Photocatalytic Activity for Degradation of Nitrogen Oxides over Visible Light Responsive Titania-Based Photocatalysts

Abstract

This study investigates photocatalytic degradation of nitrogen oxides overtitania-based photocatalysts illuminated by ultraviolet and visible light. The TiO2 photocatalyst was synthesized in a sol-gel process using titanium butoxide as the precursor. After calcination between 150 and 300 degrees C, the synthesized TiO2 responded strongly to visible light photocatalytically degrading NO(x), probably because of the existence of carbonaceous species that act as sensitizers. The optimum calcination temperature was found to be around 200 degrees C. Additionally, platinum ion-doped TiO2 was prepared by impregnation using Pt(NH3)4(NO3)2 as a dopant, which improved the photocatalytic activity that degraded NO(x) in the visible light region. The Pt ion was doped in oxide form at the surface of TiO2 and was expected to be responsible for sensitization. At an optimum calcination temperature of around 200 degrees C, the Pt ion-doped TiO2 exhibited higher activity in the further oxidation of NO2 to NO3- clearly reducing NO2 selectivity. The TiO2 catalysts chemically prepared by either the sol-gel process or impregnation exhibited stronger activity than conventional TiO2 when illuminated under a fluorescent lamp. Rinsing with water was responsible for the restored reactivity of prepared TiO2 catalysts for NO(x) degradation.

Interaction of NO<sub>2</sub> with TiO<sub>2</sub> surface under UV irradiation: measurements of the uptake coefficient

“…In previous studies, HONO (Gustafsson et al, 2006;Ndour et al, 2008;Monge et al, 2010;Beaumont et al, 2009) and NO (Ohko et al, 2008;Monge et al, 2010) in the gas phase as well as nitric acid/nitrate anion on the surface (e.g. Dalton et al, 2002;Devahasdin et al, 2003;Lin et al, 2006;Ndour et al, 2008;Negishi et al, 1998;Ohko et al, 2008) were observed as the NO 2 + TiO 2 reaction products. In the present study we have observed HONO, NO and, in addition, N 2 O to be released into the gas phase as a result of the heterogeneous reaction of NO 2 with TiO 2 surface.…”

“…In several previous studies (e.g. Lin et al, 2006;Ohko et al, 2008) it was observed that the photocatalytic activity of the TiO 2 film can be fully regenerated after rinsing with water. In the present work, we have observed similar behaviour: the deactivated TiO 2 sample was regenerated after being immersed in water.…”

Full scale demonstration of air-purifying pavement

“…This process involves a solid semiconductor catalyst, most often anatase titanium dioxide (TiO 2 ), which is activated with ultraviolet light of the appropriate wavelength. To date, a number of researchers have investigated the dynamics of the photocatalysis of nitrogen oxides [2][3][4][5][6][7][8]. Photocatalytic oxidation of NO x offers the following distinctive advantages: (1) no extra reactants are required and (2) NO x is converted to nitrates, a significantly less harmful material.…”

Thermal evolution of structure and photocatalytic activity in polymer microsphere templated TiO2 microbowls

“…The photocatalytic NO(g) oxidation with O 2 (g) was used as a model reaction [27][28][29][30][31][32]. Fig.…”