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Promoting nitrogen electroreduction to ammonia with bismuth nanocrystals and potassium cations in water

Abstract

The electrochemical nitrogen reduction reaction (ENRR) can allow the production of ammonia from nitrogen and water under ambient conditions and is regarded as a sustainable alternative to the industrial Haber–Bosch process. However, electrocatalytic systems that selectively and efficiently catalyse nitrogen reduction remain elusive due to the strong competition with the hydrogen evolution reaction. Here, we report a strategy to simultaneously promote ENRR selectivity and activity using bismuth nanocrystals and potassium cations. Bismuth exhibits higher intrinsic ENRR activity than transition metals due to the strong interaction between the Bi 6p band and the N 2p orbitals. Potassium cations stabilize key nitrogen-reduction intermediates and regulate proton transfer to increase the selectivity. A high Faradaic efficiency of 66% and ammonia yield of 200 mmol g–1 h–1 (0.052 mmol cm–2 h–1) are obtained in aqueous electrolyte under ambient conditions. This strategy represents a general method to expand the library of catalysts and promoters for the selective electrochemical reduction of stable molecules.

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The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Change history

  • 08 March 2019

    In the version of this Article originally published, all labels for the orange, blue and red trends in Fig. 3b read ‘BiNCs’, but the orange labels should have read ‘BiNPs’, and the blue ‘BiBPs’. This has now been corrected.

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Acknowledgements

The authors thank W. Sun, G. Wang and Z. Zhou for helpful discussions. The authors acknowledge the Analytical and Testing Center of BIT for technical support and the High-Performance Computing Platform of PKU for supporting the computational work. A.X.Y. acknowledges financial support from the National Natural Science Foundation of China (grant no. 21601015) and the Beijing Institute of Technology Research Fund Program for Young Scholars. Y.W.Z. acknowledges financial support from the National Key Research and Development Program of China (no. 2016YFB0701100), the National Natural Science Foundation of China (nos. 21832001, 21771009, 21573005 and 21621061) and the Beijing Natural Science Foundation (no. 2162019). C.H.Y. acknowledges financial support from the National Natural Science Foundation of China (nos. 21331001, 21590791 and 21461162001) and the National Key Research and Development Program of China (nos. 2014CB643800 and 2017YFA0205101).

Author information

A.-X.Y., Y.-W.Z. and C.-H.Y. designed the research. Y.-C.H. synthesized the catalysts, conducted the structure analysis and electrocatalytic studies. Y.G., X.-Y.W., Y.-W.Z. and C.-H.Y. performed the DFT calculations. Y.-C.H., L.-W.C., M.S. and R.S. performed the in situ XANES analysis. L.-W.C., Y.G., T.-A.B., W.-Y.G., N.Z., X.S., X.F., J.-W.Z., B.W. and C.-W.H. assisted with material characterizations and catalysis measurements. A.-X.Y., Y.-C.H. and Y.G. co-wrote the paper. A.-X.Y., Y.-W.Z. and C.-H.Y. supervised the research. All authors discussed the results and assisted during manuscript preparation.

Competing interests

The authors declare no competing interests.

Correspondence to An-Xiang Yin or Rui Si or Ya-Wen Zhang or Chun-Hua Yan.

Supplementary information

  1. Supplementary Information

    Supplementary Figures 1–33, Supplementary Tables 1–4 and Supplementary References.

  2. Supplementary Data

    The optimized atomic coordinates of the adsorption configurations for *NNH on Bi(012), (104) and (110)

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Fig. 1: Promoting the ENRR with bismuth catalysts and potassium cations.
Fig. 2: Structure, morphology and composition characterizations for BiNCs.
Fig. 3: ENRR performance for BiNCs, BiNPs and BiBPs in nitrogen-saturated electrolytes (0.5 mol l–1 of K2SO4, pH 3.5).
Fig. 4: Promotion of ENRR on BiNCs by potassium cations (−0.60 V versus RHE, pH 3.5).
Fig. 5: Thermodynamics for ENRR on solvated Bi surfaces under conditions with and without K+.