Promotion Of Photocatalytic Activitiy Of Titania And It Gaseous Pollutants Degradation Ability

Titania is the most effective photocatalyst and can be applied in decomposition of some pollute substances, such as nitrogen monoxide or acetaldehyde in atmosphere under light irradiation. However, titania can only be encouraged by UV light because of its large band gap. Most methods of nitrogen doping are high temperature processes, using expensive precursors or preparation instruments. In this research, a microwave-assisted hydrothermal method was employed to synthesize nitrogen doped titania nanoparticles. The efforts of time and temperature of treatment and pH value of starting solutions were investigated in detail. Due to the high heating efficiency of microwave, rapid synthesis could be achieved in comparison with the conventional oven. TiO2-xNy with monoclinic phase was found existing in the obtained product, and the phase transformation behaviour under calcination was studied by XRD measurement together with Raman spectroscopy in details. The obtained nitrogen doped titania showed high specific surface area, about 300m2 g-1. Photocatalytic activity in destructing NOx gas by the prepared sample exceeded that of commercial titania (P-25) or nitrogen doped titania synthesized by conventional hydrothermal method, under both visible-light and ultraviolet-light irradiation.Titania/nitrogen-doped titania composite was prepared by mechanical milling in liquid medium and the phase compostition, specific surface area, photo chemical properties and photocatalytic activities were characterized. TiO2/TiO2-xNy composites showed excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide and acetaldehyde. It is suggested that the doped nitrogen in TiO2-xNy acts as the acceptor of photoinduced holes on TiO2 to depress the recombination of the electron-hole and improve the photocatalytic activity.The photocatalytic deNOx activities and acetaldehyde destruction ability of Ag-doped titania, Pt-doped titania and Fe-doped titania were characterized. The prepared samples showed improved photocatalytic activity in the deNOx, and decreased activity in the acetaldehyde destruction due to the decrease of BET sepcif surface area. The photocatalytic deNOx activities of titania, nitrogen-doped titania, Fe-loaded nitrogen-doped titania, and Pt-loaded nitrogen-doped titania under irradiation from monochrome LED lamps using various light wavelengths were investigated in detail. The improvement of visible light induced photocatalytic activity was successfully realized using Fe and Pt loading. Both Fe-loaded nitrogen-doped titania and Pt-loaded nitrogen-doped titania showed excellent visible light response ability. The photocatalytic activity exhibited by Pt-loaded nitrogendoped titania was several times higher than that of nitrogen-doped titania under the visible light irradiation ofλ=627 and 530 nm. The relationship between photocatalytic activity and irradiation light wavelength was investigated in detail. The relationship between the intensity of low-level chemiluminescence generated by singlet oxygen (1O2) and photocatalytic activity was also discussed.