A cathode material for a medium temperature solid oxide fuel cell and a method of making the same

Abstract

This invention relates to a medium-temperature solid oxide fuel cell cathode material and its preparation method. The invention employs a sol-gel method to synthesize perovskite oxide Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3‑δ The material contains PrBaCo2O with a double perovskite structure. 5+δ BaCo with single perovskite structure 0.8 Zr 0.1 Y 0.1 O 3‑δ Two phases. Multiphase Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3‑δ The sample achieved a conductivity of 100 S / cm within the operating temperature range of a mid-temperature solid oxide fuel cell. ‑1 At 700℃, the polarization impedance is 0.06 Ωcm. 2 This meets the requirements for cathode materials in solid oxide fuel cells. The electrolyte-supported single cell achieved a maximum power density of 710 mW / cm³ at 800℃. ‑2 The single cell underwent continuous and stable discharge at a constant current for 200 hours without performance degradation, demonstrating excellent output performance stability. In summary, perovskite oxide Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3‑δ It is a potential cathode material for intermediate-temperature solid oxide fuel cells.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, and in particular to a medium-temperature solid oxide fuel cell cathode material and its preparation method. Background Technology

[0002] Solid oxide fuel cells (SOFCs) are advanced energy conversion devices with advantages such as environmental friendliness, high efficiency, and fuel flexibility, attracting widespread attention. The main obstacles to the large-scale commercialization of SOFCs are high cost, poor redox stability, and poor compatibility among different battery components. Lowering the operating temperature of the battery to 600-800℃ can solve most of these problems and shorten the start-up time. However, as the battery temperature decreases, the performance of the cathode material deteriorates significantly, becoming a major obstacle to reducing the operating temperature of SOFCs. An ideal cathode material should meet the following requirements: excellent catalytic activity for the oxygen reduction reaction in the medium-low temperature range, a matching coefficient of thermal expansion with other battery components, good electrical conductivity, and ease of synthesis. Further research has revealed that single-phase materials are difficult to meet all the requirements for SOFC cathode materials. Therefore, using composite phase materials as the cathode may be a better choice. This invention studies in detail Pr-doped BaCo... 0.8 Zr 0.1 Y 0.1 O 3-δ The material is used as a cathode material for intermediate-temperature solid oxide fuel cells. Summary of the Invention

[0003] This invention provides a medium-temperature solid oxide fuel cell cathode material and its preparation method. The invention employs a sol-gel wet chemical method to synthesize a composite phase oxide Pr. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ This solves the problem of insufficient catalytic activity of single-phase perovskite oxides in the medium and low temperature range.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A medium-temperature solid oxide fuel cell cathode material, wherein the cathode material is a composite phase structure and has the molecular formula Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ .

[0006] Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The average coefficient of thermal expansion is 20.2 × 10⁻⁶ at 100-800℃. -6 K -1 .

[0007] Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The oxygen temperature-programmed desorption test curves at 100-700℃ showed two oxygen desorption peaks, generating a large number of oxygen vacancies.

[0008] Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ , to La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ Single-cell tests using the electrolyte showed a maximum power density of 715 mW / cm² at a test temperature of 800°C. -2 .

[0009] Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ , to La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ Single-cell tests using the electrolyte showed that the battery operated stably at a constant current discharge for no less than 200 hours at a test temperature of 700℃, demonstrating good output performance stability.

[0010] Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Thermogravimetric analysis at 30-1000℃ showed a weight loss of 1.1%, demonstrating good stability.

[0011] A method for preparing a medium-temperature solid oxide fuel cell cathode material includes: using Ba(NO3)2, Co(NO3)2·6H2O, Zr(NO3)4·5H2O, Pr(NO3)3·6H2O, and Y(NO3)3·6H2O as raw materials, and anhydrous ethylene glycol and citric acid as complexing agents, a precursor is prepared by sol-gel method; the precursor synthesized by sol-gel method is ground into powder in an agate mortar, and then calcined in a muffle furnace at 600℃ for 10 hours and 900℃ for 10 hours respectively; then, alcohol is added and ground for more than 2 hours, pressed into shape at 220MPa, and sintered at 1050℃ for 10 hours to obtain the composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ .

[0012] The sol-gel method involves adjusting the pH of the solution to 9 by adding NH3·H2O, stirring the solution at 80°C to form a gel, and then keeping it at 150°C in an oven for 5 hours to obtain a black precursor.

[0013] The method for fabricating the cathode of a solid oxide fuel cell using the cathode material of the present invention is the same as that in the prior art.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. This invention synthesizes a composite phase perovskite oxide Pr using a wet chemical method. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ It has good sintering properties.

[0016] 2. The cathode material of this invention is similar to the commonly used solid oxide fuel cell electrolyte material BaZr. 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ and oxygen ion conductor electrolyte Sm 0.2 Ce 0.8 O 2-δ It has good chemical compatibility.

[0017] 3. All cathode materials of this invention have good electrical conductivity, reaching 100 Scm in the temperature range of 600-800℃. -1 about.

[0018] 4. The Pr of the present invention 0.1 Ba0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The average coefficient of thermal expansion of the cathode material is 20.2 × 10⁻⁶ °C within the range of 100–800 °C. -6 K -1 .

[0019] 5. The Pr of the present invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The cathode material has good structural stability.

[0020] 6. The Pr of the present invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ As the temperature rises, the cathode material can generate a large number of oxygen vacancies.

[0021] 7. The Pr of the present invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ For example, as a cathode material for mid-temperature solid oxide fuel cells, it has shown good electrochemical performance on lanthanum gallate-doped electrolyte, and is a potential mid-temperature solid oxide cathode material.

[0022] 8. The composite phase cathode material Pr of the present invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ It exhibited good electrochemical performance in impedance testing. Attached Figure Description

[0023] Figure 1 The cathode material Pr prepared by this invention through sintering at 1050℃ for 10 hours 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ XRD pattern of the sample.

[0024] Figure 2 The Pr of this invention 0.1 Ba 0.9 Co 0.8 Zr0.1 Y 0.1 O 3-δ Sample, Sm 0.2 Ce 0.8 O 2-δ (SDC) samples and Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ –Sm 0.2 Ce 0.8 O 2-δ XRD pattern of the mixed sample.

[0025] Figure 3 The Pr of this invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Sample, BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYY) sample and Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ XRD pattern of the BZCYY mixed sample.

[0026] Figure 4 The Pr of this invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The relationship between the conductivity of the cathode material and temperature.

[0027] Figure 5 This is the invention Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Thermal expansion curve of cathode material.

[0028] Figure 6 This is the invention Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Thermogravimetric curve of cathode material.

[0029] Figure 7 This is the invention Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Oxygen programmable desorption curve of cathode material.

[0030] Figure 8 This is the invention Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Polarization impedance test results of cathode material.

[0031] Figure 9 The Pr of this invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Cathode material in La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ Current-voltage characteristic curves and power density curves of electrolyte-supported single cells at different temperatures.

[0032] Figure 10 The Pr of this invention 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Cathode material in La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ Results of stability tests on electrolyte-supported single cells. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to examples:

[0034] Example 1:

[0035] Composite phase intermediate-temperature solid oxide fuel cell cathode material, with the general molecular formula: Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δδThe preparation method is as follows:

[0036] 1) Analytical grade Ba(NO3)2, Co(NO3)2·6H2O, Zr(NO3)4·5H2O, Pr(NO3)3·6H2O, and Y(NO3)3·6H2O were used as experimental raw materials. Appropriate amounts of experimental raw materials were weighed according to the stoichiometric ratio: Pr:Ba:Co:Zr:Y=1:9:8:1:1.

[0037] 2) Weigh out an appropriate amount of anhydrous ethylene glycol and citric acid (molar ratio: metal cation: ethylene glycol: citric acid = 1:1:2) as complexing agents, and dissolve them together with the experimental raw materials weighed in step 1) in deionized water. Add NH3·H2O to adjust the pH of the solution to 9.

[0038] 3) Heat the solution from step 2) to 80°C on a magnetic stirrer and stir until a gel is formed.

[0039] 4) Place the gel sample from step 3) in an oven at 150°C and dry for 5 hours to form a dry gel.

[0040] 5) Grind the dry gel precursor formed in step 4) into powder in an agate mortar, and then calcine it in a muffle furnace at 600°C for 10 hours and at 900°C for 10 hours respectively.

[0041] 6) After calcining the sample at 900℃ for 10 hours in step 5), grind it with alcohol for 2 hours, then press it into shape at 220MPa. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The cathode material was sintered at 1050℃ for 10 hours to obtain the corresponding composite phase cathode material.

[0042] This embodiment uses a sol-gel wet chemical method to prepare Pr, a medium-temperature solid oxide fuel cell cathode material with a double perovskite structure. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ , Figure 1 The image shows the XRD pattern of the sample after sintering at 1050℃ for 10 hours. From... Figure 1 As can be seen, the obtained sample is a composite phase, containing PrBaCo2O with a double perovskite structure. 5+δ and BaCo 0.8 Zr 0.1 Y 0.1 O 3-δ Two phases.

[0043] To verify the chemical compatibility between the prepared cathode material and the intermediate-temperature electrolyte material, we will use Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Cathode materials and Sm 0.2 Ce 0.8 O 1.9 (SDC), BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYY) were mixed and ground at a mass ratio of 1:1 and then calcined at 950℃ for 10 hours. The chemical compatibility of the two powders was studied by XRD spectrum of the mixed powder. Figure 2 Pr for composite phase 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Sample, SDC, Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ –XRD pattern of the SDC mixed sample. Figure 3 For Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Samples, BZCYY samples and Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ XRD pattern of the BZCYY mixed sample. Figure 2 and Figure 3 The peaks in the middle are diffraction peaks of both cathode and electrolyte materials. After mixing, no new diffraction peaks appeared and there was no obvious peak position shift, indicating that Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The cathode material exhibits good chemical compatibility with SDC and BZCYY electrolyte materials after calcination at 950℃ for 10 hours.

[0044] Electrical conductivity is an important factor affecting the performance of cathode materials. We tested the Pr content after sintering at 1050℃ for 10 hours using the van der Berg four-terminal method. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The electrical conductivity of the sample in the temperature range of 300-850℃. Figure 4 Pr is given 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The relationship between the conductivity of the cathode material and temperature. Figure 4 As can be seen from this, Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The conductivity of the sample continuously increases with increasing temperature. The reason for the increase in conductivity is Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Co ions in the sample 3+ Co 4+ Thermal excitation leads to increased activity of small polarons.

[0045] Figure 5 It is sample Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Thermal expansion curves within a temperature range of 100-800℃. From... Figure 5 As can be seen, the thermal expansion curve of the sample exhibits a linear relationship with temperature within the range of 100-800℃. The differential curve of thermal expansion indicates that the sample remains structurally stable within the test temperature range, without any structural phase transition. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The average coefficient of thermal expansion of the sample in the temperature range of 100-800℃ is 20.2×10⁻⁶. -6 K -1 .

[0046] Figure 6 Pr is given 0.1Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Thermogravimetric curves were obtained within the temperature range of 50-1000℃. Throughout the entire test temperature range, the cathode material exhibited a weight loss of 1.1%, demonstrating good stability.

[0047] Figure 7 Pr is given 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Oxygen desorption curves were obtained within the temperature range of 100-700℃. Oxygen desorption peaks appeared at 200-350℃ and 350-550℃, corresponding to changes in the oxidation state of Co in the composite cathode material, resulting in a large number of oxygen vacancies.

[0048] Figure 8 Pr is given 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Polarization impedance test results of the cathode in a symmetrical cell on an LSGM electrolyte. The polarization impedance at 700℃ is 0.06 Ωcm. 2 It exhibited excellent oxygen reduction catalytic activity.

[0049] Figure 9 The following is given in Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ NiO-SDC is the cathode, and La is the anode. 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ The current-voltage characteristic curves and output power curves of a single cell with an electrolyte at different temperatures are shown. In the study of La... 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ In the electrolyte-supported single cell, the electrolyte thickness is 0.3 mm, and Sm is introduced. 0.2 Ce 0.8 O 1.9 The buffer layer prevents La 0.9 Sr 0.1 Ga 0.8 Mg0.2 O 3-δ It reacts chemically with NiO. Figure 9 As can be seen, the output power density of a single cell increases linearly with the test temperature. With increasing test temperature, the internal resistance of the cell decreases, the catalytic activity of the electrodes increases, and the performance of the single cell also increases. At 800℃, the maximum output power density of the single cell reaches 710 mW / cm². -2 . Figure 10 The stability test results of a single cell under constant current for 200 hours are presented. The battery performance did not degrade, demonstrating good output performance stability. The above research indicates that Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ It is a potential cathode material for intermediate-temperature solid oxide fuel cells.

Claims

1. A medium-temperature solid oxide fuel cell cathode material, characterized in that, The cathode material is a composite phase battery cathode material with the molecular formula Pr. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ ; The method for preparing the intermediate-temperature solid oxide fuel cell cathode material includes: using Ba(NO3)2, Co(NO3)2·6H2O, Zr(NO3)4·5H2O, Pr(NO3)3·6H2O, and Y(NO3)3·6H2O as raw materials, and anhydrous ethylene glycol and citric acid as complexing agents, a precursor is prepared by sol-gel method. The precursor synthesized by sol-gel method is ground into powder in an agate mortar, and then calcined in a muffle furnace at 600 ºC for 10 hours and 900 ºC for 10 hours respectively; then, alcohol is added and ground for more than 2 hours, pressed into shape at 220 MPa, and sintered at 1050 ºC for 10 hours to obtain the composite phase cathode material Pr. 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ ; The sol-gel method involves adjusting the pH of the solution to 9 by adding NH3·H2O, stirring the solution at 80ºC to form a gel, and then keeping it at 150ºC in an oven for 5 hours to obtain a black precursor. The experimental raw materials, namely Ba(NO3)2, Co(NO3)2·6H2O, Zr(NO3)4·5H2O, Pr(NO3)3·6H2O, and Y(NO3)3·6H2O, were weighed according to the stoichiometric ratio of Pr:Ba:Co:Zr:Y = 1:9:8:1:

1. The molar ratio of the metal cation, ethylene glycol, and citric acid is 1:1:

2.

2. The intermediate-temperature solid oxide fuel cell cathode material according to claim 1, characterized in that, Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The average coefficient of thermal expansion is 20.2 × 10⁻⁶ at 100–800 °C. -6 K -1 .

3. The intermediate-temperature solid oxide fuel cell cathode material according to claim 1, characterized in that, Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ The oxygen desorption test curves at 100-700 °C showed two oxygen desorption peaks.

4. The intermediate-temperature solid oxide fuel cell cathode material according to claim 1, characterized in that, Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ , to La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ Single-cell tests using the electrolyte showed a maximum power density of 715 mW cm⁻¹ at a test temperature of 800 ºC. -2 .

5. The intermediate-temperature solid oxide fuel cell cathode material according to claim 1, characterized in that, Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ , to La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ Single-cell tests using the electrolyte showed that it operated stably for at least 200 hours under constant current discharge at a test temperature of 700 ºC.

6. The intermediate-temperature solid oxide fuel cell cathode material according to claim 1, characterized in that, Composite phase cathode material Pr 0.1 Ba 0.9 Co 0.8 Zr 0.1 Y 0.1 O 3-δ Thermogravimetric analysis at 30-1000 °C showed a weight loss of 1.1%.

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