Experimental Observation of Redox-Induced Fe鈥揘 Switching Behavior as a Determinant Role for Oxygen Reduction Activity

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• 作者：Qingying Jia ; Nagappan Ramaswamy ; Hasnain Hafiz ; Urszula Tylus ; Kara Strickland ; Gang Wu ; Bernardo Barbiellini ; Arun Bansil ; Edward F. Holby ; Piotr Zelenay ; Sanjeev Mukerjee
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：December 22, 2015
• 年：2015
• 卷：9
• 期：12
• 页码：12496-12505
• 全文大小：651K
• ISSN：1936-086X

文摘

The commercialization of electrochemical energy conversion and storage devices relies largely upon the development of highly active catalysts based on abundant and inexpensive materials. Despite recent achievements in this respect, further progress is hindered by the poor understanding of the nature of active sites and reaction mechanisms. Herein, by characterizing representative iron-based catalysts under reactive conditions, we identify three Fe鈥揘₄-like catalytic centers with distinctly different Fe鈥揘 switching behaviors (Fe moving toward or away from the N₄-plane) during the oxygen reduction reaction (ORR), and show that their ORR activities are essentially governed by the dynamic structure associated with the Fe^2+/3+ redox transition, rather than the static structure of the bare sites. Our findings reveal the structural origin of the enhanced catalytic activity of pyrolyzed Fe-based catalysts compared to nonpyrolyzed Fe-macrocycle compounds. More generally, the fundamental insights into the dynamic nature of transition-metal compounds during electron-transfer reactions will potentially guide rational design of these materials for broad applications.