Low-voltage anodizing of copper in sodium bicarbonate solutions. (1st March 2023)

• Record Type: Journal Article
• Authors: Brudzisz, Anna; Giziński, Damian; Liszewska, Malwina; Wierzbicka, Ewa; Tiringer, Urša; Taha, Safeya A.; Zając, Marcin; Orzechowska, Sylwia; Jankiewicz, Bartłomiej; Taheri, Peyman; Stępniowski, Wojciech J.
• Is Part Of: Electrochimica acta. Volume 443(2023)
• Publication Date: 2023-03-01
• Subjects: Copper -- Electrooxidation -- Malachite -- Carbon dioxide reduction reaction -- Anodic films; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2023.141918
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Anodizing voltage influence the morphology of layers formed on copper in NaHCO3 . Ribbons clusters composed of crystalline malachite and amorphous Cu2 O are formed. Ribbons clusters growth is reflected by current density changes during anodizing. Obtained materials can be successfully applied for CO2 reduction reaction. Abstract: The low-voltage (< 5 V) anodization of copper in aqueous solutions of sodium bicarbonate was studied for the first time. As demonstrated, this method leads to the formation of microstructures on a copper surface, that are composed of malachite (CuCO3 ·Cu(OH)2 ). Moreover, by tuning the operating conditions, i.e., applied cell voltage and electrolyte concentration, different surface morphologies can be grown. As shown by electron microscopy investigation, clusters of ribbons corrosion pits or nonuniformly located powdery precipitates are formed when the low anodizing voltage is applied. Anodization at 1.0 V in 0.4 M sodium bicarbonate solution led to the formation of a velvet-like, deep black anodic layer that covered the whole metal surface with ribbon-resembling structures. A thorough investigation of the obtained anodic layers with X-ray diffraction (XRD), X-ray adsorption (XAS), Raman, and X-ray Photoelectron Spectroscopy (XPS) uncovered the mixed crystalline-amorphous nature of the anodic copper species. Besides dominating the crystalline malachite phase, the amorphous cupric oxide was also identified. This composition offers promising features for catalytic applications, hence, low-voltage anodized copper was tested in an electrochemical CO2 reduction reaction to explore one possible application of the presented material. The current density of 4.7 mA cm −2 was registered for the selected sample. Graphical abstract: Image, graphical abstract