Room-temperature ammonia gas sensor based on multi-heterojunction gas-sensitive material and preparation method of room-temperature ammonia gas sensor

Abstract

The invention discloses a room-temperature ammonia gas sensor based on a multi-heterojunction gas-sensitive material and a preparation method of the room-temperature ammonia gas sensor, and belongs to the technical field of gas sensors. The room temperature ammonia gas sensor comprises a multi-heterojunction gas sensitive material which comprises a triple heterojunction of Ti3C2Tx-TiO2, a triple heterojunction of TiO2-ZnTiO3 and a triple heterojunction of ZnTiO3-ZnO, and the room temperature ammonia gas sensor is prepared by taking Ti3C2Tx as a substrate and adopting an in-situ growth method. The room-temperature ammonia gas sensor disclosed by the invention has the advantages of high sensitivity, short response / recovery time, strong selectivity, good stability and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and in particular relates to a room temperature ammonia sensor based on a multiple heterojunction gas-sensitive material and a preparation method thereof. Background Art

[0002] The continuous development of science and technology and the significant improvement of productivity have brought great convenience to human society. However, the consumption of chemical products and the resulting pollutants have led to increasingly serious environmental pollution. Air pollution poses a huge threat to human health. It is urgent to monitor and prevent toxic and harmful gases in the air. Ammonia, as a toxic and harmful gas, not only pollutes the environment, but also has significant harm to human health. Long-term exposure to high concentrations of ammonia may cause respiratory diseases and damage the ecological environment. Therefore, it is particularly important to develop a gas sensor that can efficiently and sensitively detect ammonia at room temperature. Traditional gas detection methods include gas chromatography, spectrophotometry, liquid chromatography, and ion mobility spectrometry. These methods have the advantages of high detection accuracy and good stability, but usually require complex equipment and high operational expertise, which makes it difficult to promote them on a large scale.

[0003] In recent years, metal oxide semiconductor gas sensors have become the focus of scientific researchers due to their low cost and easy operation. Among them, ZnO and TiO2 have been considered to be extremely promising gas-sensitive materials in gas sensors due to their high carrier mobility, stable chemical and thermal properties, and low cost. In addition, TiO2 and ZnO can diffuse into each other to form a binary oxide ZnTiO3, which has a lower work function and excellent gas sensing performance. In addition, a heterojunction is formed at the interface of oxides with different work functions, further improving the gas-sensitive performance of the sensor. However, ZnO, TiO2, and ZnTiO3 compounds are typical n-type semiconductors with wide band gaps and require large activation energy when used as gas-sensitive materials. The commonly used methods at present are to use operating temperature (200-500℃) or ultraviolet light irradiation, but high operating temperature and additional ultraviolet light irradiation will cause high energy consumption and the risk of igniting flammable gases, which greatly limits the application of metal oxide semiconductor gas sensors. It is crucial to develop gas-sensitive materials that can work at room temperature.

[0004] Ti3C2T xIt is a two-dimensional transition metal carbide (MXene) with the characteristics of large specific surface area, metallic conductivity and adjustable surface chemical properties. Its almost free electronic state can provide an ideal electron transport channel for fast and low-loss carrier transfer, making it an ideal candidate for room-temperature gas sensing. When gas molecules are exposed to the surface of the MXene layered structure, charge transfer occurs, thereby regulating the overall conductivity of the sensing layer. In general, oxidizing gases will take electrons from MXenes, while most volatile organic compounds will donate electrons to MXenes. However, single MXenes gas-sensitive materials have low sensitivity, slow response recovery speed and poor stability, which cannot meet the needs of practical applications. Therefore, based on the high gas-sensing performance of multi-heterojunction metal oxides and the room-temperature gas response characteristics of MXenes, the development of new composite gas-sensitive materials based on multi-heterojunction metal oxides and MXenes has become an effective way to construct high-performance room-temperature gas-sensitive materials. In this context, based on Ti3C2T x The new ammonia sensor made of a composite material of aluminum and metal oxide can respond quickly to ammonia gas at room temperature, showing significant application prospects. Summary of the invention

[0005] In view of the above technical problems, the main purpose of the present invention is to provide a multi-heterojunction gas-sensitive material, which has the advantages of high sensitivity, short response / recovery time, strong selectivity and good stability. x Loading multiple heterojunction metal oxide structures has the following functions:

[0006] (1) Substrate Ti3C2T x It provides an ideal channel for electron transport and can achieve rapid carrier migration at room temperature.

[0007] (2) The loaded multiple heterojunction metal oxides provide abundant carriers and enhance the chemical and thermal stability of the material.

[0008] (3) The multiple heterojunctions formed at the interface can effectively generate Schottky barriers, promote the efficient separation of charge carriers, and further enhance the transfer efficiency of space charges through the built-in electric field.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned multiple heterojunction gas-sensitive material, which is simple to operate and the process is easy to control.

[0010] Another object of the present invention is to provide the use of the above-mentioned multiple heterojunction gas-sensitive material in the preparation of a room temperature ammonia sensor, which has the properties of high sensitivity, short response / recovery time, strong selectivity and good stability.

[0011] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0012] The present invention provides a multi-heterojunction gas-sensitive material, which is based on Ti3C2T x As a substrate, it contains Ti3C2T x -TiO2, TiO2-ZnTiO3 and ZnTiO3-ZnO triple heterojunctions.

[0013] The present invention also provides a method for preparing the multiple heterojunction gas-sensitive material, which is prepared by an in-situ growth method and comprises the following steps:

[0014] Step 1: Ti3C2T with a mass ratio of 10:1 to 1:5 x and Zn(NO3)2·6H2O are added to the solvent, mixed evenly, heated to 30-100°C under the condition of water / oil bath, and the solvent in the mixture is evaporated to obtain Zn(NO3)2 / Ti3C2T x Precursor;

[0015] Step 2: Under an inert atmosphere of nitrogen, the Zn(NO3)2 / Ti3C2T x The precursor is heated to 100-1000° C. at a heating rate of 1-20° C. / min, maintained at the temperature for 1-5 hours, and then cooled to room temperature to obtain the product.

[0016] Preferably, in step 1, the solvent is selected from one or a combination of two or more of deionized water, anhydrous ethanol, methanol, and diethyl ether.

[0017] Preferably, in step 1, Ti3C2T x The mass ratio of Zn(NO3)2·6H2O is 1:1.

[0018] Preferably, in step 2, the Zn(NO3)2 / Ti3C2T x The precursor was heated to 300 °C at a heating rate of 10 °C / min and kept at this temperature for 2 h.

[0019] The multi-heterojunction gas-sensitive material can be used to prepare a room temperature ammonia sensor. First, the electrode sheet is welded to the substrate. By using appropriate conductive materials for electrode welding, it is ensured that the connection between the electrode and the substrate is stable and the electrical contact is good. Then, the prepared Ti3C2T x Multiple heterojunction gas-sensitive materials are evenly coated on the electrode sheet to ensure that the gas-sensitive material layer is evenly distributed and in good contact with the electrode. After the gas-sensitive material coating is completed, the sensor is packaged.

[0020] The present invention also provides application of the multiple heterojunction gas-sensitive material in preparing a room temperature ammonia sensor.

[0021] The present invention also provides a room temperature ammonia sensor, which comprises the multiple heterojunction gas-sensitive material.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In the multi-heterojunction gas-sensitive material of the present invention, the multi-heterojunction ZnO / ZnTiO3 / TiO2 is loaded on Ti3C2T x On the substrate, its use in room temperature ammonia sensor has the advantages of high sensitivity, short response / recovery time, strong selectivity and good stability.

[0024] 2. The present invention adopts an in-situ growth method to prepare multiple heterojunction gas-sensitive materials, which is simple to operate, easy to control the process, has a high yield, and is highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 For ZnO / ZnTiO3 / TiO2@Ti3C2T in Example 1 x X-ray diffraction spectrum of multiple heterojunction gas-sensitive materials.

[0026] Figure 2 For ZnO / ZnTiO3 / TiO2@Ti3C2T in Example 1 x Scanning electron microscope image of multiple heterojunction gas-sensitive materials.

[0027] Figure 3 For ZnO / ZnTiO3 / TiO2@Ti3C2T in Example 1 x Transmission electron microscope image of multiple heterojunction gas-sensitive materials.

[0028] Figure 4 For ZnO / ZnTiO3 / TiO2@Ti3C2T in Example 2 x Response radar diagram of multiple heterojunction gas-sensitive materials to 500ppm of different gases.

[0029] Figure 5 For ZnO / ZnTiO3 / TiO2@Ti3C2T in Example 2 x Response recovery curve of multiple heterojunction gas-sensitive materials to 100 ppm ammonia.

[0030] Figure 6 Fe2O3 / FeTiO3 / TiO2@Ti3C2T in Example 3 x Scanning electron microscope image of multiple heterojunction gas-sensitive materials. DETAILED DESCRIPTION

[0031] In order to more fully understand and demonstrate the technical solutions, purposes and advantages of the present invention, the technical effects produced by the present invention are further described in detail and completely in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all. It should be pointed out that for ordinary technicians in this field, other embodiments obtained without departing from the concept of the present invention all belong to the protection scope of the present invention.

[0032] Example 1

[0033] In this example, ZnO / ZnTiO3 / TiO2@Ti3C2T was prepared x Multiple heterojunction gas-sensitive materials, the steps are as follows:

[0034] Step 1: 0.12g Ti3C2T x and 0.12 g Zn(NO3)2·6H2O were added to 25 mL deionized water and ultrasonically mixed. The solvent in the mixture was slowly evaporated under heating at 30 °C water bath to obtain Zn(NO3)2 / Ti3C2T x Precursor.

[0035] Step 2: Take the Zn(NO3)2 / Ti3C2T obtained in the first step x The precursor was placed in a tube furnace and carbonized under a nitrogen atmosphere. The temperature was raised to 300°C at a heating rate of 10°C / min and maintained at this temperature for 2 hours, then cooled to room temperature to obtain the product.

[0036] ZnO / ZnTiO3 / TiO2@Ti3C2T prepared in Example 1 x Multi-heterojunction gas-sensitive materials performance Figure 1-3 As shown. It can be seen that the material presents obvious ZnO, ZnTiO3, TiO2 and Ti3C2T x The diffraction peaks ( Figure 1 ), and in Ti3C2T x The surface and interlayer regions are densely covered with a large number of nanoparticles ( Figure 2 ), high-resolution transmission electron microscopy images show that the nanoparticles are multiple heterojunctions of ZnO / ZnTiO3 / TiO2 ( Figure 3 ).

[0037] Example 2

[0038] ZnO / ZnTiO3 / TiO2@Ti3C2T prepared in Example 1 xAfter the multiple heterojunction gas-sensitive materials are ground with an agate mortar, they are added to 10 mL of anhydrous ethanol and ultrasonically vibrated for 10 minutes to form a uniformly dispersed dispersion. Use a pipette to measure 5 μL of the dispersion, apply it on the cleaned ceramic tube electrode, and place it in a 30°C drying oven to dry. After drying, connect the entire gas-sensitive element to the CGS-8 gas-sensitive test analyzer, power on the prepared gas-sensitive element, and age it at 100°C for 12 hours to make the resistance of the gas-sensitive material reach a relatively stable state. Place the aged gas-sensitive element in the sealed chamber of the gas-sensitive test analyzer, pass current, and record the resistance value R of the gas-sensitive element at this time. a Then inject a certain concentration of ammonia, acetone, xylene, formaldehyde, acetaldehyde, and isopropionaldehyde into the sealed chamber, and record the resistance value R of the gas sensor after injecting the gas. g , using the formula S = R a / R g ×100% to calculate the sensitivity of the gas sensor.

[0039] Figure 4 For the preparation of ZnO / ZnTiO3 / TiO2@Ti3C2T x When the multi-heterojunction gas-sensitive material is used as a room temperature gas-sensitive material, the response values ​​to different gases at 500ppm show that the material has high sensitivity to ammonia and good selectivity; Figure 5 This is the response recovery curve of the material to 100 ppm gas. The response and recovery times are 44 s and 83 s, respectively.

[0040] Example 3

[0041] In this example, Fe2O3 / FeTiO3 / TiO2@Ti3C2T was prepared by in-situ growth method. x Multiple heterojunction gas-sensitive materials, as follows:

[0042] Step 1: 0.12g Ti3C2T x and 0.12 g Fe(NO3)3·6H2O were added to 25 mL deionized water and ultrasonically mixed. The solvent in the mixture was slowly evaporated under heating at 30 °C water bath to obtain Fe(NO3)3 / Ti3C2T x Precursor.

[0043] Step 2: Take the Fe(NO3)3 / Ti3C2T obtained in the first step x The precursor was placed in a tube furnace and carbonized under a nitrogen atmosphere. The temperature was raised to 300°C at a heating rate of 10°C / min and maintained at this temperature for 2 hours, then cooled to room temperature to obtain the product.

[0044] Figure 6Fe2O3 / FeTiO3 / TiO2@Ti3C2T x Scanning electron microscope image of multiple heterojunction gas-sensitive materials shows that the multilayer Ti3C2T x The surface of the ZnO / ZnTiO3 / TiO2@Ti3C2T prepared in Example 1 has nano-thorns growing uniformly. x The methods used for multiple heterojunctions are similar, which proves that the method for in-situ growth preparation of multiple heterojunction gas-sensitive materials proposed in the present invention is universal.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-heterojunction gas-sensitive material, characterized in that: Ti3C2T x As a substrate, it contains Ti3C2T x -TiO2, TiO2-ZnTiO3 and ZnTiO3-ZnO triple heterojunctions.

2. The method for preparing the multiple heterojunction gas-sensitive material according to claim 1, characterized in that: The in-situ growth method is used for preparation, including the following steps: Step 1: Ti3C2T with a mass ratio of 10:1 to 1:5 x and Zn(NO3)2·6H2O are added to the solvent, mixed evenly, heated to 30-100°C under the condition of water / oil bath, and the solvent in the mixture is evaporated to obtain Zn(NO3)2 / Ti3C2T x Precursor; Step 2: Under an inert atmosphere of nitrogen, the Zn(NO3)2 / Ti3C2T x The precursor is heated to 100-1000° C. at a heating rate of 1-20° C. / min, maintained at the temperature for 1-5 hours, and then cooled to room temperature to obtain the product.

3. The method for preparing the multiple heterojunction gas-sensitive material according to claim 2, characterized in that: In step 1, the solvent is selected from one or a combination of two or more of deionized water, anhydrous ethanol, methanol, and ether.

4. The method for preparing the multiple heterojunction gas-sensitive material according to claim 2, characterized in that: In step 1, Ti3C2T x The mass ratio of Zn(NO3)2·6H2O is 1:

1.

5. The method for preparing the multiple heterojunction gas-sensitive material according to claim 2, characterized in that: In step 2, the Zn(NO3)2 / Ti3C2T x The precursor was heated to 300 °C at a heating rate of 10 °C / min and kept at this temperature for 2 h.

6. Use of the multiple heterojunction gas-sensitive material according to claim 1 in preparing a room temperature ammonia sensor.

7. A room temperature ammonia sensor, characterized in that: It comprises the multiple heterojunction gas-sensitive material as claimed in claim 1.

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