Fe(II)Ti(IV)O3 mixed oxide monolayer at rutile TiO2(011): Structures and reactivities

Abstract

Mixed-metal oxide monolayer grown at an oxide support is of great potential in applications like heterogeneous catalysis. In this work, the experimentally obtained ordered mixed FeTiO3 oxide monolayer supported by rutile TiO2(011) surface has been carefully studied with density functional theory calculations. The genetic algorithm based optimization scheme has been employed to improve the searching capacity for possible structures, and a well ordered mixed Fe(II)Ti(IV)O3 monolayer oxide structure much more stable than the one proposed previously has been successfully located. The new surface structure consists of uniformly distributed Ti and Fe cations in the ratio of 2:1. The simulated Scanning Tunneling Microscopy image based on this model is well consistent with the experimental one. Our calculations have shown that the O vacancy formation energy is rather high at the surface. We have also studied the adsorption of O2 and CO at the exposed Fe sites on the surface as well as their reactions. The adsorption energies of O2 are generally higher than those of CO. The catalytic cycle of CO oxidation following an Eley-Rideal type mechanism has been located for CO to react with surface adsorbed O2 and O.