Visible-light-induced photocatalytic oxidation of carboxylic acids and aldehydes over N-doped TiO2 loaded with Fe, Cu or Pt

The rates of photocatalytic oxidation of gaseous formic acid, acetic acid, acetaldehyde and toluene over N-doped TiO2 (TiO2−xNx) loaded with Fe, Cu or Pt were determined under visible light irradiation (>410nm). It was found that the loading of Fe, Cu or Pt resulted in similar rates of enhancement of acetaldehyde oxidation, and that Cu and Pt gave the highest rates of acetic acid and toluene oxidation, respectively. It was also confirmed that the rate of formic acid photooxidation was enhanced by factors of 5 and 22 on loading of Fe and Pt, respectively. The extremely high rate enhancement of formic acid oxidation over Pt–TiO2−xNx was found to be due to a combined effect of photocatalysis and thermal catalysis at room temperature facilitated by nanoscale (1–2nm) Pt. These results indicate several important points as to enhancement of the activity of TiO2−xNx modified with metallic species.