Enhanced electrochemical performance of olive stones-derived activated carbon by silica coating for supercapacitor applications

Porous activated carbon (AC) was successfully elaborated from olive stones and valued as an electrode material for electrical double-layer supercapacitors. The activated carbon surface was subsequently coated by silica to improve its physico-chemical and electrochemical properties. The treated activated carbon surface (AC-Si) exhibited a meso-microporous nature. From electrochemical investigations, an improvement of the capacitive behavior was demonstrated after the silica coating. When the bare activated carbon is used as electrode materials, the specific capacitance delivered by the assembled symmetric supercapacitor is 11 F g−1 at a current density of 0.5 A g−1 for an operating voltage of 0.6 V. However, the supercapacitor based on carbon–silica electrodes showed an obvious enhancement of the specific capacitance up to 141 F g−1 at 0.5 A g−1 and operated over a larger cell voltage of 1.25 V. For the AC-Si//AC-Si device, the exhibited specific energy is 30.6 Wh kg−1 and the specific power is 1661 W kg−1 at a current density of 0.5 A g−1. Therefore, the activated carbon derived from olive stones and coated by silica is a promising electrode material for supercapacitor devices.