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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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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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.
The authors declare no competing interests.
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Supplementary Figures 1–25, Supplementary Tables 1–2 and Supplementary References
Cartesian coordinates of the relaxed ex situ model
Cartesian coordinates of the relaxed open circuit model
Cartesian coordinates of the –0.04 V relaxed model
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Cao, L., Luo, Q., Liu, W. et al. Identification of single-atom active sites in carbon-based cobalt catalysts during electrocatalytic hydrogen evolution. Nat Catal 2, 134–141 (2019). https://doi.org/10.1038/s41929-018-0203-5
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