Characterization of tungsten monomeric oxide species supported on hydroxylated silica; a DFT study

Abstract

A DFT based characterization of tungsten oxide supported on amorphous hydroxylated silica is presented. The different molecular organizations are investigated on the surface topology and tungsten oxygen coordination. The presence of mono- and di-grafted species is discussed and rationalized, using an atomistic thermodynamic approach. The presence of WO groups are preferred over W–OH groups and the grafting coordination is dominated by the degree of hydration of the silica surface. At room temperature di-oxo digrafted and mono-oxo-tetragrafted species are in competition regulated by the ambient degree of hydration which also affects the silanol density of the silica support. A comparison between tungsten and the other group VI elements confirms a greater chemical difference with Cr than with Mo.