JP5843899B2 - Method for evaluating catalytic activity of electrode catalyst for fuel cell - Google Patents

Description

  The present invention relates to an electrolyte material for a catalyst electrode layer used for a catalyst electrode layer in a method for evaluating the catalytic activity of a fuel cell electrode catalyst.

  The polymer electrolyte fuel cell is a fuel cell using a solid polymer such as an ion exchange resin as an electrolyte, and has a feature that its operating temperature is relatively low. As shown in FIG. 1, such a polymer electrolyte fuel cell has a space in the cell partition wall 1 having a fuel circulation hole 2 and an oxidant gas circulation hole 3 communicating with the outside, respectively. The fuel chamber side catalyst electrode layer 4 and the oxidant chamber side catalyst electrode layer 5 are separated from each other by a joined body, and the fuel chamber side diffusion electrode (current collector) 6 and the oxidation are further formed on each electrode layer. A base in which an agent chamber side gas diffusion electrode (current collector) 7 is installed, and a fuel chamber 9 communicating with the outside through the fuel circulation hole 2 and an oxidant chamber 10 communicating with the outside through the oxidant gas circulation hole 3 are formed. It has a structure. In the polymer electrolyte fuel cell having such a basic structure, a fuel made of hydrogen gas or methanol is supplied to the fuel chamber 9 through the fuel circulation hole 2 and an oxidant gas circulation hole is supplied to the oxidant chamber 10. 3 is used to supply an oxidant gas such as oxygen or air as an oxidant and to connect an external load circuit between both diffusion electrodes (current collectors) to generate electrical energy by the following mechanism. ing.

  When a cation exchange resin electrolyte membrane (hereinafter also referred to as a cation exchange membrane) is used as the solid polymer electrolyte membrane 8, in the fuel chamber side catalyst electrode layer 4, the electrode catalyst and fuel contained in the electrode are separated. Protons (hydrogen ions) generated by the contact are conducted through the solid polymer electrolyte membrane 8 and move to the oxidant chamber 10 and react with oxygen in the oxidant gas in the oxidant chamber side catalyst electrode layer 5. To produce water. On the other hand, electrons generated simultaneously with protons in the fuel chamber side catalyst electrode layer 4 move to the oxidant chamber side catalyst electrode layer 5 through the external load circuit, so that the energy of the reaction can be used as electric energy.

  When an anion exchange resin electrolyte membrane (hereinafter also referred to as an anion exchange membrane) is used as the solid polymer electrolyte membrane 8, a fuel made of hydrogen or methanol is supplied to the fuel chamber side, and the oxidant chamber side is supplied. In the oxidant chamber side catalyst electrode layer 5, hydroxide ions generated by contacting the electrode catalyst contained in the electrode with oxygen and water are converted into a solid polymer electrolyte membrane. 8 is conducted to the fuel chamber 9 and reacts with the fuel in the fuel chamber side catalyst electrode layer 4 to generate water. On the other hand, electrons generated simultaneously with water in the fuel chamber side catalyst electrode layer 4 move to the oxidant chamber side catalyst electrode layer 5 through the external load circuit, so that the energy of the reaction can be used as electric energy.

As the cation exchange membrane, a perfluorocarbon sulfonic acid resin electrolyte membrane is most commonly used. However, the following problems have been pointed out in such a cation exchange membrane fuel cell.
(I) Since the reaction field is strongly acidic, only a noble metal catalyst can be used, and the perfluorocarbon sulfonic acid resin electrolyte membrane is also expensive, so there is a limit to cost reduction.
(Ii) Since physical strength is low, it is difficult to reduce electrical resistance by thinning.
(Iii) When methanol is used as the fuel, the methanol permeability to the electrolyte membrane is high, and the methanol that has reached the oxidant chamber side gas diffusion electrode reacts with oxygen on its surface, so the output voltage decreases.

  In order to solve such a problem, particularly the above problem (i), the use of a hydrocarbon-based anion exchange membrane in place of the perfluorocarbon sulfonic acid resin electrolyte membrane has been studied. Several fuel cells have been proposed (Patent Documents 1 to 3). Moreover, according to these proposals, since the hydrocarbon-based anion exchange membrane is used, the above problems (ii) and (iii) can be solved.

  By the way, conventionally, in order to evaluate the catalytic activity of a fuel cell, a catalytic activity evaluation method using a rotating electrode method capable of accurately controlling the supply rate of the reactant to the electrode catalyst has been frequently used. In this method, the reactant is supplied to the electrode by rotating the electrode in an electrolytic solution in which the reactant is dissolved, and the catalytic activity is evaluated from the current value of the electrode reaction occurring on the electrode catalyst. The reactant can be evaluated using an oxidant such as oxygen as well as fuel such as hydrogen and methanol.

  There are two rotating electrode methods, the rotating disk electrode method and the rotating ring disk electrode method. The rotating disk electrode method is a method of positively utilizing the convection-diffusion of the electrolyte solution by rotating the disk electrode. For example, a low-activity electrode such as glassy carbon is used as a material for the disk electrode, and a catalyst electrode layer is formed on the disk electrode. When the disk electrode is rotated in the solution, mass transfer is regulated by the number of rotations, and a good current-potential curve can be obtained. For example, when the rotational speed is increased and the mass transfer becomes rate-limiting, a limiting current is observed, and the rate constant of the electron transfer process can be obtained by analysis.

  In addition to the information obtained by the above rotating disk electrode method, the rotating ring disk electrode method can be adopted when it is desired to obtain quantitative knowledge about the reaction mechanism. Specifically, the disk electrode and the ring electrode are combined, the ring electrode is arranged concentrically around the disk electrode, and an insulator is placed between the two. The electrode reactant generated at the disk electrode moves by convection diffusion and reaches the ring electrode. From the result of the current-potential curve at the ring electrode, it is possible to analyze the electrode reaction on the ring electrode and estimate the product at the disk electrode. This is an effective method for analyzing unstable intermediates. In the performance evaluation of an electrode catalyst for a fuel cell, it is often used for determination of hydrogen peroxide as an intermediate, measurement of a 4-electron reaction rate, and the like. In order to evaluate the catalytic activity of an electrode catalyst for a fuel cell, a rotating ring disk electrode method is frequently used.

  In the evaluation of the activity of an anion exchange membrane fuel cell electrode catalyst, Nafion (registered trademark), which is strongly acidic, is used as a binder for the catalyst electrode layer as described in Non-Patent Documents 1 and 2. Yes.

Japanese Patent Laid-Open No. 11-273695 JP-A-11-135137 JP 2000-331693 A

L. Demarconay, C.I. Coucanceau, J. et al. -M. L'eger: Electrochimica Acta 53 (2008) 3232-3241 Wenmig Wang, Dan Zheng, Cong Du: Journal of Power Sources 167 (2008) 243-249

  When Nafion is used as a binder, there is no problem if the electrode catalyst is a noble metal, but in the case of a non-noble metal, the electrode catalyst may be dissolved in Nafion, which is a strongly acidic substance, when the catalyst electrode layer is prepared. There is a problem that it is difficult to accurately evaluate the catalytic activity. In addition, when the present inventors examined using a non-ion exchange resin or an anion exchange resin having a high anion exchange capacity as a binder instead of Nafion, the catalyst electrode layer can be prepared, but the catalytic activity ability was evaluated. It has been found that there is a problem that it may not be sufficiently reflected in.

  This invention solves the above problems, and provides the electrolyte material for catalyst electrode layers which can fully exhibit and reflect the catalytic activity ability which an electrode catalyst originally has.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problem is the ease of movement of hydroxide ions (OH ⁻ ), which are conductive ions in the binder forming the catalyst electrode layer. This is due to the difference and the difference in the amount of reactant supplied to the catalyst due to the swelling of the ion exchange resin in the electrolyte, and the anion exchange capacity as a binder for the electrolyte material for the catalyst electrode layer is in a specific range. By using the anion exchange resin as described above, the inventors have found that the above object can be achieved and have completed the present invention.

  That is, according to the present invention, the electrode catalyst, the conductive material, and the anion exchange capacity are 0.1 to 0.7 mmol / g on the surface of the disk electrode of the rotating electrode method using the electrolytic solution in which the reactant of the fuel cell is dissolved. -Forming a catalyst electrode layer formed of an electrolyte material for a catalyst electrode layer used in contact with a water-containing liquid, comprising a composition containing a water-insoluble anion exchange resin of a dry resin, and changing the potential of the electrode; Catalytic activity of a fuel cell electrode catalyst characterized by detecting current and evaluating the catalytic activity of a fuel electrode reaction or oxygen electrode reaction in a fuel cell of an electrode catalyst contained in the catalyst electrode layer electrolyte material It is an electrolyte material for the catalyst electrode layer on the disk electrode surface of the rotating electrode method used in the evaluation method and the method for evaluating the catalytic activity of the fuel cell electrode catalyst.

  Since the electrolyte material for a catalyst electrode layer of the present invention uses an anion exchange resin as a binder, not only a noble metal catalyst but also a non-noble metal catalyst can be used as an electrode catalyst.

In addition, since the electrolyte material for the catalyst electrode layer of the present invention uses an anion exchange resin as a binder, the hydroxide ion (OH ⁻ ), which is a conductive ion, uses a cation exchange resin or a non-ion exchange resin. The anion exchange resin that is easy to move and has an anion exchange capacity within a specific range has a small volume change, and therefore can improve the decrease in the amount of reactant supplied to the catalyst due to the volume change. The inherently active catalytic activity can be sufficiently reflected.

  Therefore, if the electrolyte material for a catalyst electrode layer of the present invention is used for a catalyst electrode layer for evaluating the catalyst activity, a catalyst activity evaluation method capable of sufficiently reflecting the catalyst activity originally possessed by the catalyst is provided. can do.

FIG. 1 is a conceptual diagram showing a basic structure of a polymer electrolyte fuel cell. FIG. 2 is a conceptual diagram showing the basic structure of the rotating electrode method apparatus. FIG. 3 is a schematic view showing the structure of the rotating ring disk electrode.

  The electrolyte material for the catalyst electrode layer used for the catalyst electrode layer on the disk electrode surface of the rotating electrode method used in the method for evaluating the catalytic activity of the electrode catalyst for fuel cells of the present invention includes an electrode catalyst, a conductive material, and an anion exchange capacity. Is an electrolyte material for a catalyst electrode layer used in contact with a water-containing liquid, comprising a composition containing a water-insoluble anion exchange resin of 0.1 to 0.7 mmol / g-dry resin.

  In the present invention, as the electrode catalyst, since an anion exchange resin is used for the binder, any known electrode catalyst can be used without limitation regardless of whether it is a noble metal or a non-noble metal. Specifically, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, osmium, tin, iron, cobalt, nickel, molybdenum, tungsten, vanadium, titanium, manganese, copper, or alloys thereof, and further Fine particles such as oxides, nitrides and carbides can be mentioned.

Furthermore, a perovskite oxide represented by ABO ₃ can also be suitably used. Specifically, LaMnO ₃ , LaFeO ₃ , LaCrO ₃ , LaCoO ₃ , LaNiO _3, etc., or a part of the A site partially substituted with Sr, Ca, Ba, Ce, Ag, etc., and the B site Perovskite-type oxides in which a part of these are partially substituted with Pd, Pt, Ru, Ag or the like can also be suitably used as an electrode catalyst.

  The particle diameter of these electrode catalysts is usually 0.1 to 100 nm, more preferably 0.5 to 10 nm.

  The conductive material is not particularly limited as long as it is an electron conductive material. For example, carbon black such as furnace black and acetylene black, activated carbon, graphite and the like are generally used alone or in combination. is there. In the present invention, an embodiment in which the electrode catalyst is used after being previously supported on a conductive material is also preferably employed.

  The anion exchange resin used for the catalyst electrode layer electrolyte material of the present invention is a water-insoluble anion exchange resin having an anion exchange capacity of 0.1 to 0.7 mmol / g-dry resin.

  When the anion exchange capacity of the anion exchange resin is less than 0.1 mmol / g-dry resin, the conductivity of the hydroxide ion becomes insufficient, and the catalyst activity ability inherent to the catalyst may not be sufficiently exhibited. . In addition, when the anion exchange capacity exceeds 0.7 mmol / g-dry resin, the resin swells in an aqueous solution and inhibits the supply of the reactants into the catalyst electrode layer, and the catalytic activity inherent in the catalyst. Performance may not be fully demonstrated. There is also a concern that it becomes soluble in water and cannot serve as a binder. The anion exchange capacity of the anion exchange resin is preferably in the range of 0.2 to 0.6 mmol / g-dry resin, more preferably in the range of 0.4 to 0.6 mmol / g-dry resin, from the points shown above. Is preferred.

  Further, when the anion exchange resin used in the electrolyte material for the catalyst electrode layer of the present invention is not insoluble in water, the electrolyte material for the catalyst electrode layer is eluted from the catalyst electrode layer, and the catalytic activity ability cannot be accurately evaluated. Problems such as deterioration of the performance of the fuel cell may occur. Here, being insoluble in water means that the solubility in water at 20 ° C. is less than 0.1% by mass, preferably 0.05% by mass or less, more preferably 0.03% by mass or less. Say.

The anion exchange resin used for the electrolyte material for the catalyst electrode layer of the present invention is not particularly limited as long as it is a water-insoluble anion exchange resin having an anion exchange capacity of 0.1 to 0.7 mmol / g-dry resin. Or the high molecular compound synthesize | combined by a well-known method can be used without a restriction | limiting.
Particularly preferably, the polymer compound is an elastic hydrocarbon polymer (hereinafter also referred to as a hydrocarbon polymer elastomer).

  Here, the hydrocarbon polymer means a polymer compound in which most of the molecules other than the ion exchange groups present in the molecule are composed of hydrocarbons. However, as long as the effect of the present invention is not impaired, atoms other than carbon atoms and hydrogen atoms may be contained in a portion other than the anion exchange group in the molecule. For example, in addition to carbon-carbon bonds and carbon = carbon bonds (double bonds) as bonds constituting the main and side chains of the molecule, ether bonds, ester bonds, amide bonds, etc. are introduced by such bonds. Oxygen, nitrogen, silicon, sulfur, boron, phosphorus, etc. may be contained in an amount such that the total amount is 40% or less, preferably 10% or less of the total number of atoms constituting the molecule. Furthermore, if the number of hydrogen atoms present in the molecule is 40% or less, preferably 10% or less, chlorine, bromine, fluorine, iodine and other atoms are bonded directly or as a substituent to the main chain and side chain. May be.

  The anion exchange group present in the hydrocarbon polymer elastomer is not particularly limited as long as it is a substituent having anion exchange ability, a quaternary ammonium base, a pyridinium base, an imidazolium base, a tertiary amine group, Known anion exchange groups such as a phosphonium group can be employed, but it is preferable to employ a quaternary ammonium base or a pyridinium base from the viewpoint of strong basicity.

When the anion exchange resin used in the present invention is used as an electrolyte material for a catalyst electrode layer containing an electrode catalyst and a conductive material, the anion exchange resin may be present uniformly in the vicinity of the joint surface and on the electrode catalyst. From the viewpoint that a catalyst electrode layer having good bonding properties and high activity can be produced, it is preferable that the catalyst electrode layer is dissolved in an organic solvent and used in a solution state. For these reasons, it is preferable that the anion exchange resin is soluble in an organic solvent. The organic solvent is not particularly limited, but a low-boiling organic solvent is preferable because it can be easily dried when used as a solution-like anion exchange resin. Examples of such organic solvents are methanol, ethanol, 1-propanol, 2-propanol, n-butanol, methyl ethyl ketone, acetonitrile, nitromethane, dimethyl sulfoxide, N-methylpyrrolidone, N, N-dimethylformamide, N, N -Dimethylacetamide, tetrahydrofuran, toluene, methylene chloride, dichloromethane etc. are mentioned, The above can be used alone or as a mixed solvent in which two or more kinds are mixed. The mixed solvent may contain a small amount of water in such a range that the anion exchange resin does not become insoluble. The content of water in the mixed solvent is 3% by mass or less, preferably 1% by mass or less.
As the anion exchange resin, it is particularly preferable to use one having a solubility in such an organic solvent (concentration of the anion exchange resin in a saturated solution at 20 ° C.) of 1% by mass or more, particularly 3% by mass or more. is there.

  The anion exchange resin used in the present invention can polymerize a monomer having a functional group capable of introducing an anion exchange group or a monomer having an anion exchange group and a conjugated diene compound, and then an anion exchange group can be introduced. When a monomer having a functional group is used, in the method for introducing an anion exchange group, the types of monomers used, combinations thereof, quantitative ratios, presence or absence of use of a crosslinking agent, or It can be synthesized by adjusting the amount used, the amount of anion exchange group introduced, the degree of polymerization of the polymer, and the like.

  Examples of the monomer having a functional group capable of introducing an anion exchange group used in the above method include aromatic vinyl compounds such as styrene, α-methylstyrene, chloromethylstyrene, vinylpyridine, vinylimidazole, and vinylnaphthalene. However, styrene and α-methylstyrene are preferably used from the viewpoint of easy introduction of anion exchange groups. Examples of the monomer having an anion exchange group include amine monomers such as vinylbenzyltrimethylamine and vinylbenzyltriethylamine, nitrogen-containing heterocyclic monomers such as vinylpyridine and vinylimidazole, salts and esters thereof. Etc. are used.

  Examples of the conjugated diene compound used in the above method include butadiene, isoprene, chloroprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and the like. The content is not particularly limited, but the content of the conjugated diene compound unit in the hydrocarbon polymer elastomer is generally 5 to 75% by mass, particularly 10 to 50% by mass.

  In addition to the monomer having a functional group into which the anion exchange group can be introduced, the monomer having an anion exchange group or a conjugated diene compound, a crosslinkability capable of copolymerizing with these monomers as necessary. A monomer may be added. In addition, the crosslinkable monomer used in the above method is not particularly limited, and examples thereof include polyfunctional vinyl compounds such as divinylbenzenes, divinylsulfone, divinylbiphenyl, trivinylbenzene, and trimethylolmethane. Polyfunctional methacrylic acid derivatives such as trimethacrylic acid ester, methylene bisacrylamide, hexamethylene dimethacrylamide are used. When these crosslinkable monomers are used, the amount used is generally from 0.1 to 100 parts by mass of a monomer having a functional group into which an anion exchange group can be introduced or a monomer having an anion exchange group. It is selected from 01 to 5 parts by mass, preferably 0.05 to 1 part by mass. When the crosslinkable monomer is 0.01 parts by mass or less, the resulting hydrocarbon polymer elastomer having an anion exchange group is easily soluble in water, and at 5% by mass or more, it is insoluble in an organic solvent. Easy to be.

  In addition to the monomer having a functional group into which the anion exchange group can be introduced, the monomer having an anion exchange group, the conjugated diene compound or the crosslinkable monomer, these monomers may be used as necessary. Other monomers capable of copolymerization may be added. As such other monomers, for example, vinyl compounds such as ethylene, propylene, butylene, acrylonitrile, vinyl chloride, and acrylate are used. The amount used is preferably 0 to 100 parts by mass with respect to 100 parts by mass of the monomer having a functional group into which an anion exchange group can be introduced or the monomer having an anion exchange group.

  As the polymerization method in the above method, known polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization and the like are employed. Such production conditions depend on the composition of the monomer composition and the like, and are not particularly limited and may be appropriately selected. Here, in the case of polymerizing the hydrocarbon polymer elastomer having the above properties, the average molecular weight of 10,000 to 1,000,000, preferably 20,000 to 200,000, for example, the above-described monomer such as styrene is used. The polymerization is preferably performed under various polymerization conditions. When a monomer having an anion exchange group is used, the hydrocarbon polymer elastomer used in the present invention can be obtained by performing polymerization in this manner. In addition, when a monomer having a functional group into which an anion exchange group can be introduced is used, a desired anion exchange group is obtained by a known method such as amination or alkylation for a polymer obtained by such polymerization. Should be introduced.

  In addition, among the above methods, since the highly effective hydrocarbon polymer elastomer can be easily obtained, a monomer having a functional group into which an anion exchange group can be introduced or a unit having an anion exchange group can be obtained. Multiple types of monomers that form a hard segment and a soft segment as a polymer (usually a polymer block of an aromatic vinyl compound forms a hard segment and a polymer block of a conjugated diene compound forms a soft segment) In particular, when a monomer having a functional group into which an anion exchange group can be introduced is used after performing block copolymerization with a so-called thermoplastic elastomer, a method of introducing an anion exchange group is particularly preferable. It is.

  In this case, a combination of monomers to be copolymerized may be determined according to a general method for synthesizing a thermoplastic elastomer, and polymerization may be performed according to a conventional method. Specific examples of the thermoplastic elastomer into which an anion exchange group can be introduced include polystyrene-polybutadiene-polystyrene triblock copolymer (SBS), polystyrene-polyisoprene-polystyrene triblock copolymer (SIS), and SBS, SIS. Polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer (SEBS) and polystyrene-poly (ethylene-propylene) -polystyrene triblock (SEPS) copolymer, each of which is hydrogenated with an anion exchange group. Examples of the thermoplastic elastomer having polystyrene-polyvinylpyridine-polybutadiene triblock copolymer, polystyrene-polyvinylpyridine-polyisoprene triblock copolymer, etc. include such a copolymer. It may be employed a combination of monomers that gives. In the thermoplastic elastomer into which anion exchange groups can be introduced, polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer (SEBS), polystyrene from the viewpoint of stability in the step of introducing ion exchange groups. -Poly (ethylene-propylene) -polystyrene triblock copolymer (SEPS) is preferred.

  Further, the monomer composition at the time of polymerization is not particularly limited, but the content of the aromatic vinyl compound unit in the block copolymer to be a hard segment in the thermoplastic elastomer is 5 to 5 in terms of electrical characteristics and mechanical characteristics. Since 70 mass%, especially 10-50 mass% is preferable, it is suitable to make it the composition which becomes such a content rate.

  The copolymerization method of the aromatic vinyl compound and the conjugated diene compound is not particularly limited, and a known method such as anion polymerization, cation polymerization, coordination polymerization, radical polymerization, etc. is adopted, but the block structure is easily controlled. For the reason, living anionic polymerization is particularly preferably employed. The form of block copolymerization may be any of diblock copolymerization, triblock copolymerization, radial block copolymerization, and multiblock copolymerization, but the end blocks aggregate together to form a domain. Triblock copolymerization is preferred because it is easy. Furthermore, since it is easy to mold and process like a thermoplastic resin, polymerization is performed under polymerization conditions such that the average molecular weight of each block copolymer is 10,000 to 300,000, particularly 20,000 to 150,000. Is preferred. Furthermore, when hydrogenating the conjugated diene portion of the block copolymer, it is preferable to add hydrogen so that the hydrogenation rate is 95% or more. The introduction of an anion exchange group when using a monomer having a functional group into which an anion exchange group can be introduced can be carried out in the same manner as described above.

The electrolyte material for a catalyst electrode layer of the present invention is a disk electrode of a rotating electrode method using an aqueous solution which is an acidic aqueous solution to which HClO ₄ , H ₂ SO ₄ or the like is added or an alkaline aqueous solution to which KOH or NaOH is added as an electrolytic solution. It is used for forming a catalyst electrode layer on the surface.

  The anion exchange resin used for the electrolyte material for the catalyst electrode layer of the present invention is insoluble in water and has an anion exchange capacity of 0.1 to 0.7 mmol / g-dry resin. The reactants are supplied smoothly. Therefore, when the catalyst electrode layer electrolyte material of the present invention is used in contact with a water-containing liquid, the catalyst activity ability inherent to the catalyst can be sufficiently exhibited.

  The electrolyte material for a catalyst electrode layer of the present invention is used by forming a catalyst electrode layer on the surface of a disk electrode of the rotating electrode method as shown in FIG. The basic structure of the rotating electrode method apparatus is shown in FIG. 2, and the sectional structure of the rotating ring disk electrode is shown in FIG. The cross-sectional structure of the rotating ring disk electrode includes a disk electrode 18 and a ring electrode 19 on which the catalyst electrode layer 12 is formed. The rotating ring disk electrode is placed in an electrolytic cell 14 containing an electrolytic solution 13 and subjected to electrochemical evaluation while being rotated. When the reactant is a gas, it is supplied while bubbling from the fuel circulation hole 15, and when the reactant is a liquid, it is added directly to the electrolyte. Platinum can be used for the counter electrode 16, and a silver / silver chloride electrode, a reversible hydrogen electrode, a saturated calomel electrode, or the like can be used for the reference electrode 17.

As a disk electrode substrate of such a rotating ring disk electrode, a glassy carbon disk or gold disk that is inert to the electrode reaction and chemically stable, and a ring electrode is highly active to facilitate detection of a reaction intermediate. Platinum or the like is used. On the substrate of the disk electrode, a catalyst electrode layer 12 made of a composition using an electrode catalyst, a conductive material, an ion exchange resin, and the like as a binder is formed. In addition, an acidic electrolyte such as an aqueous solution to which HClO ₄ or H ₂ SO ₄ is added is used for the evaluation of the activity of the cation exchange membrane fuel cell electrode catalyst. For the evaluation of activity, it is usual to use an alkaline electrolyte such as KOH or NaOH aqueous solution.

  In evaluating the catalytic activity of an electrode catalyst for a fuel cell, a rotating electrode method using a rotating ring disk electrode that can accurately control the supply rate of a reactant to the electrode catalyst is used. In this method, a reactant is supplied to an electrode by rotating the electrode in an electrolyte solution in which a compound used as a fuel for a fuel cell or a compound used as an oxidant, which is a reactant for a fuel cell, is dissolved, This is a method for obtaining a current value derived from catalytic activity when the potential is changed. The disk substrate of the rotating ring disk electrode is not particularly limited, but a glassy carbon disk that is inert to the electrode reaction and chemically stable is often used.

  In the present invention, an alkaline electrolyte to which KOH or NaOH is added is used, but there is no particular limitation. Usually, the alkali concentration is preferably in the range of 0.1 mol / l to 8 mol / l.

  The electrolyte material for the catalyst electrode layer used for evaluating the catalytic activity of the electrode catalyst for fuel cells has a total mass of the electrode catalyst and the conductive material of 10 to 1500 parts by mass, preferably 100 parts by mass of the anion exchange resin. The amount is preferably 50 to 800 parts by mass, particularly preferably 100 to 600 parts by mass. If the mass of the electrode catalyst and the conductive material is too small relative to the mass of the anion exchange resin, the anion exchange resin may completely cover the electrode catalyst, which may hinder the supply of reactants. In addition, if the mass of the electrode catalyst and the conductive material is excessive with respect to the mass of the anion exchange resin, the anion exchange resin cannot serve as a binder and the catalyst electrode layer may be fragile.

  The amount of the electrode catalyst is preferably from 0.1 to 1000 parts by weight, preferably from 0.5 to 500 parts by weight, particularly preferably from 1 to 200 parts by weight, based on 100 parts by weight of the conductive material.

  In the step of preparing the electrolyte material for the catalyst electrode layer, it is preferable that the anion exchange resin, the electrode catalyst, and the conductive material are uniformly dispersed. At this time, the dispersion method is not particularly limited. Usually, the electrolyte material for catalyst electrode layers stably dispersed can be obtained by ultrasonic dispersion treatment.

  Application of the electrolyte material for the catalyst electrode layer to the substrate surface of the disk electrode is generally performed by a method in which a predetermined amount of the electrolyte material for the catalyst electrode layer is applied to the horizontally stationary substrate surface or the substrate is rotated to cover the substrate surface. You can do it.

  Next, it is desirable to dry the catalyst electrode layer formed as described above in order to evaporate the organic solvent and moisture contained in the catalyst electrode layer electrolyte material. The drying conditions are not particularly limited. For example, drying is preferably performed at room temperature in air for one day or more, or is preferably dried at 50 ° C. for about 30 minutes, more preferably about 80 ° C. for about 30 minutes. By completely evaporating the solvent, it is possible to obtain a catalyst electrode layer that hardly swells when in contact with the water-containing liquid.

  By the way, as a formation method of a catalyst electrode layer, the following formation methods can be employ | adopted besides the method of apply | coating the electrolyte material for catalyst electrode layers of this invention. That is, in this method, an electrode catalyst and a conductive material are dispersed in a suitable solvent, applied and dried on an electrode substrate, and then a solution of an anion exchange resin is applied thereon to form a catalyst electrode layer. At this time, the solvent used for dispersing the electrode catalyst and the conductive material is not particularly limited.

  As described above, the catalyst electrode layer formed using the electrolyte material for the catalyst electrode layer of the present invention is used in contact with a water-containing liquid such as an electrolyte, and the electrode potential is scanned in that state. It is suitably employed in a method for measuring a flowing current value. Rotating electrode methods such as rotating disk electrode method and rotating ring disk electrode method, as well as methods for evaluating electrochemical catalytic activity of other electrode catalysts, such as cyclic voltammetry, pulse voltammetry, chronopotentiometry , Chronoamperometry, coulometry, AC impedance method and the like can be suitably employed. Moreover, as an application, it is useful not only as a fuel cell but also as an electrochemical device that operates in a state where the catalyst electrode layer is in contact with the water-containing liquid, for example, as an electrode for various batteries and electrolytic cells.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated, this invention is not limited at all by these examples. In addition, the characteristic of the electrolyte material for catalyst electrode layers shown in an Example shows the value measured with the following method.

(1) Anion exchange capacity First, a solution in which an anion exchange resin is dissolved in 1-propanol so as to be 5% by mass is dropped on a petri dish and dried at room temperature to form a film having a width of 2.0 cm and a length. A 4.0 cm, 50 μm-thick strip cut out is immersed in a 1 mol / l HCl aqueous solution for 10 hours or longer to form a chloride ion type, and then replaced with a 1 mol / l NaNO ₃ aqueous solution to a nitrate ion type. The released chlorine ions were quantified with a potentiometric titrator (the quantified value at this time is Amol). Next, the quantified anion exchange resin membrane was immersed in a 1 mol / l NaCl aqueous solution for 4 hours or longer to form a chloride ion type, washed with water, dried under reduced pressure at 60 ° C. for 5 hours, and its mass was measured (at this time) The mass of Wg is Wg. Based on the measured value, the anion exchange capacity (mmol / g-dry resin) was determined by the following formula.

    Anion exchange capacity = A × 1000 / W

(2) Ionic conductivity An anion exchange resin was dried to form a membrane, and left in an air atmosphere for several days to prepare a sample of an anion exchange resin membrane in which the counter ion of the ion exchange group was a carbonate ion type. Next, the membrane was immersed in ion-exchanged water for 24 hours or longer to make it completely wet, and then cut into strips having a width of 2.0 cm and a length of 4.0 cm. Using an insulating substrate in which five platinum wires having a line width of 0.3 mm were arranged parallel to each other at intervals of 5 mm, the wet strip-shaped film having a width of 2.0 cm was pressed against the platinum wire. The AC impedance was measured when an alternating current of 1 kHz was applied between the platinum wires while the membrane was always kept wet in a constant temperature and humidity chamber at 40 ° C.

  Each alternating current impedance was measured when the distance between the platinum wires was changed by 5 mm between 0.5 and 2.0 cm. By calculating the specific resistance of the anion exchange resin membrane from the gradient (impedance between terminals) when the impedance was plotted against the distance between the platinum wires, the influence of the contact resistance generated between the platinum wires and the membrane was excluded. A good linear relationship was obtained between the distance between the platinum wires and the measured impedance. The ion conductivity of the anion exchange resin membrane was calculated from the gradient between terminals and the film thickness by the following formula. In this measurement, the film thickness of the anion exchange resin membrane was measured with a film thickness meter by sandwiching an anion exchange resin membrane wetted with pure water between glass plates.

σ = 1 / {S × L × W × 1000)}
σ: ion conductivity [mS / cm]
S: Gradient between terminals [Ω / cm]
L: Film thickness [cm]
W: width of anion exchange resin membrane [cm]

(3) Swelling rate Six anion-exchange resin-dried membranes were cut out in a size of 2.0 cm × 1.0 cm, and a dry membrane was obtained from an average value obtained by measuring the film thickness of each sample at five points. Volume (V _dry cm ³ ) was determined. The film thickness was measured with a film thickness meter by sandwiching an anion exchange resin film wetted with pure water between glass plates. After immersing this membrane in ion exchange water at room temperature for 2 hours, the size of the membrane was measured again to determine the volume of the wet membrane (V _wet cm ³ ), and the swelling rate at room temperature was determined from the following formula. In addition, when measuring the size of the wet membrane, it was performed on a filter paper sufficiently containing ion-exchanged water in order to prevent the membrane from drying.

Swelling ratio = (V _wet −V _dry ) / V _dry × 100

(4) Solubility in water First, it was left at room temperature and immersed in water at 20 ° C. so as to be 5 mass% using a dried anion exchange resin. After centrifuging the liquid, the solid content concentration in the supernatant was measured to determine the solubility (mass%) of the anion exchange resin in water.

Examples 1-3
SEBS {polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer, mass average molecular weight 54,000}, or SEPS {polystyrene-poly (ethylene-propylene) -polystyrene tri, which is a thermoplastic elastomer shown in Table 1. The block copolymer, mass average molecular weight 74,000} 20 g was dissolved in 1000 ml of chloroform, 100 g of chloromethyl ethyl ether and 100 g of anhydrous tin chloride were added under ice cooling, and the mixture was reacted at 100 ° C. for 3 hours. Next, the reaction product was precipitated using 40 liters of methanol and then separated, and 23 g of a chloromethylated thermoplastic elastomer was obtained by vacuum drying. The obtained chloromethylated product was quaternized in a room temperature amination bath comprising 10 parts by mass of a 30% by mass trimethylamine aqueous solution, 5 parts by mass of water, and 5 parts by mass of acetone. By adjusting the immersion time in the amination bath, an anion exchange resin having an anion exchange capacity of 0.1 mmol / g to 0.7 mmol / g-dry resin was obtained. The obtained anion exchange resin was measured for anion exchange capacity, ion conductivity, swelling rate, and solubility in water, and the results are shown in Table 1.

  Using the quaternized anion exchange resin, electrode catalyst, and conductive material, an electrolyte material for a catalyst electrode layer was prepared, and the catalytic activity for an oxygen reduction reaction was evaluated by a linear sweep voltammetry method. Here, linear sweep voltammetry is a method in which the electrode potential is linearly changed with respect to time, and the current response at that time is measured. By slowing down the scanning speed, the starting potential of the oxygen reduction reaction, the diffusion limit current, and the like can be observed. The electrochemical evaluation apparatus used was BAS Electrochemical Analyzer Model 700C, and the rotating electrode apparatus used was ROTATING RING DISC ELECTRODE RRDE-1 manufactured by Nisatsu Keiki Co., Ltd.

First, using a rotating ring disk electrode made of a glassy carbon rotating ring disk electrode (disk electrode diameter 6 mm, area 0.283 cm ² ) with a platinum ring electrode, pretreatment was performed by the following method. The disk electrode was polished with a lapping film sheet having a particle size of 1 μm, and then polished with a lapping film of 0.5 μm and finally 0.3 μm. Next, a degreasing process by ultrasonic cleaning was performed in methanol, and finally the electrode was pretreated by performing ultrasonic cleaning in ultrapure water.

Formation of the catalyst electrode layer was performed as follows. First, 20 mg of platinum-supported carbon (TEC10E50E, manufactured by Tanaka Kikinzoku Co., Ltd.) having a platinum content of 45% by mass as an electrode catalyst and a conductive material is placed in 2 ml of a 1-propanol solution having an anion exchange resin concentration of 1% by mass. The electrolyte material for catalyst electrode layers was prepared by carrying out a dispersion treatment for 30 minutes using a bath. 5 μl of the catalyst electrode layer electrolyte material was applied on a glassy carbon disk electrode, then rotated at 100 rpm, and dried at room temperature for 30 minutes. Next, the catalyst electrode layer was formed by drying at 80 ° C. for 30 minutes. The area of the catalyst electrode layer is 0.283 cm ² and the thickness is 1.5 μm.

  Using the rotating ring disk electrode on which the catalyst electrode layer produced above was formed, the catalytic activity for the oxygen reduction reaction was evaluated. The electrolyte used for the measurement was a saturated concentration obtained by bubbling a 0.1 mol / l KOH aqueous solution at 70 ° C. with pure oxygen as an oxidant as a reactant of the fuel cell. A silver / silver chloride electrode was used as a reference electrode. Linear sweep voltammetry was measured while rotating the ring disk electrode at 400 rpm. The sweep conditions were such that the potential was 0.2 V to -0.8 V (relative to the silver / silver chloride electrode) and the sweep rate was 0.005 V / s. Table 2 shows the current value at the potential of −0.1 V (relative to the silver / silver chloride electrode), which is the peak value of the oxidation-reduction current curve.

  The starting potential of the oxygen reduction reaction (the potential when the current value was 10 μA was taken as the starting potential) was 0.1 V in all Examples and Comparative Examples. Further, when the 4-electron reaction rate was measured from the current value when the disk electrode detected by the ring electrode was −0.1 V (relative to the silver / silver chloride electrode), all the examples and the comparative examples were almost 100. %Met.

Comparative Examples 1-4
In the production of the anion exchange resin of Example 1, the immersion time of the amination bath during quaternization was adjusted, and an anion exchange resin having an anion exchange capacity of 0 mmol / g and an anion exchange resin exceeding 0.7 mmol / g Then, an electrolyte material for a catalyst electrode layer was prepared in the same manner as in Example 1, a catalyst electrode layer was formed, and the catalytic activity for the oxygen reduction reaction was evaluated. Table 1 shows the anion exchange capacity, ion conductivity, swelling rate, and water solubility of the obtained anion exchange resin. Table 2 shows the potential when the potential is −0.1 V (relative to the silver / silver chloride electrode). Current values are shown.

Comparative Example 5
An electrolyte material for a catalyst electrode layer was prepared in the same manner as in Example 1 using Nafion (product number 274704), which is a cation exchange resin, instead of the anion exchange resin used in Example 1, and a catalyst electrode layer was formed. The catalytic activity for the reduction reaction was evaluated. Table 1 shows the cation exchange capacity, ion conductivity, swelling rate, and solubility in water of Nafion, and Table 2 shows the current value at a potential of -0.1 V (relative to the silver / silver chloride electrode). . The conduction ion of Nafion is H ⁺ or K ⁺ .

As described above, a catalyst electrode layer using the electrolyte material for a catalyst electrode layer of the present invention using a water-insoluble anion exchange resin having an anion exchange capacity in the range of 0.1 to 0.7 mmol / g-dry resin. Had a high current value and high activity for the oxygen reduction reaction. This is because the conductive ions in the binder forming the catalyst electrode layer are hydroxide ions (OH ⁻ ), and there is little swelling of the ion exchange resin in the electrolyte, and does not inhibit the diffusion of the reactants. This is because the catalyst activity ability inherent to the catalyst can be sufficiently reflected.

  On the other hand, when an anion exchange resin having an anion exchange capacity lower than 0.1 mmol / g-dry resin or higher than 0.7 mmol / g-dry resin is used, the current value of oxygen reduction is relatively It turned out to be low. When the anion exchange capacity is too high, the ionic conductivity is good, but since the swelling rate is high, the diffusion of the reactant (oxygen) into the catalyst electrode layer is hindered, resulting in a low current value. It is considered a thing. Further, when the anion exchange capacity is zero, although the swelling rate is low, the ionic conductivity is also low, so that the flow of ions from the electrolytic solution to the electrode surface is deteriorated, and it is considered that the current does not flow easily.

  In addition, when Nafion which is a cation exchange resin shown in Comparative Example 5 was used, since the electrolytic solution was alkaline, the ionic conduction between the electrolytic solution and the catalyst electrode layer did not go smoothly, so the current value was low. It is thought that.

Example 4 and Comparative Example 6
Using a rotating ring disk electrode on which a catalyst electrode layer produced in the same manner as in Example 2 and Comparative Example 2 was formed, the catalytic activity for methanol oxidation reaction was evaluated. The electrolyte used for the measurement is a 1 mol / l KOH aqueous solution to which methanol as a fuel is added as a reactant of the fuel cell so as to be 1 mol / l. Further, linear sweep voltammetry was measured at a temperature of the electrolyte of 25 ° C. and a rotation speed of the ring disk electrode of 3000 rpm. The sweep conditions were such that the potential was 0.2 V to -0.8 V (relative to the silver / silver chloride electrode) and the sweep rate was 0.005 V / s. Table 3 shows the current value at a potential of −0.2 V (relative to the silver / silver chloride electrode) which is the peak value of the oxidation current curve.

As can be seen from the above results, it was found that the electrolyte material for the catalyst electrode layer of the present invention has a high oxidation current value of fuel (methanol). This is because the conductive ions in the binder forming the catalyst electrode layer are hydroxide ions (OH ⁻ ), and there is little swelling of the ion exchange resin in the electrolyte, and does not inhibit the diffusion of the reactants. This is because the catalyst activity ability inherent to the catalyst can be sufficiently reflected.

1; battery partition wall 2; fuel gas flow hole 3; oxidant gas flow hole 4; fuel chamber side catalyst electrode layer 5; oxidant chamber side catalyst electrode layer 6; fuel chamber side gas diffusion electrode (current collector)
7; Oxidant chamber side gas diffusion electrode (current collector)
8; Solid polymer electrolyte membrane 9; Fuel chamber 10; Oxidant chamber 11; Rotating electrode 12; Catalyst electrode layer 13; Electrolyte 14; Electrolytic layer 15; Fuel flow hole 16; Counter electrode 17; 19: Rotating ring electrode

Claims (4)

Using an electrolytic solution in which a reactant of a fuel cell is dissolved, the electrode electrode, a conductive material, and an anion exchange capacity of 0.1 to 0.7 mmol / g-dry resin are insoluble in water on the surface of a rotating electrode method disk electrode Forming a catalyst electrode layer formed of an electrolyte material for a catalyst electrode layer used in contact with a water-containing liquid, comprising a composition containing an anion exchange resin, and detecting a current by changing the potential of the electrode; A method for evaluating the catalytic activity of an electrode catalyst for a fuel cell, comprising evaluating the catalytic activity of a fuel electrode reaction or an oxygen electrode reaction in a fuel cell of an electrode catalyst contained in an electrolyte material for a catalyst electrode layer. Electrocatalyst, conductive material, and anion exchange capacity for 0.1 to 0.7 mmol / g for catalyst electrode layer on disk electrode surface of rotating electrode method, used for catalyst activity evaluation method of electrode catalyst for fuel cell An electrolyte material for a catalyst electrode layer used in contact with a water-containing liquid, comprising a composition containing a water-insoluble anion exchange resin of a dry resin. The method for evaluating the catalytic activity of a fuel cell electrode catalyst according to claim 1, wherein the water-insoluble anion exchange resin has an anion exchange capacity of 0.2 to 0.6 mmol / g-dry resin. The electrolyte material for a catalyst electrode layer according to claim 2, wherein the water-insoluble anion exchange resin has an anion exchange capacity of 0.2 to 0.6 mmol / g-dry resin.

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