Electronic structure of the palladium monoxide and its interaction with a methane molecule has been investigated by means of density functional theory. The two triplets, 3Π and 3Σ−, lie very close in energy, with the indication at the 3Π ground state of the oxide. A methane molecule interacts with the open shell PdO and forms two stable adsorption complexes: in collinear on palladium and bridging conformations. The scission of the C–H bond in adsorbed methane requires moderate activation energy of 24.5 kcal/mol and the dissociation product is very stable, however, the singlet–triplet crossing occurs at the transition state.

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Simple functional models for elementary steps in the total oxidation of methane over supported palladium catalysts were investigated using density functional theory. Three simple cluster models were proposed, namely, the palladium dimer and PdO diatomic and linear Pd O, to probe the mechanism of the methane activation on metallic and 2 oxidized palladium phases, respectively. The strongest adsorption was found on Pd , 2 where also the CᎏH bond became easily activated; however, no stable product of the C ᎏH bond scission was indicated. Similar hydrogen activation took place on Pd O and, in 2 addition, adsorbed methyl and OH species formed the most stable system after crossing a moderate energy barrier. The same product was previously found stable also in the case of PdO dimer but the activation barrier was high. On the Pd O cluster, the process 2 of energy barrier crossing was accomplished in two steps: easy formation of a free hydrogen moiety and actual oxidation, which made the overall process less demanding energetically.

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