Effects of TiO2Pretreatments on the Photocatalytic Oxidation of Gas-Phase Aromatic Contaminants

The effects of various halide salt and inorganic acid pretreatments on the photocatalytic destruction of toluene were examined to determine the source of activity enhancements seen previously with HCl pretreatments. Pretreatments with chloride salts (NaCl, KCl) are found to have little influence on photocatalyst activity, suggesting that the presence of an acid is needed. Acid pretreatments either increase (sulfuric, nitric, phosphoric) or decrease (hydrobromic, hydroiodic, and perchloric) the catalyst activity. These results indicate that acidification alone is not responsible for the observed changes in catalyst activity and that both protons and anions influence photocatalyst behavior.