Nitrogen-doped nanoporous carbon materials derived from folic acid: Simply introducing redox additive of p-phenylenediamine into KOH electrolyte for greatly improving the supercapacitor performance

• Folic acid serves as excellent carbon/nitrogen sources.
• Mg(OAc)2·4H2O has been utilized as template for pore formation.
• p-Phenylenediamine acts as effective redox additive.
• Redox reaction occurs at the electrode–electrolyte interface.

In the present work, we have demonstrated a simple but effective template carbonization approach to convert folic acid into highly nitrogenated nanoporous carbon materials, using Mg(OAc)2·4H2O as template. For the C-800/900/1000 samples, the nitrogen contents can reach up to 9.03%, 6.81%, and 6.65%, respectively, and they also deliver large BET surface areas of 1242.2, 1559.1, and 1302.8 m2 g− 1, and high pore volumes of 1.36, 2.26, and 1.44 cm3 g− 1, respectively. On the other hand, it is revealed that the incorporation of p-phenylenediamine as a redox additive into KOH electrolyte has greatly improved the capacitances, mostly due to the occurrence of pseudo-capacitance derived from the redox reaction of p-phenylenediamine at the electrode/electrolyte interface. For instance, the capacitances of the C-900-6/9/12 samples can reach up to 105.1, 232.8, and 317.6 F g− 1 at 5 A g− 1, respectively, and all of which are much higher than that of the pristine C-900 sample (42. F g− 1). Obviously, we have provided a simple but highly efficient approach for the improvement of the supercapacitor capacitance by introducing the p-phenylenediamine into KOH electrolyte, which exhibits the advantages of low cost, easy operation, high efficiency, etc.