LiBH4/Mg17Al12-氢化物复合体系的放氢行为改善及其机制

摘要

Mg17Al12-hydride (abbreviated as MAH) was selected as a destabilization agent to improve de/rehydrogenation properties of LiBH4. 58LiBH4+Mg17Al12-hydride composite was prepared by ball-milling. It is found that the dehydrogenation of ball-milled LiBH4/MAH composite presents a two-step reaction for hydrogen release. The composite starts desorbing hydrogen at about 300 °C and yields 9.8%of hydrogen (mass fraction) below 500 °C. By adding MAH, the dehydrogenation kinetics of LiBH4 is improved and the dehydrogenation temperature of LiBH4 is also lowered by 20 °C. High rehydriding capacity of 8.3% was obtained for the dehydrogenated composite in the first cycle at 450 °C. The XRD analysis shows the formation of MgB2 and AlB2 in the dehydrogenation process, which reduces the thermodynamics stability of LiBH4 system and is beneficial to the reversible hydrogen storage behaviors of LiBH4/MAH composite.%选择 Mg17Al12-氢化物作为失稳剂与 LiBH4进行球磨以改善 LiBH4体系的吸放氢性能。研究表明， LiBH4/Mg17Al12-氢化物复合体系发生两步放氢过程。复合体系在300°C开始放氢并在500°C下产生9.8%的放氢量。通过添加Mg17Al12-氢化物，LiBH4的放氢动力学得到有效改善，并且其放氢温度降低20°C。复合体系的放氢产物在450°C的首次再加氢容量可高达8.3%。XRD分析表明，复合体系在放氢过程中所形成的MgB2和AlB2可降低LiBH4的热力学稳定性，进而有效改善LiBH4/Mg17Al12-氢化物复合体系的可逆储氢行为。