Electrodeposition of copper in quasi-two dimensions from solutions containing sodium sulfate

Electrolysis of copper(II) sulfate solutions in a radial quasi-two-dimensional thin cell showed typical tree-like morphologies of the copper deposit when low concentrations of a supporting electrolyte of sodium sulfate were added. When the concentration of sodium sulfate was one-tenth that of the copper(II) sulfate a small tree-like copper deposit surrounded by a blue ring was observed. With greater concentrations of sodium sulfate a continuous blue disc was observed which turned brown as the experiment proceeded. X-ray diffraction patterns revealed the deposit to be copper(II) oxide. It is proposed that this forms from an initial hydrogel of copper(II) hydroxide. A maximum in the current may correspond to the deposition of a concentrated outer ring of copper(II) hydroxide.