Superior reversible hydrogen storage in eutectic LiBH4–KBH4 system via Ni–based catalysts synergized with graphene

Light metal borohydrides are promising candidates for solid–state hydrogen storage due to their high hydrogen storage capacities; however, the reversibility and kinetics of de/hydrogenation still require significant improvement. The present work focuses on the improvement of the hydrogen storage properties of the eutectic borohydride system of LiBH 4 –KBH 4 (Li/KBH 4 ). A layered composite of graphene supported with ultrafine Ni 3 B nanoparticles (Ni 3 B/G) is designed and synthesized, which acts as catalyst and confinement carrier for Li/KBH 4 . Assisted with a heating of the mixture of Li/KBH 4 and Ni 3 B/G to 110 °C in the molten state of Li/KBH 4 , an interlayer structure of graphene dispersed with Ni 3 B nanoparticles and sheet–like Li/KBH 4 is constructed. The graphene effectively disperses Ni 3 B nanoparticles and confines the Li/KBH 4 in its interlayers. The confinement of Li/KBH 4 and the catalysis of Ni 3 B nanoparticles, assisted with the high thermal conductivity of graphene, contribute synergistically the hydrogen storage of Li/KBH 4 . The main dehydrogenation peak temperature of the system is lowered to 278 °C. The system can release 8.5 wt% H 2 within 30 min at 350 °C. The capacity retention achieves 81.2% after 50 cycles. DFT theoretical analysis shows that there is strong charge transfer interaction between Ni 3 B and LiBH 4 /KBH 4 , which destabilizes the [BH 4 ] – structure and promotes the dehydrogenation. This work provides a new approach for the design of new structural LiBH 4 –based eutectic system with high capacity, low dehydrogenation temperature, high reversibility and long cycling life.