Enhancing the pore wettability of coal-based porous carbon as electrode materials for high performance supercapacitors

The current drawback in supercapacitor (SCs) performance is mainly due to their low energy density. Increased specific capacitance (C) is not only related to the specific surface area (SBET) but also to the inner surface of the micropores that are wetted by electrolyte. In this paper, water vapor assisted trace KOH (alkali to carbon ratio of 0.02) activation is used to achieve the synergistic regulation of coal-based porous carbon pores and wettability based on the pore-forming of K-based components in high-temperature etching reactions. The results show that AC-K-V, modified by H2O-assisted trace KOH, forms a developed micropores and mesopores, high graphitization degree (ID/IG is 0.83) and abundant oxygen-containing functional groups. The mesopores provide a transport channel for electrolyte to smoothly enter the internal pores, high graphitization degree reduces the charge transfer resistance, and oxygen-containing functional groups enhances the wettability of electrode, which synergistically improves the SBET utilization of the activated carbon. The C of AC-K-V increases significantly: 202% higher than that of the control group (AC). Additionally, the C retention is up to 92.5% after 5,000 times cycles. Furthermore, the assembled symmetric SCs of AC-K-V can deliver an energy density as high as 7.64 Wh/kg in aqueous electrolyte. [Display omitted] •The poor wettability is the main reason for the low specific capacitance.•H2O-assisted trace potassium achieved synergistic regulation porosity and wettability.•The AC-K-V electrode exhibits high specific capacitance of 254 F/g at 0.5 A/g.•The AC-K-V electrode shows excellent rate performance and superior cycling stability.