Enhancing Reversible Hydrogen Storage Performance of LiBH<sub>4</sub> Catalyzed by N-Doped Carbon Nanosheet Networks Embedded with Co Nanoparticles
Wei Chen, Yukun Liu, Chaoqun Li, Yuchen Pang, Xuebin Yu, Guanglin Xia
Abstract
LiBH 4 is one of the most promising candidates for onboard solid-state hydrogen storage. Nevertheless, the implementation of this material in practical systems is limited due to its high operational temperature, slow kinetic behavior, and compromised reversible capacity. Herein, N-doped carbon nanosheet networks embedded with Co nanoparticles (Co/N-CNSNs) are designed as functional scaffolds to improve the hydrogen storage performance of LiBH 4 . Co NPs and the in situ formed CoB in Co/N-CNSNs during the initial hydrogen desorption process could catalytically weaken the B–H bonds in LiBH 4, resulting in the reduction of H dissociation energy to 0.34 and 0.31 eV, respectively, much lower than that of pure LiBH 4 (1.95 eV). Benefiting from the synergistic effect of the catalytic role of Co NPs and the in situ formed CoB and the nanoconfinement role of Co/N-CNSNs, 10.1 wt % hydrogen could be released from LiBH 4 @Co/N-CNSNs at 300 °C within 180 min, while this value is decreased to only 1.5 wt % for bulk LiBH 4 under the identical condition. Moreover, the homogeneous molecular interaction between Co/N-CNSNs and LiBH 4 leads to the formation of σ-bonds between Li + and the nonconjugated lone pair electrons of pyridinic N and pyrrolic N, which enables Co/N-CNSNs to act as anchoring sites for inhibiting the grain growth of LiBH 4, contributing to improving its reversibility. Hence, LiBH 4 nanoconfined within Co/N-CNSNs demonstrates a reversible hydrogen storage capacity of 9.7 wt % at 300 °C, even after 10 cycles of hydrogen storage.