Carbon material for catalyst carrier of solid polymer fuel cell, catalyst layer for solid polymer fuel cell, and fuel cell

Abstract

This carbon material for a catalyst carrier of a solid polymer fuel cell comprises porous activated carbon black satisfying requirements (A), (B), (C), and (D). (A) The average primary particle diameter is more than 30 nm but not more than 100 nm. (B) The BET specific surface area is 350-800 m2 / g. <sp / > (C) In an X-ray diffraction (XRD) spectrum obtained by XRD measurement, Lc (002) obtained by analyzing a peak within diffraction angles of 2θ=20° to 26.5° is 1.7-4.0 nm. (D) In an X-ray diffraction (XRD) spectrum obtained by XRD measurement, La (110) obtained by analyzing a peak within diffraction angles of 2θ=70° to 80° is 3.5 nm or less.

Description

Technical Field

[0001] The present disclosure relates to a carbon material for a catalyst support of a polymer electrolyte fuel cell, a catalyst layer for a polymer electrolyte fuel cell, and a fuel cell.

Background Art

[0002] A polymer electrolyte fuel cell, which is a type of fuel cell, includes a pair of catalyst layers disposed on both sides of a polymer electrolyte membrane, a gas diffusion layer disposed outside each catalyst layer, and a separator disposed outside each gas diffusion layer. Of the pair of catalyst layers, one catalyst layer serves as the anode of the polymer electrolyte fuel cell, and the other catalyst layer serves as the cathode of the polymer electrolyte fuel cell. In a normal polymer electrolyte fuel cell, a plurality of unit cells having the above-described components are stacked to obtain a desired output.

[0003] A reducing gas such as hydrogen is introduced into the separator on the anode side. The gas diffusion layer on the anode side diffuses the reducing gas and then introduces it into the anode. The anode includes a catalyst component, a catalyst support that supports the catalyst component, and an electrolyte material (such as an ionomer) having proton conductivity. The catalyst support is often composed of a carbon material. On the catalyst component, an oxidation reaction of the reducing gas occurs, generating protons and electrons. For example, when the reducing gas is hydrogen gas, the following oxidation reaction occurs. H2→2H + +2e - (E0=0V)

[0004] The protons generated by this oxidation reaction are introduced into the cathode through the electrolyte material in the anode and the polymer electrolyte membrane. Also, the electrons are introduced into the external circuit through the catalyst support, the gas diffusion layer, and the separator. These electrons perform work (generate electricity) in the external circuit and are then introduced into the separator on the cathode side. Then, these electrons are introduced into the cathode through the separator on the cathode side and the gas diffusion layer on the cathode side.

[0005] The solid polymer electrolyte membrane is composed of an electrolyte material having proton conductivity. The solid polymer electrolyte membrane introduces the protons generated in the above oxidation reaction to the cathode.

[0006] An oxidizing gas such as oxygen gas or air is introduced into the separator on the cathode side. The gas diffusion layer on the cathode side diffuses the oxidizing gas and then introduces it to the cathode. The cathode includes a catalyst component, a catalyst carrier that supports the catalyst component, and an electrolyte material (ionomer) having proton conductivity. The catalyst carrier is often composed of a carbon material. On the catalyst component, a reduction reaction of the oxidizing gas occurs and water is generated. For example, when the oxidizing gas is oxygen gas or air, the following reduction reaction occurs. O2+4H + +4e - →2H2O (E0=1.23V)

[0007] The water generated in the reduction reaction is discharged to the outside of the fuel cell together with the unreacted oxidizing gas. Thus, in the solid polymer fuel cell, power is generated by utilizing the energy difference (potential difference) between the oxidation reaction and the reduction reaction. In other words, the electrons generated in the oxidation reaction do work in the external circuit.

[0008] By the way, from the viewpoint of the power generation performance of fuel cells, it has been conventionally proposed to use porous carbon black as the catalyst carrier. In Non-Patent Document 1, it is reported that the catalyst metal supported in the pores formed inside the porous carbon black is highly active because it is not subject to reaction inhibition (poisoning) by the coating of the ionomer coexisting in the catalyst layer. In Patent Document 1, porous carbon black having an average particle diameter of 20 to 100 nm and a pore volume of 0.23 to 0.78 cm 3 / g and a pore diameter of 4 to 20 nm has been proposed. In Patent Document 2, as a method for making carbon black porous and increasing the surface area, a method of bringing a carbon black starting material into contact with an oxidizing agent in a fluidized bed has been proposed.

[0009] In addition, from the perspective of the durability performance of fuel cells, it has been proposed to calcine porous carbon black to achieve high crystallization. In Patent Document 3, in order to impart durability, highly crystalline carbon black having a BET specific surface area of 300 to 700 m 2 / g and a crystallite size Lc of 2.0 nm or more has been proposed. In Patent Document 4, Lc(002) is 2.0 nm or more, and the ratio D / G of the peak area of the D1-band (1350 cm -1 ) to the peak area of the G-band (1590 cm -1 ) in the spectrum of the carbon surface by Raman spectroscopy is 0.5 to 2.5, it has pores including mesopores, and a porous carbon having a mesopore volume of 0.35 to 1.3 cm 3 / g has been proposed. In particular, the porous carbon black used for the positive electrode becomes a high potential in air or water containing oxygen, so the oxidation and consumption of carbon proceed. To suppress this, in Patent Documents 3 to 4, the porous carbon black is heat-treated at a high temperature to enhance the crystallinity of carbon.

[0010] In addition, in Patent Document 1 described above, it is described that if the average particle diameter of the porous carbon black is 20 to 100 nm, the mechanical strength can be maintained even when the porous carbon black is provided with a pore structure.

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-109856 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-052967 Patent Document 3: Japanese Patent No. 6478677 Patent Document 4: International Publication No. 17 / 208742

[0012] Non-Patent Document 1: Kongkanand et al., ACS Energy Lett. 2018, 3, 618-621

Summary of the Invention

Problems to be Solved by the Invention

[0013] However, among all the documents, there has been no proposal in the prior art that can highly achieve both durability and low humidification performance required for large commercial mobility (hereinafter also referred to as "HDV") applications.

[0014] For example, in Patent Document 1, by making the material porous, power generation performance including low humidification performance can be enhanced, and by using carbon black with an average primary particle diameter of a certain size, the mechanical strength required for the carbon material for the catalyst support can be ensured. However, in the HDV application that requires a balance between high durability and low humidification performance, it could not be said to have sufficient performance. Particularly regarding the particle diameter, although an average particle diameter of 20 to 100 nm is proposed in Patent Document 1, only carbon black with a particle diameter of 30 nm is exemplified in the examples. Also, means for making carbon black with an average primary particle diameter exceeding 30 nm porous are not exemplified at all in Patent Document 1. The carbon black with a particle diameter of 30 nm exemplified in the examples was heat-treated at various temperatures to examine its properties, but it was not possible to achieve both high durability and low humidification performance at a high level.

[0015] For example, in Patent Document 3, although durability can be enhanced by graphitized carbon black, it was inevitable that the hydrophilicity of the surface decreased and the low humidification performance decreased. In Patent Document 3, it is proposed to achieve both high power generation performance due to porosity and high durability due to high crystallization by heat-treating porous carbon black. However, according to the additional tests by the inventors of the present invention, it was difficult to achieve both high durability and low humidification performance at a high level only with the proposed constituent requirements.

[0016] Therefore, an object of the present disclosure is to provide a carbon material for a catalyst support of a polymer electrolyte fuel cell in which high durability and low humidification performance are achieved, a catalyst layer for a polymer electrolyte fuel cell using the same, and a fuel cell.

Means for Solving the Problem

[0017] The means for solving the problem includes the following aspects. <1> A carbon material for a catalyst support of a polymer electrolyte fuel cell, which is made of porous activated carbon black and satisfies the following requirements (A), (B), (C), and (D). (A) The average primary particle diameter is more than 30 nm and 100 nm or less. (B) The BET specific surface area is 350 m 2 / g or more and 800 m 2 / g or less. (C) In the XRD spectrum obtained by XRD (X-ray diffraction) measurement, Lc(002) obtained by analyzing the peak between diffraction angles 2θ = 20° to 26.5° is 1.7 nm or more and 4.0 nm or less. (D) In the XRD spectrum obtained by XRD (X-ray diffraction) measurement, La(110) obtained by analyzing the peak between diffraction angles 2θ = 70° to 80° is 3.5 nm or less. <2> Furthermore, the carbon material for a catalyst support of a polymer electrolyte fuel cell according to <1>, which satisfies the following requirement (E). (E) The ratio (Lc(002) / La(110)) of the Lc(002) to the La(110) is 0.6 or more and 1.2 or less. <3> The carbon material for a catalyst support of a polymer electrolyte fuel cell according to <1> or <2>, wherein the average primary particle diameter is 40 nm or more and 100 nm or less. <4> A catalyst layer for a polymer electrolyte fuel cell, which contains the carbon material for a catalyst support of a polymer electrolyte fuel cell according to any one of <1> to <3>. <5> A fuel cell, which contains the catalyst layer for a polymer electrolyte fuel cell according to <4>. <6> The fuel cell according to <5>, wherein the catalyst layer for a polymer electrolyte fuel cell is a cathode-side catalyst layer.

Advantages of the Invention

[0018] According to the present disclosure, there are provided a carbon material for a catalyst support of a polymer electrolyte fuel cell in which high durability and low humidification performance are compatible, a catalyst layer for a polymer electrolyte fuel cell using the same, and a fuel cell.

Brief Description of the Drawings

[0019]

Figure 1

Embodiments for Carrying Out the Invention

[0020] In the present disclosure, a numerical range represented by “~” means a range including the numerical values described before and after “~” as a lower limit value and an upper limit value. Further, when a numerical value before and after “~” is attached with “more than” or “less than”, the numerical range means a range not including these numerical values as a lower limit value or an upper limit value. In the present disclosure, the term “step” includes not only an independent step but also this term as long as the intended purpose of the step is achieved even when it cannot be clearly distinguished from other steps. In the present disclosure, the “electrolyte material having proton conductivity” used in the catalyst layer of the fuel cell is also referred to as “ionomer”.

[0021] <Carbon Material for Catalyst Support of Polymer Electrolyte Fuel Cell> The carbon material for a catalyst support of the polymer electrolyte fuel cell of the present disclosure is composed of porous activated carbon black that satisfies the requirements (A), (B), (C), and (D) described below. Here, the porous activated carbon black is carbon black made porous by activation. The porous activated carbon black is also referred to as “porous carbon black”.

[0022] The carbon material for a catalyst support of the present disclosure is a carbon material in which high durability and low humidification performance are compatible. The carbon material of the present disclosure was found based on the following findings.

[0023] In the prior art, generally when heat-treating porous carbon black, the crystallites grow larger and the durability improves. However, as the crystallites grow larger, the number of edges where functional groups can exist decreases, resulting in the disappearance of micropores and a decrease in specific surface area. When the micropores and specific surface area decrease, it becomes difficult to highly disperse the catalytic metal as fine particles. Therefore, large particles or aggregated catalytic metals are supported, and the specific surface area of the catalytic metal tends to decrease, and the power generation performance also tends to decrease. Also, since the decrease in the number of micropores and edges reduces the adsorption density of adsorbed water, it is easily affected by the weakening of the network of adsorbed water that can desorb adsorbed water and propagate protons when the relative humidity decreases, and the low humidification performance tends to decrease.

[0024] In order to prevent these, attempts have been made to further porousize the porous carbon black to prevent a decrease in specific surface area and the disappearance of micropores. However, with further porousization, the Lc(002) of the crystallites tends to decrease strongly, and it becomes necessary to heat-treat at a relatively high temperature in order to have the required durability. As a result, the La(110) becomes large, the edge density decreases, and the low humidification performance decreases.

[0025] Therefore, as a result of the study by the present inventors, it was found that the structural requirements for achieving both high durability and low humidification performance required for HDV applications are as follows. (1) The specific surface area is high enough to have internal pores so that the catalytic metal can be finely dispersed and high power generation performance can be obtained. (2) The Lc(002) has a size of a certain value or more so that high durability can be obtained. (3) In order to obtain high low humidification performance, a certain edge density or more is required, and for that purpose, the La(110) should not become larger than a certain value.

[0026] The primary particles of carbon black are composed of an aggregate of carbon network laminates (crystallites), and the crystallites are oriented concentrically (onion-like). The size of the crystallites is larger closer to the outer periphery of the primary particle and tends to become smaller toward the center. In many cases, the central part is composed of amorphous with low crystallinity. Also, even in the part with relatively high crystallinity on the outer periphery, the crystallites are bonded with a structure having low crystallinity, resulting in a structure with many defects compared to the hexagonal network plane constituting the crystallites. Further, the primary particles fuse together in plural numbers during the production of carbon black and form a bead-like structure called an aggregate. This three-dimensional structure creates a network of voids between aggregates in the catalyst layer when carbon black is used as a catalyst support for a fuel cell. This network of voids serves to diffuse hydrogen in the case of the anode and oxygen in the air and the generated water in the case of the cathode during power generation.

[0027] When activation is performed on the raw material carbon black for the purpose of making it porous and increasing the specific surface area using carbon black having such a structure as a raw material, the structure part with many defects between the crystallites constituting the part near the outer periphery of the primary particles of the raw material carbon black is oxidized and consumed, and that part becomes micropores. When activation is advanced for a long time to obtain a sufficient specific surface area, the activator diffused through the micropores generated in the part near the outer periphery oxidizes and consumes the internal amorphous part, resulting in a hollow structure in which the outer periphery where the crystallites are relatively large remains as an outer shell. At this time, the crystallites of the outer shell are also partially oxidized and consumed. If excessive activation is performed, the oxidation and consumption of the crystallites forming the outer shell progress, and the primary particles may disappear due to oxidation and consumption.

[0028] The hollowed porous carbon black can support a catalyst metal in the space formed inside. Since it is difficult for the ionomer coexisting when forming the catalyst layer to penetrate into the internal space of the moderately activated porous carbon black, the catalyst metal supported inside is less likely to be inhibited by ionomer adsorption, and in particular, the reaction overvoltage can be reduced in the oxygen reduction reaction proceeding at the cathode, enabling a high-performance fuel cell to be obtained.

[0029] Generally, raw carbon black having a small average primary particle size has a thinner outer shell composed of crystallites and smaller crystallite sizes that make up the outer shell, so it is easier to activate. Even in the prior art, it was possible to relatively easily achieve porosity and a high specific surface area of the raw carbon black. However, in order to achieve both high durability and low humidification performance required for HDV applications, porous carbon black obtained by activating raw carbon black with a small particle size cannot provide sufficient durability. This is because the crystallites constituting the remaining outer shell are too small for the target durability, resulting in a thinner outer shell of the resulting hollow-structured particles. It is also because the primary particles of the raw carbon black are likely to disappear due to oxidative consumption during soot cleaning in the environment where a fuel cell is used, and the voids in the catalyst layer where gas can diffuse are eliminated.

[0030] If excessive heat treatment is performed as a countermeasure to make the crystallites as large as possible and difficult to oxidize, the disappearance of micropores and edges occurs, leading to a decrease in specific surface area and a decrease in low humidification performance. On the other hand, if the raw carbon black has an average primary particle size of a certain size or more, it originally tends to be composed of large crystallites, so it can be expected that large crystallites will remain even after activation. However, raw carbon black having an average primary particle size of a certain size or more usually has large crystallites near the outer surface and a thick outer shell composed of crystallites. Therefore, it is difficult to achieve porosity to obtain a sufficiently large specific surface area, and in the prior art, it is difficult to satisfy the above structural requirements using raw carbon black having an average primary particle size of a certain size or more.

[0031] Therefore, as a result of investigations by the present inventors, the following findings were obtained. Raw carbon black having a relatively large average primary particle diameter (exceeding 30 nm) is processed in the order of "first activation", "graphitization", and "second activation". When "first activation" is performed by pressurizing and slowly activating at a low temperature while slightly varying the flow rate, the above structural requirements can be satisfied. In particular, in the first activation, by pressurizing and slightly varying the flow rate, even large particles can oxidatively consume the "less crystalline part" existing between crystallites, and the atmosphere in the defects (pores) generated by oxidative consumption can be quickly replaced with the activation gas. Therefore, it is presumed that even large particles can be efficiently made porous. Also, when the first activation is performed on carbon black having a relatively large average primary particle diameter (exceeding 30 nm) by such a method, the required durability can be ensured without performing excessive heat treatment in the subsequent graphitization. By using carbon black having a relatively large average primary particle diameter (exceeding 30 nm), Lc(002) can be increased without performing excessive heat treatment, so the durability can be ensured, and the growth of La(110) can be suppressed by relatively low-temperature graphitization, so it is presumed that the decrease in low-humidity performance can be suppressed.

[0032] From the above findings, it has been found that the carbon material for a catalyst carrier of the present disclosure is a carbon material in which high durability and low-humidity performance are compatible.

[0033] Hereinafter, requirements (A), (B), (C), and (D) will be described. Here, from the viewpoint of further achieving both higher durability and lower-humidity performance, the carbon material for a catalyst carrier of the present disclosure preferably satisfies requirement (E) in addition to requirements (A), (B), (C), and (D).

[0034] (Requirement (A)) (A) The average primary particle diameter is more than 30 nm and 100 nm or less. If the average primary particle diameter of the porous carbon black is more than 30 nm and 100 nm or less, the durability required for HDV applications with a relatively short total travel distance can be obtained. When the average primary particle diameter of the porous carbon black becomes 30 nm or less, the durability is low and it becomes unsuitable for most HDV applications. If the average primary particle diameter of the porous carbon black is 40 nm or more and 100 nm or less, it is more preferable because the durability required including HDV applications with a relatively long total travel distance can be obtained. On the other hand, if the average primary particle diameter of the porous carbon black exceeds 100 nm, it is assumed that it becomes difficult to obtain a structure of the porous carbon black that substantially satisfies requirements (B) to (E), which is not preferable.

[0035] The average primary particle diameter is a value measured by the method described in the examples below.

[0036] (Requirement B) (B) The BET specific surface area is 350 m 2 / g or more and 800 m 2 / g or less. If the BET specific surface area of the porous carbon black is 350 m 2 / g or more and 800 m 2 / g or less, the supported catalyst metal can be dispersed well with a practical supported ratio and particle diameter, and the porous carbon black can have a crystallite structure necessary for obtaining the durability required for fuel cells, which is preferable. If the BET specific surface area of the porous carbon black is less than 350 m 2 / g, when the supported ratio of the catalyst metal is increased, the particle diameter of the catalyst metal becomes large or the catalyst metal particles aggregate, making it difficult to obtain high battery performance. If the BET specific surface area of the porous carbon black is 800 m 2 / g or more, although high power generation performance can be obtained, the porous carbon black tends not to obtain the crystallite structure necessary for maintaining durability, and it becomes difficult to achieve both high durability and low humidification performance. The BET specific surface area of the porous carbon black is preferably 400 m 2 / g or more and 700 m 2 / g or less.

[0037] The BET specific surface area is a value measured by the method described in the examples below.

[0038] (Requirement (C)) (C) XRD spectrum obtained by XRD (X-ray diffraction) measurement In the spectrum, Lc(002) obtained by analyzing the peaks between the diffraction angles 2θ=20° to 26.5° is 1.7 nm or more and 4.0 nm or less. When the Lc(002) of the porous carbon black is 1.7 nm or more and 4.0 nm or less, it is possible to achieve both durability and low humidification performance. If the Lc(002) of the porous carbon black is less than 1.7 nm, the durability tends to be insufficient. If the Lc(002) of the porous carbon black exceeds 4.0 nm, the specific surface area of ​​the porous carbon black tends to be small, and the power generation performance tends to be insufficient. The Lc(002) of the porous carbon black is more preferably 1.7 nm or more and 3.5 nm or less.

[0039] Incidentally, Lc(002) is a value measured by the method described in the Examples section below.

[0040] (Requirement (D)) (D) In ​​the XRD spectrum obtained by XRD (X-ray diffraction) measurement, the La (110) peak obtained by analyzing the peak between the diffraction angles 2θ = 70° to 80° is 3.5 nm or less. When the La(110) of the porous carbon black is 3.5 nm or less, it is possible to ensure high durability while maintaining the power generation performance, particularly the low humidification characteristics, at the level required for HDV. When the La(110) of porous carbon black exceeds 3.5 nm, the edge density (edge ​​amount per specific surface area) of the crystallites that make up the carbon black decreases, making it difficult for adsorbed water to be retained on the carbon black surface when the relative humidity is low, which tends to reduce low humidification performance. The lower limit of La(110) of the porous carbon black is not particularly limited as long as the required durability is obtained. Judging from the substantially obtained data, the lower limit of La(110) of the porous carbon black is 2.0 nm or more. In the porous carbon black, it is presumed that the possibility that La(110) is less than 2.0 nm and Lc(002) is 1.7 nm or more is low. The La(110) of the porous carbon black is preferably 3.0 nm or less.

[0041] Note that La(110) is a value measured by the method described in the examples below.

[0042] (Requirement (E)) (E) The ratio of Lc(002) to La(110) (Lc(002) / La(110)) is 0.6 or more and 1.2 or less. When the ratio of the porous carbon black (Lc(002) / La(110)) is 0.6 or more and 1.2 or less, high durability and low humidification performance tend to be compatible. When the ratio of the porous carbon black (Lc(002) / La(110)) is 0.6 or more, it is possible to suppress the excessive thinning of the outer shell thickness of the primary particles of the porous carbon black, and the durability is improved. As a result, the mechanical strength when forming the catalyst layer is sufficient, and it is difficult for the voids in the catalyst layer to collapse when power generation continues. In addition, the edge density increases with respect to the size of the network surface, and the low humidification performance when the relative humidity decreases is improved. When the ratio of the porous carbon black (Lc(002) / La(110)) is 1.2 or less, the edge density becomes appropriate with respect to the size of the network surface, and the durability is improved. As a result, it becomes difficult to be oxidized and consumed during the use of the fuel cell, and the durability tends to be high. The ratio of the porous carbon black (Lc(002) / La(110)) is preferably 0.65 or more and 1.1 or less.

[0043] Note that the ratio (Lc(002) / La(110)) is a value measured by the method described in the examples below.

[0044] <Method for Producing Carbon Material for Catalyst Support of Polymer Electrolyte Fuel Cell> Hereinafter, an example of a method for producing a carbon material for a catalyst support of a polymer electrolyte fuel cell of the present disclosure (hereinafter, also referred to as "method for producing a carbon material") will be described.

[0045] The method for producing a carbon material of the present disclosure treats raw material carbon black having a relatively large average primary particle diameter (30 nm or more) in the order of "first activation", "graphitization", and "second activation". In the "first activation", it is a method of pressurizing and slowly activating at a low temperature while slightly varying the flow rate. By the method for producing a carbon material of the present disclosure, a carbon material satisfying requirements (A) to (D), preferably, a carbon material satisfying requirement (E) in addition to requirements (A) to (D) (that is, porous activated carbon black) can be obtained.

[0046] Hereinafter, the details of the method for producing a carbon material of the present disclosure will be described.

[0047] In the first activation, by "pressurizing" the activation gas and "slightly varying" the flow rate, even for large raw material carbon black, the "low-crystallinity part" existing between crystallites can be oxidized and consumed, and the atmosphere in the defects (pores) generated by the oxidation and consumption can be quickly replaced with the activation gas. Therefore, even large raw material carbon black can be efficiently made porous.

[0048] In the graphitization performed after the first activation, by performing heat treatment in an inert atmosphere, the crystallites constituting the raw material carbon black subjected to the first activation are grown, and the durability required for the fuel cell is imparted. When the first activation is performed on raw material carbon black having a relatively large average primary particle diameter (more than 30 nm), the required durability can be ensured without performing excessive heat treatment in the subsequent graphitization. By using raw material carbon black having a relatively large average primary particle diameter (more than 30 nm), the durability can be ensured because Lc(002) is kept large, and the growth of La(110) can be suppressed by graphitization at a relatively low temperature, thereby suppressing the decrease in low-humidification performance.

[0049] In the second activation, by reopening the pores blocked by graphitization, it has the effect of increasing the specific surface area and pore volume that have decreased due to the graphitization treatment. If the second activation is not performed, it tends not to obtain a sufficient specific surface area and pore volume, which is not preferable.

[0050] The types of activation gases for the first activation and the second activation are not particularly limited as long as they contain a gas that can oxidatively consume the carbon constituting the raw material carbon black by reaction. Examples of the gas that can oxidatively consume the carbon constituting the raw material carbon black by reaction include air, oxygen, ozone, water vapor, carbon dioxide, nitrogen dioxide, nitric oxide, nitrous oxide, etc. These gases may be mixed to be used as the activation gas. Or it may be a gas diluted with an inert gas such as nitrogen, argon, or helium. Furthermore, it may be an exhaust gas containing these gases. Preferably, it is water vapor or carbon dioxide, or an activation gas containing these. The types of gases for the first activation and the second activation may be changed.

[0051] In the reaction vessel where at least the first activation is performed, the pressure of the activation gas is preferably pressurized. The preferable range of pressurization is, for example, if the indicated value (gauge pressure) of the pressure gauge installed downstream of the reaction vessel is more than 0.0 MPaG, the effect can be expected, but more preferably it is 0.1 MPaG or more and 0.9 MPaG or less. Within this range, even a large carbon black can be made porous up to the target high specific surface area. If the pressure is less than 0.1 MPaG, although there is an effect, it may not be able to reach the required specific surface area. If the pressure is more than 0.9 MPaG, although the effect tends to be stronger, the effect tends to level off. The pressure is more preferably 0.1 MPaG or more and less than 0.5 MPaG. Within this range, carbon black with an average primary particle diameter of 30 nm to 100 nm can be efficiently made porous up to the target high specific surface area.

[0052] In a reaction vessel for activating the raw material carbon black for the first activation and the second activation, it is preferable to supply an amount of gas sufficient for the mass of the raw material carbon black filled in the reaction vessel as the average flow rate of the activation gas. When the mass of the raw material carbon black filled in the reaction vessel is W (g) and the average flow rate of the activation gas supplied under standard conditions (0 °C, 1 atm) is F (Nml / min.), it is preferable that the value of W / F is 0.005 or more and 0.1 or less because a non-uniform activation reaction is suppressed. If the value of W / F is less than 0.005, the activation reaction of the raw material carbon black near the downstream of the reactor does not proceed compared to the upstream, and a portion with a locally small specific surface area is generated, which is not preferable. If the value of W / F exceeds 0.1, the proportion of unreacted activation gas becomes excessive, which is not economical. More preferably, it is 0.01 or more and 0.05 or less. When in this range, the difference in specific surface area between the upstream and downstream of the reactor is sufficiently small, which is preferable.

[0053] In a reaction vessel for performing the first activation and the second activation, it is preferable that the activation gas fluctuates around the average flow rate. When it fluctuates, even if the raw material carbon black has a large average primary particle diameter, the inside of the particles can be efficiently made porous to form a hollow structure. This is presumably because when it fluctuates, the product gas generated in the activation reaction can be efficiently discharged outside the pores in the pores generated in the activation reaction, and the concentration of the activation gas can be increased.

[0054] The fluctuation range is preferably in the range of ±2% or more and ±50% or less with respect to the average flow rate of the activation gas. If it is in this range, the raw material carbon black with an average primary particle diameter of 30 nm to 100 nm can be efficiently made porous to the target high specific surface area. If the fluctuation range is less than 2%, it may not be possible to reach the target specific surface area. If the fluctuation range exceeds 50%, it may be difficult to control the pressure when the activation gas is pressurized.

[0055] The period of variation is preferably 1 or more and 30 or less times per minute. Within this range, raw material carbon black with an average primary particle diameter of 30 nm to 100 nm can be efficiently made porous up to the target high specific surface area. If the period of variation is less than once per minute, it becomes difficult to obtain the effect of variation, and there is a possibility that the target specific surface area may not be reached. If it exceeds 30 times, when the activation gas is pressurized, it may become difficult to control the pressure.

[0056] The atmosphere for graphitization performed between the first activation and the second activation is not particularly limited as long as it is in an inert gas or vacuum where carbon is not consumed. Examples of inert gases are N2, Ar, and He. The temperature of graphitization is preferably the minimum temperature at which crystal growth can be carried out to obtain the required durability. Examples of the temperature of graphitization are 1400 °C or higher and 2000 °C or lower. If the temperature of graphitization is less than 1400 °C, a long treatment time may be required to obtain the required durability, or sufficient crystal growth for obtaining sufficient durability may not be expected even with long-term holding. If the temperature of graphitization exceeds 2000 °C in the case of carbon black, excessive crystal growth may occur, and the possibility of a decrease in low-humidification performance increases. More preferably, it is 1500 °C or higher and 1900 °C or lower.

[0057] <Catalyst Layer for Solid Polymer Fuel Cell and Solid Polymer Fuel Cell> Together with the catalyst layer for the solid polymer fuel cell of the present disclosure, the solid polymer fuel cell will be described. The carbon material of the present disclosure is applicable, for example, to the catalyst layers 150 and 160 provided in the solid polymer fuel cell 100 shown in FIG. 1. FIG. 1 is a schematic diagram showing an example of the schematic configuration of the fuel cell of the present disclosure. The solid polymer fuel cell 100 shown in FIG. 1 includes separators 110 and 120, gas diffusion layers 130 and 140, catalyst layers 150 and 160, and an electrolyte membrane 170.

[0058] Separator 110 is the separator on the anode side and introduces a reducing gas such as hydrogen into the gas diffusion layer 130. Separator 120 is the separator on the cathode side and introduces an oxidizing gas such as oxygen gas or air into the gas diffusion and aggregation phase. The types of separators 110 and 120 are not particularly limited, and any separator used in a conventional fuel cell (for example, a polymer electrolyte fuel cell) may be used.

[0059] Gas diffusion layer 130 is the gas diffusion layer on the anode side. After diffusing the reducing gas supplied from separator 110, it supplies the gas to the catalyst layer 150. Gas diffusion layer 140 is the gas diffusion layer on the cathode side. After diffusing the oxidizing gas supplied from separator 120, it supplies the gas to the catalyst layer 160. The types of gas diffusion layers 130 and 140 are not particularly limited, and any gas diffusion layer used in a conventional fuel cell (for example, a polymer electrolyte fuel cell) may be used. Examples of gas diffusion layers 130 and 140 include porous carbon materials (carbon cloth, carbon paper, etc.), porous metal materials (metal mesh, metal wool, etc.). In addition, preferred examples of gas diffusion layers 130 and 140 include gas diffusion layers having a two-layer structure. Specifically, in gas diffusion layers 130 and 140, the layers on the sides of separators 110 and 120 become gas diffusion fiber layers mainly composed of fibrous carbon materials, and the layers on the sides of catalyst layers 150 and 160 become micropore layers mainly composed of carbon black, which are two-layer structured gas diffusion layers.

[0060] Catalyst layer 150 is a so-called anode. In catalyst layer 150, an oxidation reaction of a reducing gas occurs, generating protons and electrons. For example, when the reducing gas is hydrogen gas, the following oxidation reaction occurs. H2 → 2H + +2e - (E0 = 0V)

[0061] Protons generated by the oxidation reaction reach the catalyst layer 160 through the catalyst layer 150 and the electrolyte membrane 170. Electrons generated by the oxidation reaction reach the external circuit through the catalyst layer 150, the gas diffusion layer 130, and the separator 110. After the electrons do work (generate electricity) in the external circuit, they are introduced into the separator 120. Then, the electrons reach the catalyst layer 160 through the separator 120 and the gas diffusion layer 140.

[0062] The configuration of the catalyst layer 150 serving as the anode is not particularly limited. The configuration of the catalyst layer 150 may be the same as that of a conventional anode, may be the same as that of the catalyst layer 160, or may be a configuration with higher hydrophilicity than the catalyst layer 160.

[0063] The catalyst layer 160 is a so-called cathode. In the catalyst layer 160, a reduction reaction of an oxidizing gas occurs and water is generated. For example, when the oxidizing gas is oxygen gas or air, the following reduction reaction occurs. The water generated by the oxidation reaction is discharged to the outside of the polymer electrolyte fuel cell 100 together with the unreacted oxidizing gas. O2+4H + +4e - →2H2O (E0=1.23V)

[0064] Thus, in the polymer electrolyte fuel cell 100, electricity is generated by utilizing the energy difference (potential difference) between the oxidation reaction and the reduction reaction. In other words, the electrons generated by the oxidation reaction do work in the external circuit.

[0065] The catalyst layer 160 contains the carbon material for catalyst carrier of the present disclosure. That is, the catalyst layer 160 contains the carbon material for catalyst carrier of the present disclosure, an electrolyte material (such as an ionomer), and a catalyst component (such as platinum). Thereby, the durability and low humidification performance in the catalyst layer 160 can be enhanced. And the durability and low humidification performance of the polymer electrolyte fuel cell 100 can be enhanced.

[0066] Note that the catalyst loading ratio in the catalyst layer 160 is not particularly limited, and it is preferably 30% by mass or more and less than 80% by mass. When the catalyst loading ratio is within this range, the durability and low-humidification performance are further enhanced. Here, the catalyst loading ratio is represented by the mass percentage of the catalyst component with respect to the total mass of the catalyst-supported particles (particles obtained by supporting the catalyst component on the carbon material for the catalyst support). When the catalyst loading ratio is less than 30% by mass, it may be necessary to increase the thickness of the catalyst layer 160 in order to enable the solid polymer fuel cell 100 to withstand practical use. On the other hand, when the catalyst loading ratio is 80% by mass or more, catalyst aggregation is likely to occur. In addition, the catalyst layer 160 may become too thin, leading to the possibility of flooding.

[0067] The mass ratio I / C of the mass I of the electrolyte material to the mass C of the carbon material for the catalyst support in the catalyst layer 160 is not particularly limited, and it is preferably more than 0.5 and less than 5.0. In this case, the pore network and the electrolyte material network can coexist, and the durability and low-humidification performance are enhanced. On the other hand, when the mass ratio I / C is 0.5 or less, the electrolyte material network becomes weak, and the proton conduction resistance tends to increase. When the mass ratio I / C is 5.0 or more, the pore network may be disrupted by the electrolyte material. In either case, the durability and low-humidification performance may decrease.

[0068] Also, the thickness of the catalyst layer 160 is not particularly limited, and it is preferably more than 5 μm and less than 20 μm. In this case, the oxidizing gas easily diffuses into the catalyst layer 160, and flooding is less likely to occur. When the thickness of the catalyst layer 160 is 5 μm or less, flooding is likely to occur. When the thickness of the catalyst layer 160 is 20 μm or more, the oxidizing gas hardly diffuses within the catalyst layer 160, and the catalyst components near the electrolyte membrane 170 are less likely to function. That is, the catalyst utilization rate may decrease.

[0069] The electrolyte membrane 170 is composed of an electrolyte material having proton conductivity. The electrolyte membrane 170 introduces the protons generated in the above oxidation reaction into the catalyst layer 160 (cathode). Here, the type of the electrolyte material is not particularly limited, and any electrolyte material used in conventional fuel cells, for example, polymer electrolyte fuel cells, may be used. Examples of suitable electrolyte materials include electrolyte resins. Examples of electrolyte resins include polymers into which phosphate groups, sulfonic acid groups, etc. are introduced. Specifically, for example, perfluorosulfonic acid polymers, polymers into which benzenesulfonic acid, etc. are introduced, etc. may be mentioned. Of course, the electrolyte material may be other types of electrolyte materials. Examples of such electrolyte materials include inorganic, inorganic-organic hybrid, etc. electrolyte materials. Note that the polymer electrolyte fuel cell 100 may be a fuel cell that operates within the range of normal temperature (25°C) to 150°C.

[0070] <Method for manufacturing a polymer electrolyte fuel cell> The manufacturing method of the polymer electrolyte fuel cell 100 is not particularly limited, and any manufacturing method similar to the conventional one may be used. However, the carbon material for the catalyst carrier of the present disclosure is used for the catalyst carrier. Among the catalyst layers 150 and 160, it is preferable to use the carbon material for the catalyst carrier of the present disclosure for the catalyst carrier in at least the catalyst layer 160 that becomes the cathode. Of course, the carbon material for the catalyst carrier of the present disclosure may be used for the catalyst carriers of both catalyst layers in the catalyst layer 150 that becomes the anode and the catalyst layer 160 that becomes the cathode.

Examples

[0071] Experimental examples of the carbon material for the catalyst carrier of the present disclosure will be described. First, the measurement methods for each parameter will be described.

[0072] <Measurement methods for each parameter> (Measurement of average primary particle diameter) Using a scanning electron microscope (SEM), the carbon material for the catalyst support was observed in any 10 to 20 fields of view, and observation images were obtained. In the observation images, for the 30 intersections that occurred or the particles closest to each other when six vertical and five horizontal straight lines were arranged at equal intervals for each field of view, the longest distance between two points on the contour line of the carbon material for the catalyst support was taken as the particle diameter (diameter), and the average value of 300 particles was taken as the average primary particle diameter.

[0073] <Measurement of BET specific surface area> Using the carbon material for the catalyst support as a sample, about 30 mg of this was weighed, vacuum-dried at 200 °C for 2 hours, and then using an automatic specific surface area measuring device (AUTOSORB iQ manufactured by Anton Paar Japan Co., Ltd.), the nitrogen gas adsorption / desorption isotherm was measured using nitrogen gas as the adsorbate. BET analysis was carried out in the range where the relative pressure of the adsorption isotherm is 0.30 or less to calculate the BET specific surface area.

[0074] (Measurement of Lc(002), La(110)) Using the carbon material for the catalyst support as a sample, about 3 mg of this was weighed, placed on a silicon non-reflecting plate, set in an X-ray diffractometer (RINT-TTRIII manufactured by Rigaku Corporation), and measured at room temperature with a scanning step of 0.02°, an angular sweep rate of 1° / min, and using Cu-Kα as the radiation source. For the obtained XRD spectrum in the range of 2θ from 10° to 40° and in the range of 2θ from 70 to 90°, the background was removed and smoothing processing was performed respectively. For the XRD spectrum in the range of 2θ from 10° to 40°, Lc(002) was determined using Scherrer's equation (Lc = Kλ / βcosθ) for the waveform after background removal and smoothing processing. The diffraction peaks where 2θ exists in the range of 70 to 90° are a mixture of the (110) plane, (112) plane, and (006) plane. In the XRD spectrum in the range of 2θ from 70 to 90°, for the waveform after background removal and smoothing processing, the waveform on the smaller angle side than the diffraction peak angle on the smallest angle side and the waveform using the Voigt function (Forkert function) are made to match (the square of the difference is minimized), and the waveform using the Forkert function is set, and La(110) is obtained using Scherrer's formula (La = Kλ / βcosθ). Here, in Scherrer's formula, the shape factor K is 1, the X-ray wavelength λ is 1.54184 Å, and β is the half-width at half maximum of the diffraction peak.

[0075] <Example: Preparation of Carbon Material for Catalyst Support> (Example 1) (1) First activation 5 g of Nitron #10 (catalog value of average primary particle diameter 39 nm) manufactured by Nippon Steel Carbon as the raw material carbon black was filled into a 1-inch tubular reactor, and CO2 gas at 400 Nml / min was circulated with a mass flow controller set upstream of the tubular reactor. At this time, a pressure controller (automatically controlled to the set pressure by a combination of a pressure sensor, a back pressure controller, and a control unit), a needle valve, and a mass flow meter were arranged in this order downstream of the tubular reactor, and the back pressure was set to a gauge pressure of 0.3 MPaG with the pressure controller. Also, the opening degree of the needle valve was adjusted so that the indicated value of the downstream mass flow meter fluctuated with a fluctuation range of about ±100 ml / min centered on 400 Nml / min and a fluctuation period of about 12 times / min. In this state, the tubular reactor was heated to 850 °C at 20 °C / min and held at 850 °C for 34 hours to perform the first activation. After holding, the flowing gas was switched to N2, the temperature was lowered, and the first activation sample was recovered.

[0076] (2) Graphitization(2) Graphitization The entire amount of the recovered first activation sample was filled into a graphite crucible, and graphitization treatment was performed at 1600 °C for 1 hour under Ar flow in a graphitization furnace at a heating rate of 15 °C / min, and the graphitization sample was recovered.

[0077] (3) Second activation The entire amount of the graphitized sample was refilled into a tubular reactor with a diameter of 1 inch, and CO2 gas at 400 Nml / min was circulated using a mass flow controller set upstream of the tubular reactor. At this time, the pressure controller and the needle valve were fully opened and set to a gauge pressure of 0.0 MPaG. In this state, the temperature of the tubular reactor was raised to 850 °C at 20 °C / min and held at 850 °C for 3 minutes to perform the second activation. After holding, the flowing gas was switched to N2, the temperature was lowered, and the second activation sample was recovered as the carbon material for the catalyst carrier in Example 1 (i.e., porous activated carbon black).

[0078] (Example 2) A carbon material for the catalyst carrier (i.e., porous activated carbon black) was obtained in the same manner as in Example 1, except that the holding time of the second activation was 30 minutes.

[0079] (Example 3) A carbon material for the catalyst carrier (i.e., porous activated carbon black) was obtained in the same manner as in Example 1, except that the variation range and holding time of the first activation were about ±50 ml / min and 37 hours, respectively.

[0080] (Example 4) A carbon material for the catalyst carrier (i.e., porous activated carbon black) was obtained in the same manner as in Example 1, except that the raw material carbon black was Niton #SH manufactured by Nippon Steel Carbon Co., Ltd. (average primary particle diameter catalog value 61 nm), the holding time of the first activation was 43 hours, the holding temperature of graphitization was 1700 °C, and the holding temperature and holding time of the second activation were 930 °C and 30 minutes, respectively.

[0081] (Example 5) A carbon material for the catalyst carrier (i.e., porous activated carbon black) was obtained in the same manner as in Example 1, except that the holding temperature and holding time of the first activation were 900 °C and 20 hours, respectively, the holding temperature of graphitization was 1800 °C, and the holding temperature and holding time of the second activation were 950 °C and 30 minutes, respectively.

[0082] (Comparative Example 1) A carbon material for a catalyst support (i.e., porous activated carbon black) was obtained in the same manner as in Example 3, except that the needle valve was adjusted so that the variation range of the first activation was about ±5 ml / min.

[0083] (Comparative Example 2) A carbon material for a catalyst support (i.e., porous activated carbon black) was obtained in the same manner as in Example 5, except that the needle valve was adjusted so that the variation range of the first activation was about ±5 ml / min.

[0084] (Comparative Examples 3, 4, 5) As a raw material carbon black, 2 g of Ketjenblack EC300J (catalog value of average primary particle diameter: 39.5 nm) from Lion Specialty Chemicals Co., Ltd. was graphitized in a graphitization furnace under Ar flow for 1 hour to obtain a carbon material for a catalyst support. The one with a holding temperature of 1400°C was Comparative Example 3, the one with 1600°C was Comparative Example 4, and the one with 1800°C was Comparative Example 5.

[0085] (Comparative Examples 6, 7, 8) As a raw material carbon black, 2 g of Ketjenblack EC600JD (catalog value of average primary particle diameter: 34 nm) from Lion Specialty Chemicals Co., Ltd. was graphitized in a graphitization furnace under Ar flow for 1 hour to obtain a carbon material for a catalyst support. The one with a holding temperature of 1400°C was Comparative Example 6, the one with 1600°C was Comparative Example 7, and the one with 1800°C was Comparative Example 8.

[0086] (Comparative Examples 9, 10) 2 g of the carbon materials for catalyst supports of Comparative Example 5 and Comparative Example 8 were respectively filled into a tubular reactor with a diameter of 1 inch, and 400 Nml / min of CO2 gas was passed through with a mass flow controller set upstream of the tubular reactor. At this time, the pressure controller and the needle valve were fully opened and set to a gauge pressure of 0.0 MPaG. In this state, the tubular reactor was heated to 950°C at 20°C / min, held at 950°C for 30 minutes for activation. After holding, the flowing gas was switched to N2, cooled down, and the recovered samples were taken as Comparative Example 9 and Comparative Example 10 respectively.

[0087] (Comparative Example 11) The raw carbon black was Nitron #300IH manufactured by Nippon Steel Carbon Co., Ltd. (catalog value of average primary particle diameter: 22 nm). A carbon material for catalyst support was obtained in the same manner as in Example 5, except that the holding time of the first activation was 8 hours, the graphitization holding temperature was 1600°C, and the holding time of the second activation was 5 minutes.

[0088] <Preparation of catalyst, preparation of catalyst layer, fabrication of MEA, assembly of fuel cell, and evaluation of battery performance (power generation performance, durability)> Using the carbon materials for catalyst support of each example, a catalyst for a polymer electrolyte fuel cell with a supported catalyst metal was prepared as follows. Also, a catalyst layer ink solution was prepared using the obtained catalyst. Then, a catalyst layer was formed using this catalyst layer ink solution. Further, a membrane electrode assembly (MEA) was fabricated using the formed catalyst layer. This fabricated MEA was incorporated into a fuel cell, and a power generation test was conducted using a fuel cell measurement device. Hereinafter, the preparation of each member and the cell evaluation by the power generation test will be described in detail.

[0089] (1) Preparation of catalyst for polymer electrolyte fuel cell (platinum-supported carbon material) The carbon materials for catalyst support of each example were dispersed in distilled water. Formaldehyde was added to this dispersion, and it was set in a water bath set at 40°C. After the temperature of the dispersion became the same as that of the bath, which was 40°C, an aqueous solution of dinitrodiamine Pt complex nitrate was slowly poured into this dispersion under stirring. Then, after continuing stirring for about 2 hours, filtration was performed, and the obtained solid was washed. The solid thus obtained was vacuum-dried at 90°C, pulverized in a mortar, and then heat-treated at 200°C for 1 hour in an argon atmosphere containing 5% by volume of hydrogen to produce a platinum-supported carbon material. The platinum loading amount of this platinum-supported carbon material was adjusted to be 35% by mass based on the total mass of the carbon material for catalyst support and platinum particles, and was measured and confirmed by inductively coupled plasma - atomic emission spectrometry (ICP-AES).

[0090] (2) Preparation of the Catalyst Layer Using the platinum-supported carbon material (Pt catalyst) prepared as described above, and also using a 5 mass% Nafion solution (DE2020CS manufactured by DuPont, registered trademark: Nafion) as the electrolyte resin, these Pt catalyst and Nafion were blended in an Ar atmosphere at a ratio such that the mass of the Nafion solid content was 1.0 times the mass of the porous carbon black component (the mass of only the porous carbon black excluding the Pt component in the Pt catalyst), and after gently stirring, the Pt catalyst was crushed by ultrasonic waves, and further ethanol was added to adjust the total solid content concentration of the combined Pt catalyst and electrolyte resin to 0.5 mass%, thereby preparing a catalyst layer ink solution in which the Pt catalyst and the electrolyte resin were mixed.

[0091] Using the catalyst layer ink solution prepared in this way, the mass per unit area of the platinum catalyst layer (hereinafter referred to as the "platinum coating weight") was 0.18 mg / cm 2 The spraying conditions were adjusted so as to achieve this, and after spraying the above catalyst layer ink onto a Teflon (registered trademark) sheet, a drying treatment was carried out at 120 °C in argon for 60 minutes to produce a catalyst layer.

[0092] (3) Preparation of the MEA Using the catalyst layer prepared as described above, an MEA (membrane electrode assembly) was produced by the following method. A square electrolyte membrane with a side length of 6 cm was cut out from a Nafion membrane (NR211 manufactured by Dupont). Also, for each of the anode and cathode catalyst layers coated on a Teflon (registered trademark) sheet, each was cut out into a square shape with a side length of 2.5 cm using a cutter knife. Between each of the anode and cathode catalyst layers cut out in this way, this electrolyte membrane was sandwiched so that each catalyst layer contacted the center part of the electrolyte membrane and there was no shift between them, and it was pressed at 120 °C and 100 kg / cm 2 for 10 minutes, and then after cooling to room temperature, only the Teflon (registered trademark) sheet was carefully peeled off from both the anode and the cathode, and a catalyst layer - electrolyte membrane bonded body in which each of the anode and cathode catalyst layers was fixed to the electrolyte membrane was prepared.

[0093] Next, as the gas diffusion layer, a pair of square carbon papers with a side length of 2.5 cm were cut out from carbon paper (39BC manufactured by SGL Carbon). Between these carbon papers, the above catalyst layer - electrolyte membrane assembly was sandwiched so that the catalyst layers of the anode and cathode were aligned without displacement, and pressed at 120 °C and 50 kg / cm 2 for 10 minutes to produce an MEA. Regarding the areal amounts of the respective components of the catalyst metal component, carbon material, and electrolyte material in each produced MEA, the mass of the catalyst layer fixed to the Nafion membrane (electrolyte membrane) was determined from the difference between the mass of the Teflon (registered trademark) sheet with the catalyst layer before pressing and the mass of the Teflon (registered trademark) sheet peeled off after pressing, and calculated from the mass ratio of the composition of the catalyst layer.

[0094] (4) Assembly of fuel cell and evaluation of low - humidity performance Regarding the MEAs produced using the carbon materials for the catalyst support of each example, they were each incorporated into a cell, set in a fuel cell measurement device, and the initial power generation performance of the fuel cell was evaluated according to the following procedure. Air was supplied to the cathode side and pure hydrogen was supplied to the anode side. The pressure was adjusted with back - pressure valves provided downstream of the cell so that the utilization rates were 40% and 70% respectively, and the gauge pressure of the back - pressure was 0.1 MPaG for each. Also, the cell temperature was set to 80 °C, and the air and pure hydrogen supplied to the fuel cell were passed through distilled water kept at 80 °C in a humidifier (that is, bubbling was performed) to humidify them. As a result, the relative humidity of the anode and cathode was set to about 100%.

[0095] Under the condition of supplying reaction gases to the cell with such settings, the operation of gradually increasing the current density until the cell terminal voltage reached 0.3 V was repeated 10 times. Next, the pressure was adjusted with the back - pressure valves provided downstream of the cell so that the gauge pressure of the back - pressure was 0.05 MPaG for each. Also, the cell temperature was 80 °C, and the air and pure hydrogen supplied to the fuel cell were each passed through distilled water kept warm in a humidifier (that is, bubbling was performed), and the relative humidity of the anode and cathode was set to about 50%.

[0096] Under the condition of supplying the reaction gas to the cell under such settings, the operation of gradually increasing the current density until the voltage between the cell terminals reaches 0.3 V was repeated 10 times. Thereafter, the voltage between the cell terminals when the current density was fixed at 0.1 A / cm2 and held for 10 minutes was recorded, and the low-humidity performance evaluation was performed according to the following acceptance ranks A and B and rejection rank C criteria. The results are shown in Table 1. 〔Acceptance Rank〕 A: Those with the voltage between the cell terminals at a current density of 0.1 A / cm 2 being 0.84 V or higher. B: Those with the voltage between the cell terminals at a current density of 0.1 A / cm 2 being 0.82 V or higher. 〔Rejection Rank〕 C: Those not meeting the acceptance rank B.

[0097] (5) Evaluation of Durability After the above initial power generation performance evaluation, a durability test was conducted under the following conditions. First, the cell temperature was 80°C, the relative humidity was 100%, the cell back pressure was set to 0.0 MPaG, and the cathode gas was switched to argon gas. Next, after performing the operation of setting the cell voltage to 0.6 V and holding for 4 seconds, the operation of setting the cell voltage to 1.2 V and holding for 4 seconds was defined as one cycle, and this repetitive operation of rectangular-wave voltage fluctuation was performed 1000 cycles. Thereafter, the gas utilization rates of the anode and cathode were set to 40% and 70% respectively, the gauge pressure of the cell back pressure was 0.1 MPaG respectively, the cell temperature was 80°C, and the relative humidity was 100% respectively. When the cell voltage was set to 0.6 V, the current density was recorded, and the durability evaluation was performed according to the following acceptance ranks A and B and rejection rank C criteria. The results are shown in Table 1. 〔Acceptance Rank〕 A: Those with the current density after 1000 cycles being 80% or more of the current density at the time of the initial power generation performance evaluation. B: Those with the current density after 1000 cycles being 70% or more of the current density at the time of the initial power generation performance evaluation. 〔Rejection Rank〕 C: Those not meeting the acceptance rank B.

[0098]

Table 1

[0099] From the above results, it can be seen that Examples 1 to 5 achieve both high durability performance and low humidification performance. Comparative Examples 1 and 2 are examples in which the variation of the activation gas is small with respect to Example 3 and Example 5, respectively. However, due to insufficient activation, the specific surface area is small, resulting in insufficient low humidification performance. Comparative Examples 3 to 8 are examples in which commercially available porous carbon black is heat-treated at various temperatures. However, those that simultaneously satisfy the requirements (A) to (D) of the present disclosure cannot be obtained, and a performance that achieves both low humidification performance and durability cannot be obtained. Comparative Examples 9 and 10 are examples in which commercially available porous carbon black is heat-treated and then activated. However, those that simultaneously satisfy the requirements (A) to (D) of the present disclosure cannot be obtained, and a performance that achieves both low humidification performance and durability cannot be obtained. Comparative Example 11 is an example in which the average primary particle diameter is less than 30 nm. However, the Lc(002) is small, resulting in insufficient durability.

[0100] The explanations of the reference signs are as follows. 100 Polymer electrolyte fuel cell 110, 120 Separator 130, 140 Gas diffusion layer 150, 160 Catalyst layer 170 Electrolyte membrane

[0101] Note that the disclosure of Japanese Patent Application No. 2023-108950 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A carbon material for a catalyst support in a polymer electrolyte fuel cell, comprising a porous activated carbon black that satisfies the following requirements (A), (B), (C) and (D): (A) The average primary particle diameter is more than 30 nm and not more than 100 nm. (B) BET specific surface area is 350 m ２ / g or more 800m ２ / g or less. (C) In an XRD spectrum obtained by XRD (X-ray diffraction) measurement, Lc(002) obtained by analyzing peaks between diffraction angles 2θ=20° to 26.5° is 1.7 nm or more and 4.0 nm or less. (D) In ​​an XRD spectrum obtained by XRD (X-ray diffraction) measurement, La(110) obtained by analyzing the peak between the diffraction angles 2θ=70° to 80° is 3.5 nm or less.

2. The carbon material for a catalyst support of a polymer electrolyte fuel cell according to claim 1, further satisfying the following requirement (E): (E) The ratio of the Lc(002) to the La(110), (Lc(002) / La(110)), is 0.6 or more and 1.2 or less.

3. 2. The carbon material for a catalyst support of a polymer electrolyte fuel cell according to claim 1, wherein the average primary particle size is from 40 nm to 100 nm.

4. 4. A catalyst layer for a polymer electrolyte fuel cell, comprising the carbon material for a catalyst support of a polymer electrolyte fuel cell according to claim 1.

5. A fuel cell comprising the catalyst layer for a polymer electrolyte fuel cell according to claim 4.

6. 6. The fuel cell according to claim 5, wherein the catalyst layer for a polymer electrolyte fuel cell is a catalyst layer on a cathode side.

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