JP2005135647A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell enabled to greatly reduce crossover even with the use of organic fuel such as methanol, and therefore capable of augmenting discharge capacity without taking heed of the crossover even with the use of high-density organic fuel. <P>SOLUTION: A solid electrolyte film 1 is a single-layer film, at a part of which, in this case at a center part, a region with a lower transmission factor of the organic fuel (in this case, methanol) than at peripheral parts is formed, that is, with the center part as a low-transmission-factor region 21 and the peripheral parts as a high-transmission-factor region 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell that uses an organic fuel, and more particularly to a fuel cell that does not have an auxiliary device that controls the temperature of a power generation part by using an external power source or power generated by self-power generation.

  In recent years, portable devices such as notebook PCs, PDAs, and mobile phones have become more sophisticated and multifunctional, so that conventional Ni-Cd batteries and nickel metal hydride batteries can be made lighter, smaller, and operated longer. Instead of these, lithium ion secondary batteries having a high energy density have been widely adopted. In addition, due to the recent enhancement of information communication functions of mobile devices and the increase in operation time due to the spread of advanced information communication networks, there is a strong demand for batteries to have higher capacities.

  However, in the lithium ion secondary batteries currently used, the performance improvement is almost the limit in terms of material and structure, and it is difficult to cope with the increase in capacity. Therefore, as a new high-capacity drive power source, attention is focused on a fuel cell that is expected to have a capacity several times higher than that of a lithium ion battery. This fuel cell is classified into a phosphoric acid type, a solid electrolyte type, a molten carbonate type, a polymer solid electrolyte type, etc., but for a portable small fuel cell, a polymer solid electrolyte type capable of operating near room temperature. A fuel cell is suitable.

  In particular, in this polymer solid oxide fuel cell, energy density was improved by supplying methanol aqueous solution or the like as organic fuel directly on the electrode without supplying hydrogen reformed from organic fuel as fuel. A so-called direct methanol fuel cell is suitable for light weight and small size. In this direct methanol type system, protons and carbon dioxide are generated from organic fuel by a catalyst on the negative electrode (fuel electrode: anode), and the protons permeate through the polymer solid electrolyte membrane to combine with oxygen to generate water. . At this time, electric power can be taken out by connecting the negative electrode and the positive electrode (air electrode: cathode) to an external circuit. The water produced at the positive electrode is discharged out of the system or recovered and supplied to the negative electrode, and discharged from the positive electrode surface.

JP-A-11-259592 JP 2001-185162 A

  However, in the case of the direct methanol type method, in addition to the large overvoltage of the oxidation reaction of methanol, which is an organic fuel, a phenomenon called crossover in which methanol permeates from the negative electrode side to the positive electrode side occurs, which reduces the positive electrode potential. As a result, there is a problem that the output is greatly deteriorated as compared with the hydrogen fuel cell. For this reason, in order to obtain sufficient output in the direct methanol method, in order to reduce the crossover of methanol and minimize the decrease in the positive electrode potential due to the oxidation reaction of the permeated methanol, excessive heat generation, and fuel loss, Fuel is supplied at a methanol concentration of several vol%.

  However, in applications with large volume restrictions such as those for portable devices, it is difficult to ensure a sufficient energy density when such a methanol dilute aqueous solution is used as a fuel. Also, attempts have been made to increase energy density by diluting pure methanol or high-concentration methanol fuel with water and supplying it to the power generation unit, collecting the water produced on the positive electrode side, and using it for the reaction on the negative electrode side. However, it is necessary to use an auxiliary machine for diluting fuel and collecting water, and as a result, the total amount of fuel cannot be increased, and it is necessary to supply a part of the generated power to the auxiliary machine. It is difficult to improve the size and reduce the size.

  The present invention has been made in view of the above problems, and even when an organic fuel such as methanol is used, it is possible to greatly reduce the crossover. Therefore, even when a high concentration organic fuel is used, the crossover is prevented. It is an object of the present invention to provide a fuel cell that can increase the discharge capacity without causing problems.

  The fuel cell of the present invention includes a battery cell including an electrolyte membrane, a negative electrode catalyst layer that oxidizes fuel, and a positive electrode catalyst layer that reduces oxygen, and supplies the fuel to the negative electrode catalyst layer and the positive electrode catalyst layer. In the fuel cell in which the oxidant gas is supplied to generate electricity, the electrolyte membrane has a change in the fuel permeability in the plane thereof.

  The fuel cell of the present invention includes a battery cell including an electrolyte membrane, a negative electrode catalyst layer that oxidizes fuel, and a positive electrode catalyst layer that reduces oxygen, and supplies the fuel to the negative electrode catalyst layer and the positive electrode catalyst layer. The positive electrode catalyst layer contains a mixture of carbon carrying a catalyst and carbon not carrying a catalyst.

  According to the present invention, even when an organic fuel such as methanol is used, it is possible to greatly reduce the crossover. Therefore, even if a high concentration organic fuel is used, the discharge capacity is increased without considering the crossover as a problem. The fuel cell which can be made to realize is realized.

  Hereinafter, specific embodiments to which the present invention is applied will be described.

(First embodiment)
In the fuel cell for supplying an organic fuel to the fuel electrode, the inventor separately arranges a methanol oxidation reaction site for supplying heat necessary for maintaining the electrode activity of the power generation unit and a positive electrode catalyst layer for reducing oxygen. Thus, it has been found that high output and high capacity can be achieved. In this case, desired characteristics can be obtained by setting the fuel permeability of the solid electrolyte membrane in contact with the positive electrode catalyst layer to be smaller than the solid electrolyte membrane at the methanol oxidation reaction site where heat is supplied.

Details of this embodiment will be described below.
FIG. 1 is a schematic cross-sectional view showing a configuration of a fuel cell according to the present embodiment, FIG. 2 is a schematic diagram of a fuel cell having the fuel cell, and FIG. 2 is a perspective view schematically showing the principle configuration of FIG.

  The fuel cell 10 is disposed so as to sandwich the solid electrolyte membrane 1 having proton conductivity, a negative electrode catalyst layer (anode electrode catalyst layer) 2 that oxidizes the fuel, and the negative electrode catalyst layer 2 together with the solid electrolyte membrane 1. , A positive electrode catalyst layer (cathode electrode catalyst layer) 3 for reducing oxygen, a carbon paper 4 disposed on the negative electrode catalyst layer 2 and serving as a diffusion layer, and a carbon paper disposed on the positive electrode catalyst layer 3 and serving as a diffusion layer 5, a negative electrode current collector layer (not shown) arranged on the carbon paper 4, and a positive electrode current collector layer (not shown) arranged on the carbon paper 5.

  In the fuel cell, the fuel cell 10 is arranged in the cell housing 8 together with the fuel tank 13 having the fuel inlet 12, the negative electrode terminal 9 on the negative electrode (anode) side, and the positive electrode terminal on the positive electrode (cathode) side. 11 are provided.

The solid electrolyte membrane 1 is a single-layer membrane, and a part of the solid electrolyte membrane 1 here, in which a region having a low organic fuel permeability is formed in the central portion compared to the peripheral portion that is the other portion, that is, the central portion has a low permeability. The rate region 21 and its peripheral part are configured as a high transmittance region 22.
The high transmittance region 22 is composed of, for example, a proton conductive solid electrolyte having high methanol permeability such as perfluoroalkylsulfonic acid represented by the product name Nafion manufactured by DuPont. On the other hand, the low transmittance region 21 is configured, for example, by impregnating the above-mentioned Nafion or the like with a reactive compound such as an acrylic monomer and polymerizing it in the film to reduce the transmittance of methanol. The low transmittance region 21 or this reactive compound is irradiated with heat treatment (heat curing treatment), light, etc., for example, ultraviolet rays, radiation, electron beams, etc. The surface structure may be altered to a state with low transmittance.

  Alternatively, the film may be mixed with a polymer such as polyvinylidene fluoride to reduce the methanol permeability, and may be joined to a high permeability electrolyte membrane such as Nafion. However, in general, the permeability of methanol is suppressed and the proton conductivity is lowered at the same time. Therefore, it is necessary to perform the treatment to such an extent that the necessary proton conductivity is ensured at the temperature during cell operation.

  The shape and arrangement of the films having different transmittances may be combined in any shape and arrangement as long as the effects of the present invention are not impaired. Furthermore, the high permeability region 22 of the membrane used for the solid electrolyte membrane 1 only needs to be methanol permeable and does not necessarily have proton conductivity.

  In this embodiment, the low-permeability region 21 corresponding to the power generation site is fuel oxidation in the high-permeability region 22 regardless of the air electrode potential, despite the low methanol permeability of the electrolyte and a small amount of self-heating. Since it is heated by the heat generation based on and can be kept at a high temperature, high output can be expressed. Further, if necessary, an insulating material is provided between the negative electrode catalyst layer 3 in contact with the high transmittance region 22 and the negative electrode catalyst layer 3 in contact with the low transmittance region 21 as indicated by a broken line in FIG. It is also possible to electrically separate them by using the same method.

Here, the negative electrode catalyst layer 2 is produced as follows.
First, a catalyst fine particle in which a Pt-Ru catalyst having a particle size of about 2 nm to 5 nm is supported on a conductive material such as ketjen black, furnace black, or carbon black, and a combination of proton conductivity and a catalyst particle binder. An electrode paste is prepared by dispersing and defoaming a proton conductive polymer such as fluoroalkylsulfonic acid in a water-alcohol mixed solvent. Then, the catalyst paste is applied to a Teflon (R) sheet substrate and dried to form a catalyst layer, which is transferred to the solid electrolyte membrane 1 by hot pressing or the like to form the negative electrode catalyst layer 2.

  The positive electrode catalyst layer 3 is produced in the same manner as the negative electrode catalyst layer 2 using carbon black carrying Pt fine particles having a particle diameter of about 2 nm to 5 nm as in the negative electrode catalyst layer 2.

  Thus, in the fuel cell of the present embodiment, a so-called MEA (Membrane Electrode Assembly) structure in which the solid electrolyte membrane 1 is hot pressed by the positive electrode catalyst layer 3 and the negative electrode catalyst layer 2 is formed. Similarly, carbon paper 4 and 5 are joined together by hot pressing, and sandwiched between both current collector layers, thereby forming a fuel cell 10 serving as a power generation unit. After the current collector lead is taken out from the fuel cell 10, the fuel cell 10 is packed with a negative electrode exterior material and a positive electrode exterior material including a fuel tank. Electric power generation is started by supplying a methanol aqueous solution fuel to the negative electrode thus packed and an oxidizing gas containing oxygen to the positive electrode and connecting both current collector layers to an external circuit.

  As described above, according to the fuel cell of the present embodiment, the solid electrolyte membrane 1 including the low transmittance region 21 and the high transmittance region 22 having different transmittances of the aqueous methanol solution that is an organic fuel is disposed in the plane. By adopting a configuration, it is possible to suppress a decrease in the air electrode output by performing functional separation such that the low transmittance region 21 performs power generation and the high transmittance region 22 performs heating and high temperature holding of the power generation unit. The fuel concentration can be increased and the capacity can be increased. That is, even when an organic fuel such as methanol is used, the crossover can be greatly reduced. Therefore, even when a high concentration organic fuel is used, the discharge capacity can be increased without considering the crossover as a problem. A fuel cell is realized.

-Modification-
Here, various modifications of the first embodiment will be described. In these modified examples, a fuel cell having a solid electrolyte membrane composed of a low transmittance region and a high transmittance region is disclosed as in the first embodiment, but is different in that the structure of the solid electrolyte membrane is different.

(Modification 1)
In this modification, as shown in FIG. 4 (a), the solid electrolyte membrane 31 is a single-layer membrane, and a part thereof, in this case, a region having a lower transmittance than the peripheral portion which is the other portion in the central portion. In other words, the central part is configured as a low transmittance region 23 and the peripheral part thereof is configured as a high transmittance region 22. As shown in FIG. 4B, the low transmittance region 23 is formed from one surface of the solid electrolyte membrane 31 to the middle in the thickness direction, and the low permeability is mainly transmitted through the positive electrode catalyst layer 3 that is responsible for power generation. The negative electrode catalyst layer 2 is disposed on the high transmittance region 22 on the rate region 23.

  With this structure, the low-permeability region 23 corresponding to the power generation site is capable of oxidizing the fuel in the high-permeability region 22 regardless of the air electrode potential, despite the low methanol permeability of the electrolyte and the small amount of self-heating. Since it is heated by the exothermic heat and can be kept at a high temperature, high output can be expressed. If necessary, the negative electrode catalyst layer 3 in contact with the high transmittance region 22 and the negative electrode catalyst layer 3 in contact with the low transmittance region 23 can be electrically separated.

  According to the fuel cell of the modified example 1, the solid electrolyte membrane 1 composed of the low transmittance region 23 and the high transmittance region 22 having different transmittances of the aqueous methanol solution that is an organic fuel is disposed in the plane. By performing functional separation such that the low transmittance region 23 performs power generation and the high transmittance region 22 performs heating and high temperature holding of the power generation unit, it is possible to suppress a decrease in the output of the air electrode and to increase the fuel concentration. The capacity can be increased. That is, even when an organic fuel such as methanol is used, the crossover can be greatly reduced. Therefore, even when a high concentration organic fuel is used, the discharge capacity can be increased without considering the crossover as a problem. A fuel cell is realized.

(Modification 2)
In this modified example, as shown in FIG. 5A, the solid electrolyte membrane 32 is composed of two types of electrolyte layers 41 and 42 having different transmittances, and as shown in FIG. An electrolyte layer 41 having a smaller occupied area than the electrolyte layer 42 is laminated on the center of the substrate. Here, the electrolyte layer 41 is a low-permeability region of organic fuel, and the electrolyte layer 42 is a high-permeability region. The positive electrode catalyst layer 3 mainly responsible for power generation is disposed on the electrolyte layer 41, and the negative electrode catalyst layer 2 is disposed. The structure is arranged on the electrolyte layer 42.

  As described above, the electrolyte membrane 41 corresponding to the power generation site has the methanol permeability of the electrolyte by configuring the solid electrolyte membrane 32 so that the electrolyte membranes 41 and 42 having different methanol transmittances are laminated in the same plane. In spite of the low self-heating amount, regardless of the air electrode potential, it is heated by the heat generation based on the fuel oxidation in the electrolyte layer 42 and can be maintained at a high temperature, so that a high output can be expressed. If necessary, the negative electrode catalyst layer 3 in contact with the electrolyte layer 42 and the negative electrode catalyst layer 3 in contact with the electrolyte layer 41 can be electrically separated.

  As described above, according to the fuel cell of this modification, by disposing the solid electrolyte membrane 32 in which the electrolyte layers 41 and 42 having different transmittances of the methanol aqueous solution that is an organic fuel are laminated in the plane, By performing functional separation such that the electrolyte layer 41 performs power generation and the electrolyte layer 42 heats and maintains a high temperature of the power generation unit, it is possible to suppress a decrease in the air electrode output and to increase the fuel concentration. High capacity is achieved. That is, even when an organic fuel such as methanol is used, the crossover can be greatly reduced. Therefore, even when a high concentration organic fuel is used, the discharge capacity can be increased without considering the crossover as a problem. A fuel cell is realized.

(Example)
Here, an example based on the above-described first embodiment will be described.
The product name Nafion 117 (manufactured by DuPont) having a shape of 5 cm × 5 cm (not including 1 cm around the packing portion) was used as the solid electrolyte membrane having high methanol permeability. The central part of this solid electrolyte membrane is impregnated with 2 μl / cm ² of 10% polyoxyethylene diacrylate at a portion of about 3.5 cm × 3.5 cm shape, and irradiated with ultraviolet light having an intensity of 50 mJ / cm ^2. A low transmittance region in which the methanol transmittance was reduced to 1/3 of the peripheral portion (high transmittance region) was formed.

  Each electrode catalyst layer was produced as follows. First, 2 g of catalyst particles in which about 50% of a Pt catalyst having a particle size of about 2 nm to 5 nm is supported on Ketjen Black (product name Ketjen Black EC manufactured by Lion), 4.8 g of a solution of Nafion (manufactured by DuPont), 7 g of water and 10 g of propanol were mixed with a ball mill and defoamed to obtain a paste. This was applied to a Teflon (R) sheet, dried at 80 ° C. for 30 minutes, and the above-described Nafion solid electrolyte membrane having portions with different transmittances was hot-pressed at 160 ° C. for 2 minutes to form a positive electrode catalyst layer.

  Similarly, for the negative electrode catalyst layer, an alloy catalyst of Pt (platinum) -Ru (ruthenium) having a particle diameter of 2 nm to 5 nm and a molar ratio of 1: 1 is added to Ketjen Black (product name Ketjen Black EC manufactured by Lion). 2 g of 50% supported catalyst particles, 4.8 g of Nafion (DuPont) solution, 7 g of water and 10 g of propanol were mixed with a ball mill and defoamed to obtain a paste. Similarly, this was applied to a Teflon (R) sheet, dried at 80 ° C. for 30 minutes, and the above-mentioned Nafion solid electrolyte membrane having a portion with different transmittance was hot-pressed at 160 ° C. for 2 minutes to form a negative electrode catalyst layer. Thus, an MEA was produced.

  Subsequently, carbon paper (product name TGP-H-090, 290 μm manufactured by Toray Industries, Inc.) was pressure-bonded by hot pressing on both sides of the MEA to produce a power generation unit. After the current collector leads were taken out from both electrodes of the produced power generation unit, the power generation unit was packed with a fuel electrode exterior material and an air electrode exterior material including a fuel tank. The fuel tank of the manufactured fuel cell was filled with a 20 vol% aqueous solution of methanol and connected to an external load to generate power. Here, it is preferable that the methanol aqueous solution has a concentration of 10 vol%.

(Comparative example)
Here, the comparative example of a present Example is demonstrated.
The product name Nafion 117 (manufactured by DuPont) having a shape of 5 cm × 5 cm (not including 1 cm around the packing portion) was used as the solid electrolyte membrane having high methanol permeability.

  Each electrode catalyst layer was produced as follows. First, 2 g of catalyst particles in which about 50% of a Pt catalyst having a particle size of about 2 nm to 5 nm is supported on Ketjen Black (product name Ketjen Black EC manufactured by Lion), 4.8 g of a solution of Nafion (manufactured by DuPont), 7 g of water and 10 g of propanol were mixed with a ball mill and defoamed to obtain a paste. This was applied to a Teflon (R) sheet, dried at 80 ° C. for 30 minutes, and the above-described Nafion solid electrolyte membrane having portions with different transmittances was hot-pressed at 160 ° C. for 2 minutes to form a positive electrode catalyst layer.

  Similarly, the negative electrode catalyst layer is a catalyst in which about 50% of a Pt—Ru (molar ratio is 1: 1) alloy catalyst having a particle diameter of 2 nm to 5 nm is supported on Ketjen Black (product name Ketjen Black EC manufactured by Lion). 2 g of particles, 4.8 g of Nafion (manufactured by DuPont), 7 g of water, and 10 g of propanol were mixed with a ball mill and defoamed to obtain a paste. Similarly, this was applied to a Teflon (R) sheet, dried at 80 ° C. for 30 minutes, and the above-mentioned Nafion solid electrolyte membrane having a portion with different transmittance was hot-pressed at 160 ° C. for 2 minutes to form a negative electrode catalyst layer. Thus, an MEA was produced.

  Subsequently, carbon paper (product name TGP-H-090, 290 μm manufactured by Toray Industries, Inc.) was pressure-bonded by hot pressing on both sides of the MEA to produce a power generation unit. After the current collector leads were taken out from both electrodes of the produced power generation unit, the power generation unit was packed with a fuel electrode exterior material and an air electrode exterior material including a fuel tank. The fuel tank of the manufactured fuel cell was filled with a 20 vol% aqueous solution of methanol and connected to an external load to generate power.

  FIG. 6 shows the transition of the continuous discharge characteristics and the temperature in the fuel tank of this example and the comparative example. As is clear from FIG. 6, the region having different permeability is arranged in the solid electrolyte membrane as in this embodiment, and the fuel concentration is increased to about 20 vol%, so that the output is higher than that of the conventional method of the comparative example. It can be seen that both capacity and capacity are improved.

(Second Embodiment)
In a fuel cell, it is considered effective to use a high-concentration aqueous methanol solution to increase the capacity. However, in practice, methanol flowing out to the positive electrode due to crossover undergoes an oxidation reaction, thereby generating heat. The generated heat increases the fuel temperature, and as a result, crossover is promoted. That is, the discharge capacity is reduced by using a high-concentration aqueous methanol solution.

  In a fuel cell, a platinum catalyst having a strong oxygen reducing ability is generally used for the positive electrode catalyst layer. However, when a platinum catalyst is used, the oxidation reaction of crossover methanol tends to occur simultaneously. The present inventor paid attention to this fact, and in order to relatively reduce the catalyst in the positive electrode catalyst layer, came up with the idea of forming a positive electrode catalyst layer by mixing carbon carrying a catalyst with carbon not carrying a catalyst. . As a result, even when a high-concentration aqueous methanol solution is used, it is possible to suppress a temperature rise and ensure a sufficient discharge capacity.

Details of this embodiment will be described below.
FIG. 7 is a schematic cross-sectional view showing the principle configuration of (the main part of) the fuel battery cell according to the present embodiment.
The fuel battery cell is disposed so as to sandwich a solid electrolyte membrane 51 having proton conductivity, a negative electrode catalyst layer (anode electrode catalyst layer) 52 for oxidizing fuel, and the negative electrode catalyst layer 2 together with the solid electrolyte membrane 51. , A positive electrode catalyst layer (cathode electrode catalyst layer) 52 for reducing oxygen, a carbon paper 4 disposed on the negative electrode catalyst layer 2 and serving as a diffusion layer, and a carbon paper disposed on the positive electrode catalyst layer 52 and serving as a diffusion layer. 5, a negative electrode current collector layer 6 disposed on the carbon paper 4, and a positive electrode current collector layer 7 disposed on the carbon paper 5.

  The negative electrode catalyst layer 2 is composed of catalyst fine particles, carbon powder, and a polymer that forms an electrolyte layer, and is formed by a transfer method or the like. The negative electrode current collector layer 6 is made of a metal mesh such as SUS. The positive electrode generates water from ions generated by reducing oxygen and electrons and protons generated at the negative electrode. As described above, from the solid electrolyte layer 51 side, the positive electrode catalyst layer 52, carbon paper 5, positive electrode collection. The electrical conductor layers 7 are stacked in this order. The positive electrode catalyst layer 52 is composed of catalyst fine particles, carbon powder, and a polymer that forms an electrolyte layer. The positive electrode catalyst layer 52 is formed by a transfer method or the like, and is a mixture of carbon carrying a catalyst and carbon not carrying a catalyst. It is made. The positive electrode current collector layer 7 is made of a metal mesh such as SUS.

  The solid electrolyte layer 51 constitutes a path for transporting protons generated on the negative electrode side to the positive electrode side, and is formed of an ionic conductor having no electronic conductivity. For example, a polyperfluorosulfonic acid resin film, specifically, a product name Nafion manufactured by DuPont.

  A fuel tank is formed on the negative electrode surface not facing the solid electrolyte layer 51, and the fuel is supplied to the negative electrode through the fuel introduction path by natural movement such as flow and diffusion. Further, the positive electrode surface that does not face the solid electrolyte layer 51 is released in the form of a gap so that outside air can be introduced by natural diffusion.

  As described above, according to the fuel cell of the present embodiment, the cathode catalyst layer 53 is configured by mixing the catalyst-supporting carbon and the carbon not supporting the catalyst, thereby suppressing the temperature rise and crossover. Can be reduced. Accordingly, a high concentration aqueous methanol solution can be used, and a significant increase in discharge capacity is realized.

(Example)
Here, an example based on the second embodiment will be described.
Based on the structure shown above, a fuel cell was fabricated as follows.
Carbon in which Pt—Ru is supported is used for the negative electrode catalyst layer, and carbon (50 wt%) in which Pt is supported and carbon without catalyst are mixed in a weight ratio of 1: 0.5 in the positive electrode catalyst layer. Was used. The product name Nafion 117 (manufactured by DuPont) was used for the solid electrolyte membrane, and 3.0 cc of each of 10, 20, and 30 vol% methanol aqueous solutions were used for the organic fuel.

(Comparative example)
As a comparative example of this example, a fuel cell was manufactured as follows.
Carbon carrying Pt—Ru was used for the negative electrode catalyst layer, and carbon carrying Pt (50 wt%) was used for the positive electrode catalyst layer. Further, the product name Nafion 117 (manufactured by DuPont) was used for the solid electrolyte membrane, and 3.0 cc each of 10, 20, and 30 vol% methanol aqueous solutions were used for the organic fuel.

As a test condition for the discharge capacity, a continuous discharge of 300 mA was performed, and the voltage value and fuel temperature at that time were measured.
The evaluation results of the voltage value and the fuel temperature are shown in FIGS. FIG. 8 corresponds to the comparative example, and FIG. 9 corresponds to the present embodiment.
When the methanol aqueous solution concentration is 10 vol%, the discharge capacities are both about 90 to 100 minutes and there is no big difference. In the case of 20 vol%, due to the temperature rise, in the comparative example there is almost no change in the discharge capacity of about 100 minutes, whereas in this example the discharge capacity is greatly increased to over 130 minutes. Further, at 30 vol%, since the temperature rises drastically, both discharge capacities are reduced. Therefore, it can be seen that long-term discharge capacity can be secured by using a methanol aqueous solution of less than 10-30 vol%, preferably around 20 vol%, as the organic fuel in the configuration of this example.

  The present invention is not limited to the first and second embodiments described above. For example, the configuration adopting both embodiments, that is, the solid electrolyte membrane is formed so that the central portion is a low-permeability region of organic fuel and the peripheral portion is a high-permeability region, and the positive electrode catalyst layer carries a catalyst. It is also preferable to adopt a configuration in which the carbon is made of a material in which carbon that does not carry a catalyst is mixed.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1) an electrolyte membrane;
A negative electrode catalyst layer that oxidizes the fuel;
A battery cell including a positive electrode catalyst layer for reducing oxygen,
A fuel cell for supplying power to the negative electrode catalyst layer and generating power by supplying an oxidant gas to the positive electrode catalyst layer;
The fuel membrane, wherein the electrolyte membrane has a change in the transmittance of the fuel in a plane thereof.

  (Supplementary note 2) The fuel cell according to claim 1, wherein a region of the electrolyte membrane having a lower fuel permeability than other portions is formed in a part thereof.

  (Supplementary Note 3) The electrolyte membrane is formed by laminating and arranging at least two types of electrolyte layers having different fuel transmittances in the same plane, and the electrolyte layer having a low transmittance has a high portion of the electrolyte layer. The fuel cell according to claim 1, wherein the electrolyte layer having a transmittance constitutes the other part.

  (Supplementary note 4) The low-permeability electrolyte layer is disposed on the positive electrode catalyst layer side, and the high-permeability electrolyte layer is disposed on the negative electrode catalyst layer side. The fuel cell as described.

  (Supplementary note 5) The fuel cell according to claim 1 or 2, wherein the electrolyte membrane has a surface structure altered to a state in which the part has a lower fuel permeability than the other part.

  (Appendix 6) The fuel cell according to claim 5, wherein the electrolyte membrane is formed such that the part of the fuel having a low transmittance is formed from one surface of the electrolyte membrane to the middle in the thickness direction. .

  (Additional remark 7) The said electrolyte membrane changes in the state of the said low transmittance | permeability by irradiating the heat treatment, the ultraviolet-ray, a radiation, or an electron beam to the reactive compound impregnated in the said part. Item 7. The fuel cell according to Item 6.

  (Supplementary Note 8) The low fuel permeability is arranged so that the part of the fuel having a low transmittance is on the positive electrode catalyst layer side and the other part having the high fuel permeability is on the negative electrode catalyst layer side. The fuel cell according to claim 6 or 7.

(Supplementary note 9) an electrolyte membrane;
A negative electrode catalyst layer that oxidizes the fuel;
A battery cell including a positive electrode catalyst layer for reducing oxygen,
A fuel cell for supplying power to the negative electrode catalyst layer and generating power by supplying an oxidant gas to the positive electrode catalyst layer;
The positive electrode catalyst layer comprises a mixture of carbon carrying a catalyst and carbon not carrying a catalyst.

  (Supplementary note 10) The fuel cell according to claim 9, wherein a region of the electrolyte membrane having a lower fuel permeability than the other portion is formed in a part thereof.

  (Supplementary Note 11) The electrolyte membrane is formed by laminating and arranging at least two types of electrolyte layers having different fuel transmittances in the same plane, and the electrolyte layer having a low transmittance has the high part. The fuel cell according to claim 10, wherein the electrolyte layer having a transmittance constitutes the other part.

  (Supplementary Note 12) The electrolyte membrane is arranged such that the electrolyte layer with low transmittance is on the positive electrode catalyst layer side and the electrolyte layer with high transmittance is on the negative electrode catalyst layer side. The fuel cell according to claim 11.

  (Supplementary note 13) The fuel cell according to claim 10, wherein the electrolyte membrane has a surface structure altered to a state in which the part has a lower permeability of the fuel than the other part.

  (Additional remark 14) The said electrolyte membrane changes in the state of the said low transmittance | permeability by irradiating the reactive compound impregnated in the said part with heat processing, an ultraviolet-ray, a radiation, or an electron beam, It is characterized by the above-mentioned. Item 14. The fuel cell according to Item 13.

  (Additional remark 15) The said catalyst is platinum or its alloy, The fuel cell of any one of Claims 1-14 characterized by the above-mentioned.

  (Supplementary note 16) The fuel cell according to any one of claims 1 to 15, wherein the carbon is ketjen black.

  (Supplementary note 17) The fuel cell according to any one of claims 1 to 16, wherein the fuel is an aqueous methanol solution.

It is a schematic sectional drawing which shows the structure of the fuel battery cell by 1st Embodiment. It is a perspective view showing typically a fuel cell which has a fuel cell. It is a perspective view which shows typically the principle structure of the fuel battery cell by 1st Embodiment (the main part). It is a schematic diagram which shows the modification 1 of the fuel battery cell by 1st Embodiment (the main part). It is a schematic diagram which shows the modification 2 of the fuel battery cell by 1st Embodiment (the main part). It is a characteristic view which shows transition of the continuous discharge characteristic and fuel tank temperature of the Example and comparative example of 1st Embodiment. It is a schematic sectional drawing which shows the principle structure of the fuel cell by 2nd Embodiment. It is a characteristic view which shows the evaluation result of the voltage value and fuel temperature in the comparative example of 2nd Embodiment. It is a characteristic view which shows the evaluation result of the voltage value and fuel temperature in the Example of 2nd Embodiment.

Explanation of symbols

1, 31, 32, 51 Solid electrolyte membrane 2 Negative electrode catalyst layer (anode electrode catalyst layer)
3,52 Cathode catalyst layer (cathode electrode catalyst layer)
4 Carbon paper on the negative electrode catalyst layer side 5 Carbon paper on the positive electrode catalyst layer side 6 Negative electrode current collector layer 7 Positive electrode current collector layer 8 Cell housing 9 Negative electrode terminal 10 Fuel cell 11 Positive electrode terminals 21 and 23 Low transmittance region 22 High transmittance region 41, 42 Electrolyte layer

Claims (5)

An electrolyte membrane;
A negative electrode catalyst layer that oxidizes the fuel;
A battery cell including a positive electrode catalyst layer for reducing oxygen,
A fuel cell for supplying power to the negative electrode catalyst layer and generating power by supplying an oxidant gas to the positive electrode catalyst layer;
The fuel membrane, wherein the electrolyte membrane has a change in the transmittance of the fuel in a plane thereof.   2. The fuel cell according to claim 1, wherein a region of the electrolyte membrane having a lower fuel permeability than the other portion is formed in a part thereof.   The electrolyte membrane is formed by laminating and arranging at least two types of electrolyte layers having different fuel transmittances in the same plane, the electrolyte layer having a low transmittance having the portion having the high transmittance. The fuel cell according to claim 2, wherein an electrolyte layer constitutes each of the other portions.   3. The fuel cell according to claim 1, wherein a part of the electrolyte membrane is modified in a surface structure so that the fuel permeability is lower than that of the other part. An electrolyte membrane;
A negative electrode catalyst layer that oxidizes the fuel;
A battery cell including a positive electrode catalyst layer for reducing oxygen,
A fuel cell for supplying power to the negative electrode catalyst layer and generating power by supplying an oxidant gas to the positive electrode catalyst layer;
The positive electrode catalyst layer comprises a mixture of carbon carrying a catalyst and carbon not carrying a catalyst.

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