Defect–dopant synergy in graphene/fullerene hybrid nanocomposites with defective and Li-doped defective fullerenes for enhanced hydrogen storage

Abstract

This study presents a defect–dopant co-engineering strategy for developing high-performance hydrogen adsor bents based on graphene and its nanocomposites. Pristine C60 was sequentially converted into defective C60 (D–C60) and Li-doped defective C60 (Li-D-C60), followed by hybridization with graphene to construct defectrich hybrid architectures. Textural analyses revealed Type IV adsorption isotherms with combined micro –mesoporosity, while kinetic modeling confirmed pseudo-second-order behavior (R2 > 0.99). Hydrogen adsorption isotherms were measured in the pressure range of 0–100 bar at 77 K and were best described by the dual-Langmuir model, indicating the presence of two energetically distinct adsorption environments within the hybrid carbon framework. The optimized Graphene-P2.5-Li-D-C60 sample achieved a hydrogen storage capacity of 2.53 wt% at 77 K and 100 bar, exceeding those of pristine graphene (1.81 wt%) and D-C60-based systems (2.17 wt%). Mechanistic analyses indicated a multistep adsorption pathway dominated by boundary-layer diffusion at the initial stage and intraparticle diffusion as equilibrium was approached. This stepwise mecha nism, together with defect-induced active site enrichment and Li-driven surface polarization, enhances hydrogen accessibility and adsorption strength. Pearson correlation analysis (r = 0.50 for BET surface area and r = 0.51 for micropore volume) demonstrates that hydrogen storage performance is governed by the synergistic interplay between porosity, diffusion kinetics, and electronic polarization effects.