Studies On The Surface Photoelectric And Photocatalytic Properties Of Ag_xM_yO_z (M=Sb, Nb) And Related Composites

Multiphase semiconductor photocatalysis, the problems of the pollution and preparation of hydrogen have been paid wide attention since Fuji and Shima reported"Honda-Fujishima Effect". Traditional photocatalysis, TiO₂ with non-toxic, stable performance and low-cost price has been widely applied. But, titanium dioxide is not able to absorb visible light due to its wide band gap, in order to make full use of solar energy, developing photoctalysis in visible region has been one of numerous research focuses in photocatalytic field.Silver oxide semiconductor is a type of photocatalysis material with responding to visible light. Silver antimonite with band gap of 2.6 eV and silver niobate with band gap of 2.8 eV not only absorb visible light but only possess photocatalytic property. In this work, samples were prepared by controlling composition, prepared methods and formation of composite materials. Surface photovoltaic and photocatalytic properties of samples were researched. The specific research work is as follows:1) Silver antimonite with different molar ratio of Ag/Sb were prepared by an ion change method. Firstly, Ag_xH_ySb₂O₆·nH₂O were prepared by the ion exchange of AgNO₃ and H₂Sb₂O₆·nH₂O, and were calcined at 700 oC for 1 hour, in result that the samples of Ag_xSb₂O_y (x=0.5,y=4.83;x=1.0,y=5.18;x=1.5,y=5.52;x=1.7,y=5.77) were obtained. Their phases, surface morphology and surface photovoltaic property were characterized by X-ray diffraction, UV-visible spectrophotometer, Raman scattering, scanning electron microscopy and surface photovoltage spectroscopy, respectively. The photocatalytic property was estimated by degradation of Rhodamine B. The results show that the optical band gap decreases, the surface photovoltage decreases and the photocatalytic activity for Rhodamine B decomposition increases with increasing the Ag/Sb ratio in silver antimonites. The surface photovoltaic and photocatalytic properties were impacted by the percent of Sb³⁺ in the samples. The photocatalytic activity variation with the amount of Sb3+ implies that appropriate amount of Sb³⁺ in the sample was favorable for photocatalytic activity.2) Silver niobate was prepared by a solvothermal method at different temperatures (170-240 oC). Firstly, approppriate amount of EG, silver nitrate and columbium pentachloride are put into 100 mL reactor,then react for 24 hours at different temperatures. Last, the precursor is calcained for 2 hours at 800 oC, in result samples of AN170, AN180, AN190, AN200 and AN240 are obtained. Their phases, surface morphology and surface photovoltaic property were characterized by X-ray diffraction, UV-visible spectrophotometer, Raman scattering, scanning electron microscopy and surface photovoltage spectroscopy. The photocatalytic property was estimated by degradation of Rhodamine B. The results show that different morphologies may be due to different morphologies of Ag particles and that AN190 with the weakest photovoltage and the highest photocatalytic activity may be due to synergetic effect between silver niobate and Nb2O5. Both the temperature and the amount of Nb₂O₅ are crucial for the morphologies, the photoelectric and photocatalytic properties of the samples.3) The compound with different molar ratio of silver niobium and sodium antimony were prepared by solid state reaction method. Firstly, appropriate amount Ag₂O,Sb₂O₃, Na₂CO₃ and Nb₂O₅ were well mixed respectively, then are calcained at 750 oC for 4 hours and 900 oC for 8 hours in turn. The samples of xAgSbO3/NaNO3 (x=0.5, 1.0, 2.0, 4.0, 6.0)are obtained. Their phases, surface morphology and surface photovoltaic property were characterized by X-ray diffraction, UV-visible spectrophotometer, Raman scattering, scanning electron microscopy and surface photovoltage spectroscopy. The photocatalytic property is estimated by degradation of Rhodamine B. The results show that the surface photovoltage and photocatalytic activities were sensitive to the molar percentage of sodium antimony in the samples; the highest photocatalytic activity was observed on the composite of silver niobium and sodium antimony due to the better dispersiveness, electron transfer and surface photoelectric properties, these results indicate that making the composite is an effective method to modify the photophysical and photochemical properties of photocatalyst.