Interfacial analysis of the ion-transport process controlling the steady-state current in a two-phase electrodeposition system using polyelectrolyte membranes

Abstract

Effluent-free selective copper electrodeposition based on ion transport via ion-exchange reactions within polyelectrolyte membranes is described. The new solid-phase electrodeposition system includes a thin layer of electrolyte solution between the anode and the membrane that comes into contact with the cathode. This layer was introduced to enable the electrolyte solution to be circulated to maintain the concentration of copper ions in the solution phase during electrodeposition. This membrane–solution layered system has a greater steady-state current density under constant-voltage electrodeposition compared with the previous system in which the membrane was sandwiched between the electrodes. The higher current density was attributed to the higher ion penetration rate at the interface between the electrolyte solution and the membrane, as verified by the results of the numerical analysis of the ion transport kinetics in the new system. By positioning the anode such that it is set slightly apart from the polyelectrolyte membrane to allow the electrolyte phase to be introduced, but as close as possible to it, a current density that was at maximum 50% greater than that of the sandwiched system was realized at steady state. This increase, which is attributed to the maximum ion penetration rate and minimum resistivity of the electrolyte layer, ensures a more efficient deposition setup for high-performance electrodeposition.