Calcium-decorated graphyne nanotubes as promising hydrogen storage media: A first-principles study

First principles calculations based on density functional theory are carried out to study the hydrogen storage properties of Ca-decorated graphyne nanotubes. The results show that Ca atoms can be adsorbed stably on the acetylenic ring of the graphyne nanotube (GNT) without Ca atom clustering. Both the polar interactions and the orbital hybridizations contribute to the adsorption of H-2 molecules. The average adsorption energy is in the range of 0.13-0.33 eV/H-2 which is almost independent of the tube diameter. Each Ca atom can adsorb up to four H-2 molecules due to the steric hindrance of the H-2 molecules. With a hydrogen uptake of 7.44-8.96 wt%, the Ca-decorated GNT is an optimal choice for hydrogen recycling at near ambient conditions. (C) 2012 Elsevier Inc. All rights reserved.