Targeted preparation of metallic materials via innovative electrochemical approaches

Metallic functional materials and surfaces are of great importance in modern society to upgrade traditional industries and boost the development of advanced technologies. The demand for these materials is ever-increasing due to global population growth and more widespread industrialization, while the required state-of-art manufacturing techniques are facing high-grade raw materials depletion and growing environmental concerns. Consequently, there is a need for effective exploitation of currently underutilized resources coupled with more sustainable manufacturing. In this thesis, the direct preparation of functional materials and surfaces from hydrometallurgical Zn process solution (tens g/L Zn) containing ppm or lower concentrations of Ag and/or Cu has been investigated using a novel electrochemical method based on combined electrodeposition and redox replacement (EDRR). EDRR experiments were initially performed in two-component solutions (containing Zn-Ag and Zn-Cu), after which a more complicated Zn-Cu-Ag three-component solution was investigated. Selected surfaces obtained by EDRR were subject to electrochemical dealloying to further modify their properties. The effects of the operating parameters and the process mechanisms were studied in detail through the application of various analytical techniques like scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), anodic linear sweep voltammetry (ALSV), X-ray diffraction (XRD) and electrochemical quartz crystal microbalance (EQCM). Moreover, selected experimental surfaces were examined by ultraviolet-visible (UV/VIS) spectroscopy or potentiodynamic polarization to explore characteristics for potential applications. Results indicate that the EDRR technique can produce various metallic materials from Zn process solutions including Ag/Zn and Ag/Cu nanoparticles, Ag/Zn, Cu/Zn and Cu/Zn/Ag alloys with controllable morphology, crystalline phase and chemical composition. In contrast to traditional electrodeposition, EDRR can combine different metals with distinct redox potentials without the addition of complexing agents. Furthermore, the use of electrochemical dealloying allowed porous/dendritic Ag-rich materials to be obtained by selective dissolution of Zn from the EDRR produced Ag/Zn alloys. Additionally, by careful selection of experimental conditions, tunable SPR behavior for both porous/dendritic Ag-rich materials and Cu/Ag nanoparticles and desirable corrosion properties for the Cu/Zn and Cu/Zn/Ag surfaces could be obtained. Overall, this study demonstrates that EDRR offers a promising approach for the direct preparation of functional materials and surfaces from existing metallurgical process solutions. The method decreases the use of virgin raw materials as no dedicated bath solutions, with separated and high purity chemicals or additives are needed. This paves the way toward increased sustainability in the manufacturing of functional materials and surfaces.