The adsorption of CH2O at low-coordinated sites (edge and corner) of MgO (001) surface was studied by using cluster models in the framework of density functional theory. Two adsorption states of CH2O, i.e. heterolytically dissociative adsorption and molecular adsorption were found. In the former case, the CH2O adsorbed over the Mg3C–O3C pair site was dissociated into 2 separate sub-species, CHO− and H+ through the C–H bond cleavage with the rather low activation energy of 4.58kcal/mol. Due to the similarity in adsorption energy, it could be expected that both adsorption states, molecular and dissociative adsorption, should simultaneously exist for CH2O over the Mg3C–O3C pair site of MgO (001) surface. By analogy, for CH4, C2H2 and CH3OH, the edge and corner sites of MgO (001) surface exhibited the catalytic reactivity towards C–H bond cleavage; thus leading to the dissociative sub-species, which was reinforced by quantum chemical calculations and experiments.

Cluster Model Study of CH2O Adsorption and Dissociation at Defect Sites of MgO (001) Surface. Y.J.Xu, Y.F.Zhang, N.X.Lu, J.Q.Li: Physica B, 2004, 348[1-4], 190-7