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

Abstract

Provided are: a carbon material for a catalyst carrier of a solid polymer fuel cell that is composed of a porous carbon material which satisfies requirements (A) to (D); a catalyst layer and a fuel cell using the same; and a method for manufacturing a carbon material for a catalyst carrier. (A) The value of the pore volume VA5-10 that is exhibited by pores having a pore diameter of 5 nm or larger but smaller than 10 nm, as determined from a nitrogen adsorption isotherm, is 0.1 mL / g or more but less than 0.2 mL / g. (B) The difference between the pore volume VA5-10 that is exhibited by pores having a pore diameter of 5 nm or larger but smaller than 10 nm, as determined from the nitrogen adsorption isotherm, and the pore volume VD5-10 that is exhibited by pores having a pore diameter of 5 nm or larger but smaller than 10 nm, as determined from a nitrogen desorption isotherm, is 0.06 mL / g or more. (C) In an XRD spectrum, Lc (LcA) of a component A among components that have a clear peak in the range of 2θ=26.0 ± 0.2° and that are obtained by waveform separation of 2θ=20-30° is 0.9 nm or more. (D) The nitrogen adsorption amount Vmacro at a relative pressure of 0.95-0.99 in the nitrogen adsorption isotherm is 300-1200 mL / g.

Description

Carbon material for catalyst support of polymer electrolyte fuel cell, catalyst layer for polymer electrolyte fuel cell, fuel cell, and method for manufacturing carbon material for catalyst support of polymer electrolyte 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, a fuel cell, and a method for producing a carbon material for a catalyst support of a polymer electrolyte 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 includes a catalyst component, a catalyst support that supports the catalyst component, and an electrolyte material that has proton conductivity. The catalyst support 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 separator on the cathode side. The oxidizing gas is diffused into the gas diffusion layer on the cathode side and then introduced into the cathode. The cathode includes a catalyst component, a catalyst support that supports the catalyst component, and an electrolyte material with 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] Meanwhile, porous carbon materials to be used as catalyst carriers for polymer electrolyte fuel cells have been studied and various proposals have been made.

[0009] For example, Patent Document 1 describes a porous carbon material in which the specific surface area SA of mesopores with pore diameters of 2 to 50 nm, as determined by analyzing the nitrogen adsorption isotherm during the adsorption process using the Dollimore-Heal method, is 600 m ２ / g or more 1600m ２ / g or less, and the relative intensity ratio (IG' / IG) of the peak intensity (IG') of the G'-band peak present in the range of 2650 to 2700 cm-1 and the peak intensity (IG) of the G-band peak present in the range of 1550 to 1650 cm-1 in the Raman spectroscopy spectrum is 0.8 to 2.2, and the peak position of the G'-band is 2660 to 2670 cm-1. －１ "A carbon support material for a polymer electrolyte fuel cell, characterized in that:

[0010] In Patent Document 2, "relative pressure P / P ０ The carbon material for a catalyst support of a polymer electrolyte fuel cell, in which the nitrogen adsorption / desorption isotherm shows two hysteresis loops, a first hysteresis loop and a second hysteresis loop, when the carbon material has a hysteresis loop of 0.4 or more.

[0011] Patent Document 3 describes a method for producing a granular material having a particle diameter of 10 to 20 nm and a BET specific surface area of ​​200 to 700 m ２ / g, and the relative pressure P / P ０ The carbon material for a catalyst support for a polymer electrolyte fuel cell is characterized in that the difference between the nitrogen desorption isotherm value and the nitrogen adsorption isotherm value at .DELTA.=0.5 is 0.10 ml / g or less, the DBP oil absorption is 300 to 520 ml / 100 g, and the half-width .DELTA.G of the G band obtained from Raman spectroscopy is 40 to 70 cm.

[0012] Patent Document 4 proposes "a carbon material for a catalyst carrier, which is used for a catalyst carrier of a polymer electrolyte fuel cell and has a three-dimensionally branched dendritic structure, and which is characterized by simultaneously satisfying the following (1) and (2): (1) In particle size distribution measurement using a laser diffraction / scattering particle size distribution analyzer, the DL / DH ratio is 1.5 or more, where DL is the cumulative distribution [%] of particles having a particle diameter of 1 μm or less on a volumetric diameter basis, and DH is the cumulative distribution [%] of particles having a particle diameter of more than 1 μm. (2) The mode diameter of pores in the range of 20 nm to 200 nm in diameter measured by mercury porosimetry is 40 nm to 70 nm."

[0013] Patent Document 5 proposes "a catalyst layer for a fuel cell, comprising: a carbon support having pores with a pore diameter of 1 nm to 5 nm, the pores having a pore volume of 15.0 mL / g or more; a catalyst containing a catalytic metal supported in the pores of the carbon support; and an ionomer having a glass transition temperature of 160°C or more."

[0014] Patent Document 6 proposes "an air electrode catalyst layer having the following configuration: (1) the air electrode catalyst layer comprises a first catalyst-supported carbon having first catalyst particles supported on the surface of a first support, a second catalyst-supported carbon having second catalyst particles supported on the surface of a second support, and a catalyst layer ionomer; (2) the first support is made of a first monodisperse spherical mesoporous carbon having a most frequent pore diameter of 2.0 nm or more and 3.0 nm or less; and (3) the second support is made of a second monodisperse spherical mesoporous carbon having a most frequent pore diameter of 3.5 nm or more and 5.0 nm or less."

[0015] Patent Document 1: International Publication No. 2015 / 141810 Patent Document 2: Japanese Patent Application Publication No. 2022-066847 Patent Document 3: Japanese Patent Application Publication No. 2020-042927 Patent Document 4: Japanese Patent Application Publication No. 2022-156985 Patent Document 5: Japanese Patent No. 6315348 Patent Document 6: Japanese Patent No. 7167792

[0016] Catalyst carriers for polymer electrolyte fuel cells (hereinafter also simply referred to as "fuel cells") are required to have durability in addition to power generation characteristics.

[0017] In particular, in recent years, devices that use fuel cells have been required to operate for even longer periods of time. For example, in the automotive field, large vehicles such as large trucks and large buses are required to transport large distances, so there is an increasing demand for improved power generation characteristics (particularly, large current characteristics) of catalyst supports. In addition to power generation characteristics, there is also an increasing demand for improved durability (particularly, resistance to electrochemical oxidation consumption) of catalyst supports, because fuel cells are exposed to high voltages during use.

[0018] As described above, due to recent demands, there is currently a demand for further improvements in power generation characteristics and durability compared to conventional catalyst supports including those described in Patent Documents 1 to 6.

[0019] Therefore, an object of the present invention is to provide a carbon material for a catalyst support of a polymer electrolyte fuel cell that has excellent power generation characteristics and durability, a catalyst layer for a polymer electrolyte fuel cell and a fuel cell that utilize the same, and a method for manufacturing a carbon material for a catalyst support of a polymer electrolyte fuel cell.

[0020] The means for solving the problems include the following aspects: <1> A carbon material for a catalyst support of a polymer electrolyte fuel cell, which is made of a porous carbon material that satisfies the following requirements (A), (B), (C), and (D): (A) a pore volume VA of pores having a pore diameter of 5 nm or more and less than 10 nm, which is determined by analyzing a nitrogen adsorption isotherm using the Dollimore-Heal (DH) method; ５－１０ (B) The pore volume VA of pores having a pore diameter of 5 nm or more and less than 10 nm, which is determined by analyzing a nitrogen adsorption isotherm using the Dollimore-Heal (DH) method, is 0.1 mL / g or more and less than 0.3 mL / g. ５－１０ and the pore volume VD of pores with a pore diameter of 5 nm or more and less than 10 nm, which is obtained by analyzing the nitrogen desorption isotherm using the DH (Dollimore-Heal) method. ５－１０ Difference (VA ５－１０ -VD ５－１０ ) is 0.06 mL / g or more. (C) In the XRD spectrum obtained by XRD (X-ray diffraction) measurement, there is a clear peak between the diffraction angle 2θ = 26.0 ± 0.2 °, and the range of the diffraction angle 2θ = 20 ° to 30 ° is divided into three peaks, namely, peak A where the diffraction angle 2θ is 25.5 ° or less, peak G1 where the diffraction angle 2θ is in the range of 26.0 ° ± 0.2 °, and peak G2 where the diffraction angle 2θ is in the range of 26.5 ° ± 0.2 °, and the Lc (LcA) of component A among the peaks obtained by waveform separation using a Voigt function is 0.9 nm or more. (D) In ​​the nitrogen adsorption isotherm, the nitrogen adsorption amount V at a relative pressure of 0.95 to 0.99 is ｍａｃｒｏ <2> The carbon material for a catalyst support of a polymer electrolyte fuel cell according to <1>, further satisfying at least one of the following requirements (E) and (F): (E) A pore volume VD of pores having a pore diameter of 5 nm or more and less than 10 nm, which is determined by analyzing a nitrogen desorption isotherm using the Dollimore-Heal (DH) method, is 300 to 1200 mL / g. ５－１０(F) The porous carbon material has a three-dimensional dendritic structure, and the branch diameter of the three-dimensional dendritic structure is 40 to 100 nm. <3> 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 <1> or <2>. <4> A fuel cell, comprising the catalyst layer for a polymer electrolyte fuel cell according to <3>. <5> The fuel cell according to <4>, wherein the catalyst layer for a polymer electrolyte fuel cell is a catalyst layer on the cathode side. <6> A carbon material for a catalyst support of a polymer electrolyte fuel cell, comprising: a silver acetylide production step of blowing acetylene gas into a reaction solution of an aqueous ammonia solution of silver nitrate to synthesize silver acetylide; a decomposition step of drying the silver acetylide and then applying a voltage to cause the silver acetylide to undergo a self-decomposition explosion reaction to obtain a carbon material intermediate; a cleaning step of contacting the carbon material intermediate with a nitric acid solution to clean the carbon material intermediate; a heat treatment step of heat-treating the cleaned carbon material intermediate in vacuum or in an inert gas atmosphere at a temperature of 1900 to 2300°C to obtain a heat-treated carbon material intermediate; and a crushing step of crushing the heat-treated carbon material intermediate.

[0021] According to the present disclosure, there are provided a carbon material for a catalyst support of a polymer electrolyte fuel cell that has excellent power generation characteristics and durability, a catalyst layer for a polymer electrolyte fuel cell and a fuel cell that use the same, and a method for manufacturing a carbon material for a catalyst support of a polymer electrolyte fuel cell.

[0022] FIG. 1 is a graph showing an example of pore size distribution based on a nitrogen adsorption isotherm and a nitrogen desorption isotherm for a carbon material for a catalyst support of a polymer electrolyte fuel cell according to the present disclosure. FIG. 2A is a graph showing an example of an XRD spectrum and an XRD spectrum after background (BG) correction obtained by XRD (X-ray diffraction) measurement for a carbon material for a catalyst support of a polymer electrolyte fuel cell according to the present disclosure. FIG. 2B is a graph showing an example of an XRD spectrum, peak A, and peak G1 after background correction (BG) for a carbon material for a catalyst support of a polymer electrolyte fuel cell according to the present disclosure. FIG. 3 is an explanatory diagram showing a method for measuring the branch diameter of a carbon material for a catalyst support of a polymer electrolyte fuel cell according to the present disclosure. FIG. 4 is a schematic diagram showing an example of the general configuration of a fuel cell according to the present disclosure.

[0023] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Furthermore, when "greater than" or "less than" is added to the numerical values ​​before and after "to", the numerical range means a range that does not include these numerical values ​​as the lower or upper limit. In the present disclosure, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0024] <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 a porous carbon material (hereinafter also simply referred to as "carbon material" or "porous carbon material") that satisfies the requirements (A), (B), (C), and (D) described below. The carbon material for catalyst support of the present disclosure is a carbon material that is excellent in both power generation characteristics and durability. The carbon material of the present disclosure was discovered based on the following findings.

[0025] Conventionally, porous carbon materials with internal mesopores and a high specific surface area have been designed to support catalytic components in the internal mesopores, which reduces the amount of catalyst that is coated with an electrolyte material (e.g., ionomer) and inhibits reaction compared to porous carbon materials without internal pores, thereby improving catalyst activity and power generation performance.

[0026] Here, fuel cells generate water during power generation according to a reaction formula. Therefore, it is believed that the porous carbon material of the catalyst support is sufficiently wetted with the generated water during high-current power generation. Therefore, proton conduction to the catalyst is smoothly achieved by the water present in the pores inside the porous carbon material. On the other hand, if the generated water fills the mesopores inside the porous carbon material, oxygen gas cannot be supplied to the catalyst inside the mesopores, causing a phenomenon known as flooding, in which the catalyst cannot contribute to the reaction. To suppress flooding, it is important to increase the pore volume of the mesopores inside the porous carbon material. Furthermore, it is important to discharge the generated water from the mesopores inside the porous carbon material during high-current power generation. Specifically, it is important that the internal mesopores have pores that communicate with the outside of the porous carbon material as a water discharge path. -Reaction formula- Cathode: 1 / 2O ２ +2e － → O ２－ Anode: O ２－ +H ２ → H ２ O + 2e － Overall: 1 / 2O ２ +H → H ２ O

[0027] However, when the pore volume of the mesopores inside the porous carbon material is increased, as in the carbon material for catalyst support described in Patent Document 4, the pores that serve as passages connecting the mesopores to the outside of the porous carbon material also expand, allowing the electrolyte material (e.g., ionomer) to penetrate into the mesopores inside the porous carbon material, resulting in a deterioration in power generation characteristics.

[0028] Therefore, the inventors have conducted research and have found the following: First, the nitrogen adsorption amount V that satisfies the requirement (D) ｍａｃｒｏ In a porous carbon material having a three-dimensional dendritic structure, the pore volume VA of requirement (A) is within a specific range. ５－１０ Increasing the value of (B) (pore volume VA ５－１０ and pore volume VD ５－１０By satisfying the above condition (difference between the pore volume of the mesopores and the volume of the porous carbon material), the pore volume of the mesopores inside the porous carbon material can be increased while preventing excessive expansion of the pores that serve as passages through the mesopores to the outside. This maintains water dischargeability and prevents flooding, while also preventing the intrusion of electrolyte materials (e.g., ionomers). As a result, the electromotive performance (particularly, large current characteristics) is improved.

[0029] The cathode potential of the fuel cell becomes, for example, 1.0 V (vs. SHE) or higher during start-up and shutdown. When such a high voltage is applied, the porous carbon material ２ Therefore, resistance to oxidation is important for improving durability.

[0030] The inventors have therefore conducted research and have found the following: Requirement (C) (the XRD spectrum has a clear peak between 2θ=26.0±0.2°, and the Lc (LcA) of component A obtained by peak separation is highly correlated with the resistance of the porous carbon material to oxidative consumption, and by satisfying requirement (C), a porous carbon material with high durability can be obtained.

[0031] The inventors then investigated a method for producing a porous carbon material that satisfies requirements (A) to (D) and discovered the following: In the silver acetylide decomposition method, silver acetylide is decomposed by applying electricity, rather than by conventional heating. This suppresses the deactivation of silver acetylide by heating, thereby suppressing excessive expansion of the pores that serve as passages through which the internal mesopores communicate with the outside, and thereby producing a porous carbon material with a three-dimensional dendritic structure and large internal mesopore volumes. In addition, by performing heat treatment at a high temperature, a porous carbon material with high durability can be obtained.

[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 is excellent in both power generation characteristics and durability.

[0033] The requirements (A), (B), (C), and (D) are explained below. From the viewpoint of improving power generation characteristics and durability, the carbon material for a catalyst support according to the present disclosure preferably satisfies at least one of the requirements (E), (F), and (G) in addition to the requirements (A), (B), (C), and (D).

[0034] (Requirement (A)) (A) The pore volume VA of pores having a pore diameter of 5 nm or more and less than 10 nm, which is determined by analyzing a nitrogen adsorption isotherm using the DH (Dollimore-Heal) method. ５－１０ The value of VA of mesopores having a pore diameter of 5 nm or more and 10 nm or less contained in the porous carbon material is 0.1 mL / g or more and less than 0.3 mL / g. ５－１０ By increasing the pore volume VA of mesopores with a pore diameter of 5 nm to 10 nm, flooding due to water generated during power generation in the fuel cell is suppressed, and power generation characteristics (especially large current power generation characteristics) are improved. ５－１０ If is too large, the skeleton of the porous carbon material becomes thin, the physical strength decreases, and it becomes difficult to maintain the structure under pressure when pressing to form the catalyst layer or when fastening the catalyst layer to the cell. ５－１０ The value of pore volume VA is within the above range. ５－１０ The value is preferably 0.128 mL / g or more and 0.29 mL / g or less, and more preferably 0.148 mL / g or more and 0.28 mL / g or less.

[0035] The pore volume VA ５－１０ The value is measured by the measurement method shown in the examples below.

[0036] (Requirement (B)) (B) The pore volume VA of pores having a pore diameter of 5 nm or more and less than 10 nm, which is determined by analyzing a nitrogen adsorption isotherm using the DH (Dollimore-Heal) method. ５－１０ and the pore volume VD of pores with a pore diameter of 5 nm or more and less than 10 nm, which is obtained by analyzing the nitrogen desorption isotherm using the DH (Dollimore-Heal) method. ５－１０ Difference (VA ５－１０ -VD ５－１０ ) is 0.06 mL / g or more. ５－１０ and pore volume VD５－１０ By increasing the difference between the pore volume VA and the mesopore volume VA, a structure is ensured in which the pores that serve as passages connecting the mesopores inside the porous carbon material to the outside are not excessively expanded. This prevents the electrolyte material (ionomer, etc.) from penetrating into the mesopores inside the porous carbon material, and prevents a decrease in power generation characteristics (particularly large current power generation characteristics). ５－１０ and pore volume VD ５－１０ The difference between the pore volume VA and the pore volume VA is within the above range. ５－１０ and pore volume VD ５－１０ The difference between the pore volume VA and the internal mesopore volume VA is preferably 0.10 mL / g or more, and more preferably 0.15 mL / g or more. However, from the viewpoint of supplying oxygen gas to the internal mesopores and discharging the generated water, the difference between the pore volume VA and the internal mesopore volume VA is preferably 0.10 mL / g or more, and more preferably 0.15 mL / g or more. ５－１０ and pore volume VD ５－１０ The difference is preferably 0.30 mL / g or less, and more preferably 0.245 mL / g or less.

[0037] The pore volume VD ５－１０ The value is measured by the measurement method shown in the examples below.

[0038] (Requirement (C)) (C) In an XRD spectrum obtained by XRD (X-ray diffraction) measurement, there is a clear peak within a diffraction angle 2θ=26.0±0.2°, and the LcA of component A obtained by waveform separation using a Voigt function within the diffraction angle 2θ=20° to 30° range into three peaks: Peak A where the diffraction angle 2θ is 25.5° or less, Peak G1 where the diffraction angle 2θ is in the range of 26.0°±0.2°, and Peak G2 where the diffraction angle 2θ is in the range of 26.5°±0.2° is 0.9 nm or more.

[0039] Here, the peaks present at diffraction angles 2θ between 26.0°±0.2° are diffraction peaks of the (002) plane of turbostratic carbon. The peaks at diffraction angles 2θ in the range of 26.5°±0.2° are diffraction peaks of the (002) plane of highly crystalline carbon similar to graphite. Peaks G1 and G2 represent peaks derived from graphitized materials, and peak A represents a peak derived from the main component of the porous carbon material. LcA is considered to represent the wall thickness of the pores of the porous carbon material (crystallite size in the c-axis direction of the carbon material). Therefore, when LcA is large, the pore walls of the main component of the porous carbon material are sufficiently thick, making it less likely for the pores to be lost due to oxidative wear, and improving durability (resistance to electrochemical oxidation). Therefore, LcA is set to the above range. LcA is preferably 0.94 nm or more, more preferably 0.95 nm or more, and even more preferably 1.00 nm or more. However, if LcA is too large, the thickness of the pore wall increases too much, the edge amount of the carbon network plane forming the pore wall decreases excessively, and the supportability of the catalyst component on the pore wall tends to decrease. Therefore, LcA is preferably 1.4 nm or less.

[0040] The LcA is a value measured by the measurement method shown in the examples below.

[0041] (Requirement (D)) (D) In ​​the nitrogen adsorption isotherm, the nitrogen adsorption amount V at a relative pressure of 0.95 to 0.99 ｍａｃｒｏ The nitrogen adsorption amount V at a relative pressure of 0.95 to 0.99 is 300 to 1200 mL / g. ｍａｃｒｏ indicates the size of the macropores of the porous carbon material. ｍａｃｒｏ When the temperature is high, the three-dimensional dendritic structure of the porous carbon material is highly developed. By developing the three-dimensional dendritic structure, the raw material gas (H ２ , O ２ ) and the discharge of the generated water are improved. This improves the power generation characteristics (especially the large current power generation characteristics). On the other hand, the nitrogen adsorption amount V ｍａｃｒｏ If V is too large, the carbon content of the catalyst layer decreases when the catalyst layer is formed, making it difficult to maintain the shape of the catalyst layer. ｍａｃｒｏ is within the above range. ｍａｃｒｏis preferably 500 to 1200 mL / g, more preferably 900 to 1200 mL / g.

[0042] The nitrogen adsorption amount V ｍａｃｒｏ is a value measured by the measurement method shown in the examples below.

[0043] (Requirement (E)) (E) The pore volume VD of pores having a pore diameter of 5 nm or more and less than 10 nm, which is determined by analyzing a nitrogen desorption isotherm using the DH (Dollimore-Heal) method, ５－１０ is preferably less than 0.08 mL / g. ５－１０ indicates the size of the pores that serve as passages through which the mesopores inside the porous carbon material communicate with the outside. ５－１０ When the pore volume VD is small, the pores that serve as passages connecting the mesopores inside the porous carbon material to the outside are thin, and furthermore, the intrusion of the electrolyte material (ionomer, etc.) of the catalyst component into the mesopores inside the porous carbon material is suppressed, and the deterioration of the power generation characteristics (particularly the large current power generation characteristics) is suppressed. ５－１０ is preferably in the above range. ５－１０ However, from the viewpoint of supplying oxygen gas to the internal mesopores and discharging the generated water, the pore volume VD ５－１０ is preferably 0.03 mL / g or more.

[0044] (Requirement (F)) (F) The porous carbon material has a three-dimensional dendritic structure, and the branch diameter of the porous carbon material is 40 to 100 nm. The three-dimensional dendritic structure refers to a structure in which rod-shaped or ring-shaped bodies are branched three-dimensionally. Here, in order to reduce the overvoltage during a large current, it is sufficient to reduce the mass transfer resistance during a large current. In other words, it is good to reduce the diffusion resistance of the source gas inside the porous material. Therefore, when the porous carbon material has a three-dimensional dendritic structure with a branch diameter of 40 to 100 nm, the diffusion resistance of the source gas is reduced (i.e., the diffusibility of the source gas is increased), and the power generation characteristics are improved. The branch diameter value of the porous carbon material is a value measured by the method described in the examples below.

[0045] (Requirement (G)) Requirement (G): A BET (Brunauer, Emmett, Teller) specific surface area determined by nitrogen adsorption isotherm analysis is 450 m ２ / g~1500m ２ / g. When the BET specific surface area is within the above range, a larger amount of catalyst component can be supported. Increasing the BET specific surface area improves the supportability of the catalyst component. If the BET specific surface area is too high, it tends to be difficult to achieve both the physical strength and durability (electrical oxidation wear resistance) of the porous carbon material. Therefore, it is preferable that the BET specific surface area is within the above range. The BET specific surface area is a value measured by the method described in the Examples below.

[0046] <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.

[0047] The method for producing a carbon material according to the present disclosure includes: a silver acetylide production step of synthesizing silver acetylide by injecting acetylene gas into a reaction solution of an aqueous ammonia solution of silver nitrate; a decomposition step of drying the silver acetylide and then applying a voltage to cause the silver acetylide to undergo a self-decomposition explosive reaction to obtain a carbon material intermediate; a cleaning step of contacting the carbon material intermediate with a nitric acid solution to clean the carbon material intermediate; a heat treatment step of heat-treating the cleaned carbon material intermediate at a temperature of 1900 to 2300°C in a vacuum or in an inert gas atmosphere to obtain a heat-treated carbon material intermediate; and a milling step of milling the heat-treated carbon material intermediate.

[0048] In the method for producing a carbon material according to the present disclosure, a carbon material that satisfies requirements (A) to (D), preferably a carbon material that satisfies at least one of requirements (E) to (G) in addition to requirements (A) to (D), can be obtained through the above steps.

[0049] Each step will be described in detail below.

[0050] (Silver acetylide production process) In the silver acetylide production process, silver acetylide is synthesized by blowing acetylene gas into a reaction solution consisting of an aqueous ammonia solution of silver nitrate (hereinafter also referred to as "aqueous silver nitrate solution"). The synthesis of silver acetylide is carried out by adjusting the mass ratio of acetylene gas to silver nitrate. For example, the acetylene gas can be passed through the aqueous silver nitrate solution, more specifically, by blowing acetylene gas into the aqueous silver nitrate solution. Furthermore, ultrasonic waves can be applied to the aqueous silver nitrate solution during contact between the silver nitrate and acetylene gas. This promotes dissolution and dispersion of the acetylene gas in the aqueous silver nitrate solution. It is preferable to stir the aqueous silver nitrate solution during contact between the silver nitrate and acetylene gas. This increases the frequency of contact between the acetylene gas and silver nitrate, resulting in efficient production of silver acetylide. Stirring can be performed using a conventional stirring blade or a stirring bar such as a magnetic stirrer. This allows silver acetylide to be obtained as a bulky precipitate of white crystals.

[0051] (Decomposition Step) In the decomposition step, the silver acetylide is dried, and then a voltage is applied to cause the silver acetylide to undergo a self-decomposition explosive reaction, thereby obtaining a carbon material intermediate.

[0052] Silver acetylide is dried, for example, by heating under reduced pressure (e.g., under vacuum) at a temperature of 40°C to 100°C. This allows the solvent remaining in the reaction solution to be removed from the silver acetylide, prevents the thermal energy of the explosion from being consumed as sensible heat for the phase transition of the solvent to a gas phase, and makes the decomposition of silver acetylide more efficient. Note that silver acetylide does not decompose at this temperature.

[0053] In the self-decomposition explosion reaction of silver acetylide, silver acetylide explodes at a nanoscale, undergoing phase separation into silver and carbon, resulting in a composite material (carbon material intermediate) containing silver and carbon. During this process, silver forms nano-sized particles, which are gasified by the heat of the reaction and ejected onto the surface of the particles. Carbon has a highly aromatic structure because three acetylene-based compounds, such as acetylene molecules, easily form benzene rings. During this process, mesopores are formed in a self-organized manner. Furthermore, because silver forms nanoparticles and adheres to the carbon phase, the carbon phase after silver removal becomes a porous structure. The basic structure of the carbon phase of the composite material (carbon material intermediate) containing silver and carbon is primarily composed of several layers of graphene due to the formation of polycyclic aromatic compounds by the acetylene-based compounds. Therefore, after silver removal, the carbon material can be obtained as a carbon material with a large specific surface area and high porosity.

[0054] Here, the autolytic explosion reaction of silver acetylide is carried out by applying a voltage to silver acetylide. Compared to when silver acetylide is autolytically exploded by heating, when silver acetylide is autolytically exploded by applying a voltage, the autolytic explosion of silver acetylide is promoted while suppressing thermal deactivation of silver acetylide. This results in a porous carbon material satisfying requirements (A), (B), (C), and (D) (preferably a porous carbon material satisfying requirements (A), (B), (C), and (D) as well as at least one of requirements (E) to (G)). The conditions for applying a voltage to silver acetylide are, for example, at room temperature (25°C) and atmospheric pressure (1 atm), with a voltage of 1 to 50 kV and a heat quantity of 0.1 to 10 J applied. When sufficiently dried, silver acetylide is partially autolyzed, the autolysis proceeds in a chain reaction, resulting in the entire silver acetylide being autolyzed. The greater the amount of silver acetylide present per unit volume during decomposition, the greater the amount of energy generated during decomposition, resulting in an increase in mesopore volume.

[0055] (Cleaning Treatment Step) In the cleaning treatment step, the carbon material intermediate is brought into contact with a nitric acid solution to clean the carbon material intermediate. Silver is removed from the carbon material intermediate by cleaning the carbon material intermediate. A known method can be used for cleaning. For example, the carbon material intermediate is immersed in hot nitric acid to dissolve the silver, thereby obtaining a cleaned carbon material intermediate from which silver remaining on the surface and inside has been removed.

[0056] (Heat Treatment Step) In the heat treatment step, the purified carbon material intermediate is heat-treated in a vacuum or in an inert gas (nitrogen, argon, etc.) atmosphere at a temperature of 1900 to 2300°C (preferably 2000 to 2200°C) to obtain a heat-treated carbon material intermediate. By heat-treating the carbon material intermediate at 1900°C or higher, highly aromatic carbon crystals that will form the skeleton of the porous carbon material develop, and the pore walls become sufficiently thick, resulting in a porous carbon material that satisfies requirement (C). By heat-treating the carbon material intermediate at 2300°C or lower, a decrease in the pore volume of mesopores due to excessive carbon crystallization is suppressed, and a porous carbon material that satisfies requirements (A), (B), (C), and (D) (preferably a porous carbon material that satisfies requirements (A), (B), (C), and (D), as well as at least one of requirements (E) to (G)) is obtained.

[0057] The heat treatment step can be carried out, for example, under a reduced pressure or an inert gas atmosphere, although it is not particularly limited thereto, and is preferably carried out under an inert gas atmosphere, such as, but not limited to, nitrogen or argon.

[0058] Through the above steps, the carbon material of the present disclosure is obtained.

[0059] <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 catalyst layers 150 and 160 provided in a polymer electrolyte fuel cell 100 shown in FIG. 4, for example. FIG. 4 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. 4 includes separators 110 and 120, gas diffusion layers 130 and 140, catalyst layers 150 and 160, and an electrolyte membrane 170.

[0060] 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).

[0061] 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.

[0062] 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)

[0063] 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.

[0064] 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.

[0065] 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)

[0066] 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.

[0067] 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 increase the catalyst utilization rate in the catalyst layer 160. This can also increase the catalyst utilization rate of the polymer electrolyte fuel cell 100.

[0068] The catalyst support rate in the catalyst layer 160 is not particularly limited, and is preferably 30% by mass or more but less than 80% by mass. A catalyst support rate within this range further increases the catalyst utilization rate. Here, the catalyst support rate is expressed as the mass % of the catalyst component relative to the total mass of the catalyst-supported particles (particles in which the catalyst component is supported on a carbon material for a catalyst support). If the catalyst support rate is less than 30% by mass, it may be necessary to thicken the catalyst layer 160 to make the polymer electrolyte fuel cell 100 practical. On the other hand, if the catalyst support 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.

[0069] 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 a pore network and an electrolyte material network can be achieved, resulting in a high catalyst utilization rate. 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 be high. If the mass ratio I / C is 5.0 or more, the pore network may be disrupted by the electrolyte material. In either case, the catalyst utilization rate may be reduced.

[0070] 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.

[0071] 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.

[0072] <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.

[0073] <Method of measuring each parameter> Experimental examples of the carbon material for a catalyst support according to the present disclosure will be described. First, the method of measuring each parameter will be described.

[0074] <Nitrogen adsorption / desorption isotherm (VA ５－１０ , V.D. ５－１０、 V.A. ５－１０ -V.D. ５－１０ , V ｍａｃｒｏMeasurement of BET specific surface area)> Approximately 30 mg of a sample of the carbon material for catalyst support was weighed and vacuum dried at 200°C for 2 hours, and then nitrogen adsorption / desorption isotherms were measured using an automatic specific surface area measuring device (AUTOSORB iQ manufactured by Anton Paar Japan) with nitrogen gas as the adsorbate. ５－１０ , and VD with a pore diameter of 5 to 10 nm ５－１０ The pore volume VA was calculated by analyzing the nitrogen adsorption / desorption isotherm by the DH method using the software attached to the apparatus. ５－１０ to the pore volume VD ５－１０ Difference (VA ５－１０ -V.D. ５－１０ The amount of nitrogen adsorption V ｍａｃｒｏ For V, the difference between the adsorption amount [cc (STP) / g] when the relative pressure of the nitrogen adsorption isotherm is 0.95 and the adsorption amount [cc (STP) / g] when the relative pressure is 0.99 is calculated. ｍａｃｒｏ The BET specific surface area was calculated by the relative pressure P / P ０ was calculated by BET analysis of the nitrogen adsorption isotherm in the range of 0.05 to 0.15. Here, Fig. 1 shows an example of the pore distribution of the carbon material for a catalyst support according to the present disclosure, which is determined by the nitrogen adsorption isotherm and the nitrogen desorption isotherm.

[0075] <Measurement of the Peak Between 2θ = 26.0 ± 0.2° in the XRD Spectrum, and LcA> First, approximately 30 mg of a sample of the carbon material for a catalyst support was weighed and placed on a silicon anti-reflection plate. The reflector plate on which the sample was placed was set in an X-ray diffractometer (RINT-TTRIII, manufactured by Rigaku Corporation), and measurement was performed at room temperature (25°C) with a scan step of 0.02°, an angle sweep rate of 1° / min, and a Cu-Kα radiation source. An XRD spectrum was thus obtained. Here, FIG. 2A shows an example of an XRD spectrum (i.e., an XRD spectrum before background (BG) correction) and an XRD spectrum after background (BG) correction of the carbon material for a catalyst support of the present disclosure. Next, the background of the obtained XRD spectrum was removed, i.e., background (BG) correction was performed, and the spectrum was smoothed (see FIG. 2A). Next, in the XRD spectrum after background (BG) correction, the range of 2θ = 20° to 30° was subjected to waveform separation using a Voigt function into three peaks: Peak A with a peak position of 25.5° or less, Peak G1 with a peak position of 26.0° ± 0.2°, and Peak G2 with a peak position of 26.5° ± 0.2°, and the presence or absence of clear peaks was confirmed (see Figure 2B). Here, "clear peaks between 2θ = 26.0 ± 0.2°" refers to Peak G1 in the XRD spectrum obtained by waveform separation with a half-width of 5° or less between 2θ = 26.0 ± 0.2°, which has an intensity ratio of 0.5 or more to Peak A with a half-width of 5° or less (see Figure 2B). Note that in Figure 2B, I Ｇ１ is the intensity of peak G1, I Ａ indicates the intensity of peak A. When peak G1 satisfying the above conditions is exhibited, a clear peak is exhibited between 2θ = 26.0 ± 0.2° in the XRD spectrum before waveform separation from which the background has been removed. Furthermore, for peak A obtained by waveform separation, which is below 2θ = 25.5°, LcA was calculated using Scherrer's formula (LcA = Kλ / β cos θ). Here, the shape factor K is 1, the X-ray wavelength λ is 1.54184 Å, and β is the half-width of peak A.

[0076] <Measurement of branch diameter of three-dimensional tree-like structure> The branch diameter of a three-dimensional tree-like structure was measured by observing SEM images of five fields of view at a magnification of 100,000 times (2.5 μm × 2 μm) using a scanning electron microscope (SEM; SU-9000 manufactured by Hitachi High-Tech Corporation), measuring the branch diameter at 20 locations on each field of view, and taking the average value of the measurements for a total of 100 locations as the branch diameter value. The branch diameter to be measured is the thickness of the central portion between two adjacent branch points (the middle portion of the branched branch) of the branch of interest (see Figure 3. In Figure 3, D indicates the branch diameter per location). Here, a method for measuring branch diameter will be explained with reference to Figure 3. Figure 3 shows a branch of interest at one location. For this branch of interest, branch points BP1 and BP2 are identified. Next, the thickness (width) of the branch is measured at the position of the perpendicular bisector BC connecting the identified branch points BP1 and BP2. This measured branch thickness is the branch diameter D per location. The branch length is expressed as the distance from branch point BP1 to branch point BP2 (see Figure 3).

[0077] Example: Preparation of Porous Carbon Material for Catalyst Support (Example 1) (1) Silver Acetylide Formation Step: 25.8 g of silver nitrate was dissolved in 61.2 g of 25% by mass aqueous ammonia solution, and 42.5 g of water was added. Residual oxygen was then removed by blowing in dry nitrogen. Next, while the solution was stirred and an ultrasonic vibrator was immersed in the solution to vibrate, acetylene gas was blown into the solution at a flow rate of 18.5 mL / min for 47 minutes. This resulted in the precipitation of silver acetylide solids in the solution. The resulting precipitate was then filtered through a membrane filter. During the filtration, the precipitate was washed with pure water, and a small amount of pure water was added to impregnate the precipitate. (2) Decomposition Step: 1 g of the silver acetylide obtained in the silver acetylide formation step, while still impregnated with pure water, was placed in a 30 cm diameter stainless steel container equipped with an electrode for applying static electricity. The container was then depressurized, and the container was vacuum-dried at 30 to 40°C for 1 hour. After vacuum drying, a voltage of 0.4 J was applied at 20 kV without removing the sample from the container. The application of voltage caused a nanoscale decomposition reaction of the silver acetylide within the container, ejecting the encapsulated silver. A silver-encapsulated nanostructure with numerous ejection holes formed on its surface and interior was obtained as a carbon material intermediate (i.e., a composite material containing silver and carbon). (3) Washing Process: 10 g of the carbon material intermediate obtained in the decomposition process was immersed in 200 mL of a 30% by mass nitric acid solution and washed at 90°C for 2 hours to remove any remaining silver particles. Nitric acid was then removed from the washed carbon material intermediate using a centrifuge. To thoroughly remove any remaining nitric acid, the centrifuged carbon material intermediate was dispersed in pure water and centrifuged again to separate the solid from the liquid. This water washing process was repeated twice to remove the nitric acid, yielding a purified carbon material intermediate. The purified carbon material intermediate was then treated at 140°C in an air atmosphere for 2 hours to remove moisture and dry. (4) Heat Treatment Step The purified carbon material intermediate was subjected to a first heat treatment at 1100°C for 2 hours under a flow of argon to obtain a porous carbon material intermediate. The porous carbon material intermediate was then heated to 2000°C at a rate of 15°C / min under a flow of argon. After reaching 2000°C, the temperature was maintained at that temperature for 1 hour to perform a second heat treatment.(5) Pulverization Step The carbon material intermediate obtained in the heat treatment step was subjected to pulverization and classification simultaneously using an airflow pulverizer / classifier SJ-100GMP manufactured by Nisshin Engineering Inc. under conditions of a pulverization pressure of 0.8 MPa and a powder insertion rate of 100 g / hr.

[0078] Through the above steps, a porous carbon material was produced.

[0079] Example 2 A porous carbon material was produced in the same manner as in Example 1, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 2100°C.

[0080] Example 3 A porous carbon material was produced in the same manner as in Example 1, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 2200°C.

[0081] Example 4 A porous carbon material was produced in the same manner as in Example 1, except that in the decomposition step, the amount of silver acetylide charged in the stainless steel container was changed from 1 g to 10 g.

[0082] (Example 5) A porous carbon material was produced in the same manner as in Example 1, except that in the decomposition step, the amount of silver acetylide charged into the stainless steel container was changed from 1 g to 10 g, and in the heat treatment step, the holding temperature of the second heat treatment was changed from 2000°C to 2200°C.

[0083] Example 6 A porous carbon material was produced in the same manner as in Example 1, except that in the decomposition step, the amount of silver acetylide charged in the stainless steel vessel was changed from 1 g to 20 g.

[0084] (Example 7) A porous carbon material was produced in the same manner as in Example 1, except that in the decomposition step, the amount of silver acetylide charged in the stainless steel container was changed from 1 g to 20 g, and in the heat treatment step, the holding temperature of the second heat treatment was changed from 2000°C to 2100°C.

[0085] (Example 8) Instead of the cleaning treatment step, 10 g of the carbon material intermediate obtained by the silver acetylide decomposition step was weighed and placed in a graphite crucible, and in a Tammann furnace capable of heating up to 3000° C. in an argon atmosphere, the pressure was purged with argon gas, the pressure was reduced to 0.5 Pa, and the temperature was raised to 1400° C. at a rate of 15° C. / min. After reaching the predetermined temperature, the temperature was maintained for 10 hours to remove the silver, and a purified carbon material intermediate from which the silver had been removed was obtained. Porous carbon was produced in the same manner as in Example 1, except for this.

[0086] Example 9 A porous carbon material was produced in the same manner as in Example 8, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 2200°C.

[0087] Example 10 A porous carbon material was produced in the same manner as in Example 1, except that in the silver acetylide production step, the acetylene gas spraying time was changed from 47 minutes to 60 minutes.

[0088] Example 11 A porous carbon material was produced in the same manner as in Example 10, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 2200°C.

[0089] Comparative Example 1 A porous carbon material was produced in the same manner as in Example 1, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 1600°C.

[0090] Comparative Example 2 A porous carbon material was produced in the same manner as in Example 1, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 1800°C.

[0091] Comparative Example 3 A porous carbon material was produced in the same manner as in Example 1, except that the holding temperature in the heat treatment step was changed from 2000°C to 2400°C.

[0092] Comparative Example 4 A porous carbon material was produced in the same manner as in Example 1, except that in the heat treatment step, the holding temperature in the second heat treatment was changed from 2000°C to 2600°C.

[0093] Comparative Example 5 1 g of silver acetylide obtained in the silver acetylide production step was placed in a stainless steel container having a diameter of 30 cm while still impregnated with pure water, and the container was depressurized and vacuum-dried at 30 to 40°C for 1 hour. After vacuum-drying, the material was rapidly heated to 160 to 200°C without being removed from the container, and heated for 20 minutes. A porous carbon material was produced in the same manner as in Example 1, except for carrying out these operations.

[0094] Comparative Example 6 1 g of silver acetylide obtained in the silver acetylide production step was placed in a stainless steel container having a diameter of 30 cm while still impregnated with pure water, and the container was depressurized and vacuum-dried at 30 to 40°C for 1 hour. After vacuum drying, the product was rapidly heated to 160 to 200°C without being removed from the container, and heated for 20 minutes, and the holding temperature in the heat treatment step was changed from 2000°C to 2200°C. A porous carbon material was produced in the same manner as in Example 1, except for carrying out these operations.

[0095] (Comparative Example 7) The carbon material obtained in Comparative Example 5 was subjected to the pulverization step and then the following steps (6) and (7). (6) Contact with Carbon Dioxide (Activation) Step: Several grams of the pulverized material obtained in the pulverization step (5) was placed in an alumina boat and placed inside a tubular electric furnace, and the atmosphere inside the tubular electric furnace was replaced with carbon dioxide gas using 100% by volume of carbon dioxide gas. Heat treatment was carried out at a temperature of 1050°C for 0.5 hours while flowing carbon dioxide gas. (7) Second Pulverization Step: The pulverized material after activation was pulverized and classified in the same manner as in the pulverization step (5).

[0096] Comparative Example 8 A porous carbon material was produced in the same manner as in Comparative Example 7, except that the heat treatment time in the contact (activation) step with carbon dioxide was set to 1 hour.

[0097] Comparative Example 9 KB300 (Ketjen Black, manufactured by Lion Specialty Chemicals, EC300J) was heated to 1600°C at a rate of 15°C / min under argon flow. After reaching 1600°C, the material was held at that temperature for 1 hour for heat treatment. This produced a porous carbon material.

[0098] Comparative Example 10 KB600 (Ketjen Black, manufactured by Lion Specialty Chemicals, ECP600JD) was heated to 1600°C at a rate of 15°C / min under argon flow. After reaching 1600°C, the material was held at that temperature for 1 hour for heat treatment. This produced a porous carbon material.

[0099] Comparative Example 11 A CNovel-MH (manufactured by Toyo Tanso Co., Ltd.) was heated to 2000°C at a rate of 15°C / min under a flow of argon. After the temperature reached 2000°C, the temperature was maintained for 1 hour to carry out a heat treatment. Thus, a porous carbon material was produced.

[0100] Comparative Example 12 CNovel_MJ(4)010 (manufactured by Toyo Tanso Co., Ltd.) was heated to 2000°C at a rate of 15°C / min under argon flow. After reaching 2000°C, the temperature was maintained for 1 hour to perform a heat treatment. In this way, a porous carbon material was produced.

[0101] <Preparation of catalyst, preparation of catalyst layer, fabrication of MEA, assembly of fuel cell, and evaluation of cell performance (power generation characteristics, durability)> A catalyst for a polymer electrolyte fuel cell carrying a catalyst metal was prepared using the porous carbon material of each example 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.

[0102] (1) Preparation of a catalyst (platinum-supported carbon material) for a polymer electrolyte fuel cell. Each porous carbon material prepared in each example was dispersed in distilled water, and formaldehyde was added to this dispersion. 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 while stirring. Stirring was continued for approximately 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 catalyst particle-supported carbon material. The amount of platinum carried in this platinum-supporting carbon material was adjusted to 25 mass % with respect to the total mass of the porous carbon material and platinum particles, and was confirmed by measurement using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0103] (2) Preparation of Catalyst Layer Using the platinum-supported carbon material (Pt catalyst) prepared as described above, and using 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 platinum catalyst particle-supported carbon material, and after light stirring, the Pt catalyst was crushed by ultrasonic waves. Further, ethanol was added to adjust the total solid content concentration of the Pt catalyst and the electrolyte resin to 1.0 mass%, thereby preparing a catalyst layer ink liquid containing a mixture of the Pt catalyst and the electrolyte resin. Further, ethanol was added to each catalyst layer ink liquid thus prepared with a solid content concentration of 1.0 mass%, to prepare a catalyst layer ink liquid for spray application with a platinum concentration of 0.5 mass%, and the mass of platinum per unit area of ​​the catalyst layer (hereinafter referred to as "platinum coverage") was 0.2 mg / cm ２ The spray conditions were adjusted so that the catalyst layer ink for spray application was sprayed onto a Teflon (registered trademark) sheet, and then dried in argon at 120° C. for 60 minutes to prepare a catalyst layer.

[0104] (3) Fabrication of MEA Using the catalyst layer prepared 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, with each catalyst layer in contact with the center of the electrolyte membrane and ensuring no misalignment between them. The mixture was pressed at 120°C and 100 kg / cm² for 10 minutes, then cooled to room temperature. The Teflon (registered trademark) sheets were carefully peeled off from both the anode and cathode, resulting in a catalyst layer-electrolyte membrane assembly in which the anode and cathode catalyst layers were fixed to the electrolyte membrane. 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 component 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) by calculating the mass of the catalyst layer from the difference between the mass of the Teflon sheet with the catalyst layer before pressing and the mass of the Teflon sheet peeled off after pressing, and then calculated from the mass ratio of the catalyst layer composition.

[0105] (4) Fuel Cell Assembly and Evaluation of Fuel Cell Power Generation Characteristics The MEAs fabricated using the porous carbon materials of each Example and Comparative Example were assembled into cells and set in a fuel cell measuring device, and the fuel cell performance was evaluated according to the following procedure. Air was supplied as an oxidizing gas to the cathode side, and pure hydrogen was supplied as a reactant gas to the anode side at a back pressure of 0.05 MPa, with the pressure adjusted by a back pressure valve installed downstream of the cell so that the utilization rates were 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 65°C in a humidifier (i.e., bubbling). This set the relative humidity of the anode and cathode to approximately 100%. Under these settings, with the reactant gas supplied to the cell, the load was gradually increased until a current density of 1300 mA / cm was reached. ２ The cell terminal voltage at this point was recorded as the output voltage, and the performance of the fuel cell was evaluated using the following criteria: pass rank A or B, and fail rank C. The results are shown in Table 1. [Pass rank] A+: 1300 mA / cm ２ The output voltage at 1300mA / cm is 0.55V or more. ２ The output voltage at 1300 mA / cm is 0.50 V or more. ２ The output voltage at this point is 0.45 V or more. [Failure Rank] C: Not meeting the pass rank B.

[0106] (5) Evaluation of Durability In the above cell, while the anode was left as it was, argon gas was passed through the cathode under the same humidification conditions as above, and the cell voltage was set to 0.6 V and held for 4 seconds, and then set to 1.2 V and held for 4 seconds, repeating this cycle (repeated square-wave voltage fluctuation). After 200 cycles of this repeated square-wave voltage fluctuation, durability was investigated in the same manner as in the power generation characteristic evaluation described above, and the cells were evaluated using the following criteria: pass ranks A and B, and fail rank C. The results are shown in Table 1. [Pass rank] A+: The output voltage after 200 cycles was 98% or more of the output voltage at the first cycle. A: The output voltage after 200 cycles was 95% or more of the output voltage at the first cycle. B: The output voltage after 200 cycles was 90% or more of the output voltage at the first cycle. [Fail rank] C: The cells did not meet pass rank B.

[0107]

[0108] The above results show that the carbon materials for catalyst supports of the Examples, which satisfy the requirements of the present disclosure, are superior in power generation characteristics and durability to the carbon materials for catalyst supports of the Comparative Examples, which do not satisfy the requirements of the present disclosure.

[0109] 100 Solid polymer fuel cell 110, 120 Separator 130, 140 Gas diffusion layer 150, 160 Catalyst layer 170 Electrolyte membrane

[0110] The disclosure of Japanese Patent Application No. 2023-058262 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 support in a polymer electrolyte fuel cell, comprising a porous carbon material that satisfies the following requirements (A), (B), (C), and (D): (A) The pore volume VA of pores having a pore diameter of 5 nm or more and less than 10 nm, determined by analyzing the nitrogen adsorption isotherm using the DH (Dollimore-Heal) method ５－１０ The value is 0.1 mL / g or more and less than 0.3 mL / g. (B) The pore volume VA of pores having a pore diameter of 5 nm or more and less than 10 nm, determined by analyzing the nitrogen adsorption isotherm using the DH (Dollimore-Heal) method. ５－１０ and the pore volume VD of pores with a pore diameter of 5 nm or more and less than 10 nm, which is obtained by analyzing the nitrogen desorption isotherm using the DH (Dollimore-Heal) method. ５－１０ Difference (VA ５－１０ -VD ５－１０ ) is 0.06 mL / g or more. (C) In an XRD spectrum obtained by XRD (X-ray diffraction) measurement, there is a clear peak between diffraction angles 2θ = 26.0 ± 0.2°, and the range of diffraction angles 2θ = 20 ° to 30 ° is divided into three peaks using a Voigt function: Peak A where the diffraction angle 2θ is 25.5 ° or less, Peak G1 where the diffraction angle 2θ is in the range of 26.0 ° ± 0.2 °, and Peak G2 where the diffraction angle 2θ is in the range of 26.5 ° ± 0.2 °; and the Lc (LcA) of component A among the three peaks obtained is 0.9 nm or more. (D) In ​​the nitrogen adsorption isotherm, the amount of nitrogen adsorbed V at a relative pressure of 0.95 to 0.99 ｍａｃｒｏ is 300 to 1200 mL / g.

2. 2. The carbon material for a catalyst support of a polymer electrolyte fuel cell according to claim 1, further satisfying at least one of the following requirements (E), (F) and (G): (E) The pore volume VD of pores having a pore diameter of 5 nm or more and less than 10 nm obtained by analyzing the nitrogen desorption isotherm using the DH (Dollimore-Heal) method ５－１０ is less than 0.08 mL / g. (F) The porous carbon material has a three-dimensional dendritic structure, and the branch diameter of the three-dimensional dendritic structure is 40 to 100 nm. (G): The BET (Brunauer, Emmett, Teller) specific surface area determined by BET analysis of a nitrogen adsorption isotherm is 450 m 2 / g to 1500 m 2 / g.

3. 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 or 2.

4. A fuel cell comprising the catalyst layer for a polymer electrolyte fuel cell according to claim 3.

5. 5. The fuel cell according to claim 4, wherein the catalyst layer for a polymer electrolyte fuel cell is a catalyst layer on the cathode side.