Noble metal-free zeolitic imidazolate framework-based composite for photocatalytic production of green hydrogen

Photocatalytic water splitting could become a major pillar in addressing future demands for carbon-free energy supply. To develop noble-metal-free photocatalyst microstructures, a heterostructure photocatalytic system containing hexagonal Zeolitic Imidazolate Framework-8 (ZIF-8) and oxygen-deficient spherical CuWO4 nanoparticles was designed. In addition to preventing CuWO4 aggregation, ZIF-8 promotes the accessibility of active sites, interfacial charge transfer, and separation in the ZIF-8@CuWO4 composite. In this composite, UV-visible diffuse reflectance spectroscopy reveals substantial light absorption in the UV range, while photoluminescence spectroscopy indicates suppressed electron-hole recombination relative to pristine materials. The as-synthesised ZIF-8@CuWO4 exhibits a photocatalytic H2 evolution rate of 2,531 μmol g-1 h-1 under UV irradiation, higher than that of pristine ZIF-8 and CuWO4. The composite achieves a maximum H2 production rate of 79 μmol g-1 h-1 under visible light irradiation using Na2S/Na2SO3 (0.35/0.25 M) as the sacrificial hole scavenger. These results highlight that integrating ZIF-8 with CuWO4 could offer an effective option for improving photocatalytic green hydrogen production in CuWO4-based heterojunction systems.