Influence of ionic equilibrium in the CuSO(4)-H(2)SO(4)-H(2)O system on the formation of irregular electrodeposits of copper
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The relative concentration of hydrogen ion (H(+)) as a function of sulfuric acid (H(2)SO(4)) concentration (calculated using Pitzer's model) and the electrochemical processes by which irregular copper deposits are formed were correlated. Irregular deposits are formed by potentiostatic electrodeposition at a high overpotential where the hydrogen evolution reaction occurs parallel to copper electrodeposition. Two sets of acid sulfate solutions were analyzed. In one set of experiments, the concentration of CuSO(4) was constant while the concentration of H(2)SO(4) was varied. The other set of experiments was performed with a constant concentration of H(2)SO(4) and different concentrations of CuSO(4). Then, the volumes of the evolved hydrogen (calculated as the average current efficiencies of hydrogen evolution) and the morphologies of copper deposits, characterized by the SEM technique, obtained for the same ratio of CuSO(4)/H(2)SO(4) were mutually compared and discussed in terms of the re...lative concentrations of hydrogen ions (H(+)) as a function of the H(2)SO(4) concentration. Good agreement between the ionic equilibrium in the CuSO(4)-H(2)SO(4)-H(2)O system and the results of the electrochemical processes was obtained. In this way, it was shown how this ionic equilibrium can be applied to predict and analyze the solution composition in electrolytic copper deposition processes.
Keywords:electrochemistry / electrolysis / hydrodynamics / morphology / hydrogen / copper
Source:Chemical Engineering Science, 2008, 63, 10, 2824-2828
- Pergamon-Elsevier Science Ltd, Oxford