Improvement of hydrogen storage property of three-component Mg(NH2)2–LiNH2–LiH composites by additives†
Abstract
The three-component Mg(NH2)2–LiNH2–4LiH composite reversibly stores hydrogen exceeding 5 wt% at a temperature as low as 150 °C. In this work, a number of additives such as CeF4, CeO2, TiCl3, TiH2, NaH, KBH4 and KH are added to the Mg(NH2)2–LiNH2–4LiH composite in order to improve its kinetics, thermodynamics and cycling properties. Addition of 3 wt% of KH reduces the dehydrogenation onset temperature of the Mg(NH2)2–LiNH2–4LiH composite to below 90 °C without emission of NH3 during the whole dehydrogenation process up to 450 °C. Moreover, the dehydrogenation kinetics and cycling ability are remarkably enhanced upon KH-addition. The reaction model of the Mg(NH2)2–LiNH2–4LiH composite is altered upon KH-addition with the active molecule density improved by about 200 times. In addition, by optimization of the ratio of Mg2+ to Li+ in the Mg(NH2)2–LiNH2–LiH system, several novel composites, e.g., Mg(NH2)2–2LiNH2–5.9LiH–0.1KH and Mg(NH2)2–LiNH2–5.9LiH–0.1KH, with the hydrogen storage capacity exceeding 6 wt% without emission of NH3 below 250 °C are developed. Our study demonstrates that there are various undiscovered candidates with promising hydrogen storage properties in the three-component Li–Mg–N–H system.