Carbon monoxide gas-sensitive material, preparation method, and application

Abstract

The present invention provides a carbon monoxide gas-sensitive material and its preparation method and application, which belongs to the field of gas sensing technology. The structural formula of the carbon monoxide gas-sensitive material is X2W n‑1 O 3n , X is cadmium or chromium, and n is 2, 3 or 4. The carbon monoxide gas-sensitive material of the present invention has both high sensitivity and selectivity, has good gas-sensing performance for relatively low concentrations of carbon monoxide, reduces the power consumption of the carbon monoxide sensor, and can perform long-term monitoring of carbon monoxide leakage.

Description

Technical Field

[0001] The present invention relates to the field of gas sensing technology, and in particular to a carbon monoxide gas-sensitive material and a preparation method and application thereof. Background Art

[0002] Carbon monoxide (CO) is a colorless, odorless, toxic gas. It is produced by incomplete fossil fuel combustion, industrial combustion, and automobile exhaust. Compared to oxygen, human blood has an exponentially higher affinity for CO. CO molecules bind to hemoglobin in the blood, leading to a loss of oxygen circulation and potentially causing serious and irreversible harm. Therefore, for safety reasons, the development of high-performance CO gas sensors is crucial.

[0003] Gas sensors are used to detect the composition and concentration of gases. Common gas sensors include electrochemical sensors, infrared sensors, and semiconductor sensors. Electrochemical CO sensors have a short service life and high power consumption. Infrared CO sensors have disadvantages such as large size and high price. In contrast, semiconductor CO sensors offer advantages such as low cost, strong interference resistance, and long life, making them widely used in CO monitoring.

[0004] Due to the limitations of the sensing mechanism, the current gas sensors using semiconductor materials as gas-sensitive materials have poor selectivity and low sensitivity to lower concentrations of carbon monoxide gas. Summary of the Invention

[0005] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides a carbon monoxide gas-sensitive material and a preparation method and application thereof.

[0006] According to an embodiment of one aspect of the present invention, a carbon monoxide gas-sensitive material is provided. The structural formula of the carbon monoxide gas-sensitive material is X2W n-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium.

[0007] In one embodiment, the mass fraction of X in the carbon monoxide gas-sensitive material is 5-15%.

[0008] According to another embodiment of the present invention, a method for preparing a carbon monoxide gas-sensitive material is provided, comprising: adding a transition metal salt and a tungsten source compound to an acidic solution containing a chelating agent and stirring to obtain a mixed solution, wherein the transition metal ions and tungsten ions are adsorbed onto micelles formed by the chelating agent; drying the mixed solution to obtain a gel adsorbed with the transition metal ions and tungsten ions; and calcining the gel adsorbed with the transition metal ions and tungsten ions in air to obtain a carbon monoxide gas-sensitive material, wherein the carbon monoxide gas-sensitive material has a structural formula of X2Wn-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium.

[0009] In one embodiment, the chelating agent comprises a butyl silicone-acrylate solution.

[0010] In one embodiment, the transition metal salt includes at least one of chromium nitrate, cadmium chloride, and sodium chromate; and the tungsten source compound includes at least one of sodium tungstate nitrate and tungsten chloride.

[0011] In one embodiment, the stirring temperature is 70-90° C.; the drying conditions are: drying at 250-300° C. for 2-3 hours; and the calcination conditions are: calcining at 550-650° C. for 2-3 hours.

[0012] According to another embodiment of the present invention, a carbon monoxide sensor is provided, comprising a carbon monoxide gas-sensitive layer, wherein the carbon monoxide gas-sensitive layer comprises the carbon monoxide gas-sensitive material as described above or the carbon monoxide gas-sensitive material prepared by the method for preparing the carbon monoxide gas-sensitive material as described above.

[0013] In one embodiment, the carbon monoxide sensor further includes: a substrate, and a metal electrode heating layer, an insulating layer, and a metal pattern layer sequentially formed on the substrate; wherein the carbon monoxide gas-sensitive layer covers the metal pattern layer, and the metal pattern layer is composed of a periodically arranged pattern array.

[0014] In one embodiment, the pattern array includes a square array, a checkerboard array, and a honeycomb array.

[0015] In one embodiment, the material of the substrate includes at least one of zirconium oxide and aluminum oxide; the material of the metal electrode heating layer includes at least one of platinum, gold, and aluminum; the material of the insulating layer includes oxide, and the thickness of the insulating layer is 200~500nm; the material of the metal pattern layer includes at least one of platinum, gold, and aluminum; the thickness of the metal electrode heating layer and the metal pattern layer are 100~200nm respectively; the thickness of the carbon monoxide gas sensitive layer is 2~4μm.

[0016] According to an embodiment of the present invention, a sol-gel method is used to immobilize chromium ions or cadmium ions and tungsten ions to form oxide nanoparticles with a single structure. The incorporation of the chromium ions or cadmium ions provides oxygen vacancies, which reduces the band gap of the carbon monoxide gas-sensitive material. The introduction of the chromium ions or cadmium ions affects the position of the band center, helping to change the material's attraction to electrons, thereby increasing the material's electrophilicity and resulting in a higher adsorption capacity for CO. The resulting gas sensor has improved selectivity and sensitivity for CO. The use of a chelating agent to immobilize the chromium or cadmium ions and then calcining them helps promote the formation of a porous structure in the oxide nanoparticles, increasing their specific surface area and further facilitating the selective adsorption of CO.

[0017] According to an embodiment of the present invention, the carbon monoxide sensor of the present invention optimizes the electrode structure to form a stacked structure of metal heating layer / insulating layer / metal pattern layer, roughens the electrode surface, helps to increase the amount of thermal radiation, and the periodically arranged pattern array makes the heat distribution more uniform; and this stacked structure is a photonic crystal structure, which can emit photons, so that energy is transmitted between adjacent photonic crystals, thereby reducing energy loss and reducing the power consumption of the carbon monoxide sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart showing a method for preparing a carbon monoxide gas-sensitive material according to an embodiment of the present invention is shown;

[0019] Figure 2 A cross-sectional view showing the structure of a carbon monoxide sensor according to an embodiment of the present invention is shown;

[0020] Figure 3a A schematic diagram showing an arrangement of a square array of a pattern array according to an embodiment of the present invention is shown;

[0021] Figure 3b A schematic diagram showing an arrangement of a chessboard array of a pattern array according to an embodiment of the present invention is shown;

[0022] Figure 3c A schematic diagram showing the arrangement of a honeycomb array of a pattern array according to an embodiment of the present invention is shown;

[0023] Figure 4 shows the X-ray diffraction spectrum of the carbon monoxide gas-sensitive material of Example 1 of the present invention;

[0024] Figure 5 The scanning electron microscope image of the carbon monoxide gas-sensitive material of Example 1 of the present invention is shown;

[0025] Figure 6 A bar graph showing sensitivity tests of Examples 1 to 3 of the present invention and Comparative Examples 1 and 2 to different gases; and

[0026] Figure 7 A graph showing the change in power consumption of the carbon monoxide sensors of Example 1 of the present invention and Comparative Example 1 versus heating temperature is shown.

[0027] [Description of Reference Numerals]

[0028] 1-carbon monoxide gas sensitive layer;

[0029] 2-base;

[0030] 3-metal electrode heating layer;

[0031] 4-Insulation layer;

[0032] 5-Metal pattern layer. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0034] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0035] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.). When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.).

[0036] Prolonged inhalation of air containing carbon monoxide (CO) gradually reduces the oxygen content of the blood, potentially causing serious harm. For both human and environmental safety, convenient and accurate CO monitoring is crucial, leading to widespread use of semiconductor CO sensors. However, achieving high sensitivity and selectivity in CO detection using semiconductor materials is difficult.

[0037] In the process of realizing the concept of the present invention, the inventors discovered that metal oxides have the characteristics of broad spectrum response, and single-component metal oxides are difficult to have high selectivity for carbon monoxide. In addition, the sensitivity of metal oxides is prioritized, making it difficult to monitor changes in low-concentration carbon monoxide concentrations for a long time.

[0038] In order to solve the above problems, the inventors tried to dope transition metal chromium or cadmium into tungsten oxide. The incorporation of transition metal chromium or cadmium provides oxygen vacancies, reduces the band gap of the carbon monoxide gas-sensitive material and increases its electrophilicity, promotes the adsorption of carbon monoxide gas molecules, and thereby improves the selectivity and sensitivity of the carbon monoxide sensor to carbon monoxide.

[0039] Specifically, according to an embodiment of one aspect of the present invention, a carbon monoxide gas-sensitive material is provided. The structural formula of the carbon monoxide gas-sensitive material is X2W n-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium.

[0040] According to some embodiments of the present invention, a chelating agent is used to form a coordination bond between the chelating agent and the chromium ions, cadmium ions, or tungsten ions, thereby facilitating the stable and uniform dispersion of the above-mentioned metal ions in the solution; the above-mentioned metal ions are then fixed; and calcination is then performed to promote the formation of oxide nanoparticles with a single structure in which the chromium ions, cadmium ions, and tungsten ions are uniformly dispersed in the carbon monoxide gas-sensitive material. Since the number of valence electrons of chromium ions or cadmium ions is different from that of tungsten, the incorporation of chromium ions or cadmium ions causes a charge imbalance in the tungsten oxide lattice, thereby introducing additional energy level states. The additional energy level is located in the band gap, thereby narrowing the energy band gap and making it easier for electrons to be excited. Since the radius of chromium ions or cadmium ions is different from that of tungsten ions, doping will cause lattice distortion and change the lattice parameters, which may lead to an increase in the polarity of the WO bond and improve the electrophilicity of the carbon monoxide gas-sensitive material.

[0041] Furthermore, oxygen vacancies in the doped chromium or cadmium ion material interact with each other, contributing to the formation of composite defects. Composite defects may have higher chemical activity, thereby increasing the electrophilicity of the carbon monoxide gas-sensitive material. The incorporation of chromium or cadmium ions increases oxygen vacancies, resulting in a higher adsorption capacity for CO. The resulting carbon monoxide sensor can improve its selectivity and sensitivity to carbon monoxide. In addition, the carbon monoxide gas-sensitive material of the present invention, after being fixed with a metal element and then calcined in air, helps to promote the formation of a porous structure in the carbon monoxide gas-sensitive material, thereby increasing its specific surface area and further improving its selectivity for CO adsorption.

[0042] In one embodiment, the mass fraction of X in the carbon monoxide gas-sensitive material is 5-15%. When the mass fraction of the transition metal X (chromium or cadmium) is within this range, the carbon monoxide gas-sensitive material exhibits excellent gas-sensing performance. When the mass fraction of the transition metal X is too high, the carbon monoxide gas-sensitive material's response to gas is reduced; when it is too low, the doping effect is insignificant, making it difficult to create sufficient oxygen vacancies. Specifically, the mass fraction of the transition metal X can be, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. Preferably, the mass fraction of the transition metal X is 10%.

[0043] Preferably, the carbon monoxide gas-sensitive material has a structural formula of Cr2WO6.

[0044] According to another embodiment of the present invention, a method for preparing a carbon monoxide gas-sensitive material is provided. Figure 1 FIG. 1 is a flow chart showing a method for preparing a carbon monoxide gas-sensitive material according to an embodiment of the present invention. Figure 1 As shown, the method includes operations S101 to S103.

[0045] In operation S101 , a transition metal salt and a tungsten source compound are added to an acidic solution containing a chelating agent and stirred to obtain a mixed solution, wherein transition metal ions and tungsten ions are adsorbed onto micelles formed by the chelating agent.

[0046] According to some embodiments of the present invention, the transition metal salt can be a cadmium salt or a chromium salt, and the chelating agent is an organic compound capable of forming a coordination bond with the transition metal ion and the tungsten ion. Agitation facilitates the uniform dispersion of the transition metal ions and the tungsten ion. The chelating agent molecules form micelles around the transition metal ions and the tungsten ions, and the transition metal ions and the tungsten ions are uniformly adsorbed onto the micelles formed by the chelating agent. The acidic solution provides an acidic environment, maintaining the transition metal ions and the tungsten ions in a stable dispersion state in the solution, thereby preventing premature hydrolysis and precipitation of the transition metal ions and the tungsten ions.

[0047] In operation S102 , the mixed solution is dried to obtain a gel adsorbing transition metal ions and tungsten ions.

[0048] According to some embodiments of the present invention, drying a mixed solution containing micelles can produce a gel with elasticity and a network structure. This is because after removing the solvent, the mixed solution transforms into a gel state. The gel has a high specific surface area and a porous structure, which helps provide a large number of adsorption sites and a highly dispersed support environment for transition metal ions and tungsten ions. Drying helps maintain the gel's porous structure, which is beneficial for the selective adsorption of CO in subsequent applications in gas sensors.

[0049] In operation S103, the gel adsorbed with transition metal ions and tungsten ions is calcined in air to prepare a carbon monoxide gas-sensitive material. The structural formula of the carbon monoxide gas-sensitive material is X2W n-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium.

[0050] According to some embodiments of the present invention, during the calcination process in air, the increase in temperature causes the remaining organic components in the gel to decompose and combust, oxidizing the transition metal ions and tungsten ions and converting them into corresponding transition metal-doped carbon monoxide gas-sensitive materials. Furthermore, the volatilization of the organic components leaves pores in the resulting carbon monoxide gas-sensitive material, further forming a porous structure. The carbon monoxide gas-sensitive material, namely tungsten oxide doped with a transition metal, has high catalytic activity, and the porous structure formed thereby has a high active site exposure rate.

[0051] According to some embodiments of the present invention, the present invention incorporates transition metal chromium or cadmium into a tungsten oxide gas-sensitive material by using a sol-gel method, and fixes the transition metal ions and tungsten ions into a uniformly dispersed state through the adsorption of a chelating agent, thereby providing an appropriate amount of oxygen vacancies for the carbon monoxide gas-sensitive material, which helps to improve the selective adsorption of CO. Subsequent drying and calcination help to form a carbon monoxide gas-sensitive material with a single structure, which is an oxide nanoparticle, and promotes the formation of a porous structure of the gas-sensitive material, further promoting high sensitivity and selectivity to CO. In addition, the present invention uses a chelating agent as a soft template, which eliminates the complex steps of synthesizing and removing the hard template compared to the use of a hard template method, greatly simplifies the material preparation operation, and is conducive to subsequent large-scale preparation.

[0052] In one embodiment, the chelating agent includes a butyl siloxane-acrylate solution. The butyl siloxane-acrylate solution is diluted with a polar solvent, and the polar solvent can be, for example, ethylene glycol. The butyl siloxane-acrylate solution can form a stable complex with transition metal ions and tungsten ions, thereby improving its adsorption effect on the above-mentioned metal ions. The chelating agent combined with the acidic solution helps to reduce the hydrolysis and coagulation of the above-mentioned metal ions, improve the stability of the formed sol, and reduce unnecessary side reactions during the preparation process. In addition, the acrylate group in the butyl siloxane-acrylate solution can copolymerize with a variety of substances, which helps to enhance the electrophilicity of the carbon monoxide gas-sensitive material.

[0053] In one embodiment, the transition metal salt includes at least one of chromium nitrate, cadmium chloride, and sodium chromate; and the tungsten source compound includes at least one of sodium tungstate nitrate and tungsten chloride. These raw materials have good solubility and can be fully dissolved in an acidic solution under appropriate heating conditions, facilitating the subsequent uniform dispersion of transition metal ions and tungsten ions.

[0054] In one embodiment, the solvent used to form the acidic solution can be, for example, at least one of water, tetrahydrofuran, anhydrous ethanol, and isopropanol, preferably water, and more preferably deionized water. When the solvent used to form the acidic solution is one of the above solvents, it can dissolve the transition metal salt, tungsten source compound, and chelating agent, thereby ensuring the uniformity of the mixed solution. The acidic solution can be, for example, a nitric acid solution. Nitric acid is a strong acid that can relatively quickly reduce the pH value of the solution, helping to maintain the stability of the transition metal ions and tungsten ions in the acidic solution and preventing premature hydrolysis and precipitation of the transition metal ions and tungsten ions. Furthermore, the addition of nitric acid can increase the acidic solution's strength, helping to reduce the hydrolysis tendency of the transition metal ions and tungsten ions.

[0055] In one embodiment, the stirring temperature is 70-90°C, for example, 70°C, 75°C, 80°C, 85°C, or 90°C, preferably 80°C. Maintaining the stirring temperature within the above range helps promote the dissolution of the raw materials. The drying process can be, for example, drying in a forced air drying oven. The drying process conditions are: 250-300°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C, or 300°C, preferably 300°C. The heating rate to the above temperature is 4-6°C / s, for example, 4°C / s, 5°C / s, or 6°C / s, preferably 5°C / s. The drying time is 2-3 hours, for example, 2 hours, 2.5 hours, or 3 hours, preferably 3 hours. The calcination process conditions are: 550-650°C, for example, 550°C, 570°C, 590°C, 610°C, 630°C, or 650°C, preferably 600°C. The calcination time is 2 to 3 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, preferably 2 hours.

[0056] According to another embodiment of the present invention, a carbon monoxide sensor is provided. Figure 2 FIG1 shows a cross-sectional view of the structure of a carbon monoxide sensor according to an embodiment of the present invention. Figure 2 As shown, the carbon monoxide sensor includes a carbon monoxide gas-sensitive layer 1, and the carbon monoxide gas-sensitive layer 1 includes the above-mentioned carbon monoxide gas-sensitive material or the carbon monoxide gas-sensitive material prepared by the above-mentioned method for preparing the carbon monoxide gas-sensitive material.

[0057] According to some embodiments of the present invention, since the incorporation of transition metal chromium or cadmium into the tungsten oxide gas-sensitive material provides an appropriate amount of oxygen vacancies, and the transition metal chromium or cadmium has a low chemical strength and a low chemical potential, it is conducive to the adsorption of carbon monoxide, so that the carbon monoxide gas-sensitive layer 1 has high selectivity and sensitivity to CO, which helps to monitor lower concentrations of CO.

[0058] In one embodiment, the carbon monoxide sensor further includes a substrate 2, and a metal electrode heating layer 3, an insulating layer 4, and a metal pattern layer 5 sequentially formed on the substrate 2. The carbon monoxide gas-sensitive layer 1 covers the metal pattern layer 5, and the metal pattern layer 5 is composed of a periodically arranged pattern array.

[0059] According to some embodiments of the present invention, by depositing an insulating layer 4 on the metal electrode heating layer 3 and a metal pattern layer 5 on the insulating layer 4, a special electrode structure of metal layer / insulating layer / metal layer is formed. This special electrode structure helps to make the electrode temperature distribution more uniform, and the temperature difference of the entire carbon monoxide sensor is controlled within 10°C, while ensuring rapid activation of the CO gas-sensitive material and significantly reducing power consumption. The periodic pattern array arrangement helps to form a periodic magnetic field distribution. By setting up a periodic pattern array arrangement, the response of the carbon monoxide sensor to CO is improved.

[0060] According to some embodiments of the present invention, tungsten oxide is doped with transition metals such as chromium or cadmium to provide oxygen vacancies. This, combined with optimized electrode structure and roughened surface roughness, not only improves the sensor's sensitivity and selectivity for CO but also significantly reduces its power consumption, meeting on-site requirements for gas leak monitoring, long-term monitoring, and rapid response.

[0061] In one embodiment, the pattern array includes a square array, a checkerboard array, and a honeycomb array. Figure 3a A schematic diagram showing an arrangement of a square array of a pattern array according to an embodiment of the present invention is shown; Figure 3b A schematic diagram showing an arrangement of a chessboard array of a pattern array according to an embodiment of the present invention is shown; Figure 3c FIG. 1 shows a schematic diagram of the arrangement of a honeycomb array of a pattern array according to an embodiment of the present invention. Figure 3a to Figure 3c As shown, the periodically arranged pattern array increases the surface area of the metal pattern layer 5, improving the contact opportunities between the carbon monoxide gas-sensitive layer 1 on its surface and CO gas molecules, allowing more gas molecules to be adsorbed on the surface of the carbon monoxide gas-sensitive layer 1. By providing this specific pattern array, the present invention optimizes the response speed and selectivity of the carbon monoxide sensor for CO. The periodic structure generates a plasmon resonance effect, which helps to improve the signal strength of the gas sensor. This correspondingly increased signal strength also improves the detection efficiency of CO, further reducing the power consumption of the entire gas sensor.

[0062] In one embodiment, the material of the substrate 2 includes at least one of zirconium oxide and aluminum oxide. The material of the metal electrode heating layer 3 includes at least one of platinum, gold, and aluminum; the material of the insulating layer 4 includes an oxide, for example, tungsten oxide or aluminum oxide. The thickness of the insulating layer 4 is 200~500nm, for example, it can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm; the material of the metal pattern layer 5 includes at least one of platinum, gold, and aluminum; the thickness of the metal electrode heating layer 3 and the metal pattern layer 5 are respectively 100~200nm, for example, they can be 100nm, 120nm, 140nm, 160nm, 180nm or 200nm, and the thickness of the metal electrode heating layer 3 and the metal pattern layer 5 can be the same or different. The thickness of the carbon monoxide gas sensitive layer 1 is 2~4μm, for example, it can be 2μm, 3μm or 4μm, preferably 3μm. When the metal heating layer 3, the insulating layer 4, and the metal pattern layer 5 are respectively set in the above ranges, the energy generated by the formed photonic crystal structure is presented within a specific absorption peak of CO (i.e., the 4.67μm characteristic absorption peak of CO), thereby further improving the response to CO.

[0063] In one embodiment, the carbon monoxide sensor uses a broad-spectrum voltage, that is, a voltage with a certain variation range of 1.2 to 3.3 V, which can cooperate with the periodically arranged pattern array to further improve the selectivity and response to CO and further reduce the power consumption of the carbon monoxide sensor.

[0064] In one embodiment, the surface of the carbon monoxide sensor can be covered with a surface insulating layer (not shown) as needed. The surface insulating layer can be made of, for example, aluminum oxide and has a thickness of 5 to 20 nm. This surface insulating layer helps protect the underlying electrode structure from oxidation.

[0065] According to an embodiment of another aspect of the present invention, a method for preparing a carbon monoxide sensor is provided, comprising: ball-milling a carbon monoxide gas-sensitive material to obtain a gas-sensitive slurry; sequentially depositing a metal electrode heating layer 3, an insulating layer 4, and a metal pattern layer 5 on the surface of a substrate 2 by magnetron sputtering; spraying the gas-sensitive slurry on the surface of the metal pattern layer 5, and performing a sintering treatment to form a carbon monoxide gas-sensitive layer 1, thereby obtaining a carbon monoxide sensor.

[0066] In one embodiment, the metal electrode heating layer 3 is formed by first forming a metal heating electrode pattern through coating, soft baking, exposure, post-baking, flooding, and development, and then obtaining the metal heating layer 3 by magnetron sputtering. The metal heating electrode pattern is formed by photolithography using a mask. The formation of the metal heating electrode pattern is not the focus of the present invention and can be obtained through conventional steps, which will not be described in detail here.

[0067] In one embodiment, the metal pattern layer 5 is formed by forming a periodically arranged pattern array through a process of coating, soft baking, exposure, post-baking, flood exposure, and development, and then magnetron sputtering is used to obtain the metal pattern layer 5. The preparation method of the metal pattern layer 5 is the same as that of the metal electrode heating layer 3 and will not be repeated here.

[0068] In one embodiment, ball-milling a carbon monoxide gas-sensitive material to obtain a gas-sensitive slurry may include: mixing the carbon monoxide gas-sensitive material and an organic slurry and ball-milling them to obtain a gas-sensitive slurry for spraying. The organic slurry includes terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil in a mass ratio of (50-70): (20-40): (5-15): (4-8): (2-6): (0.5-4): (0.1-1). The ball milling speed is 200-400 rpm, and the ball milling time is 5-7 hours.

[0069] In one embodiment, spraying the gas-sensitive slurry on the surface of the metal pattern layer 5 and performing a sintering treatment may include: using a needle with a pore size of 55~65μm to spray the gas-sensitive slurry on the surface of the metal pattern layer 5, drying at 75~85°C for 18~22h, and sintering at 380~420°C for 2~4h to remove the organic slurry remaining in the carbon monoxide gas-sensitive layer 1.

[0070] The present invention will be further described below by way of examples, drawings, and related test experiments and results thereof. In the detailed description that follows, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments may be arbitrarily combined into other feasible embodiments, unless conflicting.

[0071] It should be noted that the following specific examples are for illustration only and the scope of protection of the present invention is not limited thereto. The chemicals and raw materials used in the following examples were either commercially available or prepared in-house using recognized processing methods.

[0072] Example 1:

[0073] Preparation of carbon monoxide gas-sensitive materials:

[0074] Dissolve 0.01 mol of Cr(NO₃)₂ •9H₂O in nitric acid solution. Then, slowly add 0.01 mol of Na₂WO₄ •2H₂O under magnetic stirring to form a mixed solution. Add 0.24 mol of a butyl silicone-acrylate emulsion dispersion (4.5% solids content) to the mixed solution, with a molar ratio of the total metal cations to the chelating agent of 2:3, followed by 0.16 mol of ethylene glycol. Maintain the mixture at 80°C under magnetic stirring until a gel forms.

[0075] The resulting gel was placed in an oven and heated to 300°C at a rate of 5°C / s. The product was then degreased for 3 hours to eliminate organic solvents and other impurities. The product was then sintered in a muffle furnace at 600°C for 2 hours and then ground into powder to obtain Cr2WO6 powder. Figure 4 FIG1 shows the X-ray diffraction spectrum of the carbon monoxide gas-sensitive material of Example 1 of the present invention. Figure 4 As shown, the structure of the prepared Cr2WO6 can be determined. Figure 5 The scanning electron microscope image of the carbon monoxide gas-sensitive material of Example 1 of the present invention is shown. Figure 5 As shown, it can be seen that the specific surface area of the carbon monoxide gas-sensitive material is much larger than that of traditional spherical nanoparticles. A high specific surface area means more active surfaces and better dispersibility, which can improve the activity and electrochemical properties of the carbon monoxide gas-sensitive material.

[0076] Cr2WO6 powder and organic slurry were mixed and ball-milled at 300 r / min for 6 h to obtain a gas-sensing slurry for spraying. The organic slurry used was composed of terpineol, butyl carbitol acetate, dibutyl phthalate, ethyl cellulose, Span 85, 1,4-butyrolactone, and hydrogenated castor oil in a mass ratio of (50-70): (20-40): (5-15): (4-8): (2-6): (0.5-4): (0.1-1).

[0077] Preparation of carbon monoxide sensor A:

[0078] Zirconia was air-gathered and evenly coated, then soft-baked at 100°C for 2 minutes and exposed for 1 minute. After post-baking at 120°C for 2 minutes and flood-exposing for 90 seconds, the zirconium oxide was placed in a developer and developed for 2 minutes to produce a metal Pt / Au heating electrode pattern. The Pt / Au heating layer and the tungsten oxide layer were then obtained in sequence by magnetron sputtering to obtain a metal / insulating material.

[0079] Continue to absorb and evenly coat the metal / insulating material, then soft bake at 100°C for 2 minutes, expose for 1 minute, then post-bake at 120°C for 2 minutes, and flood expose for 90 seconds. Then, place the metal / insulating material in a developer for 2 minutes to produce a surface Pt / Au pattern array. The produced Pt / Au pattern array is as follows: Figure 3a The square array shown is then subjected to magnetron sputtering to obtain a Pt / Au pattern layer.

[0080] The gas-sensitive slurry was sprayed onto the Pt / Au pattern layer using a needle with a 60 μm pore size, placed in a constant temperature drying oven and dried at 80°C for 20 h, and then sintered at 400°C for 3 h to remove the organic slurry to form a gas-sensitive layer, thereby obtaining a carbon monoxide sensor A.

[0081] Example 2:

[0082] Preparation of carbon monoxide gas-sensitive materials:

[0083] Dissolve 0.01 mol of Cr(NO₃)₂•9H₂O in nitric acid solution. Then, slowly add 0.02 mol of Na₂WO₄•2H₂O under magnetic stirring to form a mixed solution. To this mixed solution, add 0.345 mol of a butyl silicone-acrylate emulsion dispersion (4.5% solids content) at a molar ratio of 2:3 between the total metal cations and the chelating agent, followed by 0.23 mol of ethylene glycol. Maintain the mixture at 80°C under magnetic stirring until a gel forms.

[0084] The same operation as in Example 1 was used to prepare Cr2W2O6 powder and obtain gas-sensitive slurry. Figure 3b The checkerboard array shown is used to prepare carbon monoxide sensor B.

[0085] Example 3:

[0086] Preparation of carbon monoxide gas-sensitive materials:

[0087] Dissolve 0.01 mol of Cr(NO₃)₂ •4H₂O in nitric acid solution. Then, slowly add 0.03 mol of Na₂WO₄ •2H₂O under magnetic stirring to form a mixed solution. Add 0.45 mol of a butyl silicone-acrylate emulsion dispersion (4.5% solids content) to the solution, with a molar ratio of 2:3 between the total metal cations and the chelating agent, followed by 0.3 mol of ethylene glycol. Maintain the mixture at 80°C under magnetic stirring until a gel forms.

[0088] The same operation as in Example 1 was used to prepare Cr2W2O6 powder and obtain gas-sensitive slurry. Figure 3c The checkerboard array shown is used to prepare the carbon monoxide sensor C.

[0089] Comparative Example 1:

[0090] Comparative Example 1 provides a carbon monoxide sensor A', which is prepared in substantially the same manner as Example 1, except that no electrode structure modification is performed during the preparation of the carbon monoxide sensor, and only the gas-sensitive material is doped.

[0091] Comparative Example 2:

[0092] Comparative Example 2 provides a carbon monoxide sensor B'. Compared with Example 1, the carbon monoxide gas-sensitive material used is tungsten oxide, and tungsten oxide is used for spraying the gas-sensitive layer.

[0093] The carbon monoxide sensors of Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to sensitivity tests on different gases at 400° C. The sensitivity results are shown in Table 1 below.

[0094] Table 1 Sensitivity test results to different gases at 400℃

[0095]

[0096] Figure 6 The bar graphs of the sensitivity tests of Examples 1 to 3 and Comparative Examples 1 to 2 to different gases are shown. Figure 6 It can be seen that the carbon monoxide sensor doped only with chromium has the best selectivity for CO. This is because the chemical strength and chemical potential of the gas-sensitive material Cr2WO6 used are relatively low, which is conducive to the adsorption of CO. At the same time, the special heating structure regulates the local electron distribution, providing sufficient charge for the CO oxidation reaction. Oxygen vacancies act as active sites, promoting the gas adsorption process, further enhancing the sensing performance of the carbon monoxide sensor.

[0097] The power consumption of the carbon monoxide sensors of Example 1 and Comparative Example 1 was tested. Figure 7 The graphs showing the power consumption of the carbon monoxide sensor of Example 1 and Comparative Example 1 as a function of the heating temperature are shown. Figure 7As can be seen, compared to conventional heating electrodes, the metal layer / insulating layer / metal layer electrode heating structure significantly reduces heating power, reaching only 4.2mW at 400°C. This structure achieves more uniform surface temperature distribution, while also creating a special magnetic field that regulates the distribution of oxygen vacancies, promoting CO adsorption and desorption, as well as chemical reactions.

[0098] The present invention incorporates a certain amount of transition metal into a tungsten oxide gas-sensitive material through a sol-gel method. On the one hand, the incorporation of Cr provides moderate oxygen vacancies, reducing the band gap and increasing electrophilicity, resulting in a high specific adsorption capacity for CO. On the other hand, the resulting porous structure has a large specific surface area, which is conducive to the selective adsorption of carbon monoxide. Furthermore, through electrode surface regulation, a heating electrode structure capable of emitting surface plasma is obtained. On the one hand, this structure can locally regulate the surface electron distribution, thereby increasing the surface adsorption of oxygen and further promoting the occurrence of CO oxidation reactions. On the other hand, this structure makes the temperature distribution more uniform, and the maximum temperature difference can be controlled within 10°C, ensuring rapid activation of the CO gas-sensitive material while significantly reducing power consumption. The coordinated effect of these two factors not only improves the sensor's sensitivity to CO and selectivity for CO, but also significantly reduces the sensor's power consumption, meeting on-site requirements for real-time, long-term monitoring and rapid response to gas leaks.

[0099] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A carbon monoxide sensor, characterized in that: It includes a carbon monoxide gas-sensitive layer, wherein the carbon monoxide gas-sensitive layer includes a carbon monoxide gas-sensitive material, and the structural formula of the carbon monoxide gas-sensitive material is X2W n-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium; The carbon monoxide sensor further includes: a substrate, and a metal electrode heating layer, an insulating layer, and a metal pattern layer sequentially formed on the substrate; The carbon monoxide gas-sensitive layer covers the metal pattern layer, and the metal pattern layer is composed of a periodically arranged pattern array; the material of the substrate is at least one of zirconium oxide and aluminum oxide, and the material of the metal electrode heating layer includes at least one of platinum, gold, and aluminum; the material of the insulating layer includes an oxide, and the thickness of the insulating layer is 200-500 nm; the material of the metal pattern layer includes at least one of platinum, gold, and aluminum; the thickness of the metal electrode heating layer and the metal pattern layer are respectively 100-200 nm; and the thickness of the carbon monoxide gas-sensitive layer is 2-4 μm; The carbon monoxide sensor uses a broad-spectrum voltage, and the variation range of the broad-spectrum voltage is 1.2-3.3V.

2. The carbon monoxide sensor according to claim 1, characterized in that The pattern array includes a square array, a chessboard array, and a honeycomb array.

3. The carbon monoxide sensor according to claim 1, characterized in that The mass fraction of X in the carbon monoxide gas-sensitive material is 5-15%.

4. The carbon monoxide sensor according to claim 1, characterized in that The carbon monoxide gas-sensitive material is prepared by the following method: adding a transition metal salt and a tungsten source compound to an acidic solution containing a chelating agent and stirring the mixture to obtain a mixed solution, wherein the transition metal ions and tungsten ions are adsorbed on micelles formed by the chelating agent; Drying the mixed solution to obtain a gel adsorbing transition metal ions and tungsten ions; The gel adsorbed with transition metal ions and tungsten ions is calcined in air to prepare the carbon monoxide gas-sensitive material.

5. The carbon monoxide sensor according to claim 4, characterized in that The chelating agent includes a butyl silicone-acrylate solution.

6. The carbon monoxide sensor according to claim 4, characterized in that The transition metal salt includes at least one of chromium nitrate, cadmium chloride, and sodium chromate; The tungsten source compound includes at least one of sodium tungstate nitrate and tungsten chloride.

7. The carbon monoxide sensor according to claim 4, characterized in that The stirring temperature is 70-90°C; The drying conditions are: drying at 250-300°C for 2-3 hours; The calcination treatment conditions are: calcination at 550-650° C. for 2-3 hours.

Images