Hydrogenation reactions and adsorption : From CO to methanol on a graphene surface

Abstract

Successive hydrogenation reactions of isolated CO molecules adsorbed on a bare graphene surface have been studied by density functional theory using a van der Waals functional. Three hydrogenation scenarios, leading to the formation of methanol via the intermediate species: HCO, H₂CO, HCOH, H₃CO and H₂COH, have been considered. Hydrogenation and adsorption energies on the surface have been calculated for all the species. The fractions of molecules released in the gas phase after formation on the surface have been calculated with two different chemical desorption models. Our results show that the fraction of methanol molecules released in the gas phase is low ( < 6%) whatever the scenario. Conversely, the highest fractions of molecules released in the gas phase have been obtained for formaldehyde, H₂CO, and the hydroxymethyl radical, H₂COH. The methoxy radical, H₃CO, is characterized by a high adsorption energy on the substrate (−0.337 eV).