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Affiliation of Author(s):材料科学与技术学院

Journal:ACS Catal.

Abstract:Even though Fe-N/C electrocatalysts with abundant Fe-Nxactive sites have been developed as one of the most promising alternatives to precious metal materials for oxygen reduction reaction (ORR), further improvement of their performance requires precise control over Fe-Nxsites at the molecular level and deep understanding of the catalytic mechanism associated with each particular structure. Herein, we report a host-guest chemistry strategy to construct Fe-mIm nanocluster (NC) (guest)@zeolite imidazole framework-8 (ZIF-8) (host) precursors that can be transformed into Fe-N/C electrocatalysts with controllable structures. The ZIF-8 host network exhibits a significant host-guest relationship dependent confinement effect for the Fe-mIm NCs during the pyrolysis process, resulting in different types of Fe-Nxsites with two- to five-coordinated configurations on the porous carbon matrix confirmed by X-ray absorption near edge structure (XANES) and Fourier transform (FT) extended X-ray absorption fine structure (EXAFS) spectra. Electrochemical tests reveal that the five-coordinated Fe-Nxsites can significantly promote the reaction rate in acid media, due to the small ORR energy barrier and the low adsorption energy of intermediate OH on these sites suggested by density functional theory (DFT) calculations. Such a synthesis strategy provides an effective route to realize the controllable construction of highly active sites for ORR at the molecular level. (Chemical Equation Presented). © 2017 American Chemical Society.

Translation or Not:no

Date of Publication:2017-03-03

Co-author:Zheng, Lirong,lyz,hjp,Zhao, Jingxiang,Chen, Junhong

Correspondence Author:Lai Qingxue