Gas sensor as well as preparation method and application thereof

Abstract

The invention relates to the technical field of gas sensors and elements, and discloses a gas sensor as well as a preparation method and application thereof. The gas sensor comprises an electrode substrate and cobalt vanadate coated on the surface of the electrode substrate, the preparation method comprises the following steps: mixing ammonium metavanadate, cobalt salt, an alkali source and water, and reacting; carrying out solid-liquid separation on the obtained product, and calcining the solid product; and coating the surface of an electrode substrate with the obtained product, and aging. Compared with a single metal oxide gas sensor, the gas sensor has lower working temperature, excellent response sensitivity to carbon monoxide and good working stability; according to the preparation method, a surfactant or a template is not used, compared with the prior art, the technological process for synthesizing cobalt vanadate is reduced, operation is easy, cost is low, and industrial popularization is easy.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application 202410843492.4 filed on June 27, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of gas sensors and components, and in particular to a gas sensor and a preparation method and application thereof. Background Art

[0004] Environmental pollution caused by carbon monoxide has become a global concern. It is colorless, odorless and highly toxic. It easily combines with hemoglobin to form carboxyhemoglobin, which makes hemoglobin lose its oxygen-carrying function, causing tissue suffocation, nausea, headache, dyspnea and accelerated heartbeat, and even hallucinations, confusion, epilepsy and other symptoms. It can also lead to left ventricular dysfunction accompanied by systolic and diastolic dysfunction, and in the most serious cases, respiratory arrest. Its sources are also very rich, such as industrial emissions, mining, automobile exhaust, daily combustion, etc., so it is very important to detect carbon monoxide in the environment.

[0005] At present, there are many types of carbon monoxide sensors on the market. According to their detection signals, they can be divided into two categories: electrical signals and optical signals. The electrical signal mainly achieves the detection purpose by the change of electrical properties of the gas sensor caused by exposure to carbon monoxide gas, and the optical signal is detected by the change of optical properties caused by contact with carbon monoxide. In recent years, metal oxides are often used in the sensing research of reducing gases such as carbon monoxide due to their good conductivity, chemical and thermal stability, and adsorption of gases. Metal oxide-based carbon monoxide sensors are currently the most widely used carbon monoxide gas sensors. However, oxide-type sensors generally have disadvantages such as high energy consumption and high operating temperature (200℃-300℃). They are usually doped with precious metals Pd or Pt to improve their sensitivity, but the cost is high and it is not suitable for mass production, which also limits their commercial application in carbon monoxide sensors. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art, such as poor gas-sensing performance of a single material of a metal oxide (MOS) type gas sensor and high doping cost of a noble metal gas sensor, and provide a gas sensor and a preparation method and application thereof. The gas sensor comprises an electrode substrate and cobalt vanadate coated on the surface of the substrate. Since the cobalt vanadate is a binary transition metal oxide material, it has a lower operating temperature and good working stability compared with a single metal oxide gas sensor. The method prepares the cobalt vanadate by a hydrothermal synthesis method to obtain the gas sensor. The preparation method is simple to operate, reduces the process flow of synthesizing cobalt vanadate compared with the prior art, has low cost and is easy to promote industrially. The gas sensor prepared by the method has excellent sensitivity to detecting carbon monoxide, and the sensor has a low operating temperature and good stability.

[0007] In order to achieve the above object, the first aspect of the present invention provides a carbon monoxide gas sensor, the gas sensor comprising an electrode substrate and cobalt vanadate coated on the surface of the electrode substrate.

[0008] Preferably, the electrode substrate is selected from one of a gold electrode, a gold-titanium alloy electrode and an interdigitated electrode.

[0009] Preferably, the particle size of the cobalt vanadate is 100-300 nm.

[0010] Preferably, the specific surface area of ​​the cobalt vanadate is 29-38m 2 / g.

[0011] A second aspect of the present invention provides a method for preparing a carbon monoxide gas sensor, the method comprising the following steps:

[0012] (1) mixing ammonium metavanadate, a cobalt salt, an alkali source and water and reacting them;

[0013] (2) separating the product obtained in step (1) into solid and liquid, and calcining the solid product;

[0014] (3) coating the product obtained in step (2) on the surface of the electrode substrate and then aging the electrode substrate.

[0015] Preferably, the cobalt salt is selected from one or more of cobalt nitrate, cobalt sulfate, cobalt acetate and cobalt chloride.

[0016] Preferably, the alkali source is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water.

[0017] Preferably, the molar ratio of the ammonium metavanadate to the cobalt salt is 1-4:1.

[0018] Preferably, in step (1), the reaction conditions include: temperature of 120-220°C, preferably 160-200°C; time of 2-18h, preferably 4-16h.

[0019] Preferably, in step (2), the calcination conditions include: temperature of 400-600° C., heating rate of 2-4° C. / min, and time of 2-5 h.

[0020] Preferably, in step (1), the specific step of mixing comprises: dissolving ammonium metavanadate and cobalt salt in water respectively, then dropping an alkali source into the obtained ammonium metavanadate solution, and then dropping a cobalt salt solution into the obtained mixed solution.

[0021] Preferably, in step (1), the concentration of ammonium metavanadate is 0.1-0.8 mol / L.

[0022] Preferably, in step (1), the concentration of the cobalt salt solution is 0.1-0.5 mol / L.

[0023] Preferably, in step (1), the concentration of the alkali source solution is 0.2-2 mol / L.

[0024] Preferably, in step (1), the pH of the mixed solution obtained after adding the alkali source is 8-10.

[0025] Preferably, in step (1), the rate of adding the cobalt salt solution dropwise is 1-3 drops / s.

[0026] Preferably, in step (3), the aging conditions include: temperature of 40-60° C., current of 20-40 mA, and time of 20-72 h.

[0027] The third aspect of the present invention also provides a gas sensor prepared by the method described above.

[0028] The fourth aspect of the present invention also provides an application of a gas sensor prepared by the method described above in detecting carbon monoxide.

[0029] Compared with the prior art, the present invention has at least the following advantages:

[0030] (1) In the present invention, the gas sensor comprises an electrode substrate and cobalt vanadate coated on the surface of the substrate. Cobalt vanadate is a binary transition metal oxide material, which can improve the conductivity of electrons and ions, the reversibility of the Faraday reaction and the cycle stability of the gas sensor in application. At the same time, cobalt vanadate has a variable crystal structure, synergistic effect and interface effect between multiple metals. Therefore, the gas sensor has a lower operating temperature than a single metal oxide gas sensor, and has excellent response sensitivity to carbon monoxide and good working stability.

[0031] (2) In the present invention, the method prepares cobalt vanadate by hydrothermal synthesis to obtain the gas sensor. The preparation method does not use surfactants or templates. Compared with the prior art, the process flow of synthesizing cobalt vanadate is reduced, the operation is simple, the cost is low, and it is easy to promote in industry. Compared with the prior art, the cobalt vanadate prepared by the method has a uniform structure and a large specific surface area, which can further improve the sensitivity of cobalt vanadate to carbon monoxide response and reduce the working temperature.

[0032] (3) In the present invention, the gas sensor prepared by the method has excellent sensitivity to carbon monoxide, low operating temperature and good stability. In a preferred embodiment, the gas sensor has a response of up to 349.1% to carbon monoxide under an environment of 120°C and 500ppmCO, and has good stability. At the same time, compared with carbon dioxide and reducing gas methane, the sensor has better selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a SEM image of the cobalt vanadate prepared in Example 1;

[0034] Figure 2 This is a comparison chart of the responses of the gas sensor prepared in Example 1 to three gases with a concentration of 50-500 ppm;

[0035] Figure 3 This is a comparison chart of the responses of the gas sensors prepared in Example 1 and Comparative Example 1 to 50-500 ppm concentration of CO;

[0036] Figure 4 This is a comparison chart of the responses of the gas sensors obtained in Example 1 and Comparative Example 2 to 50-500 ppm concentration of CO;

[0037] Figure 5 This is a comparison chart of the responses of the gas sensors prepared in Examples 1-4 to 50-500 ppm CO concentration;

[0038] Figure 6It is a comparison chart of the responses of the gas sensors prepared in Example 1 and Examples 5-7 to 50-500 ppm CO concentration. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0040] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0041] A first aspect of the present invention provides a gas sensor, which comprises an electrode substrate and cobalt vanadate coated on the surface of the electrode substrate.

[0042] In a specific embodiment, the electrode substrate can be selected conventionally in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the electrode can be one of a gold electrode, a gold-titanium alloy electrode and an interdigital electrode.

[0043] In a further preferred embodiment, the electrode is a gold electrode.

[0044] In a specific embodiment, the cobalt vanadate may be a nano material. In a preferred embodiment, the particle size of the cobalt vanadate may be 100-300 nm.

[0045] In a specific embodiment, the specific surface area of ​​the cobalt vanadate is about 29-38 m 2 In a preferred embodiment, the specific surface area of ​​the cobalt vanadate is about 35-38 m 2 / g.

[0046] In a preferred embodiment, the cobalt vanadate may have a uniform structure, and the particle size of the cobalt vanadate may be 150-250 nm.

[0047] In a further preferred embodiment, the cobalt vanadate may be a hexagonal pill-like structure. According to the above preferred embodiment, the cobalt vanadate has a uniform nanostructure, which can increase the specific surface area of ​​the cobalt vanadate and the adsorption capacity of carbon monoxide, further improve the sensitivity of the gas sensor to carbon monoxide response, reduce the temperature required for the reaction, and improve the cycle stability of the gas sensor.

[0048] In a specific embodiment, the gas sensor may further include a protective housing device, which may be selected conventionally in the art as long as the purpose of the present invention can be achieved.

[0049] In the present invention, the gas sensor contains an electrode substrate and cobalt vanadate coated on the surface of the substrate. The cobalt vanadate is a binary transition metal oxide material, which can improve the conductivity of electrons and ions, the reversibility of the Faraday reaction and the cycle stability of the gas sensor in application. At the same time, the cobalt vanadate has a variable crystal structure, a synergistic effect and an interface effect between multiple metals. Therefore, the gas sensor has a lower operating temperature than a single metal oxide gas sensor, and has excellent response sensitivity to carbon monoxide and good working stability.

[0050] A second aspect of the present invention provides a method for preparing a gas sensor, the method comprising the following steps:

[0051] (1) mixing ammonium metavanadate, a cobalt salt, an alkali source and water and reacting them;

[0052] (2) separating the product obtained in step (1) into solid and liquid, and calcining the solid product;

[0053] (3) coating the product obtained in step (2) on the surface of the electrode substrate and then aging the electrode substrate.

[0054] In a specific embodiment, the cobalt salt can be selected conventionally in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the cobalt salt can be one or more of cobalt nitrate, cobalt sulfate, cobalt acetate and cobalt chloride.

[0055] In a further preferred embodiment, the cobalt salt may be cobalt nitrate or cobalt nitrate hexahydrate.

[0056] In a specific embodiment, the alkali source can be selected from conventional sources in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the alkali source can be one or more of sodium hydroxide, potassium hydroxide and ammonia water.

[0057] In a further preferred embodiment, the alkali source may be a sodium hydroxide solution.

[0058] In a specific embodiment, the molar ratio of the ammonium metavanadate to the cobalt salt may be 1-4:1. Specifically, the molar ratio of the ammonium metavanadate to the cobalt salt may be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0059] In a specific embodiment, in step (1), the water added can be any conventionally selected water in the art, as long as the purpose of the present invention can be achieved.

[0060] In a preferred embodiment, the molar ratio of the ammonium metavanadate to the cobalt salt may be 3:1.

[0061] In a specific embodiment, in step (1), the reaction conditions include: temperature of 120-220°C, and time of 2-18 hours. In a preferred embodiment, in step (1), the reaction conditions include: temperature of 160-200°C, and time of 4-16 hours.

[0062] In a further preferred embodiment, in step (1), the reaction conditions include: temperature of 180° C. and reaction time of 12 h.

[0063] In a specific embodiment, in step (1), the reaction can be carried out in a conventional device in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, in step (1), the reaction can be carried out in an autoclave.

[0064] In a preferred embodiment, in step (1), the capacity of the autoclave liner is 50 mL and the filling degree is about 2 / 3.

[0065] In a specific embodiment, in step (1), the product obtained by the reaction needs to be washed and dried.

[0066] In a specific embodiment, in step (1), the washing can be selected conventionally in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, in step (1), the washing can be performed by alternating deionized water and anhydrous ethanol for 2-3 times.

[0067] In a specific embodiment, in step (1), the drying can be a conventional method in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, in step (1), the drying can be carried out in a forced air oven.

[0068] In a specific embodiment, in step (1), the drying conditions may include: a temperature of 40-80°C and a time of 30-60 hours. In a preferred embodiment, in step (1), the drying conditions may include: a temperature of 50-70°C and a time of 36-48 hours.

[0069] In a specific embodiment, in step (1), the specific step of mixing includes: dissolving ammonium metavanadate and cobalt salt in water respectively, then dropping an alkali source into the obtained ammonium metavanadate solution, and then dropping a cobalt salt solution into the obtained mixed solution.

[0070] In a specific embodiment, in step (1), the concentration of ammonium metavanadate is 0.1-0.8 mol / L, specifically 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L or 0.8 mol / L.

[0071] In a preferred embodiment, in step (1), the concentration of ammonium metavanadate is 0.1-0.5 mol / L, specifically 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L or 0.5 mol / L.

[0072] In a specific embodiment, in step (1), the concentration of the cobalt salt solution is 0.1-0.5 mol / L, specifically 0.1 mol / L, 0.13 mol / L, 0.16 mol / L, 0.18 mol / L, 0.2 mol / L, 0.23 mol / L, 0.26 mol / L, 0.28 mol / L, 0.3 mol / L, 0.33 mol / L, 0.36 mol / L, 0.38 mol / L, 0.4 mol / L, 0.43 mol / L, 0.46 mol / L, 0.48 mol / L or 0.5 mol / L.

[0073] In a preferred embodiment, in step (1), the concentration of ammonium metavanadate is 0.2-0.3 mol / L, specifically 0.2 mol / L, 0.23 mol / L, 0.26 mol / L, 0.28 mol / L or 0.3 mol / L.

[0074] In a specific embodiment, in step (1), the concentration of the alkali source solution is 0.2-2 mol / L, specifically 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L or 2 mol / L.

[0075] In a preferred embodiment, in step (1), the concentration of the alkali source solution is 0.8-1.5 mol / L, specifically 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L.

[0076] In a specific embodiment, in step (1), the dissolution of the ammonium metavanadate is carried out under stirring conditions, as long as the ammonium metavanadate solution is stirred until a yellow clear solution is obtained. In a preferred embodiment, in step (1), the stirring conditions include: a temperature of 60-100°C, a time of 30-75 min, and a rotation speed of 300-400 r / min.

[0077] In a specific embodiment, in step (1), the alkali source is added dropwise to the ammonium metavanadate solution under stirring, as long as the ammonium metavanadate solution can be turned colorless. In a preferred embodiment, in step (1), the stirring speed is 350-500 r / min.

[0078] In a specific embodiment, in step (1), the pH value of the mixed solution obtained after the alkali source is added dropwise is 8 to 10. In a preferred embodiment, in step (1), the pH value of the mixed solution obtained after the alkali source is added dropwise is 9.

[0079] In a specific embodiment, in step (1), the cobalt salt solution is added dropwise to the mixed solution under stirring. In a preferred embodiment, in step (1), the conditions for the dropwise addition include: the cobalt salt solution is added dropwise at a speed of 1-3 drops / s, a rotation speed of 350-500 r / min, and a time of 20-40 min.

[0080] In a specific embodiment, in step (2), the solid-liquid separation can be a conventional choice in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, the solid-liquid separation can be centrifugation.

[0081] In a preferred embodiment, in step (2), the centrifugal conditions include: a rotation speed of 8000-10000 r / min and a time of 10 min-20 min.

[0082] In a specific embodiment, in step (2), the calcination can be carried out in a conventional device in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, in step (2), the calcination can be carried out in a muffle furnace.

[0083] In a specific embodiment, in step (2), the calcination conditions include: temperature of 400-600°C, heating rate of 2-4°C / min, and time of 2-5h. In a preferred embodiment, the calcination conditions include: temperature of 500°C, heating rate of 3°C / min, and time of 3h.

[0084] In the present invention, through the aforementioned preferred embodiment, compared with the prior art, the cobalt vanadate gas-sensitive material prepared by the method has a larger specific surface area and a uniform and complete hexagonal tablet-like structure, which avoids sintering and agglomeration, and is beneficial to improving the adsorption of carbon monoxide by the gas-sensitive material, thereby improving the sensitivity of the cobalt vanadate gas-sensitive material to carbon monoxide response when used in a gas sensor.

[0085] In a specific embodiment, in step (3), the aging further comprises the following steps: adding the product obtained in step (2) to a solvent and grinding it, and then coating it on an electrode for aging.

[0086] In a specific embodiment, in step (3), the solvent can be selected conventionally in the art, as long as the purpose of the present invention can be achieved. In a preferred embodiment, in step (3), the solvent can be alcohol and / or deionized water.

[0087] In a specific embodiment, in step (3), the grinding time can be 10-20 min. In a preferred embodiment, in step (3), the grinding time can be 15 min.

[0088] In a specific embodiment, in step (3), the aging conditions include: temperature of 40-60°C, current of 20-40mA, and time of 20-72h. In a preferred embodiment, the aging conditions include: temperature of 60°C, current of 30mA, and time of 36-60h.

[0089] In the present invention, the method prepares cobalt vanadate by a hydrothermal synthesis method, and then obtains the gas sensor. The preparation method does not use a surfactant or a template, and compared with the prior art, the process flow of synthesizing cobalt vanadate is reduced, the operation is simple, the cost is low, and it is easy to promote industrially; the cobalt vanadate prepared by the method has a uniform structure and a large specific surface area, and can further improve the sensitivity of cobalt vanadate to carbon monoxide response and reduce the working temperature.

[0090] The present invention also provides a gas sensor prepared by the method described above.

[0091] In the present invention, the sensor prepared by the method has a large specific surface area and a uniform hexagonal pill-like structure, which is beneficial to improving the sensitivity of the response to carbon monoxide, and has a lower operating temperature and good working stability compared to a single metal oxide gas sensor.

[0092] The present invention also provides an application of a gas sensor prepared by the method described above in detecting carbon monoxide.

[0093] In a preferred embodiment, the gas sensor can be applied to safety early warning of lithium-ion batteries.

[0094] In a further preferred embodiment, the gas sensor can be used for thermal runaway warning of lithium-ion batteries.

[0095] In the present invention, the gas sensor prepared by the method has excellent sensitivity to carbon monoxide, low operating temperature and good stability. In a preferred embodiment, the gas sensor has a response of up to 349.1% to carbon monoxide under an environment of 120°C and 500ppmCO, and good stability. At the same time, compared with carbon dioxide and reducing gas methane, the sensor has better selectivity, which is conducive to application in safety warning of lithium-ion batteries.

[0096] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0097] In the following examples and comparative examples, unless otherwise specified, the reagents used are all commercially available products.

[0098] Example 1

[0099] (1) Weigh 0.01 mol of ammonium metavanadate and dissolve it in 30 mL of deionized water. Place the solution in an 80° C. water bath and stir until the solution turns yellow and transparent. Weigh 0.005 mol of cobalt nitrate and dissolve it in 20 mL of deionized water. Take the ammonium metavanadate solution out of the water bath and transfer it to a magnetic stirrer. Add NaOH solution dropwise to make it colorless and the pH value of the solution is about 9. Then, add the cobalt nitrate solution dropwise to the ammonium metavanadate solution. Stir continuously for about 30 minutes and then transfer it to an autoclave. Heat it at 180° C. for 12 hours and cool it to room temperature.

[0100] (2) After centrifuging the product obtained in step (1), the solid product is repeatedly washed with deionized water and anhydrous ethanol for three times, and then placed in a blast oven to dry for about 48 hours; the dried solid product is ground and placed in a crucible, and calcined in a muffle furnace at 500° C. for 3 hours to obtain a cobalt vanadate gas-sensitive material.

[0101] (3) Take about 10 mg of cobalt vanadate gas-sensitive material, add 7 drops of alcohol (about 0.3-0.5 mL) to it, grind for 15 minutes, then apply the obtained cobalt vanadate gas-sensitive material to the hexagonal plate electrode of the gold electrode, and age it at 30 mA (60°C) for 48 hours to prepare a gas sensor.

[0102] Example 2

[0103] This embodiment is implemented by the method of embodiment 1, except that in step (1), the temperature of the hydrothermal reaction is 140°C.

[0104] Example 3

[0105] This embodiment is implemented by the method of embodiment 1, except that in step (1), the temperature of the hydrothermal reaction is 160°C.

[0106] Example 4

[0107] This embodiment is implemented by the method of embodiment 1, except that in step (1), the temperature of the hydrothermal reaction is 200°C.

[0108] Example 5

[0109] This embodiment is implemented by the method of embodiment 1, except that in step (1), the hydrothermal reaction time is 4 hours.

[0110] Example 6

[0111] This embodiment is implemented by the method of embodiment 1, except that in step (1), the hydrothermal reaction time is 8 hours.

[0112] Example 7

[0113] This example is implemented using the method of Example 1, except that in step (1), the hydrothermal reaction time is 16 hours.

[0114] Comparative Example 1

[0115] This comparative example is implemented by the method of Example 1, except that in step (2), the solid product obtained by centrifugation is not calcined.

[0116] Comparative Example 2

[0117] This comparative example is a commercially available MQ-7B CO sensor.

[0118] Test Example 1

[0119] The cobalt vanadate gas-sensitive material prepared in Example 1-7 was characterized by SEM;

[0120] The cobalt vanadate gas-sensitive material prepared in Examples 1-7 was characterized by nitrogen adsorption.

[0121] According to the attached picture Figure 1 It can be seen that the cobalt vanadate prepared in the preferred embodiment, i.e., Example 1, has a particle size of 150-250nm and a uniform hexagonal tablet-like structure without thermal sintering or agglomeration. The gas sensor prepared from the cobalt vanadate gas-sensitive material has a higher sensitivity in detecting carbon monoxide and a lower operating temperature.

[0122] Test Example 2

[0123] The gas sensor prepared in Example 1 is placed in the calibration cover of a gas-sensitive performance electrical tester, and background gas (dry high-purity argon) is introduced for more than half an hour. At the same time, the working current of the device is set to 54mA (120°C). When the sensor enters the working state and stabilizes, the dry target gas is started to be tested, and the total gas flow rate is set to 500mL / min. 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, and 500ppm of CO, CO2, and CH4 are respectively introduced through a dynamic gas distribution device or a gas flow control mixing device for sensitivity testing.

[0124] The results are as follows Figure 2 shown.

[0125] According to the attached picture Figure 2 It can be seen that by adopting the technical solution of the present invention, the gas sensor has excellent sensitivity to carbon monoxide. In an environment of 120°C and 500ppmCO, the response to carbon monoxide is as high as 349.1%, the operating temperature is low, and the stability is good. At the same time, compared with carbon dioxide and reducing gas methane, the sensor has better selectivity.

[0126] Test Example 3

[0127] The gas sensors prepared in Example 1 and Comparative Example 1 were placed in the calibration cover of a gas-sensitive performance electrical tester, and background gas (dry high-purity argon) was introduced for more than half an hour. At the same time, the working current of the device was set to 54 mA (120°C). When the sensor entered the working state and stabilized, the dry target gas was started to be tested, and the total gas flow rate was set to 500 mL / min. 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm of CO gas were introduced through a dynamic gas distribution device or a gas flow control mixing device for sensitivity testing.

[0128] The results are as follows Figure 3 shown.

[0129] According to the attached picture Figure 3It can be seen that in the technical solution of the present invention, the gas sensor prepared by using the calcined cobalt vanadate gas-sensitive material has a response of up to 349.1% to carbon monoxide under an environment of 120°C and 500ppmCO, a low operating temperature, and good stability; while in Comparative Example 1, since the cobalt vanadate gas-sensitive material is not calcined, its sensitivity to carbon monoxide is far less than that of the gas sensor prepared by the technical solution of the present invention.

[0130] Test Example 4

[0131] The gas sensors in Example 1 and Comparative Example 2 were placed in the calibration cover of a gas-sensitive performance electrical tester, and background gas (dry high-purity argon) was introduced for more than half an hour. At the same time, the working current of the device was set to 54 mA (120°C). When the sensor entered the working state and stabilized, the dry target gas was started to be tested, and the total gas flow rate was set to 500 mL / min. 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm of CO gas were introduced through a dynamic gas distribution device or a gas flow control mixing device for sensitivity testing.

[0132] The results are as follows Figure 4 shown.

[0133] According to the attached picture Figure 4 It can be seen that by adopting the technical solution of the present invention, at the same temperature and carbon monoxide concentration, the response of the gas sensor prepared in Example 1 to carbon monoxide is much higher than that of the commercially available MQ-7B CO sensor in Comparative Example 2, and the gas sensor prepared in Example 1 has a lower operating temperature and good stability, which is conducive to market promotion and application.

[0134] Test Example 5

[0135] The gas sensor prepared in Examples 1-4 was placed in the calibration cover of a gas-sensitive performance electrical tester, and background gas (dry high-purity argon) was introduced for more than half an hour. At the same time, the working current of the device was set to 54 mA (120°C). When the sensor entered the working state and stabilized, the dry target gas was started to be tested, and the total gas flow rate was set to 500 mL / min. 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm of CO gas were introduced through a dynamic gas distribution device or a gas flow control mixing device for sensitivity testing.

[0136] The results are as follows Figure 5 shown.

[0137] According to the attached picture Figure 5It can be seen that in the technical solution of the present invention, the hydrothermal temperature is preferably in the range of 160-200°C, and the gas sensor prepared when the hydrothermal temperature is 180°C has the highest sensitivity to carbon monoxide, which is beneficial to further improve the sensitivity of the gas sensor and reduce the operating temperature of the gas sensor.

[0138] Test Example 6

[0139] The gas sensors prepared in Example 1 and Examples 5-7 were placed in the calibration cover of a gas-sensitive performance electrical tester, and background gas (dry high-purity argon) was introduced for more than half an hour. At the same time, the working current of the device was set to 54 mA (120°C). When the sensor entered the working state and stabilized, the dry target gas was started to be tested, and the total gas flow rate was set to 500 mL / min. 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm of CO gas were introduced through a dynamic gas distribution device or a gas flow control mixing device for sensitivity testing.

[0140] The results are as follows Figure 6 shown.

[0141] According to the attached picture Figure 6 It can be seen that in the technical solution of the present invention, the hydrothermal time is preferably in the range of 8-16 hours, and the gas sensor prepared when the hydrothermal time is 12 hours has the highest sensitivity to carbon monoxide, which is beneficial to further improve the sensitivity of the gas sensor and reduce the operating temperature of the gas sensor.

[0142] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A gas sensor, characterized in that: The gas sensor comprises an electrode substrate and cobalt vanadate coated on the surface of the electrode substrate.

2. The gas sensor according to claim 1, characterized in that The electrode substrate is selected from one of a gold electrode, a gold-titanium alloy electrode and an interdigital electrode.

3. The gas sensor according to claim 1 or 2, characterized in that: The particle size of the cobalt vanadate is 100-300 nm; Preferably, the specific surface area of ​​the cobalt vanadate is 29-38m 2 / g.

4. A method for preparing a gas sensor, characterized in that: The method comprises the following steps: (1) mixing ammonium metavanadate, a cobalt salt, an alkali source and water and reacting them; (2) separating the product obtained in step (1) into solid and liquid, and calcining the solid product; (3) coating the product obtained in step (2) on the surface of the electrode substrate and then aging the electrode substrate.

5. The method according to claim 4, characterized in that The cobalt salt is selected from one or more of cobalt nitrate, cobalt sulfate, cobalt acetate and cobalt chloride; Preferably, the alkali source is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water; Preferably, the molar ratio of the ammonium metavanadate to the cobalt salt is 1-4:

1.

6. The method according to claim 4 or 5, characterized in that: In step (1), the reaction conditions include: temperature of 120-220°C, preferably 160-200°C; time of 2-18h, preferably 4-16h.

7. The method according to any one of claims 4 to 6, characterized in that: In step (2), the calcination conditions include: temperature of 400-600°C, heating rate of 2-4°C / min, and time of 2-5h.

8. The method according to any one of claims 4 to 7, characterized in that: In step (1), the specific steps of mixing include: dissolving ammonium metavanadate and cobalt salt in water respectively, then dropping an alkali source into the obtained ammonium metavanadate solution, and then dropping a cobalt salt solution into the obtained mixed solution.

9. The method according to claim 8, characterized in that The concentration of the ammonium metavanadate is 0.1-0.8 mol / L; Preferably, the concentration of the cobalt salt solution is 0.1-0.5 mol / L; Preferably, the concentration of the alkali source solution is 0.2-2 mol / L.

10. The method according to claim 8 or 9, characterized in that: The pH value of the mixed solution obtained after adding the alkali source is 8-10; Preferably, the speed of adding the cobalt salt solution dropwise is 1-3 drops / s.

11. The method according to any one of claims 4 to 10, characterized in that: In step (3), the aging conditions include: temperature of 40-60° C., current of 20-40 mA, and time of 20-72 h.

12. A gas sensor prepared by the method according to any one of claims 4 to 11.

13. Use of the gas sensor according to any one of claims 1 to 3 or the gas sensor according to claim 12 in detecting carbon monoxide.

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