Structurally tuned g-C3N4 nanosheets via thermal exfoliation for superior photocatalytic oxidative degradation of industrial food dye pollutants

Graphitic carbon nitride (g-C3N4), an attractive metal-free photocatalyst, has received significant interest for the treatment of wastewater due to its high chemical stability and visible light responsiveness. The photocatalytic effectiveness of pure g-C3N4 (GCN) is limited due to its low surface area a3nd fast recombination of charge carriers generated by photons. In this work, the physicochemical properties of bulk GCN were systematically modified by direct thermal exfoliation to the thermally exfoliated GCN. The photocatalytic efficiency of the synthesized samples was assessed through the degradation of food dyes Carmoisine (CM) and Indigo Carmine (IC) under UV, visible, and natural sunlight exposure. Structural and morphological analysis (i.e., FTIR, XRD, FE-SEM, EDAX, BET, and UV-DRS) revealed the improved surface properties and optical characteristics of the material. BET surface area measurements significantly increased from 5. 03 m²/g (bulk GCN) to 26.2 m²/g for exfoliated GCN (GCN 550 ˚C). Radical trapping experiments revealed that the superoxide radicals (•O2-) exerted more significant effects on degradation than hydroxyl radicals (•OH) and photoinduced holes (h+) did. The photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) results indicated that exfoliated GCN had lower charge carrier recombination and higher interfacial charge transfer. Moreover, the catalyst displayed remarkable recyclability with only a slight decrease in activity from 92% to 86% across five cycles. The obtained results demonstrate that the exfoliated graphitic carbon nitride is an efficient, stable, and sustainable photocatalyst for wastewater treatment applications.