Boosting the electrochemical performance of nitrogen-oxygen co-doped carbon nanofibers based supercapacitors through esterification of lignin precursor

A facile esterification and electrospinning method is utilized to convert the waste lignin into nitrogen-oxygen co-doped esterified lignin/polyacrylonitrile based carbon nanofibers (E-CNFs). The analysis of FTIR and H1-NMR shows that the esterification reaction occurs between the hydroxyl group and the anhydride group and the ester bond is established in precursor. The lignin after esterification has lower glass transition temperature (Tg), and hence the obtained E-CNFs exhibit inter-fiber bonding structure, higher heteroatom content, and better wettability, rendering an efficient electron transport network and contributing pseudo capacitance. Such unique structure and morphology endow E-CNFs electrode with ultra-high specific capacitance of 320 F g−1 at 1 A g−1 and 200.4 F g−1 at 20 A g−1 with 6 M KOH aqueous as electrolyte, revealing outstanding rate capability. Moreover, the assembled E-CNFs//E-CNFs symmetric supercapacitors using 1 M Na2SO4 aqueous as electrolyte deliver a high coulombic efficiency of 112.5% at the current density 1 A g−1, a remarkable energy density of 17.92 Wh kg−1 at the power density of 800 W kg−1, and excellent cycling stability (∼5.5% loss after 5000 cycles). This inter-fiber bonding structure control strategy provides a perspective and avenue for the further development of high-performance electrode material for supercapacitors applications.