The reduction of oxygen on titanium oxide electrodes

The cathodic reduction of oxygen in 1 mol dm^-3 sodium hydroxide solutions has been investigated at several types of titanium oxide cathodes. Layers of TiO₂ were prepared on titanium by spraying and thermal decomposition of solutions of titanium n-butoxide in 2-propanol and titanium tetrachloride in methanol+water and also by anodization; the reduction was also studied at Ebonex®, a conducting ceramic consisting mainly of Ti₅O₉. In all cases, the reduction of oxygen occurs largely by a 4e^- reaction to water and the reaction occurs at potentials close to -1.0 V vs. SCE. Cyclic voltammetry in the absence of oxygen shows that, at these potentials, the surfaces undergo reduction and the electrochemistry of the Fe(CN)₆^4- /Fe(CN)₆^3- couple has been used to probe further the properties of the TiO₂ surfaces.