Influence of humidity and acidity of the titanium dioxide surface on the kinetics of photocatalytic oxidation of volatile organic compounds

The influence of the humidity and acidity of the TiO2 surface on the kinetics of the photocatalytic processes of deep oxidation of volatile organic compounds was studied. At ∼20 °C the rates of acetone and benzene oxidation are maximum at the coverages of TiO2 with water close to monolayer and are 3—5 times higher than that in the dry atmosphere. The activation energy of benzene oxidation (E a = 6.3±0.4 and 43.0±3.2 kJ mol–1 at relative humidities of 8 and 70%, respectively) at a humidity higher than 30% decreases according to the exponential law with an increase in the surface acidity when multilayer water films are formed on the surface. Under the real conditions of operation of photocatalytic air purifiers, a TiO2 particle is covered by water nanofilms. As in aqueous solutions, photoprocesses on the TiO2 surface depend substantially on the solvation of the participants of the reaction, the formation of the double electric layer, and the concentration of the electrolyte (due to the dissociation of the surface acid-base groups).