We have investigated electronic structures and charge transfers of Au and Pt supported on the TiO2(110) surface, using first-principles calculation. In order to investigate the effect of stoichiometry, we examined Au or Pt adsorption on three kinds of TiO2(110) surface with different stoichiometry; the stoichiometric surface, the surface formed by removing bridging-oxygen atoms (Ti-rich surface), and the surface formed by removing bridging-oxygen and sixfold titanium atoms (O-rich surface). We considered the on-top site above the bridging-oxygen atom (site A) or above the fivefold titanium atom (site B) for the stoichiometric surface, the bridging-oxygen vacant site (site C) for the Ti-rich surface, and the sixfold titanium vacant site (site D) for the O-rich surface as the adsorption site. The adhesive energies between the metal layer and the TiO2(110) surface for the nonstoichiometric surfaces are much lager than that of the stoichiometric surface. Moreover, the Pt atom is adsorbed more stable than the Au atom for the all surface stoichiometry. The interaction between the metal and the TiO2(110) surface depends on the surface stoichiometry and the kind of metal. The reason is that the charge transfers and the electronic structures of adsorbed metal depend on those. (c) 2005 Springer Science + Business Media, Inc.