Due to high conductivity and ion mobility, generally acidic electrolyte such as 1 M H2SO4 was commonly used as an electrolyte in supercapacitor (SC) applications. The high conductivity due to proton comes with a penalty of high corrosion rate of cell components. In order to decrease the acidity of the electrolyte without sacrificing the SC performance, a mixed electrolyte was explored combining 0.25 M H2SO4 with 1 M KNO3. As electrode, activated carbon derived from Borassus flabellifer tree fruit pericarp was used, which is tested in both three and two electrode modes (symmetric SC). Symmetric SC exhibited a power density of 5 kW kg(-1) at 10 A g(-1) and energy density of 6.94 Wh kg(-1) at 1 A g(-1).