Dye degradation over the multivalent charge- and solid solution-type n-MoS2/p-WO3 based diode catalyst under dark condition with a self-supporting charge carrier transfer mechanism

Abstract

Pollution of water by synthetic dyes is of great concern because of the large production and usage of dyestuffs throughout the world. For dye elimination purpose, the p-n heterojunction Sb-doped MW-x composite catalysts prepared with different Mo:W precursor molar contents were synthesized via one-pot hydrothermal method. The selection in metal precursors is intended to design a composite catalyst with multiple valency in each phase. The structural, morphological, electrochemical property, and optical band gap of the composite catalyst were studied. The catalytic performance of Sb-MW composite catalysts was studied for the degradation of MB without light irradiation. It was observed that Sb-MW-4 showed superior catalytic performance to completely degrade 20 ppm MB dye solution with 20 mg catalyst in 14 min under dark condition. The composite catalyst was composed of n-(Mo,W)(O,S)2 oxysulfide in a disordered MoS2 framework and p-(W,Mo)(S,O)3 sulfo-oxide in a WO3 structure or was abbreviatedly named as n-MoS2/p-WO3 based catalyst. The degradation reaction for MB dye had an apparent rate constant of 3.5 × 10−1 min−1. This catalyst also showed excellent stability and reusability for degrading MB dye pollutant. The degradation mechanism under dark condition is proposed.