Harnessing Dirac Semi-Metallicity in a Metal-Free Stand-alone Borophene Composite Electrode for High-Performance Supercapacitors

Borophene, a semimetallic Dirac material with exceptional mechanical and electronic properties, shows great energy storage potential but requires conductive substrates for stability. A strategy for fabricating flexible and conductive rGO-supported borophene supercapacitor electrodes is proposed, featuring a layered assembly of borophene nanosheets sandwiched between rGO layers. This architecture prevents rGO nanosheet restacking, maintaining interlayer spacing at 5.75 Å, which promotes rapid electrolyte ion diffusion and enhances electroactive site accessibility. The rGO/borophene electrode demonstrates a capacitance of 328 F g^-1 at 1 A g^-1 current density with excellent cycling stability. The flexible supercapacitor achieves an energy density of 24.3 Wh kg^-1 at a power density of 600 W kg^-1 and maintains stability even under bending angles of up to 180°. Density functional theory calculations indicate that boron and carbon contribute to an increase in electron density near the Fermi level, enabling semimetallic behavior which allows rapid electron transfer and high performance.