Question

Both oxidation and reduction occur in a TiO2 photocatalysis system. (a) Explain why TiO2 photocatalyst has...

Both oxidation and reduction occur in a TiO2 photocatalysis system.

(a) Explain why TiO2 photocatalyst has both oxidation and reduction ability

(b) List three oxidants which are involved in the photocatalytic oxidation of organic pollutants by TiO2 under light irradiation.

(c) Discuss why the quantum efficiency of TiO2 photocatalysis is quite low in all applications.

Engineering   Chemical-Engineering   
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Answer #1

a.) Tio2 is a photocatalytic material so it consists of a valence band which has electrons and vacant conduction band these two are separated by a bandgap. When Tio2 absorbs the photon energy electron present in valency band get excited and jump to the conduction band, leaves holes behind in valency band. Electron in conduction band reacts with the electron acceptor, a reduction reaction occurs, While holes in valency band react with electron donor and oxidation reaction occurs. This is how Tio2 shows both oxidation and reduction.

b.) Three oxidant which involved in oxidation of organic pollutantd by Tio2 under light radiation are:

   1) Hydrogen Peroxide

2) Ozone and hydrogen peroxide

3) Iron and Hydrogen Peroxid

c.) The Tio2 has a large bandgap (around 3.2 eV) so its required more ultraviolet light for photoactivation. Because of this, it shows very less efficiency in the utilization of solar light. So that the quantum efficiency of Tio2 is quite low.

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