JP2008218228A - Tube type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tube type fuel cell capable of suppressing flooding, and of improving and stabilizing power generation performance of the cell. <P>SOLUTION: This tube type fuel cell is provided with: a hollow structure having a hollow electrolyte membrane, a first electrode and a second electrode; an inner collector arranged on an inner peripheral surface side of the structure; and an outer collector arranged in contact with an outer peripheral surface of the structure. In the tube type fuel cell, the inner collector is composed of a plurality of wires arranged concentrically around an axis of the structure in a region surrounded by the first electrode; the adjacent wires on the concentric circle within the wires contact each other; the wires on the outermost concentric circle come into contact with the structure; the wires arranged next to each other on the same circle within the wires come into contact with each other; and at least the wires arranged on the outermost concentric circle have water repellency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tube type fuel cell, and more particularly to a tube type fuel cell that can suppress flooding and improve and stabilize the power generation performance of a cell.

  In a conventional polymer electrolyte fuel cell (hereinafter sometimes referred to as “PEFC”), a flat electrolyte membrane and electrodes (cathode and anode) disposed on both sides of the electrolyte membrane are provided. Electric energy generated by an electrochemical reaction in a membrane electrode assembly (hereinafter, sometimes referred to as “MEA”) provided is taken out through separators provided on both sides of the MEA. The electrochemical reaction proceeds in the following steps. First, hydrogen delivered to the fuel electrode is decomposed into hydrogen ions and electrons in the presence of the catalyst. The generated hydrogen ions pass through the electrolyte membrane, which is an ion conductor, and move to the air electrode, and the generated electrons move to the air electrode through an external circuit. In PEFC, electricity is generated by such movement of electrons. On the other hand, the oxygen delivered to the air electrode reacts with hydrogen ions and electrons that have moved to the air electrode, thereby generating water.

  PEFC is attracting attention as a power source and portable power source for electric vehicles because it can be operated in a low temperature region, exhibits high energy conversion efficiency, has a short start-up time, and has a compact and lightweight system. A single cell of PEFC includes constituent members such as an electrolyte membrane, a cathode and an anode including at least a catalyst layer, and a separator, and its theoretical electromotive force is 1.23V. Since such a low electromotive force is not sufficient as a power source for an electric vehicle or the like, a stack type fuel cell is usually configured by disposing end plates and the like at both ends in the stacking direction of a stacked body in which single cells are stacked in series. Is used. In order to further improve the power generation performance of PEFC, it is preferable to reduce the size of a single cell and increase the output per unit volume (power density).

  In order to improve the power density and improve the power generation performance in a conventional PEFC (hereinafter sometimes referred to as “flat-plate type PEFC”), it is necessary to reduce the thickness of the constituent members. However, if the thickness of the component members in the flat plate type PEFC is less than a certain level, the function and strength of each component member may be reduced. Therefore, it is structurally necessary to improve the output density to a certain level or more by using the flat plate type PEFC. Have difficulty.

  From this point of view, research on tube-type PEFC (hereinafter sometimes referred to as “tube-type PEFC”) has been underway for the purpose of improving the output density to a certain level or more. A tube-type PEFC single cell (hereinafter sometimes referred to as a “tube-type cell”) is generally disposed on a hollow electrolyte membrane and the inner and outer peripheral surfaces of the electrolyte membrane. A hollow MEA including a catalyst layer. Then, an electrochemical reaction is caused by supplying a reaction gas (hydrogen-containing gas and oxygen-containing gas) to the inner peripheral surface side and the outer peripheral surface side of the MEA, and the electric energy generated by this electrochemical reaction is converted into a hollow shape. Current collectors disposed on the inner peripheral surface side and the outer peripheral surface side of the MEA (hereinafter, the current collector disposed on the inner peripheral surface side is referred to as “inner current collector”, and is disposed on the outer peripheral surface side. The current collector is described as “outer current collector”). That is, in the tube type PEFC, one reaction gas (hydrogen-containing gas or oxygen-containing gas) is provided on the inner peripheral surface side of the hollow MEA provided in each single cell, and the other reaction gas (oxygen-containing gas) is provided on the outer peripheral surface side. (Or hydrogen-containing gas) to extract power generation energy. Therefore, according to the tube type PEFC, the reaction gas supplied to the outer peripheral surface side of two adjacent single cells can be made the same. Therefore, in the conventional flat plate type PEFC, a separator having both gas shielding performance is provided. It becomes unnecessary. Therefore, according to the tube type PEFC, it is possible to effectively downsize the single cell.

  As a technique related to the tube-type PEFC, for example, Patent Document 1 includes a pair of electrodes disposed on the inner surface and the outer surface of a hollow electrolyte membrane, and a current collector connected to the pair of electrodes, respectively. At least one of the inner surface and the outer surface has a nano-columnar body supporting an electrode catalyst, and the nano-columnar body is provided on the current collector and at least a part thereof is oriented to the electrolyte membrane. A feature of the fuel cell module is disclosed.

Patent Document 2 discloses a technique for suppressing flooding in a flat plate type fuel cell by making the catalyst layer side of the porous substrate water repellent and making the separator side hydrophilic. Patent Document 3 discloses a technology for making the outside of a MEA water-repellent and making the outside hydrophilic in a flat plate fuel cell. Patent Document 4 discloses a technique for increasing the water repellency on the side close to the catalyst layer in the diffusion layer of the flat plate type fuel cell.
JP 2005-353493 A JP 2004-39416 A JP-A-5-41223 JP 2003-331850 A

  PEFC is used at an operating temperature such as around 80 ° C. in order to reduce the specific resistance of the electrolyte membrane and maintain high power generation efficiency. Then, when the electrolyte membrane is saturated and hydrated, the specific resistance is reduced and proton conductivity is exhibited. Therefore, in order to maintain the power generation efficiency of PEFC, it is necessary to maintain the water content of the electrolyte membrane at saturation. On the other hand, a method of preventing the electrolyte membrane from drying by supplying water to the PEFC with a reaction gas whose humidity has been increased has been adopted. However, since the water generated during the power generation of PEFC is discharged to the outside of the single cell together with the surplus reaction gas, the amount of moisture contained in the reaction gas in the single cell varies depending on the position in the flow direction of the reaction gas. That is, the reaction gas on the downstream side (outlet side) contains an extra amount of water corresponding to the generated water as compared with the upstream side (inlet side). For this reason, when the reactive gas humidified to be saturated in order to keep the water content of the electrolyte membrane saturated is supplied to the single cell, the water vapor is supersaturated on the outlet side and mixed with water droplets. If the water produced in this way accumulates in the catalyst layer during the power generation of the tube type PEFC (flooding state), there is a problem that the gas diffusion to the catalyst is hindered and the power generation performance is lowered. However, in the technique described in Patent Document 1, the drainage of the current collector in contact with the MEA is low, and flooding cannot be suppressed. In addition, it is difficult to apply a tube PEFC to an ordinary film-like water-repellent layer (gas diffusion layer) material used in a flat type fuel cell.

  Therefore, an object of the present invention is to provide a tubular fuel cell that can suppress flooding and improve and stabilize the power generation performance of the cell.

In order to solve the above problems, the present invention takes the following means. That is,
The invention according to claim 1 is a hollow electrolyte membrane, a hollow first electrode disposed along the inner peripheral surface of the electrolyte membrane, and a hollow disposed along the outer peripheral surface of the electrolyte membrane. A hollow structure having a second electrode in shape, an inner current collector disposed on the inner peripheral surface side of the structure, and an outer current collector disposed in contact with the outer peripheral surface of the structure, The inner current collector is constituted by a plurality of wires arranged concentrically around the axis of the structure within a region surrounded by the first electrode. Among the wires of the inner current collector, adjacent concentric wires are in contact with each other, and among the wires of the inner current collector, the wires on the outermost concentric circle are in contact with the structure, Among the wires of the current collector, the wires arranged next to each other on the same circle are in contact with each other, and the inner current collector Of wire rod, at least the outermost arranged wire on a concentric circle, characterized in that the water-repellent by a tube-type fuel cell, to solve the above problems.

  Here, “the hollow first electrode disposed along the inner peripheral surface of the electrolyte membrane” is a hollow shape formed so that the outer peripheral surface is in contact with the inner peripheral surface of the hollow electrolyte membrane. The first electrode. When the hydrogen-containing gas flows on the inner peripheral surface side of the first electrode, the first electrode functions as a fuel electrode, and when the oxygen-containing gas flows on the inner peripheral surface side of the first electrode, the first electrode The electrode functions as an air electrode. In addition, “a hollow second electrode disposed along the outer peripheral surface of the electrolyte membrane” means a hollow-shaped second electrode formed so that the inner peripheral surface is in contact with the outer peripheral surface of the hollow electrolyte membrane. Refers to two electrodes. When the hydrogen-containing gas flows on the outer peripheral surface side of the second electrode, the second electrode functions as a fuel electrode, and when the oxygen-containing gas flows on the outer peripheral surface side of the second electrode, the second electrode Functions as an air electrode.

  Further, “the inner current collector is composed of a plurality of wires arranged concentrically around the axis of the structure within the region surrounded by the first electrode” means that the inner current collector is The body is composed of a collection of a plurality of wires arranged on the inner peripheral surface side of the first electrode, and the hollow structure and the plurality of wires are cut in a direction perpendicular to the longitudinal direction of the structure. In other words, the plurality of wire rods are arranged on a plurality of circles (including the axis center in some cases) centering on the axis center of the structure. In addition, the “wires on adjacent concentric circles” means a wire on a circle adjacent to the outside of a certain circle and a wire on a circle adjacent to the inside of a plurality of circles centered on the axis of the structure. I mean. That is, “adjacent concentric circles” means that there are two of each of a plurality of circles centered on the axis of the structure. However, when the wire is arranged on the axial center of the structure, adjacent concentric circles exist only outside the axial center for the wire. For the outermost circle, there are concentric circles adjacent only inside the circle. Furthermore, “the wires arranged on adjacent concentric circles are in contact with each other” means that at least one of the wires arranged on different circles among the adjacent concentric circles may be in contact. That means. Furthermore, “the wire arranged on the outermost concentric circle among the wires of the inner current collector” means the wire arranged on the outermost circle among the plurality of wires arranged concentrically. Say. In the present invention, the wires arranged on the outermost circle are in contact with the inner peripheral surface of the structure. Furthermore, “wires arranged on the same circle next to each other” means a plurality of wires arranged on a certain circle out of concentric circles centered on the axis of the structure. It refers to the wire that is placed. That is, two wires arranged adjacent to each other on the same circle are present for every wire among a plurality of wires arranged on the same circle. However, when the wire is arranged on the axial center of the structure, there is no other wire arranged on the same circle as the wire. In the present invention, the wires arranged next to each other are in contact with each other. Furthermore, in the present invention, at least the wire disposed on the outermost concentric circle has water repellency. Here, the water repellency means that the contact angle is 110 ° or more, preferably 130 ° or more and 180 ° or less.

  The invention according to claim 2 is the tube type fuel cell according to claim 1, wherein the hydrophilicity of the wire arranged on one concentric circle of the inner current collector is arranged on the concentric circle inside the concentric circle. It is characterized by being lower than or equal to the hydrophilicity of the formed wire.

  In the present invention, the hydrophilicity of the wire disposed on one circle centered on the axis of the structure is lower or equal to the hydrophilicity of the wire disposed on the concentric circle in contact with the inside of the circle. It is preferable. In the present invention, it is preferable that at least the outermost wire of the inner current collector has water repellency and the innermost wire has hydrophilicity. The hydrophilicity here means, for example, a contact angle of 90 ° or less, preferably 0 ° or more and 80 ° or less.

  According to a third aspect of the present invention, in the tube type fuel cell according to the first or second aspect, the diameter of the outermost concentric wire of the inner current collector is arranged at the innermost side of the inner current collector. It is characterized by being smaller than the diameter of the wire.

  Here, “in the inner current collector, the diameter of the wire on the outermost concentric circle is smaller than the diameter of the wire arranged on the innermost side of the inner current collector” means that the inner current collector has the innermost diameter. A wire having a diameter larger than that of the outermost concentric wire and smaller than that of the outermost concentric wire of the inner current collector is the other current constituting the inner current collector. It means not existing in the wire. Furthermore, “the wire disposed at the innermost side of the inner current collector” refers to the wire when the wire is disposed on the axis of the structure, and the wire is disposed on the axis of the structure. Is not arranged, it means a wire arranged on the innermost concentric circle among the wires of the inner current collector.

  According to a fourth aspect of the present invention, in the tube type fuel cell according to the third aspect, the diameter of the wire rod arranged on one concentric circle of the inner current collector is arranged on the concentric circle in contact with the inner side of the concentric circle It is characterized by being smaller than or equal to the diameter of the formed wire.

  According to a fifth aspect of the present invention, in the tubular fuel cell according to any one of the first to fourth aspects, the inner current collector gradually becomes higher in drainage as it goes from the inlet side to the outlet side of the reaction gas. It is characterized by having.

  Here, “reactive gas inlet side” and “reactive gas outlet side” mean the inlet side and outlet side of the reactive gas flowing on the inner peripheral surface side of the structure, respectively. Since the reaction gas flows on the inner peripheral surface side of the structure, when the inner current collector is viewed in the longitudinal direction, one of them becomes the reaction gas inlet side and the other becomes the reaction gas outlet side.

  A sixth aspect of the present invention is the tube type fuel cell according to any one of the first to fifth aspects, wherein the outer current collector has water repellency.

  Here, the water repellency means that the contact angle is 110 ° or more, preferably 130 ° or more and 180 ° or less.

  According to the first aspect of the present invention, water repellency is imparted to at least the wire constituting the inner current collector in contact with the structure. By adopting such a configuration, drainage from the first electrode can be improved and flooding can be suppressed, so that a tubular fuel cell capable of improving and stabilizing the power generation performance of the cell can be provided.

  According to the second aspect of the present invention, the outer wire and the inner wire constituting the inner current collector have a hydrophilic gradient. By mixing a water-repellent wire and a hydrophilic wire in the inner current collector, water can be prevented from being scattered. Furthermore, water can be collected toward the inner side of the inner current collector having high hydrophilicity by increasing the hydrophilicity from the outer side to the inner side of the inner current collector. Therefore, drainage from the first electrode can be easily improved.

  According to the invention described in claim 3, the diameter of the wire of the inner current collector in contact with the structure is small. Therefore, the contact area between the structure and the wire is increased, and water is easily taken into the gap between the wires. The water taken into the gap moves to the inside of the inner current collector. Therefore, drainage from the first electrode can be easily improved.

  According to the invention described in claim 4, it is possible to give a gradient to the size of the gap formed between the wires by making a difference in the size of the diameter of the wires of the inner current collector. The water near the first electrode gradually aggregates with the surrounding water and becomes larger water droplets as you move away from the first electrode, but the size of the gap between the wires also increases, so the water is inside the inner current collector. It's easy to get together. In addition, since the inner wire of the inner current collector is thick, a gap formed between the wires increases at the center of the inner current collector. Therefore, the water collected inside the inner current collector is easily discharged by the gas flowing inside the structure.

  According to the fifth aspect of the present invention, a drainage gradient can be provided in the longitudinal direction of the inner current collector. By improving the drainage on the outlet side of the reactive gas where water tends to accumulate, the balance of water on the inner peripheral surface side of the structure can be kept constant, and the performance stability of the tube fuel cell can be improved. it can.

  According to the invention described in claim 6, water repellency is imparted to the outer current collector. By setting it as this structure, the drainage property in the outer peripheral surface side of a structure can be improved.

  During power generation of the tube type fuel cell, hydrogen delivered to the anode electrode is decomposed into hydrogen ions and electrons in the presence of the catalyst. The generated hydrogen ions pass through the electrolyte membrane, which is an ion conductor, and move to the cathode electrode together with water. The hydrogen ions that have moved to the cathode electrode react with the electrons that have moved to the cathode electrode through the external circuit and oxygen supplied to the cathode electrode, thereby generating water. Therefore, on the cathode electrode side, the generated water is likely to be accumulated in the catalyst layer (flooded state), and there is a problem that the power generation performance is deteriorated when the diffusion of gas to the catalyst is hindered by the generated water. Therefore, it is desired to provide a tube-type fuel cell that can suppress flooding and improve and stabilize the power generation performance of the cell.

  The present invention has been made from such a viewpoint, and the gist of the present invention is to provide a tube type fuel cell capable of suppressing flooding and improving and stabilizing the power generation performance of a cell by improving drainage.

  The present invention will be described below with reference to the drawings. In the following description, an oxygen-containing gas (hereinafter sometimes referred to as “air”) is supplied to the inner peripheral surface side of the tubular fuel cell, and a hydrogen-containing gas (hereinafter referred to as “hydrogen”) is referred to as the outer peripheral surface side. Is provided), but the present invention is not limited to this form. In the following description, the side closer to the axial center of the tube type fuel cell may be referred to as “axial side”, and the far side as “outside”.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing a tube fuel cell according to the first embodiment of the present invention. 1 is the longitudinal direction of the inner current collector 6. As shown in the figure, a tube type fuel cell 10 of the present invention (hereinafter simply referred to as “fuel cell 10”) includes a structure 3 having an electrolyte membrane 1, a first electrode 2a, and a second electrode 2b. An outer current collector 4 wound around the outer peripheral surface of the structure 3 and an inner current collector 6 disposed on the inner peripheral surface side of the structure 3 are provided. The inner current collector 6 includes a plurality of wires 5a, 5a,..., Wires 5b, 5b,..., Wires 5c, 5c,. , Wire rods 5b, 5b,..., Wire rods 5c, 5c,..., And wire rods 5d (hereinafter collectively referred to as “wire rods”). 5, 5,... ”) Is formed of a conductive wire (for example, a metal wire). The diameter of the structure 3 is, for example, about 0.5 [mm] to 10 [mm].

  When air is supplied to the inner peripheral surface side of the fuel cell 10 and hydrogen is supplied to the outer peripheral surface side, the first electrode 2a and the second electrode 2b function as a cathode electrode and an anode electrode, respectively (hereinafter referred to as the first electrode). One electrode 2a may be referred to as “cathode electrode 2a”, and the second electrode 2b may be referred to as “anode electrode 2b”. Hydrogen supplied to the anode electrode 2b is decomposed into hydrogen ions and electrons in the presence of the catalyst. The hydrogen ions generated at the anode electrode 2b pass through the anode electrode 2b and the electrolyte membrane 1 and move to the cathode electrode 2a. On the other hand, electrons move to the cathode electrode 2a through an external circuit. In the cathode electrode 2a, water is generated by the reaction of hydrogen ions, electrons, and oxygen.

  FIG. 2 is an enlarged cross-sectional view showing a part of the fuel cell 10 shown in FIG. 2 is the longitudinal direction of the inner current collector 6. The arrows in the figure indicate the direction in which water is discharged. In the fuel cell 10, water repellency is imparted to the wires 5a, 5a, ... and the wires 5b, 5b, ..., and hydrophilicity is imparted to the wires 5c, 5c, ..., and the wire 5d. By increasing the hydrophilicity of the wire on the axial center side of the inner current collector 6, the water on the inner peripheral surface side of the structure 3 moves toward the axial center side (higher hydrophilicity) of the inner current collector 6. Since it moves, the drainage of the cathode electrode 2a can be improved. In this way, the water collected on the axial center side of the inner current collector 6 is discharged by the gas flowing on the inner peripheral surface side of the structure 3.

  1 and 2, in the fuel cell 10 of the present invention, the diameters of the wires 5a, 5a, ... and the wires 5b, 5b, ... are the same as those of the wires 5c, 5c, ... and the wire 5d. Smaller than the diameter. By reducing the diameter of the wires 5a, 5a, ... that are in contact with the structure 3, the contact area between the wires 5a, 5a, ... and the structure 3 can be increased, and a plurality of wires 5, 5, ... It becomes easy to take in water into the gap formed by. Since the water taken into the gap moves toward the axial center side of the inner current collector 6, the drainage of the cathode electrode 2a is improved by adopting such a configuration.

  Further, in the fuel cell 10 of the present invention, small-diameter wire rods 5a, 5a,... And wire rods 5b, 5b,. By using the wire 5d, the gradient of the diameter of the wire is given from the axial center side of the inner current collector 6 to the outside. By providing a gradient in the diameter of the wire, the size of the gap formed by the wires 5, 5,... Increases from the outside toward the axial center, and a large amount of air flows through the large gap. Cheap. On the other hand, the water present in the vicinity of the cathode electrode 2a gradually aggregates with the surrounding water, and thus becomes larger water droplets as the distance from the cathode electrode 2a increases. In the fuel cell 10, water droplets increase as the distance from the cathode electrode 2 a increases, but the size of the gap formed by the wires 5, 5,... Also increases, so that water easily collects on the axial center side of the inner current collector 6. Since a large amount of air flows through the large gap on the axial center side of the inner current collector 6, according to the fuel cell 10, the water collected on the axial center side of the inner current collector 6 can be discharged together with a large amount of air. it can. Therefore, according to the fuel cell 10 of the present invention, drainage can be improved.

  FIG. 3A is a perspective view showing a tube fuel cell according to the first embodiment with a part thereof omitted. The left-right direction in FIG. 3A is the longitudinal direction of the inner current collector 6. The arrows in the figure indicate the direction of air flow, with the left side of the paper being the air inlet side and the right side of the paper being the air outlet side. As shown in FIG. 3A, in the fuel cell 10, the plurality of wires 5, 5,... Constituting the inner current collector 6 have a twisted wire structure. When the wire rods 5, 5,... Are twisted into a twisted wire, the wire rods 5c, 5c,... And the wire rods 5b, 5b,. The wires 5a, 5a,... Are also wound so that the axial directions intersect. By doing so, it is possible to prevent a situation in which the wire rods 5, 5,... Enter the gap formed by the other wire rods 5, 5,. Moreover, by making the wire rods 5, 5,... Have a twisted wire structure, the bending rigidity is increased, and the performance as a current collector can be stabilized. Furthermore, by setting it as a twisted wire structure, it becomes easy to bundle each wire 5,5, ..., and a production efficiency improves. As a specific example of the method of forming the structure, for example, the wire 5c, 5c,... Is wound around the outside of the wire 5d in the clockwise direction, and the wire 5b, 5b,. Furthermore, the form etc. which wind the wire 5a, 5a, ... clockwise on the outer side can be mentioned.

  FIG.3 (b) is a figure which shows the gradient of the drainage property in the longitudinal direction of the tube type fuel cell of this invention concerning 1st Embodiment. The horizontal axis corresponds to the longitudinal direction of the fuel cell 10 shown in FIG. 3A. The left side of the paper is the air inlet side, and the right side of the paper is the air outlet side. The vertical axis represents the drainage of the inner current collector 6. In the fuel cell 10, water tends to accumulate on the inner peripheral surface side of the structure 3 on the gas outlet side. Therefore, in the fuel cell 10, as shown in FIG. 3B, the drainage property on the outlet side is improved from the gas inlet side. By setting it as this form, a wetness degree can be made constant over the longitudinal direction full length of the structure 3, and the performance of the fuel cell 10 can be stabilized.

  IV characteristics of a tube-type fuel cell (hereinafter sometimes referred to as “non-gradient fuel cell”) having no drainage gradient in the longitudinal direction of the inner current collector and the fuel cell 10 of the present invention When the performance comparison is performed, the fuel cell 10 of the present invention can reduce the variation in performance that occurs at each power generation as compared with a non-gradient fuel cell. For example, when evaluated by the current density at a voltage of 0.6 [V], when the operation / stop is repeated under the same conditions, a non-gradient fuel cell has a performance variation of about 10% for each operation. However, in the fuel cell 10 of the present invention, the variation can be reduced to 3% or less. The reason why the non-gradient fuel cell has a variation of about 10% is considered to be because water is easily clogged in the gap formed between the wires constituting the inner current collector. In a non-gradient fuel cell, it is difficult to keep the balance of water on the inner peripheral surface side of the structure constant. For this reason, among the gaps formed between the wires constituting the inner current collector, water is easily clogged in the gap on the gas outlet side. If water is clogged in the gap during operation, that is, if the operation is stopped as it is, the water trapped in the gap is hindered during the next operation, and the power generation performance is reduced. On the other hand, in the fuel cell 10 of the present invention, it is easy to keep the balance of water constant over substantially the entire length in the longitudinal direction of the structure 3 by improving drainage on the gas outlet side of the inner current collector 6. is there. Therefore, in the entire inner peripheral surface side of the structure 3, it is possible to create a state in which water is not easily clogged in the gap formed between the wires 5, 5,. Therefore, according to the fuel cell 10 of the present invention, it is possible to reduce the variation in performance that occurs at each operation, and to improve the stability of the power generation performance of the cell.

  As a method for imparting water repellency to the wires 5a, 5a,... And the wires 5b, 5b,..., For example, a polytetrafluoroethylene dispersion (hereinafter referred to as “PTFE dispersion”) is coated on the surface of the wires. The method etc. can be mentioned. However, in order to function as a current collector, it is necessary to ensure conductivity. In order to achieve both water repellency and conductivity, for example, a method of coating a mixed material in which a PTFE dispersion is mixed with a hydrophobic carbon material (such as vapor grown carbon fiber (hereinafter referred to as “VGCF”)), etc. It is preferable to impart water repellency. As a specific coating method, for example, a method of dipping a wire in a solution of a water repellent material (dipping), a method of spraying a solution of the water repellent material on the surface of the wire, and the like can be considered. However, the method for imparting water repellency to the wire is not limited to the method exemplified here as long as it is a method that can achieve both water repellency and conductivity. The term “water repellency” as used herein means, for example, that the contact angle is 110 ° or more, and preferably 130 ° or more and 180 ° or less.

  Examples of the method for imparting hydrophilicity to the wires 5c, 5c,... And the wire 5d include a method of coating a hydrophilic carbon (carbon added with a COOH group) on the surface of the wire. However, the method for imparting hydrophilicity to the wires 5, 5,... Constituting the inner current collector 6 may be any method that can achieve both hydrophilicity and conductivity, and is not limited to the method exemplified here. The hydrophilicity here means, for example, that the contact angle is 90 ° or less, preferably 0 ° or more and 80 ° or less.

  As shown in FIG. 3B, in order to give a drainage gradient in the longitudinal direction of the fuel cell 10, for example, the water repellency of the inner current collector 6 may be given a gradient in the longitudinal direction. As a method of giving the plurality of wires 5, 5,... Constituting the inner current collector 6 a gradient of water repellency in the longitudinal direction, for example, among the inner current collectors 6, the wires 5 a that are in contact with the structure 3, What is necessary is just to change the quantity of the water repellent material coated on the surface of 5a, ... in a longitudinal direction. When the water repellent material is coated on the wire by the dip coating method, the thickness of the water repellent material on the surface of the wire can be changed by gradually changing the pulling speed of the wire immersed in the water repellent material solution. Specifically, when the pulling speed of the wire is increased, the thickness of the water repellent material on the surface of the wire is increased, and when the speed is decreased, the thickness of the water repellent material is decreased. For example, when a mixture of PTFE dispersion and VGCF (mixing mass ratio 1: 1) is used as the water repellent material and the wire pulling speed is 0.5 to 5 [mm / s], the thickness of the coating material is 1 To 10 [μm]. It is also possible to give a gradient of water repellency by changing the composition of the water repellent material coated on the surface in the longitudinal direction of the wire. Specifically, when a mixture of PTFE dispersion and VGCF is used as the water repellent material, the water repellency can be increased by increasing the ratio of the PTFE dispersion. In the present invention, it is only necessary to provide a drainage gradient in the longitudinal direction of the wire, and the method is not limited to that exemplified here. Further, as shown in FIG. 3B, the drainage gradient is preferably applied in an inclined manner, but may be stepwise.

(Second Embodiment)
Hereinafter, the tube type fuel cell according to the second embodiment of the present invention will be described with reference to FIGS. 4 to 6, members having the same configurations as those in FIGS. 1 to 3 are denoted by the same reference numerals as those used in FIGS. 1 to 3, and description thereof is omitted as appropriate.

  FIG. 4 is a cross-sectional view schematically showing a tube fuel cell according to the second embodiment of the present invention. 4 is the longitudinal direction of the inner current collector 26. As shown in the figure, the tube-type fuel cell 20 of the present invention (hereinafter simply referred to as “fuel cell 20”) includes an inner current collector 26 disposed on the inner peripheral surface side of the structure 3. The inner current collector 26 has a plurality of wires 25a, 25a,..., Wires 25b, 25b,..., Wires 25c, 25c,. And a wire 25d disposed on the axis of the structure 3. Wire rods 25a, 25a,..., Wire rods 25c, 25c,..., And wire rods 25d (hereinafter referred to simply as “wire rods 25, 25,...”). May be formed of a conductive wire (for example, a metal wire).

  FIG. 5 is an enlarged cross-sectional view showing a part of the fuel cell 20 shown in FIG. The back / front direction in FIG. 5 is the longitudinal direction of the inner current collector 26. The arrows in the figure indicate the direction in which water is discharged. In the fuel cell 20, the water repellent treatment is performed only on the outermost wire rods 25 a, 25 a,. Therefore, the water repellency of the wire rods 25a, 25a,... Can be made higher than the water repellency of the wire rods 25b, 25b,..., The wire rods 25c, 25c,. By doing so, the water on the inner peripheral surface side of the structure 3 moves toward the axial center side (higher hydrophilicity) of the inner current collector 26, so that the drainage of the cathode electrode 2a is improved. Can be made. Further, the water collected on the axial center side of the inner current collector 26 is discharged by the gas flowing on the inner peripheral surface side of the structure 3.

  As a method for imparting water repellency to the wires 25a, 25a,..., The same method as the above method for imparting water repellency to the wires 5a, 5a,.

  FIG. 6 is a perspective view showing a tube fuel cell according to the second embodiment with a part thereof omitted. The left-right direction in FIG. 6 is the longitudinal direction of the inner current collector 26. The arrows in the figure indicate the direction of air flow, with the left side of the paper being the air inlet side and the right side of the paper being the air outlet side. As shown in FIG. 6, in the fuel cell 20, a plurality of wires 25, 25,... Constituting the inner current collector 26 are arranged in parallel. Also with this form of fuel cell 20, the drainage of the structure 3 can be improved, so flooding can be suppressed and power generation performance can be improved.

(material)
The electrolyte membrane 1 provided in the fuel cells 10 and 20 of the present invention is a hollow electrolyte membrane containing a proton conductive polymer. Specific examples of the proton conductive polymer contained in the electrolyte membrane 1 include a fluorine-based polymer having at least one of a sulfonic acid group, a phosphonic acid group, and a phosphoric acid group with a fluorine-containing polymer as a skeleton. Examples thereof include hydrocarbon-based polymers having a hydrocarbon skeleton. Specific examples of the electrolyte membrane containing the fluorine polymer include Nafion ("Nafion" is a registered trademark of DuPont, USA) and Flemion ("Flemion" is a registered trademark of Asahi Glass Co., Ltd.). On the other hand, as a specific example of the electrolyte membrane containing the hydrocarbon-based polymer, there can be mentioned Selemion and the like (“Selemion” is a registered trademark of Asahi Glass Co., Ltd.).

  The cathode electrode 2a and the anode electrode 2b are a substance (catalyst) that functions as a catalyst for an electrochemical reaction generated at the anode and cathode of the fuel cells 10 and 20, and a substance that can conduct protons generated by the electrochemical reaction (proton conductivity). As long as it has (substance), its form is not particularly limited. Specific examples of the catalyst are selected from the group consisting of Pt, Co, Ru, Ir, Au, Ag, Cu, Ni, Fe, Cr, Mn, V, Ti, Mo, Pd, Rh, and W. Examples thereof include a Pt alloy having one or more metals and Pt. Specific examples of the proton conductive substance include the proton conductive polymer that can be contained in the electrolyte membrane.

  If the wire rods 5, 5,... And the wire rods 25, 25,... Constituting the inner current collectors 6, 26 and the outer current collector 4 are made of a material having good electron conductivity, The constituent material is not particularly limited. Specific examples of the constituent material include metals such as copper, silver, gold, and platinum. When copper is used as a constituent material of the current collector, the surface is preferably covered with silver, gold, platinum, or the like in order to improve acid resistance.

(Other forms)
So far, the mode in which air is supplied to the inner peripheral surface side of the tube type fuel cells 10 and 20 and hydrogen is supplied to the outer peripheral surface side has been described. However, hydrogen is supplied to the inner peripheral surface side of the tube type fuel cells 10 and 20. May be supplied, and air may be supplied to the outer peripheral surface side. In the said form, the 1st electrode 2a becomes an anode electrode and the 2nd electrode 2b becomes a cathode electrode.

  Moreover, the inner side collector of the tube type fuel cell of this invention is not limited to the form shown in FIGS. The inner current collector provided in the tube-type fuel cell of the present invention may be constituted by a plurality of wires arranged concentrically around the axis of the structure within a region surrounded by the first electrode. It ’s fine.

  Furthermore, the first embodiment shows a form in which all of the wires 5, 5,... Are subjected to water repellent treatment or hydrophilic treatment, and in the second embodiment, only the outermost wires 5a, 5a,. Although the form to which a process is performed was shown, the tube type fuel cell of this invention is not limited to the said form. In the present invention, it is sufficient that at least a plurality of wires that are in contact with the inner peripheral surface of the structure have water repellency.

  FIG. 7 shows another embodiment that can be adopted by the tubular fuel cell of the present invention. 7 is the longitudinal direction of the inner current collector 26. The arrows in the figure indicate the direction in which water is drained. In FIG. 7, members having the same configurations as those in FIGS. 1 to 6 are denoted by the same reference numerals as those used in FIGS. 1 to 6, and description thereof is omitted as appropriate.

  The tube-type fuel cell 30 of the present invention shown in FIG. 7 (hereinafter simply referred to as “fuel cell 30”) also imparts water repellency to the outer current collector 34. When the winding method of the outer current collector 34 is sparse, water is likely to flow along with the gas flowing on the outer peripheral surface side of the structure 3, so that the outer current collector 34 may not be provided with water repellency. However, when the outer current collector 34 is wound in a dense manner, the drainage on the outer peripheral surface side of the structure 3 is likely to be deteriorated. Therefore, it is preferable to impart water repellency to the outer current collector 34 as well.

  In the above description regarding the fuel cells 10, 20, and 30 of the present invention, the mode in which the diffusion layer is not provided on the inner peripheral surface side and the outer peripheral surface side of the structure 3 is illustrated, but the tube fuel cell of the present invention is It is not limited to the said form. From the viewpoint of allowing the reactant gas to be supplied uniformly to the structure while suppressing flooding, it is preferable that a diffusion layer is provided on the inner peripheral surface side and / or the outer peripheral surface side of the structure 3. In the case where the tubular fuel cell of the present invention is provided with a diffusion layer, the diffusion layer can be composed of carbon paper, carbon cloth, or the like.

1. Fabrication of tube-type fuel battery cell Ketjen black and conductive resin (Dotite (manufactured by Fujikura Kasei Co., Ltd.)) treated with nitric acid on a plurality of copper wires with a diameter of 0.23 [mm] with gold plating on the surface The mixture was mixed with a solvent (alcohol) and subjected to a hydrophilic treatment in which the mixture was baked while being held at 200 [° C.] for 10 minutes or longer. On the other hand, a mixed solution of PTFE dispersion and VGCF (mixing mass ratio 1: 1) is mixed at 300 [° C.] for 10 minutes on a plurality of copper wires having a diameter of 0.08 [mm] with gold plating on the surface. A water repellent treatment for holding and firing was performed. Then, a plurality of wires subjected to the hydrophilic treatment are spirally wound in a clockwise direction around the one wire subjected to the hydrophilic treatment, and then the water-repellent treatment is further provided on the outside thereof. After winding a plurality of wires with a spiral in a counterclockwise direction, the plurality of wires subjected to the water-repellent treatment are wound spirally in a clockwise direction on the outer side. Thus, an inner current collector was produced.

  In addition, a Pt / C catalyst in which platinum was supported on ketjen black and Nafion were mixed, and ethanol and water were added as solvents to prepare an electrode catalyst ink. The obtained electrode catalyst ink was applied and dried on the outer side of the inner current collector, and the electrolyte membrane composition (Nafion) in a fluid state was further applied and dried on the outer side. MEA was produced by applying and drying electrode catalyst ink. The MEA thus produced had an inner diameter of 1 [mm], an outer diameter of 1.3 [mm], and a length of 150 [mm]. Furthermore, the copper wire which gave the surface gold plating was wound around the outer peripheral surface of MEA, and it was set as the outer side electrical power collector. The diameter of the outer current collector was 0.08 [mm]. Through the above steps, a tubular fuel cell according to the example was manufactured.

  Furthermore, in order to perform performance comparison with the tube type fuel cell according to the example, the tube type fuel cell according to the comparative example was manufactured. The tube-type fuel cell according to the comparative example is a tube-type fuel cell in which the inner current collector and the outer current collector are not subjected to water repellent treatment and hydrophilic treatment, and other configurations are the tube-type fuel cells according to the embodiment. Same as battery.

2. IV Characteristics Evaluation FIG. 8 shows the results of evaluating the power generation characteristics of the tube fuel cell according to the example and the tube fuel cell according to the comparative example. An oxygen-containing gas was supplied to the inner peripheral surface side of the tube-type fuel cell according to the example and the tube-type fuel cell according to the comparative example, and a hydrogen-containing gas was supplied to the outer peripheral surface side. At this time, the temperature of the tubular fuel cell according to the example and the tubular fuel cell according to the comparative example is 80 [° C.], and the temperature of the reaction gas (hydrogen-containing gas and oxygen-containing gas) is 80 [° C.]. It was. When the tube-type fuel cell according to the comparative example and the tube-type fuel cell according to the example were compared, a difference in performance in a high current density region was observed. In the tube type fuel cell according to the comparative example, the performance is greatly deteriorated in the high current density region, whereas in the tube type fuel cell according to the example, the degree of the decrease is small. It is considered that the reason why the tubular fuel cell greatly deteriorates the performance in the high current density region is that the diffusion of gas to the catalyst is prevented by flooding. In the tubular fuel cell according to the example, the drainage was improved, so that the performance degradation due to flooding in the high current density region was suppressed.

1 is a cross-sectional view schematically showing a fuel cell 10. FIG. 2 is an enlarged cross-sectional view showing a part of the fuel cell 10. FIG. FIG. 3A is a perspective view in which a part of the fuel cell 10 is omitted. FIG. 3B is a diagram illustrating a gradient of drainage in the longitudinal direction of the fuel cell 10. 2 is a cross-sectional view schematically showing a fuel cell 20. FIG. 2 is an enlarged cross-sectional view showing a part of a fuel cell 20. FIG. 2 is a perspective view showing a part of the fuel cell 20 omitted. FIG. 1 is a diagram showing a form of a fuel cell 30. FIG. It is a figure which shows the result of electric power generation characteristic evaluation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrolyte membrane 2a ... 1st electrode 2b ... 2nd electrode 3 ... Structure 4, 34 ... Outer collector 5a, 5b, 5c, 5d, 25a, 25b, 25c, 25d ... Wire rod 6, 26 ... Inner collector Body 10, 20, 30 ... Tube type fuel cell

Claims (6)

A hollow electrolyte membrane, a hollow first electrode disposed along the inner peripheral surface of the electrolyte membrane, and a hollow second electrode disposed along the outer peripheral surface of the electrolyte membrane, A tube type comprising: a hollow structure having an inner current collector disposed on the inner peripheral surface side of the structure; and an outer current collector disposed in contact with the outer peripheral surface of the structure A fuel cell,
The inner current collector is constituted by a plurality of wires arranged concentrically around the axis of the structure within a region surrounded by the first electrode,
Among the wires of the inner current collector, the wires on adjacent concentric circles are in contact with each other, and among the wires of the inner current collector, the wires on the outermost concentric circle are the structure and Touching,
Among the wires of the inner current collector, the wires arranged adjacent to each other on the same circle are in contact with each other,
The tube fuel cell according to claim 1, wherein at least the wire arranged on the outermost concentric circle among the wires of the inner current collector has water repellency. The hydrophilic property of the wire disposed on one concentric circle of the inner current collector is lower than or equal to the hydrophilic property of the wire disposed on the concentric circle in contact with the concentric circle. The tube type fuel cell according to claim 1. The diameter of the wire on the outermost concentric circle of the inner current collector is smaller than the diameter of the wire arranged on the innermost side of the inner current collector. A tube type fuel cell according to the above. The diameter of the wire disposed on one concentric circle of the inner current collector is smaller than or equal to the diameter of the wire disposed on the concentric circle in contact with the inner side of the concentric circle. Item 4. The tubular fuel cell according to Item 3. The tube-type fuel cell according to any one of claims 1 to 4, wherein the inner current collector has a drainage property that gradually increases from the reaction gas inlet side toward the outlet side. The tube-type fuel cell according to any one of claims 1 to 5, wherein the outer current collector has water repellency.

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