Effects of Firing Temperature on Photocatalytic and Photoelectrocatalytic Properties of TiO 2

This paper describes studies of the effect of firing temperature on the photocatalytic and photoelectrocatalytic degradation of formic acid (HCOOH) using ultraviolet (UV) illuminated TiO 2 thin films. Other variables, such as the potential applied [versus saturated calomel electrode (SCE)] to the film and the number of layers of film applied to the support were examined to determine optimum conditions for degradation. The transformation of TiO 2 from anatase to rutile in the thin films was significantly retarded by placing the films on SnO 2 -covered glass. Results indicate that films fired at 500°C showed the best efficiency for pure photocatalytic degradation, while films fired at 600°C had the best efficiency for the photoelectrocatalytic degradation of HCOOH. The efficiency of these photoelectrocatalytic reactions increased with increasing potential until 2 V (versus SCE) was obtained. A film with one layer (0.27 μm thickness) showed the maximum degradation of HCOOH for photoelectrocatalytic reactions at 2 V (versus SCE), as no further increase in the rate of degradation of HCOOH was obtained by using thicker films.