Study On Modification And Properties Of Semiconductor Photocatalysts

Semiconductor photocatalysis technology is of great significance in solving energy crisis and environmental pollution.However,conventional semiconductors,such as TiO₂,have been limited their applications due to band width and low visible light utilization rate（less than 5%）,and the faster coupling of photogenerated carriers.In recent years,developed bismuthum-based photocatalysts such as Bi PO₄ and Bi OBr have better catalytic activity than titanium dioxide but like titanium dioxide,low visible light utilization rate and faster photocarrier coupling still limit them applications.Therefore,it is very necessary to modify them to obtain a highly efficient catalyst,and metal loading and construction of a heterojunction structure are simple and effective methods for solving the above problems.In this paper,black TiO₂ reduced by conventional TiO₂ and new bismuthum-based photocatalysts such as Bi PO₄ and Bi OBr were used as the matrix,and the heterostructures were constructed by loading Ni metal nanoparticles or other semiconductor materials respectively,and their photocatalytic properties were studied,respectively.The main research contents of this paper are as follows:（1）Preparation of Ti³⁺self-doped IO-B-TiO₂/Ni composite and its photocatalytic reduction of CO₂Monodisperse polystyrene microspheres were prepared by emulsion polymerization,and then a polystyrene photonic crystal template was prepared by a vertical deposition method.Tetrabutyltitanate（TBOT）,nickel chloride（Ni Cl₂）precursor is immersed in the template gap,and then the template is removed by calcination in a muffle furnace,and a part of the metal Ni is reduced by hydrogenation of TiO₂ by a one-step reduction method.TiO₂ with a black anti-protein structure supported by Ti³⁺doping and metal Ni was prepared.The products were characterized by Fourier transform infrared spectroscopy,scanning electron microscopy and fluorescence spectroscopy.The photocatalytic reduction of CO₂ in commercial P25 and IO-B-TiO₂/Ni composites was compared under visible light irradiation.The results show that the CO formation rate of IO-B-TiO₂/Ni composites is12.13μ·mol·g^-1·h^-1,which is 10.1,5.1 and 2 times of P25,IO-W-TiO₂ and IO-B-TiO₂,respectively,and proposes a mechanism for photocatalytic reduction of CO₂.（2）Preparation of Bi PO₄/Bi₂MoO₆ heterojunction composite with oxygen vacancy and Z-scheme and its photocatalytic activity for degradation of methylene blueThe Bi PO₄/Bi₂MoO₆ heterojunction composites with different proportions were synthesized by a simple pot solvothermal method using ethylene glycol as solvent and high temperature and high pressure reactor as reaction conditions.The effects of different ratios on the morphology of the catalyst and the degradation properties of methylene blue were investigated.The products were characterized by scanning electron microscopy,X-ray diffraction（XRD）,UV and other test methods.Photocatalytic activities of Bi and Mo with different proportions were compared under visible light irradiation.The results show that BMo P-1-3 catalyst has the highest catalytic activity and its degradation.The rate is 0.02036min^-1,which is 1.65 and 1.22 times of Bi PO₄ and Bi₂MoO₆,respectively,and the mechanism of photocatalytic degradation of methylene blue by Bi PO₄/Bi₂MoO₆heterojunction is proposed.（3）In situ synthesis of 3D Pt/Cd S/hydrogenated Bi OBr microspheres and its photocatalytic activity for degradation of methylene blueThree-dimensional Bi OBr nanoflower microspheres were synthesized by one-pot simple solvothermal method using ethylene glycol and isopropanol as cosolvents.Then hydrogenated Bi OBr（h-Bi OBr）is that Bi₂O₃ and Bi OBr spherical heterojunction is formed after hydrogenation of Bi OBr at a high tempature.The Cd S/h-Bi OBr heterojunction was synthesized in situ by introducing cadmium chloride（Cd Cl₂）and sodium sulfide（Na₂S）precursors onto h-Bi OBr spheres with h-Bi OBr as carrier.Afterwards,chloroplatinic acid（H₂Pt CI₆）was introduced into Cd S/h-Bi OBr,and three-dimensional Pt/Cd S/h-Bi OBr microspheres were prepared by Na BH₄ reduction.The product was characterized by scanning electron microscopy,XRD,UV and other test methods.Under visible light irradiation,the photocatalytic rate constant of MB degradation was 0.02658 min^-1,which was 1.17,1.67 and 3.39 times of h-Bi OBr/Cd S,h-Bi OBr and Bi OBr,respectively.On this basis,the mechanism of photocatalytic degradation of methylene blue by three-dimensional Pt/Cd S/h-Bi OBr microspheres was studied.