Structural elucidation of physical and chemical activation mechanisms based on the microdomain structure model

Abstract

Activated carbons (ACs) prepared by chemical activation commonly show higher specific surface areas and higher yields than those prepared by physical activation. In this study, the differences in the pore development mechanisms between physical and chemical activation processes for AC preparation were studied from a structural point of view, based on the microdomain structure model. Phenol resin-based spherical carbon was used as the starting material. AC preparation via potassium hydroxide (KOH) activation (chemical activation) did not induce noticeable changes in the particle or microdomain sizes, despite the abundant development of pores. On the other hand, ACs produced via steam activation (physical activation) showed remarkable reductions in both particle and microdomain sizes, depending on the activation temperature. Considering the differences in activation yield and degree of developed porosity between chemical and physical activations, we concluded that, in the case of KOH activation, pore development homogeneously progressed overall for all microdomains consisting of carbon particles without apparent morphological change; however, steam activation caused inhomogeneous gasification from the outer surface of the carbon particles and microdomains. For this reason, KOH-ACs showed higher yield and superior pore development.