catalyst

Abstract

To provide a catalyst that contains an organic nitrogen compound and can prevent cracking of a catalyst layer.SOLUTION: A catalyst contains a metal particle with oxygen reduction activity, a carrier, an additive, and a binder. The metal particle is supported on the carrier. The additive is at least one organic nitrogen compound. The binder is a polyelectrolyte with an ion exchange group. The binder weight is 0.85 or more relative to the carrier weight.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to catalysts. [Background technology]

[0002] Various studies have been conducted on catalysts for electrochemical oxygen reduction. Patent Document 1 discloses an electrochemical oxygen reduction catalyst containing platinum-containing nanoparticles and at least one selected from the group consisting of a melamine compound, a thiocyanuric acid compound, and a polymer containing the melamine compound or the thiocyanuric acid compound as a monomer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 221156 Summary of the Invention [Problem to be solved by the invention]

[0004] When an organic nitrogen compound is added as an additive to a catalyst having oxygen reduction activity in order to improve the catalytic performance, cracks may occur in the catalyst layer.

[0005] The present disclosure has been made in view of the above-mentioned circumstances, and has as its main object to provide a catalyst that contains an organic nitrogen compound and that can suppress the occurrence of cracks in the catalyst layer. [Means for solving the problem]

[0006] In the present disclosure, there is provided a catalyst comprising metal particles having oxygen reduction activity, a carrier, an additive, and a binder, the metal particles are supported on the support, the additive is at least one organic nitrogen compound; the binder is a polymer electrolyte having an ion exchange group, The catalyst is characterized in that the weight ratio of the binder to the weight of the carrier is 0.85 or more.

[0007] In the catalyst of the present disclosure, the organic nitrogen compound may be a monomer represented by the following general formula (1), or a polymer containing at least a portion of the monomer:

[0008] [ka]

[0009] [In general formula (1), R1, R2, and R3 each represent a hydrogen atom, a halogen atom, or a nitrile group, an amide group, an imine group, an amino group, a thiol group, a hydroxyl group, a sulfo group, a carboxylic acid group, a phosphate group, a ketone group, an aldehyde group, an ester group, an alkoxy group, a phenol group, a cyclopentyl group, a cyclohexyl group, an alkylamino group having 1 to 10 carbon atoms, an alkylsulfonic acid group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, a hydroxyl group, a hydroxyl group, a nitrile group, an amide group, an imine group, an amino group, a thiol group, a hydroxyl group, a carboxylic acid group, a phosphate group, a ketone group, an aldehyde group, an ester group, an alkoxy group, a phenol group, a cyclopentyl group, a cyclohexyl group, an alkylamino group having 1 to 10 carbon atoms, an alkylsulfonic acid group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, a hydroxyl ... and a functional group selected from the group consisting of an alkenylamino group having 1 to 10 carbon atoms, an alkenylsulfonic acid group having 1 to 10 carbon atoms, a perfluoroalkenyl group having 1 to 10 carbon atoms, and an alkenyl group having 1 to 10 carbon atoms, and each of the functional groups may have in its molecular chain at least one functional group selected from the group consisting of an aromatic ring, a heterocycle, an oxygen atom, a sulfur atom, a nitrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and a hydrogen atom.]

[0010] In the catalyst of the present disclosure, the metal particles may be at least one type selected from the group consisting of platinum particles, platinum alloy particles, and composite particles containing platinum.

[0011] In the catalyst of the present disclosure, the weight ratio of the additive to the weight of the support may be greater than 0 and not greater than 0.2.

[0012] In the catalyst of the present disclosure, the weight ratio of the binder to the weight of the support may be 0.85 or more and 1.15 or less.

[0013] In the catalyst of the present disclosure, the weight of the metal particles per unit area is 0.2 mg / cm 2 More than 0.4mg / cm 2 It may be the following:

[0014] The present disclosure provides a method for producing a catalyst comprising metal particles having oxygen reduction activity, a support, an additive, and a binder, the method comprising: the metal particles are supported on the support, the additive is at least one organic nitrogen compound; the binder is a polymer electrolyte having an ion exchange group, the weight of the binder relative to the weight of the carrier in the catalyst is 0.85 or more; a catalyst ink preparation step of mixing the metal particles supported on the carrier with a solvent to obtain a catalyst ink; a binder introducing step of introducing the binder into the catalyst ink and mixing the catalyst ink with the binder; and an additive introducing step of introducing the additive into the catalyst ink and mixing the catalyst ink with the additive.

[0015] In the method for producing a catalyst according to the present disclosure, the additive introduction step may be carried out after the binder introduction step or simultaneously with the binder introduction step. [Effects of the Invention]

[0016] The present disclosure can provide a catalyst that contains an organic nitrogen compound and can suppress the occurrence of cracks in the catalyst layer. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present disclosure will be described. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of the catalyst that do not characterize the present disclosure) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. Any combination of upper and lower limits in the numerical range can be adopted.

[0018] 1. Catalyst In the present disclosure, there is provided a catalyst comprising metal particles having oxygen reduction activity, a carrier, an additive, and a binder, the metal particles are supported on the support, the additive is at least one organic nitrogen compound; the binder is a polymer electrolyte having an ion exchange group, The catalyst is characterized in that the weight ratio of the binder to the weight of the carrier is 0.85 or more.

[0019] Cracking in the catalyst layer reduces product durability, lowers product yield, and directly leads to the issue of being unable to fabricate a membrane-electrode assembly. Cracking in the catalyst layer occurs when organic nitrogen compounds, which are additives, combine with binders that have acidic functional groups, inhibiting the binder's ability to bind the catalyst layer. The organic nitrogen compounds have basic functional groups, and the binders have acidic functional groups. The two form bonds through acid-base interactions. Binders originally interact with the metals contained in the catalyst and their carriers (supports), preventing cracking in the catalyst layer and promoting bonding between the primary and secondary particles of the catalyst. Adding organic nitrogen compounds inhibits the binder's function, inducing cracking in the catalyst layer. The catalyst of the present disclosure can suppress the occurrence of cracks in the catalyst layer by adding an excess amount of binder relative to the amount of additive. Introducing the additive after or simultaneously with the addition of the binder can further suppress the occurrence of cracks in the catalyst layer. Furthermore, polymerizing the additive reduces the degree of freedom of reaction points, thereby reducing the probability of the additive and binder bonding. Introducing the additive after the binder and catalyst have been bonded can suppress cracks. The timing of adding the additive may be simultaneous with or after the addition of the binder.

[0020] The catalyst of the present disclosure comprises metal particles having oxygen reduction activity, a support, an additive, and a binder.

[0021] The additive is at least one organic nitrogen compound. As organic nitrogen compounds, the nitrogen equivalent, which represents the dry weight per mole of nitrogen, is 20 to 270 g·eq. -1 It may be a compound that satisfies 20 to 70 g·eq -1 The compound may satisfy the following conditions. The nitrogen equivalent can be calculated from the following formula: In the case of a polymer, the nitrogen equivalent of the monomer is regarded as the nitrogen equivalent of the polymer. Nitrogen equivalent (g·eq -1 ) = molecular weight (g / mol) ÷ amount of nitrogen in the molecule (mol N / mol) The organic nitrogen compound may be a compound having an amine functional group, a compound having pyridine-type nitrogen, or a compound containing a triazine ring. The organic nitrogen compound may be a monomer represented by the following general formula (1), or a polymer containing at least a portion of the monomer:

[0022] [ka]

[0023] [In general formula (1), R1, R2, and R3 each represent a hydrogen atom, a halogen atom, or a nitrile group, an amide group, an imine group, an amino group, a thiol group, a hydroxyl group, a sulfo group, a carboxylic acid group, a phosphate group, a ketone group, an aldehyde group, an ester group, an alkoxy group, a phenol group, a cyclopentyl group, a cyclohexyl group, an alkylamino group having 1 to 10 carbon atoms, an alkylsulfonic acid group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, a hydroxyl group, a hydroxyl group, a nitrile group, an amide group, an imine group, an amino group, a thiol group, a hydroxyl group, a carboxylic acid group, a phosphate group, a ketone group, an aldehyde group, an ester group, an alkoxy group, a phenol group, a cyclopentyl group, a cyclohexyl group, an alkylamino group having 1 to 10 carbon atoms, an alkylsulfonic acid group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, a hydroxyl ... and a functional group selected from the group consisting of an alkenylamino group having 1 to 10 carbon atoms, an alkenylsulfonic acid group having 1 to 10 carbon atoms, a perfluoroalkenyl group having 1 to 10 carbon atoms, and an alkenyl group having 1 to 10 carbon atoms, and each of the functional groups may have in its molecular chain at least one functional group selected from the group consisting of an aromatic ring, a heterocycle, an oxygen atom, a sulfur atom, a nitrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and a hydrogen atom.]

[0024] In general formula (1), R1, R2, and R3 may each be a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium cation.

[0025] Examples of organic nitrogen compounds include melamine compounds (nitrogen equivalent: 21 g eq -1 ), thiocyanuric acid compound (nitrogen equivalent 59 g eq -1 ), cyanuric acid compound (nitrogen equivalent 34g·eq -1 ), oleylamine (nitrogen equivalent 267g eq -1 ), tetradecylamine (nitrogen equivalent 213g eq -1 ), 2,4,6-Tris[bis(methoxymethyl)amino]-1,3,5-triazine (nitrogen equivalent 65g·eq -1 ), 6-(Dibutylamino)-1,3,5-triazine-2,4-dithiol (nitrogen equivalent 68 g eq -1 ), 2,4-Diamino-6-butylamino-1,3,5-triazine (nitrogen equivalent 30 g eq-1 ), 2,4,6-Tris(pentafluoroethyl)-1,3,5-triazine (nitrogen equivalent 145g eq -1 ) and polymers containing these as monomers, and Poly(melamine-co-formaldehyde) methylated (nitrogen equivalent: 20-40 g eq) -1 ), and Poly(melamine-co-formaldehyde) isobutylated (nitrogen equivalent: 20-40 g eq) -1 ) etc. In addition, two or more of the above-mentioned additives may be contained. The melamine compound may be melamine, a derivative of melamine, etc. The thiocyanuric acid compound may be thiocyanuric acid, a derivative of thiocyanuric acid, etc. The cyanuric acid compound may be cyanuric acid, a derivative of cyanuric acid, etc. Examples of polymers containing a melamine compound, a thiocyanuric acid compound, or a cyanuric acid compound as a monomer include melamine resins, thiocyanuric acid resins, and cyanuric acid resins having the above-mentioned melamine compound, thiocyanuric acid compound, or cyanuric acid compound in the main chain of repeating units. Among the additives listed above, melamine (1,3,5-triazine-2,4,6-triamine) or a polymer of the melamine may be used. The polymer is more difficult to desorb after adsorption onto metal particles than the monomer, improving adsorption stability. The polymer may have a degree of polymerization in the range of 1 to 10,000.

[0026] The metal particles may be any metal having oxygen reduction activity (oxygen reduction catalytic activity), such as platinum, ruthenium, iridium, rhodium, palladium, osnium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, and yttrium, or two or more of these metals may be used. Furthermore, the metal may be an oxide, nitride, sulfide, phosphide, or the like. Among the above, the metal particles may be at least one type selected from the group consisting of platinum particles, platinum alloy particles, and composite particles containing platinum. Examples of metals other than platinum contained in platinum alloys and platinum-containing composite particles include ruthenium, iridium, rhodium, palladium, osnium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, and yttrium, and the particles may contain two or more of these metals. The element ratio of metals other than platinum in the platinum alloy is not particularly limited, and may be 0.11 to 50 atm %. The particle size (particle diameter) of the metal particles is not particularly limited and may be 1 to 100 nm.

[0027] In the present disclosure, the particle size is the average crystallite size measured by X-ray diffraction. The particle size of the particles may be determined by measuring the particle sizes of 100 to 1000 particles using an electron microscope and averaging these values ​​to obtain the average particle size. In the present disclosure, particle size was measured by the above two methods.

[0028] The catalyst of the present disclosure includes a support such as carbon and an oxide. The metal particles are supported on a carrier. The method for supporting the metal particles on the carrier is not particularly limited, and any conventionally known method can be appropriately adopted. The carrier may be either a primary particle or a secondary particle. The particle size of the primary particles of the carrier may be, for example, 5 to 500 nm. The metal loading ratio of the metal particles loaded on the carrier is not particularly limited, and may be 1 to 60%, or may be 18 to 48%. The support may be a conductive carbon, an oxide, or a mixture containing at least two of these. The carbon may be carbon black (acetylene black, ketjen black, channel black, roller black, disc black, oil furnace black, gas furnace black, lamp black, thermal black, VULCAN (registered trademark) type carbon, etc.), activated carbon, graphite, glassy carbon, graphite, graphene, carbon fiber, carbon nanotubes, carbon nitride, carbon sulfide, carbon phosphide, or a mixture containing at least two of these. The oxide may be titanium oxide, niobium oxide, tin oxide, tungsten oxide, molybdenum oxide, or a mixture containing at least two of these.

[0029] The binder is a polyelectrolyte having ion exchange groups. A polymer electrolyte having an ion exchange group may be referred to as an electrolyte, ionomer, or binder. Hereinafter, the binder will be referred to as a binder. The binder may be any polymer capable of exchanging ions, and may have ion exchange groups such as sulfonic acid, phosphoric acid, and quaternary ammonium cations. The binder may be a perfluorocarbon sulfonic acid polymer, an anion exchange polymer, or a polymer primarily composed of polyether ether ketone, polybenzimidazole, or the like.

[0030] [Binder weight relative to carrier weight] In the catalyst of the present disclosure, the weight ratio of the binder to the weight of the carrier may be 0.85 or more, and may be 0.85 or more and 1.15 or less. The binder weight relative to the carrier weight is defined as (binder weight) / (carrier weight).

[0031] [Weight of additive relative to weight of carrier] In the catalyst of the present disclosure, the weight ratio of the additive to the weight of the support may be greater than 0 and not greater than 0.2, or may be 0.03 or greater and 0.05 or less. The weight of the additive relative to the weight of the carrier is defined as (weight of the additive) / (weight of the carrier).

[0032] [Weight of metal particles relative to weight of support] In the catalyst of the present disclosure, the ratio of the weight of the metal particles to the weight of the support may be greater than 0 and equal to or less than 1.0.

[0033] [Weight of metal particles per unit area] In the catalyst of the present disclosure, the weight of the metal particles per unit area is 0.2 mg / cm 2 More than 0.4mg / cm 2 It may be the following:

[0034] [Additive weight evaluation method] Methods for evaluating the weight of the additive contained in the catalyst of the present disclosure include a method for measuring the nitrogen content by CHN elemental analysis, and a method for extracting the additive from the catalyst and measuring the additive directly. The method of measuring nitrogen content using CHN elemental analysis involves burning a sample with oxygen for a certain period of time, then quantifying the amounts of carbon, hydrogen, and nitrogen atoms contained in the sample by quantifying the amounts of carbon dioxide, water, and nitrogen oxides produced.By comparing the amount of nitrogen in the sample before and after adding the additive, it is possible to evaluate the amount of the additive. The method of extracting additives from oxygen reduction catalysts and measuring them directly involves extracting the additives in a solvent that dissolves the additives contained in the catalyst and then qualitatively and quantitatively analyzing the additives. Analytical techniques include chromatography, ultraviolet-visible spectroscopy (UV-vis), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR).

[0035] [Method for evaluating metal particle weight, carrier weight, and binder weight] Methods for evaluating the weight of the metal particles, the weight of the carrier, and the weight of the binder contained in the catalyst of the present disclosure include thermogravimetric analysis (TG), high-frequency inductively coupled plasma emission spectroscopy (ICP), and the like. Thermogravimetric analysis (TG) is a method for measuring weight when the gas atmosphere, temperature, etc. are changed. After heating and burning off moisture, conductive carriers, polymers with ion exchange groups, and impurities, the remaining weight is taken as the weight of the metal particles. Inductively coupled plasma optical emission spectroscopy (ICP) is a technique for qualitatively and quantitatively determining the elements contained in a substance based on the wavelength and intensity of the emission lines emitted by atoms excited by plasma. By controlling the measurement temperature and gas atmosphere, it is possible to calculate the weight of any substance. It is possible to directly quantify the weight of metal particles, carrier, and binder contained in the catalyst.

[0036] The catalyst of the present disclosure may be used for a fuel cell or a metal-air battery. The catalyst of the present disclosure may be used in a cathode of a fuel cell, an anode of a fuel cell, or an air electrode of a metal-air battery. Furthermore, the catalyst of the present disclosure may be used in an anode for water electrolysis, which is the reverse reaction of a fuel cell, or in a cathode for water electrolysis, or in an anode for CO reduction, or in a cathode for CO reduction.

[0037] The catalyst of the present disclosure may be in the form of a layer, i.e., the catalyst of the present disclosure may be a catalyst layer.

[0038] 2. Catalyst manufacturing method The present disclosure provides a method for producing a catalyst comprising metal particles having oxygen reduction activity, a support, an additive, and a binder, the method comprising: the metal particles are supported on the support, the additive is at least one organic nitrogen compound; the binder is a polymer electrolyte having an ion exchange group, the weight of the binder relative to the weight of the carrier in the catalyst is 0.85 or more; a catalyst ink preparation step of mixing the metal particles supported on the carrier with a solvent to obtain a catalyst ink; a binder introducing step of introducing the binder into the catalyst ink and mixing the catalyst ink with the binder; and an additive introducing step of introducing the additive into the catalyst ink and mixing the catalyst ink with the additive.

[0039] The catalyst manufacturing method of the present disclosure includes (1) a catalyst ink preparation step, (2) a binder introduction step, (3) an additive introduction step, and usually further includes (4) a catalyst ink application step. In the method for producing a catalyst of the present disclosure, (1) the catalyst ink preparation step, (2) the binder introduction step, and (3) the additive introduction step may be carried out simultaneously. In the catalyst manufacturing method of the present disclosure, the (3) additive introduction step may be performed before, after, or simultaneously with the (2) binder introduction step. From the viewpoint of suppressing the occurrence of cracks in the catalyst layer, the (3) additive introduction step may be performed after, or simultaneously with the (2) binder introduction step.

[0040] (1) Catalyst ink preparation process The catalyst ink preparation step is a step of mixing the metal particles carried on the carrier with a solvent to obtain a catalyst ink. First, a predetermined amount of a carrier carrying metal particles (metal particle-carrying carrier) and a solvent are placed in a container, and these are stirred using a stirrer to prepare a catalyst ink. The type of solvent is not particularly limited, and any liquid can be used, and may be water, alcohol, or a mixed solution of at least one alcohol and water. Examples of the alcohol include methanol, diacetone alcohol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, and propylene glycol. Examples of the agitator used for mixing include an ultrasonic homogenizer, a jet mill, a ball mill such as a bead mill, a high shear mill, a film mix, etc. The agitation conditions such as the agitation speed, agitation time, and a rotation speed are not particularly limited and can be set appropriately.

[0041] (2) Binder introduction process The binder introduction step is a step of introducing the binder into the catalyst ink and mixing the catalyst ink with the binder. The mixing conditions and the stirrer used for mixing can be the same as those in (1) catalyst ink preparation step.

[0042] (3) Additive introduction process The additive introduction step is a step of introducing the additive into the catalyst ink and mixing the catalyst ink with the additive. The mixing conditions and the stirrer used for mixing can be the same as those in (1) catalyst ink preparation step. After the above steps (1) to (3), a vacuum degassing treatment may be performed. There is no limit to the time for leaving the mixture to stand, and it may be left to stand for one day. It is also possible to use the mixture without leaving it to stand. It is also possible to perform the vacuum degassing treatment again.

[0043] (4) Catalyst ink coating process The catalyst ink application step is a step in which the prepared catalyst ink is applied onto a substrate, and the solvent is removed after application to form a catalyst layer on the substrate. For example, the catalyst ink is applied to a substrate, and the applied catalyst ink is heated to dry and remove the solvent. Examples of the substrate include polytetrafluoroethylene (PTFE), an electrolyte membrane having an ion exchange group, a gas diffusion layer (GDL) made of carbon fiber or metal fiber, and a gas diffusion layer made of carbon fiber or metal fiber with a microporous layer (MPL). The coating method may be any method that can uniformly coat the catalyst ink on the substrate, and examples thereof include die coating, spin coating, screen printing, doctor blade, squeegee, spray coating, and applicator methods. The heating rate and heating time can be appropriately set depending on the type of solvent, etc. The removal rate may also be increased by degassing simultaneously with heating. The coating thickness and the metal particle content can also be changed. The coating thickness may be 5 to 30 μm, and the platinum content may be 0.1 to 0.6 mg cm -2 The coating may be carried out so as to satisfy the above. Thereafter, the electrolyte membrane may be sandwiched between two catalyst layers to form a membrane electrode assembly.

[0044] 3. Air electrode The present disclosure provides an air electrode for a fuel cell or a metal-air battery, which includes the catalyst. The cathode of the present disclosure includes the catalyst of the present disclosure. The cathode of the present disclosure may also include the catalyst layer of the present disclosure. The cathode of the present disclosure may be for use in a fuel cell or a metal-air battery.

[0045] 4.Fuel cell The present disclosure provides a fuel cell having the air electrode as a cathode.

[0046] The fuel cell of the present disclosure has the air electrode of the present disclosure as the cathode (cathode catalyst layer). The fuel cell of the present disclosure can appropriately adopt the configuration of a conventionally known fuel cell, except that it has the air electrode of the present disclosure as a cathode. The fuel cell of the present disclosure may have an anode containing the catalyst of the present disclosure. The fuel cell of the present disclosure may have the catalyst layer of the present disclosure as an anode (anode catalyst layer). The fuel cell of the present disclosure uses an air electrode containing the catalyst of the present disclosure, which has few cracks, as a cathode, and therefore can improve the power generation performance and durability of the fuel cell.

[0047] 5. Metal-air battery The present disclosure provides a metal-air battery having the air electrode as a cathode.

[0048] The metal-air battery of the present disclosure has the air electrode of the present disclosure as a cathode. The metal-air battery of the present disclosure can appropriately adopt the configuration of a conventionally known metal-air battery, except that it has the air electrode of the present disclosure as the cathode. The metal-air battery of the present disclosure uses, as a cathode, an air electrode containing the catalyst of the present disclosure, which is less prone to cracking, and therefore can improve the power generation performance and durability of the metal-air battery. [Example]

[0049] Example 1 Platinum-cobalt alloy particles (metal particle diameter 3-4 nm) were used as the metal particles, 1,3,5-triazine-2,4,6-triamine (melamine, Fujifilm Wako Pure Chemical Industries) was used as the additive, carbon (acetylene black) was used as the support, and perfluorocarbon sulfonic acid polymer (DE2020, Chemours) was used as the binder. A layer (catalyst layer) consisting of these catalysts was formed using the following method. The ratio of the metal particle weight to the support weight was set to 1.0. The weight ratio of the additive to the carrier was 0.05, and the weight ratio of the binder to the carrier was 0.85.

[0050] [Catalyst layer formation method] (1) Catalyst ink preparation process A predetermined amount of a carrier carrying metal particles (metal particle-carrying carrier, metal loading ratio 48 wt%), water as a solvent, and diacetone alcohol were placed in a container and stirred to prepare a catalyst ink. (2) Binder introduction process Thereafter, a predetermined amount of binder was added to the container in which the catalyst ink was prepared, and the mixture was stirred. (3) Additive introduction process Thereafter, a predetermined amount of additive was further added to the container, and the mixture was stirred. Stirring was carried out at 300 rpm using a bead mill in steps (1) to (3), for a total of 4 hours in steps (1) to (3). The catalyst ink was subjected to vacuum degassing treatment and left to stand for one day. Thereafter, the catalyst ink was again subjected to vacuum degassing treatment. (4) Catalyst ink coating process The prepared catalyst ink was applied to a polytetrafluoroethylene (PTFE) substrate using a die coating method, and the applied catalyst ink was heated to dry and remove the solvent, forming a catalyst layer. The amount of platinum contained in the catalyst layer (electrode) was 0.20 mg. _金属 cm -2 _電極 , 0.30 mg _金属 cm -2 _電極 , 0.40 mg _金属 cm -2 _電極 Three types of catalyst layers were formed by coating so that Each catalyst layer formed was observed under a microscope at 40x and 500x magnification. The magnification can also be changed. The crack area ratio (%) of the catalyst layer was evaluated from the area ratio in the photographed image observed at 500x magnification. A cracked area of ​​less than 1% was rated as ◯, a cracked area of ​​1 to 15% was rated as △, and a cracked area of ​​more than 15% was rated as ×. The results are shown in Table 1.

[0051] (Examples 2 and 3) In Example 2, the (2) binder introduction step and the (3) additive introduction step were carried out simultaneously, and in Example 3, the (3) additive introduction step was carried out before the (2) binder introduction step. Except for this, a catalyst layer was formed under the same conditions as in Example 1, and the crack area ratio (%) of the catalyst layer was evaluated. The results are shown in Table 1.

[0052] Examples 4 to 6 In Examples 4 to 6, the weight of additive relative to the weight of carrier was set to 0.03, and in Example 5, the (2) binder introduction step and the (3) additive introduction step were carried out simultaneously, and in Example 6, the (3) additive introduction step was carried out before the (2) binder introduction step. Except for this, catalyst layers were formed under the same conditions as in Example 1, and the crack area ratio (%) of the catalyst layer was evaluated. The results are shown in Table 2.

[0053] (Comparative Example 1, Examples 7 and 8) A catalyst layer was formed under the same conditions as in Example 1, except that the binder weight relative to the carrier weight was 0.70 in Comparative Example 1, 1.0 in Example 7, and 1.15 in Example 8, and the crack area ratio (%) of the catalyst layer was evaluated. The results are shown in Table 3.

[0054] (Comparative Example 2) A catalyst layer was formed under the same conditions as in Example 1 except that no additive was used, and the crack area ratio (%) of the catalyst layer was evaluated. Note that, since no additive was used, the additive weight relative to the carrier weight in Comparative Example 2 was 0. The results are shown in Table 3.

[0055] [Table 1]

[0056] [Table 2]

[0057] [Table 3]

[0058] [Evaluation results] As shown in Table 3, when Comparative Example 1 is compared with Examples 7 and 8, it is found that when the weight of the binder relative to the weight of the carrier is less than 0.85, the crack area of ​​the catalyst layer becomes large. As shown in Tables 1 and 2, in Examples 1 to 6, it can be seen that the crack area of ​​the catalyst layer can be made smaller by adding the additive at the same time as the binder or after the binder is added. The above results demonstrate that when an organic nitrogen compound is contained, the occurrence of cracks in the catalyst layer can be suppressed by setting the binder weight to the carrier weight ratio to 0.85 or more.

Claims

1. The catalyst comprises metal particles having oxygen reduction activity, a carrier, an additive, and a binder, the metal particles are supported on the support, the metal particles are at least one selected from the group consisting of platinum particles, platinum alloy particles, and platinum-containing composite particles; the support is conductive carbon, the additive is at least one organic nitrogen compound; the binder is a polymer electrolyte having an ion exchange group, The weight ratio of the binder to the weight of the carrier is 0.85 or more, the ion exchange group is sulfonic acid or phosphoric acid; A catalyst characterized in that the organic nitrogen compound is melamine (1,3,5-triazine-2,4,6-triamine) or a polymer of said melamine.

2. The metal particles are platinum-cobalt alloy particles having a particle size of 3 to 4 nm, the carrier is acetylene black, the binder is a perfluorocarbon sulfonic acid polymer; 2. The catalyst of claim 1, wherein the organic nitrogen compound is melamine.

3. 2. The catalyst according to claim 1, wherein the weight ratio of the additive to the weight of the support is greater than 0 and is 0.2 or less.

4. 2. The catalyst according to claim 1, wherein the weight ratio of the binder to the weight of the support is 0.85 to 1.

15.

5. The weight of the metal particles per unit area is 0.2 mg / cm ２ 0.4mg / cm or more ２ 2. The catalyst of claim 1, wherein:

6. A method for producing a catalyst comprising metal particles having oxygen reduction activity, a support, an additive, and a binder, the method comprising: the metal particles are supported on the support, the metal particles are at least one selected from the group consisting of platinum particles, platinum alloy particles, and platinum-containing composite particles; the support is conductive carbon, the additive is at least one organic nitrogen compound; the binder is a polymer electrolyte having an ion exchange group, the weight of the binder relative to the weight of the carrier in the catalyst is 0.85 or more; the ion exchange group is sulfonic acid or phosphoric acid; the organic nitrogen compound is melamine (1,3,5-triazine-2,4,6-triamine) or a polymer of the melamine; a catalyst ink preparation step of mixing the metal particles supported on the carrier with a solvent to obtain a catalyst ink; a binder introducing step of introducing the binder into the catalyst ink and mixing the catalyst ink with the binder; an additive introducing step of introducing the additive into the catalyst ink and mixing the catalyst ink with the additive.

7. The method for producing a catalyst according to claim 6 , wherein the additive introduction step is carried out after the binder introduction step or simultaneously with the binder introduction step.

8. The metal particles are platinum-cobalt alloy particles having a particle size of 3 to 4 nm, the carrier is acetylene black, the binder is a perfluorocarbon sulfonic acid polymer; The method for producing a catalyst according to claim 6, wherein the organic nitrogen compound is melamine.

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