JP2019510874A - Method and battery for converting dinitrogen to ammonia - Google Patents

Abstract

The present invention relates to a process for the reduction of dinitrogen to ammonia, and to an electrochemical cell for said reduction, which electrochemical cell comprises a cathode working electrode comprising a nanostructured catalyst, a counter electrode and an electrolyte. The invention comprises the step of introducing a source of dinitrogen and hydrogen into the electrolyte, wherein the dinitrogen is reduced to ammonia at the cathode working electrode. The electrolyte comprises one or more liquid salts formed from a combination of a specific cation and a specific anion. 【Selection chart】 None

Description

The present invention relates to an electrochemical device and method for converting dinitrogen (N ₂ ) to ammonia.

  In one form, the invention relates to the cathode reduction of dinitrogen.

  In one particular aspect, the present invention is suitable for use in the industrial production of ammonia.

  It should be understood that any discussion of documents, devices, acts or knowledge in this document is included to explain the context of the present invention. Furthermore, the discussion throughout this specification may arise from the recognition of the inventor and / or the identification by the inventor of a particular related area of the problem. Also, any discussion of documents, devices, acts or findings herein is included to explain the context of the present invention in terms of the inventor's knowledge and experience. Accordingly, any such discussion takes form part of the prior art basis or common general knowledge of the relevant art in Australia prior to the priority date of the present disclosure and claims, or elsewhere. It should not be admitted that things form.

  Ammonia production is a very energy consuming process, consuming 1-3% of the world's electrical energy and about 5% of the world's natural gas production. Global production is currently about 2 million tons annually, reflecting the huge demand for this chemical in agricultural, pharmaceutical manufacturing and many other industrial processes.

Ammonia is also considered a carbon-free solar energy storage material due to its useful characteristics as a chemical energy carrier. Ammonia is safer, environmentally friendly, and most importantly does not emit any CO ₂ compared to other chemicals (such as hydrogen) that can be used to store solar energy. When stored in this manner, energy is readily recovered by the ammonia fuel cell.

For more than 100 years, ammonia has been produced from dinitrogen and hydrogen in the presence of an iron-based catalyst at high pressure and high temperature according to the following reaction

  This method is known as the Harbor-Bosch method and is of great importance in the inexpensive fertilizer production that has been favored over the past century. The Harbor Bosch process uses very high temperatures and pressures and requires a significant amount of energy in the form of natural gas, oil or coal for the required hydrogen production.

  While there is a need to support the growing world population, at the same time to reduce global carbon emissions, it is highly desirable to break the link between industrial nitrogen fertilizer production and the use of fossil fuels. Thus, there is strong interest in alternative pathways for ammonia synthesis.

The ideal system for the conversion of dinitrogen to ammonia would be profitable, easily expandable, operate at ambient conditions, and be connected to renewable energy sources such as wind, water or sun . An electrochemical approach can potentially achieve this goal. The electrochemical reduction process involves dinitrogen gas as the starting material and uses various aqueous electrolytes or H ₂ gas as a source of H ⁺ . The electrochemical reduction of dinitrogen is largely dependent on the structure, components, and surface morphology of the electrocatalyst. (Van der Ham et al., Chemical Society Reviews 43, 5183-5191 (2014)).

For example, Koleli and Ropke examined polyaniline electrodes in methanol / LiClO ₄ / H ⁺ solution and achieved maximum current efficiency of 16% (vs normal hydrogen electrode) at -0.12 V at room temperature and elevated pressure . (Koleli, F. and Ropke, T. Applied Catalysis B-Environmental 62, 306-310, (2006))

By using a battery based on a membrane electrode assembly with a Pt electrode, Lan et al. Demonstrated that, from air and water, 1.14 × 10 ⁻⁵ mol. m ^-2 . An ammonia production rate of s ^-1 was achieved. (Lan et al., Scientific Reports 3, (2013)).

Further, ammonia is produced using a mixture of _{N 2} and steam in the molten hydroxide suspension of nano _-Fe 2 _{O 3} at 1.2V battery voltage and 35% niobium efficiency. (Licht et al., Science 3455, 637-640 (2014)). The advancements with this technology have considerable potential for competition with current ammonia industrial processes, but the high temperatures used (~ 200 ° C) still require significant power of heating and energy. Until now, electrochemical conversion has not been sufficiently successful to be considered as a viable replacement for the Haber-Bosch method. Furthermore, prior art electrochemical conversions have not reached levels of efficiency high enough such as those exhibited by dinitrogen fixing bacteria. (Rosca et al., Chemical Reviews, 2009, 109, 2209-2244).

U.S. Patent Application Publication No. 2006/0049063 and U.S. Patent No. 6,712,950 disclose the use of nitrogen containing species or dinitrogen gas in a non-aqueous liquid electrolyte such as a molten salt or ionic liquid. It is described to synthesize ammonia gas by anodic reaction with hydrogen-containing species or hydrogen gas. The method involves the production of N ₃ ^- ions in the electrolyte followed by the reaction of N ₃ ^- ions at the anode to produce ammonia. This method is limited by the need to select a medium so that it can dissolve useful amounts of N ₃ ⁻ to support the practical rate of ammonia production.

  US Patent Application Publication No. 2016/0138176 (Yoo et al.) Describes a method of synthesizing ammonia using an electrolytic cell containing an aqueous or liquid electrolyte of an alkali metal (salt) or ionic liquid . The document discloses the use of electrolytes formed from a wide range of cations and anions (does not form the liquid salt that many of them form), some of which relate to the efficiency of ammonia synthesis Stability and usefulness are limited.

  Thus, there is a continuing need to identify new electrolytes and an improved method of cathode dinitrogen reduction leading to ammonia synthesis.

In contrast to hydrogen production or CO ₂ reduction, very little prior art of electrocatalyst or photocatalyst is reported to show useful activity for N ₂ reduction. Little is known about the requirements or possible mechanisms for such reactions. However, it is known that the commercially viable electrochemical conversion of dinitrogen needs to overcome the obstacles exhibited by the high stability and chemically inert nature of dinitrogen.

  So far, catalyst development has focused on catalysts for the thermal synthesis of ammonia. Current electrochemical catalysts for ammonia synthesis include conducting polymers (Koleli, F. and Ropke, T. Applied Catalysis B-Environmental 62, 306-310, (2006)), meso Ni-Cu alloys (Licht et al. Science And limited to commercial Pt / C catalysts (Lan et al., Scientific Reports 3, (2013)).

Metal nanocatalysts are widely used for fuel cells and CO ₂ reduction. It is well known that the performance of nanocatalysts depends on their particle size, morphology and crystal structure.

  Greenlee et al. Report the synthesis of electrochemically synthesized NiFe nanocatalysts for ammonia synthesis (Nov. 8-13, 2015, AlChE annual meeting, Salt Lake City, UT https://aiche.confex.com/aiche /2015/webprogram/Paper422270.html). No further characterization or performance of the catalyst was reported.

Prior art electrocatalysts typically do not have high enough efficiency, catalytic activity and stability for dinitrogen reduction. In addition, the low solubility of dinitrogen in water (20 mg / L, 20 ^° C., 1 bar) results in lower reaction rates as reported in the prior art.

  The object of the present invention is to provide an efficient electrochemical process for the production of ammonia.

  Another object of the present invention is to provide an electrochemical cell suitable for the electrochemical process of cathode dinitrogen reduction.

  Another object of the present invention is to provide an improved method of cathode dinitrogen reduction.

  A further object of the present invention is to alleviate at least one disadvantage associated with the prior art dinitrogen cathode reduction process.

  The purpose of the embodiments described herein is to overcome or alleviate at least one of the above-mentioned drawbacks of the related art systems, or at least a useful alternative to the related art systems. It is to provide.

In a first aspect of the embodiments described herein, a battery is provided for the electrochemical reduction of dinitrogen to ammonia. The battery is
-A cathode working electrode comprising a nanostructured catalyst for the reduction of dinitrogen;
-Counter electrode,
An electrolyte comprising one or more liquid salts in contact with the working electrode, the liquid salt comprising
(I) Cations selected from the group consisting of PR _1-4 (phosphonium), NR _1-4 (tetraalkyl ammonium), and C ₄ H ₈ NR ₂ (pyrrolidinium) (wherein each of the R groups is independently linear , Branched or cyclic, preferably containing 1 to 18 carbon atoms, optionally partially or completely halogenated, optionally containing heteroatoms, optionally It preferably contains a functional group selected from ether, alcohol, carbonyl (acetate), thiol, sulfoxide, sulfonate, amine, azo or nitrile, and the two R groups combine to form a single ring or a heterocyclic ring. Also good) and
_{(Ii) (RO) x PF} 6-x ( _{phosphate), (RO) x BF 4} -x ( _{borate), R'SO 2 NSO 2 R '} ( _{imide), R'SO 2 C (SO 2} R') (SO ₂ R ') (methide), FSO ₂ NSO ₂ F, C ₂ O ₄ BF ₂ , C ₂ O ₄ PF _4, RC ₂ O ₄ BF ₂ , RC ₂ O ₄ PF _4, CF ₃ SO ₃ (trif Rate), R'SO ₃ (sulfonate), R'CO ₂ , (carboxylate), CF ₃ COO (trifluoroacetate), R ' _x PF _6-x (FAP), R' _x BF _4-x (formula Wherein each R ′ group is independently linear, branched or cyclic, preferably contains 1 to 18 carbon atoms and is optionally partially or completely fluorinated, optionally Preferably, ether, alcohol, carboni (Acetate), which contains a functional group selected from thiol, sulfoxide, sulfonate, amine, azo or nitrile, and two R ′ groups may be combined to form a single ring or a heterocyclic ring). It is formed from the combination with the anion selected from the group.

In a preferred embodiment, the liquid salt is C ₄ mpyr (butyl-methyl pyrrolidinium), P _6,6,6,14 (trihexyl tetradecyl phosphonium), P (C ₂ R _f ) ₄ , wherein: R _f is a cation selected from the group consisting of perfluoroalkyls, eFAP (C ₂ F ₅ PF ₃ ), NfO (nonafluorobutanesulfonate), PFO (perfluorooctanesulfonate), FSI (bis (fluorosulfonyl) imide) , NTf ₂ (bis (trifluoromethylsulfonyl) imide), B (otfe) ₄ (tetrakis (2,2,2-trifluoroethane) borate, and CF ₃ COO (trifluoroacetate); In combination with the anion.

In a particularly preferred embodiment, the liquid salt comprises a cation selected from PR _1-4 (phosphonium) cations.

In a particularly preferred embodiment, the liquid salt comprises an anion selected from RSO ₃ (sulfonate) cations, in particular perfluorobutanesulfonate or perfluoropropanesulfonate, or trifluorophosphates, in particular eFAP (tris (perfluoroethyl) trifluorophosphate). .

  In another preferred embodiment, the cations and / or anions of the liquid salt are fluorinated or perfluorinated.

  It is also particularly preferred to have relatively high nitrogen solubility (eg, as compared to prior art liquid salts such as imidazolium salts and nitrile anions such as dicyanamide).

  In a particularly preferred embodiment of the cell for the electrochemical reduction of dinitrogen to ammonia, the reduction of dinitrogen to ammonia mainly occurs in the region adjacent to the three-phase boundary on the working surface of the cathode working electrode. .

  Typically, a nanostructured electrocatalyst is applied to the working surface of the cathode working electrode to create a gas / electrolyte / metal three phase boundary region where electrolysis mainly occurs.

  Electrolytic cells can include other features well known to those skilled in the art for performing the electrolytic reaction and controlling the current between the electrodes. For example, the electrolytic cell can be configured to control the temperature or pressure of operation using known means such as a heater, cooling unit or pressurizing means. Additionally, the battery may include an ultrasound generator that generates sound waves of energy above 20 kHz.

  The electrolytic cell preferably comprises a gas flow layer having the function of introducing into the cell a stream of nitrogen and hydrogen or a gas comprising steam, and an outlet of the gas containing ammonia. Ammonia is optionally recovered outside the cell.

  In a further embodiment, an assembly can be formed if two or more cells according to the invention are stacked in series. One or more stacked cells may be further folded or wound. The gas can be introduced at any convenient location, including from the "end" of the longest dimension of the assembly or from either side of the assembly.

In a second aspect of the presently described embodiments, a method of electrochemically reducing dinitrogen to ammonia is provided. The method is
(1) contacting a cathode working electrode comprising a nanostructured catalyst with an electrolyte comprising one or more liquid salts;
(2) introducing a source of dinitrogen and hydrogen into the electrolyte;
Liquid salt is
(I) PR _1-4 (phosphonium), NR _1-4 (tetraalkyl ammonium), C ₄ H ₈ NR ₂ (pyrrolidinium) (wherein the R groups are each independently linear, branched or cyclic, Preferably, it contains 1 to 18 carbon atoms, optionally partially or completely halogenated, optionally containing a heteroatom, and optionally preferably an ether, alcohol, carbonyl ( Acetate), a functional group selected from thiols, sulfoxides, sulfonates, amines, azos or nitriles, and two R groups may be combined to form a single ring or a heterocyclic ring). The cation to be selected
_{(Ii) (RO) x PF} 6-x ( _{phosphate), (RO) x BF 4} -x ( _{borate), R'SO 2 NSO 2 R '} ( _{imide), R'SO 2 C (SO 2} R') (SO ₂ R ') (methide), FSO ₂ NSO ₂ F, C ₂ O ₄ BF ₂ , C ₂ O ₄ PF _4, RC ₂ O ₄ BF ₂ , RC ₂ O ₄ PF _4, CF ₃ SO ₃ (trif Rate), R'SO ₃ (sulfonate), R'CO ₂ , (carboxylate), CF ₃ COO (trifluoroacetate), R ' _x PF _6-x (FAP), R' _x BF _4-x (formula Wherein each R ′ group is independently linear, branched or cyclic, preferably contains 1 to 18 carbon atoms and is optionally partially or completely fluorinated, optionally Preferably, ether, alcohol, carboni (Acetate), which contains a functional group selected from thiol, sulfoxide, sulfonate, amine, azo or nitrile, and two R ′ groups may be combined to form a single ring or a heterocyclic ring). Formed from the combination with anions selected from the group, dinitrogen is reduced to ammonia at the cathode working electrode.

  The method may further comprise a step (3) comprising recovering the ammonia generated at the cathode working electrode and separating the ammonia from other liquid and gas present using a separate trap or separation unit.

  Typically, dinitrogen is reduced to ammonia at the cathode working electrode in the presence of a source of hydrogen, preferably hydrogen gas or water. In a particularly preferred embodiment of the method, dinitrogen gas is humidified with steam to a controlled degree, and then the humidification gas is flowed over the cathode where dinitrogen is electrochemically reduced to form ammonia.

  Typically, when the source of hydrogen is water, the counter electrode of the anode converts hydroxyl ions formed at the cathode to water and oxygen.

  The counter electrode may be placed in the same electrolyte as the working electrode, or alternatively may be separated by some means such as an electrolyte membrane or a separator material. In another embodiment, the counter electrode may be located in a compartment that optionally contains a different electrolyte medium, such as an aqueous solution.

  The reaction of the counter electrode may be hydroxylation or another convenient oxidation reaction such as sulfite oxidation.

Electrolyte The electrolyte in contact with the working electrode may comprise one or more salts, which may be in solid or liquid state, or a combination thereof.

  The electrolyte is typically in the form of a layer. Preferably, the electrolyte comprises a spacer or electrolyte membrane (which itself can act as an electrolyte), eg a polymer electrolyte such as NafionTM or NafionTM-liquid salt blend, or a gelled liquid salt electrolyte, or It is an electrolyte immersed in a porous separator such as paper or CeleguardTM.

  In a further embodiment of the present invention, there is provided an electrolyte membrane comprising a thin layer of material in combination with one or more liquid salts described herein for use in the battery of the present invention.

  Preferably, the electrolyte of the present invention has high solubility in dinitrogen and low solubility in water. Preferably, the solubility of dinitrogen is at least 100 mg / L, more preferably more than 200 mg / L, most preferably more than 400 mg / L at the operating temperature and pressure of the cell. The solubility of water in the liquid salt is preferably less than 5% by weight, more preferably less than 2%, most preferably less than 1% at the operating temperature and pressure of the cell.

Liquid Salt As used herein, liquid salt is intended to refer to an electrolyte medium which is liquid at the temperature of use and which contains one or more salts, which may be solid or liquid in their pure state, respectively. The salt may be selected from any suitable metal salt, organic salt, protonate, complex ion salt or the like.

  Also, a liquid salt medium can be formed by mixing solid salts to produce a liquid salt of desired characteristics.

The liquid salt medium may contain additional components, including water or other molecular liquids that are miscible with the liquid salt electrolyte. As those skilled in the art will appreciate, such materials include dimethylsulfoxide, tetraglyme and other oligo- and poly-ethers, glutaronitrile and other high boiling nitriles, trifluorotoluene and other complete And partially fluorinated solvents, and propylene carbonate and other carbonate solvents. If the molecular liquid component is a volatile substance, the N ₂ gas stream can be presaturated by bubbling through the vessel of molecular solvent before the gas stream is passed to the reduction cell, and Any molecular liquid leading to the outside can either condense or be captured for reuse. Preferably, the molecular liquid is fluorinated or perfluorinated. Preferably, the molecular liquid is present in the liquid salt medium at a concentration of 90 vol% to 0.1 vol%, more preferably 20 vol% to 0.2 vol%, most preferably 50 vol% to 0.5 vol%.

Electrolytes containing liquid salts result in an ionically conductive, low water content medium in which process reactions occur. Also, the electrolytes of the present invention offer the advantage of low or no volatility, and some gases are more soluble in these electrolytes, including liquid salts, than water. In particular, some electrolytes, including liquid salts, can increase their solubility in N ₂ gas (compared to aqueous and other electrolytes), thereby increasing the concentration of N ₂ at the electrolyte / electrode interface It can be done.

  In another aspect of the presently described embodiments, the present invention provides an electrolyte medium for the electrochemical reduction of dinitrogen to ammonia according to the method of the present invention, said medium being high relative to dinitrogen It contains one or more liquid salts with solubility and low solubility in water.

In a preferred embodiment, the electrolyte comprises one or more eFAP liquid salts, as it exhibits high N ₂ solubility (see S. Stevanovic et al., Chem. Thermodynamics 59 (2013) 65-71).

Also, electrolytes containing liquid salts provide controlled water activity for electrochemical reactions and are high enough to support N ₂ reduction but not high enough to support rapid reduction of water to H ₂ It can indicate the degree of hydrophobicity. In a preferred embodiment, the electrolyte comprises one or more hydrophobic liquids based on P _6,6,6,14 cations. In a particularly preferred embodiment, the electrolyte consists essentially of the liquid salt [P _6,6,6,14 ] [eFAP].

In a particularly preferred embodiment, the electrolyte is preconditioned, such as by contact with an aqueous hydroxide solution, prior to use. Without being bound by theory, by preconditioning, traces of OH ^- are introduced into the liquid salt, resulting in the defined proton activity of the electrolyte of the invention.

  The temperature range applied to the electrolyte material of the battery according to the invention may be -35 to 200 ° C, preferably 0 ° C to 150 ° C, most preferably 15 ° C to 130 ° C.

  The pressure range of application is typically from 0.7 bar nitrogen pressure to 100 bar nitrogen pressure, preferably from 1 bar to 30 bar, most preferably from 1 bar to 12 bar. The pressure can be continuous, ie constant, or always increase with time. Alternatively, the pressure may be discontinuous, ie pulsed with time, alternating between higher and lower pressure values within said range.

The combination of pressure and temperature causes the N ₂ solubility and electrochemical kinetics to rise, and ammonia can be selected to be generated near but below its aggregation point (eg at 25 ° C.) 10 bar or 40 bar at 79 ° C).

  Typically, continuous current is passed between the cathode working electrode and the counter electrode, but in some applications, such as a wind power solar panel powered drive process, intermittent or pulsed current is suitable It can be

Nanostructured Catalysts In a third aspect of the presently described embodiments, there is provided a catalyst for the electrochemical reduction of dinitrogen to ammonia. The catalyst is indicated by double layer capacity was determined by adjacent electrolyte layer, 0.1 mF / cm ^2, preferably above includes nanostructured materials having a high electrochemical activity surface area of 1 mF / cm ² greater.

  Preferably, the nanostructured catalyst comprises one or more metals in the form of elemental metals or inorganic compounds comprising metals. The nanostructured catalyst may be in the form of discrete particles or sheets or films or three dimensional structures. The nanostructured catalyst embodies morphological features that may be any shape having at least one dimension in the range of 1 nm to 1000 nm.

  Suitable metals include any of the transition or lanthanide metals including Fe, Ru, Mo, Cu, Pd, Ti, Ce and La and alloys thereof with other metals and metalloids.

  The metals mentioned above may be surface decorated with oxides or sulfides of the metal or complexes of the metal and its oxide or sulfide may be formed.

  The catalyst also contains a metal complex consisting of two metals bridged by sulfide. Preferably, the metals are Fe and Mo.

  The catalyst nanoparticle film can be prepared preferably by cyclic voltammetry or pulsed voltammetric electrodeposition method.

  In another preferred embodiment, the catalyst may comprise a conductive polymer material, such as PEDOT.

  In yet another preferred embodiment, the catalyst may comprise a doped carbon material, in particular N and / or S doped carbon.

  The catalyst is preferably supported or decorated on a conductive, chemically inert support. Suitable supports include fluorine-doped tin oxide, graphene, reduced graphene oxide, porous carbon, carbon cloth, carbon nanotubes, conductive polymers and porous metals.

Faraday efficiency is a notable defect of related processes of the prior art. Faraday efficiency can be used to represent a portion of the current utilized for the N ₂ reduction reaction. The remaining part, ie (100-Faraday efficiency)%, is consumed with unwanted side reactions including the formation of H ₂ and hydrazine. These by-products represent wasted energy and also require complex separation methods from the desired product. One of the objects of the present invention is to provide a process for the preparation of ammonia with relatively high Faraday efficiency.

  Other aspects and preferred embodiments are disclosed in the specification and / or defined in the appended claims and are part of the description of the invention.

In essence, embodiments of the present invention can improve the efficiency of ammonia production by selecting a specific non-aqueous electrolyte that increases the concentration of dissolved N ₂ gas, increasing the dinitrogen activity of the reduction reaction On the one hand, it derives from the recognition that it plays a role in certain homogeneous catalysis which reduces the rate of undesirable competing reactions such as H ₂ formation. The efficiency is further improved by using a specific nanostructured catalyst.

The advantages provided by the present invention compared to prior art processes include:
Conversion of dinitrogen to ammonia with high Faraday efficiency;
The reaction can be carried out at ambient temperature and pressure;
Greater solubility of dinitrogen in the electrolyte;
・ Increased activity of dinitrogen in reduction reaction;
Lower speed of undesirable competing reactions such as H ₂ production;
Water can be used as a source of hydrogen and hence does not require extra hydrogen;
-Suitable catalysts are cheap and available from abundant materials on earth;
・ The corrosiveness of the electrolyte is not high.

  Further scope of the applicability of embodiments of the present invention will become apparent from the following detailed description. However, since various changes and modifications within the spirit and scope of the present disclosure will be apparent to those skilled in the art from this detailed description, the detailed description and the specific examples illustrate preferred embodiments of the present invention, but are illustrative. It should be understood that only

Further disclosure, objects, advantages and aspects of the preferred and other embodiments of the present application will be better understood by those skilled in the art who made reference to the following description of the embodiments in conjunction with the accompanying drawings, which are by way of illustration only. It is not limited.
FIG. 1 is a schematic view showing a typical electrochemical cell for N ₂ reduction according to the present invention. FIG. 1 is a schematic of a hybrid electrode based N ₂ reduction battery according to the present invention. FIG. 3 is a schematic view of a stacked N ₂ reduction cell arrangement according to the invention showing the cells according to FIG. 2 stacked in series connection.

Abbreviations As used herein, abbreviations refer to the following chemical species:
B _{(OTFE) 4} - tetrakis (2,2,2-trifluoroethene Tano carboxymethyl) borate _{(B (OCH 2 CF 3)} 4)
C ₄ mpyr-butyl-methyl pyrrolidinium EMIM-ethylmethyl imidazolium eFAP-tris (perfluoroethyl) trifluorophosphate FSI-bis (fluorosulfonyl) imide ((FSO ₂ ) ₂ N)
HMIM-Hexylmethylimidazolium NfO-nonafluorobutanesulfonate (CF ₃ (CF ₂ ) ₃ SO ₃ )
NTf2-Bis (trifluoromethylsulfonyl) amide P _6,6,6,14 -trihexyltetradecylphosphonium P _1,4,4,4 -tributylmethylphosphonium PEDOT-poly (3,4-ethylenedioxythiophene)
Perfluorobutyl sulfonate (F ₉ C ₄ SO ₃ )
PFO-perfluorooctane sulfonate (F ₁₇ C ₈ SO ₃ )
PFB-perfluorobutyrate R _f -perfluoroalkyl- (CF ₂ ) _n-1 (CF ₃ ) (n = even number)

Detailed Description The invention will be further described with reference to the following non-limiting examples. These examples examine the electrocatalytic activity of new catalyst materials in liquid salt electrolytes.

  Also, examples illustrate the preparation of electrodes based on various metal nanostructures (nanoparticles or films) using chemical and electrodeposition methods and investigation of their electrocatalytic properties in electrolytes containing one or more liquid salts. I will illustrate. Using an electrolyte containing a liquid salt, dinitrogen was successfully converted to ammonia with> 60% Faraday efficiency at ambient temperature and pressure, which exceeds the room temperature efficiency of the prior art process.

The process of the present invention which utilizes a liquid salt based process not only can significantly increase the solubility of dinitrogen but also increases the activity of dinitrogen in the reduction reaction while at the same time making it desirable to produce H ₂ etc. Not play a role in certain homogeneous catalysis which lowers the rate of competing reactions.

Fe based N ₂ electroreduction catalyst films were prepared by electrodepositing Fe onto a commercially available fluorine-doped tin oxide or porous metal (or carbon) substrate. The fluorine-doped tin oxide coated glass is conductive and is ideal for use in a wide range of devices. Fluorine-doped tin oxide is relatively stable under atmospheric conditions, chemically inert, mechanically hard, heat resistant to high temperatures, and has high resistance to physical abrasion. Stainless steel mesh or cloth is useful as a high surface area substrate.

The deposited electrolyte consists of 10 mM FeSO ₄ , 10 mM NaOH and 10 mm citric acid. Electrodeposition was controlled by a potentiostat using a three-electrode system, using fluorine-doped tin oxide glass, Ti mesh, and saturated mercuric chloride electrode (SCE) as working, counter and reference electrodes, respectively. Typical electrodeposition of this type was performed using cyclic voltammetry method of -1.8V to -0.8V. A black, glossy film was formed after several cycles. Varying the number of cycles allows control of the thickness of the film, and a typical film is electrodeposited by 10 cycles at a scan rate of 20 mVs- ¹ .

  The films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), and electrochemical surface area (ECSA) measurements.

N ₂ cathodic reduction Electrochemical N ₂ reduction was performed in a three electrode system using Fe / fluorine doped tin oxide (or porous metal) electrode and platinum wire as reference and counter electrodes respectively. Cyclic voltammetry while measuring at a cell of one compartment, was N ₂ reduction at a cell separated by separating the counter electrode separated with a glass frit. A typical reduction was performed at -1.2 V vs Pt for 3 hours.

Before bubbling to the electrolyte, N ₂ gas was bubbled through a water trap to saturate the water. The synthetic ammonia carried at the outlet gas was captured by passing the gas stream through a weak acid solution (1 mM H ₂ SO ₄ ).

Product Analysis Ammonia produced in the gas phase was bubbled and recovered through a 1 mM H ₂ SO ₄ solution. The ammonia remaining in the ionic liquid after completion of the electrolytic reduction was extracted by washing the ionic liquid with 1 mM KOH. The total amount of ammonia is the sum of ammonia in the acid trap and the basic wash solution and was later quantified using the indophenol blue method.

In a typical analysis, 0.5 ml of 0.5 M sodium hypochlorite is added to a 0.5 ml aliquot solution, followed by 5% (by mass) salicylic acid and 5% (by mass) sodium citrate Was added, and 0.01 ml of 0.5% (by mass) sodium nitroferricyanide was added. After 2 hours, the absorption of the solution at 700 nm was measured with a UV-Vis spectrometer. Control experiments were performed to validate the analytical method by adding different concentrations of NH ₄ Cl to 1 mM H ₂ SO ₄ or 1 mM KOH solution.

6 electronic processes,
The induced current efficiency was calculated based on.

FIG. 1 is a schematic diagram showing a typical electrochemical cell for reduction of N ₂ according to the present invention, which cell comprises a power source (1), a cathode (2), a membrane (3) and an anode (4). And. The counter electrode reaction in the process may be water or hydroxide oxidation as shown. Alternatively, if desired the product is a fertilizer ammonium sulfate, the counter electrode reaction _may be _SO ^{4 -2} from ^{SO 3 -2.} The latter advantage is that the total energy cost of the process is lower than when oxygen is the cathode reaction product.

Battery In accordance with the present invention, a hybrid electrode based N ₂ reduction battery is described in the following paragraphs. The electrolytic cell is designed to optimally support the electrolysis when the reactant, which is one or more gases, has low solubility only in the electrolyte, and thus, three phases in the body of the hybrid electrode It is desirable to cause the reaction to occur in or near the area of the boundary (ie, the boundary between the electrode material, the gas phase and the electrolyte).

  The hybrid electrode of the invention preferably comprises a porous conductive electrode material, said electrode optionally having a surface area of high electrochemical activity and a gas access in the electrode body They are decorated with nanostructured catalysts to have a large number of pores that allow for both and electrolyte access.

In the present invention, the gas remains on one adjacent surface, and the pores of the hybrid electrode are at least partially filled with the ion conducting material, so that the migration of reactants and products is the NH ₂ N _{2 It} occurs in the area where reduction to ₃ occurs.

  This avoids one of the severe limitations of prior art electrodes designed to support gas diffusion in porous electrodes, and this diffusion process leads to undesirable overpotentials and inefficiencies of the operating cell. Give rise to sex.

  In this embodiment, the cathode working electrode is prepared by making a porous metal membrane and impregnating the porous structure with an ion conductive material such as NafionTM or NafionTM gel or gel-like liquid salt. Hybrid ion conducting electrodes or "electrode membranes". Decorating the cathode with an electrocatalyst creates a gas / electrolyte / metal three phase boundary region where electrolysis can occur.

  Reactive gases are introduced directly from the fluidizing gas into the electrocatalyst. Reactant or product ions diffuse through the electrolyte portion of the electrode membrane and gaseous products pass directly into the fluidizing gas phase.

  As shown in FIG. 2, the battery according to this embodiment consists of two porous electrodes (11, 12) separated by an electrolyte layer (13). The electrode 1 is a cathode working electrode where nitrogen is reduced and the electrode (12) is a counter electrode (anode) where water oxidation or other desirable oxidation takes place. Behind each electrode is a spacer layer (14, 15) that directs the gas into and out of the cell.

  The electrodes comprise a layer of flexible, porous, conductive electrode sheet material with an electrocatalyst (16), each loaded on a sheet and exposed directly to the gas layer (14, 15). Optionally, the catalyst (16) may be deposited through the structure of the electrode (11) to form multiple areas where the gas, electrolyte, catalyst and conductive electrode are in contact. The porosity of the conductor sheet is preferably such that the sheet is porous from one side to the other.

  The porous conductive electrode material may be a macro- or micro- or nano-porous metal such as stainless steel in the form of mesh, foam or wool, iron, nickel, copper, ruthenium or alloys thereof. Porous carbon materials comprising carbon cloth, carbon particles / binder composites, graphene and reduced graphene oxide and conductive polymers are also suitable as porous conductive electrode materials.

  Outer packaging surrounds the battery. In one form of battery, the battery is rolled or z-folded.

  In a further embodiment of the invention, the assembly is formed by a number of cells stacked in series. In this manner, the electrolytes in the battery layers (18) must be separated from one another, the package (17) is a conductive material, and thus a series connection occurs between the batteries. In addition, the laminated battery may be folded or rolled.

  The electrolyte may comprise a spacer or may be in the form of an electrolyte membrane, eg a polymer electrolyte, such as NafionTM or gel NationTM or gel liquid salt electrolyte, or in the battery field. Well known electrolytes impregnated in porous separators such as paper or CeleguardTM type materials.

  In one form of assembly, the layers (11, 13 and 12) are pressed together and then the electrolyte is gelled in situ to produce a self-adhesive assembly.

  The gas fluidized bed (14) has the function of enabling the introduction of a stream of flowing gas containing nitrogen and water vapor. The exhaust gas contains ammonia which is optionally trapped outside the cell.

  The gas fluidized bed (15) is designed to allow reaction of the gas or ingress and egress of products produced on the side of the cell, optionally with the introduction of a flow of air or other gas, to this gas Dilute and carry out of the battery. The gas fluidized bed (14, 15) is made using a highly porous separator or mesh, or by printing, or by creating a pattern on one or both sides of the layer (17).

  In a stacked battery assembly, gas may be introduced into any convenient location, including from the "end" of the longest dimension of the assembly, or from either side of the assembly. Each of these arrangements requires an alternating sealing arrangement of layers (17).

  The entire assembly is as small as 1 mm thick to maximize surface area and minimize the amount of electrolyte material needed.

Example 1 Preparation of Nanostructured Fe Catalyst The following example illustrates the preparation of a nanostructured catalyst suitable for use in the present invention. A fluorine-doped tin oxide electrode (5 × 5 mm) was provided in the electrochemical cell and connected as a cathode. Standard mercuric chloride electrode (SCE) functions as a reference electrode, and Ti mesh functions as a counter electrode. The electrolyte solution for the catalyst preparation include water, and 10 mM FeSO _4, and 10 mM NaOH, the 10mm citric acid.

  Electrodeposition of Fe was carried out by cycling the potential of the fluorine-doped tin oxide electrode at -0.8 to -1.8 V vs SCE, 20 mV / s for 10 cycles. The electrodeposited Fe nanostructured layer appeared as a porous black layer containing nanoparticles on fluorine doped tin oxide. The deposited material consists mainly of metallic Fe, in which partially oxidized iron (with 10% oxide) is homogeneously distributed. Iron oxide forms during the anodic part of the deposition cycle. The formation of iron oxide can control iron nano particle size. Iron oxide is at least partially reduced during the initial stages of use as a cathode for ammonia production. The Fe / iron oxide complex can increase catalytic activity by the synergy of the two oxidation states of iron.

The electrochemical surface area is determined by measuring the charging current of the bilayer at 0 V vs Pt by cyclic voltammetry at 5 mV / s at room temperature in butyl methyl pyrrolidinium eFAP liquid salt. The capacity of the ² mF / cm ² bilayer was measured under these conditions.

Example 2 Reduction of N ₂ with n [P _6,6,6,14 ] [eFAP] A fluorine-doped tin oxide electrode with an Fe electrocatalyst layer was provided as a cathode in an electrochemical cell. The electrolyte contained a liquid salt [P _6,6,6,14 ] [eFAP]. The electrolyte was preconditioned by shaking with 1 mm aqueous KOH prior to use. The aqueous solution was only sparingly soluble in liquid salt so that the excess solution could be removed as a separate layer in the separatory funnel.

Preconditioning can introduce trace amounts of OH ^- into the salt, resulting in defined proton activity in the electrolyte.

A counter electrode (Pt) was provided on the frit portion which also contained saturated liquid salt. The reference electrode is Pt. Dinitrogen gas was introduced into the cell at 10 ml / min using a bubbler to direct the N ₂ bubble onto the cathode. The dinitrogen was presaturated with water by bubbling through the low water vapor pressure solution.

Flowing from the cell, the exhaust gas containing unreacted dinitrogen and the reduction product were led to a further trap containing 1 mM H ₂ SO ₄ to capture the ammonia produced as NH ₄ ⁺ . At the end of the electrolysis, the solution was analyzed for ammonia.

  The electrolysis was carried out at a voltage of -1.0 to -2.0 V for 2 to 5 hours. At the end of the electrolysis, the electrolyte was washed three times with 1 mm KOH solution to extract any retained ammonia. Three washes were also analyzed for ammonia. The results were combined with the results from trap solution analysis. The Faraday efficiency was 73% (+/- 5%).

  The solution was also analyzed for hydrazine, but no hydrazine was detected (LOD = 5 μmol / L).

Example _3: Except for the [C 4 mpyr] that reduction electrolyte _{N 2} in [eFAP] is that contained the liquid salt _{[C 4 mpyr] [eFAP]} , N 2 as described in Example 2 The reduction was carried out. The Faraday efficiency in this case was 47% (+/- 5%).

Example _{4: [P 6,6,6,14]} Following the same procedure the reduction in Example 2 of _{N 2} at _{[F 9 C 4 SO 3]} , electrolyte, liquid salt _{[P 6,6,6,14]} It contained [F ₉ C ₄ SO ₃ ]. A constant current of 4 uA cm ^-2 was applied for 2 hours. Ammonia measurements showed that the Faraday efficiency for ammonia was 51%.

Example 5 Reduction of N ₂ in [P _6,6,6,14 ] [PFO] According to the same method as in Example 2, the electrolyte comprises a liquid salt [P _6,6,6,14 ] [PFO] It was. A constant current of 4 uA cm ^-2 was applied for 2 hours. Ammonia measurements show that the Faraday efficiency% for ammonia was 39%.

Example 6: Example of N ₂ reduced below using decomposition by ultrasound, by incorporating additional physical and / or chemical processes, illustrates that ammonia production is increased.

After the same procedure as in Example 2, the entire electrochemical cell was immersed in the solution bath of the ultrasonic crusher. -1.2 V vs 30min applied to the working electrode a constant potential of NHE, by applying a decomposition by ultrasound in an electrochemical cell, to promote _{N 2} reduction. In the presence of ultrasonic degradation, the current increased by about 125% compared to its previous value.

Example 7 Reduction of N _{2 in} the Presence of Molecular Liquid Components As mentioned above, the electrolyte can be combined with two or more salts to produce a liquid salt of the desired characteristics. In addition, the liquid salt may contain additional components including water or other molecular liquids exemplified by the following examples.

  Following the same procedure as in Example 3, trifluorotoluene 10% v / v was added as a further component to the electrolyte to reduce the viscosity of the liquid salt and to facilitate mass transport of the electrochemical reaction. A constant potential of -1.2 V vs NHE was applied for 30 minutes. The current was increased by 50% compared to the value in the absence of trifluorotoluene.

Example 8: [C ₄ mpyr] [perfluorobutane sulfonate]
[C ₄ mpyr] [perfluorobutane sulfonate] has an elevated melting point (112 ° C.) and may be used for N ₂ reduction at temperatures above this melting point. The melting point can also be lowered by the addition of the molecular liquid component described in Example 7.

Example 9: [C ₄ mpyr] [PFO]
[C ₄ mpyr] [PFO] has an elevated melting point (87 ° C.) and may be used for N ₂ reduction at temperatures above this melting point. The melting point can also be lowered by the addition of the molecular liquid component described in Example 7.

Example 10 Preparation and Use of an Electrolyte Comprising a Gel Membrane Containing a Liquid Salt As noted above, the electrolyte used in the present invention may be an electrolyte itself, such as NafionTM or a gelled liquid salt electrolyte, for example It may include a spacer or electrolyte membrane that is a polymer electrolyte, or an electrolyte immersed in a porous separator such as paper or CeleguardTM. The procedure described in Example 10 below, which is an example of preparation of a PVDF-HFP copolymer gel electrolyte membrane, can be used generally for the preparation of any gel membrane containing a liquid salt.

  A PVDF-HFP copolymer gel electrolyte membrane was prepared as follows using a liquid salt as described in Example 3. The liquid salt and copolymer were dissolved in dimethylformamide in a weight ratio of 9: 1 and heated slightly. The solution was spread onto a 34 mm diameter circle of SolupourTM membrane and left to dry. After drying, excess gel on the outside of the membrane was removed.

  The gas flow cell consisted of carbon paper / platinum plated carbon anode, membrane and Fe electrodeposited stainless steel mesh (400 mesh) cathode. Hydrogen gas was introduced to the anode side of the gas flow cell at a rate of 180 mL / min and nitrogen gas was passed to the cathode side. The pressure of the gas inside the battery was 1 atm. A constant potential of -1.2 V with respect to the anode was applied to the cathode for 30 minutes.

The gases flowing through the cell were mixed and bubbled through 40 mL of 1 mM H ₂ SO ₄ solution followed by 20 mL of 1 mM H ₂ SO ₄ solution. The gas was bubbled for a period of time during which the voltage was applied and for 30 minutes after it ended.

  Ammonia produced over 30 minutes of voltage application was 87.0 nmole, and the Faraday efficiency was 24.9%.

Example 11 Preparation and Use of a Gel Membrane Having a [C ₄ mpyr] [eFAP] Liquid Salt Suitable for Use as an Independent Membrane The mass ratio of liquid salt to polymer is 7: 3 and the solution is poured A membrane was prepared in the same manner as Example 10 except that an independent membrane was formed. Ammonia produced over a 30 minute voltage application was 59.5 nmole and the Faraday efficiency was 71.5%.

Example 12 Preparation and Use of NafionTM Gel Membrane with [C ₄ mpyr] [eFAP] Liquid Salt The electrolyte comprises a NafionTM-gel membrane, prepared as described in the following example A battery was constructed as described in Example 10, except as described.

A solution containing NafionTM and [C ₄ mpyr] [eFAP] in a 1: 9 mass ratio is supplied by Aldrich with 9 parts of [C ₄ in a lower aliphatic alcohol and water as supplied by Aldrich. Prepared by mixing mpyr] [eFAP] with 20 parts of a 5% w / w solution of Nafion. This was dropped onto a 34 mm diameter SolupourTM membrane and the membrane was completely coated with the solution. Thereafter, it was dried overnight in a 60 ° C. oven. The NafionTM-gel membrane was used to construct a gas flow cell between the cathode and the anode. The produced ammonia had a 93.1 nmole Faraday efficiency of 30.6%.

Example 13 Preparation and Use of a Separate Electrolyte Membrane Comprising a NafionTM Membrane with a Liquid Salt The cell as described in Example 11 except that the membrane was a NafionTM-gel membrane Configured. Membranes were prepared as follows. A 3: 7 mixture of NafionTM and liquid salt was prepared and drop cast as described in Example 12. Thereafter, it was dried overnight in a 60 ° C. oven.

  It will be apparent to those skilled in the art that further variations of the above-described cells can be constructed such as by removing SolupourTM as a support for the electrolyte membrane, or by using other supports.

Example _{14: [P 6,6,6,14]} Following the same procedure _{N 2} reduction Example 3 in _[PFB], was used _{[P 6,6,6,14] [PFB]} Liquid salt electrolyte . A constant potential of 0.8 V vs NHE was applied for 3 hours. The Faraday efficiency for ammonia formation in this system was 18%.

Example 15: Following the same procedure as N ₂ reduction Example 3 in Ru catalyst was deposited ruthenium film onto the working electrode. A constant potential of -0.8 V vs NHE was applied to the working electrode for 30 minutes. The current density was about twice that of Example 3. Ammonia measurements show that the Faraday efficiency for ammonia formation in this system was 28%.

Use of Other Electrode Substrates Because the N ₂ reduction current obtained with planar fluorine-doped tin oxide glass substrates is too small to be practical, using various high surface area and porous substrates such as nickel foam, stainless steel mesh, etc. And acted, increased the surface area of the electrochemical. The current density is increased for the use of porous substrates, for example, when the current is less than 0.012 A.D. with fluorine-doped tin oxide. m- ² to 0.1 A. with stainless steel mesh. m ^-2 , 0.25A with nickel foam. It increases to m- ² and the corresponding Faraday efficiencies are 59% and 45% respectively. Due to the increase of the current, the production rate is 2.9 mg. 14 mg. on a stainless steel substrate from m ^-2 h ^-1 . It greatly increases to m ⁻² h ⁻¹ . The stainless steel cathode used here is very thin and flexible, thus further increasing the yield by optimizing the cathode thickness and implementing a high surface area, thin layer or spiral type cell construction It is important to note that there is a considerable range.

The [C ₄ mpyr] [eFAP] liquid salt produces a higher current, as compared to [P _6,6,6,14 ] [eFAP]. This is probably due to the lower viscosity and promotes better mass diffusion during the reaction. The Faraday efficiency for N ₂ reduction at the stainless steel electrode in [C ₄ mpyr] [eFAP] is only slightly lower, and the N ₂ solubility of this ionic liquid is 0.28 mg / g 0.28 mg / g [P _{6 , 6, 6, 14} ] [eFAP] as much as possible. Nevertheless, the yield is higher at [C ₄ mpyr] [eFAP].
[00100]
The reason for the high solubility of N ₂ in selected ionic liquids was further investigated by DFT calculations. The interaction of various common anions with N ₂ is relatively weak with ions such as Cl ⁻ and fluorinated anions such as BF ₄ ⁻ and PF ₆ ⁻ . On the other hand, the interaction with [eFAP] is exceptionally strong.
[00101]
Without being bound by theory, two modes can be distinguished in the calculation, the first clearly indicating the interaction of N ₂ with the F atom bound to the alkyl chain, while the second Have an interaction of N ₂ with the phosphorus-bonded F atom, the latter being a stronger interaction. From all these calculations it can be seen that the stronger delocalized charge is on the adjacent group and the interaction of the N ₂ bond is stronger. The EFAP complex of the binding energy and PF ₆ ^- as the difference is remarkable in the case of EFAP, additional delocalization of the charge onto three _C 2 _{F 5} groups, the charge on P binding fluorine adjusted, thereby facilitating the interaction with the N _2. Introduced in the cation and these calculations it is shown that the interaction becomes stronger due to the additional charge interaction between the anion and the cation.

Comparative Examples The prior art contains a general disclosure of the use of electrolytes containing liquid salts, but many of these electrolytes are inadequate and / or the Faraday efficiency in the reduction of dinitrogen according to the method of the invention is Unfavorably low.

  This can be illustrated, for example, with reference to US Patent Application Publication No. 2016/0138176 (Yoo et al.). US Patent Application Publication No. 2016/0138176 describes a method of synthesizing ammonia using an electrolytic cell containing an aqueous or liquid electrolyte of a specific alkali metal (salt) or ionic liquid . In particular, Comparative Examples 16 and 17 relate to the salts disclosed in US Patent Application Publication No. 2016/0138176, but in the method of the present invention, the salt of Comparative Example 16 results in an unfavorably low Faraday efficiency. On the other hand, the salt of Comparative Example 17 becomes unstable.

  Comparative Example 18 more generally illustrates that certain ionic salts become unstable and therefore unsuitable when used in the methods of the present invention.

Comparative Example 16: [HMIM] include [NTf _2] reducing liquid salt of _{N 2} in the electrolyte [HMIM] [NTf _2], except that the working electrode using a catalyst of Example 1, Example 2 N ₂ reduction was performed as described. [HMIM] [NTf ₂ ] can be considered as an ionic liquid, as it is widely considered as a salt with a melting point <100 ° C. The reduction was carried out in the liquid state at 70 ° C., since the melting point of this salt is about 70 ° C.

  The Faraday efficiency in this case was only 0.64%.

Comparative Example 17 Reduction of N ₂ with [EMIM] [B (CN) ₄ ] Electrolyte contains liquid salt [EMIM] [B (CN) ₄ ], except that the working electrode uses the catalyst of Example 1 Carried out the N ₂ reduction as described in Example 2.

The apparent Faraday efficiency in this case was only 14%. However, the same apparent Faraday efficiency was measured when argon gas feed was used instead of N ₂ feed. In the latter case, ammonia is formed by decomposition of the electrolyte containing the liquid salt, since ammonia is not produced from N ₂ supplied, and such a liquid group containing a cyano group is used as the electrolyte, The liquid salt shows to be not stable to reduction under these conditions.

Comparative Example 18: Reduction of N ₂ with [EMIM] [eFAP] The procedure described in Example 2 except that the electrolyte comprises the liquid salt [EMIM] [eFAP] and the working electrode used the catalyst of Example 1. N ₂ reduction was performed as usual.

Ammonia production measurements show that both argon-saturated and N ₂ -saturated electrolytes produce ammonia (or detectable amines) with a% Faraday efficiency of 35% and 16%, respectively. Indicates that. This indicates that the ionic liquid decomposes during electrolysis to form an amine product and ammonia. Thus, this liquid salt is not suitable for nitrogen reduction to ammonia.

  While the invention has been described in conjunction with specific embodiments thereof, it will be appreciated that further modifications are possible. The present application generally follows the essence of the present invention, is within the practice known or routine within the field to which the present invention pertains, and includes such developments from the present disclosure which may be applied to the essential features described above. It is intended to include any variations, uses or modifications.

  Because the invention can be embodied in several forms without departing from the spirit of the essential features of the invention, the above embodiments are not intended to limit the invention unless otherwise specified. Rather, it should be interpreted broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects only as illustrative and not restrictive.

  Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the present invention and the appended claims. Accordingly, the specific embodiments are to be understood as illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function close is intended to cover not only structures that perform the defined function and structural equivalents, but also equivalent structures.

  "Comprises / comprising" and "includes / including" as used herein identify the presence of the stated feature, integer, step or component, but one or more It is not intended to exclude the presence or addition of other features, integers, steps, components or groups thereof, and thus unless the context clearly dictates otherwise, throughout the specification and claims. ',' Including ',' includes ',' including 'etc., as opposed to exclusive or exhaustive meaning, have an inclusive meaning, ie,' including, but not limited to not limited to) should be interpreted.

Claims (51)

(1) contacting a cathode working electrode and a counter electrode comprising a nanostructured catalyst with an electrolyte comprising one or more liquid salts;
(2) introducing a source of dinitrogen and hydrogen into the electrolyte;
The liquid salt is
(I) PR _1-4 , NR _1-4 , C ₄ H ₈ NR _{2 wherein} the R groups are each independently linear, branched or cyclic, and preferably contain 1 to 18 carbon atoms , Optionally partially or completely halogenated, optionally containing heteroatoms, optionally, preferably, ethers, alcohols, carbonyls, thiols, sulfoxides, sulfonates, amines, azos or It contains a functional group selected from nitriles, and two R groups may combine to form a single ring or a heterocyclic ring)
A cation selected from the group consisting of
_{(Ii) (RO) x PF} 6-x, (RO) x BF 4-x, R'SO 2 NSO 2 R ', R'SO 2 C (SO 2 R') (SO 2 R '), FSO 2 NSO ₂ F, C ₂ O ₄ BF ₂ , C ₂ O ₄ PF _4, RC ₂ O ₄ BF ₂ , RC ₂ O ₄ PF _4, CF ₃ SO ₃ , R'SO ₃ , R'CO ₂ , CF ₃ COO , R ′ _x PF _6-x , R ′ _x BF _4-x (wherein each R ′ group is independently linear, branched or cyclic, preferably contains 1 to 18 carbon atoms, and is optional Optionally, partially or completely fluorinated, optionally comprising a functional group preferably selected from ether, alcohol, carbonyl, thiol, sulfoxide, sulfonate, amine, azo or nitrile, 2 R 'groups combine to form a single or heterocyclic ring Formed by a combination of anion selected from the group consisting of may also.) Which was,
A method of electrochemical reduction of dinitrogen to ammonia, characterized in that dinitrogen is reduced to ammonia at the cathode working electrode. The liquid salt is
(I) a cation selected from the group consisting of C ₄ mpyr, P _6, 6, 6, _14, P (C ₂ R _fn ) ₄ (wherein R _f is a perfluoroalkyl moiety),
_{(Ii) eFAP, NfO, PFO} , FSI, NTf 2, B (otfe) 4 and _CF 3 The method of claim 1 formed by the combination of the anion selected from the group consisting of COO. The method according to claim 1, wherein the liquid salt is [P _6,6,6,14 ] [eFAP]. The method according to claim 1, wherein the liquid salt is [C ₄ mpyr] [eFAP]. The method according to claim 1, wherein the liquid salt is [P _{6, 6,} 6, ₁₄ ] [F ₉ C ₄ SO ₃ ]. The method according to claim 1, wherein the liquid salt is [P _6,6,6,14 ] [PFO]. The method of claim 1 wherein the liquid salt is _[C 4 _{mpyr] [perfluorobutane} sulfonate. The method according to claim 1, wherein the liquid salt is [C ₄ mpyr] [PFO].   The method according to claim 1, further comprising the step of raising the temperature of the electrolyte to between -35 ° C and 200 ° C, preferably between 0 ° C and 150 ° C, more preferably between 15 ° C and 130 ° C.   The method according to claim 1, further comprising the step of applying a pressure of 0.7 bar nitrogen to 100 bar nitrogen, preferably 1 bar to 30 bar, most preferably 1 bar to 12 bar to the electrolyte.   11. The method of claim 10, wherein the pressure is pulsed.   The method of claim 1, wherein the current passing between the cathode working electrode and the counter electrode is intermittent.   The method of claim 1, further comprising the step of applying ultrasonic frequency energy to the electrolyte.   The method of claim 1, further comprising the steps of humidifying dinitrogen gas and flowing humidified dinitrogen gas onto the cathode working electrode.   The method of claim 1, wherein the electrolyte further comprises a membrane.   The method according to claim 15, wherein the membrane is selected from a polymer electrolyte, a gelled ionic liquid electrolyte or a porous separator. A cathode working electrode comprising a nanostructured catalyst for the reduction of dinitrogen;
A counter electrode,
An electrolyte comprising one or more liquid salts in contact with the working electrode,
The liquid salt is
(I) PR _1-4 , NR _1-4 , C ₄ H ₈ NR _{2 wherein} the R groups are each independently linear, branched or cyclic, and preferably contain 1 to 18 carbon atoms , Optionally partially or completely halogenated, optionally containing heteroatoms, optionally, preferably, ethers, alcohols, carbonyls, thiols, sulfoxides, sulfonates, amines, azos or nitriles A cation selected from the group consisting of a functional group selected from: and two R groups may be combined to form a single ring or a heterocyclic ring);
_{(Ii) (RO) x PF} 6-x, (RO) x BF 4-x, R'SO 2 NSO 2 R ', R'SO 2 C (SO 2 R') (SO 2 R '), FSO 2 NSO ₂ F, C ₂ O ₄ BF ₂ , C ₂ O ₄ PF _4, RC ₂ O ₄ BF ₂ , RC ₂ O ₄ PF _4, CF ₃ SO ₃ , R'SO ₃ , R'CO ₂ , CF ₃ COO R ′ _x PF _6-x (FAP), R ′ _x BF _4-x (wherein the R ′ groups are each independently linear, branched or cyclic, preferably 1 to 18 carbon atoms Containing, optionally partially or completely fluorinated, optionally containing a functional group preferably selected from ether, alcohol, carbonyl, thiol, sulfoxide, sulfonate, amine, azo or nitrile And two R ′ groups are combined to form a single ring or multiple rings. Dinitrogen electrochemical reduction battery of the ammonia being formed from a combination of anion selected from the group consisting of may form a ring.). The liquid salt is
(I) a cation selected from the group consisting of C ₄ mpyr, P _6,6,6,14 and P (C ₂ R _fn ) ₄ (wherein R is a perfluoroalkyl moiety),
_{(Ii) eFAP, NfO, PFO} , FSI, NTf 2, B cell according to claim 17 formed by the combination of the anion selected from the group consisting of _{(OTFE) 4} and _CF 3 COO. The battery according to claim 17, wherein the liquid salt is [P _6,6,6,14 ] [eFAP]. The battery according to claim 17, wherein the liquid salt is [C ₄ mpyr] [eFAP]. The battery according to claim 17, wherein the liquid salt is [P _{6, 6,} 6, ₁₄ ] [F ₉ C ₄ SO ₃ ]. The battery according to claim 17, wherein the liquid salt is [P _6, 6, 6, ₁₄ ] [PFO]. The battery according to claim 17, wherein the liquid salt is [C ₄ mpyr] [perfluorobutane sulfonate]. The battery according to claim 17, wherein the liquid salt is [C ₄ mpyr] [PFO].   A battery assembly formed by stacking two or more of the batteries according to claim 17 or 18 in series.   The battery according to claim 17, further comprising heating means for maintaining the temperature of the electrolyte at -35 ° C to 200 ° C, preferably 0 ° C to 150 ° C, more preferably 15 ° C to 130 ° C.   18. A battery according to claim 17, comprising pressing means for applying a pressure of 0.7 bar nitrogen to 100 bar nitrogen, preferably 1 bar to 30 bar, most preferably 1 bar to 12 bar to the electrolyte.   18. The battery of claim 17, wherein the battery is configured to pass an intermittent current between the cathode working electrode and the counter electrode.   The battery of claim 17 further comprising a humidifier for humidifying dinitrogen gas, configured to flow a stream of humidified dinitrogen gas onto the cathode working electrode.   18. The battery of claim 17, wherein the electrolyte comprises a membrane.   The battery according to claim 17, wherein the membrane is selected from a polymer electrolyte, a gelled ionic liquid electrolyte or a porous separator.   The battery of claim 17 including an ultrasound source that applies ultrasonic frequency energy to the electrolyte.   18. The cell of claim 17, wherein the reduction of dinitrogen to ammonia occurs in a region adjacent to the three phase boundary on the working surface of the cathode working electrode.   The cell of claim 17 wherein a nanostructured electrocatalyst is adjacent to the outer surface of the cathode working electrode resulting in a gas / electrolyte / metal three phase boundary region where electrolysis mainly occurs. Comprises nanoparticles were measured in the adjacent electrolyte layer, 0.1 mF / cm ^2, preferably above characterized in that it has a high electrochemical active surface area indicated by the double layer capacitance of 1 mF / cm ² than Nanostructured catalyst for the electrochemical reduction of dinitrogen to ammonia.   36. The nanostructured catalyst according to claim 35, comprising nanoparticles of one or more metals selected from transition metals or lanthanide metals, including inorganic compounds thereof.   37. The nanostructured catalyst of claim 36, wherein the one or more metal nanoparticles are supported on a conductive, chemically inert support.   Dinitrogen solubility of at least 100 mg / L, more preferably more than 200 mg / L, most preferably more than 400 mg / L at battery operating temperature and pressure, less than 5 wt%, more preferably less than 2% at battery operating temperature and pressure An electrolyte for the electrochemical reduction of dinitrogen to ammonia according to the process of claim 1, characterized in that it comprises one or more salts, most preferably having a water solubility of less than 1%.   39. The electrolyte of claim 38, further comprising a membrane.   40. The electrolyte according to claim 39, wherein the membrane is selected from a polymer electrolyte or a blend of a polymer electrolyte and a liquid salt, or a gelled liquid salt electrolyte, or an electrolyte immersed in a porous separator.   39. The method according to claim 38, further comprising a molecular liquid present in the liquid salt medium at a concentration of 90 vol% to 0.1 vol%, more preferably 20 vol% to 0.2 vol%, most preferably 50 vol% to 0.5 vol%. Electrolyte.   Dimethyl sulfoxide, tetraglyme and other oligo-, present in the liquid salt medium at a concentration of 90 vol% to 0.1 vol%, more preferably 20 vol% to 0.2 vol%, most preferably 50 vol% to 0.5 vol% 39. The electrolyte of claim 38, further comprising a molecular liquid selected from poly-ethers, glutaronitrile and other high boiling point nitriles, trifluorotoluene.   It has a hybrid structure including a porous conductive electrode material and a nanostructured catalyst, and is configured to allow both gas and electrolyte access within the body of the electrode and the electrochemically active surface area An electrode for the electrochemical reduction of dinitrogen to ammonia according to the method of claim 1 having a large number of pores.   44. The electrode of claim 43, wherein the holes are at least partially filled with an ion conductive material.   An electrode for the electrochemical reduction of dinitrogen to ammonia according to the method of claim 1, which is a membrane comprising a porous metal or carbon impregnated with a catalytic material or a gelled liquid salt. An electrolyte membrane comprising a thin layer of material in combination with one or more liquid salts, for use in the battery according to claim 1, wherein the liquid salt is
(I) PR _1-4 , NR _1-4 , C ₄ H ₈ NR _{2 wherein} the R groups are each independently linear, branched or cyclic, and preferably contain 1 to 18 carbon atoms , Optionally partially or completely halogenated, optionally containing heteroatoms, optionally from preferably an ether, alcohol, carbonyl, thiol, sulfoxide, sulfonate, amine, azo or nitrile A cation selected from the group consisting of selected functional groups, and two R groups may be combined to form a single ring or a heterocyclic ring);
_{(Ii) (RO) x PF} 6-x, (RO) x BF 4-x, R'SO 2 NSO 2 R ', R'SO 2 C (SO 2 R') (SO 2 R '), FSO 2 NSO ₂ F, C ₂ O ₄ BF ₂ , C ₂ O ₄ PF ₄ , RC ₂ O ₄ BF ₂ , RC ₂ O ₄ PF ₄ , CF ₃ SO ₃ , R'SO ₃ , R'CO ₂ , CF ₃ COO , R ′ _x PF _6-x , R ′ _x BF _4-x (wherein each R ′ group is independently linear, branched or cyclic, preferably contains 1 to 18 carbon atoms, and is optional Optionally partially or completely fluorinated, optionally comprising a functional group preferably selected from ether, alcohol, carbonyl, thiol, sulfoxide, sulfonate, amine, azo or nitrile, two R 'groups are combined to form a single or heterocyclic ring Electrolyte membrane characterized in that it is formed by a combination of anion selected from the group consisting of may also.) To.   47. The electrolyte membrane of claim 46, wherein the thin layer of material is selected from the group comprising polymers, gels or porous separator materials.   47. The electrolyte membrane of claim 46, wherein the liquid salt is combined with a polymer.   47. The electrolyte membrane of claim 46, wherein the liquid salt is combined with a gel.   47. The electrolyte membrane of claim 46, wherein the liquid salt is combined with a porous separator.   The electrochemical reduction of dinitrogen to ammonia according to claim 1 carried out using the electrochemical cell according to claim 17, the nanostructured catalyst according to claim 35 and the electrolyte according to claim 38 Method.