A study of Electrochemical Reactions on Poly-Crystalline Nickel Surfaces in Nickel Sulfamate Electrolyte by Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy measurements under a smal alternating current were performed to investigate the electrochemical reactions on poly-crystalline nickel surfaces in nickel sulfamate electrolyte. The Nyquist diagrams exhibit the absence of inductive loops for the frequency range from 50MHz to 100kHz. A condition for the existence of inductive loops derived in this study suggests that the electrocrystallization of Ni^ ions may take place in the slow reaction step Ni^+e^-→Ni^+_ and fast reaction step Ni^+_+e^-→Ni. In addition, the reaction impedances are found to have two exponents that slightly deviate from the values predicted by a homogeneous charge-transfer reaction model