Hierarchical porous carbon with high specific surface area and superb capacitance made from palm shells for supercapacitors

The preparation of high-performance porous carbon for supercapacitors was attempted using palm kernel shells (PKS), a waste derived from the production of palm oil. The objective was to expand the application of PKS and add value to it. Specifically, KOH was used as the activation agent to generate PKS-based porous carbons via two different activation processes, namely the one-step and two-step method. The results showed that the activated carbon 2-PSPC-5 obtained with the two-step method exhibited a larger specific surface area of 2521 m2/g, which is 47 % higher than that of 1-PSPC made from the one-step method. 2-PSPC-5 also had a higher specific capacitance of 360 F/g, 50 % higher than that of 1-PSPC. In addition, O, P, S self-doping was achieved with the hierarchical porous carbon prepared via the two-step method without needing to add other O, P, S sources. The characterizations of the prepared samples indicated that the two-step porous carbon was dominated by meso-pores, which are only achieved at a high mass ratio. Finally, the symmetric supercapacitor assembled using 2-PSPC-5 achieved an energy density of 11.38 W/kg at the power density of 500 W/kg, which is much higher than that reported in most literature. In summary, this study confirmed that palm shells could be a suitable source used for the preparation of porous carbon, which has great potential for future applications in supercapacitors.