Study On Phase Composition And Photocatalytic Activity Of Ni, Co And Ag Doped Nano - TiO 2 By Sol - Gel Method

Nano-scaled TiO2 materials are expected to play an improtant role in photocatalyst, dye sensitized solar energy, sensor, ceramic and so on due to its good characteristics of small size, large specific surface area, strong ability to absorb ultraviolet light and high surface activity. But the nanometer TiO2 can only absorb the ultraviolet ray which is less than 387nm, so it can only absorb about 5% of the sun’s light, which greatly affects its application. The doping can broaden the range of light response and improve its photocatalytic activity. Anatase has better photocatalytic performance than rutile, so it is mainly used in environmental protection and light cell material and so on. Rutile is mainly used in cosmetics, ceramics and other fields. Therefore, it is very important to study the phase transformation process of TiO2, and analyze the different crystal form and distribution of TiO2. The phase transition mechanism and control conditions of TiO2 have a certain guiding significance to the performance of TiO2.Ni2+-doped titania, Co2+-doped titania and Ag+-doped titania were synthesized by sol-gel method. The influence of dopant on the phase compositions, average grain size, microstructures, chemical states, atomic bonding and the visible light absorbable range of titania were investigated, which were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), X ray photoelectron spectroscopy analysis (XPS), Fourier Transform Infrared Spectoscopy(FT-IR), Raman spectrometer(Raman) and UV-Vis spectrophotometer (UV-Vis). And experimental test of photocatalytic degradation of methyl orange using. The main draw the following conclusion:(1)TiO2 powders prepared by Ni2+ doping, The anatase to rutile phase transition temperature between 650℃ to 750℃, and it inhibited the phase transition of TiO2. And with the increase of the calcination temperature, the grain size is increased. And the second phase of NiTiO3 was precipitated at 750℃. In the crystal structure of TiO2, Ti exists in the form of Ti4+, and the doping of Ni ions in the crystal structure is in the form of Ni2+. With the increase of the calcination temperature, the anatase to rutile phase transition and began to produce Ti-O-Ni and Ni-O, and the content of Ti-O-Ni and Ni-O bonds increased with the increase of calcination temperature. With the increase of the calcination temperature, the absorption band edge of the optical absorption band is blue shifted, and the band gap increases.(2)TiO2 powders prepared by Co2+ doping, the phase transition temperature is higher than that of Ni2+ doping and the doping of Co2+ is more inhibited by the phase transition of TiO2. With the increase of the calcination temperature, the grain size is increased and the second phase of CoTiO3 was precipitated at 750℃. The content of oxygen in the crystal structure is higher than that of adsorbed oxygen, and increases with the increase of temperature. In the crystal structure of TiO2, Ti exists in the form of Ti4+, and the doping of Co ions in the crystal structure is in the form of Co2+. The Ti-O-Co and Co-O bonds are produced in 750℃, and the content of Ti-O-Co and Co-O bonds increased with the increase of calcination temperature. With the increase of the calcination temperature, the absorption band edge of the optical absorption band is blue shifted, and the band gap increases.(3)TiO2 powders prepared by Ag+ doping, the phase transition temperature is higher than that of Ni2+ doping and Co2+ doping. The doping of Co2+ is more inhibited than Ni2+ doping and Co2+ doping by the phase transition of TiO2. With the increase of the calcination temperature, the grain size is increased. In the crystal structure, Ti exists in the form of Ti4+, Ag doping is existed in the form of elemental Ag0. With the increase of the calcination temperature, the absorption band edge of the optical absorption band is blue shifted, and the band gap increases. The degradation rate of methyl orange doped Ag+ fastest, in the light of 60 minutes, the concentration of methyl orange 1.07mol/L.