What is the Real Origin of the Activity of Fe-N-C Electrocatalysts in the O2 Reduction Reaction? Critical Roles of Coordinating Pyrrolic N and Axially Adsorbing Species

Xu Hu; Suya Chen; Letian Chen; Yun Tian; Sai Yao; Zhengyu Lu; Xu Zhang; Zhen Zhou

doi:10.1021/jacs.2c08743

What is the Real Origin of the Activity of Fe-N-C Electrocatalysts in the O₂ Reduction Reaction? Critical Roles of Coordinating Pyrrolic N and Axially Adsorbing Species

J Am Chem Soc. 2022 Oct 5;144(39):18144-18152. doi: 10.1021/jacs.2c08743. Epub 2022 Sep 22.

Authors

Xu Hu¹, Suya Chen¹, Letian Chen¹, Yun Tian², Sai Yao¹, Zhengyu Lu¹, Xu Zhang², Zhen Zhou^{1

2}

Affiliations

¹ School of Materials Science and Engineering, Institute of New Energy Material Chemistry, Renewable Energy Conversion and Storage Center (ReCast), Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300350, China.
² School of Chemical Engineering, Zhengzhou University, Zhengzhou 450001, Henan, China.

PMID: 36135972
DOI: 10.1021/jacs.2c08743

Abstract

Fe-N-C electrocatalysts have emerged as promising substitutes for Pt-based catalysts for the oxygen reduction reaction (ORR). However, their real catalytic active site is still under debate. The underlying roles of different types of coordinating N including pyridinic and pyrrolic N in catalytic performance require thorough clarification. In addition, how to understand the pH-dependent activity of Fe-N-C catalysts is another urgent issue. Herein, we comprehensively studied 13 different N-coordinated FeN_xC configurations and their corresponding ORR activity through simulations which mimic the realistic electrocatalytic environment on the basis of constant-potential implicit solvent models. We demonstrate that coordinating pyrrolic N contributes to a higher activity than pyridinic N, and pyrrolic FeN₄C exhibits the highest activity in acidic media. Meanwhile, the in situ active site transformation to *O-FeN₄C and *OH-FeN₄C clarifies the origin of the higher activity of Fe-N-C in alkaline media. These findings can provide indispensable guidelines for rational design of better durable Fe-N-C catalysts.