Integration of Redox Additive in H2SO4 Solution and the Adjustment of Potential Windows for Improving the Capacitive Performances of Supercapacitors

Nanoporous carbon material with large specific surface area (2208 m 2 g –1 ) and high pore volume (4.15 cm 3 g –1 ) has been synthesized by the template carbonization method, using a glucose–zinc nitrate complex as the precursor. Moreover, adding redox-mediated ferrous ammonium sulfate (FAS) to an H 2 SO 4 electrolyte and regulating the potential windows in a two-electrode system can result in an ultrahigh specific capacitance of 1499 F g –1 at 10 A g –1 and a high energy density of 58.70 Wh kg –1, which are higher than those of the pristine one without any FAS. These remarkable improvements are attributed to Faradaic pseudocapacitances by the reversible Faradaic reactions of FAS as well as the edge active carbons showing excellent electrosorption toward Fe 2+/3+, NH 4 +, and H + . Furthermore, regulating the potential windows also exerts crucial roles in the capacitive performances. It is revealed that the potential of the −0.5–0.5 V window can lead to optimum capacitance and energy efficiency.