Effects of surface chemical properties of activated carbon modified by amino-fluorination for electric double-layer capacitor

Abstract

The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1M H2SO4 electrolyte, in which it was observed that the specific capacitances increased from 215 to 389Fg−1 and 119 and 250Fg−1 with the current densities of 0.1 and 1.0Ag−1, respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43molL−1 ammonium hydroxide and 2.06molL−1 hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material.