A DFT-D3 investigation on Li, Na, and K decorated C6O6Li6 cluster as a new promising hydrogen storage system

Abstract

Because of the increasing demand for energy sources, searching for reversible and high-capacity hydrogen storage materials plays a vital role in the extensively utilizing of hydrogen as a clean energy source. In this study, dispersion-corrected density functional theory (DFT-D3) calculations are utilized to examine the possibility of storing H2 molecules on Li, Na, and K alkali metals decorated C6O6Li6 cluster. To evaluate H2 adsorption capability, the adsorption energies, electron density difference iso-surfaces, and charge-transfers are calculated and discussed. The results indicate that a hydrogen molecule is physisorbed on the Li@C6O6Li6, Na@C6O6Li6, and K@C6O6Li6 with average adsorption energies of −0.264, −0.150, and −0.109 eV, respectively. Double-sided alkali metal atoms decoration can lead to the maximum gravimetric density of 15.68, 14.49, and 13.79 wt% for 2Li@C6O6Li6–8H2, 2Na@C6O6Li6–10H2, and 2K@C6O6Li6–12H2 complexes, respectively. Finally, desorption temperatures reveal that the systems can operate as reversible hydrogen storage materials.