Metalized B40 fullerene as a novel material for storage and optical detection of hydrogen: a first-principles study

Abstract

The first experimentally observed all-boron fullerene (B₄₀) has potential applications in hydrogen storage [Nat. Chem., 6, 727 (2014)]. The surface of B₄₀ fullerene contains 4 heptagonal rings and 2 hexagonal rings, which may facilitate metal atom adsorption. Based on (van der Waals corrected) density functional theory, we show that alkali metal (AM) adsorbed on B₄₀ can serve as a promising candidate not only for hydrogen storage, but also for hydrogen detection. The binding energy of AM atoms on B₄₀ strengthens, due to the energetically favorable B 2p-AM p orbital hybridization. Thus, AM atoms are not likely to form clusters on B₄₀, indicating a good reversible hydrogen storage. The (AM)₆B₄₀ can reach a gravimetric capacity of ∼8 wt% hydrogen with an optimal adsorption energy that is intermediate between the physisorbed and chemisorbed state. Interestingly, the number of adsorbed H₂ molecules per AM atom depends on the position of the AM atoms adsorbed on the B₄₀ surface. Furthermore, the optical absorption spectra of (AM)₆B₄₀ before and after hydrogen molecule adsorption are computed and a clear red (blue) shift is observed. These results can serve as a guide in the design of promising hydrogen storage materials and optical sensors based on the B₄₀ fullerene.