Kinetic hydrogenation of the electrode-electrolyte interface for LaY2Ni9 Nickel Metal Hydride accumulators

Impedance spectrum for the hydrogen adsorption-absorption mechanism of LaY
2
Ni
9
electrode was analyzed through an equivalent circuit based on a well understanding of the various processes happening at the interface electrode/electrolyte. The equivalent circuit model takes into account the charge transfer phenomenon, the transition phase of the atomic hydrogen between adsorbed/absorbed states before its diffusion within the alloy. Kinetic parameters such as the specific exchange current density, I
0,EIS
, the double layer capacitance, C
dl
and the adsorption capacitance, C
ad
, were determined for the LaY
2
Ni
9
electrode versus cycle number using impedance spectroscopy technique. The results of EIS measurements indicate a correlation between the evolution of these kinetic parameters and those determined by other electrochemical techniques. Another correlation is observed between the exchange current density determined by EIS, I
0,EIS
, and that determined by cyclic voltammetry, I
0,CV
which related to the applied perturbation type.