Electrochemical Kinetics of CuCl(aq)/HCl(aq) Electrolyzer for Hydrogen Production via a Cu-Cl Thermochemical Cycle

Abstract

An electrochemical kinetics investigation of the CuCl(aq)/HCl(aq) electrolyzer identified methods to significantly reduce the platinum loadings required to achieve a high cell current density of 0.5 A/cm2 at 0.7 V. As the CuCl(aq)/HCl(aq) electrolyzer is a key component of the Cu-Cl thermochemical cycle, the economic viability of the Cu-Cl thermochemical cycle was significantly improved by reducing the loading required to achieve 0.5 A/cm2. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) with a rotating disc electrode were employed to investigate the kinetics of the aqueous CuII/CuI chloride complexes reaction on platinum and glassy carbon using a three-electrode cell. It was found that the standard exchange current density of the anodic CuII/CuI electrochemical reaction on platinum, 4–12 A/cm2, was significantly larger than the values reported for the HER cathodic reaction thus far. In addition, SEM was used to observe the effectiveness of different catalyst application techniques. Through SEM observations, and electrochemical data analysis, the amount of platinum used in a laboratory scale CuCl(aq)/HCl(aq) electrolyzer was reduced from 0.8 mg/cm2 applied to both electrodes to 0.4 mg/cm2 on the cathode and zero at the anode while still maintaining a current density of 0.5 A/cm2 at 0.7 V of applied potential difference.