Coverage-dependent structure and reactivity of vanadia clusters supported on anatase TiO2(1 0 1) surface

Abstract

The atomic structures of VOx clusters supported on anatase TiO2(101) surface (A(101)) at different coverages are explored based on an evolutionary method. The structures exhibit clear coverage-dependent feature. Unlike those supported on rutile TiO2 surface, monomeric vanania clusters supported on anatase surface do not favor aggregation. At low coverage, monomeric clusters (VO2 or VO3) are the main products, while at higher coverage (≥0.25 ML) polymeric clusters become more popular. Using the hydrogenation energy and oxygen vacancy formation energy as descriptors, and the dissociation of NH3 as example, the reactivity of each stable structure is studied. The results show that VO3/A(101) possesses particularly high reactivity, and the supporting of V2O5 and V3O6 clusters can also improve the chemical reactivity of A(101) surface. The molecular adsorption of NH3 can be enhanced on all the supported VmOn/A(101) structures, while its dissociation can only occur on VO3/A(101), which implies that the one-site mechanism of the selective catalytic reduction (SCR) reaction of NOx with ammonia only acts at low coverage of vanadium oxide (<0.25 ML).