Water dissociation at the GaN(101̄0) surface: Structure, dynamics and surface acidity

Pure GaN is known to show a very high photocatalytic water oxidation activity in the UV range. Recently Shen et al. [ J. Phys. Chem. C 2010, 114, 13695 ] have proposed a sequence of intermediate steps for the water oxidation process at the GaN(101̄0) GaN/water interface. In this contribution we show that when spontaneous water dissociation occurs, the acidity of the surface can be accurately computed using first principles molecular dynamics simulations. The electronic structure analysis of the adsorbed water and hydroxyl groups shows large differences between GaN and the well studied photocatalyst TiO ₂. On the basis of our results we argue that the search for efficient photocatalytic materials needs to take into account the water dissociation activity of candidate material surfaces.