Reversible Hydrogen Storage Performance of 2LiBH4-MgH2 Enabled by Dual Metal Borides

2LiBH4-MgH2 is a typical reactive hydride composite with a capacity of 11.5 wt % that has attracted intensive attention. Its practical application, however, is hindered by sluggish kinetics, poor reversibility, and different reaction pathways under various temperatures and hydrogen back pressures. Herein, bimetallic (NiCo) sheet-like nanoporous carbon (NiCo@NC) is designed to improve the hydrogen storage performance of 2LiBH4-MgH2 composite. During the initial H2 desorption process of 2LiBH4-MgH2 under 4 atm H2 pressure, NiCo NPs in NiCo@NC would be in situ transformed into MgNi3B2, acting as the heterogeneous nucleation sites for MgB2, and CoB, serving as the effective catalyst for H2 desorption of 2LiBH4-MgH2 composite. Due to the synergistic effect of in situ formed CoB and MgNi3B2, the incubation period for 2LiBH4-MgH2 is reduced to 1.5 h in the initial H2 desorption process and almost vanished in the following H2 desorption and adsorption cycles, while the incubation time for bulk 2LiBH4-MgH2 composite reaches 16 h. More importantly, induced by the catalysis of NiCo@NC, 2LiBH4-MgH2 exhibits improved cycling stability with a reversible capacity of 8.4 wt % after 10 cycles of hydrogen storage process, corresponding to 95.5% of H2 desorption capacity of the second cycle. This work provides a potential strategy for the design of dual-functional catalysts to improve reversible hydrogen storage performance of reactive hydride composites.

Automated summary

In this study, a bimetallic sheet-like nanoporous carbon material was designed to improve the hydrogen storage performance of 2LiBH4-MgH2 composite. The material successfully reduced the incubation period and improved the cycling stability of hydrogen storage process.