The influence of Mg content on microstructure and hydrogen storage properties of Nd1-xMgxNi3.50 alloys

A 2 B 7 -type La–Mg–Ni-based alloys are considered as promising hydrogen storage materials . However, low absorption/desorption platform pressure and poor cycling stability restricts their practical application. The neodymium element could improve the hydrogen absorption/desorption platform pressure and the cycling stability with its smaller atomic radius and larger electronegativity . In this study the Nd 1– x Mg x Ni 3.50 ( x  = 0.25, 0.30, 0.36) alloys were prepared and Mg variation was adopted to tailor the microstructure and hydrogen storage performances. All the alloys consist of Gd 2 Co 7 -type and Ce 2 Ni 7 -type superlattice structure , and the cell parameters ( a , c and V ) are reduced by increasing Mg content. The higher Mg content yields a higher plateau pressure, a higher cycling stability and an easier hydrogen release. The x  = 0.30 alloy shows a plateau pressure of 0.81 MPa, a 100th-cycle capacity retention rate of 91.0 %, and a dehydriding enthalpy change of 19.18 kJ mol −1 . These good comprehensive hydrogen storage performances are attributed to the promoted crystallographic stability and reduced cell parameters.