Anti-siloxane poisoning VOC gas sensor and preparation method therefor

Abstract

The present application relates to the technical field of sensors, and the present application discloses an anti-siloxane poisoning VOC gas sensor, and a preparation method therefor. The anti-siloxane poisoning VOC gas sensor comprises a gas-sensitive unit. The gas-sensitive unit comprises a gas-sensitive layer (3), and an anti-poisoning protective layer (4) arranged on the gas-sensitive layer (3), the anti-poisoning protective layer (4) having a mesoporous structure. The anti-poisoning protective layer (4) is made of aluminum silicate fibers, a gas-sensitive material and an electronic paste. The preparation method for the gas sensor comprises the following steps: step 1, mixing aluminum silicate fibers, the gas-sensitive material and the electronic paste, to prepare an anti-poisoning protective layer paste; step 2, forming a toothed electrode on the substrate (1), and forming a gas-sensitive layer (3) on the toothed electrode, then spraying the anti-poisoning protective layer paste prepared in step 1 onto the gas-sensitive layer (3) of step 2, and performing sintering, to obtain a gas sensor. The gas sensor prepared by the present application is effective against siloxane poisoning.

Description

A VOCs gas sensor resistant to siloxane poisoning and its preparation method Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a VOCs gas sensor resistant to siloxane poisoning and a preparation method thereof. Background Art

[0002] VOCs, or volatile organic compounds, are a general term for organic compounds with a boiling point between 50°C and 260°C at room temperature. In confined spaces, when VOC concentrations reach a certain level, they can cause nausea and headaches, and in severe cases, even convulsions and coma.

[0003] Indoors, VOCs primarily originate from finishing materials such as latex paint, wallpaper, and floor insulation. In cars, VOCs primarily originate from seats, dashboards, and interior trim. With rising demands for quality of home living, increasing car ownership, and the amount of time people spend in their cars, a safe and comfortable indoor and in-car experience has become increasingly important. Therefore, accurate and efficient VOC monitoring is essential.

[0004] Semiconductor metal oxide gas sensors are devices that convert chemical gas signals into electrical signals and are currently widely used in indoor home environment monitoring, the automotive industry, the mining industry, and the healthcare industry. The structure of an existing gas sensor is shown in Figure 1 and includes a substrate 1, a heating electrode and a test electrode 2 disposed on substrate 1, and a gas-sensitive layer 3 covering the test electrode 2. The gas-sensitive layer is the core component of a semiconductor metal oxide gas sensor. It is typically made of metal oxide materials such as tin dioxide and titanium dioxide. When a target gas is present, the gas-sensitive layer chemically reacts with the target gas, causing its electrical properties (such as resistance) to change, thereby achieving the purpose of accurately detecting the target gas.

[0005] Semiconductor metal oxide gas sensors have become the mainstream equipment for detecting VOCs due to their convenience and speed. However, the detection environment often contains large siloxane molecules. Siloxane is a polymer with a main chain structure composed of Si-O-Si bonds. Under high temperature conditions, siloxane easily forms a dense silicon oxide on the surface of the gas-sensitive material, resulting in a reduction in the active sites of the gas-sensitive layer and sensor poisoning. This reduces the sensor's response to the target gas and may even make it unable to accurately detect the target gas. Therefore, gas sensors are required to be resistant to siloxane poisoning, but the VOCs gas sensors currently on the market do not have good resistance to siloxane poisoning.

[0006] Summary of the Invention

[0007] In order to solve at least one of the above technical problems, a gas sensor that can effectively resist siloxane poisoning and has good responsiveness to VOCs gas is developed. The present application provides a VOCs gas sensor that is resistant to siloxane poisoning and a preparation method thereof.

[0008] In one aspect, the present application provides a VOCs gas sensor resistant to siloxane poisoning, comprising: a substrate, a slotted electrode disposed on the substrate, and a gas sensing unit disposed on the slotted electrode;

[0009] The gas-sensing unit includes a gas-sensing layer and an anti-poisoning protective layer provided on the gas-sensing layer, wherein the anti-poisoning protective layer has a mesoporous structure;

[0010] The anti-poisoning protective layer is made of aluminum silicate fiber, gas-sensitive material and electronic paste.

[0011] By adopting the above-mentioned technical solution, the gas-sensitive unit of the present application adopts a double-layer structure, the outer layer is an anti-poisoning protective layer, and the inner layer is a gas-sensitive layer. The anti-poisoning protective layer has a mesoporous structure, and the pore size of the mesopores is smaller than the size of the siloxane macromolecules but larger than the size of the VOCs small molecules. Therefore, the anti-poisoning protective layer can effectively prevent the siloxane gas molecules from contacting the gas-sensitive layer, while allowing the VOCs molecules to pass through. The VOCs molecules passing through the anti-poisoning protective layer can better contact with the gas-sensitive layer, thereby effectively improving the sensor's resistance to siloxane poisoning, extending the sensor's service life, and having a better response to VOCs gas.

[0012] In the present application, aluminum silicate fibers are compounded with gas-sensitive materials and electronic pastes as the material of the anti-poisoning protective layer, which can not only effectively block siloxane gas molecules but also improve the responsiveness of the sensor.

[0013] Aluminum silicate fiber is a mesoporous material with a pore size of 10 to 20 nm, which can effectively filter siloxane gas macromolecules without affecting the gas response of the gas-sensitive layer.

[0014] Optionally, the method for preparing the gas-sensitive material comprises the following steps:

[0015] S1. Taking SnO2 nanoparticles and dispersing the SnO2 nanoparticles in deionized water, stirring, and preparing a suspension;

[0016] S2. Take an Al2O3 dispersion and add the Al2O3 dispersion to the suspension prepared in step S1, stir, filter, dry and calcine to obtain the gas-sensitive material.

[0017] By adopting the above technical solution, the gas-sensitive material prepared in this application is nano-scale and can be mixed more fully with the aluminum silicate fiber. The gas-sensitive material is added to the anti-poisoning protective layer, which can improve the responsiveness of the sensor to a certain extent.

[0018] In this application, Al2O3 is added to the suspension, filtered, and then dried and calcined. Before calcination, the filtrate is first dried to effectively remove the solvent, making the calcination more sufficient and uniform, thereby ensuring the quality of the calcined product, i.e., the gas-sensitive material.

[0019] Optionally, step S2 includes the following steps:

[0020] S21, taking a solution containing a precious metal catalyst and adding the solution containing a precious metal catalyst to the suspension prepared in step S1, stirring to prepare a mixed solution;

[0021] S22, adding the Al2O3 dispersion to the mixed solution obtained in step S21, stirring, filtering, drying and calcining to obtain the gas-sensitive material.

[0022] By adopting the above technical solution, the present application dopes the gas-sensitive material with a noble metal catalyst, thereby further improving the responsiveness of the sensor.

[0023] Optionally, in step S1, the mass of the SnO2 nanoparticles is 0.5 to 2 g;

[0024] In step S21, the volume of the solution containing the noble metal catalyst is 20 to 40 mL;

[0025] In the step S22, the mass of the Al2O3 dispersion is 0.1 to 0.3 g.

[0026] Optionally, in step S2, drying is performed under vacuum conditions, the drying temperature is 60-80° C., and the drying time is 1-2 hours.

[0027] Optionally, the mass ratio of the aluminum silicate fiber, the gas-sensitive material and the electronic paste is 1:(0.1-0.5):6.

[0028] By adopting the above-mentioned technical solution, the aluminum silicate fiber, gas-sensitive material and electronic paste of the present application are compounded in a specific proportion. The anti-poisoning protective layer obtained can not only be well covered on the gas-sensitive layer to block the siloxane macromolecular gas, but also improve the sensor's responsiveness to VOCs gas to a certain extent.

[0029] Optionally, the gas-sensitive layer is made of a gas-sensitive material and an electronic paste, and the mass ratio of the gas-sensitive material to the electronic paste is 1:(4-10).

[0030] By adopting the above technical solution, the gas-sensitive material and electronic paste of the present application are compounded in a specific ratio, and the obtained gas-sensitive layer can not only adhere well to the tooth electrode, but also ensure the responsiveness of the sensor to VOCs gas.

[0031] Optionally, the raw materials of the electronic paste include silver powder, a binder and a solvent.

[0032] In a second aspect, the present application provides a method for preparing the above-mentioned VOCs gas sensor resistant to siloxane poisoning, comprising the following steps:

[0033] Step 1: Mix aluminum silicate fiber, gas sensitive material and electronic slurry to prepare anti-poisoning protective layer slurry for later use;

[0034] Step 2: forming a tooth electrode on the substrate, and forming a gas sensitive layer on the tooth electrode;

[0035] Step 3: Spray the anti-poisoning protective layer slurry prepared in step 1 onto the gas-sensitive layer prepared in step 2, and perform sintering treatment to obtain the VOCs gas sensor that is resistant to siloxane poisoning.

[0036] By adopting the above technical solution, the raw material cost used in this application is low, the preparation process is simple, the preparation cycle is short, and it can be produced in large quantities and industrially. The gas sensor prepared can effectively resist siloxane poisoning and extend the service life of the sensor. The gas sensor prepared in this application can be well applied to the detection of in-vehicle and indoor environments.

[0037] Optionally, in step 2, forming a gas-sensitive layer on the tooth electrode includes the following steps: mixing the gas-sensitive material and the electronic paste in a mass ratio of 1:(4 to 10) to prepare a gas-sensitive layer slurry; spraying the gas-sensitive layer slurry on the tooth electrode and sintering the gas-sensitive layer slurry to form a gas-sensitive layer.

[0038] In summary, the present invention includes at least one of the following beneficial technical effects:

[0039] 1. The gas-sensitive unit of the present application adopts a double-layer structure, with the outer layer being an anti-poisoning protective layer and the inner layer being a gas-sensitive layer. The anti-poisoning protective layer has a mesoporous structure, which can effectively prevent the contact between the siloxane gas molecules and the gas-sensitive layer, while allowing VOCs molecules to pass through, thereby effectively improving the sensor's resistance to siloxane poisoning, extending the sensor's service life, and having a better response to VOCs gas.

[0040] 2. In this application, aluminum silicate fibers are compounded with gas-sensitive materials and electronic pastes as the material for the anti-poisoning protective layer, which can not only effectively block siloxane gas molecules but also improve the responsiveness of the sensor.

[0041] 3. The raw materials used in this application are low in cost, and the preparation process is simple and the preparation cycle is short. It can be produced in large quantities and industrially. The gas sensor produced can effectively resist siloxane poisoning and extend the service life of the sensor. The gas sensor produced in this application can be well applied to the detection of in-vehicle and indoor environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a schematic structural diagram of an existing gas sensor;

[0043] FIG2 is a schematic structural diagram of a VOCs gas sensor resistant to siloxane poisoning provided by the present application;

[0044] FIG3 is an XRD pattern of aluminum silicate fiber in Example 1;

[0045] FIG4 is an XRD pattern of the gas-sensitive material in Example 1;

[0046] FIG5 is a graph showing the specific surface area of ​​the anti-poisoning protective layer slurry in Example 1;

[0047] FIG6 is a SEM image of the anti-poisoning protective layer in Example 1;

[0048] Figure 7 is a test curve of the responsivity of the gas sensors prepared in Example 1 and Comparative Example 1 to isobutylene in performance test 1; description of the accompanying symbols: 1. substrate; 2. test electrode; 3. gas-sensitive layer; 4. anti-poisoning protective layer. DETAILED DESCRIPTION

[0049] The present application is further described in detail below with reference to the accompanying drawings and examples.

[0050] Ingredients

[0051] EDTA, ethylenediaminetetraacetic acid, CAS number 60-00-4, molecular formula C 10 H 16 N2O8;

[0052] Deionized water, CAS number 7732-18-5, purity 99%;

[0053] Concentrated nitric acid, the mass percentage of nitric acid is 70%;

[0054] Tin granules, CAS number 7440-31-5, purity ≥99.0%, particle size 1000 mesh;

[0055] Chloroplatinic acid aqueous solution, H2PtCl6·6(H2O) dissolved in deionized water to form a chloroplatinic acid aqueous solution, the mass percentage of chloroplatinic acid is 8%;

[0056] Al2O3 dispersion, nano-Al2O3 alcohol dispersion, Hengge Nanotechnology, model HN-L20W;

[0057] Binder, glass powder, average particle size 2.5±0.5μm;

[0058] Solvent, N-methylpyrrolidone, CAS number 872-50-4, molecular formula C5H9NO;

[0059] Dispersant, polyoxyethylene lauryl ether, CAS number 9004-98-2, molecular formula C 20 H 40 O2;

[0060] Silver powder, conductive silver powder, purity 99.9%, Yamei Nano Technology;

[0061] Aluminum silicate fiber, molecular formula is Al 2.3 Si 0.7 O 4.85 , particle size ≤ 10 μm, with mesopores of 10 to 20 nm, and its XRD diffraction pattern is shown in Figure 3;

[0062] Zeolite, mesoporous ZSM-5 zeolite, particle size ≤ 10 μm, with mesopores of 10 to 15 nm;

[0063] Silica, mesoporous silica, particle size ≤ 10 μm, with mesopores of 10 to 13 nm.

[0064] Specific embodiments

[0065] Example 1

[0066] A method for preparing a VOCs gas sensor resistant to siloxane poisoning comprises the following steps:

[0067] S1. Preparation of gas-sensitive materials

[0068] S11, dissolving 0.55 g of EDTA in 30 ml of deionized water, adding 50 ml of concentrated nitric acid, stirring thoroughly, adding 5 g of tin particles, and bathing the mixture in a water bath at 60° C. for 50 min with stirring. After the bath, removing the reactant, filtering, washing, and drying the reactant, and sintering the mixture at 500° C. for 1 h to obtain SnO2 nanoparticles;

[0069] S12, taking 1 g of the SnO2 nanoparticles prepared in step S11, and dispersing 1 g of the SnO2 nanoparticles in 15 ml of deionized water, stirring at a stirring rate of 100 rpm at room temperature for 1 hour to prepare a suspension;

[0070] S13, taking 20 ml of chloroplatinic acid aqueous solution, and adding 20 ml of chloroplatinic acid aqueous solution to the suspension prepared in step S12, stirring at a stirring rate of 100 rpm at room temperature for 30 minutes to prepare a mixed solution;

[0071] S14. Take 0.25 g of Al2O3 dispersion and add 0.25 g of Al2O3 dispersion to the mixed solution prepared in step S13, stir magnetically for 1.5 hours, filter to obtain a solid, place the solid in a vacuum drying oven and dry it at a temperature of 70°C and a drying time of 1.5 hours. The dried solid is calcined at a temperature of 450°C and a calcination time of 2 hours to obtain a gas-sensitive material for standby use. The XRD pattern of the gas-sensitive material is shown in Figure 4.

[0072] S2. Preparation of electronic paste

[0073] S21, adding 6.5 g of the binder to 50 ml of the solvent, stirring at a stirring rate of 50 rpm for 10 min to prepare a binder solution;

[0074] S22. Add 1 g of dispersant and 60 g of silver powder to the binder solution, and stir at a stirring rate of 100 rpm for 15 minutes to prepare an electronic paste for later use.

[0075] S3. Preparation of gas-sensitive layer slurry

[0076] Mix 1 part of the gas-sensitive material prepared in step S1 with 4 parts of the electronic slurry prepared in step S2, and then ball-mill them in a ball mill for 30 minutes using a closed wet milling method to prepare a gas-sensitive layer slurry for later use.

[0077] S4. Preparation of anti-poisoning protective layer slurry

[0078] Mix 1 part of the gas-sensitive material prepared in step S1, 0.25 parts of aluminum silicate fiber, and 6 parts of the electronic slurry prepared in step S2, and then perform ball milling treatment. The ball milling conditions are the same as those in step S3 to obtain an anti-poisoning protective layer slurry for later use. The specific surface area diagram of the anti-poisoning protective layer slurry is shown in Figure 5.

[0079] S5. Preparation of sensor

[0080] S51. Take a zirconia substrate 1, grow an alumina insulating layer on the substrate surface by thermal oxidation, and form a heating electrode and a test electrode 2 on the insulating layer by magnetron sputtering. The test electrode is a slotted electrode. The heating electrode and the test electrode are made of platinum. The structure of the slotted electrode is the same as that disclosed in Patent Publication No. CN 114384124A.

[0081] S52. The gas-sensitive layer slurry prepared in step S3 is sprayed onto the slotted electrode by micro-spraying, and then sintered. The sintering temperature is 300°C, and the sintering time is 1 hour. The gas-sensitive layer slurry forms an airtight layer 3, and the thickness of the gas-sensitive layer is 8±2μm. S53. The anti-poisoning protective layer slurry prepared in step S4 is sprayed onto the gas-sensitive layer by micro-spraying, and then sintered. The sintering conditions are the same as those in step S52, and a sensor is obtained, wherein the anti-poisoning protective layer slurry forms an anti-poisoning protective layer 4, and the thickness of the anti-poisoning protective layer is 8±2μm. The SEM image of the anti-poisoning protective layer is shown in Figure 6.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that in step S5, step S53 is missing, that is, the gas sensor prepared in this comparative example lacks the anti-poisoning protection layer.

[0084] Performance test 1

[0085] Pre-siloxane impact test: The gas sensors prepared in Example 1 and Comparative Example 1 were placed in a test chamber and introduced with nitrogen for 8 hours. Then, isobutylene gas with a concentration of 200 ppm was introduced for 150 seconds. The response curve before siloxane impact was obtained, as shown in Figure 7.

[0086] Post-siloxane impact test: The gas sensors prepared in Example 1 and Comparative Example 1 were placed in a test chamber. Hexamethyldisiloxane at a concentration of 100 ppm was introduced for 2 hours. Then, isobutylene gas at a concentration of 200 ppm was introduced for 150 seconds. The response curve after siloxane impact was obtained, as shown in Figure 7.

[0087] As shown in FIG7 , before the addition of hexamethyldisiloxane, that is, before the impact of siloxane, the gas sensors prepared in Example 1 and Comparative Example 1 can both detect isobutylene gas. Specifically, at t=80s, the measured resistance of Comparative Example 1 begins to drop significantly, and the resistance change rate is 65.7%. At t=75s, the measured resistance of Example 1 begins to drop significantly, and the resistance change rate is 74.9%. It can be seen that before the impact of siloxane, the gas sensor prepared in Example 1 has a faster response than that in Comparative Example 1. Wherein, the resistance change rate = (R0-R t ) / R0, R0 is the maximum resistance value before the resistance drops significantly in the curve, R t is the resistance value at time t in the curve graph.

[0088] After filling with hexamethyldisiloxane, i.e., after siloxane impact, the gas sensor prepared in Comparative Example 1 has been poisoned and inactivated, while the gas sensor prepared in Example 1 still has good responsiveness and can perform normal detection because the anti-poisoning protective layer blocks the siloxane gas.

[0089] Example 2

[0090] The difference between this embodiment and embodiment 1 is that in the preparation of the gas-sensitive material in step S1, step S13 is lacking, and the precious metal Pt is not introduced. During the preparation, 0.25 g of Al2O3 dispersion is directly added to the suspension prepared in step S12. Other conditions are the same as those in embodiment 1.

[0091] Examples 3-4

[0092] The difference between Examples 3 and 4 and Example 1 is that in step S4, the amount of aluminum silicate fiber used is different, as shown in Table 1 below.

[0093] Table 1 Amounts of gas-sensitive materials, aluminum silicate fibers, and electronic paste (unit: parts by weight)

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that an equal amount of zeolite is used to replace the aluminum silicate fiber.

[0096] Comparative Example 3

[0097] The difference between this comparative example and Example 1 is that an equal amount of silicon dioxide is used to replace the aluminum silicate fiber.

[0098] Comparative Example 4

[0099] The difference between this comparative example and Example 1 is that the preparation method of the anti-poisoning protective layer slurry is different. The preparation method of the anti-poisoning protective layer slurry in this comparative example is: 1 part of Al2O3, 0.01 part of metal Pt, 0.25 part of aluminum silicate fiber and 6 parts of electronic slurry are mixed, and then ball milled. The ball milling conditions are the same as step S3 to obtain the anti-poisoning protective layer slurry.

[0100] Performance Test 2

[0101] The gas sensors prepared in Examples 2 to 4 and Comparative Examples 2 to 4 were subjected to performance tests according to the test method after silicone impact in Performance Test 1. The time when the resistance began to decrease significantly and the corresponding resistance change rate are shown in Table 2 below.

[0102] Table 2 Resistance obvious drop time and resistance change rate

[0103] From the test results in Table 2, it can be seen that the gas sensor prepared in this application has a good anti-siloxane effect and has a good response to VOCs gas. Compared with Example 1, Example 2 does not introduce the precious metal Pt, resulting in a decrease in the response of the prepared gas sensor to VOCs gas compared with Example 1. Compared with Example 1, Examples 3 to 4 have changed the amount of aluminum silicate fiber used, resulting in a change in the response of the prepared gas sensor to VOCs gas. Although the response of the gas sensor prepared in Example 3 is higher than that of the example, the increase is not significant, and the amount of aluminum silicate fiber used in Example 3 is twice that of Example 1. Considering factors such as cost, Example 1 is a better example. Compared with Example 1, Comparative Examples 2 to 3 use zeolite and silica to replace aluminum silicate fiber, resulting in a significant decrease in the responsiveness of the prepared gas sensor to VOCs gas. The preparation method of the anti-poisoning protective layer slurry in Comparative Example 4 is different from that in Example 1, resulting in a significant decrease in the responsiveness of the prepared gas sensor to VOCs gas.

[0104] Examples 5 to 10

[0105] The difference between Examples 5 to 10 and Example 1 is that in the preparation of the gas-sensitive material in step S1, the amounts of raw materials used are different, as shown in Table 3 below.

[0106] Table 3 Raw material dosage of gas-sensitive materials

[0107] Performance Test 3

[0108] The gas sensors prepared in Examples 5 to 10 were subjected to performance tests according to the test method after silicone impact in Performance Test 1. The time when the resistance began to decrease significantly and the corresponding resistance change rate are shown in Table 4 below.

[0109] Table 4 Resistance obvious drop time and resistance change rate

[0110] From the test results in Table 4, it can be seen that compared with Example 1, the amount of SnO2 nanoparticles used in Examples 5-6 has changed, and the responsivity of the gas sensors to VOCs has also changed. Although the responsivity of the gas sensor prepared in Example 6 is higher than that in Example 1, the increase is not significant. In addition, the amount of SnO2 nanoparticles used in Example 6 is twice that of Example 1. Considering factors such as comprehensive cost, Example 1 is the preferred embodiment. Compared with Example 1, the amount of chloroplatinic acid solution used in Examples 7-8 has changed, and the responsivity of the gas sensors to VOCs has also changed. Example 7 is the preferred embodiment. Compared with Example 7, the amount of Al2O3 dispersion used in Examples 9-10 has changed, and the responsivity of the gas sensors to VOCs has also changed.

[0111] Examples 11-12

[0112] The difference between Examples 11 to 12 and Example 7 is that in step S3, the amount of electronic paste used is different, as shown in Table 5 below.

[0113] Table 5 Amount of gas-sensitive materials and electronic paste (unit: parts by weight)

[0114] Examples 13 to 15

[0115] The difference between Examples 13 to 15 and Example 7 is that in step S14 of preparing the gas-sensitive material, pre-sintering is performed before sintering. The temperature and time of the pre-sintering are shown in Table 6 below.

[0116] Table 6 Sintering conditions for preparing gas-sensitive materials

[0117] Performance Test 4

[0118] The gas sensors prepared in Examples 11 to 15 were subjected to performance tests according to the test method after silicone impact in Performance Test 1. The time when the resistance began to drop significantly and the corresponding resistance change rate are shown in Table 7 below.

[0119] Table 7 Resistance obvious drop time and resistance change rate

[0120] The test results in Table 7 show that, compared with Example 7, the amount of electronic paste used in Examples 11-12 changed, resulting in changes in the responsivity of the resulting gas sensors to VOCs. Compared with Example 7, Examples 13-15 included a pre-sintering step before sintering, with the sintering time remaining unchanged. This added pre-sintering step improved the responsivity of the resulting gas sensors, and the pre-sintering temperature also had a certain impact on the responsivity of the gas sensors.

[0121] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A VOCs gas sensor resistant to siloxane poisoning, characterized in that: include: A substrate, a toothed electrode disposed on the substrate, and a gas sensing unit disposed on the toothed electrode; The gas sensing unit comprises a gas sensing layer and an anti-poisoning protective layer arranged on the gas sensing layer, wherein the anti-poisoning protective layer has a mesoporous structure; The anti-poisoning protective layer is made of aluminum silicate fiber, gas-sensitive material and electronic paste.

2. The VOCs gas sensor resistant to siloxane poisoning according to claim 1, characterized in that: The preparation method of the gas-sensitive material comprises the following steps: S1, taking SnO2 nanoparticles and dispersing the SnO2 nanoparticles in deionized water, stirring, and preparing a suspension; S2, taking Al2O3 dispersion and adding the Al2O3 dispersion into the suspension obtained in step S1, stirring, filtering, drying and calcining to obtain the gas-sensitive material.

3. The VOCs gas sensor resistant to siloxane poisoning according to claim 2, characterized in that: The step S2 comprises the following steps: S21, taking a solution containing a precious metal catalyst and adding the solution containing a precious metal catalyst to the suspension obtained in step S1, stirring to obtain a mixed solution; S22, adding the Al2O3 dispersion into the mixed solution obtained in step S21, stirring, filtering, drying and calcining to obtain the gas-sensitive material.

4. The VOCs gas sensor resistant to siloxane poisoning according to claim 3, characterized in that: In the step S1, the mass of SnO2 nanoparticles is 0.5-2 g; In the step S21, the volume of the solution containing the precious metal catalyst is 20 to 40 mL; In the step S22, the mass of the Al2O3 dispersion is 0.1 to 0.3 g.

5. The VOCs gas sensor resistant to siloxane poisoning according to claim 2, characterized in that: In the step S2, drying is performed under vacuum conditions, the drying temperature is 60-80° C., and the drying time is 1-2 hours.

6. The VOCs gas sensor resistant to siloxane poisoning according to claim 1, characterized in that: The mass ratio of the aluminum silicate fiber, the gas-sensitive material and the electronic paste is 1:(0.1-0.5):

6.

7. The VOCs gas sensor resistant to siloxane poisoning according to claim 1, characterized in that: The gas-sensitive layer is made of a gas-sensitive material and an electronic paste, and the mass ratio of the gas-sensitive material to the electronic paste is 1:(4-10).

8. The VOCs gas sensor resistant to siloxane poisoning according to claim 1, characterized in that: The raw materials of the electronic paste include silver powder, a binder and a solvent.

9. A method for preparing a VOCs gas sensor resistant to siloxane poisoning according to claim 1, characterized in that: The following steps are involved: Step 1: Mix aluminum silicate fiber, gas sensitive material and electronic slurry to prepare anti-poisoning protective layer slurry for standby use; Step 2: forming a toothed electrode on the substrate, and forming a gas-sensitive layer on the toothed electrode; Step three: spray the anti-poisoning protective layer slurry prepared in step one onto the gas sensitive layer in step two, and perform sintering treatment to obtain the VOCs gas sensor that is resistant to siloxane poisoning.

10. The method for preparing a VOCs gas sensor resistant to siloxane poisoning according to claim 9, characterized in that: In the step 2, forming a gas-sensitive layer on the tooth electrode includes the following steps: mixing the gas-sensitive material and the electronic slurry in a mass ratio of 1: (4-10) to prepare a gas-sensitive layer slurry; spraying the gas-sensitive layer slurry on the test electrode, and sintering the gas-sensitive layer slurry to form a gas-sensitive layer.

Images