Mechanism of the Phase Evolution and Hydrogen Storage Thermodynamics and Kinetics of Ternary Ce5Mg90Sm5 Alloys
Greatly stable thermodynamics and sluggish kinetics impede the practicable applications of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in tuning these hydrogen storage properties.In this study,Mg-based Ce5Mg90Sm5 ternary alloy which was fabricated by vacuum induction melting was investigated to explore their performance and reaction mechanism as hydrogen storage alloy by X-ray diffraction(XRD),transmission electron microscopy(TEM),pressure-composition isotherms(PCI)measurements.The results indicate that the Mg-based Ce5Mg90Sm5 ternary alloy consists of two solid solution phases,including the major phase(Ce,Sm)5Mg41 and the minor phases(Ce,Sm)Mg12.After hydrogen absorption,these phases transformed into MgH2 and(Ce,Sm)H2.73 phase,while after hydrogen desorption,MgH2 transformed into Mg phase,but the(Ce,Sm)H2.73 phases were not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt.%H2,and exhibits well isothermal hydrogen absorption kinetics.An activation energy of 106 kJ/mol has been obtained from the hydrogen desorption data between 573K to 633K,which also exhibits enhanced kinetics compared with the pure MgH2 sample,as a result of the twin-engine function of(Ce,Sm)H2.73 phases.The rate of the hydrogen desorption is dominated by surface controlled.Furthermore,the changes of enthalpy and entropy for hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.
Hydrogen storage Reaction mechanism Kinetics Thermodynamics Activation energy
Yong Hui Zhang Yanghuan Guo Shihai Yuan Zeming Qi Yan Zhao Dongliang
Department of Functional Material Research,Central Iron and Steel Research Institute,Beijing 100081, Department of Functional Material Research,Central Iron and Steel Research Institute,Beijing 100081,
国际会议
北京
英文
1782-1792
2018-09-16（万方平台首次上网日期，不代表论文的发表时间）