Unraveling the Origin of Sulfur-Doped Fe-N-C Single-Atom Catalyst for Enhanced Oxygen Reduction Activity: Effect of Iron Spin-State Tuning

Zhaoyang Chen; Huan Niu; Jie Ding; Heng Liu; Pei-Hsuan Chen; Yi-Hsuan Lu; Ying-Rui Lu; Wenbin Zuo; Lei Han; Yuzheng Guo; Sung-Fu Hung; Yueming Zhai

doi:10.1002/anie.202110243

Unraveling the Origin of Sulfur-Doped Fe-N-C Single-Atom Catalyst for Enhanced Oxygen Reduction Activity: Effect of Iron Spin-State Tuning

Angew Chem Int Ed Engl. 2021 Nov 22;60(48):25404-25410. doi: 10.1002/anie.202110243. Epub 2021 Oct 21.

Authors

Zhaoyang Chen¹, Huan Niu², Jie Ding¹, Heng Liu³, Pei-Hsuan Chen⁴, Yi-Hsuan Lu⁴, Ying-Rui Lu⁵, Wenbin Zuo⁶, Lei Han³, Yuzheng Guo², Sung-Fu Hung⁴, Yueming Zhai¹

Affiliations

¹ The Institute for Advanced Studies, Wuhan University, Wuhan, 430072, China.
² School of Electrical Engineering, Wuhan University, Wuhan, Hubei, 430072, China.
³ College of Materials Science and Engineering, Hunan University, 410082, Changsha, Hunan, China.
⁴ Department of Applied Chemistry, National Yang Ming Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, Republic of China.
⁵ National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, Republic of China.
⁶ Key Laboratory of Artificial Micro and Nanostructures of Ministry of Education, Hubei Key Laboratory of Nuclear Solid Physics, School of Physics and Technology, Wuhan University, Wuhan, 430072, China.

PMID: 34550627
DOI: 10.1002/anie.202110243

Abstract

Heteroatom doped atomically dispersed Fe₁ -NC catalysts have been found to show excellent activity toward oxygen reduction reaction (ORR). However, the origin of the enhanced activity is still controversial because the structure-function relationship governing the enhancement remains elusive. Herein, sulfur(S)-doped Fe₁ -NC catalyst was obtained as a model, which displays a superior activity for ORR towards the traditional Fe-NC materials. ⁵⁷ Fe Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy revealed that incorporation of S in the second coordination sphere of Fe₁ -NC can induce the transition of spin polarization configuration. Operando ⁵⁷ Fe Mössbauer spectra definitively identified the low spin single-Fe³⁺ -atom of C-FeN₄ -S moiety as the active site for ORR. Moreover, DFT calculations unveiled that lower spin state of the Fe center after the S doping promotes OH* desorption process. This work elucidates the underlying mechanisms towards S doping for enhancing ORR activity, and paves a way to investigate the function of broader heteroatom doped Fe₁ -NC catalysts to offer a general guideline for spin-state-determined ORR.

Keywords: Mössbauer spectroscopy; iron; oxygen reduction reaction; spin states; sulfur.

Abstract

Grants and funding