Sol-gel synthesis and photocatalytic performance of ZnO toward oxidation reaction of NO

ZnO oxide was prepared by different routes of synthesis such as precipitation, solvothermal, solvothermal assisted with polyethylene glycol and the sol-gel method. The physical properties of the oxides were studied by X-ray powder diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy and adsorption-desorption N-2 isotherms. The photocatalytic activity of ZnO samples was evaluated in the oxidation reaction of nitric oxide (NO). The conversion degree of NO reached by each sample used as photocatalyst was associated with their physical properties. By far the best performance was obtained with the sample prepared by sol-gel, in which a degree of conversion of about 70 % was reached. Beyond the elimination of NO, the selective formation of innocuous nitrate ions as the main product of reaction (> 80 %) was also confirmed. The effect of the relative humidity and the charge of photocatalyst in the conversion degree of NO was analyzed.