Composite gas sensor with enhanced uv activation after vacuum annealing and method of manufacture

Abstract

The present application relates to the technical field of gas sensor, in particular to a kind of composite gas sensor and preparation method of ultraviolet activation enhancement after vacuum annealing, comprising the following steps: step 1, the preparation of sensitive material;Step 2, the preparation of gas sensitive element;Step 3, setting light source;Step 4, performance test;Step 5, data analysis.The present application can preferably improve the sensitivity and selectivity of gas detection, especially for the detection of carbon dioxide gas.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, and more specifically, to a composite gas sensor enhanced by ultraviolet activation after vacuum annealing and its preparation method. Background Technology

[0002] With increasing global attention to climate change and environmental issues, monitoring carbon dioxide (CO2) emissions has become particularly important. CO2 sensors, as a key technology for monitoring air quality, are widely used in environmental protection, medicine, agriculture, industry, and other fields. In the research field of CO2 sensors, researchers worldwide have developed various high-precision detection technologies, including colorimetric fluorescence, surface plasmon resonance (SPR), surface acoustic wave (SAW), and microcantilever beam sensors. Colorimetric fluorescence sensors, based on the principle of light absorption and emission, exhibit extremely high sensitivity to minute changes in refractive index; however, they have shortcomings in gas selectivity, reliability, and anti-pollution capabilities, limiting their application in a wider range of environments. SPR sensors have attracted attention due to their extremely low detection limits and label-free detection, but challenges in gas selectivity and multi-platform compatibility limit their application in large-scale studies. SAW and microcantilever beam CO2 sensors demonstrate exceptional detection limits, but there is a lack of sufficient research and reporting on key parameters such as gas selectivity, stability, and response / recovery time. Furthermore, nondispersive infrared spectroscopy (NDIR) utilizes the unique optical fingerprint of CO2 gas, making it well-suited for detecting low concentrations of CO2. However, it may encounter cross-sensitivity issues in the presence of interfering gases. Electrochemical methods offer good gas selectivity and stability, but their deployment in wider applications is limited by complex component configurations, high operating temperatures, and high operating costs. Chemielectric resistance, as a cost-effective and easily miniaturized technique, operates on the principle of a reversible carbonization reaction, achieved through charge transfer between metal oxides and chemically adsorbed CO2 molecules.

[0003] The current technical solution is the ultraviolet differential absorption spectroscopy sensor (UV-DOAS), which is a sensor that uses ultraviolet light absorption spectroscopy to analyze gas composition. While UV-DOAS has many advantages, it also has some drawbacks and limitations:

[0004] (1) Spectral overlap problem: When detecting multiple gases, the absorption spectra of the gases may overlap, which makes it difficult to accurately distinguish the concentrations of different gases. This spectral overlap is a major challenge for UV-DOAS technology, especially in complex gas mixtures.

[0005] (2) Noise interference: Due to the limitation of short optical path, the measurement process may be affected by noise, which will reduce the accuracy of concentration inversion. Noise interference may lead to unstable and inaccurate measurement results.

[0006] (3) Light source lifespan: The lifespan of an ultraviolet light source is limited and it usually needs to be replaced periodically to maintain the accuracy and stability of the sensor. This increases maintenance costs and operational complexity.

[0007] (4) Environmental dependence: The performance of UV-DOAS sensors may be affected by environmental conditions (such as temperature, humidity, etc.), which may lead to fluctuations in measurement results.

[0008] (5) Cost issues: Although UV-DOAS sensors have performance advantages, their initial investment and maintenance costs are relatively high, which may limit their widespread use in some applications.

[0009] (6) Response time: Although the response time of the UV-DOAS sensor is relatively fast, it may still be slower than other types of sensors in some cases, which may be a disadvantage in applications that require real-time monitoring. Summary of the Invention

[0010] The present invention provides a composite gas sensor enhanced by vacuum annealing and ultraviolet activation, and its preparation method, which can overcome the shortcomings of existing sensors in terms of anti-interference ability, lifespan, limitations and cost.

[0011] The method for preparing a composite gas sensor enhanced by vacuum annealing and UV activation according to the present invention includes the following steps:

[0012] Step 1: Preparation of sensitive materials;

[0013] Step 2: Preparation of the gas-sensitive element;

[0014] Step 3: Set the light source;

[0015] Step 4: Performance Testing;

[0016] Step 5: Data Analysis.

[0017] As a preferred option, step 1 specifically includes:

[0018] 1.1) Dissolve La(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O and citric acid in a molar ratio of 1:0.8:0.2 in deionized water and stir with a magnetic stirrer until the chemical reagents are completely dissolved.

[0019] 1.2) The well-mixed solution was transferred to a reaction vessel and reacted at 180°C for 9 hours. After naturally cooling to room temperature, the precipitate generated by the reaction was collected, washed with anhydrous ethanol to obtain the LFCO precursor precipitate, and dried at 60°C for 3 hours to remove water and organic matter.

[0020] 1.3) The dried precipitate was calcined in a tube furnace at 600℃ for 2 hours to obtain sample LFCO. Sample LFCO was dissolved in deionized water, and nanoparticles of Zn(NO3)2·6H2O and Co(NH2) with a molar ratio of 1:1 were added to it. The mixture was stirred thoroughly using a magnetic stirrer.

[0021] 1.4) Transfer the thoroughly mixed solution back to the reactor and react at 150°C for 10 h. Repeat the above steps to obtain a dried precipitate, and then place it in a tube furnace and calcine at 500°C for 3 h to obtain the LFCO-ZNO composite material.

[0022] Preferably, in step 1.1), the certain proportion is: (La) 3+ +Fe 3+ +Co 2+ ):(citric acid) = 1:2.

[0023] Preferably, in step 1.3), the sample LFCO is dissolved in deionized water with a solution concentration of 1 mmol / L and 60 ml of deionized water.

[0024] As a preferred option, step 2 specifically involves:

[0025] 2.1) In an agate mortar, add an appropriate amount of LFCO-ZNO powder, propolis and glass fiber, then add terpineol and grind until a uniform and fine slurry is formed;

[0026] 2.2) Spray the slurry evenly onto the surface of the ceramic tube to form a dense coating;

[0027] 2.3) The ceramic tube coated with LFCO-ZNO composite material was placed in a muffle furnace and sintered at a constant temperature of 200℃ for 2 hours to achieve densification of the ceramic tube and complete the sensor D. LFCO-ZNO The production;

[0028] 2.4) Insert the nickel-chromium alloy heating wire into the ceramic tube and weld it to the base;

[0029] 2.5) After 24 hours of aging treatment, the fabrication of the side-heated sintered sensor is completed.

[0030] Preferably, in step 2.1), the ratio of LFCO-ZNO powder, propolis, glass fiber and terpineol is 10:1:1:2.

[0031] Preferably, in step 3, a low-power ultraviolet light-emitting diode is used as the excitation source during the gas-sensitive element test to form a photoexcited gas sensor.

[0032] Preferably, in step 4, the gas-sensing performance of the gas-sensitive element is obtained by testing with an intelligent gas sensing and analysis system. First, turn on the intelligent gas sensing and analysis system, place the device in the test chamber in a certain order, turn on the ultraviolet lamp for irradiation, and set a certain temperature, ranging from 20℃ to 200℃. Inject a certain amount of the gas to be tested into the test chamber, and release the gas after the resistance of the device stabilizes.

[0033] As a preferred option, in step 5, the experimental data is analyzed to evaluate the impact of ultraviolet light excitation on the performance of the gas sensor and to determine the optimal operating conditions.

[0034] This invention provides a composite gas sensor enhanced by vacuum annealing and ultraviolet activation, which is prepared using the above-described method for preparing a composite gas sensor enhanced by vacuum annealing and ultraviolet activation.

[0035] The sensor of the present invention has the following advantages:

[0036] A) High sensitivity, selectivity, and fast response:

[0037] By employing vacuum annealing and ultraviolet (UV) excitation techniques, the detection sensitivity and selectivity for specific gases, such as carbon dioxide, can be improved. Vacuum annealing alters the electronic structure of the material surface, increasing adsorption sites by removing impurities and defects, thereby optimizing electron transfer characteristics. UV excitation provides high-energy photons that excite electrons on the material surface, increasing their activity and thus improving the sensor's response speed and sensitivity to gas molecules.

[0038] B) Low-temperature operation:

[0039] Traditional metal-oxide-semiconductor (MOS) chemical resistance sensors require heating to high temperatures (above 200°C) to achieve sensing functionality. However, this sensor, through material design and photoexcitation technology, can operate at high performance at 100°C, reducing energy consumption and improving safety.

[0040] C) Strong anti-interference capability:

[0041] By optimizing sensor materials and design, cross-sensitivity to other gases can be reduced, and selectivity to the target gas (carbon dioxide) can be improved.

[0042] D) Low cost and easy integration:

[0043] This sensor is designed with cost-effectiveness and ease of integration into existing systems in mind.

[0044] E) High stability and repeatability:

[0045] This sensor was designed with long-term stability and repeatability in mind, which is crucial to ensuring that the sensor can provide reliable data under different environmental conditions.

[0046] F) Multi-domain applications:

[0047] The technological advantages of the new sensor make it a promising candidate for applications in various fields such as environmental monitoring, industrial production, and biomedicine, especially in greenhouse gas monitoring and energy conservation and emission reduction.

[0048] In summary, the technological advantages of developing this novel gas sensor are mainly concentrated in improved sensitivity, selectivity, reduced operating temperature, rapid response, interference resistance, cost-effectiveness, and broad application potential. These advancements contribute to the efficient monitoring of key gases such as carbon dioxide, which is of great significance for environmental protection and industrial safety. Attached Figure Description

[0049] Figure 1 This is a flowchart illustrating a method for preparing a composite gas sensor enhanced by vacuum annealing followed by UV activation, as described in this embodiment.

[0050] Figure 2 This is a schematic diagram of the X-ray diffraction pattern of LFCO-ZnO in the example;

[0051] Figure 3 The images shown are SEM and EDS images of LFCO-ZnO in the examples.

[0052] Figure 4 The image shows the experimental test results of the LFCO-ZNO nanosensor under ultraviolet light irradiation in the example.

[0053] Figure 5 The figure shows the resistance curve of the LFCO-ZNO nanosensor as a function of temperature and the corresponding activation energy in the example.

[0054] Figure 6 Device D in the embodiment LFCO-ZNO Schematic diagram of the response to 500ppm CO2 gas as a function of operating temperature;

[0055] Figure 7 This is a schematic diagram of the dynamic response of the LFCO-ZNO nanosensor to 500ppm CO2 in the example. Detailed Implementation

[0056] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0057] Example

[0058] like Figure 1 As shown, this embodiment provides a method for preparing a composite gas sensor enhanced by ultraviolet activation after vacuum annealing. The experimental objective is:

[0059] A novel vacuum annealing and photoexcitation composite gas sensor was developed, which utilizes vacuum annealing and ultraviolet light excitation to improve the sensitivity and selectivity of gas detection, and achieves high-sensitivity detection of carbon dioxide gas.

[0060] Experimental materials and instruments:

[0061] Experimental reagents: Lanthanum nitrate (La(NO3)3·6H2O), ferric nitrate (Fe(NO3)3·9H2O), cobalt nitrate (Co(NO3)3·6H2O), citric acid (C6H8O7), zinc nitrate (Zn(NO3)2·6H2O), urea (Co(NH2)), terpineol (C 10 H 18 O), propolis, and fiberglass.

[0062] Tube furnace (vacuum annealing).

[0063] Ultraviolet light-emitting diodes (UV-LEDs) are used as the excitation light source.

[0064] Gas sensor substrate and electrode materials.

[0065] The gases required for the experiment, such as carbon dioxide (CO2).

[0066] Experimental steps:

[0067] Step 1: Preparation of sensitive materials;

[0068] Specifically:

[0069] 1.1) Dissolve La(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, and citric acid in a molar ratio of 1:0.8:0.2 in deionized water, and stir with a magnetic stirrer until the chemical reagents are completely dissolved; the specified ratio is: (La... 3+ +Fe 3+ +Co 2+ Citric acid: citric acid = 1:2;

[0070] 1.2) The well-mixed solution was transferred to a reaction vessel and reacted at 180°C for 9 hours. After naturally cooling to room temperature, the precipitate generated by the reaction was collected, washed with anhydrous ethanol to obtain the LFCO precursor precipitate, and dried at 60°C for 3 hours to remove water and organic matter.

[0071] 1.3) The dried precipitate was calcined in a tube furnace at 600℃ for 2h to obtain sample LFCO. Sample LFCO was dissolved in deionized water (solution concentration was 1mmol / L, deionized water was 60ml). Zn(NO3)2·6H2O and Co(NH2) nanopowder with a molar ratio of 1:1 were added to the solution and stirred thoroughly with a magnetic stirrer.

[0072] 1.4) The thoroughly mixed solution was transferred back to the reactor and reacted at 150°C for 10 hours. After repeating the above steps to obtain a dried precipitate, it was placed in a tube furnace and calcined at 500°C for 3 hours to obtain LFCO-ZNO(LaFe). 0.8 Co 0.2 O3-ZnO composite material.

[0073] Step 2: Preparation of the gas-sensitive element;

[0074] Specifically:

[0075] 2.1) In an agate mortar, add an appropriate amount of LFCO-ZNO powder, propolis, and glass fiber, then add terpineol and grind until a uniform and fine slurry is formed; the ratio of LFCO-ZNO powder, propolis, glass fiber, and terpineol is 10:1:1:2; the amount of terpineol is needed to form a uniform slurry with moderate moisture, neither too dry nor too wet;

[0076] 2.2) Spray the slurry evenly onto the surface of the ceramic tube to form a dense coating;

[0077] 2.3) The ceramic tube coated with LFCO-ZNO composite material was placed in a muffle furnace and sintered at a constant temperature of 200℃ for 2 hours to achieve densification of the ceramic tube and complete the sensor D. LFCO-ZNO The production;

[0078] 2.4) Insert the nickel-chromium alloy heating wire into the ceramic tube and weld it to the base;

[0079] 2.5) After 24 hours of aging treatment, the fabrication of the side-heated sintered sensor is completed.

[0080] Step 3: Set the light source;

[0081] Low-power ultraviolet light-emitting diodes are used as excitation sources during gas-sensitive element testing to form a photoexcited gas sensor.

[0082] Step 4: Performance Testing;

[0083] The gas-sensing performance of the gas-sensitive element was tested using an intelligent gas sensing and analysis system. First, the intelligent gas sensing and analysis system (CGS-8, Beijing Elite Technology Co., Ltd.) was turned on, and the device was placed in the test chamber in a certain order. The ultraviolet lamp was turned on for irradiation, and a certain temperature was set (range 20℃-200℃). A certain amount of the gas to be tested was injected into the test chamber. After the resistance of the device stabilized, the gas was released.

[0084] Step 5: Data Analysis;

[0085] Analyze experimental data to evaluate the impact of ultraviolet light excitation on the performance of gas sensors and determine the optimal operating conditions.

[0086] Experiment time

[0087] The specific timeframe for an experiment depends on its scale and complexity, but typically includes the preparation of sensitive materials (1-2 days), device fabrication and testing (1-2 days), and data analysis and optimization (1-2 days). Therefore, the entire experiment may take about a week to complete.

[0088] This embodiment provides a composite gas sensor enhanced by vacuum annealing followed by ultraviolet activation, which is prepared using the aforementioned method for preparing a composite gas sensor enhanced by vacuum annealing followed by ultraviolet activation.

[0089] The sensor provided in this embodiment has the following characteristics:

[0090] a) Enhanced anti-interference capability: Through careful selection of materials and structural design, the sensor can effectively resist interference from other non-target gases in the environment, providing more accurate gas detection results.

[0091] b) Simplified operation process: The sensor design takes into account the user's ease of operation and realizes simplified operation steps, so that even non-professionals can easily perform gas detection.

[0092] c) Reduced production costs: Optimizations were made in material selection and production processes to reduce the production cost of the sensors, making them more competitive in the market.

[0093] d) Improved sensitivity: To address the issue of low sensitivity in traditional electrochemical sensors, this invention draws on the ultraviolet irradiation technology used in UV-DOAS sensors. By enhancing the activity of gas molecules through ultraviolet irradiation, the sensitivity of the sensor is improved.

[0094] e) Application of vacuum annealing process: The vacuum annealing process can improve the crystallinity and stability of materials, further improving the performance of the sensor.

[0095] f) Meeting the needs of environmental monitoring: This combination of technologies enables sensors to have broader application prospects in environmental monitoring and carbon emission control, and can meet the growing demand for environmental monitoring.

[0096] These features significantly improve the performance of the gas sensor of this invention, enabling it to provide more reliable and accurate technical support for environmental monitoring and industrial process control.

[0097] The specific testing procedures for gas-sensitive elements are as follows:

[0098] In this experiment, the CGS-8 intelligent gas-sensitive analysis system was used to accurately test the CO2 sensitivity of the gas-sensitive element. The detailed experimental steps are as follows: First, the gas-sensitive element to be tested was accurately inserted into the socket groove of the system's gas chamber base in a specific order. Then, the evaporation and fan devices were activated to ensure a stable experimental environment, and the gas chamber lid was immediately closed. Next, the computer power was turned on, and the heating current was finely adjusted to the required experimental level to preheat the gas-sensitive element. The ultraviolet light-emitting diode on the side of the instrument was then turned on. During this process, data acquisition was performed simultaneously. After obtaining a stable initial resistance value, a certain amount of target gas was precisely extracted using a micro-sampler. Then, the target gas was slowly and steadily injected into the gas chamber through the injection port, and the change in the material's resistance within the target gas was closely observed. When the resistance value reached a stable state again and remained so for a period of time, the gas chamber was opened, and the change in resistance value was observed again. When the resistance value returned to the initial resistance value and remained so for a period of time, data acquisition was stopped, and the obtained data was saved. Throughout the experiment, a rigorous and steady attitude must be maintained to ensure the accuracy and reliability of the experimental results.

[0099] Results and Data Analysis

[0100] Material bulk structure characterization: Figure 2 X-ray diffraction (XRD) patterns of the composite material LFCO-ZnO are presented. The test results show that the characteristic peaks of the composite material agree with all diffraction peaks in the standard card of orthorhombic perovskite phase LaFeO3 (PDF#75-0541) and the standard card of hexagonal wurtzite ZnO (PDF#36-1451), and there are no other impurity peaks or other doping substances, confirming the high purity of the prepared composite material.

[0101] Material morphology and elemental characterization: Figure 3The (ac) section shows scanning electron microscope (SEM) images of the sample (LFCO-ZnO). These images clearly show that the sample generally exhibits a regular spherical structure with ZnO nanosheets distributed on the surface. This unique surface morphology greatly increases the specific surface area of ​​the material, thus providing more adsorption sites and diffusion channels for gas molecules. Furthermore, the PN heterojunction structure formed between LFCO and ZnO effectively promotes carrier transfer, thereby significantly improving the sensor's response speed and sensitivity. Figure 3 The (dj) section provides the energy dispersive spectroscopy (EDS) analysis results for this sample, confirming that ZnO has been successfully composited in LaFe. 0.8 Co 0.2 The O3 surface and this composite structure are of great significance for improving the gas-sensitive properties of materials.

[0102] Material performance test results and analysis: Figure 4 In the test curves shown, the responsivity ratio Rg / Ra was greater than zero at all test temperatures, indicating that the LFCO-ZNO sample maintained its responsiveness throughout the test. Furthermore, the device DL... LFCO-ZNO The response peak occurred at 1700s, and the sensing temperature decreased slightly. This is because ultraviolet light irradiation can excite electrons in the material and generate electron-hole pairs. This excitation can replace traditional thermal excitation to achieve gas detection, reduce the operating temperature, and reduce energy consumption.

[0103] exist Figure 5 D shown LFCO-ZNO In the sensor test curve, the resistance (R) decreases exponentially with increasing temperature (T), a phenomenon consistent with the conductivity mechanism of semiconductor materials. The relationship between the change in resistance (R) and temperature can be described by the following formula:

[0104]

[0105] Where R0 is a constant, Ea is the band gap energy (activation energy) of the semiconductor, and k B Here, T is Boltzmann's constant, and T is the absolute temperature. As temperature increases, the carrier concentration increases, leading to a decrease in resistivity, consistent with experimentally observed trends of decreasing resistance with increasing temperature. Secondly, the conductivity of a semiconductor is also related to its band gap energy; at lower energy values, electrons can more easily overcome defect barriers and achieve transitions. Calculations show that the activation energy of this device is only 0.34 eV, thus resulting in high sensitivity in subsequent gas-sensitive responses.

[0106] Figure 6 This demonstrates that D... LFCO-ZNOThe sensor's response to 500 ppm CO2 gas was analyzed. Data analysis showed a significant improvement in the sensor's response value, indicating that vacuum annealing and ultraviolet irradiation have a positive impact on improving the gas sensor's response.

[0107] from Figure 7 As can be seen in the image, device D LFCO-ZNO It exhibits a short response and recovery time, with the fastest response time reaching 2 seconds and the recovery time reaching 18 seconds, achieving a rapid adsorption and dissociation process for CO2.

[0108] In summary, this embodiment successfully prepared LaFe using a hydrothermal method. 0.8 Co 0.2 O3-ZnO composite nanomaterials, utilizing the characteristics of a PN heterostructure, significantly improve the gas-sensing properties for CO2. Under ultraviolet light irradiation at an ambient temperature of 100℃, the material exhibits a response value of 5.91 to 500 ppm CO2 gas, a five-fold improvement compared to pure LaFeO3, whose sensor response to 1000 ppm CO2 gas at 300℃ is only 1.74. Furthermore, as shown in Table 1, this study significantly improves the sensitivity and response-recovery time to carbon dioxide gas compared to previous studies.

[0109] Table 1 Comparison of CO2 Sensor Performance

[0110]

[0111]

[0112] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite gas sensor enhanced by vacuum annealing and UV activation, characterized in that: Includes the following steps: Step 1: Preparation of sensitive materials; Step 1 specifically involves: 1.1) Dissolve La(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O and citric acid in a molar ratio of 1:0.8:0.2 in deionized water and stir with a magnetic stirrer until the chemical reagents are completely dissolved. 1.2) The well-mixed solution was transferred to a reaction vessel and reacted at 180°C for 9 h. After naturally cooling to room temperature, the precipitate generated by the reaction was collected, washed with anhydrous ethanol to obtain the LFCO precursor precipitate, and dried at 60°C for 3 h to remove water and organic matter. 1.3) The dried precipitate was calcined in a tube furnace at 600℃ for 2 h to obtain sample LFCO. Sample LFCO was dissolved in deionized water, and nanoparticles of Zn(NO3)2·6H2O and Co(NH2) in a molar ratio of 1:1 were added to it. The mixture was stirred thoroughly using a magnetic stirrer. 1.4) The thoroughly mixed solution was transferred back to the reactor and reacted at 150°C for 10 h. After obtaining the dried precipitate, it was placed in a tube furnace and calcined at 500°C for 3 h to obtain the LFCO-ZNO composite material. Step 2: Preparation of the gas-sensitive element; Step 2 specifically involves: 2.1) In an agate mortar, add an appropriate amount of LFCO-ZNO powder, propolis and glass fiber, then add terpineol and grind until a uniform and fine slurry is formed; 2.2) Spray the slurry evenly onto the surface of the ceramic tube to form a dense coating; 2.3) The ceramic tube coated with LFCO-ZNO composite material was placed in a muffle furnace and sintered at a constant temperature of 200℃ for 2 hours to achieve densification of the ceramic tube and complete the sensor D. LFCO-ZNO The production; 2.4) Insert the nickel-chromium alloy heating wire into the ceramic tube and weld it to the base; 2.5) After 24 hours of aging treatment, the fabrication of the side-heated sintered sensor is completed; Step 3: Set the light source; In step 3, a low-power ultraviolet light-emitting diode is used as the excitation source during the gas-sensitive element test to form a photoexcited gas sensor; Step 4: Performance Testing; Step 5: Data Analysis.

2. The method for preparing the composite gas sensor enhanced by vacuum annealing and UV activation according to claim 1, characterized in that: In step 1.3), the sample LFCO is dissolved in deionized water with a solution concentration of 1 mmol / L and 60 ml of deionized water.

3. The method for preparing the composite gas sensor enhanced by vacuum annealing and UV activation according to claim 2, characterized in that: In step 4, the gas-sensing performance of the gas-sensitive element is tested by an intelligent gas sensing and analysis system. First, the intelligent gas sensing and analysis system is turned on, the device is placed in the test chamber in a certain order, the ultraviolet lamp is turned on for irradiation, and a certain temperature is set. The temperature range is 20℃-200℃. A certain amount of the gas to be tested is injected into the test chamber. After the resistance of the device stabilizes, the gas is released.

4. The method for preparing the composite gas sensor enhanced by ultraviolet activation after vacuum annealing according to claim 3, characterized in that: In step 5, the experimental data are analyzed to evaluate the impact of ultraviolet light excitation on the performance of the gas sensor and to determine the optimal operating conditions.

5. A composite gas sensor enhanced by vacuum annealing and ultraviolet activation, characterized in that: it is prepared by the preparation method of the composite gas sensor enhanced by vacuum annealing and ultraviolet activation as described in any one of claims 1-4.

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