for the Baeyer-Villiger oxygenation and also alkene epoxidation.
- Herman, Adi,Mathias, Jenny-Lee,Neumann, Ronny
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p. 4149 - 4155
(2022/04/12)
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- Transformation synthesis of SSZ-13 zeolite from ZSM-35 zeolite
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Interzeolite conversion as a promising alternative strategy for zeolite synthesis has received extensive attention. It is of great significance to understand the potential rules of conversion between zeolites with different topologies for effective regulation of zeolite synthesis. Hydrothermal conversion of ZSM-35 (FER-type) zeolite containing the mor composite building units into SSZ-13 zeolite (CHA-type) using N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as template was performed for the first time. The effects of TMAdaOH/SiO2 ratio, Na2O/SiO2 ratio, the additional starting zeolite and crystallization time on the interzeolite conversion of ZSM-35 into SSZ-13 were investigated. The interzeolite conversion mechanism concerning the synthesis of SSZ-13 from ZSM-35 zeolite was proposed and verified by DFT calculation. The results of DFT calculations suggested that ZSM-35 zeolite with mor composite building unit had the potential to decompose into 6-Membered Rings, and further transform into CHA-type zeolite containing d6r composite building unit. Therefore, zeolites containing mor structure have the potential to be converted into zeolites containing d6r structure.
- Bing, Liancheng,Cong, Wenwen,Han, Dezhi,Li, Kexu,Li, Qiang,Wang, Fang,Wang, Guangjian,Xu, Changyou
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- STABLE, HIGH SELECTIVITY CATALYSTS AND CATALYST SYSTEMS, AND PROCESSES FOR THEIR USE
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The present invention relates to catalysts, catalyst systems, and processes for the production of valuable light olefins, such as C2-C4 olefins (ethylene, propylene, and/or butenes) from paraffinic hydrocarbons, such as propane, through dehydrogenation and metathesis. Some particular aspects relate to the discovery of non-precious metal catalysts and catalyst systems utilizing such catalysts, for example in the case of being in an admixture with a metathesis catalyst, which advantageously exhibit high performance in terms of activity, selectivity, and stability. Other advantages can include a reduced production of byproducts (e.g., methane and ethane) that result from undesired side reactions, in addition to benefits that may be attained through the addition of a sulfur-bearing compound (e.g., H2S).
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Paragraph 84-87; 104; 105
(2021/08/06)
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- Oxidative Cracking of Propane in the Presence of Hydrogen
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The effect of H2 additions to the initial mixture on the parameters of the oxidative cracking of propane at atmospheric pressure, temperatures of 500°C–750°C, reaction time of 2 s, and С3H8/О2 initial ratio ~2 was experimentally evaluated. Results revealed that small amounts of H2 promoted the process due to the formation of additional active radicals OH? and H?. Performance of the oxidative cracking of propane in a large excess of H2 led to an increase in the yield of methane and ethane, while the yield of ethylene, the target product of the process, decreased.
- Arutyunov, V. S.,Nikitin, A. V.,Ozerskii, A. V.,Sedov, I. V.,Timofeev, K. A.,Zimin, Ya. S.
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p. 787 - 792
(2021/08/13)
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- Insight into Carbocation-Induced Noncovalent Interactions in the Methanol-to-Olefins Reaction over ZSM-5 Zeolite by Solid-State NMR Spectroscopy
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Carbocations such as cyclic carbenium ions are important intermediates in the zeolite-catalyzed methanol-to-olefins (MTO) reaction. The MTO reaction propagates through a complex hydrocarbon pool process. Understanding the carbocation-involved hydrocarbon pool reaction on a molecular level still remains challenging. Here we show that electron-deficient cyclopentenyl cations stabilized in ZSM-5 zeolite are able to capture the alkanes, methanol, and olefins produced during MTO reaction via noncovalent interactions. Intermolecular spatial proximities/interactions are identified by using two-dimensional 13C–13C correlation solid-state NMR spectroscopy. Combined NMR experiments and theoretical analysis suggests that in addition to the dispersion and CH/π interactions, the multiple functional groups in the cyclopentenyl cations produce strong attractive force via cation-induced dipole, cation–dipole and cation–π interactions. These carbocation-induced noncovalent interactions modulate the product selectivity of hydrocarbon pool reaction.
- Cai, Wenjin,Chu, Yueying,Deng, Feng,Hu, Min,Li, Shenhui,Qi, Guodong,Wang, Chao,Wang, Qiang,Xu, Jun
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supporting information
p. 26847 - 26854
(2021/11/17)
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- Controlling the Surface Oxidation of Cu Nanowires Improves Their Catalytic Selectivity and Stability toward C2+ Products in CO2 Reduction
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Copper nanostructures are promising catalysts for the electrochemical reduction of CO2 because of their unique ability to produce a large proportion of multi-carbon products. Despite great progress, the selectivity and stability of such catalysts still need to be substantially improved. Here, we demonstrate that controlling the surface oxidation of Cu nanowires (CuNWs) can greatly improve their C2+ selectivity and stability. Specifically, we achieve a faradaic efficiency as high as 57.7 and 52.0 % for ethylene when the CuNWs are oxidized by the O2 from air and aqueous H2O2, respectively, and both of them show hydrogen selectivity below 12 %. The high yields of C2+ products can be mainly attributed to the increase in surface roughness and the generation of defects and cavities during the electrochemical reduction of the oxide layer. Our results also indicate that the formation of a relatively thick, smooth oxide sheath can improve the catalytic stability by mitigating the fragmentation issue.
- Lyu, Zhiheng,Zhu, Shangqian,Xie, Minghao,Zhang, Yu,Chen, Zitao,Chen, Ruhui,Tian, Mengkun,Chi, Miaofang,Shao, Minhua,Xia, Younan
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supporting information
p. 1909 - 1915
(2020/12/07)
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- Multiple Cuprous Centers Supported on a Titanium-Based Metal-Organic Framework Catalyze CO2Hydrogenation to Ethylene
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Hydrogenation of carbon dioxide (CO2) to ethylene (C2H4) can be achieved in two routes via tandem reactions: (1) CO2hydrogenation to methanol (CH3OH) followed by methanol-to-olefin conversion and (2) reverse water-gas shift reaction followed by Fischer-Tropsch synthesis. Here we present another tandem route for CO2-to-C2H4conversion via (3) CO2hydrogenation to ethanol (C2H5OH) followed by C2H5OH dehydration. Multiple cuprous (CuI) centers were loaded onto the Ti8(μ2-O)8(μ2-OH)4secondary building units of a Ti-based metal-organic framework (MOF), MIL-125-NH2, via deprotonation and ion exchange of the μ2-OH groups. These multiple CuIcenters catalyzed CO2hydrogenation to C2H5OH, while the Ti2-μ2-O-M+(M+= H+, Li+) sites converted C2H5OH to C2H4. The MOF achieved CO2-to-C2H4generation rates of up to 2598 μmol gCat-1h-1in supercritical CO2(CO230 MPa, H25 MPa) at 85 °C and 514 μmol gCat-1h-1in the gas phase at 5 MPa (H2:CO2= 3) and 100 °C, respectively. This work opens another path to selectively producing C2H4via the hydrogenation of CO2
- An, Bing,Cao, Yonghua,Dai, Yiheng,Li, Han,Li, Zhe,Lin, Wenbin,Wang, Cheng,Wang, Yongke,Zeng, Lingzhen,Zhang, Jingzheng,Zhou, Yang
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p. 11696 - 11705
(2021/09/28)
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- Facet-Selective Deposition of Ultrathin Al2O3 on Copper Nanocrystals for Highly Stable CO2 Electroreduction to Ethylene
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Catalysts based on Cu nanocrystals (NCs) for electrochemical CO2-to-C2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C2+ product remain obstacles for realizing sustainable carbon-neutral cycles. Here, we used the facet-selective atomic layer deposition (FS-ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al2O3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C2H4/CH4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al2O3-10C) reaches a C2H4 faradaic efficiency of 60.4 % at a current density of 300 mA cm?2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al2O3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al2O3-10C shown in stability tests.
- Li, Hui,Yu, Peiping,Lei, Renbo,Yang, Feipeng,Wen, Peng,Ma, Xiao,Zeng, Guosong,Guo, Jinghua,Toma, Francesca M.,Qiu, Yejun,Geyer, Scott M.,Wang, Xinwei,Cheng, Tao,Drisdell, Walter S.
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supporting information
p. 24838 - 24843
(2021/10/15)
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- Dehydrogenation of Propane in the Presence of CO2 on Supported Monometallic MOy/SiO2 and CrOxMOy/SiO2 (M = Fe, Co, and Ni) Bimetallic Catalysts
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Abstract: An analysis is performed of the physicochemical properties of M/SiO2 (M = Fe, Co, and Ni) oxide monometallic and CrM/SiO2 (M = Fe, Co, and Ni) bimetallic catalysts supported on amorphous silica. The catalysts are characterized via TGA, XRD, UV–Vis diffuse reflectance spectroscopy, and SEM. Adding 1?wt?% of a second transition metal (Fe, Ni, and Co) to the 3% CrOx/SiO2 chromium oxide catalyst substantially raises the conversion of propane to 64% with a drop in the selectivity towards propylene and formation of methane as a main by-product in the case of nickel. Introducing iron and cobalt raises the selectivity towards propylene to 72% with a drop in the conversion of propane.
- Tedeeva,Kustov,Pribytkov,Strekalova,Kalmykov,Dunaev,Kustov
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- Synergistic effect of Fe and Ga incorporation into ZSM-5 to increase propylene production in the cracking ofn-hexane utilizing a microchannel reactor
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In the present study, the effect of various amounts of Fe and Ga in the catalytic cracking ofn-hexane in a microchannel reactor was investigated using experimental design by the D-optimal method. Nano zeolites incorporated with Fe and Ga metals were synthesized in a fluorine environment to investigate the synergistic effect of the metals on the textural and acidic properties of the catalysts, which ultimately improved the performance of the synthesized catalysts in the efficient production of light olefins, in particular propylene. Three synthesis parameters including the Si/Al, Si/Fe and Si/Ga ratios were considered as the main factors to determine the optimal conditions for obtaining the maximum conversion ofn-hexane, yield of light olefins, and P/E ratio and minimum yield of alkanes as the responses. In sample FeGa-1, the P/E ratio reached 3.97, indicating the significant effect of the substituted metals in improving the desirable routes for propylene production. According to the results of the acidic properties, Fe, Al and Ga increased the number of total acid sites and the strengths of strong and weak acid sites, respectively. In addition, according to the results obtained from sample FeGa-7, the synergistic effect of Fe and Ga increased the number of weak acid sites.
- Halimitabrizi, Parya,Rashidzadeh, Mehdi,Sakha, Mohsen Rostami,Salari, Darush,Soltanali, Saeed
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p. 13833 - 13846
(2021/08/16)
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- Visualizing Element Migration over Bifunctional Metal-Zeolite Catalysts and its Impact on Catalysis
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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.
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supporting information
p. 17735 - 17743
(2021/07/02)
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- Promotion effect of iron addition on the structure and CO2 hydrogenation performance of Attapulgite/Ce0.75Zr0.25O2 nanocomposite supported Cu-ZnO based catalyst
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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
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- In situ Irradiated XPS Investigation on S-Scheme TiO2@ZnIn2S4 Photocatalyst for Efficient Photocatalytic CO2 Reduction
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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
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- Tunable Fe3O4 nanoparticles assembled porous microspheres as catalysts for Fischer-Tropsch synthesis to lower olefins
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Fe catalyzed Fischer-Tropsch synthesis to lower olefins (FTO) has been recognized as a structure-sensitive reaction. Nanostructure Fe-based catalysts can expose more active surface. But bulk nanostructure Fe catalysts without support interaction show easily sintered and agglomerated, which makes hard to investigate size effect. Therefore, the effect of particle size on bulk Fe catalysts have rarely been reported. Herein, nanoparticles assembled Fe3O4 bulk catalysts were synthesized via a PAA-mediated solvothermal method to solely investigate the size effect of Fe phase. By tuning preparation parameters, a series of porous-Fe3O4 microspheres assembled by different nanoparticle size (8.5–16.5 nm) was obtained, maintaining constant microspheres size. When Fe3O4 nanoparticles are smaller than 10 nm, catalysts show similar catalytic activity (FTY). Beyond 10 nm, the FTY obviously decreases with increasing of particle size. Particularly, Fe3O4 with nanoparticle size of 9.9 nm performs the highest activity as well as C2-C4= selectivity and O/P ratio. The smaller particles attribute to C5+ formation, while inhibit CH4 selectivity. By CO-TPD, TPH-MS and XRD analysis, we discuss size effect on CO adsorption, surface carbon species and carburization degree, building relationship between particle size and catalytic activity. It is found that the carburization degree of iron phase correlates positively with catalytic activity. These results deepen understanding of the structure-performance relationship for bulk iron catalysts in FTO.
- Zhao, Qiao,Liang, Haoting,Huang, Shouying,Han, Xiaoxue,Wang, Hongyu,Wang, Jian,Wang, Yue,Ma, Xinbin
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p. 133 - 139
(2020/05/18)
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- Effect of preparation method on physicochemical properties of a novel Co–Fe nano catalyst
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The main approach of this study was to investigate the effect of the type of synthesis method on the improvement of catalyst performance in Fischer–Tropsch reaction. For this purpose, a series of the novel catalysts were synthesized using iron and cobalt nitrate salts, tetraethoxysilane and novolac phenolic resin by different method. These catalysts were abbreviated as M1–Co–Fe–novolac/SiO2, M2–Co–Fe–novolac/SiO2, and M3–Co–Fe–novolac/SiO2 and characterized using different techniques. The results of the Brunauer–Emmett–Teller and Fourier transform infrared techniques showed that M2–Co–Fe–novolac/SiO2 catalyst has a higher surface area than the other two ones. This catalyst was analyzed by using X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray, and temperature-programed reduction (TPR) techniques. The XRD results confirmed the appearance of suitable active phases, such as metal phase, carbide, and low oxidation state of metals. Based on TPR results, the lower reduction temperature, compared with similar samples, confirmed the high activity of the M2–Co–Fe–novolac/SiO2 catalyst. Catalytic activity and selectivity for Fischer–Tropsch reaction were investigated in the standard conditions by using catalytic tests. The high conversion percentage of CO indicated high activity of the catalyst. On the other hand, the olefin to paraffin ratio (O/P), which was a criterion for catalytic efficiency in industrial, was also acceptable.
- Ehsani Nia, Mahsa,Sedighi, Behnam,Joshaghani, Mohammad
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p. 2009 - 2015
(2021/02/01)
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- The catalytic activity of microporous and mesoporous NiCoBeta zeolite catalysts in Fischer–Tropsch synthesis
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Two kinds of microporous and mesoporous NiCoBeta zeolite catalysts were prepared. The effect of bimetallic zeolite preparation method, dealumination degree, the presence of micropores in the support structure and the effect of nickel addition on the activity and selectivity of cobalt-based microporous and mesoporous dealuminated and non-dealuminated zeolite catalysts in Fischer–Tropsch synthesis were determined. These catalysts were obtained by sequential impregnation (Ni3.0Co20AlBeta and Ni3.0Co20SiBeta) and co-impregnation (co-Ni3.0Co20AlBeta and co-Ni3.0Co20SiBeta). The study showed that the presence of Ni leads to a lower cobalt oxide reduction temperature and an increase in CO conversion. Nickel–cobalt zeolite systems showed high activity and selectivity throughout the lifetime of the reaction. The use of a two-step post-synthesis method and the promotion of cobalt systems with nickel allow to obtain active, selective, and stable zeolite catalysts for Fischer–Tropsch synthesis.
- Chalupka, Karolina A.,Sadek, Renata,Szkudlarek, Lukasz,Mierczynski, Pawel,Maniukiewicz, Waldemar,Rynkowski, Jacek,Gurgul, Jacek,Casale, Sandra,Brouri, Dalil,Dzwigaj, Stanislaw
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p. 397 - 418
(2021/02/03)
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- Application of magnetic field to CO hydrogenation using a confined-space catalyst: effect on reactant gas diffusivity and reactivity
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An external magnetic field has recently been applied in reaction processes to promote movement and avoid agglomeration of magnetic particles, and also reduce the activation energy through improving the gas-solid contact. In this work, the effect of an external magnetic field on reactant gas diffusivity and reactivity in CO hydrogenation within a confined-space catalyst was investigated for the first time using a conventional reactor packed with a bimetallic 5Fe-5Co/ZSM-5 molecular sieve catalyst. The synergistic effect between magnetic field and limited mass transfer within zeolite cavities improved the mass transfer ability and reaction phenomena of the reactant molecules, leading to enhancement of catalytic activity with tailored reaction pathways. As a result, CO conversion and CH4 selectivity were increased by factors of 1.9 and 1.3 compared to those without a magnetic field. These synergistic interactions are able to provide an innovative challenge for green and sustainable chemical processes and separation processes by means of selective reactant and product mass transfer designed for selective catalytic conversion in the future.
- Donphai, Waleeporn,Kunthakudee, Naphaphan,Munpollasri, Sirapat,Sangteantong, Pariyawalee,Tonlublao, Surangrat,Limphirat, Wanwisa,Poo-Arporn, Yingyot,Kiatphuengporn, Sirapassorn,Chareonpanich, Metta
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p. 3990 - 3996
(2021/02/02)
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- A PdCu nanoalloy catalyst for preferential CO oxidation in the presence of hydrogen
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Catalytic oxidation of carbon monoxide (CO) is one of the essential steps for several environment- and energy-related applications. Here, we report the synthesis of alloy PdCu nanoparticles supported on an Al2O3support as a catalyst for effective removal of CO from H2-rich flue gases. The alloy phase between Pd and Cu was formed by deposition of organometallic Pd- and Cu-precursors on the Al2O3support followed by thermal reduction under H2. The alloy PdCu nanoparticles (average size: 30 nm) are in a spherical shape and they are distributed in the range between 10 and 80 nm. The alloy PdCu catalyst showed improved CO oxidation performance both in the presence and absence of H2compared to that of the reference Pd catalyst. It is also inferred that the alloy PdCu catalyst showed an onset temperature (To) of 50 °C in the presence of H2compared to that of CO oxidation in the absence of H2(To= 100 °C). In addition, the alloy PdCu catalyst showed selective CO oxidation performance below a temperature range of 300 °C. Therefore, the formation of the Pd-based alloy structures may have potential as the preferential CO oxidation catalyst for the catalytic removal of CO from various flue gases.
- Khobragade, Rohini,Dahake, Pranali,Labhsetwar, Nitin,Saravanan, Govindachetty
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p. 4246 - 4252
(2021/03/15)
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- Facile Fabrication of CeO2-Al2O3Hollow Sphere with Atomically Dispersed Fe via Spray Pyrolysis
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A facile spray pyrolysis method is introduced to construct the hollow CeO2-Al2O3 spheres with atomically dispersed Fe. Only nitrates and ethanol were involved during the one-step preparation process using the ultrasound spray pyrolysis approach. Detailed explorations demonstrated that differences in the pyrolysis temperature of the precursors and heat transfer are crucial to the formation of the hollow nanostructure. In addition, iron species were in situ atomically dispersed on the as-formed CeO2-Al2O3 hollow spheres via this strategy, which demonstrated promising potential in transferring syn-gas to valuable gasoline products.
- Fu, Xin-Pu,Jia, Chun-Jiang,Li, Meng-Yuan,Ma, Chao,Si, Rui,Yu, Wen-Zhu
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supporting information
p. 5183 - 5189
(2021/05/04)
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- Fischer-Tropsch to olefins over Co2C-based catalysts: Effect of thermal pretreatment of SiO2 support
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SiO2 supported Co2C-based catalysts were used for Fischer-Tropsch to olefins (FTO), and the effect of thermal pretreatment of SiO2 support under different temperatures on the Co2C morphology and catalytic performance was investigated. It was found that the interaction between cobalt and support was weakened when SiO2 was pretreated at high temperature (990 °C) due to the decreased content of surface Si[sbnd]OH groups. The relative weak interaction between cobalt and support benefited the formation of cobalt manganese composite oxide after calcination and reduction, and thus promoted the generation of Co2C nanoprisms with promising FTO performance. In contrast, for the SiO2 support pretreated at 350 °C or 650 °C, the strong interaction between cobalt and support led to phase separation of cobalt and manganese. As a result, only Co2C nanospheres were generated which displayed low activity and high methane selectivity.
- An, Yunlei,Li, Liusha,Li, Xiao,Lin, Tiejun,Sun, Yuhan,Yu, Fei,Zhong, Liangshu
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- On the reaction mechanism of MnOx/SAPO-34 bifunctional catalysts for the conversion of syngas to light olefins
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MnOx/SAPO-34 bifunctional catalysts are efficient for the conversion of syngas to light olefins. However, the reaction mechanism is still debated in particular the nature of the intermediate formed on MnOx(ketenevs.methanol). In this study, it was evidenced from catalytic data andin situDRIFT measurements that methanol is a key reaction intermediate produced on MnOxthat synergistically reacts with SAPO-34 to produce light olefins.
- Afanasiev, Pavel,Checa, Ruben,Coudercy, Christophe,L'hospital, Valentin,Le Valant, Anthony,Loridant, Stéphane
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p. 7844 - 7849
(2021/12/27)
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- The Nature of the Activity of СoО/ZrO2 Catalysts in CO Oxidation with Oxygen in Excess Hydrogen
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Abstract: The (5–15)%CoO/ZrO2(T + M) catalysts were studied by XRD and TPR-H2. In the oxidized samples, 80–90% of cobalt oxide is present in the form of finely dispersed Co3O4, which interacts with the support ((Formula presented.) clusters), and the rest of it (10–20%) are the Co3O4 phase and dispersed CoO. In the CO oxidation to CO2, the most active samples were CoO/ZrO2(T + M) containing 10 and 15% cobalt at T50?= 120°C. Nearly 100% conversion of CO to CO2 was observed on 10%CoO/ZrO2(T + M) at 160–200°C. The conversion decreases at 220–260°C as a result of competition for oxygen in the oxidations of CO and H2, and at 280–360°C, as a result of increased consumption of CO in the methanation reaction. The CO oxidation in the range 50–200°C occurs on the clusters localized on the ZrO2(T) particles. The Co3O4 phase in pure oxide and in the 5%CoO/(SiO2, ZrO2(M)) catalysts has low activity under these conditions. The temperature dependence of CO conversion was discussed based on the data on the properties of adsorption complexes formed with participation of oxygen clusters and the gas phase.
- Bykhovsky, M. Ya.,Fattakhova, Z. T.,Il’ichev, A. N.,Korchak, V. N.,Shashkin, D. P.
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p. 787 - 797
(2022/01/13)
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- Enhanced Catalytic Performance of Fe-containing HZSM-5 for Ethane Non-Oxidative Dehydrogenation via Hydrothermal Post-Treatment
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A facile strategy is applied to construct Fe supported ZSM-5 (Fe/HZ5-HTS) via hydrothermal post-treatment and applied to ethane non-oxidative dehydrogenation. Compared with Fe/HZ5-IWI prepared by incipient wetness impregnation, Fe/HZ5-HTS exhibits superior catalytic activity and long catalyst stability with 6000 minutes time-on-stream. An obvious volcanic curve is observed between the ethylene generation rate and Fe content, and 1.0Fe/HZ5-HTS exhibits the highest ethylene generation rate with 0.166 mmol C2H4 s?1 gFe?1 over different Fe loading, which is twice as much as that of 1.0Fe/HZ5-IWI. According to various characterizations, isolated Fe3+ species and carburized Fe species are active sites, and the better catalytic performance over 1.0Fe/HZ5-HTS is ascribed to more disperse Fe species and exposing more Fe species in the surface. Besides, the lower ethylene desorption temperature and higher ethane desorption temperature over Fe/HZ5-HTS could suppress the overreaction of the ethylene to generate coke and increase ethane residence reaction time, resulting in less coke deposition and facilitating the catalytic performance.
- Wu, Lizhi,Fu, Zhiyuan,Ren, Zhuangzhuang,Wei, Jinhe,Gao, Xinhua,Tan, Li,Tang, Yu
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p. 4019 - 4028
(2021/08/03)
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- Integrated Capture and Conversion of CO2 to Methane Using a Water-lean, Post-Combustion CO2 Capture Solvent
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Integrated carbon capture and conversion of CO2 into materials (IC3M) is an attractive solution to meet global energy demand, reduce our dependence on fossil fuels, and lower CO2 emissions. Herein, using a water-lean post-combustion capture solvent, [N-(2-ethoxyethyl)-3-morpholinopropan-1-amine] (2-EEMPA), >90 % conversion of captured CO2 to hydrocarbons, mostly methane, is achieved in the presence of a heterogenous Ru catalyst under relatively mild reaction conditions (170 °C and 2 pressure). The catalytic performance was better in 2-EEMPA than in aqueous 5 m monoethanol amine (MEA). Operando nuclear magnetic resonance (NMR) study showed in situ formation of N-formamide intermediate, which underwent further hydrogenation to form methane and other higher hydrocarbons. Technoeconomic analyses (TEA) showed that the proposed integrated process can potentially improve the thermal efficiency by 5 % and reduce the total capital investment and minimum synthetic natural gas (SNG) selling price by 32 % and 12 %, respectively, compared to the conventional Sabatier process, highlighting the energetic and economic benefits of integrated capture and conversion. Methane derived from CO2 and renewable H2 sources is an attractive fuel, and it has great potential as a renewable hydrogen carrier as an environmentally responsible carbon capture and utilization approach.
- Burton, Sarah D.,Dagle, Robert A.,Heldebrant, David J.,Jiang, Yuan,Kothandaraman, Jotheeswari,Saavedra Lopez, Johnny,Walter, Eric D.
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p. 4812 - 4819
(2021/10/07)
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- Development of Highly Stable Ni-Al2O3 Catalysts for CO Methanation
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Abstract: A series of Ni-Al2O3 catalysts with attractive catalytic activity and thermal stability have been developed via a facile hydrolysis-precipitation technique (xNiAl-HP, x representing the weight percentage of NiO). Based on the high nickel active surface area, good dispersion of NiO and high content of α- and β1-type NiO, outstanding CO conversion (99%) and CH4 yield (96%) can be achieved over 40NiAl-HP under mild conditions [T = 220?°C, P = 1.0?MPa, and WHSV = 20,000?mL/(g·h)]. The reaction-sintering at high temperature (800?°C) evolves through: (a) the migration of nickel crystals, (b) the phase transformation from γ- to θ- and then to α-Al2O3, and (c) the agglomeration of catalyst particles. The 40NiAl-HP catalyst could still maintain CO conversion over 99% at 300?°C after being used at 800?°C for 100?h. Herein, the high catalytic activity, good sintering resistance and noble-metal-/promoter-free nature might make 40NiAl-HP a competitive candidate for industrial methanation. Graphic Abstract: [Figure not available: see fulltext.].
- Qin, Zhifeng,Ban, Hongyan,Wang, Xiaoyue,Wang, Zhibin,Niu, Yanxia,Yao, Ying,Ren, Jun,Chang, Liping,Miao, Maoqian,Xie, Kechang,Li, Congming
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p. 2647 - 2657
(2021/01/06)
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- Steric effect induces CO electroreduction to CH4on Cu-Au alloys
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The electrocatalytic reduction of carbon monoxide (CO) is an emerging direction with new catalyst structures, among which the bimetallic component catalysts feature both functional diversity and high-density of active sites. In this work, we demonstrate that the fine tuning of adjacent bimetallic sites can allow us to select different reaction pathways toward C1or C2products in the electroreduction of CO. Cu and Cu-Au alloy catalysts with different atomic ratios were fabricated and investigated for appropriate molecular distances. The pure Cu catalyst was found to be active for electroreducing CO to C2H4, as the adjacent Cu sites were beneficial for adsorbing multiple CO molecules and subsequent C-C coupling. On the other hand, alloying Cu with Au introduced steric hindrance and a larger intermolecular distance between adjacent adsorbed *CO intermediates, thus leading to a decrease of C2H4selectivity but an enhanced CH4pathway. Our work revealed the importance of spacing between active sites for CO electroreduction, which can benefit the catalyst design to further improve activities and selectivities in electrocatalytic CO reduction.
- Guan, Anxiang,Ji, Yali,Li, Si,Qian, Linping,Wang, Qihao,Wu, Limin,Yang, Chao,Zhang, Lijuan,Zheng, Gengfeng
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supporting information
p. 21779 - 21784
(2021/10/12)
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- Machine-Learning-Guided Discovery and Optimization of Additives in Preparing Cu Catalysts for CO2Reduction
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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
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supporting information
p. 5755 - 5762
(2021/05/07)
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- CuAg nanoparticle/carbon aerogel for electrochemical CO2reduction
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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
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p. 18290 - 18295
(2021/10/19)
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- Highly dispersed Co nanoparticles embedded in a carbon matrix as a robust and efficient Fischer-Tropsch synthesis catalyst under harsh conditions
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Preventing the deactivation behavior of Co-based catalysts is a significant challenge during the Fischer-Tropsch synthesis reaction. In this study, a series of catalysts with Co nanoparticles embedded in a matrix of porous carbon are directly synthesizedviaa unique melting approach. It is demonstrated in this work that the loading of Co is highly controllable, and ranges from 20.6-44.0 wt% in the as-prepared samples. The catalyst shows a higher selectivity towards heavy hydrocarbons and a lower selectivity towards methane when compared to the MOF-derived Co@C catalyst tested at a similar CO level. Notably, no obvious deactivation of the catalysts is observed at a high operating temperature of 260 °C, with high CO conversion levels recorded. The special carbon rich environment of the catalyst could inhibit the oxidization and agglomeration of the active phase to prevent deactivation.
- Cai, Zhe,Lyu, Shuai,Chen, Yao,Liu, Chengchao,Zhang, Yuhua,Yu, Faquan,Li, Jinlin
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p. 1059 - 1066
(2021/02/26)
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- Synthesis of C2oxygenates from syngas over UiO-66 supported Rh-Mn catalysts: The effect of functional groups
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UiO-66 and its modified forms (UiO-66-NH2 and UiO-66-OH) were used as supports to prepare Rh-Mn catalysts by using a co-impregnation method, and their catalytic activities were investigated for the direct synthesis of ethanol-based C2+ oxygenates from CO hydrogenation. The catalysts were comprehensively characterized using N2 sorption, XRD, XPS, DRIFT, and TPSR analyses. The structural and textural properties of the catalysts clearly show that Rh and Mn are highly dispersed in the pores of MOFs, but the order of the original structure is partially sacrificed due to the loading of metals and the synergistic effect of Rh, Mn, and Zr would be influenced by various functional groups present in UiO-66. On combining both in situ FT-IR and TPSR analyses, it is confirmed that the higher number of active sites of Rh0 on RM/UiO-66 promotes the CO dissociation ability and hydrogenation rate, which result in its best catalytic activity with the highest yield of C2+ oxygenates, 197.3 g (kg h)-1. This journal is
- Han, Ying,Yu, Jun,Guo, Qiangsheng,Xiao, Xiuzhen,Guo, Xiaoming,Mao, Haifang,Mao, Dongsen
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p. 696 - 704
(2021/01/25)
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- Effect of sodium loading on Pt/ZrO2 during ethanol steam reforming
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Ethanol steam reforming (ESR) was investigated on unpromoted and several sodium promoted Pt/ZrO2 catalysts. From DRIFTS experiments, the following steps during ESR were inferred: dissociation of ethanol to produce ethoxy species; oxidative dehydrogenation of ethoxy species to acetate; and acetate decomposition. Acetate decomposition depends on the catalyst formulation. Decarboxylation is the most favored route at high sodium loading (2.5 and 5 wt.%); acetate decomposes in the forward direction to CH4 and a carbonate, which further decomposes to CO2. In contrast, decarbonylation is prevalent for the unpromoted catalyst or catalysts having low sodium loading. Acetate likely decomposes to CH3OH and CO. Adsorbed methanol may undergo further steam reforming by oxidative dehydrogenation to formate species, which decarbonylates via reverse decomposition to CO and H2O. Temperature programmed desorption/reaction and activity data confirmed that alkali promotion, especially at 1.8 %Na and higher loading, facilitates the forward acetate decomposition step, favoring decarboxylation over decarbonylation.
- Alhraki, Nour,Castro, Jonathan D.,Cronauer, Donald C.,Jacobs, Gary,Kropf, A. Jeremy,Martinelli, Michela,Matamoros, Maria E.
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- Elucidation of the role of support in Rh/perovskite catalysts used in ethanol steam reforming reaction
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Rh/perovskite catalysts were prepared and evaluated in ethanol steam reforming reaction. The samples were characterized by SBET, XRD, XPS, TPR, TG and SEM techniques. It could be possible to obtain perovskites supports with high purity, stability and suitable specific surface areas. The partial substitution of La with Ca and Ce in a LaAlO3 based perovskite structure was reached and changes in its porosity and surface features were detected. The inclusion of Ca into the structure increased specific surface area of support and Ce inclusion activated oxygen mobility on catalyst surface. The supports influenced the degree of reduction of Rh species at the surface of catalysts. All catalyst showed complete ethanol conversion on 6 h on stream. The best catalytic performance was achieved with Rh/LaAlO3 0.3 % catalyst which presented the highest mean value of H2 product distribution, low production of byproducts (CH4 and CO) and presented an excellent long term experience performance during 24 h on stream. Rh/LaCeAlO3 0.3 % presented the lowest carbon accumulation during 6 h on stream but it suffered deactivation after 14 h on stream. The deactivation was attributed to the partial oxidation of Rh° species to Rh3+ which are less active favoring a reaction pathway that produce carbonaceous deposits.
- Martínez, Asiel Hernández,Lopez, Eduardo,Cadús, Luis E.,Agüero, Fabiola N.
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- Chelating agent effects in the synthesis of supported Ni nanoparticles as catalysts for hydrogen production
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A series of Ni supported over MgAl2O4–CeO2 catalysts have been prepared by the wet impregnation method as catalysts for steam ethanol reforming. The synthesis was performed using nitrilotriacetic acid (NTA) or citric acid (CA) as chelating agents (L) with different L/Ni molar ratios. The features of catalytic solids were determined by DR–UV–Vis–NIR, FTIR, BET, TGA, XRD, H2–TPR, XPS, Raman, HRTEM and SEM. Changes in the crystallite size of NiO and CeO2 were evidenced with the use of NTA, while the addition of CA allowed to reduce the crystallite size of NiO and Ni with a slight effect in CeO2 size. The use of chelating agents induced changes in the Ni-CeO2 interactions and an increase in the Ce/Ni0 surface ratio. Catalytic systems prepared using an L/Ni ratio leading to the most stable complex formation (NTA/Ni=1 and CA/Ni=2) exhibited the best performances in the reforming reaction under the operation conditions studied.
- Abello, María C.,Barroso, Mariana N.,López, Carlos A.,Llorca, Jordi,Villagran?Olivares, Alejandra C.
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- A stable low-temperature H2-production catalyst by crowding Pt on α-MoC
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The water–gas?shift (WGS) reaction is an industrially important source of pure hydrogen (H2) at the expense of carbon monoxide and water1,2. This reaction is of interest for fuel-cell applications, but requires WGS catalysts that are durable and highly active at low temperatures3. Here we demonstrate that the structure (Pt1–Ptn)/α-MoC, where isolated platinum atoms (Pt1) and subnanometre platinum clusters (Ptn) are stabilized on α-molybdenum carbide (α-MoC), catalyses the WGS reaction even at 313?kelvin, with a hydrogen-production pathway involving?direct carbon monoxide dissociation identified. We find that it is critical to crowd the α-MoC surface with Pt1 and Ptn species, which prevents oxidation of the support that would cause catalyst deactivation, as seen with gold/α-MoC (ref. 4), and gives our system high stability and a high metal-normalized turnover number of 4,300,000 moles of hydrogen per mole of platinum.?We anticipate that?the strategy demonstrated here will be pivotal for?the design of highly active and stable catalysts for effective activation of important molecules such as?water and carbon monoxide for energy production.
- Zhang, Xiao,Zhang, Mengtao,Deng, Yuchen,Xu, Mingquan,Artiglia, Luca,Wen, Wen,Gao, Rui,Chen, Bingbing,Yao, Siyu,Zhang, Xiaochen,Peng, Mi,Yan, Jie,Li, Aowen,Jiang, Zheng,Gao, Xingyu,Cao, Sufeng,Yang, Ce,Kropf, A. Jeremy,Shi, Jinan,Xie, Jinglin,Bi, Mingshu,van Bokhoven, Jeroen A.,Li, Yong-Wang,Wen, Xiaodong,Flytzani-Stephanopoulos, Maria,Shi, Chuan,Zhou, Wu,Ma, Ding
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p. 396 - 401
(2021/01/28)
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- CATALYST AND METHOD FOR PREPARING LIGHT OLEFIN USING DIRECT CONVERSION OF SYNGAS
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A catalyst for preparing light olefin using direct conversion of syngas is a composite catalyst and formed by compounding component I and component II in a mechanical mixing mode. The active ingredient of component I is a metal oxide; and the component II is one or more than one of zeolite of CHA and AEI structures or metal modified CHA and/or AEI zeolite. A weight ratio of the active ingredients in the component Ito the component II is 0.1-20. The reaction process has high product yield and selectivity, wherein the sum of the selectivity of the propylene and butylene reaches 40-75%; and the sum of the selectivity of light olefin comprising ethylene, propylene and butylene can reach 50-90%. Meanwhile, the selectivity of a methane side product is less than 15%.
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Paragraph 0082; 0085
(2021/04/30)
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- CATALYST, AND METHOD FOR DIRECT CONVERSION OF SYNGAS TO PREPARE LIGHT OLEFINS
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A process for direct synthesis of light olefins uses syngas as the feed raw material. This catalytic conversion process is conducted in a fixed bed or a moving bed using a composite catalyst containing components A and B (A+B). The active ingredient of catalyst A is metal oxide; and catalyst B is an oxide supported zeolite. A carrier is one or more of Al2O3, SiO2, TiO2, ZrO2, CeO2, MgO and Ga2O3 having hierarchical pores; the zeolite is one or more of CHA and AEI structures. The loading of the zeolite is 4%-45% wt. A weight ratio of the active ingredients in the catalyst A and the catalyst B is within a range of 0.1-20, and preferably 0.3-5. The total selectivity of the light olefins comprising ethylene, propylene and butylene can reach 50-90%, while the selectivity of a methane byproduct is less than 15%.
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Paragraph 0064-0067
(2021/01/26)
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- METHOD FOR PREPARING LIGHT OLEFIN THROUGH CATALYTIC SYNGAS WITH HIGH SELECTIVITY BY HETEROATOM-DOPED ZEOLITE
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A composite catalyst containing heteroatom-doped zeolite for preparing light olefin using direct conversion of syngas formed by compounding component I and component II in a mechanical mixing mode. The active ingredient of component I is a metal oxide, and the component II is a heteroatom-doped zeolite. The zeolite topology is CHA or AEI, and the skeleton atoms include Al—P—O or Si—Al—P—O; the heteroatoms is at least one of divalent metal Mg, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, Mo, Cd, Ba and Ce, trivalent metal Ti and Ga, and tetravalent metal Ge. A weight ratio of the active ingredient in the component I to the component II is 0.1-20. The reaction process has high light olefin selectivity; the sum selectivity of the light olefin including ethylene, propylene and butylene can reach 50-90%, while the selectivity of a methane side product is less than 7%.
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Paragraph 0077-0079
(2021/11/13)
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- Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity
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An efficient tandem hydrosilylation of CO2, which uses a combination of a simple, homoleptic lanthanum aryloxide and B(C6F5)3, was performed. Use of a less sterically hindered silane led to an exclusive reduction of CO2to CH4, with a turnover frequency of up to 6000 h?1at room temperature. The catalytic system is robust, and 19?400 turnovers could be achieved with 0.005 mol% loading of lanthanum. The reaction outcome depended highly on the nature of the silane reductant used. Selective production of the formaldehyde equivalent,i.e., bis(silyl)acetal, without over-reduction, was observed when a sterically bulky silane was used. The reaction mechanism was elucidated by stoichiometric reactions and DFT calculations.
- Chang, Kejian,Maron, Laurent,Xu, Xin,Zheng, Xizhou,del Rosal, Iker
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supporting information
p. 7804 - 7809
(2021/06/16)
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- Highly active carbon nanotube–promoted Rh-Mn-Li/SiO2 catalysts for the synthesis of C2+ oxygenates from syngas
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The effect of carbon nanotubes on the catalytic properties of Rh-Mn-Li/SiO2 catalysts was investigated for CO hydrogenation. The catalysts were comprehensively characterized by means of X-ray power diffraction, N2 sorption, transmission electron microscope, H2–temperature-programmed reduction, CO–temperature-programmed desorption, temperature-programmed surface reaction, and X-ray photoelectron spectroscopy. The results showed that an appropriate amount of carbon nanotubes can be attached to the surface of the SiO2 sphere and can improve the Rh dispersion. Moderate Rh-Mn interaction can be obtained by doping with the appropriate amount of carbon nanotubes, which promotes the formation of strongly adsorbed CO and facilitates the progress of CO insertion, resulting in the increase in the selectivity of C2+ oxygenate synthesis.
- Chen, Guoqing,Han, Ying,Mao, Dongsen,Mao, Haifang,Xiao, Xiuzhen,Yu, Jun
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p. 436 - 442
(2021/01/11)
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- Symmetry-Broken Au–Cu Heterostructures and their Tandem Catalysis Process in Electrochemical CO2 Reduction
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Symmetry-breaking synthesis of colloidal nanocrystals with desired structures and properties has aroused widespread interest in various fields, but the lack of robust synthetic protocols and the complex growth kinetics limit their practical applications. Herein, a general strategy is developed to synthesize the Au–Cu Janus nanocrystals (JNCs) through the site-selective growth of Cu nanodomains on Au nanocrystals, which is directed by the substantial lattice mismatch between them, with the assistance of judicious manipulation of the growth kinetics. This strategy can work on Au nanocrystals with different architectures for the achievement of diverse asymmetric Au–Cu hybrid nanostructures. Of particular note, the obtained Au nanobipyramids (Au NBPs)-based JNCs facilitate the conversion of CO2 to C2 hydrocarbon production during electrocatalysis, with the Faradaic efficiency and maximum partial current density being 4.1-fold and 6.4-fold higher than those of their monometallic Cu counterparts, respectively. The excellent electrocatalytic performances benefit from the special design of the Au–Cu Janus architectures and their tandem catalysis mechanism as well as the high-index facets on Au nanocrystals. This research provides a new approach to synthesize various hybrid Janus nanostructures, facilitating the study of structure-function relationship in the catalytic process and the rational design of efficient heterogeneous electrocatalysts.
- Jia, Henglei,Yang, Yuanyuan,Chow, Tsz Him,Zhang, Han,Liu, Xiyue,Wang, Jianfang,Zhang, Chun-yang
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- Partial Coordination-Perturbed Bi-Copper Sites for Selective Electroreduction of CO2 to Hydrocarbons
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In the electrochemical CO2 reduction reaction (CO2RR), it is challenging to develop a stable, well-defined catalyst model system that is able to examine the influence of the synergistic effect between adjacent catalytic active sites on the selective generation of C1 or C2 products. We have designed and synthesized a stable crystalline single-chain catalyst model system for electrochemical CO2RR, which involves four homomorphic one-dimensional chain-like compounds (Cu-PzH, Cu-PzCl, Cu-PzBr, and Cu-PzI). The main structural difference of these four chains is the substituents of halogen atoms with different electronegativity on the Pz ligands. Consequently, different synergistic effects between bi-copper centers lead to changes in the faradic efficiency (FE (Formula presented.) :FE (Formula presented.)). This work provides a simple and stable crystalline single-chain model system for systematically studying the influence of coordination microenvironment on catalytically active centers in the CO2RR.
- Dong, Long-Zhang,Huang, Qing,Lan, Ya-Qian,Li, Shun-Li,Liu, Jiang,Wang, Rui
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supporting information
p. 19829 - 19835
(2021/08/03)
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- Facile preparation of ZnO:g-C3N4 heterostructures and their application in amiloride photodegradation and CO2 photoreduction
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Semiconductor heterojunctions are interesting strategies for the development of efficient photocatalysts. In this paper we report the synthesis of ZnO:g-C3N4 heterostructures with different percentages of g-C3N4
- de Jesus Martins, Nailma,Gomes, Isabel C.H.,da Silva, Gelson T.S.T.,Torres, Juliana A.,Avansi, Waldir,Ribeiro, Caue,Malagutti, Andréa R.,Mour?o, Henrique A.J.L.
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- Photocatalytic C-C coupling from carbon dioxide reduction on copper oxide with mixed-valence copper(I)/copper(II)
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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
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supporting information
p. 2984 - 2993
(2021/03/01)
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- Copper Nanocrystal Morphology Determines the Viability of Molecular Surface Functionalization in Tuning Electrocatalytic Behavior in CO2Reduction
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Molecular surface functionalization of metallic catalysts is emerging as an ever-developing approach to tuning their catalytic performance. Here, we report the synthesis of hybrid catalysts comprising copper nanocrystals (CuNCs) and an imidazolium ligand for the electrochemical CO2 reduction reaction (CO2RR). We show that this organic modifier steers the selectivity of cubic CuNCs toward liquid products. A comparison between cubic and spherical CuNCs reveals the impact of surface reconstruction on the viability of surface functionalization schemes. Indeed, the intrinsic instability of spherical CuNCs leads to ejection of the functionalized surface atoms. Finally, we also demonstrate that the more stable hybrid nanocrystal catalysts, which include cubic CuNCs, can be transferred into gas-flow CO2RR cells for testing under more industrially relevant conditions.
- Pankhurst, James R.,Iyengar, Pranit,Okatenko, Valery,Buonsanti, Raffaella
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supporting information
p. 6939 - 6945
(2021/05/06)
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- Highly Selective CO2Electroreduction to C2H4Using a Metal-Organic Framework with Dual Active Sites
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Conversion from CO2 to C2H4 is important for the development of energy and the environment, but the high energy barrier of hydrogenation of the *CO intermediate and C-C coupling step tend to result in C1 compounds as the main product and thus restrict the generation of C2H4. Here, we report a metal-organic framework (denoted as PcCu-Cu-O), composed of 2,3,9,10,16,17,23,24-octahydroxyphthalo-cyaninato)copper(II) (PcCu-(OH)8) ligands and the square-planar CuO4 nodes, as the electrocatalyst for CO2 to C2H4. Compared with the discrete molecular copper-phthalocyanine (Faradaic efficiency (FE) of C2H4 = 25%), PcCu-Cu-O exhibits much higher performance for electrocatalytic reduction of CO2 to C2H4 with a FE of 50(1)% and a current density of 7.3 mA cm-2 at the potential of -1.2 V vs RHE in 0.1 M KHCO3 solution, representing the best performance reported to date. In-situ infrared spectroscopy and control experiments suggested that the enhanced electrochemical performance may be ascribed to the synergistic effect between the CuPc unit and the CuO4 unit, namely the CO on the CO-producing site (CuO4 site) can efficiently migrate and dimerize with the *CO intermediate adsorbed on the C2H4-producing site (CuPc), giving a lower C-C dimerization energy barrier.
- Qiu, Xiao-Feng,Zhu, Hao-Lin,Huang, Jia-Run,Liao, Pei-Qin,Chen, Xiao-Ming
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supporting information
p. 7242 - 7246
(2021/05/26)
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