Compositional tuning of A2B7-type La0.7–xYxMg0.3Ni3.5 alloys for gaseous hydrogen storage

Rare earth-based superlattice alloys have great potential for gaseous hydrogen storage, as well as successful application as nickel-metal hydride batteries anodes. In this work, Y substitution was carried out to adjust the gaseous hydrogen storage properties of A₂B₇-type La_0.7Mg_0.3Ni_3.5 alloys. The results indicate a multiphase structure in the alloys comprised of the main rhombohedral Gd₂Co₇ and PuNi₃ phases, with a small amount of CaCu₅ phase. Moreover, the Y substitution results in higher abundance of the Gd₂Co₇ phase. The alloy La_0.42Y_0.28Mg_0.3Ni_3.5 exhibits a hydrogen storage capacity of 1.55 wt% at 298 K and a desorption plateau pressure of 0.244 MPa. In addition, this alloy demonstrates a stable cycle life by a capacity retention of 94.2% after 50 cycles, with the main capacity degradation occurring during the initial 20 cycles. This work accentuates the potential of the La–Y–Mg–Ni-based superlattice alloys for applications in solid-state hydrogen storage.