The origin of enhanced photocatalytic activity in g-C3N4/TiO2 heterostructure revealed by DFT calculations

The oxide-based hybrid photocatalysts, especially TiO2-based, have attracted tremendous attentions because of their prominent photocatalytic performance. Currently, theoretical understandings on the relationship between the interface of TiO2-based heterostructures and their photocatalytic activity are still lacking. Here we systematically investigated the effects of interface structure on electronic properties of the g-C3N4/TiO2 heterostructure using density functional theory (DFT) calculation. The interaction between monolayer g-C3N4 and TiO2 surface [with Anatase (1 0 1)/(0 0 1) facet] was explored, where a van der Waals heterojunction is formed. The presence of oxygen vacancy, nitrogen doping and hydrogen passivation on TiO2 surface is found to dramatically alter the electronic properties of g-C3N4/TiO2 heterostructure. Furthermore, the enhanced separation of electron − hole pairs and inhibited carrier recombination in the g-C3N4/TiO2 interface was analyzed based on the Bader charge analysis and charge density difference. The theoretical analysis revealed that oxygen vacancy and hydrogen passivation on TiO2 A001 surface induces the more significant charge separation, which may be the origin of enhanced photocatalytic efficiency of the g-C3N4/TiO2 heterostructures.