Photocatalytic Degradation of Gaseous Formaldehyde Using TiO₂ Film

The photocatalytic degradation of gaseous formaldehyde a major cause of sick building syndrome was studied using a TiO 2 thin film. TiO 2 thin films have many unique photoinduced properties, for example, self-cleaning, anti-fouling, and anti-bacterial functions. UV illumination of the TiO 2 thin film placed in a gaseous formaldehyde/air environment resulted in the total mineralization of formaldehyde to CO 2 and H 2 O. We invoked a Langmuir−Hinshelwood kinetic model to analyze the dependence of reaction rates on the concentration of formaldehyde. In addition, the overall decomposition rate constant for formaldehyde was comparable to that of acetaldehyde (a standard test reactant) for initial concentrations of up to 1000 ppmv. However, the apparent adsorption constant K app of formaldehyde onto TiO 2 was ca. 2.5 times larger than that of acetaldehyde. Thus in the low concentration regime, the reactivity of formaldehyde appeared to be greater than that of acetaldehyde. In like manner, a dark adsorption experiment also showed the high adsorption capacity of TiO 2 for formaldehyde. Therefore, we conclude that TiO 2 serves as both a good adsorbent and a photocatalyst for the elimination of gaseous formaldehyde.