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We present a method to analyze the photocatalytic oxidation of ethanol (EtOH) in an aqueous TiO 2 suspension by measuring the consumption of dissolved oxygen (DO) as a function of varying EtOH and H 2 O 2 concentrations in the suspension. The consumption of DO was analyzed by means of Langmuir–Hinshelwood (L–H) kinetics. The parameter K D-DO calculated from L–H kinetics, defined as (O 2 consumption rate constant) (O 2 reproduction rate constant) −1 , reflects the adsorption equilibrium of EtOH and the photocatalytic reaction mechanisms. The observed K D-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 H 2 O 2 as active oxygen species on TiO 2 photocatalysis.

We proposed a novel method to analyze photocatalytic reaction of TiO2 suspension by measuring the consumption process of dissolved oxygen (DO). The decay rates for DO consumption could be analyzed with Langmuir–Hinshelwood (L–H) kinetics as the effects of reactants such as ethanol and iso-propanol. Two parameters in the L–H kinetics, the maximum consumption rate rmax and adsorption equilibrium constant KD were obtained. The rate constants, kt and kp, which express O2 consumption and O2 reproduction, respectively, could be estimated from dependence of rmax on excitation intensity. Participation of O2 − in the decomposition of alcohols was examined by measuring the amount of O2 −. An increase of O2 − concentration was observed by the addition of a small amount of the reactants, and a decrease was observed for the reactant concentration of more than few mM. Based on these results, we analyzed the DO consumption process and suggested the applicability that the DO consumption efficiency can be used as a relative photonic efficiency to compare the differences in the photocatalytic activities and in the stabilities of reactants.