Elucidating the Structural Composition of a Fe-N-C Catalyst by Nuclear- and Electron-Resonance Techniques
Elucidating the Structural Composition of a Fe-N-C Catalyst by Nuclear- and Electron-Resonance Techniques
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DOI：
10.1002/anie.201903753
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发表时间：
2019-07-01
影响因子：
16.6
通讯作者：
Kramm, Ulrike, I
中科院分区：
文献类型：
--
作者：
Wagner, Stephan;Auerbach, Hendrik;Kramm, Ulrike, I
Fe-N-C催化剂是非常有前途的燃料电池和金属-空气电池材料。这项工作为Fe-N-C催化剂的结构组成提供了基本的见解，并强调了深入表征的重要性。通过核磁共振和电子共振技术，我们能够证明，即使经过温和的热解和酸浸，催化剂中也含有相当一部分的α-铁，令人惊讶的是，还含有氧化铁。我们的工作使得在900℃及以上热解制备的Fe-N-C催化剂中FeN4位的存在程度受到质疑。对声子态的铁部分密度的模拟使我们能够在我们的催化剂中识别出三种FeN4物种，其中一种包括与作为轴向配体之一的端面键合氧的六重配位。
Fe-N-C catalysts are very promising materials for fuel cells and metal-air batteries. This work gives fundamental insights into the structural composition of an Fe-N-C catalyst and highlights the importance of an in-depth characterization. By nuclear- and electron-resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of alpha-iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe-N-C catalysts prepared by pyrolysis at 900 degrees C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end-on bonded oxygen as one of the axial ligands.