Electrochemical and structural characteristics of activated carbon-based electrodes modified via phosphoric acid

To improve the electrochemical performance of an activated carbon (AC)-based electric double-layer capacitor (EDLC), the AC surface, which is used as an electrode, was modified using different concentrations of phosphoric acid. The effects of the treatment on the surface and electrochemical properties of the AC electrodes were investigated. The specific capacitance increased from 256 F/g for an untreated sample to 452 F/g for a sample treated with a 2 M solution at a scan rate of 5 mV/s. This increase can be attributed to an increase in the mesopore volume caused by the etching effect of the reaction between the carbon surfaces and phosphoric acid. In addition, oxygen functional groups, which were introduced by the treatment, improved the electrochemical properties of the resulting AC-based electrode. Therefore, simultaneous etching and oxygen introduction with phosphoric acid can easily bind oxygen functional groups (particularly CO) onto the surface of an AC electrode. This method is effective at preparing AC for use in an EDLC with improved electrochemical properties.

The enhancement of the capacitance can be attributed to the synergistic effect of the increased electrochemical activity in the AC and mesopore volume, which were induced by the phosphoric acid treatment.Figure optionsDownload as PowerPoint slideHighlights
► The H3PO4 treated AC samples showed the enhanced specific capacitances.
► The texture properties of AC increased due to phosphoric acid treatment.
► The CO groups onto the surface of AC increased via phosphoric acid treatment.
► The etching and introduction of CO groups proved effective in the capacity.