Ab initio study of proton adsorption on different oxygen sites of MoO3 surface

The bonding properties and electronic structure of the inequivalent oxygen atoms on MoO3 (100) and (010) crystal surfaces were studied by ab initio Ha rtree-Fock method. The adsorption of proton on different, oxygen sites as w ell as the desorption of the formed OH from the surfaces were investigated. It was shown that the bonding in MoO3 is of mixed ionic and covalent chara cter. In addition, the bonding features for different oxygen are different, the terminal oxygen and the asymmetrically bridging oxygen exhibit more co valent character, while the symmetrically bridging oxygen is more ionic. Th e proton can be adsorbed stably at all oxygen sites on MoO3(100) and (010) crystal surfaces and the most stable adsorption sites come from the termina l oxygen. The OH groups formed from proton adsorption have strong interacti on with the surface, and those on terminal oxygen sites are difficult to be desorbed, while those on bridging oxygen sites are more mobile and therefo re the bridging oxygen sites may be the active sites for hydrogen abstracti on during oxidation of propylene to acrolein.