The effect of hydrogen co-deposition on the morphology of copper electrodeposits. II. Correlation between the properties of electrolytic solutions and the quantity of evolved hydrogen

Abstract

Formation of irregular deposits by electrodeposition from acid sulfate solutions of various H2SO4 concentrations was examined by the determination of the average current efficiency of hydrogen evolution and by the scanning electron microscopic (SEM) analysis of the copper deposits morphology. Copper dendrites were the dominant morphological form obtained at overpotentials corresponding to the plateaus of the limiting diffusion current density. The number of the formed dendrites was increasing with the decreasing H2SO4 concentration. Holes formed due to the attached hydrogen bubbles were the basic morphological form of electrodeposited copper from all analyzed copper sulfate solutions at overpotentials outside the plateau of the limiting diffusion current density. The honeycomb-like structures (holes of the detached hydrogen bubbles with cauliflower-like agglomerates of copper grains between them) were formed if electrodepositions were performed from 0.15 M CuSO4 in both 0.250 M and 1.0 M H2SO4. On the other hand, aside from the holes and cauliflower-like forms, electrodeposition from 0.15 M CuSO4 in 0.125 M H2SO4 led to the formation of degenerated dendrites and dendritic particles inside channels formed of evolved hydrogen. Holes with shoulders of degenerated dendrites were also formed. The formation of different morphological forms under hydrogen co-deposition was discussed in the terms of hydrodynamic conditions in the near-electrode layer using the values for the break-off diameter of hydrogen bubbles.