Chemistry of NOx on TiO2 Surfaces Studied by Ambient Pressure XPS: Products, Effect of UV Irradiation, Water, and Coadsorbed K+

O. ROSSELER; M. SLEIMAN; V.N. MONTESINOS; A. SHAVORSKIY; V. KELLER; N. KELLER; M.I. LITTER; H. BLUHM; M. SALMERON; H. DESTAILLATS

The Journal of Physical Chemistry Letters

American Chemical Society

Lugar: Washington DC; Año: 2013 vol. 4 p. 536 - 541

1948-7185

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.