In this experiment, the deposition of copper metal was achieved by means of electrolysis of the aqueous solution of copper(II) chloride (CuCl2).
Electrolysis was carried out in a thin solution layer placed between two microscopy glass slides. Thin copper wires were used as electrodes. The experiment was recorded under an optical microscope.
In aqueous solution, copper(II) chloride dissociates into ions:
CuCl2 → Cu2+(aq) + 2Cl-(aq)
The following processes take place during the electrochemical deposition of copper:
1) when direct current is applied, Cu2+ ions diffuse towards (-) electrode, i.e., cathode.
Cu2+ in solution → Cu2+ to the cathode.
2) when arriving at the cathode, copper cations bind electrons and neutral solid copper deposits on the electrode.
Cu2+(aq) + 2e- → Cu(s)
In a dilute salt solution, the deposition of copper is diffusion-limited, i.e., transfer of electrons is faster than the diffusion of copper cations from the solution to the cathode.
Under such conditions, copper deposits in the form of long branched dendrites.