Preparation method of gas sensitive material, gas sensor and preparation method thereof

Abstract

The application discloses a preparation method of a gas-sensitive material, a gas sensor and a preparation method thereof, and relates to the field of sensors. The method comprises the following steps: mixing a hydrofluoric acid solution and a MAX phase material to prepare an MXene solution; mixing a graphene oxide solution, a tungsten ion compound, ascorbic acid and the MXene solution, so that the ascorbic acid reduces graphene oxide in the graphene oxide solution to prepare an rGO / MXene / WO3 mixed solution; and performing a hydrothermal reaction on the rGO / MXene / WO3 mixed solution to prepare an rGO / MXene / WO3 gas-sensitive material. The application aims to solve the problem that the poor gas-sensitive performance of the existing gas-sensitive material leads to the inability to accurately and quickly detect NO2.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, and particularly relates to a preparation method of a gas-sensitive material, a gas sensor and a preparation method thereof. BACKGROUND

[0002] Nitrogen dioxide (NO2) is a toxic and harmful gas with a pungent odor, and its emission mainly comes from motor vehicle exhaust and fossil fuel combustion. When the content of NO2 in the atmosphere is too high, it will cause pollution events such as acid rain, photochemical smog, near-surface ozone, etc., and NO2 will also cause serious damage to the skin, eyes and respiratory system of the human body. In order to protect human health and the environment, it is urgent to realize accurate and rapid detection of NO2.

[0003] In the related art, semiconductor oxides such as ZnO, SnO2 and In2O3 materials have been widely used in the field of NO2 detection. However, the traditional gas-sensitive material can generally only meet the detection requirements of NO2 at high temperatures, and under low temperature conditions, the gas-sensitive performance (such as sensitivity, selectivity, stability, etc.) of the gas-sensitive material still cannot meet the detection requirements of NO2, especially at room temperature (about 25℃), the gas-sensitive performance of the gas-sensitive material prepared in the related art is poor. SUMMARY

[0004] The present application provides a preparation method of a gas-sensitive material, a gas sensor and a preparation method thereof, aiming to solve the problem that the poor gas-sensitive performance of the existing gas-sensitive material leads to the inability to accurately and rapidly detect NO2.

[0005] In a first aspect, the present application provides a preparation method of a gas-sensitive material, which comprises:

[0006] mixing a hydrofluoric acid solution and a MAX phase material to obtain a MXene solution;

[0007] mixing a graphene oxide solution, a tungsten ion compound, ascorbic acid and the MXene solution to reduce the graphene oxide in the graphene oxide solution by the ascorbic acid, to obtain an rGO / MXene / WO3 mixed solution;

[0008] subjecting the rGO / MXene / WO3 mixed solution to a hydrothermal reaction to obtain an rGO / MXene / WO3 gas-sensitive material.

[0009] In a second aspect, the present application provides a preparation method of a gas sensor, which comprises:

[0010] obtaining an rGO / MXene / WO3 gas-sensitive material by using the above preparation method of a gas-sensitive material;

[0011] The rGO / MXene / WO3 gas-sensitive material is added into a dispersant solution to obtain a gas-sensitive material ink;

[0012] Printing is performed using the gas-sensitive material ink to form a gas-sensitive film on the surface of a micro-hotplate;

[0013] The micro-hotplate on which the gas-sensitive film is formed is subjected to a packaging process to obtain a gas sensor.

[0014] In a third aspect, the present application provides a gas sensor prepared by using the preparation method of the gas sensor.

[0015] The present application provides a preparation method of a gas-sensitive material, a gas sensor and a preparation method thereof. The preparation method comprises the following steps: mixing a hydrofluoric acid solution and a MAX phase material to obtain a MXene solution; mixing a graphene oxide solution, a tungsten ion compound, ascorbic acid and the MXene solution to reduce the graphene oxide in the graphene oxide solution by ascorbic acid to obtain an rGO / MXene / WO3 mixed solution; and performing a hydrothermal reaction on the rGO / MXene / WO3 mixed solution to obtain an rGO / MXene / WO3 gas-sensitive material. Thus, the tungsten ion compound can be introduced in the preparation process of the gas-sensitive material, so that the rGO / MXene / WO3 gas-sensitive material with a loose porous structure is formed, more active sites are provided for the contact between the gas-sensitive material and the gas, meanwhile, the presence of tungsten trioxide can promote the adsorption of surface oxygen molecules and increase the content of surface chemisorbed oxygen, thereby facilitating the gas-sensitive reaction, so that the prepared gas sensor exhibits excellent gas-sensitive performance to NO2 gas, has excellent selectivity and stability, and has a simple manufacturing process and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0017] Figure 1 is a step flow schematic diagram of the preparation method of the gas-sensitive material provided by the embodiments of the present application;

[0018] Figure 2 is a scanning electron microscope schematic diagram of the rGO / MXene / WO3 gas-sensitive material provided by the embodiments of the present application;

[0019] Figure 3 is a step flow schematic diagram of the preparation method of the gas sensor provided by the embodiments of the present application;

[0020] Figure 4 A response recovery curve of the gas sensor provided by each embodiment and the comparative example of the present application in a 10ppm NO2 gas environment is shown in the following figure:

[0021] Figure 5 A response value change curve of the gas sensor prepared by embodiment 1 of the present application in a 10ppm NO2 gas environment at different working temperatures is shown in the following figure:

[0022] Figure 6 A response recovery curve of the gas sensor prepared by embodiment 1 of the present application in a NO2 gas environment with different concentrations is shown in the following figure. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0024] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0025] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0026] It should be further understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0027] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0028] With the increasing prominence of environmental problems, air pollution has become the focus of social attention. Among the many pollutants, nitrogen dioxide (NO2) has attracted much attention due to its serious impact on human health and the environment. This gas is mainly derived from industrial combustion, transportation emissions, and the mining process of coal mines. Long-term exposure to high concentrations of NO2 puts people at risk of respiratory diseases, cardiovascular diseases, and lung cancer. Therefore, effective monitoring of NO2 content is crucial for maintaining the ecological environment and public health.

[0029] Reference is made to Figure 1 , Figure 1 The embodiment of the present application provides a schematic flow chart of a preparation method of a gas sensitive material. The preparation method of the gas sensitive material introduces tungsten ion compounds in the preparation process, so as to form a rGO / MXene / WO3 gas sensitive material with a loose porous structure, which can provide more active sites for the contact between the gas sensitive material and the gas. At the same time, the presence of tungsten trioxide can also promote the adsorption of surface oxygen molecules, increase the content of surface chemisorbed oxygen, and thus facilitate the gas sensitive reaction.

[0030] Among them, the gas sensitive material can be applied in the fields of gas sensor, super capacitor, lithium battery electrode material and heat storage material, etc., which is not limited here.

[0031] Exemplarily, since the rGO / MXene / WO3 gas sensitive material has a loose porous structure, it can provide more active sites for the contact between the gas sensitive material and the gas, and the presence of tungsten trioxide can also promote the adsorption of surface oxygen molecules, increase the content of surface chemisorbed oxygen, and thus facilitate the gas sensitive reaction. Therefore, the rGO / MXene / WO3 gas sensitive material provided by the present application can be applied in the field of gas sensor.

[0032] Exemplarily, since the rGO / MXene / WO3 gas sensitive material also has the characteristics of porous high specific surface area and good electrical conductivity, the rGO / MXene / WO3 gas sensitive material provided by the present application can also be applied in the fields of super capacitor and lithium battery electrode material, so as to improve the specific capacitance and electrical conductivity, and enhance the energy density and power density of lithium battery.

[0033] Exemplarily, since MXene and rGO themselves have good thermal conductivity, the composite can improve the thermal conductivity of the material. WO3 as a material with thermal stability can improve the application ability of rGO / MXene / WO3 composite material at high temperature, therefore, the rGO / MXene / WO3 gas sensitive material provided by the present application can also be applied in the field of heat storage material.

[0034] The following will be described in detail taking the application of the gas sensitive material in the field of gas sensor as an example.

[0035] As Figure 1 shown, the preparation method of the gas-sensitive material includes steps S101 to S103.

[0036] Step S101, mixing hydrofluoric acid solution and MAX phase material to prepare MXene solution.

[0037] The MAX phase material is a kind of layered high-performance ceramic material with a hexagonal close-packed structure, and has excellent characteristics of both metal and ceramic. At the same time, the MAX phase material performs well in high-temperature oxidation resistance, high electrical conductivity and thermal conductivity, excellent radiation resistance, etc.

[0038] In the embodiments of the present application, the MAX phase material can be titanium-based MAX phase material, niobium-based MAX phase material, etc.

[0039] For example, the MXene solution can be a solution prepared from hydrofluoric acid solution and MAX phase material. MXene has a structure similar to graphene and novel properties, and has excellent flexibility, good electronic conductivity and excellent mechanical properties. It is composed of metal carbide or nitride, and its chemical formula is M n+1 X n T X wherein n = 1, 2 or 3, representing three common structures. "M" represents a metal element, mainly a transition metal (such as Ti, V, Nb, Ta, Cr, Mo, etc.); "X" represents a carbon or nitrogen element; "T" represents a functional group on the surface of the material, such as a hydroxyl group (-OH), a halogen group (-F, -Cl), etc.

[0040] In some embodiments, a method for preparing a hydrofluoric acid solution is provided. A fluorine ion compound is mixed with an acidic solvent to react the fluorine ions of the fluorine ion compound with the hydrogen ions of the acidic solvent to obtain a hydrofluoric acid solution. In this way, a hydrofluoric acid solution for reacting with the MAX phase material can be prepared from a fluorine ion compound and an acidic solvent.

[0041] For example, the fluorine ion compound can be lithium fluoride (LiF), sodium fluoride (NaF), ammonium fluoride (NH4F), or other compounds containing fluorine ions, which are not limited here.

[0042] For example, the acidic solvent can be a strong acid solution such as hydrochloric acid or sulfuric acid, which is used to provide hydrogen ions to react with fluorine ions, which is not limited here.

[0043] For example, 1g of lithium fluoride is mixed with 20mL of 9mol / L hydrochloric acid and stirred for 20min to react the fluorine ions of lithium fluoride with the hydrogen ions of hydrochloric acid to prepare a hydrofluoric acid solution.

[0044] In some embodiments, the MAX phase material is added into a hydrofluoric acid solution to obtain a MXene suspension; and the MXene suspension is filtered to obtain a MXene solution. Thus, the MXene solution can be prepared by reacting the MAX phase material with the hydrofluoric acid solution.

[0045] In the embodiments of the present application, the conductive two-dimensional material matrix (MXene) is introduced in the preparation of the gas-sensitive material, so that the performance of detecting harmful gases can be improved by preparing a nanocomposite. The MXene material is favored due to its excellent electron mobility and large specific surface area. In addition, the adsorption capacity of NO2 gas can be effectively controlled by adjusting the surface chemical properties.

[0046] For example, the MAX phase material can be titanium aluminum carbide (Ti3AlC2, Ti4AlN3), niobium aluminum carbide (Nb2AlC, Nb3AlC2), etc., which is not limited herein.

[0047] For example, 1 g of Ti3AlC2 powder can be weighed and added into the above hydrofluoric acid solution and stirred. After the stirring is completed, the above solution is transferred into a water bath with a temperature of 40-60°C for reaction for 8-24 hours, so as to obtain Ti3AlT X MXene suspension.

[0048] In some embodiments, the MXene suspension is washed, ultrasonically treated and dried to obtain a MXene powder; and the MXene powder is ultrasonically dispersed in a mixed solvent to obtain a MXene solution, wherein the ratio of deionized water to ethanol in the mixed solvent is 1:(1-10), and the concentration of the MXene solution is 0.5-10 mg / g.

[0049] The MXene powder is a powder extracted from the MXene suspension, which can be Ti3AlT X MXene powder.

[0050] For example, the MXene suspension is repeatedly washed with deionized water until the pH value of the supernatant in the MXene suspension approaches 6, so as to wash away the residual acidic solvent in the MXene suspension; then the precipitate after the last washing is dispersed in ethanol and ultrasonically treated for 120 minutes, so as to increase the delamination and evaporation rate of the MXene; finally, the MXene is transferred into a vacuum oven with a temperature of 60°C for drying treatment for 12 hours, so as to obtain Ti3AlT X MXene powder.

[0051] For example, the mixed solvent can be formed by deionized water and ethanol, and the ratio of deionized water to ethanol in the mixed solvent can be set according to actual conditions. For example, the ratio of deionized water to ethanol in the mixed solvent can be 1:1-1:10, such as 1:1, 1:2, 1:5, 1:10, etc. Preferably, the ratio of deionized water to ethanol in the mixed solvent is 1:2, so that the dispersion effect of the MXene powder in the mixed solvent is better.

[0052] For example, the concentration of the MXene solution can be prepared according to actual conditions. For example, the concentration of the MXene solution can be 0.5-10 mg / g, such as 0.5 mg / g, 1 mg / g, 5 mg / g and 10 mg / g, etc. Preferably, the concentration of the MXene solution is 1 mg / g, so that the dispersion effect of the MXene powder in the mixed solvent is better.

[0053] For example, a mixed solvent can be prepared according to the ratio of deionized water to ethanol 1:2, and then a certain amount of MXene powder is ultrasonically dispersed in the above mixed solution, so that the concentration of MXene in the mixed solution is 1 mg / g, that is, the MXene solution is prepared.

[0054] In step S102, the graphene oxide solution, the tungsten ion compound, the ascorbic acid and the MXene solution are mixed to reduce the graphene oxide in the graphene oxide solution by the ascorbic acid, so as to prepare an rGO / MXene / WO3 mixed solution.

[0055] The graphene oxide solution is a liquid formed by dispersing graphene oxide (GO) in a solvent. The tungsten ion compound can be any compound containing tungsten ions, and the valence of the tungsten ions in the tungsten ion compound can be +2, +4, +5 or +6, which is not limited here. The ascorbic acid can adjust the pH value of the solution and can be used as a reducing agent to reduce the graphene oxide solution.

[0056] Specifically, the graphene oxide solution, the tungsten ion compound and the ascorbic acid are mixed to reduce the graphene oxide in the graphene oxide solution by the ascorbic acid, so as to prepare an rGO / WO3 mixed solution; the MXene solution is added to the rGO / WO3 mixed solution, so as to prepare an rGO / MXene / WO3 mixed solution.

[0057] The rGO / WO3 mixed solution is a mixed solution of reduced graphene oxide and tungsten trioxide. The rGO / MXene / WO3 mixed solution is a mixed solution of reduced graphene oxide, MXene solution and tungsten trioxide.

[0058] In some embodiments, the graphene oxide solution is added into the deionized water to obtain a graphene oxide mixed solution; the tungsten ion compound and the ascorbic acid are added into the graphene oxide mixed solution to prepare the rGO / WO3 mixed solution, and the mass ratio of the graphene oxide solution to the tungsten ion compound is 1:1-5:1.

[0059] The graphene oxide mixed solution is a mixed solution of the graphene oxide solution and the deionized water.

[0060] For example, the tungsten ion compound can be a tungstate, tungstic acid, tungsten carbide or the like, such as sodium tungstate (Na2WO4·2H2O), calcium tungstate (CaWO4), cobalt tungstate (CoWO4), cadmium tungstate (CdWO4), ferrous tungstate (FeWO4), zinc tungstate (5ZnO·12WO3), tungsten dioxide (WO2), and tungsten chloride such as tungsten hexachloride (WCl6), tungsten pentachloride (WCl5), tungsten tetrachloride (WCl4), tungsten dichloride (WCl2) or the like.

[0061] For example, 1 mL of graphene oxide (GO) solution with a concentration of 10 mg / mL is dispersed in 40 mL of deionized water, and then 0.032 g of Na2WO4·2H2O and 0.053 g of ascorbic acid are added. At this time, the ascorbic acid can reduce the graphene oxide (GO) in the graphene oxide solution into reduced graphene oxide (rGO), thereby preparing the rGO / WO3 mixed solution.

[0062] For example, the mass ratio of the graphene oxide solution to the tungsten ion compound can be 1:1-5:1. If the tungsten ion compound is excessive, a large amount of WO3 is likely to be formed in the rGO / WO3 mixed solution, thereby destroying the 3D porous structure. Therefore, the mass ratio of the graphene oxide solution to the tungsten ion compound is at least 1:1, and preferably, the added mass of the graphene oxide solution is controlled to be greater than the added mass of the graphene oxide solution, for example, the mass ratio of the graphene oxide solution to the tungsten ion compound is 3:1.

[0063] In the embodiments of the present application, the valence of the tungsten ion in the tungsten ion compound can be +2, +4, +5 or +6. If the tungsten ion compound is any one of WO2, WCl5, WCl4 or WCl2, the valence of the tungsten ion in the tungsten ion compound is +2, +4 or +5. Therefore, an oxidizing agent needs to be added to the rGO / WO3 mixed solution to increase the valence of W to +6, so as to form WO3, thereby preparing the rGO / WO3 mixed solution.

[0064] Preferably, the valence of the tungsten ion in the tungsten ion compound is +6.

[0065] Since the valence of W in the rGO / WO3 mixed solution is +6, if the valence of tungsten ions in the tungsten ion compound is +6, such as Na2WO4·2H2O, CaWO4, etc., the valence of W remains unchanged in the process of forming WO3, and there is no need to use an oxidizing agent to perform an oxidation reaction to increase the valence of W, which is more conducive to preparing WO3, and can reduce the preparation cost of the gas-sensitive material to a certain extent.

[0066] In some embodiments, the MXene solution is added to the rGO / WO3 mixed solution under an acidic environment to prepare an rGO / MXene / WO3 mixed solution, and the mass ratio of reduced graphene oxide to the MXene solution is 1:1-5:1.

[0067] The acidic environment can be an environment with a pH value of 1-5, and the acidic environment is more conducive to the reaction of the MXene solution and the rGO / WO3 mixed solution.

[0068] For example, the MXene solution is added to the rGO / WO3 mixed solution, and the pH value of the solution is adjusted to about 2. After sufficient stirring for 15 min, the rGO / MXene / WO3 mixed solution is prepared.

[0069] It should be noted that the pH value of the solution can be adjusted by controlling the amount of ascorbic acid added, and can also be adjusted by adding another acidic solvent, which is not limited here.

[0070] For example, the mass ratio of reduced graphene oxide (rGO) to the MXene solution can be 1:1-5:1. Since the role of reducing graphene oxide (GO) to form reduced graphene oxide (rGO) is to enter the MXene interlayer to form a 3D layered structure, and a curled 3D network structure will be formed during the drying process, the mass ratio of reduced graphene oxide (rGO) to the MXene solution is at least 1:1. Preferably, the mass of rGO needs to be much greater than the mass of the MXene solution, for example, the mass ratio of rGO to the MXene solution is 3:1, so as to ensure that all rGO enters the MXene interlayer to form a 3D layered structure.

[0071] Step S103, performing a hydrothermal reaction on the rGO / MXene / WO3 mixed solution to prepare an rGO / MXene / WO3 gas-sensitive material.

[0072] The rGO / MXene / WO3 gas-sensitive material is a composite material formed by reduced graphene oxide (rGO), a two-dimensional material (MXene) and tungsten trioxide (WO3). The rGO / MXene / WO3 gas-sensitive material significantly improves the overall conductivity of the gas-sensitive material by combining the characteristics of MXene and rGO. In addition, due to the synergistic effect between the multi-layer structure of MXene and the high porosity of rGO, the rGO / MXene / WO3 gas-sensitive material has the characteristics of fast response speed and high sensitivity.

[0073] In the embodiments of the present application, WO3 in the rGO / MXene / WO3 gas-sensitive material can form a P-N junction after being combined with P-type rGO and MXene as an N-type semiconductor. Since WO3 has a higher work function, electrons will flow from rGO and MXene to WO3, thereby increasing the surface electron density of WO3 and promoting the adsorption of surface oxygen molecules and increasing the content of surface chemisorbed oxygen, which is conducive to the gas-sensitive reaction.

[0074] In some embodiments, the reaction conditions of the hydrothermal reaction include a hydrothermal temperature of 120-240℃, a hydrothermal time of 8-24h, and a capacity of the hydrothermal container of 20-120mL. This can provide a high-temperature and high-pressure reaction environment for the rGO / MXene / WO3 mixed solution reaction, thereby improving the atomic arrangement order, increasing the crystallinity, and controlling the crystal surface of the crystal, thereby improving the binding force with gas molecules and the catalytic efficiency.

[0075] The hydrothermal container can be a reaction kettle or other container that can be used for hydrothermal reaction. The capacity of the hydrothermal container can control the pressure of the hydrothermal container. In order to make the pressure of the hydrothermal container higher and more stable, the smaller the capacity of the hydrothermal container is, the better.

[0076] For example, the rGO / MXene / WO3 mixed solution is transferred to a reaction kettle with a capacity of 50mL, and reacted at a temperature of 180℃ for 12h. Selecting a smaller volume of the reaction kettle can effectively control the pressure in the reaction kettle, thereby improving the atomic arrangement order, increasing the crystallinity, and controlling the crystal surface of the crystal, thereby improving the binding force with gas molecules and the catalytic efficiency. Then, the reaction product after the hydrothermal reaction is repeatedly cleaned with deionized water and ethanol, and then the separation of the rGO / MXene / WO3 gas-sensitive material from impurities such as deionized water and ethanol is completed in a centrifuge. Finally, the rGO / MXene / WO3 gas-sensitive material is dried at a temperature of 60℃ for 24h.

[0077] Please refer to Figure 2 , Figure 2 A scanning electron microscope diagram of the rGO / MXene / WO3 gas-sensitive material provided in the embodiments of the present application.

[0078] As shown in Figure 2 , the figure shows that the rGO / MXene composite material forms a porous network structure, and the sheet-shaped WO3 is uniformly grown in the porous network structure, that is, there are a large number of active sites for the gas-sensitive material to contact with the gas, indicating that the rGO / MXene / WO3 gas-sensitive material can promote the adsorption of surface oxygen molecules, increase the content of surface chemisorbed oxygen, and be beneficial to the gas-sensitive reaction.

[0079] The preparation method of the gas-sensitive material provided in the present application introduces tungsten ion compounds in the preparation process of the gas-sensitive material, thereby forming the rGO / MXene / WO3 gas-sensitive material with a loose porous structure, which can provide more active sites for the gas-sensitive material to contact with the gas. At the same time, the presence of tungsten trioxide can also promote the adsorption of surface oxygen molecules, increase the content of surface chemisorbed oxygen, and be beneficial to the gas-sensitive reaction.

[0080] Please refer to Figure 3 , Figure 3 The embodiment of the present application provides a schematic flow chart of a preparation method of a gas sensor. The preparation method of the gas sensor has simple manufacturing process and low cost, and can make the prepared gas sensor exhibit excellent gas-sensitive performance to NO2 gas, and has excellent selectivity and stability.

[0081] As shown in Figure 3 , the preparation method of the gas sensor comprises steps S201 to S204.

[0082] Step S201, using the preparation method of the gas-sensitive material to prepare the rGO / MXene / WO3 gas-sensitive material.

[0083] Since the preparation method of the gas-sensitive material has been described in the foregoing, the specific steps of preparing the rGO / MXene / WO3 gas-sensitive material by the preparation method of the gas-sensitive material can be referred to the above embodiment, which will not be repeated here.

[0084] Step S202, adding the rGO / MXene / WO3 gas-sensitive material into a dispersant solution to obtain a gas-sensitive material ink.

[0085] The dispersant solution mainly plays the roles of reducing viscosity, dispersing, and wetting. The gas-sensitive material ink generally contains the gas-sensitive material, has high sensitivity to specific gases (such as nitrogen dioxide and ammonia), and can maintain stable performance in different humidity environments.

[0086] For example, the dispersant can be selected from one or more of the following: a high-molecular dispersant of Yilvle DS-195L, isopropyl alcohol, polyvinyl alcohol, polyethylene glycol, sodium polyacrylate, and polyacrylamide, which are not limited here.

[0087] Exemplarily, 0.1 g of the rGO / MXene / WO3 gas-sensitive material, 10 mL of isopropyl alcohol, 2 mL of glycerol (used as a stabilizer), and 0.6 g of a surfactant can be mixed uniformly and subjected to ultrasonic dispersion treatment, so that the rGO / MXene / WO3 gas-sensitive material forms a gas-sensitive material ink that is uniformly dispersed and has stable particles without agglomeration.

[0088] In step S203, printing is performed using the gas-sensitive material ink to form a gas-sensitive film on the surface of the micro-hotplate.

[0089] The micro-hotplate (MHP for short) is manufactured by using integrated circuit technology and micro-machining technology on a silicon substrate. The micro-hotplate has the advantages of low heating power, fast response time, small heat loss, compatibility with CMOS technology, and easy integration with other microelectronic devices, and thus has great development potential in the fields of gas sensors, infrared emitters, gas flow meters, and the like. The gas-sensitive film can be used to prepare a gas sensor.

[0090] Exemplarily, the printing manner can include inkjet printing, electrohydrodynamic (EHD) printing, and the like, which are not specifically limited herein.

[0091] Exemplarily, the gas-sensitive material ink can be printed on the MEMS micro-hotplate by inkjet printing, and then sintered at a temperature of 200-400°C for 0.5-4 h, so as to remove the solvent and organic matter in the gas-sensitive material ink, and thus improve the stability of the gas sensor.

[0092] In some embodiments, electrohydrodynamic printing is performed using the gas-sensitive material ink to form a gas-sensitive film on the surface of the micro-hotplate.

[0093] The electrohydrodynamic (EHD) printing is controlled by the electric field force to control the droplet ejection, and has high printing precision and is suitable for film formation on a micro-hotplate with a size of hundreds of microns. The highly programmed printing can ensure the efficiency and batch consistency of film formation. Therefore, the EHD printing is used to form a film on the micro-hotplate by using the gas-sensitive material ink.

[0094] In step S204, the micro-hotplate on which the gas-sensitive film is formed is encapsulated to obtain a gas sensor.

[0095] The gas sensor can accurately and quickly detect NO2 gas. In addition, the gas sensor prepared by using the rGO / MXene / WO3 gas-sensitive material can operate at room temperature, and thus can exhibit extremely high sensitivity to ultra-low concentration NO2 gas.

[0096] Specifically, the micro-hot plate with the surface formed with the gas sensitive thin film is pasted in the ceramic tube shell, and wire bonding, capping and other treatments are performed to form the gas sensor. Since the gas sensitive thin film has high film forming precision, good film forming effect and good gas sensitive performance, the gas sensor prepared by the gas sensitive thin film exhibits excellent gas sensitive performance to NO2 gas, has excellent selectivity and stability, and has simple manufacturing process, low cost, and wide application prospect in large-scale preparation of gas sensors.

[0097] The preparation method of the gas sensor and the performance of the gas sensor are described below by specific examples. Specifically, the gas sensor prepared by each of the following examples can be connected to a circuit, the heating voltage is adjusted to make the working temperature at 25-80℃, and aging treatment is performed for 48h. After the aging is completed, the gas sensitive performance test is performed respectively.

[0098] Example 1:

[0099] (1), 1g of lithium fluoride is mixed with 20mL of hydrochloric acid with a concentration of 9mol / L and stirred for 20min, then 1g of Ti3AlC2 powder is weighed and added to the above solution and continue to stir, then the above solution is transferred to a water bath with a temperature of 40℃ for reaction for 24h to obtain Ti3AlT X MXene suspension. The above solution is repeatedly washed with deionized water until the pH value of the supernatant is close to 6, and then the precipitate of the last washing is dispersed in ethanol and ultrasonic treated for 120min, and finally dried in a vacuum oven at 60℃ for 12h to obtain Ti3AlT X MXene powder.

[0100] (2), 1g of Ti3AlT X MXene powder is ultrasonically dispersed in a mixed solvent of deionized water and ethanol, so that the concentration of Ti3AlT X MXene powder in the mixed solvent is 1mg / g, and Ti3AlT X MXene solution.

[0101] (3), take 3mL of graphene oxide (GO) solution with a concentration of 10mg / mL, disperse in 40mL of deionized water, add 0.032g of Na2WO4·2H2O, 0.011g of ascorbic acid and 0.043g of sodium chloride, and add 3mL of Ti3AlT XMXene solution, and the pH value was adjusted to about 2. After 15 min of sufficient stirring, the mixed solution was transferred to a reaction kettle and reacted at a temperature of 180°C for 12 h. The reaction product was repeatedly washed with deionized water and ethanol, and then separated from impurities such as deionized water, ethanol, etc. in a centrifuge. Finally, the rGO / MXene / WO3 gas sensitive material was dried at a temperature of 60°C for 24 h to obtain the rGO / MXene / WO3 gas sensitive material.

[0102] (4) 0.1 g of the rGO / MXene / WO3 gas sensitive material, 10 mL of isopropyl alcohol, 2 mL of glycerol, and 0.6 g of a surfactant were mixed and ultrasonically dispersed to form an ink with uniformly dispersed rGO / MXene / WO3 gas sensitive material and stable and non-agglomerated particles. Finally, the ink was printed on a MEMS micro-hot plate by inkjet printing, and then sintered at a temperature of 400°C for 2 h. Finally, the MEMS micro-hot plate was bonded to a ceramic shell, and wire bonding, packaging, etc. were performed to form a gas sensor.

[0103] Example 2:

[0104] (1) 1 g of lithium fluoride was mixed with 20 mL of hydrochloric acid with a concentration of 9 mol / L and stirred for 20 min. Then, 1 g of Ti3AlC2 powder was weighed and added to the above solution and stirred. The solution was then transferred to a water bath at a temperature of 40°C for reaction for 24 h to obtain Ti3AlT X MXene suspension. The solution was repeatedly washed with deionized water until the pH value of the supernatant was close to 6. Then, the precipitate from the last washing was dispersed in ethanol and ultrasonically treated for 120 min. Finally, the Ti3AlT X MXene powder was dried in a vacuum oven at 60°C for 12 h to obtain the Ti3AlT

[0105] (2) The Ti3AlT X MXene powder was ultrasonically dispersed in a mixed solvent of deionized water and ethanol to obtain a Ti3AlT X MXene powder with a concentration of 1 mg / g in the mixed solvent to obtain the Ti3AlT X MXene solution.

[0106] (3) 3 mL of graphene oxide (GO) solution with a concentration of 10 mg / mL was dispersed in 40 mL of deionized water. Then, 0.032 g of Na2WO4·2H2O, 0.011 g of ascorbic acid, and 0.043 g of sodium chloride were added. Finally, 30 mL of Ti3AlT XMXene solution, and the pH value was adjusted to about 2. After 15 min of sufficient stirring, the mixed solution was transferred to a reaction kettle and reacted at a temperature of 180°C for 12 h. The reaction product was repeatedly washed with deionized water and ethanol, and then separated from impurities such as deionized water, ethanol, etc. in a centrifugal machine. Finally, the rGO / MXene / WO3 gas sensitive material was dried at a temperature of 60°C for 24 h to obtain the rGO / MXene / WO3 gas sensitive material.

[0107] (4) 0.1 g of the rGO / MXene / WO3 gas sensitive material, 10 mL of isopropyl alcohol, 2 mL of glycerol, and 0.6 g of a surfactant were mixed and ultrasonically dispersed to form an ink with uniformly dispersed rGO / MXene / WO3 gas sensitive material and stable and non-agglomerated particles. Finally, the ink was printed on a MEMS micro-hot plate by inkjet printing, and then sintered at a temperature of 400°C for 2 h. Finally, the MEMS micro-hot plate was bonded to a ceramic shell, and wire bonding, packaging, etc. were performed to form a gas sensor.

[0108] Example 3:

[0109] (1) 1 g of lithium fluoride was mixed with 20 mL of hydrochloric acid with a concentration of 9 mol / L and stirred for 20 min. Then, 1 g of Ti3AlC2 powder was weighed and added to the above solution and stirred. Then, the solution was transferred to a water bath at a temperature of 40°C for reaction for 24 h to obtain Ti3AlT X MXene suspension. The above solution was repeatedly washed with deionized water until the pH value of the supernatant was close to 6. Then, the precipitate of the last washing was dispersed in ethanol and ultrasonically treated for 120 min. Finally, the Ti3AlT X MXene powder was dried in a vacuum oven at 60°C for 12 h to obtain the Ti3AlT

[0110] (2) The Ti3AlT X MXene powder was ultrasonically dispersed in a mixed solvent of deionized water and ethanol to obtain a Ti3AlT X MXene powder with a concentration of 1 mg / g in the mixed solvent to obtain the Ti3AlT X MXene solution.

[0111] (3) 3 mL of graphene oxide (GO) solution with a concentration of 10 mg / mL was dispersed in 40 mL of deionized water. Then, 0.096 g of Na2WO4·2H2O, 0.011 g of ascorbic acid, and 0.043 g of sodium chloride were added, and 3 mL of Ti3AlT XMXene solution, and the pH value was adjusted to about 2. After 15 min of sufficient stirring, the above mixed solution was transferred to a reaction kettle and reacted at a temperature of 180°C for 12 h. The reaction product was repeatedly washed with deionized water and ethanol, and then separated from impurities such as deionized water, ethanol, etc. in a centrifugal machine. Finally, the rGO / MXene / WO3 gas sensitive material was dried at a temperature of 60°C for 24 h to obtain the rGO / MXene / WO3 gas sensitive material.

[0112] (4) 0.1 g of the rGO / MXene / WO3 gas sensitive material, 10 mL of isopropyl alcohol, 2 mL of glycerol, and 0.6 g of a surfactant were mixed and ultrasonically dispersed to form an ink with uniformly dispersed rGO / MXene / WO3 gas sensitive material and stable particles without agglomeration. Finally, the ink was printed on a MEMS micro-hot plate by inkjet printing, and then sintered at a temperature of 400°C for 2 h. Finally, the MEMS micro-hot plate was bonded to a ceramic shell, and wire bonding, packaging, etc. were performed to form a gas sensor.

[0113] Comparative Example:

[0114] (1) 1 g of lithium fluoride was mixed with 20 mL of hydrochloric acid with a concentration of 9 mol / L and stirred for 20 min. Then, 1 g of Ti3AlC2 powder was weighed and added to the above solution for continuous stirring. Then, the above solution was transferred to a water bath with a temperature of 40°C for reaction for 24 h to obtain Ti3AlT X MXene suspension. The above solution was repeatedly washed with deionized water until the pH value of the supernatant was close to 6. Then, the precipitate of the last washing was dispersed in ethanol and ultrasonically treated for 120 min. Finally, the Ti3AlT X MXene powder was dried in a vacuum oven at 60°C for 12 h to obtain the Ti3AlT

[0115] (2) The Ti3AlT X MXene powder was ultrasonically dispersed in a mixed solvent of deionized water and ethanol to obtain the Ti3AlT X MXene powder was ultrasonically dispersed in a mixed solvent of deionized water and ethanol to obtain the Ti3AlT X MXene solution.

[0116] (3) 3 mL of graphene oxide (GO) solution with a concentration of 10 mg / mL was dispersed in 40 mL of deionized water, and then 0.011 g of ascorbic acid and 0.043 g of sodium chloride were added. Then, 3 mL of Ti3AlT XThe MXene solution is adjusted to a pH value of about 2, and after 15 min of sufficient stirring, the mixed solution is transferred to a reaction kettle for reaction at a temperature of 180°C for 12 h. The reaction product is repeatedly washed with deionized water and ethanol, and then separated from impurities such as deionized water, ethanol, etc. in a centrifuge. Finally, the rGO / MXene / WO3 gas-sensitive material is dried at a temperature of 60°C for 24 h.

[0117] (4) 0.1 g of the rGO / MXene / WO3 gas-sensitive material, 10 mL of isopropyl alcohol, 2 mL of glycerol, and 0.6 g of a surfactant are mixed and ultrasonically dispersed to form an ink with uniformly dispersed rGO / MXene / WO3 gas-sensitive material and stable particles without agglomeration. Finally, the ink is printed on a MEMS micro-hot plate by inkjet printing, and then dried and sintered at a temperature of 400°C for 2 h. Finally, the MEMS micro-hot plate is bonded to a ceramic shell, and wire bonding, packaging, etc. are performed to form a gas sensor.

[0118] As shown in FIG. 6, Figure 4 As shown in FIG. 7, Figure 4 The response-recovery curves of the gas sensors prepared in the above examples and comparative examples in a 10 ppm NO2 gas environment are shown. It can be seen that, under the condition of controlling the tungsten ion compound not to exceed a certain amount, the gas sensors corresponding to Example 1 and Example 2 both have better response speed and recovery speed in a 1 ppm NO2 gas environment, and are better than the gas sensors corresponding to the comparative examples, i.e., the gas sensors provided in the examples of the present application have excellent gas-sensitive performance.

[0119] As shown in FIG. 8, Figure 5 As shown in FIG. 9, Figure 5 The response value change curves of the gas sensor prepared in Example 1 at different working temperatures for 10 ppm NO2 gas are shown. It can be seen that the response value of the gas sensor prepared in Example 1 for NO2 gas is the highest at 25°C, i.e., the gas sensor provided in the example of the present application can work at room temperature.

[0120] As shown in FIG. 10, Figure 6 As shown in FIG. 11, Figure 6 The response-recovery curves of the gas sensor prepared in Example 1 in different concentrations of NO2 gas environment are shown. It can be seen that the gas sensor prepared in Example 1 has better response speed and recovery speed in different concentrations of NO2 gas environment, i.e., the working stability of the gas sensor provided in the example of the present application is higher.

[0121] In summary, the gas sensor provided by the embodiments of the present application exhibits excellent gas sensing performance for NO2 gas, and can be used for detecting NO2 at low temperature or room temperature. When the working temperature is 25 DEG C and the test concentration is 10 ppm, the response value [(Ra-Rg) / Rg] is 311%, the response and recovery time is 164 s / 95 s, and the detection lower limit reaches 0.5 ppm. In terms of detecting NO2 gas, the gas sensor has excellent selectivity and long-term stability.

[0122] The embodiments of the present application also provide a gas sensor prepared by using the preparation method provided by any of the above embodiments.

[0123] The specific preparation method of the gas sensor can refer to the corresponding embodiments described in the specification of the present application, and will not be described here again. The gas sensor provided by the embodiments of the present application exhibits excellent gas sensing performance for NO2 gas, and has excellent selectivity and stability.

[0124] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a gas sensitive material, characterized by, The method comprises: mixing a hydrofluoric acid solution with a MAX phase material to obtain a MXene solution; adding a graphene oxide solution into deionized water to obtain a graphene oxide mixed solution; adding a tungsten ion compound and ascorbic acid into the graphene oxide mixed solution to reduce the graphene oxide in the graphene oxide solution by the ascorbic acid to obtain an rGO / WO3 mixed solution; adding the MXene solution into the rGO / WO3 mixed solution to obtain an rGO / MXene / WO3 mixed solution; performing a hydrothermal reaction on the rGO / MXene / WO3 mixed solution to obtain an rGO / MXene / WO3 gas-sensitive material.

2. The method of claim 1, wherein, The mixing of the hydrofluoric acid solution with the MAX phase material to obtain the MXene solution comprises: adding the MAX phase material into the hydrofluoric acid solution to obtain a MXene suspension; performing a filtration treatment on the MXene suspension to obtain the MXene solution.

3. The method of claim 2, wherein, The filtration treatment on the MXene suspension to obtain the MXene solution comprises: performing a cleaning, ultrasonic and drying treatment on the MXene suspension to obtain a MXene powder; ultrasonically dispersing the MXene powder in a mixed solvent to obtain the MXene solution, wherein a ratio of deionized water to ethanol in the mixed solvent is 1:(1-10), and a concentration of the MXene solution is 0.5-10 mg / g.

4. The method of claim 1, wherein, The reaction conditions of the hydrothermal reaction comprise: a hydrothermal temperature of 120-240 ℃, a hydrothermal time of 8-24 h, and a capacity of a hydrothermal container of 20-120 mL.

5. The method of claim 1, wherein, A mass ratio of the graphene oxide solution to the tungsten ion compound is 1:1-5:

1.

6. The method of claim 1, wherein, The adding of the MXene solution into the rGO / WO3 mixed solution to obtain the rGO / MXene / WO3 mixed solution comprises: adding the MXene solution into the rGO / WO3 mixed solution in an acidic environment to obtain the rGO / MXene / WO3 mixed solution, and a mass ratio of reduced graphene oxide to the MXene solution is 1:1-5:

1.

7. The method according to any one of claims 1 to 6, characterized in that, A valence of tungsten ions in the tungsten ion compound is +6.

8. A method of manufacturing a gas sensor, characterized by, The method comprises: obtaining an rGO / MXene / WO3 gas-sensitive material by using the preparation method of the gas-sensitive material according to any one of claims 1-7; adding the rGO / MXene / WO3 gas-sensitive material into a dispersant solution to obtain a gas-sensitive material ink; performing printing by using the gas-sensitive material ink to form a gas-sensitive film on a surface of a micro-hotplate; performing a packaging treatment on the micro-hotplate with the gas-sensitive film to obtain a gas sensor.

9. A gas sensor, characterized by The gas sensor is obtained by using the preparation method of the gas sensor according to claim 8.

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