Hydrogen sorption kinetics and suppression of NH3 emission of LiH-sandwiched LiNH2-LiH-TiF4-MWCNTs pellets upon cycling

Abstract

NH3 emission during decomposition of LiNH2-LiH composite reduces hydrogen storage capacity and poisons fuel cell catalysts. The idea of sandwiching LiNH2-LiH pellet with LiH layers (10–30 wt%), reacting with NH3 and transforming into H2 is proposed. The LiH-sandwiched LiNH2-LiH pellets show no sign of NH3 release with the hydrogen capacitates of 3.5–4.0 wt% H2 during the 1st cycle. Upon cycling (the 2nd-6th cycles), decomposition of LiH-sandwiched LiNH2-LiH pellet with the low amount of LiH layer (10 wt%) shows NH3 signal, while that with 30 wt% LiH layers liberates only hydrogen with the storage capacities of 2.3–2.6 wt% H2. Effective dehydrogenation and reversibility of the 30 wt% LiH-sandwiched LiNH2-LiH pellet are explained by not only sufficient content and mechanical stability of LiH layers but also the formation of the new active phases (LiH1−xFx and Li2NH1−yFy).