Hydrogen Adsorption on Free-Standing and Ag-Pt Supported TiO 2 Thin Films

The adsorption of hydrogen single atoms and the dissociation of hydrogen molecules on free-standing and metal-supported TiO 2 lepidocrocite films is studied by means of density functional theory calculations. The free-standing film results slightly less prone to reduction upon hydrogenation compared to anatase surfaces, due to the larger band gap. On the metal-supported films, the charge transfer at the metal oxide interface influences remarkably the stability of the adsorbates on the surface: while on Pt(111), where the charge transfer is small, the hydrogenation of lepidocrocite is slightly more favorable compared to the case of the free-standing film, on Ag(100), where there is a net charge flow from the metal to the oxide film, the hydrogenation results unfavorable due to charge accumulation in the oxide.