Redox Processes of Manganese Oxide in Catalyzing Oxygen Evolution and Reduction: An
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acs.jpcc.7b05592.pdf
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1.81 MB
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Author(s)
Regier, Tom Z.
Peak, Derek
Sayed, Sayed Youssef
Wei, Chao
Xu, Zhichuan
Risch, Marcel
Stoerzinger, Kelsey Ann
Han, Binghong
Shao-Horn, Yang
Date Issued
August 2017
Journal
Journal of Physical Chemistry C
Publisher
American Chemical Society (ACS)
Citation
Risch, Marcel et al. “Redox Processes of Manganese Oxide in Catalyzing Oxygen Evolution and Reduction: An in Situ Soft X-Ray Absorption Spectroscopy Study.” The Journal of Physical Chemistry C 121, 33 (August 2017): 17682–17692 © 2017 American Chemical Society
Version
Final published version
Abstract
Manganese oxides with rich redox chemistry have been widely used in (electro)catalysis in applications of energy and environmental consequence. While they are ubiquitous in catalyzing the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), redox processes occurring on the surface of manganese oxides are poorly understood. We report valence changes at OER- and ORR-relevant voltages of a layered manganese oxide film prepared by electrodeposition. X-ray absorption spectra were collected in situ in O[subscript 2]-saturated 0.1 M KOH using inverse partial fluorescence yield (IPFY) at the Mn L[subscript 3,2]-edges and partial fluorescence yield (PFY) at the O K-edge. Overall, we found reversible yet hysteretic Mn redox and qualitatively reproducible spectral changes by Mn L[subscript 3,2]IPFY XAS. Oxidation to a mixed Mn[superscript 3+/4+] valence preceded the oxygen evolution at 1.65 V vs RHE, while manganese reduced below Mn[superscript 3+] and contained tetrahedral Mn[superscript 2+] during oxygen reduction at 0.5 V vs RHE. Analysis of the pre-edge in O K-edge XAS provided the Mn-O hybridization, which was highest for Mn[superscript 3+](e[subscript g][superscript 1]). Our study demonstrates that combined in situ experiments at the metal L- and oxygen K-edges are indispensable to identify both the active valence during catalysis and the hybridization with oxygen adsorbates, critical to the rational design of active catalysts for oxygen electrocatalysis.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Department of Mechanical Engineering
Massachusetts Institute of Technology. Research Laboratory of Electronics
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DOI of Published Version
https://doi.org/10.1021/ACS.JPCC.7B05592
