Effect of Ni doping on hydrogen storage kinetics and thermodynamic properties of ball-milled Nd-Mg alloy

In the present study, the synthesis of NdMg 12 + x wt%Ni( x  = 0, 5, 10, 15) alloy was effectively accomplished through the technique of ball milling , and the profound impact of Ni on the microstructural attributes, as well as the hydrogen absorption and desorption characteristics of NdMg 12 alloy, was meticulously examined. The microstructural analysis reveals that Ni can notably facilitate the development of nanocrystalline and amorphous structural configurations. Subsequent investigations uncovered that a portion of Ni was transformed into the Mg 2 Ni phase on the surface of the NdMg 12 alloy, thereby increasing the number of hydrogen absorption active sites and subsequently enhancing the hydrogen absorption and desorption capabilities of the NdMg 12 +Ni alloy. A thermodynamic analysis reveals that the incorporation of Ni exerts a substantial elevating effect on the hydrogen desorption plateau pressure of NdMg 12 +Ni alloy. As the Ni content escalates from 0 wt% to 5 wt%, the enthalpy of the hydrogen desorption process plummets significantly, from 89.1888 kJ/mol H 2 to 80.2806 kJ/mol H 2 . Concurrently, the addition of Ni markedly diminishes the hysteresis coefficient during hydrogen absorption and desorption, thereby enhancing the overall hydrogen absorption and desorption efficiency of NdMg 12 +Ni alloy. Moreover, the inclusion of Ni not only expedites the hydrogen absorption rate within the NdMg 12 +Ni alloy but also substantially diminishes the activation energy for hydrogen desorption, effectively lowering the minimal hydrogen desorption temperature from 261℃ to 199℃. Notably, the NdMg 12 + 10 wt%Ni alloy exhibited the lowest activation energy (Ea = 114.4995 kJ/mol) and demonstrated superior hydrogen desorption kinetics.