Abstract
Abstract. The interaction of NO2 with TiO2 solid films was studied under UV irradiation using a low pressure flow reactor (1–10 Torr) combined with a modulated molecular beam mass spectrometer for monitoring of the gaseous species involved. The NO2 to TiO2 reactive uptake coefficient was measured from the kinetics of NO2 loss on TiO2 coated Pyrex rods as a function of NO2 concentration, irradiance intensity (JNO2 = 0.002–0.012 s−1), relative humidity (RH = 0.06–69 %), temperature (T = 275–320 K) and partial pressure of oxygen (0.001–3 Torr). TiO2 surface deactivation upon exposure to NO2 was observed. The initial uptake coefficient of NO2 on illuminated TiO2 surface (with 90 ppb of NO2 and JNO2≅0.006 s−1) was found to be γ0 = (1.2±0.4) ×10−4 (calculated using BET surface area) under dry conditions at T = 300 K. The steady state uptake, γ, was several tens of times lower than the initial one, independent of relative humidity, and was found to decrease in the presence of molecular oxygen. In addition, it was shown that γ is not linearly dependent on the photon flux and seems to level off under atmospheric conditions. Finally, the following expression for γ was derived, γ = 2.3×10−3 exp(−1910/T)/(1 + P0.36) (where P is O2 pressure in Torr), and recommended for atmospheric applications (for any RH, near 90 ppb of NO2 and JNO2 = 0.006 s−1).
Highlights
Titanium dioxide (TiO2) is a very efficient photocatalyst leading to the degradation of organic species under UV irradiation (e.g. Henderson, 2011)
TiO2 is known to transform nitrogen oxides (NO/NO2), via catalytic heterogeneous reactions, to HNO3, which remains on the TiO2 surface (Ibusuki and Takeuchi, 1994; Dalton et al, 2002; Devahasdin et al, 2003; Negishi et al, 1998; Ohko et al, 2008)
This paper reports results of measurements of the uptake coefficient of NO2 to the TiO2 surface as a function of different parameters such as NO2 concentration, irradiance intensity, relative humidity, temperature and partial pressure of oxygen
Summary
Titanium dioxide (TiO2) is a very efficient photocatalyst leading to the degradation of organic species under UV irradiation (e.g. Henderson, 2011). TiO2 is known to transform nitrogen oxides (NO/NO2), via catalytic heterogeneous reactions, to HNO3, which remains on the TiO2 surface (Ibusuki and Takeuchi, 1994; Dalton et al, 2002; Devahasdin et al, 2003; Negishi et al, 1998; Ohko et al, 2008). Due to these photocatalytic properties TiO2 is widely used in a variety of so-called de-polluting building materials aimed to remove the nitrogen oxides from the atmosphere. The question seems to remain open, pending further studies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
