Cluster models study of CH 2O adsorption and dissociation at defect sites of MgO (0 0 1) surface

Abstract

The adsorption of CH 2O at low-coordinated sites (edge and corner) of MgO (0 0 1) surface has been studied using cluster models in the framework of density functional theory. Two adsorption states of CH 2O, i.e. heterolytically dissociative adsorption and molecular adsorption were found. In the former case, the CH 2O adsorbed over Mg 3C–O 3C pair site was dissociated into two separate subspecies, “CHO −” and “H +” through the C–H bond cleavage with rather low activation energy, 4.58 kcal/mol. Due to the quite similarity in adsorption energy, it can be expected that both two adsorption states, namely molecular and dissociative adsorption, should simultaneously exist for CH 2O over Mg 3C–O 3C pair site of MgO (0 0 1) surface. In analogy, for CH 4, C 2H 2 and CH 3OH, the edge and corner sites of MgO (0 0 1) surface exhibit the catalytic reactivity toward the C–H bond cleavage, thus leading to the dissociative subspecies, which was reinforced by the quantum chemical calculations and the respective experiments.