Photocatalytic reduction of dioxygen by colloidal semiconductors and macrocyclic cobalt(III) complexes in Nafion and cellulose matrices

Abstract

The colloidal semiconductors TiO₂ and CdS are used for the photosensitized reduction of MV²⁺ and Co(III) complexes. Photoinduced electron transfer reactions are carried out using the semiconductors in colloidal state, adsorbed and intercalated into Nafion and cellulose matrices. The back electron transfer reaction between h_vb⁺(TiO₂ or CdS) and MV^+· or Co(II) complex is prevented by the reaction of the hole with an electron donor triethanolamine (TEA). Hydrogen peroxide (H₂O₂) is produced by the reaction of the photoproduced MV^+· or Co(II) complex with dissolved molecular oxygen (O₂). The photosensitized reaction mechanisms of the formation of MV^+· and Co(II) complex and the photocatalytic reduction of O₂ to yield H₂O₂ in the semiconductor modified systems are explained.