Design,Preparation And Catalytic Performance Study Of Bismuth Vanadate And Its Composite Semiconductor Nano-catalyst

In recent years,with the booming of economy,the environmental pollutionand energy crisis caused by the rapid consumption of fossil energy have become increasingly prominent and posed a serious threat to human survival and health.It is the new requirement and task for us to select suitable catalytic materials and make full use of solar energy to solve environmental pollution and produce sustainable green energy.BiVO₄ is a narrow band gap semiconductor catalytic material with excellent catalytic performance under visible light.In this thesis,BiVO₄ catalyst is used as the main line to design and synthesize the composite materials,through the modification of crystal phase structure,noble metal doping and semiconductor compound,so as to improve the catalytic activity.Adopt a series of characterization methods to discuss its catalytic properties and reaction mechanism of catalytic materials.The research details are as follows:1.By regulating the pH of precursor,the different BiVO₄ powders were synthesized through hydrothermal method.The crystal phase structure,morphology and specific surface area were studied by means of XRD,SEM,TEM,BET and other characterization methods.The photo-catalytic performance was evaluated by photocatalytic oxygen evolution in the water under the visible light.In the end,it makes clear that the optimal photolysis photolytic water performance was obtained by the ms-BiVO₄ with the precursors pH value was eight.The rate of oxygen evolution was 173.19?mol·g^-1·h^-1.So we further make a calculation based on the density functional theory?DFT?to discuss the influence of the energy band structure and the electronic excitation of the BiVO₄ on the performance.2.The BiVO₄ of different morphology was synthesized by improved hydrothermal process and calcination two step synthesis methods.The catalytic activity was tested by 4-nitrophenol reduction experiment and its catalytic activity kinetics and universality were further studied.The XAg/BiVO₄ catalysts with different Ag content were prepared by photo-deposition method,and it showed higher activity and stability,that is because the load of Ag added more active site and accelerated the electron transfer rate.The 99.7%of 4-nitrophenol?20 mg/L?was reducted by 8Ag/BiVO₄ in 2 min and the reduction rate constant was 1.967 min^-1.Finally,the mechanism of catalytic reduction 4-NP was proposed and further proved by theory.3.Design synthesis Au/g-C₃N₄/BiVO₄ three-phase Z-scheme heterojunction to improve photo carrier separation and transfer rate and increase the capability of oxidation reduction through Au nanoparticles as electron transport intermediates to regulate interface charge transfer way.So the photo-catalytic hydrogen evolution performance was enhanced remarkably by SPR synergistic effect of noble Au.So,the4Au9C1B catalyst presented the greatest performance and the average rate of hydrogen production reached 390?mol·g^-1·h^-1 under visible light,which was far higher than that of pure phase CN,xCyB,xAu CN.Finally,the reaction mechanism was convincingly demonstrated by photocurrent test and active species capture experiment.