Z-Scheme g-C3N4/ZnS Heterojunction with redox synergy for high-efficiency pollutant degradation

Abstract Simultaneously achieving high charge separation efficiency and structural stability in solar-driven photocatalysts remains a critical challenge. Here, we report a Z-scheme g-C3N4/ZnS heterojunction synthesized via hydrothermal deposition, which enhances redox capabilities through efficient charge carrier transfer/separation to improve photocatalytic activity and stability. The direct interfacial chemical bonds between g-C3N4 and ZnS enable unidirectional electron transfer and minimized recombination losses. The optimized heterojunction achieves 95.75% degradation of methylene blue under visible light within 2 h—6.38-fold and 4.76-fold higher than pristine g-C3N4 and ZnS, respectively. Mechanistic studies reveal superoxide radicals (•O2-) as the dominant active species, synergistically supported by hydroxyl radicals (•OH) and holes. Remarkably, the heterojunction composite retains 75.12% efficiency after four cycles, demonstrating exceptional stability attributed to its robust interfacial structure and suppressed ZnS oxidation. This work advances Z-scheme photocatalysts with dual redox capabilities toward scalable environmental remediation.