| dc.description.abstract | Cyclic voltammetry scans were obtained using a PAR model
175 Universal programmer in conjuction with PAR 173
potentiostat/galvanostat. The output signal were fed into
a PAR RE 0089 X-Y recorder. The three electrodes assembly
used were, carbon graphite as the working electrode,
saturated calomel electrode(SCE) as reference electrode and
platinum wire as the counter electrode.
The polyaniline film used in all the experiments were
electrodeposited by cycling the potential between -0.2v to
0.75v and scan rate of 20mV/Sec. In a solution containing
1M sulphuric acid and 0.1M aniline monomer.
When a fresh polyaniline was transferred to 1M sulphuric
acid( no aniline monomer) and the potential window varied,
it was found that anodic peak current is directly
proportional to time at low potential windows (below 0.75v,
positive limit) si nce- the plots of anodic peak current
versus time gave straight line graphs.
This relationship did not hold for higher potential
windows ( above 0.75v) since the plots of anodic peak
current versus time gave curves. Also at higher potential
windows a second-peak which is due to formation of quinone
derivates was observed. The appearance of quinone
derivative peak resulted to faster polyaniline degradation,
since the conversion of polyaniline to quinones is
irreversible.
The electron charge transfer was found to be faster at high
acid concentrations(low pH). This was proposed to be due
to decrease in solution conductivity as the solution
concentration is lowered. It was further found that the
rate of degradation of polyaniline in acid media depends on
the type of acid (media), but independent of pH of the
solution, since in all the concentrations of sulphuric acid
used the slopes of anodic peak current versus time was the
same(2.6 MiliAmperes per second), and that for the ranges
of Hydrochloric acid used was 1.3 miliAmperes per second.
Degradation of polyaniline in salt solution was found to be
totally suppressed. This was proposed to be due to the
fact that, the anions from the salt solutions formed an
ion-pair compound with the imine, and this leads to
stabilization of the imine to hydrolysis. When the
electrode was transferred to acidic media, the voltammetric
response obtained was of the same magnitude as the
originally deposited polyaniline. | en |
