CO gas sensor based on MEMS chip as well as preparation method and application of CO gas sensor

Abstract

The invention discloses a CO gas sensor based on an MEMS chip as well as a preparation method and application of the CO gas sensor, and belongs to the field of gas sensors. The preparation method provided by the invention comprises the following steps: modifying stannous chloride dehydrate to obtain a Pt / SnO2 nano composite material; adding the Pt / SnO2 nano composite material into a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone, and uniformly mixing the Pt / SnO2 nano composite material and the mixed solution to obtain gas-sensitive slurry; and coating an electrode of the MEMS chip with the gas-sensitive slurry, and carrying out heat treatment on the MEMS chip coated with the gas-sensitive slurry to obtain the CO gas sensor based on the MEMS chip. The MEMS chip CO sensor prepared by the invention has second-level response time to thermal runaway of a battery, and can detect trace CO gas before thermal runaway of the battery.

Description

Technical Field

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

[0002] While the energy storage industry is developing rapidly, energy storage accidents are not uncommon, and there are still significant safety problems in lithium battery energy storage technology. During the long-term charge and discharge cycle of lithium batteries, gas by-products such as hydrogen and carbon monoxide will inevitably be generated. The accumulation of these gases will not only have a negative impact on the overall performance of the battery, but more importantly, they may also pose a severe challenge to the safety of the battery. Especially when the gas emission reaches a certain level, it will cause a sharp rise in the internal pressure of the battery, which may trigger the thermal runaway phenomenon of the battery.

[0003] MEMS (Micro-Electro-Mechanical System) is a micro-electromechanical system, and a MEMS chip is a micron-nano-level mechanical system with sensing functions. This mechanical system can convert external physical and chemical signals into electrical signals. Gas-sensitive materials are the key components of MEMS-type CO sensors. In order to improve the performance of MEMS-type CO gas sensors, tin dioxide (SnO2) with high sensitivity, fast response, and low energy consumption characteristics is usually used as the sensitive material. At the same time, the loading process is also the key to obtaining a MEMS chip with good sensing performance. The traditional process has uneven loading of the gas-sensitive slurry, and the bonding force between the gas-sensitive slurry and the sensitive electrode is weak, which affects the stability and gas response ability of the sensor at different working temperatures.

[0004] Based on this, the purpose of the present invention is to provide a slurry loading process for a MEMS chip-based CO gas sensor with a fast response to CO gas. Summary of the Invention

[0005] In order to solve the problem that the traditional gas-sensitive slurry loading process often has uneven loading, resulting in a weak bonding force with the sensitive electrode, and further affecting the stability and gas response ability of the sensor at different working temperatures, the present invention provides a CO gas sensor based on a MEMS chip, a preparation method thereof, and an application thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a preparation method of a CO gas sensor based on a MEMS chip, including: The tin dioxide nanomaterial is added to an ethanol solution and mixed evenly to obtain a first solution. In an ultraviolet light irradiation environment, chloroplatinic acid is added to the first solution for reaction to obtain crude Pt / SnO2, and the crude Pt / SnO2 is heat-treated to obtain a Pt / SnO2 nanocomposite material; The 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 paste; the gas-sensitive paste is drop-coated on the electrodes of a MEMS chip, and the MEMS chip coated with the gas-sensitive paste is heat-treated to obtain a CO gas sensor based on the MEMS chip.

[0007] The mass ratio of the tin dioxide nanomaterial to the chloroplatinic acid is (5~10):1.

[0008] The wavelength of the ultraviolet light is 315~400 nm, and the ultraviolet light irradiation time is 30~45 min. The heat treatment of the crude Pt / SnO2 to obtain the Pt / SnO2 nanocomposite material specifically is: the crude Pt / SnO2 is placed in a vacuum environment at 80~100 °C and dried for 12~16 h to obtain the Pt / SnO2 nanocomposite material.

[0009] The mass ratio of the polyvinylidene fluoride to the N-methyl-2-pyrrolidone is 1:(200~300). The mass ratio of the Pt / SnO2 to the mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(2~3).

[0010] The drop-coating of the gas-sensitive paste on the electrodes of the MEMS chip specifically is: 0.5~1 μL of the gas-sensitive paste is taken and drop-coated on the electrodes of the MEMS chip.

[0011] The heat treatment of the MEMS chip coated with the gas-sensitive paste to obtain the CO gas sensor based on the MEMS chip specifically is: the MEMS chip coated with the gas-sensitive paste is placed at a temperature of 80~100 °C and dried for 2~3 h to obtain the CO gas sensor based on the MEMS chip.

[0012] The present invention also provides a CO gas sensor based on a MEMS chip, which is prepared according to the preparation method of the above-mentioned CO gas sensor based on the MEMS chip.

[0013] The present invention also provides an application of the above-mentioned CO gas sensor based on the MEMS chip, and the CO gas sensor based on the MEMS chip is applied in a lithium battery.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The preparation method of the present invention uses modified tin dioxide. Platinum is loaded on the surface of the original rough tin dioxide nanospheres, which can improve the gas-sensing performance of SnO2 and its selectivity to 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-sensing slurry. The Pt / SnO2-NMP-PVDF system has a synergistic advantage. NMP ensures that the Pt / SnO2 nanoparticles do not agglomerate, and PVDF fixes the positions of the nanoparticles to form a porous sensitive layer. At the same time, the catalytic effect of Pt is combined with the semiconductor characteristics of SnO2, and the NMP-PVDF system does not interfere with the gas-sensing reaction, effectively improving the response performance of the sensor to CO gas. This preparation method also uses the drop-coating method to load the gas-sensing slurry on the surface of the MEMS chip, improving the adhesion of the sensitive material on the MEMS chip. Compared with the traditional loading process, the MEMS chip prepared by the present invention can achieve a rapid response to CO gas in a wide concentration range. This enables the sensor to accurately and quickly detect changes in CO gas under various environmental conditions, especially suitable for application scenarios that require high sensitivity and rapid response, such as early warning of battery thermal runaway. The preparation method proposed by the present invention is simple, rapid, economical and efficient, and at the same time has good reproducibility and stability, can meet the requirements of the production line, and promotes the popularization of the sensor in practical applications.

[0015] The MEMS chip CO sensor prepared by the present invention has a response time of seconds to battery thermal runaway. In the range of CO concentration from 10 ppm to 1500 ppm, it can achieve a response within 15 s. At the same time, it can detect trace amounts of CO gas before the battery undergoes thermal runaway. The MEMS chip CO sensor provided by the present invention can monitor the battery state in real time and give an early warning before danger occurs, effectively reducing the safety risk. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0017] Figure 1 It is the scanning electron microscope image of SnO2 prepared in Example 1 of the present invention; Figure 2 It is the scanning electron microscope image of Pt / SnO2 prepared in Example 1 of the present invention; Figure 3 These are the physical pictures of the MEMS chip before and after coating with the gas-sensitive paste in the present invention. Among them, (a) is the physical picture of the MEMS chip, and (b) is the physical picture of the MEMS chip after coating with the gas-sensitive paste; Figure 4 These are the optical microscope pictures of the MEMS chip before and after coating with the gas-sensitive paste in the present invention. Among them, (a) is the optical microscope picture of the MEMS chip; (b) is the optical microscope picture of the MEMS chip after coating with the gas-sensitive paste; Figure 5 This is the 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); Figure 6 This is the 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; Figure 7 This is the 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; Figure 8 This is the 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; Figure 9 This is the temperature record of the battery thermal runaway test of the CO gas sensor of the MEMS chip prepared in Example 1 of the present invention; Figure 10 This is the signal change diagram of the CO gas sensor based on the MEMS chip prepared in Example 1 of the present invention for detecting CO gas; Figure 11 This is the scanning electron microscope image of Pt / SnO2 prepared in Example 2 of the present invention; Figure 12 This is the 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; Figure 13 This is the scanning electron microscope image of Pt / SnO2 prepared in Example 3 of the present invention; 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 implementation manners

[0018] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] In the present invention, the term "and / or" describes the association relationship of associated objects and indicates that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0020] In the present invention, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or plural respectively.

[0021] It should be understood that in various embodiments of the present invention, the magnitudes of the serial numbers of the above processes do not mean the sequence of execution. Some or all steps can be executed in parallel or sequentially. The execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0022] 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", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0023] The weights of the relevant components mentioned in the specification of the embodiments of the present invention not only can refer to the specific contents of each component, but also can represent the proportional relationship of the weights between each component. Therefore, as long as the contents of the relevant components in the specification of the embodiments of the present invention are enlarged or reduced in proportion, they are within the scope disclosed in the specification of the embodiments of the present invention. Specifically, the mass described in the specification of the embodiments of the present invention can be mass units well known in the chemical industry such as μg, mg, g, kg, etc.

[0024] The embodiment of the present invention provides a preparation method of a CO gas sensor based on a MEMS chip, which includes adding tin dioxide nanomaterials into an ethanol solution and mixing evenly to obtain a first solution, adding chloroplatinic acid into the first solution in an ultraviolet light irradiation environment for reaction to obtain metal Pt-modified SnO2 nanomaterials, namely crude Pt / SnO2, and performing heat treatment on the crude Pt / SnO2 to obtain a Pt / SnO2 nanocomposite material; adding the Pt / SnO2 nanocomposite material into a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and mixing evenly to obtain a gas-sensitive paste; dropping the gas-sensitive paste on the electrodes of the MEMS chip, and performing heat treatment on the MEMS chip coated with the gas-sensitive paste to obtain a CO gas sensor based on the MEMS chip.

[0025] The preparation method provided by the present invention first modifies SnO2 to obtain a Pt / SnO2 nanocomposite material to improve its selectivity to CO. Then, a uniform gas-sensitive paste is obtained by mixing the Pt / SnO2 nanocomposite material with NMP and PVDF. NMP is a strongly polar aprotic solvent with excellent solubility, which can effectively dissolve PVDF to form a homogeneous and stable solution, facilitating subsequent mixing with the Pt / SnO2 nanomaterials; it has good dispersibility for Pt / SnO2 nanoparticles, reducing aggregation and improving the uniformity of the gas-sensitive paste. At the same time, it does not react with the Pt / SnO2 nanomaterials, avoiding the degradation of the sensitive material properties; PVDF is a fluoropolymer with strong adhesion, enabling the Pt / SnO2 nanoparticles to firmly adhere to the interdigital electrodes, improving the mechanical stability of the device; and PVDF is resistant to acids and bases and organic solvents and is not easily degraded in the gas-sensitive working environment, extending the sensor life; at the same time, it can form a uniform film in cooperation with NMP to optimize the gas diffusion path and improve the response / recovery speed. Loading the gas-sensitive paste on the MEMS chip is beneficial for the gas-sensitive paste to adhere to the chip; the prepared CO gas sensor based on the MEMS chip can achieve a rapid response to CO in a wide concentration range. The preparation method provided by this embodiment is simple, fast and economical, and is suitable for large-scale industrial production.

[0026] In some embodiments, the method for preparing the tin dioxide nanomaterial is as follows: stannous chloride dihydrate is added to a mixed solution of concentrated hydrochloric acid and absolute ethanol and mixed evenly to obtain a mixed solution, and the mixed solution is hydrothermally treated at a temperature of 200-220 °C for 12-14 h to carry out a reaction to obtain crude tin dioxide. The addition ratio of the absolute ethanol, concentrated hydrochloric acid and stannous chloride dihydrate is (15-25) ml:(1-2) ml:0.5 g, and the concentration of the concentrated hydrochloric acid is 37%; the crude tin dioxide is washed 3 times with absolute ethanol and deionized water respectively, and the washed crude tin dioxide is placed in a vacuum environment at 60-80 °C and dried for 12-14 h 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 avoids the agglomeration phenomenon of platinum particles.

[0027] In some embodiments, the mass ratio of the tin dioxide nanomaterial to chloroplatinic acid is (5-10):1. The appropriate dosage ratio of the two can avoid the agglomeration phenomenon of platinum particles, improve the platinum loading rate, enable platinum to be evenly dispersed on the surface of the tin dioxide nanomaterial, and the platinum-modified SnO2 nanomaterial can have a faster response ability to CO gas and can maintain stable performance.

[0028] 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 wavelength and reaction time of the ultraviolet light can improve the reaction efficiency and reduce the occurrence of side reactions.

[0029] In some embodiments, the crude Pt / SnO2 is washed 3 times with absolute ethanol and deionized water respectively, and the washed crude Pt / SnO2 is placed in a vacuum environment at 80-100 °C and dried for 12-16 h to obtain the Pt / SnO2 nanocomposite material. Washing and drying the crude Pt / SnO2 can improve the purity of the Pt / SnO2 nanocomposite material and avoid the influence of impurities on the response performance of the Pt / SnO2 nanocomposite material.

[0030] In some embodiments, the mass ratio of polyvinylidene fluoride to N-methyl-2-pyrrolidone is 1:(200-300); the mass ratio of the Pt / SnO2 to the mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(2-3). Limiting the dosage ratio of these substances can ensure that the gas-sensitive slurry has an appropriate solution viscosity and enables the gas-sensitive slurry to adhere better to the chip.

[0031] In some embodiments, the Pt / SnO2 nanocomposite is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone, and ultrasonic and magnetic stirring are carried out for 20 - 30 min to obtain a gas-sensitive paste; 0.5 - 1 μL of the gas-sensitive paste is taken and drop-coated on the electrodes of the MEMS chip, and the MEMS chip coated with the gas-sensitive paste is placed in a temperature of 80 - 100 °C and dried for 2 - 3 h to obtain a CO gas sensor based on the MEMS chip. The gas-sensitive paste is coated by the drop-coating method, which can control the addition amount of the gas-sensitive paste, avoid poor contact between too much gas-sensitive material and the electrodes on the chip; in addition, it can avoid direct contact between the coating process and the metal electrodes, causing electrode contamination or damage.

[0032] An embodiment of the present invention also provides a CO gas sensor based on the MEMS chip prepared according to the above method. The CO gas sensor based on the MEMS chip can achieve a rapid response to CO gas within a wide concentration range; the CO gas sensor based on the MEMS chip can be applied to lithium batteries, can monitor the battery state in real time, and give an early warning before danger occurs, effectively reducing the safety risk.

[0033] In the following embodiments, unless otherwise specified, all materials used can be obtained through ordinary channels; the testing methods adopted are conventional methods in the art.

[0034] Example 1 Preparation of SnO2 nanomaterial: 20 ml of absolute ethanol is added to a beaker, then 1.5 ml of concentrated hydrochloric acid with a concentration of 37% is added and stirred for 3 min, and then 0.5 g of stannous chloride dihydrate (SnCl2·2H2O) is added and ultrasonicated for 3 min to completely dissolve SnCl2·2H2O. Continue magnetic stirring for 60 min until the solution is mixed evenly to obtain a mixed solution. The mixed solution is transferred to the PPL (Polyparaphenylene) tetrafluoro inner liner of the reaction kettle, and the reaction kettle is placed in an electrothermal blast drying oven and hydrothermally treated at 200 °C for 12 h to obtain crude tin dioxide. After the reaction kettle is completely cooled, the crude tin dioxide is taken out, and the crude tin dioxide is washed 3 times with absolute ethanol and deionized water respectively. Then the washed crude tin dioxide is placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain SnO2 nanomaterial; as Figure 1 shown, the scanning electron microscope image of the prepared SnO2 nanomaterial is presented, and it can be seen that the microscopic morphology of the material is spherical with uniform particle size, the particle diameter is about 200 nm, and the surface structure is rough.

[0035] Preparation of Pt / SnO2 nanocomposites: Weigh 0.04 g of the prepared SnO2 nanomaterials and add them to a mixed solution of 20 mL of deionized water and 20 mL of absolute ethanol. Ultrasonicate for 30 min to uniformly disperse the SnO2 nanomaterials to obtain the first solution. Under the condition of 365 nm ultraviolet light irradiation, add 0.004 g of chloroplatinic acid to the first solution and carry out a 30-min photoreduction reaction to obtain crude Pt / SnO2. Wash the crude Pt / SnO2 three times with absolute ethanol and deionized water respectively, and dry the washed crude Pt / SnO2 in a vacuum drying oven at 80 °C for 12 h to obtain the Pt / SnO2 nanocomposites; as Figure 2 shown, the scanning electron microscope image of the prepared Pt / SnO2 nanocomposites shows that the material still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterials.

[0036] Preparation of gas-sensitive slurry: Weigh 299 mg of N-methyl-2-pyrrolidone (NMP), add 1 mg of polyvinylidene fluoride (PVDF) to the NMP and ultrasonically stir until the PVDF is completely dissolved. Then add 100 mg of the Pt / SnO2 nanocomposites and mix them uniformly by ultrasonic and magnetic stirring for 30 min to obtain the gas-sensitive slurry; use a pipette to suck 0.5 μL of the gas-sensitive slurry and uniformly drop it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with the gas-sensitive slurry in an electrothermal blast drying oven and dry it at 90 °C for 2 h to obtain a CO gas sensor based on the MEMS chip.

[0037] Figure 3 are the physical pictures of the MEMS chip before and after coating the gas-sensitive slurry, Figure 4 are the optical microscope pictures of the MEMS chip before and after coating the gas-sensitive slurry. From Figure 3 (a) and (b) in, and Figure 4 (a) and (b) in, it can be observed that the gas-sensitive material has been uniformly loaded on the interdigital electrodes on the surface of the MEMS chip after drying.

[0038] Test the CO gas sensor based on the MEMS chip prepared in Example 1: Carry out a CO responsiveness test on the CO gas sensor based on the MEMS chip: Install the CO gas sensor based on the MEMS chip prepared in Example 1 in a test mold, and then put it into a CGS-8 intelligent gas-sensitive analysis system. Adopt a static test method: Use an aluminum foil gas collection bag to collect different volumes of CO gas from a gas cylinder, then inject it into the chamber of the analysis system and wait for the response to complete and stabilize for a period of time, and then open the chamber to restore the MEMS chip.

[0039] As Figures 5 - 8As 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 presented. It can be seen the sensitivity, response time, and recovery time (in seconds) of the CO gas sensor based on the MEMS chip to CO gas at different concentrations. The response time and recovery time of the CO gas sensor based on the MEMS chip are both relatively fast, both less than 15 s, and it can still respond at a low concentration of 10 ppm. When the CO concentration is relatively high, the sensitivity of the CO gas sensor based on the MEMS chip also increases accordingly.

[0040] Verification of the response effect of the CO gas sensor based on the MEMS chip to battery thermal runaway: The CO gas sensor based on the MEMS chip prepared in Example 1 was encapsulated and applied to battery thermal runaway early warning. A fire experiment was conducted using a lithium iron phosphate battery module. The size of the battery box was 1170 mm in length × 808 mm in width × 240 mm in height. One 280 Ah lithium iron phosphate battery was selected as the research object, and the other positions were filled with models. Overcharging at 0.5 P was used to induce battery thermal runaway. Thermocouples were arranged on the large surface, side, and safety valve position of the battery to record the temperature changes. A detector was installed on the front panel of the battery box to verify the responsiveness of the detector to battery thermal runaway.

[0041] As Figure 9 shown, the data of the recorded temperature (Temperature) changing with time (Time) were obtained. It can be seen that as the battery started to be overcharged, the battery temperature continued to rise, and the time was about 3929 s. The battery opened the valve, and the temperature at the safety valve position was the highest, reaching 77.89 °C, and the temperature of the large surface of the battery reached 55.59 °C. A small amount of gas and smoke escaped. At about 4500 s, the battery reached thermal runaway, releasing a large amount of combustible gas and smoke, and the temperature of the overcharged and thermally runaway battery cell reached a maximum of 440 °C.

[0042] As Figure 10 shown, the change situation of the CO gas concentration signal detected by the CO gas sensor based on the MEMS chip during the battery thermal runaway process can be seen. Before the single battery cell opened the valve, the CO concentration began to rise. After the battery opened the valve for about 3929 s, the CO concentration instantaneously (within 2 s) reached the set threshold (1000 ppm), showing good responsiveness to battery thermal runaway and being able to play a warning role.

[0043] Through verification by the battery thermal runaway test, the CO gas sensor based on the MEMS chip can achieve early warning.

[0044] Example 2 Preparation of SnO2 nanomaterials: Add 25 ml of absolute ethanol into a beaker, then add 1 ml of concentrated hydrochloric acid with a concentration of 37% and stir for 3 min. Next, add 0.5 g of SnCl2·2H2O and ultrasonicate for 3 min to completely dissolve SnCl2·2H2O. Continue magnetic stirring for 60 min until the solution is well mixed to obtain a mixed solution. Transfer the mixed solution to the PPL tetrafluoro inner liner of the reaction kettle, place the reaction kettle in an electrothermal blast drying oven, and perform hydrothermal treatment at 200 °C for 12 h to obtain crude tin dioxide. After the reaction kettle has completely cooled, take out the crude tin dioxide, wash the crude tin dioxide 3 times with absolute ethanol and deionized water respectively. Then place the washed crude tin dioxide in a vacuum drying oven and dry it at 60 °C for 12 h to obtain SnO2 nanomaterials. The prepared SnO2 nanomaterials have uniform particle sizes, with a particle diameter of about 200 nm, and are spherical with a rough surface structure; Preparation of Pt / SnO2 nanocomposites: Weigh 0.04 g of the prepared SnO2 nanomaterials and add them to a mixed solution of 20 mL of deionized water and 20 ml of absolute ethanol. Ultrasonicate for 30 min to uniformly disperse the SnO2 nanomaterials to obtain a first solution. Under the condition of 365 nm ultraviolet light irradiation, add 0.006 g of chloroplatinic acid to the first solution and carry out a 30 min photoreduction reaction to obtain crude Pt / SnO2. Wash the crude Pt / SnO2 3 times with absolute ethanol and deionized water respectively. Dry the washed crude Pt / SnO2 in a vacuum drying oven at 80 °C for 12 h to obtain Pt / SnO2 nanocomposites; Preparation of gas-sensitive slurry: Weigh 300 mg of NMP, add 1 mg of PVDF to NMP and ultrasonically stir until PVDF is completely dissolved. Then add 120 mg of Pt / SnO2 nanocomposites to it and use ultrasonic and magnetic stirring for 30 min to mix evenly to obtain a gas-sensitive slurry; Use a pipette to suck 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 electrothermal blast drying oven and dry it at 90 °C for 2 h to obtain a CO gas sensor based on the MEMS chip.

[0045] As Figure 11 shown, the Pt / SnO2 nanocomposites prepared in Example 2 still maintain the microscopic morphology of rough nanospheres, and Pt is evenly dispersed on the surface of the SnO2 nanomaterials.

[0046] As Figure 12As shown, it can be seen that for the CO gas sensor based on the MEMS chip prepared in Example 2, the sensitivity, response time, and recovery time for a CO gas concentration of 1000 ppm are as follows. The response time of the CO gas sensor based on the MEMS chip is 10 s, and the recovery time only requires 3 s, with good responsiveness and sensitivity.

[0047] Example 3 Preparation of SnO2 nanomaterials: Add 15 ml of absolute ethanol to a beaker, then add 1.5 ml of concentrated hydrochloric acid with a concentration of 37% and stir for 3 min. Then add 0.5 g of SnCl2·2H2O and sonicate for 3 min to completely dissolve SnCl2·2H2O. Continue magnetic stirring for 60 min until the solution is well mixed to obtain a mixed solution. Transfer the mixed solution to the PPL tetrafluoro liner of the reaction kettle, place the reaction kettle in an electrothermal blast drying oven, and perform hydrothermal treatment at 200 °C for 12 h to obtain crude tin dioxide. After the reaction kettle has completely cooled, take out the crude tin dioxide, wash the crude tin dioxide 3 times with absolute ethanol and deionized water respectively. Then place the washed crude tin dioxide in a vacuum drying oven and dry it at 60 °C for 12 h to obtain SnO2 nanomaterials; the prepared SnO2 nanomaterials have uniform particle sizes, with a particle diameter of about 200 nm, and are spherical with a rough surface structure. Preparation of Pt / SnO2 nanocomposites: As Figure 2 shown, weigh 0.04 g of the prepared SnO2 nanomaterials and add them to a mixed solution of 20 mL of deionized water and 20 ml of absolute ethanol. Sonicate for 30 min to uniformly disperse the SnO2 nanomaterials to obtain the first solution. Under the condition of ultraviolet light irradiation at 365 nm, add 0.008 g of chloroplatinic acid to the first solution and carry out a photoreduction reaction for 30 min to obtain crude Pt / SnO2. Wash the crude Pt / SnO2 3 times with absolute ethanol and deionized water respectively. Dry the washed crude Pt / SnO2 in a vacuum drying oven at 80 °C for 12 h to obtain Pt / SnO2 nanocomposites. Preparation of gas-sensitive slurry: Weigh 300 mg of NMP, add 1 mg of PVDF to NMP and sonicate and stir until PVDF is completely dissolved. Then add 150 mg of Pt / SnO2 nanocomposites to it and use ultrasonic and magnetic stirring for 20 min to mix evenly to obtain a gas-sensitive slurry; use a pipette to suck 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 electrothermal blast drying oven and dry it at 90 °C for 2 h to obtain a CO gas sensor based on the MEMS chip.

[0048] As Figure 13As shown, the Pt / SnO2 nanocomposite prepared in Example 3 still maintains the microscopic morphology of rough nanospheres, and Pt is evenly dispersed on the surface of the SnO2 nanomaterial.

[0049] As Figure 14 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. The response time of the CO gas sensor based on the MEMS chip is 9 s, the recovery time is 10 s, and the responsiveness and sensitivity are good.

[0050] Example 4 Preparation of Pt / SnO2 nanocomposite: Weigh 0.04 g of the SnO2 nanomaterial prepared in Example 1 and add it to a mixed solution of 20 mL of deionized water and 20 ml of absolute ethanol. Ultrasonic for 30 min to evenly disperse the SnO2 nanomaterial to obtain the first solution. Under the condition of 315 nm ultraviolet light irradiation, add 0.004 g of chloroplatinic acid to the first solution and carry out a 40 min photoreduction reaction to obtain crude Pt / SnO2. Wash the crude Pt / SnO2 3 times with absolute ethanol and deionized water respectively, and dry the washed crude Pt / SnO2 in a vacuum drying oven at 100 °C for 14 h to obtain the Pt / SnO2 nanocomposite; Preparation of gas-sensitive slurry: Weigh 200 mg of NMP, add 1 mg of PVDF to NMP and stir ultrasonically until PVDF is completely dissolved. Then add 100 mg of Pt / SnO2 nanocomposite to it and mix evenly by ultrasonic and magnetic stirring for 25 min to obtain the gas-sensitive slurry; Use a pipette to suck 1 μL of the gas-sensitive slurry and evenly drop it on the interdigital electrode of the MEMS chip. Put the MEMS chip coated with the gas-sensitive slurry into an electrothermal blast drying oven and dry it at 80 °C for 3 h to obtain a CO gas sensor based on the MEMS chip.

[0051] The Pt / SnO2 nanocomposite prepared in Example 4 still maintains the microscopic morphology of rough nanospheres, and Pt is evenly dispersed on the surface of the SnO2 nanomaterial.

[0052] The response performance of the CO gas sensor based on the MEMS chip prepared in Example 4 to 1000 ppm of CO gas is as follows: the response time is 9 s, the recovery time only needs 8 s, and the responsiveness and sensitivity are good.

[0053] Example 5 Preparation of Pt / SnO2 nanocomposite: Weigh 0.04 g of the SnO2 nanomaterial prepared in Example 1 and add it to a mixed solution of 20 mL of deionized water and 20 mL of absolute ethanol. Ultrasonicate for 30 min to uniformly disperse the SnO2 nanomaterial to obtain the first solution. Under the condition of ultraviolet light irradiation at 400 nm, add 0.004 g of chloroplatinic acid to the first solution and carry out a photoreduction reaction for 45 min to obtain crude Pt / SnO2. Wash the crude Pt / SnO2 3 times with absolute ethanol and deionized water respectively, and dry the washed crude Pt / SnO2 in a vacuum drying oven at 90 °C for 16 h to obtain the Pt / SnO2 nanocomposite; Preparation of gas-sensing paste: Weigh 250 mg of NMP, add 1 mg of PVDF to the NMP and ultrasonically stir until the PVDF is completely dissolved. Then add 100 mg of the Pt / SnO2 nanocomposite to it and mix uniformly by ultrasonic and magnetic stirring for 30 min to obtain the gas-sensing paste. Use a pipette to aspirate 1 μL of the gas-sensing paste and uniformly drop-coat it on the interdigital electrodes of the MEMS chip. Place the MEMS chip coated with the gas-sensing paste in an electrothermal blast drying oven and dry it at 80 °C for 3 h to obtain a CO gas sensor based on the MEMS chip.

[0054] The Pt / SnO2 nanocomposite prepared in Example 5 still maintains the microscopic morphology of rough nanospheres, and Pt is uniformly dispersed on the surface of the SnO2 nanomaterial.

[0055] The CO gas sensor based on the MEMS chip prepared in Example 5 has the following response performance to 1000 ppm of CO gas: the response time is 10 s, the recovery time only needs 7 s, and the responsiveness and sensitivity are good.

[0056] Example 6 Preparation of Pt / SnO2 nanocomposite: Weigh 0.04 g of the SnO2 nanomaterial prepared in Example 1 and add it to a mixed solution of 20 mL of deionized water and 20 mL of absolute ethanol. Ultrasonicate for 30 min to uniformly disperse the SnO2 nanomaterial to obtain the first solution. Under the condition of ultraviolet light irradiation at 350 nm, add 0.004 g of chloroplatinic acid to the first solution and carry out a photoreduction reaction for 35 min to obtain crude Pt / SnO2. Wash the crude Pt / SnO2 3 times with absolute ethanol and deionized water respectively, and dry the washed crude Pt / SnO2 in a vacuum drying oven at 100 °C for 15 h to obtain the Pt / SnO2 nanocomposite; Preparation of gas-sensitive paste: Weigh 270 mg of NMP. Add 1 mg of PVDF to the NMP and stir it ultrasonically until the PVDF is completely dissolved. Then add 100 mg of the Pt / SnO2 nanocomposite to it and mix them evenly by ultrasonic and magnetic stirring for 30 min to obtain the gas-sensitive paste. Use a pipette to suck 1 μL of the gas-sensitive paste and evenly drop it on the interdigital electrodes of the MEMS chip. Put the MEMS chip coated with the gas-sensitive paste into an electrothermal blast drying oven and dry it at 100 °C for 2.5 h to obtain a CO gas sensor based on the MEMS chip.

[0057] The Pt / SnO2 nanocomposite prepared in Example 6 still maintains the microscopic morphology of rough nanospheres, and Pt is evenly dispersed on the surface of the SnO2 nanomaterial.

[0058] The CO gas sensor based on the MEMS chip prepared in Example 6 has the following response performance to 1000 ppm of CO gas: the response time is 12 s, the recovery time only needs 9 s, and the responsiveness and sensitivity are good.

[0059] In the ranges disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article. In the following text, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed in this article.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify the specific implementation manners of the present invention or make equivalent replacements. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of the claims of the present invention pending approval.

Claims

1. A preparation method of a CO gas sensor based on a MEMS chip, characterized in that, Including: Adding tin dioxide nanomaterials into an ethanol solution and mixing evenly to obtain a first solution. In an ultraviolet light irradiation environment, adding chloroplatinic acid into the first solution for reaction to obtain crude Pt / SnO2, and performing heat treatment on the crude Pt / SnO2 to obtain a Pt / SnO2 nanocomposite material; Adding the Pt / SnO2 nanocomposite material into a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone and mixing evenly to obtain a gas-sensitive paste; dropping the gas-sensitive paste onto the electrode of a MEMS chip, and performing heat treatment on the MEMS chip coated with the gas-sensitive paste to obtain a CO gas sensor based on the MEMS chip.

2. The manufacturing method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, The mass ratio of the tin dioxide nanomaterials to the chloroplatinic acid is (5 - 10):

1.

3. The preparation method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, The wavelength of the ultraviolet light is 315 - 400 nm, and the ultraviolet light irradiation time is 30 - 45 min.

4. The manufacturing method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, Performing heat treatment on the crude Pt / SnO2 to obtain a Pt / SnO2 nanocomposite material, specifically: placing the crude Pt / SnO2 in a vacuum environment at 80 - 100 °C and drying for 12 - 16 h to obtain a Pt / SnO2 nanocomposite material.

5. The manufacturing method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, The mass ratio of the polyvinylidene fluoride to the N-methyl-2-pyrrolidone is 1:(200 - 300).

6. The preparation method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, The mass ratio of the Pt / SnO2 to the mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone is 1:(2 - 3).

7. The manufacturing method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, Dropping the gas-sensitive paste onto the electrode of the MEMS chip, specifically: taking 0.5 - 1 μL of the gas-sensitive paste and dropping it onto the electrode of the MEMS chip.

8. The preparation method of the CO gas sensor based on the MEMS chip according to claim 1, characterized in that, Performing heat treatment on the MEMS chip coated with the gas-sensitive paste to obtain a CO gas sensor based on the MEMS chip, specifically: placing the MEMS chip coated with the gas-sensitive paste in a temperature of 80 - 100 °C and drying for 2 - 3 h to obtain a CO gas sensor based on the MEMS chip.

9. A CO gas sensor based on a MEMS chip, characterized in that, Prepared by the preparation method of the CO gas sensor based on the MEMS chip according to any one of claims 1 - 8.

10. An application of the CO gas sensor based on the MEMS chip according to claim 9, characterized in that, The CO gas sensor based on the MEMS chip is applied in a lithium battery.

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