Electrochemical capacitance of MWCNT/polyaniline composite coatings grown in acidic MWCNT suspensions by microwave-assisted hydrothermal digestion

摘要

Acidic suspensions of multi-walled carbon nanotubes ( MWCNTs) in 5 M HNO3 solutions have been readily obtained by microwave-assisted hydrothermal digestion. FT-IR and XPS analyses indicated rapid functionalization of the surface of the MWCNTs could be achieved by a less environmentally hazardous approach. Composite coatings of MWCNTs and polyaniline ( PANI) were grown in situ onto graphite electrodes in an acidified suspension of MWCNTs and aniline. The as-grown MWCNT/PANI composites were characterized by SEM, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The results confirmed that the composite coatings had a lower resistance and much improved mechanical integrity than the pure PANI ones. The capacitance per geometric electrode surface area ( F cm(-2)) of the composites increases linearly relative to the deposition charge, reaching as high as 3.6 F cm(-2), which can be compared favorably with the capacitance of 2.3 F cm(-2) of the pure PANI, and comparable to a capacitance of 3.5 F cm(-2) for the similar composite coating with the traditionally acid-treated carbon nanotubes. The advantage of the integrity of the MWCNTs after microwave exposure was used to improve the conductivity and the mechanical strength of the composite coatings, especially when an utmost thick coating was attempted for a high capacitance.