A first-principle study of dehydrogenation mechanism from Sr(NH2BH3)2 was performed. Three different pathways were explored for Sr(NH2BH3)2 monomer, and the most favorable dehydrogenation pathway involved the formation of the Sr-H group firstly, and then becoming the key hydride source for the consecutive H2 evolution. The intrinsic activation free energy barriers were 29.2, 30.7, 42.7, and 42.4 kcal/mol for four equivalent of H2 release at 298.15 K, which were slightly decreased by 0.3~2 kcal/mol at experimental temperature 333 and 366 K. For Sr(NH2BH3)2 dimer, the estimated intrinsic free energy barriers are 22.7, 30.4, 40.1, and 45.4 kcal/mol for four equivalent of H2 release, respectively. Although it seemed that the energy barriers for the second equivalent of H2 were still higher, considering the energy gain in the formation of dimer, − 18.1 kcal/mol, the first two equivalents of H2 release easily took place at experiment temperature. Thus, our calculations indicated that the most favorable dehydrogenation mechanism involved the strongly basic H− from Sr-H acting as a hydride source to accelerate the H2 release, and the effect of neighboring molecules in the solid phase should not be neglected. These results will shed some light on the design of the future hydrogen storage media.

中文翻译：

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Sr(NH2BH3)2脱氢机理的理论研究

对 Sr(NH2BH3)2 的脱氢机理进行了第一性原理研究。对 Sr(NH2BH3)2 单体探索了三种不同的途径，最有利的脱氢途径涉及首先形成 Sr-H 基团，然后成为连续 H2 演化的关键氢化物来源。在 298.15 K 释放四当量 H2 时，本征活化自由能垒分别为 29.2、30.7、42.7 和 42.4 kcal/mol，在实验温度 333 和 366 K 时略微降低了 0.3~2 kcal/mol。对于 Sr( NH2BH3)2 二聚体，对于四当量的 H2 释放，估计的内在自由能垒分别为 22.7、30.4、40.1 和 45.4 kcal/mol。尽管考虑到二聚体形成中的能量增益 - 18，第二当量 H2 的能垒似乎仍然更高。1 kcal/mol，前两个当量的 H2 释放很容易在实验温度下发生。因此，我们的计算表明，最有利的脱氢机制涉及来自 Sr-H 的强碱性 H− 作为氢化物源以加速 H2 释放，并且不应忽视固相中相邻分子的影响。这些结果将为未来储氢介质的设计提供一些启示。