KR101187713B1 - The cathode of SOFC including silver nanoparticles coated with carbon and the method for preparing it - Google Patents

Abstract

The present invention provides a cathode of a solid oxide fuel cell including carbon nanoparticles coated with carbon and a method for manufacturing the same, more specifically, the step of preparing carbon nanoparticles coated with carbon (step 1); Preparing a cathode slurry including silver nanoparticles and LSCF (La _0.6 Sr _0.4 Co _0.3 Fe _0.7 O _3-y , wherein y is (0.0 ≦ y ≦ 0.5)) particles (step 2); Coating the cathode slurry on an electrolyte layer (step 3); And a step (step 4) of sintering the coated cathode slurry. The cathode of the SOFC including the carbon-coated silver nanoparticles according to the present invention is coated with carbon so that the nanoparticles of silver nanoparticles may be evenly distributed on the cathode of the fuel cell. Since the fuel cell unit cell operates at a low temperature of 650 ° C. or lower, output is obtained. In addition, the silver nanoparticles are prevented from agglomerating during the sintering process for manufacturing the electrode from the slurry manufacturing process of the fuel cell cathode, thereby increasing the output efficiency of the fuel cell.

Description

The cathode of a solid oxide fuel cell comprising carbon nanoparticles coated with carbon and a method for manufacturing the same.The cathode of SOFC including silver nanoparticles coated with carbon and the method for preparing it}

The present invention relates to a cathode of a solid oxide fuel cell including carbon nanoparticles coated with carbon and a method of manufacturing the same.

A fuel cell is an electrochemical energy conversion device that converts chemical energy of a fuel (hydrogen, hydrocarbon, alcohol, etc.) directly into electrical energy by an electrochemical reaction. After the discovery of Wilhelm Nernst theory in 1899, the first solid oxide fuel cell (SOFC) was developed by Baur and Preis in 1937.

Fuel cells are generally classified according to the type of electrolyte. Fuel cells that are operated at low temperatures include polymer type (PEMFC), phosphoric acid type (PAFC), and alkali type (AFC). Fuel cells in operation include molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC). A solid oxide fuel cell uses a high ion conductive ceramic material such as yttriastabilized zirconia (YSZ) as an electrolyte, which can use a lower cost material than other fuel cells, has a higher tolerance to impurities in the fuel, and an internal reforming fuel. It is possible to simplify the fuel cell system by using hydrocarbon-based fuels without the need for reforming outside the system. In addition, since solid oxide fuel cells operate at high temperatures, their power generation efficiency is higher than that of other fuel cells, and it is possible to operate under pressurized conditions, thereby increasing the performance of fuel cells and enabling combined power generation through linkage with gas turbines. The efficiency of the power generation system can be increased by more than 70%.

However, since solid oxide fuel cells usually operate at high temperatures of 750 ~ 800 ℃, various problems related to materials such as reaction between materials may occur. Accordingly, various technologies such as large area electrolytes and electrodes having excellent characteristics of long life and high performance, single cell manufacturing, stack manufacturing, and fuel cell power generation system technologies are being developed for practical application and demand expansion of solid oxide fuel cells. In particular, the cell material, which is the core of the solid oxide fuel cell, plays a key role in determining the performance and durability of the fuel cell.

The unit cell of a solid oxide fuel cell generally has an electrolyte at the center, an anode and a cathode at both sides, and an interconnect at the outside thereof. In order to improve the performance of the cell, a double electrode structure may be used or a functional layer may be used between the electrode and the electrolyte. When oxygen and hydrogen are supplied to both electrodes with an electrolyte in between, an oxygen partial pressure difference is formed between the air electrode and the fuel electrode side, thereby generating a driving force to move oxygen through the electrolyte. At the air electrode, oxygen receives electrons, becomes oxygen ions, passes through the electrolyte membrane, and moves to the fuel electrode. At the fuel electrode, oxygen ions release electrons and react with hydrogen gas to become water vapor. Electrical energy is generated through the emitted electrons, and the electrical energy is extracted to produce power. The electrolyte must have a compact structure in order not to permeate the gas directly. The higher the oxygen ion conductivity is, the better the electron conductivity must be. Fuel electrode and air electrode should be porous and have high electronic conductivity so that fuel gas and oxygen can be diffused well.

Among the components of the solid oxide fuel cell (SOFC), the cathode has a high ion conductivity and an electron conductivity of 50 Ω / cm or more, is stable in an oxidizing atmosphere, free from chemical reactions and mutual diffusion with other components, and thermal expansion. It should be a porous (more than 30%) membrane with similar modulus. The cathodes used in SOFC are materials in which additives are added to the LaMnO ₃ and LaCoO ₃ systems of perovskite structure, and ion / electron conductive mixed conductors are used to increase electrode activity at lower operating temperatures.

The catalyst used in the cathode has been used Pt, Pd, etc. as a noble metal, but the use of silver (silver, Ag) as an economic problem has been studied. Silver has an advantage of excellent oxygen reduction reaction, high electrical conductivity, and low cost compared to the precious metals. However, when silver is added as nanoparticles, there is a problem in that the aggregation phenomenon is very severe so that all of the particles are aggregated during the sintering process for the preparation of the electrode from the slurry manufacturing process, thereby not showing the advantages of the nanoparticles.

US Patent Publication No. 2010/0143761 dissolves silver nitrate in an organic solvent of the same polarity as acetonitrile and uses it in a perovskite cathode LSCF. This method has the effect of reducing the electrical resistance of the air electrode.

As reported in the Journal of Power Sources 161 (2006) 115122, using a mechanofusion system in which particles are complexed by mechanical energy, atomized spherical silver particles up to 53 μm in diameter (1 μm thick) _{La 0 .6 Sr 0 .4) 0.98} Co 0 .2 Fe 0 .8 O 3 δ ( LSCF by coating) layer was used as the air electrode. The fuel cell using the cathode produced a relatively stabilized power. However, the problem of volatilization of silver has an unproven problem.

Accordingly, the present inventors fabricated the cathode by performing carbon coating on the silver nanoparticles so that the silver nanoparticles did not aggregate, and confirmed that the highly efficient solid oxide fuel cell could be manufactured by using the prepared cathode in the solid oxide fuel cell. This invention was completed.

An object of the present invention is to provide an air electrode of a solid oxide fuel cell including silver nanoparticles whose properties are suppressed to aggregate with each other.

Another object of the present invention is to provide a method for manufacturing a cathode of a solid oxide fuel cell including carbon nanoparticles coated with carbon.

In order to achieve the above object, the present invention provides a cathode of a solid oxide fuel cell comprising carbon nanoparticles coated with carbon.

In addition, preparing a carbon nano-particles coated with carbon (step 1); Preparing a cathode slurry including silver nanoparticles and LSCF (La _0.6 Sr _0.4 Co _0.3 Fe _0.7 O _3-y , wherein y is (0 ≦ _y ≦ 0.5)) particles (step 2); Coating the cathode slurry on an electrolyte layer (step 3); And it provides a method for producing a solid oxide fuel cell cathode comprising carbon nanoparticles coated with carbon comprising the step of sintering the coated cathode slurry (step 4).

The cathode of the solid oxide fuel cell including carbon nanoparticles coated with carbon according to the present invention is coated with carbon, so that the nanoparticles of silver nanoparticles are uniformly dispersed in the cathode of the fuel cell without being agglomerated with each other. Since the battery unit cell has high catalytic activity at a temperature of 600 to 800 ° C. and uses silver having excellent oxygen solubility and mobility as a catalyst, the battery unit cell can operate at a low temperature of 650 ° C. or lower to obtain an output. In addition, the silver nanoparticles are prevented from agglomerating with each other during the sintering process for manufacturing the electrode from the slurry manufacturing process of the fuel cell cathode, thereby increasing the output efficiency of the fuel cell.

1 is a flow chart showing the manufacturing process of the carbon-coated silver nanoparticles according to the present invention,
2 is a SEM and HRTEM photograph of silver nanoparticles prepared in a mixed gas atmosphere of argon / methane,
Figure 3 is a SEM photograph of the silver nanoparticles prepared in (a) a mixed gas atmosphere of argon / 10% by volume methane, and (b) argon atmosphere,
Figure 4 is a SEM photograph of the silver nanoparticles heat-treated for 1 hour at 400 ℃ temperature in (a) argon atmosphere and (b) mixed gas atmosphere of argon / 10% by volume methane,
5 is a TEM photograph of silver-coated carbon nanoparticles (a) heat treated at 200 ° C. and (b) 800 ° C.
6 is (a) XRD spectrum and (b) TEM photograph of silver nanoparticles heat treated in argon atmosphere,
7 is a TEM photograph observing the shape of the silver nanoparticles according to the heat treatment time,
8 (a) is 1 hour at a temperature of 800 ° C. in a nitrogen atmosphere, and (b) is 3 hours at a temperature of 800 ° C. in a mixed gas atmosphere of argon and 4% hydrogen, and (c) is a mixture of argon and 4% hydrogen. TEM image of silver nanoparticles heat treated for 1 hour at 850 ° C. in a mixed gas atmosphere.
9 is a SEM photograph of the cross section of the cathode according to the content and sintering temperature of the silver nanoparticles coated with carbon,
10 is a graph of sintering temperature and power density of operating temperature of carbon-coated silver nanoparticles,
11 is a graph of power density by operating temperature of the cathode according to the content of carbon nanoparticles coated with carbon.

Hereinafter, the present invention will be described in detail.

The present invention

It provides a cathode of a solid oxide fuel cell comprising carbon nano-particles coated with carbon.

The silver nanoparticles included in the cathode according to the present invention are coated with carbon and are evenly dispersed in the cathode without being agglomerated with each other. In the fuel cell according to the present invention, the fuel cell unit cell using the cathode has a temperature of 600 to 800 ° C. Since silver, which has high catalytic activity and excellent oxygen solubility and mobility, is used as a catalyst, the fuel cell unit cell operates at a low temperature of 650 ° C. or lower, thereby obtaining output. In addition, the silver nanoparticles are prevented from agglomerating with each other during the sintering process for manufacturing the electrode from the slurry manufacturing process of the fuel cell cathode, thereby increasing the output efficiency of the fuel cell.

The coated carbon is preferably laminated to silver nanoparticles in multiple layers. The carbon coating not only prevents the silver nanoparticles from agglomerating with each other, but also serves to minimize the influence of the silver nanoparticles by the external environment. For example, when carbon-coated silver nanoparticles are left in the air, the carbon layer reacts with the air to form carbon dioxide (CO ₂ ) and fly away. Therefore, multilayers, rather than monolayers, are advantageous for protecting silver nanoparticles.

In addition,

Preparing carbon nanoparticles coated with carbon (step 1);

Preparing a cathode slurry including silver nanoparticles and LSCF (La _0.6 Sr _0.4 Co _0.3 Fe _0.7 O _3-y , wherein y is (0.0 ≦ y ≦ 0.5)) particles (step 2);

Coating the cathode slurry on an electrolyte layer (step 3); And

Provided is a method of manufacturing a solid oxide fuel cell cathode including carbon nanoparticles coated with carbon, including sintering a coated cathode slurry (step 4).

Hereinafter, the present invention will be described in detail step by step.

Step 1 according to the present invention is to prepare a silver nanoparticles coated with carbon,

Putting silver into the reaction chamber and supplying an inert gas and a carbon containing gas (step A); And

Electroblasting and recovering silver in the reaction chamber of step A (step B).

Step A according to the present invention is a step of supplying an inert gas and a carbon containing gas into the reaction chamber. In order to produce carbon coated silver nanoparticles, an inert gas and a carbon containing gas are first supplied to a reaction chamber having high purity silver wire. The inert gas of step A is argon gas, and the carbon-containing gas is methane gas. Argon gas has an effect of preventing silver from being oxidized as an inert gas, but when the methane gas that supplies carbon is not added, silver nanoparticles are relatively formed. When a mixture of argon and methane gas is supplied, high-temperature metal vapor reacts with carbon atoms during electric explosion to further condense the metal vapor in the carbon layer formed on the surface to grow or to grow particles by agglomeration. It will play a role.

The concentration of the carbon-containing gas in step A is preferably 5 to 15% by volume. When the carbon-containing gas is supplied at less than 5% by volume, there is a problem in that the silver nanoparticles are not sufficiently coated with a carbon coating, thereby preventing the silver nanoparticles from performing aggregation and protecting. Even if the carbon-containing gas is supplied in excess of 15% by volume, there is no advantageous effect because the thickness is uniformly coated, there is a problem such as methane gas emissions after manufacturing.

Step B according to the present invention is a step of electroexploding and recovering silver in the reaction chamber of step A. For example, argon and methane gas are formed at a predetermined pressure, and the electric explosion is performed at regular intervals.

During the electrical explosion in the step B, the metal vapor generated during the overheating and explosion of the metal wire is blown and scattered toward the inner wall of the chamber, and at the same time, the methane gas in the reaction gas is monoatomic due to the electric energy applied to the two electrodes. May be decomposed into H and C. The carbon atoms are coated on the surface of the metal nanopowder through reaction with the metal vapor during the condensation and cooling of the metal vapor. Since carbon has low solubility with silver and its carbon sublimation temperature is higher than silver, the carbon atoms are in a mixed state with the explosive initial metal vapor and then physically adsorbed to the liquid or semi-liquid silver surface. Precipitates in, and may then form on the surface of the silver nanoparticles in the form of multilayer graphite shells.

The silver nanoparticles condensed and cooled in the reaction chamber after the electric explosion reaction in step B are forcibly circulated by a blower and transported to a collecting unit, and the transported silver nanoparticles are cyclone and mesh filters. Classified and collected through It is preferable that the said mesh filter is 50 micrometers or less. When the filter exceeds 50 μm, the silver nanoparticles may pass through, and thus, when the slurry is manufactured, particle coagulation may occur rapidly by using the large particles as nuclei.

Step 2 according to the present invention, the silver nanoparticles and _{LSCF (La 0 .6 Sr 0 .4} Co 0 .3 Fe 0 .7 O 3 -y, y stage is (0≤y≤0.5)) containing particles It is a step of preparing a cathode slurry. The slurry is prepared by a ball mill mixing silver nanoparticles and LSCF. When the content of silver nanoparticles is less than 20% by mass, the content of silver nanoparticles is relatively low, and thus may not be smoothly performed as compared to when the role of the oxygen catalyst exceeds 20% by mass, and the content of silver nanoparticles is 40%. In the case of exceeding the mass%, the silver nanoparticles may elute to the surface of the cathode during sintering and aggregate into large agglomerates, and the area of contact with the cathode layer is slightly lowered, thus serving as an oxygen catalyst. If less than, it may not appear in a relatively even area. The slurry may further comprise a _{CGO (Ce 0 .9 Gd 0 .1} O 3), if the substance capable of producing an air electrode is not limited to this. The cathode manufactured by further including CGO in the LSCF assists in bonding to the interface with the electrolyte layer during sintering.

Step 3 according to the present invention is a step of coating the cathode slurry on an electrolyte layer. Coating of the cathode slurry in step 3 is preferably performed by a dip coating method. The dip coating method has the advantage of easy coating without using a special device. The coating method is not limited to this, as well as dip coating, as long as it can coat the cathode slurry on the electrolyte layer.

Furthermore, it is preferable to further include the step of heat treatment after the cathode slurry coating of step 3. When the heat treatment is performed after coating the slurry, pores are formed by burning the polymer binder in the cathode, and gas circulation such as oxygen is improved.

Step 4 according to the invention is a step of sintering the coated cathode slurry. The sintering temperature of the step 4 is preferably 750 ~ 950 ℃, more preferably sintered for about 3 hours at 850 ℃. If the sintering temperature is less than 750 ℃ the LSCF layer is not sintered to form a healthy air cathode layer, if it exceeds 950 ℃ there is a problem that the silver is close to the melting point of the silver may volatilize.

Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are merely to illustrate the invention, the contents are not limited by the following examples.

< Example  1> Solid Oxide Fuel Cell Air pole  Manufacturing 1

Step 1. preparing carbon coated silver nanoparticles

99.9% high purity silver wire was continuously injected into the reaction chamber of the electric explosion apparatus, and 10 vol% argon / 90 vol% methane gas was supplied. The discharge voltage was set at 26 kV and the specific energy value (ratio of applied energy to the sublimation energy of the metal wire, K = W / W _B ) to 2.1. After 500 electric wire explosions, carbon nanoparticles coated with carbon were selected using a 50 μm mesh filter using a cyclone and collected into a collecting unit.

Step 2. Air pole The slurry  Manufacturing steps

Of a 10% by mass prepared in Step 1 and mixed using a CGO (Ce Gd _{0 0 .9 .1} O ₃₎ of the LSCF, 45 mass% of the nanoparticles, 45 wt%, a ball mill, whereby 50 mL of toluene Was prepared as a solvent to prepare a cathode slurry.

Step 3. Air pole The slurry  Coating on the electrolyte layer

The cathode slurry prepared in step 2 was coated on the electrolyte layer by dipping.

Step 4. Coated Air pole The slurry  Sintering step

The cathode slurry coated in step 3 was sintered at a temperature of 750 ° C. for 3 hours in a mixed gas atmosphere of argon and 4% hydrogen to prepare an anode of a solid oxide fuel cell.

< Example  2> solid oxide fuel cell Air pole  Manufacture 2

Except that the sintering temperature of step 4 of Example 1 is 850 ℃ to perform the same method as in Example 1 to prepare a cathode of a solid oxide fuel cell.

< Example  3> Solid Oxide Fuel Cell Air pole  Manufacturing 3

Except that the sintering temperature of step 4 of Example 1 is 950 ℃, the cathode of the solid oxide fuel cell was prepared in the same manner as in Example 1.

< Example  4> Solid Oxide Fuel Cell Air pole  Manufacturing 4

Except that the content of silver nanoparticles added to the cathode slurry of step 2 of Example 1 is 30% by mass, and the contents of LSCF and CGO are 35 and 35% by mass (70% by mass in total), respectively. The cathode of the solid oxide fuel cell was manufactured by the same method as described above.

< Example  5> Solid Oxide Fuel Cell Air pole  Manufacture 5

The content of the silver nanoparticles added to the cathode slurry of step 2 of Example 1 is 30% by mass, and the contents of LSCF and CGO are 35 and 35% by mass (70% by mass in total), respectively. A cathode of a solid oxide fuel cell was manufactured in the same manner as in Example 1 except that the sintering temperature of 850 was obtained.

< Example  6> Solid Oxide Fuel Cell Air pole  Manufacture 6

The content of the silver nanoparticles added to the cathode slurry of step 2 of Example 1 is 30% by mass, and the contents of LSCF and CGO are 35 and 35% by mass (70% by mass in total), respectively. A cathode of a solid oxide fuel cell was manufactured in the same manner as in Example 1 except that the sintering temperature of 950 ° C. was obtained.

< Example  7> Solid Oxide Fuel Cell Air pole  Manufacture 7

Except that the content of silver nanoparticles added to the cathode slurry of step 2 of Example 1 is 50% by mass, and the contents of LSCF and CGO are 25 and 25% by mass (50% by mass in total), respectively. The cathode of the solid oxide fuel cell was manufactured by the same method as described above.

< Example  8> Solid Oxide Fuel Cell Air pole  Manufacture 8

The content of the silver nanoparticles added to the cathode slurry of step 2 of Example 1 is 50% by mass, and the contents of LSCF and CGO are 25 and 25% by mass (50% by mass in total), respectively. A cathode of a solid oxide fuel cell was manufactured in the same manner as in Example 1 except that the sintering temperature of 850 was obtained.

< Example  9> Solid Oxide Fuel Cell Air pole  Manufacture 9

The content of the silver nanoparticles added to the cathode slurry of step 2 of Example 1 is 50% by mass, and the contents of LSCF and CGO are 25 and 25% by mass (50% by mass in total), respectively. A cathode of a solid oxide fuel cell was manufactured in the same manner as in Example 1 except that the sintering temperature of 950 ° C. was obtained.

< Example  10> Solid Oxide Fuel Cell Air pole  Manufacture 10

After performing the dip coating of Step 3 of Example 1, the cathode of the solid oxide fuel cell was manufactured in the same manner as in Example 1 except that the heat treatment was performed for 3 hours at 950 ° C.

< Experimental Example  1> of silver nanoparticles HRTEM  analysis

In order to determine the form and coating state of the silver nanoparticles prepared in step 1 of Example 1, the analysis was performed using HRTEM, and the results are shown in FIG. 2.

As shown in FIG. 2, most of the silver nanoparticles exist in the form of a sphere having a size of 10 to 40 nm, and carbon is coated on the surface of the silver nanoparticles to form a core / shell structure. can confirm. At this time, the surface coating layer is a carbon layer is laminated in the form of layer-by-layer (LbL) it can be seen that the distribution of the thickness of about 2-4 nm.

< Experimental Example  2> of silver nanoparticles SEM  Analysis 1

Except that the gas supplied in Step 1 of Example 1 is 100% argon, to determine the form and coating state of the silver nanoparticles prepared in the same manner as in Step 1 of Example 1 for each silver nanoparticle Analysis using SEM, and the results are shown in FIG.

As shown in Figure 3, when prepared in step 1 of Example 1 it can be seen that a relatively small silver nanoparticles are formed. In the case of silver nanoparticles prepared under a 10 vol% methane and argon mixed gas atmosphere, the metal vapor of the carbon layer formed on the surface grows or aggregates when the hot metal vapor reacts with the carbon atoms during the electrical explosion. Since it suppresses the growth of the particles by, it can be seen that the powder of a relatively small size compared to the silver nanoparticles prepared using only argon gas.

< Experimental Example  3> silver nanoparticles SEM  Analysis 2

In order to confirm the protective effect of the carbon coating was carried out the following experiment.

Except that the gas supplied in Step 1 of Example 1 is 100% argon, the silver nanoparticles prepared in the same manner as Step 1 of Example 1 were exposed to air for 10 days and then at 400 ° C. in an argon atmosphere. Each heat treatment was performed for 1 hour. Thereafter, each silver nanoparticle was identified through SEM, and the results are shown in FIG. 4.

As shown in FIG. 4, the density of the carbon-coated silver nanoparticles (Step 1 of Example 1) was much smaller than that of the pure silver nanoparticles prepared in the argon atmosphere. This can be judged that particle growth is suppressed during the time that the carbon layer reacts with oxygen in the air to form CO ₂ and fly away. Therefore, it was confirmed that silver, which is an internal metal particle, was effectively protected by the coated carbon film.

< Experimental Example  4> Microscopic analysis of silver nanoparticles according to heat treatment conditions

In order to determine the effect of the silver nanoparticles prepared in Step 1 of Example 1 according to the heat treatment conditions, the carbon nanoparticles coated with carbon at 200 ℃ and 800 ℃ in air for 1 hour and observed under a microscope The results are shown in FIG.

As shown in FIG. 5, the silver nanoparticles heat treated at 200 ° C. may confirm that the coating layer is removed or the coating layer is released. On the other hand, the silver nanoparticles heat-treated at 800 ℃ can be seen that after the carbon layer is removed, the silver nanoparticles are formed with a neck (neck) between the particles are aggregated in a chain structure to form a cluster (cluster). Therefore, even when the carbon film is coated, it can be seen that in the case of heat treatment in air, the coating layer cannot act as a protective film of the internal metal powder.

< Experimental Example  5> Crystallinity and particle state analysis according to heat treatment conditions

In order to confirm the crystallinity and the state of the particles according to the heat treatment conditions were carried out the following experiment.

The silver nanoparticles prepared in the same manner as in Step 1 of Example 1 were exposed to air for 10 days and then heat-treated at 250 ° C., 600 ° C. and 800 ° C. for 1 hour in an Ar atmosphere, which is an inert gas, followed by TEM and Analysis through XRD, the results are shown in FIG.

As shown in FIG. 6, when the heat treatment was performed in an argon atmosphere, the XRD spectrum prepared in Step 1 of Example 1 may identify only peaks corresponding to a single silver metal phase. This shows that no carbide is formed and only silver is present inside the carbon coating layer. In addition, even after the heat treatment shows that almost the same spectrum as before the heat treatment, regardless of the presence or absence of the heat-treated carbon is confirmed that the crystallinity.

In addition, according to the TEM photograph of the silver nanoparticles under the same conditions, it can be observed that the silver nanoparticles of the carbon coating layer were partially grown in the carbon coating layer compared to the heat treatment under each temperature condition. You can see that there is almost no change. However, it can be seen that the carbon layer grows slowly from 600 ° C. and grows to a very thick thickness at 800 ° C., showing a tendency to escape from the nanoparticles.

< Experimental Example  6> Silver Nanoparticles with Heat Treatment Time TEM  analysis

In order to determine the effect of the heat treatment time on the silver nanoparticles, the following experiment was performed.

The silver nanoparticles prepared in Step 1 of Example 1 were heat-treated for 1, 1.5 and 2 hours at 850 ° C. in an argon atmosphere, and analyzed by TEM, and the results are shown in FIG. 7.

As shown in FIG. 7, when the heat treatment is performed at 850 ° C., the carbon coating layer is rapidly released as time passes, and when the heat treatment is performed, the coating layer is rapidly released to agglomerate to several tens of microns.

 < Experimental Example  7> Silver Nanoparticles According to Heat Treatment Atmosphere TEM  analysis

In order to determine the shape of the silver nanoparticles according to the heat treatment conditions, the following experiment was performed.

The silver nanoparticles prepared in Step 1 of Example 1 were heat-treated for 1 hour at a temperature of 800 ° C. in a nitrogen atmosphere, at a temperature of 800 ° C. for 3 hours and at 850 ° C. in a mixed gas atmosphere of argon and 4% hydrogen. After each heat treatment for 1 hour at a temperature and analyzed by TEM, the results are shown in FIG.

As shown in Figure 8, when the heat treatment in a nitrogen atmosphere it can be seen that the coated carbon starts to escape similarly to the heat treatment in an argon atmosphere. On the other hand, when the heat treatment was performed at 800 ° C. for 3 hours and 850 ° C. for 1 hour in a mixed gas atmosphere of argon and 4% hydrogen as a reducing atmosphere, the carbon layer was found to be in good condition. It can be seen that it is desirable to perform.

< Experimental Example  8> Microstructure Analysis According to Silver Nanoparticle Content and Sintering Temperature

In order to determine the microstructure of the cathode of the solid oxide fuel cell according to the content of the silver nanoparticles and the sintering temperature, prepared in Examples 1 to 9, the cross section of the cathode was analyzed using SEM, and the result is illustrated in FIG. 9. Shown in

As shown in FIG. 9, it can be seen that the silver nanoparticles grow as the sintering temperature and the content of the silver nanoparticles increase. In the cathode layer sintered at 950 ° C., the silver content is relatively lower than that at other temperatures. It can be seen. This is thought to be somewhat volatilized as it approaches the melting point of silver.

In addition, in the temperature range of 750 to 950 ° C., grain boundary growth of the ceramic cathode does not appear to be active, but a connection point between particles appears to be generated. Therefore, if the sintering temperature and the content of the silver nanoparticles are properly controlled, it is determined that the low temperature cathode can be evenly distributed.

< Experimental Example  9> Solid Oxide Fuel Cell Air cathode  According to sintering temperature Unit cell  Performance measurement

In order to examine the performance of the solid oxide fuel cell equipped with the cathode of the solid oxide fuel cell including carbon nanoparticles coated with carbon, the following experiment was performed.

A fuel cell unit cell was manufactured by a known method using the cathode of the solid oxide fuel cell prepared in Examples 4-6. Hydrogen gas was flowed to the anode of the unit cell of the manufactured fuel cell at 15 mL / min, and air was flowed at the rate of 1.5 L / min to the cathode, and the current at operating temperatures of 500, 550, 600, 650 and 700 ℃. The voltage IV was measured and the results are shown in FIG. 10 and Table 1. FIG.

As can be seen from FIG. 10 and Table 1, when the unit cell including the air electrode sintered at 850 ℃ operating at 500 ℃ ~ 700 ℃, the power density of the unit cell is high, the unit cell performance is excellent You can check it. Meanwhile, when the sintering temperature is 950 ° C., the decrease in power density may be due to the fact that the silver nanoparticles in the cathode are volatilized in part due to the high sintering temperature, thereby lowering the silver content.

Per area
Power density

Example 4
(a)
Example 5
(b)
Example 6
(b)
Working temperature 700 ℃

380 mW / cm ²
490 mW / cm ²
175 mW / cm ²
Working temperature 650 ℃

240 mW / cm ²
295 mW / cm ²
125 mW / cm ²
Working temperature 600 ℃

160 mW / cm ²
130 mW / cm ²
75 mW / cm ²

< Experimental Example  10> Solid Oxide Fuel Cell Air cathode  According to the silver nanoparticle content Unit cell  Performance measurement

In order to determine the unit cell performance according to the silver nanoparticle content of the solid oxide fuel cell cathode, the following experiment was performed.

A fuel cell unit cell was manufactured using the cathode of the solid oxide fuel cell prepared in Examples 2, 5, and 8, and hydrogen gas was flowed at 15 mL / min to the anode of the manufactured unit cell of the fuel cell. The current-voltage (IV) was measured at operating temperatures of 500, 550, 600, 650 and 700 ° C. while flowing air at a rate of 1.5 L / min, and the results are shown in FIGS. 11 and 2.

As shown in FIG. 11, the power density of the unit cell manufactured using Example 5 (30 mass% of silver nanoparticles) was 300 mW / cm ^{2, which} is the highest, and thus the performance was excellent. . On the other hand, the performance of Example 2 (10% by mass of silver nanoparticles) is rather low, it is determined that the role of the oxygen catalyst is relatively smooth compared to Example 5 due to the low content of silver nanoparticles, Example The low performance of 8 (50% by mass of silver nanoparticles) is due to the fact that silver nanoparticles are partially eluted to the surface of the cathode during the sintering process and are aggregated into large agglomerates, resulting in a relatively low area of contact with the material of the cathode layer. .

Per area
Power density

Example 2
(a)
Example 5
(b)
Example 8
(b)
Sintering Temperature 850 ℃

108 mW / cm ²

300 mW / cm ²

228 mW / cm ²

Claims (12)

A cathode of a solid oxide fuel cell comprising carbon nanoparticles coated with silver nanoparticles.
The cathode of claim 1, wherein the coated carbon is laminated on the silver nanoparticles in multiple layers.
Preparing carbon nanoparticles coated with carbon (step 1);
Preparing a cathode slurry including silver nanoparticles and LSCF (La _0.6 Sr _0.4 Co _0.3 Fe _0.7 O _3-y , wherein y is (0.0 ≦ y ≦ 0.5)) particles (step 2);
Coating the cathode slurry on an electrolyte layer (step 3); And
A method of manufacturing a solid oxide fuel cell cathode including carbon nanoparticles coated with carbon, including sintering a coated cathode slurry (step 4).
The method of claim 3, wherein step 1
Putting silver into the reaction chamber and supplying an inert gas and a carbon containing gas (step A); And
A method of manufacturing a solid oxide fuel cell cathode including carbon nanoparticles coated with carbon, characterized in that it is carried out including the step of electroexploding and recovering silver in the reaction chamber of step 1 (step B).
5. The method of claim 4, wherein the inert gas of step A is argon gas, and the carbon-containing gas is methane gas. 6.
5. The method of claim 4, wherein the concentration of the carbon-containing gas in step A is 5 to 15% by volume. 5.
4. The method of claim 3, wherein the mixing ratio of the silver nanoparticles in step 2 is 20 to 40 wt%.
4. The method of claim 3, wherein the cathode slurry of Step 2 further comprises CGO (Ce _0.9 Gd _0.1 O ₃ ).
4. The method of claim 3, wherein the coating of the cathode slurry in step 3 is performed by a dip coating method.
4. The method of claim 3, further comprising heat-treating the cathode slurry after coating the cathode slurry in step 3.
4. The method of claim 3, wherein the sintering temperature of step 4 is 750 to 950 ° C. 5.
4. The method of claim 3, wherein the sintering of step 4 is performed in an inert gas or a reducing gas atmosphere. 5.

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