Study On Optimization Of Nanometer ZnWO₄ Photocatalytic Performance And Mechanism

ZnWO₄ is a wolframite metal oxide with d¹⁰s²-d⁰ electronic configuration,which has its wide range of applications in the field of semiconductor photocatalysis.In this thesis,ZnWO₄ nanorods were prepared by hydrothermal method,and the samples were systematically modified to optimize their photocatalytic performance,including compounding with Ag₂MoO₄ nanoparticles to form Z-scheme heterojunctions and with CdS/ZnS quantum dots to design double Z-type heterojunctions.The samples were characterized by XRD,SEM,TEM,FT-IR,UV-Vis DRS,XPS,EPR,LC-MS,photoelectrochemical tests,RSM and DFT calculations.The photocatalytic properties of the samples were analyzed by photocatalytic degradation of methylene blue（MB）and possible photocatalytic mechanisms were p roposed.The details of the study are as follows:（1）The Ag₂MoO₄ nanoparticles were modified on ZnWO₄ nanorods by hydrothermal method to form Ag₂MoO₄/ZnWO₄（AMO/ZWO）composite photocatalyst.Various characterization methods and density flooding theory（DFT）were used to investigate the performance of AMO/ZWO heterojunctions and the potential photocatalytic mechanism.The photocatalytic experiments showed t hat 8%AMO/ZWO heterojunction can degrade MB up to 99.8%within 60 mi n with a first-order kinetic reaction rate constant of 0.10199 min^-1.Compared with ZWO and AMO monomer,the catalytic efficiency of 8%AMO/ZWO heterojunction is enhanced by 6.8 and 4.9 times,respectively.Combining the experiments and DFT calculations,a possible photocatalytic mechanism of AMO/ZWO heterojunctions was proposed.In addition,the photodegradation of various organic pollutants by the optimal ratio of sample 8%AMO/ZWO was further compared.（2）Zero-dimensional（0D）CdS and ZnS quantum dots were modified on one-dimensional（1D）ZWO nanorods by co-precipitation method to construct0D/1D/0D dual Z-scheme CdS/ZWO/ZnS heterojunction photocatalysts.The catalytic activity of the photocatalysts was compared using methylene blue（MB）as the target pollutant and simulated sunlight as the irradiation source.The results showed that the double Z-scheme heterojunction photocatalyst with composition 40%ZnS/（40%CdS-ZWO）exhibited extremely high photodegradation activity withη（50 min）=99.9%and k_app=0.14867 min^-1 compared to other monomers and binary heterojunctions.In addition,the degradation process of MB was systematically investigated with 40%ZnS/（40%CdS-ZWO）as the photocatalyst and the toxicity of the intermediates was predicted.