High-activity nanofiber air electrode material and preparation method thereof

Abstract

The invention provides a high-activity nanofiber air electrode material and a preparation method thereof, and the preparation method comprises the following steps: S1, mixing deionized water and N, N-dimethylformamide, and stirring for 30-60 min to obtain a solvent; s2, weighing lanthanum nitrate, strontium carbonate, cobalt nitrate and ferric nitrate according to the stoichiometric ratio of (La < 0.6 > Sr < 0.4 >) < 0.95 > Co < 0.2 > Fe < 0.8 > O < 3-delta >, then sequentially adding lanthanum nitrate, strontium carbonate, cobalt nitrate and ferric nitrate into the solvent, and stirring for 30-60 minutes to obtain a metal salt solution; s3, adding a spinning aid into the metal salt solution, and stirring for 20-24 hours to obtain a spinning precursor solution; s4, standing the spinning precursor solution for 10-20 minutes until the spinning precursor solution is uniform and free of bubbles, and then sucking the spinning precursor solution into an injector for spinning to obtain a nanofiber membrane; and S5, sintering the nanofiber membrane in a muffle furnace to obtain the high-activity nanofiber air electrode material. The preparation method is simple in process, batch production can be realized, the sintering temperature of a single battery is low, the cost is low, and the prepared high-activity nanofiber air electrode material is good in catalytic activity and excellent in CO2 surface poisoning resistance.

Description

Technical Field

[0001] The present invention relates to an electrode material, in particular to a highly active nanofiber air electrode material and a preparation method thereof. Background Art

[0002] Solid oxide electrolysis cells (SOECs) have attracted wide attention in green hydrogen production technology due to their high energy conversion efficiency, strong environmental compatibility, and wide fuel adaptability. However, their commercialization process is restricted by the problems of increased costs caused by high-temperature operating conditions (conventional operating temperature 800 - 1000 °C) and durability decay of key materials. In recent years, reducing the operating temperature of SOECs has become an important direction for their technological optimization. However, problems such as the increase in oxygen electrode polarization resistance and the increase in activation energy of redox reactions have severely restricted the hydrogen production efficiency under low- and medium-temperature conditions.

[0003] Currently, the perovskite-type oxide LSCF with mixed ion - electron conduction characteristics is widely used as an air electrode material for SOECs. Its advantage lies in the efficient charge transfer at the gas - solid - ion triple-phase interface, and its thermal expansion coefficient is highly matched with the mainstream electrolyte material. However, during long-term operation, the separation and enrichment of Sr on the surface and interface of the LSCF-based oxygen electrode are likely to cause CO2 poisoning and significantly reduce its catalytic activity and stability. Existing modification strategies (such as element doping and nanostructure regulation) can partially alleviate the performance degradation process, but it is difficult to achieve synergistic optimization between activity improvement and structural stability.

[0004] Chinese Patent CN118588955B discloses a preparation method of a fiber composite air electrode with high catalytic activity. The preparation method of the composite air electrode is novel and has good electrochemical performance. However, this method does not study the common CO2 tolerance problem of air electrodes. In addition, the single-cell sintering temperature of this method is slightly high, which may damage the original structure of the nanofibers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a highly active nanofiber air electrode material. The preparation method has a simple process, can be mass-produced, has a low single-cell sintering temperature, low cost, and the prepared highly active nanofiber air electrode material has good catalytic activity and excellent CO2 surface poisoning resistance.

[0006] To solve the above technical problem, the technical solution of the present invention is as follows: A preparation method of a highly active nanofiber air electrode material, comprising the following steps: S1. Mix deionized water and N,N-dimethylformamide, and stir for 30 - 60 min to obtain a solvent; S2. According to (La 0.6 Sr0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ Weigh lanthanum nitrate, strontium carbonate, cobalt nitrate, and iron nitrate in stoichiometric ratios, and then add lanthanum nitrate, strontium carbonate, cobalt nitrate, and iron nitrate to the solvent obtained in step S1 in sequence. After stirring for 30 - 60 min, a metal salt solution is obtained. Among them, the operation of adding lanthanum nitrate, strontium carbonate, cobalt nitrate, and iron nitrate in sequence can effectively avoid the formation of precipitation; S3. Add a spinning aid to the metal salt solution obtained in step S2, and stir for 20 - 24 h to obtain a spinning precursor solution; S4. Let the spinning precursor solution obtained in step S3 stand for 10 - 20 minutes until it is uniform and bubble-free, and then suck it into a syringe for spinning to obtain a nanofiber membrane; S5. Place the nanofiber membrane obtained in step S4 in a muffle furnace for sintering to obtain a highly active nanofiber air electrode material.

[0007] Furthermore, in step S1 of the present invention, the volume ratio of deionized water to N,N-dimethylformamide is 1:1.

[0008] Furthermore, in step S1 of the present invention, the stirring speed is 200 - 300 r / min.

[0009] Furthermore, in step S2 of the present invention, the ratio of the total mass of lanthanum nitrate, strontium carbonate, cobalt nitrate, and iron nitrate to the mass of the solvent obtained in step S1 is 1:(2 - 14).

[0010] Furthermore, in step S2 of the present invention, the stirring speed is 200 - 300 r / min.

[0011] Furthermore, in step S3 of the present invention, the spinning aid is polyacrylonitrile, and the mass fraction of polyacrylonitrile in the spinning precursor solution is 8 - 10%.

[0012] Furthermore, in step S3 of the present invention, the stirring speed is 200 - 300 r / min.

[0013] Furthermore, in step S4 of the present invention, the parameters of the spinning process are: the feeding speed is 0.1 - 0.5 mL / h, the needle head model is 22 - 25G, the spinning temperature is 25 - 30 °C, the rotation speed of the roller winder is 100 - 250 r / min, the vertical distance between the needle head and the winder is 10 - 20 cm, and the spinning voltage is 15 - 20 kv.

[0014] Further, in step S5 of the present invention, the specific sintering process is as follows: First, the temperature is raised from 30°C to 400 - 600°C at a heating rate of 1 - 3.5°C per minute, and held for 1 - 3 hours. Subsequently, the temperature is raised to 750 - 900°C at a heating rate of 3 - 7°C per minute, and held for 1 - 3 hours. Finally, the temperature is lowered to room temperature at a cooling rate of 2°C / min.

[0015] Another technical problem to be solved by the present invention is to provide a highly active nanofiber air electrode material prepared by the above preparation method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention uses electrospinning technology to prepare a highly active nanofiber air electrode material. The addition of the co-spinning agent polyacrylonitrile can make the reaction between metal salts more sufficient, greatly reduce the phase formation temperature, and thus reduce energy consumption.

[0017] 2) The highly active nanofiber air electrode material prepared by the present invention has a larger specific surface area and more surface adsorbed oxygen compared with traditional granular materials, increasing the gas-solid interface between the reaction gas and the perovskite oxide, providing more active sites for ion adsorption. At the same time, the continuous fiber structure also accelerates the charge transfer ability.

[0018] 3) The entangled structure of electrospinning induces compressive strain on the perovskite lattice, which can stabilize the Sr-O bond and inhibit Sr segregation, thereby enhancing the electrode stability and the anti-CO2 surface poisoning ability of the highly active nanofiber air electrode material of the present invention. The polarization resistance of the symmetrical battery prepared from the highly active nanofiber air electrode material of the present invention did not change significantly during the 400-hour performance test.

[0019] 4) The maximum current density of the highly active nanofiber air electrode material prepared by the present invention is as high as 1.49 A·cm at 750°C and 1.5V -2 , so it can meet the requirements of water electrolysis for air electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is the X-ray powder diffraction pattern (XRD) of the electrode materials prepared in Examples 1 - 4 of the present invention; Figure 2 is the stability test chart of the symmetrical batteries prepared in Examples 3 and 5 of the present invention; Figure 3 is the single cell performance test chart of the symmetrical batteries prepared in Examples 3 and 5 of the present invention, Figure 3The left half is Example 3 and the right half is Example 5. Detailed implementation manners

[0021] The present invention will be described in detail below in conjunction with specific embodiments. Here, the illustrative embodiments of the present invention and the descriptions are used to explain the present invention, but not to limit the present invention. Embodiment

[0022] Prepare a highly active nanofiber air electrode material according to the following steps: S1. Mix deionized water and N,N-dimethylformamide with a volume ratio of 1:1, and stir for 60 minutes at a rotation speed of 200 r / min to obtain a solvent; S2. Weigh lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate according to the stoichiometric ratio of (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ Then add lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the solvent obtained in step S1 in sequence. The ratio of the total mass of lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the mass of the solvent obtained in step S1 is 1:14, and stir for 60 minutes at a rotation speed of 200 r / min to obtain a metal salt solution; S3. Add polyacrylonitrile to the metal salt solution obtained in step S2, and stir for 24 hours at a rotation speed of 200 r / min to obtain a spinning precursor solution. The mass fraction of polyacrylonitrile in the spinning precursor solution is 10%; S4. Let the spinning precursor solution obtained in step S3 stand for 20 minutes until it is uniform and bubble-free, and then suck it into a syringe for spinning to obtain a nanofiber membrane. The parameters of the spinning process are: the propulsion speed is 0.2 mL / h, the needle model is 23G, the spinning temperature is 30 °C, the rotation speed of the drum winder is 100 r / min, the vertical distance between the needle and the winder is 11 cm, and the spinning voltage is 18 kv; S5. Place the nanofiber membrane obtained in step S4 in a muffle furnace for sintering to obtain a highly active nanofiber air electrode material. The specific sintering process is: first, heat from 30 °C to 500 °C at a heating rate of 2 °C per minute, keep warm for 1 h, then heat to 800 °C at a heating rate of 3 °C per minute, keep warm for 2 h, and finally cool to room temperature at a cooling rate of 2 °C / min. Embodiment

[0023] Prepare a highly active nanofiber air electrode material according to the following steps: S1. Mix deionized water and N,N-dimethylformamide with a volume ratio of 1:1, and stir for 30 minutes at a rotation speed of 300 r / min to obtain a solvent; S2. Weigh lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate according to the stoichiometric ratio of (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ , and then add lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate into the solvent obtained in step S1 in sequence. The ratio of the total mass of lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the mass of the solvent obtained in step S1 is 1:7. After stirring at 300 r / min for 30 min, a metal salt solution is obtained; S3. Add polyacrylonitrile into the metal salt solution obtained in step S2, and stir at 300 r / min for 20 h to obtain a spinning precursor solution. The mass fraction of polyacrylonitrile in the spinning precursor solution is 9%; S4. Let the spinning precursor solution obtained in step S3 stand for 10 minutes until it is uniform and bubble-free, and then suck it into a syringe for spinning to obtain a nanofiber membrane. The parameters of the spinning process are: the pushing speed is 0.1 mL / h, the needle type is 22G, the spinning temperature is 28 °C, the rotation speed of the drum winder is 250 r / min, the vertical distance between the needle and the winder is 10 cm, and the spinning voltage is 20 kv; S5. Place the nanofiber membrane obtained in step S4 in a muffle furnace for sintering to obtain a highly active nanofiber air electrode material. The specific sintering process is as follows: First, heat from 30 °C to 400 °C at a heating rate of 1 °C / min, hold for 3 h, then heat to 750 °C at a heating rate of 5 °C / min, hold for 3 h, and finally cool to room temperature at a cooling rate of 2 °C / min. Example

[0024] Prepare a highly active nanofiber air electrode material according to the following steps: S1. Mix deionized water and N,N-dimethylformamide with a volume ratio of 1:1, and stir at 300 r / min for 40 min to obtain a solvent; S2. Weigh lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate according to the stoichiometric ratio of (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ , and then add lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate into the solvent obtained in step S1 in sequence. The ratio of the total mass of lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the mass of the solvent obtained in step S1 is 1:4. After stirring at 300 r / min for 40 min, a metal salt solution is obtained; S3. Add polyacrylonitrile to the metal salt solution obtained in step S2, and stir at a speed of 300 r / min for 21 h to obtain a spinning precursor solution, where the mass fraction of polyacrylonitrile in the spinning precursor solution is 10%; S4. Let the spinning precursor solution obtained in step S3 stand for 20 minutes until it is uniform and bubble-free, and then suck it into a syringe for spinning to obtain a nanofiber membrane. The parameters of the spinning process are: the propulsion speed is 0.4 mL / h, the needle model is 23G, the spinning temperature is 30 °C, the rotation speed of the drum winder is 100 r / min, the vertical distance between the needle and the winder is 11 cm, and the spinning voltage is 18 kv; S5. Place the nanofiber membrane obtained in step S4 in a muffle furnace for sintering to obtain a highly active nanofiber air electrode material. The specific sintering process is as follows: First, heat from 30 °C to 600 °C at a heating rate of 2 °C / min, hold for 2 h, then heat to 900 °C at a heating rate of 3 °C / min, hold for 2 h, and finally cool to room temperature at a cooling rate of 2 °C / min.

[0025] Prepare an electrolyte-supported symmetric cell: Use the tape casting method to prepare an SSZ electrolyte with a diameter of 20 mm, and calcine it at 1500 °C for 5 h to obtain a dense SSZ electrolyte layer with particles. Screen-print the SDC barrier layer on both sides of the SSZ electrolyte layer and then calcine it at 1200 °C for 3 hours to obtain SDC|SSZ|SDC. Grind the highly active nanofiber air electrode material prepared in Example 3 for 10 min, and then mix it with an organic binder (composed of ethyl cellulose and terpineol with a mass ratio of 1:19) at a mass ratio of 1:1.2 and grind for 40 min to obtain an air electrode slurry. Uniformly coat the air electrode slurry on both sides of SDC|SSZ|SDC to obtain a symmetric cell.

[0026] Use the tape casting method to prepare a YSZ|NiO+YSZ anode-supported single cell: Sinter the YSZ|NiO+YSZ sheet in air at 1350 °C for 5 h, and then screen-print the SDC barrier layer on the YSZ surface and calcine it at 1200 °C for 3 h to avoid the reaction between YSZ and the oxygen electrode to obtain SDC|YSZ|NiO+YSZ. Finally, screen-print the air electrode slurry on SDC|YSZ|NiO+YSZ to obtain a single cell.

[0027] Calcine the symmetric cell and the single cell at 830 °C for 2 h respectively, and the working area is 0.5 cm -2 Finally, print Ag paste on the electrode surface and sinter it at 800 °C for 1 hour.

[0028] The symmetric battery and the single cell use a silver mesh composed of silver wires and silver paste as the current collector. Then, the battery is tied to the test device and placed in the test furnace, and heated to 800 °C at a heating rate of 4 °C / min. The test temperature range is 800 - 650 °C (measurement is carried out every 50 °C). The test environment of the symmetric battery is air. The test environment of the single cell is as follows: Water is heated to 81.4 °C and hydrogen is injected at a flow rate of 50 sccm to obtain a 50% water vapor content with H2 as the carrier and the electrolytic cell mode test is carried out. Example

[0029] Prepare the high - activity nanofiber air electrode material according to the following steps: S1. Mix deionized water and N,N - dimethylformamide with a volume ratio of 1:1, and stir for 50 min at a rotation speed of 200 r / min to obtain a solvent; S2. Weigh lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate according to the stoichiometric ratio of (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ . Then, add lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the solvent obtained in step S1 in sequence. The ratio of the total mass of lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the mass of the solvent obtained in step S1 is 1:2, and stir for 50 min at a rotation speed of 200 r / min to obtain a metal salt solution; S3. Add polyacrylonitrile to the metal salt solution obtained in step S2, and stir for 22 h at a rotation speed of 200 r / min to obtain a spinning precursor solution. The mass fraction of polyacrylonitrile in the spinning precursor solution is 8%; S4. Let the spinning precursor solution obtained in step S3 stand for 15 minutes until it is uniform and bubble - free, then suck it into a syringe for spinning to obtain a nanofiber membrane. The parameters of the spinning process are: the propulsion speed is 0.5 mL / h, the needle model is 25G, the spinning temperature is 25 °C, the rotation speed of the drum winder is 200 r / min, the vertical distance between the needle and the winder is 20 cm, and the spinning voltage is 15 kv; S5. Place the nanofiber membrane obtained in step S4 in a muffle furnace for sintering to obtain the high - activity nanofiber air electrode material. The specific sintering process is as follows: First, heat from 30 °C to 520 °C at a heating rate of 3.5 °C / min, hold for 2 h, then heat to 870 °C at a heating rate of 7 °C / min, hold for 1 h, and finally cool to room temperature at a cooling rate of 2 °C / min.

[0030] Example 5 (actually a comparative example) Fabrication of an electrolyte-supported symmetric cell: The SSZ electrolyte with a diameter of 20 mm was prepared by the tape-casting method and calcined at 1500 °C for 5 h to obtain a dense SSZ electrolyte layer. The SDC barrier layer was screen-printed on both sides of the SSZ electrolyte layer and then calcined at 1200 °C for 3 h to obtain SDC|SSZ|SDC. The commercial LSCF powder material (purchased from Angxing New Carbon Materials Changzhou Co., Ltd., with a particle size of 3 μm) was ground for 10 min and then mixed and ground with an organic binder (composed of ethyl cellulose and terpineol with a mass ratio of 1:19) at a mass ratio of 1:1.2 for 40 min to obtain the air electrode slurry. The air electrode slurry was uniformly coated on both sides of SDC|SSZ|SDC to obtain the symmetric cell.

[0031] Fabrication of a YSZ|NiO+YSZ anode-supported single cell using the tape-casting method: The YSZ|NiO+YSZ sheet was sintered in air at 1350 °C for 5 h, and then the SDC barrier layer was screen-printed on the YSZ surface and calcined at 1200 °C for 3 h to avoid the reaction between YSZ and the oxygen electrode to obtain SDC|YSZ|NiO+YSZ. Finally, the air electrode slurry was screen-printed on SDC|YSZ|NiO+YSZ to obtain the single cell.

[0032] The symmetric cell and the single cell were respectively calcined at 830 °C for 2 h, and the working area was 0.5 cm -2 Finally, the Ag paste was printed on the electrode surface and sintered at 800 °C for 1 h.

[0033] The symmetric cell and the single cell used a silver mesh composed of silver wires and silver paste as the current collector. Then, the cells were tied to the test device and placed in the test furnace, and heated to 800 °C at a heating rate of 4 °C / min. The test temperature range was 800 - 650 °C (measurement was taken every 50 °C). The test environment for the symmetric cell was air. The test environment for the single cell was as follows: Water was heated to 81.4 °C and hydrogen was injected at a flow rate of 50 sccm to obtain a 50% water vapor content with H2 as the carrier and the electrolytic cell mode test was carried out.

[0034] Experimental Example 1 The highly active nanofiber air electrode materials prepared in Examples 1 - 4 were subjected to XRD and SEM tests. The test results are as Figure 1 shown: The XRD results showed that the materials prepared in Examples 1 - 4 were in good agreement with the standard card, and no impurity peaks were observed.

[0035] Experimental Example 2 The materials of Example 3 and Example 5 were respectively subjected to single cell performance tests and symmetric cell stability tests.

[0036] The results of the single cell performance tests are as Figure 3 shown: The performance of the single cell prepared with the high-activity nanofiber air electrode material in Example 3 is as high as 1.49 A·cm at 750 °C and 1.5 V -2 , while the performance of the single cell prepared with the commercial material in Example 5 is only 1.28 A·cm -2 .

[0037] The results of the symmetric cell stability test are as Figure 2 shown: In the stability test lasting up to 400 h, the symmetric cell prepared with the high-activity nanofiber air electrode material in Example 3 showed excellent stability in terms of polarization resistance, while the polarization resistance of the symmetric cell prepared with the commercial material in Example 5 changed greatly.

[0038] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation method of a highly active nanofiber air electrode material, characterized in that: It includes the following steps: S1. Mix deionized water and N,N-dimethylformamide, and stir for 30 - 60 min to obtain a solvent; S2. Weigh lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate according to the stoichiometric ratio of (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ , then add lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate into the solvent obtained in step S1 in sequence, and stir for 30 - 60 min to obtain a metal salt solution; S3. Add a spinning aid to the metal salt solution obtained in step S2, and stir for 20 - 24 h to obtain a spinning precursor solution; S4. Let the spinning precursor solution obtained in step S3 stand for 10 - 20 minutes until it is uniform and bubble-free, then suck it into a syringe for spinning to obtain a nanofiber membrane; S5. Place the nanofiber membrane obtained in step S4 in a muffle furnace for sintering to obtain a highly active nanofiber air electrode material.

2. The preparation method of a highly active nanofiber air electrode material according to claim 1, wherein: In the said step S1, the volume ratio of deionized water to N,N-dimethylformamide is 1:

1.

3. The preparation method of a highly active nanofiber air electrode material according to claim 1, characterized in that: In the said step S1, the stirring speed is 200 - 300 r / min.

4. The preparation method of a highly active nanofiber air electrode material according to claim 1, characterized in that: In the said step S2, the ratio of the total mass of lanthanum nitrate, strontium carbonate, cobalt nitrate and iron nitrate to the mass of the solvent obtained in step S1 is 1:(2 - 14).

5. The preparation method of a highly active nanofiber air electrode material according to claim 1, characterized in that: In the said step S2, the stirring speed is 200 - 300 r / min.

6. The preparation method of a highly active nanofiber air electrode material according to claim 1, characterized in that: In the said step S3, the spinning aid is polyacrylonitrile, and the mass fraction of polyacrylonitrile in the spinning precursor solution is 8 - 10%.

7. The preparation method of a highly active nanofiber air electrode material according to claim 1, characterized in that: In the said step S3, the stirring speed is 200 - 300 r / min.

8. The preparation method of a highly active nanofiber air electrode material according to claim 1, characterized in that: In the said step S4, the parameters of the spinning process are: the pushing speed is 0.1 - 0.5 mL / h, the needle head model is 22 - 25G, the spinning temperature is 25 - 30 °C, the rotating speed of the roller wire collector is 100 - 250 r / min, the vertical distance between the needle head and the wire collector is 10 - 20 cm, and the spinning voltage is 15 - 20 kv.

9. The preparation method of a high-activity nanofiber air electrode material according to claim 1, characterized in that: In the said step S5, the specific sintering process is: first, heat from 30 °C to 400 - 600 °C at a heating rate of 1 - 3.5 °C per minute, keep it warm for 1 - 3 h, then heat to 750 - 900 °C at a heating rate of 3 - 7 °C per minute, keep it warm for 1 - 3 h, and finally cool to room temperature at a cooling rate of 2 °C / min.

10. A highly active nanofiber air electrode material prepared by the preparation method according to claims 1 - 9.

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