KR20180112798A - Method and cell for converting nitrogen dioxide into ammonia - Google Patents

Abstract

The present invention relates to a method for reduction of dinitrogen to ammonia and to an electrochemical cell comprising a cathode working electrode comprising a nanostructured catalyst, a counter electrode and an electrolyte. The present invention comprises introducing a heterogeneous and hydrogen source into the electrolyte, wherein the heterogeneous is reduced to ammonia at the cathode working electrode. The electrolyte comprises at least one liquid salt formed from a combination of a specified set of cations and a specified set of anions.

Description

Method and cell for converting nitrogen dioxide into ammonia

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

In one aspect, the present invention relates to cathodic reduction of nitrogen.

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

It is understood that the discussion of documents, apparatus, acts or knowledge herein is included to illustrate the context of the present invention. In addition, throughout this specification, such discussion arises due to realization of the inventor and / or identification of problems of the related art by the present inventors. Further, discussion materials such as literature, apparatus, acts or knowledge herein are included to illustrate the context of the present invention in the light of the present inventor's knowledge, and such discussion is therefore not intended to limit the scope of the present disclosure Days or prior to that date, in Australia or elsewhere, to form part of the general knowledge common to the prior art level or related art.

Ammonia production is a high energy intensive process that consumes 1 to 3% of the world's electrical energy and about 5% of the world's natural gas production. Global production is currently around 200 million tonnes annually, reflecting the vast needs of these chemicals in agriculture, drug manufacturing and other industrial processes.

Ammonia is also considered as a non-carbon solar energy storage material because of its useful properties as a chemical energy carrier. Compared to other chemicals (such as hydrogen) that can be used to store solar energy, ammonia is safe, environmentally friendly, and most importantly, does not release CO ₂ . When stored in this form, energy is easily recovered through the ammonia fuel cell.

For over a hundred years, ammonia has been produced from both nitrogen and hydrogen in the presence of iron-based catalysts at high pressure and elevated temperatures according to the following reaction:

식 1

Equation 1

This process, known as the Haber-Bosch process, was critical to the production of low-cost fertilizers that supported large world population growth over the past century. The Haber-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.

Given the need to feed the growing world population and the need to reduce global carbon emissions, it is highly desirable to break the link between industrial nitrogen fertilizer production and the use of fossil fuels. Therefore, attention is focused on alternative routes to ammonia synthesis.

The ideal system for conversion of dinitrogen to ammonia is economically feasible, easily scalable, will operate in ambient conditions, and will be combined with renewable energy sources such as wind, hydro, or solar. An electrochemical approach can potentially accomplish this purpose. Electrochemical reduction process is used, and involves a heterogeneous predetermined gas as a starting material, a variety of water-based electrolyte, or H ₂ gas as a source of H ^+. The electrochemical reduction of heterogeneous species depends mainly on the structure, composition and surface morphology of the electrochemical catalyst (van der Ham et al., Chemical Society Reviews 43 , 5183-5191 (2014)).

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

By using a cell based on a membrane electrode assembly having a Pt electrode, Lan et al produced ammonia from air and water at 1.14 x 10 ^-5 mol.m ^-2 s ^-1 at ambient temperature and pressure and a total cell voltage of 1.6 V (Lan et al, Scientific Reports 3, (2013)).

Ammonia was also produced using a mixture of N ₂ and steam in a molten hydroxide suspension of nano-Fe ₂ O ₃ at a cell voltage of 1.2 V and a Coulomb efficiency of 35% (Licht et al. Science 345 , 637-640 (2014). These developments have great prospects for competition with the current ammonia industry processes, but the high temperatures used (~ 200 ° C) still require significant heat and energy inputs. To date, electrochemical conversion has not been successful enough to be considered a viable replacement for the Haber-Bosch process. In addition, the prior art electrochemical conversion has not reached a sufficiently high level of efficiency as indicated by heterozygous-fixing bacteria (Rosca et al, Chemical Reviews , 2009 , 109, 2209-2244).

U.S. Patent Application Nos. 2006/0049063 and 6,712,950 disclose a process for the preparation of a fuel cell from a nitrogen-containing species or a heterogeneous gas in a non-aqueous liquid electrolyte, such as a molten salt or an ionic liquid, Teach synthesis of ammonia gas. The process involves the production of N ₃ ^- ions in the electrolyte and the production of ammonia by the reaction of N ₃ ^- ions at the anode. The process is limited by the need for the medium to be selected such that it can dissolve a useful amount of N < ₃ > ^- to support realistic ammonia production rates.

U.S.A. Patent No. 2016/0138176 (Yoo et al) describes a method of synthesizing ammonia using an electrolytic cell containing an aqueous or alkali metal (salt) or liquid electrolyte of an ionic liquid. The disclosure encompasses the teaching of the use of electrolytes having various cations and anions (many of which do not form liquid salts) and some of which have limited stability and availability for ammonia synthesis efficiency.

Thus, there is a continuing need to identify new electrolytes and improved methods for reducing cathode isotopes that result in ammonia synthesis.

In contrast to hydrogen evolution or CO ₂ reduction, very few prior art electrocatalysts or photocatalysts have been reported to exhibit useful activity for N ₂ reduction. Little is known about the requirements or possible mechanisms for such a reaction. However, in order to be commercially feasible, it is known that the electrochemical conversion of heterogeneous nitrogen must overcome the difficulty presented by the high stability and chemically inert nature of the heterogeneous nitrogen.

So far, catalyst development has been focused on catalysts for thermal synthesis of ammonia. Currently, electrocatalysts for ammonia synthesis have been limited to conductive polymers (Koleli, F. & Ropke, T. Applied Catalysis B-Environmental 62 , 306-310, (2006)), meso Ni-Cu alloy (Licht et al. Science 345, 637-640 (2014)), and commercial Pt / C catalysts (Lan et al, Scientific Reports 3, (2013)).

Metallic nano-catalysts have been extensively used for fuel cell and CO ₂ reduction. The performance of nanocatalysts is well known to depend on their particle size, morphology and crystal structure.

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

Prior art electrocatalysts typically do not have sufficient efficiency, catalytic activity, and stability for heterogeneous reduction. In addition, the low solubility (20 mg / L, 20 DEG C, 1 bar) of dioxin in water results in the low reaction rate reported in the prior art.

Summary of the Invention

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

It is another object of the present invention to provide an electrochemical cell suitable for an electrochemical process for reducing cathode isotopes.

It is another object of the present invention to provide an improved method for reducing cathode isotopes.

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

It is an object of embodiments described herein to overcome or alleviate at least one of the noted drawbacks of the related art systems, or at least provide a useful alternative to the related art systems.

In a first aspect of an embodiment described herein, there is provided a cell for electrochemical reduction of dinitrogen with ammonia,

A cathode working electrode comprising a nanostructured catalyst for the reduction of nitrogen,

- a counter electrode, and

An electrolyte comprising at least one liquid salt in contact with said working electrode

/ RTI >

The liquid salt

(i) a cation selected from the group consisting of PR _1-4 (phosphonium), NR _1-4 (tetraalkylammonium), C ₄ H ₈ NR ₂ (pyrrolidinium), wherein each R group is independently Linear or branched, linear, branched, or cyclic, preferably containing from 1 to 18 carbon atoms, optionally partially or fully halogenated, optionally comprising heteroatoms, optionally and preferably comprising an ether, an alcohol, a carbonyl (acetate) A sulfoxide, a sulfonate, an amine, an azo or a nitrile, wherein two R groups may combine to form a monocyclic or heterocyclic ring; And

(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 (Tree plate). R'SO ₃ (sulfonate). R'CO ₂ (carboxylate). CF ₃ COO (trifluoroacetate). An anion selected from the group consisting of R ' _x PF _6-x (FAP), R' _x BF _4-x wherein each R 'group is independently linear, branched or cyclic, Includes a functional group selected from an ether, an alcohol, a carbonyl (acetate), a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, optionally containing a carbon atom and optionally partially or completely fluorinated, R ' groups may be joined to form a monocyclic or heterocyclic ring)

As shown in FIG.

In a preferred embodiment, the liquid salt is _selected from the group consisting of C ₄ mpr (butyl-methylpyrrolidinium), P _6,6,6,14 (trihexyltetradecylphosphonium), P (C ₂ R _fn ) ₄ wherein R _{and f} is perfluoroalkyl); And _{eFAP (C 2 F 5 PF 3} ), NfO ( in nano-fluoro-butane sulfonate), PFO (perfluoro octane sulfonate), FSI (bis (sulfonyl fluorophenyl) imide), NTf ₂ (bis (tri (Trifluoromethylsulfonyl) imide), B (otfe) ₄ (tetrakis (2,2,2-trifluoroethane) borate) and CF ₃ COO (trifluoroacetate) As shown in FIG.

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 is selected from the group consisting of RSO ₃ (sulphonate), in particular perfluorobutanesulfonate or perfluoropropanesulfonate, or trifluorophosphate, especially eFAP (tris) perfluoroethyl) trifluoro Phosphate). ≪ / RTI >

In another preferred embodiment, the cation and / or anion of the liquid salt is fluorinated or perfluorinated.

It is particularly preferred for said liquid salt to have a relatively high solubility in nitrogen (for example, as compared to prior art liquid salts such as imidazolium salts and nitrile anions such as dicyanamides).

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

Typically, the nanostructured electrochemical catalyst is applied to the working surface of the cathode working electrode to form a gas / electrolyte / metal three-phase boundary region where electrolysis predominates.

The electrolysis cell may include other features well known to those skilled in the art for performing the electrolysis reaction and for controlling the inter-electrode current. For example, the electrolysis cell may be adjusted to adjust the operating temperature or pressure using well known means such as a heater, a cooling device or a pressurizing means. In addition, the cell may comprise an ultrasonic generator for generating a sound wave of energy greater than 20 kHz.

The electrolytic cell preferably includes a gas fluidized bed that is operable to introduce into a cell of a gas stream comprising nitrogen and hydrogen or water vapor, and to permit the discharge of a gas containing ammonia. Ammonia is optionally collected outside the cell.

In a further embodiment, an assembly may be formed when two or more cells according to the present invention are stacked in series. The one or more stacked cells may also be folded or rolled. Gas may be introduced at any convenient location, including from the " end " of the longest dimension of the assembly or from both sides of the assembly.

In a second aspect of the embodiments described herein, there is provided a method of electrochemical reduction of dinitrogen with ammonia,

(1) contacting a cathode working electrode comprising a nanostructured catalyst with an electrolyte comprising at least one liquid salt,

- wherein said liquid salt is

(i) a cation selected from the group consisting of PR _1-4 (phosphonium), NR _1-4 (tetraalkylammonium), C ₄ H ₈ NR ₂ (pyrrolidinium), wherein each R group is independently Linear or branched, linear, branched, or cyclic, preferably containing from 1 to 18 carbon atoms, optionally partially or fully halogenated, optionally comprising heteroatoms, optionally and preferably comprising an ether, an alcohol, a carbonyl (acetate) A sulfoxide, a sulfonate, an amine, an azo or a nitrile, wherein two R groups may combine to form a monocyclic or heterocyclic ring; And

(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 (Tree plate). R'SO ₃ (sulfonate). R'CO ₂ (carboxylate). CF ₃ COO (trifluoroacetate). An anion selected from the group consisting of R ' _x PF _6-x (FAP), R' _x BF _4-x wherein each R 'group is independently linear, branched or cyclic, Includes a functional group selected from an ether, an alcohol, a carbonyl (acetate), a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, optionally containing a carbon atom and optionally partially or completely fluorinated, R ' groups may be joined to form a monocyclic or heterocyclic ring)

, ≪ / RTI > and

(2) introducing a heterogeneous and hydrogen source into the electrolyte

Lt; / RTI >

The nitrogen is reduced to ammonia at the cathode working electrode.

The method may further comprise collecting ammonia produced in the cathode working electrode and separating ammonia from other liquids and gases present using a separation trap or separator.

Typically, the nitrogen is reduced to ammonia at the cathode working electrode in the presence of a hydrogen source, preferably hydrogen gas or water. In a particularly preferred embodiment of the method, the heterogeneous gas is humidified to a degree controlled by water vapor, and then humidified gas is passed through the cathode in which the nitrogen is electrochemically reduced to form ammonia.

Typically, when the hydrogen source is water, the anode counter electrode converts the 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 separator material. In other embodiments, the counter electrode may be disposed in a compartment that optionally includes another electrolyte medium, such as an aqueous solution.

The counter electrode reaction may be another favorable oxidation reaction such as water oxidation or sulfurous acid 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 an electrolyte membrane (which may serve as electrolyte itself), for example a polymer electrolyte, such as a Nafion ^TM or Nafion ^TM liquid salt blend, or a gelled liquid salt electrolyte, Electrolyte immersed in a porous separator such as Celeguard ^TM .

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

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

Liquid salt

The term liquid salt as used herein is intended to refer to an electrolyte medium which is liquid at the use temperature and contains one or more salts, each of which may be a solid or liquid in pure state. The salts may be selected from any suitable metal salt, organic salt, protic salt, complex salt, and the like.

The liquid salt medium may also be formed by mixing solid salts to form a liquid salt of the desired characteristics.

The liquid salt medium may contain additional components including water or other molecular liquids compatible with the liquid salt electrolyte. As will be understood by those skilled in the art, such materials include dimethylsulfoxide, tetraglyme and other oligo- and poly-ethers, glutaronitrile and other high boiling nitriles, trifluorotoluene and other wholly or partially fluorinated solvents and propylene Carbonates and other carbonate solvents. When the molecular components of the volatile liquid, N ₂ gas stream by bubbling through a vessel of the injection solvent prior to passing into the reduction cell, the gas stream may be pre-saturated, and; Any molecular liquid that passes out of the cell in the product gas stream can be condensed or captured for reuse. Preferably, the molecular liquid is fluorinated or perfluorinated. Preferably, the molecular liquid is present in the liquid salt medium at a level of from 90% by volume to 0.1% by volume, more preferably from 20% by volume to 0.2% by volume, most preferably from 50% by volume to 0.5% by volume.

An electrolyte comprising a liquid salt provides an ion conducting, low moisture content medium in which process reactions occur. The electrolyte of the present invention also provides low or no volatility advantages, and some gases are more soluble in the electrolyte, including liquid salts, than in water. In particular, some electrolytes, including liquid salts, have increased solubility for N ₂ gas (compared to aqueous and other electrolytes), increasing the N ₂ concentration at the electrolyte / electrode interface.

In another aspect of the embodiments described herein, the present invention provides an electrolyte medium for electrochemical reduction of nitrogenous species to ammonia in accordance with the method of the present invention, wherein the medium has a high solubility for the nitrogen and a low solubility for water The branch comprises one or more liquid salts.

In a preferred embodiment, the electrolyte comprises eFAP liquid salts above the hina, since the eFAP liquid salt exhibits high N ₂ solubility (ref S. Stevanovic et al, Chem. Thermodynamics 59 (2013) 65-71) .

The electrolyte comprising the liquid salt also exhibits a degree of hydrophobicity which is high enough to provide controlled water activity to the electrochemical reaction and to support N ₂ reduction but not high enough to support rapid reduction with H ₂ of water . In a preferred embodiment, the electrolyte comprises at least one hydrophobic liquid of a _P6,6,6,14 cationic substrate. In a particularly preferred embodiment, the electrolyte is substantially a liquid salt, [P _6,6,6,14 ] [ eFAP].

In a particularly preferred embodiment, the electrolyte is pre-conditioned prior to use, such as by contacting it with an aqueous hydroxide solution. Without wishing to be bound by theory, the preconditioning may introduce a small amount of OH into the liquid salt to provide the desired protonic activity in the electrolyte of the present invention.

The temperature range applicable to the in-cell electrolyte material according to the present invention may be from -35 to 200 캜, preferably from 0 캜 to 150 캜, and most preferably from 15 캜 to 130 캜.

The applied pressure range is typically from 0.7 bar nitrogen pressure to 100 bar nitrogen pressure, preferably from 1 bar to 30 bar, and most preferably from 1 bar to 12 bar. The pressure can be continuous, i.e. constant or continuously increasing with time. Alternatively, the pressure may be discontinuous, i.e. pulsed over time - that is, alternating between higher and lower pressure values within the aforementioned range.

The pressure-temperature combination allows for increased N ₂ solubility and electrochemical kinetics, and can be selected such that ammonia is brought close to but below the set point (e.g., at 25 ° C at 10 bar or 79 ° C 40 bar).

Typically, a continuous current will pass between the cathode working electrode and the counter electrode, but intermittent or pulsed currents may be suitable for some applications such as wind power photovoltaic panel power drive processes.

Nano-structured catalyst

In a third aspect of the embodiments described herein, there is provided a catalyst for electrochemical reduction of dinitrogen with ammonia, wherein the catalyst has a concentration of greater than 0.1 mF / cm < ² >, preferably 1 mF / It includes nanostructured materials having a high surface area electrochemical operation represented by a large double layer capacity than the cm ^2.

Preferably, the nanostructured catalyst comprises an elemental metal or at least one metal in the form of an inorganic compound comprising a metal. The nanostructured catalyst may be in the form of segmented particles or sheets or films or three-dimensional structures. The nanostructured catalysts embody morphological features that can be of any shape with at least one dimension ranging from 1 nm to 1000 nm.

Suitable metals include any transition metal or lanthanide metal, including Fe, Ru, Mo, Cu, Pd, Ti, Ce and La, and other metals and semimetals and their alloys.

The above-described metal may be surface-decorated with a metal oxide or a sulfide, or may be formed of a composite with the metal and its oxide or sulfide.

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

The catalyst nanoparticle film may preferably be manufactured by a cyclic voltage current or pulse voltage current electrodeposition method.

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

In another preferred embodiment, the catalyst may comprise a doped carbon material, particularly carbon doped with N and / or S.

The catalyst is preferably supported or decorated on an electrically 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.

The ferrodefficiency is a particular defect in related processes of the prior art. The Faraday efficiency can be used to describe the fraction of the current used in the N ₂ reduction reaction. The remaining fraction, i.e., (100 - Faraday efficiency)% is consumed in unwanted side reactions involving the production of H ₂ and hydrazine. These by-products represent waste energy and may require a complex separation method from the desired product. One of the objects of the present invention is to provide a method for producing ammonia having a relatively high Faraday efficiency.

Other aspects and preferred forms are defined in the claims and / or claims set forth herein, which form part of the description of the present invention.

Substantially, embodiments of the present invention are directed to specific non-aqueous catalysts that act as specific homogeneous catalysts to increase dissolved N ₂ gas concentration and increase heterogeneous activity in a reducing reaction while reducing undesired competitive reaction rates, such as H ₂ production. And the ammonia production efficiency can be improved by the selection of the aqueous electrolyte. The efficiency is further improved by the use of specific nanostructured catalysts.

Advantages provided by the present invention in comparison with prior art processes include:

· Conversion to heterogeneous ammonia with high Faraday efficiency;

The reaction can be carried out at ambient temperature and pressure;

Greater solubility of the nitrogenous elements in the electrolyte;

Increased heterogeneous activity in the reduction reaction;

, A lower rate of undesirable competing reaction, such as H ₂ production;

Water can be used as a hydrogen source so that no additional hydrogen is required;

Suitable catalysts are available from cheap and abundant materials;

· High corrosive electrolyte.

Additional applicability of embodiments of the present invention will become apparent from the following detailed description. However, it should be understood that the detailed description and specific examples, while indicating various changes and modifications within the spirit and scope of the disclosure, will become apparent to those skilled in the art from the foregoing description, .

The present invention provides an efficient electrochemical process for the production of ammonia.

BRIEF DESCRIPTION OF THE DRAWINGS Further disclosures, objects, advantages and aspects of preferred and other embodiments of the present invention will become better understood by those of ordinary skill in the art with reference to the following description of embodiments with reference to the accompanying drawings, Not limited.
1 is a schematic diagram showing a typical electrochemical cell for N ₂ reduction according to the present invention.
Figure 2 is a schematic diagram of a N ₂ reduction cells based on hybridoma electrode according to the present invention.
3 is a schematic view of a stacked N ₂ reduction cell arrangement according to the present invention showing the cells shown in FIG. 2 stacked in series.

Abbreviation

Abbreviations used herein refer to the following species:

B (otfe) ₄ - tetrakis (2,2,2-trifluoroethanoxy) borate (B (OCH ₂ CF ₃ ) ₄ )

C ₄ mpyr -butyl-methylpyrrolidinium

EMIM -ethylmethylimidazolium

eFAP -tris (perfluoroethyl) trifluorophosphate

FSI -bis (fluorosulfonyl) imide ((FSO ₂ ) ₂ N)

HMIM -hexyl methyl imidazolium

NfO - nonafluoro butane sulfonate _{(CF 3 (CF 2) 3} SO 3)

NTf2 -bis (trifluoromethylsulfonyl) amide

P _6,6,6,14 -trihexyltetradecylphosphonium

P _1,4,4,4 -tributyl methylphosphonium

PEDOT -poly (3,4-ethylenedioxythiophene)

Perfluorobutylsulfonate (F ₉ C ₄ SO ₃ )

PFO -perfluorooctanesulfonate (F ₁₇ C ₈ SO ₃ )

PFB - Perfluorobutyrate

R _f -perfluoroalkyl- (CF ₂ ) _n-1 (CF ₃ ) where n is an even number

details

The invention will now be further described with reference to the following non-limiting examples. These embodiments analyze the electrocatalytic activity of new catalytic materials in liquid salt electrolytes.

Embodiments also illustrate the fabrication of electrodes based on various metal nanostructures (nanoparticles or films) using chemical and electrodeposition processes, and the investigation of their electrocatalytic properties in electrolytes comprising one or more liquid salts. By using an electrolyte comprising a liquid salt, the nitrogen dioxide could successfully be converted to ammonia at ambient temperature and pressure, with a Faraday efficiency of> 60%, which exceeds the room temperature efficiency of the prior art process.

The method of the present using a process that is based on the liquid salt invention and at the same time a homogeneous catalyst which not only can greatly increase the heterogeneity of cattle solubility, increase the heterogeneity of cattle activity in the reduction reaction, not preferred as H ₂ production Which slows down the speed of uncompromising competition.

An Fe-based N ₂ electrocatalytic reduction catalyst film was prepared by electrodepositing Fe onto a commercially available fluorine-doped tin oxide or porous metal (or carbon) substrate. Fluorine-doped tin oxide coated glass is electrically conductive and is ideal for use in a wide range of devices. Fluorine-doped tin oxide is relatively stable at atmospheric conditions, chemically inert, mechanically stiff, high temperature resistant, and highly resistant to physical abrasion. Stainless steel mesh or cloth is useful as a high surface area substrate.

Depositing electrolyte is contained a 10 mM FeSO _4, 10 mM NaOH and 10 mM citrate. Electrodeposition was controlled by a potentiostat using a three-electrode system using fluorine-doped tin oxide glass, Ti mesh, and a saturated calomel electrode (SCE) as working, counter and standard electrodes, respectively. A typical electrodeposition of this type is performed using a cyclic voltammetric technique between -1.8 V and -0.8 V. A black shiny film was formed after several cycles. The cycle number change allowed for film thickness control, and typical films were electrodeposited by 10 cycles at a scan rate of 20 mV s ^-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  Cathode reduction

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

N ₂ gas was bubbled through a water trap to saturate it before bubbling into the electrolyte. The synthesized ammonia carried in the exhaust gas was trapped by passing the gas stream through a slightly acidic solution (1 mM H ₂ SO ₄ ).

Product analysis

The ammonia produced in the gaseous phase was bubbled and collected through 1 mM H ₂ SO ₄ solution. Ammonia remaining in the ionic liquid after completion of the electro-reduction was extracted by washing the ionic liquid with 1 mM KOH. The total amount of ammonia was the sum of the ammonia in the acidic trap and the basic wash and was later quantified using the indian phenol blue method.

In a typical assay 0.5 ml of 0.5 M sodium hypochlorite is added to 0.5 ml aliquots followed by addition of 5% (by weight) of salicylic acid and 5% (by weight) of sodium citrate and 0.05 ml of 1 M NaOH, and 0.5% Weight) 0.01 ml of sodium nitroperi- canide was added. After 2 hours, the absorption of the solution at 700 nm was measured on a UV-Vis spectrometer. Control experiments were performed by adding different concentrations of NH ₄ Cl to 1 mM H ₂ SO ₄ or 1 mM KOH solution to verify the assay.

The Faraday efficiency is a six-electron process,

2 NH₃ + 6 OH^- N ₂ + 6e ^- + 6 H ₂ O

2 NH ₃ + 6 OH ^-

.

Figure 1 is a schematic diagram illustrating a typical electrochemical cell for N ₂ reduction according to the present invention, including a power source 1, a cathode 2, a membrane 3 and an anode 4. In this process, the counter electrode reaction may be water or hydroxide oxidation as illustrated. Alternatively, if the desired product is ammonium fertilizer sulfate, the counter electrode reaction may be SO < ₄ > ^-2 at 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.

Cell

An N ₂ reduction cell according to the present invention based on a hybrid electrode is described in the next paragraph. Such an electrolytic cell is characterized in that the reactant, which is one or more gases, has a low solubility in the electrolyte and thus the reaction is mainly carried out in the region of the three-phase boundary in the hybrid electrode body (i.e. the boundary between the electrode material, When it is desired to occur, electrolysis is best assisted.

Such a hybrid electrode of the present invention is preferably characterized in that the electrode has a high electrochemically active surface area and has a plurality of pores that allow both gas access and electrolyte access within the electrode body, Conductive electrode material.

In the present invention, the gas remains adjacent to one surface, and the pores of the hybrid electrode are at least partially filled with an ion conductive material, so that transfer of reactants and products takes place in the region where reduction of N ₂ to NH ₃ takes place.

This avoids one of several limitations of prior art electrodes designed to aid gas diffusion in porous electrodes; This diffusion process creates undesirable over-potential and inefficiencies in the cell during operation.

In this embodiment, the cathode working electrode is a hybrid ion-conducting electrode or " cathode " electrode, which is made by forming a porous metal film and impregnating the porous structure with an ion conductive material, such as Nafion ™ or Nafion ™ gel or gelled liquid salt, Electrode film ". The cathode is decorated with an electrocatalyst to form a gas / electrolyte / metal three-phase boundary region where electrolysis may occur.

The reactive gas is directly introduced into the electrocatalyst from the flowing gas. The reactant or product ions diffuse through the electrolyte portion of the electrode membrane and the gaseous product passes directly into the flowing gas phase.

2, the cell according to this embodiment is composed of two porous electrodes 11, 12 separated by an electrolyte layer 13. The porous electrode 11, Electrode 11 is a cathode working electrode where nitrogen is reduced and electrode 12 is a counter electrode (anode) where water oxidation or other desirable oxidation takes place. On the backside of each electrode is a spacer layer 14,15 which conducts gas into and out of the cell.

The electrodes include layers of flexible porous conductive electrode sheet material having an electrocatalyst 16 loaded onto the sheet and directly exposed to the gas layers 14 and 15, respectively. Optionally, the catalyst 16 may be deposited throughout the structure of the electrode 11 to form a plurality of regions in contact with the gas, the electrolyte, the catalyst, and the conductive electrode. 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, iron, nickel, copper, ruthenium or their alloys in mesh, foam or wool form. Porous carbon materials including carbon cloths, carbon particle / binder composites, graphene and reduced graphene oxide and conductive polymers are also suitable as porous conductive electrode materials.

An outer container encloses the cell. In one form of cell, the cell is rolled or z-folded.

In a further embodiment of the invention, an assembly is formed by a plurality of cells stacked in series. In this format, the electrolytes in the cell layers 18 must be separated from each other, and the container 17 is a conductive material such that a series connection is formed between the cells. The stacked cells may also be folded or rolled.

The electrolyte may comprise a spacer or a polymer electrolyte, for example a polymer electrolyte comprising a Nafion (TM) or gelling Nafion (TM) or gelled liquid salt electrolyte, or a paper or Celeguard (TM) type material well known in the battery art, Lt; / RTI > electrolyte.

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

The gas fluidized bed 14 has the function of allowing introduction of a flowing gas stream 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 for the ingress or egress of gas reactants or products produced on that side of the cell and optionally a stream of air or other gas may be introduced to dilute and carry the gas out of the cell. The gas fluidized bed 14, 15 may be formed by printing or forming a pattern using a high porosity separator or mesh, or on one or both sides of the layer 17.

Within the assembly of stacked cells, gas may be introduced at any convenient location, including from the longest " end " of the assembly or from both sides of the assembly. Each of these arrangements requires an alternative sealing arrangement of the layers 17.

The entire assembly can be as small as 1 mm thick, and it is required to maximize its surface area and minimize the amount of electrolyte material.

Example 1. Preparation of nanostructured Fe catalyst

The following examples describe the preparation of nanostructured catalysts suitable for use in the present invention. A fluorine doped tin oxide electrode (5 x 5 mm) was placed in the electrochemical cell and connected as a cathode. A standard calomel electrode (SCE) acted as a standard electrode, and a Ti mesh acted as a counter electrode. Electrolyte solution for catalyst preparation are included in the 10 mM FeSO _4, 10mM NaOH, 10 mM citric acid and water.

Electrodeposition of Fe was performed by circulating the potential of the fluorine doped tin oxide electrode between -0.8 to -1.8 V vs SCE for 10 cycles at 20 mV / s. 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, with partially oxidized iron being uniformly distributed (10% oxide). The iron oxide is formed during the anode portion of the deposition cycle. Formation of iron oxide can control iron nanoparticle size. Iron oxide is at least partially reduced during the early stages of use as the cathode in ammonia production. The Fe / FeOxide composite can enhance the catalytic activity through the synergistic effect of the two oxidation states of iron.

The electrochemical surface area was measured by measuring the double layer charge current at 0 V vs Pt by cyclic voltammetry at 5 mV / s in butyl methylpyrrolidinium eFAP liquid salt at room temperature. A bilayer capacity of 2 mF / cm < ² > was measured under these conditions.

Example 2. Preparation of [P _6,6,6,14 ] [eFAP] My N ₂ Reduction of

A fluorine doped tin oxide electrode having a Fe electrocatalyst layer was placed as a cathode in an electrochemical cell. The electrolyte contained a liquid salt [P _6,6,6,14 ] [eFAP]. The electrolyte was shaken with 1 mM aqueous KOH solution and adjusted before use. The aqueous solution was insoluble in the liquid salt such that an excess of the solution could be removed as a separation layer in the separation funnel.

The preconditioning may introduce a small amount of OH < - > into the salt to provide the desired protonic activity in the electrolyte.

The counter electrode Pt was placed in a fritted compartment also containing a saturated liquid salt. The standard electrode is Pt. At 10 ml / min, the heterogeneous gas was introduced into the cell using a bubbler which led the N ₂ bubbles to the cathode. The nitrogen was pre-saturated with water by bubbling through a solution of low water vapor pressure.

The exhaust gas flowing from the cell and containing unreacted nitrogen and reduction products was led into an additional trap containing 1 1 mM H ₂ SO ₄ to trap ammonia produced as NH ₄ ⁺ . The solution was analyzed for ammonia in the second half of the electrolysis.

The electrolysis was carried out at a voltage between -1.0 and -2.0 V for 2 to 5 hours. In the latter half of the electrolysis, the electrolyte was washed three times with 1 mM KOH solution to extract any remaining ammonia. Three washings were also analyzed for ammonia. The results were combined with the results from the trap solution analysis. The Faraday efficiency was 73% (+/- 5%).

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

Example 3: [C ₄ mpyr] [eFAP] N ₂ Reduction of

N ₂ reduction was performed as described in Example 2 except that the electrolyte contained a liquid salt [C ₄ mpyr] [eFAP]. Faraday efficiency was 47% (+/- 5%) in this case.

Example 4: [P _6,6,6,14  ] [F ₉ C ₄ SO ₃ ] My N ₂ Reduction of

_Was carried out in the same manner as in Example 2, and the electrolyte contained a liquid salt [P _6,6,6,14 ] [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: Preparation of [P _6,6,6,14  ] [PFO] My N ₂ Reduction of

_Was carried out in the same manner as in Example 2, and the electrolyte contained a liquid salt [P _6,6,6,14 ] [PFO]. A constant current of 4 uA cm ^-2 was applied for 2 hours. The ammonia measurement showed a Faraday efficiency of 39% for ammonia.

Example 6: Sound wave processing assistant N ₂  restoration

The following examples illustrate increased ammonia production by including additional physical and / or chemical processes.

The same procedure as in Example 2 was followed, and the entire electrochemical cell was immersed in a sonicator bath. The electrostatic potential of -1.2 V vs NHE was applied on the working electrode for 30 min and the N ₂ reduction was promoted by applying the acoustic wave to the electrochemical cell. The current increased approximately 125% compared to the previous value in the presence of sonication.

Example 7: Preparation of N < RTI ID = 0.0 > ₂ Reduction of

As noted above, the electrolyte can form liquid salts of the desired characteristics by combination of two or more salts. In addition, the liquid salt may contain additional ingredients, including water or other molecular liquids, as illustrated by the following examples.

Was carried out in the same manner as in Example 3, and 10% v / v trifluoro toluene was added into the electrolyte as an additional component to reduce the viscosity of the liquid salt and promote the material transport in the electrochemical reaction. A constant potential of -1.2V vs NHE was applied for 30 minutes. The current is increased by 50% compared to the value in the absence of trifluoro toluene.

Example 8: Preparation of [C ₄ mpyr] [perfluorobutanesulfonate]

[C ₄ mpyr] [perfluorobutanesulfonate] has an elevated melting point (112 ° C) and could be used for N ₂ reduction at temperatures above that. The melting point can also be lowered by the addition of a molecular liquid component as described in Example 7.

Example 9: Preparation of [C ₄ mpyr] [PFO]

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

Example 10: Preparation and use of an electrolyte comprising a gel membrane containing a liquid salt

As described above, the electrolyte used in the present invention is a spacer or an electrolyte membrane itself. For example, a polymer electrolyte, such as Nafion (TM) or a gelled liquid salt electrolyte, or an electrolyte immersed in a paper or porous separator such as Celeguard (TM). The procedure described in Example 10 is illustrative of the preparation of a PVDF-HFP copolymer gel electrolyte membrane, but more generally can be used for the preparation of any gel membrane containing a liquid salt.

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

Gas flow cells were fabricated as electrodeposited Fe cathodes on carbon paper / plated carbon anodes, membranes and stainless steel mesh (400 mesh). Hydrogen gas was introduced into the anode side of the gas flow cell and nitrogen gas was passed through the cathode surface at a rate of 180 mL / min each. The gas pressure inside the cell was 1 atmospheric pressure. A constant potential of -1.2 V for the anode was applied to the cathode for 30 minutes.

Combining the gas flowing through the cell, which was bubbled through 20 mL of a solution bubbled through the solution 40 mL of 1 mM H ₂ SO _4, and then 1 mM H ₂ SO _4. The gas was bubbled through the potential application period and 30 minutes after it was terminated.

Ammonia produced over a 30 minute period with potentials was 87.0 nmoles with 24.9% Faraday efficiency.

Example 11: Preparation of [C ₄ mpyr] [eFAP] Preparation and use of gel membranes containing liquid salts

The liquid salt to polymer ratio was adjusted to 7: 3 by weight, and a film was prepared in the same manner as in Example 10, except that the solution was cast to form a free standing film. Ammonia produced over 30 minutes with potentials was 59.5 nmoles with 71.5% Faraday efficiency.

Example 12: Preparation of [C ₄ mpyr] [eFAP] Preparation and use of Nafion ™ gel membranes containing liquid salts

A cell was prepared as described in Example 10, except that the electrolyte contained a Nafion ™ -gel membrane and was prepared as described in the following examples.

In a lower aliphatic alcohol and water, supplied by _{Aldrich [C 4 mpyr] [eFAP} ] 9 unit and Nafion 5 w / w%, by mixing a solution of 20 parts of 1: 9 weight ratio of Nafion ™ and [C ₄ mpyr] [ eFAP] was prepared. This was dropped onto a 34 mm diameter Solupour ™ membrane to achieve complete coverage of the solution on the membrane. It was then dried overnight in an oven at 60 < 0 > C. A gas flow cell was fabricated between the cathode and anode using this Nafion ™ -gel membrane. The produced ammonia was found to be 93.1 mnoles with a 30.6% Faraday efficiency.

Example 13: Preparation and use of a free standing electrolyte membrane comprising a Nafion (TM) gel membrane containing a liquid salt

The cell was prepared as described in Example 11 except that the membrane was a Nafion ™ -gel membrane. The membrane was prepared as follows. A 3 to 7 weight ratio mixture of Nafion ™ and liquid salt was prepared and dropped cast as described in Example 12. Next, it was dried overnight in a 60 ° C oven.

It will be apparent to those skilled in the art that additional modifications of the above-described cells can be made, such as by excluding Solupour ™ as a support for the electrolyte membrane or using other supports.

Example 14: [P6,6,6,14] [PFB] N ₂ Reduction of

[P _6,6,6,14 ] [PFB] was used as a liquid salt electrolyte. The electrostatic potential of 0.8 V vs NHE was applied for 3 hours. The Faraday efficiency of ammonia production in this system was 18%.

Example 15: Preparation of N ₂ Reduction of

The procedure of Example 3 was followed and a ruthenium film was deposited on the working electrode. A static potential of -0.8 V vs NHE was applied on 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 production in this system was 28%.

Use of other electrode substrates

The N ₂ reduction current obtained on the flat fluorine doped tin oxide glass substrate was too small to be implemented and thus increased the working electrochemical surface area using various high surface area and porous substrates such as nickel foam and stainless steel mesh. The current density increased when using a porous substrate, for example, the current increased from 0.012 Am ^-2 for fluorine doped tin oxide to 0.1 Am ^-2 for stainless steel mesh and 0.25 Am ^-2 for nickel foam, The efficiencies correspond to 59% and 45%, respectively. Due to the increased current, the production rate increases from 2.9 mg.m ^-2 h ^-1 on a fluoro-doped tin oxide substrate to 14 mg.m ^-2 h ^-1 on a stainless steel substrate. It is important to note that the stainless steel cathode used here is somewhat thin and flexible, so there is a significant opportunity to further increase the yield by optimizing the cathode thickness and to perform a high surface area thin layer or spiral cell structure.

[P _6,6,6,14 ] Compared to [eFAP], the [C ₄ mpyr] [eFAP] liquid salt produces higher currents. This is probably due to its lower viscosity, which promotes better material diffusion during the reaction. [C ₄ mpyr] [eFAP] ionic liquid solubility in N ₂ 0.20 mg / g is [P _6,6,6,14] [eFAP] is lower than that in the 0.28 mg / g, as predicted, [C ₄ mpyr] [eFAP] The Faraday efficiency of N ₂ reduction for the stainless steel electrodes is slightly lower. Nevertheless, the yield is higher in [C ₄ mpyr] [eFAP].

The reason for the high solubility of N _{2 in} the selected ionic liquid is further investigated by DFT calculation. The interaction of N ₂ with various conventional anions is relatively weak with ions such as Cl ^- and fluoride anions such as BF ₄ ^- and PF ₆ ^- . On the other hand, the interaction with [eFAP] is obviously stronger.

While not intending to be bound by theory, two modes of computation can be distinguished; The first is exposed to N ₂ to interact with F- atom attached to the alkyl chain, the second one has a N ₂ interacting with the F atoms bonded phosphorus, the latter is a stronger interaction. From all of the calculations, the more stronger delocalized in groups to the neighboring charge, N ₂ appears to have a stronger binding interaction. The distinction between this binding energy in the eFAP complex and the binding energy of PF ₆ ^- is significant; In the case of eFAP, the additional delimitation of the charge on the three C ₂ F ₅ groups modulates the charge on the P-bonded fluorine, thereby enhancing the interaction with N ₂ . When introducing cations into these calculations, the interaction is much stronger due to the additional charge interactions between the anions and the cations.

Comparative Example

The prior art includes a general disclosure of the use of electrolytes comprising liquid salts, but many of these electrolytes are not suitable for the reduction of nitrogen oxides according to the process of the present invention and / or have unacceptably low paradigm efficiencies.

This can be illustrated, for example, with reference to U.S. Patent Application No. 2016/0138176 (Yoo et al), which discloses an electrolytic cell containing an aqueous or a specific alkali metal (salt) liquid electrolyte or ionic liquid A method for synthesizing ammonia will be described. In particular, Comparative Examples 16 and 17 relate to the salts disclosed in US 2016/0138176, but in the process of the present invention, the salts of Comparative Example 16 result in unacceptably low Faraday efficiencies, and the salts of Comparative Example 17 are unstable do.

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

Comparative Example 16: [HMIM] [NTf ₂ ] My N ₂ Reduction of

N ₂ reduction was performed as described in Example 2, except that the liquid salt contained the electrolyte [HMIM] [NTf ₂ ] and the working electrode used the catalyst of Example 1. Since an ionic liquid is generally regarded as a salt having a melting point of < 100 캜, [HMIM] [NTf ₂ ] can be regarded as an ionic liquid. Since the melting point of this salt is about 70 캜, the reduction was carried out at 70 캜 in a liquid state.

In this case, the Faraday efficiency was only 0.64%.

Comparative Example 17: [EMIM] [B (CN) ₄ ] My N ₂ Reduction of

N ₂ reduction was performed as described in Example 2, except that the electrolyte contained a liquid salt [EMIM] [B (CN) ₄ ] and the working electrode used the catalyst of Example 1.

In this case the Faraday efficiency was only 14%. However, the same Faraday efficiency was measured when an argon gas feed was used in place of the N ₂ feed. In the latter case, ammonia is not produced from the supplied N ₂ and is formed by the decomposition of an electrolyte comprising a liquid salt, which indicates that the cyano group-containing liquid salt is not stable to reduction under these conditions when used as an electrolyte.

Comparative Example 18: [EMIM] [eFAP] N ₂ Reduction of

N ₂ reduction was performed as described in Example 2, except that the electrolyte contained the liquid salt [EMIM] [eFAP] and the working electrode used the catalyst of Example 1.

Ammonia production measurements yield ammonia (or detectable amines) for both argon and N ₂ saturated electrolytes, with the% Faraday efficiency of 35% and 16%, respectively. This indicates that during electrolysis the ionic liquid is decomposed to produce amine products and ammonia. These liquid salts are therefore not amenable to nitrogen reduction with ammonia.

While the invention has been described with respect to specific embodiments, it will be understood that additional modifications are possible. It is intended that the present invention cover the modifications and variations of this invention that come within the scope of the invention as publicly known or common in the art to which this invention pertains and which can be applied to the essential features set forth hereinabove, Modification, use, or adaptation of the invention.

The present invention can be embodied in several forms without departing from the spirit of essential characteristics of the present invention, so that the above embodiments do not limit the present invention unless otherwise specified, Should be construed broadly within the spirit and scope of the following claims. The implementations described 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 invention and the appended claims. Accordingly, it is to be understood that the specific embodiments are examples of many ways in which the principles of the invention may be practiced. In the following claims, means-to-function clauses are intended to include equivalent structures as well as structures and structural equivalents that perform the defined functions.

As used herein, the term "comprising" is used to specify the presence of stated features, integers, steps or components and does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof . Accordingly, the word " comprises, " " including, " or " comprising ", etc. throughout the specification and claims, unless the context clearly dictates otherwise, is to be construed in an inclusive sense, It should be interpreted as meaning.

Claims (51)

A method of electrochemically reducing nitrogen dioxide with ammonia,
The method
(1) contacting a cathode working electrode comprising a nanostructured catalyst and a counter electrode with an electrolyte comprising at least one liquid salt,
- the liquid salt
_{(i) PR 1- 4, NR} 1 - 4, C 4 H 8 as a cation selected from the group consisting of NR _2, and each R group is a linear, branched or cyclic independently, preferably 1 to 18 carbon Includes a functional group selected from an ether, an alcohol, a carbonyl, a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, optionally containing an atom, optionally partially or fully halogenated and optionally containing a heteroatom A cation in which two R groups may be joined to form a monocyclic or heterocyclic ring; And
(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, and preferably has 1 to 18 carbon atoms Optionally containing a functional group selected from an ether, an alcohol, a carbonyl, a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, two R 'groups being bonded Which may form a monocyclic or heterocyclic ring,
, &Lt; / RTI &gt; and
(2) introducing a heterogeneous and hydrogen source into the electrolyte
Lt; / RTI &gt;
Characterized in that the isomer is reduced to ammonia in the cathode working electrode. The method according to claim 1,
The liquid salt
(i) a cation selected from the group consisting of C ₄ mpr, P _{6, 6, 6, 14,} P (C ₂ R _fn ) ₄ wherein R _f is a perfluoroalkyl moiety; And
(ii) anions selected from the group consisting of eFAP, NfO, PFO, FSI, NTf ₂ , B (otfe) ₄ and CF ₃ COO
. &Lt; / RTI &gt; The method according to claim 1,
_Wherein the liquid salt is [ _P6,6,6,14 ] [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 characterized in that the _[6,6,6,14 P] [C ₄ F ₉ SO _3]. The method according to claim 1,
_Wherein the liquid salt is [ _P6,6,6,14 ] [PFO]. The method according to claim 1,
Wherein the liquid salt is [C ₄ mpyr] [perfluorobutanesulfonate]. The method according to claim 1,
Wherein the liquid salt is [C ₄ mpyr] [PFO]. The method according to claim 1,
Further comprising raising the temperature of the electrolyte to from -35 占 폚 to 200 占 폚, preferably from 0 占 폚 to 150 占 폚, more preferably from 15 占 폚 to 130 占 폚. 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, and most preferably 1 bar to 12 bar to the electrolyte. 11. The method of claim 10,
Wherein the pressure is a pulse. The method according to claim 1,
Wherein the current passing between the cathode working electrode and the counter electrode is intermittent. The method according to claim 1,
Further comprising applying energy of an ultrasonic frequency to the electrolyte. The method according to claim 1,
Humidifying the heterogeneous gas and passing the humidified heterogeneous gas in the stream to the cathode working electrode. The method according to claim 1,
&Lt; / RTI &gt; wherein the electrolyte further comprises a membrane. 16. The method of claim 15,
Wherein the membrane is selected from a polymer electrolyte, a gelled ionic liquid electrolyte or a porous separator. 1. A cell for electrochemically reducing nitrogen as an ammonia,
The cell
A cathode working electrode comprising a nanostructured catalyst for the reduction of nitrogen,
- a counter electrode, and
An electrolyte comprising at least one liquid salt in contact with said working electrode
/ RTI &gt;
The liquid salt
_{(i) PR 1- 4, NR} 1 - 4, C 4 H 8 as a cation selected from the group consisting of NR _2, and each R group is a linear, branched or cyclic independently, preferably 1 to 18 carbon Includes a functional group selected from an ether, an alcohol, a carbonyl, a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, optionally containing an atom, optionally partially or fully halogenated and optionally containing a heteroatom A cation in which two R groups may be joined to form a monocyclic or heterocyclic ring; And
(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 as an anion selected from the group consisting of, each of the R 'group is independently a linear, branched or cyclic, preferably from 1 to 18 Includes a functional group selected from an ether, an alcohol, a carbonyl, a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, optionally containing a carbon atom and optionally partially or completely fluorinated, Groups may be combined to form an anion capable of forming a monocyclic or heterocyclic ring
Of the cell. 18. The method of claim 17,
The liquid salt
(i) a cation selected from the group consisting of C ₄ mpr, P _{6, 6, 6, 14,} P (C ₂ R _fn ) ₄ , wherein R _f is a perfluoroalkyl moiety; And
(ii) anions selected from the group consisting of eFAP, NfO, PFO, FSI, NTf ₂ , B (otfe) ₄ and CF ₃ COO
Of the cell. 18. The method of claim 17,
_Wherein the liquid salt is [ _P6,6,6,14 ] [eFAP]. 18. The method of claim 17,
Wherein the liquid salt is [C ₄ mpyr] [eFAP]. 18. The method of claim 17,
Wherein the liquid salt is a cell, characterized in that _[6,6,6,14 P] [C ₄ F ₉ SO _3]. 18. The method of claim 17,
_Wherein the liquid salt is [ _P6,6,6,14 ] [PFO]. 18. The method of claim 17,
Wherein the liquid salt is [C ₄ mpyr] [perfluorobutanesulfonate]. 18. The method of claim 17,
Wherein the liquid salt is [C ₄ mpyr] [PFO]. A cell assembly formed by laminating two or more cells according to claim 17 or 18 in series. 18. The method of claim 17,
And a heating means for maintaining the temperature of the electrolyte between -35 캜 and 200 캜, preferably between 0 캜 and 150 캜, more preferably between 15 캜 and 130 캜. 18. The method of claim 17,
And a pressure means for applying a pressure of 0.7 bar nitrogen to 100 bar nitrogen, preferably 1 bar to 30 bar, and most preferably 1 bar to 12 bar to the electrolyte. 18. The method of claim 17,
The cathode being adapted to pass an intermittent current between the cathode working electrode and the counter electrode. 18. The method of claim 17,
Further comprising a humidifier for humidifying the heterogeneous gas, the humidifier being adapted to pass humidified gaseous gas through the cathode to the cathode working electrode. 18. The method of claim 17,
Wherein the electrolyte comprises a membrane. 18. The method of claim 17,
Wherein the membrane is selected from a polymer electrolyte, a gelled ionic liquid electrolyte or a porous separator. 18. The method of claim 17,
A cell comprising an ultrasonic source for applying energy of an ultrasonic frequency to the electrolyte. 18. The method of claim 17,
Wherein the reduction to the ammonia of the heterogeneous species takes place primarily in the region adjacent to the three-phase boundary on the working surface of the cathode working electrode. 18. The method of claim 17,
Wherein said nanostructured electrochemical catalyst is adjacent to an outer surface of said cathode working electrode and forms a gas / electrolyte / metal three-phase boundary region where electrolysis predominates. As a nanostructured catalyst for electrochemical reduction of dinitrogen to ammonia,
The nanostructured catalyst comprises nanoparticles and has a high electrochemical working surface area as measured in an adjacent electrolyte layer, expressed as a bilayer capacity greater than 0.1 mF / cm ² , preferably greater than 1 mF / cm ² Lt; RTI ID = 0.0 &gt; nano-structured &lt; / RTI &gt; 36. The method of claim 35,
Transition metal, or a nano-structured catalyst comprising at least one metal nanoparticle selected from a lanthanide metal and an inorganic compound thereof. 37. The method of claim 36,
Wherein the nanoparticles of the at least one metal are supported on an electrically conductive, chemically inert support. An electrolyte for electrochemically reducing a nitrogenous material into ammonia according to the method of claim 1,
The electrolyte has a solubility in the cell of at least 100 mg / L, more preferably greater than 200 mg / L, most preferably greater than 400 mg / L at the working temperature and pressure of the cell, At least one salt having a solubility in water of less than 2 wt%, more preferably less than 2 wt%, and most preferably less than 1 wt%. 39. The method of claim 38,
&Lt; / RTI &gt; wherein the electrolyte further comprises a membrane. 40. The method of claim 39,
Wherein the membrane is selected from a polymer electrolyte or a polymer electrolyte-liquid salt blend, or a gelled liquid salt electrolyte, or an electrolyte immersed in a porous separator. 39. The method of claim 38,
Adding a molecular liquid present in the liquid salt medium at a level of between 90 vol% and 0.1 vol%, more preferably between 20 vol% and 0.2 vol%, and most preferably between 50 vol% and 0.5 vol% . 39. The method of claim 38,
Is present in the liquid salt medium at a level of between 90 vol% and 0.1 vol%, more preferably between 20 vol% and 0.2 vol%, and most preferably between 50 vol% and 0.5 vol% Tetraglyme and other oligo- and poly-ethers, glutaronitrile and other high boiling nitriles, trifluoro toluene. An electrode for electrochemically reducing a nitrogenous material to ammonia according to the method of claim 1,
Said electrode having a hybrid structure comprising a porous conductive electrode material and a nanostructured catalyst, said electrode having a plurality of pores adapted to allow both an electrochemically active surface area and both gas access and electrolyte access within the electrode body . 44. The method of claim 43,
Wherein the pores are at least partially filled with an ion conductive material. 10. An electrode for electrochemically reducing nitrogen to ammonia according to the method of claim 1, wherein the electrode is a porous metal or a film containing carbon impregnated with a catalytic material or a gelled liquid salt. An electrolyte membrane for use in the cell of claim 1 comprising a thin layer of material in combination with at least one liquid salt,
The liquid salt
_{(i) PR 1- 4, NR} 1 - 4, C 4 H 8 as a cation selected from the group consisting of NR _2, and each R group is a linear, branched or cyclic independently, preferably 1 to 18 carbon Includes a functional group selected from an ether, an alcohol, a carbonyl, a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, optionally containing an atom, optionally partially or fully halogenated and optionally containing a heteroatom A cation in which two R groups may be joined to form a monocyclic or heterocyclic ring; And
(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, and preferably has 1 to 18 carbon atoms Optionally containing a functional group selected from an ether, an alcohol, a carbonyl, a thiol, a sulfoxide, a sulfonate, an amine, an azo or a nitrile, two R 'groups being bonded Which may form a monocyclic or heterocyclic ring,
Wherein the electrolyte membrane is formed by a combination of the electrolyte membrane and the electrolyte membrane. 47. The method of claim 46,
Wherein the thin material layer is selected from the group consisting of a polymer, a gel, or a porous separator material. 47. The method of claim 46,
Wherein the liquid salt is combined with a polymer. 47. The method of claim 46,
Wherein the liquid salt is combined with a gel. 47. The method of claim 46,
Wherein the liquid salt is combined with a porous separator. A method for electrochemically reducing nitrogen oxides in ammonia according to claim 1, carried out using the electrochemical cell of claim 17, the nanostructured catalyst of claim 35, and the electrolyte of claim 38.

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