Microtexture of High Surface Area Activated Carbons

Abstract

Activated carbons with high surface areas ranging from 800 to 4, 000 m²/g (M8, M15, M30, M40), which were prepared by use of the reaction of carbonaceous mesophase spherules with KOH, were studied by transmission electron microscopy and X-ray diffraction. With an increase in the surface area of the carbons, microtextures are changed from an anisotropic discotic of the non-activated carbon to the microtexture consisting of both single sinuous layers and stacks of 2-3 layers with 1-2 nm in size. As a result of the penetration of KOH into the mesophase spherules, homogeneous large pores with over several tens nm in diameter are formed in M8 and M15 carbons having surface areas of 800 and 1, 500 m²/g, respectively. In these carbons, slit-like pores are also present between the stacks divided by the destruction of one or two layers and a small quantity of single sinuous layers is locally distributed. A carbon with the highest area of 4, 000 m²/g, M40 is composed almost all of the single sinuous layers and the small stacks, in which stacks more than 4 layers can not be observed. The extraordinarily high surface area in these carbons can well be explained in terms of the appearance of the single sinuous layers and the small stacks on activation.