Vacancy-Mediated Z-Scheme Heterostructure in SnO₂-Decorated Spinel In_3-S₄ with Boosted Photocatalytic Activity

The widespread application of dyes and heavy metals causes increasing environmental pollution. One effective way to mitigate environmental pollution is to use semiconductor photocatalysts for redox purification of pollutants. Heterostructured photocatalysts can reduce the electron-hole recombination rate and improve light utilization. In this work, a novel SnO₂/In_3-S₄ composite with oxygen vacancy defect-mediated Z-scheme heterostructure is constructed for the first time by a one-pot method, in which SnO₂ ultrasmall nanocrystals are decorated on nanopetals of flower-like In_3-S₄. Material analyses show that the as-built three-dimensional hierarchical architecture is able to essentially increase the specific surface area and thus the active sites of the products. More importantly, the formation of Z-scheme heterojunction between the oxygen vacancy-induced SnO₂ defect level and the In_3-S₄ band structure not only promotes the separation of photogenerated charges but also makes them more reactive. Through the optimization of the composition ratio between the two phases, the visible-light-driven photocatalytic reaction rates of rhodamine B degradation and Cr(VI) reduction for the developed SnO₂/In_3-S₄ composite photocatalyst are 12.8 and 6.3 times of bare In_3-S₄ and 32.0 and 76.0 times of bare SnO₂, respectively. This work should provide a promising implication for designing new high-performance composite photocatalysts.