Lignin based carbon fiber fabrics with hybrid doping approach as self-standing electrodes for supercapacitors

•Heteroatom doped lignin-based carbon fiber fabrics using a hybrid doping approach.•In-situ doping using a lignin/polyacrylonitrile precursor in carbonization process.•Ex-situ doping with carbon dots addition during fiber formation via electrospinning.•Carbon fibers with largely microporous structure and high electrical conductivity.•Sustainable and binder-free electrode materials for high capacitive supercapacitors. Novel carbon fiber (CF) mats were fabricated from tobacco leaf-based carbon dots (TL-CDs) filled rubber wood chip-extracted lignin (RWC-L)/polyacrylonitrile (PAN) composite fibers with a hybrid doping method. The ex-situ doping was applied during fiber formation via electrospinning by adding functionalized TL-CDs in the spinning solution. The in-situ doping was carried out in carbonization process for nitrogen (N) and oxygen (O) atom generation by utilizing RWC-L and PAN as a mixed precursor. The CF properties and electrochemical performances were evidently influenced by TL-CD content and carbonization temperature. The CF fabric containing 0.4% w/v of TL-CDs and carbonized at 1200 °C provided optimal specific capacitance (Cs ≅ 225 F g−1), energy density (ED ≅ 53 W h kg−1), and power density (PD ≅ 130 W kg−1) at a current density of 0.2 A g−1 in 6 M KOH electrolyte. It also had excellent cycling stability of ≅ 90% after 12,000 cycles at a current density of 5 A g−1. This could be combined effects of a small fiber diameter (≅ 0.65 μm), a high heteroatom content (≅ 21 wt% of N and O atoms), a large surface area (≅ 1063 m2 g−1), a high micropore volume (≅ 2.41 cm3 g−1), high graphitic carbon (ID/IG ratio ≅ 0.97), and high electrical conductivity (≅ 62 S cm−1). Moreover, the electrochemical properties of the TL-CD added CF sheet were superior to those of the bare CF mat. Therefore, this work introduces a sustainable and efficient approach to develop lignin-based CF fabrics as self-standing electrodes for advanced energy-storage devices. [Display omitted]