What is a photocatalyst?
A photocatalyst, as the name can imply, is a catalyst that accelerates chemical reactions related to light (typically UV light). While the field originally began with zinc oxide, photocatalysis was finally popularized by the findings and applications of titanium dioxide (TiO2) in the 1970s.
Rising of TiO2 Photocatalyst
The turning point for photocatalyst occurred when it was that titanium dioxide, as a photocatalyst, exhibited the ability to break water into its subparticles: hydrogen and oxygen. This discovery sparked excitement in the potential of using this essentially renewable resource as a means of energy production.
During further research, it was later discovered that the decomposing ability of TiO2 extends beyond water and can also apply to microorganisms (like bacteria, viruses, fungi, etc) as well as other environmental contaminants (such as VOCs), while also having a superhydrophillic effect. These two properties drove further research into using this photocatalyst as an antimicrobial and self-cleaning additive.
How does TiO2 work?
Once applied to a surface and dried, TiO2 would form a light-activated film. This light requirement depends on the specific TiO2 photocatalyst technology being utilized. Once the TiO2 is activated, the chemical reaction causes hydroxyl radicals (OH-) to form. The interaction of these electrons and electron holes with organic foreign molecules (such as pollutants, dirt particles, bacteria, viruses, etc) results in the latter being oxidized, decomposing back into harmless components.