Use of In Situ X-ray Absorption to Probe Reactivity: A Catalysis Golden Rule

S Ted Oyama; Yong-Kul Lee

doi:10.1021/jacs.4c14098

Use of In Situ X-ray Absorption to Probe Reactivity: A Catalysis Golden Rule

J Am Chem Soc. 2024 Dec 25. doi: 10.1021/jacs.4c14098. Online ahead of print.

Authors

S Ted Oyama^{1

2}, Yong-Kul Lee^{2

3}

Affiliations

¹ Department of Chemical Systems Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
² Department of Chemical Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States.
³ Department of Chemical Engineering, Dankook University, Yongin 16890, South Korea.

PMID: 39722563
DOI: 10.1021/jacs.4c14098

Abstract

The decomposition of ozone on supported manganese oxide catalysts, studied here, exemplifies reactions involving electron transfer. In situ extended X-ray absorption fine-structure spectra (Mn K-edge) on in situ treated samples show that the supported phase in MnO_x/SiO₂ resembles Mn₃O₄ while that in MnO_x/Al₂O₃ samples resembles MnO₂. In situ Raman spectroscopy shows the involvement of a common peroxide surface species. Kinetic data indicate a nonuniform surface and a rate-determining step (rds) involving electron transfer from the peroxide intermediate. The activation energy for all the catalysts is the same, indicating that the pre-exponential factor controls the rate. This can be associated with the electronic partition function (unoccupied density of states (DOS)), and X-ray absorption near-edge spectroscopy duly shows that the areas of the pre-edge peaks due to 1s to 3d transitions track the reactivity trends. The relation to the unoccupied DOS is analogous to Fermi's Golden Rule for electronic transitions, and we denote the finding here, applicable to reactions involving electron transfer, as a Catalysis Golden Rule.