g‐C₃N₄ S‐Scheme Homojunction through Van der Waals Interface Regulation by Intrinsic Polymerization Tailoring for Enhanced Photocatalytic H₂ Evolution and CO₂ Reduction

The effective S-scheme homojunction relies on the precise regulation of band structure and construction of advantaged charge migration interfaces. Here, the electronic structural properties of g-C₃N₄ were modulated through meticulous polymerization of self-assembled supramolecular precursors. Experimental and DFT results indicate that both the intrinsic bandgap and surface electronic characteristics were adjusted, leading to the formation of an in-situ reconstructed homojunction interface facilitated by intrinsic van der Waals forces. The homojunction catalyst, composed of g-C₃N₄ nanodots and ultra-thin g-C₃N₄ nanoflakes, exhibited a significant S-scheme carrier separation mechanism, which enhances the utilization of electrons and holes. Consequently, under AM 1.5 light irradiation (~100 mW/cm²), the g-C₃N₄ homojunction photocatalyst achieved a remarkable hydrogen evolution rate of 580 μmol h^-1. Furthermore, a reversed CH₄ selectivity in CO₂ reduction was observed, yielding 80.30 μmol g^-1 h^-1 with a selectivity of 96.86 %, in contrast to the performance of bulk g-C₃N₄, which produced only 2.22 μmol g^-1 h^-1 with the 15.69 % CH₄ selectivity. These findings not only highlight the significant potential of the g-C₃N₄ homojunction photocatalyst for hydrogen production and CO₂ reduction but also propose a superior and effective strategy for optimizing the structural properties of g-C₃N₄, which are crucial for the design of photocatalytic reactions.