JP2016103410A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell restricted in output density decrease.SOLUTION: A fuel cell 1 comprises: a film-electrode assembly 16 including an anion exchange film 4, a fuel-side electrode 2 provided on one side of the anion exchange film in the thickness direction thereof, and an oxygen-side electrode 3 provided on the other side of the anion exchange film in the thickness direction thereof; a fuel diffusion layer 5 provided on one side of the fuel-side electrode 2 in the thickness direction thereof; and a fuel supply member 7 provided on one side of the fuel diffusion layer 5 in the thickness direction thereof and configured to supply liquid fuel. The fuel diffusion layer 5 is felt.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell.

  Conventionally, various fuel cells such as alkaline type (AFC), solid polymer type (PEFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid electrolyte type (SOFC) are known as fuel cells. Yes. These fuel cells are being studied for use in various applications such as automobile applications.

  For example, a polymer electrolyte fuel cell is usually formed as a stack structure in which a plurality of fuel cells are stacked. A fuel cell includes a fuel-side electrode (anode catalyst layer) to which fuel is supplied, an oxygen-side electrode (cathode catalyst layer) to which oxygen is supplied, and a solid polymer electrolyte layer sandwiched between these electrodes -An electrode assembly (MEA) is provided, and a gas diffusion layer and the like are arranged opposite to each other with the MEA interposed therebetween.

  For example, it has a solid electrolyte membrane in which the anion component can move and a catalyst layer (anode catalyst layer or cathode catalyst layer) formed on both sides thereof, and diffusion layers are formed on both sides of the electrolyte membrane so as to cover the catalyst layer. A stacked fuel cell is known (see Patent Document 1). And in patent document 1, liquid fuels, such as a hydrazine, are used as a fuel.

JP 2010-238445 A

  However, in the fuel cell of Patent Document 1, the liquid fuel supplied to the fuel side electrode passes through the fuel side electrode and the solid polymer film without causing an electrochemical reaction, and leaks to the oxygen side electrode (cross). Leak). When the fuel cell is used for a long time, the influence of the cross leak gradually increases, and as a result, there is a problem that the power generation efficiency such as the output density is lowered.

  Therefore, an object of the present invention is to provide a fuel cell in which a decrease in output density is suppressed.

  The fuel cell of the present invention comprises a membrane-electrode junction comprising an anion exchange membrane, a fuel side electrode provided on one side in the thickness direction of the anion exchange membrane, and an oxygen side electrode provided on the other side in the thickness direction of the anion exchange membrane. Body, a diffusion layer provided on one side in the thickness direction of the fuel side electrode, and a fuel supply member provided on one side in the thickness direction of the diffusion layer and supplying liquid fuel, and the diffusion layer is made of felt. It is characterized by being.

  In the fuel cell of the present invention, since the diffusion layer is felt, a decrease in output density is suppressed. Therefore, a stable output density can be maintained for a long time.

FIG. 1 is a schematic configuration diagram showing an embodiment of a fuel cell of the present invention. FIG. 2 is a schematic configuration diagram of an experimental apparatus for measuring the hydrazine permeation amount and the KOH permeation amount in Examples.

  In FIG. 1, a fuel cell 1 is a polymer electrolyte fuel cell, and includes a plurality of fuel cells S and is formed as a stack structure (cell stack 15) in which these fuel cells S are stacked. Has been.

  In FIG. 1, one fuel cell S is taken out and shown in an enlarged view for easy illustration.

  The fuel cell S includes a membrane-electrode assembly 16 (hereinafter abbreviated as “MEA”) and a diffusion layer provided on one side in the thickness direction and the other side in the thickness direction of the membrane-electrode assembly 16. Yes.

  The MEA 16 includes an anion exchange membrane 4, a fuel side electrode 2 that is opposed to the anion exchange membrane 4 and is supplied with fuel (described later), and an oxygen side electrode 3 that is supplied with oxygen.

The anion exchange membrane 4 is not particularly limited as long as it is a medium in which an anion component (for example, hydroxide ion (OH ⁻ )) can move, and for example, an anion exchange group such as a quaternary ammonium group or a pyridinium group. And a solid polymer membrane (anion exchange resin).

  Examples of the solid polymer that forms the anion exchange membrane include hydrocarbon solid polymers such as polystyrene and modified products thereof. The solid polymer forming the anion exchange membrane may have a cross-linked structure in its molecular structure.

  Such an anion exchange membrane is not particularly limited, and can be obtained by, for example, the method described in JP2013-47309A.

  Moreover, an anion exchange membrane is available as a commercial item, for example, Selemion (made by Asahi Glass Co., Ltd.), Neoceptor (made by Astom Corp.), etc. are mentioned.

  Moreover, the film thickness of the anion exchange membrane 4 is 10-100 micrometers, for example.

  The fuel side electrode (anode electrode) 2 is formed of, for example, an electrode material containing a catalyst and an ion exchange resin.

  The catalyst is not particularly limited, and examples thereof include platinum group elements (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt)), iron group elements ( According to a periodic table such as iron (Fe), cobalt (Co), nickel (Ni)) (IUPAC Periodic Table of the Elements (version date 22 June 2007), the same applies hereinafter) Group 8 to 10 (VIII) elements, For example, periodic table 11th group (IB) elements, such as copper (Cu), silver (Ag), and gold (Au), and simple metals such as zinc (Zn), and alloys thereof may be used. Preferably, an iron group element is mentioned. These can be used alone or in combination of two or more.

  The catalyst may be a supported catalyst in which a catalyst is supported on a catalyst carrier. Examples of the catalyst carrier include porous substances such as carbon. The amount of the catalyst supported on the catalyst carrier is not particularly limited, and is appropriately set according to the purpose and application.

  The ion exchange resin is preferably an anion exchange resin. Specific examples include ionomers such as hydrocarbon ionomers, fluorine ionomers, and urethane ionomers.

  The content ratio of the ion exchange resin is, for example, 100 parts by mass or more, preferably 300 parts by mass or more, and, for example, 5000 parts by mass or less, preferably 1000 parts by mass or less with respect to 100 parts by mass of the catalyst. is there.

  The fuel side electrode 2 is formed as follows. That is, for example, a fuel-side electrode ink in which a catalyst and an ion exchange resin are dispersed in an organic solvent is prepared. The fuel side electrode ink is applied to one side of the anion exchange membrane 4 by a known method (for example, spray method, die coater method, etc.) and dried. Thereby, the fuel side electrode 2 is formed on one surface of the anion exchange membrane 4 as a thin film electrode membrane.

  Examples of the organic solvent include lower alcohols such as methanol, ethanol, propanol and isopropanol, cyclic ethers such as tetrahydrofuran, and mixed solvents thereof.

  The thickness of the fuel side electrode 2 is, for example, 10 μm or more, preferably 20 μm or more, and for example, 500 μm or less, preferably 200 μm or less.

The catalyst content is, for example, 0.01 to 5 mg / cm ² .

  The oxygen side electrode (cathode electrode) 3 is formed of, for example, an electrode material containing a complex metal catalyst and an ion exchange resin.

  The complex metal catalyst is formed by coordination of a complex-forming organic compound with a transition metal (catalyst metal).

  Examples of the transition metal (catalyst metal) include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), and nickel (Ni). , Copper (Cu), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag) , Lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and the like. Preferably, iron is used. These can be used alone or in combination of two or more.

  Examples of the complex-forming organic compounds include complex-forming organic compounds such as phenanthroline, aminoantipyrine, pyrrole, porphyrin, tetramethoxyphenylporphyrin, dibenzotetraazaannulene, phthalocyanine, choline, chlorin, and salcomine, or polymers thereof. Preferably, aminoantipyrine is used. These can be used alone or in combination of two or more.

  Moreover, the said transition metal can also be used without using a complex metal catalyst.

  Examples of the ion exchange resin include the same ion exchange resin as that of the fuel side electrode 2.

  The content ratio of the ion exchange resin is, for example, 10 parts by mass or more, preferably 30 parts by mass or more, and for example, 1000 parts by mass or less, preferably 200 parts by mass with respect to 100 parts by mass of the complex metal catalyst. It is as follows.

  The oxygen side electrode 3 may contain a known polymer additive such as a resin component for imparting water repellency (for example, a fluorine resin such as polytetrafluoroethylene (PTFE)). The content ratio of the polymer additive is not particularly limited, and is appropriately set according to the purpose and application.

  The oxygen side electrode 3 is formed as follows. That is, for example, an oxygen-side electrode ink in which a complex metal catalyst, an ion exchange resin, and, if necessary, an additive are dispersed in an organic solvent is prepared. The oxygen side electrode ink is applied to the other surface of the anion exchange membrane 4 by a known method (for example, a spray method, a die coater method, etc.) and dried. Thereby, the oxygen side electrode 3 is formed in the other surface of the anion exchange membrane 4 as a thin film-like electrode film.

  The thickness of the oxygen side electrode 3 is, for example, 10 μm or more, preferably 20 μm or more, and preferably 300 μm or less, preferably 150 μm or less.

The content (supported amount) of the complex metal catalyst is, for example, 0.01 to 5 mg / cm ² .

  Thereby, the anion exchange membrane 4 and the fuel side electrode 2 and the oxygen side electrode 3 sandwiching the anion exchange membrane 4 are integrally formed as MEA.

  The battery cell S includes a diffusion layer on each of the MEA 16 on one side in the thickness direction and on the other side in the thickness direction. That is, the fuel diffusion layer 5 is provided on one surface (one surface) in the thickness direction of the fuel side electrode 2, and the gas diffusion layer 6 is provided on the other surface (other surface) in the thickness direction of the oxygen side electrode 3. Yes.

  The fuel diffusion layer 5 is disposed on one surface of the anion exchange membrane 4 so as to cover the fuel side electrode 2. Specifically, the fuel diffusion layer 5 is formed to have the same shape as the fuel-side electrode 2 when projected in the thickness direction, and the upper end surface and the lower end surface of the fuel diffusion layer 5 The side electrode 2 is disposed so as to be flush with each of the upper end surface and the lower end surface.

  The fuel diffusion layer 5 has pores for passing and diffusing fuel (particularly liquid fuel) and is made of felt.

  A felt is a sheet made by irregularly tangling fibers by applying heat, pressure, vibration, etc. to a large number of fibers (for example, carbon fibers), and a carbon cloth in which the fibers are regularly arranged in a network structure. It is distinguished from a woven fabric such as carbon paper such as carbon paper produced by mixing a fiber with a binder and manufacturing a sheet by a method such as paper cutting.

  The fiber constituting the felt is preferably a carbon fiber.

  The fuel diffusion layer 5 is preferably made of carbon felt.

  Examples of such carbon felt include “H1410” and “H2415” manufactured by Freudenberg.

  The thickness of the fuel diffusion layer 5 is, for example, 100 μm or more, preferably 150 μm or more, and for example, 500 μm or less, preferably 300 μm or less.

The amount of hydrazine permeated through the fuel diffusion layer 5 is, for example, 2000 g / m ² · h or less, preferably 1500 g / m ² · h or less, for example, 500 g / m ² · h or more, preferably 1000 g / m ² · h or more.

The permeation amount of alkali metal (particularly KOH) of the fuel diffusion layer 5 is, for example, 1500 g / m ² · h or less, preferably 500 g / m ² · h or less, and for example, 100 g / m ² · h. As mentioned above, Preferably, it is 200 g / m < ² > * h or more.

  When the permeation amount of hydrazines and alkali metals in the fuel diffusion layer 5 is in the above range, it is possible to suppress a decrease in output density regardless of the occurrence of cross leak.

  The permeation amount of hydrazines and alkali metals can be measured by the method described in Examples described later.

  The gas diffusion layer 6 has pores for passing and diffusing gas (oxygen), and is formed in substantially the same shape as the fuel diffusion layer 5. The gas diffusion layer 6 is disposed on the other surface of the anion exchange membrane 4 so as to cover the oxygen side electrode 3. Specifically, the gas diffusion layer 6 is formed so as to have the same shape as the oxygen-side electrode 3 when projected in the thickness direction, and each of the upper end surface and the lower end surface of the gas diffusion layer 6 has oxygen The side electrode 3 is arranged so as to be flush with each of the upper end surface and the lower end surface.

  Examples of the gas diffusion layer 6 include carbon cloth and carbon felt.

  The thickness of the gas diffusion layer 6 is, for example, 100 μm or more, preferably 150 μm or more, and for example, 500 μm or less, preferably 300 μm or less.

  The battery cell S further includes a fuel supply member 7 and an oxygen supply member 8.

  The fuel supply member 7 is stacked on one side in the thickness direction of the MEA 16 so as to be in contact with one surface of the fuel diffusion layer 5. The fuel supply member 7 is formed of a gas impermeable conductive member. The fuel supply member 7 has a fuel flow path 9.

  The fuel flow path 9 is formed on the other surface of the fuel supply member 7 in order to supply liquid fuel (described later) to the fuel side electrode 2 and bring the liquid fuel into contact with the entire fuel side electrode 2. The fuel flow path 9 is a groove that is recessed from the other surface in the thickness direction of the fuel supply member 7 to one side in the thickness direction, and is folded in the vertical direction while being folded back in the width direction (the direction perpendicular to the thickness direction and the vertical direction). It is formed into a shape. The fuel flow path 9 faces the fuel diffusion layer 5. That is, the fuel diffusion layer 5 is interposed between the fuel flow path 9 and the fuel side electrode 2.

  The fuel flow path 9 is formed with a fuel supply port 10 and a fuel discharge port 11 passing through the fuel supply member 7 at the upstream end and the downstream end thereof, respectively. Specifically, a fuel supply port 10 is formed at the upstream end (lower side in FIG. 1), and a fuel discharge port 11 is formed at the downstream end (upper side in FIG. 1).

  The oxygen supply member 8 is laminated on the other side in the thickness direction of the MEA 16 so as to be in contact with the other surface of the gas diffusion layer 6. The oxygen supply member 8 is formed from a gas impermeable conductive member. The oxygen supply member 8 has an oxygen flow path 12.

  The oxygen flow path 12 is formed on one surface of the oxygen supply member 8 in order to supply oxygen to the oxygen side electrode 3 and to bring oxygen into contact with the entire oxygen side electrode 3. The oxygen channel 12 is a concave groove that is recessed from one surface in the thickness direction of the oxygen supply member 8 to the other in the thickness direction, and is formed in a folded shape extending in the vertical direction while being folded back in the width direction. The oxygen flow path 12 faces the gas diffusion layer 6. That is, the gas diffusion layer 6 is interposed between the oxygen channel 12 and the oxygen side electrode 3.

  Note that the oxygen supply port 13 and the oxygen discharge port 14 penetrating the oxygen supply member 8 are also formed continuously at the upstream end portion and the downstream end portion of the oxygen channel 12, respectively. Specifically, an oxygen supply port 13 is formed at the upstream end (upper side in FIG. 1), and an oxygen discharge port 14 is formed at the downstream end (lower side in FIG. 1).

Power density of the fuel cell S is a power of the initial time (just after the start power), for example, 50 mW / cm ² or more, preferably at most 80 mW / cm ² or more, and is, for example, is 300 mW / cm ² or less .

  In the fuel cell S, the slope of the output density in the graph in which the power generation time is plotted on the X-axis and the output density on the Y-axis is, for example, −0.050 or more, and for example, 0.000 or less. The measurement of the slope of the output density will be described in detail in the examples.

  As shown in FIG. 1, the fuel cell 1 is formed as a stack structure in which a plurality of fuel cells S are stacked. Therefore, although not shown, the fuel supply member 7 and the oxygen supply member 8 are configured (also used) as separators in which the fuel flow path 9 and the oxygen flow path 12 are formed on both surfaces.

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

  Next, power generation by the fuel cell 1 will be described.

  In the fuel cell 1, oxygen (air) is supplied to the oxygen flow path 12 and liquid fuel containing a fuel compound is supplied to the fuel flow path 9 to generate power.

In the fuel cell 1, the liquid fuel supplied to the fuel flow path 9 includes, for example, a liquid fuel containing methanol, dimethyl ether, hydrazines, etc. as the fuel compound, and preferably a liquid fuel containing hydrazines, etc. Can be mentioned. Specific examples of the liquid fuel containing hydrazines include aqueous solutions of hydrazines. The hydrazines, for example, anhydrous hydrazine _(NH 2 NH 2), hydrazine hydrate _{(NH 2 NH 2 · H 2} O), triazane _{(NH 2} NHNH 2), Tetorazan _{(NH 2} NHNHNH 2), and the like.

  Further, for example, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide can be added to the liquid fuel as additives. Preferably, potassium hydroxide is used.

  The addition amount of the additive is, for example, 0.1 mol / L or more, preferably 0.5 mol / L or more, and for example, 10 mol / L or less, preferably 5 mol / L or less.

  The fuel compound may be supplied as it is, or may be supplied as a solution of water and / or alcohol (for example, lower alcohols such as methanol, ethanol, propanol, isopropanol). In this case, the concentration of the fuel compound in the solution varies depending on the type of the fuel compound, but is, for example, 1% by mass or more, preferably 5% by mass or more, and, for example, 90% by mass or less, preferably 30% by mass or less.

The power generation in the fuel cell 1 will be described more specifically. The above-described fuel is supplied to the fuel flow path 9 of the fuel supply member 7 while supplying oxygen (air) to the oxygen flow path 12 of the oxygen supply member 8. Then, in the oxygen side electrode 3, as described below, electrons (e ⁻ ), water (H ₂ O), oxygen (O ₂ ) generated in the fuel side electrode 2 and moved through the external circuit ) React with each other to produce hydroxide ions (OH ⁻ ). The generated hydroxide ions (OH ⁻ ) move through the anion exchange membrane 4 from the oxygen side electrode 3 to the fuel side electrode 2. In the fuel-side electrode 2, the hydroxide ions (OH ⁻ ) that have passed through the anion exchange membrane 4 react with the fuel to generate electrons (e ⁻ ). The generated electrons (e ⁻ ) are moved from the fuel supply member 7 to the oxygen supply member 8 via an external circuit 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.

For example, when hydrazine (NH ₂ NH ₂ ) is used as the fuel, the above 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)
Although the operating conditions of the fuel cell 1 are not particularly limited, the flow rate of the liquid fuel with respect to the fuel side electrode 2 is, for example, 0.05 L / min / cell or more as the flow rate per one fuel cell S, For example, it is 0.5 L / min / cell or less. The back pressure in the transportation of the liquid fuel is, for example, 1 kPa or more, for example, 15 kPa or less. The pressure with respect to the fuel side electrode 2 is, for example, 1 kPa or more, for example, 15 kPa or less.

  The flow rate of air with respect to the oxygen-side electrode 3 is, for example, 2.0 L / min / cell or more, for example, 20 L / min / cell or less, as the flow rate per fuel cell S. The back pressure in air transportation is, for example, 5 kPa or more, for example, 60 kPa or less. The pressure on the oxygen side electrode 3 is, for example, 10 kPa or more, for example, 60 kPa or less.

  The operating temperature of the fuel cell 1 is not particularly limited. For example, the temperature of the fuel cell S is 30 ° C. or higher, preferably 60 ° C. or higher, and for example, 100 ° C. or lower, preferably 90 ° C. or lower. Is set.

  In the fuel cell 1 described above, since the fuel diffusion layer 5 provided on one surface of the fuel side electrode 2 is felt, the permeation of liquid fuel and additives is suppressed while permeating water. Therefore, only water can be cross-leaked out of the water generated in the fuel side electrode 2 and the supplied liquid fuel. Thereby, while appropriately supplying water to the oxygen side electrode 3 by cross leak, it is possible to suppress the movement of liquid fuel or the like that affects the reaction of the oxygen side electrode 3 to the oxygen side electrode 3. As a result, a decrease in the output density of the fuel cell 1 can be suppressed, and a stable output density can be maintained for a long time.

  Examples of the use of the fuel cell 1 include a power source for a driving motor in an automobile, a ship, and an aircraft, and a power source in a communication terminal such as a mobile phone.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example. In addition, specific numerical values such as a blending ratio (content ratio), physical property values, and parameters used in the following description are described in the above-mentioned “Mode for Carrying Out the Invention”, and a blending ratio corresponding to them ( Substituting the upper limit value (numerical value defined as “less than” or “less than”) or the lower limit value (number defined as “greater than” or “exceeded”) such as content ratio), physical property values, parameters, etc. be able to.

Example 1
(Preparation of fuel side electrode ink)
0.15 g of nickel-supported carbon catalyst and ion exchange resin solution (hydrocarbon ionomer (trade name: A3, AS4), solvent: 1-propanol: THF = 1: 1 (mass ratio), 2 mass% concentration, Tokuyama Corporation (Manufactured) 3.75 g was mixed, and the resulting mixture was dispersed in 2.0 g of a solvent (1-propanol: THF = 1: 1 (mass ratio)) to prepare a fuel-side electrode ink.

(Preparation of oxygen-side electrode ink)
0.05 g of complex metal catalyst (iron complex catalyst of aminoantipyrine, manufactured by CABOT), ion exchange resin solution (hydrocarbon ionomer (trade name: A3, AS4), solvent: 1-propanol: THF = 1: 1 ( (Mass ratio) 2 mass% concentration, manufactured by Tokuyama Corporation) 1.25 g and polytetrafluoroethylene water-soluble dispersion (trade name: D210C, 60 mass% concentration, manufactured by Daikin Industries) 3.8 μL, The obtained mixture was dispersed in 2.0 g of a solvent (1-propanol: THF = 1: 1 (mass ratio)) to prepare an oxygen-side electrode ink.

(Production of MEA)
The amount of the nickel-supported carbon catalyst is 3.2 mg / cm ² on one surface of the anion exchange electrolyte membrane (trade name: A201CE, manufactured by Tokuyama Corporation), and the surface area after drying is 4 cm ² (2 cm × 2 cm). The fuel side electrode ink was applied and dried at room temperature so that the thickness was 150 μm. Further, the oxygen side electrode is formed so that the amount of the complex metal catalyst is 1.0 mg / cm ² on the other side surface, the surface area after drying is 4 cm ² (2 cm × 2 cm), and the thickness is 60 μm. Ink was applied and dried at room temperature. This manufactured the membrane electrode assembly (MEA).

  Thereafter, the solvent was evaporated in the air at normal temperature, and MEA (electrolyte membrane, fuel side electrode and oxygen side electrode) was pressurized for 2 minutes from both sides in the thickness direction of the electrolyte membrane with a hydraulic press at a pressure of 3.2 MPa. Then, it was immersed in 1M KOH for 12 hours or more.

(Production of battery cells)
On one surface of the MEA, carbon felt (“H2415” manufactured by Freudenberg, thickness 185 μm, 2 cm × 2 cm) was laminated as a fuel diffusion layer so as to cover the fuel side electrode.

  Further, a carbon cloth (GTI, thickness: 245 μm, 2 cm × 2 cm) as a gas diffusion layer was laminated on the other surface of the MEA so as to cover the oxygen side electrode.

  Subsequently, a fuel supply member was laminated on the fuel diffusion layer side of the MEA, and an oxygen supply member was laminated on the gas diffusion layer side to produce a battery cell (see FIG. 1).

Comparative Example 1
A battery cell was obtained in the same manner as in Example 1 except that carbon cloth (GTI, thickness: 245 μm, 2 cm × 2 cm) was used as the fuel diffusion layer instead of carbon felt.

(Measurement of hydrazine permeation and KOH permeation)
With respect to the fuel diffusion layers (carbon felt and carbon cloth) used in Examples and Comparative Examples, hydrazine permeation amount and KOH permeation amount were measured.

  Specifically, as shown in FIG. 2, the fuel diffusion layer 5 of Example 1 or the fuel diffusion layer of Comparative Example 1 is arranged in the center (circular cross section) of the H-type glass cell 20, and one cell is arranged. Into 21, 200 g of liquid fuel was injected, and 200 g of pure water was injected into the other cell 22. The liquid fuel was an aqueous solution having a hydrazine concentration of 10% by mass and a KOH concentration of 1 mol / L.

  The contact surface (center portion) where the fuel diffusion layer 5 and the liquid fuel are in contact was a circular shape with a diameter of 25 mm.

  Subsequently, the stirrer 23 arrange | positioned at the bottom part of each cell was rotated at 200 rpm, and the temperature inside each cell was set to 30 degreeC.

  A sample solution was taken from the cell 22 on the pure water side every hour for a total of 5 hours, and the hydrazine and potassium concentrations of the sample solution were measured by ion chromatography. The hydrazine permeation amount and the KOH permeation amount were calculated by the following formula.

(Hydrazine permeation amount) = (hydrazine concentration of sample solution) / (collection time) / (area of contact surface)
(KOH permeation amount) = (potassium concentration of sample solution) / (collection time) · (area of contact surface)
For each transmission amount, an average for a total of 5 hours was calculated. The results are shown in Table 1.

(Output density stability)
Liquid fuel (hydrated hydrazine 10% by mass + 1 mol / L KOH) is supplied to the fuel side flow path of the fuel cell of the example and the comparative example, while air (20% oxygen / 80% nitrogen) is supplied to the oxygen supply path. Supplied. The back pressure at the fuel side electrode and the back pressure at the oxygen side electrode were each 10 kPa. The cell temperature was set to 60 ° C.

Next, (1) the rated current density is set to 200 mA / cm ² , power is generated for 6 hours, (2) the cell voltage and impedance are measured at the current density, and (3) the OCV (open voltage) is 0.2 V. The IV measurement was performed three times until (4) the rated current density was set to 200 mA / cm ² and the cell voltage and impedance were measured. The durability protocol (1) to (4) was repeated.

The power generation time (time) at this time was plotted on the graph with the power density (mW / cm ² ) as the Y axis and the slope of the graph (power density) up to 250 hours was calculated.

  The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Fuel side electrode 3 Oxygen side electrode 4 Anion exchange membrane 5 Fuel diffusion layer 7 Fuel supply member 16 Membrane-electrode assembly

Claims (1)

A membrane-electrode assembly comprising an anion exchange membrane, a fuel side electrode provided on one side in the thickness direction of the anion exchange membrane, and an oxygen side electrode provided on the other side in the thickness direction of the anion exchange membrane;
A diffusion layer provided on one side in the thickness direction of the fuel side electrode;
A fuel supply member that is provided on one side in the thickness direction of the diffusion layer and that supplies liquid fuel;
The fuel cell according to claim 1, wherein the diffusion layer is felt.

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