Preparation, characterization and electrocatalytic properties of polynuclear mixed-valent ruthenium oxide/hexacyanoruthenate film modified electrodes

Abstract

Polynuclear mixed-valent ruthenium oxide/ruthenocyanide (ruthenium oxide/hexacyanoruthenate or mvRuO/RuCN) films were prepared using consecutive cyclic voltammetry directly from the mixing of Ru 3+ and Ru(CN) 6 4− ions from solutions of two divalent cations (Ba 2+ and Ca 2+), and seven monovalent cations (H +, Li +, Na +, K +, Rb +, Cs +, and Ga +). The films exhibited three redox couples with Ba(NO 3) 2 or BaCl 2 aqueous solutions, and the formal potentials of the redox couples showed a cation and pH effect. An electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, UV–visible spectroscopy, and the stopped-flow method (SFM) were used to study the growth mechanism of the mvRuO/RuCN films. The results indicated that the redox process was confined to the immobilized ruthenium oxide/ruthenocyanide. The EQCM results showed a Ba 2+ ion exchange reaction for the two most negative redox couples. The electrocatalytic reduction properties of SO 5 2−, and S 2O 8 2− by the ruthenium oxide/ruthenocyanide films were determined. The electrocatalytic oxidation of NADH and dopamine were also determined, and revealed two different types of properties. The electrocatalytic oxidations of SO 3 2−, S 2O 3 2−, and N 2H 4 were also investigated. The electrocatalytic reactions of the ruthenium oxide/ruthenocyanide films were investigated using the rotating ring-disk electrode method.