High storage capacity for hydrogen and low price suggest that magnesium and its alloys could be advantageous for use in battery electrodes and gaseous-hydrogen storage systems, combined with a fuel cell to convert the hydrogen into electrical energy. Research is necessary into Mg based alloys that form less stable hydrides and proton-conducting membranes for raising the operation temperatures. Best materials for the negative electrode of small Ni-MH (nickel-metal hydride) batteries are alloys of the type (RE)Ni5 (RE = rare-earth elements). Absorption-desorption characteristics are given and discussed for LaNi5 and for the eutectic alloy Mg-23.5 wt-%Ni. Pressure and temperature requirements for large energy-storage systems are quite different from those for household electronic applications (careful management of the enthalpy of hydride formation/dissociation; near-ambient pressure is not indispensable; stable hydrides may be advantageous for safety). Thermodynamic data for selected metal/hydrogen systems (LaNi5, FeTi, Mg2Ni, Mg Mg-23.5 wt-%Ni) are presented and discussed. Faster hydrogen absorption/desorption kinetics are recorded for a composite La2Mg17 with LaNi5 and for fluorination of a Mg-Ni alloy. Special considerations for large-capacity H2 storage systems are given (possibilities for supplying the enthalpy of hydride decomposition). Future prospects refer to the protonic membrane (operating temperatures), increasing the unit-cell volume of the crystalline metal host and nanocrystalline materials. Their low cost and availability make the Mg-based hydrides most promising for fuel-cell vehicles.
Hydrogen storage in magnesium-based alloys
MRS Bulletin ; 24 , 11 ; 40-44
1999
5 Seiten, 3 Bilder, 1 Tabelle, 23 Quellen
Aufsatz (Zeitschrift)
Englisch
Magnesiumlegierung , Magnesium , Wasserstoffspeicher , Wasserstoffelektrode , Temperaturbereich , Druckbereich , Dissoziation , Metallhydrid , Reaktionsenthalpie , Membran , Reaktionskinetik , Wasserstoffzelle , Korrosionswiderstand , Mikrostruktur , Elementarzelle , Automobilindustrie , reversibler Prozess , Wasserstoffspeicherlegierung , Magnesiumnickellegierung
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