a L.M.M.P, ESSTT, 5 Avenue Taha Hussein, 1008, Tunis, Tunisia
b L.C.M.T.R, G.L.T, CNRS, 2-8 Rue Henri Dunant, 94320, Thiais Cedex, France
Abstract:
The effect of iron substitution on the electrochemical behaviour of LaNi3.55Mn0.4Al0.3Co0.75−xFex compounds (x=0, 0.15, 0.55) has been studied by chronopotentiometry and cyclic voltammetry techniques. The maximum capacity decreases linearly from 308 to 239 mAhg−1 when the iron content increases from 0 to 7.3 wt.% (x=0.55). This decrease can be explained by the corrosion of the alloy in the aqueous KOH electrolyte. In spite of this decrease and of the long time needed for the activation, a good stability of discharge capacity was observed in LaNi3.55Mn0.4Al0.3Co0.75−xFex compounds. The reversibility of the electrochemical redox reaction of LaNi3.55Mn0.4Al0.3Co0.75−xFex alloy electrodes has been observed in the alloys least rich in iron. The hydrogen diffusivity in LaNi3.55Mn0.4Al0.3Co0.75−xFex alloy electrodes decreases when increasing the iron content. The obtained values of the hydrogen diffusion coefficient DH, varies between 2.1×10−7 and 8.2×10−9 cm2 s−1 depending on the iron content of the electrode.