Activity analysis of a water oxidation catalyst adsorbed on an inorganic particle matrix

A highly active electrocatalytic system to oxidise water to dioxygen (O2) has been established using electrodeposited platinum black with an adsorbed trinuclear ruthenium complex (Ru-red). The catalyst turnover number for O2 evolution was 1500 h–1, four orders of magnitude greater than that of neat Pt-black. This high activity was ascribed to efficient charge transport from the electrode to the catalyst. The amount of O2 evolved increased almost linearly with the amount of Ru-red for low loadings on Pt-black but decreased after passing an optimum loaded amount. This decrease was ascribed to bimolecular decomposition of the catalysts. The catalyst activity was analysed in terms of critical decomposition distance (rd/nm) by a surface adsorption model (SAM) and a void-space adsorption model (VAM); rd was estimated to be 1.37 nm for the SAM and 1.21 nm for the VAM.