Unveiling reversible hydrogen storage mechanism on transition metal decorated 2D holey graphyne: a density functional study

Abstract

This study investigates hydrogen adsorption and storage in pristine and transition metal (TM = V, Nb, Cr) doped 2D graphene allotrope, Holey Graphyne (HGY), using density functional theory. The TM-decorated HGY systems demonstrate impressive hydrogen storage capacities, with each TM atom capable of binding up to 16H2 molecules. The gravimetric densities for vanadium, chromium, and niobium doping are 14.09 wt%, 14.02 wt%, and 11.93 wt%, respectively, all meeting U.S. Department of Energy standards. Adsorption energies range from −0.17 eV to −0.58 eV per H2 molecule for n = 4 to 32, with calculated desorption temperatures of 326 K, 273 K, and 386 K for 2V.HGY.32H2, 2Cr.HGY.32H2, and 2Nb.HGY.32H2, indicating practical suitability for hydrogen storage. Molecular dynamics and NEB calculations confirm structural stability and sufficient diffusion barriers to prevent metal clustering. Overall, TM-doped HGY emerges as a promising candidate for advanced hydrogen storage, paving the way for innovative energy solutions.