Theoretical Study of Hydrogen on LaFeO3 (010) Surface Adsorption and Subsurface Diffusion

Abstract

Based on density functional theory, this paper studies the adsorption and the subsurface occupation by H on LaFeO3 (010) surface and their corresponding transition states. As shown from the results, the best storage positions of hydrogen are on the O top position of the LaFeO3 (010) surface and the interstice near the oxygen of the subsurface. In addition, the position of surface Fe atom can also store hydrogen, but H atom prefers to adsorb on O atom first. Whether the H atom is adsorbed on O or Fe atom, it is easy diffuse to the nearby more stable O atom. However, the diffusion between the Fe atoms is difficult to occur. The main diffusion path of the H atom from the surface to the subsurface is the process of inward layer by layer around the O atom. With the fracture of the old H–O bond and the formation of the new H–O bond, the H is around O atom to constantly repeat the process of a hopping-rotational diffusion. H diffuses through the nearest neighbor position, which is more favorable than the direct diffusion.