First-principles investigations of the structure and stability of oxygen adsorption and surface oxide formation at Au(111)

We perform density-functional theory calculations to investigate the adsorption of oxygen at the Au(111) surface, including on-surface, subsurface, and surface oxide formation. We find that atomic oxygen adsorbs weakly on the surface and is barely stable with respect to molecular oxygen, while pure subsurface adsorption is only metastable. Interestingly, however, we find that the most favorable structure investigated involves a thin surface-oxide-like configuration, where the oxygen atoms are quasithreefold-coordinated to gold atoms, and the gold atoms of the surface layer are twofold, linearly coordinated to oxygen atoms. By including the effect of temperature and oxygen pressure through the description of ab initio atomistic thermodynamics, we find that this configuration is the most stable for realistic catalytic temperatures and pressures, e.g., for low-temperature oxidation reactions, and is predicted to be stable up to temperatures of around $420\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ at atmospheric pressure. This gives support to the notion that oxidized Au, or surface-oxide-like regions, could play a role in the behavior of oxide-supported nanogold catalysts.