Photocatalytic Water Oxidation in a Buffered Tris(2,2‘-bipyridyl)ruthenium Complex-Colloidal IrO₂ System

Abstract

A buffered tris(2,2′-bipyridyl)ruthenium complex-colloidal IrO 2 system was studied as a photocatalyst for the production of O 2 from water. Phosphate buffer, which has historically been used to control the pH in this system, accelerates the decomposition of the photosensitizer and inhibits O 2 evolution, whereas sodium hexafluorosilicate (Na 2 SiF 6 )-base solutions are ideal buffers for the reaction. Na 2 SiF 6 -containing buffers poise the solution under visible light irradiation at ca. pH 5, preventing the pH drop that accompanies oxidation of water in unbuffered solutions. Decomposition of the photosensitizer is not kinetically competitive with oxygen evolution in these buffers. In particular, the Na 2 SiF 6 -NaHCO 3 buffer greatly improves the turnover number 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 on the surface of the colloidal IrO 2 particles contributes to the increased turnover number of the photosensitizer.

Chemiluminescence Determination of Local Anaesthetic Mepivacaine in Human Plasma and Pharmaceuticals

“…The resulting Ru(phen) 3 3+ complex produced in the oxidation reaction is a powerful oxidant and can oxidize water to protons and O 2 molecules. 40 Therefore, Ru(phen) 3 3+ complex returns slowly to its reduced state, Ru(phen) 3 2+ . Reducing agents can reduce Ru(phen) 3 3+ very fast.…”

Photoelectrochemistry and Photocatalysis in Nanoscale Inorganic Chemical Systems

“…57 Colloidal IrO 2 is a particularly interesting colloidal catalyst because of its stability, and the ease of analysis of the photocatalytic cycle (10) with simple UV-Vis spectrophotometry. 58 Colloidal catalysts also typically have a surface charge that can be used to incorporate them into photosynthetic assemblies constructed from inorganic sheets and organic polyelectrolytes. As a result, the photocatalytic potential of IrO 2 colloids has been further investigated in our laboratory beyond the previous studies by Harrimann and coworkers.…”

Porous–Hybrid Polymers as Platforms for Heterogeneous Photochemical Catalysis

“…In addition to photoelectrical applications of Ru dyes [6][7][8] , Ru and Co complexes have desirable photocatalytic properties for photochemical energy conversion applications, primarily for photocatalytic water splitting. [9][10] Of particular interest are heterogeneous photocatalysts that can easily be separated and recycled from a reaction mixture. [11][12][13] In efforts to address certain demanding applications, like gas storage and separation, CO 2 capture, catalysis, and energy conversion, a large number of porous solids, namely metalorganic frameworks (MOFs), 14 conjugated microporous polymers (CMPs), 15 porous cross-linked polymers (PCPs), [16][17] and porous-organic polymers (POPs), 18 are being actively investigated.…”