Dehydrogenation and Rehydrogenation of Ammonia Borane under Shock Loading: Ab Initio Molecular Dynamics Simulations
Dehydrogenation and Rehydrogenation of Ammonia Borane under Shock Loading: Ab Initio Molecular Dynamics Simulations
复制标题
冲击载荷下氨硼烷的脱氢和再氢化：从头算分子动力学模拟
DOI：
10.1021/acs.jpcc.0c07748
复制
发表时间：
2020-12-17
影响因子：
3.7
通讯作者：
Ji, Guang-Fu
中科院分区：
文献类型：
--
作者：
Huang, Yao-Yao;Ji, Lin-Xiang;Ji, Guang-Fu
氨硼烷（AB，NH3 BH 3）作为一种富氢材料，在储氢领域引起了人们极大的兴趣。然而，它的脱氢和再氢化的机理还没有得到充分的理解。采用从头算分子动力学方法研究了AB在冲击载荷作用下的初始分解过程。结果表明，B-H键断裂在反应引发中起着重要作用。H-2释放的三个主要反应途径被揭示。(I)异极二氢相互作用（N-H δ +中心点中心点H δ-B）和（II）同极二氢相互作用（B-H δ-中心点中心点H δ-B）仍然是最常用的反应机理。然而，一个直接的氢吸附和H-2释放机制（III）被发现。H自由基容易吸附B原子以形成五配位含硼物质，并有效地活化相邻的B-H键，其进一步断裂以形成H-2分子。此外，我们还发现了新生成的H-2与BNH化合物之间的氢化行为。此外，还探讨了H2-辅助下的类似H交换反应。根据我们的研究结果提出了可能的再氢化机理。这些理论计算不仅使人们对AB在冲击载荷下的分解过程有了全面的了解，而且对AB在冲击载荷下的再氢化储氢也有一定的指导意义。
Ammonia borane (AB, NH3BH3), as a hydrogen-rich material, has been attracting great interest in the field of hydrogen storage. However, the mechanism of its dehydrogenation and rehydrogenation is not sufficiently understood yet. In this work, the initial decomposition process of AB under shock loading is investigated using the ab initio molecular dynamics method. The results show that the B-H bond breaking plays a more important role in the reaction initiation. Three main reaction pathways for H-2 release are revealed. (I) Heteropolar dihydrogen interaction (N-H delta+center dot center dot center dot H delta--B) and (II) homopolar dihydrogen interaction (B-H delta-center dot center dot center dot H delta--B) are still the most popular reaction mechanisms. However, a direct hydrogen adsorption and H-2 liberation mechanism (III) is uncovered. The H radical readily adsorbs a B atom to form the pentacoordinate boron-containing species and efficiently activates the adjacent B-H bond, which further ruptures to form H-2 molecules. What is more, we discover the unexpected hydrogenation behaviors between new-formed H-2 and BNH compounds. In addition, the similar H exchange reactions assisted by H-2 are also explored. The probable rehydrogenation mechanisms are proposed based on our results. These theoretical calculations not only give a comprehensive understanding about AB decomposition under shock loading but also shed light on its rehydrogenation for hydrogen storage.