| Abstract
| - A buffered tris(2,2‘-bipyridyl)ruthenium complex-colloidal IrO2 system was studied as a photocatalyst forthe production of O2 from water. Phosphate buffer, which has historically been used to control the pH in thissystem, accelerates the decomposition of the photosensitizer and inhibits O2 evolution, whereas sodiumhexafluorosilicate (Na2SiF6)−base solutions are ideal buffers for the reaction. Na2SiF6-containing bufferspoise the solution under visible light irradiation at ca. pH 5, preventing the pH drop that accompanies oxidationof water in unbuffered solutions. Decomposition of the photosensitizer is not kinetically competitive withoxygen evolution in these buffers. In particular, the Na2SiF6−NaHCO3 buffer greatly improves the turnovernumber of the photosensitizer, relative to previously used phosphate buffers, without any decrease in activity.Photocatalytic reactions studied under various conditions suggest that adsorbed carbonate or bicarbonate onthe surface of the colloidal IrO2 particles contributes to the increased turnover number of the photosensitizer.
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