JP6471979B2 - Electrode catalyst and method for producing the same - Google Patents

Description

  The present invention relates to an electrode catalyst suitably used for a fuel cell and a method for producing the same.

  The polymer electrolyte fuel cell has a proton conductive polymer membrane such as a perfluoroalkylsulfonic acid type polymer as a solid electrolyte, and an oxygen electrode in which an electrode catalyst is applied to each surface of the solid polymer membrane. A membrane electrode assembly having a fuel electrode is provided.

  The electrode catalyst is generally formed by supporting various precious metal catalysts such as platinum on the surface of a conductive carbon material such as carbon black as a carrier. In the electrode catalyst, it is known that carbon is oxidized and corroded due to a potential change during operation of the fuel cell, and the supported metal catalyst is aggregated or dropped off. As a result, the performance of the fuel cell decreases as the operating time elapses. Therefore, in the manufacture of fuel cells, performance degradation is prevented by supporting a noble metal catalyst in a larger amount than is actually required on the carrier. However, this is not advantageous from an economic point of view.

  Therefore, various studies on electrode catalysts have been made for the purpose of improving the performance and improving the economic efficiency of solid polymer fuel cells. For example, it has been proposed to use a conductive oxide carrier that is a non-carbon material instead of the conductive carbon that has been used as a carrier until now (see Patent Document 1). In this document, tin oxide is used as a support for the electrode catalyst. This document describes that this tin oxide may be doped with other elements. Examples of other elements include Sb, Nb, Ta, W, In, V, Cr, Mn, and Mo.

  In Patent Document 1, tin oxide particles doped with various elements are used in an aggregated state, whereas in Patent Document 2, five or more tin oxide particles are fused to each other. Electrocatalysts having a chain-like or tuft-like structure structure have been proposed.

US2010 / 0233574A1 US2012 / 0295184A1

  According to the technique described in Patent Document 2, an electrode catalyst having both high conductivity and a high specific surface area is obtained. However, there is a need for an electrode catalyst with higher conductivity from the viewpoint of further improving the performance in the field of use of fuel cells.

  Accordingly, an object of the present invention is to provide an electrode catalyst whose performance is further improved as compared with the above-described prior art and a method for easily producing such an electrode catalyst.

  As a result of intensive studies by the present inventors to solve the above-mentioned problems, it has been found that the conductivity of an electrode catalyst is improved by supporting a catalyst containing a noble metal on a carrier having a specific structure by a specific method. did. Furthermore, it has also been found that the conductivity of the electrode catalyst is further improved by alloying the noble metal with tin which is a constituent element of the support when the catalyst containing the noble metal is supported.

  The present invention has been made based on the above knowledge, and a plurality of particles containing tin oxide and one or more additive elements selected from the group consisting of Nb, Sb, Ta, In and V are beaded. An electrocatalyst comprising a support having a continuous chain structure portion and a catalyst containing a noble metal supported on the surface of the support, wherein at least a part of the noble metal forms an alloy with tin. By providing this, the above-mentioned problems are solved.

The present invention also provides a method for producing the electrode catalyst, wherein a reducing agent is added to a liquid containing a precursor of a colloid containing a noble metal, the precursor is reduced to produce a colloid containing a noble metal,
A support having a chain structure portion in which a plurality of particles containing tin oxide and one or more additive elements selected from the group consisting of Nb, Sb, Ta, In, and V are arranged in a bead shape includes a noble metal. Dispersed in a liquid containing the colloid, supported on the carrier as fine particles containing a noble metal,
Separating the liquid from the carrier carrying fine particles containing the noble metal, and drying the carrier;
The present invention provides a method for producing an electrocatalyst comprising a step of heat-treating the carrier after drying supporting fine particles containing the noble metal in a reducing atmosphere.

  According to the present invention, an electrode catalyst with further improved conductivity is provided. Moreover, according to the present invention, such an electrode catalyst can be easily produced.

FIG. 1 is a schematic view showing a flame method apparatus used in the present invention. FIG. 2 is a schematic diagram showing a partial view of a spray nozzle in the flame method apparatus shown in FIG. FIG. 3 is a transmission electron microscope image of the electrode catalyst obtained in Example 2. FIG. 4 is a graph showing the XPS measurement results of the electrode catalyst obtained in Example 1. FIG. 5 is a diffraction diagram showing the XRD measurement results of the electrode catalysts obtained in Examples 1, 4 and 5. FIG. 6 is a graph showing XPS measurement results of the electrode catalysts obtained in Examples 4 and 5. FIG. 7 is a transmission electron microscope image of the carrier used in Example 6. FIG. 8 is a transmission electron microscope image of the carrier used in Comparative Example 4. FIG. 9 is a schematic diagram showing a method for measuring the conductivity of the electrode catalysts obtained in the examples and comparative examples.

Hereinafter, the present invention will be described based on preferred embodiments thereof. The electrode catalyst of the present invention has a support and a catalyst containing a noble metal supported on the surface of the support. The carrier is one in which tin oxide contains one or more elements selected from the group consisting of Nb, Sb, Ta, In, and V (hereinafter, these elements are referred to as “added elements”). The tin oxide used in the present invention is composed of an oxide of tin. It is known that tin oxide is a highly conductive substance. Examples of the tin oxide include SnO ₂ which is a tetravalent tin oxide and SnO which is a divalent tin oxide. In particular, the tin oxide is preferably composed mainly of SnO ₂ from the viewpoint of improving acid resistance. “Mainly composed of SnO ₂ ” means that the ratio of SnO _{2 in} the tin oxide is 50 mol% or more in terms of tin element.

  Tin oxide containing the additive element is in the form of particles. A plurality of these particles are aggregated to form a specific structure which will be described later, thereby forming an electrode catalyst carrier. The particle size of the individual particles constituting this structure is preferably 5 nm or more and 100 nm or less, more preferably 5 nm or more and 30 nm or less, from the viewpoint that the specific surface area of the electrode catalyst support can be increased. There is no restriction | limiting in particular in the shape of particle | grains, What is necessary is just a shape which can enlarge a specific surface area. For example, various shapes such as a spherical shape, a polyhedral shape, a plate shape, a spindle shape, or a mixture thereof can be adopted. A spherical shape is particularly preferable.

  The particle size of the tin oxide particles containing the additive element is measured by observing the electrode catalyst of the present invention with an electron microscope. The ferret diameter of 100 or more particles is measured by electron microscope observation, and the average value is taken as the particle diameter.

  The additive elements can be present inside the tin oxide particles or both inside and outside. When the additive element is present inside the tin oxide particles, the additive element is dissolved in the tin oxide or is present in the state of the additive element compound (for example, an oxide of the additive element) in the tin oxide. doing. The fact that the additive element is dissolved in the tin oxide means that the tin site in the tin oxide is replaced by the additive element. It is preferable that the additive element is dissolved in the tin oxide because the conductivity of the tin oxide containing the additive element as the carrier is increased.

When the additive element is present outside the tin oxide particle in addition to being present inside the tin oxide particle, the additive element is mainly present on the surface of the tin oxide particle in the state of the compound. For example, the additive element is present on the surface of the tin oxide particle in the form of its oxide. When the additive element is, for example, niobium, examples of niobium oxide include Nb ₂ O ₅ , but are not limited thereto.

  The content of the additive element contained in the tin oxide containing the additive element is represented by Nb (mol) / (Sn (mol) + Nb (mol)) × 100, taking the case where the additive element is Nb as an example. It is 0.1 mol% or more and 40 mol% or less. Hereinafter, this value is referred to as “additive element content”. By setting the additive element content to 0.1 mol% or more, the conductivity of tin oxide containing the additive element can be sufficiently increased. Even if the additive element content exceeds 8 mol%, the conductivity as a carrier is not greatly improved. However, from the viewpoint of percolation theory, it is presumed that the conductivity as a carrier similarly maintains a high value up to about 40 mol% even if the additive element content exceeds 8 mol%. From the viewpoint of further increasing the conductivity of tin oxide containing an additive element and sufficiently increasing the specific surface area, the additive element content may be 0.5 mol% or more and 8 mol% or less, particularly 1 mol% or more and 4 mol% or less. More preferred.

  The additive element content of the support composed of tin oxide containing the additive element can be measured, for example, by the following method. The electrode catalyst is dissolved by an appropriate method to form a solution, this solution is analyzed by ICP emission analysis, and the concentration of tin and the concentration of additive elements are measured. Instead of ICP emission analysis, fluorescent X-ray (XRF) analysis can also be used.

  As described above, one or more elements selected from the group consisting of Nb, Sb, Ta, In, and V are used as the additive element. Of these elements, Nb or Ta is preferably used from the viewpoint of a balance between performance and price.

The carrier, which is an aggregate of tin oxide particles containing an additive element, has a chain structure portion in which a plurality of the particles are connected in a bead shape. When attention is paid to any one particle (excluding the particle located at the end) constituting the chain structure site, the particle is bonded to two or more other particles. “Coupled” means that two particles are fused and integrated, and the distance R _C between the centers of gravity of each particle is smaller than the sum of the ferret diameters (R ₁ , R ₂ ) of the particles (R _C <R ₁ + R ₂ )

  In the chain structure portion of the tin oxide particles containing the additive element, each particle may be linear, or may be a wavy curve, random zigzag, or fractal. Furthermore, a single chain structure portion may be branched into two or more lines at any position of the chain structure portion. In any case, the number of particles constituting the chain structure portion is 5 or more from the viewpoint of increasing the specific surface area of the support, reducing the contact resistance, and forming a conductive path. Preferably, the number is 50 or more, more preferably 5000 or more. The upper limit of the number is not particularly limited, but if a large number of particles are connected to about 5000, a satisfactory increase in specific surface area can be obtained.

  The carrier may be composed only of the chain structure portion of the tin oxide particles containing the additive element, or may be composed of both the chain structure portion and other form portions. Examples of other forms of sites include agglomerated sites of tin oxide particles containing an additive element. It is necessary that at least one chain structure site exists in the carrier. When two or more chain structure sites are present, the number of particles constituting each chain structure site may be the same or different.

  A catalyst containing a noble metal is supported on the surface of the support. The catalyst containing a noble metal is a catalyst forming a noble metal itself or an alloy containing a noble metal. As the alloy containing a noble metal, one kind of noble metal described below can be used alone, or two or more kinds can be used in combination. Or the alloy which consists of said noble metal and other metals, Comprising: The said noble metal is included 10 mass% or more. Noble metals that can be suitably used in the present invention are not particularly limited as long as they have electrochemical catalytic activity for oxygen reduction (and hydrogen oxidation), and known materials can be used. Specifically, the noble metal is selected from Pt, Ru, Ir, Pd, Rh, Os, Au, Ag, and the like. “Other metals” are not particularly limited, but Sn, Ti, Ni, Co, Fe, W, Ta, Nb, and Sb can be given as preferable examples. These can be used alone or in combination of two or more. Among these catalysts containing noble metals, Pt and alloys containing Pt are electrochemical catalysts for oxygen reduction (and hydrogen oxidation) in the temperature range around 80 ° C., which is the operating temperature of a polymer electrolyte fuel cell. Since the activity is high, it can be particularly preferably used.

  The catalyst containing the noble metal is advantageously supported on the surface of the support in the form of fine particles. The particle diameter of the fine particles containing the noble metal is preferably set to, for example, 1 nm to 20 nm. By supporting fine particles containing a noble metal having a particle size in this range, elution of the noble metal during the progress of the electrode reaction can be effectively prevented, and the specific surface area of the fine particles containing the noble metal is also effectively reduced. Can be prevented. The particle diameter of the fine particle containing the noble metal can be obtained by the average value of the crystallite diameter obtained from the half-value width of the diffraction peak of the catalyst containing the noble metal in X-ray diffraction or the particle diameter of the catalyst containing the noble metal examined from an electron microscope image. it can.

  The supported amount of the catalyst containing the noble metal is preferably more than 0.2 mass% and 50 mass% or less with respect to the total mass of the electrode catalyst, that is, the total mass of the support and the mass of the catalyst containing the noble metal. The content is more preferably 0% by mass or more and 18.0% by mass or less, and further preferably 3.0% by mass or more and 9.0% by mass or less. By setting the loading amount within this range, the electrode reaction can be performed sufficiently smoothly. The supported amount of the catalyst containing the noble metal can be obtained by dissolving the electrode catalyst by a suitable method to form a solution and analyzing this solution by ICP emission analysis.

  As a result of the inventor's investigation, it has been found that it is advantageous from the viewpoint of improving the conductivity that at least a part of the noble metal forms an alloy with tin, which is one of the constituent elements of the support. . The crystal system and presence / absence of this alloy (hereinafter also referred to as noble metal tin alloy) in the electrode catalyst can be confirmed by, for example, X-ray diffraction (XRD) or X-ray photoelectron spectroscopy (XPS). In particular, it is preferable that the crystal system of the noble metal tin alloy is hexagonal or cubic because conductivity is further improved.

The value of [A1 (mol) / A (mol)] × 100 (%), which is the ratio of the noble metal that is a noble metal tin alloy in the catalyst containing the noble metal, is preferably large, particularly 100%. preferable. The lower limit is not particularly limited, but is preferably 1% or more, and particularly preferably 20% or more from the viewpoint of the effect of the noble metal tin alloy on improving the conductivity of the carrier. In the formula, A1 represents the number of moles of the noble metal that is a noble metal tin alloy, and A represents the number of moles of the entire noble metal. Although it is not easy to calculate the values of A1 and A accurately, for example, the results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) can be referred to. In ordinary X-ray diffraction (XRD), when the abundance ratio of the phase is several mol% or less, the diffraction peak cannot be sufficiently confirmed. From this, when the noble metal simple phase is not confirmed but only the alloy phase is confirmed, it can be interpreted that 100 mol% of the alloy exists with an error of about several mol%. Moreover, when an alloy phase is confirmed, it can be interpreted that several mol% or more exists.
On the other hand, the present inventors consider that the relative alloy degree can be evaluated by using X-ray photoelectron spectroscopy (XPS). Non-Patent Document 1 According to J. Llorca, P. Ramirez de la Piscina, JLG Fierro, J. Sales, N, Homs, J. Mol. Catal., 118 (1997) 101-111. As for Sn binding energy of PtSn / SiO ₂ in the case of forming Sd, 3d _5/2 can be attributed to three peaks, 486.8 eV: Sn oxide, 484.9 eV: Sn of Pt and Sn alloy, respectively. , 483.6 eV: Sn ⁰ . In ordinary SnO ₂ , other than the binding energy of Sn corresponding to the oxide is not detected, so that it is less than the binding energy (486.0 eV or more) derived from the ordinary oxide (SnO ₂ , SnO) and 484.9 eV or more. By calculating the area of the peak having the apex in the range, the alloying degree of Pt can be relatively confirmed. Here, in the case where an alloy is formed with tin, which is one of the constituent elements of the support, a spectrum derived from the tin (oxide) of the support is also detected at the time of XPS measurement. However, the term “relative” was used because the above two spectral peak areas do not become 100% and the detection intensity is considered to vary depending on the chemical state of tin.
Analysis software such as XPSPEAK version 4.1 and SpecSurf can be used for the analysis of the peak area.

  The catalyst containing the noble metal may cover the entire surface of the support evenly according to the amount of the catalyst supported.However, if the reaction area of the catalyst containing the noble metal is too large for the oxygen diffusion amount in the oxygen reduction reaction, the oxygen diffusion rate is controlled. Therefore, the original catalytic activity may not be sufficiently exhibited. Therefore, it is preferable to discontinuously coat the support so that the surface of the support is exposed at an appropriate distance.

The electrode catalyst has a large specific surface area due to the special shape of the carrier constituting the electrode catalyst. Specifically, the specific surface area is preferably 20 m ² / g or more and 130 m ² / g or less, more preferably 30 m ² / g or more and 100 m ² / g or less. By having such a large specific surface area, the catalytic activity of a catalyst containing a noble metal can be effectively utilized. The specific surface area is generally measured using physical adsorption such as nitrogen gas. For example, it can be measured by the BET method. Specifically, SA3100 manufactured by Bechman Coulter or flowsorb II manufactured by Micromeritics can be used for measurement of the specific surface area by the BET method.

  Next, the suitable manufacturing method of the electrode catalyst of this invention is demonstrated. This production method is roughly divided into (i) a carrier production step and (ii) a catalyst loading step including a noble metal. Hereinafter, each process will be described.

  First, the production process of the carrier (i) will be described. Since this carrier has a chain structure, such a carrier can be preferably produced by a chemical flame method. In the chemical flame method, a raw material liquid containing a compound containing a tin compound and an additive element and an organic solvent capable of dissolving these compounds is used. As the tin compound, an organic tin compound is preferably used. As the organic tin compound, for example, a tin salt of an organic acid such as tin octylate or dibutyltin bisacetylacetonate (“Narsem Tin” (trade name) manufactured by Nippon Chemical Industry Co., Ltd.) can be used. A tin compound can be used individually by 1 type or in combination of 2 or more types. On the other hand, as the compound containing an additive element, an organic compound containing the additive element is preferably used. For example, when the additive element is niobium, it is preferable to use an organic niobium compound. As the organic niobium compound, for example, a niobium salt of an organic acid such as niobium octylate can be used. The compound containing an additional element can be used individually by 1 type or in combination of 2 or more types.

  As an organic solvent for dissolving a compound containing a tin compound and an additive element, aromatics or alcohols such as terpene oil, mineral spirits, octylic acid, methanol, ethanol, an aqueous solution thereof, a mixture thereof, or the like is used. be able to. Of these, it is preferable to use turpentine oil in view of viscosity and heat of combustion.

  The concentration of the tin compound in the raw material liquid is preferably 1% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 14% by mass or less in terms of tin. On the other hand, the concentration of the compound containing the additive element in the raw material liquid is preferably 0.004% by mass to 3.4% by mass in terms of the additive element, and 0.012% by mass to 0.95% by mass. More preferably. The ratio of the tin compound and the compound containing the additive element in the raw material solution is adjusted to match the ratio of tin and the additive element in the target carrier.

  The raw material liquid obtained in this way is supplied into a chemical flame with a fuel gas such as propane, methane, acetylene, hydrogen or nitrous oxide and burned to have a target carrier, that is, a chain structure site. A carrier is obtained. When the raw material liquid is supplied into the chemical flame, the reaction and cooling are instantaneously performed to produce the intended primary particles, and as a result, the primary particles are partially fused and bonded together, resulting in a high specific surface area. A carrier having From this viewpoint, the temperature of the chemical flame is preferably set to 600 ° C. or higher and 2000 ° C. or lower, more preferably set to 1200 ° C. or higher and 1600 ° C. or lower.

  When the support is obtained as described above, it is subjected to the step (ii) for supporting a catalyst containing a noble metal. In the supporting step, the support is dispersed in a liquid containing a colloid containing a noble metal, and the colloid containing the noble metal is supported on the support as fine particles containing the noble metal, and then heat treatment is performed. Specifically, (ii-a) a reducing agent is added to a liquid containing a colloidal precursor containing a noble metal to reduce the precursor to produce a colloid containing the noble metal, and the produced noble metal is contained. A carrier is dispersed in a liquid containing a colloid, the colloid containing the noble metal is supported on the carrier as fine particles containing the noble metal, and (ii-b) the liquid is separated from the carrier carrying the fine particles containing the noble metal. Then, the support is dried, and (ii-c) the dried support carrying fine particles containing a noble metal is heat-treated in a reducing atmosphere. Surprisingly, by using a liquid containing a colloid containing a noble metal to support the catalyst containing the noble metal on the support made of the structure, the conductivity of the obtained electrode catalyst is not only reduced but also in the air. As a result of the study by the present inventors, it has been found that the improvement is greatly improved.

  The conditions for preparing the liquid containing the colloid containing the noble metal used in (ii-a) are not particularly limited, and may be set appropriately according to the selected noble metal precursor and the reducing agent. As the noble metal precursor, for example, when platinum is used as the noble metal, chloroplatinic acid can be used. Further, the form when the carrier is dispersed in the solution containing the colloid containing the noble metal may be in a powder state or in a state dispersed in a liquid medium such as water or ethanol. The latter is desirable because a uniform solution can be reliably formed.

Examples of the reducing agent used for the reduction of the colloidal precursor containing the noble metal include sodium bisulfite (NaHSO ₃ ), sodium borohydride, sodium triethylborohydride, hydrogen peroxide, and hydrazine. These may be used singly or in combination of two or more. Of these reducing agents, it is particularly preferable to use sodium bisulfite. Furthermore, after performing reduction with a certain reducing agent, reduction may be performed again with another reducing agent. By performing multistage reduction treatment in the liquid phase as described above, fine particles containing a noble metal can be supported in a highly dispersed state on a carrier. As a preferred specific example of performing multi-stage reduction using two or more kinds of reducing agents, there is a method in which sodium bisulfite is first used as the reducing agent and then hydrogen peroxide is used. It is preferable to adjust the pH of the liquid to the value described below after the reduction using sodium hydrogen sulfite and before the reduction using hydrogen peroxide.

  After the reduction, the pH of the liquid containing the colloidal precursor containing the noble metal can be, for example, 1 or more and 10 or less, and 4 or more and 6 or less is particularly preferable. By setting to this pH range, a colloid solution in which a colloid containing a noble metal is uniformly dispersed without aggregation can be prepared.

  A suitable temperature range when reducing the colloidal precursor containing a noble metal is 20 ° C. or more and 100 ° C. or less, and particularly preferably 50 ° C. or more and 70 ° C. or less. By carrying out the reduction in this temperature range, the noble metal precursor can be sufficiently reduced, and a decrease in dispersibility of the fine particles containing the noble metal due to boiling of the liquid can be prevented. The reduction time is usually from 10 minutes to 2 hours, provided that the temperature range is within this range.

  The colloid precursor containing noble metal is not particularly limited, and a liquid medium that is suitably used as a solvent, for example, water or one that is soluble in lower alcohols such as methanol and ethanol is selected. Specific examples include halides, nitrates, sulfates, oxalates and acetates of noble metal elements.

  In (ii-b), the said liquid is isolate | separated from the support | carrier which carry | supported the microparticles | fine-particles containing a noble metal, and this support | carrier is dried. The method for separating the liquid is not particularly limited, and usually a method is selected in which most of the liquid is removed by filtration, centrifugation, etc., and then the remaining liquid is evaporated and dried. As a drying method, any of heat drying, reduced pressure drying, and natural drying may be used. The atmosphere in which drying is performed is not particularly limited, and the atmospheric conditions such as an oxidizing atmosphere containing oxygen or an air atmosphere, an inert atmosphere containing nitrogen or argon, or a reducing atmosphere containing hydrogen are arbitrarily selected. You can choose. Usually, it is performed in an air atmosphere. The temperature at which drying is performed is not particularly limited, and is preferably performed at a temperature of less than 150 ° C. from the viewpoint of preventing oxidation of the catalyst containing the noble metal. Before the separation, an operation for removing impurities contained in the carrier may be performed. For example, when chloroplatinic acid is used as the noble metal precursor, chloride ions may remain in the carrier. For the purpose of removing the chloride ions, the carrier is diluted with ultrapure water to form a slurry. It is preferable to prepare and boil the slurry. The boiling can be performed under atmospheric pressure. In order to ensure the removal of impurities, the dilution and boiling operations with ultrapure water may be repeated a plurality of times.

  (Ii-c) is a step of activating fine particles containing a noble metal supported on a carrier. Since the fine particles containing a noble metal dried through (ii-b) contain a large amount of non-stoichiometric noble metal oxide, the catalytic activity may be low. Therefore, in this step, the electrochemical catalytic action of the noble metal is activated by heat treatment in a reducing atmosphere. Further, the heat treatment generates an alloy of the noble metal element and tin contained in the support.

  The temperature of the heat treatment is preferably set to 150 ° C. or higher and 500 ° C. or lower, more preferably 250 ° C. or higher and 300 ° C. or lower, from the viewpoint of successfully activating the noble metal and alloying with tin. The heating temperature in the latter range is higher than a conventionally employed temperature, for example, the heating temperature described in Patent Document 1. By adopting such a high temperature setting, it becomes possible to further promote alloying of noble metal and tin. However, if the heating temperature is excessively high, aggregation of the formed alloy particles proceeds, and the electrochemically active surface area in the oxygen reduction reaction may decrease. Therefore, it is preferable to perform the heat treatment at a temperature within the above range. The heating holding time after reaching the set holding temperature is preferably 1 minute to 4 hours, preferably 10 minutes to 2 hours, provided that the heating temperature is within this range. preferable. The rate of temperature rise is preferably 1 ° C./min or more and 20 ° C./min, preferably 3 ° C./min or more and 10 ° C./min or less when the temperature rise starts from room temperature. The temperature lowering rate can also be within this range, but it is preferable to rapidly cool to room temperature.

  Examples of the reducing atmosphere include hydrogen and carbon monoxide. Hydrogen is preferable in that it is free from problems such as catalyst poisoning of fine particles containing noble metals and is easily available. When hydrogen is used, it may be used at a concentration of 100%, or preferably 0.1 to 50% by volume, more preferably 1 to 10% by volume with an inert gas such as nitrogen, helium or argon. You may dilute and use.

  The target electrode catalyst is obtained as described above. This electrode catalyst is used by being contained in at least one of an oxygen electrode and a fuel electrode in a membrane electrode assembly having an oxygen electrode disposed on one surface of a solid polymer electrolyte membrane and a fuel electrode disposed on the other surface. be able to. The electrode catalyst can be preferably contained in both the oxygen electrode and the fuel electrode.

  In particular, the oxygen electrode and the fuel electrode preferably include a catalyst layer containing the electrode catalyst of the present invention and a gas diffusion layer. In order for the electrode reaction to proceed smoothly, the electrode catalyst is preferably in contact with the solid polymer electrolyte membrane. The gas diffusion layer functions as a supporting current collector having a current collecting function. Furthermore, it has a function of sufficiently supplying gas to the electrode catalyst. As the gas diffusion layer, those similar to those conventionally used in this kind of technical field can be used. For example, carbon paper and carbon cloth which are porous materials can be used. Specifically, it can be formed by, for example, a carbon cloth woven with yarns having a predetermined ratio of carbon fibers whose surfaces are coated with polytetrafluoroethylene and carbon fibers that are not coated.

  As the solid polymer electrolyte, those similar to those conventionally used in this kind of technical field can be used. For example, a perfluorosulfonic acid polymer-based proton conductor film, a hydrocarbon polymer compound doped with an inorganic acid such as phosphoric acid, or an organic / inorganic hybrid polymer partially substituted with a proton conductor functional group And proton conductors in which a polymer matrix is impregnated with a phosphoric acid solution or a sulfuric acid solution.

  The membrane electrode assembly is provided with a separator on each surface to form a polymer electrolyte fuel cell. As the separator, for example, a separator in which a plurality of protrusions (ribs) extending in one direction are formed at a predetermined interval on the surface facing the gas diffusion layer can be used. Between adjacent convex parts, it is a groove part with a rectangular cross section. The groove is used as a supply / discharge flow path for an oxidant gas such as fuel gas and air. The fuel gas and the oxidant gas are supplied from the fuel gas supply unit and the oxidant gas supply unit, respectively. Each separator disposed on each surface of the membrane electrode assembly is preferably disposed so that the grooves formed therein are orthogonal to each other. The above configuration constitutes the minimum unit of the fuel cell, and a fuel cell can be configured from a cell stack in which several tens to several hundreds of this configuration are arranged in parallel.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the above-described embodiment, the example in which the electrode catalyst of the present invention is used as an electrode catalyst of a solid polymer electrolyte fuel cell has been mainly described. However, the electrode catalyst of the present invention is not a solid polymer electrolyte fuel cell. It can be used as an electrode catalyst in various fuel cells such as alkaline fuel cells, phosphoric acid fuel cells, direct methanol fuel cells, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” and “part” mean “% by mass” and “part by mass”, respectively.

[Example 1]
(I) Production of carrier The flame method synthesizer shown in FIGS. 1 and 2 was used. This apparatus is the same as that described in FIGS. 2 and 3 of Patent Document 2 (US2012 / 0295184A1). Niobium was used as an additive element. Carrier oxygen for transferring the raw material into the flame, oxygen for forming the flame and propane gas at a flow rate of 9 L / min, 5 L / min and 1 L / min, respectively, as shown in FIG. The gas was introduced from the gas inlets 31 and 32 and mixed in the gas mixer 33. The mixed gas was introduced into the stainless steel tube 34 and a chemical flame was generated by the burner 40.

  A solution is prepared by dissolving tin octylate and niobium octylate in terpene oil at a molar ratio of tin and niobium of 0.99: 0.01, and this solution is supplied to the solution introduction unit 35 of the flame method synthesizer. While introducing in an amount of 1 to 10 g per minute, the mixer 37 and the stainless steel tube 38 were passed by the oxygen gas put in the carrier gas introduction part 36. The concentrations of tin octylate and niobium octylate in the solution were 13.6% and 0.11%, respectively, in terms of tin and niobium.

This solution was made into a mist through a fluid nozzle, an air nozzle, and a retainer cap 39 and introduced into the chemical flame by the burner 40. The temperature of the chemical flame was raised to about 1400 ° C. by the combustion heat of propane gas and terpene oil, and a support made of niobium-containing tin oxide was obtained in the chemical flame. The powder produced in FIG. 2 was recovered by the recovery filter 27.
In the flame method, the environment during powder synthesis can often be in a non-equilibrium state, so that the obtained powder may change over time. Then, the support | carrier obtained by said procedure was heat-processed using the rotary kiln (made by Alpha Giken) for the purpose of stabilization by the heat processing in an equilibrium state.
5 g of niobium-containing tin oxide was inserted into a Tamman tube having a diameter of 5 cm, and the core tube was rotated at a rotation speed of 6 rpm. In an open air environment, the temperature was raised at 5 ° C./min and held at 800 ° C. for 4 hours. Thereafter, the temperature was lowered to about room temperature at 5 ° C./min, and the powder was recovered. When this support was observed with a transmission electron microscope, it was confirmed that five or more particles had a chain structure portion connected in a bead shape. The average particle size of the particles was 20 nm.

(Ii) Loading of catalyst containing noble metal 5 ml of a H ₂ PtCl ₆ solution (corresponding to 1 g of Pt) was dissolved in 295 mL of distilled water, reduced with 15.3 g of NaHSO ₃ and diluted with 1400 mL of distilled water. NaOH 5% aqueous solution was added to adjust the pH to about 5, and 35% hydrogen peroxide (120 mL) was added dropwise to obtain a liquid containing platinum colloid. At this time, NaOH 5% aqueous solution was appropriately added to maintain the pH of the solution at about 5. The colloidal solution obtained by the above procedure contains 1 g of platinum. Here, the colloidal solution was fractionated so that the theoretical concentration of platinum when it was supported on 4 g of carrier was 5 mass% (the amount of platinum contained in the solution was 0.21 g). Then 4 g of carrier was added and mixed at 90 ° C. for 3 hours. Thereafter, the liquid was cooled and further solid-liquid separated. In order to remove chloride ions from the water-containing powder obtained by solid-liquid separation, it was diluted again with 1500 mL of distilled water and boiled at 90 ° C. for 1 hour, and the liquid was cooled and solid-liquid separated. This washing operation was performed four times. Finally, after solid-liquid separation, it was dried at 60 ° C. for 12 hours in the atmosphere. As a result, platinum containing a non-stoichiometric noble metal oxide was supported on the surface of the support. The support was then heat-treated at 150 ° C. for 2 hours in a 1 vol% hydrogen atmosphere diluted with nitrogen. Thereby, reduction of platinum and alloying of platinum and tin were performed. Thus, the target electrode catalyst was obtained. The amount of platinum supported on this electrode catalyst was 3.9%. Moreover, the alloying of platinum and tin was confirmed by X-ray photoelectron spectroscopy (XPS). The XPS measurement uses the ULVAC-PHI 5800 series, the X-ray source is Al Kα monochromatic light (hν = 1486.58 eV), the energy step is 0.025 eV, the angle between the sample and the detector is 45 °, the analysis area of the sample Was performed with a circle having a diameter of 0.8 mm. Calibration of the detector was performed using three points of Ag3d _5/2 (368.26 eV), Pt4f _7/2 (71.12 eV), and Fermi Edge (0 eV). The sample used was a pellet obtained by compressing 0.15 g of powder at 150 MPa for 1.5 minutes. The result is shown in FIG. As is clear from the figure, a 3d _5/2 peak of Sn was confirmed in the vicinity of 485.3 eV, and it was confirmed that an alloy was formed.
On the other hand, XRD used Ulima 4 manufactured by Rigaku Corporation, and Cu Kα (0.15406 nm, 40 kV, 40 mA) was used as the X-ray source. The result confirmed by XRD is shown in FIG. As is clear from the figure, no PtSn alloy was confirmed, and a peak slightly shifted from the Pt simple peak was confirmed, and the crystal system was cubic.
The proportion of platinum alloyed with tin was 1.8%. This is the ratio of the peak area having a peak at 485.3 eV in the total Sn3d _5/2 spectral peak area in XPS. Hereinafter, the ratio of the peak area having the apex in the range of less than 486.0 eV and 484.9 eV or more to the total Sn3d _5/2 spectral peak area is referred to as an alloying ratio 1.
On the other hand, since alloying is thought to be formed only in the portion where platinum is present on the support, the area ratio of the alloy per contact area of platinum and the support was converted in consideration of the area coverage of the support by platinum. This is hereinafter referred to as an alloying ratio of 2. As a result, the ratio was 22.3%. The BET specific surface area of the electrode catalyst carrier was 25 m ² / g.
The contact area was calculated as follows. The amount (g) of platinum present per 1 g of the carrier was calculated from the platinum loading analyzed by ICP, and converted to volume using the density of platinum. Thereafter, the number of platinum particles per 1 g of the carrier was calculated in terms of true spheres using the particle diameter of platinum. The contact area between platinum and the carrier was the number of platinum particles × 2 × the hemispherical cross-sectional area of platinum particles (see FIG. 3 described later). The platinum particle diameter was calculated by observing about 100 platinum particles with a transmission electron microscope (TEM). As a result of observation, the supported platinum and its alloy particles were often hemispherically bonded to the support, and therefore a factor of x2 was adopted (see FIG. 3 described later).

[Examples 2 and 3 and Comparative Example 1]
In Example 1 (ii), the theoretical concentration of platinum when supported on 4 g of carrier is the desired concentration (10% (Example 2), 20% (Example 3), 0.5% (Comparative Example 1). )) An electrode catalyst was obtained in the same manner as in Example 1 except that the amount of the colloidal solution was adjusted. Table 1 shows the amount of platinum supported in the electrode catalysts in Examples 2 and 3 and Comparative Example 1, and the proportion of platinum alloyed with tin (alloying proportions 1 and 2). FIG. 3 shows a TEM image of the electrode catalyst obtained in Example 2. As is clear from the figure, most of the catalysts containing noble metals are attached to the support in a hemispherical shape.

[Examples 4 and 5]
In Example 3 (ii), except that the temperature of the heat treatment for activation of platinum and alloying of platinum and tin was set to 250 ° C. (Example 4) and 300 ° C. (Example 5). In the same manner as in Example 3, an electrode catalyst was obtained.
In Example 4, the amount of platinum supported on the electrode catalyst was 13.3% by mass. The result of XPS measurement is shown in FIG. As is clear from the figure, a 3d _5/2 peak of Sn was confirmed in the vicinity of 485.9 eV, and it was confirmed that an alloy was formed. On the other hand, the result of the XRD measurement is shown in FIG. As is clear from the figure, no PtSn alloy was confirmed, and a peak slightly shifted from the peak of Pt was confirmed, and the crystal system of the alloy confirmed by XRD was cubic. Of platinum, the alloying ratio 1 alloyed with tin was 7.6%. The alloying ratio 2 was 39.0%. The BET specific surface area of the electrode catalyst carrier was 25 m ² / g.
In Example 5, the amount of platinum supported on the electrode catalyst was 13.3% by mass. The result of XPS measurement is shown in FIG. As is clear from the figure, a 3d _5/2 peak of Sn was confirmed in the vicinity of 485.7 eV, and it was confirmed that an alloy was formed. On the other hand, the result of the XRD measurement is shown in FIG. As is clear from the figure, the alloy was PtSn and its crystal system was hexagonal. Of platinum, the alloying ratio 1 alloyed with tin was 4.4%. The alloying ratio 2 was 31.0%. The BET specific surface area of the electrode catalyst carrier was 25 m ² / g.

Example 6
An electrode catalyst was obtained in the same manner as in Example 1 except that the niobium content in the support was 4% in Example 1 (i). A transmission electron microscope image of this carrier is shown in FIG. As is apparent from the figure, this carrier has a chain structure portion in which a plurality of particles are linked in a beaded manner.

Example 7
In Example 4, the heat treatment for activation of platinum and alloying of platinum and tin was performed for 2 hours in a hydrogen atmosphere with a concentration of 100%. Except this, it carried out similarly to Example 4, and obtained the electrode catalyst. Evaluation similar to Example 4 was performed about the obtained electrode catalyst. The results are shown in Table 1.

[Comparative Example 2]
This comparative example is an example using a carrier not containing niobium. In Example 1 (i), niobium octylate was not used during the production of the carrier. Except for this, an electrode catalyst was obtained in the same manner as in Example 1.

[Comparative Example 3]
In this comparative example, platinum is not supported on the carrier. In Example 6, the step (ii) was not performed. Except this, the procedure was the same as in Example 6.

[Comparative Example 4]
This comparative example is an example in which a carrier having no chain structure portion in which particles are arranged in a bead shape is used. 88.493 g of sodium stannate trihydrate was weighed, and pure water was added thereto to make 1064 g, followed by stirring and dissolution to obtain a sodium stannate solution. 3.6322 g of niobium chloride (NbCl ₅ ) was weighed and dissolved in 83 ml of absolute ethanol, and 902 g of a 12 g / L nitric acid solution was added thereto to obtain a niobium chloride nitric acid solution. The niobium chloride nitric acid solution was added to the sodium stannate solution and stirred for 1 hour. Filtration and pure water washing were performed until the electrical conductivity of the supernatant liquid during filtration was 45 mS / cm or less. The obtained cake was dried at 120 ° C. overnight and crushed with a mortar. After the pulverized product was calcined at 800 ° C. for 5 hours in the atmosphere, 25 g of the calcined powder was mixed with 100 g of pure water to form a slurry, and this slurry was pulverized with a ball mill for 16 hours. Thereafter, the slurry was filtered, the filter cake was dried at 120 ° C. in the air, and the dried product was sieved at 100 μm. The particles thus obtained were used as a carrier. Except this, it carried out similarly to Example 6, and obtained the electrode catalyst. A transmission electron microscope image of this carrier is shown in FIG. As is apparent from the figure, this carrier does not have a chain structure portion in which a plurality of particles are linked in a bead shape.

[Comparative Example 5]
In this comparative example, platinum was not supported on the carrier in Comparative Example 4. The rest was the same as in Comparative Example 4.

[Comparative Example 6]
This comparative example is an example in which platinum was not supported on a carrier in a Nb 1 mol% system. Specifically, in Example 1, the step (ii) was not performed. Except for this, an electrode catalyst was obtained in the same manner as in Example 1.

[Comparative Example 7]
This comparative example is an example where no noble metal was reduced in Example 4. Specifically, the step (ii-c) was not performed in Example 4. Except this, it carried out similarly to Example 4, and obtained the electrode catalyst.

[Evaluation 1]
The conductivity of the electrode catalyst obtained in the examples and comparative examples was measured. Specifically, the electrical conductivity under a pressure of 1 MPa was measured by the two-terminal method using the method shown in FIG. Resistance meter 3565 of Tsuruga Electric Co., Ltd. was used for resistance measurement. The pressure of 1 MPa simulates the pressure normally applied to the electrode catalyst layer of the polymer electrolyte fuel cell. An aluminum foil (2.5 cm × 12 cm and 3 cm × 17 cm) serving as an electrode was pressed in a state where it was placed above and below the sample, and the conductivity was measured. The contact resistance usually included in the two-terminal method was removed by the following method. In the graph where the “sample thickness” under a constant pressure is adjusted by changing the filling amount such as 0.5 g, 1.5 g, and 2.0 g, and the sample thickness is plotted on the x axis and the resistance is plotted on the y axis, The y-intercept with a thickness of 0 was calculated as the contact resistance in the two-terminal method, and the resistance of the sample was calculated by subtracting from the measured value. The resistivity was calculated from the dimensions of the green compact, and the reciprocal thereof was used to calculate the conductivity. The measurement results are shown in Table 1 below. The same measurement was performed on the carrier before carrying platinum, and the change in conductivity before and after carrying platinum (conductivity after carrying / conductivity before carrying) was determined. The results are also shown in Table 1.

  Furthermore, the alloys of the electrode catalysts obtained in Examples and Comparative Examples were evaluated by XRD and XPS. These results are shown in Table 1.

  As is clear from the results shown in Table 1, it can be seen that the electrocatalysts obtained in the respective examples have higher electrical conductivity than the electrocatalysts of the comparative examples. It can also be seen that the change in conductivity before and after platinum loading is very large.

In particular, compared to Comparative Example 6 (without platinum support) and Comparative Example 7 (with the same amount of platinum support and no reduction alloying as in Example 4), the conductivity of Examples 1 to 4 whose alloys were confirmed by XPS It can be seen that is greatly improved. This shows the effect of improving conductivity by alloying.
Further, when the improvement rate of the conductivity after platinum loading / reduction in Comparative Examples 4 and 5 is compared with the improvement rate of the conductivity after platinum loading / reduction in Comparative Example 3 and Example 6, the latter is about 10%. You can see that it is twice as big. This result shows that the support (see FIG. 7) having a chain structure part in which the particles are arranged in a bead shape is based on platinum loading / reduction as compared with the support (see FIG. 8) not having such a part. It shows that the conductivity improvement effect is excellent.

  Furthermore, from Examples 4 and 5, it can be seen that the crystal system of the alloy is either cubic or hexagonal, but the conductivity is improved, but the hexagonal crystal has a higher conductivity.

Furthermore, it can be seen from the comparison between Comparative Example 2 and Example 1 and Example 6 that the higher the niobium content, the better the improvement rate of the conductivity after reduction. In particular, it can be seen that in Comparative Example 2, the improvement in conductivity after platinum loading and reduction is about twice, which is much smaller than in Examples 1 and 6. This is considered to indicate that the presence of the dopant Nb is extremely important, and it is important that the conductivity of the carrier is improved to some extent by the presence of the dopant. When Pt is not supported or reduced, in the system in which tin oxide is doped with niobium, the conductivity enhancement effect by the dopant is observed from a niobium concentration of about 0.1 mol%, so the lowest niobium concentration in this example Is 1 mol%, but it is estimated that the effect of improving conductivity is exhibited from about 0.1 mol%.
Further, the present inventor shows that even when doping niobium until its concentration reaches about 8 mol%, the conductivity of the carrier, which is not related to Pt loading or reduction, does not change significantly compared to the niobium concentration of 4 mol%. Have confirmed. From the viewpoint of percolation theory, it is presumed that the conductivity of the carrier unrelated to Pt loading or reduction similarly maintains a high value up to about 40 mol% even if the niobium concentration exceeds 8 mol%. Therefore, it is presumed that there is an effect of improving the conductivity at least until the niobium concentration is about 40 mol%.

[Evaluation 2]
The electrode catalysts obtained in Examples 3 and 5 were subjected to cyclic voltammetry (CV) and convective voltammetry (LSV) using a rotating disk electrode. Specifically, operations were performed in the following order of “electrode preparation”, “CV measurement”, and “ORR activity evaluation”.

The glassy carbon (GC) disk electrode of the electrode fabricated diameter 5 mm 1 [mu] m, 0.3 [mu] m, and sequentially polished using 0.05μm alumina paste was then ultrasonically washed with pure water. A sample carrying platinum and subjected to the reduction heat treatment described in (ii-c) was 90 vol. In addition to an aqueous ethanol solution, the mixture was dispersed with an ultrasonic homogenizer. This was dropped onto a GC disk and dried at room temperature for 12 hours or more. After drying, a 5% Nafion (registered trademark) solution was dropped onto the catalyst on the GC disk so as to have a film thickness of 50 nm, and dried at room temperature for 12 hours or more.

The CV measurement was performed using an electrochemical measurement system HZ-5000 manufactured by Hokuto Denko Corporation. After purging N _{2 in} 0.1 M HClO ₄ aqueous solution for 1 hour or more, using a reversible hydrogen electrode (RHE) as a reference electrode, cleaning was performed 60 times at a potential range of 0.05 to 1.15 V and a sweep rate of 0.5 V / s. Carried out. Then, it replaced with new electrolyte solution and implemented CV measurement in the electric potential range 0.05-1.0V, and was set as this measurement. The analysis of the electrochemical active surface area (ECSA) was carried out using an adsorption wave of hydrogen found at 0.4 V or less.

Evaluation of ORR activity After purging the electrolyte solution with oxygen gas for 1 hour or longer, LSV was performed. Data of a total of 8 conditions were acquired while increasing the rotation speed from 1000 rpm to 2750 rpm in increments of 250 rpm at a temperature of 25 ° C., a potential range of 0.25 to 1.00 V, a sweep speed of 5 mV / s. The results obtained were analyzed using Koutecky-Levich plotted, the value obtained active dominant current density _j k (mA / cm ²⁾ and the mass specific activity _{(A / g -Pt)} in 0.85V. These results are shown in Table 2 below.

As is clear from the results shown in Table 2, the activity-dominated current density j _k (mA / cm ² ) and mass specific activity (A / g _−Pt ) of Example 5 were equivalent to Example 3. As described above, the conductivity of the electrode catalyst is improved by the progress of alloying. As a result, it was confirmed that the oxygen reduction activity was ensured without decreasing.

Example 8
(I) Production of carrier In this example, a carrier in which tantalum was contained as an additive element in tin oxide was produced. In the production process of the carrier in Example 1, dibutyltin bisacetylacetonate (“Narsemtin” (trade name) manufactured by Nippon Chemical Industry Co., Ltd.) was used instead of tin octylate, and octyl was substituted for niobium octylate. Tantalum acid was used. Dibutyltin bisacetylacetonate and tantalum octylate were blended so that the molar ratio of tin to tantalum was 0.975: 0.025, and dissolved in terpene oil to prepare a solution. The concentrations of dibutyltin bisacetylacetonate and tantalum octylate in the solution were 13.6% and 0.53%, respectively, in terms of tin and tantalum. A carrier was obtained in the same manner as in Example 1 except for this. When this support was observed with a transmission electron microscope, it was confirmed that five or more particles had a chain structure portion connected in a bead shape. The average particle size of the particles was 20 nm.

(Ii) Loading of catalyst containing noble metal Example 1 except that the amount of colloidal liquid was adjusted so that the theoretical concentration of platinum when supported on 4 g of support was 3.6% in (ii) of Example 1. In the same manner as above, an electrode catalyst was obtained. The obtained electrode catalyst was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Examples 9 and 10]
In Example 8 (ii), the amount of colloidal solution was adjusted so that the theoretical concentration of platinum when supported on 4 g of the carrier was the desired concentration (10% (Example 9), 20% (Example 10)). An electrode catalyst was obtained in the same manner as in Example 1 except for the adjustment. The obtained electrode catalyst was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Comparative Example 8]
This comparative example is an example in which platinum was not supported on the support made of tin oxide containing tantalum in Example 8. That is, in Example 8, the step (ii) was not performed. The rest was the same as in Example 8.

  As is clear from the results shown in Table 3, it can be seen that the electrocatalysts obtained in each Example have a very large change in conductivity before and after the loading of platinum.

Claims (10)

A carrier having a chain structure portion in which a plurality of particles containing tin oxide and one or more additive elements selected from the group consisting of Nb, Sb, Ta, In and V are connected in a bead shape; An electrode catalyst comprising a noble metal-supported catalyst supported on a surface, wherein at least a part of the noble metal forms an alloy with tin of the carrier;
An electrode catalyst having a content of the additive element in the carrier of 0.1 mol% or more and less than 4 mol%.   The electrode catalyst according to claim 1, wherein a crystal system of the alloy is hexagonal or cubic.   The electrode catalyst according to any one of claims 1 to 2, wherein a loading amount of the catalyst containing the noble metal is more than 0.2 mass% and not more than 50 mass% with respect to the electrode catalyst. The electrode catalyst according to any one of claims 1 to 3 , wherein the additive element is Nb or Ta. In a membrane electrode assembly in which a pair of electrodes consisting of an oxygen electrode and a fuel electrode are disposed on each surface of a solid polymer electrolyte membrane,
The membrane electrode assembly in which at least one of the oxygen electrode or the fuel electrode contains the electrode catalyst according to any one of claims 1 to 4 . A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 5 and a separator disposed on each surface of the membrane electrode assembly. An electrode catalyst comprising a support having a chain structure portion in which a plurality of particles containing tin oxide and one or more additive elements selected from the group consisting of Nb, Sb, Ta, In, and V are arranged in a bead shape A manufacturing method comprising:
The manufacturing method includes:
Adding a reducing agent to a liquid containing a precursor of a colloid containing a noble metal, reducing the precursor to produce a colloid containing a noble metal;
The carrier is dispersed in a liquid containing the colloid containing a noble metal, and supported on the carrier as fine particles containing a noble metal,
Separating the liquid from the carrier carrying the noble metal-containing fine particles, and drying the carrier;
A step of heat-treating the carrier after drying supporting fine particles containing the noble metal in a reducing atmosphere;
A method for producing an electrode catalyst, wherein a temperature of the heat treatment is set to 150 ° C. or more and 500 ° C. or less, and a part of the supported noble metal is alloyed with tin of the support. The manufacturing method according to claim 7 , wherein a temperature of the heat treatment is set higher than 250 ° C. and lower than 300 ° C., and a part of the noble metal is alloyed with tin. The raw material solution containing an organic solvent capable of dissolving the compound and of the compounds containing a tin compound and the additional element, by supplying in the chemical flame combustion, according to claim 7 or 8 for producing said carrier Manufacturing method. The production method according to any one of claims 7 to 9, wherein the content of the additive element in the carrier is 0.1 mol% or more and less than 4 mol% .