I am trying to prepare g-C3N4 Catalyst from thiourea and urea. but it get starts to fume when I calcinating @ 550 degrees Celsius (heating rate 10 degrees/min). I have used a 25ml silica crucible for calcinating 10g urea and it was closed with a lid, Is there any problem? what is the reason behind this? how can I correctly calcinate urea and thiourea for the preparation of g-C3N4?
I think the problem is that you should seal the utensil that you use for calcination. Because, the product at 550 degrees Celsius is very volatile and loses the product.
Seal the covered crucible with Al foil, Al foils can hold upto 660 oC. Once the pyrolysis process is complete remove the lid and foil carefully to avoid contamination of the product. Second step, disperse the product in 200 mL water and heat at 100 oC for few hours to remove any unpolymerized urea or thiourea.
Hello, I don't see any problem if you get the g-C3N4 material. There is no step to get g-C3N4 before urea calcination unless you want to try to modify the urea somehow, but that is not the case now.
When you use nitrogen-rich precursor such as urea, thiourea, melamine, dicynandiamide,... to prepare g-C3N4, you do polymerization reaction. In the case of urea, it means that the molecules of urea 2HN-CO-NH2 loses "hydrogen and NH2 groups" forming by-product NH3, and together with other by-products such as H2O and CO, they are released and you can observe a "fume".
If you used 10 g of urea, the g-C3N4 yield is about 5%, it means that you lose ca 9.5 g of starting material, it is a lot, causing a great fume. In the case of melamine, the yield of prepared g-C3N4 is around 50 % and then the fume is more moderate, but still observed. For this reason, we have our furnace in fume hood during g-C3N4 preparation.
The Al foil won't increase the yield of g-C3N4 according to my experience. We also tested a closed reactor, but with no significant changes in yield compared to a crucible with a lid.
Dear Swathi a C thanks for this very interesting technical question. I think that Ladislav Svoboda already provided a rather comprehensive and very good answer. Although heating of urea and / or thiourea in a crucible to ca. 550 °C is a standard method for preparing g-C3N4, we should not forget that both are small molecules. Thus at elevated temperatures they are significantly volatile. As mentioned by Ladislav, gaseous by-products also add to the loss of starting materials and "fuming". For a typical reference please have a look at the following RG link:
Facile synthesis of exfoliated graphitic carbon nitride for photocatalytic degradation of ciprofloxacin under solar irradiation
Article Facile synthesis of exfoliated graphitic carbon nitride for ...
Good luck with your work and best wishes!
Dears,
find the link.
Article Investigations on effect of graphitic carbon nitride loading...
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