As to the efficiency parameter (as required by the IUPAC), the calculation can be carried out at several levels. The quantum efficiency or yield (the most accurate measurement) can be calculated in liquid or gas phase reactions as exemplified in the following contributions:
https://www.researchgate.net/publication/315054089_Measuring_and_interpreting_quantum_efficiency_for_hydrogen_photoproduction_using_Pt-titania_catalysts
https://www.researchgate.net/publication/280934188_Heterogeneous_photocatalysis_Light-matter_interaction_and_chemical_effects_in_quantum_efficiency_calculations
Hope that this helps. Regards.
Article Measuring and interpreting quantum efficiency for hydrogen p...
Article Heterogeneous photocatalysis: Light-matter interaction and c...
Hi Noureen
Professor Marcos Fernández-García has provided you with two excellent articles about measurement of quantum yields. I have attached here an earlier, though still relevant, article.
Regarding turnover numbers (TON), or molecules converted per active site per unit time. These are not especially meaningful and often misleading for many photocatalytic reactions. Consider the photo-oxidation of methylene blue in aqueous solution by anatase TiO2. UV photoexcitation of anatase generates hydroxyl radicals which migrate into solution and attack aqueous methylene blue. Thus, the dye photo-oxidation reaction monitored by UV-vis is mainly a solution reaction involving hydroxyl radicals and methylene blue. In this context, determination of a TON for MB photo-oxidation on anatase would not be appropriate.
Best
Geoff
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