Catalytic oxidation of benzyl alcohol over MnO2: Structure-activity description and reaction mechanism

Activity evaluation of metal oxide catalysts with different crystal structures has been an important prerequisite for industrial applications. This work systematically elucidates the structure-activity relationship of alpha-, beta-, gamma- and delta-MnO2 catalysts toward the selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). Exposed surfaces of MnO2 are evaluated by a combined theoretical and experimental investigation. On this basis, a catalytic activity descriptor is established considering the surface energies, formation energies of oxygen vacancies (OVs), O-2 adsorption energies, and areal densities of OVs and unsaturated Mn. Inspired by this, we fabricate beta-MnO2 with a high surface area and it delivers the highest BA conversion among all MnO2 . Furthermore, a developed Mars-van Krevelen (MvK) mechanism is proposed to describe the BA oxidation process on the beta-MnO2 (1 1 0) surface. The research paradigm opens a door to the rational design of metal oxide catalysts.