I have synthesized CeO2 nanorod for photocatalytic degradation of Methylen Blue. not only it didnot showd the photocatalytic properties, but also it prolonged the degradation of MB. this result is in contrary to literature, I was wondering if someone help me with this issue.
MB: 200, 5ppm
CeO2: 0.02g,
lamp: UV
without CeO2, the degradation takes 2 hour
with CeO2, the degradation takes 4 hour
The possible reason could be that you did not successfully synthesise the pure CeO2 photocatalyst. May I ask what is the colour of the final product you obtained after the synthesis? and did you check the band gap and XRD pattern of the product?
The photocatalytic activity depends on various factor:
1. Crystal structure (kindly confirm the XRD pattern of your product with published data)
2. The band gap of the CeO2 is critical to its photo-activity (can you state the band gap you obtained?
3. Also, you may increase the dose of CeO2 and carry out the degradation under both UV and visible light irradiation
Thank you for your help.
I have attached Xrd-pattern of CeO2.
Their band gap, according to the attached results are around 3.5eV
In case you have partially reduced the tetravalent ceria during manufacturing or application you may have some charge transfer effects which inhibit photocatalysis. We observed such effects in case of vanadium and chromium oxide doped titania although the bandgap values looked promising..
The absorption spectra of your CeO2 nanorod is quite good and the band gap is in the range. Also, from the XRD pattern no oxygen vacancies or disorder noticed. However, I equally support the idea that the photocatalytic activity of your nanorod might have been hindered due to some serious charge transfer effects. .....But the charge transfer between the O 2p and Ce 4f states which might have caused this effect mostly emerges at UV range of 270–330 nm, however, lacking in your spectra.
Kindly change the irradiation source to: visible light irradiation
If that does not work, I may suggest you prepare another CeO2 using another technique and ensure no reduction in the tetravalency of the ceria.
Dear Dr. Kern and Dr. Oladipo
Thank you for your helpful recommendations.
I also suggest you to prepare a CeO2 sample with the classical method to precipitation with KOH or urea, to can compare his performance with your nanorods. I actually work with TiO2-CeO2 based materials and as correctly suggested the presence of Ce3+ ions is essential to promote the redox cycle of cerium oxide that is beneficial for the oxidation reaction. However also in accordance with your results the bare CeO2 despite his band-gap is not very active, probably because the charge carrier recombination in his surface is very fast.
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