Thermally expanded graphite (TEG) was prepared from graphite hydrogensulfate, 1st and 2nd stage, at 550 degrees C. Surprisingly, the intercalation redox capacity and the cyclic voltammetric (CV) profiles in 18 M H2SO4 do not change significantly with respect to pristine graphite. CV in 10 M H2SO4 revealed a higher concentration of redox active surface groups. This is attributed to an oxidative attack by SO3 in the course of the exfoliation process.