Synthesis of a ternary amide LixKy（NH2）x+y and a novel Li3K（NH2）4–xMgH2 combination system for hydrogen storage  

作　　者：Chao Li Changlong Li Meiqiang Fan Haichao Chen Kangying Shu Yu Zhang Mingxia Gao Yongfeng Liu Hongge Pan 

机构地区：[1]College of Materials Science and Engineering, China Jiliang University,Hangzhou 310018, Zhejiang, China [2]State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University,Hangzhou 310027, Zhejiang, China [3]School of Materials Science and Engineering, Hubei University of Automotive Technology,Shiyan 442002, Hubei, China

出　　处：《Journal of Energy Chemistry》2019年第8期37-43,I0002,共8页能源化学（英文版）

基　　金：supported by the National Natural Science Foundation(Grant number 51501175 and 51671172);the Zhejiang Provincial Natural Science Foundation of China(Grant number LQ16E010001 and LR16E010002);the Hubei Provincial Natural Science Foundation of China(Grant number 2015CFB498)

摘　　要：The ternary amides LiK2(NH2)3, LiK(NH2)2, and Li3 K(NH2)4 are successfully synthesized by ball milling mixtures of LiNH2 and KNH2, and the hydrogen storage properties of Li3K(NH2)4–xMgH2(x = 1, 2, 3,4) are systematically investigated. The Li3K(NH2)4–2 Mg H2 sample displays optimized hydrogen storage properties, releasing 6.37 wt% of hydrogen in a two-stage reaction with an onset temperature of 60 °C.The first dehydrogenation stage exhibits good reaction kinetics and thermodynamic properties because of a lower activation energy and appropriate enthalpy change. After full dehydrogenation at 130 °C, the Li3K(NH2)4–2 MgH2 sample absorbs 3.80 wt% of H2 below 160 °C in a variable temperature hydrogenation mode. Mechanistic investigations indicate that Li3 K(NH2)4 reacts with Mg H2 to produce Mg(NH2)2, LiH,and KH during ball milling. In the heating process, Mg(NH2)2 first reacts with Li H to form Li2 Mg2 N3 H3 and Li NH2, while KH works as a catalyst, and then, KH reacts with Li2Mg2N3H3 and Li NH2 to generate a new K-containing compound.The ternary amides LiK2（NH2）3, LiK（NH2）2, and Li3 K（NH2）4 are successfully synthesized by ball milling mixtures of LiNH2 and KNH2, and the hydrogen storage properties of Li3K（NH2）4–xMgH2（x = 1, 2, 3,4） are systematically investigated. The Li3K（NH2）4–2 Mg H2 sample displays optimized hydrogen storage properties, releasing 6.37 wt% of hydrogen in a two-stage reaction with an onset temperature of 60 °C.The first dehydrogenation stage exhibits good reaction kinetics and thermodynamic properties because of a lower activation energy and appropriate enthalpy change. After full dehydrogenation at 130 °C, the Li3K（NH2）4–2 MgH2 sample absorbs 3.80 wt% of H2 below 160 °C in a variable temperature hydrogenation mode. Mechanistic investigations indicate that Li3 K（NH2）4 reacts with Mg H2 to produce Mg（NH2）2, LiH,and KH during ball milling. In the heating process, Mg（NH2）2 first reacts with Li H to form Li2 Mg2 N3 H3 and Li NH2, while KH works as a catalyst, and then, KH reacts with Li2Mg2N3H3 and Li NH2 to generate a new K-containing compound.

关 键 词：Hydrogen storage Complex hydrides AMIDES REVERSIBILITY Reaction mechanisms 

分 类 号：TB34[一般工业技术—材料科学与工程]