CO Oxidation on a Au/TiO2 Nanoparticle Catalyst via the Au-Assisted Mars–van Krevelen Mechanism

Abstract

Recently, there has been increasing evidence that CO oxidation on TiO2 supported Au catalysts proceeds predominantly via a Au-assisted Mars–van Krevelen mechanism for reaction temperatures of 80 °C and above. We here present results of a combined experimental and theoretical study, aiming at the identification of activated steps in this reaction. O2 multipulse experiments, performed in a temporal analysis of products (TAP) reactor at different temperatures between −80 and +240 °C, revealed that the replenishment of surface lattice oxygen vacancies at perimeter sites, at the perimeter of the interface between TiO2 support and Au nanoparticles, proceeds with essentially constant efficiency, independent of the reaction temperature. Hence, this reaction step is barrier-free. Previous studies (Widmann and Behm Angew. Chem. Int. Ed. 2011, 50, 10241) had shown that the preceding step, the formation of a surface lattice oxygen vacancy at these sites, is activated, requiring temperatures above room temperature. De...