Iron(III)-titanium(IV)-oxide electrodes: Their structural, electrochemical and photoelectrochemical properties

Iron(III)-titanium(IV)-oxides of the general composition Fe_xTi_1-xO_y were prepared in the composition range x=0-0.9 by thermal decomposition of the corresponding metal salt solutions. For a medium range of composition, 0.1≤x≤0.7, amorphous oxides were formed under the given conditions of preparation. Electrochemical properties such as reduction and re-oxidation of the oxide, electrode capacity behaviour, oxygen evolution and reduction and the redox reaction, Fe²⁺/Fe³⁺, were investigated. Photoelectrochemical properties were obtained from photocurrent spectra and the dependence on potential of the photocurrent. Annealing experiments showed that crystallization yields lower photocurrents and a shift of the photocurrents spectra to shorter wavelengths. Thus, amorphous semiconductors seem worth being investigated for a possible application in electrochemical solar cells. An attempt is made to describe the impact of non-crystallinity on the photoelectrochemical behaviour of semiconductors. A model of the oxide is proposed to explain the electrochemical and photoelectrochemical properties of the oxides Fe_xTi_1-xO_y.