Kinetic Behavior of Metal Hydride Electrode by Means of AC Impedance

A mathematical model for the electrochemical impedance spectroscopy of a metal‐hydride electrode was developed. The model was used to study the effect of various parameters on predicted kinetic behavior. The simulations obtained using the model show that the first arc appearing in the higher frequency range is due to a charge‐transfer reaction, the second arc in the middle frequency range represents the hydrogen transfer between the absorption and adsorption, and the third arc (or curve) at low frequency corresponds to the diffusion of absorbed hydrogen in the alloy. As the rate constant of the charge‐transfer reaction, the rate constant of hydrogen transfer, and the diffusion coefficient increase, all of the three arcs moved toward higher frequency range and the diameter of the arcs decreases. The model simulations also show that the state of discharge plays an important role in the Nyquist plot of the metal‐hydride electrode. The kinetic parameters used in the model predictions are those for .