Electrophilic Fluorination of Graphitic Carbon for Enhancement in Electric Double-Layer Capacitance

Graphitic carbon is the ultimate source of carbon electrodes for practical application in energy storage devices as it is commercially available at a much lower cost in contrast to other forms of nanostructured carbon. Recently, fluorinated carbon with improved electrical conductivity and wettability has been found to possess better and efficient electrochemical storage properties. However, the development of a simple fluorination process is still a challenge. Herein, Selectfluor (F-TEDA) is explored as a fluorinating agent for Vulcan carbon. Fluorination of carbon material results in the formation of semi-ionic C—F (F = 8.02 at%) and ionic C—F (F = 2.71 at%) bonds as observed in X-ray photoelectron spectroscopy analysis along with an increase in defect density (ID/IG) by 33.4%. Symmetric two-electrode supercapacitor cells are assembled in Swagelok-type geometry, and the specific capacitance of fluorinated carbon is found to increase by ≈15 times in contrast to pristine carbon due to induced surface polarization despite the decrease in specific surface area by ≈34%, which is remarkable. The fabricated device is stable with ≈96% capacitance retention over 10 000 cycles, resulting in enhanced supercapacitive performance.