Ultra-high hydrogen storage capacity of Li-decorated graphyne: A first-principles prediction

Graphyne, consisting of sp- and sp(2)-hybridized carbon atoms, is a new member of carbon allotropes which has a natural porous structure. Here, we report our first-principles calculations on the possibility of Li-decorated graphyne as a hydrogen storage medium. We predict that Li-doping significantly enhances the hydrogen storage ability of graphyne compared to that of pristine graphyne, which can be attributed to the polarization of H-2 molecules induced by the charge transfer from Li atoms to graphyne. The favorite H-2 molecules adsorption configurations on a single side and on both sides of a Li-decorated graphyne layer are determined. When Li atoms are adsorbed on one side of graphyne, each Li can bind four H-2 molecules, corresponding to a hydrogen storage capacity of 9.26 wt. %. The hydrogen storage capacity can be further improved to 15.15wt. % as graphyne is decorated by Li atoms on both sides, with an optimal average binding energy of 0.226 eV/H-2. The results show that the Li-decorated graphyne can serve as a high capacity hydrogen storage medium. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759235]