High-capacity reversible hydrogen storage properties of metal-decorated nitrogenated holey graphenes

Motivated by the need for an effective way of storing hydrogen (H₂), a promising energy carrier, we have performed density functional theory (DFT) calculations with different van der Waals corrections coupled with the statistical thermodynamic analysis and ab initio molecular dynamics (AIMD) on the light-metal decorated nitrogenated holey graphene (C₂N) monolayers. We have found that the decoration by selected light metals (Na, Mg, Ca) improves the H₂ adsorption on the C₂N to the desired levels (>150 meV/H₂). Moreover, the metal dopants strongly bonded with C₂N even at higher doping concentrations, which invalidates the metal clusters formation. Among considered metals, Na and Mg resulted in H₂ storage capacities of 5.5 and 6.9 wt%, respectively, which exceed the target set by the U.S. Department of Energy's for 2025. Thermodynamic analysis and the AIMD simulations were employed to investigate the H2 sorption at varied conditions of temperature and pressure for practical applications.