Two-dimensional g-C3N4/InSe heterostructure as a novel visible-light photocatalyst for overall water splitting: a first-principles study

The enhanced visible-light harvesting, low recombination of electron–hole pairs and high carrier mobility are found in a novel g-C3N4/InSe hybrid two-dimensional (2D) heterostructure photocatalyst by using first-principles calculations for the first time. The photocatalytic mechanism of g-C3N4/InSe is comprehensively investigated. Our calculations show that 2D g-C3N4/InSe heterostructure has a direct band gap of 1.93 eV and a typical type-II band alignment with holes and electrons located in metal-free g-C3N4 monolayer and non-noble metal InSe nanosheet, respectively. A remarkable visible-light absorption can thus be expected. The electrons and holes located in InSe and g-C3N4 monolayers have a high mobility (104 and 102 cm2 V−1 s−1), which is beneficial for improving the catalytic efficiency. The charge density difference and type-II band structure indicate that the photo-generated electrons easily transfer from g-C3N4 monolayer to InSe nanosheet, and the holes are transferred from InSe to g-C3N4, reducing the electron–hole recombination. Compared with the well-known 2D g-C3N4/MoS2 hybrid photocatalyst composed of g-C3N4 nanosheet and MoS2 monolayer with a low electron mobility (<200 cm2 V−1 s−1) and fast electron–hole recombination due to its direct bandgap, g-C3N4/InSe heterostructure photocatalyst has a distinctive advantage in improving the photocatalytic hydrogen evolution performance due to the high carrier mobility and suppressing the recombination of photo-generated electrons and holes by the indirect band gap of InSe monolayer. These clearly prove that g-C3N4/InSe is an energetic photocatalyst for overall water splitting under visible-light irradiation.