Acid Washed, Steam Activated, Coconut Shell Derived Carbon for High Power Supercapacitor Applications

The suitability of steam activated, coconut shell derived carbon (CSC) and its three variants obtained by acid washing of the CSC is investigated in detail for high power super capacitor applications using in depth electrochemical characterization. The CHNS and PIXE analysis is used to verify the purity of the samples. The structural and surface studies using Raman spectroscopy and BET techniques reveal that, after washing with acids, the structural features of the activated carbon get improved to a significant extent. Out of the three acid washing procedures, washing with HF is found to yield the activated carbon sample AC4 with maximum purity, structural order and surface morphology with optimum ratio of micropores to mesopores, suitable to facilitate fast electrolyte ion diffusion and transport. The two electrode measurements with organic electrolyte using symmetric AC4 electrode based supercapacitor test cells give an electrode capacitance of 162 F g −1 and an energy density of 35.2 Wh kg −1 at a current density of 1 A g −1 , and a power density of 3967 W kg −1 at 10 A g −1 along with good cycling stability. It is also observed that 96% of the initial capacitance is retained after 5000 cycles at a current density of 10 A g −1 .