Photocatalytic Properties of g‑C₆N₆/g‑C₃N₄ Heterostructure: A Theoretical Study

As a promising photocatalytic material in water splitting and organic degradation, the polymeric graphitic g-C₃N₄ has attracted intensive research interest during the past decade due to the visible light response, nontoxicity, abundance, easy preparation, as well as high thermal and chemical stability. However, the low efficiency owing to the fast charge recombination limits its practical applications. In the present work, we systematically investigated the electronic structure and photocatalytic properties of layered g-C₆N₆/g-C₃N₄ heterostructure on the basis of first-principles calculations. The results show that the type-II heterojunction can be established between g-C₆N₆ and g-C₃N₄ monolayers due to a perfect lattice match and aligned band edges, facilitating the separation of photogenerated carriers. In addition, it is worthwhile to note that hole effective masses of g-C₆N₆/g-C₃N₄ heterostructure can be significantly reduced compared to pristine g-C₃N₄ due to orbital hybridization between the two monolayers, which is extremely favorable for the migration of photogenerated holes. The g-C₆N₆/g-C₃N₄ heterostructure has a reduced band gap compared to that of pristine g-C₃N₄, which can further be tuned by biaxial strain. This work not only provides new insights into the physical and chemical properties of the g-C₃N₄-based heterostructures, but also suggests viable ways to prepare highly efficient photocatalytic materials.