LiBH_4·NH_3的热分解合成及其放氢行为

Thermal-decomposition synthesis and hydrogen desorption behavior of LiBH_4·NH_3

研究了LiBH4·NH3的热分解合成、结构及其放氢行为。在密闭反应器中,将LiBH4的饱和氨合物加热至60~80℃进行热分解,成功制备得到LiBH4·NH3。研究表明：该方法制备的LiBH4·NH3的晶胞参数为a=0.597 4（1）nm,b=0.4466（2）nm,c=1.434 1（3）nm;在氩气流下,热分解制备得到的LiBH4·NH3的分解过程是一个两步反应,其在较低温（〈300℃）时即可分解释放出氢气;在密闭反应器中,样品的热分解可分为2个阶段,在室温至300℃的范围内,LiBH4·NH3主要释放氨气,同时伴随放氢,从300℃至600℃,主要发生的是放氢反应,所释放的氨与LiBH4反应放氢,同时伴随着LiBH4的分解放氢。比较发现,通过水浴热解饱和氨合物的方法制备得到的LiBH4·NH3的放氢性能较常温抽真空制备样品有明显改善。

This study focuses on thermal-decomposition synthesis,structure and dehydrogenation behaviors of lithium borohydride monoammoniate（LiBH4 ·NH3 ）.LiBH4 ＆#183;NH3 was synthesized by thermal decomposition of the saturated ammoniateof LiBH4 at 60-80 ℃ in a closed reactor.The lattice parameters of the as-prepared LiBH4 ＆#183;NH3 were a=0.597 4（1）nm,b=0.446 6（2） nmand c=1.434 1（3）nm.Under Ar flow,the thermal decomposition of the as-prepared LiBH4 ＆#183;NH3 was a two-step reaction, and hydrogen was released below 300 ℃.While the as-prepared LiBH4 ·NH3 decomposed within the close reactor,it was also a two-step reaction.Simultaneous release of ammonia and hydrogen was observed below 300 ℃.At 300-600 ℃,the released am-monia combined with the intermediate LiBH4 to release hydrogen concurrent with the decomposition of LiBH4 .Compared to the performance of the sample synthesized by vacuuming at room temperature,the dehydrogenation performance of LiBH4 ＆#183;NH3 pre-pared by thermal decomposition of saturated ammoniate of LiBH4 was significantly improved.