Electrochemical preparation, characterization and application of electrodes modified with hybrid hexacyanoferrates of copper and cobalt

Hybrid copper-cobalt hexacyanoferrate (CuCoHCF) films were electrodeposited on a platinum electrode or a glassy carbon electrode by cyclic voltammetry and characterized by electrochemistry, XRD, ICP-AES and XPS. The results indicated that CuCoHCF was a substitution-type hybrid hexacyanoferrate. With the increase of Cu2+ content in the deposition solution, the Cu2+ content in the films increased correspondingly, while the lattice constant of the films decreased gradually. The CuCoHCF modified platinum electrode exhibited stable electrochemical responses in a wide pH range of 4-10 and permeability for monovalent cations in the order of K+ > Li+ > Na+ > NH4+, both of which are different from those of the respective single component copper or cobalt hexacyanoferrates. XPS gave direct evidence that the iron element existed in the form of Fe(III) in oxidized films and was reduced to Fe(II) during X-ray scanning. K+ was incorporated into and excluded from CuCoHCF films to maintain electrical neutrality during the reduction and oxidation process, respectively. The CuCoHCF modified glassy carbon electrode exhibited obvious electrocatalytic activity towards both reduction and oxidation of hydrogen peroxide. When a cathodic catalytic current was used, the sensor exhibited a linear response in a hydrogen peroxide concentration range of 2.3 x 10(-3)-8.1 x 10(-7) M with a detection limit of 6.6 x 10(-8) M. The hydrogen peroxide sensor showed excellent stability and anti-interference ability towards oxygen and other easily oxidized compounds due to a low applied potential of 0.02 V, which is a great merit for further application in the field of biosensors. (C) 2002 Published by Elsevier Science B.V.