JP2008171674A - Fuel cell - Google Patents

Abstract

An object of the present invention is to provide a fuel cell having a high output even if it is small by increasing the reaction efficiency of the fuel and the discharge efficiency of the reaction product at the fuel electrode.
A flow path plate (6) is provided that forms a first flow path (13) for supplying liquid fuel to a fuel electrode and a second flow path (15) for discharging exhaust gas from the fuel electrode. And the fuel electrode has an electrode layer containing a catalyst on the electrolyte membrane side and a diffusion layer on the channel plate side, and A permeation suppression layer 51 that suppresses the supply of liquid fuel from the first flow path to the diffusion layer, and the permeation suppression layer has a through hole 52 or a through groove in the thickness direction, and the through hole or the through hole The above problem is solved by a fuel cell in which a conductor is disposed in the groove.
[Selection] Figure 2

Description

  The present invention relates to a fuel cell using liquid fuel, and more particularly to a fuel cell suitable for miniaturization that can be incorporated in a small electronic device such as a mobile phone.

  A fuel cell is a power generator that generates power when fuel and an oxidant are supplied. Usually, air can be used as the oxidizer, so that power can be generated continuously by supplying fuel. For this reason, fuel cells are attracting a great deal of attention not only as stationary power sources but also as portable power sources.

Usually, in a stationary fuel cell or the like, hydrogen or a gas containing hydrogen is used as a fuel. However, as a portable power source, it is advantageous to be able to generate power for a long time with fuel stored in a container of the same size, so it is advantageous to use liquid fuel with high energy density per volume as the fuel. Become.
Although hydrogen can be generated from liquid fuel using a reformer and used for power generation, the entire fuel cell system becomes complicated, so liquid fuel is supplied directly to reduce the size of the fuel cell. It is considered easier to do.

  A fuel cell of a type that directly supplies liquid fuel to the fuel electrode is disclosed in Patent Document 1 (Japanese Patent Publication No. 11-510311). This fuel cell is a direct methanol fuel cell that uses a mixture of methanol and water as fuel.

A typical direct methanol fuel cell will be described with reference to FIG.
FIG. 8 is a diagram schematically showing a direct methanol fuel cell 101 provided with a fuel electrode 104, an oxidant electrode 106, and an electrolyte membrane 108 in a housing 102. A fuel in which methanol and water are mixed is supplied from the fuel tank 109 to the anode chamber 112 by the fuel pump 110. The fuel supplied into the fuel electrode chamber 112 permeates into the fuel electrode 104 and reacts to generate protons (hydrogen ions), electrons, and carbon dioxide.

Usually, a porous material is used for the fuel electrode 104, and a reaction at the fuel electrode 104 occurs in a layer on which a catalyst is supported in the vicinity of the interface with the electrolyte membrane. Protons generated at the fuel electrode 104 pass through the electrolyte membrane 108 and move to the oxidant electrode 106, and electrons flow from the fuel electrode 104 to the oxidant electrode 106 via an external circuit (not shown). These electrons are used as the output of the fuel cell.
Carbon dioxide is discharged from the fuel electrode 104 to the fuel electrode chamber 112 and discharged from the outlet port 121 together with unreacted fuel. The carbon dioxide discharged from the outlet port 121 and unreacted fuel are collected in the fuel tank 109, and the carbon dioxide is discharged from a discharge port 114 provided in the fuel tank 109.

  On the other hand, on the oxidant electrode 106 side, oxygen is supplied to the oxidant electrode chamber 118 by the oxygen compressor 116, and this oxygen diffuses from the oxidant electrode chamber 118 into the oxidant electrode 106. In the oxidant electrode 106, oxygen reacts with protons diffused from the fuel electrode 104 to generate water. The generated water is normally converted into water vapor and discharged from the oxidizer electrode chamber 118 through the outlet port 120 together with unreacted oxygen. In the example shown in FIG. 8, oxygen is used as the oxidizing agent. In addition, although oxygen concentration becomes low, air can also be used as an oxidizing agent.

  In the conventional direct methanol fuel cell, a mixture of methanol and water as fuel is supplied to the fuel electrode chamber 112 and penetrates from the fuel electrode chamber 112 to the diffusion layer of the fuel electrode 104 as shown in FIG. It reacts in the layer containing the catalyst in the vicinity of the interface with the membrane 108. Carbon dioxide, which is a reaction product, is discharged into the fuel electrode chamber 112, joins the supplied fuel, and is discharged from the outlet port 121 together with unreacted fuel. In order to perform highly efficient and stable power generation with a fuel cell, it is necessary to efficiently and stably supply fuel and discharge carbon dioxide as a reaction product.

  By the way, the main flow of the fuel supplied by the fuel pump 110 is sent to the fuel electrode chamber 112 and then discharged from the outlet port 121 provided in the fuel electrode chamber 112. For this reason, the flow of fuel in the porous material of the fuel electrode 104 that directly contributes to the reaction of the fuel electrode 104 deviates from the main flow of fuel in the fuel electrode chamber 112. Furthermore, in the porous material of the fuel electrode 104, although the capillary action works, it is difficult to supply the fuel into the fuel electrode 104 efficiently and stably because of restrictions on the shape and direction. This makes it difficult to improve the output as a fuel cell and to generate power with high efficiency for a long time. Further, when a pump that pumps fuel at a high pressure is used, the power supply device is increased in size, so that it is particularly difficult to adopt it as a power source for portable devices and the like.

By the way, in patent document 2 (Unexamined-Japanese-Patent No. 2002-175817), the fuel penetration member which a fuel osmose | permeates is arrange | positioned in the fuel flow path where a fuel is supplied, and the fuel supply to a fuel electrode is promoted.
However, in the fuel cell described in Patent Document 2, the fuel is supplied to the fuel electrode by permeation by the fuel permeation member, so that the reaction efficiency of the fuel at the fuel electrode is insufficient, and the output of the cell is not good. It was enough.
Japanese National Patent Publication No. 11-510311 JP 2002-175817 A

  Accordingly, an object of the present invention is to provide a fuel cell having a high output even if it is small by increasing the reaction efficiency of the fuel at the fuel electrode and the discharge efficiency of the reaction product.

  In order to solve the above-described problems, a fuel cell according to the present invention includes a fuel electrode that generates cations and electrons from a liquid fuel, a fuel electrode that is disposed so as to face the fuel electrode, and a cation generated from the fuel electrode. An electrolyte membrane that can permeate, an oxidant electrode that reacts with the cation and the oxidant that has permeated through the electrolyte membrane, and an anode that faces the fuel electrode. And a flow path plate that forms a first flow path for supplying the liquid fuel to the fuel electrode and a second flow path for discharging exhaust gas from the fuel electrode, and the first flow path. And the second flow path are separated from each other, and the fuel electrode includes an electrode layer containing a catalyst on the electrolyte membrane side and a diffusion layer on the flow path plate side, A permeation suppression layer that suppresses the supply of liquid fuel from the flow path to the diffusion layer. Direction has a through hole or through groove, wherein the conductor is disposed in the through hole or through groove.

  According to the fuel cell of the present invention, a sufficient reaction at the fuel electrode can be realized even when the liquid fuel is supplied to the first flow path at a low pressure. Further, according to the fuel cell of the present invention, the resistance value of the electrical connection between the flow path plate of the fuel electrode and the diffusion layer can be lowered, the loss of the battery output due to the resistance component is reduced, and the net that can be taken out of the battery. Therefore, it is possible to realize a small and high-output fuel cell that can obtain a stable output regardless of the direction in which the fuel cell is installed or held. Therefore, the fuel cell of the present invention is particularly suitable as a power source for small electronic devices such as portable devices that are difficult to install, such as a pump for pumping fuel supply.

  In general, in the case of a small fuel cell for mobile electronic devices, the flow path needs to be made in a very narrow space, so the fuel pressure loss in the flow path is large, and in particular, the fuel can be distributed over the entire flow path. Therefore, it is difficult to produce a stable pressure difference across the entire flow path. However, the fuel cell of the present invention can solve such problems.

In a preferred embodiment of the fuel cell of the present invention, the through hole or the through groove of the permeation suppression layer is a position facing the flow path wall that separates the first flow path and the second flow path. Arranged at least.
According to this embodiment, the through-hole or through-groove has a local fuel permeation rate from the first flow path to the diffusion layer, and a local exhaust gas permeation from the diffusion layer to the second flow path. Since the speed is not affected, uniform fuel supply and discharge of reaction products such as carbon dioxide can be realized throughout the fuel cell.

In a preferred embodiment of the fuel cell of the present invention, the through hole or the through groove is disposed so as to surround at least the periphery of the first flow path.
According to this embodiment, when laminating the power generation cell and the flow path, the joint surface between the flow path wall and the permeation suppression layer around the first flow path is easily and uniformly adhered, and the flow path wall and the permeation suppression layer It is possible to more reliably suppress fuel leakage from the first flow path to the second flow path via the interface. This makes it easy to fill the first flow path with the liquid fuel even when the fuel supply pressure is low, and the second flow path portion is opposed to the first flow path portion with the flow path wall interposed therebetween. A pressure difference caused by a pressure drop in a path through which the fuel flows through the diffusion layer of the fuel electrode can be stably generated across the entire flow path. Therefore, even if a reaction product such as carbon dioxide is generated by the reaction in the fuel electrode, the discharge of carbon dioxide to the first flow path is suppressed and carbon dioxide is efficiently discharged from the second flow path. Thus, the reaction at the fuel electrode (generation of cations and electrons) can be promoted.

Further, a preferred embodiment of the fuel cell of the present invention includes a fuel storage unit that is connected to the first flow path and stores the liquid fuel, and includes the fuel storage section and the first flow path. And a pressure adjusting unit that adjusts the pressure of the liquid fuel supplied from the fuel storage unit to the first flow path.
According to this embodiment, the liquid fuel can be supplied from the first flow path to the fuel electrode at a stable pressure by a pressure adjusting unit such as a pressure adjusting valve, and the battery output from the power generation cell can be reduced with low resistance. Stable output as a fuel cell can be obtained because it can be taken out with reduced output.

In addition, a preferred embodiment of the fuel cell of the present invention includes a third flow path for supplying an oxidant to the oxidant electrode, and a third flow path connected to the third flow path. A fourth channel into which the exhaust gas is introduced, a fifth channel into which the exhaust gas from the second channel connected to the second channel is introduced, and the fourth channel And a gas discharge section connected to the fifth flow path and the fifth flow path for discharging the exhaust gas from the fourth flow path and the exhaust gas from the fifth flow path.
According to this embodiment, since both the gas discharged from the second flow path and the exhaust gas from the oxidizer electrode can be efficiently discharged from the same gas discharge section, the discharge becomes easy.

Hereinafter, specific examples of the fuel cell of the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to these embodiments.
(First embodiment)
FIG. 1 is a plan view showing the configuration of the first embodiment of the fuel cell of the present invention. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1, and FIG. 3 is a cross-sectional view taken along the line BB ′ of FIG.
(1) Configuration of Fuel Cell As shown in FIG. 2, the fuel cell according to this embodiment includes a fuel electrode 1, an electrolyte membrane 2 disposed so as to face the fuel electrode 1, and an opposite side of the fuel electrode 1. An oxidant electrode 3 is provided so as to face the electrolyte membrane 2. The fuel electrode 1, the electrolyte membrane 2, and the oxidizer electrode 3 are accommodated in the housing 5 with the electrolyte membrane 2 sandwiched between the fuel electrode 1 and the oxidizer electrode 3. On one surface 5A of the housing 5, an edge portion 6A of a flow path plate 6 disposed so as to face the fuel electrode 1 is joined and attached.

As shown in FIG. 1, the flow path plate 6 includes a through-hole forming a liquid fuel supply port 7, a through-hole forming an exhaust gas discharge port 8, and a first extending from the supply port 7 in a comb shape. And a second channel groove 11 extending from the discharge port 8 in a comb-tooth shape.
The first channel groove 10 and the second channel groove 11 are separated by a wall 12 having a predetermined thickness. The wall 12 of the flow path plate 6 is in contact with the fuel electrode 1. Therefore, the first flow path 13 formed by the first flow path groove 10 and the fuel electrode 1 and the second flow path 15 formed by the second flow path groove 11 and the fuel electrode 1 are They are separated by a wall 12.

  In the first embodiment, for example, the opening width at which the first flow path 13 opens to the diffusion layer 17 side of the fuel electrode 1 can be set to about 2 μm to 200 μm. Moreover, the opening width which the 2nd flow path 15 opens to the diffusion layer 17 side can be made into the same grade as the opening width of the 1st flow path 13, for example. However, in the present invention, the size of the flow path is not particularly limited to this.

  As shown in FIG. 2, the fuel electrode 1 includes an electrode layer 16 on the electrolyte membrane 2 side and a diffusion layer 17 on the flow path plate 6 side. The fuel electrode 1 further includes a permeation suppression layer 51 sandwiched between the flow path plate 6 and the diffusion layer 17 of the fuel electrode 1.

  As shown in FIG. 4, the permeation suppression layer 51 has a through hole 52 in the thickness direction, and a conductor 53 is disposed in the through hole 52. Thereby, the resistance value of the electrical connection between the flow path plate 6 and the diffusion layer 17 can be lowered, the loss of the battery output due to the resistance component can be reduced, and the net output that can be taken out of the battery can be improved. . The through hole 52 is not particularly limited in shape or size, but a diameter of about 50 μm to 200 μm is desirable in order to reduce the resistance value.

The through hole 52 is disposed at a position facing at least the flow path wall 12 separating the flow paths of the first flow path 13 and the second flow path 15 formed in the flow path plate 6.
The position of the through hole is not limited to this, and it may be arranged at a place other than the flow path wall 12 that separates the first flow path 13 and the second flow path 15 as in the through hole 54 shown in FIG. Good. Thereby, the resistance value of the electrical connection between the flow path plate 6 and the diffusion layer 17 can be further effectively reduced.

  In a more preferred embodiment, the through hole 52 is disposed at a position facing the flow path wall 12 so as to surround the periphery along at least the first flow path. Thus, when the power generation cell and the flow path are stacked, the joint surface between the flow path wall 12 and the permeation suppression layer 51 around the first flow path 13 is easily and uniformly adhered. It is possible to more reliably suppress fuel leakage from the first flow path 13 to the second flow path 15 via the interface.

  Further, the permeation suppression layer 51 may have a continuous through groove along the flow path wall 12, and thereby the electrical connection between the flow path plate 6 and the diffusion layer 17 may be performed. Thereby, not only the flow path plate 6 and the diffusion layer 17 are electrically connected with low resistance but also the flow path wall 12 around the first flow path 13 and the permeation when the power generation cell and the flow path are stacked. The joint surface of the suppression layer 51 can be easily adhered uniformly, and fuel leakage from the first flow path 13 to the second flow path 15 via the interface between the flow path wall 12 and the permeation suppression layer 51 can be more reliably suppressed. It is obvious that you can do it.

The oxidant electrode 3 is covered with a cover part 20 extending from the other surface 5B of the housing 5, and the cover part 20 includes, for example, an oxidant introduction port 20A to which air is supplied as an oxidant, and an exhaust gas. Has a discharge port 20B for discharging the gas. A channel 21 on the oxidant electrode side is formed between the lid 20 and the oxidant electrode 3.
The oxidant electrode 3 includes an electrode layer 18 on the electrolyte membrane 2 side and a diffusion layer 22 on the lid 20 side.

(2) Operation of Fuel Cell In this first embodiment, for example, a mixture of methanol and water is supplied as liquid fuel from the supply port 7 of the flow path plate 6 into the first flow path 13. As the liquid fuel, in addition to a mixture of methanol and water, hydrocarbon organic fuels such as ethanol, dimethyl ether, propanol, and ethylene glycol can be used instead of methanol. This liquid fuel is supplied from the first flow path 13 to the diffusion layer 17 of the fuel electrode 1 through the permeation suppression layer 51, diffuses and penetrates through the diffusion layer 17, reaches the electrode layer 16, reacts, and becomes a cation ( H ⁺ ) and electrons and carbon dioxide as exhaust gas are produced. The cation (H ⁺ ) reaches the electrode layer 18 of the oxidant electrode 3 through the electrolyte membrane 2.

  The generated electrons are guided from the electrode layer 16 to the electrode layer 18 of the oxidant electrode 3 via an external circuit (not shown). Further, the carbon dioxide generated at the fuel electrode 1 diffuses in the diffusion layer 17 below the wall 12 to reach the second flow path 15, and passes through the second flow path 15 from the discharge port 8. Discharged.

On the other hand, the air as an example of the oxidant introduced from the introduction port 20A of the lid 20 diffuses into the diffusion layer 22 of the oxidant electrode 3, and from the fuel electrode 1 in the electrode layer 18 of the oxidant electrode 3. It reacts with cations (H ⁺ ) and electrons to produce water vapor. The generated water vapor is discharged from the discharge port 20B through the flow path 21.

  In the fuel cell of the present invention, the type and supply direction of the oxidant are not particularly limited, oxygen may be used instead of air, and the flow path 21 on the oxidant electrode side is eliminated to provide a fan or air blower. The oxidant may be directly supplied to the exposed surface of the oxidant electrode 3 using a blower mechanism such as a pump.

In the present embodiment, since the first flow path 13 and the second flow path 15 in contact with the fuel electrode 1 are separated by the wall 12, the liquid fuel supplied to the first flow path 13 is It does not flow directly through the second flow path 15 without passing through the fuel electrode 1. That is, as indicated by an arrow 40 in FIG. 3, the liquid fuel supplied to the first flow path 13 flows to the second flow path 15 via the diffusion layer 17 of the fuel electrode 1. Therefore, the fuel supply efficiency to the fuel electrode 1 can be improved, and the fuel supply amount can be reduced.
Further, along the flow as shown by the arrow 40, between the portion of the first flow path 13 shown in FIG. 3 and the portion of the second flow path 15 facing this portion with the wall 12 interposed therebetween, A pressure difference caused by a pressure drop in a path through which the fuel flows through the diffusion layer 17 of the fuel electrode 1 can be generated. When such a local pressure difference is generated between the first flow path 13 and the second flow path 15, carbon dioxide or the like is generated as a reaction product due to the reaction in the fuel electrode 1. In addition, the discharge to the first flow path 13 can be suppressed, and the second flow path 15 can be efficiently discharged.

  In the first embodiment, as shown in FIG. 1, the distance between the second flow path 15 and the first flow path 13 separated by the wall 12 is along the first flow path 13. They are arranged to be almost equal. Since the liquid fuel can be spread all over the tip of the branch flow path of the first flow path 13, the pressure of the liquid fuel in the first flow path 13 is opposed across the wall 12. The pressure difference between the pressure of the liquid fuel in the second flow path 15 can be made substantially uniform over substantially the entire region facing the fuel electrode 1. Therefore, efficient supply of fuel and efficient discharge of reaction products can be performed uniformly over the entire fuel electrode 1.

  In a more preferred embodiment, the pressure in the first flow path 13 is given a predetermined pressure difference with respect to the pressure in the second flow path 15 facing the wall 12. This stabilizes the flow of fuel in the diffusion layer 17 from the first flow path 13 to the second flow path 15 even if the orientation in which the fuel cell of the first embodiment is installed or held varies. In addition, since the discharge efficiency of carbon dioxide, which is a reaction product, is also stabilized, the fuel supply to the electrode layer 16 containing the catalyst can be stabilized.

  Usually, if liquid fuel is simply flowed into the diffusion layer 17 made of a porous material having a pore diameter of about 0.5 μm to 1 μm, the gap between the first flow path 13 and the second flow path 15 will be described. Must have a pressure difference of about 1 to 2 atmospheres. However, according to the first embodiment, a pressure difference can be given to a short path locally. Further, since the reaction product at the fuel electrode 1 can be efficiently discharged, stable fuel supply is possible even when the pressure difference is set to about 0.0001 atm to 0.1 atm, for example.

  Furthermore, since the permeation suppression layer 51 is made of a material having a liquid fuel permeability coefficient lower by about 1 to 2 digits than that of the diffusion layer 17, the diffusion of the liquid fuel from the first flow path 13 to the diffusion layer 17. Is suppressed. This allows the liquid fuel to reach the end of the first flow path 13 before the liquid fuel locally penetrates the diffusion layer 17 and fills the flow path with the liquid fuel. You can also. Thus, since it becomes easier to fill the first flow path 13 with liquid fuel at a lower supply pressure than when the fuel is directly supplied from the first flow path 13 to the diffusion layer 17, the first flow path Between the portion 13 and the portion of the second flow path 15 opposed to this portion with the wall 12 interposed therebetween, and the pressure caused by the pressure drop in the path through which the fuel flows through the diffusion layer 17 of the fuel electrode 1 The difference can be generated stably over the entire flow path. Therefore, even if carbon dioxide or the like is generated due to a reaction in the fuel electrode 1, it can be efficiently discharged from the second flow path 15 by suppressing the discharge to the first flow path 13, Reaction (generation of cations and electrons) at the fuel electrode 1 can be promoted.

In general, the liquid fuel necessary for the reaction at the fuel electrode is, for example, about several μl / min per unit area assuming a power generation of about 150 mW / cm ^{2 in a} fuel cell using methanol and water as fuel. . Therefore, even if more fuel is supplied, this excess fuel can be used to push out the fuel that fills the diffusion layer, or it can diffuse the electrolyte membrane and cause a decrease in output. Efficiency will decrease more. In other words, the reaction of the fuel electrode is not rate-determined by the amount of fuel supplied, and the reaction proceeds in a reaction-controlled state. Therefore, even if the permeation suppression layer 51 is used as in the present invention, the reaction is necessary. A sufficient amount of fuel can be supplied to continue the reaction.

  As described above, in order to improve the reaction efficiency of the fuel in the fuel cell, the liquid fuel is supplied to the entire flow path through the narrow first flow path 13 rather than supplying more liquid fuel to the diffusion layer 17. It is important to distribute evenly. In the fuel cell of the present invention, since the permeation suppression layer 51 prevents the liquid fuel from penetrating the diffusion layer 17 more than necessary in the middle of the flow path, and the liquid fuel can flow into the flow path, The supply amount (supply pressure) can also be reduced. That is, the utilization efficiency of the fuel used for the liquid reaction can be increased.

(3) Fuel electrode Conventionally known materials can be used for the diffusion layer 17 of the fuel electrode 1, for example, carbon paper, a sintered body of carbon, a sintered metal such as nickel, and a porous material such as foam metal. Can be mentioned.
The pore diameter of the porous material is not particularly limited as long as the liquid fuel from the first flow path 13 can be drawn into the diffusion layer 17. In this embodiment, the pore diameter of the porous material forming the diffusion layer 17 is about several μm to several tens of μm. If fuel is to flow through the porous material at a predetermined flow rate, a predetermined pressure must be applied, but if a reaction occurs at the end of the porous material and the fuel is consumed, the pressure is lower. It has been confirmed that the same flow rate of fuel can be flowed.

  Said electrode layer 16 can be produced with a conventionally well-known material, for example, the resin layer containing a metal catalyst is mentioned. As the metal catalyst, for example, a platinum-ruthenium alloy or the like is used, but other alloys such as platinum and gold, platinum and osmium, platinum and rhodium can be used. Further, as the resin layer of the electrode layer 16, for example, a perfluoroalkyl sulfonic acid resin is used.

  As the permeation suppression layer 51, a material having a supply suppression structure that is less permeable to liquid fuel than the diffusion layer 17 of the fuel electrode 1 can be used. As said penetration suppression layer, fluororesins, such as a polyimide and polytetrafluoroethylene (PTFE), can be used, for example. The permeation suppression layer is preferably a porous material.

  The film thickness of the permeation suppression layer 51 and the pore diameter of the porous material are relatively determined according to the film thickness and the pore diameter of the diffusion layer 17, and are not particularly limited. For example, the film thickness is about 1 μm to 30 μm, A porous material having a pore diameter of about 0.01 μm to 1 μm can be used. Preferably, the permeation suppression layer 51 has a permeation rate that is lower than the permeation rate of the diffusion layer 17 by, for example, about one to two digits as the air permeability measured by the Gurley tester method. The permeation suppression layer 51 is not limited to a porous material as long as the fuel permeation rate is lower by about 1 to 2 digits than the permeation rate of the diffusion layer 17, and may not have micropores. .

  Examples of a method for forming the through hole arranged in the permeation suppression layer 51 include mechanical constriction means such as laser ablation, punching, and drill. As the conductor 53 in the through hole 52, a gold thin film formed by electroless plating can be used. Further, the through groove can be produced by continuously processing by a laser ablation method.

In the fuel electrode 1, the electrode layer 16 and the diffusion layer 17 are formed by pressing the diffusion layer 17 on the electrode layer 16 by hot pressing or the like, or when the electrode layer 16 is a resin, the material of the diffusion layer 16 on the diffusion layer 17. It can be laminated by impregnating a resin to be heat treated.
Further, the permeation suppression layer 51 can be obtained by impregnating the diffusion layer 17 with the above-mentioned resin, which is a material of the permeation suppression layer, and performing a heat treatment. Alternatively, the porous resin may be formed on the electrode layer 16 and the diffusion layer 17 and heat-treated.
The order of forming these layers constituting the fuel electrode is not particularly limited, and the permeation suppression layer may be formed after laminating the electrode layer and the diffusion layer, or after laminating the permeation suppression layer and the diffusion layer. An electrode layer may be formed.

(4) Electrolyte membrane The material of the electrolyte membrane 2 may be proton-conductive, heat-resistant material that can withstand the reaction (exothermic reaction) of the fuel electrode and the oxidant electrode, and acid-resistant material that can withstand proton-conductive acidic atmosphere. There is no particular limitation, and either an organic material or an inorganic material can be used. In this embodiment, sulfonic acid group-containing perfluorocarbon (Nafion 117 (registered trademark) (manufactured by DuPont)) having an organic fluorine-containing polymer as a skeleton is used. The electrolyte membrane 2 only needs to have a proton-conducting function, and may be one in which the electrolyte membrane is embedded in another base material.
(5) Oxidant Electrode The electrode layer 18 of the oxidant electrode is made of a resin layer containing a metal catalyst, like the electrode layer 16 of the fuel electrode 1. The diffusion layer 22 may be made of a porous material such as carbon paper, a sintered body of carbon, a sintered metal such as nickel, or a foam metal, as in the diffusion layer 17 of the fuel electrode 1.

  The oxidant electrode 3 can be manufactured by a conventionally known method. For example, the oxidant electrode 3 can be manufactured by using the method described for laminating the electrode layer and the diffusion layer of the fuel electrode.

(6) Flow path plate As the flow path plate 6, a substrate that is not permeable to liquid fuel can be used. For example, a substrate made of a metal such as nickel, a silicon substrate, a glass substrate, a resin such as acrylic or PDMS. A substrate or the like can be used. In the present embodiment, a nickel substrate subjected to fine processing is used as the flow path plate 6.

  When the channel plate 6 is made of an insulating material such as a non-conductive glass substrate, the conductive wiring layer 61 may be inserted between the channel plate and the permeation suppression layer as shown in FIG. Good. In the present embodiment, as the wiring layer 61, a gold thin film formed by electroless plating is used similarly to the conductor 53 in the through hole 52.

(7) Housing The housing 5 may be made of a material used as a casing of a conventionally known fuel cell. For example, as with the carbon resin or the flow path plate, glass, acrylic, PDMS, etc. Resin etc. are mentioned.

  In the fuel cell of the present invention, when a flexible resin material such as PDMS is used for the flow path plate 6 and the housing 5, the flow path plate 6 and the housing are bent as shown in FIG. In this case, the flow path plate 6 and the diffusion layer 17 can be stably connected with low electrical resistance. Further, when the power generation cell and the flow path are stacked, the adhesion between the joint surface of the flow path wall 12 and the permeation suppression layer 51 around the first flow path 13 can be maintained. It is possible to more reliably suppress fuel leakage from the first flow path 13 to the second flow path 15 via the interface.

(8) Assembly of fuel cell The fuel cell of the present invention can be obtained by a conventionally known method. For example, the fuel electrode 1 and the oxidant electrode 3 are joined to the electrolyte membrane 2 obtained as described above by hot pressing. Then, the membrane electrode composite is prepared, the membrane electrode composite is laminated on the flow path plate 6, and the housing 5 integrated with the oxidant chamber is covered with the flow path plate 6 and the housing 5. It can be obtained by bonding.

(9) Comparison with Conventional Fuel Cell In the conventional fuel cell without the permeation suppression layer 51, the liquid fuel is in the vicinity of the first flow path 13 near the fuel supply start position in the first flow path 13. As a result, the amount of diffusion from the diffusion layer 17 to the diffusion layer 17 increases and it becomes difficult for the fuel to reach the end of the first flow path 13, so a very high fuel supply pressure is required.

  Even if the diffusion rate of the diffusion layer 17 itself is lowered without using the permeation suppression layer 51, the liquid fuel can be distributed to the first flow path 13 with a low fuel supply pressure. However, the permeation of fuel in the diffusion layer 17 can be achieved. Since (diffusion) itself becomes slow, the fuel necessary for the reaction cannot be sufficiently supplied (supplemented), and the output of the fuel cell is lowered.

  As in the prior art, the main flow of the supplied fuel has a flow path that does not pass through the diffusion layer (that is, the flow path is not separated into the first flow path and the second flow path), When a fuel cell having no permeation suppression layer was produced, it was necessary to supply a fuel of several hundred μl / min. On the other hand, in the fuel cell of this embodiment in which the main flow passes through the diffusion layer, an output equivalent to the above-described conventional fuel cell can be obtained with a fuel supply of several tens of microliters / minute or less. That is, it has been confirmed that the fuel cell of the present invention improves the fuel utilization efficiency by about one digit compared to the conventional fuel cell.

(Second embodiment)
Next, FIG. 7 schematically shows a fuel cell as a second embodiment of the present invention. In the second embodiment, in addition to the configuration of the fuel cell of the first embodiment described above, a pressure adjusting unit 81, a fuel storage unit 82, and a channel plate connected in sequence to the supply port 7 of the channel plate 6 6, a gas discharge portion 83 connected to the discharge port 8, and an oxidant pumping portion 84 connected to the oxidant introduction port 20 of the lid portion 20. Therefore, in the second embodiment, parts having the same configuration as those in the first embodiment are denoted by the same reference numerals, and different points from the first embodiment will be mainly described.

The fuel storage unit 82 is connected to the pressure adjustment unit 81 through a flow path 85, and the pressure adjustment unit 81 is connected to the supply port 7 through a flow path 86. Further, the flow path 21 formed between the lid 20 and the oxidant electrode 3 forms a third passage for supplying oxygen or air as an example of the oxidant to the oxidant electrode 3. The oxidant pumping unit 84 supplies the oxidant to the flow path 21 from the oxidant inlet 20A.
One end of a fourth flow path 87 into which exhaust gas (for example, water vapor) from the flow path 21 is introduced is connected to the discharge port 20B of the lid portion 20, and the other end of the fourth flow path 87 is a gas discharge. Connected to the unit 83. The gas discharge part 83 is connected to the other end of the fifth flow path 88 whose one end is connected to the discharge port 8. Exhaust gas (for example, carbon dioxide) from the second flow path 15 is introduced into the fifth flow path 88.

The fuel storage unit 82 may be a container made of a material resistant to fuel. Such materials include hard vinyl chloride resin, PTFE and epoxy hard resin, silicon resin such as PDMS, resin materials such as resin combined with glass fiber and carbon fiber, aluminum and titanium, magnesium alloy treated with anticorrosion, etc. A metal material is mentioned.
The flow paths 85, 86, 87 and 88 are made of a tubular member made of a material resistant to fuel. Examples of the material include hard vinyl chloride resin, PTFE and epoxy hard resin, and silicon resin.

  According to the second embodiment, the liquid fuel (for example, a mixture of methanol and water) stored in the fuel storage unit 82 is liquidated using the pressure adjusting unit 81 that can be configured by a pressure reducing valve or a pressure adjusting valve. The fuel can be stably supplied from the first flow path 13 to the fuel electrode 1, and the output of the fuel cell can be improved. In addition, since power consumption is less than when a pump that is always operated is used, it is possible to suppress power loss and increase the output as a fuel cell.

  Further, according to the second embodiment, both exhaust gas as spent fuel from the fuel electrode 1 and exhaust gas such as water vapor from the oxidant electrode 3 are discharged from the same single gas discharge unit 83. Since it can be discharged, it is easy to collect the exhaust gas.

  In the second embodiment, a pressure sensor (not shown) may be provided as means for detecting a pressure difference between the pressure in the first flow path 13 and the pressure in the second flow path 15. In this case, the pressure adjustment unit 81 adjusts the pressure in the first flow path 13 based on the pressure difference detected by the pressure sensor, so that the pressure difference is within a predetermined range (for example, 0. 0001 atmospheres to about 0.1 atmospheres). Therefore, even when an environmental change such as a temperature change or a pressure change occurs, the amount of fuel supply can be stabilized and the output of the fuel cell can be stabilized.

It is a top view which shows 1st Embodiment of the fuel cell of this invention. It is A-A 'sectional drawing of FIG. It is B-B 'sectional drawing of FIG. It is sectional drawing of a permeation suppression layer. It is sectional drawing which shows 1st Embodiment of the fuel cell of this invention. It is sectional drawing which shows 1st Embodiment of the fuel cell of this invention. It is a schematic diagram which shows 2nd Embodiment of the fuel cell of this invention. It is sectional drawing of the conventional direct methanol fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel electrode 2 Electrolyte membrane 3 Oxidant electrode 5 Housing 6 Flow path plate 7 Supply port 8 Discharge port 10 1st flow path groove 11 2nd flow path groove 12 Wall 13 1st flow path 15 2nd flow path 16 Electrode layer 17 Diffusion layer 18 Electrode layer 20 Lid 21 Oxidant electrode side flow path 22 Diffusion layer 51 Permeation suppression layer 52 Through hole 53 Conductor 61 Wiring layer 81 Pressure adjustment unit 82 Fuel storage unit 83 Gas discharge unit 84 Oxidation Agent pressure feeding section 85 flow path 86 flow path 87 fourth flow path 88 fifth flow path

Claims (5)

An anode that generates cations and electrons from liquid fuel;
An electrolyte membrane disposed so as to face the fuel electrode and capable of transmitting a cation generated from the fuel electrode;
An oxidant electrode disposed so as to face the electrolyte membrane and reacting the cation and the oxidant that have permeated the electrolyte membrane;
A flow path plate arranged to face the fuel electrode and forming a first flow path for supplying the liquid fuel to the fuel electrode and a second flow path for discharging exhaust gas from the fuel electrode; Prepared,
The first flow path and the second flow path are separated;
The fuel electrode is
An electrode layer containing a catalyst on the electrolyte membrane side and a diffusion layer on the flow path plate side;
A permeation suppression layer that suppresses the supply of the liquid fuel from the first flow path to the diffusion layer;
The permeation suppression layer has a through hole or a through groove in the thickness direction,
A fuel cell in which a conductor is disposed in the through hole or the through groove.   2. The fuel cell according to claim 1, wherein the through-hole or the through-groove is at least disposed at a position facing a flow path wall that separates the first flow path and the second flow path.   The fuel cell according to claim 2, wherein the through hole or the through groove is disposed so as to surround at least the periphery of the first flow path. A fuel storage unit connected to the first flow path for storing the liquid fuel;
The pressure adjustment part which connects between the said fuel storage part and the said 1st flow path, and adjusts the pressure of the liquid fuel supplied to the said 1st flow path from the said fuel storage part. 4. The fuel cell according to any one of 3 above. A third flow path for supplying the oxidant to the oxidant electrode;
A fourth flow path into which exhaust gas from the third flow path connected to the third flow path is introduced;
A fifth flow path into which exhaust gas from the second flow path connected to the second flow path is introduced;
A gas discharge section connected to the fourth flow path and the fifth flow path for discharging the exhaust gas from the fourth flow path and the exhaust gas from the fifth flow path to be discharged; The fuel cell according to claim 4 provided.

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