comparative DFT study on the CO oxidation reaction over Al- and Ge-embedded graphene as efficient metal-free catalysts

In the present study, by means of density functional theory (DFT) calculations, the catalytic oxidation of CO by O-2 molecule is investigated over Al- and Ge-embedded graphene. The large atomic radius of these dopant atoms can induce a local surface curvature and modulate the electronic structure properties of the graphene sheet through the charge redistribution. It is found that the adsorption of molecular O-2 over Al- or Ge-embedded graphene is stronger than that of CO molecule. The CO oxidation reaction by molecular O-2 on Al- and Ge-embedded graphene is comparably studied. The results indicate that a twostep process can occur, namely, CO + O-2 -> CO2 ads O-ads and CO + O-ads -> CO2. Furthermore, the computed activation energy (E-act) for the first reaction on Ge-doped graphene is lower than that of Al-doped one, and the formation of second CO2 molecule on both surfaces can occur rapidly due to its low energy barrier (0.1 eV). (C) 2016 Elsevier B.V. All rights reserved.