Abstract:

The rational construction of step-scheme (S-scheme) heterojunctions has been demonstrated as an effective strategy to optimize interfacial charge carrier separation dynamics in semiconductor photocatalysts. In this work, a hierarchical ReSe₂/ZnCdS S-scheme heterojunction with well-defined architectures was successfully synthesized via an ultrasonication-assisted synthetic strategy, achieving precise nanostructure control and enhanced interfacial coupling for optimized photogenerated charge dynamics. The disordered nanoflower-like ReSe₂ architecture enhances light-harvesting efficiency and the density of surface reaction sites, and significantly suppresses ZnCdS nanoparticle aggregation. The optimized 5%ReSe₂/ZnCdS composite exhibits an exceptional hydrogen evolution rate of 13.96 mmol∙g⁻¹∙h⁻¹ under visible light irradiation, representing a 5.91-fold enhancement over pristine ZnCdS (2.36 mmol∙g⁻¹∙h⁻¹) and outperforming most conventional heterojunction systems. The outstanding photocatalytic performance is attributed to the formation of the ReSe₂/ZnCdS S-scheme heterojunction, which promotes the separation of photogenerated electrons and holes, enhancing the photo-redox capacity. Combining in situ X-ray photoelectron spectroscopy (XPS) analysis and density functional theory (DFT) calculations further conform the S-scheme charge transfer mechanism at the heterointerface of ReSe₂/ZnCdS. Furthermore, Gibbs free energy calculations of hydrogen adsorption confirm that ReSe₂ as the predominant catalytic center provides more favorable hydrogen adsorption kinetics than ZnCdS. This work provides a universal framework to design ZnCdS-based S-scheme heterojunctions for high-efficiency photocatalytic hydrogen evolution.

Key words: S-scheme, Photocatalytic hydrogen evolution, ZnCdS, ReSe₂, Internal electric field