Visually resolving the direct Z-scheme heterojunction in CdS@ZnIn₂S₄ hollow cubes for photocatalytic evolution of H₂ and H₂O₂ from pure water

The direct Z-scheme heterojunction has been recently emerging as an appealing architecture for photocatalysts design. Its efficiency depends on the interfacial and structural features of the photocatalysts. Herein, the two-dimensional ZnIn₂S₄ nanosheets are grown on the surface of CdS hollow cubes to construct the CdS@ZnIn₂S₄ hierarchical hollow photocatalysts with chemically bonded interface. The visualized measurements based on spatial-resolved surface photovoltage spectroscopy, combined with other spectroscopic and simulation investigations, clearly disclose that the CdS@ZnIn₂S₄ hollow cubes constitute a highly efficient direct Z-scheme system. This accounts for the stoichiometric generation of H₂ and H₂O₂ from pure water observed for the CdS@ZnIn₂S₄ sulfide-only photocatalysts under visible light irradiation with an apparent quantum efficiency of 1.63 % at 400 nm. The present work demonstrates an effective protocol to achieve comprehensive insights into the charge transfer route at semiconductor heterojunction, and offers a viable way for constructing efficient sulfide-only photocatalysts for driving water splitting reaction.