Gas sensor based on Pt-supported NiFe2O4 gas sensitive material and preparation method of gas sensor

Abstract

The invention discloses a gas sensor based on a Pt-supported NiFe2O4 gas sensitive material and a preparation method of the gas sensor. The preparation method comprises the following steps: preparing Pt-supported NiFe2O4 powder by utilizing an ultrasonic spray pyrolysis method; uniformly mixing the Pt-supported NiFe2O4 powder with deionized water to form slurry, and uniformly coating a ceramic tube with the slurry to form a sensing film; the resistance wire is inserted into the ceramic tube, and the ceramic tube and the resistance wire are welded to the sensor base to form the gas sensor. According to the preparation method disclosed by the invention, the Pt-supported NiFe2O4 powder prepared by utilizing an ultrasonic spray pyrolysis method is low in cost and high in efficiency; the prepared gas sensor has good response and recovery characteristics to n-valeraldehyde gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and in particular relates to a gas sensor based on a Pt-loaded NiFe2O4 gas-sensitive material and a preparation method thereof. Background Art

[0002] At present, oxide semiconductor gas sensors are a technical means to detect gas based on concentration. They are widely used in indoor and industrial harmful gas detection due to their simple structure, high sensitivity, fast response speed and good stability. Chemical resistance gas sensors based on semiconductor oxides are also the most widely used material for gas sensing.

[0003] In recent years, some bimetallic oxides, such as ZnFe2O4, NiFe2O4, CoFe2O4 and MnFe2O4, have become gas sensing materials due to their defect effects and excellent catalytic activity. As a special cubic spinel material, NiFe2O4 consists of 32 oxygen atoms, including 8 tetrahedral sites and 16 octahedral sites. 2+ Existing in the octahedral site, Fe 3+ Existing in tetrahedral and octahedral sites, its advantages are high temperature resistance, high hardness, high strength and good thermal stability, which enables NiFe2O4 to effectively detect gases such as acetone, n-propanol, toluene and formaldehyde.

[0004] There are many methods for preparing NiFe2O4 gas-sensitive materials, such as chemical co-precipitation, anodized aluminum template, hydrothermal method, sol-gel method, solid phase method, hydrothermal method, ultrasonic spray pyrolysis method, etc. These methods can be used to prepare NiFe2O4 with various nanostructures, such as thin films, nanotubes, nanoparticles, nanorods, nanocubes, nanowires, etc.

[0005] However, existing NiFe2O4 sensors are rarely able to detect n-valeraldehyde gas, indicating that gas sensors are still immature in the field of n-valeraldehyde gas detection. NiFe2O4 gas sensors usually show unsatisfactory sensing characteristics in terms of their low-concentration gas response and high detection limit. Therefore, it is a problem that technicians in this field need to solve to prepare a NiFe2O4 gas sensor with simple process steps, low cost, good selectivity and strong recovery. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0007] The present invention provides a method for preparing a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material, comprising:

[0008] Pt-loaded NiFe2O4 powder was prepared by ultrasonic spray pyrolysis;

[0009] The Pt-loaded NiFe2O4 powder is uniformly mixed with deionized water to form a slurry, and the slurry is uniformly coated on a ceramic tube to form a sensing membrane;

[0010] The gas sensor is formed by inserting a resistance wire into the ceramic tube and welding the ceramic tube and the resistance wire to a sensor base.

[0011] In one embodiment of the present invention, the Pt-supported NiFe2O4 powder is prepared by ultrasonic spray pyrolysis, comprising:

[0012] Add a predetermined amount of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O to deionized water until they are completely dissolved, then add a predetermined amount of sodium dodecyl sulfate and perform ultrasonic treatment to completely dissolve the sodium dodecyl sulfate to obtain a precursor solution;

[0013] Adding a predetermined amount of H2PtCl6·6H2O to the precursor solution to form a mixed solution, then pouring the mixed solution into an ultrasonic sprayer, and sending the spray formed by the mixed solution into a quartz tube at 570-625° C. with nitrogen as a carrier gas for chemical vapor deposition to form a precursor powder;

[0014] The precursor powder is collected in a conical flask filled with deionized water, the precursor powder in the conical flask is centrifuged and dried, and then annealed to obtain Pt-loaded NiFe2O4 powder.

[0015] In one embodiment of the present invention, the molar ratio of the Ni(NO3)2·6H2O, the Fe(NO3)3·9H2O and the sodium dodecyl sulfate is 1:(1.98-2.05):0.15.

[0016] In one embodiment of the present invention, the molar ratio of the H2PtCl6·6H2O to the Ni(NO3)2·6H2O is (0.0298-0.0302):1.

[0017] In one embodiment of the present invention, the Pt-loaded NiFe2O4 powder has a morphology of nanospheres with a size of 300nm to 600nm, wherein Pt exists in the form of PtO2 nanoparticles.

[0018] In one embodiment of the present invention, the Pt-supported NiFe2O4 powder is uniformly mixed with deionized water to form a slurry, and the slurry is uniformly coated on a ceramic tube to form a sensing membrane, comprising:

[0019] The Pt-loaded NiFe2O4 powder is uniformly mixed with deionized water to obtain a slurry, the slurry is uniformly coated on a ceramic tube to form a sensing membrane, and the ceramic tube coated with the sensing membrane is calcined in a muffle furnace at 300-400° C. for a predetermined time so that the sensing membrane is firmly attached to the ceramic tube.

[0020] In one embodiment of the present invention, the resistance wire is a Ni-Cr alloy coil.

[0021] In one embodiment of the present invention, after inserting the resistance wire into the ceramic tube and welding the ceramic tube and the resistance wire to the sensor base to form the gas sensor, the method further comprises:

[0022] The resistance wire in the prepared gas sensor is connected to a current of 450-550 mA for aging treatment to make the electrical signal of the gas sensor more stable.

[0023] Another aspect of the present invention provides a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material, which is prepared using the preparation method described in any one of the above embodiments. The gas sensor comprises a Pt-supported NiFe2O4 gas-sensitive material, a ceramic tube, a resistance wire and a sensor base, wherein:

[0024] The Pt-loaded NiFe2O4 gas-sensitive material is coated on the ceramic tube, the resistance wire is inserted into the ceramic tube, and the ceramic tube is welded to the sensor base.

[0025] In one embodiment of the present invention, the optimal operating temperature of the gas sensor is 275-285°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention provides a method for preparing a gas sensor based on Pt-loaded NiFe2O4 gas-sensitive material. The preparation method uses Pt-loaded NiFe2O4 powder prepared by ultrasonic spray pyrolysis, which has low cost and high efficiency.

[0028] 2. The gas sensor based on Pt-loaded NiFe2O4 gas-sensitive material prepared by the present invention has an optimal operating temperature of 280°C, a morning response value of 21.12 to 100 ppm n-valeraldehyde gas, and response recovery times of 6s and 11s, respectively, showing good response and recovery characteristics for n-valeraldehyde gas.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a method for preparing a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention;

[0031] Figure 2 This is an X-ray diffraction (XRD) diagram of a Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention;

[0032] Figure 3 This is a scanning electron microscope (SEM) image of a Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention;

[0033] Figure 4 This is a transmission electron microscope (TEM) image of a Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention;

[0034] Figure 5 The gas sensor based on Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention has response values ​​to 100 ppm of n-valeraldehyde, nonanal, octanal, decanal and formaldehyde at different temperatures;

[0035] Figure 6 This is a response recovery curve of a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention to 100 ppm of n-valeraldehyde at 260°C;

[0036] Figure 7 The present invention provides a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention, and the gas sensor has a concentration gradient response curve of 1ppm, 3ppm, 5ppm, 10ppm, 20ppm, 40ppm, 60ppm, 80ppm and 100ppm of n-valeraldehyde at 280°C;

[0037] Figure 8 A gas sensor based on Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention shows: (a) 10-time repeated response recovery curve; (b) 60-day long-term stability. DETAILED DESCRIPTION

[0038] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of a gas sensor based on Pt-loaded NiFe2O4 gas-sensitive material and a preparation method thereof proposed in accordance with the present invention, in combination with the accompanying drawings and specific implementation methods.

[0039] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0040] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the statement "including one..." do not exclude the existence of other identical elements in the article or device including the elements.

[0041] Embodiment 1

[0042] This embodiment provides a method for preparing a gas sensor based on Pt-loaded NiFe2O4 gas-sensitive material. The prepared gas sensor consists of Pt-loaded NiFe2O4 gas-sensitive material, a ceramic tube, a resistance wire and a sensor base, wherein the Pt-loaded NiFe2O4 gas-sensitive material is coated on the surface of the ceramic tube.

[0043] like Figure 1 As shown, the preparation method of the gas sensor includes:

[0044] S1: Preparation of Pt-loaded NiFe2O4 gas-sensitive material.

[0045] Specifically, a predetermined amount of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O are added to deionized water until they are completely dissolved, and then a predetermined amount of sodium dodecyl sulfate is added and ultrasonic treatment is performed to completely dissolve the sodium dodecyl sulfate to obtain a precursor solution; a predetermined amount of H2PtCl6·6H2O is respectively added to the precursor solution to form a mixed solution, and then the mixed solution is poured into an ultrasonic sprayer, and the spray formed by the mixed solution is sent into a quartz tube at 570-625°C with nitrogen as a carrier gas for chemical vapor deposition to form a precursor powder; the precursor powder is collected in a conical flask filled with deionized water, the precursor powder in the conical flask is centrifuged and dried, and then annealed to obtain Pt-loaded NiFe2O4 powder, that is, Pt-loaded NiFe2O4 powder.

[0046] In this embodiment, the molar ratio of Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and sodium dodecyl sulfate is 1:(1.98-2.05):0.15, preferably 1:2:0.15.

[0047] H2PtCl6·6H2O is a dopant, and the molar ratio of H2PtCl6·6H2O to Ni(NO3)2·6H2O is (0.0298-0.0302):1, preferably 3%. For example, when the required molar number of Ni(NO3)2·6H2O is 2mmol, the required molar number of H2PtCl6·6H2O is 2×3%=0.062mmol.

[0048] The Pt-loaded NiFe2O4 powder prepared in this step has the morphology of nanospheres with a size of 300nm to 600nm, in which Pt exists in the form of oxidized (PtO2) nanoparticles. Figure 2 , Figure 2 This is an X-ray diffraction (XRD) diagram of a Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention. It can be seen that the successful synthesis of NiFe2O4 meets the diffraction peaks in the standard card, indicating that the synthesized material has good crystallinity. Figure 3 and Figure 4 , Figure 3 and Figure 4 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of a Pt-supported NiFe2O4 gas-sensitive material provided in an embodiment of the present invention are shown respectively. The microscopic morphology of NiFe2O4 can be seen from the SEM image, and the (311) and (111) crystal planes of NiFe2O4 can be seen from the TEM image, which are consistent with the diffraction peaks in XRD, successfully proving the synthesis of NiFe2O4.

[0049] S2: Pt-loaded NiFe2O4 powder is uniformly mixed with deionized water to form a slurry, and the slurry is uniformly coated on a ceramic tube to form a sensing membrane.

[0050] Specifically, the Pt-loaded NiFe2O4 powder is mixed with deionized water to obtain a uniform slurry, the slurry is uniformly coated on a ceramic tube to form a sensing membrane, and the coated ceramic tube is calcined in a muffle furnace at 300-400° C. for 2 h (the heating rate of the muffle furnace is 1° C. / min) so that the sensing membrane is more firmly attached to the ceramic tube. The ceramic tube of this embodiment can be an alumina ceramic tube.

[0051] S3: Insert the resistance wire into the ceramic tube and weld the ceramic tube and the resistance wire to the sensor base to form a gas sensor.

[0052] The resistance wire used in this embodiment is a Ni-Cr alloy coil. Specifically, the Ni-Cr alloy coil is inserted into an alumina ceramic tube coated with a sensing film, and the alumina ceramic tube and the Ni-Cr alloy coil are welded to the sensor base to form a gas sensor. Finally, the prepared gas sensor is aged for 3 days at a current of 500mA, that is, the resistance wire is connected to a current of 450-550mA and aged for 3 days to make the electrical signal of the prepared gas sensor more stable. Preferably, the connected current is 500mA.

[0053] Another embodiment of the present invention also provides a gas sensor based on Pt-loaded NiFe2O4 gas-sensitive material, the gas sensor comprising Pt-loaded NiFe2O4 gas-sensitive material, a ceramic tube, a resistance wire and a sensor base, wherein the Pt-loaded NiFe2O4 gas-sensitive material is coated on the ceramic tube, the resistance wire is inserted into the ceramic tube, and the ceramic tube is welded to the sensor base. The optimal operating temperature of the gas sensor is 275-285°C, preferably 280°C.

[0054] The gas sensor based on the Pt-supported NiFe2O4 gas-sensitive material of the present invention is a resistive semiconductor gas sensor, and its working principle is as follows:

[0055] The resistive semiconductor gas sensor mainly uses the change in resistance of oxide semiconductors when they come into contact with gas to detect gas. NiFe2O4 is a typical p-type semiconductor metal oxide, and holes are the main carriers. The change in sensor resistance is the main mechanism of sensing. During the use of the gas sensor, the gas sensor is placed in the environment of the gas to be detected, and the resistance wire is connected to a current of 500mA. The oxygen molecules adsorbed from the air on the surface of the NiFe2O4 gas-sensitive material on the ceramic tube will combine with free electrons to form O2 - and O - , the loss of electrons leads to an increase in holes in the p-type semiconductor, thereby reducing the resistance of the gas sensor. Subsequently, when the gas sensor is exposed to the environment of the gas to be detected, such as n-valeraldehyde gas, the chemically adsorbed oxygen will react with the gas molecules and release electrons back to the conduction band, thereby increasing the resistance of the gas sensor. Secondly, the Pt nanoparticles exist in the form of an oxidized state (PtO2), which expands the depletion layer on NiFe2O4, thereby increasing the conductivity. The overflow catalytic effect of Pt and the Schottky barrier formed at the interface between the Pt nanoparticles and the NiFe2O4 nanoparticles can also increase the gas-sensitive response.

[0056] Embodiment 2

[0057] On the basis of Example 1, this example provides a detailed preparation method of a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material, the preparation method comprising:

[0058] Step 1: Prepare Pt-loaded NiFe2O4 powder using ultrasonic spray pyrolysis.

[0059] In this embodiment, Pt-loaded NiFe2O4 powder was prepared by ultrasonic spray pyrolysis. First, 0.58 g (2 mmol) of Ni(NO3)2·6H2O and 1.62 g (4 mmol) of Fe(NO3)3·9H2O were added to 50 mL of deionized water until they were completely dissolved, and then 0.09 g of sodium dodecyl sulfate (SDS) was added to adjust the material structure. The mixed solution was ultrasonically treated with an ultrasonic power of 240 W to 260 W and an ultrasonic time of 3 minutes to completely dissolve the SDS and obtain a precursor solution. Among them, the main function of SDS is a surfactant, which is used to adjust the morphology of the material.

[0060] Subsequently, 1230 μL of H2PtCl6·6H2O was added to the precursor solution to form a mixed solution, that is, the molar ratio of H2PtCl6·6H2O to Ni(NO3)2·6H2O was 3%. Subsequently, the mixed solution was poured into an ultrasonic sprayer, and the spray formed by the mixed solution was sent into a quartz tube at 600° C. with nitrogen as a carrier gas (the carrier gas flow rate was 500 mL / min) for chemical vapor deposition to form a precursor powder.

[0061] Next, the precursor powder is collected in a conical flask filled with deionized water, the precursor powder precipitated in the conical flask is first centrifuged once with deionized water, and then centrifuged once with ethanol, the resulting product is dried at 60°C for 2 days, and calcined in a 500°C muffle furnace for 2 hours to obtain Pt-loaded NiFe2O4 powder, wherein the heating rate of the muffle furnace is 2°C / min. In other words, the product after centrifugal drying is placed in a muffle furnace, and the muffle furnace is heated to 500°C at a heating rate of 2°C / min and maintained for 2 hours to obtain Pt-loaded NiFe2O4 powder. The morphology of the Pt-loaded NiFe2O4 powder prepared in this step is nanospheres with a size of 300nm to 600nm.

[0062] Step 2: Evenly mix the Pt-loaded NiFe2O4 powder and deionized water to form a slurry, and evenly coat the slurry on the ceramic tube to form a sensing membrane.

[0063] First, the Pt-loaded NiFe2O4 powder prepared in step 1 is uniformly mixed with deionized water to obtain a slurry, and the slurry is uniformly coated on an alumina ceramic tube to form a sensing film, and the ceramic tube coated with the sensing film is calcined in a muffle furnace at 350°C for 2h (the heating rate of the muffle furnace is 1°C / min) so that the sensing film is more firmly attached to the ceramic tube. In other words, the ceramic tube coated with the sensing film is placed in a muffle furnace, and the muffle furnace is heated to 350°C at a heating rate of 1°C / min and maintained for 2h, so that the sensing film is more firmly attached to the ceramic tube.

[0064] Step 3: Insert the resistance wire into the ceramic tube and weld the ceramic tube to the sensor base to form a gas sensor.

[0065] Specifically, the Ni-Cr alloy coil was inserted into the alumina ceramic tube, the temperature of the sensor was controlled by current, and the alumina ceramic tube was welded to the sensor base to form a gas sensor based on Pt-loaded NiFe2O4 gas-sensitive material. Finally, the prepared gas sensor was aged for 3 days at a current of 500 mA to make the performance of the gas sensor more stable.

[0066] The performance of the gas sensor based on the Pt-supported NiFe2O4 gas-sensitive material prepared in this embodiment is further described below through experiments. It should be noted that the gas sensors used in the following experiments are all the gas sensors prepared in Embodiment 2.

[0067] See also Figure 5 , Figure 5 The following are the response values ​​of a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention to 100 ppm of n-valeraldehyde, nonanal, octanal, decanal, and formaldehyde at different temperatures, wherein the horizontal axis is the operating temperature and the vertical axis is the response value. By comparison, it can be seen that at an operating temperature of 280°C, the sensor has the highest response to n-valeraldehyde. The responses of all gases first increase and then decrease with the increase of the operating temperature. The optimal operating temperature is 280°C.

[0068] See also Figure 6 , Figure 6 This is a response recovery curve of a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention to 100 ppm n-valeraldehyde at 260°C, wherein the horizontal axis is time and the vertical axis is resistance. It can be seen that when in the air, the resistance of the gas sensor remains stable. When it comes into contact with the target gas, the resistance rises sharply and gradually reaches the maximum value. As the gas is released, the resistance gradually returns to the initial value. It can be seen that the response recovery time of the sensor is 6s and 11s respectively.

[0069] See also Figure 7 , Figure 7 The following is a concentration gradient response curve of a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention to 1ppm, 3ppm, 5ppm, 10ppm, 20ppm, 40ppm, 60ppm, 80ppm and 100ppm of n-valeraldehyde at 280°C. It can be seen that the gas sensor has good linearity within a certain range, and as the gas concentration gradually increases, the sensor response continues to increase, and each concentration has good response and recovery characteristics.

[0070] See also Figure 8 , Figure 8 The following are (a) 10 repeated response recovery curves and (b) 60-day long-term stability of a gas sensor based on a Pt-supported NiFe2O4 gas-sensitive material provided by an embodiment of the present invention. It can be seen that the gas sensor has good repeatability and long-term stability. The sensor maintains good response and recovery characteristics in 10 consecutive measurements. In the test for 60 consecutive days, the decrease in response remains within a certain range.

[0071] The preparation method of the embodiment of the present invention adopts ultrasonic spray pyrolysis to obtain Pt-supported NiFe2O4 nanoparticles. The method is simple and inexpensive, and is a Pt-supported NiFe2O4 preparation scheme with low investment and simple process flow. The gas sensor based on Pt-supported NiFe2O4 gas-sensitive material prepared by the present invention has an optimal operating temperature of 280°C, a response value of 21.12 to 100ppm of n-valeraldehyde gas, and a response recovery time of 6s and 11s, respectively, and has good response and recovery characteristics for n-valeraldehyde gas.

[0072] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material, characterized in that: include: Pt-loaded NiFe2O4 powder was prepared by ultrasonic spray pyrolysis; The Pt-loaded NiFe2O4 powder is uniformly mixed with deionized water to form a slurry, and the slurry is uniformly coated on a ceramic tube to form a sensing membrane; The gas sensor is formed by inserting a resistance wire into the ceramic tube and welding the ceramic tube and the resistance wire to a sensor base.

2. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 1, characterized in that: The method comprises the following steps: preparing Pt-supported NiFe2O4 powder by ultrasonic spray pyrolysis method; Add a predetermined amount of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O to deionized water until they are completely dissolved, then add a predetermined amount of sodium dodecyl sulfate and perform ultrasonic treatment to completely dissolve the sodium dodecyl sulfate to obtain a precursor solution; Adding a predetermined amount of H2PtCl6·6H2O to the precursor solution to form a mixed solution, then pouring the mixed solution into an ultrasonic sprayer, and sending the spray formed by the mixed solution into a quartz tube at 570-625° C. with nitrogen as a carrier gas for chemical vapor deposition to form a precursor powder; The precursor powder is collected in a conical flask filled with deionized water, the precursor powder in the conical flask is centrifuged and dried, and then annealed to obtain Pt-loaded NiFe2O4 powder.

3. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 2, characterized in that: The molar ratio of the Ni(NO3)2·6H2O, the Fe(NO3)3·9H2O and the sodium dodecyl sulfate is 1:(1.98-2.05):0.

15.

4. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 2, characterized in that: The molar ratio of the H2PtCl6·6H2O to the Ni(NO3)2·6H2O is (0.0298-0.0302):

1.

5. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 1, characterized in that: The Pt-loaded NiFe2O4 powder has a morphology of nanospheres with a size of 300nm to 600nm, wherein Pt exists in the form of PtO2 nanoparticles.

6. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 2, characterized in that: The Pt-supported NiFe2O4 powder is uniformly mixed with deionized water to form a slurry, and the slurry is uniformly coated on a ceramic tube to form a sensing membrane, comprising: The Pt-loaded NiFe2O4 powder is uniformly mixed with deionized water to obtain a slurry, the slurry is uniformly coated on a ceramic tube to form a sensing membrane, and the ceramic tube coated with the sensing membrane is calcined in a muffle furnace at 300-400° C. for a predetermined time so that the sensing membrane is firmly attached to the ceramic tube.

7. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 1, characterized in that: The resistance wire is a Ni-Cr alloy coil.

8. The method for preparing a gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 1, characterized in that: After the resistance wire is inserted into the ceramic tube and the ceramic tube and the resistance wire are welded to the sensor base to form the gas sensor, the method further includes: The resistance wire in the prepared gas sensor is connected to a current of 450-550 mA for aging treatment to make the electrical signal of the gas sensor more stable.

9. A gas sensor based on Pt-supported NiFe2O4 gas-sensitive material, characterized in that: The gas sensor is prepared by the preparation method according to any one of claims 1 to 8, wherein the gas sensor comprises a Pt-supported NiFe2O4 gas-sensitive material, a ceramic tube, a resistance wire and a sensor base, wherein: The Pt-loaded NiFe2O4 gas-sensitive material is coated on the ceramic tube, the resistance wire is inserted into the ceramic tube, and the ceramic tube is welded to the sensor base.

10. The gas sensor based on Pt-supported NiFe2O4 gas-sensitive material according to claim 9, characterized in that: The optimal operating temperature of the gas sensor is 275-285°C.

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