Process for the preparation of an oxygen pump electrode and oxygen pump electrode

Abstract

The application provides a preparation method of an oxygen pump electrode and the oxygen pump electrode. The preparation method of the oxygen pump electrode comprises the following steps: brushing a composite electrode slurry on a solid electrolyte substrate, the composite electrode slurry being an ion-electron mixed conductor material; performing first sintering on the solid electrolyte substrate after the brushing of the composite electrode slurry, so as to form a composite electrode layer; brushing a metal slurry on the composite electrode layer, connecting an electrode lead wire with the metal slurry; performing second sintering on the solid electrolyte substrate after the brushing of the metal slurry, so as to form a metal electrode layer, and obtaining the oxygen pump electrode. According to the scheme of the application, the multi-layer electrode structure is realized by twice sintering, the oxygen reduction rate is improved, the penetration rate of oxygen ions is increased, and the efficiency of the oxygen pump at a lower working temperature is improved, thereby providing a basis for the wide application of the oxygen pump oxygen control on the fourth-generation lead-based stack coolant.

Description

Technical Field

[0001] This invention relates to electrode fabrication technology, and in particular to a liquid lead-bismuth alloy oxygen sensor. Background Technology

[0002] Fourth-generation lead-based reactors use liquid lead-bismuth eutectic alloys or liquid lead metal as coolants, offering significant advantages such as high safety, ease of miniaturization, good economy, and feasibility. However, these coolants are prone to causing severe corrosion to reactor structural materials during use and can also easily lead to blockages in the reactor coolant loop. These problems need to be addressed using oxygen control technology based on liquid metals.

[0003] When the oxygen partial pressure in liquid lead-based alloys is lower than that required for the oxidation reaction, oxides cannot be formed, and the structural material exhibits dissolution corrosion. Conversely, when the oxygen partial pressure in the liquid metal increases to a level exceeding that required for the oxidation reaction, an oxide film forms on the surface of the structural material. If the oxygen concentration in the liquid lead-bismuth alloy is too high, it can induce the formation of Pb and Bi oxide impurities. In severe cases, these oxide impurities can clog the coolant circuit, and excessively high oxygen concentrations can also accelerate the oxidation corrosion of the material, causing serious damage. By controlling the oxygen concentration in the liquid metal, a uniform oxide film can be formed on the surface of the structural material. This oxide film can then isolate the structural material from the liquid metal, effectively controlling the corrosion problem caused by the liquid metal.

[0004] Currently, oxygen control technology in liquid metals can be classified into three categories according to the medium and method of implementation: gas phase oxygen control, solid phase oxygen control, and oxygen pump oxygen control.

[0005] Gas-phase oxygen control involves introducing a fixed proportion of mixed gas (e.g., H2 / O2 / Ar, H2 / H2O / Ar, or CO / CO2) into liquid metal, allowing for chemical reactions at the gas / liquid interface to control the oxygen concentration in liquid lead-bismuth. However, gas-phase oxygen control methods suffer from drawbacks such as slow reaction rates, difficulty in precisely controlling oxygen concentration, high requirements for system sealing, and the potential for oxide scum formation over prolonged use. Furthermore, its application in nuclear systems generates radioactive gaseous waste.

[0006] Solid-phase oxygen control utilizes the dissolution and precipitation of solid lead oxide in liquid lead-based metals to regulate oxygen concentration. This method places high demands on the design of the mass exchanger, requires high mechanical properties of the lead oxide particles, and must prevent lead oxide poisoning. Furthermore, it is difficult to replace oxides or hydrides in the mass exchanger online once they are depleted.

[0007] Oxygen pump oxygen control is an oxygen control method that uses an applied voltage to directionally and quantitatively transport oxygen ions from one side of a solid electrolyte to the other, based on Faraday's law. Currently, the oxygen pump oxygen control method is still in its early stages of research. The oxygen pump's oxygen ion transport efficiency is relatively low, especially at low temperatures where the ionic conductivity of the solid electrolyte is greatly reduced, severely affecting its application in low-temperature environments (e.g., below 200°C).

[0008] Electrodes are extremely important components in oxygen pump oxygen control technology, as they directly affect the oxygen reduction rate. Existing electrodes cannot meet the requirements of oxygen pump oxygen control technology in liquid metal coolants. Summary of the Invention

[0009] One object of the present invention is to provide an oxygen pump electrode and a method for preparing the same, which improves the oxygen ion transport efficiency of an oxygen pump.

[0010] A further objective of this invention is to meet the performance requirements of the electrodes in oxygen pump oxygen control technology.

[0011] In particular, the present invention provides a method for preparing an oxygen pump electrode, comprising:

[0012] A composite electrode slurry is brushed onto a solid electrolyte substrate. The composite electrode slurry is an ion-electron hybrid conductor material.

[0013] The solid electrolyte substrate after being coated with composite electrode slurry is sintered for the first time to form a composite electrode layer;

[0014] Apply metal paste to the composite electrode layer and connect the electrode leads to the metal paste.

[0015] The solid electrolyte substrate after being coated with metal slurry is sintered a second time to form a metal electrode layer, thus obtaining the oxygen pump electrode.

[0016] Optionally, the ion-electron hybrid conductor material is a mixture of LSM and YSZ, and the solid electrolyte matrix is ​​made of YSZ material.

[0017] Optionally, the step of first sintering the solid electrolyte substrate after applying the composite electrode slurry includes:

[0018] Heat to a first target temperature at a first heating rate and maintain the temperature for a first set time;

[0019] The temperature is heated to a second target temperature at a second heating rate and held at that temperature for a second set time, wherein the second heating rate is greater than the first heating rate;

[0020] The temperature is lowered to ambient temperature at the first cooling rate to complete the first sintering.

[0021] Optionally, the range of the first heating rate is 10 to 50℃ / h, the range of the second heating rate is 50 to 150℃ / h, and the range of the first cooling rate is 50 to 150℃ / h.

[0022] The first target temperature ranges from 300℃ to 700℃, and the second target temperature ranges from 1000℃ to 1500℃; the first set duration ranges from 1 to 7 hours, and the second target temperature ranges from 0.5 hours to 4 hours.

[0023] Optionally, the metal paste is made of platinum, and the electrode leads are made of any of the following materials: platinum, gold, silver, copper, molybdenum, tantalum, or stainless steel.

[0024] Optionally, the step of performing a second sintering on the solid electrolyte matrix after brushing with metal slurry includes:

[0025] Heat to the third target temperature at the third heating rate, and maintain the temperature for the third set time;

[0026] Cool down to ambient temperature to complete the second sintering.

[0027] Optionally, the third heating rate ranges from 10 to 60℃ / min, the third target temperature ranges from 500 to 1000℃, and the third set duration ranges from 0.5h to 2h.

[0028] Optionally, the step of brushing the composite electrode slurry onto the solid electrolyte substrate includes: uniformly brushing the composite electrode slurry onto the solid electrolyte substrate multiple times, so that the composite electrode slurry on the solid electrolyte substrate reaches a preset electrode slurry amount.

[0029] The step of brushing metal paste onto the composite electrode layer includes: brushing metal paste evenly onto the composite electrode layer multiple times, so that the composite electrode paste on the composite electrode layer reaches the preset amount of metal paste.

[0030] Optionally, the composite electrode layer forms a loose porous structure.

[0031] In particular, according to another aspect of the invention, a method for preparing an oxygen pump electrode using any of the above-described methods is also provided.

[0032] The oxygen pump electrode preparation method of the present invention utilizes two sintering processes to achieve a multilayer electrode structure. By increasing the number of three-phase reaction sites (TPB), the oxygen reduction rate is improved, thereby increasing the oxygen ion penetration rate and thus improving the efficiency of the oxygen pump at lower operating temperatures. This provides a foundation for the widespread application of oxygen pump oxygen control in fourth-generation lead-based reactor coolants.

[0033] Furthermore, the preparation method of the oxygen pump electrode of the present invention improves the electrode material by using a mixture of LSM and YSZ to prepare a composite electrode layer and using metal materials such as Pt to prepare a metal electrode layer, thus preparing a multi-layered oxygen pump electrode. The bottom layer is a dense YSZ solid electrolyte, the middle layer is a loose and porous composite electrode layer, and the top layer is a metal electrode layer. This allows electrons to be guided to the middle layer more efficiently, enabling a large number of oxygen ions to undergo oxygen reduction reaction in the middle layer.

[0034] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0035] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0036] Figure 1 This is a schematic diagram of a method for preparing an oxygen pump electrode according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of a method for preparing an oxygen pump electrode according to another embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of a reaction in which an electrochemical oxygen pump controls the oxygen concentration in liquid metal.

[0039] Figure 4 This is a schematic diagram of the oxygen reaction region of an existing monolayer PT electrode;

[0040] Figure 5 yes Figure 4 An enlarged view of region A shown below;

[0041] Figure 6 This is a schematic diagram of the reaction region of an oxygen pump electrode according to one embodiment; and

[0042] Figure 7 yes Figure 6 An enlarged view of region B shown. Detailed Implementation

[0043] Figure 1 This is a schematic diagram of a method for preparing an oxygen pump electrode according to an embodiment of the present invention. The method for preparing the oxygen pump electrode in this embodiment generally includes the following steps:

[0044] Step S101: A composite electrode slurry is brushed onto a solid electrolyte substrate. The composite electrode slurry is an ion-electron hybrid conductor material. The ion-electron hybrid conductor material is a perovskite-structured La... 1-x Sr x MnO 3-δ A composite electrode slurry containing a mixture of LSM (x can range from 0.2 to 0.8, abbreviated as LSM) and partially yttrium-stabilized zirconium oxide (YSZ), with the solid electrolyte matrix made of YSZ material. The mixing ratio of LSM and YSZ in the composite electrode slurry can be adjusted. In some optional embodiments, a composite electrode slurry containing only LSM can also be used. The mixing ratio of LSM and YSZ in the composite electrode slurry can be adjusted, and the ratio range can be from 9:1 to 1:1, for example, 9:1, 5:1, 1:1, etc. In some optional embodiments, a composite electrode slurry containing only LSM can also be used.

[0045] A solid electrolyte substrate can be fabricated into a solid electrolyte tube, and a composite electrode slurry can be repeatedly applied to the bottom of the solid electrolyte tube. In other words, the step of applying the composite electrode slurry to the solid electrolyte substrate can include: uniformly applying the composite electrode slurry multiple times to achieve a predetermined amount of slurry on the solid electrolyte substrate. For example, a predetermined amount of composite electrode slurry can be pre-applied and repeatedly brushed onto the bottom of a sealed YSZ solid electrolyte tube several times.

[0046] Step S102 involves first sintering the solid electrolyte substrate after applying the composite electrode slurry to form a composite electrode layer. The first sintering may include three stages: a first heating stage, heating to a first target temperature at a first heating rate and holding at that temperature for a first set time; a second heating stage, heating to a second target temperature at a second heating rate and holding at that temperature for a second set time, wherein the second heating rate is greater than the first heating rate; and a cooling stage, cooling to ambient temperature at a first cooling rate to complete the first sintering. In some embodiments, the parameters in the first sintering process are as follows: the first heating rate ranges from 10 to 50 °C / h (e.g., 20 to 40 °C / h), the second heating rate ranges from 50 to 150 °C / h (e.g., 80 to 120 °C / h), and the first cooling rate ranges from 50 to 150 °C / h (e.g., 80 to 120 °C / h); the first target temperature ranges from 300 °C to 700 °C (e.g., 400 to 600 °C / h), and the second target temperature ranges from 1000 °C to 1500 °C (e.g., 1200 to 1300 °C / h); the first set time ranges from 1 to 7 h (e.g., 3 to 5 h), and the second target temperature ranges from 0.5 h to 4 h (e.g., 1.5 to 3 h). The sintered composite electrode layer forms a loose, porous structure.

[0047] Regarding the values ​​of the first heating rate and the first target temperature, as well as the coordination between the second heating rate and the second target temperature, in some embodiments, a higher selected heating rate allows for a higher target temperature. Correspondingly, a lower holding temperature can be set.

[0048] Step S103: Apply metal paste to the composite electrode layer and connect the electrode leads to the metal paste. The metal paste is made of platinum, and the electrode leads are made of any of the following materials: platinum, gold, silver, copper, molybdenum, tantalum, or stainless steel. The process of applying the metal paste can be as follows: apply the metal paste evenly to the composite electrode layer multiple times until the composite electrode paste on the composite electrode layer reaches the preset amount.

[0049] Step S104 involves a second sintering of the solid electrolyte substrate coated with the metal slurry to form a metal electrode layer, resulting in an oxygen pump electrode. The second sintering process of the solid electrolyte substrate coated with the metal slurry may include: heating at a third heating rate to a third target temperature and holding at that temperature for a third set time; then cooling to ambient temperature to complete the second sintering. The third heating rate can range from 10 to 60°C / min (e.g., 30 to 40°C / min), the third target temperature can range from 500 to 1000°C (e.g., 700 to 800°C), and the third set time can range from 0.5 h to 2 h (e.g., 1 to 1.5 h). The values ​​of the third heating rate and the third target temperature are coordinated; in some embodiments, a higher heating rate allows for a higher target temperature.

[0050] The oxygen pump electrode fabrication method of this embodiment utilizes a multilayer electrode structure achieved through two sintering processes. By increasing the number of three-phase reaction sites (TPBs), the oxygen reduction rate is improved, thereby increasing the oxygen ion penetration rate and thus improving the efficiency of the oxygen pump at lower operating temperatures.

[0051] Figure 2 This is a schematic diagram of a method for preparing an oxygen pump electrode according to another embodiment of the present invention. The method for preparing the oxygen pump electrode includes the following steps:

[0052] Step S201: Take a certain amount of composite electrode slurry of LSM and YSZ mixed material and brush it several times on the bottom of the YSZ solid electrolyte tube that is closed at one end.

[0053] Step S202: The YSZ solid electrolyte tube coated with composite electrode slurry is sintered in air atmosphere. The temperature is increased from ambient temperature to 300℃ to 700℃ at a heating rate of 10 to 50℃ / h and held for 1 to 7 hours. Then the temperature is increased to 1000℃ to 1500℃ at a heating rate of 50 to 150℃ / h and held for 0.5 to 4 hours. Finally, the temperature is decreased to ambient temperature (e.g., 20℃) at a cooling rate of 50 to 150℃ / h.

[0054] Step S203: Take a certain amount of platinum metal slurry and brush it evenly several times on the YSZ solid electrolyte tube after the first sintering.

[0055] Step S204: Connect the Pt electrode with Pt metal electrode leads;

[0056] In step S205, the solid electrolyte tube coated with Pt slurry and connected with Pt metal electrodes is sintered in an air atmosphere, heated from ambient temperature to 500-1000℃ at a rate of 10-60℃ / min, then held at that temperature for 0.5-2 hours, and then cooled to ambient temperature in the furnace.

[0057] The oxygen pump electrode preparation method of the above embodiment provides parameter ranges for brushing slurry and sintering. According to actual tests, the above parameter range can ensure that the prepared oxygen pump electrode achieves the required performance.

[0058] This embodiment also provides an oxygen pump electrode, which is made by the oxygen pump electrode preparation method of the above embodiment. The bottom layer of the oxygen pump electrode is a dense YSZ solid electrolyte, the middle layer is a loose and porous composite electrode layer, and the top layer is a metal electrode layer. This allows electrons to be guided to the middle layer more efficiently, so that a large number of oxygen ions can undergo oxygen reduction reaction in the middle layer.

[0059] The main improvement of the oxygen pump electrode in this embodiment lies in its multi-layer electrode structure. By increasing the number of triple phase bounding sites (TPBs), the efficiency of the oxygen pump at low temperatures is improved. In contrast, existing oxygen pumps use a single-layer electrode structure (such as a single platinum layer or a single other electrode material).

[0060] The oxygen pump electrode in this embodiment is applied to an electrochemical oxygen pump. Utilizing the principle of an electrochemical electrolytic cell, the flow of oxygen ions in the solid electrolyte is controlled by applying an external voltage in a certain direction, thereby adjusting the oxygen concentration at both the anode and cathode of the solid electrolyte.

[0061] Figure 3 This is a schematic diagram illustrating the reaction of an electrochemical oxygen pump controlling the oxygen concentration in liquid metal. Taking a liquid lead-bismuth eutectic alloy as an example, when the electrode material is Pt, the reactions occurring at the cathode during oxygen supplementation include:

[0062] Reaction (1): O2，air →O 2，ad ;

[0063] Reaction (2): O 2，ad →2O atm，ad ;

[0064] Reaction (3): O atm，ad →O 2，TPB ;

[0065] Reaction (4): O 2，TPB +2e - ，TPB →O 2- ，TPB ;

[0066] Reaction (5): O 2- ，TPB →O 2- ，lattice ;

[0067] Reaction (4) occurs at the Pt electrode / YSZ / air three-phase interface, which is also called the three-phase reaction site (TPB).

[0068] Figure 4 This is a schematic diagram of the oxygen reaction region of an existing monolayer PT electrode. Figure 5 yes Figure 4 The enlarged view of region A is shown. In contrast, Figure 6 This is a schematic diagram of the reaction region of an oxygen pump electrode according to one embodiment. Figure 7 yes Figure 6 The image shows an enlarged view of region B. As can be seen from the figure, when the oxygen pump electrode is a single-layer Pt structure, the TPB region is very small, and there are fewer three-phase reaction sites, which greatly reduces the oxygen reduction reaction rate and also decreases the oxygen ion penetration rate. In contrast, the multilayer oxygen pump electrode of this embodiment adds a hybrid composite electrode layer on the YSZ substrate, significantly increasing the number of TPBs, improving the oxygen reduction rate, and thus increasing the oxygen ion penetration rate.

[0069] In some alternative embodiments, the mixture of LSM and YSZ can be replaced with other ionic conductors, such as 5% YSZ, 8% YSZ, 6ScSZ, 10ScSZ, CGO, LSCF, etc., while the metal paste, in addition to Pt, can also be Pt, NiO, Cu, Au, Ag, LSM, etc. The electrode leads can also be other metallic electrode leads, including but not limited to Pt wires, Au wires, Ag wires, Cu wires, stainless steel leads (316L, 304, etc.), Mo wires, Ta wires, etc.

[0070] Those skilled in the art should understand that the sintering method provided in this embodiment is for illustrative purposes only, and the electrode obtained by sintering it can achieve superior performance. Other sintering processes that sinter slurry onto a solid electrolyte can also produce similar electrode structures, but the performance will be somewhat reduced. Actual testing shows that the oxygen pump electrode provided in this embodiment, by increasing the number of three-phase reaction sites (TPBs), improves the oxygen reduction rate, thereby increasing the oxygen ion penetration rate and improving the efficiency of the oxygen pump at lower operating temperatures.

[0071] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A method for preparing an oxygen pump electrode, comprising: A composite electrode slurry is brushed onto a solid electrolyte substrate. The composite electrode slurry is an ion-electron hybrid conductor material, which is a mixture of LSM and YSZ. The solid electrolyte substrate is made of YSZ material. Heat to a first target temperature at a first heating rate and maintain the temperature for a first set time; The material is heated to a second target temperature at a second heating rate and held at that temperature for a second set time, wherein the second heating rate is greater than the first heating rate; then cooled to ambient temperature at a first cooling rate to complete the first sintering, thereby forming a composite electrode layer; wherein the first heating rate ranges from 10 to 50°C / h, the second heating rate ranges from 50 to 150°C / h, and the first cooling rate ranges from 50 to 150°C / h; the first target temperature ranges from 300°C to 700°C, and the second target temperature ranges from 1000°C to 1500°C; the first set time ranges from 1 to 7 hours, and the second target temperature ranges from 0.5 hours to 4 hours; A metal paste is brushed onto the composite electrode layer, and the electrode leads are connected to the metal paste. The solid electrolyte substrate, after being coated with the metal slurry, is subjected to a second sintering to form a metal electrode layer, thereby obtaining the oxygen pump electrode.

2. The method for preparing the oxygen pump electrode according to claim 1, wherein, The metal paste is made of platinum, and the electrode leads are made of any one of the following materials: platinum, gold, silver, copper, molybdenum, tantalum, or stainless steel.

3. The method for preparing the oxygen pump electrode according to claim 2, wherein, The step of performing a second sintering on the solid electrolyte matrix after brushing with the metal slurry includes: Heat to the third target temperature at the third heating rate, and maintain the temperature for the third set time; Cool down to ambient temperature to complete the second sintering.

4. The method for preparing the oxygen pump electrode according to claim 3, wherein, The third heating rate ranges from 10 to 60°C / min, the third target temperature ranges from 500 to 1000°C, and the third set duration ranges from 0.5h to 2h.

5. The method for preparing the oxygen pump electrode according to claim 1, wherein, The step of brushing the composite electrode slurry onto the solid electrolyte substrate includes: uniformly brushing the composite electrode slurry onto the solid electrolyte substrate multiple times, so that the composite electrode slurry on the solid electrolyte substrate reaches a preset electrode slurry amount; The step of brushing the metal paste onto the composite electrode layer includes: uniformly brushing the metal paste onto the composite electrode layer multiple times, so that the composite electrode paste on the composite electrode layer reaches a preset amount of metal paste.

6. The method for preparing the oxygen pump electrode according to claim 1, wherein, The composite electrode layer forms a loose, porous structure.

7. An oxygen pump electrode, manufactured using the method for preparing an oxygen pump electrode according to any one of claims 1 to 6.

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