Cyclic time-separated redox reaction using accumulated electrons in titanium(iv) oxide in a two-phase system

Abstract

A time-separated redox reaction using accumulated electrons in titanium(IV) oxide (TiO₂) was cyclically repeated in order to increase the amount of the reduction product that has been limited by the saturation value of accumulated electrons in TiO₂. Repetition of the reaction was carried out by utilizing an organic/aqueous two-phase system and the insolubility of substrates and target products in the aqueous phase. The reaction proceeded by repeating two steps: (1) electron accumulation in TiO₂ at the bottom of the aqueous phase was induced under ultraviolet irradiation with low-speed stirring and (2) reduction by accumulated electrons in the two-phase interface was performed in the dark with high-speed stirring. Results indicated that the amount of the product monotonically increased as a function of the number of repetition cycles. The relationship of the product amount with the physical and chemical properties of TiO₂ is discussed.