Fabrication of Activated Multiporous Carbon Nanofibers Using Vacuum Plasma for High-Capacity Energy Storage

Abstract

Porous carbon nanofibers are widely used as supercapacitor electrode materials due to their excellent physical adsorption/desorption operation and smooth transport of ions. The acid/base activation method is commonly used to generate micropores on the surface of carbon nanofibers, but controlling the activation level and minimizing the release of harmful chemicals pose challenges. This study proposed a method for producing activated multiporous carbon nanofibers that is easier to operate and more environmentally friendly. It utilizes the vacuum plasma process to enhance surface area and introduce functional groups onto the electrospun polymer nanofibers. Subsequent heat treatment results in the formation of activated multiporous carbon nanofibers. The type and density of the functional group introduced into the carbon structure were adjusted to the type of plasma gas (O2, NH3 and C4F8) being exposed. Among them, oxygen plasma-treated carbon nanofibers (O-MPCNFs) not only have a much larger active surface (517.84 m2 g−1) than other gases (290.62 m2 g−1 for NH3 and 159.29 m2 g−1 for C4F8), but also generate a lot of micropores, promoting rapid adsorption/desorption-inducted charges; therefore, they have excellent energy storage capacity. The O-MPCNF-based symmetrical two-electrode supercapacitor has a high specific capacitance (173.28 F g−1), rate capability and cycle stability (94.57% after 5000 cycles).