JP2014107231A - Fuel battery pretreatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery pretreatment method capable of obtaining a fuel battery with an excellent power generation performance.SOLUTION: Power is generated in a fuel battery 1 comprising an electrolyte layer 4 made of an anion exchange membrane, and a fuel side electrode 2 supplied with fuel and an oxygen side electrode 3 supplied with oxygen that are opposed to each other across the electrolyte layer 4 (power generation step). After power generation is stopped, water is supplied to the oxygen side electrode 3 (water supply step). Then, the water is drained from the oxygen side electrode 3 (water drainage step), so as to pretreat the fuel battery 1.

Description

  The present invention relates to a fuel cell pretreatment method, and more particularly to a fuel cell pretreatment method including an electrolyte layer made of an anion exchange membrane.

  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 includes a fuel-side electrode (anode catalyst layer) to which fuel is supplied and an oxygen-side electrode (cathode catalyst layer) to which oxygen is supplied. Oppositely arranged with an electrolyte layer made of a polymer membrane in between.

  As such a polymer electrolyte fuel cell, specifically, for example, a fuel cell including an electrolyte membrane, and a fuel electrode and an oxygen electrode arranged to face each other with the electrolyte membrane interposed therebetween is known. A fuel cell, a fuel supply means for supplying hydrazines as fuel to the fuel electrode, an oxygen supply means for supplying oxygen to the oxygen electrode, and an exhaust containing hydrazines discharged from the oxygen electrode side There has been proposed a fuel cell system including a storage section, and a detoxifying means for supplying oxygen supplied from an oxygen supply means to the storage section so as to detoxify the waste accumulated in the storage section.

  In general, in such a fuel cell system, fuel is moved to the oxygen electrode side by crossover, the oxygen electrode is wetted by moisture in the fuel, and the oxygen electrode is activated.

  In this fuel cell system, fuel (unreacted hydrazines) that has moved from the fuel electrode side to the oxygen electrode side due to crossover is stored in the storage unit as an emission, and is detoxified by oxygen.

JP 2009-224219 A

  On the other hand, such fuel cells are required to further improve power generation performance.

  Therefore, an object of the present invention is to provide a fuel cell pretreatment method capable of obtaining a fuel cell having excellent power generation performance.

  In order to achieve the above object, a pretreatment method for a fuel cell according to the present invention comprises an electrolyte layer made of an anion exchange membrane, a fuel-side electrode that is disposed to face the electrolyte layer and is supplied with fuel, and oxygen A pretreatment method for a fuel cell comprising an oxygen side electrode to which is supplied, a power generation step for generating power in the fuel cell, a water supply step for supplying water to the oxygen side electrode after stopping the power generation, and A water discharge step of discharging the water from the oxygen side electrode is provided.

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

  In the fuel cell pretreatment method of the present invention, first, fuel is supplied to the fuel side electrode to generate power, the fuel supply is stopped to stop power generation, and then water is supplied to the oxygen side electrode. , Let it drain. According to such a method, the oxygen-side electrode can be moistened and activated as a whole in a power generation stop state, that is, in a state where the pressure distribution is relatively small, and as a result, the power generation performance is improved. Can be achieved.

FIG. 1 is a schematic configuration diagram showing a fuel cell used in one embodiment of a fuel cell pretreatment method of the present invention. FIG. 2 is a flowchart showing one embodiment of the fuel cell pretreatment method of the present invention. FIG. 3 is a graph showing the power generation performance of the fuel cells of Example 1 and Comparative Example 1.

  FIG. 1 is a schematic configuration diagram showing a fuel cell used in one embodiment of a fuel cell pretreatment method of the present invention.

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

  In FIG. 1, one fuel cell S is taken out for easy illustration.

  The fuel cell S includes an electrolyte layer 4, a fuel-side electrode 2 that is disposed to face the electrolyte layer 4 and is supplied with fuel (described later), and an oxygen-side electrode 3 that is supplied with oxygen. .

  The electrolyte layer 4 is a layer in which an anion component can move, and is formed using, for example, an anion exchange membrane.

The anion exchange membrane 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 can be used. And a solid polymer membrane (anion exchange resin).

  Examples of the solid polymer forming the anion exchange membrane include hydrocarbon-based solid polymer membranes 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 JP 2010-165459 A.

  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 electrolyte layer 4 is 10-100 micrometers, for example.

  The fuel side electrode 2 is formed of, for example, an electrode material such as a catalyst carrier carrying a catalyst. Alternatively, a catalyst may be used as the electrode material without using the catalyst carrier, and the catalyst may be formed directly as the fuel-side electrode 2.

  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.

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

  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 thickness of the fuel side electrode 2 is, for example, 10 to 200 μm, preferably 20 to 100 μm.

  The oxygen side electrode 3 is formed of, for example, an electrode material such as a catalyst carrier carrying a catalyst, similarly to the fuel side electrode 2 described above. Alternatively, a catalyst may be used as the electrode material without using the catalyst carrier, and the catalyst may be formed directly as the oxygen side electrode 3.

  In the oxygen-side electrode 3, as the electrode material, for example, a complex formed of a complex-forming organic compound and / or a conductive polymer and carbon (hereinafter, this complex is referred to as “carbon composite”), a transition metal. A catalyst on which is supported can also be used.

  Examples of the transition metal include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), 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. Among these, Preferably, silver and cobalt are mentioned. These may be used alone or in combination of two or more.

  The complex-forming organic compound is an organic compound that forms a complex with the metal atom by coordinating with the metal atom. For example, pyrrole, porphyrin, tetramethoxyphenylporphyrin, dibenzotetraazaannulene, phthalocyanine, choline, chlorin , A complex-forming organic compound such as phenanthroline or sarcomine, or a polymer thereof. Of these, polypyrrole, phenanthroline, and sarcomin, which are pyrrole polymers, are preferable. These may be used alone or in combination of two or more.

  As the conductive polymer, there is a compound overlapping with the above complex-forming organic compound, for example, polyaniline, polypyrrole, polythiophene, polyacetylene, polyvinylcarbazole, polytriphenylamine, polypyridine, polypyrimidine, polyquinoxaline, polyphenylquinoxaline, Examples include polyisothianaphthene, polypyridinediyl, polythienylene, polyparaphenylene, polyflurane, polyacene, polyfuran, polyazulene, polyindole, and polydiaminoanthraquinone. Among these, Preferably, a polypyrrole is mentioned. These may be used alone or in combination of two or more.

  The thickness of the oxygen side electrode 3 is, for example, 10 to 300 μm, preferably 20 to 150 μm.

  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 opposed to the surface of the fuel side electrode 2 opposite to the surface in contact with the electrolyte layer 4. . 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 is formed with a fuel supply port 8 and a fuel discharge port 9 that pass through the fuel supply member 5 continuously at the upstream end and the downstream end, respectively. Specifically, a fuel supply port 8 is formed at the upstream end (lower side in FIG. 1), and a fuel discharge port 9 is formed at the downstream end (upper side in FIG. 1).

  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 opposite to the surface in contact with the electrolyte layer 4 in the oxygen side electrode 3. Opposite contact is made with the side surface. 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 an oxygen supply port 11 and an oxygen discharge port 12 that pass through the oxygen supply member 6 continuously formed at the upstream end portion and the downstream end portion thereof. Specifically, an oxygen supply port 11 is formed at the upstream end (upper side of the paper in FIG. 1), and an oxygen discharge port 12 is formed at the downstream end (lower side of the paper in FIG. 1).

  The fuel cell 1 is formed as a stack structure in which a plurality of fuel cells S are stacked as described above. Therefore, although not shown, the fuel supply member 5 and the oxygen supply member 6 are configured (also used) 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 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.

  Further, on a test (model) basis, the fuel supply member 5 and the oxygen supply member 6 are connected by an external circuit 13, and a voltmeter 14 is interposed in the external circuit 13, thereby generating the fuel cell 1. The voltage can also be measured.

  Although not shown, in the cell laminate 15, a known gas diffusion layer or the like can be laminated together with the fuel supply member 5 and the oxygen supply member 6 as necessary. Etc. can also be provided.

  FIG. 2 is a flowchart showing one embodiment of the fuel cell pretreatment method of the present invention.

  Hereinafter, such a pretreatment method of the fuel cell 1 will be described in detail with reference to FIG.

  In this pretreatment method, first, the fuel cell 1 is prepared, air (oxygen) is supplied to the oxygen side electrode 3, and liquid fuel as fuel is supplied to the fuel side electrode 2 to generate power (power generation step). S1).

  Specifically, in the fuel cell 1, power is generated by supplying air to the oxygen-side channel 10 and supplying liquid fuel containing a fuel compound to the fuel-side channel 7.

In the fuel cell 1, examples of the liquid fuel supplied to the fuel side channel 7 include a liquid fuel containing hydrazines as a fuel compound, and specifically, an aqueous solution 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. The addition amount of the additive is not particularly limited, and is appropriately set according to the purpose and application.

  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 to 90% by mass, preferably 1 to 30% by mass.

The power generation in the fuel cell 1 will be described more specifically. While supplying oxygen (air) to the oxygen side channel 10 of the oxygen supply member 6, the fuel described above is supplied to the fuel side channel 7 of the fuel supply member 5. In the oxygen side electrode 3, electrons (e ⁻ ), water (H ₂ O), oxygen, which are generated in the fuel side electrode 2 and move via the external circuit 13, as described below, are supplied. Reaction with (O ₂ ) produces hydroxide ions (OH ⁻ ). 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.

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)
The operating conditions of the fuel cell 1 are not particularly limited. For example, the pressure on the fuel side electrode 2 side is 100 kPa or less, preferably 50 kPa or less, and the pressure on the oxygen side electrode 3 side is 100 kPa or less. Preferably, it is 50 kPa or less, and the temperature of the fuel cell S is set to 30 to 100 ° C., preferably 60 to 90 ° C.

  The operation time of the fuel cell 1 in the power generation step S1 is, for example, 1 hour or more, for example, 30 hours or less, preferably 20 hours or less.

  After the operation time has elapsed, power supply is stopped by stopping the supply of air to the oxygen-side channel 10 and stopping the supply of fuel to the fuel-side channel 7.

  Next, in this method, after power generation is stopped, if necessary, water (pure water) is supplied to the fuel side channel 7 to clean the fuel side electrode 2 (fuel electrode-water supply / discharge step S2).

  Specifically, in a state where the fuel discharge port 9 is opened, water is injected from the fuel supply port 8 (lower side of the paper) to fill the fuel side flow path 7 with water, and the fuel discharge port 9 (upper side of the paper surface). ) To drain water.

  Then, after confirming that water has been discharged from the fuel discharge port 9, that is, that the inside of the fuel side channel 7 has been filled with water, the supply of water is stopped, and then the water is discharged from the fuel side channel 7. Is discharged.

  In this method, if necessary, the fuel-side flow path 7 can be held for an arbitrary period of time with water filled.

  By repeating such an operation a plurality of times as necessary (for example, 2 to 5 times (see the broken line arrows in FIG. 2)), water is repeatedly supplied to and discharged from the fuel side flow path 7 to clean the fuel side electrode 2. And moisten.

  Next, in this method, water (pure water) is supplied to the oxygen side channel 10 to wet the oxygen side electrode 3 (oxygen electrode-water supply step S3).

  Specifically, first, water is injected from the oxygen supply port 11 (upper side of the paper) in a state where the oxygen discharge port 12 (lower side of the paper) is sealed, and the oxygen-side flow path 10 is filled with water. Thereby, water is supplied to the oxygen-side electrode 3 and penetrated.

  Further, in this method, if necessary, the oxygen-side flow path 10 can be held for a predetermined time while being filled with water. The holding time is, for example, 1 minute or more, preferably 3 minutes or more, for example, 10 minutes or less, preferably 5 minutes or less.

  Next, in this method, the oxygen discharge port 12 (the lower side in the drawing) is opened, and water is discharged from the oxygen side flow path 10. Thereby, a part of the water that has permeated the oxygen side electrode 3 is discharged from the oxygen side electrode 3 (oxygen electrode-water discharge step S4). The remainder of the water that has permeated the oxygen side electrode 3 is not discharged from the oxygen side electrode 3 but wets the oxygen side electrode 3.

  By repeating such an operation a plurality of times as necessary (for example, 2 to 10 times (see the broken line arrow in FIG. 2)), water is repeatedly supplied to and discharged from the oxygen side electrode 3, and the oxygen side electrode 3 is washed. Moisten.

  Thereby, the fuel cell 1 can be pre-processed.

  Further, by supplying air to the oxygen-side flow path 10 of the fuel cell 1 pretreated in this way, and supplying liquid fuel containing a fuel compound to the fuel-side flow path 7, the same as in the power generation step S1 described above. Thus, the fuel cell 1 can be generated.

  And the fuel cell 1 pre-processed by said pre-processing method is equipped with the outstanding electric power generation performance.

  That is, in the conventional fuel cell, the pretreatment as described above is not performed, and during power generation, the fuel is moved to the oxygen electrode side by crossover, and the oxygen electrode is moistened by the moisture in the fuel. Is activated.

  However, the fuel crossover in such a fuel cell is not originally desirable, and in the fuel crossover, water cannot be supplied uniformly to the oxygen electrode, the activation becomes uneven, and sufficient power generation performance is obtained. You may not get.

  On the other hand, in the above-described pretreatment method for the fuel cell 1, first, the fuel is supplied to the fuel side electrode 2 to generate power, the fuel supply is stopped to stop power generation, and then the oxygen side electrode 3 is stopped. Supply and drain water. According to such a pretreatment method of the fuel cell 1, the oxygen-side electrode 3 can be wetted and activated as a whole and uniformly in a power generation stop state, that is, in a state where the pressure distribution is relatively biased, As a result, the power generation performance can be improved.

  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. The numerical values of the examples shown below can be substituted for the numerical values (that is, the upper limit value or the lower limit value) described in the embodiment.

Production Example 1
<Preparation of fuel side electrode ink>
Using an electronic balance, 3 g of unsupported metal catalyst (NiZn alloy (Ni: Zn = 87: 13 (molar ratio)), manufactured by Cabot), solvent (mixed solvent of 1-propanol and tetrahydrofuran (mass ratio 1: 1) ) 28.8 g (14.4 g + 14.4 g) and ionomer (hydrocarbon anion exchange resin having a quaternary ammonium group at the molecular end, manufactured by Tokuyama Corporation) 16.6 g were weighed and mixed.

Subsequently, the obtained liquid mixture was stirred for about 10 minutes by operating a homogenizer (manufactured by Taitec Corp., VP-050) at an output of about 35% to obtain a fuel-side electrode ink as a dispersion (slurry).
<Preparation of oxygen side electrode ink>
In an electronic balance, 2.2 g of a metal complex catalyst (compound name: cobalt polypyrrole carbon, product number D8L001, manufactured by Hokuko Chemical Co., Ltd.), solvent (mixed solvent of 1-propanol and tetrahydrofuran (mass ratio 1: 1)) 36.0 g (18.0 g + 18.0 g) and ionomer (hydrocarbon anion exchange resin having a quaternary ammonium group at the molecular end, manufactured by Tokuyama Corporation) 36.2 g were weighed and mixed.

Next, the obtained liquid mixture was stirred for about 3 minutes by operating a homogenizer (manufactured by Taitec Corp., VP-050) at an output of about 40%, to obtain an oxygen-side electrode ink as a dispersion (slurry).
<Fabrication of fuel cell>
Using a hand spray gun, fuel side electrode ink is sprayed on one side of the electrolyte layer (hydrocarbon anion exchange resin having a quaternary ammonium group at the molecular end, manufactured by Tokuyama), and oxygen side electrode ink is applied on the other side. the spraying amount of supported catalyst after drying (after solvent volatilization) is, 2.5 mg / cm ² in the fuel side electrode was uniformly applied so as to be 1.0 mg / cm ² at the oxygen side electrode.

Then, it dried at 25 degreeC for 30 minutes, the fuel side electrode was formed in the one side surface of the electrolyte layer, respectively, and the oxygen side electrode was formed in the other side surface, and the fuel cell was obtained.
<Assembly>
Sixty fuel cell units were stacked via a fuel supply member and an oxygen supply member to form a fuel cell as a cell stack.

Example 1
Liquid fuel (hydrated hydrazine 20% by mass + 1 mol / L KOH) is supplied at a flow rate of 0.1 L / min / cell to the fuel-side flow path of the fuel cell obtained in Production Example 1, while the oxygen supply path is supplied The fuel cell was generated by supplying air at 13.7 L / min / cell (power generation step S1).

  At this time, the back pressure on the oxygen side electrode side was 60 kPa, and the temperature of the fuel cell was 75 degrees.

  Next, power generation was stopped by stopping the supply of liquid fuel and air.

  Thereafter, water is supplied from the supply port (lower side) of the fuel supply path, the fuel side electrode is moistened with water, and it is confirmed that water is discharged from the discharge port (upper side), and the water supply is stopped. Thus, the fuel side electrode was washed (fuel electrode-water supply / discharge step S2). This operation was repeated three times.

  Next, the discharge port of the oxygen side channel is sealed, water is injected from the supply port, the water is filled into the oxygen side channel, and the water is supplied to the oxygen side electrode by holding for 3 minutes. And moistened (oxygen electrode-water supply step S3). Thereafter, the discharge port was opened, water was discharged from the oxygen side flow path, and a part of the water that permeated the oxygen side electrode was discharged from the oxygen side electrode. This operation was repeated three times.

  The fuel cell was pretreated by the above operation.

  Thereafter, liquid fuel (hydrated hydrazine 20% by mass + 1 mol / L KOH) is supplied to the fuel cell side flow passage at a flow rate of 0.1 L / min / cell, while air is supplied to the oxygen supply passage 13.7 L. By supplying at / min / cell, the fuel cell was caused to generate power, and the power generation performance was evaluated. The result is shown in FIG.

Comparative Example 1
Without pretreatment, liquid fuel (hydrated hydrazine 20% by mass + 1 mol / L KOH) is supplied to the fuel-side flow path of the fuel cell at a flow rate of 0.1 L / min / cell, while air is supplied to the oxygen supply path. Was supplied at 13.7 L / min / cell to generate power in the fuel cell and evaluate the power generation performance. The result is shown in FIG.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Fuel side electrode 3 Oxygen side electrode 4 Electrolyte layer 15 Cell laminated body S Fuel cell

Claims (2)

A fuel cell pretreatment method comprising: an electrolyte layer made of an anion exchange membrane; a fuel-side electrode to which fuel is supplied; and an oxygen-side electrode to which oxygen is supplied. ,
A power generation step for generating the fuel cell;
A water supply step of supplying water to the oxygen-side electrode after stopping the power generation; and
A pretreatment method for a fuel cell, comprising a water discharge step of discharging the water from the oxygen side electrode.   The fuel cell pretreatment method according to claim 1, wherein the fuel is hydrazines.

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