Properties of intermetallic compounds suitable for hydrogen storage applications

Hydrides of intermetallic compounds (IMC) belong to the class of functional materials whose possible applications cover a wide temperature range, from a few Kelvin up to 500 K. Each application is correlated to a well-defined property, i.e. chemical reactivity for purification, temperature/pressure relationship for sensors, hydrogen storage capacity converted into energy for hydride chemical engines, or converted into electrical current for hydride batteries. Up to now, only the hydride batteries have reached the consumer level while for hydrides obtained by direct reaction between hydrogen gas and the parent solid phase, applications have not yet been successful suggesting that many problems remain to be solved. In this paper, we will be concerned with the factors influencing the absorption properties according to the type of application. It will also be shown that the dynamic behavior of these highly defective materials is difficult to control due to the hysteresis accompanying the formation-decomposition of the hydrides compounds. Hysteresis reflects irreversibility and contributes to the degradation of the absorption properties over the long-term behavior. (C) 2002 Elsevier Science B.V. All rights reserved.