JP2007207685A - Fuel cell and method of manufacturing fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell in which a local submerged region is hard to occur even if a current value per surface area of a power generating layer member is set high by improving draining characteristics in a direction along a surface of the power generating layer member. <P>SOLUTION: A fuel diffusion layer 6 is arranged on an upper face side and an oxygen flow passage material 2 is arranged on a lower face side of a membrane electrode assembly 4. The oxygen flow passage material 2 supplies oxygen in the atmosphere taken in from an air intake port formed on a side face opposing to a power generating cell to the membrane electrode assembly 4. A diffusion layer 3 of the carbon particles is formed on a surface of the oxygen flow passage material 2, and numerous parallel drain ditches 3M are formed in a face contacted with the membrane electrode assembly 4 of the diffusion layer 3. By making a groove width 30 μm, product water of the membrane electrode assembly 4 is strongly collected and submersion (flooding) of the membrane electrode assembly 4 can be evaded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell including an oxygen supply layer that supplies oxygen to a power generation layer member and carries out water molecules generated by the power generation layer member. Relates to the surface structure of the oxygen supply layer that discharges oxygen.

  A fuel cell having a hydrogen gas supply space sealed on one surface side of a power generation layer member and an oxygen supply layer on the other surface side of the power generation layer member has been put into practical use. The power generation layer member takes in hydrogen ions from the hydrogen gas supply space and combines the hydrogen ions with oxygen on the surface on the oxygen supply layer side to generate power. The oxygen supply layer supplies a necessary amount of oxygen to the surface of the power generation layer member and functions as a diffusion path or a discharge path for carrying out water molecules generated on the oxygen supply layer side of the power generation layer member.

  Patent Document 1 discloses a fuel cell in which power generation cells having power generation layer members are stacked and connected in series. Then, oxygen in the atmosphere is taken in through the opening on the side surface of each power generation cell, and the moisture in the oxygen supply layer is evaporated and diffused into the atmosphere through the same opening. The power generation layer member employs a membrane electrode assembly in which a porous electroconductive catalyst layer is formed on both sides of the polymer electrolyte membrane, and the side of the oxygen supply layer that is plate-like and has air permeability is open to the atmosphere. Has been. The oxygen taken in from the side surface of the oxygen supply layer diffuses three-dimensionally in the oxygen supply layer and is supplied to the entire surface of the membrane electrode assembly through one bottom surface of the oxygen supply layer. Water molecules generated in the membrane electrode assembly are taken into the oxygen supply layer as water vapor, diffused to the side surface according to the water vapor concentration gradient, and discharged into the atmosphere through the opening.

  Patent Document 2 discloses a fuel cell in which air is forced to flow from one side of the oxygen supply layer to the other side to flow through. Then, the downstream side of the oxygen supply layer that allows air to flow through, the tissue density is lowered and the flow path resistance is made lower than the upstream side.

  Patent Document 3 shows a fuel cell in which a separator in which a groove-like air flow path that penetrates opposing side surfaces of a power generation cell is formed so as to overlap an oxygen supply layer. Then, the tissue density of the oxygen supply layer in contact with the air flow path is changed in the thickness direction, and the tissue density of the diffusion layer in contact with the membrane electrode assembly is made higher than that of the intermediate layer to increase the water retention of the intermediate layer. .

Patent Document 4 discloses a fuel cell in which a catalyst layer is formed on a surface of a polymer electrolyte membrane side of an oxygen supply layer disposed so as to overlap with a power generation layer member. Then, oxygen supply and water vapor discharge in the oxygen supply layer are passively performed depending on natural diffusion. The oxygen supply layer is penetrated in the thickness direction, and through holes with a diameter of 100 μm or less are formed at a high density of 400 holes / mm ² , so that the diffusion performance in the thickness direction is enhanced. The through-hole (conical shape) whose cross-sectional area increases from the polymer electrolyte membrane side to the opposite surface reduces the oxygen and water vapor passage resistance, and the contact area on the polymer electrolyte membrane side and the strength of the oxygen supply layer Is increasing.

US Pat. No. 6,423,437 JP 2004-273392 A JP-A-2005-174607 JP 2002-110182 A

  It is desirable that the fuel cell carried together with the device passively performs oxygen supply and water vapor discharge in the oxygen supply layer by relying on natural diffusion. Such a fuel cell preferably does not rely on external power supply at the time of start-up, and the air circulation mechanism and blower increase the number of parts, which is contrary to the reduction in size and weight of the fuel cell. The fuel cells shown in Patent Documents 2 and 3 are based on such an atmospheric circulation mechanism and blower.

  However, when relying on natural diffusion for oxygen supply and water vapor discharge in the oxygen supply layer, the water vapor discharge amount depends on the environment, and in a low temperature and high humidity environment, the water vapor discharge amount through the oxygen supply layer decreases. When water molecules are generated in the power generation layer member in excess of the amount of water vapor discharged through the oxygen supply layer, liquid water stagnates near the interface between the power generation layer member and the oxygen supply layer, and the surface of the power generation layer member partially Flooded. In the submerged area, the supply of oxygen to the power generation layer member is hindered and the power generation performance is impaired, so that the current density in the part that is not submerged is high and the electromotive force of the power generation cell is reduced. If the operation is continued as it is, the submergence region spreads in the region where the current density is increased, leading to the entire submergence of the power generation layer member, and power generation may stop.

  Therefore, compared with the active type that forcedly circulates the atmosphere in the oxygen supply layer, the passive type that relies on natural diffusion assumes the current value per surface area of the power generation layer member (= water generation amount) assuming low temperature and high humidity. It is necessary to set it extremely small. If the current value per surface area of the power generation layer member is set to be extremely small, the area of the power generation layer member becomes large and the power generation section becomes larger, and the fuel cell becomes larger than the active type.

  The fuel cell shown in Patent Document 4 has improved the water vapor discharge performance near the interface between the power generation layer member and the oxygen supply layer on the premise of such a passive type. However, in the oxygen supply layer, the water vapor diffusion performance is enhanced only in the thickness direction, and the moisture movement in the direction along the power generation layer member depends entirely on the natural diffusion of the oxygen supply layer. Therefore, the partial pressure of water vapor is locally increased in a poorly vented region (such as a position far from the side opening) in the oxygen supply layer, and a region submerged in liquid water is formed. Since there is no ability to exclude liquid water from the submerged area in the direction along the surface of the power generation layer member, the submersion area spreads over the area where the current density is increased, and there is a possibility that the power generation layer member will be fully submerged sooner or later. is there.

  It is an object of the present invention to provide a fuel cell that enhances drainage in a direction along the surface of a power generation layer member and is unlikely to generate a local submerged area even if a current value per surface area is set high. Yes.

  The fuel cell of the present invention includes a power generation layer member that generates power by moving hydrogen ions from one surface to the other surface, and oxygen that is disposed on the one surface side and reacts with the hydrogen ions on the one surface. And an oxygen supply layer which is diffused and supplied. And the drainage groove | channel which improved the retention property of liquid water rather than the surrounding said oxygen supply layer is formed in the surface at the said electric power generation layer member side of the said oxygen supply layer.

  In the fuel cell of the present invention, liquid water that causes partial submersion of the power generation layer member is collected in the drainage groove and moved in the direction of the liquid water in the direction along the drainage groove. The drainage groove having higher retention of liquid water than the surroundings prevents liquid water on the surface of the power generation layer member from being sucked and covers the surface of the power generation layer member, and submersion in a region exceeding the drainage groove width is suppressed.

  And since the force that the drainage groove collects the liquid water forms a flow of liquid water along the drainage groove, the uneven distribution of the liquid water on the surface of the power generation layer member is averaged by the movement of the liquid water through the drainage groove. The

  Since water moves from the excess region to the shortage region in the state of liquid water, the wetness of the power generation layer member is also made uniform immediately after the start of power generation. In the case of a polymer electrolyte membrane, the entire power generation layer member is high. Power generation performance (electromotive force) can be extracted. The movement of liquid water through the drainage channel does not increase the water vapor partial pressure of the oxygen supply layer as much as when the entire amount is transferred in the state of water vapor, so that the discharge performance of water vapor through the oxygen supply layer is maintained high. The The diffusion of oxygen in the reverse direction through the oxygen supply layer also becomes smooth.

  Therefore, even if the current value per surface area of the power generation layer member is set high, the local submergence region of the power generation layer member is hardly generated. Using a power generation layer member with a small area, a large current can be output without relying on an air circulation mechanism or a blower. While realizing high reliability, long life, and high performance, it is possible to provide a small, lightweight and inexpensive fuel cell with a small number of parts.

  Hereinafter, a fuel cell which is an embodiment of a fuel cell of the present invention will be described in detail with reference to the drawings. The fuel cell of the present invention is not limited to a limited configuration such as the fuel cell 10 described below. As long as water molecules are generated by providing the power generation layer member and the oxygen supply layer, another embodiment in which a part or all of the configuration of the fuel cell 10 or the like is replaced with the alternative configuration can be realized. .

  In this embodiment, power generation is performed using the hydrogen gas stored in the fuel tank 10B. However, liquid fuel such as methanol containing hydrogen atoms is stored in the fuel tank 10B, and reforming reaction is performed on the hydrogen gas as necessary. You may supply to the electric power generation cell 10S.

  The fuel cell of this embodiment can be implemented as an independent fuel cell that is detachably mounted on a portable electronic device such as a digital camera, a digital video camera, a small projector, a small printer, or a notebook computer. Further, it can be implemented in a form in which only the power generation part of the fuel cell is integrated into the electronic device and the fuel tank is attached or detached.

  In addition, the structure, operation method, catalyst layer and manufacturing method thereof, polymer electrolyte membrane, structure of membrane electrode assembly, operation principle, manufacturing method and the like shown in Patent Documents 1 to 4 can be referred to as needed. As technical common sense, some illustrations are omitted and detailed explanations are also omitted.

<First Embodiment>
FIG. 1 is an explanatory diagram of the overall configuration of the fuel cell of the first embodiment, FIG. 2 is an explanatory diagram of the configuration of the power generation cell viewed from the air intake side, and FIG. 3 is viewed from the direction in which the air intake port is placed sideways. It is explanatory drawing of a structure of a power generation cell. FIG. 4 is a perspective view of the oxygen supply layer.

  As shown in FIG. 1, the fuel cell 10 includes a cell stack 10A in which power generation cells 10S are stacked and connected in series. A fuel tank 10B that stores hydrogen gas and supplies it to the power generation cell 10S is connected below the cell stack 10A. The hydrogen gas taken out from the fuel tank 10B is adjusted to a pressure slightly higher than the atmospheric pressure and supplied to each power generation cell 10S.

  The power generation cell 10S has air intakes 8 that take oxygen in the atmosphere into the power generation cell 10S by natural diffusion on a pair of opposing side surfaces S1 and S2. The power generation cell 10S generates electricity by reacting the hydrogen gas supplied from the fuel tank 10B with the oxygen taken in from the air intake port 8.

  As shown in FIG. 2, the power generation cell 10 </ b> S includes a membrane electrode assembly 4 (MEA: Membrane Electrode Assembly) and an oxygen flow path material 2. On the lower surface of the membrane electrode assembly 4 responsible for power generation, an oxygen flow path material 2 for supplying oxygen taken from the air intake 8 (FIG. 3) to the entire surface of the membrane electrode assembly 4 is disposed.

  The separators 7 and 9 form a hydrogen gas supply space sealed from the outside on the upper surface of the membrane electrode assembly 4. The fuel flow path member 6 accommodated in the hydrogen gas supply space supplies the hydrogen gas extracted from the fuel tank 10B (FIG. 1) to the entire surface of the membrane electrode assembly 4. A main flow path of hydrogen gas is formed through the separator 9 in the thickness direction of the power generation cell 10S, and the hydrogen gas is branched from the main flow path and supplied to each power generation cell.

  The membrane / electrode assembly 4 has a catalyst layer formed by applying a catalyst material such as platinum on both surfaces of a polymer electrolyte membrane. For the polymer electrolyte membrane, Nafion (trademark) manufactured by DuPont, which is a perfluorocarbon polymer having a sulfonic acid group, was used. However, the main purpose of the polymer electrolyte membrane is to conduct hydrogen ions from the hydrogen gas supply surface to the oxygen supply surface, and any membrane can be used as long as it satisfies this purpose.

  Catalyst layers are formed on both sides of the polymer electrolyte membrane. The catalyst layer is a porous material layer composed of a substance having catalytic activity, an electron conductor, and a proton conductor. However, in the membrane / electrode assembly 4, the catalyst layer is integrated with the surface of the polymer electrolyte membrane. However, if the catalyst layer is in contact with the polymer electrolyte membrane and chemical species such as hydrogen ions can be delivered, It is not necessary to form the membrane electrode assembly 4 as one.

  On the surface of the fuel flow path member 6 in contact with the membrane electrode assembly 4, the conductive diffusion layer 3 having a finer tissue opening than the fuel flow path member 6 is disposed. The diffusion layer 3 functions as a drawing resistor and supplies hydrogen gas to the entire surface of the membrane electrode assembly 4 with an equal pressure and an equal flow density.

  On the surface of the oxygen channel material 2 on the membrane electrode assembly 4 side, a conductive diffusion layer 3 that exhibits the same effect by opening a tissue smaller than that of the oxygen channel material 2 is disposed. On the surface where the diffusion layer 3 is in contact with the membrane electrode assembly 4, there is formed a drainage groove 3M that collects liquid water generated at the interface with the membrane electrode assembly 4 and pushes it out to the water-deficient region.

  The fuel flow path member 6 diffuses hydrogen gas, which is fuel, and collects surplus electrons from the ionization of hydrogen from the catalyst layer of the membrane electrode assembly 4. The oxygen channel material 2 diffuses oxygen in the atmosphere, which is an oxidizing agent taken in from the air intake port 8, and supplies electrons necessary for generating water molecules to the catalyst layer of the membrane electrode assembly 4. The oxygen channel material 2 also guides the water vapor generated in the membrane electrode assembly 4 along with power generation to the air intake 8 and discharges it into the atmosphere. Therefore, a conductive porous body is preferred for the oxygen channel material 2. As a specific material, foam metal, stainless wool, or the like is used. The diffusion layer 3 is made of carbon paper, carbon cloth, or the like, and a conductive fine particle layer may be formed on the contact surface with the membrane electrode assembly 4 as described later.

  As shown in FIG. 4, the diffusion layer 3 formed on the surface of the oxygen channel material 2 is connected to a pair of opposing side surfaces 2A and 2B facing the air intake port 8 so that a large number of parallel drainage grooves 3M. Is formed. The drainage grooves 3M are actually formed on the surface in contact with the catalyst layer of the membrane electrode assembly 4 (FIG. 2) at a high density of 100 per width of 30 μm, depth of 50 μm, and 25 mm. Drain grooves 3M are formed in the diffusion layer 3 in a pattern as shown in FIG. The oxygen channel material 2 is preferably made of a conductive porous material, and at least a portion of the diffusion layer 3 up to the depth of the drain groove 3M is preferably subjected to a hydrophobic treatment. This is because water droplets that have been crushed in a water-repellent environment and increased in pressure due to surface tension increase the thickness in the drainage groove 3M and decrease the pressure. By the driving force due to this surface tension, the surface of the membrane electrode assembly 4 and the liquid water in the diffusion layer 3 are pushed into the drainage groove 3M, move along the drainage groove 3M, and are pushed out to the water-deficient region. In the water-deficient region, the water vapor pressure increases due to the evaporation of the liquid water that has flowed in, the humidification of the membrane electrode assembly 4 proceeds, and the water vapor discharge to the oxygen channel material 2 also becomes active.

  The drainage groove 3M is preferably processed by the diffusion layer 3 rather than the diffusion layer 5, and the direction of the drainage groove 3M is such that at least one end is open with respect to the direction of the air intake 8 when the power generation cell 10S is assembled. It is desirable to be formed. This is to improve the drainage of the power generation cell 10S by guiding the liquid water to the vicinity of the air intake 8 where the liquid water is easy to evaporate.

  In the drainage groove 3M of the first embodiment, excess liquid water generated by the electrode reaction is smoothly discharged through the air intake 8 in the fuel cell 10 that generates power using the polymer electrolyte membrane. It is difficult for the flooding that the liquid water stays in the gap between the oxygen channel material 2 or the diffusion layer 3 and the membrane electrode assembly 4 to block the oxygen supply. The submergence of the three-phase interface in the catalyst layer of the diffusion layer 3 or the membrane electrode assembly 4 is avoided and the electrode reaction is not directly inhibited.

Second Embodiment
FIG. 5 is an explanatory diagram of the configuration of the oxygen supply layer in the second embodiment. In the second embodiment, only the external shape of the drain groove 3N formed in the diffusion layer 3 is different, and the fuel cell is assembled in the same manner using the same components as in the first embodiment. Therefore, description will be made with reference to FIGS.

  As shown in FIG. 5, in the second embodiment, the diffusion layer 3 of the oxygen flow path material 2 is formed with a drainage groove 3N whose cross-sectional area gradually increases toward the side surfaces 2A and 2B facing the air intake port 8. ing. By using this structure, the following effects can be obtained.

  First, droplet water generated by power generation activity in the vicinity of the catalyst layer of the membrane electrode assembly 4 becomes energetically unstable because the oxygen channel material 2 and the diffusion layer 3 are hydrophobic. On the other hand, the portion of the drainage groove 3N formed as described above is a place that is energetically stable with respect to the droplet moisture because the space is formed. Accordingly, the droplet water moves and stays so as to be sucked into the drainage groove 3N for stability. Then, since the supply of oxygen revives about the place which was submerged in liquid water until then, the characteristic of the fuel cell 10 is maintained.

  However, if the droplet moisture is only induced in the drainage groove 3N, it only stays in that portion of the drainage groove 3N, and the region where it is submerged and deactivated again increases due to the subsequent power generation activity and the accumulation of generated water. Concerned.

  Therefore, a mechanism for driving the water staying in the drain groove 3N to move along the drain groove 3N is required. For this purpose, first, as a minimum condition, it is desirable that at least one end of the drainage groove 3M extends in the direction of the air intake 8 as in the drainage groove 3M shown in FIG. Furthermore, it is desirable that the drainage groove 3M communicates with the air intake port 8. However, even if the discharge groove 3M is not directly exposed, the water in the drain groove 3M is expected to be discharged due to the evaporation effect of the liquid water, and therefore it is not necessarily exposed.

In the second embodiment, the capillary pressure is added as a driving force for moving the water staying in the drainage groove 3N toward the air intake 8. The capillary pressure Pc is defined as follows in an elongated circular tube with a radius r.
Pc = − (2γ / r) cos θ (1)
Here, γ represents the surface tension constant, and θ represents the contact angle between the droplet water, the oxygen channel material 2 and the diffusion layer 3. From equation (1), as the radius r of the circular tube increases, the capillary pressure Pc decreases in inverse proportion to it.

  This means the following. Where the radius r of the hydrophobic circular tube is changing, the capillary pressure Pc at the portion where the radius r is small is larger than the portion where the radius r is large. For this reason, an imbalance occurs in the pressure, and the liquid water at the location where the radius r is small moves in the circular tube toward the direction where the radius is large.

  That is, as shown in FIG. 5, the drainage groove 3N is formed so that the cross-sectional radius at the side surfaces 2A and 2B closest to the air intake port 8 is maximized. Thereby, the droplet water staying in the vicinity of the middle between the side surfaces 2A and 2B is guided to the outside by the capillary pressure Pc. Since the side surfaces 2A and 2B are close to the air intake 8, the liquid water is easily evaporated and discharged into the atmosphere. Thus, by devising the shape of the drain groove 3N, the discharge of liquid water becomes easier and the stability of the fuel cell 10 is improved.

  The width of the drainage groove 3N may be within a range where water can be guided. If it is too narrow, it will be difficult to aggregate water, and if it is too wide, the volume of droplets generated in the drainage groove 3N will be too large, and it will be difficult to discharge with capillary pressure Pc. In addition, the non-contact area between the diffusion layer 3 and the membrane electrode assembly 4 increases, which hinders the current collection effect that is one of the purposes of the oxygen channel material 2. Therefore, the diameter of the drainage groove 3N is desirably 5 μm or more, and desirably 1000 μm or less.

<Third Embodiment>
FIG. 6 is an explanatory diagram of the configuration of the oxygen supply layer in the third embodiment. In the third embodiment, the fuel cell is assembled in the same manner using the same components as in the first embodiment except that the external shape of the drain groove 3P formed in the diffusion layer 3 is different. Therefore, description will be made with reference to FIGS.

  As shown in FIG. 6, in the third embodiment, the diffusion layer 3 is formed with drainage grooves 3 </ b> P that branch out toward the side surfaces 2 </ b> A and 2 </ b> B facing the air intake 8 and increase in number. In the case of the first embodiment, there is a drain groove 3M for guiding the liquid water generated by the catalytic reaction of the fuel cell 10 to the outside of the power generation cell 10S. In this case, in the portion near the air intake port 8 of the power generation cell 10S, the water generated by the power generation reaction and the inflow water that has moved from the central side may accumulate and the drain groove 3M may be saturated. Therefore, it is conceivable to increase the width of the drainage groove 3N as in the second embodiment, but the drainage groove 3P may be branched halfway as shown in FIG.

  In the third embodiment, the liquid that moves in the drainage groove 3P is bifurcated in the middle. As a result, drainage is efficiently performed in the outer region where the liquid is concentrated, and at the same time, in the central portion where the liquid is not concentrated so much, a large contact area with the electrode assembly is ensured, which is the original purpose of the oxygen channel material 2. A current collecting effect can be sufficiently obtained. The branch point of the drainage groove 3P does not need to be one in the middle, and a plurality of branch points may be provided as necessary, or may be separated into three or more. The expansion of the groove width and the branching may be combined.

<Fourth embodiment>
FIG. 7 is a perspective view illustrating the configuration of the fuel cell according to the fourth embodiment, FIG. 8 is an explanatory view of the cross-sectional shape of the drainage groove formed in the diffusion layer, and FIG. 9 is an explanatory view of a modification of the cross-sectional shape of the drainage groove. is there.

  As shown in FIG. 7, the fuel cell device 20 of the fourth embodiment includes a cell stack 20A in which a plurality of power generation cells 29 are stacked and connected in series. The power generation cell 29 is sandwiched and stacked between the separator 24 and the separator 28, and is assembled by restraining the whole in the stacking direction using the pressure plates 31 and 36.

  In the power generation cell 29, the fuel supply layer 25 is brought into contact with the lower surface of the membrane electrode assembly 26 in which the catalyst layers are formed on both surfaces of the polymer electrolyte membrane, and the diffusion layer 27 is brought into contact with the upper surface. In the catalyst layer in contact with the fuel supply layer 25, hydrogen gas is decomposed and ionized by catalytic reaction to supply hydrogen ions to the polymer electrolyte membrane. In the catalyst layer in contact with the diffusion layer 27, oxygen combines with hydrogen ions picked up from the polymer electrolyte membrane by overcoming the electromotive force of the power generation cell 29 by a catalytic reaction to generate water molecules. The polymer electrolyte membrane moves hydrogen ions from the fuel supply layer 25 side to the diffusion layer 27 side.

  The fuel supply layer 25 is disposed in a recess 23 formed in the separator 24. The outer periphery of the recess 23 is sealed so that hydrogen gas does not leak out. A part of the side surface and the upper surface of the diffusion layer 27 is released to the atmosphere through the ventilation groove 38 of the separator 28 that also serves as an oxygen channel material.

  The separator 28, the power generation cell 29 (membrane electrode assembly 26), the separator 24, and the pressure plate 31 of each stage are formed with a hydrogen gas supply path 21 in the same plane position. A fuel tank 37 is connected to the hydrogen gas supply path 21 via a pressure reducing valve 34. The hydrogen gas supply path 21 is supplied with hydrogen gas which is taken out from the fuel tank 37 and adjusted to a pressure slightly higher than the atmospheric pressure by the pressure reducing valve 34, and is branched to the recess 23 by the separator 24. It flows into the fuel supply layer 25.

  The pressure plate 36, the separators 28 of each stage, the power generation cells 29 (membrane electrode assemblies 26), and the separators 24 are formed with discharge paths 22 that are aligned in plan view. A purge valve 35 that is normally closed and manually opened as necessary is connected to the discharge path 22.

  As shown in FIG. 8, in the membrane electrode assembly 26 according to the fourth embodiment, catalyst layers 26B and 26C are integrally formed on the surface of a polymer electrolyte membrane 26A having hydrogen ion conductivity. A diffusion layer 27 is in contact with the catalyst layer 26 </ b> B of the membrane electrode assembly 26. A drain groove 27M that opens to the catalyst layer 26B side is provided on the contact surface of the diffusion layer 27 sandwiched between the catalyst layer 26B and the separator 27 with the catalyst layer 26B. Then, by providing the drain groove 27M in the diffusion layer 27, it is possible to efficiently drain excess water generated in the catalyst layer 26B without reducing the catalyst layer 26B directly related to the electrode reaction of the membrane electrode assembly 26.

  The drain groove 27M sucks up the droplet water generated at the interface between the water-repellent catalyst layer 26B containing carbon particles and the water-repellent diffusion layer 27 containing carbon fibers by the driving force of the surface tension described above. In order to make this driving force effective, the groove width a was set to 30 μm.

  In addition, the planar arrangement pattern of the drainage grooves 27M has a uniform width (250 lines) so that liquid water can easily move from an excessively generated region of water accidentally and locally during operation to a region of insufficient moisture. / Inch). Thereby, no matter where the water content is excessive in the membrane electrode assembly 26, the pressure of the sucked liquid water pushes the liquid water in a planar shape to the surrounding water-deficient region through the drainage groove 27M.

  The diffusion layer 27 is desirably made of a material having high gas permeability and high electrical conductivity, and carbon paper, carbon cloth, metal mesh, or the like is used as a material having these properties. In particular, it is preferable to use carbon cloth from the viewpoint of processability, availability, and cost. When such a material is used, the drain groove 27M can process the drain groove 27M whose cross-sectional shape and depth are controlled by laser processing or ion beam processing.

  The cross-sectional shape of the drainage groove 27M is not limited to the semicircular shape shown in FIG. 8, and the triangular cross-sectional shape shown in FIG. 9 and a polygonal cross-sectional shape such as a square can be easily processed by these methods. Even in the planar arrangement of the discharge grooves 27M on the plane in contact with the catalyst layer 26B, it is possible to easily process the arrangement in a mesh or regularly arranged in a certain direction.

  The fact that the discharge groove 27M having a circular, semi-circular or polygonal cross-sectional shape or a pattern in a planar arrangement can be freely processed is that the membrane electrode assembly 26, the diffusion layer 27, This is preferable in optimizing the relationship.

<Fifth Embodiment>
FIG. 10 is an explanatory view of the configuration of the oxygen supply layer and the drainage groove in the fifth embodiment, and FIG. 11 is an explanatory view of a modified example of the structure of the drainage groove. In the fuel cell 40 of the fifth embodiment, a conductive fine particle layer (carbon particle layer 48) having a minute tissue opening is formed on the surface where the oxygen supply layer 47 is in contact with the membrane electrode assembly 26. A drainage groove 48M is formed in the fine particle layer. However, since the other configuration is the same as that of the fourth embodiment, FIG. 7 is also referred to, and the same reference numerals are given to the configurations common to FIGS. 8 and 9 and the detailed description is omitted.

  As shown in FIG. 10, in order to improve the electrical conductivity by improving the adhesion between the catalyst layer 26B of the membrane electrode assembly 26 and the oxygen supply layer 47, the particle size between the two layers is about 10 nm to 50 nm. A carbon particle layer 48 made of carbon particles and having a thickness of 50 μm was provided. The carbon particle layer 48 is provided with a drain groove 48M that opens to the catalyst layer 26B side. The carbon particle layer 48 is obtained by applying a mixed solution in which carbon powder is dispersed in a volatile liquid on a carbon cloth oxygen supply layer 47 (using the same material as the diffusion layer 27 of the fourth embodiment) or a doctor blade method or a screen. It is produced by applying and drying by a printing method or the like.

  The drainage groove 48M is formed by pressing a male mold or wire against the surface of the semi-dried mixed liquid and transferring it. After the surface of the mixed liquid is rapidly dried, the whole can be gradually dried and shrunk to form shrinkage cracks on the surface. That is, it can be formed by adjusting the drying atmosphere and drying time in the drying process.

  Alternatively, the drainage groove 48M can also be formed by applying the liquid mixture on the concavely curved diffusion layer 27 and drying it, and then returning the diffusion layer 27 to a flat shape to form an intentional crack pattern. Drainage that extends in the direction (see FIG. 4) in which moisture is to be transported when the diffusion layer 27 is flattened by curving in a direction perpendicular to the direction in which moisture is to be transported and applying / drying the mixture. A groove 48M can be formed.

  The catalyst layer 26B of the membrane electrode assembly 26 is required to have high electron conductivity, high hydrogen ion conductivity, and high oxygen diffusibility. Therefore, it is desirable to dispose the catalyst fine particle reaction sites in the catalyst layer 26B close to the ion transmission layer with high density while saving the total amount of catalyst metal used. Therefore, on the catalyst layer 26B, catalyst-supported carbon and polymer electrolyte in which ultrafine catalyst metal particles such as platinum particles having a particle size of about 1 to 5 nm are dispersed / attached on the surface of carbon carrier particles having a particle size of about 50 nm. A solution mixed with a solution and applied / dried is used.

  In the catalyst layer 26B thus formed, countless voids of about 0.1 μm are generated due to secondary aggregation during drying of the carbon support particles. The void functions as an oxygen diffusion path and a generated water discharge path.

  For this reason, as for the drain groove 48M provided in the adjacent carbon particle layer 48, it is desirable for the groove width a by the side of the catalyst layer 26B to be 0.1 micrometer or more and 1 mm or less. The drainage groove 27M (FIG. 8) provided in the diffusion layer 27 is the same. If the groove width a of the drain groove 48M (27M) is larger than the size of the gap existing in the catalyst layer 26B, the liquid water present in the gap of the catalyst layer 26B naturally moves to the drain groove 48M (27M) by capillary action. . Thereby, excess water is efficiently removed from the catalyst layer 26B. The groove width a is the diameter of the cross-sectional shape if the drainage groove has a circular or semicircular cross-sectional shape, and the width of the drainage groove is in contact with the catalyst layer 26B in the case of a polygonal shape.

  As shown in FIG. 11, when the drainage groove 48N is provided in the carbon particle layer 48 located between the catalyst layer 26B and the oxygen supply layer 47 of the membrane electrode assembly 26, the drainage groove 48N penetrates the carbon particle layer 48. It may be. The drainage groove 48N not only opens to the catalyst layer 26B side, but also opens to the oxygen supply layer 47.

  At this time, if the gap between carbon fibers such as carbon cloth used for the oxygen supply layer 47 is about 1 μm, the groove width b on the oxygen supply layer 47 side is preferably 1 μm to 1 mm. If the groove width b of the drainage groove 48N is made larger than the space of the tissue of the oxygen supply layer 47, the water accumulated in the space of the tissue of the oxygen supply layer 47 can be efficiently sucked up by capillary action. is there.

  The size and distribution state of the voids in the structure of the catalyst layer 26B and the oxygen supply layer 47 can be measured using methods such as a mercury porosimeter and a gas adsorption method. Using these methods, the void distribution of the catalyst layer 26B and the oxygen supply layer 47 is measured. The groove width a on the catalyst layer 26B side is larger than the measured main void diameter of the catalyst layer 26B, and the groove width b on the oxygen supply layer 47 side is larger than the main void diameter of the oxygen supply layer 47. It is desirable to form drainage grooves 48N satisfying such a relationship in the carbon particle layer 48. However, the groove widths a and b do not exceed 1 mm. This is because if the thickness exceeds 1 mm, the mass of the liquid water to be driven becomes too large compared to the driving force due to surface tension or capillary action, and the liquid water will not move.

<Sixth Embodiment>
The drainage groove 48M was formed by controlling the conditions for forming the carbon layer 34 shown in FIG. 10 and forming intentional dry cracks. And drainage performance was confirmed. 12 is an explanatory diagram of X-ray imaging for measuring the water distribution of the fuel cell during operation, FIG. 13 is a captured image of the liquid water distribution in the plane of the carbon particle layer, and FIG. 14 is the liquid in the cross section of the power generation cell. It is a photographed image of water distribution. 13 and 14, (a) is a captured image, and (b) is a binarized image for helping understanding.

  As shown in FIG. 10, platinum-supported carbon catalyst layers were prepared on both surfaces of the polymer electrolyte membrane 26A as the catalyst layers 26B and 26C of the membrane electrode assembly 26. As a transfer layer to the polymer electrolyte membrane 26A, a platinum-supported carbon catalyst layer was formed on a fluororesin (PTFE) sheet using a doctor blade method. The applied catalyst slurry is a mixture of platinum-supported carbon (manufactured by Johnson Matthey), Nafion (manufactured by DuPont), PTFE, IPA, and water. A solid polymer electrolyte membrane (manufactured by DuPont) 26A is sandwiched between catalyst layers 26B and 26C on a PTFE sheet semi-dried after coating, and hot pressing is performed under press conditions of 8 MPa, 150 ° C., and 1 min. Then, the catalyst layers 26B and 26C are produced on both surfaces of the polymer electrolyte membrane 26A by peeling off the PTFE sheets on both surfaces.

  Next, a carbon particle layer 48 is formed on the surface of the oxygen supply layer 47 (carbon cloth). Carbon powder and PTFE powder are mixed at an equal weight ratio, sufficiently pulverized / stirred, and then ethanol and pure water are added and mixed. The obtained mixed solution is applied onto the oxygen supply layer 47 by a doctor blade method, and then slowly dried at room temperature to form a carbon particle layer 48 and an oxygen supply layer 47.

  Next, the catalyst layer 26B and the carbon particle layer 48 were brought into contact with each other, and the oxygen supply layer 47 and the fuel supply layer 25 (FIG. 7) were stacked on the membrane electrode assembly 26 and integrated by pressure bonding. Finally, the integrated whole is sandwiched between separators 24 and 28 (FIG. 7) that also serve as current collecting metal electrodes and stacked in a plurality of stages to form a cell stack 20A (FIG. 7). Parts required for the cell stack 20A were assembled to obtain a polymer electrolyte fuel cell 20.

  Next, in order to confirm that the drainage groove 48M formed in the carbon particle layer 48 functions as a drainage channel, as shown in FIG. A transmission image was taken by irradiating the line 51. The transmission image was analyzed to measure the absorption change and refraction effect of the X-ray 51.

  X-rays 51 emitted from the X-ray source are formed into the size of the measurement region and then enter the polymer electrolyte fuel cell 20. X-rays 52 that have passed through the fuel cell 20 are detected by a two-dimensional detector (X-ray CCD camera) 53. The amount of absorption of each member of the fuel cell 20 with respect to the X-ray 51 does not change before and during the operation of the fuel cell 20. However, during operation, the absorptance of X-rays that pass through the fuel cell 20 varies depending on the amount of water aggregated by the power generation reaction. Therefore, by measuring the amount of change in the absorptance, the water distribution inside the surface of the membrane electrode assembly 26 and the surface and the change in the amount of aggregation were visualized as shown in FIGS.

  As shown in FIG. 13, a mesh-like water channel 67 having a width of 30 to 50 μm is formed in the plane of the catalyst layer 26 </ b> B with good reproducibility when the fuel cell 20 is driven.

  As shown in FIG. 14, in the cross section of the fuel cell 20, what functioned as the water channel 67 is a drainage groove (48M: FIG. 10) formed in the carbon particle layer 48 and opened to the catalyst layer 26B side. It has been found. A part of the water channel 67 reaches the oxygen supply layer 47 like a drain groove 48N shown in FIG. Thereby, it was confirmed that the drain grooves 48M of the carbon particle layer 48 using the drying shrinkage cracks are effective in discharging the liquid water on the surface of the catalyst layer 26B.

  The distribution shape of the drain grooves 48M in the plane of the catalyst layer 26B is not particularly limited. It may be spread in the form of a mesh shown in FIG. 13, or may be regularly arranged in a certain direction shown in FIG. By configuring the diffusion layer 27 side shown in FIG. 7 as in the sixth embodiment, a great effect is exhibited. However, by implementing the configuration of the sixth embodiment also on the fuel supply layer 25 side, it is possible to quickly move excess water that has been reversely diffused from the diffusion layer 27 side from the excess region to the insufficient region, preferable.

  Therefore, in the configurations of the fourth to sixth embodiments, by specifying the shape of the drain grooves 27M and 48M formed in the diffusion layers 27 and 47, excess generated water can be quickly removed from the catalyst layer 26B or the diffusion layers 27 and 47. Can be discharged. As a result, the polymer electrolyte fuel cell 28 capable of stable operation can be provided.

<Fuel cell of comparative example>
The polymer electrolyte fuel cell is expected as a future energy source because it has a high energy change rate and is quiet in addition to being clean. Its applications range from large ones such as automobiles and household power supplies to small ones that are mounted on devices such as notebook computers, mobile phones, and digital cameras. The life of such a small fuel cell is expected to be longer than that of a conventional secondary battery, and has been actively developed.

  FIG. 15 is an explanatory view of a typical example of the cross-sectional shape of the polymer electrolyte fuel cell, and FIG. 16 is an explanatory view of the configuration of the power generation cell. As shown in FIGS. 15 and 16, the solid polymer fuel cell has a polymer electrolyte membrane 104 at the center. In many cases, the fuel electrode is supplied to one side of the fuel and serves as an anode, and the other side of the fuel electrode is provided with an oxidant and serves as a cathode. Each pole has diffusion layers 103 and 105 for diffusing fuel or oxidant on the outside and collecting generated power. Supply channel members 102 and 106 for supplying fuel or oxidant to the entire power generation cell 100S are provided outside the diffusion layers 103 and 105.

  As the members of the diffusion layers 103 and 105, for example, carbon cloth is used as a conductive porous medium. Although nothing is installed in the supply flow path materials 102 and 106, a porous medium having a high porosity may be installed as a current collecting and supporting member.

  The fuel or oxidant is supplied through the supply flow path materials 102 and 106 by a method such as pressure by a pump, natural diffusion or natural convection, for example. The fuel or oxidant diffuses from the supply channel materials 102 and 106 through the diffusion layers 103 and 105 and reaches the polymer electrolyte membrane 104, respectively.

  At the anode of the polymer electrolyte membrane 104, the reached fuel is oxidized by the oxidizing action of the catalyst of the anode, becomes hydrogen ions, and moves through the polymer electrolyte membrane 104 toward the cathode. As this fuel, a gas such as hydrogen gas or a liquid such as methanol / ethanol is used.

  At the cathode of the polymer electrolyte membrane 104, an oxidizing agent, for example, oxygen that has reached the supply channel material 102 through the diffusion layer 103 and hydrogen ions that have moved through the polymer electrolyte membrane 104 react with the oxidizing agent to generate water molecules. Generated. A part of the energy generated by this series of chemical reactions is taken out as electric energy.

  As described above, water is generated by the power generation reaction at the cathode of the polymer electrolyte membrane 104. This water usually becomes water vapor or droplet water, moves from the diffusion layer of the oxidant to the flow path, and is discharged. In some cases, the MEA may pass through and be discharged from the anode side. At this time, when the fuel or oxidant is supplied using a pump, the water moves together with the fuel or oxidant as it is depending on the pressure of the pump and is discharged from the discharge port.

  In general, since a fuel cell cannot obtain sufficient power by itself, it has a cell stack structure in which several power generation cells as described above are stacked in series (see FIG. 1). This type of fuel cell is attracting attention mainly as a power source for automobiles that replace gasoline and as a cogeneration application for business use or home use.

  In recent years, since the use is expected also as a battery of portable electronic devices, such as a notebook personal computer and PDA, the whole fuel cell system must be reduced in size extremely. For this reason, since a control mechanism such as a fuel or oxidant supply device using a pressure gradient cannot be used, the fuel and the oxidant must be supplied by diffusion or natural convection.

  Patent Document 1 discloses a technique of a passive fuel cell that supplies oxygen as an oxidant by natural diffusion. FIG. 4 of Patent Document 1 shows the structure of the power generation cell. Oxygen as an oxidant diffuses through the diffusion cell unit 39 and reaches the MEA 55. Hydrogen as fuel is supplied from the flow path 58 and reaches the MEA 55.

  A polymer electrolyte fuel cell generates electricity, heat, and water by electrochemically reacting a fuel such as hydrogen and an oxidant such as air using a hydrogen ion conductive solid polymer membrane as an electrolyte. Let The polymer electrolyte fuel cell can be operated at a relatively low temperature from room temperature to about 100 ° C., and a high output density can be obtained. For this reason, compared with other fuel cells, it has excellent startability and can be reduced in size and weight.

  A general power generation unit of a polymer electrolyte fuel cell has a catalyst layer on both sides of a polymer electrolyte membrane, a gas diffusion layer is disposed so as to sandwich the catalyst layer, and a fuel electrode (anode) so as to sandwich them. The electrode of the air electrode (cathode) is arranged. Then, power generation is performed by flowing a fuel containing hydrogen from the anode side and air from the cathode side.

  The polymer electrolyte membrane plays a role of isolating the anode side and the cathode side so that the fuel and the oxidant do not directly react and transporting hydrogen ions generated on the anode side to the cathode side. In general, fluorine resin ion exchange membranes having excellent durability are widely used. In the polymer electrolyte membrane, since hydrogen ions move in the membrane with water, the membrane needs to contain sufficient moisture in order to obtain high hydrogen ion conductivity.

  The catalyst layer formed on the surface of the polymer electrolyte membrane carries platinum fine particles having a particle size of about 1 to 5 nm on carbon particles having a particle size of several tens of nm in order to achieve high catalyst performance and a large reaction area. Often used is platinum-supported carbon. In such a catalyst layer, voids of about 0.1 μm are present due to secondary aggregation of the carbon particles, and this gap serves as a reaction gas inflow passage and a generated water drainage passage. The electrode reaction in such a catalyst layer is said to occur at the part called the three-phase interface where the catalyst such as platinum, the polymer electrolyte, and the reaction gas are in contact. It is important to realize the battery.

  For the diffusion layer, a conductive porous material such as carbon cloth or carbon paper that is excellent in gas permeability and conductivity is generally used. These carbon fibers form voids of about 1 μm, which serve as reaction gas inflow passages and product water drainage passages. Since the diffusion layer is disposed so as to sandwich the electrolyte membrane and the catalyst layer, it is necessary to have a good balance between drainage for the catalyst layer and moisture retention for the polymer electrolyte membrane.

  In general, in a polymer electrolyte fuel cell, a power generation cell is configured by sandwiching a power generation unit with a separator having a reaction gas flow path. Furthermore, a fuel cell is configured by stacking power generation cells and connecting them in series.

<Correspondence with Invention>
The fuel cell 10 according to the first embodiment includes a membrane electrode assembly 4 that generates power by moving hydrogen ions from one surface to the other surface, and oxygen that is disposed on the one surface side and reacts with hydrogen ions. An oxygen flow path material 2 and a diffusion layer 3 are provided to diffuse and supply to the one surface. A drainage groove 3 </ b> M is formed on the surface of the diffusion layer 3 on the side of the membrane electrode assembly 4, which has higher liquid water retention than the surrounding diffusion layer 3.

  The fuel cell 10 collects liquid water that causes partial submersion of the membrane electrode assembly 4 in the drainage groove 3M and moves it in a state of liquid water in a direction along the drainage groove 3M. The drainage groove 3M having higher retention of liquid water than the surroundings prevents the liquid water on the surface of the membrane electrode assembly 4 from being sucked to cover the surface of the membrane electrode assembly 4, and the drainage groove 3M exceeds the width of the drainage groove 3M. Submergence is suppressed.

  And since the force which the drainage groove | channel 3M collects liquid water forms the flow of the liquid water along the drainage groove 3M, the uneven distribution of the liquid water on the surface of the membrane electrode assembly 4 causes the liquid water to pass through the drainage groove 3M. Averaged by movement.

  Since water moves from the excess region to the insufficient region in the state of liquid water, the wetness of the membrane electrode assembly 4 is also made uniform immediately after the start of power generation. In the case of a polymer electrolyte membrane, the membrane electrode assembly 4 High power generation performance (electromotive force) can be extracted from the whole. The movement of liquid water through the drainage groove 3M does not increase the partial pressure of water vapor in the oxygen channel material 2 and the diffusion layer 3 as much as when the entire amount is moved in the state of water vapor. The performance of discharging water vapor to the outside is maintained high. The diffusion of oxygen in the reverse direction through the oxygen channel material 2 and the diffusion layer 3 is also smooth.

  Therefore, even if the current value per surface area of the membrane / electrode assembly 4 is set high, a local submerged region of the membrane / electrode assembly 4 is hardly generated. Using the membrane electrode assembly 4 having a small area, a large current can be output without relying on an air circulation mechanism or a blower. While realizing high reliability, long life, and high performance, it is possible to provide a fuel cell 10 that is small, lightweight, and inexpensive with a small number of parts.

  In the membrane electrode assembly 26 of the fuel cell 20, a conductive catalyst layer 26B is integrally formed on the surface of the polymer electrolyte membrane 26A, and a drain groove 27M is formed on the surface where the diffusion layer 27 is in contact with the membrane electrode assembly 26. Is formed.

  The width of the drain groove 27M on the catalyst layer 26B side is larger than the average opening diameter of the structure of the catalyst layer 26B.

  The width of the drain groove 3M of the fuel cell 10 is not less than 5 μm and not more than 1000 μm.

  The power generation cell 10 </ b> S includes an oxygen flow channel material 2 having air permeability and a diffusion layer formed on the surface of the oxygen flow channel material 2 on the membrane electrode assembly 4 side and having a smaller opening than the oxygen flow channel material 2. 3 has an oxygen supply layer. A drainage groove 3M is formed on the surface where the diffusion layer 3 is in contact with the membrane electrode assembly 4.

  The diffusion layer 47 of the fifth embodiment has a conductive carbon particle layer 48 having an average opening diameter of the tissue smaller than that of the diffusion layer 47 on the surface in contact with the membrane electrode assembly 26. The drainage groove 48N is formed to a depth that penetrates the carbon fine particle layer 48 and reaches the diffusion layer 47, and the width of the drainage groove 48N on the separator 28 side that also serves as the oxygen channel material is larger than the average opening diameter of the diffusion layer 47. Is also big.

  In the fuel cell 10, the power generation cells 10 </ b> S including the membrane electrode assembly 4, the oxygen channel material 2, and the diffusion layer 3 are stacked and connected in series. An air intake port 8 that is opened to the atmosphere and discharges moisture generated in the membrane electrode assembly 4 to the atmosphere is disposed on the side surface side of the power generation cell 10S. The drainage groove 3M is formed in a direction toward the air intake 8.

  A plurality of drain grooves 3 </ b> N in the second embodiment are arranged in parallel in contact with the side surface facing the air intake 8, and the cross-sectional area of the drain grooves 3 </ b> M gradually increases toward the air intake 8.

  A plurality of drain grooves 3 </ b> P in the third embodiment are arranged in parallel in contact with the side surface facing the air intake port 8, branching toward the air intake port 8 and increasing in number.

  The fuel cell 10 is water repellent because the region of the oxygen channel material 2 at least including the drain groove 3M is a carbon fiber.

  In the sixth embodiment, a mixed liquid of carbon particles and a volatile solvent is applied to the surface of the oxygen supply layer 47 having three-dimensional air permeability, and the mixed liquid applied to the surface is dried to remove the solvent. It is evaporating. As a result, minute drying shrinkage cracks were formed in the carbon particle layer 48 of the carbon particles to form the drain grooves 48N.

  It can be formed by the method of the drainage groove 48M or less of the fifth embodiment. A mixed liquid of carbon particles and a volatile solvent is applied to the surface of the oxygen supply layer 47 having three-dimensional air permeability, and the applied mixed liquid is dried. After that, the oxygen supply layer 47 was deformed in the direction of enlarging the surface, and a fine fracture crack was formed in the carbon particle layer 48 of carbon particles to form a drain groove 48M.

  The oxygen flow path member 2 in the first embodiment diffuses oxygen taken from the side surface side of the plate-like appearance to one plane side through the air intake ports 8 respectively formed on the pair of opposed side surfaces of the fuel cell 10. Supply. And it has many drain grooves 3M which connect a pair of side surface side which faces the air intake port 8 in the said plane side.

  In the oxygen flow path member 2 according to the second embodiment, the cross-sectional area of the drainage grooves 3N gradually increases toward the side surface of the numerous drainage grooves 3N.

  In the oxygen nucleic acid layer 2 according to the third embodiment, the number of drainage grooves 3P is branched toward the side surface and the number of the drainage grooves 3P is increased.

It is explanatory drawing of the whole structure of the fuel cell of 1st Embodiment. It is explanatory drawing of a structure of the power generation cell seen from the air intake side. It is explanatory drawing of a structure of the power generation cell seen from the direction which put the air intake side. It is a perspective view of an oxygen supply layer. It is explanatory drawing of the structure of the oxygen supply layer in 2nd Embodiment. It is explanatory drawing of the structure of the oxygen supply layer in 3rd Embodiment. It is a perspective view explaining the structure of the fuel cell of 4th Embodiment. It is explanatory drawing of the cross-sectional shape of the drainage groove formed in the diffusion layer. It is explanatory drawing of the modification of the cross-sectional shape of a drainage groove. It is explanatory drawing of the structure of the oxygen supply layer and drainage in 5th Embodiment. It is explanatory drawing of the modification of the structure of a drainage groove. It is explanatory drawing of the X-ray imaging for measuring the water distribution of the fuel cell in driving | operation. It is a figure which shows the picked-up image of the liquid water distribution in the plane of a carbon particle layer. It is a figure which shows the picked-up image of the liquid water distribution in the cross section of a power generation cell. It is explanatory drawing of the typical example of the cross-sectional shape of a polymer electrolyte fuel cell. It is explanatory drawing of a structure of a power generation cell.

Explanation of symbols

2, 3, 27, 47 Oxygen supply layer (oxygen channel material, diffusion layer)
3, 47 Diffusion layer 4, 26 Power generation layer member (membrane electrode assembly)
5, 25 Fuel supply layer (fuel channel material)
6 Fuel channel material 8 Opening (air intake)
1, 7, 9, 24, 28 Separator 10, 20 Fuel cell 10A Cell stack 10B Fuel tank 10S Power generation cell 26A Polymer electrolyte membrane 26B, 26C Catalyst layer 48 Fine particle layer (carbon particle layer)
3M, 3N, 3P, 27M, 48M, 48N

Claims (15)

A power generation layer member for generating power by moving hydrogen ions from one surface to the other surface;
A fuel cell comprising: an oxygen supply layer disposed on the one surface side and supplying oxygen to be reacted with the hydrogen ions by diffusing to the one surface;
The fuel cell according to claim 1, wherein a drainage groove having a higher retention of liquid water than the surrounding oxygen supply layer is formed on a surface of the oxygen supply layer on the power generation layer member side. The power generation layer member is a membrane electrode assembly in which a conductive catalyst layer is integrally formed on the surface of a polymer electrolyte membrane,
2. The fuel cell according to claim 1, wherein the drainage groove is formed on a surface where the oxygen supply layer is in contact with the membrane electrode assembly.   The fuel cell according to claim 2, wherein the width of the drainage groove on the catalyst layer side is larger than an average opening diameter of the structure of the catalyst layer.   The fuel cell according to claim 3, wherein the drainage groove has a width of 5 μm to 1000 μm. An oxygen carrying layer with breathability,
The oxygen supply layer has a conductive diffusion layer formed on a surface of the oxygen carrying layer on the power generation layer member side and having a finer opening than the oxygen carrying layer,
5. The fuel cell according to claim 1, wherein the drainage groove is formed on a surface of the diffusion layer in contact with the membrane electrode assembly. The diffusion layer has a conductive fine particle layer having a smaller average opening diameter of the tissue than the diffusion layer on the surface in contact with the membrane electrode assembly,
The drainage groove is formed to a depth reaching the diffusion layer through the fine particle layer,
6. The fuel cell according to claim 5, wherein a width of the drainage groove on the oxygen carrying layer side is larger than the average opening diameter of the diffusion layer. A power generation cell including the power generation layer member and the oxygen supply layer is stacked and connected in series,
An opening that is open to the atmosphere and discharges moisture generated by the power generation layer member to the atmosphere is disposed on the side of the power generation cell,
The fuel cell according to claim 1, wherein the drainage groove is formed in a direction toward the opening. A plurality of the drain grooves are arranged in parallel in contact with the side surface of the oxygen supply layer facing the opening,
The fuel cell according to claim 7, wherein a cross-sectional area of the drainage groove gradually increases toward the opening. A plurality of the drain grooves are arranged in parallel in contact with the side surface of the oxygen supply layer facing the opening,
The fuel cell according to claim 7, wherein the number of the fuel cells is increased by branching toward the opening.   The fuel cell according to any one of claims 1 to 9, wherein a region having a depth including at least the drainage groove in the oxygen supply layer is water repellent. Applying a mixture of carbon particles and a volatile solvent to the surface of the diffusion layer,
7. The drainage groove is formed by forming a fine drying shrinkage crack in the fine particle layer of the carbon particles by drying the mixed solution applied to the surface and evaporating the solvent. Fuel cell manufacturing method. Applying a mixture of carbon particles and a solvent to the surface of the diffusion layer,
After solidifying the mixed solution applied to the surface, the diffusion layer is deformed in the direction of expanding the surface, and a minute fracture crack is formed in the fine particle layer of the carbon particles to form the drainage groove. The method for producing a fuel cell according to claim 6. In the oxygen supply layer that diffuses and supplies oxygen taken from the side surface side of the plate-like appearance to the bottom surface side of one through the openings formed on the pair of opposing side surfaces of the power generation cell,
An oxygen supply layer having a plurality of drainage grooves connecting the pair of side surfaces facing the opening on the one bottom surface side.   The oxygen supply layer according to claim 13, wherein the drainage grooves have a cross-sectional area that gradually increases toward the opening. The oxygen supply layer according to claim 13 or 14, wherein the number of drain grooves is diverging toward the opening to increase the number of drain grooves.

Images