Influence of inlet concentration and light intensity on the photocatalytic oxidation of nitrogen(II) oxide at the surface of Aeroxide® TiO2 P25

Light intensity dependence of the kinetics of the photocatalytic oxidation of nitrogen(ii) oxide at the surface of TiO2

“…This behaviour can be explained by the displacement of air initially present inside the pipes and the photoreactor and by the dark adsorption of NO followed by the saturation of the surface of the photocatalyst sample and the exposed surface area of the photoreactor and the pipes with adsorbed NO. 64 After the NO concentration was found to be stable for at least five minutes, a shutter between the UV(A) light source and the photoreactor was removed to start the photocatalytic reaction (time t 0,hn ). An immediate decrease of the NO concentration was observed.…”

“…The respective photocatalytic oxidation pathway of NO, where water and all nitrogen compounds present at the photocatalyst surface are in equilibrium with the gas phase, is outlined in Table 2. [62][63][64] Profound objections have been raised against this pathway by Ohko and co-workers, 24,25,74 who claimed the contribution of a terminal (bridging) oxygen species, TiO 2 (O s ), and oxygen vacancies, TiO 2 (&), at the TiO 2 surface to the photocatalytic NO oxidation. The NO reaction pathway suggested by this group is presented in Table 3.…”

“…[53][54][55][56]60,62,64 Very recently some papers were published discussing the influence of the light intensity and the humidity on the kinetic parameters in eqn (2). Hunger et al 60 have employed this rate law (eqn (2)) to analyze the kinetics of the photocatalytic NO oxidation over TiO 2 -containing concrete.…”

“…Very recently, Dillert et al 64 have investigated the photocatalytic oxidation of NO over pure titania samples (EvonikDegussa Aeroxide s TiO 2 P25) varying the inlet concentration of NO and the light intensity E at constant temperature T and humidity h a . The results were analyzed in terms of LangmuirHinshelwood kinetics, and it was observed that k NO E E +(0.86AE0.14) and K NO E E À(0.94AE0.…”

“…Based on the assumption that the coverage of the photocatalyst surface by the oxidizing species is directly proportional to the flux of the incoming UV(A) photons they derived a Langmuir-Hinshelwood-type rate law with the light-dependent kinetic parameters k NO = r k NO E and K NO = a k NO 0 /( d k NO + r k NO E). 64 Nowadays, numerical methods combining mass transport and surface kinetics are used to predict the performance of photocatalytically active construction materials under environmental conditions. 35,[65][66][67][68][69][70] However, for the precise prediction of the rate of the photocatalytic reaction under consideration a reliable rate law including all relevant environmental variables, i.e., photon flux, humidity, temperature, and pollutant concentrations, is essential but still a desideratum.…”