Core-shell nanofiber structure electrode material and preparation method and application thereof

Abstract

The invention relates to a core-shell nanofiber structure electrode material as well as a preparation method and application thereof, and belongs to the technical field of solid oxide electrolytic cells. The preparation method comprises the following steps: S1, preparing an LSCF-NF substrate by using an electrostatic spinning technology; s2, weighing nitric acid M and cerous nitrate according to the stoichiometric ratio of M0. 2Ce0. 8O2, and then mixing the nitric acid M, the cerous nitrate and a solvent to obtain an impregnation liquid; s3, impregnating the LSCF-NF in the impregnation liquid, and stirring to obtain a dispersion solution; and S4, drying and sintering the dispersed solution to obtain the core-shell nanofiber electrode material. The prepared core-shell nanofiber has good catalytic activity and CO2 surface poisoning resistance, and the maximum current density of the core-shell nanofiber reaches 2.2 A.cm <-2 > at the temperature of 750 DEG C and under the voltage of 1.5 V, so that the requirement of electrolyzed water on an air electrode material can be met.

Description

Technical Field

[0001] This invention relates to a core-shell nanofiber structure electrode material, its preparation method, and its application, belonging to the field of solid oxide electrolytic cell technology. Background Technology

[0002] Solid oxide electrolyzers (SOECs) have attracted much attention in green hydrogen production technology due to their high energy conversion efficiency, strong fuel adaptability, and environmental friendliness. However, their commercialization is still limited by the increased costs and material durability degradation caused by high-temperature operation. Lowering the operating temperature has become an optimization direction for SOECs, but at medium and low temperatures, the polarization resistance of the oxygen electrode increases and the activation energy of the redox reaction increases, severely limiting hydrogen production efficiency. Currently widely used perovskite oxide LSCFs possess mixed ion-electron conduction characteristics, enabling efficient three-phase interface charge transport and exhibiting good compatibility with mainstream electrolytes. However, LSCFs are prone to Sr migration and enrichment during long-term operation, leading to CO2 poisoning and a significant decrease in activity and stability. Although strategies such as doping and morphology control have been developed to partially improve their performance degradation, it is difficult to simultaneously achieve a synergistic improvement in both high activity and high stability.

[0003] Chinese patent CN104752734B, entitled "A Low-Temperature Solid Oxide Fuel Cell Cathode with a Core-Shell Nanofiber Structure and Its Electrospinning Preparation Method," describes a method that constructs a core-shell nanofiber structure to effectively improve the oxygen reduction activity and interfacial stability of the cathode. It also demonstrates good electrochemical performance and resistance to CO2 poisoning under medium- and low-temperature conditions, providing a new approach for optimizing solid oxide oxygen electrode materials. However, this method relies on coaxial electrospinning, independent preparation of multiple precursor solutions, precise and coordinated control of spinning parameters, and subsequent multi-stage drying and high-temperature sintering steps. The overall process is cumbersome and highly sensitive to operating conditions, thus limiting its practical application in related fields. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a core-shell nanofiber structure electrode material, its preparation method, and its applications. The preparation process of this invention is simple, allows for mass production, has low sintering power consumption per cell, and the resulting core-shell nanofiber structure electrode material exhibits good catalytic activity and excellent resistance to CO2 surface poisoning.

[0005] To achieve the above-mentioned objectives, the technical solution of this invention is as follows: A method for preparing a core-shell nanofiber structured electrode material includes the following steps: S1. Prepared using electrospinning technology (La) 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O3-δ Nanofiber (LSCF-NF) substrate, where 0 < δ < 1; S2. According to M 0.2 Ce 0.8 Weigh nitric acid M and cerium nitrate in stoichiometric proportions to O2, wherein M is selected from any one of Sm, Pr, La, Ga, Nd or Ce. Then mix nitric acid M, cerium nitrate, deionized water and organic solvent to obtain impregnation solution; the organic solvent is any one of anhydrous ethanol, propanol or isopropanol, preferably anhydrous ethanol.

[0006] S3. Add the obtained LSCF-NF substrate to the impregnation solution and stir for 2-3 hours to obtain a uniform dispersion solution; S4. The dispersion solution is dried and sintered to obtain the core-shell nanofiber electrode material; The specific sintering process is as follows: first, the temperature is increased from 30℃ to 400-600℃ at a heating rate of 1-3.5℃ / min, and held for 1-3 hours; then, the temperature is increased to 750-1100℃ at a heating rate of 3-7℃ / min, and held for 1-3 hours; finally, the temperature is reduced to room temperature at a cooling rate of 2℃ / min.

[0007] Furthermore, in step S2 of the present invention, the volume ratio of deionized water to organic solvent is 1:(1-2), preferably 1:1; the total metal ion concentration in the impregnation solution is 0.1-4 mol / L, preferably 0.5 mol / L.

[0008] Furthermore, in step S3 of the present invention, the LSCF-NF substrate and the M in the impregnation solution... 0.2 Ce 0.8 The mass ratio of O2 is (9-6):(1-4).

[0009] Furthermore, in step S3 of the present invention, the stirring speed is 200-300 r / min.

[0010] Furthermore, in step S4 of the present invention, the drying temperature is 100-220℃ and the drying time is 10-16h.

[0011] The present invention also includes the core-shell nanofiber structure electrode material obtained by the above preparation method, and the application of the core-shell nanofiber structure electrode material in solid oxide electrolytic cell electrodes.

[0012] Another technical problem this invention aims to solve is to provide a method for testing and evaluating electrode materials in solid oxide electrolytic cells. The main steps are as follows: (1) Preparation of half-cells using the tape casting method: The YSZ|NiO+YSZ green embryo was sintered in air at 1350℃ for 5h, and then Sm 0.2 Ce0.8 O 1.9 (SDC) barrier layer is screen-printed on the surface of YSZ and calcined at 1200℃ for 3h to obtain SDC|YSZ|NiO+YSZ half cell. Finally, the electrode paste prepared by the core-shell nanofiber powder obtained in this invention is screen-printed on the surface of SDC to obtain single cell. (2) The single cells were calcined at 830℃ for 2 hours, and the working area of ​​each cell was 0.5 cm². 2 Finally, Ag paste is printed onto the electrode surface and sintered at 800℃ for 1 hour. (3) Tie the battery to the test device and put it into the test furnace, and heat it to 800°C at a heating rate of 4°C / min; the test temperature range is 800-650°C, and a measurement is performed every 50°C. The single-cell test environment was as follows: water was heated to 81.4℃ and hydrogen was injected at a flow rate of 50 ml / min to obtain a water vapor content of 50% with H2 as the carrier, and then the electrolysis cell mode test was carried out.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The core-shell nanofiber oxygen electrode proposed in this invention consists of an LSCF fiber core and an M 0.2 Ce 0.8 It consists of an O2 nanoshell. The LSCF is responsible for providing the electrons needed for the oxygen reduction reaction, while M... 0.2 Ce 0.8 The introduction of O2 as an oxygen ion conductor can significantly improve the oxygen ion conductivity of the electrode, promote the surface exchange and transport of oxygen, and thus enhance the overall oxygen reduction catalytic activity. Furthermore, M... 0.2 Ce 0.8 O2 can also reduce the thermal expansion coefficient of the cathode and form a protective outer shell, effectively inhibiting CO2 surface adsorption poisoning and improving the structural stability and durability of the electrode. At the same time, the nanofiber structure has a high specific surface area and continuous conduction channels, which can increase the reaction interface and accelerate the surface exchange and bulk diffusion of oxygen, further enhancing the comprehensive electrochemical performance of the cathode under medium and low temperature conditions.

[0014] (2) The core-shell nanofiber structure electrode material prepared by this invention has a maximum current density of up to 2.2 A·cm at 750℃ and 1.5V. -2 Therefore, it can meet the requirements of air electrode materials for water electrolysis. Attached Figure Description

[0015] Figure 1 The XRD curves obtained in Examples 1 and 3 are shown below. Figure 2 TEM image of the core-shell nanofiber electrode prepared in Example 3; Figure 3To obtain the single-cell IV curve of Example 2; Figure 4 The IV curve of the single cell obtained in Example 3. Detailed Implementation

[0016] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that the following specific embodiments are merely exemplary, and any modifications or changes that do not depart from the technical solution design of the present invention should be within the scope of protection of the claims of the present invention. The present invention will be described in detail below with reference to embodiments.

[0017] Example 1: Core-shell nanofiber structured electrode materials were prepared according to the following steps: S1. Prepared using electrospinning technology (La) 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ (0<δ<1) Nanofibers (LSCF-NF).

[0018] S2. with 0.5 mol M 0.2 Ce 0.8 Taking O2 as an example, weigh 0.1 mol of samarium nitrate and 0.4 mol of cerium nitrate according to the stoichiometric ratio. Then dissolve the samarium nitrate and cerium nitrate in a 1 L mixture of deionized water and anhydrous ethanol to obtain a 0.5 mol / L impregnation solution. The volume ratio of deionized water to anhydrous ethanol is 1:1.

[0019] S3. Add LSCF-NF to the above impregnation solution, and LSCF-NF reacts with Sm in the impregnation solution. 0.2 Ce 0.8 A uniformly dispersed solution was obtained by stirring at 260 r / min for 3 h with an O2 mass ratio of 9:1. S4. The dispersion solution was dried at 150℃ for 11 hours. Then, the temperature was increased from 30℃ to 450℃ at a rate of 2.5℃ / min and held for 1 hour. Subsequently, the temperature was increased to 1100℃ at a rate of 3.5℃ / min and held for 2 hours. Finally, the temperature was reduced to room temperature at a rate of 2℃ / min to obtain the core-shell nanofiber electrode material. Figure 1 The image shows the XRD pattern of the SDC-coated LSCF-NF core-shell structure electrode powder obtained in Example 1.

[0020] YSZ|NiO+YSZ was prepared by tape casting. The YSZ|NiO+YSZ green embryo was sintered in air at 1350℃ for 5 h. Then, the SDC barrier layer was screen-printed onto the surface of YSZ and calcined at 1200℃ for 3 h to obtain the SDC|YSZ|NiO+YSZ half cell. Finally, the paste prepared by nanofiber electrode was screen-printed onto the surface of SDC to obtain the single cell.

[0021] The single cells were calcined at 830℃ for 2 hours, and the working area of ​​each cell was 0.5 cm². 2 Finally, Ag paste is printed onto the electrode surface and sintered at 800℃ for 1 hour.

[0022] The battery was attached to the testing device and placed in the testing furnace, heated to 800℃ at a heating rate of 4℃ / min. The testing temperature range was 800-650℃ (measurements were taken every 50℃). The testing environment for a single cell was as follows: water was heated to 81.4℃ and hydrogen was injected at a flow rate of 50ml / min to obtain a water vapor content of 50% with H2 as the carrier, and then tested in electrolysis cell mode.

[0023] Example 2: The difference between Example 2 and Example 1 is that in step S3, LSCF-NF reacts with Sm in the impregnation solution. 0.2 Ce 0.8 The mass ratio of O2 is 8:2. Figure 3 The image shows the IV curve of the core-shell nanofiber electrolyzer obtained in Example 2.

[0024] Example 3: The difference between Example 3 and Example 1 is that in step S3, LSCF-NF and Sm in the impregnation solution... 0.2 Ce 0.8 The mass ratio of O2 is 6:4. Figure 1 The XRD pattern of the core-shell nanofiber electrode powder obtained in Example 3 is shown. Figure 2 The TEM morphology of the core-shell nanofiber electrode prepared in Example 3 is shown. Figure 4 The IV curve of the single cell obtained in Example 3.

[0025] Example 4: The difference between Example 4 and Example 3 is that the impregnation solution in step S2 contains Pr 0.2 Ce 0.8 O2. Weigh 0.1 mol of praseodymium nitrate and 0.4 mol of cerium nitrate according to the stoichiometric ratio. Then dissolve the praseodymium nitrate and cerium nitrate in a 1 L mixture of deionized water and anhydrous ethanol to obtain a 0.5 mol / L impregnation solution. The volume ratio of deionized water to anhydrous ethanol is 1:1.

[0026] Example 5: The difference between Example 5 and Example 3 is that the impregnation solution in step S2 contains La. 0.2 Ce 0.8 O2. Weigh 0.1 mol of lanthanum nitrate and 0.4 mol of cerium nitrate according to the stoichiometric ratio. Then dissolve the lanthanum nitrate and cerium nitrate in a 1 L mixture of deionized water and anhydrous ethanol to obtain a 0.5 mol / L impregnation solution. The volume ratio of deionized water to anhydrous ethanol is 1:1.

[0027] Example 6: The difference between Example 6 and Example 3 is that the impregnation solution in step S2 contains Gd. 0.2 Ce 0.8 O2. Weigh 0.1 mol of gadolinium nitrate and 0.4 mol of cerium nitrate according to the stoichiometric ratio. Then dissolve the gadolinium nitrate and cerium nitrate in a 1 L mixture of deionized water and anhydrous ethanol to obtain a 0.5 mol / L impregnation solution. The volume ratio of deionized water to anhydrous ethanol is 1:1.

[0028] Example 7: The difference between Example 7 and Example 3 is that the impregnation solution in step S2 contains Nd. 0.2 Ce 0.8 O2. Weigh 0.1 mol of neodymium nitrate and 0.4 mol of cerium nitrate according to the stoichiometric ratio. Then dissolve the neodymium nitrate and cerium nitrate in a 1 L mixture of deionized water and anhydrous ethanol to obtain a 0.5 mol / L impregnation solution. The volume ratio of deionized water to anhydrous ethanol is 1:1.

[0029] Example 8: The difference between Example 8 and Example 4 is that the sintering temperature in step S4 is 900°C.

[0030] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the LSCF used in step S1 is commercially available LSCF nanoparticles produced by Wuxi Kaitianxing Electro-optical Materials Co., Ltd.

[0031] Comparative Example 2: Prepare LSCF composite Sm according to the following steps 0.2 Ce 0.8 O2 (SDC) material: (1) LSCF and SDC produced by Wuxi Kaitianxing Electro-optical Materials Co., Ltd. were mixed in a mass ratio of 6:4. After mixing, the slurry was coated onto the surface of SDC in Example 1, and then sintered at 1100°C for 2 hours to obtain a full cell.

[0032] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the impregnation solution in step S3 is CeO2. 0.5 mol of cerium nitrate was weighed according to the stoichiometric ratio, and then dissolved in 1 L of a mixture of deionized water and anhydrous ethanol to obtain a 0.5 mol / L impregnation solution. The volume ratio of deionized water to anhydrous ethanol was 1:1.

[0033] The electrochemical performance results for Examples 1-8 and Comparative Examples 1-3 are shown in Table 1: Table 1 ; As can be seen from Table 1, the single-cell polarization resistance of Examples 1-8 of the present invention is smaller than that of the comparative examples, and the corresponding current density for hydrogen production through water electrolysis is also larger, indicating that the core-shell nanofiber electrode materials obtained in the examples have higher catalytic activity. It can also be seen that the catalytic performance of the LSCF-NF core-shell structure electrode coated with pure cerium nitrate in Comparative Example 3 is worse than that of the SDC-coated LSCF-NF electrode in Comparative Example 1, while the PDC-coated LSCF-NF in Example 4 is better than that in Example 1. This is mainly due to the different ionic conductivity of the coating material in the outer shell, indicating that the ionic conductivity of the material in the shell has a significant impact on the performance of the core-shell nanofiber electrode.

[0034] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a core-shell nanofiber structured electrode material, characterized in that, The preparation method includes the following steps: S1. preparing a (La 0.6 Sr 0.4 ) 0.95 Co 0.2 Fe 0.8 O 3-δ nanofiber (LSCF-NF) substrate, wherein 0 < δ < 1; S2. According to M 0.2 Ce 0.8 Weigh nitric acid M and cerium nitrate in a stoichiometric ratio to O2, wherein M is selected from any one of Sm, Pr, La, Ga, Nd, or Ce. Then mix nitric acid M, cerium nitrate, deionized water, and an organic solvent to obtain an impregnation solution; the organic solvent is any one of anhydrous ethanol, propanol, or isopropanol. S3. Add the obtained LSCF-NF substrate to the impregnation solution and stir for 2-3 hours to obtain a uniform dispersion solution; S4. The dispersion solution is dried and sintered to obtain the core-shell nanofiber electrode material; The specific sintering process is as follows: first, the temperature is increased from 30℃ to 400-600℃ at a heating rate of 1-3.5℃ / min, and held for 1-3 hours; then, the temperature is increased to 750-1100℃ at a heating rate of 3-7℃ / min, and held for 1-3 hours; finally, the temperature is reduced to room temperature at a cooling rate of 2℃ / min.

2. The preparation method according to claim 1, characterized in that, The organic solvent in S2 is anhydrous ethanol.

3. The preparation method according to claim 1, characterized in that, The volume ratio of deionized water to organic solvent in S2 is 1:(1-2); the total metal ion concentration in the impregnation solution is 0.1-4 mol / L.

4. The preparation method according to claim 3, characterized in that, The volume ratio of deionized water to organic solvent in S2 is 1:1; the total metal ion concentration in the impregnation solution is 0.5 mol / L.

5. The preparation method according to claim 1, characterized in that, The LSCF-NF substrate in S3 and the M in the impregnation solution 0.2 Ce 0.8 The mass ratio of O2 is (9-6):(1-4).

6. The preparation method according to claim 1, characterized in that, The stirring speed in S3 is 200-300 r / min.

7. The preparation method according to claim 1, characterized in that, The drying temperature in S4 is 100-220℃, and the drying time is 10-16h.

8. The core-shell nanofiber structure electrode material obtained by the preparation method according to any one of claims 1-7.

9. Application of the core-shell nanofiber structure electrode material as described in claim 8 in solid oxide electrolytic cell electrodes.

10. A method for testing and evaluating electrode materials for solid oxide electrolytic cells, characterized in that, The steps of the evaluation method are as follows: (1) Preparation of half-cells using the tape casting method: The YSZ|NiO+YSZ green embryo was sintered in air at 1350℃ for 5h, and then Sm 0.2 Ce 0.8 O 1.9 (SDC) barrier layer is screen-printed on the surface of YSZ and calcined at 1200℃ for 3h to obtain SDC|YSZ|NiO+YSZ half cell. Finally, the electrode paste prepared by the core-shell nanofiber powder obtained in this invention is screen-printed on the surface of SDC to obtain single cell. (2) The single cells were calcined at 830℃ for 2 hours, and the working area of ​​each cell was 0.5 cm². 2 Finally, Ag paste is printed onto the electrode surface and sintered at 800℃ for 1 hour. (3) Tie the battery to the test device and put it into the test furnace, and heat it to 800°C at a heating rate of 4°C / min; the test temperature range is 800-650°C, and a measurement is performed every 50°C. The single-cell test environment was as follows: water was heated to 81.4℃ and hydrogen was injected at a flow rate of 50 ml / min to obtain a water vapor content of 50% with H2 as the carrier, and then the electrolysis cell mode test was carried out.

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