Solid oxide fuel cell cathode material and preparation method and application thereof

Abstract

The invention discloses a solid oxide fuel cell cathode material as well as a preparation method and application thereof, and belongs to the technical field of fuel cells. The composition of the cathode material of the solid oxide fuel cell is YBa < 2-x > Sr < x > Cu < 2 > Co < 0.7 > Cu < 0.3 > O < 7 + delta >. The preparation method comprises the following steps: dissolving a yttrium source, a barium source, a strontium source, a copper source and a cobalt source, adding EDTA and citric acid as complexing agents, adjusting the pH to be neutral, and reacting at 60-80 DEG C for 6-10 hours; heating the reaction liquid until the reaction liquid is combusted to obtain precursor powder after the reaction liquid is combusted; and grinding the precursor powder, calcining at 350-450 DEG C for 6-10 hours, calcining at 800-900 DEG C for 6-10 hours, and calcining at 950-1000 DEG C for 10-15 hours to obtain the solid oxide fuel cell cathode material. According to the layered perovskite structure YBa < 2-x > Sr < x > Cu < 2 > Co < 0.7 > Cu < 0.3 > O < 7 + delta > material prepared by the preparation method disclosed by the invention, the oxygen vacancy concentration and the oxygen transport capability are improved, and the electrochemical performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a cathode material for a solid oxide fuel cell, a preparation method thereof, and an application thereof. Background Art

[0002] Energy is the core driving force for the development of modern society. Currently, global energy consumption still mainly relies on fossil fuels (accounting for nearly 80%). As a major energy producer and consumer country, the proportion of fossil fuels in China exceeds 90%. Coal has long been the main energy source and will still be an important foundation for ensuring energy security even under the "dual carbon" goal. Power generation dominates in coal utilization, and the installed capacity and power generation of coal-fired power respectively account for more than 55% and 60% of the total national power scale. However, it faces problems such as low power generation efficiency (about 40% on average) and concentrated pollutant emissions. Improving energy efficiency and reducing carbon emissions have become the key to energy transformation. Fuel cells generate electricity directly through electrochemical reactions, breaking through the Carnot cycle limitation of traditional thermal power generation, and are an important direction of energy conversion technology. Among various fuel cells, solid oxide fuel cells (SOFCs) have significant advantages: the power generation efficiency is 50%-60%, and the comprehensive energy efficiency combined with waste heat recovery exceeds 80%; the all-solid-state electrolyte design makes it highly stable with a service life of tens of thousands of hours; it has a wide fuel adaptability and can directly utilize gaseous and liquid fuels such as natural gas, methanol, and diesel, and can also consume carbon-containing gases such as coal gasification gas and biomass gas through reforming technology, which highly matches China's coal-based energy structure and diversified fuel system. Under the background of "dual carbon" and the energy revolution, the value of SOFCs is prominent: it not only adapts to the traditional energy system and can be used in scenarios such as the transformation of coal-fired power plants and industrial waste heat power generation to achieve high-efficiency carbon reduction, but also is compatible with renewable fuels and has broad prospects in the fields of distributed energy, off-grid power supply, and hydrogen energy storage. Therefore, carrying out research and development on SOFCs is an important way to improve energy utilization efficiency and solve the problem of clean utilization of fossil fuels, and is even more a choice for building a multi-energy complementary system and achieving the "dual carbon" goal.

[0003] However, traditional SOFCs usually operate at high temperatures of 800-1000°C, which brings great difficulties in sealing and material selection, and also affects their operating stability. Reducing the operating temperature of SOFCs to the intermediate temperature (IT, 500-800°C) range can significantly reduce costs and improve battery stability, which is crucial for promoting the wide commercial application of SOFC technology. However, reducing the operating temperature may bring other problems, such as a decrease in electrolyte ionic conductivity and insufficient cathode electrocatalytic activity. For example, the traditional cathode material La 1-x Sr x MnO 3-δ(LSM) has a significantly increased polarization impedance at lower temperatures, severely limiting its application in medium and low temperature SOFCs. Therefore, the development of potential cathode materials that can operate efficiently in the medium temperature range is crucial for promoting the development of SOFC technology. Summary of the Invention

[0004] Aiming at the problems of significantly increased polarization impedance and low catalytic activity of oxygen reduction reaction of SOFC cathode materials in the temperature range in the prior art, the present invention provides a cathode material for solid oxide fuel cells, its preparation method and application. As a SOFC cathode material, it can increase the oxygen vacancy concentration and oxygen transport ability, and improve the electrochemical performance.

[0005] The present invention is achieved through the following technical solutions: The present invention discloses a cathode material for solid oxide fuel cells, and the composition of the cathode material for solid oxide fuel cells is: YBa 2-x Sr x Cu2Co 0.7 Cu 0.3 O 7+δ , 0 ≤ x ≤ 2, δ represents oxygen defects. Generally, 0 ≤ δ ≤ 0.5.

[0006] Furthermore, the composition of the cathode material for solid oxide fuel cells is: YBa 2- x Sr x Cu2Co 0.7 Cu 0.3 O 7+δ , 0 < x < 2; by partially substituting Ba ions at the A site and Cu ions at the B site, Sr ions and Co ions with smaller ionic radii are introduced respectively, causing mild lattice distortion, and at the same time obtaining certain cation defects, increasing the oxygen vacancy concentration and oxygen transport ability of the material, and improving the electrochemical performance.

[0007] In the present invention, a preparation method of the cathode material for solid oxide fuel cells is also disclosed, including the following steps: (1) Dissolve yttrium source, barium source, strontium source, copper source and cobalt source, add EDTA and citric acid as complexing agents, adjust the pH to neutral, and react at 60 - 80 °C for 6 - 10 h; (2) Heat the reaction solution in step (1) until combustion, and obtain a precursor powder after combustion; (3) Grind the precursor powder in step (2) preliminarily, calcine at 350 - 450 °C for 6 - 10 h, and grind sufficiently; (4) Calcine the powder sufficiently ground in step (3) at 800 - 900 °C for 6 - 10 h, and grind sufficiently; (5) The powder obtained after sufficient grinding in step (4) is calcined at 950 - 1000 °C for 10 - 15 h to obtain the cathode material for solid oxide fuel cells.

[0008] In the present invention, it is calcined at 350 - 450 °C for 6 - 10 h to ensure the complete decomposition of the precursor hydrocarbon; it is calcined at 800 - 900 °C for 6 - 10 h to ensure the complete decomposition of the precursor powder nitrate and form metal oxides; it is calcined at 950 - 1000 °C for 10 - 15 h to form the desired layered oxide structure.

[0009] Furthermore, in step (1), the yttrium source is Y(NO3)3·6H2O or Y2O3, the barium source is Ba(CH3COO)2 or Ba(NO3)2, the strontium source is SrCO3 or Sr(CO3)2, the copper source is Cu(NO3)2·3H2O, CuO or CuCl2, and the cobalt source is Co(NO3)2·6H2O or Co2O3.

[0010] Furthermore, in step (1), the molar ratio of metal ions, EDTA and citric acid is 1:1:1.6.

[0011] Furthermore, in step (1), ammonia water is added to adjust the pH to neutral; the solvent for dissolving the yttrium source, barium source, strontium source, copper source and cobalt source in step (1) is a mixed solution of concentrated nitric acid and water, and the volume ratio of concentrated nitric acid to water is 1:5.

[0012] Furthermore, the sufficient grinding in steps (3) and (4) means sufficient grinding after adding anhydrous ethanol.

[0013] In the present invention, the application of the cathode material for solid oxide fuel cells or the cathode material for solid oxide fuel cells prepared by the preparation method according to any one of claims 3 - 7 in the preparation of solid oxide cells.

[0014] Furthermore, a solid oxide fuel cell half-cell is prepared by the following method: 1) The cathode material for solid oxide fuel cells is added to an organic binder and mixed and ground to make a uniformly mixed slurry as the cathode slurry; 2) The cathode slurry is coated on both sides of the electrolyte layer and calcined at 950 °C for 2 h in air to obtain the solid oxide fuel cell half-cell.

[0015] Furthermore, the organic binder is a mixture of ethyl cellulose and terpineol with a mass ratio of 9:1; the mass ratio of the cathode material for solid oxide fuel cells to the organic binder is 1:2.

[0016] The beneficial effects achieved by the present invention are: The layered perovskite structure YBa 2-x Srx Cu2Co 0.7 Cu 0.3 O 7+δ The material is a new cathode material for solid oxide fuel cells, with characteristics such as uniform composition and relatively simple synthesis process; through partial substitution of Ba ions at the A site and ions at the B site, Sr ions and Co ions with smaller ionic radii are introduced respectively, causing mild lattice distortion, while obtaining certain cationic defects, improving the oxygen vacancy concentration and oxygen transport ability of the material, and improving the electrochemical performance. Description of the Drawings

[0017] Figure 1 is the X-ray diffraction pattern of YBa2Cu2Co 0.7 Cu 0.3 O 7+δ 、YBaSrCu2Co 0.7 Cu 0.3 O 7+δ and YBa2Cu2CoO 7.25 ; Figure 2 is the scanning electron microscope image of YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O 7+δ , (a) YBa2Cu2Co 0.7 Cu 0.3 O 7+δ , (b) YBaSrCu2Co 0.7 Cu 0.3 O 7+δ ; Figure 3 is the energy-dispersive X-ray spectroscopy of YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O 7+δ , (a) YBa2Cu2Co 0.7 Cu 0.3 O 7+δ , (b) YBaSrCu2Co 0.7 Cu 0.3 O 7+δ ; Figure 4 is YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O7+δ In Ce 0.9 G 0.1 O 2-δ AC impedance spectra of the (GDC) electrolyte at 600℃, 650℃, 700℃, 750℃, and 800℃; (a) 600℃, (b) 650℃, (c) 700℃, (d) 750℃, and (e) 800℃. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0019] Example 1 (1) Add 11.490 g of Y(NO3)3·6H2O, 15.325 g of Ba(CH3COO)2, 16.670 g of Cu(NO3)2·3H2O and 6.112 g of Co(NO3)2·6H2O into a beaker containing 100 ml of deionized water, then add 20 ml of concentrated nitric acid, stir with a magnetic stirrer until dissolved, add 52.603 g of EDTA and 56.738 g of citric acid, adjust the solution pH to 7 with ammonia water, and react at 80°C for 6 h; (2) The reaction solution in step (1) is transferred to an evaporating dish and heated until combustion occurs, to obtain a precursor powder; (3) Grind the precursor powder in step (2), put it into a box furnace, calcine it at 400°C for 6h, add anhydrous ethanol into a mortar and grind it thoroughly; (4) The fully ground powder of step (3) was calcined in a box furnace at 900°C for 10 h, and anhydrous ethanol was added to a mortar and fully ground; (5) The fully ground powder of step (4) was calcined in a box furnace at 950°C for 10 h to obtain a solid oxide fuel cell cathode material (YBa2Cu2Co 0.7 Cu 0.3 O 7+δ ); (6) adding an organic binder (a mixture of ethyl cellulose and pinene alcohol in a mass ratio of 9:1) to a solid oxide fuel cell cathode material and mixing and grinding the mixture (the mass ratio of the cathode material to the organic binder is 1:2) to prepare a uniformly mixed slurry as a cathode slurry; (7) Apply cathode slurry to Ce 0.9 G 0.1 O 2-δ (GDC) electrolyte layer on both sides, and calcined at 950 ° C for 2 h in air to obtain a solid oxide fuel cell half-cell.

[0020] Example 2 (1)11.490 g of Y(NO3)3·6H2O, 7.663 g of Ba(CH3COO)2, 4.429 g of SrCO3, 16.670 g of Cu(NO3)2·3H2O and 6.112 g of Co(NO3)2·6H2O were added into a beaker containing 100 ml of deionized water, and then 20 ml of concentrated nitric acid was added. It was stirred with a magnetic stirrer until dissolved, 52.603 g of EDTA and 56.738 g of citric acid were added, and the pH of the solution was adjusted to 7 with ammonia water, and the reaction was carried out at 80 °C for 6 h; (2)The reaction solution in step (1) was transferred to an evaporating dish and heated to combustion to obtain a precursor powder; (3)The precursor powder in step (2) was preliminarily ground, placed in a box furnace, calcined at 400 °C for 6 h, and fully ground in a mortar with anhydrous ethanol; (4)The powder fully ground in step (3) was calcined in a box furnace at 900 °C for 10 h, and fully ground in a mortar with anhydrous ethanol; (5)The powder fully ground in step (4) was calcined in a box furnace at 950 °C for 10 h to obtain a cathode material for a solid oxide fuel cell (YBaSrCu2Co 0.7 Cu 0.3 O 7+δ ). The CuO2 plane is composed of Cu atoms and two oxygen atoms, and the Co 0.7 Cu 0.3 Ox plane is composed of Co 0.7 Cu 0.3 atoms and two oxygen vacancies; (6)The cathode material of the solid oxide fuel cell was added to an organic binder (a mixture of ethyl cellulose and terpineol with a mass ratio of 9:1) and mixed and ground (the mass ratio of the cathode material to the organic binder was 1:2) to form a uniformly mixed slurry as the cathode slurry; (7)The cathode slurry was coated on both sides of the Ce 0.9 Gd 0.1 O 2-δ (GDC) electrolyte layer and calcined at 950 °C for 2 h in air to obtain a solid oxide fuel cell half-cell.

[0021] The X-ray diffraction patterns of the cathode materials for solid oxide fuel cells prepared in Example 1 and Example 2 and YBa2Cu2CoO 7.25 (parent) are as Figure 1 shown, and from Figure 1It can be seen that both the modified sample and the matrix show several main diffraction peaks of (103), (200), and (213), which basically coincide with the diffraction peak distribution in the standard card (PDF#97-006-5355). According to the positions of the above main diffraction peaks, YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O 7+δ still maintain the crystal structure of the tetragonal system of the matrix material, and the space group is P4 / mmm. At the same time, in addition to the main characteristic peaks belonging to the matrix YBa2Cu2CoO 7.25 , for YBa2Cu2Co 0.7 Cu 0.3 O 7+δ , YBaSrCu2Co 0.7 Cu 0.3 O 7+δ , no obvious impurity peaks appear, nor is there any peak shift. This result indicates that the YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O 7+δ materials have high purity, no impurity phase appears, and still maintain the tetragonal structure.

[0022] Scanning electron micrographs of the cathode materials of the solid oxide fuel cells prepared in Example 1 and Example 2 are as shown in Figure 2 , (a) YBa2Cu2Co 0.7 Cu 0.3 O 7+δ , (b) YBaSrCu2Co 0.7 Cu 0.3 O 7+δ ; It can be seen from Figure 2 that the particle size of the YBa2Cu2Co 0.7 Cu 0.3 O 7+δ sample is small, the arrangement is uniform, and at the same time, the grains are tightly combined and there are few voids, which is not conducive to gas diffusion. However, for the YBaSrCu2Co 0.7 Cu 0.3 O 7+δ sample modified by Sr, the grain size has been significantly improved, mainly columnar grains, and there are more voids between the grains, which is conducive to gas diffusion. At the same time, the larger grains reduce the number of grain boundaries, which helps to reduce the grain boundary resistance.

[0023] The energy-dispersive X-ray spectroscopy diagrams of the solid oxide fuel cell cathode materials prepared in Example 1 and Example 2 are as follows Figure 3 shown, (a) YBa2Cu2Co 0.7 Cu 0.3 O 7+δ , (b) YBaSrCu2Co 0.7 Cu 0.3 O 7+δ . It can be seen from the figure that the element distributions of YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O 7+δ are uniform, and there is no segregation or aggregation. Good element dispersion is a necessary condition for the cathode material to have high oxygen reduction reaction (ORR) catalytic activity.

[0024] The alternating current impedance spectroscopy diagrams of the solid oxide fuel cell cathode materials prepared in Example 1 and Example 2 on Ce 0.9 Gd 0.1 O 2-δ (GDC) electrolyte at 800 °C and 750 °C are as follows Figure 4 shown, (a) 750 °C, (b) 800 °C. It can be seen from the figure that the polarization resistances of the YBa2Cu2Co 0.7 Cu 0.3 O 7+δ and YBaSrCu2Co 0.7 Cu 0.3 O 7+δ cathode materials decrease with the increase of the test temperature. This is because when the temperature increases, the activity of the cathode material increases, improving the catalytic performance of the ORR reaction. At 600 °C, 650 °C, 700 °C, 750 °C, and 800 °C, the polarization resistances of the YBa2Cu2Co 0.7 Cu 0.3 O 7+δ cathode are 4.921 Ω cm 2 , 2.538 Ω cm 2 , 1.327 Ω cm 2 , 0.715 Ω cm 2 , and 0.399 Ω cm 2 , respectively. The polarization resistances of the YBaSrCu2Co 0.7 Cu 0.3 O 7+δ cathode are 1.660 Ω cm 2 , 0.596 Ω cm 2 , 0.279 Ω cm 2, 0.156 Ω cm 2 and 0.101 Ω cm 2 . Obviously, compared with the YBa2Cu2Co 0.7 Cu 0.3 O 7+δ cathode, the YBaSrCu2Co 0.7 Cu 0.3 O 7+δ cathode has a lower polarization resistance. This is because after Sr 2+ (~1.18 Å) with a smaller ionic radius replaces Ba 2+ (~1.35 Å), the lattice parameter decreases, causing slight lattice distortion, increasing the oxygen vacancy concentration inside the material, improving the oxygen transport ability of the material, and thus enhancing the catalytic activity of the oxygen reduction reaction. Preliminary results show that the YBa 2-x Sr x Cu2Co 0.7 Cu 0.3 O 7+δ cathode has good electrochemical performance, and the performance of the YBaSrCu2Co 0.7 Cu 0.3 O 7+δ cathode is more superior.

Claims

1. A cathode material for a solid oxide fuel cell, characterized in that, The composition of the solid oxide fuel cell cathode material is: YBa 2-x Sr x Cu2Co 0.7 Cu 0.3 O 7+δ , where 0 ≤ x ≤ 2.

2. The cathode material of the solid oxide fuel cell according to claim 1, characterized in that, The composition of the solid oxide fuel cell cathode material is: YBa 2-x Sr x Cu2Co 0.7 Cu 0.3 O 7+δ , where 0 < x < 2.

3. A method for preparing the cathode material of the solid oxide fuel cell according to claim 1 or 2, characterized in that, It includes the following steps: (1) Dissolve yttrium source, barium source, strontium source, copper source and cobalt source, add EDTA and citric acid as complexing agents, adjust the pH to neutral, and react at 60 - 80 °C for 6 - 10 h; (2) Heat the reaction solution in step (1) until combustion occurs, and obtain a precursor powder after combustion; (3) Grind the precursor powder in step (2) preliminarily, calcine at 350 - 450 °C for 6 - 10 h, and grind thoroughly; (4) Grind the powder obtained by thorough grinding in step (3) at 800 - 900 °C for 6 - 10 h, and grind thoroughly; (5) Grind the powder obtained by thorough grinding in step (4) at 950 - 1000 °C for 10 - 15 h to obtain a cathode material for solid oxide fuel cells.

4. The cathode material for a solid oxide fuel cell according to claim 3, characterized in that, The yttrium source in step (1) is Y(NO3)3·6H2O or Y2O3, the barium source is Ba(CH3COO)2 or Ba(NO3)2, the strontium source is SrCO3 or Sr(CO3)2, the copper source is Cu(NO3)2·3H2O, CuO or CuCl2, and the cobalt source is Co(NO3)2·6H2O or Co2O3.

5. The cathode material of the solid oxide fuel cell according to claim 3, wherein In step (1), the molar ratio of metal ions, EDTA and citric acid is 1:1:1.

6.

6. The cathode material for a solid oxide fuel cell according to claim 3, wherein In step (1), ammonia water is added to adjust the pH to neutral; the solvent for dissolving the yttrium source, barium source, strontium source, copper source and cobalt source in step (1) is a mixed solution of concentrated nitric acid and water, and the volume ratio of concentrated nitric acid to water is 1:

5.

7. The cathode material for a solid oxide fuel cell according to claim 3, characterized in that, The thorough grinding in steps (3) and (4) means thorough grinding after adding absolute ethanol.

8. Application of the cathode material for solid oxide fuel cells described in any one of claims 1 - 2 or the cathode material for solid oxide fuel cells prepared by the preparation method described in any one of claims 3 - 7 in the preparation of solid oxide cells.

9. The application according to claim 8, wherein A solid oxide fuel cell half - cell is prepared by the following method: 1) Add the cathode material for solid oxide fuel cells to an organic binder and grind them together to make a uniformly mixed slurry as the cathode slurry; 2) Coat the cathode slurry on both sides of the electrolyte layer and calcine at 950 °C in air for 2 h to obtain a solid oxide fuel cell half - cell.

10. The application according to claim 9, wherein The organic binder is a mixture of ethyl cellulose and terpineol with a mass ratio of 9:1; the mass ratio of the cathode material for solid oxide fuel cells to the organic binder is 1:2.

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