Patent Application
20240120510
The present invention relates to a gas diffusion layer, a separator, and an electrochemical reactor (an electrochemical reaction device).
In the technical field of a polymer electrolyte fuel cell (PEFC), there has been known a fuel cell stack capable of uniformly supplying and defusing a fuel cell gas (an anode gas, a cathode gas) (for example, see WO2015/072584).
The conventional fuel cell stack 920 has, as described in
In the field of the electrochemistry, the generation of power using a chemical reaction of gases and an electrolysis are two sides of the same coin. As described above, it is considered that the fuel cell gas supply diffusion layer, the separator and the fuel cell stack can be converted into an electrolysis (the generation of a cathode gas and an anode gas) by using water in place of a gas while substantially maintaining the same configuration. Further, the fuel cell gas supply diffusion layer, the separator and the fuel cell stack can be converted into a methanol fuel cell (a methanol aqueous solution anode, an air cathode), a lithium ion-air cell (air cathode) or a redox flow cell (anode and cathode for supplying vanadium ion aqueous solution) that uses a liquid that is a fluid in the same manner as a gas in place of a gas while maintaining the same configuration. Accordingly, in this specification, as the expression that includes “fuel cell gas supply diffusion layer” (expression irrelevant to fuel cell use and electrolysis use), “gas diffusion layer” is used. As the expression that includes “fuel cell stack”, “electrochemical reactor” is used. The “gas diffusion layer” roughly means the “layer mainly provided for diffusing a gas”, and includes a layer that allows the diffusion or the communication of a substance other than a gas (particularly, a liquid such as water) in the layer.
By the way, in the technical field of electro chemistry, there has been a request for a technique that can increase reaction efficiency (power generation efficiency in case of a fuel cell) compared to the prior art. In view of such circumstances, it is an object of the present invention to provide a gas diffusion layer, a separator and an electrochemical reactor that can exhibit high reaction efficiency compared to the prior art.
A gas diffusion layer according to an aspect of the present invention is a gas diffusion layer that includes: a sheet-shaped porous body layer having conductivity, the porous body layer allowing permeation and diffusion of a gas therethrough; and a plurality of gas flow path grooves formed on one surface of the porous body layer in a direction directed from a gas inflow side to a gas outflow side, wherein the plurality of gas flow path grooves includes: a plurality of gas inflow side grooves formed on the gas inflow side and a plurality of gas outflow side grooves formed on the gas outflow side, and the plurality of gas inflow side grooves include two or more kinds of gas inflow side grooves that have different lengths.
A separator according to one aspect of the present invention is a separator that includes: a gas shied plate; and a gas diffusion layer disposed on at least one surface of the gas shield plate, wherein the gas diffusion layer is the gas diffusion layer of the present invention, is disposed with respect to the gas shield plate such that the plurality of gas flow path grooves are positioned on a gas shield plate side, and a gas flow path is formed by the gas flow path groove and the gas shield plate.
An electrochemical reactor according to one aspect of the present invention is an electrochemical reactor formed by stacking a separator and a membrane electrode assembly, wherein the separator is a separator according to the present invention, and the separator and the membrane electrode assembly are stacked with a positional relationship where the membrane electrode assembly is positioned on a surface of the gas diffusion layer on a side where the plurality of gas flow path grooves are not formed.
According to the present invention, it is possible to provide a gas diffusion layer, a separator and an electrochemical reactor that can increase reaction efficiency compared to the prior art.
Hereinafter, a gas diffusion layer, a separator and an electrochemical reactor according to the present invention are described in detail with reference to embodiments illustrated in the drawings.
The fuel cell stack 20 (electrochemical reactor) according to an embodiment 1 is a fuel cell stack formed by stacking fuel cell separators 21, 22, 23A, 24 (separators) and membrane electrode assemblies 81. To further describe the configuration, the fuel cell stack 20 is a solid polymer fuel cell (PEFC: Polymer Electrolyte Fuel Cell). The fuel cell stack 20 includes a plurality of single cells. Each cell of the fuel cell stack 20 includes: the membrane electrode assembly 81; and an element that forms a cathode side and an element that forms an anode side in a state where these elements sandwich the membrane electrode assembly 81 therebetween.
In the fuel cell separator 21 (the separator of a type CA), a cathode gas supply diffusion layer C is formed on one surface of a metal plate 30 (gas shielding plate), and an anode gas supply diffusion layer A is formed on the other surface of the metal plate 30. In the fuel cell separator 22 (the separator of a type A), an anode gas supply diffusion layer A is formed on one surface of a metal plate 30. In the fuel cell separator 23A (the separator of a type C), a cathode gas supply diffusion layer C is formed on one surface of a metal plate 30. In the fuel cell separator 24 (the separator of a type CW), a cathode gas supply diffusion layer C is formed on one surface of the metal plate 30, and a cooling water supply diffusion layer W is formed on the other surface.
The respective cells are arranged such that a cathode side and an anode side appear alternately. The cathode gas supply diffusion layer C and the anode gas supply diffusion layer A are disposed on sides opposite to each other with the membrane electrode assembly (MEA) 81 sandwiched therebetween. In the embodiment, the cooling water supply diffusion layer W for supplying cooling water is provided each time two single cells are arranged. The cooling water supply diffusion layer W may be disposed every one single cell, or may be disposed every three or more single cells. The fuel cell separators 21, 22, 23A, 24 are stacked in a combined manner such that the metal plate 30 (preferably the metal plate 30 of the separator of a type A or the separator of a type C) faces the cooling water supply diffusion layer W.
Although not illustrated in
Current collectors 27A, 27B are disposed on both end portions of the stacked cells. Further, outside the current collectors 27A, 27B, end plates 75, 76 are disposed by way of insulation sheets 28A, 28B. The fuel cell separators 21, 22, 23A, 24, are pressed from both sides by the end plates 75, 76. With respect to the separators that are positioned on both ends of the fuel cell stack 20 and are brought into contact with the current collectors 27A, 27B, it is preferable that the metal plates 30 (corrosion layers) of the separators be directed outward.
In
On one end portion of the end plate 75 on an anode side, an anode gas supply port 71in, a cathode gas discharge port 72out and a cooling water discharge port 73out are respectively formed. On the other hand, on one end portion of the end plate 76 on a cathode side (a side opposite to the above-mentioned one end portion of the end plate 75), an anode gas discharge port 71out, a cathode gas supply port 72in, and a cooling water supply port 73in (in
The fuel cell separators 21, 22, 23A, and 24 each include: an anode gas inlet port 61in that communicates with the anode gas supply port 71in; a cathode gas (and generated water) outlet port 62out that communicates with the cathode gas discharge port 72out, and a cooling water outlet port 63out that communicates with the cooling water discharge port 73out. Further, the fuel cell separators 21, 22, 23A, and 24 each include: an anode gas outlet port 61out that communicates with the anode gas discharge port 71out; a cathode gas inlet port 62in that communicates with the cathode gas supply port 72in, and a cooling water inlet port 63in that communicates with a cooling water supply port 73in.
A cathode gas, an anode gas, and cooling water are supplied through the anode gas supply port 71in, the cathode gas supply port 72in and the cooling water supply port 73in. In the embodiment 1, the case is exemplified where a hydrogen gas is used as an anode gas, and air is used as a cathode gas.
Next, the membrane electrode assembly 81 is described.
As shown in
Next, the fuel cell gas supply diffusion layer 42A (gas supply diffusion layer) is described by taking the fuel cell separator 23A as an example.
Although
As illustrated in
In the fuel cell separator 23A, at one end portion (a lower portion InFIG. 4) ofthemetalplate 30 in a longitudinal direction, the cathode gas inlet port 62in, the cooling water inlet port 63in, and the anode gas outlet port 61out are disposed in the order of the right, the center and the left in
A periphery of each of respective regions where the respective inlet ports 61in, 62in, 63in, the respective outlet ports 61out, 62out, 63out, and the fuel cell gas supply diffusion layer 42A are formed is surrounded by a dense frame 32 having electron conductivity or non-electron conductivity. The dense frame 32 prevents a leakage of an anode gas, a cathode gas, and cooling water. On an outer surface of the dense frame 32, a groove is formed along the dense frame 32 such that the groove surrounds a region where the respective inlet ports 61in, 62in, 63in, the respective outlet ports 61out, 62out, 63out, and the fuel cell gas supply diffusion layer 42A are formed (not illustrated in the drawing). A gasket (a seal member such as a packing, or an O ring) 33 is disposed in this groove.
On both surfaces of the metal plate 30, except for portions where the respective inlet ports 61in, 62in, 63in and the respective outlet ports 61out, 62out, and 63out are formed as described above, a corrosion layer having electron conductivity (not illustrated in
The fuel cell separator 23A is a separator of a type C. As illustrated in
In this specification, “from the inflow side to the outflow side of the gas” means “substantially along the direction that the gas flows”, and the direction that “a gas flows from the inflow side to the outflow side” is the direction that a gas in the porous body layer 40 flows in a case where the porous body layer 40 is viewed as a whole. This means that, in the case where the cathode gas inlet port 62in and the cathode gas outlet port 62out are arranged at positions on a diagonal line of the metal plate 30 like the fuel cell gas supply diffusion layer 42A according to the embodiment 1, it is unnecessary that gas flow paths are formed along the above-mentioned diagonal line. That is, as described in the embodiment 1 with respect to the direction that “the gas flows from the inflow side to the outflow side”, in the case where “the direction of the flow of a gas in the porous body layer 40 when the porous body layer 40 is viewed as a whole extends in the vertical direction from a lower side to an upper side on a paper surface on which
The plurality of gas flow path grooves include: a plurality of the gas inflow side grooves 53a, 53b that are formed on the gas inflow side (a lower portion in
In the fuel cell gas supply diffusion layer 42A, the two gas inflow side grooves 53a, 53b disposed adjacently to each other have different lengths (see
In this specification, “at least one gas inflow side groove has a length different from lengths of other gas inflow side grooves out of three gas inflow side grooves disposed adjacently to each other” and “at least one gas inflow side groove has a length different from lengths of other gas inflow side grooves out of four gas inflow side grooves disposed adjacently to each other” mean “to define three gas inflow side grooves disposed adjacently to each other as one set of gas inflow side groove group, whichever set of gas inflow side groove group is viewed out of a plurality of set of gas inflow side groove groups included in the gas diffusion layer, at least one gas inflow side groove has a length different from lengths of other gas inflow side grooves out of three gas inflow side grooves” and “to define four gas inflow side grooves disposed adjacently to each other as one set of gas inflow side groove group, whichever set of gas inflow side groove group is viewed out of a plurality of set of gas inflow side groove groups included in the gas diffusion layer, at least one gas inflow side groove has a length different from lengths of other gas inflow side grooves out of four gas inflow side grooves”. The same goes for the case of the gas outflow side grooves described later.
In the fuel cell gas supply diffusion layer 42A, a plurality of gas outflow side grooves 54a, 54b include two kinds or more (in this case two kinds) gas outflow side grooves 54a, 54b having different lengths. Two gas outflow side grooves 54a, 54b disposed adjacently to each other have different lengths (see
In the fuel cell gas supply diffusion layer 42A, the gas inflow side grooves 53a having the shortest length out of the plurality of gas inflow side grooves 53a, 53b have a length less than 30% of the length of the porous body layer 40 along a flow path from the inflow side to the outflow side of the gas. The gas inflow side groove 53b having the longest length out of the plurality of gas inflow side grooves 53a, 53b has a length that is 40% or more of the length of the porous body layer 40 along a flow path from the inflow side to the outflow side of the gas.
In the fuel cell gas supply diffusion layer 42A, the gas inflow side groove 53a having the shortest length out of the plurality of gas inflow side grooves 53a, 53b has a length less than 30% of the length of the porous body layer 40 along a flow path from the inflow side to the outflow side of the gas. Further the gas outflow side groove 54b having the longest length out of the plurality of gas outflow side grooves 54a, 54b has a length that is 30% or more of the length of the porous body layer 40 along a flow path from the inflow side to the outflow side of the gas.
Further, the plurality of the gas flow path grooves include, in addition to the plurality of gas inflow side grooves 53a, 53b and the plurality of gas outflow side grooves 54a, 54b, a plurality of relay grooves 55a to 55d formed between the gas inflow side grooves 53a, 53b and the gas outflow side grooves 54a, 54b. The plurality of relay grooves 55a to 55d communicate with each other in the direction (x direction) perpendicular to the direction directed from the inflow side to the outflow side of the gas. To be more specific, the relay grooves 55a, 55b communicate with each other by a communication groove 56a, and the relay grooves 55c, 55d communicate with each other by a communication groove 56b (see
The plurality of gas inflow side grooves 53a, 53b, the plurality of gas outflow side grooves 54a, 54b and the plurality of relay grooves 55a to 55d are formed so as to be alternately interposed to each other (see
Air (an oxygen gas and a nitrogen gas) that forms a cathode gas diffuses in the porous body layer 40 (gas diffusion layer 43). The porous body layer 40 contains a mixture of an electrically conductive material (preferably a caron-based conductive material) and a polymer resin. By mixing the carbon conductive material in the polymer resin, it is possible to impart high conductivity to the polymer resin, and it is also possible to enhance moldability of a carbon material by bonding property of the polymer resin. The flow fluid resistance of the porous body layer 40 depends on porosity of the porous body layer and an area of surface of the porous body layer through which a fluid flows. The larger the porosity, the smaller the fluid resistance becomes. The larger the area through which the fluid flows, the smaller the fluid resistance becomes. As an approximately standard, in the fuel cell gas supply diffusion layer 42A (for a cathode gas), porosity of the porous body layer 40 is approximately 50% to 85%. With respect to the fuel cell gas supply diffusion layer 41 (for an anode gas), porosity of the porous body layer 40 is approximately 30% to 85%.
By setting porosity of the porous body layer 40 as described above, the communication of a cathode gas, vapor and condensed water between the gas flow path grooves and the porous body layer 40 is properly performed through inner surfaces of the plurality of gas flow path grooves. As a result, it is possible to uniformly supply a large amount of gas to the membrane electrode assembly. Further, it is possible to efficiently discharge a cathode gas that is not used at the time of generating electricity and vapor and condensed water generated at the time of generating electricity to the outside of the gas flow paths. As a result, it is not necessary to form a gas permeation filter where a large number of minute gas flow holes are formed in a gas impermeable layer made of metal, ceramics, a resin or the like on inner surfaces of the gas flow path grooves.
Porosity of the fuel cell gas supply diffusion layer 42A can be adjusted by adjusting the content of the carbon conductive material. As a result, the movement resistance of the fuel cell gas supply diffusion layer 42A can be adjusted. Particularly, in a case where the content of the carbon conductive material is increased, the movement resistance is decreased (porosity is increased). As an opposite case, in a case where the content of the carbon conductive material is decreased, the movement resistance is increased (porosity is decreased). Both the corrosion layer and the dense frame 32 are made of a mixture of a carbon conductive material and a polymer resin and hence, it is preferable to provide the corrosion layer and the dense frame 32 that are densified while ensuring conductivity by setting the content of the carbon conductive material to a suitable value.
The carbon conductive material is not particularly limited. For example, graphite, carbon black, diamond-coated carbon black, silicon carbide, titanium carbide, carbon fibers, carbon nanotubes and the like can be used. As a polymer resin, both a thermosetting resin and a thermoplastic resin can be used. As an example of the polymer resin, a phenol resin, an epoxy resin, a melamine resin, a rubber-based resin, a furan resin, a vinylidene fluoride resin and the like are named.
An inflow path 57 is formed between the cathode gas inlet port 62in and a region where the porous body layer 40 is formed (see
The porous body layer 40, the inflow path 57 and the outflow path 58 are formed having the same height (thickness) as the dense frame 32. Ona surface of the fuel cell gas supply diffusion layer 42A that opposedly face the metal plate 30, a plurality of gas flow path grooves each formed of a gap are formed. A plurality of gas flow paths are formed between these plurality of gas flow grooves and the metal plate 30. The plurality of gas inflow side grooves 53a, 53b communicate with the inflow path 57 by way of the gas inflow side stepped portion 51, and the plurality of gas outflow side grooves 54a, 54b communicate with the outflow paths 58 by way of the gas outflow side stepped portion 52. The numbers and the structures of the gas flow path grooves are not limited to the structures illustrated in the drawing.
A case is considered where the fuel cell gas supply diffusion layer 42A according to the embodiment 1 is used as a fuel cell for transportation equipment. In this case, although it depends on a kind and a size of the transportation equipment, a lateral width of the porous body layer 40 is approximately 30 mm to 300 mm, for example. A width of the gas flow path groove is approximately 0.3 mm to 2 mm, for example. A thickness of the porous body layer 40 is approximately 150 μm to 400 μm, for example. A depth of the gas flow path groove is 100 μm to 300 μm, for example. A distance between a bottom of the gas flow path groove and the other surface of the porous body layer 40 (a ceiling thickness) is approximately 100 μm to 300 μm, for example. In a case where the fuel cell gas supply diffusion layer 42A according to the embodiment 1 is used in a fuel cell or a device for electrolysis in applications other than transportation equipment (for example, stationary equipment), the sizes of the respective components are not limited to the above-mentioned sizes, and components having suitable sizes corresponding to required performances or the like can be used.
The fuel cell gas supply diffusion layer 41 in the fuel cell separator 22 of a type A also has basically substantially the same configuration as the fuel cell gas supply diffusion layer 42A. However, a gas supplied to the gas supply diffusion layer is a hydrogen gas and hence, the fuel cell gas supply diffusion layer 41 has lower porosity than the fuel cell gas supply diffusion layer 42A, and has a small thickness (see
In the fuel cell separator 21 of a type CA, as the gas diffusion layer, the fuel cell gas supply diffusion layer 41 and the fuel cell gas supply diffusion layer 42A are used (see
When the fuel cell stack 20 according to the embodiment 1 is operated, proton (WE) is generated at a fuel pole to which an anode gas (a hydrogen gas) is introduced. Proton diffuses in the membrane electrode assembly 81 and moves toward an oxygen pole side, and reacts with oxygen so as to generate water. The generated water is discharged from an oxygen pole side. At this stage of the operation, in the fuel cell separator 23A provided with the fuel cell gas supply diffusion layer 42A having the above-mentioned structure, air flown into the fuel cell separator 23A from the cathode gas inlet port 62in passes through the inflow path 57 and the gas inflow side stepped portion 51, and flows into the gas inflow side grooves 53a, 53b. A part of air that flows into the gas inflow side stepped portion 51 enters the gas flow path grooves, enters the porous body layer 40 (the gas diffusion layer 43) from the gas flow path grooves, while the other portion directly enters the porous body layer 40 (the gas diffusion layer 43) from an end surface of the porous body layer 40 (the gas diffusion layer 43), and diffuses in the porous body layer 40 (the gas diffusion layer 43).
Air diffuses also in a thickness direction while diffusing in an in-plane direction in the porous body layer 40 (gas diffusion layer 43), is supplied to the membrane electrode assembly 81 mounted on the porous body layer 40 (gas diffusion layer 43) in a state where the membrane electrode assembly 81 is in contact with the porous body layer 40, and contributes to a power generation reaction. A gas that is not used in power generation (an oxygen gas and a nitrogen gas not used) and water (vapor or condensed water) that is generated at the time of power generation flow out to the outflow path 58 through the porous body layer 40 (gas diffusion layer 43), the gas flow path groove and the gas outflow side stepped portion 52. An oxygen gas, a nitrogen gas, and water that flows out into the outflow path 58 is finally discharged from the outflow path 58 through the cathode gas outlet port 62out and the cathode gas discharge port 72out. At this stage of the operation, because of the structure of the fuel cell gas supply diffusion layer 42A, all water is not discharged and a portion of water remains in the porous body layer 40 (gas diffusion layer 43).
The fuel cell gas supply diffusion layer 42A according to the embodiment 1 includes the above-mentioned technical features. Accordingly, at the time of generating power, water (vapor or condensed water) generated by the membrane electrode assembly 81 can be efficiently discharged to the outside of the gas flow path through the porous body layer 40 and the gas flow path grooves.
According to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of gas flow path grooves (the gas inflow side grooves 53a, 53b, the gas outflow side grooves 54a, 54b and the relay grooves 55a to 55d) are formed on one surface of the porous body layer 40 and hence, the gas movement resistance is reduced compared to the prior art, whereby a large amount of gas can be supplied to the membrane electrode assembly compared to the prior art.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of gas flow path grooves are formed on one surface of the porous body layer 40 and hence, the supply of gas to the membrane electrode assembly 81 arranged on the other surface of the porous body layer 40 never fails to be performed through the porous body layer 40. Accordingly, a gas can be uniformly supplied to the membrane electrode assembly 81 compared to the case where the plurality of gas flow paths are opened from one surface to the other surface of the porous body layer 40.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of gas flow path grooves are formed on one surface of the porous body layer 40 and hence, the gas not used in the power generation (in this case, a cathode gas (an oxygen gas, a nitrogen gas) for the fuel cell) can be efficiently discharged to the outside of the gas flow path grooves through the porous body layer 40 and the gas flow path grooves. Further, in an underflow gas region formed between the plurality of gas inflow side grooves 53a, 53b and the plurality of gas outflow side grooves 54a, 54b, a gas that is not used for the power generation can be efficiently discharged to the outside of the gas flow path grooves in a form that the gas is pushed out into an underflow gas flow. Accordingly, the movement resistance of the gas can be maintained at a low level compared to the prior art and hence, the reaction gas concentration can be maintained at high level whereby it is possible to provide the gas diffusion layer where reaction efficiency (power generation efficiency of the fuel cell in the case of the embodiment 1) can be enhanced compared to the prior art.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of gas flow path grooves are formed on one surface of the porous body layer 40. Accordingly, moisture (vapor or condensed water) generated in the membrane electrode assembly 81 at the time of power generation can be efficiently discharged to the outside of the gas flow path grooves through the porous body layer 40 and the gas flow path grooves. Further, in the underflow gas region, the moisture (vapor or condensed water) can be efficiently discharged to the outside of the gas flow path grooves in a form that the moisture is pushed out by the underflow gas flow thus providing the gas diffusion layer having excellent water discharge ability compared to the prior art.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of the gas flow path grooves include the plurality of gas inflow side grooves 53a, 53b and the plurality of gas outflow side grooves 54a, 54b, and among these grooves, the plurality of gas inflow side grooves 53a, 53b include two or more kinds of gas inflow side grooves 53a, 53b having different lengths. Accordingly, out of the plurality of gas flow inflow side grooves, due to an action of the gas inflow side groove 53a having a relatively small length (an outflow side terminal portion), the porous body layer 40 in the inflow side region that is originally likely to be dried is minimally dried and hence, lowering of a reaction efficiency due to excessive drying of the porous body layer 40 can be suppressed. Further, out of the plurality of gas inflow side grooves 53a, 53b, due to an action of the gas inflow side grooves 53b having a relatively large length, moisture (vapor or condensed water) that is originally liable to be stagnated is efficiently discharged through the gas inflow side grooves 53b thus enhancing water discharge property. Further, in a region that is away from the inflow side region and where a gas pressure is originally liable to be lowered, the gas pressure is minimally lowered and hence, lowering of a reaction efficiency due to lowering of the gas pressure can be suppressed. With such advantages, the fuel cell gas supply diffusion layer 42A according to the embodiment 1 can increase a reaction efficiency (power generation efficiency of the fuel cell in the case of embodiment 1) compared to the prior art and, further, the fuel cell gas supply diffusion layer 42A according to the embodiment 1 becomes a gas diffusion layer having excellent water discharge property compared to the prior art.
Further, in the fuel cell gas supply diffusion layer 42A according to the embodiment 1, two gas inflow side grooves 53a, 53b disposed adjacently to each other have different lengths. That is, the positions of outflow side terminal portions (dead end portions) of two gas inflow side grooves 53a, 53b disposed adjacently along the above-mentioned x direction exist at locations spaced apart from each other in the above-mentioned y direction and hence, the flow outflow side terminal portions are further dispersed. Accordingly, the fuel cell gas supply diffusion layer 42A according to the embodiment 1 can further increase a reaction efficiency. The fuel cell gas supply diffusion layer 42A according to the embodiment 1 also becomes a gas diffusion layer having more excellent water discharge property.
In the present invention, out of four or three gas inflow side grooves disposed adjacently to each other, at least one gas inflow side groove may have a length different from the length of other gas inflow side grooves. Also in this case, the fuel cell gas supply diffusion layer acquires an advantageous effect of the same nature as in the case where two gas inflow side grooves disposed adjacently to each other have different lengths.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, out of the plurality of gas inflow side grooves 53a, 53b, the gas inflow side groove 53a having the shortest length has the length less than 30% of a length from a gas inflow side to a gas outflow side of the porous body layer 40 and hence, lowering of reaction efficiency due to excessive drying of the porous body layer 40 can be further suppressed. Further, according to the fuel cell gas diffusion layer 42A of the embodiment 1, out of the plurality of gas inflow side grooves 53a, 53b, the gas inflow side groove 53b having the largest length has the length that is 40% or more of the length of the gas inflow side to the gas outflow side of the porous body layer 40 and hence, water discharge property can be further increased, and lowering of reaction efficiency due to lowering of a gas pressure can be further suppressed.
Further, in the fuel cell gas supply diffusion layer 42A according to the embodiment 1, the plurality of gas outflow side grooves 54a, 54b include two kinds or more gas outflow side grooves 54a, 54b having different lengths. In this manner, in the fuel cell gas supply diffusion layer 42A according to the embodiment 1, the plurality of gas outflow side grooves 54a, 54b also include two or more kinds of gas outflow side grooves 54a, 54b having the different lengths. With such a configuration, out of the plurality of gas outflow side grooves 54a, 54b, due to an action of the gas outflow side grove 54b having the relatively large length, discharge efficiency of the moisture (vapor or condensed water) that is originally liable to be stagnated is increased and hence, the gas diffusion is enhanced whereby reaction efficiency (power generation efficiency in case of the embodiment 1) is enhanced. On the other hand, with respect to the plurality of the gas outlet grooves 54a, 54b, due to action of the gas outflow side groove 54a having the relatively small length, also in a region on a gas outflow side, a predetermined reaction (power generation in the case of the embodiment 1) is performed by an underflow of a gas from the gas diffusion groove on an upstream side and hence, reaction efficiency (power generation efficiency in the case of embodiment 1) can be increased as a whole.
Further, in the fuel cell gas supply diffusion layer 42A according to the embodiment 1, two gas outflow side grooves 54a, 54b disposed adjacently to each other have different lengths and hence, the long groove and the short groove are arranged in a dispersed manner. With such a configuration, the fuel cell gas supply diffusion layer 42A according to the embodiment 1 can further increase reaction efficiency and, further, becomes the gas diffusion layer having the further excellent water discharge property.
In the present invention, out of four or three gas outflow side grooves disposed adjacently to each other, at least one gas outflow side groove may have a length different from the length of other gas outflow side grooves. In this case, the fuel cell gas supply diffusion layer acquires an advantageous effect of the same nature as in the case where two gas outflow side grooves disposed adjacently to each other have different lengths.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, out of the plurality of gas inflow side grooves 53a, 53b, the gas inflow side groove 53a having the shortest length has the length less than 30% of a length from a gas inflow side to a gas outflow side of the porous body layer 40 and hence, drying of the porous body layer 40 on the inflow side that is liable to be easily dried can be minimized whereby reaction efficiency can be further enhanced. Further, according to the fuel cell gas diffusion layer 42A of the embodiment 1, out of the plurality of gas outflow side grooves 54a, 54b, the gas outflow side groove 54b having the largest length has the length that is 30% or more of the length of the gas inflow side to the gas outflow side of the porous body layer 40 and hence, moisture (vapor or condensed water) that is liable to be stagnated can be efficiently discharged through the gas outflow side groove 54b whereby the diffusion of the gas can be enhanced. Also, from this point of view, the reaction efficiency can be further increased.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of gas flow path grooves include the plurality of relay grooves 55a to 55d and hence, the number of outflow side terminal portions (dead end portions) can be increased whereby an amount of gas that passes the underflow region is increased so that reaction efficiency can be further increased. Further, it is also possible to realize the prevention of drying of the porous body layer 40 and the optimization of the balance in the enhancement of discharge efficiency of moisture (vapor or condensed water).
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of relay grooves 55a to 55d communicate with each other along the direction (x direction) perpendicular to the direction that a gas flows from the inflow side to the outflow side and hence, it is possible to make a gas pressure uniform along the direction that the plurality of relay grooves 55a to 55d communicate with each other.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the plurality of gas inflow side grooves 53a, 53b, the plurality of gas outflow side grooves 54a, 54b and the plurality of relay grooves 55a to 55d are formed so as to be alternately interposed to each other and hence, a gas pressure can be made uniform and an amount of underflow gas can be increased.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, in a plan view of the fuel cell gas supply diffusion layer 42A, a rate of an area of a gas flow path groove forming region with respect to an entire area of the porous body layer 40 falls within a range of 30% to 80% and hence, the fuel cell gas supply diffusion layer 42A can acquire both the sufficient gas supply ability and the sufficient mechanical strength.
Further, according to the fuel cell gas supply diffusion layer 42A of the embodiment 1, the fuel cell gas supply diffusion layer 42A is a fuel cell gas supply diffusion layer for a cathode gas and hence, it is possible to increase the performance of the fuel cell stack.
The fuel cell separator 23A according to the embodiment 1, is a separator that includes: the metal plate 30 that is a gas shield plate; and the fuel cell gas supply diffusion layer 42A disposed on at least one surface of the metal plate 30. The fuel cell gas supply diffusion layer 42A is the fuel cell gas supply diffusion layer 42A according to the embodiment 1, and is arranged with respect to the metal plate 30 such that the plurality of gas flow path grooves (the gas inflow side grooves 53a, 53b, the gas outflow side grooves 54a, 54b and the relay grooves 55a to 55d) are disposed on the metal plate 30 side. Accordingly, the gas flow paths are formed by the gas flow path grooves and the metal plate 30 and hence, it is possible to provide the separator that can increase the reaction efficiency compared to the prior art.
The fuel cell stack 20 according to the embodiment 1, is a fuel cell stack where the separators and the membrane electrode assemblies 81 are stacked to each other. The separator is the fuel cell separator 23A according to the embodiment 1 where the fuel cell separators 23A and the membrane electrode assemblies 81 are stacked with each other with the positional relationship that the membrane electrode assembly 81 is positioned on the surface of the fuel cell gas supply diffusion layer 42A on a side where the plurality of the gas flow path grooves (gas inflow side grooves 53a, 53b, the gas outflow side grooves 54a, 54b and the relay grooves 55a to 55d) are not formed. Accordingly, the fuel cell stack 20 according to the embodiment 1 becomes the fuel cell stack that can increase reaction efficiency compared to the prior art.
Further, according to the fuel cell stack 20 of the embodiment 1, the fuel cell stack 20 is a fuel cell stack and hence, the fuel cell stack 20 according to the embodiment 1 becomes a fuel cell stack that can increase the power generation efficiency of a fuel cell compared to the prior art.
[Method of Manufacturing Fuel Cell Separator 23A]
As an example, the corrosion layer, the dense frame 32, the fuel cell gas supply diffusion layer 42A and the like can be formed by isostatic pressing using a paste-like material obtained by mixing a thermosetting resin (or a thermoplastic resin), carbon-based conductive powder (and carbon fibers depending on a situation), resin powder and a volatile solvent to each other. Unique shapes of the respective members and portions can be formed by printing, stamping, squeezing or the like, for example. Further, the respective members can be also arranged or formed by thermocompression bonding or roll pressing (hot pressing).
The above-mentioned manufacturing method is also appliable to the manufacture of the separators (the fuel cell separators 21, 22, 24, 25) other than the fuel cell separator 23A.
[Separators Other than Fuel Cell Separator 23A]
The gas diffusion layer according to the present invention is applicable to the (cathode gas) fuel cell gas supply diffusion layer 42A and/or the (anode gas) fuel cell gas supply diffusion layer 41 of the fuel cell separator 21 (see
In this manner, even in the case where the gas diffusion layer according to the present invention is applied to the fuel cell gas supply diffusion layers of the fuel cell separators 21, 22, 24, 25 described above, the gas diffusion layer according to the present invention becomes a gas diffusion layer that can increase reaction efficiency (power generation efficiency in case of the fuel cell) compared to the prior art.
The fuel cell gas supply diffusion layer 42B of the fuel cell separator 23B according to the embodiment 2 includes basically substantially the same configuration as the fuel cell gas supply diffusion layer 42A according to the embodiment 1. However, the fuel cell gas supply diffusion layer 42B differs from the fuel cell gas supply diffusion layer 42A according to the embodiment 1 with respect to the configuration of the gas flow path grooves. In the fuel cell gas supply diffusion layer 42B according to the embodiment 2, as illustrated in
The fuel cell gas supply diffusion layer 42B and the fuel cell separator 23B according to the embodiment 2 become, in the same manner as the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1, a gas diffusion layer and a separator respectively that can increase reaction efficiency compared to the prior art. Further, according to the fuel cell gas supply diffusion layer 42B and the fuel cell separator 23B according to the embodiment 2, it is also possible to acquire common advantageous effects brought about by common technical features with the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1.
The fuel cell gas supply diffusion layer 42C in the fuel cell separator 23C according to the embodiment 3 includes basically substantially the same configuration as the fuel cell gas supply diffusion layer 42A according to the embodiment 1. However, the fuel cell gas supply diffusion layer 42C differs from the fuel cell gas supply diffusion layer 42A according to the embodiment 1 with respect to the configuration of gas flow path grooves. As illustrated in
The fuel cell gas supply diffusion layer 42C and the fuel cell separator 23C according to the embodiment 3 become, in the same manner as the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1, a gas diffusion layer and a separator that can increase reaction efficiency compared to the prior art. Further, according to the fuel cell gas supply diffusion layer 42C according to the embodiment 3, the fuel cell gas diffusion layer 42c includes, as the plurality of relay grooves, a plurality of relay grooves 55f to 55h where a pair of relay grooves that is formed such that two relay grooves disposed adjacently to each other communicate with each other are formed along a direction perpendicular to a direction directed from the gas inflow side to the gas outflow side. With such a configuration, a pressure loss can be reduced and hence, a gas, vapor or condensed water that form an underflow can be made to flow easily toward a downstream side whereby a gas can be more uniformly dispersed and further, vapor or condensed water can be more efficiently discharged to the outside of the fuel cell gas supply diffusion layer 42C. Further, according to the fuel cell gas supply diffusion layer 42C according to the embodiment 3, with respect to some of the plurality of gas flow path grooves, “a branching portion where one groove is bifurcated to two grooves” is provided. Accordingly, a gas pressure can be made uniform at limited locations. Further, the number of outflow side terminal portions (dead end portions) can be increased and hence, an amount of gas that passes through an underflow region can be increased and hence, a reaction efficiency can be further increased. Further, according to the fuel cell gas supply diffusion layer 42C and the fuel cell separator 23C according to the embodiment 3, common advantageous effects can be also acquired because of common technical features with the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1.
The fuel cell gas supply diffusion layer 42D in the fuel cell separator 23D according to the embodiment 4 includes basically substantially the same configuration as the fuel cell gas supply diffusion layer 42A according to the embodiment 1. However, the fuel cell gas supply diffusion layer 42D differs from the fuel cell gas supply diffusion layer 42A according to the embodiment 1 with respect to the configuration of gas flow path grooves. As illustrated in
The fuel cell gas supply diffusion layer 42D and the fuel cell separator 23D according to the embodiment 4 become, in the same manner as the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1, a gas diffusion layer and a separator that can increase reaction efficiency compared to the prior art. Further, according to the fuel cell gas supply diffusion layer 42D according to the embodiment 4, some of the plurality of the gas flow grooves have “a merging portion where two grooves are merged into one groove” and hence, a gas pressure can be made uniform at limited locations. Further, according to the fuel cell gas supply diffusion layer 42D and the fuel cell separator 23D according to the embodiment 4, common advantageous effects can be also acquired because of common technical features with the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1.
The fuel cell separators 23E to 23H and fuel cell gas supply diffusion layers 42E to 42H according to the embodiments 5 to 8 include basically substantially the same configuration as the fuel cell separators 23A to 23D and the fuel cell gas supply diffusion layers 42A to 42D according to the embodiments 1 to 4. However, an aspect rate of the fuel cell gas supply diffusion layer differs from an aspect rate of the fuel cell gas supply diffusion layer in the case of the fuel cell separators 23A to 23D and the fuel cell gas supply diffusion layers 42A to 42D according to the embodiments 1 to 4. Further, in the fuel cell gas supply diffusion layers 42E to 42H according to embodiments 5 to 8, a width or the like of each of respective grooves that form gas flow path grooves differs from the width of the corresponding groove in the fuel cell separators 23A to 23D according to the embodiments 1 to 4. However, with respect to a pattern of the gas flow path grooves, the groove pattern adopted by the fuel cell gas supply diffusion layer 42E according to the embodiment 5 is substantially equal to the groove pattern adopted by the fuel cell gas supply diffusion layer 42A according to the embodiment 1, the groove pattern adopted by the fuel cell gas supply diffusion layer 42F according to the embodiment 6 is substantially equal to the groove pattern adopted by the fuel cell gas supply diffusion layer 42B according to the embodiment 2, the groove pattern adopted by the fuel cell gas supply diffusion layer 42G according to the embodiment 7 is substantially equal to the groove pattern adopted by the fuel cell gas supply diffusion layer 42C according to the embodiment 3, and the groove pattern adopted by the fuel cell gas supply diffusion layer 42H according to the embodiment 8 is substantially equal to the groove pattern adopted by the fuel cell gas supply diffusion layer 42D according to the embodiment 4 (see
The fuel cell gas supply diffusion layers 42E to 42H and the fuel cell separators 23E to 23H according to the embodiments 5 to 8 become, in the same manner as the fuel cell gas supply diffusion layer 42A and the fuel cell separator 23A according to the embodiment 1, fuel cell gas supply diffusion layers and fuel cell separators that can increase reaction efficiency compared to the prior art. Further, according to the fuel cell separators 23E to 23H and the fuel cell gas supply diffusions layers 42E to 42H according to the embodiments 5 to 8, it is possible to acquire substantially the same advantageous effects as the corresponding fuel cell gas supply diffusion layers 42A to 42D and the corresponding fuel cell separators 23A to 23D.
Next, a gas diffusion layer and a separator according to the present invention were actually manufactured thus forming unit cells each form a minimum unit of a fuel cell, and a test how the difference in a pattern of gas flow path grooves affects properties of the fuel cell was performed. The result of the test was described hereinafter. With respect to an example 1, an example 2 and a comparison example described later, in carrying out the test, “the relationship between current density and voltage” was measured (test example 1), the “the relationship between current density and pressure of cathode gas” was measured (test example 2), and “distribution of current density” was measured (test example 3). These tests were performed for comparing the test results with respect to the example 1, the example 2, and the comparison example to each other and hence, these tests may be also referred to as “comparative tests”.
First, the unit cell manufactured by the test example is described. The test was performed by using three kinds of unit cells, that is, the unit cell according to the example 1 (hereinafter simply referred to as “example 1”), the unit cell according to the example 2 (hereinafter simply referred to as “example 2”) and the unit cell according to the comparison example (hereinafter simply referred to as “comparison example”). As the unit cell, a unit cell that was manufactured by sandwiching a membrane electrode assembly by a fuel cell separator (a separator of a type C) for a cathode gas and a fuel cell separator (a separator of a type A) for an anode gas was used (not illustrated in the drawings). In the fuel cell gas supply diffusion layer for the cathode gas according to the example 1, the gas flow path groove adopted the shape described in embodiment 5 (see
In the respective test examples (test examples 1 to 3), as the power generation conditions, “a dry condition, no back pressure (power generation condition 1)”, “a dry condition, a back pressure being present (a power generation condition 2)”, and “a wet condition, no back pressure (a power generation condition 3)” were adopted by taking into account the use condition of the fuel cell. A temperature of a unit cell at the time of performing the test was set to 80 C°. Air was used as a cathode gas, and a hydrogen gas was used as an anode gas. A cathode gas use ratio is set to 40%, and an anode gas use ratio is set to 70%. As a catalyst, a platinum catalyst (TEC10E50E made by Tanaka precious metals) was used, and a carrying amount of platinum catalyst on each of both poles was set to approximately 0.3 mg/cm2. As a polymer membrane, NAFION (registered t rademark) NR211 having a thickness of 25 μm was used. An effective area was set to 29.16 cm2 (3 cm×9.72 cm). A moisture of a cathode gas and an anode gas in “dry condition” was set to 30% RH, and a moisture of the cathode gas and the anode gas in “wet condition” was set to 80% RH. A back pressure in “no back pressure” means 0 kPaG, that is, an atmospheric pressure. The back pressure in “back pressure being present” was set to 150 kPaG, that is, a value obtained by adding 150 kpa to an atmospheric pressure.
In the test examples 1 to 3, a fuel cell unit cell evaluation apparatus manufactured by Panasonic Production Engineering Company, Ltd. was used. Then, the measurement of “relationship between current density and voltage” in the test example 1, and the measurement of “relationship between current density and pressure of cathode gas” in the test example 2 were performed by measuring a voltage and a pressure of a cathode gas on an inflow side by gradually increasing current density by changing a current value of an electronic load device. During such measurement, a gas use ratio is set to a constant value by adjusting a supply amount of a reaction gasses (an anode gas and a cathode gas) inconformity with a current value.
In the test example 3, a current density distribution sensor “Current scan lin” manufactured by S++ Inc. is also used. Then, the measurement of “current density distribution” in the test example 3 was performed such that a region where power is generated in a unit cell is divided into zones of 20 rows and 6 columns, and current density was measured for each zone. The measurement was performed under a condition that average current density becomes constant.
Next, results of the tests are described.
In the power generation condition 1, when current density was increased, the obtained voltage was sharply lowered and hence, a significant result was not obtained. Accordingly, as illustrated in
As the result of the test example 1, it was found that also in cases where either one of power generation conditions is adopted, the example 1 and the example 2 acquire a higher voltage than the comparison example when the comparison is made at any current density and hence, power generation efficiency is increased (see
As the result of the test example 2, it was found that also in the cases where either one of power generation conditions is adopted, a pressure loss in the fuel cell gas supply diffusion layer of a cathode gas generated when the same current density is obtained was low in the case of the test example 1 and the test example 2 compared to the comparison example (see
These results means that the power generation efficiency can be increased in the example 1 and the example 2 compared to the case of the comparison example.
First, average current density (Jm) is a value obtained by dividing a sum of individual current densities (Ji) obtained in respective zones (i) including the regions 1 to 20 illustrated in
A catalyst layer and a fuel cell gas supply diffusion layer have electron conductivity and hence, a voltage (Ei) obtained relating to the individual zones exhibits the same value as a potential measured as the whole electrode ((E) substantially agreeing with a voltage (V) illustrated in
First, in the power generation condition 1, “dry condition, no back pressure” (see
Next, also in the power generation condition 2 “dry condition back pressure being present (see
Further, with respect to current density distributions of the example 1 and the example 2 in the power generation condition 2, compared to the current density distribution of the comparison example in the power generation condition 2 and the current density distributions of the example 1, the example 2, and the comparison example in the power generation condition 1, the power generation region is apparently shifted through the gas input side (region numbers 1 to 10). It is considered that, in case of the example 1 and the example 2, particularly due to an action of the gas inflow side grooves having a relatively short length, an amount of moisture generated by the power generation in the regions in the gas inflow side is increased and hence, drying of the porous body layer in the region is further suppressed whereby an activated overvoltage (Ea) and a gas diffusion overvoltage (Ed) are reduced thus allowing the electrode to obtain the higher battery output as a whole.
Next, also in the power generation condition 3 “wet condition, no back pressure” (see
The patterns of the plurality of gas flow path grooves according to the present invention are not limited to the patterns described in the above-mentioned respective embodiments.
In a fuel cell gas supply diffusion layer 42J of the fuel cell separator 23J according to the modification 1, two more kinds of (two kinds in this case) gas inflow side grooves 53p, 53q having different lengths are formed. Among these gas inflow side grooves, two long gas inflow side grooves 53q communicate with communication grooves 56f formed over the entire fuel cell gas supply diffusion layer 42J in the x direction (see
In a fuel cell gas supply diffusion layer 42K of the fuel cell separator 23K according to the modification 2, two more kinds of (two kinds in this case) gas inflow side grooves 53t, 53u having different lengths are formed. Among these gas inflow side grooves, two long gas inflow side grooves 53u are formed so as to divide the fuel cell gas supply diffusion layer 42K into three regions (see
In a fuel cell gas supply diffusion layer 42L of a fuel cell separator 23L according to the modification 3, not only the grooves having different lengths are formed, but also grooves that are branched or merged in multiple stages such as gas inflow side grooves 53v, gas outflow side grooves 54o and relay grooves 55v are formed (see
In a fuel cell gas supply diffusion layer 42M of a fuel cell separator 23M according to the modification 4, a basic pattern of a plurality of gas flow path grooves is substantially equal to the fuel cell gas supply diffusion layer 42A of the fuel cell separator 23A according to the embodiment 1. However, gas inflow grooves 53w, the gas inflow grooves 53x, gas outlet grooves 54q, 54r and relay grooves 55x to 55z are formed in a zigzag shape respectively. In the present invention, the gas flow path grooves may be formed in a wave shape or an arcuate shape. Further, in the present invention, the gas flow path groove may have a shape where a width of the gas flow path groove changes. That is, in the present invention, the gas flow path grooves may be formed in shapes other than a straight-line shape. In this manner, the pattern of the gas flow path grooves in the present invention can be formed in a desired shape corresponding to the individual circumstances provided that advantageous effects of the present invention are not impaired.
In the above-mentioned respective embodiments, as a membrane electrode assembly, the membrane electrode assembly 81 that includes the catalyst layer 85 having substantially the same area as the fuel cell gas supply diffusion layer is used. However, the present invention is not limited to such a configuration. As the membrane electrode assembly, a membrane electrode assembly that includes a catalyst layer 85 having a smaller area than the fuel cell gas supply diffusion layer may be used.
In the above-mentioned respective embodiments, as the gas outlet groove, the gas flow path groove where a width of the gas flow path groove on a surface of the porous body layer 40 (or the gas flow path groove) and a width of the gas flow path groove at a bottom of the gas flow path groove are equal, and the gas flow path groove has a rectangular shape in cross section is used (see
In the above-mentioned respective embodiments, as the gas diffusion layer, the fuel cell gas supply diffusion layer that includes the porous body layer 40 having one surface on which the gas flow path grooves are formed is used (see
In the above-mentioned respective embodiments, the metal plate 30 is used as the gas shield plate. However, the present invention is not limited to such a confirmation. Besides the metal plate 30, a plate made of a material having property of shielding a gas (for example, a conductive composite material plate that is formed of conductive fine particles and a resin, or a ceramic plate or a resin plate combined with a current collector sheet) can be used.
The technical features described in the respective modifications are applicable to all of the gas diffusion layer, the separator and the electrochemical reactor according to the present invention. For example, the technical features described in the respective modifications are applicable to the fuel cell separator 21 of a type CA, the fuel cell separator 24 of a type CW, the fuel cell separator 22 of a type A, the fuel cell separator 25 of a type AW, a fuel cell separator and a fuel cell stack provided with such fuel cell gas supply diffusion layer.
The diffusion layer, the separator, and electrochemical reactor according to the present invention can be used for an electrolysis.
The gas diffusion layer, the separator, and electrochemical reactor according to the present invention have been described heretofore based on the embodiments illustrated in the drawings. However, the present invention is not limited to the above-mentioned respective embodiments, and various modifications can be carried out without departing from the gist of the present invention.
This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2021/004686, filed on Feb. 8, 2021. The entire disclosure of the above application is expressly incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/004686 | 2/8/2021 | WO |
