Charge Carriers Separation at the Graphene/(101) Anatase TiO2 Interface

Graphene/TiO2 nanocomposites are successfully applied in both photocatalysis and photovoltaics. The enhanced performances are attributed to their improved interfacial charged transfer and charge separation, which reduce the recombination rate of the photoexcited charge carriers. Here, it is shown that only density functional methods which provide corrections for the spurious self-interaction and for the van der Waals forces can correctly describe the electronic structure, the adhesion energy, and the atomic equilibrium distances. It is also proven that residual O atoms at the interface largely enhances the binding energy and causes further electronic states hybridization between G and TiO2, which is expected to favor interfacial electron transfers. Finally, evidence that electrons are preferentially trapped at subsurface layers of TiO2, while holes are preferentially delocalized on the G sheet, is provided. This opposite tendency is proposed to be at the basis of the reduced recombination leading to the observed improved outcomes in photocatalytic and photovoltaic applications. Separation of photoexcited e-/h+ pairs at the interface between graphene and (101) anatase TiO2 surface is investigated through dispersion corrected hybrid density functional calculations. Electrons are preferentially trapped at second layer Ti3+ sites while holes tend to fully delocalize in the carbon layer with relevant consequences for photocatalysis and photovoltaics