Construction of immobilized direct Z-scheme ZnS QDs-Fe2O3 QDs|430-SSF photocatalyst film for methylene blue degradation with simultaneous hydrogen production.

Traditional photocatalysts have the disadvantages of low sunlight utilization efficiency, weak interaction with contaminants and difficulty in recycling. In this study, ZnS QDs and Fe2O3 QDs prepared by hydrodynamic cavitation method and 430 stainless steel foil (430-SSF) are used to synthesize immobilized direct Z-scheme photocatalyst film. This photocatalytic has higher sunlight utilization rate, organic contaminants degradation and hydrogen production. Moreover, the small size and large specific surface area of quantum dots can enable photocatalysts to provide more reactive sites, increasing contact probability between contaminants and catalyst. ZnS QDs-Fe2O3 QDs heterojunction is constructed through hydrothermal reaction and coated on 430-SSF to prepare the photocatalyst film with 38.4 μm thickness. This design scheme completely overcomes the above defects. The experimental results show degradation efficiency of MB reaches 89.46% and hydrogen production reaches 422.5 μmol under simulated sunlight irradiation for 3.0h when mass proportion of ZnS QDs and Fe2O3 QDs is 1:3. The degradation efficiencies of MB using ZnS QDs-Fe2O3 QDs composite as photocatalyst are 2.19 times and 11.1 times higher than ones of using ZnS QDs and Fe2O3 QDs alone. More importantly, after multiple cycles of use, the performance and hydrogen production efficiency of photocatalyst show little decline, indicating excellent structural stability and good reusability. This research provides an innovative and practical idea for the preparation of immobilized direct Z-scheme photocatalysts for the efficient degradation of organic contaminants and simultaneous hydrogen production, which is of great significance for promoting large-scale application of photocatalytic technology in wastewater treatment and clean energy production.