First principle study on cobalt-decorated graphyne for hydrogen storage

The adsorptions of hydrogen on cobalt-decorated graphyne are investigated by first principles study. The results show that isolate Co atom is preferred to locate hollow site above the center of the acetylenic ring (H ₁ ) with binding energies of 3.98 eV. A maximum of five hydrogen molecules can bind to cobalt-decorated graphyne on the one side. The average binding energy per H ₂ molecule for Co-decorated graphyne is around 0.26 eV, which is higher than that of pure graphyne. In addition, more H ₂ molecules would bind with cobalt-decorated graphyne when more metal atoms are dispersed at graphyne. Our calculations offer explanation for the nature of bonding between the metal and the hydrogen molecules, which the coordination bonding between the empty d states in the metal atom and the occupied s states in hydrogen molecules.