A study of charge-transfer reactions on (110) single-crystal nickel surfaces in nickel sulfamate electrolyte using electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy measurements under a small alternating current density were performed to investigate electrochemical reactions on (110) single-crystalline nickel surfaces in nickel. sulfamate electrolyte. The reaction impedance shows a power law of the ac modulation frequency, and two exponents for the reaction resistance and reaction capacitance are found to approximately agree with the values predicted by a homogeneous charge-transfer reaction model. In addition, the Nyquist diagrams exhibit the absence of inductive loops for the frequency range from 50 mHz to 100 kHz. A condition for the existence of inductive loops derived in this study suggests that the electrocrystallization of Ni2+ ions may take place in the slow reaction step Ni2+ + e(-) --> Ni-abs(+) and in the fast reaction step Ni-abs(+) + e(-) --> Ni.