Study On Preparation Of New Photocatalyst TaON And Degradation Of Phenol By Visible-Light

TiO2 has been studied for many years because of its higher photocatalytic activity,higher stability,nontoxicity and low-cost.However, TiO2 may show photocatalytic activity only by irradiation of ultra violet(UV)light for its wide band gap(Eg=3.2eV). It is vital for study on photocatalyst with the highest photocatalytic activity by visible-light in order to apply sun-light effectively.Considering the problem that the band gap energy of traditional photocatalysts, such as TiO2,is so big that they can only show their catalytic activity in ultra violet (UV) light, a new kind of photocatalyst TaON with small band gap energy has been prepared, which is based on the theory of the catalysis of semi-conductor photocatalysts. TaON has been synthesized with Ta2O5 as the raw material and being nitrified by gas-solid reaction under high temperature.In addition, XRD, XPS, and UV-VIS analysis are made for prepared photocatalysts. The effects of the reaction temperature, time, and the flux of ammonia gas on the structure and composition of prepared catalysts are investigated. The result of the analysis shows that the XRD pattern of the prepared sample, which is prepared when the reaction temperature is 850℃, the reaction time is 10 hours and the flux of ammonia gas is 100 ml/min, is the same as that of TaON. The result of XPS analysis of the samples that has been made in different reaction condition indicates that the combined energy peaks of Ta4f 7/2 of Ta2O5 shifts to the lower combined energy. In addition, the combined energy peaks of N1s has been found in the XPS spectra, indicating Ta-N bond with lower energy is formed. Non-stoichiometric sample,TaO1.2N0.8 , is formed under the above reaction condition. Thus the most optimal technical parameter of synthesizing the catalyst has been determined as follows: reaction temprature 850℃, reaction time 10 h, the flow rate of ammonia gas 100ml/min. In order to investigate the responding area to the light, UV-VIS analysis has been made for the sample which has been synthesized under the most optimal reaction condition. The result indicates that the responding area to the light has been widened to 500 nm, proving that the prepared TaON shows the responding ability to the visible-light.Furthermore, the photocatalytic activities of TaON for degradation of phenol under irradiation of sunlight imitation are also investigated in the paper. The rate of phenol degradation are studied by analyzing the concentration of phenol with 721 spectral photometers. The result shows that TaON can decompose phenol under irradiation of visible light. The degradation rate is 81% during 120 minutes reaction with adding 0.4g photocatalyst in 400 mL solution . When the loading amount of Pt is 1.5 wt%, the degradation rate is 92%. Finally, the investigation on dynamics of photocatalytic degradation for phenol by TaON shows that it is in agreement with one order dynamics model.