Construction of S-scheme melem hydrate/g-C3N5 heterojunction for enhanced photocatalytic performance under LED light irradiation

The optical and electronic properties of g-C₃N₅ make it a promising photocatalytic material, yet bulk g-C₃N₅ suffers from high charge recombination and trapping, limiting its effectiveness. Our study addresses these challenges through a controlled acid treatment of bulk g-C₃N₅ using a concentrated H₂SO₄/HNO₃ mixture. This process exfoliates g-C₃N₅ into nanosheets while simultaneously fragmenting it into melem units and assembling these fragments into rod-like melem structures. These interconnected structures within the melem hydrate/g-C₃N₅ composite form effective charge-transfer bridges, enabling enhanced charge migration between melem hydrate and g-C₃N₅ components. The hybrid melem hydrate/g-C₃N₅ catalyst demonstrated a remarkable tetracycline hydrochloride (TCH) degradation efficiency of 98.80 %, significantly outperforming the 50.55 % degradation achieved by bulk g-C₃N₅. This is due to increased surface area and the formation of an S-scheme heterojunction, promoting effective charge separation. The study also examines the impact of reaction parameters like pH and catalyst concentration on degradation efficiency, and investigates degradation pathways and toxicity using LC-MS and ECOSAR. This research provides an effective strategy for designing S-scheme heterojunction materials based on g-C₃N₅, significantly enhancing the photocatalytic activity of g-C₃N₅ and broadening the potential application of of g-C₃N₅-based systems.