NiFeOxHy are the most active catalysts for oxygen evolution in a base. For this reason, they are used widely in alkaline electrolysers. Several open questions remain as to the reason for their exceptionally high catalytic activity. Here we use a model system of mass-selected NiFe nanoparticles and isotope labelling experiments to show that oxygen evolution in 1 M KOH does not proceed via lattice exchange. We complement our activity measurements with electrochemistry–mass spectrometry, taken under operando conditions, and transmission electron microscopy and low-energy ion-scattering spectroscopy, taken ex situ. Together with the trends in particle size, the isotope results indicate that oxygen evolution is limited to the near-surface region. Using the surface area of the particles, we determined that the turnover frequency was 6.2 ± 1.6 s−1 at an overpotential of 0.3 V, which is, to the best of our knowledge, the highest reported for oxygen evolution in alkaline solution.

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This work was supported by a research grant (9455) from VILLUM FONDEN. We also acknowledge UPCAT under project no. 2015-1-12315.

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Author notes

  1. These authors contributed equally: C. Roy, B. Sebok, S. B. Scott.


  1. SurfCat, Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark

    • C. Roy
    • , B. Sebok
    • , S. B. Scott
    • , J. E. Sørensen
    • , A. Bodin
    • , D. B. Trimarco
    • , P. C. K. Vesborg
    • , I. E. L. Stephens
    • , J. Kibsgaard
    •  & I. Chorkendorff
  2. Center for Electron Nanoscopy, Technical University of Denmark, Kgs. Lyngby, Denmark

    • E. M. Fiordaliso
    •  & C. D. Damsgaard
  3. Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby, Denmark

    • O. Hansen
  4. Department of Materials, Imperial College London, Royal School of Mines, London, UK

    • I. E. L. Stephens


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I.E.L.S., J.K. and I.C. conceived the experiments. C.R. participated in the conception of the experiments and performed the electrochemical measurements. B.S. participated in the conception of the experiments, prepared the nanoparticles and performed the UHV experiments. S.B.S. performed and helped in the design of the EC–MS experiments. D.B.T., P.C.K.V. and O.H. designed and helped with the interpretation of the EC–MS experiments. E.M.F. and C.D.D. performed the microscopy characterization. J.E.S. and A.B. contributed to the LEIS measurements. C.R., B.S. and S.B.S. co-wrote the manuscript. All the authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to I. Chorkendorff.

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