Influence of the activating agent and the inert gas (type and flow) used in an activation process for the porosity development of carbon nanofibers

Carbon nanofibers (CNFs) were activated with different activating agents (KOH, KHCO3 and K2CO3). The effects of different activations conditions, including type of protector gas (He, Ar and N2) and helium flow rate on the properties of activated carbon nanofibers were studied. The structural changes in activated CNFs were investigated using the following characterization techniques: N2 adsorption isotherms at 77 K, XRD, temperature-programmed desorption of hydrogen, TEM, TPO and elemental composition.The results showed that the surface area increased by a factor of 3.3, 2.0 and 1.8 referred to the parent CNFs after the treatment with KOH, K2CO3 and KHCO3, respectively. In addition, KOH generated a greater pore volume than the other activating agents; micropores were mainly generated during the process. Finally, different carrier gases were added during the activation in order to study their influence on the pore opening behavior of CNFs. It was found that the activation degree increased in the following order: Ar < N2 < He. When He was used as the carrier gas, the microporosity was strongly developed.

The proportions of ultramicropores, supermicropores and mesopores of activated carbon nanofibers is quite influenced of the type of protector gas (He, Ar or N2) used during activation. The porosity development was higher when helium was used as protector gas.Figure optionsDownload as PowerPoint slide