Physico-chemical surface modification of activated carbon by oxyfluorination and its electrochemical characterization

The surface of a phenol-based activated carbons (ACs) used as an electrode in an electric double-layer capacitor (EDLC) was oxyfluorinated at room temperature with different F2:O2 gas mixtures, and the effects of these surface modifications on EDLC electrical performance were investigated. The specific capacitance of the oxyfluorinated AC-based EDLC was measured in a 1 M H2SO4 electrolyte, in which it was observed that the specific capacitances increased from 375 and 145 F g−1 to 391 and 189 F g−1 with the scan rates of 5 and 50 mV s−1, respectively, over compared to those of an untreated AC-based EDLC when the oxyfluorination ratio was at the optimal F2:O2 = 5:5. This was attributed to the synergistic effect of surface chemical compositions and textural properties of the resulting oxyfluorinated AC, which had the highest micropore volume, an optimal mesopore volume, and electrochemically active surface functional groups, such as C–F and quinone CO.

The specific capacitance of the activated carbon-based electrode remarkably increased after oxyfluorination at 1 bar with a F2:O2 (5:5) gas mixture (FO55-AC), compared to that of the untreated one, due to the increased micropore volume and electrochemically active groups, such as quinone CO and C–F.Figure optionsDownload as PowerPoint slideHighlights
► Activated carbon (AC) surface was modified by oxyfluorination to enhance specific capacitance of the AC-based electrode.
► Electrochemically active C–F and quinone CO functional groups were introduced by oxyfluorination.
► Meso and micropore volume was increased by oxyfluorination.
► The specific capacitance of the AC-based electrodes improved by the above-mentioned changes induced by oxyfluorination.