One-pot synthesis of ZnIn2S4 graphene aerogels with S vacancies for efficient photocatalytic reduction of Cr(VI) and hydrogen evolution

The construction of aerogel photocatalyst materials is a practical and effective strategy for hydrogen evolution and the reduction of heavy metal ions. Herein, ZnIn2S4 nanosheets with S vacancies were in-situ grown on graphene aerogels (S-ZISA) by a facile one-pot oil bath method. The construction of S vacancies can improve light absorption by modulating the electron band structure, and becoming an effective active site for electron capture. Under visible light illumination, the optimum ratio of S-ZISA-2 achieved 98% reduction of photo-reduced Cr(VI) for 60 min, and with a rate constant (0.054 min−1) was 4.5 times higher than that of pure ZnIn2S4 (0.012 min−1). The cycling experiments show that S-ZISA-2 has good cyclability, and the coexisting anions and effects of pH value in solution on the photo-reduction of Cr(VI) were studied. In addition, the S-ZISA-2 exhibits a high rate of hydrogen evolution (2011.7 μmol g−1). The excellent photocatalytic activity is mainly attributed to the graphene aerogel backbone, which not only provides more active sites but also a unique three-dimensional network that provides abundant electron transport channels, accelerating the carrier transport rate and prolonging the visible light lifetime. In addition, the ZnIn2S4 nanosheets can form Schottky heterojunction with graphene, which effectively enhances the migration of photo-induced carriers, hinders carrier recombination, and enhances the photocatalytic activity. This study provides new strategy in the synthesis of aerogel photocatalysts.