Abstract: | Polynuclear ruthenium oxide/cyanoruthenate films on carbon substrates were grown by cycling the potential between 0.5 and 1.0 V (vs SCE) for 5–90 min in fresh 2 mM RuCl3·3 H2O, 2 mM K4Ru(CN)6·3 H2O, 0.5 M KCl solution at pH 2. During the positive scans, the cationic Ru(III,IV)-oxo polynuclear species interacted with the simultaneously formed anionic CN-bridged Ru dimers to yield sparingly soluble deposits on the electrode surfaces. Different thicknesses, typically corresponding to 2–50×10−10 mol cm−2, could be obtained by varying the cycling times. The absorption spectra of the coatings obtained at SnO2-covered glass electrodes were different from those known for RuO2 films and exhibited two absorption bands at about 400 and 700 nm. IR spectroscopic measurements confirmed the presence of a CN group in the deposit, as well as showing significant aquation of the entire coating. Ru, O, N and K (from KCl) were detected by means of Auger electron spectroscopy. The surface electrochemistry and stability of the film were significantly enhanced in K+-containing supporting electrolytes. The system provides a durable catalytic surface which allows the voltammetric oxidation of methanol; in 0.5 M H2SO4+0.5 M K2SO4 electrolyte the resulting anodic peak is at 1.01 V (vs. SCE). Electrooxidation was not possible at bare carbon electrodes, at least before the onset of the electrolyte decomposition. |