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High pressure synthesis and stability of cobalt hydrides
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2018-04-13 , DOI: 10.1063/1.5026535
Mengnan Wang 1 , Jack Binns 1 , Mary-Ellen Donnelly 1 , Miriam Peña-Alvarez 2 , Philip Dalladay-Simpson 1 , Ross T. Howie 1
Affiliation  

In situ high-pressure high-temperature X-ray powder diffraction studies of the cobalt-hydrogen system reveal the direct synthesis of both the binary cobalt hydride (CoH) and a novel cobalt dihydride (CoH2). We observe the formation of fcc CoH at pressures of 4 GPa, which persists to pressures of 45 GPa. At this pressure, we see the emergence with time of a further expanded fcc lattice, which we identify as CoH2, where the hydrogen atoms occupy the tetrahedral vacancies. We have explored alternative synthesis routes of CoH2 and can lower the synthesis pressure to 35 GPa by the application of high temperature. CoH2 is stable to at least 55 GPa and decomposes into CoH below 10 GPa, releasing molecular hydrogen before further decomposing completely into its constituent elements below 3 GPa. As a first-row transition metal, cobalt has a relatively lower mass than other hydride-forming transition metals, and as a result, CoH2 has a high hydrogen content of 3.3 wt. % and a volumetric hydrogen density of 214 g/l.

中文翻译:

高压合成和氢化钴的稳定性

钴-氢系统的原位高压X射线粉末衍射研究表明,直接合成了二元氢化钴(CoH)和新型二氢化钴(CoH 2)。我们观察到在4 GPa的压力下会形成fcc CoH,并持续到45 GPa的压力。在此压力下,随着时间的推移,我们看到了进一步扩展的fcc晶格的出现,我们将其标识为CoH 2,其中氢原子占据了四面体空位。我们已经探索了CoH 2的替代合成路线,并且通过施加高温可以将合成压力降低到35 GPa。CoH 2稳定在至少55 GPa并在低于10 GPa时分解为CoH,释放出分子氢,然后进一步分解为低于3 GPa的组成元素。作为第一行过渡金属,钴的质量要比其他形成氢化物的过渡金属的质量低,因此,CoH 2的氢含量较高,为3.3 wt%。%和体积氢密度为214g / l。
更新日期:2018-04-14
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