A pt modified mn3o4 composite material, a preparation method thereof, a gas sensing element and application thereof

Abstract

The application belongs to the technical field of gas sensitive materials, and particularly relates to a Pt modified Mn3O4 composite material, a preparation method thereof, a gas sensitive element and application thereof. The preparation method of the Pt modified Mn3O4 composite material comprises the following steps: step S1, performing a hydrothermal reaction on a first solution containing a manganese source, performing solid-liquid separation after the reaction is completed, drying and calcining the obtained solid to obtain Mn3O4 nanorods; step S2, uniformly mixing a dispersion solution of the Mn3O4 nanorods with a H2PtCl6.6H2O solution to obtain a second solution; step S3, heating the second solution, adding a C6H8O6 solution, and stirring and reacting; performing solid-liquid separation after the reaction is completed, washing and drying to obtain the Pt modified Mn3O4 composite material. The Pt modified Mn3O4 composite material has good ethylene sensing performance, a low optimal working temperature, good selectivity and repeatability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas sensitive materials, and particularly relates to a Pt modified Mn3O4 composite material, a preparation method thereof, a gas sensitive element and application thereof. BACKGROUND

[0002] Ethylene is an important raw material for the production of polyethylene, vinyl alcohol, vinyl chloride and other chemical products. The petrochemical industry needs to monitor ethylene gas to ensure the safety and stability of the production process. As an important industrial raw material and chemical intermediate, although ethylene itself has low toxicity, due to its flammability and high reactivity under certain conditions, it may cause various industrial accidents. Due to the low explosion limit and high explosion intensity of ethylene, there is a great risk of explosion in the production and use process. Ethylene is a flammable gas with a low explosion limit (2.7%-36%), which is easy to form an explosive mixture in the air. Under high temperature or fire conditions, ethylene may cause serious fire or explosion accidents. Therefore, it is necessary to develop a reliable and relatively inexpensive ethylene gas sensor to detect the concentration of ethylene in the air.

[0003] In the research of gas sensitive sensors, one of the main directions is to rely on the change of the resistance of sensitive materials such as SnO2, ZnO, In2O3, WO3, etc. in the gas environment to make gas sensitive sensors, because these metal oxide semiconductors have the advantages of high sensitivity, rapid response, low cost and good stability, so the research on them as gas sensitive materials has always been highly valued.

[0004] However, although the existing sensitive materials show certain responsiveness to ethylene, most of the response temperatures are high, mostly concentrated in the range of 300-500℃, and the response value is low.

[0005] Therefore, it is necessary to provide an improved technical solution to overcome the above-mentioned deficiencies of the prior art. SUMMARY

[0006] The purpose of the present application is to provide a Pt modified Mn3O4 composite material, a preparation method thereof, a gas sensitive element and application thereof, so as to help solve or improve at least one of the problems of poor sensitivity of the existing gas sensitive material to ethylene, high working temperature and difficulty in stable use.

[0007] The application provides a preparation method of a Pt modified Mn3O4 composite material.

[0008] Preferably, in step S1, the temperature of the hydrothermal reaction is 120-130 DEG C, and the reaction time is 10-12 h; in step S1, the calcination temperature is 650-700 DEG C, and the calcination time is 5-6 h; and the calcination is carried out in an argon atmosphere.

[0009] Preferably, in step S3, after the second solution is heated to 40-70 DEG C, the C6H8O6 solution is added, and the reaction is stirred for 1-4 h; in step S3, the molar ratio of H2PtCl6.6H2O to C6H8O6 is 9.7:(98-100), and the molar concentration of H2PtCl6.6H2O is 0.0097 M; and in step S3, the atomic molar ratio of Pt in H2PtCl6.6H2O to Mn is ≤5%.

[0010] Preferably, in step S1, the manganese source is a water-soluble manganese salt and / or a hydrate of a water-soluble manganese salt.

[0011] Preferably, the manganese source is at least one of potassium permanganate, manganese chloride, manganese sulfate, manganese nitrate, a manganese nitrate hydrate, a manganese chloride hydrate and a manganese sulfate hydrate.

[0012] Preferably, in step S1, the solvent of the first solution is a mixture of ethylene glycol and water, and the volume ratio of ethylene glycol to water is 1:(70-75); and in step S3, the drying temperature is 50-70 DEG C, and the drying time is 8-10 h.

[0013] The application further provides a Pt modified Mn3O4 composite material.

[0014] The application further provides a gas sensitive element.

[0015] The application further provides a preparation method of the gas sensor, which adopts the technical scheme that the preparation method of the gas sensor comprises the following steps: step one, mixing the Pt modified Mn3O4 composite material with a solvent, grinding to obtain a slurry; step two, coating the slurry on the surface of a substrate, drying and aging to obtain the gas sensor.

[0016] Preferably, the solvent in step one is at least one of distilled water, anhydrous ethanol and terpineol.

[0017] More preferably, the use ratio of the Pt modified Mn3O4 composite material to the solvent is (10-50) mg:(0.1-1) mL.

[0018] The application further provides an application of the Pt modified Mn3O4 composite material or the gas sensor, which adopts the technical scheme that the Pt modified Mn3O4 composite material or the gas sensor is applied to detection of ethylene.

[0019] Advantages:

[0020] (1) The Pt modified Mn3O4 composite material has good ethylene sensing performance. The response value of the Pt modified Mn3O4 composite material to 1000 ppm of ethylene gas is as high as 7.4, the optimal working temperature is as low as 180℃, and the Pt modified Mn3O4 composite material has good selectivity and repeatability.

[0021] (2) The application uses Mn3O4 nanorods as semiconductor materials, which have uniform morphology, are easy to diffuse ethylene gas, have simple material preparation process, low cost, and raw materials are easy to obtain, and are beneficial to large-scale popularization and utilization.

[0022] The Pt modified Mn3O4 composite material as a gas sensitive material is used for ethylene detection, and can be applied to detection of 50 ppm-2000 ppm of C2H4 at 140℃-260℃, and has good ethylene sensing performance to 50 ppm-2000 ppm of C2H4. BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings accompanying the specification of the application form a part of the specification, serve to further understand the application, and together with the illustrative embodiments of the application and their descriptions serve to explain the application, and do not constitute an improper limitation on the application. Among them:

[0024] Figure 1 is an XRD graph of the Pt modified Mn3O4 composite material prepared in the embodiments of the application, and in the graph, the samples from top to bottom correspond to example 3, example 2, example 1 and comparative example 1;

[0025] Figure 2Fig. 1 is a response curve of the Pt modified Mn304 gas sensor prepared in the embodiments 1-3 and the Mn304 gas sensor of the comparative example 1 to 1000 ppm ethylene at different temperatures; wherein, the left graph is the response curve of the Mn304 gas sensor of the comparative example 1 at 280-400℃; the right graph is the response curve of the Pt modified Mn304 gas sensor of the embodiments 1-3 and the comparative example 1 at 140-260℃;

[0026] Figure 3 Fig. 2 is a dynamic response recovery curve of different gas sensors to different concentrations of ethylene gas; wherein, (a) is the dynamic response recovery curve of the Mn304 gas sensor of the comparative example 1, (b) is the dynamic response recovery curve of the Pt modified Mn304 gas sensor of the embodiments 1-3, (c) is a partial enlarged view of the dynamic response recovery curve of the Pt modified Mn304 gas sensor of the embodiment 2;

[0027] Figure 4 Fig. 3 is a selective test result graph of the Mn304 gas sensor of the comparative example 1 and the Pt modified Mn304 gas sensor prepared in the embodiments 1-3 to different kinds of gas;

[0028] Figure 5 Fig. 4 is a cycle test result graph of the Pt modified Mn304 gas sensor of the embodiment 2 to 1000 ppm ethylene. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in the present application belong to the scope of protection of the present application.

[0030] The present application will be described in detail below with reference to the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0031] The present application provides a preparation method of a Pt modified Mn304 composite material, aiming at at least one problem of the current gas sensitive material, such as poor sensitivity to ethylene, high working temperature, high cost and difficulty in stable use.

[0032] The preparation method of the Pt modified Mn3O4 composite material of the embodiment of the present application comprises the following steps: step S1, performing hydrothermal reaction on a first solution containing a manganese source, after the reaction is completed, performing solid-liquid separation, drying and calcining the obtained solid to obtain Mn3O4 nanorods; step S2, uniformly mixing a dispersion liquid of the Mn3O4 nanorods with a H2PtCl6·6H2O solution to obtain a second solution; step S3, heating the second solution, adding a C6H8O6 solution (ascorbic acid solution), and stirring and reacting; after the reaction is completed, performing solid-liquid separation, washing and drying to obtain the Pt modified Mn3O4 composite material.

[0033] In the preferred embodiment of the preparation method of the Pt modified Mn3O4 composite material of the present application, in step S1, the temperature of the hydrothermal reaction is 120-130°C (for example, 120°C, 124°C, 128°C or 130°C), and the reaction time is 10-12h (for example, 10h, 10.5h, 11h, 11.5h or 12h); in step S1, the temperature of the calcination is 650-700°C (for example, 650°C, 660°C, 670°C, 680°C, 690°C or 700°C), and the calcination time is 5-6h (for example, 5h, 5.2h, 5.5h, 5.8h or 6h); the calcination is performed in an argon atmosphere. If the temperature or time of the hydrothermal reaction is smaller or larger, the product morphology is not uniform, and the performance is reduced. If the temperature or time of the calcination is smaller or larger, the product prepared is not pure, and the performance is reduced. By performing the calcination in an argon atmosphere, the performance of the product is improved (compared with performing the calcination in a nitrogen atmosphere; if the calcination is performed in an air atmosphere, the target product Mn3O4 cannot be obtained).

[0034] In the preferred embodiment of the preparation method of the Pt modified Mn3O4 composite material of the present application, in step S3, the molar ratio of H2PtCl6·6H2O to C6H8O6 is 9.7:(98-100) (for example, 9.7:98, 9.7:99 or 9.7:100), and the molar concentration of H2PtCl6·6H2O is 0.0097M; in step S3, the atomic molar ratio of Pt in H2PtCl6·6H2O to Mn is ≤5%. If the amount of C6H8O6 is too large, the chloroplatinic acid is fully reduced, and excessive ascorbic acid can further reduce Mn in Mn3O4 to generate low-valence Mn; if the amount of C6H8O6 is too small, the amount of platinum nanoparticles generated is small, or the size distribution is not uniform. In addition, if the amount of chloroplatinic acid is too large, the excess PtCl6 2- may slowly react with Mn3O4, the product is not pure, and the performance is reduced.

[0035] In the preferred embodiment of the preparation method of the Pt modified Mn3O4 composite material of the present application, in step S3, after the second solution is heated to 40-70 DEG C (for example, 40 DEG C, 50 DEG C, 60 DEG C or 70 DEG C), the C6H8O6 solution is added, and the reaction is stirred for 1-4 h (for example, 1 h, 2 h, 3 h or 4 h). Wherein, (1) if the reaction temperature exceeds 70 DEG C, the reduction rate is further accelerated, and ascorbic acid is significantly decomposed, which may lead to incomplete reduction or increase of by-products; if the reaction temperature is lower than 40 DEG C, the reaction may be incomplete, and Pt particles may be aggregated and non-uniform. 4+ The generated Pt NPs may be re-oxidized, and the yield is greatly reduced.

[0036] In the preferred embodiment of the preparation method of the Pt modified Mn3O4 composite material of the present application, in step S1, the manganese source is a water-soluble manganese salt and / or a hydrate of a water-soluble manganese salt.

[0037] In the preferred embodiment of the preparation method of the Pt modified Mn3O4 composite material of the present application, the manganese source is at least one of potassium permanganate, manganese chloride, manganese sulfate, manganese nitrate, manganese nitrate hydrate, manganese chloride hydrate and manganese sulfate hydrate.

[0038] In the preferred embodiment of the preparation method of the Pt modified Mn3O4 composite material of the present application, in step S1, the solvent of the first solution is a mixture of ethylene glycol and water, and the volume ratio of ethylene glycol to water is 1:(70-75) (for example, 1:70, 1:71, 1:72, 1:73, 1:74 or 1:75); in step S3, the drying temperature is 50-70 DEG C (for example, 50 DEG C, 55 DEG C, 60 DEG C, 65 DEG C or 70 DEG C), and the drying time is 8-10 h (for example, 8 h, 8.5 h, 9 h, 9.5 h or 10 h). Wherein, the use ratio of ethylene glycol and water in step S1 will affect the reduction efficiency and the morphology of the product.

[0039] The present application also provides a Pt modified Mn3O4 composite material, which is prepared by the method as described above.

[0040] The application further provides a gas sensor, which comprises the Pt modified Mn3O4 composite material.

[0041] The application further provides a preparation method of the gas sensor, which comprises the following steps: step one, mixing the Pt modified Mn3O4 composite material with a solvent, grinding to obtain a slurry; and step two, coating the slurry on a surface of a substrate, drying and aging to obtain the gas sensor.

[0042] In a preferred embodiment of the preparation method of the gas sensor, the solvent in step one is at least one of distilled water, anhydrous ethanol and terpineol.

[0043] In step one of the preparation method of the gas sensor, the ratio of the Pt modified Mn3O4 composite material to the solvent is (10-50) mg:(0.1-1) mL (for example, 10 mg:1 mL, 10 mg:0.1 mL, 50 mg:1 mL, 50 mg:0.1 mL, 30 mg:0.5 mL, 30 mg:1 mL, 30 mg:0.1 mL, 20 mg:0.5 mL, 40 mg:0.5 mL, 20 mg:1 mL, 20 mg:0.1 mL, 40 mg:0.1 mL, 40 mg:1 mL, etc.).

[0044] Preferably, the substrate in step two is a gold electrode substrate; the drying is performed at room temperature; and the aging is performed in a gas sensor test platform.

[0045] The application further provides the Pt modified Mn3O4 composite material or the gas sensor, and the Pt modified Mn3O4 composite material or the gas sensor is used for detecting ethylene.

[0046] The Pt modified Mn3O4 composite material, the preparation method thereof, the gas sensor and the application thereof will be described in detail in the following specific embodiments.

[0047] The raw materials used in the following examples are commercially available unless otherwise specified. The main raw materials are as follows: potassium permanganate (KMnO4, ≥99.5%) is purchased from Sigma-Aldrich Trading Co., Ltd.; ethylene glycol (C2H6O2, ≥99.8%) is purchased from Henan Luoyang Chemical Reagent Factory, China; chloroplatinic acid hexahydrate (H2PtCl6·6H2O, Pt≥37.5%) is purchased from Shanghai Microlin Biochemical Technology Co., Ltd., China; ascorbic acid (C6H8O6, ≥99.7%) is purchased from Tianjin Kemio Chemical Reagent Co., Ltd., China; all chemical reagents used in the experiment are analytical pure and do not need to be further purified for direct use. Distilled water is used for operation throughout the experiment.

[0048] Example 1

[0049] The Pt-modified Mn3O4 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 1.0%, and the preparation method specifically includes the following steps:

[0050] S1, 0.1185g KMnO4 is dissolved in a mixed solution of 0.6mL ethylene glycol and 44mL distilled water, and a first solution is formed after 5h of vigorous stirring;

[0051] S2, the first solution is moved into a high-pressure reaction kettle, and reacted at 120℃ in an oven for 10h. The product is washed and centrifuged three times with deionized water and alcohol alternately (after the reaction is completed, deionized water is added to the obtained product system, shaken, centrifuged, and the lower precipitate is taken; then the deionized water is replaced with alcohol and the above process is repeated; the above process is referred to as washing and centrifuging once, and a total of three times), and the precipitate is collected and dried in a vacuum oven at 50℃ for 12h, and then calcined at 700℃ in a tube furnace for 5h to obtain Mn3O4 nanorods;

[0052] S3, 0.088mmol of Mn3O4 nanorods corresponding to the mass of Mn3O4 is dispersed in 15mL of distilled water, and after sufficient stirring, 0.27mL of 0.01M H2PtCl6·6H2O solution is added. Continue to stir the second solution in a water bath, and when the water bath temperature reaches 60℃, add 2mL of 0.1M C6H8O6 solution, and continue to stir for 2.5h;

[0053] Step S4, the product is separated by solid-liquid separation, and the obtained solid is washed and dried to obtain 1% of Pt-modified Mn3O4 composite material, which is referred to as 1.0at.%Pt / Mn3O4.

[0054] The preparation method of the Pt-modified Mn3O4 gas sensitive element of this example includes the following steps:

[0055] Step one, 20 mg of Pt modified Mn304 composite material is mixed with 0.2 mL of distilled water in a mortar, and ground into a thick slurry;

[0056] Step two, the mixed solution is dropped on a gold electrode substrate (length, width and height are 8 mm x 4 mm x 0.38 mm) to form a sensing film, which is air dried at room temperature and aged at 60℃ for 12 h, and then dried to obtain a Pt modified Mn304 gas sensitive element.

[0057] Example 2

[0058] The Pt modified Mn304 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 3.0%; the only difference between the preparation method and that of Example 1 is that 0.81 mL of H2PtCl6·6H2O solution is used in step S3; other parameters and the preparation method of the corresponding gas sensitive element are the same as in Example 2, and will not be repeated here.

[0059] The Pt modified Mn304 composite material of this example is denoted as 3.0 at.%Pt / Mn304.

[0060] Example 3

[0061] The Pt modified Mn304 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 5.0%; the only difference between the preparation method and that of Example 1 is that 1.36 mL of H2PtCl6·6H2O solution is used in step S3; other parameters and the preparation method of the corresponding gas sensitive element are the same as in Example 1, and will not be repeated here.

[0062] The Pt modified Mn304 composite material of this example is denoted as 5.0 at.%Pt / Mn304.

[0063] Example 4

[0064] The Pt modified Mn304 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 3.0%; the difference between the preparation method and that of Example 1 is that 0.81 mL of H2PtCl6·6H2O solution is used in step S3, the heating temperature of the second solution is 40℃, and the stirring reaction time is 4 h; other parameters and the preparation method of the corresponding gas sensitive element are the same as in Example 2, and will not be repeated here.

[0065] The Pt modified Mn304 composite material of this example is denoted as 3.0 at.%Pt / Mn304.

[0066] Example 5

[0067] The Pt modified Mn304 composite material of the present example was prepared according to an atomic molar ratio of Pt to Mn of 3.0%; the difference between the preparation method and that of Example 1 is that 0.81 mL of H2PtCl6·6H2O solution was used in step S3, the heating temperature of the second solution was 70°C, and the stirring reaction time was 1 h; the other parameters and the preparation method of the corresponding gas sensitive element were the same as in Example 2, and will not be repeated here.

[0068] The Pt modified Mn304 composite material of the present example is denoted as 3.0 at. % Pt / Mn304.

[0069] Example 6

[0070] The Pt modified Mn304 composite material of the present example was prepared according to an atomic molar ratio of Pt to Mn of 5.0%; the difference between the preparation method and that of Example 1 is that 1.36 mL of H2PtCl6·6H2O solution was used in step S3, and the volume ratio of ethylene glycol to water was 1:70; the other parameters and the preparation method of the corresponding gas sensitive element were the same as in Example 2, and will not be repeated here.

[0071] The Pt modified Mn304 composite material of the present example is denoted as 5.0 at. % Pt / Mn304.

[0072] Example 7

[0073] The Pt modified Mn304 composite material of the present example was prepared according to an atomic molar ratio of Pt to Mn of 5.0%; the difference between the preparation method and that of Example 1 is that 1.36 mL of H2PtCl6·6H2O solution was used in step S3, and the volume ratio of ethylene glycol to water was 1:75; the other parameters and the preparation method of the corresponding gas sensitive element were the same as in Example 2, and will not be repeated here.

[0074] The Pt modified Mn304 composite material of the present example is denoted as 5.0 at. % Pt / Mn304.

[0075] Comparative Example 1

[0076] The present comparative example does not add Pt, i.e. is prepared according to an atomic molar ratio of Pt to Mn of 0.0%, and the preparation method specifically comprises the following steps:

[0077] S1, dissolve 0.1185 g of KMnO4 in a mixed solution of 0.6 mL of ethylene glycol and 44 mL of distilled water, and form a first solution after vigorous stirring for 5 h;

[0078] S2, the first solution is moved into a high-pressure reaction kettle, and is reacted at 120°C in an oven for 10 hours. The product is washed and centrifuged three times with deionized water and alcohol alternately, and the precipitate is collected. After drying in a vacuum drying oven at 50°C overnight, the product is calcined at 700°C in an argon atmosphere for 5 hours in a tube furnace, to obtain Mn304 nanorods, which are denoted as 0.0 at.% Pt / Mn304.

[0079] Experimental Example

[0080] The Pt-modified Mn304 composite materials in the above examples are characterized and tested, and the performance of the Pt-modified Mn304 gas sensing elements in the above examples is tested, and the results are as follows.

[0081] (1) Figure 1 is the X-ray diffraction pattern of the Pt-modified Mn304 composite materials provided in Examples 1-4 of the present application and the Mn304 nanorods of Comparative Example 1, in which the Mn304 corresponds to the standard peak of Mn304 (JCPDS: 24-0734), and the Pt corresponds to the standard peak of Pt (JCPDS: 87-0640), proving that the Pt-modified Mn304 composite materials are successfully prepared and have good crystallinity.

[0082] (2) Figure 2 is the response value of the Pt-modified Mn304 gas sensing elements provided in Examples 1-3 of the present application and the Mn304 nanorods of Comparative Example 1 to 1000 ppm ethylene as a function of temperature.

[0083] It can be seen from the figure that after Pt modification, the optimal working temperature of the sensor is reduced from 360°C to 180°C, and the sensitivity (i.e. the response value) can be as high as 7.5 (the optimal working temperature of 1 at.% Pt / Mn304 is 220°C, and the sensitivity is 5.3; the optimal working temperature of 5 at.% Pt / Mn304 is 180°C, and the sensitivity is 5.2; the optimal working temperature of the Mn304 nanorods of Comparative Example 1 is 360°C, and the sensitivity is less than 1.8). Among them, the sensitivity is the ratio of the resistance value R g of the sensor in the gas to be measured to the resistance value R a in air, and is expressed as: S = R g / R a .

[0084] (3) Figure 3 is the dynamic response recovery curve of the Pt-modified Mn304 gas sensing elements provided in Examples 1-3 of the present application and the Mn304 gas sensing elements of Comparative Example 1 to C2H4 gas with different concentrations (50-2000 ppm).

[0085] It can be seen from the figures that the response of the Pt modified Mn3O4 composite materials of Examples 1-3 is higher than that of pure Mn3O4 at all concentrations:

[0086] The R of 1 at.%Pt / Mn3O4 of Example 1 to ethylene of 50ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm and 2000ppm at the optimum working temperature is 1.34, 1.67, 2.49, 3.38, 4.33, 5.08, 6.69, respectively. g / R a The R of 1 at.%Pt / Mn3O4 of Example 1 to ethylene of 50ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm and 2000ppm at the optimum working temperature is 1.34, 1.67, 2.49, 3.38, 4.33, 5.08, 6.69, respectively.

[0087] The R of 3 at.%Pt / Mn3O4 of Example 2 to ethylene of 50ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm and 2000ppm at the optimum working temperature (180℃) is 1.56, 1.95, 2.94, 4.28, 5.45, 7.5, 9.85, respectively. g / R a The response time of 3 at.%Pt / Mn3O4 of Example 2 is 42s, and the recovery time is 83s.

[0088] The R of 5 at.%Pt / Mn3O4 of Example 3 to ethylene of 50ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm and 2000ppm at the optimum working temperature is 1, 1.24, 1.6, 1.9, 2.26, 2.79, 5.26, respectively. g / R a The R of 5 at.%Pt / Mn3O4 of Example 3 to ethylene of 50ppm, 100ppm, 300ppm, 500ppm, 800ppm, 1000ppm and 2000ppm at the optimum working temperature is 1, 1.24, 1.6, 1.9, 2.26, 2.79, 5.26, respectively.

[0089] The R of Mn3O4 nanorods of Comparative Example 1 to ethylene of 20ppm, 50ppm, 100ppm, 300ppm, 500ppm, 1000ppm, 6000ppm at the optimum working temperature (360℃) is 1.09, 1.2, 1.28, 1.42, 1.5, 1.71, 1.86, respectively. g / R a The R of Mn3O4 nanorods of Comparative Example 1 to ethylene of 20ppm, 50ppm, 100ppm, 300ppm, 500ppm, 1000ppm, 6000ppm at the optimum working temperature (360℃) is 1.09, 1.2, 1.28, 1.42, 1.5, 1.71, 1.86, respectively.

[0090] The above experimental results show that the Pt modified Mn3O4 gas sensing element of the present application can be used in a larger concentration range, and is more suitable for actual application scenarios.

[0091] (4) Figure 4The Pt modified Mn3O4 gas sensitive element provided by the embodiment 1-3 of the present application and the Mn3O4 gas sensitive element of the comparative example 1 are respectively connected with 1000ppm of methane, 500ppm of CO, H2, CH4, methanol gas, triethylamine gas, 10ppm of H2S, NO2 at the optimum working temperature, so as to investigate the selectivity of the Pt modified Mn3O4 gas sensitive element to ethylene. It can be seen from the figure that the Pt modified Mn3O4 composite material prepared by the present application has good selectivity to ethylene.

[0092] (5) Figure 5 The figure of the cycle test result of the Pt modified Mn3O4 gas sensitive element provided by the embodiment 2 of the present application and the Mn3O4 gas sensitive element of the comparative example 1 to 1000ppm of ethylene. It can be seen from the figure that the Pt modified Mn3O4 gas sensitive element has good repeatability for detecting ethylene. Figure 5

[0093] In summary, the application of the Pt modified Mn3O4 gas sensitive element of the present application to the ethylene sensor can improve the high sensitivity of the ethylene gas detection, reduce the working temperature, reduce the cost and ensure the stable operation of the equipment.

[0094] The detection performance of the Pt modified Mn3O4 gas sensitive element of the present application to ethylene is compared with the gas sensitive performance of the reported ethylene gas sensitive sensor, and the comparison is shown in the following table 1.

[0095] Table 1: Comparison of gas sensitive performance

[0096]

[0097] It can be seen from table 1 that the Pt modified Mn3O4 gas sensitive element of the present application can significantly reduce the working temperature and has better sensitivity.

[0098] The above description is only the preferred embodiment of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a Pt-modified Mn3O4 composite material, characterized in that, Includes the following steps: Step S1: Perform a hydrothermal reaction on the first solution containing manganese source. After the reaction is completed, separate the solid and liquid, and dry and calcine the obtained solid to obtain Mn3O4 nanorods. Step S2: Mix the dispersion of the Mn3O4 nanorods with the H2PtCl6·6H2O solution until homogeneous to obtain a second solution; Step S3: Heat the second solution, add C6H8O6 solution, and stir to react; after the reaction is complete, separate the solid and liquid, wash and dry to obtain the Pt-modified Mn3O4 composite material.

2. The method for preparing the Pt-modified Mn3O4 composite material as described in claim 1, characterized in that, In step S1, the hydrothermal reaction temperature is 120-130 ℃, and the reaction time is 10-12 h; In step S1, the calcination temperature is 650-700 ℃, and the calcination time is 5-6 h; The calcination is carried out in an argon atmosphere.

3. The method for preparing the Pt-modified Mn3O4 composite material as described in claim 1, characterized in that, In step S3, the second solution is heated to 40-70 °C, and then C6H8O6 solution is added and the reaction is stirred for 1-4 h. In step S3, the molar ratio of H2PtCl6·6H2O to C6H8O6 is 9.7:(98-100), and the molar concentration of H2PtCl6·6H2O is 0.0097M. In step S3, the atomic molar ratio of Pt to Mn in H2PtCl6·6H2O is ≤5%.

4. The method for preparing the Pt-modified Mn3O4 composite material as described in claim 1, characterized in that, In step S1, the manganese source is a water-soluble manganese salt and / or a hydrate of a water-soluble manganese salt.

5. The method for preparing the Pt-modified Mn3O4 composite material as described in claim 4, characterized in that, The manganese source is at least one of potassium permanganate, manganese chloride, manganese sulfate, manganese nitrate, manganese nitrate hydrate, manganese chloride hydrate, and manganese sulfate hydrate.

6. The method for preparing the Pt-modified Mn3O4 composite material as described in claim 1, characterized in that, In step S1, the solvent of the first solution is a mixture of ethylene glycol and water, and the volume ratio of ethylene glycol to water is 1:(70-75). In step S3, the drying temperature is 50-70 ℃ and the drying time is 8-10 h.

7. A Pt-modified Mn3O4 composite material, characterized in that, The Pt-modified Mn3O4 composite material was prepared by the method described in any one of claims 1-6.

8. A gas-sensitive element, characterized in that, The gas-sensitive element contains the Pt-modified Mn3O4 composite material as described in claim 7.

9. The method for preparing a gas-sensitive element as described in claim 8, characterized in that, Includes the following steps: Step 1: Mix the Pt-modified Mn3O4 composite material with a solvent and grind it to obtain a slurry; Step 2: Coat the slurry onto the surface of the substrate, dry and age it to obtain the gas-sensitive element.

10. The method for preparing a gas-sensitive element as described in claim 9, characterized in that, The solvent in step one is at least one of distilled water, anhydrous ethanol, and terpineol.

11. The method for preparing a gas-sensitive element as described in claim 10, characterized in that, The ratio of the Pt-modified Mn3O4 composite material to the solvent is (10-50) mg:(0.1-1) mL.

12. The application of the Pt-modified Mn3O4 composite material as described in claim 7 or the gas-sensitive element as described in claim 8 in the detection of ethylene.

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