Improved hydrogen storage performance of as-milled Sm–Mg–Ni alloy by adding CeO2
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To investigate the influence of adding CeO2 on the hydrogen storage characteristics of Sm–Mg–Ni-based SmMg11Ni-type alloy, mechanical milling was utilized to synthesize SmMg11Ni and SmMg11Ni + 5 wt.% CeO2 (named SmMg11Ni–5CeO2) alloys. The microstructure of as-cast and as-milled samples was measured via X-ray diffractometer and transmission electron microscope. Sieverts device was utilized to measure the isothermal hydriding and dehydriding kinetics. The non-isothermal dehydrogenation performance was explored by thermogravimetry and differential scanning calorimetry. The hydrogen desorption activation energy of the compound metal hydride can be computed by both Arrhenius and Kissinger methods. The related data show that adding CeO2 can engender a very slight influence on the hydrogen storage thermodynamics, but it can result in an obvious reduction in hydrogen absorption and desorption capacities. Furthermore, the hydrogen desorption performance of experimental alloys is conspicuously ameliorated by the addition of CeO2, viz. lowering the initial hydrogen desorption temperature and enhancing hydrogen desorption rate. The hydrogen desorption activation energies with and without CeO2 addition are 84.28 and 100.31 kJ/mol, respectively, with an obvious decrease of 16.03 kJ/mol. This is thought to be responsible for the ameliorated hydrogen desorption kinetics by adding CeO2.
KeywordsMg-based alloy Mechanical milling Activation energy Catalysis Hydrogen storage kinetics
The authors would like to acknowledge the National Natural Science Foundation of China (Grant Nos. 51761032, 51471054 and 51871125) for giving financial support to this work.