Adsorption and dissociation of water on halogen pre-adsorbed Ni(111) and Ni-Cr(111) surfaces: A DFT study

Theoretical study of the adsorption and dissociation of water on halogen pre-adsorbed Ni(111) and Ni-Cr(111) surfaces has been investigated systematically. The stable co-adsorption configurations and corresponding adsorption energies for H2O molecule and halogen atom were obtained. It was found that the halogen atom strengthens the interaction of H2O with Ni surfaces. The corresponding activation barriers and reaction energies of complete water dissociation were determined. The results show that the pre-adsorbed halogen changes the rate-determining step from the dissociation of OH group to the first step dissociation of H2O molecule. The activation barrier for H2O dissociation step increases significantly by halogen atom, together with lower exothermicity. These phenomena indicate that pre-adsorbed halogen can hinder the dissociation of H2O further retard the formation of protective oxide film.