A CZS-decorated Al-MOF S-scheme heterojunction for concurrent photocatalytic H2 generation and methylene blue degradation under visible light

Abstract

Photocatalytic hydrogen production coupled with the degradation of dye wastewater is deemed a promising strategy to overcome the challenges of both the energy crisis and water pollution. Here, a novel heterojunction photocatalyst was constructed by decorating Cd_0.5Zn_0.5S (CZS) on the surface of a flower-shaped Al-MOF. It has been confirmed that the built-in electric field (IEF) at the interface between Al-MOF and CZS forces S-scheme photoelectron transfer from the conduction band of Al-MOF to the valence band of CZS, thereby enhancing the photocarrier separation and boosting the photocatalytic efficiency of H₂ evolution and methylene blue (MB) degradation. Al-MOF/0.3CZS was demonstrated to have remarkable activity, with the H₂ amount generated in 4 h reaching 17 049.93 µmol g⁻¹, representing the highest H₂ generation rate of Al-MOF-based photocatalysts to date, when lactic acid was used as the hole sacrificial agent; concurrently, nearly 100% of MB was degraded within 1 h under visible light irradiation. Notably, when integrating the oxidation and reduction processes as a whole, high hydrogen production activity was still maintained (16 028.6 µmol g⁻¹), but the degradation efficiency of MB slightly decreased to 74.3%. Meanwhile, MB also undertakes the role of a photosensitizer in the coupled process of H₂ generation and MB degradation. This work provides a valuable strategy for simultaneous H₂ production and treatment of dye wastewater and extends the application boundary of Al-MOF-based materials.