Hydrogen storage in metal hydrides

The storage of hydrogen as a metal hydride is discussed. Properties of some representative hydrogen-storage mediums (MgH/sub 2/, Mg/sub 2/NiH/sub 4/, VH/sub 2/, FeTiH/sub 1/ /sub 95/, LaNi/sub 5/H/sub 7/, liquid hydrogen, and gaseous hydrogen) are compared. Magnesium hydride, the more promising of the two binary hydrides, is thought to be only a borderline possibility as a hydrogen-storage medium at present. Of the three ternary hydrides listed the leading contender is iron-titanium hydride. It's main advantage over lanthanum-pentanickel hydride is one of cost. All the metal hydrides listed have a higher hydrogen storage capacity than an equal volume of liquid or gaseous hydrogen has. Energy densities (watt-hours per kilogram) of various automotive power sources either already in existence or proposed are tabulated. Metal hydrides lag far behind gasoline in terms of energy density, but they are competitive with electric batteries in this respect.