Effect of KOH addition on electrochemical properties of coal-based active carbon foams

Using strong-caking coking coal as raw material, coal-based carbon foam (NCF) was prepared by constant pressing and self-foaming method and used as carbon base to produce coal-based active carbon foamed (HPCs) together with KOH activator, which was used as electrode material for double-layer capacitor. The effects of KOH added by mechanical mixing, aqueous solution impregnation and ethanol solution impregnation methods on microstructure and electrochemical properties of the prepared materials were studied. The results show that formation of pore structure, crystal structure, surface chemistry and electrochemical performance of HPCs are significantly affected by KOH dispersion and adhesion. The NCF itself has a three-dimensional connected bubble pore structure, which is conducive to the activator (KOH) penetrating into the bubble pore and providing a large number of attachment sites, thus increasing the contact area between the activator and the carbon matrix and resulting in efficient activation. The good fluidity of KOH solution can make K⁺ more effectively interspersed in the bubble structure of NCF, act on the defect site during activation, and generate more micropores and mesoporous structures on the internal matrix of carbon matrix, effectively amplifying the activation effect. ACF-W obtained by KOH aqueous impregnation has the highest specific surface area (3098.35 m²/g), total pore volume (1.68 cm³/g), mesoporous volume ratio (59.13%). It shows excellent specific capacitance (310 F/g) and cycle stability when used as electrode material.