Mesoporous nano material as well as preparation method and application thereof

Abstract

The invention discloses a mesoporous nano material as well as a preparation method and application thereof. The mesoporous nano material is composed of semiconductor metal oxide stannic oxide nano particles. The material has a unique mesoporous structure and a large specific surface area, the sensor shows good linear response to hydrogen with different concentrations, the actual hydrogen detection is very simple and convenient, in addition, the sensor still shows a high response value to hydrogen as low as 25ppb, has stable physicochemical properties, and has a good application prospect in multiple cycle tests and long-term tests. Stable response can still be kept, and excellent stability is shown.

Description

Technical Field

[0001] This application relates to a mesoporous nanomaterial, its preparation method, and its application, belonging to the field of sensors. Background Technology

[0002] Energy shortages and the greenhouse effect caused by increased consumption of non-renewable energy sources such as fossil fuels are intractable problems facing humanity in the 21st century. Hydrogen, with its high energy density, environmental friendliness, and wide availability, is considered the most promising clean energy source to replace conventional energy. Currently, hydrogen is widely used in hydrogen fuel cell vehicles, hydrogen power generation, industrial ammonia synthesis, methanol and other chemicals, as well as as fuel in the aerospace industry. A global hydrogen energy industry chain has been formed, encompassing hydrogen production, storage, transportation, use, and recycling. However, as a colorless, odorless, flammable, and explosive gas, hydrogen must be stored and used under high pressure and low temperature. Hydrogen leaks are extremely dangerous. Therefore, real-time monitoring of hydrogen is essential and crucial.

[0003] Over the past few decades, metal-oxide-semiconductor (MOS) gas sensors have been widely used in gas detection due to their advantages such as low cost, small size, and ease of manufacture. The working principle of MOS gas sensors is based on the change in conductivity caused by the interaction between oxygen and the target gas on the surface of the MOS material. Tin dioxide, as a typical n-type semiconductor, is well-suited for gas sensing applications due to its wide bandgap, excellent electrical properties, and good stability, and has been widely used in these applications. Therefore, tin dioxide has the potential to achieve high-performance hydrogen detection. However, tin dioxide commonly used for hydrogen sensing has many drawbacks, including low sensitivity, unsatisfactory selectivity, and high detection limits. Developing a high-performance hydrogen sensor based on tin dioxide is a significant challenge and an urgent need. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a high-performance hydrogen sensor that can generate a high response to hydrogen, detect even hydrogen at extremely low concentrations, and possesses advantages such as good selectivity, cycleability, and stability.

[0005] According to one aspect of this application, a mesoporous nanomaterial is provided, said mesoporous nanomaterial being composed of semiconductor metal oxide tin dioxide nanoparticles;

[0006] The diameter of the semiconductor metal oxide tin dioxide nanoparticles is 100-300 nm;

[0007] The pore size of the mesoporous nanomaterial is 3–300 nm;

[0008] The specific surface area of ​​the mesoporous nanomaterial is 5–200 m². 2 / g.

[0009] According to another aspect of this application, a method for preparing the above-mentioned mesoporous nanomaterial is provided, comprising the following steps:

[0010] The tin source was mixed evenly with water, a template agent was added, and the mixture was stirred. Then, an alkali was added, and the mixture was stirred, reacted, washed, centrifuged, dried, and calcined to obtain the mesoporous nanomaterial.

[0011] The tin source is selected from at least one of stannous chloride, stannous sulfate, and stannous tetrachloride;

[0012] The template agent is selected from at least one of polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, hexadecyltrimethylammonium bromide, and polyethylene glycol;

[0013] The molecular weight of the template agent is 10,000 to 2,000,000;

[0014] The alkali is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, and ammonia water;

[0015] The concentration of the sodium hydroxide solution is 0.01–2 mol / L;

[0016] The concentration of the potassium hydroxide solution is 0.01–2 mol / L;

[0017] The concentration of the ammonia water is 20% to 28%;

[0018] The ratio of tin source to water is (1-10):(10-3000);

[0019] The ratio of the template agent to the tin source is (1-10):(0.1-100);

[0020] During the mixing process, stirring is maintained at a speed of 400–700 rpm;

[0021] The drying temperature is 40–80°C;

[0022] The drying time is 3–48 hours;

[0023] The calcination temperature is 300–800°C;

[0024] The calcination time is 0.5 to 10 hours;

[0025] The heating rate during calcination is 0.5–10 °C / min.

[0026] The washing solution is water and ethanol.

[0027] According to another aspect of this application, a sensing membrane is provided, which is composed of the above-described mesoporous nanomaterial.

[0028] According to another aspect of this application, a hydrogen sensor is provided, comprising the aforementioned sensing membrane.

[0029] The hydrogen sensor operates at a temperature of 100–300°C.

[0030] Optionally, the hydrogen sensor operates at a temperature of 160–240°C.

[0031] The hydrogen sensor consists of a sensing membrane, a heating wire, a ceramic tube with electrodes, and an insulating substrate. The ceramic tube is fixed on the substrate, and the sensing membrane is uniformly covered on the ceramic tube. The heating wire passes through the ceramic tube to heat the sensing membrane.

[0032] This application uses a membrane made of mesoporous tin dioxide nanomaterials as the sensing element. The mesoporous tin dioxide nanomaterials are uniformly coated on a ceramic substrate with electrodes and a heating wire to prepare a resistive thin-film hydrogen sensor. The concentration of hydrogen is analyzed by measuring the resistance value of the mesoporous tin dioxide nanomaterial sensing membrane in air and hydrogen.

[0033] Mesoporous tin dioxide nanomaterials possess a unique mesoporous structure due to their composition of numerous nanoparticles, resulting in a high specific surface area. This unique mesoporous structure and high specific surface area provide transport channels and numerous active sites for hydrogen sensing, significantly enhancing the hydrogen sensing performance.

[0034] The beneficial effects that this application can produce include:

[0035] 1. The prepared mesoporous tin dioxide nanomaterial has a unique mesoporous structure with a maximum average pore size of 23.9 nm. Hydrogen has a larger mean free path than other gases. The unique mesoporous structure makes hydrogen more easily transported through mesopores than other gases. Therefore, the sensor has excellent selectivity for hydrogen.

[0036] 2. The prepared mesoporous tin dioxide nanomaterial is composed of many nanoparticles, which gives the mesoporous tin dioxide a large specific surface area and exposes more active sites, thereby adsorbing more active oxygen and hydrogen to participate in the sensing reaction, greatly enhancing the sensing performance. At the optimal operating temperature, it has a response value of about 41 to 10 ppm hydrogen.

[0037] 3. The sensor of the present invention exhibits good linear response to different concentrations of hydrogen, making it very convenient for actual hydrogen detection. In addition, the sensor of the present invention still shows a high response value for hydrogen as low as 25 ppb, indicating that the sensor of the present invention has an extremely low hydrogen detection limit.

[0038] 4. The prepared mesoporous tin dioxide nanomaterials have stable physicochemical properties. In multiple cyclic tests and long-term tests, the mesoporous tin dioxide sensor of the present invention can still maintain a stable response, showing excellent stability. Attached Figure Description

[0039] Figure 1 This is a scanning electron microscope image of the mesoporous tin dioxide nanomaterials prepared in Example 1, with a scale of 200 nm.

[0040] Figure 2 This is a transmission electron microscope (TEM) image of the mesoporous tin dioxide nanomaterials prepared in Example 1, with a scale of 50 nm.

[0041] Figure 3 These are the adsorption and desorption curves of nitrogen physisorption on the mesoporous tin dioxide nanomaterials prepared in Example 1.

[0042] Figure 4 This is the pore size distribution of the mesoporous tin dioxide nanomaterial prepared in Example 1.

[0043] Figure 5 The hydrogen sensor based on the mesoporous tin dioxide nanomaterial sensing membrane prepared in Example 1 responds to 10 ppm hydrogen at different operating temperatures.

[0044] Figure 6 The hydrogen sensor based on the mesoporous tin dioxide nanomaterial sensing membrane prepared in Example 1 responds to different concentrations of hydrogen at an operating temperature of 200°C.

[0045] Figure 7 The response curve of the hydrogen sensor using the mesoporous tin dioxide nanomaterial sensing membrane prepared in Example 1 to 25 ppb hydrogen at an operating temperature of 200°C is shown.

[0046] Figure 8 The gas selectivity of the hydrogen sensor is based on the mesoporous tin dioxide nanomaterial sensing membrane prepared in Example 1.

[0047] Figure 9 The cyclic response performance of the hydrogen sensor based on the mesoporous tin dioxide nanomaterial sensing membrane prepared in Example 1 is shown.

[0048] Figure 10 The long-term stability of the hydrogen sensor using the mesoporous tin dioxide nanomaterial sensing membrane prepared in Example 1 is demonstrated. Detailed Implementation

[0049] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0050] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0051] Example 1

[0052] Preparation of mesoporous tin dioxide nanomaterial sensing membrane:

[0053] Includes the following steps:

[0054] Add 100 mL of deionized water to a beaker, then add 0.45 g of stannous chloride dihydrate, followed by 0.2 g of polyvinylpyrrolidone. Continue stirring for 1 hour. The molecular weight of polyvinylpyrrolidone is 1.3 million.

[0055] After stirring for 1 hour, 25 mL of freshly prepared 0.1 mol / L sodium hydroxide solution was added dropwise to the above solution, and stirring was continued for another hour to obtain a precipitate. The precipitate was washed with deionized water and ethanol, centrifuged, and then dried at 60 °C. The dried precipitate was calcined at 550 °C for 4 hours at a heating rate of 2 °C / min to obtain mesoporous tin dioxide nanomaterials.

[0056] like Figure 1 As shown, the mesoporous tin dioxide nanomaterial is composed of many nanoparticles with a diameter between 100 and 300 nm.

[0057] Figure 2 These are transmission electron microscope images of mesoporous tin dioxide nanomaterials, which reveal numerous pores between the mesoporous tin dioxide nanoparticles.

[0058] Nitrogen physical adsorption tests were performed on mesoporous tin dioxide nanomaterials, such as... Figure 3 As shown, the mesoporous tin dioxide nanomaterials exhibit a typical Type IV curve with a distinct H1 hysteresis loop, indicating that the material possesses a significant mesoporous structure. The specific surface area of ​​the mesoporous tin dioxide nanomaterials is 23.64 m². 2 / g.

[0059] like Figure 4 As shown, the maximum average pore size of the mesoporous tin dioxide nanomaterial is 23.9 nm.

[0060] Construction of a hydrogen sensor:

[0061] A hydrogen sensor comprises a sensing membrane, a heating wire, a ceramic tube with electrode pairs, and an insulating substrate. The sensing membrane is the same as described in Example 1.

[0062] The mesoporous tin dioxide nanomaterial described in Example 1 was uniformly drop-coated onto the surface of a ceramic tube to form a sensing film. The prepared sensor was then aged at 200°C for more than 3 days to obtain a high-performance hydrogen sensor based on mesoporous tin dioxide nanomaterial.

[0063] Performance testing of hydrogen sensor:

[0064] A digital multimeter is used to measure the change in resistance of the sensor in air and the gas atmosphere to be measured. This change is used as the sensor signal. The sensor response value is defined as: S = Ra / Rg, where Ra and Rg are the resistance values ​​of the sensor in air and the gas atmosphere to be measured, respectively.

[0065] The response values ​​of the hydrogen sensor to 10 ppm hydrogen at different operating temperatures are as follows: Figure 5 As shown, for comparison, the response values ​​of a commercial tin dioxide-based hydrogen sensor to 10 ppm hydrogen at different operating temperatures are also similar. Figure 5 As shown, at an operating temperature of 200°C, the hydrogen sensor exhibits a response value as high as 41 for 10 ppm hydrogen, significantly higher than the 9.5 response value of commercial tin dioxide hydrogen sensors at 200°C for 10 ppm hydrogen, and also significantly higher than the highest response value of 14.6 exhibited by commercial tin dioxide hydrogen sensors at 300°C for 10 ppm hydrogen. This indicates that the hydrogen sensor not only exhibits an extremely high response value to hydrogen but also significantly reduces the sensor's operating temperature; 200°C is the optimal operating temperature for the mesoporous tin dioxide hydrogen sensor.

[0066] The response curves of the hydrogen sensor to different concentrations of hydrogen at an operating temperature of 200℃ are shown below. Figure 6 As shown in the figure, it can be seen that this hydrogen sensor has a very good linear response to hydrogen.

[0067] The hydrogen sensor, operating at 200°C, responds as follows to hydrogen concentrations as low as 25 ppb: Figure 7 As shown, even when the hydrogen concentration is as low as 25 ppb, the hydrogen sensor still exhibits a stable response value of around 2, indicating that the hydrogen sensor has an extremely low detection limit.

[0068] The hydrogen sensor, operating at 200°C, responds to hydrogen and other interfering gases as follows: Figure 8 As shown, the hydrogen sensor exhibits a high response value only to hydrogen, while showing a very low response to other gases, indicating that the hydrogen sensor has excellent selectivity for hydrogen.

[0069] The hydrogen sensor exhibits the following cycling performance at an operating temperature of 200℃: Figure 9 As shown, the hydrogen sensor maintains a stable response to hydrogen during multiple cycles, indicating that the hydrogen sensor has good cycle stability.

[0070] The long-term stability of the hydrogen sensor is as follows: Figure 10As shown, even after 60 days, the response value of the hydrogen sensor to 10 ppm hydrogen still remains at around 40, without a significant decrease compared to the initial response value, indicating that the hydrogen sensor has good long-term stability.

[0071] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A mesoporous nanomaterial, characterized in that, The mesoporous nanomaterial is composed of semiconductor metal oxide tin dioxide nanoparticles; The diameter of the semiconductor metal oxide tin dioxide nanoparticles is 100-300 nm; The pore size of the mesoporous nanomaterial is 3–300 nm; The specific surface area of ​​the mesoporous nanomaterial is 5–200 m². 2 / g.

2. A method for preparing the mesoporous nanomaterial according to claim 1, characterized in that, Includes the following steps: The tin source was mixed with water, a template agent was added, then an alkali was added, the mixture was reacted, washed, centrifuged, dried, and calcined to obtain the mesoporous nanomaterial.

3. The preparation method according to claim 2, characterized in that, The tin source is selected from at least one of stannous chloride, stannous sulfate, and stannous tetrachloride; The template agent is selected from at least one of polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, hexadecyltrimethylammonium bromide, and polyethylene glycol; The molecular weight of the template agent is 10,000 to 2,000,000; The alkali is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

4. The preparation method according to claim 2, characterized in that, The ratio of tin source to water is (1-10):(10-3000); The ratio of the template agent to the tin source is (1-10):(0.1-100).

5. The preparation method according to claim 2, characterized in that, During the mixing process, stirring is maintained at a speed of 400–700 rpm; The drying temperature is 40–80°C; The drying time is 3–48 hours; The calcination temperature is 300–800°C; The calcination time is 0.5 to 10 hours; The heating rate during calcination is 0.5–10 °C / min.

6. A sensing membrane, characterized in that, It is composed of the mesoporous nanomaterials described in claim 1.

7. A hydrogen sensor, characterized in that, It contains the sensing membrane as described in claim 6.

8. The hydrogen sensor according to claim 7, characterized in that, The hydrogen sensor operates at a temperature of 100–300°C.

9. The hydrogen sensor according to claim 7, characterized in that, The hydrogen sensor operates at a temperature of 160–240°C.

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