TiO2/graphene nanocomposites from the direct reduction of graphene oxide by metal evaporation

We demonstrate that graphene oxide can be efficiently reduced by evaporating metal Titanium in high vacuum. A detailed description of this reaction is provided by combining in situ photoemission spectroscopy measurements and DFT calculations: the titanium atoms readily react with the oxygenated groups of graphene oxide, disrupting the C-O bonds, with the consequent formation of titania and the recovery of the sp2 hybridized carbon atoms. When all surface oxygen is consumed, titanium can react with the carbon substrate and form carbidic species. Resonant photoemission spectroscopy measurements allow identifying the presence and exact energy position in the valence band of the Ti-C and Ti-O-C states, which are supposed to control the electron and energy transfer across the TiO2/graphene interface. Therefore with this study we provide a versatile method and the rationale for controlling, at the atomic level, the nature of the interface of graphene/metal oxide nanocomposites.