Center for Materials Crystallography, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark.
Chemistry, Combustion, and Materials Center, Sandia National Laboratories, Livermore, California 94551, USA.
Phys Chem Chem Phys. 2018 Jun 13;20(23):16266-16275. doi: 10.1039/c7cp07776a.
The hydrogen absorption properties of metal closo-borate/metal hydride composites, M2B10H10-8MH and M2B12H12-10MH, M = Li or Na, are studied under high hydrogen pressures to understand the formation mechanism of metal borohydrides. The hydrogen storage properties of the composites have been investigated by in situ synchrotron radiation powder X-ray diffraction at p(H2) = 400 bar and by ex situ hydrogen absorption measurements at p(H2) = 526 to 998 bar. The in situ experiments reveal the formation of crystalline intermediates before metal borohydrides (MBH4) are formed. On the contrary, the M2B12H12-10MH (M = Li and Na) systems show no formation of the metal borohydride at T = 400 °C and p(H2) = 537 to 970 bar. 11B MAS NMR of the M2B10H10-8MH composites reveal that the molar ratio of LiBH4 or NaBH4 and the remaining B species is 1 : 0.63 and 1 : 0.21, respectively. Solution and solid-state 11B NMR spectra reveal new intermediates with a B : H ratio close to 1 : 1. Our results indicate that the M2B10H10 (M = Li, Na) salts display a higher reactivity towards hydrogen in the presence of metal hydrides compared to the corresponding [B12H12]2- composites, which represents an important step towards understanding the factors that determine the stability and reversibility of high hydrogen capacity metal borohydrides for hydrogen storage.
研究了金属 closo-硼酸盐/金属氢化物复合材料 M2B10H10-8MH 和 M2B12H12-10MH（M = Li 或 Na）在高压氢气下的吸氢性能，以了解金属硼氢化物的形成机制。通过在 p(H2) = 400 bar 下进行原位同步辐射粉末 X 射线衍射和在 p(H2) = 526 至 998 bar 下进行的外场氢吸收测量研究了复合材料的储氢性能。原位实验揭示了在形成金属硼氢化物 (MBH4) 之前形成了结晶中间体。相反，在 T = 400°C 和 p(H2) = 537 至 970 bar 下，M2B12H12-10MH（M = Li 和 Na）体系没有形成金属硼氢化物。M2B10H10-8MH 复合材料的 11B MAS NMR 表明，LiBH4 或 NaBH4 和剩余 B 物种的摩尔比分别为 1：0.63 和 1：0.21。溶液和固态 11B NMR 谱表明，具有接近 1：1 的 B：H 比的新中间体。我们的结果表明，与相应的 [B12H12]2-复合材料相比，在金属氢化物存在下，M2B10H10（M = Li，Na）盐对氢气具有更高的反应性，这是理解决定高储氢容量金属硼氢化物稳定性和可逆性的因素的重要一步。
