Methane dissociation on Ni, Pd, Pt and Cu metal (111) surfaces - A theoretical comparative study

A theoretical comparative study of methane dissociation on Ni, Pd, Pt and Cu metal (111) surfaces has been carried out using a quasirelativistic density functional method. Reaction energies for the steps involved in the dissociation of methane are determined. The activation energies have been estimated using the analytic BOC-MP formula. The results support the notion that the transition metals are active in methane dissociation. The calculated total dissociation energies for the complete dissociation of CH₄ to surface C and H on the transition metals fall in the order Ni < Pd ≈ Pt, which corresponds to the order of the catalytic activities over the metals in methane conversion (Ni > Pd ≈ Pt). The complete dissociation on Cu is calculated to be endothermic. Thus methane dissociation on a Cu catalyst is unlikely, in agreement with the experimental observations. The dissociation of methane in the presence of adsorbed oxygen has also been examined.