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

Abstract

Motivated by the need for an effective way of storing hydrogen (H 2 ), 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 (C 2 N) monolayers. We have found that the decoration by selected light metals (Na, Mg, Ca) improves the H 2 adsorption on the C 2 N to the desired levels (>150 meV/H 2 ). Moreover, the metal dopants strongly bonded with C 2 N even at higher doping concentrations, which invalidates the metal clusters formation. Among considered metals, Na and Mg resulted in H 2 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 H 2 sorption at varied conditions of temperature and pressure for practical applications. • Metal decorated C 2 N monolayer is investigated for hydrogen (H 2 ) storage. • Light metals (Na, K, Mg) bind strongly to C 2 N even at higher doping concentrations. • Mg and Na doped C 2 N adsorb H 2 with preferred binding of 150 meV. • Na-, and Mg-doped C 2 N show high H 2 storage capacities of 5.5 and 6.9 wt%, respectively.