Experimental Observation of Redox-Induced Fe?N Switching Behavior as a Determinant Role for Oxygen Reduction Activity [electronic resource]

• Ngôn ngữ: eng
• Ký hiệu phân loại: 621.38 Electronics, communications engineering
• Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2015
• Mô tả vật lý: Size: p. 12496-12505 : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 255823
• Chủ đề: 1. 30 direct energy conversion; 2. 37 inorganic, organic, physical, and analytical chemistry; 3. Active sites; 4. Dynamic structure; 5. Energy sciences; 6. Non-pgm catalysts; 7. Oxygen reduction reaction; 8. Redox transition

Tóm tắt

 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?N<
 sub>
 4<
 /sub>
 -like catalytic centers with distinctly different Fe?N switching behaviors (Fe moving toward or away from the N<
 sub>
 4<
 /sub>
 -plane) during the oxygen reduction reaction (ORR), and show that their ORR activities are essentially governed by the dynamic structure associated with the Fe<
 sup>
 2+/3+<
 /sup>
  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.