Abstract:

Nitrogen-doped activated carbon(NAC) was prepared by synchronous doping method using phosphoric acid lignin-based activated carbon(LAC) as raw material, melamine as nitrogen source and KOH as activator. The structure and composition of the modified activated carbon were characterized by BET, XRD, Raman spectroscopy and XPS characterization. The electrochemical performance of the modified activated carbon as the electrode material of supercapacitor in several electrolytes with different properties was tested by electrochemical characterization, and the influence mechanism of the electrolyte on the electrochemical performance of electrode material was preliminatively explored. The results indicated that the modified activated carbon has abundant pore structure, with specific surface area of 2 332 m²/g, micropore volume of 1.37 cm³/g, middle pore volume of 0.74 cm³/g, average pore size of 2.79 nm, and nitrogen content of 7.5%, of which graphite-like nitrogen(N-Q) structure content of 34.6%. The rich pore structure and nitrogen content greatly improved the electrochemical performance of activated carbon, and it exhibited high specific capacitance in the aqueous electrolyte. The maximum specific capacitance was 424 F/g at the current density of 1 A/g. In organic electrolyte, its specific capacitance was only 87 F/g at a current density of 1 A/g, while it had higher energy density owing to the wider operating voltage window(0-2.5 V). The results showed that the performance of activated carbon electrode material in aqueous electrolyte was mainly determined by the hydration ion radius of electrolyte, while the performance in organic electrolyte was mainly affected by the viscosity of electrolyte.

Key words: lignin-based activated carbon, nitrogen doping, supercapacitor, specific capacitance