Enhanced photocatalytic activity of SnS2 quantum dot modified Sn3O4 nanosheet composite photocatalysts for wastewater treatment applications

The construction of heterojunction is a practical way to boost the separation of photogenerated carriers and photocatalytic activity of single photocatalyst. In this paper, a novel SnS2 quantum dots/Sn3O4 nanosheets (SS/SO) heterojunction was successfully constructed by an in-situ solvothermal method with the aid of ultrasonic exfoliation, where the SnS2 quantum dots were successfully loaded on Sn3O4 nanosheets to form a close contact interface. The prepared SS/SO heterojunction presented much enhanced visible-light photocatalytic degradation of methyl orange (MO) and the reduction of chromium (Cr(VI)) compared with SnS2 quantum dots and Sn3O4. Especially, SS/SO-2 sample showed the best degradation performance of 98.16 % for methyl orange (MO) in 24 min, and its rate constant was 0.1494 min(-1), which was 15.42 and 49.87 times higher than those of pure Sn3O4 (0.0097 min(-1)) and SnS2 (0.0030 min(-1)), respectively. The performance for MO degradation was also much superior to some recently reported photocatalysts. In addition, the reduction efficiency of Cr(VI) could reach to 96.22 % at 105 min for SS/SO-2. The uniform distribution of SnS2 quantum dots and the synergistic effects of SnS2 and Sn3O4 effectively separated the photogenerated charge carriers, resulting in the superior photocatalytic performance of the SO/SS composites. The photoreaction mechanism was also carefully investigated. Parallel experiment and LC-MS were applied to investigate the degradation pathways and intermediates of MO. The construction of SnS2/Sn3O4 heterojunction will lay the foundation for the development of new visible photocatalysts and the efficient removal of pollutants such as dyes and heavy metals Cr (VI) from wastewater.