Preparation method of platinum-zirconia porous composite low-temperature catalytic electrode slurry and catalytic electrode

Abstract

The application provides a platinum-zirconia porous composite low-temperature catalytic electrode slurry and a preparation method of a catalytic electrode. The slurry comprises the following components in a weight ratio: 60-70% of platinum powder, 10-20% of an organic precursor, 2-5% of 8YSZ, 5-10% of a pore-forming agent, 2-5% of a metal carbide powder and 10-20% of an organic carrier. The particle size of the platinum powder is 10-200 nm, and the organic precursor is decomposed into a metal or a metal oxide at 700-1000 DEG C. In the application, the organic precursor is decomposed at 700-1000 DEG C, and forms an atomic three-phase interface with the platinum powder and the 8YSZ. In combination with the high dispersibility of the nano platinum powder (10-200 nm), the catalytic response activity at 350 DEG C is increased by 40-50%.

Description

Technical Field

[0001] This invention relates to the field of electronic paste technology, and in particular to a platinum-zirconia porous composite low-temperature catalytic electrode paste and a method for preparing the catalytic electrode. Background Technology

[0002] In engines using three-way catalytic converters to reduce exhaust emissions, oxygen sensors are essential components. Their function is to measure the oxygen content in the exhaust gas after combustion and convert it into a voltage signal, which is then transmitted to the engine computer to achieve closed-loop control targeting the excess air factor. This ensures that the three-way catalytic converter effectively controls hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). X The three pollutants achieve maximum conversion efficiency and are widely used in multiple industries such as petroleum, chemical, automotive, and gas emission monitoring.

[0003] Currently, zirconia-based oxygen sensors function by leveraging the high-temperature ionic conductivity of zirconia and the catalytic properties of platinum. However, as an ionic electrolyte, zirconia requires temperatures above 300°C at the catalytic site to function and output an electrical signal, with the fastest response to changes in the gas mixture occurring at approximately 800°C. Therefore, existing zirconia-based oxygen sensors generally require external heating rods or internal heating wires to reach their normal operating temperature of 700-800°C. This not only consumes a significant amount of electrical energy but also severely impacts the sensor's lifespan. Therefore, reducing the operating temperature is crucial for oxygen sensors.

[0004] However, in the field of low-temperature catalytic electrodes, traditional technologies face numerous bottlenecks:

[0005] Insufficient catalytic activity at low temperatures: Conventional platinum-based electrodes exhibit low catalytic response efficiency in the low-temperature range of 300-400℃, making it difficult to meet the requirements for rapid reactions. This is mainly due to the poor dispersion of platinum particles and insufficient active sites.

[0006] Poor stability of the three-phase interface: The platinum-ion electrolyte-gas three-phase catalytic interface is easily affected by temperature fluctuations. High-temperature sintering (especially for platinum-based electrode materials used as oxygen sensors, where the forming temperature needs to be above 1400℃ when co-firing zirconium oxide with platinum electrodes) can lead to platinum particle agglomeration and electrolyte grain coarsening, which can damage the interface structure. Even for platinum catalytic electrodes formed by post-firing, it is difficult to guarantee the stability of the "zirconia-platinum-gas" nanoporous three-phase interface if the process and composition design are not appropriate.

[0007] Carbon residue and pore defects: Traditional pore-forming agents need to decompose at high temperatures (>400℃), which can easily produce carbon residue that blocks active sites. At the same time, the residual carbon can block the interface bonding between the substrate and the electrode, reduce the bonding force, and affect the electrode's ion conduction and aging performance.

[0008] Therefore, it is necessary to design a platinum-zirconia porous composite low-temperature catalytic electrode slurry and a method for preparing the catalytic electrode to solve the above problems. Summary of the Invention

[0009] The purpose of this invention is to provide a platinum-zirconia porous composite low-temperature catalytic electrode slurry with low sintering temperature and high low-temperature catalytic activity.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: a platinum-zirconia porous composite low-temperature catalytic electrode slurry, comprising the following components in the following weight ratios: 60%-70% platinum powder, 10%-20% organic precursor, 2%-5% 8YSZ, 5%-10% pore-forming agent, 2%-5% metal carbide powder, and 10%-20% organic support, wherein the particle size of the platinum powder is 10-200 nm, and the organic precursor decomposes into metal or metal oxide at 700-1000℃.

[0011] As a further improvement of the present invention, the metal carbide powder is zirconium carbide with a particle size of 200nm-1μm.

[0012] As a further improvement of the present invention, the organic precursor is a mixed powder of rhodium acetylacetone and zirconium acetylacetone, or a mixed powder of rhodium acetylacetone and yttrium acetylacetone.

[0013] As a further improvement of the present invention, in the organic precursor, the weight ratio of rhodium acetylacetone is 40%-60% and the weight ratio of zirconium acetylacetone is 40%-60%.

[0014] As a further improvement of the present invention, the particle size of the pore-forming agent is 200nm-1μm, and the temperature at which the pore-forming agent forms pores in the catalytic electrode is 250-350℃.

[0015] As a further improvement of the present invention, the particle size of the 8YSZ is 200nm-1μm.

[0016] As a further improvement of the present invention, the organic carrier includes acrylic resin and solvent, wherein the solvent is selected from one or more of terpineol, butyl carbitol acetate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and diethylene glycol butyl ether acetate.

[0017] The present invention also aims to provide a method for preparing a platinum-zirconia porous composite low-temperature catalytic electrode, so that the obtained catalytic electrode has high low-temperature catalytic activity.

[0018] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a platinum-zirconia porous composite low-temperature catalytic electrode, comprising the following steps:

[0019] Step 1: Stir the solvent and acrylic resin until they are evenly mixed to obtain an organic carrier;

[0020] Step 2: Mix platinum powder with 8YSZ, ball mill, and dry to obtain platinum-8YSZ premixed powder;

[0021] Step 3: Place the platinum-8YSZ premixed powder, organic precursor, pore-forming agent, metal carbide powder and organic carrier into a homogenizer and homogenize to obtain a slurry semi-finished product;

[0022] Step 4: Transfer the semi-finished slurry obtained in Step 3 into a three-roll mill for grinding and degassing under reduced pressure to obtain the finished slurry;

[0023] Step 5: Print the finished paste onto zirconia ceramic and sinter it.

[0024] As a further improvement of the present invention, in step 5, the sintering temperature is 850-1000℃ for 30-120 minutes, and the working temperature of the catalytic electrode after sintering is 300-400℃.

[0025] As can be seen from the above technical solutions, the platinum-zirconia porous composite low-temperature catalytic electrode slurry of the present invention, through component ratio, particle size control and process optimization, simultaneously solves the problems of low low-temperature activity and poor stability, achieving efficient low-temperature catalysis, specifically including:

[0026] 1. After decomposition at 700-1000℃, rhodium acetylacetonate forms an atomic-level three-phase interface with platinum powder and 8YSZ. Combined with the high dispersibility of nano-platinum powder (10-200nm), the catalytic response activity at 350℃ is increased by 40%-50%. The doping of rhodium acetylacetonate effectively optimizes the catalytic site structure of platinum, enhances the catalytic reaction kinetics at low temperatures, solves the problem of insufficient low-temperature activity of traditional electrodes, and significantly improves low-temperature catalytic activity.

[0027] 2. Nanoparticles such as platinum powder, yttrium-doped zirconium oxide (8YSZ), and zirconium carbide serve as nuclei for the decomposition of acetylacetone-based nanoparticles, promoting uniform distribution of nanoparticles and facilitating the formation of a rough, undulating surface. This not only creates a more stable supporting framework but also increases the number of catalytic active sites and three-phase interfaces. Low-temperature pore-forming agents (polystyrene spheres) can form voids at temperatures as low as 250-350℃, avoiding carbon residue caused by high-temperature pore-forming agents, which affects catalytic activity and interfacial stability. Simultaneously, the sintering temperature of 850-1000℃ reduces platinum particle agglomeration and substrate reaction, significantly improving stability.

[0028] 3. Stepwise ball milling, homogenization and three-roll milling processes ensure uniform mixing of components. Zirconium acetylacetonate / yttrium decomposes into zirconium oxide or yttrium oxide, which can form a bond with the zirconium oxide substrate at temperatures below 1000℃. After decomposition, it forms a strong bond with the zirconium oxide substrate, preventing electrode detachment. Attached Figure Description

[0029] Figure 1 The image shows a scanning electron microscope image of the surface of the sintered sample from Example 1.

[0030] Figure 2 This is a scanning electron microscope image of the surface of the sintered sample of Comparative Example 1.

[0031] Figure 3 This is a scanning electron microscope image of the surface of the sintered sample in Comparative Example 2.

[0032] Figure 4 The current density curves of the electrode samples in Example 1, Comparative Example 1, and Comparative Example 2 are shown under different operating voltages. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] Step 1: Stir terpineol and acrylic resin until homogeneous to obtain an organic carrier;

[0036] Step 2: Mix platinum powder, 8YSZ, water, and zirconia balls, then ball mill, wash, and dry to obtain platinum-8YSZ premixed powder; wherein, the amount of water added is 5 times the total weight of platinum powder and 8YSZ, the amount of zirconia balls added is 5 times the total weight of platinum powder and 8YSZ, the particle size of the zirconia balls is 1.0 mm, and the ball milling time is 25 h;

[0037] Step 3: Homogenize the premixed powder, organic precursor, pore-forming agent, zirconium carbide and organic carrier in a homogenizer for 25 minutes to obtain a slurry semi-finished product;

[0038] Step 4: Add the semi-finished slurry to a three-roll mill for grinding. Adjust the roller gap to 5μm and grind 3 times. Degas under reduced pressure for 15 minutes to obtain the finished slurry A1.

[0039] Step 5: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and the sintering temperature is 900℃ for 60min.

[0040] Slurry A1 is prepared according to the following formula:

[0041] Platinum powder: 60%, particle size 100nm;

[0042] Organic precursor: 15%, a mixed powder of rhodium acetylacetone (50%) and zirconium acetylacetone (50%);

[0043] 8YSZ: 3%, particle size 500nm;

[0044] Pore-forming agent: 8%, polystyrene spheres, particle size 300nm;

[0045] Metal carbide powder: 3%, zirconium carbide, particle size 500nm;

[0046] Organic carrier: 11%, containing acrylic resin (13%) and terpineol (87%).

[0047] Example 2

[0048] Steps 1-4 are the same as in Example 1, the difference being the different components and their amounts, please refer to Table 1 for details;

[0049] Step 5: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and the sintering temperature is 900℃ for 90min.

[0050] Slurry A2 is prepared according to the following formula:

[0051] Platinum powder: 65%, particle size 100nm;

[0052] Organic precursor: 10%, a mixed powder of rhodium acetylacetone (45%) and yttrium acetylacetone (55%);

[0053] 8YSZ: 4%, particle size 800nm;

[0054] Pore-forming agent: 6%, in the form of polystyrene spheres with a particle size of 800 nm;

[0055] Metal carbide powder: 4%, zirconium carbide, particle size 1μm;

[0056] Organic carrier: 11%, containing acrylic resin (15%) and terpineol (85%).

[0057] Example 3

[0058] Steps 1-4 are the same as in Example 1, the difference being the different components and their amounts, please refer to Table 1 for details;

[0059] Step 5: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and sintered at 850℃ for 90min.

[0060] Slurry A3 is prepared according to the following formula:

[0061] Platinum powder: 70%, particle size 200nm;

[0062] Organic precursor: 10%, a mixed powder of rhodium acetylacetone (60%) and zirconium acetylacetone (40%);

[0063] 8YSZ: 2%, particle size 200nm;

[0064] Pore-forming agent: 5%, in the form of polystyrene spheres with a particle size of 1μm;

[0065] Metal carbide powder: 2%, zirconium carbide, particle size 200nm;

[0066] Organic carrier: 11%, containing acrylic resin (15%) and terpineol (85%).

[0067] Example 4

[0068] Steps 1-4 are the same as in Example 1, the difference being the different components and their amounts, please refer to Table 1 for details;

[0069] Step 5: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and the sintering temperature is 900℃ for 90min.

[0070] Slurry A4 is prepared according to the following formula:

[0071] Platinum powder: 60%, particle size 10nm;

[0072] Organic precursor: 10%, a mixed powder of rhodium acetylacetone (40%) and yttrium acetylacetone (60%);

[0073] 8YSZ: 5%, particle size 1μm;

[0074] Pore-forming agent: 5%, in the form of polystyrene spheres with a particle size of 200 nm;

[0075] Metal carbide powder: 5%, zirconium carbide, particle size 1μm;

[0076] Organic carrier: 15%, containing acrylic resin (15%) and terpineol (85%).

[0077] Comparative Example 1

[0078] Step 1, same as in Example 1;

[0079] Step 2: Homogenize the platinum powder, pore-forming agent, zirconium carbide and organic carrier in a homogenizer for 25 minutes to obtain a slurry semi-finished product;

[0080] Step 3: Add the semi-finished slurry to a three-roll mill for grinding. Adjust the roller gap to 5μm and grind 3 times. Degas under reduced pressure for 15 minutes to obtain the finished slurry B1.

[0081] Step 4: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and sintered at 850℃ for 90min.

[0082] Slurry B1 is prepared according to the following weight ratio:

[0083] Platinum powder: 70%, particle size 50nm;

[0084] 8YSZ: 3%, particle size 500nm;

[0085] Pore-forming agent: 8%, polystyrene spheres, particle size 300nm;

[0086] Metal carbide powder: 3%, zirconium carbide, particle size 500nm;

[0087] Organic carrier: 16%, containing acrylic resin (13%) and terpineol (87%).

[0088] Comparative Example 2

[0089] Step 1, same as in Example 1;

[0090] Step 2, same as in Example 1;

[0091] Step 3: Homogenize the premixed powder, organic precursor, pore-forming agent, zirconium carbide and organic carrier in a homogenizer for 25 minutes to obtain a slurry semi-finished product;

[0092] Step 4: Add the semi-finished slurry to a three-roll mill for grinding. Adjust the roller gap to 5μm and grind 3 times. Degas under reduced pressure for 15 minutes to obtain the finished slurry B2.

[0093] Step 5: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and sintered at 850℃ for 90min.

[0094] Slurry B2 is prepared according to the following formula:

[0095] Platinum powder: 60%, particle size 100nm;

[0096] Organic precursor: 15%, a mixed powder of rhodium acetylacetone (50%) and zirconium acetylacetone (50%);

[0097] 8YSZ: 3%, particle size 500nm;

[0098] Pore-forming agent: 8%, carbon powder, particle size 300nm;

[0099] Metal carbide powder: 3%, zirconium carbide, particle size 500nm;

[0100] Organic carrier: 11%, containing acrylic resin (13%) and terpineol (87%).

[0101] Comparative Example 3

[0102] Step 1, same as in Example 1;

[0103] Step 2, same as in Example 1;

[0104] Step 3: Homogenize the premixed powder, pore-forming agent, and organic carrier in a homogenizer for 25 minutes to obtain a slurry semi-finished product;

[0105] Step 4: Add the semi-finished slurry to a three-roll mill for grinding. Adjust the roller gap to 5μm and grind 3 times. Degas under reduced pressure for 15 minutes to obtain the finished slurry B2.

[0106] Step 5: The paste is screen-printed onto the zirconia ceramic to a thickness of 100μm, and sintered at 850℃ for 90min.

[0107] Slurry B2 is prepared according to the following formula:

[0108] Platinum powder: 65%, particle size 300nm;

[0109] 8YSZ: 5%, particle size 500nm;

[0110] Pore-forming agent: 5%, carbon powder, particle size 300nm;

[0111] Organic carrier: 25%, containing acrylic resin (13%) and terpineol (87%).

[0112] Performance tests were conducted on the slurry samples after sintering from Examples 1-4 and Comparative Examples 1-3:

[0113] Determination of catalytic activity at 350℃: The sintered electrode sample was placed in a tube furnace and heated to 350℃. The initial catalytic activity of the electrode sample was assessed by measuring the response time of the electrode to oxygen. Specifically, the IV curve of the sample was measured by connecting the leads at both ends of the electrode sample to an IV analyzer. The results are available in the [reference needed]. Figure 4 Table 2 shows the current density of the electrodes in each embodiment and comparative example at a voltage of 300mV.

[0114] 100h stability test: After using the electrodes from Examples 1-4 and Comparative Examples 1-3 in simulated application scenarios for 100h, the catalytic activity of the electrodes was measured again; the comparison results of the catalytic activity after 100h with the initial activity are shown in Table 2.

[0115] Table 1 Comparison of component parameters in Examples 1-4 and Comparative Examples 1-3

[0116]

[0117] Table 2 Comparison of test data in Examples 1-4 and Comparative Examples 1-3

[0118]

[0119] Considering the differences in slurry composition and content, and the role of organic precursors and other components in the sintering process, the electrode test results of the examples and comparative examples differ, specifically as follows:

[0120] 1. Differences in catalytic activity

[0121] The catalytic activity (at 300 mV) of Examples 1-4 at 350 °C was 8.41-8.56 (mA / cm²). 2 ), compared with conventional processes (Comparative Example 3, 5.74 (mA / cm) 2 Compared to the control group, the catalytic activity can be improved by 40%-50%. The catalytic activity of Comparative Example 1 was 8.05 (mA / cm²). 2 The catalytic activity of Comparative Example 2 was 7.41 (mA / cm). 2 Because the examples contain organic precursors such as rhodium acetylacetonate, which decompose to form an atomic-level three-phase interface, combined with the high dispersibility of nano-platinum powder, the structure of the platinum catalytic sites is optimized (please refer to...). Figure 1 The SEM image of Example 1 shows bright spots (nanocatalytic dots representing the decomposition of organic precursors), enhancing low-temperature catalytic activity; please refer to... Figure 2 As shown, Comparative Example 1 lacked nanocatalytic points generated by the decomposition of organic precursors due to the absence of added organic precursors, resulting in relatively low catalytic activity. Comparative Example 2 had a high decomposition temperature of the pore-forming agent, which affected catalytic activity. In contrast, Comparative Example 3 lacked both organic precursors and had a high decomposition temperature of the pore-forming agent, which combined to significantly reduce catalytic activity.

[0122] 2. Differences in pore uniformity

[0123] according to Figure 1-3 As can be seen from the SEM images and Table 2, the pore uniformity in Examples 1-4 and Comparative Example 1 is relatively good, while the uniformity of pore size, the number and uniformity of active sites in Comparative Examples 2 and 3 are poor. Therefore, using polystyrene microspheres as a pore-forming agent allows for controllable particle size and facilitates uniform pore formation; the decomposition characteristics of the pore-forming agent (carbon powder) in Comparative Examples 2 and 3 lead to pore non-uniformity; and good pore uniformity is beneficial to improving catalytic activity, stability and other properties.

[0124] Please refer to Figure 4As shown, the slope of the curve in Example 1 is greater than that in Comparative Examples 1 and 2. At another voltage point (e.g., V = 300mV), the current density in Example 1 is higher; at the same voltage, the current density in Example 1 is consistently higher than that in Comparative Examples 1 and 2. This further demonstrates that the catalytic activity of the examples is higher than that of the comparative examples.

[0125] 3. Stability Analysis

[0126] The 100-hour stability test results showed that the samples in the examples still retained high catalytic activity (over 85%) after 100 hours of application, while the catalytic activity of the comparative examples decreased significantly, especially that of Comparative Example 3. This indicates that the use of appropriate pore-forming agents in the examples avoided carbon residue, achieved better pore uniformity and pore size at lower sintering temperatures, and reduced platinum agglomeration and substrate reaction. Comparative Examples 1 and 3 lacked organic precursors and had poor structural stability. In contrast, the pore-forming agents (carbon powder) in Comparative Examples 2 and 3 may have decomposed and left residues, affecting stability.

[0127] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. The understanding of this specification should be based on those skilled in the art. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still make modifications or equivalent substitutions to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A platinum-zirconia porous composite low-temperature catalytic electrode slurry, characterized in that: The slurry comprises the following components in the indicated weight ratios: 60%-70% platinum powder, 10%-20% organic precursor, 2%-5% 8YSZ, 5%-10% pore-forming agent, 2%-5% metal carbide powder, and 10%-20% organic support. The platinum powder has a particle size of 10-200 nm. The organic precursor decomposes into a metal or metal oxide at 700-1000℃. The organic precursor is a mixed powder of rhodium acetylacetone and zirconium acetylacetone, or a mixed powder of rhodium acetylacetone and yttrium acetylacetone. The 8YSZ has a particle size of 200 nm-1 μm. The pore-forming agent has a particle size of 200 nm-1 μm, and the temperature at which the pore-forming agent forms pores in the catalytic electrode is 250-350℃. The metal carbide powder is zirconium carbide with a particle size of 200 nm-1 μm. The slurry is prepared according to the following steps: Step 1: Stir the solvent and acrylic resin until they are evenly mixed to obtain an organic carrier; Step 2: Mix platinum powder with 8YSZ, ball mill, and dry to obtain platinum-8YSZ premixed powder; Step 3: Place the platinum-8YSZ premixed powder, organic precursor, pore-forming agent, metal carbide powder and organic carrier into a homogenizer and homogenize to obtain a slurry semi-finished product; Step 4: Transfer the semi-finished slurry obtained in Step 3 into a three-roll mill for grinding and degassing under reduced pressure to obtain the finished slurry.

2. The platinum-zirconia porous composite low-temperature catalytic electrode slurry as described in claim 1, characterized in that: In the organic precursor, the weight ratio of rhodium acetylacetone is 40%-60%, and the weight ratio of zirconium acetylacetone is 40%-60%.

3. The platinum-zirconia porous composite low-temperature catalytic electrode slurry as described in claim 1, characterized in that: The organic carrier includes an acrylic resin and a solvent, wherein the solvent is selected from one or more of terpineol, butyl carbitol acetate, diethylene glycol butyl ether, diethylene glycol ethyl ether, and diethylene glycol butyl ether acetate.

4. A method for preparing a platinum-zirconia porous composite low-temperature catalytic electrode using the slurry as described in any one of claims 1-3, characterized in that: Includes the following steps: The paste is printed onto zirconia ceramic and then sintered.

5. The method for preparing the platinum-zirconia porous composite low-temperature catalytic electrode as described in claim 4, characterized in that: The sintering temperature is 850-1000℃, the sintering time is 30-120min, and the working temperature of the catalytic electrode after sintering is 300-400℃.

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