Understanding the pore-structure dependence of supercapacitive performance for microporous carbon in aqueous KOH and H2SO4 electrolytes

Abstract Fifteen microporous carbons with variable nanotextural characteristics were prepared by KOH activation through tuning the KOH/carbon ratio and activation temperature. The prepared porous carbons have a high ratio of micropores and specific surface area up to 95% and 1410 m2 g−1, respectively. Combining the pore-structure analyses and electrochemical measurements in aqueous KOH and H2SO4 electrolytes, it is shown that the complexity of the pore structure has a significant effect on the electrochemical performance. The solvated/naked K+ can penetrate across the narrow pore entrance of the microporous carbons with an average pore size smaller than 0.6 nm and form electric double-layer (EDL) capacitance, while solvated/naked SO42− cannot due to its larger ionic size. However, the penetration of SO42− followed by hydrated H+ become available when the average pore size is larger than 0.6 nm. With the combination of pseudocapacitance and EDL capacitance, microporous carbon shows a much higher supercapacitive performance in H2SO4 than that in KOH electrolyte. This work on pore-structure dependence of supercapacitive performance paves a guide for tailoring pore-structure suitable for aqueous KOH and H2SO4 electrolytes.