Preparation method and application of a porous ceramic substrate electrochemical gas sensor

Abstract

The application discloses a preparation method and application of a porous ceramic substrate electrochemical gas sensor, and the method comprises the following steps: pressing Fe, Mn and Al2O3 composite ceramic powder into a porous ceramic blank, and firing to obtain a porous FeMn@Al2O3 ceramic substrate; printing platinum paste on the FeMn@Al2O3 ceramic substrate, and sintering to obtain a porous electrochemical gas sensor substrate; dotting catalyst slurry on working electrodes and counter electrodes on the modified porous electrochemical gas sensor substrate, uniformly coating pretreated nafion solution on surfaces of the working electrodes and the counter electrodes after drying, and drying and solidifying to form a proton exchange membrane; dotting dilute sulfuric acid solution on the proton exchange membrane, and sealing one side of the whole electrode by using silica sol, so that the porous ceramic substrate electrochemical gas sensor is obtained. The electrochemical gas sensor has the advantages of good selectivity, high stability, simple preparation, low cost, strong adaptability, environmental friendliness and the like.

Description

Technical Field

[0001] This invention relates to the field of electrochemical gas sensor technology, specifically to a method for preparing and applying a porous ceramic substrate electrochemical gas sensor. Background Technology

[0002] The basic structure of an electrochemical gas sensor includes components such as a diffusion hole, a dustproof film, an electrode film, a working electrode, a reference electrode, a counter electrode, an electrolyte, and a packaging shell. Currently, most commercially available electrochemical gas sensors use ceramic substrates such as Al2O3 (alumina) and YSZ (yttrium-stabilized zirconium oxide), typically designed as a chip structure. A typical example of this type of sensor is the ES1-AG1-10000 All Gas sensor developed by EC Sense in Germany. This sensor uses an alumina ceramic substrate, with laser-drilled holes on the back side of the substrate to create gas diffusion holes, allowing the target gas to reach the electrode surface and undergo electrochemical oxidation and reduction reactions. Furthermore, patent (CN117665069 A) discloses an electrochemical gas sensor that uses an electrochemical etching method to create a porous structure in the working electrode, ultimately increasing the sensing current density and enhancing its performance.

[0003] Humidity is one of the most significant factors affecting the lifespan of existing electrochemical gas sensors. The ideal operating conditions for electrochemical gas sensors are 20%-60% relative humidity. Too low a humidity level causes the internal electrolyte to dry out, affecting response time. Conversely, too high a relative humidity level dilutes the electrolyte, impacting sensor performance and even causing pin corrosion. Furthermore, existing electrochemical gas sensors suffer from zero-point drift, necessitating frequent sensor replacements and resulting in a short lifespan. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a porous ceramic substrate electrochemical gas sensor, which changes the original packaging form of electrochemical gas sensors. In addition to having a high-strength structure, the ceramic substrate also has hydrophobic and gas-permeable functions, which greatly improves the stability and service life of electrochemical sensing and reduces production costs.

[0005] In one aspect of the present invention, a method for fabricating an electrochemical gas sensor on a porous ceramic substrate is provided. According to an embodiment of the present invention, the method includes the following steps:

[0006] (1) Mix alumina, starch and deionized water and ball mill them. Then add MnO, Fe2O3, methylcellulose and dispersant and continue ball milling. Dry, grind and sieve the slurry obtained by ball milling to obtain uniform Fe and Mn composite Al2O3 ceramic powder.

[0007] (2) Press the Fe, Mn composite Al2O3 ceramic powder into porous ceramic blanks, and then fire them to obtain porous FeMn@Al2O3 ceramic substrates.

[0008] (3) The FeMn@Al2O3 ceramic substrate is polished and washed, and then platinum paste is printed on the FeMn@Al2O3 ceramic substrate and sintered to obtain a porous electrochemical gas sensor substrate.

[0009] (4) The porous electrochemical gas sensor substrate is modified by wetting with a hydrophobic agent solution and then dried. The catalyst slurry is then applied to the working electrode and counter electrode on the modified porous electrochemical gas sensor substrate. After drying, the pretreated Nafion solution is uniformly coated on the surface of the working electrode and counter electrode. The substrate is then dried and cured to form a proton exchange membrane. A dilute sulfuric acid solution is applied to the proton exchange membrane. Finally, silica sol is used to seal one side of the entire electrode to obtain the porous ceramic substrate electrochemical gas sensor.

[0010] In addition, the method for fabricating a porous ceramic substrate electrochemical gas sensor according to the above embodiments of the present invention may also have the following additional technical features:

[0011] In some embodiments of the present invention, in step (1): the mass ratio of alumina to starch is (3.8:1)-(4:1), the mass ratio of MnO to Fe2O3 is (1:1)-(1.5:1), 0.1g of methylcellulose is added, and 50-150μm of dispersant is added; the second ball milling time is 3-5h, and the rotation speed is 700-800r / min; the sieve used for sieving is 80-100 mesh.

[0012] In some embodiments of the present invention, in step (2): the pressing pressure is 10-22T, the pressing time is 1-5min; the porous ceramic blank is circular with a diameter of 6-7cm and a thickness of 1-3mm; the firing parameters are as follows: the heating rate is 2-3℃ / min from 0-500℃, the temperature is held at 500℃ for 100-120min, the temperature is further increased to 1400-1500℃ and held for 100-120min, and then cooled to room temperature.

[0013] In some embodiments of the present invention, in step (3): the polishing is performed using sandpaper; the cleaning is performed using 5wt%-15wt% dilute sulfuric acid and deionized water to remove excess impurities and organic residues, which facilitates subsequent modification treatment; the printing is performed using screen printing technology, with a mesh size of 450-480 mesh; the sintering temperature is 800-900℃, the sintering time is 30-45min, and the heating rate is 2-5℃ / min.

[0014] In some embodiments of the present invention, in step (4), the hydrophobic agent includes one or more of methyltriethoxysilane, polytetrafluoroethylene (PTFE), perfluorooctyltriethoxysilane (FAS-17), palmitic acid, ethyl acetate, and polyvinyl alcohol, with a mass percentage of 60%-80%, and the impregnation time is 24-48h; the drying temperature after the impregnation treatment is 80-120℃, and the drying time is 0.5-1.5h.

[0015] In some embodiments of the present invention, in step (4), the catalyst slurry includes one or more of Pt / C catalyst and isopropanol, water, ethylene glycol, polyethylene glycol, glycerol, Nafion, PVA, and methylcellulose; the drying temperature after spot coating is 100-140℃ and the drying time is 4-5h.

[0016] In some embodiments of the present invention, in step (4), the Nafion solution pretreatment method is as follows: the Nafion solution is mixed with one of glycerol, ethylene glycol, ionic liquid, neopentyl glycol ester, and DMF at a volume ratio of 1:1 to obtain the pretreated Nafion solution. By introducing plasticizers that can improve the adhesion between Nafion and the porous ceramic substrate, film formation is improved. Furthermore, these plasticizers can reduce the amount of Nafion used, thus reducing costs.

[0017] In another aspect of the present invention, the present invention provides a porous ceramic substrate electrochemical gas sensor prepared according to the aforementioned method for preparing a porous ceramic substrate electrochemical gas sensor.

[0018] In another aspect of the invention, the invention proposes the application of the porous ceramic substrate electrochemical gas sensor in the detection of hydrogen.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) By adding Fe2O3 and MnO for ball milling, the sintering temperature of ceramics is reduced, the strength and flatness of ceramic sheets are improved, which is beneficial to electrode printing. In addition, the introduced Fe and Mn metals can improve the corrosion resistance of the substrate and improve the stability and long-term life of the sensor.

[0021] (2) By adding corn starch, the present invention makes the final porosity of the ceramic substrate appropriate, which meets the air permeability requirements and helps the subsequent hydrophobic modification treatment; by adding dispersant, the friction coefficient between material particles is reduced, the ball milling efficiency and the forming performance of the blank are improved; by sieving the ceramic powder, the ceramic powder particles are made uniform, which facilitates the subsequent pressing operation and sintering.

[0022] (3) The present invention treats the ceramic substrate with dilute sulfuric acid and sinters at 900°C, which is beneficial to the curing and bonding between the Pt electrode and the porous substrate and improves the reliability of the electrode.

[0023] (4) The present invention modifies the porous ceramic substrate with 60wt%-80wt% hydrophobic agent, which can improve the surface hydrophobicity of the porous ceramic substrate and prevent internal liquid leakage, thus ensuring the long-term stability of the sensor.

[0024] (5) The present invention mixes a certain proportion of plasticizer into Nafion, which can improve its adhesion to the porous substrate during the film formation process, while avoiding the proton transport capability being affected.

[0025] (6) The electrochemical gas sensor based on FeMn@Al2O3 porous ceramic substrate designed in this invention has the advantages of good selectivity, high stability, simple fabrication, low cost, strong adaptability and environmental friendliness.

[0026] (7) This invention improves the bonding force between the current collector Pt and the porous substrate, sintersulates the Pt electrode at high temperature, removes impurities and organic matter, and reduces its own resistance. In addition, the hydrophobic modification technology of the porous substrate will greatly improve the stability of the sensor, reduce the influence of humidity and particulate matter in the environment, and interfere with the gas, thereby solving the zero drift problem of existing electrochemical gas sensors. Attached Figure Description

[0027] Figure 1 A top view of the screen-printed electrode in Embodiment 1 of the present invention. In the figure, 1 is the platinum paste after screen printing, and the remaining shaded areas are also platinum paste. 2 is a circular porous ceramic substrate.

[0028] Figure 2 A schematic diagram of the porous electrochemical gas sensor substrate structure prepared in step 3 of Embodiment 1 of the present invention. In the figure, 3 is the working electrode, 4 is the reference electrode, 5 is the counter electrode, and 6 is the pin.

[0029] Figure 3 Hydrophobicity test image of the porous electrochemical gas sensor substrate prepared in step 3 of Example 1 of this invention;

[0030] Figure 4 Welding strength test diagram of the porous electrochemical gas sensor substrate prepared in step 3 of Example 1 of this invention;

[0031] Figure 5 Resistance test pattern of the porous electrochemical gas sensor substrate prepared in step 3 of Example 1 of this invention;

[0032] Figure 6 Sintering curve of the circular porous ceramic blank prepared in step 2 of Example 1 of this invention;

[0033] Figure 7 A physical image of the porous ceramic substrate electrochemical gas sensor prepared in Example 1 of this invention;

[0034] Figure 8 Sensitivity test diagram of the porous ceramic substrate electrochemical gas sensor prepared in Example 1 of this invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for fabricating an electrochemical gas sensor on a porous ceramic substrate includes the following steps:

[0038] Step 1: Preparation of FeMn@Al2O3 ceramic material

[0039] Weigh 5.5g of alumina and 1.4g of starch into an agate ball mill jar using an analytical balance. Add 25ml of deionized water to the jar using a graduated cylinder. Mill for 30 minutes to ensure thorough mixing of the powders, then stop milling. Next, weigh 0.5g each of MnO, Fe2O3, and 0.1g of methylcellulose into the jar and add them to the ball mill jar. Use a pipette to add 150μL of dispersant (glycerol to PEG 400 in a 2:1 volume ratio) to the jar. Place the jar in a ball mill and mill for 3 hours at 800 rpm. Remove the milled slurry and pour it into a 100ml beaker. Rinse the slurry with a suitable amount of deionized water to remove any remaining slurry. Place the slurry in a forced-air drying oven at 80℃ for 10 hours to dry. The dried powder is taken out and then ground and sieved in sequence. An 80-mesh sieve is selected to obtain uniform Fe and Mn composite Al2O3 ceramic powder.

[0040] Step 2: Preparation of FeMn@Al2O3 porous ceramic substrate

[0041] Weigh 3.2g of the Fe, Mn composite Al2O3 ceramic powder into a mold using a balance. Use a leveling tool to evenly spread the powder in the mold. Place the mold in a hydraulic press and maintain a pressure of 22T for 5 minutes. Demolding yields a circular porous ceramic blank with a diameter of 6.5cm and a thickness of 2mm. Arrange the blank according to the attached... Figure 6The porous FeMn@Al2O3 ceramic substrate can be obtained by firing according to the sintering curve shown (heating rate of 2℃ / min from 0-500℃, holding at 500℃ for 120min, continuing to heat to 1500℃ and holding for 120min, then cooling to room temperature). Figure 6 As shown, when the temperature is raised to 500℃, it is kept at that temperature for 2 hours to facilitate the volatilization of organic matter, remove pollutants and release internal stress, ensure the flatness and integrity of the substrate, and facilitate the subsequent printing of electrodes and the fabrication of electrochemical sensors.

[0042] Step 3: Fabrication of porous electrochemical gas sensor substrate

[0043] First, use sandpaper to polish the surface of the ceramic substrate to make it smooth and flat. Then, perform surface treatment sequentially with 5wt% dilute sulfuric acid and deionized water to remove excess impurities and organic residues, facilitating subsequent modification treatment. Figure 1 The diagram shows how commercially available PE-PT-7840 platinum paste (from Guizhou Platinum Industry Co., Ltd.) is used for circuit printing via screen printing technology. The screen printing mesh size is 460 mesh. The ceramic sheet after platinum paste printing is then sintered at 900 degrees Celsius (heating rate 2℃ / min) to sinter the platinum paste into platinum electrodes and solidify them onto the ceramic sheet. After cutting and edge polishing, a porous electrochemical gas sensor substrate is obtained. Figure 2 As shown, the size of the porous electrochemical gas sensor substrate after cutting is 10.5mm*10.5mm, and the thickness is 0.9mm.

[0044] Step 4: Fabrication of a porous ceramic substrate electrochemical gas sensor

[0045] The porous electrochemical gas sensor substrate prepared in step 3 was modified by impregnating it with a 60wt% FAS-17 and ethyl acetate mixed solution as a hydrophobic agent for 48 hours, followed by drying at 80℃. A catalyst slurry was prepared by mixing 0.2g of Pt / C catalyst with 50μL isopropanol, 10μL Nafion, and 0.02g of methylcellulose. The catalyst slurry was then spot-coated onto the working and counter electrodes of the ceramic substrate, as shown in the attached figure. Figure 2 Positions 3 and 5 on the electrode were dotted. After dotting, the electrode was placed in an oven at 120°C for 5 hours. A pretreated Nafion solution (a 1:1 volume ratio of Nafion to glycerol) was uniformly coated onto the electrode surface and placed in a drying oven at 150°C for 20 minutes to cure the proton exchange membrane on the porous ceramic substrate. 5 μL of 0.1 M dilute sulfuric acid solution was dotted onto the cured Nafion membrane. Finally, one side of the electrode was sealed with silica sol to obtain an electrochemical gas sensor based on a FeMn@Al2O3 porous ceramic substrate.

[0046] The hydrophobicity of the porous electrochemical gas sensor substrate prepared in step 3 was tested, such as... Figure 3 As shown, the angle between the droplet and the surface was tested by adding water droplets to the surface. The hydrophobic angle θ was measured to be 120°, which is significantly greater than 90°, indicating that the surface material has good hydrophobicity.

[0047] The porous electrochemical gas sensor substrate prepared in step 3 was subjected to a solder strength test. A small amount of solder paste was applied to the electrode surface, and the surface was cleaned by blowing with a hot air gun at 350°C. Figure 4 As shown, the pins are soldered, with solder balls attached to the surface, ensuring a firm bond. The Pt electrode on the substrate surface also does not fall off, guaranteeing the mass production and reliability of the sensor.

[0048] The resistance of the reference electrode-pin terminal of the porous electrochemical gas sensor substrate prepared in step 3 was measured to be 2.4Ω, indicating that the surface circuitry of the ceramic substrate is conductive. In addition, the resistance values ​​of the working electrode-pin terminal and the counter electrode-pin terminal were also measured. The test results are consistent with... Figure 5 The results were consistent.

[0049] like Figure 7 As shown, from top to bottom, the layers are: silica sol sealing layer, dilute sulfuric acid solution (trace amount), Nafion membrane, Pt / C catalyst, hydrophobic layer, Pt electrode, FeMn@Al2O3 porous ceramic substrate, and hydrophobic layer.

[0050] Sensitivity testing was performed on a porous ceramic substrate electrochemical gas sensor. During testing, the sensor leads were connected to an electrochemical workstation and sealed within a closed chamber. 50 ml of standard gas (a 2% hydrogen-air mixture) was drawn from a standard gas bag using a syringe and injected into the chamber. Multiple injections were performed to gradually increase the concentration within the chamber, forming a current step response graph. Figure 7 As shown, the porous ceramic substrate electrochemical gas sensor was tested for H2 sensitivity, and the response current value reached 1500nA at 480ppm.

[0051] Example 2

[0052] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 1, the mass ratio of MnO to Fe2O3 is 1:3, and the remaining steps and parameters are the same as in Example 1.

[0053] Example 3

[0054] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 1, the mass ratio of MnO to Fe2O3 is 3:1, and the remaining steps and parameters are the same as in Example 1.

[0055] Example 4

[0056] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 1, the dispersant is ethylene glycol and PEG 600 in a volume ratio of 2:1. The remaining steps and parameters are the same as in Example 1.

[0057] Example 5

[0058] A method for preparing a porous ceramic substrate electrochemical gas sensor is disclosed. The difference between this embodiment and Example 1 lies only in the following step: in step 2, 3.5g of Fe, Mn composite Al2O3 ceramic powder is weighed and molded. All other steps and parameters are the same as in Example 1. The resulting preform is excessively thick (2mm), leading to poor gas permeability and a poor sensor response.

[0059] Example 6

[0060] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Embodiment 1 is that in step 3, 15wt% dilute sulfuric acid is used for surface treatment of the ceramic substrate. All other steps and parameters are the same as in Embodiment 1.

[0061] Example 7

[0062] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 4, a 60wt% FAS-17 and ethyl acetate mixed solution is used as a hydrophobic agent to impregnate the porous ceramic substrate for 6 hours. The remaining steps and parameters are the same as in Example 1.

[0063] Example 8

[0064] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 4, a 60wt% FAS-17 and ethyl acetate mixed solution is used as a hydrophobic agent to wet the porous ceramic substrate for 12 hours. The remaining steps and parameters are the same as in Example 1.

[0065] Example 9

[0066] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 4, a 60wt% FAS-17 and ethyl acetate mixed solution is used as a hydrophobic agent to wet the porous ceramic substrate for 24 hours. The remaining steps and parameters are the same as in Example 1.

[0067] Example 10

[0068] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 4, 60wt% PTFE emulsion is used as a hydrophobic agent to impregnate the porous ceramic substrate for 48h. The remaining steps and parameters are the same as in Example 1.

[0069] Example 11

[0070] A method for preparing a porous ceramic substrate electrochemical gas sensor. The only difference between this embodiment and Example 1 is that in step 4, 0.2g of Pt / C catalyst is mixed with 50μL of PEG400 and 10μL of Nafion to prepare a catalyst slurry. The remaining steps and parameters are the same as in Example 1.

[0071] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a porous ceramic substrate electrochemical gas sensor, characterized in that, Includes the following steps: (1) Mix alumina, starch and deionized water and ball mill them. Then add MnO, Fe2O3, methylcellulose and dispersant and continue ball milling. Dry, grind and sieve the slurry obtained by ball milling to obtain uniform Fe and Mn composite Al2O3 ceramic powder. The mass ratio of alumina to starch is (3.8:1)-(4:1) and the mass ratio of MnO to Fe2O3 is (1:1)-(1.5:1). (2) Press the Fe and Mn composite Al2O3 ceramic powder into porous ceramic blanks, and then fire them to obtain porous FeMn@Al2O3 ceramic substrates; (3) The FeMn@Al2O3 ceramic substrate is polished and washed, and then platinum paste is printed on the FeMn@Al2O3 ceramic substrate and sintered to obtain a porous electrochemical gas sensor substrate. (4) The porous electrochemical gas sensor substrate is modified by wetting with a hydrophobic agent solution and then dried. The catalyst slurry is then applied to the working electrode and counter electrode on the modified porous electrochemical gas sensor substrate. After drying, the pretreated Nafion solution is uniformly coated on the working and counter electrode surfaces. The substrate is then dried and cured to form a proton exchange membrane. A dilute sulfuric acid solution is applied to the proton exchange membrane. Finally, silica sol is used to seal one side of the entire electrode to obtain the porous ceramic substrate electrochemical gas sensor. The hydrophobic agent solution includes one or more of methyltriethoxysilane, polytetrafluoroethylene, perfluorooctyltriethoxysilane, palmitic acid, ethyl acetate, and polyvinyl alcohol.

2. The method for preparing a porous ceramic substrate electrochemical gas sensor according to claim 1, characterized in that, In step (1): The second ball milling time is 3-5 hours, and the rotation speed is 700-800 r / min; The sieve used for sieving is 80-100 mesh.

3. The method for preparing a porous ceramic substrate electrochemical gas sensor according to claim 1, characterized in that, In step (2): The pressing pressure is 10-22 T, and the pressing time is 1-5 min; The porous ceramic blank is circular, with a diameter of 6-7 cm and a thickness of 1-3 mm; The firing parameters are as follows: the heating rate is 2-3℃ / min from 0 to 500℃, the temperature is held at 500℃ for 100-120 minutes, the temperature is then increased to 1400-1500℃ and held for 100-120 minutes, and then cooled to room temperature.

4. The method for preparing a porous ceramic substrate electrochemical gas sensor according to claim 1, characterized in that, In step (3): The polishing was done using sandpaper; The washing process uses 5wt%-15wt% dilute sulfuric acid and deionized water. The printing process employs screen printing technology, with a mesh size of 450-480. The sintering temperature is 800-900℃, the sintering time is 30-45min, and the heating rate is 2-5℃ / min.

5. The method for preparing a porous ceramic substrate electrochemical gas sensor according to claim 1, characterized in that: In step (4), the mass percentage of the hydrophobic agent solution is 60%-80%, the soaking time is 24-48h, the drying temperature after soaking treatment is 80-120℃, and the drying time is 0.5-1.5h.

6. The method for preparing a porous ceramic substrate electrochemical gas sensor according to claim 1, characterized in that: In step (4), the catalyst slurry includes one or more of the following: Pt / C catalyst and isopropanol, water, ethylene glycol, polyethylene glycol, glycerol, Nafion, PVA, and methylcellulose; the drying temperature after spot coating is 100-140 ℃, and the drying time is 4-5 h.

7. The method for preparing a porous ceramic substrate electrochemical gas sensor according to claim 1, characterized in that: In step (4), the Nafion solution pretreatment method is as follows: the Nafion solution is mixed with one of glycerol, ethylene glycol, ionic liquid, neopentyl glycol ester, and DMF at a volume ratio of 1:1 to obtain the pretreated Nafion solution.

8. A porous ceramic substrate electrochemical gas sensor prepared by the method of preparing a porous ceramic substrate electrochemical gas sensor according to any one of claims 1-7.

9. The application of the porous ceramic substrate electrochemical gas sensor according to claim 8 in the detection of hydrogen.

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