Hydrogen absorption–desorption characteristics of a Gd2Co7-type Sm1.6Mg0.4Ni7 compound
Hydrogen absorption–desorption characteristics of a Gd2Co7-type Sm1.6Mg0.4Ni7 compound
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DOI：
10.1039/c6ta02889f
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发表时间：
2016-06
影响因子：
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通讯作者：
Lu Zhang;Ding Yanqiao;Yuan Li;Yumeng Zhao;Xin Zhao;Baozhong Liu;Shumin Han
中科院分区：
文献类型：
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作者：
Lu Zhang;Ding Yanqiao;Yuan Li;Yumeng Zhao;Xin Zhao;Baozhong Liu;Shumin Han
在本文中，我们报道了一种新型Gd2Co7型Sm1.6Mg0.4Ni7化合物作为储氢材料，具有特殊的吸/脱附过程和良好的储氢能力。 Gd2Co7型Sm1.6Mg0.4Ni7化合物在10 MPa H2、298 K、17 min内吸收1.88 wt% H2。同时，在3 MPa氢气下，使用1.44 wt%氢气进行20次加氢/脱氢循环后，吸氢速度加快至3.4 min。特别是，该化合物在第100次循环时的容量保持率为99.3%。我们发现该化合物的吸氢/脱附经历了两个平衡阶段，即在较低浓度的H2阶段，H2在H固溶体相和氢化物相之间以较低的速率和较高的焓变转化，以及在较高浓度的H2阶段，以较高的速率和较低的焓变在H2和氢化物相之间直接转化。两步模式降低了H2阶段浓度较低时H2转化引起的吸氢/解吸过程中化合物的分子内应变和亚基体积失配，从而导致良好的结构稳定性和优异的循环稳定性。这些新见解有望提供可行的金属间材料作为储氢高压罐材料，具有良好的储氢性能。
In this paper, we report a new Gd2Co7-type Sm1.6Mg0.4Ni7 compound as a hydrogen storage material with a special hydrogen absorption/desorption process and good hydrogen storage ability. The Gd2Co7-type Sm1.6Mg0.4Ni7 compound absorbs 1.88 wt% H2 within 17 min at 298 K under 10 MPa H2. Meanwhile, the hydrogen absorption speed accelerates to 3.4 min after 20 hydrogenation/dehydrogenation cycles with a 1.44 wt% H2 under 3 MPa H2. Especially, the capacity retention of the compound is 99.3% at the 100th cycle. We found the hydrogen absorption/desorption of the compound undergoes two equilibrium stages, relating to the transformation of H2 between H-solid solution phase and hydride phase with a lower rate and higher enthalpy change at the lower concentration H2 stage, and the direct conversion between H2 and the hydride phase with a higher rate and lower enthalpy change at the higher concentration H2 stage. The two step mode lowers the inner-molecular strain and mismatch in subunit volumes of the compound in hydrogen absorption/desorption, caused by the transformation of H2 at the lower concentration of H2 stage, thus leading to good structural stability and excellent cycling stability. The new insights are expected to provide viable intermetallic materials as high-pressure tank materials for hydrogen storage with nice hydrogen storage properties.