Effect of the anodic current density on copper electrodeposition in the hydrogen co-deposition range by the reversing current (RC) regime

Abstract

In this study, the effect of the anodic current density in the regime of reversing current (RC) on the quantity of evolved hydrogen and morphology of copper deposits was considered. The quantity of evolved hydrogen was quantified by the determination of the average current efficiency for hydrogen evolution reaction, while morphology and internal structures of electrodeposited copper were analyzed using scanning electron (SEM) and optical microscopy techniques, respectively. In all RC experiments, the cathodic current density of 440 mA/cm 2, cathodic pulse of 10 ms and anodic pulse of 5 ms were applied, while the analyzed anodic current densities were: 40, 240, 440 and 640 mA/cm 2. The number, size and shape of holes formed of detached hydrogen bubbles strongly depended on the selected parameters of square waves RC. Due to the decrease of the quantity of evolved hydrogen with the increasing anodic current density, the change of morphology of copper deposits formed around holes from cauliflower-like agglomerates of copper grains to dendrites was observed. Honeycomb-like structures were formed with the anodic current density values up to 440 mA/cm 2. The compactness of the honeycomb-like structures increased with the increase of the anodic current density. The improvement of structural characteristics of the honeycomb-like electrodes was achieved by the application of the RC regime in comparison with both the pulsating current (PC) and constant galvanostatic regimes. It was found that the regime of reversing current is superior in the production of the honeycomb-like electrodes in relation to other current regimes of electrolysis.