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 H-2 on 2D Ti2C monolayer with end-on configuration. However, for the side-on configuration, the H-2 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 H-2 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. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.