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Tandem electrocatalytic N2 fixation via proton-coupled electron transfer

Nature volume 609, pages 71–76 (2022)Cite this article

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Abstract

New electrochemical ammonia (NH3) synthesis technologies are of interest as a complementary route to the Haber–Bosch process for distributed fertilizer generation, and towards exploiting ammonia as a zero-carbon fuel produced via renewably sourced electricity1. Apropos of these goals is a surge of fundamental research targeting heterogeneous materials as electrocatalysts for the nitrogen reduction reaction (N2RR)2. These systems generally suffer from poor stability and NH3 selectivity; the hydrogen evolution reaction (HER) outcompetes N2RR3. Molecular catalyst systems can be exquisitely tuned and offer an alternative strategy4, but progress has been thwarted by the same selectivity issue; HER dominates. Here we describe a tandem catalysis strategy that offers a solution to this puzzle. A molecular complex that can mediate an N2 reduction cycle is partnered with a co-catalyst that interfaces the electrode and an acid to mediate proton-coupled electron transfer steps, facilitating N−H bond formation at a favourable applied potential (−1.2 V versus Fc+/0) and overall thermodynamic efficiency. Certain intermediates of the N2RR cycle would be otherwise unreactive via uncoupled electron transfer or proton transfer steps. Structurally diverse complexes of several metals (W, Mo, Os, Fe) also mediate N2RR electrocatalysis at the same potential in the presence of the mediator, pointing to the generality of this tandem approach.

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Fig. 1: Approaches to N2RR electrocatalysis.
Fig. 2: Electrocatalytic N2RR via tandem catalysis.
Fig. 3: Mechanistic insights into tandem PCET N2RR.
Fig. 4: Electrocatalytic N2RR using reported molecular catalysts.

Data availability

Details on the procedures and the corresponding datasets generated during and/or analysed during the current study are available within the paper and its Supplementary Information files, and from the corresponding author on reasonable request.

References

  1. Martín, A. J., Shinagawa, T. & Pérez-Ramírez, J. Electrocatalytic reduction of nitrogen: from Haber–Bosch to ammonia artificial leaf. Chem 5, 263–283 (2019).

    Article  Google Scholar 

  2. Qing, G. et al. Recent advances and challenges of electrocatalytic N2 reduction to ammonia. Chem. Rev. 120, 5437–5516 (2020).

    Article  CAS  Google Scholar 

  3. Ren, Y. et al. Strategies to suppress hydrogen evolution for highly selective electrocatalytic nitrogen reduction: challenges and perspectives. Energy Environ. Sci. 14, 1176–1193 (2021).

    Article  CAS  Google Scholar 

  4. Chalkley, M. J., Drover, M. W. & Peters, J. C. Catalytic N2-to-NH3 (or -N2H4) conversion by well-defined molecular coordination complexes. Chem. Rev. 120, 5582–5636 (2020).

    Article  CAS  Google Scholar 

  5. Yandulov, D. V. & Schrock, R. R. Catalytic reduction of dinitrogen to ammonia at a single molybdenum center. Science 301, 76–78 (2003).

    Article  ADS  CAS  Google Scholar 

  6. Arashiba, K., Miyake, Y. & Nishibayashi, Y. A molybdenum complex bearing PNP-type pincer ligands leads to the catalytic reduction of dinitrogen into ammonia. Nat. Chem. 3, 120–125 (2010).

    Article  Google Scholar 

  7. Anderson, J. S., Rittle, J. & Peters, J. C. Catalytic conversion of nitrogen to ammonia by an iron model complex. Nature 501, 84–87 (2013).

    Article  ADS  CAS  Google Scholar 

  8. Lindley, B. M. et al. Mechanism of chemical and electrochemical N2 splitting by a rhenium pincer complex. J. Am. Chem. Soc. 140, 7922–7935 (2018).

    Article  CAS  Google Scholar 

  9. Merakeb, L. & Robert, M. Advances in molecular electrochemical activation of dinitrogen. Curr. Opin. Electrochem. 29, 100834 (2021).

    Article  CAS  Google Scholar 

  10. Bruch, Q. J. et al. Considering electrocatalytic ammonia synthesis via bimetallic dinitrogen cleavage. ACS Catal. 10, 10826–10846 (2020).

    Article  CAS  Google Scholar 

  11. Chalkley, M. J., Del Castillo, T. J., Matson, B. D. & Peters, J. C. Fe-mediated nitrogen fixation with a metallocene mediator: exploring pKa effects and demonstrating electrocatalysis. J. Am. Chem. Soc. 140, 6122–6129 (2018).

    Article  CAS  Google Scholar 

  12. Helm, M. L., Stewart, M. P., Bullock, R. M., DuBois, M. R. & DuBois, D. L. A synthetic nickel electrocatalyst with a turnover frequency above 100,000 s−1 for H2 production. Science 333, 863–866 (2011).

    Article  ADS  CAS  Google Scholar 

  13. Francke, R., Schille, B. & Roemelt, M. Homogeneously catalyzed electroreduction of carbon dioxide—methods, mechanisms, and catalysts. Chem. Rev. 118, 4631–4701 (2018).

    Article  CAS  Google Scholar 

  14. Pegis, M. L., Wise, C. F., Martin, D. J. & Mayer, J. M. Oxygen reduction by homogeneous molecular catalysts and electrocatalysts. Chem. Rev. 118, 2340–2391 (2018).

    Article  CAS  Google Scholar 

  15. Pickett, C. J. & Talarmin, J. Electrosynthesis of ammonia. Nature 317, 652–653 (1985).

    Article  ADS  CAS  Google Scholar 

  16. Becker, J. Y. & Avraham Tsarfaty, S. Nitrogen fixation: part III. Electrochemical reduction of hydrazido (-NNH2) Mo and W complexes. Selective formation of NH3 under mild conditions. J. Electroanal. Chem. Interf. Electrochem. 280, 119–127 (1990).

    Article  CAS  Google Scholar 

  17. Wang, Y. et al. Scaling relationships for binding energies of transition metal complexes. Catal. Lett. 146, 304–308 (2016).

    Article  CAS  Google Scholar 

  18. Chalkley, M. J., Garrido-Barros, P. & Peters, J. C. A molecular mediator for reductive concerted proton-electron transfers via electrocatalysis. Science 369, 850–854 (2020).

    Article  ADS  CAS  Google Scholar 

  19. Derosa, J., Garrido-Barros, P. & Peters, J. C. Electrocatalytic reduction of C–C π-bonds via a cobaltocene-derived concerted proton–electron transfer mediator: fumarate hydrogenation as a model study. J. Am. Chem. Soc. 143, 9303–9307 (2021).

    Article  CAS  Google Scholar 

  20. Badalyan, A. & Stahl, S. S. Cooperative electrocatalytic alcohol oxidation with electron-proton-transfer mediators. Nature 535, 406–410 (2016).

    Article  ADS  CAS  Google Scholar 

  21. Galvin, C. M. & Waymouth, R. M. Electron-rich phenoxyl mediators improve thermodynamic performance of electrocatalytic alcohol oxidation with an Iridium pincer complex. J. Am. Chem. Soc. 142, 19368–19378 (2020).

    Article  CAS  Google Scholar 

  22. Bevan, P. C., Chatt, J., Dilworth, J. R., Henderson, R. A. & Leigh, G. J. The preparation and reactions of azidobis[1,2-bis(diphenylphosphino)-ethane]nitridotungsten(IV). J. Chem. Soc., Dalton Trans. 821–824 (1982).

  23. Mohammed, M. Y. & Pickett, C. J. From metal imides and molecular nitrogen to ammonia and dinitrogen complexes. J. Chem. Soc., Chem. Commun. 1119–1121 (1988).

  24. Alias, Y. et al. Electrochemistry of molybdenum imides: cleavage of molybdenum–nitrogen triple bonds to release ammonia or amines. J. Chem. Soc., Dalton Trans. 4807–4816 (1997).

  25. Tyburski, R., Liu, T., Glover, S. D. & Hammarström, L. Proton-coupled electron transfer guidelines, fair and square. J. Am. Chem. Soc. 143, 560–576 (2021).

    Article  CAS  Google Scholar 

  26. Agarwal, R. G. et al. Free energies of proton-coupled electron transfer reagents and their applications. Chem. Rev. 122, 1–49 (2022).

    Article  CAS  Google Scholar 

  27. Chalkley, M. J., Del Castillo, T. J., Matson, B. D., Roddy, J. P. & Peters, J. C. Catalytic N2-to-NH3 conversion by Fe at lower driving force: a proposed role for metallocene-mediated PCET. ACS Cent. Sci. 3, 217–223 (2017).

    Article  CAS  Google Scholar 

  28. Fajardo, J. Jr. & Peters, J. C. Catalytic nitrogen-to-ammonia conversion by osmium and ruthenium complexes. J. Am. Chem. Soc. 139, 16105–16108 (2017).

    Article  CAS  Google Scholar 

  29. Chatt, J. & Leigh, G. J. Nitrogen fixation. Chem. Soc. Rev. 1, 121–144 (1972).

    Article  CAS  Google Scholar 

  30. Ashida, Y., Arashiba, K., Nakajima, K. & Nishibayashi, Y. Molybdenum-catalysed ammonia production with samarium diiodide and alcohols or water. Nature 568, 536–540 (2019).

    Article  ADS  CAS  Google Scholar 

  31. Arashiba, K. et al. Catalytic nitrogen fixation via direct cleavage of nitrogen–nitrogen triple bond of molecular dinitrogen under ambient reaction conditions. Bull. Chem. Soc. Jpn. 90, 1111–1118 (2017).

    Article  CAS  Google Scholar 

  32. van der Ham, C. J. M., Koper, M. T. M. & Hetterscheid, D. G. H. Challenges in reduction of dinitrogen by proton and electron transfer. Chem. Soc. Rev. 43, 5183–5191 (2014).

    Article  Google Scholar 

  33. Lazouski, N., Chung, M., Williams, K., Gala, M. L. & Manthiram, K. Non-aqueous gas diffusion electrodes for rapid ammonia synthesis from nitrogen and water-splitting-derived hydrogen. Nat. Catal. 3, 463–469 (2020).

    Article  CAS  Google Scholar 

  34. Lanzilotta, W. N., Christiansen, J., Dean, D. R. & Seefeldt, L. C. Evidence for coupled electron and proton transfer in the [8Fe-7S] cluster of nitrogenase. Biochemistry 37, 11376–11384 (1998).

    Article  CAS  Google Scholar 

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Acknowledgements

We thank the Dow Next Generation Educator Funds and Instrumentation Grants for their support of the NMR facility at Caltech. We also thank the Resnick Water and Environment Laboratory (WEL) and the Molecular Materials Resource Center at Caltech for the use of their instrumentation. We thank the following funding agencies: Department of Energy, Office of Basic Energy Sciences (DOE-0235032), Catalysis Science Program (for the development and applications of CPET mediators); National Institutes of Health (R01 GM-075757) (for studies of Fe-mediated N2RR). P.G.-B. thanks the Ramón Areces Foundation for a postdoctoral fellowship. J.D. thanks the Arnold and Mabel Beckman Foundation for a postdoctoral fellowship. M.J.C. thanks the Resnick Sustainability Institute for a graduate fellowship.

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  1. Matthew J. Chalkley

    Present address: Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA

Authors and Affiliations

  1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA

    Pablo Garrido-Barros, Joseph Derosa, Matthew J. Chalkley & Jonas C. Peters

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Contributions

P.G.-B., M.J.C. and J.C.P. conceptualized the work. P.G.-B. designed and executed the experiments. J.D. assisted with the execution of the catalytic experiments. All authors analysed and interpreted the data and co-wrote the manuscript.

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Correspondence to Jonas C. Peters.

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Supplementary Sections 1–15, Figs. 1–108, Table 1 and references.

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Garrido-Barros, P., Derosa, J., Chalkley, M.J. et al. Tandem electrocatalytic N2 fixation via proton-coupled electron transfer. Nature 609, 71–76 (2022). https://doi.org/10.1038/s41586-022-05011-6

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