Visible-light-driven double-shell SnIn4S8/TiO2 heterostructure with enhanced photocatalytic activity for MO removal and Cr(VI) cleanup

Schematic diagrams of the possible photocatalytic mechanism of photocatalytic Cr(VI) cleanup(a) and MO removal(b) [Display omitted] •The novel double-shell SnIn4S8/TiO2 heterostructure was firstly constructed.•The SISTOHS heterostructures exhibited efficient photocatalytic activity.•The double-shell interface could facilitate the rapid separation of carriers.•Surface potential and hydrophilicity ensure outstanding photoactivity.•The tentative type II heterojunction was proposed. Construction and design the various heterojunction structures are effective and promising strategies to improve the photocatalytic performances of semiconductors. In this work, a novel visible-light-driven SnIn4S8 nanosheet/TiO2 hollow sphere (SISTOHS) heterojunction with the intimate contact structure was successfully constructed by the facile hydrothermal process. The as-prepared SISTOHS heterostructures displayed outstanding photocatalytic removal activities of methyl orange (MO) and Cr (VI). The optimized sample SISTOHS2 presented the highest photodegradation efficiency of MO (90.08%) and photoreduction efficiency of Cr (VI) (94.44%) within 60 min. Significantly, the rate constants of photodegradation for MO and photoreduction for Cr (VI) over SISTOHS2 were 15.03 and 28.39 folds as high as those of TiO2 hollow spheres, 2.37 and 4.02 folds as high as those of SnIn4S8 nanosheets, respectively. Through the systemic characterizations, the improvement of photocatalytic performance could be not only contributed to the intimate contact double-shell interface introduced a strong interaction between SnIn4S8 and TiO2 to accelerate the separation and migration of charge carriers, but also the increased visible light harvesting ability and abundant reactive sites ensuring the excellent photoactivity. The photocatalytic mechanism of typical type-II heterojunction was discussed in-depth. This work will provide a favorable theoretical and practical experience of designing TiO2 related photocatalyst for wastewater purification.