Electronic Structures and Photocatalytic Responses of SrTiO3(100) Surface Interfaced with Graphene, Reduced Graphene Oxide, and Graphane: Surface Termination Effect

The enhanced photocatalytic activity of SrTiO3(STO), a promising photocatalyst for decomposing organic compounds and overall water splitting for H-2/O-2 evolution, has been experimentally demonstrated by coupling the graphene (GR) sheet. Here, we reveal the mechanism of the enhanced photocatalytic activity of STO/GR composites using ab initio calculations. Due to C 2p states forming the bottom of the conduction band or the top of the valence band, the band gap is reduced to about 0.6 eV, resulting in a strong absorption in the visible region. The composites of STO coupled with reduced graphene oxide (RGO) and graphane (GRH) are also explored to investigate their potential photocatalytic activity. We demonstrate that the surface termination layer of the STO (100) surface plays an important role in determining the formation energy, interfacial distance, band gap, and optical absorption of these composites. Moreover, the GR sheet is a sensitizer for STO with a termination layer of TiO2; on the contrary, it is an electron shuttle carrying excited electrons from the STO with a termination layer of SrO. Interestingly, a type II, staggered band alignment is formed in the interface, thus improving photoexcited charge separation. The negatively charged 0 atoms in the RGO are considered to be active sites in photocatalytic reactions, leading to enhanced photocatalytic activity. The calculated results can rationalize the available experimental reports and provide design principles for optimizing the photocatalytic performance of the STO-based composites.