Jin Ou, Shang Yuanyuan, Huang Xiaohui, Szabó Dorothée Vinga, Le Thi Thu, Wagner Stefan, Klassen Thomas, Kübel Christian, Pistidda Claudio, Pundt Astrid
Institute for Applied Materials, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany.
Molecules. 2022 Oct 18;27(20):7005. doi: 10.3390/molecules27207005.
The reactive hydride composite (RHC) LiBH-MgH is regarded as one of the most promising materials for hydrogen storage. Its extensive application is so far limited by its poor dehydrogenation kinetics, due to the hampered nucleation and growth process of MgB. Nevertheless, the poor kinetics can be improved by additives. This work studied the growth process of MgB with varying contents of 3TiCl·AlCl as an additive, and combined kinetic measurements, X-ray diffraction (XRD), and advanced transmission electron microscopy (TEM) to develop a structural understanding. It was found that the formation of MgB preferentially occurs on TiB nanoparticles. The major reason for this is that the elastic strain energy density can be reduced to ~4.7 × 10 J/m by creating an interface between MgB and TiB, as opposed to ~2.9 × 10 J/m at the original interface between MgB and Mg. The kinetics of the MgB growth was modeled by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation, describing the kinetics better than other kinetic models. It is suggested that the MgB growth rate-controlling step is changed from interface- to diffusion-controlled when the nucleation center changes from Mg to TiB. This transition is also reflected in the change of the MgB morphology from bar- to platelet-like. Based on our observations, we suggest that an additive content between 2.5 and 5 mol% 3TiCl·AlCl results in the best enhancement of the dehydrogenation kinetics.
反应性氢化物复合材料（RHC）LiBH - MgH被认为是最有前景的储氢材料之一。迄今为止，由于MgB的成核和生长过程受阻，其脱氢动力学较差限制了它的广泛应用。然而，添加剂可以改善这种较差的动力学性能。这项工作研究了添加不同含量的3TiCl·AlCl时MgB的生长过程，并结合动力学测量、X射线衍射（XRD）和先进的透射电子显微镜（TEM）来加深对其结构的理解。研究发现，MgB优先在TiB纳米颗粒上形成。主要原因是通过在MgB和TiB之间形成界面，弹性应变能密度可降低至约4.7×10 J/m，而在MgB和Mg之间的原始界面处约为2.9×10 J/m。MgB生长的动力学由约翰逊 - 梅厄 - 阿夫拉米 - 科尔莫戈罗夫（JMAK）方程建模，该方程比其他动力学模型能更好地描述动力学。结果表明，当成核中心从Mg变为TiB时，MgB生长速率控制步骤从界面控制转变为扩散控制。这种转变也反映在MgB形态从棒状到片状的变化上。基于我们的观察，我们认为2.5至5 mol%的3TiCl·AlCl添加剂含量能最佳地增强脱氢动力学。
