Regulating the Coordination Geometry and Oxidation State of Single-Atom Fe Sites for Enhanced Oxygen Reduction Electrocatalysis

Minjie Wang; Li Wang; Qingbin Li; Dan Wang; Liu Yang; Yongjun Han; Yuan Ren; Gang Tian; Xiaoyang Zheng; Muwei Ji; Caizhen Zhu; Lishan Peng; Geoffrey I N Waterhouse

doi:10.1002/smll.202300373

Regulating the Coordination Geometry and Oxidation State of Single-Atom Fe Sites for Enhanced Oxygen Reduction Electrocatalysis

Small. 2023 Jun;19(24):e2300373. doi: 10.1002/smll.202300373. Epub 2023 Mar 15.

Authors

Minjie Wang¹, Li Wang¹, Qingbin Li¹, Dan Wang², Liu Yang¹, Yongjun Han¹, Yuan Ren³, Gang Tian¹, Xiaoyang Zheng⁴, Muwei Ji⁵, Caizhen Zhu⁶, Lishan Peng^{7

8}, Geoffrey I N Waterhouse⁸

Affiliations

¹ School of Chemistry and Environmental Engineering, Pingdingshan University, Pingdingshan, 467000, P. R. China.
² School of Ceramic, Pingdingshan University, Pingdingshan, 467000, P. R. China.
³ Department of Chemistry, Fudan University, Shanghai, 200433, P. R. China.
⁴ Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8573, Japan.
⁵ Department of Chemistry, College of Science, Shantou University, Shantou, 515063, P. R. China.
⁶ College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518060, P. R. China.
⁷ Ganjiang Innovation Academy, Chinese Academy of Sciences, Ganzhou, 341100, P. R. China.
⁸ School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand.

PMID: 36919312
DOI: 10.1002/smll.202300373

Abstract

FeNC catalysts demonstrate remarkable activity and stability for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells and Zn-air batteries (ZABs). The local coordination of Fe single atoms in FeNC catalysts strongly impacts ORR activity. Herein, FeNC catalysts containing Fe single atoms sites with FeN₃ , FeN₄ , and FeN₅ coordinations are synthesized by carbonization of Fe-rich polypyrrole precursors. The FeN₅ sites possess a higher Fe oxidation state (+2.62) than the FeN₃ (+2.23) and FeN₄ (+2.47) sites, and higher ORR activity. Density functional theory calculations verify that the FeN₅ coordination optimizes the adsorption and desorption of ORR intermediates, dramatically lowering the energy barrier for OH^- desorption in the rate-limiting ORR step. A primary ZAB constructed using the FeNC catalyst with FeN₅ sites demonstrates state-of-the-art performance (an open circuit potential of 1.629 V, power density of 159 mW cm^-2 ). Results confirm an intimate structure-activity relationship between Fe coordination, Fe oxidation state, and ORR activity in FeNC catalysts.

Keywords: Fe coordination geometry; Fe single atoms; FeN x sites; oxygen reduction reaction; zinc-air batteries.

Abstract

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