Electroplating of Ni Using a Polyelectrolyte Membrane: Effect of Deposition Conditions on Interfacial Ion-transport Kinetics and Current Efficiency (Supporting Information)

In this study, we investigated the ion penetration rate into a solid electrolyte membrane, the nickel deposition rate, the current efficiency, and the effects of HCl addition under various electrodeposition conditions using a recently developed electrodeposition process (solid electrodeposition, SED), in which a solid electrolyte membrane serving as the ion-transport phase is placed on the cathode. Constant-voltage electrolysis was performed while varying the deposition conditions, and the resulting current efficiencies were calculated. The highest current efficiency (85.7 %) was obtained at a nickel (II) chloride (NiCl2) concentration of 1.0 mol L−1, an hydrochloric acid (HCl) concentration of 0.2 mol L−1, a reaction temperature of 70 °C, and an applied voltage of 0.8 V. Characterization of the deposited films by scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed that dense, crystalline nickel films were formed under conditions that yielded high current efficiency. These results demonstrate that the SED process, previously applicable only to copper deposition, can be successfully extended to nickel electroplating without producing mist, sludge, or waste effluents.