Strong metal-support interactions between highly dispersed Cu^(+) species and ceria via mix-MOF pyrolysis toward promoted water-gas shift reaction

The modulation of metal-support interfacial interaction is significant but challenging in the design of high-efficiency and high-stability supported catalysts.Here,we report a synthetic strategy to upgrade Cu-CeO_(2)interfacial interaction by the pyrolysis of mixed metal-organic framework(MOF)structure.The obtained highly dispersed Cu/CeO_(2)-MOF catalyst via this strategy was used to catalyze water-gas shift reaction(WGSR),which exhibited high activity of 40.5μmolCOgcat^(-1).s^(-1)at 300℃and high stability of about 120 h.Based on comprehensive studies of electronic structure,pyrolysis strategy has significant effect on enhancing metal-support interaction and then stabilizing interfacial Cu^(+)species under reaction conditions.Abundant Cu^(+)species and generated oxygen vacancies over Cu/CeO_(2)-MOF catalyst played a key role in CO molecule activation and H2O molecule dissociation,respectively.Both collaborated closely and then promoted WGSR catalytic performance in comparison with traditio nal supported catalysts.This study shall offer a robust approach to harvest highly dispersed catalysts with finely-tuned metal-support interactions for stabilizing the most interfacial active metal species in diverse heterogeneous catalytic reactions.

Effects of the partial replacement of La by M(M=Ce,Ca and Sr) in La_(2-x)M_xCuO_4 perovskites on catalysis of the water-gas shift reaction

The performance of La2-x M x CuO4 perovskites （where M=Ce,Ca or Sr） as catalysts for the water-gas shift reaction was investigated at 290℃ and 360℃.The catalysts were characterized by EDS,XRD,N2 adsorption-desorption,XPS and XANES.The XRD results showed that all the perovskites exhibited a single phase （the presence of perovskite structure）,suggesting the incorporation of metals in the perovskite structure.The XPS and XANES results showed the presence of Cu2＋ on the surface.The perovskites that exhibited the best catalytic performance were La 2 x Ce x CuO 4 perovskites,with CO conversions of 85% 90%.Moreover,these perovskites have higher surface areas and larger amounts of Cu on the surface.And Ce has a higher filled energy level than the other metals,increasing the energy of the valence band of Ce and providing more electrons for the reaction.Besides,the La1.80Ca0.20CuO4 perovskite showed a good catalytic performance.

Copper Promoted Au/ZnO-CuO Catalysts for Low Temperature Water-gas Shift Reaction

Various copper promoted Au/ZnO-CuO catalysts with different atomic ratios of Cu to Zn prepared by means of co-precipitation were tested for the low temperature water-gas shift（WGS） reaction. The catalytic activity of the catalyst depends largely on the ratio of Cu to Zn. The addition of an appropriate amount of copper can considerably improve both the catalytic activity and the stability of the catalyst in comparison with those of copper-free Au/ZnO cata- lysts. The enhanced reducibility of copper oxide in the Au/ZnO-CuO ternary-component catalysts, which was confirmed by H2-TPR, may be related to the high activity and stability of the catalyst for the low temperature WGS reaction.

Effects of CeO_2 on structure and properties of Ni-Mn-K/bauxite catalysts for water-gas shift reaction

Multiple-metal catalysts （Ni-Mn-Ce-K/bauxite） for Water-Gas Shift （WGS） reaction were prepared by impregnation, and the catalytic structure and properties were investigated by N2 physical, XRD, H2-TPR, and CO-TPD. The results indicated that the addition of 7.5% CeO2 improved the activity of the WGS reaction obviously, and also increased the specific surface area and pore volume of the catalysts. The addition of CeO2 decreases the reduction temperature, enhanced the adsorption and activation of H2O2, and improved the adsorption content of CO. Besides, active sites were not changed and the number of active sites on catalysts did not increase obviously.

La_(2-x)CexCu_(1-y)Zn_yO_4 perovskites for high temperature water-gas shift reaction

The performance of La2-xCexCu1-yZnyO4 perovskites as catalysts for the high temperature water-gas shift reaction （HT-WGSR） was investigated. The catalysts were characterized by EDS, XRD, BET surface area, TPR, and XANES. The results showed that all the perovskites exhibited the La2CuO4 orthorhombic structure, so the Pechini method is suitable for the preparation of pure perovskite. However, the La1.90Ce0.10CuO4 perovskite alone, when calcined at 350/700℃, also showed a （La0.935Ce0.065）2CuO4 perovskite with tetragonal struc- ture, which produced a surface area higher than the other perovskites. The perovskites that exhibited the best catalytic performance were those calcined at 350/700℃ and, among these, La1.90Ce0.10CuO4 was outstanding, probably because of the high surface area associated with the presence of the （La0.935Ce0.065）2CuO4 perovskite with tetragonal structure and orthorhombic La2CuO4 phase.

Kinetics of the water-gas shift reaction in Fischer-Tropsch synthesis over a nano-structured iron catalyst

Based on formate and direct oxidation mechanisms,three Langmuir-Hinshelwood-Hougen-Watson （LHHW） kinetic models of the water-gasshift （WGS） reaction over a nano-structured iron catalyst under Fischer-Tropsch synthesis （FTS） reaction conditions were derived and compared with those over the conventional catalyst.The conventional and nanostructured Fe/Cu/La/Si catalysts were prepared by co-precipitation of Fe and Cu nitrates in aqueous media and water-oil micro-emulsion,respectively.The WGS kinetic data were measured by experiments over a wide range of reaction conditions and comparisons were also made for various rate equations.WGS rate expressions based on the formate mechanism with the assumption that the formation of formate is rate determining step were found to be the best.

Direct identification of the carbonate intermediate during water-gas shift reaction at Pt-NiO interfaces using surface-enhanced Raman spectroscopy

Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction.However,the molecular reaction mechanism of water-gas shift reaction at these interfaces still remains unclear.Herein,water-gas shift reaction at Pt-NiO interfaces has been in-situ explored using surface-enhanced Raman spectroscopy by construction of Au@Pt@NiO nanostructures.Direct Raman spectroscopic evidence demonstrates that water-gas shift reaction at Pt-NiO interfaces proceeds via an associative mechanism with the carbonate species as a key intermediate.The carbonate species is generated through the reaction of adsorbed CO with gaseous water,and its decomposition is a slow step in water-gas shift reaction.Moreover,the Pt-NiO interfaces would promote the formation of this carbonate intermediate,thus leading to a higher activity compared with pure Pt.This spectral information deepens the fundamental understanding of the reaction mechanism of water-gas shift reaction,which would promote the design of more efficient catalysts.

Effects of ZrO_2 Content on Structure and Performance of Cu/CeO_2-ZrO_2 Catalysts for Water-Gas Shift Reaction

Cu/CeO2-ZrO2 catalysts for water-gas shift （WGS） reaction were prepared with co-precipitation method, and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis, XRD and H2-TPR. The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2. With increasing ZrO2 content, the pore size distribution is centered on 1.9 nm. ZrO2 can efficiently restrain the growth of Cu crystal particles. The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction, which can lead to both higher catalytic activity and better thermal stability. When ZrO2 content is 10% （atom fraction）, Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7% at the reaction temperature of 200℃.

Molybdenum carbide clusters for thermal conversion of CO2 to CO via reverse water-gas shift reaction

Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift(RWGS)reaction, however the large grain size up to micrometers renders its relatively lower active sites utilization efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molybdenum carbide hybrid catalyst with sub-nanosized cluster(the average size as small as 0.5 nm) is prepared via a facile carbothermal treatment for highly selective CO2-CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μmol gMo2C-1s-1 at 400 ℃ with a superior selectivity toward CO(> 99.5%). This work 2 highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.

Three-dimensionally ordered macro-porous Pt/TiO_2 catalyst used for water-gas shift reaction

Three-dimensionally ordered macro-porous （3DOM） Pt/TiO2 catalysts were prepared by template and impregnation methods, and the resultant samples were characterized by using TG-DTA, XRD, SEM, TEM, and TPR techniques. The catalytic performance for water-gas shift （WGS） reaction was tested, and the influences of some conditions, such as reduction temperature of catalysts, the amount of Pt loadings and space velocity on catalytic performance were investigated. It was shown that Pt particles were homogeneously dispersed on 3DOM TiO2. The reduction of TiO2 surface was important for the catalytic performance. The activity test results showed that the 3DOM Pt/TiO2 catalysts exhibited very good catalytic performance for WGS reaction even at high space velocity, which was owing to the better mass transfer of 3DOM porous structure besides the high intrinsic activity of Pt/TiO2.

Highly mass activity electrocatalysts with ultralow Pt loading on carbon black for hydrogen evolution reaction

Pt-based nanocatalysts offer excellent prospects for various industries.However,the low loading of Pt with excellent performance for efficient and stable nanocatalysts still presents a considerable challenge.In this study,nanocatalysts with ultralow Pt content,excellent performance,and carbon black as support were prepared through in-situ synthesis.These~2-nm particles uniformly and stably dispersed on carbon black because of the strong s-p-d orbital hybridizations between carbon black and Pt,which suppressed the agglomeration of Pt ions.This unique structure is beneficial for the hydrogen evolution reaction.The catalysts exhibited remarkable catalytic activity for hydrogen evolution reaction,exhibiting a potential of 100 mV at 100 mA·cm^(-2),which is comparable to those of commercial Pt/C catalysts.Mass activity(1.61 A/mg)was four times that of a commercial Pt/C catalyst(0.37 A/mg).The ultralow Pt loading(6.84wt%)paves the way for the development of next-generation electrocatalysts.

Potassium-decorated active carbon supported Co-Mo-based catalyst for water-gas shift reaction

The effect of potassium-decoration was studied on the activity of water-gas shift （WGS） reaction over the Co-Mo-based catalysts supported on active carbon （AC）, which was prepared by incipient wetness co-impregnation method. The decoration of potassium on active carbon in advance enhances the activities of the CoMo-K/AC catalysts for WGS reaction. Highest activity （about 92% conversion） was obtained at 250 ？ C for the catalyst with an optimum K 2 O/AC weight ratio in the range from 0.12 to 0.15. The catalysts were characterized by TPR and EPR, and the results show that activated carbon decorated with potassium makes Co-Mo species highly dispersed, and thus easily reduced and sulfurized. XRD results show that an appropriate content of potassium-decoration on active carbon supports may favors the formation of highly dispersed Co 9 S 8 -type structures which are situated on the edge or a site in contact with MoS 2 , K-Mo-O-S, Mo-S-K phase. Those active species are responsible for the high activity of CoMo-K/AC catalysts.

Effect of yttrium addition on water-gas shift reaction over CuO/CeO_2 catalysts

This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction （XRD）, Raman spectroscopy, H2-TPR, cyclic voltammetry （CV） and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity （CO conversion reaches 93.4% at 250 ℃） and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile （i.e., the reduction of surface copper oxide （crystalline forms） interacted with surface oxygen vacancies on ceria）, and the area of peak C2 and A1 （Cu^0→←Cu^2＋ in cyclic voltammetry process）, respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.

A Modified Co-precipitation Method to Prepare Cu/ZnO/Al2O3 Catalyst and Its Application in Low Temperature Water-gas Shift(LT-WGS)Reaction

A modified co-precipitation method for the production of Cu/ZnO/Al2O3 complex was studied. The modification was that part of Al was introduced by adding Al^（3＋） into Cu^（2＋）/Zn^（2＋） solution, and the rest of Al was added after co-precipitation step in the form of pseudo-boehmite. The prepared samples were characterized by different techniques such as X-ray diffraction, N2 adsorption, H2-N2O titration, temperature programmed reduction and scanning electron microscopy. X-ray diffraction characterizations revealed that Al^（3＋） can be doped in aurichalcite lattice, and the maximum doping amount of Al^（3＋） was 5.0% of total Cu and Zn atoms. The Cu/ZnO/Al2O3 sample produced by the modified method, in which co-precipitated Al^（3＋） was 2.5% of total Cu and Zn atoms showed much better activity and stability in water-gas shift reaction than commercial sample. The high Cu surface area（26.1 m^2/g） obtained by decompositon of doped aurichalcite is believed to be responsible for the activity enhancement. The stability was enhanced mainly because of the support effect of γ-Al2O3, which was decomposed from pseudo-boehmite in the calcination step.

Boosting Oxygen Evolution Reaction Performance on NiFe‑Based Catalysts Through d‑Orbital Hybridization

Anion-exchange membrane water electrolyzers(AEMWEs)for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant NiFe-based catalysts.By introducing a third metal into NiFe-based catalysts to construct asymmetrical M-NiFe units,the d-orbital and electronic structures can be adjusted,which is an important strategy to achieve sufficient oxygen evolution reaction(OER)performance in AEMWEs.Herein,the ternary NiFeM(M:La,Mo)catalysts featured with distinct M-NiFe units and varying d-orbitals are reported in this work.Experimental and theoretical calculation results reveal that the doping of La leads to optimized hybridization between d orbital in NiFeM and 2p in oxygen,resulting in enhanced adsorption strength of oxygen intermediates,and reduced rate-determining step energy barrier,which is responsible for the enhanced OER performance.More critically,the obtained NiFeLa catalyst only requires 1.58 V to reach 1 A cm^(−2) in an anion exchange membrane electrolyzer and demonstrates excellent long-term stability of up to 600 h.

Preparation and characterization of Cu-Ce-La mixed oxide as water-gas shift catalyst for fuel cells application

Cu-Ce-La mixed oxides were prepared by three precipitation methods （coprecipitation, homogeneous precipitation, and deposition precipitation） with variable precipitators and characterized using X-ray diffraction, BET, temperature-programmed reduction, and catalytic reaction for the water-gas shift. The Cu-Ce-La mixed oxide prepared by coprecipitation method with NaOH as precipitator presented the highest activity and thermal stability. Copper ion substituted quadrevalent ceria entered CeO2 （111） framework was in favor of activity and thermal stability of catalyst. The crystallinity of fresh catalysts increased with the reduction process. La^3＋ or Ce^4＋ substituted copper ion entered the CeO2 framework during reduction process. The coexistence of surface copper oxide （crystalline） and pure bulk crystalline copper oxide both contributed to the high activity and thermal stability of Cu-Ce-La mixes oxide catalyst.

Reaction视频中用户弹幕信息交互行为的情感反应生成机理研究

深入挖掘Reaction视频中弹幕信息交互行为的情感反应机理有助于理解用户弹幕创作背后的情感生成原因及情感变化过程。本文基于情感反应模型,利用定向内容分析法对哔哩哔哩网站中11个热门视频的弹幕信息资源、视频内容以及reactor反应情况展开编码研究,构建了Reaction视频中用户弹幕信息交互行为的情感反应生成机理模型。研究发现,Reaction视频弹幕信息交互行为中的情感反应生成机理总体上遵循“信息刺激-情感反应”的路径,信息刺激有时会独立唤醒情绪或特定情感态度,有时也会通过唤醒特定情感态度进而影响情绪或内化情感态度的生成。该模型有助于提升情感反应理论在计算机协助交流中的情境化探索,也将为社交媒体中用户与信息交互提供优化建议。

Tuning electronic structure of RuO_(2)by single atom Zn and oxygen vacancies to boost oxygen evolution reaction in acidic medium

The poor stability of RuO_(2)electrocatalysts has been the primary obstacles for their practical application in polymer electrolyte membrane electrolyzers.To dramatically enhance the durability of RuO_(2)to construct activity-stability trade-off model is full of significance but challenging.Herein,a single atom Zn stabilized RuO_(2)with enriched oxygen vacancies(SA Zn-RuO_(2))is developed as a promising alternative to iridium oxide for acidic oxygen evolution reaction(OER).Compared with commercial RuO_(2),the enhanced Ru–O bond strength of SA Zn-RuO_(2)by forming Zn-O-Ru local structure motif is favorable to stabilize surface Ru,while the electrons transferred from Zn single atoms to adjacent Ru atoms protects the Ru active sites from overoxidation.Simultaneously,the optimized surrounding electronic structure of Ru sites in SA ZnRuO_(2)decreases the adsorption energies of OER intermediates to reduce the reaction barrier.As a result,the representative SA Zn-RuO_(2)exhibits a low overpotential of 210 mV to achieve 10 mA cm^(-2)and a greatly enhanced durability than commercial RuO_(2).This work provides a promising dual-engineering strategy by coupling single atom doping and vacancy for the tradeoff of high activity and catalytic stability toward acidic OER.

Influence of Gas Components on the Formation of Carbonyl Sulfide over Water-Gas Shift Catalyst B303Q

Water-gas shift reaction catalyst at lower temperature （200-400 ℃） may improve the conversion of carbon monoxide. But carbonyl sulfide was found to be present over the sulfided cobaltmolybdenum/alumina catalyst for water-gas shift reaction. The influences of temperature, space velocity, and gas components on the formation of carbonyl sulfide over sulfided cobalt-molybdenum/alumina catalyst B303Q at 200-400 ℃ were studied in a tubular fixed-bed quartz-glass reactor under simulated water-gas shift conditions. The experimental results showed that the yield of carbonyl sulfide over B303Q catalyst reached a maximum at 220 ℃ with the increase in temperature, sharply decreased with the increase in space velocity and the content of water vapor, increased with the increase in the content of carbon monoxide and carbon dioxide, and its yield increased and then reached a stable value with the increase in the content of hydrogen and hydrogen sulfide. The formation mechanism of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was discussed on the basis of how these factors influence the formation of COS. The yield of carbonyl sulfide over B303Q catalyst at 200-400 ℃ was the combined result of two reactions, that is, COS was first produced by the reaction of carbon monoxide with hydrogen sulfide, and then the as-produced COS was converted to hydrogen sulfide and carbon dioxide by hydrolysis. The mechanism of COS formation is assumed as follows： sulfur atoms in the Co9Ss-MoS2/Al2O3 crystal lattice were easily removed and formed carbonyl sulfide with CO, and then hydrogen sulfide in the water-gas shift gas reacted with the crystal lattice oxygen atoms in CoO-MoOa/Al2O3 to form Co9S8-MoS2/Al2O3. This mechanism for the formation of COS over water-gas shift catalyst B303Q is in accordance with the Mars-Van Krevelen＇s redox mechanism over metal sulfide.

Exciting lattice oxygen of nickel–iron bi-metal alkoxide for efficient electrochemical oxygen evolution reaction

High efficiency,cost-effective and durable electrocatalysts are of pivotal importance in energy conversion and storage systems.The electro-oxidation of water to oxygen plays a crucial role in such energy conversion technologies.Herein,we report a robust method for the synthesis of a bimetallic alkoxide for efficient oxygen evolution reaction(OER)for alkaline electrolysis,which yields current density of 10 mA cm^(-2)at an overpotential of 215 mV in 0.1 M KOH electrolyte.The catalyst demonstrates an excellent durability for more than 540 h operation with negligible degradation in activity.Raman spectra revealed that the catalyst underwent structure reconstruction during OER,evolving into oxyhydroxide,which was the active site proceeding OER in alkaline electrolyte.In-situ synchrotron X-ray absorption experiment combined with density functional theory calculation suggests a lattice oxygen involved electrocatalytic reaction mechanism for the in-situ generated nickel–iron bimetal-oxyhydroxide catalyst.This mechanism together with the synergy between nickel and iron are responsible for the enhanced catalytic activity and durability.These findings provide promising strategies for the rational design of nonnoble metal OER catalysts.