Enhanced Hydrogen Storage Kinetics and Stability by Synergistic Effects of in Situ Formed CeH2.73 and Ni in CeH2.73-MgH2-Ni Nanocomposites

作者：Liuzhang Ouyang, Xusheng Yang, Min Zhu, J. W. Liu, Hanwu Dong, D.L. Sun, Jin Zou, Xiangdong Yao · 发表于：The Journal of Physical Chemistry C · 年份：2014 · DOI：10.1021/jp500439n · 被引用次数：447 · 研究领域：Hydrogen Storage and Materials、Ammonia Synthesis and Nitrogen Reduction、Hybrid Renewable Energy Systems

Mg-based materials are promising candidates for high capacity hydrogen storage. However, their poor hydrogenation/dehydrogenation kinetics and high desorption temperature are the main obstacles to their applications. This paper reports a method for in situ formation of cycle stable CeH 2.73 -MgH 2 -Ni nanocomposites, from the hydrogenation of as-melt Mg 80 Ce 18 Ni 2 alloy, with excellent hydrogen storage performance. The nanocomposites demonstrate reversible hydrogen storage capacity of more than 4.0 wt %, at a low desorption temperature with fast kinetics and long cycle life. The temperature for the full hydrogenation/dehydrogenation cycle of the composites is significantly decreased to 505 K, which is about 100 K lower than that for pure Mg. The hydrogen desorption activation energy is 63 ± 3 kJ/mol H 2 for the composites, which is significantly lower than those of Mg 3 Ce alloy and pure Mg (104 ± 7 and 158 ± 2 kJ/mol H 2, respectively). X-ray diffraction and transmission electron microscopy have been used to reveal the mechanism that delivers this excellent cycle stability and fast hydriding/dehydriding kinetics. It is found that the hydriding/dehydriding process is catalyzed by the combination of in situ formed extremely fine CeH 2 /CeH 2.73 and Ni to Mg/MgH 2 . In addition, this nanocomposite structure can effectively suppress Mg/MgH 2 grain growth and enable the material to maintain its high performance for more than 500 hydrogenation dehydrogenation cycles.