JP2012129191A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell showing excellent power generation performance, containing a compound containing at least hydrogen and nitrogen as a fuel, and using an anion exchange membrane as an electrolyte layer.SOLUTION: A fuel cell 1 comprises an electrolyte layer 4 composed of an anion exchange membrane, and a fuel electrode 2 and an air electrode 3 facing each other with the electrolyte layer 4 sandwiched. The fuel electrode 2 contains lanthanum and cobalt as a metal catalyst, and the percentage of lanthanum content is in the range of 20 to 40 mol% with respect to the total number of moles of lanthanum and cobalt. A compound containing at least hydrogen and nitrogen, such as hydrazine, is used as a fuel.

Description

  The present invention relates to a fuel cell, and more particularly to a polymer electrolyte fuel cell.

  To date, various types of fuel cells such as alkaline type (AFC), solid polymer type (PEFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), and solid electrolyte type (SOFC) are known. It has been. Especially, since a polymer electrolyte fuel cell can be operated at a relatively low temperature, use in various applications such as an automobile application is being studied.

  As such a polymer electrolyte fuel cell, for example, an electrolyte layer composed of an anion exchange membrane and a compound (for example, hydrazine) which are disposed opposite to each other with the electrolyte layer interposed therebetween and which contains cobalt and also contains hydrogen and nitrogen. Etc.) has been proposed (see, for example, Patent Document 1). The fuel cell includes a fuel-side electrode to which fuel is supplied and an oxygen-side electrode to which oxygen is supplied.

JP 2006-244961 A

  However, in recent years, it is increasingly desired to improve the power generation performance of fuel cells.

  An object of the present invention is to provide a fuel cell having excellent power generation performance in a fuel cell that contains a compound containing at least hydrogen and nitrogen as a fuel and uses an anion exchange membrane as an electrolyte layer.

  In order to achieve the above object, a fuel cell according to the present invention comprises an electrolyte layer, a fuel-side electrode that is disposed opposite to the electrolyte layer, to which fuel is supplied, and an oxygen-side electrode to which oxygen is supplied. In the fuel cell, the electrolyte layer is an anion exchange membrane, the fuel contains a compound containing at least hydrogen and nitrogen, the fuel side electrode contains lanthanum and cobalt, and the lanthanum in the fuel side electrode The content ratio of is 40 to 40 mol% with respect to the total mole of lanthanum and cobalt.

  In the fuel cell of the present invention, it is preferable that the fuel is hydrazines.

  According to the fuel cell of the present invention, the fuel-side electrode contains lanthanum and cobalt, and the content of lanthanum in the fuel-side electrode is 20 to 40% with respect to the total mole of lanthanum and cobalt. Therefore, the power generation performance can be improved.

It is a schematic block diagram which shows one Embodiment of the fuel cell of this invention. It is a graph which shows the result of the activity measurement of a fuel side electrode.

  FIG. 1 is a schematic configuration diagram showing an embodiment of a fuel cell of the present invention. In FIG. 1, the fuel cell 1 includes a fuel cell S, and the fuel cell S includes a fuel side electrode 2, an oxygen side electrode 3, and an electrolyte layer 4, and the fuel side electrode 2 and the oxygen side electrode 3. However, they are opposed to each other with the electrolyte layer 4 sandwiched therebetween.

  The fuel side electrode 2 is in opposed contact with one surface of the electrolyte layer 4. The fuel side electrode 2 contains lanthanum (La) and cobalt (Co) as metal catalysts.

  Specific examples of the metal catalyst include a mixture of lanthanum and cobalt (mixed catalyst), an alloy of lanthanum and cobalt (lanthanum-cobalt alloy), a mixture of lanthanum, cobalt, and a lanthanum-cobalt alloy. Can be mentioned.

  In order to produce such a metal catalyst, for example, first, a dispersion containing a lanthanum salt and a cobalt salt is prepared, then lanthanum and cobalt are dried, and then calcined.

  More specifically, in order to produce a metal catalyst, for example, first, a lanthanum salt and a cobalt salt are dispersed in a solvent to prepare a dispersion.

  Examples of the lanthanum salt include an inorganic metal salt of lanthanum and an organic metal salt of lanthanum.

  Examples of the inorganic metal salt of lanthanum include inorganic acid salts such as sulfates, nitrates, and phosphates, such as chlorides and ammonium salts.

  Examples of lanthanum organometallic salts include lanthanum carboxylates such as acetates and propionates, such as β-diketone compounds or β-ketoester compounds represented by the following general formula (1), and / or Examples thereof include a metal chelate complex of lanthanum formed from a β-dicarboxylic acid ester compound represented by the general formula (2).

R ₁ COCHR ₃ COR ₂ (1)
(In the formula, R1 represents an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, or an aryl group, and R2 represents an alkyl group having 1 to 6 carbon atoms or a fluoro having 1 to 6 carbon atoms. An alkyl group, an aryl group, or an alkoxy group having 1 to 4 carbon atoms, and R3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)
R ₅ CH (COR ₄ ) ₂ (2)
(In the formula, R4 represents an alkyl group having 1 to 6 carbon atoms, and R5 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)
In the general formula (1) and the general formula (2), examples of the alkyl group having 1 to 6 carbon atoms of R1, R2, and R4 include methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, Examples include t-butyl, t-amyl, t-hexyl and the like. Moreover, as a C1-C4 alkyl group of R3 and R5, methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, t-butyl etc. are mentioned, for example.

  In the general formula (1), examples of the fluoroalkyl group having 1 to 6 carbon atoms of R1 and R2 include trifluoromethyl. Examples of the aryl group for R1 and R2 include phenyl. Moreover, as a C1-C4 alkoxy group of R1, a methoxy, an ethoxy, a propoxy, an isopropoxy, n-butoxy, s-butoxy, t-butoxy etc. are mentioned, for example.

  More specifically, β-diketone compounds are, for example, 2,4-pentanedione, 2,4-hexanedione, 2,2-dimethyl-3,5-hexanedione, 1-phenyl-1,3-butanedione. 1-trifluoromethyl-1,3-butanedione, hexafluoroacetylacetone, 1,3-diphenyl-1,3-propanedione, dipivaloylmethane and the like.

  More specific examples of the β-keto ester compound include methyl acetoacetate, ethyl acetoacetate, t-butyl acetoacetate, and the like.

  Specific examples of the β-dicarboxylic acid ester compound include dimethyl malonate and diethyl malonate.

  These lanthanum salts can be used alone or in combination of two or more.

  The lanthanum salt is preferably an inorganic metal salt of lanthanum, more preferably an inorganic acid salt of lanthanum.

  Examples of the cobalt salt include an inorganic metal salt of cobalt and an organic metal salt of cobalt.

  Examples of the inorganic metal salt of cobalt include inorganic acid salts such as sulfates, nitrates, and phosphates, such as chlorides and ammonium salts.

  Examples of cobalt organic metal salts include cobalt carboxylates formed from acetates, propionates, and the like, such as β-diketone compounds or β-ketoester compounds represented by the above general formula (1), and / or Alternatively, a metal chelate complex of cobalt formed from the β-dicarboxylic acid ester compound represented by the general formula (2) can be used.

  These cobalt salts can be used alone or in combination of two or more.

  The cobalt salt is preferably an inorganic metal salt of cobalt, more preferably an inorganic acid salt of cobalt.

  Examples of the solvent include water, alcohols (eg, 2-propanol), ethers (eg, tetrahydrofuran (THF)), ketones, esters, aliphatic hydrocarbons, aromatic hydrocarbons, and the like. Can be mentioned.

  These solvents can be used alone or in combination of two or more.

  As the solvent, water, alcohols, ethers and the like are preferable.

  The dispersion can be prepared by, for example, a method of blending a lanthanum salt and a cobalt salt in a solvent, a method of blending a mixture of a lanthanum salt and a solvent, and a mixture of a cobalt salt and a solvent, or the like. . Preferably, the dispersion is prepared by a method of blending a mixture of a lanthanum salt and a solvent and a mixture of a cobalt salt and a solvent.

  In such a case, the lanthanum salt concentration of the mixture of the lanthanum salt and the solvent is, for example, 0.0001 to 1 mol / L, preferably 0.01 to 0.1 mol / L. Moreover, the cobalt salt density | concentration of the mixture of a cobalt salt and a solvent is 0.0001-1 mol / L, for example, Preferably, it is 0.01-0.1 mol / L.

  In the dispersion (mixture of lanthanum salt, cobalt salt and solvent) obtained by blending them, the concentration (total amount) of the lanthanum salt and cobalt salt is, for example, 0.0001 to 1 mol / L, preferably 0. 0.01 to 0.1 mol / L.

  Next, in this method, for example, the solvent is removed from the obtained dispersion by a known method such as heat drying or vacuum freeze drying, and the compound containing lanthanum and cobalt is dried. Preferably, it is freeze-dried in vacuum.

  More specifically, in vacuum lyophilization, first, the dispersion is, for example, at −200 to 0 ° C., preferably at −196 to −100 ° C., for example, for 5 to 120 minutes, preferably 20 to 40 minutes. Cool and freeze (pre-freeze).

  Next, the solvent is sublimated from the frozen product under vacuum (specifically, for example, 0.1 to 100 Pa) to obtain a dried product. In addition, although a solvent sublimes by putting a frozen thing on vacuum conditions, temperature conditions can be operated (heating or cooling) as needed. In the case of temperature operation, the temperature condition is appropriately set as necessary.

Next, in this method, the obtained dried product is fired under a reducing atmosphere (for example, a H ₂ / Ar mixed gas).

  In firing, the dried product is heated, for example, gradually and intermittently. In such a case, the rate of temperature increase during heating is, for example, 0.1 to 20 ° C./min, and preferably 1 to 12 ° C./min. Moreover, the maximum attainment temperature is 200-1200 degreeC, for example, Preferably, it is 600-900 degreeC, and the retention time in the maximum attainment temperature is 30-600 minutes, for example, Preferably, it is 180-360 minutes.

  Thereby, a metal catalyst containing lanthanum and cobalt can be obtained.

  As the metal catalyst, for example, a fine powder of lanthanum metal obtained as a commercial product, a fine powder of cobalt metal obtained as a commercial product, and, if necessary, a fine powder of lanthanum-cobalt alloy obtained as a commercial product. It is also possible to use a mixture obtained by mixing powder.

  In the metal catalyst, lanthanum (lanthanum metal atom) and cobalt (cobalt metal atom) are necessarily contained, and the content ratio thereof is lanthanum (lanthanum-cobalt alloy with respect to the total moles of lanthanum and cobalt). Lanthanum contained in the lanthanum-cobalt alloy), and 20 to 40 mol%, preferably 20 to 30 mol%, more preferably 20 mol%. Inclusive)) is 60 to 80%, preferably 70 to 80 mol%, more preferably 80 mol%.

  When the content ratio of lanthanum is the above ratio, excellent power generation performance can be obtained.

  In addition, the metal catalyst whose content rate of a lanthanum and cobalt is said range can be manufactured by adjusting the mixture ratio of a lanthanum and cobalt in the manufacturing method of an above-described metal catalyst, for example.

  More specifically, in the above-described method for producing a metal catalyst, a lanthanum salt and a cobalt salt are mixed with lanthanum (a lanthanum metal atom) in which the number of moles of lanthanum (a lanthanum metal atom) is included in the lanthanum salt Atoms) and the total moles of cobalt (cobalt metal atoms) contained in the cobalt salt so as to have the above ratio.

  Thereby, the metal catalyst whose content rate of a lanthanum and cobalt is said range can be manufactured.

  In the present invention, the metal catalyst can also be produced by supporting lanthanum and cobalt obtained as described above on carbon.

  In order to support lanthanum and cobalt on carbon, for example, in the above-described method for producing a metal catalyst, for example, a porous carbon support is blended together with a lanthanum salt and a cobalt salt.

  In addition, when it is difficult to uniformly mix the solvent and the carbon carrier when blending the carbon carrier, for example, an alcohol (for example, ethanol) is blended together with the carbon carrier. You can also.

  In the case of using lanthanum and cobalt supported on carbon, the lanthanum and cobalt are, for example, 0.1 to 50 weights based on the total amount of lanthanum, cobalt and carbon. %, Preferably 5 to 40% by weight.

  Moreover, although it does not restrict | limit especially in forming the fuel side electrode 2 from such a metal catalyst, For example, a membrane-electrode assembly is formed. The membrane-electrode assembly can be formed by a known method. For example, first, the above-described metal catalyst and electrolyte solution are mixed, and if necessary, an appropriate solvent such as alcohol is added to adjust the viscosity, thereby preparing a dispersion of the above-described metal catalyst. Next, the dispersion is coated on the surface of the electrolyte layer 4 (anion exchange membrane), thereby fixing the above-described metal catalyst on the surface of the electrolyte layer 4.

The usage-amount of a metal catalyst is 0.01-5 mg / cm < ² >, for example.

In the fuel-side electrode 2, as will be described later, a supplied compound containing at least hydrogen and nitrogen (hereinafter referred to as “fuel compound”) and hydroxide ions (OH ⁻ ) that have passed through the electrolyte layer 4 are supplied. To produce electrons (e ⁻ ), nitrogen (N ₂ ), and water (H ₂ O).

  The oxygen side electrode 3 is in opposed contact with the other surface of the electrolyte layer 4. Although this oxygen side electrode 3 is not specifically limited, For example, it forms as a porous electrode with which a catalyst is carry | supported.

The catalyst is not particularly limited as long as it has a catalytic action for generating hydroxide ions (OH ⁻ ) from oxygen (O ₂ ) and water (H ₂ O), as will be described later. , Platinum group elements (Ru, Rh, Pd, Os, Ir, Pt), periodic table 8-10 (VIII) group elements such as iron group elements (Fe, Co, Ni), Cu, Ag, Au, for example The 11th (IB) group element of a periodic table, etc., these combinations, etc. are mentioned further. Of these, Co is preferable. The supported amount of the catalyst is, for example, 0.1 to 10 mg / cm ² , preferably 0.1 to 5 mg / cm ² . The catalyst is preferably supported on carbon.

  The formation of the oxygen side electrode 3 from such a catalyst is not particularly limited. For example, a membrane-electrode assembly is formed in the same manner as the fuel side electrode 2 described above.

In the oxygen-side electrode 3, as will be described later, the supplied oxygen (O ₂ ), water (H ₂ O), and the electrons (e ⁻ ) that have passed through the external circuit 13 are reacted to form a hydroxide. Ion (OH ⁻ ) is generated.

The electrolyte layer 4 is formed from an anion exchange membrane. The anion exchange membrane is not particularly limited as long as it is a medium that can move hydroxide ions (OH ⁻ ) generated at the oxygen side electrode 3 from the oxygen side electrode 3 to the fuel side electrode 2. Examples thereof include a solid polymer membrane (anion exchange resin) having an anion exchange group such as a quaternary ammonium group or a pyridinium group.

  The fuel cell S further includes a fuel supply member 5 and an oxygen supply member 6. The fuel supply member 5 is made of a gas-impermeable conductive member, and one surface thereof is in opposed contact with the fuel-side electrode 2. The fuel supply member 5 is formed with a fuel-side flow path 7 for bringing fuel into contact with the entire fuel-side electrode 2 as a distorted groove recessed from one surface. The fuel-side flow path 7 has a supply port 8 and a discharge port 9 that pass through the fuel supply member 5 formed continuously at the upstream end and the downstream end, respectively.

  Similarly to the fuel supply member 5, the oxygen supply member 6 is made of a gas-impermeable conductive member, and one surface thereof is opposed to the oxygen side electrode 3. The oxygen supply member 6 is also formed with an oxygen-side flow channel 10 for contacting oxygen (air) with the entire oxygen-side electrode 3 as a distorted groove recessed from one surface. The oxygen-side flow path 10 also has a supply port 11 and a discharge port 12 that pass through the oxygen supply member 6 continuously formed at the upstream end portion and the downstream end portion thereof.

  The fuel cell 1 is actually formed as a stack structure in which a plurality of the fuel cells S described above are stacked. Therefore, the fuel supply member 5 and the oxygen supply member 6 are actually configured as separators in which the fuel side flow path 7 and the oxygen side flow path 10 are formed on both surfaces.

  Although not shown, the fuel cell 1 is provided with a current collector plate formed of a conductive material, and an electromotive force generated in the fuel cell 1 is taken out from a terminal provided on the current collector plate. It is configured to be able to.

  Further, on a test (model) basis, the fuel supply member 5 and the oxygen supply member 6 of the fuel cell S are connected by an external circuit 13, and a voltmeter 14 is interposed in the external circuit 13 to generate the fuel cell S. The voltage can also be measured.

  In the present invention, the fuel containing the fuel compound is directly supplied without going through reforming or the like.

  In this fuel compound, hydrogen is preferably bonded directly to nitrogen. The fuel compound preferably has a nitrogen-nitrogen bond, and preferably does not have a carbon-carbon bond. Moreover, the carbon number is preferably as small as possible (zero if possible).

  Further, such a fuel compound may contain an oxygen atom, a sulfur atom, etc. within a range not impairing its performance, and more specifically, a carbonyl group, a hydroxyl group, a hydrate, a sulfonic acid group or a sulfuric acid group. It may be contained as a salt or the like.

From this point of view, specific examples of the fuel compound in the present invention include hydrazine (NH ₂ NH ₂ ), hydrazine hydrate (NH ₂ NH ₂ .H ₂ O), and hydrazine carbonate ((NH ₂ NH). _{2) 2} CO _2), hydrazine sulfate _{(NH 2 NH 2 · H 2} SO 4), monomethyl hydrazine _(CH 3 NHNH _2), dimethylhydrazine _{((CH 3) 2 NNH 2} , CH 3 NHNHCH 3), a carboxylic hydrazide ( Hydrazines such as (NHNH ₂ ) ₂ CO), eg urea (NH ₂ CONH ₂ ), eg ammonia (NH ₃ ) eg imidazole, 1,3,5-triazine, 3-amino-1,2, heterocyclic compounds such as 4-triazoles, e.g., hydroxylamine _(NH 2 OH), hydroxylamine sulfate (NH OH _· H 2 SO _4), and the like hydroxylamines such. Such fuel compounds can be used alone or in combination of two or more. Preferably, hydrazines are used.

Among the above fuel compounds, compounds not containing carbon, that is, hydrazine (NH ₂ NH ₂ ), hydrazine hydrate (NH ₂ NH ₂ .H ₂ O), hydrazine sulfate (NH ₂ NH ₂ .H ₂ SO ₄ ) , Ammonia (NH ₃ ), hydroxylamine (NH ₂ OH), and hydroxylamine sulfate (NH ₂ OH · H ₂ SO ₄ ) are durable because there is no poisoning of the catalyst by CO as in the case of hydrazine reaction described later. Can be improved and substantially zero emission can be realized.

  As the fuel, the fuel compound exemplified above may be used as it is, but the fuel compound exemplified above is used as a solution such as water and / or alcohol (for example, lower alcohol such as methanol, ethanol, propanol, isopropanol). Can be used. In this case, the concentration of the fuel compound in the solution varies depending on the type of fuel compound, but is, for example, 1 to 90% by weight, preferably 1 to 30% by weight.

  Further, as the fuel, the above-described fuel compound can be used as a gas (for example, vapor).

Then, if the above-described fuel is supplied to the fuel-side channel 7 of the fuel supply member 5 while supplying oxygen (air) to the oxygen-side channel 10 of the oxygen supply member 6, As described, the electrons (e ⁻ ) generated in the fuel side electrode 2 and moving via the external circuit 13 react with water (H ₂ O) and oxygen (O ₂ ) to generate hydroxide ions. (OH ⁻ ) is generated. The generated hydroxide ions (OH ⁻ ) move from the oxygen side electrode 3 to the fuel side electrode 2 through the electrolyte layer 4 made of an anion exchange membrane. In the fuel-side electrode 2, the hydroxide ions (OH ⁻ ) that have passed through the electrolyte layer 4 react with the fuel to generate electrons (e ⁻ ). The generated electrons (e ⁻ ) are moved from the fuel supply member 5 to the oxygen supply member 6 via the external circuit 13 and supplied to the oxygen side electrode 3. An electromotive force is generated by such an electrochemical reaction in the fuel side electrode 2 and the oxygen side electrode 3, and power generation is performed.

In such an electrochemical reaction, in the fuel side electrode 2, a one-stage reaction in which hydroxide ions (OH ⁻ ) are directly reacted with the fuel, and the fuel is hydrogen (H ₂ ) and nitrogen (N ₂ ). There are two types of reactions: a two-stage reaction in which a hydroxide ion (OH ⁻ ) is reacted with hydrogen (H ₂ ) generated by the decomposition.

For example, when hydrazine (NH ₂ NH ₂ ) is used as the fuel, the one-stage reaction can be expressed by the following reaction formulas (1) to (3) as the fuel side electrode 2, the oxygen side electrode 3 and the whole. it can.
(1) NH ₂ NH ₂ + 4OH ⁻ → 4H ₂ O + N ₂ + 4e ⁻ (fuel side electrode)
(2) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (oxygen side electrode)
(3) NH ₂ NH ₂ + O ₂ → 2H ₂ O + N ₂ (whole)
The two-stage reaction can be expressed by the following reaction formulas (4) to (7) as the fuel side electrode 2, the oxygen side electrode 3, and the whole.
(4) NH ₂ NH ₂ → 2H ₂ + N ₂ (decomposition reaction; fuel side electrode)
(5) H ₂ + 2OH ⁻ → 2H ₂ O + 2e ⁻ (fuel side electrode)
(6) 1 / 2O ₂ + H ₂ O + 2e ⁻ → 2OH ⁻ (oxygen side electrode)
(7) H ₂ + 1 / 2O ₂ → H ₂ O (Overall)
As shown in the above reaction formula (4), in the two-stage reaction, hydrazine (NH ₂ NH ₂ ) is once decomposed into hydrogen (H ₂ ) and nitrogen (N ₂ ). Causes energy loss. For this reason, when the ratio of the two-stage reaction to the one-stage reaction is increased, the fuel utilization efficiency is decreased and the calorific value is increased.

However, in the fuel cell 1, as described above, the fuel-side electrode 2 always contains lanthanum and cobalt as metal catalysts, and the lanthanum content ratio is based on the total moles of lanthanum and cobalt. And 20 to 40 mol%. This metal catalyst suppresses the decomposition reaction (decomposition reaction represented by the above formula (4)) of the fuel (hydrazine in the above example) and directly reacts the fuel with hydroxide ions (OH ⁻ ) (the above formula ( The reaction shown in 1) can be promoted. Therefore, it is possible to improve fuel utilization efficiency and suppress the amount of heat generation, and consequently improve power generation performance.

  The operating conditions of the fuel cell 1 are not particularly limited. For example, the pressure on the fuel side electrode 2 side is 200 kPa or less, preferably 100 kPa or less, and the pressure on the oxygen side electrode 3 side is 200 kPa or less. Preferably, it is 100 kPa or less, and the temperature of the fuel cell S is set to 0 to 120 ° C., preferably 20 to 80 ° C.

  As mentioned above, although embodiment of this invention was described, embodiment of this invention is not limited to this, A design can be suitably changed in the range which does not change the summary of this invention.

  Applications of the fuel cell of the present invention include, for example, power sources for driving motors in automobiles, ships, airplanes, etc., and power sources in communication terminals such as mobile phones.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.

Example 1
<Preparation of metal salt solution>
The following metal salt solution was prepared with an autosampler (manufactured by GILSON, GX-271LH).
-Lanthanum nitrate (La (NO ₃ ) ₃ ) aqueous solution (concentration 0.012 mol / L)
Cobalt nitrate (Co (NO ₃ ) ₂ ) aqueous solution (concentration 0.023 mol / L)
<Preparation of mixed dispersion>
With an autosampler (manufactured by GILSON, GX-271LH), an aqueous lanthanum nitrate solution (3.337 mL) (converted to lanthanum nitrate 8.0 × 10 ⁻⁵ mol) and an aqueous cobalt nitrate solution (6.963 mL) (converted to cobalt nitrate 1.6 × 10 × 10) ^-4 mol).

  In the mixed solution, the total concentration of metal salts, that is, the concentration (total amount) of lanthanum nitrate and cobalt nitrate is 0.047 mol / L, and the charged content is lanthanum with respect to the total moles of lanthanum and cobalt. Was 20 mol% and cobalt was 80 mol% (La: Co = 20: 80 (molar ratio)).

  Next, 0.05 g of a carbon support (manufactured by Lion Corporation, ECP-600JD) was added to the mixed solution. At this time, the weight ratio (total amount) of lanthanum and cobalt was 23% by weight with respect to the total amount of the carbon support, lanthanum and cobalt.

Thereafter, a homogenizer (manufactured by Taitec, VP-050) was operated at an output of 10 to 20% and stirred for about 3 minutes to obtain a dispersion (slurry).
<Preliminary freezing>
The dispersion was cooled with liquid nitrogen (−196 ° C.) for 30 minutes at atmospheric pressure and frozen.
<Vacuum freeze drying>
In a vacuum freeze dryer (Labconco, FZ-12 type), the temperature was controlled according to the drying program shown in Table 1 to sublimate the solvent. Thereby, a dried product was obtained.

<Baking>
In a gas flow firing furnace (manufactured by Round Science), the temperature of the dried product was controlled according to the firing program shown in Table 2 in the presence of a H ₂ / Ar mixed gas (H ₂ / Ar = 10/90 (volume ratio)). And fired. Thereby, a metal catalyst was obtained.

  Thereafter, the inside of the firing furnace was replaced with a nitrogen atmosphere, and the metal catalyst was taken out.

(Examples 2-3 and Comparative Examples 1-8)
A metal catalyst was obtained in the same manner as in Example 1 except that the mixing ratio of the aqueous lanthanum nitrate solution and the aqueous cobalt nitrate solution was as shown in Table 3.

  In Examples 1 to 3 and Comparative Examples 1 to 8, in Examples 1 to 3 and Comparative Examples 1 to 8, several drops (1 to 5 drops) of ethanol were blended in order to uniformly mix the carbon support.

(Evaluation)
About the fuel side electrode which consists of a metal catalyst obtained by each Example and each comparative example, each test piece was produced and activity was measured.
<Create test piece>
First, 0.005 g of the metal catalyst of each example and each comparative example, 4 mL of pure water, and 0.75 mL of 2-propanol were mixed and dispersed for 10 minutes with an ultrasonic disperser.

  Next, a mixed solution of 0.23 mL of tetrahydrofuran and 20 μL of ionomer was added to the dispersion, and dispersion treatment was performed for 10 minutes using an ultrasonic disperser.

Thereafter, 40 μL of the obtained dispersion was taken with a micropipette, dropped onto a working electrode for electrochemical activity evaluation, and dried at room temperature for about 1 hour. Thereby, the test piece of each Example and each comparative example was obtained.
<Activity measurement>
Each test piece was used, and the oxidation activity of hydrazine was evaluated using a mixed solution of 1M KOH and 1M hydrazine as an electrolytic solution.

The measurement conditions are shown below.
(Measurement i (before durability test))
Potential width: −0.13 V to 0.22 V (vs. hydrogen reversible potential (RHE))
Scanning speed: 5 mV / s
Measurement temperature: 60 ° C
Reference electrode: Zn / ZnO (0.43 V vs. RHE (60 ° C.) / 1 MKOH)
Auxiliary electrode; number of Pt wire cycles; 6 cycles (measurement ii (endurance test))
Potential width: −0.13 V to 0.22 V (vs. hydrogen reversible potential (RHE))
Scanning speed: 20 mV / s
Measurement temperature: 60 ° C
Reference electrode: Zn / ZnO (0.43 V vs. RHE (60 ° C.) / 1 MKOH)
Auxiliary electrode; number of Pt wire cycles; 100 cycles (measurement iii (after endurance test))
Potential width: −0.13 V to 0.22 V (vs. hydrogen reversible potential (RHE))
Scanning speed: 5 mV / s
Measurement temperature: 60 ° C
Reference electrode: Zn / ZnO (0.43 V vs. RHE (60 ° C.) / 1 MKOH)
Auxiliary electrode: Number of Pt wire cycles: 6 cycles The results of activity evaluation in measurement i (before durability test) and measurement iii (after durability test) are shown in FIG.

  In FIG. 2, the result of measurement i (before the durability test) is indicated by a broken line, and the result of measurement iii (after the durability test) is indicated by a solid line.

  Moreover, evaluation of the comparative example 1 (catalyst containing only cobalt) is shown as a reference line.

  As shown in FIG. 2, the metal catalyst of each example had a lower oxidation start potential and excellent power generation performance than the metal catalyst of each comparative example. In Comparative Example 6 and Comparative Example 8, the results of activity evaluation in Measurement i and Measurement iii were the same value.

2 Fuel side electrode 3 Oxygen side electrode 4 Electrolyte layer S Fuel cell

Claims (2)

In a fuel cell comprising an electrolyte layer, a fuel-side electrode that is disposed to face the electrolyte layer and is supplied with fuel, and an oxygen-side electrode that is supplied with oxygen,
The electrolyte layer is an anion exchange membrane;
The fuel includes a compound containing at least hydrogen and nitrogen,
The fuel side electrode includes lanthanum and cobalt,
The fuel cell, wherein a content ratio of lanthanum in the fuel side electrode is 20 to 40 mol% with respect to a total mole of lanthanum and cobalt.   The fuel cell according to claim 1, wherein the fuel is hydrazines.

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