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Redox Processes of Manganese Oxide in Catalyzing Oxygen Evolution and Reduction: An

Author(s)
Regier, Tom Z.; Peak, Derek; Sayed, Sayed Youssef; Wei, Chao; Xu, Zhichuan; Risch, Marcel; Stoerzinger, Kelsey Ann; Han, Binghong; Shao-Horn, Yang; ... Show more Show less
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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.
Date issued
2017-08
URI
http://hdl.handle.net/1721.1/120964
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
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
ISSN
1932-7447
1932-7455

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