First-principles calculations of CH 4 dissociation on Ni(1 0 0) surface along different reaction pathways

Abstract

First-principles calculations based on density functional theory and the generalized gradient approximation have been used to study the adsorption and dissociation of CH 4 on Ni(1 0 0) surface. The favored adsorption sites of H, CH 3, and CH 4 are identified by considering the energy and stability of various binding sites. H atoms prefer the fourfold Hollow sites, while CH 3 species favors the Bridge site with one of the C–H bonds pointing towards the neighbor Ni atom. When H and CH 3 are coadsorbed on Ni(1 0 0) surface, several stable configurations are found, in which the atomic H and CH 3 species are adsorbed at the Hollow and Bridge site, respectively, because of their little energetic difference. Through the electronic and vibrational calculations, the C–H–Ni three-center bond is regarded as the key factor determining the CH 3 adsorption. The CH 4 dissociation on Ni(1 0 0) surface is investigated with three different CH 4 orientations considered. The energy barriers are calculated to be 0.61, 0.61 and 0.62 eV, corresponding to the CH 4 molecules orientated with one, two and three C–H bonds pointing towards the surface, respectively. All calculated activation energies have been corrected by including zero-point energy and dispersion energy, and are in good agreement with the experimental result (0.61 ± 0.02 eV). Because the energy barriers for the different reaction pathways take similar values, the CH 4 orientation has a minor effect on the reactivity.