The diffuse reflection spectra and the photoelectrochemical properties of the ferrites ZnFe204, MgFe204, and Li0. sFe2. 504 with spinel structure are presented. A marked difference between the reflection spectra and the photocurrent action spectra is discussed. The onset wavelength of the photocurrent lies at about 550 nm. Steady-state photocurrents are severely limited by a relatively low absorptivity in the visible region and by surface recombination at low potentials. From an admittance spectra analysis, a value for the flatband potential of ZnFe204 was obtained, viz.,-0.5 V vs. SCE in 1M NaOH.

The use of n-type semiconducting materials in photoelectrochemical (PEC) cells for solar energy conversion has been studied extensively in the last decade (1). In this period, much attention has been paid to iron (III)-oxide, a-Fe203. With its bandgap of 2.2 eV,~ Fe203 is quite suitable for solar energy conversion (2-12). Stoichiometric a-Fe20~ is an insulator. It can be made n-type semiconducting by doping with higher valent ions. Shinar and Kennedy (10) studied extensively the way in which the performance of doped a-Fe203 anodes depends on the nature and the concentration of the dopant. Doping with lower valent ions can lead to p-type semiconducting~-Fe203, which acts as a photocathode in a PEC cell (13, 14).