JP6600816B2 - Catalyst evaluation apparatus and evaluation method - Google Patents

Description

  The present invention relates to a catalyst evaluation apparatus and a catalyst evaluation method. In particular, the present invention relates to a catalyst evaluation apparatus and a catalyst evaluation method for evaluating a catalyst used in a fuel cell.

  In the polymer electrolyte fuel cell (PEFC), a membrane electrode assembly is formed by joining a catalyst layer and a gas diffusion layer in this order on both outer surfaces of an electrolyte membrane that causes a power generation reaction, and sandwiching them with a separator. A single unit cell is used as a single unit, and a necessary number of unit cells are stacked.

  In recent years, proton conductive ion exchange membranes have been used as the electrolyte membrane, and in particular, cation exchange membranes made of perfluorocarbon polymers having sulfonic acid groups are widely studied because of their excellent basic characteristics.

  A fuel gas containing hydrogen and an oxidant gas containing oxygen such as air are supplied to the polymer electrolyte fuel cell, and the fuel gas and the oxidant gas are reacted electrochemically through the electrolyte membrane. , Electricity, heat and water are generated simultaneously.

  In the polymer electrolyte fuel cell, reactions of the following formulas 1 and 2 occur, and electric energy is generated.

H _{2 for the} negative electrode → 2H ⁺ + 2e ⁻ (Formula 1)
In the positive electrode ^{_{1 / 2O 2 + 2H + +}} 2e - → H 2 O ··· ( Equation 2)
Hydrogen ions (H ⁺ : protons) generated by the reaction at the negative electrode move through the electrolyte membrane and are used for the reaction at the positive electrode.

  Such an electrode reaction is performed in the catalyst layer. The catalyst layer is composed of catalyst-supported carbon and an electrolyte, and an electrode reaction is performed at the interface between the catalyst supported on the carbon and the electrolyte. In addition, the carbon connection in the catalyst layer becomes an electron path, and the electrolyte connection becomes a hydrogen ion path. The supported catalyst contains a large amount of platinum for both the positive electrode and the negative electrode, but a platinum-based alloy catalyst may be used to improve the activity of the positive electrode or the CO resistance of the negative electrode.

  Thus, the performance of the catalyst is directly linked to the performance of the fuel cell. Further, since metals such as platinum used for the catalyst are very expensive materials, it is important to determine the catalyst performance at an early stage of development and with a smaller amount of use.

  The evaluation of the catalyst includes a method of evaluating a single catalyst using a rotating disk electrode (RDE method) and a method of producing a membrane electrode assembly (MEA) and evaluating power generation with a single cell structure.

  However, in the evaluation by the RDE method, a very high characteristic value expected from the catalyst activity value obtained by the RDE method can be obtained. However, when a membrane electrode assembly (MEA) is actually manufactured and evaluated for power generation in a single cell structure, the high characteristic value is often not obtained. It seems that other factors are included.

Moreover, in the method of actually producing a membrane electrode assembly (MEA) and evaluating power generation with a single cell structure, there is a standard cell manufactured by Japan Automobile Research Institute (JARI) as a commercially available single cell. However, since the electrode area is as large as 25 cm ² , many catalysts are required for evaluation. Moreover, since there are many parts for constituting the cell, it is difficult to consider only the influence of the catalyst from the evaluation results.

  Further, as a method for evaluating power generation without constituting a single cell structure, it has been proposed to arrange a positive electrode and a negative electrode on a plane (Patent Document 1). The structure of Patent Document 1 is shown in the sectional view of FIG. In Patent Document 1, the electrolyte membrane 50 is divided into two regions by a partition wall 53. In one area, the catalyst layer 51 is printed and the cathode 56 is disposed. In the other region, the same catalyst layer 52 as that on the anode side of the fuel cell is printed and the anode 55 is disposed. Hydrogen is supplied to the region where the cathode 56 is arranged, and oxygen-containing gas (for example, air) is supplied to the other region where the anode 55 is arranged. In this way, a fuel cell can be constructed and power generation characteristics can be evaluated.

Japanese Patent No. 4624528

  However, in the configuration of Patent Document 1, the region is divided in the plane direction of the electrolyte membrane 50 by the partition wall 53 and the anode 55 and the cathode 56 are arranged, and the actual fuel cell generates power in the thickness direction of the electrolyte membrane 50. The structure is different.

  In addition, since there is no mechanism for diffusing the supplied gas and a structure for applying a load to the electrodes, it is impossible to measure accurate power generation characteristics.

  The present invention has been made in view of such problems, and provides a catalyst evaluation apparatus and an evaluation method capable of measuring the power generation characteristics of a catalyst simply, with high accuracy, and with a small amount of catalyst. Objective.

  To achieve the above object, a first electrode having a pipe structure having a first gas flow path, a second electrode having a planar structure, a mounting table for holding a catalyst, and between the first electrode and the second electrode And a catalyst evaluation apparatus including a measurement unit for measuring electrical characteristics. A first step of flowing a first gas to a first electrode of a pipe structure having a first gas flow path; a second step of supplying a second gas to a second electrode of a planar structure; the first electrode and the second A catalyst evaluation method is used in which a catalyst to be measured is sandwiched between electrodes, and electrical characteristics between the first electrode and the second electrode are measured.

  A first step of flowing a first gas to a first electrode of a pipe structure having a first gas flow path; a second step of supplying a second gas to a second electrode of a planar structure; the first electrode; A catalyst evaluation method is used in which a catalyst to be measured is sandwiched between second electrodes, and electrical characteristics between the first electrode and the second electrode are measured.

  According to this configuration, an electrode having a pipe structure is provided with a gas flow path and a gas diffusion function, and the electrode area can be reduced. In addition, by making the electrode of the pipe structure movable, the load can be varied during measurement, so that accurate power generation characteristics can be achieved with a small amount of catalyst.

Schematic diagram of electrode part of catalyst evaluation apparatus of the present embodiment Schematic diagram of the subject of the present embodiment Schematic diagram of arrangement relationship between electrode and subject of catalyst evaluation apparatus of this embodiment Schematic diagram of catalyst evaluation apparatus of the present embodiment Schematic diagram of a conventional fuel cell power generation characteristic evaluation device The figure which shows the measurement result (voltage value) of an Example The figure which shows the measurement result (resistance value) of an Example

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
<Electrode part of catalyst evaluation device>
FIG. 1 shows a schematic diagram of a pipe-type electrode unit 10 of the catalyst evaluation apparatus of the present embodiment.
The pipe-type electrode unit 10 includes a pipe-type electrode 1, gas flow paths 9 a and 9 b, a porous body 11, a resin block 2, an exhaust block 3, and a pad rubber 4.

  The pipe-type electrode 1 is made of an electrically conductive material. The pipe-type electrode 1 has a pipe shape. The pipe-type electrode 1 includes a gas flow path 9 a and a porous body 11.

  The porous body 11 (second porous body) is a porous body at the tip of the pipe-type electrode 1 and having electrical conductivity such as a sintered metal. The porous body 11 has a role of diffusing the supplied gas and a role of conducting electrons generated by the reaction.

  The gas flow path 9a has a role of supplying a gas necessary for the reaction.

  The resin block 2 is made of an electrically insulating material, and connects the pipe-type electrode 1 and the exhaust block 3 while being electrically insulated from each other.

  The exhaust block 3 is made of an electrically conductive material, and includes a gas flow path 9b and a pad rubber 4 (cover).

  The gas flow path 9b has a role of exhausting a gas not used in the reaction.

  The pad rubber 4 is a cover that is in close contact with the electrolyte membrane 5 (described later) and has a role to prevent the supplied gas and the gas not used in the reaction from leaking out of the gas flow paths 9a and 9b.

<Subject 20>
FIG. 2 shows a schematic cross section of a subject 20 that is an object to be examined.

  The subject 20 to be inspected is obtained by holding the catalyst layer 22 on the porous body 21 (first porous body) having electrical conductivity.

  The catalyst layer 22 is composed of catalyst-supported carbon and an electrolyte, and an electrode reaction is performed at the interface between the catalyst supported on the carbon and the electrolyte. In addition, the carbon connection in the catalyst layer becomes an electron path, and the electrolyte connection becomes a hydrogen ion path. The supported catalyst contains a large amount of platinum for both the positive electrode and the negative electrode, but a platinum-based alloy catalyst may be used to improve the activity of the positive electrode or the CO resistance of the negative electrode.

  The porous body 21 is made of an electrically conductive material, and has a role of diffusing and supplying gas to the catalyst layer 22 and a role of transmitting electrons generated by the reaction.

  Since the catalyst layer 22 has a thickness of several μm to several tens of μm, it is difficult to directly handle the catalyst layer 22 alone, but the catalyst layer 22 is easily handled by being held on the porous body 21. Moreover, since the catalyst layer 22 is not directly applied to the electrolyte membrane 5 (FIG. 3), the electrolyte membrane 5 can be reused.

  The porous body 21 is not an essential component and is preferably used.

<Relationship between the electrode of the catalyst evaluation apparatus and the specimen>
FIG. 3 shows a cross-sectional view of the arrangement relationship between the distal end portion 10a of the pipe-type electrode unit 10 and the subject 20 in the present embodiment. The tip portion 10a of the pipe-type electrode unit 10 is an enlarged schematic view of the tip portion of the pipe-type electrode unit 10 shown in FIG.

  In the above configuration, the tip portion 10a of the pipe-type electrode unit 10, the electrolyte membrane 5, the catalyst layer 6, the gas diffusion layer 7, and the planar electrode 8 are arranged at positions that face each other so as to sandwich the subject 20. .

A proton conductive ion exchange membrane is used as the electrolyte membrane 5. In particular, a cation exchange membrane made of a perfluorocarbon polymer having a sulfonic acid group is preferable because of its excellent basic characteristics. Hydrogen ions (H ⁺ : protons) generated by the reaction at the negative electrode move through the electrolyte membrane 5 and are used for the reaction at the positive electrode.

  The catalyst layer 6 is composed of catalyst-carrying carbon and an electrolyte, and an electrode reaction is performed at the interface between the catalyst-carrying carbon and the electrolyte. Further, the carbon connection in the catalyst layer 6 becomes a path for electrons, and the connection for electrolyte becomes a path for hydrogen ions. The supported catalyst contains a large amount of platinum for both the positive electrode and the negative electrode, but a platinum-based alloy catalyst may be used to improve the activity of the positive electrode or the CO resistance of the negative electrode.

  The gas diffusion layer 7 is made of an electrically conductive material. The gas diffusion layer 7 has a role of diffusing and supplying gas to the catalyst layer 6 and a role of transmitting electrons generated by the reaction to the planar electrode 8.

<Process>
The gas supplied from the gas flow path 9 a of the pipe-type electrode 1 is discharged from the gas flow path 9 b of the exhaust block 3 after being used for the reaction in the subject 20.

  The pad rubber 4 provided in the exhaust block 3 is in close contact with the electrolyte membrane 5, and prevents gas leakage outside the gas flow paths 9a and 9b.

  The planar electrode 8 is composed of a porous body having electrical conductivity such as a mesh metal or sintered metal, and the gas supplied from the side surface or the bottom surface is supplied to the catalyst layer 6 through the gas diffusion layer 7. (Not shown).

  With the above configuration, the polymer electrolyte fuel cell 40 is configured between the pipe electrode 1 and the planar electrode 8. That is, the polymer electrolyte fuel cell 40 is configured by the catalyst layer 6, the gas diffusion layer 7, the electrolyte membrane 5, the subject 20, and the porous body 11.

  The gas supplied from the gas flow path 9 a of the pipe-type electrode 1 passes through the porous body 11 and is supplied to the subject 20. The gas supplied from the planar electrode 8 passes through the gas diffusion layer 7 and is supplied to the catalyst layer 6. In this way, an electrochemical reaction is performed between the analyte 20 and the catalyst layer 6 holding the electrolyte membrane 5, and a power generation state is established.

  The pipe electrode 1, the porous body 11, and the planar electrode 8 are preferably plated with gold, platinum or the like in order to reduce electrical resistance.

A portion where the pipe-type electrode 1 and the planar electrode 8 are opposed to each other, that is, a portion of the area of the porous body 11 at the tip of the pipe-type electrode 1 acts as an electrode. The area of the porous body 11 at the tip of the pipe-type electrode 1 is desirably 1 mm ² or more and 1 cm ² or less. When the area is smaller than 1 mm ² , it becomes difficult to accurately face the electrode to the subject, and accurate measurement is performed. Can not be carried out. When the area is larger than 1 cm ² , the amount of catalyst necessary for measurement increases.

  The area of the planar electrode 8 (the area of the surface facing the pipe electrode 1) may be larger than the area of the porous body 11 at the tip of the pipe electrode 1 (the area of the surface facing the planar electrode 8).

  Note that the catalyst layer 22 of the subject 20 may be directly held on the porous body 11 at the tip of the pipe-type electrode 1. In that case, the pipe-type electrode 1, the porous body 11, the electrolyte membrane 5, the catalyst layer 6, the gas diffusion layer 7, and the planar electrode 8 are arranged at positions facing each other.

<Catalyst evaluation device>
FIG. 4 shows a cross-sectional view of the catalyst evaluation apparatus 30 of the present embodiment.

  An electronic load 31, an ohmmeter 32, and a voltmeter 33 are connected in parallel between the pipe-type electrode 1 and the planar electrode 8, respectively. Evaluate the electrical characteristics between the electrodes.

  In addition, the subject 20, the electrolyte membrane 5, the catalyst layer 6, and the gas diffusion layer 7 are stacked on the planar electrode 8 and are disposed in a place sandwiched by the pipe electrode 1.

  The pipe-type electrode unit 10 includes a pipe-type electrode 1, a porous body 11, a resin block 2, and an exhaust block 3, and is connected to the movable means 35 of the pipe-type electrode unit 10 in the exhaust block 3.

  The pipe-type electrode unit 10 is moved by the moving means 35 of the pipe-type electrode unit 10, the porous body 11 is brought into contact with the subject 20, and a predetermined pressure is applied in the direction of the planar electrode 8.

  In order to evaluate the catalyst in the above arrangement, gas is supplied to the pipe electrode 1 side and the planar electrode 8 side, respectively. The gas container 34 supplies gas to the planar electrode 8 side.

  As a result, the polymer electrolyte fuel cell 40 is configured between the two electrodes and enters a power generation state. A resistance value and a voltage value when the current taken out from the polymer electrolyte fuel cell 40 is changed are measured. Since the catalyst layer 22 to be evaluated is located in the polymer electrolyte fuel cell 40, the gas container 34 can be said to be a mounting table for holding the catalyst layer 22 to be evaluated.

  In this measurement, an electronic load 31, an ohmmeter 32, and a voltmeter 33 are used. The power generation characteristics of the subject 20 can be evaluated from the current value, resistance value, and voltage value obtained from the measurement.

  A plurality of specimens 20 may be arranged side by side on the electrolyte membrane 5, and the evaluation can be performed by moving the pipe-type electrode unit 10 by the moving means 35 of the pipe-type electrode unit 10, and the conditions other than the specimen can be made the same. Power generation characteristics can be evaluated.

  In FIG. 4, the positional relationship between the porous body 11 and the subject 20 is illustrated so as to be clear from each other. However, when the measurement is actually performed, It is arranged in contact with the subject 20.

For ease of explanation, hydrogen gas (H ₂ ) is supplied to the pipe-type electrode 1 to supply the negative electrode, and oxygen gas (O ₂ ) is supplied to the planar electrode 8 side to form a positive electrode. However, when the evaluation is actually performed, the pipe-type electrode 1 may be used as the positive electrode and the planar electrode 8 may be used as the negative electrode by switching the supplied gas according to the subject 20.

<Effect>
According to the present invention, by performing measurement using the movable pipe-type electrode unit 10, it is possible to evaluate power generation characteristics with high accuracy with a small amount of catalyst.
(Example)
<Production of measuring device>
The pipe-type electrode 1 was made of a stainless steel material (SUS304). A sintered metal (model number: stainless steel element, manufactured by SMC) was welded to the tip as the porous body 11. The tip of the pipe-type electrode 1 was a circle having a diameter of 6 mm.

  The pipe-type electrode 1 was fixed to an exhaust block 3 made of a stainless steel material (SUS304) through a resin block 2 made of polyphenylene sulfide resin (Polyphenylene Sulfide Resin). A pad rubber 4 (model number: KPP-20-F, manufactured by Koganei) was attached to the exhaust block 3.

The planar electrode 8 was manufactured with an area of 36 cm ² using a metal mesh (model number: Absolta, manufactured by Takenaka Wire Mesh Co., Ltd.). It attached to the gas container 34 manufactured with the stainless steel material (SUS304) through the sealing material.

  A gas diffusion layer 7 (model number: FCPJGDL, manufactured by Panasonic Corporation) was formed on the planar electrode 8. A catalyst ink prepared by mixing catalyst-supported carbon (model number: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and ionomer (model number: Aquivion, Solvay Solexis Co., Ltd.) was spray-coated to form a catalyst layer 6. . On top of this, an electrolyte membrane 5 (model number: NR-211, manufactured by DUPONT) was formed.

  The movable means 35 of the pipe-type electrode unit 10 is an XY robot (model number: ROBO CYLINDER, manufactured by IAI) for moving in the horizontal direction, and an air slide table (model number: MXQ8-20Z-M9NV, manufactured by SMC) for moving in the vertical direction. ) Was prepared. A pressure-sensitive element (model number: LMA-A-20N, manufactured by Kyowa Dengyo Co., Ltd.) was used as a pressing pressure measuring unit of the pipe-type electrode unit 10 to adjust to 7.5 kgf / cm 2.

  A heater was attached to the gas container 34 to which the pipe-type electrode unit 10 and the planar electrode 8 were attached, and heated to 80 ° C.

<Create measurement target>
A gas diffusion layer (model number: FCPJGDL, manufactured by Panasonic Corporation) was prepared as the porous body 21. A catalyst-supporting carbon (model number: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and an ionomer (model number: Aquivion, manufactured by Solvay Solexis) were mixed as a catalyst ink. A catalyst ink was applied onto the porous body 21 to produce a catalyst layer 22, which was used as the specimen 20.

Two types with different coating amounts were prepared. Sample A was coated with 7.5 μL (platinum amount: 0.6 mg / cm ² equivalent), and sample B was coated with 2.0 μL (platinum amount: 0.16 mg / cm 2 equivalent).

<Installation of measurement target>
A subject A and a subject B were individually arranged on the electrolyte membrane 5.

<Measurement method of power generation characteristics>
A low resistance meter (model number: 3566, manufactured by Tsuruga Electric Co., Ltd.) having both functions was prepared as an electronic load 31 (model number: LSA-165V1, manufactured by TEXIO), an ohmmeter 32 and a voltmeter 33. First, the pipe electrode unit 10 was aligned with the subject A by an XY robot, and a predetermined load was applied by an air slide table. Humidified hydrogen gas was supplied to the gas flow path 9a side of the pipe-type electrode 1 as a negative electrode, and humidified air was supplied to the planar electrode 8 side to generate power as a positive electrode. The gas dew point was 65 ° C. for all. The change of the voltage value and the resistance value when the current value taken out by the electronic load 31 is changed is plotted.

  Subsequently, the pipe-type electrode unit 10 was aligned with the subject B using an air slide table and an XY robot, and the same measurement as the subject A was performed.

In addition, the subject A was subjected to aging in which the power generation state and the non-power generation state were repeatedly performed, and the first data and the fourth data (after aging) were acquired.
The results are shown in FIGS.

In FIG. 6, the horizontal axis represents a current amount (A / cm ² ) per unit area taken out by an electronic load, and the vertical axis represents a voltage value (V).

In FIG. 7, the horizontal axis represents the amount of current per unit area (A / cm ² ) taken out by the electronic load, and the vertical axis represents the resistance value (Ω).

  The power generation performance was compared between two specimens with different ink application amounts. When the amount of catalyst applied was small, it was confirmed that the generated voltage tends to be low.

  Also, in the confirmation of the aging effect of the subject A, the voltage is increased and the resistance value is decreased by performing aging. Even in a method for evaluating power generation with a general single cell structure, it is said that the power generation performance is improved by aging due to insufficient initial power generation characteristics.

  Thus, this measurement method can easily and accurately measure the power generation performance with a small amount of catalyst. In addition, it was confirmed that the same result as the power generation evaluation in the single cell structure can be obtained.

  <Effect> The catalyst evaluation apparatus and evaluation method of the embodiment can easily and accurately measure the power generation performance with a small amount of catalyst. Improving the performance of the catalyst is directly linked to improving the durability and power generation performance of the polymer electrolyte fuel cell, and early identification of the performance is important in catalyst development. Solid polymer fuel cells are characterized by their low-temperature operation, high output current density, and miniaturization, and promise for applications such as home cogeneration systems, fuel cell vehicles, and mobile communication base stations. Has been. In addition to fuel cell catalysts, various catalysts can be evaluated.

  The catalyst evaluation apparatus and the evaluation method of the present application can evaluate not only the fuel cell but also a catalyst used in various fields.

DESCRIPTION OF SYMBOLS 1 Pipe type electrode 2 Resin block 3 Exhaust block 4 Pad rubber 5 Electrolyte membrane 6 Catalyst layer 7 Gas diffusion layer 8 Planar electrode 9a Gas flow path 9b Gas flow path 10 Pipe type electrode unit 10a Tip part 11 Porous body 20 Subject 21 Porous body 22 Catalyst layer 30 Catalyst evaluation device 31 Electronic load 32 Resistance meter 33 Voltmeter 34 Gas container 35 Movable means 40 Solid polymer fuel cell 50 Electrolyte membrane 51 Catalyst layer 52 Catalyst layer 53 Partition wall 55 Anode 56 Cathodes A and B Subject

Claims (8)

A first electrode of a pipe structure having a first gas flow path;
A second electrode having a planar structure facing the first electrode with a catalyst interposed therebetween ;
A mounting table for holding the second electrode on the upper surface ;
An apparatus for evaluating a catalyst, comprising: a measurement unit that measures electrical characteristics between the first electrode and the second electrode. The catalyst evaluation apparatus according to claim 1, wherein the catalyst is held in a first porous body. The catalyst evaluation apparatus according to claim 1 or 2, wherein a gas diffusion layer, a catalyst layer, and an electrolyte membrane are disposed between the second electrode and the catalyst. The said 1st electrode is an evaluation apparatus of the catalyst for fuel cells of any one of Claims 1-3 provided with the 2nd porous body which has electrical conduction in the front-end | tip. 5. The fuel cell catalyst evaluation apparatus according to claim 1, wherein the second electrode has a large surface area facing the first electrode. 6. The apparatus for evaluating a fuel cell catalyst according to any one of claims 1 to 5, further comprising a cover that covers a space between a tip of the first electrode and the second electrode. The fuel cell catalyst evaluation apparatus according to any one of claims 1 to 6, wherein a fuel cell is formed by the first electrode, the second electrode, and the catalyst. A first step of flowing a first gas through a first electrode of a pipe structure having a first gas flow path;
A second step of supplying a second gas to the second electrode having a planar structure;
A catalyst evaluation method comprising: a measurement step of sandwiching a catalyst to be measured between the first electrode and the second electrode and measuring electrical characteristics between the first electrode and the second electrode.

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