Microstructure and morphology of porous carbons derived from sucrose

Abstract

Amorphous porous carbon samples with porosities up to 80% were synthesized from a sucrose solution using a dehydrating acid and a cationic component. The impact of different synthesis parameters like acid type, acid content, sucrose concentration and cationic component on the microstructure and morphology were evaluated. The carbons were characterized with small-angle X-ray scattering (SAXS), gas sorption and electron microscopy. SAXS and electron microscopy indicate μm sized carbon structures without any substructure on the nanoscale except for microporosity. The SAXS-data reveal a basic microporosity created upon pyrolysis resulting in micropore volumes up to about 0.30 cm 3/g. Although microporosity is present, the analysis of certain carbon samples with nitrogen sorption fails as the pores are not accessible for nitrogen. The addition of ammonium components in combination with sulphuric acid promotes the accessibility of the micropores for nitrogen and leads to specific surface areas as deduced via sorption of up to 530 m 2/g and micropore volumes of 0.28 cm 3/g. Comparison of the micropore volumes detected by SAXS and CO 2-sorption reveals an unexpected systematic deviation of the sorption derived values towards higher micropore volumes. An appendix discusses in detail the assessment of microporosity by the two methods.