Au-TiO2/SiO2 photocatalysts with NOx depolluting activity: Influence of gold particle size and loading

Abstract

The air pollution is becoming one of most important health problems around the world. Thus, the development of depolluting building materials is a crucial challenge. TiO2 is a photocatalyst with demonstrated performance for degradation of NOx and other typical pollutants. However, its limited absorption of solar light reduces its performance. In this study, Au-TiO2NPs are integrated into a silica matrix in order to produce long-lasting coatings with de-pollutant performance and applicability in building. The interaction between Au and TiO2 improves the photoactivity of TiO2 and it promotes a considerably increase in visible light absorption. A significant role of the AuNPs size and their loading on the material photoactivity has been also demonstrated. The lowest AuNPs size enhances the activity due to their better dispersion and subsequently, the higher Au-TiO2 interaction observed. Regarding the Au loading, the maximum photoactivity, in terms of NO conversion and dye degradation, was reached for the intermedium Au loading. It can be mainly associated to the abrupt increase of Au-TiO2 agglomeration for the highest loading evaluated. Finally, it has been stablished that AuNPs also increased the selectivity of the NO oxidation to nitrates and nitrites, reducing the amount of NO2 released.