KR100898219B1 - Porous nano composite powder, method of fabricating thereof, solid oxide fuel electrode and fuel cell using the same - Google Patents

Abstract

The present invention relates to a porous nano composite powder, a method of manufacturing the same, and a solid oxide anode and a fuel cell using the same. Porous nanocomposite powder according to the present invention is a nano-coated metal oxide coated on the surface of the ceramic powder, the electrode prepared using the porous nanocomposite powder can secure sufficient porosity without using a pore former, The homogeneous distribution of components and the expansion of the electrode specific surface area and three-phase interface provide excellent electrical conductivity and gas permeability, resulting in improved battery performance and reproducibility.

Description

Porous nano composite powder, method of fabricating one, solid oxide fuel electrode and fuel cell using the same}

1 is a flow chart showing a method of manufacturing a porous nanocomposite powder according to the present invention.

Figure 2 is a schematic view showing the structure of the porous nano composite powder according to the present invention ((a) single composite powder, (b) hetero composite powder).

3 is a view of the porous nano-composite powder according to the present invention with a scanning electron microscope (SEM).

4 is a view illustrating the microstructure of the solid oxide Ni-YSZ anode according to the present invention with an optical microscope and a scanning electron microscope (SEM).

((a): optical image (metal: white, ceramic powder: gray, pore: black),

(b): scanning electron microscope image).

Figure 5a is a diagram observed after transmission of a solid oxide fuel electrode according to the invention with a thin film, the transmission electron microscope (TEM),

FIG. 5B is a diagram of an energy distribution X-ray of the EDX point region of FIG. 5A (nickel and YSZ are present in a similar ratio).

Figure 6 is a view showing the porosity and the shrinkage rate according to the sintering temperature of the solid oxide fuel electrode according to the present invention.

7 is a view showing a change in electrical conductivity according to the heat cycle and oxidation / reduction cycle of the solid oxide fuel electrode according to the present invention,

Figure 7a is a diagram showing the heat cycle test and redox test conditions,

Figure 7b is a diagram showing the electrical conductivity change of the electrode by the heat cycle and redox test.

FIG. 8 is a diagram illustrating current density values corresponding to 0.7 V electromotive force values on an IV curve of a solid oxide fuel cell of the present invention according to a holding time of 100 hours or more at 800 ° C., and resistance values measured through impedance analysis. .

9 is an IV curve of a solid oxide fuel cell of the present invention (components: anode (LSM + YSZ) / electrolyte (YSZ) / electrode (EDC: electrode prepared using the composite powder of the present invention) according to the temperature. The figure shown.

FIG. 10 is a diagram evaluating long-term performance stability of the solid oxide fuel cell of the present invention at 800 ° C. under an electronic load condition of 1.0 A / cm 2.

The present invention relates to a porous nano composite powder, a method for manufacturing the same, and a solid oxide anode and a fuel cell using the same.

A solid oxide fuel cell is a fuel cell operating at a high temperature in the range of 600 to 1000 ° C. It has the advantages of being the most efficient, the least polluting, without the need for a fuel reformer, and the combined power generation. have.

Nickel and yttria stabilized zirconia (Y ₂ O ₃ -stabilized ZrO ₂ , hereinafter referred to as YSZ), which are used as representative anode materials of solid oxide fuel cells, are known to be stable in a high temperature reducing atmosphere. However, long-term use at high temperature may cause coagulation and structural variation due to surface diffusion of nickel, and may be vulnerable to heat cycles, and thus, the electrode structure may be damaged when repeatedly exposed to an oxidizing / reducing atmosphere. In addition, this problem may occur more seriously if the YSZ network is not connected efficiently. The electrode structure may show a great difference depending on the molding method and the electrode material. In general, when YSZ or more is added in an amount of 50 wt% or more, the YSZ network structure is efficiently formed in the nickel-YSZ (cermet) electrode.

When operating for a long time in a high temperature solid oxide fuel cell operating atmosphere, the structural variation of nickel particles in the electrode reduces the three-phase system area to reduce battery performance. The sintering phenomenon of the nickel particles is affected by the nickel and YSZ particle size / distribution and mutual wettability, and in general, when the nickel content is high, the sintering proceeds a lot. Due to the network structure of nickel and YSZ, electrons and ions generated through the electrode reaction are conducted. Therefore, the performance of the electrode is greatly affected by the porous microstructure.

The anode used as a support in a solid oxide fuel cell is a very important component that must satisfy the electrochemical properties along with structural properties. Looking at the physical properties required in the fuel electrode, mechanical strength, electrical conductivity, gas permeability, electrochemical activity and the like can be mentioned. Therefore, in order to satisfy these properties simultaneously, the anode must be a three-phase composite material consisting of an ion conductive oxide, a metal having electrochemical activity and excellent electrical conductivity, and pores for gas delivery.

An example of the most representative anode composition can be found in the porous Yttria Stabilized Zirconia (Ni-YSZ) metal-ceramic composite (cermet). In this case, it is widely known to form a mixed powder of NiO and YSZ, or to add a solid precursor powder as a pore forming agent to secure additional pores.

In general, it is known that the anode of a solid oxide fuel cell is manufactured by extrusion molding (US Pat. No. 6,248,468 and Korean Patent No. 10-0344936) and tape casting (US Pat. No. 5,922,486). The extrusion method and the tape casting method have the advantage of easy large area and mass production, and generally have the advantage of easily forming other functional layers and components (for example, electrolytes). However, many organics have to be added for the production of casting slurry and extrusion dough, and large particles or pore-forming agents (e.g. carbon, graphite, starch, resin, polymethyl) can be added to produce porous Ni-YSZ electrodes. Since methacrylate (PMMA), etc. must be added, it is difficult to control the pore shape, distribution, and connectivity of the electrode, and there are problems in that impurities are mixed and it is difficult to realize a homogeneous microstructure.

In addition, US Patent No. 4,023,979 and Republic of Korea Patent No. 10-0534764 describes a method for producing an electrode by producing granules of anode powder and hot compression molding it. The electrode manufactured by using the powder granulation and compression molding has the advantage that the pore connection and the electrical conductivity are high and the large area is possible, but when synthesizing the powder, such as phenol resin, polyester resin, polyvinyl alcohol resin and acrylic resin It has the disadvantage of using a large amount of highly toxic carcinogens.

Accordingly, there is a need for a solid oxide fuel cell anode capable of realizing a homogeneous microstructure that solves the above problems.

Therefore, while the present inventors are studying the anode for a solid oxide fuel cell that can realize a homogeneous microstructure, the porous metal oxide of the nano-crystal grains in the YSZ particles by using an environmentally friendly water-based process for a simple, low time and low cost A porous nanocomposite powder was prepared by coating, and the solid oxide fuel electrode and the fuel cell prepared by using the porous nanocomposite powder exhibit high porosity, homogeneity, electrical conductivity and gas permeability without using a pore-forming agent. It confirmed that the durability is excellent and completed the present invention.

The present invention is to provide a porous nano-composite powder and a preparation method thereof.

In addition, the present invention is to provide a solid oxide anode prepared by using the porous nano-composite powder.

In addition, the present invention is to provide a fuel cell comprising the solid oxide fuel electrode.

The present invention provides a porous nanocomposite powder having a nanocrystalline metal oxide porous coated on the surface of a ceramic powder.

In addition, the present invention

1) dissolving and dispersing a metal salt in distilled water;

2) adding an organic acid and a polyhydric alcohol to the aqueous solution in which the metal salt is dispersed;

3) adding a ceramic powder to the solution prepared in step 2);

4) heat-treating the solution prepared in step 3) to form a resin and carbonize it;

5) calcining the carbonized resin; And

6) provides a method for producing a porous nanocomposite powder comprising milling and drying the calcined powder.

Hereinafter, the present invention will be described in detail.

In the porous nanocomposite powder according to the present invention, a polymer resin is formed by adding an organic acid and a polyhydric alcohol to an aqueous solution in which a metal salt is dispersed, and then ceramic powder is added / dispersed to the nanocrystal grains crystallized from the metal salt on the surface of the ceramic powder. It is characterized in that the metal oxide is prepared by the porous coating.

The metal salt includes nickel, copper, zirconium, yttrium, cerium, gadolinium and the like, and salts of various metals used in the production of electrodes for solid fuel cells in the art, and a single metal salt or two or more metal salts may be used. Preferred multi-metal salts include nickel-nitrate hexahydrate, zirconyl-nitrate hydrate and yttrium-nitrate hexahydrate. ; Nickel-nitrate hexahydrate, gadolinium-nitrate hydrate, and cerium-nitrate hexahydrate; And copper-nitrate hexahydrate, gadolinium-nitrate hydrate, and cerium-nitrate hexahydrate. Combinations of multiple metal salts can be used and the invention is not limited to the use of these specific groups of multi-metal salts.

The organic acid includes citric acid, acetic acid, butyric acid, palmitic acid, oxalic acid and tartaric acid, and preferably citric acid.

The polyhydric alcohols include glycerin, ethylene glycol, propylene glycol, butylene glycol, sorbitol, dipropylene glycol, and the like, and preferably ethylene glycol.

The ceramic powder may also be used in the art, and yttria stabilized zirconia (YSZ) or gerialin coated ceria (GDC) may be particularly preferably used in the present invention.

Hereinafter, the method for preparing the porous nanocomposite powder of the present invention will be described in detail.

Steps 2) and 3) may be performed by stirring at 50 ° C. to 90 ° C., preferably at 60 ° C. for 1 hour.

Step 4) is a step of heat-treating at 180 ~ 250 ℃ for 2-6 hours, preferably 4 hours to form a polymer resin, and carbonization.

Step 5) is performed by calcination for 1 hour at 400 ~ 800 ℃, preferably at 600 ℃.

In the method for producing a composite powder using the polymer resin according to the present invention, (1) chelation reaction and (2) polyesterification reaction are used as basic chemical reactions. The chelation reaction consists of a bond between a metal cation on an aqueous metal salt solution and an organic acid, and the polyesterification reaction is a process using an esterification reaction between a organic acid and a polyhydric alcohol and a condensation polymerization reaction. According to the molar ratio of organic acid and polyhydric alcohol, polymer resin is formed and carbonized at 180-250 ° C, and calcined at 400-800 ° C. At this time, citric acid is used as the organic acid and ethylene glycol is used as the polyhydric alcohol, and a molar ratio of organic acid: polyhydric alcohol is about 1: 3 to 6, preferably about 1: 4. When the resin reaches the gelation zone, an exothermic peak appears, which means vigorous burning of the polymeric gel, which occurs at approximately 400 ° C. As a result of this phenomenon, a polymer resin having a large swelling and porous microstructure after drying at 180 ° C. is formed. At this time, other organic substances present in the reaction solution are burned and decomposed at the charring and calcination stages. Thus, only the crystal grains of the metal salt with organic matter decomposed and having a porous microstructure are bonded onto the ceramic powder surface.

After carbonization, the remaining amount of organic matter is burned away by ignition in the calcination step of the powder, and in this process, partial aggregation occurs. The appropriate amount of water initially helps to homogeneously mix the metal cation with the organic acid, 75-200 cc of water is suitable for approximately 1 mol of polymer gel, preferably 150 cc of water. If initially containing excess water, the mixture in aqueous solution is heated rapidly at the carbonization temperature before the oven is preheated, causing the water to evaporate violently. In addition, when a small amount of water is initially contained (75 cc / mol or less), the reactants may be mixed heterogeneously to form aggregates.

The ceramic powder coated / bonded with the porous nanocrystalline metal oxide formed as described above is subjected to milling and drying as in step 6), thereby preparing a porous nanocomposite powder according to the present invention.

Porous nanocomposite powder according to the present invention can be prepared in various ways depending on the type and composition of the added oxide and metal salt. For example, (1) a single metal salt, (2) a multi-metal salt containing elements with similar atomic characteristics (electronegativeness, atomic size, electron valence, etc.), and (3) a multi-metal salt with different atomic characteristics may be used as starting materials. Composite powder wherein (1 ') nano size single metal oxide is bonded to ceramic powder surface, (2') nano powder solid solution is bonded to ceramic powder surface, and (3 ' ) It is possible to prepare a composite powder in which several nano-sized metal oxides are bonded to the ceramic powder surface in the form of a mixture. When the solid solution is heat treated at a high temperature of a multi-metal oxide containing an element having similar atomic characteristics (electronegativity, atomic size, electron valence, etc.), the multi-metal oxide having similar characteristics may be formed by a solid-state reaction. It means the formation of one metal oxide form homogenized in the molecular or atomic range.

Therefore, as prepared in the specific example of the present invention, when only nickel oxide is used as the single metal salt, nanoparticles of nickel oxide are bonded to the ceramic powder surface in a porous form. In addition, amorphous metals of nickel oxide (NiO) and yttrium stabilized zirconia (YSZ) on the surface of ceramic powder when nickel-nitrate hexahydrate, zirconyl-nitrate hydrate, and yttrium-nitrate hexahydrate were used as the multi-metal salts. The nanoparticles in the form are bonded in a porous form.

The particle size of the porous nanocomposite powder prepared according to the present invention is about 0.3 to 0.6 m, preferably about 0.4 m, and the surface area is about 20 to 30 m 2 / g, preferably about 22 to 25 m 2 / g. In addition, the nano-size of the metal oxide coated on the particles of the porous nanocomposite powder has a size in the range of approximately 10 ~ 30 nm.

The present invention also provides a solid oxide fuel electrode prepared using the porous nanocomposite powder.

The solid oxide fuel electrode according to the present invention,

1) preparing a molded body by filling the porous nanocomposite powder of the present invention into a mold and then uniaxially pressurizing it;

2) sintering the molded body, and

3) It can be prepared including the step of reducing the sintered porous oxide support in a hydrogen atmosphere, the production method of such an electrode is a method generally known to those skilled in the art.

Specifically, the pressing step in the step 1) is preferably carried out at 60 ~ 80 kg / ㎠. In addition, the sintering step in the step 2) is preferably performed at 1300 ~ 1500 ℃, the reduction step in the 3) is preferably carried out in a hydrogen atmosphere (20 cm 3 · min ^-1 ) of 500 ~ 800 ℃.

The solid oxide fuel electrode according to the present invention has a very homogeneous distribution of metal-ceramic (YSZ) -pore three phases by using porous nano composite powder, and can secure sufficient porosity even without using a pore-forming agent. Gas permeability, mechanical strength and electrical conductivity are superior to the prepared electrode, and the surface roughness of the molded electrode is very low, and thus a thin and dense electrolyte can be synthesized by the coating method. In a specific embodiment of the present invention, the Ni-YSZ electrode was manufactured, but the present invention is not limited thereto, and various composite electrodes such as Ni-ScSZ, Ni-GDC, and Ni-SDC may be manufactured by replacing the oxide. The solid oxide fuel electrode according to the preferred embodiment of the present invention exhibits a porosity of 40% and a contraction rate of 22% at a sintering temperature of 1400 ° C., and shows little change in electrical conductivity according to heat cycle and oxidation / reduction cycle (FIGS. 6 to 6). 7).

In addition, the present invention provides a fuel cell including the fuel electrode.

In the solid oxide fuel cell according to the present invention, an electrolyte slurry is made of YSZ or the like and coated on the anode support, the anode support coated with the electrolyte slurry is calcined, and the cathode is coated on the top of the anode support by screen printing. The coated cathode may be manufactured by firing, and a method of manufacturing such a fuel cell is a method generally known to those skilled in the art.

In the solid oxide fuel cell according to the preferred embodiment of the present invention, the current density at 0.7V according to the holding time of 100 hours is uniformly about 0.9 A / cm 2 under the operating conditions of 800 ° C., and the change according to the time of the surface resistance is 0.8. It shows evenly in Ω / ㎠, the maximum output density according to the current density at 800 ℃ is 1.2 W / ㎠, the maximum output density is very high compared to the existing battery, the battery performance is excellent, 1.0 A / ㎠ electron at 800 ℃ Long term performance stability over 550 hours under load conditions is also consistent (see FIGS. 8-10).

Therefore, the solid oxide anode and the fuel cell according to the present invention can ensure a sufficient porosity without using a pore-forming agent by using a porous nano composite powder, homogeneous distribution of constituents (metal, ceramic powder, pores) The expansion of the electrode specific surface area and the three-phase interface provides excellent electrical conductivity and gas permeability, improving battery performance and reproducibility. In particular, long-term performance of fuel cells is suppressed by high temperature surface diffusion and aggregation of nickel by the constrained structure between the fine YSZ skeleton and the nickel particles produced by heterogeneous (heterogeneous) sintering of nickel zirconia nano composite powder. Stability, heat cycle stability and redox stability are significantly improved.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

Example  One  : Preparation of Porous Nanocomposite Powder Using Single Metal Salt

Porous nanocomposite powder according to the present invention was prepared by modifying the Pechini method.

60 g of a metal salt of nickel-nitrate hexahydrate (Ni (NO ₃ ) ₂ .6H ₂ 0) was dispersed in 150 cc of distilled water, followed by citric acid and ethylene glycol. Was added at a molar ratio of 1: 4 and stirred at 60 ° C. for 1 hour. After YSZ powder was added to the polymer resin containing the metal salt, heat treatment was performed at 180 ° C. for at least 4 hours to remove all moisture, followed by vigorous stirring to carbonize. The core of the nickel oxide then solidifies on the surface of the yttrium stabilized zirconia (YSZ) particles, which are ceramic powders. A nanocomposite powder for electrodes was prepared by heat-treating an amorphous core containing a metal salt in an oxidizing (air or oxygen) atmosphere at a temperature of 600 ° C. or higher to crystallize the surface of yttrium stabilized zirconia. The prepared composite powder was milled and dried in ethanol for 3 hours, and then used by grinding and filtering.

Example  2  : Preparation of Porous Nanocomposite Powder Using Multi-Metal Salt

In Example 1, 60 g of nickel-nitrate hexahydrate, and zirconyl-nitrate hydrate (2 g), instead of a single metal salt, nickel-nitrate hexahydrate, was used. Porous nanocomposite powder was prepared in the same manner as in Example 1, except that 0.45 g of yttrium-nitrate and hexahydrate was used.

In the prepared porous nanocomposite powder, amorphous nanoparticles of nickel oxide and yttrium stabilized zirconia are bonded to the surface of ceramic powder (YSZ powder) in a porous form.

A flow chart illustrating a method of preparing a porous nanocomposite powder according to the present invention is shown in FIG. 1, and a schematic structure of the porous nanocomposite powder according to the present invention is shown in FIG. 2, and the porous nanocomposite powder according to the present invention is injected. The photograph observed with an electron microscope (SEM) is shown in FIG. 3.

Example  3  : Solid oxide fuel electrode according to the present invention of  Produce

After filling the porous nanocomposite powder prepared in Example 2 into a mold, a molded article was prepared by uniaxial press at 70 kg / cm 2. At this time, the diameter of the molded body was 38 mm and the thickness was 1.2 mm. The molded body was sintered at 1400 ° C. and then reduced in 800 ° C. hydrogen atmosphere (20 cm 3 · min ⁻¹ ) to prepare a fuel electrode.

The microstructure of the solid oxide Ni-YSZ anode according to the present invention is shown in FIG. 4 observed with an optical microscope and a scanning electron microscope (SEM): an optical image (metal: white) , Ceramic powder: gray, pore: black), (b): scanning electron microscope image).

As shown in FIG. 4, the solid oxide fuel electrode manufactured using the porous composite powder according to the present invention has a very homogeneous distribution of metal (nickel) -ceramic (YSZ) -pore three phases (FIG. 4A), and a pore-forming agent. Sufficient porosity was shown without using (FIG. 4B).

The prepared anode was formed into flakes and observed by transmission electron microscopy (TEM) to simultaneously bond the composite microstructure sintered in the Ni-YSZ cathode, and the nickel sintered body and nano yttria stabilized zirconia formed on the surface of the composite powder. The microstructure of the site is shown in Figure 5a, the analysis of the EDX point site of Figure 5a by energy distribution x-ray (EDX) is shown in Figure 5b.

The porosity and bowing rate according to the sintering temperature of the solid oxide fuel electrode according to the present invention are shown in FIG. 6.

As shown in FIG. 6, the solid oxide fuel electrode according to the present invention exhibited a porosity of 40% and a contraction rate of 22% at a sintering temperature of 1400 ° C. FIG. In the case of the general electrode, porosity of about 20% is shown at the sintering temperature of 1400 ° C., which is considered to be affected by the sintering.

The change in electrical conductivity according to the heat cycle and the oxidation / reduction cycle of the solid oxide fuel electrode according to the present invention is shown in FIG. 7.

As shown in Figure 7, Praxair (USA) electrodes manufactured using the fuel cell, powder thermal cycle 50 times, and then the electric conductivity is reduced by about 56.8% at 1208.8 S · ㎝ ^-1 to 522.7 S · ㎝ ^-1 rapidly degraded However, in the solid oxide fuel electrode according to the present invention, the electrical conductivity decreases by about 11.4% after 50 heat cycles, indicating that there is almost no change in electrical conductivity.

Example  4  : Fabrication of solid oxide fuel cell

An YSZ electrolyte slurry was prepared using the anode prepared in Example 3, and coated on the anode support by immersion-impression. The anode support coated with the YSZ electrolyte slurry was calcined at 1400 ° C. A cathode paste was prepared from lanthanum perovskite (LSM: (La, Sr) MnO ₃ ) powder and coated on the top of the anode supported electrolyte by screen printing. The coated cathode was calcined at 1100 ° C. to manufacture a fuel cell.

8 shows current density values corresponding to 0.7 V electromotive force values on the IV curve of the solid oxide fuel cell of the present invention according to the holding time of at least 100 hours at 800 ° C. and resistance values measured through impedance analysis. The IV curve of the solid oxide fuel cell of the present invention (components: anode (LSM + YSZ) / electrolyte (YSZ) / electrode (EDC: electrode prepared using the composite powder of the present invention) according to the temperature is shown in FIG. Indicated. In addition, the long-term performance stability evaluation of the solid oxide fuel cell of the present invention at 800 ° C. under 1.0 A / cm 2 electronic load condition is shown in FIG. 10.

As shown in FIGS. 8 to 10, the solid oxide fuel cell according to the present invention showed a current density at about 0.7 A / cm 2 at 0.7 V according to a holding time of 100 hours under an operating condition of 800 ° C., and specific surface resistance. The change over time was evenly 0.8 Ω / ㎠. In addition, the solid oxide fuel cell of the present invention showed a maximum output density of 1.2 W / cm 2 at 800 ° C. according to the current density, which is very high compared to the conventional battery. In addition, the 550 hours long-term performance stability of the solid oxide fuel cell of the present invention was constant at 800 A under 1.0 A / cm 2 electronic load conditions.

Therefore, it can be seen that the solid oxide fuel cell according to the present invention has excellent cell performance and long-term performance stability.

The porous nanocomposite powder according to the present invention can be manufactured using an environmentally friendly water-based process with a simple, low time and low cost. Therefore, the electrode prepared using the porous nanocomposite powder of the present invention can secure sufficient porosity even without using a pore-forming agent, homogeneous distribution of constituents (metal, ceramic powder, pores), and the electrode specific surface area and The expansion of the three-phase interface provides excellent electrical conductivity and gas permeability, improving battery performance and reproducibility. In particular, long-term performance of fuel cells is suppressed by high temperature surface diffusion and aggregation of nickel by the constrained structure between the fine YSZ skeleton and the nickel particles produced by heterogeneous (heterogeneous) sintering of nickel zirconia nano composite powder. Stability, heat cycle stability and redox stability are significantly improved.

Claims (14)

1) dissolving and dispersing a metal salt in distilled water; 2) adding an organic acid and a polyhydric alcohol to the aqueous solution in which the metal salt is dispersed; 3) adding a ceramic powder to the solution prepared in step 2); 4) heat-treating the solution prepared in step 3) to form a resin and carbonize it; 5) calcining the carbonized resin; And 6) milling and drying the calcined powder, In this case, the metal salt is a method for producing a porous nanocomposite powder of two or more multi-type metal salt. delete delete The method of claim 1, wherein the multi-metal salt is nickel-nitrate hexahydrate, zirconyl-nitrate hydrate and yttrium-nitrate hexahydrate nitrate hexahydrate); Nickel-nitrate hexahydrate, gadolinium-nitrate hydrate, and cerium-nitrate hexahydrate; And copper-nitrate hexahydrate, gadolinium-nitrate hydrate, and cerium-nitrate hexahydrate. Method for producing a porous nanocomposite powder, characterized in that. The method of claim 1, wherein the organic acid is selected from the group consisting of citric acid, acetic acid, butyric acid, palmitic acid, oxalic acid and tartaric acid. The method of claim 5, wherein the organic acid is citric acid. The method of claim 1, wherein the polyhydric alcohol is selected from the group consisting of glycerin, ethylene glycol, propylene glycol, butylene glycol, sorbitol and dipropylene glycol. The method of claim 7, wherein the polyhydric alcohol is ethylene glycol. The method of claim 1, wherein the organic acid and the polyhydric alcohol are mixed at a molar ratio of 1: 3 to 6. The method of claim 1, wherein the ceramic powder is yttria stabilized zirconia (YSZ) or gadolinium-coated ceria (GDC). A porous nanocomposite powder having a nanocrystalline metal oxide porous coated on a surface of a ceramic powder prepared by the method of any one of claims 1 and 4 to 10. The porous nanocomposite powder of claim 11, wherein the porous nanocomposite powder has a particle size of 0.3 μm to 0.6 μm. A solid oxide fuel electrode prepared using the porous nanocomposite powder of claim 11. A solid oxide fuel cell comprising the solid oxide fuel electrode of claim 13.

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