Method for regulating and controlling linearity of gas sensor

Abstract

The invention relates to a method for regulating and controlling the linearity of a gas sensor, which comprises the following steps: quantitatively measuring the type and content of oxygen species on the surface of a metal oxide semiconductor by adopting a cantilever-temperature programmed desorption method, and regulating and controlling the content of specific oxygen species by adopting a gas phase reduction method so as to improve the linearity of the gas sensor for detecting different gases. Cantilever-TPD quantitative detection is combined, the content of specific oxygen species is regulated and controlled, the linear detection range of ethyl alcohol can be widened to 2-200 ppm, and R2 is larger than or equal to 99.7%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas sensing, and particularly relates to a method for regulating linearity of a gas sensor. BACKGROUND

[0002] Gas sensors are widely used in environmental monitoring, industrial production, medical safety and other fields. Among them, metal oxide semiconductor (MOS) gas sensors such as SnO2 have become a research hotspot due to their low cost, high sensitivity and good stability. However, the existing SnO2 gas sensors generally have a narrow linear measurement range when detecting reducing gases (such as H2, ethanol and CO, etc.), that is, the response deviates from the linear relationship at high or low concentrations, resulting in a decrease in measurement accuracy, and causing more costs and difficulties for circuit design and actual product application. Traditional methods usually optimize material morphology, doping or structure design to improve sensor performance, but rarely improve sensing linearity from the perspective of quantitative control of adsorbed oxygen species.

[0003] Oxygen species on the surface of metal oxide semiconductors (such as SnO2, ZnO and WO3, etc.) refer to oxygen atoms or oxygen molecules adsorbed on the surface or near the surface of the material, existing in different chemical states and directly participating in gas sensing reactions. They are the key active substances for detecting reducing / oxidizing gases in gas sensors. Adsorbed oxygen species (such as O2- and O-, etc.) as the key medium of sensing reactions directly affect the detection range, sensitivity and selectivity of the sensor. At present, there is a lack of an effective method for screening high-linearity gas sensing materials, and there is also a lack of linear range optimization technology based on fine regulation of oxygen species. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for regulating the linearity of a gas sensor, which solves the problem of limited linear measurement range of existing gas sensors and improves the detection sensitivity.

[0005] The present application provides a method for regulating the linearity of a gas sensor, comprising the following steps:

[0006] The type and content of oxygen species on the surface of metal oxide semiconductors are quantitatively measured by a cantilever-programmed temperature desorption method, and the content of specific oxygen species is regulated by a gas phase reduction method to improve the linearity of the gas sensor for detecting different gases.

[0007] Further, the metal oxide semiconductor is selected from one of SnO2, ZnO or WO3.

[0008] Further, the oxygen species include one or more of alpha oxygen species O2-, beta oxygen species O- and gamma oxygen species O 2

[0009] ​Furthermore, the gas includes hydrogen or ethanol.

[0010] Furthermore, the regulation includes any of the following situations described in a1 to a3:

[0011] a1) The content of the α-oxygen species is 1.0-1.75 wt‰, the detection range for hydrogen is 50-200 ppm, and the detection temperature is 250℃. 2 The percentage was 95.8%-98.1%.

[0012] a2) The content of the α-oxygen species is 1.25-1.75 wt‰, the detection range for hydrogen is 50-200 ppm, and the detection temperature is 250℃. 2 The percentage was 96.3%-98.1%.

[0013] a3) The content of the α-oxygen species is 1.75 wt‰, the detection range for hydrogen is 50-200 ppm, and the detection temperature is 250℃. 2 It is 98.1%.

[0014] Furthermore, the regulation includes any of the following situations described in b1 to b3:

[0015] b1) The content of the β-oxygen species is 1.48-2.93 wt‰, the detection range for ethanol is 5-100 ppm, and the detection temperature is 350℃. 2 The percentage was 95.6%-99.8%.

[0016] b2) The content of the β-oxygen species is 2.93 wt‰, the detection range for ethanol is 5-100 ppm, and the detection temperature is 350℃. 2 It is 99.8%;

[0017] b3) The content of the β-oxygen species is 2.93 wt‰, the detection range for ethanol is 2-200 ppm, and the detection temperature is 350℃. 2 It is 99.7%.

[0018] Beneficial effects

[0019] (1) This invention selects cantilever-TPD for quantitative detection of oxygen species, with a resolution of up to 0.1 ng, far exceeding the resolution of traditional thermogravimetric analysis (1 μg). Combined with cantilever-TPD quantitative detection, by adjusting the content of specific oxygen species, the linear detection range of ethanol can be broadened to 2-200 ppm, and R 2≥99.7%, the detection linear range of ethanol is as low as 2ppm, and it is suitable for trace gas detection. (2) The present application only needs to test each metal oxide semiconductor once, and the performance of the material required for different gas sensitivity can be analyzed, the efficient use of oxygen species is realized, and the traditional trial and error method is innovated, thereby greatly reducing the time required for optimizing the performance and working temperature of the gas sensor. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The SEM photo of the pure high-temperature-resistant nanomaterial prepared in Example 1.

[0021] Figure 2 The TEM photos of the pure high-temperature-resistant nanomaterial (a) prepared in Example 1 and SnO2-200 (b) in Example 2. Figure 3 The device and method for quantitatively detecting the oxygen species on the surface of the gas-sensitive material in Example 3, wherein a is a schematic diagram of a chip test, b is a mass-type temperature programmed desorption curve, c is a desorption rate type TPD curve, and d is the extraction of active energy and oxygen species content.

[0022] Figure 4 The test flow for determining the influence of the type and content of the surface oxygen species of the metal oxide semiconductor on the linearity of gas detection.

[0023] Figure 5 The SEM photo of the MEMS sensor prepared in Example 4.

[0024] Figure 6 The change of the resistance of the pure SnO2 gas-sensitive material with time under different hydrogen concentrations.

[0025] Figure 7 The linear response fitting curve of the SnO2 gas-sensitive material to different concentrations of hydrogen.

[0026] Figure 8 The change of the resistance of SnO2-150 with time under different hydrogen concentrations.

[0027] Figure 9 The linear response fitting curve of the SnO2-150 gas-sensitive material to different concentrations of hydrogen.

[0028] Figure 10 The change of the resistance of SnO2-200 with time under different hydrogen concentrations.

[0029] Figure 11 The linear response fitting curve of the SnO2-200 gas-sensitive material to different concentrations of hydrogen.

[0030] Figure 12The resistance of SnO2-300 over time at different hydrogen concentrations.

[0031] Figure 13 The linear response fitting curve of SnO2-300 gas sensitive material to different concentrations of hydrogen.

[0032] Figure 14 The resistance of pure SnO2 gas sensitive material over time at different ethanol concentrations.

[0033] Figure 15 The linear response fitting curve of pure SnO2 gas sensitive material to different concentrations of ethanol.

[0034] Figure 16 The resistance of SnO2-150 over time at different ethanol concentrations.

[0035] Figure 17 The linear response fitting curve of SnO2-150 gas sensitive material to different concentrations of ethanol.

[0036] Figure 18 The resistance of SnO2-200 over time at different ethanol concentrations.

[0037] Figure 19 The linear response fitting curve of SnO2-200 gas sensitive material to different concentrations of ethanol.

[0038] Figure 20 The linear response fitting curve of SnO2-200 gas sensitive material to different concentrations of ethanol, with the linearity extended to the range of 2ppm-200ppm.

[0039] Figure 21 The resistance of SnO2-300 over time at different ethanol concentrations.

[0040] Figure 22 The linear response fitting curve of SnO2-300 gas sensitive material to different concentrations of ethanol. DETAILED DESCRIPTION

[0041] The application will be further described below in connection with specific embodiments. It should be understood that these embodiments are intended to illustrate the application and not to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or changes to the application upon reading and understanding the content of the application, and these equivalent forms also fall within the scope of the appended claims.

[0042] The embodiment proposes a method for regulating the linearity of a gas sensor, the core idea of which is to accurately control the types, distribution and desorption activation energy of active oxygen species on the surface of SnO2 metal oxide conductor, thereby improving the consistency and linearity of the sensing reaction. Specifically, the following steps are included:

[0043] (1) Quantitative detection of surface oxygen species and calculation of activation energy

[0044] The cantilever-TPD (temperature programmed desorption) method is used to quantitatively measure the adsorbed oxygen species α (O2-), β (O-) and γ (O 2 -) on the surface of SnO2 nanobelt, and the desorption temperatures of α, β and γ oxygen species are determined by Gaussian peak fitting;

[0045] (2) Optimization of oxygen vacancies and adsorbed oxygen of gas sensitive material

[0046] The concentration of oxygen vacancies (O v ) on the surface of SnO2 nanobelt is regulated by gas phase reduction method (200℃, H2 treatment) to increase the oxygen species with the strongest reactivity;

[0047] (3) MEMS gas sensor test is used to verify the influence of adsorbed oxygen species on ethanol / hydrogen sensing response: at medium-high temperature (350℃), O - 2- (β) (E d is higher) dominates the linear detection of ethanol (1-200ppm); at low working temperature (250℃), O2- (α) (E d is lower) dominates the linear detection of H2 (1-100ppm);

[0048] (4) Widening the linear detection range: by regulating the content of O - 2- (β), the linear detection range of ethanol can be widened to 200ppm, and R 2 ≥ 99.7%.

[0049] In the present invention, the cantilever-TPD (temperature programmed desorption) method is used according to patent 202210320215.6 (named "a metal oxide catalyst activity testing device and testing method"), and the specific testing process is not described in detail in the present invention.

[0050] Figure 4 The test flow for determining the influence of the types and contents of surface oxygen species of metal oxide semiconductor on the linearity of gas detection is determined for the present invention.

[0051] The present invention optimizes the linearity of the sensor according to the number of oxygen species. In the research of gas sensors, when fitting the relationship between response value and gas concentration, R 2 is a key indicator for measuring linearity: when R 2The closer to 1, the higher the degree of coincidence of the fitting straight line with the data points, and the more significant the linear relationship is; when R 2 The closer to 0, the less the fitting straight line can explain the data change, and the weaker the linear relationship is.

[0052] The present application adopts MEMS gas sensor testing to verify the influence of the type of oxygen species adsorbed by the gas-sensitive sensing material on the sensing response of ethanol or hydrogen, wherein when C2H5OH (ethanol) and β oxygen (O - ) occur reduction reaction, free electrons are released into the conduction band of the material, resulting in resistance drop, and the reaction equation of the surface oxygen species is:

[0053] C2H5OH + 6O - (suf) → 2CO2 + 3H2O + 6e - .

[0054] When hydrogen (H2) and α oxygen (O2 - ) occur reduction reaction, free electrons are released into the conduction band of the material, resulting in resistance drop, and the reaction equation of the surface oxygen species is:

[0055] 2H2 + O2 - (suf) → 2H2O + e - .

[0056] Embodiment 1

[0057] In this embodiment, CVD (chemical vapor deposition) is adopted, a Kechuang double-temperature-zone tube furnace (model OTF-1200X) is used, high-purity tin powder (200 mesh) is used as an evaporation source, a silicon wafer is selected as a growth substrate, and a pure high-temperature-resistant nanomaterial is synthesized, and the specific steps are as follows:

[0058] S1. 200 mg of high-purity tin powder is loaded in an alumina ceramic boat, then the alumina ceramic boat is placed in the high-temperature zone of the tube furnace, and the growth substrate silicon wafer is placed on a high-temperature-resistant quartz sheet in the low-temperature zone 2 cm downstream of the evaporation source (i.e. the alumina ceramic boat containing tin powder);

[0059] S2. The synthesis system is vacuumized until the vacuum degree in the system reaches 2×10 -3 Torr, under vacuum conditions, 100 sccm of Ar gas containing 0.4 vol% O2 is introduced into the system;

[0060] S3. The high-temperature zone is heated at a rate of 20℃ / min to 900℃, and at the same time, the low-temperature zone is also heated at the same heating time to 600℃, when the high-temperature zone and the low-temperature zone both reach the set temperature, the temperature of each zone is kept for 2h;

[0061] S4. After the heat preservation procedure, keep the vacuum state, and continuously input 100 sccm of argon gas containing oxygen until the temperature of the high-temperature zone is lower than 200℃, stop the vacuum, but continue to maintain the input gas until the system returns to normal pressure, and the substrate is naturally cooled to obtain a white cotton-like single-crystal nanomaterial, that is, a pure high-temperature-resistant nanomaterial. Figure 1 The middle line strip structure is SnO2 nanobelt, which is uniformly distributed.

[0062] Example 2

[0063] The oxygen species on the surface of the pure high-temperature-resistant nanomaterial prepared in Example 1 is regulated by a reducing atmosphere treatment to obtain a gas-sensitive material. The reducing treatment is used to regulate the chemical state of the α and β adsorbed oxygen on the surface.

[0064] The oxygen vacancy (O v ) concentration of the SnO2 nanobelt is regulated by a reducing method to increase the O-(β) species with the strongest reaction activity. The tin dioxide nanobelt is reduced in an Ar atmosphere containing 5% H2 at 150℃, 200℃ and 300℃ respectively to obtain different non-stoichiometric tin dioxide gas-sensitive materials, which are numbered as SnO2-150, SnO2-200 and SnO2-300.

[0065] It can be seen that the material structure is not changed after the hydrogen treatment, and only the surface oxygen species of the material is changed. Figure 2

[0066] Example 3

[0067] The oxygen species on the SnO2-150, SnO2-200 and SnO2-300 of Example 2 and the pure high-temperature-resistant nanomaterial (i.e. pure SnO2) of Example 1 are quantitatively detected. The present application uses the following equipment for testing: a high-precision gas flow controller, a resonant cantilever beam detection chip (as shown in FIG. 1a), a chip-type thermogravimetric analyzer (model: μ-CITA) and a computer equipped with resonant signal analysis software and calculation software. Figure 3

[0068] Before quantitative detection, the sample is first dispersed in ethanol by ultrasonic, and after in-situ heating at 200℃, the excess solvent is removed by blowing inert gas (Ar or N2). During the test, the gas-sensitive material is placed in an Ar atmosphere of 100 sccm. First, the mass of the sample is tested (determined by the change of the resonant frequency of the cantilever beam, which can reach pg level accuracy); then, through dynamic testing, the temperature is raised at a heating rate of 20℃ / min, and the specific mass and desorption temperature point of the desorbed oxygen species are recorded. The mass-type temperature programmed desorption data are recorded, the abscissa is the temperature in Celsius (℃), and the ordinate is the accurate desorption mass of the oxygen species normalized according to the sample mass, to obtain the mass-type temperature programmed desorption curve (as shown in FIG. 2a). Figure 3 ​​b).

[0069] The mass-type temperature programmed desorption data of the gas sensitive material obtained by the test is differentiated once to obtain rate-type temperature programmed desorption data with desorption rate as the ordinate. The peak value is extracted after the first differentiation, which corresponds to the maximum desorption rate of α, β and γ oxygen species respectively. The desorption rate is divided into peaks according to Gauss, the peak center at about 200°C is the α oxygen distribution peak, the peak center at about 400°C is the β oxygen distribution peak, and the peak center at about 550°C is the γ distribution peak, to obtain the desorption rate type TPD curve (as shown in Figure 3 c).

[0070] The area obtained by integration is the specific quantitative oxygen species desorption value. The α oxygen is an oxygen species adsorbed in a molecular form, the physical adsorption oxygen α1 below 100°C, and the α2 oxygen species at 150-350°C is a weakly active chemisorbed oxygen which reacts with a gas with strong reducing property such as H2. According to the activity and oxygen species content extraction of the desorption rate type TPD curve, the measured value of the α oxygen content is 1.0wt.‰ (SnO2), 1.75wt.‰ (SnO2-150), 1.25wt.‰ (SnO2-200) and 0.4wt.‰ (SnO2-300) respectively. The β oxygen is an oxygen species adsorbed in an oxygen atom form, and the chemical formula is O - . The measured value of the β oxygen content in the sample is 1.39wt.‰ (SnO2), 1.48wt.‰ (SnO2-150), 2.93wt.‰ (SnO2-200) and 1.75wt.‰ (SnO2-300), wherein the β oxygen content of the SnO2-200 sample is the highest (as shown in Figure 3 d).

[0071] Example 4

[0072] In this embodiment, the SnO2-150, SnO2-200 and SnO2-300 in Example 3 and the SnO2 in Example 1 are made into MEMS sensors, Figure 5 , and the center position of the powdery substance is the SnO2 gas sensitive material.

[0073] In this embodiment, the working temperature is adjusted for different target gases (such as H2 and ethanol) to maximize the reaction efficiency of the adsorbed oxygen species and the gas molecules, and the specific adjustment is as follows:

[0074] Low working temperature (250°C): The mass of the α (O2-) species is quantitatively detected, the sample with the highest activation energy of the α oxygen species has higher sensitivity to H2, the more the mass of the oxygen species detected quantitatively, the larger the linear range of the corresponding detection, and the details are shown in Table 1.

[0075] Medium-high temperature (350℃): The mass of β (O-) species was quantitatively detected, and the sample with the highest β oxygen content had the best linearity. The sample with the lowest activation energy of β oxygen species had the best ethanol response sensitivity. The higher the O- content, the more active sites on the sensor surface that could participate in the reaction, the more continuous electron transport under high concentration of ethanol, the linear range was widened, see Table 1.

[0076] Table 1

[0077] Name of the gas sensitive material Alpha oxygen content H2 detection R 2 ]] Beta oxygen content Ethanol detection R 2 ]] pure Sn02 1.0 wt. ‰ 95.8％ 1.39 wt. ‰ 93.9％ SnO2-150 1.75 wt. ‰ 98.1 % (optimum) 1.48 wt. ‰ 99.6％ SnO2-200 1.25 wt. ‰ 96.3％ 2.93 wt. ‰ 99.8 % (optimum) SnO2-300 0.4 wt. ‰ 87.7％ 1.75 wt. ‰ 95.6％

[0078] Figure 6 The resistance of pure SnO2 gas sensitive material changes with time under different hydrogen concentrations (50ppm, 100ppm, 150ppm and 200ppm).

[0079] Figure 7 The linear response fitting curve of pure SnO2 gas sensitive material to different concentrations of hydrogen, the test temperature is 250℃, R 2 = 95.8%, the detection range is 50-200ppm.

[0080] Figure 8 The resistance of SnO2-150 changes with time under different hydrogen concentrations (50ppm, 100ppm, 150ppm and 200ppm).

[0081] Figure 9 The linear response fitting curve of SnO2-150 gas sensitive material to different concentrations of hydrogen, the test temperature is 250℃, R 2 = 98.1%, this material contains the most α2 oxygen, and has the best linearity for hydrogen response, far exceeding the linearity of conventional sensors (R 2 ≤ 95%), the detection range is 50-200ppm.

[0082] Figure 10 The resistance of SnO2-200 changes with time under different hydrogen concentrations (50ppm, 100ppm, 150ppm and 200ppm).

[0083] Figure 11 The linear response fitting curve of SnO2-200 gas sensitive material to different concentrations of hydrogen, the test temperature is 250℃, R 2 = 96.3%, the detection range is 50-200ppm.

[0084] Figure 12 The resistance of SnO2-300 changes with time under different hydrogen concentrations (50ppm, 100ppm, 150ppm and 200ppm).

[0085] Figure 13 The curves showing the linear response of SnO2-300 gas-sensitive material to different concentrations of hydrogen are provided. The test temperature was 250℃. 2 =87.7%, detection range is 50-200ppm.

[0086] Figure 14 The resistance of pure SnO2 gas-sensitive material changes over time under different ethanol concentrations (5ppm, 20ppm, 50ppm and 100ppm).

[0087] Figure 15 The linear response curves of pure SnO2 gas-sensitive material to different concentrations of ethanol are shown. The test temperature is 350℃. R 2 =93.9%, detection range is 5-100ppm.

[0088] Figure 16 The resistance of SnO2-150 changes over time under different ethanol concentrations (5ppm, 20ppm, 50ppm and 100ppm).

[0089] Figure 17 The curves showing the linear response of SnO2-150 gas-sensitive material to different concentrations of ethanol are provided. The test temperature was 350℃. 2 =99.6%, detection range is 5-100ppm.

[0090] Figure 18 The resistance of SnO2-200 changes over time under different ethanol concentrations (5ppm, 20ppm, 50ppm and 100ppm).

[0091] Figure 19 The curves showing the linear response of SnO2-200 gas-sensitive material to different concentrations of ethanol are provided. The test temperature was 350℃. 2 =99.8%, detection range 5-100ppm. This material has the highest β-oxygen content, and the linearity of ethanol sensing is the best among the tested materials, far exceeding that of conventional sensors (R... 2 ≤95%.

[0092] Figure 20 To extend the linearity of the SnO2-200 gas-sensitive material to different concentrations of ethanol in the range of 2ppm-200ppm, the test temperature was 350℃. 2 =99.7%.

[0093] Figure 21 The resistance of SnO2-300 changes over time under different ethanol concentrations (5ppm, 20ppm, 50ppm and 100ppm).

[0094] Figure 22 The linear response fitting curve of SnO2-300 gas sensitive material to different concentrations of ethanol was obtained, and the test temperature was 350°C, R 2 = 95.6%, and the detection range was 5ppm-100ppm.

[0095] Through the experiment, it can be proved that when the amount of molecular state adsorbed oxygen species α oxygen (O2 - ) on the surface of the metal oxide sensing material is in the range of 1.0wt‰-1.75wt‰, the response of the sensing material to the reducing gas has a linearity of R 2 > 95%. For example, the linearity of the hydrogen sensor of the sample SnO2-300 with the content of α oxygen species lower than the range is not good (R 2 is only 87.7%), and SnO2-150 has the highest content of α oxygen species, and the linearity of the hydrogen detection is the best (R 2 is only 98.1%).

[0096] The single atom adsorbed oxygen β (O - ) on the surface of the metal oxide sensing material has strong activity, and is the main working oxygen species of common ethanol, carbon dioxide, VOC and other sensors. When the content of β oxygen species is in the range of 1.48wt‰-2.93wt‰, the sensing material has a linearity of R 2 > 95% to general reducing gases such as ethanol. When the content of β oxygen species of the sample is 1.39wt‰, the linearity of the ethanol sensor is not good (R 2 is only 93.9%), and SnO2-200 has the highest content of β oxygen species (2.93wt.‰), and the linearity of the ethanol detection is the best (R 2 is 99.8%).

[0097] By comparing Figure 7 and Figure 11 , the response Ra / Rg of the SnO2-200 sample to ethanol gas under 100ppm is 4.6, and the response Ra / Rg of the pure SnO2 to ethanol gas is 1.2, which is sufficient to prove that by regulating the type and content of oxygen species, the sensitivity of the SnO2-200 sample is 3.8 times higher than that of the pure SnO2 sensor.

[0098] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for regulating linearity of a gas sensor, comprising the steps of: quantitatively measuring the type and content of surface oxygen species of a metal oxide semiconductor by a cantilever-programmed temperature desorption method, and regulating the content of a specific oxygen species by a gas phase reduction method to improve the linearity of the gas sensor for detecting different gases.

2. The method of claim 1, wherein: The metal oxide semiconductor is selected from one of Sn02, ZnO or W03.

3. The method of claim 1, wherein: The oxygen species include an alpha oxygen species O2-, a beta oxygen species O- and a gamma oxygen species O 2 one or several of the following:

4. The method of claim 1, wherein: The gas includes hydrogen or ethanol.

5. The method according to claim 3 or 4, characterized in that: The regulation includes any one of the following a1-a3: a1) the content of the alpha oxygen species is 1.0-1.75 wt‰, the detection range of hydrogen is 50-200 ppm, the detection temperature is 250°C, R 2 is 95.8-98.1%; a2) the content of the alpha oxygen species is 1.25-1.75 wt‰, the detection range for hydrogen is 50-200 ppm, the detection temperature is 250 °C, R 2 is 96.3-98.1%; a3) the content of the alpha oxygen species is 1.75 wt‰, the detection range for hydrogen is 50-200 ppm, the detection temperature is 250 °C, R 2 was 98.1%.

6. The method of claim 3 or 4, wherein: The regulation includes any one of the following b1-b3: b1) the content of the beta oxygen species is 1.48-2.93 wt‰, the detection range of ethanol is 5-100 ppm, the detection temperature is 350℃, R 2 is 95.6-99.8%; b2) the content of the beta oxygen species is 2.93 wt‰, the detection range for ethanol is 5-100 ppm, the detection temperature is 350 °C, R 2 is 99.8%; b3) the content of the beta oxygen species is 2.93 wt‰, the detection range for ethanol is 2-200 ppm, the detection temperature is 350 °C, R 2 is 99.7%.

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