Synthesis And Photocatalytic Properties Of WO₃,W-Zn-O And W-La-O

Tungsten trioxide,a typical n type semiconductor,has excellent photocatalysis,gas sensing,photochromism,photoelectric conversion performance.Compared with other semiconductor photocatalyst,WO3 has a lower energy gap,and higher visible light absorption than that of TiO2 under the same condition,resulting in a good application prospect in the aspect of environmental pollution control.WO3 has various crystal,and researches proved that only monoclinic WO3 is stable during the photocatalysis.However,the preparation methods of monoclinic WO3 reported in the corresponding research are awaiting to be further improved.Studies show that doping can improve the photocatalytic efficiency of WO3,but the crystal of monoclinic WO3 will be changed after doping,so the corresponding synthetic method need to be improved.Based on the above scientific problems,monoclinic WO3 was successfully synthesized by the hydrothermal method using different additives such as polyvinylpyrrolidone(PVP),Polyethylene oxide-polypropylene oxide-polyethylene oxide three block copolymer polymer(P123),Cetyltrimethyl ammonium bromide(CTAB),etc.and its photocatlytic performance was carried out.Besides,solid state grinding was used to prepare Zn,La doping WO3,to enhence the photocatalytic performence of WO3.The contents of this research are as follows:1.Preparation and photocatalytic study of monoclinic WO3.Faint yellow precursor was prepared by the hydrothermal method using sodium tungstate as reactant,PVP as additive in the hydrochloric acid aqueous solution.The WO3 with monoclinic phase was successfully synthesized via the high temperature calcination of precursor,and the structrue of the resulted WO3 was characterized by XRD,SEM,FT-IR,UV-vis,and N2 absorption-desorption technologe.The effect of calcination temperature on the photocatalytic activity of WO3 with monoclinic phase was studied and the results show that the activity of photocatalysis of WO3 calcinated at 550? is best.Furthermore,effect of H2O2,pH,degradation time,dye concentration on the activity of photocatalyst was also investigated.The results of FT-IR from WO3 and the recycled WO3 show that the degradation of dye is due to photocatalysis,rather than absorption.2.Preparation and photocatalytic study of W-Zn-O.WO3 doped with different concentration of zinc were prepared by the hydrothermal method and grinding method to improve the photocatalytic efficiency of tthe resulted materials.The composition and structure of the synthesized products were characterized by XRD,Raman,SEM,UV-vis,XPS,etc.The photocatalytic degradation of rhodamine B and acid orange7 over zinc doped WO3 was investigated under the irradiation of ultraviolet light and the results show that doped WO3 has a good photocatalytic efficiency at pH=4:91.4%removal efficiency of rhodamine B(RhB)over Zn doped WO3 after irradiation of 30 min,while 76.3%over the undoped one;80.2%removal efficiency of Acid Orange 7(A07)over Zn doped WO3 after irradiation of 30 min,while 71.9%over the undoped one.3-Preparation and photocatalytic study of W-La-O.Lanthanum doped WO3 was successfully prepared by the hydrothermal method and grinding method.The composition and structure of the synthesized products were characterized by XRD,Raman,SEM,UV-vis,XPS,etc.The photocatalytic properties of La doped WO3 were investigated using RhB and A07 as molecular probes,and the results show that the photocatalytic performance of WO3 was better than that of undoped one at the initial solution pH= 4:94.5%removal efficiency of RhB over La doped WO3 after irradiation of 1.5 h,while 36.9%over the undoped one;84.3%removal efficiency of A07 over La doped WO3 after irradiation of 1.5 h,while 71.9%over the undoped one.