Fluorinated Carbon Nanofibrous Aerogel Electrode Material Derived from Hydrofluoric Acid Treatment on Stabilized Polyacrylonitrile for High-Performance Supercapacitors

Carbon nanofibrous materials from electrospinning are good candidate electrode materials for supercapacitor applications due to their straightforward processability, chemical stability, high porosity, and large surface area. In this research, a straightforward and effective way was revealed to significantly enhance the electrochemical performance of carbon nanofibrous electrode material from electrospinning of polyacrylonitrile (PAN). Fluorination of the electrospun carbon nanofibers (ECNF) was studied by comparing two types of hydrofluoric acid (HF) treatment, i.e., direct HF acid treatment on ECNF (Type I) vs. HF acid treatment on the stabilized PAN (Type II) followed by carbonization. The latter was found to be an advantageous way to introduce C-F bonds in the resultant carbon nanofibrous electrode material that contributed to pseudocapacitance. Furthermore, the Type II HF acid treatment demonstrated exciting synergistic effects with ECNF aerogel formation on carbon structure and porosity development and generated a superior fluorinated electrospun carbon nanofibrous aerogel (ECNA-F) electrode material for supercapacitor uses. The resultant ECNA-F electrode material demonstrated excellent electrochemical performance with great cyclic stability due to the large improvements in both pseudocapacitance and electrical double-layer capacitance. ECNA-F achieved a specific capacitance of 372 F/g at a current density of 0.5 A/g with 1 M H₂SO₄ electrolyte, and the device with ECNA-F and 1 M Na₂SO₄ electrolyte possessed an energy density of 29.1 Wh/kg at a power density of 275 W/kg. This study provided insight into developing high-performance and stable carbon nanofibrous electrode materials for supercapacitors.