WO2021177359A1 - Ammonia decomposition method and fuel cell using same - Google Patents

Abstract

This ammonia decomposition method is a method for obtaining nitrogen, protons, and electrons by oxidative decomposition of ammonia in the presence of a base, using as a catalyst a salen-manganese complex in which manganese is used as a base metal. The present invention furthermore provides a fuel cell in which ammonia is used as a fuel, whereby electricity can be generated under mild conditions through use of the ammonia decomposition method of the present invention.

Description

Fuel cell by decomposing ammonia and its utilization

The present invention relates to a method for decomposing ammonia and a fuel cell by utilizing the method.

Ammonia is a desirable candidate as an energy carrier for a sustainable society, and has multiple advantages such as ease of handling, high energy density, and carbon neutrality (Non-Patent Document 1). In recent years, there have been reports of catalytic oxidation reactions from ammonia to nitrogen using transition metal complexes to extract energy from ammonia (Non-Patent Documents 2 to 4). As the fuel cell using ammonia as a fuel, for example, there are reports of an ammonia fuel cell using an electrolyte in which potassium hydroxide is melted, a fuel cell using ammonia as a fuel for an alkaline fuel cell, and the like (Non-Patent Documents 5 to 5). 9).

The problem with the above-mentioned reported example is that it uses ruthenium, which is a transition metal complex. From the viewpoint of utilizing ammonia as an energy carrier, catalytic oxidation of ammonia to nitrogen by a base metal that can supply a large amount of catalyst. A metal complex capable of realizing the reaction has been desired. Further, in the above-mentioned reported example of the fuel cell, in the anode catalyst of the fuel cell, a fuel using ammonia as a fuel using a solid catalyst in which a single metal such as platinum or manganese or an alloy is fixed to carbon, alumina, an inorganic substance or the like. The battery was disclosed, and there was a problem that a high temperature and a large overvoltage were required.

The present invention has been made to solve the above-mentioned problems, and mainly avoids the use of noble metals, decomposes ammonia by using a complex of a base metal, and extracts nitrogen molecules, electrons, and protons. The purpose. Further, from the viewpoint of utilization of the ammonia decomposition method using the salen manganese complex, the molecular salen manganese complex according to the present invention is used at the anode of the fuel cell without using the conventional solid catalyst or metal particle catalyst. The purpose is to embody the power generation of fuel cells that use ammonia as fuel under mild conditions.

In order to achieve the above-mentioned object, the present inventors focused on the salene manganese complex used for organic synthesis such as asymmetric epoxidation reaction, and oxidatively decomposed ammonia in the presence of a base. It was found that nitrogen, protons and electrons can be obtained well, and from the viewpoint of utilization of the ammonia decomposition method using the salen manganese complex, the oxidative decomposition method of ammonia using the salen manganese complex is used in the anode catalyst layer of the fuel cell. We have also found that it functions as a catalyst for the above, and have completed the present invention.

That is, the method for decomposing ammonia of the present invention is a method for decomposing ammonia by oxidatively decomposing ammonia in the presence of a salene manganese complex and a base to obtain nitrogen, protons and electrons. ), Equation (1b) or Equation (1c)

(In the formula, R ¹ and R ² represent C1-C4 alkyl groups which may be the same or different, and X is a monovalent anion, axial ligand or halogen atom). It is a complex.

According to the method for decomposing ammonia of the present invention, ammonia can be oxidatively decomposed in the presence of a salene manganese complex that is not a noble metal complex and a base to obtain nitrogen, protons and electrons, and ammonia can be decomposed at low cost. Allows mass decomposition of ammonia. Further, the present invention provides power generation of a fuel cell using ammonia as a fuel under mild conditions using the method for decomposing ammonia.

It is a schematic diagram which shows the structure of the fuel cell in embodiment. It is a graph of the current-potential curve obtained by CV measurement.

100 Fuel cell 101 Cathode side gas diffusion layer 102 Anode side gas diffusion layer 103 Anode catalyst layer 105 Cathode catalyst layer 107 Electrolyte film 109 Separator

In the present specification, "n" is normal, "s" is secondary, "t" is tertiary, "o" is ortho, "m" is meta, "p" is para, and " ^t Bu". Represents a tertiary butyl group. In the present specification, (R) and (S) indicate the molecular configuration of a chiral molecule in which central chirality exists, and the configuration of carbon atoms indicated by “*” is (R) or. Represents (S).

The method for decomposing ammonia of the present invention and a suitable embodiment of the fuel cell by utilizing the method are shown below. Twice

The catalyst used in the method for decomposing ammonia of the present embodiment is of formula (1a), formula (1b) or formula (1c).

(In the formula, R ¹ and R ² represent C1 to C4 alkyl groups which may be the same or different, and X represents a monovalent anion or halogen atom). Specific examples of the C1 to C4 alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group and the like. -Butyl groups are preferred. Examples of the monovalent anion include hexafluorophosphate ion, hexachloroantimonate ion, trifluoromethanesulfonate ion, tetrafluoroborate ion, phosphate ion, sulfonate ion, and hydroxydone. Examples of the halogen atom include chloride, bromide and iodide. The complex of formula (1a) and the complex of formula (1b) have an enantiomeric relationship. The complex of the formula (1c) has the same configuration as the formula (1a) in the cases of (R) and (R) because the configuration of the carbon atom represented by * is (R) or (S). , (R) and (S) are meso-form complexes, and (S) and (S) are the same as in formula (1b), and even if they are single as described above. It may be a mixture thereof.

In the method for decomposing ammonia of the present embodiment, the preferred salene manganese complex is the formula (1A) or the formula (1B).

And formula (4A) or formula (4B)

(In the formula, Z is a monovalent anion, axial ligand or halogen atom. For example, Z is hexachloroantimonate ion, hexafluorophosphate ion, chloride, bromide, iodide, hydroxide, phosphate ion, Examples thereof include sulfonate ion and trifluoromethanesulfonate ion, of which hexafluorophosphate ion is preferable.)
It is a complex represented by.

In the method for decomposing ammonia of the present embodiment, the base plays a role of trapping the protons generated when ammonia is oxidatively decomposed. The base is not particularly limited as long as it plays such a role, but for example, a pyridine derivative is preferable. Examples of the pyridine derivative include pyridine and pyridine having at least one substituent from the 2-position to the 6-position. The substituent is not particularly limited, and examples thereof include an alkyl group, a dialkylamino group, an alkoxy group, an aryl group, and a halogen atom. Examples of the alkyl group (including the alkyl group in the dialkylamino group), the alkoxy group, the aryl group, and the halogen atom include the same as those already exemplified. Specific examples of the pyridine derivative include pyridine, 2,6-lutidine, 2,4,6-cholidine, 4-dimethylaminopyridine (DMAP), and the like, of which 2,4,6-cholidine is preferable. When ammonia is produced by the reaction of an ammonium salt with a base in the system, the base is also used in this reaction.

In the method for decomposing ammonia of the present embodiment, ammonia may be produced by the reaction of an ammonium salt and a base in the system, although ammonia gas may be used. When it is necessary to quantify ammonia, it is preferable to generate ammonia in the system as in the latter case. The ammonium salt is not particularly limited as long as it quantitatively produces ammonia by reaction with a base, but for example, ammonium trifurate, ammonium hexafluorophosphate, ammonium chloride, ammonium bromide, and ammonium iodide. , Ammonium hydroxide, ammonium acetate, ammonium sulfate, ammonium phosphate and the like. Of these, ammonium triflate is preferred.

In the method for decomposing ammonia of the present embodiment, the oxidative decomposition of ammonia may be carried out by using an oxidizing agent containing a one-electron oxidant of triarylamine, or may be carried out under electrochemical oxidation conditions. An oxidant containing a one-electron oxidant of triarylamine serves to trap the electrons generated when ammonia is oxidatively decomposed. An example of such an oxidizing agent is the formula (2).

Examples thereof include the compounds shown in. In formula (2), ^Ra and R ^b may be the same or different, and are an alkyl group, a halogen atom or a hydrogen atom. Examples of the alkyl group and the halogen atom include the same ones already exemplified. Of these, those in which ^Ra is a bromine atom and R ^b is a hydrogen atom are preferable. Y is a monovalent anion, and examples thereof include hexachloroantimonate ion, hexafluorophosphate ion, chloride, bromide, iodide, hydroxydo, phosphate ion, sulfonate ion, and trifluoromethanesulfonate ion. Of these, hexachloroantimonate ion is preferable.

In the method for decomposing ammonia of the present embodiment, oxidative decomposition of ammonia may be carried out in a solvent. The solvent is not particularly limited, and examples thereof include a nitrile solvent, a halogenated hydrocarbon solvent, a ketone solvent, an alcohol solvent, a cyclic ether solvent, a chain ether solvent, and water. Examples of the nitrile solvent include acetonitrile, propionitrile and the like. Examples of the halogenated hydrocarbon solvent include methylene chloride and chloroform. Examples of the ketone solvent include acetone and methyl ethyl ketone. Examples of the alcohol solvent include methanol and ethanol. Examples of the cyclic ether solvent include tetrahydrofuran (THF), 1,4-dioxane and the like. Examples of the chain ether solvent include diethyl ether and the like.

In the method for decomposing ammonia of the present embodiment, oxidative decomposition of ammonia proceeds even if the reaction temperature is low. For example, −80 ° C. to 60 ° C. is preferable, and −50 ° C. to 30 ° C. is more preferable. The reaction atmosphere may be, for example, an inert atmosphere (Ar atmosphere, etc.) or an atmosphere. Further, it is not necessary to create a pressurized atmosphere, and a normal pressure atmosphere may be used. The reaction time is not particularly limited, but is usually set in the range of several tens of minutes to several tens of hours.

In the method for decomposing ammonia of the present embodiment, it is presumed that the reaction mechanism of oxidative decomposition of ammonia proceeds as shown in the scheme below.

From the above reaction mechanism, the cations of the salen manganese complex represented by the formula (1A) and the salen manganese complex represented by the formula (3A ^{+) function as catalysts.}

Ammonia-fueled fuel cell using the method for decomposing ammonia in this embodiment will be described.

<Ammonia-fueled fuel cell>
FIG. 1 is a cross-sectional view schematically showing the configuration of a fuel cell 100 using ammonia as fuel. A fuel cell 100 using ammonia as fuel will be described. The fuel cell 100 has an anode catalyst layer 103, a cathode catalyst layer 105, and an electrolyte film 107 sandwiched between both catalyst layers, and the cathode catalyst layer 105 has a gas diffusion layer 101 on the outside, and the anode catalyst layer 103. Has a gas diffusion layer 102 on the outside. A device composed of the gas diffusion layer 102, the anode catalyst layer 103, the electrolyte membrane 107, the cathode catalyst layer 105, and the gas diffusion layer 101 is referred to as a membrane electrode assembly (Membrane Electrode Assembly, hereinafter abbreviated as "MEA"). .. In the fuel cell 100, this MEA is usually sandwiched between the separators 109. Further, a component composed of a catalyst layer and a gas diffusion layer is referred to as a gas diffusion electrode (Gas Diffusion Electrode, hereinafter abbreviated as "GDE").

The fuel cell 100 uses an ion exchange resin film or the like as the electrolyte film 107, and reacts with oxygen, electrons, and water at the oxidizing agent electrode of the cathode catalyst layer 105 (O ₂ + 4e ⁻ + 4H ₂ O → 4OH ⁻ ). The hydroxide ion generated by the above moves through the electrolyte membrane 107 to the fuel electrode, which is the anode catalyst layer 103, and reacts with ammonia at the fuel electrode (2NH ₃ → N ₂ + 6e ⁻ + 6H ⁺ ) to produce nitrogen. , Generates electrons and protons. The ion exchange resin membrane is not particularly limited as long as it can move the hydroxide ions generated at the oxidant electrode to the fuel electrode, and examples thereof include a cation exchange membrane and an anion exchange membrane. .. Of these, an anion exchange membrane is preferable. Examples of the anion exchange membrane include a solid polymer membrane containing an anion exchange resin having an anion exchange group such as a quaternary ammonium group and a pyridinium group. Of these, an anion exchange membrane is preferable. Specific examples of the anion exchange membrane include FAP, FAP-450, FAA-3, FAS, FAB, AMI-7001, which are anion exchange membranes manufactured by Fumasep, and AMV, AMT, which are anion exchange membranes manufactured by AGC. , DSV, AAV, ASV, ASV-N, AHO, APS4 and the like, of which FAP-450, FAA-3 manufactured by Membrane and ASV-N manufactured by AGC are preferable.

The anode catalyst layer 103 contains a catalyst component (the above-mentioned salen manganese complex according to the present invention), a catalyst carrier for adsorbing the catalyst component, and an electrolyte. On the other hand, the cathode catalyst layer 105 contains a catalyst component, a catalyst carrier for supporting the catalyst component, and an electrolyte. As the catalyst component in the cathode catalyst layer 105, a known catalyst can be used without particular limitation. Examples of the catalyst component used in the cathode catalyst layer 105 include platinum, gold, silver, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and the like. Examples thereof include metals such as aluminum and alloys thereof, of which platinum is preferable.

Examples of the catalyst carrier in each of the catalyst layers 103 and 105 include carbon black such as channel black, furnace black, thermal black, acetylene black, and Ketjen black, activated carbon obtained by carbonizing and activating a material containing various carbon atoms, and coke. , Natural graphite, artificial graphite, carbonic materials such as graphitized carbon, metal meshes such as nickel or titanium, metal foams and the like. Of these, carbon black is preferable as the catalyst carrier because it has a high specific surface area and excellent electron conductivity.

Examples of the electrolyte in each of the catalyst layers 103 and 105 include Fusion FAA-3-SOLUT-10 manufactured by Fumasep, which is an anion exchange ionomer, and A3ver. 2. AS-4 (A3 ver.2 and AS-4 are described in, for example, magazine "Hydrogen Energy System", Vo1.35, No.2, 2010, page 9), Nafion (registered trademark, DuPont stock). Fluorophilic sulfonic acid polymers such as Aquivion (registered trademark, manufactured by Solvay Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), etc. Of these, Fusion FAA-3-SOLUT-10 and AS-4 are preferable.

The separator 109 may be a gas-impermeable conductive member, for example, a carbon plate obtained by compressing carbon to make it gas-impermeable, or a solid metal plate. A flow path for supplying ammonia is provided between the separator 109 and the gas diffusion layer 102 on the anode side. A gas passage to which oxygen or air is supplied is formed between the separator 109 and the gas diffusion layer 101 on the cathode side.

It goes without saying that the present invention is not limited to the above-described embodiment, and can be implemented in various embodiments as long as it belongs to the technical scope of the present invention.

Hereinafter, examples of the present invention will be described. The following examples do not limit the present invention in any way.

[Experimental Example 1]
An attempt was made to oxidatively decompose ammonia using a catalyst, an oxidizing agent, and a base. The salen manganese complex (1A) is available from Strem, Tokyo Chemical Industry, etc., and the salen manganese complex (1B), which is an enantiomer of the salen manganese complex (1A), is Strem, Fujifilm Wako Pure Chemical Industries, Ltd., etc. Available from.

In Example 1, salen manganese complex (1A) (6.4mg, 0.01mmol) and, ammonium triflate as an ammonium salt (501 mg, 3.0 mmol) and, as an oxidizing agent _{[(p-BrC 6 H 4} ) ₃ N ^· ] ⁺ [SbCl ₆ ] ^- (2a) (735 mg, 0.9 mmol) and 2,4,6-cholidine (0.4 mL, 3.0 mmol) as a base in 5 mL of acetonitrile, 1 After stirring at −40 ° C. for 2 hours under an argon atmosphere at atmospheric pressure, the mixture was stirred at room temperature for 4 hours. As a result, 4.3 equivalents (29% yield based on the oxidizing agent) of nitrogen was confirmed.

[Experimental Example 2]
In Experimental Example 2, cyclic voltammetry (CV) measurement was performed in order to obtain knowledge about the decomposition of ammonia under electrochemical oxidation conditions. That is, using a glassy carbon electrode as a working electrode and tetrabutylammonium hexafluorophosphate as a supporting electrolyte, salene manganese complex (1a) (0.01 mmol, 1 mM) and ammonia (0) were used in 10 mL of acetonitrile. CV measurement was performed at a scanning rate of 1 mV / s in the presence of .15 mmol). The graph of the obtained current-potential curve is shown in FIG. From this graph, the steady current in the oxidative decomposition of ammonia was confirmed. The value was 80 μA.

[Comparative Example 1]
As Comparative Example 1, when CV measurement was performed under the same experimental conditions as in Experimental Example 2 except that the salen manganese complex (1a) was not used, the graph shown in Comparative Example 1 in FIG. 2 was obtained, and the steady current was measured. Not observed. From this result, it was confirmed that the oxidative decomposition of ammonia proceeds even under electrochemical oxidation conditions.

[Synthesis Example 1]
Salen manganese complex (3A) according to the following formula

Was synthesized. By stirring the salen manganese complex (1A) (63.5 mg, 0.1 mmol) in methanol (10 mL) containing ammonium hexafluorophosphate (163 mg, 1 mmol), the salen manganese complex (3A) is crude. I took it out with. Subsequently, the salen manganese complex (3A) (74.4 mg, 0.10 mmol) was stirred in an ammonia-methanol solution (2 mol / L, 2 mL) for 10 minutes. Next, the salene manganese complex (3A) was obtained as a crystalline solid by recrystallization at −30 ° C. (27.6 mg, yield 36%). The spectral data of the salen manganese complex (3A) is as follows.
Magnetic susceptibility (Evans' Method):
_{μ eff = 4.8 μ B in CDCl} 3 at 298K.
Anal. calcd. for C ₃₆ H ₅₅ F ₆ O ₂ N ₃ PMn (3A):
C, 56.76; H, 7.28; N, 5.52.
Found:
C, 56.80; H, 7.31; N, 5.12.
ESI-TOF-MS (MeOH): 616.5 (m / z).

[Experimental Example 3]
In Example 3, salen manganese complex (3A) (7.6mg, 0.01mmol) and, ammonium triflate as an ammonium salt (501 mg, 3.0 mmol) and, as an oxidizing agent _{[(p-BrC 6 H 4} ) ₃ N ^· ] ⁺ [SbCl ₆ ] ^- (2a) (735 mg, 0.9 mmol) and 2,4,6-cholidine (0.4 mL, 3.0 mmol) as a base in 5 mL of acetonitrile, 1 After stirring at −40 ° C. for 2 hours under an ammonium atmosphere at atmospheric pressure, the mixture was stirred at room temperature for 4 hours. As a result, 3.0 equivalents (20% yield based on the oxidizing agent) of nitrogen was confirmed.

[Example 4] Fuel cell power generation test 1
A power generation test of an ammonia-fueled fuel cell using the salen manganese complex (1A) as a catalyst for the anode catalyst layer was carried out. The MEA of the fuel cell was made of GDE on the cathode side, GDE on the anode side, and an electrolyte membrane.

The GDE on the cathode side was prepared as follows. The catalyst ink used in the cathode catalyst layer is an electrode catalyst made of platinum-supported carbon (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., platinum content: 46.5% by weight, product name "TEC10E50E"), deionized water, ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.). Prepared using an anionic conduction ionomer dispersion (Fumion FAA-3-SOLUT-10 (10% by weight & N-methyl-2-pyrrolidone dispersion) manufactured by Fumasep). Here, the proportion of anionic conduction ionomers in the catalyst ink was adjusted to be 28% by weight. Electrode catalyst, deionized water, ethanol and anionic conduction ionomer dispersion are added in this order to a glass vial, and the obtained dispersion is added to the ultrasonic homogenizer Smart NR-50M manufactured by Microtech Nithion. The catalyst ink was prepared by setting the output of ultrasonic waves to 40% and irradiating the particles for 30 minutes. Next, a gas diffusion layer which is a carbon paper (“TGP-H-090” manufactured by Toray Industries, Inc. cut into a rectangle of 2.5 cm × 3 cm) fixed on a hot plate set at 80 ° C. with this catalyst ink. Was applied to. The coating amount is ^{such that the amount of platinum per 1 cm 2} of the coated surface is 1 mg, and the cathode side GDE composed of the cathode catalyst layer and the gas diffusion layer (the platinum catalyst (7.5 mg) is included on the GDE). ) Was prepared.

The ratio of anionic conduction ionomers in the above-mentioned catalyst ink will be described. In the preparation of the catalyst ink, the proportion (% by weight) of the anion conductive ionomer calculated from the following formula was set to 28% by weight. In the formula, the anion conductive ionomer is abbreviated as "ionomer".
Ratio of ionomer (% by weight) =
[Ionomer solids (weight) / [Electrode catalyst (weight) + Ionomer solids (weight)]] x 100
Specifically, when a 10 wt% anion conductive ionomer dispersion was used, the amount of the electrode catalyst was 100.0 mg, the amount of the anionic ionomer dispersion was 389.0 mg, and the amount of deionized water was 0.6 mL. , The amount of ethanol was set to 5.1 mL.

The GDE on the anode side was prepared as follows. The catalyst ink used in the anode catalyst layer is salene manganese complex (1A) (46.5 mg), carbon black (53.5 mg, manufactured by Lion, Ketjen Black, product name "EC300J"), deionized water, ethanol (Fuji). It was prepared using Film Wako Pure Chemical Industries, Ltd.) and an anion conducting ionomer dispersion liquid [Fumion FAA-3-SOLUT-10 (10% by weight & N-methyl-2-pyrrolidone dispersion) manufactured by Fumasep]. Here, the proportion of anionic conduction ionomers in the catalyst ink was adjusted to be 28% by weight. Salen manganese complex, carbon black, deionized water, ethanol and anionic conduction ionomer dispersion are added in this order to a glass vial, and the obtained dispersion is added to an ultrasonic homogenizer manufactured by Microtech Nithione. A catalyst ink was prepared by irradiating ultrasonic waves at an output of 40% for 30 minutes using a Smart NR-50M. Next, a gas diffusion layer which is a carbon paper (“TGP-H-090” manufactured by Toray Industries, Inc. cut into a rectangle of 2.5 cm × 3 cm) fixed on a hot plate set at 80 ° C. with this catalyst ink. Was applied to. The coating amount is ^{such that the amount of the salene manganese complex per 1 cm 2} of the coated surface is 1 mg, and the GDE on the anode side composed of the anode catalyst layer and the gas diffusion layer (7.5 mg of the salene manganese complex (7.5 mg) on the GDE). ) Is included).

The ratio of anionic conduction ionomers in the above-mentioned catalyst ink will be described. In the preparation of the catalyst ink, the proportion (% by weight) of the anion conductive ionomer calculated from the following formula was set to 28% by weight. In the formula, the anion conductive ionomer is abbreviated as "ionomer".
Ratio of ionomer (% by weight) =
[Ionomer solids (weight) / [manganese complex (weight) + carbon black (weight) + ionomer solids (weight)]] x 100
Specifically, when a dispersion of 10% by weight of anion conducting ionomer was used, the amount of the dispersion of salen manganese complex (46.5 mg), carbon black (53.5 mg), and anion conducting ionomer was 389.0 mg. The amount of deionized water was set to 0.6 mL and the amount of ethanol was set to 5.1 mL.

As the electrolyte membrane, FAA-3 (thickness 50 μm) manufactured by Fumasep was used.

MEA was prepared by combining the GDE on the anode side, the electrolyte membrane, and the GDE on the cathode side in this order. The MEA is placed in a single cell (manufactured by Nissan Chemical Co., Ltd., fuel cell) having a rectangular electrode area of 2.5 cm × 3 cm, and the power generation test of the fuel cell is performed by an electrochemical measurement system (manufactured by Princeton Applied Research Co., Ltd.). , VersaSTAT4), and the current density and voltage were measured. In addition, the open circuit voltage (Open Circuit Voltage, hereinafter abbreviated as "OCV") was measured. The OCV is a potential in a state where no voltage or current is applied to the single cell. The conditions for the power generation test are as follows.

<Power generation test conditions>
Single cell temperature: 25-28 ° C (room temperature)
Fuel supply on the anode side: Supply fuel solution on the anode side (7 mL) in a lump. Fuel supply on the cathode side: Supply by attaching an oxygen-filled experimental balloon to the supply port. An anode-side fuel solution prepared by adding ammonium trifurate (1.00 g, 6.0 mmol), deionized water (10 mL) and 2,4,6-cholidine (0.80 mL, 6.0 mmol) was used.

The OCV of a single cell was 0.46V. The results of current density and voltage are shown in Table 1. Twice

　 

[Example 5] Fuel cell power generation test 2
Here, a power generation test of a fuel cell using ammonia as a fuel was carried out in the same manner as in Example 4 except that ASV-N (thickness 100 μm) manufactured by AGC was used as the electrolyte membrane. The OCV of the single cell was 0.11V. The results of current density and voltage are shown in Table 2.

　 

The salen manganese complex used in the oxidative decomposition method of ammonia according to the present invention can be used for decomposition of ammonia, and further can be used as a catalyst in the anode catalyst layer of a fuel cell using ammonia as fuel.

Claims (16)

1. A method for decomposing ammonia in which ammonia is oxidatively decomposed to obtain nitrogen, protons and electrons in the presence of a salen manganese complex and a base.
   

   

   (In the formula, R ¹ and R ² represent C1-C4 alkyl groups which may be the same or different, and X is a monovalent anion, axial ligand or halogen atom.)
   Is a complex represented by,
   Ammonia decomposition method.
2. The salen manganese complex has the following formula (1A) or formula (1B).
   

   

   The method for decomposing ammonia according to claim 1, which is a complex represented by.
3. The method for decomposing ammonia according to claim 1 or 2, wherein the ammonia is produced by a reaction between an ammonium salt and a base in the system.
4. The method for decomposing ammonia according to any one of claims 1 to 3, wherein the base is pyridine having a substituent at at least one of the 2-position to the 6-position.
5. The method for decomposing ammonia according to claim 4, wherein the base is 2,4,6-colysine.
6. The method for decomposing ammonia according to any one of claims 1 to 5, wherein the oxidative decomposition is carried out by using an oxidizing agent containing a one-electron oxidant of triarylamine.
7. The method for decomposing ammonia according to any one of claims 1 to 6, wherein the oxidative decomposition is carried out at a reaction temperature of −80 ° C. to 60 ° C.
8. A fuel cell using a fuel containing ammonia using a method for decomposing ammonia to obtain nitrogen, protons and electrons by oxidatively decomposing ammonia in the presence of a salen manganese complex and a base, wherein the salen manganese complex has the formula ( 1a), formula (1b) or formula (1c)
   

   

   (In the formula, R ¹ and R ² represent C1-C4 alkyl groups which may be the same or different, and X is a monovalent anion, axial ligand or halogen atom.)
   Is a complex represented by,
   Ammonia fuel cell.
9. The salen manganese complex has the following formula (1A) or formula (1B).
   

   

   The ammonia fuel cell according to claim 8, which is a complex represented by.
10. The ammonia fuel cell according to claim 8 or 9, wherein the ammonia is generated by a reaction between an ammonium salt and a base in the system.
11. The ammonia fuel cell according to any one of claims 8 to 10, wherein the base is pyridine having a substituent at at least one of the 2-position to the 6-position.
12. The method for decomposing ammonia according to claim 11, wherein the base is 2,4,6-colysine.
13. The ammonia fuel cell according to any one of claims 8 to 12, wherein the oxidative decomposition is carried out by using an oxidizing agent containing a one-electron oxidant of triarylamine.
14. The ammonia fuel cell according to any one of claims 8 to 13, wherein the oxidative decomposition is carried out at a reaction temperature of −80 ° C. to 60 ° C.
15. Formula (4A) or formula (4B)
    

    

    (In the formula, Z is a monovalent anion, axial ligand or halogen atom.)
    The complex indicated by.
16. The complex according to claim 15, wherein Z is a hexafluorophosphate ion.

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