ABSTRACT
Self-cleaning surfaces containing TiO2 nanoparticles have been postulated to efficiently remove NOx from the atmosphere. However, UV irradiation of NOx adsorbed on TiO2 also was shown to form harmful gas-phase byproducts such as HONO and N2O that may limit their depolluting potential. Ambient pressure XPS was used to study surface and gas-phase species formed during adsorption of NO2 on TiO2 and subsequent UV irradiation at λ = 365 nm. It is shown here that NO3(-), adsorbed on TiO2 as a byproduct of NO2 disproportionation, was quantitatively converted to surface NO2 and other reduced nitrogenated species under UV irradiation in the absence of moisture. When water vapor was present, a faster NO3(-) conversion occurred, leading to a net loss of surface-bound nitrogenated species. Strongly adsorbed NO3(-) in the vicinity of coadsorbed K(+) cations was stable under UV light, leading to an efficient capture of nitrogenated compounds.
ABSTRACT
Here we put forward for the first time that the negative effect of humidity on CO photooxidation at room temperature can be overcome by adjusting the composition of Pd-Pt bimetallic particles supported on TiO(2). Consequently, optimized Pd(x)Pt(1-x)/TiO(2) materials can be considered as common and efficient photocatalysts for simultaneous elimination of CO and VOCs in the presence of humidity, i.e. for real indoor air treatment.