INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Chemical mechanisms of photocatalytic de-soiling and de-polluting processes in indoor environments and urban surfaces.
MOHAMAD SLEIMAN; OLIVIER ROSSELER; NAHUEL MONTESINOS; MARTA I. LITTER; DAMIÁN BIKIEL; THOMAS KIRSCHTETTER; HENDRIK BLUHM; MUSAHID AHMED; MIQUEL SALMERON; HUGO DESTAILLATS
Conferencia; American Gephysical Union Fall Meeting; 2013
Photocatalysis has been postulated as a promising approach for the de-pollution of indoor air and urban atmospheres, and for self-cleaning surfaces. Building materials and coatings containing nano-sized TiO2 photocatalytic functionalities are gaining market share, including self-cleaning building envelope materials (coatings, mortar, plaster, architectural fabrics and tiles) and indoor air purifiers. We present results from two studies that used synchrotron-based surface spectroscopic and mass spectrometric methods to better understand the photocatalytic mechanisms that regulate the de-soiling and de-polluting activity. Two photocatalytic processes were studied: de-noxification (NOx removal) and de-soiling (removal of deposited black carbon or soot). 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. The results illustrate how NOx chemistry on TiO2 surfaces can be affected by the presence of water vapor, heteroatoms present as impurities, and carbonaceous soiling. The reactivity of NOx and NO3? on surfaces leads to reduced adsorbed and gas-phase nitrogenated species. These processes need to be considered in the engineering of depolluting materials and incorporated into atmospheric models. De-soiling properties were investigated by analyzing soot oxidation on TiO2 surfaces. Model soot samples were used as surrogates of urban grime. Using laser desorption coupled with time-of-flight (TOF) mass spectrometry synchrotron ionization, we investigated the mechanisms of photocatalytic soot removal under UVA irradiation. Ancillary reflectance measurements were performed to determine the efficiency and kinetics of soot removal.