A DF-vdW study of the CH4 adsorption on different Ni surfaces

A systematic density functional (DF) theory based study of methane (CH4) adsorption on the three lowest-index Miller Ni surfaces plus two stepped Ni surfaces is presented. A standard GGA type functional (PBE) has been used to compute the total energy and the van der Waals (vdW) contribution included to properly described the weak molecular interaction of CH4 with the Ni metal surfaces. The surfaces are represented by a periodic supercell approach and several sites and molecular orientations have been explored with one, two and three H atoms pointing towards the surface. Although all adsorption energy values are small, taking into account dispersion terms allows one to distinguish the effect of the surface structure on methane adsorption.