Regulating the surface state of ZnIn2S4 by gamma-ray irradiation for enhanced photocatalytic hydrogen evolution

Surface vacancies have been demonstrated to be active sites in the photocatalytic hydrogen-evolution reaction (HER) over sulfides and oxides. In this work, the surface S vacancies were regulated by high-energy gamma-ray radiation over ZnIn2S4. It was found that gamma-ray irradiation had a strong effect on changing the electronic structure, and ZnIn2S4 had a variable band gap under different radiation doses. With the dose of 40 kGy, the band gap of ZnIn2S4 was reduced from 2.11 to 2.01 eV. The H-2-generation rate under visible light could be as high as 154.1 mu mol h(-1) over 40 kGy gamma-ray-irradiated ZnIn2S4, which was approximately 11.5 times higher than that over the original ZnIn2S4. Furthermore, the ESR, XPS, and fluorescence spectroscopy provided evidence of gamma-ray radiation-introduced surface S vacancies on the Zn side. DFT calculations demonstrated that the surface S vacancies accelerated H2O adsorption and H-2 desorption. Nevertheless, a higher irradiation energy (>40 kGy) may create more bulk vacancies, resulting in a lower H-2-evolution activity. Therefore, gamma-ray irradiation is beneficial to regulating the surface S vacancies on ZnIn2S4, thereby improving the photocatalytic H-2-evolution efficiency. This work provides a detailed understanding of gamma-ray radiation-induced surface vacancies and a reasonable inspiration to regulate the surface defects of photocatalysts with efficient activity.

Automated summary

Surface vacancies have been proven to be active sites in photocatalytic hydrogen-evolution reaction. Gamma-ray irradiation can regulate the surface vacancies on ZnIn2S4 and improve the hydrogen evolution efficiency.