Fuel cell and fuel cell use gas diffusion electrode

Abstract

A fuel cell comprised of a proton conductive electrolyte film sandwiched between a pair of catalyst layers, wherein the catalyst layer of at least the cathode is comprised of a mixture including a catalyst ingredient, an electrolytic material, and a carbon material, the carbon material is comprised of a catalyst-carrying carbon material carrying the catalyst ingredient and a gas-diffusing carbon material not carrying the catalyst ingredient, and the catalyst-carrying carbon material has an amount of adsorption of water vapor at 25° C. and a relative humidity of 90% of 50 ml/g or more.

Claims

1. A fuel cell comprised of a proton conductive electrolyte film sandwiched by a pair of catalyst layers, and a separate gas diffusion layer, wherein at least a catalyst layer of a cathode is comprised of a mixture of a catalyst ingredient, an electrolytic material, and a carbon material, said carbon material is comprised of a catalyst-carrying carbon material carrying said catalyst ingredient and a gas-diffusing carbon material not carrying said catalyst ingredient, and said catalyst-carrying carbon material has an adsorption of water vapor in the range of 103.5 ml/g to 1500 ml/g at 25° C. and a relative humidity of 90% and said gas-diffusing carbon material has an amount of adsorption of water vapor of 1 ml/g or more and 100 ml/g or less at 25° C. and a relative humidity of 90%, wherein the carbon materials are respectively coagulated, and the coagulated phases of 1 μm or less in size made of the gas-diffusing carbon material and the coagulated phases of 1 μm or less in size made of the catalyst-carrying carbon material are uniformly and evenly distributed throughout the mixture.

2. The fuel cell as set forth in claim 1, wherein said catalyst-carrying carbon material is activated carbon, a surface area BET evaluated by BET satisfies SBET≧1500 m.sup.2/g, and a ratio of the surface area of micropores having a diameter of 2 nm or less, S micro (m.sup.2/g), to the total pore area, S total (m.sup.2/g), satisfies S micro/S total is greater than or equal to 0.5.

3. The fuel cell as set forth in claim 2, characterized in that said activated carbon has an average diameter of micropores having a diameter of 2 nm or less of 0.7 nm to 1.5 nm.

4. The fuel cell as set forth in claim 2 or 3, characterized in that said activated carbon has an oxygen content of 5 mass % or less.

5. The fuel cell as set forth in claim 1, wherein said catalyst-carrying carbon material has a volume of micropores having a diameter of 2 nm or less of 0.1 ml/g or more, and said catalyst-carrying carbon material has a DBP oil absorption of 300 ml/100 g or more.

6. The fuel cell as set forth in claim 5, characterized in that said catalyst-carrying carbon material has a specific surface area SBET by the BET method of 500 m.sup.2/g or more.

7. The fuel cell as set forth in any one of claim 1, 2 or 5, characterized in that said gas-diffusing carbon material is included in the catalyst layer in an amount of 5 mass % to 50 mass %.

8. The fuel cell as set forth in any one of claim 1, 2 or 5, characterized in that said gas-diffusing carbon material has an amount of adsorption of water vapor of 1 ml/g to 50 ml/g at 25° C. and a relative humidity of 90%.

9. The fuel cell as set forth in any one of claim 1, 2 or 5 characterized in that said catalyst ingredient contains an N4-chelate-type metal complex.

10. The fuel cell as set forth in claim 9, characterized in that said metal complex is a N4-chelate-type complex structure and two or more of the N atoms bonded with a center metal are imine types.

11. The fuel cell as set forth in claim 9, characterized in that said metal complex has an 0-0 bond distance of oxygen molecules bonded with the complex center metal in an adsorption structure of a metal complex and oxygen molecules calculated by the B3LYP density function method of 0.131 nm or more.

12. The fuel cell as set forth in claim 11, characterized in that said N4-chelate-type metal complex is one or both of the following general formula 1 or general formula 2, ##STR00004## (wherein, M is a metal atom, and each of R.sup.1 to R.sup.10 is hydrogen or a substituent group) ##STR00005## (wherein, M is a metal atom, and each of R.sup.11 to R.sup.24 is hydrogen or a substituent group).

13. The fuel cell as set forth in claim 9, characterized in that said metal complex has a complex center metal of one or more types of metal selected from the transition metals of Group V, Group VI, Group VII, or Group VIII of the Periodic Table.

14. The fuel cell as set forth in claim 9, characterized by further containing as said catalyst ingredient a precious metal.

15. The gas diffusion electrode of any one of claim 1, 2 or 5, further comprising: a micropore layer having carbon black as its main ingredient formed opposite a surface of said catalyst layer, and a gas diffusion fiber layer having fibrous carbon material as its main ingredient formed on said micropore layer, wherein the carbon black of said micropore layer has an amount of adsorption of water vapor of 100 ml/g or less at 25° C. and a relative humidity of 90%.

16. The gas diffusion electrode as set forth in claim 15, characterized in that the main ingredient carbon black of said micropore layer has a ratio X/Y of a DBP oil absorption X ml/100 g and a nitrogen adsorption specific area Y m.sup.2/g of 1 or more.

17. The fuel cell as set forth in claim 11 wherein the N4-chelate-type metal complex is selected from the group consisting of 5, 7, 12, 14-tetramethyl-1, 4, 8, 11-tetraazacyclotetradeca-2, 4, 6, 9, 11, 13-hexaene; 5, 7, 12, 14-tetramethyl-1, 4, 8, 11-tetraazacyclotetradeca-4, 6, 11, 13-tetraene; and 6, 13-diphenyl-1, 4, 8, 11-tetraazacyclotetradeca-2, 4, 6, 9, 11, 13-hexaene.

18. The fuel cell as set forth in claim 12 wherein R.sup.1 through R.sup.24 are independently selected from the group consisting of hydrogen, alkyl and aryl substituents.

19. The fuel cell as set forth in claim 12 wherein R.sup.1 through R.sup.24 are independently a hydrogen or a methyl substituent.

20. The fuel cell as set forth in claim 12 wherein M is cobalt or iron.

21. The fuel cell as set forth in claim 1 wherein the catalyst-carrying carbon material is chemically treated to increase the amount of adsorption of water vapor.

22. The fuel cell as set forth in any one of claim 1, 2 or 5, characterized in that said gas-diffusing carbon material is included in the catalyst layer in an amount of 10 mass % to 35 mass %.

23. The fuel cell as set forth in claim 1 wherein the catalyst layer is obtained by mixing the catalyst-containing carbon material, gas-diffusing carbon material, and a solution containing an electrolyte dissolved or dispersed in the solution, and a sufficient amount of a solvent to prepare an ink, and drying the ink in a film state.

24. The fuel cell as set forth in claim 1 characterized in that said catalyst layer is formed by drying an ink film prepared by mixing an electrolytic material, a catalyst-carrying carbon material carrying said catalyst ingredient and a gas diffusing carbon material not carrying said catalyst ingredient in a sufficient amount of solvent.

25. The fuel cell as set forth in claim 1 characterized in that the catalyst-containing carbon material, the gas-diffusing carbon material and the electrolyte material are dispersed within the catalyst layer.

26. The fuel cell as set forth in claim 1 characterized in that said gas-diffusing carbon material has a primary particle size of 1 μm or less.

Description

EXAMPLES

(1) <Measurement of Amount of Adsorption of Steam of Carbon Material>

(2) As the carbon material contained in the catalyst layer, a total of six types of carbon black A, B, C, D, E, and F with different amounts of adsorption of water vapor were prepared. B, D, and E are commercially available types of carbon black, while A and C are B and D heat treated in argon. Further, F is E treated in warmed concentrated nitric acid, then rinsed and dried.

(3) These types of carbon black were measured for amounts of adsorption of water vapor using a fixed capacity type water vapor adsorption device (made by Bel Japan, BELSORP18). Samples pretreated at 120° C. and 1 Pa or less for 2 hours to deaerate them were held in a 25° C. constant temperature tank, water vapor was gradually supplied from the vacuum state to the saturated water vapor pressure at 25° C. to change the relative humidity in stages, and the amounts of water vapor adsorbed by the samples were measured.

(4) An adsorption isotherm was drawn from the obtained measurement results. The amount of adsorption of water vapor at the time of a relative humidity of 90% was read from the FIGURE. The results are shown in Table 1. Note that the “amount of adsorption of water vapor” is the amount of water vapor adsorbed per 1 g of sample converted to the volume of water vapor in the standard state.

(5) TABLE-US-00001 TABLE 1 Amount of adsorption Pt Pt Type of of water Micropore Micropore Oxygen DBP oil particle Cata- carbon vapor S.sub.BET S.sub.micro/ dia. vol. content absorption size lyst material ml/g m.sup.2/g S.sub.total nm ml/g mass % ml/100 g nm no. A 0.28 32 0.65 0.51 0.01 or 0.12 58 3.9 1 less B 3.82 45 0.16 0.58 0.01 or 0.19 85 4.2 2 less C 35.6 62 0.39 0.62 0.01 or 0.56 96 4.0 3 less D 59.8 215 0.35 0.82 0.030 0.85 195 3.6 4 E 82.1 168 0.42 0.61 0.022 1.23 119 3.4 5 F 127 285 0.33 0.64 0.030 1.35 92 3.5 6

(6) Further, Table 1 also shows the values of the physical properties used in the present invention. The methods of measurement will be shown below.

(7) From measurement of the adsorption isotherm of the nitrogen gas, the specific surface area SBET by the BET method, the area Smicro and the total surface area Stotal of the micropores (pores of diameter of 2 nm or less) found by t-plot analysis, micropore volume Vmicro, and element analysis value of oxygen content.

(8) The gas adsorption was measured using a Bel Japan BELSORP36, the t-plot analysis was performed using an analysis program attached with the device to calculate the above-mentioned physical properties.

(9) The DBP oil absorption was measured by using an Absorptometer (made by Brabender) and converting the amount of DBP added at the time of 70% of the maximum torque to the DBP oil absorption per 100 g of the sample.

(10) The particle size (diameter) of the Pt fine particles was estimated by the Scherrer method from the half value of the (111) peak of platinum obtained by an X-ray diffraction device (made by Rigaku Corporation, Model RAD-3C).

Example 1

(11) A catalyst-carrying carbon material of each of the carbon blacks A, B, C, D, E, and F was dispersed in a hydrogen hexachloroplatinate aqueous solution. While holding this at 50° C. and stirring, hydrogen peroxide was added, then an Na.sub.2S.sub.2O.sub.4 aqueous solution was added to obtain a catalyst precursor.

(12) Each of these catalyst precursors was filtered, rinsed, and dried, then reduced in a 100% H.sub.2 stream at 300° C. for 3 hours to prepare each of the Pt catalysts 1 to 6 comprised of the catalyst-carrying carbon materials carrying 30 mass % of Pt. The Pt particle sizes of the Pt catalysts 1 to 6 are shown together in Table 1. The Pt particle sizes of the catalysts were 3 to 4 nm.

(13) Each of the prepared Pt catalysts 1 to 6 was placed in a container, a 5% Nafion solution (made by Aldrich) was added to give a mass ratio of the Pt catalyst and Nafion of 1/1.4, this was lightly stirred, then the catalyst was crushed by ultrasonic waves, and butyl acetate was added while stirring to give a solid concentration of the Pt catalyst and Nafion combined of 6 mass % so as to prepare each of the catalyst inks 1 to 6.

(14) Next, a gas-diffusing carbon material comprised of carbon black B was placed in a separate container, butyl acetate was added to give a concentration of carbon black of 6 mass %, and the carbon black was crushed by ultrasonic waves to prepare a gas-diffusing carbon material ink 1.

(15) Next, 10 g of each of the prepared catalyst inks 1 to 6 was placed in a container and 2.5 g of the gas-diffusing carbon material ink 1 was added while stirring to prepare each of the catalyst layer inks 1 to 6.

(16) Each of these catalyst layer inks 1 to 6 was coated and dried on a thin Teflon sheet to form a catalyst layer on the Teflon sheet. This was cut into a 2.5 cm×2.5 cm square to prepare each of the cathode-use catalyst layer-Teflon sheet laminates 1 to 6.

(17) Further, the catalyst ink 4 was coated and dried repeatedly on a thin Teflon sheet to form a catalyst layer on the Teflon sheet. This was cut into 2.5 cm×2.5 cm squares to prepare anode-use catalyst layer-Teflon sheet laminates A.

(18) Each of these prepared cathode-use catalyst layer-Teflon sheet laminates 1 to 6 and an anode-use catalyst layer-Teflon sheet laminate A were used to sandwich an electrolyte film (Nafion 112). These assemblies were hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes, then the Teflon sheets were peeled off to thereby form the catalyst layer-electrolyte film laminates 1 to 6.

(19) At this time, the difference between the mass of each catalyst layer-Teflon sheet laminate and the mass of the peeled off Teflon sheets was used to determine the mass of the catalyst layer transferred to the electrolyte film. The Pt content was found from this and the composition of the ink.

(20) At this time, the amounts of the catalyst layer inks coated on the Teflon sheets were adjusted so that the Pt content of the cathodes became 0.07 mg/cm.sup.2 and the Pt content of the anodes became 0.04 mg/cm.sup.2.

(21) Further, carbon paper treated in advance by PTFE to make it hydrophobic was cut into 2.5 cm×2.5 cm squares, two pieces were used to sandwich each catalyst layer-electrolyte film laminate, and these were further hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes to obtain carbon paper-catalyst layer-electrolyte film laminates 1 to 6 (MEA1 to MEA6).

(22) Below, the carbon paper-catalyst layer-electrolyte film laminates will be abbreviated as “MEA”.

(23) The obtained MEA1 to MEA6 were attached to fuel cell measurement devices and measured for cell performances. The cell performances were measured by changing the voltage between cell terminals in stages from the open voltage (usually 0.9V to 1.0V) to 0.2V and measuring the current density when a voltage of 0.6V was flowing between the cell terminals.

(24) As the gas, the cathode was supplied with air and the anode with pure hydrogen to give rates of utilization of 50% and 80%. These gases were adjusted in pressure to 0.1 MPa by a back pressure valve provided downstream from the cell. The cell temperature was set at 80° C., and the supplied air and pure hydrogen were bubbled through distilled water warmed to 80° C. and 90° C. to wet them.

(25) TABLE-US-00002 TABLE 2 Anode Content of Cathode Type of Pt gas- Type of Pt catalyst- carrying diffusing catalyst- carrying Gas-diffusing Current carrying rate of carbon carrying rate of carbon material density MEA carbon catalyst material carbon catalyst Content at 0.6 V no. material mass % mass % material mass % Type mass % (mA/cm.sup.2) Comp. MEA1 D 30 0 A 30 B 20 508 ex. MEA2 D 30 0 B 30 B 20 583 MEA3 D 30 0 C 30 B 20 612 Inv. MEA4 D 30 0 D 30 B 20 885 ex. MEA5 D 30 0 E 30 B 20 1060 MEA6 D 30 0 F 30 B 20 1032

(26) Table 2 shows the results of measurement of the cell performance of MEA1 to MEA6 together with the compositions of the catalyst layers. As shown in Table 1, MEA4 to MEA6 of the examples of the present invention, where the catalyst-carrying carbon materials had amounts of adsorption of water vapor at 25° C. and a relative humidity of 90% of 50 ml/g or more, exhibited superior cell performances compared with the MEA1 to MEA3 of the comparative examples.

Example 2

(27) A catalyst-carrying carbon material comprised of the carbon black D was dispersed in a hydrogen hexachloroplatinate aqueous solution. While holding this at 50° C. and stirring, hydrogen peroxide was added, then an Na.sub.2S.sub.2O.sub.4 aqueous solution was added to obtain a catalyst precursor.

(28) The catalyst precursor was filtered, rinsed, and dried, then reduced in a 100% H.sub.2 stream at 300° C. for 3 hours to prepare the Pt catalyst 7 comprised of the catalyst-carrying carbon material carrying 20 mass % of Pt. The Pt particle size of the Pt catalyst 7 was 3 to 4 mm.

(29) The prepared Pt catalyst 7 was placed in a container, a 5% Nafion solution (made by Aldrich) was added to give a mass ratio of the Pt catalyst and Nafion of 1/1.6, this was lightly stirred, then the catalyst was crushed by ultrasonic waves, and butyl acetate was added while stirring to give a solid concentration of the Pt catalyst and Nafion combined of 6 mass % so as to prepare the catalyst ink 7.

(30) Next, a gas-diffusing carbon material comprised of carbon black C was placed in a separate container, butyl acetate was added to give a concentration of carbon black of 6 mass %, and the carbon black was crushed by ultrasonic waves to prepare a gas-diffusing carbon material ink 2.

(31) Next, 10 g amounts of the prepared catalyst ink 7 were placed in seven containers and 0 g, 0.204 g, 0.870 g, 1.111 g, 2.500 g, 4.286 g, and 12.222 g of the gas-diffusing carbon material ink 2 were added while stirring to prepare the catalyst layer inks 7 to 13.

(32) Each of these catalyst layer inks 7 to 13 was repeatedly coated and dried on a thin Teflon sheet to form a catalyst layer on the Teflon sheet. This was cut into a 2.5 cm×2.5 cm square to prepare each of the cathode-use catalyst layer-Teflon sheet laminates 7 to 13.

(33) Each of these prepared cathode-use catalyst layer-Teflon sheet laminates 7 to 13 and an anode-use catalyst layer-Teflon sheet laminate A prepared in Example 1 were used to sandwich an electrolyte film (Nafion 112). These assemblies were hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes, then the Teflon sheets were peeled off to thereby form the catalyst layer-electrolyte film laminates 7 to 13. At this time, the difference between the mass of each catalyst layer-Teflon sheet laminate and the mass of the peeled off Teflon sheets was used to determine the mass of the catalyst layer transferred to the electrolyte film. The Pt content was found from this and the composition of the ink. At this time, the amounts of the catalyst layer inks coated on the Teflon sheets were adjusted so that the Pt content of the cathodes became 0.07 mg/cm.sup.2 and the Pt content of the anodes became 0.04 mg/cm.sup.2.

(34) Further, carbon paper treated in advance by PTFE to make it hydrophobic was cut into 2.5 cm×2.5 cm squares, two pieces were used to sandwich each catalyst layer-electrolyte film laminate, and these were further hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes to the MEA7 to MEA13.

(35) The obtained MEA7 to MEA13 were measured for cell performance under conditions similar to Example 1.

(36) TABLE-US-00003 TABLE 3 Anode Content of Cathode Type of Pt gas- Type of Pt catalyst- carrying diffusing catalyst- carrying Gas-diffusing Current carrying rate of carbon carrying rate of carbon material density MEA carbon catalyst material carbon catalyst Content at 0.6 V no. material mass % mass % material mass % Type mass % (mA/cm.sup.2) Comp. MEA7 D 30 0 D 20 C 0 306 Ex. Inv. MEA8 D 30 0 D 20 C 2 354 Ex. MEA9 D 30 0 D 20 C 8 528 MEA10 D 30 0 D 20 C 10 624 MEA11 D 30 0 D 20 C 20 721 MEA12 D 30 0 D 20 C 30 571 MEA13 D 30 0 D 20 C 55 321

(37) Table 3 shows the results of measurement of the cell performance of MEA7 to MEA13 together with the compositions of the catalyst layers. As shown in Table 3, MEA8 to MEA13 of the examples of the present invention, where gas-diffusing carbon materials were included in the cathodes, exhibited superior cell performances compared with the MEA7 of the comparative example where a gas-diffusing carbon material was not included.

(38) Further, among the MEA7 to MEA13 of the examples, MEA9 to MEA12, where gas-diffusing carbon materials were included in amounts of 5 mass % to 50 mass %, exhibited particularly superior performances.

Example 3

(39) A catalyst-carrying carbon material comprised of the carbon black F was dispersed in a hydrogen hexachloroplatinate aqueous solution. While holding this at 50° C. and stirring, hydrogen peroxide was added, then an Na.sub.2S.sub.2O.sub.4 aqueous solution was added to obtain a catalyst precursor. The catalyst precursor was filtered, rinsed, and dried, then reduced in a 100% H.sub.2 stream at 300° C. for 3 hours to prepare the Pt catalyst 8 comprised of the catalyst-carrying carbon material carrying 50 mass % of Pt. The Pt particle size of the Pt catalyst 8 was 3 to 4 nm.

(40) The prepared Pt catalyst 8 was placed in a container, a 5% Nafion solution (made by Aldrich) was added to give a mass ratio of the Pt catalyst and Nafion of 1/2, this was lightly stirred, then the catalyst was crushed by ultrasonic waves, and butyl acetate was added while stirring to give a solid concentration of the Pt catalyst and Nafion combined of 6 mass % so as to prepare the catalyst ink 8.

(41) Next, a gas-diffusing carbon material comprised of each of the carbon black A, B, C, D, E, and F was placed in a separate container, butyl acetate was added to give a concentration of carbon black of 6 mass %, and the carbon black was crushed by ultrasonic waves to prepare each of the gas-diffusing carbon material inks 3 to 8.

(42) Next, 10 g amounts of the prepared catalyst ink 8 were placed in six containers and 3.333 g of the gas-diffusing carbon material inks 3 to 8 were added while stirring to prepare the catalyst layer inks 14 to 19.

(43) Each of these catalyst layer inks 14 to 19 was coated and dried on a thin Teflon sheet to form a catalyst layer on the Teflon sheet. This was cut into a 2.5 cm×2.5 cm square to prepare each of the cathode-use catalyst layer-Teflon sheet laminates 14 to 19.

(44) Each of these prepared cathode-use catalyst layer-Teflon sheet laminates 14 to 19 and an anode-use catalyst layer-Teflon sheet laminate A prepared in Example 1 were used to sandwich an electrolyte film (Nafion 112). These assemblies were hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes, then the Teflon sheets were peeled off to thereby form the catalyst layer-electrolyte film laminates 14 to 19. In the same way as in Example 1, the amounts of the catalyst layer inks were adjusted so that the Pt content of the cathodes became 0.07 mg/cm.sup.2 and the Pt content of the anodes became 0.04 mg/cm.sup.2.

(45) Further, in the same way as in Example 1, carbon paper treated in advance by PTFE was bonded to obtain each of the MEA14 to MEA19.

(46) The obtained MEA14 to MEA19 were measured for cell performance under conditions similar to Example 1.

(47) TABLE-US-00004 TABLE 4 Anode Content Cathode Type of Pt of gas- Type of Pt catalyst- carrying diffusing catalyst- carrying Gas-diffusing Current carrying rate of carbon carrying rate of carbon material density MEA carbon catalyst material carbon catalyst Content at 0.6 V no. material mass % mass % material mass % Type mass % (mA/cm.sup.2) Ex. MEA14 D 30 0 F 50 A 25 659 MEA15 D 30 0 F 50 B 25 1087 MEA16 D 30 0 F 50 C 25 1028 MEA17 D 30 0 F 50 D 25 781 MEA18 D 30 0 F 50 E 25 639 MEA19 D 30 0 F 50 F 25 328

(48) Table 4 shows the results of measurement of the cell performance of MEA14 to MEA19 together with the compositions of the catalyst layers. As shown in Table 4, MEA14 to MEA19 of the examples of the present invention, where gas-diffusing carbon materials were included in the cathodes, exhibited superior cell performances compared with the MEA7 of the comparative example where a gas-diffusing carbon material was not included.

(49) Further, among the MEA14 to MEA19 of the examples, MEA14 to MEA18, where the gas-diffusing carbon materials had amounts of adsorption of water vapor at 25° C. and a relative humidity of 90% of 100 ml/g or less, exhibited particularly superior cell performances. Further, MEA15 and 16, where the gas-diffusing carbon materials had amounts of adsorption of water vapor at 25° C. and a relative humidity of 90% of 1 ml/g to 50 ml/g, exhibited extremely superior cell performances.

Example 4

(50) Coal-based raw coke material was treated by so-called water vapor activation treatment in a heating furnace warmed to 800° C. to 1100° C. for 2 hours to 3 hours while running nitrogen gas containing a certain amount of water vapor to prepare activated carbon.

(51) Further, to control the oxygen content, this was heat treated for reduction in a nitrogen gas atmosphere containing 10 vol % to 30 vol % of hydrogen at 500° C. to 900° C. for 1 hour

(52) Table 5 shows the various physical properties of a series of activated carbon prepared by the above-mentioned method. The values of these physical properties were measured by the above-mentioned methods.

(53) TABLE-US-00005 TABLE 5 Pt Type of Steam Micropore Micropore Oxygen DBP oil particle carbon adsorption S.sub.BET S.sub.micro/ diameter volume content absorption size material ml/g m.sup.2/g S.sub.total nm ml/g mass % ml/100 g nm Activated 195.3 1550 0.55 0.73 0.311 4.93 35 1.9 carbon 1 Activated 183.3 1640 0.52 0.85 0.362 4.33 45 1.7 carbon 2 Activated 165.1 1890 0.68 1.18 0.758 4.62 75 1.7 carbon 3 Activated 205.3 2310 0.85 1.32 1.300 3.55 70 1.6 carbon 4 Activated 166.6 1750 0.95 1.05 0.873 3.81 60 1.8 carbon 5 Activated 45.6 1320 0.41 0.75 0.203 4.51 35 3.8 carbon 6 Activated 31.9 1650 0.31 0.55 0.141 10.5 25 4.5 carbon 7 G 46.6 225 0.12 0.55 0.01 or 1.56 220 5.3 less H 29.6 80 0.09 0.45 0.01 or 0.96 170 6.7 less

(54) Each of these activated carbons was processed as follow to make it carry platinum fine particles. 150 ml of distilled water in a flask was charged with 0.5 g of the carbon material used for the carrier and hexachloroplatinic (IV) acid to give a mass ratio of the platinum to the carrier of ratio 1:1, the mixture was sufficiently dispersed by ultrasonic waves, then the mixture was held in a oil bath in the boiling state and a reducing agent comprised of formaldehyde was added dropwise at a constant speed over 3 to 10 hours.

(55) After finishing the dropping, the mixture was separated by filtration by a membrane filter, then the recovered matter was again dispersed in distilled water and separated by filtration. This operation was repeated three times. The result was dried in vacuo at 100° C. to obtain a catalyst for an electrode.

(56) The amount of platinum carried on the catalyst was quantitatively analyzed by dissolving this in hot aqua regia and measuring it by plasma spectrometry, whereupon it was found to be 50 mass % in the case of each sample.

(57) The activated carbon defined by the present invention, despite having a high density of 50 mass % compared with other activated carbon or carbon black, had a particle size of 2.0 nm or less, so clearly has a smaller Pt particle size and is deemed more excellent as a carrier.

(58) Each of the series of platinum catalyst-carrying carbon materials and a gas-diffusing carbon material comprised of the carbon black B of Example 1 were used by the same method as Example 1 to prepare cathode-use catalyst layer-Teflon sheet laminates.

(59) Each of these prepared cathode-use catalyst layer-Teflon sheet laminates and an anode-use catalyst layer-Teflon sheet laminate A prepared in Example 1 were used to sandwich an electrolyte film (Nafion 112). These assemblies were hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes, then the Teflon sheets were peeled off to thereby form the catalyst layer-electrolyte film laminates. These were prepared so that the cathode had a Pt content of 0.08 mg/cm.sup.2 and the anode had a Pt content of 0.05 mg/cm.sup.2.

(60) Further, in the same way as in Example 1, each was bonded with carbon paper treated in advance by PTFE to make it hydrophobic to obtain MEAs. The obtained MEAs were measured for cell performance under conditions similar to Example 1.

(61) TABLE-US-00006 TABLE 6 Anode Content cathode Type of Pt of gas- Type of Pt catalyst- carrying diffusing catalyst- carrying Gas-diffusing Current carrying rate of carbon carrying rate of carbon material density MEA carbon catalyst material carbon catalyst Content at 0.6 V no. material mass % mass % material mass % Type mass % (mA/cm.sup.2) Inv. MEA20 D 30 0 Activated 50 B 20 1028 ex. carbon 1 MEA21 D 30 0 Activated 50 B 20 1051 carbon 2 MEA22 D 30 0 Activated 50 B 20 1025 carbon 3 MEA23 D 30 0 Activated 50 B 20 1013 carbon 4 MEA24 D 30 0 Activated 50 B 20 1030 carbon 5 Comp. MEA25 D 30 0 Activated 50 B 20 941 ex. carbon 6 MEA26 D 30 0 Activated 50 B 20 929 carbon 7 MEA27 D 30 0 G 50 B 20 961 MEA28 D 30 0 H 50 B 20 936

(62) Table 6 shows the results of cell performance of the prepared MEAs. The MEAs using platinum catalysts having the activated carbon defined in the present invention as carrier were observed to clearly exhibit superior output characteristics compared with the MEAs of the activated carbon and carbon black used for comparison.

Example 5

(63) To study how the catalyst life is improved by using the activated carbon defined in the present invention for a carrier, the five types of carbon materials shown in Table 7 among the carbon materials used in Example 4 were used to carry platinum fine particles by a method similar to Example 4.

(64) In this study, to evaluate the changes in particle sizes of catalysts as deterioration, it is necessary make the particle sizes of the platinum fine particles before deterioration accurately match. The catalysts were prepared to have platinum carrying rates of 30 mass % and diameters of the platinum fine particles of 2.3 nm. Table 7 shows the physical properties of the series of carbon materials and the catalysts particles sizes. The particle sizes of the catalysts used were values measured by X-ray diffraction.

(65) The five types of catalysts of Table 7 were used to prepare MEAs by a method similar to Example 4. The MEAs were prepared so that the cathodes had Pt contents of 0.08 mg/cm.sup.2 and the anodes had Pt contents of 0.05 mg/cm.sup.2. The obtained HEAs were attached to cells and used for evaluation by a method similar to Example 1.

(66) The catalyst life was evaluated by the ratio of the surface areas of the platinum used for the cathode before deterioration and after deterioration operation. That is, if the surface area of the platinum does not change at all due to the deterioration operation, the rate of deterioration is evaluated as 0%, while if the surface area of the platinum after deterioration operation becomes half of that before deterioration, the rate of deterioration is evaluated as 50%.

(67) The surface area of platinum of a cathode was evaluated by the following method. The anode was supplied with wet hydrogen gas, the cathode was supplied with wet argon gas, and the cell was cycled 10 times by a 50 mV/sec scan rate in a range of cell voltage of 0.05V to 0.9V to measure the cyclic voltammogram.

(68) The wetting conditions and the cell temperature were made the same as in Example 1. The number of hydrogen atoms disassociated from the area of the so-called hydrogen disassociation wave of the 10th cycle graph was calculated and the known average area which one hydrogen atom occupies on the platinum surface was used to find the surface area of the platinum from the number of hydrogen atoms (see Fujijima, Aizawa, Inoue ed., Electrochemical Measurement Methods (I), Gihodo Shuppan, Chapter 4, 4.4. Pretreatment of Electrodes and Electrode Surface Area).

(69) In this evaluation, each MEA was attached, then the cyclic voltammogram was measured. Next, the gas of the cathode was changed to pure oxygen, the cell voltage was held at OCV (open voltage no load) for 15 seconds, then a load was applied so that the cell voltage became a constant 0.5V and this state was held for 15 seconds. This operation was repeated for 3000 cycles.

(70) After this, the gas of the cathode was again changed to argon and the surface area of the platinum was found under the same conditions as before deterioration. The rate of deterioration was the surface area of the platinum after deterioration divided by the value before deterioration expressed as a %.

(71) TABLE-US-00007 TABLE 7 Pt particle Carbon size Rate of material nm deterioration % Inv. Activated 2.26 41 ex. carbon 1 Activated 2.29 40 carbon 2 Activated 2.26 37 carbon 4 Comp. Activated 2.28 55 ex. carbon 6 Activated 2.30 59 carbon 7 G 2.29 63 H 2.32 69

(72) As clear from Table 7, the activated carbon defined in the present invention clearly suffers from less of a degree of deterioration than a platinum catalyst using another activated carbon or usual carbon black for the carrier.

Example 6

(73) In this example, as catalyst carriers, including the comparative examples, carbon materials with different pore volumes, nitrogen adsorption specific areas, DBP oil absorptions, and amounts of adsorption of water vapor were used. Table 8 shows the values of the various physical properties of the carbon materials used.

(74) TABLE-US-00008 TABLE 8 Amount of adsorption Pt Type of of water Micropore Micropore Oxygen DBP oil particle carbon vapor S.sub.BET S.sub.micro/ dia. vol. content absorption size material ml/g m.sup.2/g S.sub.total nm ml/g mass % ml/100 g nm I 25.3 72 0.41 0.68 0.01 1.12 170 6.3 J 78.5 1370 0.39 0.63 0.17 0.78 521 2.0 K 82.9 796 0.73 0.69 0.2 1.23 360 2.5 L 113.5 1436 0.77 0.71 0.39 0.96 313 2.0 M 103.5 950 0.35 0.66 0.11 0.86 380 2.4 N 48.3 227 0.48 0.92 0.05 2.1 219 3.5 O 46.1 195 0.25 0.81 0.02 0.98 127 4.5 P 41.6 460 0.40 0.77 0.07 1.63 150 3.0 Q 43.9 265 0.37 0.82 0.04 1.22 119 3.5 R 39.8 583 0.11 0.99 0.03 1.41 95 2.8 S 37.7 40 0.52 0.97 0.01 0.82 159 7.2 T 68.8 1582 0.69 0.71 0.39 1.26 515 1.8

(75) The above-mentioned physical properties were measured by the above-mentioned methods. The carbon materials of Table 8 were used as catalyst carriers to prepare platinum-carrying catalysts by the following method.

(76) Each of the catalyst-carrying carbon materials comprised of the carbon materials of Table 8 was dispersed in water. While holding this at 50° C. and stirring, a hydrogen hexachloroplatinate aqueous solution and formaldehyde aqueous solution were added to obtain a catalyst precursor.

(77) Each catalyst precursor was filtered, rinsed, and is dried, then reduced in a 100% H.sub.2 stream at 300° C. for 3 hours to prepare a Pt catalyst comprised of the catalyst-carrying carbon material carrying 20 mass % of Pt.

(78) The Pt particle sizes of the obtained platinum catalysts are shown in Table 8. As shown in Table 8, the carbon materials I, O, and S had extremely large crystal grain sizes and therefore are not expected to have that high performances as fuel cell catalysts.

(79) Each of these 12 types of catalyst-carrying carbon material and a gas-diffusing carbon material comprised of the carbon black B of Example 1 were used by the same method as in Example 1 to prepare a cathode use catalyst layer-Teflon sheet laminate.

(80) Each of these prepared cathode-use catalyst layer-Teflon sheet laminates and an anode-use catalyst layer-Teflon sheet laminate A prepared in Example 1 were used to sandwich an electrolyte film (Nafion 112). These assemblies were hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes, then the Teflon sheets were peeled off to thereby form the catalyst layer-electrolyte film laminates. These were prepared so that the cathode had a Pt content of 0.08 mg/cm.sup.2 and the anode had a Pt content of 0.05 mg/cm.sup.2.

(81) Further, the same procedure was performed as in Example 1 to bond carbon paper treated for hydrophobicity in advance by PTFE to obtain MEA29 to MEA40.

(82) The obtained MEA29 to MEA40 were measured for cell performance under conditions similar to Example 1.

(83) TABLE-US-00009 TABLE 9 Anode Gas- Cathode Type of Pt diffusing Type of Pt catalyst- carrying carbon catalyst- carrying Gas-diffusing Current carrying rate of material carrying rate of carbon material density MEA carbon catalyst content carbon catalyst Content at 0.6 V no. material mass % mass % material mass % Type mass % (mA/cm.sup.2) Comp. MEA29 D 30 0 I 20 B 20 969 ex. Inv. MEA30 D 30 0 J 20 B 20 1067 Ex. MEA31 D 30 0 K 20 B 20 1034 MEA32 D 30 0 L 20 B 20 1028 MEA33 D 30 0 M 20 B 20 1038 Comp. MEA34 D 30 0 N 20 B 20 987 ex. MEA35 D 30 0 O 20 B 20 961 MEA36 D 30 0 P 20 B 20 981 MEA37 D 30 0 Q 20 B 20 982 MEA38 D 30 0 R 20 B 20 974 MEA39 D 30 0 S 20 B 20 803 Inv. MEA40 D 30 0 T 20 B 20 1104 Ex.

(84) Table 9 shows the results of the cell performance of the 12 types of MEAs prepared. The MEA30 to MEA33 and MEA40 of the present invention exhibited superior cell characteristics compared with the comparative examples.

(85) Among these, the MEA40 using a carbon material T having a volume of pores of 2 nm or less size of 0.3 ml/g or more and a nitrogen adsorption specific area of 800 m.sup.2/g or more and further having a DBP oil absorption of 400 ml/g or more was particularly superior in load characteristics.

Example 7

(86) Method of Synthesis of Transition Metal Complex>

(87) The method of synthesis of the N4-chelate type transition metal complex defined in the present invention is shown below.

(88) Synthesis of complex 1: The method described in the Document (R. H. Holm, J. Am. Chem. Soc., Vol. 94, p. 4529 (1972)) was used to synthesize a cobalt (II) complex of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-2,4,6,9,11,13-hexaene (abbreviated as “complex 1”). The yield was 12%.

(89) Synthesis of complex 2: The method described in the Documents ((a) T. Hayashi, Bull. Chem. Soc. Jpn., Vol. 54, p. 2348 (1981), (b) R. H. Holm, Inorg. Syn., Vol. 11, p. 72, (1968)) was used to synthesize a cobalt (ITI) complex of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraene (abbreviated as “complex 2”). The yield was 8%.

(90) <Preparation of Catalyst>

(91) A total of three types of materials were used for the carbon material carrier for the catalyst: the carbon material F used in Example 1, the carbon material 3 used in Example 4, and the activated carbon 4. Hydrogen hexachloroplatinate 6-hydrate (made by Wako Pure Chemical Industries) was weighed so as to give a predetermined mass % and was diluted by water to a suitable amount. Each of the carbon materials used as the carrier were added to such an aqueous solution and sufficiently stirred, then this was dispersed by an ultrasonic wave generator.

(92) After this, an evaporator was used to dry each dispersion to a solid to prepare a carrier carrying the precursor.

(93) Each precursor-carrying carrier was heated to 300° C. in an electric furnace through which a hydrogen/argon mixed gas was circulated (ratio of hydrogen gas: 10 to 50 vol %) so as to reduce the hydrogen hexachloroplatinate. The Pt particle size was 2.0 to 2.3 nm.

(94) Each of the above transition metal complexes was weighed to 1 mass % converted to transition metal element and a suitable amount of N,N′-dimethyl formamide (reagent special grade) or pyridine (reagent special grade) was added. The above-mentioned platinum-containing carbon materials (Pt—C) was added to this solution and sufficiently stirred, then was dispersed using an ultrasonic wave generator.

(95) Each dispersion was held in temperature by a 70° C. oil bath and refluxed for 8 hours or more (under flow of argon), then was poured, while stirring, into distilled water of five or more times the dispersion to immobilize the transition metal complex on the Pt—C.

(96) After this, each catalyst was separated by vacuum filtration and again washed by distilled water of a temperature of 60° C. or so. The catalyst was obtained by vacuum filtration and dried in vacuo at 100° C.

(97) This was further treated in an argon gas atmosphere at 700° C. for 1 hour to obtain an evaluation use catalyst.

(98) The transition metal complexes used in the examples were the above complex 1, complex 2, and a cobalt (II) complex of 5,10,15,20-tetraphenylpolyporphyrin (abbreviated as “CoTPP”).

(99) Note that catalysts carrying only transition metal complexes were prepared by omitting the above-mentioned platinum carrying process and performing the transition metal complex carrying process, while a catalyst carrying on platinum was prepared by omitting the transition metal complex carrying process and performing only the platinum carrying process so as to prepare the respective catalysts.

(100) <Method of Evaluation of Catalyst Activity>

(101) (1) Preparation of Samples for Evaluation

(102) Each catalyst was crushed in advance by a mortar. 15 mg of the catalyst powder, 300 mg of a polymer solid electrolyte solution (ElectroChem, EC-NS-05; Nafion 5 mass % solution), and 300 mg of ethanol were placed in a sample bottle and stirred for 15 minutes by a stirrer to prepare a sufficiently mixed slurry.

(103) (2) Preparation of Test Electrodes

(104) A disk electrode of a rotary ring-disk electrode was coated and dried with the above-mentioned slurry to form a test electrode. The disk electrode is a column of a diameter of 6 mm made by glassy carbon. The sample was coated on the bottom surface. The amount of coating was adjusted to 0.03 mg.

(105) Further, the ring electrode is a cylinder of an inside diameter of 7.3 mm and an outside diameter of 9.3 mm made by platinum. The rotary ring-disk electrode is structured with the disk electrode and ring electrode positioned concentrically and with the disk electrode and ring electrode insulated from each other and the outside of the ring electrode insulated by Teflon resin.

(106) (3) Method of Evaluation

(107) A rotary ring-disk evaluator (RRDE-1) made by Nikko Keisoku was used to evaluate the electrochemical activity of the catalysts. For the electrochemical evaluation, two Solatron SI1287 units were used. The ring electrode and the disk electrode were independently controlled for bipolar measurement.

(108) For the electrolyte, a 0.1N sulfuric acid aqueous solution was used. For the reference electrode, an SCE electrode was used, while for the counter electrode, a Pt plate was used in the cell. The evaluation conditions were as follows:

(109) In the state of the electrolyte saturated with oxygen by bubbling of oxygen gas, the potential of the disk electrode of the electrode rotating at 2500 rpm was changed from 1.0V (SCE standard) to −0.2V at a speed of 10 mV/sec. At that time, the potential of the ring electrode was held at 1.1V (SCE standard). The changes of the currents flowing through the disk electrode and the ring electrode over time were measured to obtain plots of the disk current and ring current with respect to the potential of the disk electrode.

(110) (4) Method of Evaluation of Overvoltage

(111) The potential (E1/2) when the current value became half of the saturated current value was read from the plot of the disk potential vs. disk current. The ΔE1/2=E1/2−E1/20 of each catalyst of the examples and comparative examples was evaluated based on the potential E1/20 when the current value became half of the saturated current value of the catalyst EC10PTC made by ElectroChem of the U.S. (catalyst comprised of carbon black carrying 10 mass % of platinum).

(112) That is, at ΔE1/2=0, the overvoltage is the same as EC10PTC. If ΔE1/2>0, the overvoltage is smaller than EC10PTC. This corresponds to a high catalyst activity.

(113) (5) Method of Evaluation of Four-Electron Reaction Rate

(114) The four-electron reaction rate η was calculated based on the following equation from the plots of the ring current and disk current with respect to the disk potential.
η(%)=[Id−(Ir/n)]/[Id+(Ir/n)]

(115) where, Id indicates the disk current, Ir indicates the ring current, and n indicates the rate of the ring electrode trapping the disk reaction product.

(116) The experimental method of measurement of the trapping rate was evaluated in accordance with the “Fujijima et al., Electrochemical Measurement Methods (II), Gihodo Shuppan (1991)”. As a result, in the electrodes used for the examples, n=0.36.

(117) Further, the η changes in accordance with the disk potential (the poorer the potential, the smaller the η). In the evaluation, the η when the disk potential is 0V (SCE standard) is employed so that the difference of η by the catalyst becomes clear.

(118) Table 11 shows the type of the transition metal, the amount of the platinum carried, and, as indicators of the catalyst activity, the overcurrent value ΔE1/2 and the four-electron reaction rate η.

(119) TABLE-US-00010 TABLE 11 Type of Metal complex Carrier metal Co carrying Pt carried carbon ΔE.sub.1/2 complex amount, mass % amount, mass % material η % mV Ex. Catalyst 1 Complex 1 0.5 0 F 93 2 Catalyst 2 Complex 1 0.5 0 Activated 95 7 carbon 3 Catalyst 3 Complex 1 0.5 6 F 99 28 Catalyst 4 Complex 2 0.5 6 F 99 24 Catalyst 5 Complex 1 0.5 6 Activated 99 33 carbon 3 Catalyst 6 Complex 1 0.5 6 Activated 99 43 carbon 4 Catalyst 7 CoTPP 0.5 0 F 82 −12 Catalyst 8 None None 12 F 99 13

(120) From the results of Table 11, a transition metal of the specific structure defined in the present invention is recognized as being excellent in both catalyst activity in an oxygen reduction reaction and four-electron reaction rate.

(121) Further, a complex catalyst comprised of a transition metal complex defined in the present invention and platinum combined together clearly exhibits a superior catalyst characteristic compared with platinum alone or a transition metal complex alone. A coordinated effect of the transition metal complex and platinum is recognized.

(122) Further, the effect of the carrier is also recognized. By using activated carbon having a large specific surface area for the carrier, a superior catalyst activity not obtainable by an ordinary carbon carrier can be observed.

(123) Next, each of five types of catalysts of a catalyst 3, catalyst 4, catalyst 5, catalyst 6, and catalyst 8 and a gas-diffusing carbon material comprised of the carbon black B of Example 1 were used in the same method as in Example 1 to prepare a cathode-use catalyst layer-Teflon sheet laminate.

(124) Each of these prepared cathode-use catalyst layer-Teflon sheet laminates and an anode-use catalyst layer-Teflon sheet laminate A prepared in Example 1 were used to sandwich an electrolyte film (Nafion 112). These assemblies were hot pressed under conditions of 140° C. and 100 kg/cm.sup.2 for 3 minutes, then the Teflon sheets were peeled off to thereby form the catalyst layer-electrolyte film laminates. These were prepared so that the anodes had a Pt content adjusted to 0.03 mg/cm.sup.2.

(125) They were also prepared so that the cathodes had a Pt content of 0.03 mg/cm.sup.2 in the case of the catalyst 3, catalyst 4, catalyst 5, and catalyst 6 and 0.06 mg/cm.sup.2 in the case of the catalyst 8.

(126) Further, these were bonded with carbon paper treated in advance by PTFE to make it hydrophobic to obtain the MEA41 to MEA45 in the same way as Example 1.

(127) The obtained MEA41 to MEA45 were measured for cell performance under conditions similar to Example 1.

(128) TABLE-US-00011 TABLE 12 Anode Content of Cathode Type of Pt gas- Pt catalyst- carrying diffusing carrying Gas-diffusing Current carrying rate of carbon rate of carbon material density MEA carbon catalyst material Type of catalyst Content at 0.6 V no. material mass % mass % catalyst mass % Type mass % (mA/cm.sup.2) Example MEA41 D 30 0 Catalyst 3 6 B 20 460 MEA42 D 30 0 Catalyst 4 6 B 20 425 MEA42 D 30 0 Catalyst 5 6 B 20 625 MEA44 D 30 0 Catalyst 6 6 B 20 705 MEA45 D 30 0 Catalyst 8 6 B 20 385

(129) Table 12 shows the results of cell performance of the five types of MEAs prepared. The MEA41 to MEA44 exhibited superior cell characteristics regardless of the amount of platinum of the cathode being half that of MEA45.

Example 8

(130) Three types of carbon black U, V, and W were prepared in the same way as shown in the examples of the gas diffusion electrodes of the present invention. Table 13 shows the amount of adsorption of water vapor, DBP oil absorption (X ml/100 g), nitrogen adsorption specific area (Ym.sup.2/g), and ratio X/Y of the DBP oil absorption and nitrogen adsorption specific area of each type of the carbon black.

(131) TABLE-US-00012 TABLE 13 Amount of adsorption Nitrogen of water DBP oil absorption adsorption Type of vapor (X) specific area (Y) carbon black ml/g ml/100 g m.sup.2/g X/Y U 8.96 232 128 1.81 V 59.8 230 225 1.02 W 127 536 1370 0.39

(132) <Preparation of Gas Diffusion Layer>

(133) Commercially available carbon cloth (made by ElectroChem, EC-CC1-060) was prepared, dipped in a Teflon dispersion diluted to 5%, then dried and further raised in temperature in an argon stream to 340° C. to prepare a gas diffusion fiber layer. Further, 99 g of ethanol was added to 1 g of carbon black U, then the carbon black was crushed by a ball mill to prepare a primary dispersion.

(134) After this, 0.833 g of a 30% Teflon dispersion was added dropwise a little at a time to the primary dispersion while stirring to prepare a micropore layer slurry.

(135) The slurry was spray coated on the previously prepared gas diffusion fiber layer and dried in an argon stream at 80° C., then the temperature was raised to 340° C. to thereby prepare a gas diffusion layer CC-U comprised of a stacked gas diffusion fiber layer and micropore layer.

(136) As a comparison, a gas diffusion layer CC of carbon cloth not coated with a micropore layer was also prepared.

(137) Each of the carbon black V and W of Table 13 was dispersed in a hydrogen hexachloroplatinate aqueous solution as a catalyst-carrying carbon material. While holding this at 50° C. and stirring, hydrogen peroxide was added, then an Na.sub.2S.sub.2O.sub.4 aqueous solution was added to obtain a catalyst precursor. Each catalyst precursor was filtered, rinsed, dried, then reduced in a 100% H2 stream at 300° C. for 3 hours to thereby prepare two types of Pt catalysts comprised of the catalyst-carrying carbon material carrying 20 mass % of Pt.

(138) These two types were placed in containers. A 5% Nafion solution (made by Aldrich) was added to each of these in an argon stream to give a mass of the Nafion solid of two times the mass of the platinum catalyst, this was lightly stirred, then the catalyst was crushed by ultrasonic waves, and butyl acetate was added while stirring to give a solid concentration of the Pt catalyst and Nafion combined of 6 mass % so as to thereby prepare two types of catalyst slurry.

(139) The carbon black U shown in Table 13 was placed in a separate container, butyl acetate was added to give carbon black of 6 mass %, and the carbon black was crushed by ultrasonic waves to prepare a carbon black slurry.

(140) Each of the two types of the above prepared catalyst slurries and the carbon material slurry were mixed by a mass ratio of 8:2, then sufficiently stirred to prepare two types of catalyst layer slurry.

(141) Each of the two types of catalyst layer slurry was spray coated on a gas diffusion layer CC-U and dried at 80° C. in an argon stream for 1 hour to prepare two types of gas diffusion electrodes of the present invention containing the carbon black V and W as the catalyst-carrying carbon material and the carbon black U as the gas-diffusing carbon material.

(142) Further, for comparison, gas diffusion electrodes comprised of carbon cloth CC not coated with a micropore layer and catalyst layers containing the carbon black W as the catalyst-carrying carbon material and the carbon black U as the gas-diffusing carbon material were obtained as comparative examples.

(143) Note that the spray and other conditions were set so that the electrodes had amounts of platinum used of 0.10 mg/cm.sup.2. The amounts of platinum used were found by measuring the dry masses of the electrodes before and after spray coating and calculating the amounts from the difference.

(144) Further, two 2.5 cm square pieces were cut out from each of the obtained solid polymer type fuel cell electrodes, two of the same type of electrodes were used to sandwich an electrolyte film (Nafion 112), and the assemblies were hot pressed at 130° C. by a total pressure of 0.625 t for 3 minutes to prepare the MEA46 to MEA48.

(145) The obtained MEAs were attached to fuel cell measurement devices and measured for cell performances. The cell performances were measured by changing the voltage between cell terminals in stages from the open voltage (usually 0.9V to 1.0V) to 0.2V and measuring the current density when voltages of 0.8V and 0.5V were flowing between the cell terminals.

(146) As the gas, the cathode was supplied with air and the anode with pure hydrogen to give rates of utilization of 50% and 80%. These gases were adjusted in pressure to 0.1 MPa by a back pressure valve provided downstream from the cell. The cell temperature was set at 80° C., and the supplied air and pure hydrogen were bubbled through distilled water warmed to 80° C. and 90° C. to wet them.

(147) Table 14 shows the obtained three types of MEA and the results of their cell performance. As shown in Table 14, the MEAs of the present invention exhibited superior characteristics.

(148) In particular, the MEA46 and MEA47 having micropore layers containing carbon black with an amount of adsorption of water vapor at 25° C. and a relative humidity of 90% of 100 ml/g or less as main ingredients in the gas diffusion layers exhibited superior characteristics compared with MEA48 without the micropore layer.

(149) Among these, the MEA47 including a catalyst-carrying carbon material having an amount of adsorption of water vapor at 25° C. and a relative humidity of 90% of 100 ml/g or more in the catalyst layer exhibited extremely superior performance.

(150) TABLE-US-00013 TABLE 14 Current density Type of catalyst- Type of gas- (mA/cm.sup.2) Type of gas carrying carbon diffusing carbon Cell Cell Type of diffusion material contained material contained voltage voltage MEA layer in catalyst layer in catalyst layer 0.8 V 0.5 V Remarks MEA46 CC-U V U 153 1260 Ex. MEA47 CC-U W U 178 1330 MEA48 CC W U  68 1100

Example 9

(151) A carbon cloth (made by ElectroChem, EC-CC1-060) was prepared, dipped in a Teflon dispersion diluted to 5%, then dried and further raised in temperature in an argon stream to 320 to 350° C. to prepare a gas diffusion fiber layer.

(152) Further, 99 g of ethanol was added to 1 g of each the two types of carbon black of Table 15, then the carbon materials were crushed by a ball mill to prepare primary dispersions.

(153) After this, 0.833 g of a 30% Teflon dispersion was added a little at a time to each primary dispersion to prepare a micropore layer slurry.

(154) Each slurry was spray coated on one surface of a previously prepared gas diffusion fiber layer and dried in an argon stream at 80° C., then the temperature was raised to 320 to 350° C. to thereby prepare two types of gas diffusion layers comprised of stacked gas diffusion fiber layers and micropore layers.

(155) Table 15 shows the physical properties of the carbon black used for the micropore layers all together.

(156) TABLE-US-00014 TABLE 15 Amount of Nitrogen DBP adsorption Carbon black adsorption oil absorption of water used for specific area (Y) (X) vapor micropore layer m.sup.2/g ml/100 g X/Y ml/g AA 78 160 2.05 4.5 AB 219 221 1.01 62

(157) For the catalyst, a platinum catalyst having the activated carbon with the physical properties shown in Table 16 was used as the carrier. This activated carbon was processed as follows to carry the platinum fine particles.

(158) 150 ml of distilled water in a flask was charged with 0.5 g of activated carbon as the catalyst carrier and hexachloroplatinic (IV) acid to give a mass ratio of the platinum to the carrier of ratio 1:1, the mixture was sufficiently dispersed by ultrasonic waves, then the mixture was held in a oil bath in the boiling state and a reducing agent comprised of formaldehyde was added dropwise at a constant speed.

(159) After finishing the dropping, the mixture was separated by filtration by a membrane filter, then the recovered matter was again dispersed in distilled water and separated by filtration. This operation was repeated three times. The result was dried in vacuo at 100° C. to obtain a catalyst for an electrode. The amount of platinum carried on the catalyst was quantitatively analyzed by dissolving this in hot aqua regia and measuring it by plasma spectrometry, whereupon it was found to be 50 mass %.

(160) The Pt particle size of the obtained platinum catalyst is shown in Table 16. The particle size of the Pt fine particles was estimated using the method of Scherrer from the half value of the (111) peak of platinum obtained by an X-ray diffraction device (made by Rigaku Corporation, Model RAD-3C).

(161) The activated carbon defined by the present invention, despite having a high density of 50 mass % compared with other activated carbon or carbon black, had a particle size of 2.0 nm or less, so clearly has a smaller Pt particle size and is deemed more excellent as a carrier.

(162) TABLE-US-00015 TABLE 16 Micropore Oxygen DBP oil Pt particle Carbon S.sub.EST S.sub.micro/ diameter content absorption size material m.sup.2/g S.sub.total nm mass % ml/100 g nm Activated 2310 0.85 1.32 3.5 70 1.6 carbon

(163) A 5% Nafion solution (made by Aldrich) was added to this platinum catalyst in an argon stream to give a mass of the Nafion solid of two times the mass of the platinum catalyst, this was lightly stirred, then the catalyst was crushed by ultrasonic waves, and butyl acetate was added while stirring to give a solid concentration of the Pt catalyst and Nafion combined of 6 mass % so as to prepare the catalyst slurry.

(164) The carbon material AA shown in Table 16 was placed in a separate container, butyl acetate was added to give a carbon material of 6 mass %, and the carbon material was crushed by ultrasonic waves to prepare a carbon material slurry. The above prepared catalyst slurry and carbon material slurry were mixed by a mass ratio of 8:2, then sufficiently stirred to prepare a catalyst layer slurry.

(165) The catalyst layer slurry was spray coated on the micropore layer sides of the above two types of the gas diffusion layers and dried at 80° C. in an argon stream for 1 hour to prepare two types of solid polymer type fuel cell electrodes of the present invention.

(166) Note that the spray and other conditions were set so that the electrodes had amounts of platinum used of 0.10 mg/cm.sup.2. The amounts of platinum used were found by measuring the dry masses of the electrodes before and after spray coating and calculating the amounts from the difference.

(167) Further, two 2.5 cm square pieces were cut out from each of the obtained solid polymer type fuel cell electrodes, two of the same type of electrodes were used to sandwich an electrolyte film (Nafion 112) so that the catalyst layers contacted the electrolyte film, and the assemblies were hot pressed at 130° C. by a total pressure of 0.625 t for 3 minutes to prepare the MEA49 and MEA50.

(168) The obtained HEAs were attached to fuel cell measurement devices and measured for cell performances.

(169) The cell performances were measured by changing the voltage between cell terminals in stages from the open voltage (usually 0.9V to 1.0V) to 0.2V and measuring the current density when voltages of 0.8V and 0.5V were flowing between the cell terminals.

(170) As the gas, the cathode was supplied with air and the anode with pure hydrogen to give rates of utilization of 50% and 80%. These gases were adjusted in pressure to 0.1 MPa by a back pressure valve provided downstream from the cell. The cell temperature was set at BOOC, and the supplied air and pure hydrogen were bubbled through distilled water warmed to 80° C. and 90° C. to wet them.

(171) Table 17 shows the results of the cell performance of the obtained MEA49 and MEA50. The MEA49 and MEA50 provided with the micropore layers exhibited excellent current density of the cell voltage of 0.8V and 0.5V.

(172) In particular, the MEA49 using carbon black A having an amount of adsorption of water vapor of 100 ml/g or less and a ratio X/Y of the DBP oil absorption X and the nitrogen adsorption specific area Y of 1.0 or more for the intermediate layer exhibited extremely superior cell performance.

(173) TABLE-US-00016 TABLE 17 Carbon Current density (mA/cm.sup.2) Type of black used for Cell Cell MEA micropore layer voltage 0.8 V voltage 0.5 V Remarks MEA49 AA 170 1310 Example MEA50 AB 160 1170

Example 10

(174) Carbon cloth (made by ElectroChem, EC-CC1-060) was prepared, then dipped in a Teflon dispersion diluted to 5%, then dried and was further raised in temperature in an argon stream to 340° C. to prepare a gas diffusion fiber layer.

(175) Further, 99 g of ethanol was added to each of the carbon materials AC, AD, and AE shown in Table 18, then the carbon material was crushed by a ball mill to obtain a primary dispersion. After this, while stirring the primary dispersion, 0.833 g of a 30% Teflon dispersion was added dropwise bit by bit to prepare a micropore layer slurry.

(176) Each slurry was spray coated on one surface of a previously prepared gas diffusion fiber layer and dried in an argon stream at 80° C., then the temperature was raised to 340° C. to thereby prepare three types of gas diffusion layers comprised of stacked gas diffusion fiber layers and micropore layers.

(177) TABLE-US-00017 TABLE 18 Nitrogen Amount of Volume of adsorption DBP oil adsorption Type of pores of 2 nm specific area absorption of water carbon or less size (Y) (X) vapor material ml/g m.sup.2/g ml/100 g X/Y ml/g AC 0.01 72 170 2.36 3.86 AD 0.05 227 219 0.96 59.8 AE 0.01 40 159 3.98 3.56 AF 0.39 1582 515 0.33 158

(178) A catalyst carrier comprised of the carbon material AF shown in Table 18 was dispersed in water. While holding this at 50° C. and stirring, a hydrogen hexachloroplatinate aqueous solution and a formaldehyde aqueous solution were added to obtain a catalyst precursor.

(179) The catalyst precursor was filtered, rinsed, and dried, then reduced in a 100% H.sub.2 stream at 300° C. for 3 hours to prepare the Pt catalyst comprised of the catalyst-carrying carbon material carrying 20 mass % of Pt.

(180) The Pt particle size of the Pt catalyst was 1.8 nm. The crystal particle size was estimated by the Scherrer method from the half value of the (111) peak of platinum obtained by an X-ray diffraction device (made by Rigaku Corporation, Model RAD-3C).

(181) A 5% Nafion solution (made by Aldrich) was added to this catalyst in an argon stream to give a mass of the Nafion solid of two times the mass of the platinum catalyst, this was lightly stirred, then the catalyst was crushed by ultrasonic waves, and butyl acetate was added while stirring to give a solid concentration of the Pt catalyst and Nafion combined of 6 mass % so as to prepare the catalyst slurry.

(182) The carbon material shown in Table 18 was placed in a separate container, butyl acetate was added to give a carbon material of 6 mass %, and the carbon material was crushed by ultrasonic waves to prepare a carbon material slurry.

(183) The above prepared catalyst slurry and carbon material slurry were mixed by a mass ratio of 8:2, then sufficiently stirred to prepare a catalyst layer slurry.

(184) The catalyst layer slurry was spray coated on the micropore layer sides of the above three types of the above gas diffusion layers and dried at 80° C. in an argon stream for 1 hour to prepare three types of solid polymer type fuel cell electrodes having the carbon material AC contained in the catalyst layers as catalyst-carrying carbon materials.

(185) Note that the spray and other conditions were set so that the electrodes had amounts of platinum used of 0.10 mg/cm.sup.2.

(186) The amounts of platinum used were found by measuring the dry masses of the electrodes before and after spray coating and calculating the amounts from the difference.

(187) Further, two 2.5 cm square pieces were cut out from each of the obtained solid polymer type fuel cell electrodes, two of the same type of electrodes were used to sandwich an electrolyte film (Nafion 112) so that the catalyst layers contacted the electrolyte film, and the assemblies were hot pressed at 130° C. by a total pressure of 0.625 t for 3 minutes to prepare three types of MEA51 to MEA53.

(188) The obtained three types of MEA were attached to fuel cell measurement devices and measured for cell performances. The cell performances were measured by changing the voltage between cell terminals in stages from the open voltage (usually 0.9V to 1.0V) to 0.2V and measuring the current density when voltages of 0.9V and 0.5V were flowing between the cell terminals.

(189) As the gas, the cathode was supplied with air and the anode with pure hydrogen to give rates of utilization of 50% and 80%. These gases were adjusted in pressure to 0.1 MPa by a back pressure valve provided downstream from the cell. The cell temperature was set at 80° C., and the supplied air and pure hydrogen were bubbled through distilled water warmed to 80° C. and 90° C. to wet them.

(190) Table 19 shows the results of the cell performance of the three types of MEAs obtained. As a result, the MEAs of the present invention exhibited excellent cell characteristics.

(191) Among these, the MEA51 and MEA53 using carbon materials AC and AE with amounts of adsorption of water vapor of 50 ml/g or less and ratios X/Y of DBP oil absorption X and nitrogen adsorption specific area Y of 1.5 or more for the micropore layers exhibited superior cell performance.

(192) TABLE-US-00018 TABLE 19 Type of carbon Current density Type of material used for Cell Cell MEA micropore layer voltage 0.8 V voltage 0.5 V Remarks MEA51 AC 174 1310 Example MEA52 AD 165 1170 MEA53 AE 172 1307

INDUSTRIAL, APPLICABILITY

(193) As explained above, a fuel cell using the catalyst layer defined in the present invention for at least the cathode is superior in gas diffusion, electron conduction, proton conduction, and wet management in the catalyst layer and is improved in rate of utilization of the catalyst ingredient, so the amount of the platinum or other precious metal used for the catalyst can be reduced, that is, a fuel cell achieving both lower cost and improved output characteristic can be provided.

(194) Further, according to the present invention, since the characteristics of the carbon black used for the gas diffusion layer are suitable, the inside of the catalyst layer is sufficiently wetted, the produced drops of water etc. are prevented from blocking the gas diffusion paths, and a higher output characteristic can be realized.

(195) Therefore, the present invention has great industrial applicability.