Influence of the activation conditions on the porosity development of herringbone carbon nanofibers

The influence of different activation conditions, including activating agent/CNFs mass ratio, activation temperature, activation time and He flow rate, on the pore structure development of herringbone carbon nanofibers (CNFs) has been studied. Activation conditions with a KOH/CNFs mass ratio = 5/1, activation temperature = 850 °C, activation time = 3 h and He flow rate = 700 mL min−1 gave rise to a material with a very high micropore volume, a quite narrow micropore distribution and the highest surface area (increased by a factor of 4.5 in comparison to the raw CNFs). The conditions outlined above also led to the creation of some mesopores in the activation process due to the strong interaction between the CNFs and the activating agent. On the other hand, the use of other activation conditions led to activated CNFs with different structural properties. For example, activated CNFs with the lowest mesopore volume were obtained when the activation conditions were KOH/CNFs mass ratio = 5/1, activation temperature = 900 °C, activation time = 3 h and He flow rate = 500 mL min−1. Therefore, depending on the final application of the activated CNFs, it is possible to control their pore structure by selecting appropriate activation conditions.