The adsorption and dissociation of water molecule on goethite (010) surface: A DFT approach

Abstract

Using density functional theory (DFT) calculation, we investigate the configuration, stability and electronic properties of fresh cleaved (010) goethite surface (Pnma) and this surface exposed to water monolayer at low, medium and high coverage. Water is predicted to be chemisorbed to the surface, together with the surface reconstruction. The interaction energy of the most stable configuration of both low and medium coverage per water molecule is almost the same (−1.17eV), while that of high coverage is much lower (less than 1.03eV). It indicates that highly hydrated surface is less stable. PDOS analysis reveals the adsorption of H2O is due to the formation of FeO bond, caused by overlapping of Fe's 3d and O's 2p orbitals. Dissociation processes at low and medium water coverage are non-spontaneous; while at high coverage, it can undertake spontaneously both thermodynamically and dynamically. The dissociation paths of all three water coverage are the similar. The proton from one adsorbed water is likely to dissociate to bind to the vicinal surface μ3O as an intermediate product; the proton belonged to μ3O transferred to the neighbor surface μ2O as the dissociative configuration.