Catalysts for nitrogen reduction to ammonia

Abstract

The production of synthetic ammonia remains dependent on the energy- and capital-intensive Haber–Bosch process. Extensive research in molecular catalysis has demonstrated ammonia production from dinitrogen, albeit at low production rates. Mechanistic understanding of dinitrogen reduction to ammonia continues to be delineated through study of molecular catalyst structure, as well as through understanding the naturally occurring nitrogenase enzyme. The transition to Haber–Bosch alternatives through robust, heterogeneous catalyst surfaces remains an unsolved research challenge. Catalysts for electrochemical reduction of dinitrogen to ammonia are a specific focus of research, due to the potential to compete with the Haber–Bosch process and reduce associated carbon dioxide emissions. However, limited progress has been made to date, as most electrocatalyst surfaces lack specificity towards nitrogen fixation. In this Review, we discuss the progress of the field in developing a mechanistic understanding of nitrogenase-promoted and molecular catalyst-promoted ammonia synthesis and provide a review of the state of the art and scientific needs for heterogeneous electrocatalysts.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Nitrogenase enzyme structure and functions.
Fig. 2: Single electron–proton transfer model for nitrogenase-mediated nitrogen fixation.
Fig. 3: Associative nitrogen reduction pathways.
Fig. 4: Computational predictions and theory-based limitations for heterogenous (electro)catalysts.

References

  1. 1.

    Montoya, J. H., Tsai, C., Vojvodic, A. & Nørskov, J. K. The challenge of electrochemical ammonia synthesis: a new perspective on the role of nitrogen scaling relations. ChemSusChem 8, 2180–2186 (2015). Density functional theory results for close-packed and stepped metal surfaces suggest that linear scaling between N-surface binding and other N2Hxor NHx intermediates limits activity and selectivity for electrochemical ammonia synthesis, and successful catalyst design must break or circumvent these linear scaling relationships.

    Article  CAS  PubMed  Google Scholar 

  2. 2.

    Strait, R. & Nagveka, M. Carbon dioxide capture and storage in the nitrogen and syngas industries. Nitrogen Syngas 303, 16–19 (2010).

    CAS  Google Scholar 

  3. 3.

    Lipman, T. & Shah, N. Ammonia as an alternative energy storage medium for hydrogen fuel cells: scientific and technical review for near-term stationary power demonstration project, final report. Univ. California, Research Report UCB-ITS-RR-2007-5 (eScholarship Repository, Berkeley, 2007); http://www.escholarship.org/uc/item/7z69v4wp

  4. 4.

    Licht, S. et al. Ammonia synthesis by N2 and steam electrolysis in molten hydroxide suspensions of nanoscale Fe2O3. Science 345, 637–640 (2014). Nanoscale iron oxide, combined with steam and air in a molten hydroxide electrolyte, enable Faradaic efficiencies of up to 35% for electrochemical nitrogen reduction to ammonia.

    Article  CAS  PubMed  Google Scholar 

  5. 5.

    Zhou, F. et al. Electro-synthesis of ammonia from nitrogen at ambient temperature and pressure in ionic liquids. Energy Environ. Sci. 10, 2516–2520 (2017).

    Article  CAS  Google Scholar 

  6. 6.

    Seefeldt, L. C., Hoffman, B. M. & Dean, D. R. Electron transfer in nitrogenase catalysis. Curr. Opin. Chem. Biol. 16, 19–25 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. 7.

    Chan, J. M., Christiansen, J., Dean, D. R. & Seefeldt, L. C. Spectroscopic evidence for changes in the redox state of the nitrogenase P-cluster during turnover. Biochemistry 38, 5779–5785 (1999).

    Article  CAS  PubMed  Google Scholar 

  8. 8.

    Danyal, K., Dean, D. R., Hoffman, B. M. & Seefeldt, L. C. Electron transfer within nitrogenase: evidence for a deficit-spending mechanism. Biochemistry 50, 9255–9263 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  9. 9.

    Thorneley, R. N. F. & Lowe, D. J. Nitrogenase of Klebsiella pneumoniae. Kinetics of the dissociation of oxidized iron protein from molybdenum-iron protein: identification of the rate-limiting step for substrate reduction. Biochem. J. 215, 393–403 (1983).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. 10.

    Yang, Z.-Y. et al. Evidence that the Pi release event is the rate-limiting step in the nitrogenase catalytic cycle. Biochemistry 55, 3625–3635 (2016).

    Article  CAS  PubMed  Google Scholar 

  11. 11.

    Spatzal, T. et al. Evidence for interstitial carbon in nitrogenase FeMo cofactor. Science 334, 940–940 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  12. 12.

    Doan, P. E. et al. 57Fe ENDOR spectroscopy and ‘electron inventory’ analysis of the nitrogenase E4 intermediate suggest the metal-ion core of FeMo-cofactor cycles through only one redox couple. J. Am. Chem. Soc. 133, 17329–17340 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  13. 13.

    Bjornsson, R. et al. Identification of a spin-coupled Mo(III) in the nitrogenase iron–molybdenum cofactor. Chem. Sci. 5, 3096–3103 (2014).

    Article  CAS  Google Scholar 

  14. 14.

    Bjornsson, R., Neese, F., Schrock, R. R., Einsle, O. & DeBeer, S. The discovery of Mo(III) in FeMoco: reuniting enzyme and model chemistry. J. Biol. Inorg. Chem. 20, 447–460 (2015).

    Article  CAS  PubMed  Google Scholar 

  15. 15.

    Varley, J. B., Wang, Y., Chan, K., Studt, F. & Nørskov, J. K. Mechanistic insights into nitrogen fixation by nitrogenase enzymes. Phys. Chem. Chem. Phys. 17, 29541–29547 (2015).

    Article  CAS  PubMed  Google Scholar 

  16. 16.

    Spatzal, T., Perez, K. A., Einsle, O., Howard, J. B. & Rees, D. C. Ligand binding to the FeMo-cofactor: structures of CO-bound and reactivated nitrogenase. Science 345, 1620–1623 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  17. 17.

    Rao, L., Xu, X. & Adamo, C. Theoretical investigation on the role of the central carbon atom and close protein environment on the nitrogen reduction in Mo nitrogenase. ACS Catal. 6, 1567–1577 (2016).

    Article  CAS  Google Scholar 

  18. 18.

    Danyal, K. et al. Uncoupling nitrogenase: catalytic reduction of hydrazine to ammonia by a MoFe protein in the absence of Fe protein-ATP. J. Am. Chem. Soc. 132, 13197–13199 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. 19.

    Dance, I. Calculated details of a mechanism for conversion of N2 to NH3 at the FeMo cluster of nitrogenase. Chem. Commun., 165–166 (1997).

  20. 20.

    Dance, I. The controlled relay of multiple protons required at the active site of nitrogenase. Dalton Trans. 41, 7647–7659 (2012).

    Article  CAS  PubMed  Google Scholar 

  21. 21.

    Hoffman, B. M., Lukoyanov, D., Yang, Z.-Y., Dean, D. R. & Seefeldt, L. C. Mechanism of nitrogen fixation by nitrogenase: the next stage. Chem. Rev. 114, 4041–4062 (2014). A thorough review provides recently discovered details about the nitrogenase structures and functions, including definitive determination of the central carbon atom of the FeMo cofactor.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  22. 22.

    Durrant, M. C., Francis, A., Lowe, D. J., Newton, W. E. & Fisher, K. Evidence for a dynamic role for homocitrate during nitrogen fixation: the effect of substitution at the α-Lys426 position in MoFe-protein of Azotobacter vinelandii. Biochem. J. 397, 261–270 (2006).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  23. 23.

    Milton, R. D. et al. Nitrogenase bioelectrocatalysis: heterogeneous ammonia and hydrogen production by MoFe protein. Energy Environ. Sci. 9, 2550–2554 (2016).

    Article  CAS  Google Scholar 

  24. 24.

    Milton, R. D. et al. Bioelectrochemical Haber–Bosch process: an ammonia-producing H2/N2 fuel cell. Angew. Chem. Int. Ed. 56, 2680–2683 (2017).

    Article  CAS  Google Scholar 

  25. 25.

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

    Article  CAS  PubMed  Google Scholar 

  26. 26.

    Tanaka, H. et al. Unique behaviour of dinitrogen-bridged dimolybdenum complexes bearing pincer ligand towards catalytic formation of ammonia. Nat. Commun. 5, 3737 (2014).

    Article  PubMed  PubMed Central  Google Scholar 

  27. 27.

    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 

  28. 28.

    Wickramasinghe, L. A., Ogawa, T., Schrock, R. R. & Müller, P. Reduction of dinitrogen to ammonia catalyzed by molybdenum diamido complexes. J. Am. Chem. Soc. 139, 9132–9135 (2017).

    Article  CAS  PubMed  Google Scholar 

  29. 29.

    Eizawa, A. et al. Remarkable catalytic activity of dinitrogen-bridged dimolybdenum complexes bearing NHC-based PCP-pincer ligands toward nitrogen fixation. Nat. Commun. 8, 12 (2017).

    Article  CAS  Google Scholar 

  30. 30.

    Barney, B. M., Igarashi, R. Y., Dos Santos, P. C., Dean, D. R. & Seefeldt, L. C. Substrate interaction at an iron–sulfur face of the FeMo-cofactor during nitrogenase catalysis. J. Biol. Chem. 279, 53621–53624 (2004).

    Article  CAS  PubMed  Google Scholar 

  31. 31.

    Seefeldt, L. C., Hoffman, B. M. & Dean, D. R. Mechanism of Mo-dependent nitrogenase. Annu. Rev. Biochem. 78, 701–722 (2009).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  32. 32.

    Kim, C. H., Newton, W. E. & Dean, D. R. Role of the MoFe protein α-subunit histidine-195 residue in FeMo-cofactor binding and nitrogenase catalysis. Biochemistry 34, 2798–2808 (1995).

    Article  CAS  PubMed  Google Scholar 

  33. 33.

    Igarashi, R. Y. et al. Trapping H bound to the nitrogenase FeMo-cofactor active site during H2 evolution: characterization by ENDOR spectroscopy. J. Am. Chem. Soc. 127, 6231–6241 (2005).

    Article  CAS  PubMed  Google Scholar 

  34. 34.

    Dos Santos, P. C., Mayer, S. M., Barney, B. M., Seefeldt, L. C. & Dean, D. R. Alkyne substrate interaction within the nitrogenase MoFe protein. J. Inorg. Biochem. 101, 1642–1648 (2007).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  35. 35.

    Scott, D. J., May, H. D., Newton, W. E., Brigle, K. E. & Dean, D. R. Role for the nitrogenase MoFe protein α-subunit in FeMo-cofactor binding and catalysis. Nature 343, 188–190 (1990).

    Article  CAS  PubMed  Google Scholar 

  36. 36.

    Hendrich, M. P. et al. On the feasibility of N2 fixation via a single-site Fei/Feiv cycle: spectroscopic studies of Fei (N2) Fei, Feiv ≡N, and related species. Proc. Natl. Acad. Sci. USA 103, 17107–17112 (2006).

    Article  CAS  PubMed  Google Scholar 

  37. 37.

    Arnet, N. A. et al. Synthesis, characterization, and nitrogenase-relevant reactions of an iron sulfide complex with a bridging hydride. J. Am. Chem. Soc. 137, 13220–13223 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  38. 38.

    Coric, I. & Holland, P. L. Insight into the iron-molybdenum cofactor of nitrogenase from synthetic iron complexes with sulfur, carbon, and hydride ligands. J. Am. Chem. Soc. 138, 7200–7211 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  39. 39.

    Smith, J. M. et al. Studies of low-coordinate iron dinitrogen complexes. J. Am. Chem. Soc. 128, 756–769 (2006).

    Article  CAS  PubMed  Google Scholar 

  40. 40.

    Rodriguez, M. M., Bill, E., Brennessel, W. W. & Holland, P. L. N2 reduction and hydrogenation to ammonia by a molecular iron-potassium complex. Science 334, 780–783 (2011).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  41. 41.

    MacLeod, K. C., Vinyard, D. J. & Holland, P. L. A multi-iron system capable of rapid N2 formation and N2 cleavage. J. Am. Chem. Soc. 136, 10226–10229 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. 42.

    Grubel, K., Brennessel, W. W., Mercado, B. Q. & Holland, P. L. Alkali metal control over N–N cleavage in iron complexes. J. Am. Chem. Soc. 136, 16807–16816 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  43. 43.

    MacLeod, K. C. & Holland, P. L. Recent developments in the homogeneous reduction of dinitrogen by molybdenum and iron. Nat. Chem. 5, 559–565 (2013). A review of molecular catalyst advances provides recent developments and recommended next steps, including the need for redox active ligands, ligand-driven steric control, and structural correlations between molecular catalysts and the nitrogenase enzyme.

    Article  CAS  PubMed  Google Scholar 

  44. 44.

    Lee, Y., Mankad, N. P. & Peters, J. C. Triggering N2 uptake via redox-induced expulsion of coordinated NH3 and N2 silylation at trigonal bipyramidal iron. Nat. Chem. 2, 558–565 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  45. 45.

    Schrock, R. R. Catalytic reduction of dinitrogen to ammonia by molybdenum: theory versus experiment. Angew. Chem. Int. Ed. 47, 5512–5522 (2008).

    Article  CAS  Google Scholar 

  46. 46.

    Figg, T. M., Holland, P. L. & Cundari, T. R. Cooperativity between low-valent iron and potassium promoters in dinitrogen fixation. Inorg. Chem. 51, 7546–7550 (2012).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  47. 47.

    Chiang, K. P., Bellows, S. M., Brennessel, W. W. & Holland, P. L. Multimetallic cooperativity in activation of dinitrogen at iron–potassium sites. Chem. Sci. 5, 267–274 (2014).

    Article  CAS  Google Scholar 

  48. 48.

    Hinrichsen, S., Broda, H., Gradert, C., Söncksen, L. & Tuczek, F. Recent developments in synthetic nitrogen fixation. Inorg. Chem. 108, 17–47 (2012).

    CAS  Google Scholar 

  49. 49.

    Ritleng, V. et al. Molybdenum triamidoamine complexes that contain hexa-tertbutylterphenyl, hexamethylterphenyl, or p-bromohexaisopropylterphenyl substituents. An examination of some catalyst variations for the catalytic reduction of dinitrogen. J. Am. Chem. Soc. 126, 6150–6163 (2004).

    Article  CAS  PubMed  Google Scholar 

  50. 50.

    Thompson, N. B., Green, M. T. & Peters, J. C. Nitrogen fixation via a terminal Fe(iv) nitride. J. Am. Chem. Soc. 139, 15312–15315 (2017).

    Article  CAS  PubMed  Google Scholar 

  51. 51.

    Creutz, S. E. & Peters, J. C. Catalytic reduction of N2 to NH3 by an Fe–N2 complex featuring a C-atom anchor. J. Am. Chem. Soc. 136, 1105–1115 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  52. 52.

    Ung, G. & Peters, J. C. Low-temperature N2 binding to two-coordinate L2Fe0 enables reductive trapping of L2FeN2 and NH3 generation. Angew. Chem. Int. Ed. 54, 532–535 (2015).

    CAS  Google Scholar 

  53. 53.

    Higuchi, J. et al. Preparation and reactivity of iron complexes bearing anionic carbazole-based PNP-type pincer ligands toward catalytic nitrogen fixation. Dalton Trans. 47, 1117–1121 (2018).

    Article  CAS  PubMed  Google Scholar 

  54. 54.

    Kuriyama, S. et al. Direct transformation of molecular dinitrogen into ammonia catalyzed by cobalt dinitrogen complexes bearing anionic PNP pincer ligands. Angew. Chem. Int. Ed. 55, 14291–14295 (2016).

    Article  CAS  Google Scholar 

  55. 55.

    Del Castillo, T. J., Thompson, N. B., Suess, D. L. M., Ung, G. & Peters, J. C. Evaluating molecular cobalt complexes for the conversion of N2 to NH3. Inorg. Chem. 54, 9256–9262 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  56. 56.

    Arashiba, K. et al. Catalytic reduction of dinitrogen to ammonia by use of molybdenum-nitride complexes bearing a tridentate triphosphine as catalysts. J. Am. Chem. Soc. 137, 5666–5669 (2015).

    Article  CAS  PubMed  Google Scholar 

  57. 57.

    Coric, I., Mercado, B. Q., Bill, E., Vinyard, D. J. & Holland, P. L. Binding of dinitrogen to an iron–sulfur–carbon site. Nature 526, 96–99 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  58. 58.

    Ballmann, J., Munha, R. F. & Fryzuk, M. D. The hydride route to the preparation of dinitrogen complexes. Chem. Commun. 46, 1013–1025 (2010).

    Article  CAS  Google Scholar 

  59. 59.

    Yuki, M. et al. Iron-catalysed transformation of molecular dinitrogen into silylamine under ambient conditions. Nat. Commun. 3, 1254 (2012).

    Article  CAS  PubMed  Google Scholar 

  60. 60.

    MacKay, B. A., Johnson, S. A., Patrick, B. O. & Fryzuk, M. D. Functionalization and cleavage of coordinated dinitrogen via hydroboration using primary and secondary boranes. Can. J. Chem. 83, 315–323 (2005).

    Article  CAS  Google Scholar 

  61. 61.

    Hidai, M. & Mizobe, Y. Research inspired by the chemistry of nitrogenase — novel metal complexes and their reactivity toward dinitrogen, nitriles, and alkynes. Can. J. Chem. 83, 358–374 (2005).

    Article  CAS  Google Scholar 

  62. 62.

    Ohki, Y. & Fryzuk, M. D. Dinitrogen activation by group 4 metal complexes. Angew. Chem. Int. Ed. 46, 3180–3183 (2007).

    Article  CAS  Google Scholar 

  63. 63.

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

    Article  CAS  PubMed  Google Scholar 

  64. 64.

    McWilliams, S. F. & Holland, P. L. Dinitrogen binding and cleavage by multinuclear iron complexes. Acc. Chem. Res. 48, 2059–2065 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  65. 65.

    McWilliams, S. F. et al. Alkali metal variation and twisting of the FeNNFe core in bridging diiron dinitrogen complexes. Inorg. Chem. 55, 2960–2968 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  66. 66.

    Vojvodic, A. et al. Exploring the limits: a low-pressure, low-temperature Haber–Bosch process. Chem. Phys. Lett. 598, 108–112 (2014). A theoretical study that suggests that a low-pressure, low-temperature process is energetically possible for nitrogen reduction to ammonia.

    Article  CAS  Google Scholar 

  67. 67.

    Spencer, M. S. On the rate-determining step and the role of potassium in the catalytic synthesis of ammonia. Catal. Lett. 13, 45–53 (1992).

    Article  CAS  Google Scholar 

  68. 68.

    Strongin, D. R., Carrazza, J., Bare, S. R. & Somorjai, G. A. The importance of C7 sites and surface roughness in the ammonia synthesis reaction over iron. J. Catal. 103, 213–215 (1987).

    Article  CAS  Google Scholar 

  69. 69.

    Ertl, G., Prigge, D., Schloegl, R. & Weiss, M. Surface characterization of ammonia synthesis catalysts. J. Catal. 79, 359–377 (1983).

    Article  CAS  Google Scholar 

  70. 70.

    Ozaki, A., Taylor, H. & Boudrart, M. Kinetics and mechanism of the ammonia synthesis. Proc. R. Soc. Lond. Ser. A 258, 47–62 (1960).

    Article  CAS  Google Scholar 

  71. 71.

    Aika, K. et al. Support and promoter effect of ruthenium catalyst: I. Characterization of alkali-promoted ruthenium/alumina catalysts for ammonia synthesis. J. Catal. 92, 296–304 (1985).

    Article  CAS  Google Scholar 

  72. 72.

    Rosowski, F. et al. Ruthenium catalysts for ammonia synthesis at high pressures: preparation, characterization, and power-law kinetics. Appl. Catal. A 151, 443–460 (1997).

    Article  CAS  Google Scholar 

  73. 73.

    Bossi, A., Garbassi, F., Petrini, G. & Zanderighi, L. Support effects on the catalytic activity and selectivity of ruthenium in CO and N2 activation. J. Chem. Soc. Faraday Trans. 1 78, 1029–1038 (1982).

    Article  CAS  Google Scholar 

  74. 74.

    Fastrup, B. On the interaction of N2 and H2 with Ru catalyst surfaces. Catal. Lett. 48, 111–119 (1997).

    Article  CAS  Google Scholar 

  75. 75.

    Szmigiel, D. et al. The kinetics of ammonia synthesis over ruthenium-based catalysts: the role of barium and cesium. J. Catal. 205, 205–212 (2002).

    Article  CAS  Google Scholar 

  76. 76.

    Brown, D. E., Edmonds, T., Joyner, R. W., McCarroll, J. J. & Tennison, S. R. The genesis and development of the commercial BP doubly promoted catalyst for ammonia synthesis. Catal. Lett. 144, 545–552 (2014). The only other commercialized catalyst for the Haber–Bosch process is based on a highly active ruthenium–alkali metal–carbon catalyst, with an activity that is 20 times greater than the iron-based commercial Haber–Bosch catalyst.

    Article  CAS  Google Scholar 

  77. 77.

    Liu, H. Ammonia synthesis catalyst 100 years: practice, enlightenment and challenge. Chin. J. Catal. 35, 1619–1640 (2014).

    Article  CAS  Google Scholar 

  78. 78.

    Hrbek, J. Coadsorption of oxygen and hydrogen on ruthenium (001): blocking and electronic effects of preadsorbed oxygen. J. Phys. Chem. 90, 6217–6222 (1986).

    Article  CAS  Google Scholar 

  79. 79.

    Jacobsen, C. J. Boron nitride: a novel support for ruthenium-based ammonia synthesis catalysts. J. Catal. 200, 1–3 (2001).

    Article  CAS  Google Scholar 

  80. 80.

    Akay, G. & Zhang, K. Process intensification in ammonia synthesis using novel coassembled supported micro-porous catalysts promoted by nonthermal plasma. Ind. Eng. Chem. Res. 56, 457–468 (2016).

    Article  CAS  Google Scholar 

  81. 81.

    Yang, X. L. et al. Low temperature ruthenium catalyst for ammonia synthesis supported on BaCeO3 nanocrystals. Catal. Commun. 11, 867–870 (2010).

    Article  CAS  Google Scholar 

  82. 82.

    Niwa, Y. & Aika, K. I. The effect of lanthanide oxides as a support for ruthenium catalysts in ammonia synthesis. J. Catal. 162, 138–142 (1996).

    Article  CAS  Google Scholar 

  83. 83.

    Saito, M., Itoh, M., Iwamoto, J., Li, C. Y. & Machida, K. I. Synergistic effect of MgO and CeO2 as a support for ruthenium catalysts in ammonia synthesis. Catal. Lett. 106, 107–110 (2006).

    Article  CAS  Google Scholar 

  84. 84.

    Liang, C., Li, Z., Qiu, J. & Li, C. Graphitic nanofilaments as novel support of Ru–Ba catalysts for ammonia synthesis. J. Catal. 211, 278–282 (2002).

    Article  CAS  Google Scholar 

  85. 85.

    Fishel, C. T., Davis, R. J. & Garces, J. M. Ammonia synthesis catalyzed by ruthenium supported on basic zeolites. J. Catal. 163, 148–157 (1996).

    Article  CAS  Google Scholar 

  86. 86.

    Hara, M., Kitano, M. & Hosono, H. Ru-loaded C12A7:e electride as a catalyst for ammonia synthesis. ACS Catal. 7, 2313–2324 (2017). New results on an electride-based catalyst suggest that an electron-donating character accelerates N 2 cleavage and opens a potential pathway for understanding how to better design heterogeneous catalysts for nitrogen fixation.

    Article  CAS  Google Scholar 

  87. 87.

    Skulason, E. et al. A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction. Phys. Chem. Chem. Phys. 14, 1235–1245 (2012). One of the first extensive theoretical efforts to evaluate transition metals for electrochemical nitrogen reduction predicts optimal metal surfaces and demonstrates most metal surfaces will be dominated by *H rather than *N species on the surface.

    Article  CAS  PubMed  Google Scholar 

  88. 88.

    Wang, S. et al. Universal transition state scaling relations for (de)hydrogenation over transition metals. Phys. Chem. Chem. Phys. 13, 20760–20765 (2011).

    Article  CAS  PubMed  Google Scholar 

  89. 89.

    Köleli, F., Röpke, D., Aydin, R. & Röpke, T. Investigation of N2-fixation on polyaniline electrodes in methanol by electrochemical impedance spectroscopy. J. Appl. Electrochem. 41, 405–413 (2010).

    Article  CAS  Google Scholar 

  90. 90.

    Pappenfus, T. M., Lee, K. M., Thoma, L. M. & Dukart, C. R. Wind to ammonia: electrochemical processes in room temperature ionic liquids. ECS Trans. 16, 89–93 (2009).

    Article  CAS  Google Scholar 

  91. 91.

    Shi, M.-M. et al. Au sub-nanoclusters on TiO2 toward highly efficient and selective electrocatalyst for N2 conversion to NH3 at ambient conditions. Adv. Mater. 29, 1606550 (2017). One of the highest Faradaic efficiencies reported to date for ambient temperature and pressure electrochemical nitrogen reduction suggests that this reported catalyst structure and composition may be promising for greater N 2 selectivity.

    Article  CAS  Google Scholar 

  92. 92.

    Murakami, T., Nishikiori, T., Nohira, T. & Ito, Y. Electrolytic synthesis of ammonia in molten salts under atmospheric pressure. J. Am. Chem. Soc. 125, 334–335 (2003).

    Article  CAS  PubMed  Google Scholar 

  93. 93.

    Nash, J. et al. Electrochemical nitrogen reduction reaction on noble metal catalysts in proton and hydroxide exchange membrane electrolyzers. J. Electrochem. Soc. 164, F1712–F1716 (2017).

    Article  CAS  Google Scholar 

  94. 94.

    Chen, S. et al. Room-temperature electrocatalytic synthesis of NH3 from H2O and N2 in a gas–liquid–solid three-phase reactor. ACS Sustain. Chem. Eng. 5, 7393–7400 (2017). A nanoparticulate iron oxide catalyst on a carbon nanotube support is tested in a gas-phase electrochemical cell, and the data show that electrolyte and nanoparticle loading can impact ammonia production and are important design considerations.

  95. 95.

    Kong, J. et al. Electrochemical synthesis of NH3 at low temperature and atmospheric pressure using a γ-Fe2O3 catalyst. ACS Sustain. Chem. Eng. 5, 10986–10995 (2017). Experimental results are presented for an iron oxide nanoparticle catalyst in both aqueous and gas-phase electrochemical test cells, and results of lower Faradaic efficiency and ammonia production rate in a membrane electrode assembly demonstrate the need for optimized membrane electrode assembly engineering.

    Article  CAS  Google Scholar 

  96. 96.

    Igarashi, R. Y. et al. Localization of a catalytic intermediate bound to the FeMo-cofactor of nitrogenase. J. Biol. Chem. 279, 34770–34775 (2004).

    Article  CAS  PubMed  Google Scholar 

  97. 97.

    Fisher, K., Dilworth, M. J. & Newton, W. E. Differential effects on N2 binding and reduction, HD formation, and azide reduction with α-195His-and α-191Gln-substituted MoFe proteins of Azotobacter vinelandii nitrogenase. Biochemistry 39, 15570–15577 (2000).

    Article  CAS  PubMed  Google Scholar 

  98. 98.

    Del Castillo, T. J., Thompson, N. B. & Peters, J. C. A synthetic single-site Fe nitrogenase: high turnover, freeze-quench 57Fe Mössbauer data, and a hydride resting state. J. Am. Chem. Soc. 138, 5341–5350 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  99. 99.

    Buscagan, T. M., Oyala, P. H. & Peters, J. C. N2‐to‐NH3 conversion by a triphos–iron catalyst and enhanced turnover under photolysis. Angew. Chem. Int. Ed. 56, 6921–6926 (2017).

    Article  CAS  Google Scholar 

  100. 100.

    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  PubMed  PubMed Central  Google Scholar 

  101. 101.

    Kuriyama, S. et al. Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand. Nat. Commun. 7, 12181 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  102. 102.

    Sekiguchi, Y. et al. Synthesis and reactivity of iron-dinitrogen complexes bearing anionic methyl- and phenyl-substituted pyrrole-based PNP-type pincer ligands toward catalytic nitrogen fixation. Chem. Commun. 53, 12040–12043 (2017).

    Article  CAS  Google Scholar 

  103. 103.

    Hill, P. J., Doyle, L. R., Crawford, A. D., Myers, W. K. & Ashley, A. E. Selective catalytic reduction of N2 to N2H4 by a simple Fe complex. J. Am. Chem. Soc. 138, 13521–13524 (2016).

    Article  CAS  PubMed  Google Scholar 

  104. 104.

    Kuriyama, S. et al. Catalytic formation of ammonia from molecular dinitrogen by use of dinitrogen-bridged dimolybdenum–dinitrogen complexes bearing PNP-pincer ligands: remarkable effect of substituent at PNP-pincer ligand. J. Am. Chem. Soc. 136, 9719–9731 (2014).

    Article  CAS  PubMed  Google Scholar 

  105. 105.

    Kuriyama, S. et al. Nitrogen fixation catalyzed by ferrocene-substituted dinitrogen-bridged dimolybdenum–dinitrogen complexes: unique behavior of ferrocene moiety as redox active site. Chem. Sci. 6, 3940–3951 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  106. 106.

    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  PubMed  Google Scholar 

  107. 107.

    Medford, A. J. et al. From the Sabatier principle to a predictive theory of transition-metal heterogeneous catalysis. J. Catal. 328, 36–42 (2015).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

S.L.F. and L.F.G. gratefully acknowledge support from the US Department of Agriculture Small Business Innovation Research Program, under award # EC-015996-02. S.I.P.B., R.D., S.M., M.J.J., J.N.R. and L.F.G. gratefully acknowledge support from the US Department of Energy, Office of Science, Basic Energy Sciences, Catalysis Science Program, under award # DE-SC0016529. R.D.M. and S.D.M. thank the Army Research Office Multidisciplinary University Research Initiative (MURI) (W911NF-14-1-0263) for funding.

Author information

Affiliations

Authors

Corresponding authors

Correspondence to Shelley D. Minteer or Michael J. Janik or Julie N. Renner or Lauren F. Greenlee.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Foster, S.L., Bakovic, S.I.P., Duda, R.D. et al. Catalysts for nitrogen reduction to ammonia. Nat Catal 1, 490–500 (2018). https://doi.org/10.1038/s41929-018-0092-7

Download citation

Further reading

Search

Nature Briefing

Sign up for the Nature Briefing newsletter for a daily update on COVID-19 science.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing