Development and characterization of a graphene quantum dot/g-C₃N₄ photocatalyst for efficient degradation of Rhodamine B

Traditional water treatment methods face limitations in removing persistent organic pollutants due to slow degradation rates and incomplete mineralization. This study presents a novel metal-free heterostructured nanocomposite graphene quantum dots/g-C₃N₄ (GQCN) comprising graphene quantum dots (GQDs) and graphitic carbon nitride (g-CN) for enhanced photocatalytic degradation. GQDs were synthesized via pyrolysis, while g-CN was obtained through thermal treatment. Components were integrated through sonication-assisted mechanochemical approach to form efficient heterojunctions promoting charge separation. GQCN demonstrated superior photocatalytic performance for Rhodamine B (RhB) degradation under visible light compared to individual components. Optimal performance achieved 95.2% degradation efficiency within 120 min following pseudo-first-order kinetics with 35 mg/L catalyst loading. Maximum efficiency 98.2% was attained at pH 4.2 due to enhanced electrostatic interactions. The nanocomposite exhibited remarkable stability over five consecutive cycles. Comprehensive characterization using XRD, FT-IR, TEM, FESEM, EDX, UV-Vis DRS, fluorescence, DLS, zeta potential analysis, and PL spectroscopy confirmed successful heterostructure formation. Scavenger studies revealed hydroxyl radicals as predominant reactive species. This work introduces a practical strategy for fabricating metal-free photocatalysts with enhanced visible light activity, addressing scalability and environmental compatibility challenges, demonstrating significant potential for sustainable water treatment applications.