General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities

Abstract

Single-atom catalysts (SACs) have recently attracted broad research interest as they combine the merits of both homogeneous and heterogeneous catalysts. Rational design and synthesis of SACs are of immense significance but have so far been plagued by the lack of a definitive correlation between structure and catalytic properties. Here, we report a general approach to a series of monodispersed atomic transition metals (for example, Fe, Co, Ni) embedded in nitrogen-doped graphene with a common MN4C4 moiety, identified by systematic X-ray absorption fine structure analyses and direct transmission electron microscopy imaging. The unambiguous structure determination allows density functional theoretical prediction of MN4C4 moieties as efficient oxygen evolution catalysts with activities following the trend Ni > Co > Fe, which is confirmed by electrochemical measurements. Determination of atomistic structure and its correlation with catalytic properties represents a critical step towards the rational design and synthesis of precious or nonprecious SACs with exceptional atom utilization efficiency and catalytic activities.

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Fig. 1: The preparation route to M–NHGFs.
Fig. 2: Structural characterizations of M–NHGFs by EXAFS spectroscopy.
Fig. 3: Structural characterization by XANES spectroscopy on M–NHGFs.
Fig. 4: Atomic structure characterizations of M–NHGFs by ADF-STEM.
Fig. 5: Evaluation of catalytic activity by DFT simulations and electrochemical measurements.

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Acknowledgements

Y.H. acknowledges support from the Office of Naval Research under award number N000141712608. X.D. acknowledges financial support from the National Science Foundation EFRI-1433541. I.S. acknowledges the financial support from the Deanship of Scientific Research at the King Saud University for funding this research through the International Research Group Project No: IRG14-19. J.D. acknowledges support from the National Natural Science Foundation of China (grant 11605225), Youth Innovation Promotion Association, Chinese Academy of Sciences  (CAS) and Jialin Xie Foundation of the Institute of High Energy Physics, CAS. We thank Z. Zhuang for the help with in situ XAFS characterization. We thank Diamond Light Source for access and support in use of the electron Physical Science Imaging Centre (EM16967) that contributed to the results presented here. A.I.K. acknowledges financial support from EPSRC (platform grants EP/F048009/1 and EP/K032518/1) and from the EU (ESTEEM2; Enabling Science and Technology through European Electron Microscopy), 7th Framework Programme of the European Commission. Y.F. acknowledges support from the National Science Foundation of China (grants 11604092 and 11634001). M.L. acknowledges the support from the US Department of Energy, Office of Basic Energy Sciences, under contract DE-SC0012704.

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X.D. and Y.H. designed the research. H.F. performed the synthesis, most of the structural characterizations, and electrochemical tests. J.D., P.A., W.C., Z.G., D.C. and T.H. performed the XAFS measurement and analysed the EXAFS and XANES data. Y.F. and M.L. performed DFT simulations. C.W., B.V., M.L., Z.Z. and H.S. assisted in the electrochemical tests. Y.W. and C.L. assisted in the XRD and BET surface area analysis. C.S.A. conducted the aberration-corrected STEM characterization under the supervision of A.I.K. I.S. contributed to the discussion and analysis of the electrochemical testing results. The paper was co-written by X.D., H.F., J.D., Y.F., I.S. and Y.H. The research was supervised by X.D. and Y.H. All authors discussed the results and commented on the manuscript.

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Correspondence to Imran Shakir or Xiangfeng Duan or Yu Huang.

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Supplementary Figures 1–42, Supplementary Tables 1–7, Supplementary Notes 1–3, Supplementary References.

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Fei, H., Dong, J., Feng, Y. et al. General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities. Nat Catal 1, 63–72 (2018). https://doi.org/10.1038/s41929-017-0008-y

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