Electrochemical studies on the reduction behaviour of ruthenium nitrosyl ions in nitric acid medium

Abstract

To understand the low recovery of ruthenium from ruthenium nitrosyl nitrate solution by electro-deposition technique, electro-reduction behaviour of ruthenium nitrosyl complex [RuII–NO+]3+ in nitric acid medium was investigated using the potentiostatic electrolysis techniques, cyclic voltammetry and chronopotentiometry at Pt and glassy carbon working electrodes. Reduction of [RuNO]3+ was found to be quasi-reversible, one electron transfer process at both the electrodes. The diffusion coefficient (D 0) of [RuNO]3+ species estimated by these techniques was in the order of 10−8 cm2 s−1 and the heterogeneous electron transfer rate constant (k s) for the reduction of [RuNO]3+ was estimated to be about 10−5 cm s−1 using Klingler and Kochi equation. The very low diffusion coefficient value and the low separation percentage of Ru from ruthenium nitrosyl nitrate solution by electro-deposition technique are attributed to the existence of Ru(II) in different stable complexes instead of bare Ru(II) ions, in nitric acid medium.