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

To understand the low recovery of ruthenium from ruthenium nitrosyl nitrate solution by electro-deposition technique, electro-reduction behaviour of ruthenium nitrosyl complex [Ru II –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 cm 2 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.