| dc.description.abstract | The influence of chemical oxidation on the electrochemical behavior against hydrogen peroxide of long
and short multi-walled carbon nanotubes (MWCNT) has been investigated. Different degrees of oxidation
with a sulfo-nitric mixture and with nitric acid were used and a complete physical and oxygen functional
group characterization was performed by Raman spectroscopy, Fourier transform infrared spectroscopy
(FTIR), acid group titration, transmission and scanning electron microscopies (TEM/SEM), elemental
analysis, thermogravimetric analysis (TGA), nitrogen adsorption isotherms and cyclic voltammetry. The
results revealed that electrodes modified using pristine short CNT (s-NC) present higher amperometric
response against hydrogen peroxide than that obtained using long CNT (l-NC), which correlates with the
greater degree of packing observed for l-NC by SEM and the long and thin structures observed in s-NC. On
the other hand, the chemical oxidation process increases slightly the sensitivity of resulting electrodes,
in about 25%, for both s-NC and l-NC indicating that for hydrogen peroxide oxidation the metal catalyst
impurities, that are removed in the oxidation process, are not as relevant in the electrocatalysis as the
increase in the capacitance values observed in the oxidized CNTs. The presence of oxygen groups introduces
(a) new sites for redox reaction (pseudocapacitance) and (b) strong polar sites that would adsorb
water molecules favoring double-layer formation (double-layer capacitance). | |
