Electrode Kinetic Study of Cu Electrodeposition with Supercritical CO2 by High Pressure Rotating Disk Electrode Method

The electrochemical reaction mechanism on the electrode surface for the activation of Cu electrodeposition in a sulfate-based Cu plating solution containing poly ethylene glycol (PEG) and supercritical CO 2 (Sc-CO 2 ) was studied by hydrodynamic voltammetry experiments and electrochemical impedance spectroscopy performed using a rotating disk electrode system specially designed for high pressure environment. The experimental results demonstrated that the mixed Sc-CO 2 had a significant inhibitory effect on Cu electrodeposition. In addition, a kinetics model was attempted to be constructed for the Sc-CO 2 mixed system based on the conventional model for the system with suppressor. As a result, the same mechanism as in the conventional model can be used to explain the Sc-CO 2 mixed system, Sc-CO 2 micelles in the solution were suggested to adsorb on the electrode surface in the same manner as the PEG molecules, which affected the reaction mechanism and was expected to inhibit the reduction reaction of Cu ions. Furthermore, the mixed Sc-CO 2 was presumed to reduce the transition coefficient by suppressing the reduction reaction of Cu 2+ ions to the Cu + complex by adsorption on the electrode surface.