Fuel cell catalyst carrier, fuel cell catalyst, electrode catalyst layer, and fuel cell

Abstract

The present invention provides a catalyst carrier for fuel cells, the catalyst carrier being formed of carbon black, wherein: the specific surface area is 170 m2 / g to 400 m2 / g; and the ratio (S2 / S1) of the peak area (S2)of the m / z 128 peak to the peak area (S1) of the m / z 57 peak as determined by programmed-temperature desorption gas analysis is less than 2.00.

Description

[Technical Field]

[0001] The present invention relates to a catalyst support for a fuel cell, a catalyst for a fuel cell, an electrode catalyst layer, and a fuel cell. [Background technology]

[0002] Conventionally, a fuel cell having a cell structure of separator / gas diffusion layer / electrode catalyst layer / electrolyte membrane / electrode catalyst layer / gas diffusion layer / separator has been used as a polymer electrolyte fuel cell. Here, the electrode catalyst layer is, for example, a layer in which carbon black carrying metal particles such as platinum particles is dispersed in an electrolyte.

[0003] As a method for efficiently dispersing carbon black in an electrode catalyst layer, for example, a method for producing a catalyst paste for a fuel cell has been disclosed, which includes a first step of mixing catalyst-supported carbon black, an ion exchange resin, and a solvent, and then subjecting the mixture to external shearing using an external shearing machine, a second step of subjecting the mixture to internal shearing (liquid-liquid shearing) using an internal shearing machine, and a third step of subjecting the mixture to external shearing again. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-216661 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method described in Patent Document 1, there is a limit to the crushing capacity of the device, so sufficient dispersibility may not necessarily be obtained, and there may be problems such as the inclusion of foreign matter in the crushing process and reduced productivity.

[0006] Furthermore, in fuel cells, in order to maximize the performance of expensive metal particles, it is desirable that the catalytic activity per unit mass of the metal particles in the electrode catalyst layer (reaction efficiency of the electrode catalyst layer) be high.

[0007] The present invention aims to provide a fuel cell catalyst carrier that can realize a fuel cell catalyst that can achieve both high dispersibility and high reaction efficiency. Another object of the present invention is to provide a fuel cell catalyst that can achieve both high dispersibility and high reaction efficiency. Another object of the present invention is to provide an electrode catalyst layer and a fuel cell that contain the fuel cell catalyst. [Means for solving the problem]

[0008] The present invention relates to, for example, the following: <1> ~ <8> Regarding. <1> A fuel cell catalyst carrier made of carbon black, Specific surface area is 170m 2 / g or more 400m 2 / g or less, The ratio (S2 / S1) of the peak area (S2) of the m / z 128 peak to the peak area (S1) of the m / z 57 peak, as detected by thermal desorption spectroscopy, is less than 2.00. Carrier for fuel cell catalyst. <2> When prepared as a 3% by mass slurry using N-methyl-2-pyrrolidone as a dispersion medium, the temperature was 25°C and the shear rate was 10 s -1 The viscosity of the slurry is 400 mPa·s or more and 1500 mPa·s or less. <1> The fuel cell catalyst carrier according to claim 1. <3> Hydrochloric acid absorption capacity is 39mL / 5g or more. <1> or <2> The fuel cell catalyst carrier according to claim 1. <4> DBP absorption is 200 mL / 100 g or more and 400 mL / 100 g or less. <1> ~ <3> 2. The fuel cell catalyst carrier according to claim 1, wherein the catalyst carrier is a carrier for a fuel cell. <5> <1> ~ <4> 1. A fuel cell catalyst comprising the fuel cell catalyst carrier according to any one of the above items, and at least one type of metal particles selected from the group consisting of platinum particles and platinum alloy particles, supported on the fuel cell catalyst carrier according to any one of the above items. <6> <5> An electrode catalyst layer comprising the fuel cell catalyst according to claim 1 and an electrolyte. <7> <6> A fuel cell comprising the electrode catalyst layer according to claim 1. <8> a first separator, a first gas diffusion layer, an anode electrode catalyst layer, an electrolyte membrane, a cathode electrode catalyst layer, a second gas diffusion layer, and a second separator; At least one of the anode electrode catalyst layer and the cathode electrode catalyst layer <6> 2. A fuel cell comprising the electrode catalyst layer according to claim 1. [Effects of the Invention]

[0009] According to the present invention, there is provided a fuel cell catalyst support capable of realizing a fuel cell catalyst that is capable of achieving both high dispersibility and high reaction efficiency. Also, according to the present invention, there is provided a fuel cell catalyst that is capable of achieving both high dispersibility and high reaction efficiency. Furthermore, according to the present invention, there are provided an electrode catalyst layer and a fuel cell containing the above fuel cell catalyst. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a chart showing m / z 57 and m / z 128 of the carbon black used in Example 1 detected by thermal desorption spectroscopy. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below. In this specification, unless otherwise specified, a numerical range indicated with "to" means a range "greater than or equal to" the number on the left and "less than or equal to" the number on the right. For example, "A to B" means greater than or equal to A and less than or equal to B.

[0012] <Catalyst carrier for fuel cells> The fuel cell catalyst carrier of this embodiment is made of carbon black, and is a carrier that forms a fuel cell catalyst by supporting metal particles, which will be described later.

[0013] The fuel cell catalyst carrier of this embodiment (hereinafter also simply referred to as carbon black) is 170 m 2 / g or more 400m 2 / g or less.

[0014] Specific surface area is 170m 2 If the specific surface area is less than 170 m / g, the metal particles cannot be supported with high dispersion, and the reaction efficiency (catalytic activity per unit mass of metal particles) will be low. 2 When the specific surface area is 180 m / g or more, the metal particles can be supported with high dispersion, and the reaction efficiency (catalytic activity per unit mass of the metal particles) is increased. When the supported amount is constant, the reaction efficiency can be determined by comparing the voltage at the same current value in the current-potential curve in fuel cell evaluation, and it can be said that the higher the voltage, the higher the reaction efficiency. From the viewpoint of achieving the above-mentioned effect more significantly, the specific surface area is 180 m / g or more. 2 / g or more, 190m 2 / g or more, 200m 2 / g or more, 210m 2 / g or more, 220m 2 / g or more, or 230m 2 / g or more.

[0015] Specific surface area is 400m 2 If the specific surface area exceeds 400 m / g, the catalyst paste obtained by mixing the fuel cell catalyst, electrolyte, and solvent is likely to become non-uniform, and the fuel cell catalyst is likely to form agglomerated particles in the electrode catalyst layer obtained by coating the catalyst paste. The agglomerated particles in the electrode catalyst layer can cause protrusions and potentially damage the membrane electrode assembly (MEA). Furthermore, if the fuel cell catalyst agglomerates in the electrode catalyst layer, the contact area between the gas and the metal particles decreases, reducing the reaction efficiency. In this embodiment, the specific surface area is 400 m / g. 2 / g or less, it is easy to obtain a uniform catalyst paste, an electrode catalyst layer with few agglomerated particles, and long-term reliability and reaction efficiency are improved. 2 / g or less, or 390m 2 / g or less. That is, the specific surface area is, for example, 170 to 400 m 2 / g, 170-395m 2 / g, 170-390m 2 / g, 180-400m 2 / g, 180-395m 2 / g, 180-390m 2 / g, 190-400m 2 / g, 190-395m 2 / g, 190-390m 2 / g, 200-400m 2 / g, 200-395m 2 / g, 200-390m 2 / g, 210-400m 2 / g, 210-395m 2 / g, 210-390m 2 / g, 220-400m 2 / g, 220-395m 2 / g, 220-390m 2 / g, 230-400m 2 / g, 230-395m 2 / g or 230-390m 2 / g.

[0016] The specific surface area is measured in accordance with JIS K6217-2:2017, Method A flow method (thermal conductivity measurement method).

[0017] In the carbon black of this embodiment, when the peak area of ​​the peak at m / z 57 detected by thermal desorption spectroscopy is S1 and the peak area of ​​the peak at m / z 128 is S2, the ratio (S2 / S1) is less than 2.00. Here, the ratio (S2 / S1) indicates the proportion of organic components present on the carbon black surface, for example, the proportion of polycyclic aromatic hydrocarbons to aliphatic hydrocarbons.

[0018] As explained in, for example, J. Mass Spectrom. Soc. Jpn. Vol. 54, No. 5, 2006, m / z is a symbol that represents the value on the horizontal axis of a mass spectrum. The number to the right of m / z is a dimensionless quantity obtained by dividing the mass of the target ion by the unified atomic mass unit (UMM), and then dividing that value by the charge on the ion. This number, together with m / z, indicates the peak position in the mass spectrum.

[0019] The ratio (S2 / S1) can be determined by evolved gas mass spectrometry (EGA-MS). Specifically, carbon black is placed in a gas chromatograph mass spectrometer equipped with a pyrolysis device, held at 50°C for 5 minutes in an atmospheric pressure He flow, and then heated to 800°C at 80°C / min. Mass analysis of the components desorbed by the temperature increase is performed under the following conditions, and the ratio (S2 / S1) is calculated by taking the ratio of the peak area (S1) of the m / z 57 peak to the peak area (S2) of the m / z 128 peak. Column: Ultra ALLOY-D™ (2.5 m length, 0.15 mm I.D., 0.47 mm O.D.) manufactured by Frontier Labs Gas chromatograph inlet temperature: 300℃ Column temperature: 300℃, maintained for 80 minutes Split ratio: 30:1 Column flow rate: 1.0 mL / min Ionization method: EI Measurement range: m / z=10~200

[0020] In this specification, the peak area refers to the area of ​​the part surrounded by the horizontal axis baseline, which is an intensity of 0, and the curve of each detection intensity in a graph (e.g., Figure 1) showing the relationship between temperature and each detection intensity (arbitrary unit) of a component (component corresponding to m / z 57 or m / z 128) desorbed from carbon black upon heating and detected in thermal desorption spectrometry.

[0021] As a result of extensive research to solve the above problems, the present inventors have found that, for carbon black having a large specific surface area, the surface properties analyzed by thermal desorption spectroscopy have a significant effect on the number of agglomerated particles in an electrode catalyst layer. That is, when the carbon black of this embodiment has a ratio (S2 / S1) of less than 2.00, it is possible to achieve a practically sufficiently low number of agglomerated particles while having a large specific surface area.

[0022] Trace amounts of organic components are present on the surface of carbon black due to various reactions during carbon black synthesis (e.g., pyrolysis and combustion reactions of fuel oil, pyrolysis and combustion reactions of raw materials, quenching and reaction termination by a cooling medium, etc.). These organic components are detected by thermal desorption spectroscopy. The detected peak at m / z 128 is a peak derived from polycyclic aromatic hydrocarbons, such as naphthalene, and the peak at m / z 57 is a peak derived from aliphatic hydrocarbons. In other words, a small ratio (S2 / S1) indicates a low proportion of polycyclic aromatic hydrocarbons present on the carbon black surface. According to the findings of the present inventors, in carbon black with a high specific surface area, the contribution of surface organic components to dispersibility is significant. Furthermore, a low proportion of strongly hydrophobic polycyclic aromatic hydrocarbons present on the surface increases affinity and wettability with the dispersion medium, improving dispersibility. Note that the organic components inferred from the peaks detected by thermal desorption spectroscopy are completely different from the surface functional groups imparted to conventional carbon black.

[0023] In this embodiment, by setting the ratio (S2 / S1) to less than 2.00, even carbon black with a well-developed structure and a large specific surface area is less likely to aggregate in the electrode catalyst layer, thereby preventing a decrease in reaction efficiency and reliability due to aggregated particles. Furthermore, a uniform electrode catalyst layer is easily obtained, local variations in catalytic efficiency are suppressed, and a fuel cell with high output voltage and long life is easily obtained.

[0024] In this embodiment, the specific surface area of ​​the carbon black is 170 m 2 / s, it is desirable that the ratio (S2 / S1) be less than 2.00 in order to sufficiently reduce the number of agglomerated particles in the electrode catalyst layer. From the viewpoint of obtaining the above-mentioned effect more significantly, the ratio (S2 / S1) may be less than 1.80, less than 1.60, less than 1.40, less than 1.20, less than 1.00, less than 0.80, less than 0.60, or less than 0.50.

[0025] The lower limit of the ratio (S2 / S1) is not particularly limited, but from the viewpoint of excellent productivity, the ratio (S2 / S1) may be 0.05 or more, 0.10 or more, or 0.20 or more. That is, the ratio (S2 / S1) is, for example, 0.05 or more and less than 2.00, 0.05 or more and less than 1.80, 0.05 or more and less than 1.60, 0.05 or more and less than 1.40, 0.05 or more and less than 1.20, 0.05 or more and less than 1.00, 0.05 or more and less than 0.80, 0.05 or more and less than 0.60, 0.05 or more and less than 0.50, 0.10 or more and less than 2.00, 0.10 or more and less than 1.80, 0.10 or more and less than 1.60, 0.10 or more and less than 1.4 ...80, 0.10 or more and less than 1.6 It may be 0.10 or more and less than 1.20, 0.10 or more and less than 1.00, 0.10 or more and less than 0.80, 0.10 or more and less than 0.60, 0.10 or more and less than 0.50, 0.20 or more and less than 2.00, 0.20 or more and less than 1.80, 0.20 or more and less than 1.60, 0.20 or more and less than 1.40, 0.20 or more and less than 1.20, 0.20 or more and less than 1.00, 0.20 or more and less than 0.80, 0.20 or more and less than 0.60, or 0.20 or more and less than 0.50.

[0026] The carbon black of this embodiment preferably has a hydrochloric acid absorption capacity of 39 mL / 5 g or more. The hydrochloric acid absorption capacity is the amount of hydrochloric acid that can be retained on the particle surface of the carbon black and in the voids formed by the structure and agglomerates (secondary aggregation of the structure), and is an index for evaluating the degree of structure and agglomerate development. When carbon black having a structure in which the structure and agglomerates are fully developed is used as a fuel cell catalyst carrier, voids are formed in the electrode catalyst layer through which hydrogen gas and protons can efficiently diffuse. This makes it easier to obtain good fuel cell characteristics.

[0027] Here, the term "carbon black structure" refers to the structure of connected primary particles. The carbon black structure develops into a complex, intertwined shape as the primary particles become smaller. The degree of development of the structure and agglomerates (secondary aggregation of the structure) of carbon black varies greatly depending on factors such as the thermal history during synthesis (e.g., thermal history resulting from the thermal decomposition and combustion reaction of fuel oil, the thermal decomposition and combustion reaction of raw materials, rapid cooling by a cooling medium, and reaction termination), and the frequency of collisions between primary particles.

[0028] The hydrochloric acid absorption capacity can be measured according to JIS K1469: 2003. Specifically, it is determined by adding hydrochloric acid little by little to 5 g of carbon black placed in an Erlenmeyer flask while shaking, and measuring the amount of hydrochloric acid required to form a single lump.

[0029] In the carbon black of this embodiment, the hydrochloric acid absorption may be 39 mL / 5 g or more, 40 mL / 5 g or more, or 41 mL / 5 g or more, from the viewpoint of more significantly achieving the above-mentioned effect.

[0030] In the carbon black of this embodiment, if the hydrochloric acid absorption capacity becomes significantly large, excessive structure development will result in a high slurry viscosity, as described below. Therefore, the hydrochloric acid absorption capacity of the carbon black of this embodiment is preferably such that the slurry viscosity, as described below, is 1500 mPa s or less. In other words, the upper limit of the preferred range of the hydrochloric acid absorption capacity of the carbon black of this embodiment may be determined by the slurry viscosity, as described below.

[0031] In the carbon black of this embodiment, the hydrochloric acid absorption amount may be, for example, 49 mL / 5 g or less, or 48 mL / 5 g or less, from the viewpoint that the slurry viscosity described below is likely to be 1500 mPa·s or less. That is, the carbon black of this embodiment may have a hydrochloric acid absorption capacity of, for example, 39 to 49 mL / 5g, 39 to 48 mL / 5g, 40 to 49 mL / 5g, 40 to 48 mL / 5g, 41 to 49 mL / 5g, or 41 to 48 mL / 5g.

[0032] The carbon black of this embodiment preferably has a slurry viscosity of 400 mPa·s or more and 1500 mPa·s or less.

[0033] In this specification, the term "slurry viscosity" refers to the viscosity of a slurry in which 3% by mass of carbon black is dispersed in N-methyl-2-pyrrolidone as a dispersion medium. More specifically, 3% by mass of carbon black and 97% by mass of N-methyl-2-pyrrolidone as a dispersion medium were kneaded for 30 minutes at a rotation-revolution type mixer (Thinky Corporation's "Awatori Rentaro ARV-310") at a rotation speed of 2000 rpm to obtain a slurry. The viscosity of this slurry at 25°C was measured using a viscoelasticity measuring device (Anton Paar's "MCR102", using a 30 mm diameter, 3° angle cone plate, and a 1 mm gap) at a shear rate of 0.01 s -1 From 100s -1 The shear rate was changed to 10 s -1 The viscosity measured in this way is 25°C and a shear rate of 10 s -1 The viscosity at this point is defined as the slurry viscosity.

[0034] Slurry viscosity is an indicator of the ease of dispersion and stability of carbon black under shear. When carbon black with a slurry viscosity of 400 mPa·s or more and 1500 mPa·s or less is used as a fuel cell catalyst support, the catalyst paste, which is a mixture of the fuel cell catalyst, electrolyte, and solvent, tends to become uniform. This makes it difficult for the fuel cell catalyst to form agglomerated particles in the electrode catalyst layer obtained by coating the catalyst paste. This makes it easier to achieve better long-term reliability and reaction efficiency.

[0035] The carbon black of this embodiment may have a slurry viscosity of 450 mPa·s or more or 500 mPa·s or more, from the viewpoint of more significantly achieving the above-mentioned effects, and may have a slurry viscosity of 1400 mPa·s or less or 1300 mPa·s or less, from the viewpoint of more significantly achieving the above-mentioned effects. That is, the slurry viscosity of the carbon black of this embodiment may be, for example, 400 to 1500 mPa·s, 400 to 1400 mPa·s, 400 to 1300 mPa·s, 450 to 1500 mPa·s, 450 to 1400 mPa·s, 450 to 1300 mPa·s, 500 to 1500 mPa·s, 500 to 1400 mPa·s, or 500 to 1300 mPa·s.

[0036] The viscosity of the carbon black slurry may be adjusted appropriately depending on the average primary particle size of the carbon black, the surface properties of the carbon black, the shape of the carbon black structure, and the like.

[0037] The DBP absorption of the carbon black of this embodiment may be, for example, 200 mL / 100 g or more, 210 mL / 100 g or more, or 220 mL / 100 g or more, and may be, for example, 400 mL / 100 g or less, 390 mL / 100 g or less, or 380 mL / 100 g or less. That is, the DBP absorption amount of the carbon black of this embodiment may be, for example, 200 to 400 mL / 100 g, 200 to 390 mL / 100 g, 200 to 380 mL / 100 g, 210 to 400 mL / 100 g, 210 to 390 mL / 100 g, 210 to 380 mL / 100 g, 220 to 400 mL / 100 g, 220 to 390 mL / 100 g, or 220 to 380 mL / 100 g.

[0038] DBP absorption is an index used to evaluate the ability of carbon black to absorb dibutyl phthalate (DBP) into the particle surfaces and voids formed by the structure. In this specification, DBP absorption is a value measured according to Method B of JIS K6221 and converted into a value equivalent to JIS K6217-4:2008 using the following formula (a): DBP absorption amount = (A-10.974) / 0.7833 …(a) [In the formula, A represents a value corresponding to the DBP absorption amount measured according to the method described in JIS K6221.]

[0039] Carbon black with a well-developed structure has a high DBP absorption due to the increased number of necks formed by the fusion of primary particles and the increased voids formed between particles. If the DBP absorption is too low, the viscosity of the catalyst paste obtained by mixing the fuel cell catalyst, electrolyte, and solvent may be too low, making it difficult to apply shear force during mixing and making it difficult to achieve good dispersibility. On the other hand, if the DBP absorption is too high, the viscosity of the catalyst paste may be too high, making it difficult to achieve good dispersibility. In other words, when the DBP absorption is within the above-mentioned preferred range, it becomes easier to obtain a uniform catalyst paste with appropriate viscosity, making it easier to obtain an electrode catalyst layer with fewer agglomerated particles, and tends to improve long-term reliability and reaction efficiency.

[0040] Furthermore, when carbon black with a moderately developed structure is used as a fuel cell catalyst carrier, voids are formed in the electrode catalyst layer through which hydrogen gas and protons can diffuse efficiently. This facilitates the achievement of good fuel cell performance. From this perspective, the DBP absorption amount is preferably within the above range.

[0041] The average primary particle size of the carbon black of this embodiment may be, for example, less than 30 nm, less than 29 nm, less than 28 nm, less than 27 nm, less than 26 nm, or less than 25 nm, and may be, for example, 10 nm or more. According to the findings of the present inventors, when two types of carbon black that satisfy the above ratio (S2 / S1) are compared, with similar specific surface areas but different average primary particle sizes, the metal particles formed on the carbon black with a smaller particle size are smaller. This is thought to be because, while large-particle-size carbon black has a higher specific surface area due to its porous surface, small-particle-size carbon black can achieve a high specific surface area even with a relatively smooth surface, increasing the surface area in contact with the dispersion medium and increasing the reaction sites for forming metal particles.

[0042] Conventionally, it has been difficult to obtain a smooth electrode catalyst layer from carbon black used in fuel cell catalyst supports when the average primary particle diameter is small (for example, less than 30 nm). However, the carbon black of the present embodiment satisfies the above-mentioned ratio (S2 / S1), and therefore a smooth electrode catalyst layer can be obtained even when the average primary particle diameter is small (for example, less than 30 nm), and fuel cells using it can exhibit high output voltage and long life.

[0043] The average primary particle size of carbon black can be determined by measuring the primary particle sizes of 100 or more carbon black particles randomly selected from a 50,000x magnification image taken with a transmission electron microscope (TEM) and calculating the average value. Primary particles of carbon black have a small aspect ratio and are close to being spherical, but are not perfectly spherical. Therefore, in this embodiment, the primary particle size of carbon black is determined as the largest line segment connecting two points on the periphery of a primary particle in a TEM image.

[0044] The ash content of the carbon black of this embodiment may be, for example, 0.05% by mass or less, 0.03% by mass or less, or 0.02% by mass or less. The ash content can be measured in accordance with JIS K1469:2003, and can be reduced, for example, by classifying the carbon black using a device such as a dry cyclone.

[0045] The sulfur content of the carbon black of this embodiment may be, for example, 50 ppm by mass or less. The sulfur content in the carbon black is present on the surface of the carbon black as acidic functional groups such as sulfate groups. When the sulfur content is 50 ppm by mass or less, the generation of gases such as SOx due to electrochemical reactions inside the battery is suppressed, and deterioration of fuel cell performance caused by such gases is significantly suppressed. The sulfur content of the carbon black can be calculated by burning the carbon black in an oxygen stream, absorbing the generated combustion gas into hydrogen peroxide water, and measuring it by ion chromatography.

[0046] The method for producing carbon black according to the present embodiment is not particularly limited. For example, carbon black can be obtained by supplying a raw material such as a hydrocarbon through a nozzle installed upstream of a reactor, generating carbon black through a thermal decomposition reaction and / or a combustion reaction, and collecting the carbon black through a bag filter directly connected downstream of the reactor.

[0047] The raw materials used are not particularly limited, and include gaseous hydrocarbons such as acetylene, methane, ethane, propane, ethylene, propylene, and butadiene, and oily hydrocarbons such as toluene, benzene, xylene, gasoline, kerosene, light oil, and heavy oil. Among these, acetylene, which contains few impurities, is preferred. Acetylene generates a larger heat of decomposition than other raw materials, allowing for higher temperatures in the reactor. This allows carbon black nucleation to prevail over particle growth via addition reactions, thereby reducing the primary particle size of the carbon black. Furthermore, the inventors conducted extensive research to control the surface properties of carbon black and found that using multiple raw materials and heating the raw materials before feeding them into the reactor is effective. In conventional production methods, carbon black produced through high-temperature and low-temperature parts of the reactor is mixed, resulting in significant variation in properties. However, using multiple raw materials ensures a uniform temperature in the reactor and a uniform reaction history for the pyrolysis and combustion processes, which is believed to reduce the proportion of polycyclic aromatic hydrocarbons present on the carbon black surface. It is also believed that heating the raw materials promotes mixing of the multiple raw materials, allowing for the formation of a more uniform temperature field. It is preferable to mix the multiple raw materials before supplying them to the reactor. When using oily hydrocarbons, it is preferable to gasify them by heating before supplying them. The heating method is not particularly limited, and for example, the tank and transport piping can be heated by heat exchange with a heat medium.

[0048] In addition, it is preferable to supply oxygen, hydrogen, nitrogen, steam, or the like to the reactor in addition to the raw material carbon source. These non-raw material gases promote gas agitation in the reactor and increase the frequency of collisions and fusion between primary particles of carbon black produced from the raw materials. Therefore, the use of non-raw material gases tends to develop the carbon black structure and increase the DBP absorption amount. Oxygen is preferably used as the non-raw material gas. The use of oxygen burns part of the raw material, raising the temperature in the reactor, making it easier to obtain carbon black with a small particle size and a high specific surface area. Multiple gases can also be used as non-raw material gases. The non-raw material gases are preferably supplied upstream of the reactor, preferably from a nozzle separate from the raw material. This allows for efficient agitation of the raw material, which is also supplied upstream, and facilitates the development of the structure.

[0049] In conventional carbon black production, a cooling medium such as water may be introduced from the downstream part of the reactor to stop the thermal decomposition and combustion reaction of the raw material. However, this does not have any effect on the development of the structure and may have an adverse effect on the surface properties. Therefore, in this embodiment, it is preferable not to introduce a cooling medium from the downstream part of the reactor.

[0050] <Fuel cell catalyst> The fuel cell catalyst of this embodiment is a fuel cell catalyst carrier (carbon black) having at least one metal particle selected from the group consisting of platinum particles and platinum alloy particles supported on the surface thereof. The metal particles are preferably firmly supported on the carrier surface.

[0051] The average particle size of the metal particles may be, for example, 2 nm or more. When the average particle size is 2 nm or more, dissolution, corrosion, etc. during potential fluctuations are suppressed. The average particle size of the metal particles may be, for example, 5 nm or less. When the average particle size is 5 nm or less, a sufficient active surface area is ensured, making it easier to obtain better fuel cell characteristics. The particle size of the metal particles is defined as the length of the longest line segment connecting two points on the periphery of the metal particle when observed with a transmission electron microscope. The average particle size of the metal particles can be determined by measuring the particle sizes of 1,000 metal particles and calculating the average value.

[0052] Platinum particles are particles made of platinum, while platinum alloy particles are particles made of an alloy of platinum and another metal (hereinafter referred to as an alloying metal).

[0053] Examples of alloy-forming metals include palladium, rhodium, iridium, ruthenium, iron, titanium, nickel, cobalt, gold, silver, copper, chromium, manganese, molybdenum, tungsten, aluminum, silicon, rhenium, zinc, tin, etc. Among these, in the case of catalysts for direct methanol fuel cells, platinum-ruthenium alloys are preferred because they are effective in preventing carbon monoxide poisoning.

[0054] The composition of the alloy is not particularly limited, but may be, for example, 30 to 90 mass % platinum and 10 to 70 mass % alloying metal.

[0055] The amount of metal particles supported in the fuel cell catalyst may be, for example, 5 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of carbon black.

[0056] The method for supporting metal particles on carbon black is not particularly limited, and may be, for example, the following method: Carbon black is suspended in water to form a slurry, to which a metal source is added to form mixed solution A, to which 10 equivalents of sodium borohydride relative to the metal are added, causing metal particles to precipitate on the surface of the carbon black, followed by filtration, washing, and drying to obtain a fuel cell catalyst.

[0057] Among the metal sources, examples of the platinum source include an aqueous solution of hexachloroplatinum, an aqueous solution of hexahydroxoplatinum, and an aqueous solution of dinitrodiammineplatinum.

[0058] Among the metal sources, an example of an alloy-forming metal source is an aqueous solution of ruthenium (III) trichloride.

[0059] When depositing metal particles, a pH adjuster such as an aqueous solution of sodium hydroxide may be added as needed.

[0060] After the metal particles are supported on the carbon black, the fuel cell catalyst may be subjected to an annealing treatment before being used in the fuel cell. The annealing treatment can be carried out by heating to 800 to 1000°C in an inert atmosphere such as argon gas or nitrogen gas, or in a reducing atmosphere such as hydrogen gas.

[0061] Evaluation of the fuel cell catalyst of this embodiment can be performed, for example, in the case of a polymer electrolyte fuel cell, as follows. The fuel cell catalyst is mixed with a Nafion solution, and alcohol is added to form a paste. This paste is then applied to one side of carbon paper and dried to form an electrode catalyst layer (evaluation electrode). Next, the electrode to be evaluated is placed on one side of a Nafion membrane (perfluorosulfonic acid electrolyte membrane), and a known electrode is placed on the other side. These are then thermocompressed in a hot press at 130°C to obtain a membrane-electrode assembly (MEA). The MEA is sandwiched between a separator and a current collector to complete a single cell, and the fuel cell can be evaluated by connecting an electronic load device and a gas supply device. The above evaluation can also be performed more easily using a commercially available single fuel cell evaluation device.

[0062] <Electrode catalyst layer> The electrode catalyst layer of this embodiment contains the above fuel cell catalyst and an electrolyte.

[0063] The electrolyte is not particularly limited, and any electrolyte used in known fuel cells can be used without particular limitation. As the electrolyte, a perfluorosulfonic acid polymer is preferably used, such as Nafion (manufactured by DuPont), Aciplex (manufactured by Asahi Kasei Corporation), or Flemion (manufactured by Asahi Glass Co., Ltd.).

[0064] The thickness of the electrode catalyst layer may be, for example, 5 μm or more, or 10 μm or more, and may be, for example, 50 μm or less, 40 μm or less, or 30 μm or less. That is, the thickness of the electrode catalyst layer may be, for example, 5 to 50 μm, 5 to 40 μm, 5 to 30 μm, 10 to 50 μm, 10 to 40 μm, or 10 to 30 μm.

[0065] <Fuel cell> The fuel cell of this embodiment includes the electrode catalyst layer of this embodiment described above.

[0066] In this embodiment, the configuration other than the electrode catalyst layer is not particularly limited, and may be the same as that of a known fuel cell.

[0067] The fuel cell of the present embodiment may include, for example, a first separator, an anode electrode catalyst layer, an electrolyte membrane, a cathode electrode catalyst layer, and a second separator, or may include a first separator, a first gas diffusion layer, an anode electrode catalyst layer, an electrolyte membrane, a cathode electrode catalyst layer, a second gas diffusion layer, and a second separator.

[0068] In the fuel cell of this embodiment, it is sufficient that either the anode electrode catalyst layer or the cathode electrode catalyst layer is the electrode catalyst layer of this embodiment described above.

[0069] The first separator and the second separator may be separators having gas flow channels. The first separator and the second separator may be separators used in known fuel cells. The first separator and the second separator may be made of a material such as stainless steel, aluminum alloy, or carbon.

[0070] The first gas diffusion layer and the second gas diffusion layer may be gas diffusion layers used in known fuel cells, and may be, for example, layers in which a coating layer (e.g., a coating layer made of a carbon material and a water-repellent material) is provided on the surface of a substrate (e.g., carbon fiber paper, woven fabric, nonwoven fabric, etc.).

[0071] One of the anode electrode catalyst layer and the cathode electrode catalyst layer may be the electrode catalyst layer of the present embodiment described above, and the other may be an electrode catalyst layer other than the above. Alternatively, both the anode electrode catalyst layer and the cathode electrode catalyst layer may be the electrode catalyst layer of the present embodiment described above. The electrode catalyst layer other than the electrode catalyst layer of the present embodiment may be an electrode catalyst layer used in a known fuel cell.

[0072] The electrolyte membrane may be any electrolyte membrane used in known fuel cells. The electrolyte membrane is preferably made of a perfluorosulfonic acid polymer, such as Nafion (manufactured by DuPont), Aciplex (manufactured by Asahi Kasei Corporation), or Flemion (manufactured by Asahi Glass Co., Ltd.).

[0073] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. [Example]

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] Example 1 <Carbon black production> The raw material, acetylene, was injected at 12 Nm from a nozzle installed upstream of a carbon black reactor (furnace length 6 m, furnace diameter 0.65 m). 3 / h, toluene 32 kg / h, oxygen 21 Nm as a gas other than the raw material 3 / h to produce carbon black, which was then collected in a bag filter installed downstream of the reactor. The carbon black was then passed through a dry cyclone device and an iron-removing magnet before being collected in a tank. The acetylene, toluene, and oxygen were heated to 115°C before being fed to the reactor. The following physical properties of the resulting carbon black were measured. The evaluation results are shown in Tables 1 and 2.

[0076] (1) Specific surface area Measurement was performed according to JIS K6217-2:2017, Method A Flow Method (thermal conductivity measurement method). (2) Ratio (S2 / S1) measured by thermal desorption spectroscopy 2 to 5 mg of carbon black was weighed into a sample cup and placed in a gas chromatograph mass spectrometer (Shimadzu Corporation, "QP-2010") equipped with a pyrolysis apparatus (Frontier Labs, "PY-2020iD"). After being held at 50°C for 5 minutes in an atmospheric pressure He flow, the temperature was raised to 800°C at 80°C / min, and the desorbed components were subjected to mass spectrometry under the following conditions: The peak area ratio (S2 / S1) was calculated by taking the ratio of the peak areas of m / z 128 and m / z 57. Figure 1 shows a chart of m / z 57 and m / z 128 detected by thermal desorption spectrometry for the carbon black of Example 1. Column: Frontier Labs Ultra ALLOY-D™, 2.5 m long, 0.15 m I.D., 0.47 mm O.D. Gas chromatograph inlet temperature: 300℃ Column temperature: 300℃, maintained for 80 minutes Split ratio: 30:1 Column flow rate: 1.0 mL / min Ionization method: EI Mass range: m / z=10~200 (3) Hydrochloric acid absorption capacity Measurement was performed in accordance with JIS K1469-4:2003. (4) DBP absorption The value measured by the method described in JIS K6221, Method B was converted into a value corresponding to JIS K6217-4:2008 using the above formula (a). (5) Average primary particle diameter The primary particle diameters of 100 or more randomly selected carbon black particles were measured from a 50,000x magnification image taken with a transmission electron microscope, and the average value was calculated. (6)Ash content Measurement was performed in accordance with JIS K1469:2003. (7) Iron content The sample was pretreated by acid decomposition according to JIS K0116:2014, and then measured by high-frequency inductively coupled plasma mass spectrometry. (8) Evaluation of slurry viscosity Three parts by mass of carbon black and 97 parts by mass of N-methyl-2-pyrrolidone (Kanto Chemical Co., Ltd.) as a dispersion medium were mixed in a planetary centrifugal mixer (Thinky Corporation's "Awatori Rentaro ARV-310") at a rotation speed of 2000 rpm for 30 minutes to prepare a carbon black slurry. The viscosity of this slurry at 25°C was evaluated using a viscoelasticity measuring device (Anton Paar's "MCR102," using a 30 mm diameter, 3° angle cone plate, and a 1 mm gap). The shear rate was 0.01 s -1 From 100s -1 The shear rate was changed to 10 s -1 The viscosity was measured at 100°C. The measurement results are shown in Table 2. (9) Sulfur content A 1g sample of carbon black was precisely weighed into a magnetic boat and inserted into the reaction tube of a combustion absorption apparatus heated to 1300°C. An absorption bottle containing an absorption solution (3.5ml of hydrogen peroxide diluted with pure water to 1L) was connected, oxygen gas was passed through, and combustion gas was passed through the absorption bottle. The resulting absorption solution was introduced into an ion chromatography analyzer, the peak area of ​​sulfate ions was measured, and the sulfur content of the sample was calculated based on a calibration curve prepared in advance from a sulfate ion standard solution.

[0077] <Production of fuel cell catalysts> Platinum particles were supported on carbon black by the following method. A platinum solution of 1,000 g (46 g of platinum content) of dinitrodiammine platinum nitrate solution with a platinum concentration of 4.6% by mass was prepared. 46 g of carbon black was immersed in this platinum solution and stirred. 100 mL of 100% ethanol was added as a reducing agent. The mixture was then stirred and mixed under reflux for 7 hours to support the platinum particles on the carbon black. After filtration and drying, a fuel cell catalyst was obtained with a platinum particle loading of 50 parts by mass per 100 parts by mass of carbon black. The particle sizes of 1,000 platinum particles were measured for the resulting fuel cell catalyst using a TEM (magnification: 100,000 times) and the average particle size was calculated. The evaluation results are shown in Table 2. The resulting fuel cell catalyst was annealed by holding it in 100% hydrogen gas at 900°C for 1 hour.

[0078] <Production of electrode catalyst layer> 0.1 g of a 5 mass % Nafion solution (manufactured by Sigma-Aldrich, Nafion 1100EW) and 0.6 g of 2-propanol were added to 0.05 g of the fuel cell catalyst and mixed to prepare a catalyst paste. 2 The catalyst paste was applied to carbon paper so that the surface area was 100 μm and dried at room temperature to obtain an electrode catalyst layer. The surface of the obtained electrode catalyst layer was observed using an SEM (magnification 1000x), and the number of agglomerated particles of 10 μm or more present in an area of ​​100 μm length x 100 μm width was determined. The size of the agglomerated particles was calculated from the diameter of the smallest circle that could enclose each agglomerated particle. The results are shown in Table 3.

[0079] <Fuel cell manufacturing> A fuel cell was produced using the electrode catalyst layer obtained above as a cathode electrode. First, an anode electrode was fabricated in the same manner as in the above <Fabrication of Electrode Catalyst Layer>, except that the fuel cell catalyst was changed to "TEC10E50E" (Tanaka Kikinzoku Kogyo Co., Ltd.). The Nafion membrane, cathode electrode, and anode electrode were stacked so that the cathode electrode and anode electrode faced each other with the Nafion membrane in between, and pressed at 130°C and 9.8 MPa for 3 minutes to obtain an MEA. Next, a separator, gasket, and end plate were stacked on the top and bottom surfaces of the MEA, respectively, in that order, and secured in place with four screws to produce a fuel cell.

[0080] For the obtained fuel cell, hydrogen gas with a relative humidity of 100% was supplied to the anode electrode at 1 L / min, and oxygen gas with a relative humidity of 100% was supplied to the cathode electrode at 1 L / min at 70°C. 2 The device was operated at a constant current of 0 mA / cm and the initial output voltage was measured. 2 and 500mA / cm 2 The voltage was then repeatedly changed between 500mA / cm and 500mA / cm for 30,000 cycles. 2 The output voltage was measured after the durability test using a constant current drive of 1000V. The evaluation results are shown in Table 3.

[0081] Examples 2 and 3 The oxygen supply in the production of carbon black is 22 Nm 3 / h (Example 2) or 24 Nm 3 / h (Example 3), carbon black was produced and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0082] Example 4 Carbon black was produced and evaluated in the same manner as in Example 1, except that in <Production of Carbon Black>, the temperature during toluene supply was changed to 100°C. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0083] Example 5 Carbon black was produced and evaluated in the same manner as in Example 1, except that in <Production of Carbon Black>, the temperature during acetylene supply was changed to 85°C and the temperature during toluene supply was changed to 100°C. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0084] Example 6 Carbon black was produced and evaluated in the same manner as in Example 1, except that in <Production of Carbon Black>, the temperature during acetylene supply was changed to 85°C and the temperature during toluene supply was changed to 85°C. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0085] Example 7 Acetylene supply volume: 13 Nm 3 / h, toluene supply rate 35 kg / h, oxygen supply rate 26 Nm 3 / h, respectively. Carbon black was produced and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0086] Example 8 Carbon black was produced and evaluated in the same manner as in Example 1, except that 32 kg / h of benzene heated to 115°C was supplied instead of toluene. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0087] (Comparative Example 1) Oxygen supply: 20Nm 3 Carbon black was produced and evaluated in the same manner as in Example 1, except that the heating rate was changed to 1 / h. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0088] (Comparative Example 2) Acetylene supply volume: 11 Nm 3 / h, toluene supply rate 30 kg / h, oxygen supply rate 24 Nm 3 Carbon black was produced and evaluated in the same manner as in Example 1, except that the heating rate was changed to 1 / h. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0089] Example 9 The carbon black obtained in Comparative Example 1 was subjected to an oxidation treatment in an electric furnace heated to 720°C to obtain carbon black. The obtained carbon black was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0090] Example 10 Carbon black was produced and evaluated in the same manner as in Example 1, except that the classification conditions of the dry cyclone device were changed to adjust the ash content. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0091] Example 11 Carbon black was produced and evaluated in the same manner as in Example 1, except that the magnetic flux density conditions of the iron-removing magnet were changed to adjust the iron content. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0092] (Comparative Example 3) Acetylene supply volume: 38 Nm 3 / h, toluene was not supplied, and the oxygen supply was changed to 10 Nm 3 Carbon black was produced and evaluated in the same manner as in Example 1, except that the heating rate was changed to 1 / h. The results are shown in Tables 1 and 2. Furthermore, using the obtained carbon black, a fuel cell catalyst, an electrode catalyst layer, and a fuel cell were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0093] [Table 1]

[0094] [Table 2]

[0095] [Table 3]

[0096] As described above, by using the carbon black of the examples as a support for a fuel cell catalyst, aggregation in the electrode catalyst layer was suppressed, resulting in a high-performance fuel cell. These results confirmed that the fuel cell catalyst of the examples can achieve both high dispersibility and high reaction efficiency. [Industrial Applicability]

[0097] The fuel cell catalyst carrier of the present invention can be suitably used to realize a fuel cell catalyst that can achieve both high dispersibility and high reaction efficiency. Furthermore, the fuel cell catalyst of the present invention can achieve both high dispersibility and high reaction efficiency and can be suitably used as a fuel cell catalyst.

Claims

1. A fuel cell catalyst carrier made of carbon black, Specific surface area is 170m ２ / g or more 400m ２ / g or less, The peak area (S １ ) to the peak area of ​​the m / z 128 peak (S ２ ) ratio (S ２ / S １ ) is less than 2.00; Carrier for fuel cell catalyst.

2. When prepared as a 3% by mass slurry using N-methyl-2-pyrrolidone as a dispersion medium, the －１ 2. The fuel cell catalyst carrier according to claim 1, wherein the slurry has a viscosity of 400 mPa·s or more and 1500 mPa·s or less.

3. 2. The fuel cell catalyst carrier according to claim 1, which has a hydrochloric acid absorption capacity of 39 mL / 5 g or more.

4. 2. The fuel cell catalyst carrier according to claim 1, wherein the DBP absorption amount is 200 mL / 100 g or more and 400 mL / 100 g or less.

5. A fuel cell catalyst comprising the fuel cell catalyst carrier according to any one of claims 1 to 4, and at least one type of metal particles selected from the group consisting of platinum particles and platinum alloy particles supported on the carrier.

6. An electrode catalyst layer comprising the fuel cell catalyst according to claim 5 and an electrolyte.

7. A fuel cell comprising the electrode catalyst layer according to claim 6.

8. a first separator, a first gas diffusion layer, an anode electrode catalyst layer, an electrolyte membrane, a cathode electrode catalyst layer, a second gas diffusion layer, and a second separator; A fuel cell, wherein at least one of the anode electrode catalyst layer and the cathode electrode catalyst layer is the electrode catalyst layer according to claim 6.

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