Abstract
The electrochemical behaviour of LaNi
3.55Mn
0.4Al
0.3Co
0.75−
x
Fe
x
(
x
=
0, 0.15, 0.55, 0.75) intermetallic compounds has been studied and presented [C. Khaldi, H. Mathlouthi, J. Lamloumi, A. Percheron-Guégan, Int. J. Hydrogen Energy 29 (2004) 307–311; C. Khaldi, H. Mathlouthi, J. Lamloumi, A. Percheron-Guégan, J. Alloys Compd. 360 (2003) 266–271; C. Khaldi, H. Mathlouthi, J. Lamloumi, A. Percheron-Guégan, J. Alloys Compd. 384 (2004) 249–253]. It has been deduced that the LaNi
3.55Mn
0.4Al
0.3Co
0.4Fe
0.35 compound has interesting electrochemical properties. In this paper we present the electrochemical study of LaNi
3.55Mn
0.4Al
0.3Co
0.4Fe
0.35 compound properties compared with the parent LaNi
3.55Mn
0.4Al
0.3Co
0.75 compound. Several techniques, such as, the chronopotentiometry, the constant potential discharge (CPD), the cyclic voltammetry (CV) and the linear polarization (LP) were applied to characterize these electrochemical properties. The electrochemical discharge capacity of the LaNi
3.55Mn
0.4Al
0.3Co
0.75 alloy increases to reach 294
mAh
g
−1 after few cycles only (five cycles). However, the activation of the LaNi
3.55Mn
0.4Al
0.3Co
0.4Fe
0.35 alloy takes more than 20 cycles to be achieved and the obtained maximum discharge capacity is 194
mAh
g
−1. The hydrogen diffusion coefficient
D
H was determined by constant potential discharge and cyclic voltammetry techniques. The obtained values of the LaNi
3.55Mn
0.4Al
0.3Co
0.75 and LaNi
3.55Mn
0.4Al
0.3Co
0.4Fe
0.35 compounds are 6.29
×
10
−11 and 7.62
×
10
−11, and 2
×
10
−8 and 7.5
×
10
−8
cm
2
s
−1 by CPD and CV techniques, respectively. The exchange current density values, determined by a linear polarization technique, are 44 and 27
mA
g
−1, respectively, for LaNi
3.55Mn
0.4Al
0.3Co
0.75 and LaNi
3.55Mn
0.4Al
0.3Co
0.4Fe
0.35 alloys.