Investigations on the interaction of hydrogen with platinum-containing titania have shown that the adsorption of spilt-over hydrogen (H*) species is connected with a partial electron transfer from H* to TiO2. The experimental results depict an enhanced n-type conductivity as well as a formation of neutral oxygen vacancies (V-OX(X)) from singly ionized vacancies (V-OX(+)) in the surface region of the semiconducting metal oxide. The influence on the electronic state of the oxygen vacancies was concluded from fluorescence measurements by means of FT NIR Raman spectroscopy

The charge transfer to TiO2 can be explained by a model describing the H* species after the primary spillover step from the metal onto the support as electron donors located at the surface. Therefore, the effects are not restricted to the vicinity of the metal/support interface because the H* species are able to cover the whole titania surface. Even a migration to another, platinum-free macroscopic phase (secondary spillover) takes place.