Atomically-dispersed metal-based materials represent an emerging class of photocatalysts attributed to their high catalytic activity,abundant surface active sites,and efficient charge separation.Nevertheless,the roles...Atomically-dispersed metal-based materials represent an emerging class of photocatalysts attributed to their high catalytic activity,abundant surface active sites,and efficient charge separation.Nevertheless,the roles of different forms of atomically-dispersed metals(i.e.,single-atoms and atomic clusters)in photocatalytic reactions remain ambiguous.Herein,we developed an ethylenediamine(EDA)-assisted reduction method to controllably synthesize atomically dispersed Au in the forms of Au single atoms(Au_(SA)),Au clusters(Au_(C)),and a mixed-phase of Au_(SA)and Au_(C)(Au_(SA+C))on CdS.In addition,we elucidate the synergistic effect of Au_(SA)and Au_(C)in enhancing the photocatalytic performance of CdS substrates for simultaneous CO_(2)reduction and aryl alcohol oxidation.Specifically,Au_(SA)can effectively lower the energy barrier for the CO_(2)→*COOH conversion,while Au_(C)can enhance the adsorption of alcohols and reduce the energy barrier for dehydrogenation.As a result,the Au_(SA)and Au_(C)co-loaded CdS show impressive overall photocatalytic CO_(2)conversion performance,achieving remarkable CO and BAD production rates of 4.43 and 4.71 mmol g^(−1)h^(−1),with the selectivities of 93%and 99%,respectively.More importantly,the solar-to-chemical conversion efficiency of Au_(SA+C)/CdS reaches 0.57%,which is over fivefold higher than the typical solar-to-biomass conversion efficiency found in nature(ca.0.1%).This study comprehensively describes the roles of different forms of atomically-dispersed metals and their synergistic effects in photocatalytic reactions,which is anticipated to pave a new avenue in energy and environmental applications.展开更多
Atomically dispersed catalysts have shown promising prospects in catalysis studies.Among all of the developed methods for synthesizing atomically dispersed catalysts,the photochemical approach has recently aroused muc...Atomically dispersed catalysts have shown promising prospects in catalysis studies.Among all of the developed methods for synthesizing atomically dispersed catalysts,the photochemical approach has recently aroused much attention owing to its simple procedure and mild preparation conditions involved.In the present study,we demonstrate the application of the photochemical method to synthesize atomically dispersed Pd catalysts on(001)‐exposed anatase nanocrystals and commercial TiO2(P25).The as‐prepared catalysts exhibit both high activity and stability in the hydrogenation of styrene and catalytic oxidation of CO.展开更多
Top‐down synthesis has been used to prepare catalytic materials with nanometer sizes,but fabricating atomically dispersed metal catalysts remains a challenge because surface single metal atoms are prone to aggregatio...Top‐down synthesis has been used to prepare catalytic materials with nanometer sizes,but fabricating atomically dispersed metal catalysts remains a challenge because surface single metal atoms are prone to aggregation or coalescence.A top‐down strategy is used to synthesize atomically dispersed metal catalysts,based on supported Ag nanoparticles.The changes of the geometric and electronic structures of the Ag atoms during the top‐down process are studied using the in situ synchrotron X‐ray diffraction technique,ex situ X‐ray absorption spectroscopy,and transmission electron microscopy.The experimental results,coupled with the density functional theory calculations,demonstrate that the electronic perturbation of the Ag frontier orbitals,induced by the Ag‐O interactions at the perimeter of the metal‐support interface,is the driving force of the top‐down process.The top‐down synthesis has two important functions:to increase the number of catalytic active sites and to facilitate the study of complex reaction mechanisms(e.g.,formaldehyde oxidation)by developing single‐site model catalysts.展开更多
Single atom catalysts have recently attracted interest due to their maximization of the utilization of expensive noble metals as well as their unique catalytic properties. Based on its surface atomic properties, CeO2 ...Single atom catalysts have recently attracted interest due to their maximization of the utilization of expensive noble metals as well as their unique catalytic properties. Based on its surface atomic properties, CeO2 is one of the most common supports for stabilizing single metal atoms. Many single atom catalysts are limited in their metal contents by the formation of metal nanoparticles once the catalyst support capacity for single atoms has been exceeded. Currently, there are no direct measurements to determine the capacity of a support to stabilize single atoms. In this work we develop a nanoparticle-based technique that allows for quantification of that capacity by redispersing Ru nanoparticles into single atoms and taking advantage of the different catalytic properties of Ru single atoms and nanoparticles in the CO2 hydrogenation reaction. This method avoids complications in metal loading caused by counterions in incipient wetness impregnation and can eventually be applied to a variety of different metals. Results using this technique follow trends in oxygen vacancy concentration and surface oxygen content and show promise as a new method for quantifying support single atom stabilization capacity.展开更多
文摘Atomically-dispersed metal-based materials represent an emerging class of photocatalysts attributed to their high catalytic activity,abundant surface active sites,and efficient charge separation.Nevertheless,the roles of different forms of atomically-dispersed metals(i.e.,single-atoms and atomic clusters)in photocatalytic reactions remain ambiguous.Herein,we developed an ethylenediamine(EDA)-assisted reduction method to controllably synthesize atomically dispersed Au in the forms of Au single atoms(Au_(SA)),Au clusters(Au_(C)),and a mixed-phase of Au_(SA)and Au_(C)(Au_(SA+C))on CdS.In addition,we elucidate the synergistic effect of Au_(SA)and Au_(C)in enhancing the photocatalytic performance of CdS substrates for simultaneous CO_(2)reduction and aryl alcohol oxidation.Specifically,Au_(SA)can effectively lower the energy barrier for the CO_(2)→*COOH conversion,while Au_(C)can enhance the adsorption of alcohols and reduce the energy barrier for dehydrogenation.As a result,the Au_(SA)and Au_(C)co-loaded CdS show impressive overall photocatalytic CO_(2)conversion performance,achieving remarkable CO and BAD production rates of 4.43 and 4.71 mmol g^(−1)h^(−1),with the selectivities of 93%and 99%,respectively.More importantly,the solar-to-chemical conversion efficiency of Au_(SA+C)/CdS reaches 0.57%,which is over fivefold higher than the typical solar-to-biomass conversion efficiency found in nature(ca.0.1%).This study comprehensively describes the roles of different forms of atomically-dispersed metals and their synergistic effects in photocatalytic reactions,which is anticipated to pave a new avenue in energy and environmental applications.
基金supported by the Ministry of Science and Technology of nano major research projects(2015CB932303)the National Natural Science Foundation of China(21420102001,21131005,21333008,21390390)~~
文摘Atomically dispersed catalysts have shown promising prospects in catalysis studies.Among all of the developed methods for synthesizing atomically dispersed catalysts,the photochemical approach has recently aroused much attention owing to its simple procedure and mild preparation conditions involved.In the present study,we demonstrate the application of the photochemical method to synthesize atomically dispersed Pd catalysts on(001)‐exposed anatase nanocrystals and commercial TiO2(P25).The as‐prepared catalysts exhibit both high activity and stability in the hydrogenation of styrene and catalytic oxidation of CO.
基金supported by the National Natural Science Foundation of China(21477023)the Science and Technology Commission of Shanghai Municipality(14JC1400400)~~
文摘Top‐down synthesis has been used to prepare catalytic materials with nanometer sizes,but fabricating atomically dispersed metal catalysts remains a challenge because surface single metal atoms are prone to aggregation or coalescence.A top‐down strategy is used to synthesize atomically dispersed metal catalysts,based on supported Ag nanoparticles.The changes of the geometric and electronic structures of the Ag atoms during the top‐down process are studied using the in situ synchrotron X‐ray diffraction technique,ex situ X‐ray absorption spectroscopy,and transmission electron microscopy.The experimental results,coupled with the density functional theory calculations,demonstrate that the electronic perturbation of the Ag frontier orbitals,induced by the Ag‐O interactions at the perimeter of the metal‐support interface,is the driving force of the top‐down process.The top‐down synthesis has two important functions:to increase the number of catalytic active sites and to facilitate the study of complex reaction mechanisms(e.g.,formaldehyde oxidation)by developing single‐site model catalysts.
基金support from the Stanford Precourt Institute for Energysupport from the School of Engineering at Stanford University+3 种基金a Terman Faculty Fellowshipsupport from a Stanford Graduate Fellowship(SGF)an EDGE fellowshipsupported by the National Science Foundation under award ECCS-1542152。
文摘Single atom catalysts have recently attracted interest due to their maximization of the utilization of expensive noble metals as well as their unique catalytic properties. Based on its surface atomic properties, CeO2 is one of the most common supports for stabilizing single metal atoms. Many single atom catalysts are limited in their metal contents by the formation of metal nanoparticles once the catalyst support capacity for single atoms has been exceeded. Currently, there are no direct measurements to determine the capacity of a support to stabilize single atoms. In this work we develop a nanoparticle-based technique that allows for quantification of that capacity by redispersing Ru nanoparticles into single atoms and taking advantage of the different catalytic properties of Ru single atoms and nanoparticles in the CO2 hydrogenation reaction. This method avoids complications in metal loading caused by counterions in incipient wetness impregnation and can eventually be applied to a variety of different metals. Results using this technique follow trends in oxygen vacancy concentration and surface oxygen content and show promise as a new method for quantifying support single atom stabilization capacity.
