Efficiencies Evaluation of Photocatalytic Paints Under Indoor and Outdoor Air Conditions

Abstract

The removal of indoor and outdoor air pollutants is crucial to prevent environmental andhealth issues. Photocatalytic building materials are an energy-sustainable technology thatcan completely oxidize pollutants, improving in situ the air quality of contaminated sites. Inthis work, different photoactive TiO2 catalysts (anatase or modified anatase) and amountswere used to formulate photocatalytic paints in replacement of the normally used TiO2(rutile) pigment. These paints were tested in two different experimental systems simulatingindoor and outdoor environments. In one, indoor illumination conditions were used inthe photoreactor for the oxidation of acetaldehyde achieving conversions between 37and 55%. The other sets of experiments were performed under simulated outdoorradiation for the degradation of nitric oxide, resulting in conversions between 13 and35%. This wide range of conversions made it difficult to directly compare the paints.Thus, absorption, photonic, and quantum efficiencies were calculated to account forthe paints photocatalytic performance. It was found that the formulations containingcarbon-doped TiO2 presented the best efficiencies. The paint with the maximum amountof this photocatalyst showed the highest absorption and photonic efficiencies. On theother hand, the paint with the lowest amount of carbon-doped TiO2 presented thehighest value of quantum efficiency, thus becoming the optimal formulation in terms ofenergy use.