  Based on first principles density functional theory calculations we explore
the energetics of the conversion of carbon mono and dioxide to methane over
graphene oxide surfaces. Similar to the recently discovered hydration of
various organic species over this catalyst, the transfer of hydrogen atoms from
hydroxyl groups of graphene oxide provide a step by step transformation
hydrogenation of carbon oxides. Estimated yields of modeled reactions at room
temperature are about 0.01% for the carbon mono and dioxide. For the modeling
of graphene oxide/metal oxide composites, calculations in the presence of MO_2
(where M = V, Cr, Mn, Fe) have been performed. Results of these calculations
demonstrate significant decreases of the energy costs and increases of reaction
yields to 0.07%, which is comparable to the efficiency of these reactions over
platinum and ruthenium-based photocatalysts. Increasing the temperature to the
value 100C should provide the total conversion of carbon mono and dioxides.
