Roughness Factors of Electrodeposited Nanostructured Copper Foams

Copper-based electrocatalytic materials play a critical role in various electrocatalytic processes, including the electroreduction of carbon dioxide and nitrate. Three-dimensional nanostructured electrodes are particularly advantageous for electrocatalytic applications due to their large surface area, which facilitates charge transfer and mass transport. However, the real surface area (RSA) of electrocatalysts is a crucial parameter that is often overlooked in experimental studies of high-surface-area copper electrodes. In this study, we investigate the roughness factors of electrodeposited copper foams with varying thicknesses and morphologies, obtained using the hydrogen bubble dynamic template technique. Underpotential deposition (UPD) of metal adatoms is one of the most reliable methods for estimating the RSA of highly dispersed catalysts. We aim to illustrate the applicability of UPD of lead for the determination of the RSA of copper deposits with hierarchical porosity. To find the appropriate experimental conditions that allow for efficient minimization of the limitations related to the slow diffusion of lead ions in the pores of the material and background currents of the reduction of traces of oxygen, we explore the effect of lead ion concentration, stirring rate, scan rate, monolayer deposition time and solution pH on the accuracy of RSA estimates. Under the optimized measurement conditions, Pb UPD allowed to estimate roughness factors as high as 400 for 100 µm thick foams, which translates into a specific surface area of ~6 m²·g^-1. The proposed measurement protocol may be further applied to estimate the RSA of copper deposits with similar or higher roughness.