Interface-Mediated Catalysis for Improved Hydrogen Storage in Reactive Hydride Composites.

Improving the hydrogen storage properties of reactive hydride composite (RHC) systems remains challenging due to their high reaction barriers and multi-step transformation pathways. Here, we report markedly enhanced hydrogen storage properties by incorporating Co@C and Ni@C catalysts into 2LiH + MgB2 system via an interface-driven catalytic mechanism. Kinetic measurements exhibit significantly accelerated hydrogenation/dehydrogenation processes, accompanied by lower apparent activation energies. Temperature-dependent investigations and synchrotron radiation powder x-ray diffraction studies demonstrate a two-step dehydrogenation process, in which the catalytic effect is mainly associated with LiBH4 decomposition. Multiscale structural characterization shows that the catalysts refine the hydride matrix and provide stable nanoscale interfaces that are maintained during cycling. Density functional theory calculations further reveal that the strong interfacial interactions between transition metal sites and LiBH4 lead to charge transfer and distortion of BH4 - units. The catalyst-hydride interfaces increase active site density, facilitate mass transport, and induce electronic interactions that weaken the B─H bonds and lower the dehydrogenation energy barrier. These findings demonstrate that the improved hydrogen storage properties predominantly result from interface-driven processes rather than uniform bulk activation. This work provides a mechanistic framework for catalyst design through interfacial engineering, offering a general strategy for optimizing reactive hydride composites for energy storage applications.