Dynamic high potential treatment with dilute acids for lifting the capacitive performance of carbon nanotube/conducting polymer electrodes

摘要

The capacitive behavior of the electrodes, fabricated from multiwalled carbon nanotubes (MWCNTs) and poly-3,4-ethlyenedioxythiophene-polystyrene sulfonate (PEDOT-PSS), before and after dynamic high potential treatment with dilute HNO3 solutions, is investigated. The specific capacitance (Csp) of the treated MWCNTs/PEDOT-PSS electrodes can be ~ 2.5 times higher than that of the untreated electrodes. The drop of Csp in cycliability study for the treated electrodes is 0.8%, and much less than that for the untreated electrodes (16%). However, excessive treatment can deteriorate the capacitive performance of the electrodes. The morphology of MWCNTs/PEDOT-PSS composites revealed by transmission electron microscopy has no change after the treatment. The data of Raman spectroscopy show that the chemical structure of MWCNTs in the treated MWCNTs/PEDOT-PSS composites remains unchanged. The newly formed functional groups (COOH, C=O and S=O) are deemed to be generated by electrochemical oxidation of PEDOT, according to the X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy data. It is suggested that the Csp of the treated MWCNTs/PEDOT-PSS electrodes is due to the interplay between two effects: 1) the degradation of PEDOT leads to the loss of capacitive characteristics; and 2) the newly formed functional groups in PEDOT in the treated electrodes result in the increase in the Csp.