Heteroatom-doped graphene nanoribbons as high-performance electrodes for lithium-ion hybrid supercapacitors

Abstract

Electrochemical unzipping of multiwalled carbon nanotubes (MWCNTs; 6-40 nm) offers a controllable route to graphenic architectures with enriched edge sites, tuneable defect densities, and controllable functionality. Here, we report the room-temperature synthesis of pristine graphene nanoribbons (GNRs), fluorine-doped GNRs (F-GNRs), and boron, nitrogen, fluorine co-doped GNRs (B, N, F-GNRs) using protic acids, super-acids, and ionic liquids as electrolytes, respectively. A systematic structural and chemical analysis including TEM, PXRD, and FT-IR spectroscopy confirms complete longitudinal unzipping of MWCNTs, revealing significant heteroatom-induced lattice distortion, expanded interlayer spacing, and defect-rich ribbon morphologies. Electrochemical studies demonstrate that heteroatom engineering dramatically enhances the capacitive and faradaic contributions, while F- and B, N, F-GNRs exhibit superior cyclic voltametric responses, reduced charge-transfer resistance, and markedly improved Li-ion storage capability. In the half-cell configuration, F-GNRs deliver a high reversible capacity of 342 mAh g⁻¹ with ∼80% retention after 75 cycles, outperforming pristine GNRs and graphene. These findings reveal how unzipping pathways govern the electronic structure, wettability, ion-accessible surface area, and reaction kinetics, establishing the promise of engineered GNR frameworks as high-performance electrode materials for next-generation lithium-ion hybrid supercapacitors.