Tailoring the microenvironment in Fe-N-C electrocatalysts for optimal oxygen reduction reaction performance

Qing Wang; Ruihu Lu; Yuqi Yang; Xuanze Li; Guangbo Chen; Lu Shang; Lishan Peng; Dongxiao Sun-Waterhouse; Bruce C C Cowie; Xiangmin Meng; Yan Zhao; Tierui Zhang; Geoffrey I N Waterhouse

doi:10.1016/j.scib.2022.04.022

Tailoring the microenvironment in Fe-N-C electrocatalysts for optimal oxygen reduction reaction performance

Sci Bull (Beijing). 2022 Jun 30;67(12):1264-1273. doi: 10.1016/j.scib.2022.04.022. Epub 2022 Apr 29.

Authors

Qing Wang¹, Ruihu Lu², Yuqi Yang³, Xuanze Li⁴, Guangbo Chen⁴, Lu Shang⁴, Lishan Peng¹, Dongxiao Sun-Waterhouse¹, Bruce C C Cowie⁵, Xiangmin Meng⁴, Yan Zhao⁶, Tierui Zhang⁷, Geoffrey I N Waterhouse⁸

Affiliations

¹ School of Chemical Sciences, The University of Auckland, Auckland 1142, New Zealand.
² State Key Laboratory of Silicate Materials for Architectures, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China.
³ iHuman Institute, ShanghaiTech University, Shanghai 201210, China.
⁴ Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
⁵ Australian Synchrotron, 800 Blackburn Rd., Clayton, Victoria 3168, Australia.
⁶ State Key Laboratory of Silicate Materials for Architectures, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China. Electronic address: yan2000@whut.edu.cn.
⁷ Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China. Electronic address: tierui@mail.ipc.ac.cn.
⁸ School of Chemical Sciences, The University of Auckland, Auckland 1142, New Zealand. Electronic address: g.waterhouse@auckland.ac.nz.

PMID: 36546156
DOI: 10.1016/j.scib.2022.04.022

Abstract

Fe-N-C electrocatalysts, comprising FeN₄ single atom sites immobilized on N-doped carbon supports, offer excellent activity in the oxygen reduction reaction (ORR), especially in alkaline solution. Herein, we report a simple synthetic strategy for improving the accessibility of FeN₄ sites during ORR and simultaneously fine-tuning the microenvironment of FeN₄ sites, thus enhancing the ORR activity. Our approach involved a simple one-step pyrolysis of a Fe-containing zeolitic imidazolate framework in the presence of NaCl, yielding a hierarchically porous Fe-N-C electrocatalyst containing tailored FeN₄ sites with slightly elongated Fe-N bond distances and reduced Fe charge. The porous carbon structure improved mass transport during ORR, whilst the microenvironment optimized FeN₄ sites benefitted the adsorption/desorption of ORR intermediates. Accordingly, the developed electrocatalyst, possessing a high FeN₄ site density (9.9 × 10¹⁹ sites g^-1) and turnover frequency (2.26 s^-1), delivered remarkable ORR performance with a low overpotential (a half-wave potential of 0.90 V vs. reversible hydrogen electrode) in 0.1 mol L^-1 KOH.

Keywords: Fe–N–C; Microenvironment; Optimized FeN(4) site; Oxygen reduction reaction; Zinc–air battery.