JP2011146245A - Pre-processing method for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique by which a fuel cell having an oxide-based catalyst is aged without impairing its power generation performance. <P>SOLUTION: When a fuel cell stack 300 is started, a raw fuel is supplied to a reforming part 40 to generate a hydrogen-rich reformed gas. A CO denaturing part 46 and a CO eliminating part 48 reduce the CO concentration of the reformed gas generated by the reforming part 40, and then a fuel moisture-heat exchanger 60 puts the reformed gas in an excessively humidified state. The reformed gas in the excessively humidified state is then supplied to the anode 322 of the fuel cell stack 300. Meanwhile, air put in an excessively humidified state by an oxidizer moisture-heat exchanger 70 is supplied to the cathode 324 of the fuel cell stack 300. In this condition, a voltage between the anode 322 and the cathode 324 is kept constant, and the reformed gas and air are kept supplied until a current flows between the anode 322 and the cathode 324 converge. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell that generates electricity by an electrochemical reaction between hydrogen and oxygen. In particular, the present invention relates to a pretreatment method that is performed when a fuel cell is started.

  In recent years, fuel cells that have high energy conversion efficiency and do not generate harmful substances due to power generation reactions have attracted attention. As one of such fuel cells, a polymer electrolyte fuel cell that operates at a low temperature of 100 ° C. or lower is known.

A polymer electrolyte fuel cell has a basic structure in which a polymer electrolyte membrane, which is an electrolyte membrane, is disposed between an anode (fuel electrode) and a cathode (air electrode). A fuel gas containing hydrogen at the anode and a cathode It is an apparatus that supplies an oxidant gas containing oxygen and generates electricity by the following electrochemical reaction.
Anode: H ₂ → 2H ⁺ + 2e ⁻ (1)
^{_{Cathode: 1 / 2O 2 + 2H +}} + 2e - → H 2 O ··· (2)

  The anode and cathode each have a structure in which a catalyst layer and a gas diffusion layer are laminated. The catalyst layers of the electrodes are arranged to face each other with the solid polymer membrane interposed therebetween, thereby forming a membrane electrode assembly. The catalyst layer is a layer formed by binding carbon particles carrying a catalyst with an ionomer. The gas diffusion layer becomes a passage for the oxidant gas and the fuel gas.

  At the anode, hydrogen contained in the supplied fuel is decomposed into hydrogen ions and electrons as shown in the above formula (1). Among these, hydrogen ions move inside the solid polymer electrolyte membrane toward the air electrode, and electrons move to the air electrode through an external circuit. On the other hand, in the cathode, oxygen contained in the oxidant gas supplied to the cathode reacts with hydrogen ions and electrons that have moved from the fuel electrode, and water is generated as shown in the above formula (2). Thus, in the external circuit, electrons move from the fuel electrode toward the air electrode, so that electric power is taken out (see Patent Document 1).

  A platinum catalyst is known as a catalyst used in the catalyst layer. In a fuel cell containing a platinum catalyst in the catalyst layer, humidified gas is supplied to the anode (fuel electrode) and cathode (air electrode) at the start-up to reduce the resistance of the membrane electrode assembly during power generation. ) Is done. Specifically, the power generation performance of the membrane electrode assembly is improved by causing proton conduction and water movement from the anode to the cathode.

  On the other hand, in recent years, development of a technique using an oxide-based catalyst such as TaCNO for a catalyst layer has been advanced. Since the oxide-based catalyst is less expensive than the platinum catalyst, the manufacturing cost of the fuel cell can be reduced. The oxide-based catalyst in the present invention refers to a catalyst obtained by partially oxidizing a carbide, nitride, or carbonitride containing at least a group IV or group V metal such as Ta, Nb, Zr, or Ti.

Japanese Patent Laid-Open No. 2002-20369 Japanese Patent Laid-Open No. 06-196187 JP 2004-349050 A

  Oxide catalysts tend to change the state of partial oxidation under a reducing atmosphere. When aging is performed in a fuel cell having an oxide catalyst in the same manner as a fuel cell having a platinum catalyst, the oxide catalyst The catalyst is exposed to a reducing atmosphere, which causes a problem that sufficient power generation performance cannot be obtained.

  The present invention has been made in view of these problems, and an object thereof is to provide a technique capable of performing aging without impairing power generation performance in a fuel cell having an oxide-based catalyst.

  An embodiment of the present invention includes an electrolyte membrane, a cathode catalyst layer formed on one surface of the electrolyte membrane and including a proton conductor and an oxide catalyst, and an anode catalyst formed on the other surface of the electrolyte membrane. A pretreatment method for a fuel cell having a membrane electrode assembly including a layer, wherein a hydrogen-containing gas in an excessively humid state is supplied to an anode catalyst layer, and an oxidant gas in an excessively humid state is supplied to a cathode catalyst layer It is characterized by.

  Another aspect of the present invention includes an electrolyte membrane, a cathode catalyst layer formed on one surface of the electrolyte membrane and containing a proton conductor and an oxide catalyst, and an anode catalyst formed on the other surface of the electrolyte membrane. A fuel cell pretreatment method having a membrane electrode assembly including a layer, wherein a saturated humidified hydrogen-containing gas is supplied to an anode catalyst layer, and a saturated humidified oxidant gas is supplied to a cathode catalyst layer It is characterized by.

  According to the fuel cell pretreatment method of any one of the aspects described above, aging can be performed in a fuel cell having an oxide-based catalyst in the catalyst layer without impairing power generation performance.

In the fuel cell pretreatment method of the above aspect, the dew point temperature of the hydrogen-containing gas and the oxidant gas may be equal to or higher than the cell temperature. Further, the hydrogen content of the hydrogen-containing gas may be 50% by mass or more, and the oxygen content of the oxidant gas may be 10% by mass or more. In a state where the output voltage of the fuel cell is kept constant, the hydrogen-containing gas and the oxidant gas may be supplied until the increase rate of the current density flowing through the fuel cell reaches 10 mA / (cm ² · 30 minutes).

  According to the present invention, aging can be performed without impairing power generation performance in a fuel cell having an oxide-based catalyst in a catalyst layer.

1 is a schematic diagram showing an overall configuration of a fuel cell system according to an embodiment. 1 is a perspective view schematically showing the structure of a fuel cell according to an embodiment. It is sectional drawing on the AA line of FIG. It is a graph which shows the time change of the current density at the time of implementing the pre-processing method of an Example. It is a graph which shows the relationship between aging time and cell impedance. It is a graph which shows the time change of the voltage at the time of implementing the aging method which concerns on a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(Embodiment)
FIG. 1 is a schematic diagram showing the overall configuration of a fuel cell system 10 according to the first embodiment. Note that the schematic diagram of FIG. 1 is a diagram schematically showing mainly the functions and connections of each component, and does not limit the positional relationship or arrangement of each component.

  The fuel cell system 10 mainly includes a reforming unit 40, a CO conversion unit 46, a CO removal unit 48, a fuel cell stack 300, a wet heat exchanger for fuel 60, a wet heat exchanger for oxidant 70, a converter 90, and an inverter. 92 and a control unit 200.

  The reforming unit 40 is supplied with clean water that has been subjected to water treatment by the water treatment device 42 as reforming water. The water treatment device 42 treats water from the clean water using a reverse osmosis membrane and an ion exchange resin. The water that has been subjected to water treatment by the water treatment device 42 is used for steam reforming in the reforming unit 40.

  The battery off-gas that is the reformed gas discharged without being reacted in the fuel cell stack 300 is sent to the reforming unit 40 via the gas-liquid separator 44. In the gas-liquid separator 44, only the gas component of the battery off-gas is taken out and sent to the reforming unit 40 and used as fuel for the burner. The gas-liquid separator 44 also has a heat exchange function that allows the battery off gas and the reforming water to exchange heat, and the reforming water is heated by the heat of the battery off gas.

  The reformed gas generated by the reforming unit 40 is supplied to the CO conversion unit 46. In the CO conversion unit 46, carbon monoxide is converted to hydrogen by a shift reaction. Thereby, the hydrogen concentration is increased and the CO concentration is reduced to about 1%.

  The reformed gas whose CO concentration has been reduced by the CO conversion unit 46 is supplied to the CO removal unit 48. In the CO removing unit 48, the CO concentration is reduced to 10 ppm or less by the CO oxidation reaction using the CO selective oxidation catalyst. Note that air necessary for the CO oxidation reaction is supplied to the reformed gas whose CO concentration has been reduced by the CO shifter 46.

  The reformed gas whose CO concentration is further reduced by the CO removing unit 48 is sent to the wet heat exchanger 60 for fuel. The fuel wet heat exchanger 60 adjusts the humidity and temperature of the reformed gas by bubbling the reformed gas using the water stored in the tank according to the instruction of the control unit 200. The reformed gas humidified and heated by the fuel wet heat exchanger 60 is supplied to the anode 322 of the fuel cell stack 300.

  On the other hand, the air taken in from the outside is first sent to the oxidant wet heat exchanger 70. The oxidant wet heat exchanger 70 adjusts the humidity and temperature of the air by bubbling air using the water stored in the tank in accordance with an instruction from the control unit 200. The air gas humidified and heated by the oxidant wet heat exchanger 70 is supplied to the cathode 324 of the fuel cell stack 300.

  The fuel cell system 10 is provided with a cooling water circulation system 210 that circulates cooling water for cooling the fuel cell stack 300. As the cooling water flows through the cooling water plate 390 provided in each cell of the fuel cell stack 300, the fuel cell stack 300 is cooled. A part of the cooling water discharged from the fuel cell stack 300 is stored in the tank of the fuel wet heat exchanger 60 and then stored in the tank of the oxidant wet heat exchanger 70 and is discharged from the fuel cell stack 300. The remaining water is sent directly to the oxidant wet heat exchanger 70 and stored in the tank of the oxidant wet heat exchanger 70.

The fuel cell stack 300 generates power using hydrogen contained in the reformed gas and oxygen contained in the air. Specifically, in each cell (unit cell) constituting the fuel cell stack 300, an electrode reaction represented by the formula (1) occurs at the anode 322 in contact with one surface of the solid polymer electrolyte membrane 320. On the other hand, at the cathode 324 in contact with the other surface of the solid polymer electrolyte membrane 320, an electrode reaction represented by the formula (2) occurs. Each cell is cooled by cooling water flowing through the cooling water plate 390 and adjusted to an appropriate temperature of about 70 to 80 ° C.
Anode: H ₂ → 2H ⁺ + 2e ⁻ (1)
^{_{Cathode: 1 / 2O 2 + 2H +}} + 2e - → H 2 O ··· (2)

  The DC power generated in the fuel cell stack 300 is converted into DC power having a predetermined voltage (for example, 24V) by the converter 90, and then converted to AC power (for example, 100V) by the inverter 92. The AC power converted by the inverter 92 is output to the system 94. Further, the DC power of a predetermined voltage converted by the converter 90 is used as a power source for the control unit 200 and the like.

  The fuel cell stack 300 is provided with a temperature sensor 392 that measures the cell temperature, and the cell temperature measured by the temperature sensor 392 is transmitted to the control unit 200.

  The controller 200 controls the amount of power generated by the fuel cell stack 300 by adjusting the amount of fuel supplied from the reforming unit 40 and the amount of air supplied from the outside. In addition, the control unit 200 controls the amount of cooling water by adjusting the opening of a control valve provided in the piping for cooling water and the circulation pump. In addition, the control unit 200 uses the fuel wet heat exchanger 60 and the oxidant wet heat exchanger 70 according to the cell temperature measured by the temperature sensor 392 to supply the reformed gas, air, and the like. Adjust the temperature and humidity respectively. Furthermore, the control unit 200 transmits and receives electrical signals to and from the converter 90 and the inverter 92 and controls these various devices. The control unit 200 can perform infrared communication with the remote controller 96. The user can set the operation of the fuel cell system 10 using the remote controller 96.

  FIG. 2 is a perspective view schematically showing the structure of the fuel cell (cell) 310 constituting the fuel cell stack 300. 3 is a cross-sectional view taken along the line AA in FIG. The fuel cell 310 includes a flat membrane electrode assembly 350, and a separator 334 and a separator 336 are provided on both sides of the membrane electrode assembly 350. A stacked body is configured by stacking a plurality of fuel cells 310 via the separator 334 and the separator 336.

  The membrane electrode assembly 350 includes a solid polymer electrolyte membrane 320, an anode 322, and a cathode 324. The anode 322 has a laminate composed of an anode catalyst layer 326 and an anode gas diffusion layer 328. On the other hand, the cathode 324 has a laminate composed of a cathode catalyst layer 330 and a cathode gas diffusion layer 332. The anode catalyst layer 326 and the cathode catalyst layer 330 are provided so as to face each other with the solid polymer electrolyte membrane 320 interposed therebetween. The anode gas diffusion layer 328 is provided on the surface of the anode catalyst layer 326 opposite to the solid polymer electrolyte membrane 320. The cathode gas diffusion layer 332 is provided on the surface of the cathode catalyst layer 330 opposite to the solid polymer electrolyte membrane 320.

  A gas flow path 338 is provided in the separator 334 provided on the anode 322 side. The reformed gas is distributed to the gas flow path 338 from a fuel supply manifold (not shown), and the reformed gas is supplied to the membrane electrode assembly 350 through the gas flow path 338. Similarly, a gas flow path 340 is provided in the separator 336 provided on the cathode 324 side. Air as an oxidant is distributed to the gas flow path 340 from an oxidant supply manifold (not shown), and air is supplied to the membrane electrode assembly 350 through the gas flow path 340.

  The solid polymer electrolyte membrane 320 exhibits good ionic conductivity in a wet state and functions as an ion exchange membrane that moves protons between the anode 322 and the cathode 324. The solid polymer electrolyte membrane 320 is formed of a solid polymer material such as a fluorine-containing polymer or a non-fluorine polymer. For example, the polymer electrolyte membrane 320 is a sulfonic acid type perfluorocarbon polymer, a polysulfone resin, a perfluorocarbon group, or a perfluorocarbon group. A fluorocarbon polymer or the like can be used. Examples of the sulfonic acid type perfluorocarbon polymer include Nafion (manufactured by DuPont: registered trademark). Examples of non-fluorine polymers include sulfonated aromatic polyetheretherketone and polysulfone.

  The cathode catalyst layer 330 of this embodiment is composed of an ionomer, a conductive material, and an oxide catalyst. The ionomer connects the oxide catalyst and the solid polymer electrolyte membrane 20, and has a role of transmitting protons between the two. The ionomer may be formed from the same polymer material as the solid polymer electrolyte membrane 20. Examples of the conductive material include carbon particles such as acetylene black, ketjen black, fullerene, carbon nanotube, and carbon nano-onion. As oxide-based catalysts, Ta—C—N—O, Ta—O—N, Zr—C—N—O, Zr—O—N, Zr—N, Co—C—N, Ba—Nb—O— N, Ba—Nb—O—N, Nb—Fe—O—N, Ti—La—O—N, Ba—Ti—O—N, and the like.

  The cathode gas diffusion layer 332 is formed of a cathode gas diffusion base material. The cathode gas diffusion base material is preferably composed of a porous body having electron conductivity. For example, a metal plate, a metal film, a conductive polymer, carbon paper, a carbon woven fabric or a non-woven fabric can be used. .

  On the other hand, the anode catalyst layer 326 includes an ionomer, a conductive material, a platinum catalyst, an oxide catalyst, and the like. The ionomer connects the catalyst and the solid polymer electrolyte membrane 20, and has a role of transmitting protons between the two. The ionomer may be formed from the same polymer material as the solid polymer electrolyte membrane 20. Examples of the conductive material include carbon particles such as acetylene black, ketjen black, fullerene, carbon nanotube, and carbon nano-onion.

  The anode gas diffusion layer 328 is formed of an anode gas diffusion base material. The anode gas diffusion base material is preferably composed of a porous body having electronic conductivity. For example, a metal plate, a metal film, a conductive polymer, carbon paper, a carbon woven fabric or a nonwoven fabric can be used.

  According to the fuel cell described above, an oxide-based catalyst is used as the catalyst, so that the manufacturing cost can be reduced compared to the case where a platinum-based catalyst is used.

(Production method of membrane electrode assembly)
Here, a manufacturing method of the membrane electrode assembly of the present embodiment will be described.

<Cathode catalyst ink adjustment>
First, an oxide catalyst using Ta oxide or the like as a raw material, an ionomer, and a solvent are mixed to prepare a catalyst ink. Each ratio at this time varies depending on the oxide catalyst. When the oxide catalyst, ionomer, carbon powder, and solvent are TaCNO, Nafion, Ketjen Black, and 1-propanol, respectively, the weight ratio of the oxide catalyst, ionomer, and carbon powder is 1: 1: 1.

<Anode catalyst ink adjustment>
A platinum-based catalyst, an ionomer and a solvent are mixed to prepare an anode catalyst ink. Each ratio at this time varies depending on the platinum-based catalyst. When platinum-based catalyst, ionomer, carbon powder, and solvent are Pt-Ru / C, Nafion, Ketjen black, and 1-propanol, respectively, the weight ratio of platinum-based catalyst, ionomer, and carbon powder is 1: 1: 1. It is.

  The composition and adjustment method of the catalyst ink are not limited to the above composition and adjustment method, and can be changed according to the characteristics required for the membrane electrode assembly.

<Catalyst layer formation>
When the cathode catalyst ink and the anode catalyst layer are formed using the cathode catalyst ink and the anode catalyst ink, respectively, even if the direct coating method is directly applied to the solid polymer electrolyte membrane, it is indirectly formed. Any of the indirect application methods can be employed. As a coating method, screen printing, a die coating method, an inkjet method, a spray coating method, or the like can be used. In the case of employing the spray coating method, it is formed by repeatedly applying the catalyst ink to the solid polymer electrolyte membrane so as to obtain a desired catalyst weight using a spray coating apparatus. The spray application conditions are, for example, a spray pressure of 15 kPa, an atomizing air of 150 kPa, and a spray table temperature of 60 ° C.

<Bonding of solid polymer electrolyte membrane and gas diffusion layer>
The solid polymer electrolyte membrane is sandwiched between the catalyst-coated surface of the anode-side gas diffusion layer and the catalyst-coated surface of the cathode-side gas diffusion layer, further sandwiched between the gas diffusion layers from both sides, and bonded using a hot press machine. The conditions at the time of hot pressing are, for example, a pressure of 1 MPa, a temperature of 120 ° C., and 2 minutes. In addition, the temperature, time, and pressure of joining by a hot press machine can be arbitrarily changed according to the catalyst layer.

(Pre-processing method)
A pretreatment method (aging method) performed at the time of starting the fuel cell system according to the embodiment will be described. Examples of the pretreatment method include the following saturated humid aging and over humidification aging.

(Saturated humidification aging)
First, raw fuel is supplied to the reforming unit 40 to generate a hydrogen-rich reformed gas. After the CO concentration of the reformed gas generated in the reforming unit 40 is reduced by the CO conversion unit 46 and the CO removing unit 48, the reformed gas is brought into a saturated wet state using the fuel wet heat exchanger 60. The saturated humidified state refers to a state where the relative humidity is 100% at the cell temperature of the fuel cell stack 300. The reformed gas in the saturated humid state is supplied to the anode 322 of the fuel cell stack 300. The dew point temperature of the reformed gas supplied to the anode 322 of the fuel cell stack 300 is set to be equal to the cell temperature measured by the temperature sensor 392 using the fuel wet heat exchanger 60. The hydrogen concentration in the reformed gas supplied to the anode 322 is more preferably 50% by mass or more.

  On the other hand, air that has been saturated and humidified using the oxidant wet heat exchanger 70 is supplied to the cathode 324 of the fuel cell stack 300. The dew point temperature of the air supplied to the cathode 324 of the fuel cell stack 300 is set to be equal to the cell temperature measured by the temperature sensor 392 using the oxidant wet heat exchanger 70. The oxygen concentration in the air supplied to the cathode 324 is more preferably 10% by mass or more.

A constant voltage (for example, 5 mV) is maintained between the anode 322 and the cathode 324, and the supply of the reformed gas and air is continued until the current flowing between the anode 322 and the cathode 324 converges. Concerning the convergence of the current, when the reference time is T1, the rate of increase in the current density of the current flowing between the anode 322 and the cathode 324 from time T0 to T1 30 minutes before T1 is 10 mA / (cm ²・ 30 minutes) means less than Incidentally, the rate of increase in current density is preferably from 3mA / ^(cm 2 · 30 min), more preferably a 1mA / ^(cm 2 · 30 min).

(Over humidified aging)

  First, raw fuel is supplied to the reforming unit 40 to generate a hydrogen-rich reformed gas. After the CO concentration of the reformed gas generated in the reforming unit 40 is reduced by the CO conversion unit 46 and the CO removing unit 48, the reformed gas is brought into an excessively humidified state using the wet heat exchanger 60 for fuel. The overhumidified state refers to a state where the dew point is higher than the cell temperature of the fuel cell stack 300. The overhumidified reformed gas is supplied to the anode 322 of the fuel cell stack 300. The dew point temperature of the reformed gas supplied to the anode 322 of the fuel cell stack 300 is set to be higher than the cell temperature measured by the temperature sensor 392 using the fuel wet heat exchanger 60. The dew point temperature of the reformed gas supplied to the anode 322 is preferably 10 ° C. higher than the cell temperature of the fuel cell stack 300. Note that the hydrogen concentration in the reformed gas supplied to the anode 322 is preferably 50% by mass or more.

  On the other hand, air that has been excessively humidified using the oxidant wet heat exchanger 70 is supplied to the cathode 324 of the fuel cell stack 300. The temperature of the air supplied to the cathode 324 of the fuel cell stack 300 is set to be higher than the cell temperature measured by the temperature sensor 392 using the oxidant wet heat exchanger 70. The temperature of the air supplied to the cathode 324 is preferably 10 ° C. higher than the cell temperature of the fuel cell stack 300. Note that the oxygen concentration in the air supplied to the cathode 324 is preferably 10% by mass or more.

A constant voltage (for example, 5 mV) is maintained between the anode 322 and the cathode 324, and the supply of the reformed gas and air is continued until the current flowing between the anode 322 and the cathode 324 converges. Concerning the convergence of the current, when the reference time is T1, the rate of increase in the current density of the current flowing between the anode 322 and the cathode 324 from time T0 to T1 30 minutes before T1 is 10 mA / (cm ²・ 30 minutes) means less than Incidentally, the rate of increase in current density is preferably from 3mA / ^(cm 2 · 30 min), more preferably a 1mA / ^(cm 2 · 30 min).

  According to this pretreatment method, the power generation performance of the membrane electrode assembly can be improved by supplying a current between the anode and the cathode while supplying sufficient water to the catalyst layer. This is presumed that the oxidizing atmosphere environment contributes to the maintenance or improvement of the specific activity of the catalyst, and the sufficient amount of water and current running contribute to the formation of a proton transport path to the catalytic activity point.

Example 1
The layer structure of the membrane electrode assembly used in the pretreatment method of the example is shown below.
<Solid polymer electrolyte membrane>
Material: Napon (registered trademark) NRE-212 manufactured by DuPont
Film thickness: 50 μm
<Anode catalyst layer and cathode catalyst layer>
Ionomer: Nafion 20% by mass solution oxide catalyst manufactured by DuPont: TaCNO
Conductive material: Ketjen Black Film thickness: 15μm
<Anode gas diffusion layer and cathode gas diffusion layer>
Material: TEC 10E50E
Film thickness: 20 μm

  An over humidified reformed gas (hydrogen) at a temperature of 90 ° C. is supplied to the anode of the fuel cell stack (temperature 80 ° C.), and an over humidified nitrogen gas at a temperature of 90 ° C. is supplied to the cathode. The current density of the current flowing between the anode and the cathode was measured with the voltage between them held constant (5 mV).

FIG. 4 is a graph showing a change with time of current density when the pretreatment method of Example 1 is performed. FIG. 5 is a graph showing the relationship between aging time and cell impedance. The rate of increase in current density when the aging time is 30 minutes, 1 hour, 2.5 hours, and 4 hours is 15, 10, 3, 1 mA / (cm ² · 30 minutes), respectively. It was confirmed that when the rate of increase in current density was 10 mA / (cm ² · 30 minutes) or less, the actual resistance was significantly reduced.

(Comparative Example 1)
In the pretreatment method according to Comparative Example 1, the aging method used in the fuel cell having a platinum catalyst was applied to the membrane electrode assembly having the same layer configuration as the pretreatment method of Example 1. Specifically, an over humidified reformed gas (hydrogen gas) at a temperature of 90 ° C. is supplied to the anode of the fuel cell stack (temperature 80 ° C.), and an over humidified nitrogen gas at a temperature of 90 ° C. is supplied to the cathode. The anode and cathode were shorted until the voltage converged.

  FIG. 6 is a graph showing a change in voltage over time when the aging method according to Comparative Example 1 is performed. The anode and cathode were short-circuited until the time change in voltage converged to ± 3 mV.

(Evaluation result 1)
The current density was measured for the fuel cell subjected to the pretreatment method according to Example 1 (aging time: 4 hours) and the fuel cell subjected to the pretreatment method according to Comparative Example 1. Table 1 shows the results. As shown in Table 1, the current density when the pretreatment method according to Example 1 is performed is higher than the current density when the pretreatment method according to Comparative Example 1 is performed. With the pretreatment method according to the present invention, it was confirmed that aging is possible without impairing power generation performance in a fuel cell having an oxide-based catalyst.

(Example 2)
In the pretreatment method according to the second embodiment, the saturated humidified state at a temperature of 80 ° C. is modified on the anode of the fuel cell stack (temperature of 80 ° C.) with respect to the membrane electrode assembly having the same layer configuration as the pretreatment method of the first embodiment. After supplying gas (hydrogen) and supplying the cathode with saturated humidified air (oxidant) at a temperature of 80 ° C., keeping the voltage between the anode and the cathode constant (5 mV) for 1 hour, The current density of the current flowing between the cathode and the cathode was measured.

(Comparative Example 2)
In the pretreatment method according to Comparative Example 2, the saturation humidification state at a temperature of 60 ° C. was improved on the anode of the fuel cell stack (temperature of 80 ° C.) with respect to the membrane electrode assembly having the same layer configuration as the pretreatment method of Example 2. After supplying a gas (hydrogen), supplying air with a low humidity of 60 ° C. (oxidant) to the cathode, keeping the voltage between the anode and the cathode constant (5 mV) and holding it for 1 hour, The current density of the current flowing between the cathode and the cathode was measured.

(Evaluation result 2)
A fuel cell subjected to the pretreatment method according to Example 2 (anode: saturated humidification, cathode: saturation humidification) and a fuel cell subjected to the pretreatment method according to Comparative Example 2 (anode: low humidification, cathode low humidification) Density was measured. Table 2 shows the results. As shown in Table 2, the current density when the pretreatment method according to Example 2 is performed is higher than the current density when the pretreatment method according to Comparative Example 2 is performed. With the pretreatment method according to the present invention, it was confirmed that aging is possible without impairing power generation performance in a fuel cell having an oxide-based catalyst.

(Example 3)
In the pretreatment method according to Example 3, the saturated humidified state at a temperature of 80 ° C. is modified on the anode of the fuel cell stack (temperature of 80 ° C.) with respect to the membrane electrode assembly having the same layer configuration as that of the pretreatment method of Example 1. The gas density (hydrogen) is supplied, and the cathode is supplied with saturated humidified air (oxidant) at a temperature of 80 ° C., and the voltage between the anode and cathode is kept constant (5 mV), and the current density increases. After maintaining the rate until 10 mA / (cm ² · 30 minutes), the current density of the current flowing between the anode and the cathode was measured.

(Comparative Example 3)
In the pretreatment method according to Comparative Example 3, the saturated humidified state at a temperature of 80 degrees is modified on the anode of the fuel cell stack (temperature of 80 ° C.) with respect to the membrane electrode assembly having the same layer configuration as the pretreatment method of Example 3. The gas density (hydrogen) is supplied, the saturated humidified air (oxidant) at a temperature of 80 degrees is supplied to the cathode, and the voltage between the anode and the cathode is kept constant (5 mV), and the current density increases. After maintaining the rate until it reached 12 mA / (cm ² · 30 minutes), the current density of the current flowing between the anode and the cathode was measured.

(Evaluation result 3)
A fuel cell subjected to the pretreatment method according to Example 3 (current density increase rate: 10 mA / (cm ² .30 minutes)) and the pretreatment method according to Comparative Example 3 (current density increase rate: 12 mA / ( The current density of the fuel cell subjected to cm ² · 30 minutes) was measured. Table 3 shows the results. As shown in Table 2, the current density when the pretreatment method according to Example 3 is performed is higher than the current density when the pretreatment method according to Comparative Example 3 is performed. With the pretreatment method according to the present invention, it was confirmed that aging is possible without impairing power generation performance in a fuel cell having an oxide-based catalyst.

DESCRIPTION OF SYMBOLS 10 Fuel cell system, 320 Solid polymer electrolyte membrane, 300 Fuel cell stack, 322 Anode, 324 Cathode, 326 Anode catalyst layer, 328 Anode gas diffusion layer, 330 Cathode catalyst layer, 332 Cathode gas diffusion layer, 350 Membrane electrode assembly

Claims (8)

Membrane electrode junction comprising an electrolyte membrane, a cathode catalyst layer formed on one surface of the electrolyte membrane and containing a proton conductor and an oxide catalyst, and an anode catalyst layer formed on the other surface of the electrolyte membrane A pretreatment method for a fuel cell having a body,
A pretreatment method for a fuel cell, comprising supplying an over-humidified hydrogen-containing gas to an anode catalyst layer and supplying an over-humidified oxidant gas to a cathode catalyst layer. Membrane electrode junction comprising an electrolyte membrane, a cathode catalyst layer formed on one surface of the electrolyte membrane and containing a proton conductor and an oxide catalyst, and an anode catalyst layer formed on the other surface of the electrolyte membrane A pretreatment method for a fuel cell having a body,
A fuel cell pretreatment method, wherein a saturated humidified hydrogen-containing gas is supplied to an anode catalyst layer, and a saturated humidified oxidant gas is supplied to a cathode catalyst layer.   The fuel cell pretreatment method according to claim 1, wherein at least one of dew point temperatures of the hydrogen-containing gas and the oxidant gas is higher than a cell temperature.   The fuel cell pretreatment method according to claim 2, wherein at least one of dew point temperatures of the hydrogen-containing gas and the oxidant gas is equal to a cell temperature.   The fuel cell pretreatment method according to any one of claims 1 to 4, wherein a hydrogen content of the hydrogen-containing gas is 50 mass% or more.   The pretreatment method for a fuel cell according to any one of claims 1 to 5, wherein an oxygen content of the oxidant gas is 10% by mass or more.   7. The hydrogen-containing gas and the oxidant gas are supplied until the change in the current density flowing through the fuel cell converges while the output voltage of the fuel cell is kept constant. A pretreatment method for a fuel cell as described in 1). With the output voltage of the fuel cell kept constant, the hydrogen-containing gas and the oxidant gas are supplied until the rate of increase in the current density flowing through the fuel cell reaches 10 mA / (cm ² .30 minutes). The fuel cell pretreatment method according to any one of claims 1 to 7.

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