JP5624879B2 - Solid polymer electrolyte fuel cell and method for producing the same - Google Patents

Description

  The present invention relates to a solid polymer electrolyte fuel cell using a solid polymer having hydrogen ion conductivity as an electrolyte and a method for producing the same.

  In recent years, fuel cells have attracted attention as highly efficient energy conversion devices. Such fuel cells are classified into several types according to the difference in electrolyte. Among these, a solid polymer electrolyte fuel cell using a solid polymer having hydrogen ion conductivity as an electrolyte can obtain a high output density with a compact structure and can be operated by a simple system. Therefore, it is attracting a great deal of attention as a power source for space, vehicles, and households.

  A solid polymer electrolyte fuel cell is generally configured as a laminated structure in which a plurality of unit cells are stacked. The unit cell includes a joined body in which a solid polymer electrolyte membrane is sandwiched between a fuel electrode and an oxidant electrode, and a set of separators arranged outside the joined body. The fuel electrode and oxidant electrode substrates are each made of a conductive porous material. Gas diffusion layers containing carbon powder and a water repellent material are formed on the fuel electrode and oxidant electrode substrates, respectively. Further, the catalyst and the polymer electrolyte, or a catalyst layer further added with a water repellent material are formed on the gas diffusion layers of the fuel electrode and the oxidant electrode. In addition, as a method for forming a joined body, a method in which a fuel electrode and an oxidizer electrode are joined by thermocompression bonding to a polymer electrolyte membrane and integrated is performed.

  In order to stably operate this type of fuel cell, it is desirable to keep the polymer electrolyte material in a wet state, and it is necessary to supply water vapor together with the reaction gas supplied to both the fuel electrode and the oxidant electrode. On the other hand, when power generation is started, water generated by the cell reaction is generated on the catalyst of the oxidant electrode. Depending on the operating conditions of the cell, if the water vapor of the produced water becomes supersaturated in the catalyst layer, it may aggregate and form aggregated water droplets. The water generated by the water vapor or the cell reaction aggregates to form droplets, blocking the gas diffusion path in the gas diffusion layer or the catalyst layer. This phenomenon is called flooding, and is remarkable at the oxidizer electrode where the generated water is generated, leading to insufficient supply of the reaction gas and causing a voltage drop. Therefore, in order to operate the fuel cell stably, it is necessary to satisfy the conflicting demands such that the inside of the catalyst layer of the joined body is sufficiently humidified while the condensed water is discharged quickly.

  Conventional catalyst layer preparation methods include water repellent treatment of the catalyst layer with an additive such as water repellent treated carbon powder, a method of imparting hydrophilicity to the catalyst layer, and further supporting hydrophobic particles. A method of incorporating hydrophilic particles in the catalyst layer has been proposed (see, for example, Patent Document 1). However, in this type of method, when the cell is operated for a long time under the pressure to fasten the cells, each particle forming a gap moves in the gas diffusion path and the gas diffusion path is crushed, so that the performance at the time of production can be exhibited. Sometimes it disappeared.

  Therefore, in order to effectively prevent clogging of the gas diffusion path by the condensed water, focusing on the hydration (hydration power) directly related to the water retention capacity rather than the hydrophilicity, the conductive material of the catalyst layer is optimally hydrated. Therefore, a fuel cell having a catalyst layer that exhibits high performance regardless of humidification conditions has been proposed (see, for example, Patent Document 2). Further, the catalyst layer of the oxidizer electrode is formed of a mixture containing a catalyst component, an ionomer (polymer electrolyte) and a carbon material, and the water vapor adsorption amount at 25 ° C. and 90% relative humidity of the catalyst support carbon material is 50 mL / g or more. A fuel cell has been proposed (see, for example, Patent Document 3).

  However, when the amount of ionomer inside the electrode catalyst layer increases, the gas permeability decreases inside the electrode catalyst layer even though the actual catalyst layer should be hydrophilic because the ionomer is hydrophilic. A phenomenon occurs in which the gas adsorption amount to the catalyst particles coated with ionomer (polymer electrolyte) decreases and the water vapor adsorption amount also decreases. For this reason, even if the water vapor adsorption amount is defined by the method as described above, the influence of the ionomer and the catalyst material is not taken into consideration, and the accurate wet state of the electrode cannot be evaluated.

  In addition, as a new indicator of the wet state when the ionomer amount in the electrode catalyst layer is different, the nitrogen adsorption amount by nitrogen gas is measured, and the difference in gas permeability is canceled by dividing the water vapor adsorption amount by the nitrogen adsorption amount. There is also a method for evaluating the exact wet state of the electrode. However, even in this method, the preferable content of the carbon support in the catalyst layer is affected by the type and content of the carbon support and the type and supporting rate of the catalyst component. I can't.

JP 2004-342505 A JP 2007-273145 A Japanese Patent Laying-Open No. 2005-332807

  As described above, when the catalyst layer is formed of a mixture containing a catalyst component, a polymer electrolyte, and a carbon material, the accurate wet state of the electrode can be evaluated even if the water vapor adsorption amount is defined by a conventionally proposed method. I can't. For this reason, it is difficult to optimally prepare a solid polymer electrolyte fuel cell catalyst layer containing a noble metal catalyst component, a catalyst-supporting carbon, and a polymer electrolyte.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a solid polymer electrolyte fuel cell capable of stabilizing the battery characteristics and extending the life, and a method for producing the same.

In order to solve the above problems, a method for producing a solid polymer electrolyte membrane fuel cell according to the present invention includes a solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, and the solid polymer electrolyte membrane. A fuel electrode and an oxidant electrode disposed so as to be sandwiched by each other, and surfaces of the fuel electrode and the oxidant electrode facing the solid polymer electrolyte membrane, respectively, and a noble metal catalyst-supported carbon particle and polymer containing Pt A method for producing a solid polymer electrolyte membrane fuel cell comprising a catalyst layer formed by including an electrolyte, wherein a plurality of types of evaluation fuel cells having different compositions of the catalyst layer are produced; A step of measuring cell characteristics of each produced fuel cell for evaluation, a step of scraping and collecting the catalyst layer from each fuel cell for evaluation, measuring a water vapor adsorption amount of the catalyst layer, and the plurality of types The catalyst From the measurement results of the cell characteristics and water vapor adsorption amount for the catalyst layer, a step of determining the relationship between the water vapor adsorption amount per Pt weight contained in the catalyst layer and the cell characteristics, and the relationship between the water vapor adsorption amount and the cell characteristics A step of obtaining a water vapor adsorption amount for obtaining a cell voltage; a composition of the catalyst layer is determined so as to obtain the obtained water vapor adsorption amount; and a solid polymer electrolyte fuel cell using the catalyst layer having the determined composition And a step of manufacturing .

(1) It adjusts so that the water vapor adsorption amount of the said catalyst layer per Pt weight contained in a catalyst layer may become the range contained in 200-500 [m < ² > / gPt].

(2) It adjusts so that the nitrogen adsorption amount of the said catalyst layer per Pt weight contained in a catalyst layer may become the range contained in 250-650 [m < ² > / gPt].

(3) The ratio of the water vapor adsorption amount per Pt weight of the catalyst layer to the mesopore volume (unit: [cm ³ / cm ³ ]) of the catalyst layer is 600 [m ² / g Pt] / [cm ³ / cm ³ ] Adjust so that it becomes above.

(4) The ratio of the nitrogen adsorption amount per Pt weight of the catalyst layer to the mesopore volume of the catalyst layer is adjusted to be 700 [m ² / g Pt] / [cm ³ / cm ³ ] or more.

  According to the present invention, it is possible to stabilize the battery characteristics and extend the life.

1 is a cross-sectional view showing a schematic configuration of a solid polymer electrolyte fuel cell according to a first embodiment. The figure for demonstrating 1st Embodiment, and shows the relationship between a cell voltage characteristic and the water vapor | steam adsorption amount per Pt weight of a catalyst layer. The figure which is for demonstrating 1st Embodiment, and shows the result of having calculated the cell voltage fall amount from the difference of the cell voltage in the electric power generation initial stage and after 200 hours progress. The figure which is for demonstrating 2nd Embodiment, and shows the relationship between a cell voltage characteristic and the nitrogen adsorption amount per Pt weight of a catalyst layer. The figure for demonstrating 2nd Embodiment, and shows the relationship between the water vapor adsorption amount of a catalyst layer, and nitrogen adsorption amount. The figure for demonstrating 3rd Embodiment, and shows the relationship between the ratio of the water vapor adsorption amount per Pt weight of a catalyst layer with respect to the mesopore volume of a catalyst layer, and a cell voltage characteristic. The figure which is for demonstrating 3rd Embodiment, and shows the result of having calculated the cell voltage fall amount from the difference of the cell voltage at the time of the electric power generation initial stage and 200 hours after. The figure for demonstrating 4th Embodiment, and shows the relationship between ratio of the nitrogen adsorption amount per Pt weight of a catalyst layer with respect to the mesopore volume of a catalyst layer, and a cell voltage characteristic.

  Before describing the embodiment, the basic principle will be described.

  As described above, the formation of the catalyst layer requires a step of adjusting the content of each component, and further, while maintaining the polymer electrolyte material in the catalyst layer in a suitable wet state under low humidification conditions, It is necessary to determine the specifications of the catalyst layer that can prevent the gas diffusion path from being blocked by condensed water even under humidified conditions. At this time, in addition to the humidified steam that is transmitted through the gas diffusion path in the catalyst layer, the generated water generated on the catalyst of the oxidant electrode (cathode) by the cell reaction and the catalyst on the fuel electrode (anode) It is necessary to adjust the wet state including the accompanying water that moves with the hydrogen ions generated in the water, not only the difference in gas permeability determined from the ratio of the nitrogen adsorption amount and the water vapor adsorption amount, but also the produced water and the accompanying water An index that takes into account the catalyst component as the supply source is necessary.

  Therefore, in the present invention, the specification of the catalyst layer is optimally set by evaluating the water vapor adsorption amount or the nitrogen adsorption amount per Pt weight contained in the catalyst layer rather than simply evaluating the water vapor adsorption amount of the catalyst layer. Making it possible. In addition, by evaluating the ratio of the amount of water vapor adsorption per Pt weight or the ratio of nitrogen adsorption amount to the mesopore volume indicating the void amount of the catalyst layer, the specification of the catalyst layer can be set optimally. ing.

  Hereinafter, details of embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
[Constitution]
FIG. 1 is a sectional view showing a schematic configuration of a solid polymer electrolyte fuel cell according to a first embodiment of the present invention.

  As shown in FIG. 1, a polymer electrolyte membrane-electrode assembly (hereinafter simply referred to as a “joint”) 101 in a unit cell 100 sandwiches a polymer electrolyte membrane 102 and the polymer electrolyte membrane 102 from each other. The fuel electrode 103 and the oxidant electrode 104 are arranged in such a manner. The substrates 105 and 106 of the fuel electrode 103 and the oxidant electrode 104 are each made of a conductive porous material. Gas diffusion layers 107 and 108 containing carbon powder and a water repellent material are formed on the substrates 105 and 106 of the fuel electrode 103 and the oxidant electrode 104, respectively. Further, catalyst layers 109 and 110 to which a catalyst and a polymer electrolyte or further a water repellent material are added are formed on the gas diffusion layers 107 and 108 of the fuel electrode 103 and the oxidant electrode 104, respectively. In addition, as a method for forming the bonded body 101, a method in which the fuel electrode 103 and the oxidant electrode 104 are bonded to the polymer electrolyte membrane 102 by thermocompression bonding and integrated is performed.

  Sealing materials 111 and 112 are disposed on the outer periphery of the fuel electrode 103 of the joined body 101 and the substrates 105 and 106 of the oxidant electrode 104, respectively. A fuel electrode separator 113 having a gas supply groove for supplying fuel gas is disposed on the surface in contact with the fuel electrode 103. Further, an oxidant electrode separator 114 having a gas supply groove for supplying an oxidant gas is disposed on the surface in contact with the oxidant electrode 104. These constitute the unit cell 100.

  In the battery reaction in the unit cell 100, the reaction gas, particularly hydrogen as the fuel gas, diffuses in the fuel electrode side catalyst layer 109 using the pores in the fuel electrode side gas diffusion layer 107 as gas diffusion paths, and on the carbon carrier. When it reaches a catalyst such as platinum, it reacts and is separated into hydrogen ions and electrons. The electrons move from the fuel electrode 103 side to the oxidant electrode 104 side through the external circuit. The hydrogen ions move into the polymer electrolyte membrane 102 using the polymer electrolyte close to the catalyst in the fuel electrode side catalyst layer 109 as a hydrogen ion transmission path, and reach the oxidant electrode 104. Then, the polymer electrolyte in the oxidant electrode side catalyst layer 110 is diffused as a hydrogen ion transfer path, reaches the catalyst of the oxidant electrode, and reacts with oxygen in the air supplied as the oxidant gas to generate water. It becomes. The generated water moves through the catalyst layers 110 and 109 and the gas diffusion layers 108 and 107 of the oxidant electrode 104 or the fuel electrode 103 or evaporates and is removed to the outside of the substrates 105 and 106 of the gas diffusion layer.

[Preparation of catalyst layer material]
In manufacturing the catalyst layer of the solid polymer electrolyte membrane fuel cell of the present embodiment, the material used is, for example, the following configuration.

  Noble metal catalyst-supporting carbon particles containing Pt are generally used as carbon black powders such as Ketjen EC (Ketjen Black International) and Vulcan (Cabot), graphite, carbon fiber, activated carbon, Carbon nanotubes and the like are applicable.

  In addition to platinum, noble metal catalysts containing Pt supported on carbon particles include metals such as cobalt, palladium, ruthenium, gold, rhodium, osmium, iridium, or alloys or metal oxides of two or more of the above metals. Etc.

  Furthermore, as the polymer electrolyte used in the catalyst layer, a fluorine-based ion exchange resin into which hydrogen ion conductive sulfonic acid group or the like is introduced can be applied. For example, perfluorocarbon sulfonic acid polymer resin (manufactured by DuPont) ( Nafion). Further, a polymer resin having a polysulfone resin, a phosphoric acid group, a phosphonic acid group or a carboxylic acid group may be used.

  Subsequently, a noble metal catalyst-supporting carbon particle containing Pt and a solution containing a polymer electrolyte are added together with pure water or an organic solvent such as alcohol, followed by dispersion treatment with a commercially available homogenizer or the like, thereby forming a catalyst layer. An ink was prepared. Here, as the catalyst layer forming ink, various kinds of inks were prepared by changing the composition ratios of the noble metal catalyst-supporting carbon particles containing Pt, the solution containing the polymer electrolyte, and pure water or the organic solvent. Next, the catalyst layer is formed by applying the ink for forming the catalyst layer on the gas diffusion layer of the fuel electrode or the oxidant electrode substrate of the joined body and drying it. Alternatively, a catalyst layer may be formed on the polymer electrolyte membrane by transferring the catalyst layer forming ink applied onto a separately prepared coating substrate and drying it onto the polymer electrolyte membrane. good.

  The method for producing the catalyst layer of the present embodiment is not particularly limited to the above, and any method may be used as long as it is prepared using the catalyst layer material.

[Production of joined body]
In order to investigate the cell characteristics of the catalyst layer manufactured as described above, a joined body was manufactured as follows.

  That is, as in FIG. 1, the joined body 101 uses, for example, carbon paper as the substrates 105 and 106 of the fuel electrode 102 and the oxidant electrode 103. The carbon electrode and the fluororesin powder were mixed on the surface of the carbon paper, and applied and baked to form the fuel electrode side gas diffusion layer 107 and the oxidant electrode side gas diffusion layer 108, respectively. Next, the catalyst layers 109 and 110 containing the noble metal catalyst-supporting carbon particles containing Pt and the polymer electrolyte on the surface adjacent to the fuel electrode side gas diffusion layer 107 and the oxidant electrode side gas diffusion layer 108 are shown above. As described above, the ink is manufactured using the ink for forming the catalyst layer.

  Further, the fuel electrode 102 and the oxidant electrode 103 on which the catalyst layers 109 and 110 are formed are assembled with the polymer electrolyte membrane 102 sandwiched so that the catalyst layers 109 and 110 face each other. The assembled member 101 is formed by integrating the assembled members by heat pressing in the stacking direction. Here, a plurality of types of ink for forming a catalyst layer are manufactured by the method described in the section “Preparation of catalyst layer material”, and a plurality of types of joined bodies using different types of inks are formed.

<Measurement of water vapor adsorption amount of catalyst layer>
The catalyst layer powder used for the measurement of the amount of water vapor adsorption was collected by scraping the catalyst layer from the substrate after the ink for forming the catalyst layer was applied and dried.

The amount of water vapor adsorption that is an index in the present embodiment was measured as follows. That is, about 100 mg of the catalyst layer powder is weighed and vacuum degassed at 80 ° C. for 24 hours. This powder was measured for water vapor adsorption / desorption isotherm by a constant volume method using BELSORP-aqua3 (trade name) manufactured by Nippon BEL Co., Ltd. The calculated specific surface area was defined as the water vapor adsorption amount (measurement unit: [m ² / g]). Furthermore, the water vapor adsorption amount (unit: [m ² / g Pt]) of the catalyst layer per Pt weight contained in the catalyst layer was calculated from the measured Pt composition ratio contained in the catalyst layer powder. The measurement was performed at a water vapor of 298.15 K, and the calculation was performed with a saturated vapor pressure of 3.169 kPa and an adsorbate cross-sectional area of 0.125 nm ² .

[Cell characteristics evaluation]
A battery for evaluation was configured by sandwiching a bonded body manufactured for cell characteristic evaluation from both sides with a carbon separator and tightening with a predetermined battery assembly jig.

Furthermore, as a test condition at the time of power generation, a test apparatus equipped with a control device capable of the following settings was used. That is, the cell temperature was maintained at 80 ° C., hydrogen was used as the fuel and supplied at a humidification temperature of 65 ° C., and air was used as the oxidant and supplied at a humidification temperature of 65 ° C. Furthermore, the cell voltage is evaluated based on the cell voltage value after holding for 200 hours under the conditions of a load current of 200 mA / cm ² , a hydrogen utilization rate of 70% (normal pressure), and an oxygen utilization rate of 40% (normal pressure). went.

<Evaluation results>
FIG. 2 shows the relationship between the cell voltage characteristics and the water vapor adsorption amount per Pt weight of the catalyst layer. Furthermore, the amount of cell voltage reduction was calculated from the difference in cell voltage between the initial stage of power generation and after 200 hours in FIG.

As the water vapor adsorption amount increases, the cell voltage increases. When the water vapor adsorption amount is about 350 [m ² / gPt], the cell voltage becomes maximum, and when the water vapor adsorption amount exceeds this value, the cell voltage decreases. A cell voltage of 750 mV or higher was obtained when the water vapor adsorption amount was in the range of 200 [m ² / g Pt] to 500 [m ² / g Pt].

Therefore, in order to obtain a high cell voltage characteristic of 750 mV or more in 200 hours of power generation, as shown in FIG. 2, the water vapor adsorption amount of the catalyst layer per Pt weight contained in the catalyst layer is 200 to 500. It has been found that the adjustment may be made so as to be within the range included in [m ² / gPt]. Furthermore, as shown in FIG. 3, it was found that the cell voltage drop amount increased and unstable characteristics were exhibited in a range of less than 200 [m ² / g Pt] or more than 500 [m ² / g Pt].

  Here, when the composition of the catalyst layer is changed, the water vapor adsorption area with respect to the unit amount of Pt naturally changes. However, as the composition of the catalyst layer used in [Preparation of catalyst layer material] changes, it is confirmed that the relationship between the water vapor adsorption area and the cell voltage with respect to the unit amount of Pt shows a correlation as shown in FIG. doing. That is, the water vapor adsorption area with respect to the unit amount of Pt varies depending on the composition ratio of each material of the catalyst layer, but the relationship between the water vapor adsorption area with respect to the unit amount of Pt and the cell voltage depends on the composition ratio of each material of the catalyst layer. Regardless, the correlation is as shown in FIG. From these facts, it has been found that it is important to determine the composition of the catalyst layer so that the water vapor adsorption amount relative to the unit amount of Pt falls within the above range, rather than uniquely determining the composition of the catalyst layer.

  The amount of water vapor adsorbed indicates the amount of water molecules with polarity that are adsorbed or absorbed inside the polar part of the molecular structure on the surface of the catalyst layer. The higher the amount of water molecules adsorbed, the more the catalyst layer It is considered that the ability is high and the catalyst layer has a function of keeping it wet. On the other hand, the Pt component of the catalyst layer is a reaction site of the cell reaction, and in particular, a site where generated water is generated at the oxidizer electrode, and a site where accompanying water needs to be supplied to hydrogen ions generated by the cell reaction at the fuel electrode. Become. The Pt component exhibiting catalytic action is generally used in the form of particles distributed in the range of several nm to several tens of nm and supported on a carbon support. For example, in the case of using a commercially available noble metal catalyst containing Pt, the number or area of the reaction sites per unit area in the cell surface on which the catalyst layer is formed, assuming the general particle distribution as described above. Cell power generation characteristics are evaluated using the amount of Pt supported per unit area as a parameter.

  That is, in order to improve the cell voltage characteristics, in order to optimize the wettability in the cell, in particular, in the catalyst layer having the reaction site, it is necessary to consider the influence of the Pt component contained in the catalyst layer. Therefore, it is extremely effective to use the water vapor adsorption amount per Pt weight contained in the catalyst layer as an index as in this embodiment.

As described above, according to the present embodiment, the specification of the catalyst layer is within the range of 200 to 500 [m ² / gPt] using the water vapor adsorption amount of the catalyst layer per Pt weight contained in the catalyst layer as an index. By adjusting, it becomes possible to prepare the catalyst layer so as to exhibit high cell voltage characteristics. As a result, it is possible to form a joined body with the composition and structure in the catalyst layer optimized, thereby realizing a high-performance solid polymer electrolyte fuel cell with stable battery characteristics and improved lifespan. Can do.

(Second Embodiment)
For the sample prepared in the same manner as in the first embodiment, the nitrogen adsorption amount was measured instead of the water vapor adsorption amount.

  The catalyst layer powder used for measuring the nitrogen adsorption amount was collected by scraping the catalyst layer from the substrate after the ink for forming the catalyst layer was applied and dried.

The nitrogen adsorption amount was measured as follows. That is, about 100 mg of electrode powder is weighed and vacuum degassed at 80 ° C. for 24 hours. This powder was measured for nitrogen adsorption / desorption isotherm by a constant volume method using BELSORP-mini (trade name) manufactured by Nippon BEL Co., Ltd., and measurement data having a relative pressure of 0.3 or less was calculated by the BET method. The specific surface area was defined as the nitrogen adsorption amount (measurement unit: [m ² / g]). Furthermore, the nitrogen adsorption amount (unit: [m ² / gPt]) of the catalyst layer per Pt weight contained in the catalyst layer was calculated from the measured Pt composition ratio contained in the catalyst layer powder. Measurement temperature nitrogen 77K, the saturated vapor pressure is measured, calculated by the adsorbate cross sectional area 0.162nm ^2.

  FIG. 4 shows the relationship between the cell voltage characteristics and the nitrogen adsorption amount per Pt weight of the catalyst layer. Further, FIG. 5 shows the relationship between the water vapor adsorption amount of the catalyst layer and the nitrogen adsorption amount.

As shown in FIG. 4, as the nitrogen adsorption amount increases, the cell voltage increases. When the nitrogen adsorption amount is about 400 [m ² / gPt], the cell voltage becomes maximum, and when the nitrogen adsorption amount exceeds this value, the cell voltage becomes Decrease. A cell voltage of 750 mV or higher was obtained when the nitrogen adsorption amount was in the range of 250 [m ² / g Pt] to 650 [m ² / g Pt].

The amount of nitrogen adsorption indicates the amount of symmetric and nonpolar nitrogen molecules physically adsorbed on the catalyst layer surface, and the more the shape of the catalyst layer surface is polar, the more the nitrogen adsorption amount is. Become more. Furthermore, the finer the catalyst layer surface is, the more the area for supporting Pt particles having reaction sites increases. Therefore, by optimizing the amount of nitrogen adsorption with respect to the amount of Pt component, the Pt particle support state becomes more homogeneous. There is a possibility. Further, as shown in FIG. 5, the nitrogen adsorption amount of the catalyst layer correlates with the water vapor adsorption amount. Therefore, as the specification of the catalyst layer in the present embodiment, the catalyst per Pt weight contained in the catalyst layer is used. The nitrogen adsorption amount of the layer can be used as an index. Furthermore, as a condition for obtaining a high cell voltage characteristic of 750 mV or more in 200 hours of power generation, as shown in FIG. 4, the nitrogen adsorption amount of the catalyst layer per Pt weight contained in the catalyst layer is 250 to 650. It can provide by adjusting in the range contained in [m < ² > / gPt].

As described above, according to the present embodiment, the specification of the catalyst layer is adjusted within the range of 250 to 650 [m ² / gPt] using the nitrogen adsorption amount per Pt weight contained in the catalyst layer as an index. The catalyst layer can be prepared so as to exhibit high cell voltage characteristics. Therefore, the same effect as that of the first embodiment can be obtained in this embodiment.

(Third embodiment)
For the sample produced in the same manner as in the first embodiment, the ratio of the water vapor adsorption amount per Pt weight to the mesopore volume of the catalyst layer was measured instead of the water vapor adsorption amount.

  As in the first embodiment, the catalyst layer powder used for the water vapor adsorption amount was collected by scraping the catalyst layer from the substrate after applying and drying the catalyst layer forming ink.

In addition, the mesopore volume was measured by the BJH plot method from the water vapor adsorption volume introduced into a predetermined measurement system for the water vapor adsorption / desorption isotherm measurement data (measurement unit: [cm ³ / g]). Furthermore, the value of the mesopore volume converted per apparent density (unit: [g / cm ³ ]) determined as described below was used (unit [cm ³ / cm ³ ]). That is, the apparent density was calculated from the catalyst layer thickness calculated from the difference in thickness measured with a micrometer and the result of measuring the catalyst layer coating weight per unit area for the substrates before and after forming the catalyst layer. Here, the apparent density was measured as described above. However, another measurement method may be employed as long as it has the same main point in showing the density of the formed catalyst layer.

  FIG. 6 shows the relationship between the cell voltage characteristics and the ratio of the water vapor adsorption amount per Pt weight of the catalyst layer to the mesopore volume of the catalyst layer. Further, FIG. 7 shows the cell voltage drop from the difference in cell voltage between the initial power generation and after 200 hours.

In order to obtain a high cell voltage characteristic of 750 mV or more in 200 hours of power generation, the water vapor adsorption amount per Pt weight of the catalyst layer with respect to the mesopore volume of the catalyst layer as shown in FIG. ^{[m 2 / gPt] / [} cm 3 / cm 3] it is necessary to adjust so that the range of the above, 600 as shown in FIG. ^{7 [m 2 / gPt] /} [cm 3 / cm ³ ], it was found that the cell voltage drop increased and unstable characteristics were exhibited.

The mesopore volume indicates a volume in which nitrogen molecules are adsorbed and accumulated in the fine pores of the catalyst layer powder to fill the pores, and the value converted in the unit cm ³ / cm ³ as described above is the catalyst layer. The void amount in the unit volume, that is, the pore volume ratio.

In general, it is presumed that a gas having a pore structure having a large opening such as a catalyst layer has a large amount of voids, and the gas permeates into the pores to relatively increase the gas permeation amount. For this reason, it is considered that the mesopore volume that quantitatively indicates the void amount can be applied as one of the characteristics exhibiting gas permeability. Furthermore, in order to optimize the gas permeation amount while maintaining wettability, the mesopore volume of the catalyst layer is based on the component amount of the Pt particles as the generation source and transfer source of the generated water as the reaction site of the battery reaction. It is necessary to show the relationship. For this reason, as a specification of the catalyst layer according to the present embodiment, as a condition for obtaining a high cell voltage characteristic showing 750 mV or more in 200 hours of power generation, as shown in FIG. Provided by adjusting the water vapor adsorption amount per Pt weight of the catalyst layer (unit [m ² / g Pt]) as an index, and adjusting within a range of 600 [m ² / g Pt] / [cm ³ / cm ³ ] or more it can.

Thus, according to the present embodiment, as the specification of the catalyst layer, the ratio of the water vapor adsorption amount (unit [m ² / g Pt]) per Pt weight of the catalyst layer to the mesopore volume of the catalyst layer is 600 [m. By adjusting in the range of ² / gPt] / [cm ³ / cm ³ ] or more, it becomes possible to prepare the catalyst layer so as to exhibit high cell voltage characteristics. Therefore, the same effect as the first embodiment can be obtained.

(Fourth embodiment)
For the sample produced in the same manner as in the first embodiment, the ratio of the nitrogen adsorption amount per Pt weight to the mesopore volume of the catalyst layer was measured instead of the nitrogen adsorption amount.

  As in the first embodiment, the catalyst layer powder used for the nitrogen adsorption amount was collected by scraping the catalyst layer from the substrate after applying and drying the catalyst layer forming ink.

The mesopore volume was measured from the nitrogen adsorption volume of the nitrogen adsorption / desorption isotherm measurement data introduced into a predetermined measurement system by the BJH plot method (measurement unit: [cm ³ / g]). Furthermore, the value of the mesopore volume converted per apparent density (unit: [g / cm ³ ]) determined as described below was used (unit [cm ³ / cm ³ ]). That is, the apparent density was calculated from the catalyst layer thickness calculated from the difference in thickness measured with a micrometer and the result of measuring the catalyst layer coating weight per unit area for the substrate before and after forming the catalyst layer. . Here, the apparent density was measured as described above. However, another measurement method may be employed as long as it has the same main point in showing the density of the formed catalyst layer.

FIG. 8 shows the relationship between the cell voltage characteristics and the ratio of the nitrogen adsorption amount per Pt weight of the catalyst layer to the mesopore volume of the catalyst layer. The nitrogen adsorption amount per Pt weight of the catalyst layer takes into account the correlation with the water vapor adsorption amount as obtained in FIG. Therefore, as a condition for obtaining a high cell voltage characteristic indicating 750 mV or more in 200 hours of power generation as a specification of the catalyst layer, as shown in FIG. 8, the mesopore volume of the catalyst layer (unit: [cm ³ / cm ³ ]) with respect to the ratio of the amount of nitrogen adsorbed per unit Pt weight of the catalyst layer (unit [m ² / g Pt]) as an index, adjustment is made within a range of 700 [m ² / g Pt] / [cm ³ / cm ³ ] Can be provided.

As described above, according to the present embodiment, as the specification of the catalyst layer, the ratio of the nitrogen adsorption amount (unit [m ² / g Pt]) per Pt weight of the catalyst layer to the mesopore volume of the catalyst layer is 700 [m. By adjusting in the range of ² / gPt] / [cm ³ / cm ³ ] or more, it becomes possible to prepare the catalyst layer so as to exhibit high cell voltage characteristics. Therefore, the same effect as the first embodiment can be obtained.

(Modification)
The present invention is not limited to the above-described embodiments. In the embodiment, the carbon particles are used as the material for supporting the noble metal catalyst containing Pt. However, any material can be used as long as the material fulfills the same function as long as it satisfies the gist of the present invention. Furthermore, in the embodiment, the composition of the catalyst layer on both the oxidant electrode side and the fuel electrode side is adjusted. However, if a sufficient effect can be obtained even by preparing one catalyst layer on the fuel electrode side and the oxidant electrode side. May be only to adjust the composition of any one of the catalyst layers. Since the water produced by the battery reaction is generated in the catalyst layer on the oxidant electrode side, the demand for the catalyst layer on the oxidant electrode side is stricter. Be expected.

  Further, the device configuration as a fuel cell is not limited to that shown in FIG. 1, and is a configuration in which a catalyst layer is disposed between a solid polymer electrolyte membrane and a fuel electrode and an oxidant electrode sandwiching the polymer electrolyte membrane. Any layer can be used as long as it is formed by containing noble metal catalyst-supporting carbon particles containing Pt and a polymer electrolyte.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100 ... Unit cell 101 ... Assembly 102 ... Polymer electrolyte membrane 103 ... Fuel electrode 104 ... Oxidant electrode 105 ... Fuel electrode substrate 106 ... Oxidant electrode substrate 107 ... Fuel electrode gas diffusion layer 108 ... Oxidant electrode gas diffusion layer 109 ... Fuel electrode catalyst layer 110 ... Oxidant electrode catalyst layer 111 ... Fuel electrode seal material 112 ... Oxidant electrode seal material 113 ... Fuel electrode separator 114 ... Oxidant electrode separator

Claims (4)

A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, a fuel electrode and an oxidizer electrode arranged so as to sandwich the solid polymer electrolyte membrane, and the fuel electrode and oxidizer A solid polymer electrolyte membrane fuel cell comprising a noble metal catalyst-supporting carbon particle containing Pt and a catalyst layer formed on the surface of the electrode facing the solid polymer electrolyte membrane and containing a polymer electrolyte A manufacturing method of
Producing a plurality of evaluation fuel cells having different compositions of the catalyst layer;
Measuring the cell characteristics of each of the produced fuel cells for evaluation;
Scraping and collecting the catalyst layer from each evaluation fuel cell, and measuring the water vapor adsorption amount of the catalyst layer;
Obtaining the relationship between the cell characteristics and the water vapor adsorption amount per Pt weight contained in the catalyst layer from the measurement results of the cell characteristics and the water vapor adsorption amount for the plurality of types of catalyst layers;
Obtaining a water vapor adsorption amount for obtaining a predetermined cell voltage from the relationship between the water vapor adsorption amount and the cell characteristics;
Determining the composition of the catalyst layer to achieve the determined water vapor adsorption amount, and producing a solid polymer electrolyte fuel cell using the catalyst layer having the determined composition;
A method for producing a solid polymer electrolyte fuel cell, comprising: A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, a fuel electrode and an oxidizer electrode arranged so as to sandwich the solid polymer electrolyte membrane, and the fuel electrode and oxidizer A solid polymer electrolyte membrane fuel cell comprising a noble metal catalyst-supporting carbon particle containing Pt and a catalyst layer formed on the surface of the electrode facing the solid polymer electrolyte membrane and containing a polymer electrolyte A manufacturing method of
Producing a plurality of evaluation fuel cells having different compositions of the catalyst layer;
Measuring the cell characteristics of each of the produced fuel cells for evaluation;
Scraping and collecting the catalyst layer from each of the fuel cells for evaluation, and measuring the nitrogen adsorption amount of the catalyst layer;
Obtaining a relationship between the cell characteristics and the nitrogen adsorption amount per Pt weight contained in the catalyst layer from the measurement results of the cell characteristics and the nitrogen adsorption amount for the plurality of types of catalyst layers;
Obtaining a nitrogen adsorption amount for obtaining a predetermined cell voltage from the relationship between the nitrogen adsorption amount and the cell characteristics;
Determining the composition of the catalyst layer to achieve the determined nitrogen adsorption amount, and producing a solid polymer electrolyte fuel cell using the catalyst layer of the determined composition;
A method for producing a solid polymer electrolyte fuel cell, comprising: A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, a fuel electrode and an oxidizer electrode arranged so as to sandwich the solid polymer electrolyte membrane, and the fuel electrode and oxidizer A solid polymer electrolyte membrane fuel cell comprising a noble metal catalyst-supporting carbon particle containing Pt and a catalyst layer formed on the surface of the electrode facing the solid polymer electrolyte membrane and containing a polymer electrolyte A manufacturing method of
Producing a plurality of evaluation fuel cells having different compositions of the catalyst layer;
Measuring the cell characteristics of each of the produced fuel cells for evaluation;
Scraping and collecting the catalyst layer from each evaluation fuel cell, and measuring the water vapor adsorption amount of the catalyst layer;
A step of obtaining a relationship between the cell characteristics and the water vapor adsorption amount per Pt weight with respect to the mesopore volume of the catalyst layer from the measurement results of the cell characteristics and the water vapor adsorption amount for the plurality of types of catalyst layers;
Obtaining a water vapor adsorption amount for obtaining a predetermined cell voltage from the relationship between the water vapor adsorption amount and the cell characteristics;
Determining the composition of the catalyst layer to achieve the determined water vapor adsorption amount, and producing a solid polymer electrolyte fuel cell using the catalyst layer having the determined composition;
A method for producing a solid polymer electrolyte fuel cell, comprising: A solid polymer electrolyte membrane using a solid polymer having hydrogen ion conductivity as an electrolyte, a fuel electrode and an oxidizer electrode arranged so as to sandwich the solid polymer electrolyte membrane, and the fuel electrode and oxidizer A solid polymer electrolyte membrane fuel cell comprising a noble metal catalyst-supporting carbon particle containing Pt and a catalyst layer formed on the surface of the electrode facing the solid polymer electrolyte membrane and containing a polymer electrolyte A manufacturing method of
Producing a plurality of evaluation fuel cells having different compositions of the catalyst layer;
Measuring the cell characteristics of each of the produced fuel cells for evaluation;
Scraping and collecting the catalyst layer from each of the fuel cells for evaluation, and measuring the nitrogen adsorption amount of the catalyst layer;
A step of determining the relationship between the cell characteristics and the nitrogen adsorption amount per Pt weight with respect to the mesopore volume of the catalyst layer from the measurement results of the cell characteristics and the nitrogen adsorption amount for the plurality of types of catalyst layers;
Obtaining a nitrogen adsorption amount for obtaining a predetermined cell voltage from the relationship between the nitrogen adsorption amount and the cell characteristics;
Determining the composition of the catalyst layer to achieve the determined nitrogen adsorption amount, and producing a solid polymer electrolyte fuel cell using the catalyst layer of the determined composition;
A method for producing a solid polymer electrolyte fuel cell, comprising:

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