Methane dissociation and methyl diffusion on PdO{100}.

The CH(4)-->CH(3)+H dissociation on the defect-free Pd-2O terminated PdO{100} surface is investigated by first principles calculations. CH(3) chemisorbs preferentially at O sites, where the adsorption is 0.68 eV more stable than at Pd sites. Analysis of the electronic structure of adsorption geometries reveals that the enhanced stability is due to the strongly covalent character of the bonding between surface O and CH(3). However, transition state searches suggest that the Pd atom is the most likely active site for CH(4) dissociation. An alternative route toward the most stable chemisorbed state is proposed that involves diffusion of CH(3) on the surface.