Electrochemical study of hydrogen diffusion behavior in Mg2Ni-type hydrogen storage alloy electrodes

Hydrogen diffusion behavior in Mg2Ni-type hydrogen storage alloy electrodes was characterized by using both potentiostatic polarization method, based on a spherical diffusion model, and electrochemical impedance spectroscopy (EIS) technique. The values of the diffusion coefficients of hydrogen in Mg 2Ni and Mg(1.)9Vo(0.1)Ni(0.)8Al(0.2) are 1.2 x 10(-11) similar to 1.57 x 10 (-10) and 3.1 similar to 7.6 x 10(-9) cm(2)/s, respectively. The values of diffusion coefficients decline notably with the increase in depth of discha rge (DOD). The decay rate of diffusion coefficient in Mg2Ni with DOD is muc h quicker than that in Mg1.9V0.1Ni0.8Al0.2. The experimental results sugges ted that the substitutions of V and Al for Mg and Ni in Mg2Ni could signifi cantly improve the hydrogen diffusion performance in this alloy and thus su bstantially increase discharge capacity of the electrode. (C) 1999 Internat ional Association for Hydrogen Energy. Published by Elsevier Science Ltd. A ll rights reserved.