Hierarchical S-scheme heterojunctions of ZnIn2S4-decorated TiO2 for enhancing photocatalytic H2 evolution
Photocatalytic water splitting to produce H2 using semiconductor photocatalysts is a reliable ap-proach to alleviating energy shortages and environmental pollution.However,the inadequate light-harvesting ability,rapid photogenerated carrier recombination,and inferior redox capacity of the individual photocatalysts restrict their photocatalytic activity.To address these limitations,a hierarchical S-scheme heterojunction of Znln2S4-nanosheet-decorated flower-like TiO2 micro-spheres for enhancing photocatalytic H2 evolution,purposely constructed through in situ chemical bath deposition,has been reported.The as-synthesized TiO2/ZnIn2S4 heterojunctions exhibited ZnIn2S4-content-dependent photocatalytic activity for solar-driven H2 evolution.As a result,the optimized TiO2/ZnIn2S4 heterojunction exhibited a superior photocatalytic H2 evolution rate of 6.85 mmol g-1 h-1,approximately 171.2-and 3.9-fold with respect to that obtained on pure TiO2 and ZnIn2S4,respectively,mainly attributed to the unique hierarchical structure,extended light-harvesting ability,enhanced redox capacity,and improved separation and transfer efficiencies of the photogenerated carriers induced by the S-scheme heterojunctions.Simultaneously,a detailed analysis of the S-scheme electron transfer pathway in the TiO2/ZnIn2S4 heterojunction was per-formed using in situ irradiated X-ray photoelectron spectroscopy and electron paramagnetic reso-nance spectroscopy.This study provides insights into the design of highly active heterojunction photocatalysts for sustainable solar-to-fuel energy conversion.
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