Electroless immobilization and electrochemical characteristics of nickel hexacyanoruthenate film at an aluminum substrate

The surface of an aluminum (Al) electrode was modified with a thin film of nickel hexacyanoruthenate (NiHCR) as a novel electrode material. The modification procedure of Al surface, includes two consecutive procedures: (i) the electroless deposition of metallic nickel on the Al electrode surface from NiCl2 solution, and (ii) the chemical transformation of deposited nickel to nickel hexacyanoruthenate films in solution of 20 mM K3[Ru(CN)6] + 0.5 M KNO3. Cyclic voltammogram of the modified Al electrode showed a well-defined redox reaction due to [NiIIRuIII/II(CN)6]1−/2− system. The effects of different supporting electrolytes and solution pH were studied on the electrochemical characteristics of the modified electrode. The diffusion coefficients of K+ and Na+ cations in the film (D), the transfer coefficient (α), and the charge transfer rate constant at the modifying film/electrode interface (ks), were calculated in the presence of both K+ and Na+ cations. The stability of the modified electrode was investigated under various experimental conditions.