Catalyst layer for fuel cell electrode, and fuel cell

Abstract

A catalyst layer for a fuel cell electrode includes a metal carrying catalyst containing a carbon carrier and a metal catalyst carried on the carbon carrier, and an ionomer, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores of the carbon carrier is 4.5 ml/g to 9.3 ml/g, and a weight ratio of the carbon carrier to the ionomer is 1:0.50 to 1:0.85. A fuel cell includes the catalyst layer for a fuel cell electrode.

Claims

1. A catalyst layer for a fuel cell electrode, comprising: a metal carrying catalyst containing a carbon carrier and a metal catalyst carried on the carbon carrier, and an ionomer, wherein the metal catalyst comprises one or more of platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum or platinum cobalt, the carbon carrier comprises one or more of acetylene black or thermal black, the ionomer comprises one or more of a fluorinated resin electrolyte, a sulfonated plastic electrolyte, or a sulfoalkylated plastic electrolyte, a volume of micropores having a diameter of 5 nm to 40 nm in micropores of the carbon carrier is 4.5 ml/g to 9.3 ml/g, a weight ratio of the carbon carrier to the ionomer is 1:0.50 to 1:0.85, and the micropores having the diameter of 5 nm to 40 nm have inner surfaces and outer surfaces of the micropores are coated with the ionomer.

2. A fuel cell comprising: a membrane electrode assembly including a solid polymer electrolyte, an air electrode and a fuel electrode wherein the air electrode and the fuel electrode are bonded to both surfaces of the solid polymer electrolyte, respectively, wherein at least one of the air electrode and the fuel electrode comprises the catalyst layer for a fuel cell electrode according to claim 1.

3. The catalyst layer for the fuel cell electrode according to claim 1, wherein the volume of micropores having a diameter of 5 nm to 40 nm in micropores of the carbon carrier is 7.0 ml/g to 9.3 ml/g.

4. The catalyst layer for the fuel cell electrode according to claim 1, wherein the volume of micropores having a diameter of 5 nm to 40 nm in micropores of the carbon carrier is 5.0 ml/g to 8.0 ml/g.

5. The catalyst layer for the fuel cell electrode according to claim 1, wherein the ionomer comprises one or more clusters having a length of 5 nm to 40 nm.

6. The catalyst layer for the fuel cell electrode according to claim 1, wherein the metal catalyst comprises platinum cobalt.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A-1C are diagrams schematically illustrating the relationship between a volume of micropores having a diameter of 5 nm to 40 nm in micropores of a carbon carrier and coating of an ionomer to micropores; and

(2) FIG. 2 is a diagram illustrating a voltage against a volume of micropores having a diameter of 5 nm to 40 nm in micropores of a carbon carrier in MEGAs in Comparative Examples 1 and 2 and Examples 1 to 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) Preferred embodiment will now be described.

(4) Herein, the features of the exemplary embodiments will be appropriately described with reference to the drawings. In the drawings, dimensions and shapes of parts are exaggerated for clarification, and actual dimensions and shapes are not exactly illustrated. Accordingly, the dimensions and shapes of parts illustrated in these diagrams are not construed to limit the technical scope of the exemplary embodiments. The catalyst layer for a fuel cell electrode and the fuel cell described herein are not limited to the following embodiment, and can be implemented in a variety of forms changed or modified by persons skilled in the art without departing from the gist of the exemplary embodiments.

(5) The catalyst layer for a fuel cell electrode described herein (also simply referred to as a “catalyst layer” in this specification (including WHAT IS CLAIMED IS: and the drawings, the same is applied below)) comprises a metal carrying catalyst including a carbon carrier and a metal catalyst, and an ionomer.

(6) In the carbon carrier of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein, a volume of micropores having a diameter of 5 nm to 40 nm in micropores of the carbon carrier is 4.5 ml/g to 9.3 ml/g, preferably 5.0 ml/g to 8.0 ml/g.

(7) In the micropores of the carbon carrier of the metal carrying catalyst of the catalyst layer for a fuel cell electrode described herein, the volume of the micropores having a diameter of 5 nm to 40 nm is measured by a BET multi-point method through nitrogen adsorption at a liquid nitrogen temperature using a pre-treated carbon carrier. The pre-treatment to measure the volume of the micropores in the carbon carrier is performed under a condition allowing sufficient removal of volatile substances such as the moisture content in the carbon carrier. For example, the pre-treatment is performed as follows: The carbon carrier is placed in vacuum, and is kept at a temperature of usually 100° C. to 125° C., preferably 110° C. to 120° C. for usually 5 hours to 8 hours, preferably 6 hours to 9 hours.

(8) In the catalyst layer for a fuel cell electrode described herein, a weight ratio of the carbon carrier to the ionomer (carbon carrier:ionomer) is 1:0.50 to 1:0.85, preferably 1:0.55 to 1:0.75. In calculation of the weight ratio of the carbon carrier to the ionomer herein, the weight of the carbon carrier and that of the ionomer are each a weight of the solid content after removal of volatile substances therefrom, for example, a weight after a heat treatment at usually 100° C. to 150° C., preferably 110° C. to 130° C. for usually 5 hours to 8 hours, preferably 6 hours to 9 hours.

(9) FIGS. 1A-1C schematically illustrate the relationship between a volume of micropores having a diameter of 5 nm to 40 nm in micropores of a carbon carrier and coating of an ionomer to micropores.

(10) As illustrated in FIG. 1A, if the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier is less than 4.5 ml/g and even if the weight ratio of the carbon carrier to the ionomer is within the optimal range, only the outer surfaces of the micropores of the metal carrying catalyst are coated with the ionomer. As a result, the catalyst metal in the inner surfaces of the micropores is slightly coated with the ionomer, causing a reduced effective usage rate of the catalyst metal

(11) In contrast, as illustrated in FIG. 1C, if the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier is more than 9.3 ml/g and even if the weight ratio of the carbon carrier to the ionomer is within the optimal range, only the inner surfaces of the micropores of the metal carrying catalyst are coated with the ionomer. As a result, a large amount of the ionomer is buried in the micropores, causing disconnection of the ionic conduction path to the surface of the carbon carrier and thus a reduced effective usage rate of the catalyst metal.

(12) Accordingly, as illustrated in FIG. 1B, if the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier is 4.5 ml/g to 9.3 ml/g and the weight ratio of the carbon carrier to the ionomer is within the range specified above, the inner surfaces and the outer surfaces of the micropores of the metal carrying catalyst can be coated with the ionomer, achieving the compatibility between the network of ionomers and the contact of the ionomer with the metal catalyst and an enhanced effective usage rate of the catalyst metal.

(13) Any known carbon carrier in the technical field can be used as the carbon carrier of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein except that the volume of the micropores having a specific size is within the range specified above. Examples of the carbon carrier include, but should not be limited to, acetylene black, and thermal black.

(14) For example, the carbon carrier of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein is preferably prepared with YS carbon manufactured by SN2A. For example, YS carbon can be subjected to a heat treatment for control of the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier to within the above range. For example, YS carbon is fired in the air at a firing temperature of usually 515° C. to 545° C., preferably 520° C. to 540° C. for usually 4 hours to 6 hours, preferably 4.5 hours to 5.5 hours.

(15) As properties of the carbon carrier of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein, for example, the specific surface area measured by the BET method is, but should not be limited to, usually 400 m.sup.2/g to 500 m.sup.2/g, preferably 430 m.sup.2/g to 460 m.sup.2/g.

(16) As properties of the carbon carrier of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein, for example, the particle diameter measured by SEM is, but should not be limited to, usually 10 μm to 50 μm, preferably 20 μm to 40 μm.

(17) As properties of the carbon carrier of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein, for example, the crystallinity measured by Raman spectroscopy is, but should not be limited to, usually 1.0 to 1.5, preferably 1.2 to 1.4 in the ratio D/G.

(18) The metal catalyst in the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein is carried on the carbon carrier. The metal catalyst is carried on the surface of the carbon carrier or the surfaces of the micropores of the carbon carrier.

(19) Any metal catalyst that exhibits a catalytic action in the following reactions at the electrodes of an MEA or an MEGA:
air electrode (cathode): O.sub.2+4H.sup.++4e.sup.−.fwdarw.2H.sub.2O
fuel electrode (anode): 2H.sub.2.fwdarw.4H.sup.++4e.sup.−
can be used, and any known metal catalyst in the technical field can be used. Examples of the metal catalyst include, but should not be limited to, metals such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum; or alloys thereof such as platinum cobalt.

(20) Preferred is platinum cobalt as a metal catalyst of the metal carrying catalyst in the catalyst layer for a fuel cell electrode described herein.

(21) The metal catalyst can be used in any amount, and the amount of the metal catalyst is usually 10% by weight to 50% by weight, preferably 30% by weight to 40% by weight relative to the total weight of the metal carrying catalyst.

(22) The catalyst layer for a fuel cell electrode described herein can contain the metal carrying catalyst in any amount as long as the weight ratio of the carbon carrier to the ionomer is within the range specified above. The amount of the metal carrying catalyst is usually 60% by weight to 80% by weight, preferably 70% by weight to 80% by weight relative to the total weight of the catalyst layer for a fuel cell electrode.

(23) In the catalyst layer for a fuel cell electrode described herein, the ionomer is also referred to as a cation exchange resin, and is present as clusters formed of ionomer molecules. Any known ionomer in the technical field can be used. Examples of usable ionomers include, but should not be limited to, fluorinated resin electrolytes such as perfluorosulfonic acid resin materials; sulfonated plastic electrolytes such as sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyether ethersulfone, sulfonated polysulfone, sulfonated polysulfide, and sulfonated polyphenylene; and sulfoalkylated plastic electrolytes such as sulfoalkylated polyether ether ketone, sulfoalkylated polyethersulfone, sulfoalkylated polyether ethersulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, and sulfoalkylated polyphenylene.

(24) A preferred ionomer in the catalyst layer for a fuel cell electrode described herein is a perfluorosulfonic acid resin material having a hydrophobic carbon-fluorine Teflon skeleton and a sulfonate group, such as Nafion, which is a fluorinated resin electrolyte.

(25) As properties of the ionomer in the catalyst layer for a fuel cell electrode described herein, for example, the cation exchange amount measured by the titration method is usually 1.0×10.sup.−3 mol/g to 1.5×10.sup.−3 mol/g, preferably 1.1×10.sup.−3 mol/g to 1.2×10.sup.−3 mol/g.

(26) The catalyst layer for a fuel cell electrode described herein can contain the ionomer in any amount as long as the weight ratio of the carbon carrier to the ionomer is within the range specified above. The amount of the ionomer is usually 20% by weight to 40% by weight, preferably 20% by weight to 30% by weight relative to the total weight of the catalyst layer for a fuel cell electrode.

(27) The catalyst layer for a fuel cell electrode described herein used as an air electrode and/or a fuel electrode of an MEA or an MEGA in a variety of electrochemical devices such as solid polymer electrolyte fuel cells can improve the cell performance of the devices.

(28) Furthermore, exemplary embodiments relate to a fuel cell comprising a membrane electrode assembly (“fuel electrode-solid polymer electrolyte membrane-air electrode”) (MEA) including a solid polymer electrolyte, an air electrode and a fuel electrode wherein the air electrode and the fuel electrode are bonded to both surfaces of the solid polymer electrolyte, respectively, wherein at least one of the air electrode and the fuel electrode comprises the catalyst layer for a fuel cell electrode described herein.

(29) Any known solid polymer electrolyte in the technical field can be used as the solid polymer electrolyte in the fuel cell according to the exemplary embodiments. For example, Nafion (manufactured by E. I. du Pont de Nemours and Company) can be used, but should not be limited thereto.

(30) The fuel cell according to the exemplary embodiments can include the catalyst layer for a fuel cell electrode described herein as one or both of the air electrode and the fuel electrode.

(31) The fuel cell according to the exemplary embodiments has optimized output performance through optimization of the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier.

(32) The catalyst layer for a fuel cell electrode described herein can be prepared by any known method in the technical field except that in the micropores of the carbon carrier of the metal carrying catalyst, the volume of the micropore having a diameter of 5 nm to 40 nm and the weight ratio of the carbon carrier to the ionomer are as specified above. For example, the catalyst layer for a fuel cell electrode described herein can be prepared as follows.

(33) (i) Step of carrying a metal catalyst on a carbon carrier to prepare a metal carrying catalyst

(34) A carbon carrier having the above-specified volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier and an oxidized metal catalyst precursor are suspended in a solvent, such as pure water, at usually 15° C. to 30° C., preferably 20° C. to 25° C. to prepare a suspension. The metal catalyst precursor in the suspension is reduced into a metal catalyst by a reducing agent, such as ethanol or sodium borohydride, at usually 55° C. to 95° C., preferably 60° C. to 90° C. to prepare a dispersion solution. The dispersion solution is filtered, and the obtained cake is dried at usually 80° C. to 100° C., preferably 85° C. to 95° C. for usually 13 hours to 17 hours, preferably 14 hours to 16 hours to yield a powder. The powder is fired under an inert atmosphere, such as under a nitrogen atmosphere, at usually 600° C. to 1000° C., preferably 700° C. to 900° C. for usually 1 hour to 6 hours, preferably 1 hour to 3 hours to yield a metal carrying catalyst. Here, the firing is performed to enhance the durability of the metal carrying catalyst in use at high temperature. The firing is performed within the range not changing the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier.

(35) (ii) Step of mixing the metal carrying catalyst prepared in (i) with an ionomer to prepare a catalyst ink

(36) The metal carrying catalyst prepared in (i) is mixed with an ionomer such that the weight ratio of the carbon carrier to the ionomer is within the range specified above. The mixture is suspended in a solvent, such as pure water, at usually 15° C. to 30° C., preferably 20° C. to 25° C. to prepare a suspension. An organic solvent, such as ethanol, is added to the suspension. The suspension is further dispersed by a known dispersion process, for example, the suspension is further ultrasonically dispersed, at usually 5° C. to 15° C., preferably 5° C. to 10° C. for usually 30 minutes to 70 minutes, preferably 50 minutes to 60 minutes to prepare a catalyst ink.

(37) (iii) Step of forming a catalyst layer with the catalyst ink prepared in (ii)

(38) The catalyst ink prepared in (ii) is applied onto a releasable substrate, such as a Teflon sheet, at usually 15° C. to 30° C., preferably 20° C. to 25° C. by a known spraying, adhering, or applying process, such as a process using gravity, atomizing force, or electrostatic force, such as an applicator, to form a catalyst layer precursor. The catalyst layer precursor on the substrate is dried by a known drying process, such as a process using an air dryer at usually 60° C. to 90° C., preferably 75° C. to 85° C. for usually 1 minute to 10 minutes, preferably 4 minutes to 6 minutes to remove volatile substances such as a solvent. The catalyst layer is thereby formed, and the catalyst layer is peeled from the substrate.

(39) Here, the catalyst ink is sprayed, adhered, or applied onto the substrate, and then is dried and peeled to obtain the catalyst layer. Alternatively, the catalyst ink can be directly sprayed, adhered, or applied onto the surface of the solid polymer electrolyte membrane, and then dried to bond the catalyst layer to the solid polymer electrolyte membrane.

(40) In the steps (i) to (iii) above, the materials can be added in any order and/or by any process.

(41) Furthermore, the fuel cell according to the exemplary embodiments can be produced with the catalyst layer for a fuel cell electrode described herein by any known method in the technical field. For example, the fuel cell according to the exemplary embodiments can be prepared as follows.

(42) (iv) Step of combining the catalyst layer formed in (iii) with a solid polymer electrolyte membrane and a gas diffusion layer to produce an MEGA

(43) The obtained catalyst layer is used as an air electrode and/or a fuel electrode. The air electrode is disposed on one surface of the solid polymer electrolyte membrane, and the fuel electrode is disposed on the other surface of the solid polymer electrolyte membrane to produce a layer assembly. Here, the air electrode and the fuel electrode are prepared so as to match the catalyst layer to each electrode by varying the metal catalyst to be used. Furthermore, gas diffusion layers are disposed on the outer surfaces of the air electrode and the fuel electrode.

(44) Here, examples of the solid polymer electrolyte membrane include, but should not be limited to, GORE-SELECT (manufactured by W. L. Gore & Associates, Co., LTD.).

(45) Examples of the gas diffusion layer include, but should not be limited to, Torayca (manufactured by Toray Industries, Inc.).

(46) The layer assembly composed of gas diffusion layer-air electrode-solid polymer electrolyte membrane-fuel electrode-gas diffusion layer is press bonded with a hot press at a temperature of usually 100° C. to 150° C., preferably 130° C. to 140° C. and a pressure of usually 2 MPa to 5 MPa, preferably 3 MPa to 4 MPa for usually 60 seconds to 240 seconds, preferably 120 seconds to 180 seconds to yield an MEGA.

(47) (v) Step of manufacturing a fuel cell from the MEGA produced in (iv)

(48) The obtained MEGA is used as a single cell, and several cells are combined to manufacture a fuel cell.

(49) The fuel cell produced with the catalyst layer for a fuel cell electrode described herein has high cell performance.

EXAMPLES

(50) Some examples of the exemplary embodiments will now be described, but the exemplary embodiments are not construed to be limited to these examples.

(51) 1. Preparation of Sample

(52) 1-1. Raw Materials

(53) 1-1-1. Raw Materials for Carbon Carrier

(54) YS carbon manufactured by SN2A (specific surface area: about 110±10 m.sup.2/g, purity: 99.5% or more, resistance: 0.5 to 0.6 ohm (Ω)

(55) 1-1-2. Noble Metals

(56) platinum (Pt) (aqueous dinitroamine platinum solution (60% by weight or more of Pt))

(57) cobalt (Co) (aqueous cobalt nitrate solution (65% by weight or more of Co))

(58) 1-2. Production of a Membrane Electrode Gas Diffusion Layer Assembly (MEGA)

Comparative Example 1

(59) an MEGA produced with a catalyst layer for a fuel cell electrode containing a metal carrying catalyst containing a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 3.5 ml/g, and an ionomer

(60) (1) Preparation of a Noble Metal Carrying Catalyst PtCo/C (PtCo Carrying Carbon)

(61) (i) YS carbon manufactured by SN2A was heated in the air to 510° C. over 1.5 hours, and was fired while being kept at 510° C. for 5 hours to prepare a carbon carrier wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 3.5 ml/g. Here, the volume of the micropores having a diameter of 5 nm to 40 nm in the micropores of the carbon carrier was determined by a BET multi-point method with a TriStar 3000 analyzer manufactured by SHIMADZU Corporation after the carbon carrier was placed in vacuum, and was kept at a temperature of 150° C. for 2 hours or longer to be pre-treated.

(62) (ii) 0.1 N nitric acid (350 g) and the carbon carrier (20 g) prepared in (i) were placed into a 2000 ml beaker, and were mixed under stirring at 25° C. for one day to prepare a suspension.

(63) (iii) An aqueous dinitroamine platinum solution (60% by weight of Pt) containing platinum (5.72 g) as a platinum precursor such that 38% by weight of platinum relative to the total weight of the final product was carried was added to the suspension prepared in (ii) at 25° C., and the suspension was heated to 60 to 90° C. for 3 hours.

(64) (iv) The dispersion solution prepared in (iii) was filtered, and the obtained cake was dried at 80° C. for 15 hours to yield a powder.

(65) (v) The powder yielded in (iv) was fired under an argon atmosphere at 800° C. for 2 hours to yield a 38% by weight noble metal carrying catalyst Pt/C.

(66) (vi) Pure water was added in an amount 80 times the total weight of the 38% by weight noble metal carrying catalyst Pt/C yielded in (v) and the materials were mixed with stirring at 25° C. for 5 minutes to prepare a suspension.

(67) (vii) An aqueous cobalt nitrate solution as a cobalt precursor was added to the suspension prepared in (vi) at 25° C. such that the molar ratio of the platinum to the cobalt was 7:1. 1 to 6 mol equivalent of sodium borohydride relative to a cobalt atom in the cobalt nitrate was added to reduce the cobalt precursor into cobalt. A dispersion solution was thereby prepared.

(68) (viii) The dispersion solution prepared in (vii) was filtered out, and the obtained cake was dried at 80° C. for 15 hours to yield a powder.

(69) (ix) The powder yielded in (viii) was fired under an argon atmosphere at 800° C. for 2 hours to prepare a 40% by weight noble metal carrying catalyst PtCo/C.

(70) (2) Preparation of a Catalyst Ink

(71) (i) Ultrapure water (8 g), the noble metal carrying catalyst PtCo/C (1 g) prepared in (1), and ethanol (6 g) were placed into a 50 ml beaker, and were mixed with stirring at 25° C. for 5 minutes to prepare a suspension.

(72) (ii) An ionomer solution (10% by weight solution containing an ionomer (exchange amount: 1.11×10.sup.−3 mol/g) and a solvent) was added to the suspension prepared in (i) at 25° C. such that the weight ratio of the ionomer solid content to the carbon carrier (ionomer solid content/carbon carrier) was 0.75. The solution was ultrasonically dispersed at 5 to 10° C. for 55 minutes to prepare a mixed solution.

(73) (iii) The mixed solution prepared in (ii) was dispersed at 30 m/s for 15 minutes at room temperature with a thin film rotary high-speed mixer (FILMIX) manufactured by PRIMIX Corporation to prepare a homogeneous catalyst ink.

(74) (3) Preparation of a Catalyst Layer

(75) (i) The catalyst ink prepared in (2) was uniformly applied onto a Teflon sheet with a doctor blade such that the film thickness was 10 μm. A catalyst layer precursor was disposed on the Teflon sheet.

(76) (ii) The catalyst layer precursor disposed on the Teflon sheet prepared in (i) was dried at 80° C. for 5 minutes with an air dryer to form a catalyst layer on the Teflon sheet.

(77) (iii) The catalyst layer was peeled from the Teflon sheet to obtain the catalyst layer.

(78) (4) Production of an MEGA (Single Cell)

(79) (i) The catalyst layer formed in (3) was used as an air electrode (cathode), and the catalyst layer formed in (3), wherein the steps (vi) to (ix) in (1) were excluded, was used as a fuel electrode (anode). A solid polymer electrolyte membrane GORE-SELECT (manufactured by W. L. Gore & Associates, Co., LTD.) was disposed between the air electrode and the fuel electrode to produce a layer assembly (air electrode-solid polymer electrolyte membrane-fuel electrode). The layer assembly was press bonded with a hot press at 140° C. for 180 seconds to produce an MEA.

(80) (ii) A gas diffusion layer Torayca (manufactured by Toray Industries, Inc.) was disposed on both the electrodes of the MEA produced in (i) to produce a layer assembly (gas diffusion layer-MEA-gas diffusion layer). The layer assembly was press bonded with a hot press at 140° C. for 180 seconds to produce an MEGA.

Comparative Example 2

(81) an MEGA produced with a catalyst layer for a fuel cell electrode containing a metal carrying catalyst containing a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 12.8 ml/g, and an ionomer

(82) An MEGA was produced by the same method as that in Comparative Example 1 except that in (i) of (1) in Comparative Example 1, YS carbon manufactured by SN2A was heated in the air to 550° C. over 1.5 hours, and was fired while being kept at 550° C. for 5 hours to prepare a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 12.8 ml/g, and then the resulting carbon carrier was used.

Example 1

(83) an MEGA produced with a catalyst layer for a fuel cell electrode containing a metal carrying catalyst containing a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 4.5 ml/g, and an ionomer

(84) An MEGA was produced by the same method as that in Comparative Example 1 except that in (i) of (1) in Comparative Example 1, YS carbon manufactured by SN2A was heated in the air to 520° C. over 1.5 hours, and was fired while being kept at 520° C. for 5 hours to prepare a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 4.5 ml/g, and then the resulting carbon carrier was used.

Example 2

(85) an MEGA produced with a catalyst layer for a fuel cell electrode containing a metal carrying catalyst containing a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 7.0 ml/g, and an ionomer

(86) An MEGA was produced by the same method as that in Comparative Example 1 except that in (i) of (1) in Comparative Example 1, YS carbon manufactured by SN2A was heated in the air to 530° C. over 1.5 hours, and was fired while being kept at 530° C. for 5 hours to prepare a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 7.0 ml/g, and then the resulting carbon carrier was used.

Example 3

(87) an MEGA produced with a catalyst layer for a fuel cell electrode containing a metal carrying catalyst containing a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 9.3 ml/g, and an ionomer

(88) An MEGA was produced by the same method as that in Comparative Example 1 except that in (i) of (1) in Comparative Example 1, YS carbon manufactured by SN2A was heated in the air to 540° C. over 1.5 hours, and was fired while being kept at 540° C. for 5 hours to prepare a carbon carrier, wherein a volume of micropores having a diameter of 5 nm to 40 nm in micropores was 9.3 ml/g, and then the resulting carbon carrier was used.

(89) 2. Evaluation of Samples

Example 4

Measurement of Current-Voltage (I-V)

(90) In the MEGAs produced in Comparative Examples 1 and 2 and Examples 1 to 3, the voltage at a current density of 2.5 A/cm.sup.2 and a relative humidity of 165% was measured with a fuel cell evaluation system manufactured by TOYO Corporation by the following process. Each MEGA was heated to a temperature of 45° C. and humidified air (2 ml/min) and humidified hydrogen (0.5 ml/min) passing through a bubbler heated to 55° C. were then fed to the cathode electrode and the anode electrode to perform I-V measurement.

(91) The results are shown in Table 1 and FIG. 2.

(92) TABLE-US-00001 TABLE 1 Firing temperature of YS carbon, volume of micropores having diameter of 5 nm to 40 nm, voltage Firing Volume of micropores temperature having diameter of Voltage@2.5 A/cm.sup.2 (° C.) 5 nm to 40 nm (V) Comparative 510 3.5 0.42 Example 1 Comparative 550 12.8 0.43 Example 2 Example 1 520 4.5 0.46 Example 2 530 7.0 0.53 Example 3 540 9.3 0.48

(93) Table 1 and FIG. 2 show that the MEGAs produced with the carbon carriers, wherein the volume of micropores having a diameter of 5 nm to 40 nm in micropores was 4.5 ml/g to 9.3 ml/g, had increased voltages at a current density of 2.5 A/cm.sup.2 and a relative humidity of 165%.

(94) All publications, patents and patent applications cited in the present description are herein incorporated by reference as they are.