Electrochemical transformation of SWNT/Nafion composites
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The electrochemical performance of single wall carbon nanotube (SWNT)/Nafion composite electrodes were studied in sulfuric acid solutions. Electrochemical oxidation of the highly dispersed SWNTs within the Nafion matrix results in a dramatic morphological change in the SWNTs. As evidenced by transmission electron microscopy, small bundles of straight-line SWNTs change into curved bundles with relatively sharp contours. Electrochemical impedance spectroscopy indicates increased electrochemical impedance in the oxidized SWNT/Nafion composites. Reduction of the composites at low potentials reverses impedance to near original values. However, the morphological change of the SWNTs is irreversible. In addition, the electrochemical capacitance of the composite electrode increases significantly after the oxidation-reduction cycle. Our results demonstrate that electrochemical oxidation and reduction treatment of the composite is also potentially useful for modifying the SWNT sidewalls, which results in an enhancement of the electrochemical capacitance of SWNTs.