CN115849450B - Preparation method of tungsten oxide homojunction gas-sensitive material, gas-sensitive sensor and application - Google Patents
Preparation method of tungsten oxide homojunction gas-sensitive material, gas-sensitive sensor and application Download PDFInfo
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Abstract
The invention provides a preparation method of a tungsten oxide homojunction gas-sensitive material, a gas-sensitive sensor and application. According to the preparation method, the tungsten oxide composite material with a homojunction is prepared by utilizing a hydrothermal reaction and subsequent annealing; the homojunction gas-sensitive material formed by orthorhombic phase WO 3·0.33H2 O and hexagonal phase tungsten trioxide is characterized in that free electrons are transferred from hexagonal phase to orthorhombic phase at a phase interface until the Fermi energy levels of the free electrons reach balance, an electron accumulation layer is formed at one side of the orthorhombic phase, an electron depletion layer is formed at one side of the hexagonal phase, and an n-n homojunction is formed at the interface. The electron accumulation layer at one side of the orthogonal phase is favorable for adsorbing more oxygen to form oxygen anions to react with the gas, thereby being beneficial to improving the sensitivity of the gas to the gas and integrally improving the performance of the gas sensor; moreover, such in-plane homojunction helps to increase the carrier transport rate, thereby increasing the rate of reaction with the gas, and thus improving its detection performance of the gas as a whole.
Description
Technical Field
The invention relates to the technical field of gas-sensitive materials, in particular to a preparation method of a tungsten oxide homojunction gas-sensitive material, a gas-sensitive sensor and application.
Background
In the context of rapid social development, people are increasingly concerned about physical health and environmental protection, and effective monitoring of pollutant gases harmful to people in the atmospheric environment and indoor areas is particularly important. Ozone is a typical pollutant gas and is mainly produced by photochemical reactions of artificially discharged pollutants such as NO x, VOCs and the like. Ozone is used as a strong oxidant, and can cause yellowing and even wilting of plant leaves, damage to plants, yield reduction of agriculture and forestry plants, economic benefit reduction and the like. International ambient air quality standards (National Ambient Air Quality Standards, NAAQS) suggest that the limiting concentration of acceptable ozone in one hour is 130ppb. The cough, dyspnea and lung function decline can be caused when the human body moves for 1h in the environment of 160ppb ozone, and the symptoms such as fatigue, cough, chest distress and chest pain, skin wrinkling, nausea and headache, pulse acceleration, memory decline, vision decline and the like can also appear for the human body directly contacted with high-concentration ozone for a long time.
Gas sensitive materials refer to a class of materials that have sensitivity to different gases and that undergo a change in a property, such as a change in electrical resistance. Among the many gas sensitive materials, metal Oxide Semiconductor (MOS) materials are widely used because of their high sensitivity, low cost and easy integration with other devices, while tungsten oxide (WO 3) has been attracting attention in the field of gas sensitive materials because of its stable properties, easy structure control and diversity. The homojunction and heterojunction structure is constructed through regulation and control, so that the electron migration efficiency of the material is improved, and the gas sensitivity performance is improved.
The existing tungsten oxide-based gas-sensitive material has some problems such as higher working temperature, unstable response performance, low sensitivity and incapability of detecting low-concentration gas.
Based on the defects of the current tungsten oxide-based gas-sensitive materials, improvements are needed.
Disclosure of Invention
In view of the above, the invention provides a preparation method of a tungsten oxide homojunction gas-sensitive material, a gas-sensitive sensor and application thereof, so as to solve or partially solve the technical problems existing in the prior art.
In a first aspect, the invention provides a method for preparing a tungsten oxide homojunction gas-sensitive material, which comprises the following steps:
Adding tungsten powder into hydrogen peroxide solution for reaction, and mixing the supernatant after the reaction with water to obtain precursor solution;
Carrying out hydrothermal reaction on the precursor solution at 180-220 ℃, separating the product after the reaction is finished, and drying to obtain precursor powder;
And (3) annealing the precursor powder to obtain the tungsten oxide homojunction gas-sensitive material.
Preferably, the preparation method of the tungsten oxide homojunction gas-sensitive material comprises the step of annealing precursor powder at 200-450 ℃ to obtain the tungsten oxide homojunction gas-sensitive material.
Preferably, in the preparation method of the tungsten oxide homojunction gas-sensitive material, the mass concentration of the hydrogen peroxide solution is 28-30%.
Preferably, the preparation method of the tungsten oxide homojunction gas-sensitive material has the hydrothermal reaction time of 8-12 h.
Preferably, the preparation method of the tungsten oxide homojunction gas-sensitive material comprises the steps of heating precursor powder to 200-450 ℃ at a speed of 3-5 ℃/min, and annealing for 1-3h to obtain the tungsten oxide homojunction gas-sensitive nano material.
Preferably, in the preparation method of the tungsten oxide homojunction gas-sensitive material, tungsten powder is added into hydrogen peroxide solution for reaction, wherein the mass volume ratio of the tungsten powder to the hydrogen peroxide solution is (1.35-2.7) g (10-20) mL;
in the step of mixing the reacted supernatant with water, the volume ratio of the supernatant to the water is (3-6) (12-24).
Preferably, the preparation method of the tungsten oxide homojunction gas-sensitive material comprises the steps of adding tungsten powder into hydrogen peroxide solution, stirring and reacting for 5-30 min, mixing and stirring the reacted supernatant with water for 5-30 min, and obtaining precursor solution.
In a second aspect, the invention also provides a gas sensor, which comprises a matrix and a gas-sensitive material coated on the matrix, wherein the gas-sensitive material is the tungsten oxide homojunction gas-sensitive material prepared by the preparation method.
In a third aspect, the invention also provides a tungsten oxide homojunction gas-sensitive material prepared by the preparation method or application of the gas-sensitive sensor in detecting ozone gas concentration.
Preferably, the temperature at the time of detection is 90-140 ℃ in the application.
The preparation method of the tungsten oxide homojunction gas-sensitive material has the following beneficial effects compared with the prior art:
1. According to the preparation method of the tungsten oxide homojunction gas-sensitive material, the prepared tungsten oxide homojunction gas-sensitive material has the advantages that the n-n homojunction structure of the tungsten oxide provides abundant free electrons for the surface of the material, the separation of electron hole pairs is promoted, the electron migration efficiency is improved, and the method has important significance in improving the gas-sensitive performance of the tungsten oxide-based material at low temperature;
2. the tungsten oxide homojunction gas-sensitive material effectively solves a series of problems of low sensitivity, poor stability, high working temperature and the like existing in the existing pure tungsten oxide semiconductor gas-sensitive material, and expands the application range of the tungsten oxide homojunction gas-sensitive material. The tungsten oxide homojunction gas-sensitive material has high sensitivity and stability for low-concentration ozone gas response, can work at a lower temperature of 90-140 ℃ and has good performance;
3. The preparation method of the tungsten oxide homojunction gas-sensitive material has the advantages of simple operation, easily obtained raw materials and low equipment use cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 is a schematic flow chart of a preparation method of a tungsten oxide homojunction gas-sensitive material;
FIGS. 2 to 3 are SEM images of the tungsten oxide homojunction gas-sensitive material prepared in example 1 of the present invention at different magnifications;
FIG. 4 is an XRD pattern of a homogeneous junction gas sensitive material of tungsten oxide prepared in example 1 of the present invention;
FIG. 5 is a graph showing the response speed and recovery speed of the gas sensor prepared in example 1 of the present invention to 3ppm ozone gas at 120 ℃;
FIG. 6 shows the response values of the tungsten oxide homojunction gas-sensitive materials prepared in example 1 and examples 3 to 4;
FIG. 7 is a graph showing the response repeatability of a gas sensor using the tungsten oxide homojunction gas sensitive material prepared in example 1 of the present application;
FIG. 8 is a graph showing the response stability of a gas sensor using the tungsten oxide homojunction gas sensitive material prepared in example 1 of the present application;
FIG. 9 is a graph showing the response of the gas sensor prepared in inventive example 1 to ozone gas of different concentrations at 120 ℃.
Detailed Description
The following description of the embodiments of the present invention will be made in detail and with reference to the embodiments of the present invention, but it should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
The embodiment of the application provides a preparation method of a tungsten oxide homojunction gas-sensitive material, which is shown in figure 1 and comprises the following steps:
S1, adding tungsten powder into hydrogen peroxide solution for reaction, and mixing the supernatant after the reaction with water to obtain a precursor solution;
s2, carrying out hydrothermal reaction on the precursor solution at 180-220 ℃, separating a product after the reaction is finished, and drying to obtain precursor powder;
and S3, annealing the precursor powder to obtain the tungsten oxide homojunction gas-sensitive material.
The preparation method of the tungsten oxide homojunction gas-sensitive material comprises the steps of adding tungsten powder into hydrogen peroxide solution, uniformly reacting and mixing, taking supernatant fluid, adding water and uniformly mixing to obtain precursor solution; carrying out hydrothermal reaction on the precursor solution, carrying out solid-liquid separation, washing and drying on the product after the reaction is finished to obtain precursor powder, and calcining the precursor powder to obtain the tungsten oxide homojunction gas-sensitive nanomaterial; according to the preparation method, the tungsten oxide composite material with a homojunction is prepared by utilizing a hydrothermal reaction and subsequent annealing; the homojunction gas-sensitive material formed by orthorhombic phase WO 3·0.33H2 O and hexagonal phase tungsten trioxide is characterized in that free electrons are transferred from hexagonal phase to orthorhombic phase at a phase interface until the Fermi energy levels of the free electrons reach balance, an electron accumulation layer is formed at one side of the orthorhombic phase, an electron depletion layer is formed at one side of the hexagonal phase, and an n-n homojunction is formed at the interface. The electron accumulation layer at one side of the orthogonal phase is favorable for adsorbing more oxygen to form oxygen anions to react with the gas, thereby being beneficial to improving the sensitivity of the gas to the gas and integrally improving the performance of the gas sensor; moreover, such in-plane homojunction helps to increase the carrier transport rate, thereby increasing the rate of reaction with the gas, and thus improving its detection performance of the gas as a whole.
In some embodiments, the precursor powder is annealed at 200-450 ℃ to obtain the tungsten oxide homojunction gas-sensitive material.
In some embodiments, the hydrogen peroxide solution has a mass concentration of 28 to 30%.
In some embodiments, the hydrothermal reaction time is 8 to 12 hours.
In some embodiments, the precursor powder is heated to 200-450 ℃ at 3-5 ℃/min and annealed for 1-3 hours to obtain the tungsten oxide homojunction gas-sensitive nanomaterial. Specifically, annealing is performed under an air atmosphere.
In some embodiments, in the step of adding tungsten powder to hydrogen peroxide solution for reaction, the mass to volume ratio of tungsten powder to hydrogen peroxide solution is (1.35-2.7) g (10-20) mL.
In some embodiments, the step of mixing the reacted supernatant with water has a supernatant to water volume ratio of (3-6): 12-24.
In some embodiments, tungsten powder is added into hydrogen peroxide solution to be stirred and reacted for 5 to 30 minutes, and the reacted supernatant is mixed and stirred in water for 5 to 30 minutes to obtain precursor solution.
In some embodiments, the precursor solution is subjected to hydrothermal reaction at 180-220 ℃, after the reaction is completed, the solid and the liquid of the product are separated, and the product is washed for a plurality of times by deionized water and absolute ethyl alcohol and then dried at 50-70 ℃ for 10-15 hours, so that the precursor powder is obtained.
Based on the same inventive concept, the embodiment of the application also provides a gas sensor, which comprises a matrix and a gas-sensitive material coated on the matrix, wherein the gas-sensitive material is the tungsten oxide homojunction gas-sensitive material prepared by the preparation method.
Specifically, uniformly mixing the tungsten oxide homojunction gas-sensitive material prepared by the method and water according to the mass ratio of (3-5): 1, and then performing ultrasonic treatment for 60 seconds to obtain a mixture; coating the mixture on the surface of a substrate, and drying for 1-3 min at 50-80 ℃ to obtain the gas sensor; specifically, the substrate may be a ceramic tube.
Based on the same inventive concept, the embodiment of the application also provides an application of the tungsten oxide homojunction gas-sensitive material prepared by the preparation method or the gas-sensitive sensor in detecting the concentration of ozone gas.
In some embodiments, the tungsten oxide homojunction gas-sensitive material and the gas-sensitive sensor can detect low-concentration ozone gas at low temperature, specifically, the low-temperature is 90-140 ℃, and the concentration of the low-concentration ozone gas is less than or equal to 0.08ppm.
The method for preparing the tungsten oxide homojunction gas-sensitive material of the present application is further described in the following specific examples. This section further illustrates the summary of the application in connection with specific embodiments, but should not be construed as limiting the application. The technical means employed in the examples are conventional means well known to those skilled in the art, unless specifically stated. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present application are those conventional in the art.
Example 1
The embodiment of the application provides a preparation method of a tungsten oxide homojunction gas-sensitive material, which comprises the following steps:
s1, adding 1.35g of tungsten powder into 10mL of hydrogen peroxide solution with the mass concentration of 30% for mixing reaction, taking 3mL of supernatant and 12mL of water after the reaction, stirring for 15min, and uniformly mixing to obtain precursor liquid;
s2, carrying out hydrothermal reaction on the precursor solution at 200 ℃ for 12 hours, carrying out solid-liquid separation on the reacted product, washing four times by using water and absolute ethyl alcohol, and then drying at 60 ℃ for 12 hours to obtain precursor powder;
And S3, placing the precursor powder in a muffle furnace, heating to 330 ℃ from room temperature at 5 ℃/min, and annealing for 2 hours to obtain the tungsten oxide homojunction gas-sensitive material.
The embodiment of the application also provides a preparation method of the gas sensor, which comprises the following steps:
the tungsten oxide homojunction gas-sensitive material prepared in the example 1 and water are mixed according to the mass ratio of 4:1, after uniformly mixing, carrying out ultrasonic treatment for 60s to obtain a mixture;
And (3) coating the mixture on the surface of a ceramic tube, then placing the ceramic tube in an oven for drying at 60 ℃ for 1min, and welding the dried ceramic tube on a base to obtain the gas sensor.
Example 2
The embodiment of the application provides a preparation method of a tungsten oxide homojunction gas-sensitive material, which is similar to embodiment 1, and is different in that the hydrothermal reaction time in step S2 is 10h, and the rest of the process parameters are the same as those in embodiment 1.
The gas sensor provided by the embodiment of the application is the same as that of the embodiment 1.
Example 3
The embodiment of the application provides a preparation method of a tungsten oxide homojunction gas-sensitive material, which is similar to embodiment 1, and is different in that the annealing temperature in step S3 is 300 ℃, and the rest of process parameters are the same as those in embodiment 1.
The gas sensor provided by the embodiment of the application is the same as that of the embodiment 1.
Example 4
The embodiment of the application provides a preparation method of a tungsten oxide homojunction gas-sensitive material, which is similar to embodiment 1, and is different in that the annealing temperature in step S3 is 360 ℃, and the rest of process parameters are the same as those in embodiment 1.
The gas sensor provided by the embodiment of the application is the same as that of the embodiment 1.
Performance testing
Fig. 2 to 3 are SEM images of the tungsten oxide homojunction gas-sensitive material prepared in example 1 of the present application at different magnifications.
As can be seen from fig. 2 to 3, the powder particles of the tungsten oxide homojunction gas-sensitive material annealed at 330 ℃ are uniformly distributed, the surface is smooth, the nano-sheets are relatively dispersed, no obvious agglomeration phenomenon exists, no impurity residue exists, and the 330 ℃ is the optimal annealing temperature.
Fig. 4 is an XRD pattern of the tungsten oxide homojunction gas sensitive material prepared in example 1 of the present application.
As can be seen from fig. 4, the diffraction pattern showed good alignment peaks at 14.0°、22.7°、24.3°、26.9°、28.2°、33.6°、36.6°、37.6°、42.9°、44.4°、46.5°、48.9°、50.0°、52.1°、50.0°、55.3°、57.6°、58.3°、63.5° and the like, corresponding to (100)、(001)、(110)、(101)、(200)、(111)、(201)、(210)、(300)、(211)、(002)、(102)、(220)、(310)、(202)、(311)、(400)、(401) and the like of the hexagonal phase WO 3 structure (JCPDS-33-1387), and good alignment peaks at 14.1 °, 18.1 °, 24.2 ° and the like, corresponding to (020), (111), (002) and the like of the orthogonal phase WO 3·0.33H2 O structure (JCPDS-35-0270), and no characteristic peaks of other impurity phases were detected from the material, indicating that a composite material of hexagonal phase WO 3 and orthogonal phase WO 3·0.33H2 O was formed.
FIG. 5 is a graph showing the response speed and recovery speed of the tungsten oxide homojunction gas-sensitive material prepared in example 1 of the present application when applied at 120 ℃, the gas-sensitive characteristics of the gas-sensitive sensor were tested by using JF02F test system, and when 120 ℃ was detected, the sensitivity of the sensor was the highest, and then 120 ℃ was the optimal working temperature of the gas sensor.
FIG. 6 is a graph comparing the gas-sensitive properties of the tungsten oxide homojunction gas-sensitive material prepared in example 1 (i.e., h/O-WO 3 in FIG. 6) and the pure orthorhombic phase WO 3·0.33H2 O prepared in example 3 (i.e., O-WO 3·0.33H2 O in FIG. 6) with the pure hexagonal phase tungsten oxide prepared in example 4 (i.e., h-WO 3 in FIG. 6), it can be seen that the tungsten oxide homojunction gas-sensitive material prepared in example 1 has higher sensitivity than the two pure phase tungsten oxide materials under the same conditions, wherein the tungsten oxide homojunction material response value is 321, the pure orthorhombic phase WO 3·0.33H2 O material response value is 56, and the pure hexagonal phase tungsten oxide material response value is 79.
FIG. 7 is a graph showing the response repeatability of a gas sensor using the tungsten oxide homojunction gas sensitive material prepared in example 1 of the present application; FIG. 8 is a graph showing the response stability of a gas sensor using the tungsten oxide homojunction gas sensor material prepared in example 1 of the present application.
As can be seen from fig. 5 to 8, the gas sensor applied to the tungsten oxide homojunction gas-sensitive material prepared in example 1 has high response sensitivity, quick response time and quick recovery time, good stability and reliable gas detection performance.
As can be seen from FIG. 9, the tungsten oxide homojunction gas-sensitive material prepared in example 1 can detect ozone gas with low concentration, the low concentration is less than or equal to 0.08ppm, the response value of the material shows an increasing trend along with the increase of the concentration, and has a high response value when the concentration reaches 3ppm, and the calculated response value is 321.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (4)
1. The preparation method of the tungsten oxide homojunction gas-sensitive material is characterized by comprising the following steps of:
S1, adding 1.35g of tungsten powder into 10mL of hydrogen peroxide solution with the mass concentration of 30% for mixing reaction, taking 3mL of supernatant and 12mL of water after the reaction, stirring for 15min, and uniformly mixing to obtain a precursor solution;
s2, carrying out hydrothermal reaction on the precursor solution at 200 ℃ for 12 hours, carrying out solid-liquid separation on the reacted product, washing four times by using water and absolute ethyl alcohol, and then drying at 60 ℃ for 12 hours to obtain precursor powder;
and S3, placing the precursor powder in a muffle furnace, and heating to 330 ℃ from room temperature at 5 ℃/min for annealing for 2 hours to obtain the tungsten oxide homojunction gas-sensitive material.
2. The gas sensor is characterized by comprising a matrix and a gas-sensitive material coated on the matrix, wherein the gas-sensitive material is the tungsten oxide homojunction gas-sensitive material prepared by the preparation method of claim 1.
3. Use of a tungsten oxide homojunction gas-sensitive material prepared by the preparation method according to claim 1 or a gas-sensitive sensor according to claim 2 for detecting ozone gas concentration.
4. The use according to claim 3, wherein the temperature at the time of detection is 90-140 ℃.
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| CN101767826A (en) * | 2009-10-30 | 2010-07-07 | 陕西科技大学 | Preparation method of hexagon snow shaped WO3 nanometer disc |
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| CN105954325A (en) * | 2016-04-28 | 2016-09-21 | 华北水利水电大学 | Preparation method for preparing rod-shaped tungsten trioxide nano gas-sensitive material |
| WO2016153231A1 (en) * | 2015-03-20 | 2016-09-29 | 아주대학교산학협력단 | Hydrogen detection sensor and method for producing same |
| CN110255621A (en) * | 2019-07-18 | 2019-09-20 | 东北大学 | A kind of WO3The preparation and its application in gas sensor of nanometer floral material |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101767826A (en) * | 2009-10-30 | 2010-07-07 | 陕西科技大学 | Preparation method of hexagon snow shaped WO3 nanometer disc |
| CN101805023A (en) * | 2010-04-01 | 2010-08-18 | 中国科学院宁波材料技术与工程研究所 | Method for preparing tungstic oxide nano-sheets |
| WO2016153231A1 (en) * | 2015-03-20 | 2016-09-29 | 아주대학교산학협력단 | Hydrogen detection sensor and method for producing same |
| CN105954325A (en) * | 2016-04-28 | 2016-09-21 | 华北水利水电大学 | Preparation method for preparing rod-shaped tungsten trioxide nano gas-sensitive material |
| CN110255621A (en) * | 2019-07-18 | 2019-09-20 | 东北大学 | A kind of WO3The preparation and its application in gas sensor of nanometer floral material |
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