Notable improvement of capacitive performance of highly nanoporous carbon materials simply by a redox additive electrolyte of p-nitroaniline

Highly nanoporous carbon materials have been produced by a synchronous carbonization/graphitization process, using magnesium citrate serves as the carbon source and nickel nitrate as graphitization catalyst. The carbonization temperature plays a crucial role in determining the porosity and graphitization. The lower temperature favors for the formation of larger porosity, whilst higher temperature for better crystallinity. Resultantly, a high BET surface area of 2587.13 m2 g−1 and large total pore volume of 4.64 cm3 g−1 appear, the case of C-800 sample, thereby resulting in a large specific capacitance of 305.3 F g−1 at 1 A g−1 from the contribution of electric double layer capacitances. More importantly, we demonstrate a novel redox active additive of p-nitroaniline (PNA) into the 6 mol L−1 KOH electrolyte to largely improve the capacitance by the quick self-discharge redox reaction of H+/e−. The C-800-2 sample with the PNA concentration of 2 mmol delivers largely improved capacitance of 502.1 F g−1 at 1 A g−1, which is almost 1.65 fold increase. Apparently, the present PNA is commercially available, and highly effective for elevating the specific capacitance and might be implemented for the wide supercapacitor application.