Step-Scheme SnO₂/Zn₃In₂S₆ Catalysts for Solar Production of Hydrogen Peroxide From Seawater

Photocatalytic generation of H₂O₂, involving both oxygen reduction and water oxidation without sacrificial agents, necessitates maximized light absorption, suitable band structure, and efficient carrier transport. Leveraging the redox capacity this study designs and constructs a step-scheme heterostructured SnO₂/Zn₃In₂S₆ catalyst for H₂O₂ production from seawater under ambient conditions for the first time. This photocatalyst demonstrates a remarkable H₂O₂ production rate of 43.5 µmol g⁻¹ min⁻¹ without sacrificial agents, which can be increased to 80.7 µmol g⁻¹ min⁻¹ with additional O₂ injection. Extensive in situ and ex situ characterizations, supported by theoretical calculations, reveal efficient carrier transport and robust redox ability, enabling complete photosynthesis of H₂O₂ at the oxidation and reduction sites in the S-scheme SnO₂/Zn₃In₂S₆ heterojunction. Furthermore, it is hypothesized that substituting SnO₂ with other semiconductors such as TiO₂, WO₃, and BiVO₄ can all form S-scheme and the results confirm the feasibility of such catalyst design. Additionally, it demonstrates the recycling and further utilization of the H₂O₂ produced. These findings offer new insights into the design of heterostructure catalyst architectures and present new opportunities for H₂O₂ production from seawater at ambient conditions without sacrificial agents.