This work sheds light on the role of the alkali cations, halide anion substitution as well as borohydride anion vacancies on the de-hydrogenation properties of ammine zinc borohydrides. A new liquid ammonia-based synthesis approach employed in this study enabled direct solvothermal synthesis of several novel and previously reported ammine zinc borohydride compounds such as A_xZn(BH_4)_(2+x)(NH_3)_2 for x = 0; 1 and M = Li; Na; K. The experimental results are supported by first principle calculations and molecular dynamics techniques for the interpretation of inherently complex hydrogen release mechanisms. We demonstrate that the salt metathesis reaction heavily relied upon in literature for synthesis of these compounds can result in preferential halide anion substitution of certain borohydride sites in the structure which have significant consequences for hydrogen storage properties. Conclusions of this work is applicable not only to zinc system but to any ammine metal borohydride system.
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机译:本工作揭示了碱阳离子、卤化物阴离子取代以及硼氢化物阴离子空位对氨硼氢化锌脱氢性能的作用。本研究采用一种新的液氨基合成方法,能够直接溶剂热合成几种新型和先前报道的氨硼氢化锌化合物,例如 A_xZn(BH_4)_(2+x)(NH_3)_2 for x = 0;1 和 M = Li;那;K.实验结果得到了第一性原理计算和分子动力学技术的支持,用于解释固有的复杂氢释放机制。我们证明,文献中严重依赖的盐复分解反应可以导致结构中某些硼氢化物位点的优先卤化物阴离子取代,这对储氢性能有重大影响。本工作的结论不仅适用于锌体系,也适用于任何氨金属硼氢化物体系。
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