Study On Photoelectrocatalytic Degradation Of Typical Organic Pollutants By Mos₂ Electrode

In recent years,photoelectric catalytic oxidation technology?PEC?has been widely studied as a promising environmental remediation technology.Photoelectric catalytic oxidation technology is developed on the basis of photocatalysis and is a new type of advanced oxidation technology.This technology can effectively promote the separation of photo-generated electrons and holes,improve the quantum efficiency,and accelerate the degradation rate of organic pollutants.In this study,vertically aligned MoS₂ nanoflakes on Ti foil were synthesized by hydrothermal method.The effects of solvents and calcination temperatures on the properties of the composites were investigated.The crystal phase structure,morphology,crystal form,chemical composition and valence state,and microstructure and structure of the material were characterized by X-ray diffractometer?XRD?,field emission scanning electron microscope?SEM?,micro-laser confocal Raman spectroscopy?Raman?,X-ray photoelectron spectroscopy?XPS?,field emission transmission electron microscope?TEM?and Ultraviolet visible absorption spectrometer?UV?respectively.The few-layer MoS₂?4-10 nm?nanoflakes electrode synthesized in water exhibits a strong photocurrents under visible light irradiation,and the stability of the few-layer MoS₂ electrode was obtained after calcination annealing at 300°C.The excellent photoelectrochemical performance of the few-layer MoS₂ nanosflakes are related to their crystal phase,number of layers and photon absorption efficiency etc.In addition,the photoelectrochemical degradation of organic chemicals including rhodamine B dye,chlorpyrifos and ciprofloxacin selected as different types of pollutants in wastewater,and the degradation tests of separate pollutants and mixed pollutants were conducted respectively.Based on MoS₂-300°C of PEC pollutants degradation in the system when the bias was 0.3 V,the electrolyte was0.02 M Na₂SO₄,the pH was 3 and the time was 2 hours,the degradation rate of rhodamine B,chlorpyrifos and ciprofloxacin were 71.2%,90.5%and 6.7%.The PEC degradation efficiency follows the order of CPF>RhB>CIP.In a system where hydroxyl radicals play a leading role in oxidation,the high electron cloud density sites induced by the electron-withdrawing functional groups in different substrates can determine the substrate-specific PEC degradation efficiency.In the mixture degradation system,in order to further improve the photoelectric catalytic degradation efficiency,MoS₂ photoanode was used to activate sulfite ions and oxidative species such as oxysulfide free radicals?SOx·^-?and hydroxyl free radicals were produced to selectively degrade different pollutants.when the bias was 0.3 V,the electrolyte was 0.02 M Na₂SO₃,the pH was 3 and the time was 4 hours,the degradation rate of rhodamine B,chlorpyrifos and ciprofloxacin were 99.8%,95.6%and 66.3%.The PEC degradation rate was CPF>RhB>CIP.The experiments of free radical quenching capture confirmed that a variety of free radicals,including·OH,h⁺,SO3·^-,SO4·^-and SO5·^-,work together in the mixed degradation system.