Study On The UV/VIS Light Photocatalytic Activity Of TiO₂Powder Prepared By Plasma

Nano-TiO2is a kind of high-performance semiconductor photocatalytic material. It has the advantages of stable photochemical property, high photocatalytic efficiency, good oxidation, non-toxic and harmlessness, lower price, no secondary pollution and so on. But the energy gap of nano-TiO2is broad, which results in only3%solar energy utilization. So preparing TiO2photocatalyst with high photocatalytic activity and which can make full use of sunlight will become a breakthrough for the photocatalytic oxidation technology in practical application.The paper studied the ultraviolet and visible light photocatalytic activity of nano-TiO2photocatalyst prepared by non-thermal plasma. The results are as follows.Fristly, the TiO2nanostructures were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The result indicates that as-prepared TiO2consists of anatase and rutile phases. And we know that it contains67.3%anatase phase by calculating. From the XPS analysis, the sample composition is Ti, O, C, and no N is detected. So maybe the visible light photocatalytic activity of TiO2photocatalyst is related to C.Then, we did evaluation of liquid, solid and gas phase photocatalysis for the as-prepared TiO2powder. Based on methylene blue as the liquid degradation agent, the visible light photocatalytic activity of nano-TiO2prepared in different conditions were evaluated in the photochemistry reaction instrument. The result shows that when the discharge power is100W and the radio of O2/TTIP is27, it has the highest activity.In a continuous flowing photocatalytic reactor, we did evaluation of solid and gas phase photocatalysis for TiO2which was prepared under the specified experiment condition. We chosed stearic acid as the solid degradation agent, the paper investigated factors such as the ultraviolet light intensity, gas flow and humidity on stearic acid photocatalytic oxidation rate. The result indicates, in arrange of light intensity in the experiment, the conversation of stearic acid to CO2is increasing as the light intensity strengthens. And when the light intensity is strong enough, the conversation tends to be stable. At the same time, the conversation of stearic acid to CO2decreases slowly when reactant gas flow increases. In arrange of humidity in the experiment, the conversation rises as the water content increases. In addition, the as-prepared TiO2photocatalyst shows more visible light photocatalytic activity than DegussaP25.When using formaldehyde as the gas degradation agent, the light intensity and the initial concentration of formaldehyde were tested as the influent factors for the flowing formaldehyde photocatalysis. The result indicates that when the intensity of UV light with254nm ranges from0.18to1.88mW·cm-2, the conversation of formaldehyde to CO2increases rapidly first, then slowly as the intensity increases, and is finally almost unchanged when the intensity reaches1.32mW·cm-2. If changing the initial concentration of formaldehyde from35to61ppm, the conversation is almost unchanged as the initial concentration of formaldehyde varies. What’s more, the formaldehyde adsorption photocatalytic experiment indicates that nano-TiO2powder prepared by plasma shows visible light photocatalytic activity.