How Exactly Does Photocatalytic Oxidation Work?
What is photocatalytic oxidation? How does it work? What does it do?
Photocatalytic oxidation (PCO) occurs when a photocatalyst is bombarded with photons. In the case of PCO applied to air purification, the photocatalyst is titanium dioxide and the photon source is a UVC bulb.
When UV light hits the titanium dioxide surface, electrons are excited and are promoted from the valence band to conduction band, meaning the electrons are no longer attached to a single atom and are now able to move freely between titanium dioxide atoms and/or react with other molecules. This also leaves highly reactive positive hole in the titanium dioxide.
These two newly formed species - conduction band electrons and positive holes - react with water and dioxide molecules in the air to form hydroxyl radicals, highly effective and reactive oxidizing agents. Hydroxyl radicals oxidize and break down bioaerosols and volatile organic compounds, leaving behind water and carbon dioxide.
Essentially, PCO breaks down gaseous contaminants in the air such as odors, bioaerosols, and volatile organic compounds (i.e. benzene, formaldehyde, acetone, chloroform, etc) that are emitted from everyday household objects from paint and paint strippers to disinfectants and dry cleaned clothing.
1. United States. United State Environmental Protection Agency.Introduction to Indoor Air Quality. 2012. Web.
2. Tompkins, Dean T., Benjamin J. Lawnicki, et al. "Evaluation of Photocatalysis for Gas-Phase Air Cleaning— Part 1: Process, Technical, and Sizing Considerations."ASHRAE Transactions. 111.2 (2005): n. page. Print.
3. Jacoby, Bill. "Photocatalytic Oxidation." Department of Architectual Engineering. Pennsylvania State University, n.d. Web. 29 Jan 2014.