Recyclable hydrogen storage system composed of ammonia and alkali metal hydride

Ammonia (NH3) reacts with alkali metal hydrides MH (M = Li, Na, and K) in an exothermic reaction to release hydrogen (H2) at room temperature, resulting that alkali metal amides (MNH2) which are formed as by-products. In this work, hydrogen desorption properties of these systems and the condition for the recycle from MNH2 back to MH were investigated systematically. For the hydrogen desorption reaction, the reactivities of MH with NH3 were better following the atomic number of M on the periodic table, Li < Na < K. It was confirmed that the hydrogen absorption reaction of all the systems proceeded under 0.5 MPa of H2 flow condition below 300 °C.