Photoelectrochemistry of semiconductor electrodes made of solid solutions in the system Fe2O3–Nb2O5

Ceramic semiconductor photoelectrodes made from solid solutions in the system Fe2O3–Nb2O5 were synthesized. The spectral and capacitance–voltage characteristics of the photoelectrodes were determined, and the dynamic polarization with chopped light was investigated. The anodic photocurrent onset potential, the flat band potential and the shallow and deep donor density of these materials were determined. The threshold photon energies corresponding to the inter-band optical transitions near the edge of the fundamental absorption of the semiconductor photoelectrode were calculated. Analysis of the frequency dispersion of the real and imaginary parts of the complex impedance of photoelectrochemical cell was carried out. On the basis of this analysis, equivalent circuits describing the structure of the double electrical layer of the semiconductor–electrolyte interface were proposed and their parameters calculated. The main limiting steps of the electrode processes, which determine the electrode polarization and current, are defined.