An NH3 gas sensor based on highly conductive bimetallic Co / Cu-HHTP sensitive material and its preparation method

Abstract

A NH3 gas sensor based on a highly conductive bimetallic Co / Cu‑HHTP sensitive material and a preparation method thereof belong to the technical field of gas sensors. It is a room temperature sensor that realizes the function of measuring the NH3 concentration by measuring the DC resistance between the gold interdigital electrodes in different atmospheres. It is composed of a polyimide substrate (called interdigital electrodes) with several interdigitated, strip-shaped, and alternately arranged gold electrodes on the surface, and a highly conductive bimetallic Co / Cu‑HHTP sensitive material coated on the polyimide substrate and the gold electrode surface. The NH3 gas sensor with high-performance bimetallic Co / Cu‑HHTP sensitive material developed by the present invention has a sensitivity increased by 13.3% compared to a single metal Cu‑HHTP sensor, a response time shortened from 796s to 352s, a flatter baseline of the recovery curve, a reduced drift from 14.1% to 7.8%, and good repeatability, and thus has good application prospects in monitoring NH3 gas in a room temperature environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and in particular relates to an NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensitive material and a preparation method thereof. Background Art

[0002] Gas sensors are devices that detect and measure gas concentrations in the environment. They are widely used in industry, healthcare, security, environmental protection, and other fields. In recent years, with the continuous development of IoT scenarios such as smart industry, smart homes, and environmental monitoring, the demand for gas sensors has increased significantly. NH3 is a recognized harmful gas that is directly corrosive to contact areas such as the skin, eyes, and respiratory tract. Excessive inhalation can cause pulmonary edema and lead to death. Therefore, the detection of ammonia is crucial. Chemiresistance gas sensors are widely used due to their advantages such as good selection, high sensitivity, and low cost. However, since most chemiresistance gas sensors operate at high temperatures during normal operation, they inevitably lead to energy consumption issues.

[0003] Driven by this demand and driven by the need to reduce power consumption, research is increasingly focused on gas sensors that can operate at room temperature. Metal-organic frameworks (MOFs) are composed of metal ions or ion clusters and organic ligands. Dozens of metal ions and ion clusters are combined with hundreds of organic ligands to form a diverse MOF family. MOFs have attracted widespread attention due to their advantages, such as large surface area, tunable porosity, and room-temperature operation. However, the insulating nature of most MOFs has limited their development. Recent studies have shown that two-dimensional MOFs composed of ligands such as HHTP (2,3,6,7,10,11-hexahydroxytriphenylene) and HITP (2,3,6,7,10,11-hexaiminotriphenylene) exhibit certain conductive properties. Due to their impressive conductivity and mobility, conductive two-dimensional MOFs hold great potential and are rapidly developing in fields such as electrochemistry, catalysis, and gas sensors. So far, given that the research on two-dimensional conductive HHTP-MOF in the field of gas sensors has been focused on single-metal MOFs such as M3(HHTP)2 (M=Co, Ni, Cu), the room-temperature NH3 sensor developed in the present invention based on the highly conductive bimetallic Co / Cu-HHTP modified by two-dimensional conductive Cu-HHTP is of great significance in various fields such as environmental detection. Summary of the Invention

[0004] The purpose of the present invention is to provide an NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensitive material and a preparation method thereof, wherein the highly conductive bimetallic Co / Cu-HHTP sensitive material has an extended planar two-dimensional structure.

[0005] The present invention discloses an NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensitive material. The sensor comprises a PI (polyimide) substrate with gold interdigital electrodes on its surface, and a highly conductive bimetallic Co / Cu-HHTP sensitive material coated on the PI substrate and the gold interdigital electrodes. The sensor operates at room temperature and does not require an additional DC heating element. The sensor measures NH3 concentration by measuring the DC resistance between the gold interdigital electrodes in different atmospheres. The highly conductive bimetallic Co / Cu-HHTP sensitive material is prepared by the following steps:

[0006] (1) 5–20 mg of Co(OAc)2·4H2O, 5–20 mg of Cu(OAc)2·H2O, and 10–20 mg of HHTP (2,3,6,7,10,11-hexahydroxytriphenylene) were dissolved in a solvent consisting of 0.5–1.5 mL of deionized water and 500–1000 μL of N-methylpyrrolidone, and ultrasonicated for 5–30 min to obtain a precursor solution.

[0007] (2) reacting the precursor solution obtained in step (1) at 60-100° C. for 8-24 hours to obtain a dark brown solution;

[0008] (3) The dark brown solution obtained in step (2) was first dissolved in deionized water and centrifuged and washed 2 to 4 times, then dissolved in methanol and centrifuged and washed 2 to 4 times, and then placed in air and dried naturally at room temperature to obtain a black powder product;

[0009] (4) Soaking the black powder product obtained in step (3) in acetonitrile for 12 to 72 hours, replacing the acetonitrile every 8 to 20 hours; then drying the soaked product under vacuum at 50 to 100° C. for 8 to 24 hours to obtain a highly conductive bimetallic Co / Cu-HHTP sensitive material.

[0010] The present invention provides a method for preparing an NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensitive material, comprising the following steps:

[0011] (1) Take 1-2 mg of Co / Cu-HHTP sensitive material and mix it evenly with 100-300 μL of isopropyl alcohol to form a slurry; use a pipette to take 5-10 μL of the slurry and drop it onto the PI substrate and the surface of the gold interdigital electrode to obtain a 15-30 μm thick sensitive material film; the number of interdigital electrodes is 10-20 pairs, the length of the interdigital electrodes is 5-10 mm, the width is 5-10 mm, and the finger spacing is 40-100 μm;

[0012] (2) The PI substrate coated with the sensitive material film is dried at 50-100°C under vacuum for 8-24 hours to obtain an NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material.

[0013] The working principle of the NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material described in the present invention is as follows:

[0014] (1) From a physical perspective, “hopping theory” and “band theory” can reflect the intrinsic charge transport properties of conductive MOFs;

[0015] (2) From the perspective of chemical design, the carrier transport channels for constructing conductive MOFs can be divided into two categories, namely, “through space” (constructing conductive MOFs through space is to construct charge transport pathways through non-covalent interactions (such as π-π stacking) between electrochemically active fragments, because the rigid MOF structure can force close stacking and form sufficient orbital overlap between adjacent ligands) and “through bonds” (constructing conductive MOFs through valence bonds is to promote charge transport through the appropriate space and high-energy orbital overlap generated by covalent bonding between metal centers and organic ligands to achieve the purpose of conductivity).

[0016] Since the highly conductive bimetallic Co / Cu-HHTP sensitive material has a honeycomb porous structure composed of AB stacking of extended hexagonal 2Dπ conjugated layers, the NH3 gas sensing mechanism of this sensitive material can be analyzed from the intralayer and interlayer perspectives:

[0017] (1) In-layer analysis: N in the NH3 molecule has a lone pair of electrons, Cu 2+ There is an empty orbital in the center that can accept electrons. The two contact and interact with each other to form a coordination bond, which changes the lattice structure of the crystal and changes the potential field in the crystal, thereby causing a change in the energy band structure. 2+ / Cu 2+ After the center interacts, the band gap widens, resulting in increased resistance and decreased conductivity;

[0018] (2) Interlayer analysis: Due to the force of the lone pair of electrons in the NH3 molecule, the original molecular structure is a planar square Co 2+ / Cu 2+ The center is bent to a certain extent, which leads to the increase of the gap between layers and the increase of material resistance. For different metal centers, due to the Co 2+ With Cu 2+Different radii and different bending degrees caused by the applied force will lead to different changes in the interlayer gap, resulting in enhanced sensitivity of the bimetallic Co / Cu-HHTP sensitive material to NH3 compared to the single metal Cu-HHTP sensitive material.

[0019] The change in material resistivity is converted into an electrical signal by the sensor and received by the measuring end, thereby achieving the purpose of detecting NH3. That is, the resistance meter in the electrochemical workstation measures the DC resistance Rg and Ra between the two poles of the interdigital electrodes of the sensor in different concentrations of NH3 gas and air atmosphere respectively during the working stage, and calculates the sensitivity of the sensor at different concentrations S = Rg / Ra, and then establishes the "NH3 concentration and sensitivity relationship curve", such as Figure 7 As shown; then the DC resistance between the two electrodes of the interdigital electrode in the working stage in the unknown concentration atmosphere is measured by a resistance measuring meter, and the sensor sensitivity value at the concentration is calculated by S=Rg / Ra, and the NH3 concentration is calculated by the "NH3 concentration and sensitivity relationship curve".

[0020] Advantages of the present invention:

[0021] (1) The present invention constructs a structural model of bimetallic Co / Cu-HHTP-MOF.

[0022] (2) The present invention studies the sensitization effect of NH3 on the sensor prepared by the highly conductive bimetallic Co / Cu-HHTP sensitive material with Co atom substitution.

[0023] (3) The highly conductive bimetallic Co / Cu-HHTP sensor obtained after metal ion replacement has a stronger adsorption effect on NH3. The gas sensing results show that the sensitivity of the highly conductive bimetallic Co / Cu-HHTP sensor is increased by 13.3% compared with the single metal Cu-HHTP sensor.

[0024] (4) The response time of the highly conductive bimetallic Co / Cu-HHTP sensor obtained after metal ion replacement was shortened from 796s to 352s.

[0025] (5) The developed sensor has good repeatability and a stable baseline.

[0026] (6) The NH3 gas sensor made of the highly conductive bimetallic Co / Cu-HHTP sensitive material produced by the present invention has a simple production process, simple preparation steps and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : Schematic diagram of the structure of the highly conductive bimetallic Co / Cu-HHTP sensitive material of the present invention.

[0028] Figure 2: The measured XRD curve and simulated characteristic peaks (Simulated) (a) of the Cu-HHTP sensitive material of the present invention, the XRD curve and simulated characteristic peaks (Simulated) (b) of the Co-HHTP sensitive material, and the XRD curve and simulated characteristic peaks (Simulated) (c) of the highly conductive bimetallic Co / Cu-HHTP sensitive material.

[0029] Figure 3 : SEM image (a) of the Cu-HHTP sensitive material of the present invention, SEM image (b) of the Co-HHTP sensitive material, and SEM image (c) of the highly conductive bimetallic Co / Cu-HHTP sensitive material.

[0030] Figure 4 : TEM-EDS image of the elements C1s (purple), O 1s (yellow), and Cu 2p (cyan) of the Cu-HHTP sensitive material of the present invention (a), TEM-EDS image of the elements C1s (purple), O 1s (yellow), and Co 2p (green) of the Co-HHTP sensitive material (b), and TEM-EDS image of the highly conductive bimetallic Co / Cu-HHTP sensitive material C1s (purple), O 1s (yellow), Co 2p (green), and Cu 2p (cyan) (c).

[0031] Figure 5 At room temperature, the interdigital electrode response value (R) of the NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material of the present invention is 100 ppm in the atmosphere of CO, ethanol, xylene, formaldehyde, acetone, benzene, and NH3. max and R min The resistance Ra in the air and the resistance Rg in the test gas are the larger and smaller values ​​in the resistance response test, respectively. max / R min ≥1, in order to more intuitively show the difference in selectivity, the response value is subtracted by 1, and the resulting response value |R max / R min |-1 fully represents the absolute change in response when the sensor enters the gas to be measured from air).

[0032] Figure 6: At room temperature, the NH3 gas sensor made of the Cu-HHTP sensitive material of the present invention is placed in a 100ppm NH3 atmosphere and then in an air atmosphere for one cycle, and the function curve (a) shows the change of the resistance between the interdigital electrodes of the NH3 gas sensor made of the two-dimensional Co-HHTP sensitive material of the present invention as a function of time during the cycle. The NH3 gas sensor based on the high-conductivity bimetallic two-dimensional Co / Cu-HHTP sensitive material of the present invention is placed in a 100ppm NH3 atmosphere and then in an air atmosphere for one cycle. The function curve (c) shows the change of the resistance between the interdigital electrodes of the NH3 gas sensor based on the high-conductivity bimetallic two-dimensional Co / Cu-HHTP sensitive material of the present invention as a function of time during the cycle.

[0033] Figure 7 : At room temperature, the NH3 gas sensor of the two-dimensional Cu-HHTP sensitive material of the present invention is a function curve of the NH3 gas concentration and the change of the resistance between the interdigital electrodes in a 1-100ppm NH3 atmosphere, and the 21 repeatability curves in a 100ppm NH3 atmosphere (Figure a and the illustration in Figure a), the NH3 gas sensor of the two-dimensional Co-HHTP sensitive material of the present invention is a function curve of the NH3 gas concentration and the change of the resistance between the interdigital electrodes in a 1-100ppm NH3 atmosphere, and the 21 repeatability curves in a 100ppm NH3 atmosphere (Figure b and the illustration in Figure b), the NH3 gas sensor of the two-dimensional Co / Cu-HHTP sensitive material of the present invention is a function curve of the NH3 gas concentration and the change of the resistance between the interdigital electrodes in a 1-100ppm NH3 atmosphere, and the 21 repeatability curves in a 100ppm NH3 atmosphere (Figure c and the illustration in Figure c).

[0034] like Figure 1 As shown, Figure 1 Schematic diagram of the synthesis of highly conductive bimetallic two-dimensional Co / Cu-HHTP sensitive material and the topological structure of the material. The sensitive material has a honeycomb porous structure composed of AB stacking of extended hexagonal 2Dπ conjugated layers.

[0035] like Figure 2 As shown, the XRD patterns of (a) conductive two-dimensional Cu-HHTP sensitive material, (b) conductive two-dimensional Co-HHTP sensitive material, and (c) highly conductive bimetallic two-dimensional Co / Cu-HHTP all show obvious characteristic peaks at 4.7°, 9.5°, 12.6°, and 28.0°, which are consistent with the simulated characteristic peaks, corresponding to the (1 0 0), (2 0 0), (2 1 0), and (0 0 2) planes, respectively.

[0036] like Figure 3As shown, the SEM images of (a) conductive two-dimensional Cu-HHTP sensitive material, (b) conductive two-dimensional Co-HHTP sensitive material, and (c) highly conductive bimetallic two-dimensional Co / Cu-HHTP show that the structure of the sensitive materials is hexagonal rod-shaped, and the cross-sectional width of the hexagonal rod is about 100 nm.

[0037] like Figure 4 As shown, (a) the TEM-EDS image of the conductive two-dimensional Cu-HHTP sensitive material shows that the material contains Cu, C, and O elements, and they are evenly distributed in the material; (b) the TEM-EDS image of the conductive two-dimensional Co-HHTP sensitive material shows that the material contains Co, C, and O elements, and they are evenly distributed in the material; (c) the TEM-EDS image of the highly conductive bimetallic two-dimensional Co / Cu-HHTP sensitive material shows that the material contains Co, Cu, C, and O elements, and they are evenly distributed in the material.

[0038] like Figure 5 As shown, the NH3 gas sensor based on the highly conductive bimetallic two-dimensional Co / Cu-HHTP sensitive material of the present invention has the highest sensitivity to NH3 and good selectivity.

[0039] like Figure 6 As shown, it can be seen that (a) when the environmental composition of the NH3 gas sensor made of conductive two-dimensional Cu-HHTP sensitive material changes from air to 100ppm NH3, the sensor resistance increases, the sensitivity S is 1.534 (S=Rg / Ra, Rg is the resistance between the interdigital electrodes in NH3 gas, Ra is the resistance between the interdigital electrodes in clean air), and the response time is 796s; (b) when the environmental composition of the NH3 gas sensor made of conductive two-dimensional Co-HHTP sensitive material changes from air to 100ppm NH3, the sensor resistance increases, the sensitivity S is 1.340, and the response time is 759s; (c) when the environmental composition of the NH3 gas sensor made of highly conductive bimetallic two-dimensional Co / Cu-HHTP sensitive material changes from air to 100ppm NH3, the sensor resistance increases, the sensitivity S is 1.738, and the response time is 352s.

[0040] like Figure 7 As shown, it can be seen that when the environmental component of the NH3 gas sensor of (a) the conductive two-dimensional Cu-HHTP sensitive material and (b) the conductive two-dimensional Co-HHTP sensitive material changes from air to NH3, as the concentration of the detection gas NH3 increases, the resistance change of the sensor becomes more obvious, that is, as the NH3 concentration increases, the sensitivity increases, the repeatability of the sensor is good, but the recovery curve has an obvious upward drift trend; when the environmental component of the NH3 gas sensor of (c) the highly conductive bimetallic two-dimensional Co / Cu-HHTP sensitive material changes from air to NH3, as the NH3 concentration increases, the sensitivity increases, the repeatability of the sensor is good, and the baseline of the recovery curve is stable. DETAILED DESCRIPTION

[0041] Comparative Example 1

[0042] The conductive two-dimensional Cu-HHTP is used as the sensitive material to make an NH3 gas sensor. The specific production process is as follows:

[0043] 1. First, dissolve 16 mg of Cu(OAc)2·H2O and 13 mg of HHTP (2,3,6,7,10,11-hexahydroxytriphenylene) in a mixture of 1 mL of deionized water and 1000 μL of N-methylpyrrolidone. The solvent was placed in a 10 mL glass vial and sonicated for 15 min to obtain a precursor solution.

[0044] 2. Place the above solution in an 85°C constant temperature oven and react for 12 hours to obtain a blue-black product solution;

[0045] 3. The blue-black solution obtained above was first dissolved in deionized water and centrifuged and washed twice, then dissolved in methanol and centrifuged and washed three times. After washing, the solution was placed in the air and dried naturally at room temperature to obtain a black powder product;

[0046] 4. The black powder product obtained in step 3 was soaked in acetonitrile for 48 hours, and the acetonitrile was replaced every 12 hours. The soaked product was then placed in a vacuum oven at 70°C for 12 hours to obtain a conductive two-dimensional Cu-HHTP sensitive material;

[0047] 5. Use tape to fix the four edges of a PI substrate with gold interdigital electrodes on its surface (the number of interdigital electrodes is 15, and their size is 10mm*10mm; the distance between two adjacent gold electrodes is 50μm). Stack them up to a height of 2000μm. Take 1.5mg of the conductive two-dimensional Cu-HHTP sensitive material and mix it evenly with 300μL of isopropyl alcohol to form a slurry. Use a pipette to take 10μL of this slurry and add it dropwise five times onto the surface of the interdigital electrodes fixed with tape to completely cover the gold electrodes, resulting in a sensitive material film about 30μm thick.

[0048] 6. The PI substrate coated with the sensitive material film was dried in a vacuum oven at 70°C for 12 hours to obtain an NH3 gas sensor based on the conductive two-dimensional Cu-HHTP sensitive material;

[0049] 7. Test the various gas-sensitive properties of the sensor to NH3 at room temperature.

[0050] Comparative Example 2:

[0051] The NH3 gas sensor is made using conductive two-dimensional Co-HHTP as the sensitive material. The specific production process is as follows:

[0052] 1. First, dissolve 18.8 mg of Co(OAc)2·4H2O and 16.2 mg of HHTP (2,3,6,7,10,11-hexahydroxytriphenylene) in a mixture of 1.35 mL of deionized water and 500 μL of N,N-dimethylformamide. Place the solvent in a 10 mL glass vial and sonicate for 15 min.

[0053] 2. Place the above solution in an 85°C constant temperature oven and react for 15 hours to obtain a yellow-brown product solution;

[0054] 3. The yellow-brown solution obtained above was first dissolved in deionized water and centrifuged and washed twice, then dissolved in methanol and centrifuged and washed three times. After washing, the solution was placed in air and dried naturally at room temperature to obtain a black powder product;

[0055] 4. The black powder product obtained in step 3 was soaked in acetonitrile for 48 hours, and the acetonitrile was replaced every 12 hours. The soaked product was then placed in a vacuum oven at 70°C for 12 hours to obtain a conductive two-dimensional Co-HHTP sensitive material;

[0056] 5. Use tape to fix the four sides of the PI substrate with gold interdigital electrodes on the surface (the number of interdigital electrodes is 15, and their size is 10mm*10mm; the distance between two adjacent gold electrodes is 50μm) and stack them up to a height of 2000μm. Take 1.5mg of the conductive two-dimensional Co-HHTP sensitive material and mix it evenly with 300μL of isopropyl alcohol to form a slurry. Use a pipette to take 10μL of this slurry and add it dropwise five times onto the surface of the interdigital electrodes fixed with tape to completely cover the gold electrodes, resulting in a sensitive material film about 30μm thick;

[0057] 6. The PI substrate coated with the sensitive material film was dried in a vacuum oven at 70°C for 12 hours to obtain an NH3 gas sensor based on the conductive two-dimensional Co-HHTP sensitive material;

[0058] 7. Test the various gas-sensitive properties of the sensor to NH3 at room temperature.

[0059] Example 1:

[0060] The NH3 gas sensor is made using highly conductive bimetallic Co / Cu-HHTP as the sensitive material. The specific production process is as follows:

[0061] 1. First, dissolve 9.98 mg of Co(OAc)2·H2O, 8 mg of Cu(OAc)2·H2O, and 13 mg of HHTP (2,3,6,7,10,11-hexahydroxytriphenylene) in a mixture of 1 mL of deionized water and 1000 μL of N,N-dimethylformamide. The solvent was placed in a 10 mL glass vial and sonicated for 15 min.

[0062] 2. Place the above solution in an 85°C constant temperature oven and react for 12 hours to obtain a dark brown product solution;

[0063] 3. The dark brown solution obtained above was first dissolved in deionized water and centrifuged and washed twice, then dissolved in methanol and centrifuged and washed three times. After washing, the solution was placed in air and dried naturally at room temperature to obtain a black powder product;

[0064] 4. The black powder product obtained in step 3 was soaked in acetonitrile for 48 hours, and the acetonitrile was replaced every 12 hours. The soaked product was then placed in a vacuum oven at 70°C for 12 hours to obtain a highly conductive bimetallic Co / Cu-HHTP sensitive material;

[0065] 5. Use tape to fix the four sides of the PI substrate with gold interdigital electrodes on the surface (the number of interdigital electrodes is 15, and their size is 10mm*10mm; the distance between two adjacent gold electrodes is 50μm) and stack them up to a height of 2000μm. Take 1.5mg of highly conductive bimetallic Co / Cu-HHTP sensitive material and mix it evenly with 300μL of isopropyl alcohol to form a slurry. Use a pipette to take 10μL of the slurry and add it dropwise five times onto the surface of the interdigital electrodes fixed with tape to completely cover the gold electrodes, resulting in a sensitive material film about 30μm thick;

[0066] 6. The PI substrate coated with the sensitive material film was dried in a vacuum oven at 70°C for 12 hours to obtain an NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material;

[0067] 7. Test the various gas-sensitive properties of the sensor to NH3 at room temperature.

[0068] Matters not covered by this invention are known in the art. The above embodiments are intended only to illustrate the technical concepts and features of this invention. Their purpose is to enable those skilled in the art to understand the contents of this invention and implement them accordingly. They are not intended to limit the scope of protection of this invention. Any equivalent changes or modifications made in accordance with the spirit and essence of this invention are intended to be covered by the scope of protection of this invention.

Claims

1. An NH3 gas sensor based on highly conductive bimetallic Co / Cu-HHTP sensitive material, characterized by: The method comprises a polyimide substrate with gold interdigital electrodes on the surface, and a highly conductive bimetallic Co / Cu-HHTP sensitive material film coated on the polyimide substrate and the surface of the gold interdigital electrodes; and the highly conductive bimetallic Co / Cu-HHTP sensitive material is prepared by the following steps: (1) 5-20 mg Co(OAc)2·4H2O, 5-20 mg Cu(OAc)2·H2O, and 10-20 mg HHTP were dissolved in a solvent consisting of 0.5-1.5 mL deionized water and 500-1000 μL N-methylpyrrolidone, and ultrasonicated for 5-30 min to obtain a precursor solution; HHTP is 2,3,6,7,10,11-hexahydroxytriphenylene; (2) reacting the precursor solution obtained in step (1) at 60-100° C. for 8-24 hours; (3) dissolving the solution obtained in step (2) in deionized water and washing it by centrifugation for 2 to 4 times, then dissolving it in methanol and washing it by centrifugation for 2 to 4 times, and then placing it in air and drying it naturally at room temperature to obtain a powder product; (4) Soaking the powder product obtained in step (3) in acetonitrile for 12 to 72 hours, replacing the acetonitrile every 8 to 20 hours; then drying the soaked product under vacuum at 50 to 100° C. for 8 to 24 hours to obtain a highly conductive bimetallic Co / Cu-HHTP sensitive material.

2. The NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material according to claim 1, characterized in that: The number of pairs of interdigital electrodes is 10 to 20, the length of the interdigital electrodes is 5 to 10 mm, the width is 5 to 10 mm, and the distance between the fingers is 40 to 100 μm.

3. The NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material according to claim 1, characterized in that: The thickness of the highly conductive bimetallic Co / Cu-HHTP sensitive material film is 15 to 30 μm.

4. A method for preparing an NH3 gas sensor based on a highly conductive bimetallic Co / Cu-HHTP sensitive material according to any one of claims 1 to 3, comprising the following steps: (1) Take 1-2 mg of Co / Cu-HHTP sensitive material and mix it evenly with 100-300 μL of isopropyl alcohol to form a slurry; use a pipette to take the slurry and drop it onto the surface of the polyimide substrate and the gold interdigitated electrode to obtain a sensitive material film; (2) The polyimide substrate coated with the sensitive material film is dried at 50-100°C under vacuum for 8-24 hours to obtain an NH3 gas sensor based on the highly conductive bimetallic Co / Cu-HHTP sensitive material.

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