Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

In this study, the newly synthesized TiO₂ and N doped TiO₂ clusters were added to silica sol to synthesize N-TiO₂/SiO₂ composites via the sol-gel method. Afterwards, the prepared sols were applied by brushing on portland cement. Doping with nitrogen significantly increased the absorption of TiO₂ towards the visible region, thus, increasing the photocatalytic activity. SEM characterization of the treated samples showed that the clusters were distributed in form of aggregates on the samples' surface. The self-cleaning and air de-polluting performances were assessed through methylene blue degradation and the oxidation of nitrogen oxide, resulting in methylene blue (MB) removal of 85% and 78% after 60 min of irradiation for SN10TiO₂ and STiO₂, respectively. Regarding air de-pollution performance, the newly synthesized photocatalysts showed the ability of NOx reduction. However, their efficiency was somewhat lower, in which 23.81% of NO has been oxidized by the sample SN10TiO₂, while SP25 showed a total NO conversion of 38.98%. The powdered xerogels of the newly synthesized nanoparticles revealed high photocatalytic efficiency concerning NO oxidation, resulting in a higher performance compared to those obtained by the xerogel containing P25.