Spatial‐Decoupled Synergy between Asymmetric Ni‐N ₃ Sites and Ni Nanoparticles Extending the Air‐Tolerant Poisoning Limit of MgH ₂ Hydrogen Storage

ABSTRACT

Solid‐state MgH ₂ holds immense promise for high‐capacity hydrogen storage, yet its practical deployment is severely hindered by extreme atmospheric susceptibility and an elusive activated dehydrogenation mechanism. Herein, we report a armor like architectural design featuring asymmetric Ni‐N ₃ sites and nanoparticles (NPs) co‐decorated within a flexible nitrogen‐doped graphene (NG). Driven by the electronic synergy between the Ni‐N ₃ sites and the highly active Ni NPs, the NG achieves robust encapsulation of MgH ₂ , providing a rigid size‐exclusion barrier against ambient O ₂ /H ₂ O infiltration. Concurrently, strong electronic interactions between MgH ₂ and Ni species optimize the MgH ₂ electronic structure, which further reduces its reactivity toward O ₂ /H ₂ O, enabling the MgH ₂ to preserve its full capacity even after a 28‐day cumulative air exposure. Furthermore, the encapsulated Ni NPs undergo an in situ reaction to form Mg ₂ Ni nanorivets, which serve as high‐flux interfacial hydrogen pumps, while creating a vital spatial buffer during dynamic cycling, thereby achieving 95% capacity retention over 360 cycles at 300°C. Density functional theory calculations confirm that the electronic hybridization induced by the asymmetric Ni‐N ₃ sites, Ni NPs, and Mg ₂ Ni nanorivets destabilizes Mg‐H bonds. This multi‐scale engineering of environmental isolation, electronic modulation, and structural riveting presents a robust blueprint for air‐tolerant, fast‐kinetics solid‐state hydrogen storage.