The impact of photocatalytic paint’s porosity on indoor NOx and HONO levels
Photocatalytic materials are potentially an effective remediation technology for indoor air purification. Here, we assess the impact of photocatalytic paint’s porosity on indoor nitrogen oxides (NOx) and nitrous acid (HONO) levels. We observed that the porosity of photocatalytic paints plays a paramount role for the NO2 removal. The increase of porosity from PVC 53 % to PVC 80 % leads to an increase of the geometric NO2 uptake coefficient from (3.3±0.5)·10-6 to (2.7±0.1)·10-5. At the same time, high quantity of HONO formed by NO2 conversion on photocatalytic paint is emitted in the air. The formation of HONO which is considered as a harmful compound and a major player in the oxidative capacity of indoor air is reduced as the paint porosity increases. Based on these results, further optimizations should be considered for future commercialization of photocatalytic paints aimed for indoor applications.