Electrochemical impedance spectroscopy and constant potential discharge studies of LaNi_(3.55)Mn_(0.4)Al_(0.3)Co_(0.75-x)Fe_x hydrides alloy electrodes

摘要

The electrochemical behaviour of LaNi_(3.55)Mn_(0.4)Al_(0.3)Co_(0.75-x)Fe_x(x = 0, 0.15, 0.55, 0.75) intermetallic compounds was investigated using chronopotentiometry, electrochemical impedance spectroscopy (EIS) and constant potential discharge (CPD) techniques. The maximum capacity decreases linearly from 338 to 295mAhg~(-1) when the iron content increases from 0 to 10wt. percent (x = 0.75). This decrease can be explained by the corrosion of the alloys in the aqueous KOH electrolyte. The hydrogen diffusion coefficient was determined by EIS and CPD. The obtained values are between 7 x 10~(-10) and 2 x 10~(-9) cm~2 s~(-1). The exchange current densities of MH electrodes were estimated by EIS. The obtained values are between 15 and 66 mA cm~(-2).