Comparative study of CO adsorption on planar and tetrahedral Pt nanoclusters supported on TiO2(110) stoichiometric and reduced surfaces

Abstract

TiO2 is a widely used material due to its electronic and catalytic properties, which are of interest for technological applications. In catalysis it is generally used as support for different catalyzers, such as for example Pt subnanoclusters given that they improve the efficiency of the material. In this work we use an ab initio DFT + U modeling method to study the structure and energetic of Pt4 clusters deposited on rutile TiO2(110) stoichiometric and reduced surfaces. For the Pt-titania system we examine the relative stability between the flat versus 3D tetrahedral Pt4 structures, and characterize the cluster/substrate interaction. We determine their equilibrium geometries, adsorption energies, charge transfer effects and electronic density of states to characterize different aspects of the metal-oxide interaction. For both, the stoichiometric and reduced rutile TiO2(110), we find that the flat square configuration is preferred, as experiments indicate. In particular, we are interested in the potential activity of these cluster-supported systems for the oxidation of CO adsorbed on Pt. To examine this behavior we evaluate the structure, electronic DOS properties and charge transfer effects for the adsorption of CO on both the flat and tetrahedral Pt4 isomers over the stoichiometric and reduced TiO2 rutile surfaces. The results point to the planar cluster on the stoichiometric surface as the most stable configuration for CO adsorption, while for the CO conversion to CO2 the tetrahedral Pt4 cluster on the stoichiometric TiO2 surface would be the most favorable catalytic substrate.