A method for preparing a fuel electrode, a fuel electrode, a fuel cell and an electrolytic cell

Abstract

The present invention discloses a method for preparing a fuel electrode, comprising the following steps: preparing an adhesion layer precursor; preparing an adhesion layer suspension slurry; preparing a functional layer precursor; preparing a functional layer suspension slurry; preparing a current collecting layer precursor; preparing a current collecting layer suspension slurry; preparing a fuel electrode embryo: applying the adhesion layer suspension slurry, the functional layer suspension slurry, and the current collecting layer suspension slurry to the electrolyte surface in sequence to obtain a fuel electrode embryo having a three-layer structure of an adhesion layer, a functional layer, and a current collecting layer; and preparing a fuel electrode: subjecting the fuel electrode embryo to a fourth calcination to obtain a fuel electrode. The preparation process of the fuel electrode preparation method of the present invention is simple and efficient, and the obtained fuel electrode has good mass transfer and electrochemical reaction performance. The present invention also discloses a fuel electrode, a solid oxide fuel cell, and a solid oxide fuel electrolyzer.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells or electrolytic cells, and in particular to a method for preparing a fuel electrode, a fuel electrode, a solid oxide fuel cell and a solid oxide fuel electrolytic cell. Background Art

[0002] A solid oxide fuel cell (SOFC) is a power generation device that directly converts the chemical energy of fuel into electrical energy. It is not limited by the Carnot cycle and therefore has higher efficiency. The solid oxide electrolytic cell (SOEC) can be regarded as the reverse mode of SOFC. Its high-temperature operating conditions can overcome the disadvantage of limited electrolysis reaction activity at low temperatures, achieving efficient electrolysis of water and carbon dioxide to produce hydrogen, carbon monoxide and other renewable fuels. The cycle of hydrogen production and power generation based on SOFC / SOEC (hereinafter collectively referred to as solid oxide cell, SOC) technology can not only achieve the purpose of energy storage, but also realize the resource utilization and reduction of carbon dioxide emissions, which is of great significance to solving the energy crisis and global warming.

[0003] According to the type of support used, SOC can be divided into three types: electrolyte-supported, electrode-supported, and metal-based. Electrode-supported SOC uses a thinner electrolyte with lower ohmic impedance, but the electrode thickness needs to be significantly increased to meet the mechanical strength requirements of the SOC, making the mass transfer process, the polarization process of the supporting electrode, the physical and chemical properties of the supporting electrode, and the microstructural changes become the main factors limiting performance. The thickness of the electrolyte and electrode of the metal-supported SOC is relatively thin, which effectively solves the problems of electrolyte ohmic impedance and electrode polarization impedance while taking into account the mechanical strength and mechanical properties of the SOC. However, the metal support also causes some negative effects, which not only increases the complexity of the SOC preparation process and limits the selectivity of the connector material, but also limits the high-temperature working ability of the metal-supported SOC (<600°C). Therefore, the inherent structural stability and high-temperature tolerance of the electrolyte-supported SOC make it more suitable for use as a core component for renewable fuels such as high-temperature water electrolysis, carbon dioxide to produce hydrogen, and carbon monoxide. The electrolyte thickness of the electrolyte-supported SOC is relatively thick and has a high ohmic impedance. The optimization of electrode function is a key issue in realizing high-temperature electrolysis with the electrolyte-supported SOC as the core component. The fuel-side electrode (hereinafter referred to as the fuel electrode) is the main area where the redox reaction of the fuel occurs, and therefore has a vital impact on the performance of the SOC.

[0004] In the preparation of fuel electrodes, the physical and chemical properties of the metal oxide and oxygen ion conductor mixture powder, such as particle size, the powder-binder ratio, and additives, especially pore-forming agents, have a significant impact on the microstructure, mass transfer process, and electrochemical reaction process of the fuel electrode. Rational regulation of these important parameters is of great significance for improving the performance of electrolyte-supported SOC fuel electrodes. Among them, the mainstream fuel electrode for large-scale application in electrolyte-supported SOCs is a composite thin film of a mixture of metal oxides and oxygen ion conductors, such as nickel oxide / gadolinium-doped ceria (NiO / CGO). The melting point of metallic nickel (Ni) can reach 1453°C, so it is widely used to prepare fuel electrodes under high-temperature working conditions. Nickel oxide / gadolinium-doped ceria (NiO / CGO) also has high electron transport performance, ion transport performance, and electrocatalytic activity.

[0005] In the prior art, for example, patent application number CN202211684484.7, entitled "Solid Oxide Fuel Cell Anode and Preparation Method, Single Cell, and Stack," discloses a solid oxide fuel cell anode comprising nickel foam and a YSZ / NiO porous ceramic supported on the nickel foam. By using nickel foam as a carrier, utilizing its naturally abundant pores, good ductility, and ease of cutting into various shapes, a NiYSZ composite slurry is loaded onto the nickel foam to prepare a SOFC anode. This naturally possesses a large number of pores, good ductility, and a formed Ni network, resulting in excellent mechanical properties and electronic conductivity, capable of meeting diverse application requirements.

[0006] Ye Fei. Preparation and Characterization of Gradient Cathode Materials for Solid Oxide Fuel Cells [D]. Zhejiang University, 2008. The literature reports that a functionally gradient cathode layer was prepared by spin coating by varying the contents of the slurry components, viscosity enhancer, and pore-forming agent. The design of a multi-layered functionally gradient cathode layer solves the problem of rapidly increasing cathode polarization resistance at low and medium temperatures.

[0007] As can be seen from the above, existing technologies use carriers to control the microstructure of the fuel electrode. However, this reliance on carriers makes the fuel electrode microstructure dependent on the carrier structure, thus severely limiting the range of controllable microstructures. Alternatively, the microstructure of the fuel electrode can be controlled primarily through the use of pore-forming agents. The working principle of pore-forming agents is that at a certain temperature, the pore-forming agent evaporates into a gas that escapes from the material, creating a porous structure. However, the range of pore sizes that can be controlled using pore-forming agents is limited, and precise control is not possible. Therefore, it is desirable to achieve control of the fuel electrode microstructure without the use of pore-forming agents or carriers, and to produce a fuel electrode with superior electrochemical performance. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a fuel electrode and a preparation method thereof.

[0009] In a first aspect, an embodiment of the present invention discloses a method for preparing a fuel electrode, comprising the following steps:

[0010] Preparation of adhesion layer precursor: Gadolinium-doped ceria (CGO) is subjected to a first calcination to obtain an adhesion layer precursor, wherein the first calcination temperature is 1000-1100°C;

[0011] Preparation of adhesion layer suspension slurry: mixing adhesion layer precursor and binder to form adhesion layer suspension slurry;

[0012] Preparation of the functional layer precursor: Nickel oxide (NiO) and gadolinium-doped ceria (CGO) are ball-milled and then subjected to a second calcination to obtain a functional layer precursor. The nickel oxide (NiO) has a particle size of 1 to 2 μm, the gadolinium-doped ceria (CGO) has a particle size of 300 to 500 nm, the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 1 to 2:1, and the second calcination temperature is 1000 to 1100°C.

[0013] Preparation of functional layer suspension slurry: mixing the functional layer precursor, the binder and the dispersant to form a functional layer suspension slurry;

[0014] Preparation of a collector layer precursor: After ball milling nickel oxide (NiO) and gadolinium-doped ceria (CGO), the third calcination is performed to obtain a collector layer precursor, wherein the particle size of the nickel oxide (NiO) is 4-5 μm, the particle size of the gadolinium-doped ceria (CGO) is 300-500 nm, the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 3-5:1, and the temperature of the third calcination is 1000-1100°C;

[0015] Preparation of collector layer suspension slurry: mixing collector layer precursor, binder and dispersant to form collector layer suspension slurry;

[0016] Preparation of fuel electrode embryo: The adhesion layer suspension slurry, the functional layer suspension slurry and the current collecting layer suspension slurry are sequentially coated on the electrolyte surface to obtain a fuel electrode embryo with a three-layer structure of adhesion layer, functional layer and current collecting layer;

[0017] Preparation of fuel electrode: The fuel electrode embryo body is subjected to the fourth calcination to obtain the fuel electrode. The temperature of the fourth calcination is 1200-1300°C.

[0018] The above-mentioned technical solution is used to prepare a fuel electrode with a gradient pore structure through a solid-phase synthesis method, which facilitates precise control, is simple and efficient, and has a wide range of applicability. The fuel electrode pores obtained by the preparation method of the present invention are stacked pores, which effectively ensure pore connectivity, further promoting fuel gas transport within the fuel electrode and improving its electrochemical performance. The stacked pore structure also promotes crosslinking between nickel oxide (NiO) and gadolinium-doped ceria (CGO), increasing three-phase active sites and greatly increasing the rate of electrochemical reactions. Furthermore, regulating the mass ratio and particle size of nickel oxide (NiO) and gadolinium-doped ceria (CGO) facilitates pore control and improves the connectivity between nickel oxide (NiO) and gadolinium-doped ceria (CGO). In addition, by controlling the first calcination temperature and the second calcination temperature, it is beneficial to precisely control the growth kinetics of nickel oxide (NiO) and gadolinium-doped ceria (CGO), thereby improving the precision of controlling the pore size and connectivity of the fuel electrode. The combination of ball milling and first calcination facilitates more accurate control of the pores of the fuel electrode, reducing the influence of pore control on the loss of raw material particle size during the preparation process. The preparation process of the fuel electrode of the present invention is simple, efficient, and suitable for large-scale production.

[0019] According to another specific embodiment of the present invention, in the step of preparing the adhesion layer precursor, the particle size of the gadolinium-doped ceria (CGO) is 300-500 nm.

[0020] According to another specific embodiment of the present invention, in the adhesion layer precursor preparation step, the doping amount of gadolinium in the gadolinium-doped cerium oxide (CGO) is 0.15 to 0.3; in the functional layer precursor preparation step, the doping amount of gadolinium in the gadolinium-doped cerium oxide (CGO) is 0.05 to 0.15; in the current collecting layer precursor preparation step, the doping amount of gadolinium in the gadolinium-doped cerium oxide (CGO) is 0.05 to 0.15.

[0021] According to another specific embodiment of the present invention, in the steps of preparing the adhesion layer precursor, preparing the functional layer precursor and preparing the current collecting layer precursor, the duration of the first calcination, the second calcination and the third calcination is 2 to 4 hours, and the heating rate and the cooling rate of the first calcination, the second calcination and the third calcination are equal, and the heating rate and the cooling rate are 2 to 8°C / min.

[0022] According to another specific embodiment of the present invention, the fuel electrode embryo preparation step further includes heating and drying after each coating, wherein the heating and drying temperature is 120-150° C. and the heating and drying time is 1-3 minutes.

[0023] According to another specific embodiment of the present invention, in the fuel electrode preparation step, the fourth calcination lasts for 2 to 4 hours, and the heating rate and cooling rate of the fourth calcination are equal, and the heating rate and cooling rate are 2 to 8°C / min.

[0024] According to another specific embodiment of the present invention, in the adhesion layer suspension slurry preparation step, the mass ratio of the adhesion layer precursor and the binder is 1 to 3:1; in the functional layer suspension slurry preparation step, the mass ratio of the functional layer precursor and the binder is 1 to 3:1; in the collector layer suspension slurry preparation step, the mass ratio of the collector layer precursor and the binder is 1 to 3:1.

[0025] According to another specific embodiment of the present invention, the binder is ethyl cellulose and diethylene glycol butyl ether acetate; in the adhesion layer suspension slurry preparation step, ethyl cellulose accounts for 3 to 5 wt% of the binder mass; in the functional layer suspension slurry preparation step and the collector layer suspension slurry preparation step, ethyl cellulose accounts for 2 to 4 wt% of the binder mass.

[0026] According to another specific embodiment of the present invention, in the steps of preparing the functional layer suspension slurry and the collector layer suspension slurry, the dispersant accounts for 1 to 1.5 wt % of the total mass of the functional layer precursor and the binder, and the dispersant accounts for 1 to 1.5 wt % of the total mass of the collector layer precursor and the binder.

[0027] According to another specific embodiment of the present invention, the dispersant is FA196.

[0028] According to another specific embodiment of the present invention, the thickness of the adhesion layer is 6-9 μm, the thickness of the functional layer is 15-20 μm, and the thickness of the current collecting layer is 10-15 μm.

[0029] According to another specific embodiment of the present invention, the pores formed in the fuel electrode are stacked pores.

[0030] According to another specific embodiment of the present invention, the porosity of the formed adhesion layer, functional layer and collecting layer satisfies: the porosity of the adhesion layer is less than the porosity of the functional layer and less than the porosity of the collecting layer. The porosity of the adhesion layer is 35% to 42%, the porosity of the functional layer is 46% to 50%, and the porosity of the collecting layer is 53% to 60%.

[0031] In a second aspect, an embodiment of the present invention discloses a fuel electrode, which is coated on the surface of an electrolyte and comprises, in order from the outside relative to the electrolyte, an adhesion layer, a functional layer, and a current collecting layer;

[0032] The adhesion layer is located between the electrolyte and the functional layer and includes gadolinium-doped ceria (CGO);

[0033] The functional layer includes nickel oxide (NiO) with a particle size of 1 to 2 μm and gadolinium-doped ceria (CGO) with a particle size of 300 to 500 nm, and the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 1 to 2:1;

[0034] The current collecting layer includes nickel oxide (NiO) with a particle size of 4 to 5 μm and gadolinium-doped ceria (CGO) with a particle size of 300 to 500 nm, and the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 3 to 5:1; wherein the porosity of the adhesion layer, the functional layer, and the current collecting layer satisfies:

[0035] The porosity of the adhesion layer is less than the porosity of the functional layer and less than the porosity of the current collecting layer.

[0036] Utilizing the above-mentioned technical solution, the fuel electrode of the present invention features a three-layer gradient pore structure, promoting excellent ion and electron transport performance. The current collector layer has a high porosity, which helps reduce ohmic resistance and facilitates fuel gas transmission, enabling rapid fuel gas transport to the functional layer and reducing concentration polarization caused by differential gas partial pressures inside and outside the fuel electrode. Controlling the content of the electronic conductor nickel oxide (NiO) in the current collector layer not only improves electronic conductivity but also enhances fuel gas catalysis. The functional layer, the primary region where redox reactions occur, has a lower porosity, effectively increasing the specific surface area and thereby increasing the number of active sites for the electrochemical reaction. The adhesion layer matches the thermal expansion coefficient of the electrolyte, providing mechanical stability for the overall structure. Furthermore, by adjusting the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO), the electrochemical reaction proceeds stably and rapidly, further promoting electron and ion transport. The synergistic effect of the adhesion layer, functional layer, and current collector layer significantly improves the electrochemical reaction rate and stability of the fuel electrode.

[0037] According to another specific embodiment of the present invention, in the adhesion layer, the particle size of gadolinium-doped ceria (CGO) is 300-500 nm.

[0038] According to another specific embodiment of the present invention, in the adhesion layer, the doping amount of gadolinium in the gadolinium-doped ceria (CGO) is 0.15-0.3; in the functional layer, the doping amount of gadolinium in the gadolinium-doped ceria (CGO) is 0.05-0.15; in the collector layer, the doping amount of gadolinium in the gadolinium-doped ceria (CGO) is 0.05-0.15.

[0039] According to another specific embodiment of the present invention, the thickness of the adhesion layer is 6-9 μm, the thickness of the functional layer is 15-20 μm, and the thickness of the current collecting layer is 10-15 μm.

[0040] According to another specific embodiment of the present invention, the pores of the fuel electrode are stacked pores.

[0041] In a third aspect, an embodiment of the present invention discloses a solid oxide fuel cell, comprising a fuel electrode obtained by the preparation method in any embodiment of the first aspect, or comprising a fuel electrode in any embodiment of the second aspect.

[0042] By adopting the above technical solution, a solid oxide fuel cell with good electrochemical performance and stability can be obtained.

[0043] In a fourth aspect, an embodiment of the present invention discloses a solid oxide fuel electrolysis cell, comprising a fuel electrode obtained by the preparation method in any embodiment of the first aspect, or comprising a fuel electrode in any embodiment of the second aspect.

[0044] By adopting the above technical solution, a solid oxide fuel electrolyzer with good electrochemical performance and stability can be produced, which can be used to realize high-temperature electrolysis with an electrolyte-supported SOC as the core component, and serve as a core device for high-temperature electrolysis of water and carbon dioxide to produce hydrogen, carbon monoxide and other renewable fuels. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of the fuel electrode of the present invention;

[0046] Figure 2 Schematic diagram of the process for preparing the fuel electrode according to Example 1 of the present invention;

[0047] Figure 3 This is an SEM image of the microstructure of the fuel electrode of Example 1 of the present invention;

[0048] Figure 4 This is an SEM image of the microstructure of the fuel electrode of Comparative Example 1 of the present invention;

[0049] Figure 5 It is a structural schematic diagram of the test bench of the present invention;

[0050] Figure 6 This is a test diagram of voltage-current-power density of the fuel electrode in SOFC mode in Example 1 of the present invention;

[0051] Figure 7 This is a test diagram of the voltage-current-power density of the fuel electrode in Example 1 of the present invention under the SOEC mode.

[0052] Explanation of symbols:

[0053] 1. Electrolyte, 2. Adhesion layer, 3. Functional layer, 4. Collector layer, 5. Ceramic fixture, 6. Collector wire, 7. High-temperature resistant metal collector mesh, 8. Battery under test, 9. Sealing material, X. Outward direction relative to the electrolyte DETAILED DESCRIPTION

[0054] The following is an explanation of the embodiments of the present invention by specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will contain many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0055] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0056] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0057] Existing technologies primarily utilize pore-forming agents to manipulate the microstructure of the fuel electrode. Through careful research and exploration of existing technologies, the inventors discovered that the existing pore-forming agent method for manipulating the microstructure of nickel oxide / gadolinium-doped cerium oxide (NiO / CGO) fuel electrodes exhibits poor electrochemical performance. The operating principle of existing pore-forming agents is that at a certain temperature, the pore-forming agent volatilizes into a gas that escapes from the material, creating a porous structure. The range of pore sizes that can be manipulated using pore-forming agents is limited. Furthermore, the process of pore-forming agent volatilization to form a porous structure can significantly reduce the mechanical properties of the fuel electrode, making it susceptible to fracture during operation. The inventors also discovered that the porous structure formed using pore-forming agents is, in fact, a porous sponge-like structure, with isolated pores and low pore connectivity, which severely restricts the mass transfer and electrochemical reaction processes of the fuel electrode. The inventors aim to improve the mass transfer and electrochemical reaction performance of the fuel electrode.

[0058] In the first aspect, the embodiments of the present invention propose for the first time a fuel electrode for nickel oxide / gadolinium doped cerium oxide (NiO / CGO) (reference Figure 1 ) is prepared by solid phase synthesis, comprising the following steps:

[0059] Preparation of adhesion layer precursor: Gadolinium-doped ceria (CGO) is subjected to a first calcination to obtain an adhesion layer precursor, wherein the first calcination temperature is 1000-1100°C;

[0060] Preparation of adhesion layer suspension slurry: mixing adhesion layer precursor and binder to form adhesion layer suspension slurry;

[0061] Functional layer precursor preparation: Nickel oxide (NiO) and gadolinium-doped ceria (CGO) are ball-milled and then subjected to a second calcination to obtain a functional layer precursor. The nickel oxide (NiO) particle size is 1-2 μm, the gadolinium-doped ceria (CGO) particle size is 300-500 nm, and the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 1-2:1 (i.e., the mass ratio is between 1 and 2). The second calcination temperature is 1000-1100°C.

[0062] Preparation of functional layer suspension slurry: mixing the functional layer precursor, the binder and the dispersant to form a functional layer suspension slurry;

[0063] Preparation of a collector layer precursor: After ball milling nickel oxide (NiO) and gadolinium-doped ceria (CGO) to mix, perform the third calcination to obtain a collector layer precursor, wherein the nickel oxide (NiO) has a particle size of 4 to 5 μm, the gadolinium-doped ceria (CGO) has a particle size of 300 to 500 nm, the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 3 to 5:1 (i.e., the mass ratio is between 3 and 5), and the temperature of the third calcination is 1000 to 1100°C;

[0064] Preparation of collector layer suspension slurry: mixing collector layer precursor, binder and dispersant to form collector layer suspension slurry;

[0065] Preparation of fuel electrode embryo: The adhesion layer suspension slurry, the functional layer suspension slurry and the current collecting layer suspension slurry are sequentially applied to the surface of the electrolyte 1 to obtain a fuel electrode embryo with a three-layer structure of adhesion layer 2, functional layer 3 and current collecting layer 4;

[0066] Preparation of fuel electrode: The fuel electrode embryo body is subjected to the fourth calcination to obtain the fuel electrode. The temperature of the fourth calcination is 1200-1300°C.

[0067] The present invention prepares nickel oxide / gadolinium-doped ceria (NiO / CGO) fuel electrodes with gradient pore structures by a solid-phase synthesis method, achieving precise control of parameters such as the particle size of the nickel oxide (NiO) and gadolinium-doped ceria (CGO) used, thereby precisely controlling key parameters such as the porosity and pore size of the prepared fuel electrode. No pore-forming agent is required, and the method is simple, efficient, and has a wide range of applicability. However, although the solid-phase synthesis method can eliminate the need for a pore-forming agent, it is still unclear how the specific solid-phase synthesis method can obtain a functional layer 3 and a current collecting layer 4 with suitable porosity, whether the specific microstructure of the obtained fuel electrode can be maintained, and whether the fuel electrode prepared by the solid-phase synthesis method can have excellent electrochemical performance. To this end, the inventors have determined the above technical solution after various attempts and experiments, and proposed a solid-phase synthesis gradient pore preparation method specifically suitable for nickel oxide / gadolinium-doped ceria type fuel electrodes.

[0068] Specifically, the present invention first controls the temperature of the first calcination, the second calcination, the third calcination and the fourth calcination of the adhesion layer 2, the functional layer 3 and the current collecting layer 4 during the solid-phase synthesis process, and at the same time sets the mass ratio between the raw material powders nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) and the particle size of the raw material powder, which is conducive to precisely controlling the growth kinetics of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) to obtain a nickel oxide / gadolinium-doped cerium oxide (NiO / CGO) fuel electrode with a porous structure.

[0069] Furthermore, during their research, the inventors discovered that for nickel oxide (NiO) / gadolinium-doped ceria (CGO) fuel electrodes, the electrochemical reaction is characterized by the simultaneous presence of three phases: nickel oxide (NiO), gadolinium-doped ceria (CGO), and fuel gas. These three phases are referred to as three-phase active sites. The presence of these three-phase active sites enhances catalytic activity and the rate of the electrochemical reaction, thereby improving the electrical performance of the fuel electrode. The pores formed in the fuel electrode obtained by the present invention, which utilizes a preparation method that controls solid-phase synthesis and the particle size of the synthetic raw material powder, are stacked pores. Stacked pores refer to the spaces between particles created by particle stacking. Stacked pores can increase pore connectivity, further facilitating the transport of fuel gas within the fuel electrode, thereby improving its electrochemical performance. The inventors also discovered that the catalytic activity of the nickel oxide-gadolinium-doped ceria-fuel gas system can be enhanced through the solid-phase synthesis method of the present invention and the specific design of the preparation method during solid-phase synthesis. The reason for this is that, on the one hand, specific improvements in the preparation method of the present invention form a stacked pore structure with a specific stacking state and pore structure that is particularly suitable for nickel oxide (NiO) / gadolinium-doped ceria (CGO) fuel electrodes. This unique stacked pore structure is beneficial for catalytic activity. On the other hand, in the fuel electrode prepared by the present invention, nickel oxide (NiO) is used to transport electrons, and gadolinium-doped ceria (CGO) is used to transport ions. The stacked pore structure promotes crosslinking between nickel oxide (NiO) and gadolinium-doped ceria (CGO), thereby increasing the number of active sites in the three-phase nickel oxide-gadolinium-doped ceria-fuel gas structure.

[0070] Obtaining a fuel electrode structure with a stable structure and capable of ensuring excellent electrochemical performance is the result of comprehensive settings of the following parameters, and the ranges of the parameter settings are specifically as described above. Set the mass ratio of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) in the functional layer 3 and the particle size of nickel oxide and gadolinium-doped cerium oxide, set the mass ratio of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) in the collector layer 4 and the particle size of nickel oxide and gadolinium-doped cerium oxide, and match the calcination temperature at different stages to obtain stacked pores with a specific pore structure, and the obtained fuel electrode satisfies the gradient pore structure of the porosity of the adhesion layer 2 < the porosity of the functional layer 3 < the porosity of the collector layer 4. The larger porosity of the collector layer 4 is conducive to reducing the ohmic current. The functional layer 3 is the primary region for redox reactions. By providing a smaller porosity than the collector layer 4, the fuel gas transferred from the collector layer 4 can fully react with the functional layer 3. Furthermore, the improved preparation method creates a stacked pore structure suitable for the functional layer 3. This stacked pore structure provides a larger number of three-phase active sites, thereby enhancing the catalytic activity of the functional layer 3 and promoting the catalytic reaction. The adhesion layer 2 has the smallest porosity, more closely matching the thermal expansion coefficient of the electrolyte 1, which significantly improves the mechanical stability of the battery. In addition, by controlling the first calcination temperature, the second calcination temperature and the third calcination temperature at 1000-1100°C, calcination is first performed, which is beneficial to the formation of a stable interface between each layer of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) in the fuel electrode and prevents excessive growth, leaving space for the fourth calcination to control continued growth; then the fourth calcination is performed at a temperature of 1200-1300°C, and combined with the above steps, the three-layer structure of the adhesion layer, the functional layer and the current collection layer is sintered into a whole, which is closer to each other, promoting the connectivity between the stacked pores, and thereby improving the accuracy of controlling the pore size and connectivity of the fuel electrode.

[0071] Furthermore, during the preparation of the functional layer precursor and the current collecting layer precursor, the pores of the fuel electrode are precisely controlled by combining ball milling with the second calcination, and by combining ball milling with the third calcination. Specifically, the second calcination or the third calcination promotes the growth of the particle size of the raw nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO), thereby reducing the particle size loss of the raw nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) during ball milling.

[0072] Therefore, the present invention achieves a fuel electrode with a gradient pore structure through the aforementioned technical solution. Specifically, the present invention's fuel electrode preparation method utilizes solid-phase synthesis, a combination of adjusting the mass ratio and particle size of the raw material powders, calcination temperatures at different stages, and ball milling to achieve a fuel electrode with excellent mass transfer and electrical properties. The preparation process is simple, efficient, and suitable for large-scale production.

[0073] The gadolinium-doped cerium oxide (CGO) is a composite oxide material in which the gadolinium (Gd) element is doped into the lattice structure of cerium oxide (CeO2). The chemical formula is usually expressed as Ce 1-x Gd x O2, where x represents the molar ratio of gadolinium doping in ceria, 0 < x < 1. Gadolinium doping can increase the electrical conductivity of ceria. After doping, gadolinium-doped ceria (CGO) maintains the excellent redox properties of ceria and exhibits good chemical and structural stability at high temperatures.

[0074] Furthermore, in the above embodiment, the gadolinium-doped cerium oxide (CGO) particles used in the functional layer 3 and the current collecting layer 4 are of equal size, which is beneficial to simplifying the process control parameters and facilitating better regulation of the porosity of the functional layer 3 and the current collecting layer 4.

[0075] In the above embodiment, ball milling is performed before the second calcination in the functional layer precursor preparation step, and before the third calcination in the current collector layer precursor preparation step. For example, the ball milling speed is 150-200 rpm, and the ball milling time is 4-8 hours, to better coordinate with the second or third calcination and precisely control the growth kinetics of nickel oxide (NiO) and gadolinium-doped ceria (CGO).

[0076] The adhesion layer can be made into a layer with a high density, thereby serving to isolate the functional layer 3 from the electrolyte 1 and the fuel gas. In another embodiment of the present invention, in the adhesion layer precursor preparation step, gadolinium-doped cerium oxide (CGO) with a particle size of 300-500 nm is selected. After a first calcination at 1000-1100°C and a fourth calcination at 1200-1300°C, it can have a small porosity. This can not only prevent the functional layer 3 from contacting the electrolyte 1 and prevent the fuel gas from reaching the electrolyte 1, but also help reduce mass transfer resistance, promote ion transport to the electrolyte, and increase the catalytic reaction rate. Furthermore, in the adhesion layer precursor preparation step, the selected 300-500 nm gadolinium-doped cerium oxide can be ball-milled at a speed of 150-200 rpm for 4-8 hours, followed by the first calcination.

[0077] In the adhesion layer precursor preparation step of the present invention, the gadolinium doping amount in the gadolinium-doped ceria (CGO) is 0.15-0.3; in the functional layer precursor preparation step, the gadolinium doping amount in the gadolinium-doped ceria (CGO) is 0.05-0.15; and in the current collector layer precursor preparation step, the gadolinium doping amount in the gadolinium-doped ceria (CGO) is 0.05-0.15. The inventors have discovered that the stability of the fuel electrode structure is beneficial to improving the electrochemical cycling stability of the fuel electrode. Specifically, adjusting the difference in thermal expansion coefficients between the adhesion layer 2 and the electrolyte 1 so that the thermal expansion coefficients of the adhesion layer 2 and the electrolyte 1 match can improve the stability of the fuel electrode, thereby reducing the thermal stress generated during the sintering process and enhancing the bonding strength between the electrolyte 1 and the adhesion layer 2. Therefore, the possibility of delamination between the adhesion layer 2 and the electrolyte 1 is reduced, the ion transport resistance of the fuel electrode is reduced, and the electrochemical performance is improved. Based on this, the inventors have discovered that when the gadolinium doping level in the gadolinium-doped ceria (CGO) in the adhesion layer 2 is set within the above range, its thermal expansion coefficient approaches that of the electrolyte 1, significantly improving the mechanical stability of the solid oxide fuel cell or solid oxide fuel electrolyzer. Furthermore, setting the gadolinium doping level in the gadolinium-doped ceria (CGO) in the adhesion layer 2 to 0.15-0.3 also improves the ability to transport ions and carry electrons, facilitating their transport through the electrolyte 1 to the counter electrode side of the fuel electrode. Preferably, the gadolinium doping level in the gadolinium-doped ceria (CGO) in the adhesion layer 2 can be 0.2-0.25. Furthermore, the gadolinium doping amount in the gadolinium-doped ceria (CGO) in the functional layer 3 is 0.05 to 0.15, which can match the thermal expansion coefficients of the gadolinium-doped ceria (CGO) and nickel oxide (NiO), preventing nickel oxide (NiO) and gadolinium-doped ceria (CGO) from separating due to mechanical property differences at the same temperature, which is conducive to the bonding of the two. Furthermore, the gadolinium doping amount in the gadolinium-doped ceria (CGO) in the current collector layer 4 is 0.05 to 0.15, which can also match the thermal expansion coefficients of the gadolinium-doped ceria (CGO) and nickel oxide (NiO) in the current collector layer 4. Ultimately, by setting the gadolinium doping amount in the gadolinium-doped ceria (CGO) of the adhesion layer 2, the functional layer 3, and the current collector layer 4 within the above range, the overall stability of the fuel electrode is improved, thereby improving the electrochemical cycling stability of the fuel electrode. In addition, the above-mentioned doping amount refers to the molar ratio of the gadolinium (Gd) element in the cerium oxide (CeO2) lattice.

[0078] Furthermore, the doping amount of gadolinium in the gadolinium-doped cerium oxide (CGO) of the collector layer 4 is equal to the doping amount of gadolinium in the gadolinium-doped cerium oxide (CGO) of the functional layer 3, so that the expansion coefficients of the collector layer 4 and the functional layer 3 are matched, which is more conducive to the stability of the fuel electrode structure.

[0079] In the steps of preparing the adhesion layer precursor, the functional layer precursor, and the current collecting layer precursor, the first calcination has a calcination time of 2-4 hours, a heating rate of 2-8°C / min, a cooling rate of 2-8°C / min, and the heating rate and cooling rate are equal; the second calcination has a calcination time of 2-4 hours, a heating rate of 2-8°C / min, a cooling rate of 2-8°C / min, and the heating rate and cooling rate are equal; the third calcination has a calcination time of 2-4 hours, a heating rate of 2-8°C / min, a cooling rate of 2-8°C / min, and the heating rate and cooling rate are equal. The combination of the above conditions is conducive to better control of the growth dynamics of the precursor preparation.

[0080] The fuel electrode embryo preparation step also includes heating and drying after each coating, and the heating and drying temperature is 120-150°C, and the heating and drying time is 1-3 minutes. The above conditions are used to ensure that each layer of the three-layer fuel electrode embryo is a stable structure. For example, after the adhesion layer suspension slurry is coated on the electrolyte surface, a solid adhesion layer 2 is formed by the above drying, and the functional layer suspension slurry is continuously coated on the solid adhesion layer surface, and a solid functional layer 3 is formed by the above drying, and the current collection layer suspension slurry is continuously coated on the solid functional layer surface, and a solid current collection layer 4 is formed by the above drying, so as to obtain a fuel electrode embryo with a three-layer structure of adhesion layer 2, functional layer 3 and current collection layer 4.

[0081] During the fuel electrode preparation step, the fourth calcination lasts for 2 to 4 hours, with equal heating and cooling rates of 2 to 8°C / min. These conditions facilitate better control of the growth kinetics of the raw material powder during the fourth calcination.

[0082] In the adhesion layer suspension slurry preparation step, the mass ratio of the adhesion layer precursor and the binder is 1 to 3:1 (that is, the mass ratio is between 1 and 3); in the functional layer suspension slurry preparation step, the mass ratio of the functional layer precursor and the binder is 1 to 3:1 (that is, the mass ratio is between 1 and 3); in the collector layer suspension slurry preparation step, the mass ratio of the collector layer precursor and the binder is 1 to 3:1 (that is, the mass ratio is between 1 and 3). By adjusting the content of the binder, it helps to better prepare the film of each layer structure of the adhesion layer 2, the functional layer 3 and the collector layer 4, and enhance the connectivity of the pore structure. Combined with the above-mentioned preparation method, a more stable and uniform fuel electrode is obtained.

[0083] Furthermore, the binder is ethyl cellulose and diethylene glycol butyl ether acetate; in the adhesion layer suspension slurry preparation step, ethyl cellulose accounts for 3-5wt% of the binder mass; in the functional layer suspension slurry preparation step and the collector layer suspension slurry preparation step, ethyl cellulose accounts for 2-4wt% of the binder mass. Using a solution of ethyl cellulose and diethylene glycol butyl ether acetate as a binder facilitates the bonding and crosslinking of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO), resulting in good film-forming ability. Since adhesion layer 2 only contains gadolinium-doped cerium oxide (CGO) with a particle size of 300-500nm, in order to avoid agglomeration of nanoparticles and affect the pore structure, the mass content of ethyl cellulose in the binder during the adhesion layer suspension slurry preparation step is higher than that of the other two layers. A high mass content of ethyl cellulose means that the binder has a high viscosity. By optimizing the mixing ratio of the binder and the precursor and optimizing the binder composition, the connectivity of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) is ensured, thereby further improving the performance of the fuel electrode of the present invention, so that the prepared fuel electrode has good electronic conductivity and ionic conductivity at the same time.

[0084] In the steps of preparing the functional layer suspension slurry and the collector layer suspension slurry, the dispersant accounts for 1 to 1.5 wt % of the total mass of the functional layer precursor and the binder, and the dispersant accounts for 1 to 1.5 wt % of the total mass of the collector layer precursor and the binder. The dispersant is set to the above range to avoid the dispersion unevenness caused by the large particle size difference between nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) in the functional layer and the collector layer, which is beneficial to promote the cross-linking of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) in the fuel electrode and increase the connectivity of its structure, thereby increasing more active sites, and is more conducive to maintaining a certain viscosity of each layer of slurry, which is beneficial to film formation. Furthermore, the dispersant is FA196, which further improves the cross-linking and dispersion uniformity of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO).

[0085] In any of the above embodiments, the thickness of the adhesion layer 2 is 6-9 μm, the thickness of the functional layer 3 is 15-20 μm, and the thickness of the current collecting layer 4 is 10-15 μm. The pores of the fuel electrode are stacked pores. Specifically, the pores formed by solid-phase synthesis in the functional layer and the current collecting layer are stacked pores. Furthermore, the adhesion layer formed by calcining 300-500 nm of gadolinium-doped cerium oxide (CGO) also has stacked pores. Among them, the porosity of the adhesion layer 2, the functional layer 3, and the current collecting layer 4 satisfies: the porosity of the adhesion layer 2 < the porosity of the functional layer 3 < the porosity of the current collecting layer 4, the porosity of the adhesion layer 2 is 35%-42%, the porosity of the functional layer 3 is 46%-50%, and the porosity of the current collecting layer 4 is 53%-60%. Combined with the mutual cooperation of the above features, the fuel electrode of the present invention has good mass transfer and electrochemical reaction performance.

[0086] Second, continue to refer to Figure 1 The embodiment of the present invention discloses a fuel electrode, which is coated on the surface of the electrolyte and includes: an adhesion layer 2, a functional layer 3 and a current collecting layer 4 in order outward relative to the electrolyte, and the direction outward relative to the electrolyte is, for example, Figure 1 The X direction in

[0087] The adhesion layer 2 is located between the electrolyte 1 and the functional layer 3;

[0088] The adhesion layer 2 includes gadolinium-doped ceria (CGO);

[0089] Functional layer 3 includes nickel oxide (NiO) with a particle size of 1 to 2 μm and gadolinium-doped ceria (CGO) with a particle size of 300 to 500 nm, with a mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) being 1 to 2:1 (i.e., a mass ratio between 1 and 2).

[0090] The current collecting layer 4 includes nickel oxide (NiO) with a particle size of 4 to 5 μm and gadolinium-doped ceria (CGO) with a particle size of 300 to 500 nm, and the mass ratio of nickel oxide (NiO) to gadolinium-doped ceria (CGO) is 3 to 5:1 (i.e., the mass ratio is between 3 and 5);

[0091] The porosity of the adhesion layer 2 is less than the porosity of the functional layer 3 and less than the porosity of the current collecting layer 4 .

[0092] Utilizing the above-mentioned technical solution, the fuel electrode of the present invention features a three-layer gradient pore structure, promoting excellent ion and electron transport performance. The adhesion layer 2 matches the thermal expansion coefficient of the electrolyte 1 and exhibits catalytic activity; the functional layer 3 serves as the primary region for redox reactions; and the current collector layer 4 is used to transport electrons and fuel gas and exhibits catalytic activity. The high porosity of the current collector layer 4 facilitates reduced ohmic resistance and fuel gas transport, enabling rapid fuel gas transport to the functional layer 3 and reducing concentration polarization caused by differential gas partial pressures inside and outside the fuel electrode. Controlling the nickel oxide (NiO) content of the electronic conductor in the current collector layer 4 not only improves electronic conductivity but also enhances the catalytic performance of the fuel gas. The lower porosity of the functional layer 3, the primary region for redox reactions, effectively increases the specific surface area, thereby increasing the number of active sites for the electrochemical reaction. The adhesion layer 2 matches the thermal expansion coefficient of the electrolyte 1, providing mechanical stability for the overall structure. By regulating the mass ratio of nickel oxide (NiO) and gadolinium-doped ceria (CGO), the electrochemical reaction proceeds stably and rapidly, further promoting the transport of electrons and ions. The interaction between the adhesion layer 2, functional layer 3, and current collection layer 4 significantly improves the electrochemical reaction rate and stability of the fuel electrode.

[0093] In adhesion layer 2, the gadolinium-doped ceria (CGO) has a particle size of 300 to 500 nm. This allows adhesion layer 2 to have a relatively low porosity, which helps reduce mass transfer resistance and gives the fuel electrode of the present invention an excellent three-layer gradient pore structure, further facilitating fuel gas transport and achieving higher catalytic activity. This, combined with any of the aforementioned embodiments, further enhances the electrochemical performance of the fuel electrode of the present invention.

[0094] Furthermore, the gadolinium doping level of the gadolinium-doped ceria (CGO) in the adhesion layer 2 is 0.15-0.3; the gadolinium doping level of the gadolinium-doped ceria (CGO) in the functional layer 3 is 0.05-0.15; and the gadolinium doping level of the gadolinium-doped ceria (CGO) in the current collector layer 4 is 0.05-0.15. By controlling the gadolinium doping level of each CGO layer, the thermal expansion coefficients of the four-layer structure (electrolyte 1, adhesion layer 2, functional layer 3, and current collector layer 4) are matched, thereby forming a fuel electrode with a stable structure and strong mass transfer capabilities. The thickness of the adhesion layer 2 is 6-9 μm, the thickness of the functional layer 3 is 15-20 μm, and the thickness of the current collector layer 4 is 10-15 μm. The adhesion layer 2 is set to the above thickness to reduce the ion transmission resistance while ensuring sufficient mechanical strength to match the electrolyte 1; the functional layer 3 is set to the above thickness to ensure a high specific surface area, thereby ensuring more active sites, ensuring high catalytic activity, and reducing resistance; the current collecting layer 4 is set to the above thickness to facilitate the collection of electrons and promote electron transmission.

[0095] In any of the above embodiments, the pores of the fuel electrode are stacked pores. The stacked pore structure promotes cross-linking between nickel oxide (NiO) and gadolinium-doped ceria (CGO) and pore connectivity, facilitating diffusion and mass transfer of reactant gases within the fuel electrode. It also increases the number of three-phase active sites where nickel oxide (NiO), gadolinium-doped ceria (CGO), and fuel gas come into contact. The presence of these three-phase active sites significantly enhances catalytic activity.

[0096] In a third aspect, an embodiment of the present invention discloses a solid oxide fuel cell, comprising a fuel electrode obtained by the preparation method in any embodiment of the first aspect, or comprising a fuel electrode in any embodiment of the second aspect.

[0097] By adopting the above technical solution, a solid oxide fuel cell with good electrochemical performance and stability can be obtained.

[0098] In a fourth aspect, an embodiment of the present invention discloses a solid oxide fuel electrolysis cell, comprising a fuel electrode obtained by the preparation method in any embodiment of the first aspect, or comprising a fuel electrode in any embodiment of the second aspect.

[0099] By adopting the above technical solution, a solid oxide fuel electrolyzer with good electrochemical performance and stability can be produced, which can be used to realize high-temperature electrolysis with an electrolyte-supported SOC as the core component, and serve as a core device for high-temperature electrolysis of water and carbon dioxide to produce hydrogen, carbon monoxide and other renewable fuels.

[0100] Example 1

[0101] The schematic flow diagram of the preparation method of the fuel electrode in Example 1 is as follows: Figure 2 As shown, the specific steps include:

[0102] Preparation of adhesion layer precursor: Weigh 10g of gadolinium-doped cerium oxide (CGO) with a particle size of 400nm and a gadolinium doping amount of 0.2, also known as CG 0.2 O. CG 0.2 O was placed in a reactor for the first calcination, and the temperature was increased from room temperature to the first calcination temperature of 1100°C at a heating rate of 3°C / min under an air atmosphere for 2 hours, and then cooled to room temperature at a cooling rate of 3°C / min to obtain an adhesion layer precursor.

[0103] Preparation of adhesion layer suspension slurry: Weigh 5 g of adhesion layer precursor, add 2.5 g of a binder containing 4 wt% ethyl cellulose, and mix thoroughly to obtain an adhesion layer suspension slurry; wherein the binder is ethyl cellulose and diethylene glycol butyl ether acetate, and the mass ratio of the adhesion layer precursor to the binder is 2:1.

[0104] Preparation of functional layer precursor: Weigh 6g of NiO with a particle size of 1-2μm, weigh 4g of gadolinium-doped cerium oxide (CGO) with a particle size of 400nm and a gadolinium doping amount of 0.1, that is, CG 0.1 O, NiO and CG 0.1 O was placed in an agate ball mill jar and ball-milled in a planetary ball mill at a speed of 180 rpm for 6 hours. The mixture was then placed in a ceramic reactor and heated from room temperature to a second calcination temperature of 1100°C at a heating rate of 3°C / min in an air atmosphere and calcined for 2 hours. The temperature was then cooled to room temperature at a cooling rate of 3°C / min to obtain a functional layer precursor. The mass ratio of nickel oxide (NiO) to gadolinium-doped cerium oxide (CGO) was 1.5:1.

[0105] Preparation of functional layer suspension slurry: Weigh 5 g of functional layer precursor, add 2.5 g of a binder containing 3 wt% ethyl cellulose and 0.0375 g of a dispersant, mix thoroughly, and obtain a functional layer suspension slurry; wherein the binder is ethyl cellulose and diethylene glycol butyl ether acetate, the mass ratio of the functional layer precursor to the binder is 2:1, the dispersant is FA196, and the dispersant accounts for 0.5 wt% of the total mass of the functional layer precursor and the binder.

[0106] Preparation of collector layer precursor: Weigh 8g of NiO with a particle size of 4-5μm, weigh 2g of gadolinium-doped cerium oxide (CGO) with a particle size of 400nm and a gadolinium doping amount of 0.1, that is, CG 0.1 O, NiO and CG 0.1 The O powder was placed in an agate ball mill and ball-milled in a planetary ball mill at a speed of 180 rpm for 6 hours. The mixture was then placed in a ceramic reactor and heated from room temperature to a third calcination temperature of 1100°C at a heating rate of 3°C / min in an air atmosphere for 2 hours. The temperature was then cooled to room temperature at a cooling rate of 3°C / min to obtain the collector layer precursor. The mass ratio of nickel oxide (NiO) to gadolinium-doped cerium oxide (CGO) was 4:1.

[0107] Preparation of the collector layer suspension slurry: Weigh 5 g of the collector layer precursor, add 2.5 g of a binder containing 3 wt% ethyl cellulose and 0.0375 g of a dispersant, mix thoroughly, and obtain a collector layer suspension slurry; wherein the binder is ethyl cellulose and diethylene glycol butyl ether acetate, the mass ratio of the collector layer precursor to the binder is 2:1, the dispersant is FA196, and the dispersant accounts for 0.5 wt% of the total mass of the collector layer precursor and the binder.

[0108] Preparation of fuel electrode embryo: Take the adhesion layer suspension slurry, functional layer suspension slurry and collector layer suspension slurry, and use a screen printing machine to sequentially coat them on a 3YSZ electrolyte with an area of ​​60mm×60mm and a thickness of 90±10μm; the thickness of the adhesion layer is 6~9μm, the thickness of the functional layer is 15~20μm, and the thickness of the collector layer is 10~15μm.

[0109] Preparation of fuel electrode: After drying the fuel electrode embryo, transfer it to a muffle furnace and heat it from room temperature to the fourth calcination temperature of 1300℃ at a heating rate of 3℃ / min in an air atmosphere for 2h. Then cool it to room temperature at a cooling rate of 3℃ / min to obtain the fuel electrode. The SEM image of the microstructure of the fuel electrode is shown in the figure below. Figure 3 shown.

[0110] In the fuel electrode of Example 1 of the present invention, the porosity of the adhesion layer 2 is 41.52%, the porosity of the functional layer 3 is 49.85%, and the porosity of the current collecting layer 4 is 53.36%.

[0111] Depend on Figure 3 It can be seen that the fuel electrode of the present invention has a gradient pore structure, the porosity of the adhesion layer 2 is less than the porosity of the functional layer 3 and less than the porosity of the current collecting layer 4, and the pores of the fuel electrode of the present invention are stacked pores.

[0112] Comparative Example 1

[0113] The preparation method of the fuel electrode of Comparative Example 1 specifically includes the following steps:

[0114] Preparation of adhesion layer suspension slurry: Weigh 5g of gadolinium-doped cerium oxide (CGO) with a particle size of 400nm and a gadolinium doping amount of 0.2, also known as CG 0.2 O, add 4g of a binder containing 4wt% ethyl cellulose, mix thoroughly, and obtain an adhesion layer suspension slurry; wherein the binder is ethyl cellulose and diethylene glycol butyl ether acetate, and the mass ratio of the adhesion layer precursor to the binder is 1.25:1.

[0115] Preparation of functional layer precursor: Weigh 6g of NiO with a particle size of 1-2μm, weigh 4g of gadolinium-doped cerium oxide (CGO) with a particle size of 400nm and a gadolinium doping amount of 0.1, that is, CG 0.1 O, NiO and CG 0.1 O was placed in an agate ball mill jar and ball-milled in a planetary ball mill at a speed of 300 rpm for 24 hours to obtain a functional layer precursor; wherein the mass ratio of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) was 1.5:1.

[0116] Preparation of functional layer suspension slurry: Weigh 5 g of functional layer precursor, add 3.25 g of binder containing 4 wt% ethyl cellulose, 0.25 g of pore-forming agent with an average particle size of 5 μm and 0.0425 g of dispersant, mix thoroughly to obtain a functional layer suspension slurry; wherein the binder is ethyl cellulose and diethylene glycol butyl ether acetate, the mass ratio of the functional layer precursor to the binder is 1:0.65, the pore-forming agent is polymethyl methacrylate (PMMA) powder, and the mass ratio of the pore-forming agent to the functional layer precursor is 20:1; the dispersant is FA196, and the dispersant accounts for 0.5 wt% of the total mass of the functional layer precursor, pore-forming agent and binder.

[0117] Preparation of collector layer precursor: Weigh 8g of NiO with a particle size of 4-5μm, weigh 2g of gadolinium-doped cerium oxide (CGO) with a particle size of 400nm and a gadolinium doping amount of 0.1, that is, CG 0.1 O, NiO and CG 0.1 O was placed in an agate ball mill jar and ball-milled in a planetary ball mill at a speed of 300 rpm for 24 hours to obtain a collector layer precursor; wherein the mass ratio of nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) was 4:1.

[0118] Preparation of collector layer suspension slurry: Weigh 5 g of collector layer precursor, add 3.25 g of binder containing 4 wt% ethyl cellulose, 0.25 g of pore-forming agent with an average particle size of 5 μm and 0.0425 g of dispersant, mix thoroughly to obtain collector layer suspension slurry; wherein, the binder is ethyl cellulose and diethylene glycol butyl ether acetate, the mass ratio of collector layer precursor to binder is 1:0.65, the pore-forming agent is polymethyl methacrylate (PMMA) powder, and the mass ratio of pore-forming agent to collector layer precursor is 20:1; the dispersant is FA196, and the dispersant accounts for 0.5 wt% of the total mass of collector layer precursor, pore-forming agent and binder.

[0119] Preparation of fuel electrode embryo: Take the adhesion layer suspension slurry, the functional layer suspension slurry and the collector layer suspension slurry, and use a screen printing machine to sequentially coat them on a 3YSZ electrolyte with an area of ​​60mm×60mm and a thickness of 90±10μm; After drying the fuel electrode embryo, transfer it to a muffle furnace, and heat it from room temperature to the fourth calcination temperature of 1300℃ at a heating rate of 3℃ / min in an air atmosphere. The calcination time is 2h, and then the temperature is cooled to room temperature at a cooling rate of 3℃ / min to obtain the fuel electrode. The SEM image of the microstructure of the fuel electrode of comparative example 1 is shown in FIG. Figure 4 shown.

[0120] In the preparation process of Comparative Example 1, although the mass ratio between the raw material powder and the particle size of the raw material powder are the same as those of the present invention, Figure 4 It can be seen that the powders in the fuel electrode of Comparative Example 1 are bonded together and do not form pores like those in the fuel electrode of the present invention. Figure 4 It can also be seen that the pores prepared by the PMMA pore-forming agent method in Comparative Example 1 are isolated from each other, and are pores formed by the volatilization of the pore-forming agent itself under heat.

[0121] To facilitate understanding of the present invention, the voltage-current-power density test method of the fuel electrode in SOFC and SOEC modes is described below:

[0122] The performance of Example 1 in SOFC and SOEC modes was tested on a test bench using a four-wire method, such as Figure 5 As shown, the high temperature resistant metal current collecting net 7 on both sides of the fuel electrode and the air electrode of the battery to be tested 8 is fixed by a ceramic fixture 5, and a sealing material 9 is placed between the battery to be tested 8 and the ceramic fixture 5 to pass hydrogen and air into the fuel electrode and the air electrode respectively. The current collecting wire 6 is led outward from the high temperature resistant metal current collecting net 7 and connected to the electrochemical workstation, electronic load and other measuring instruments to measure the battery performance. Among them, the air electrode is an LSC / CGO composite air electrode, and the fuel electrode and air electrode are printed on both sides of the electrolyte in the battery to be tested 8. The test results are shown in FIG. Figure 6-7 shown.

[0123] like Figure 6 The test diagram of the fuel electrode in the SOFC mode of Example 1 is shown. Figure 4 It can be seen that the maximum output power density of the fuel electrode in Example 1 of the present invention is 0.445W / cm 2 , which is approximately the maximum output power density of comparative example 1, 0.223 W / cm 2 The absolute value of the slope of the voltage-current density curve in the figure corresponds to the surface resistance of the fuel electrode. The surface resistance of the fuel electrode in Example 1 of the present invention is 0.783Ω·cm 2 , which is about the surface resistance of Comparative Example 1, 1.480Ω·cm 2 50% of.

[0124] like Figure 7 The test diagram of the fuel electrode in the SOEC mode of Example 1 is shown. Figure 7 It can be seen that the absolute value of the slope of the voltage-current density curve in the figure corresponds to the surface resistance of the fuel electrode. The surface resistance of the fuel electrode in Example 1 of the present invention is 1.209Ω·cm 2 , which is lower than the surface resistance of comparative example 1 (1.431Ω·cm) 2Since the greater the power density of the fuel electrode, the smaller the surface resistance, it can be seen that the electrochemical performance of the battery using the fuel electrode of Example 1 of the present invention is better.

[0125] In summary, the present invention uses a solid-phase synthesis method to prepare a fuel electrode with a gradient pore structure from nickel oxide (NiO) and gadolinium-doped cerium oxide (CGO) powders. The raw materials are readily available and widely sourced. Furthermore, through ball milling and calcination, parameters such as the particle size of the powder material can be controlled, making it highly adaptable to raw material powders from different sources. Furthermore, by controlling the particle size of the powder, key parameters such as the porosity and pore size of the prepared fuel electrode can be directly controlled without the use of a pore-forming agent, making the process simpler and more efficient. The pores of the fuel electrode thus prepared are stacked pores, which effectively ensure the connectivity of the pores and are more conducive to gas transport within the fuel electrode. Furthermore, the fuel electrode of the present invention has a gradient pore structure. The prepared fuel electrode uses powders of different particle sizes in different structural layers. By rationally regulating the preparation parameters, a stepped pore structure can be obtained, which is more conducive to mass transfer and electrochemical reactions within the fuel electrode. By optimizing the binder composition and the binder-to-precursor mixing ratio, the connectivity of nickel oxide (NiO) and gadolinium-doped ceria (CGO) was ensured, resulting in the prepared fuel electrode having both good electronic and ionic conductivity. Furthermore, the fuel electrode of the present invention can be used to implement high-temperature electrolysis with an electrolyte-supported SOC as the core component, serving as a core device for high-temperature electrolysis of water and carbon dioxide to produce hydrogen, carbon monoxide, and other renewable fuels.

[0126] Although the present invention has been illustrated and described with reference to certain preferred embodiments thereof, it should be understood by those skilled in the art that the above description is provided as a further detailed description of the present invention in conjunction with specific embodiments thereof, and that the specific implementation of the present invention is not limited to these descriptions. Those skilled in the art may make various changes in form and details, including simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a fuel electrode, characterized in that: The following steps are involved: Preparation of an adhesion layer precursor: performing a first calcination on gadolinium-doped cerium oxide to obtain the adhesion layer precursor, wherein the temperature of the first calcination is 1000-1100° C. and the particle size of the gadolinium-doped cerium oxide is selected to be 300-500 nm; Preparation of adhesion layer suspension slurry: mixing the adhesion layer precursor and the binder to form an adhesion layer suspension slurry; Preparation of a functional layer precursor: Nickel oxide and gadolinium-doped cerium oxide are ball-milled and then subjected to a second calcination to obtain the functional layer precursor, wherein the nickel oxide has a particle size of 1 to 2 μm, the gadolinium-doped cerium oxide has a particle size of 300 to 500 nm, the mass ratio of the nickel oxide to the gadolinium-doped cerium oxide is 1 to 2:1, and the temperature of the second calcination is 1000 to 1100°C. Preparation of functional layer suspension slurry: mixing the functional layer precursor, binder and dispersant to form functional layer suspension slurry; Preparation of a collector layer precursor: Nickel oxide and gadolinium-doped cerium oxide are ball-milled and then subjected to a third calcination to obtain the collector layer precursor, wherein the nickel oxide has a particle size of 4 to 5 μm, the gadolinium-doped cerium oxide has a particle size of 300 to 500 nm, the mass ratio of the nickel oxide to the gadolinium-doped cerium oxide is 3 to 5:1, and the temperature of the third calcination is 1000 to 1100°C; Preparation of the collector layer suspension slurry: mixing the collector layer precursor, the binder and the dispersant to form a collector layer suspension slurry; Preparation of a fuel electrode embryo: applying the adhesion layer suspension slurry, the functional layer suspension slurry and the current collecting layer suspension slurry on the electrolyte surface in sequence to obtain a fuel electrode embryo with a three-layer structure of adhesion layer, functional layer and current collecting layer; Preparation of fuel electrode: The fuel electrode embryo body is subjected to a fourth calcination to obtain the fuel electrode, and the temperature of the fourth calcination is 1200-1300°C.

2. The method for preparing a fuel electrode according to claim 1, wherein: In the adhesion layer precursor preparation step, the doping amount of gadolinium in the gadolinium-doped cerium oxide is 0.15~0.3; in the functional layer precursor preparation step, the doping amount of gadolinium in the gadolinium-doped cerium oxide is 0.05~0.15; in the current collecting layer precursor preparation step, the doping amount of gadolinium in the gadolinium-doped cerium oxide is 0.05~0.

15.

3. The method for preparing a fuel electrode according to claim 1, wherein: In the steps of preparing the adhesion layer precursor, preparing the functional layer precursor and preparing the current collecting layer precursor, the duration of the first calcination, the second calcination and the third calcination is 2 to 4 hours, the heating rate and cooling rate of the first calcination, the second calcination and the third calcination are equal, and the heating rate and cooling rate are 2 to 8 ° C / min.

4. The method for preparing a fuel electrode according to claim 1, wherein: The fuel electrode embryo preparation step further includes heating and drying after each coating, wherein the heating and drying temperature is 120-150° C. and the heating and drying time is 1-3 minutes.

5. The method for preparing a fuel electrode according to claim 1, wherein: In the fuel electrode preparation step, the fourth calcination is performed for 2 to 4 hours, and the heating rate and cooling rate of the fourth calcination are equal, and the heating rate and cooling rate are 2 to 8°C / min.

6. The method for preparing a fuel electrode according to claim 1, wherein: In the adhesion layer suspension slurry preparation step, the mass ratio of the adhesion layer precursor to the binder is 1~3:1; in the functional layer suspension slurry preparation step, the mass ratio of the functional layer precursor to the binder is 1~3:1; in the collector layer suspension slurry preparation step, the mass ratio of the collector layer precursor to the binder is 1~3:

1.

7. The method for preparing a fuel electrode according to claim 6, wherein: The binder is ethyl cellulose and diethylene glycol butyl ether acetate; in the adhesion layer suspension slurry preparation step, the ethyl cellulose accounts for 3-5wt% of the binder mass; in the functional layer suspension slurry preparation step and the collector layer suspension slurry preparation step, the ethyl cellulose accounts for 2-4wt% of the binder mass.

8. The method for preparing a fuel electrode according to claim 1, wherein: In the steps of preparing the functional layer suspension slurry and the collector layer suspension slurry, the dispersant accounts for 1-1.5 wt % of the total mass of the functional layer precursor and the binder, and the dispersant accounts for 1-1.5 wt % of the total mass of the collector layer precursor and the binder.

9. The method for preparing a fuel electrode according to claim 8, wherein: The dispersant is FA196.

10. The method for preparing a fuel electrode according to claim 1, wherein: The thickness of the adhesion layer is 6-9 μm, the thickness of the functional layer is 15-20 μm, and the thickness of the current collecting layer is 10-15 μm.

11. The method for preparing a fuel electrode according to claim 1, wherein: The pores formed in the fuel electrode are accumulation pores.

12. The method for preparing a fuel electrode according to claim 2, wherein: The porosity of the formed adhesion layer, the functional layer and the collecting layer satisfies: the porosity of the adhesion layer is less than the porosity of the functional layer and less than the porosity of the collecting layer. The porosity of the adhesion layer is 35% to 42%, the porosity of the functional layer is 46% to 50%, and the porosity of the collecting layer is 53% to 60%.

13. A fuel electrode, characterized in that: The fuel electrode is obtained by the preparation method of any one of claims 1 to 12, wherein the fuel electrode is coated on the surface of the electrolyte, and the fuel electrode comprises an adhesion layer, a functional layer and a current collecting layer in order from the outside relative to the electrolyte; The adhesion layer is located between the electrolyte and the functional layer and includes gadolinium-doped cerium oxide with a particle size of 300 to 500 nm; The functional layer comprises nickel oxide with a particle size of 1 to 2 μm and gadolinium-doped cerium oxide with a particle size of 300 to 500 nm, and the mass ratio of the nickel oxide to the gadolinium-doped cerium oxide is 1 to 2:1; The current collecting layer comprises nickel oxide with a particle size of 4 to 5 μm and gadolinium-doped cerium oxide with a particle size of 300 to 500 nm, wherein the mass ratio of the nickel oxide to the gadolinium-doped cerium oxide is 3 to 5:1; wherein the porosity of the adhesion layer, the functional layer, and the current collecting layer satisfies: The porosity of the adhesion layer is less than the porosity of the functional layer and is less than the porosity of the current collecting layer.

14. The fuel electrode according to claim 13, wherein In the adhesion layer, the doping amount of gadolinium in the gadolinium-doped cerium oxide is 0.15-0.3; in the functional layer, the doping amount of gadolinium in the gadolinium-doped cerium oxide is 0.05-0.15; in the current collecting layer, the doping amount of gadolinium in the gadolinium-doped cerium oxide is 0.05-0.

15.

15. The fuel electrode according to claim 13, wherein The thickness of the adhesion layer is 6-9 μm, the thickness of the functional layer is 15-20 μm, and the thickness of the current collecting layer is 10-15 μm.

16. The fuel electrode according to any one of claims 13 to 15, characterized in that: The pores of the fuel electrode are stacked pores.

17. A solid oxide fuel cell, characterized in that: The fuel electrode comprises the fuel electrode obtained by the preparation method according to any one of claims 1 to 12, or the fuel electrode comprises the fuel electrode according to any one of claims 13 to 16.

18. A solid oxide fuel electrolysis cell, characterized in that: The fuel electrode comprises the fuel electrode obtained by the preparation method according to any one of claims 1 to 12, or the fuel electrode comprises the fuel electrode according to any one of claims 13 to 16.

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