C-O bond scission of methoxide on Pd nanoparticles: A density functional study

Methoxide is an intermediate of methanol dehydrogenation on Pd-based catalysts. Formation of methoxide is assumed to be the initial step of such important catalytic processes as methanol dehydrogenation (decomposition) and methanol steam reforming. C-O bond scission of methoxide species adsorbed at the surface of Pd nanoparticle was studied. To determine the different locations of adsorbed intermediates as well as the transition state of C-O bond scission, a substrate model was used, which allows one to consider adsorbates without any local geometry restrictions. Because methoxide species were stabilized at cluster edges, the scission of C-O bond was calculated to be exothermic on the nanoclusters, by ∼ 40 kJ/mole, whereas this reaction was determined to be endothermic on the Pd(111) surface. However, the rather high calculated activation barrier, ∼ 140 kJ/mole, implies that methoxide decomposition on Pd via the C-O bond breaking route proceeded very slowly, even in the presence of edge sites.