KR101611254B1 - Method of manufacturing anode materials for solid oxide fuel cell - Google Patents

Abstract

The present invention provides a method for manufacturing a solid oxide fuel cell including an anode material with excellent thermal and chemical stabilities and high conductivity. The method for manufacturing a solid oxide fuel cell includes the following steps: providing an anode material made of a double perovskite crystal structure material including cobalt; and thermally processing the anode material in a reducing atmosphere to elute the cobalt from the double perovskite crystal structure material and crystallize the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solid oxide fuel cell,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell, and more particularly, to a method of manufacturing a solid oxide fuel cell including an oxide having a perovskite crystal structure and using an elution phenomenon as an anode.

A solid oxide fuel cell (SOFC) is a highly efficient, environmentally friendly electrochemical power generation technology that directly converts the chemical energy of a fuel gas into electrical energy. Since all components are solid, SOFC has a simple structure, relatively low cost, and is free from electrolyte loss and replacement and corrosion problems compared to other fuel cells. Solid oxide fuel cells can also use relatively high impurity fuels and have many advantages such as hybrid power generation capability and high efficiency. In addition, hydrocarbon fuel can be directly used without reforming the fuel into hydrogen, leading to simplification of the fuel cell system and reduction of production cost.

The SOFC includes an anode (anode or anode, cathode) in which a fuel such as hydrogen or a hydrocarbon is oxidized, a cathode (cathode or cathode, anode) where oxygen gas is reduced to oxygen ion (O ^2- ) A solid electrolyte, and specific physical properties are required depending on the type of material used.

As the anode electrode, a nickel-based material is mainly used. Nickel is a very good conversion catalyst and has excellent advantages such as excellent electroconductivity as an electrocatalyst and helping the electrochemical oxidation of hydrogen. Nickel-cermet, which is currently used mainly, is inexpensive and stable in a reducing atmosphere of high temperature. Ni-YSZ is most widely studied due to its thermal expansion coefficient similar to that of Yttria-stabilized zirconia (YSZ) and its low charge transfer resistance at the Ni-YSZ interface.

On the other hand, nickel-cermet has a low resistance to carbon (C) and sulfur (S) contained in hydrocarbon-based fuels. Direct oxidation of hydrocarbons and carbon monoxide without the supply of steam to the dry fuel gas and without the application of a sufficiently high current density results in the formation of anodic materials by carbon deposition because nickel has the catalytic properties of forming carbon- There is a problem in that it is destroyed rapidly. Nickel is an excellent electrochemical catalyst for the electrochemical oxidation of hydrogen. However, when natural gas or hydrocarbon is directly used as a fuel, its activity is lowered by carbon deposition. When carbon is deposited on nickel particles, activation polarization ) Becomes very high, and the anode performance is deteriorated. In addition, it is very important that the structure phase should be stable in a hydrogen environment, and at the same time, it is necessary to maintain an electric conductivity higher than a certain value. In such a hydrogen environment, there is a fear that the performance of the anode may deteriorate during long-term use. Therefore, an anode material having excellent thermal and chemical stability and high electrical conductivity is required.

Japanese Patent Application Laid-Open No. 2007-515745

The present invention also provides a method for producing a solid oxide fuel cell having excellent thermal and chemical stability and high electrical conductivity.

It is another object of the present invention to provide a solid oxide fuel cell manufactured by the method for manufacturing the solid oxide fuel cell.

According to an aspect of the present invention, there is provided a method of manufacturing a solid oxide fuel cell, the method including: providing an anode material composed of a double layered perovskite crystal structure material including cobalt; And heat treating the anode material in a reducing atmosphere to exsolution and crystallize the cobalt from the bilayer perovskite crystal structure material.

In one embodiment of the present invention, the bilayer perovskite crystal structure material may include a compound represented by the following formula (1).

≪ Formula 1 >

RECo ₂ O _{5 + δ}

In Formula 1, R may include one or more elements selected from a rare earth group or a lanthanide group, and E may include one or more elements selected from an alkaline earth metal group, O is oxygen , X is a number of more than 0 and less than 2, and? Is a positive number of 0 or 1 or less.

In one embodiment of the present invention, the bilayer perovskite crystal structure material may include a compound of the following formula (2).

(2)

RET _2-x Co _x O _{5 +?}

In the above formula (2), R may include one or more elements selected from a rare earth group or a lanthanide group, and E may include one or more elements selected from an alkaline earth metal group, Metal, O is oxygen, x is a number of more than 0 and less than 2, and? Is a positive number of 0 or 1 or less, and the compound of the formula (2) to be.

In one embodiment of the present invention, the R is at least one selected from the group consisting of Y, Sc, Sm, Gd, La, Ne, Pr, Sm, gadolinium, europium, terbium, erbium, or mixtures thereof.

In one embodiment of the present invention, E may include barium Ba, calcium Ca, strontium Sr, or a mixture thereof.

In one embodiment of the present invention, the T may include manganese (Mn), iron (Fe), or a mixture thereof.

In one embodiment of the present invention, the bilayer perovskite crystal structure material may include a compound represented by the following formula (3).

(3)

PrBaMn _2-x Co _x O _{5 +?}

In the formula (3), O is oxygen, x is a number of more than 0 and less than 1, and? Is a positive number of 0 or 1 or less.

In one embodiment of the present invention, the bilayer perovskite crystal structure material may include a compound represented by the following formula (4).

≪ Formula 4 >

RET _2-x T ' _x O _{5 +?}

In Formula 4, R may include one or more elements selected from a rare earth group or a lanthanide group, and E may include one or more elements selected from an alkaline earth metal group, and T and T 'May contain different elements selected from transition metals, O is oxygen, x is a number greater than 0 and less than 1, and the delta is a positive number equal to or less than 0 or 1, .

In one embodiment of the present invention, the reducing atmosphere may include a hydrogen atmosphere.

According to an aspect of the present invention, there is provided a method of manufacturing a solid oxide fuel cell, including: providing an anode material comprising a double layered perovskite crystal structure material including a transition metal; And heat treating the anode material in a reducing atmosphere to exsolution and crystallize the transition metal from the double layered perovskite crystal structure material.

According to an aspect of the present invention, there is provided a solid oxide fuel cell comprising: an anode; A cathode disposed facing the anode; And an electrolyte disposed between the anode and the cathode, wherein the anode is formed by heat-treating an anode material composed of a bilayer perovskite crystal structure material containing cobalt in a reducing atmosphere to form the double layer perovskite crystal structure material And cobalt which has been crystallized by exsolution.

The method of manufacturing a solid oxide fuel cell according to the technical idea of the present invention includes cobalt which is eluted and crystallized from a double layer perovskite crystal structure material containing cobalt. The cobalt particles thus eluted and crystallized can function as a conversion catalyst to help electrochemical oxidation of hydrogen instead of conventional nickel and the like. The embodiment of the present invention showed a very high electric conductivity at a high temperature, especially at 800 ° C, and the maximum power density was higher than when cobalt was not eluted. In addition, excellent thermal and chemical stability at high temperatures can be provided.

Further, when nickel is used as an anode material and a hydrocarbon-based fuel is used as a fuel according to the prior art, resistance to carbon (C) and sulfur (S) contained in the fuel is low. However, since the solid oxide fuel cell according to the technical idea of the present invention can exclude nickel as a constituent element of the anode and can use eluted cobalt as a catalyst instead of nickel, problems such as carbon deposition of nickel .

In addition, since the step of separately adding the catalyst to the anode material can be omitted, the process can be simplified and the cost can be reduced.

The effects of the present invention described above are exemplarily described, and the scope of the present invention is not limited by these effects.

1 is a schematic view showing a solid oxide fuel cell according to an embodiment of the present invention.
2 is a flow chart schematically showing a method of manufacturing a solid oxide fuel cell according to an embodiment of the present invention.
3 is a flow chart schematically illustrating a method of manufacturing a solid oxide fuel cell according to an embodiment of the present invention.
4 is a schematic view showing a double layer perovskite crystal structure material constituting the anode material of a solid oxide fuel cell according to an embodiment of the present invention.
5 and 6 are SEM micrographs showing the cobalt elution phenomenon of the anode material of the solid oxide fuel cell according to an embodiment of the present invention.
FIG. 7 is a graph showing the Nyquist plot showing the frequency spectrum of the impedance after heat treatment in the hydrogen atmosphere for the anode material manufactured according to the embodiment of the present invention. FIG.
8 is a graph showing IV polarization curves and maximum power densities of a fuel cell when hydrogen is used as a fuel for a solid oxide fuel cell including an anode material manufactured according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail. In interpreting the terms or words used in the present specification and claims, it is to be understood that the interpretation of terms or words used herein is necessarily conventional, based on the principle that the inventor can properly define the concept of the term to describe its invention in the best way It is to be understood that the invention is not to be interpreted as being limited only by the precautionary sense, but should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention as described in the present specification.

1 is a schematic view of a solid oxide fuel cell 100 according to an embodiment of the present invention.

Referring to Figure 1, a solid oxide fuel cell 100 includes an anode 110, a cathode 120 disposed opposite the anode 110, and a cathode 120 disposed between the anode 110 and the cathode 120, And an electrolyte 130 which is a solid oxide. And optionally a buffer layer 140 disposed between the anode 110 and the electrolyte 130.

The electrochemical reaction of the solid oxide fuel cell 100 can be performed by an anode reaction in which the oxygen gas O ₂ of the cathode 120 is changed to oxygen ions O ^2- and the anode reaction of the anode 110 in the form of H ₂ or hydrocarbons ) And oxygen ions that have moved through the electrolyte.

<Reaction Scheme>

Anode reaction: 1/2 O ₂ + 2e ^- -> O ^2-

Cathode reaction: H ₂ + O ^2- -> H ₂ O + 2e ^-

In the cathode 120 of the solid oxide fuel cell 100, the oxygen adsorbed on the surface of the electrode is dissociated and diffused to form a triple phase boundary where the electrolyte 130, the cathode 120, and the pores (not shown) The oxygen ions are converted into oxygen ions, and the generated oxygen ions are transferred to the anode 110, which is a fuel electrode, through the electrolyte 130.

In the anode 110 of the solid oxide fuel cell 100, the moved oxygen ions combine with the hydrogen contained in the fuel to generate water. At this time, hydrogen evolves electrons to hydrogen ions (H ⁺ ) and binds to the oxygen ions. The discharged electrons move to the cathode 120 through wiring (not shown) to change oxygen to oxygen ions. Through such electron transfer, the solid oxide fuel cell 100 can perform the battery function.

Since the solid oxide fuel cell 100 can be manufactured by a conventional method known in the art, a detailed description thereof will be omitted here. In addition, the solid oxide fuel cell 100 may be applied to various structures such as a tubular stack, a flat tubular stack, a planar type stack, and the like.

The solid oxide fuel cell 100 may be in the form of a stack of unit cells. For example, a unit cell (MEA, membrane and electrode assembly) composed of an anode 110, a cathode 120, and an electrolyte 130 is stacked in series, and a separator plate a stack of unit cells can be obtained with a separator interposed therebetween.

Hereinafter, the constituent elements of the solid oxide fuel cell 100 will be described in detail.

The anode 110 may be made of an anode material according to the technical idea of the present invention, and the anode material will be described in detail below.

The cathode 120 is not particularly limited and a known cathode may be used. The cathode 120 may include, for example, LaSrFe-YSZ, and may include, for example, La _0.8 Sr _0.2 Fe-YSZ. The cathode 120 may comprise, for example, NBSCF-40GDC (NdBa _0.5 Sr _0.5 Co _1.5 Fe _0.5 O _{5 +?} -Ce _0.9 Gd _0.1 O _1.95 ).

The electrolyte 130 is not particularly limited as long as it can be generally used in the art. For example, the electrolyte 130 may be a stabilized zirconia based system such as yttria stabilized zirconia (YSZ) and scandia stabilized zirconia (ScSZ); Ceria systems doped with rare earth elements such as samaria-doped ceria (SDC), gadolinia-doped ceria (GDC) and the like; Other LSGM ((La, Sr) (Ga, Mg) O ₃ ) system; And the like. In addition, the electrolyte 130 may include strontium or magnesium-doped lanthanum gallate. For example, the electrolyte 130 may include La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _{3 -δ} .

The buffer layer 140 may be positioned between the anode 110 and the electrolyte 130 to provide a smooth contact. The buffer layer 140 may function to mitigate the crystal lattice distortion of the anode 110 and the electrolyte 130, for example. The buffer layer 140 may include, for example, LDC (La _0.4 Ce _0.6 O _{2 -δ} ). The buffer layer 140 may be omitted as an optional component.

2 is a flow chart schematically showing a method (S100) for producing a solid oxide fuel cell according to an embodiment of the present invention.

Referring to FIG. 2, there is shown a method of manufacturing an anode material constituting the anode 110, which is a component of the solid oxide fuel cell 100. Referring to FIG. 3, a method (S100) for producing a solid oxide fuel cell includes the steps of providing (S110) an anode material composed of a bilayer perovskite crystal structure material including cobalt; And a step (S120) of heat-treating the anode material in a reducing atmosphere to exsolution and crystallizing the cobalt from the bilayer perovskite crystal structure material (S120).

The heat treatment may be performed under a hydrogen atmosphere. The heat treatment may be performed at a temperature in the range of, for example, about 700 ° C to about 800 ° C. The heat treatment may be performed under a hydrogen pressure of, for example, from about 0.1 atm to about 10 atm, for example, under a hydrogen pressure of about 3 atm.

Further, the technical idea of the present invention is not limited to the case where cobalt is eluted from the double layer perovskite crystal structure material to crystallize. For example, the case where the above-mentioned double-layered perovskite crystal structure material may contain various transition metals and in which the various transition metals are eluted from the double-layered perovskite crystal structure material to crystallize is included in the technical idea of the present invention do.

3 is a flow chart schematically showing a method of manufacturing a solid oxide fuel cell (S200) according to an embodiment of the present invention.

Referring to FIG. 3, a method of manufacturing a solid oxide fuel cell (S200) comprises the steps of: S210 providing an anode material composed of a bilayer perovskite crystal structure material containing a transition metal; And a step (S220) of heat-treating the anode material in a reducing atmosphere to exsolution and crystallizing the transition metal from the bilayer perovskite crystal structure material (S220).

The anode material constituting the anode 110 of the solid oxide fuel cell 100 may be composed of a perovskite crystal structure material and may be composed of, for example, a double perovskite crystal structure material have. The perovskite crystal structure material can be largely divided into a single perovskite crystal structure material and a double layer perovskite crystal structure material.

A simple perovskite crystal structure material may have the formula ABO ₃ . The single perovskite crystal structure may include elements having relatively large ionic radii in the A-site at the corner of the cubic lattice, CN, Coordination number). For example, a rare earth element, an alkaline rare earth element, and an alkaline element may be located in the A-site. The B-site, which is the body center of the cubic lattice, may contain elements having relatively small ionic radii, and may have six coordination numbers by oxygen ions. For example, cobalt (Co), iron (Fe), and the like and a transition metal may be located in the B-site. Oxygen ions may be located at each face center of the cubic lattice. Such a single perovskite structure can generally result in structural displacements when other materials are substituted on the A-site, and it is often the case that the nearest oxygen ions in the octahedron of BO ₆ consisting of six) it may cause structural variations.

4 is a schematic view showing a double layer perovskite crystal structure material constituting the anode material of a solid oxide fuel cell according to an embodiment of the present invention.

Referring to FIG. 4, the bilayer perovskite crystal structure material has a crystal lattice structure in which two or more elements are regularly arranged on the A-site, for example, a structure of AA'B ₂ O _{5 +} Lt; / RTI &gt; Specifically, a lanthanide compound having a bilayer perovskite crystal structure can be basically repeated with the lamination permutation of [BO ₂ ] - [AO] - [BO ₂ ] - [A'O] along the c axis. For example, B may be manganese (Mn), and A may be a lanthanide group including yttrium (Y) or praseodymium (Pr), and A 'may be barium (Ba).

Upon reduction in a hydrogen atmosphere, the anode material changes from a single perovskite crystal structure to a double perovskite crystal structure. Such double-perovskite crystal structure can accelerate oxygen ion movement and improve thermal and chemical stability. In addition, an anode having higher electrical conductivity in a hydrogen atmosphere and thermo-chemical stability than the conventional anode and exhibiting excellent performance can be realized.

The anode according to one embodiment of the present invention may include a compound represented by the following formula (1).

&Lt; Formula 1 >

RECo ₂ O _{5 + δ}

In Formula 1, R may include one or more elements selected from a rare earth group or a lanthanide group, and E may include one or more elements selected from an alkaline earth metal group, O is oxygen , X is a number of more than 0 and less than 2, and? Is a positive number of 0 or 1 or less.

The R may comprise one or more elements selected from rare earth metals and may include, for example, yttrium (Y), scandium (Sc), samarium (Sm), gadolinium (Gd) . The R may include one or more elements selected from the group consisting of lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), gadolinium (Gd) Eu), terbium (Tb), erbium (Er), or mixtures thereof.

The E may include one or more elements selected from the group of the alkaline metal, and may include, for example, barium (Ba), calcium (Ca), strontium (Sr), or a mixture thereof.

O is oxygen. Is a positive number of 1 or less, and the value of the compound of the formula (1) is an electrical neutrality. The above 隆 represents interstitial oxygen in the following double layer perovskite structure and the value of 隆 can be determined according to a specific crystal structure.

The anode according to an embodiment of the present invention may include a compound represented by the following formula (2).

(2)

RET _2-x Co _x O _{5 +?}

In the above formula (2), R may include one or more elements selected from a rare earth group or a lanthanide group, and E may include one or more elements selected from an alkaline earth metal group, Metal, O is oxygen, x is a number of more than 0 and less than 2, and? Is a positive number of 0 or 1 or less, and the compound of the formula (2) to be.

The R may comprise one or more elements selected from rare earth metals and may include, for example, yttrium (Y), scandium (Sc), samarium (Sm), gadolinium (Gd) .

The R may include one or more elements selected from the group consisting of lanthanum (La), neodymium (Nd), praseodymium (Pr), samarium (Sm), gadolinium (Gd) Eu), terbium (Tb), erbium (Er), or mixtures thereof.

The E may include one or more elements selected from the group of the alkaline metal, and may include, for example, barium (Ba), calcium (Ca), strontium (Sr), or a mixture thereof.

The T may comprise one or more elements selected from transition metals and may include, for example, manganese (Mn), iron (Fe), or mixtures thereof. The T may be an element that substitutes the cobalt to occupy the position of the cobalt in the compound of Formula 2. The substitution may increase the thermal stability and the chemical stability of the anode.

O is oxygen. Is a positive number of 1 or less, and the value of the compound of the formula (2) is an electrical neutrality. The above 隆 represents interstitial oxygen in the following double layer perovskite structure and the value of 隆 can be determined according to a specific crystal structure.

The anode according to an embodiment of the present invention may include a compound represented by the following formula (3).

(3)

PrBaMn _2-x Co _x O _{5 +?}

In the formula (3), O is oxygen, x is a number of more than 0 and less than 1, and? Is a positive number of 0 or 1 or less.

The above-mentioned PrBaMn _2-x Co _x O _{5 + delta} compound of the above formula (3) may have various ranges of x, for example, the above x may include a compound having a range of 0.2 to 0.4. For example, the PrBaMn _2-x Co _x O _{5 + delta} compound of Formula 3 may be PrBaMn _1.8 Co _0.2 O _{5 + delta} compound, PrBaMn _1.7 Co _0.3 O _{5 + delta} compound, or PrBaMn _1.6 Co _0.4 O _{5 +} &Lt; / RTI &gt; compounds.

The perovskite crystal structure material constituting the anode as described above is exemplified and the technical idea of the present invention is not limited thereto and the case where various perovskite crystal structure materials are included is also included in the technical idea of the present invention . For example, the anode according to one embodiment of the present invention may include a Sr ₂ Mg _1-x Ni _x MoO ₆ -δ compound.

Although the above embodiments have been described with respect to the case where cobalt is eluted from the bilayer perovskite crystal structure material to crystallize, the technical idea of the present invention is not limited thereto. That is, the case where the transition metal other than cobalt constituting the bilayer perovskite crystal structure material is eluted and crystallized is also included in the technical idea of the present invention. Therefore, the anode material according to one embodiment of the present invention may include a compound of the following formula (4).

&Lt; Formula 4 >

RET _2-x T ' _x O _{5 +?}

In Formula 4, R may include one or more elements selected from a rare earth group or a lanthanide group, and E may include one or more elements selected from an alkaline earth metal group, and T and T 'May contain different elements selected from transition metals, O is oxygen, x is a number greater than 0 and less than 1, and the delta is a positive number equal to or less than 0 or 1, . In the compound of Formula 4, T 'may be an element that substitutes the T to occupy the position of T, and the substitution may increase the thermal stability and chemical stability of the anode.

Hereinafter, a method for manufacturing an anode material for a solid oxide fuel cell according to the technical idea of the present invention will be described.

The method for producing the anode material may include a step of preparing each metal precursor metered to the composition of the RECO ₂ O _{5 + δ} compound of the formula (1) or the RET _{2 -x} Co _x O _{5 + δ} compound of the formula (2) (Wet) mixture using a solvent, obtaining a solid from the (wet) mixture, firing the solid in air to obtain a fired product, and polishing the fired product.

The metal precursor is mixed in a stoichiometric ratio to obtain the compound of the above formula. Examples of the metal precursor include, but are not limited to, nitrides, oxides, halides, and the like of each component constituting the anode material of the above formula. For example, when the compound forming the anode is PrBaMn _2-x Co _x O _{5 +?} Compound of formula (3), for example, the compound forming the anode is PrBaMn _1.7 Co _0.3 O _{5 +} The precursor may be a nitride, oxide, halide, or the like containing at least one of Pr, Ba, Mn, Co, and the like.

In the step of mixing the metal precursor with the solvent, water may be used as a solvent, but the present invention is not limited thereto. The metal precursor can be used without limitation as long as it can dissolve the metal precursor. For example, a lower alcohol having 5 or less carbon atoms, such as methanol, ethanol, 1-propanol, 2-propanol and butanol; Acidic solutions such as nitric acid, hydrochloric acid, sulfuric acid, and citric acid; water; Organic solvents such as toluene, benzene, acetone, diethyl ether and ethylene glycol; May be used alone or in combination.

The step of mixing the metal precursor with the solvent may be performed at a temperature in the range of about 100 ° C to about 200 ° C and may be carried out for a predetermined time under agitation so that each component can be thoroughly mixed. The mixing process, removing the solvent, and addition of additives required for this purpose are well known, for example, by the pechini method, and therefore are not described here.

After the mixing process, ultrafine solid material can be obtained by spontaneous combustion. The ultrafine solid can then be heat treated (calcined, sintered) for a time period ranging from about 400 ° C. to about 950 ° C. for a time period ranging from about 1 hour to about 5 hours, for example, at about 600 ° C. for about 4 hours.

If necessary, a second heat treatment (calcination, sintering) may be performed after the firing. This second heat treatment step is a step of calcining in air for about 12 hours at a temperature in the range of about 950 ° C to about 1500 ° C, for a period of about 1 hour to about 24 hours, for example, at a temperature in the range of about 950 to about 1500 ° C To obtain a powdery product.

Then, the fired product may be ground or pulverized to obtain a fine powder having a predetermined size. For example, milling and mixing by ball milling in acetone for about 24 hours. Next, the mixed powder is put into a metal mold and pressed, and then the pressurized pellet is sintered in the atmosphere to produce an anode material. Sintering may be performed at a temperature in the range of about 950 ° C to about 1500 ° C for a period ranging from about 12 hours to about 24 hours, for example, at a temperature in the range of from about 950 to about 1500 ° C for a period of about 24 hours, . The fired product may be ground or pulverized to obtain a fine powder having a predetermined size.

An anode can be prepared from the composition for an anode. For example, the anode can be formed by coating a composition for the anode-forming material on a substrate and then performing heat treatment. The heat treatment may be performed in a reducing atmosphere such as a hydrogen atmosphere so that cobalt is eluted from the anode and crystallized. The heat treatment may be performed at a temperature in the range of, for example, about 700 ° C to about 800 ° C. The heat treatment may be performed under a hydrogen pressure of, for example, about 3 atm.

The thickness of the anode can typically range from about 1 [mu] m to about 100 [mu] m in a solid oxide fuel cell. For example, the thickness of the anode may range from about 5 [mu] m to about 50 [mu] m.

[Example]

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The above embodiments are not intended to limit the scope of the present invention.

The PrBaMn _1.7 Co _0.3 O _{5 +?} Compound derived from the above formula (3) was selected as the anode material. In order to form the anode material, the metal precursors were dissolved in a solvent mixed with ethylene glycol, citric acid, and distilled water. After melting, ultrafine solid can be obtained through self-combustion process. The ultrafine solid was heat-treated at 600 ° C. for 4 hours, pulverized and mixed in a ball mill for 24 hours in acetone, dried, compressed with pellets at 5 MPa and air-dried at 1500 ° C. for 24 hours Lt; / RTI &gt; And reduced in an atmosphere of 100% H ₂ (corresponding to 3% H ₂ O) to form a bilayer perovskite structure to form an anode material. The anode material includes cobalt which is eluted and crystallized, as shown in Fig. 6 below.

The anode material was then mixed with an organic binder (Heraeus V006) to synthesize an anode slurry.

The full single cell was compacted with pellets of LSGM powder and sintered in air at about 1475 ° C for 5 hours and polished to obtain a dense electrolyte with a thickness of about 250 μm. Next, a cathode slurry containing NdBa _0.5 Sr _0.5 Co _1.5 Fe _0.5 O _{5 +?} -Ce _0.9 Gd _0.1 O ₂ -δ, a buffer layer slurry containing La _0.4 Ce _0.6 O ₂ -δ (LDC), and PrBaMn _1.7 An anode slurry containing Co _0.3 O _{5 + delta} (PBMCO) was screen-printed on the electrolyte, respectively, and then sintered in air at about 950 ° C for about 4 hours to prepare a fuel cell.

The thicknesses of the anode, cathode, and electrolyte formed as described above were about 50 mu m, about 50 mu m, and about 250 mu m, respectively, and silver wire was attached to the cathode and anode using silver paste for current collection.

According to the above manufacturing method, a solid oxide fuel cell composed of an anode, an LDC buffer layer, an LSGM electrolyte, and an NBSCF-GDC cathode was fabricated.

5 and 6 are SEM micrographs showing the cobalt elution phenomenon of the anode material of the solid oxide fuel cell according to an embodiment of the present invention. Fig. 5 is a photograph before cobalt elution, and Fig. 6 is a photograph after cobalt elution.

The material shown in FIG. 5 is PrBaMn _1.7 Co _0.3 O _{5 + delta} single perovskite crystal structure material before reduction in a hydrogen atmosphere, and the material shown in FIG. 6 is PrBaMn _1.7 Co _0.3 O _{5 + delta} Layered perovskite crystal structure material.

Hereinafter, the phenomenon in which cobalt is eluted from the bilayer perovskite crystal structure material will be described. The exsolution refers to a phenomenon in which a substance is separated and crystallized separately from a solid solution material. The separately crystallized material may generally be arranged along the crystallographic orientation of the parent material of the solid solution.

Referring to Figure 5, the anode material comprised of the bilayer perovskite crystal structure material has a smooth surface before the cobalt is eluted.

Referring to FIG. 6, when the anode material composed of the bilayer perovskite crystal structure material is reduced in a reducing atmosphere such as a hydrogen atmosphere, cobalt is separated from the bilayer perovskite structure material and granulated. Such particles are formed to protrude from the smooth surface of Fig.

The cobalt particles thus eluted and crystallized can function as a conversion catalyst to help electrochemical oxidation of hydrogen instead of conventional nickel and the like.

FIG. 7 is a graph showing the Nyquist plot showing the frequency spectrum of the impedance after heat treatment in the hydrogen atmosphere for the anode material manufactured according to the embodiment of the present invention. FIG.

Referring to FIG. 7, as the elution phenomenon of cobalt occurs, cobalt particles are catalyzed on the surface, thereby exhibiting an effect of reducing the resistivity.

8 is a graph showing I-V polarization curves and maximum power density of a fuel cell when hydrogen is used as a fuel for a solid oxide fuel cell including an anode material manufactured according to an embodiment of the present invention.

In FIG. 8, the solid symbols represent the voltage according to the current density, and the open symbols represent the power density according to the current density.

The I-V polarization curves of FIG. 8 were measured at 800 DEG C using a constant potential device from BioLogic. Specifically, the I-V polarization curves used humidified hydrogen gas (3% moisture) at 800 ° C as fuel and ambient air as stationary oxidant.

The maximum power density of the solid oxide fuel cell according to the embodiment of the present invention was 1.12 W / cm ² at 800 ° C. On the other hand, the PrBaMn _2-x Co _x O _{5 + δ} compound (PBM) without cobalt elution was 0.661 W / cm ² at 800 ° C. Therefore, the case where eluted cobalt is included has a higher maximum power density.

The method of manufacturing a solid oxide fuel cell according to the technical idea of the present invention includes cobalt which is eluted and crystallized from a double layer perovskite crystal structure material containing cobalt. The cobalt particles thus eluted and crystallized can function as a conversion catalyst to help electrochemical oxidation of hydrogen instead of conventional nickel and the like. The embodiment of the present invention showed a very high electric conductivity at a high temperature, especially at 800 ° C, and the maximum power density was higher than when cobalt was not eluted. In addition, excellent thermal and chemical stability at high temperatures can be provided.

According to the prior art, when nickel is used as an anode material and a hydrocarbon hydrocarbon is used as a fuel, resistance to carbon (C) and sulfur (S) contained in the fuel is low. Direct oxidation of hydrocarbons and carbon monoxide without the supply of steam to the dry fuel gas and without the application of a sufficiently high current density results in the formation of anodic materials by carbon deposition because nickel has the catalytic properties of forming carbon- There is a problem in that it is destroyed rapidly. Nickel is an excellent electrochemical catalyst for the electrochemical oxidation of hydrogen. However, when natural gas or hydrocarbon is directly used as a fuel, its activity is lowered by carbon deposition. When carbon is deposited on nickel particles, activation polarization ) Becomes very high, and the anode performance is deteriorated.

However, since the solid oxide fuel cell according to the technical idea of the present invention can exclude nickel as a constituent element of the anode and can use eluted cobalt as a catalyst instead of nickel, problems such as carbon deposition of nickel . In addition, since the step of separately adding the catalyst to the anode material can be omitted, the process can be simplified and the cost can be reduced.

While the present invention has been particularly shown and described with reference to certain exemplary embodiments thereof, it should be understood that the same is by way of illustration and example only and is not to be taken by way of limitation. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. .

Accordingly, all equivalents of the claims and their equivalents, as well as the embodiments described hereinabove and the appended claims, are also within the scope of the inventive concept.

100: solid oxide fuel cell, 110: anode,
120: cathode, 130: electrolyte, 140: buffer layer

Claims (11)

Providing an anode material comprised of a bilayer perovskite crystal structure material comprising cobalt; And
And heat treating the anode material in a reducing atmosphere to exsolution and crystallize the cobalt from the double layered perovskite crystal structure material,
Wherein the double layer perovskite crystal structure material comprises a compound represented by the following formula (2): < EMI ID =
(2)
RBaMn _2-x Co _x O _{5 +?}
Wherein R is one or more elements selected from a rare earth group or a lanthanide group, O is oxygen, x is a number of more than 0 and less than 2, and? Is a positive number of 0 or 1 or less , And the compound of formula (2) is a value that is electrically neutral. delete delete The method according to claim 1,
The R may be at least one selected from the group consisting of Y, Sc, Sm, Gd, La, Nd, Pr, Si, Gd, (Eu), terbium (Tb), erbium (Er), or mixtures thereof. delete delete delete delete The method according to claim 1,
Wherein the reducing atmosphere comprises a hydrogen atmosphere. &Lt; Desc / Clms Page number 20 &gt; delete delete

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