Carbon monoxide gas-sensitive material as well as preparation method and application thereof

Abstract

The invention provides a carbon monoxide gas-sensitive material as well as a preparation method and application thereof, and belongs to the technical field of gas sensing. The structural formula of the carbon monoxide gas sensitive material is X2Wn-1O3n, X is cadmium or chromium, and n is 2, 3 or 4. The carbon monoxide gas-sensitive material has high sensitivity and selectivity, has good gas-sensitive performance on low-concentration carbon monoxide, reduces the power consumption of a carbon monoxide sensor, and can monitor carbon monoxide leakage for a long time.

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. Incomplete fossil fuels, industrial combustion, and automobile exhaust emissions produce carbon monoxide gas. Compared with oxygen, human blood has an affinity for CO that is multiple times higher. Carbon monoxide gas molecules will bind to hemoglobin in the blood, resulting in a lack of oxygen circulation in the body, which can easily cause serious and irreversible harm to the human body. Therefore, for safety reasons, it is of great significance to develop carbon monoxide gas sensors with excellent performance.

[0003] Gas sensors are sensors used to detect the composition and concentration of gases. Common gas sensors include electrochemical sensors, infrared sensors, and semiconductor sensors. Among them, 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 comparison, semiconductor CO sensors have the advantages of low cost, strong anti-interference and long life, so they have been 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 X 2 W 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 on micelles formed by the chelating agent; drying the mixed solution to obtain a gel adsorbed with the transition metal ions and tungsten ions; 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 X 2 W n-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium.

[0009] In one embodiment, the chelating agent includes 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; 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 condition is: drying at 250-300°C for 2-3 hours; the calcination condition is: calcining at 550-650°C for 2-3 hours.

[0012] According to another embodiment of the present invention, there is provided a carbon monoxide sensor, 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 chessboard 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, the present invention uses a sol-gel method to fix chromium ions or cadmium ions and tungsten ions to form oxide nanoparticles with a single structure, wherein the incorporation of chromium ions or cadmium ions provides oxygen vacancies, reduces the energy band gap of the carbon monoxide gas-sensitive material, and the introduction of chromium ions or cadmium ions affects the position of the energy band center, which helps to change the attraction of the material to electrons, thereby improving the electrophilicity of the material, so that it has a higher adsorption capacity for CO, and the formed gas sensor improves the selectivity and sensitivity to CO. Since the chromium ions or cadmium ions are fixed by using a chelating agent and then calcined, it helps to promote the oxide nanoparticles to form a porous structure, increase its specific surface area, and is more conducive to 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, and roughens the electrode surface, which helps to increase the amount of thermal radiation. The periodically arranged pattern array makes the heat distribution more uniform; and this stacked structure belongs to 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;

[0019] Figure 2 A cross-sectional view of 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;

[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 chart showing sensitivity tests of Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 to different gases; and

[0026] Figure 7 A curve diagram showing the variation of power consumption of the carbon monoxide sensor of Example 1 of the present invention and Comparative Example 1 with the heating temperature is shown.

[0027] [Description of Reference Numerals]

[0028] 1-Carbon monoxide gas sensitive layer;

[0029] 2- substrate;

[0030] 3-Metal electrode heating layer;

[0031] 4-Insulation layer;

[0032] 5-Metal pattern layer. DETAILED DESCRIPTION

[0033] Below, 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 concepts 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] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally 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 a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally 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 a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0036] As the air containing carbon monoxide is inhaled by the human body for a long time, the oxygen carrying capacity of the blood gradually decreases, which can easily cause serious harm to the human body. Considering the safety of the human body and the environment, it is more important to monitor carbon monoxide conveniently and accurately, and semiconductor carbon monoxide sensors have been widely used. However, it is difficult for sensors using semiconductor materials as gas-sensitive materials to achieve high sensitivity and high selectivity for carbon monoxide monitoring.

[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, and it is difficult to monitor the 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, and the structural formula of the carbon monoxide gas-sensitive material is X 2 W n-1 O 3n , n is 2, 3 or 4; X is cadmium or chromium.

[0040] According to some embodiments of the present invention, by using a chelating agent, a coordination bond is formed between the chelating agent and the chromium ions, cadmium ions, and tungsten ions, which helps the above metal ions to be stably and evenly dispersed in the solution; then the above metal ions are fixed; and then calcined to promote the carbon monoxide gas-sensitive material to form oxide nanoparticles with a single structure in which the chromium ions, cadmium ions, and tungsten ions are evenly dispersed. Since the number of valence electrons of chromium ions or cadmium ions is different from that of tungsten, after doping, a charge imbalance is caused in the tungsten oxide lattice, thereby introducing an additional energy level state. The additional energy level is located in the forbidden band, 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, the oxygen vacancies in the doped chromium ion or cadmium ion material interact with each other to help form composite defects, which may have higher chemical activity, thereby improving the electrophilicity of the carbon monoxide gas-sensitive material. The incorporation of chromium ions or cadmium ions increases the oxygen vacancies, so that it has a higher adsorption capacity for CO, and the formed carbon monoxide sensor can improve the selectivity and sensitivity to carbon monoxide. In addition, the carbon monoxide gas-sensitive material of the present invention is calcined in air after being fixed with metal elements, which helps to promote the carbon monoxide gas-sensitive material to form a porous structure, 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 the above range, the gas-sensitive performance of the carbon monoxide gas-sensitive material is better. When the mass fraction of the transition metal X is too high, the response of the carbon monoxide gas-sensitive material to the gas will be reduced; when it is too low, the doping effect is not obvious, and it is difficult to bring about 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 the structural formula of Cr 2 WO 6 .

[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, and 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 may 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 ions and tungsten ions. Stirring helps to uniformly disperse the transition metal ions and tungsten ions, and the chelating agent molecules form micelles around the transition metal ions and tungsten ions, and the transition metal ions and tungsten ions are uniformly adsorbed on the micelles formed by the chelating agent. The acidic solution provides an acidic environment to keep the transition metal ions and tungsten ions in a stable dispersed state in the solution to prevent premature hydrolysis and precipitation of the two.

[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, after the mixed solution containing micelles is dried, a gel with elasticity and network structure can be obtained. The reason is that after the solvent is removed, the mixed solution is converted into a gel state, and the gel state has a higher specific surface area and porous structure, which helps to provide a larger number of adsorption sites and provide a highly dispersed support environment for transition metal ions and tungsten ions. The drying process helps to maintain the porous structure of the gel, which is beneficial to the selective adsorption of CO when it is subsequently applied to 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 X 2 W 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 burn, so that the transition metal ions and tungsten ions are oxidized and converted into corresponding carbon monoxide gas-sensitive materials doped with transition metals. And due to the volatilization of the organic components, pores will be left in the formed carbon monoxide gas-sensitive material, further forming a porous structure. The carbon monoxide gas-sensitive material is tungsten oxide doped with transition metals, which has high catalytic activity, and the porous structure formed by it 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 promote 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 omits the complex steps of synthesizing a hard template 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; the tungsten source compound includes at least one of sodium tungstate nitrate and tungsten chloride. The above raw materials have good solubility and can be fully dissolved in an acidic solution under appropriate heating conditions, which is conducive to the subsequent uniform dispersion of transition metal ions and tungsten ions.

[0054] In one embodiment, the solvent used to form the acidic solution may 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 the above solvent, it can dissolve the transition metal salt, the tungsten source compound, and the chelating agent, and can ensure the uniformity of the mixed solution. The acidic solution may be, for example, a nitric acid solution. Nitric acid is a strong acid that can relatively quickly reduce the Ph value of the solution, which helps to maintain the stability of the transition metal ions and tungsten ions in the acidic solution and prevent the transition metal ions and tungsten ions from being hydrolyzed and precipitated prematurely. At the same time, the addition of nitric acid can increase the strength of the acidic solution and help 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. Keeping the stirring temperature in the above range helps to promote the dissolution of the raw materials. The drying process can be, for example, drying with a blast drying oven. The drying process conditions are: at 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 2-3h, for example, 2h, 2.5h or 3h, preferably 3h. The conditions for the calcination process are: at 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, it can be 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 FIG. 2 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 comprises a carbon monoxide gas-sensitive layer 1, and the carbon monoxide gas-sensitive layer 1 comprises 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 smaller chemical strength and a lower chemical potential, which is beneficial to the adsorption of carbon monoxide, the carbon monoxide gas-sensitive layer 1 has a higher 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 depositing a metal pattern layer 5 on the insulating layer 4, a special electrode structure of a metal layer / insulating layer / metal layer is formed. The specific 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, which significantly reduces power consumption while ensuring rapid activation of the CO gas-sensitive material. And by arranging the pattern array in a periodic arrangement, it helps to form a periodic magnetic field distribution. By setting a periodically arranged pattern array arrangement, it helps to improve the response of the carbon monoxide sensor to CO.

[0060] According to some embodiments of the present invention, by doping transition metal chromium or cadmium into tungsten oxide to provide oxygen vacancies, the electrode structure of the carbon monoxide sensor is optimized and the electrode surface is roughened. The synergistic effect of the two not only improves the sensitivity and selectivity of the carbon monoxide sensor to CO, but also significantly reduces the power consumption of the carbon monoxide sensor, meeting the on-site requirements for gas leakage, long-term monitoring and rapid response.

[0061] In one embodiment, the pattern array includes a square array, a chessboard 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; Figure 3c FIG. 2 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~Figure 3c As shown, the periodically arranged pattern array can increase the surface area of ​​the metal pattern layer 5, increase the contact opportunity between the carbon monoxide gas-sensitive layer 1 on its surface and the CO gas molecules, and enable more gas molecules to be adsorbed on the surface of the carbon monoxide gas-sensitive layer 1. The present invention can optimize the response speed and selectivity of the carbon monoxide sensor to CO by setting the above-mentioned specific pattern array. The periodic structure produces a plasma resonance effect, which helps to improve the signal strength of the gas sensor. Accordingly, the signal strength is improved, and the detection efficiency of CO is also improved, 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, such as 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 is 100~200nm, for example, it 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 the specific absorption peak of CO (that is, 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 1.2~3.3V, 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 may be covered with a surface insulating layer (not shown in the figure) as required, and the material of the surface insulating layer may be, for example, aluminum oxide with a thickness of 5 to 20 nm. The surface insulating layer helps to protect the electrode structure below from being oxidized.

[0065] According to an embodiment of yet 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 sintering the gas-sensitive slurry 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 firstly made into a metal heating electrode pattern by means of coating, soft baking, exposure, post-baking, flooding, and development, and then the metal heating layer 3 is obtained by means of magnetron sputtering. The metal heating electrode pattern is formed by photolithography using a mask plate. The formation of the metal heating electrode pattern is not the focus of the present invention and can be obtained by conventional steps, which will not be described in detail here.

[0067] In one embodiment, the metal pattern layer 5 is prepared by coating, soft baking, exposure, post-baking, flooding, and developing to form a periodically arranged pattern array, and then the metal pattern layer 5 is obtained by magnetron sputtering. The preparation method of the metal pattern layer 5 is consistent with that of the metal electrode heating layer 3, and will not be repeated here.

[0068] In one embodiment, ball milling the carbon monoxide gas-sensitive material to obtain the gas-sensitive slurry may include: mixing the carbon monoxide gas-sensitive material and the organic slurry and ball milling them to obtain the gas-sensitive slurry for spraying. The organic slurry includes pinene alcohol, 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 r / min, and the ball milling 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 is further described below by examples, drawings and related test experiments and results thereof. In the detailed description below, 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 obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined arbitrarily into other feasible embodiments.

[0071] It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are all commercially available or homemade by recognized processing methods.

[0072] Embodiment 1:

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

[0074] 0.01 mol of Cr(NO 3 ) 2 •9H 2 O was dissolved in nitric acid solution, and then 0.01 mol of Na 2 WO 4 •2H2 O to form a mixed solution. 0.24 mol of butyl siloxane-acrylate emulsion dispersion (solid content 4.5%) was added to the mixed solution at a molar ratio of the sum of the above metal cations to the chelating agent of 2:3, and then 0.16 mol of ethylene glycol was added. The mixture was maintained at 80°C under magnetic stirring until gel appeared.

[0075] The obtained gel was placed in an oven, heated to 300°C at 5°C / s, and kept for degreasing for 3 hours to eliminate organic solvents and other impurities. The product was placed in a muffle furnace, sintered at 600°C for 2 hours, and then ground into powder to obtain Cr 2 WO 6 powder. Figure 4 FIG. 1 shows the X-ray diffraction spectrum of the carbon monoxide gas-sensitive material of Example 1 of the present invention. Figure 4 As shown, it can be determined that the prepared Cr 2 WO 6 structure. 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] Cr 2 WO 6 The powder and the organic slurry are mixed and ball-milled at a speed of 300 r / min for 6 hours to obtain a gas-sensitive slurry for spraying. The organic slurry used is 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] The zirconium oxide was air-blown and then soft-baked at 100°C for 2 minutes and exposed for 1 minute. Then, it was post-baked at 120°C for 2 minutes and exposed 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 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 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 an aperture of 60 μm, placed in a constant temperature drying oven for drying 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] Embodiment 2:

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

[0083] 0.01 mol of Cr(NO 3 ) 2 • 9H 2 O was dissolved in nitric acid solution, and then 0.02 mol of Na 2 WO 4 •2H 2 O to form a mixed solution. 0.345 mol of butyl siloxane-acrylate emulsion dispersion (solid content 4.5%) was added to the mixed solution at a molar ratio of the sum of the above metal cations to the chelating agent of 2:3, and then 0.23 mol of ethylene glycol was added. The mixture was maintained at 80°C under magnetic stirring until gelation occurred.

[0084] The same operation as in Example 1 was used to prepare Cr 2 W 2 O 6 The same operation as in Example 1 was continued, except that the gas sensitive slurry was used in Example 2. Figure 3b The checkerboard array shown is used to prepare carbon monoxide sensor B.

[0085] Embodiment 3:

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

[0087] 0.01 mol of Cr(NO 3 ) 2 •4H 2 O was dissolved in nitric acid solution, and then 0.03 mol of Na 2 WO 4 •2H 2O to form a mixed solution. 0.45 mol of butyl siloxane-acrylate emulsion dispersion (solid content 4.5%) was added to the solution at a molar ratio of the sum of the above metal cations to the chelating agent of 2:3, and then 0.3 mol of ethylene glycol was added. The mixture was maintained at 80°C under magnetic stirring until gelation occurred.

[0088] The same operation as in Example 1 was used to prepare Cr 2 W 2 O 6 The same operation as in Example 1 was continued, except that the gas sensitive slurry was used in Example 3. 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 steps as Example 1, except that no improvement is made to the electrode structure during the preparation of the carbon monoxide sensor, and only doping is performed on the gas sensitive material.

[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 for 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 of the present invention 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, because the gas-sensitive material Cr used 2 WO 6 The chemical strength is small and the chemical potential is 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. The oxygen vacancies as active sites also promote 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 power consumption of the carbon monoxide sensor of Example 1 of the present invention and Comparative Example 1 varies with the heating temperature. Figure 7 It can be seen that compared with ordinary heating electrodes, the electrode heating structure of metal layer / insulating layer / metal layer can greatly reduce the heating power, and the heating power consumption at 400°C is only 4.2mW. This structure makes the surface temperature distribution more uniform, and the special magnetic field formed can regulate the distribution of oxygen vacancies, promote the adsorption and desorption of CO and the chemical reaction process.

[0098] The present invention incorporates a certain amount of transition metal into the tungsten oxide gas-sensitive material by a sol-gel method. On the one hand, the incorporation of Cr provides appropriate oxygen vacancies, reduces the energy band gap and improves the electrophilicity, which is manifested as a high special adsorption capacity for CO. On the other hand, the porous structure formed has a large specific surface area, which is conducive to the selective adsorption of carbon monoxide gas. In addition, a heating electrode structure that can emit surface plasma is obtained by regulating the electrode surface. On the one hand, the structure can locally regulate the surface electron distribution, thereby increasing the surface adsorption of oxygen and further promoting the occurrence of CO oxidation reaction; on the other hand, the structure makes the temperature distribution more uniform, and the maximum temperature difference can be controlled within 10°C, which ensures the rapid activation of the CO gas-sensitive material while significantly reducing the power consumption. The coordinated effect of the two not only improves the sensitivity of the sensor to CO and the selectivity of CO, but also significantly reduces the power consumption of the sensor, meeting the on-site needs of 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 description is only a specific embodiment of the present invention and is 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 gas-sensitive material, characterized in that: 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.

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

3. A method for preparing a carbon monoxide gas-sensitive material, characterized in that: include: 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 transition metal ions and tungsten ions are adsorbed onto 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. 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.

4. The preparation method according to claim 3, characterized in that: The chelating agent includes a butyl silicone-acrylate solution.

5. The preparation method according to claim 3, 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.

6. The preparation method according to claim 3, characterized in that: The stirring temperature is 70-90°C; The drying conditions are: drying at 250-300°C for 2-3h; The calcination treatment conditions are: calcination at 550-650° C. for 2-3 hours.

7. A carbon monoxide sensor, characterized in that: It comprises a carbon monoxide gas-sensitive layer, wherein the carbon monoxide gas-sensitive layer comprises the carbon monoxide gas-sensitive material according to claim 1 or 2 or the carbon monoxide gas-sensitive material prepared by the preparation method of the carbon monoxide gas-sensitive material according to any one of claims 3 to 6.

8. The carbon monoxide sensor according to claim 7, characterized in that: 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.

9. The carbon monoxide sensor according to claim 8, characterized in that: The pattern array includes a square array, a chessboard array, and a honeycomb array.

10. The carbon monoxide sensor according to claim 8, characterized in that: 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 200-500 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 100-200 nm respectively; The carbon monoxide gas sensitive layer has a thickness of 2-4 μm.

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