Chemija / Chemistry
 ISSN 0235-7216 ISSN 2424-4538 (online) |
2011 m. Nr. 2 Impedance of copper electrode in acid Cu(II) solutions containing gluconic acid
Electrochemical impedance spectroscopy was applied to study the processes taking place on the Cu electrode in 0.01 M Cu(II) solutions containing 0.04 M gluconic acid and 0.3 M K2SO4 (pH 3.0). The Nyquist plots obtained under open-circuit and cathodic polarization conditions present the arcs centred below the abscissa axis. The description code of the adequate equivalent circuit is RΩ (Cdl[R1W1] [R2W2]) (here, elements in series are written in angle brackets and parallel elements are given in parentheses). The settled exchange current densities obtained for the two-step charge transfer process (i01 = 4.8 μA cm–2 and i02 = 440 μA cm–2) are in good agreement with the quantities obtained earlier from voltammetric data.
The double-layer admittance was found to increase with the cathodic overvoltage approaching the values that are typical of additive-free Cu(II) solutions. Desorption of gluconate is supposed to occur at potentials adjacent to the plateau of the limiting current. Keywords: copper, gluconic acid, impedance, equivalent circuit |
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