Surface Catalysis of Water Oxidation by the Blue Ruthenium Dimer

Abstract

Single-electron activation of multielectron catalysis has been shown to be viable in catalytic water oxidation with stepwise proton-coupled electron transfer, leading to high-energy catalytic precursors. For the blue dimer, cis,cis-[(bpy)(2)(H(2)O)Ru(III)ORu(III)(H(2)O)(bpy)(2)](4+), the first well-defined molecular catalyst for water oxidation, stepwise 4e(-)/4H(+) oxidation occurs to give the reactive precursor [(O)Ru(V)ORu(V)(O)](4+). This key intermediate is kinetically inaccessible at an unmodified metal oxide surface, where the only available redox pathway is electron transfer. We report here a remarkable surface activation of indium-tin oxide (In(2)O(3):Sn) electrodes toward catalytic water oxidation by the blue dimer at electrodes derivatized by surface phosphonate binding of [Ru(4,4'-((HO)(2)P(O)CH(2))(2)bpy)(2)(bpy)](2+). Surface binding dramatically improves the rate of surface oxidation of the blue dimer and induces water oxidation catalysis.