Density-functional calculations of the conversion of methane to methanol on platinum-decorated sheets of graphene oxide

By means of calculations based on density-functional theory (DFT), we have investigated the conversion of methane on two platinum atoms supported with a graphene-oxide sheet (Pt2/GO). In our calculations, a CH4 molecule can be adsorbed around the Pt atoms of the Pt2/GO sheet with adsorption energies within -0.11 to -0.53 eV; an elongated C-H bond indicates that Pt atoms on that sheet can activate the C-H bond of a CH4 molecule. The role of the GO sheet in the activation of CH4 was identified according to an analysis of the electronic density: the GO sheet induces the d-band of Pt atoms to generate several specific dz(2) state features above the Fermi level, which enabled the activation of the C-H bond of CH4 in generating an evident area of overlap with the hydrogen s orbital of the C-H bond. Upon a dioxygen molecule being added onto the Pt2/GO sheet, this molecule can react with activated CH4 according to mechanisms of form 2CH4 + O2 [Pt2/GO]--> 2CH3OH, and restore the original Pt2/GO sheet.