Carbon monoxide gas sensor, preparation method and application thereof

Abstract

The present application belongs to the technical field of gas sensitive sensor, and particularly relates to a carbon monoxide gas sensitive sensor and a preparation method and application thereof. The gas sensitive sensor provided by the present application adopts a micro-hotplate chip structure of Pt@LaTiO2N gas sensitive material + Na-LEV adsorption and desorption material double-material synergistic integration, and temperature control and resistance detection can be performed on the two materials respectively. Na-LEV realizes selective pre-concentration of CO in the low-temperature stage, and desorbs CO in the high-temperature stage to improve the local CO concentration on the surface of the gas sensitive material, thereby effectively reducing the lower limit of detection; at the same time, the micro-cavity structure formed by the gasket, the cover plate and the micro-hotplate chip, in cooperation with the outer packaging of the tube shell and the cover plate, can isolate the interference of environmental factors such as humidity and dust, thereby prolonging the service life and detection stability of the sensor. In addition, the sensor supports constant-temperature working mode and programmed temperature desorption working mode, and can meet different scene requirements such as indoor air quality monitoring and early warning of industrial leakage.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, and specifically relates to a carbon monoxide gas sensor, its preparation method, and its application. Background Technology

[0002] Carbon monoxide (CO) is a colorless, odorless, and non-irritating gas, but it is highly toxic. Large amounts of CO can be released during incomplete combustion processes such as home heating, industrial smelting, and transportation. Even a small amount of CO inhaled within a short period can hinder the binding of oxygen to hemoglobin in the blood, leading to hypoxia and poisoning, which can be life-threatening in severe cases. Therefore, developing highly sensitive, selective, and rapid-response carbon monoxide detection sensors has significant value for public safety and industrial applications.

[0003] Currently, existing carbon monoxide sensors are mainly classified into three categories: electrochemical, optical, and semiconductor resistive. Electrochemical sensors offer high sensitivity, but their electrolytes suffer from limited lifespan and poor environmental adaptability. Optical sensors are costly and bulky, hindering portable and large-scale applications. Semiconductor resistive sensors, on the other hand, are widely studied due to their simple structure, low cost, and ease of integration. However, traditional semiconductor gas-sensitive materials are primarily metal oxides such as SnO2, ZnO, and In2O3. Their response to CO often requires high temperatures (300-400℃), and they suffer from cross-interference with gases such as H2 and CH4, resulting in insufficient selectivity, which has become a bottleneck for further development.

[0004] To improve the performance of traditional metal oxide gas-sensitive materials, a series of improvement studies have been conducted in related fields. For example, Chinese invention patent CN104649222A discloses a gas-sensitive material for CO detection and a method for fabricating a gas-sensitive element. This gas-sensitive material is composed of palladium (Pd)-doped tin dioxide hollow nanospheres, wherein the palladium-doped tin dioxide hollow nanospheres are tetragonal rutile phase, with a diameter of 180-200 nm and a wall thickness of 8-10 nm. Through palladium doping and hollow nanostructure design, this material reduces the optimal operating temperature of the sensor to a certain extent and improves the selectivity and sensitivity for CO detection. In addition, Chinese invention patent CN119528207A discloses an indium oxide carbon monoxide gas-sensitive material and its preparation method and application. This gas-sensitive material adopts a heterogeneous three-level hierarchical structure, which is formed by a hollow structure composed of small-diameter nanorods and a high specific surface area indium oxide sheet. Through the design of abundant active crystal faces and adsorption oxygen bonds, the adsorption capacity for oxygen and carbon monoxide gas molecules is enhanced, thereby improving the CO detection accuracy.

[0005] Although the aforementioned existing technologies have optimized the performance of traditional metal oxide gas-sensitive materials through material doping and structural design—for example, patent CN104649222A uses Pd doping to reduce the operating temperature, and patent CN119528207A uses a tertiary structure to increase the specific surface area—they still do not completely escape the inherent limitations of traditional metal oxide material systems. The former relies on the gas-phase oxygen adsorption / desorption mechanism of tin dioxide, which, while reducing the operating temperature, has limited shielding ability against interfering components in complex gases; the latter, while improving detection accuracy, requires multiple coating and drying processes for gas-sensitive element fabrication, making the process relatively cumbersome, and still requires aging treatment at 300℃, leaving room for improvement in energy consumption control. Therefore, developing a novel carbon monoxide gas-sensitive material system and corresponding sensor that combines low energy consumption, high selectivity, high sensitivity, and good stability remains a pressing technical challenge in this field. Summary of the Invention

[0006] To address the aforementioned problems, in a first aspect, the present invention proposes a carbon monoxide gas sensor, comprising a micro-hot plate chip covered with a gas-sensitive material and an adsorption / desorption material;

[0007] The gas-sensitive material is a Pt-modified LaTiO2N gas-sensitive material Pt@LaTiO2N, and the adsorption-desorption material is a sodium-type nano-LEV zeolite adsorption-desorption material Na-LEV.

[0008] Furthermore, the mass fraction of Pt in the gas-sensitive material Pt@LaTiO2N is 0.1-1.0 wt%;

[0009] The Pt@LaTiO2N was prepared by ammoniation of La2Ti2O7 precursor powder to obtain LaTiO2N, followed by loading Pt on the surface of LaTiO2N and reduction activation.

[0010] The adsorption-desorption material Na-LEV was prepared by LEV seed pre-synthesis, LEV seed purification and ion exchange.

[0011] Secondly, this invention proposes a method for preparing a carbon monoxide gas sensor, comprising the following steps:

[0012] A micro hot plate chip was fabricated by coating the electrodes with slurries of gas-sensitive material Pt@LaTiO2N and adsorption-desorption material Na-LEV, respectively.

[0013] The gasket and cover plate are bonded to the micro hot plate chip to form a microcavity structure. The microcavity structure is bonded to the tube shell and encapsulated with an outer cover plate to form an outer protective layer.

[0014] The circuitry of the micro-hot plate chip is soldered to the circuit board, and the micro-hot plate chip is integrated onto the circuit board to obtain a carbon monoxide gas sensor.

[0015] Further, the gas-sensitive material Pt@LaTiO2N is prepared according to the following steps:

[0016] Preparation of La2Ti2O7 precursor powder: La(NO3)3•6H2O and Ti(OBu)4 were dissolved in proportion, citric acid and methanol were added, and then ethylene glycol was added. The mixture was stirred to obtain a homogeneous transparent sol. The homogeneous transparent sol was dried to form a solid resin. The solid resin was pre-calcined and then heated to obtain crystallized La2Ti2O7 precursor powder.

[0017] Preparation of LaTiO2N powder: La2Ti2O7 precursor powder was placed in a reaction vessel, and oxygen was first removed by N2, then NH3 was introduced and the temperature was programmed to reach the set temperature and then held. After holding, NH3 was introduced to cool the powder, and then N2 was introduced to cool it to room temperature to obtain LaTiO2N powder.

[0018] Preparation of gas-sensitive material Pt@LaTiO2N: LaTiO2N powder was dispersed in ethanol and ultrasonically treated. H2PtCl6 solution was added dropwise, stirred and dried. Then, it was reduced and activated by temperature programmable increase and holding under an inert atmosphere containing H2. Finally, it was cooled to room temperature under an inert atmosphere to obtain gas-sensitive material Pt@LaTiO2N.

[0019] Furthermore, in the process of preparing La2Ti2O7 precursor powder;

[0020] The molar ratio of La(NO3)3•6H2O to Ti(OBu)4 is 1:0.95-1.05;

[0021] The mass ratio of citric acid, methanol, and ethylene glycol is 1:1.8-2.2:1.2-1.4.

[0022] The temperature during the stirring process is 70-80℃;

[0023] The drying temperature is 100-120℃;

[0024] The pre-firing conditions are 400-450℃ for 2-3 hours;

[0025] The calcination conditions are to heat to 650-700℃ and then calcine for 2-3 hours.

[0026] Furthermore, in the process of preparing LaTiO2N powder,

[0027] The conditions for programmed temperature rise are to heat to 900-950℃ at a heating rate of 5-10℃ / min and hold for 10-12 hours;

[0028] Cool to 150-200℃ by passing NH3 through.

[0029] Furthermore, in the process of preparing the gas-sensitive material Pt@LaTiO2N,

[0030] The solid-liquid ratio of LaTiO2N powder to ethanol is 1g:30-70mL, and the ultrasonic time is 10-20min.

[0031] The drying temperature is 80-100℃, and the temperature is increased to 180-200℃ at a heating rate of 2-5℃ / min.

[0032] Further, the adsorption-desorption material Na-LE is prepared according to the following steps:

[0033] LEV seed crystal pre-synthesis: N,N-dimethylpiperidine chloride was dissolved in water, and NaOH aqueous solution and NaAlO2 were added sequentially. After stirring, Ludox AS-40 solution was added dropwise to obtain a gel. After stirring, the gel was heated to obtain LEV seed crystals.

[0034] LEV seed purification: A new gel was prepared according to the seed pre-synthesis method. After stirring, LEV seeds were added to the new gel for hydrothermal reaction. The hydrothermal reaction product was washed, dried, and then calcined in air to remove the template agent to obtain (H,Na)-LEV nano-zeolite.

[0035] Ion exchange: (H,Na)-LEV nano-zeolite was ion exchanged with NH4NO3 solution and the process was repeated multiple times to obtain NH4-LEV. Then, NH4-LEV was ion exchanged with NaNO3 solution and the process was repeated multiple times. The exchange products were washed and dried to obtain the adsorption-desorption material Na-LEV.

[0036] Furthermore, during the LEV seed crystal pre-synthesis process,

[0037] The mass ratio of N,N-dimethylpiperidine chloride, water, NaOH aqueous solution, NaAlO2, and Ludox AS-40 solution is 1:5-6:0.90-1.1:0.18-0.22:3.0-3.2, specifically 1:5.4:0.93:0.2:3.2; wherein the mass concentration of the NaOH aqueous solution is 50%.

[0038] The heating reaction is carried out at 160-170°C for 240-264 hours.

[0039] Furthermore, during the LEV seed crystal purification process,

[0040] The mass ratio of the gel to LEV seeds is 1:0.001-0.005;

[0041] The hydrothermal reaction conditions are 80-90℃ for 10-12 hours;

[0042] The calcination conditions are 500-600℃ for 6-8 hours.

[0043] Furthermore, during the ion exchange process,

[0044] The mass ratio of (H,Na)-LEV nano-zeolite to NH4NO3 solution is 1:10-30;

[0045] The mass ratio of NH4-LEV to NaNO3 solution is 1:10-30;

[0046] The conditions for ion exchange are 80-90℃ for 3-4 hours;

[0047] The drying conditions are 80-100℃ for 10-12 hours.

[0048] Thirdly, the present invention proposes the application of the aforementioned carbon monoxide gas sensor in the detection of carbon monoxide.

[0049] The beneficial effects of this invention are:

[0050] This invention applies the perovskite-type oxynitride LaTiO2N to the field of gas sensors, breaking its previous limitations to applications such as photocatalytic water splitting and nitrogen reduction reactions. LaTiO2N possesses a moderate band gap of approximately 2 eV, excellent electron transport performance, and high lattice oxygen mobility and reversibility due to its oxygen-nitrogen synergistic structure, providing a novel pathway for the generation and recovery of oxygen vacancies—the core of gas sensing. Simultaneously, a Pt@LaTiO2N gas-sensitive material system is constructed through Pt modification. Utilizing the high-temperature adsorption and oxidation catalytic selectivity of Pt for CO, a synergistic effect between the Pt catalytic active site and the LaTiO2N lattice oxygen is formed. This allows Pt-activated CO to rapidly react with LaTiO2N lattice oxygen to generate CO2, efficiently promoting the dynamic cycling of oxygen vacancies. Compared to traditional metal oxides that rely solely on gas-phase oxygen adsorption / desorption, this significantly improves the material's response sensitivity and selectivity to CO, filling the gap in LaTiO2N's application in gas sensing and enhancing the performance of gas-sensitive materials.

[0051] This invention establishes a high-temperature catalysis-conductivity coupling mechanism, distinct from traditional gas sensors that rely solely on gas-phase oxygen adsorption / desorption to alter carrier concentration. In this mechanism, oxygen vacancies generated by the Pt-catalyzed activation of CO and the reaction with LaTiO2 lattice oxygen directly induce a change in carrier concentration. This change is rapidly converted into a resistance signal via Pt / LaTiO2 interface barrier coupling, simultaneously achieving efficient linkage between CO catalytic conversion and resistance signal response. This significantly improves sensor response speed and avoids the response lag caused by slow gas-phase oxygen diffusion in traditional mechanisms. Furthermore, the combination of Pt's catalytic selectivity for CO and the targeted supply of oxygen from the LaTiO2N lattice, along with the selective adsorption of Na-LEV adsorption-desorption materials, effectively shields against common interfering gases such as benzene, toluene, and acetone, ensuring high accuracy and anti-interference capability for CO detection in complex gas environments.

[0052] The sensor proposed in this invention employs a micro-hotplate chip structure that integrates Pt@LaTiO2N gas-sensitive material and Na-LEV adsorption-desorption material, allowing for separate temperature control and resistance detection for each material. Na-LEV selectively pre-concentrates CO at low temperatures and desorbs CO at high temperatures to increase the local CO concentration on the surface of the gas-sensitive material, effectively lowering the detection limit. Simultaneously, the microcavity structure formed by the gasket, cover plate, and chip, combined with the outer encapsulation of a ceramic tube and metal cover plate, isolates the sensor from environmental factors such as humidity and dust, extending its lifespan and detection stability. Furthermore, the sensor supports both a constant-temperature operating mode (suitable for real-time monitoring of conventional CO concentrations) and a programmed temperature-ramp desorption operating mode (suitable for high-precision detection of trace CO), meeting the needs of various scenarios such as indoor air quality monitoring and early warning of industrial leaks, significantly broadening its application scope.

[0053] The preparation process of the gas-sensitive material Pt@LaTiO2N, the adsorption-desorption material Na-LEV, and the sensor in this invention has easily controllable process parameters, high repeatability, and can achieve large-scale production. Moreover, the preparation process does not use rare or highly toxic reagents, which meets the requirements of green chemical industry, reduces industrialization costs and environmental burden, and provides reliable technical support for subsequent actual production and market application.

[0054] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 The XRD pattern of the synthesized LaTiO2N in an embodiment of the present invention is shown;

[0057] Figure 2 The TEM image of the synthesized LaTiO2N in an embodiment of the present invention is shown;

[0058] Figure 3 The XRD pattern of Pt@LaTiO2N synthesized in an embodiment of the present invention is shown;

[0059] Figure 4 The XRD pattern of the synthesized Na-LEV adsorbent material in an embodiment of the present invention is shown;

[0060] Figure 5 A schematic cross-sectional view of the gas sensor prepared according to the present invention is shown.

[0061] Figure 6 The concentration-gas-sensitive response amplitude curve of the Pt@LaTiO2N / LaTiO2N sensor to carbon monoxide in an embodiment of the present invention is shown.

[0062] Figure 7 The gas-sensitive response of Pt@LaTiO2N sensors with different phthalate ratios to 500 ppm carbon monoxide in embodiments of the present invention is shown.

[0063] Figure 8 The desorption peak heights of 50 ppm gas by Pt@LaTiO2N sensors with different adsorption materials in embodiments of the present invention are shown. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] Example 1

[0066] This embodiment prepares a Pt-modified LaTiO2N gas-sensitive material system (Pt@LaTiO2N), specifically including the following steps:

[0067] Preparation of La2Ti2O7 precursor powder: 13.05g La(NO3)3·6H2O and 8.55g Ti(OBu)4 were dissolved in a clean container at a 1:1 molar ratio. 76.40g citric acid and 153.00g methanol were added, followed by 98.8g ethylene glycol as a polycondensation crosslinking agent. The mixture was stirred at 80℃ for 2h to obtain a homogeneous transparent sol. Drying was continued at 120℃ for 12h until completely dried into a solid resin. The dried resin was pre-calcined in air at 400℃ (2h) to remove organic matter, and then heated to 650℃ and held for 2h to obtain crystallized La2Ti2O7 precursor powder.

[0068] Ammoniation of La2Ti2O7 precursor (preparation of LaTiO2N powder): La2Ti2O7 precursor powder was placed in a quartz boat and then placed in a tube furnace. Pre-purging with N2 for 30 min was used to remove oxygen. NH3 was then turned on, and the temperature was increased to 900℃ at a rate of 5℃ / min according to the program, and held at this temperature for 12 h. NH3 was then turned off, and the temperature was first cooled to <200℃ with NH3, then switched to nitrogen to cool to room temperature to prevent high-speed re-oxidation, yielding LaTiO2N powder. The XRD pattern of the LaTiO2N powder is shown below. Figure 1 As shown, the XRD pattern of LaTiO2N is consistent with the standard card (PDF#00-048-1230), and the diffraction peaks are sharp with flat baselines, indicating that the precursor La2Ti2O7 was successfully and completely converted into the highly crystalline LaTiO2N phase. No diffraction peaks were observed for La2O3, TiO2, or other titanate impurities, demonstrating the high purity of the phase, which is attributed to the properly controlled ammoniation temperature, time, and atmosphere.

[0069] TEM image of LaTiO2N powder as follows Figure 2 As shown, the LaTiO2N powder exhibits a uniform particle size of approximately 30-70 nm. This smaller nanoscale size implies a larger specific surface area, which is crucial for subsequent gas-sensitive or catalytic applications, as more surface active sites contribute to improved material performance. Furthermore, the particles demonstrate good dispersion and no significant hard agglomeration, indicating that the synthesis process effectively controls particle growth and aggregation.

[0070] Pt was loaded onto the surface of LaTiO2N (preparation of gas-sensitive material Pt@LaTiO2N): LaTiO2N powder was dispersed in ethanol (solid-liquid ratio 1g:50mL); sonicated for 10-20 min. H2PtCl6 solution was added dropwise to achieve a final Pt mass fraction of 0.1-1.0 wt%. The mixture was stirred for 2 h, then evaporated to dryness at room temperature or dried overnight at 80℃. Reduction activation was completed in a tube furnace at 2℃ / min to 200℃, and held at this temperature for 1-2 h under a 5% H2 / 95% Ar atmosphere. The mixture was then cooled to room temperature under an inert gas atmosphere to obtain the gas-sensitive material Pt@LaTiO2N. The XRD pattern of Pt@LaTiO2N is shown below. Figure 3 As shown, comparison Figure 1 All characteristic diffraction peaks of LaTiO2N were present without shift or broadening, demonstrating that the crystal structure of LaTiO2N remained stable and intact during subsequent impregnation, drying, and low-temperature (200℃) H2 / Ar atmosphere reduction. Furthermore, no obvious diffraction peaks of metallic Pt were observed in the XRD pattern. This is because the low loading and extremely high dispersion of Pt resulted in extremely small nanoparticles, to the point that their diffraction signals were either overwhelmed or broadened to indistinguishable levels by the support signal. This is an ideal condition for catalytic materials, as the highly dispersed Pt nanoparticles provide a maximum number of surface active sites, greatly promoting gas adsorption and reaction, thereby significantly enhancing the sensitivity of the gas-sensitive material.

[0071] Example 2

[0072] In this embodiment, sodium-type nano-LEV zeolite (Na-LEV) is prepared as follows:

[0073] (1) Pre-synthesis of LEV seed crystals: 2.10 g of N,N-dimethylpiperidine chloride (DMP) was dissolved in 11.33 g of H2O, and 1.95 g of NaOH (50% aqueous solution) and 0.42 g of NaAlO2 were added sequentially. After stirring until clear, 6.75 g of Ludox AS-40 (colloidal silica) solution was slowly added dropwise under vigorous stirring. After stirring for another 30 minutes, the gel was transferred to a polytetrafluoroethylene high-pressure reactor and reacted in an oven at 160 °C for 240 hours to obtain LEV seed crystals.

[0074] (2) LEV seed purification: A new gel was prepared according to the LEV seed pre-synthesis formula. After stirring for 30 minutes, 0.081 g of the pre-synthesized seed was added before the hydrothermal reaction, and then the hydrothermal reaction was carried out for 96 hours. The product was washed by centrifugation with deionized water and sonicated 3 times each. After treatment, it was dried in an oven at 80℃ for 12 hours. The obtained nano-LEV powder was calcined in air at 550℃ for 6 hours to remove the template agent, and (H,Na)-LEV nano-zeolite was obtained.

[0075] (3) Ion exchange: (H,Na)-LEV nano-zeolite was first exchanged with 0.6M NH4NO3 solution at 80℃ for 3 hours. After repeating the operation three times, the product was converted into NH4-LEV. Then, it was exchanged with 1M sodium nitrate (NaNO3) solution at 80℃ for 3 hours. After repeating the operation three times, sodium-type nano-LEV zeolite was obtained. The final sample was centrifuged three times, washed with deionized water, and dried in an oven at 80℃ for 12 hours to obtain the adsorption-desorption material Na-LEV.

[0076] The XRD pattern of the adsorption-desorption material Na-LEV is shown below. Figure 4 As shown, the X-ray diffraction pattern of the synthesized Na-LEV exhibits typical LEV structural characteristic diffraction peaks without any impurity peaks, indicating that the product has high purity and good crystallinity. Its characteristic peaks are located at 2θ = 8.56°, 10.2°, 12.5°, 17.18°, 20.77°, 21.77°, and 31.95°.

[0077] Example 3

[0078] This embodiment prepares a gas sensor based on the gas-sensitive material Pt@LaTiO2N prepared in Example 1 and the Na-LEV adsorbent material prepared in Example 2, including the following steps:

[0079] (1) Chip fabrication: The micro hot plate chip circuit was generated on the ceramic substrate using ultraviolet lithography and magnetron sputtering process; the micro hot plate shape was processed using laser etching process; the Pt@LaTiO2N gas-sensitive material slurry prepared in Example 1 and the Na-LEV adsorption-desorption material slurry prepared in Example 2 were coated onto the electrode by electrostatic micro-spraying technology to fabricate a micro hot plate chip that can perform temperature control and resistance detection on the two materials respectively.

[0080] (2) Device packaging: The gasket and cover plate are bonded together with the micro hot plate chip. The thickness of the gasket is used to form a micro cavity structure between the micro hot plate chip and the cover plate. The micro cavity structure is then bonded to the tube shell and the outer shell cover plate is encapsulated to form an outer layer of protection. Then the circuit of the micro hot plate chip is soldered together with the circuit board to integrate the micro hot plate chip onto the circuit board to form a gas sensor.

[0081] The formed gas-sensitive sensor, such as Figure 5As shown, the outer cover is located on the top layer of the sensor, protecting the internal structure and isolating it from external dust, impurities, and other interference, creating a relatively stable working environment for the sensor. The micro-hot plate chip can control the operating temperature of the gas-sensitive material and the adsorption-desorption material through heating, providing the necessary thermal energy for the gas-sensitive reaction and adsorption-desorption process, ensuring that the sensor operates efficiently at a suitable temperature. The gas-sensitive material contacts the target gas within the formed microcavity structure. The housing, as the main support structure of the sensor, houses and fixes the micro-hot plate chip, gas-sensitive material, adsorption-desorption material, and other internal components, ensuring an orderly combination of all parts and also providing a certain degree of protection for the internal structure. The gas-sensitive material is the key component for target gas detection, capable of undergoing a specific gas-sensitive reaction with the target gas, converting the target gas concentration signal into a detectable electrical signal, thereby achieving the sensing of the target gas. The adsorption-desorption material can adsorb and desorb the target gas. During the detection process, it can first adsorb carbon monoxide to enrich the target gas, and then desorb it under suitable conditions, improving the contact efficiency between the gas-sensitive material and the target gas, and enhancing the sensor's detection sensitivity and response performance. The cover plate, in conjunction with the gasket, further encapsulates and secures the internal structure, ensuring the relative stability of the components and maintaining the airtightness of the sensor's interior. This guarantees the overall structural stability and operational reliability of the sensor. In this embodiment, the gasket, cover plate, and housing are all ceramic, the outer cover plate is a metal cover plate, the gas-sensitive material is Pt@LaTiO2N gas-sensitive material slurry, and the adsorption-desorption material is Na-LEV adsorption-desorption material, enabling the detection of carbon monoxide.

[0082] Comparative Example 1

[0083] LaTiO2N gas-sensitive material was prepared according to the two steps in Example 1: preparation of La2Ti2O7 precursor powder and ammoniation of La2Ti2O7 precursor.

[0084] Test Example 1

[0085] Performance testing of the gas-sensitive material Pt@LaTiO2N was conducted as follows:

[0086] During the testing process, the sensor operates in a constant temperature mode, with the working temperature of the gas-sensitive material set to 300℃. The adsorption and desorption materials do not operate, and only the gas-sensitive performance of the sensor is tested.

[0087] The test subjects were two gas-sensitive materials, Pt@LaTiO2N and LaTiO2N. These were prepared into slurries through ball milling and then sprayed onto a micro-hotplate chip to create sensors with different gas-sensitive materials. Carbon monoxide and nitrogen standard gas cylinders were used for testing. Carbon monoxide and nitrogen were mixed using a mixing device, and different concentration gradients of carbon monoxide gas (10ppm, 20ppm, 50ppm, 80ppm, 100ppm, 150ppm, 200ppm, 300ppm, 500ppm, 800ppm, and 1000ppm) were introduced into the sensor test chamber for testing.

[0088] After power-on testing, nitrogen gas is first introduced to stabilize the sensor's resistance signal. Once the signal is stable, carbon monoxide test gas is introduced and continuously introduced until the resistance stabilizes again, obtaining the response resistance value of the gas-sensitive material to carbon monoxide. Then, nitrogen gas is introduced again to purge the carbon monoxide gas from the test chamber, and the sensor's response signal recovers. By calculating the ratio of the stable resistance of the gas-sensitive material under nitrogen to that under a carbon monoxide atmosphere, the gas-sensitive response amplitude of the material is obtained.

[0089] Test results are as follows Figure 6 As shown, the gas sensor made of Pt@LaTiO2N material has higher sensitivity to carbon monoxide than the gas sensor made of LaTiO2N material.

[0090] Test Example 2

[0091] The response intensity of the gas-sensitive material Pt@LaTiO2N to carbon monoxide gas was analyzed based on the mass fraction of Pt (0.1%-1%). The results are as follows: Figure 7 As shown, the higher the Pt mass fraction, the stronger the response of the gas sensor to carbon monoxide gas and the better its sensitivity.

[0092] Test Example 3

[0093] Na-LEV molecular sieve adsorption performance screening test:

[0094] Test conditions: During the test, the sensor was set to programmed temperature rise desorption mode. The gas-sensitive material was heated at a constant 300℃, and the adsorption / desorption material was set at 50℃ during the adsorption stage and 400℃ during the desorption stage. The test materials were Na-LEV, Beta, SBA3, TS-1, and ZSM-5 molecular sieves. These molecular sieve materials were ball-milled into slurries and then sprayed onto a micro-hotplate chip to fabricate Pt@LaTiO2N sensors with different adsorption materials. The test gases were benzene, toluene, xylene, acetone, ethanol, formaldehyde, acetic acid, ethyl acetate, carbon monoxide, and ammonia at a concentration of 50 ppm.

[0095] Test Procedure: After the test begins, nitrogen gas is first introduced into the sensor cavity. Once the resistance of the gas-sensitive material stabilizes, different types of test gases are introduced. The adsorption material then undergoes low-temperature adsorption at 50°C for 180 seconds. After adsorption, the test gas input is cut off, and nitrogen gas is introduced again to expel any residual test gas from the sensor cavity. Once the gas-sensitive resistance stabilizes again, the adsorption-desorption material is heated to 400°C and held at that temperature. At this point, the test gas originally adsorbed on the molecular sieve desorbs onto the surface of the gas-sensitive material, causing it to produce a gas-sensitive response. The ratio of the peak resistance at high-temperature desorption to the resistance before desorption is recorded as the desorption peak height. A higher desorption peak height indicates a better adsorption effect of the corresponding adsorption material on the test gas. If the desorption peak height for a certain gas is significantly higher than for other gases, it indicates that the sensor has good selectivity for that gas.

[0096] Test results: The test results are as follows Figure 8 As shown, the Na-LEV sensor exhibits optimal adsorption performance for carbon monoxide, with a significant improvement in response height compared to the gas-sensing performance test. This indicates that the molecular sieve can pre-concentrate carbon monoxide during the adsorption stage, which is beneficial for lowering the sensor's detection limit. It can be seen that the Na-LEV&Pt@LaTiO2N sensor demonstrates a significantly higher selectivity for carbon monoxide compared to other common gases. Therefore, the Na-LEV&Pt@LaTiO2N sensor using the temperature-programmed analysis method is suitable for targeted detection of carbon monoxide gas.

[0097] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carbon monoxide gas sensor, characterized in that, This includes micro-hot plate chips covered with gas-sensitive materials and adsorption-desorption materials; The gas-sensitive material is a Pt-modified LaTiO2N gas-sensitive material Pt@LaTiO2N, and the adsorption-desorption material is a sodium-type nano-LEV zeolite adsorption-desorption material Na-LEV.

2. The carbon monoxide gas sensor according to claim 1, characterized in that, The mass fraction of Pt in the gas-sensitive material Pt@LaTiO2N is 0.1-1.0 wt%; The Pt@LaTiO2N was prepared by ammoniation of La2Ti2O7 precursor powder to obtain LaTiO2N, followed by loading Pt on the surface of LaTiO2N and reduction activation. The adsorption-desorption material Na-LEV was prepared by LEV seed pre-synthesis, LEV seed purification and ion exchange.

3. A method for preparing a carbon monoxide gas sensor, used to prepare the carbon monoxide gas sensor according to claim 1 or 2, characterized in that, Includes the following steps: A micro hot plate chip was fabricated by coating the electrode with gas-sensitive material Pt@LaTiO2N slurry and adsorption-desorption material Na-LEV slurry, respectively. The gasket, cover plate and the micro hot plate chip are bonded together to form a microcavity structure, the microcavity structure is bonded to the tube shell and the outer cover plate is encapsulated to form an outer layer of protection; The circuitry of the micro-hot plate chip is soldered to the circuit board, and the micro-hot plate chip is integrated onto the circuit board to obtain a carbon monoxide gas sensor.

4. The method for preparing a carbon monoxide gas sensor according to claim 3, characterized in that, The gas-sensitive material Pt@LaTiO2N is prepared according to the following steps: Preparation of La2Ti2O7 precursor powder: La(NO3)3•6H2O and Ti(OBu)4 were dissolved in proportion, citric acid and methanol were added, and then ethylene glycol was added. The mixture was stirred to obtain a homogeneous transparent sol. The homogeneous transparent sol was dried to form a solid resin. The solid resin was pre-calcined and then heated to obtain crystallized La2Ti2O7 precursor powder. Preparation of LaTiO2N powder: La2Ti2O7 precursor powder was placed in a reaction vessel, and oxygen was first removed by N2, then NH3 was introduced and the temperature was programmed to reach the set temperature and then held. After holding, NH3 was introduced to cool the powder, and then N2 was introduced to cool it to room temperature to obtain LaTiO2N powder. Preparation of gas-sensitive material Pt@LaTiO2N: LaTiO2N powder was dispersed in ethanol and ultrasonically treated. H2PtCl6 solution was added dropwise, stirred and dried. Then, it was reduced and activated by temperature programmable increase and holding under an inert atmosphere containing H2. Finally, it was cooled to room temperature under an inert atmosphere to obtain gas-sensitive material Pt@LaTiO2N.

5. The method for preparing a carbon monoxide gas sensor according to claim 4, characterized in that, In the process of preparing La2Ti2O7 precursor powder; The molar ratio of La(NO3)3•6H2O to Ti(OBu)4 is 1:0.95-1.05; The mass ratio of citric acid, methanol, and ethylene glycol is 1:1.8-2.2:1.2-1.

4. The temperature during the stirring process is 70-80℃; The drying temperature is 100-120℃; The pre-firing conditions are 400-450℃ for 2-3 hours; The calcination conditions are to heat to 650-700℃ and then calcine for 2-3 hours.

6. The method for preparing a carbon monoxide gas sensor according to claim 4, characterized in that, In the process of preparing LaTiO2N powder The conditions for programmed temperature rise are to heat to 900-950℃ at a heating rate of 5-10℃ / min and hold for 10-12 hours; Cool to 150-200℃ by passing NH3 through.

7. The method for preparing a carbon monoxide gas sensor according to claim 4, characterized in that, In the process of preparing the gas-sensitive material Pt@LaTiO2N The solid-liquid ratio of LaTiO2N powder to ethanol is 1g:30-70mL, and the ultrasonic time is 10-20min. The drying temperature is 80-100℃, and the temperature is increased to 180-200℃ at a heating rate of 2-5℃ / min.

8. The method for preparing a carbon monoxide gas sensor according to claim 3, characterized in that, The adsorption-desorption material Na-LEV is prepared according to the following steps: LEV seed crystal pre-synthesis: N,N-dimethylpiperidine chloride was dissolved in water, and NaOH aqueous solution and NaAlO2 were added sequentially. After stirring, Ludox AS-40 solution was added dropwise to obtain a gel. After stirring, the gel was heated to obtain LEV seed crystals. LEV seed purification: A new gel was prepared according to the seed pre-synthesis method. After stirring, LEV seeds were added to the new gel for hydrothermal reaction. The hydrothermal reaction product was washed, dried, and then calcined in air to remove the template agent to obtain (H,Na)-LEV nano-zeolite. Ion exchange: (H,Na)-LEV nano-zeolite was ion exchanged with NH4NO3 solution and the process was repeated multiple times to obtain NH4-LEV. Then, NH4-LEV was ion exchanged with NaNO3 solution and the process was repeated multiple times. The exchange products were washed and dried to obtain the adsorption-desorption material Na-LEV.

9. The method for preparing a carbon monoxide gas sensor according to claim 8, characterized in that, During the LEV seed crystal pre-synthesis process The mass ratio of N,N-dimethylpiperidine chloride, water, NaOH aqueous solution, NaAlO2, and Ludox AS-40 solution is 1:5-6:0.90-1.1:0.18-0.22:3.0-3.2; wherein the mass concentration of the NaOH aqueous solution is 50%. The heating reaction is carried out at 160-170°C for 240-264 hours.

10. The method for preparing a carbon monoxide gas sensor according to claim 8, characterized in that, During the purification process of LEV seed crystals The mass ratio of the gel to LEV seeds is 1:0.001-0.005; The hydrothermal reaction conditions are 80-90℃ for 10-12 hours; The calcination conditions are 500-600℃ for 6-8 hours.

11. The method for preparing a carbon monoxide gas sensor according to claim 8, characterized in that, During the ion exchange process. The mass ratio of (H,Na)-LEV nano-zeolite to NH4NO3 solution is 1:10-30; The mass ratio of NH4-LEV to NaNO3 solution is 1:10-30; The conditions for ion exchange are 80-90℃ for 3-4 hours; The drying conditions are 80-100℃ for 10-12 hours.

12. The application of the carbon monoxide gas sensor as described in claim 1 or 2 in the detection of carbon monoxide.

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