Influence of potential pulse conditions on the formation of honeycomb-like copper electrodes

Abstract

Electrodeposition of copper by pulsating overpotential (PO) regime in the hydrogen co-deposition range was examined by the determination of the average current efficiency of hydrogen evolution and by microscopic analysis of the morphology of the formed deposits. The techniques of scanning electron microscopy (SEM) and optical microscopy were used for the structural analysis of the copper deposits. Honeycomb-like electrodes were formed with an amplitude overpotential of 1000 mV, a pause of 10 ms, and deposition pulses of 3, 5, 10 and 20 ms. Holes formed by attached hydrogen bubbles were surrounded by dendrites (for deposition pulses of 3 and 5 ms) or agglomerates of copper grains (for 10 and 20 ms). In an interval of deposition pulses between 3 and 10 ms, the length of deposition pulse did not affect the size, number and depth of holes. The change of morphology of copper formed around holes was discussed by the effect of quantity of evolved hydrogen on effectiveness of stirring of solution in the near-electrode layer. The application of square-wave PO with the shorter deposition pulses enabled energy savings in the production of such copper electrodes. For example, the applied deposition pulse of 3 ms enabled energy saving of about 15% in relation to the copper electrode obtained with a deposition pulse of 10 ms (for the unchanged number, size and depth of holes).