Semiconductor photoanodes in the system Fe_2O_3-Nb_2O_5 for photoelectrochemical water splitting

摘要

Ceramic semiconductor photoelectrodes made of the Fe_2O_3-Nb_2O_5 solid solutions 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 were calculated. The main limiting steps of the electrode processes, which determine the electrode polarization and current, are determined.