Novel core–shell structured MgH2/AlH3@CNT nanocomposites with extremely high dehydriding–rehydriding properties derived from nanoconfinement

Abstract

In this work, a simple and efficient nanoconfinement method is developed to construct a novel “core–shell” structured MgH₂/AlH₃@CNT nanocomposite (MgH₂/AlH₃@CNTs). CNTs with a high specific surface area (550 m² g⁻¹) and a small diameter (approximately 6–8 nm) contribute to finer crystal size (60–80 nm) of the core–shell structured MgH₂/AlH₃@CNT nanoparticles. Owing to the special “core–shell” structure, this nanocomposite shows significantly better H₂ de- and absorption thermodynamics and kinetics. The composite releases H₂ at ∼71 °C, which is substantially below the temperatures observed for the MgH₂, nano-AlH₃, and other MgH₂/AlH₃ composites. It also shows dramatically improved dehydriding and rehydriding kinetics, rapidly releasing 8.20 wt% H₂ in 1 h at 200 °C and taking up 5.61 wt% H₂ in 0.16 h at 250 °C. During dehydrogenation and rehydrogenation, the CNTs can effectively prevent the aggregation of the nanocomposite particles and enhance the MgH₂ and AlH₃ direct contact. Thus, the application of these noteworthy core–shell MgH₂/AlH₃@CNTs offers a very promising way to improve the kinetics of the nanoconfinement system.