JP5500567B2 - Molten carbonate fuel cell electrode, method for producing the same, and molten carbonate fuel cell - Google Patents

Description

  The present invention relates to an electrode of a molten carbonate fuel cell, a method for producing the same, and a molten carbonate fuel cell, and is particularly useful when applied to preimpregnation of carbonate to an electrode.

  As a method for impregnating a carbonate in a molten carbonate fuel cell (hereinafter abbreviated as MCFC), there is a method in which a carbonate sheet is prepared in advance and impregnation is performed in-situ when the MCFC is started up. (See Patent Document 1).

  In this method, the MCFC height is reduced by the thickness of the carbonate sheet during the temperature rise, so that the variation in the stack tightening distribution is large, which causes damage to the electrolyte plate. Damage to the electrolyte plate leads to gas leakage and must be avoided as much as possible.

  On the other hand, a method (hereinafter referred to as a pre-impregnation method) in which carbonate is previously charged in an electrode has also been proposed (see Patent Document 2). According to such a method, there is an advantage that not only the height reduction at the time of start-up of the MCFC does not occur, but also the cost can be reduced because there is no step of producing the carbonate sheet.

Japanese Patent Laid-Open No. 06-267570 JP 11-329453 A

  In the pre-impregnation method as described above, it is desired to impregnate as much carbonate as possible in the electrode. However, as the amount of impregnation increases, gas permeability becomes a problem. That is, if all of the pores of the electrode, which is a porous plate, are filled with carbonate, the flow of gas is hindered. As a result, the electrolyte plate necessary for starting up the MCFC cannot be degreased.

  However, in the pre-impregnation method according to the prior art, it has not been studied what conditions are optimal for impregnation with carbonate.

  The present invention provides an MCFC electrode pre-impregnated with carbonate under optimum conditions in view of the above prior art, and a method for manufacturing an MCFC electrode that can be pre-impregnated with carbonate under optimum conditions. An object is to provide, and to provide an MCFC having the electrode.

  First, in examining the method of charging carbonate into the electrode, the material of the instrument used for pre-impregnation was examined. Preliminary experiments have shown that it is easy to add carbonate to the electrode itself, but it has also become clear that when the molten carbonate solidifies, it is difficult to separate it from other members. This is because. In consideration of peelability from carbonate, wettability is relevant. The wetting angle with carbonate is mainly data for the active components (anode, cathode) of the electrode, but it is known that the wettability of metallic nickel (anode) in the reducing atmosphere is the smallest.

  Therefore, it is expected that the electrode underlay is relatively easily peeled off if a nickel plate is used in a reducing atmosphere. However, the electrode itself impregnated with carbonate is a porous nickel plate and tends to be difficult to impregnate with carbonate. Therefore, while it is easy to suck carbonate into the porous nickel plate, it is important to determine a condition that prevents the carbonate from adhering to the nickel plate.

According to the thermogravimetric change (TG data) of the differential thermal balance of nickel in the air atmosphere obtained so far, nickel begins to increase in weight from about 400 ° C. This means the temperature at which oxidation begins. Therefore, an electrode with an overwhelming specific surface area is slightly oxidized at 400 ° C., and it is easy to suck carbonate. However, since the nickel plate is not oxidized so much, carbonate should be difficult to adhere to. is there. That is, it is considered that the temperature is increased to 400 ° C. in an air atmosphere, and the carbonate impregnation step is performed in a reducing atmosphere or an inert atmosphere at 400 ° C. or higher. In addition, when considering a temperature of 400 ° C., a carbon plate is also a candidate. This is because the carbon plate is relatively easy to repel carbonate and does not thermally decompose up to this temperature.
Furthermore, the present inventors have found that the porosity, which is the ratio of the respective pores in the volume of the anode formed of the porous nickel plate and the cathode formed of the porous nickel oxide plate, greatly affects the output voltage characteristics of the MCFC. I figured out what to do. That is, it has been found that a higher output voltage can be obtained when the cathode has a larger porosity than the anode. This is considered as follows. The molten carbonate held dispersedly in the anode, cathode and electrolyte plate is most often held in the electrolyte plate, and then tends to be held in the order of cathode and anode. This is based on the capillary phenomenon resulting from the wettability between each member and carbonate. That is, it is considered that the retained amount of molten carbonate is determined by tension of molten carbonate at the anode and the cathode. Therefore, I came up with the idea of improving the output voltage of MCFC by optimizing the balance of the porosity of the anode and cathode.

A first aspect of the present invention that achieves the above-described object based on the results of the examination is an electrode of a molten carbonate fuel cell that is formed of a porous conductor plate with an electrolyte plate interposed therebetween, and is a nickel plate or Carbon powder is spread on the surface of the electrode with a carbon plate as an underlay, and the temperature is raised in an air atmosphere up to 400 ° C., while the temperature is raised in a nitrogen atmosphere at 400 ° C. or higher and heated at 650 ° C. for 60 minutes or more. Thus, in a state before being sandwiched between the electrolyte plates, an amount of carbonate up to 80% of the total volume of the pores of the electrode is charged into the pores of the electrode. The anode, and the cathode, which is the ratio of the pores to the volume of the anode and the cathode, is the same between the anode and the cathode, or the cathode is more than the anode porosity. The porosity of the anode or cathode is a value obtained by dividing the volume of carbonate contained in the pores of the cathode by the volume of the pores. The electrode of the molten carbonate fuel cell is characterized in that the overvoltage has a minimum value in the overvoltage characteristic representing the relationship between the amount and the overvoltage representing the voltage drop generated during the electrode reaction .

According to a second aspect of the present invention, in the molten carbonate fuel cell electrode according to the first aspect, another nickel plate or carbon plate is placed on the carbonate powder dispersed on the electrode. In addition, the present invention provides an electrode for a molten carbonate fuel cell, characterized in that the temperature is raised and heated by applying pressure from above.

According to a third aspect of the present invention, there is provided an electrode for a molten carbonate fuel cell according to the first or second aspect, wherein the electrode is formed of a nickel plate. It is in.

According to a fourth aspect of the present invention, in the electrode of the molten carbonate fuel cell according to any one of the first to third aspects, the cathode porosity and the anode porosity before oxidation are as follows: The difference is 0 to 13% in the electrode of the molten carbonate fuel cell .

According to a fifth aspect of the present invention, in the electrode of the molten carbonate fuel cell according to any one of the first to fourth aspects, the porosity of the cathode before oxidation is 80% or less. It is in the electrode of the featured molten carbonate fuel cell .

According to a sixth aspect of the present invention, in the electrode of the molten carbonate fuel cell according to any one of the first to fifth aspects , the porosity of the anode to the cathode is the overvoltage in the overvoltage characteristics. The electrode of the molten carbonate fuel cell is characterized in that the carbonate charging amount is larger than a minimum value.

A seventh aspect of the present invention is the first to sixth molten carbonate fuel cell characterized by having that electrodes be according to any one of the aspects of the.

In an eighth aspect of the present invention, carbonate powder is dispersed on the surface of an electrode formed of a porous conductor plate with a nickel plate or carbon plate as an underlay, and the temperature is raised in an air atmosphere up to 400 ° C. At 400 ° C. or higher, the temperature is raised in a nitrogen atmosphere, and by heating at 650 ° C. for 60 minutes or longer, an amount of carbonate up to 80% of the total volume of the electrode pores is charged into the electrode pores. A method for producing an electrode of a molten carbonate fuel cell, characterized in that it is configured as described above.

According to a ninth aspect of the present invention, in the method for manufacturing an electrode for a molten carbonate fuel cell according to the eighth aspect, another nickel plate or carbon plate is placed on the carbonate powder dispersed on the electrode. In the method for producing an electrode of a molten carbonate fuel cell , the electrode is placed and pressurized from above to perform the temperature raising and heating.

A tenth aspect of the present invention is the manufacturing method of the eighth or ninth molten carbonate fuel cell according to aspects of the electrode, the molten carbonate, wherein the electrode is obtained by forming a nickel plate It is in the manufacturing method of the electrode of a salt type fuel cell .

  According to the present invention, the electrode can be impregnated with as much carbonate as possible within a range in which the degreasing process at the time of starting the cell can be satisfactorily performed.

  Further, by adjusting the porosity of the anode and the cathode, the output voltage of the MCFC can be increased so that more carbonate remains on the anode side.

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

FIG. 1 is an exploded perspective view showing an MCFC according to an embodiment of the present invention. As shown in the figure, the MCFC according to this embodiment includes a cathode gas holder 1, a flow path plate 2, a SUS mesh plate 3, a cathode 4, an electrolyte plate 5, an anode 6, a flow path plate 7, and an anode gas holder 8. Yes. Here, air (O ₂ ) and carbon dioxide (CO ₂ ) are supplied to the cathode gas holder 1. The anode gas holder 8 is supplied with hydrogen (H ₂ ) and carbon monoxide (CO) as fuel. The cathode 4 is formed of a nickel oxide plate, which is a porous conductive plate, and is housed in the cathode gas holder 1 via the SUS mesh plate 3 and the flow path plate 2. Here, the SUS mesh plate 3 serves to mechanically reinforce the cathode 4, which is a brittle nickel oxide plate, and to make the surface pressure distribution acting on the cathode 4 uniform. The anode 6 is formed of a nickel plate, which is a porous conductive plate, and is housed in an anode gas holder 8 via a flow path plate 7. The electrolyte plate 5 is formed of a ceramic porous plate in which carbonate is immersed, and is sandwiched between the anode 6 and the cathode 4.

On the cathode side in the MCFC, air (O ₂ ) and carbon dioxide (CO ₂ ) supplied via the cathode gas holder 1 come into contact with the cathode 4 via the flow path plate 2 and the SUS mesh plate 3. As a result, the cathode 4 reacts with electrons supplied from the external circuit to generate carbonate ions, and the carbonate ions move through the electrolyte plate 5 and reach the anode side.

On the other hand, on the anode side, hydrogen (H ₂ ) and carbon monoxide (CO) as fuel supplied via the anode gas holder 1 come into contact with the anode 6 via the flow path plate 7. As a result, the anode 6 reacts with the electrons moving through the electrolyte plate 5 and hydrogen to generate carbon dioxide, water, and electrons. The electrons thus generated move to the cathode side via the external circuit and the same reaction is repeated, whereby a current can be continuously passed through the external circuit.

  The anode 6 and the cathode 4 in this embodiment are charged with carbonate in advance by a pre-impregnation method. Here, the carbonate impregnated in the anode 6 and the cathode 4 is impregnated in 75% of each pore volume of the anode 6 and the cathode 4 in consideration of gas permeability, and the remaining necessary carbonate is on the cathode side. The flow path is charged. Specifically, a carbonate dissolved in a solvent (for example, ethanol or water) is applied to the channel plate 2 on the cathode side.

  Here, a specific method of pre-impregnation for the anode 6 and the cathode 4 will be described. As shown in FIG. 2, a nickel plate 11 is used as an underlay, and a carbonate 10 powder is dispersed on the surface of the anode 6 or the cathode 4 which is a porous nickel plate, and is separately provided on the carbonate 10 powder. The nickel plate 12 is placed and a predetermined load is applied. By applying a load in this way, warping of the anode 6 and the cathode 4 during temperature drop was prevented.

  In this state, the temperature was raised in an air atmosphere up to 400 ° C., while the temperature was raised in a nitrogen atmosphere above 400 ° C. and maintained at 650 ° C. for 60 minutes.

  FIG. 3 is an explanatory diagram showing the result of measuring the distribution of the carbonate impregnation amount from the weight increase amount for each divided area by dividing the anode 6 and the cathode 4 after the carbonate pre-impregnation into nine. Incidentally, the initial weight was 42.5 g of the anode 6 and the cathode 4 and the weight of carbonate was 9.88 g. After impregnation, the total weight was 34.42 g (including about 2% oxidation). In addition, the number of each division area in a figure is the weight (g) of the carbonate impregnated in the said area.

  According to the pre-impregnation as described above, it was found that the anode 6 and the cathode 4 were impregnated with almost 100% of the carbonate 10 amount, and there was no extreme distribution as shown in FIG. Further, the increase in weight was 102%, and it became clear that the oxidation of the anode 6 and the cathode 4 was also generated by about 2%.

  Therefore, as a method for impregnating the carbonate 10, an impregnation test was conducted using the carbonate preparation amount (carbonate volume / pore volume in the electrode), the set temperature and the holding time as parameters. The test results are as shown in Table 1.

As shown in Table 1, all of the carbonate 10 cannot be impregnated in the anode 6 and the cathode 4 at any amount of carbonate charged at 550 ° C. for 30 minutes. The result was that carbonate 10 adhered in powder form. This is presumably because the carbonate composition was Li ₂ CO ₃ / Na ₂ CO ₃ = 60/40% non-eutectic salt, so that the melting point of the carbonate 10 was not reached. Therefore, when the temperature was raised to 650 ° C., all the impregnation was performed at a carbonate charge rate of 75%. However, when the charging rate was 100%, all was not impregnated, and the molten carbonate 10 adhered to the underlying nickel plate 11. Furthermore, when it was kept at 650 ° C. for 1 hour, it was revealed that it could be impregnated to a charging rate of 85%. However, when the carbonate impregnation rate was set to 85%, the porosity of the pre-impregnated anode 6 and cathode 4 was theoretically 15%, and it became clear that there was no gas permeability. Since the electrolyte plate 5 is degreased at the time of starting the cell, the anode 6 and the cathode 4 are required to have gas permeability. For this reason, either the anode 6 or the cathode 4 must be set to a carbonate charging rate of 80 or less. Accordingly, the shortest pre-impregnation conditions for the anode 6 and the cathode 4 require 650 ° C. for 60 minutes, and the charging amount must be 80% as the upper limit.

  The upper limit of the amount of carbonate that can be charged into the anode 6 and the cathode 4 is determined from the above-described method of pre-impregnating the anode 6 and the cathode 4 with the carbonate. On the other hand, the porosity of the anode 6 and the cathode 4 is determined from the viewpoint of battery performance, and the thickness is determined in consideration of the thickness of the current collector plate. Therefore, in order to cover the amount of carbonate necessary for the cell only by pre-impregnation of the anode 6 and the cathode 4, it is necessary to make the thickness of the electrolyte plate 5 below a certain value. When the upper limit of the thickness of the electrolyte plate 5 is calculated based on the specifications of the actual members shown in Table 2, it becomes 0.04 cm, and only the considerably thin electrolyte plate 5 can be used only by pre-impregnation of the anode 6 and the cathode 4. .

  From the viewpoint of durability against cracking of the electrolyte plate 5 and suppression of nickel short-circuiting, 0.075 cm based on the configuration of two electrolyte plates 5 of 0.037 cm is considered to be a reasonable thickness at present. When the electrolyte plate 5 having a thickness of 0.075 cm is used, about 10% of the total amount of carbonate required for the anode 6, the cathode 4, and the electrolyte plate 5 must be charged elsewhere. Therefore, the remaining necessary carbonate is charged in the flow path on the cathode side as described above. The reason for charging to the cathode side is to fill the anode flow path plate with the internal reforming catalyst in the case of the internal reforming type MCFC.

  As a method of charging the carbonate 10 into the flow path, ethanol or pure water can be considered as a solvent. In this embodiment, ethanol is selected. This is to shorten the drying time after brushing the channel, and from the results of single-cell disassembly analysis, carbonate in the cathode channel is more carbonated in the case of carbonate dissolved in pure water. This is because no salt remained and a tendency of the impregnation into the cathode was recognized. On the other hand, when pure water is used as a solvent, except for the point that it takes time to dry, the adhesive strength is good and the handling property is good. The method is also worth considering.

  Next, a method for raising the temperature of MCFC will be described. The basic process for raising the temperature of the cell is as follows. First, 1) improvement of adhesion by hot pressing (uniaxial pressure pressing in a high temperature state) between the electrolyte plate 5, the anode 6 and the cathode 4, 2) a degreasing step in the electrolyte plate 5, and 3) carbonate 10) impregnation step into the electrolyte plate 5 4) formation of an oxide film on the cathode current collector plate 5) oxidation of the cathode 4 and doping of the oxidized cathode (nickel oxide) with a small amount of lithium ( 6) Power generation process.

To elaborate further,
1) The hot press temperature between the electrolyte plate 5 and the anode 6 and the cathode 4 depends on the binder (binder) used in the electrolyte plate 5. The electrolyte plate binder (SM15 methylcellulose) used in this embodiment is sufficiently soft at around 100 ° C., and the adhesion is improved by biting into the electrolyte plate 5 in which the hard anode 6 and the cathode 4 are softened. For this reason, it is necessary to apply a sufficient load (2.0 to 2.8 kg / cm ² ) to the cell at room temperature.

  2) For the degreasing step in the electrolyte plate 5, the temperature range to be held by the binder used must be taken into account. The thermal decomposition behavior of SM15 Metroze, which is a binder, begins with a weight loss starting from 200 ° C, carbonization begins at 280 ° C to 300 ° C, and sudden weight loss (80% to 350 ° C in air and 380 ° C in a nitrogen atmosphere). ) Occurs. Thereafter, 100% weight loss occurs by 480 ° C. in air, but only 90% weight loss occurs in a nitrogen atmosphere, and 10% binder remains at 1000 ° C. Since it has the above characteristics, it is first held at 210 ° C. where the weight loss starts in the air atmosphere (the heater temperature above and below the cell is assumed to be 200 ° C.). The degreasing step was performed at a temperature of 255 ° C. (cell temperature of 245 ° C.) and a temperature of 410 ° C. (cell temperature of 400 ° C.) at which almost 80% of the binder was lost. Since oxidation of the anode 6 occurs in the temperature range of 400 ° C. or higher, the atmosphere is changed to a nitrogen atmosphere here.

  3) Since the impregnation of the carbonate 10 starts from around 500 ° C., which is the melting point of the carbonate 10, the temperature is once maintained at a cell temperature of 520 ° C. or more, and the electrolyte plate 5 is sufficiently impregnated with the carbonate 10 wait. At this point, a gas seal between the anode 6 and the cathode 4 is secured.

  4) Since the stainless steel material that is the cathode current collector has a temperature range that reacts violently with Li / Na carbonate, it is necessary to form a passive film on the metal surface before reaching that temperature range. is there. For this reason, water vapor is supplied to the cathode 4 at a cell temperature between 520 ° C. and 550 ° C. to form an oxide film on the stainless steel surface by the water vapor.

  5) Supply air / carbon dioxide / nitrogen mixed gas to the cathode 4 and change the cathode oxidation process from metallic nickel to nickel oxide and from nickel oxide to lithium-doped nickel oxide. Here, when a gas having a high oxygen concentration is supplied suddenly, a rapid oxidation reaction occurs, and particularly in the case of a stack or a large-area cell, there is a danger of causing a rapid rise in cell temperature. Therefore, it is necessary to adjust the oxygen concentration. The nickel oxidation reaction at the cathode 4 is performed in a temperature range of 550 ° C to 600 ° C. During this time, the anode 6 supplies a reducing atmosphere gas to keep the metallic nickel.

6) When the cell temperature reaches 600 ° C. or higher, power generation can be started. In the initial stage, the operation is performed for a predetermined time under conditions of low load (50 to 100 mA / cm ² ) and cell voltage of 750 mV or more with the meaning of habituation operation.

  Furthermore, the relationship between the porosity of the cathode 4 and the anode 6 according to this embodiment is adjusted as follows. The porosity is the ratio (%) of pores to the volume of the cathode 4 and the anode 6.

  FIG. 4 is an analysis and evaluation of the cause of the voltage drop, which is the difference between the theoretical value of the output voltage determined by the Nernst equation based on the gas composition and gas temperature (1060 mV in this example) and the output voltage that can actually be taken out to the outside. FIG. 4A shows the case where the porosity of the anode is 62%, and the porosity of the anode> the porosity of the cathode (conventional technology), FIG. In the case where the anode porosity is increased to 55%, and as a result, the anode porosity = the cathode porosity, FIG. 4 (c) is more cathode than in FIG. 4 (b). This is a case where the porosity of the material is coarsened to 61%, and as a result, the porosity of the anode <the porosity of the cathode. In addition, the porosity of the cathode in the case of FIG. 4B was formed to be the same as in the case of FIG. 4A (however, a slight variation occurs). Further, the porosity of the anode in the case of FIG. 4C was formed to be the same as in the case of FIG. 4B (however, a slight variation occurs).

Referring to FIG. 4, the cathode O ₂ reaction loss and internal resistance are greatly improved from (a) to (c), and the output voltage that was 817 mV in (a) showing the prior art is 847 mV in (b). It can be seen that in (c), it has increased to 860 mV.

  Further, Table 3 shows the output voltage per cell of each sample measured by changing various combinations of the anode porosity and the cathode porosity.

  Sample 1 in Table 3 is a combination of the anode 6 and the cathode 4 that give the characteristics shown in FIG. 4A, the sample 5 shown in FIG. 4B, and the sample 7 shown in FIG. 4C. Here, the time of oxidation in Table 3 means the porosity after the cathode 4 is oxidized. For example, a cathode 4 formed by firing a porous nickel plate is oxidized when it is actually used for MCFC, for example, becomes a porous nickel oxide plate, but immediately before firing and before being used as the cathode 4. The porosity of the cathode is larger than the porosity of the cathode 4 after use. This is because the pores shrink due to the expansion of the material after the cathode 4 is oxidized. Therefore, MCFC evaluates the relationship with the output voltage based on the cathode porosity after oxidation.

  FIG. 5 shows the output voltage characteristics with respect to the difference between the anode porosity and the cathode porosity (during oxidation) based on the results in Table 3. Referring to the figure, it has been found that the output voltage characteristics with respect to the difference between the anode porosity and the cathode porosity (during oxidation) tend to increase as the difference increases as a negative value. In particular, the relationship of anode porosity <cathode porosity is established, and the higher the absolute value of the difference between the two, the higher the output voltage is obtained.

  The experimental results of FIGS. 4 and 5 show that the output voltage of the MCFC can be increased by adopting the configuration of the anode 6 and the cathode 4 so that more carbonate remains on the anode side.

  Therefore, in this embodiment, the porosity is the same for the anode 6 and the cathode 4, or the cathode 4 is configured to have a larger porosity than the anode 6.

  According to the present embodiment, the structure is such that more carbonate remains on the anode side, and a large output voltage can be obtained.

  Furthermore, specifically, the MCFCs having the anode 6 and the cathode 4 shown as samples 5, 6, and 7 in Table 3 all satisfy the conditions of the above-described embodiment, and are all compared with the sample 1 that is the prior art. High output voltage is obtained. Therefore, the following three can be cited as examples of the present invention. Note that the anode 6 and the cathode 4 described below are charged with a predetermined amount of carbonate 10 by the above-described pre-impregnation method.

<Example 1>
This is the case where the porosity of the anode 6 is 55% and the porosity of the cathode 4 is 55%. According to this embodiment, an output voltage of 847 mV can be obtained.

<Example 2>
This is the case where the porosity of the anode 6 is 57% and the porosity of the cathode 4 is 59%. According to this embodiment, an output voltage of 842 mV can be obtained.

<Example 3>
This is the case where the porosity of the anode 6 is 58% and the porosity of the cathode 4 is 61%. According to this embodiment, an output voltage of 860 mV can be obtained.

  In this embodiment, basically, the porosity of the anode 6 and the porosity of the cathode 4 are the same, or the porosity of the cathode 4 is larger than the porosity of the anode 6. Although good, the porosity of the cathode 4 is limited by its mechanical strength. This is because the mechanical strength required for the electrode cannot be maintained if the porosity is too high, in combination with the fact that nickel oxide, which is a member for forming the cathode 4, becomes brittle due to oxidation. Therefore, it is considered that the upper limit of the porosity of the cathode 4 is about 80% (68% after oxidation) in the state of the nickel plate before oxidation. Therefore, based on the results of Table 3 and FIG. 5, the difference between the porosity of the cathode 4 and the porosity of the anode 6 is preferably 0 to 13%.

  FIG. 6 is a characteristic diagram showing an overvoltage characteristic representing the relationship between the carbonate charge amount contained in the anode or cathode pores and the overvoltage representing the voltage drop generated during the electrode reaction. As shown in the figure, it is known that the overvoltage characteristic has a minimum value A with respect to the amount of carbonate charged in the anode 6 to the cathode 4. And when the overvoltage is extremely small, the output voltage of the MCFC is considered to be maximum. Therefore, by adjusting the amount of carbonate charged so that the overvoltage has a minimum value A as well as the relationship with the porosity of the anode 6 and the cathode 4, a high output voltage can be obtained more easily. Here, the amount of carbonate charged in the anode 6 and the cathode 4 decreases due to evaporation or the like when power generation is continued as MCFC. Therefore, it is optimal to initially set the amount slightly larger than the amount that provides the minimum value A. By setting the optimum value B in this way, the amount of carbonate decreases with the use of MCFC, and the characteristic toward the minimum value A is obtained, so that the overvoltage can be reduced by use.

  In the pre-impregnation described above, the nickel plates 11 and 12 are used as the underlay and pressurizing plates in consideration of the wettability with the carbonate and the like. can get. Therefore, a nickel plate or a carbon plate is suitable as the pre-impregnated underlay or pressure plate.

  The present invention can be effectively used in the industry that manufactures, sells, and operates electric power equipment.

It is a disassembled perspective view which shows MCFC which concerns on embodiment of this invention. It is explanatory drawing which shows notionally the aspect of the pre-impregnation based on embodiment of this invention. It is explanatory drawing which shows the result of having measured the distribution of carbonate impregnation amount from the weight increase amount for every division | segmentation area | region, dividing the anode and cathode after carbonate pre-impregnation into 9 parts. It is a graph which shows the result of having analyzed and evaluated the cause of the voltage drop which is the difference between the theoretical value of the output voltage determined by the Nernst equation and the output voltage actually taken out to the outside. It is a characteristic view which shows the output voltage characteristic with respect to the difference of an anode porosity and a cathode porosity. FIG. 5 is a characteristic diagram showing an overvoltage characteristic representing a relationship between an amount of carbonate charged contained in pores of an anode or a cathode and an overvoltage representing a voltage drop generated during an electrode reaction.

Explanation of symbols

4 Cathode 5 Electrolyte plate 6 Anode
10 Carbonate 11, 12 Nickel plate

Claims (10)

An electrode of a molten carbonate fuel cell sandwiched between electrolyte plates and formed of a porous conductor plate,
While a nickel plate or a carbon plate is used as an underlay and carbonate powder is sprayed on the surface of the electrode, the temperature is raised in an air atmosphere up to 400 ° C., while the temperature is raised in a nitrogen atmosphere at 400 ° C. or higher and 60 minutes at 650 ° C. By heating above, in a state before being sandwiched between the electrolyte plates, the amount of carbonate up to 80% of the total volume of the pores of the electrode is charged in the pores of the electrode ,
The electrodes are an anode and a cathode, and the porosity, which is the proportion of the pores in the volume of the anode and the cathode, is the same between the anode and the cathode, or from the porosity of the anode Is configured to increase the porosity of the cathode,
The porosity of the anode to the cathode represents the amount of carbonate charged and the voltage drop generated during the electrode reaction, which is a value obtained by dividing the volume of carbonate contained in the cathode pore by the volume of the pore. An electrode of a molten carbonate fuel cell, characterized in that the overvoltage has a minimum value in an overvoltage characteristic representing a relationship with the overvoltage . The electrode of the molten carbonate fuel cell according to claim 1,
A molten carbonate fuel characterized in that another nickel plate or carbon plate is placed on the carbonate powder sprayed on the electrode and the temperature is raised and heated by pressing from above. Battery electrode. In the molten carbonate fuel cell electrode according to claim 1 or 2,
An electrode of a molten carbonate fuel cell, wherein the electrode is formed of a nickel plate. In the electrode of the molten carbonate fuel cell according to any one of claims 1 to 3 ,
The electrode of a molten carbonate fuel cell, wherein the difference between the porosity of the cathode before oxidation and the porosity of the anode is 0 to 13%. In the electrode of the molten carbonate fuel cell according to any one of claims 1 to 4 ,
An electrode for a molten carbonate fuel cell, wherein the porosity of the cathode before oxidation is 80% or less. In the electrode of the molten carbonate fuel cell according to any one of claims 1 to 5 ,
The porosity of the anode to the cathode is set to a value such that the carbonate charging amount is larger than a value at which the overvoltage takes a minimum value in the overvoltage characteristics. Electrodes. A molten carbonate fuel cell comprising the electrode according to any one of claims 1 to 6 .   Carbonate powder is sprayed on the surface of an electrode formed of a porous conductive plate with a nickel plate or carbon plate as an underlay, and the temperature is raised in an air atmosphere up to 400 ° C, while in a nitrogen atmosphere above 400 ° C. The melting is characterized by charging the pores of the electrode with an amount of carbonate up to 80% of the total volume of the pores of the electrode by heating at 650 ° C. for 60 minutes or more. A method for producing an electrode of a carbonate fuel cell. In the manufacturing method of the electrode of the molten carbonate fuel cell according to claim 8 ,
An electrode of a molten carbonate fuel cell, wherein another nickel plate or carbon plate is placed on the carbonate powder dispersed on the electrode, and the temperature is raised and heated by pressing from above. Manufacturing method. In the manufacturing method of the electrode of the molten carbonate fuel cell of Claim 8 or Claim 9 ,
The method for producing an electrode for a molten carbonate fuel cell, wherein the electrode is formed of a nickel plate.