Interaction of oxygen with the Pt(111) surface in wide conditions range.: A DFT-based thermodynamical simulation

We present the results of ab initio calculations of oxygen atomic adsorption in a wide range of coverage on Pt(1 1 1). At theta = 0.25 ML, the O adsorption at fcc hollow site is clearly favoured over the hcp site. At theta = 0.5 ML, the O adsorption energy decreases but the same site is favoured. When experimental or theoretical previously reported data are available, the calculated adsorption energies and site preferences are in good agreement. Among the various configurations and coverages investigated in the present work, no adsorption is stable beyond theta = 0.5 ML, except by occupation of a subsurface tetrahedral site. In that case, a total O coverage of 0.75 ML could be achieved, which is only slightly less stable than the theta = 0.5 ML configuration. The use of thermodynamics permitted to explore the temperature pressure stability domain corresponding to 0.25 ML, 0.5 ML and 0.75 ML. From this, we conclude that subsurface O species could be stable at temperatures lower than 700 K, with O-2 pressures of 1 bar or less. (c) 2005 Elsevier B.V. All rights reserved.