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Evolution of Oxygen–Metal Electron Transfer and Metal Electronic States During Manganese Oxide Catalyzed Water Oxidation Revealed with In Situ Soft X‐Ray Spectroscopy
Author(s) -
Tesch Marc F.,
Bonke Shan A.,
Jones Travis E.,
Shaker Maryam N.,
Xiao Jie,
Skorupska Katarzyna,
Mom Rik,
Melder Jens,
Kurz Philipp,
KnopGericke Axel,
Schlögl Robert,
Hocking Rosalie K.,
Simonov Alexandr N.
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201810825
Subject(s) - x ray absorption spectroscopy , manganese , chemistry , absorption spectroscopy , oxide , electron transfer , inorganic chemistry , catalysis , spectroscopy , transition metal , analytical chemistry (journal) , photochemistry , physics , organic chemistry , quantum mechanics , biochemistry , chromatography
Manganese oxide (MnO x ) electrocatalysts are examined herein by in situ soft X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS) during the oxidation of water buffered by borate (pH 9.2) at potentials from 0.75 to 2.25 V vs. the reversible hydrogen electrode. Correlation of L‐edge XAS data with previous mechanistic studies indicates Mn IV is the highest oxidation state involved in the catalytic mechanism. MnO x is transformed into birnessite at 1.45 V and does not undergo further structural phase changes. At potentials beyond this transformation, RIXS spectra show progressive enhancement of charge transfer transitions from oxygen to manganese. Theoretical analysis of these data indicates increased hybridization of the Mn−O orbitals and withdrawal of electron density from the O ligand shell. In situ XAS experiments at the O K‐edge provide complementary evidence for such a transition. This step is crucial for the formation of O 2 from water.