As photocatalytic materials are making their way into the tile industry, it is fairly clear that most people really don’t understand how the mechanism works. A photocatalytic reaction requires three things: light, water and of course, a photocatalyst. Photocatalysts are always a semi-conducting metal such as titanium dioxide. When the photocatalyst is in the presence of a particular light wavelength range, some fairly complicated chemistry occurs. It at this point, when I am explaining the photocatalytic reaction technically, that I wave my hands above my head and use terms like “valence band,” “electron hole” and “d-orbitals” and the listener looks very impressed or very confused.

The simplified version is this – the surface becomes charged, reacts with water and generates free radicals, which are those thingies that that you’ve heard about in the news being responsible for aging and cancer. Now in reality, not all free radicals are bad, so don’t go thinking photocatalytic materials are going to cause cancer and give people wrinkles. In fact without them, we wouldn’t exist as they are necessary for many metabolic functions. Free radicals are highly reactive with other molecules and it is this property that gives photocatalytic materials antibacterial, air-purifying and self-cleaning attributes. Basically, the “bad stuff” gets neutralized into “better stuff” by the free radicals.