Reversible Hydrogen Storage in a Superalkali NLi4-Decorated Biphenylene Monolayer: Insights from a First-Principles Study

Hydrogen (H2) energy has been recognized as a prominent choice for sustainable green energy applications. The primary obstacle lies in its storage, emphasizing the need for an efficient storage medium. Taking this into consideration and utilizing first-principles density functional theory, we conducted an extensive study to explore the H2 adsorption potential of the biphenylene (BPN) monolayer decorated with superalkali NLi4 clusters. The NLi4 cluster exhibits a binding energy of −3.21 eV/NLi4, when positioned on both sides of the BPN. The cluster binds to the BPN monolayer via an electronic charge transfer mechanism, leading to the creation of a positive charge on the Li atoms, which facilitates the polarized H2 adsorption through electrostatic and van der Waals interactions. Under maximum hydrogenation, the 2NLi4@BPN complex can adsorb 24 H2 molecules with a gravimetric density of 11.5 wt %, surpassing the latest criterion of the Department of Energy, 5.5 wt %. Ab initio molecular dynamics simulations at 300 K unveil H2 reversibility and the thermal stability of the 2NLi4@BPN complex. Thermodynamic analysis and desorption temperature studies reveal the feasibility of reversible H2 storage under ambient conditions. The energetics and high gravimetric density of NLi4-decorated BPN make it a prospective material for reversible hydrogen storage.