Pt-modified Mn3O4 composite material, preparation method thereof, gas sensitive element and application of gas sensitive element

Abstract

The invention 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 of the gas sensitive element. The preparation method of the Pt modified Mn3O4 composite material comprises the following steps: S1, carrying out hydrothermal reaction on a first solution containing a manganese source, carrying out solid-liquid separation after the reaction is finished, and drying and calcining the obtained solid to obtain a Mn3O4 nanorod; step S2, uniformly mixing the dispersion liquid of the Mn3O4 nanorod with an H2PtCl6. 6H2O solution, so as to obtain a second solution; s3, heating the second solution, adding a C6H8O6 solution, and stirring for reaction; and after the reaction is finished, carrying out solid-liquid separation, washing and drying to obtain the Pt modified Mn3O4 composite material. The Pt modified Mn3O4 composite material disclosed by the invention has relatively good ethylene sensing performance, is low in optimal working temperature, and has relatively good selectivity and repeatability.

Description

Technical Field

[0001] The present invention 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 an application thereof. Background Art

[0002] Ethylene is an important raw material for the production of chemical products such as polyethylene, vinyl alcohol, and vinyl chloride. The petrochemical industry needs to monitor ethylene gas to ensure the safety and stability of the production process. Although ethylene itself has low toxicity, due to its flammability and high reactivity under specific conditions, it may lead to various industrial accidents. Because the explosion limit of ethylene is relatively low and the explosion intensity is relatively high, there is a relatively high explosion risk during its production and use. Ethylene is a combustible gas with a low explosion limit (2.7%-36%) and is prone to forming explosive mixtures in the air. Under high-temperature or fire-source conditions, ethylene may trigger serious fire or explosion accidents. Therefore, it is very necessary to develop a reliable and relatively inexpensive ethylene gas sensor to detect the ethylene concentration in the air.

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

[0004] However, although the existing sensitive materials show a certain responsiveness to ethylene, most of them have a relatively high response temperature, mostly concentrated in the range of 300-500°C, and the response value is relatively low.

[0005] Therefore, it is necessary to provide an improved technical solution for the deficiencies of the above-mentioned existing technologies. Summary of the Invention

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

[0007] The present invention provides a method for preparing a Pt-modified Mn3O4 composite material, which adopts the following technical solution: A method for preparing a Pt-modified Mn3O4 composite material includes the following steps: Step S1, perform a hydrothermal reaction on a first solution containing a manganese source, after the reaction ends, perform solid-liquid separation, and dry and calcine the obtained solid to obtain Mn3O4 nanorods; Step S2, uniformly mix the dispersion of the Mn3O4 nanorods with an H2PtCl6·6H2O solution to obtain a second solution; Step S3, heat the second solution, add a C6H8O6 solution, and stir and react; after the reaction ends, perform solid-liquid separation, wash and dry to obtain the Pt-modified Mn3O4 composite material.

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

[0009] Preferably, in Step S3, after heating the second solution to 40 - 70 °C, add a C6H8O6 solution, and stir and react 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; 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, manganese nitrate hydrate, manganese chloride hydrate, and 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); in Step S3, the drying temperature is 50 - 70 °C, and the drying time is 8 - 10 h.

[0013] The present invention also provides a Pt-modified Mn3O4 composite material, which adopts the following technical solution: A Pt-modified Mn3O4 composite material is prepared by the method described above.

[0014] The present invention also provides a gas sensor element, which adopts the following technical solution: A gas sensor element contains the Pt-modified Mn3O4 composite material described above.

[0015] The present invention also provides a method for preparing the gas-sensitive element as described above, which adopts the following technical solution: The method for preparing the gas-sensitive element as described above includes the following steps: Step 1: Mix the Pt-modified Mn3O4 composite material with a solvent and grind to obtain a slurry; Step 2: Coat the slurry on the surface of a substrate, dry and age to obtain the gas-sensitive element.

[0016] Preferably, the solvent in Step 1 is at least one of distilled water, absolute ethanol, and terpineol.

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

[0018] The present invention also provides the application of the Pt-modified Mn3O4 composite material or the gas-sensitive element as described above, which adopts the following technical solution: The application of the Pt-modified Mn3O4 composite material or the gas-sensitive element as described above in detecting ethylene.

[0019] Beneficial effects:

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

[0021] (2) The present invention uses Mn3O4 nanorods as a semiconductor material, with uniform morphology, easy diffusion of ethylene gas, simple material preparation process, low cost, and easily available raw materials, which is beneficial for large-scale popularization and utilization.

[0022] The Pt-modified Mn3O4 composite material of the present invention is used as a gas-sensitive material for ethylene detection, and can be applied to detect C2H4 with a concentration of 50 ppm - 2000 ppm at 140 °C - 260 °C, and has good ethylene sensing performance for C2H4 with a concentration of 50 ppm - 2000 ppm. Description of the drawings

[0023] The specification drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. Among them:

[0024] Figure 1 is the XRD pattern of the Pt-modified Mn3O4 composite material prepared in the embodiment of the present invention. In the figure, the corresponding samples from top to bottom are Example 3, Example 2, Example 1, and Comparative Example 1;

[0025] Figure 2It is the response curve of the Pt-modified Mn3O4 gas sensor prepared in Examples 1-3 of the present invention and the Mn3O4 gas sensor of Comparative Example 1 to 1000 ppm ethylene varying with temperature; among them, the left figure is the response curve of the Mn3O4 gas sensor of Comparative Example 1 at 280-400 °C; the right figure is the response curves of Examples 1-3 and Comparative Example 1 at 140-260 °C;

[0026] Figure 3 It is the dynamic response and recovery curves of different gas sensors to ethylene gas with different concentrations; among them, (a) is the Mn3O4 gas sensor of Comparative Example 1, and (b) is the Pt-modified Mn3O4 gas sensor of Examples 1-3; (c) is a partial enlarged view of the dynamic response and recovery curve of the Pt-modified Mn3O4 gas sensor of Example 2;

[0027] Figure 4 It is the selectivity test result diagram of the Mn3O4 gas sensor of Comparative Example 1 and the Pt-modified Mn3O4 gas sensors prepared in Examples 1-3 to different types of gases;

[0028] Figure 5 It is the cyclicity test result diagram of the Pt-modified Mn3O4 gas sensor of Example 2 of the present invention to 1000 ppm ethylene. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0030] Next, the present invention will be described in detail in conjunction with the embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0031] In view of the problems of at least one of poor sensitivity to ethylene, high working temperature, high cost, and difficulty in stable use existing in current gas-sensitive materials, the present invention provides a preparation method for a Pt-modified Mn3O4 composite material.

[0032] The preparation method of the Pt-modified Mn3O4 composite material according to the embodiment of the present invention includes the following steps: Step S1, perform a hydrothermal reaction on a first solution containing a manganese source, after the reaction is completed, perform solid-liquid separation, and dry and calcine the obtained solid to obtain Mn3O4 nanorods; Step S2, uniformly mix the dispersion of the Mn3O4 nanorods with an H2PtCl6·6H2O solution to obtain a second solution; Step S3, heat the second solution, add a C6H8O6 solution (ascorbic acid solution), and stir and react; after the reaction is completed, perform solid-liquid separation, wash and dry to obtain the Pt-modified Mn3O4 composite material.

[0033] In a preferred embodiment of the preparation method of the Pt-modified Mn3O4 composite material of the present invention, in Step S1, the temperature of the hydrothermal reaction is 120-130 °C (for example, 120 °C, 124 °C, 128 °C, 130 °C), and the reaction time is 10-12 h (for example, 10 h, 10.5 h, 11 h, 11.5 h, 12 h); in Step S1, the calcination temperature is 650-700 °C (for example, 650 °C, 660 °C, 670 °C, 680 °C, 690 °C, 700 °C), and the calcination time is 5-6 h (for example, 5 h, 5.2 h, 5.5 h, 5.8 h or 6 h); the calcination is carried out in an argon atmosphere. Among them, if the temperature or time of the hydrothermal reaction is smaller or larger, the morphology of the product will be uneven and the performance will be reduced. If the calcination temperature or time is respectively smaller or larger, the prepared product will be impure and the performance will be reduced. By carrying out the calcination in an argon atmosphere, it helps to improve the performance of the product (compared with calcination in a nitrogen environment; if carried out in an air atmosphere, the Mn3O4 target product cannot be obtained).

[0034] In a preferred embodiment of the preparation method of the Pt-modified Mn3O4 composite material of the present invention, in Step S3, the molar ratio of H2PtCl6·6H2O to C6H8O6 is 9.7:(98-100) (for example, 9.7:98, 9.7:99, 9.7:100), and the molar concentration of H2PtCl6·6H2O is 0.0097 M; in Step S3, the atomic molar ratio of Pt to Mn in H2PtCl6·6H2O ≤ 5%. Among them, if the dosage of C6H8O6 is too large, the chloroplatinic acid is fully reduced, resulting in that the excessive ascorbic acid may further reduce Mn in Mn3O4 to generate low-valent Mn; if the dosage of C6H8O6 is too small, the amount of platinum nanoparticles generated is small, or the size distribution is uneven. In addition, if the dosage of chloroplatinic acid is too large, the excess PtCl6 2- may slowly react with Mn3O4, resulting in an impure product and a reduction in performance.

[0035] In a preferred embodiment of the preparation method of the Pt-modified Mn3O4 composite material of the present invention, in step S3, after heating the second solution to 40-70 °C (for example, 40 °C, 50 °C, 60 °C or 70 °C), add the C6H8O6 solution and stir for reaction for 1-4 h (for example, 1 h, 2 h, 3 h or 4 h). Among them, (1) if the reaction temperature exceeds 70 °C, the reduction rate further accelerates, and ascorbic acid decomposes significantly, which may lead to incomplete reduction or an increase in by-products; if the reaction temperature is lower than 40 °C, the reaction will be incomplete, and Pt particles will agglomerate and be uneven. (2) If the stirring time is too long or too short, it will have a significant impact on the particle size, dispersibility, purity and catalytic performance of the product; too short stirring time leads to incomplete reduction, impure product and uneven particles; too long stirring time, ascorbic acid is oxidized and decomposed, and the solution pH may increase. The alkaline environment of Mn3O4 may cause its dissolution and the reduction ability to decline, and the uncompletely reduced Pt 4+ may re-oxidize the generated Pt NPs, resulting in a significant reduction in yield.

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

[0037] In a preferred embodiment of the preparation method of the Pt-modified Mn3O4 composite material of the present invention, 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 a preferred embodiment of the preparation method of the Pt-modified Mn3O4 composite material of the present invention, 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 °C (for example, 50 °C, 55 °C, 60 °C, 65 °C or 70 °C), and the drying time is 8-10 h (for example, 8 h, 8.5 h, 9 h, 9.5 h or 10 h). Among them, the dosage ratio of ethylene glycol to water in step S1 will affect the reduction efficiency and product morphology.

[0039] The present invention also provides a Pt-modified Mn3O4 composite material, and the Pt-modified Mn3O4 composite material of the embodiment of the present invention is prepared by the method described above.

[0040] The present invention also provides a gas sensor element. The gas sensor element of the embodiment of the present invention contains the Pt-modified Mn3O4 composite material as described above. The gas sensor element of the present invention has the advantages of high sensitivity, low operating temperature, low cost and good stability. The gas sensor element of the present invention can be further used to construct an ethylene gas sensor.

[0041] The present invention also provides a method for preparing the gas sensor element as described above. The method for preparing the gas sensor element of the embodiment of the present invention includes the following steps: Step 1: Mix the Pt-modified Mn3O4 composite material with a solvent and grind to obtain a slurry; Step 2: Coat the slurry on the surface of a substrate, dry and age to obtain the gas sensor element.

[0042] In a preferred embodiment of the method for preparing the gas sensor element of the embodiment of the present invention, the solvent in Step 1 is at least one of distilled water, absolute ethanol and terpineol.

[0043] In a preferred embodiment of the method for preparing the gas sensor element of the embodiment of the present invention, in Step 1, the dosage 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 2 is a gold electrode substrate; drying is carried out at room temperature; aging is carried out in a gas sensor test bench.

[0045] The present invention also provides an application of the Pt-modified Mn3O4 composite material or the gas sensor element as described above. The application of the Pt-modified Mn3O4 composite material or the gas sensor element as described above in detecting ethylene.

[0046] The Pt-modified Mn3O4 composite material of the present invention, its preparation method, the gas sensor element and its application will be described in detail below through specific examples.

[0047] Unless otherwise specified, the raw materials used in the following examples are all commercially available; sources of the main raw materials: potassium permanganate (KMnO4, ≥99.5%) was purchased from Sigma-Aldrich Trading Co., Ltd.; ethylene glycol (C2H6O2, ≥99.8%) was purchased from Luoyang Chemical Reagent Factory, Henan Province, China; chloroplatinic acid hexahydrate (H2PtCl6·6H2O, Pt≥37.5%) was purchased from Macklin Biochemical Co., Ltd., Shanghai, China; ascorbic acid (C6H8O6, ≥99.7%) was purchased from Tianjin Kemiou Chemical Reagent Co., Ltd., China. All chemical raw materials and reagents in the experiment are of analytical grade and can be used directly without further purification. Throughout the experiment, distilled water was used for operations.

[0048] Example 1

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

[0050] 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 vigorously stir for 5 h to form the first solution;

[0051] S2. Transfer the first solution into a high-pressure reaction kettle, keep it at a constant temperature of 120 °C in an oven for 10 h, wash and centrifuge it three times alternately with deionized water and alcohol (after the reaction is completed, add deionized water to the obtained product system, shake well and centrifuge, take the lower precipitate; then replace the deionized water with alcohol and repeat the above process; the above process is recorded as one wash and centrifuge, and it is carried out three times in total), collect the precipitate, dry it in a vacuum oven at 50 °C for 12 h, and then place it in a tube furnace and calcine it at 700 °C for 5 h to obtain Mn3O4 nanorods;

[0052] S3. Disperse the Mn3O4 nanorods corresponding to the mass of 0.088 mmol of Mn3O4 in 15 mL of distilled water, stir well, add 0.27 mL of 0.01 M H2PtCl6·6H2O solution, continue to stir the second solution in a water bath, when the water bath temperature reaches 60 °C, add 2 mL of 0.1 M C6H8O6 solution, and continue to stir for 2.5 h;

[0053] Step S4. Separate the solid and liquid of the product, wash and dry the obtained solid to obtain a 1% Pt-modified Mn3O4 composite material, denoted as 1.0 at.% Pt / Mn3O4.

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

[0055] Step 1: Mix 20 mg of Pt-modified Mn3O4 composite material with 0.2 mL of distilled water in a mortar and grind it into a viscous slurry;

[0056] Step 2: Drop the mixture onto a gold electrode substrate (with length, width, and height of 8 mm × 4 mm × 0.38 mm) to form a sensing film. After air-drying at room temperature, age it at 60 °C for 12 h, and then dry it to obtain a Pt-modified Mn3O4 gas sensor element.

[0057] Example 2

[0058] The Pt-modified Mn3O4 composite material in this example is prepared according to an atomic molar ratio of Pt to Mn of 3.0%; the only difference in the preparation method from 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 sensor element are the same as those in Example 2 and will not be elaborated.

[0059] The Pt-modified Mn3O4 composite material in this example is denoted as 3.0 at.% Pt / Mn3O4.

[0060] Example 3

[0061] The Pt-modified Mn3O4 composite material in this example is prepared according to an atomic molar ratio of Pt to Mn of 5.0%; the only difference in the preparation method from 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 sensor element are the same as those in Example 1 and will not be elaborated.

[0062] The Pt-modified Mn3O4 composite material in this example is denoted as 5.0 at.% Pt / Mn3O4.

[0063] Example 4

[0064] The Pt-modified Mn3O4 composite material in this example is prepared according to an atomic molar ratio of Pt to Mn of 3.0%; the difference in the preparation method from 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 °C, and the stirring reaction time is 4 h; other parameters and the preparation method of the corresponding gas sensor element are the same as those in Example 2 and will not be elaborated.

[0065] The Pt-modified Mn3O4 composite material in this example is denoted as 3.0 at.% Pt / Mn3O4.

[0066] Example 5

[0067] The Pt-modified Mn3O4 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 3.0%; the difference in the preparation method from Example 1 is that: in step S3, 0.81 mL of H2PtCl6·6H2O solution is used, the heating temperature of the second solution is 70 °C, and the stirring reaction time is 1 h; other parameters and the preparation method of the corresponding gas sensor element are the same as those in Example 2 and will not be elaborated.

[0068] The Pt-modified Mn3O4 composite material of this example is denoted as 3.0 at.% Pt / Mn3O4.

[0069] Example 6

[0070] The Pt-modified Mn3O4 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 5.0%; the difference in the preparation method from Example 1 is that: in step S3, 1.36 mL of H2PtCl6·6H2O solution is used, and the volume ratio of ethylene glycol to water is 1:70; other parameters and the preparation method of the corresponding gas sensor element are the same as those in Example 2 and will not be elaborated.

[0071] The Pt-modified Mn3O4 composite material of this example is denoted as 5.0 at.% Pt / Mn3O4.

[0072] Example 7

[0073] The Pt-modified Mn3O4 composite material of this example is prepared according to an atomic molar ratio of Pt to Mn of 5.0%; the difference in the preparation method from Example 1 is that: in step S3, 1.36 mL of H2PtCl6·6H2O solution is used, and the volume ratio of ethylene glycol to water is 1:75; other parameters and the preparation method of the corresponding gas sensor element are the same as those in Example 2 and will not be elaborated.

[0074] The Pt-modified Mn3O4 composite material of this example is denoted as 5.0 at.% Pt / Mn3O4.

[0075] Comparative Example 1

[0076] In this comparative example, no Pt is added, that is, it is prepared according to an atomic molar ratio of Pt to Mn of 0.0%, and the preparation method specifically includes 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 vigorously stir for 5 h to form a first solution;

[0078] S2. Transfer the first solution into a high-pressure reactor, react at a constant temperature of 120 °C in an oven for 10 h, wash and centrifuge three times alternately with deionized water and alcohol, and collect the precipitate (after the reaction, add deionized water to the obtained product system, shake well and centrifuge, take the lower precipitate; then replace the deionized water with alcohol and repeat the above process; the above process is recorded as one time of washing and centrifuging, and it is carried out three times in total), and dry overnight at 50 °C in a vacuum drying oven, then place it in a tube furnace and calcine at 700 °C for 5 h in an argon atmosphere to obtain Mn3O4 nanorods, denoted as 0.0 at.% Pt / Mn3O4.

[0079] Experimental Example

[0080] The Pt-modified Mn3O4 composite materials in the above examples were characterized and tested, and the performance of the Pt-modified Mn3O4 gas sensors in the above examples was tested. The results are as follows.

[0081] (1) Figure 1 This is the X-ray diffraction pattern of the Pt-modified Mn3O4 composite materials provided in Examples 1-4 of the present invention and the Mn3O4 nanorods of Comparative Example 1. In the figure, Mn3O4 completely corresponds to the Mn3O4 standard peak (JCPDS: 24-0734), and Pt completely corresponds to the Pt standard peak (JCPDS: 87-0640), which proves that the Pt-modified Mn3O4 composite material was successfully prepared and has good crystallinity.

[0082] (2) Figure 2 This is the curve of the response value of the Pt-modified Mn3O4 gas sensors provided in Examples 1-3 of the present invention and the Mn3O4 nanorods of Comparative Example 1 to 1000 ppm ethylene varying with temperature.

[0083] As can be seen from the figure, after Pt modification, the optimal operating temperature of the sensor is reduced from 360 °C to 180 °C, and the sensitivity (i.e., the response value) can reach up to 7.5 at most (the optimal operating temperature of 1 at.% Pt / Mn3O4 is 220 °C, and the sensitivity is 5.3; the optimal operating temperature of 5 at.% Pt / Mn3O4 is 180 °C, and the sensitivity is 5.2; the optimal operating temperature of the Mn3O4 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 the air, which is expressed as: S = R g / R a .

[0084] (3) Figure 3 This is the dynamic response and recovery curve of the Pt-modified Mn3O4 gas sensors provided in Examples 1-3 of the present invention and the Mn3O4 gas sensors of Comparative Example 1 to C2H4 gas with different concentrations (50-2000 ppm).

[0085] It can be seen from the figure that at all concentrations, the responses of the Pt-modified Mn3O4 composites of Examples 1-3 are higher than those of pure Mn3O4:

[0086] For 1 at.% Pt / Mn3O4 of Example 1, the R of ethylene at 50 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, and 2000 ppm at the optimal operating temperature g / R a are 1.34, 1.67, 2.49, 3.38, 4.33, 5.08, and 6.69 in sequence;

[0087] For 3 at.% Pt / Mn3O4 of Example 2, the R of ethylene at 50 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, and 2000 ppm at its optimal operating temperature (180 °C) g / R a are 1.56, 1.95, 2.94, 4.28, 5.45, 7.5, and 9.85 in sequence; the response time of 3 at.% Pt / Mn3O4 of Example 2 is 42 s, and the recovery time is 83 s.

[0088] For 5 at.% Pt / Mn3O4 of Example 3, the R of ethylene at 50 ppm, 100 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, and 2000 ppm at the optimal operating temperature g / R a are 1, 1.24, 1.6, 1.9, 2.26, 2.79, and 5.26 in sequence;

[0089] For the Mn3O4 nanorods of Comparative Example 1, the R of ethylene at 20 ppm, 50 ppm, 100 ppm, 300 ppm, 500 ppm, 1000 ppm, and 6000 ppm at its optimal operating temperature (360 °C) g / R a is 1.09, 1.2, 1.28, 1.42, 1.5, 1.71, and 1.86).

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

[0091] (4) Figure 4The Pt-modified Mn3O4 gas sensor provided in Embodiments 1-3 of the present invention and the Mn3O4 gas sensor of Comparative Example 1 were respectively introduced with 1000 ppm of methane, 500 ppm of CO, H2, CH4, methanol gas, triethylamine gas, 10 ppm of H2S, and NO2 at the optimal operating temperature to investigate the selectivity of the Pt-modified Mn3O4 gas sensor to ethylene. It can be seen from the figure that the Pt-modified Mn3O4 composite material prepared in the present invention has good selectivity to ethylene.

[0092] (5) Figure 5 Figure is the cyclic test result diagram of the Pt-modified Mn3O4 gas sensor provided in Embodiment 2 of the present invention and the Mn3O4 gas sensor of Comparative Example 1 for 1000 ppm of ethylene. Figure 5 It can be seen that the gas sensor of Pt-modified Mn3O4 has good repeatability for detecting ethylene.

[0093] In summary, the application of the Pt-modified Mn3O4 gas sensor of the present invention in ethylene sensors can improve the detection sensitivity of ethylene gas, reduce the operating temperature, reduce the cost, and ensure the stable operation of the device.

[0094] The gas sensing performance comparison of the Pt-modified Mn3O4 gas sensor of the present invention and the reported ethylene gas sensors is shown in Table 1 below.

[0095] Table 1 Gas sensing performance comparison table

[0096]

[0097] It can be seen from Table 1 that the Pt-modified Mn3O4 gas sensor of the present invention can significantly reduce the operating temperature and has good sensitivity.

[0098] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a Pt-modified Mn3O4 composite material, characterized in that, It includes the following steps: Step S1: Perform hydrothermal reaction on the first solution containing a manganese source. After the reaction, perform solid-liquid separation, 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 evenly to obtain a second solution; Step S3: Heat the second solution, add the C6H8O6 solution, and stir for reaction; after the reaction, perform solid-liquid separation, wash and dry to obtain the Pt-modified Mn3O4 composite material.

2. The preparation method of the Pt-modified Mn3O4 composite material according to claim 1, characterized in that, In step S1, the temperature of the hydrothermal reaction is 120 - 130 °C, and the reaction time is 10 - 12 h; In step S1, the temperature of the calcination is 650 - 700 °C, and the calcination time is 5 - 6 h; The calcination is carried out in an argon atmosphere.

3. The preparation method of the Pt-modified Mn3O4 composite material according to claim 1, characterized in that, In step S3, after heating the second solution to 40 - 70 °C, add the C6H8O6 solution, and stir for reaction 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; In step S3, the atomic molar ratio of Pt in H2PtCl6·6H2O to Mn is ≤5%.

4. The preparation method of the Pt-modified Mn3O4 composite material according to 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 preparation method of the Pt-modified Mn3O4 composite material according to claim 4, wherein 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 preparation method of the Pt-modified Mn3O4 composite material according to claim 1, wherein, 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 temperature of the drying is 50 - 70 °C, and the drying time is 8 - 10 h.

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

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

9. The preparation method of the gas sensitive element according to claim 8, characterized in that, It includes the following steps: Step 1: Mix the Pt-modified Mn3O4 composite material with a solvent, and grind to obtain a slurry; Step 2: Coat the slurry on the surface of a substrate, dry and age to obtain the gas sensor element; Preferably, the solvent in step 1 is at least one of distilled water, absolute ethanol, and terpineol; More preferably, the dosage ratio of the Pt-modified Mn3O4 composite material to the solvent is (10 - 50) mg:(0.1 - 1) mL.

10. Application of the Pt-modified Mn3O4 composite material described in claim 7 or the gas sensor element described in claim 8 in detecting ethylene.

Images