Monitoring atomic and electronic structure changes on active sites under realistic working conditions is crucial for the rational design of efficient electrocatalysts. Identification of the active structure during the alkaline hydrogen evolution reaction (HER), which is critical to industrial water–alkali electrolysers, remains elusive and is a field of intense research. Here, by virtue of operando X-ray absorption spectroscopy on a uniform cobalt single-site catalyst, we report the atomic-level identification of the dynamic structure of catalytically active sites under alkaline HER. Our results reveal the formation of a high-valence HO–Co1–N2 moiety by the binding between isolated Co1–N4 sites with electrolyte hydroxide, and further unravel the preferred water adsorption reaction intermediate H2O–(HO–Co1–N2). Theoretical simulations rationalize this structural evolution and demonstrate that the highly oxidized Co sites are responsible for the catalytic performance. These findings suggest the electrochemical susceptibility of active sites, providing a coordination-engineered strategy for the advance of single-site catalysis.

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This work was supported by the China Ministry of Science and Technology under contracts nos. 2017YFA0402800 and 2017YFA0208300, the National Natural Science Foundation of China (grants nos. 21471143, 21533007, 11621063 and 21703222), the Fundamental Research Funds for the Central Universities (KY2310000020 and KY2310000019, and the Youth Innovation Promotion Association CAS (CX2310000091). The authors thank NSRL, BSRF and SSRF for synchrotron beam time. Calculations were conducted on the supercomputing system in the Supercomputing Center of USTC.

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Author notes

  1. These authors contributed equally: Linlin Cao, Qiquan Luo, Wei Liu


  1. National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China

    • Linlin Cao
    • , Wei Liu
    • , Xiaokang Liu
    • , Yuanjie Cao
    • , Wei Zhang
    • , Tao Yao
    •  & Shiqiang Wei
  2. Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China

    • Qiquan Luo
    • , Yue Lin
    •  & Jinlong Yang
  3. Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, China

    • Yuen Wu


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T.Y. and S.W. developed the idea and designed experiments. L.C., X.L., Y.C., W.L. and W.Z. performed the catalyst synthesis and characterizations, XAFS measurements and electrochemical experiments. Q.L. and J.Y. conducted and discussed the theoretical calculations. L.C., Y.L. and Y.W. performed the aberration-corrected STEM characterization. L.C., T.Y. and S.W. co-wrote the paper. All authors discussed the results and commented on the manuscript.

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The authors declare no competing interests.

Corresponding authors

Correspondence to Tao Yao or Shiqiang Wei.

Supplementary information

  1. Supplementary Information

    Supplementary Figures 1–25, Supplementary Tables 1–2 and Supplementary References

  2. Supplementary Data 1

    Cartesian coordinates of the relaxed ex situ model

  3. Supplementary Data 2

    Cartesian coordinates of the relaxed open circuit model

  4. Supplementary Data 3

    Cartesian coordinates of the –0.04 V relaxed model

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