Investigating the Role of Cerium in Interfacial Evolution During Nickel Electrodeposition

ABSTRACT To clarify how Ce 3+ regulates the interfacial evolution during nickel electrodeposition and how such regulation affects deposit microstructure, this study investigates the electrodeposition of Ni from a nickel sulfate electrolyte onto a copper substrate. By introducing varying concentrations of Ce 2 (SO 4 ) 3 into a laboratory‐prepared Watts bath, the regulatory role of Ce 3+ in nickel electrodeposition kinetics was systematically examined using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). In situ, microscale mapping of the spatial distribution of local surface reactivity during deposition was carried out via scanning electrochemical microscopy (SECM). These observations were complemented by SEM, AFM, and XRD to provide a comprehensive assessment of the deposit's surface morphology and crystalline structure. The results demonstrate that an appropriate Ce 3+ addition markedly increases the initial nucleation density, enhances interfacial reaction uniformity, and thereby promotes grain refinement and deposit densification; conversely, excessive Ce 3+ —through an intensified interfacial coverage effect—partially suppresses deposition uniformity. SECM findings further corroborate, at the microscale, that Ce 3+ acts primarily to homogenize the distribution of local electrochemical activity, modulating the electrode/solution interfacial environment rather than intrinsically altering the deposit's crystal structure.