Effects of surface hydration on the electron injection rate from graphene to anatase and rutile TiO2 surfaces

Abstract

The effect of hydration of anatase (0 0 1), and rutile (0 0 1), (1 0 1) and (1 1 0) surfaces of TiO2 on the rate of electron capture from an adsorbed graphene sheet is elucidated by means of computation at a level of tight-binding density functional theory. Initially, the clean surfaces are allowed to interact with bulk water. Following an equilibration period, the first solvation shell is exposed to vacuum at 300 K for a sufficiently long period of time to allow any weakly bound water molecules to evaporate or be displaced from the surface. The resultant hydroxylated and originally clean surfaces are used for studying the interaction with a graphene sheet. Comparison of the calculated surface-graphene interaction energies and electron transfer probabilities of a cold electron to clean and hydroxylated surfaces shows that the water-sourced OH layer of these surfaces acts as an insulator in interfacial charge transport of the cold electron.