Highly-nitrogenated porous carbon for supercapacitor: Structure design and redox mechanism of amine/nitro/hydroxyl groups in KOH solution

Abstract

In this work, using folic acid as a carbon/nitrogen precursor and Zn(NO3)2·6H2O as the template, largely nitrogenated (12.4%) and highly porous carbon material has been produced by a synchronous template carbonization and nitridation approach. More importantly, two effective redox additives of magneson Ι (MI) and alizarin yellow R (AYR) have been implemented in KOH electrolyte, and, at the electrode-electrolyte interface, quick electron transfers and reversible redox reactions occur, thus resulting in additional pseudocapacitive contribution. It obviously indicates that the concentrations and functional groups including amine/nitro/hydroxyl groups adhering to phenyl ring have exerted crucial roles in the determination of incrementally capacitive behaviors. In the case of MI as redox additive, the M-10 sample delivers a largely improved capacitance of 451 F g−1 at 3 A g−1, compared with the pristine one without any additives (180 F g−1). As for the case of AYR, the resultant A-10 sample's capacitance also has highly elevated up to 405 F g−1. The redox reaction mechanisms have been fully investigated, and in particular, the nitro groups can be reduced into amine in this system. The present MI and AYR substances can serve as effective redox additives for largely improving the capacitive performance of carbon-based supercapacitors.