Photoelectrochemistry in colloidal systems. Part 2.—A photogalvanic cell based on TiO2 semiconductor colloid

Abstract

Thiazine and oxazine dyes have been photoelectrochemically reduced in colloidal TiO₂ suspensions with bandgap excitation. The one-electron reduction of the dye, which resulted in the production of the semireduced radical ion, with quantum yield up to 0.1, further disproportionated to yield a stable leuco dye. The efficiency of the interfacial electron-transfer process is found to be dependent on the standard reduction potential of the dye. The feasibility of employing a colloidal semiconductor system in the operation of a photogalvanic cell is demonstrated. A photogalvanic power conversion efficiency of 0.002% was achieved with thionine and colloidal TiO₂ upon bandgap excitation. The use of TiO₂ colloid as a carrier for the deposition of a photoactive or an electroactive species on the electrode surface is also discussed.