Reversible hydrogen storage on alkali metal (Li and Na) decorated C20 fullerene: A density functional study

This work reports the reversible hydrogen storage capacities of Li and Na decorated C-20 fullerene using dispersion corrected density functional theory calculation. The alkali metal (AM) atoms are found to bind on the C-C bridge position of C-20 through non covalent closed-shell interaction. Their thermodynamic stabilities are verified through HOMO-LUMO gaps and different reactivity descriptors. Each Li and Na atoms decorated on C-20 adsorb maximum up to five H2 molecules through Niu-Rao-Jena interaction. The adsorption energy decreases with successive addition of H-2 molecules with average binding energy lying in the range of 0.12 eV-0.13 eV. The systems can have a maximum gravimetric density of 13.08 wt% and 10.82 wt% for C20Li4-20H(2) and C20Na4-20H(2) respectively. ADMP molecular dynamic simulations illustrate the reversibility of adsorbed hydrogen molecules at higher temperature (S 300 K). The calculated thermodynamic useable hydrogen capacity shows the room temperature H-2 desorption condition of AM decorated C-20. Consistent with criteria set by the US-DOE, C20Li4 and C20Na4 can be used as promising hydrogen storage materials. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the reversible hydrogen storage capacities of Li and Na decorated C-20 fullerene using dispersion corrected density functional theory calculation. The systems can adsorb up to five H2 molecules and have shown promising potential as hydrogen storage materials at room temperature. The calculated thermodynamic usable hydrogen capacity demonstrates the reversibility of adsorbed hydrogen molecules, meeting the criteria set by the US-DOE.