Oxygen electrode of a reversible solid oxide cell membrane electrode and method for producing the same

Abstract

The present application relates to the field of fuel cell and electrolytic cell, and particularly relates to an oxygen electrode of a reversible solid oxide cell membrane electrode and a preparation method thereof. 1‑x Sr x CoO3, 0 1‑x Sr x CoO3, 0 2‑y Sr y CoO4, 0 2‑y Sr y CoO4, 0 The oxygen electrode is of a core-shell structure, the core layer is La Sr CoO3, 0 Sr CoO3, 0 The particle size of La Sr CoO4, 0 Sr CoO4, 0 The particle size of La Sr CoO4, 0 The oxygen electrode structure is reformed in situ at high temperature during the firing of the electrode, the oxygen electrode is suitable for reversible solid oxide cell application, and the membrane electrode using the oxygen electrode shows excellent cell and electrolysis performance.

Description

Technical Field

[0001] This invention relates to the field of fuel cells and electrolyzers, specifically to an oxygen electrode for a reversible solid oxide cell membrane electrode and its preparation method. Background Technology

[0002] A reversible solid oxide cell (SOC) is an all-solid-state electrochemical device. It can convert the chemical energy of fuel into electrical energy at high temperatures, with a power generation efficiency of up to 60% and a combined heat and power efficiency of up to 90%. At the same time, it can also electrolyze water vapor into hydrogen and oxygen with an electrical efficiency of up to 100%, and is considered the most efficient hydrogen electrolysis technology.

[0003] Membrane electrode assemblies (MEAs) are core components of reversible solid oxide batteries (SOBs), featuring a "sandwich" structure with a dense electrolyte layer in the middle and porous hydrogen and oxygen electrodes on either side. Lowering the operating temperature of reversible SOBs has become a research hotspot in this field. Lowering the operating temperature expands the range of key materials available and reduces manufacturing costs, while also improving the reliability of the battery stack. However, compared to the rapid hydrogen oxidation or water dissociation processes at the hydrogen electrode, the slower oxygen reduction (ORR) or oxygen evolution reaction (OER) kinetics at the oxygen electrode are a major factor limiting MEA performance. The ORR or OER involves oxygen molecule diffusion in the electrode channels, oxygen molecule adsorption and desorption, surface diffusion of oxygen intermediates, charge transfer reactions, and oxygen ion-electron transfer. These reaction processes require electrode materials to possess high electronic conductivity, high oxygen ion conductivity, excellent catalytic oxygen surface reaction activity, and a suitable pore structure. However, electrode materials with a single-phase composition or structure struggle to meet these requirements simultaneously, making it difficult to achieve both high performance output and stable operation. Currently, researchers are using methods such as impregnation to prepare nanoelectrodes to enhance active sites and improve electrode performance. However, electrodes prepared by this method tend to grow rapidly under operating conditions, leading to the loss of active sites and a decrease in battery performance. Summary of the Invention

[0004] The purpose of this invention is to provide an oxygen electrode for a reversible solid oxide battery membrane electrode and its preparation method, which can form a core-shell structured composite electrode in situ during the electrode sintering process, exhibiting excellent electrochemical performance and good stability.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] In one aspect, this invention provides an oxygen electrode for a reversible solid oxide battery film electrode, wherein the oxygen electrode has a core-shell structure and its core layer is La. 1-x Sr x CoO3, 0 < x ≤ 0.5, La 1-xSr x The particle size of CoO3 is 0.1–0.8 micrometers, and its shell is La. 2-y Sr y CoO4, 0 < y ≤ 0.3, La 2-y Sr y The particle size of CoO4 is 10–100 nanometers.

[0007] In the above technical solution, further, the La 1-x Sr x The particle size of CoO3 is 0.2–0.5 micrometers, and La 2- y Sr y The particle size of CoO4 is 20–50 nanometers.

[0008] Another aspect of the present invention provides a method for preparing the oxygen electrode of the above-mentioned reversible solid oxide battery film electrode, the method comprising the following steps:

[0009] (1) La 1-x Sr x CoO3 powder is mixed and ground evenly with pore-forming agent, binder and organic solvent in a mass ratio of 100:100~200:2~6:40~80 to obtain electrode skeleton slurry. The slurry is coated on the surface of the electrolytic cell membrane and calcined at 800~1200℃ for 1~10h to obtain oxygen electrode skeleton.

[0010] (2) Prepare a mixed solution of Sr(NO3)2 and alcohol, wherein the concentration of Sr(NO3)2 is 1-3M and the molar ratio of alcohol to Sr is 3:1-1:1. Immerse the above mixed solution into the oxygen electrode skeleton obtained in step (1) and sinter at 600-1000℃ for 1-5h to obtain the oxygen electrode.

[0011] In the above technical solution, further, in step (1), the pore-forming agent is one or more of graphite, corn starch, and PMMA; the binder is one or more of ethyl cellulose, polyvinyl butyral, and polyvinyl alcohol; and the organic solvent is one of ethanol, n-butanol, terpineol, and n-pentanol.

[0012] In the above technical solution, further, in step (2), the alcohol is one of ethylene glycol, glycerol, and polyvinyl alcohol.

[0013] In the above technical solution, further, in step (2), the sintering temperature is 700-850℃.

[0014] The beneficial effects of this invention are as follows:

[0015] (1) The oxygen electrode of the present invention has a core-shell structure, and its core layer is La. 1-x Srx CoO3, with a particle size of 0.1–0.8 micrometers; the shell is La. 2-y Sr y CoO4 particles with a size of 10–100 nanometers. This micro-nano composite structure forms a large number of reactive sites at the core-shell interface, enhancing the electrode's OER / ORR activity and enabling it to exhibit excellent electrochemical performance in both battery and electrolytic cell modes.

[0016] (2) The oxygen electrode of the present invention has a core-shell structure, and its core layer is La. 1-x Sr x CoO3, with a particle size of 0.1–0.8 micrometers; the shell is La. 2-y Sr y CoO4. This structure is formed by impregnating Sr elements with the La core. 1-x Sr x In-situ reconstruction of the CoO3 surface formed a nanoshell La 2-y Sr y CoO4. This tightly reconstructed core-shell structure increases the structural stability of the nanoelectrode under actual operating conditions, resulting in good operation of the reversible battery.

[0017] (3) The electrode preparation method of the present invention is simple. Both the preparation of the electrode skeleton and the preparation of the impregnation solution are relatively easy to scale up and are suitable for the production of large-area electrodes. Attached Figure Description

[0018] Figure 1 This is a SEM image of the oxygen electrode prepared in Example 1 of the present invention. Detailed Implementation

[0019] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0020] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0021] Example 1

[0022] A reversible solid oxide battery membrane electrode has a hydrogen electrode made of NiO-YSZ, an electrolyte of YSZ, a separator of GDC, and an oxygen electrode with a core-shell structure, the core of which is La. 0.8 Sr 0.2 CoO3, with a La shell 1.8 Sr 0.2 CoO4. The oxygen electrode is prepared by the following process: First, 1g of La... 0.8 Sr 0.2CoO3 powder was mixed and ground for 1 hour with 1.5 g of spherical graphite (approximately 3–5 μm in diameter), 0.06 g of ethyl cellulose, and 0.8 g of terpineol to obtain an electrode framework slurry. This slurry was coated onto the surface of an electrolytic cell membrane and calcined at 900 °C for 3 hours to obtain an oxygen electrode framework. Then, a mixed solution of Sr(NO3)2 and ethylene glycol was prepared, with a Sr concentration of 1 M and a molar ratio of ethylene glycol to Sr of 1:1. This solution was impregnated into the oxygen electrode framework at a concentration of 3 mL / g, and finally sintered at 800 °C for 2 hours to obtain a core-shell structured oxygen electrode. The core particle size of the oxygen electrode was 0.3–0.5 μm, and the shell particle size was 20–50 nm. (See...) Figure 1 .

[0023] Electrochemical tests were performed on the above-mentioned membrane electrode, and the water electrolysis current density reached -1.49 Acm at 800℃. -2 Operating at a constant electrolysis voltage of 1.3V for 200 hours, the current density was -1.48 Acm. -2 @1.3V; reaches 1.67Acm in fuel cell mode. -2 @0.7V, electrolytic voltage operation and discharge for 200 hours, current density is 1.66Acm. -2 @1.3V. At a constant current ±0.4Acm -2 The cell-electrolysis cycle was performed for 1 minute per cycle. After 100 cycles, the membrane electrode performance remained unchanged.

[0024] Example 2

[0025] A reversible solid oxide battery membrane electrode has a hydrogen electrode made of NiO-YSZ, an electrolyte of YSZ, a separator of GDC, and an oxygen electrode with a core-shell structure, the core of which is La. 0.8 Sr 0.2 CoO3, with a La shell 1.8 Sr 0.2 CoO4. The oxygen electrode is prepared by the following process: First, 1g of La... 0.8 Sr 0.2 CoO3 powder was mixed and ground with 1.5g of spherical graphite (approximately 3-5 μm in diameter), 0.06g of ethyl cellulose, and 0.8g of terpineol for 1 hour to obtain an electrode framework slurry. This slurry was coated onto the surface of an electrolytic cell membrane and calcined at 900℃ for 3 hours to obtain an oxygen electrode framework. Then, a mixed solution of Sr(NO3)2 and ethylene glycol was prepared, with a Sr concentration of 3M and a molar ratio of ethylene glycol to Sr of 2:1. This solution was impregnated into the oxygen electrode framework at a controlled impregnation amount of 3 mL / g. Finally, the mixture was sintered at 800℃ for 2 hours to obtain a core-shell structured oxygen electrode. The core particle size of the oxygen electrode was 0.3-0.5 μm, and the shell particle size was 50-80 nm.

[0026] Electrochemical tests were performed on the above-mentioned membrane electrode, and the water electrolysis current density reached -1.37 Acm at 800℃. -2 @1.3V, constant electrolysis voltage operation for 200 hours, current density is -1.35Acm -2 @1.3V; reaches 1.42Acm in fuel cell mode. -2 @0.7V, electrolytic voltage operation and discharge for 200 hours, current density is 1.41Acm. -2 @1.3V. At a constant current ±0.4Acm -2 The cell-electrolysis cycle was performed for 1 minute per cycle. After 100 cycles, the membrane electrode performance remained unchanged.

[0027] Example 3

[0028] A reversible solid oxide battery membrane electrode has a hydrogen electrode made of NiO-YSZ, an electrolyte of YSZ, a separator of GDC, and an oxygen electrode with a core-shell structure, the core of which is La. 0.5 Sr 0.5 CoO3, with a La shell 1.8 Sr 0.2 CoO4. The oxygen electrode is prepared by the following process: First, 1g of La... 0.5 Sr 0.5 CoO3 powder was mixed and ground with 1.5 g PMMA (approximately 3–5 μm in diameter), 0.06 g ethyl cellulose, and 0.8 g terpineol for 1 h to obtain an electrode framework slurry. This slurry was coated onto the surface of an electrolytic cell membrane and calcined at 950 °C for 3 h to obtain an oxygen electrode framework. Then, a mixed solution of Sr(NO3)2 and n-butanol was prepared, with a Sr concentration of 2 M and a molar ratio of n-butanol to Sr of 2:1. This solution was impregnated into the oxygen electrode framework at a controlled impregnation amount of 3 mL / g. Finally, the mixture was sintered at 850 °C for 2 h to obtain a core-shell structured oxygen electrode. The core particle size of the oxygen electrode was 0.3–0.5 μm, and the shell particle size was 80–100 nm.

[0029] Electrochemical tests were performed on the above-mentioned membrane electrode, and the water electrolysis current density reached -1.27 Acm at 800℃. -2 Operating at a constant electrolysis voltage of 1.3V for 200 hours, the current density was -1.27 Acm. -2 @1.3V; reaches 1.35Acm in fuel cell mode. -2 @0.7V, electrolytic voltage operation and discharge for 200 hours, current density is 1.33Acm. -2 @1.3V. At a constant current ±0.4Acm -2 The cell-electrolysis cycle was performed for 1 minute per cycle. After 100 cycles, the membrane electrode performance remained unchanged.

[0030] Comparative Example 1

[0031] A reversible solid oxide battery membrane electrode, wherein the hydrogen electrode is NiO-YSZ, the electrolyte is YSZ, the separator is GDC, and the oxygen electrode is La. 0.8 Sr 0.2 CoO3. The oxygen electrode is prepared by the following process: First, 1g of La... 0.8 Sr 0.2 CoO3 powder was mixed and ground with 1.5g of spherical graphite (about 3-5 micrometers in diameter), 0.06g of ethyl cellulose and 0.8g of terpineol for 1 hour to obtain an electrode slurry. The slurry was coated on the surface of the electrolytic cell membrane and calcined at 900℃ for 3 hours to obtain an oxygen electrode with a particle size of 0.3-0.5 micrometers and a porosity of 40-50%.

[0032] Electrochemical tests were performed on the above-mentioned membrane electrode, and the water electrolysis current density was -0.99 Acm at 800℃. -2 At 1.3V, under constant electrolysis voltage for 200 hours, the current density decreased to -0.85Acm. -2 @1.3V; 0.87Acm in fuel cell mode. -2 At 0.7V, after 200 hours of constant voltage discharge operation, the current density decreased to 0.78Acm. -2 @1.3V.

[0033] Comparative Example 2

[0034] A reversible solid oxide battery membrane electrode, wherein the hydrogen electrode is NiO-YSZ, the electrolyte is YSZ, the separator is GDC, and the oxygen electrode is La. 1.8 Sr 0.2 CoO4. The oxygen electrode is prepared by the following process: First, 1g of La... 1.8 Sr 0.2 CoO4 powder was mixed and ground with 1.5g of spherical graphite (about 3-5 micrometers in diameter), 0.06g of ethyl cellulose and 0.8g of terpineol for 1 hour to obtain an electrode slurry. The slurry was coated on the surface of the electrolytic cell membrane and calcined at 900℃ for 3 hours to obtain an oxygen electrode with a particle size of 0.2-0.5 micrometers and a porosity of 40-50%.

[0035] Electrochemical tests were performed on the above-mentioned membrane electrode, and the water electrolysis current density was -0.68 Acm at 800℃. -2 At 1.3V, under constant electrolysis voltage for 200 hours, the current density decreased to -0.57Acm. -2 @1.3V; 0.78Acm in fuel cell mode. -2 At 0.7V, after 200 hours of constant voltage discharge operation, the current density decreased to 0.69Acm. -2@1.3V.

[0036] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing an oxygen electrode for a reversible solid oxide battery film electrode, characterized in that: The method includes the following steps: (1) La 1-x Sr x CoO3 powder is mixed and ground evenly with pore-forming agent, binder and organic solvent in a mass ratio of 100:100~200:2~6:40~80 to obtain electrode skeleton slurry. The slurry is coated on the surface of the electrolytic cell membrane and calcined at 800~1200℃ for 1~10h to obtain oxygen electrode skeleton. (2) Prepare a mixed solution of Sr(NO3)2 and alcohol, wherein the concentration of Sr(NO3)2 is 1~3M and the molar ratio of alcohol to Sr is 3:1~1:

1. Immerse the above mixed solution into the oxygen electrode skeleton obtained in step (1) and sinter at 600~1000℃ for 1~5h to obtain the oxygen electrode.

2. The preparation method according to claim 1, characterized in that: In step (1), the pore-forming agent is one or more of graphite, corn starch, and PMMA; the binder is one or more of ethyl cellulose, polyvinyl butyral, and polyvinyl alcohol; and the organic solvent is one of ethanol, n-butanol, terpineol, and n-pentanol.

3. The preparation method according to claim 1, characterized in that: In step (2), the alcohol is one of ethylene glycol, glycerol, and polyvinyl alcohol.

4. The preparation method according to claim 1, characterized in that: In step (2), the sintering temperature is 700~850℃.

5. An oxygen electrode for a reversible solid oxide battery film electrode prepared by the preparation method according to any one of claims 1-4, characterized in that: The oxygen electrode has a core-shell structure, with its core layer being La. 1-x Sr x CoO3, 0 < x ≤ 0.5, La 1-x Sr x CoO3 particles have a size of 0.1–0.8 micrometers, and their shell is La. 2-y Sr y CoO4, 0 < y ≤ 0.3, La 2-y Sr y The particle size of CoO4 is 10~100 nanometers.

6. The oxygen electrode of the reversible solid oxide battery film electrode according to claim 5, characterized in that: The La 1- x Sr x The particle size of CoO3 is 0.2~0.5 micrometers, and La... 2-y Sr y The particle size of CoO4 is 20-50 nanometers.

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