Hydrogen adsorption, dissociation and diffusion on two-dimensional Ti2C monolayer

The adsorption, dissociation and diffusion of hydrogen on two-dimensional (2D) Ti2C monolayer with and without carbon vacancies have been investigated by first-principles calculations based on density functional theory. Weak molecular physisorption was observed for the adsorption of H2 on 2D Ti2C monolayer with end-on configuration. However, for the side-on configuration, the H2 molecule decomposes spontaneously and then the two H atoms prefer to bond to the surface Ti atoms at the monolayer. Based on the chemical bonding analysis, the mechanism of the dissociation of H2 has been elucidated. Moreover, the hydrogen diffusion on the Ti2C surface with and without carbon vacancies was investigated. A better hydrogen diffusion property was found for the Ti2C monolayer with carbon vacancies. The energetics for H penetration from surface to the solute site in the bulk was also studied.