KR102399154B1 - Cathode material for solid oxide fuel cell containing layered perovskite substituted with Co and Ti, and cathode for solid oxide fuel cells including the same - Google Patents

Abstract

The present invention relates to a cathode material for a solid oxide fuel cell including a layered perovskite oxide satisfying chemical formula of LnMCo_2-xTi_xO_5+δ (0 < x < 2, 0 < δ <= 0. 5, Ln is a lanthanide element, and m is an alkaline earth metal group element), and a manufacturing method thereof.

Description

Cathode material for solid oxide fuel cell containing layered perovskite substituted with Co and Ti, and cathode for solid oxide fuel cell comprising the same solid oxide fuel cells including the same}

The present invention relates to a cathode material for a solid oxide fuel cell comprising layered perovskite substituted with Co and Ti, and a cathode for a solid oxide fuel cell comprising the same.

Solid oxide fuel cells (SOFCs) are energy conversion devices that use the chemical energy of oxygen and hydrogen to directly convert them into electrical energy at high temperatures. Solid oxide fuel cells are made of ceramic and have the advantage that they do not require additional noble metal catalysts because they are driven at high temperatures (600-1000°C). There are problems with long-term performance.

To solve this problem, many domestic and foreign research institutes are focusing on research and development of intermediate temperature-operating solid oxide fuel cells (IT-SOFCs).

However, in the case of IT-SOFC, as problems such as low ion conductivity and oxygen reduction reaction (ORR) have been reported when operating at a relatively low temperature, research and development of cathode materials with better cathode properties are required. the current situation.

As a similar prior document for this, Republic of Korea Patent Publication No. 10-1213060 has been proposed.

Republic of Korea Patent Publication No. 10-1213060 (2012.12.11)

In order to solve the above problems, an object of the present invention is to provide a cathode material for a solid oxide fuel cell exhibiting excellent cathode characteristics, and a cathode for a solid oxide fuel cell including the same.

However, the above purpose is illustrative, and the technical spirit of the present invention is not limited thereto.

One aspect of the present invention for achieving the above object relates to a cathode material for a solid oxide fuel cell comprising a layered perovskite oxide satisfying the following formula (1).

[Formula 1]

LnMCo _2-x Ti _x O _5+δ (0 < x < 2, 0 < δ ≤ 0.5)

(In Formula 1, Ln is a lanthanide element, and M is an alkaline earth metal element.)

In the above aspect, the cathode material may satisfy 0.5 ≤ x ≤ 1.5.

In one aspect, Ln is Sm, La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, and M may be Ba, Sr or Ca and, more specifically, Ln may be Sm, and M may be Ba.

In the above aspect, the cathode material may satisfy the following relational expression (1).

[Relational Expression 1]

100 <

(In Relation 1, A ₉₀₀ , A ₅₀₀ , H ₉₀₀ and H ₅₀₀ are the electrical conductivity (S/cm) of the cathode material measured by the 4-probe method (4-probe), and the A ₉₀₀ is 900 under an air atmosphere. Electrical conductivity at °C (S/cm), A ₅₀₀ is electrical conductivity at 500°C under an air atmosphere (S/cm), H ₉₀₀ is electrical conductivity at 900°C under hydrogen atmosphere (S/cm), the above H ₅₀₀ is the electrical conductivity (S/cm) at 500°C under a hydrogen atmosphere.)

In the above aspect, the cathode material may have A ₉₀₀ of 3 to 15, H ₉₀₀ of 0.0001 to 0.01, A ₅₀₀ of 1 to 10, and H ₅₀₀ of 0.1 to 1.

In addition, another aspect of the present invention relates to an air electrode for a solid oxide fuel cell comprising the above-described cathode material for a solid oxide fuel cell.

In addition, another aspect of the present invention is the above-described cathode for a solid oxide fuel cell;

an anode disposed to face the cathode; and an electrolyte disposed between the cathode and the anode.

In addition, another aspect of the present invention is a method for producing a cathode material for a solid oxide fuel cell comprising a layered perovskite oxide satisfying the following formula (1),

a) preparing a powder mixture by weighing and ball milling the Ln precursor powder, the M precursor powder, the Co precursor powder, and the Ti precursor powder to satisfy the composition of the following Chemical Formula 1; b) first heat-treating the powder mixture at 800 to 1100°C; and c) secondary heat treatment of the powder mixture subjected to the primary heat treatment at 1200 to 1400° C.

[Formula 1]

LnMCo _2-x Ti _x O _5+δ (0 < x < 2, 0 < δ ≤ 0.5)

(In Formula 1, Ln is a lanthanide element, and M is an alkaline earth metal element.)

The cathode material for a solid oxide fuel cell according to the present invention may include a layered perovskite substituted with Co and Ti, and through this, excellent electrochemical properties can be secured at a medium and high temperature of 700° C. or higher, and the solid oxide It can be used as a cathode material for fuel cells of

In addition, in an air or nitrogen atmosphere, the semiconductor behavior increases as the temperature increases, but in a hydrogen atmosphere, the electrical conductivity gradually increases as the temperature increases. Therefore, it can be used as a hydrogen sensor material.

1 is an XRD (X-ray diffraction) analysis data of SmBaCoTiO _5+δ (SBCTO).
2 is an XRD analysis data of SmBaCo _2-x Ti _x O _5+δ .
3 is an XRD analysis data of a mixture of SmBaCoTiO _5+δ (SBCTO) and CGO91 (Ce _0.9 Gd _0.1 O ₂ ).
4 is an XRD analysis data of a mixture of SmBaCoTiO _5+δ (SBCTO) and yttria stabilized zirconia (YSZ).
5 to 8 are electrochemical analysis results of a half-cell manufactured using SmBaCoTiO _5+δ (SBCTO), FIG. 5 is an analysis result at 550°C, FIG. 6 is 650°C, and FIG. 7 is an analysis result at 750°C, 8 is a graph organized by converting the area-ratio resistance according to the temperature into logarithms.
9 is an analysis result of electrical conductivity of SmBaCoTiO _5+δ (SBCTO) according to the ambient atmosphere.
10 is an analysis result of electrical conductivity in air of SmBaCo _2-x Ti _x O _5+δ .

Hereinafter, the cathode material for a solid oxide fuel cell including the layered perovskite substituted with Co and Ti according to the present invention, and the cathode for a solid oxide fuel cell including the same will be described in detail. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical terms and scientific terms used, it has the meaning commonly understood by those of ordinary skill in the technical field to which this invention belongs, and the summary of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted.

In general, the electrochemical reaction of the solid oxide fuel cell is an anode reaction in which oxygen gas O ₂ of the cathode, which is the cathode, changes to oxygen ion O ² — as shown in the following reaction equation, and the fuel (H ₂ or hydrocarbon) and electrolyte of the anode, which is the anode, as shown in the following reaction formula. It consists of an anode reaction in which oxygen ions that have migrated through the reaction react.

<reaction formula>

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

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

At the cathode of a solid oxide fuel cell, oxygen adsorbed on the electrode surface undergoes dissociation and surface diffusion, and moves to the triple phase boundary where the electrolyte, cathode, and pores meet to obtain electrons and become oxygen ions. Since it moves to the anode through the electrolyte, the reaction rate of the electrode can be improved by increasing the area of the three-phase interface where the anode reaction occurs.

On the other hand, one aspect of the present invention relates to a cathode material used in a solid oxide fuel cell, and more particularly, to a cathode material for a solid oxide fuel cell comprising a layered perovskite oxide satisfying the following formula (1).

[Formula 1]

LnMCo _2-x Ti _x O _5+δ (0 < x < 2, 0 < δ ≤ 0.5)

(In Formula 1, Ln is a lanthanide element, and M is an alkaline earth metal element.)

As such, the cathode material for a solid oxide fuel cell according to the present invention may include a layered perovskite substituted with Co and Ti, and through this, excellent electrochemical properties can be secured at a medium and high temperature of 700 ° C. or higher, It may be possible to use solid oxide as a cathode material for fuel cells.

In addition, in an air or nitrogen atmosphere, the semiconductor behavior increases as the temperature increases, but in a hydrogen atmosphere, the electrical conductivity gradually increases as the temperature increases. Therefore, it can be used as a hydrogen sensor material.

As a more specific example, in Formula 1, Ln is Sm, La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, and M is Ba, It may be Sr or Ca, and more specifically, for example, Ln may be Sm, and M may be Ba.

In Formula 1, x represents the content of Co and Ti, and may be a real number greater than 0 and less than 2, preferably 0.5 ≤ x ≤ 1.5. In this range, it is possible to secure more excellent cathode characteristics.

In addition, in Formula 1, δ may represent interstitial oxygen, and by including it, the conductivity of oxygen ions may be improved. As a specific example, δ may be a real number greater than 0 and less than or equal to 0.5, but is not limited thereto, and the value of δ may be determined according to a specific crystal structure.

On the other hand, as described above, the cathode material according to an embodiment of the present invention may have different electrical conductivity behavior depending on the temperature in air or nitrogen atmosphere and hydrogen atmosphere. Specifically, for example, the cathode material is can be satisfied

[Relational Expression 1]

100 <

(In Relation 1, A ₉₀₀ , A ₅₀₀ , H ₉₀₀ and H ₅₀₀ are the electrical conductivity (S/cm) of the cathode material measured by the 4-probe method (4-probe), and the A ₉₀₀ is 900 under an air atmosphere. Electrical conductivity at °C (S/cm), A ₅₀₀ is electrical conductivity at 500°C under an air atmosphere (S/cm), H ₉₀₀ is electrical conductivity at 900°C under hydrogen atmosphere (S/cm), the above H ₅₀₀ is the electrical conductivity (S/cm) at 500°C under a hydrogen atmosphere.)

은 150 내지 1000일 수 있으며, 더욱 구체적으로 예를 들면 200 내지 600일 수 있다.That is, at a low and medium temperature of 500 °C, the difference in electrical conductivity between the air atmosphere and the hydrogen atmosphere is not large, but at the high temperature of 900 °C, the electrical conductivity difference between the air atmosphere and the hydrogen atmosphere is large. and, more specifically, for example

may be 150 to 1000, more specifically, for example, may be 200 to 600.

Further, under the condition that the above relation 1 is satisfied, A ₉₀₀ may be 3 to 15, H ₉₀₀ may be 0.0001 to 0.01, A ₅₀₀ may be 1 to 10, and H ₅₀₀ may be 0.1 to 1. . More specifically, in the cathode material, A ₉₀₀ may be 5 to 10, H ₉₀₀ may be 0.001 to 0.01, A ₅₀₀ may be 3 to 6, and H ₅₀₀ may be 0.3 to 1.

Accordingly, the present cathode material for a solid oxide fuel cell may be used as a cathode for a mobile fuel cell, a fuel cell for power generation, or a solid oxide water electrolysis cell, as well as as a material for a hydrogen sensor.

On the other hand, the manufacturing method of the layered perovskite oxide satisfying the formula (1) can be performed through a traditional solid state reaction (SSR) method, specifically, for example, a) to satisfy the composition of the following formula (1) preparing a powder mixture by weighing and ball milling the Ln precursor powder, the M precursor powder, the Co precursor powder, and the Ti precursor powder; b) first heat-treating the powder mixture at 800 to 1100°C; and c) secondary heat treatment of the powder mixture subjected to the primary heat treatment at 1200 to 1400° C.; may include. In this case, the Ln precursor powder, the M precursor powder, the Co precursor powder, and the Ti precursor powder may each be an oxide or a carbide of each element.

[Formula 1]

LnMCo _2-x Ti _x O _5+δ (0 < x < 2, 0 < δ ≤ 0.5)

(In Formula 1, Ln is a lanthanide element, and M is an alkaline earth metal element.)

For example, if you want to prepare SmBaTiCoO _5+δ layered perovskite oxide, Sm ₂ O ₃ powder, BaCO ₃ powder, Co ₃ O ₄ powder and TiO ₂ According to the composition of the perovskite oxide to be prepared powder After preparing a powder mixture by weighing and ball milling, a layered perovskite oxide can be prepared through a primary heat treatment and a secondary heat treatment. As such, it is possible to prepare a layered perovskite oxide having excellent electrical conductivity and areal resistivity characteristics by passing through the secondary heat treatment process.

In addition, another aspect of the present invention relates to an air electrode for a solid oxide fuel cell comprising the above-described cathode material for a solid oxide fuel cell.

Specifically, the cathode for a solid oxide fuel cell according to an example of the present invention may be prepared from ink for a cathode including the cathode material for a solid oxide fuel cell, an organic binder and a solvent, and the content of each component is at a normal level. Although not particularly limited, for example, the ink for the cathode may include 1 to 10 parts by weight of an organic binder and 50 to 500 parts by weight of a solvent based on 100 parts by weight of the cathode material for a solid oxide fuel cell.

The organic binder is used to increase the adhesion between the cathode material granules for the solid oxide fuel cell and the electrolyte layer, and may be used without particular limitation as long as it is commonly used in the art. As a specific example, polyvinyl butyral, poly It may be any one or two or more selected from the group consisting of vinyl acetal, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polybutyl acetate, and polyvinylpyrrolidone.

The solvent is to ensure that each component is well mixed, and can be used without particular limitation as long as it is commonly used in the art, and as a specific example, water, methanol, ethanol, isopropanol, acetone, toluene, etc. It may be any one or a mixed solvent of two or more selected from the group.

When the ink for the cathode is prepared as described above, the cathode for a solid oxide fuel cell can be prepared by coating the ink for the cathode on the electrolyte layer by screen printing and then heat-treating it at 800 to 1500° C. for 30 minutes to 3 hours, Of course, this is only an example and is not necessarily limited thereto.

In addition, another aspect of the present invention relates to a solid oxide fuel cell including the above-described cathode for a solid oxide fuel cell, and more particularly, to a cathode for a solid oxide fuel cell; an anode disposed to face the cathode; and an electrolyte disposed between the cathode and the anode. In this case, any known anode and electrolyte may be used.

Hereinafter, the cathode material for a solid oxide fuel cell including the layered perovskite substituted with Co and Ti according to the present invention, and the cathode for a solid oxide fuel cell including the same according to the present invention through Examples will be described in more detail. However, the following examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of effectively describing particular embodiments only and is not intended to limit the invention. In addition, the unit of additives not specifically described in the specification may be weight %.

[Example 1]

For accurate experiments, reagent-grade Sm ₂ O ₃ , BaCO ₃ , Co ₃ O ₄ and TiO ₂ are heat-treated in an electric furnace at 150° C. for 1 hour to remove moisture, and then the perovskite oxide (SmBaCoTiO _5+δ ) was weighed accurately according to the composition A layered perovskite oxide was prepared.

[Examples 2 to 6]

As shown in Table 1 below, all processes except for changing the composition of the perovskite oxide (SmBaCo _2-x Ti _x O _5+δ ) were performed in the same manner as in Example 1 to prepare a layered perovskite oxide did

Furtherance x Example 1 SmBaCoTiO _5+δ 1.0 Example 2 SmBaCo _0.5 Ti _1.5 O _5+δ 1.5 Example 3 SmBaCo _0.7 Ti _1.3 O _5+δ 1.3 Example 4 SmBaCo _0.9 Ti _1.1 O _5+δ 1.1 Example 5 SmBaCo _1.3 Ti _0.7 O _5+δ 0.7 Example 6 SmBaCo _1.5 Ti _0.5 O _5+δ 0.5

[Characteristic evaluation]

1) Crystal structure analysis:

To confirm the crystal structure of the layered perovskite oxide, XRD (X-ray diffraction) analysis was performed, and analysis was performed using a Cu Kα filter at 9 kW, 45 kV, and 200 mA conditions.

As a result, as shown in FIG. 1, in the case of Example 1, it was confirmed that a single-phase SmBaCoTiO _5+δ was prepared, and as shown in FIG. 2 , as the content of Ti increased, SmTiO ₃ increased, and the amount of Co As the content increased, the SmBaCo ₂ O _5+d phase increased.

Additionally, in order to confirm the reactivity to the electrolyte layer, SmBaCoTiO _5+δ (SBCTO) and CGO91 (Ce _0.9 Gd _0.1 O ₂ ) or YSZ (yttria stabilized zirconia) were mixed in a 1:1 weight ratio and heat-treated at 1000°C, followed by XRD Analysis was performed, and as a result, as shown in FIGS. 3 and 4, it was confirmed that it did not react with CGO91 or YSZ.

2) Area resistivity (Ωcm2) analysis:

For electrochemical analysis, the layered perovskite oxide (SmBaCoTiO _5+δ ) of Example 1 and Ce _0.9 Gd _0.1 O ₂ (CGO91, Rhodia) powder and a vehicle (vehicle, fuelcell materials) were mixed to produce cathode ink, then coated on a support by screen printing, and then sintered at 1000° C. for 1 hour to prepare a half cell.

The electrochemical characteristics of the half-cell were confirmed by using an electrochemical analyzer (Model nStat, HS Technologies) to determine the impedance results in the frequency range of 0.05 Hz to 2.5 MHz in a temperature range of 500 to 900° C. in an air atmosphere.

5 to 7 are impedance results measured at 550 ° C., 650 ° C. and 750 ° C., respectively, and Figure 8 is a graph showing the impedance results in the range of 500-900 ° C. SmBaCoTiO _{5 + δ} (SBCTO) of Example 1 The half-cell used showed excellent electrochemical properties of 0.140 Ωcm2 at 750°C.

In more detail, R ₁ , R ₂ , and R ₃ are the resistances generated when oxygen moves to the cathode->electrolyte, the cathode->air electrode, the air->the cathode, respectively, and SmBaCoTiO _5+δ (SBCTO) of Example 1 is The highest resistance (R ₁ ) was exhibited at all temperatures except 500°C. Therefore, SmBaCoTiO _5+δ (SBCTO) can show a great performance improvement when the resistance to R ₁ is reduced.

3) Electrical conductivity analysis:

For the measurement of the electrical conductivity of the layered perovskite oxide, the layered perovskite oxide prepared in Examples 1 to 6 was compression molded into a rectangular specimen of 5.5 mm × 4 mm × 25 mm, and then at 1100° C. under an air atmosphere. A bar-shaped specimen was prepared by heat treatment for 3 hours.

Then, to measure the specimen by the DC 4-probe method (4-probe), a platinum wire (Pt-wire) and platinum ink (Pt paste) were used to connect the specimen, and a temperature of 50 to 900°C using a Keithley 2400 Source meter equipment. The electrical conductivity was measured at intervals of 50° C. in the range, but the electrical conductivity was measured under different conditions in air, nitrogen, and hydrogen atmosphere.

As a result, as shown in FIG. 9, the SmBaCoTiO _5+δ (SBCTO) of Example 1 showed a semiconductor behavior in which the electrical conductivity increased as the temperature increased in an air and nitrogen atmosphere, but as the temperature increased in a hydrogen atmosphere, As a result, the electrical conductivity gradually increased, but at 600℃ or higher, the electrical conductivity dropped sharply, showing properties similar to those of an insulator. In other words, it was confirmed that it can be used as a hydrogen sensor material because it reacts with hydrogen at high temperature to exhibit insulating properties.

On the other hand, as shown in FIG. 10, the layered perovskite oxides of Examples 1 to 6 showed a tendency to gradually decrease the electrical conductivity as the Ti content increased, but under different conditions with air, nitrogen, and hydrogen atmospheres. Therefore, when the electrical conductivity was measured, it showed an electrical conductivity behavior similar to that of SmBaCoTiO _5+δ (SBCTO) of Example 1 in all compositions.

In contrast, La _0.75 Sr _0.25 MnO ₃ [ RARE METALS, Vol.28, 2009, p.361 ], SmBaMn ₂ O _5+d [ Chem. Mater. Vol.31, 2019, p.3793 ], PrBa _0.8 Ca _0.2 Mn ₂ O _5+d [ J. Mater. Chem. A, Vol.4, 2016, p.1747 ], and SrTi _0.9 Co _0.1 O ₃ [J. Electrochem. En. Conv. Stor., Vol.8, 2011, 501010 ], the electrical conductivity behavior in H ₂ /Ar atmosphere or H ₂ atmosphere was similar to that in air atmosphere, It showed stable behavior even in a high-temperature hydrogen atmosphere.

Although the present invention has been described with reference to specific matters and limited examples as described above, these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and the present invention pertains to Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims described below, but also all of the claims and all equivalents or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (10)

A cathode material for a solid oxide fuel cell comprising a layered perovskite oxide satisfying the following formula (1).
[Formula 1]
SmBaCo _2-x Ti _x O _5+δ (0 < x < 2, 0 < δ ≤ 0.5) The method of claim 1,
The cathode material is a cathode material for a solid oxide fuel cell, characterized in that it satisfies 0.5 ≤ x ≤ 1.5. delete delete The method of claim 1,
The cathode material is a cathode material for a solid oxide fuel cell, characterized in that it satisfies the following relation (1).
[Relational Expression 1]
100 <

(In Relation 1, A ₉₀₀ , A ₅₀₀ , H ₉₀₀ and H ₅₀₀ are the electrical conductivity (S/cm) of the cathode material measured by the 4-probe method (4-probe), and the A ₉₀₀ is 900 under an air atmosphere. Electrical conductivity at ℃ (S/cm), the A ₅₀₀ is the electrical conductivity at 500 ℃ under an air atmosphere (S/cm), the H ₉₀₀ is the electrical conductivity at 900 ℃ under a hydrogen atmosphere (S/cm), the above H ₅₀₀ is the electrical conductivity (S/cm) at 500°C under a hydrogen atmosphere.) 6. The method of claim 5,
The cathode material is a cathode material for a solid oxide fuel cell, characterized in that A ₉₀₀ is 3 to 15, and H ₉₀₀ is 0.0001 to 0.01. 6. The method of claim 5,
The cathode material is a cathode material for a solid oxide fuel cell, characterized in that A ₅₀₀ is 1 to 10, and H ₅₀₀ is 0.1 to 1. A cathode for a solid oxide fuel cell comprising the cathode material for a solid oxide fuel cell of any one of claims 1, 2, and 5 to 7. The cathode for the solid oxide fuel cell of claim 8;
an anode disposed to face the cathode; and
an electrolyte disposed between the cathode and the anode;
A solid oxide fuel cell comprising a. A method for producing a cathode material for a solid oxide fuel cell comprising a layered perovskite oxide satisfying the following formula (1),
a) preparing a powder mixture by weighing and ball milling the Sm precursor powder, the Ba precursor powder, the Co precursor powder, and the Ti precursor powder to satisfy the composition of the following Chemical Formula 1;
b) first heat-treating the powder mixture at 800 to 1100°C; and
c) secondary heat treatment of the powder mixture subjected to the primary heat treatment at 1200 to 1400° C.;
A method of manufacturing a cathode material for a solid oxide fuel cell, comprising a.
[Formula 1]
SmBaCo _2-x Ti _x O _5+δ (0 < x < 2, 0 < δ ≤ 0.5)

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