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

Abstract

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 CO2 (Sc-CO2) 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-CO2 had a significant inhibitory effect on Cu electrodeposition. In addition, a kinetics model was attempted to be constructed for the Sc-CO2 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-CO2 mixed system, Sc-CO2 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-CO2 was presumed to reduce the transition coefficient by suppressing the reduction reaction of Cu2+ ions to the Cu+ complex by adsorption on the electrode surface.