Electrocatalytic water oxidation was carried out using a basal-plane pyrolytic graphite (BPG) electrode coated with electrodeposited Au particles adsorbing Ru-red ([(NH3)(5)Ru-O-Ru(NH3)(4)-O-Ru(NH3)(5)](6+)). The amount of O-2 evolved, V-O2 (mol h(-1)), increased remarkably by adsorbing the complex onto Au particles. The plots of V-O2 versus the complex amount on Au particles gave an almost straight line at its: low surface coverage, but deviated downward with an increase in its amount, which is ascribed to the bimolecular decomposition. The intrinsic turnover number (TN) of the complex is larger than that of the Au particle by three orders of magnitude, The catalytic activity of the complex was analyzed in terms of its intrinsic TN, k (h(-1)) and critical decomposition distance, r(d) (nm) based on intermolecular distance distribution to obtain k = 21.4 h(-1) and r(d) = 1.11 nm.