Photoelectrocatalytic removal of color from water using TiO2 and TiO2/Cu2O thin film electrodes under low light intensity

  • Feleke Zewge Department of Chemistry, Faculty of Science, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia
  • Roel van de Krol Department of Chemical Technology, Faculty of Applied Science, Delft University of Technology, Julianalaan 136, 2628 BL Delft, the Netherlands
  • P.W. Appel Department of Chemical Technology, Faculty of Applied Science, Delft University of Technology, Julianalaan 136, 2628 BL Delft, the Netherlands
Keywords: Photoelectrocatalysis, Titanium dioxide, Cuprous oxide, Composite thin film, Photo electrode

Abstract

This work describes, photoelectrocatalytic degradation of organic pollutants by using methyl orange (an azo dye) as a model compound. The TiO2 thin film and TiO2/Cu2O composite electrodes were used as semiconductor photo electrodes. Photo catalysis by UV light corresponding to the light intensity range of the solar light was employed with the aim of using renewable and pollution-free energy. Result showed that the rate of removal of color was enhanced when potential bias of 1.5 V was applied. The degradation rate was also increased either in acidic (pH 2) or alkaline (pH 10) conditions. The application of a positive potential higher than the flat-band potential on the TiO2 electrode decreases the rapid charge recombination process, and enhanced the degradation of organic compound. When the TiO2/Cu2O thin film electrode was used, more efficient electron and hole separation was observed in the composite system under very low potential. It is considered that the photo-generated holes migrate towards the interface while the electrons migrate towards TiO2 and then to the back contact transparent fluorine doped tin-oxide-coated glass (TCO), making the behavior of the composite film analogous to that of an n-type semiconductor. In all cases, the kinetics of the photo catalytic oxidation of methyl orange followed a pseudo first order model and the apparent rate constant may depend on several factors such as, the nature and concentration of the organic compound, radiant flux, the solution pH and the presence of other organic substances.

 

KEY WORDS: Photoelectrocatalysis, Titanium dioxide, Cuprous oxide, Composite thin film, Photo electrode

 

 

Bull. Chem. Soc. Ethiop. 2008, 22(1), 27-40.

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