The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes.This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets...The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes.This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets on the chemical looping oxidative propane dehydrogenation(CL-ODH).During CL-ODH,the oxygen concentration at the pellet surface initially decreased and then maintained stable before the final decrease.At the stage with the stable surface oxygen concentration,the reaction showed a stable C3H6 formation rate and high C3H6 selectivity.Therefore,based on Fick’s second law,the oxygen distribution and evolution in the oxygen carrier at this stage were further analyzed.It was found that main reactions of selective oxidation and over-oxidation were controlled by the oxygen bulk diffusion.C3H8 conversion rate kept decreasing during this stage due to the decrease of the oxygen flux caused by the decline of oxygen gradient within the oxygen carrier,while C3H6 selectivity increased due to the decrease of overoxidation.In addition,reaction rates could increase with the propane partial pressure due to the increase of the oxygen gradient within the oxygen carrier until the bulk transfer reached its limit at higher propane partial pressure.This study provides fundamental insights for the diffusion-controlled chemical looping reactions.展开更多
Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with h...Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with high selectivity. A high Faradaic efficiency(FE) of NH3 cannot be obtained under strong acid or alkaline conditions due to the uncontrollable adsorption energy and coverage of hydrogen species(H*) on active sites. This article describes the design and fabrication of a copper-palladium(Cu-Pd) alloy nanocrystal catalyst that inhibits H2 and nitrite generation in electrolytes with different nitrate concentrations and varied pH. The interfacial sites of Cu-Pd alloys could enhance the adsorption energy and coverage of H* while increasing the reaction rate constant of NO_(2)*-to-NO*, which achieves a rapid conversion of NO_(2)* along with a decreased FE of NO_(2)-. Under ambient conditions, optimal FE(NH3) is close to 100% at a wide pH range, with the solar-to-chemical conversion efficiency approaching 4.29%. The combination of thermodynamics and kinetics investigations would offer new insights into the reduction mechanism of NO_(2)* for further development of nitrate reduction.展开更多
CoCu-based catalysts are widely used in CO_(x) hydrogenation reactions to produce higher alcohols due to the C–C coupling ability of Co and the ability of Cu to produce alcohols.This work describes the role of easily...CoCu-based catalysts are widely used in CO_(x) hydrogenation reactions to produce higher alcohols due to the C–C coupling ability of Co and the ability of Cu to produce alcohols.This work describes the role of easily happened CO_(2)dissociation on the CoCu surface during the reaction,using different silica support to tune the metal–support interaction,reaches different selectivity to ethanol.CoCu supported on mesoporous silica MCM-41 shows ethanol selectivity as high as 85.3%,the ethanol space-time yield(STY)is 0.229 mmol/(gmetal∙h),however,poor selectivity to ethanol as low as 28.8%is observed on CoCu supported on amorphous silica.The different selectivity is due to the different intensities of CO_(2)dissociation on the catalysts.The adsorbed O*produced via CO_(2)dissociation can occupy the cobalt hollow sites on CoCu surfaces,which are also the adsorption sites of C1 intermediates for further C–C coupling.展开更多
CONSPECTUS:As one of the essential pathways to carbon neutrality or carbon negativity,the electrochemical reduction of CO_(2) offers tremendous prospects for platform chemicals and fuel production.Copper(Cu)is current...CONSPECTUS:As one of the essential pathways to carbon neutrality or carbon negativity,the electrochemical reduction of CO_(2) offers tremendous prospects for platform chemicals and fuel production.Copper(Cu)is currently the only metal material that is able to reduce CO_(2) to multicarbon(C2+)products.Despite the fact that copper-based materials have been investigated for decades,we still confront numerous challenges on the path to the fundamental understanding and large-scale deployment of copper-based electrocatalysts for CO_(2) reduction.For fundamental investigations,it remains a variety of open questions about the CO_(2) reduction mechanisms.The convoluted C−C coupling pathways and product bifurcation processes confuse the design of efficient catalysts.The active sites of copper-based catalysts remain ambiguous due to surface reconstruction.As for theoretical calculations,the construction of electrolyte−electrode models and the investigation of solvation effects are premature for obtaining confident conclusions.In addition,simple and easily scalable techniques for catalyst synthesis still need to be continuously developed.For practical applications,the CO_(2) electrolyzer with copper-based materials must be operated with high current densities,high Faradaic efficiencies,high energetic efficiencies,high single-pass conversion rates(high product concentration),and long stability.Nevertheless,due to the intricate nature of electrochemical systems,a high-performance copper-based electrocatalyst alone is not sufficient to meet all of the above commercialization requirements.Therefore,reactor design involving mass transfer enhancement calls for more research input.Based on the above background and the urgency of the net-zero goal,we initiated our research on CO_(2) electrolysis using copper-based materials with an emphasis on active site identification and mass transfer enhancement.This Account describes our contribution to the field of C_(2+)products formation.We first discuss the synthesis of copper-based materials with a controlled atomic arrangement and valence states based on neural network-accelerated computational simulations.Using the synthesized catalyst,the selectivity of the target product is improved and the energy consumption of CO_(2) electrolysis is reduced.Then,we describe the efforts to investigate the reaction mechanisms,such as using first-principles calculations at the atomic level,in situ surface-enhanced vibrational spectroscopies at the micrometer level,and electrochemical kinetics studies at the apparent performance level.We also overview our efforts in the field of reaction system engineering,consisting of a vapor-fed CO_(2) threecompartment flow cell and a large-scale CO_(2) membrane electrode assembly,which can increase the reaction rates and single-pass yield.Furthermore,we put forward the main technical obstacles that currently need to be surmounted and provide insights into the commercial application of CO_(2) electrolysis technology.展开更多
Heterogeneous catalysts,especially metal oxides,play a curial role in improving energy conversion efficiency and production of valuable chemicals.However,the surface structure at the atomic level and the nature of act...Heterogeneous catalysts,especially metal oxides,play a curial role in improving energy conversion efficiency and production of valuable chemicals.However,the surface structure at the atomic level and the nature of active sites are still ambiguous due to the dynamism of surface structure and difficulty in structure characterization under electrochemical conditions.展开更多
Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation,especially for the ethanol synthesis.However,this reaction usually suffers low CO2 conversion and alcohols selectivity due to the for...Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation,especially for the ethanol synthesis.However,this reaction usually suffers low CO2 conversion and alcohols selectivity due to the formation of byproducts methane and CO.This paper describes an efficient vanadium oxide promoted Rh-based catalysts confined in mesopore MCM-41.The Rh-0.3VO/MCM-41 catalyst shows superior conversion(〜12%)and ethanol selectivity(〜24%)for CO2 hydrogenation.The promoting effect can be attributed to the synergism of high Rh dispersion by the confinement effect of MCM-41 and the formation of VOr-Rh interface sites.Experimental and theoretical results indicate the formation of til-CO at VOv-Rh interface sites is easily dissociated into*CH X,and then*CH X can be inserted by CO to form CH3,*CO followed by CH3*CO hydrogenation to ethanol.展开更多
The hydrogen evolution reaction (HER),which generates molecular hydrogen through the electrochemical reduction of water,is an important clean-energy technology.Platinum (Pt) is an ideal material for HER electrocatalys...The hydrogen evolution reaction (HER),which generates molecular hydrogen through the electrochemical reduction of water,is an important clean-energy technology.Platinum (Pt) is an ideal material for HER electrocatalysts in terms of low overpotential and fast kinetics.An effective method to improve the atom utilization efficiency of Pt is to fabricate Pt-based core-shell or nanocage structures with ultra-thin walls.This paper describes the construction of bilayer palladium (Pd)-Pt alloy nanocages catalyst with enhanced HER catalytic activity.The nanocages were fabricated by etching away the Pd templates of multishelled nanocubes composed of alternate shells of Pd and Pt with well-defined (100) facets.The bilayer Pd-Pt nanocages with sub-nanometer shells have a high dispersion of the active atoms on the outside and inside surfaces of outer layer and inner layer,respectively.Moreover,the Pd-Pt alloy lowers the overpotential for HER and speeds up the reaction rate of HER due to the synergies between Pd and Pt.The rational design of bilayer nanocages provided a novel route for boosting the atom utilization efficiency of Pt catalysts.展开更多
Defects are ubiquitous in oxide supports and can often tune the catalytic property of supported metal catalysts.This work describes the distinct role of titanium and oxygen vacancies of TiO2 supports in the catalytic ...Defects are ubiquitous in oxide supports and can often tune the catalytic property of supported metal catalysts.This work describes the distinct role of titanium and oxygen vacancies of TiO2 supports in the catalytic performance of supported Pt catalysts for CO oxidation.Pt was loaded on the TiO2 supports with oxygen vacancies(VO-TiO2)and titanium vacancies(VTiTiO2).It was found that different defects of TiO2 could distinctively modify the electron property of Pt and thereby CO adsorption strength.The strength of CO adsorption on Pt/VTi-TiO2 is enhanced,while that of Pt/VO-TiO2 becomes weaker.Additionally,the presence of defects would also promote the reducibility of catalysts.On the account of the superior redox ability,both Pt/VTi-TiO2 and Pt/VO-TiO2 exhibit a higher activity than Pt supported on normal TiO2 for CO oxidation.展开更多
Clearly understanding the structure-function relationship and rational design of efficient CO2 electrocatalysts are still the challenges.This article describes the molecular origin of high selectivity of formic acid o...Clearly understanding the structure-function relationship and rational design of efficient CO2 electrocatalysts are still the challenges.This article describes the molecular origin of high selectivity of formic acid on N-doped SnO2 nanoparticles,which obtained via thermal treatment of g-C3N4 and SnCl2·2H2O precursor.Combined with density functional theory(DFT)calculations,we discover that N-doping effectively introduces oxygen vacancies and increases the charge density of Sn sites,which plays a positive role in CO2 activation.In addition,N-doping further regulates the adsorption energy of^*OCHO,^*COOH,^*H and promotes HCOOH generation.Benefited from above modulation,the obtained N-doped SnO2 catalysts with oxygen vacancies(Ov-N-SnO2)exhibit faradaic efficiency of 93% for C1 formation,88% for HCOOH production and well-suppression of H2 evolution over a wide range of potentials.展开更多
Noble metal alloys are one of the most commonly used heterogeneous catalysts.During many reactions,the surface composition and oxidation states of the noble metal alloy particles have been reported to be dynamic.This ...Noble metal alloys are one of the most commonly used heterogeneous catalysts.During many reactions,the surface composition and oxidation states of the noble metal alloy particles have been reported to be dynamic.This paper describes a density functional theory study to explore the initial oxidation stages of the Ptbased surfaces,which are widely-used catalysts in various clean energy conversion processes.By applying a genetic algorithm based global optimization,we identified new surface phases at relatively high O coverages,1 ML and 3/2 ML,on Pt and Pt alloy(111)surfaces.The existence of O transforms the metallic surfaces,creating oxide skins with different morphology and composition.Metals with higher reducibility are pulled out to the outmost surface,to bind with O atoms.The lattice constant affects the binding strength of O atoms over certain oxide skins.Moreover,the strain effect plays a crucial role in the formation of oxide overlayers.展开更多
CONSPECTUS:Propylene serves as one of the most significant compounds in the chemical industry.Propane dehydrogenation(PDH),an“on purpose”propylene production technology is developing.Pt-and CrOx-based catalysts are ...CONSPECTUS:Propylene serves as one of the most significant compounds in the chemical industry.Propane dehydrogenation(PDH),an“on purpose”propylene production technology is developing.Pt-and CrOx-based catalysts are widely applied in commercialized PDH processes,and both exhibit high activity and propylene yields.However,as an intensively endothermic process,PDH requires operation at high temperatures(generally above 500°C),which restricts the C3H6 selectivity and catalyst structure stability on account of coking side reactions,particle sintering,and so forth.Nanostructured catalysts(NCs)based on metals and/or metal oxides with tunable geometric and electronic properties play significant roles because such features intrinsically influence the adsorption of propyl intermediates on the catalyst surface.However,thermodynamical metastability of these NCs results in grand challenges in their structure-controlled preparation.The regulation of material structure and reaction performance at the molecular and atomic levels has attracted extended attention over the past few years.This Account describes our recent advances in controllable regulation of metal and oxide NCs toward efficient propane dehydrogenation.As a structure-insensitive reaction,the dehydrogenation of propane can occur on an individual active site,while larger ensembles of active sites also induce structure-sensitive side reactions,leading to C−C cracking and coke deposition.This paper is aimed at delivering general fundamentals for rational design of NCs in PDH reactions.We start with the catalytic kinetics on the active sites regarding the adsorption of key propyl intermediates on the surface.In subsequent sections,we present the effective regulation strategies for metal and oxide NCs by promoter and support effects.Upon metal NCs,coke deposition and nanoparticles(NPs)sintering tend to occur,which can be suppressed with the increase of geometric separation and charge density of surface active sites by changing alloy compositions,ordered intermetallic alloys,single-atom catalysts,core−shell,and metal−oxide interface structures.Notably,the confinement approach of embedding active sites in zeolite frameworks significantly inhibits the sintering of metal NPs.As alternatives to metals,metal oxides exhibit lower cost but higher barriers of C−H activation and coking inclination.The C−H bond cleavage has been promoted by inducing intrinsic defect sites,such as oxygen vacancies,hydroxyls,and hydrides on the surface and heterogeneous doping in the bulk.Importantly,the structures of the submonolayer/monolayer triggered by spontaneous dispersion and confinement in mesoporous materials significantly improve the oxide activity and stability.All of these strategies have been essential for the efficient PDH reactions.Moreover,the challenges and perspectives are also discussed.It is hoped that the deliberate manipulation of nanostructured catalysts to regulate the reaction mechanism will hold the key to efficient alkane conversion.展开更多
Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation.In contrast,trial–and–error is still the common method people take.Therefore,it is important to develop methods...Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation.In contrast,trial–and–error is still the common method people take.Therefore,it is important to develop methods to intrinsically enhance the performance of catalysts.The most effective solutions are the one from a kinetic perspective based on clear knowledge of the reaction mechanism.This paper describes rate-determining step cognition and modulation to promote CO oxidation on highly dispersed Pt on CeO_(2).The different degrees of metal–support interactions due to variation of hydroxyl density of support could alter the structure of active species and the ability of oxygen activation apparently,further shift the rate-determining step from oxygen activation to oxygen reverse spillover kinetically.The transformation of rate-determining step could enhance the intrinsic activity significantly,and decrease the T_(50) approximately 140℃.The findings of this research exemplify the universal and effective method of performance elevation by rate-determining step modulation,which is promising for application in different systems.展开更多
Developing a descriptor to understand the reactivity of a catalyst is critical in achieving the rational design of heterogeneous catalysts.Ideally,the descriptor should be simple,predictive,as well as applicable to di...Developing a descriptor to understand the reactivity of a catalyst is critical in achieving the rational design of heterogeneous catalysts.Ideally,the descriptor should be simple,predictive,as well as applicable to diverse types of reactions.This paper describes the development of a descriptor that could meet such ideal requirements based on its element-specific fundamental property,ionization energy.Our results indicated that ionization energies could be utilized to describe successfully the adsorption energies of oxygen(O*)and hydroxyl(OH*)groups on various materials.Moreover,we constructed a bond formation scheme to parse this phenomenon.展开更多
基金the National Key Research and Development Program of China (2021YFA1501302)the National Natural Science Foundation of China (22122808, U20B6002)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations and the Program of Introducing Talents of Discipline to Universities (BP0618007) for financial supportsupported by the XPLORER PRIZE by Tencent Foundation
文摘The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes.This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets on the chemical looping oxidative propane dehydrogenation(CL-ODH).During CL-ODH,the oxygen concentration at the pellet surface initially decreased and then maintained stable before the final decrease.At the stage with the stable surface oxygen concentration,the reaction showed a stable C3H6 formation rate and high C3H6 selectivity.Therefore,based on Fick’s second law,the oxygen distribution and evolution in the oxygen carrier at this stage were further analyzed.It was found that main reactions of selective oxidation and over-oxidation were controlled by the oxygen bulk diffusion.C3H8 conversion rate kept decreasing during this stage due to the decrease of the oxygen flux caused by the decline of oxygen gradient within the oxygen carrier,while C3H6 selectivity increased due to the decrease of overoxidation.In addition,reaction rates could increase with the propane partial pressure due to the increase of the oxygen gradient within the oxygen carrier until the bulk transfer reached its limit at higher propane partial pressure.This study provides fundamental insights for the diffusion-controlled chemical looping reactions.
基金supported by the National Key R&D Program of China (2022YFE0102000)the National Natural Science Foundation of China (22121004 and U22A20409)+1 种基金Haihe Laboratory of Sustainable Chemical Transformations, the Program of Introducing Talents of Discipline to Universities (BP0618007)the XPLORER PRIZE for financial support。
基金supported by the National Key R&D Program of China(2021YFA1501302)the National Natural Science Foundation of China(22121004,U1862207,and 22122808)+1 种基金Haihe Laboratory of Sustainable Chemical Transformations,the Program of Introducing Talents of Discipline to Universities(BP0618007)the XPLORER PRIZE.
基金supported by the National Key R&D Program of China(2021YFA1500804)the National Natural Science Foundation of China(22121004,51861125104)+1 种基金the Natural Science Foundation of Tianjin City(18JCJQJC47500)Haihe Laboratory of Sustainable Chemical Transformations,the Program of Introducing Talents of Discipline to Universities(BP0618007)and the Xplorer Prize.
文摘Ammonia production via electrochemical nitrate reduction is essential for environmental protection and the emerging hydrogen economy. Complex nitrate wastewater with a wide pH range calls for flexible catalysts with high selectivity. A high Faradaic efficiency(FE) of NH3 cannot be obtained under strong acid or alkaline conditions due to the uncontrollable adsorption energy and coverage of hydrogen species(H*) on active sites. This article describes the design and fabrication of a copper-palladium(Cu-Pd) alloy nanocrystal catalyst that inhibits H2 and nitrite generation in electrolytes with different nitrate concentrations and varied pH. The interfacial sites of Cu-Pd alloys could enhance the adsorption energy and coverage of H* while increasing the reaction rate constant of NO_(2)*-to-NO*, which achieves a rapid conversion of NO_(2)* along with a decreased FE of NO_(2)-. Under ambient conditions, optimal FE(NH3) is close to 100% at a wide pH range, with the solar-to-chemical conversion efficiency approaching 4.29%. The combination of thermodynamics and kinetics investigations would offer new insights into the reduction mechanism of NO_(2)* for further development of nitrate reduction.
基金the National Key R&D Program of China(No.2021YFA1500704)the National Natural Science Foundation of China(No.22121004)+2 种基金the Haihe Laboratory of Sustainable Chemical Transformations(No.CYZC202107)the Program of Introducing Talents of Discipline to Universities(No.BP0618007)the XPLORER PRIZE for financial support.
文摘CoCu-based catalysts are widely used in CO_(x) hydrogenation reactions to produce higher alcohols due to the C–C coupling ability of Co and the ability of Cu to produce alcohols.This work describes the role of easily happened CO_(2)dissociation on the CoCu surface during the reaction,using different silica support to tune the metal–support interaction,reaches different selectivity to ethanol.CoCu supported on mesoporous silica MCM-41 shows ethanol selectivity as high as 85.3%,the ethanol space-time yield(STY)is 0.229 mmol/(gmetal∙h),however,poor selectivity to ethanol as low as 28.8%is observed on CoCu supported on amorphous silica.The different selectivity is due to the different intensities of CO_(2)dissociation on the catalysts.The adsorbed O*produced via CO_(2)dissociation can occupy the cobalt hollow sites on CoCu surfaces,which are also the adsorption sites of C1 intermediates for further C–C coupling.
基金We acknowledge the National Key R&D Program of China(2021YFA1501503)the National Natural Science Foundation of China(22121004,22038009,and 51861125104)+2 种基金the Natural Science Foundation o f Tianjin City(18JCJQJC47500),Haihe Laboratory of Sustainable Chemical Transformations(CYZC202107)the Program of Introducing Talents of Discipline to Universities(no.BP0618007)the Xplorer Prize for financial support.
文摘CONSPECTUS:As one of the essential pathways to carbon neutrality or carbon negativity,the electrochemical reduction of CO_(2) offers tremendous prospects for platform chemicals and fuel production.Copper(Cu)is currently the only metal material that is able to reduce CO_(2) to multicarbon(C2+)products.Despite the fact that copper-based materials have been investigated for decades,we still confront numerous challenges on the path to the fundamental understanding and large-scale deployment of copper-based electrocatalysts for CO_(2) reduction.For fundamental investigations,it remains a variety of open questions about the CO_(2) reduction mechanisms.The convoluted C−C coupling pathways and product bifurcation processes confuse the design of efficient catalysts.The active sites of copper-based catalysts remain ambiguous due to surface reconstruction.As for theoretical calculations,the construction of electrolyte−electrode models and the investigation of solvation effects are premature for obtaining confident conclusions.In addition,simple and easily scalable techniques for catalyst synthesis still need to be continuously developed.For practical applications,the CO_(2) electrolyzer with copper-based materials must be operated with high current densities,high Faradaic efficiencies,high energetic efficiencies,high single-pass conversion rates(high product concentration),and long stability.Nevertheless,due to the intricate nature of electrochemical systems,a high-performance copper-based electrocatalyst alone is not sufficient to meet all of the above commercialization requirements.Therefore,reactor design involving mass transfer enhancement calls for more research input.Based on the above background and the urgency of the net-zero goal,we initiated our research on CO_(2) electrolysis using copper-based materials with an emphasis on active site identification and mass transfer enhancement.This Account describes our contribution to the field of C_(2+)products formation.We first discuss the synthesis of copper-based materials with a controlled atomic arrangement and valence states based on neural network-accelerated computational simulations.Using the synthesized catalyst,the selectivity of the target product is improved and the energy consumption of CO_(2) electrolysis is reduced.Then,we describe the efforts to investigate the reaction mechanisms,such as using first-principles calculations at the atomic level,in situ surface-enhanced vibrational spectroscopies at the micrometer level,and electrochemical kinetics studies at the apparent performance level.We also overview our efforts in the field of reaction system engineering,consisting of a vapor-fed CO_(2) threecompartment flow cell and a large-scale CO_(2) membrane electrode assembly,which can increase the reaction rates and single-pass yield.Furthermore,we put forward the main technical obstacles that currently need to be surmounted and provide insights into the commercial application of CO_(2) electrolysis technology.
基金We acknowledge the National Key R&D Program of China(2021YFA1500704)the National Natural Science Foundation of China(nos.22121004,22250008,and 22038009)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations,the Program of Introducing Talents of Discipline to Universities(BP0618007)the XPLORER PRIZE for financial support.
文摘Heterogeneous catalysts,especially metal oxides,play a curial role in improving energy conversion efficiency and production of valuable chemicals.However,the surface structure at the atomic level and the nature of active sites are still ambiguous due to the dynamism of surface structure and difficulty in structure characterization under electrochemical conditions.
基金supported by the National Key R&D Program of China (2016YFB0600901)the National Natural Science Foundation of China (21525626, 21603159, 21676181)the Program of Introducing Talents of Discipline to Universities (B06006)
文摘Metal oxide-promoted Rh-based catalysts have been widely used for CO2 hydrogenation,especially for the ethanol synthesis.However,this reaction usually suffers low CO2 conversion and alcohols selectivity due to the formation of byproducts methane and CO.This paper describes an efficient vanadium oxide promoted Rh-based catalysts confined in mesopore MCM-41.The Rh-0.3VO/MCM-41 catalyst shows superior conversion(〜12%)and ethanol selectivity(〜24%)for CO2 hydrogenation.The promoting effect can be attributed to the synergism of high Rh dispersion by the confinement effect of MCM-41 and the formation of VOr-Rh interface sites.Experimental and theoretical results indicate the formation of til-CO at VOv-Rh interface sites is easily dissociated into*CH X,and then*CH X can be inserted by CO to form CH3,*CO followed by CH3*CO hydrogenation to ethanol.
基金We acknowledge the National Key R&D Program of China(No.2016YFB0600901)the National Natural Science Foundation of China(Nos.U1463205,21525626,and 21606169)for financial supportthe Program of Introducing Talents of Discipline to Universities(B06006)for financial support.
文摘The hydrogen evolution reaction (HER),which generates molecular hydrogen through the electrochemical reduction of water,is an important clean-energy technology.Platinum (Pt) is an ideal material for HER electrocatalysts in terms of low overpotential and fast kinetics.An effective method to improve the atom utilization efficiency of Pt is to fabricate Pt-based core-shell or nanocage structures with ultra-thin walls.This paper describes the construction of bilayer palladium (Pd)-Pt alloy nanocages catalyst with enhanced HER catalytic activity.The nanocages were fabricated by etching away the Pd templates of multishelled nanocubes composed of alternate shells of Pd and Pt with well-defined (100) facets.The bilayer Pd-Pt nanocages with sub-nanometer shells have a high dispersion of the active atoms on the outside and inside surfaces of outer layer and inner layer,respectively.Moreover,the Pd-Pt alloy lowers the overpotential for HER and speeds up the reaction rate of HER due to the synergies between Pd and Pt.The rational design of bilayer nanocages provided a novel route for boosting the atom utilization efficiency of Pt catalysts.
基金the National Key Research and Development Program of China(2016YFB0600901)the National Science Foundation of China(21525626,U1862207)the Program of Introducing Talents of Discipline to Universities(B06006)。
文摘Defects are ubiquitous in oxide supports and can often tune the catalytic property of supported metal catalysts.This work describes the distinct role of titanium and oxygen vacancies of TiO2 supports in the catalytic performance of supported Pt catalysts for CO oxidation.Pt was loaded on the TiO2 supports with oxygen vacancies(VO-TiO2)and titanium vacancies(VTiTiO2).It was found that different defects of TiO2 could distinctively modify the electron property of Pt and thereby CO adsorption strength.The strength of CO adsorption on Pt/VTi-TiO2 is enhanced,while that of Pt/VO-TiO2 becomes weaker.Additionally,the presence of defects would also promote the reducibility of catalysts.On the account of the superior redox ability,both Pt/VTi-TiO2 and Pt/VO-TiO2 exhibit a higher activity than Pt supported on normal TiO2 for CO oxidation.
基金supported by the National Key R&D Program of China (2016YFB0600901)the National Natural Science Foundation of China (21525626, 21606169, 21722608)the Program of Introducing Talents of Discipline to Universities (B06006)
文摘Clearly understanding the structure-function relationship and rational design of efficient CO2 electrocatalysts are still the challenges.This article describes the molecular origin of high selectivity of formic acid on N-doped SnO2 nanoparticles,which obtained via thermal treatment of g-C3N4 and SnCl2·2H2O precursor.Combined with density functional theory(DFT)calculations,we discover that N-doping effectively introduces oxygen vacancies and increases the charge density of Sn sites,which plays a positive role in CO2 activation.In addition,N-doping further regulates the adsorption energy of^*OCHO,^*COOH,^*H and promotes HCOOH generation.Benefited from above modulation,the obtained N-doped SnO2 catalysts with oxygen vacancies(Ov-N-SnO2)exhibit faradaic efficiency of 93% for C1 formation,88% for HCOOH production and well-suppression of H2 evolution over a wide range of potentials.
基金supported by the National Natural Science Foundation of China (21525626 and 21761132023)the Program of Introducing Talents of Discipline to Universities (BP0618007)。
基金We acknowledge the National Key Research and Development Program of China(2016YFB0600901)the National Science Foundation of China(21525626,21761132023,and 21606169)the Program of Introducing Talents of Discipline to Universities(B06006)for financial support.
文摘Noble metal alloys are one of the most commonly used heterogeneous catalysts.During many reactions,the surface composition and oxidation states of the noble metal alloy particles have been reported to be dynamic.This paper describes a density functional theory study to explore the initial oxidation stages of the Ptbased surfaces,which are widely-used catalysts in various clean energy conversion processes.By applying a genetic algorithm based global optimization,we identified new surface phases at relatively high O coverages,1 ML and 3/2 ML,on Pt and Pt alloy(111)surfaces.The existence of O transforms the metallic surfaces,creating oxide skins with different morphology and composition.Metals with higher reducibility are pulled out to the outmost surface,to bind with O atoms.The lattice constant affects the binding strength of O atoms over certain oxide skins.Moreover,the strain effect plays a crucial role in the formation of oxide overlayers.
基金We acknowledge the National Natural Science Foundation of China(21525626,U1862207)the Program of Introducing Talents of Discipline to Universities(No.B06006)for financial support.
文摘CONSPECTUS:Propylene serves as one of the most significant compounds in the chemical industry.Propane dehydrogenation(PDH),an“on purpose”propylene production technology is developing.Pt-and CrOx-based catalysts are widely applied in commercialized PDH processes,and both exhibit high activity and propylene yields.However,as an intensively endothermic process,PDH requires operation at high temperatures(generally above 500°C),which restricts the C3H6 selectivity and catalyst structure stability on account of coking side reactions,particle sintering,and so forth.Nanostructured catalysts(NCs)based on metals and/or metal oxides with tunable geometric and electronic properties play significant roles because such features intrinsically influence the adsorption of propyl intermediates on the catalyst surface.However,thermodynamical metastability of these NCs results in grand challenges in their structure-controlled preparation.The regulation of material structure and reaction performance at the molecular and atomic levels has attracted extended attention over the past few years.This Account describes our recent advances in controllable regulation of metal and oxide NCs toward efficient propane dehydrogenation.As a structure-insensitive reaction,the dehydrogenation of propane can occur on an individual active site,while larger ensembles of active sites also induce structure-sensitive side reactions,leading to C−C cracking and coke deposition.This paper is aimed at delivering general fundamentals for rational design of NCs in PDH reactions.We start with the catalytic kinetics on the active sites regarding the adsorption of key propyl intermediates on the surface.In subsequent sections,we present the effective regulation strategies for metal and oxide NCs by promoter and support effects.Upon metal NCs,coke deposition and nanoparticles(NPs)sintering tend to occur,which can be suppressed with the increase of geometric separation and charge density of surface active sites by changing alloy compositions,ordered intermetallic alloys,single-atom catalysts,core−shell,and metal−oxide interface structures.Notably,the confinement approach of embedding active sites in zeolite frameworks significantly inhibits the sintering of metal NPs.As alternatives to metals,metal oxides exhibit lower cost but higher barriers of C−H activation and coking inclination.The C−H bond cleavage has been promoted by inducing intrinsic defect sites,such as oxygen vacancies,hydroxyls,and hydrides on the surface and heterogeneous doping in the bulk.Importantly,the structures of the submonolayer/monolayer triggered by spontaneous dispersion and confinement in mesoporous materials significantly improve the oxide activity and stability.All of these strategies have been essential for the efficient PDH reactions.Moreover,the challenges and perspectives are also discussed.It is hoped that the deliberate manipulation of nanostructured catalysts to regulate the reaction mechanism will hold the key to efficient alkane conversion.
基金the National Key R&D Program of China (2021YFA1501302)the National Natural Science Foundation of China (22121004,U1862207)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations and the Program of Introducing Talents of Discipline to Universities (BP0618007) for financial supportsupported by the XPLORER PRIZE
文摘Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation.In contrast,trial–and–error is still the common method people take.Therefore,it is important to develop methods to intrinsically enhance the performance of catalysts.The most effective solutions are the one from a kinetic perspective based on clear knowledge of the reaction mechanism.This paper describes rate-determining step cognition and modulation to promote CO oxidation on highly dispersed Pt on CeO_(2).The different degrees of metal–support interactions due to variation of hydroxyl density of support could alter the structure of active species and the ability of oxygen activation apparently,further shift the rate-determining step from oxygen activation to oxygen reverse spillover kinetically.The transformation of rate-determining step could enhance the intrinsic activity significantly,and decrease the T_(50) approximately 140℃.The findings of this research exemplify the universal and effective method of performance elevation by rate-determining step modulation,which is promising for application in different systems.
基金supported from the National Natural Science Foundation of China(nos.21525626,21761132023,and 21676181)the Program of Introducing Talents of Discipline to Universities(no.B06006)。
文摘Developing a descriptor to understand the reactivity of a catalyst is critical in achieving the rational design of heterogeneous catalysts.Ideally,the descriptor should be simple,predictive,as well as applicable to diverse types of reactions.This paper describes the development of a descriptor that could meet such ideal requirements based on its element-specific fundamental property,ionization energy.Our results indicated that ionization energies could be utilized to describe successfully the adsorption energies of oxygen(O*)and hydroxyl(OH*)groups on various materials.Moreover,we constructed a bond formation scheme to parse this phenomenon.
