Lithium‐Decorated Square–Hexagon–Octagon Graphene as a Promising Two‐Dimensional Material for High‐Capacity Hydrogen Storage: Insights From Density Functional Theory With Dispersion Corrections and Molecular Dynamics Simulations

In the quest for efficient hydrogen storage, this study proposes for the first time a novel two‐dimensional carbon allotrope, SHO‐graphene, composed of square, hexagonal, and octagonal rings. First‐principles Density Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD) simulations show excellent stability and high surface area of the pristine framework. The decoration effect of lithium is critical for enhancing the performance of hydrogen storage, where binding energy between the lithium atom and the substrate is −2.12 eV, and 0.785 e is transferred to the carbon framework, which polarizes the surface and increases the binding energy between the H 2 molecule and the surface. Optimized Li 6 @SHO‐graphene system adsorbs up to 30 molecules of H 2 with an extraordinary theoretical gravimetric capacity of 10.38 wt% with a thermodynamically accessible gravimetric capacity of 5.81 wt% under realistic conditions, both of which are above the DOE targets. The average adsorption energy of 0.187 eV/H 2 and desorption temperature of 204.5 K will provide a good balance of storage and reversible release. The results provide an excellent proof of the suitability of SHO‐graphene as a superior, reversible solid‐state hydrogen storage medium.