Stable hydrogen storage of lithium borohydrides via the catalytic effect of Ni2B induced by thermodynamic destabilization reaction
Yukun Liu, Wei Chen, Shunlong Ju, Xuebin Yu, Guanglin Xia
Abstract
Lithium borohydride (LiBH 4 ) 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 LiBH 4 but also promotes efficiently homogeneous destabilization reaction between LiBH 4 and Ni nanoparticles . The introduction of Ni nanoparticles leads to the decrease of the Gibbs free energy change for H 2 desorption of LiBH 4 based on the formation of Ni 2 B down to −0.95 eV while this value reaches 1.19 eV for bulk LiBH 4 , validating the effective role of Ni in thermodynamically destabilizing H 2 desorption. Impressively, the average B–H bond length of LiBH 4 on Ni 2 B reaches 1.291 Å and thus the corresponding dissociation energy of removing one H atom from LiBH 4 is lowered to 1.00 eV, much lower than bulk LiBH 4 (4.22 eV) and even LiBH 4 on Ni (1.27 eV), which verifies superior role of Ni 2 B than Ni in catalytically enhancing H 2 desorption. Therefore, a capacity of 8.86 wt.% is obtained for LiBH 4 confined into Ni/C at 320 °C after 10 cycles.