Design, Preparation And Photocatalytic Performances Of Pt/Bi₅Nb₃O₁₅

Photocatalytic oxidation technology is an effective way of controlling environmentalpollution, TiO₂photocatalyst can be excited only under ultraviolet light, low efficient use ofsunlight. In this thesis, we focus on development and design of new and efficientnon-TiO₂-based visible-response photocatalyst by hydrothermal method. Bi₅Nb₃O₁₅and Ptdoping Pt/Bi₅Nb₃O₁₅are synthesized and characterized. The photocatalytic performance isalso systematically researched.1. Metastable structure Bi₅Nb₃O₁₅was prepared in the presence of cetyl trimethylammonium bromide （CTAB） or polyvinylpyrrolidone （PVP） by hydrothermal treatment,which is difficult to obtain by the traditional high temperature solid state method. X raypowder diffraction, UV Vis diffuse reflectance spectra, X ray photoelectron spectroscopy,scanning electron microscopy and nitrogen adsorption-desorption isotherms were used tocharacterize the crystal structure, morphology, optical absorption property and Surfacephysical and chemical properties of products. The crystal structure of Bi₅Nb₃O₁₅influencedby hydrothermal temperature and time, pH value of initial materials were studied, themorphology of the products influenced by type and quantity of the surfactants alsoinvestigated. The results indicate that we obtained perfect crystal structure of Bi₅Nb₃O₁₅atpH=10.7and hydrothermal treatment at200oC for24h, in the presence of CTAB weobtained sheet-like Bi₅Nb₃O₁₅, in the presence of PVP we got octahedral-like Bi₅Nb₃O₁₅.Thesimulated sunlight photocatalytic activity of the products was evaluated by degradation ofaqueous methyl orange and4-nitrophenol. The results show that81%of dyes methyl orangewas decomposed after2h simulated sunlight irradiation. In addition, the p-nitrophenol, whichhas no absorption in the visible region, is selected as target pollutant, to further prove thevisible light photocatalytic activity of Bi₅Nb₃O₁₅, after4h irradiation the degradation ratereach70%.2. Pt-doped Pt/Bi₅Nb₃O₁₅was successfully prepared by photo-deposition method. Thequality of Pt was characterized by inductively coupled plasma atomic emission spectroscopy;X-ray powder diffraction, UV-Vis diffuse reflectance spectra, X-ray photoelectronspectroscopy and nitrogen adsorption-desorption isotherms were used to characterize thecrystal structure, morphology,optical absorption property and Surface physical and chemicalproperties of products. The visible-light photocatalytic activity is examined by thedegradation of methyl orange and4-nitrophenol at different range of wavelengths, the resultsare compared with pure Bi₅Nb₃O₁₅. The experimental results show that Pt/Bi₅Nb₃O₁₅-0.5%exhibits higher photocatalytic activity under simulated sunlight irradiation （320nm <<680 nm） and visible light （400nm <<680nm）. Compared with other methods of noble metaldoping, the Pt atoms can be uniformly deposited on the catalyst surface, the noble metal Ptcan captures electrons, inhibition of photoinduced electron-hole recombination, enhance thequantum efficiency. The noble mental Pt has surface plasmon resonance （SPR）, which canimprove the visible-light photocatalytic activity. Therefore, Pt/Bi₅Nb₃O₁₅shows excellentvisible-light photocatalytic activity.