First-principles analysis of the stability of water on oxidised and reduced CuO(111) surfaces

We use first-principles density functional theory calculations including the Hubbard + U correction (PBE + U) on Cu-3d states to investigate the interaction of water with a CuO(111) surface. We compute adsorption energies and the stability of different water coverages, with a particular focus on the interaction of water with oxygen vacancy sites, and how vacancy stabilization occurs. We study the energetics, geometry and electronic structure of relevant configurations, finding that there are only small changes to the local geometry around the water adsorption site(s) and the electronic properties. The inclusion of van der Waals interactions has no significant impact on the stability of water on CuO(111). We extend the analysis to include realistic environmental conditions within the ab initio atomistic thermodynamics framework, which allows us to assess the stability of the water/copper-oxide system as a function of ambient conditions, and focus on three important surface processes: water adsorption/desorption on the stoichiometric surface, conditions for dissociation, and oxygen vacancy stabilization.