A multitechnique study of C₂H₄ adsorption on a model single-atom Rh₁ catalyst

C. Wang, P. Sombut, L. Puntscher, M. Ulreich, J. Pavelec, D. Rath, J. Balajka, M. Meier, M. Schmid, U. Diebold, C. Franchini, G. S. Parkinson

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Faculty of Physics & Center for Computational Materials Science, University of Vienna, 1090 Wien, Austria
Dipartimento di Fisica e Astronomia, Università di Bologna, 40126 Bologna, Italy

J. Phys. Chem. C 128 (2024) 15404-15411

Single-atom catalysts are potentially ideal model systems to investigate structure–function relationships in catalysis if the active sites can be uniquely determined. In this work, we study the interaction of C₂H₄ with a model Rh/Fe₃O₄(001) catalyst that features 2-, 5-, and 6-fold coordinated Rh adatoms, as well as Rh clusters. Using multiple surface-sensitive techniques in combination with calculations of density functional theory (DFT), we follow the thermal evolution of the system and disentangle the behavior of the different species. C₂H₄ adsorption is strongest at the 2-fold coordinated Rh₁ with a DFT-determined adsorption energy of −2.26 eV. However, desorption occurs at lower temperatures than expected because the Rh migrates into substitutional sites within the support, where the molecule is more weakly bound. The adsorption energy at the 5-fold coordinated Rh sites is predicated to be −1.49 eV, but the superposition of this signal with that from small Rh clusters and additional heterogeneity leads to a broad C₂H₄ desorption shoulder in TPD above room temperature.

Corresponding author: Gareth S. Parkinson (parkinson).

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