Photocatalysis, like the photosynthesis reaction of plants, is based on the absorption of light to activate the reaction. In photocatalytic processes, the absorption of light energy is used for the degradation of various atmospheric pollutants such as NOx, SOx and VOCs.
In particular, the degradation of these pollutants is carried out by a photochemical reaction that takes advantage of the energy coming from the sun to the generation of free radicals, these causes the oxidation and reduction reactions that occur on the surface. As a catalyst or substrate of these redox reactions a semiconductor material with a band gap is presented as small as possible to facilitate the generation of electron-hole pairs.
This chemical process can be observed on a macroscopic scale in the attached figure. In these, the photocatalytic material present on the surface absorbs the solar radiation and allows to transform the atmospheric pollutants into compounds for health, such as nitrates, CO2 and water.
Through the photocatalysis can eliminate most of the pollutants in the air of urban centers, such as NOx, SOx, Volatile Organic Compounds, CO and other organic compounds derived from halogens.