Electrochemical Behavior of a Copper Electrode in Solid RbCu4Cl3I2Electrolyte

The electrochemical behavior of a copper electrode in solid RbCu₄Cl₃I₂electrolyte is studied by galvanostatic and potentiostatic methods. It is found that a Cu₂O layer 1 m thick exists at the interface between the Cu electrode and RbCu₄Cl₃I₂. The layer blocks the electrochemical reaction Cu⁰– e Cu⁺, which involves with metallic copper. At low overpotentials, the Cu electrode acts as an inert redox electrode. At the Cu₂O/RbCu₄Cl₃I₂interface, the electrochemical reaction Cu⁺– e Cu²⁺occurs, which involves Cu²⁺ions. The reaction rate is limited by slow diffusion of Cu²⁺ions in RbCu₄Cl₃I₂. The initial concentration of Cu²⁺ions in the electrolyte near this interface is about 1.4 × 10¹⁷cm^–3. The exchange current density is (4 ± 2) × 10^–6A/cm². At potentials exceeding 8–10 mV, an electric breakdown of the Cu₂O layer occurs, and the reaction with metallic copper becomes unblocked. At 10 mV < < 100 mV, the rate of this reaction is limited by the nucleation of copper crystals and the nuclei growth. At > 120 mV, the reaction rate is limited by charge transfer.