JP5649320B2 - Method for producing electrode catalyst layer for fuel cell and fuel cell - Google Patents

Description

  The present invention relates to a method for producing an electrode catalyst layer for a fuel cell used in a fuel cell and a fuel cell.

  A fuel cell includes an electrolyte membrane, an electrode catalyst layer, a gas diffusion layer, and a separator, and a combination of four members forms a basic structure called a cell. In the cell, an anode electrode catalyst layer and a cathode electrode catalyst layer are formed on both surfaces of the electrolyte membrane. A gas diffusion layer and then a separator are disposed in contact with the bipolar catalyst layer.

  The electrode catalyst layer is mainly composed of platinum-supported carbon and an electrolyte. In the anode electrode catalyst layer, electrons are taken out by hydrogen oxidation reaction to generate protons. The generated protons move through the electrolyte and electrolyte membrane in the electrode catalyst layer and are supplied to the cathode electrode catalyst layer. In the cathode electrode catalyst layer, a reduction reaction of oxygen occurs, and water is generated by reaction with protons. As the catalyst in the electrode catalyst layer, an expensive metal catalyst such as platinum is generally used, and if many defects occur during production, it causes a cost increase.

  As the breakdown of the defective production of the electrode catalyst layer, the amount of platinum contained in the electrode catalyst layer is insufficient, excessive, missing, or poor appearance.

  Among them, defects due to the shortage or excess of platinum contained in the electrode catalyst layer are affected by individual differences in the base material on which the electrode catalyst layer is produced during production, time changes in the state of the production equipment, and changes in the production atmosphere. The frequency of occurrence is high and difficult to control. In addition, since it is impossible to confirm the amount of platinum in the electrode catalyst layer during production, the amount of catalyst is often confirmed to be defective as a result of confirmation of the amount of catalyst after production.

  Patent Document 1 describes a production method using dry catalyst powder as a production method of an electrode catalyst layer of a fuel cell. In this method, an electrode catalyst layer is formed by placing the catalyst powder on a carrier gas flow, passing the gas through a gas-permeable substrate, and depositing the catalyst powder on the substrate. In this invention, it can apply to manufacture of the electrode catalyst layer in the said method.

JP 55-6793 A

  The amount of the catalyst powder in the electrode catalyst layer is generally confirmed by measuring the weight of the electrode catalyst layer after completion of production. As a result, it is unclear whether the electrocatalyst layer is within the design specification range until the final stage of production, and if the weight measurement value is outside the allowable range of the target design specification, There is a possibility that all the lots that have been produced become defective products, which is a cause of low yield and increased manufacturing costs.

  The present invention has been made to solve the above problems, and provides a method for producing an electrode catalyst layer for a fuel cell, which can be produced while confirming the amount of catalyst powder in the electrode catalyst layer, and a fuel cell produced thereby. For the purpose.

(1) In the method for producing an electrode catalyst layer for a fuel cell according to the present invention, an air-permeable base material constituting the fuel cell is placed on the air-permeable table, and the upper surface side of the base material on the air-permeable table And a predetermined amount of catalyst powder accompanying the carrier gas is introduced into the first space surrounded by the surrounding member, and the second space on the lower surface side of the base material is exhausted , Based on the differential pressure between the internal pressure of the first space and the internal pressure of the second space , the catalyst powder is deposited on the upper surface of the base material to a desired thickness.

  (2) In the method for producing an electrode catalyst layer for a fuel cell according to the present invention, a base material having air permeability is placed on a gas permeable table, and the upper surface side of the base material on the gas permeable table is surrounded by a surrounding member. And introducing a predetermined amount of catalyst powder accompanied by the carrier gas into the first space surrounded by the enclosure member under the condition that the carrier gas flow rate through the substrate is a predetermined flow rate, The second space on the lower surface side is evacuated, the internal pressures of the first and second spaces are detected, and the differential pressure between the detected internal pressure of the first space and the detected internal pressure of the second space And the supply of the catalyst powder to the first space is stopped when the differential pressure becomes a predetermined value or more.

  (3) In the method for producing an electrode catalyst layer for a fuel cell according to the present invention, a base material having air permeability is placed on a gas permeable table, and the upper surface side of the base material on the gas permeable table is surrounded by a surrounding member. And introducing a predetermined amount of catalyst powder accompanied by the carrier gas into the first space surrounded by the enclosure member under the condition that the carrier gas flow rate through the substrate is a predetermined flow rate, The second space on the lower surface side is evacuated, the internal pressures of the first and second spaces are detected, and the differential pressure between the detected internal pressure of the first space and the detected internal pressure of the second space And the carrier gas flow rate supplied to the first space is gradually decreased so that the differential pressure is maintained at a predetermined value, and the first space is reduced when the carrier gas flow rate becomes a predetermined set value or less. The supply of catalyst powder to the .

  According to the present invention, the production can be performed while confirming the amount of the catalyst powder in the electrode catalyst layer during the production, so that the yield is improved and the production cost is reduced.

The block diagram which shows the outline | summary of the manufacturing apparatus used for this invention. The top view of a mask. (A)-(d) is process sectional drawing which shows the manufacturing method of the electrode catalyst layer for fuel cells which concerns on embodiment of this invention. The flowchart for demonstrating the method of this invention. Sectional drawing which shows typically a mode that particle | grains accumulate on a board | substrate and form an electrode catalyst layer. The characteristic line figure which shows the pressure gradient which arises in a gas flow direction. The characteristic diagram which shows the relationship between the pressure loss in an electrode catalyst layer, and the weight relative value of the deposited catalyst powder. The cross-sectional schematic diagram which shows the principal part of the fuel cell manufactured using the method of other embodiment of this invention.

  Various preferred embodiments of the present invention will be described.

  (1) In the method for producing an electrode catalyst layer for a fuel cell of the present invention, a base material having air permeability is placed on an air permeable table, and the upper surface side of the base material on the air permeable table is surrounded by an enclosing member, By introducing a predetermined amount of catalyst powder accompanied by a carrier gas into the first space surrounded by the enclosing member and exhausting the second space on the lower surface side of the base material, the upper surface of the base material The catalyst powder is deposited to a desired thickness.

  In the present invention, the carrier gas passes through the gas-permeable base material by exhausting the second space while supplying the catalyst powder in the flow of the carrier gas into the first space, while the catalyst powder is Deposit on the substrate. Since the supply amount of the catalyst powder to the first space is set to a predetermined amount in advance, the catalyst powder can be deposited on the substrate in a desired thickness. In addition, as a base material, desired water-resistant process (water-repellent process) is given, it has predetermined | prescribed thickness (for example, 0.1-0.5 mm, more preferably 0.1-0.3 mm), and predetermined | prescribed porosity (for example, 50-) It is preferable to use carbon paper having 90%, more preferably 70 to 90%. In this case, it is advantageous from the viewpoint of manufacturing man-hours to use carbon paper as a battery component as a base material, but the present invention is not limited to this, and a fiber material having air permeability. Any material such as a non-woven fabric, a net-like material, or a porous material can be used as a base material. Further, as the catalyst powder, it is preferable to use platinum particles having a predetermined average particle diameter (for example, 0.1 to 10 μm, more preferably 0.5 to 10 μm) and sufficiently dried.

  (2) In the method for producing an electrode catalyst layer for a fuel cell of the present invention, a base material having air permeability is placed on a gas permeable table, and an upper surface side of the base material on the gas permeable table is surrounded by a surrounding member, Under the condition that the carrier gas flow rate passing through the base material is a predetermined flow rate, a predetermined amount of catalyst powder accompanied by the carrier gas is introduced into the first space surrounded by the enclosure member, and the lower surface of the base material The second space on the side is evacuated, the internal pressures of the first and second spaces are detected, and the detected differential pressure between the internal pressure of the first space and the internal pressure of the second space is determined. The supply of the catalyst powder to the first space is stopped when the differential pressure is equal to or lower than a predetermined value.

  In the present invention, under the condition that the carrier gas flows at a constant flow rate, the pressure difference ΔP (pressure loss) between the internal pressure of the first space and the internal pressure of the second space and the deposition of the catalyst powder on the substrate Correlation data with the amount Q (or catalyst layer thickness T) is obtained in advance by a demonstration test or the like, and the differential pressure ΔP / deposition amount Q correlation data and the target thickness of the electrode catalyst layer are calculated based on the differential pressure. A value ΔPc1 is calculated, and this differential pressure value ΔPc1 is stored in a state where it can be called at any time. The internal pressures P1 and P2 in the first and second spaces are detected, and the difference from the detected pressures P1 and P2 is detected. The pressure ΔP is obtained, and the obtained differential pressure ΔP is compared with the predetermined value ΔPc1 that has been called. When the former differential pressure ΔP is equal to or greater than the latter predetermined value ΔPc1, the supply of the catalyst powder to the first space is performed. Stop. Thereby, the deposition amount Q of the catalyst powder on the base material is controlled for each base material, the thickness T of the electrode catalyst layer formed on the base material can be made appropriate, and it is placed on the base material. The defective rate of the product due to the amount of the catalyst powder being outside the determined range can be reduced, and the yield is improved.

  (3) In the method for producing an electrode catalyst layer for a fuel cell of the present invention, a base material having air permeability is placed on an air permeable table, and the upper surface side of the base material on the air permeable table is surrounded by an enclosing member, Under the condition that the carrier gas flow rate passing through the base material is a predetermined flow rate, a predetermined amount of catalyst powder accompanied by the carrier gas is introduced into the first space surrounded by the enclosure member, and the lower surface of the base material The second space on the side is evacuated, the internal pressures of the first and second spaces are detected, and the detected differential pressure between the internal pressure of the first space and the internal pressure of the second space is determined. The carrier gas flow rate supplied to the first space is gradually decreased so that the differential pressure is maintained at a predetermined value, and when the carrier gas flow rate becomes a predetermined set value or less, the first space is entered. The supply of the catalyst powder is stopped.

  In the present invention, the carrier gas flow rate V into the first space and the pressure difference ΔP (pressure loss) between the internal pressure of the first space and the internal pressure of the second space are set to a constant value ΔPc2. Correlation data with the deposition amount Q (or catalyst layer thickness T) of the catalyst powder on the base material is grasped beforehand by a verification test or the like, and the correlation data of the carrier gas flow rate V / deposition amount Q and the electrode catalyst layer The carrier gas flow rate Vc2 is calculated on the basis of the target thickness, and the set value Vc2 and the predetermined value ΔPc2 are stored in a state where they can be called at any time, and the internal pressures P1, P2 in the first and second spaces are stored. Are detected from the detected pressures P1 and P2, and the obtained differential pressure ΔP is compared with a predetermined value ΔPc2 that is called, so that the first differential pressure is maintained at the predetermined value ΔPc2. Gradually reduce the flow rate of the carrier gas supplied to the space Carrier gas flow rate to stop the supply of the catalyst powder to the first space when the set value Vc2 below. Thus, the amount Q of catalyst powder deposited on the base material is controlled for each base material, and the thickness T of the electrode catalyst layer formed on the base material can be set to a target thickness. The defective rate of the product due to the amount of the catalyst powder on the outside of the range of the determined value can be reduced, and the yield is improved.

  (4) The fuel cell according to the present invention is formed in a state in contact with the solid electrolyte membrane, the anode electrode catalyst layer and the cathode electrode catalyst layer formed on both surfaces of the solid electrolyte membrane, and both the electrode catalyst layers. The electrode catalyst layer is manufactured by the method according to any one of (1) to (3).

  (5) The fuel cell according to the present invention is formed in a state in which the solid electrolyte membrane, the anode electrode catalyst layer and the cathode electrode catalyst layer formed on both surfaces of the solid electrolyte membrane, and the electrode catalyst layer are in contact with each other. It has a gas diffusion layer and a separator formed on the gas diffusion layer, and the electrode catalyst layer is manufactured by the method according to any one of (1) to (3).

  Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  First, an outline of a manufacturing apparatus used in the manufacturing method of the present invention will be described with reference to FIGS.

  The manufacturing apparatus 10 includes an exhaust box 11, a breathable table 12, a blower 13, a mask 16, a hood 18, a gas supply device 21, a powder supply device 22, and a controller 23. The operation of the manufacturing apparatus 10 is comprehensively controlled by the controller 23.

  The hood 18 functions as a surrounding member surrounding the upper surface side of the base material 2, and defines a first space 19 as a powder supply diffusion space for supplying catalyst powder to the upper surface of the base material 2. . The exhaust box 11 functions as a means for exhausting the lower surface (back surface) side of the base material 2, and serves as an exhaust space for exhausting gas that has passed through the base material 2 from the upper surface side to the back surface side. Two spaces 14 are defined.

  The hood 18 has a quadrangular pyramid shape in which the main body gradually expands from the upper part toward the lower part, has a small-diameter powder introduction part 18a at the upper part, and has a large-diameter opening 18b connected to the exhaust box 11 at the lower part. Have. The powder introduction part 18a of the hood 18 communicates with the gas supply device 21 via the line L1, and communicates with the powder supply device 22 via the lines L2 and L1. The powder supply line L2 merges at an appropriate position of the gas supply line L1, and a predetermined amount of catalyst powder is added to the carrier gas flowing through the line L1 via the line L2. In this embodiment, dry platinum (Pt) particles having a predetermined particle size are used as the catalyst powder.

  The exhaust port of the exhaust box 11 is connected to the blower 13 via a line L3, and the second space 14 defined by the exhaust box 11 and the air permeability table 12 is exhausted. The drive power switch of the blower 13 is connected to the output unit of the controller 23, and its operation is controlled by the controller 23.

  The lower opening 18b of the hood and the upper opening 11b of the exhaust box have substantially the same size and shape, and the hood 18 is placed on the flange 11a of the exhaust box 11 so that the lower opening 18b overlaps the upper opening 11b. .

  A net-like breathable table 12 is attached so as to close the upper opening 11 b of the exhaust box, and the base material 2 is placed on the breathable table 12. As the breathable table 12, various materials such as ceramic, cardboard, metal mesh, foam metal, and resin can be used. For example, from a metal mesh made of a corrosion resistant alloy such as stainless steel, or a fluoroethylene resin such as PTFE. A resin mesh can be used.

  A mask 16 is disposed immediately above the substrate 2 on the breathable table 12. The mask 16 faces the base material 2 in a non-contact state and is surrounded by a presser rubber frame 17 that presses the four sides of the base material 2 so that the base material 2 does not float from the air permeable table 12. That is, the mask 16 is surrounded by the rubber frame 17 on four sides as shown in FIG. Note that reference numeral 16a in the figure denotes an opening of the mask.

  A first sensor 20 is disposed in a first space 19 surrounded by the hood 18 and the breathable table 12. The first sensor 20 detects the internal pressure of the first space 19 and sends the pressure detection signal S 1 to the input unit of the controller 23.

  A second sensor 15 is arranged in a second space 14 surrounded by the exhaust box 11 and the air permeable table 12. The second sensor 15 detects the internal pressure of the second space 14 and sends the pressure detection signal S <b> 2 to the input unit of the controller 23.

  The controller 23 includes a memory that stores a predetermined value ΔPc1 of the differential pressure in a state where it can be called at any time. The controller 23 obtains the internal pressure P1 of the first space 19 and the internal pressure P2 of the second space 14 based on the input signals S1, S2 from the first and second pressure sensors 20, 15, respectively. A differential pressure ΔP (= P1−P2) is calculated from the pressures P1 and P2, a predetermined value ΔPc1 of the differential pressure is called, the differential pressure ΔP is compared with the predetermined value ΔPc1, and the differential pressure ΔP is equal to or greater than the predetermined value ΔPc1. At this time, the control signals S3 and S4 are sent to the gas supply device 21 and the powder supply device 22, and the supply of the catalyst powder to the first space 19 is stopped. Incidentally, the predetermined value ΔPc1 of the differential pressure is equal to the differential pressure ΔP (pressure loss) between the internal pressure of the first space and the internal pressure of the second space and the deposition amount Q (or catalyst) of the catalyst powder on the substrate. Correlation data with the layer thickness T) are obtained in advance by a verification test or the like.

  The gas supply device 21 supplies a carrier gas (such as nitrogen gas) to the first space 19 in the hood 18 via the line L1. Dry air or nitrogen gas can be used as the carrier gas. The powder supply device 22 introduces and introduces platinum particles 31 as catalyst powder into the carrier gas flowing through the line L1 via the line L2. As the platinum particles, those having a predetermined average particle diameter and sufficiently dried are used.

  Next, various embodiments for producing an electrode catalyst layer for a fuel cell using the above apparatus will be described.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.

  A rectangular base material 2 made of carbon paper is placed on a breathable table 12. The size of the base material 2 is, for example, 1 m (1000 × 1000 mm) in length and width and an average thickness of 0.2 mm (preferably in the range of 0.1 to 0.5 mm, more preferably in the range of 0.1 to 0.3 mm). Further, the opening ratio (porosity) of the substrate 2 is about 80%.

  In order to prevent the powder-containing gas from the first space 19 on the upstream side of the base material from flowing around the base material 2 and flowing into the second space 14 on the downstream side of the base material, the presser rubber frame 17 around the mask. Then, the peripheral edge of the substrate 2 is pressed and sealed. The hood 18 is lowered or the exhaust box 11 is raised, the hood 18 is placed on the exhaust box 11, and the first space 19 is formed by the hood 18 and the breathable table 12 at the upper part of the exhaust box. The first space 19 becomes an airtight powder supply and diffusion space surrounding the upper surface side of the substrate 2.

  Next, the controller 23 activates the blower 13, exhausts the second space 14, and pulls the processing system to a negative pressure. Subsequently, the gas supply device 21 is activated to create a carrier gas flow that flows through the first and second spaces 19, 14, and then a signal is sent to a carbon powder supply device (not shown) from the carbon powder supply device to the line. Carbon powder is supplied into the carrier gas flowing through L1, and carbon powder is further deposited on the base material 2 to form a gas diffusion layer (C powder layer) 3 having a desired thickness, as shown in FIG. An electrode laminated body is obtained (step K1).

  After stopping the supply of the carbon powder from the carbon powder supply device, the controller 23 activates the powder supply device 22, and platinum particles are added to the carrier gas flowing through the first and second spaces 19 and 14. A catalyst powder 41 made of

  When the gas carrying the catalyst powder 41 passes through the base material 2, the base material 2 captures the catalyst powder 31 like a filter membrane, and the platinum particles 31 are gradually deposited on the gas diffusion layer 3. Go. On the other hand, the carrier gas sequentially passes through the inside of the base material 2 and the breathable table 12 and escapes to the second space 14 on the downstream side of the base material, but the amount of platinum particles 41 deposited increases as shown in FIG. As a result, the opening ratio of the laminate of the base material 2 / gas diffusion layer 3 decreases, gas becomes difficult to pass through the second space 14 on the downstream side of the base material, and the internal pressure P1 of the first space 19 increases, The internal pressure P2 in the second space 14 gradually decreases. The controller 23 constantly monitors the differential pressure ΔP between the internal pressure P1 in the first space and the internal pressure P2 in the second space, and when the differential pressure ΔP becomes a predetermined value ΔPc1 or more, the powder supply device 22 is used. To stop the supply of the catalyst powder to the first space 19.

  As a result, the amount Q of catalyst powder deposited on the base material is controlled for each base material, the thickness T of the electrode catalyst layer formed on the base material can be made appropriate, and expensive platinum particles 41 can be formed. The electrode catalyst layer 4 having a desired target thickness is formed on the substrate 2 as shown in FIG. 3B without wasting waste (step K2). As a result, it is possible to reduce the defective rate of the product due to the amount of the catalyst powder placed on the base material being outside the range of the determined value, and the yield is improved.

  As shown in FIG. 3C, the solid electrolyte membrane 6 is disposed between the pair of electrode laminates 5 so that the gas diffusion layer 3 is located inside, and hot pressing is performed. The hot pressing temperature is preferably 120 to 180 ° C. and the pressing pressure is preferably 10 to 40 kgf / cm 2. These are further sandwiched between the oxidant electrode side separator 7a and the fuel electrode side separator 7b (step K3), and this assembly is integrally formed again by hot pressing to obtain a fuel battery cell 8 shown in FIG. Step K4). The hot press temperature was 100 to 180 ° C., and the press pressure was 5 to 40 kgf / cm 2.

  In the method of this embodiment, the catalyst powder 31 is always supplied to the gas passing through the base material in a certain amount. Therefore, the amount of platinum in the electrode catalyst layer is reduced as compared with the conventional method for producing a catalyst layer using ink such as a die coater. There are advantages that there are few factors to change and the factors are not complicated. Specifically, the amount of catalyst is only reduced due to adhesion to the inner wall of the catalyst layer manufacturing apparatus and leakage of catalyst powder downstream of the substrate. Therefore, by supplying a fixed amount of catalyst powder that takes into account the unused portions related to the two points described above, an electrode catalyst layer containing platinum with a value close to the target can be manufactured, and reduction in manufacturing defects of the electrode catalyst layer can be realized. . In addition, since an apparatus for supplying a fixed amount of catalyst powder can be manufactured at a relatively low cost, there is a merit in terms of capital investment.

(Second Embodiment)
Next, a second embodiment will be described. In addition, description of the part which this embodiment overlaps with said embodiment is abbreviate | omitted.

  A second embodiment of the present invention will be described with reference to FIGS.

  A rectangular base material 2 made of carbon paper is placed on a breathable table 12. In order to prevent the powder-containing gas from the first space 19 on the upstream side of the base material from flowing around the base material 2 and flowing into the second space 14 on the downstream side of the base material, the presser rubber frame 17 around the mask. Then, the peripheral edge of the substrate 2 is pressed and sealed. The hood 18 is lowered or the exhaust box 11 is raised, the hood 18 is placed on the exhaust box 11, and the first space 19 is formed by the hood 18 and the breathable table 12 at the upper part of the exhaust box. The first space 19 becomes an airtight powder supply and diffusion space surrounding the upper surface side of the substrate 2.

  Next, the controller 23 activates the blower 13, exhausts the second space 14, and pulls the processing system to a negative pressure (step S1). Subsequently, the gas supply device 21 is activated to create a carrier gas flow that flows through the first and second spaces 19, 14, and then a signal is sent to a carbon powder supply device (not shown) from the carbon powder supply device to the line. Carbon powder is supplied into the carrier gas flowing through L1, and carbon powder is further deposited on the base material 2 to form a gas diffusion layer (C powder layer) 3 having a desired thickness, as shown in FIG. An electrode laminated body is obtained (step K1).

  After stopping the supply of the carbon powder from the carbon powder supply device, the controller 23 activates the powder supply device 22, and platinum particles are added to the carrier gas flowing through the first and second spaces 19 and 14. The catalyst powder 41 made of is placed (step S2).

  When the gas carrying the catalyst powder 41 passes through the base material 2, the base material 2 captures the catalyst powder 31 like a filter membrane, and the platinum particles 31 are gradually deposited on the gas diffusion layer 3. Go. On the other hand, the carrier gas sequentially passes through the inside of the base material 2 and the breathable table 12 and escapes to the second space 14 on the downstream side of the base material, but the amount of platinum particles 41 deposited increases as shown in FIG. As a result, the opening ratio of the laminate of the base material 2 / gas diffusion layer 3 decreases, gas becomes difficult to pass through the second space 14 on the downstream side of the base material, and the internal pressure P1 of the first space 19 increases, The internal pressure P2 in the second space 14 gradually decreases. In the present embodiment, the internal pressure P2 of the second space 14 is detected using the second sensor 15, and this is constantly monitored by the controller 23.

  The controller 23 calculates a differential pressure (pressure loss) ΔP of the gas passing from the first space 19 to the second space 14 based on the two signals S1 and S2 from the first and second sensors 20 and 15. On the other hand, the predetermined value ΔPc1 is called, and the calculated differential pressure ΔP is compared with the called predetermined value ΔPc1 (step S3). When the calculated differential pressure ΔP is less than the predetermined value ΔPc1, a series of operations including detection of the internal pressure in the first and second spaces → calculation of the differential pressure ΔP → comparison between the differential pressure ΔP and the predetermined value ΔPc1 The supply of catalyst powder is continued. On the other hand, when the calculated differential pressure ΔP is equal to or greater than the predetermined value ΔPc1, the controller 23 sends a stop command signal S4 to the powder supply device 22 and immediately stops the supply of the catalyst powder to the processing system ( Step S3 → S4). As a result, the target electrode catalyst layer 4 having a desired thickness is formed on the laminate of the substrate 2 as shown in FIG. 3B without wasting expensive platinum particles 41 (step). K1). As a result, the electrode laminate 5 shown in FIG. 3B is obtained (step K2).

  As shown in FIG. 3C, the solid electrolyte membrane 6 is disposed between the pair of electrode laminates 5 so that the electrode catalyst layer 4 is on the inner side, and hot pressing is performed. The hot pressing temperature is preferably 120 to 180 ° C. and the pressing pressure is preferably 10 to 40 kgf / cm 2. These are further sandwiched between the oxidant electrode side separator 7a and the fuel electrode side separator 7b (step K3), and this assembly is integrally formed by hot pressing to obtain a fuel cell stack 8 shown in FIG. 3 (d) (step). K4). The hot press temperature was 100 to 180 ° C., and the press pressure was 5 to 40 kgf / cm 2.

  The above-described manufacturing method for supplying the fixed amount of catalyst layer powder to the gas is inexpensive as an apparatus, but does not include variations in sealing properties around the base material during manufacturing. Sealing is performed for the purpose of preventing the catalyst powder from flowing around the base material and flowing the catalyst powder downstream of the base material. The amount of the catalyst powder flowing downstream depends on the state of the seal and the solid state of the base material. It varies depending on the difference.

  For this reason, the amount of platinum in the catalyst layer deposited on the substrate may fluctuate, which may affect the production yield. Therefore, if it can manufacture while confirming the amount of platinum in the electrode catalyst layer, the manufacturing yield can be further improved.

  When the electrode catalyst layer is produced by the method shown in FIG. 5, a pressure gradient is generated in the gas flow direction of the apparatus, and the amount of platinum on the substrate can be confirmed using this pressure difference.

  FIG. 6 shows an outline of the pressure gradient generated in the manufacturing apparatus 10. The horizontal axis of this figure takes from the first space 19 upstream of the base material to the second space 14 downstream of the base material along the gas flow direction, and the vertical axis of the figure shows the pressure for each of these regions. It is what I took. The entry of the pressure loss of the electrode catalyst layer in the figure corresponds to the differential pressure ΔP.

  FIG. 7 shows the result of examining the relationship between the weight of the deposited catalyst powder and the pressure loss by taking the pressure loss (kPa) in the electrode catalyst layer on the horizontal axis and the weight relative value of the deposited catalyst powder on the vertical axis. FIG. As is clear from this figure, the pressure loss generated in the electrode catalyst layer 3 increases as the amount of catalyst powder deposited during the production increases. When the gas flow rate through the base material 2 and the electrode catalyst layer 3 formed on the upper surface of the base material 2 is constant, the amount of catalyst powder deposited and the pressure loss generated in the electrode catalyst layer 3 are correlated. If the pressure loss is monitored, the amount of the deposited catalyst can be confirmed, and the amount of platinum particles can be grasped. When the pressure loss ΔP becomes equal to or greater than the predetermined threshold value ΔPc1, the supply of the catalyst powder onto the substrate is stopped.

  Thereby, the deposition amount Q of the catalyst powder on the base material is controlled for each base material, and as a result, an electrode catalyst layer containing platinum having a value close to the target can be manufactured.

  By the manufacturing method of this embodiment, the defect of an electrode catalyst layer can be reduced and manufacturing cost can be reduced.

(Third embodiment)
Next, a third embodiment will be described. In addition, description of the part which this embodiment overlaps with said embodiment is abbreviate | omitted.

  A third embodiment of the present invention will be described with reference to FIG.

  In the present embodiment, the carbon paper 2 uses the composite base material 2 + 3 including the gas diffusion layer 3 as the base material, and the electrode catalyst layer 4 is formed thereon. In the present embodiment, the supply of the catalyst powder 41 is stopped when the gas flow rate becomes the set value Vc2 or less.

  The operation of this embodiment will be described.

  The composite base material 2 + 3 is placed on the breathable table 12. In order to prevent the powder-containing gas from the first space 19 on the upstream side of the base material from flowing around the composite base material 2 + 3 and flowing into the second space 14 on the downstream side of the base material, the presser around the mask The peripheral part of the composite base material 2 + 3 is pressed and sealed with the rubber frame 17. The hood 18 is lowered or the exhaust box 11 is raised, the hood 18 is placed on the exhaust box 11, and the first space 19 is formed by the hood 18 and the breathable table 12 at the upper part of the exhaust box. The first space 19 becomes an airtight powder supply diffusion space surrounding the upper surface side of the composite base material 2 + 3.

  Next, the controller 23 activates the blower 13, exhausts the second space 14, and pulls the processing system to a negative pressure. Subsequently, the gas supply device 21 is activated to create a carrier gas flow that flows through the first and second spaces 19 and 14.

  Next, the controller 23 activates the powder supply device 22 to place the catalyst powder 41 made of platinum particles on the flow of the carrier gas that flows through the first and second spaces 19 and 14. When the gas carrying the catalyst powder 41 passes through the base material 2, the base material 2 captures the catalyst powder 31 like a filter membrane, and the platinum particles 31 are gradually deposited on the gas diffusion layer 3. Go. On the other hand, the carrier gas sequentially passes through the inside of the base material 2 and the breathable table 12 and escapes to the second space 14 on the downstream side of the base material, but the amount of platinum particles 41 deposited increases as shown in FIG. Accordingly, the aperture ratio of the composite base material 2 + 3 decreases, the gas does not easily pass through the second space 14 on the downstream side of the base material, the internal pressure P1 of the first space 19 rises, and the second space 14 The internal pressure P2 gradually decreases.

  In the present embodiment, the internal pressure P2 of the second space 14 is detected using the second sensor 15 and is constantly monitored by the controller 23, and the flow rate of the carrier gas from the gas supply device 21 is controlled by a flow rate sensor (not shown). I always try to monitor it. Furthermore, in the present embodiment, the carrier gas flow rate to the first space under the condition that the differential pressure ΔP (pressure loss) between the internal pressure of the first space and the internal pressure of the second space is a constant value ΔPc2. Correlation data between V and the catalyst powder deposition amount Q (or catalyst layer thickness T) on the substrate is obtained in advance by a demonstration test, etc., and the correlation data between the carrier gas flow rate V / deposition amount Q and the electrode catalyst A set value Vc2 of the carrier gas flow rate is obtained based on the target thickness of the layer, and the set value Vc2 and the predetermined value ΔPc2 are stored in a state where they can be recalled at any time, and the internal pressures in the first and second spaces are stored. P1 and P2 are detected, a differential pressure ΔP is obtained from the detected pressures P1 and P2, and the obtained differential pressure ΔP is compared with a predetermined value ΔPc2 that is called, so that the differential pressure is maintained at the predetermined value ΔPc2. The carrier gas flow rate supplied to the first space It is next reduced to stop the supply of the catalyst powder to the first space when the carrier gas flow rate reaches the set value Vc2 below. That is, the gas flow rate passing through the base material and the electrode catalyst layer formed on the upper surface thereof is reduced so that the pressure loss becomes constant. When the gas flow rate becomes equal to or less than the predetermined set value Vc2, it is considered that the platinum amount in the electrode catalyst layer has reached the target value, and the supply of the catalyst powder onto the substrate is stopped.

  Thereby, the deposition amount Q of the catalyst powder on the base material is controlled for each base material, and the thickness T of the electrode catalyst layer formed on the base material can be set as a target thickness. An electrode catalyst layer containing platinum having a value close to the target can be manufactured.

  By the manufacturing method of this embodiment, the defect of an electrode catalyst layer can be reduced and manufacturing cost can be reduced.

2 ... Base material (carbon paper),
3. Gas diffusion layer (C powder layer),
4 ... Electrode catalyst layer (Pt catalyst powder layer), 41 ... Platinum particles (catalyst powder),
5 ... Electrode laminate, 6 ... Solid electrolyte membrane,
7a, 7b ... separator, 8, 8A ... fuel cell,
DESCRIPTION OF SYMBOLS 10 ... Manufacturing apparatus, 11 ... Exhaust box, 12 ... Breathable table (mesh),
13 ... Blower, 14 ... Second space (exhaust space), 15 ... Second pressure sensor,
16 ... Mask, 16a ... Opening, 17 ... Presser pad (rubber frame),
18 ... Hood (enclosure member), 18a ... Powder introduction part,
19 ... 1st space (powder supply diffusion space), 20 ... 1st pressure sensor,
21 ... Gas supply device, 22 ... Powder supply device, 23 ... Controller,
L1 ... carrier gas line, L2 ... powder supply line, L3 ... exhaust line.

Claims (3)

The base material having air permeability constituting the fuel cell is placed on the air permeability table,
Surrounding the upper surface side of the base material on the breathable table with a surrounding member,
A predetermined amount of catalyst powder accompanied by a carrier gas is introduced into the first space surrounded by the enclosing member, and the second space on the lower surface side of the base material is evacuated, and the inside of the first space A method for producing an electrode catalyst layer for a fuel cell , comprising depositing catalyst powder in a desired thickness on an upper surface of the base material based on a differential pressure between a pressure and an internal pressure of the second space . Place the base material with air permeability on the air permeability table,
Surrounding the upper surface side of the base material on the breathable table with a surrounding member,
Under the condition that the carrier gas flow rate passing through the base material is a predetermined flow rate, a predetermined amount of catalyst powder accompanied by the carrier gas is introduced into the first space surrounded by the enclosure member, and the lower surface of the base material Exhaust the second space on the side,
Detecting the internal pressure of each of the first and second spaces;
Obtaining a differential pressure between the detected internal pressure of the first space and the internal pressure of the second space;
A method for producing an electrode catalyst layer for a fuel cell, wherein supply of catalyst powder to the first space is stopped when the differential pressure exceeds a predetermined value. Place the base material with air permeability on the air permeability table,
Surrounding the upper surface side of the base material on the breathable table with a surrounding member,
Under the condition that the carrier gas flow rate passing through the base material is a predetermined flow rate, a predetermined amount of catalyst powder accompanied by the carrier gas is introduced into the first space surrounded by the enclosure member, and the lower surface of the base material Exhaust the second space on the side,
Detecting the internal pressure of each of the first and second spaces;
Obtaining a differential pressure between the detected internal pressure of the first space and the internal pressure of the second space;
Gradually reducing the flow rate of the carrier gas supplied to the first space so that the differential pressure is maintained at a predetermined value;
A method for producing an electrode catalyst layer for a fuel cell, wherein supply of catalyst powder to the first space is stopped when the carrier gas flow rate is equal to or lower than a predetermined set value.

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