The copper particles plated onto the ITO electrode in this study were heterogeneous and representative of a real-world catalyst (Figure ). A significant number of particles were faceted. The most prevalent particle facet families were the <100> and <111> (Figure ). The heterogeneous morphology of the electroplated copper particles is linked to their electrodeposition within confined volumes, influenced by minor hydrodynamic fluctuations and substrate imperfections (Figure ). This is a difference from several previous works that evaluated the stability of copper nanoparticles with well-defined size and morphology.