Kt. Kawagoe et al., PH-DEPENDENT PROCESSES AT NAFION(R)-COATED CARBON-FIBER MICROELECTRODES, Journal of electroanalytical chemistry [1992], 359(1-2), 1993, pp. 193-207
Cyclic voltammetry has been used to examine pH-dependent processes in
aqueous solution at carbon-fiber electrodes with scan rates above 100
V s(-1). Specifically, the reduction of p-benzoquinone and the oxidati
on of dopamine have been investigated. The mechanism of electrolysis o
f quinoidal compounds has been extensively characterized at slow scan
rates with conventional electrodes in prior work. Digital simulations
based on the reported rates and E(o) values show that the electrode re
action mechanisms can be diagnosed at high rates of scan by examinatio
n of the pH dependence of the peak potentials of cyclic voltammograms.
However, the experimentally determined pH dependences of the voltamme
tric peak potentials for these compounds differ from those obtained by
simulation suggesting the electrode mechanism differs at carbon-fiber
electrodes. The altered mechanism may reflect surface catalysis since
the data show a correlation between the position of the surface volta
mmetric waves found at carbon-fiber electrodes and the voltammetric pe
ak positions of the compounds. When the electrodes are coated with Naf
ion(R), the pH dependence of the voltammetric waves is further altered
. The surface waves are found to shift linearly with pH, and can be us
ed to diagnose alterations in the pH of the solution.