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Revealing nitrogen-containing species in commercial catalysts used for ammonia electrosynthesis

Nature Catalysis volume 3, pages 1055–1061 (2020)Cite this article

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A Publisher Correction to this article was published on 22 February 2021

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Abstract

Stimulated by the growing demand for sustainable and/or economical distributed ammonia synthesis, the electrochemical nitrogen reduction reaction has attracted considerable interest. The nitrogen-containing impurities in commercial metal-based nitrogen reduction reaction catalysts such as metal oxides and metallic irons have, however, been overlooked. Herein we report the presence of nitrogen-containing species in NOx− or nitrides at substantial levels revealed from many commercial catalysts. We call attention to the necessity to screen the NOx−/nitrides impurities in commercial catalysts, as the nitrogen impurities are not commonly listed in vendors’ assay documents. A simple two-step procedure (alkaline/acidic treatment followed by HPLC/UV–vis analysis) is recommended as a reliable protocol for screening NOx−/nitrides impurities in catalyst materials. A case analysis is also carried out on the previously reported H2O–NaOH–KOH system with both 15N-isotopic labelling and nitrogen elemental tracking, reassigning the true nitrogen source of the electrochemically produced NH3 from gaseous N2 to nitrogen-containing impurities in catalysts.

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Fig. 1: NOx− impurities detected in commercial metal oxides.
Fig. 2: Revealing nitrogen-containing impurities in commercial metal oxides and metallic irons.
Fig. 3: Electrolysis in the H2O–NaOH–KOH systems.
Fig. 4: Area- and mass-normalized NH3 production of reported NRR electrocatalysts.

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Source data are provided with this paper. All data supporting the findings of this study are available from the corresponding author on reasonable request.

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Acknowledgements

This research was partly supported by ARPA-E agency through REFUEL program (grant no. DE-AR0000812) and by Iowa Economic Development Authority (IEDA, grant no. AWD-019199). We are grateful to S. D. Cady, D. Jing, and B. W. Boote from Iowa State University for their generous assistance in NMR and material characterization. We also acknowledge fruitful discussions with J. Li, E. A. Smith, H. Lin, B. H. Shanks, R. C. Brown, J. L. Trettin (Iowa State University), K. Kim (University of Illinois at Urbana-Champaign) and G. Soloveichik (ARPA-E) on the electrosynthesis of ammonia. W. Li thanks his Bailey Research Career Development Award and Richard Seagrave Professorship. Y. Chen acknowledges his Catron Graduate Fellowship from Catron Center for Solar Energy Research at Iowa State University.

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Authors and Affiliations

  1. Department of Chemical & Biological Engineering, Iowa State University, Ames, IA, USA

    Yifu Chen, Hengzhou Liu & Wenzhen Li

  2. Department of Mechanical Engineering, Wichita State University, Wichita, KS, USA

    Nguon Ha & Shuang Gu

  3. Department of Chemistry, George Washington University, Washington, DC, USA

    Stuart Licht

  4. DOE’s Ames Laboratory, Ames, IA, USA

    Wenzhen Li

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  1. Yifu Chen
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Contributions

W.L., S.G. and S.L. proposed the research and supervised the project. Y.C. performed material characterization. H.L. carried out HPLC measurements. Y.C. and N.H. set up the electrolytic cell system with the assistance from S.G. and S.L. and performed the electrochemical studies. Y.C., S.G., S.L. and W.L. co-wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Stuart Licht, Shuang Gu or Wenzhen Li.

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Supplementary Information

Supplementary Tables 1–4, Figs. 1–8 and references.

Supplementary Data 1

Experimental Source Data for Supplementary Table 1 and Supplementary Figs. 2, 3 and 5–7.

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Experimental Source Data.

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Experimental Source Data.

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Chen, Y., Liu, H., Ha, N. et al. Revealing nitrogen-containing species in commercial catalysts used for ammonia electrosynthesis. Nat Catal 3, 1055–1061 (2020). https://doi.org/10.1038/s41929-020-00527-4

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