PHOTOELECTROCHEMICAL CHARACTERIZATION OF ELECTRODEPOSITED POLYANILINE

Photoelectrochemistry is based on interfacial electron transfer, where one of the phases is the excited state of a semiconductor. We used th e a.c. impedance technique in order to investigate these interface pro cesses. Polyaniline films galvanostatically grown on platinum electrod es showed variation of photocurrent responses with d.c. bias with two maxima, 0.4 and 0.7 V, and a minimum at 0.65 V. Electrochemical impeda nce spectra were used to model the interface in terms of the variation of space-charge layer capacitance with d.c. bias, observed in lower f requencies. The flat-band potential, in the order of 0.65 V versus Ag/ AgCl, was determined from Mott-Schottky plots and was also observed in photoelectrochemical experiments. From the slope of the Mott-Schottky plot we observed that the charge carriers concentration is higher whe n polyaniline is irradiated. The polyaniline gap, 2.85 eV, was determi ned by the Kubelka-Munk function. (C) 1997 Elsevier Science S.A.