Activated charge transfer by interfacial S−O “bridge” at MnIn2S4/WO3 for eliminating kanamycin: Z-scheme mechanism, pathways and toxicity assessment

Abstract

In the realm of heterojunction photocatalysis, the efficiency of carrier separation and overall photocatalytic reactions are significantly influenced by the accompanying resistance at the interface as well as the pathway of charge transfer. Herein, a covalently linked Z-scheme MnIn2S4/WO3 heterojunction with interfacial S−O bonds was synthesized through simple calcination and hydrothermal strategies. This tight heterostructure exerted the collaborative impact of interfacial covalent bonding in a Z-scheme model, and its significant role in facilitating the separation of charge carriers was investigated. 19 wt% WO3 combined MnIn2S4 (MIS/WO-19) delivered a remarkable degradation efficiency of 97.4 % for kanamycin, which was 8.8 times higher than that of pure MnIn2S4. The formation of S−O linkages between MnIn2S4 and WO3 was confirmed through experimental analyses and theoretical modeling. The proposed Z-scheme charge transfer pathway was examined by integrating quenching experiments, ESR tests, and DFT computations. This distinctive S−O bond, acting as a specialized “bridge”, in combination with the Z-scheme pathway, efficiently promoted the migration and segregation of photo-induced charges, leading to a notable enhancement in the degradation of kanamycin. Furthermore, the decomposition pathways of kanamycin were investigated through a collaborative approach involving mass spectrometry and DFT simulations, and a toxicity analysis of the intermediates was conducted by the computational toxicology.