Journal of Magnesium and Alloys | 2021
Catalytic effect comparison of TiO2 and La2O3 on hydrogen storage thermodynamics and kinetics of the as-milled La-Sm-Mg-Ni-based alloy
Abstract
Abstract In this investigation, mechanical grinding was applied to fabricating the Mg-based alloys La7Sm3Mg80Ni10\u202f+\u202f5\u202fwt.% M (M\u202f=\u202fNone, TiO2, La2O3) (named La7Sm3Mg80Ni10–5\u202fM (M\u202f=\u202fNone, TiO2, La2O3)). The result reveals that the structures of as-milled alloys consist of amorphous and nanocrystalline. The particle sizes of the added M (M\u202f=\u202fTiO2, La2O3) alloys obviously diminish in comparison with the M\u202f=\u202fNone specimen, suggesting that the catalysts TiO2 and La2O3 can enhance the grinding efficiency. What s more, the additives TiO2 and La2O3 observably improve the activation performance and reaction kinetics of the composite. The time required by releasing 3\u202fwt.% hydrogen at 553, 573 and 593\u202fK is 988, 553 and 419\u202fs for the M= None sample, and 578, 352 and 286\u202fs for the M\u202f=\u202fTiO2 composite, and 594, 366, 301\u202fs for the La2O3 containing alloy, respectively. The absolute value of hydrogenation enthalpy change |ΔH| of the M (M\u202f=\u202fNone, TiO2, La2O3) alloys is 77.13, 74.28 and 75.28\u202fkJ/mol. Furthermore, the addition of catalysts reduces the hydrogen desorption activation energy ( E a de ).