Analysis by X-ray photoelectron spectroscopy of ruthenium stabilised polynuclear hexacyanometallate film electrodes

The role and effects of ruthenium on the electrochemical stabilisation of s ome metal-hexacyanometallate film electrodes was investigated by X-ray phot oelectron spectroscopy (XPS). The following inorganic films were studied, c obalt(II)-hexacyanoferrate(II/III) (CoHCFe), nickel(II)-hexacyanoferrate(nm ]I) (NiHCFe), and iron(II/III)-hexacyanorutenate(II/III) (FeHCRu), and thei r corresponding ruthenium stabilised ones, Ru-CoHCFe, Ru-NiHCFe and Ru-FeHC Ru. A mass increase of CoHCFe, NiHCFe, and FeHCRu, during continuous redox cycles (75-90 times) in a millimolar solution of RuCl3, was monitored by an electrochemical quartz crystal microbalance. Detailed XPS analysis of C 1s , O 1s, Fe 2p, Ni 2p, Co 2p, and Ru 3d peaks has allowed a comprehensive de scription of changes that occurred. The results obtained demonstrate that t he insertion of ruthenium oxo species (e.g., Ru2O63+) was effective for the increase in lifetimes and for the electrocatalytic properties of ruthenium -modified metal-hexacyanometallate film electrodes. Three possible models o f stabilisation are discussed. (C) 2000 Elsevier Science B.V. All rights re served.