Effects of aqueous buffers on electrocatalytic water oxidation with an iridium oxide material electrodeposited in thin layers from an organometallic precursor.

A thin layer of an amorphous, mixed-valence iridium oxide (electrodeposited from an organometallic precursor, [Cp*Ir(H(2)O)(3)](2+)) is a heterogeneous catalyst among the most active and stable currently available for electrochemical water oxidation. We show that buffers can improve the oxygen-evolution activity of such thin-layer catalysts near neutral pH, but that buffer identity and concentration, as well as the solution pH, remain key determinants of long-term electrocatalyst activity and stability; for example, phosphate buffer can reduce the overpotential by up to 173 mV.