In situ-charge transfer optimization in Cu–BCN/ZnIn2S4 heterojunctional photocatalysts for simultaneous HER/CO2RR

Photocatalysis has emerged as a promising solution for environmental remediation, but developing photocatalysts that are both highly efficient and stable for sustainable hydrogen production remains a challenge. This study presents the development of Cu–BCN/ZnIn 2 S 4 heterojunction photocatalysts, synthesized through a combination of chemical vapor deposition and solvothermal methods, with Cu–Cu coordination sites incorporated to enhance performance. The resulting composite demonstrates impressive hydrogen production, generating approximately 2180 μmol h −1 under simulated sunlight and achieving a quantum efficiency of 45.4 % at 420 nm—nearly 20 times higher than pure CN. Notably, the Cu–BCN/ZnIn 2 S 4 heterostructure maintains strong activity even under natural sunlight and in diverse aqueous environments, showcasing its real-world applicability. Its intrinsic magnetism allows for easy recovery via magnetic separation, promoting recyclability. Cyclic stability tests reveal that the heterojunction design prevents photocorrosion and preserves structural integrity. Electrochemical and charge-carrier dynamic analyses show that the material's interface reduces electron-hole recombination by enhancing visible-light absorption and charge separation, offering a promising strategy for solar-to-hydrogen conversion in complex environment. • Cu and B co-doped into CN, forming Cu–BCN for enhanced light absorption and photoelectron mobility. • Cu doping generated Cu–Cu bonds, increasing active site density for CO 2 reduction and water splitting. • Cu–BCN/ZnIn 2 S 4 achieved 2180 μmol g −1 h −1 H 2 evolution rate under visible light, outperforming CN/ZnIn 2 S 4 . • Composite demonstrated 96 % selectivity for CO and CH 4 , with yields 35.6 times higher than pure CN.