The formation of heterojunction and scheme are discussed in detail in our recent article, you can find it here

Article Graphene quantum dot and iron co-doped TiO2 photocatalysts: ...

Dear Zakarya Zebiri

In order to explore heterojunction formation in multi-component photocatalysts, XPS analysis is a versatile instrument. Because in this technique, binding energy of elements is very sensitive to changes of electronic environment of elements. Hence, you can simply compare the binding energy of C, N, Co, and O elements in the composite relative to the pure components. For more information, please refer to the following valuable paper, pages 6-8:

-Liuyang Zhang, Jianjun Zhang, Huogen Yu, Jiaguo Yu, Emerging S-Scheme Photocatalyst, Adv. Mater. 2022, 2107668.

Regards

Aziz Habibi-Yangjeh

Numerous methods can be employed to study the kind of charge transfer at the interface of multicomponent semiconductors in your case 2. First, you need to find the band edge positions of your materials by either experimental or theoretical means. Experiments involves XPS and M-S plots. Theoretically you can use the Mulliken electronegativity theory or DFT calculations.

From band positions, determine the reactive species using EPR/ESR, Radical trapping experiments, etc... then you can deduce the plausible mechanism that allows for the presence of such radicals formation. Depending on what techniques you have access to, you can use some information from XPS as suggested by Aziz Habibi-Yangjeh or others like CO2 reduction. Good luck.

See some of this work for your reference

Dear Dr. Aziz

The type of photocatalytic mechanism is described based on the transfer route of photo-induced charge carriers between the semiconductors. Please see the following link:

Article Emerging 2D/0D g-C3N4/SnO2 S-scheme photocatalyst: New gener...

Dear Zakarya Zebiri,

First you can understand the band structure of your material. To do that, you can calculate the Mott-schottky, UV- Vis reflectance and XPS valence band. With these three values you could get an idea of your band structure and able to calculate the CB potential, valence band potential and band gap. By calculating the individual materials, you can find out whether it can be S scheme or Z scheme or even type II staggered. In addition, calculating the hybrid (composite ) structure's CB , VB and BG, will give you an idea of how the lattice structure has changed upon the composite formation.