Manganese Oxide as an Inorganic Catalyst for the Oxygen Evolution Reaction Studied by X‐Ray Photoelectron and Operando Raman Spectroscopy,ChemCatChem

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Manganese Oxide as an Inorganic Catalyst for the Oxygen Evolution Reaction Studied by X‐Ray Photoelectron and Operando Raman Spectroscopy
ChemCatChem ( IF 3.8 ) Pub Date : 2020-11-24 , DOI: 10.1002/cctc.202001756
Hannes Radinger _{1,

2} , Paula Connor ₁ , Robert Stark ₃ , Wolfram Jaegermann ₁ , Bernhard Kaiser ₁

Affiliation

Manganese oxide (MnO_x) is considered a promising material for the oxygen evolution reaction (OER) to replace noble metal catalysts in water splitting. The improvement of MnO_x requires mechanistic and kinetic knowledge of the four‐electron transfer steps of the OER. X‐ray photoelectron spectroscopy, a widely used tool to characterize the electronic structure of thin films, is used in combination with surface‐enhanced Raman spectroscopy to gain a deeper knowledge of the different mixed MnO_x types and their respective change in chemical composition. Using Raman spectroscopy during electrochemical measurements, all samples were found to reveal Birnessite‐type MnO₂ motifs in alkaline media at an applied potential. Their activity correlates with two shifting Raman active modes, one of them being assigned to the formation of Mn^III species, and one to the expansion of layers of MnO₆ octahedra. A special activation treatment leads independent of the starting material to a highly amorphous mixed‐valence oxide, which shows the highest OER activity.

中文翻译：

X射线光电子能谱和Operando拉曼光谱法研究氧化锰作为无机催化剂的产氧反应

氧化锰（MnO _x）被认为是氧分解反应（OER）的有希望的材料，可代替水分解中的贵金属催化剂。MnO _x的改善需要OER的四电子转移步骤的机械和动力学知识。X射线光电子能谱是表征薄膜电子结构的一种广泛使用的工具，与表面增强拉曼光谱结合使用可以更深入地了解不同的混合MnO _x类型及其化学成分的变化。在电化学测量过程中使用拉曼光谱法，发现所有样品都显示出Birnessite型MnO ₂在碱性介质上施加电势的图案。它们的活性与两种移动的拉曼活性模式相关，其中一种对应于Mn ^III物种的形成，一种对应于MnO ₆八面体层的扩展。特殊的活化处理可导致与原料无关的高度非晶态混合价氧化物，该氧化物具有最高的OER活性。

更新日期：2020-11-24

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