Probing the Structure and Binding Mode of EDTA on the Surface of Mn3O4 Nanoparticles for Water Oxidation by Advanced Electron Paramagnetic Resonance Spectroscopy.,Inorganic Chemistry

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Probing the Structure and Binding Mode of EDTA on the Surface of Mn3O4 Nanoparticles for Water Oxidation by Advanced Electron Paramagnetic Resonance Spectroscopy.
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2020-06-05 , DOI: 10.1021/acs.inorgchem.0c00611
Jin Kim ₁ , Sunghak Park ₂ , Yoo Kyung Go ₁ , Kyoungsuk Jin ₂ , Yujeong Kim _{1,

3} , Ki Tae Nam ₂ , Sun Hee Kim _{1,

3}

Affiliation

Identification of the surface structure of nanoparticles is important for understanding the catalytic mechanism and improving the properties of the particles. Here, we provide a detailed description of the coordination modes of ethylenediaminetetraacetate (EDTA) on Mn₃O₄ nanoparticles at the atomic level, as obtained by advanced electron paramagnetic resonance (EPR) spectroscopy. Binding of EDTA to Mn₃O₄ leads to dramatic changes in the EPR spectrum, with a 5-fold increase in the axial zero-field splitting parameter of Mn(II). This indicates significant changes in the coordination environment of the Mn(II) site; hence, the binding of EDTA causes a profound change in the electronic structure of the manganese site. Furthermore, the electron spin echo envelope modulation results reveal that two ¹⁴N atoms of EDTA are directly coordinated to the Mn site and a water molecule is coordinated to the surface of the nanoparticles. An Fourier transform infrared spectroscopy study shows that the Ca(II) ion is coordinated to the carboxylic ligands via the pseudobridging mode. The EPR spectroscopic results provide an atomic picture of surface-modified Mn₃O₄ nanoparticles for the first time. These results can enhance our understanding of the rational design of catalysts, for example, for the water oxidation reaction.

中文翻译：

用先进的电子顺磁共振光谱技术研究Mn3O4纳米颗粒表面EDTA在水氧化中的结构和结合方式。

识别纳米颗粒的表面结构对于理解催化机理和改善颗粒的性质很重要。在这里，我们提供了通过高级电子顺磁共振（EPR）光谱获得的乙二胺四乙酸盐（EDTA）在Mn ₃ O ₄纳米粒子上的原子级配位模式的详细描述。EDTA与Mn ₃ O _4的结合导致EPR频谱发生剧烈变化，其中Mn（II）的轴向零场分裂参数增加了5倍。这表明Mn（II）位点的配位环境发生了显着变化。因此，EDTA的结合导致锰位点的电子结构发生了深刻的变化。此外，电子自旋回波包络调制结果表明，EDTA的两个¹⁴ N原子直接配位到Mn位置，水分子配位到纳米颗粒的表面。傅里叶变换红外光谱研究表明，Ca（II）离子通过假桥联模式与羧酸配体配位。EPR光谱结果提供了表面改性的Mn ₃ O ₄的原子图首次使用纳米颗粒。这些结果可以增强我们对催化剂合理设计的理解，例如用于水氧化反应的催化剂。

更新日期：2020-07-06

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