An approach to elucidating photocatalytic reaction mechanisms by monitoring dissolved oxygen: Effect of H2O2 on photocatalysis

We present a method to analyze the photocatalytic oxidation of ethanol (EtOH) in an aqueous TiO2 suspension by measuring the consumption of dissolved oxygen (DO) as a function of varying EtOH and H2O2 concentrations in the suspension. The consumption of DO was analyzed by means of Langmuir–Hinshelwood (L–H) kinetics. The parameter KD-DO calculated from L–H kinetics, defined as (O2 consumption rate constant) (O2 reproduction rate constant)−1, reflects the adsorption equilibrium of EtOH and the photocatalytic reaction mechanisms. The observed KD-DO values for the photocatalytic oxidation of EtOH reflected to the proposed reaction mechanism measured by HPLC and starch–Iodine methods. By using this DO analysis method, we elucidated the photocatalytic reaction mechanism of EtOH oxidation and discussed the effect of H2O2 as active oxygen species on TiO2 photocatalysis.