Enhancement of Hydrogen Storage in Destabilized LiNH2 with KMgH3 by Quick Conveyance of N‑Containing Species

The advantage of potassium–magnesium bimetallic hydride as novel destabilization agent for LiNH2 is demonstrated by a comparative study among MgH2-, NaMgH3-, and KMgH3- systems. LiNH2 combined with KMgH3 not only results in a substantial decreased desorption temperature by >60 °C and suppression of NH3 release but also enhances sorption kinetics two to five times in comparison with the single MgH2 or NaMgH3. A high reversible capacity of >65% is also achieved, even recharging under milder conditions. Through detailed structural analysis on the desorption products in various stages of these combined systems, we proposed a “self-concerted” reaction mechanism in which the in situ formed active MgH2 and KH by KMgH3 are involved in LiNH2 decomposition. In addition, the remarkable promotion in conveyance of N-containing species by highly active KH compared with NaH is believed to be responsible for the superior destabilizing effect of KMgH3 over NaMgH3 in improving hydrogen sorption kinetics of LiNH2.