Dynamics of TiO2-based photoelectrochemical cell

The present work reports the effect of light on the open-circuit voltage of a photoelectrochemical cell (PEC) formed of TiO2 photoanode, Pt cathode and Na2SO4 (0.35 M) aqueous solution as electrolyte. The studies included the measurements of the electromotive force (EMF) during the light-off and light-on cycles for the PEC involving photoanode that was made of both oxidised and reduced TiO2 thin films. These specimens were formed by oxidation of the titanium metal at high and low oxygen activities. This was achieved by the imposition of the gas phase of two different compositions, including air, p(O2)"‰="‰21 kPa, and the hydrogen-water vapour mixture, p(O2)=10−10 Pa, at 1,123 K and subsequent cooling to room temperature. The determined data indicate that the PEC formed of the oxidised specimen exhibits larger EMF and a substantially better stability in time. It is, therefore, concluded that the TiO2 obtained in air exhibits superior performance-related properties compared to the reduced specimen. The obtained experimental EMF data are considered in terms of the effect of light on the reactivity of TiO2 with oxygen and water and the related charge transfer.