Methane oxidation over Pd and Pt studied by DFT and kinetic modeling

Methane dissociation and subsequent formation of water and carbon-dioxide over Pd and Pt are investigated with density functional theory calculations and microkinetic modeling. Adsorption energies for reaction intermediates and activation barriers for CH4 dissociation and water formation are calculated for the (111), (100), (211) and (321) facets. The dissociative adsorption of methane is found to be the rate determining step on all considered facets. The results show that Pt has higher catalytic activity than Pd and that the (100) surface is the most active facet at moderate temperatures for both Pd and Pt. At low temperatures, the reaction is limited, in particular on Pd(100), by poisoning of OH-groups.