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Can TiO2 promote the reduction of nitrates in water?
Monometallic palladium catalysts were synthesized using different titanium supports and tested for the reduction of nitrates from aqueous solutions using hydrogen as a reductant. The Pd/TiO2 catalysts were characterized by electron paramagnetic resonance (EPR), low-temperature Fourier transform infrared (FTIR) spectroscopy of adsorbed CO, and X-ray diffraction (XRD). The catalysts studied exhibited a high activity for nitrate removal with a lower tendency for nitrite formation than the conventional bimetallic Pd catalysts. Although ammonium formation was greater than desired, the use of a monometallic catalyst for this two-step reduction process is significant and suggests that a single site may be responsible for both reduction stages. The titanium support (particularly the Ti3+ centers generated during prereduction in the presence of Pd) appear to play an important role in the nitrate degradation process. The potential role of Pd β-hydride in generating these Ti 3+ centers is discussed.
Sa, Jacinto,Berger, Thomas,Foettinger, Karin,Riss, Alexander,Anderson, James A.,Vinek, Hannelore
p. 282 - 291
(2005)
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Complexation of nitrous oxide by frustrated lewis pairs
(Figure Presented) Frustrated Lewis pairs comprised of a basic yet sterically encumbered phosphine with boron Lewis acids bind nitrous oxide to give intact PNNOB linkages. The synthesis, structure, and bonding of these species are described.
Otten, Edwin,Neu, Rebecca C.,Stephan, Douglas W.
p. 9918 - 9919
(2009)
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Reaction between NOx and NH3 on Iron Oxide-Titanium Oxide Catalyst
The reduction of NOx (NO2 alone or mixture of NO and NO2) with NH3 on iron oxide-titanium oxide catalyst was studied using a flow reactor.The reaction between NO2 and NH3 proceeds at 3:4 mole ratio in the presence or absence of oxygen.When the reaction gas mixture contain equal amounts of NO and NO2, the reaction consuming equimolal NO and NO2 proceeds preferentially at a NH3/NOx ratio of unity.The rate of the reaction is faster than either the NO-NH3 or NO2-NH3 reaction.The overall reactions between NOx (NO2, NO+NO2) and NH3 are given as 6NO2+8NH3->7N2+12H2O and NO+NO2+2NH3->2N2+3H2O.Reaction mechanisms are proposed to explain the experimental results.
Kato, Akira,Matsuda, Shimpei,Kamo, Tomoichi,Nakajima, Fumito,Kuroda, Hiroshi,Narita, Tsuneo
p. 4099 - 4102
(1981)
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Characterization of vanadium and titanium oxide supported SBA-15
Supported vanadium and titanium oxide catalysts were prepared by adsorption and subsequent calcination of the vanadyl and titanyl acetylacetonate complexes, respectively, on mesoporous SB A-15 by the molecular designed dispersion (MDD) method. Liquid and gas phase depositions at different temperatures were carried out with vanadyl acetylacetonate, and the different results together with those of titanyl acetylacetonate in the liquid phase deposition were discussed. The bonding mechanism, the influence of the metal interaction with the support material, and differences due to the way of deposition and the temperature were investigated by TGA, chemical analysis, FTIR, and Raman spectroscopy. Elevated dissolving temperatures in the liquid phase led to higher final loadings on the SBA-15 without the formation of clusters, even at high loadings. The decomposition of the anchored vanadium and titanium complexes, their thermal stability, and the conversion to the covalently bound VOX and TiOx species on SBA-15 were studied and investigated by in situ transmission IR spectroscopy. In general, the titanium complex is more reactive than the vanadium complex toward the surface of SBA-15 and has a higher thermal stability. The MDD method of the VO(acac)2 and TiO(acac)2 enables to create a dispersed surface of supported VOx and TiOx, respectively. The structure configurations of VOx and TiOx oxide catalysts obtained at different metal loadings were studied by Raman spectroscopy. Pore size distributions, XRD, and N2 sorption confirmed the structural stability of these materials after grafting. VOx/SBA-15 and TiO x/SBA-15 samples, with different metal loadings, were also catalytically tested for the selective catalytic reduction (SCR) of NO with ammonia. ? 2005 American Chemical Society.
Segura,Cool,Kustrowski,Chmielarz,Dziembaj,Vansant
p. 12071 - 12079
(2005)
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The 193 (and 248) nm photolysis of HN3: Formation and internal energy distributions of the NH (a1Δ, b1Σ+, A3Π, and c1Π) states
The UV photolysis of HN3 at 193 nm was investigated in detail in the bulk phase at 300 K.NH radicals in the X, a, b, A, and c states were found to be formed with quantum yields 0.0019 , 0.4, 0.017, 0.00015, and 0.000 61, respectively.Relative rotational and vibrational populations were measured for all states except for NH(X).Average translational energies were estimated for NH(a,ν = 0 and 1 ) and NH(b,ν = 0).The 248 nm photolysis of HN3 was reinvestigated with respect to processes forming NH radicals other than NH(a).The observed energy distributions differ for both laser wavelengths and for high and low lying NH states.The distribution can be better described by a simple impulsive than by a statistical model.Some conclusions are drawn concerning the upper HN3 potential surfaces involved.
Rohrer, F.,Stuhl, F.
p. 4788 - 4799
(1988)
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Photocatalytic reduction of nitrate over chalcopyrite CuFe0.7Cr0.3S2 with high N2 selectivity
Photocatalytic reduction of nitrate (NO3-) is a green and potentially inexpensive technique for reducing NO3- pollution in ground water. TiO2-based photocatalysts have been studied extensively for this purpose. In the present study, the semiconducting catalyst CuFe0.7Cr0.3S2 was applied to NO3- reduction. Loading this catalyst with metal co-catalysts (Ru, Au, Cu, Ag, Pt, and Pd) greatly increased the rate of NO3- reduction and the N2 selectivity. In addition, there was a synergistic enhancement of the photocatalytic performance when the catalyst was loaded two co-catalysts. For example, the catalyst loaded with Pd and Au at mass fractions of 0.75% and 3%, respectively, could photocatalyze the complete reduction of NO3- in a 100 ppm N aqueous solution with 100% N2 selectivity in less than 5 h with UV irradiation. However, with an inner irradiation from a full-arc Xe lamp, the NO3- conversion rate reduced to 0.065 mg N/h, probably because of the low density of the photoexcited electrons. The results show the potential of metal sulfides for photocatalytic reduction of NO3-, and the possibility of use of visible light.
Wang, Rong,Yue, Mufei,Cong, Rihong,Gao, Wenliang,Yang, Tao
p. 731 - 736
(2015)
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Oscillations in the N2O-H2 reaction over Ir(1 1 0). Route to chaos
The study described in the present paper is focused on the N2O-H2 reaction on the Ir(1 1 0) surface and, in particular, on different kinds of oscillatory behaviour, including the route to chaos. Oscillations in rate were observed in the temperature range between 460 and 464 K, at a N2O pressure of 1 × 10-6 mbar with H2/N2O ratios close to 1. Upon minor changes in the H2/N2O ratio, a series of period doublings is observed, resulting finally in aperiodic behaviour.
Carabineiro, Sónia A.C.,Van Noort, Wibo D.,Nieuwenhuys, Bernard E.
p. 96 - 102
(2003)
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Nature and catalytic role of active silver species in the lean NO x reduction with C3H6 in the presence of water
A study of the lean NOx reduction activity with propene in the presence of water over Ag/Al2O3 catalysts with different silver loadings (1.5-6 wt%) has been done using X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy, and in situ diffuse reflectance infrared and X-ray absorption spectroscopies under reaction conditions. The catalysts were prepared by an impregnation method employing EDTA complexes that allow highly dispersed silver phases to be obtained, which are stabilized under reaction conditions by strong interactions with the support. It is shown that the active species corresponds to silver aluminate-like phases with tetrahedral local symmetry. The role of silver in the reaction mechanism is shown to be mainly in the activation of NO x and propene species. In particular, the silver entities have been found to offer a new reaction path for propene activation which involves generation of acrylate species as a partially oxidized active intermediate. Differences between two active catalysts containing 1.5 and 4.5 wt% of Ag suggest that optimization of the SCR activity can be related to the oxygen lability of the tetrahedral silver aluminate-like phase present in the catalyst. As postulated previously, the high nonselective propene oxidation activity of the highest loaded sample (with 6 wt% Ag) appears to be related to formation of metallic silver surface states at low reaction temperatures which are active for NO dissociation.
Iglesias-Juez,Hungria,Martinez-Arias,Fuerte,Fernandez-Garcia,Anderson,Conesa,Soria
p. 310 - 323
(2003)
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Nano-spatially confined Pd-Cu bimetals in porous N-doped carbon as an electrocatalyst for selective denitrification
Bimetals have attracted considerable attention as electrocatalysts towards selective reduction of nitrate to benign dinitrogen. Design of highly efficient and stable bimetallic catalysts by taking the effects of both active sites increasing and synergistic composition into account is of paramount importance but still a grand challenge. Herein we report novel bimetallic Pd-Cu nanoparticles (NPs) incorporated in porous N-doped carbon octahedra prepared by a spatial confinement strategy ofin situpyrolysis of metal-organic frameworks with the assistance of polyvinyl pyrrolidone (PVP) as electrocatalysts achieving targeted denitrification. Pd-Cu NPs exhibit superior dispersity with a N-doped matrix and are strongly dependent on the variation of PVP, Pd precursor and pyrolysis temperature. The material shows high efficiency (~97.1%) for the reduction of nitrate from 100 to 2.9 mg NO3--N L-1(well below drinking water standards of 10 mg NO3--N L-1), and especially the selectivity over 83% for benign N2at neutral pH within 24 h. Encapsulated and well-dispersed Pd-Cu NPs and doped N in the carbonaceous matrix synergistically enhance the interfacial electron transfer for transformation of NO3--N(v). Porous structures endow the catalyst with outstanding stability after eight cycles and over a wide pH of 4-10. More importantly, the nanocatalyst performs well with real contaminated water (selectivity of 91% for nitrogen) in laboratory batch reactors. This nanocatalyst shows promise in wastewater treatment and environmental remediation due to the spatial confinement strategy and introduction of heterogeneous atoms.
Bai, Nan,Chen, Zehan,Fan, Jianwei,Gu, Tianhang,Teng, Wei,Zhang, Wei-Xian,Zhao, Dongyuan
p. 9545 - 9553
(2020)
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Promotional effects of Zr on K+-poisoning resistance of CeTiOx catalyst for selective catalytic reductionof NOx with NH3
CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 (NH3-SCR). Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K+-poisoning resistance of the CeTiOx catalyst. The NH3-SCR performance of the catalysts showed that the NOx removal activity of the Zr-modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunauer-Emmett-Teller data indicated that the Zr-containing catalyst had a larger specific surface area and pore volume both before and after K+ poisoning. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X-ray photoelectron spectra showed that the Ce3+/Ce4+ ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K+ loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3-SCR performance; the temperature-programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K+-poisoning resistance of the CeTiOx catalyst.
Xu, Baoqiang,Xu, Haidi,Lin, Tao,Cao, Yi,Lan, Li,Li, Yuanshan,Feng, Xi,Gong, Maochu,Chen, Yaoqiang
p. 1354 - 1361
(2016)
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Deactivation of Cu-Exchanged Automotive-Emission NH3-SCR Catalysts Elucidated with Nanoscale Resolution Using Scanning Transmission X-ray Microscopy
To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NOx with an ammonia reductant, we employed scanning transmission X-ray microscopy (STXM) to study Cu-exchanged zeolites with the CHA and MFI framework structures before and after simulated 135 000-mile aging. X-ray absorption near-edge structure (XANES) measurements were performed at the Al K- and Cu L-edges. The local environment of framework Al, the oxidation state of Cu, and geometric changes were analyzed, showing a multi-factor-induced catalytic deactivation. In Cu-exchanged MFI, a transformation of CuII to CuI and CuxOy was observed. We also found a spatial correlation between extra-framework Al and deactivated Cu species near the surface of the zeolite as well as a weak positive correlation between the amount of CuI and tri-coordinated Al. By inspecting both Al and Cu in fresh and aged Cu-exchanged zeolites, we conclude that the importance of the preservation of isolated CuII sites trumps that of Br?nsted acid sites for NH3-SCR activity.
Chen, Tiehong,Meirer, Florian,Oord, Ramon,Schmidt, Joel E.,Wang, Ru-Pan,Weckhuysen, Bert M.,Ye, Xinwei,de Groot, Frank,van Ravenhorst, Ilse K.
p. 15610 - 15617
(2020)
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MnO2-GO-scroll-TiO2-ITQ2 as a low-temperature NH3-SCR catalyst with a wide SO2-tolerance temperature range
Three steps are needed to improve the steam-resistance and SO2-resistance of a catalyst for the selective catalytic reduction of NOx through NH3 at low temperature: the first is to introduce a protective layer to reduce the direct contact between SO3 and the catalyst. Then, there is delayed oxidation, which fundamentally reduces the oxidation of SO2 to SO3. If the catalyst is used at a relatively high temperature, it will inevitably produce SO3. The third step is to add a strong acid site in addition to reducing the acidity of the catalyst, which first absorbs NH3 and then absorbs SO3, to seize NH4HSO4, so that it does not cover the active site. GO was used to curl and wrap around the outside of MnO2 nanowires as a protective layer. TiO2 was selectively deposited on oxygen-containing functional groups on GO, which delayed the oxidation ability of the catalyst. ITQ2 molecular sieves acted as strong acid sites to absorb NH4HSO4. The curling behavior of GO outside MnO2 nanowires, the deposition location of TiO2 and the distribution of ITQ2 were explained by morphology and elemental analysis. In the range of 150 °C to 280 °C, the MnO2-GO-scroll-TiO2-ITQ2 catalyst conversion of NO to N2 was more than 85%. Combined with H2-TPR and activity testing, the source of the wide SO2-tolerance temperature range of the catalyst was described in detail.
Sun, Liwei,Zhang, Zeshu,Tian, Heyuan,Liu, Peng,Zhang, Yibo,Yang, Xiangguang
p. 1733 - 1738
(2020)
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Study of anode catalysts and fuel concentration on direct hydrazine alkaline anion-exchange membrane fuel cells
A platinum-free fuel cell using liquid hydrazine hydrate (N 2H4·H2O) as the fuel and comprised of a cobalt or nickel anode and a cobalt cathode exhibits high performance. In this study, the fuel cell performances using nic
Asazawa, Koichiro,Sakamoto, Tomokazu,Yamaguchi, Susumu,Yamada, Koji,Fujikawa, Hirotoshi,Tanaka, Hirohisa,Oguro, Keisuke
p. B509-B512
(2009)
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Enhanced NH3 Selective catalytic reduction for NO xAbatement
Enhanced NO reduction efficiencies, close to those obtained under the conditions of fast selective catalytic reduction (SCR; see diagram), were achieved over commercial vanadium and ironexchanged zeolite SCR catalysts at low temperatures (200-300°C) in th
Forzatti, Pio,Nova, Isabella,Tronconi, Enrico
p. 8366 - 8368
(2009)
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Photoelectrochemical conversion of NO3- to N 2 by using a photoelectrochemical cell composed of a nanoporous TiO2 film photoanode and an O2 reducing cathode
Photoelectrochemical conversion of nitrate anions into dinitrogen was successfully achieved by using a photoelectrochemical cell composed of a nanoporous TiO2 film photoanode and an O2 reducing cathode in the presence of NH3/su
Saito, Rie,Ueno, Hirohito,Nemoto, Junichi,Fujii, Yuki,Izuoka, Akira,Kaneko, Masao
p. 3231 - 3233
(2009)
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Promoting effects of Na and Fe impurities on the catalytic activity of CaO in the reduction of NO by CO and H2
The heterogeneous reduction of NO by H2 and CO over different CaO materials is investigated. The dependence of the specific NO reduction rate on the impurity content is demonstrated for both reducing species. The roles of two specific impurities, i.e., Na and Fe, as well as their combined effect are investigated. The apparent activation energies for the NO + CO and NO + H2 reactions are determined for three different calcium oxides. Values between 26 and 28 kcal/mol are obtained. The influence of impurity content is found in the preexponential factor of the Arrhenius equation. A reaction mechanism based on a rate-determining surface-oxygen-abstraction step is suggested. This mechanistic understanding is explored to compare the activities of other alkaline-earth oxides. Particularly, a linear correlation between the apparent activation energy and the lattice parameter is observed.
Acke, Filip,Panas, Itai
p. 5127 - 5134
(1998)
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Catalytic oxidation of ammonia on RuO2(110) surfaces: Mechanism and selectivity
The selective oxidation of ammonia to either N2 or NO on RuO2(110) single-crystal surfaces was investigated by a combination of vibrational spectroscopy (HREELS), thermal desorption spectroscopy (TDS) and steady-state rate measurements under continuous flow conditions. The stoichiometric RuO2(110) surface exposes coordinatively unsaturated (cus) Ru atoms onto which adsorption of NH3 (NH3-cus) or dissociative adsorption of oxygen (O-cus) may occur. In the absence of O-cus, ammonia desorbs completely thermally without any reaction. However, interaction between NH3-cus and O-cus starts already at 90 K by hydrogen abstraction and hydrogenation to OH-cus, leading eventually to N-cus and H 2O. The N-cus species recombine either with each other to N 2 or with neighboring O-cus leading to strongly held NO-cus which desorbs around 500 K. The latter reaction is favored by higher concentrations of O-cus. Under steady-state flow condition with constant NH3 partial pressure and varying O2 pressure, the rate for N2 formation takes off first, passes through a maximum and then decreases again, whereas that for NO production exhibits an S-shape and rises continuously. In this way at 530 K almost 100% selectivity for NO formation (with fairly high reaction probability for NH3) is reached.
Wang,Jacobi,Sch?ne,Ertl
p. 7883 - 7893
(2005)
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Facile synthesis of Pd-Co-P ternary alloy network nanostructures and their enhanced electrocatalytic activity towards hydrazine oxidation
Porous ternary Pd-Co-P alloy network nanostructures were synthesized by reducing K2PdCl4/K3Co(CN)6 cyanogel with a mixture of NaH2PO2 and NaBH4 at room temperature, which show superior electrocatalytic activity and stability towards hydrazine oxidation reaction.
Zhang, Lu,Lu, Dingkun,Chen, Yu,Tang, Yawen,Lu, Tianhong
p. 1252 - 1256
(2014)
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A remarkable catalyst combination to widen the operating temperature window of the selective catalytic reduction of NO by NH3
On the basis of the idea of combining high selective catalytic reduction (SCR) activity, high N2 selectivity, and broad operating temperature window, we developed a combined catalyst process that was found to be a convenient way to design a highly efficient SCR process for NO with NH 3. The single catalysts of MnOx-CeO2/TiO 2 and V2O5-WO3/TiO2 as well as combined catalysts with different configurations were fully characterized by XRD, temperature-programmed reduction of H2, and temperature-programmed desorption of NO/O2. In addition, they were tested for the oxidation of NO or NH3 as well as the SCR of NO with NH3. The correlations between combining configurations and SCR activity results were also revealed. Furthermore, fundamental evidences were given for the rational design of the process and its efficiency maximization (assembly order and catalytic bed volume). An adequate configuration, with MnOx-CeO2/TiO2 and V2O 5-WO3/TiO2 active materials, ensures an excellent SCR performance (NO conversion >85%, N2 yield >70%, and decreased N2O production) over a wide operating temperature window (from 150 to 400°C).
Zhang, Runduo,Liu, Ning,Luo, Zhen,Yang, Wei,Liang, Xin,Xu, Ruinian,Chen, Biaohua,Duprez, Daniel,Royer, Sebastien
p. 2263 - 2269
(2014)
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Structural properties and photocatalytic activity of ceria nanoparticles on vermiculite matrix
Clay mineral matrices and metal oxides are of current interest because of their high thermal stability, large surface area, and good catalytic and adsorption properties. Cerium oxide (ceria, CeO2) nanoparticles was obtained by interaction of ve
Valá?ková, Marta,Kupková, Jana,Ko?í, Kamila,Ambro?ová, Nela,Klemm, Volker,Rafaja, David
p. 7844 - 7848
(2016)
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Selective catalytic reduction of NO by ammonia over Fe-ZSM-5 catalysts
In the selective catalytic reduction (SCR) of NO by ammonia, over-exchanged Fe-ZSM-5 prepared by sublimation of FeCl3 into H-ZSM-5, shows superior catalytic activity and stability in a wide temperature range; its activity is promoted by the presence of water in the feed while SO2 is a weak poison at low but a promoter at high temperatures; its remarkable durability towards H2O and SO2 makes this zeolite catalyst a potential choice in Denox applications for stationary sources and heavy Diesel engines with ammonia or urea reductants.
Ma, Ai-Zeng,Gruenert
p. 71 - 72
(1999)
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Anisotropy and Energy Disposal in the 193-nm N2O Photodissociation Measured by VUV Laser-Induced Fluorescence of O(1D)
Laser induced fluorescence near 115 nm has been used to measure the Doppler profile of the O(1D) product of 193-nm N2O photolysis.The anisotropy of product recoil vectors is characterized by the paramter β = 0.50 +/- 0.05.The measured velocity distribution can be used to calculate a distribution of recoil energies that is in reasonable agreement with that reported recently by Felder, Haas, and Huber; an average of 27.3 kcal/mol is deposited into translation, leaving ca. 37 kcal/mol for the internal excitation of the N2 fragment.
Springsteen, L. L.,Satyapal, S.,Matsumi, Y.,Dobeck, L. M.,Houston, P. L.
p. 7239 - 7241
(1993)
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Catalytic Oxidation of Ammonia over the SiO2-Pillared Oxycompounds Containing Titanium and Manganese with Layered Structure
A SiO2-pillared manganese titanate (SiO2-MTO) with layered structure, which has a surface area as large as more than 700 m2/g, effectively catalyzed the NH3 oxidation with high selectivity to N2. The H2 temperature-programmed reduction results suggested that the manganese ions in SiO2-MTO were in an oxidation state of +3 even in the absence of either Rb+ or C10H21NH3+ ions as a charge-balancing cation. The observed high selectivity to N2 is attributable to oxygen vacancies associated with Mn3+ ions in the layer.
Yahiro, Hidenori,Nakai, Toshihiro,Shiotani, Masaru,Yamanaka, Shoji
p. 249 - 252
(1999)
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Low-temperature hydrogen-selective catalytic reduction of NOx on Pt/sulfated-ZrO2 catalysts under excess oxygen conditions
Platinum catalysts supported on sulfated zirconia powders highly promote the hydrogen-selective catalytic reduction (H2-SCR) of NOX at 100°C with formation of ammonia intermediate species derived from protons of the sulfonate groups
Saito, Makoto,Itoh, Masahiro,Iwamoto, Jun,Machida, Ken-Ichi
p. 1210 - 1211
(2008)
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The selective catalytic reduction of NO2 by NH3 over HZSM-5
We have studied the reduction of NO2 by NH3 over HZSM-5 and find that this reaction is several hundred times faster than the corresponding reduction of NO under similar conditions. In addition, the kinetics of the reduction of NOsub
Stevenson, Scott A.,Vartuli, Jim C.
p. 100 - 105
(2002)
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Kinetics, Kinetic Deuterium Isotope Effects, and Mechanism of Nitrous Oxide Reaction with Hydrogen on Supported Precious-Metal Catalysts
The kinetics and kinetic deuterium isotope effects have been precisely measured for the reaction of nitrous oxide with hydrogen on Ru/Al2O3, Rh/Al2O3, Ir/Al2O3, and Pt/Al2O3 catalysts.The reaction apparently proceeds through the two following elementary s
Miyamoto, Akira,Baba, Shigeo,Mori, Mitsushi,Murakami, Yuichi
p. 3117 - 3122
(1981)
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Temperature-programmed desorption/surface reaction (TPD/TPSR) study of Fe-exchanged ZSM-5 for selective catalytic reduction of nitric oxide by ammonia
NO, NO2, and N2O from combustion of fossil fuels have been a major source of air pollution. The abatement of these NOx emissions is urgent due to their implication in photochemical smog, acid rain, ozone depletion, and greenhouse effects. TPD and temperature-programmed surface reaction (TPSR) were used to study Fe-exchanged ZSM-5 for SCR of NO with ammonia. TPD profiles revealed that NOx and NH3 adsorbed on Fe-ZSM-5. Physisorbed NOx and NH3 were not considerably affected by Fe content. Chemisorbed NOx increased with increasing Fe content, while chemisorbed NH3 decreased due to substitution of protons by Fe ions. TPSR results showed that NH3 adsorbed species were quite active in reacting with O2, NO, NO + O2, and NO2, following the reactivity rank order NO2 ～ NO + O2 > NO > O2. NOx adsorbed species were also reactive to NH3 at high temperatures. With NOx and NH3 coadsorbed on Fe-ZSM-5, TPSR with gaseous He, NO2, and NO exhibited two types of reactions for N2 formation. One reaction near 55°C originated from decomposition of ammonium nitrate that was not affected by Fe3+ content. The other reaction at 170°-245°C was due to an adsorbed complex, possibly [NH4/+]2NO2, reacting with NO2 or NO. A possible reaction path was proposed for NO reduction involving NO2 and [NH4/+]2NO2 as intermediates. Since the reactivity of [NH4/+]2NO2 to NO was higher than that to NO2, it was deduced that [NH4/+]2NO2 preferred to react with NO and not NO2, both of which were present in the SCR reaction. This could be the reason for N2 being the only product for SCR on Fe-ZSM-5.
Long,Yang
p. 20 - 28
(2001)
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Synthesis of Complex Boron-Nitrogen Heterocycles Comprising Borylated Triazenes and Tetrazenes under Mild Conditions
The reactions of organic azides with diaryl(dihalo)diboranes(4) were explored, resulting in the observation of a number of surprising reactivity patterns. The reaction of phenyl azide with 1,2-diaryl-1,2-dihalodiboranes(4) resulted in the formation of five-membered rings comprising diboryl-triazenes with retention of the boron-boron bond, while the reaction of the peculiar 1,1-di(9-anthryl)-2,2-difluorodiborane(4) with phenyl azide yielded a six-membered ring bearing a diboryl-triazene, whereby the B-B bond was ruptured by the insertion of an arylnitrene-like reactive intermediate. Both types of heterocycles feature unprecedented connectivity patterns and are very rare examples of boryl triazenes beyond the more common 1,2,3-triazolatoboranes. They are also the product of a unique type of aryl migration from a boron center to the phenyl azide ?-nitrogen center. Lastly, the substitution of 1,2-diaryl-1,2-dihalodiboranes(4) with azide groups, using trimethylsilyl azide as the transfer reagent, yielded boryl-tetrazaboroles and diboryldiazadiboretidines (as side-products), invoking the intermediacy of the first N-boryl-substituted iminoboranes, which are BN isosteres of monoborylated alkynes. The synthetic results are complemented with mechanistic proposals derived from quantum-chemical calculations.
Bélanger-Chabot, Guillaume,Braunschweig, Holger,Dietz, Maximilian,Guo, Xueying,Krummenacher, Ivo,Lin, Zhenyang,Müller, Marcel,Prieschl, Dominic
p. 1065 - 1076
(2020)
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Very active CeO2-zeolite catalysts for NOx reduction with NH3
Selective catalytic reduction of NO with NH3 over high weight percentage CeO2-zeolites showed excellent NOx conversions at very high space velocities under simulated exhaust gas conditions in the presence of H2O
Krishna,Seijger,Van den Bleek,Calis
p. 2030 - 2031
(2002)
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Fe-Ce-ZSM-5 a new catalyst of outstanding properties in the selective catalytic reduction of NO with NH3
A Fe-Ce-ZSM-5 catalyst elaborated from a new synthesis route exhibits very high NO conversion (75-100%) in the selective catalytic reduction of NO by NH3 in a wide temperature window (523-823 K), even in the presence of H2O and SO2.
Carja,Delahay,Signorile,Coq
p. 1404 - 1405
(2004)
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N2O Reductase Activity of a [Cu4S] Cluster in the 4CuI Redox State Modulated by Hydrogen Bond Donors and Proton Relays in the Secondary Coordination Sphere
The model complex [Cu4(μ4-S)(dppa)4]2+ (1, dppa=μ2-(Ph2P)2NH) has N2O reductase activity in methanol solvent, mediating 2 H+/2 e? reduction of N2O to N2+H2O in the presence of an exogenous electron donor (CoCp2). A stoichiometric product with two deprotonated dppa ligands was characterized, indicating a key role of second-sphere N?H residues as proton donors during N2O reduction. The activity of 1 towards N2O was suppressed in solvents that are unable to provide hydrogen bonding to the second-sphere N?H groups. Structural and computational data indicate that second-sphere hydrogen bonding induces structural distortion of the [Cu4S] active site, accessing a strained geometry with enhanced reactivity due to localization of electron density along a dicopper edge site. The behavior of 1 mimics aspects of the CuZ catalytic site of nitrous oxide reductase: activity in the 4CuI:1S redox state, use of a second-sphere proton donor, and reactivity dependence on both primary and secondary sphere effects.
Hsu, Chia-Wei,Rathnayaka, Suresh C.,Islam, Shahidul M.,MacMillan, Samantha N.,Mankad, Neal P.
p. 627 - 631
(2020)
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Oxygen photoevolution on a tantalum oxynitride photocatalyst under visible-light irradiation: How does water photooxidation proceed on a metal-oxynitride surface?
The mechanism of water photooxidation (oxygen photoevolution) on a TaON photocatalyst was studied on the basis of our previous studies on the mechanism of this reaction on TiO2 and N-doped TiO2. We have confirmed that photocatalytic O2 evolution occurs from an aqueous TaON suspension in the presence of Fe3+, as reported. In-situ MIR-IR experiments have indicated that the TaON surface is slightly oxidized under visible-light irradiation, indicating that the oxygen photoevolution on TaON actually occurs on a thin Ta-oxide overlayer. The in-situ MIR-IR experiments have also shown that a certain surface peroxo species, tentatively assigned to adsorbed HOOH, is formed as an intermediate of the O2 photoevolution reaction. Studies on the effect of addition of reductants to the electrolyte on the IPCE have shown that photogenerated holes at the TaON surface cannot oxidize reductants such as SCN-, Br-, methanol, ethanol, 2-propanol, and acetic acid, though they can oxidize H2O into O 2. Detailed considerations of these results have strongly suggested that the water photooxidation reaction on TaON proceeds by our recently proposed new mechanism, that is, the reaction is initiated by a nucleophilic attack of a water molecule (Lewis base) on a surface-trapped hole (Lewis acid). ? 2005 American Chemical Society.
Nakamura, Ryuhei,Tanaka, Tomoaki,Nakato, Yoshihiro
p. 8920 - 8927
(2005)
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Nickel-doped Mn/TiO2 as an efficient catalyst for the low-temperature SCR of NO with NH3: Catalytic evaluation and characterizations
The Mn/TiO2 and a series of Mn-Ni/TiO2 catalysts were prepared by adopting incipient wetness technique and investigated for the low-temperature SCR of NO with NH3 in the presence of excess oxygen. Our XPS results illustrated that the MnO2 is the dominant phase with respect to the Mn2O3 phase (Mn4+/Mn 3+ = 22.31, 96%), thus leading to a large number of Mn4+ species (Mn4+/Ti) over the titania support for the Mn-Ni(0.4)/TiO2 catalyst. It is remarkable to note that the SCR performance of all the nickel-doped Mn/TiO2 catalysts is accurately associated with the surface Mn4+ concentrations. The co-doping of nickel into the Mn/TiO2 with 0.4 Ni/Mn atomic ratio promotes the formation of surface MnO2 phase and inhibits the formation of surface Mn2O3 sites. Our TPR results revealed that the addition of nickel oxide to titania-supported manganese results in the stabilization of the former in the form of MnO2 rather than Mn2O 3. Our TPR data results are in agreement with XPS results that the absence of the high-temperature (736 K) peak indicates that the dominant phase in the Mn-Ni/TiO2 catalysts is MnO2. The low-temperature reduction peak is shifted to much lower temperatures in nickel-doped Mn/TiO 2 catalysts. This increase in reducibility and the extremely dominant MnO2 phase seem to be the reason for the high SCR activity of the Mn-Ni/TiO2 catalysts.
Thirupathi, Boningari,Smirniotis, Panagiotis G.
p. 74 - 83
(2012)
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Effect of postsynthesis preparation procedure on the state of copper in CuBEA zeolites and its catalytic properties in SCR of NO with NH3
Copper-containing BEA zeolites, Cu2.0SiBEA and Cu2.0HAlBEA, with 2?wt% of Cu were prepared by a two-step postsynthesis method and a conventional wet impregnation, respectively. These zeolites were characterized by XRD, DR UV–vis, EPR, FTIR and TPR physicochemical techniques. The incorporation of Cu into framework of SiBEA was evidenced by XRD. The state of copper in both zeolites was investigated by DR UV–vis and EPR. The acidity of Cu2.0SiBEA and Cu2.0HAlBEA was determined by FTIR of adsorbed CO and pyridine. The reducibility of the Cu species present in both zeolites was studied by TPR and their catalytic properties were investigated in selective catalytic reduction of NO with NH3. Both Cu2.0SiBEA and Cu2.0HAlBEA zeolite catalysts showed very high activity in this reaction with the NO conversion higher than 80% and N2 selectivity higher than 95% in the temperature range between 473 and 623?K. The higher NO conversion and N2 selectivity in SCR of NO with ammonia at the high temperature range for the Cu2.0HAlBEA than for Cu2.0SiBEA suggest that the strong Br?nsted and Lewis acidic sites related to the framework and extra-framework aluminum atoms play an important role in SCR of NO process.
Baran, Rafal,Averseng, Frederic,Wierzbicki, Dominik,Chalupka, Karolina,Krafft, Jean-Marc,Grzybek, Teresa,Dzwigaj, Stanislaw
p. 332 - 342
(2016)
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Selective Catalytic Reduction over Cu/SSZ-13: Linking Homo- and Heterogeneous Catalysis
Active centers in Cu/SSZ-13 selective catalytic reduction (SCR) catalysts have been recently identified as isolated Cu2+ and [CuII(OH)]+ ions. A redox reaction mechanism has also been established, where Cu ions cycle between CuI and CuII oxidation states during SCR reaction. While the mechanism for the reduction half-cycle (CuII → CuI) is reasonably well-understood, that for the oxidation half-cycle (CuI → CuII) remains an unsettled debate. Herein we report detailed reaction kinetics on low-temperature standard NH3-SCR, supplemented by DFT calculations, as strong evidence that the low-temperature oxidation half-cycle occurs with the participation of two isolated CuI ions via formation of a transient [CuI(NH3)2]+-O2-[CuI(NH3)2]+ intermediate. The feasibility of this reaction mechanism is confirmed from DFT calculations, and the simulated energy barrier and rate constants are consistent with experimental findings. Significantly, the low-temperature standard SCR mechanism proposed here provides full consistency with low-temperature SCR kinetics.
Gao, Feng,Mei, Donghai,Wang, Yilin,Szanyi, János,Peden, Charles H. F.
p. 4935 - 4942
(2017)
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Selective reduction of NO with propene over Ga2O3-Al2O3: Effect of sol-gel method on the catalytic performance
SCR of NOx to N2 by hydrocarbons has received extensive attention because of its potential for practical applications to diesel and lean-burn engine exhausts. The advantage of this process is the ability to reduce NOx in t
Haneda, Masaaki,Kintaichi, Yoshiaki,Shimada, Hiromichi,Hamada, Hideaki
p. 137 - 148
(2000)
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Ruthenium-catalysed oxidative conversion of ammonia into dinitrogen
Conversion of ammonia into dinitrogen has attracted broad scientific interest in relation to molecular models of the heterogeneous nitrogen fixation process, environmental treatment for denitrification and utilization of ammonia as an energy carrier. Here we show that some ruthenium complexes bearing 2,2′-bipyridyl-6,6′-dicarboxylate ligands work as catalysts for the ammonia oxidation reaction. Production of dinitrogen is observed when ammonium salts are treated with a triarylaminium radical as an oxidant and 2,4,6-collidine as a base in the presence of the ruthenium catalysts. Based on the characterization of some intermediates, we propose a reaction pathway via a bimetallic nitride–nitride coupling process. The proposed reaction pathway is supported by density functional theory calculations. Further investigation of the ammonia oxidation reaction under the electrochemical conditions revealed that the ruthenium complex works as a new anode catalyst for ammonia oxidation.
Nakajima, Kazunari,Toda, Hiroki,Sakata, Ken,Nishibayashi, Yoshiaki
p. 702 - 709
(2019)
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Ammonia blocking of the "Fast SCR" reactivity over a commercial Fe-zeolite catalyst for Diesel exhaust aftertreatment
The ammonia blocking effect on the Fast SCR catalytic mechanism at low temperature has been studied by means of dedicated transient reactivity runs performed over a state-of-the-art commercial Fe-zeolite catalyst. We show that the reduction of surface nitrates by NO is the key step in the mechanism, and is active already at 50 °C. However, in the presence of ammonia the reaction between NO and nitrates is stopped, and proceeds only on raising the temperature up to 140-160 °C, which thus represents an intrinsic lower bound to the Fast SCR activity. Evidence is provided that such a blocking effect is associated with a strong interaction between ammonia and surface nitrates, which prevents nitrates from reacting with NO: only upon increasing the temperature or decreasing the NH3 concentration nitrates are released due to dissociation of the ammonia-nitrate complex. The present data thus provide evidence that the blocking effect of NH3 on the Fast SCR activity at low temperature occurs not because of the ammonia competitive chemisorption on the catalytic sites, but because ammonia captures a key intermediate in an unreactive form.
Grossale, Antonio,Nova, Isabella,Tronconi, Enrico
p. 141 - 147
(2009)
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In situ IR spectroscopic and XPS study of surface complexes and their transformations during ammonia oxidation to nitrous oxide over an Mn-Bi-O/α-Al2O3 catalyst
Surface complexes resulting from the interaction between ammonia and a manganese-bismuth oxide catalyst were studied by IR spectroscopy and XPS. At the first stage, ammonia reacts with the catalyst to form the surface complexes [NH] and [NH2] via abstraction of hydrogen atoms even at room temperature. Bringing the catalyst into contact with flowing air at room temperature or with helium under heating results in further hydrogen abstraction and simultaneous formation of [N] from [NH2] and [NH]. The nitrogen atoms are localized on both reduced (Mn2+) and oxidized (Mn δ+, 2 δ+-N) active site. The nitrogen atoms localized on oxidized sites play the key role in N2O formation. Nitrous oxide is readily formed through the interaction between two Mnδ+-N species. N2 molecules result from the recombination of nitrogen atoms localized on reduced (Mn2+-N) sites.
Slavinskaya,Chesalov,Boronin,Polukhina,Noskov
p. 555 - 564
(2005)
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VIBRATIONAL-STATE DISTRIBUTION OF N2(B3Πg) PRODUCED FROM THE Ar(3P2,0)+N2O REACTION
The N2(B3Πg) product-state distribution for ν'=0-12 has been analyzed from the fluorescence observed in an Ar(3P2,0)+N2O afterglow.This vibronic distribution shows a non-Boltzmann property, inverted at ν'=4.N2(B) was found to be formed via predissociation of the Rydberg state converging into the ground state of N2O+.The golden-rule model and the half-collision model in the collinear configuration are applied to this reaction system to explain the dynamical features.The results show that both Franck-Condon-like effects and final-state interactions are important in the predissociative excitation of N2O.Potential curves are proposed for the effective harmonic oscillator and the repulsive states to reproduce the experimental vibronic-state distribution of N2(B) and to interpret the predissociation mechanism.
Wu, Konrad T.
p. 2657 - 2662
(1988)
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Electron beam initiated discharges in HN3 gas mixtures
The behaviour of electron beam initiated discharges in HN3 and inert gas mixtures for different E/N values are presented.These results are the first reported investigations of this highly energetic azide gas under plasma conditions.Using a 3 ns. 600 KeV ionizing electron beam, the temporal decay of the discharge current shows HN3 is electronegative.HN3 attachment rate constants in Ar are 5.0-10.0x10-11 cm3 s-1 for E/N values in the range 1-4 Td (10-17 V cm2).With the other inert gases (He, Ne, Kr, and Xe), HN3 attachment rate constants are 0.5-4.5x10-10cm3 s-1 for the E/N range of 0.5-7.0 Td.Plasma excitation of Ar and HN3 gas mixtures produce intense N2(C -> B, υ' = 0 -> υ'' = 0) electronic transition radiation at 3371 Angstroem.
Schlie, L. A.,Wright, M. W.
p. 394 - 400
(1990)
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Kinetics of selective catalytic reduction of nitric oxide by ammonia over vanadia/titania
A kinetic model based on a previously proposed reaction scheme was used to describe reaction kinetics measurements for the selective catalytic reduction of nitric oxide by ammonia over a 6 wt% vanadia/titania catalyst in the presence of oxygen (2 mol%) at nitric oxide and ammonia concentrations from 100 to 500 ppm and at temperatures of 523 and 573 K. This reaction scheme involves adsorption of ammonia on Bronsted acid sites (V5+-OH), followed by activation of ammonia via reaction with redox sites (V=O). This activated form of ammonia reacts with gaseous or weakly adsorbed NO, producing N2 and H2O, and leading to partial reduction of the catalyst. The V4+-OH species formed by the selective catalytic reduction (SCR) reaction combine to form water, and the catalytic cycle is completed by reaction of the reduced sites with O2. Water adsorbs competitively with ammonia on acid sites. This reaction scheme can be used to describe the kinetics of the SCR reaction under laboratory as well as under industrially relevant reaction conditions.
Dumesic,Topsoe,Topsoe,Chen,Slabiak
p. 409 - 417
(1996)
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Measurement of heterogeneously catalyzed gas reactions by DSC
Gas reactions, catalyzed by solid catalysts, can be measured by DSC. In the experimental setup an open sample pan with catalyst (powder or pellet) is placed on the sample side of the DSC sensor. The reactive gas mixture flows through the cell and reacts on the catalyst surface. The heat effect, caused by this reaction, results into a DSC signal. The calibration procedure is described for quantitative evaluation of the DSC measurements. For illustration four different reaction systems are discussed.
Hakvoort
p. 445 - 452
(1996)
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Dual Nanoislands on Ni/C Hybrid Nanosheet Activate Superior Hydrazine Oxidation-Assisted High-Efficiency H2 Production
Clean hydrogen evolution through electrochemical water splitting underpins various innovative approaches to the pursuit of sustainable energy conversion technologies, but it is blocked by the sluggish anodic oxygen evolution reaction (OER). The hydrazine oxidation reaction (HzOR) has been considered as one of the most promising substitute for OER to improve the efficiency of hydrogen evolution reaction (HER). Herein, we construct novel dual nanoislands on Ni/C hybrid nanosheet array: one kind of island represents the part of bare Ni particle surface, while the other stands for the part of core–shell Ni@C structure (denoted as Ni-C HNSA), in which exposed Ni atoms and Ni-decorated carbon shell perform as active sites for HzOR and HER respectively. As a result, when the current density reaches 10 mA cm?2, the working potentials are merely ?37 mV for HER and -20 mV for HzOR. A two-electrode electrolyzer exhibits superb activity that only requires an ultrasmall cell voltage of 0.14 V to achieve 50 mA cm?2.
Li, Yapeng,Li, Ziyun,Liu, Yi,Qian, Qizhu,Xiao, Chong,Xie, Yi,Zhang, Genqiang,Zhang, Jihua,Zhu, Yin
supporting information

(2021/12/09)

Synthesis, characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes
Thiolate-bridged hetero-bimetallic complexes [Cp*M(MeCN)N2S2FeCl][PF6] (2, M = Ru; 3, M = Co, Cp* = η5-C5Me5, N2S2 = N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate) were prepared by self-assembly of dimer [N2S2Fe]2 with mononuclear precursor [Cp*Ru(MeCN)3][PF6] or [Cp*Co(MeCN)3][PF6]2 in the presence of CHCl3 as a chloride donor. Complexes 2 and 3 exhibit obviously different redox behaviors investigated by cyclic voltammetry and spin density distributions supported by DFT calculations. Notably, iron-cobalt complex 3 possesses versatile reactivities that cannot be achieved for complex 2. In the presence of CoCp2, complex 3 can undergo one-electron reduction to generate a stable formally CoIIFeII complex [Cp*CoN2S2FeCl] (4). Besides, the terminal chloride on the iron center in 3 can be removed by dehalogenation agent AgPF6 or exchanged with azide to afford the corresponding complexes [Cp*Co(MeCN)N2S2Fe(MeCN)][PF6]2 (5) and [Cp*Co(MeCN)N2S2Fe(N3)][PF6] (6). In addition, complexes 2, 3 and 4 show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia. These results may be helpful to understand the vital role of the heterometal in some catalytic transformations promoted by heteromultinuclear complexes.
Guo, Chao,Qu, Jingping,Su, Linan,Wang, Baomin,Yang, Dawei
(2021/08/10)

Single Co-Atoms as Electrocatalysts for Efficient Hydrazine Oxidation Reaction
Single-atom catalysts (SACs) have aroused great attention due to their high atom efficiency and unprecedented catalytic properties. A remaining challenge is to anchor the single atoms individually on support materials via strong interactions. Herein, single atom Co sites have been developed on functionalized graphene by taking advantage of the strong interaction between Co2+ ions and the nitrile group of cyanographene. The potential of the material, which is named G(CN)-Co, as a SAC is demonstrated using the electrocatalytic hydrazine oxidation reaction (HzOR). The material exhibits excellent catalytic activity for HzOR, driving the reaction with low overpotential and high current density while remaining stable during long reaction times. Thus, this material can be a promising alternative to conventional noble metal-based catalysts that are currently widely used in HzOR-based fuel cells. Density functional theory calculations of the reaction mechanism over the material reveal that the Co(II) sites on G(CN)-Co can efficiently interact with hydrazine molecules and promote the N-H bond-dissociation steps involved in the HzOR.
Kadam, Ravishankar G.,Zhang, Tao,Zaoralová, Dagmar,Medve?, Miroslav,Bakandritsos, Aristides,Tomanec, Ond?ej,Petr, Martin,Zhu Chen, Johnny,Miller, Jeffrey T.,Otyepka, Michal,Zbo?il, Radek,Asefa, Tewodros,Gawande, Manoj B.
(2021/04/05)

Synthesis of Zeolitic Mo-Doped Vanadotungstates and Their Catalytic Activity for Low-Temperature NH3-SCR
Mo was successfully introduced into a vanadotungstate (VT-1), which is a crystalline microporous zeolitic transition-metal oxide based on cubane clusters [W4O16]8- and VO2+ linkers (MoxW4-x. x: number of Mo in VT-1 unit cell determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES)). It was confirmed that W in the cubane units was substituted by Mo. The resulting materials showed higher microporosity compared with VT-1. The surface area and the micropore volume increased to 296 m2·g-1 and 0.097 cm3·g-1, respectively, for Mo0.6W3.4 compared with the those values for VT-1 (249 m2·g-1 and 0.078 cm3·g-1, respectively). The introduction of Mo changed the acid properties including the acid amount (VT-1: 1.06 mmol g-1, Mo0.6W3.4: 2.18 mmol·g-1) and its strength because of the changes of the chemical bonding in the framework structure. MoxW4-x showed substantial catalytic activity for the selective catalytic reduction of NO with NH3 (NH3-selective catalytic reduction (SCR)) at a temperature as low as 150 °C.
Tao, Meilin,Ishikawa, Satoshi,Murayama, Toru,Inomata, Yusuke,Kamiyama, Akiho,Ueda, Wataru
supporting information
p. 5081 - 5086
(2021/04/09)

Cu, Fe and Mn oxides intercalated SiO2 pillared magadiite and ilerite catalysts for NO decomposition
Synthesized magadiite and ilerite samples were pillared with SiO2 and then intercalated with Cu, Fe and Mn oxides to utilize for direct NO decomposition between 400 and 600 °C. Cu-SiO2-pil-ile and Cu-SiO2-pil-mag catalysts exhibited high NO decomposition activity compared to Fe and Mn oxide intercalated catalysts. Remarkably, Cu-SiO2-pil-ile offered 90 % NO conversion and 83 % N2 selectivity at 600 °C. Elemental analysis, XRD, FESEM, DR UV-vis, Raman spectroscopy, N2-adsorption, H2-TPR, O2-TPD and XPS were utilized to study physicochemical characteristics of the materials. The results from XRD and N2 adsorption demonstrated that the samples possessed different pore structures from SiO2-pillared silicates, due to different nature of metal oxides. The Cu-SiO2-pil-ile and Cu-SiO2-pil-mag samples possess a smaller number of Lewis and Br?nsted acid sites compared with Fe and Mn oxide intercalated samples. Presence of Cu2+/Cu+ and Fe3+/Fe2+, and synergism between redox centers are major reason for superior performance in NO decomposition. Therefore, the impact of redox properties and NO adsorption on the surface of the catalyst are significant.
Katabathini, Narasimharao,El Maksod, Islam Hamdy Abd,Mokhtar, Mohamed
(2021/03/22)

Investigation of the NO reduction by CO reaction over oxidized and reduced NiOx/CeO2catalysts
CeO2-supported NiOxcatalysts have been widely studied in various catalytic reactions including NO reduction by CO. This work is mainly focused on investigation of the impact of catalyst synthesis conditions (e.g., oxidation and reduc
Boscoboinik, Jorge Anibal,Hwang, Sooyeon,Kim, Taejin,Kwon, Gihan,Lee, Kyung-Min
p. 7850 - 7865
(2021/12/27)

Magnetically recyclable Co/ZnO@NiFe2O4nanoparticles as highly active and reusable catalysts for hydrazine monohydrate hydrogen generation
This research investigates the improvement of novel and cost-effective highly magnetic nanoparticle (NP) catalysts for hydrazine monohydrate dehydrogenation, which are viewed as some of the greatest solid chemical hydrogen storage materials because of their high gravimetric hydrogen storage capacity. The improvement of a new catalytic material, Co supported on ZnO@NiFe2O4NPs, was also studied. The experimental results indicate that the resultant Co/ZnO@NiFe2O4NPs (2.0 wt% Co) exhibits excellent catalytic performance, 100% H2selectivity and recyclability for hydrogen generation from hydrazine monohydrate (N2H4·H2O) at 25 °C in alkaline solution conditions. The turnover frequency (TOF) value was approximately 4445.37 h?1, which is higher than that obtained with 0.5 wt% Co NPs (TOF value 997.42 h?1). Moreover, Co/ZnO@NiFe2O4demonstrates outstanding catalytic performance and excellent recycle stability through high hydrazine monohydrate dehydrogenation. The superior catalytic properties may be the result of electronic interactions between Co, Zn and Ni NPs. The tested catalysts were easily recovered by utilizing a permanent magnet and were reused for up to 15 cycles without losing their characteristic catalytic activity. In summary, Co/ZnO@NiFe2O4NP catalysts have been successfully developed and show a good future application potential.
Prabu, Samikannu,Chiang, Kung-Yuh
p. 1544 - 1557
(2021/03/14)

Kinetically Controlled Synthesis of Rhodium Nanocrystals with Different Shapes and a Comparison Study of Their Thermal and Catalytic Properties
We report the synthesis of Rh nanocrystals with different shapes by controlling the kinetics involved in the growth of preformed Rh cubic seeds. Specifically, Rh nanocrystals with cubic, cuboctahedral, and octahedral shapes can all be obtained from the same cubic seeds under suitable reduction kinetics for the precursor. The success of such a synthesis also relies on the use of a halide-free precursor to avoid oxidative etching, as well as the involvement of a sufficiently high temperature to remove Br- ions from the seeds while ensuring adequate surface diffusion. The availability of Rh nanocrystals with cubic and octahedral shapes allows for an evaluation of the facet dependences of their thermal and catalytic properties. The data from in situ electron microscopy studies indicate that the cubic and octahedral Rh nanocrystals can keep their original shapes up to 700 and 500 °C, respectively. When tested as catalysts for hydrazine decomposition, the octahedral nanocrystals exhibit almost 4-fold enhancement in terms of H2 selectivity relative to the cubic counterpart. As for ethanol oxidation, the order is reversed, with the cubic nanocrystals being about three times more active than the octahedral sample.
Zhao, Ming,Chen, Zitao,Shi, Yifeng,Hood, Zachary D.,Lyu, Zhiheng,Xie, Minghao,Chi, Miaofang,Xia, Younan
p. 6293 - 6302
(2021/05/07)

Selective catalytic reduction of NOx by H2 over a novel Pd/FeTi catalyst
Selective catalytic reduction (SCR) of NOx by H2 over Pd/Ti, Pd/Fe and Pd/FeTi catalysts was systematically investigated. Compared with Pd/Ti and Pd/Fe catalysts, Pd/FeTi catalyst exhibited higher H2-SCR activity and the optimal ratio of Fe/Ti is 1. Over Pd/FeTi catalysts FeTi solid solution is formed, and Pd is highly dispersed on the support. XPS analysis showed that there is strong interaction among Pd, Fe and Ti species. In-situ DRIFTS results revealed that more and new adsorbed NOx species, which are reactive to reacting with H2, formed over Pd/FeTi. All these factors account for the improved H2-SCR activity of Pd/FeTi catalyst.
Zhang, Yiyang,Zeng, Hui,Jia, Bin,Liu, Zhiming
p. 213 - 219
(2020/05/18)

Atomically Dispersed Copper Sites in a Metal-Organic Framework for Reduction of Nitrogen Dioxide
Metal-organic framework (MOF) materials provide an excellent platform to fabricate single-atom catalysts due to their structural diversity, intrinsic porosity, and designable functionality. However, the unambiguous identification of atomically dispersed metal sites and the elucidation of their role in catalysis are challenging due to limited methods of characterization and lack of direct structural information. Here, we report a comprehensive investigation of the structure and the role of atomically dispersed copper sites in UiO-66 for the catalytic reduction of NO2 at ambient temperature. The atomic dispersion of copper sites on UiO-66 is confirmed by high-angle annular dark-field scanning transmission electron microscopy, electron paramagnetic resonance spectroscopy, and inelastic neutron scattering, and their location is identified by neutron powder diffraction and solid-state nuclear magnetic resonance spectroscopy. The Cu/UiO-66 catalyst exhibits superior catalytic performance for the reduction of NO2 at 25 °C without the use of reductants. A selectivity of 88% for the formation of N2 at a 97% conversion of NO2 with a lifetime of >50 h and an unprecedented turnover frequency of 6.1 h-1 is achieved under nonthermal plasma activation. In situ and operando infrared, solid-state NMR, and EPR spectroscopy reveal the critical role of copper sites in the adsorption and activation of NO2 molecules, with the formation of {Cu(I)···NO} and {Cu···NO2} adducts promoting the conversion of NO2 to N2. This study will inspire the further design and study of new efficient single-atom catalysts for NO2 abatement via detailed unravelling of their role in catalysis.
Chansai, Sarayute,Cheng, Yongqiang,Da Silva, Ivan,Haigh, Sarah J.,Han, Xue,Hardacre, Christopher,Lee, Daniel,Li, Weiyao,Ma, Yujie,Manuel, Pascal,McInnes, Eric J. L.,Nikiel, Marek,Ramirez-Cuesta, Anibal J.,Rudi?, Svemir,Schr?der, Martin,Sheveleva, Alena M.,Tuna, Floriana,Wang, Zi,Xu, Shaojun,Yang, Sihai,Zou, Yichao
supporting information
p. 10977 - 10985
(2021/08/03)

Reduction of Nitrogen Oxides by Hydrogen with Rhodium(I)–Platinum(II) Olefin Complexes as Catalysts
The nitrogen oxides NO2, NO, and N2O are among the most potent air pollutants of the 21st century. A bimetallic RhI–PtII complex containing an especially designed multidentate phosphine olefin ligand is capable of catalytically detoxifying these nitrogen oxides in the presence of hydrogen to form water and dinitrogen as benign products. The catalytic reactions were performed at room temperature and low pressures (3–4 bar for combined nitrogen oxides and hydrogen gases). A turnover number (TON) of 587 for the reduction of nitrous oxide (N2O) to water and N2 was recorded, making these RhI–PtII complexes the best homogeneous catalysts for this reaction to date. Lower TONs were achieved in the conversion of nitric oxide (NO, TON=38) or nitrogen dioxide (NO2, TON of 8). These unprecedented homogeneously catalyzed hydrogenation reactions of NOx were investigated by a combination of multinuclear NMR techniques and DFT calculations, which provide insight into a possible reaction mechanism. The hydrogenation of NO2 proceeds stepwise, to first give NO and H2O, followed by the generation of N2O and H2O, which is then further converted to N2 and H2O. The nitrogen?nitrogen bond-forming step takes place in the conversion from NO to N2O and involves reductive dimerization of NO at a rhodium center to give a hyponitrite (N2O22?) complex, which was detected as an intermediate.
Abels, Anne Sofie,Aebli, Marcel,Baker, Matthew G.,Eiler, Frederik,Fernández, Israel,Gamboa-Carballo, Juan José,Gauthier, Sébastien,Gianetti, Thomas L.,Grützmacher, Hansj?rg,Jurt, Pascal,Le Corre, Grégoire,Müller, Fabian,Trincado, Monica,Verel, René,W?rle, Michael
supporting information
p. 25372 - 25380
(2021/10/25)

A rigorous electrochemical ammonia electrolysis protocol with: In operando quantitative analysis
Ammonia has emerged as an attractive liquid fuel for hydrogen production owing to its facile transportation, high capacity of hydrogen storage, and ecofriendly environmental products (N2 and H2). Moreover, the electrolysis of ammonia to produce nitrogen a
Yang, Yejin,Kim, Jeongwon,Jo, Hyoi,Seong, Arim,Lee, Minzae,Min, Hyung-Ki,Seo, Myung-Gi,Choi, Youngheon,Kim, Guntae
p. 11571 - 11579
(2021/05/25)

Manganese-Catalyzed Ammonia Oxidation into Dinitrogen under Chemical or Electrochemical Conditions**
Earth-abundant metal-catalyzed oxidative conversion of ammonia into dinitrogen is a promising process to utilize ammonia as a transportation fuel. Herein, we report the manganese-catalyzed ammonia oxidation under chemical or electrochemical conditions using a manganese complex bearing (1S,2S)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine. Under chemical conditions using oxidant, up to 17.1 equivalents of N2 per catalyst are generated. Also, mechanistic studies by stoichiometric reactions reveal that a nucleophilic attack of ammonia on manganese nitrogenous species occurs to form a nitrogen–nitrogen bond leading to dinitrogen. Moreover, we conduct density functional theory (DFT) calculations to confirm the plausible reaction mechanism. In addition, this reaction system is applicable under electrochemical conditions. The catalytic reaction proceeds with 96 % faradaic efficiency (FE) in bulk electrolysis to give up to 6.56 equivalents of N2 per catalyst.
Toda, Hiroki,Kuroki, Kaito,Kanega, Ryoichi,Kuriyama, Shogo,Nakajima, Kazunari,Himeda, Yuichiro,Sakata, Ken,Nishibayashi, Yoshiaki
p. 1511 - 1516
(2021/09/16)

The Effects of Platinum Dispersion and Pt State on Catalytic Properties of Pt/Al2O3 in NH3 Oxidation
Dependence of NH3 oxidation on the state and dispersion of Pt species in Pt/γ-Al2O3 catalysts was investigated. Prereduced Pt/γ-Al2O3 catalysts containing Pt0 nanoparticles exhibited significantly higher activity than preoxidized ones with the same Pt dispersion. The most significant improvement of the catalytic activity (TOF increased by 30 times) was observed when the size of Pt0 particles increased from ～1 to ～8 nm. N2 selectivity was found to be mainly determined by the reaction temperature, with a minor influence of Pt particle size. Preoxidized catalysts containing ionic Pt were activated by the reaction medium, while partial deactivation was observed for the prereduced ones. The activity improvement was associated with the presence of Pt4+/Pt2+ species on the surface of preoxidized catalysts. The activity decrease of the prereduced catalysts was due to the partial oxidation and subsequent redispersion of Pt particles. Introduction of H2O and CO2 to the reaction mixture only moderately influenced NH3 oxidation activity shifting NH3 conversion curves by about +15 °C.
Slavinskaya, Elena M.,Kibis, Lidiya S.,Stonkus, Olga A.,Svintsitskiy, Dmitry A.,Stadnichenko, Andrei I.,Fedorova, Elizaveta A.,Romanenko, Anatolii V.,Marchuk, Vasyl,Doronkin, Dmitry E.,Boronin, Andrei I.
p. 313 - 327
(2020/10/30)

Catalytic Method for the Synthesis of Deuterium-Labeled N-Heterocyclic Carbenes Enabled by a Coordinatively Unsaturated Ruthenium N-Heterocyclic Carbene Catalyst
The wide usage of N-heterocyclic carbenes (NHCs) has raised the quest for their deuterated molecules. Effective synthesis method to obtain them, however, has remained elusive. We present here a catalytic method for the preparation of deuterated NHCs, namely, the catalytic hydrogen-deuterium exchange reaction between NHCs and deuterated benzene using a coordinatively unsaturated Ru NHC catalyst. The catalytic system enables selective deuteration of the C(sp3)-H bonds of the alkyl groups on N-substituents, as well as the sterically nonhindered C(sp2)-H bonds of NHCs as demonstrated by the preparation of 16 deuterium-labeled NHCs that have a deuteration ratio on specified sites higher than 90%. The gram-scale synthesis of deuterated IMes indicated the applicability of this catalytic method. Mechanistic studies revealed that the high regio-selectivity toward those C(sp3)-H bonds on NHCs originates from the regio-selectivity of cyclometalation reactions of coordinatively unsaturated Ru NHC species.
Chen, Qi,Liu, Qing,Xiao, Jie,Leng, Xuebing,Deng, Liang
supporting information
p. 19956 - 19965
(2021/12/01)

Electrochemical Nitric Oxide Reduction on Metal Surfaces
Electrocatalytic denitrification is a promising technology for removing NOx species (NO3?, NO2? and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity-volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2-to-CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR.
Bagger, Alexander,Rossmeisl, Jan,Wan, Hao
supporting information
p. 21966 - 21972
(2021/09/02)

Promoting urea oxidation and water oxidation through interface construction on a CeO2@CoFe2O4heterostructure
Spinel ferrites are considered practical and promising oxygen evolution reaction (OER) and urea oxidation reaction (UOR) electrocatalysts because of their advantages in the adsorption and activation of electrocatalytic substances. A CeO2functional metal oxide was used to modify a spinel oxide in order to further improve the electrocatalytic performance of the spinel oxide. In this work, a CeO2@CoFe2O4/NF hybrid nanostructure was synthesized for the first time by typical hydrothermal and calcination methods. In an alkaline medium, CeO2@CoFe2O4/NF displays superior OER activity and needs an overpotential of 213 mV to deliver a current density of 100 mA cm?2, which makes it one of the most active catalysts reported so far. In addition, the as-prepared CeO2@CoFe2O4/NF material needs a potential of 1.40 V at the same current density in 1.0 M KOH with 0.5 M urea, which displays superior UOR activity. The CeO2@CoFe2O4/NF catalyst also displays good durability and the performance of the electrode is negligibly attenuated at a large current intensity of 125 mA cm?2. Experimental results demonstrate that the activity of the CeO2@CoFe2O4/NF catalyst is ascribed to the exposure of more active centers and a faster electron transfer rate. This work develops a novel method for exploiting Earth-abundant, robust and environmentally friendly OER and UOR electrocatalysts.
Dai, Zhixin,Du, Xiaoqiang,Han, Xinghua,Wang, Yanhong,Zhang, Xiaoshuang
p. 12301 - 12307
(2021/09/20)

Crystal structure of the high-temperature polymorph of C(NH2)3PbI3 and its thermal decomposition
The synthesis of guanidinium lead iodide, C(NH2)3PbI3 (GUAPbI3), was conducted by slow evaporation of the mixture obtained by dissolving PbI2 and C(NH2)3I in acetonitrile. When the evaporation is done at 40 oC, a yellow needle-like crystals are being formed. The sample was characterized by elemental analysis, density measurements, scanning electron microscopy, thermal analyses, high-temperature X-ray powder diffraction and infrared spectroscopy measurements. The elemental analysis of the obtained crystals confirmed the proposed stoichiometry. The performed thermal analyses showed an endothermic peak associated with structural transition around 160 oC. On the other hand, the endothermic temperature effects above 300 oC are accompanied with mass loss and were interpreted as compound degradation. The crystal structure of high temperature polymorph between 160 oC and 300 oC was determined using high-temperature powder diffraction data measurements at 280 oC using simulated annealing technique in order to obtain initial structural model. The structure was refined using the Rietveld method. At temperatures higher than 160 oC, C(NH2)3PbI3 crystallizes in hexagonal space group P63mc with unit cell parameter a increasing from 9.269 ? to 9.337 ? between 160 oC and 300 oC and c parameter increasing from 15.211 ? to 15.287 ? in the same temperature range. The structure consists of PbI6 octahedra couples sharing a common face, linked with corners. Guanidinium cations are situated in the channels between Pb2I9 couples in a manner that the plane of the molecule is perpendicular to the c-axis.
Dimitrovska-Lazova, Sandra,Bukleski, Miha,Tzvetkov, Peter,Aleksovska, Slobotka,Kovacheva, Daniela
(2020/12/13)

Biochemical Characterization, Phytotoxic Effect and Antimicrobial Activity against Some Phytopathogens of New Gemifloxacin Schiff Base Metal Complexes
String of Fe(III), Cu(II), Zn(II) and Zr(IV) complexes were synthesized with tetradentateamino Schiff base ligand derived by condensation of ethylene diamine with gemifloxacin. The novel Schiff base (4E,4′E)-4,4′-(ethane-1,2-diyldiazanylylidene)bis{7-[(4Z
Mohamed, Amira A.,Elshafie, Hazem S.,Sadeek, Sadeek A.,Camele, Ippolito
(2021/07/26)

FeVO4-supported Mn-Ce oxides for the low-temperature selective catalytic reduction of NOxby NH3
Iron vanadate (FeVO4) nanorods are used as a carrier to support manganese (Mn) and cerium (Ce) oxides for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with NH3for the first time. Among these developed Ce-Mn/FeVO4catalysts with different molar ratios of Ce/Mn, the Ce0.2Mn0.2/FeVO4catalyst exhibits the best de-NOxperformance and N2selectivity, which are higher than 90% in a wide temperature window of 90-420 °C. Through a series of characterization techniques, it is found that the synergistic effect between Ce and Mn enhances the reduction ability and the number of acid sites on the catalyst, which facilitates the adsorption and conversion of flue gas. The introduction of an appropriate ratio of Ce/Mn increases the concentration of Mn4+and chemisorbed oxygen (OS) on the catalyst, leading to a “fast SCR reaction” with oxidizing NO to NO2, which significantly improves the low-temperature de-NOxefficiency. In addition, the interaction between the active components (Ce/Mn) and the support (FeVO4) increases the de-NOxperformance of Ce0.2Mn0.2/FeVO4at high temperatures. In the meantime, the Mn4++ Ce3+? Mn3++ Ce4+reduction electron pair formed between Ce and Mn promotes the transport of electrons, which is also beneficial for the SCR reaction at low temperature. Thein situdiffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals that the SCR reaction over Ce0.2Mn0.2/FeVO4catalyst follows both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction mechanisms.
Cheng, Yonghong,He, Chi,Liu, Wei,Ma, Dandan,Niu, Cihang,Shi, Jian-Wen,Wang, Baorui,Wang, Hongkang,Xiao, Lei,Zhao, Shuqi
p. 6770 - 6781
(2021/10/25)

Complete denitrification of nitrate and nitrite to N2gas by samarium(ii) iodide
The reduction of nitrogen oxides (NxOyn?) to dinitrogen gas by samarium(ii) iodide is reported. The polyoxoanions nitrate (NO3?) and nitrite (NO2?), as well as nitrous oxide (Ns
Marks, Walker R.,Baumgardner, Douglas F.,Reinheimer, Eric W.,Gilbertson, John D.
supporting information
p. 11441 - 11444
(2020/10/12)

Catalytic disproportionation of hydrazine by thiolate-bridged diiron complexes
Treatment of a thiolate-bridged diiron complex [N2S2FeClFe(MeCN)Cp*][PF6] (1, Cp* = η5-C5Me5, N2S2 = N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate) with CO or tBuNC resulted in ligand exchange to facilely generate [N2S2FeClFeLCp*][PF6] (2, L = CO; 3, L = tBuNC). Further electrochemical studies indicate the co-ligand has an obvious influence on the redox properties of these complexes. Importantly, these complexes with different redox behaviors show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia.
Su, Linan,Yang, Dawei,Wang, Baomin,Qu, Jingping
(2019/12/30)

An Iodido-Bridged Dimer of Cubane-Type RuIr3S4 Cluster: Structural Rearrangement to New Octanuclear Core and Catalytic Reduction of Hydrazine
Nitrogen-fixing enzymes contain octanuclear metal–sulfur clusters at the active site, which are constructed on the basis of combined two cubic M4S3C skeletons. In this study, the dimer of cubane-type RuIr3S4 cluster [{(Cp*Ir)3(μ3-S)4Ru}2(μ2-I)3]I (2: Cp* = η5-C5Me5) was synthesized via oxidation of [(Cp*Ir)3(μ3-S)4(CymRu)] (Cym = η6-p-iPrC6H4Me) with I2 followed by ligand exchange. Two cubane cores are bridged by three iodido ligands in 2, while these cubes are fused into a unique Ru2Ir6S8 framework by 2e-reductuion to give [(Cp*Ir)6Ru2(μ3-S)8][I]2. Addition of excess PhNHNH2 to 2 cleaved the dimer structure to form the hydrazine adduct of single cubane [(Cp*Ir)3(μ3-S)4{RuI(NH2NHPh)2}]I. Reduction of N2H4 with Cp2Co and [HNEt3][BF4] was catalyzed by 2 in much higher rate than disproportionation of N2H4. The molecular structures of all new cluster compounds were characterized by X-ray diffraction studies.
Seino, Hidetake,Hirata, Keiichi,Arai, Yusuke,Jojo, Risa,Okazaki, Masaaki
p. 1483 - 1489
(2020/01/03)

Catalytic Disproportionation of Hydrazine Promoted by Biomimetic Diiron Complexes with Benzene-1,2-Dithiolate Bridge Modified by Different Substituents
A series of thiolate-bridged diiron nitrogenase mimics featuring benzene-1,2-dithiolate (bdt) ligand modified by different substituents were synthesized and characterized by X-ray crystallography. Electrochemical studies by cyclic voltammetry demonstrate the redox potentials of these complexes depend on the electron-withdrawing or electron-donating nature of different substituents. Importantly, all these complexes can serve as catalysts for disproportionation of hydrazine to ammonia and dinitrogen, wherein the complex with the most negative reduction potential induced by strong electron-donating NMe2 group exhibits the best catalytic activity. This result bodes well for efficient catalyst design for N–N bond cleavage of hydrazine. In addition, a well-defined diiron diazene complex can be independently synthesized and also catalyze the hydrazine disproportionation to ammonia. However, relatively low yield suggests this species may not be a key intermediate during the catalytic cycle, unlike the other reported bimetallic systems.
Qu, Jingping,Su, Linan,Sun, Tie,Wang, Baomin,Xu, Sunlin,Yang, Dawei
p. 4263 - 4269
(2020/11/30)

Nitrogen Bubbles at Pt Nanoelectrodes in a Nonaqueous Medium: Oscillating Behavior and Geometry of Critical Nuclei
Gas bubble evolution is present in many electrochemical and photoelectrochemical processes. We previously reported the formation of individual H2, N2, and O2 nanobubbles generated from electrocatalytic reduction of H+ and oxidation of N2H4 and H2O2, respectively, at Pt nanodisk electrodes in an aqueous solution. All the nanobubbles formed display a dynamic stationary state of a three-phase boundary with an invariant residual current. Here, we test the hypothesis that gas nanobubbles can also be electrogenerated in a nonaqueous medium. Interestingly, we found oscillating bubble behavior corresponding to nucleation, growth, and dissolution in dimethyl sulfoxide and methanol. One possible explanation of the oscillation mechanism is provided by the instable dynamic equilibrium between the gas influx due to supersaturation and outflux due to Laplace pressure. Furthermore, the critical gas concentrations for N2 nanobubble nucleation are estimated to be 148, 386, 200, and 16 times supersaturation and the contact angles of the critical nuclei to be 164°, 151°, 160°, and 174° in water, dimethyl sulfoxide, ethylene glycol, and methanol, respectively. This is the first report on electrochemical nucleation of gas bubbles in nonaqueous solvents. Our electrochemical gas bubble study based on a nanoelectrode platform has proven to be a prototypical example of single-entity electrochemistry.
Chen, Qianjin,Edwards, Martin A.,Liu, Yulong,Liu, Yuwen,White, Henry S.
p. 6408 - 6414
(2020/05/22)

Effect of intercalants inside birnessite-type manganese oxide nanosheets for sensor applications
Hydrazine is a common reducing agent widely used in many industrial and chemical applications; however, its high toxicity causes severe human diseases even at low concentrations. To detect traces of hydrazine released into the environment, a robust sensor with high sensitivity and accuracy is required. An electrochemical sensor is favored for hydrazine detection owing to its ability to detect a small amount of hydrazine without derivatization. Here, we have investigated the electrocatalytic activity of layered birnessite manganese oxides (MnO2) with different intercalants (Li+, Na+, and K+) as the sensor for hydrazine detection. The birnessite MnO2 with Li+ as an intercalant (Li-Bir) displays a lower oxidation peak potential, indicating a catalytic activity higher than the activities of others. The standard heterogeneous electron transfer rate constant of hydrazine oxidation at the Li-Bir electrode is 1.09- and 1.17-fold faster than those at the Na-Bir and K-Bir electrodes, respectively. In addition, the number of electron transfers increases in the following order: K-Bir (0.11 mol) Na-Bir (0.17 mol) Li-Bir (0.55 mol). On the basis of the density functional theory calculation, the Li-Bir sensor can strongly stabilize the hydrazine molecule with a large adsorption energy (-0.92 eV), leading to high electrocatalytic activity. Li-Bir also shows the best hydrazine detection performance with the lowest limit of detection of 129 nM at a signal-to-noise ratio of ~3 and a linear range of 0.007-10 mM at a finely tuned rotation speed of 2000 rpm. Additionally, the Li-Bir sensor exhibits excellent sensitivity, which can be used to detect traces of hydrazine without any effect of interference at high concentrations and in real aqueous-based samples, demonstrating its practical sensing applications.
Wuamprakhon, Phatsawit,Krittayavathananon, Atiweena,Kosasang, Soracha,Ma, Nattapol,Maihom, Thana,Limtrakul, Jumras,Chanlec, Narong,Kidkhunthod, Pinit,Sawangphruk, Montree
p. 15595 - 15605
(2020/09/15)

Boosting the electrocatalysis of nitrate to nitrogen with iron nanoparticles embedded in carbon microspheres
Human activities have increased the global nitrogen cycle imbalance, leading to serious water pollution. Inexpensive iron nanoparticles with large surface areas are in high demand in the field of environment restoration. Here, we report a hydrothermal method for the preparation of iron-carbon composites (Fe@C) with iron nanoparticles embedded in carbon microspheres. The resulting Fe@C catalyst shows a high nitrate conversion to nitrogen of 75.9% and a nitrogen selectivity of 98%. This study not only provides a simple strategy for the preparation of iron-carbon composites, but also boosts the practical application of Fe@C catalysts for water treatment. This journal is
Hong, Wen,Su, Li,Wang, Jiancheng,Jiang, Min,Ma, Yuanyuan,Yang, Jianping
supporting information
p. 14685 - 14688
(2020/12/02)

Ce regulated surface properties of Mn/SAPO-34 for improved NH3-SCR at low temperature
Ce modified MnOx/SAPO-34 was prepared and investigated for low-temperature selective catalytic reduction of NOx with ammonia (NH3-SCR). The 0.3Ce-Mn/SAPO-34 catalyst had nearly 95% NO conversion at 200-350 °C at a space velocity of 10000 h-1. Microporous SAPO-34 as the support provided the catalyst with increased hydrothermal stability. XPS and H2-TPR results proved that the Mn4+ and Oα content increased after incorporation of Ce, this promoted the conversion of NO at low temperature via a 'fast SCR' route. NH3-TPD measurements combined oxidation experiments of NO, NH3 indicated the reduction of both the surface acidity and the amount of acid sites, which effectively decreased the NH3 oxditaion to NO or N2O at elevated temperature and promoted the catalytic selectivity for nitrogen. A redox cycle between manganese oxide and Ce was assumed for the active oxygen transfer and facilitated the catalyst durability.
Chen, Qizhi,Du, Jun,Liu, Zuohua,Luo, Hang,Tao, Changyuan,Tong, Zhangfa,Yang, Yong
p. 40047 - 40054
(2020/11/18)

Design of Prussian blue analogue-derived double-cone structure Ce-Fe catalysts and their enhanced performance for the selective catalytic reduction of NOxwith NH3
Prussian blue (PB) and its analogues (PBA) with different structures and adjustable compositions have been recognized as promising materials for catalysis, energy storage, and biological applications. Herein, a simple surface anchoring strategy is proposed to achieve the uniform deposition of CeO2 nanocrystals on the double-cone structure surface of PBA (denoted as Ce@Ce-Fe catalyst) for the selective catalytic reduction of NOx with NH3 (NH3-SCR). Compared with Ce-Fe and Ce@CeO2-Fe2O3, the Ce@Ce-Fe catalyst exhibited the best catalytic activity, widest working temperature window, and highest SO2 tolerance, implying its good application in the process of NH3-SCR. Moreover, the catalysts were characterized systematically to elucidate their surface properties and morphological structure. Taking advantage of the excellent redox performance, unique morphology, mesoporous structure with large surface area and pore diameter, and greater acid content, the Ce@Ce-Fe catalyst exhibited a higher NOx performance. In addition, the Ce@Ce-Fe catalyst also exhibited significant resistance to H2O and SO2 due to its higher content of Fe atoms, implying that Fe plays a critical role in this Ce-Fe based catalytic system. More importantly, the present study indicates that well-dispersed active components and unique architectures can effectively enhance the performance of catalysts. This journal is
Guo, Jie,Zhang, Guodong,Tang, Zhicheng,Zhang, Jiyi
supporting information
p. 21244 - 21254
(2020/12/31)

Fe/Fe3C nanoparticle-decorated N-doped carbon nanofibers for improving the nitrogen selectivity of electrocatalytic nitrate reduction
Nanoscale zero-valent iron has been considered to be the most promising electrocatalyst for denitrification due to its abundant resources, low price and non-toxicity. Nevertheless, the low utilization of active ingredients, inferior removal capacities (mg N g-1 Fe), and poor nitrogen selectivity are still major challenges during practical nitrate reduction. Herein, we have synthesized a one-dimensional architecture with homogeneously distributed Fe/Fe3C nanoparticles immobilized in a monodispersed carbonaceous matrix, embedded in ultra-high N-doped carbon nanofibers (Fe/Fe3C-NCNF) via a simple electrospinning strategy followed by confined reduction under a H2 atmosphere. The as-prepared Fe/Fe3C-NCNF nanostructure features well-dispersed Fe/Fe3C nanoparticles, confined reactive spaces, an interconnected nanofiber framework, and rich nitrogen doping sites, which are beneficial for integrating the synergistic catalytic effect of Fe and Fe3C, providing high-reactivity sites, boosting electron transfer, enlarging the catalyst-electrolyte interface and enhancing the surface adsorption capacity. The results reveal ultra-high nitrogen selectivity of 95% within 6 h and nearly 100% in 12 h, which are superior to other reported catalysts, and a maximum removal capacity of 2928.42 mg N g-1 Fe can be achieved, greatly improving the utilization of active ingredients. In addition, the catalysis material also shows good catalysis stability due to its structural features. The results of this study provide broad potential for the further development of iron-based functional nanostructures for electrocatalytic denitrification. This journal is
Chen, Junliang,Lan, Yue,Yang, Jianping,Zhang, Hui,Zhang, Wei-Xian
p. 15853 - 15863
(2020/10/02)

Relating N–H Bond Strengths to the Overpotential for Catalytic Nitrogen Fixation
Nitrogen (N2) fixation to produce bio-available ammonia (NH3) is essential to all life but is a challenging transformation to catalyze owing to the chemical inertness of N2. Transition metals can, however, bind N2 and activate it for functionalization. Significant opportunities remain in developing robust and efficient transition metal catalysts for the N2 reduction reaction (N2RR). One opportunity to target in catalyst design concerns the stabilization of transition metal diazenido species (M-NNH) that result from the first N2 functionalization step. Well-characterized M-NNH species remain very rare, likely a consequence of their low N–H bond dissociation free energies (BDFEs). In this essay, we discuss the relationship between the BDFEN–H of a given M-NNH species to the observed overpotential and selectivity for N2RR catalysis with that catalyst system. We note that developing strategies to either increase the N–H BDFEs of M-NNH species, or to avoid M-NNH intermediates altogether, are potential routes to improved N2RR efficiency.
Chalkley, Matthew J.,Peters, Jonas C.
(2020/04/20)

Supports materialization of Pd based catalysts for NOx removal by hydrogen assisted selective catalytic reduction in the presence of oxygen
The Pt and Pd based bimetallic catalyst are developed to address the NOx reduction activity. For this, a series of supports containing three different amounts of CeO2?MgO (9 : 1, 3 : 1, and 3 : 2) are prepared by the co-precipitation method, followed by impregnation of Pd metal precursors. The physicochemical properties of the catalytic system are investigated using various techniques such as Brunauer-Emmett-Teller (BET), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy, Transmission Electron Microscopy (TEM), Raman spectroscopy, and H2-TPR. Among all, Pd/CeO2?MgO (3 : 1) gave the best NOx reduction activity. Furthermore, the effects of hydrogen concentration (0.2–0.8 vol %) on NOx reduction were tested. It was found that 0.8 vol % of H2 shows the highest NOx conversion. Subsequently, the successive impregnation of Pt metal over Pd based catalyst enhanced the catalytic properties. The bimetallic Pt?Pd/CeO2?MgO (3 : 1) catalyst showed an 89 % NOx reduction with about 97 % N2 selectivity in broad temperature windows (100–300 °C).
Patel, Vivek Kumar,Sharma, Sweta
p. 5173 - 5184
(2020/09/09)

Ammonia Oxidation Enhanced by Photopotential Generated by Plasmonic Excitation of a Bimetallic Electrocatalyst
We study how visible light influences the activity of an electrocatalyst composed of Au and Pt nanoparticles. The bimetallic composition imparts a dual functionality: the Pt component catalyzes the electrochemical oxidation of ammonia to liberate hydrogen
Chen, Changqiang,Heo, Jaeyoung,Jain, Prashant K.,Wang, Jun,Wilson, Andrew J.
supporting information
p. 18430 - 18434
(2020/08/27)

Enhancing electrochemical nitrate reduction toward dinitrogen selectivity on Sn-Pd bimetallic electrodes by surface structure design
Bimetallic palladium (Pd) and tin (Sn) catalysts were electrochemically deposited on stainless steel mesh support by controlling the metal deposition sequence, total electrical charge, and metal composition. Results showed that the preparation procedure a
Chen, Ching-Lung,Huang, Chin-Pao,Kuan, Wei-Fan,Su, Jenn Fang
(2020/09/18)

Effective hydrogen release from ammonia borane and sodium borohydride mixture through homopolar based dehydrocoupling driven by intermolecular interaction and restrained water supply
Non-catalytic dehydrogenation of solid-state ammonia borane (AB) and sodium borohydride (SB) mixtures is achieved in this work by water vapor facilitated hydrothermolysis with a maximum release rate of 560 ml g?1s?1at 53.5 °C and dehydrogenation capacity between 7.8 wt% (measured) and 11.7 wt% (theoretical). A novel dehydrogenation pathway is identified, in which intermolecular interaction causes the formation of intermediates and further enables the prevalence of homopolar dehydrocoupling between -BH moieties in AB and SB. The low-temperature heat used in hydrothermolysis enhances the intermolecular interaction, and the oxygen and hydrogen supplied by water vapor promote the dehydrogenation by forming products. This new hydrogen liberation method can uniquely operate without any catalyst, liquid solvent, or high temperature, and provides a compelling solution for disposable hydrogen source application. The present work also unveils for the first time the unique hydride-hydride homopolar dehydrogenation mechanism, which may unlock the true potential of chemical hydride based hydrogen storage systems.
Cannon, Mark,Kjeang, Erik,Pei, Pei,Quan, Grace
p. 19050 - 19056
(2020/10/02)

Selective catalytic oxidation of ammonia over LaMAl11O19-: δ (M = Fe, Cu, Co, and Mn) hexaaluminates catalysts at high temperatures in the Claus process
A method for the selective catalytic oxidation of ammonia at high temperature was innovatively proposed to substitute the traditional combustion method to remove the ammonia impurity in the Claus process. In the present work, transition metal (Fe, Cu Co, and Mn)-substituted La-hexaaluminate catalysts were synthesized and investigated for the selective catalytic oxidation of ammonia (NH3-SCO) at high temperature. It was observed that Cu-substituted catalysts could achieve the highest N2 yield at around 520 °C. It was confirmed that the conversion of NH3 was closely related to the reducibility of the prepared catalyst. In particular, it was observed that the molecular O2 could not be dissociatively adsorbed on the prepared catalyst surface. However, both lattice oxygen and gas-phase O2 could participate in NH3-SCO, with gas-phase O2 being the most favorable under the experimental conditions. It was evidenced that the NH3-SCO reaction over the prepared catalysts followed the i-SCR mechanism. Moreover, monodentate nitrates were the main reactive intermediates toward forming N2. Therefore, the development of high-temperature SCO technology and an efficient catalyst are beneficial for the sustainable development of the chemical industry.
Hao, Zhengping,Jiang, Guoxia,Lin, Caihong,Sun, Yu,Wang, Zhuo,Wei, Zheng,Zhang, Fenglian,Zhang, Xin,Zhang, Yumeng
p. 1477 - 1491
(2020/03/23)

Evaluation of Co/SSZ-13 Zeolite Catalysts Prepared by Solid-Phase Reaction for NO-SCR by Methane
Co/SSZ-13 zeolites were prepared by heating the finely dispersed mixture of NH4-SSZ-13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into
Ayari, Faouzi,Charrad, Rania,Hancsók, Jen?,Lónyi, Ferenc,Mhamdi, Mourad,Solt, Hanna E.,Trif, László,Valyon, József
p. 1123 - 1134
(2020/12/03)

Diversion of Catalytic C-N Bond Formation to Catalytic Oxidation of NH3 through Modification of the Hydrogen Atom Abstractor
We report that (TMP)Ru(NH3)2 (TMP = tetramesitylporphryin) is a molecular catalyst for oxidation of ammonia to dinitrogen. An aryloxy radical, tri-tert-butylphenoxyl (ArO·), abstracts H atoms from a bound ammonia ligand of (TMP)Ru(NH3)2, leading to the discovery of a new catalytic C-N coupling to the para position of ArO· to form 4-amino-2,4,6-tri-tert-butylcyclohexa-2,5-dien-1-one. Modification of the aryloxy radical to 2,6-di-tert-butyl-4-tritylphenoxyl radical, which contains a trityl group at the para position, prevents C-N coupling and diverts the reaction to catalytic oxidation of NH3 to give N2. We achieved 125 ± 5 turnovers at 22 °C for oxidation of NH3, the highest turnover number (TON) reported to date for a molecular catalyst.
Bullock, R. Morris,Dunn, Peter L.,Johnson, Samantha I.,Kaminsky, Werner
supporting information
p. 3361 - 3365
(2020/03/06)

The role of cobalt oxide or magnesium oxide in ozonation of ammonia nitrogen in water
In this study, the reaction mechanisms for ozonation of ammonia nitrogen in the presence of Co3O4 or MgO were investigated. For the reaction over Co3O4, Cl– in the reaction solution was indispensable and ClO– was formed by a non-catalytic oxidation of Cl–. Co3O4 promoted the reaction of NH4+ with ClO– to give the products including NO3–, chloramines and gaseous products. In contrast, Cl– was unnecessary for the reaction with MgO. pH of the reaction solution was maintained at around 9 throughout the reaction owing to partial dissolution of MgO. Ammonia nitrogen was decomposed to mainly NO3– by non-catalytic radical reaction involving OH·, which was formed by the reaction of OH– with O3 in weakly basic solution. To keep the reaction solution weakly basic, H+ formed with the decomposition of NH4+ was neutralized. As a result, about the same amount of Mg2+ as that of decomposed ammonia nitrogen was dissolved.
Anggo Krisbiantoro, Philip,Togawa, Tomokazu,Mahardiani, Lina,Aihara, Haruka,Otomo, Ryoichi,Kamiya, Yuichi
(2020/03/23)

Decomposition of ammonium perchlorate: Exploring catalytic activity of nanocomposites based on nano Cu/Cu2O dispersed on graphitic carbon nitride
Copper (Cu) and its oxides are well-known catalysts for thermal decomposition of ammonium perchlorate (AP). Nano Cu/Cu2O dispersed on graphitic carbon nitride (g-C3N4) based nanocomposites were synthesised by single displa
Chandrababu, Parvathy,Raghavan, Rajeev,Sukumaran Nair, Vishnu,Thankarajan, Jayalatha
(2020/07/27)

Two-State Reactivity in Iron-Catalyzed Alkene Isomerization Confers σ-Base Resistance
A low-coordinate, high spin (S = 3/2) organometallic iron(I) complex is a catalyst for the isomerization of alkenes. A combination of experimental and computational mechanistic studies supports a mechanism in which alkene isomerization occurs by the allyl mechanism. Importantly, while substrate binding occurs on the S = 3/2 surface, oxidative addition to an η1-allyl intermediate only occurs on the S = 1/2 surface. Since this spin state change is only possible when the alkene substrate is bound, the catalyst has high immunity to typical σ-base poisons due to the antibonding interactions of the high spin state.
Lutz, Sean A.,Hickey, Anne K.,Gao, Yafei,Chen, Chun-Hsing,Smith, Jeremy M.
supporting information
p. 15527 - 15535
(2020/10/20)

Highly Efficient Hydrogen Production Using a Reformed Electrolysis System Driven by a Single Perovskite Solar Cell
Efficient hydrogen production by a photovoltaic-electrolysis cell (PV–EC) system requires a low electrolyzer overpotential and a high coupling efficiency between both the components. Herein, Ni5P4 is proposed as a cost-effective bifunctional electrocatalyst for hydrogen evolution and hydrazine oxidation in a reformed electrolyzer. Experiments indicate that the electrolytic overpotential could be significantly reduced by replacing the oxygen evolution reaction with the hydrazine oxidation reaction at the anode. Furthermore, a scenario for hydrogen production is demonstrated by utilizing a stable and low-cost perovskite solar cell (PSC) with a carbon back electrode to drive a reformed electrolyzer. Importantly, a single PSC can drive three reformed electrolyzers in series for hydrogen production by carefully matching the operating point of the electrolyzer with the maximum power point of the photovoltaic device, thereby, yielding a H2 evolution rate of 1.77 mg h?1 for the whole PV–EC system. This can be a potential starting point for hydrogen production using a single PSC-driven electrolysis system.
Xiao, Xin,Liu, Shuangshuang,Huang, Dekang,Lv, Xiaowei,Li, Man,Jiang, Xingxing,Tao, Leiming,Yu, Zehui,Shao, Yong,Wang, Mingkui,Shen, Yan
p. 434 - 440
(2019/01/11)

Atomically Dispersed Semimetallic Selenium on Porous Carbon Membrane as an Electrode for Hydrazine Fuel Cells
Electrochemically functional porous membranes of low cost are appealing in various electrochemical devices used in modern environmental and energy technologies. Herein we describe a scalable strategy to construct electrochemically active, hierarchically porous carbon membranes containing atomically dispersed semi-metallic Se, denoted SeNCM. The isolated Se atoms were stabilized by carbon atoms in the form of a hexatomic ring structure, in which the Se atoms were located at the edges of graphitic domains in SeNCM. This configuration is different from that of previously reported transition/noble metal single atom catalysts. The positively charged Se, enlarged graphitic layers, robust electrochemical nature of SeNCM endow them with excellent catalytic activity that is superior to state-of-the-art commercial Pt/C catalyst. It also has long-term operational stability for hydrazine oxidation reaction in practical hydrazine fuel cell.
Wang, Tongzhou,Wang, Qiang,Wang, Yucheng,Da, Yunli,Zhou, Wu,Shao, Yue,Li, Debao,Zhan, Sihui,Yuan, Jiayin,Wang, Hong
supporting information
p. 13466 - 13471
(2019/08/12)

Hydroxylamine Oxidation on Polycrystalline Gold Electrodes in Aqueous Electrolytes: Quantitative On-Line Mass Spectrometry under Forced Convection
Herein, a method is presented that allows quantitative determination of faradaic efficiencies for dinitrogen (N2) generation during the electrochemical oxidation of hydroxylamine (NH2OH), (Formula presented.), on a polycrystalline gold Au(poly) disk electrode in aqueous electrolytes over a wide pH range. This tactic involves the use of an impinging jet electrolyte configuration incorporating a gas porous ring connected in turn to a mass spectrometer. The actual amount of N2 generated at the Au(poly) disk was assayed using the oxidation of hydrazine (N2H4) in aqueous phosphate buffer (pH 7). This redox process yields N2 as the only product, allowing a direct correlation to be established between the changes in the partial pressures of N2 and the current flowing through the disk electrode. An analysis of the data collected revealed a strong dependence of (Formula presented.) both on pH and the applied potential. Although values of (Formula presented.) as high as 20 to 30 % were found in acid and neutral media over a narrow potential region, those in alkaline solution were far smaller in the entire potential range examined.
Pozniak, Boguslaw,Treufeld, Imre,Scherson, Daniel
p. 3128 - 3133
(2019/11/03)

Sulfurization-induced edge amorphization in copper-nickel-cobalt layered double hydroxide nanosheets promoting hydrazine electro-oxidation
The electrocatalytic hydrazine oxidation reaction (HzOR) has drawn extensive attention due to its high energy conversion efficiency and wide applications in hydrazine-assisted water splitting and direct hydrazine fuel cells (DHFC). In this study, a ternary copper-nickel-cobalt layered double hydroxide (CuNiCo LDH) nanosheet array catalyst with sulfurization-induced edge amorphization was fabricated as a highly efficient electrocatalyst for HzOR. The amorphous species at the edge region remarkably enrich the coordinatedly unsaturated metal atoms, which are catalytically active for the electro-oxidation reactions. In addition, the optimal ratio of ternary metal ions further modulates the electronic structure and optimizes the HzOR kinetics, thereby realizing improved catalytic activity. With the combined merits of enriched active species, large surface area, enhanced charge transfer behavior, and favorable reaction kinetics as well as its robust microstructure, a synergistically optimized HzOR catalyst with high activity and superior durability was achieved, which could be applied for hydrogen production via hydrazine-assisted water splitting and for generating electricity from DHFC.
Liu, Weiwei,Xie, Junfeng,Guo, Yanqing,Lou, Shanshan,Gao, Li,Tang, Bo
supporting information
p. 24437 - 24444
(2019/11/11)