A simple and high-effective electrolyte mediated with p-phenylenediamine for supercapacitor

A redox intermedium p -phenylenediamine (PPD) with quick reversible faradaic processes is introduced into KOH electrolyte, referred to as pseudocapacitive effect occurring on the electrode/electrolyte surface. The KOH + PPD electrolyte as potential electrolyte for supercapacitors is investigated by UV-Vis spectroscopy and electrochemical methods. As expected, the supercapacitor with KOH + PPD electrolyte has a much higher electrode specific capacitance (605.225 F g 1 ) than the one with conventional KOH electrolyte (144.037 F g 1 ) at the same current density of 1 A g 1 . Simultaneously, the supercapacitor with KOH + PPD electrolyte exhibits a much higher energy density (19.862 W h kg 1 ) than the supercapacitor with conventional KOH electrolyte (4.458 W h kg 1 ). Furthermore, the supercapacitor with KOH + PPD electrolyte shows superior charge-discharge stability. After 4000 cycles, its capacitive retention ratio is still as high as 94.530%. Supercapacitor with alkaline p -phenylenediamine electrolyte exhibits large specific capacitance (605 F g 1 ), high energy density (20 W h kg 1 ), and excellent charge-discharge stability.