Distinctions between Supported Au and Pt Catalysts for CO Oxidation: Insights from DFT Study

Distinctions between supported Au and Pt catalysts on TiO₂(110) for CO oxidation have been investigated by means of density functional theory calculations. Our study shows that the following factors determine the obvious differences between two kinds of catalysts for CO oxidation: (1) The adsorption strength of Au₁₁ is much weaker than that of Pt₁₁ on TiO₂(110), but both are strongly dependent on the surface properties of TiO₂. The addition of Pt increases the interaction between the alloyed cluster and TiO₂ support. (2) O₂ can adsorb only on the interfacial site between Au and TiO₂(110), whereas O₂ can adsorb on both the interfacial and metal sites of supported Pt nanoparticles. (3) CO is directly activated by the adsorbed molecular oxygen on the interfacial site of Au₁₁/TiO₂(110)<i>_OH</i>. While on Pt₁₁/TiO₂(110)<i>_OH</i>, the main reaction pathway is the dissociated oxygen reacting with CO. Once a Pt ensemble is formed on Au clusters (such as Au₈Pt₃/TiO₂(110)<i>_OH</i>), both of the reaction mechanisms work