Co-adsorption of water and hydroxyl on a Pt2Ru surface

Gradient-corrected periodic density functional theory calculations are performed to explain the mobility of surface-bonded hydroxyl on a Pt2Ru(111) surface in the presence of co-adsorbed water, as recently observed by Desai and Neurock [S.K. Desai, M. Neurock, Phys. Rev. B 68 (2003) 075420] in ab initio molecular dynamics calculations. The effect can to a large extent be explained by an energetic compensation effect: the loss in energy associated with transferring OH from a Ru site to a Pt site is compensated by a gain in energy with the associated transfer of H2O from the Pt to the Ru site. The calculated property of the Pt2Ru(111) surface would support the OH spillover mechanism suggested by Davies et at. [J.C. Davies, B.E. Hayden, D.J. Pegg, M.E. Rendall, Surf. Sci. 496 (2002) 110], at least in as far as it concerns OH spillover to Pt site neighboring a Ru site, and provides new insight into the classical bifunctional mechanism of CO electro-oxidation. (c) 2006 Elsevier B.V. All rights reserved.