Graphical abstract

Photocatalytic hydrogen production is a promising method to address the increasing energy demand and depletion of fossil fuels. Among various photocatalysts, g-C₃N₄ (CN) has attracted significant attention due to its favorable properties and tunable band structure. CN-based heterojunctions have been developed to enhance photocatalytic efficiency through improved charge separation via interfacial charge transfer. However, traditional heterojunctions formed between CN and other semiconductors often face challenges related to material compatibility and stability. In this work, we explored the formation of homojunctions, which involve identical semiconductors and offer superior charge separation and electron mobility due to perfect lattice matching. To further enhance individual oxidation and reduction capabilities, we employed band structure engineering through B doping and O doping. The homojunction between B-doped CN (BCN) and O-doped CN (OCN) was successfully synthesized using simple electrostatic self-assembly, resulting in significantly improved hydrogen production of 519.3 μmol g⁻¹h⁻¹ compared to BCN (34.7 μmol g⁻¹h⁻¹) and CN (167.2 μmol g⁻¹h⁻¹). This approach enhances visible light absorption, charge separation, and mobility, demonstrating the potential for developing advanced CN-based photocatalysts for various applications.