JP5345865B2 - Method for producing air electrode for solid oxide fuel cell and solid oxide fuel cell - Google Patents

Description

  The present invention relates to a method for manufacturing an air electrode for a solid oxide fuel cell containing either praseodymium or terbium, and a solid oxide fuel cell including an air electrode manufactured by the manufacturing method.

  There is a growing interest in solid oxide fuel cells using zirconia-based oxygen ion conductors, which are excellent electrolyte materials. In particular, from the viewpoint of effective use of energy, solid fuel cells have essentially high energy conversion efficiency because they are not restricted by Carnot efficiency, and have excellent features such as good environmental conservation. have.

  The solid oxide fuel cell initially had a high operating temperature of 900 to 1000 ° C., and all members were made of ceramic. For this reason, it was not easy to reduce the manufacturing cost of the cell stack. Here, if the operating temperature can be lowered to 800 ° C. or less, a heat-resistant alloy material can be used for the interconnector, and the manufacturing cost can be reduced. However, as the operating temperature decreases, the electrochemical resistance at the air electrode, that is, the overvoltage, suddenly increases and the output voltage decreases.

In order to solve the problem of the air electrode due to such a decrease in operating temperature, La _1-X Sr _X Fe _1-Y Co _Y O ₃ (LSFC: X = 0.1 to 0.3, Y = 0.1 ~0.6, X + Y <0.7) , La 1-X Sr X CoO 3 (X = 0.1~0.5), LaNi 1-X Fe X O 3 (LNF: X = 0.3~0 There is a technique using a perovskite type metal oxide (perovskite type oxide) having high electrode activity (electrochemical reaction performance). These materials are perovskite oxides containing La and Sr at the A site and Ni, Co, and Fe at the B site. Some of the A sites contain La and Ca. These materials are suitable for an air electrode for low temperature operation.

However, since the air electrode is manufactured by firing in contact with an electrolyte containing zirconia, an insulator such as La ₂ Zr ₂ O ₇ is generated in a portion in contact with the electrolyte, and this product is This is one of the causes of deteriorating characteristics in the air electrode. In order to prevent this problem, a ceria layer made of a cerium oxide (ceria compound) added with rare earths such as Ce _0.9 Gd _0.1 O ₂ and Ce _0.8 Sm _0.2 O ₂ is provided between the air electrode and the electrolyte. A method of breaking the contact between the pole-side perovskite oxide and the electrolyte-side zirconia has been studied (Non-Patent Document 1). The ceria layer thus provided has high oxygen ion conductivity, and a reaction that generates an insulator with the perovskite oxide is less likely to occur.

  In addition, in order to further improve the low-temperature characteristics of a solid oxide fuel cell using an air electrode composed of the above-mentioned materials, a method of providing a mixture of perovskite oxide particles and ceria compounds in the vicinity of an electrolyte is known. (See Non-Patent Document 2). By forming the air electrode in a state where the perovskite oxide powder (powder) and the fine powder of the ceria compound are mixed, the active area of the electrode generated at the junction between the electrolyte and the air electrode is increased, and the electrode It is possible to reduce the interface resistance.

The ceria compound is suitable as a material to be mixed with the air electrode because the reaction deterioration with the Co-based and Fe-based air electrode materials described above hardly occurs. In the air electrode composed of this mixture, the perovskite oxide particles are covered with ceria compound particles, and the direct contact between the perovskite oxide material and the zirconia material constituting the electrolyte is suppressed. In addition, formation of reaction products with harmful zirconia such as La ₂ Zr ₂ O ₇ is suppressed.

  In addition, the use of cerium oxide to which praseodymium (Pr) or terbium (Tb) is added as the above-mentioned ceria compound can be expected to improve the characteristics of the air electrode.

A. Mai, et al., "Ferrite-based perovskites as cathode materials for anode-suported solid oxide fuel cells Part II influence of the CGO recycling", Solid State Ionics 177, pp.2103-2107, 2006. Y. Matsuzaki, et al., "Electrochemical properties of reduced-temperature SOFCs with mixed ionic-electronic conductors in electrodes and / or ables", Solid State Ionics 152-153, pp.463-468, 2002.

  However, when Pr or the like is added, if this addition amount exceeds 5 at%, the thermal expansion coefficient becomes very large, and the cell may be cracked or peeled off due to a temperature change caused by operation stop. There is a problem that occurs. It can be expected to improve the characteristics of the air electrode by adding more Pr and Tb, but as described above, problems such as cracking and peeling occur due to an increase in the addition amount. There is a limit to improving the characteristics of the air electrode.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to improve the characteristics of the air electrode while suppressing the occurrence of problems such as cracks and peeling. .

The method for producing an air electrode for a solid oxide fuel cell according to the present invention includes a first step of forming a porous air electrode composed of a sintered body containing a metal oxide, praseodymium, The second step of impregnating the porous pores of the air electrode with a liquid containing two or more metal elements including any of terbium, and the air electrode impregnated with the liquid is heated to contain the liquid . the oxide which is composed of metal elements comprising at least a third step of introducing the air electrode, the liquid comprises a cell potassium in addition to any of praseodymium and terbium, the total content of metal elements contained in the liquid When 1, or praseodymium and terbium in the range of ratio of 0.02 to 1.0, in addition, liquid, samarium, gadolinium, and the selected rare earth source from among yttrium Hints in the range of ratio of 0-0.8 and the sum of either the rare earth element praseodymium and terbium, the range of ratio of 0.05 to 1.0.

  The solid oxide fuel cell according to the present invention includes an air electrode manufactured by the above-described method for manufacturing an air electrode for a solid oxide fuel cell.

  As described above, according to the present invention, a solution containing two or more metal elements containing either praseodymium or terbium in a porous air electrode composed of a sintered body containing a metal oxide. As a result of impregnating the air electrode, the characteristics of the air electrode can be improved while suppressing the occurrence of problems such as cracks and peeling.

It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is process drawing for demonstrating the manufacturing method of the air electrode for solid oxide fuel cells in embodiment of this invention. It is the top view and side view which show the structure of a solid oxide fuel cell. It is sectional drawing which shows the structure of a solid oxide fuel cell.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, the first embodiment of the present invention will be described. 1A to 1G are process diagrams for explaining a method of manufacturing an air electrode for a solid oxide fuel cell according to an embodiment of the present invention. First, as shown in FIG. 1A, Sc ₂ O ₃ , Al ₂ O ₃ added zirconia (0.89ZrO ₂ −0.10 Sc ₂ O ₃ −0) formed into a sheet by a well-known doctor blade method and fired. Electrolyte substrate 101 made of .01Al ₂ O ₃ : SASZ) is prepared. The electrolyte substrate 101 is formed to a thickness of 0.2 mm.

Next, a mixture of zirconia powder (40 wt%) with an average particle diameter of about 0.3 μm added with 8 mol% Y ₂ O ₃ and NiO powder (60 wt%) with an average particle diameter of 0.8 μm was mixed. A slurry of powder is prepared, and this slurry is applied to one surface of the above-described electrolyte substrate 101 by a well-known screen printing method to form a fuel electrode coating film 102. In addition, a Pt paste is applied onto the fuel electrode coating film 102, and a current collector (not shown) made of Pt mesh is disposed thereon, and these are subjected to heat treatment conditions of 1400 ° C. for 4 hours. As shown in FIG. 1B, the fuel electrode 103 having a thickness of 60 μm and made of a sintered body of the mixed powder is formed. The fuel electrode 103 is a sintered body of the powder described above, and is formed in a porous state having a plurality of pores present between the respective sintered body particles.

Next, a slurry of Ce _0.90 Gd _0.10 O ₂ (GDC) powder having an average particle size of 0.2 μm is prepared, and this slurry is applied to the other surface of the electrolyte substrate 101 by the screen printing method. A one-layer coating film is formed. In addition, a slurry of LaNi _0.6 Fe _0.4 O ₃ (LNF) powder having an average particle size of 1.0 μm is prepared, and this slurry is applied on the first layer coating film by the screen printing method and dried. The second layer coating film is formed. As a result, the air electrode coating film 104 is formed on the other surface of the electrolyte substrate 101 as shown in FIG. 1C. Note that any one of LSC, LSCF, LSF, LSM, and SSC may be used instead of LNF.

  Next, a Pt paste is applied on the air electrode coating film 104, a Pt mesh current collector (not shown) is placed thereon, and the electrolyte substrate 101 including these is baked under heat treatment conditions of 1150 ° C. for 2 hours. Then, as shown in FIG. 1D, the air electrode 105 made of a sintered body of the powder is formed. The air electrode 105 according to the first embodiment is a second layer made of LNF formed on the first layer made of GDC disposed on the electrolyte substrate 101 side and the first layer opposite to the electrolyte substrate 101. It is composed of layers. The air electrode 105 is a powder sintered body described above, and is formed in a porous state having a plurality of pores present between the respective sintered body particles. As a result, a single cell in which the fuel electrode 103 is formed on one surface of the electrolyte substrate 101 and the air electrode 105 is formed on the other surface is obtained.

  Next, as shown in FIG. 1E, the exposed surface of the electrolyte substrate 101 other than the fuel electrode 103 and the fuel electrode 103 is covered with a mask layer 111. These are immersed in a solution (impregnating solution) containing Pr or Tb inside a container that is decompressed to a predetermined pressure. For example, a solution in which Gd and Ce are dissolved as an organometallic compound in addition to Pr may be used. Moreover, you may use the aqueous solution which melt | dissolved the compound (salt) with the acid of these metals (element) and neutralized to some extent. Moreover, you may make it use the solution of the said organic acid of a metal.

  Next, by increasing the internal pressure of the container to atmospheric pressure, for example, the air electrode 105a impregnated with the above solution is formed in the plurality of porous pores of the air electrode 105 as shown in FIG. 1F. . In the above description, the impregnation is performed under reduced pressure, but the present invention is not limited to this. When the air electrode 105 is as thin as about 100 μm, it is sufficiently impregnated by dropping the solution onto the air electrode 105.

  After impregnating the solution as described above, this single cell (air electrode 105a) is dried, and then the dried single cell is subjected to heat treatment at 700 ° C. for 4 hours in the atmosphere. As a result, the corner elements contained in the impregnating liquid impregnated are oxidized, and an oxide containing Pr, Gd, and Ce is introduced (arranged) into a plurality of porous pores as shown in FIG. 1G. ) To obtain a state in which the impregnated air electrode 115 in which the interface resistance value and the like are in a desired state (value) is formed. In addition, the temperature of heat processing should just be the range of 800-900 degreeC. Further, the mask layer 111 is preferably removed before heat treatment.

  By manufacturing as described above, an oxide containing Pr, Gd, and Ce that is not included in the state where the sintered body is formed can be introduced into the impregnated air electrode 115 as a constituent material of the air electrode. According to the solid oxide fuel cell using the impregnated air electrode 115 obtained in this way, even when more Pr and Tb are added, the occurrence of cracks and delamination can be suppressed. The characteristics of the pole can be further improved.

  Next, the characteristic measurement of the impregnated air electrode 115 produced by the manufacturing method described above will be described. Hereinafter, a solid oxide fuel cell is assembled using the single cell described above, and measurement of the assembled solid oxide fuel cell will be described.

  First, the configuration of the solid oxide fuel cell will be described. In the solid oxide fuel cell to be assembled, as shown in FIG. 2A, the fuel electrode 201 is disposed on one side of the electrolyte substrate 202 serving as a support substrate, the air electrode 203 is disposed on the other side of the electrolyte substrate 202, and the electrolyte 202 A single cell having a reference electrode 204 on the air electrode side is used. The reference electrode 204 is formed in the same manner as the air electrode 203. Further, a solid oxide fuel cell as shown in the cross-sectional view of FIG. The solid oxide fuel cell shown in FIG. 2B will be described. The single-cell fuel electrode 201 is provided with a current collector layer 211 made of platinum mesh, and the air electrode 203 is also made of a current collector layer made of platinum mesh. 212 is provided.

  Further, a fuel gas exhaust pipe 213 is fixed to the periphery of the electrolyte substrate 202 on the side of the fuel electrode 201 of the single cell via a ring 214, and a fuel gas supply pipe 215 is provided inside the fuel gas exhaust pipe 213. Is arranged. On the other hand, on the air electrode 203 side of the single cell, an oxidant gas exhaust pipe 216 is fixed to the periphery of the electrolyte substrate 202 via a ring 217, and an oxidant gas supply is provided inside the oxidant gas exhaust pipe 216. A pipe 218 is arranged. The ring 214 and the ring 217 are made of glass having a softening point near the test temperature.

  Note that the reference electrode 204 is disposed in a region outside the exhaust pipe 216. In addition, a terminal wire 219 made of platinum is connected to the current collector layer 211, and a terminal wire 220 made of platinum is connected to the current collector layer 212. A terminal wire 221 made of platinum is also connected to the reference electrode 204. Note that the solid oxide fuel cell having the above-described configuration is disposed inside the electric furnace 230.

In the solid oxide fuel cell configured as described above, the fuel gas is supplied from the fuel gas supply pipe 215 to the fuel electrode 201, and the oxidant gas is supplied from the oxidant gas supply pipe 218 to the air electrode 203. Then, test the power generation operation. This power generation operation is performed in the electric furnace 230 while being heated to 700 ° C. Here, hydrogen (humidified H ₂ ) added with 3 vol% of water vapor is used as the fuel gas. On the other hand, air (oxygen: nitrogen = 1: 4, volume ratio) is used as the oxidant gas.

  In the test, the interfacial resistance, which is an index of electrode performance, is measured by the AC impedance method. At the time of measurement, it is performed under the condition of the open circuit voltage, a minute AC signal is applied between the air electrode and the fuel electrode, and the minute potential change between the air electrode and the reference electrode (fuel electrode) is measured. The impedance is obtained from the result (3-terminal AC impedance method).

  Next, sample cells (# 1-1-0 to # 1-1-8, # 1-2-4 to # 1-2-6, # 1-3-4) manufactured by the manufacturing method according to the present embodiment ~ # 1-3-6, # 1-4-1 ~ # 1-4-8, # 1-5-4 ~ # 1-5-6, # 1-6-4 ~ # 1-6-6) The measurement results will be described. Sample cell # 1-1-0 is a sample prepared without impregnating the impregnating liquid into the air electrode, and serves as a reference sample cell.

  The sample cells (# 1-1-1 to # 1-1-8) were produced by impregnating an air electrode with an impregnating solution containing Pr, Gd, and Ce. The sample cells (# 1-2-4 to # 1-2-6) were prepared by impregnating an air electrode with an impregnating solution containing Pr, Sm, and Ce. The sample cells (# 1-3-4 to # 1-3-6) were prepared by impregnating an air electrode with an impregnation solution containing Pr, Y, and Ce. The sample cells (# 1-4-1 to # 1-4-8) are produced by impregnating an air electrode with an impregnating liquid containing Tb, Gd, and Ce. The sample cells (# 1-5-4 to # 1-5-6) are produced by impregnating an air electrode with an impregnating liquid containing Tb, Sm, and Ce. The sample cells (# 1-6-4 to # 1-6-6) were prepared by impregnating an air electrode with an impregnating solution containing Tb, Y, and Ce.

  When the above-described measurement is performed in these sample cells, as shown in Table 1 below, any sample cell (# 1-1-1 to ##) is compared with the comparative sample cell (# 1-1-0). 1-1-8, # 1-2-4 to # 1-2-6, # 1-3-4 to # 1-3-6, # 1-4-1 to # 1-4-8, # 1 In -5-4 to # 1-5-6 and # 1-6-4 to # 1-6-6), good results were obtained with low interface resistance. In the table, “Gd0.00” in the column of “metal composition in the impregnating solution” indicates that the impregnating solution contains no Gd.

[Embodiment 2]
Next, a second embodiment of the present invention will be described. In the present embodiment, the first layer of the air electrode in the first embodiment is configured from a mixture of GDC and LNF, and other configurations are the same as in the first embodiment. is there.

  Next, sample cells (# 2-1-0 to # 2-1-8, # 2-2-4 to # 2-2-6, # 2-3-4) manufactured by the manufacturing method according to the present embodiment ~ # 2-3-6, # 2-4-1 ~ # 2-4-8, # 2-5-4 ~ # 2-5-6, # 2-6-4 ~ # 2-6-6) The measurement results will be described. Sample cell # 2-1-0 is a sample prepared without impregnating the impregnating liquid into the air electrode, and serves as a reference sample cell.

  The sample cells (# 2-1-1 to # 2-1-8) were produced by impregnating an air electrode with an impregnating solution containing Pr, Gd, and Ce. The sample cells (# 2-2-4 to # 2-2-6) were prepared by impregnating an air electrode with an impregnating solution containing Pr, Sm, and Ce. The sample cells (# 2-3-4 to # 2-3-6) were prepared by impregnating the air electrode with an impregnation liquid containing Pr, Y, and Ce. The sample cells (# 2-4-1 to # 2-4-8) were prepared by impregnating an air electrode with an impregnating solution containing Tb, Gd, and Ce. The sample cells (# 2-5-4 to # 2-5-6) are prepared by impregnating an air electrode with an impregnating solution containing Tb, Sm, and Ce. The sample cells (# 2-6-4 to # 2-6-6) were prepared by impregnating an air electrode with an impregnating solution containing Tb, Y, and Ce.

  When the same measurement as in the first embodiment is performed on these sample cells, as shown in Table 3 below, any sample cell (# 2-1-0) is compared with the comparative sample cell (# 2-1-0). 2-1-1 to # 2-1-8, # 2-2-4 to # 2-2-6, # 2-3-4 to # 2-3-6, # 2-4-1 to # 2 In -4-8, # 2-5-4 to # 2-5-6, and # 2-6-4 to # 2-6-6), good results were obtained with low interface resistance. In the table, “Gd0.00” in the column of “metal composition in the impregnating solution” indicates that the impregnating solution contains no Gd.

[Embodiment 3]
Next, a third embodiment of the present invention will be described. In the present embodiment, the second layer of the air electrode in the first embodiment described above is made of La _0.8 Sr _0.2 Fe _0.8 Co _0.2 O ₃ (LSCF) instead of LNF. The configuration is the same as in the first embodiment.

  Next, the measurement results of the sample cells (# 3-1-0 to # 3-1-6) manufactured by the manufacturing method according to the present embodiment will be described. Sample cell # 3-1-0 is a sample prepared without impregnating the impregnating liquid into the air electrode, and serves as a reference sample cell. The sample cells (# 3-1-1 to # 3-1-3) are prepared by impregnating an air electrode with an impregnating solution containing Pr, Gd, and Ce. The sample cells (# 3-1-4 to # 3-1-6) were prepared by impregnating an air electrode with an impregnating solution containing Tb, Gd, and Ce.

  When the same measurement as in the first embodiment is performed on these sample cells, as shown in Table 3 below, any sample cell (# 3-1-0) is compared with the comparative sample cell (# 3-1-0). Also in 3-1-1 to # 3-1-6), the interface resistance is low and good results are obtained.

[Embodiment 4]
Next, a fourth embodiment of the present invention will be described. In the present embodiment, the air electrode in the first embodiment described above has a single-layer structure composed of La _0.8 Sr _0.2 MnO ₃ (LSM), and other configurations are the same as in the first embodiment. It is.

  Next, measurement results of the sample cells (# 3-2-0 to # 3-2-6) manufactured by the manufacturing method according to the present embodiment will be described. Sample cell # 3-2-0 is a sample prepared without impregnating the impregnating liquid into the air electrode, and serves as a reference sample cell. The sample cells (# 3-2-1 to # 3-2-3) are produced by impregnating an air electrode with an impregnation liquid containing Pr, Gd, and Ce. The sample cells (# 3-2-4 to # 3-2-6) are prepared by impregnating an air electrode with an impregnating liquid containing Tb, Gd, and Ce.

  When the same measurement as that of the first embodiment described above is performed in these sample cells, as shown in Table 4 below, any sample cell (# Also in 3-2-1 to # 3-2-6), good results have been obtained with low interface resistance.

[Embodiment 5]
Next, a fifth embodiment of the present invention will be described. In the present embodiment, the second layer of the air electrode in the first embodiment described above is configured from a mixture of LSCF and GDC, and the other configurations are the same as those in the first embodiment. is there.

  Next, the measurement results of the sample cells (# 4-1-0 to # 4-1-6) manufactured by the manufacturing method according to the present embodiment will be described. Sample cell # 4-1-0 is a sample prepared without impregnating the impregnating solution into the air electrode, and serves as a reference sample cell. The sample cells (# 4-1-1 to # 4-1-3) are manufactured by impregnating an air electrode with an impregnating solution containing Pr, Gd, and Ce. The sample cells (# 4-1-4 to # 4-1-6) were produced by impregnating an air electrode with an impregnating solution containing Tb, Gd, and Ce.

  When the same measurement as in the first embodiment is performed in these sample cells, as shown in Table 5 below, any sample cell (# 4-1-1 to # 4-1-6) also show good results with low interface resistance.

[Embodiment 6]
Next, a sixth embodiment of the present invention will be described. In the present embodiment, the air electrode in the first embodiment described above has a one-layer structure composed of LSM and YSZ, and other configurations are the same as those in the first embodiment.

  Next, the measurement results of the sample cells (# 5-2-0 to # 5-2-6) manufactured by the manufacturing method according to the present embodiment will be described. Sample cell # 5-2-0 is a sample prepared without impregnating the impregnating liquid into the air electrode, and serves as a reference sample cell. The sample cells (# 5-2-1 to # 5-2-3) were prepared by impregnating an air electrode with an impregnation liquid containing Pr, Gd, and Ce. The sample cells (# 5-2-4 to # 5-2-6) are prepared by impregnating an air electrode with an impregnating liquid containing Tb, Gd, and Ce. The composition ratio of LSM and YSZ is 1: 1.

  When the same measurement as in the first embodiment is performed in these sample cells, as shown in Table 6 below, any sample cell (# 5-2-0) is compared with the comparative sample cell (# 5-2-0). Also in 5-2-1 to # 5-2-6), good results were obtained with low interface resistance.

  From the above, with respect to the total content of either praseodymium or terbium and rare earth elements and cerium contained in the impregnating solution, either praseodymium or terbium is 0.02 to 1.0, and rare earth elements are 0 to 0.0. 8. It can be seen that the sum of either praseodymium or terbium and the rare earth element may be in the range of 0.05 to 1.0. Note that the air electrode formed by impregnation of the impregnating liquid in the above-described embodiment is also considered to be composed of the composition ratio of each element of the impregnating liquid described above.

  In addition, the particle diameter mentioned above is an average particle diameter obtained from the measurement of the light intensity distribution pattern by the well-known laser diffraction scattering method. For example, the particle size can be measured by using a laser diffraction / scattering particle size distribution measuring device LA-910 manufactured by HORIBA, Ltd.

  DESCRIPTION OF SYMBOLS 101 ... Electrolyte substrate, 102 ... Fuel electrode coating film, 103 ... Fuel electrode, 104 ... Air electrode coating film, 105 ... Air electrode, 105a ... Air electrode, 111 ... Mask layer, 115 ... Impregnation air electrode.

Claims (2)

In the method for producing an air electrode of a solid oxide fuel cell comprising a fuel electrode, an electrolyte, and an air electrode,
A first step of forming the air electrode in a porous state composed of a sintered body containing a metal oxide;
A second step of impregnating the porous pores of the air electrode with a liquid containing two or more metal elements including either praseodymium and terbium;
And at least a third step of introducing an oxide composed of a metal element contained in the liquid into the air electrode by heating the air electrode impregnated with the liquid,
It said liquid includes a cell potassium in addition to any of praseodymium and terbium,
When the total content of metal elements contained in the liquid is 1 , either praseodymium or terbium is in the range of a ratio of 0.02 to 1.0 ,
In addition, the liquid includes a rare earth element selected from samarium, gadolinium, and yttrium in a range of 0 to 0.8;
And, wherein the one of praseodymium and terbium total of the rare earth elements, solid oxide fuel cell manufacturing method of the air electrode, characterized in that the range of proportions of 0.05 to 1.0. Solid oxide fuel cell characterized by comprising a cathode manufactured by the method of claim 1 wherein the solid oxide fuel cell air electrode.

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