On the ability of metal-nitroprusside complexes as electrode modifiers: Characterization and electrochemical study of palladized aluminum electrode modified with iron pentacyanonitrosylferrate

• Palladized aluminum electrode was modified with ferrous nitroprusside by fully electroless procedure.
• Chemical composition change of modifier on the electrode surface was investigated.
• A dissociative mechanism for metal-nitroprusside type modifiers conversion was proposed.

In this work we introduce the concept of “directed assembly” based on multiple sequential adsorption of iron pentacyanonitrosylferrate (FePCNF) multilayer on the surface of the palladized aluminum electrode (Pd-Al) by alternately exposing it to positively charged Fe2+ cations and negatively charged [Fe(CN)5NO]2− anions. The adsorbed FePCNF on the Pd-Al electrode is pure and very stable. The preliminary cyclic voltammetric studies showed that freshly prepared modified electrodes have no defined electroactivity in the potential range of −0.2–1 V/SCE, but after exerting negative potential, two couples of redox peaks are emerged at 0.17 and 0.8 V/SCE due to outer and inner Fe(II) ↔ Fe(III) redox transitions of FePCNF modifier. The pH effect of supporting electrolyte on the electrochemical behavior of the electroactivated FePCNF/Pd-Al was studied. Also, the electron transfer rate constant (ks) and charge transfer coefficient (α) were calculated. We found out that the chemical composition of adsorbed FePCNF on the electrode surface is changed by exerting negative potential. On the basis of results obtained by FT-IR spectroscopy and electrochemical techniques, a probable dissociative mechanism was proposed for the modifier conversion. We ascribe this conversion to the generation and dissociation of [Fe(CN)4NO]2− as predominant reduced species in acidic solution, which in turn releases NO and probably leads to formation of stable Prussian Blue type precipitate.