CN109468661B - A kind of composite oxygen electrode for solid oxide electrolysis cell and preparation method thereof - Google Patents

Abstract

The invention discloses a composite oxygen electrode for a solid oxide electrolytic cell and a preparation method thereof, wherein the composite oxygen electrode comprises an electrolyte layer, a substrate layer and an active coating layer; the substrate layer is made of BSCF-SDC composite porous material and covers the electrolyte layer; the active coating layer is coated on the outer surface and the inner surface of the pores of the BSCF-SDC composite porous material. The invention takes BSCF-SDC composite porous material as electrode main material, and forms good conductivity and CO on the surface and in pores of the composite porous material₂Ln of tolerance₂NiO₄The active coating layer obviously improves the electrochemical performance and long-term stability of the composite oxygen electrode material.

Description

A kind of composite oxygen electrode for solid oxide electrolysis cell and preparation method thereof

technical field

The invention belongs to the technical field of solid oxide electrolytic cells, and particularly relates to a composite oxygen electrode for solid oxide electrolytic cells and a preparation method thereof.

Background technique

At present, in my country's energy structure, fossil fuels such as coal still occupy the main part. The long-term use of fossil fuels has led to a sharp increase in the content of pollutants such as carbon dioxide, sulfur dioxide and nitrogen oxides in the atmosphere, resulting in frequent occurrence of smog and other extreme weather, and causing huge damage to my country's ecological environment.

Solid oxide electrolysis cell (SOEC) is an electrochemical device that can convert electrical energy into chemical energy, and its basic principle is the reverse process of solid oxide fuel cell (SOFC). Through the operation of SOEC, water can be converted into hydrogen, and carbon dioxide and water can also be co-electrolyzed. The products are mainly hydrogen and carbon monoxide, that is, water gas, which can be used as production fuel. In the co-electrolysis process, carbon dioxide can be recycled without increasing carbon dioxide emissions during the entire energy cycle. Therefore, compared with traditional coal, oil and other production methods, carbon dioxide co-electrolysis can effectively reduce carbon dioxide emissions. At the same time, the SOEC electrolysis process is carried out at high temperature, which has higher electrolysis efficiency than other low-temperature electrolysis processes, and high temperature can reduce the consumption of electric energy in electrolysis. Therefore, SOEC high-temperature electrolysis has great application prospects in energy saving and emission reduction.

Large amounts of electricity can be produced by means of water power, wind power, etc., but electricity production is greatly affected by climate and has seasonality. At the same time, residential electricity consumption is also phased. Residential electricity demand varies greatly in different time periods, which all affect the power grid. Stable load has a huge impact. How to use the excess power during peak power generation and low power consumption is of great significance to the full utilization of resources. Using excess electrical energy for SOEC electrolysis, converting electrical energy into chemical energy for temporary storage, and using SOFC to convert chemical energy into electrical energy during peak electricity consumption is a beneficial attempt to level the peak of intermittent power production. By combining SOEC with excess electric energy, various chemical raw materials can be produced through different electrolysis processes, which are widely used and are expected to achieve full utilization of resources.

The double-doped perovskite material Ba _1-x Sr _x Co _0.8 Fe _0.2 O _3-δ (BSCF) has mixed ionic conductivity and good electrochemical catalytic activity at medium temperature, and is expected to be the next-generation SOEC oxygen electrode material. However, due to the presence of alkaline earth metal elements, BSCF has high reactivity with _CO2 in air under the oxygen electrode environment, poor performance stability, and low electrode conductivity, resulting in a significant decrease in the performance of BSCF electrodes after long-term operation. Therefore, it is necessary to improve the long-term stability of BSCF electrodes.

Metal oxides with tetragonal perovskite intergrowth structure have a layered perovskite-like structure (typical structure K ₂ NiF ₄ ), in which Ln ₂ NiO ₄ (Ln is La, Pr, Nd) has a good oxygen surface at moderate temperatures exchange coefficient, while having higher electrical conductivity and better _CO tolerance than BSCF. However, due to its layered structure with anisotropic ion transport properties, Ln ₂ NiO ₄ has lower electrode activity when the thickness is larger, and is not suitable as a host material for oxygen electrodes.

SUMMARY OF THE INVENTION

In order to solve the defects in the prior art, the purpose of the present invention is to provide a composite oxygen electrode for a solid oxide electrolytic cell, which uses a BSCF-SDC composite porous material as the main electrode material, and then impregnates the surface of the composite porous material in situ. _{A Ln2NiO4} active coating layer with good electrical conductivity and _CO2 tolerance was formed within the pores and pores, which significantly improved the electrochemical performance and long-term stability of the composite oxygen electrode material.

It should be noted that, in the present invention, SOEC is a solid oxide electrolytic cell, SOFC is a solid oxide fuel cell, and BSCF is barium-doped cobalt strontium ferrite (Ba _1-x Sr _x Co _0.8 Fe _0.2 O _3-δ ) , Ln ₂ NiO ₄ is a nickel-based layered material (Ln is La, Pr or Nd), SDC is samarium-doped cerium oxide, PMMA is polymethyl methacrylate, and PVP is polyethylene glycol.

In order to achieve the above technical purpose, the present invention provides a composite oxygen electrode for a solid oxide electrolytic cell, comprising an electrolyte layer, a base layer and an active coating layer;

The base layer is a BSCF-SDC composite porous material, which is covered on the electrolyte layer;

The active coating layer is coated on the outer surface and the inner surface of the pores of the BSCF-SDC composite porous material.

Preferably, the material of the electrolyte layer is SDC, and the thickness is 500-1000 μm.

Preferably, the molar ratio of BSCF to SDC in the BSCF-SDC composite porous material is 1:4 to 4:1, more preferably 3:2 to 4:1, and most preferably 7:3.

Preferably, the material of the active coating layer is Ln ₂ NiO ₄ material, where Ln is La, Pr or Nd, and the coating amount is 2-20wt% of the composite oxygen electrode.

The invention also provides a preparation method of the composite oxygen electrode for the solid oxide electrolytic cell. First, a layer of BSCF-SDC composite porous material base layer is printed on the electrolyte layer of the electrolytic cell sheet, and then an immersion method is used to make the active package The coating layer is deposited in-situ on the outer surface and the inner surface of the pores of the BSCF-SDC composite porous material to obtain a composite oxygen electrode.

Preferably, the electrolyte layer and SDC are first prepared by the sol-gel method, and the BSCF is prepared by the glycine-nitrate method; then the mixed paste of BSCF and SDC is printed on the electrolyte layer of the electrolytic cell by the screen printing method, and after calcination The base layer of BSCF-SDC composite porous material is obtained; finally, the active coating layer is uniformly deposited on the outer surface and the inner surface of the pores of the BSCF-SDC composite porous material by dipping method, and then sintered at high temperature to obtain a composite oxygen electrode.

More preferably, the preparation method specifically comprises the following steps:

Step 1: The material of the electrolyte layer is SDC, Ce(NO ₃ ) ₂ ·6H ₂ O, Sm(NO ₃ ) ₃ ·6H ₂ O are used as raw materials, and citric acid monohydrate is used as complexing agent and sintering aid , prepare the SDC precursor by the sol-gel method, and finally calcine the SDC precursor at a temperature of 600-800 ° C for 1-4 hours to obtain the SDC powder;

Step 2: Using Ba(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) ₂ ·6H ₂ O, Fe(NO ₃ ) ₃ ·9H ₂ O as raw materials, and using glycine as complexing agent and auxiliary A sintering agent is used to prepare the BSCF precursor by the glycine-nitrate method, and the BSCF precursor is calcined for 1 to 4 hours at a temperature of 800 to 1100 ° C to obtain the BSCF powder;

Step 3: mix ethyl cellulose and terpineol to prepare an organic binder; then mix and grind SDC powder, BSCF powder, organic binder and pore-forming agent to obtain a mixed slurry, the The amount of porosity agent is 2-12wt% of the total amount of SDC powder and BSCF powder; the mixed paste is printed on the electrolyte layer of the electrolytic cell sheet by screen printing method, and then calcined at a temperature of 900-1200 ° C for 1 ~4 hours, the BSCF-SDC composite porous material base layer is obtained;

Step 4: Prepare a nitrate solution according to the stoichiometric ratio of each element in the chemical formula Ln ₂ NiO ₄ , and then add glycine and PVP to fully mix to obtain a Ln ₂ NiO ₄ precursor solution; use the dipping method to deposit the Ln ₂ NiO ₄ precursor solution on the BSCF- The outer surface and the inner surface of the pores of the SDC composite porous material; and then sintered at a temperature of 800 to 1000° C. for 1 to 4 hours to obtain a composite oxygen electrode.

Preferably, the pore-forming agent is at least one of PMMA, starch, and activated carbon, and the added amount of the pore-forming agent is 2-12 wt % of the total amount of SDC powder and BSCF powder.

The present invention also provides the solid oxide electrolytic cell of the above-mentioned composite oxygen electrode.

The composite oxygen electrode for the solid oxide electrolytic cell prepared by the invention uses the composite porous material BSCF-SDC as the base layer and the nickel-based material Ln ₂ NiO ₄ as the surface active layer, which is a solid oxide with excellent performance. Composite oxygen electrode for electrolysis cells.

The beneficial effects of the present invention are:

BSCF material as the main electrode material has good bulk oxygen anion migration ability, but the surface will react with CO ₂ in the air, and the electronic conductivity of the material is low; while the surface oxygen migration ability of Ln ₂ NiO ₄ is strong, and electronic conductivity It has better properties than BSCF materials and has good stability in air, but due to its anisotropic ionic conductivity, it is not suitable as an electrode host material with large thickness. By adjusting the electrode structure, the latter is used as the surface active coating layer and the former is used as the base layer to form a composite cathode, which can combine the advantages of the two and significantly improve the electrochemical performance of the BSCF oxygen electrode in solid oxide fuel electrolysis cells. long-term stability.

The present invention mainly adjusts the overall structure of the electrode from two aspects. One is to form a composite oxygen electrode material by mixing BSCF and Sm _0.2 Ce _0.8 O _1.9 (SDC) material, which can change the three-phase interface of the electrode from the interface of the electrode and the electrolyte to the main body of the electrode. Extend, increase the electrochemical reaction active area, which is beneficial to improve the electrochemical catalytic activity of the electrode; the second is to adjust the internal surface structure of the electrode, and modify the internal surface of the porous oxygen electrode by in-situ dipping method, and form a more uniform in-situ formation on the electrode surface. The coating layer formed can combine the advantages of the impregnating material and the electrode material to alleviate the problem of the performance degradation of the BSCF electrode. At the same time, the internal surface of the modified electrode has rich microstructures, and the internal area of the electrode can be expanded laterally, increasing the internal area of the electrode. surface area and improve the electrocatalytic activity of the electrode.

Description of drawings

1 is a schematic cross-sectional view of a half-cell;

Figure 2 is a partial schematic diagram of the interface between the electrode and the electrolyte;

1 is the BSCF-SDC porous oxygen electrode layer, 2 is the SDC electrolyte support layer, 3 is the BSCF material, 4 is the SDC material, and 5 is the LNO active coating layer;

Figure 3 is a comparison chart of the AC impedance of BSCF-SDC composite electrodes with different molar ratios at 700 °C;

Figure 4 is a comparison chart of the AC impedance of BSCF electrode, BSCF-SDC (molar ratio 7:3) electrode, and LNO/BSCF-SDC (molar ratio 7:3) electrode prepared by impregnation method and impregnation method at 700 °C;

In Figure 5, a and b are the cross-section of the electrode after immersion and the partial scanning electron microscope image, respectively.

Detailed ways

To further illustrate the embodiments of the present invention, a novel solid oxide electrolytic cell composite oxygen electrode with a core-shell-like structure and a preparation method thereof are described below with examples.

Example 1

This example is Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ -SDC porous complex electrode with different molar ratios;

The specific steps to prepare the novel BSCF-SDC porous composite oxygen electrode:

Step 1: Preparation of Sm _0.2 Ce _0.8 O _1.9 (SDC) electrolyte material powder _by sol-gel _method Ce(NO ₃ ) _{2 ·6H 2 O} , Sm(NO ₃ ) _{3.6H 2 O} solution, using citric acid monohydrate as a complexing agent and a sintering aid, the amount of citric acid monohydrate added is 1.5 times the molar amount of the total metal ions, and the mixed solution is heated in a water bath at 70°C to The gel is in the form of a gel, and the gel is continuously heated in a universal furnace to burn to form an SDC precursor powder, and finally calcined at a temperature of 800 ° C for 2 hours to obtain the SDC target powder;

Step 2: Preparation of Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ (BSCF) material powder by glycine-nitrate method (GNP)

Ba(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) ₂ .6H ₂ O, Fe(NO ₃ ) ₃ .9H ₂ O solutions were prepared according to Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ , using glycine as a complexing agent and a sintering aid, wherein the ratio of glycine to the total number of moles of metal ions is 1.5:1, and the mixed solution is heated to combustion in a universal furnace to prepare BSCF precursor powder, at a temperature of 900 ℃. calcined for 2 hours to obtain the BSCF target powder;

Step 3: Preparation of electrolyte substrate and printing of BSCF-SDC porous complex oxygen electrode layer

The SDC target powder obtained in step 1 is used to prepare an electrolyte substrate sheet with a diameter of about 2 cm by a tableting method.

Use the BSCF powder prepared in step 2 to prepare BSCF electrode slurry:

Mix ethyl cellulose and terpineol to prepare an organic binder, in which ethyl cellulose accounts for 1wt% and terpineol accounts for 99wt%; then SDC powder, BSCF powder and PMMA are mixed and ground for 1 hours, the molar ratios of SDC and BSCF powders are 7:3, 5:5 and 3:7, and the mass of PMMA accounts for 2% of the total mass of the powder; finally, the mass ratio of SDC, BSCF and PMMA mixed powder is 1 Add organic binder in the ratio of :10 (binder: mixed powder), mix and grind for 1 hour to obtain mixed slurry;

The mixed paste was printed on the SDC substrate by screen printing, dried at 50 °C for 30 min, and then calcined at 1100 °C for 3 hours to obtain BSCF- For SDC/SDC half cells, the thickness of the electrode layer is 40 μm and the area is about 0.25 cm ² .

Example 2

In this example, La ₂ NiO ₄ (LNO) was used as the active material, and the Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ -SDC porous multiphase electrode with a molar ratio of 7:3 was modified by the solution in-situ dipping method. Finally, a new type of LNO/BSCF-SDC composite oxygen electrode and its preparation steps are obtained.

The specific steps to prepare the novel LNO/BSCF-SDC porous composite oxygen electrode:

Step 1: Preparation of Sm _0.2 Ce _0.8 O _1.9 (SDC) electrolyte material powder _by sol-gel _method Ce(NO ₃ ) _{2 ·6H 2 O} , Sm(NO ₃ ) _{3.6H 2 O} solution, using citric acid monohydrate as a complexing agent and a sintering aid, the amount of citric acid monohydrate added is 1.5 times the molar amount of the total metal ions, and the mixed solution is heated in a water bath at 70°C to The gel is in the form of a gel, and the gel is continuously heated in a universal furnace to burn to form an SDC precursor powder, and finally calcined at a temperature of 800 ° C for 2 hours to obtain the SDC target powder;

Step 2: Preparation of Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ (BSCF) material powder by glycine-nitrate method (GNP)

Ba(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) ₂ .6H ₂ O, Fe(NO ₃ ) ₃ .9H ₂ O solutions were prepared according to Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ , using glycine as a complexing agent and a sintering aid, wherein the ratio of glycine to the total number of moles of metal ions is 1.5:1, and the mixed solution is heated to combustion in a universal furnace to prepare BSCF precursor powder, at a temperature of 900 ℃. calcined for 2 hours to obtain the BSCF target powder;

Step 3: Preparation of electrolyte substrate and printing of BSCF-SDC porous complex oxygen electrode layer

The SDC target powder obtained in step 1 is used to prepare an electrolyte substrate sheet with a diameter of about 2 cm by a tableting method.

Use the BSCF powder prepared in step 2 to prepare BSCF electrode slurry:

Mix ethyl cellulose and terpineol to prepare an organic binder, in which ethyl cellulose accounts for 1wt% and terpineol accounts for 99wt%; then SDC powder, BSCF powder and PMMA are mixed and ground for 1 hour, the molar ratio of SDC and BSCF powder is 3:7, and the mass of PMMA accounts for 2% of the total mass of the powder; finally, the mass ratio of SDC, BSCF and PMMA mixed powder is 1:10 (binder: mixed powder), add organic binder, mix and grind for 1 hour to obtain mixed slurry;

The mixed paste was printed on the SDC substrate by screen printing, dried at 50 °C for 30 min, and then calcined at 1100 °C for 3 hours to obtain a BSCF-SDC composite porous material base layer with a molar ratio of 7:3. The thickness of the bottom layer is 40 μm, and the area is about 0.25 cm ² ;

Step 4: In situ generation of LNO active coating layer on the base layer of BSCF-SDC composite porous material

Accurately weigh La(NO ₃ ) ₃ .6H ₂ O and Ni(NO ₃ ) ₂ .6H ₂ O according to the molar ratio of 2:1, and dissolve them in 2ml of ethanol aqueous solution. The volume ratio of ethanol to water in the ethanol solution is 1: 1; Then add glycine and PVP to the nitrate ethanol aqueous solution to mix and dissolve, wherein the total mole ratio of glycine to metal ions is 1.5:1, and the mass ratio of PVP to LNO is 5:100; after stirring for 1 hour, transfer to a volumetric flask to determine capacity, to prepare LNO metal ion salt solutions with concentrations of 0.05, 0.1, and 0.2 mol/L;

The volume of precursor solution for each impregnation was determined according to the required active material loading, and the required volume of precursor solution was evenly distributed on the base layer of the BSCF-SDC composite porous material through a micro-injector, and dried under negative pressure for 30 minutes; The LNO/BSCF-SDC/SDC half-cell was obtained by sintering at 850 °C for 2 hours. According to the different initial concentrations, the loading of LNO active material was about 4, 8, and 12 wt%, and the thickness of the active coating layer was about 300 , 500, 700nm.

Comparative Example 1

This example is a Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ porous electrode;

Specific steps are as follows:

Step 1: Preparation of Sm _0.2 Ce _0.8 O _1.9 (SDC) electrolyte material powder _by sol-gel _method Ce(NO ₃ ) _{2 ·6H 2 O} , Sm(NO ₃ ) _{3.6H 2 O} solution, using citric acid monohydrate as a complexing agent and a sintering aid, the amount of citric acid monohydrate added is 1.5 times the molar amount of the total metal ions, and the mixed solution is heated in a water bath at 70°C to The gel is in the form of a gel, and the gel is continuously heated in a universal furnace to burn to form an SDC precursor powder, and finally calcined at a temperature of 800 ° C for 2 hours to obtain the SDC target powder;

Step 2: Preparation of Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ (BSCF) material powder by glycine-nitrate method (GNP)

Ba(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) ₂ .6H ₂ O, Fe(NO ₃ ) ₃ .9H ₂ O solutions were prepared according to Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ , using glycine as a complexing agent and a sintering aid, wherein the ratio of glycine to the total number of moles of metal ions is 1.5:1, and the mixed solution is heated to combustion in a universal furnace to prepare BSCF precursor powder, at a temperature of 900 ℃. calcined for 2 hours to obtain the BSCF target powder;

Step 3: Preparation of electrolyte substrate and printing of BSCF porous oxygen electrode layer

The SDC target powder obtained in step 1 is used to prepare an electrolyte substrate sheet with a diameter of about 2 cm by a tableting method.

Use the BSCF powder prepared in step 2 to prepare BSCF electrode slurry:

Mix ethyl cellulose and terpineol to prepare an organic binder, in which ethyl cellulose accounts for 1 wt % and terpineol accounts for 99 wt %; then BSCF powder and PMMA are mixed and ground for 1 hour, wherein PMMA The mass accounts for 2% of the total mass of the powder; finally, the organic binder is added to the mixed powder of BSCF and PMMA according to the mass ratio of 1:10 (binder: mixed powder), and the mixed slurry is obtained by mixing and grinding for 1 hour. material;

The mixed paste was printed on the SDC substrate by screen printing, dried at 50 °C for 30 min, and then calcined at 1100 °C for 3 hours to obtain a BSCF/SDC half-cell. The thickness of the BSCF electrode layer was 40 μm and the area was about 0.25cm ² .

Comparative Example 2

In this example, La ₂ NiO ₄ (LNO) powder is used as the active material, and the Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ -SDC porous complex phase with a molar ratio of 7:3 is infiltrated with the powder suspension. The electrode is modified to finally obtain a powder-impregnated LNO-BSCF-SDC composite oxygen electrode and its preparation steps.

Specific steps are as follows:

Step 1: Preparation of Sm _0.2 Ce _0.8 O _1.9 (SDC) electrolyte material powder by sol-gel method

According to Sm _0.2 Ce _0.8 O _1.9 , Ce(NO ₃ ) ₂ ·6H ₂ O and Sm(NO ₃ ) ₃ ·6H ₂ O solutions were prepared respectively, citric acid monohydrate was used as complexing agent and sintering aid, citric acid monohydrate The added amount is 1.5 times the molar amount of the total metal ions. The mixed solution is heated in a water bath at 70 °C to a gel state, and the gel is heated in a universal furnace to burn to form SDC precursor powder. Finally, the temperature is 800 °C. Lower calcination for 2 hours to obtain SDC target powder;

Step 2: Preparation of Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ (BSCF) material powder and La ₂ NiO ₄ (LNO) active material powder by glycine-nitrate method (GNP)

Ba(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) ₂ .6H ₂ O, Fe(NO ₃ ) ₃ .9H ₂ O solutions were prepared according to Ba _0.5 Sr _0.5 Co _0.8 Fe _0.2 O _3-δ , using glycine as a complexing agent and a sintering aid, wherein the ratio of glycine to the total number of moles of metal ions is 1.5:1, and the mixed solution is heated to combustion in a universal furnace to prepare BSCF precursor powder, at a temperature of 900 ℃. calcined for 2 hours to obtain the BSCF target powder;

La(NO ₃ ) ₃ .6H ₂ O and Ni(NO ₃ ) ₂ .6H ₂ O solutions were prepared according to La ₂ NiO ₄ , and glycine was used as a complexing agent and a sintering aid. The ratio of glycine to the total number of moles of metal ions was At a ratio of 1.1:1, the mixed solution was heated to combustion in a universal furnace to prepare LNO precursor powder, which was calcined at a temperature of 850 °C for 2 hours to obtain LNO active material powder;

Step 3: Preparation of electrolyte substrate and printing of BSCF-SDC porous complex oxygen electrode layer

The SDC target powder obtained in step 1 is used to prepare an electrolyte substrate sheet with a diameter of about 2 cm by a tableting method.

The BSCF-SDC electrode slurry was prepared by using the BSCF powder obtained in step 2:

Mix ethyl cellulose and terpineol to prepare an organic binder, in which ethyl cellulose accounts for 1wt% and terpineol accounts for 99wt%; then SDC powder, BSCF powder and PMMA are mixed and ground for 1 hour, the molar ratio of SDC and BSCF powder is 3:7, and the mass of PMMA accounts for 2% of the total mass of the powder; finally, the mass ratio of SDC, BSCF and PMMA mixed powder is 1:10 (binder: mixed powder), add organic binder, mix and grind for 1 hour to obtain mixed slurry;

The mixed paste was printed on the SDC substrate by screen printing, dried at 50 °C for 30 min, and then calcined at 1100 °C for 3 hours to obtain a BSCF-SDC composite porous material base layer with a molar ratio of 7:3. The thickness of the bottom layer is 40 μm, and the area is about 0.25 cm ² ;

Step 4: Generate LNO active coating layer on the base layer of BSCF-SDC composite porous material by infiltration method

Accurately weigh 0.1 g of the LNO powder material prepared in step 2, dissolve it in 2 ml of an aqueous ethanol solution, and the volume ratio of ethanol to water in the aqueous ethanol solution is 1:1, and after ultrasonic stirring for 10 hours, transfer to a volumetric flask to constant volume, and prepare 0.1g/mL LNO powder suspension.

Determine the volume of the powder suspension for each impregnation according to the required active material loading, distribute the required volume of the suspension evenly on the base layer of the BSCF-SDC composite porous material through a micro-injector, and dry it under negative pressure 30min; then sintered at 850°C for 2 hours to obtain the LNO/BSCF-SDC/SDC half-cell, and the LNO active material loading is about 8wt%.

The electrode impedance performance of the half-cell was tested by a three-electrode system, that is, the composite porous electrode prepared in each example was used as the working electrode, the Pt-air electrode was used as the reference electrode and the auxiliary electrode, and the platinum wire was used as the electrode lead. , using an electrochemical workstation, in the frequency range of 10 ^-2 ~ 10 ⁵ Hz, with an AC amplitude of 10mV, under the condition of open circuit voltage, the AC impedance spectra of different electrodes at 600 ~ 800 ℃ were measured.

As shown in Figure 3, it is a comparison chart of the AC impedance of BSCF-SDC composite electrodes with different molar ratios at 700 °C. When the molar ratio of BSCF and SDC is 7:3, the electrode impedance is the smallest and the electrochemical performance is the best.

As shown in Fig. 4, for BSCF electrode, BSCF-SDC (molar ratio 7:3) electrode and LNO/BSCF-SDC (molar ratio 7:3) electrode prepared by impregnation method and impregnation method respectively at 700 ℃ The impedance comparison diagram shows that the polarization resistance of the BSCF-SDC composite electrode is significantly smaller than that of the BSCF electrode. At the same time, compared with the powder suspension impregnation method, the LNO/BSCF-SDC electrode prepared by the solution in-situ impregnation method has a smaller Polarization resistance.

Claims (9)

1. A composite oxygen electrode for a solid oxide electrolytic cell, characterized in that: comprises an electrolyte layer, a substrate layer and an active coating layer;

the substrate layer is made of BSCF-SDC composite porous material and covers the electrolyte layer;

the active coating layer is coated on the outer surface and the inner surface of pores of the BSCF-SDC composite porous material;

the material of the active coating layer is Ln₂NiO₄The material is characterized in that Ln is La, Pr or Nd, and the coating amount is 2-20 wt% of the composite oxygen electrode.

2. The composite oxygen electrode of claim 1, wherein: the electrolyte layer is made of SDC, and the thickness of the electrolyte layer is 500-1000 mu m.

3. The composite oxygen electrode of claim 1, wherein: the BSCF-SDC composite porous material has the BSCF-SDC molar ratio of 1: 4-4: 1.

4. The composite oxygen electrode of claim 3, wherein: the mole ratio of BSCF to SDC in the BSCF-SDC composite porous material is 7: 3.

5. The method for producing a composite oxygen electrode according to any one of claims 1 to 4, characterized in that: firstly, printing a BSCF-SDC composite porous material substrate layer on an electrolyte layer of an electrolytic cell sheet, and then depositing an active coating layer on the outer surface and the inner surfaces of pores of the BSCF-SDC composite porous material in situ by adopting an immersion method to obtain the composite oxygen electrode.

6. The method of claim 5, wherein: firstly, preparing an electrolyte layer and SDC by adopting a sol-gel method, and preparing BSCF (barium strontium carbonate) by adopting a glycine-nitrate method; printing the BSCF and SDC mixed slurry on an electrolyte layer of the electrolytic cell sheet by adopting a screen printing method, and calcining to obtain a BSCF-SDC composite porous material substrate layer; and finally, uniformly depositing an active coating layer on the outer surface and the inner surfaces of pores of the BSCF-SDC composite porous material by adopting an immersion method, and then sintering at high temperature to obtain the composite oxygen electrode.

7. The method of claim 6, wherein: the preparation method specifically comprises the following steps:

the method comprises the following steps: the material of the electrolyte layer is SDC and Ce (NO)₃)₂·6H₂O、Sm(NO₃)₃·6H₂Using citric acid monohydrate as a complexing agent and a sintering aid as a raw material, preparing an SDC precursor by a sol-gel method, and finally calcining the SDC precursor for 1-4 hours at the temperature of 600-800 ℃ to prepare SDC powder;

step two: using Ba (NO)₃)₂、Sr(NO₃)₂、Co(NO₃)₂·6H₂O、Fe (NO₃)₃·9H₂Taking O as a raw material, adopting glycine as a complexing agent and a sintering aid, preparing a BSCF precursor by a glycine-nitrate method, and calcining the BSCF precursor for 1-4 hours at the temperature of 800-1100 ℃ to prepare BSCF powder;

step three: mixing ethyl cellulose and terpineol to prepare an organic binder; then mixing and grinding the SDC powder, the BSCF powder, the organic binder and the pore-forming agent to obtain mixed slurry; printing the mixed slurry on an electrolyte layer of an electrolytic cell sheet by a screen printing method, and calcining for 1-4 hours at the temperature of 900-1200 ℃ to obtain a BSCF-SDC composite porous material substrate layer;

step four: according to the formula Ln₂NiO₄Preparing nitrate solution according to the stoichiometric ratio of the elements, adding glycine and PVP, and fully mixing to obtain Ln₂NiO₄A precursor solution; using a dipping method to dip Ln₂NiO₄Depositing the precursor solution on the outer surface and the inner surface of the pores of the BSCF-SDC composite porous material; and sintering at 800-1000 ℃ for 1-4 hours to obtain the composite oxygen electrode.

8. The method of claim 7, wherein: the pore-forming agent is at least one of PMMA, starch and activated carbon, and the addition amount of the pore-forming agent is 2-12 wt% of the total amount of the SDC powder and the BSCF powder.

9. A solid oxide electrolytic cell comprising the composite oxygen electrode according to any one of claims 1 to 4 or the composite oxygen electrode produced by the production method according to any one of claims 5 to 8.

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