Lattice-matching formed covalent heterointerfaces based on epitaxial growth of ZnIn2S4 nanosheet on Cu2S nanobox to accelerate charge separation for effective antibiotic degradation cooperated with hexavalent chromium reduction

Abstract

Nowadays, water pollution issues caused by antibiotics and heavy metals have become a focus of global concern, and it is greatly significant to develop effective methods to remove heavy metal and organic contaminant from wastewater. Herein, newly-designed Cu₂S/ZnIn₂S₄ p-n heterojunction with internal electric field is constructed by using epitaxial growth strategy. Importantly, lattice well-matched heterointerface between Cu₂S and ZnIn₂S₄ presents very low charge transfer resistance. Under the mediation of internal electric field, the generation and separation of photogenerated carriers are effectively improved, and the formation of hollow structure enhances visible light absorption capability. Benefiting from these changes, photogenerated electrons and holes can be directly involved in tetracycline (TC) degradation and Cr(VI) reduction, avoiding intermediate reaction processes. Under visible light illumination, thus, Cu₂S/ZnIn₂S₄ composite shows superb performance in the treatment of wastewater containing both antibiotic and Cr(VI). The removal efficiencies of TC and Cr(VI) are as high as 96.7 % and 94.1 % within 32 min, respectively. Interestingly, Cr(VI) reduction over Cu₂S/ZnIn₂S₄ is a stepwise process, and Cr(VI) is first reduced to Cr(V) and then transformed into Cr(III). Notably, Cr(V) with strong oxidation ability as transition intermediate can further promote antibiotic degradation.