Hydrogen Gas Phase and Electrochemical Hydriding of LaNi(5−x)M(x) (M = Sn, Co, Al) Alloys

Hydriding/dehydriding properties of a series of LaNi(5) based alloys were compared by applying both hydrogen gas phase and electrochemical hydrogen charge/discharge methods. The highest hydrogen absorption capacity of 1.4 wt.% H(2) was found for LaNi(4.3)Co(0.4)Al(0.3), although LaNi(4.8)Sn(0.2) also reveals comparable hydrogen capacity (>1.3%). A significant difference in the hydriding kinetics was observed for all studied alloys before and after activation. The activated alloys (5 cycles at 65 °C, 40 atm. H(2)) reach their maximum capacities after less than a minute, whereas the pure LaNi(5) alloy needs several minutes for complete hydriding. The electrochemical hydriding/dehydriding behavior of the alloys reveals superior performance of LaNi(4.3)Co(0.4)Al(0.3) and LaNi(4.8)Sn(0.2) compared to the other compositions studied, as the capacity of LaNi(4.8)Sn(0.2) decreases by only 10% for 60 charge/discharge cycles at a current density of 100 mA/g. Good agreement between the hydrogen sorption kinetics of the alloys obtained electrochemically and from hydrogen gas phase has also been observed.