JP5920664B2 - Fuel cell catalyst layer - Google Patents

Description

  The present invention relates to a fuel cell catalyst layer constituting a membrane electrode assembly of a polymer fuel cell.

  A fuel cell of a polymer electrolyte fuel cell includes a membrane electrode assembly (MEA) formed by forming catalyst layers on both surfaces of an electrolyte membrane having hydrogen ion conductivity, and respective catalyst layers of the membrane electrode assembly. A gas diffusion layer (gas diffusion layer for fuel cell) laminated on the substrate and a separator are formed outside the diffusion layer. Actually, these fuel cells are stacked in the number corresponding to the power generation performance to form a fuel cell stack.

  The catalyst layer is obtained by supporting platinum on carbon and further containing an electrolyte resin (ionomer), and constitutes an electrode layer that generates a power generation reaction by the supplied reaction gas. The catalyst layer formed on one surface of the membrane electrode assembly (MEA) constitutes an anode (fuel electrode layer), and the catalyst layer formed on the other surface constitutes a cathode (air electrode).

  In this fuel cell, hydrogen gas or the like is provided as a fuel gas to an anode electrode, and oxygen or air is provided as an oxidant gas to a cathode electrode to cause an electrochemical reaction. In this electrochemical reaction, hydrogen ions and water generated at the anode electrode pass through the electrolyte membrane in a hydrated state to reach the cathode electrode, and generated water is generated at the cathode electrode. Therefore, depending on the movement mode of water in the membrane electrode assembly and the generation mode of water generated by electrochemical reaction, the anode electrode is easily dried with the progress of power generation, and in some cases, it is dry up, while the cathode electrode is likely to be excessively watery. In some cases, there is a problem that flooding is likely to occur.

  By the way, among the electrodes composed of the catalyst layer and the gas diffusion layer, the surface of the catalyst layer is generally smooth. Therefore, the reaction gas such as fuel gas and oxidant gas does not effectively touch the catalyst layer, the catalyst becomes more dense and the catalyst is easily corroded during power generation, contact between the gas diffusion layer and the catalyst layer There is a problem that the electrical resistance at the interface between them is small and the electrical resistance is large. Therefore, in Patent Document 1 below, there is a content in which irregularities are formed on the diffusion layer side surface of the catalyst layer, and the irregularities of the catalyst layer are bitten into the carbon fibers of the gas diffusion layer laminated on the catalyst layer. Have been described.

JP 2006-286476 A

  The catalyst layer formed by the method described in Patent Document 1 contains an electrolyte resin, and this electrolyte resin may be present in many portions other than the convex portions on the diffusion layer side surface of the catalyst layer. . Then, although the adhesion between the catalyst layer and the diffusion layer can be improved, there is a problem that the gas diffusibility is lowered due to the electrolyte resin present in the portion other than the convex portion on the diffusion layer side surface of the catalyst layer. It was.

  This invention is made | formed in view of such a subject, The objective is to make compatible suppression of the fall of gas diffusibility, and the adhesive improvement of a catalyst layer and the layer laminated | stacked next to it. An object of the present invention is to provide a fuel cell catalyst layer.

In order to solve the above problems, a catalyst layer for a fuel cell according to the present invention is a catalyst layer for a fuel cell used in a polymer fuel cell, and is a surface on one side of a porous substrate formed in a sheet shape And a catalyst layer containing carbon particles carrying a catalyst and an electrolyte resin, and a protrusion formed on the surface of the catalyst layer, wherein the first of the surfaces of the catalyst layer is inside the protrusion. The first ratio of the weight C1 of the carbon particles and the weight I1 of the first electrolyte resin is X1, and the weight C2 and the second weight C2 of the second carbon particles on the surface of the catalyst layer on which the protrusions are not formed. When the second ratio of the second electrolyte resin to the weight I2 is defined as X2, X1 is larger than X2.

  With this configuration, the electrolyte resin is deflected to the protrusion, and the amount of the electrolyte resin on the surface other than the protrusion is suppressed. As a result, a decrease in gas diffusibility can be suppressed while ensuring adhesion between the catalyst layer formed by the protrusions and a layer (for example, a gas diffusion layer) laminated adjacent thereto.

  In the fuel cell catalyst layer according to the present invention, the angle formed by the surface of the catalyst layer and one surface of the protrusion is a first angle, and the surface of the catalyst layer and the other surface of the protrusion are formed. When the angle is defined as the second angle, one of the first angle and the second angle may be larger than 90 degrees.

  By comprising in this way, since the protrusion formed on the surface of the catalyst layer can be made to easily bite into the diffusion layer side surface, the adhesion between the catalyst layer and the diffusion layer side surface can be further improved. Can do.

  According to the present invention, it is possible to achieve both suppression of a decrease in gas diffusibility and improvement in adhesion between the catalyst layer and a layer laminated adjacent thereto.

It is sectional drawing of the fuel cell containing the membrane electrode assembly obtained by one Embodiment of this invention. (A)-(f) is process drawing for demonstrating the manufacturing method of the catalyst layer in the fuel cell shown in FIG. (A) is the figure which showed the conventional catalyst layer, (b)-(d) is the figure which showed the catalyst layer obtained by one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  FIG. 1 is a cross-sectional view of a fuel cell including a membrane electrode assembly obtained according to an embodiment of the present invention. The fuel cell 1 is a so-called flat plate type polymer electrolyte fuel cell (PEFC), and is formed in a rectangular shape in plan view. As shown in FIG. 1, the fuel cell 1 includes a membrane electrode assembly 10, a pair of gas diffusion layers 20, and a pair of separators 30.

  The membrane electrode assembly 10 has catalyst layers 12a and 12b on both surfaces of an electrolyte membrane 11 having hydrogen ion conductivity, respectively, and is so-called MEA. Each of the catalyst layers 12a and 12b is formed on both surfaces of the electrolyte membrane 11 as a catalyst layer (electrode layer) in which platinum fine particles are supported on carbon particles and an electrolyte (ionomer) is further contained. The catalyst layer 12a is a cathode electrode layer that reacts with an oxidant gas (for example, air), and the catalyst layer 12b is an anode electrode layer that reacts with a fuel gas (for example, hydrogen). The specific configuration and manufacturing method of the membrane electrode assembly 10 will be described in detail later.

  The gas diffusion layer 20 is a layer for improving the diffusibility of the reaction gas, and is disposed so as to sandwich the membrane electrode assembly 10 from both sides. That is, the fuel cell 1 has two gas diffusion layers 20 including a cathode side gas diffusion layer 20a and an anode side gas diffusion layer 20b. A cathode side gas diffusion layer 20 a is laminated on the catalyst layer 12 a of the electrolyte membrane 11, and an anode side gas diffusion layer 20 b is laminated on the catalyst layer 12 b of the electrolyte membrane 11.

  The separator 30 is a conductive layer disposed on the outermost side of the fuel cell 1 and is made of carbon. The separator 30 includes a cathode side separator 30a disposed adjacent to the cathode side gas diffusion layer 20a and an anode side separator 30b disposed adjacent to the anode side gas diffusion layer 20b. These are the same as each other. It has a shape.

  A plurality of grooves 31a having a rectangular cross section are formed in parallel with each other on the surface of the cathode separator 30a that is in contact with the cathode gas diffusion layer 20a. These grooves 31a are flow paths for supplying oxidant gas from the outside. Similarly, a plurality of grooves 31b having a rectangular cross section are formed in the anode side separator 30b so as to be arranged in parallel to each other. These grooves 31b are flow paths for supplying fuel gas from the outside.

  Although FIG. 1 shows only one fuel cell 1 (single cell), in a fuel cell actually used as a power supply source, a plurality of fuel cells 1 are stacked and are mutually connected via a separator 30. Electrically connected in series (cell stack). Although the power generation voltage of one fuel cell 1 is about 1V, a high voltage of several hundreds V can be output by connecting a plurality of fuel cells 1 in series as described above. Note that a refrigerant flow path for cooling the fuel cell 1 may be formed between the cathode side separator 30a and the anode side separator 30b adjacent to each other.

  Next, an example of a method for producing a membrane electrode assembly according to the present invention will be described with reference to FIG. FIG. 2 is a diagram for explaining a manufacturing method of the membrane electrode assembly 10 among the components of the fuel battery cell 1 shown in FIG. 1.

  As shown in FIG. 2A, a masking sheet 50 is applied on the resin sheet 40. Then, a cut is made in the surface of the resin sheet 40. This notch is, for example, when the angle between the surface of the resin sheet 40 and one surface of the notch is θ1, and the angle between the surface of the resin sheet 40 and the other surface of the notch is θ2, θ1 and θ2 Either one is formed to have an obtuse angle. As shown in FIG. 2B, a catalyst ink 60 having a high ionomer / carbon ratio is applied to the cut formed in FIG. As shown in FIG. 2C, the masking sheet 50 applied to the upper surface of the resin sheet 40 is peeled off. As shown in FIG. 2 (d), a catalyst ink 70 having a low ionomer / carbon ratio is applied to the surfaces of the resin sheet 40 and the catalyst ink 60. Thereafter, as shown in FIG. 2 (e), the catalyst layer 12b formed of the catalyst ink 60 and the catalyst ink 70 is overlaid on the electrolyte membrane 11 and joined together by hot pressing to be integrated. Finally, as shown in FIG. 2 (f), the protrusion 13 is formed on the surface of the catalyst layer 12b by peeling the resin sheet.

  As shown in FIG. 3A, carbon particles CB carrying a catalyst are formed in the conventional catalyst layer 12b. On the lower surface of the catalyst layer 12b, a bonding layer 100 is formed for suppressing the size of the electrolyte membrane. The bonding layer 100 is formed from a material containing carbon particles CB and a resin. That is, many carbon particles CB are arranged on the surface of the catalyst layer 12b.

  On the other hand, as shown in FIG. 3B, in the catalyst layer 12b according to the present embodiment, protrusions 13 are formed on the surface of the catalyst layer 12b. Here, as shown in FIG. 3 (d), the carbon weight inside the protrusion 13 is C1, the ionomer weight is I1, and the carbon weight present on the surface of the catalyst layer 12b where the protrusion 13 is not formed is C2. When the ionomer weight is defined as I2, ionomer weight I1 / carbon weight C1 = X1 (first ratio), and ionomer weight I2 / carbon weight C2 = X2 (second ratio), there is a relationship of X1> X2.

  With this configuration, the electrolyte resin is deflected to the protrusions 13 and the amount of the electrolyte resin on the surface of the catalyst layer 12b where the protrusions 13 are not formed is suppressed. As a result, it is possible to improve the adhesion between the catalyst layer 12b and the cathode-side gas diffusion layer 20a by the protrusions 13 without hindering the gas diffusivity.

  In the present embodiment, as shown in FIG. 3C, the angle formed between the surface of the catalyst layer 12b and one surface of the protrusion 13 is θ1, and the surface of the catalyst layer 12b and the other surface of the protrusion 13 are When θ2 is defined as θ2, either θ1 or θ2 has an obtuse angle.

  With this configuration, the protrusions 13 formed on the surface of the catalyst layer 12b can be easily bited into the gas diffusion layer 20 side surface, so that the catalyst layer 12b and the cathode side gas diffusion layer 20a are in close contact with each other. The property can be further improved.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

DESCRIPTION OF SYMBOLS 10 Membrane electrode assembly 11 Electrolyte membrane 12a Catalyst layer 12b Catalyst layer 13 Protrusion 20 Gas diffusion layer 20a Cathode side gas diffusion layer 20b Anode side gas diffusion layer 30 Separator 30a Cathode side separator 30b Anode side separator 31a Groove 31b Groove 40 Resin sheet 50 Masking sheet 60 Catalyst ink 70 Catalyst ink 100 Bonding layer

Claims (1)

A fuel cell catalyst layer used in a polymer fuel cell,
A catalyst layer formed on one surface of a porous substrate formed in a sheet shape and containing carbon particles carrying a catalyst and an electrolyte resin;
A protrusion formed on the porous substrate side surface of the catalyst layer,
The ratio I1 / C1 of the weight I1 of the first electrolyte resin to the weight C1 of the first carbon particles in the protrusions on the surface of the catalyst layer is X1, and the catalyst on which the protrusions are not formed. the second of the ratio I2 / C2 carbon weight of the second said electrolyte resin to the weight C2 of the particles I 2 at the surface of the layer when defined as X2, the X1 is rather larger than the X2,
The protrusion has a triangular shape in a cross-sectional view with a part of the porous substrate side surface of the catalyst layer as a bottom surface and a side surface protruding from the porous substrate side surface of the catalyst layer,
Angle a first angle formed in the protrusion inside of the angle formed between the one surface of the side surface and the porous substrate side surface of the catalyst layer, the side with the porous base material side surface of the catalyst layer When the angle formed with the other surface of the projection is defined as the second angle,
Only one of the first angle and the second angle is greater than 90 degrees.

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