Electrocatalytic oxidation of hydrazine on a carbon paste electrode modified by hybrid hexacyanoferrates of copper and cobalt films

A stable electroactive thin film of hybrid copper-cobalt hexacyanoferrate (CuCoHCF) was electrodeposited on a carbon paste electrode by cyclic voltammetry. The modified electrode exhibits good catalytic activity for the oxidation of hydrazine at a reduced overpotential with good sensitivity in the wide concentration range 0.1-12 mM hydrazine. A Tafel plot, derived from voltammograms, indicated a one-electron charge transfer process to be the rate-limiting step and the overall number of electrons involved in the catalytic oxidation of hydrazine was found to be 4. The CuCoHCF modified-electrode exhibited stable electrochemical responses in a wide pH range 2-10 and showed excellent electrocatalytic activity toward the oxidation of hydrazine in 0.1 M phosphate buffer, pH 7. The diffusion coefficient of hydrazine and rate constant for the catalytic reaction were also evaluated. Finally the proposed modified electrode exhibited several attractive features, such as simple preparation, fast response, good stability and repeatability and could be applied as an amperometric sensor for hydrazine. (C) 2004 Elsevier B.V. All rights reserved.