In situ construction of dual-functional Ni/NixB catalysts for the hydrogenation and dehydrogenation of magnesium hydride

Abstract

Hydrogen sorption catalysts loaded on porous supports can promote reversible H ↔ H⁰ and metal ↔ metal ion reactions. However, uniform dispersion of catalytic nanoparticles in the matrix is required to synergistically promote MgH₂ hydrogenation, diffusion, and dehydrogenation. In this study, we decorated hexagonal boron nitride (h-BN) in situ with Ni_xB. Experimental characterization demonstrated the uniform distribution of Ni_xB in the h-BN matrix. The nickel atoms were introduced into the porous h-BN matrix through Ni–B bonds, which effectively limited nanoparticle growth. Simulations of the hydrogenation and dehydrogenation pathways of several Ni/Ni_xB@MgH₂ composites suggested that the Ni/Ni_xB catalyst should have efficient catalytic performance. The composite had a hydrogen storage capacity of approximately 7.0 wt% at 200 °C and released approximately 4.5 wt% H₂ within 10 min, with rapid kinetics and stable reversible cycling. Finally, the thermodynamics and kinetics of hydrogenation/dehydrogenation in the presence of the composite catalysts were theoretically evaluated.