JP7722286B2 - catalyst - Google Patents

Description

This disclosure relates to catalysts.

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.

International Publication No. 2019/221156

Even when an organic nitrogen compound is added as an additive to a catalyst with oxygen reduction activity to improve catalytic performance, conventional technology has found that depending on the type of additive, the catalyst performance improvement effect may not be fully realized. Depending on the operating conditions of the battery, the additive may dissolve into the produced water, preventing the additive's catalytic performance improvement effect from being realized. During the manufacturing process, the additive's low solubility in the solvent may prevent the additive from adsorbing to the metal particles with oxygen reduction activity, preventing the additive's catalytic performance improvement effect from being realized.

The present disclosure was made in consideration of the above-mentioned circumstances, and its primary objective is to provide a catalyst that contains an organic nitrogen compound and can improve catalytic performance.

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 additive has a solubility in water at 20°C of less than 3.5 g/L and a solubility in at least one alcohol selected from the group consisting of diacetone alcohol, ethanol, isopropanol, and tert-butyl alcohol of 40 g/L or more at 20°C;
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 0.5 or more and 1.5 or less.

The present disclosure provides a catalyst that contains an organic nitrogen compound and can improve catalytic performance.

FIG. 1 is a graph showing the relationship between the nitrogen equivalent of the additives used in Examples 1 and 2 and Comparative Examples 1 and 2 and the catalyst mass activity improvement factor.

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 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.

1. Catalyst In the present disclosure, a catalyst is provided which comprises metal particles having oxygen reduction activity, a support, an additive, and a binder,
the metal particles are supported on the support,
the additive is at least one organic nitrogen compound;
the additive has a solubility in water at 20°C of less than 3.5 g/L and a solubility in at least one alcohol selected from the group consisting of diacetone alcohol, ethanol, isopropanol, and tert-butyl alcohol of 40 g/L or more at 20°C;
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 0.5 or more and 1.5 or less.

Even when additives used in conventional technologies can be confirmed to have a significant effect of improving catalytic performance in a half-cell test (RDE method), they may not exhibit a significant effect of improving catalytic performance in an actual cell test equipped with an anode and a cathode.
In the present disclosure, it has been discovered that by using an additive with controlled solubility in water and alcohol, the catalyst performance improving effect of the additive can be confirmed in an actual cell test equipped with an anode and a cathode.

The catalyst disclosed herein comprises metal particles having oxygen reduction activity, a support, an additive, and a binder.

The additive is at least one organic nitrogen compound.
The additive may be any additive as long as it has a solubility in water at 20°C of less than 3.5 g/L and a solubility in at least one alcohol selected from the group consisting of diacetone alcohol, ethanol, 2-propanol (isopropanol), and tert-butyl alcohol at 20°C of 40 g/L or more.
The organic nitrogen compound as an additive may be any of the following compounds as long as it satisfies the above-mentioned conditions of the predetermined solubility in water at 20°C and the predetermined solubility in alcohol at 20°C.
The organic nitrogen compound may be a compound having a nitrogen equivalent, which represents the dry weight per mole of nitrogen, of 20 to 270 g·eq ⁻¹ , or may be a compound having a nitrogen equivalent of 20 to 70 g·eq ⁻¹ .
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 substance in 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 at least partially containing the monomer:

[In general formula (1), R ₁ , R ₂ , and R ₃ 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, or an alkenyl group having 1 to 10 carbon atoms. It is one functional group selected from the group consisting of an amino group, 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 the functional group may have, in the molecular chain, at least one functional group selected from the group consisting of the above functional groups, 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 at least one atom selected from the group consisting of a hydrogen atom.]

Examples of organic nitrogen compounds include thiocyanuric acid compounds (nitrogen equivalent: 59 g·eq ⁻¹ ), oleylamine (nitrogen equivalent: 267 g·eq ⁻¹ ), tetradecylamine (nitrogen equivalent: 213 g·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 30.4 g eq ^-1 ),
2,4,6-Tris(pentafluoroethyl)-1,3,5-triazine (nitrogen equivalent: 145 g·eq ⁻¹ ), and polymers containing these as monomers, and
Poly(melamine-co-formaldehyde) methylated (nitrogen equivalent: 20 to 40 g·eq ⁻¹ ), and
Poly(melamine-co-formaldehyde) isobutylated (nitrogen equivalent: 20 to 40 g·eq ⁻¹ ), etc. Also, two or more of the above-mentioned additives may be contained.
The thiocyanuric acid compound may be thiocyanuric acid, a derivative of thiocyanuric acid, or the like.
Examples of polymers containing a thiocyanuric acid compound as a monomer include the above-mentioned resins having the thiocyanuric acid compound as a repeating unit in the main chain.
Among the additives listed above, oleylamine, 2,4-Diamino-6-butylamino-1,3,5-triazine, or a polymer thereof may be used. The polymer is less likely to be released after adsorption onto the metal particles than the monomer, improving adsorption stability. The polymer may have a degree of polymerization in the range of 1 to 10,000.

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, and 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 the platinum alloy and the 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.

In the present disclosure, the particle size of particles is the average crystallite size measured by X-ray diffraction.
The particle size of the particles may be measured by an electron microscope for 100 to 1000 particles, and the average value of these particles may be used as the average particle size. In the present disclosure, particle size was measured by the above two methods.

The catalyst of the present disclosure includes a support (carrier) 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, 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.

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 that exchanges 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.

[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 0.5 or more and 1.5 or less, and may be 0.5 or more and 0.85 or less.
The binder weight relative to the carrier weight is defined as (binder weight)/(carrier weight).

[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 0.01 or more and 0.10 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).

[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 contained in the catalyst using a solvent that dissolves the additives, 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).

[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), 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.

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 _CO2 reduction, or in a cathode for _CO2 reduction.

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.
Examples of the method for forming the catalyst layer include the following methods.

[Catalyst ink preparation process]
First, a predetermined amount of a carrier carrying metal particles (metal particle-carrying carrier), a binder, an additive, 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 type of alcohol and water.
Examples of the alcohol include methanol, diacetone alcohol, ethanol, 1-propanol, 2-propanol (isopropanol), tert-butyl alcohol, ethylene glycol, and propylene glycol, and may be at least one selected from the group consisting of diacetone alcohol, ethanol, isopropanol, and tert-butyl alcohol.
Examples of the stirrer include an ultrasonic homogenizer, a jet mill, a ball mill such as a bead mill, a high shear mill, a film mix, etc. The stirring conditions such as the stirring speed, stirring time, and rotation speed are not particularly limited and can be set appropriately.
Thereafter, 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 a vacuum degassing treatment again.

[Catalyst ink coating process]
The prepared catalyst ink is applied to a substrate, and the solvent is removed after application. 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 having 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 be changed.
The coating thickness may be 5 to 30 μm, and the coating may be carried out so that the platinum amount satisfies 0.1 to 0.6 mg cm ⁻² .

2. 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.

3. Fuel Cell The present disclosure provides a fuel cell having the air electrode as a cathode.

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 as a cathode, and therefore the power generation performance of the fuel cell can be improved.

4. Metal-Air Battery The present disclosure provides a metal-air battery having the air electrode as a cathode.

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 an air electrode containing the catalyst of the present disclosure as a cathode, and therefore the power generation performance of the metal-air battery can be improved.

Example 1
Platinum particles (metal particle diameter: 2 to 4 nm) were prepared as metal particles, oleylamine as an additive, carbon (acetylene black) as a carrier, and perfluorocarbon sulfonic acid polymer (DE520 manufactured by Chemours) as a binder. An electrode for evaluation was fabricated using a catalyst containing these as follows.
[Preparation of evaluation electrodes]
A carrier carrying metal particles (metal particle-carrying carrier, metal loading ratio 29 wt%), a binder, and additives were dispersed in a mixed solvent of 2-propanol and ultrapure water. The dispersion was added dropwise to a Hokuto Denko glassy carbon rotating electrode (diameter 5 mm) so that the carrier amount was 20 μg/ ^cm² , and then dried to prepare an electrode for evaluation.
The ratio of the binder weight to the carrier weight in the catalyst was set to 0.5.
The weight ratio of the additive to the weight of the carrier in the catalyst was 0.10.

(Example 2, Comparative Examples 1 and 2)
Evaluation electrodes using catalysts were prepared under the same conditions as in Example 1, except that the additive used was changed from oleylamine to 2,4-Diamino-6-butylamino-1,3,5-triazine in Example 2, 2,4,6-Tris[bis(methoxymethyl)amino]-1,3,5-triazine in Comparative Example 1, and 1,3,5-triazine-2,4,6-triamine (melamine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in Comparative Example 2.

[Evaluation of catalyst mass activity in half-cell test (RDE method)]
Each of the evaluation electrodes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was used as a working electrode, a reversible hydrogen electrode as a reference electrode, and a carbon rod as a counter electrode, and electrochemical measurements (half-cell tests) were carried out using a three-electrode system.
As the electrolyte, an aqueous solution of perchloric acid adjusted to 0.1 M with ultrapure water was used.
Cyclic voltammetry was carried out under an inert gas atmosphere.
Thereafter, the gas atmosphere was changed to oxygen, and linear sweep voltammetry was performed from the low potential side.
The electrode rotation speed was changed to 400, 900, 1600, 2000, 2500, and 3600 rpm, and the linear sweep voltammetry measurement was repeated.
From the obtained potential-current characteristics, a Kouteckey-Levich plot was created, and the catalyst mass activity (A/g) at 0.9 Vvs RHE was calculated.
Catalyst mass activity is the current per unit weight of metal particles. The current represents the reaction rate of an electrochemical reaction, and the larger the current, the higher the catalytic activity.
In addition, the catalytic mass activity of a catalyst containing an additive (catalytic mass activity of the catalyst after the additive was introduced) and the catalytic mass activity of a catalyst having the same configuration except that it did not contain an additive (catalytic mass activity of the catalyst before the additive was introduced) were calculated, and the catalytic mass activity improvement ratio was calculated from these.
The catalyst mass activity improvement factor is defined as (catalyst mass activity of the catalyst after the addition of the additive)/(catalyst mass activity of the catalyst before the addition of the additive).
The results are shown in Table 1 and FIG.
FIG. 1 is a graph showing the relationship between the nitrogen equivalent of the additives used in Examples 1 and 2 and Comparative Examples 1 and 2 and the catalyst mass activity improvement factor.

Example 3
Platinum-cobalt alloy particles (metal particle diameter: 3 to 4 nm) were prepared as metal particles, oleylamine as an additive, carbon (acetylene black) as a carrier, and perfluorocarbon sulfonic acid polymer (DE2020 manufactured by Chemours) as a binder, and a layer (catalyst layer) made of a catalyst containing these was formed by the following method.
The ratio of the binder weight to the carrier weight in the catalyst was 0.85.
The weight ratio of the additive to the weight of the carrier in the catalyst was 0.01.

[Catalyst layer formation method]
A predetermined amount of a carrier carrying metal particles (metal particle-carrying carrier, metal loading ratio 50 wt %), a binder, an additive, and water and diacetone alcohol as a solvent were placed in a container, and these were stirred at 300 rpm using a bead mill for a total of 4 hours to prepare a catalyst ink.
The catalyst ink was subjected to a vacuum degassing treatment and left to stand for one day.
Thereafter, the catalyst ink was again subjected to vacuum degassing treatment.
The 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 catalyst layer was coated so that the platinum content was 0.20 mg cm ^-2 .

(Example 4, Comparative Examples 3 and 4)
A layer made of a catalyst (catalyst layer) was formed under the same conditions as in Example 3, except that the additive used was changed from oleylamine to 2,4-Diamino-6-butylamino-1,3,5-triazine in Example 4, 2,4,6-Tris[bis(methoxymethyl)amino]-1,3,5-triazine in Comparative Example 3, and 1,3,5-triazine-2,4,6-triamine (melamine, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in Comparative Example 4.

[Method for producing membrane-electrode gas diffusion layer assembly]
Each of the catalyst layers produced in Examples 3 and 4 and Comparative Examples 3 and 4 was prepared as a cathode catalyst layer, an electrolyte membrane (Nafion NR211) was prepared, and an anode catalyst layer containing TEC10E50E manufactured by Tanaka Kikinzoku Kogyo Kogyo was prepared as an anode catalyst.
The electrolyte membrane was sandwiched between the cathode catalyst layer and the anode catalyst layer, and a temperature (130°C) and pressure (3 MPa) were applied to thermocompression bond the cathode catalyst layer, the electrolyte membrane, and the anode catalyst layer to form a membrane-electrode assembly. Any electrolyte membrane can be used, and the temperature and pressure during thermocompression bonding can be set to any appropriate temperature and pressure.
Two gas diffusion layers made of carbon fiber (GDL 22BB manufactured by SGL) were prepared and placed on both sides of the membrane-electrode assembly to produce the membrane-electrode gas diffusion layer assemblies of Examples 3 and 4 and Comparative Examples 3 and 4. Any gas diffusion layer can be used as the gas diffusion layer.

[Actual 1cm ^2- cell evaluation]
Cell evaluation was carried out using each membrane-electrode gas diffusion layer assembly with an electrode area of 1 cm ² .
The current-voltage characteristics were evaluated under low humidity conditions (30% RH) and high humidity conditions (80% RH).
The current-voltage characteristics were acquired at a sweep rate of 20 mA/s using anodic sweep.
The cell temperature was 80°C, the pressure was 150 kPa_ABS, the cathode gas was air, the cathode gas flow rate was 2.0 L/min, the anode gas was hydrogen, and the anode gas flow rate was 1.0 L/min. It is possible to obtain the current-voltage curve under any conditions.
From the evaluation results of the current-voltage characteristics, the improvement in cell voltage (mV) under highly humidified conditions (80% RH) was calculated compared to the case where no additive was added. These results are shown in Table 2.
The criteria for judging the cell voltage improvement were as follows: when the cell voltage improvement was more than 10 mV, it was marked as ◎; when it was more than 8 mV and not more than 10 mV, it was marked as ◯; when it was more than 1 mV and not more than 8 mV, it was marked as △; and when it was not more than 1 mV, it was marked as ×.

[Evaluation results]
As shown in FIG. 1 and Table 1, the catalyst activity improvement rate in the half-cell test was higher when an additive with a smaller nitrogen equivalent was used.
On the other hand, as shown in Table 2, in the actual cell test, even if an additive with a small nitrogen equivalent is used, if the additive has a high solubility in water at 20°C and a low solubility in alcohol at 20°C, the improvement in cell voltage is small.
The above results demonstrate that the use of additives with controlled solubility in water and alcohol can improve the performance of the additive-based catalyst in actual cell tests equipped with an anode and cathode.

Claims (2)

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 additive is at least one organic nitrogen compound;
the additive has a solubility in water at 20°C of less than 3.5 g/L and a solubility in at least one alcohol selected from the group consisting of diacetone alcohol, ethanol, isopropanol, and tert-butyl alcohol of 40 g/L or more at 20°C;
the binder is a polymer electrolyte having an ion exchange group,
The organic nitrogen compound is a monomer represented by the following general formula (1) or a polymer at least partially containing the monomer:
A catalyst characterized in that the weight ratio of the binder to the weight of the carrier is 0.5 .
[In general formula (1), R ₁ , R ₂ , and R ₃ each represent an amino group, a thiol group, a hydroxyl group, an alkylamino group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms, and each may have at least one atom selected from the group consisting of 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.] The catalyst described in claim 1, wherein the metal particles are at least one selected from the group consisting of platinum particles, platinum alloy particles, and platinum-containing composite particles.