Effect of Reducing Agents on Electrolyte Purification: Mechanism, Electrochemical Properties, and Microstructural Analysis of Deposits

This study focused on preparing electrowinning nickel for superalloys and examining the purification effects of reducing agents on the electrolyte. The electrochemical behaviors of the electrolyte before and after purification with the optimal reducing agent were analyzed using linear sweep voltammetry, cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS). The microstructure of the deposited layer was characterized using X‐ray diffraction, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The results showed that with 1 g/L sodium borohydride, the electrolyte achieved deep purification, with main reduction products including elemental nickel, nickel boride, and nickel borate. Electrochemical results indicated that the deposition kinetics of the purified electrolyte were superior to those of the industrial electrolyte, with a reduction potential of 1.14 V versus SCE, and the nucleation mechanism of nickel electrodeposition was unaffected. Impedance results showed no influence on the interfacial reaction mechanism. Microstructure analysis revealed the deposited layers exhibited <210> and <100> fiber textures, with the purified electrolyte sample showing the highest Σ3 boundary content (42.5%). These findings indicate that sodium borohydride achieves more efficient impurity removal than conventional reducing agents while maintaining favorable electrochemical behavior and microstructural characteristics, highlighting its significant potential as a high‐efficiency and industrially viable purification strategy.