JP6524856B2 - Method of producing catalyst for electrode - Google Patents

Description

  The present invention relates to a method of producing a catalyst for an electrode. Furthermore, in detail, even if the electrode catalyst precursor containing relatively high concentration of bromine (Br) species is used as a raw material of the electrode catalyst, the content of bromine (Br) species is relatively easy to operate. The present invention relates to a method for producing a catalyst for an electrode, the amount of which can be reliably and sufficiently reduced.

  The so-called polymer electrolyte fuel cell (hereinafter referred to as "PEFC" as required) has an operating temperature of about room temperature to about 80 ° C. Moreover, since PEFC can adopt inexpensive general purpose plastic etc. as a member which constitutes a fuel cell main body, weight reduction becomes possible. Furthermore, PEFC can thin the solid polymer electrolyte membrane, can reduce the electrical resistance, and can relatively easily reduce the power generation loss. As described above, PEFC has many advantages, so that it can be applied to fuel cell vehicles, home cogeneration systems, and the like.

As an electrode catalyst for PEFC, an electrode catalyst in which platinum (Pt) or a platinum (Pt) alloy as an electrode catalyst component is supported on carbon as a carrier has been proposed (for example, Non-Patent Document 1).
Conventionally, among the halogens contained in the electrode catalyst for PEFC, it has been disclosed that the chlorine content is 100 ppm or more among the halogens contained in the electrode catalyst (for example, Patent Document 3). ). Regarding the reason, when the chlorine content contained in the electrode catalyst is 100 ppm or more, sufficient catalytic activity can not be obtained as the electrode catalyst for the fuel cell, corrosion of the catalyst layer occurs, and the fuel cell It is disclosed that the life is shortened.

Therefore, a PEFC is provided with a membrane electrode assembly in which electrodes are joined on both sides of an electrolyte membrane, and some of protons of acid groups contained in the electrolyte in the catalyst layer included in the electrode are exchanged with phosphonium ions It is proposed (for example, patent document 1). In the PEFC, the counter anion of the phosphonium ion is a compound not containing a halogen element. For this reason, it is disclosed that if the halogen element remains in the electrode, the battery performance is degraded. Specifically, among halide ions, fluoride ion, chloride ion and bromide ion may reduce battery performance by remaining in the electrode, and in particular, chloride ion may cause an electrode reaction when it remains in the electrode. It is described that poisoning or Pt of the catalyst is eluted from the catalyst layer as a complex ion such as PtCl ₄ ^2- or PtCl ₆ ^2- to cause the performance of the battery to be greatly reduced.

Moreover, PEFC provided with the membrane electrode assembly (MEA) in which the electrode which contains a catalyst layer on both surfaces of an electrolyte membrane was joined is proposed (for example, patent documents 2). Pd and Pt, which are catalyst components of Pd / Pt particles contained in the catalyst layer of PEFC, are derived from halides.
For this reason, in the method of producing Pd / Pt particles described in Patent Document 2, a compound containing no halogen is adopted as an ion exchange solution, as an ion exchange solution used when producing Pd and Pt. Patent Document 2 discloses that halogen ions should be avoided in order to reduce battery performance. Further, Patent Document 2 exemplifies hot water washing as a dehalogenation ion treatment method.

Furthermore, a method for producing a powder of platinum (Pt) or platinum (Pt) alloy containing less than 100 ppm of chlorine as a catalyst component of the electrode catalyst has been proposed (for example, Patent Document 3).
The following method is disclosed as a method for producing the above-mentioned platinum (Pt) or platinum (Pt) alloy powder. That is, after forming a melt of a chlorine-free platinum compound and a chlorine-free alloying element as starting materials, the melt is heated to give an oxide, and the oxide is cooled and then dissolved in water. A preparation process is disclosed which involves a process of reducing the oxides formed.

On the other hand, in the development of the PEFC in the future, it is important to reduce various costs while maintaining or further improving the power generation performance for practical use.
Therefore, it is important to study from the same point of view also for the development of electrode catalysts, and studies of electrode catalysts (core-shell catalysts) having a so-called core-shell structure are also conducted (for example, patent documents 4, Patent Document 5). In the process of producing the core-shell catalyst, metal chloride salts are often used as raw materials.
For example, Patent Document 4 and Patent Document 5 disclose a core-shell catalyst having a configuration in which palladium is used as a constituent element of the core portion and platinum is used as a constituent element of the shell portion. Potassium is illustrated.
As described above, the core-shell catalyst having a configuration in which palladium is used as a constituent element of the core portion and platinum as a constituent element of the shell portion is chlorine such as chloride salt of platinum (Pt) and chloride salt of palladium (Pd) Materials containing (Cl) species are often used as raw materials. The reason is considered to be that chloride salts of platinum (Pt) and palladium (Pd) are easily available, easy to handle in the production conditions, and the raw material cost is relatively low. Therefore, in the case of a core-shell catalyst, it is difficult to cope with this by adopting a compound which does not contain a halogen element (in particular, chlorine) positively as a starting material in order to exert sufficient catalytic activity.

  Similar to chlorine, bromine, which is a halogen element, is an element similar to chlorine (7B), and its physical properties are similar as represented by the ion radius and the like. For this reason, a metal compound containing bromine may be used as a raw material of the core part and shell part of the above-mentioned core-shell catalyst instead of platinum (Pt) and a chloride salt of palladium (Pd). Also, a metal compound containing bromine may be used as a precursor for producing a chloride salt of platinum (Pt) employed as a raw material of a core-shell catalyst. Furthermore, bromine (Br) species may be unintentionally mixed in the manufacturing process, and the bromine (Br) species may be deposited as impurities on the electrocatalyst.

  In addition, a method of producing core-shell type particles is proposed, which has a high effective utilization rate of the catalyst metal and can reduce the amount of the catalyst metal used (for example, Patent Document 6). The method for producing such a core-shell type particle has a technical object to selectively deposit a metal to be a shell on the surface of the core metal particle. According to Patent Document 6, the core-shell type particles produced by the method of producing core-shell type particles are obtained by filtering a dispersion in which the core-shell type particles are dispersed in a solvent using an ultra filter or the like. It is described that it can be obtained after washing and solvent substitution, if necessary. Specifically, it is disclosed that in the step of preparing the core metal particle dispersion, the core metal particle dispersion was washed until Cl ions were not detected.

  In addition, the applicant of this patent presents the following publication as a publication in which the above-mentioned publication well-known invention was described.

JP, 2009-238560, A (patent 5358997) Unexamined-Japanese-Patent No. 2008-293737 (patent 5169025) Unexamined-Japanese-Patent No. 2003-129102 (patent 4286499) JP 2011-526655 gazette JP, 2013-215701, A JP, 2010-214330, A

MATSUOKA et al., “Degradation of polymer fuel cells under the existence of anion species”, J. Power Sources, 2008.05.01, Vol. 179 No. 2, p. 560-565

In view of the above technical background, in particular, in an electrode catalyst having a so-called core-shell structure, halide salts such as chloride salts and bromide salts of metals such as platinum (Pt) and palladium (Pd) as raw materials In addition to the chlorine (Cl) species contained in the electrode catalyst, the production process of the electrode catalyst can be studied which can reliably and sufficiently reduce the content of the bromine (Br) species while using Is important.
However, a method for producing a catalyst for an electrode having a core-shell structure capable of reliably and sufficiently reducing the content of bromine (Br) species by a relatively simple method has not been sufficiently studied so far. There is still room for improvement.

For example, Patent Document 1 describes that when the halogen element remains in the electrode, the battery performance is reduced. However, Patent Document 1 only describes warm water cleaning and the like as a method of removing a halogen element, and no specific measures are described.
Furthermore, in Patent Document 2, a halogen compound is used as a raw material of the electrode catalyst, and particularly when no dehalogenation treatment (washing) is performed or a halogen compound is not used as a raw material of the electrode catalyst, acid, water washing The case is only disclosed. In addition, in order to produce an electrode catalyst containing a powder such as platinum (Pt) containing less than 100 ppm of chlorine, the electrode catalyst comprising the complex process for removing chlorine disclosed in Patent Document 3 and the like There is a disadvantage that it is necessary to adopt the manufacturing method of Thus, the method for producing a catalyst for an electrode disclosed in Patent Documents 1 to 6 substantially targets only chlorine, based on the knowledge that the battery performance is reduced if the halogen element remains in the electrode. As a matter of fact, it is only a technical task to remove the removal of chlorine itself. The methods for producing an electrode catalyst disclosed in Patent Documents 1 to 6 are all provided with a specific process for removing the halogen element relatively easily and efficiently, focusing on the specific halogen element. Not.

The present invention has been made in view of such technical circumstances, and particularly focused on "bromine" among halogen elements, and a catalyst precursor for an electrode containing a relatively high concentration of bromine (Br) species It is an object of the present invention to provide a method for producing a catalyst for an electrode which can reliably and sufficiently reduce the content of bromine (Br) species by a relatively simple operation even if .
In addition, according to the method for producing a catalyst for an electrode of the present invention, a catalyst for an electrode, a composition for forming a gas diffusion electrode, a gas diffusion electrode, a membrane electrode assembly (MEA), and a fuel cell comprising the catalyst for the electrode A stack is provided.

As a result of intensive studies, the present inventors have found the following findings in an electrode catalyst having a core-shell structure, and have completed the present invention.
That is, the present inventors have found that the concentration of bromine (Br) species measured by ultrapure water, reducing agent and X-ray fluorescence (XRF) analysis is relatively high (eg, concentration exceeding 1900 ppm, further 3000 ppm or more) And treating the liquid containing the electrode catalyst precursor and the electrode catalyst precursor under certain conditions under certain conditions, the content of bromine (Br) species in the obtained electrode catalyst can be reliably and sufficiently reduced, The present invention has been completed.
More specifically, the present invention comprises the following technical matters.

That is, the present invention
(1) Production of a catalyst for an electrode having a core-shell structure including a carrier, a core portion formed on the carrier, and a shell portion formed to cover at least a part of the surface of the core portion Method,
Step (1): The concentration of bromine (Br) species manufactured using ultrapure water, a reducing agent, and a material containing bromine (Br) species and measured by X-ray fluorescence (XRF) analysis A solution containing an electrode catalyst precursor having a concentration of the first bromine (Br) or more preset in advance is set in advance at at least one stage of preset temperature preset in the range of 10 ° C. to 95 ° C. A first step of holding at a fixed holding time,
Step (2): Ultrapure water is added to the solution obtained after the first step,
A second step of preparing a first liquid in which a catalyst precursor contained in the liquid obtained after the first step is dispersed in ultrapure water;
Step (3): The catalyst precursor contained in the first liquid is filtered and washed using ultrapure water,
The washing is repeated until the electric conductivity ρ measured by the JIS standard test method (JIS K0552) of the filtrate obtained after washing becomes equal to or less than a first set value set in advance,
A third step of preparing a second liquid in which the catalyst precursor contained in the liquid in which the electric conductivity と な っ is less than or equal to a preset first set value is dispersed in ultrapure water;
Step (4): drying the second liquid;
And providing a method of producing an electrode catalyst.

According to the manufacturing method of the present invention, the electrode which is a product can be obtained by a relatively simple operation of adding a reducing agent which is easy to obtain and easy to handle to a liquid in which the electrode catalyst precursor is dispersed in ultrapure water. The content of bromine (Br) species in the catalyst can be reliably and sufficiently reduced.
Further, according to the present invention, since the content of bromine (Br) species can be reliably and sufficiently reduced, the resulting electrode catalyst is sufficiently reduced in the catalyst activity generated due to the influence of the bromine (Br) species. It can be easily prevented. Furthermore, the production method of the present invention is suitable for mass production of the electrode catalyst, and is also suitable for reducing the production cost.

Here, in the present invention, the bromine (Br) species refer to chemical species containing bromine as a component element. Specifically, the chemical species containing bromine includes bromine atom (Br), bromine molecule (Br ₂ ), bromide ion (Br ⁻ ), bromine radical (Br ·), polyatomic bromine ion, bromine compound (X Br and the like, where X is a counter ion).

Also, in the present invention, the concentration of bromine (Br) species is measured by X-ray fluorescence (XRF) analysis. The value obtained by measuring the bromine (Br) species contained in the electrode catalyst by fluorescent X-ray (XRF) analysis is the concentration of the bromine (Br) species.
The concentration of the bromine (Br) species is the concentration of the bromine atom converted to the bromine element contained in the electrode catalyst.

Furthermore, the present invention
(2) Production of a catalyst for an electrode having a core-shell structure including a support, a core portion formed on the support, and a shell portion formed to cover at least a part of the surface of the core portion Method,
Step (1 ′); bromine (Br) species manufactured using ultrapure water, a gas containing hydrogen, and a material containing bromine (Br) species and measured by X-ray fluorescence (XRF) analysis A solution containing an electrode catalyst precursor having a concentration of at least the first bromine (Br) concentration preset at a preset temperature of at least one stage preset in the range of 10 ° C. to 60 ° C. And the 1st process of hold | maintaining by preset holding time, and providing the manufacturing method of the catalyst for electrodes.
According to the manufacturing method of the present invention, a relatively simple operation of dissolving a gas containing hydrogen as a reducing agent which is easy to obtain and easy to handle in a liquid in which a catalyst precursor for an electrode is dispersed in ultrapure water, The content of bromine (Br) species in the electrode catalyst can be reliably and sufficiently reduced.

Also, the present invention is
(3) The method for producing an electrode catalyst according to (1) or (2), wherein the concentration of the first bromine (Br) species is 3000 ppm. The numerical value of the concentration of the first bromine (Br) species is supported by the results of the comparative examples described later. In addition, based on the result of the Example mentioned later, the density | concentration of 1st bromine (Br) seed | species may be a numerical value of the range over 1900 ppm. For example, the concentration of the first bromine (Br) species may be 3000 ppm.

Here, from the viewpoint of obtaining the effects of the present invention more reliably, it is preferable that the reducing agent used in the present invention is a substance which is easily available and easy to handle. From this viewpoint, the reducing agent is more preferably a substance that can be easily dispersed or a substance that can be easily dissolved in a liquid in which the electrode catalyst precursor is dispersed in ultrapure water. Furthermore, it is particularly preferred that the reducing agent is a material which can be obtained relatively cheaply.
From the above viewpoints, the reducing agent used in the present invention is preferably a substance listed in the following (4) to (7).

Also, the present invention is
(4) The method for producing an electrode catalyst according to (1), wherein the reducing agent is at least one compound selected from an organic acid and an organic acid salt.

Furthermore, the present invention
(5) The method for producing an electrode catalyst according to (1), wherein the reducing agent is at least one compound selected from the group consisting of formic acid and sodium formate.

Also, the present invention is
(6) The method for producing an electrode catalyst according to (1), wherein the reducing agent is at least one compound selected from inorganic acids and inorganic acid salts.

Furthermore, the present invention
(7) The method for producing an electrode catalyst according to (1), wherein the reducing agent is at least one compound selected from the group consisting of carbonic acid and sodium carbonate.

Also, the present invention is
(8) Step (5); further including a fifth step of drying the dispersion obtained after the first step or the dispersion obtained after the first step, The manufacturing method of the catalyst for electrodes in any one of (7) is provided.
Thus, the dispersion obtained after the first step (or the dispersion obtained after the first step 1) is once dried in the fifth step, and then again in the second step. The present inventors have found that by dispersing in pure water (so-called reslurrying), it is possible to more reliably reduce the type of bromine (Br) contained in the electrode catalyst precursor.
The present inventors are in ultrapure water for the powder of the electrode catalyst precursor in the first step or the first step (and the subsequent second and third steps). Despite being in a state of being dispersed and held (or in a state of being filtered and washed with ultrapure water thereafter), a portion that has not been sufficiently cleaned (eg, of the pore surface of the powder, It is considered that there is a part where ultra pure water can not contact).
Then, in the fifth step, the inventors obtained by temporarily drying the dispersion obtained after the first step (or the dispersion obtained after the first step). By reslurrying the powder of the electrode catalyst precursor to be prepared by using ultrapure water, at least a part of the portion which could not be contacted by the ultrapure water in the previous step is newly added to the ultrapure water. I think that it will contact and be cleaned.

Furthermore, the present invention
(9) Step (2): Ultrapure water is added to the solution obtained after the first step,
A second step of preparing a first liquid in which the electrode catalyst precursor contained in the liquid obtained after the first step is dispersed in ultrapure water;
Step (3): The electrode catalyst precursor contained in the first liquid is filtered and washed using ultrapure water,
The washing is repeated until the electric conductivity ρ measured by the JIS standard test method (JIS K0552) of the filtrate obtained after washing becomes equal to or less than a first set value set in advance,
A third step of preparing a second liquid in which the electrode catalyst precursor contained in the liquid in which the electric conductivity が is equal to or less than a preset first set value is dispersed in ultrapure water;
Step (4): drying the second liquid;
The method for producing an electrode catalyst according to (2), further comprising

Also, the present invention is
(10) The method for producing an electrode catalyst according to (1) or (9), wherein the first set value is a value selected from a range of 100 μS / cm or less.

Furthermore, the present invention
(11) A catalyst precursor for an electrode to be subjected to the first step or the first step;
Step (P1); a second bromine which is manufactured using a material containing a bromine (Br) species and whose concentration of the bromine (Br) species is preset by a fluorescent X-ray (XRF) analysis method (Pl) A process of preparing a solution of P1 in which the electrode catalyst precursor having a concentration of (Br) or more is added to ultrapure water to disperse the electrode catalyst precursor in ultrapure water;
Step (P2): The ultrapure water is used to wash the electrode catalyst precursor contained in the P1 solution, and the filtrate obtained after washing is measured by the JIS standard test method (JIS K0552). Is repeated until the electric conductivity .rho. Becomes equal to or less than the preset value of P1 and the obtained electrode catalyst precursor is dispersed in ultrapure water to prepare a P2 solution. When,
Step (P3); drying the liquid P2.
Is pretreated, including
The manufacturing method of the catalyst for electrodes in any one of (1)-(10) is provided.
As described above, the dispersion obtained after the step P2 is once dried in the step P3 and thereafter dispersed again in ultrapure water in the first step (or the first step) (so-called reslurry) The present inventors have found that it is possible to reduce the bromine (Br) species contained in the electrode catalyst precursor more reliably by
That is, the same effect as obtained by the reslurrying described in the description of the case where the first step (or the first step) is performed through the fifth step can be obtained.

Also, the present invention is
(12) The method for producing an electrode catalyst according to (11), wherein the concentration of the second bromine (Br) species is 3000 ppm.

Also, the present invention is
(13) The method for producing a catalyst for an electrode according to (11), wherein the preset P1 setting value is a value selected from the range of 100 μS / cm or less.

Furthermore, the present invention
(14) The shell portion contains at least one metal of platinum (Pt) and platinum (Pt) alloy,
In the core portion, at least one selected from the group consisting of palladium (Pd), palladium (Pd) alloy, platinum (Pt) alloy, gold (Au), nickel (Ni), and nickel (Ni) alloy. Contains metal,
The manufacturing method of the catalyst for electrodes as described in any one of (1)-(13) is provided.

Furthermore, the present invention
(15) The method for producing a catalyst for an electrode according to (14), wherein platinum (Pt) bromide is used as a raw material of a metal constituting the shell portion.

Also, the present invention is
(16) The first shell portion formed to cover at least a portion of the surface of the core portion, and the second shell portion formed to cover at least a portion of the surface of the first shell portion Has a shell part,
The manufacturing method of the catalyst for electrodes as described in any one of (1)-(15) is provided.

Furthermore, the present invention
There is provided the method for producing a catalyst for an electrode as described in (16), wherein platinum (Pt) bromide is used as a raw material of a metal constituting the second shell portion.

According to the method for producing a catalyst for an electrode of the present invention, a catalyst precursor for an electrode containing bromine (Br) species of relatively high concentration (for example, concentration exceeding 1900 ppm, concentration of 3000 ppm or more) is used as electrode catalyst Even when used as a raw material of the above, it is possible to obtain an electrode catalyst in which the content of bromine (Br) species is reliably and sufficiently reduced by a relatively simple operation.
Further, according to the present invention, since the content of bromine (Br) species can be reliably and sufficiently reduced, the resulting electrode catalyst is sufficiently reduced in the catalyst activity generated due to the influence of the bromine (Br) species. It can be easily prevented.
Furthermore, according to the present invention, it is possible to provide a method for producing an electrode catalyst that is suitable for mass production of an electrode catalyst and suitable for reducing the production cost.
In addition, according to the method for producing a catalyst for an electrode of the present invention, a catalyst for an electrode in which the concentration of bromine (Br) species is sufficiently reduced, a composition for forming a gas diffusion electrode including the catalyst for the electrode, a gas diffusion electrode , A membrane electrode assembly (MEA), and a fuel cell stack are provided.

It is the flowchart which showed one suitable embodiment of the 1st process of the manufacturing method of the catalyst for electrodes of this invention. It is the flowchart which showed one suitable embodiment of the 1st process of the manufacturing method of the electrode catalyst of this invention. It is the flowchart which showed one suitable embodiment of the pre-processing process of the manufacturing method of the catalyst for electrodes of this invention. It is the flowchart which showed one suitable embodiment of each process of the manufacturing method of the catalyst for electrodes containing the pre-processing process of the manufacturing method of the catalyst for electrodes of this invention, and a 1st process. It is the flowchart which showed one suitable embodiment of each process of the manufacturing method of the catalyst for electrodes containing the pre-processing process of the manufacturing method of the catalyst for electrodes of this invention, and a 1 'process. It is a schematic cross section which shows one suitable form of the electrode catalyst (core-shell catalyst) of this invention. It is a schematic cross section which shows another suitable one form of the electrode catalyst (core-shell catalyst) of this invention. It is a schematic cross section which shows another suitable one form of the electrode catalyst (core-shell catalyst) of this invention. It is a schematic cross section which shows another suitable one form of the electrode catalyst (core-shell catalyst) of this invention. FIG. 1 is a schematic view showing a preferred embodiment of a fuel cell stack of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as appropriate. First, the method for producing the electrode catalyst of the present invention will be described, and then, the electrode catalyst and the like obtained by the method for producing the electrode catalyst will be described.
<Method of producing catalyst for electrode>
The method for producing a catalyst for an electrode according to the present invention is produced by using a process (1); a material containing ultrapure water, a reducing agent, and a bromine (Br) species, and is determined by a fluorescent X-ray (XRF) analysis method A solution containing an electrode catalyst precursor having a concentration of the bromine (Br) species to be measured at a preset concentration of the first bromine (Br) species or more is preset in the range of 10 ° C. to 95 ° C. A first step of holding at least one set temperature and for a preset holding time;
Step (2): Ultrapure water is added to the solution obtained after the first step,
A second step of preparing a first liquid in which a catalyst precursor contained in the liquid obtained after the first step is dispersed in ultrapure water;
Step (3): The catalyst precursor contained in the first liquid is filtered and washed using ultrapure water,
The washing is repeated until the electric conductivity ρ measured by the JIS standard test method (JIS K0552) of the filtrate obtained after washing becomes equal to or less than a first set value set in advance,
A third step of preparing a second liquid in which the catalyst precursor contained in the liquid in which the electric conductivity と な っ is less than or equal to a preset first set value is dispersed in ultrapure water;
Step (4): drying the second liquid;
It is characterized by including.

  In addition, the method for producing a catalyst for an electrode according to the present invention comprises the steps (1 ′); ultra pure water, a gas containing hydrogen, and a material containing a bromine (Br) species, and the fluorescent X ray ( XRF) a solution containing an electrode catalyst precursor having a concentration of bromine (Br) species measured by an analysis method which is equal to or greater than a predetermined concentration of the first bromine (Br) species; A first step of holding at least one preset temperature set in the range (preferably at least one preset temperature set in the range of 20 ° C. to 40 ° C.) and for a preset holding time ,including.

  FIG. 1 is a flow chart showing each operation of a preferred embodiment of the manufacturing process of the method of manufacturing an electrode catalyst including the first to fourth processes. Each step will be described below.

(First step etc.)
The method for producing a catalyst for an electrode of the present invention includes a first step. FIG. 1 is a flow chart showing the operations of a preferred embodiment of the first step. As shown in FIG. 1, in the first step, the concentration of the first bromine (Br) species measured by the ultrapure water, the reducing agent, and the fluorescent X-ray (XRF) analysis method is preset. A solution containing an electrode catalyst precursor of a predetermined value (for example, 3000 ppm, 1900 ppm) or more at a predetermined temperature (preferably, a predetermined temperature within a range of 20 to 90 ° C.) within a range of 10 ° C. to 95 ° C. for a predetermined time Hold. In the first step, a liquid containing ultrapure water, a reducing agent, and a predetermined electrode catalyst precursor is prepared.
In the first step, a step using a gas containing hydrogen as a reducing agent is referred to as a first 'step.
FIG. 2 is a flow chart showing each operation of a preferred embodiment of the first 1 'process. As shown in FIG. 2, in the first step, the concentrations of ultrapure water, a gas containing hydrogen, and bromine (Br) species measured by X-ray fluorescence (XRF) analysis are preset. A solution containing an electrode catalyst precursor having a concentration of the first bromine (Br) or more is pre-set in at least one stage of preset temperature in the range of 10 to 60 ° C. (preferably in the range of 20 to 40 ° C.) Hold at least one set temperature setting) for a predetermined time. In the first step, a liquid containing ultrapure water, a gas containing hydrogen, and a predetermined electrode catalyst precursor is produced.
In the following description, the first step and the first step are referred to as “first step and the like” when not particularly distinguished.

[Ultra pure water]
The “ultrapure water” used in the first step and the like included in the method for producing a catalyst for an electrode according to the present invention has a specific resistance R (JIS standard test method (JIS K0552) represented by the following general formula (1) The reciprocal of the electrical conductivity measured by 2.) is 3.0 M.OMEGA.cm or more. Further, it is preferable that the "ultra pure water" has a water quality equivalent to or more than that of "A3" defined in JIS K 0 557 "Water used for testing of water and drainage".
The said ultrapure water will not be specifically limited if it is water which has the electrical conductivity which satisfy | fills the relationship represented by following General formula (1). For example, as the above-mentioned ultrapure water, ultrapure water produced using ultrapure water production apparatus "Milli-Q series" (manufactured by Merck Ltd.) and "Elix UV series" (manufactured by Nippon Millipore Ltd.) is cited. be able to.
The use of the above-mentioned ultrapure water in the first step and the like is preferable because it does not contain impurities such as bromine (Br) species.

上記一般式（１）において、Ｒは比抵抗を表し、ρはＪＩＳ規格試験法（ＪＩＳ Ｋ０５５２）により測定される電気伝導率を表す。

In the said General formula (1), R represents a specific resistance, rho represents the electrical conductivity measured by a JIS standard test method (JISK0552).

[Reductant]
The reducing agent used in the first step reacts with the catalyst component as the raw material and the bromine (Br) species derived from the treatment liquid, etc., in the production process of the electrode catalyst to remove the bromine (Br) species etc. Have a role. As a reducing agent, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt etc. are mentioned preferably. Note that the reducing agent used in the first step is a gas containing hydrogen.

  Examples of the organic acid or organic acid salt include formaldehyde, formic acid, sodium formate and the like. Preferred examples of the inorganic acid or inorganic acid salt include carbonic acid and sodium carbonate.

[Catalyst precursor for electrode]
The electrode catalyst precursor used in the first step and the like has a concentration of the first bromine (Br) species in which the concentration of the bromine (Br) species measured by X-ray fluorescence (XRF) analysis is preset The condition that (for example, the concentration of the first bromine (Br) species is 3000 ppm) or more is satisfied. The bromine (Br) species contained in the electrode catalyst precursor are derived from the catalyst component and the treatment liquid as the raw material of the electrode catalyst.
Conventionally, an electrode catalyst obtained by a method for producing an electrode catalyst that has been conventionally adopted is usually bromine measured by a fluorescent X-ray (XRF) analysis method unless removal of bromine (Br) species is particularly applied. The concentration of the Br) species is relatively high (e.g., the concentration of the first bromine (Br) species is 3000 ppm, and further 1900 ppm) that is greater than or equal to the concentration of the first bromine (Br) species. According to the study of the present inventors, the electrode catalyst (the electrode catalyst precursor in the present invention) obtained by the method for producing an electrode catalyst using a material containing bromine (Br) species employed in the prior art is The concentration of bromine (Br) species measured by the above-mentioned analytical method is 3000 ppm or more (see the results of comparative examples described later).
In the first step and the like, the concentration of the first bromine (Br) species set in advance can be appropriately changed and set according to the quality of the electrode catalyst precursor to be used. Specifically, attention is focused on the concentration of bromine (Br) species in an electrode catalyst manufactured using a material containing bromine (Br) species. It is preferable that the concentration of the first bromine (Br) species set in advance can sufficiently exhibit the catalytic performance of the electrode catalyst and is in a range compatible with the manufacturing process of the electrode catalyst.
That is, the electrode catalyst precursor used in the first step and the like corresponds to an electrode catalyst obtained by the method for manufacturing an electrode catalyst conventionally adopted.

The electrode catalyst precursor of the electrode catalyst 1 is produced by supporting the catalyst components (core portion 4 and shell portion 5) of the electrode catalyst on the carrier 2.
The method for producing the electrode catalyst precursor is not particularly limited as long as the catalyst component of the electrode catalyst 1 can be supported on the carrier 2.
For example, an impregnation method in which a solution containing the catalyst component of the electrode catalyst 1 is brought into contact with the carrier 2 to impregnate the carrier 2 with the catalyst component, a solution which is carried out by charging a reducing agent into a solution containing the catalyst component of the electrode catalyst. Employs electrochemical deposition methods such as phase reduction method, underpotential deposition (UPD) method, chemical reduction method, reduction deposition method with adsorbed hydrogen, surface leaching method of alloy catalyst, displacement plating method, sputtering method, vacuum evaporation method, etc. Can be illustrated.

[Pretreatment process]
In the method for producing a catalyst for an electrode of the present invention, as a catalyst precursor for an electrode to be subjected to the first step and the like, the "pretreatment step" including the following steps (P1) to (P3) is performed The obtained electrode catalyst precursor may be employed. FIG. 3 is a flow chart showing the operations of a preferred embodiment of the pre-treatment process.

As shown in FIG. 3, the pretreatment step is step (P1); bromine (Br) is manufactured using a material containing bromine (Br) species and is measured by X-ray fluorescence (XRF) analysis ) A relatively high concentration of the second bromine (Br) concentration higher than the predetermined concentration of the species (for example, the concentration of the second bromine (Br) species is 3000 ppm, further 1900 ppm, or a predetermined concentration exceeding 1400 ppm) A step P1 of preparing a solution of P1 in which the electrode catalyst precursor of (value) is added to the ultrapure water to disperse the electrode catalyst precursor in the ultrapure water;
Step (P2): The ultrapure water is used to wash the electrode catalyst precursor contained in the P1 solution, and the filtrate obtained after washing is measured by the JIS standard test method (JIS K0552). Is repeated until the electric conductivity .rho. Becomes equal to or less than the preset value of P1 and the obtained electrode catalyst precursor is dispersed in ultrapure water to prepare a P2 solution. When,
Step (P3): drying the solution of P2.

The method of filtration washing in the step P2 is the same as the method of filtration washing in the third step described later. The set value of P1 in the P2 step is preferably a value selected from the range of 100 μS / cm or less, and further 10 μS / cm or less. Further, the method of drying in the step P3 is the same as the method of drying in the fourth step described later.
As described above, the dispersion obtained after the step P2 is once dried in the step P3 and thereafter dispersed again in ultrapure water in the first step (or the first step) (so-called reslurry) ) Can more reliably reduce the bromine (Br) species contained in the electrode catalyst precursor.

FIG. 4 is a flow chart showing each operation of the method for producing an electrode catalyst including the pretreatment step before the first step.
Moreover, FIG. 5 is the flowchart which showed each operation of the manufacturing method of the catalyst for electrodes including a pretreatment process before a 1st process.
As shown in FIG. 4 and FIG. 5, the bromine (Br) species contained in the raw material of the electrode catalyst precursor are removed by subjecting the raw material of the electrode catalyst precursor to the pretreatment step. Then, the electrode catalyst precursor in which the concentration of bromine (Br) species is reduced is used as the electrode catalyst precursor in the first step and the like. The electrode catalyst precursor is subjected to the first step and the like. In the first step and the like, each operation is performed using the electrode catalyst precursor obtained via the steps (P1) to (P3) as a starting material. As described above, in the method for producing a catalyst for an electrode of the present invention, a pretreatment step is provided before the first step and the like to further reduce the concentration of bromine (Br) species contained in the electrode catalyst precursor. be able to.
In the pretreatment step, the concentration of the second bromine (Br) species set in advance is usually set higher than the concentration of the first bromine (Br) species set in the first step or the like.
The concentration of the first bromine (Br) species and the concentration of the second bromine (Br) species are preset according to the concentration of the bromine (Br) species contained in the electrode catalyst precursor and the manufacturing process. .

[Holding temperature etc.]
In the first step, the concentration of bromine (Br) species measured by ultrapure water, reducing agent, and X-ray fluorescence (XRF) analysis is a relatively high concentration (for example, the concentration of the first bromine (Br) species or more) A first bromine (Br) species concentration of 3000 ppm, or 1900 ppm, and further a predetermined value of more than 1400 ppm) electrode precursor and a predetermined temperature within a range of 10 ° C. to 95 ° C. (preferably A predetermined temperature in the range of 20 to 90 ° C.) is set to hold the liquid. The holding temperature is not particularly limited as long as it is in the range of 10 ° C. to 95 ° C., preferably in the range of 20 to 90 ° C., but the concentration of bromine (Br) species contained in the electrode catalyst precursor It is appropriately set depending on the type of reducing agent and the like.
When using a gas containing hydrogen as the reducing agent in the first step, the holding temperature is preferably set to at least one preset temperature set in the range of 10 to 60 ° C. It is more preferable to set to the preset temperature of at least 1 step | stage previously preset in the range of 20-40 degreeC.
The holding temperature has at least one set temperature. The holding time is not particularly limited as long as the reducing agent and the electrode catalyst precursor can sufficiently react with each other.

  The bromine (Br) species contained in the electrode catalyst precursor are removed by holding the liquid obtained by mixing the ultrapure water, the reducing agent, and the electrode catalyst precursor at the above holding temperature and holding time. Then, the concentration of bromine (Br) species in the electrode catalyst precursor measured by X-ray fluorescence (XRF) analysis is greatly reduced. Finally, the concentration of the bromine (Br) species is easily reduced to less than the concentration of the first bromine (Br) species. For example, the catalyst precursor for an electrode according to the present invention is an electrode according to the present invention in which the concentration of bromine (Br) species is easily reduced to a level of less than 3000 ppm, less than 1900 ppm, and further to 1400 ppm or less It becomes catalyst for.

  As described above, according to the method for producing a catalyst for an electrode of the present invention, by including the first step, the concentration of the bromine (Br) species measured by X-ray fluorescence (XRF) analysis is the first bromine ( Even if a catalyst precursor for an electrode having a relatively high concentration (for example, the concentration of the first bromine (Br) species is 3000 ppm) higher than the concentration of Br) species is used as a raw material, the concentration of the bromine (Br) species is It is possible to obtain an electrode catalyst which is easily reduced to less than 3000 ppm, to less than 1900 ppm, further to 1400 ppm or less, and further to a level of 0 to 900 ppm.

(Fifth step)
Furthermore, the method for producing a catalyst for an electrode of the present invention may further include a fifth step of drying the liquid obtained after the first step and the like. The dispersion obtained after the first step and the like (or the dispersion obtained after the first 1 'step) is once dried in the fifth step, and then it is made into ultrapure water again in the second step. By dispersing (so-called reslurrying), it is possible to more reliably obtain an electrode catalyst in which the concentration of the bromine (Br) species is extremely reduced.
Although the mechanism for this has not been fully elucidated, the present inventors have made the powder of the catalyst precursor for the electrode in the first step and the like (further subsequent to the second and third steps). Although it is in a state of being dispersed in ultrapure water (or in a state of being filtered and washed by I think that there is a part that can not contact).
Then, after temporarily drying the dispersion obtained after the first step and the like in the fifth step, the present inventors re-reduce the powder of the electrode catalyst precursor to be obtained into ultrapure water. By dispersing (re-slurrying), at least a part of the portion where the ultrapure water could not be contacted in the previous step is newly contacted with the ultrapure water and cleaned, so that bromine (Br (Br) ) I believe that the species will be removed more reliably.
The conditions for drying the liquid obtained after the first step and the like include a drying temperature and a drying time at which the electrode catalyst precursor contained in the liquid obtained after the first step and the like can be obtained. There is no particular restriction as long as it exists. For example, the drying temperature is 20 to 90 ° C., and the drying time is 0.5 to 24 hours.

(Second step)
The method for producing a catalyst for an electrode of the present invention includes a second step. In the second step, ultra pure water is added to the solution obtained after the first step and the like, and the electrode catalyst precursor contained in the solution obtained after the first step and the like is added to the ultra pure water And the step of preparing the first liquid dispersed in the The second step is a step of treating the electrode catalyst obtained in the first step or the like as a catalyst precursor for an electrode to prepare a first solution.
Note that the second step also includes the case of processing the liquid obtained through the first step using a gas containing hydrogen as a reducing agent.

(Third step)
The method for producing a catalyst for an electrode of the present invention includes a third step. In the third step, the electrode catalyst precursor contained in the first liquid prepared in the second step is filtered and washed, and the electric conductivity ρ of the filtrate obtained after washing is set in advance. It is the process of repeating washing until it becomes below the setting value of. In the third step, the electrode catalyst precursor is washed to reduce the concentration of bromine (Br) species contained in the electrode catalyst precursor.

  The electrical conductivity ρ of the filtrate obtained after washing is measured by the JIS standard test method (JIS K0552). In the third step, the electrode catalyst precursor contained in the first solution is filtered and washed, and the electric conductivity ρ of the filtrate obtained after washing is measured, and the electric conductivity ρ is set in advance. Repeat the washing until it falls below the set value of 1. In the third step, by determining the first set value in advance, the concentration of the bromine (Br) species contained in the electrode catalyst precursor can be precisely controlled.

The first set value can be appropriately set in accordance with the concentration of the bromine (Br) species contained in the electrode catalyst. The first set value is preferably a value selected from the range of 100 μS / cm or less. When the first set value is 100 μS / cm or less, the concentration of the above-mentioned bromine (Br) species contained in the electrode catalyst precursor can be easily reduced to less than 3000 ppm, and further to 1400 ppm or less, further 0 to 900 ppm Is preferable because it can be easily reduced to Further, the first set value is preferably a value selected from the range of 10 μS / cm or less.
When the first step or the like goes through the pre-processing step, the preset first set value is normally set to a value less than or equal to the P1 set value set in the pre-processing step or lower than the P1 set value. Be done.
However, due to the reslurry effect described above, the amount of bromine (Br) species removed by washing increases in the first step (and the second step) rather than the pretreatment step, and the concentration of bromine (Br) species increases Is larger, the first set value may be set higher than the P1 set value.

  In the third step, the electrode catalyst precursor contained in the first liquid prepared in the second step is filtered and washed, and when it falls below the first set value, the washing of the first liquid ends. Do. Let the 1st liquid at the time of becoming less than a 1st setting value be a 2nd liquid.

  In addition, the method of the said filtration washing | cleaning in a 3rd process will not be specifically limited if it is a method which does not impair the core shell structure of the catalyst for electrodes of this invention. As the method of the said filtration, the method of carrying out natural filtration, vacuum filtration, etc. are mentioned using a filter paper and a membrane filter.

(4th step)
The method for producing a catalyst for an electrode of the present invention includes a fourth step. The fourth step is a step of drying the second liquid prepared in the third step. The conditions for drying the second liquid are not particularly limited as long as the drying temperature and the drying time at which the electrode catalyst precursor contained in the second liquid can be obtained. For example, the drying temperature is 20 to 90 ° C., and the drying time is 0.5 to 24 hours.

  After the fourth step, the core-shell catalyst is dispersed in an aqueous solution prepared by adding an acid to ultrapure water, and at least one preset temperature set in a range of 10 to 95 ° C. (preferably 20) The method may further include the step of holding at least one preset temperature set in the range of -90 ° C.) and for a preset holding time. Examples of the acid include sulfuric acid, nitric acid, hydrochloric acid and acetic acid.

  According to the method for producing a catalyst for an electrode of the present invention, it is possible to reduce the species of bromine (Br) contained in the electrode catalyst precursor. The electrode catalyst obtained by the method for producing a catalyst for an electrode of the present invention contains bromine (Br) species having a concentration of 0 to 2000 ppm of bromine (Br) species measured by a fluorescent X-ray (XRF) analysis method There is.

  The catalyst for an electrode obtained by the method for producing a catalyst for an electrode of the present invention has a concentration of bromine (Br) species measured by the above-mentioned X-ray fluorescence (XRF) analysis method is less than 3000 ppm, preferably 1900 ppm or less, more preferably Since the level is reduced to 1400 ppm or less, more preferably 0 to 900 ppm, it is possible to sufficiently prevent the decrease in catalyst activity caused by the influence of the bromine (Br) species in the obtained electrode catalyst And catalyst activity can also be improved.

<Catalyst for electrode>
FIG. 6 is a schematic cross-sectional view showing a preferred embodiment of the electrode catalyst 1 (core-shell catalyst) obtained by the method of manufacturing an electrode catalyst of the present invention.
As shown in FIG. 6, the electrode catalyst 1 obtained by the method for producing an electrode catalyst includes a carrier 2 and catalyst particles 3 having a so-called “core-shell structure” supported on the carrier 2 . The catalyst particle 3 includes a core 4 and a shell 5 formed to cover at least a part of the surface of the core 4. The catalyst particle 3 has a so-called "core-shell structure" including the core 4 and the shell 5 formed on the core 4.
That is, the electrode catalyst 1 has the catalyst particles 3 supported on the carrier 2. The core particles 4 have the core 4 as a core and the shell 5 as a shell. It has a structure covering the surface of.
The constituent elements (chemical composition) of the core 4 and the constituent elements (chemical composition) of the shell 5 are different.

In the present invention, the electrode catalyst 1 is not particularly limited as long as the shell 5 is formed on at least a part of the surface of the core 4 of the catalyst particle 3.
For example, from the viewpoint of obtaining the effect of the present invention more reliably, as shown in FIG. 6, it is preferable that the electrode catalyst 1 be in a state in which substantially the entire surface of the core 4 is covered with the shell 5. .
Further, in the range in which the effects of the present invention can be obtained, even if the electrode catalyst 1 has a part of the surface of the core 4 covered by the shell 5 and the surface of the core 4 is partially exposed Good.
That is, in the present invention, the electrode catalyst may have a shell portion formed on at least a part of the surface of the core portion.

FIG. 7 is a schematic cross-sectional view showing another preferable embodiment (electrode catalyst 1A) of the electrode catalyst (core-shell catalyst) of the present invention.
As shown in FIG. 7, the electrode catalyst 1 </ b> A of the present invention covers the core 4, the shell 5 a covering a part of the surface of the core 4, and a part of the other surface of the core 4. It has catalyst particles 3a composed of a shell 5b.
In the catalyst particles 3a contained in the electrode catalyst 1A shown in FIG. 7, there is a core portion 4 which is not covered by the shell portion 5a or the shell portion 5b. Such a core portion 4 is the core portion exposed surface 4s.
That is, as shown in FIG. 7, the catalyst particles 3a included in the electrode catalyst 1A are in a state where the surface of the core portion 4 is partially exposed (for example, in the range where the effects of the present invention can be obtained). It may be in a state where 4s which is a part of the surface of the core portion 4 shown in FIG. 7 is exposed.
In other words, as in the electrode catalyst 1A shown in FIG. 7, the shell 5a is formed on a part of the surface of the core 4 and the shell 5b is formed on a part of the other surface. It may be done.

FIG. 8 is a schematic cross-sectional view showing another preferable embodiment (electrode catalyst 1B) of the electrode catalyst (core-shell catalyst) of the present invention.
As shown in FIG. 8, the electrode catalyst 1 </ b> B of the present invention has a core particle 4 and a catalyst particle 3 composed of a shell 5 covering substantially the entire surface of the core 4.
The shell portion 5 may have a two-layer structure including the first shell portion 6 and the second shell portion 7. That is, the catalyst particle 3 has a so-called "core-shell structure" including the core 4 and the shell 5 (the first shell 6 and the second shell 7) formed on the core 4.
The electrode catalyst 1 B has catalyst particles 3 supported on the carrier 2, the catalyst particles 3 having the core 4 as a core, and the first shell 6 and the second shell 7 forming the shell 5. A substantially entire area of the surface of the core portion 4 is covered.
The constituent elements (chemical composition) of the core portion 4, the constituent elements (chemical composition) of the first shell portion 6, and the constituent elements (chemical composition) of the second shell portion 7 are different from each other. .
Moreover, in addition to the 1st shell part 6 and the 2nd shell part 7, the shell part 5 with which the electrode catalyst 1B of this invention is equipped may be equipped with another shell part further.
From the viewpoint of obtaining the effect of the present invention more reliably, as shown in FIG. 8, it is preferable that the electrode catalyst 1B be in a state in which substantially the entire surface of the core 4 is covered with the shell 5.

FIG. 9 is a schematic cross-sectional view showing another preferable embodiment (electrode catalyst 1C) of the electrode catalyst (core-shell catalyst) of the present invention.
As shown in FIG. 9, the electrode catalyst 1 </ b> C of the present invention covers the core 4, the shell 5 a covering a part of the surface of the core 4, and a part of the other surface of the core 4. The catalyst particle 3a is composed of a shell portion 5b.
The shell 5a may have a two-layer structure including the first shell 6a and the second shell 7a.
Also, the shell portion 5b may have a two-layer structure including the first shell portion 6b and the second shell portion 7b.
That is, the catalyst particle 3 a includes the core 4, the shell 5 a (the first shell 6 a and the second shell 7 a) formed on the core 4, and the shell 5 b formed on the core 4 (the first shell 6 a and the second shell 7 a). It has a so-called "core-shell structure" including the first shell portion 6b and the second shell portion 7b).
In the shell part 5b which comprises the catalyst particle 3a shown by FIG. 9, the 1st shell part 6b which is not coat | covered by the 2nd shell part 7b exists. The first shell portion 6b which is not covered by the second shell portion 7b serves as the first shell portion exposed surface 6s.
As shown in FIG. 9, in the shell portion 5a constituting the catalyst particle 3a, it is preferable that substantially the entire area of the first shell portion 6a is covered by the second shell portion 7a.
Further, as shown in FIG. 9, in the shell portion 5 b constituting the catalyst particle 3 a, a part of the surface of the first shell portion 6 b is covered in the range where the effects of the present invention can be obtained. It may be in a state in which the surface is partially exposed (for example, in a state in which a portion 6s of the surface of the first shell portion 6b shown in FIG. 9 is exposed).

Furthermore, in the range in which the effects of the present invention can be obtained, the electrode catalyst 1 has a structure in which the core 2 and the shell 5 in a state in which substantially the entire surface of the core 4 is covered with the shell A composite may be mixed with a composite of the core 4 and the shell 5 in which the shell 5 partially covers the surface of the core 4.
Specifically, the electrode catalyst of the present invention can be used in electrode catalysts 1 and 1A shown in FIGS. 6 and 7 and electrode catalysts 1B shown in FIGS. 8 and 9 as long as the effects of the present invention can be obtained. It may be in a mixed state with 1C.
Furthermore, in the electrode catalyst of the present invention, as shown in FIG. 9, the shell portion 5a and the shell portion 5b may be mixed in the same core portion 4 as long as the effects of the present invention can be obtained. Good.
Furthermore, the electrode catalyst of the present invention may be in a state in which only the shell portion 5 a is present in the same core portion 4 within the range in which the effects of the present invention can be obtained. It may be in a state where only the shell part 5b exists (any state is not shown).
In addition, to the electrode catalyst 1, in addition to at least one of the electrode catalysts 1, 1A, 1B, and 1C on the carrier 2, “the core portion 4 has a shell portion in a range where the effects of the present invention can be obtained. The state in which the particle | grains which consist only of the core part which is not coat | covered by 5 may be supported may be included (not shown).
Furthermore, in addition to at least one of the electrode catalysts 1, 1A, 1B, and 1C in the range where the effects of the present invention can be obtained, "particles composed of only the constituent elements of the shell portion 5" The state supported by the carrier 2 without contacting the core portion 4 may be included (not shown).
In addition, to the electrode catalyst 1, in addition to at least one of the electrode catalysts 1, 1A, 1B, and 1C, in the range where the effects of the present invention can be obtained, “only the core 4 not coated with the shell 5 is The state in which the particle | grains of "and the particle | grains which consist only of the constituent element of the shell part 5" were each carry | supported by the support | carrier 2 independently may be included.

2-40 nm is preferable, as for the average particle diameter of the core part 4, 4-20 nm is more preferable, and 5-15 nm is especially preferable.
With respect to the thickness of the shell 5 (the thickness from the contact surface with the core 4 to the outer surface of the shell 5), a preferable range is appropriately set according to the design concept of the electrode catalyst.
For example, in the case where it is intended to minimize the amount of use of the metal element (for example, platinum etc.) which constitutes shell part 5, the thickness of shell part 5 is the metal element which constitutes shell part 5 concerned. In the case of one kind, it is preferable that the thickness is equivalent to twice the diameter (in the case of a spherical approximation) of one atom of this metal element. In addition, in the case where two or more types of metal elements constituting the shell portion 5 are used, a layer composed of one atom (a single atomic layer formed by juxtaposing two or more types of atoms on the surface of the core portion 4) It is preferable that the thickness is equivalent to
Further, for example, in the case where the durability is to be improved by increasing the thickness of the shell portion 5, the thickness is preferably 1 to 10 nm, and more preferably 2 to 5 nm.

In the case where the shell portion 5 has a two-layer structure including the first shell portion 6 and the second shell portion 7, the thickness of the first shell portion 6 and the second shell portion 7 corresponds to the electrode catalyst of the present invention. The preferred range is appropriately set according to the design concept of
For example, in the case where it is intended to minimize the amount of use of a noble metal such as platinum (Pt) which is a metal element contained in the second shell portion 7, the second shell portion 7 is composed of one atom. Layer (one atomic layer) is preferable. In this case, in the case where the thickness of the second shell portion 7 is one kind of metal element constituting the second shell portion 7, the diameter of one atom of the metal element (one atom is regarded as a sphere Preferably, the thickness is about twice that of
In addition, when the metal element contained in the second shell portion 7 is two or more types, the second shell portion 7 is a layer composed of one or more types of atoms (the core portion 4 has two or more types of atoms Preferably, it has a thickness corresponding to one atomic layer formed in parallel in the surface direction of For example, in the case where the durability of the electrode catalyst is intended to be improved by increasing the thickness of the second shell 7, the thickness of the second shell 7 should be 1.0 to 5.0 nm. It is preferable to In order to further improve the durability of the electrode catalyst, the thickness of the second shell portion 7 is preferably 2.0 to 10.0 nm.
In the present invention, the "average particle size" refers to the average value of the diameters of particles composed of an arbitrary number of particle groups, as observed by electron micrographs.

  The carrier 2 is not particularly limited as long as it can support the catalyst particles 3 which is a complex composed of the core portion 4 and the shell portion 5 and has a large surface area. Furthermore, it is preferable that the carrier 2 has good dispersibility in the composition for forming a gas diffusion electrode including the electrode catalyst 1 and has excellent conductivity.

The carrier 2 may be glassy or ceramic materials such as carbon based materials such as glassy carbon (GC), fine carbon, carbon black, graphite, carbon fiber, activated carbon, crushed material of activated carbon, carbon nanofibers, carbon nanotubes and oxides. It can be adopted as appropriate.
Among these, carbon-based materials are preferable from the viewpoint of the adsorptivity with the core 4 and the BET specific surface area of the carrier 2.
Furthermore, as the carbon-based material, conductive carbon is preferable, and as the conductive carbon, conductive carbon black is particularly preferable. As the conductive carbon black, trade names "Ketjen black EC300J", "Ketjen black EC600", "Carbon EPC", etc. (manufactured by Lion Chemical Co., Ltd.) can be exemplified.

The component which comprises the core part 4 will not be specifically limited if it is a component covered by the shell part 5. FIG.
When the shell 5 has a single-layer structure instead of the two-layer structure as in the electrode catalysts 1 and 1A shown in FIGS. 6 and 7, a noble metal can be used for the core 4. Palladium (Pd), a palladium (Pd) alloy, a platinum (Pt) alloy, gold (Au), nickel At least one metal selected from the group consisting of Ni) and nickel (Ni) alloys is included.

  The palladium (Pd) alloy is not particularly limited as long as it is a combination of palladium (Pd) and another metal that can form an alloy. For example, a two-component system palladium (Pd) alloy which is a combination of palladium (Pd) and another metal, a three-component system palladium (Pd) which is a combination of palladium (Pd) and two or more other metals ) May be an alloy. Specifically, gold palladium (PdAu), silver palladium (PdAg), copper palladium (PdCu), etc. can be illustrated as a two-component palladium (Pd) alloy. As a three-component palladium (Pd) alloy, gold silver palladium (PdAuAg) etc. can be illustrated.

  The platinum (Pt) alloy is not particularly limited as long as it is an alloy that is a combination of platinum (Pt) and another metal that can form an alloy. For example, a two-component platinum (Pt) alloy which is a combination of platinum (Pt) and another metal, a three-component platinum (Pt) which is a combination of platinum (Pt) and two or more other metals ) May be an alloy. Specifically, nickel platinum (PtNi), cobalt platinum (PtCo), etc. can be illustrated as a two-component platinum (Pt) alloy.

  The nickel (Ni) alloy is not particularly limited as long as it is an alloy that is a combination of nickel (Ni) and another metal that can form an alloy. For example, a binary nickel (Ni) alloy that is a combination of nickel (Ni) and another metal, a ternary (more than nickel nickel (Ni) that is a combination of nickel (Ni) and two or more other metals ) May be an alloy. Specifically, tungsten nickel (NiW) or the like can be exemplified as a binary nickel (Ni) alloy.

  The shell 5 contains at least one metal of platinum (Pt) and platinum (Pt) alloy. The platinum (Pt) alloy is not particularly limited as long as it is an alloy that is a combination of platinum (Pt) and another metal that can form an alloy. For example, a two-component platinum (Pt) alloy which is a combination of platinum (Pt) and another metal, a three-component platinum (Pt) which is a combination of platinum (Pt) and two or more other metals ) May be an alloy. Specifically, nickel platinum (PtNi), cobalt platinum (PtCo), platinum ruthenium (PtRu), platinum molybdenum (PtMo), platinum titanium (PtTi), etc. may be exemplified as a binary platinum (Pt) alloy. Can. In addition, in order to make the shell part 5 resistant to carbon monoxide (CO), it is preferable to use a platinum ruthenium (PtRu) alloy.

In the case of employing a two-layer structure in which the shell portion 5 is composed of the first shell portion 6 and the second shell portion 7 as in the electrode catalysts 1B and 1C shown in FIGS. From the viewpoint of reducing the manufacturing cost of the catalyst 1, metal elements other than noble metals may be used as the main component.
Specifically, the core portion 4 is preferably a metal containing a metal element other than platinum (Pt), palladium (Pd), a metal compound, and a mixture of a metal and a metal compound, and a metal element other than a noble metal It is more preferable that it is a metal containing the following, a metal compound, and a mixture of metal and metal compound.

  The amount of platinum (Pt) supported in the shell portion 5 is preferably 5 to 20% by mass, and more preferably 8 to 16% by mass, with respect to the weight of the electrode catalyst 1. It is preferable that the supported amount of platinum (Pt) is 5% by mass or more because the catalyst activity as an electrode catalyst can be sufficiently exhibited, and the supported amount of platinum (Pt) is preferably 20% by mass or less. It is preferable from the viewpoint.

In the case where the shell portion 5 has a two-layer structure including the first shell portion 6 and the second shell portion 7, the first shell portion 6 is made of palladium (Pd), palladium (Pd) alloy, platinum (Pt) It is preferable that at least one metal selected from the group consisting of an alloy, gold (Au), nickel (Ni), and a nickel (Ni) alloy be contained, and palladium (Pd) alone be contained. Is more preferred.
The first shell portion 6 is more preferably composed mainly of palladium (Pd) (50 wt% or more) from the viewpoint of obtaining the catalyst activity of the electrode catalysts 1B and 1C higher and easily. It is more preferable to be composed of only palladium (Pd) alone.
The second shell portion 7 preferably contains at least one metal of platinum (Pt) and a platinum (Pt) alloy, and more preferably contains platinum (Pt) alone.
The second shell portion 7 is more preferably composed mainly of platinum (Pt) (50 wt% or more) from the viewpoint of obtaining the catalyst activity of the electrode catalysts 1B and 1C higher and easily. It is more preferable to be composed of only platinum (Pt) alone.

(Concentration of bromine (Br) species)
The electrode catalyst obtained by the method for producing an electrode catalyst according to the present invention uses an electrode catalyst precursor having a concentration of 3,000 ppm or more of bromine (Br) measured by X-ray fluorescence (XRF) analysis. Even in this case, the present invention is technically characterized in that the concentration of the above-mentioned bromine (Br) species is reduced by passing through at least the step (1) of the method for producing an electrode catalyst.

  The method for producing a catalyst for an electrode of the present invention uses bromine (Br (Br) when a catalyst precursor for an electrode having a concentration of 3,000 ppm or more of bromine (Br) measured by X-ray fluorescence (XRF) analysis is used as a raw material The catalyst for an electrode in which the concentration of the species is reduced to 1900 ppm or less, further to 1400 ppm or less, and further to 0 to 900 ppm can be provided more easily than in the prior art.

  Here, bromine (Br) species are measured by X-ray fluorescence (XRF) analysis. The value of the bromine (Br) species contained in the electrode catalyst obtained by the method for producing an electrode catalyst according to the fluorescent X-ray (XRF) analysis method is the concentration of the bromine (Br) species. The concentration of the bromine (Br) species is the concentration of the bromine atom converted to the bromine element contained in the electrode catalyst.

  A fluorescent X-ray (XRF) analysis method irradiates a sample containing an element A with primary X-rays, generates fluorescent X-rays of the element A, and measures the intensity of fluorescent X-rays related to the element A Is a method of performing quantitative analysis of the element A contained in When performing quantitative analysis using X-ray fluorescence (XRF) analysis, a fundamental parameter method (FP method) of theoretical operation may be adopted. The FP method utilizes the fact that the intensity of each fluorescent X-ray (XRF) can be theoretically calculated if the types of elements contained in the sample and their compositions are all known. Then, the FP method estimates a composition that matches the fluorescent X-ray (XRF) of each element obtained by measuring the sample.

  Fluorescent X-ray (XRF) analysis method is general-purpose fluorescent X such as energy dispersive X-ray fluorescence (XRF) analyzer, scanning X-ray fluorescence (XRF) analyzer, multi-element simultaneous X-ray fluorescence (XRF) analyzer, etc. It is implemented by using a line (XRF) analyzer. The X-ray fluorescence (XRF) analyzer comprises software, which performs experimental data processing on the relationship between the intensity of X-ray fluorescence (XRF) of element A and the concentration of element A. The software is not particularly limited as long as it is generally adopted in a fluorescent X-ray (XRF) analysis method. For example, software “analysis software:“ UniQuant 5 ”” for general purpose fluorescent X-ray (XRF) analyzer adopting FP method can be adopted as software. As a fluorescent X-ray (XRF) analyzer, for example, a wavelength dispersive full-automatic fluorescent X-ray analyzer (trade name: Axios "Axios") (manufactured by Spectras, Inc.) can be exemplified.

The catalyst for an electrode obtained by the method for producing a catalyst for an electrode of the present invention has a bromine (Br) concentration of less than 3000 ppm, preferably 1900 ppm or less, more preferably 1400 ppm or less, which is measured by X-ray fluorescence (XRF) analysis More preferably, it is reduced to a level of 0 to 9000 ppm. From the viewpoint of sufficiently obtaining the catalytic activity and durability of the electrode reaction, the concentration of the bromine (Br) species is more preferably 3,000 ppm or less, particularly preferably 1,000 ppm or less.
When the concentration of the bromine (Br) species is 3000 ppm or less, it is possible to sufficiently prevent the decrease in catalyst activity caused by the influence of the bromine (Br) species. And since it can exhibit sufficient catalytic activity as an electrode catalyst, it is preferable.
Here, the method for producing a catalyst for an electrode of the present invention can be used as a raw material of a catalyst for an electrode, even if it is a catalyst precursor for an electrode having a concentration of bromine (Br) of 3000 ppm or less. It is preferable to use an electrode catalyst precursor having a lower concentration of bromine (Br) species because the operation for removing the bromine (Br) species and the amount of ultrapure water used can be reduced.

(X-ray fluorescence (XRF) analysis method)
X-ray fluorescence (XRF) analysis is performed, for example, as follows.
(1) Measuring device, wavelength dispersive fully automatic X-ray fluorescence analyzer Axios (Axios) (manufactured by Spectris Co., Ltd.)
(2) Measurement conditions and analysis software: "UniQuant 5" (Semi-quantitative software using the FP (four peak method) method)
・ XRF measurement room atmosphere: Helium (normal pressure)
(3) Measurement procedure
(i) Place the sample container containing the sample into the XRF sample chamber.
(ii) Replace the XRF sample chamber with helium gas.
(iii) Under a helium gas atmosphere (normal pressure), the measurement conditions are set to "UQ5 application" which is the condition for using the analysis software "UniQuant5", and the main component of the sample is "carbon (constituent element of carrier ), The calculation mode is set so that the display format of the analysis result of the sample is "element".

<Structure of Fuel Cell Stack>
FIG. 10 shows a composition for forming a gas diffusion electrode including the electrode catalyst manufactured by the method for manufacturing a catalyst for an electrode according to the present invention, a gas diffusion electrode manufactured using the composition for forming a gas diffusion electrode, and the gas FIG. 1 is a schematic view showing a preferred embodiment of a membrane electrode assembly (MEA) provided with a diffusion electrode, and a fuel cell stack provided with the membrane electrode assembly (MEA).
The fuel cell stack S shown in FIG. 10 has a configuration in which a membrane electrode assembly (MEA) 400 is used as one unit cell and a plurality of such unit cells are stacked.

Furthermore, the fuel cell stack S includes a membrane electrode assembly (MEA) 400 including an anode 200a, a cathode 200b, and an electrolyte membrane 300 disposed between the electrodes.
In addition, the fuel cell stack S has a configuration in which the membrane electrode assembly (MEA) 400 is sandwiched by the separator 100 a and the separator 100 b.

  Hereinafter, a composition for forming a gas diffusion electrode, a gas diffusion electrode 200a and a gas diffusion electrode 200b, a membrane and an electrode, which are members of a fuel cell stack S including the electrode catalyst manufactured by the method for manufacturing an electrode catalyst of the present invention The joined body (MEA) 400 will be described.

<Composition for forming gas diffusion electrode>
The electrode catalyst 1 can be used as a so-called catalyst ink component to form a composition for forming a gas diffusion electrode. The composition for forming a gas diffusion electrode is characterized by containing the catalyst for an electrode. The composition for forming a gas diffusion electrode contains the above electrode catalyst and an ionomer solution as main components. The ionomer solution contains water, an alcohol, and a polyelectrolyte having hydrogen ion conductivity.

  The mixing ratio of water to alcohol in the ionomer solution may be a ratio that gives a viscosity suitable for applying the composition for forming a gas diffusion electrode to an electrode, and the alcohol is usually added to 100 parts by weight of water. It is preferable to contain 0.1-50.0 weight part. The alcohol contained in the ionomer solution is preferably a monohydric alcohol or a polyhydric alcohol. Examples of monohydric alcohols include methanol, ethanol, propanol, butanol and the like. Polyhydric alcohols include dihydric alcohols or trihydric alcohols. Examples of dihydric alcohols include ethylene glycol, diethylene glycol, tetraethylene glycol, propylene glycol, 1,3-butanediol and 1,4-butanediol. As a trihydric alcohol, glycerin can be exemplified. Further, the alcohol contained in the ionomer solution may be a combination of one or more alcohols. The ionomer solution can also contain additives such as surfactants as appropriate.

  The ionomer solution contains a polymer electrolyte having hydrogen ion conductivity as a binder component in order to disperse the electrode catalyst and to enhance the adhesion with the gas diffusion layer which is a member constituting the gas diffusion electrode. The polymer electrolyte is not particularly limited, and can be exemplified by known perfluorocarbon resins having sulfonic acid groups and carboxylic acid groups. Examples of readily available polymer electrolytes having hydrogen ion conductivity include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Corporation), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) It can be illustrated.

  The composition for forming a gas diffusion electrode can be prepared by mixing, grinding and stirring an electrode catalyst and an ionomer solution. The composition for forming a gas diffusion electrode can be prepared using a pulverizer / mixer such as a ball mill or an ultrasonic disperser. The grinding conditions and the stirring conditions at the time of operating the grinding mixer can be appropriately set according to the aspect of the composition for forming a gas diffusion electrode.

  Each composition of the electrode catalyst, water, alcohol, and polymer electrolyte having hydrogen ion conductivity contained in the composition for forming a gas diffusion electrode has a good dispersion state of the electrode catalyst, and the electrode catalyst is a gas diffusion catalyst. It is necessary to set such that it can be widely spread over the entire catalyst layer of the electrode and that the power generation performance of the fuel cell can be improved.

  Specifically, 0.1 to 2.0 parts by weight of a polymer electrolyte, 0.01 to 2.0 parts by weight of alcohol, 2.0 to 20.0 parts by weight of water with respect to 1.0 part by weight of the electrode catalyst It is preferable to More preferably, the polymer electrolyte is 0.3 to 1.0 parts by weight, alcohol 0.1 to 2.0 parts by weight, and water 5.0 to 6.0 parts by weight with respect to 1.0 part by weight of the electrode catalyst. Is preferred. When the composition of each component is within the above range, the coating film comprising the composition for forming a gas diffusion electrode is preferable because it does not spread too much at the time of film formation on the gas diffusion electrode, and coating comprising the composition for forming a gas diffusion electrode A film is preferable because it can form a coating film of appropriate and uniform thickness.

  The weight of the polymer electrolyte is the weight in a dry state and does not contain the solvent in the polymer electrolyte solution, and the weight of water is the weight containing water contained in the polymer electrolyte solution.

<Gas diffusion electrode>
The gas diffusion electrode (200a, 200b) including the electrode catalyst manufactured by the manufacturing method of the present invention includes the gas diffusion layer 220 and the electrode catalyst layer 240 laminated on at least one surface of the gas diffusion layer 220. . The electrode catalyst layer 240 included in the gas diffusion electrodes (200a, 200b) includes the electrode catalyst 1 described above. The gas diffusion electrode 200 of the present invention can be used as an anode and can also be used as a cathode.
In FIG. 10, for the sake of convenience, the upper gas diffusion electrode 200 is an anode 200a, and the lower gas diffusion electrode 200 is a cathode 200b.

(Catalyst layer for electrode)
The electrode catalyst layer 240 is a layer on the anode 200 a in which a chemical reaction is performed in which hydrogen gas sent from the gas diffusion layer 220 is dissociated into hydrogen ions by the function of the electrode catalyst 1 contained in the electrode catalyst layer 240. It is. In the electrode catalyst layer 240, the electrode catalyst layer 240 contains, in the cathode 200b, air (oxygen gas) sent from the gas diffusion layer 220 and hydrogen ions transferred from the anode in the electrolyte membrane. It is a layer in which a chemical reaction to be bound is performed by the action of the catalyst 1.

  The electrode catalyst layer 240 is formed using the composition for forming a gas diffusion electrode. The electrode catalyst layer 240 has a large surface area so that the reaction between the electrode catalyst 1 and the hydrogen gas or air (oxygen gas) sent from the gas diffusion layer 220 can be sufficiently performed. preferable. In addition, the electrode catalyst layer 240 is preferably formed to have a uniform thickness throughout. The thickness of the electrode catalyst layer 240 may be appropriately adjusted and is not limited, but is preferably 2 to 200 μm.

(Gas diffusion layer)
The gas diffusion layer 220 included in the gas diffusion electrode 200 is a hydrogen gas introduced from the outside of the fuel cell stack S to the gas flow path formed between the separator 100a and the gas diffusion layer 220a, and the separator 100b This layer is provided to diffuse the air (oxygen gas) introduced into the gas flow path formed between the gas diffusion layer 220 b and the gas diffusion layer 220 b into the electrode catalyst layers 240. Further, the gas diffusion layer 220 has a role of supporting the electrode catalyst layer 240 on the gas diffusion electrode 200 and immobilizing the electrode catalyst layer 240 on the surface of the gas diffusion electrode 200. The gas diffusion layer 220 has a role of enhancing the contact between the electrode catalyst 1 contained in the electrode catalyst layer 240 and the hydrogen gas or air (oxygen gas).

  The gas diffusion layer 220 has a function to allow hydrogen gas or air (oxygen gas) supplied from the gas diffusion layer 220 to pass well and reach the electrode catalyst layer 240. For this reason, the gas diffusion layer 220 has a water-repellent property so as to prevent the pore structure which is a microstructure present in the gas diffusion layer 220 from being blocked by the water generated in the electrode catalyst 1 and the cathode 200b. It is preferable to have Therefore, the gas diffusion layer 220 has a water repellent component such as polyethylene terephthalate (PTFE).

  The member that can be used for the gas diffusion layer 220 is not particularly limited, and a known member used for the gas diffusion layer of the fuel cell electrode can be used. For example, carbon paper and carbon paper are main materials, and carbon powder, ion-exchanged water as an optional component, and an auxiliary material consisting of polyethylene terephthalate dispersion as a binder are applied to carbon paper. The thickness of the gas diffusion layer can be appropriately set depending on the size of the fuel cell and the like, and is not particularly limited. However, in order to shorten the diffusion distance of the reaction gas, a thin one is preferable. On the other hand, since it is also required to have mechanical strength in the coating and assembly processes, for example, one having a size of about 50 to 300 μm is usually used.

  The gas diffusion electrode 200 a and the gas diffusion electrode 200 b may have an intermediate layer (not shown) between the gas diffusion layer 220 and the electrode catalyst layer 240. The gas diffusion electrode 200a and the gas diffusion electrode 200b have a three-layer structure including a gas diffusion layer, an intermediate layer, and a catalyst layer.

(Method of manufacturing gas diffusion electrode)
The manufacturing method of a gas diffusion electrode is demonstrated.
The method for producing a gas diffusion electrode is a composition for forming a gas diffusion electrode comprising an electrode catalyst 1 having a catalyst component supported on a carrier, a polymer electrolyte having hydrogen ion conductivity, and an ionomer solution of water and alcohol. And the step of drying the gas diffusion layer 220 coated with the composition for forming a gas diffusion electrode to form the electrode catalyst layer 240.

What is important in the step of applying the composition for forming a gas diffusion electrode on the gas diffusion layer 220 is to uniformly apply the composition for forming a gas diffusion electrode on the gas diffusion layer 220. By uniformly applying the composition for forming a gas diffusion electrode, a coating film made of the composition for forming a gas diffusion electrode having a uniform thickness is formed on the gas diffusion layer 220. The application amount of the composition for forming a gas diffusion electrode can be appropriately set according to the use form of the fuel cell, but from the viewpoint of the cell performance of a fuel cell provided with a gas diffusion electrode, platinum contained in the electrode catalyst layer 240 It is preferable that it is 0.1-0.5 (mg / cm < ² >) as amount of active metals, such as 1.

  Next, after the composition for forming a gas diffusion electrode is applied on the gas diffusion layer 220, the coating film of the composition for forming a gas diffusion electrode applied to the gas diffusion layer 220 is dried, and the gas diffusion layer 220 is formed. An electrode catalyst layer 240 is formed thereon. By heating the gas diffusion layer 220 on which the coating film of the composition for forming a gas diffusion electrode is formed, water and alcohol in the ionomer solution contained in the composition for forming a gas diffusion electrode are vaporized to form a gas diffusion electrode It disappears from the composition. As a result, in the step of applying the gas diffusion electrode-forming composition, the coating film of the gas diffusion electrode-forming composition present on the gas diffusion layer 220 includes an electrode catalyst and a polymer electrolyte catalyst. It becomes the layer 240.

Membrane-Electrode Assembly (MEA)
A membrane electrode assembly 400 (Membrane Electrode Assembly: hereinafter abbreviated as MEA) containing an electrode catalyst manufactured by the manufacturing method of the present invention is an anode which is a gas diffusion electrode 200 using the electrode catalyst 1 described above. An electrolyte 300 is provided to separate the electrodes 200a, the cathode 200b, and the electrodes. The membrane electrode assembly (MEA) 400 can be manufactured by pressure bonding after laminating the anode 200a, the electrolyte 300 and the cathode 200b in this order.

<Fuel cell stack>
The fuel cell stack S including the electrode catalyst manufactured by the manufacturing method of the present invention has the separator 100a (anode side) attached to the outside of the anode 200a of the obtained membrane-electrode assembly (MEA) 400, and the cathode 200b. Each separator 100b (cathode side) is attached to the outer side, and it is set as one unit cell (cell). Then, the unit cells (unit cells) are integrated to form a fuel cell stack S. The fuel cell system is completed by attaching peripheral devices to the fuel cell stack S and assembling them.

Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to the following examples.
In addition, the present inventors confirmed that iodine (I) species were not detected by the fluorescent X-ray (XRF) analysis method about the catalyst shown to an Example and a comparative example.
Moreover, in the description of each process of the following manufacturing method, unless otherwise noted, the process was performed at room temperature in air.

<Production of catalyst precursor for electrode>
(Production Example 1)
According to the method of the present invention for producing an electrode catalyst, an electrode catalyst was produced by the following process. In the production example, the raw material of the electrode catalyst used is as follows.
-Carbon black powder: Brand name "Ketjen Black EC300" (made by Ketchen Black International)
-Tetrachloropalladium (II) sodium-Palladium nitrate-Potassium chloroplatinate

[Preparation of palladium-supported carbon]
A carbon black powder was used as a carrier for the electrode catalyst, and was dispersed in water to prepare a 5.0 g / L dispersion. To this dispersion, 5 mL of an aqueous solution of sodium tetrachloropalladium (II) (concentration 20% by mass) was dropped and mixed. After adding 100 mL of an aqueous solution of sodium formate (100 g / L) dropwise to the obtained dispersion, the insoluble component is separated by filtration, and the insoluble component separated by filtration is washed with pure water and dried to obtain carbon black. The palladium (core) supported carbon carrying palladium was obtained.

[Coating of copper (Cu) on palladium (core)]
A 50 mM aqueous solution of copper sulfate was placed in a three-electrode electrolytic cell. An appropriate amount of the palladium-supported carbon prepared above was added to this three-electrode electrolytic cell, and after stirring, it was allowed to stand. At rest, 450 mV (against reversible hydrogen electrode) was applied to the working electrode to uniformly coat copper (Cu) on the palladium on palladium on palladium. This is called copper-palladium-supported carbon.

[Coating of platinum (Pt) on palladium (core)]
By adding a potassium chloroplatinate aqueous solution containing platinum (Pt) equivalent to twice the substance mass ratio to a liquid containing copper-palladium-supported carbon in which copper is coated on palladium, to a solution containing copper. The copper (Cu) of the copper-palladium-supported carbon was replaced with platinum (Pt).

[Preprocessing]
Step (P1): The powder of the platinum-palladium-loaded carbon particles in which the copper (Cu) of the copper-palladium-loaded carbon obtained as described above is substituted with platinum (Pt) A dispersed first liquid P1 was prepared.
Step (P2): Next, the solution of P1 was filtered and washed with ultrapure water using a filter. The washing is repeated until the electric conductivity of the filtrate obtained after washing becomes 10 μS / cm or less, and the obtained electrode catalyst precursor is dispersed in ultrapure water, and the electrode catalyst precursor-ultrapure water dispersion liquid I got (I).
Step (P3): Next, the dispersion (I) was filtered, and the obtained filtrate was dried at 70 ° C. in air for about 24 hours. Thus, the electrode catalyst precursor 1 obtained in Production Example 1 was obtained.

In addition, as described later, it was confirmed that the concentration of bromine (Br) species measured by the XRF analysis method for the electrode catalyst precursor 1 was 3000 ppm or more as described in Table 1.
Thereby, in the following examples, the concentration of the first bromine (Br) species in the electrode catalyst precursor of the raw material is 3000 ppm.

<Manufacture of electrode catalyst>
Example 1
[Step 1 ']
The electrode catalyst precursor 1 obtained in Production Example 1 was weighed in 5.0 g and placed in a container. Next, 1000 (mL) of ultrapure water is added to the vessel, and while maintaining this solution at room temperature (25 ° C.), about 60 mL of hydrogen gas (about 100%) in this solution at a rate of about 10 mL / min. Aerated for a minute.
[Fifth step]
The solution after bubbling hydrogen gas was filtered, and the obtained filtrate was dried in air at a temperature of 70 ° C. for about 24 hours to obtain an electrode catalyst. The electrode catalyst obtained in Example 1 was designated as catalyst 1.

[Measurement of loading amount]
With respect to the obtained catalyst 1, the supported amounts (% by mass) of platinum and palladium were measured by the following method.
Catalyst 1 was immersed in aqua regia to dissolve the metal. Next, insoluble carbon was removed from aqua regia. Next, the aqua regia from which carbon was removed was subjected to ICP analysis.
As a result of ICP analysis, the supported amount of platinum was 20.9% by mass, and the supported amount of palladium was 22.5% by mass.

(Example 2)
[First step]
5.0 g of the electrode catalyst precursor 1 obtained in Production Example 1 was weighed and placed in a container. Next, 1000 mL of a 0.01 M aqueous solution of sodium formate was added to the vessel, and the obtained aqueous dispersion was kept at room temperature (25 ° C.) and kept for about 240 minutes with stirring.
[The second and fourth steps]
Ultrapure water was added to the solution obtained after the first step to obtain a dispersion (first solution).
Next, insoluble components contained in the dispersion were separated by filtration and washed with ultrapure water. The washing is repeated until the electric conductivity of the filtrate obtained after washing becomes 10 μS / cm or less, and the obtained electrode catalyst precursor is dispersed in ultrapure water, and the electrode catalyst precursor-ultrapure water dispersion liquid (The second liquid, hereinafter, referred to as “dispersion liquid (II)”) was obtained. The dispersion (II) was filtered, and the obtained filtrate was dried at a temperature of 70 ° C. in air for 24 hours to obtain an electrode catalyst. The electrode catalyst obtained in Example 2 is referred to as catalyst 2.
The catalyst 2 was subjected to the same ICP analysis as in Example 1, and the amounts of supported platinum and palladium shown in Table 1 were measured.

(Example 3)
A catalyst for an electrode was obtained in the same manner as in Example 2 except that the aqueous solution of sodium formate in the first step was changed to an aqueous solution of sodium carbonate in Example 2. The electrode catalyst obtained in Example 3 is referred to as catalyst 3.
The catalyst 3 was subjected to the same ICP analysis as in Example 1, and the amounts of supported platinum and palladium shown in Table 1 were measured.

(Example 4)
A catalyst for an electrode was obtained in the same manner as in Example 3 except that the holding temperature in the first step was set to 90 ° C. in Example 3. The electrode catalyst obtained in Example 4 is referred to as catalyst 4.
The catalyst 4 was subjected to the same ICP analysis as in Example 1, and the amounts of supported platinum and palladium shown in Table 1 were measured.

(Example 5)
In Example 2, except that the holding temperature in the first step is room temperature to 90 ° C., the first to fourth steps are performed, and the first to fourth steps are repeated a predetermined number of times as one set. In the same manner as in Example 2 to obtain an electrode catalyst. The electrode catalyst obtained in Example 5 is referred to as catalyst 5.
The catalyst 5 was subjected to the same ICP analysis as in Example 1, and the amounts of supported platinum and palladium shown in Table 1 were measured.

(Comparative example 1)
The electrode catalyst precursor 1 produced in Production Example 1 was used as the electrode catalyst of Comparative Example 1.

<Evaluation of electrode catalyst>
(Concentration of bromine (Br) species)
The concentrations of bromine (Br) species in the electrode catalysts obtained in Examples 1 to 5 and Comparative Example 1 were measured by X-ray fluorescence (XRF) analysis. The bromine (Br) species concentration in the electrode catalyst was measured by a wavelength dispersive fluorescent X-ray measurement apparatus Axios (manufactured by Spectris Co., Ltd.). Specifically, the following procedure was followed.

  A sample for measurement of the electrode catalyst was placed in an XRF sample container attached to a wavelength dispersive fluorescent X-ray measurement apparatus. The XRF sample container containing the sample for measurement of the electrode catalyst is placed in the XRF sample chamber, and the XRF sample chamber is replaced with helium gas. Thereafter, fluorescent X-ray measurement was performed under a helium gas atmosphere (normal pressure).

As software, analysis software "UniQuant 5" for wavelength dispersive fluorescent X-ray measurement apparatus was used. Set the measurement conditions according to the analysis software "UniQuant5" and set "UQ5 application", and the main component of the sample for measurement of the electrode catalyst is "carbon (constituent element of catalyst carrier for electrode)", display of analysis result of sample It set to the mode calculated so that a form might become "elemental." The measurement results were analyzed by analysis software "UniQuant 5" to calculate the concentration of bromine (Br) species. The measurement results are shown in Table 1.

According to Table 1, in the method for producing a catalyst for an electrode according to the present invention, even when a catalyst precursor for an electrode containing a high concentration of bromine (Br) is employed as a raw material, this catalyst precursor for an electrode Concentration of bromine (Br) species in the electrode catalyst precursor by applying a predetermined bromine (Br) species removal method to 3000 ppm (the concentration of the first bromine (Br) species or the second bromine (Br) Even when the concentration of the species is 3000 ppm or more, it is possible to easily manufacture an electrode catalyst in which the bromine (Br) species is greatly reduced to 3000 ppm or less, further to 1400 ppm or less, and further to about 0 to 900 ppm. It became clear.
Furthermore, according to Table 1, the electrode catalyst obtained by the method for producing an electrode catalyst according to the present invention is an electrode catalyst in which a predetermined bromine (Br) species removal method is not applied to the electrode catalyst precursor. In comparison, it has become clear that the content of the bromine (Br) species is sufficiently reduced, and it is possible to obtain an electrode catalyst in which the decrease in catalytic activity due to the bromine (Br) species is sufficiently prevented.
These results show that the method for producing a catalyst for an electrode of the present invention is suitable for mass production and is a production method suitable for reducing the production cost.
Here, with respect to Example 5 in Table 1, the concentration of bromine species of “0 ppm” indicates the concentration at which the bromine (Br) species is determined to be undetected in the fluorescent X-ray (XRF) analysis. The detection limit of bromine (Br) species in the X-ray fluorescence (XRF) analysis here was 100 ppm.

1 electrode catalyst 1A electrode catalyst 1B electrode catalyst 1C electrode catalyst 2 carrier 3 catalyst particle 3a catalyst particle 4 core portion 4s core portion exposed surface 5 shell portion 6 first shell portion 6s first shell portion exposed surface 7 second Shell part S Fuel cell stack 100 Separator 100a Separator (anode side)
100b separator (cathode side)
200 gas diffusion electrode 200a gas diffusion electrode (anode)
200b Gas Diffusion Electrode (Cathode)
220 Gas diffusion layer 240 Catalyst layer for electrode 300 Electrolyte 400 Membrane-electrode assembly (MEA)

According to the method for producing a catalyst for an electrode of the present invention, even if a catalyst precursor for an electrode having a high concentration of bromine content is used, the content of the bromine (Br) species by a relatively simple operation However, the electrode catalyst can be obtained reliably and sufficiently reduced.
Moreover, the method for producing a catalyst for an electrode of the present invention can simplify the production process and reduce the production cost.
Therefore, the present invention is a method of manufacturing a catalyst for an electrode applicable to energy farms, cogeneration systems, etc., as well as to the electric equipment industry such as fuel cells, fuel cell vehicles, portable mobiles, etc. Contribute to the development of technology-related.

Claims (17)

A method for producing an electrode catalyst having a core-shell structure, comprising: a support; a core portion formed on the support; and a shell portion formed to cover at least a part of the surface of the core portion. ,
Step (1): The concentration of bromine (Br) species manufactured using ultrapure water, a reducing agent, and a material containing bromine (Br) species and measured by X-ray fluorescence (XRF) analysis A solution containing an electrode catalyst precursor having a concentration of the first bromine (Br) or more preset in advance is set in advance at at least one stage of preset temperature preset in the range of 10 ° C. to 95 ° C. A first step of holding at a fixed holding time,
Step (2): Ultrapure water is added to the solution obtained after the first step,
A second step of preparing a first liquid in which a catalyst precursor contained in the liquid obtained after the first step is dispersed in ultrapure water;
Step (3): The catalyst precursor contained in the first liquid is filtered and washed using ultrapure water,
The washing is repeated until the electric conductivity ρ measured by the JIS standard test method (JIS K0552) of the filtrate obtained after washing becomes equal to or less than a first set value set in advance,
A third step of preparing a second liquid in which the catalyst precursor contained in the liquid in which the electric conductivity と な っ is less than or equal to a preset first set value is dispersed in ultrapure water;
Step (4): drying the second liquid;
A method for producing an electrode catalyst, comprising: A method for producing an electrode catalyst having a core-shell structure, comprising: a support; a core portion formed on the support; and a shell portion formed to cover at least a part of the surface of the core portion. ,
Step (1 ′); bromine (Br) species manufactured using ultrapure water, a gas containing hydrogen, and a material containing bromine (Br) species and measured by X-ray fluorescence (XRF) analysis A solution containing an electrode catalyst precursor having a concentration of at least the concentration of the first bromine (Br) species set in advance;
A method for producing a catalyst for an electrode, comprising: a first 1 'step of holding at least one set temperature preset in a range of 10 ° C. to 60 ° C. and for a preset holding time. The manufacturing method of the catalyst for electrodes according to claim 1 or 2 whose concentration of said 1st bromine (Br) kind is 3000 ppm.   The method for producing a catalyst for an electrode according to claim 1, wherein the reducing agent is at least one compound selected from an organic acid and an organic acid salt.   The method for producing a catalyst for an electrode according to claim 1, wherein the reducing agent is at least one compound selected from the group consisting of formic acid and sodium formate.   The method for producing an electrode catalyst according to claim 1, wherein the reducing agent is at least one compound selected from inorganic acids and inorganic acid salts.   The method for producing a catalyst for an electrode according to claim 1, wherein the reducing agent is at least one compound selected from the group consisting of carbonic acid and sodium carbonate.   Step (5); for the electrode according to any one of claims 1 to 7, further comprising a fifth step of drying the dispersion obtained after the first step or the first step. Method of producing a catalyst Step (2): Ultrapure water is added to the solution obtained after the first step,
A second step of preparing a first liquid in which the electrode catalyst precursor contained in the liquid obtained after the first step is dispersed in ultrapure water;
Step (3): The electrode catalyst precursor contained in the first liquid is filtered and washed using ultrapure water,
The washing is repeated until the electric conductivity ρ measured by the JIS standard test method (JIS K0552) of the filtrate obtained after washing becomes equal to or less than a first set value set in advance,
A third step of preparing a second liquid in which the electrode catalyst precursor contained in the liquid in which the electric conductivity が is equal to or less than a preset first set value is dispersed in ultrapure water;
Step (4): drying the second liquid;
Further include,
The manufacturing method of the catalyst for electrodes of Claim 2. The first set value is a value selected from the range of 100 μS / cm or less
The manufacturing method of the catalyst for electrodes of Claim 1 or 9. The electrode catalyst precursor to be subjected to the first step or the first step is:
Step (P1); a second bromine which is manufactured using a material containing a bromine (Br) species and whose concentration of the bromine (Br) species is preset by a fluorescent X-ray (XRF) analysis method (Pl) A process of preparing a solution of P1 in which the electrode catalyst precursor having a concentration of (Br) or more is added to ultrapure water to disperse the electrode catalyst precursor in ultrapure water;
Step (P2): The ultrapure water is used to wash the electrode catalyst precursor contained in the P1 solution, and the filtrate obtained after washing is measured by the JIS standard test method (JIS K0552). The process is repeated until the electric conductivity ρ becomes equal to or less than the preset value P1 set in advance, and the obtained catalyst precursor is dispersed in ultrapure water to prepare a solution P2;
Step (P3); drying the liquid P2.
Is pretreated, including
The manufacturing method of the catalyst for electrodes of any one of Claims 1-10.   The method for producing a catalyst for an electrode according to claim 11, wherein the concentration of the second bromine (Br) species is 3000 ppm. The preset P1 setting value is a value selected from the range of 100 μS / cm or less,
The manufacturing method of the catalyst for electrodes of Claim 11. The shell portion contains at least one metal of platinum (Pt) and a platinum (Pt) alloy,
In the core portion, at least one selected from the group consisting of palladium (Pd), palladium (Pd) alloy, platinum (Pt) alloy, gold (Au), nickel (Ni), and nickel (Ni) alloy. Contains metal,
The manufacturing method of the catalyst for electrodes of any one of Claims 1-13. Platinum (Pt) bromide is used as a raw material of the metal which comprises the said shell part,
The manufacturing method of the catalyst for electrodes of Claim 14. A first shell portion formed to cover at least a portion of the surface of the core portion, and a second shell portion formed to cover at least a portion of the surface of the first shell portion; ,have,
The manufacturing method of the catalyst for electrodes of any one of Claims 1-15.   The method for producing a catalyst for an electrode according to claim 16, wherein platinum (Pt) bromide is used as a raw material of a metal constituting the second shell portion.

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