A sulfur-vacancy modified SnIn4S8/C3N5 S-type heterojunction for the efficient photocatalytic reduction of Cr(VI) and the degradation of RhB

Abstract

Heterojunction construction is a key strategy for enhancing the photocatalytic efficiencies of semiconductors. An S-type heterojunction, SnIn₄S₈/C₃N₅, containing sulfur vacancies (Sv) was prepared using a hydrothermal method. After optimization, the SnIn₄S₈/C₃N₅ heterojunction exhibited RhB degradation rates that were 2.05- and 17.84-times higher than those of SnIn₄S₈ and C₃N₅, respectively, after 21 min of sunlight exposure. Similarly, under simulated sunlight, the Cr(VI) reduction rates were 6.78- and 46.66-times higher than those of SnIn₄S₈ and C₃N₅, respectively. The prepared catalyst demonstrated a good stability across a range of pH levels in the presence of both cations and anions, and using various water sources. The exceptional photocatalytic performance of the SnIn₄S₈/C₃N₅ heterojunction was attributed to the robust separation and transfer of photogenerated carriers facilitated by the intimate interfacial contact. The slit-pore structure reduced the carrier migration distance and provided additional active sites, while the Sv sites capture the carriers, working in combination with the S-type charge-transfer mechanism to ensure a high catalytic efficiency. This study offers novel perspectives on the application of SnIn₄S₈ and highlights the considerable potential of rationally engineered heterojunctions for improving the photocatalytic performance.