Kinetics of the hydrogen evolution reaction in stoichiometric and non-stoichiometric hydrogen storage alloys for nickel-hydrogen batteries

Abstract

The kinetics of the hydrogen evolution reaction in stoichiometric and non-stoichiometric hydrogen storage alloys with compositions of Mm(Ni 3.6Mn 0.4Al 0.3Co 0.7) x (Mm = misch metal, 0.88 ⩽ x ⩽ 1.12) were investigated by measuring the overvoltage decay immediately after the interruption of an applied cathodic current. The total overvoltage η for hydrogen evolution was divided into two components (η 1 and η 2) corresponding to the elementary reactions. The mechanism of the hydrogen evolution reaction was analyzed on the basis of the dependence of η 1 and η 2 on current density. The effect of the stoichiometric ratio on the performance of the alloys as a negative electrode material in nickel-hydrogen batteries was discussed from the standpoint of relative velocity of the elementary reactions.