Abstract: Developing high-performing non-noble transition metal catalysts for H₂ evolution from chemical hydro-gen storage materials is of great significance for the hydrogen economy system, yet challenging. Herein, we present for the first time that anomalous metastable hexagonal close-packed Ni nanoparticles induced by heteroatom N doping encapsulated in carbon (N-hcp-Ni/C) can exhibit admirable catalytic performance for ammonia borane (AB) dehydrogenation, prominently outperforming conventional fcc Ni counterpart with similar morphology and favorably presenting the state-of-the-art level. Comprehensive experimental and theoretical studies unravel that unusual hcp phase engineering of Ni together with N doping could induce charge redistribution and modulate electronic structure, thereby facilitating H₂O adsorption and expediting H₂O dissociation (rate-determining step). As a result, AB dehy-drogenation can be substantially boosted with the assistance of N-hcp-Ni/C. Our proposed strategy high-lights that unconventional crystal phase engineering coupled with non-metal heteroatom doping is a promising avenue to construct advanced transition metal catalysts for future renewable energy technologies.

Key words: Hcp Ni, Non-metal doping, Phase engineering, Electronic regulation, Ammonia borane dehydrogenation