New insights into interfacial photocharge transfer in TiO₂/C₃N₄ heterostructures: effects of facets and defects

More efforts are being made in hybridizing TiO₂ photocatalysts with graphene-analogue g-C₃N₄. However, a fundamental understanding of the interfacial behavior of charge carriers is still lacking. In this paper, the impact of exposed facets and structural defects on the charge transfer mechanism around heterostructured interfaces was investigated. Due to the electron-rich feature and the relatively lower CB position, integrating g-C₃N₄ with 101-TiO₂ facilitated the Z-scheme recombination of electrons in the CB of 101-TiO₂ and holes in the VB of g-C₃N₄. Creating oxygen vacancies in TiO₂ resulted in the 4- and 24-fold increased photoactivity than blank TiO₂ and g-C₃N₄. 001-Facets of TiO₂ however were prone to accept electrons from the CB of g-C₃N₄, forming the conventional Type II junction with poor photoreduction ability. For 001-TiO₂/g-C₃N₄ heterojunctions, nitrogen vacancies in g-C₃N₄ played a more important role in separating the charge carriers. Our discovery provides an efficient way to design high-performance TiO₂-based heterostructured photocatalysts through facet and defect engineering.