Global warming together with the current global energy crisis make catalyst's research ever more indispensable to enable important, environmentally relevant reactions, e.g., C02 capture and conversion, water splitting for solar fuel (H2) production, nitrogen fixation for ammonia generation and resistant pollutants degradation.[ll Classic semiconductor-based catalysts include oxides like titania, silica, hematite or ceria. These materials' performance can be enhanced through the addition of co-catalysts — commonly precious metals, like Pt, Au, Ag or Pd. However, efforts are being undertaken for moving towards more earthabundant transition metals.(2] In both cases, a non-destructive, rapid and highly sensitive analysis method is required to determine the amounts of the loaded co-catalysts relative to the oxide support. Hence, we have developed high throughput preparation method to immobilize the co-catalyst-decorated oxide nanoparticles and sensitively be able to quantify the elements of interest through TXRF.[3'41 The stability of the catalyst after reaction is another important question in the field, for which the leaching of minute amounts of the precious metals into the aqueous phase or simple decomposition of the support can also be of outmost interest. Moreover, novel materials for catalysis, like metal-organic frameworks (MOFs) or metal-organic chalcogenide assemblies (MOCHAs) have also been investigated in terms of elemental composition and stability (no leaching into the reaction media). References [1] C.-H. Liao, J.C.S. wu, et al. Catalysts 2012, 2 (4), 490-516. P. Ayala, A. Cherevan, et al. Catalysts 2021, 11 (4), 417. [3] J. Schubert, D. Eder, et al." Mater. Chem. A 2021, 9 (41), 23731-23731. [4] S. Batool, D. Eder, et a. ACS Catal. 2022, 12 (11), 6641-6650.