We have prepared TiO2 supported Fe2O3 photocatalyst by sol-gel method.
The photocatalytic performance of the prepared catalyst has been studied under UV light using paracetamol as a model compound.
The rate of degradation in the presence of oxygen was lower than that in the absence of oxygen.
There may be two effects:
1) if the light wavelength is near 200 nm, O2 may still absorb a bit in this region and the light intensity on the catalyst decrease.
2) The main reason is probably that photocatalytic reaction involve free electrons and holes produced by the light. However O2 is an excellent electron trap (O2 + e- = O2-). Thus, in the presence of O2 the amount of electrons available for the catalytic reaction may be lower than without.
Cheers,
Pierre
during the synthesing of the Fe2O3, Fe2O3 can not be obtained exactly. in the reaction medium byproduct can be found which react with O2 molecules. therefore I recommended to control reaction steps.
Hi osama,
In addition to the previous answer, first I want to know what the wavelength of your UV light irradiation you have been used? and (excuse me), what is meant of TiO2/Fe2O3 in your case ( is it TiO2 as a support or Fe2O3 as a support? since I think it is different . For instance, TiO2 as a support, it means the base of band-gap energy is TiO2 (3,2 eV) and Fe2O3, a spinel structure, as a dopant ( you want to know the effect of Fe2O3 addition on photocatalytic activity : whether increase or decrease its activity to degradate the compound ; and also what is the percentage of Fe2O3 added to TiO2 ?). Since it is obvious that oxygen addition in the photocatalytic process gives a positive effect to its activity.
regard,
Rudy
Dear Rudy,
TiO2 was deposited on the surface of Fe2O3 (i.e. Fe2O3 used as support).
Different ratios of TiO2/Fe2O3 from 10 to 50 wt/wt% were prepared.
450 W medium pressure mercury lamp, which emit broad spectra ranging from 185 to 570 nm, was used as light source.
Regards,
Osama
Hi Osama Nasr,
Thank for your information. Well, it means hematite as support (Fe2O3 : alpha, beta or gamma or FeO formation depending on temperature calcination or annealing). Also hematite band-gap is affected by annealed temperature (band-gap energy will increase as annealed temperature increase : 1.67 - 1.94 eV). In addition O2 molecule for the first excited level from ground state needs 1.62 eV and EA (energy afinity) for oxygen atom : -141 kJ/mol to become O(-) and +744 kJ/mol to become O(2-). So I hope this information will be useful (whether oxygen will decrease or increase the photocatalytic activity, in your case).
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