Electrodeposition of Cu 3D structures suitable for CO2 reduction

Porous Cu foam electrodes, suitable for cathodic CO2 reduction, were deposited in an acidic sulphate solution with different additives to obtain structures with a high real surface area and an adequate mechanical stability. The influence of the electrodeposition time and solution composition on the porosity parameters, microstructure and stiffness of Cu 3D structures was evaluated. Neither ammonium acetate nor polyethylene glycol were found to be effective additives to the Cu sulphate electrolyte to achieve the main objectives. Only the presence of Cl– ions in the deposition solution resulted in a threefold increase in the real surface area and the achievement of a sufficient mechanical stability of the Cu 3D structure. The latter effect is related to the specific influence of Cl– ions during the electrodeposition process on the microstructural characteristics, such as the size of micropores in the walls of holes and crystallite aggregates that form dendritic branches. These structural changes, in contrast to the Cu samples deposited in a solution without additives, resulted in larger real surface areas, while the denser structures deposited in the presence of Cl– ions ensured the mechanical stability of the 3D structure.