Exploring the Impact of Chelating Agents on Copper Oxide Layer Formation and Morphology

The morphological evolution of copper oxide surfaces during anodization was investigated using scanning electron microscopy (SEM), chronoamperometry, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The addition of ethylenediaminetetraacetic acid (EDTA) as a Cu²⁺ chelating agent near the anode slows key mechanistic steps, providing insight into the factors driving the formation of crystalline Cu(OH)₂ nanoneedles. The correlation of chronoamperometric data with SEM images revealed a four-stage process, beginning with the formation of an initial passive oxide layer, followed by nucleation. The comprehensive analysis of experimental results demonstrates that while electrochemical processes are necessary to initiate nanoneedle growth, the subsequent growth mechanism is not driven by direct electrochemical oxidation. Instead, supersaturation of the dissolved copper species near the electrode surface leads to nucleation and growth of Cu(OH)₂ nanoneedles. The interaction with EDTA at different concentrations results in various morphologies of copper oxide surfaces, ranging from nanoneedles to disordered porous structures. This unique mechanism of copper oxide formation during anodization enables precise control of the surface properties, offering potential applications in catalysis and various energy technologies, including both production and storage.