Formation of micro/mesopores during chemical activation in tailor-made nongraphitic carbons

The mechanism of chemical activation by potassium hydroxide (KOH) was studied in highly controlled non-graphitic carbon structures to explore the constituent reactions and the related pore formation processes involved in producing highly microporous activated materials. For this purpose, nongraphitic carbon was activated independently with intermediate species of either metallic potassium (K) or potassium carbonate (K2CO3) reduced from KOH (activating agent). Structural and morphological changes during activation were probed ex situ using X-ray diffractometry and Brunauer-Emmett-Teller (BET) nitrogen gas adsorption. Reduced K and K2CO3 disordered the stacking graphene layers to different extents. While micropore features were induced upon K evaporation following infiltration, the existing micropores were expanded into mesopores by K2CO3 gasification. Exclusive activation with K or K2CO3 induced ultra-small micropores, as measured using cyclic voltammetry. This work explains why activation using a KOH solution develops the preferable porous texture for use in many devices by creating open microporous structures as a result of the synergistic activation of both K and K2CO3. (C) 2017 Elsevier Inc. All rights reserved.