A CO gas sensor based on MEMS chip and its preparation method and application

Abstract

The present invention discloses a CO gas sensor based on a MEMS chip, its preparation method, and application, and belongs to the field of gas sensors. The preparation method provided by the present invention comprises modifying stannous chloride dihydrate to obtain a Pt / SnO2 nanocomposite material; adding the Pt / SnO2 nanocomposite material to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and mixing evenly to obtain a gas-sensitive slurry; coating the gas-sensitive slurry on the electrodes of a MEMS chip, and heat-treating the MEMS chip coated with the gas-sensitive slurry to obtain a CO gas sensor based on a MEMS chip. The MEMS chip CO sensor prepared by the present invention has a response time of seconds to battery thermal runaway and can detect trace amounts of CO gas before the battery thermal runaway occurs.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a CO gas sensor based on a MEMS chip, a preparation method thereof, and applications thereof. Background Art

[0002] While the energy storage industry is rapidly developing, energy storage accidents are also common, and lithium battery energy storage technology still faces significant safety issues. During long-term charge and discharge cycles, lithium batteries inevitably produce gaseous byproducts such as hydrogen and carbon monoxide. The accumulation of these gases not only negatively impacts the battery's overall performance but, more importantly, can pose a serious challenge to battery safety. In particular, when gas emissions reach a certain level, they can cause a sharp increase in internal battery pressure, potentially triggering thermal runaway.

[0003] MEMS (Micro-Electro-Mechanical System) is a micro-electromechanical system, and MEMS chips are micron- and nanometer-scale mechanical systems with sensing capabilities. This mechanical system can convert external physical and chemical signals into electrical signals. Gas-sensitive materials are a key component of MEMS CO sensors. To improve the performance of MEMS CO gas sensors, tin dioxide (SnO2) is typically used as the sensitive material due to its high sensitivity, fast response, and low energy consumption. Furthermore, the loading process is crucial for achieving MEMS chips with excellent sensing performance. Traditional processes result in uneven loading of the gas-sensitive slurry, resulting in weak adhesion between the gas-sensitive slurry and the sensitive electrode, which in turn affects the sensor's stability and gas response capabilities at different operating temperatures.

[0004] Based on this, the object of the present invention is to provide a slurry loading process based on a MEMS chip that responds quickly to CO gas. Summary of the Invention

[0005] In order to solve the problem of uneven loading in traditional gas-sensitive slurry loading processes, which often leads to weak adhesion with sensitive electrodes and thus affects the stability and gas response capability of the sensor at different operating temperatures, the present invention provides a CO gas sensor based on a MEMS chip, a preparation method and an application thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a CO gas sensor based on a MEMS chip, comprising:

[0008] adding a tin dioxide nanomaterial to an ethanol solution and mixing uniformly to obtain a first solution; adding chloroplatinic acid to the first solution under ultraviolet light irradiation to react to obtain a crude Pt / SnO2; and heat-treating the crude Pt / SnO2 to obtain a Pt / SnO2 nanocomposite material;

[0009] Pt / SnO2 nanocomposite material is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and mixed evenly to obtain a gas-sensitive slurry; the gas-sensitive slurry is drop-coated on the electrode of a MEMS chip, and the MEMS chip coated with the gas-sensitive slurry is heat-treated to obtain a CO gas sensor based on a MEMS chip.

[0010] The mass ratio of the tin dioxide nanomaterial to chloroplatinic acid is (5-10):1.

[0011] The wavelength of the ultraviolet light is 315-400 nm, and the ultraviolet light irradiation time is 30-45 min.

[0012] The crude Pt / SnO2 is subjected to heat treatment to obtain the Pt / SnO2 nanocomposite material, specifically, the crude Pt / SnO2 is placed in a vacuum environment at 80-100°C and dried for 12-16 hours to obtain the Pt / SnO2 nanocomposite material.

[0013] The mass ratio of the polyvinylidene fluoride to N-methyl-2-pyrrolidone is 1:(200-300).

[0014] The mass ratio of the mixed solution of Pt / SnO2 to polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(2-3).

[0015] The gas-sensitive slurry is drop-coated on the electrode of the MEMS chip, specifically: 0.5-1 μL of the gas-sensitive slurry is drop-coated on the electrode of the MEMS chip.

[0016] The heat treatment of the MEMS chip coated with the gas-sensitive slurry to obtain the CO gas sensor based on the MEMS chip is specifically as follows: the MEMS chip coated with the gas-sensitive slurry is placed at a temperature of 80-100° C. and dried for 2-3 hours to obtain the CO gas sensor based on the MEMS chip.

[0017] The present invention also provides a CO gas sensor based on a MEMS chip, which is manufactured according to the above-mentioned method for manufacturing a CO gas sensor based on a MEMS chip.

[0018] The present invention also provides an application of the above-mentioned CO gas sensor based on the MEMS chip, wherein the CO gas sensor based on the MEMS chip is applied in a lithium battery.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The preparation method of the present invention uses modified tin dioxide to load platinum on the surface of the original rough tin dioxide nanospheres, which can improve the gas sensing performance of SnO2 and its selectivity for CO. The Pt / SnO2 nanocomposite material is used as the gas sensing material and combined with N-methyl-2-pyrrolidone (NMP) and polyvinylidene fluoride (PVDF) to form a uniform gas-sensitive slurry. The Pt / SnO2-NMP-PVDF system has synergistic advantages. NMP ensures that the Pt / SnO2 nanoparticles do not agglomerate, and PVDF fixes the position of the nanoparticles to form a porous sensitive layer. At the same time, the catalytic effect of Pt is combined with the semiconductor properties of SnO2. The NMP-PVDF system does not interfere with the gas-sensitive reaction, effectively improving the sensor's response performance to CO gas. The preparation method also uses a drop coating method to load the gas-sensitive slurry on the surface of a MEMS chip, thereby improving the adhesion of the sensitive material to the MEMS chip. Compared to traditional loading processes, the MEMS chip fabricated in this invention is able to rapidly respond to CO gas over a wide concentration range. This enables the sensor to accurately and rapidly detect CO gas changes under various environmental conditions, making it particularly suitable for applications requiring high sensitivity and rapid response, such as early warning of battery thermal runaway. The fabrication method proposed in this invention is simple, rapid, cost-effective, and highly reproducible and stable, meeting production line requirements and promoting the widespread adoption of sensors in practical applications.

[0021] The MEMS chip CO sensor prepared by the present invention has a response time of seconds to battery thermal runaway. When the CO concentration ranges from 10ppm to 1500ppm, it can respond within 15s. At the same time, it can detect trace amounts of CO gas before the battery thermal runaway occurs. The MEMS chip CO sensor provided by the present invention can monitor the battery status in real time and issue an early warning before danger occurs, effectively reducing safety risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a scanning electron microscope image of SnO2 prepared in Example 1 of the present invention;

[0024] Figure 2This is a scanning electron microscope image of Pt / SnO2 prepared in Example 1 of the present invention;

[0025] Figure 3 The figures are the physical pictures of the MEMS chip before and after being coated with the gas-sensitive slurry in the present invention, wherein (a) is the physical picture of the MEMS chip, and (b) is the physical picture of the MEMS chip after being coated with the gas-sensitive slurry;

[0026] Figure 4 These are optical microscope images of the MEMS chip before and after being coated with the gas-sensitive slurry in the present invention, wherein (a) is an optical microscope image of the MEMS chip; (b) is an optical microscope image of the MEMS chip after being coated with the gas-sensitive slurry;

[0027] Figure 5 Response curve of the CO gas sensor of the MEMS chip prepared in Example 1 of the present invention to CO gas with a concentration of 10 ppm (parts per million);

[0028] Figure 6 Response curve of the CO gas sensor of the MEMS chip prepared in Example 1 of the present invention to CO gas with a concentration of 100 ppm;

[0029] Figure 7 Response curve of the CO gas sensor of the MEMS chip prepared in Example 1 of the present invention to CO gas with a concentration of 1000 ppm;

[0030] Figure 8 Response curve of the CO gas sensor of the MEMS chip prepared in Example 1 of the present invention to CO gas with a concentration of 1500 ppm;

[0031] Figure 9 Temperature record of the battery thermal runaway test of the CO gas sensor using the MEMS chip prepared in Example 1 of the present invention;

[0032] Figure 10 This is a graph showing the signal changes of the CO gas detected by the MEMS chip-based CO gas sensor prepared in Example 1 of the present invention;

[0033] Figure 11 This is a scanning electron microscope image of Pt / SnO2 prepared in Example 2 of the present invention;

[0034] Figure 12 Response curve of the CO gas sensor based on the MEMS chip prepared in Example 2 of the present invention to CO gas with a concentration of 1000 ppm;

[0035] Figure 13 This is a scanning electron microscope image of Pt / SnO2 prepared in Example 3 of the present invention;

[0036] Figure 14 This is the response curve of the CO gas sensor based on the MEMS chip prepared in Example 3 of the present invention to CO gas with a concentration of 1000 ppm. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] In this disclosure, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0039] In the present invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or plural.

[0040] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0041] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0042] The weights of the relevant components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally increased or decreased according to the description of the embodiments of the present invention, it is within the scope disclosed in the description of the embodiments of the present invention. Specifically, the mass described in the description of the embodiments of the present invention may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0043] An embodiment of the present invention provides a preparation method for a CO gas sensor based on a MEMS chip, comprising adding a tin dioxide nanomaterial to an ethanol solution and mixing the mixture uniformly to obtain a first solution; adding chloroplatinic acid to the first solution in an ultraviolet light irradiation environment for reaction to obtain a metal Pt-modified SnO2 nanomaterial, i.e., crude Pt / SnO2; and heat-treating the crude Pt / SnO2 to obtain a Pt / SnO2 nanocomposite material; adding the Pt / SnO2 nanocomposite material to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and mixing the mixture uniformly to obtain a gas-sensitive slurry; drop-coating the gas-sensitive slurry on an electrode of a MEMS chip; and heat-treating the MEMS chip coated with the gas-sensitive slurry to obtain a CO gas sensor based on the MEMS chip.

[0044] The preparation method provided by the present invention first modifies SnO2 to obtain a Pt / SnO2 nanocomposite material to improve its selectivity for CO, and then obtains a uniform gas-sensitive slurry by mixing the Pt / SnO2 nanocomposite material with NMP and PVDF. NMP is a highly polar aprotic solvent with excellent solubility and can effectively dissolve PVDF to form a uniform and stable solution, which is convenient for subsequent mixing with Pt / SnO2 nanomaterials. NMP has good dispersibility for Pt / SnO2 nanoparticles, reduces agglomeration, and improves the uniformity of the gas-sensitive slurry. At the same time, it does not react with the Pt / SnO2 nanomaterial, avoiding degradation of the performance of the sensitive material. PVDF is a fluorine-containing polymer with strong adhesion, which enables the Pt / SnO2 nanoparticles to firmly adhere to the interdigitated electrodes, thereby improving the mechanical stability of the device. PVDF is also resistant to acids, alkalis, and organic solvents, and is not easily degraded in a gas-sensitive working environment, thereby extending the life of the sensor. At the same time, it can form a uniform thin film when combined with NMP, optimize the gas diffusion path, and improve the response / recovery speed. Loading the gas-sensitive slurry onto the MEMS chip facilitates adhesion of the gas-sensitive slurry to the chip; the resulting MEMS-based CO gas sensor can rapidly respond to CO over a wide concentration range. The preparation method provided in this embodiment is simple, rapid, and economical, making it suitable for large-scale industrial production.

[0045] In some embodiments, the tin dioxide nanomaterial is prepared by adding stannous chloride dihydrate to a mixed solution of concentrated hydrochloric acid and anhydrous ethanol, mixing uniformly to obtain a mixed solution, subjecting the mixed solution to a hydrothermal treatment at a temperature of 200-220°C for 12-14 hours to react and obtain crude tin dioxide, wherein the anhydrous ethanol, concentrated hydrochloric acid, and stannous chloride dihydrate are added in a ratio of (15-25) ml:(1-2) ml:0.5 g, and the concentration of concentrated hydrochloric acid is 37%. The crude tin dioxide is washed three times with anhydrous ethanol and deionized water, respectively, and dried in a vacuum environment at 60-80°C for 12-14 hours to obtain the tin dioxide nanomaterial. The tin dioxide nanomaterial prepared by this method has a large specific surface area, can provide more loading sites, and thus effectively prevent the agglomeration of platinum particles.

[0046] In some embodiments, the mass ratio of the tin dioxide nanomaterial to chloroplatinic acid is (5-10):1. The appropriate usage ratio of the two avoids agglomeration of platinum particles, improves the platinum loading rate, and enables platinum to be evenly dispersed on the surface of the tin dioxide nanomaterial. The platinum-modified SnO2 nanomaterial can have a faster response to CO gas and maintain stable performance.

[0047] In some embodiments, the wavelength of the ultraviolet light is 315-400 nm, and the ultraviolet light irradiation time is 30-45 min. Controlling the ultraviolet light wavelength and reaction time can improve the reaction efficiency and reduce the occurrence of side reactions.

[0048] In some embodiments, crude Pt / SnO2 is washed three times with anhydrous ethanol and three times with deionized water, respectively, and then dried in a vacuum environment at 80-100°C for 12-16 hours to produce a Pt / SnO2 nanocomposite. Washing and then drying the crude Pt / SnO2 can improve the purity of the Pt / SnO2 nanocomposite and prevent the effects of impurities on the responsiveness of the Pt / SnO2 nanocomposite.

[0049] In some embodiments, the mass ratio of the polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(200~300); the mass ratio of the mixed solution of Pt / SnO2 and polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(2~3). Limiting the usage ratio of these substances can ensure that the gas-sensitive slurry has an appropriate solution viscosity, so that the gas-sensitive slurry can better adhere to the chip.

[0050] In some embodiments, a Pt / SnO2 nanocomposite material is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and subjected to ultrasonic and magnetic stirring for 20-30 minutes to produce a gas-sensing slurry. 0.5-1 μL of the slurry is then drop-coated onto the electrodes of a MEMS chip. The MEMS chip coated with the slurry is then dried at 80-100°C for 2-3 hours to produce a CO gas sensor based on a MEMS chip. Using a drop-coating method to apply the slurry allows for controlled addition of the slurry, preventing excessive gas-sensing material from poorly contacting the electrodes on the chip. Furthermore, direct contact with the metal electrodes during the coating process can be avoided, potentially contaminating or damaging the electrodes.

[0051] An embodiment of the present invention further provides a MEMS chip-based CO gas sensor prepared according to the above method. The MEMS chip-based CO gas sensor can quickly respond to CO gas over a wide concentration range. The MEMS chip-based CO gas sensor can be used in lithium batteries to monitor the battery status in real time and provide early warning before danger occurs, effectively reducing safety risks.

[0052] In the following examples, unless otherwise specified, all materials used can be obtained through common channels; and the testing methods adopted are conventional methods in the art.

[0053] Example 1

[0054] Preparation of SnO2 nanomaterials: 20 ml of anhydrous ethanol was added to a beaker, followed by 1.5 ml of 37% concentrated hydrochloric acid and stirring for 3 min. 0.5 g of stannous chloride dihydrate (SnCl2·2H2O) was then added and ultrasonicated for 3 min to completely dissolve the SnCl2·2H2O. Magnetic stirring was continued for 60 min until the solution was uniformly mixed to obtain a mixed solution. The mixed solution was transferred to the PPL (Polyparaphenylene, polyphenylene sulfide) tetrafluoroethylene liner of the reactor. The reactor was placed in an electric blast drying oven and hydrothermally treated at 200 °C for 12 h to obtain crude tin dioxide. After the reactor was completely cooled, the crude tin dioxide was taken out and washed with anhydrous ethanol and deionized water three times respectively. The washed crude tin dioxide was then placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain SnO2 nanomaterials. Figure 1 As shown in the figure, a scanning electron microscope image of the prepared SnO2 nanomaterial is shown. It can be seen that the microscopic morphology of the material is a spherical particle with uniform particle size of about 200 nm and a rough surface structure.

[0055] Preparation of Pt / SnO2 nanocomposite materials: 0.04 g of the prepared SnO2 nanomaterial was weighed and added to a mixed solution of 20 mL of deionized water and 20 ml of anhydrous ethanol. The SnO2 nanomaterial was uniformly dispersed by ultrasonication for 30 min to obtain a first solution. Under the condition of 365 nm ultraviolet light irradiation, 0.004 g of chloroplatinic acid was added to the first solution and a photoreduction reaction was carried out for 30 min to obtain crude Pt / SnO2. The crude Pt / SnO2 was washed three times with anhydrous ethanol and deionized water respectively. The washed crude Pt / SnO2 was dried in a vacuum drying oven at 80 ° C for 12 h to obtain a Pt / SnO2 nanocomposite material; Figure 2 As shown in FIG, the scanning electron microscope image of the prepared Pt / SnO2 nanocomposite material shows that the material still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0056] Preparation of gas-sensitive slurry: Weigh 299 mg of N-methyl-2-pyrrolidone (NMP), add 1 mg of polyvinylidene fluoride (PVDF) to NMP, and stir ultrasonically until PVDF is completely dissolved. Then add 100 mg of Pt / SnO2 nanocomposite material and mix evenly by ultrasonic and magnetic stirring for 30 minutes to obtain gas-sensitive slurry; use a pipette to draw 0.5 μL of gas-sensitive slurry and evenly drop it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with gas-sensitive slurry in an electric blast drying oven and dry it at 90°C for 2 hours to obtain a CO gas sensor based on the MEMS chip.

[0057] Figure 3 This is a photo of the MEMS chip before and after coating with gas-sensitive slurry. Figure 4 Optical microscope pictures of MEMS chip before and after coating with gas sensitive slurry. Figure 3 (a) and (b), and Figure 4 In (a) and (b), it can be observed that after drying, the gas-sensitive material has been evenly loaded on the interdigital electrodes on the surface of the MEMS chip.

[0058] The CO gas sensor based on the MEMS chip prepared in Example 1 was tested:

[0059] CO responsiveness test of CO gas sensor based on MEMS chip:

[0060] The MEMS chip-based CO gas sensor prepared in Example 1 was installed in a test mold and then placed in a CGS-8 intelligent gas-sensitive analysis system. A static test method was adopted: different volumes of CO gas were collected from the gas cylinder using an aluminum foil gas collection bag, and then injected into the chamber of the analysis system. After waiting for the response to be completed and stable for a period of time, the chamber was opened to allow the MEMS chip to recover.

[0061] like Figure 5-8 As shown, the response curves of the CO gas sensor based on the MEMS chip prepared in Example 1 to CO gas concentrations of 10 ppm, 100 ppm, 1000 ppm, and 1500 ppm are shown. It can be seen that the sensitivity (sensitivity), response time, and recovery time (seconds) of the CO gas sensor based on the MEMS chip to CO gas of different concentrations are relatively fast, both less than 15 s, and it can still respond at a low concentration of 10 ppm. When the CO concentration is higher, the sensitivity of the CO gas sensor based on the MEMS chip also increases accordingly.

[0062] Verification of battery thermal runaway response effect of CO gas sensor based on MEMS chip:

[0063] The MEMS chip-based CO gas sensor prepared in Example 1 was packaged and applied to battery thermal runaway warning. Fire tests were conducted using a lithium iron phosphate battery module. The battery box dimensions were 1170 mm long, 808 mm wide, and 240 mm high. A 280Ah lithium iron phosphate battery was selected as the research object, and the remaining locations were filled with model fillers. Thermal runaway was induced using a 0.5 P overcharge. Thermocouples were placed on the battery's large surface, sides, and safety valve to record temperature changes. A detector was installed on the front panel of the battery box to verify the detector's responsiveness to thermal runaway.

[0064] like Figure 9 As shown in the figure, the data of temperature change over time shows that as the battery begins to overcharge, the battery temperature continues to rise for about 3929 seconds. When the battery valve is opened, the temperature at the safety valve position is the highest, reaching 77.89°C. The temperature of the large surface of the battery reaches 55.59°C, and a small amount of gas and smoke escapes. At about 4500 seconds, the battery reaches thermal runaway, releasing a large amount of flammable gas and smoke. The temperature of the overcharge thermal runaway cell reaches as high as 440°C.

[0065] like Figure 10 The figure shows the changes in the CO gas concentration signal detected by the MEMS chip-based CO gas sensor during battery thermal runaway. The CO concentration begins to rise before the single-cell valve opens. Approximately 3929 seconds after the battery valve opens, the CO concentration instantaneously (within 2 seconds) reaches the set threshold (1000 ppm), demonstrating good responsiveness to battery thermal runaway and providing a warning.

[0066] After verification by battery thermal runaway tests, CO gas sensors based on MEMS chips can achieve early warning.

[0067] Example 2

[0068] Preparation of SnO2 nanomaterials: 25 ml of anhydrous ethanol was added to a beaker, followed by the addition of 1 ml of 37% concentrated hydrochloric acid and stirring for 3 min. 0.5 g of SnCl2·2H2O was then added and ultrasonicated for 3 min to completely dissolve the SnCl2·2H2O. Magnetic stirring was continued for 60 min until the solution was uniformly mixed to obtain a mixed solution. The mixed solution was transferred to a PPL tetrafluoroethylene liner in a reactor. The reactor was placed in an electric blast drying oven and hydrothermally treated at 200 °C for 12 h to obtain crude tin dioxide. After the reactor was completely cooled, the crude tin dioxide was taken out and washed three times with anhydrous ethanol and deionized water respectively. The washed crude tin dioxide was then placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain SnO2 nanomaterials. The prepared SnO2 nanomaterials had uniform particle size of about 200 nm and a rough spherical surface structure.

[0069] Preparation of Pt / SnO2 nanocomposite materials: 0.04 g of the prepared SnO2 nanomaterial was weighed and added to a mixed solution of 20 mL of deionized water and 20 mL of anhydrous ethanol. The SnO2 nanomaterial was uniformly dispersed by ultrasonication for 30 min to obtain a first solution. Under 365 nm ultraviolet light irradiation, 0.006 g of chloroplatinic acid was added to the first solution and photoreduction reaction was carried out for 30 min to obtain crude Pt / SnO2. The crude Pt / SnO2 was washed three times with anhydrous ethanol and deionized water, respectively. The washed crude Pt / SnO2 was dried in a vacuum drying oven at 80 °C for 12 h to obtain a Pt / SnO2 nanocomposite material.

[0070] Preparation of gas-sensitive slurry: Weigh 300 mg of NMP, add 1 mg of PVDF to the NMP and stir ultrasonically until the PVDF is completely dissolved. Then add 120 mg of Pt / SnO2 nanocomposite material and mix evenly using ultrasonic and magnetic stirring for 30 min to obtain a gas-sensitive slurry. Use a pipette to draw 0.5 μL of the gas-sensitive slurry and evenly drop it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with the gas-sensitive slurry in an electric heated forced air drying oven and dry it at 90°C for 2 h to obtain a CO gas sensor based on the MEMS chip.

[0071] like Figure 11 As shown, the Pt / SnO2 nanocomposite material prepared in Example 2 still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0072] like Figure 12As shown, it can be seen that the sensitivity, response time and recovery time of the CO gas sensor based on the MEMS chip prepared in Example 2 to a CO gas concentration of 1000 ppm are good. The response time of the CO gas sensor based on the MEMS chip is 10 s, and the recovery time is only 3 s, with good responsiveness and sensitivity.

[0073] Example 3

[0074] Preparation of SnO2 nanomaterials: 15 ml of anhydrous ethanol was added to a beaker, followed by 1.5 ml of 37% concentrated hydrochloric acid and stirring for 3 minutes. 0.5 g of SnCl2·2H2O was then added and ultrasonicated for 3 minutes to completely dissolve the SnCl2·2H2O. Magnetic stirring was continued for 60 minutes until the solution was uniformly mixed to obtain a mixed solution. The mixed solution was transferred to a PPL tetrafluoroethylene liner in a reactor. The reactor was placed in an electric blast drying oven and hydrothermally treated at 200°C for 12 hours to obtain crude tin dioxide. After the reactor was completely cooled, the crude tin dioxide was taken out and washed three times with anhydrous ethanol and deionized water respectively. The washed crude tin dioxide was then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain SnO2 nanomaterials. The prepared SnO2 nanomaterials had uniform particle size of about 200 nm and a rough spherical surface structure.

[0075] Preparation of Pt / SnO2 nanocomposites: Figure 2 As shown, 0.04 g of the prepared SnO2 nanomaterial was weighed and added to a mixed solution of 20 mL of deionized water and 20 ml of anhydrous ethanol. The SnO2 nanomaterial was uniformly dispersed by ultrasonication for 30 min to obtain a first solution. Under the condition of 365 nm ultraviolet light irradiation, 0.008 g of chloroplatinic acid was added to the first solution and a photoreduction reaction was carried out for 30 min to obtain crude Pt / SnO2. The crude Pt / SnO2 was washed three times with anhydrous ethanol and deionized water respectively. The washed crude Pt / SnO2 was dried in a vacuum drying oven at 80 ° C for 12 h to obtain a Pt / SnO2 nanocomposite material.

[0076] Preparation of gas-sensitive slurry: Weigh 300 mg of NMP, add 1 mg of PVDF to the NMP and stir ultrasonically until the PVDF is completely dissolved. Then add 150 mg of Pt / SnO2 nanocomposite material and mix evenly using ultrasonic and magnetic stirring for 20 min to obtain a gas-sensitive slurry. Use a pipette to draw 0.8 μL of the gas-sensitive slurry and evenly drop it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with the gas-sensitive slurry in an electric blast drying oven and dry it at 90 °C for 2 h to obtain a CO gas sensor based on the MEMS chip.

[0077] like Figure 13 As shown, the Pt / SnO2 nanocomposite material prepared in Example 3 still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0078] like Figure 14 As shown, it can be seen that the sensitivity, response time and recovery time of the CO gas sensor based on the MEMS chip prepared in Example 3 to a CO gas concentration of 1000 ppm are good. The response time of the CO gas sensor based on the MEMS chip is 9 s and the recovery time is 10 s, and the responsiveness and sensitivity are good.

[0079] Example 4

[0080] Preparation of Pt / SnO2 nanocomposite material: 0.04 g of the SnO2 nanomaterial prepared in Example 1 was weighed and added to a mixed solution of 20 mL of deionized water and 20 mL of anhydrous ethanol. The SnO2 nanomaterial was uniformly dispersed by ultrasonication for 30 min to obtain a first solution. Under 315 nm ultraviolet light irradiation, 0.004 g of chloroplatinic acid was added to the first solution, and a photoreduction reaction was carried out for 40 min to obtain crude Pt / SnO2. The crude Pt / SnO2 was washed three times with anhydrous ethanol and deionized water, respectively. The washed crude Pt / SnO2 was dried in a vacuum drying oven at 100°C for 14 h to obtain a Pt / SnO2 nanocomposite material.

[0081] Preparation of gas-sensitive slurry: Weigh 200 mg of NMP, add 1 mg of PVDF to the NMP and stir ultrasonically until the PVDF is completely dissolved. Then add 100 mg of Pt / SnO2 nanocomposite material and mix evenly using ultrasonic and magnetic stirring for 25 minutes to obtain a gas-sensitive slurry. Use a pipette to draw 1 μL of the gas-sensitive slurry and evenly apply it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with the gas-sensitive slurry in an electric forced air drying oven and dry it at 80°C for 3 hours to obtain a CO gas sensor based on the MEMS chip.

[0082] The Pt / SnO2 nanocomposite material prepared in Example 4 still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0083] The response performance of the CO gas sensor based on the MEMS chip prepared in Example 4 to 1000 ppm CO gas is as follows: the response time is 9 s, and the recovery time is only 8 s, with good responsiveness and sensitivity.

[0084] Example 5

[0085] Preparation of Pt / SnO2 nanocomposite material: 0.04 g of the SnO2 nanomaterial prepared in Example 1 was weighed and added to a mixed solution of 20 mL of deionized water and 20 mL of anhydrous ethanol. The SnO2 nanomaterial was uniformly dispersed by ultrasonication for 30 min to obtain a first solution. Under 400 nm ultraviolet light irradiation, 0.004 g of chloroplatinic acid was added to the first solution, and a photoreduction reaction was carried out for 45 min to obtain crude Pt / SnO2. The crude Pt / SnO2 was washed three times with anhydrous ethanol and deionized water, respectively. The washed crude Pt / SnO2 was dried in a vacuum drying oven at 90°C for 16 h to obtain a Pt / SnO2 nanocomposite material.

[0086] Preparation of gas-sensitive slurry: Weigh 250 mg of NMP, add 1 mg of PVDF to the NMP and stir ultrasonically until the PVDF is completely dissolved. Then add 100 mg of Pt / SnO2 nanocomposite material and mix evenly by ultrasonic and magnetic stirring for 30 min to obtain gas-sensitive slurry. Use a pipette to draw 1 μL of gas-sensitive slurry and evenly drop it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with gas-sensitive slurry in an electric forced air drying oven and dry it at 80 °C for 3 h to obtain a CO gas sensor based on the MEMS chip.

[0087] The Pt / SnO2 nanocomposite material prepared in Example 5 still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0088] The response performance of the CO gas sensor based on the MEMS chip prepared in Example 5 to 1000 ppm CO gas is as follows: the response time is 10 s, and the recovery time is only 7 s, with good responsiveness and sensitivity.

[0089] Example 6

[0090] Preparation of Pt / SnO2 nanocomposite material: 0.04 g of the SnO2 nanomaterial prepared in Example 1 was weighed and added to a mixed solution of 20 mL of deionized water and 20 ml of anhydrous ethanol. The SnO2 nanomaterial was uniformly dispersed by ultrasonication for 30 min to obtain a first solution. Under the condition of 350 nm ultraviolet light irradiation, 0.004 g of chloroplatinic acid was added to the first solution, and a photoreduction reaction was carried out for 35 min to obtain crude Pt / SnO2. The crude Pt / SnO2 was washed three times with anhydrous ethanol and deionized water, respectively. The washed crude Pt / SnO2 was dried in a vacuum drying oven at 100°C for 15 h to obtain a Pt / SnO2 nanocomposite material.

[0091] Preparation of gas-sensitive slurry: Weigh 270 mg of NMP, add 1 mg of PVDF to the NMP and stir ultrasonically until the PVDF is completely dissolved. Then add 100 mg of Pt / SnO2 nanocomposite material and mix evenly using ultrasonic and magnetic stirring for 30 min to obtain a gas-sensitive slurry. Use a pipette to draw 1 μL of the gas-sensitive slurry and evenly drop it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with the gas-sensitive slurry in an electric heated forced air drying oven and dry it at 100 °C for 2.5 h to obtain a CO gas sensor based on the MEMS chip.

[0092] The Pt / SnO2 nanocomposite material prepared in Example 6 still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0093] The response performance of the CO gas sensor based on the MEMS chip prepared in Example 6 to 1000 ppm CO gas is as follows: the response time is 12 s, and the recovery time is only 9 s, with good responsiveness and sensitivity.

[0094] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0095] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for preparing a CO gas sensor based on a MEMS chip, characterized in that: include: Adding a tin dioxide nanomaterial to an ethanol solution and mixing uniformly to obtain a first solution, adding chloroplatinic acid to the first solution under ultraviolet light irradiation to react to obtain a crude Pt / SnO2, and heat-treating the crude Pt / SnO2 to obtain a Pt / SnO2 nanocomposite material, wherein the mass ratio of the tin dioxide nanomaterial to the chloroplatinic acid is (5-10):1; The Pt / SnO2 nanocomposite material is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and mixed uniformly to obtain a gas-sensitive slurry; the mass ratio of the polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(200-300), and the mass ratio of the Pt / SnO2 to the mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(2-3); 0.5~1 μL of gas-sensitive slurry was drop-coated on the electrode of the MEMS chip. The MEMS chip coated with the gas-sensitive slurry was placed at 80~100 °C and dried for 2~3 h to obtain a CO gas sensor based on the MEMS chip.

2. The method for preparing a CO gas sensor based on a MEMS chip according to claim 1, wherein: The wavelength of the ultraviolet light is 315-400 nm, and the ultraviolet light irradiation time is 30-45 min.

3. The method for preparing a CO gas sensor based on a MEMS chip according to claim 1, wherein: The crude Pt / SnO2 is subjected to heat treatment to obtain the Pt / SnO2 nanocomposite material, specifically, the crude Pt / SnO2 is placed in a vacuum environment at 80-100°C and dried for 12-16 hours to obtain the Pt / SnO2 nanocomposite material.

4. A CO gas sensor based on a MEMS chip, characterized in that: The CO gas sensor based on the MEMS chip is prepared according to the preparation method of any one of claims 1 to 3.

5. An application of the CO gas sensor based on the MEMS chip according to claim 4, characterized in that: The CO gas sensor based on the MEMS chip is used in lithium batteries.

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