Electrochemical Interphases beyond Lithium for Nitrogen Reduction to Ammonia

Romain Tort^a, Alexander Bagger^b, Olivia Westhead^c, Yasuyuki Kondo^d, Artem Khobnya^c, Anna Winiwarter^c, Bethan J. V. Davies^c, Yu Katayama^d, Yuki Yamada^d, Mary P. Ryan^c, Maria-Magdalena Titirici^c, Ifan E. L. Stephens^c

^aImperial College London, Department of Chemical Engineering, London SW7 2AZ, UK

^bTechnical University of Denmark, Department of Physics, Fysikvej, 312, Kongens Lyngby, Denmark

^cImperial College London, Department of Materials, London SW7 2AZ, UK.

^dd Osaka University, SANKEN (The Institute of Scientific and Industrial Research), Mihogaoka, Ibaraki 567-0047, Osaka, Japan

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2024 Conference (MATSUSFall24)

#EEInt - Electrode-Electrolyte Interfaces in Electrocatalysis

Lausanne, Switzerland, 2024 November 12th - 15th

Organizers: Yu Katayama and Mariana Monteiro

Oral, Romain Tort, presentation 250
DOI: https://doi.org/10.29363/nanoge.matsusfall.2024.250
Publication date: 28th August 2024

Nitrogen reduction to ammonia stands amongst the hardest reactions to decarbonise, with the Haber-Bosch process dominating the market. In that regard, an electrochemical alternative holds potential for sustainable and decentralised production of fertilisers and carbon-neutral fuel. On a solid electrode, the lithium chemistry has long been the only one to split nitrogen selectively to ammonia.^1,2 Huge progress has been made both at fundamental^3,4 and device level.^5,6 However, alkali metals like Li require operation at their plating potential, far beyond the equilibrium potential for ammonia synthesis (>3 V intrinsic overpotential, >70% energy losses to metal plating).^5,7

To address this issue, we provide a theory/experiment informed guide to the discovery of alternative electrochemical systems, considering energetics both from an electrode and electrolyte perspective.⁸ Theoretical analysis pinpoints many candidates energetically relevant to mediate ammonia synthesis, including some alkali-metals. Guided by the flourishing field of beyond-Li batteries, we explore their chemistries through a series of electrolyte and solid-electrolyte interphase characterisations, model experiments and operando gas evolution measurements. This study will show how experimental validation of candidate catalysts requires control over not only the energetics of the electrode but the electrolyte too. When the right balance between the two side of that same coin is found, predicted chemistries eventually work out, with recent examples of Calcium- and Magnesium-mediated nitrogen reduction.^9,10

Learning from such systems, we will conclude on perspectives towards catalytic systems with lower intrinsic overpotentials and how to achieve them experimentally. We hope to stimulate research paths towards breaking the inherent barrier of energy efficiency that nitrogen electroreduction is currently burdened with.

References:

[1] Tsuneto, A.; Kudo, A.; Sakata, T. Lithium-Mediated Electrochemical Reduction of High Pressure N2 to NH3. J. Electroanal. Chem. 1994, 367 (1–2), 183–188.

[2] Andersen, S. Z.; Čolić, V.; Yang, S.; Schwalbe, J. A.; Nielander, A. C.; McEnaney, J. M.; Enemark-Rasmussen, K.; Baker, J. G.; Singh, A. R.; Rohr, B. A.; Statt, M. J.; Blair, S. J.; Mezzavilla, S.; Kibsgaard, J.; Vesborg, P. C. K.; Cargnello, M.; Bent, S. F.; Jaramillo, T. F.; Stephens, I. E. L.; Nørskov, J. K.; Chorkendorff, I. A Rigorous Electrochemical Ammonia Synthesis Protocol with Quantitative Isotope Measurements. Nature 2019, 570 (7762), 504–508.

[3] Steinberg, K.; Yuan, X.; Klein, C. K.; Lazouski, N.; Mecklenburg, M.; Manthiram, K.; Li, Y. Imaging of Nitrogen Fixation at Lithium Solid Electrolyte Interphases via Cryo-Electron Microscopy. Nat. Energy 2022, 8 (2), 138–148.

[4] Spry, M.; Westhead, O.; Tort, R.; Moss, B.; Katayama, Y.; Titirici, M.-M.; Stephens, I. E. L.; Bagger, A. Water Increases the Faradaic Selectivity of Li-Mediated Nitrogen Reduction. ACS Energy Lett. 2023, 8, 1230–1235.

[5] Fu, X.; Pedersen, J. B.; Zhou, Y.; Saccoccio, M.; Li, S.; Sažinas, R.; Li, K.; Andersen, S. Z.; Xu, A.; Deissler, N. H.; Mygind, J. B. V.; Wei, C.; Kibsgaard, J.; Vesborg, P. C. K.; Nørskov, J. K.; Chorkendorff, I. Continuous-Flow Electrosynthesis of Ammonia by Nitrogen Reduction and Hydrogen Oxidation. Science (80-. ). 2023, 379 (6633), 707–712.

[6] Du, H.-L.; Chatti, M.; Hodgetts, R. Y.; Cherepanov, P. V.; Nguyen, C. K.; Matuszek, K.; MacFarlane, D. R.; Simonov, A. N. Electroreduction of Nitrogen with Almost 100% Current-to-Ammonia Efficiency. Nature 2022, 609 (7928), 722–727.

[7] Westhead, O.; Tort, R.; Spry, M.; Rietbrock, J.; Jervis, R.; Grimaud, A.; Bagger, A.; Stephens, I. E. L. The Origin of Overpotential in Lithium-Mediated Nitrogen Reduction. Faraday Discuss. 2023, 243, 321–338.

[8] Tort, R.; Bagger, A.; Westhead, O.; Kondo, Y.; Khobnya, A.; Winiwarter, A.; Davies, B. J. V; Walsh, A.; Katayama, Y.; Yamada, Y.; Ryan, M. P.; Titirici, M.; Stephens, I. E. L. Searching for the Rules of Electrochemical Nitrogen Fixation. ACS Catal. 2023, 13, 14476–15218.

[9] Fu, X.; Niemann, V. A.; Zhou, Y.; Li, S.; Zhang, K.; Pedersen, J. B.; Saccoccio, M.; Andersen, S. Z.; Enemark-Rasmussen, K.; Benedek, P.; Xu, A.; Deissler, N. H.; Mygind, J. B. V.; Nielander, A. C.; Kibsgaard, J.; Vesborg, P. C. K.; Nørskov, J. K.; Jaramillo, T. F.; Chorkendorff, I. Calcium-Mediated Nitrogen Reduction for Electrochemical Ammonia Synthesis. Nat. Mater. 2023, 23, 101–107.

[10] Krebsz, M.; Hodgetts, R.; Johnston, S.; Nguyen, C. K.; Hora, Y.; MacFarlane, D. R.; Simonov, A. N. Reduction of Dinitrogen to Ammonium through a Magnesium-Based Electrochemical Process at Close-to-Ambient Temperature. Energy Environ. Sci. 2024.

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