Improved durability of hydrogen storage alloys

An effective and durable hydrogen storage module was required to fuel micro-power systems. Two primary specifications for the hydrogen fuel module in this application were a high volumic storage capacity and rapid hydrogen storage and release under atmospheric pressure or lower at room temperature. In addition, the hydrogen module should be operable for thousands of cycles with fast hydriding and dehydriding rates and be resistant to deactivation on exposure to air for many months and longer. In our prior work, mechanical grinding a small amount of palladium with the hydrogen storage alloys was shown to greatly improve the hydrogen storage performance. The palladium treatment of three intermetallic alloys, AB5 type LaNi4.7Al0.3 and CaNi5, and A2B type Mg2Ni, lowered the activation pressure to sub-atmospheric pressure at room temperature and also significantly increased the hydrogen absorption and desorption rates. This work focused on the durability of hydrogen absorption and desorption performances after exposure of the storage materials to air. The palladium treated hydrogen storage alloys retained both low activation pressures and fast absorption and desorption rates even after more than 2 years air exposure.