Abstract:
A number of models have been developed to describe electron transfer
between electrolytes and group II–VI binary semiconductors. In this report, a
study was conducted to describe and model electron transfer between an
inorganic semiconductor, (i.e. CdS) and a ferric oxidizing/reducing agent [i.e.
K3Fe(CN)6/K4Fe(CN)6]. We describe the interfacial electron transfer using the
semi-classical theory approaches as described by Marcus and later developed
by Gerischer and therefore called Gerischer model as it is applied to
heterogeneous electron transfer in a semiconductor - electrolyte interface. CdS
thin films were grown by electro-deposition method on the indium tin oxide
(ITO) substrates and were used as electrodes. The data collected was used to
determine the kinetic constant rates and re-orientation energies as measured in
the solutions with different concentration of redox system, Fe+3/ Fe+2.
Experiments showed that when concentration of oxidized species increased
and causing an increase in
EF , redox 2
activity, the kinetic constant rates
decreases inversely. Equally light induced current at 0.0V/Ag was higher
when the ratio of the oxidant-reductant (i.e. 2/0.02 and 0.2/0.02) was high. EIS
studies revealed that for the two ratios of. 2/0.02 and 0.2/0.02, the difference
of current density was comparable to the transfer of the charge carriers for the
oxidant-reductant electrolyte at 2/0.02 with respect to 0.2/0.02.
