Screen-Printed Photocatalytic Layer For Air Treatment At Low Irradiance

Screen-printed titania photocatalytic layers made from Degussa P25 were studied in order to assess the potential of this deposition technology for the production of catalytic surfaces for airborne pollutant degradation in inside real conditions. This work addresses the photocatalytic activity of pollutants at very low concentration as found indoor, on the contrary of what generally considered, i.e. high pollutant concentration. The deposited catalytic TiO2 layers were characterized by a low density (about 25% of the titania bulk crystal) typical of very porous films. The study was carried out using toluene at low concentration (12 ppb) as model pollutant and with a low UV-A irradiance level on the sample surface (200 ?W cm-2). The catalyst layers were deposited on alumina and quartz demonstrating a good catalytic depollution activity. The relationship between the layer thickness and the catalytic activity was studied in the 1 to 6.8 ?m range indicating an optimal 3~4 ?m film thickness. Thicker layers do not show significant increases in the catalytic activity. The optical transmittance was studied using quartz substrate samples, showing low residual photon flux for layers deeper than 5 ?m. The effect of post-printing thermal treatment was studied in the 500-900 °C range, demonstrating good catalytic activity for temperature <= 700 °C.