Inducing One‐Step Dehydrogenation of Magnesium Borohydride via Confinement in Robust Dodecahedral Nitrogen‐Doped Porous Carbon Scaffold

Abstract

Abstract A dodecahedral activated N‐doped porous carbon scaffold is synthesized and used for the nanoconfinement of Mg(BH 4 ) 2 . The optimized mesoporous scaffold possesses an accumulated pore width of 2.65 nm, high specific surface area (3955.9 m 2 g −1 ), and large pore volume (2.15 cm 3 g −1 ), providing ample space for the confinement of Mg(BH 4 ) 2 particles and numerous surface active sites for interactions with the same. The confined Mg(BH 4 ) 2 system features a dehydrogenation onset temperature of 81.5 °C, an extremely high capacity of 10.2 wt% H 2 , and an almost single‐step dehydrogenation profile. Moreover, the system exhibits superior capacity retention of 82.7% after 20 cycles at a moderate temperature of 250 °C. Precise activation control enables a transformation from microporous carbon materials to mesoporous ones, and hence the efficient nanoconfinement of Mg(BH 4 ) 2 and realization of one‐step dehydrogenation. The evolution of borohydride intermediates is systematically revealed throughout the cycling process. Density functional theory calculations demonstrate defective N heteroatoms within the scaffold are vital in reducing the strength of B─H bonds, and the N‐doped carbon can facilitate decomposition of the irreversible MgB 12 H 12 intermediate. This study opens up new avenues for designing robust carbon scaffolds doped with heteroatoms and analyzing intermediate evolution in nanoconfined Mg‐based borohydride systems.