DFT study of anatase-derived TiO2 nanosheets/graphene hybrid materials

In this work, we focus on the impact that the interface structure formed by graphene and a bilayer of anatase (001)‐oriented exerts on electronic and optical properties of the final nanocomposite. In order to perform such analysis, we have modeled, optimized, and investigated the electronic properties of several graphene–TiO2 hybrids by means of density functional theory based calculations. Our results suggest that the physisorbed system is less electronically coupled and does not enhance the photoresponsivity in the visible region. On the other hand, the chemical bond between graphene and TiO2 nanosheet, a TiOC bridge, clearly makes the two components highly electronically coupled and the graphene oxide (GO)/TiO2 chemisorbed system is characterized by a higher photoresponsivity in the visible region. This result is ascribed to the raise of a new valence band maximum state that lies in the pristine bandgap of TiO2 nanosheet, consequence of the hybridization between GO and TiO2. Interfaces formed by TiO2 (001)‐oriented nanosheets (NS) and graphene are investigated. In particular, both the cases of “wet” and “dry” environments (with and without water molecules) are considered. The presence of a direct bond Ti–O–C at the interface (chemisorption) induces intriguing electronic/optical features not detected for the physisorbed, dry, hybrid systems. The interface between TiO2 NS and graphene oxide (oxygen atoms in epoxidic fashion) is similarly investigated.