F. Zhao et al., Electron transfer in the reduction of cobalt porphyrin incorporated into nafion and poly(4-vinylpyridine-co- styrene) films, J PORPHYR P, 3(3), 1999, pp. 238-246
Potential step chronoamperospectrometry (PSCAS) measurement was carried out
to investigate the one-electron transfer in the reduction of tetraphenylpo
rphyrin cobait(III) ([(CoTPP)-T-III(-2)](+)) incorporated into a Nafion or
poly(4-vinylpyridine-co-styrene) (P(VP-St)) film coated on an ITO electrode
. The electron transfer of the redox centers in the two systems occurred by
a physical diffusion mechanism. The fraction of the electroactive complex
(R-ct) was independent of the CoTPP concentration in P(VP-St) but decreased
with increasing CoTPP concentration in Nafion, especially at high concentr
ations. Ln both systems the apparent diffusion coefficient D-app decreased
with increasing CoTPP concentration. The D-app value in Nafion (1.6 x 10(-8
) cm(2) s(-1) at 0.02 M) was much higher than that in P(VP-St) (1.1 x 10(-1
0) cm(2) s(-1) at 0.02 M). The difference in the electron transfer process
in the two systems was ascribed to the interaction of the redox center with
the polymer framework, the morphology of the polymer matrix, the localizat
ion of the redox species in the hydrophilic/hydrophobic region, and the cou
nterion migration under the potential step. Copyright (C) 1999 John Wiley &
Sons, Ltd.