JP2009211891A - Fuel cell, and drainage method therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to discharge certainly staying water on the downstream side of a reaction gas passage with a simple and compact structure. <P>SOLUTION: An electrolyte membrane-electrode assembly 12 is provided with a solid polymer electrolyte membrane 40 and a cathode side electrode 42 and an anode side electrode 44 to pinch the solid polymer electrolyte membrane 40. The cathode side electrode 42 and the anode side electrode 44 have gas diffusion layers 42a, 44a consisting of carbon paper or the like, first electrode catalyst layers 42b, 44b in which porous carbon particles of which on the surface platinum alloy being an electrode catalyst is carried are coated uniformly on the surface of the gas diffusion layers 42a, 44a, and second electrode catalyst layers 42c, 44c which correspond to an exit buffer part 28b of an oxidizer gas passage 26 and an exit buffer part 32b of a fuel gas passage 30, and are formed by providing an electrode catalyst of a smaller amount than the first electrode catalyst layers 42b, 44b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention has an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator, and the separator has a reaction gas flow path for supplying a reaction gas along the electrode surface, The present invention relates to a fuel cell in which an outlet buffer unit is provided at least on the downstream side of the reaction gas channel, and a drainage method thereof.

  In general, a polymer electrolyte fuel cell has an electrolyte membrane / electrode structure in which an anode side electrode and a cathode side electrode are disposed on both sides of an electrolyte membrane (electrolyte) made of a polymer ion exchange membrane, using a separator. It is equipped with a sandwiched power generation cell. This type of fuel cell is normally used as a fuel cell stack by stacking a predetermined number of power generation cells.

  In the fuel cell described above, a fuel gas flow path (hereinafter also referred to as a reaction gas flow path) for flowing a fuel gas to the anode side electrode and an oxidation for flowing an oxidant gas to the cathode side electrode in the plane of the separator. An agent gas channel (hereinafter also referred to as a reaction gas channel) is provided. Furthermore, a cooling medium flow path for flowing a cooling medium is provided along the surface direction of the separator for each power generation cell or for each of the plurality of power generation cells.

  In this type of fuel cell, generated water is generated at the cathode side electrode by the power generation reaction, while the generated water is back-diffused at the anode side electrode. For this reason, moisture tends to condense and stay on the lower end side of the reaction gas flow path, and flooding due to condensed water may occur.

  Therefore, for example, in the solid polymer electrolyte fuel cell disclosed in Patent Document 1, as shown in FIG. 5, a laminate 3 in which the anode 2 a and the cathode 2 b are respectively disposed on both sides of the electrolyte 1, A fuel distribution plate 4 provided on the anode 2a side of the laminate 3 and having a fuel flow path 4a for supplying fuel to the anode 2a; a cathode 2b side of the laminate 3; And an oxidant flow plate 5 having an oxidant flow path 5a for supplying an oxidant to 2b.

  Then, at least one of the depth and the width of the oxidant flow path 5a of the oxidant distribution plate 5 is gradually reduced from the upstream flow path area of the oxidant along the downstream flow path area. For this reason, the flow rate of the oxidizing agent in the downstream flow path area is increased, the discharge of the generated water and the moving water on the cathode electrode 2b side is improved, and the gas diffusion of oxygen in the oxidizing agent is also improved and stable. The battery reaction can be maintained.

JP-A-6-267564

  However, in Patent Document 1 described above, since the depth and width of the oxidant flow path 5a are changed, the thickness and the dimension in the surface direction of the oxidant distribution plate 5 may be increased. In addition, the groove shape of the oxidant flow path 5a is complicated, and the manufacturing cost of the oxidant distribution plate 5 is increased, which is not economical.

  The present invention solves this type of problem, and provides a fuel cell capable of reliably discharging generated water that tends to stay on the downstream side of a reaction gas flow path with a simple and economical configuration. With the goal.

  The present invention has an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator, and the separator has a reaction gas flow path for supplying a reaction gas along the electrode surface, The present invention relates to a fuel cell in which an outlet buffer unit is provided at least on the downstream side of the reaction gas channel.

  The electrolyte / electrode structure includes a first electrode catalyst layer formed by providing an electrode catalyst corresponding to the reaction gas flow path, and a smaller amount of electrode catalyst than the first electrode catalyst layer corresponding to the outlet buffer portion. And a second electrode catalyst layer formed by providing.

  Further, the present invention includes an electrolyte / electrode structure provided with a pair of electrodes on both sides of an electrolyte and a separator, and the separator is formed with a reaction gas flow path for supplying a reaction gas along the electrode surface. In addition, the present invention relates to a fuel cell drainage method in which an outlet buffer is provided at least downstream of the reaction gas flow path.

  This drainage method is formed by supplying a reaction gas to the reaction gas flow path to generate power on the electrode surface, and providing a smaller amount of electrode catalyst than the power generation surface corresponding to the outlet buffer portion. A step of removing the generated water from the outlet buffer portion under the heat generation action of the heat generation surface by supplying the reaction gas moved along the electrode surface to the heat generation surface.

  According to the present invention, power is generated in the first electrode catalyst layer (electrode surface) by supplying the reaction gas from the inlet buffer to the reaction gas flow path. The generated water at the time of power generation moves to an outlet buffer portion provided on the downstream side of the reaction gas flow path, while the second electrode catalyst layer (heat generation surface) formed corresponding to the outlet buffer portion When the reaction gas is supplied, power is generated and heat is generated.

  Therefore, the generated water that has moved to the outlet buffer portion is not vaporized and dewed, and can be satisfactorily removed from the outlet buffer portion. Thus, the reaction gas can smoothly flow along the reaction gas flow path, and efficient power generation can be reliably performed.

  Furthermore, the second electrode catalyst layer (heat generation surface) is formed by providing a smaller amount of electrode catalyst (a small amount in unit area) than the first electrode catalyst layer (electrode surface). For this reason, in the second electrode catalyst layer (heat generation surface), the activation overvoltage increases, the heat generation amount increases, the generated water is easily vaporized, the drainage performance is improved, and the electrode catalyst amount is reduced. Is.

  In addition, the second electrode catalyst layer (heat generation surface) is provided only at the portion corresponding to the outlet buffer portion, and no electrode catalyst is used at the portion corresponding to the inlet buffer portion. Therefore, the cost can be easily reduced, and no power is generated corresponding to the inlet buffer, and the generated water during power generation can be prevented from lowering the flowability of the reaction gas.

  FIG. 1 is an exploded perspective view of a main part of a fuel cell 10 according to an embodiment of the present invention. The fuel cell 10 is configured as a single cell or a stack formed by stacking a plurality of single cells, but will be described below as a single cell for convenience.

  In the fuel cell 10, an electrolyte membrane / electrode structure 12 is sandwiched between a cathode-side first separator 14 and an anode-side second separator 16. The 1st and 2nd separators 14 and 16 are constituted by a carbon separator, for example.

  The first and second separators 14 and 16 may be formed of, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or a dense metal plate that has been subjected to a surface treatment for corrosion prevention on its metal surface. Good.

  An oxidant gas supply for supplying an oxidant gas, for example, an oxygen-containing gas, communicates with each other in the direction of the arrow A at the upper edge of the long side direction (the direction of arrow C in FIG. 1) of the fuel cell 10. A communication hole 18a and a fuel gas supply communication hole 20a for supplying a fuel gas, for example, a hydrogen-containing gas, are provided.

  The lower end edge of the long side direction of the fuel cell 10 communicates with each other in the direction of arrow A, and the fuel gas discharge communication hole 20b for discharging the fuel gas and the oxidant gas discharge for discharging the oxidant gas A communication hole 18b is provided.

  At one edge of the fuel cell 10 in the short side direction (arrow B direction), there is provided a cooling medium supply communication hole 22a that communicates with each other in the arrow A direction and supplies a cooling medium. A cooling medium discharge communication hole 22b for discharging the cooling medium is provided at the other end edge.

  An oxidant gas flow path 26 is formed on the surface 14a of the first separator 14 facing the electrolyte membrane / electrode structure 12 by connecting the oxidant gas supply communication hole 18a and the oxidant gas discharge communication hole 18b. The oxidant gas flow channel 26 extends in the direction of gravity (arrow C direction) and is positioned at the upper end (upstream) and lower end (downstream) of the oxidant gas flow channel 26 in the direction of arrow C. A portion 28a and an outlet buffer portion 28b are provided. The inlet buffer portion 28a and the outlet buffer portion 28b have a plurality of embossments.

  As shown in FIGS. 1 and 2, the fuel gas flow path that connects the fuel gas supply communication hole 20 a and the fuel gas discharge communication hole 20 b to the surface 16 a of the second separator 16 facing the electrolyte membrane / electrode structure 12. 30 is formed. The fuel gas passage 30 extends in the direction of gravity (arrow C direction) and is positioned at the upper and lower ends of the fuel gas passage 30 in the direction of arrow C, and includes an inlet buffer portion 32a and an outlet buffer portion 32b. Is provided. The inlet buffer portion 32a and the outlet buffer portion 32b have a plurality of embosses.

  As shown in FIG. 1, between the surface 16b of the second separator 16 and the surface 14b of the first separator 14, a cooling medium flow path communicating with the cooling medium supply communication hole 22a and the cooling medium discharge communication hole 22b. 34 is formed. This cooling medium flow path 34 is formed extending in the direction of arrow B.

  On the surfaces 14 a and 14 b of the first separator 14, a first seal member (gasket) 36 is disposed around the outer peripheral edge of the first separator 14. A second seal member (gasket) 38 is disposed on the surfaces 16 a and 16 b of the second separator 16 so as to go around the outer peripheral edge of the second separator 16.

  The electrolyte membrane / electrode structure 12 includes, for example, a solid polymer electrolyte membrane 40 in which a perfluorosulfonic acid thin film is impregnated with water, and a cathode side electrode 42 and an anode side electrode 44 that sandwich the solid polymer electrolyte membrane 40. With.

  As shown in FIGS. 2 to 4, the cathode side electrode 42 and the anode side electrode 44 are porous carbon particles having gas diffusion layers 42 a and 44 a made of carbon paper or the like and a platinum alloy as an electrode catalyst supported on the surface. Are applied to the surfaces of the gas diffusion layers 42a and 44a uniformly, and the first electrode catalyst layers (electrode surfaces) 42b and 44b, the outlet buffer portion 28b of the oxidant gas channel 26, and the fuel gas channel A second electrode catalyst layer (heat generating surface) 42c formed by providing a small amount (a small amount in unit area) of the electrode catalyst corresponding to 30 outlet buffer portions 32b and smaller than the first electrode catalyst layers 42b and 44b. 44c. The first electrode catalyst layers 42 b and 44 b and the second electrode catalyst layers 42 c and 44 c are formed on both surfaces of the solid polymer electrolyte membrane 40.

  The cathode-side electrode 42 and the anode-side electrode 44 are not provided with electrode catalyst layers at portions corresponding to the inlet buffer portion 28 a of the oxidant gas flow channel 26 and the inlet buffer portion 32 a of the fuel gas flow channel 30.

  The operation of the fuel cell 10 configured as described above will be described below in relation to the drainage method according to the present embodiment.

  First, as shown in FIG. 1, an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas supply communication hole 18a, and a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas supply communication hole 20a. Supplied. On the other hand, a coolant such as pure water or ethylene glycol is supplied to the coolant supply passage 22a.

  The oxidant gas is introduced into the oxidant gas flow path 26 of the first separator 14 through the oxidant gas supply communication hole 18a, and along the cathode side electrode 42 of the electrolyte membrane / electrode structure 12 in the gravity direction (downward in the direction of arrow C). ) Therefore, the oxidant gas is supplied to the cathode side electrode 42 of the electrolyte membrane / electrode structure 12.

  Further, the fuel gas is introduced into the fuel gas flow path 30 of the second separator 16 from the fuel gas supply communication hole 20a, and along the anode side electrode 44 of the electrolyte membrane / electrode structure 12 in the direction of gravity (downward in the direction of arrow C). Move to. Accordingly, the fuel gas is supplied to the anode electrode 44 of the electrolyte membrane / electrode structure 12.

  Thereby, in the electrolyte membrane / electrode structure 12, the oxidant gas supplied to the cathode side electrode 42 and the fuel gas supplied to the anode side electrode 44 are electrochemically generated in the first electrode catalyst layers 42b and 44b. It is consumed by the reaction and power is generated.

  On the other hand, the cooling medium flows into the cooling medium flow path 34 between the first and second separators 14 and 16 from the cooling medium supply communication hole 22a and then flows along the arrow B direction (horizontal direction). The cooling medium is discharged from the cooling medium discharge communication hole 22b after the electrolyte membrane / electrode structure 12 is cooled.

  Next, the oxidant gas consumed by being supplied to the cathode side electrode 42 is sent to an outlet buffer unit 28 b communicating with the lower part of the oxidant gas flow channel 26 as shown in FIGS. 1 and 2. Similarly, the fuel gas consumed by being supplied to the anode side electrode 44 is sent to the outlet buffer portion 32 b that communicates with the lower portion of the fuel gas flow path 30.

  In this case, in the present embodiment, the cathode side electrode 42 and the anode side electrode 44 correspond to the outlet buffer portion 28b of the oxidant gas flow channel 26 and the outlet buffer portion 32b of the fuel gas flow channel 30, and the first electrode catalyst layer. It has the 2nd electrode catalyst layers 42c and 44c which provide a smaller amount of electrode catalysts than 42b and 44b.

  For this reason, in the 2nd electrode catalyst layers 42c and 44c, it generates heat by generating electricity with residual oxidant gas and fuel gas. Accordingly, the water generated during power generation (including the water that is reversely diffused) in the first electrode catalyst layers 42b and 44b stays in the outlet buffer portions 28b and 32b in order to vaporize after moving along the direction of gravity. There is no condensation.

  Thus, the generated water is smoothly and reliably discharged from the outlet buffer portions 28b and 32b to the oxidant gas discharge communication hole 18b and the fuel gas discharge communication hole 20b via the discharged oxidant gas and fuel gas. For this reason, the oxidant gas and the fuel gas can smoothly flow along the oxidant gas flow path 26 and the fuel gas flow path 30, and an effect that efficient power generation can be performed is obtained.

  Further, the second electrode catalyst layers 42c and 44c are formed by providing a smaller amount of electrode catalyst than the first electrode catalyst layers 42b and 44b. At this time, the amount of the electrode catalyst applied to the second electrode catalyst layers 42c and 44c may be the minimum that can generate heat that does not cause condensation in the outlet buffer portions 28b and 32b. Therefore, in the second electrode catalyst layers 42c and 44c, the activation overvoltage increases and the calorific value increases, the generated water is easily vaporized, drainage is improved, and the electrode catalyst amount is effectively reduced. Economical.

  Moreover, the second electrode catalyst layers 42c and 44c are provided only in the portions corresponding to the outlet buffer portions 28b and 32b, and no electrode catalyst is used in the portions corresponding to the inlet buffer portions 28a and 32a. For this reason, it is possible to reduce costs, and no power is generated corresponding to the inlet buffer portions 28a and 32a, and the generated water during power generation reduces the flowability of the oxidant gas and the fuel gas. It can be avoided.

It is a principal part disassembled perspective explanatory view of the fuel cell concerning the embodiment of the present invention. 2 is a cross-sectional explanatory view of the fuel cell. FIG. It is a front view explaining the cathode side electrode of the electrolyte membrane and electrode structure which comprises the said fuel cell. It is a front view explaining the anode side electrode of the said electrolyte membrane electrode structure. 1 is an explanatory diagram of a solid polymer electrolyte fuel cell of Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 12 ... Electrolyte membrane electrode assembly 14, 16 ... Separator 18a ... Oxidant gas supply communication hole 18b ... Oxidant gas discharge communication hole 20a ... Fuel gas supply communication hole 20b ... Fuel gas discharge communication hole 22a ... Cooling Medium supply communication hole 22b ... Cooling medium discharge communication hole 26 ... Oxidant gas flow path 28a, 32a ... Inlet buffer section 28b, 32b ... Outlet buffer section 30 ... Fuel gas flow path 34 ... Cooling medium flow path 42a, 44a ... Gas diffusion Layers 42b, 42c, 44b, 44c ... Electrode catalyst layer

Claims (2)

The separator has an electrolyte / electrode structure provided with a pair of electrodes on both sides of the electrolyte, and the separator has a reaction gas flow path for supplying a reaction gas along the electrode surface, and the reaction gas flow A fuel cell in which an outlet buffer is provided at least on the downstream side of the path,
The electrolyte / electrode structure includes a first electrode catalyst layer formed by providing an electrode catalyst corresponding to the reaction gas flow path,
A second electrode catalyst layer formed by providing a smaller amount of electrode catalyst than the first electrode catalyst layer corresponding to the outlet buffer portion;
A fuel cell comprising: The separator has an electrolyte / electrode structure provided with a pair of electrodes on both sides of the electrolyte, and the separator has a reaction gas flow path for supplying a reaction gas along the electrode surface, and the reaction gas flow A drainage method for a fuel cell, wherein an outlet buffer is provided at least downstream of the path,
A step of generating power on the electrode surface by supplying a reactive gas to the reactive gas flow path;
The reaction gas moved along the electrode surface is supplied to a heat generation surface formed by providing a smaller amount of electrode catalyst than the electrode surface corresponding to the outlet buffer unit, thereby Removing generated water from the outlet buffer portion under an exothermic action;
A method for draining a fuel cell, comprising:

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