Selective NdH₂ exposure enhances hydrogen storage capability of Mg-Mg₂Ni nanocomposites over 3700 cycles

Despite the development of Mg-based hydrogen storage alloys over decades, undesired particle growth and poorly controlled interfacial connectivity have remained unsolved, significantly degrading their hydrogen storage capability. These challenges majorly arise from the uniformly dispersed multiple phases of alloys. Here, we report that the NdH₂ exposed Mg-Mg₂Ni nanocomposite (NdH₂@Mg-Mg₂Ni), realized via a scalable hot-extrusion and hydrogen-induced in-situ decomposition, can address the above-mentioned issues. In it, Mg serves as hydrogen storage phase while NdH₂ and Mg₂Ni serve as catalytically active sites for hydrogen dissociation, diffusion, and nucleation, respectively. In addition, the surface exposed NdH₂ nanoparticles serve as the pinning center, not only ensuring the Mg-Mg₂Ni interfacial connection but also avoiding the direct contact of each particle. Consequently, NdH₂@Mg-Mg₂Ni enables one of the lowest hydrogen release temperatures (176.2 °C) among the Mg-based alloys, releasing 5.1 wt.% H₂ even at 180 °C. Thanks to the selective NdH₂ exposure, NdH₂@Mg-Mg₂Ni exhibits an exceptional chemical and morphological stability, enabling robust hydrogen storage capability over 3700 cycles. The present study proposes a facile and scalable approach to optimize multiple-phase morphology and chemical properties of Mg-based hydrogen storage materials.