Study On Advanced Oxidation Degradation Of Pollutants By Plasmonic Enhanced Photocatalysis

The continuous development of industrialization and urbanization has led to more and more organic pollutants being discharged into the aqueous environment.Therefore,the degradation treatment of organic pollutants in water is particularly urgent and important.In recent years,advanced oxidation processes（AOPs）,especially photocatalytic AOPs,with the advantages of simple operation,low energy consumption,high degradation efficiency and good reproducibility,have been widely used for the removal of refractory organic pollutants.The current photocatalytic AOPs methods based on hydrogen peroxide（H₂O₂）,peroxymonosulfate（PMS）,and persulfate（PS）are mainly realized by the irradiation of high-energy UV light.To address this issue,in our work,a plasmon-enhanced photocatalytic advanced oxidative degradation of pollutants under visible light conditions was carried out.Metals with local surface plasmon resonance properties are compounded with other metals with high catalytic activity,and with perovskite semiconductor materials with good optical properties,to improve the degradation efficiency of photocatalytic AOPs.Specifically,the main contents of each chapter of this thesis are as follows.Chapter 1.Firstly,the research progress of photocatalytic AOPs is introduced.Based on the discussion of their reaction mechanism and activation process,the current photocatalytic materials applied to AOPs and their modification strategies are introduced in detail.Then the new plasmon photocatalytic materials developed in recent years and their compounding strategies are futher introduced.Finally,the main research contents and innovations of this work are pointed out.Chapter 2.The study of photocatalytic activation of peroxynitrite（PS）to generate SO₄˙ˉradicals by plasmon composite metal and then their photocatalytic degradation of ionic liquids was carried out.Firstly,Ag@Pd nanocubes with core-shell structure were prepared by seed-mediated method,and the synthesized nanomaterials were characterized by TEM,XPS,and XRD,which showed that the prepared samples had cubic shape and the thickness of Pd shell layer was only 1.7 nm.Then the performance of Ag@Pd nanocubes photocatalytic activation of PS for the degradation of[C₄mim]Br and its degradation mechanism was explored.Electron paramagnetic resonance（EPR）and radical scavenging experiments showed that the main active species for the photocatalytic degradation of[C₄mim]Br was SO₄˙ˉradical.The wavelength dependence of the degradation effect of Ag@Pd samples further confirmed the plasmon-mediated properties of this photocatalytic AOPs.Finally,based on the detection of degradation intermediates by GC-MS,a plasmon-mediated photocatalytic degradation pathway for ionic liquids was proposed.Chapter 3.The study of plasmon-enhanced perovskite semiconductor photocatalytic AOPs for the degradation of methyl orange（MO）was carried out.Firstly,DMASn Br₃ perovskite was prepared by a low-temperature method,and the hydrostability of DMASn Br₃ before and after water immersion for 24 h was verified by XRD,XPS,UV-vis DRS,FTIR and PL characterization.Based on this,the composite photocatalyst Ag/DMASn Br₃ with DMASn Br₃ loading on Ag nanocubes was prepared by a simple mixing and stirring method.The results of subsequent photocatalytic degradation of MO showed that Ag/DMASn Br₃ exhibited good catalytic activity under the conditions of 420 nm visible light irradiation and the addition of H₂O₂,and the degradation rate of MO could reach 100%at 10 min.It was shown that the main active species of photocatalytic AOPs for MO degradation were·OH radical.Based on the above experimental results,the degradation mechanism of Ag nanocubes plasmon-enhanced DMASn Br₃ semiconductor photocatalytic AOPs for MO degradation was proposed.Under the visible light irradiation,the high-energy electrons generated by the surface plasmon resonance of Ag nanocubes in the composite photocatalyst were transferred to the semiconductor DMASn Br₃,and then the separated high-energy electrons could activate H₂O₂ to generate highly active·OH radicals,which ultimately degraded MO.Chapter 4.Based on the summary of the main research results of this paper,the development of plasmon-enhanced photocatalytic AOPs for the treatment of organic pollutants is prospected,and the problems faced by future research are also analyzed.