Catalytic doping of magnesium hydride (MgH₂) to improve its hydrogen ab/desorption kinetic properties is considered to be an effective and feasible method. In solid-phase catalysis, the extent of contact between the catalyst and the substrate determines the catalytic reaction in a great sense. With large specific surface area and abundant active sites, two-dimensional (2D) nanomaterials are promising catalysts for MgH₂ via providing numerous pathways for the diffusion and dissociation of hydrogen. In this regard, 2D NiMn-based layered double hydroxide and layered metallic oxide (LMO) are designed and introduced into MgH₂ to improve its hydrogen storage properties. Simultaneous enhancement in interfacial contact, desorption temperature and kinetics are achieved. The MgH₂+9wt% Ni₃Mn-LMO composites begin to discharge hydrogen at only 190 ℃ and 6.10wt% H₂ could be charged in 600 s at 150 ℃. The activation energy for de/hydrogenation is reduced by 42.43% and 46.56%, respectively, compared to pure MgH₂. Even at a low operating temperature of 235 ℃, the modified system was still able to release 4.44wt% H₂ in an hour, which has rarely been reported in previous studies. Microstructure observations and density functional theory calculations revealed that first, the hydrogen pumping effect of Mg₂Ni/Mg₂NiH₄ promotes the adsorption and desorption of hydrogen molecules on the surface of MgH₂, second, MnO_x drew electrons from Mg₂Ni, producing a new Density of State structure with a lower d-bond center. This unique change further strengthens the Mg₂Ni/Mg₂NiH₄ pump effect on MgH₂. Our work indicates that the application of 2D metal-based catalysts is a feasible and promising approach towards MgH₂ for solid-state hydrogen storage to meet technical and scientific requirements.

A designed Mg_88.7Ni_6.3Y₅ hydrogen storage alloy containing 14H type LPSO (long-period stacking ordered) and ternary eutectic structure was prepared by regulating the alloy composition and casting. The hydrogen storage performance of the alloy was improved by adding nano-flower-like TiO₂@C catalyst. The decomposition of the LPSO structure during hydrogenation led to the formation of plenty of nanocrystals which provided abundant interphase boundaries and activation sites. The nanoscale TiO₂@C catalyst was uniformly dispersed on the surface of alloy particles, and the "hydrogen overflow'' effect of TiO₂@C accelerated the dissociation and diffusion of hydrogen on the surface of the alloy particles. As a result, the in-situ endogenous nanocrystals of the LPSO structure decomposition and the externally added flower-like TiO₂@C catalyst uniformly dispersed on the surface of the nanoparticles played a synergistic catalytic role in improving the hydrogen storage performance of the Mg-based alloy. With the addition of the TiO₂@C catalyst, the beginning hydrogen desorption temperature was reduced to 200 ℃. Furthermore, the saturated hydrogen absorption capacity of the sample was 5.32 wt.%, and it reached 4.25 wt.% H₂ in 1 min at 200 ℃ and 30 bar.