First-principles identification of the origin for higher activity of surface doped carbon nanohorn: Impact on hydrogen storage

Presence of curvature is considered as a tuning parameter to activate the hydrogen storage capability of carbon nanostructures. Here, we explicate the role of Intra-curvature' in a set of single-walled carbon nanohorns (SWCNHs), to adsorb light metal ad-atoms (M) e.g. Li, Na, Ca and subsequently explore the metal-doped systems for hydrogen storage application using density functional theory. The binding strength of ad-atoms on SWCNHs of different curvature is correlated with the pi electron occupancy of the corresponding carbon ring. Higher pi electron occupancy causes significantly high binding energy of the metal ad-atoms (M), thereby indicating high stability of those M-C bonds for intracurvature values more than 11 degrees, even at a higher temperature. After full hydrogenation, Li-doped SWCNHs are found to contain a maximum of 7.5 wt % of hydrogen. Overall, our results indicate that Li-doped SWCNHs with intra-curvature values higher than 11 degrees, is a potential candidate for hydrogen storage. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.