Pd-WO3 gas-sensitive sensing material as well as preparation method and application thereof

Abstract

The invention provides a Pd-WO3 gas-sensitive sensing material as well as a preparation method and application thereof, WO3 in the gas-sensitive sensing material is a two-dimensional ultrathin nanosheet, the crystal structure is a monoclinic phase crystal structure, and Pd nanoparticles are uniformly dispersed on the surface of the WO3 material. The Pd-WO3 gas-sensitive sensing material prepared by the method can be used for preparing a gas sensor of mustard gas and a simulating agent thereof, and can realize rapid and high-performance detection of the mustard gas and the simulating agent gas thereof; the gas sensor has good response / recovery, stability, high response, selectivity and the like to mustard gas and simulation agent gas thereof under the condition of lower than 300 DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of semiconductor metal oxide nanomaterials, and specifically relates to a Pd-WO 3 Gas sensitive sensing materials and their preparation methods and applications. Background Art

[0002] Mustard gas (HD, bis(2-chloroethyl) sulfide) is a blistering agent that can cause severe blistering of the skin, damage to the eyes and respiratory tract, and even cause death. Therefore, real-time detection of mustard gas is of great significance for protecting human health and environmental safety.

[0003] Traditional detection technologies include ion mobility spectrometry (IMS), gas chromatography-mass spectrometry (GC-MS), proton transfer-reaction mass spectrometry (PTR-MS) and Raman spectroscopy, but these technologies are complex, expensive, time-consuming and not portable. In contrast, gas sensors based on semiconductor metal oxides have the advantages of small size, high stability, easy operation and low manufacturing cost, and have been widely studied around the world.

[0004] Among the numerous semiconductor metal oxides, two-dimensional nanometal oxides have unique properties due to their unique two-dimensional structure, nanometer-scale thickness and high specific surface area, and thus have been widely studied in the gas sensing detection of mustard gas and its simulants. 3 Nanomaterials are considered to be one of the main sensing materials for detecting mustard gas and its simulants due to their significant sensing response. 3 It is an n-type semiconductor with a bandgap of 2.7 eV. However, in practical applications, pure WO with different structures 3 As a gas-sensitive material, there are still some defects, such as the optimal working temperature exceeds 300°C, the response and recovery time are slow, etc. Precious metal loading is considered to be one of the effective means to solve this problem. By adjusting the amount of precious metal loading, WO can be optimized. 3 Gas-sensitive properties of materials to mustard gas and its simulants. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention proposes a Pd-WO 3 Gas-sensitive sensing materials, preparation methods and applications thereof, to solve the problem of how to manufacture Pd-WO with convenient operation and low cost 3 Technical issues of gas sensing materials.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention proposes a Pd-WO 3A method for preparing a gas sensitive sensor material, the method comprising the following steps:

[0009] S1. Preparation of WO 3 Nanosheets

[0010] Dissolve dihydrate, sodium tungstate and citric acid in distilled water, add concentrated hydrochloric acid, and after further stirring, transfer the mixed solution to a high-pressure reactor and keep it at 120-150°C for 12-14 hours. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water, dried at 80°C, and then calcined at 350-450°C for 2 hours in an air atmosphere to obtain a two-dimensional tungsten oxide nanosheet;

[0011] S2. Preparation of Pd-WO 3 Gas Sensing Materials

[0012] The tungsten oxide nanosheets obtained in step S1 were dispersed in distilled water, and the tungsten oxide nanosheets were dispersed by ultrasound. Sodium chloropalladate solution was added dropwise, and heated to 80-100°C in a sealed oil bath under magnetic stirring for 12 hours. The mixture was naturally cooled to room temperature, and the supernatant was removed by centrifugation. The mixture was washed with distilled water, and vacuum dried at 60°C for 10-12 hours. The mixture was then calcined at 250-300°C in an air atmosphere for 2 hours, and then heated to 5% H 2 Calcination under atmosphere for 1 h to obtain Pd-WO 3 Gas sensing materials.

[0013] Further, in step S1, 0.5-0.7g of dihydrate and sodium tungstate and 0.4-0.6g of citric acid are dissolved in 33ml of distilled water, and then 2-4ml of 37% concentrated hydrochloric acid is added. After further stirring for 30min, the mixed solution is transferred to a 45ml high-pressure reactor and kept at 120-150°C for 12-14h. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water for 3 times, dried at 80°C, and then calcined at 350-450°C for 2h in an air atmosphere to finally obtain a two-dimensional tungsten oxide nanosheet;

[0014] Further, in step S2, the tungsten oxide nanosheets obtained in step S1 are dispersed in 20 ml of distilled water, ultrasonicated for 15 min to fully disperse the tungsten oxide nanosheets, 0.1 to 8 ml of 1.2 to 1.4 mg / ml sodium chloropalladate solution is added dropwise, heated to 80 to 100 ° C in a closed oil bath under magnetic stirring conditions for 12 h, cooled naturally to room temperature, centrifuged to remove the supernatant, washed with distilled water 3 times, vacuum dried at 60 ° C for 10 to 12 h, and then calcined at 250 to 300 ° C in an air atmosphere for 2 h, and then heated to 5% H 2 Calcination under atmosphere for 1 h to obtain Pd-WO 3 Gas sensing materials.

[0015] In addition, the present invention also proposes a Pd-WO 3 A gas-sensitive sensing material is prepared by the method.

[0016] Furthermore, WO in gas sensing materials 3 It is a two-dimensional ultra-thin nanosheet with a monoclinic crystal structure. Pd nanoparticles are evenly dispersed in WO 3 Material surface.

[0017] In addition, the present invention also proposes a Pd-WO 3 The application of gas-sensitive sensing materials in mustard gas and its simulant gas sensors is to convert the above-mentioned Pd-WO 3 The gas sensitive sensing material is applied to an alumina ceramic tube or interdigital electrode containing a gold electrode to obtain a Pd-WO 3 Gas sensor with gas sensitive sensing material as the sensing layer.

[0018] In addition, the present invention also proposes a Pd-WO 3 The gas sensor with the gas-sensitive sensing material as the sensing layer is coated with the above-mentioned Pd-WO 3 Gas sensitive sensing materials are alumina ceramic tubes or interdigital electrodes containing gold electrodes.

[0019] (III) Beneficial effects

[0020] The present invention provides a Pd-WO3 gas-sensitive sensing material and a preparation method and application thereof. 3 It is a two-dimensional ultra-thin nanosheet with a monoclinic crystal structure. Pd nanoparticles are evenly dispersed in WO 3 Material surface. Pd-WO prepared by this method 3 The gas-sensitive sensing material can be used to prepare gas sensors for mustard gas and its simulants, and can achieve rapid and high-performance detection of mustard gas and its simulant gases. The gas sensor has good response / recovery, stability, high response and selectivity to mustard gas and its simulant gases under conditions below 300°C.

[0021] The beneficial effects of the present invention specifically include:

[0022] 1. This method prepares a tungsten oxide sensing material modified with precious metal palladium nanoparticles. Tungsten oxide nanosheets are prepared under organic solvent-free conditions, and then the obtained tungsten oxide nanosheets are reacted with sodium chloropalladate under hydrothermal conditions, and finally calcined to obtain Pd-WO 3 The gas-sensitive sensing material has a preparation method with few steps, simple operation, and is green and pollution-free.

[0023] 2. Pd-WO prepared by the present invention 3The gas sensing material has the following structural characteristics: the synthesized tungsten oxide is a two-dimensional ultra-thin nanosheet structure, and the Pd nanoparticles are evenly dispersed on the surface of the tungsten oxide nanosheets and are not easy to agglomerate. When the Pd nanoparticles are evenly dispersed on the surface of the tungsten oxide nanosheets, the synergistic effect of the Pd nanoparticles and the tungsten oxide nanosheets can significantly improve the gas sensing performance of tungsten oxide to mustard gas and its simulant gas.

[0024] 3. Pd-WO prepared by the present invention 3 The gas-sensitive sensing material has good response / recovery, stability, high response and selectivity to mustard gas and its simulants. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 For WO 3 and Pd-WO 3 XRD pattern of gas-sensitive materials;

[0026] Figure 2 2wt% Pd-WO of Example 1 3 TEM images of gas-sensitive materials;

[0027] Figure 3 2wt% Pd-WO of Example 1 3 Dynamic response recovery curve of the gas sensor to 0.015-7ppm mustard gas at 260℃;

[0028] Figure 4 2wt% Pd-WO of Example 1 3 Dynamic response recovery curve of the base gas sensor to 700ppb mustard gas at 260℃;

[0029] Figure 5 2wt% Pd-WO of Example 1 3 Long-term stability study of the base gas sensor for 2ppm mustard gas at 260℃ working temperature within 30 days;

[0030] Figure 6 10.5wt% Pd-WO of Example 2 3 TEM images of gas-sensitive materials;

[0031] Figure 7 0.5wt% Pd-WO of Example 2 3 Dynamic response recovery curve of the base gas sensor to 700ppb concentration of 2-CEES at 260℃;

[0032] Figure 8 0.5wt% Pd-WO of Example 2 3The sensitivity of the gas sensor to different target gases (ammonia, acetone, ethanol, DMMP, hydrogen sulfide, nitrogen dioxide, ethane and ethylene) at 2ppm at an operating temperature of 260℃;

[0033] Fig. 9 WO for comparative example 3 TEM images of

[0034] Fig.10 WO for comparative example 3 Dynamic response recovery curve of the base gas sensor to 700 ppb concentration of 2-CEES at 260°C. DETAILED DESCRIPTION

[0035] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0036] Example 1

[0037] Preparation of 2wt% Pd-WO 3 Gas-sensitive sensing materials and the production of mustard gas sensors, the specific process is as follows:

[0038] Take 0.61g of dihydrate, sodium tungstate and 0.49g of citric acid and dissolve them in 33ml of distilled water, then add 3ml of 37% concentrated hydrochloric acid, and stir for 30min. Then transfer the mixed solution to a 45ml high-pressure reactor and keep it at 140℃ for 12h. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water for 3 times, dried at 80℃, and then calcined at 400℃ for 2h in air atmosphere to finally obtain two-dimensional tungsten oxide nanosheets.

[0039] 80 mg of tungsten oxide nanosheets were dispersed in 20 ml of distilled water, and ultrasonicated for 15 min to fully disperse the tungsten oxide nanosheets. 4 ml of 1.38 mg / ml sodium chloropalladate solution was added dropwise, and heated to 90 ° C in a sealed oil bath under magnetic stirring for 12 h. After cooling to room temperature naturally, the supernatant was removed by centrifugation, washed with distilled water for 3 times, vacuum dried at 60 ° C for 12 h, and then calcined at 300 ° C for 2 h in an air atmosphere, and then heated to 5% H 2 Calcination was carried out for 1 hour at a heating rate of 3 °C / min to obtain Pd-WO 3 Gas sensing materials.

[0040] Take a small amount of the prepared 2wt% Pd-WO 3 The gas-sensitive material was placed in a mortar, ground with ethanol, and evenly applied on an alumina ceramic tube or interdigital electrode with gold electrodes at both ends to obtain a 2wt% Pd-WO 3 Gas sensor with gas sensitive sensing material as the sensing layer.

[0041] 2wt%Pd-WO 3 The X-ray diffraction pattern of gas-sensitive materials is as follows: Figure 1 As shown, the sample is monoclinic, and after loading Pd, WO 3 The nanosheet structure has not changed, and there is no diffraction peak of other impurities. 2wt% Pd-WO 3 TEM spectra of gas-sensitive materials such as Figure 2 As shown, a large-scale, uniform-sized, and regularly structured Pd-WO was successfully synthesized. 3 Nanosheets, with a size between 180 and 240 nm, Pd nanoparticles are uniformly loaded on WO 3 Material surface. 2wt% Pd-WO 3 The gas sensitivity test of the base gas sensor to mustard gas is as follows Figure 3 As shown, 2wt% Pd-WO 3 The base gas sensor has a good linear relationship with 0.015-7ppm mustard gas. The response value to 7ppm at 260℃ reaches 1700, the lowest practical detection limit is 15ppb, and the response value is 1.42. 2wt% Pd-WO 3 The gas sensitivity test of the base gas sensor to mustard gas is as follows Figure 4 As shown, below 300℃, 2wt% Pd-WO 3 The base gas sensor has a faster response recovery time to 0.7ppm mustard gas, which is 9S / 98S respectively, and the response value is 6.8. Figure 5 It can be seen that 2wt% Pd-WO 3 The gas sensor has long-term stability.

[0042] Example 2

[0043] Preparation of 0.5wt% Pd-WO 3 Gas sensitive sensing materials and making 2-CEES gas sensors, the specific process is as follows:

[0044] Take 0.58g of dihydrate, sodium tungstate and 0.45g of citric acid and dissolve them in 33ml of distilled water, then add 4ml of 37% concentrated hydrochloric acid, and stir for 30min. Then transfer the mixed solution to a 45ml high-pressure reactor and keep it at 150℃ for 12h. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water for 3 times, dried at 80℃, and then calcined at 380℃ for 2h in air atmosphere to finally obtain two-dimensional tungsten oxide nanosheets.

[0045] Take 80 mg of tungsten oxide nanosheets and disperse them in 20 ml of distilled water. Ultrasonicate for 15 min to fully disperse the tungsten oxide nanosheets. Add 1 ml of 1.35 mg / ml sodium chloropalladate solution dropwise. Heat to 90 ° C in a sealed oil bath under magnetic stirring for 12 h. Cool to room temperature naturally. Centrifuge to remove the supernatant. Wash with distilled water 3 times. Vacuum dry at 60 ° C for 12 h. Then calcine at 260 ° C for 2 h in air atmosphere. Then, heat at 120 ° C with 5% H 2 Calcination was carried out for 1 hour at a heating rate of 3 °C / min to obtain 0.5 wt% Pd-WO 3 Gas sensing materials.

[0046] Take a small amount of the prepared 0.5wt% Pd-WO 3 The gas-sensitive material was placed in a mortar, ground with ethanol, and evenly applied on an alumina ceramic tube or interdigital electrode with gold electrodes at both ends to obtain a 0.5wt% Pd-WO 3 Gas sensor with gas sensitive sensing material as the sensing layer.

[0047] 0.5wt%Pd-WO 3 The X-ray diffraction pattern of gas-sensitive materials is as follows: Figure 1 As shown, the sample is monoclinic, and after loading Pd, WO 3 The nanosheet structure has not changed, and there is no diffraction peak of other impurities. 0.5wt% Pd-WO 3 TEM spectra of gas-sensitive materials such as Figure 6 As shown, a large-scale, uniform-sized, and regularly structured Pd-WO was successfully synthesized. 3 Nanosheets, with a size between 180 and 240 nm, Pd nanoparticles are uniformly loaded on WO 3 Material surface. 0.5wt% Pd-WO 3 The gas-sensing test of the base gas sensor on 2-CEES is as follows Figure 7 As shown, at a temperature below 300 °C, 0.5 wt% Pd-WO 3 The base gas sensor has a faster response recovery time to 0.7ppm concentration of 2-CEES, which is 13S / 101S respectively. Figure 8 It can be seen that 0.5wt% Pd-WO 3 The based gas sensor has good selectivity for 2-CEES.

[0048] Comparative Example 1

[0049] Preparation of WO 3 Gas sensitive sensing materials and making 2-CEES gas sensors, the specific process is as follows:

[0050] Take 0.62g of dihydrate, sodium tungstate and 0.50g of citric acid and dissolve them in 33ml of distilled water, then add 2ml of 37% concentrated hydrochloric acid, and stir for 30min. Then transfer the mixed solution to a 45ml high-pressure reactor and keep it at 140℃ for 12h. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water for 3 times, dried at 80℃, and then calcined at 400℃ for 2h in air atmosphere to finally obtain two-dimensional tungsten oxide nanosheets.

[0051] Take a small amount of the prepared WO 3 The gas-sensitive material was placed in a mortar, ground with ethanol, and evenly applied on an alumina ceramic tube or interdigital electrode with gold electrodes at both ends to obtain a WO 3 Gas sensor with gas sensitive sensing material as the sensing layer.

[0052] WO 3 The X-ray diffraction pattern of gas-sensitive materials is as follows: Figure 1 As shown, the sample is monoclinic and has no diffraction peaks of other impurities. 3 TEM spectra of gas-sensitive materials such as Fig. 9 As shown, a large range of WO with uniform size and regular structure was successfully synthesized. 3 Nanosheets, with a size between 180 and 240 nm, and the main exposed crystal plane is the (020) crystal plane. 3 The gas-sensing test of the base gas sensor on 2-CEES is as follows Fig.10 As shown, under the condition of less than 300℃, WO 3 The response recovery times of the base gas sensor to 0.7 ppm concentration of 2-CEES are 42S and 25min respectively.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a Pd-WO3 gas sensitive sensor material, characterized in that: The preparation method comprises the following steps: S1. Preparation of WO3 nanosheets Dissolve dihydrate, sodium tungstate and citric acid in distilled water, add concentrated hydrochloric acid, and after further stirring, transfer the mixed solution to a high-pressure reactor and keep it at 120-150°C for 12-14 hours. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water, dried at 80°C, and then calcined at 350-450°C for 2 hours in an air atmosphere to obtain a two-dimensional tungsten oxide nanosheet; S2. Preparation of Pd-WO3 gas sensitive sensing material The tungsten oxide nanosheets obtained in step S1 are dispersed in distilled water, and the tungsten oxide nanosheets are dispersed by ultrasound. Sodium chloropalladate solution is added dropwise, and heated to 80-100° C. in a closed oil bath under magnetic stirring and maintained for 12 hours. The mixture is naturally cooled to room temperature, and the supernatant is removed by centrifugation. The mixture is washed with distilled water, and vacuum dried at 60° C. for 10-12 hours, and then calcined at 250-300° C. in an air atmosphere for 2 hours, and then calcined in a 5% H2 atmosphere for 1 hour to obtain a Pd-WO3 gas sensitive sensing material.

2. The preparation method according to claim 1, characterized in that In step S1, 0.5-0.7 g of dihydrate and sodium tungstate and 0.4-0.6 g of citric acid are dissolved in 33 ml of distilled water, and then 2-4 ml of 37% concentrated hydrochloric acid is added. After further stirring for 30 minutes, the mixed solution is transferred to a 45 ml high-pressure reactor and kept at 120-150° C. for 12-14 hours. After the high-pressure reactor is naturally cooled to room temperature, the obtained solution is centrifuged, washed with distilled water for 3 times, dried at 80° C., and then calcined at 350-450° C. for 2 hours in an air atmosphere to finally obtain a two-dimensional tungsten oxide nanosheet.

3. The preparation method according to claim 2, characterized in that: In step S2, the tungsten oxide nanosheets obtained in step S1 are dispersed in 20 ml of distilled water, ultrasonicated for 15 min to fully disperse the tungsten oxide nanosheets, 0.1 to 8 ml of 1.2 to 1.4 mg / ml sodium chloropalladate solution is added dropwise, heated to 80 to 100° C. in a closed oil bath under magnetic stirring and maintained for 12 h, cooled naturally to room temperature, centrifuged to remove the supernatant, washed with distilled water for 3 times, vacuum dried at 60° C. for 10 to 12 h, and then calcined at 250 to 300° C. in an air atmosphere for 2 h, and then calcined in a 5% H2 atmosphere for 1 h to obtain a Pd-WO3 gas sensitive sensing material.

4. A Pd-WO3 gas sensitive sensing material, characterized in that: The gas sensitive sensing material is prepared by the method according to any one of claims 1 to 3.

5. The Pd-WO3 gas sensitive sensing material according to claim 4, characterized in that: The WO3 in the gas-sensitive sensor material is a two-dimensional ultra-thin nanosheet, the crystal structure is a monoclinic crystal structure, and the Pd nanoparticles are uniformly dispersed on the surface of the WO3 material.

6. Application of Pd-WO3 gas sensitive sensing material in mustard gas and its simulant gas sensor, characterized in that: The application is to apply the Pd-WO3 gas sensitive sensing material described in claim 4 or 5 onto an alumina ceramic tube or an interdigital electrode containing a gold electrode to obtain a gas sensor with the Pd-WO3 gas sensitive sensing material as a sensing layer.

7. A gas sensor using Pd-WO3 gas sensitive sensing material as a sensing layer, characterized in that: The gas sensor is an alumina ceramic tube or interdigital electrode containing a gold electrode and coated with the Pd-WO3 gas sensitive sensing material according to claim 4 or 5.

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