Lewis and Brønsted acid synergistic catalysis in zeolite for boosting hydrogen storage performance of LiBH₄

High-capacity LiBH₄ is a promising solid hydrogen storage material. However, the large electron cloud density between the B-H bonds in LiBH₄ induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics. To solve the above problems, it is proposed to enhance the hydrogen storage properties of LiBH₄ through the synergistic effect of Brønsted and Lewis acid in Hβ zeolite. Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling. At a LiBH₄-to-Hβ mass ratio of 6:4, the 6LiBH₄-4Hβ system released hydrogen at 190 °C and achieved a hydrogen release capacity of 7.0 wt% H₂ upon heating to 400 °C. More importantly, the hydrogen release capacity of the system reached 6.02 wt% at 350 °C under isothermal conditions after 100 min and 7.2 wt% at 400 °C under isothermal conditions after 80 min, whereas the pristine LiBH₄ only achieved 2.2 wt%. The improvement in hydrogen storage performance of the system was mainly attributed to two factors: (i) Lewis acid sites with acceptable electrons in the Hβ weaken the electron density of B–H bonds in LiBH₄, and (ii) the H⁺ proton from the Brønsted acid sites and H⁻ of LiBH₄ undergo a H⁺ + H⁻ = H₂ reaction. Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβ zeolite are conducive to the weakening of B–H bonds and that storage charge transfer occurs near the Lewis acid sites. The present work provides new insights into improving the hydrogen storage performance of LiBH₄ by weakening the B–H bonds in the LiBH₄.