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

• Published in: The journal of physical chemistry letters 2013-02, Vol.4 (3), p.536-541
• Main Authors: Rosseler, Olivier, Sleiman, Mohamad, Montesinos, V Nahuel, Shavorskiy, Andrey, Keller, Valerie, Keller, Nicolas, Litter, Marta I, Bluhm, Hendrik, Salmeron, Miquel, Destaillats, Hugo
• Format: Article
• Language: English
• ISSN: 1948-7185
• DOI: 10.1021/jz302119g

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.