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Insight into pH-Dependent Formation of Manganese Oxide Phases in Electrodeposited Catalytic Films Probed by Soft X-Ray Absorption Spectroscopy.
ChemPlusChem ( IF 3.0 ) Pub Date : 2018-06-20 , DOI: 10.1002/cplu.201800055
Maryam N Shaker 1, 2 , Shannon A Bonke 3 , Jie Xiao 4 , Munirah A Khan 4 , Rosalie K Hocking 5 , Marc F Tesch 4
Affiliation  

MnOx films electrodeposited under basic, neutral, and acidic conditions from an ionic liquid were investigated by means of X-ray absorption spectroscopy at the manganese L2,3 -edges and the oxygen K-edge. Such films can serve as catalysts for the water oxidation reaction. Previous studies showed that the catalytic activity could be controlled by varying the deposition parameters, which influence the formation of MnOx phases and the film composition. Herein the film compositions are investigated in detail, indicating different ratios of MnOx structural phases in the films. All films in the series predominately consist of varying proportions of three MnOx phases-Mn2 O3 , Mn3 O4 , and birnessite, while an increase of the average Mn oxidation state in the film is identified when going from basic to acidic conditions during electrodeposition. The contribution of these three phases shows a systematic dependency on the pH during electrodeposition. While no specific single MnOx phase was found to dominate the composition of samples that were previously found to show high catalytic activity, the X-ray spectroscopic results revealed the compositions of those samples prepared under close to neutral conditions to be most sensitive to changes in pH.

中文翻译:

用软X射线吸收光谱法研究电沉积催化膜中锰氧化物相的pH依赖性形成。

利用X射线吸收光谱法研究了在碱性,中性和酸性条件下从离子液体中电解沉积的MnOx薄膜在锰的L2,3-边缘和氧K边缘。这样的膜可以用作水氧化反应的催化剂。先前的研究表明,可以通过改变沉积参数来控制催化活性,这会影响MnOx相的形成和膜的组成。在本文中,对膜组成进行了详细研究,表明膜中MnOx结构相的比率不同。该系列中的所有薄膜主要由不同比例的MnOx三种相-Mn2 O3,Mn3 O4和水钠锰矿组成,而在电沉积过程中,从碱性到酸性条件下,薄膜中平均Mn氧化态的增加被确定。这三个阶段的贡献显示出电沉积过程中对pH的系统依赖性。虽然没有发现特定的单一MnOx相占先前被发现具有高催化活性的样品组成的主要成分,但X射线光谱结果显示,在接近中性条件下制备的那些样品的组成对pH值变化最为敏感。 。
更新日期:2018-06-20
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