Electrochemical activation of molecular nitrogen to ammonia

Ib Chorkendorff^a

^aSurfCat, Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2023 Conference (MATSUSFall23)

#N2X - Recent advances on nitrogen activation and conversion

Torremolinos, Spain, 2023 October 16th - 20th

Organizers: Victor Mougel, Nella Vargas-Barbosa and Roland Marschall

Invited Speaker, Ib Chorkendorff, presentation 090
DOI: https://doi.org/10.29363/nanoge.matsus.2023.090
Publication date: 18th July 2023

Activating of molecular Nitrogen is an extremely important process as it supplies in the form of fertilizer the nitrogen that it is a prerequisite for building all amino acids and nucleic acids essential for life. After brief review of the history of activating nitrogen[1] I shall concentrate on the ammonia synthesis and motivate why an alternative route to the current commercial Haber-Bosch could be attractive Recently we found that a method published by Tsuneto et al. 25 years ago worked and proved that by simultaneous depositing Li in an N2 atmosphere it was indeed possible to activate N2 to synthesize ammonia[2]. We have subsequently followed up on this process and a very simple model for the synthesis has been proposed. Based on this insight we devised experiments that significantly improved the Faradaic and energy efficiency[3] by oscillating the potential. Further improvements have been gained by controlling the oxygen content[4] and by synthesizing of high area electrodes[5] and design of the SEI layer leading to Faradaic efficiency of ~80% and current densities towards 1A/cm2 [6]. Despite excellent recent progress there are still substantial outstanding problems. All data so far were relying on using the electrolyte as a sacrificial proton conductor. This issue was solved in a fuel cell type setup, but now we are back to 6 mA/cm2 and 60 % Faradaic efficiency on the other hand we can now talk about energy efficiencies of some 15% [7]. Further progress is under way and will be discussed

References:

[1] H. Iriawa, S. Z. Andersen, X. Zhang, B.M. Comer, J. Barrio, P. Chen, A.J. Medford, I.E.L. Stephens, I. Chorkendorff, Y. Shao-Horn, “Activation of Molecular Nitrogen by reduction and oxidation” Nature Reviews Methods Primers” (2021) 1:56

[2] S. Z. Andersen, V. Čolić, S. Yang, J. A. Schwalbe, A. C. Nielander, J. M. McEnaney, J. G. Baker, A. R. Singh, B. A. Rohr, M. J. Statt, S. J. Blair, S. Mezzavilla, K. Enemark-Rasmussen, J. Kibsgaard, P. C. K. Vesborg, M. Cargnello, S. F. Bent, T. F. Jaramillo, I. E. L. Stephens, J. K. Nørskov and I. Chorkendorff, “Benchmarking the Electrochemical Nitrogen Reduction Reaction” NATURE, 570 (2019) 504-508

[3] S. Z. Andersen, M. J. Statt, V. J. Bukas, S.G. Shapel, J. B. Pedersen, K. Krempl, Mattia Saccoccio, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. Nørskov, and I. Chorkendorff, “Increasing Stability and Efficiency of Lithium-Mediated Electrochemical Nitrogen Reduction” Energy & Environ. Sci. 13 (2020) 4291

[4] K. Li, S. Z. Andersen, M. J. Statt, M. Saccoccio, V. J. Bukas, K. Krempl, R. Sažinas1, J. B. Pedersen, V. Shadravan, Y. Zhou, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. K. Nørskov, and I. Chorkendorff, “Enhancement of Li-mediated Ammonia Synthesis by Addition of Oxygen”, Science 374 (2021) 1593-97

[5] K. Li, S. G. Shapel, D. Hochfilzer, J. B. Pedersen, K. Krempl, S. Z. Andersen, R. Sažinas, M. Saccoccio, S. Li, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. K. Nørskov, and I. Chorkendorff, “Increasing current density of Li-mediated ammonia synthesis with high surface area copper electrodes” ACS Energy Lett. 7 (2022) 36-41

[6] S. Li, Y. Zhou, K. Li, M. Saccoccio, R. Sažinas, S. Z. Andersen, J. B. Pedersen, X. Fu, V. Shadravan, D. Chakraborty, J. Kibsgaard, P. C. K. Vesborg, J. K. Nørskov, I. Chorkendorff, “Electrosynthesis of ammonia with high selectivity and high rates via engineering of the solid-electrolyte interphase“, Joule 6 (2022) 1-19

[7] X. Fu, J. B. Pedersen, Y. Zhou, M. Saccoccio, S. Li, R. Sažinas, K. Li, S. Z. Andersen, A. Xu, N. H. Deissler, J. j. V. Mygin, C. Wei, J. Kibsgaard, P. C. K. Vesborg, J. K. Nørskov, and I. Chorkendorff, “Electrosynthesis of ammonia from nitrogen reduction coupled with hydrogen oxidation in a continuous-flow reactor”, Science 379 (2023) 707-712

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