Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements

Subjects

An Author Correction to this article was published on 26 September 2019

This article has been updated

Abstract

The electrochemical synthesis of ammonia from nitrogen under mild conditions using renewable electricity is an attractive alternative1,2,3,4 to the energy-intensive Haber–Bosch process, which dominates industrial ammonia production. However, there are considerable scientific and technical challenges5,6 facing the electrochemical alternative, and most experimental studies reported so far have achieved only low selectivities and conversions. The amount of ammonia produced is usually so small that it cannot be firmly attributed to electrochemical nitrogen fixation7,8,9 rather than contamination from ammonia that is either present in air, human breath or ion-conducting membranes9, or generated from labile nitrogen-containing compounds (for example, nitrates, amines, nitrites and nitrogen oxides) that are typically present in the nitrogen gas stream10, in the atmosphere or even in the catalyst itself. Although these sources of experimental artefacts are beginning to be recognized and managed11,12, concerted efforts to develop effective electrochemical nitrogen reduction processes would benefit from benchmarking protocols for the reaction and from a standardized set of control experiments designed to identify and then eliminate or quantify the sources of contamination. Here we propose a rigorous procedure using 15N2 that enables us to reliably detect and quantify the electrochemical reduction of nitrogen to ammonia. We demonstrate experimentally the importance of various sources of contamination, and show how to remove labile nitrogen-containing compounds from the nitrogen gas as well as how to perform quantitative isotope measurements with cycling of 15N2 gas to reduce both contamination and the cost of isotope measurements. Following this protocol, we find that no ammonia is produced when using the most promising pure-metal catalysts for this reaction in aqueous media, and we successfully confirm and quantify ammonia synthesis using lithium electrodeposition in tetrahydrofuran13. The use of this rigorous protocol should help to prevent false positives from appearing in the literature, thus enabling the field to focus on viable pathways towards the practical electrochemical reduction of nitrogen to ammonia.

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: Potential range for chronoamperometric measurements of pure-metal catalysts and the detected amounts of ammonia in each measurement.
Fig. 2: An overview of literature data on the electrochemical synthesis of ammonia.
Fig. 3: Suggested protocol for the benchmarking of electrochemical nitrogen reduction.
Fig. 4: Ammonia synthesized at −3.1 V and more negative potentials vs SHE.

Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Change history

  • 26 September 2019

    An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

References

  1. 1.

    Shipman, M. A. & Symes, M. D. Recent progress towards the electrosynthesis of ammonia from sustainable resources. Catal. Today 286, 57–68 (2017).

    CAS  Article  Google Scholar 

  2. 2.

    Jewess, M. & Crabtree, R. H. Electrocatalytic nitrogen fixation for distributed fertilizer production? ACS Sustainable Chem. Eng. 4, 5855–5858 (2016).

    CAS  Article  Google Scholar 

  3. 3.

    Nørskov, J. et al. Sustainable Ammonia Synthesis – Exploring the Scientific Challenges Associated with Discovering Alternative, Sustainable Processes for Ammonia Production. https://doi.org/10.2172/1283146 (United States Department of Energy, 2016).

  4. 4.

    Ye, L., Nayak-Luke, R., Bañares-Alcántara, R. & Tsang, E. Reaction: “green” ammonia production. Chem 3, 712–714 (2017).

    CAS  Article  Google Scholar 

  5. 5.

    Singh, A. R. et al. Electrochemical ammonia synthesis—the selectivity challenge. ACS Catal. 7, 706–709 (2017).

    CAS  Article  Google Scholar 

  6. 6.

    Skúlason, E. et al. A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction. Phys. Chem. Chem. Phys. 14, 1235–1245 (2012).

    Article  Google Scholar 

  7. 7.

    Sclafani, A., Augugliaro, V. & Schiavello, M. Dinitrogen electrochemical reduction to ammonia over iron cathode in aqueous medium. J. Electrochem. Soc. 130, 734–736 (1983).

    CAS  Article  Google Scholar 

  8. 8.

    Zhang, Z., Zhong, Z. & Liu, R. Cathode catalysis performance of SmBaCuMO5+δ (M=Fe, Co, Ni) in ammonia synthesis. J. Rare Earths 28, 556–559 (2010).

    CAS  Article  Google Scholar 

  9. 9.

    Lan, R., Irvine, J. T. S. & Tao, S. Synthesis of ammonia directly from air and water at ambient temperature and pressure. Sci. Rep. 3, 1145 (2013).

    ADS  Article  Google Scholar 

  10. 10.

    Dabundo, R. et al. The contamination of commercial 15N2 gas stocks with 15N-labeled nitrate and ammonium and consequences for nitrogen fixation measurements. PLoS One 9, e110335 (2014).

    ADS  Article  Google Scholar 

  11. 11.

    Greenlee, L. F., Renner, J. N. & Foster, S. L. The use of controls for consistent and accurate measurements of electrocatalytic ammonia synthesis from dinitrogen. ACS Catal. 8, 7820–7827 (2018).

    CAS  Article  Google Scholar 

  12. 12.

    Chen, G.-F. et al. Advances in electrocatalytic N2 reduction—strategies to tackle the selectivity challenge. Small Methods 1800337 (2018).

  13. 13.

    Tsuneto, A., Kudo, A. & Sakata, T. Efficient electrochemical reduction of N2 to NH3 catalyzed by lithium. Chem. Lett. 22, 851–854 (1993).

    Article  Google Scholar 

  14. 14.

    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).

    CAS  Article  Google Scholar 

  15. 15.

    Hager, T. The Alchemy of Air (Harmony Books, 2008).

  16. 16.

    Boucher, D. L., Davies, J. A., Edwards, J. G. & Mennad, A. An investigation of the putative photosynthesis of ammonia on iron-doped titania and other metal oxides. J. Photochem. Photobiol. Chem. 88, 53–64 (1995).

    CAS  Article  Google Scholar 

  17. 17.

    Shipman, M. A. & Symes, M. D. A re-evaluation of Sn(II) phthalocyanine as a catalyst for the electrosynthesis of ammonia. Electrochim. Acta 258, 618–622 (2017).

    CAS  Article  Google Scholar 

  18. 18.

    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).

    Article  Google Scholar 

  19. 19.

    Schlesinger, W. & Hartley, A. A global budget for atmospheric NH3. Biogeochemistry 15, 191–211 (1992).

    CAS  Article  Google Scholar 

  20. 20.

    Turner, C., Španěl, P. & Smith, D. A longitudinal study of ammonia, acetone and propanol in the exhaled breath of 30 subjects using selected ion flow tube mass spectrometry, SIFT-MS. Physiol. Meas. 27, 321–337 (2006).

    Article  Google Scholar 

  21. 21.

    Song, Y. et al. A physical catalyst for the electrolysis of nitrogen to ammonia. Sci. Adv. 4, e1700336 (2018).

    Article  Google Scholar 

  22. 22.

    McEnaney, J. M. et al. Ammonia synthesis from N2 and H2O using a lithium cycling electrification strategy at atmospheric pressure. Energy Environ. Sci. 10, 1621–1630 (2017).

    CAS  Article  Google Scholar 

  23. 23.

    Wang, H. et al. Ambient electrosynthesis of ammonia: electrode porosity and composition engineering. Angew. Chem. Int. Ed. 57, 12360–12364 (2018).

    CAS  Article  Google Scholar 

  24. 24.

    Tsuneto, A., Kudo, A. & Sakata, T. Lithium-mediated electrochemical reduction of high pressure N2 to NH3. J. Electroanal. Chem. (Lausanne) 367, 183–188 (1994).

    CAS  Article  Google Scholar 

  25. 25.

    Bao, D. et al. Electrochemical reduction of N2 under ambient conditions for artificial N2 fixation and renewable energy storage using N2 /NH3 cycle. Adv. Mater. 29, 1604799 (2017).

    Article  Google Scholar 

  26. 26.

    Chen, G.-F. et al. Ammonia electrosynthesis with high selectivity under ambient conditions via a Li+ incorporation strategy. J. Am. Chem. Soc. 139, 9771–9774 (2017).

    CAS  Article  Google Scholar 

  27. 27.

    Kong, J. et al. Electrochemical synthesis of NH3 at low temperature and atmospheric pressure using a γ-Fe2O3 catalyst. ACS Sustainable Chem. Eng. 5, 10986–10995 (2017).

    CAS  Article  Google Scholar 

  28. 28.

    Yao, Y., Zhu, S., Wang, H., Li, H. & Shao, M. A spectroscopic study on the nitrogen electrochemical reduction reaction on gold and platinum surfaces. J. Am. Chem. Soc. 140, 1496–1501 (2018).

    CAS  Article  Google Scholar 

  29. 29.

    Kim, K., Yoo, C.-Y., Kim, J.-N., Yoon, H. C. & Han, J.-I. Electrochemical synthesis of ammonia from water and nitrogen in ethylenediamine under ambient temperature and pressure. J. Electrochem. Soc. 163, F1523–F1526 (2016).

    CAS  Article  Google Scholar 

  30. 30.

    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).

    CAS  Article  Google Scholar 

  31. 31.

    Čoćli, V. et al. Experimental aspects in benchmarking of the electrocatalytic activity. ChemElectroChem 2, 143–149 (2015).

    Article  Google Scholar 

  32. 32.

    Gritzner, G. Standard electrode potentials of M+|M couples in non-aqueous solvents (molecular liquids). J. Mol. Liq. 156, 103–108 (2010).

    CAS  Article  Google Scholar 

  33. 33.

    Brass, M., Pritzel, T., Schulte, E., and Keller, J. U. Measurements of vapor–liquid equilibria in the systems NH3–H2O–NaOH and NH3–H2O–KOH at temperatures of 303 and 318 K and pressures 0.1 MPa<p<1.3 MPa. Int. J. Thermophys. 21, 883–898 (2000).

    CAS  Article  Google Scholar 

  34. 34.

    Ma, L. et al. In situ DRIFTS and temperature-programmed technology study on NH3-SCR of NOx over Cu-SSZ-13 and Cu-SAPO-34 catalysts. Appl. Catal. B 156–157, 428–437 (2014).

    Article  Google Scholar 

  35. 35.

    Ma, L. et al. Characterization of commercial Cu-SSZ-13 and Cu-SAPO-34 catalysts with hydrothermal treatment for NH3-SCR of NOx in diesel exhaust. Chem. Eng. J. 225, 323–330 (2013).

    CAS  Article  Google Scholar 

  36. 36.

    Cook, R. L. & Sammells, A. F. Ambient temperature gas phase electrochemical nitrogen reduction to ammonia at ruthenium/solid polymer electrolyte interface. Catal. Lett. 1, 345–349 (1988).

    CAS  Article  Google Scholar 

  37. 37.

    Furuya, N. & Yoshiba, H. Electroreduction of nitrogen to ammonia on gas-diffusion electrodes modified by Fe-phthalocyanine. J. Electroanal. Chem. Interfacial Electrochem. 263, 171–174 (1989).

    CAS  Article  Google Scholar 

  38. 38.

    Furuya, N. & Matsui, K. Electroreduction of carbon dioxide on gas-diffusion electrodes modified by metal phthalocyanines. J. Electroanal. Chem. Interfacial Electrochem. 271, 181–191 (1989).

    CAS  Article  Google Scholar 

  39. 39.

    Kordali, V., Kyriacou, G. & Lambrou, C. Electrochemical synthesis of ammonia at atmospheric pressure and low temperature in a solid polymer electrolyte cell. Chem. Commun. 1673–1674 (2000).

  40. 40.

    Pospíšil, L. et al. Electrochemical conversion of dinitrogen to ammonia mediated by a complex of fullerene C60 and γ-cyclodextrin. Chem. Commun. 2270–2272 (2007).

  41. 41.

    Xu, G., Liu, R. & Wang, J. Electrochemical synthesis of ammonia using a cell with a Nafion membrane and SmFe0.7Cu0.3−xNixO3 (x = 0−0.3) cathode at atmospheric pressure and lower temperature. Sci. China Ser. B 52, 1171–1175 (2009).

    ADS  CAS  Article  Google Scholar 

  42. 42.

    Kugler, K., Luhn, M., Schramm, J. A., Rahimi, K. & Wessling, M. Galvanic deposition of Rh and Ru on randomly structured Ti felts for the electrochemical NH3 synthesis. Phys. Chem. Chem. Phys. 17, 3768–3782 (2015).

    CAS  Article  Google Scholar 

  43. 43.

    Li, S.-J. et al. Amorphizing of Au nanoparticles by CeOx –RGO hybrid support towards highly efficient electrocatalyst for N2 reduction under ambient conditions. Adv. Mater. 29, 1700001 (2017).

    Article  Google Scholar 

  44. 44.

    Chen, S. et al. Electrocatalytic synthesis of ammonia at room temperature and atmospheric pressure from water and nitrogen on a carbon-nanotube-based electrocatalyst. Angew. Chem. Int. Ed. 56, 2699–2703 (2017).

    CAS  Article  Google Scholar 

  45. 45.

    Marnellos, G. & Stoukides, M. Ammonia synthesis at atmospheric pressure. Science 282, 98–100 (1998).

    ADS  CAS  Article  Google Scholar 

  46. 46.

    Murakami, T., Nohira, T., Goto, T., Ogata, Y. H. & Ito, Y. Electrolytic ammonia synthesis from water and nitrogen gas in molten salt under atmospheric pressure. Electrochim. Acta 50, 5423–5426 (2005).

    CAS  Article  Google Scholar 

  47. 47.

    Wang, B. H., De Wang, J., Liu, R., Xie, Y. H. & Li, Z. J. Synthesis of ammonia from natural gas at atmospheric pressure with doped ceria–Ca3(PO4)2–K3PO4 composite electrolyte and its proton conductivity at intermediate temperature. J. Solid State Electrochem. 11, 27–31 (2006).

    CAS  Article  Google Scholar 

  48. 48.

    Köleli, F. & Kayan, D. B. Low overpotential reduction of dinitrogen to ammonia in aqueous media. J. Electroanal. Chem.  638, 119–122 (2010).

    Article  Google Scholar 

  49. 49.

    Amar, I. A. et al. Electrochemical synthesis of ammonia based on doped-ceria-carbonate composite electrolyte and perovskite cathode. Solid State Ionics 201, 94–100 (2011).

    CAS  Article  Google Scholar 

  50. 50.

    Amar, I. A., Lan, R., Petit, C. T. G., Arrighi, V. & Tao, S. Electrochemical synthesis of ammonia based on a carbonate-oxide composite electrolyte. Solid State Ionics 182, 133–138 (2011).

    CAS  Article  Google Scholar 

  51. 51.

    Amar, I. A. et al. Electrochemical synthesis of ammonia from N2 and H2O based on (Li,Na,K)2CO3–Ce0.8Gd0.18Ca0.02O2−δ composite electrolyte and CoFe2O4 cathode. Int. J. Hydrogen Energy 39, 4322–4330 (2014).

    CAS  Article  Google Scholar 

  52. 52.

    Licht, S. et al. Ammonia synthesis by N2 and steam electrolysis in molten hydroxide suspensions of nanoscale Fe2O3. Science 345, 637–640 (2014).

    ADS  CAS  Article  Google Scholar 

  53. 53.

    Lan, R., Alkhazmi, K. A., Amar, I. A. & Tao, S. Synthesis of ammonia directly from wet air at intermediate temperature. Appl. Catal. B 152–153, 212–217 (2014).

    Article  Google Scholar 

  54. 54.

    Amar, I. A., Lan, R. & Tao, S. Electrochemical synthesis of ammonia directly from wet N2 using La0.6Sr0.4Fe0.8Cu0.2O3−δ-Ce0.8Gd0.18Ca0.02O2−δ composite catalyst. J. Electrochem. Soc. 161, H350–H354 (2014).

    CAS  Article  Google Scholar 

  55. 55.

    Amar, I. A., Lan, R., Petit, C. T. G. & Tao, S. Electrochemical synthesis of ammonia based on Co3Mo3N catalyst and LiAlO2–(Li,Na,K)2CO3 composite electrolyte. Electrocatalysis 6, 286–294 (2015).

    CAS  Article  Google Scholar 

  56. 56.

    Cui, B. et al. Electrochemical synthesis of ammonia directly from N2 and water over iron-based catalysts supported on activated carbon. Green Chem. 19, 298–304 (2017).

    CAS  Article  Google Scholar 

  57. 57.

    Van Tamelen, E. E. & Akermark, B. Electrolytic reduction of molecular nitrogen. J. Am. Chem. Soc. 90, 4492–4493 (1968).

    Article  Google Scholar 

  58. 58.

    Becker, J. Y., Avraham (Tsarfaty), S. & Posin, B. Nitrogen fixation: Electrochemical reduction of titanium compounds in the presence of catechol and N2 in MeOH or THF. J. Electroanal. Chem. Interfacial Electrochem. 230, 143–153 (1987).

    CAS  Article  Google Scholar 

  59. 59.

    Köleli, F. & Röpke, T. Electrochemical hydrogenation of dinitrogen to ammonia on a polyaniline electrode. Appl. Catal. B 62, 306–310 (2006).

    Article  Google Scholar 

  60. 60.

    Kim, K. et al. Communication—electrochemical reduction of nitrogen to ammonia in 2-propanol under ambient temperature and pressure. J. Electrochem. Soc. 163, F610–F612 (2016).

    CAS  Article  Google Scholar 

  61. 61.

    Zhu, D., Zhang, L., Ruther, R. E. & Hamers, R. J. Photo-illuminated diamond as a solid-state source of solvated electrons in water for nitrogen reduction. Nat. Mater. 12, 836–841 (2013).

    ADS  CAS  Article  Google Scholar 

  62. 62.

    Dong, G., Ho, W. & Wang, C. Selective photocatalytic N2 fixation dependent on g-C3N4 induced by nitrogen vacancies. J. Mater. Chem. A 3, 23435–23441 (2015).

    CAS  Article  Google Scholar 

  63. 63.

    Banerjee, A. et al. Photochemical nitrogen conversion to ammonia in ambient conditions with FeMoS-chalcogels. J. Am. Chem. Soc. 137, 2030–2034 (2015).

    CAS  Article  Google Scholar 

  64. 64.

    Li, J., Li, H., Zhan, G. & Zhang, L. Solar water splitting and nitrogen fixation with layered bismuth oxyhalides. Acc. Chem. Res. 50, 112–121 (2017).

    CAS  Article  Google Scholar 

  65. 65.

    Liu, J. et al. Nitrogenase-mimic iron-containing chalcogels for photochemical reduction of dinitrogen to ammonia. Proc. Natl Acad. Sci. USA 113, 5530–5535 (2016).

    ADS  CAS  Article  Google Scholar 

  66. 66.

    Hu, S. et al. Effect of Cu(I)–N active sites on the N2 photofixation ability over flowerlike copper-doped g-C3N4 prepared via a novel molten salt-assisted microwave process: the experimental and density functional theory simulation analysis. ACS Sustain. Chem. Eng. 5, 6863–6872 (2017).

    CAS  Article  Google Scholar 

  67. 67.

    Hirakawa, H., Hashimoto, M., Shiraishi, Y. & Hirai, T. Photocatalytic conversion of nitrogen to ammonia with water on surface oxygen vacancies of titanium dioxide. J. Am. Chem. Soc. 139, 10929–10936 (2017).

    CAS  Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the Villum Foundation V-SUSTAIN grant 9455 to the Villum Center for the Science of Sustainable Fuels and Chemicals. 400 MHz and 800 MHz NMR spectra were recorded on the spectrometers of the NMR Center at the Technical University of Denmark supported by the Villum Foundation. We acknowledge the contribution of Albert Kravos in setting up the analytical methods to detect ammonia.

Reviewer information

Nature thanks Lauren Greenlee, Mark Symes and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author information

Affiliations

Authors

Contributions

S.Z.A., V.C., S.Y., J.K., S.M., P.C.K.V., I.E.L.S. and I.C. conceived the idea for the protocol and experimental design. S.Z.A., V.C., S.M. and S.Y. performed the experiments; V.C. performed potential scale determination and Ohmic-drop correction; S.Y. performed isotope measurements; K.E.-R. performed NMR measurements and wrote the NMR section; J.A.S., A.C.N. and J.M.M. performed Fourier transform infrared spectroscopy and wrote the corresponding section; J.K., P.C.K.V., I.E.L.S. and I.C. supervised the work; S.Z.A., V.C. and S.Y. drafted the manuscript; and all authors contributed to the editing of the manuscript.

Corresponding author

Correspondence to Ib Chorkendorff.

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.

Extended data figures and tables

Extended Data Fig. 1 Concentrations of ammonia produced by various possible contamination sources.

All measurements were performed three times; the top of the bars show the mean, the errors show the standard deviation. The following were tested for contamination: a, new and treated Nafion membranes; b, new Celgard membrane; c, 2 ml of 0.1 M solutions or MilliQ H2O left open overnight; d, 2 ml 0.1 M KOH, into which one person had breathed 3 l of air through a glass straw.

Extended Data Fig. 2 NMR data.

Spectra were acquired using a Bruker AVANCE III HD 800 MHz spectrometer equipped with a 5 mm TCI CryoProbe. Solutions contain equal concentrations of 14NH4+ and 15NH4+ from NH4Cl. a, Spectrum of a solution of 600 µl 0.1 M KOH, acidified with 0.5 M H2SO4 to a pH of 1. CH3OH (200 μM) was added as an internal reference. b, Integrated peak areas from a for both 14NH4 and 15NH4. c, Spectrum of a solution of 500 µl 0.1 M LiClO4 in THF and ethanol with a ratio of 99:1, respectively, with 2 µl 4 M HCl and 50 µl THF-d8. d, Integrated peak areas from c for both 14NH4 and 15NH4. The variation of chemical shift of the NMR peaks is due to slight differences in the pH, volume, and/or temperature of the samples. e, Magnified view of the samples in a that contain the lowest concentrations of 14NH4+ and 15NH4+. f, Spectra of samples with the same concentrations as those in a, using a Bruker AVANCE III HD 400 MHz spectrometer equipped with a 5 mm Prodigy probe.

Extended Data Fig. 3 Gas phase Fourier-transform infrared spectra of labelled and unlabelled ammonia.

Spectra were acquired on a Nicolet iS50 spectrometer fitted with a 2-m path length gas cell heated to 135 °C. The total volume of the vaporized sample was 100 μl. The ammonia concentration was 1,000 p.p.m. in H2O before vaporization.

Extended Data Fig. 4 The set-up for gas (15N2, 14N2, Ar or 10% H2 in Ar) circulation through the electrochemical cell.

a, Schematic of the set-up. b, Photograph of the set-up with the components labelled. The pump that circulates the gas through the set-up is situated behind the metal panel, and its position is outlined by the white dashed rectangle.

Extended Data Fig. 5 1H NMR spectra of 0.1 M KOH samples after purging the solution with 15N2 gas.

Spectra were acquired using a Bruker AVANCE III HD 800 MHz spectrometer equipped with a 5-mm TCI CryoProbe. No 15NH4+ was seen in the measurements.

Extended Data Fig. 6 Concentration of ammonia, nitrite and hydrazine in the gas supply.

ae, Three sequentially repeated measurements of the concentrations of: ammonia (using the indophenol method) without cleaning the gas stream (a); ammonia (using the indophenol method) with the described cleaning procedure (b); nitrite concentration without cleaning the gas stream (c); nitrite concentration with the described cleaning procedure (d); and hydrazine without cleaning the gas stream (e).

Extended Data Table 1 Literature data on the electrochemical reduction of N2 to ammonia in near-ambient conditions
Extended Data Table 2 Electrochemical reduction of N2 to ammonia at high temperature or pressure
Extended Data Table 3 Electrochemical reduction of N2 to ammonia in non-aqueous electrolytes
Extended Data Table 4 Photochemical reduction of N2 to ammonia in non-aqueous electrolytes

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Andersen, S.Z., Čolić, V., Yang, S. et al. A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature 570, 504–508 (2019). https://doi.org/10.1038/s41586-019-1260-x

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

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