3D black g-C3N4 isotype heterojunction hydrogels as a sustainable photocatalyst for tetracycline degradation and H2O2 production

The sustainable visible light active g-C3N4 hydrogel is synthesized and employed for water reclamation and H2O2 production. In this study, citric acid-assisted chemically functionalized black g-C3N4 isotype heterojunction (BCN) hydrogel was prepared using the blend-crosslinking method. The comprehensive characterization of the BCN hydrogels affirmed its tuned optical bandgap with effective visible light utilization, greater separation efficiency, and restricted recombination ratio of electrons and holes. The BCN hydrogels exhibited a phenomenal photocatalytic efficiency towards tetracycline degradation (86% in 40 min) and H2O2 production (987 µmol in 60 min). The superoxide, holes, and singlet oxygen demonstrated a synergistic role in photocatalytic activity through the effective migration of electrons. As an immobilized system, the predominant advantages of BCN hydrogel beads include ease of recovery and remarkable reusability up to 7 cycles. This study provides insights into systematically modifying g-C3N4 toward sustainable energy and environmental applications.