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Catalytic conversion of CO2 to methanol with H2 from renewable energy has attracted increasing interest as a promising strategy for reducing excessive CO2 emissions. However, the performance of reported various catalysts still suffers from low methanol yield with a passable CO2 conversion. In this work, Cu–ZnO–La2O3 interfaces are constructed with various La2O3 mole ratio. Compared to Cu/ZnO, the optimized catalyst (i.e., Cu0.6Zn0.2La0.4) exhibits a much higher mass-specific methanol formation rate (159.3 gMeOH/kgcat/h) at 240 °C and 3 MPa. A series of ex-situ and in-situ characterizations, such as X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), N2O titration measurements, and in-situ diffuse reflectance Fourier transform infrared spectroscopy (in-situ DRIFTS) study, are used to investigate its structure and mechanism study. The dispersion of Cu over Cu/ZnO/La2O3 catalyst is significantly enhanced, forming more Cu–ZnO–La2O3 interfaces. LaOx species favor CO2 activation and generate more carbon intermediates species for CO2 hydrogenation. Furthermore, more Cu+ is bonded, which stabilizes the key intermediate, inhibits its desorption, and facilitates its further hydrogenation to methanol. This work is expected to offer an effective strategy to develop new catalysts with high performance for CO2 hydrogenation to methanol. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrodeoxygenation of phenol in gas phase over Pd-VO x /SiO 2 catalysts. • Pd/SiO 2 promotes hydrogenation pathways whereas VO x addition favors deoxygenation. • Deoxygenation depends on the contact between V3+ and V4+ cations and metal particle. • Pd-VO x interface is responsible for the activation of the C = O bond. This work investigates the effect of vanadia species on the performance of Pd/VO x /SiO 2 catalysts containing different vanadia loadings for HDO of phenol in the gas phase. in situ XANES experiments reveal the presence of a mixture of V 2 O 4 and V 4 O 7 species for all catalysts after reduction at 573 K. In situ XRD and XANES demonstrate that Pd particles and VO x species are in close contact, which is likely due to the presence of polymerized vanadate species, regardless of vanadia content, as shown by UV–Vis spectroscopy. This close contact promotes the selective hydrogenation of the C = O bond or the cleavage of the C-O bond, producing benzene. The strong interaction between the oxygen of the tautomer intermediate molecule and the oxygen vacancies associated with the presence of V3+ and V4+ cations is responsible for the deoxygenation activity of Pd/VO x /SiO 2 catalysts. [ABSTRACT FROM AUTHOR]

The construction of suitable metal/substrate interfaces that can synergistically optimize the water dissociation, hydrogen transfer and hydrogen adsorption processes has proved to be a promising approach to boost the alkaline electrochemical hydrogen evolution reaction (HER) but remains challenging. Herein, a Pt/GaN heterostructure electrocatalyst is constructed using the electrochemical deposition technique and used for alkaline electrochemical HER. The as‐synthesized Pt/GaN catalyst exhibits competitive HER performance, including low overpotentials of 24 and 441 mV to reach current densities of 10 and 1000 mA cm−2, respectively, and a superior mass activity (7.34 A mgPt−1 at the overpotential of 100 mV), which is 25.7 and 5.0 times higher than commercial Pt/C and as‐synthesized Pt/CP, respectively. First‐principle calculations suggest that the Pt/GaN heterostructure can greatly reduce the energy barrier for H2O dissociation, create a local acid‐like microenvironment through a H spillover process and optimize the value of ΔGH, leading to a remarkable acceleration of the alkaline HER kinetics. This discovery provides new insights for the development of alkaline HER catalysts. [ABSTRACT FROM AUTHOR]

The methanol oxidation reaction is a promising route to eliminating trace amount of methanol in exhaust gases which aroused serious environmental concern. In this work, a novel Pd/MgAl2O4 catalyst was prepared to construct the metal-support interface and employed in the methanol oxidation reaction. The reaction results show that the Pd/MgAl2O4 catalyst could achieve 100% methanol oxidation at 198 ℃ over the Pd/MgO and Pd/Al2O3 catalysts. The high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), CO-chemisorption, H2 temperature programmed reduction (H2-TPR), and CO diffuse reflectance infrared Fourier transformed spectroscopy (CO-DRIFTS) show that the Pd was uniformly distributed over the MgAl2O4 support due to strong interaction between Pd and MgAl2O4. The mechanism studies show that the abundant Pd-MgAl2O4 interfaces significantly contributed to the reaction enhancement. The Pd-MgAl2O4 interfaces could greatly enhance the oxidation reaction at a lower temperature with the assistance of oxygen vacancies compared with traditional oxide catalysts, which was confirmed by methanol temperature program surface reaction (MeOH-TPSR) experiments. In-situ DRIFTS is carried out to elucidate the reaction mechanism and establish the structure − activity relationship: the methanol could be effectively absorbed on the MgAl2O4 support with oxygen vacancies to form bidentate formate, then the Pd species assisted the intermediates converting to CO2 product. The Pd/MgAl2O4 catalyst and its enhancement mechanism investigation provided a potential strategy in the VOCs removal catalysis development. [ABSTRACT FROM AUTHOR]

Herein, we explore how OH groups on Pt/γ‐AlOOH and Pt/γ‐Al2O3 catalysts affect CO2 hydrogenation with H2 at temperatures from 250°C to 400°C. OH groups are abundant on γ‐AlOOH, but rare at Pt‐(γ‐AlOOH) interface which is the most favorable site for CO2 conversion on Pt/γ‐AlOOH. This makes CO2 hydrogenation on Pt/γ‐AlOOH form CO weakly bonding to γ‐AlOOH, which prefers to desorption from Pt/γ‐AlOOH rather than further conversion, thus enhancing CO production on Pt/γ‐AlOOH. Different from Pt/γ‐AlOOH, OH groups are abundant at Pt‐(γ‐Al2O3) interface which is the most favorable site for CO2 conversion on Pt/γ‐Al2O3. This promotes CO2 hydrogenation on Pt/γ‐Al2O3 to form CO strongly bonding to Pt, which prefers to further hydrogenation to CH4, and thereby increases CH4 selectivity on Pt/γ‐Al2O3. Therefore, the OH groups at metal‐support interface are crucial factor influencing product distribution, and must be considered seriously when fabricating catalysts. [ABSTRACT FROM AUTHOR]

In this work, a commercial P25 (TiO2) with phase junctions between (101) and (110) faces supported Pt catalyst was prepared for glycerol selective oxidation, giving a decent 76.8% glyceric acid (GLYA) yield, and good stability. The kinetic experiments calculated apparent activation energy, turnover frequency (TOF), and reaction rates, demonstrating Pt/P25 could facilitate glyceraldehyde (GLYAD) formation and inhibit GLYA over‐oxidation. Series of structural techniques confirmed the 101/110 junctions in P25 contributed electronic effect on Pt through metal‐support interface, which improved the oxygen activation ability and optimized the GLYAD/GLYA adsorption modes. Furthermore, progressive scale‐up reactions were tested and the mass transfer limitations under different conditions were thoroughly studied. The obtained mass transfer factors suggested the gas–liquid and liquid–solid mass transfer were severely limited. Finally, through optimizing the conditions, Pt/P25 catalyst achieved 75.8% GLYA yield at 300 ml‐scale reaction, realizing equivalent magnification with the 5 ml‐scale experiment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt-based catalysts with manganese oxide octahedral molecular sieves as support. • Pt/OMS-2 catalysis shows specific selectivity for hydrogenation of C O bonds. • Hydrogenation of C O bonds followed a water-mediated mechanism. • Specific selectivity was attributed to a vertical adsorption model. Catalytic performances of supported metal catalysts are highly affected or even dominated by supports. Here, the manganese oxide octahedral molecular sieves (OMS-2) supported Pt nanoparticles (Pt/OMS-2) show specific selectivity in the hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan (BHMF) in liquid water, without ring-hydrogenation or ring-opening, even under harsh conditions. a 97.6 ± 2.1 % yield of BHMF was obtained over Pt/OMS-2 within 2 h at 30 °C and 1.5 MPa H 2. This specific selectivity was attributed to a vertical adsorption model of BHMF at the interface, where an O atom and H atom of hydroxyl attached to the Mn and O2− sites. The hydrogenation of the C O bond followed hydroxy routes through a water-mediated mechanism. Specifically, a water molecule facilitated the transfer of hydrogen atoms between the carbonyl group and the Pt surface, with the cleavage of O H bonds being a key step in the overall process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of Cu-Co/CeO x catalysts were prepared by reduction of CuCoCe-LDH. • CoCe-Vö interface structure and H 2 spillover effect were investigated. • DFT calculations reveal that CoCe-Vö interface could activate C O bond of MFA. • >95% of DMF yield was obtained over the Cu 1 -Co 8 /CeO x catalyst. The interface site between metal and support possess unique electronic and morphological structure, providing distinct active centers for favorable reaction in catalytic conversion of biomass derivatives to valuable chemicals. In this study, a series of Cu-Co/CeO x catalysts were prepared for hydrogenolysis of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) via reduction of the corresponding layered double hydroxide precursors. The characterizations indicated the formation of CoCe-Vö interface (Vö denotes oxygen vacancy) and the effect of hydrogen spillover from Cu species to CoCe-Vö interface. Furthermore, the experiments and theoretical calculations verified that CoCe-Vö interface could activate the C O bond. The optimized catalyst showed a DMF yield of > 90% at 180 °C and 1.5 MPa H 2 with no deactivation in the cycling tests. This study reveals the interfacial effects of the nanocatalysts, including the oxygen vacancies and hydrogen spillover, on hydrogenolysis of HMF, which provided a simple and efficient approach for synthesis of high-performance non-noble metal nanocatalysts applied to the hydrogenolysis of various biomass derivatives. [ABSTRACT FROM AUTHOR]

Cu‐based catalysts, which are regarded as the most promising catalysts for CO2 conversion, suffer dramatic deactivation at high temperatures. In this work, LaFeO3, a typical perovskite‐type oxide, is employed to disperse and stabilize Cu particles for the reverse water gas shift reaction. Compared to traditional Cu‐based catalysts, Cu/LaFeO3 exhibits a higher conversion with 100% CO selectivity and better stability at 873 K. Structural and spectroscopic characterization including N2O chemisorption, high‐resolution transmission electron microscopy, in situ x‐ray diffraction, and x‐ray absorption fine structure show that metallic Cu is well dispersed on LaFeO3, forming more Cu‐LaFeO3 interface. CO2 temperature‐programmed surface reaction (CO2‐TPSR), two‐step transient surface reaction (two‐step TSR), and transient in situ diffuse reflectance infrared Fourier transformed spectroscopy experiments demonstrate that the superior activity is attributed to the synergistic effect between the highly dispersed Cu particles for H2 dissociation and the abundant oxygen vacancies in LaFeO3 support for CO2 activation. The synergistic effect between metal and perovskite‐type oxide increases metal‐support interfaces and enhances CO2 activation, leading to a potential application in a variety of chemical reactions. [ABSTRACT FROM AUTHOR]

The production of nitrous oxide, N2O, via NH3 oxidation is not on a practical scale due to the lack of a suitable catalyst. Instead, it is produced via thermal decomposition of NH4NO3, rendering N2O too costly and limiting its prospective uses. Herein, we report CeO2‐supported Au nanoparticles (2–3 nm) as a highly selective catalyst for low‐temperature NH3 oxidation to N2O, exhibiting two orders of magnitude higher space–time yield than the state‐of‐the‐art Mn−Bi/α‐Al2O3 and remarkable stability over 70 h on stream. The reaction proceeds via a Mars–van Krevelen mechanism, with the density of interfacial Auδ+ species and the oxygen storage capacity of CeO2 identified as the key performance descriptors. The latter could be enhanced by cobalt doping, improving the catalytic activity and setting a new benchmark for N2O productivity. These findings establish NH3 oxidation as an efficient process for N2O manufacture and facilitate its broader utilization in selective oxidations. [ABSTRACT FROM AUTHOR]

H2 adsorption on Au catalysts is weak and reversible, making it difficult to quantitatively study. We demonstrate H2 adsorption on Au/TiO2 catalysts results in electron transfer to the support, inducing shifts in the FTIR background. This broad background absorbance (BBA) signal is used to quantify H2 adsorption; adsorption equilibrium constants are comparable to volumetric adsorption measurements. H2 adsorption kinetics measured with the BBA show a lower Eapp value (23 kJ mol−1) for H2 adsorption than previously reported from proxy H/D exchange (33 kJ mol−1). We also identify a previously unreported H‐O‐H bending vibration associated with proton adsorption on electronically distinct Ti‐OH metal‐support interface sites, providing new insight into the nature and dynamics of H2 adsorption at the Au/TiO2 interface. [ABSTRACT FROM AUTHOR]

The charge state of supported metal catalysts is the key to understand the elementary processes involved in catalytic reactions. However, high-precision charge analysis of the metal catalysts at the atomic level is experimentally challenging. To address this critical challenge, high-sensitivity electron holography has recently been successfully applied for precisely measuring the elementary charges on individual platinum nanoparticles supported on a titanium dioxide surface. In this review, we introduce the latest advancements in high-precision charge analysis and discuss the mechanisms of charge transfer at the metal-support interface. The development of charge measurements is entering a new era, and charge analyses under conditions closer to practical working environments, such as real-time, real-space, and reactive gas environments, are expected to be realized in the near future., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site–for further information please contact journals.permissions@oup.com.)

The science of heterogeneous catalysis is primarily based on surface phenomena, which occur on the surface of nanoscale structures at sub-Å dimensions. On these surfaces, only some atomic sites which have a unsaturated valence feature (under-coordinated or coordinately unsaturated) are discerned to be the active sites, i.e., active for surface processes, including adsorption, surface reactions, and desorption. With illustrative examples from the HR-TEM studies of the Cu/ZnO/Al2O3methanol synthesis catalyst and Au/TiO2 catalyst for CO oxidation reactions, we show pictorial evidences of many of the surface discontinuities and active sites at steps, edges, and perimeter areas, as well as surface terminations and crystal planes, such as (111), (100), and (110). The principal objective of this presentation is to offer new perspectives on the nature of active site (in an ensemble of atoms/a cluster) and its electronic and geometric properties. This article is organized into 2 parts. In this part I of the Series, we offer new knowledge-based analysis of the geometric effects/properties of the nanoclusters and active sites, which are governed by a specific size (at nm scale) and shape/morphology. In part II, we will elaborate on the electronic properties which arise as a result of typical metallic to nonmetallic transition. We also introduce and discuss new and fundamental concepts such as "Brønsted–Evans–Polanyi relationships" and "volcano curves" that are used to establish a partitioning between the "electronic" and "geometric" effects. Two interrelated techniques, STEM-EELS and STXM-XAS, will be used to show the atomic-scale (sub-Å) features of these morphological properties. [ABSTRACT FROM AUTHOR]

A strategy has been made to design a more active and stable metal-support interface by controlled synthesis of Ni nanoparticle on bimodal alumina support for CO 2 reforming with methane. A bimodal porous alumina support was prepared via the evaporation-induced self-assembly (EISA) method, and the nickel nanoparticles (5 wt.%) on bimodal alumina was synthesized using four different synthesis methods such as freeze drying, wet impregnation, urea deposition-precipitation, and chemical vapor deposition method. The reactivity of nickel nanoparticles was evaluated for CO 2 reforming with methane, concerning the CO 2 and CH 4 conversion as well as the H 2 to CO ratio of the produced syngas. The catalysts were thoroughly characterized before and after the reaction using different techniques such as X-ray diffraction (XRD), N 2 sorption analysis, H 2 -temperature programmed reduction (H 2 -TPR), H 2 -temperature programmed desorption (H 2 -TPD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), inductive coupled plasma-mass spectrometry (ICP-MS) and transmission electron microscopy (TEM). Characterization of various catalysts revealed that variation of synthesis procedure affects the metal-support interface and the type of nickel species present on the γ-alumina support, as well as the textural properties of the catalysts. The catalytic behavior was entirely different for each of the as-developed metal-support interface, derived in by the use of different synthesis procedures. The catalyst prepared by urea deposition-precipitation method was found to be most active and stable at 700 °C and 1atm for a period of a 100h run of time on stream with diluted gas feed and even without the dilution of feed gas for next 25h of the run. Comparing with bimodal catalyst, a unimodal catalyst with same metal loading exhibited the inferior catalytic activity and stability. The results of the comparative study showed that the stable catalytic performance of the bimodal structured catalyst is due to the combined effect of the type of metal-support interface of the catalyst, smaller size of nickel particle and bimodal structure of support material. The bimodal pore character of catalyst support has shown to prevent, Ni particles from sintering during the reaction and hence, better catalytic performance and resistance to coking. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkyltriethoxysilane (C n TES) was grafted onto commercial Al 2 O 3 prior to Ni loading. • The maximum quantity of grafted C n TES depended on the surface properties of Al 2 O 3. • The alkyl substituent of grafted C n TES influenced Ni dispersion and reducibility. • Ni particles became smaller and more metallic with increasing Si/Al ratio. • C 3 TES was the most effective for active Ni catalysts among the C n TES materials. Tuning metal–support interface in supported Ni catalysts is a promising approach for overcoming the agglomeration of Ni particles and the low reducibility of Ni species. This study describes a facile two-step method to produce active Ni catalysts for the hydrogenation of benzyltoluene. In the first step, alkyltriethoxysilanes (C n TES, n = 1, 3, and 8) were grafted onto the surface of commercial Al 2 O 3. The maximum Si/Al ratio of the prepared C n TES-on-Al 2 O 3 materials was determined to be approximately 2.9 mol.%, which can vary depending on the surface properties of Al 2 O 3. The second step was H 2 reduction of the Ni precursor loaded on the C n TES-on-Al 2 O 3 materials to remove alkyl substituents from the grafted C n TES and form Ni particles on the surface of silica grafted onto alumina (SGA). The hydrogenation performance of the obtained Ni/SGA_C n TES catalysts was improved with increasing Si/Al ratio owing to higher Ni dispersion and more abundant metallic Ni. The activity of the Ni/SGA_2.9C n TES (Si/Al = 2.9 mol.%) catalysts exhibited a volcano-shaped relationship with the length of the alkyl substituent of grafted C n TES, reaching the maximum for C 3 TES. Notably, Ni/SGA_2.9C 3 TES showed excellent ability for the adsorption of H 2 and substrate, as well as high stability, resulting from the reduced agglomeration of Ni particles and the modulated metal–support interface. Therefore, the demonstrated synthesis approach can render Ni catalysts servable to promote the commercialization of liquid organic hydrogen carrier system. [ABSTRACT FROM AUTHOR]

Copper-containing cerium oxide materials have received considerable attention both in catalysis and electro-catalysis fields due to their unique physicochemical characteristics in conjunction to their lower cost compared to noble metals (NMs)-based catalysts. Nowadays, it is well documented that the complex Copper–Ceria interactions (either geometric or electronic) have a key role on the catalytic performance. Hence, considerable efforts have been devoted on the understanding and the fine-tuning of metal–oxide interactions. Despite the growing progress in the field, several crucial issues related to the influence of: i) particle’s shape and size, ii) active site’s chemical state, iii) charge transfer between interfacial sites, and iv) intrinsic defects ( e.g. , surface oxygen vacancies) on the interfacial activity are still under investigation. This survey summarizes the recent advances in the last 10 years on the fundamental origin of Copper–Ceria interactions and their implications on the catalytic activity. The insights lately obtained by means of: i) ex situ advanced characterization techniques, ii) in situ sophisticated studies (e.g., operando techniques), iii) theoretical analysis ( e.g. , DFT calculations), and iv) innovative probing approaches (such as the inverse CeO 2 /CuO model system) are provided. The state-of-the-art catalytic applications of CuO/CeO 2 binary oxides (water gas shift (WGS) reaction, preferential oxidation (PROX) of CO, CO 2 hydrogenation, selective catalytic reduction (SCR), N 2 O decomposition, etc. ) in relation to the aforementioned aspects are discussed. Some guidelines towards the fine-tuning of the surface chemistry of CuO/CeO 2 catalysts for real life energy and environmental application are provided. [ABSTRACT FROM AUTHOR]

The importance of metal–support interfaces is widely known in commercial and fundamental heterogeneous catalysis; however, it is difficult to characterize the active interface sites. In this study, we synthesize a new class of compound comprising tetragonal [Ti 8 O 8 (OH) 4 ] 12+ clusters interlinked by terephthalates (bdc) and [Cu 2 (OH) 6 ] 2− linkers {Ti 8 O 8 (OH) 4 ·(bdc) 2 ·[Cu 2 (OH) 6 ] 4 }. The crystalline structure was refined for X-ray diffraction and direct links between [Cu 2 (OH) 6 ] 2− and [Ti 8 O 8 (OH) 4 ] 12+ are confirmed by extended X-ray absorption fine structure. This compound functions very well ( k = 0.117 min −1 in CO 63 Pa + O 2 76 Pa at 323 K) as a catalytic model of interface Cu sites on ultra-dispersed Ti [hydro]oxide for preferential oxidation of CO in predominantly H 2 gas, that is important for the purification of hydrogen used in fuel cells. In comparison, mean 1.7-nm CuO nanoparticles embedded inside the pores of MIL125 were inert ( k = 0.0035 min −1 ) because of the absence of links between Cu and [Ti 8 O 8 (OH) 4 ] 12+ clusters. In CO 0.51 kPa + O 2 0.51 kPa at 323 K, the conversion to CO 2 and CO PROX selectivity using Ti 8 O 8 (OH) 4 ·(bdc) 2 ·[Cu 2 (OH) 6 ] 4 (76% and 99%) was significantly higher than that using CuO/CeO 2 (28% and 96%, respectively) for 24 h. [ABSTRACT FROM AUTHOR]

Pt nanoparticles stabilized with alumina nanorods (Pt@Al 2 O 3 ) were synthesized by a simple preparation method using a mixture of Pt nanoparticles, an alumina precursor, an organic surfactant, and a reducing agent. Because the alumina nanorods stabilized Pt nanoparticles, the sintering of Pt nanoparticles was significantly suppressed during a high temperature water gas shift reaction, demonstrating 1.7–13.6 times higher CO conversions or 1.0–8.0 times higher TOF compared to other alumina-supported Pt catalysts. In addition, the increased metal–support interface for Pt@Al 2 O 3 significantly improved the water gas shift reaction activity. [ABSTRACT FROM AUTHOR]

Ammonia Oxidation, Au/CeO2, Metal-Support Interface, Nitrous Oxide, Reaction Mechanisms Keywords: Ammonia Oxidation; Au/CeO2; Metal-Support Interface; Nitrous Oxide; Reaction Mechanisms EN Ammonia Oxidation Au/CeO2 Metal-Support Interface Nitrous Oxide Reaction Mechanisms 1 1 1 04/27/22 20220502 NES 220502 B A game of two halves b Direct ammonia oxidation unlocks a pathway towards affordable and efficient production of nitrous oxide, a highly promising agent for selective oxidation reactions, but necessitates the development of suitable catalysts. Back Cover: Ceria-Supported Gold Nanoparticles as a Superior Catalyst for Nitrous Oxide Production via Ammonia Oxidation (Angew. [Extracted from the article]

Keywords: Ammonia Oxidation; Au/CeO2; Metal-Support Interface; Nitrous Oxide; Reaction Mechanisms EN Ammonia Oxidation Au/CeO2 Metal-Support Interface Nitrous Oxide Reaction Mechanisms 1 1 1 04/27/22 20220502 NES 220502 B Ein Spiel zweier Hälften b Die direkte Oxidation von Ammoniak eröffnet einen Weg zur kostengünstigen und effizienten Produktion von Stickstoffoxid, einem vielversprechenden Reagens für selektive Oxidationsreaktionen. Rücktitelbild: Ceria-Supported Gold Nanoparticles as a Superior Catalyst for Nitrous Oxide Production via Ammonia Oxidation (Angew. Ammonia Oxidation, Au/CeO2, Metal-Support Interface, Nitrous Oxide, Reaction Mechanisms. [Extracted from the article]

Abstract: A glow discharge plasma treatment was used to modify the impregnation method to prepare photocatalysts with the following steps: impregnation, cold plasma treatment, calcination, and reduction. The activity and properties of the catalysts were studied in comparison with those prepared with traditional impregnation method. The activities for hydrogen generation from water/alcohols mixtures were significantly promoted. The properties including the metal dispersion, near-UV absorption, and metal stability were also enhanced. The enhanced metal dispersion and optical absorption partly promoted the activity but the effect was limited. It was speculated that the plasma method produced an enhanced metal–support interaction. According to high-resolution TEM observation, a greatly distorted metal–support interface was formed on the plasma prepared catalyst. This interface allowed a close contact between the metal atoms and support lattices, which supported the existence of the enhanced interaction. This interface was expected to facilitate the electron transfer during photocatalytic reaction and be the major reason for the high activity of the plasma prepared photocatalysts. [Copyright &y& Elsevier]

Pt/Al2O3 catalysts with platinum contents of 0.1, 1.0 and 3.0 wt% were used for the low temperature combustion of methanol in the absence and the respective presence of a trace amount of ammonia. It is observed that ammonia inhibits the combustion of methanol, which is due to competition between methanol and ammonia for the same sites. For a fixed space velocity and without ammonia in the gas, the performances of the catalysts increase up to a Pt loading of 1.0 wt%. In the presence of ammonia, however, no upper limit of performance is observed with increased Pt content. The results are discussed in terms of both Pt–support interface and the Pt surface being active. [ABSTRACT FROM AUTHOR]

Nearly uniform (nearly molecular) supported metals made from molecular organometallic precursors are ideally suited to characterization by EXAFS spectroscopy at the metal edge. Among the most thoroughly investigated mononuclear metal complexes on metal oxide and zeolite supports are MgO-supported rhenium subcarbonyls, approximately Re(CO)3{OMg}3 (where the braces denote groups terminating the bulk of the support). These were made, e.g., from [HRe(CO)5] and from [H3Re3(CO)12]; the Re–Osurface distance determined by EXAFS spectroscopy is 2.15 ± 0.03 Å the support is a tridentate ligand. The Re–Osurface distances in related supported complexes of Groups 7 and 8 metals are all in the range of 2.1–2.2 Å, matching those in molecular analogues. HTa{OSi}2, prepared from [Ta(CH2C(CH3)3)3(=CHCCH3)3] on SiO2, catalyzes a new reaction, propane metathesis. Supported complexes made from [HRe(CO)5] catalyze alkene hydrogenation but not cyclopropane hydrogenolysis, whereas catalysts made from [H3Re3(CO)12] catalyze both these reactions, and EXAFS data indicate neighboring Re centers on the latter (but not the former), which are implicated in the catalysis. EXAFS data similarly indicate supported Mo and W pair sites as catalysts. Supported metal clusters made by decarbonylation of metal carbonyl clusters, e.g., Ir4/γ-Al2O3 and Ir6/γ-Al2O3 or Rh6/zeolite NaY, are indicated by EXAFS data to be tetrahedra and octahedra, respectively. Such clusters are the species detected by EXAFS spectroscopy at 298 K in the presence of propene and H2 undergoing catalytic hydrogenation, and they are identified as the catalytically active species. The catalytic activities of the clusters for toluene hydrogenation and alkene hydrogenation are almost unaffected by changes in metal oxide support composition, but they depend on the cluster size, although the catalytic reaction is structure insensitive. Thus, supported metal clusters offer new catalytic properties. [ABSTRACT FROM AUTHOR]

• Hydrodeoxygenation of phenol at gas phase over Pd-NbO x /SiO 2 catalysts. • Pd/SiO 2 promotes hydrogenation pathways whereas addition of Nb favors deoxygenation. • Deoxygenation depended on the contact between Nb cations and metal particle. • Pd-NbO x interface is responsible for the activation of the C O bond. In this work, the effect of interfacial sites between Pd particles and Nb 2 O 5 species is investigated by testing a series of Pd-Nb 2 O 5 /SiO 2 catalysts with different niobium loadings for the HDO reaction of phenol in the gas phase. Important differences in the selectivity to deoxygenated product were observed depending on the presence of niobium oxide close to Pd particles, which reveals the key role of the type of active phase in the control of reaction steps. It was found that Pd/SiO 2 catalyst promotes hydrogenation pathways, producing cyclohexanone as the major product. For Pd-Nb 2 O 5 /SiO 2 catalyst containing a Nb/Pd molar ratio of 0.5, a sharp increase in the selectivity to benzene is observed (7.5-fold). Increasing the Nb/Pd molar ratio, the formation of benzene is enhanced. The results showed that the Pd-Nb 2 O 5 interface, composed by an oxophilic oxide in the perimeter of the metal particle, is responsible for the activation of the C O bond, promoting the deoxygenation reaction. [ABSTRACT FROM AUTHOR]

• Atomic-level reaction mechanism of CO 2 methanation on Rh/TiO 2 catalyst was studied. • Metal-support interface is the active site of CO 2 methanation on Rh/TiO 2 catalyst. • CO 2 methanation on Rh/TiO 2 is dominated by the RWGS + CO hydrogenation pathway. • H-assisted COOH* dissociation is the rate-determining step of CO 2 methanation. Rh/TiO 2 has been regarded as a very promising catalyst for the low-temperature CO 2 methanation. However, the atomic-level reaction mechanism that dictates the reactivity and selectivity of CO 2 reduction over Rh/TiO 2 catalyst remains elusive. The reaction mechanism governed by a delicate interplay of surface reaction chemistry and thermodynamics was systematically investigated using density functional theory calculations. Theoretical results indicate that significant charges accumulate at the perimeter of the interface between support TiO 2 and Rh nanoparticle. Metal-support interface is identified as the most active site for CO 2 adsorption and activation over Rh/TiO 2 catalyst. Compared with the direct C–O bond cleavage pathway and formate pathway, the reverse water–gas shift (RWGS) reaction followed by CO hydrogenation is much more thermodynamically and kinetically favorable for CO 2 methanation over Rh/TiO 2 catalyst. The RWGS + CO hydrogenation pathway via H 2 COH* dissociation dominates CO 2 methanation due to the relatively lower energy barrier. CO 2 methanation via the RWGS + CO hydrogenation pathway prefers to proceed through the channel: CO 2 * → COOH* → CO* → COH* → HCOH* → H 2 COH* → CH 3 * → CH 4 *. H-assisted COOH* dissociation is identified as the rate-determining step of CO 2 methanation over Rh/TiO 2 catalyst. Finally, a reaction network is established to understand the atomic-level reaction mechanism of CO 2 methanation over Rh/TiO 2 catalyst. These mechanistic insights can guide the rational design of catalyst active centers to boost the activity and selectivity of CO 2 reduction. [ABSTRACT FROM AUTHOR]