Chemical activations of herringbone-type nanofibers

Among new carbonaceous materials, herringbone carbon nanofibers (HCNFs) are one of the most promising precursors for the production of original adsorbents. Nevertheless, little information is available in the open literature on this subject and is mainly restricted to KOH activation. In the present study, the effects of the main activating agents currently used in chemical activation of conventional precursors, namely KOH, NaOH, ZnCl2 and H3PO4, are compared for the same HCNFs. The adsorptive properties of the obtained activated fibers are described through the corresponding nitrogen isotherms and conventional textural parameters. All chemical activations led to a common microporous texture but different efficiencies in terms of developed porosity per activating agent weight. At low activation yield (first activation regime), a microporosity is initiated resulting in a sharp decrease of the apparent mean pore size (from 20 to 15 Å) and Lc002 and simultaneously to a small increase in d002. At higher activation yield (second activation regime), the mean pore size is found to be almost constant while the specific microporous volume is greatly increased (from 0.1 to 0.32 cm3 × g−1) and the d002 and Lc002 parameters remain nearly constant. It was observed that the KOH activation is much more efficient than the other ones.