The impact of ethylenediaminetetraacetic acid (EDTA) additive on anodization of copper in KHCO3 – hindering Cu2+ re-deposition by EDTA influences morphology and composition of the nanostructures

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.

Nanostructured Anodic Copper Oxides as Catalysts in Electrochemical and Photoelectrochemical Reactions

Recently, nanostructured copper oxides formed via anodizing have been intensively researched due to their potential catalytic applications in emerging issues. The anodic Cu2O and CuO nanowires or nanoneedles are attractive photo- and electrocatalysts since they show wide array of desired electronic and morphological features, such as highly-developed surface area. In CO2 electrochemical reduction reaction (CO2RR) copper and copper-based nanostructures indicate unique adsorption properties to crucial reaction intermediates. Furthermore, anodized copper-based materials enable formation of C2+ hydrocarbons and alcohols with enhanced selectivity. Moreover, anodic copper oxides provide outstanding turnover frequencies in electrochemical methanol oxidation at lowered overpotentials. Therefore, they can be considered as precious metals electrodes substituents in direct methanol fuel cells. Additionally, due to the presence of Cu(III)/Cu(II) redox couple, these materials find application as electrodes for non-enzymatic glucose sensors. In photoelectrochemistry, Cu2O-CuO heterostructures of anodic copper oxides with highly-developed surface area are attractive for water splitting. All the above-mentioned aspects of anodic copper oxides derived catalysts with state-of-the-art background have been reviewed within this paper.