A comparison between bulk and supported TiO2 photocatalysts in the degradation of formic acid

Abstract

The photocatalytic activity of bulk and supported TiO2 catalysts were tested using formic acid as a probe molecule. The supported catalysts tested were prepared by impregnation using aluminum oxide (Al2O 3) as the support and the bulk catalysts by precipitation, both in sol-gel systems. For purposes of comparison, a photocatalyst supplied by DEGUSSA (P25) was also tested. The photolysis rate was found to be less significant than the photocatalytic rate. The Langmuir-Hinshelwood model was adopted and its constants were estimated and used to compare the various catalysts. The supported catalysts showed no significant activity, in spite of their high specific surface area. The bulk catalysts tested showed the highest photocatalytic rates. The adsorption constants determined experimentally were different from the ones estimated based on the kinetic experiments. The parameter estimation procedures tested were used to clarify this issue.