Elucidating the porous structure of activated carbon fibers using direct and indirect methods

The porous structure of a series of commercial activated carbon fibers (ACFs) (with increasing surface area) was studied using both direct and indirect methods. The porous structure was characterized directly using scanning tunneling microscopy (STM) techniques and indirectly using the Dubinin-Radushkevich-Stoeckli (D-R-S) equation applied to the nitrogen adsorption isotherm at 77 K. The porous structure was imaged at both the fiber surface and fiber cross-section and compared to analyses using indirect methods in terms of pore size, pore shape and pore size distribution. An average pore size was calculated from the fiber cross-section using section analysis in the standard STM software package and image analysis software. The pore size distribution of the ACFs was determined by applying the D-R-S equation to the nitrogen adsorption isotherm at 77 K. Additionally, a series of phenolic fibers activated under inert conditions was shown to form a stable porous structure. Comparison of this system to the ACFs using STM provided an important insight into the mechanism of pore generation in the ACFs. Copyright (C) 1996 Elsevier Science Ltd