Electrocatalytic O2 Evolution from Water at an ITO Electrode Modified with [Ru(terpy){4,4′-(CH2PO3H2)2-2,2′-bpy}(OH2)]2+: Evidence for a Unimolecular Pathway

An ITO (indium tin oxide) electrode modified with [Ru(terpy){4,4′-(CH2PO3H2)2-2,2′-bpy}(OH2)]2+ was prepared to gain insight into the mechanism of O2 evolution from water catalyzed by a series of mononuclear aquaruthenium complexes, such as [Ru(terpy)(bpy)(OH2)]2+. The modified ITO electrode showed a clear decrease in overpotential for O2 evolution (1.35 V in an aqueous 0.1 M Na2SO4/H2SO4 solution, pH 4.0), indicating that the O2 evolution proceeds in a unimolecular fashion without having any intermolecular associations.