JP2007257970A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of maintaining catalytic activity of an electrode as much as possible and maintaining power generating efficiency for long period of time. <P>SOLUTION: In the fuel cell provided with an electrolyte layer 112, a first electrode 132, a second electrode, in which a first reactive fluid containing carbon monoxide or oxygen is supplied to the first electrode and a second reactive fluid is supplied to the second electrode, the first electrode 132 is provided with a catalyst layer 122 having a catalyst action, and either a carbon monoxide removal layer 134 removing carbon monoxide from the first reactive fluid supplied to the catalyst layer 122 or an oxygen removal layer 134 removing oxygen from the first reactive fluid supplied to the catalyst layer 134. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell, and more particularly to an electrode of a fuel cell.

  Although it has become an era when new technologies such as IT and biotechnology are deployed on a global scale, the energy industry is still one of the largest core industries. Recently, expectations for so-called new energy are increasing with the spread of environmental awareness including prevention of global warming. In addition to environmental properties, new energy can be produced in a distributed manner in close proximity to power consumers, so there are advantages in terms of transmission loss and power supply security. In addition, the development of new energy can be expected to have a secondary effect of creating new peripheral industries. New energy initiatives began in earnest with the oil crisis about 30 years ago, and now, renewable energy such as solar power generation, recycling energy such as waste power generation, high-efficiency energy such as fuel cells, and clean energy Energy such as new field energy represented by cars is in the stage of development for practical application.

  Among them, fuel cells are one of the most noticeable energies in the industry. A fuel cell is a device that generates electricity and heat simultaneously by chemically reacting hydrogen produced by reacting water vapor with natural gas, methanol, etc., and oxygen in the air. It is highly efficient in the area, and power generation is stable without being affected by the weather. In particular, the polymer electrolyte fuel cell is regarded as one of the next generation standard power supplies in applications such as stationary, in-vehicle use, and portable use.

For practical use of a fuel cell system using this polymer electrolyte fuel cell, at present, extending the life is one key, but in Patent Document 1, the catalytic activity of an electrode, particularly an electrode catalyst, In order to maintain for a long period of time, it is disclosed that two types of carbons having different graphitization rates are used for the carbon supporting the catalyst.
JP 2005-129457 A

  There are several possible causes for the decrease in catalytic activity in fuel cell electrodes. One of them is CO poisoning of the catalyst (particularly platinum). In order to avoid this CO poisoning, the anode side Conventionally known is a technique in which O 2 is mixed in (so-called air bleed) and is oxidized as shown in formula (1).

しかし、式（１）の反応による熱によって、黒鉛化率の低い、所謂、アモルファスカーボン（非定形炭素）が破壊され、特許文献１のように黒鉛化率の高いカーボンに触媒を担持させたものを電極触媒に混合しても、黒鉛化率の低いカーボンが流出し、次第に触媒活性が低下していくという問題があった。

However, so-called amorphous carbon (amorphous carbon) having a low graphitization rate is destroyed by heat due to the reaction of formula (1), and a catalyst is supported on carbon having a high graphitization rate as in Patent Document 1. Even when the catalyst is mixed with the electrode catalyst, carbon having a low graphitization rate flows out, and the catalytic activity gradually decreases.

  The present invention has been made in view of the above problems, and a fuel cell capable of maintaining the catalytic activity of an electrode as much as possible and maintaining power generation efficiency over a long period of time even when air bleeding is performed. The purpose is to provide.

  The present invention comprises an electrolyte layer, a first electrode provided on one surface of the electrolyte layer, and a second electrode provided on the other surface, and carbon monoxide is applied to the first electrode. In the fuel cell in which the first reaction fluid including the first reaction fluid is supplied and the second reaction fluid is supplied to the second electrode, the first electrode supplies the catalyst layer having a catalytic action and the catalyst layer. And a carbon monoxide removal layer for removing carbon monoxide from the first reaction fluid.

  The present invention also includes an electrolyte layer, a first electrode provided on one surface of the electrolyte layer, and a second electrode provided on the other surface, and oxygen is supplied to the first electrode. In the fuel cell in which the first reaction fluid including the first reaction fluid is supplied and the second reaction fluid is supplied to the second electrode, the first electrode supplies the catalyst layer having a catalytic action and the catalyst layer. And an oxygen removing layer for removing oxygen from the first reaction fluid.

  Here, the reaction fluid refers to a gas or liquid containing hydrogen atoms or oxygen atoms that contributes to the power generation reaction of the fuel cell. According to the present invention, carbon monoxide or oxygen contained in the reaction fluid is removed from the reaction fluid. Then, since the reaction fluid is supplied to the catalyst layer, the catalyst in the catalyst layer can be prevented from being poisoned with CO, or the oxidation reaction can occur on the catalyst in the catalyst layer. It can be avoided. Therefore, the catalytic activity of the catalyst layer can be maintained over a long period of time, and the power generation efficiency of the fuel cell can be maintained over a long period of time.

A third aspect of the present invention is the fuel cell according to the first or second aspect, wherein the carbon monoxide removal layer or the oxygen removal layer includes a catalyst supported on highly graphitized carbon. Here, graphite is a hexagonal layered crystal in which hexagonal networks of carbon atoms are regularly stacked. Highly graphitized carbon is a carbon containing a large amount of graphite (including a lot of hexagonal layered crystals). Specifically, the average lattice spacing d ₀₀₂ of the [002] plane is 0.337 nm or more and 0.348 nm or less, or the crystallite c-axis direction size L _c (002) is 3 nm or more and 18 nm or less. It is a certain carbon and generally has high water repellency, conductivity and corrosion resistance as compared with amorphous carbon. Since the highly graphitized carbon is not destroyed even if the reaction of the formula (1) occurs on the catalyst supported on such highly graphitized carbon, carbon monoxide is used for a long period of time. Alternatively, oxygen can be removed.

  According to a fourth aspect of the present invention, in the fuel cell according to any one of the first to third aspects, the carbon monoxide removal layer or the oxygen removal layer diffuses the first reaction fluid supplied to the catalyst layer. It is a diffusion layer. Thereby, carbon monoxide or oxygen can be efficiently removed while diffusing so that the reaction fluid is uniformly supplied to the catalyst layer.

  The invention according to claim 5 is a fuel cell system, wherein the fuel cell according to any one of claims 1 to 4, hydrogen supply means for supplying hydrogen to the first electrode, and the first electrode And oxygen supply means for supplying oxygen to the second electrode. Here, in the best mode for carrying out the invention of the present specification, the hydrogen supply means will be described with a reformer that reforms LPG, city gas, etc., but is not limited to this, and is necessary for a fuel cell. It may be a means for supplying a hydrogen molecule or an organic substance containing a hydrogen atom as a proton element. The oxygen supply means is generally a system using air, but may be a supply means using an oxygen cylinder or the like for space use or deep sea use. By using the fuel cell as described above, the power generation efficiency of the fuel cell can be maintained over a long period of time, and thus the life of the fuel cell system can be extended.

  According to the present invention, the power generation efficiency of the fuel cell can be maintained as much as possible.

  Hereinafter, the fuel cell 10 of the present invention will be described in detail with reference to the drawings. FIG. 1 is a system configuration diagram of a household fuel cell cogeneration system CGS using a fuel cell 10 according to the present invention. A household fuel cell cogeneration system CGS reforms raw fuel (hydrocarbon fuel) such as LPG and city gas, and generates a reformed gas containing about 80% hydrogen (fuel); The fuel cell 10 that generates power by the reformed gas supplied from the reformer and oxygen (oxidant) in the air, and the heat generated from the reformer and the fuel cell 10 are converted into hot water (40 ° C. or higher water ) And a hot water storage device that recovers and stores hot water in the form of a system that has both a power generation function and a hot water supply function.

  Raw fuels such as LPG and city gas installed in homes are usually odorized by sulfides as a safety measure against gas leakage, but this sulfide degrades the catalyst in the reformer. In the reformer, first, sulfide in the raw fuel is removed by the desulfurizer 52. The raw fuel desulfurized by the desulfurizer 52 is then mixed with steam, steam reformed by the reformer 54, and introduced into the transformer 56. The reformer 56 produces reformed gas of about 80% hydrogen, about 20% carbon dioxide, and 1% or less carbon monoxide, but is operated at a low temperature (100 ° C. or less) that is easily affected by carbon monoxide. In the present system CGS for supplying the reformed gas to the fuel cell 10 to be processed, the reformed gas and oxygen are further mixed, and the carbon monoxide is selectively oxidized by the CO remover 58. The carbon monoxide concentration in the reformed gas can be reduced to 10 ppm or less by the CO remover 58.

  The reformer includes at least a reformer 54 and a transformer 56, and the desulfurizer 52 is used as the fuel cell 10 when the gas laid at home is used as a raw fuel as in this system CGS. In the case of using a low temperature type fuel cell 10 such as a solid polymer fuel cell, a CO remover 58 is further included.

  Since steam reforming is an endothermic reaction, the reformer 54 is provided with a burner 60. When starting the reformer, the raw fuel is also supplied to the burner 60 to raise the temperature of the reformer 54. When the system CGS can be stably operated, the supply of the raw fuel to the burner 60 is stopped. Then, by supplying unreacted fuel discharged from the fuel cell 10 to the burner 60, heat is supplied to the reformer 54. Since the exhaust after supplying heat to the reformer 54 by the burner 60 still has a large amount of heat, this exhaust is heat-exchanged with the water in the hot water storage tank 62 by the heat exchangers HEX01 and HEX02. Then, the water exchanges heat (HEX03) with the exhaust gas from the cathode 14 of the fuel cell 10 and further exchanges heat (HEX04) with the exhaust gas from the anode 22 and returns to the hot water storage tank 62. The water pipe 64 passing through the heat exchangers HEX01, HEX02, HEX03, and HEX04 can be used for raising or cooling the cathode-side humidification tank 66 depending on the temperature of water (hot water) after passing through the heat exchanger HEX04. Further, a branch pipe 68 is provided. When the temperature of the cathode-side humidification tank 66 is low, such as when the system CGS is started, water passes through the heat exchanger HEX04 and then passes through the branch pipe 68 to heat the cathode-side humidification tank 66 in the heat exchanger HEX05. After supplying, the hot water storage tank 62 is returned.

  The cathode side humidification tank 66 also functions as a cooling water tank, and the water in the cathode side humidification tank 66 cools the fuel cell 10 and returns to the cathode side humidification tank 66. As described above, when the temperature of the fuel cell 10 is low, such as when the system CGS is activated, the fuel cell 10 can be warmed by supplying the fuel cell 10 with the cooling water warmed by the heat exchanger HEX05. . The cooling water passage 70 through which the cooling water passes is connected to a heat exchanger HEX06 provided in the anode-side humidification tank 72, and the cooling water serves to make the temperatures of the cathode-side humidification tank 66 and the anode-side humidification tank 72 substantially the same. Also plays.

  The reformed gas from the reformer is humidified (bubbled in the case of the present system CGS) in the anode side humidification tank 72 and supplied to the anode 22. As described above, since the reformed gas containing about several ppm to 10 ppm of CO is generated from the reformer of the present system CGS, a small amount of air (oxygen) is mixed before the anode-side humidifying tank 72. The catalyst of the anode 22 is prevented from being poisoned by CO. Unreacted fuel that has not contributed to power generation at the anode 22 is discharged from the fuel cell 10 and supplied to the burner 60. The fuel cell 10 is normally operated to generate power in the range of 70 to 80 ° C., and the exhaust gas discharged from the fuel cell 10 has a heat of about 80 ° C. Therefore, as described above, the heat exchanger HEX04 After the heat exchange at, the temperature of the water supplied to the cathode-side humidification tank 66 and the anode-side humidification tank 72 is further raised by the heat exchanger HEX07 and then supplied to the burner 60.

  The water supplied to the cathode-side humidification tank 66 and the anode-side humidification tank 72 is preferably clean water having low electrical conductivity and low contamination with organic substances. Supplied after water treatment with membrane and ion exchange resin. The water subjected to this water treatment is also used for steam reforming of the reformer 54. The clean water is also supplied to the hot water storage tank 62. At this time, the clean water is supplied from the lower part of the hot water storage tank 62. The water pipe 64 also draws water having a low temperature from the lower part of the hot water storage tank 62 and returns the water exchanged with each heat exchanger to the upper part.

  HEX10 is a total heat exchanger. Since the exhaust gas containing unreacted oxygen that has not contributed to power generation at the cathode 14 contains heat of about 80 ° C. and produced water generated by the reaction, it is supplied to the cathode 14 by the total heat exchanger HEX10. Supply heat and moisture to the air. The air supplied to the cathode 14 is further humidified (bubbling in the case of the present system CGS) in the cathode-side humidification tank 66 and then supplied to the cathode 14. On the other hand, heat and moisture are supplied to the total heat exchanger HEX 10. The supplied exhaust gas is further configured to be exchanged with water in the heat exchanger HEX03 and then discharged to the outside of the system CGS.

  FIG. 2 is a schematic configuration diagram showing the configuration of the fuel cell 10 according to the present invention. In the fuel cell 10 of the present invention, the diffusion layers 20 and 28 are composed of carbon paper, carbon woven fabric or non-woven fabric as a base material, and the base material is carbon black (fine particles of amorphous carbon (amorphous carbon)). It is made by applying carbon paste with As shown in FIG. 2, in consideration of productivity, the diffusion layers 20 and 28 use a common carbon paper for the base materials 18 and 26 of both the diffusion layers 20 and 28, and are applied to the base materials 18 and 26. Different pastes (filled layers) 16 and 24 are used on the cathode side and the anode side. That is, the cathode-side filling layer 16 produced by applying, drying, and heat-treating the diffusion layer paste on the base material 18 has a lower water repellency (a smaller amount of fluororesin) than the anode side. On the other hand, the anode-side filling layer 24 produced by applying, drying, and heat-treating the diffusion layer paste to the substrate 26 has high water repellency (a large amount of fluororesin). Further, the solid polymer film 12 is arranged so that the edges do not overlap over the entire circumference so that the solid polymer film 12 does not break due to concentrated stress from the edge of the electrode, and the solid polymer film 12 due to lack of protons on the cathode side. The cathode side and the anode side are designed so that the anode side becomes larger over the entire circumference so as not to cause deterioration.

  Since general fluororesin (hereinafter referred to as polymer fluororesin) has binding properties, when a large amount of polymer fluororesin is put into the diffusion layer paste, the viscosity increases due to mixing and coating operations, resulting in dumplings. become. Therefore, the coating process becomes very difficult. Therefore, the low molecular weight fluororesin has a property that the average molecular weight is smaller than that of the high molecular weight fluororesin and the binding property is very low. Thus, each diffusion layer paste has water repellency and binding properties in a balanced manner. Specifically, the carbon paper (Toray Industries, Inc .: TGPH060H) serving as the base material of the diffusion layer is carbon paper: FEP (tetrafluoroethylene-hexafluoropropylene copolymer) = 95: 5 (for cathode) by weight ratio. 60:40 (for anode), after being immersed in an FEP dispersion, dried at 60 ° C. for 1 hour, and then subjected to heat treatment (FEP water repellent treatment) at 380 ° C. for 15 minutes. Thereby, the carbon paper is subjected to water repellent treatment almost uniformly.

  FIG. 3 is a structural schematic diagram showing the structure of the anode side electrode 132 of the fuel cell 10 according to the present embodiment, and is an enlarged view in which the P1 portion of FIG. 2 is enlarged. The anode-side electrode 132 of this example is obtained by subjecting carbon paper to a water repellent treatment as described above, and then carbon black (manufactured by CABOT: Vulcan XC72R) and terpineol (manufactured by Kishida Chemical Co.) as a solvent and a nonionic interface. Triton (manufactured by Kishida Chemical Co., Ltd.), an activator, is uniformly mixed at room temperature for 1 hour with a universal mixer (manufactured by DALTON) so that the weight ratio is carbon black: terpineol: triton = 20: 150: 3. Mix to make a carbon paste. The carbon paste and low molecular fluororesin (Daikin: Lubron LDW40E) are mixed in a hybrid mixer container, and the weight ratio is carbon paste: low molecular fluororesin (hereinafter referred to as anode fluororesin) (included in the dispersion) The fluororesin component) is set to 26: 3 and mixed for 15 minutes in the mixing mode of the hybrid mixer. After mixing, the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 4 minutes. When the supernatant liquid accumulates on the upper part of the paste after defoaming, the supernatant liquid is discarded and the paste is naturally cooled to complete the anode diffusion layer paste.

  The anode diffusion layer paste cooled to room temperature is applied to the surface of the above-mentioned carbon paper that has been subjected to water repellent treatment so that the coating state in the carbon paper surface is uniform, and a hot air dryer (manufactured by Thermal Co., Ltd.) Dry at 60 ° C. for 1 hour. Finally, heat treatment is performed at 360 ° C. for 2 hours to complete the anode side diffusion layer 128. As a result, the anode-side filling layer 124 is filled with carbon black in the gaps of the carbon paper, so that the anode-side filling layer 124 is higher in density and has fine pores than the anode-side base material 126, and the capillary phenomenon is more likely to occur. It becomes. Accordingly, the water introduced and condensed from the humidification tank 72 into the fuel cell 10 is likely to move to a lower water concentration due to the capillary action of the anode side filling layer 124.

  Next, Pt-supported highly graphitized carbon in which Pt is supported on graphite carbon black (particles of highly graphitized carbon), an electrolyte solution (20% Nafion (registered trademark) solution), ethanol as a solvent, and Pt-supported highly graphite. Carbonized carbon: electrolyte solution: ethanol = 3: 8: 9 is mixed to prepare a CO oxidation catalyst solution. This CO oxidation catalyst solution is sprayed on the surface on which the filling layer 116 of the cathode side diffusion layer 120 is formed by a spray method. After spraying the CO oxidation catalyst solution, it is dried at 60 ° C. for 1 hour to drive off the solvent, and the CO oxidation layer 134 is produced. Then, Pt-Ru-supported carbon (this carbon is amorphous carbon) and an electrolyte solution (20% Nafion (registered trademark) solution) are mixed at a ratio of Pt-Ru-supported carbon: electrolyte solution = 1: 2, and the anode side catalyst Make a paste. The anode side catalyst paste is applied to the surface of the CO oxide layer 134 to produce the catalyst layer 122.

As described above, by providing the CO oxide layer 134 containing the Pt-supported highly graphitized carbon and the electrolyte solution between the packed layer 124 and the catalyst layer 122,
(A) When CO contained in the reformed gas and O ₂ supplied by the air bleed reach the CO oxide layer 134 through the diffusion layer 128, as shown in the equation (1), CO is CO next CO ₂ over Pt oxide layer 134, the catalyst of the catalyst layer 122 (Pt) can be prevented from being CO poisoning.
(B) In the CO oxide layer 134, carbon carrying Pt is graphite carbon, so that it is not destroyed by the heat of the reaction of the formula (1). Therefore, the carried Pt does not flow out.
(C) When H ₂ contained in the reformed gas and O ₂ supplied by the air bleed reach the CO oxide layer 134 and react on Pt of the CO oxide layer 134, water is absorbed in the CO oxide layer 134. Although it is produced, it is adjacent to the packed bed 124, so that the water moves to a drier one depending on the moisture concentration.
(D) When only H ₂ contained in the reformed gas reaches the CO oxide layer 134 and reacts on Pt of the CO oxide layer 134, H ₂ becomes protons (H ⁺ ) and passes through the electrolyte solution. Protons move to the solid polymer membrane 112.
Effects such as can be obtained.

  FIG. 4 is a structural schematic diagram showing the structure of the anode side electrode 232 of the fuel cell 10 according to the present embodiment, and is an enlarged view in which the portion P1 in FIG. 2 is enlarged. The anode-side electrode 232 of this example was obtained by subjecting carbon paper to a water repellent treatment as described above, and then containing carbon black, terpineol as a solvent, triton of a nonionic surfactant, and Pt-supported highly graphitized carbon, The carbon paste was mixed uniformly with a universal mixer at room temperature for 1 hour so that the weight ratio was carbon black: terpineol: triton: Pt supported highly graphitized carbon = 10: 150: 3: 10. Make it. The hybrid mixer is charged with the carbon paste and the fluororesin for anode so that the weight ratio is carbon paste: fluororesin for anode (fluorine resin component contained in the dispersion) = 26: 3. Mix for 15 minutes in the mixing mode. After mixing, the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 4 minutes. When the supernatant liquid accumulates on the upper part of the paste after defoaming, the supernatant liquid is discarded and the paste is naturally cooled to complete the anode diffusion layer paste.

  The anode diffusion layer paste cooled to room temperature is applied to the surface of the carbon paper that has been subjected to water repellent treatment so that the applied state in the carbon paper surface is uniform, and dried in a hot air dryer at 60 ° C. for 1 hour. To do. Finally, heat treatment is performed at 360 ° C. for 2 hours to complete the anode side diffusion layer 228. As a result, the anode-side packed layer 224 is filled with carbon black and Pt-supported highly graphitized carbon in the voids of the carbon paper, so that the anode-side filled layer 224 has a higher density and narrow pores than the anode-side base material 226. The capillary phenomenon is more likely to occur. Therefore, the water introduced from the humidification tank 72 to the fuel cell 10 and condensed is easily moved to a lower moisture concentration by the capillary action of the anode side filling layer 224.

  Next, Pt-Ru-supported carbon (this carbon is amorphous carbon) and an electrolyte solution (20% Nafion (registered trademark) solution) were mixed at a ratio of Pt-Ru-supported carbon: electrolyte solution = 1: 2, and the anode side A catalyst paste is prepared. The anode side catalyst paste is applied to the surface of the anode side diffusion layer 228 to which the anode diffusion layer paste has been applied, that is, the surface of the anode side filling layer 224 to produce the catalyst layer 222.

As described above, since the anode-side filling layer 224 contains Pt-supported highly graphitized carbon,
(A) When CO contained in the reformed gas and O ₂ supplied by the air bleed reach the filling layer 224 through the base material layer 226, the CO is filled as shown in the equation (1). It becomes CO ₂ on Pt supported on the graphite carbon of the layer 224, and the catalyst (Pt) of the catalyst layer 222 can be prevented from being poisoned by CO.
(B) Since the carbon carrying Pt contained in the packed bed 224 is graphite carbon, it is not destroyed by heat due to the reaction of the formula (1). Therefore, the carried Pt does not flow out.
(C) When H ₂ contained in the reformed gas and O ₂ supplied by the air bleed reach the packed bed 224 and react on Pt in the packed bed 224, water is generated in the packed bed 224. However, due to the capillary action of the packed bed 224, the water moves to a drier one.
(D) The manufacturing process of the electrode 232 is less than that of the first embodiment, and can be easily manufactured.
Effects such as can be obtained.

  FIG. 5 is a structural schematic diagram showing the structure of the anode side electrode 332 of the fuel cell 10 according to the present embodiment, and is an enlarged view in which the portion P2 in FIG. 2 is enlarged. In the anode side electrode 332 of this example, after carbon paper was subjected to water repellent treatment as described above, the weight ratio of carbon black and terpineol as a solvent and triton of a nonionic surfactant was carbon black: terpineol. : Triton = 20: 150: 3 is mixed so as to be uniform at room temperature for 1 hour in a universal mixer to prepare carbon paste A. The carbon paste A and the anode fluororesin are put into a hybrid mixer container so that the weight ratio is carbon paste A: anode fluororesin (fluorine resin component contained in the dispersion) = 26: 3, Mix for 15 minutes in the mixing mode of the hybrid mixer. After mixing, the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 4 minutes. When the supernatant liquid accumulates on the upper part of the paste after defoaming, the supernatant liquid is discarded and the paste is naturally cooled to complete the anode diffusion layer paste.

  Also, universal mixing of Pt-supported highly graphitized carbon and terpineol as a solvent and triton of nonionic surfactant so that the weight ratio is Pt-supported highly graphitized carbon: terpineol: triton = 20: 150: 3. A carbon paste G is produced by mixing uniformly at room temperature for 1 hour in a machine. The carbon paste G and the anode fluororesin are put into a hybrid mixer container so that the weight ratio is carbon paste A: anode fluororesin (fluororesin component contained in the dispersion) = 26: 3, Mix for 15 minutes in the mixing mode of the hybrid mixer. After mixing, the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 4 minutes. When the supernatant liquid accumulates on the upper part of the paste after defoaming, the supernatant liquid is discarded and the paste is naturally cooled to complete the CO oxide layer paste.

  The CO oxide layer paste and anode diffusion layer paste cooled to room temperature are applied to the surface of the carbon paper subjected to the water repellent treatment so that the application state in the carbon paper surface becomes uniform. The oxide layer paste is applied to the portion of the carbon paper near the inlet of the reformed gas to which the reformed gas is introduced when the fuel cell 10 is assembled, and the anode diffusion layer paste is applied to the carbon paper of the fuel cell 10 It is applied to a portion near the outlet of the reformed gas from which the reformed gas is discharged. After applying each paste, it is dried in a hot air dryer at 60 ° C. for 1 hour, and the anode diffusion layer paste is again applied to the surface of the carbon paper coated with the CO oxide layer paste and anode diffusion layer paste. The coating is applied so that the inner coating state is uniform, and dried in a hot air dryer at 60 ° C. for 1 hour. Finally, heat treatment is performed at 360 ° C. for 2 hours to complete the anode side diffusion layer 328.

As a result, the anode side filling layer 324 and the CO oxide layer 334 have higher density and narrow pores than the anode side substrate 326 because the carbon paper voids are filled with carbon black or Pt-supported highly graphitized carbon. Thus, the capillary phenomenon is more likely to occur. Therefore, the water introduced from the humidification tank 72 to the fuel cell 10 and condensed is easily moved to a lower moisture concentration by the capillary action of the anode side filling layer 224. In addition, since the CO oxide layer 334 is formed so as to be concentrated on the reformed gas inlet side, the reaction occurs intensively on the inlet side where the amount of CO is large, so that CO ₂ is efficiently converted. Can do.

  Next, Pt-Ru-supported carbon (this carbon is amorphous carbon) and an electrolyte solution (20% Nafion (registered trademark) solution) were mixed at a ratio of Pt-Ru-supported carbon: electrolyte solution = 1: 2, and the anode side A catalyst paste is prepared. The anode side catalyst paste is applied to the surface of the anode side diffusion layer 328 to which the anode diffusion layer paste is applied, that is, the surface of the anode side filling layer 324 to produce the catalyst layer 322.

As described above, by providing the CO oxide layer 334 by inclining the amount of Pt-supported highly graphitized carbon in the diffusion layer 328,
(A) When CO contained in the reformed gas and O ₂ supplied by the air bleed reach the CO oxide layer 334 through the base material layer 326, as shown in the equation (1), CO is It becomes CO ₂ on Pt of the CO oxidation layer 334, and the catalyst (Pt) of the catalyst layer 322 can be prevented from being poisoned by CO.
(B) In the CO oxide layer 334, the carbon carrying Pt is graphite carbon, so it is not destroyed by the heat of the reaction of the formula (1). Therefore, the carried Pt does not flow out.
(C) When H ₂ contained in the reformed gas and O ₂ supplied by the air bleed reach the CO oxide layer 334 and react on Pt of the CO oxide layer 334, water is absorbed in the CO oxide layer 334. Although generated, the capillarity of the packed bed 324 and the CO oxide layer 334 causes the water to move to the more dry side.
(D) Since the amount of CO contained in the reformed gas is large in the portion (inlet side) where the reformed gas is introduced, CO can be efficiently converted to CO ₂ on the inlet side.
Effects such as can be obtained.

  On the other hand, on the cathode side, carbon black and terpineol as a solvent and triton of a nonionic surfactant are mixed with a universal mixer so that the weight ratio is carbon black: terpineol: triton = 20: 150: 3. To mix uniformly for 60 minutes to produce a carbon paste. A low molecular fluororesin and a high molecular fluororesin (DuPont: PTFE30J) are mixed so that the weight ratio of the fluororesin contained in the dispersion is low molecular fluororesin: polymer fluororesin = 20: 3. Then, a mixed fluororesin for cathode is prepared. The carbon paste is put into a hybrid mixer container and cooled until the carbon paste reaches 10 to 12 ° C. The above-mentioned mixed fluororesin for cathode is put into the cooled carbon paste so that the weight ratio is carbon paste: mixed fluororesin for cathode (fluorine resin component contained in the dispersion) = 31: 1, and mixing in the hybrid mixer Mix in mode for 12-18 minutes. The mixing stop timing is set until the paste temperature reaches 50 to 55 ° C., and the mixing time is adjusted appropriately. After the paste temperature reaches 50 to 55 ° C., the hybrid mixer is switched from the mixing mode to the defoaming mode and defoamed for 1 to 3 minutes. The paste after defoaming is naturally cooled to complete the cathode diffusion layer paste.

  The cathode diffusion layer paste cooled to room temperature is applied to the surface of the carbon paper subjected to FEP water repellent treatment so that the coating state in the carbon paper surface is uniform, and then heated at 60 ° C. for 1 hour in a hot air dryer. dry. Finally, heat treatment is performed at 360 ° C. for 2 hours to complete the cathode side diffusion layer 20. Thus, the filling layer 16 is filled with carbon black in the gaps of the carbon paper, so that the density is higher than that of the base material layer 18 and fine pores exist, and the capillary phenomenon is more likely to occur. Therefore, the water generated by the power generation reaction or the water introduced into the fuel cell 10 from the humidifying tank 66 and condensed is easily moved to a lower water vapor partial pressure by the capillary action of the packed bed 16.

  Pt-supported carbon and an electrolyte solution (20% Nafion (registered trademark) solution) are mixed at a ratio of Pt-supported carbon: electrolyte solution = 3: 8 to prepare a cathode side catalyst paste. The cathode side catalyst paste is applied to the surface of the filling layer 16 on the surface side where the cathode side diffusion layer paste is applied, thereby producing the catalyst layer 14.

  In the fuel cell 10, an anode side electrode 32 is arranged so that the anode side catalyst layer 22 is in contact with one surface of a solid polymer membrane (Nafion 112 manufactured by DuPont), and the cathode side catalyst layer 14 is in contact with the other surface. Thus, the cathode side electrode 30 is arranged, and hot pressing is performed in a state of being sandwiched between the electrodes 30 and 32. The fuel cell 10 to be incorporated in the system CGS is formed by stacking about 50 pieces produced by hot pressing as described above in series, and is supplied from an oxygen supply means such as an air pump to the cathode 14 side and is humidified by a humidification tank 66. The generated air is supplied, and the anode 22 is supplied with reformed gas supplied from a hydrogen supply means such as a reformer and humidified in the humidification tank 72, thereby generating electric power.

  In the present embodiment, the explanation has been given using the household fuel cell cogeneration system that reforms the raw fuel with the reformer and supplies it to the fuel cell. However, the present invention is not limited to this, and the organic fuel is reformed. Even in a methanol direct supply type fuel cell system for portable devices that is supplied directly to a fuel cell, CO can be generated in the course of a reaction in which the organic fuel becomes proton and carbon dioxide. . In the present embodiment, Pt-supported highly graphitized carbon is used, but it is considered that the same effect can be obtained with manganese dioxide.

1 is a system configuration diagram of a household fuel cell cogeneration system using a fuel cell according to the present invention. 1 is a configuration schematic diagram showing an outline of a configuration of a fuel cell according to the present invention. It is an expansion schematic diagram which shows the structure of the anode electrode of the fuel cell which concerns on Example 1 of this invention. It is an expansion schematic diagram which shows the structure of the anode electrode of the fuel cell which concerns on Example 2 of this invention. It is an expansion schematic diagram which shows the structure of the anode electrode of the fuel cell which concerns on Example 3 of this invention.

Explanation of symbols

10 Fuel cell 12 Solid polymer membrane (electrolyte layer)
DESCRIPTION OF SYMBOLS 14 Cathode side catalyst layer 16 Cathode side filling layer 18 Cathode side base material layer 20 Cathode side diffusion layer 22, 122, 222, 322 Anode side catalyst layer 24, 124, 224, 324 Anode side filling layer 26, 126, 226, 326 Anode-side base material layer 28, 128, 228, 328 Anode-side diffusion layer 30 Cathode-side electrode 32, 132, 232, 332 Anode-side electrode 52 Desulfurizer 54 Reformer 56 Transformer 58 CO remover 60 Burner 62 Hot water storage Tank 64 Water pipe 66 Cathode side humidification tank 68 Branch pipe 70 Cooling water passage 72 Anode side humidification tank 74 Water treatment device 76 Cooling water flow path 78 Hot water supply pipe 134, 334 CO oxide layer CGS Domestic fuel cell cogeneration system CP01 Capraly tube HEX01, HEX02 HEX03, HEX04, HEX05 heat exchanger

Claims (5)

An electrolyte layer; a first electrode provided on one surface of the electrolyte layer; and a second electrode provided on the other surface, wherein the first electrode contains carbon monoxide. In a fuel cell in which a reaction fluid is supplied and a second reaction fluid is supplied to the second electrode,
The first electrode is
A catalytic layer having a catalytic action;
A carbon monoxide removal layer that removes carbon monoxide from the first reaction fluid supplied to the catalyst layer;
A fuel cell comprising: A first reaction fluid comprising: an electrolyte layer; a first electrode provided on one surface of the electrolyte layer; and a second electrode provided on the other surface, wherein the first electrode includes oxygen. And a second reaction fluid is supplied to the second electrode.
The first electrode is
A catalytic layer having a catalytic action;
An oxygen removal layer for removing oxygen from the first reaction fluid supplied to the catalyst layer;
A fuel cell comprising: The fuel cell according to claim 1 or 2,
The fuel cell, wherein the carbon monoxide removal layer or the oxygen removal layer includes a catalyst supported on highly graphitized carbon. The fuel cell according to any one of claims 1 to 3,
The fuel cell according to claim 1, wherein the carbon monoxide removal layer or the oxygen removal layer is a diffusion layer that diffuses the first reaction fluid supplied to the catalyst layer. A fuel cell according to any one of claims 1 to 4,
Hydrogen supply means for supplying hydrogen to the first electrode;
Oxygen supply means for supplying oxygen to the first electrode;
Oxygen supply means for supplying oxygen to the second electrode;
A fuel cell system comprising:

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