Plasma Treatment of Carbon Nanotubes Applied to Improve the High Performance of Carbon Nanofiber Supercapacitors

•The plasma modification method avoided the destruction of the length and structure of the CNTs and maintained their good electrical properties.•The highest conductivity of the CNTs-MA/CNF was 5.2 s/cm at 2.5 wt.% of CNTs-MA addition. It was increased to 8.7 time.•The CNTs-MA added to the CNFs successfully maintained the activity sites on the surface of the CNFs and provide a good electric network to enhance the supercapacitor performance of the CNFs. The highest capacitance was 382 F/g.

Plasma-treatment carbon nanotubes (CNTs) grafted with maleic anhydride (MA) were embedded in polyacryonitrile nanofibers via electrospinning and subsequently carbonizated at 800 °C to fabricate carbon nanofibers (CNFs). The grafted degree of MA on CNTs (CNTs-MA) was determined via Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The morphology, surface composition and conductivity of the CNTs-MA/CNF were characterized using electron microscopy, X-ray photoelectron and electrochemical impedance spectroscopy, respectively. CNTs-MA not only affected the conductivity of the CNFs but also the types of the nitrogen functional groups that could be represented as active sites on the CNFs to enhance the performance of the supercapacitors. When 2.5 wt.% CNTs-MA was embedded in the CNFs, the highest conductivity was obtained at 5.2 s/cm, and the amount of pyridinic and pyrrolic species increased to 70.3%. However, the highest capacitance was not obtained with 2.5 wt.% CNTs-MA added because of current leakage present in the system. The highest capacitance was 382 F/g with 1.0 wt.% CNTs-MA embedded in CNF with proper conductivity of 2.2 s/cm. Furthermore, galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy measurements also demonstrated that 1.0 wt.% CNTs-MA embedded in CNF resulted in better electrochemical reversibility and impendence properties.

Graphical abstractThis article focused on improving conductivity of carbon nanofibers (CNFs) by added plasma-treatment carbon nanotubes (CNTs). The plasma modification method avoided the destruction of the length and structure of the CNTs and maintained their good electrical properties. Through this method, the relation between conductivity and surface activity site of CNFs was investigated. The results shown that he CNTs-MA added to the CNFs successfully maintained the activity sites on the surface of the CNFs and provide a good electric network to enhance the supercapacitor performance of the CNFs.Figure optionsDownload full-size imageDownload as PowerPoint slide