Catalytic effect comparison of TiO2 and La2O3 on hydrogen storage thermodynamics and kinetics of the as-milled La-Sm-Mg-Ni-based alloy

Abstract

In this investigation, mechanical grinding was applied to fabricating the Mg-based alloys La7Sm3Mg80Ni10 + 5 wt.% M (M = None, TiO2, La2O3) (named La7Sm3Mg80Ni10–5 M (M = None, 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 = TiO2, La2O3) alloys obviously diminish in comparison with the M = None 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 wt.% hydrogen at 553, 573 and 593 K is 988, 553 and 419 s for the M= None sample, and 578, 352 and 286 s for the M = TiO2 composite, and 594, 366, 301 s for the La2O3 containing alloy, respectively. The absolute value of hydrogenation enthalpy change |ΔH| of the M (M = None, TiO2, La2O3) alloys is 77.13, 74.28 and 75.28 kJ/mol. Furthermore, the addition of catalysts reduces the hydrogen desorption activation energy (Eade).

Keywords

• Mg-based alloy
• Ball milling
• Catalysts
• Hydrogen storage kinetics