Nitrogen Reduction to Ammonia: Roads Beyond Lithium

Romain Tort^a, Alexander Bagger^a, Yasuyuki Kondo^b, Olivia Westhead^c, Artem Khobnya^c, Mary Ryan^c, Maria-Magdalena Titirici^a, Ifan Stephens^c

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

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

^cImperial College London, Department of Materials, Royal School of Mines, London SW7 2AZ, UK

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

Oral, Romain Tort, presentation 160
DOI: https://doi.org/10.29363/nanoge.matsus.2023.160
Publication date: 18th July 2023

Nitrogen reduction to ammonia stands amongst the hardest processes to decarbonise, with the Haber-Bosch process dominating the market. In that regard, electrochemical ammonia synthesis can meet this unmet need, towards sustainable and decentralised production of fertilisers and carbon-neutral fuel.

So far, the lithium-mediated synthesis is the sole process to unambiguously generate ammonia from nitrogen on a solid electrode.^1,2 Tremendous progress has been made in just a few years, both in terms of the underpinning fundamentals,^3,4 and in terms of device engineering.^5,6 However, all these improvements are burdened with the need to operate at lithium plating potential. This results in enormous overpotentials (>3.2 V) and energy losses (>70% due to lithium plating).^7,8 A solution is to identify new catalytic systems with lower intrinsic overpotential, which is highly challenging.⁹

In this talk, I will walk us through the periodic table of elements, bringing together physical descriptors obtained from theoretical calculations and literature meta-analysis. This exploration will aim at unifying the comparison of electrochemical systems for nitrogen reduction to ammonia, and pinpoint candidate elements which I will investigate experimentally. Electrochemical testing, ex situ / operando characterisation and model experiments will be performed to explore promising catalytic systems. Learning from those, I will provide fundamental explanations to the unique features of lithium and suggest pathways to breach the bottleneck of the lithium chemistry, opening the discussion for more energy efficient and sustainable chemistries.

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, 1–11

[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] 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

[6] 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

[7] Westhead, O.; Tort, R.; Spry, M.; Rietbrock, J.; Jervis, R.; Grimaud, A.; Bagger, A.; Stephens, I. The Origin of Overpotential in Lithium-Mediated Nitrogen Reduction. Faraday Discuss. 2022

[8] Tort, R.; Westhead, O.; Spry, M.; Davies, B. J. V.; Ryan, M. P.; Titirici, M.-M.; Stephens, I. E. L. Nonaqueous Li-Mediated Nitrogen Reduction: Taking Control of Potentials. ACS Energy Lett. 2023, 8, 1003–1009

[9] Westhead, O.; Barrio, J.; Bagger, A.; Murray, J. W.; Rossmeisl, J.; Titirici, M.-M.; Jervis, R.; Fantuzzi, A.; Ashley, A.; Stephens, I. E. L. Near Ambient N2 Fixation on Solid Electrodes versus Enzymes and Homogeneous Catalysts. Nat. Rev. Chem. 2023, 1–18

Acknowledgements:

R.T. and M.-M.T. acknowledge funding from the Royal Academy of Engineering Chair in Emerging Technologies Fellowship. A.B. thanks the Carlsberg Foundation (CF21-0114). Y.K. thanks the New Energy and Industrial Technology Development Organization (NEDO) under the Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration (JPNP2005). O.W. acknowledges funding from the EPSRC and SFI Centre for Doctoral Training in Advanced Characterisation of Materials (EP/S023259/1). A.K. and I.E.L.S. acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (866402). M.P.R., M.-M.T. and I.E.L.S. acknowledge fundign from the Faraday Institution (EP/3003053/1, grants FIRG001 and FIRG0024). All authors acknowledge the help of Peter Haycock for his assistance with NMR quantification measurements, as well as Dr Sarah Fearn for her assistance with ToF-SIMS, and the Imperial College Hackspace for their help in building experimental equipment.

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