Reactivity with water vapor and hydrogen storage capacity of Be2Ti compound
Reactivity with water vapor and hydrogen storage capacity of Be2Ti compound
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DOI：
10.1016/j.ijhydene.2016.02.131
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发表时间：
2016-06
影响因子：
7.2
通讯作者：
Jae-Hwan Kim;H. Iwakiri;M. Nakamichi
中科院分区：
文献类型：
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作者：
Jae-Hwan Kim;H. Iwakiri;M. Nakamichi
铍金属间化合物表现出中子倍增、耐火功能、储氢、超导等多种优异性能。 Be12M 化合物（M = Ti、V 和 Zr）已被研究作为聚变反应堆的中子倍增剂，而 Be17M2 化合物已被探索作为耐火材料。此外，已知Be2Ms具有Laves相，其特征在于具有高H2气体储存潜力的A2B型化合物。由于其密度低，从与 H2O 的反应性、氢的捕获位点以及该化合物中 H2 气体的量的角度来看，Be2Ms 的氢特性引起了人们的极大兴趣。然而，针对Be2M的研究很少，其数据库也不尽如人意。 初步合成了一种铍金属间化合物（=Be2Ti）作为储氢材料，以阐明其在高温下与水蒸气的反应性和高储氢能力。 X射线衍射图谱和电子探针显微分析结果证实，通过均匀化处理和等离子烧结初步合成了单相Be2Ti。 Be2Ti与1%H2O反应的产氢率随着测试温度的升高而增加。高温暴露于 H2O 导致表面形成 TiO2。此外，使用压力-浓度-温度曲线评估Be2Ti的氢气储存浓度在298 K时为0.56 wt.% (=0.125 H/M)，考虑到氢气压力增加至13 MPa，该浓度相对较低。根据额外的压力-成分-温度测量，氢容量似乎不存在颗粒尺寸依赖性。基于第一原理计算的模拟表明存在两个氢陷阱位，四面体和三角形中心，其溶液能量分别为-0.52和-0.05 eV，这意味着氢的最大陷阱位为5.4 wt.%。这种差异可能是由于 Be2Ti 样品含有大部分表面氧化层，这阻碍了氢的表面渗透。
Beryllium intermetallic compounds show a variety of excellent properties such as neutron multiplication, refractory function, hydrogen storage, and superconductivity. Be12M compounds (M = Ti, V, and Zr) have been investigated as neutron multipliers for fusion reactors, while Be17M2compounds have been explored as refractory materials. Furthermore, Be2Ms are known to have Laves phases, which are characterized by an A2B type compound having high H2gas storage potential. Because of its low density, the hydrogen properties of Be2Ms have attracted great interest from viewpoints of reactivity with H2O, trap site of hydrogen, and amount of H2gas in this compound. However, few studies have dealt with Be2M, and its database remains unsatisfactory.Preliminary synthesis of a beryllium intermetallic compound (=Be2Ti) as a hydrogen storage material was conducted to clarify its reactivity with water vapor at high temperatures and high hydrogen storage capacity. X-ray diffraction profiles and electron-probe microanalysis results confirmed that the preliminary synthesis of single-phase Be2Ti by homogenization treatment and plasma sintering was successful. The hydrogen generation rate of Be2Ti by reaction with 1% H2O increased as the test temperature increased. High temperature exposure to H2O led to the formation of TiO2on the surface. Furthermore, the hydrogen gas storage concentration of Be2Ti, evaluated using the pressure–concentration–temperature curve, was 0.56 wt.% (=0.125 H/M) at 298 K, which is relatively low considering that H2pressure was increased up to 13 MPa. Based on additional pressure–composition–temperature measurements, it does not appear to have particle size dependence with regard to hydrogen capacity.A simulation based on first-principles calculation indicated the presence of two hydrogen trap sites, tetrahedral and center of triangle with solution energies of −0.52 and −0.05 eV, respectively, implying that the maximum trap site of hydrogen with 5.4 wt.%. This dissimilarity might be attributed to the fact that the Be2Ti sample contained a large fraction of surface oxide layer, which disturbed the surface penetration of hydrogen.