Metal Foam Electrode as a Cathode for Copper Electrowinning

The geometry of porous materials is complex, and the determination of the true surface area is important because it affects current density, reaction progression, and rates. This work investigates the dependence of electrochemical deposition of copper coatings on the geometry of the copper substrate, specifically comparing flat plates and 3D foams. Chronoamperometric measurements reveal that copper deposition occurs three times faster on copper foams than on flat electrodes with the same geometric area in the same potential range, indicating the potential of metal foams as electrodes for electrowinning. Electrochemical impedance spectroscopy (EIS) was utilized to determine the mechanism of copper deposition at various concentrations and potentials, revealing that the double electric layer capacity for foam electrodes is up to 14 times greater than that on plate electrodes. Additionally, EIS data showed that the charge transfer resistance on the Cu foam electrode is 1.5–1.7 times lower than on the Cu plate electrode. Therefore, metal foam electrodes present excellent opportunities for applications controlled by activation polarization or adsorption of intermediate compounds, as well as processes occurring on the entire surface of the electrode.