| Pt catalysts are a kind of high efficient and stable catalysts.Its scarcity and high cost limit its wide application.Recently,Pt based bimetallic catalysts?Pt-Cu,Pt-Sn,Pt-Fe etc.?,which can greatly reduce the amount of Pt,have been promising candidates of pure Pt widely used in various fields like hetergeneous catalysis,electrocatalysis and fuel cells.Owing to alloy effect,Pt bimetallic catalysts normally exhibit much higher activity,selectivity and stability.A catalytic reaction occurs solely on the surface.So the surface composition and structure of a catalyst are the key fators affecting its performance.Present work used In-situ XPS&LEIS technologies to characterize the supported PtCux and PtSnx bimetallic nanocatalysts for exploring the surface properties,the intermetallic interaction,the relationships between the surface composition and the bulk or catalytic performance as well as the support effect.The obtained results are of great importance to design and optimize the industrial catalysts.The results show that Pt-Cu alloy of the PtCux/TiO2 is destroyed in the process of continuous oxidation.Cu species spread out on the surface,while Pt species cluster as metallic Pt and Pt?+ leading to low surface amount.In the process of continuous reduction,oxidized copper is quickly reduced and partly interacts with Pt to form alloy again.In PtSnx/SiO2 bimetallic catalysts,Sn tends to disperse on the support surface?including the alloy surface?,on the contrary Pt concentrates within the granules.Under the successive oxidation,the surface Sn components do not change much,which may be resulted from the enrichment of Sn on the surface.And the surface Pt amount gradually decreases due to dealloying and clustering.Under the successive reduction,Sn gradually spreads out on the surface,simultaneously Pt also disperses better.The addition of Sn,enhances the dispersion and the stability of Pt.High dispersion of Pt improves the catalytic activity for CO oxidation. |
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