First-principles Study Of Metal-supported Ceria Based Catalysts

Metal-supported ceria（Pt/CeO₂）catalysts show good application prospects in the field of low-temperature catalytic oxidation of CO due to their unique ability to store and release oxygen,so they have become one of the research hotspots in recent years.Controlling the surface structure and reaction conditions of Pt/CeO₂ catalysts has always been an important direction to improve the catalytic performance.Through theoretical calculation research,the influence of surface structure changes on the catalytic reaction performance of catalysts can be explored from the atomic level,and a reasonable catalyst surface structure can be explored,thereby providing theoretical reference and guidance for the synthesis of catalysts with excellent performance.In this paper,the density functional theory（DFT）method was used to systematically study the effects of controlling the surface composition of the Pt/CeO₂ support,the size of the supported clusters and the reaction conditions on the structure,electronic properties and catalytic performance of the catalyst.First,the effects of Pt atom doping on the surface of Pt/CeO₂catalysts on the catalytic performance and stability were investigated.When Pt atoms are intercalated on the CeO₂ carrier surface near the Pt cluster,it will cause charge depletion near the intercalation site,thereby reducing the oxygen hole formation energy on the nearby surface;The charge transfer increases the oxidation degree of the supported Pt clusters,while reducing their adsorption strength for CO.The reduction of the oxygen hole formation energy and CO adsorption energy leads to the reduction of the reaction energy barrier,so the Pt atoms embedded on the CeO₂ surface can significantly improve the catalytic activity of Pt/CeO₂,and the energy barrier of the CO oxidation reaction on the Pt₄/CeO₂ surface is significantly reduced 0.78eV,which proves that modifying the surface chemical composition of CeO₂ carrier is an effective means to control the catalytic activity of Pt/CeO₂.In order to explore the effect of the supported metal size effect on the catalytic activity of the supported metal catalysts,the DFT method was used to study the effect of the size change of the supported Pt clusters on the Pt/CeO₂ catalysts on the catalytic activity.When single-atom Pt₁is supported on the CeO₂ support surface,the CO oxidation reaction energy barrier is as high as 1.86 eV;while on the Pt₁₀/CeO₂ surface supported by large-sized Pt₁₀ clusters,the CO oxidation reaction energy barrier is 1.33 eV,which is significantly lower than that of Pt₁/CeO₂,but still higher than the 1.21 eV energy barrier of Pt₄/CeO₂ for CO oxidation.The calculation results show that the CeO2-supported Pt clusters have obvious size effects during the CO oxidation reaction.The order of catalytic performance is:Pt₄/CeO₂>Pt₁₀/CeO₂>Pt₁/CeO₂.It is necessary to reasonably control the catalyst design and synthesis.Cluster size.In addition,embedding Pt atoms on the support surface near the Pt₁₀clusters can reduce the reaction energy barrier of CO oxidation to 1.11eV,indicating that Pt atom doping is still effective for Pt/CeO₂ catalysts supported by Pt₁₀ large clusters.In view of the strong adsorption of CO on the surface of Pt₁₀/CeO₂,the surface of the cluster will be covered by CO in the real reaction system,so the DFT method was used to study the effect of CO coverage on the catalytic activity of CO.On the surface of small-sized Pt₄ clusters,CO tends to adsorb directly at the reaction site and react without adsorbing excess CO.On the surface of large-sized Pt₁₀ clusters,CO tends to be adsorbed on the apex of the cluster first,followed by the reactive sites at the interface.Therefore,in the reaction environment with high CO concentration,it is possible that the Pt₁₀ clusters are covered by CO molecules that do not participate in the reaction.In the CO oxidation reaction process on the surface of large-sized Pt₁₀ clusters,the formation of the second TRI still needs to overcome the large deformation of the Pt clusters;however,the charge transfer caused by the coverage of CO molecules will reduce the CO adsorption energy on the reaction site,thus The energy barrier of CO oxidation reaction at the Pt-CeO₂ interface was significantly reduced from 1.33 eV to 1.07 eV.Therefore,moderate CO coverage on the Pt clusters is favorable for the CO oxidation reaction process.