N-doped hollow porous carbon nanotubes derived from in situ activation approach for supercapacitor

Supercapacitors are widely concerned because of their fast charging and discharging speed, low cost and long operation time. N-doped porous hollow carbon nanotubes (N-PHCN) are widely used as electrode materials for supercapacitors because of their proper length–diameter ratio, high specific surface area from porous structures, good conductivity and high chemical stability. Herein, an in situ activation method for preparing N-PHCN with manganese dioxide nanorods as the core and resorcinol–formaldehyde resin as the carbon precursor was proposed by using the adsorption of KNO3 in resin and its activation on carbon skeleton. Different from the previous activation strategies of porous carbon, this KNO3 in situ activation method can provide regular morphology for carbon materials. In addition, an appropriate amount of activator can lead to a high specific surface area, which ensures its high performance as a supercapacitor for energy storage. The optimized N-PHCN shows a maximum specific surface area of 1312.9 m2 g−1 with a high specific capacitance of 283 F g−1 at a current density of 0.5 A g−1, an energy density of 12.5 Wh kg−1 at a power density of 247.9 W kg−1 and excellent cycle ability with capacitance retention rate of 94.7% after 10,000 cycles.