Water on graphene coated TiO2 : role of atomic vacancies

Beyond two dimensional (2D) materials, interfaces between 2D materials and underlying supports or 2D coated metal or metal oxide nanoparticles exhibit excellent properties and promising applications. The hybrid interface between graphene and anatase TiO₂  shows great importance in photocatalytic, catalytic and nanomedical applications due to the excellent and complementary properties of the two materials. Water, as a ubiquitous and essential element in practical conditions and in the human body, plays a significant role in the applications of graphene/TiO₂  composites for both electronic devices and nanomedicine. Carbon vacancies, as common defects in chemically prepared graphene, also need to be considered for the application of graphene-based materials. Therefore, the behavior of water on top and at the interface of defective graphene on anatase TiO₂  surface was systematically investigated by dispersion-corrected hybrid density functional calculations. The presence of the substrate only slightly enhances the on top adsorption and reduces the on top dissociation of water on defective graphene. However, at the interface, dissociated water is largely preferred compared to undissociated water on bare TiO₂  surface, showing a prominent cover effect. Reduced TiO2 may further induce oxygen diffusion into the bulk. Our results are helpful to understand how the presence of water in the surrounding environment affects structural and electronic properties of the graphene/TiO₂  interface, and, thus, its application in photocatalysis, electronic devices and nanomedicine.