The effect of electrolytic oxidation on the electrochemical properties of multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWNTs) were electrochemically oxidized by a constant-potential electrolysis method and then investigated in detail using scanning electron microscope, transmission electron microscope, FT-IR, electrical impedance spectroscopy, and cyclic voltammetry. The FT-IR spectra showed that the amount of hydroxyl generated on the surface of MWNTs increased with increasing the electrochemical oxidation time of MWNTs. The CV results, being conducted in nitrobenzene solution, showed that the nitrobenzene reduction current increased with the increase in oxidation time of the MWNTs within the first 60 min of electrolysis. An electrical equivalent circuit model for electrical impedance spectroscopy was further established to analyze the surface capacitance and resistance of the MWNTs, and the model results showed that the capacitance of the oxidized MWNTs increased greatly while the charge transfer resistance decreased, suggesting electrochemical oxidized MWNTs modified pyrolytic carbon electrode being an effective electrochemical sensor for nitrobenzene determination.