Construction of MoS2/g-C3N4 S-scheme heterojunction promotes plasma-photocatalytic degradation of methyl p-hydroxybenzoate: Electron transfer and adsorption reduction mechanisms

Abstract

A novel method of S-scheme heterojunction photocatalyst assisted with plasma was proposed to degrade the methyl p-hydroxybenzoate (MeP) in wastewater. The two-dimensional MoS₂/g-C₃N₄ composite was prepared by the thermal polycondensation method. The sheet-like morphologies and S-scheme heterogeneous structure were validated by XRD, XPS, EDS, FTIR, and TEM in the MoS₂/g-C₃N₄ composite. The addition of MoS₂/g-C₃N₄ increased the MeP degradation from 74.85% to 89.85% and the TOC removal rate from 25.16% to 40.12%. The MeP solution reduced the toxicity after treating the plasma/MoS₂/g-C₃N₄ system. Quenching experiments and electron paramagnetic resonance (EPR) spectra showed that the UV light generated by the discharge is utilized by the catalyst, which increases the yield of O₂⁻· and ¹O₂, enhancing the degradation efficiency of MeP. The absorption spectral range and electron transfer ability are improved by the interaction between MoS₂ and g-C₃N₄. The proposed charge transfer mechanism is driven by the S-scheme heterojunction built-in electric field (IEF), thereby reducing the recombination of photogenerated electron-hole pairs. The production of free radicals is increased by the adsorption-reduction reaction on the surface of MoS₂ and g-C₃N₄. In addition, the catalytic material has good photocatalytic performance after recycling. MoS₂/g-C₃N₄ combined with plasma exhibits excellent photocatalytic performance and has a wide range of application prospects.