Chemistry of NOx on TiO2 Surfaces Studied by Ambient Pressure XPS: Products, Effect of UV Irradiation, Water, and Coadsorbed K(.).
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.
†Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Material Sciences Division, Chemical Sciences Division and Advanced Light Source, Berkeley, California, United States.|‡Université de Strasbourg, Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), CNRS, Strasbourg, France.
Olivier
O
Rosseler
†Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Material Sciences Division, Chemical Sciences Division and Advanced Light Source, Berkeley, California, United States.
Mohamad
M
Sleiman
§Comisión Nacional de Energía Atómica, Gerencia Química, San Martín, Pcia. de Buenos Aires, Argentina.|∥Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.|⊥INQUIMAE, DQIAQyF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
V Nahuel
VN
Montesinos
†Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Material Sciences Division, Chemical Sciences Division and Advanced Light Source, Berkeley, California, United States.
Andrey
A
Shavorskiy
‡Université de Strasbourg, Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), CNRS, Strasbourg, France.
Valerie
V
Keller
‡Université de Strasbourg, Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), CNRS, Strasbourg, France.
Nicolas
N
Keller
§Comisión Nacional de Energía Atómica, Gerencia Química, San Martín, Pcia. de Buenos Aires, Argentina.|∥Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina.
Marta I
MI
Litter
†Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Material Sciences Division, Chemical Sciences Division and Advanced Light Source, Berkeley, California, United States.
Hendrik
H
Bluhm
†Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Material Sciences Division, Chemical Sciences Division and Advanced Light Source, Berkeley, California, United States.|#Materials Science Division, Lawrence Berkeley National Laboratory and Materials Science and Engineering Department, University of California, Berkeley, California, United States.
Miquel
M
Salmeron
†Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Material Sciences Division, Chemical Sciences Division and Advanced Light Source, Berkeley, California, United States.
Hugo
H
Destaillats
APXPS; DeNOx; HONO; NOx; TiO2; depollution; renoxification