SnS2-In2S3 p-n heterostructures with enhanced Cr6+ reduction under visible-light irradiation

Abstract

We present one-pot hydrothemal syntheis of SnS2-In2S3 p-n heterostructures for photocatalytic reduction of Cr6+ to Cr3+. The conduction bands of In2S3 and SnS2 serve as the photogenerated electron donors and acceptors, respectively, forming a p-n junction band alignment improving the photogenerated charge separation efficiency. Through a detailed investigation of photocurrent spectra, photoluminescence spectra and electrochemical impedance, the heterojunction formation is shown to enhance the photogenerated charge separation and transport properties. In addition, the analysis of 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) spin trapping electron spin resonance (ESR) spectra and band structure further testify the p-n junction of the composite catalyst that could accelerate the electron transport and change the pathway of photocatalytic process toward Cr6+ reduction. Furthermore, SnS2-In2S3 heterojunction photocatalyst achieved 3 times and 67 times higher efficiency than pure In2S3 and SnS2 photocatalysts under visible light toward Cr6+ reduction. Moreover, the SnS2-In2S3 p-n heterojunction photocatalyst demonstrates Cr6+ removal in a weak alkaline solution, breaking through the challenge of Cr6+ reduction in an alkaline environment.