JP2019061918A - Fuel cell system - Google Patents

Abstract

To provide a fuel cell system which is superior in power generation efficiency and which is arranged so that the damage accompanying its use can be suppressed.SOLUTION: A fuel cell system 2 comprises: a fuel cell 3 having an electrolyte layer 8, an anode electrode 9 and a cathode electrode 10; a fuel supply unit 21 for supplying a liquid fuel to the anode electrode 9; an air supply unit 24 for supplying oxygen to the cathode electrode 10; and a control unit 29 for controlling the fuel supply unit 21 and air supply unit 24. The liquid fuel contains hydrazine. The anode electrode includes a PtNi alloy and an elemental Pt. The control unit 29 causes the air supply unit 24 to supply air at the beginning of an operation of the fuel cell 3 and then, causes the fuel supply unit 21 to supply a liquid fuel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system provided with a liquid fuel supplied fuel cell.

  BACKGROUND Conventionally, a fuel cell system using a liquid fuel containing hydrazine is known as a fuel cell system mounted on a vehicle or the like.

  As such a fuel cell system, for example, a fuel cell provided with a membrane / electrode assembly in which an anode and a cathode are respectively joined to one surface and the other surface of an electrolyte membrane, a fuel supply path for supplying fuel to the anode There is known a fuel cell system including an air supply path for supplying air to the cathode (see, for example, Patent Document 1).

  In such a fuel cell, the liquid fuel is supplied to the fuel side electrode and the air is supplied to the oxygen side electrode, whereby the electrochemical reaction shown in the following formulas (1) and (2) occurs, and the electromotive force Occurs.

(1) N ₂ H ₄ + ₄ OH ⁻ → N ₂ + 4 H ₂ O + 4 e ⁻ (Reaction at fuel side electrode)
(2) O ₂ + 2H ₂ O + 4 e ⁻ → 4 OH ⁻ (Reaction on the oxygen side electrode)

JP, 2015-185525, A

  On the other hand, as a fuel cell system, improvement in power generation efficiency is required, and further, suppression of damage associated with use is also required.

  The present invention is a fuel cell system which is excellent in power generation efficiency and in which damage due to use is suppressed.

  The present invention [1] comprises a fuel cell having an electrolyte layer capable of moving an anion component, an anode electrode disposed on one side of the electrolyte layer, and a cathode electrode disposed on the other side of the electrolyte layer; A fuel supply unit for supplying liquid fuel to the anode electrode, an oxygen supply unit for supplying air to the cathode electrode, power extraction means for extracting electric power from the fuel cell, the fuel supply unit and the oxygen supply unit are controlled Control means, the liquid fuel includes hydrazines, the anode electrode includes PtNi alloy and Pt alone, and the control means first supplies the oxygen at the start of operation of the fuel cell. A fuel cell system for supplying the air to the unit and then supplying the liquid fuel to the fuel supply unit.

  In the fuel cell system of the present invention, the liquid fuel contains hydrazines, and the anode electrode contains PtNi alloy and Pt alone.

  In such a fuel cell system, when liquid fuel is supplied to the anode electrode, the PtNi alloy acts as a hydrazine decomposition catalyst at the anode electrode, and as shown in the following formula (3), hydrazines are nitrogen and hydrogen Disassemble.

(3) N ₂ H ₄ → N ₂ + 2H ₂
Next, at the anode electrode, Pt alone acts as a hydrogen oxidation catalyst to oxidize hydrogen generated by decomposition of hydrazine as shown in the following formula (4).

(4) 2H ₂ + 4 OH ⁻ → 4 H ₂ O + 4 e ⁻
The water thus generated permeates through the electrolyte layer and leaks to the cathode electrode to humidify the air supplied to the cathode electrode.

  Thereby, at the cathode electrode, an electrochemical reaction shown in the following formula (5) occurs.

(5) O ₂ + 2H ₂ O + 4 e ⁻ → 4 OH ⁻
That is, the reaction represented by the following formula (6) continuously occurs in the entire fuel cell, and an electromotive force is generated in the fuel cell.

(6) N ₂ H ₄ + O ₂ → N ₂ + 2H ₂ O
According to such an electrochemical reaction, electric power can be efficiently extracted as compared with the electrochemical reaction in which hydrazine is directly oxidized as represented by the above-mentioned formula (1) and the above-mentioned formula (2).

  In addition, in the fuel cell system of the present invention, at the start of operation of the fuel cell, the control means first causes the oxygen supply unit to supply air, and then causes the fuel supply unit to supply liquid fuel.

  That is, at the start of operation of the fuel cell, the supply of air is started prior to the liquid fuel.

  Therefore, as shown in the above equation (1), even when the liquid fuel is decomposed into hydrogen and nitrogen and the hydrogen leaks to the cathode electrode, the hydrogen can be carried out by the air on the cathode electrode side, so that hydrogen Can be prevented from depositing. Thereby, on the cathode electrode side, the concentration of hydrogen can be maintained at the explosion limit (4% by volume) or less.

  As a result, according to the fuel cell system of the present invention, it is possible to prevent the occurrence of hydrogen explosion on the cathode electrode side, and it is possible to suppress the damage associated with the use of the fuel cell.

FIG. 1 is a schematic configuration diagram of an electric vehicle equipped with an embodiment of a fuel cell system of the present invention. FIG. 2 is a schematic configuration view showing a unit cell of the fuel cell shown in FIG.

1. General Configuration of Fuel Cell System In FIG. 1, an electric vehicle 1 is a hybrid vehicle that selectively uses a fuel cell and a battery as a power source, and is equipped with a fuel cell system 2.

The fuel cell system 2 includes a fuel cell 3, a fuel supply and discharge unit 4, an air supply and discharge unit 5, a control unit 6, and a power unit 7.
(1) Fuel Cell The fuel cell 3 is a solid polymer fuel cell (anion exchange fuel cell) to which liquid fuel is directly supplied. The fuel cell 3 is disposed below the center of the electric vehicle 1.

  The fuel cell 3 is formed in a stack structure in which a plurality of fuel cells (unit cells) including the membrane electrode assembly 11, the fuel supply member 12, and the oxygen supply member 17 are stacked. In FIG. 2, only one of the plurality of unit cells is shown as the fuel cell 3, and the other unit cells are omitted.

  As shown in FIG. 2, the membrane electrode assembly 11 includes an electrolyte layer 8, an anode electrode 9, and a cathode electrode 10. The anode electrode 9 and the cathode electrode 10 are disposed opposite to each other with the electrolyte layer 8 interposed therebetween.

The electrolyte layer 8 is capable of moving an anion component, and is formed of an anion exchange membrane. The anion exchange membrane, anion component (e.g., a hydroxide ion (OH ^-), etc.) as long as the movable medium is not particularly limited, for example, quaternary ammonium groups, the anion-exchange group such as a pyridinium group The solid polymer membrane (anion exchange resin) which it has can be mentioned.

  The thickness of the electrolyte layer 8 is, for example, 5 μm or more, preferably 10 μm or more, and for example, 200 μm or less, preferably 50 μm or less.

  The anode electrode 9 is disposed on one side of the electrolyte layer 8. The thickness of the anode electrode 9 is, for example, 10 μm or more, preferably 20 μm or more, for example, 200 μm or less, preferably 100 μm or less. The details of the anode electrode 9 will be described later.

  The cathode electrode 10 is disposed on the other side of the electrolyte layer 8 (the opposite side of the anode electrode 9 with respect to the electrolyte layer 8). The cathode electrode 10 contains, for example, a cathode catalyst. The cathode electrode 10 is formed of, for example, a catalyst carrier (for example, a porous material such as carbon, etc.) supporting a cathode catalyst. Alternatively, the cathode catalyst may be formed directly as the cathode electrode 10 without using a catalyst carrier.

  As a cathode catalyst, a metal simple substance, a transition metal complex, etc. are mentioned, for example.

  Examples of the metal simple substance include platinum group elements (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt)), iron group elements (iron (Fe) Periodic table group 8 to 10 (VIII) elements such as cobalt (Co) and nickel (Ni), for example, periodic table 11 (IB) such as copper (Cu), silver (Ag) and gold (Au) Group elements, furthermore, zinc (Zn) and the like. Such a single metal can be used alone or in combination of two or more.

  The transition metal complex is a metal complex in which an organic compound is coordinated to a transition metal element (central metal). As a transition metal element, for example, 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). Such transition metals can be used alone or in combination of two or more.

  Examples of the organic compound which coordinates to the transition metal element include pyrrole, porphyrin, tetramethoxyphenyl porphyrin, dibenzotetraazaannulene, phthalocyanine, choline, chlorin, phenanthroline, sarcomine, nicarbazin, pipemidic acid type compound, aminobenzimidazole, amino Antipyrine or polymers thereof are mentioned. Such organic compounds can be used alone or in combination of two or more.

  The thickness of the cathode electrode 10 is, for example, 0.1 μm or more, preferably 1 μm or more, for example, 100 μm or less, preferably 10 μm or less.

  The fuel supply member 12 is made of a gas impermeable conductive member, and one surface of the fuel supply member 12 is in opposite contact with the anode electrode 9. In the fuel supply member 12, a fuel side flow passage 13 for bringing the fuel into contact with the whole of the anode electrode 9 is formed as a creased groove which is recessed from one surface. Further, the fuel supply member 12 is formed with a supply port 15 and a discharge port 14 communicating with the fuel side flow path 13 at the upstream end and the downstream end.

  Similar to the fuel supply member 12, the oxygen supply member 17 is made of a gas-impermeable conductive member, and one surface of the oxygen supply member 17 is in opposite contact with the cathode electrode 10. In the oxygen supply member 17, an oxygen-side flow passage 18 for bringing oxygen (air) into contact with the whole of the cathode electrode 10 is formed as a creased groove recessed from one surface. A supply port 19 and a discharge port 20 communicating with the oxygen-side flow path 18 are formed in the upstream side end and the downstream side end of the oxygen-side flow path 18.

(2) Fuel Supply and Discharge Unit As shown in FIG. 1, the fuel supply and discharge unit 4 includes a fuel supply unit 21 as an example of a fuel supply unit, a fuel discharge line 31, a gas-liquid separator 23, and a reflux line 32. And have.

  The fuel supply unit 21 is configured to supply liquid fuel to the anode electrode 9. The fuel supply unit 21 includes a fuel tank 22, a fuel supply line 30, a fuel supply pump 33, and a fuel supply valve 34.

  The fuel tank 22 is disposed to the rear of the electric vehicle 1 and to the rear of the fuel cell 3. The fuel tank 22 stores liquid fuel. Liquid fuel includes hydrazines.

  Specifically, the liquid fuel contains hydrazines and water, and preferably comprises hydrazines and water. That is, the liquid fuel is an aqueous solution in which hydrazines are dissolved in water.

As the hydrazines, for example, hydrazine (NH ₂ NH ₂ ), hydrazine hydrate (NH ₂ NH ₂ · H ₂ O), hydrazine carbonate ((NH ₂ NH ₂ ) ₂ CO ₂ ), hydrazine hydrochloride (NH ₂ NH ₂₎ · HCl), 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 ((NHNH _{2 2} ) CO) etc.

  The hydrazines can be used alone or in combination of two or more. Among hydrazines, preferably, non-carbon-containing hydrazines, that is, hydrazine, hydrazine hydrate, hydrazine sulfate and the like can be mentioned, and more preferably hydrazine hydrate can be mentioned.

  The concentration of hydrazines to the liquid fuel is, for example, 0.1% by volume or more, preferably 0.5% by volume or more, for example, less than 20% by volume, preferably 10% by volume or less, more preferably 5% by volume It is below.

  However, when the liquid fuel supplied to the anode electrode 9 permeates the electrolyte layer 8 and leaks to the cathode electrode 10, active species (strong In some cases, the output of the fuel cell 3 may be reduced.

  However, even if the liquid fuel passes through the electrolyte layer 8 and leaks to the cathode electrode 10 as the concentration of hydrazines to the liquid fuel is below the above-mentioned upper limit, the reaction between hydrazines and oxygen can be suppressed, and the fuel The output reduction of the battery 3 can be suppressed. Further, when the concentration of hydrazines with respect to the liquid fuel is above the lower limit, the amount of hydrogen necessary for the power generation reaction of the fuel cell 3 can be sufficiently ensured, and the output performance of the fuel cell 3 can be surely ensured.

  In addition, the liquid fuel preferably contains an alkali metal hydroxide as a supporting electrolyte. That is, the liquid fuel preferably comprises hydrazines, water and an alkali metal hydroxide.

  Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. These can be used alone or in combination of two or more. As an alkali metal hydroxide, Preferably, potassium hydroxide is mentioned.

  The concentration of the alkali metal hydroxide relative to the liquid fuel is, for example, 1% by mass or more, preferably 1.5% by mass or more, more preferably 2% by mass or more, and still more preferably 2.5% by mass or more. For example, the content is 10% by mass or less, preferably 8% by mass or less, more preferably 7% by mass or less, and still more preferably 6% by mass or less.

  If the liquid fuel contains an alkali metal hydroxide in the above proportion, the power generation efficiency can be improved.

  The fuel supply line 30 is a pipe for transporting liquid fuel from the fuel tank 22 to the fuel cell 3 (specifically, the fuel side flow path 13). The upstream end of the fuel supply line 30 is connected to the fuel tank 22. The downstream end of the fuel supply line 30 is connected to the supply port 15 of the fuel side flow path 13 (see FIG. 2).

  The fuel supply pump 33 is provided on the fuel supply line 30 between the fuel tank 22 and the fuel cell 3. The fuel supply pump 33 is, for example, a known liquid supply pump.

  The fuel supply valve 34 is provided in the fuel supply line 30 between the fuel supply pump 33 and the fuel tank 22. The fuel supply valve 34 is a known on-off valve for opening and closing the fuel supply line 30.

  Then, the fuel supply valve 34 opens the fuel supply line 30 and the fuel supply pump 33 is driven, whereby liquid fuel is supplied from the fuel tank 22 to the fuel side flow path 13 of the fuel cell 3. The fuel supply unit 21 does not include a reformer for reforming the hydrazine contained in the liquid fuel supplied from the fuel tank 22 to the fuel cell 3 into hydrogen.

  The fuel discharge line 31 is a pipe for transporting the liquid fuel discharged from the fuel cell 3 (specifically, the fuel side flow passage 13). The upstream end of the fuel discharge line 31 is connected to the discharge port 14 of the fuel flow passage 13 (see FIG. 2). The downstream end of the fuel discharge line 31 is connected to the lower part of the gas-liquid separator 23.

  The gas-liquid separator 23 is interposed between the fuel discharge line 31 and the reflux line 32. The gas-liquid separator 23 comprises, for example, a hollow container. The downstream end of the fuel discharge line 31 is connected to the lower portion of the gas-liquid separator 23. In addition, a gas discharge pipe 26 is connected to the upper portion of the gas-liquid separator 23.

  The gas discharge pipe 26 is a pipe for discharging the gas (gas) separated by the gas-liquid separator 23 from the electric vehicle 1. The upstream end of the gas discharge pipe 26 is connected to the top of the gas-liquid separator 23. The downstream end of the gas discharge pipe 26 is open to the atmosphere. A gas discharge valve 27 is provided in the middle of the gas discharge pipe 26.

  The gas exhaust valve 27 is a valve for opening the gas exhaust pipe 26 to release the pressure in the gas-liquid separator 23. For example, a known on-off valve is used.

  The reflux line 32 is a pipe for transporting the liquid fuel separated by the gas-liquid separator 23 from the gas-liquid separator 23 to the fuel supply line 30. The upstream end of the reflux line 32 is connected to the lower part of the gas-liquid separator 23. The downstream end of the return line 32 is connected to the fuel supply line 30 between the fuel supply pump 33 and the fuel supply valve 34. Thus, the fuel supply line 30, the fuel cell 3 (fuel side flow path 13), the fuel discharge line 31, the gas-liquid separator 23, and the return line 32 form a closed line (closed flow path).

  The liquid fuel discharged from the fuel cell 3 flows into the gas-liquid separator 23 through the fuel discharge line 31, and then the gas is separated, and is returned to the fuel supply line 30 through the reflux line 32.

(3) Air Supply and Discharge Unit The air supply and discharge unit 5 includes an air supply unit 24 as an example of an oxygen supply unit, and an air discharge line 42.

  The air supply unit 24 is configured to supply oxygen (air) to the cathode electrode 10. The air supply unit 24 includes an air supply line 41, an air supply pump 43, and an air supply valve 44.

  The air supply line 41 is a pipe for sending air from the outside of the electric vehicle 1 to the fuel cell 3 (specifically, the oxygen-side flow path 18). The upstream end of the air supply line 41 is open to the atmosphere. The downstream end of the air supply line 41 is connected to the supply port 19 of the oxygen-side flow path 18 (see FIG. 2).

  The air supply pump 43 is provided in the middle of the air supply line 41. The air supply pump 43 is, for example, a known gas pump.

  The air supply valve 44 is provided in the air supply line 41 between the air supply pump 43 and the fuel cell 3. The air supply valve 44 is a known on-off valve for opening and closing the air supply line 41.

  In the air supply / discharge unit 5 as described above, the air supply valve 44 opens the air supply line 41 and the air supply pump 43 is driven so that the air flows from the outside of the electric vehicle 1 to the oxygen side flow of the fuel cell 3. It is supplied to the passage 18.

  The air discharge line 42 is a pipe for sending the air discharged from the fuel cell 3 (specifically, the oxygen-side flow passage 18). The upstream end of the air discharge line 42 is connected to the discharge port 20 of the oxygen-side flow passage 18. The downstream end of the air discharge line 42 is a drain.

  Then, the air discharged from the fuel cell 3 is discharged to the outside of the electrically powered vehicle 1 via the air discharge line 42.

(4) Control part The control part 6 is equipped with the control unit 29 as an example of a control means. The control unit 29 is a unit (for example, an ECU: Electronic Control Unit) that executes electrical control in the electrically powered vehicle 1, and is configured of a microcomputer including a CPU, a ROM, a RAM, and the like.

  The control unit 29 is electrically connected to the fuel supply unit 21 and the air supply unit 24, and can control the fuel supply unit 21 and the air supply unit 24.

  More specifically, the control unit 29 is electrically connected to the fuel supply pump 33 and the fuel supply valve 34 of the fuel supply unit 21 (see the broken line in FIG. 1). Thus, the control unit 29 appropriately controls the drive and stop of the fuel supply pump 33, and appropriately controls the opening and closing of the fuel supply valve 34.

  The control unit 29 is also electrically connected to the air supply pump 43 and the air supply valve 44 of the air supply unit 24 (see the broken line in FIG. 1). Thus, the control unit 29 appropriately controls the driving and stopping of the air supply pump 43, and appropriately controls the opening and closing of the air supply valve 44.

  Furthermore, the control unit 29 is also electrically connected to the gas discharge valve 27, and thereby appropriately controls the opening and closing of the gas discharge valve 27.

(5) Power Unit The power unit 7 includes a motor 37, an inverter 38, a battery 40, and a converter 36.

  The motor 37 converts the electrical energy output from the fuel cell 3 into mechanical energy as a driving force of the electric vehicle 1. The motor 37 is disposed on the front side of the electric vehicle 1 and in front of the fuel cell 3.

  The inverter 38 is a device for converting direct current power generated by the fuel cell 3 into alternating current power. The inverter 38 is disposed between the motor 37 and the fuel cell 3. The inverter 38 is electrically connected to the fuel cell 3 and the motor 37 by wiring.

  The battery 40 stores energy regenerated by the motor 37. The battery 40 is connected by a wire between the inverter 38 and the fuel cell 3. Thereby, the battery 40 can store the electric power from the fuel cell 3 and can supply the electric power to the motor 37.

  The converter 36 has a function of boosting and lowering the output voltage of the fuel cell 3 and has a function of adjusting the power of the fuel cell 3 and the input and output power of the battery 40. Converter 36 is disposed between battery 40 and fuel cell 3. Converter 36 is electrically connected to control unit 29 (see the broken line in FIG. 1), and thereby controls the output of fuel cell 3 in accordance with the input of the output control signal output from control unit 29. .

  The converter 36 is electrically connected to the fuel cell 3 and the battery 40 by wiring, and is electrically connected to the inverter 38 by branching of the wiring. Thus, the power from converter 36 to motor 37 is converted from DC power to AC power in inverter 38 and supplied to motor 37.

2. Details of Anode Electrode As shown in FIG. 2, the anode electrode 9 contains a PtNi alloy and a single Pt as an anode catalyst.

  The PtNi alloy is a hydrazine decomposition catalyst and is an alloy of platinum (Pt) and nickel (Ni).

  The content ratio of platinum in the PtNi alloy is, for example, 1 mol% or more, preferably 5 mol% or more, for example 70 mol% or less, preferably 60 mol% or less, based on the total number of moles of platinum and nickel. is there.

  The content ratio of nickel in the PtNi alloy is, for example, 30 mol% or more, preferably 40 mol% or more, for example 99 mol% or less, preferably 95 mol% or less, based on the total number of moles of platinum and nickel. is there.

  Such PtNi alloy is preferably supported on a catalyst support. That is, preferably, the anode electrode 9 contains a catalyst support carrying a PtNi alloy (hereinafter, referred to as a PtNi carrying support).

  Examples of the catalyst carrier include porous materials such as carbon. Examples of carbon include ketjen black, acetylene black, furnace black, channel black, thermal black, lamp black and the like. Among the carbon blacks, preferably ketjen black is mentioned. These carbon blacks can be used alone or in combination of two or more.

  The average primary particle diameter of the PtNi-supported carrier is, for example, 0.001 μm or more, preferably 0.005 μm or more, for example, 0.1 μm or less, preferably 0.05 μm or less. The average primary particle size can be measured by a transmission electron microscope.

The specific surface area of the PtNi-supported carrier is, for example, 100 m ² / g or more, preferably 300 m ² / g or more, for example, 1200 m ² / g or less, preferably 1000 m ² / g or less. In addition, a specific surface area is measured by the carrier gas method based on JISZ 8830 (2013).

  In order to prepare such a PtNi alloy, for example, a salt of nickel, a platinum complex and, if necessary, a catalyst support are mixed in the above proportions to prepare a catalyst raw material.

  Examples of the salt of nickel include inorganic salts (eg, sulfate, nitrate, chloride, phosphate etc.), organic acid salts (eg, acetate, oxalate etc.) and the like, preferably inorganic Salts, more preferably nitrates. The salts of nickel can be used alone or in combination of two or more.

  As a platinum complex, a hexachloro platinum (IV) acid, a dichloro platinum (II) acid, etc. are mentioned, for example, Preferably, a hexachloro platinum (IV) acid is mentioned. The platinum complexes can be used alone or in combination of two or more.

  The mixing method is not particularly limited, and examples thereof include known methods such as wet mixing and dry mixing, and preferably include wet mixing.

  In order to wet-mix the nickel salt and the platinum complex, the nickel salt and the platinum complex are dissolved and stirred in water where the catalyst support is dispersed, if necessary.

  The mixing time (stirring time) is, for example, 5 hours or more, preferably 10 hours or more, for example, 50 hours or less, preferably 40 hours or less.

  Next, the catalyst raw material is dried if necessary and then calcined. Specifically, the catalyst raw material is fired, for example, under an atmosphere of an inert gas (for example, nitrogen gas, argon gas or the like) or a reducing gas (for example, a mixed gas of nitrogen gas and hydrogen gas). Preferably, the catalyst raw material is calcined under an inert gas atmosphere.

  As the firing conditions, the firing temperature is, for example, 400 ° C. or more, preferably 500 ° C. or more, for example, 1500 ° C. or less, preferably 1000 ° C. or less, more preferably 900 ° C. or less.

  However, in the decomposition reaction of hydrazine, it may be decomposed into ammonia or may be decomposed into nitrogen and hydrogen. When the calcination temperature is in the above range, the selectivity for decomposition to nitrogen and hydrogen can be improved in the decomposition reaction of hydrazine, and hydrogen can be efficiently generated.

  The baking time is, for example, 15 minutes or more, preferably 30 minutes or more, for example, 5 hours or less, preferably 3 hours or less. The catalyst raw material can be calcined in one step or in multiple steps.

  By this, the catalyst raw material is calcined to prepare a PtNi alloy (PtNi-supported carrier).

  Pt alone is a hydrogen oxidation catalyst and is a platinum single metal.

  The content ratio of the single Pt is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, for example, 10 parts by mass or less, preferably 5 parts by mass or less with respect to 1 part by mass of the PtNi alloy. is there.

  The content ratio of the single Pt is, for example, 9% by mass or more, preferably 33% by mass or more, for example 90% by mass or less, preferably 83% by mass or less based on the total mass of the PtNi alloy and the single Pt .

  The content ratio of Pt alone is, for example, 5% by mass or more, preferably 25% by mass or more, for example, 80% by mass or less, preferably 70% by mass or less, based on the total mass of the anode electrode 9.

  Such Pt alone is preferably supported on the above catalyst support. That is, preferably, the anode electrode 9 contains a catalyst support (hereinafter, referred to as a Pt-supporting support) supporting the Pt-supporting unit.

  The average primary particle diameter of the Pt-supported single carrier is, for example, 0.001 μm or more, preferably 0.003 μm or more, for example, 0.1 μm or less, preferably 0.05 μm or less.

The specific surface area of the single Pt-supporting carrier is, for example, 100 m ² / g or more, preferably 300 m ² / g or more, for example, 1200 m ² / g or less, preferably 1000 m ² / g or less.

  In order to prepare a Pt single-support carrier, the platinum complex and the catalyst carrier described above are mixed in the same manner as described above and then fired.

  The anode electrode 9 may further contain an ionomer. Examples of the ionomer include hydrocarbon-based ionomers, fluorine-based ionomers, urethane-based ionomers and the like, preferably hydrocarbon-based ionomers. The ionomers can be used alone or in combination of two or more.

  In addition, the content ratio of the ionomer is, for example, 0.1 parts by mass or more, preferably 0.3 parts by mass or more, for example, 1.0 part by mass, with respect to 1 part by mass of the anode catalyst (a mixture of PtNi alloy and Pt alone). It is not more than mass part, preferably not more than 0.8 mass part.

  In order to prepare such an anode electrode 9, first, a PtNi alloy (preferably, a PtNi-supported carrier) and a Pt simple substance (preferably, a Pt single-supported carrier) are mixed in the above ratio.

  The mixing method is not particularly limited, and examples thereof include known methods such as wet mixing and dry mixing, and preferred examples include dry mixing. As a mixing apparatus, well-known mixers, such as a ball mill, are mentioned, for example.

  Thus, a cathode catalyst containing PtNi alloy and Pt alone is prepared.

  Then, a cathode catalyst and, if necessary, an ionomer are dispersed in a solvent to prepare a dispersion (cathode electrode ink).

  Examples of the solvent include organic solvents such as alcohols (for example, methanol, ethanol, 1-propanol, 2-propanol and the like), ethers (for example, tetrahydrofuran and the like) and the like, for example, water and the like. These solvents can be used alone or in combination of two or more.

  Then, the dispersion is applied to one surface of the electrolyte layer 8 and dried. Thus, the anode electrode 9 fixed on one surface of the electrolyte layer 8 is prepared.

3. Power Generation by Fuel Cell System In the fuel cell system 2 described above, the air supply valve 44 is opened by the control of the control unit 29 and the air supply pump 43 is driven, whereby the air is on the oxygen side via the air supply line 41. It is supplied to the flow path 18. Further, the fuel supply valve 34 is opened and the fuel supply pump 33 is driven, whereby the liquid fuel stored in the fuel tank 22 is supplied to the fuel side flow path 13 through the fuel supply line 30.

  Then, the liquid fuel passes through the fuel channel 13 while being in contact with the anode electrode 9. As a result, electrochemical reactions shown in the following (A) and (B) occur at the anode electrode 9.

(A) N ₂ H ₄ → N ₂ + 2H ₂ (reaction at the anode electrode 9)
(B) 2H ₂ + 4 OH ⁻ → 4 H ₂ O + 4 e ⁻ (Reaction at the anode electrode 9)
In addition, when the liquid fuel passes through the fuel side flow path 13, a part of the liquid fuel passes through the electrolyte layer 8 and leaks to the cathode electrode 10. The liquid fuel contains water produced by the reaction shown in the above (B). Therefore, the water contained in the liquid fuel leaked to the cathode electrode 10 humidifies the air passing through the oxygen-side flow passage 18.

  Then, the humidified air passes through the oxygen-side flow passage 18 while being in contact with the cathode electrode 10. Thereby, in the cathode electrode 10, an electrochemical reaction shown in the following (C) occurs.

(C) O ₂ + 2H ₂ O + 4 e ⁻ → 4 OH ⁻ (Reaction at cathode electrode 10)
That is, a reaction represented by the following formula (D) continuously occurs in the entire fuel cell 3, and an electromotive force is generated in the fuel cell 3.

(D) N ₂ H ₄ + O ₂ → N ₂ + 2H ₂ O (reaction in the entire fuel cell 3)
4. Control by Control Unit On the other hand, in the above-mentioned electrochemical reaction, as shown in the above-mentioned formula (A), hydrazines supplied to the anode electrode 9 are decomposed into hydrogen and nitrogen.

  In such a case, when there is a time when the liquid fuel is supplied to the anode electrode 9 and the air is not supplied to the cathode electrode 10 at the start of operation of the fuel cell 3, hydrogen generated in the anode electrode 9 becomes the cathode electrode 10. It may leak to the side (cross leak) and stay in the oxygen side flow passage 18.

  In such a state, when air is supplied to the cathode electrode 10, a mixed gas of hydrogen and oxygen is generated in the oxygen-side flow path 18, which may cause a hydrogen explosion or the like in some cases.

  Therefore, in the fuel cell system 2 described above, air is first supplied by the air supply unit 24 at the start of operation of the fuel cell 3 under the control of the control unit 29.

  That is, with the fuel supply valve 34 closed and the operation of the fuel supply pump 33 stopped, the air supply valve 44 is opened and the air supply pump 43 is driven.

  Thus, air is first supplied to the cathode electrode 10 before the liquid fuel is supplied to the anode electrode 9.

  Next, with the air supply started, the fuel supply valve 34 is opened and the fuel supply pump 33 is driven.

  As a result, liquid fuel is supplied to the anode electrode 9 to cause the electrochemical reaction shown by the above formulas (A) to (D).

  According to such a fuel cell system 2, the liquid fuel is decomposed into hydrogen and nitrogen as shown by the above-mentioned formula (A), and the hydrogen leaks to the cathode electrode 10 side (that is, the oxygen-side flow passage 18). Also in this case, on the cathode electrode 10 side, hydrogen can be carried out by air, and hydrogen deposition can be suppressed. Thus, the concentration of hydrogen can be maintained at or below the explosion limit (4% by volume) on the cathode electrode 10 side (that is, the oxygen-side flow passage 18).

  As a result, according to the fuel cell system 2 described above, the occurrence of hydrogen explosion on the cathode electrode 10 side can be prevented, and damage associated with the use of the fuel cell 3 can be suppressed.

  In addition, such control is particularly suitable during warm-up operation of the fuel cell 3 (when the heated liquid fuel is supplied to the fuel cell 3).

5. Operation and Effect In the fuel cell system 2 described above, the liquid fuel contains hydrazines. Further, the anode electrode 9 contains a PtNi alloy and a single Pt.

  In such a fuel cell system 2, when liquid fuel is supplied to the anode electrode 9, the PtNi alloy acts as a hydrazine decomposition catalyst at the anode electrode 9 and, as shown in the above formula (A), hydrazines are nitrogen And hydrogen. Therefore, the fuel cell system 2 does not need a reformer for reforming hydrazines to hydrogen.

  Next, at the anode electrode 9, Pt alone acts as a hydrogen oxidation catalyst to oxidize hydrogen generated by the decomposition of hydrazine as shown in the above-mentioned formula (B).

  Further, the liquid fuel contains water produced by the reaction shown in the above (B). Therefore, when the liquid fuel leaks to the cathode electrode 10, the water contained in the liquid fuel humidifies the air passing through the oxygen-side flow passage 18.

  Thereby, in the cathode electrode 10, an electrochemical reaction shown in the above-mentioned formula (C) occurs.

  That is, the reaction represented by the above-mentioned formula (D) continuously occurs in the entire fuel cell 3 and an electromotive force is generated in the fuel cell.

  According to such an electrochemical reaction, electric power can be efficiently extracted as compared with the electrochemical reaction in which hydrazine is directly oxidized as represented by the following formula (E) and the following formula (F).

(E) N ₂ H ₄ + ₄ OH ⁻ → N ₂ + 4 H ₂ O + 4 e ⁻ (reaction at the anode electrode 9)
(F) O ₂ + 2H ₂ O + 4 e ⁻ → 4 OH ⁻ (Reaction at cathode electrode 10)
In addition, according to the fuel cell system 2 described above, as shown by the above formula (A), even when the liquid fuel is decomposed into hydrogen and nitrogen and the hydrogen leaks to the cathode electrode 10 side, the cathode At the electrode 10 side, hydrogen can be carried out by air, and hydrogen deposition can be suppressed. Thereby, on the cathode electrode 10 side, the concentration of hydrogen can be maintained at the explosion limit (4 volume%) or less.

  As a result, according to the fuel cell system 2 described above, the occurrence of hydrogen explosion on the cathode electrode 10 side can be prevented, and damage associated with the use of the fuel cell 3 can be suppressed.

Reference Signs List 2 fuel cell system 3 fuel cell 8 electrolyte layer 9 anode electrode 10 cathode electrode 21 fuel supply unit 24 air supply unit 29 control unit

Claims (1)

A fuel cell comprising an electrolyte layer capable of moving an anion component, an anode electrode disposed on one side of the electrolyte layer, and a cathode electrode disposed on the other side of the electrolyte layer;
A fuel supply unit for supplying liquid fuel to the anode electrode;
An oxygen supply unit for supplying air to the cathode electrode;
Power extracting means for extracting power from the fuel cell;
Control means for controlling the fuel supply unit and the oxygen supply unit;
The liquid fuel includes hydrazines,
The anode electrode contains PtNi alloy and Pt alone,
The fuel cell system, wherein the control means first causes the oxygen supply unit to supply the air and then causes the fuel supply unit to supply the liquid fuel at the start of operation of the fuel cell.

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