【摘要】 氧化物负载的金催化剂具有温和条件下优异的CO催化氧化活性。实验与理论计算表明,金与氧化物两相界面在催化反应过程中具有重要地位。反相催化剂提供了全新的角度以探究界面的重要地位。本文以Au（111）表面负载Al₂O₃团簇为反相催化剂模型,基于密度泛函理论,对催化剂模型的构型、界面性质以及O₂、CO的吸附与氧化进行了理论计算与研究。理论计算表明:电荷的迁移增强了Al₂O₃小团簇在Au（111）表面的附着,在催化剂金表面与氧化铝的两相界面位置,Au原子与Al原子的协同作用使得氧分子易于在界面位置吸附,并因此高度活化。对催化CO氧化反应路径,分别计算了缔合机理和解离机理不同路径,从活化能分析表明缔合机理比解离机理更可能发生。本文的工作揭示了反相催化剂催化CO氧化的活性本质,表明两相界面在金催化CO氧化中具有重要作用。更多还原

【Abstract】 Au catalysts supported on an oxide show excellent activity in CO oxidation under moderate conditions. Many experiments and theoretical calculations have shown the important role of the interface between Au and the oxide support during CO oxidation. Inverse catalysts provide an alternative way to probe the role of the interface. We used Al₂O₃/Au（111） as a model inverse catalyst in this study, and used density functional theory to investigate the properties of Al₂O₃/Au（111）, the interface between Al₂O₃ and Au（111）, the adsorption of O₂, and CO oxidation over Al2O3/Au（111）. Our theoretical calculations show that small Al₂O₃ clusters are strongly bound on the Au（111） surface as a result of charge transfer. The results for O₂ adsorption on different sites indicate that the interfacial site is the most stable one because of simultaneous bonding of O₂ with Au and Al atoms. The full catalytic cycles for CO oxidation by O₂ by either an association or dissociation pathway were investigated. Oxidation in the association pathway is significantly easier than that in the dissociation one; the participation of CO makes dissociation of the adsorbed O₂ easier. This study reveals not only the origin of inversecatalysts for CO oxidation but also the role of the interface in CO oxidation on Au catalysts.更多还原