Electrochemical Studies on Substituted Iron-Hexacyanoiron(III) Bi-Layered Thin Films at Glassy Carbon Electrode/Electrolyte Interface

Abstract

Thin films (30–50 nm) of bilayered HCM (hexacyanometalates) were prepared using direct electrodeposition or electrochemically driven insertion-substitution of PB (Prussian Blue) or InHCF (Indium Hexacyanoferrate) or K..Inx[Fe{CN}6]y, as starting material. The redox behavior of the immobilized counter/central ions at GCE/electrolyte interface have been investigated in aqueous KCl (pH 1) electrolytes using dynamic voltammetric techniques. Studies show that when the counter Fe or In ion is replaced by expandable partially filled d orbits elements such as Ru3+ a redox wave of the inserted counter ion is observed. Furthermore, the substitution of Fe as a counter ion with other poly-valent cations was found to be reversible if PB was the starting material. Studies were extended to include the EC (electrochemical) behavior of related HCM compounds such as K...Alx[Fe{CN}6]y K, Nix[Fe{CN}6]y Cux[Fe{CN}6]y, K..Znx[Fe{CN}6]y and, K..Ru[Fe{CN}6]3. Unlike studied 3d cations, GCE modified with thin films of copper-hexacyanoiron (III) KCux[Fe{CN}6]y or CHF showed two redox waves with Eof ≈ 0.6, 0.9 V vs Ag/AgCl. Studies showed that even immobilized Cu ions were capable of catalyzing the oxidation of hydrazine and sulfite. The mechanism for electro-oxidation is also included.