A first-principles study of efficient and reversible solid-state hydrogen storage in 3d transition metal-anchored twin graphene enabled by d-orbital mediated Kubas interactions.

The realisation of efficient and reversible solid-state hydrogen storage remains a central challenge for sustainable energy technologies. Here, we report a systematic first-principles investigation of 3d transition metal (TM)-anchored twin graphene (TG) as a promising platform for hydrogen storage. Anchoring TMs on TG significantly modifies the electronic structure and transforms the intrinsically weak physisorption of H2 into stronger yet reversible interactions. Electronic structure and Löwdin population analyses reveal that hydrogen adsorption is governed by a d-orbital mediated Kubas interaction, enabling optimal binding without dissociation. Among the investigated systems, Fe-decorated TG exhibited superior performance, achieving stable adsorption of up to eight H2 (8H2) molecules per metal site with adsorption energies in the range for reversible storage. The balance between adsorption strength and desorption feasibility suggests practical operating conditions for hydrogen release. These findings identify 3d TM-functionalized TGs as a viable class of materials for high-capacity and reversible hydrogen storage, providing mechanistic insights for the rational design of advanced energy storage systems.