原位
氧烷
扩展X射线吸收精细结构
材料科学
氧气
氧化物
氧化态
双锰矿
作者
Marcel Risch,Kelsey A. Stoerzinger,Binghong Han,Tom Regier,Derek Peak,Sayed Youssef Sayed,Chao Wei,Zhichuan J. Xu,Yang Shao-Horn
标识
DOI:10.1021/acs.jpcc.7b05592
摘要
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 O2-saturated 0.1 M KOH using inverse partial fluorescence yield (IPFY) at the Mn L3,2-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 L3,2 IPFY XAS. Oxidation to a mixed Mn3+/4+ valence preceded the oxygen evolution at 1.65 V vs RHE, while manganese reduced below Mn3+ and contained tetrahedral Mn2+ during oxygen reduction at 0.5 V vs RHE. Analysis of the pre-edge in O K-edge XAS pr...
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