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

Carbon material for catalyst support of polymer electrolyte fuel cell, catalyst layer for polymer electrolyte fuel cell, and fuel cell

[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.

[0002] A polymer electrolyte fuel cell, a type of fuel cell, comprises a pair of catalyst layers disposed on both sides of a solid polymer electrolyte membrane, gas diffusion layers disposed on the outer side of each catalyst layer, and separators disposed on the outer side of each gas diffusion layer. One of the pair of catalyst layers serves as the anode of the polymer electrolyte fuel cell, and the other serves as the cathode of the polymer electrolyte fuel cell. In a typical polymer electrolyte fuel cell, multiple unit cells each having the above components are stacked to obtain the desired output.

[0003] A reducing gas such as hydrogen is introduced into the separator on the anode side. The reducing gas is diffused into the gas diffusion layer on the anode side and then introduced into the anode. The anode contains a catalyst component, a catalyst carrier that supports the catalyst component, and an electrolyte material (ionomer, etc.) that has proton conductivity. The catalyst carrier is often made of a carbon material. An oxidation reaction of the reducing gas occurs on the catalyst component, producing protons and electrons. For example, when the reducing gas becomes hydrogen gas, the following oxidation reaction occurs: H ２ →2H ＋ +2e － (E ０ = 0 V)

[0004] Protons produced by this oxidation reaction pass through the electrolyte material in the anode and the solid polymer electrolyte membrane and are introduced into the cathode. Electrons pass through the catalyst support, gas diffusion layer, and separator to be introduced into the external circuit. After performing work (generating electricity) in the external circuit, these electrons are introduced into the cathode-side separator. These electrons then pass through the cathode-side separator and cathode-side gas diffusion layer to be introduced into the cathode.

[0005] The solid polymer electrolyte membrane is made of a proton-conductive electrolyte material and introduces the protons generated in the oxidation reaction to the cathode.

[0006] An oxidizing gas such as oxygen gas or air is introduced into the cathode separator. The cathode gas diffusion layer diffuses the oxidizing gas before introducing it into the cathode. The cathode contains a catalyst component, a catalyst support that supports the catalyst component, and an electrolyte material (ionomer) that has proton conductivity. The catalyst support is often made of a carbon material. A reduction reaction of the oxidizing gas occurs on the catalyst component, producing water. For example, when the oxidizing gas becomes oxygen gas or air, the following reduction reaction occurs: O ２ +4H ＋ +4e － →2H ２ O (E ０ = 1.23 V)

[0007] The water produced by the reduction reaction is discharged outside the fuel cell along with the unreacted oxidizing gas. In this way, solid polymer fuel cells generate electricity by utilizing the energy difference (potential difference) between the oxidation reaction and the reduction reaction. In other words, the electrons produced by the oxidation reaction perform work in the external circuit.

[0008] Incidentally, from the viewpoint of power generation performance of fuel cells, it has been proposed to use porous carbon black as a catalyst support. Non-Patent Document 1 reports that the catalytic metal supported in the pores formed inside the porous carbon black is highly active because it is not subject to reaction inhibition (poisoning) caused by the coating of ionomer coexisting in the catalyst layer. Patent Document 1 reports that the average particle diameter is 20 to 100 nm, and the pore volume of the porous carbon black with a pore diameter of 4 to 20 nm is 0.23 to 0.78 cm ３ Patent Document 2 proposes a method of making carbon black porous and increasing its surface area by contacting a carbon black starting material with an oxidizing agent in a fluidized bed.

[0009] In addition, from the viewpoint of durability of fuel cells, it has been proposed to bake porous carbon black to make it highly crystallized. ２1 / g and a crystallite size Lc of 2.0 nm or more. In Patent Document 4, a highly crystalline carbon black having a BET specific surface area of ​​2.0 nm or more and a G-band (1590 cm) in the spectrum of the carbon surface by Raman spectroscopy is proposed. －１ ) peak area relative to the D1-band (1350 cm －１ ) the peak area ratio D / G is 0.5 to 2.5, the pores include mesopores, and the mesopore volume is 0.35 to 1.3 cm ３ / g porous carbon has been proposed. In particular, porous carbon black used in positive electrodes experiences high potential in oxygen-containing air or water, which accelerates oxidative consumption of carbon. To prevent this, Patent Documents 3 and 4 propose heat-treating porous carbon black at high temperatures to increase the crystallinity of the carbon.

[0010] The above-mentioned Patent Document 1 states that if the average particle size of the porous carbon black is 20 to 100 nm, the mechanical strength can be maintained even if a pore structure is provided in the porous carbon black.

[0011] Patent Document 1: JP 2013-109856 A Patent Document 2: JP 2017-052967 A Patent Document 3: Japanese Patent No. 6478677 Patent Document 4: WO 17 / 208742

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

[0013] However, in the prior art, including any of the documents, there has been no proposal that can achieve both high levels of durability and low humidification performance, which are required for use in large commercial vehicles (hereinafter also referred to as "HDVs").

[0014] For example, in Patent Document 1, power generation performance, including low-humidity performance, is improved by increasing porosity, and carbon black with a certain average primary particle size can be used to ensure the mechanical strength required for a carbon material for a catalyst support. However, for HDV applications, which require a balance between high durability and low-humidity performance, the performance was not sufficient. Regarding particle size in particular, Patent Document 1 proposes an average particle size of 20 to 100 nm, but only exemplified carbon black with a particle size of 30 nm in the examples. Furthermore, Patent Document 1 does not provide any examples of means for making carbon black with an average primary particle size greater than 30 nm porous. The carbon black with a particle size 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 levels of durability and low-humidity performance.

[0015] For example, in Patent Document 3, although graphitized carbon black can increase durability, it inevitably reduces the hydrophilicity of the surface, resulting in poor low-humidification performance. Patent Document 3 also proposes that heat-treating porous carbon black can achieve both high power generation performance due to porosity and high durability due to high crystallization. However, according to follow-up tests conducted by the present inventors, it was difficult to achieve both high levels of durability and low-humidification performance using only the proposed components.

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

[0017] The means for solving the problems include the following aspects: <1> A carbon material for a catalyst support of 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) the 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 peaks between 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 <1>, further satisfying the following 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. <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, comprising 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, comprising 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 catalyst layer on a cathode side.

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

[0019] FIG. 1 is a schematic diagram showing an example of the general configuration of a fuel cell according to the present disclosure.

[0020] In this disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. Furthermore, when "greater than" or "less than" is added to the numerical values ​​written before and after "to", the numerical range means a range that does not include these numerical values ​​as the lower or upper limit. In this disclosure, the term "process" does not only refer to an independent process, but also includes processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In this disclosure, the "electrolyte material having proton conductivity" used in the catalyst layer of a fuel cell is also referred to as an "ionomer."

[0021] <Carbon material for catalyst support of polymer electrolyte fuel cell> The carbon material for catalyst support of polymer electrolyte fuel cell of the present disclosure is made of porous activated carbon black that satisfies the requirements (A), (B), (C), and (D) described below. Here, porous activated carbon black is carbon black that has been made porous by activation. Note that porous activated carbon black is also referred to as "porous carbon black."

[0022] The carbon material for a catalyst support according to the present disclosure is a carbon material that combines high durability and low humidification performance. The carbon material according to the present disclosure was discovered based on the following findings.

[0023] In conventional technology, heat treatment of porous carbon black generally results in larger crystallites and improved durability. However, as the crystallites become larger, fewer edges are available for functional groups to exist, resulting in the loss of micropores and a decrease in specific surface area. The decrease in micropores and specific surface area makes it difficult to support the catalytic metal in a highly dispersed state with fine particles. As a result, larger particles or aggregated catalytic metals tend to be supported, reducing the specific surface area of ​​the catalytic metal and resulting in a decrease in power generation performance. Furthermore, the decrease in micropores and edges reduces the adsorption density of adsorbed water, making the carbon black more susceptible to the effects of desorption of adsorbed water at low relative humidity, weakening the adsorbed water network capable of transmitting protons, and resulting in a decrease in low-humidity performance.

[0024] To prevent these problems, attempts have been made to further increase the porosity of porous carbon black to prevent a decrease in the specific surface area and the disappearance of micropores. However, further increasing the porosity tends to reduce the Lc(002) of the crystallites, and heat treatment at a relatively high temperature is required to ensure the required durability. As a result, the La(110) becomes larger, which reduces the edge density and leads to a deterioration in low-humidification performance.

[0025] As a result of investigations conducted 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 must be large 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) must have a certain size or larger so that high durability can be obtained; and (3) An edge density of a certain level or higher is necessary to obtain high low-humidification performance, and to achieve this, the La(110) must not be larger than a certain level.

[0026] Carbon black primary particles are composed of aggregates of carbon lattice plane layers (crystallites), which are oriented concentrically (onion-shaped). The crystallite size tends to be larger near the periphery of the primary particle and smaller toward the center. The center is often composed of a low-crystalline amorphous material. Even in the relatively highly crystalline outer regions, the crystallites are bonded together through a low-crystalline structure, resulting in a structure with more defects than the hexagonal lattice planes that make up the crystallites. Furthermore, during the carbon black manufacturing process, multiple primary particles fuse together to form a three-dimensional structure called an aggregate. When carbon black is used as a catalyst support in fuel cells, this three-dimensional structure creates a network of voids between the aggregates in the catalyst layer. This network of voids serves to diffuse hydrogen in the anode and oxygen from the air and generated water in the cathode during power generation.

[0027] When carbon black with this structure is used as a raw material and activated to increase its porosity and specific surface area, the structural portion with many defects between the crystallites that constitute the portion near the periphery of the primary particles of the raw carbon black is oxidized and consumed, forming micropores. If activation is continued for a long period of time in order to obtain a sufficient specific surface area, the activator that diffuses into the micropores that have formed near the periphery oxidizes and consumes the amorphous portion inside, leaving the outer periphery with relatively large crystallites, forming a hollow structure. At this time, the crystallites of the outer shell are also partially oxidized and consumed. Excessive activation accelerates the oxidative consumption of the crystallites that form the outer shell, and the primary particles may disappear due to oxidative consumption.

[0028] The hollow porous carbon black can support a catalytic metal in the space formed inside. Since the ionomer that coexists when forming the catalyst layer is unlikely to penetrate into the space inside the moderately activated porous carbon black, the catalytic metal supported inside is unlikely to be inhibited by ionomer adsorption, and this allows the reaction overvoltage, particularly in the oxygen reduction reaction that proceeds at the cathode, to be reduced, resulting in a high-performance fuel cell.

[0029] In general, raw carbon black with a smaller average primary particle size has a thinner crystallite shell and is easier to activate due to the smaller crystallite size. Even with conventional technology, it was relatively easy to achieve porous raw carbon black and a high specific surface area. However, to achieve both high durability and low humidification performance required for HDV applications, porous carbon black obtained by activating small-particle raw carbon black does not provide sufficient durability. This is because the remaining crystallites constituting the shell are too small for the desired durability, resulting in a thin shell of hollow particles. Furthermore, oxidative wear during fuel cell operation can easily cause the primary particles of raw carbon black to disappear, eliminating voids in the catalyst layer through which gases can diffuse.

[0030] To address this issue, excessive heat treatment is performed to increase the crystallite size and make it less susceptible to oxidation, resulting in the loss of micropores and edges, leading to a decrease in specific surface area and a decrease in low-humidification performance. On the other hand, raw carbon black with an average primary particle size above a certain level tends to be composed of large crystallites, so it is expected that large crystallites will remain even after activation. However, raw carbon black with an average primary particle size above a certain level usually tends to have large crystallites near the outer surface and a thick outer shell composed of crystallites. Therefore, it is difficult to make the carbon black porous enough to obtain a sufficiently large specific surface area, and it is difficult with conventional technology to satisfy the above structural requirements using raw carbon black with an average primary particle size above a certain level.

[0031] As a result of our investigations, we have come to the following conclusion. Raw carbon black having a relatively large average primary particle size (greater than 30 nm) can be treated in the following order: "first activation," "graphitization," and "second activation." The "first activation" involves slowly activating the raw carbon black at a low temperature while applying pressure and slightly varying the flow rate. This process satisfies the structural requirements described above. In particular, applying pressure and slightly varying the flow rate during the first activation process can oxidize and consume the "low-crystalline portions" between crystallites, even for large particles. This allows the atmosphere within the defects (pores) created by the oxidative consumption to be rapidly replaced with an activation gas, which is believed to be why even large particles can be efficiently rendered porous. Furthermore, when first activation is performed on carbon black having a relatively large average primary particle size (greater than 30 nm) in this manner, the required durability can be ensured without excessive heat treatment during the subsequent graphitization. It is estimated that by using carbon black with a relatively large average primary particle size (more than 30 nm), the Lc(002) can be increased without excessive heat treatment, ensuring durability, and that graphitization at a relatively low temperature can suppress the growth of La(110), thereby preventing a decrease in low humidification performance.

[0032] From the above findings, it has been found that the carbon material for a catalyst support according to the present disclosure is a carbon material that combines high durability and low humidification performance.

[0033] The requirements (A), (B), (C), and (D) are explained below. From the viewpoint of achieving both higher durability and low humidification performance, it is preferable that the carbon material for a catalyst support according to the present disclosure satisfies the requirement (E) in addition to the requirements (A), (B), (C), and (D).

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

[0035] The average primary particle size is a value measured by the method described in the Examples section below.

[0036] (Requirement B) (B) BET specific surface area is 350 m ２ / g or more 800m ２ / g or less. The BET specific surface area of ​​the porous carbon black is 350 m ２ / g or more 800m ２ / g or less, the catalytic metal to be supported can be supported with good dispersibility at a target loading rate and particle size within a practical range, and the porous carbon black can have a crystallite structure necessary for obtaining the durability required for fuel cells. ２ If the BET specific surface area of ​​the porous carbon black is less than 800 m / g, the particle size of the catalyst metal increases when the catalyst metal loading rate is increased, or the catalyst metal particles aggregate, making it difficult to obtain high battery performance. ２ If the BET specific surface area of ​​the porous carbon black is more than 400 m / g, high power generation performance can be obtained, but the porous carbon black tends to have a crystallite structure necessary for maintaining durability, making it difficult to achieve both high durability and low humidification performance. ２ / g or more 700m ２ / g or less.

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

[0038] (Requirement (C)) (C) In an XRD spectrum obtained by XRD (X-ray diffraction) measurement, the 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. When the Lc(002) of the porous carbon black is less than 1.7 nm, the durability tends to be insufficient. When the Lc(002) of the porous carbon black is more than 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] It should be noted that Lc(002) is a value measured by the method described in the Examples below.

[0040] (Requirement (D)) (D) In ​​an XRD spectrum obtained by XRD (X-ray diffraction) measurement, the La(110) obtained by analyzing the peak between the diffraction angle 2θ = 70° and 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 maintain the power generation performance, particularly the low humidification characteristics, required for HDV while ensuring high durability. When the La(110) of the porous carbon black exceeds 3.5 nm, the edge density (edge ​​amount per specific surface area) of the crystallites constituting the carbon black decreases, making it difficult to retain adsorbed water on the carbon black surface under reduced relative humidity conditions, which tends to result in reduced low humidification performance. The lower limit of the La(110) of the porous carbon black is not particularly limited as long as the required durability is obtained. Judging from the data obtained substantially, the lower limit of the La(110) of the porous carbon black is 2.0 nm or more. It is estimated that it is unlikely that the La(110) of porous carbon black is less than 2.0 nm and the Lc(002) is 1.7 nm or more. The La(110) of porous carbon black is preferably 3.0 nm or less.

[0041] It should be noted 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 porous carbon black ratio (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 porous carbon black ratio (Lc(002) / La(110)) is 0.6 or more, the thickness of the outer shell of the porous carbon black primary particles is prevented from becoming excessively thin, improving durability. As a result, the mechanical strength of the catalyst layer is sufficient, and the pores of the catalyst layer are less likely to collapse when power generation is continued. In addition, the edge density increases relative to the size of the mesh surface, improving low humidification performance when the relative humidity decreases. When the ratio of the porous carbon black (Lc(002) / La(110)) is 1.2 or less, the edge density becomes appropriate relative to the size of the mesh surface, and durability improves. As a result, the fuel cell is less susceptible to oxidative wear during use, and durability tends to improve. The ratio of the porous carbon black (Lc(002) / La(110)) is preferably 0.65 or more and 1.1 or less.

[0043] 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 catalyst support of a polymer electrolyte fuel cell according to the present disclosure (hereinafter also referred to as a "method for producing a carbon material") will be described.

[0045] The method for producing a carbon material according to the present disclosure involves treating raw material carbon black having a relatively large average primary particle size (30 nm or greater) in the order of "first activation," "graphitization," and "second activation," in which the "first activation" involves slowly activating the raw material at a low temperature while applying pressure and slightly varying the flow rate. The method for producing a carbon material according to the present disclosure provides a carbon material that satisfies requirements (A) to (D), and preferably a carbon material that satisfies requirement (E) in addition to requirements (A) to (D) (i.e., porous activated carbon black).

[0046] The method for producing the carbon material of the present disclosure will be described in detail below.

[0047] In the first activation step, by "pressurizing" the activation gas and "slightly varying" the flow rate, the "low-crystalline portions" that exist between the crystallites of even large raw carbon black can be oxidized and consumed, and the atmosphere inside the defects (pores) created by oxidative consumption can be quickly replaced with activation gas, so that even large raw carbon black can be efficiently made porous.

[0048] In graphitization, which is performed after the first activation, heat treatment is performed in an inert atmosphere to grow the crystallites that make up the raw carbon black that has undergone the first activation, thereby imparting the durability required for fuel cells. If the raw carbon black has a relatively large average primary particle size (more than 30 nm), the necessary durability can be ensured without excessive heat treatment in the subsequent graphitization. By using raw carbon black with a relatively large average primary particle size (more than 30 nm), the Lc(002) is maintained large, thereby ensuring durability. Graphitization at a relatively low temperature can suppress the growth of La(110), thereby suppressing a decrease in low-humidification performance.

[0049] The second activation has the effect of reopening the pores that have been closed by graphitization, thereby increasing the specific surface area and pore volume that have been reduced by the graphitization treatment. If the second activation is not performed, sufficient specific surface area and pore volume tend not to be obtained, which is undesirable.

[0050] The type of activation gas used in the first and second activation processes is not particularly limited as long as it contains a gas capable of oxidizing and consuming the carbon constituting the raw carbon black through a reaction. Examples of gases capable of oxidizing and consuming the carbon constituting the raw carbon black through a reaction include air, oxygen, ozone, water vapor, carbon dioxide, nitrogen dioxide, nitric oxide, and nitrous oxide. The activation gas may be a mixture of these gases. Alternatively, the activation gas may be a gas diluted with an inert gas such as nitrogen, argon, or helium. Furthermore, the activation gas may be an exhaust gas containing these gases. Preferably, the activation gas is water vapor or carbon dioxide, or a gas containing these gases. The types of gases used in the first and second activation processes may be different.

[0051] It is preferable that the pressure of the activation gas is increased at least in the reaction vessel where the first activation is performed. A preferable range of pressure is, for example, a pressure (gauge pressure) reading on a pressure gauge installed downstream of the reaction vessel exceeding 0.0 MPaG, which is expected to be effective, but a more preferable range is 0.1 MPaG to 0.9 MPaG. Within this range, even large carbon black can be made porous to the desired high specific surface area. If the pressure is less than 0.1 MPaG, although there is an effect, the required specific surface area may not be achieved. Even if the pressure exceeds 0.9 MPaG, the effect tends to be stronger, but the effect tends to plateau. The pressure is more preferably 0.1 MPaG to 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 to the desired high specific surface area.

[0052] In the reaction vessels used to activate the raw carbon black in the first and second activation steps, the average flow rate of the activation gas is preferably sufficient relative to the mass of raw carbon black loaded into the reaction vessel. When the mass of raw carbon black loaded into the reaction vessel is W (g) and the average flow rate of the supplied activation gas under standard conditions (0°C, 1 atmosphere) is F (N ml / min), a W / F ratio of 0.005 to 0.1 is preferred, as this suppresses uneven activation reactions. A W / F value of less than 0.005 is undesirable because the activation reaction of the raw carbon black near the downstream side of the reactor does not progress as quickly as that upstream, resulting in localized areas with small specific surface areas. A W / F value exceeding 0.1 is uneconomical due to the excessive amount of unreacted activation gas. A W / F value of 0.01 to 0.05 is more preferred. This range is preferred because it sufficiently reduces the difference in specific surface area between the upstream and downstream sides of the reactor.

[0053] In the reaction vessels where the first and second activations are performed, it is preferable for the activation gas to fluctuate around the average flow velocity. When the flow velocity fluctuates, even raw carbon black with a large average primary particle size can efficiently make the interior of the particles porous and form a hollow structure. This is presumably because, when the flow velocity fluctuates, the product gas generated in the activation reaction can be efficiently discharged from the pores formed in the activation reaction, thereby increasing the concentration of the activation gas.

[0054] The fluctuation range is preferably within a range of ±2% to ±50% of the average flow rate of the activation gas. Within this range, raw material carbon black having an average primary particle size of 30 nm to 100 nm can be efficiently made porous to the desired high specific surface area. If the fluctuation range is less than 2%, the target specific surface area may not be achieved. If the fluctuation range exceeds 50%, pressure control may become difficult when the activation gas is pressurized.

[0055] The fluctuation cycle is preferably from 1 to 30 times per minute. Within this range, raw material carbon black having an average primary particle size of 30 to 100 nm can be efficiently made porous to the desired high specific surface area. If the fluctuation cycle is less than 1 time per minute, it is difficult to obtain the effect of the fluctuation, and there is a possibility that the target specific surface area cannot be achieved. If the fluctuation cycle exceeds 30 times, it may become difficult to control the pressure when the activation gas is pressurized.

[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 in which carbon is not consumed. ２ , Ar, He. The graphitization temperature is preferably the minimum necessary temperature at which crystal growth can be performed to the extent that the required durability is obtained. An example of the graphitization temperature is 1400°C or higher and 2000°C or lower. If the graphitization temperature is lower than 1400°C, a long period of treatment may be required to obtain the required durability, or crystal growth sufficient to obtain sufficient durability may not be expected even if the graphitization temperature is maintained for a long period of time. If the graphitization temperature exceeds 2000°C, excessive crystal growth occurs in the case of carbon black, which increases the possibility of a decrease in low humidification performance. A more preferred temperature is 1500°C or higher and 1900°C or lower.

[0057] <Catalyst Layer for Polymer Electrolyte Fuel Cell and Polymer Electrolyte Fuel Cell> A catalyst layer for a polymer electrolyte fuel cell according to the present disclosure will now be described, along with a polymer electrolyte fuel cell. The carbon material according to the present disclosure can be applied to, for example, catalyst layers 150 and 160 provided in a polymer electrolyte fuel cell 100 shown in FIG. 1. FIG. 1 is a schematic diagram showing an example of the overall configuration of a fuel cell according to the present disclosure. The polymer electrolyte 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] The separator 110 is an anode-side separator that introduces a reducing gas such as hydrogen into the gas diffusion layer 130. The separator 120 is a cathode-side separator that introduces an oxidizing gas such as oxygen gas or air into the gas diffusion condensation phase. The types of the separators 110 and 120 are not particularly limited, and may be any separator used in conventional fuel cells (e.g., solid polymer fuel cells).

[0059] The gas diffusion layer 130 is an anode-side gas diffusion layer that diffuses the reducing gas supplied from the separator 110 and then supplies the gas to the catalyst layer 150. The gas diffusion layer 140 is a cathode-side gas diffusion layer that diffuses the oxidizing gas supplied from the separator 120 and then supplies the gas to the catalyst layer 160. The type of gas diffusion layers 130 and 140 is not particularly limited, and they may be any gas diffusion layer used in conventional fuel cells (e.g., polymer electrolyte fuel cells). Examples of the gas diffusion layers 130 and 140 include porous carbon materials (carbon cloth, carbon paper, etc.) and porous metal materials (metal mesh, metal wool, etc.). A preferred example of the gas diffusion layers 130 and 140 is a gas diffusion layer with a two-layer structure. Specifically, the gas diffusion layers 130 and 140 have a two-layer structure in which the layer on the separator 110 or 120 side is a gas diffusion fiber layer mainly composed of a fibrous carbon material, and the layer on the catalyst layer 150 or 160 side is a micropore layer mainly composed of carbon black.

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

[0061] Protons produced by the oxidation reaction pass through the catalyst layer 150 and electrolyte membrane 170 to reach the catalyst layer 160. Electrons produced by the oxidation reaction pass through the catalyst layer 150, gas diffusion layer 130, and separator 110 to reach the external circuit. The electrons perform work (generate electricity) in the external circuit and then enter the separator 120. The electrons then pass through the separator 120 and gas diffusion layer 140 to reach the catalyst layer 160.

[0062] There are no particular limitations on the configuration of the catalyst layer 150 that serves as the anode. The configuration of the catalyst layer 150 may be the same as that of a conventional anode, the same as that of the catalyst layer 160, or a configuration that is more hydrophilic than the catalyst layer 160.

[0063] The catalyst layer 160 is a so-called cathode. Within the catalyst layer 160, a reduction reaction of the oxidizing gas occurs, producing water. For example, when the oxidizing gas becomes oxygen gas or air, the following reduction reaction occurs. The water produced by the oxidation reaction is discharged to the outside of the polymer electrolyte fuel cell 100 together with the unreacted oxidizing gas. ２ +4H ＋ +4e － →2H ２ O (E ０ = 1.23 V)

[0064] In this way, the energy difference (potential difference) between the oxidation reaction and the reduction reaction is utilized to generate electricity in the polymer electrolyte fuel cell 100. In other words, the electrons generated in the oxidation reaction perform work in an external circuit.

[0065] The catalyst layer 160 contains the carbon material for a catalyst support of the present disclosure. That is, the catalyst layer 160 contains the carbon material for a catalyst support of the present disclosure, an electrolyte material (e.g., ionomer), and a catalyst component (e.g., platinum). This can improve the durability and low-humidification performance within the catalyst layer 160. This can also improve the durability and low-humidification performance of the solid polymer electrolyte fuel cell 100.

[0066] The catalyst loading rate in the catalyst layer 160 is not particularly limited, but is preferably 30% by mass or more and less than 80% by mass. A catalyst loading rate within this range further enhances durability and low-humidification performance. Here, the catalyst loading rate is expressed as the mass percentage of the catalyst component relative to the total mass of the catalyst-loaded particles (particles in which the catalyst component is loaded on a carbon material for catalyst support). If the catalyst loading rate is less than 30% by mass, it may be necessary to thicken the catalyst layer 160 to ensure practical use of the polymer electrolyte fuel cell 100. On the other hand, if the catalyst loading rate is 80% by mass or more, catalyst aggregation is likely to occur. Furthermore, if the catalyst layer 160 becomes too thin, flooding may occur.

[0067] The mass ratio I / C of the mass I of the electrolyte material in the catalyst layer 160 to the mass C of the catalyst support carbon material is not particularly limited, but is preferably greater than 0.5 and less than 5.0. In this case, both the pore network and the electrolyte material network can be achieved, resulting in improved durability and low-humidification performance. On the other hand, if the mass ratio I / C is 0.5 or less, the electrolyte material network tends to be weak and the proton conduction resistance tends to increase. If the mass ratio I / C is 5.0 or more, the pore network may be disrupted by the electrolyte material. In either case, durability and low-humidification performance may be reduced.

[0068] Furthermore, the thickness of the catalyst layer 160 is not particularly limited, and is preferably more than 5 μm and less than 20 μm. In this case, the oxidizing gas is more likely to diffuse within the catalyst layer 160, and flooding is less likely to occur. If the thickness of the catalyst layer 160 is 5 μm or less, flooding is more likely to occur. If the thickness of the catalyst layer 160 is 20 μm or more, the oxidizing gas is less likely to diffuse within the catalyst layer 160, and the catalytic components near the electrolyte membrane 170 become less effective. In other words, there is a possibility that the catalyst utilization rate will decrease.

[0069] The electrolyte membrane 170 is composed of a proton-conducting electrolyte material. The electrolyte membrane 170 introduces protons generated in the oxidation reaction to the catalyst layer 160 (cathode). The type of electrolyte material is not particularly limited, and any electrolyte material used in conventional fuel cells, such as solid polymer fuel cells, may be used. An example of a suitable electrolyte material is an electrolyte resin. Examples of electrolyte resins include polymers with phosphate groups, sulfonic acid groups, etc. Specific examples include perfluorosulfonic acid polymers and polymers with benzenesulfonic acid, etc. Of course, other types of electrolyte materials may also be used. Examples of such electrolyte materials include inorganic and inorganic-organic hybrid electrolyte materials. The solid polymer fuel cell 100 may be a fuel cell that operates within a temperature range from room temperature (25°C) to 150°C.

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

[0071] Experimental examples of the carbon material for a catalyst support according to the present disclosure will be described below. First, the method for measuring each parameter will be described.

[0072] <Method of measuring each parameter> (Measurement of average primary particle diameter) The carbon material for a catalyst support was observed in any 10 to 20 visual fields using a plane scanning electron microscope (SEM), and observation images were obtained. In the observation images, 30 intersections were generated when 6 vertical and 5 horizontal lines were arranged at equal intervals for each visual field. For particles present at or nearest to each other in the 30 intersections, the longest distance between two points on the outline of the carbon material for a catalyst support was taken as the particle diameter (diameter), and the average value of the 300 particles was taken as the average primary particle diameter.

[0073] <Measurement of BET specific surface area> Approximately 30 mg of the carbon material for catalyst support was weighed out and vacuum-dried at 200°C for 2 hours, and then nitrogen gas adsorption / desorption isotherms were measured using an automatic specific surface area analyzer (AUTOSORB iQ, manufactured by Anton Paar Japan) with nitrogen gas as the adsorbate. BET analysis was performed in the range of relative pressure of the adsorption isotherm of 0.30 or less, and the BET specific surface area was calculated.

[0074] (Measurement of Lc(002), La(110)) Approximately 3 mg of a carbon material for catalyst carrier was used as a sample, and it was placed on a silicon anti-reflection plate and set in an X-ray diffractometer (RINT-TTRIII manufactured by Rigaku Corporation). Measurement was performed at room temperature, with a scan step of 0.02°, an angle sweep rate of 1° / min, and a Cu-Kα radiation source. The obtained XRD spectrum was subjected to background removal and smoothing treatment in the 2θ range of 10° to 40° and in the 2θ range of 70 to 90°. For the XRD spectrum in the 2θ range of 10° to 40°, the waveform after background removal and smoothing treatment was used to determine Lc(002) using Scherrer's formula (Lc=Kλ / βcosθ). The diffraction peaks present in the 2θ range of 70 to 90° are a mixture of the (110), (112), and (006) planes. For XRD spectra with 2θ in the range of 70 to 90°, the waveform obtained after background removal and smoothing was set so that the waveform obtained using the Voigt function matched the waveform obtained using the Voigt function (minimizing the square of the difference) at angles smaller than the smallest diffraction peak angle, and La(110) was calculated using the Scherrer equation (La = Kλ / β cos θ), where K is the shape factor, λ is the X-ray wavelength, and β is the half-width of the diffraction peak.

[0075] <Example: Preparation of carbon material for catalyst support> (Example 1) (1) First activation 5 g of Nitelon #10 (catalog value of average primary particle diameter: 39 nm) manufactured by Nippon Steel Carbon Co., Ltd. was packed into a tubular reactor with a diameter of 1 inch, and a CO flow rate of 400 Nml / min was applied using a mass flow controller set up upstream of the tubular reactor. ２The gas was allowed to flow. At this time, a pressure controller (automatically controlled to a 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 downstream of the tubular reactor in this order, and the back pressure was set to a gauge pressure of 0.3 MPaG using the pressure controller. The aperture of the needle valve was adjusted so that the readings of the downstream mass flow meter fluctuated within a range of about ±100 ml / min., centered around 400 Nml / min., with a fluctuation period of about 12 times / min. In this state, the tubular reactor was heated to 850°C at a rate of 20°C / min. and maintained at 850°C for 34 hours, to perform the first activation. After maintaining the temperature, the flow gas was changed to N. ２ The temperature was lowered, and the first activated sample was collected.

[0076] (2) Graphitization The entire amount of the recovered first activated sample was placed in a graphite crucible, and the sample was placed in a graphitization furnace under a flow of Ar, with the temperature increased at a rate of 15°C / min., and graphitization was carried out at 1600°C for 1 hour, and a graphitized sample was recovered.

[0077] (3) Second activation: The entire graphitized sample was again loaded into a tubular reactor with a diameter of 1 inch, and a CO flow rate of 400 Nml / min was introduced using a mass flow controller set upstream of the tubular reactor. ２ The gas was allowed to flow. At this time, the pressure controller and needle valve were fully opened and set to a gauge pressure of 0.0 MPaG. In this state, the tubular reactor was heated to 850°C at a rate of 20°C / min and held at 850°C for 3 minutes to carry out the second activation. After holding, the flow gas was changed to N ２ The temperature was then lowered, and the second activated sample was recovered as the carbon material for a catalyst support of Example 1 (i.e., porous activated carbon black).

[0078] Example 2 A carbon material for a catalyst support (that is, porous activated carbon black) was obtained in the same manner as in Example 1, except that the holding time for the second activation was set to 30 minutes.

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

[0080] Example 4 A carbon material for a 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 Niteron #SH (catalog value of average primary particle diameter: 61 nm) manufactured by Nippon Steel Carbon Corporation, the holding time for the first activation was 43 hours, the holding temperature for graphitization was 1700°C, and the holding temperature and holding time for the second activation were 930°C and 30 minutes, respectively.

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

[0082] Comparative Example 1 A carbon material for a catalyst carrier (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 fluctuation range of the first activation was about ±5 ml / min.

[0083] Comparative Example 2 A carbon material for a catalyst carrier (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 fluctuation range of the first activation was about ±5 ml / min.

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

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

[0086] (Comparative Examples 9 and 10) 2 g of each of the carbon materials for catalyst carriers of Comparative Example 5 and Comparative Example 8 was packed into a tubular reactor having a diameter of 1 inch, and a CO flow rate of 400 Nml / min was controlled using a mass flow controller set up upstream of the tubular reactor. ２ The gas was allowed to flow. At this time, the pressure controller and 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 a rate of 20°C / min and maintained at 950°C for 30 minutes for activation. After maintaining the temperature, the flow gas was changed to N ２ The temperature was then lowered and the collected samples were designated as Comparative Examples 9 and 10, respectively.

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

[0088] <Preparation of catalyst, preparation of catalyst layer, fabrication of MEA, assembly of fuel cell, and evaluation of cell performance (power generation performance, durability)> Using the carbon material for catalyst support of each example, a catalyst for a polymer electrolyte fuel cell carrying a catalyst metal was prepared as follows. A catalyst layer ink liquid was prepared using the obtained catalyst. A catalyst layer was then formed using this catalyst layer ink liquid. A membrane electrode assembly (MEA) was then fabricated using the formed catalyst layer. The fabricated MEA was incorporated into a fuel cell, and a power generation test was performed using a fuel cell measuring device. The preparation of each component and the cell evaluation through the power generation test are described in detail below.

[0089] (1) Preparation of catalyst (platinum-supported carbon material) for polymer electrolyte fuel cell The catalyst support carbon material of each example was dispersed in distilled water, formaldehyde was added to this dispersion, and the dispersion was placed in a water bath set at 40°C. After the temperature of the dispersion reached 40°C, the same as the bath temperature, an aqueous solution of dinitrodiamine Pt complex nitric acid was slowly poured into the dispersion under stirring. Stirring was continued for about 2 hours, followed by filtration and washing of the resulting solid. 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 amount of platinum carried on this platinum-supporting carbon material was adjusted to 35 mass % with respect to the total mass of the catalyst carrier carbon material and platinum particles, and was confirmed by measurement using inductively coupled plasma atomic emission spectrometry (ICP-AES).

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

[0091] Using the catalyst layer ink liquid thus prepared, a platinum catalyst layer was prepared so that the mass of platinum per unit area of ​​the catalyst layer (hereinafter referred to as "platinum weight") was 0.18 mg / cm ２ The catalyst layer ink was sprayed onto a Teflon (registered trademark) sheet, and then dried in argon at 120° C. for 60 minutes to prepare a catalyst layer.

[0092] (3) Fabrication of MEA Using the catalyst layers fabricated as described above, an MEA (membrane electrode assembly) was fabricated by the following method. A square electrolyte membrane with sides of 6 cm was cut out from a Nafion membrane (NR211 manufactured by DuPont). The anode and cathode catalyst layers coated on Teflon (registered trademark) sheets were each cut out into a square with sides of 2.5 cm using a utility knife. The electrolyte membrane was sandwiched between the anode and cathode catalyst layers cut out in this way so that the catalyst layers were in contact with each other across the center of the electrolyte membrane and were not misaligned with each other. The MEA was then heated at 120°C and 100 kg / cm. ２ After cooling to room temperature, the Teflon (registered trademark) sheets were carefully peeled off from both the anode and cathode to prepare a catalyst layer-electrolyte membrane assembly in which the anode and cathode catalyst layers were fixed to the electrolyte membrane.

[0093] Next, a pair of square carbon paper sheets, each 2.5 cm on a side, was cut out from carbon paper (39BC manufactured by SGL Carbon Co., Ltd.) to form a gas diffusion layer. The catalyst layer-electrolyte membrane assembly was sandwiched between these carbon paper sheets so that the anode and cathode catalyst layers were aligned with each other without any misalignment. The assembly was then heated at 120°C and 50 kg / cm ２ The membrane was pressed for 10 minutes at 100°C to prepare an MEA. The basis weight of each of the catalytic metal component, carbon material, and electrolyte material in each prepared MEA was calculated from the mass of the catalyst layer fixed to the Nafion membrane (electrolyte membrane) obtained by calculating the mass of the catalyst layer 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 the mass ratio of the catalyst layer composition.

[0094] (4) Fuel Cell Assembly and Low-Humidification Performance Evaluation The MEAs fabricated using the catalyst carrier carbon materials of each example were assembled into cells and set in a fuel cell measurement device, and the initial power generation performance of the fuel cells 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 using a back-pressure valve installed downstream of the cell so that the back-pressure gauge pressure was 0.1 MPaG, with utilization rates of 40% and 70%, respectively. The cell temperature was set to 80°C, and the air and pure hydrogen supplied to the fuel cell were humidified by passing them through distilled water kept at 80°C in a humidifier (i.e., bubbling). This set the relative humidity of the anode and cathode to approximately 100%.

[0095] Under these conditions, the reactant gas was supplied to the cell, and the current density was gradually increased until the cell terminal voltage reached 0.3 V. This operation was repeated 10 times. Next, the pressure was adjusted using a back pressure valve installed downstream of the cell so that the back pressure gauge pressure was 0.05 MPaG. The cell temperature was 80°C, and the air and pure hydrogen supplied to the fuel cell were passed through distilled water kept warm in a humidifier (i.e., bubbled), and the relative humidity of the anode and cathode was approximately 50%.

[0096] Under these settings, the reaction gas was supplied to the cell, and the operation of gradually increasing the current density until the cell terminal voltage reached 0.3 V was repeated 10 times. The current density was then fixed at 0.1 A / cm2 and held for 10 minutes, at which point the cell terminal voltage was recorded, and the low humidification performance was evaluated using the following criteria: pass ranks A and B, and fail rank C. The results are shown in Table 1. [Pass rank] A: Current density 0.1 A / cm ２ B: The cell terminal voltage at a current density of 0.1 A / cm is 0.84 V or more. ２ The voltage between the cell terminals is 0.82 V or more. [Failure rank] C: Not meeting the pass rank B.

[0097] (5) Durability Evaluation After the 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 0.0 MPaG, and the cathode gas was switched to argon gas. Next, the cell voltage was set to 0.6 V and held for 4 seconds, followed by a cycle of setting the cell voltage to 1.2 V and holding for 4 seconds. This square-wave voltage fluctuation was repeated 1,000 cycles. The anode and cathode gas utilization rates were then set to 40% and 70%, respectively, the cell back pressure gauge pressure was 0.1 MPaG, the cell temperature was 80°C, and the relative humidity was 100%. The current density was recorded when the cell voltage was set to 0.6 V, and durability was evaluated using the following criteria: pass rank A, pass rank B, and fail rank C. The results are shown in Table 1. [Pass Rank] A: The current density after 1,000 cycles was 80% or more of the current density during the initial power generation performance evaluation. B: The current density after 1000 cycles is 70% or more of the current density at the time of initial power generation performance evaluation. [Failure Rank] C: Not meeting the pass rank B.

[0098]

[0099] The above results show that Examples 1 to 5 achieve both high durability and low-humidification performance. Comparative Examples 1 and 2 are examples in which the activation gas fluctuations were smaller than those of Examples 3 and 5, respectively, but the activation was insufficient, resulting in a smaller specific surface area and insufficient low-humidification performance. Comparative Examples 3 to 8 are examples in which commercially available porous carbon black was heat-treated at various temperatures, but no material was obtained that simultaneously satisfied the requirements (A) to (D) of the present disclosure, and performance that simultaneously achieved both low-humidification performance and durability was not achieved. Comparative Examples 9 and 10 are examples in which commercially available porous carbon black was heat-treated and then activated, but no material was obtained that simultaneously satisfied the requirements (A) to (D) of the present disclosure, and performance that simultaneously achieved both low-humidification performance and durability was not achieved. Comparative Example 11 is an example in which the average primary particle diameter was less than 30 nm, but the Lc(002) was small, resulting in insufficient durability.

[0100] The symbols are explained as follows: 100: polymer electrolyte fuel cell 110, 120: separator 130, 140: gas diffusion layer 150, 160: catalyst layer 170: electrolyte membrane

[0101] 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 herein 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 carrier of 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) the 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 peaks between 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. 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. 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 any one of claims 1 to 3.

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

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

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