Gaseous and Electrochemical Hydrogenation Properties of LaNi4.3(Co, Al)0.7 -xInx Alloys

In this paper the effect of indium on the hydrogenation behaviour of the LaNi4,3(Co, Al)0.7-x Inx (x = 0, 0.1, 0.2, 0.3) alloys at room temperature is presented. The pressure–composition (p–c) measurements show that the highest hydrogen concentration of 1.68 wt.% is reached for indium-free (x = 0) alloy. The partial substitution of Al or Co by In causes a slight diminishing of maximum hydrogen concentration. Indium decreases also the plateau hydrogen equilibrium pressure from peq = 0.37 bar (In-free alloy) to peq = 0.06 bar (for LaNi4.3Co0.2In0.2Al0.3Hy) hydride. The electrochemical performance of the studied alloys were characterized using dc. polarization techniques. Electrochemical galvanostatic hydrogenation experiments at 60 mA/g discharge rate revealed the largest discharge current capacity of 305 mAh/g for LaNi4.3Co0.4Al0.2In0.1 alloy. The hydrogen discharge capacity evidently drops with total substitution of aluminium by indium. There is no significant difference in the discharge potentials for the tested electrodes. The relative diffusion coefficient of hydrogen (D/a2) varies in the range of (1.2 to 3.5) ·10-5 s-1.