Hydrogen storage properties of 2LiNH 2 + LiBH 4 + MgH 2

Abstract

We have investigated the ternary mixture of complex hydrides with stoichiometry 2LiNH 2 + LiBH 4 + MgH 2, and have identified a set of novel hydrogen storage reactions. One of these reactions involves the known reversible reaction Mg(NH 2) 2 + 2LiH ↔ Li 2Mg(NH) 2 + 2H 2. Previous studies have shown that initiating this reaction from the binary mixture 2LiNH 2 + MgH 2 results in poor hydrogen desorption kinetics and a small amount of NH 3 release. In contrast to this behavior, here we demonstrate that by starting from the ternary mixture 2LiNH 2 + LiBH 4 + MgH 2, the above reaction can proceed at lower temperatures and with improved kinetics, while maintaining reversibility. The advantage of starting with the ternary mixture can be traced to the subsequent formation, melting, and reaction of Li 4BH 4(NH 2) 3 with MgH 2 to form the mixed imide phase Li 2Mg(NH) 2, which acts as a seed for the reversible reaction, and is at least partly responsible for the improved kinetic response.