High-symmetry core-shell B12@Ca20C12: A nanocluster-based hydrogen storage material

Abstract

Since the discovery of C60 fullerene, scientists devoted themselves to searching novel clusters. Among them, the high-symmetry clusters, especially clusters with Ih symmetry, has drawn increasing attention due to their special properties and stabilities. Here, a stable core-shell B12@Ca20C12 with Ih symmetry, which is featured as an icosahedral Ih-B12 centered on the dodecahedron Ca20C12, has been identified using first principles calculations. Its stability has been further confirmed by vibrational frequency analysis with the highest frequency of 834.9 cm−1 and the lowest frequency of 93.7 cm−1. Besides, molecular dynamics simulations indicate that its core-shell structure cannot be destroyed at 325 K under NVT ensembles with Nosé-Hoover chain thermostat. As for the electronic structure, 64 multi-center two-electron bonds were observed throughout the entire core-shell B12@Ca20C12 to keep the cluster maintain its core-shell configuration. More importantly, the core-shell B12@Ca20C12 can storage about 77 H2 molecules by closed-shell interactions with an average adsorption energy of −0.16 eV/H2, resulting in the gravimetric hydrogen density of 12.6 wt%. Based on these results we infer that core-shell B12@Ca20C12 is a potential high-capacity hydrogen storage material and might promote positive experimental efforts in designing excellent hydrogen storage materials.