Enhancing reversible hydrogen storage performance of 2LiBH₄–MgH₂ via in-situ building heterogeneous nucleation sites

2LiBH₄–MgH₂ composite is one of the most attractive reactive hydride composites with a theoretic hydrogen capacity of 10.8 wt%. However, the large nucleation restriction of MgB₂ during the second step of dehydrogenation results in sluggish hydrogen storage kinetics and high operating temperature, which hinders its practical application as on-board hydrogen storage materials. Herein, Al₃Ti doped Al nanoparticles (AT NPs) are prepared by a facile chemical reduction reaction to improve the hydrogen storage performance of 2LiBH₄–MgH₂ composite. During the initial H₂ desorption process, MgAlB₄ and TiB₂ that have identical crystal structure and low d-value mismatch with MgB₂ resulting from the reaction between AT NPs and 2LiBH₄–MgH₂ composite serve as effective nucleation sites for the formation of MgB₂. As a result, the apparent activation energy of the two-step H₂ desorption of AT NPs doped 2LiBH₄–MgH₂ composite are notably decreased to (110.0 ± 5.9) and (119.6 ± 1.4) kJ·mol⁻¹, which is 55.5 and 33.5 kJ·mol⁻¹ lower than that of the undoped sample. More importantly, a reversible hydrogen storage capacity of 9.2 wt% after 10 cycles of H₂ desorption and adsorption could be achieved, corresponding to a capacity retention rate of 99%. The building of reactive bimetallic catalyst towards in situ formation of heterogeneous nucleation sites provides a new strategy for improving the hydrogen storage performance of reactive hydride composites.