Abstract: Lithium borohydride (LiBH₄) is regarded as a potential hydrogen storage material due to its high gravimetric and volumetric capacity, but its practical application suffers from high operating temperature and poor reversibility. Herein, porous hollow carbon microspheres composed of carbon-coated Ni nanoparticles with high content (denoted as Ni/C) are rationally designed as functional support, which not only induces effective nanoconfinement of LiBH₄ but also promotes efficiently homogeneous destabilization reaction between LiBH₄ and Ni nanoparticles. The introduction of Ni nanoparticles leads to the decrease of the Gibbs free energy change for H₂ desorption of LiBH₄ based on the formation of Ni₂B down to -0.95 eV while this value reaches 1.19 eV for bulk LiBH₄, validating the effective role of Ni in thermodynamically destabilizing H₂ desorption. Impressively, the average B-H bond length of LiBH₄ on Ni₂B reaches 1.291 Å and thus the corresponding dissociation energy of removing one H atom from LiBH₄ is lowered to 1.00 eV, much lower than bulk LiBH₄ (4.22 eV) and even LiBH₄ on Ni (1.27 eV), which verifies superior role of Ni₂B than Ni in catalytically enhancing H₂ desorption. Therefore, a capacity of 8.86 wt.% is obtained for LiBH₄ confined into Ni/C at 320 °C after 10 cycles.

Key words: Hydrogen storage, Lithium borohydride, Thermodynamic destabilization reaction, Catalytic effect, Reversibility