Superalkali NLi4 cluster decorated γ-graphyne as a promising hydrogen storage material: A density functional theory simulation

Abstract

Based on density functional theory (DFT) calculations, we have comprehensively studied H2 adsorption behaviors on superalkali NLi4 decorated γ-graphyne (GY). Our result shows that the binding energy of NLi4 cluster can reach −4.109 eV for single side of NLi4 decorated GY and −4.041 eV for both sides of NLi4 decorated GY at the hollow site of carbon 12-membered ring, respectively. Such large binding energies significantly reveal NLi4 cluster can be tightly bound onto the surface of GY. Moreover, 2NLi4/GY complex can maximally adsorb 24 H2 molecules with adsorption energy for peer H2 molecule of −0.167 eV/H2, indicating the reversible H2 storage can be realized under ambient conditions. In addition, the hydrogen storage gravimetric density reaches 6.78 wt%, which is higher than the U.S. DOE's latest standard of 6.5 wt%. Furthermore, ab initio molecular dynamic (AIMD) simulations are carried out by using the canonical ensemble (NVT) under massive Nose-Hoover (NH) thermostat and the result exhibits H2 molecules quickly escape from the 2NLi4/GY complex under room temperature of 300 K. Our investigation confirms that NLi4 decorated γ-graphyne can act as an outstanding H2 storage media.