Stripping mechanism of PAN-based carbon fiber during anodic oxidation in NaOH electrolyte

This study is aimed to further investigate stripping mechanism of the cover graphene layers off PAN-based carbon fiber during anodic oxidation in NaOH electrolyte. The stripping is assumed to be caused by intercalation of OH- ions, which is detected by electric capacity of the carbon fiber as positive electrode. The results show that the capacitance at initial circle is about twenty times higher in NaOH electrolyte than in H2SO4, which proves intercalation happens and induces the carbon sheets to be stripped. Moreover, the stripping occurs on the carbon fiber surface in both crystalline and amorphous regions, while in H2SO4 electrolyte only etching takes place, and preferentially in amorphous region. The difference can be caused by the ion structure and size difference between OH- and SO42-. The linear structure and much smaller size of OH- ions permit them to enter into the interlayers on the carbon fiber surface, while the tetrahedral structure and much bigger size of SO42- ions can only permit them to react on the fiber surface or somewhere loose in amorphous region.