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 the a.c. impedance technique in order to investigate these interface processes. Polyaniline films galvanostatically grown on platinum electrodes 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 impedance spectra were used to model the interface in terms of the variation of space-charge layer capacitance with d.c. bias, observed in lower frequencies. 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 when polyaniline is irradiated. The polyaniline gap, 2.85 eV, was determined by the Kubelka—Munk function.