Simultaneous gas expansion and nitrogen doping strategy to prepare licorice root residues-derived nitrogen doped porous carbon for supercapacitors†
Abstract
Herein, licorice root residues-derived nitrogen doped porous carbon (NP-LRC) has been prepared via a green and scalable simultaneous gas expansion, activation and nitrogen doping strategy using ammonium chloride (NH4Cl) and potassium hydroxide (KOH) as the mixed activating agent. The decomposition of NH4Cl to produce ammonia (NH3) gas can play a dual role of a gas expansion agent and nitrogen source, while the KOH acts as a typical pore-forming agent during the carbonization process. The obtained NP-LRC has a large specific surface area, developed mesoporous structure and high nitrogen doping content (∼4 wt%). As an electrode material for supercapacitors, the NP-LRC exhibits a high specific capacitance of 221 F g−1 at 0.5 A g−1 and excellent rate capability (80.5% capacitance retention even at 20 A g−1). Moreover, the symmetric supercapacitor assembled based on the NP-LRC electrode material and 1 M Li2SO4 aqueous electrolyte exhibits an energy density of 11.7 W h kg−1 at a high power density of 450 W kg−1 operated in the voltage range of 1.8 V, and outstanding cyclability of 96% capacitance retention after 10 000 cycles.