Electrochemical reduction of nitrogen to ammonia by polyoxometalates.

Abstract

The present invention relates to a method for the electrocatalytic reduction of dinitrogen (N2) to ammonia using a polyoxometallate catalyst, an alkali metal cation, and a proton and / or electron donor.

Description

[Technical Field]

[0001] The present invention relates to a method for the electrocatalytic reduction of nitrogen to ammonia using a polyoxometallate catalyst in the presence of alkali metal cations and a proton and / or electron donor. [Background technology]

[0002] Humanity relies on the production of ammonia and its derivatives as fertilizer for food production, and the Haber-Bosch (HB) process for producing ammonia from dinitrogen is considered one of the most important inventions of the 20th century (Smith, C; Hill, AK; Torrente-Murciano, L. Current and Future Role of Haber-Bosch Ammonia in a Carbon-Free Energy Landscape. Energy Environ. Sci. 2020, 13, 331-344). The highly optimized heterogeneous catalytic process N2 + 3H2 → 2NH3 is only feasible using very high purity N2 and H2, and is carried out at high temperature (about 700 K) and pressure (about 200 bar) (Schlogl, R. in Handbook of Heterogeneous Catalysis 2501-2575 (Wiley-VCH Verlag GmbH & Co. KGaA, 2008)). The required H2 is produced from natural gas by steam reforming, and it is estimated that about 1% of global energy consumption and 1.4% of global CO2 emissions are related to the HB process (MacFarlane, DR; Cherepanov, PV; Choi, J.; Suryanto, BHR; Hodgetts, RY; Bakker, JM; Ferrero Vallana, FM; Simonov, AN. A Roadmap to the Ammonia Economy. Joule 2020, 4, 1185-1205). Therefore, NH3 is produced in locations where natural gas is abundant, but not necessarily where the end users are located. Based on the future availability of renewable electricity, two alternatives to the conventional HB process have been proposed. One option, the hybrid HB process, uses H2 obtained by water electrolysis for the synthesis of NH3 via the HB process, thereby eliminating the need for natural gas. This results in a reduction in the overall carbon footprint and decarbonization of the HB process.

[0003] The other alternative, electrocatalytic NH synthesis (e-NH), proceeds via the electrochemical nitrogen reduction reaction (e-N2RR), obtaining the required protons and electrons from water oxidation. In contrast to the hybrid-HBR process, e-N2RR is thermodynamically favorable under ambient conditions, and catalytic reactions can be achieved under milder conditions. In fact, the nitrogenase enzyme complex reduces N2 to NH3, albeit very inefficiently, using 16 equivalents of ATP (adenosine triphosphate) per N2 molecule (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. 2014, 114, 4041-4062). An economic analysis of the hybrid-HB and e-NH3 processes showed that the former is economically feasible for large-scale (mass) production, while the e-NH3 process can outperform the hybrid-HB process for small-scale production (approximately 0.03 tonnes of NH3 / day) (Fernandez, CA; Hatzell, MC. Economic Considerations for Low-Temperature Electrochemical Ammonia Production: Achieving Haber-Bosch Parity. J. Electrochem. Soc. 2020, 167, 143504). Environmental advantages of the e-NH3 process include a reduced carbon footprint due to reduced sea and land transportation, reduced storage needs, improved adaptability to intermittent power inputs, and the ability to use lower-purity nitrogen. All these factors combine to make decentralized ammonia production an attractive option in the long term (Soloveichik, G. Electrochemical synthesis of ammonia as a potential alternative to the Haber-Bosch process. Nat. Catal. 2019, 2, 377-380).

[0004] On-site, on-demand NH3 production would also improve decarbonization of the agricultural and transportation sectors and increase resilience to political and economic risks that could reduce ammonia availability, especially in rural areas (Arora, P.; Hoadley, A. F. A.; Mahajani, S. M.; Ganesh, A. Small-Scale Ammonia Production from Biomass: A Techno-Enviro-Economic Perspective. Ind. Eng. Chem. Res. 2016, 55, 6422-6434).

[0005] Despite advances in our understanding of both N2 activation and NH3 production and its electrocatalytic reduction to NH3, the development of (electro)catalysts remains very slow (Chalkley, MJ; Drover, MW; Peters, JC Catalytic N2-to-NH3 (or -N2H4) Conversion by Well-Defined Molecular Coordination Complexes. Chem. Rev. 2020, 120, 5582-5636).

[0006] It should be noted that a previous report of the e-N2RR reaction using water as the solvent and electron / proton donor has been found to be incorrect (Anderson, SZ; Coloci, V.; Yang, S.; Schwalbe, JA; Nielander, AC; McEnaney, JM; Enemark-Rassmussen, K.; Baker, JG; Singh, AR; Rohr, BA; Statt, MJ; Blair, SJ; Mezzavilla, S.; Kibsgaard, J.; Vesborg, RCK; Cargnello, M.; Bent, SF; Jaramillo, TF; Stephens, IEL; Norskov, JK; Chorkendorff, I. A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature, 570, 504-508 (2019)).

[0007] Polyoxometalates are attractive catalysts because they are easy to synthesize, thermally and oxidatively stable, their inherent properties can be easily modified, and they can be used with excellent efficiency in electron-transfer transformations (Neumann, R. Activation of Molecular Oxygen, Polyoxometalates and Liquid Phase Catalytic Oxidation. Inorg. Chem. 2010, 49, 3594-3601).

[0008] Substitution of lacunary polyoxometalates with transition metals increases the reactivity of the resulting polyanions. Generally, weakly basic oxygen atoms are present on the surface of polyanions. A rational approach to such complexes is the synthesis of α- or β-[SiWO 34 ] 9-We have prepared lacunary anions such as [SiW9M3(L)3O] (G. Herve and A. Teze, Study of alpha- and beta-enneatungstosilicates and germanates, Inorg. Chem., 1977, 16, 2115-2117) and used them to synthesize tri-transition metal-substituted polyoxometalates. 37 ] n- Anion (M=Co(II), Fe(III), Cu(II), Mn(II), Ni(II), Cr(III), Al(III), or Ga(III)) (Liu, J.; Ortega, F.; Sethuraman, P.; Katsoulis, DE; Costello, CE; Pope, MT Trimetallo Derivatives of Lacunary 9-Tungstosilicate. J. Chem. Soc., Dalton Trans. 1992, 1901-1906).

[0009] There is a need for an electrochemical method for producing ammonia from dinitrogen (N2) using water as the proton / electron donor at low negative cathode potentials. Such a method would enable small-scale ammonia production units in a distributed production scheme. Summary of the Invention [Means for solving the problem]

[0010] In some embodiments, the present invention provides a method for reducing dinitrogen (N2) to ammonia (NH3), the method comprising electrochemically reducing dinitrogen (N2) in the presence of a polyoxometallate catalyst, an alkali metal cation, and a proton and / or electron donor in an electrochemical cell.

[0011] In some embodiments, the reduction of dinitrogen (N2) according to the present disclosure is carried out in the presence of a polyoxometallate catalyst (compound) represented by the following general formula, or a solvate thereof: General formula: (Q) n [XFe2M(L)3W9O 37 ] During the ceremony, X is P, Si, As, Ge, Ga, B, or Al; M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Mg, Y, Ba, or Ca; L is HO, carboxylate, oxyanion, halide, pseudohalide, null, or any combination thereof; Q is a cation selected from the group consisting of a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen-centered cation, a phosphorus-centered cation, and any combination thereof; n is an integer from 3 to 17. [Brief explanation of the drawings]

[0012] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, the invention, both as to organization and method of operation, together with its objects, features, and advantages, may best be understood by reading the following detailed description when read in conjunction with the accompanying drawings.

[0013] [Figure 1] Figure 1 shows the polyoxometallate catalyst: (Q)n[XFe2M(H2O)3W9O37] (M is Fe). The countercation is not shown. [Figure 2A] Figure 2A shows the UV-Vis spectrum of (TBA)7[SiFe3(H2O)3W9O37] in the presence of He but without Li+. [Figure 2B] Figure 2B shows the UV-Vis spectrum of (TBA)7[SiFe3(H2O)3W9O37] in the presence of N2 and in the absence of Li+. [Figure 2C] Figure 2C shows the UV-Vis spectrum of (TBA)7[SiFe3(H2O)3W9O37] in the presence of He and with Li+. [Figure 2D]Figure 2D shows the UV-Vis spectrum of (TBA)7[SiFe3(HO)3W9O37] in the presence of N2 and containing Li+. In Figures 2A–2D, measurements were performed using 40 μM (TBA)7[SiFe3(HO)3W9O37], 0.01 M TBAPF6, and 200 μM LiClO4 in THF (Figures 2C and 2D). The standard solution was 0.01 M TBAPF6 in THF. In situ electrolysis was performed in a 1 cm quartz cuvette using a Pt gauze working electrode, a Pt wire counter electrode, and an Ag wire reference electrode at a potential of −1.8 V vs. the Ag wire (calibrated to a potential of −1.93 V vs. SHE). Black: before electrolysis; medium gray: 1 electron per (TBA)7[SiFe3(H2O)3W9O37]; very dark gray: 2 electrons per (TBA)7[SiFe3(H2O)3W9O37]; light gray: 3 electrons per (TBA)7[SiFe3(H2O)3W9O37]; gray: 4 electrons per (TBA)7[SiFe3(H2O)3W9O37]. UV-Vis spectra show that in the presence of Li+, N2 clearly binds to (TBA)7[SiFe3(H2O)3W9O37] (Figure 2B), while additional reduced species are formed (Figure 2D).

[0014] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0016] The present invention relates to a method for reducing dinitrogen (N2) to ammonia (NH3). The disclosed method for reducing dinitrogen (N2) to ammonia (NH3) is catalyzed by a polyoxometallate catalyst and an alkali metal cation in the presence of a proton and / or electron donor.

[0017] In some embodiments, the present invention provides a method for reducing dinitrogen (N2) to ammonia (NH3), the method comprising electrochemically reducing dinitrogen (N2) in an electrochemical cell in the presence of a polyoxometallate catalyst, an alkali metal cation, and a proton and / or electron donor, and optionally in the presence of a solvent.

[0018] In some embodiments, the present invention provides a method for reducing dinitrogen (N2) to ammonia (NH3), the method comprising electrochemically reducing dinitrogen (N2) in an electrochemical cell in the presence of a polyoxometallate catalyst, an alkali metal cation, and a proton and / or electron donor, and optionally in the presence of an electrolyte.

[0019] In some embodiments, the present invention provides a method for reducing dinitrogen (N2) to ammonia (NH3), the method comprising electrochemically reducing dinitrogen (N2) in an electrochemical cell in the presence of a polyoxometallate catalyst, an alkali metal cation, and a proton and / or electron donor, and optionally in the presence of an electrolyte and a solvent.

[0020] The reduction of dinitrogen (N2) to ammonia (NH3) can be carried out as shown in Scheme 1 below, where the alkali metal cation is sodium and the proton and / or electron donor is water.

[0021] [ka]

[0022] In some embodiments, the polyoxometallate catalyst comprises at least two iron (Fe) ions. In one embodiment, the polyoxometallate catalyst comprises two iron (Fe) ions. In one embodiment, the polyoxometallate catalyst comprises three iron (Fe) ions.

[0023] In some embodiments, the reduction of dinitrogen (N2) according to the present disclosure is carried out in the presence of a polyoxometallate catalyst (compound) represented by the following general formula, or a solvate thereof: General formula: (Q) n [XFe2M(L)3W9O 37 ] During the ceremony, X is P, Si, As, Ge, Ga, B, or Al; M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Mg, Y, Ba, or Ca; L is HO, carboxylate, oxyanion, halide, pseudohalide, null, or any combination thereof; Q is a cation selected from the group consisting of a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen-centered cation, a phosphorus-centered cation, and any combination thereof; n is an integer from 3 to 17.

[0024] In some embodiments, the general formula: (Q) n [XFe2M(L)3W9O 37 In the formula (I), Q is a cation selected from the group consisting of a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen-centered cation, a phosphorus-centered cation, and any combination thereof. In other embodiments, Q is a proton. In other embodiments, Q is an alkali metal cation. In other embodiments, Q is an alkaline earth metal cation. In other embodiments, Q is a lanthanide cation. In other embodiments, Q is a nitrogen-centered cation. In other embodiments, Q is a phosphorus-centered cation.

[0025] In some embodiments, the general formula: (Q) n [XFe2M(L)3W9O 37 In the formula (I), Q is an alkali metal cation.

[0026] In some embodiments, the general formula: (Q) n [XFe2M(L)3W9O 37 ] in which Q is R1R2R3R4N + and During the ceremony, R1 is H, alkyl, aryl, or alkylaryl; R2 is H, alkyl, aryl, alkylaryl, tallow, C y H 2y+1 (y≧8), or C z H 2z+1 COOH(z ≥ 7); R3 and R4 are each independently H, alkyl, aryl, alkylaryl, or (CH2CH2O) m CH2CH2R5, (CH2CH2O) m H or CH2CH2(OCH2CH2) m R5 (m≧3, R5 is H, OH, alkyl, halide, or pseudohalide).

[0027] In another embodiment, R1 is ethyl; R2 is C z H 2z+1 COOH (z≧7); R and R are (CHCHO) m H (m=6-20). In another embodiment, R1 is methyl; R2 is tetradecyl, hexadecyl, or octadecyl; and R3 and R4 are (CH2CH2O) m H(m=5~10).

[0028] In other embodiments, Q is R1R2R3R4N + wherein R1, R2, R3, and R4 are, independently of each other, H, alkyl, aryl, or alkylaryl.

[0029] In some embodiments, Q is R1R2R3R4N + wherein R2 is C y H 2y+1 (y≧8). In another embodiment, y is an integer from 8 to 50. In another embodiment, y is an integer from 8 to 40. In another embodiment, y is an integer from 8 to 30. In another embodiment, y is an integer from 8 to 20. In another embodiment, Q is tetrabutylammonium (TBA). In another embodiment, Q is R1R2R3R4N + where R1 is ethyl, R2 is tallow, and R3 and R4 are CH2CH2(OCH2CH2) m It's OH.

[0030] As used herein, the term "alkyl," used alone or as part of another group, in one embodiment, refers to "C1-C 12 "C1-C6 alkyl" refers to a straight-chain or branched, saturated or unsaturated group (e.g., alkenyl, alkynyl), the latter only if the number of carbon atoms in the alkyl chain is 2 or more, and can include mixed structures. Non-limiting examples are alkyl groups having 1 to 6 carbon atoms (C1-C6 alkyl) or alkyl groups having 1 to 4 carbon atoms (C1-C4 alkyl). Examples of saturated alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, amyl, tert-amyl, and hexyl. Examples of alkenyl groups include, but are not limited to, vinyl, allyl, butenyl, and the like. Examples of alkynyl groups include, but are not limited to, ethynyl, propynyl, and the like. Similarly, "C1-C 12 The term "alkylene" means a divalent radical containing 1 to 12 carbon atoms.

[0031] An alkyl group can be unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, hydroxy, alkoxy, aryloxy, alkylaryloxy, heteroaryloxy, oxo, cycloalkyl, phenyl, heteroaryl, heterocyclyl, naphthyl, amino, alkylamino, arylamino, heteroarylamino, dialkylamino, diarylamino, alkylarylamino, alkylheteroarylamino, arylheteroarylamino, acyl, acyloxy, nitro, carboxy, carbamoyl, carboxamido, cyano, sulfonyl, sulfonylamino, sulfinyl, sulfinylamino, thiol, alkylthio, arylthio, and alkylsulfonyl groups. Any of the substituents can be unsubstituted or further substituted with any of the above substituents.

[0032] As used herein, the term "alkylaryl," used alone or as part of another group, refers to an alkyl group, as defined above, that is, in some embodiments, substituted with an aryl group, as defined herein.

[0033] As used herein, the term "aryl," used alone or as part of another group, refers to an aromatic ring system having 6 to 14 ring carbon atoms. The aryl ring can be monocyclic, bicyclic, tricyclic, etc. Non-limiting examples of aryl groups include phenyl and naphthyl (e.g., 1-naphthyl, 2-naphthyl), etc. Aryl groups can be unsubstituted or substituted through available carbon atoms with one or more substituents selected from the group consisting of halogen, hydroxy, alkoxy, aryloxy, alkylaryloxy, heteroaryloxy, oxo, cycloalkyl, phenyl, heteroaryl, heterocyclyl, naphthyl, amino, alkylamino, arylamino, heteroarylamino, dialkylamino, diarylamino, alkylarylamino, alkylheteroarylamino, arylheteroarylamino, acyl, acyloxy, nitro, carboxy, carbamoyl, carboxamido, cyano, sulfonyl, sulfonylamino, sulfinyl, sulfinylamino, thiol, alkylthio, arylthio, and alkylsulfonyl groups. Any of the substituents may be unsubstituted or further substituted with any of the above substituents.

[0034] In some embodiments, Q is R1R2R3R4N + wherein R2 is C z H 2z+1 COOH(z≧7). In another embodiment, z is an integer from 7 to 50. In another embodiment, z is an integer from 7 to 40. In another embodiment, z is an integer from 7 to 30. In another embodiment, z is an integer from 7 to 20.

[0035] In some embodiments, Q is R1R2R3R4N + wherein R and R are the same or different from each other. In some embodiments, they are each independently selected from (CHCHO). mCH2CH2R5 (m≧3). In another embodiment, m is an integer from 3 to 50. In another embodiment, m is an integer from 3 to 40. In another embodiment, m is an integer from 3 to 30. In another embodiment, m is an integer from 3 to 20. In another embodiment, m is an integer from 3 to 10.

[0036] In some embodiments, Q is R1R2R3R4N + wherein R1 is ethyl; R2 is C z H 2z+1 COOH (z≧7); R and R are (CHCHO) m H (m=6-20). In another embodiment, Q is R1R2R3R4N + where R1 is methyl; R2 is tetradecyl, hexadecyl, or octadecyl; and R3 and R4 are (CH2CH2O) m H(m=5~10).

[0037] In some embodiments, the general formula: (Q) n [XFe2M(L)3W9O 37 In the above formula, X is P, Si, As, Ge, Ga, B, or Al. In other embodiments, X is P. In other embodiments, X is Si. In other embodiments, X is As. In other embodiments, X is Ge. In other embodiments, X is Ga. In other embodiments, X is B. In other embodiments, X is Al.

[0038] In some embodiments, the general formula: (Q) n [XFe2M(L)3W9O 37 In the above formula, n is an integer from 3 to 17. In another embodiment, n is an integer from 3 to 15. In another embodiment, n is an integer from 3 to 12. In another embodiment, n is an integer from 3 to 10. In another embodiment, n is an integer from 3 to 8. In another embodiment, n is an integer from 3 to 6. In another embodiment, n is 7.

[0039] In some embodiments, the general formula: (Q)n [XFe2M(L)3W9O 37 In the formula (Q), M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Mg, Y, Ba, or Ca. In another embodiment, M is Cr. In another embodiment, M is Mn. In another embodiment, M is Fe. In another embodiment, M is Co. In another embodiment, M is Ni. In another embodiment, M is Cu. In another embodiment, M is Zn. In another embodiment, M is Al. In another embodiment, M is Ga. In another embodiment, M is Sc. In another embodiment, M is Mg. In another embodiment, M is Y. In another embodiment, M is Ba. In another embodiment, M is Ca. In another embodiment, the polyoxometallate catalyst comprises at least two iron (Fe) ions. In another embodiment, the polyoxometallate catalyst is represented by the general formula: (Q) n [XFe2M(L)3W9O 37 ] wherein M is selected from Cr(O-III), Mn(O-V), Fe(O-IV), Co(O-III), Ni(O-III), Cu(O-III), Zn(II), Al(III), Ga(III), Sc(III), Mg(II), Y(III), Ba(II), and Ca(II).

[0040] In some embodiments, the general formula: (Q) n [XFe2M(L)3W9O 37 In the formula (I), L is HO, a carboxylate, an oxyanion, a halide, a pseudohalide, null, or any combination thereof. In other embodiments, L is HO. In other embodiments, L is a carboxylate. Non-limiting examples of carboxylates include acetate. In other embodiments, L is an oxyanion. Non-limiting examples of oxyanions include nitrate, sulfate, or perchlorate. In other embodiments, L is sulfate. In other embodiments, L is perchlorate. In other embodiments, L is a halide. In other embodiments, L is a pseudohalide. In other embodiments, L is null.

[0041] In some embodiments, the polyoxometalate is a polyoxometalate having an anion [SiFe(L)WO 37 ] n In other embodiments, the anion comprises [SiFe(H2O)3W9O 37 ] 7- is.

[0042] The reduction of dinitrogen of the present invention is carried out in the presence of an alkali metal cation provided as an alkali metal salt. As shown in Figure 2 (and as detailed in the corresponding "Brief Description of the Drawings"), the presence of the alkali cation allows for the reaction of dinitrogen (N2) under reducing conditions of at least -1.93 V vs. SHE.

[0043] In another embodiment, the alkali metal salt comprises a cation such as lithium, sodium, potassium, rubidium, or cesium ion, and an anion such as a halide, pseudohalide, perchlorate, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, triflate, or other oxyanion ion. In another embodiment, the alkali metal salt comprises sodium perchlorate, sodium triflate, or potassium triflate. In another embodiment, the molar ratio of alkali metal cation to polyoxometallate catalyst is at least 3 moles of alkali metal cation per mole of polyoxometallate catalyst. In another embodiment, the molar ratio of alkali metal cation to polyoxometallate catalyst is 3 to 1000 moles of alkali metal cation per mole of polyoxometallate catalyst. In other embodiments, the molar ratio of alkali metal cation to polyoxometallate catalyst is 3 to 500, 3 to 400, 3 to 300, 3 to 200, 3 to 100, 3 to 80, 3 to 60, 3 to 50, 3 to 40, 3 to 30, or 3 to 20 moles of metal cation per mole of polyoxometallate catalyst. In other embodiments, the concentration of the alkali metal salt is 0.01 to 1 M. In other embodiments, the concentration of the alkali metal salt is 0.01 to 0.025 M. In other embodiments, the concentration of the alkali metal salt is 0.01 to 0.05 M. In other embodiments, the concentration of the alkali metal salt is 0.01 to 0.1 M. In other embodiments, the concentration of the alkali metal salt is 0.01 to 0.5 M. In other embodiments, the concentration of the alkali metal salt is 0.025 to 1 M. In other embodiments, the concentration of the alkali metal salt is 0.025 to 0.05 M. In another embodiment, the concentration of the alkali metal salt is 0.025 to 0.1 M. In another embodiment, the concentration of the alkali metal salt is 0.025 to 0.5 M. In another embodiment, the concentration of the alkali metal salt is 0.05 to 1 M. In another embodiment, the concentration of the alkali metal salt is 0.05 to 0.1 M. In another embodiment, the concentration of the alkali metal salt is 0.05 to 0.5 M. In another embodiment, the concentration of the alkali metal salt is 0.1 to 1 M. In another embodiment, the concentration of the alkali metal salt is 0.1 to 0.5 M.In other embodiments, the concentration of the alkali metal salt is 0.5 to 1 M. In other embodiments, the concentration of the alkali metal salt is 0.025, 0.067, 0.125, or 0.1 M.

[0044] The reduction of dinitrogen of the present invention is carried out in the presence of a proton and / or electron donor. In some embodiments, the proton and / or electron donor is HO or an alcohol. In other embodiments, the donor is HO. In another embodiment, the donor is HO introduced as vapor. In other embodiments, the donor is an alcohol. Non-limiting examples of alcohols include ethanol, methanol, isopropanol, t-butanol, or any combination thereof. In other embodiments, the proton and / or electron donor is dissolved in a solvent at a concentration of 5% by volume or less. In other embodiments, the donor is dissolved in a solvent at a concentration of 2% by volume or less. In other embodiments, the donor is dissolved in a solvent at a concentration of 0.1-5% by volume. In other embodiments, the donor is dissolved in a solvent at a concentration of 0.1-2% by volume. In other embodiments, the donor is dissolved in a solvent at a concentration of 0.5-2% by volume. In another embodiment, the donor is dissolved in THF or glyme at a concentration of 2% by volume or less. In another embodiment, the donor is dissolved in THF or glyme at a concentration of 0.1-2% by volume. In another embodiment, the donor is dissolved in polyethylene glycol at a concentration of 1.5% by volume or less. In another embodiment, the donor is dissolved in polyethylene glycol at a concentration of 0.1-1.5% by volume. In another embodiment, the donor is in the gas phase. In another embodiment, the donor is dissolved in a polyethylene glycol (PEG) derivative (e.g., any ether of PEG, or a carboxylate salt of PEG).

[0045] In some embodiments, the reduction of dinitrogen (N2) of the present invention is carried out in the presence of a solvent. In some embodiments, the reduction of dinitrogen (N2) of the present invention is carried out solvent-free (in the absence of a solvent). In other embodiments, the solvent is a polyether (e.g., polyethylene glycol of any molecular weight), THF, or glyme. In other embodiments, the solvent is an ether. In other embodiments, the solvent is a polyether. In other embodiments, the solvent is polyethylene glycol. In other embodiments, the solvent is THF. In other embodiments, the solvent is glyme. In other embodiments, the solvent is an ether. In one embodiment, the solvent is a polyether.

[0046] In some embodiments, the reduction of dinitrogen (N) of the present invention is an electrocatalytic reaction carried out in an electrochemical cell. In other embodiments, the electrochemical cell includes a cathode, an anode, an alkali metal cation, and a proton and / or electron donor.

[0047] In one embodiment, the present invention relates to the electrochemical reduction of dinitrogen (N) to ammonia (NH) in an electrochemical cell comprising a cathode, an anode, a polyoxometallate catalyst, alkali metal cations, a proton and / or electron donor, and an electrolyte.

[0048] In one embodiment, the present invention relates to the electrochemical reduction of dinitrogen (N) to ammonia (NH) in an electrochemical cell comprising a cathode, an anode, a polyoxometallate catalyst, alkali metal cations, a proton and / or electron donor, and a solvent.

[0049] In one embodiment, the present invention relates to the electrochemical reduction of dinitrogen (N) to ammonia (NH) in an electrochemical cell comprising a cathode, an anode, a polyoxometallate catalyst, alkali metal cations, a proton and / or electron donor, a solvent, and optionally an electrolyte.

[0050] In one embodiment, the present invention relates to the electrochemical reduction of dinitrogen (N) to ammonia (NH) in an electrochemical cell comprising a cathode, an anode, a polyoxometallate catalyst, alkali metal cations, a solvent, water (as proton and / or electron donors), and optionally an electrolyte.

[0051] In one embodiment, the present invention relates to the electrochemical reduction of dinitrogen (N) to ammonia (NH) in an electrochemical cell comprising a cathode, an anode, a polyoxometallate catalyst, alkali metal cations, water (as proton and / or electron donors), and optionally an electrolyte, but without a solvent.

[0052] In one embodiment, the reduction proceeds in the presence of an alkali metal cation. In one embodiment, the reduction proceeds in the presence of an alkali metal cation and an electrolyte. In another embodiment, the electrolyte comprises a lithium, sodium, potassium, or quaternary ammonium salt. In yet another embodiment, the salt in the electrolyte comprises a cation comprising a lithium, sodium, potassium, or quaternary ammonium ion and an anion comprising a halide, pseudohalide, perchlorate, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, triflate, or oxyanion. In another embodiment, the electrolyte comprises lithium perchlorate. In another embodiment, the electrolyte comprises tetrabutylammonium hexafluorophosphate (TBAPF6). In another embodiment, the electrolyte comprises potassium triflate. In another embodiment, the electrolyte comprises sodium triflate.

[0053] In some embodiments, as used herein, "halide" refers to fluoride, chloride, bromide, or iodide.

[0054] In one embodiment, as used herein, "pseudohalide" refers to the non-limiting group consisting of cyanide, isocyanide, cyanate, isocyanate, thiocyanate, isothiocyanate, and azide.

[0055] In some embodiments, "oxyanion" as used herein refers to the non-limiting group consisting of nitrate, sulfate, and perchlorate, hi another embodiment, the electrolyte comprises sodium perchlorate.

[0056] In another embodiment, the electrochemical cell includes a cathode, an anode, a polyoxometallate catalyst, and optionally a reference electrode, and dinitrogen (N) is reduced when a voltage is applied to the electrochemical cell. The electrocatalytic reaction can be carried out in a divided cell configuration, with a polymer or ceramic membrane separating the anode and cathode compartments, or in an undivided cell configuration. Examples of divided cell configurations include gas-phase flow cell membrane electrolyzers and gas diffusion electrolyzers, in which the polyoxometallate is dissolved in a solvent.

[0057] In another embodiment, the electrocatalytic reduction of dinitrogen (N2) is carried out in an undivided electrochemical cell structure and an organic solvent. In another embodiment, the electrocatalytic reduction of dinitrogen is carried out in a divided cell structure having a polymer membrane separating the anode and cathode compartments. In another embodiment, the electrocatalytic reduction of dinitrogen is carried out in an organic solvent, i.e., in the electrolyte of a divided cell structure having a polymer membrane electrolyte separating the anode and cathode compartments. In another embodiment, the electrocatalytic reduction of dinitrogen is carried out in an organic solvent, i.e., in the electrolyte of a divided cell structure having a ceramic membrane separating the anode and cathode compartments. In another embodiment, the electrocatalytic reduction of dinitrogen is carried out in a gas diffusion flow cell membrane electrolyzer.

[0058] In one embodiment, the cathode in the electrochemical cell of the present invention is a metal. In one embodiment, the cathode comprises a metal. In another embodiment, the cathode comprises Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Mo, W, or any combination thereof. In another embodiment, the cathode comprises Ti. In another embodiment, the cathode comprises V. In another embodiment, the cathode comprises Cr. In another embodiment, the cathode comprises Mn. In another embodiment, the cathode comprises Fe. In another embodiment, the cathode comprises Co. In another embodiment, the cathode comprises Ni. In another embodiment, the cathode comprises Cu. In another embodiment, the cathode comprises Zn. In another embodiment, the cathode comprises Al. In another embodiment, the cathode comprises Mo. In another embodiment, the cathode comprises W. In another embodiment, the cathode comprises stainless steel. In another embodiment, the cathode is Cu wire. In another embodiment, the cathode is Cu foil. In another embodiment, the cathode is a Ni mesh. In another embodiment, the cathode is a stainless steel mesh. In some embodiments, the cathode in the electrochemical cells of the invention comprises carbon. In another embodiment, the cathode comprises microporous carbon. In another embodiment, the cathode is mesoporous carbon.

[0059] In some embodiments, the anode in the electrochemical cell of the present invention oxidizes water.

[0060] In some implementations, the anode comprises Pt. In one embodiment, the anode is a Pt wire. In one embodiment, the anode is platinized titanium.

[0061] In some embodiments, the electrochemical reduction of dinitrogen (N2) of the present invention is carried out at a potential of less than 0 V versus the SHE. In other embodiments, "potential" refers to the IUPAC rules. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a potential of less than -1 V versus the SHE. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a potential of less than -2 V versus the SHE. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a potential of -2.5 to 0 V versus the SHE. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a potential of -1.5 to -2.5 V versus the SHE. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a potential of -2, -2.15, or -2.4 V versus the SHE.

[0062] In some embodiments, the electrochemical reduction of dinitrogen (N2) of the present invention is carried out in the presence of air or nitrogen-enriched air. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out using purified nitrogen. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a dinitrogen (N2) pressure of 0.1 to 50 bar N2. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a dinitrogen (N2) pressure of 0.1 to 10 bar N2. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a dinitrogen (N2) pressure of 0.1 to 5 bar N2. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a dinitrogen (N2) pressure of 0.1 to 3 bar N2. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at atmospheric pressure. In other embodiments, the electrochemical reduction of dinitrogen of the present invention is carried out at a dinitrogen (N2) pressure of 1 bar N2.

[0063] In some embodiments, the electrocatalytic reduction of dinitrogen (N2) of the present invention is carried out at a temperature of 0 to 100°C. In other embodiments, the electrocatalytic reduction of dinitrogen of the present invention is carried out at a temperature of 25 to 60°C. In other embodiments, the electrocatalytic reduction of dinitrogen of the present invention is carried out at a temperature of 15 to 25°C. In other embodiments, the electrocatalytic reduction of dinitrogen of the present invention is carried out at a temperature of 15 to 30°C. In other embodiments, the electrocatalytic reduction of dinitrogen of the present invention is carried out at a temperature of 10 to 30°C. In other embodiments, the electrocatalytic reduction of dinitrogen of the present invention is carried out at ambient temperature.

[0064] In some embodiments, without being bound by any mechanism or theory, the electrocatalytic reduction of dinitrogen (N) of the present invention can be carried out as shown in Scheme 2 below.

[0065] [ka]

[0066] In Scheme 2 above, Q' is an alkali cation; m is an integer from 2 to 5; Q is a monovalent cation selected from the group consisting of a proton, an alkali metal cation, a nitrogen-centered cation, a phosphorus-centered cation, and any combination thereof; n is an integer from 3 to 17; n>m.

[0067] In some embodiments, as used herein, the term "proton and / or electron donor" refers to either a "proton donor and electron donor" or a "proton donor or electron donor." A proton donor or electron donor means that the chemical species can donate (a) a proton, (b) an electron, or (c) both a proton and an electron.

[0068] In some embodiments, the polyoxometalates have the general formula: (Q) n[XFe2M(L)3W9O 37 or a solvate thereof. The term "solvate" refers to a form in which a polyoxometalate is solvated with a solvent such as water (hydrate), methanol, or ethanol.

[0069] Various embodiments and aspects of the present invention as described herein and as claimed in the claims section below find experimental support in the following examples.

[0070] Example

[0071] Overview: Q7[SiW9Fe3(L)3O 37 The synthesis of NO (L = HO, Q = tetrabutylammonium (TBA)) was carried out according to the literature method (Liu, J.; Ortega, F.; Sethuraman, P.; Katsoulis, DE; Costello, CE; Pope, MT Trimetallo Derivatives of Lacunary 9-Tungstosilicate. J. Chem. Soc., Dalton Trans. 1992, 1901-1906). x N2 was purified until no ammonia or NH3 was detected. +Ammonia was detected by the classical indophenol test and NMR (Nielander, AC; McEnany, JM; Schwalbe, JA; Baker, JB; Blair, SJ; Wang, L.; Pelton, JG; Andersen, SZ; Enemark-Rasmussen, K.; Colic, V.; Tang, S. Bent. S. F.; Cargnello, M.; Kibsgaard, J.; Vesborg, PCK; Chorkendorff, I.; Jaramillo, TF. A Versatile Method for Ammonia Detection in a Range of Relevant Electrolytes via Direct Nuclear Magnetic Resonance Techniques. ACS Catal. 2019, 9, 5797-5802).

[0072] Example 1 TBA7[SiW9Fe3(H2O)3O in THF containing ethanol as proton donor and / or electron donor 37 Reduction of N2 in the presence of

[0073] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of TBA7[SiW9Fe3(H2O)3O 37 ], 0.8 mmol of TBAPF6, 0.2 mmol of LiClO4, and 1% dry ethanol in 8 mL of dry THF. After 5 h at a potential of -2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 120 μM NH3 solution was obtained. TBA7[SiW9Fe3(H2O)3O 37 In the absence of tetrabutylammonium (Bu4N), NH3 was not produced. + ) refers to

[0074] Example 2 TBA7[SiW9Fe3(H2O)3O in glyme containing ethanol as proton and / or electron donor 37 Reduction of N2 in the presence of

[0075] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of TBA7[SiW9Fe3(H2O)3O 37 The solution was circulated in 8 mL of dry glyme containing 0.8 mmol of TBAPF, 0.2 mmol of LiClOO, and 1% dry ethanol. After 5 h at a potential of -2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 125 μM NH solution was obtained. 37 In the absence of tetrabutylammonium (Bu4N), NH3 was not produced. + ) refers to

[0076] Example 3 TBA7[SiW9Fe3(H2O)3O in polyethylene glycol containing ethanol as proton donor and / or electron donor 37 Reduction of N2 in the presence of

[0077] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of TBA7[SiW9Fe3(L)3O 37 The solution was circulated in 8 mL of dry polyethylene glycol 400 containing 0.8 mmol of TBAPF, 0.2 mmol of NaClO, and 1% dry ethanol. After 5 h of application of a potential of -2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 100 μM NH solution was obtained. 37 In the absence of tetrabutylammonium (Bu4N), NH3 was not produced. + ) refers to

[0078] Example 4 TBA7[SiW9Fe3(H2O)3O in polyethylene glycol as proton and / or electron donor 37 Reduction of N2 in the presence of

[0079] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of TBA7[SiW9Fe3(L)3O 37 ], 0.8 mmol of TBAPF6, and 0.2 mmol of NaClO4 in 8 mL of dry polyethylene glycol 400. After 5 h at a potential of -2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 22 μM NH3 solution was obtained. 37 In the absence of tetrabutylammonium (Bu4N), NH3 was not produced. + ) refers to

[0080] Example 5 TBA7[SiW9Fe3(H2O)3O in polyethylene glycol containing water as proton donor and / or electron donor 37 Reduction of N2 in the presence of

[0081] In a non-divided cell consisting of a 20 mL gas-tight vial, purified N2 (1 bar) was added to 3 μmol of TBA7[SiW9Fe3(L)3O 37 ], 0.8 mmol of TBAPF6, 0.2 mmol of NaClO4, and 1% HO in 8 mL of dry polyethylene glycol 400 solution. After 5 h of application of a potential of -2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 125 μM NH3 solution was obtained. 37 In the absence of tetrabutylammonium (Bu4N), NH3 was not produced. + ) refers to

[0082] Example 6 Q7[SiW9Fe3(H2O)3O37 Synthesis of In the formula, Q is R1R2R3R4N + R1 is ethyl; R2 is tallow; R3 and R4 are (CH2CH2O)mH; m=6-20.

[0083] Potassium salt K7[SiW9Fe3(H2O)3O 37 ] was reacted with dry IoLiLyteT2EG (ethyl bis(hydroxyethyl) tallow alkyl ethyl sulfate). In a separatory funnel, 15 ml of IoLiLyteT2EG was added to 1 g of K7[SiW9Fe3(HO)3O] in 30 ml of DCM and 30 ml of DDW. 37 The mixed solution was vigorously stirred several times, and the crude bottom layer was separated and dried using a rotary evaporator to obtain a product, which was an oily liquid.

[0084] Example 7 Reduction of N2 using the catalyst of Example 6 with ethanol as the proton and / or electron donor

[0085] In a non-divided cell consisting of a 20 mL gas-tight vial, purified N (1 bar) was added to 6 mL of Q7[SiWFe(HO)O] from Example 6 containing 0.4 mmol LiClO and 1% by volume of dry ethanol. 37 After 5 h of application of a potential of −2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 9 μM NH solution was obtained.

[0086] Example 8 K7[SiW9Fe3(H2O)3O in polyethylene glycol containing water as proton and / or electron donor 37 Reduction of N2 in the presence of

[0087] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of K7[SiW9Fe3(H2O)3O 37], 0.8 mmol of potassium triflate, 0.2 mmol of NaClO4, and 1% HO in 8 mL of dry polyethylene glycol 400. After 3 h of application of a potential of -2.4 V vs. SHE using a Cu wire cathode and a Pt wire anode, a 115 μM NH3 solution was obtained. 37 ] or in the absence of NaClO4, no NH3 was produced.

[0088] Example 9 K7[SiW9Fe3(H2O)3O in polyethylene glycol containing water as proton and / or electron donor 37 Reduction of N2 in the presence of

[0089] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of K7[SiW9Fe3(H2O)3O 37 The solution was circulated through 8 mL of dry polyethylene glycol 400 containing 0.8 mmol of potassium triflate, 0.2 mmol of NaClO, and 1% HO. After 3 h at a potential of -2.4 V vs. SHE using a Cu foil cathode and a Pt wire anode, a 122 μM NH solution was obtained. 37 ] or in the absence of NaClO4, no NH3 was produced.

[0090] Example 10 K7[SiW9Fe3(H2O)3O in polyethylene glycol containing water as proton and / or electron donor 37 Reduction of N2 in the presence of

[0091] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of K7[SiW9Fe3(H2O)3O 37The solution was circulated in 8 mL of dry polyethylene glycol 400 containing 1.0 mmol of NH4, 1.0 mmol of sodium triflate, and 1% HO. After 3 h of application of a potential of −2.4 V vs. SHE using a Cu foil cathode and a Pt wire anode, a 135 μM NH4 solution was obtained.

[0092] Example 11 K7[SiW9Fe3(H2O)3O in polyethylene glycol containing water as proton and / or electron donor 37 Reduction of N2 in the presence of

[0093] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of K7[SiW9Fe3(H2O)3O 37 ], 0.8 mmol potassium triflate, 0.2 mmol NaClO, and 1% HO in 8 mL of dry polyethylene glycol 400. After 3 h of application of a potential of −2.4 V vs. SHE using a Ni mesh cathode and a Pt wire anode, a 180 μM NH solution was obtained.

[0094] Example 12 K7[SiW9Fe3(H2O)3O in polyethylene glycol dimethyl ether containing water as proton donor and / or electron donor 37 Reduction of N2 in the presence of

[0095] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of K7[SiW9Fe3(H2O)3O 37 ], 0.8 mmol potassium triflate, 0.2 mmol NaClO, and 1% HO in 8 mL of dry polyethylene glycol 400 dimethyl ether. After 3 h of application of a potential of −2.4 V vs. SHE using a Ni mesh cathode and a Pt wire anode, a 165 μM NH solution was obtained.

[0096] Example 13 K7[SiW9Fe3(H2O)3O in polyethylene glycol containing water as proton and / or electron donor 37 ] in the presence of N2 reduction

[0097] In a 20 mL undivided cell, purified N2 (1 bar) was added to 3 μmol of K7[SiW9Fe3(H2O)3O 37 ], 0.8 mmol potassium triflate, 0.2 mmol NaClO, and 1% HO in 8 mL of dry polyethylene glycol 400. After 3 h of application of a potential of −2.4 V vs. SHE using a stainless steel mesh cathode and a Pt wire anode, a 195 μM NH solution was obtained.

Claims

1. Ammonia (NH ３ ) a method for producing the same, In an electrochemical cell, dinitrogen (N ２ ) by electrochemical reduction of The polyoxometallate catalyst comprises a compound represented by the general formula: (Q) n [XFe 2 M(L) 3 W 9 O 37 ] or a solvate thereof; During the ceremony, X is P, Si, As, Ge, Ga, B, or Al; M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Mg, Y, Ba, or Ca; L is H 2 O, carboxylate, oxyanion, halide, pseudohalide, null, or any combination thereof; Q is a cation; The method wherein n is an integer from 3 to 17.

2. 10. The method of claim 1, The method wherein Q is selected from the group consisting of a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen-centered cation, a phosphorus-centered cation, and any combination thereof.

3. 3. The method of claim 1 or 2, The method wherein X is P.

4. 3. The method of claim 1 or 2, The method wherein X is Si.

5. 3. The method of claim 1 or 2, The method wherein X is As.

6. 3. The method of claim 1 or 2, The method wherein X is Ge.

7. 3. The method of claim 1 or 2, The method wherein X is Ga.

8. 3. The method of claim 1 or 2, The method wherein X is B.

9. 3. The method of claim 1 or 2, The method wherein X is Al.

10. 3. The method of claim 1 or 2, L is null, method.

11. 3. The method of claim 1 or 2, L is H ２ O is a method.

12. 3. The method of claim 1 or 2, The method wherein Q is a proton.

13. 3. The method of claim 1 or 2, The method wherein Q comprises a lanthanide cation.

14. 3. The method of claim 1 or 2, The method wherein Q comprises a nitrogen-centered cation.

15. 3. The method of claim 1 or 2, The method wherein Q comprises a phosphorus-centered cation.

16. 10. The method of claim 1, [XFe ２ M (L) ３ W ９ O ３７ ] is [SiFe ３ (L) ３ W ９ O ３７ ]A method.

17. 10. The method of claim 1, The method, wherein the electrochemical cell further comprises an electrolyte.

18. 10. The method of claim 1, The method, wherein the electrochemical cell further comprises a solvent.

19. 10. The method of claim 1, The dinitrogen (N ２ ) is reduced in the absence of a solvent.

20. 10. The method of claim 1, The electrochemical cell includes a cathode, an anode, and an electrolyte.

21. 21. The method of claim 17 or 20, The method, wherein the electrolyte comprises a lithium salt, a sodium salt, a potassium salt, or a quaternary ammonium salt.

22. 22. The method of claim 21, The electrolyte is lithium, sodium, potassium, or quaternary ammonium cations; and The method includes a salt of a halide, pseudohalide, perchlorate, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, or triflate anion, or an oxyanion.

23. 10. The method of claim 1, The alkali metal cation is a lithium, sodium, potassium, rubidium, or cesium cation; and as an alkali metal salt, including a halide, pseudohalide, perchlorate, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, or triflate anion, or an oxyanion.

24. 10. The method of claim 1, The method wherein the proton and / or electron donor is water.

25. 10. The method of claim 1, A method wherein the molar ratio of said alkali metal cations to said polyoxometallate catalyst is at least 3 moles of alkali metal cations per mole of polyoxometallate catalyst.

26. 10. The method of claim 1, The dinitrogen (N ２ ) is carried out at a potential of less than 0 V versus SHE.

27. 10. The method of claim 1, The dinitrogen (N ２ ) is carried out in the presence of air or nitrogen-enriched air.

28. 10. The method of claim 1, The dinitrogen (N ２ ) is electrochemically reduced using purified nitrogen.

29. 10. The method of claim 1, The dinitrogen (N ２ The electrochemical reduction of ２ The method used.

30. 10. The method of claim 1, The dinitrogen (N ２ The electrochemical reduction of ２ The method used.

31. 10. The method of claim 1, The dinitrogen (N ２ The electrochemical reduction of ２ The method used.

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