Investigations of the structure of the iron oxide semiconductor-electrolyte interface

The ceramic semiconductor photoelectrodes made of Fe1.99Sn0.01O3, Fe1.99Nb0.01O3, Fe1.8Nb0.2O3 and FeNbO4 are synthesized. The spectral and current-voltage characteristics of photoelectrodes are measured. The anodic photocurrent onset potential is determined. The threshold photon energies corresponding to the inter-band optical transitions near the edge of the fundamental absorption of the semiconductor photoelectrode are calculated. The analysis of the frequency dispersion of the real and imaginary parts of the complex impedance of photoelectrochemical cell with manufactured electrodes is carried out. On the basis of this analysis, equivalent circuits describing the structure of the double electrical layer on the semiconductor-electrolyte interface are proposed, their parameters are calculated. Main limiting steps of the electrode process are determined.