A LaCo 0.6 Ni 0.4 Preparation method of O3 fiber membrane electrode material and its application in solid oxide fuel cells

Abstract

The present invention discloses a LaCo 0.6 Ni 0.4 Preparation method of O3 fiber membrane electrode material and its application in solid oxide fuel cell. In the present invention, SOFC oxygen electrode material is LCN ceramic fiber membrane, and the chemical formula of the fiber membrane electrode material is: LaCo 0.6 Ni 0.4 O3 is prepared by electrospinning. The LCN fiber membrane in this invention is self-assembled onto the YSZ electrolyte surface through current polarization induction. Without undergoing a high-temperature sintering process, the fiber membrane electrode can maintain good porosity and high specific surface area. SOFC based on this fiber membrane oxygen electrode achieves excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells and ceramic materials, and in particular to a LaCo 0.6 Ni 0.4 Preparation method of O3 fiber membrane electrode material and its application in solid oxide fuel cells. Background Art

[0002] Solid oxide fuel cells (SOFCs) have many advantages, such as high efficiency, high fuel flexibility, low pollution and high reliability. First, SOFC has the characteristics of high efficiency and can directly convert fuel into electrical energy. Its electrical energy conversion efficiency is usually above 50%. Secondly, SOFC has strong adaptability to fuels and can use a variety of fuels such as hydrogen, natural gas, methane, etc., so it has a wide range of applicability and can utilize abundant different fuel resources. In addition, SOFC has extremely low emissions, and the emissions of pollutants such as nitrogen oxides (NOx) and sulfur oxides (SOx) are almost negligible, meeting strict emission standards and environmental protection requirements. Despite this, the industrialization of SOFC still faces challenges. The reason is that its high-temperature operating characteristics lead to its poor stability and short service life. Therefore, it is urgent to reduce the operating temperature of SOFC to the medium and low temperature range.

[0003] However, as the operating temperature of SOFC decreases to the medium and low temperature range, its electrochemical performance will decrease, especially the polarization loss of the oxygen electrode, which accounts for the vast majority of the polarization loss of the entire battery. This is because the oxygen electrode materials currently used are mostly perovskite oxides, which have poor electrocatalytic activity at medium and low temperatures. At present, some work has been done on the composition design and structural regulation of perovskite oxides, but the medium and low temperature performance of SOFC is still unsatisfactory. It is well known that the morphology of the catalyst has a significant impact on the catalytic performance. Nanofibrous structured oxides have a large specific surface area and rich porosity and have been tried for use in SOFC oxygen electrodes. However, due to the SOFC preparation process such as grinding and slurry preparation, high-temperature calcination, the structure of the nanofibrous structured oxygen electrode is also completely destroyed, and the performance is not much different from that of traditional particle electrodes. Therefore, there is an urgent need to find a method for in-situ utilization of nanofibrous oxygen electrodes. Summary of the Invention

[0004] One of the objects of the present invention is to provide a LaCo 0.6 Ni 0.4 Preparation method of O3 fiber membrane electrode material.

[0005] The second object of the present invention is to provide LaCo obtained by the above preparation method. 0.6 Ni 0.4 Application of O3 fiber membrane electrode materials in solid oxide fuel cells.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a LaCo 0.6 Ni 0.4 The preparation method of O3 (LCN) fiber membrane electrode material adopts electrospinning method, and the specific steps include:

[0008] (1) La(NO3)3·6H2O, Co(CH3COO)2·4H2O, and Ni(CH3COO)2·4H2O were weighed in a molar ratio of 5:3:2, dissolved in N,N-dimethylformamide (DMF), and then polyvinylpyrrolidone was added and stirred at 600 rpm for 12 h to obtain a spinning solution;

[0009] (2) transferring the spinning solution obtained in step (1) into a syringe, and obtaining a precursor electrode by electrospinning technology;

[0010] (3) The precursor electrode obtained in step (2) was vacuum dried and then calcined at 650° C. for 3 h in an air atmosphere to obtain an LCN fiber membrane electrode.

[0011] Preferably, the process conditions of the electrospinning in step (2) are: voltage 20 kV, feed rate 0.6 mL / h, and the distance between the collector and the needle tip is 14-16 cm.

[0012] Preferably, the heating rate of the calcination in step (3) is 1°C / min.

[0013] In the second aspect, the present invention also provides LaCo prepared by the above preparation method 0.6 Ni 0.4 Application of O3 fiber membrane electrode materials in solid oxide fuel cells.

[0014] The preparation process of the solid oxide fuel cell comprises the following steps:

[0015] S1, Er 0.4 Bi 1.6 Preparation of O3(ESB) buffer layer;

[0016] ESB powder, polyvinyl butyral (PVB) solvent, and ethanol were weighed according to the mass ratio and then ball-milled in a ball mill. After obtaining the ESB buffer layer slurry, the slurry was dripped onto the surface of the YSZ electrolyte.

[0017] S2, LaCo 0.6 Ni 0.4 In situ polarization self-assembly of O3 fiber membrane electrodes;

[0018] Cut the LaCo into a circle0.6 Ni 0.4 The O3 fiber membrane electrode was adhered to the surface of the ESB buffer layer and placed in an oven to dry. Then, Ag paste and Ag wire were coated on the electrode surface to assemble into a Ni-YSZ / YSZ / ESB / LCN full battery, and polarization tests were carried out in a test furnace.

[0019] Preferably, in step S1, Er 0.4 Bi 1.6 The mass ratio of O3 powder, polyvinyl butyral solvent and ethanol is 2:1:20.

[0020] Preferably, the ball milling time in step S1 is 24 hours, and the ball milling speed is 360 rpm.

[0021] Preferably, the drop-coating volume in step S1 is 10 μL.

[0022] Preferably, the polarization test temperature in step S2 is 550-700°C, and the polarization current is 0.1-1A / cm 2 , polarization time is 1-10h.

[0023] More preferably, the polarization test temperature in step S2 is 650°C and the polarization current is 0.5A / cm 2 , the polarization time is 5h.

[0024] The working principle of the solid oxide fuel cell prepared by the LCN fiber membrane electrode material of the present invention is as follows: the reaction first occurs on the surface of the oxygen electrode, oxygen (O2) in the air is adsorbed on the surface of the oxygen electrode, dissociated into oxygen atoms, and then combined with external electrons to generate oxygen ions (O 2- ), O 2- Driven by chemical potential, oxygen vacancies are used to transition through the dense electrolyte layer to the hydrogen electrode side, where they react with the fuel gas to generate water under the catalytic action of the hydrogen electrode. This process releases electrons, and the metal current collector provides a transmission channel for the electrons, forming an electric current in the external circuit.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The LCN fiber membrane electrode prepared by the present invention has a large specific surface area (56m 2 g -1 ), can provide abundant catalytic active sites, and the porous structure formed by the interweaving of fiber morphology is conducive to the mass transfer and diffusion of gas; and it does not go through the traditional oxygen electrode preparation process such as grinding and slurry configuration, high-temperature calcination, etc., so the nanofiber structure of the oxygen electrode can be well retained; by regulating the preparation process of LCN fiber membrane electrode, such as controlling the spinning time and the number of stacking layers, the membrane thickness can be controlled to meet the subsequent application requirements of solid oxide fuel cells.

[0027] 2. The present invention adopts the current polarization method to quickly form a good electrode-electrolyte interface, retain the morphology of the LCN fiber membrane electrode to a greater extent, and obtain better electrocatalytic activity at medium and low temperatures.

[0028] 3. The LCN fiber membrane electrode material prepared by the present invention can still maintain good fiber micromorphology under medium and low temperature test conditions. The addition of the ESB buffer layer can better adhere to the LCN fiber membrane electrode. The current polarization enhances the bonding strength of the electrode-electrolyte interface, further reduces the interface resistance, and achieves higher power output.

[0029] 4. The solid oxide fuel cell based on LCN fiber membrane electrode in the present invention has a maximum output power of 0.8W / cm at an operating temperature of 700°C. 2 , ohmic impedance is 0.176Ωcm 2 , polarization impedance is 0.299Ωcm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the SEM image of the LCN fiber membrane electrode prepared by electrospinning;

[0031] Figure 2 is the BET curve of the LCN fiber membrane electrode prepared by electrospinning;

[0032] Figure 3 This is the current polarization curve of the LCN fiber membrane electrode.

[0033] Figure 4 Electrochemical impedance spectroscopy of the LCN fiber membrane electrode before and after current polarization.

[0034] Figure 5 The impedance diagram of SOFC prepared by self-assembly of LCN fiber membrane electrode under humid hydrogen;

[0035] Figure 6 IVP curve of SOFC prepared by self-assembly of LCN fiber membrane electrode under humidified hydrogen. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Example 1

[0038] The LCN fiber membrane electrode material was prepared by electrospinning. The specific preparation process is as follows: 4 mmol of metal salts of La(NO3)3·6H2O, Co(CH3COO)2·4H2O and Ni(CH3COO)2·4H2O were weighed and dissolved in 10 mL of N, N-dimethylformamide (DMF) according to a molar ratio of 5:3:2. 1.3 g of polyvinylpyrrolidone (PVP) was then added and stirred vigorously for 12 hours. The resulting solution was then transferred to a 20 mL plastic syringe equipped with a No. 22 stainless steel nozzle. The static spinning parameters used a high voltage of 20 kV and a 0.6 mL h -1 The distance between the collector and the needle tip was 14-16 cm. The obtained precursor was dried at 80 °C under vacuum and finally dried at 1 °C min under air. -1 The temperature was raised to 650℃ and calcined in air for 3h to obtain LCN fiber membrane electrode. Figure 1 As shown in the figure, the LCN electrode has a clear fiber structure and is composed of layers of fibers stacked together, with a large specific surface area. Figure 2 As shown in the BET curve, its specific surface area is as high as 56m 2 g -1 , far larger than conventional powder particle electrodes. This unique microstructure forms a membrane-like morphology that, after appropriate tailoring, can be used directly as an electrode. Furthermore, the high porosity of LCM membrane electrodes also facilitates gas diffusion and transport.

[0039] Example 2

[0040] The current-polarized self-assembly of LCN fiber membrane electrodes is fabricated as follows: First, an ESB slurry is prepared by weighing 1g of ESB powder, 0.5g of PVB solvent, and 10g of ethanol in the appropriate mass ratio. The mixture is then ball-milled in a jar at 360 rpm for 24 hours. After obtaining the ESB buffer layer slurry, 10μL of the slurry is pipetted onto the surface of a YSZ electrolyte support. A cut circular LCN membrane electrode is adhered to the ESB buffer layer surface. A Pt electrode is applied to the other side of the YSZ electrolyte and dried in an oven. The LCN fiber membrane electrode is then coated with Ag slurry and Ag wire. The membrane is then mounted in a custom-made test apparatus, heated to the test temperature, and subjected to current polarization testing.

[0041] After the test furnace temperature was raised to the SOFC operating temperature, 50 mL / min of air was introduced into the LCN fiber membrane electrode. Then, different current densities were applied for discharge polarization. The polarization performance under different conditions was studied, including different temperatures (550-700 ° C), different current densities (0.1-1 A / cm 2) and different polarization times (1-10h), it was found that at 650℃, the polarization current density was 0.5A / cm 2 , the best effect is obtained when the polarization time is 5h, and the battery performance is optimal. Figure 3 The battery was demonstrated at 650°C, 0.25A / cm 2 From the changes in polarization test voltage, we can see that with the increase of time, the polarization voltage of the battery is gradually decreasing, which proves that the performance of the LCN fiber membrane electrode is gradually improving. Studies have found that if the temperature is too low, the adhesion between the LCN membrane and the electrolyte is too poor, and if the temperature is too high, the fiber morphology of the LCN membrane electrode will be destroyed. Similarly, the current density and polarization time have the same effect on the polarization effect of the LCN fiber membrane electrode. Therefore, the preferred polarization test conditions are 650℃, 0.5A / cm 2 , polarized for 5h. The electrochemical impedance spectroscopy was tested before and after the polarization current was applied, as shown in Figure 4 As shown in Figure 3, it can be seen that after the polarization current is applied, both the ohmic impedance and polarization impedance decrease, indicating that the current polarization promotes the contact between the LCN fiber membrane electrode and the electrolyte interface.

[0042] Example 3

[0043] The performance of solid oxide fuel cells prepared by self-assembly of LCN fiber membrane electrodes was tested. The specific preparation process is as follows: First, ESB was prepared into a slurry: 1g of ESB powder, 0.5g of PVB solvent, and 10g of ethanol were weighed and ball-milled in a jar at 360 rpm for 24 hours. After obtaining the ESB buffer layer slurry, 10μL of the slurry was pipetted and drop-coated on the YSZ electrolyte surface. A circular LCN fiber membrane electrode was adhered to the ESB buffer layer surface and dried in an oven. Subsequently, Ag slurry and Ag wire were coated on the electrode surface to form a Ni-YSZ / YSZ / ESB / LCN full cell. This cell was sealed in a homemade test apparatus, heated to the test temperature, and electrochemical performance testing began.

[0044] 50 mL / min hydrogen was passed into the hydrogen electrode side of the prepared solid oxide fuel cell as the fuel gas, and static air was used as the oxidant. The impedance and maximum power density were recorded at 700°C, 650°C, 600°C and 550°C, respectively. The results are shown in Figure 2. Figure 5 、 Figure 6 As shown. Figure 5 It can be seen that the ohmic impedance of SOFC with LCN fiber membrane electrode at 700℃, 650℃, 600℃ and 550℃ are 0.176, 0.246, 0.471 and 0.953Ωcm respectively. 2 , the polarization impedances are 0.299, 0.503, 1.236, and 2.667Ωcm respectively 2 ,Depend on Figure 6It can be seen that the maximum power density at 700℃, 650℃, 600℃ and 550℃ can reach 802, 446, 205 and 90mW / cm 2 .

[0045] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A LaCo 0.6 Ni 0.4 The preparation method of O3 fiber membrane electrode material is characterized in that: The electrospinning method is used for preparation, and the specific steps include: (1) La(NO3)3·6H2O, Co(CH3COO)2·4H2O, and Ni(CH3COO)2·4H2O were weighed in a molar ratio of 5:3:2, dissolved in N,N-dimethylformamide, and then polyvinylpyrrolidone was added and stirred at 600 rpm for 12 h to obtain a spinning solution; (2) transferring the spinning solution obtained in step (1) into a syringe, and obtaining a precursor electrode by electrospinning technology; (3) The precursor electrode obtained in step (2) was vacuum dried and then calcined at 650° C. for 3 h in an air atmosphere to obtain an LCN fiber membrane electrode.

2. A LaCo according to claim 1 0.6 Ni 0.4 The preparation method of O3 fiber membrane electrode material is characterized in that: The process conditions of the electrospinning in step (2) are: voltage 20 kV, feed rate 0.6 mL / h, and the distance between the collector and the needle tip is 14-16 cm.

3. A LaCo according to claim 1 0.6 Ni 0.4 The preparation method of O3 fiber membrane electrode material is characterized in that: The heating rate of the calcination in step (3) is 1°C / min.

4. LaCo obtained by the preparation method according to any one of claims 1 to 3 0.6 Ni 0.4 Application of O3 fiber membrane electrode materials in solid oxide fuel cells.

5. The use according to claim 4, characterized in that Preparation process of the solid oxide fuel cell Includes the following steps: S1, Er 0.4 Bi 1.6 Preparation of O3 buffer layer; Weigh Er according to mass ratio 0.4 Bi 1.6 O3 powder, polyvinyl butyral solvent and ethanol are then placed in a ball mill and milled. After obtaining the ESB buffer layer slurry, the slurry is dripped onto the surface of the YSZ electrolyte. S2, LaCo 0.6 Ni 0.4 In situ polarization self-assembly of O3 fiber membrane electrodes; Cut the LaCo into a circle 0.6 Ni 0.4 The O3 fiber membrane electrode was adhered to the surface of the ESB buffer layer and placed in an oven to dry. Then, Ag paste and Ag wire were coated on the electrode surface to assemble into a Ni-YSZ / YSZ / ESB / LCN full battery, and polarization tests were carried out in a test furnace.

6. The use according to claim 5, characterized in that In step S1, Er 0.4 Bi 1.6 The mass ratio of O3 powder, polyvinyl butyral solvent and ethanol is 2:1:

20.

7. The use according to claim 5, characterized in that The ball milling time in S1 was 24 h, and the ball milling speed was 360 rpm.

8. The use according to claim 5, characterized in that The drop-coating volume in step S1 was 10 μL.

9. The use according to claim 5, characterized in that The polarization test temperature in step S2 is 550-700°C, and the polarization current is 0.1-1A / cm 2 , polarization time is 1-10h.

10. The use according to claim 9, characterized in that The polarization test temperature in step S2 is 650°C and the polarization current is 0.5A / cm 2 , the polarization time is 5h.

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