Photoelectrochemical Properties of a Dinitrogen-Fixing Iron Titanate Thin Film

The band edge positions of a nitrogen-fixing nanostructured semiconductor thin film are determined both in the dark through spectroelectrochemistry and under irradiation by photovoltage measurements. Both methods afford the same result indicating that the film in addition to the dinitrogen-fixing phase Fe₂Ti₂O₇ also contains titanium dioxide. Thus, both methods enable the analysis of a mixture of semiconducting thin films. For pH 7, values of −0.4 and +1.6 V were estimated for the conduction and valence band edge of the iron titanate film, respectively. A 3-fold photocurrent increase by methanol was observed only when the film was calcined at 600 °C but not below or above this temperature; the films calcined at temperatures other than 600 °C were also inactive in the photoreduction of dinitrogen. For a matter of comparison, an iron(III) oxide film was characterized analogously.