Oxygen electrode material doped with bismuth element at B site and preparation method of oxygen electrode material

Abstract

The invention belongs to the technical field of solid oxide batteries, and discloses a B-site bismuth-doped oxygen electrode material and a preparation method thereof. The oxygen electrode material is a double perovskite oxide, the chemical formula is PrBa < 0.8 > Ca < 0.2 > Co < 1.5 > Fe < 0.5-x > Bi < x > O < 5 + delta >, x is more than 0 and less than or equal to 0.05, and delta is the content of oxygen vacancies. The oxygen electrode material is prepared through a citrate combustion method, the preparation method has the advantages of being low in sintering temperature and simple and convenient in technological process, and the prepared double perovskite material has high oxygen surface exchange rate and high electrocatalytic activity and has good electrochemical performance and stability. The oxygen electrode material is applied to an oxygen electrode of a solid oxide fuel cell and shows preferential long-term stability, so that the oxygen electrode material has the potential of serving as the oxygen electrode of the solid oxide fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of solid oxide battery technology, specifically relating to an oxygen electrode material doped with bismuth at the B site and its preparation method. Background Technology

[0002] Solid oxide cells (SOCs) have garnered significant attention in recent years due to their high-efficiency and clean power generation capabilities in the SOFC mode and their excellent hydrogen production and energy storage potential in the SOEC mode. Compared to traditional combustion power generation technologies, SOFCs can directly convert the chemical energy stored in fuel into electrical energy, overcoming the limitations of the Carnot cycle and greatly improving energy utilization efficiency. SOECs can store electrical energy generated from renewable, intermittent, and geographically limited clean energy sources (such as solar and wind power) in chemical energy, alleviating the increasingly severe energy crisis. Therefore, solid oxide cells have broad development prospects.

[0003] Currently, oxygen electrodes in solid oxide batteries face several challenges. For example, oxygen electrode materials must maintain their chemical and structural stability at high temperatures to prevent sintering, volatilization, grain boundary migration, and other performance degradation. Secondly, oxygen electrode materials and electrolyte materials must remain chemically inert at high temperatures to avoid reactions that generate impedance layers or interfacial phases, which would significantly increase charge transport impedance. Excessive difference in the thermal expansion coefficients of the oxygen electrode and electrolyte can lead to thermal stress during temperature changes, causing material cracking and delamination, ultimately resulting in battery failure. Lowering the operating temperature can slow down reactions between battery components, thereby extending battery life; however, with lower operating temperatures, the redox reaction (ORR) activity of the oxygen electrode decreases significantly, leading to a decline in performance. Therefore, developing oxygen electrode materials with superior performance is crucial. Summary of the Invention

[0004] The purpose of this invention is to provide an oxygen electrode material doped with bismuth at the B site and its preparation method. Introducing bismuth at the B site can improve the oxygen vacancy concentration and reactivity of the oxygen electrode material, thereby giving the prepared oxygen electrode material good electrochemical performance and stability.

[0005] To achieve the above objectives, this application proposes a bismuth-doped oxygen electrode material at the B site, wherein the oxygen electrode material is a double perovskite oxide with the chemical formula PrBa. 0.8 Ca 0.2 Co 1.5 Fe 0.5-x Bi x O 5+δ , where 0 < x ≤0.05, δ This represents the content of oxygen vacancies.

[0006] To achieve the above objectives, the present invention also provides a method for preparing a bismuth-doped oxygen electrode material at the B site, comprising the following steps: (1) According to the oxygen electrode material PrBa 0.8 Ca 0.2 Co 1.5 Fe 0.5-x Bi x O 5+δ The stoichiometric ratios of each element in the solution are determined. Metal nitrates containing Pr, Ba, Ca, Co, Fe, and Bi are weighed out separately. Appropriate amounts of citric acid and ethylenediaminetetraacetic acid are also weighed out. (2) Dissolve all metal nitrates in deionized water, heat and stir until the solution is clear, then add citric acid and ethylenediaminetetraacetic acid, add ammonia to adjust the pH of the solution, and continue to heat and stir until the solution becomes gel-like; (3) Place the gel obtained in step (2) into a drying oven and bake it until it becomes fluffy to obtain the precursor; (4) After grinding the precursor in step (3), put it into a muffle furnace and calcine it in an air atmosphere to obtain oxygen electrode material powder.

[0007] Preferably, in step (1), the metal nitrates containing Pr, Ba, Ca, Co, Fe and Bi are Pr(NO3)3·6H2O, Ba(NO3)2, Ca(NO3)2·4H2O, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and Bi(NO3)3·5H2O, respectively.

[0008] Preferably, in step (1), the molar ratio between the metal ions, citric acid and ethylenediaminetetraacetic acid is 1:1.5:1.

[0009] Preferably, in step (2), the pH of the solution is adjusted to 6-8 and the stirring temperature is 50-100℃.

[0010] Preferably, in step (3), the temperature of the drying oven is 150~300℃ and the drying time is 5~18h.

[0011] Preferably, in step (4), the calcination temperature is 800~1200℃ and the calcination time is 5~10h.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes an oxygen electrode material doped with bismuth at the B site, through the use of PrBa... 0.8 Ca 0.2 Co 1.5 Fe 0.5-x Bi x O 5+δDoping bismuth at the B site can improve the oxygen vacancy concentration and reactivity of the oxygen electrode material, resulting in a material with good electrochemical performance and stability, and promising application prospects in the field of solid oxide batteries.

[0013] This invention utilizes bismuth doping to reduce the phase formation temperature of oxygen electrode materials and the thermal expansion coefficient of perovskite materials, while simultaneously improving oxygen surface exchange capacity and enhancing electrocatalytic activity.

[0014] The oxygen electrode material prepared by the present invention is prepared by the percitrate combustion method. This preparation method has the advantages of low sintering temperature and simple process flow, and its composition is simple, the synthesis process is relatively simple, and it is easy to prepare. Attached Figure Description

[0015] Figure 1 This is the XRD pattern of the oxygen electrode material prepared in Example 2 of this invention; Figure 2 This is a schematic diagram showing the relationship between the coefficient of thermal expansion and temperature of the dense sample strip of oxygen electrode material prepared in Example 2 of this invention; Figure 3 This is a schematic diagram of the impedance curve of the oxygen electrode material prepared in Example 2 of this invention; Figure 4 This is a diagram showing the long-term impedance stability of the oxygen electrode material prepared in Example 2 of this invention. Detailed Implementation

[0016] The technical solutions of the embodiments of this application will be described in detail and completely below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0017] Example 1:

[0018] The chemical formula is PrBa 0.8 Ca 0.2 Co 1.5 Fe 0.475 Bi 0.025 O 5+δ The preparation steps of the oxygen electrode material are as follows: (1) Weigh out 13.0503g of Pr(NO3)3·6H2O, 6.2721g of Ba(NO3)2, 1.4169g of Ca(NO3)2·4H2O, 13.0964g of Co(NO3)2·6H2O, 5.75696g of Fe(NO3)3·9H2O and 0.3638g of Bi(NO3)3·5H2O metal nitrates according to the stoichiometric ratio of oxygen electrode materials 1:0.8:0.2:1.5:0.475:0.025; and then weigh out 34.5816g of citric acid and 35.0688g of ethylenediaminetetraacetic acid according to the molar ratio of metal ions, citric acid and ethylenediaminetetraacetic acid 1:1.5:1.

[0019] (2) Pour the metal nitrate into a beaker, add 200 mL of deionized water, place the mixed solution on a magnetic stirrer, stir at 60°C until the solution is clear, then add citric acid and ethylenediaminetetraacetic acid, then add ammonia to adjust the pH of the solution to 7, keep the solution at 90°C and stir until the water evaporates and a gel is formed.

[0020] (3) Place the obtained gel in an oven and bake at 200°C for 12 hours until the gel is fluffy to obtain the precursor.

[0021] (4) After grinding the precursor, it was placed in a muffle furnace and calcined at 1100℃ for 10 hours in air atmosphere to obtain PrBa 0.8 Ca 0.2 Co 1.5 Fe 0.475 Bi 0.025 O 5+δ Oxygen electrode material.

[0022] Example 2:

[0023] The chemical formula is PrBa 0.8 Ca 0.2 Co 1.5 Fe 0.45 Bi 0.05 O 5+δ The preparation steps of the oxygen electrode material are as follows: (1) Weigh out 13.0503g of Pr(NO3)3·6H2O, 6.2721g of Ba(NO3)2, 1.4169g of Ca(NO3)2·4H2O, 13.0964g of Co(NO3)2·6H2O, 5.45396g of Fe(NO3)3·9H2O and 0.7276g of Bi(NO3)3·5H2O metal nitrates according to the stoichiometric ratio of oxygen electrode materials 1:0.8:0.2:1.5:0.45:0.05 respectively; then weigh out 34.5816g of citric acid and 35.0688g of ethylenediaminetetraacetic acid according to the molar ratio of metal ions:citric acid:ethylenediaminetetraacetic acid 1:1.5:1.

[0024] (2) Pour the metal nitrate into a beaker, add 200 mL of deionized water, place the mixed solution on a magnetic stirrer, stir at 60°C until the solution is clear, then add citric acid and ethylenediaminetetraacetic acid, then add ammonia to adjust the pH of the solution to 7, keep the solution at 90°C and stir until the water evaporates and a gel is formed.

[0025] (3) Place the obtained gel in an oven and bake at 200°C for 12 hours until the gel is fluffy to obtain the precursor.

[0026] (4) The precursor was ground and pressed into discs, then placed in a muffle furnace and calcined at 1100℃ for 10 hours in air atmosphere to obtain PrBa. 0.8 Ca 0.2 Co 1.5 Fe 0.45 Bi 0.05 O 5+δ Oxygen electrode material.

[0027] The XRD pattern of the oxygen electrode material powder prepared in Example 2 is shown below. Figure 1 As shown, from Figure 1 As can be seen from the data, the prepared oxygen electrode material has no impurity phases, proving that the oxygen electrode material is a pure phase perovskite oxygen electrode material.

[0028] Weigh 2g of the oxygen electrode material prepared in Example 2 and place it into a molding die. Press the die under 300 MPa for 5 minutes to form a rectangular sample strip. Then, calcine the strip in a muffle furnace at 1150℃ for 10 hours to obtain a dense sample strip (approximately 0.45cm × 0.3cm × 1.8cm). Place the prepared dense sample strip in a thermal expansion meter to test its coefficient of thermal expansion. The test temperature ranges from 30 to 1000℃. The test results are as follows: Figure 2 As shown. From Figure 2As can be seen, the coefficient of thermal expansion decreases with the lower Bi element doping ratio compared to undoped material. The reduction in the coefficient of thermal expansion of the oxygen electrode material ensures that the battery will not detach from the electrolyte during the test, thus guaranteeing the stability of the battery during the test.

[0029] The catalytic performance of the oxygen electrode material samples was characterized using a symmetric cell method to study PrBa. 0.8 Ca 0.2 Co 1.5 Fe 0.45 Bi 0.05 O 5+δ The polarization impedance (ASR) of the symmetrical cell sample was measured. The ASR was tested by placing the sample in air at 700-800℃, and the EIS impedance curve and impedance stability were obtained. Figure 3 and 4 As shown. From Figure 3 As can be seen, ASR decreases with increasing temperature. Figure 4 It can be seen that ASR has good stability at 700℃.

[0030] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A bismuth-doped oxygen electrode material at the B site, characterized in that, The oxygen electrode material is a double perovskite oxide with the chemical formula PrBa. 0.8 Ca 0.2 Co 1.5 Fe 0.5-x Bi x O 5+δ , where 0 < x ≤0.05, δ This represents the content of oxygen vacancies.

2. The method for preparing a bismuth-doped oxygen electrode material at the B site as described in claim 1, characterized in that, Includes the following steps: (1) According to the oxygen electrode material PrBa 0.8 Ca 0.2 Co 1.5 Fe 0.5-x Bi x O 5+δ The stoichiometric ratios of each element in the solution are determined. Metal nitrates containing Pr, Ba, Ca, Co, Fe, and Bi are weighed out separately. Appropriate amounts of citric acid and ethylenediaminetetraacetic acid are also weighed out. (2) Dissolve all metal nitrates in deionized water, heat and stir until the solution is clear, then add citric acid and ethylenediaminetetraacetic acid, add ammonia to adjust the pH of the solution, and continue to heat and stir until the solution becomes gel-like; (3) Place the gel obtained in step (2) into a drying oven and bake it until it becomes fluffy to obtain the precursor; (4) After grinding the precursor in step (3), put it into a muffle furnace and calcine it in an air atmosphere to obtain oxygen electrode material powder.

3. The method for preparing a bismuth-doped oxygen electrode material at the B site according to claim 2, characterized in that, In step (1), the metal nitrates containing Pr, Ba, Ca, Co, Fe and Bi are Pr(NO3)3·6H2O, Ba(NO3)2, Ca(NO3)2·4H2O, Co(NO3)2·6H2O, Fe(NO3)3·9H2O and Bi(NO3)3·5H2O, respectively.

4. The method for preparing a bismuth-doped oxygen electrode material at the B site according to claim 2, characterized in that, In step (1), the molar ratio between metal ions, citric acid and ethylenediaminetetraacetic acid is 1:1.5:

1.

5. The method for preparing a bismuth-doped oxygen electrode material at the B site according to claim 2, characterized in that, In step (2), the pH of the solution is adjusted to 6-8, and the stirring temperature is 50-100℃.

6. The method for preparing a bismuth-doped oxygen electrode material at the B site according to claim 2, characterized in that, In step (3), the temperature of the drying oven is 150~300℃ and the drying time is 5~18h.

7. The method for preparing a bismuth-doped oxygen electrode material at the B site according to claim 2, characterized in that, In step (4), the calcination temperature is 800~1200℃ and the calcination time is 5~10h.

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