Fabrication of Electropolymerized Binder-Free Flexible Electrode of PANI-Fe-Doped <i>Borassus flabellifer</i> <i>-</i> Biomass-Derived (0D)-Carbon Quantum Dots for High-Performance Asymmetric Supercapacitors

The rapid evolution of energy storage technologies demands electrode materials that deliver a high energy density, flexibility, and long-term stability. In this work, a binder-free, flexible supercapacitor electrode was fabricated via electro-polymerization of polyaniline (PANI) doped with Fe ions and carbon quantum dots (CQD). The novelty of this study lies in the first-time use of biomass-derived CQDs from <i>Borassus flabellifer</i>, which exhibit a strong natural affinity toward Fe³⁺ ions, enabling uniform incorporation into the PANI matrix during electro-polymerization. This unique design integrates three complementary charge-storage mechanisms by high conductivity from the PANI backbone, reversible Fe³⁺ redox activity, and EDLC-type capacitance from the CQD, along with their role as conductive spacers to stabilize Fe³⁺ redox centers and prevent polymer aggregation. Owing to this synergy, the PANI-Fe-CQD polymerized on the CC electrode achieved a high areal capacitance of 1212.5 mF/cm² at 1 mA/cm² with 86.9% retention after 5000 cycles, while an asymmetric device (AC//PVA-H₂SO₄//PANI-Fe-CQD) delivered an energy density of 53.25 μWh/cm² at a power density of 0.9 mW/cm² and retained 91.2% capacitance after 5000 cycles. This work possesses a novel strategy of integrating biomass-derived <i>B. flabellifer</i> CQDs, not only replacing the need for binders and conductive agents but also enhancing the electrochemical performance of flexible electrodes, offering new directions for sustainable, high-performance energy storage devices.