One reviewer asked me (One cannot understand the bandgap of a composite like g-C3N4/Fe3O4/Bi2WO6/Bi2S3. Does the derived bandgap of the g-C3N4/Fe3O4/Bi2WO6/Bi2S3 composite represent the bandgap of g-C3N4, Fe3O4, Bi2WO6, Bi2S3 or others? Please clarify it??)
Please, anyone can answer?
Hi Zaid,
The bandgap of a single photocatalyst (doped/undoped) is easily defined as the difference between the HOMO and LUMO molecular orbitals. However, the story becomes a bit more complicated in a 'composite' catalyst.
In the simple case of an AB type composite, you need to consider what kind of an overlap exists between the individual HOMO and LUMO levels and consider additional effects such as band-bending and Schottky junction formation.
The story becomes even more complicated if you introduce three or more components. The way I see it, there could be an 'effective' bandgap for the structure you propose which can be determined through things like DRS. However, that is not an accurate representation.
I hope this helps.
It depends on the synthesis, then is necessary to determine it through diffuse spectroscopy, by using the Kubelka-Munk equation.
The value of band gap of the composite is expected to be an intermediate value between the compounds, but it's not always like that.
In my case, I have a TiO2/CuxO/FexOy heterojunction, and, in order to know the exact value of the conduction and valence band I will fix the compositum in an FTO electrode.
But if you want only to know the band gap difference then Diffuse Spectroscopy is enough.
For bandgap Calculation, you can follow this article...
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