Rh single atom catalysts(SACs)have been insensitively investigated recently due to the maximum utilization efficiency of Rh,one of the most expensive precious metals.Although great efforts have been made in the develo...Rh single atom catalysts(SACs)have been insensitively investigated recently due to the maximum utilization efficiency of Rh,one of the most expensive precious metals.Although great efforts have been made in the development and application of Rh SACs,there are few reports on the precise control of the local coordination environment of Rh single sites on CeO_(2) and their catalytic performance for N_(2)O decomposition.Herein,Rh/CeO_(2) catalysts with different Rh-O coordination numbers(CNs)were successfully prepared using different CeO_(2) supports and a simple incipient wetness impregnation(IWI)method.It is observed that the Rh/CeO_(2) catalyst with slightly higher CN of Rh-O(Rh/CeO_(2)-H)prepared from CeO_(2) shows much higher N_(2)O decomposition activity than the catalyst with lower CN of Rh-O(Rh/CeO_(2)-L)obtained from Ce(OH)_(x).The Rh species within Rh/CeO_(2)-H are found to be more reactive than those within Rh/CeO_(2)-L,which can better facilitate the O_(2)desorption once formed during N_(2)O deco mposition.In additio n,more surface oxygen vacancies are present on Rh/CeO_(2)-H than on Rh/CeO_(2)-L,well explaining the superior N_(2)O adsorption and activation capability on the former catalyst.It is concluded that more abundant oxygen vacancies and reactive Rh single atom sites with slightly higher CN of Rh-O and significantly higher reducibility altogether contribute to the superior N_(2)O decomposition activity on the Rh/CeO_(2)-H catalyst.展开更多
Thin-film catalysts are recently recognized as promising catalysts due to their reduced amount of materials and good catalytic activity,leading to low-cost and high-efficiency catalysts.A series of CuFeO_(x)thin-film ...Thin-film catalysts are recently recognized as promising catalysts due to their reduced amount of materials and good catalytic activity,leading to low-cost and high-efficiency catalysts.A series of CuFeO_(x)thin-film catalysts were prepared with different Fe contents using a one-step method as well as tested for the catalytic reduction of nitrous oxide(N_(2)O)in the presence of CH_(4)at a high GH SV of 185000 mL/(g·h).The increase of iron strongly affects the dispersion and leads to the creation of a less-active segregated Fe_(2)O_(3)phase,which was confirmed by XRD,EDX,and XPS outcomes.The results show that the synergistic properties between Cu and Fe,which affect the CuFeOxfilm catalysts in many aspects,such as the hollow-like texture,specific surface area,nano-crystallite size,the surface contents of Cu^(+),Fe^(3+),and oxygen species,the reductive strength and the strong active sites on the surface.Using DFT calculations,the adsorption and decomposition energy profiles of N_(2)O on the CuFeO_(2)(012)surface model were explored.The surface Fe-site and hollow-site are active for N_(2)O decomposition,and the decomposition energy barriers on the Fe-site and the hollow-site are 1.02 eV and 1.25 eV respectively at 0 K.The strategy adopted here to tailor the activity through low-doping Fe-oxide catalysts could establish a promising way to improve the catalytic reduction of N_(2)O with CH_(4).展开更多
The kinetics of the decomposition of N2O on a catalytic surface is simulatedby means of the Monte Carlo technique. The results show that the reaction rate is dependent not only to the mole fraction of N2O in gas phase...The kinetics of the decomposition of N2O on a catalytic surface is simulatedby means of the Monte Carlo technique. The results show that the reaction rate is dependent not only to the mole fraction of N2O in gas phase, but also to the surface-O coverage.The surface-O coverage increases with the increasing of the mole fraction of N2O in gas.When the reaction gas is pure N2O, the surface-O coverage can be a constant, and it isindependent to the pressuze of N2O gas.展开更多
Using Monte Carlo (MC) method, we sinuilate two possible mechanisms of N2O decomPosition reaction on a catalyst. One of them is in good agreement with the experiment. On the other hand, we also investigate the nature ...Using Monte Carlo (MC) method, we sinuilate two possible mechanisms of N2O decomPosition reaction on a catalyst. One of them is in good agreement with the experiment. On the other hand, we also investigate the nature of the reaction rate oscillation in N2O decomposition. The results show that besides simulating mechahisms of surface reactions, MC method can also be an effective tool to investigate the kinetic behavior of complex reactions.展开更多
Ab initio calculations based on density functional theory have been used to study thedecompsition of N_2O on MgO. The reaction is predicted to occur on O_3c and O_(4c) atoms, but not onO_(5c) atoms, with an activation...Ab initio calculations based on density functional theory have been used to study thedecompsition of N_2O on MgO. The reaction is predicted to occur on O_3c and O_(4c) atoms, but not onO_(5c) atoms, with an activation barrier of 25-27 kcal/mol, in agreement with the experimental valueof 35 kcal/mol. Natural bond orbital analysis shows that the reaction leaves O ad-atoms on thosesurface O anions to form a peroxide-like 'O^2_(2-)' species. The )O-O bond stretching frequency ispredicted to be in the range from 820 cm(-1) to 825 cm(-1).展开更多
The decomposition of N2O on a catalytic surface was simulated by the Monte Carlo method. The results show that both reaction rate and surface coverage oscillate with time. Fractal analysis of the time-series of surfac...The decomposition of N2O on a catalytic surface was simulated by the Monte Carlo method. The results show that both reaction rate and surface coverage oscillate with time. Fractal analysis of the time-series of surface coverages indicates that the oscillation observed has an attractor. The oscillation is chaotic in nature and the attractor is a fractal with a dimension about 3.5 when the rate constant k2 of the elementary step which produces O2 is large enough.展开更多
基金Project supported by the Startup Fund(F.L.)from the University of Central Florida(UCF)National Science Foundation grants(CHE-1955343,DMR-1920050).
文摘Rh single atom catalysts(SACs)have been insensitively investigated recently due to the maximum utilization efficiency of Rh,one of the most expensive precious metals.Although great efforts have been made in the development and application of Rh SACs,there are few reports on the precise control of the local coordination environment of Rh single sites on CeO_(2) and their catalytic performance for N_(2)O decomposition.Herein,Rh/CeO_(2) catalysts with different Rh-O coordination numbers(CNs)were successfully prepared using different CeO_(2) supports and a simple incipient wetness impregnation(IWI)method.It is observed that the Rh/CeO_(2) catalyst with slightly higher CN of Rh-O(Rh/CeO_(2)-H)prepared from CeO_(2) shows much higher N_(2)O decomposition activity than the catalyst with lower CN of Rh-O(Rh/CeO_(2)-L)obtained from Ce(OH)_(x).The Rh species within Rh/CeO_(2)-H are found to be more reactive than those within Rh/CeO_(2)-L,which can better facilitate the O_(2)desorption once formed during N_(2)O deco mposition.In additio n,more surface oxygen vacancies are present on Rh/CeO_(2)-H than on Rh/CeO_(2)-L,well explaining the superior N_(2)O adsorption and activation capability on the former catalyst.It is concluded that more abundant oxygen vacancies and reactive Rh single atom sites with slightly higher CN of Rh-O and significantly higher reducibility altogether contribute to the superior N_(2)O decomposition activity on the Rh/CeO_(2)-H catalyst.
基金financially supported by the MOST(2022YFB4003900/2021YFA0716200)Beijing Municipal Natural Science Foundation(JQ20017)National Natural Science Foundation of China NSFC(No.52161145105/51976216/51888103)。
文摘Thin-film catalysts are recently recognized as promising catalysts due to their reduced amount of materials and good catalytic activity,leading to low-cost and high-efficiency catalysts.A series of CuFeO_(x)thin-film catalysts were prepared with different Fe contents using a one-step method as well as tested for the catalytic reduction of nitrous oxide(N_(2)O)in the presence of CH_(4)at a high GH SV of 185000 mL/(g·h).The increase of iron strongly affects the dispersion and leads to the creation of a less-active segregated Fe_(2)O_(3)phase,which was confirmed by XRD,EDX,and XPS outcomes.The results show that the synergistic properties between Cu and Fe,which affect the CuFeOxfilm catalysts in many aspects,such as the hollow-like texture,specific surface area,nano-crystallite size,the surface contents of Cu^(+),Fe^(3+),and oxygen species,the reductive strength and the strong active sites on the surface.Using DFT calculations,the adsorption and decomposition energy profiles of N_(2)O on the CuFeO_(2)(012)surface model were explored.The surface Fe-site and hollow-site are active for N_(2)O decomposition,and the decomposition energy barriers on the Fe-site and the hollow-site are 1.02 eV and 1.25 eV respectively at 0 K.The strategy adopted here to tailor the activity through low-doping Fe-oxide catalysts could establish a promising way to improve the catalytic reduction of N_(2)O with CH_(4).
文摘The kinetics of the decomposition of N2O on a catalytic surface is simulatedby means of the Monte Carlo technique. The results show that the reaction rate is dependent not only to the mole fraction of N2O in gas phase, but also to the surface-O coverage.The surface-O coverage increases with the increasing of the mole fraction of N2O in gas.When the reaction gas is pure N2O, the surface-O coverage can be a constant, and it isindependent to the pressuze of N2O gas.
文摘Using Monte Carlo (MC) method, we sinuilate two possible mechanisms of N2O decomPosition reaction on a catalyst. One of them is in good agreement with the experiment. On the other hand, we also investigate the nature of the reaction rate oscillation in N2O decomposition. The results show that besides simulating mechahisms of surface reactions, MC method can also be an effective tool to investigate the kinetic behavior of complex reactions.
文摘Ab initio calculations based on density functional theory have been used to study thedecompsition of N_2O on MgO. The reaction is predicted to occur on O_3c and O_(4c) atoms, but not onO_(5c) atoms, with an activation barrier of 25-27 kcal/mol, in agreement with the experimental valueof 35 kcal/mol. Natural bond orbital analysis shows that the reaction leaves O ad-atoms on thosesurface O anions to form a peroxide-like 'O^2_(2-)' species. The )O-O bond stretching frequency ispredicted to be in the range from 820 cm(-1) to 825 cm(-1).
文摘The decomposition of N2O on a catalytic surface was simulated by the Monte Carlo method. The results show that both reaction rate and surface coverage oscillate with time. Fractal analysis of the time-series of surface coverages indicates that the oscillation observed has an attractor. The oscillation is chaotic in nature and the attractor is a fractal with a dimension about 3.5 when the rate constant k2 of the elementary step which produces O2 is large enough.
