Photocatalytic degradation of formic acid via metal-supported titania

TiO2 catalysts supported on stainless-steel plates were tested for the photocatalytic degradation of formic acid in an aqueous solution. The metal-supported TiO2 catalysts showed reaction activities comparable to the commonly used glass-supported catalysts. Preirradiation was needed to activate fully both of the supported catalysts and to obtain reproducible activity data. During the photodegradation reaction, the oxidized surface of the metallic support was reduced and bleached. The activity of the catalyst decreased with an increase in firing temperature, which implies a positive correlation of the activity with the decrease in BET surface area of the TiO2 catalyst. The apparent reaction rate, R(a), increased as the thickness of the TiO2 film on the support increased. However, the specific reaction rate, R(a), calculated per unit of catalyst weight, decreased with an increase in the film thickness for the catalysts fired at temperatures of 300 degrees C or less, and it was nearly constant irrespective of the film thickness for the catalysts fired at temperatures of 400 degrees C or more. The X-ray diffraction patterns of the supported TiO2 catalysts that were fired at temperatures up to 600 degrees C showed that all of the TiO2 films had only an anatase structure, and the particle size increased as the firing temperature increased.