Effect of Co substitution for La on hydrogen storage properties and thermal stabilities of amorphous Mg₆₀Ni₃₀La_10−xCo_x (x = 0, 2 and 4) alloys prepared by melt spinning

Abstract

A comparison of the hydrogen storage properties and thermal properties of amorphous Mg60Ni30La10−xCox hydrogen storage alloys prepared by melt spinning has been investigated. A, B and C were used to represent each alloy composition when x = 0, 2 and 4 respectively. Their microstructures, the hydrogen storage properties and the thermal stabilities were analysed by X-ray diffraction (XRD), PCTPro2000 and differential scanning calorimetry (DSC) respectively. After hydrogenation of Mg60Ni30La10−xCox (A, B and C) samples at 573 K under 2 MPa hydrogen pressure, XRD pattern results indicate the formation of new phases of MgH2 (A, B, C), Mg2NiH4 (A, B, C), La4H12·19 (A, B, C), Mg2Ni0·9Co0·1H4 (B), Mg2NiH0·26 (C) and Mg2CoH2 (C). It is observed that the experimental data of hydrogen desorption kinetics at 523, 573 and 623 K are well fitted through Avrami–Erofeev equation, and the hydrogen desorption kinetics is in the order of C>B>A. In addition, with increasing Co content, alloy C has the maximum hydrogen absorption capacity of 3·05 wt- and the maximum hydrogen desorption capacity of 2·85 wt-. Based on the results of DSC analysis, dehydrogenation activation energies of these alloys are determined to be 98·31±2·82 kJ mol−1 (A), 96·33±5·61 kJ mol−1 (B) and 78·99±2·98 kJ mol−1 (C), which are in accordance with the results of hydrogen desorption kinetics.

Electrochemical Properties of La2Mg17/Ni Electrodes Prepared via TiF3-Catalysed Mechanical Milling

“…Of the various energy conversion and storage materials that have been developed over recent years, amorphous composites based on a La-Mg system alloy that is combined with Ni powder by mechanical milling are considered amongst the most promising, by virtue of their high electrochemical discharge capacity [1][2][3]. Indeed, Y. Wang and X. Wang [4] have already demonstrated that the ball milling of Pr 5 Mg 41 with 200 wt.% Ni can achieve an excellent electrochemical hydrogen storage capacity, reaching as high as 1016.2 mAh/g.…”

Effect of Sm on hydrogen storage performance of La–Sm–Mg–Ni alloys

“…High discharge capacity and remarkable capacity retention even after 3 years greatly increase the actual performance of these Ni-MH batteries in mobile devices. Due to the high thermodynamic stability of their hydrides and an inert passive layer on the surface, the Mg based alloys such as MgH 2 , Mg 2 Ni, Mg 60 Ni 30 La 102x Co x , CeMg 12 z100%Ni, Mg-LaNi 5 [1][2][3] suffer from poor hydrogen absorption and desorption rates at the ambient temperatures, hence inhibiting the application of these alloys in Ni-MH. Therefore, A 2 B 7 type La-Mg-Ni based hydrogen storage alloy has nowadays become the best choice to manufacture this kind of Ni-MH battery.…”