Gas identification method

Abstract

The invention discloses a gas identification method, and relates to the technical field of gas identification. The method comprises the following steps: exposing the gas sensor to a detection environment containing gas to be identified; carrying out direct current heating on a heater of the gas sensor; and monitoring the current change of the gas sensitive material layer of the gas sensor and the heater, calculating the temperature change of the heater by using the TCR relationship, and determining the type and concentration of the gas to be identified. The method provided by the invention provides a new scheme for rapidly distinguishing various reducing gases, shows high accuracy in the aspects of gas classification and concentration prediction, can more accurately analyze the performance of the sensor in different gas environments, and is very suitable for the field of atmospheric environment monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of gas identification, and in particular to a gas identification method. Background Art

[0002] Gas identification is an important topic in the field of gas sensing, especially when it comes to effectively detecting and distinguishing trace gas molecules in the environment. With the continuous advancement of gas sensing technology, the demand for online detection of gases such as ammonia (NH3), carbon monoxide (CO) and hydrogen (H2) is increasing. Since these gases may be harmful or have explosion risks when leaked, it is also very important to identify and detect the concentration of these gases. Gas identification is generally accomplished through gas sensors. Among the various sensor types, metal oxide semiconductor (MOS) gas sensors have become an ideal choice for the new generation of gas sensors due to their miniaturization, direct signal readout, and excellent compatibility with the most advanced micro-electromechanical systems (MEMS) technology.

[0003] MOS gas sensors typically detect gases by measuring changes in resistance. When the reducing target gas undergoes an exothermic oxidation / reduction reaction with oxygen on the sensor surface, the resistance of the MOS material typically decreases, and this process may also be accompanied by temperature changes, which are critical for gas identification. However, gas identification using temperature changes has not yet been applied in practice, and currently high-precision gas identification cannot be achieved using only a single MOS gas sensor.

[0004] In order to achieve high-precision gas identification, it is usually necessary to use multiple sensors and combine multiple computing processing technologies to analyze the signals of these sensors. For example, the prior art has developed a ceramic tube sensor array for detecting trimethylamine, which achieves accurate identification of gases by applying neural networks and pattern recognition algorithms. However, even with advanced sensors and algorithms, it is still quite challenging to identify gas types at different concentrations. This is because the signal pattern of each sensor in the sensor array may show a unique response to different concentrations of gas, which makes signal processing more complicated. Therefore, how to further improve the accuracy and reliability of gas identification by improving signal processing methods remains a major challenge. Summary of the invention

[0005] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a method for gas identification, which uses a single semiconductor sensor to directly identify the type of gas and determine the concentration of the gas by simultaneously measuring the temperature change and the conductivity change, and the cost is greatly reduced compared with the multiple sensor arrays of the prior art.

[0006] A second aspect of the present invention provides an application of a gas identification method.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect of the present invention provides a method for gas identification, comprising the following steps:

[0009] A gas sensor is used for gas identification, the gas sensor comprising a substrate, a support film, an electrode, a heater, an insulating layer and a gas-sensitive material layer; a groove is provided on the upper surface of the substrate; the support film is arranged on the substrate; an electrode, a heater and an insulating layer are respectively arranged on the support film; the gas-sensitive material layer is arranged on the insulating layer; the gas-sensitive material layer comprises a tin dioxide layer; the heater and the electrode are arranged on the same plane;

[0010] The method comprises the following steps:

[0011] The gas sensor is exposed to a detection environment containing a gas to be identified; a heater of the gas sensor is heated by direct current; current changes in the gas-sensitive material layer and the heater of the gas sensor are monitored, and the temperature change of the heater is calculated using the TCR relationship to determine the type and / or concentration of the gas to be identified.

[0012] Specifically, the method of the present invention determines the type and / or concentration of the gas to be identified by combining the current change of the gas-sensitive material layer and the temperature change of the heater.

[0013] The gas sensor used in the method of the present invention is a micro-electromechanical system gas sensor based on tin dioxide nanosheets, which is composed of an electrode, a heater, a support film, an insulating layer, a gas-sensitive material layer and a substrate, wherein the support film is used to support the heater. The heater, the measuring electrode and the sensing electrode are arranged on the same plane, and electrical isolation is ensured at the same time. The heater is also used as a resistance thermometer in the gas identification method of the present invention to monitor temperature changes.

[0014] The gas identification method of the present invention uses a single semiconductor gas sensor to measure the current change of the sensor during the sensing process, and indirectly monitors the temperature change (ΔT) according to the current change of the heater of the gas sensor, thereby realizing the type identification and concentration prediction of the gas. Although the redox reaction of the gas and the gas-sensitive material layer has little effect on the temperature of the gas sensor, the present invention draws the correlation between the gas sensor response and the temperature change in a two-dimensional space through research, and finds that there is a macroscopic law between the temperature change and the gas sensitivity. Since the redox reaction of the gas and the gas-sensitive material layer is an exothermic reaction, the temperature rises; at the same time, the reducing gas reacts with the negative oxygen ions on the surface of the gas-sensitive material layer to release free electrons, and the conductivity channel of the gas-sensitive material layer of the gas sensor will expand accordingly, resulting in an increase in the conductivity of the gas-sensitive material layer. Therefore, by monitoring the changes in temperature and electrical response, a single sensor can effectively distinguish and measure different gases.

[0015] The present invention adopts a direct current heating method to heat the heater of the gas sensor, thereby realizing the effect of using a single gas sensor to identify the gas type and predict its concentration.

[0016] The electrical response can be obtained by the current change in the gas-sensitive material layer: electrical response = sensor current in target gas ÷ sensor current in air.

[0017] The TCR (linear temperature coefficient of resistance) relationship is: Where R1 is the resistance of the micro heater at temperature T1, R2 is the resistance of the micro heater at temperature T2, and T1 and T2 are two temperatures randomly selected during the linear temperature resistance coefficient calibration test.

[0018] In some embodiments of the present invention, the heating voltage of the DC heating is 2-5V.

[0019] In some embodiments of the present invention, the heating voltage of the DC heating is 2-4V.

[0020] In some embodiments of the present invention, the circuit voltage of the DC heating is 2-5V.

[0021] In some embodiments of the present invention, the circuit voltage of the DC heating is 2-4V.

[0022] In some embodiments of the present invention, the heating voltage of the DC heating is equal to the circuit voltage.

[0023] In some embodiments of the present invention, the heating temperature is 200-600°C.

[0024] In some embodiments of the present invention, the heating temperature is 350-390°C.

[0025] In some embodiments of the present invention, the heating temperature is 360-380°C.

[0026] In some specific embodiments of the present invention, the heating temperature is 365-375°C.

[0027] In some embodiments of the present invention, the concentration of the gas to be identified in the detection environment is 100-500 ppm.

[0028] In some embodiments of the present invention, the concentration of the gas to be identified in the detection environment is 150-500 ppm.

[0029] In some embodiments of the present invention, the gas to be identified includes an oxidizing gas and / or a reducing gas.

[0030] In some embodiments of the present invention, the gas to be identified includes H2, NH3 and CO.

[0031] In some embodiments of the present invention, the insulating layer is a silicon nitride layer.

[0032] In some embodiments of the present invention, a window is provided on the insulating layer, and the window is used to expose a portion of the electrode connected to a power source or a portion in contact with a gas-sensitive material layer.

[0033] In some embodiments of the present invention, the support film is a silicon nitride film.

[0034] In some embodiments of the present invention, the support film has a thickness of 1 to 2 μm.

[0035] In some embodiments of the present invention, the electrode is a tantalum-platinum composite electrode.

[0036] In some embodiments of the present invention, the electrodes include measuring electrodes and sensing electrodes.

[0037] Specifically, the sensing electrode is connected to a power source (source meter), and the measuring electrode is in contact with the gas-sensitive material layer; the electrode window on the insulating layer is used to expose the portion of the sensing electrode connected to the power source and the portion of the measuring electrode in contact with the gas-sensitive material layer.

[0038] The heaters of the present invention are distributed around the measuring electrode.

[0039] In some embodiments of the present invention, the sensing electrodes are divided into temperature sensing electrodes and current sensing electrodes.

[0040] The temperature sensing electrode (connected to the heater) is used to make the heater reach the preset temperature, and at the same time estimate the instantaneous temperature change of the heater by measuring the current of the heater; the current sensing electrode (measuring the gas-sensitive material layer) is used to monitor the current change of the gas-sensitive material layer of the gas sensor.

[0041] In some embodiments of the present invention, the heater is circular in shape.

[0042] The present invention further selects a circular heater design to achieve uniform heat distribution.

[0043] In some embodiments of the present invention, the support film is suspended and fixed on the groove of the substrate by four cantilever beams.

[0044] In some embodiments of the present invention, the gas sensor is connected to a source meter.

[0045] The source meter can act as a power source and monitor the current changes of the gas sensor.

[0046] In some embodiments of the present invention, the sensing electrode of the gas sensor is connected to a source meter; wherein the temperature sensing electrode of the sensing electrode measures the current change of the heater and obtains the temperature change through the TCR relationship; the current sensing electrode of the sensing electrode measures the current change of tin dioxide in the gas sensitive material layer of the gas sensor through the measuring electrode.

[0047] In some embodiments of the present invention, the method for preparing the gas sensor comprises the following steps:

[0048] depositing a support film on a substrate by low pressure chemical vapor deposition;

[0049] forming heaters and electrodes by electron beam evaporation and lift-off processes;

[0050] forming an insulating layer on the support film by plasma enhanced chemical vapor deposition;

[0051] Using inductively coupled plasma dry etching to form an electrode window and a wet etching window on the insulating layer;

[0052] The suspended membrane structure is released by anisotropic etching; the suspended membrane structure includes an electrode, a heater, and an insulating layer; the supporting membrane is suspended and fixed by four cantilever beams;

[0053] The gas-sensitive material is coated on the heater to contact with the measuring electrode, and is subjected to high-temperature aging to form a gas-sensitive material layer to obtain the gas sensor.

[0054] In some embodiments of the present invention, the method for preparing the gas sensitive material in the gas sensor comprises the following steps:

[0055] The pH value of the soluble tin salt solution is adjusted to 12-14, a hydrothermal reaction is carried out, and the solid-liquid separation and drying are performed to obtain the gas-sensitive material.

[0056] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 170-190°C.

[0057] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 180-190°C.

[0058] In some embodiments of the present invention, the hydrothermal reaction time is 8 to 9 hours.

[0059] The second aspect of the present invention provides an application of the gas identification method described in the first aspect of the present invention in atmospheric environment monitoring.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The gas identification method of the present invention can accurately identify and quantify different gases by simultaneously monitoring the temperature change and electrical response of the gas sensor. The method achieves the purpose of gas type identification and concentration prediction using only one gas sensor, and can be used to selectively detect and quantify gases, such as hydrogen, ammonia, carbon monoxide, etc.

[0062] (2) The gas identification method based on the temperature change effect provided by the present invention provides a new solution for quickly distinguishing various reducing gases, and shows a high degree of accuracy in gas classification and concentration prediction. In addition, the versatility of being able to simultaneously measure the temperature change (i.e., calorimetric signal) and conductivity of the gas sensor also enables the method to more accurately analyze the performance of the sensor in different gas environments, which is very suitable for the field of environmental monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a schematic diagram of the structure of the gas sensor used in Example 1 of the present invention.

[0064] Figure 2 This is a test schematic diagram of using a gas sensor to perform gas identification in Example 1 of the present invention.

[0065] Figure 3 is a diagram showing the relationship between the heater temperature and the heating voltage in Example 1 of the present invention; wherein, Figure 3 (a) is the temperature coefficient of resistance (TCR) diagram of the micro heater; Figure 3 (b) is the relationship between sensor temperature, heating voltage and power consumption.

[0066] Figure 4The dynamic response-recovery curve of the gas sensor when exposed to 150 to 500 ppm of H2, NH3 and CO gases in Example 1 of the present invention; wherein, Figure 4 (a) is the response-recovery curve of the gas sensor to H2, NH3, and CO. Each peak represents the concentration of a gas. Figure 4 (b) is the response of the gas sensor to different gas concentrations.

[0067] Figure 5 : is a graph showing changes in heater current and sensor temperature when the gas sensor is exposed to H2, NH3 and CO gases of different concentrations in Example 1 of the present invention; wherein, Figure 5 (a), (b), and (c) are graphs showing the changes in current and temperature when exposed to H2, NH3, and CO gases, respectively; Figure 5 (d) is the temperature variation of the gas sensor with different target gas concentrations.

[0068] Figure 6 Graph showing changes in heater temperature and current response of the gas sensitive material layer of the gas sensor used in Example 1 of the present invention.

[0069] Reference numerals:

[0070] 100 - substrate, 200 - heater, 300 - measuring electrode, 400 - gas sensitive material layer, 500 - insulating layer, 600 - supporting film, 701 - current sensing electrode, 702 - temperature sensing electrode, 800 - groove. DETAILED DESCRIPTION

[0071] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0072] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0073] Refer to the attached Figure 1 The structural schematic diagram of the gas sensor of FIG. 1 illustrates that the preparation method of the gas sensor used in the following embodiments of the present invention includes the following steps:

[0074] S1. A silicon nitride support film 600 having a thickness of 1.2 μm is deposited on a 4-inch single crystal silicon substrate 100 by low pressure chemical vapor deposition (LPCVD);

[0075] S2. Using electron beam evaporation technology, a tantalum (Ta) composite layer with an average thickness of 15 nm and a platinum (Pt) composite layer with an average thickness of 200 nm on the support film is micro-patterned to form a heater 200, a measuring electrode 300, a current sensing electrode 701, and a temperature sensing electrode 702, and then the remaining parts are removed by stripping;

[0076] S3. A silicon nitride insulating layer 500 having a thickness of 500 nm is deposited by plasma enhanced chemical vapor deposition (PECVD), and then, the current sensing electrode 701 and the temperature sensing electrode 702, a portion of the measuring electrode 300 and an anisotropic etching window are exposed by inductively coupled plasma (ICP) dry etching;

[0077] S4. Anisotropic etching is performed at 60°C using a 40% by mass KOH solution to release the suspended membrane structure; the suspended membrane structure refers to the measuring electrode 300, the current sensing electrode 701 and the temperature sensing electrode 702, the heater 200 and the four cantilever beams and part of the support film 600 and the insulating layer 500;

[0078] S5. The gas-sensitive material is coated on the heater, in contact with the measuring electrode 300, and aged at 370°C for 7 days to form a gas-sensitive material layer 400;

[0079] S6. After completing step S5, the ceramic package is cut by invisible laser cutting and wire bonded to the ceramic package for gas identification testing;

[0080] The obtained gas sensor structure is as follows Figure 1 shown.

[0081] The preparation method of the gas-sensitive material comprises the following steps:

[0082] 0.6mmol SnCl2·2H2O was dissolved in 20ml deionized water, and the pH value was adjusted to 13 to obtain a tin chloride solution; the tin chloride solution was then stirred continuously for 20min, and transferred to a polytetrafluoroethylene-lined autoclave, and subjected to a hydrothermal reaction at 185°C for 8 hours to obtain a precipitate; the obtained precipitate was washed, centrifuged, and dried at 80°C to obtain a SnO2 nanopowder material.

[0083] The gas identification method of the present invention is described in detail below in conjunction with different embodiments.

[0084] Example 1

[0085] This embodiment provides a method for gas identification, comprising the following steps:

[0086] The standard gas and dry synthetic air are mixed by a digital mass controller to form a mixed gas, which is introduced into a 3cm 3A gas identification test is performed for 1 minute in the test chamber (sealed space of PTFE);

[0087] The dry synthetic air includes oxygen and nitrogen, and the standard gas is a mixture of 1000 ppm of the gas to be identified and nitrogen. Both the dry synthetic air and the standard gas are purchased from conventional markets.

[0088] The gas sensor is placed in a test chamber containing a mixed gas; the current sensing electrode and temperature sensing electrode of the gas sensor are connected to a power supply (Keithley 2600 series source meter) respectively, and the heater is heated by DC, with the heating voltage and circuit voltage both being 3V, and heated to a temperature of 370°C and kept warm; the test schematic diagram is shown in Figure 2 As shown;

[0089] The Keithley 2600 series source meter was used to measure the heating voltage (V H ) and circuit voltage (V C ) are both 3V, record the current change and temperature change of the gas sensor to determine the type and concentration of the gas; the temperature change of the gas sensor is calculated based on the current change of the temperature sensing electrode (i.e., the heater) using the TCR relationship. The TCR (linear temperature resistance coefficient) relationship is: Where R1 is the resistance of the micro heater at temperature T1, R2 is the resistance of the micro heater at temperature T2, and T1 and T2 are two temperatures selected during the linear temperature resistance coefficient calibration test.

[0090] The gas sensor includes a single crystal silicon substrate 100, a silicon nitride support film 600, a tantalum-platinum composite measuring electrode 300, a tantalum-platinum composite current sensing electrode 701, a tantalum-platinum composite temperature sensing electrode 702, a heater 200, a silicon nitride insulating layer 500 and a gas-sensitive material layer 400;

[0091] A groove 800 is formed on the upper surface of the single crystal silicon substrate 100;

[0092] The silicon nitride support film 600 is disposed on the single crystal silicon substrate 100;

[0093] Tantalum-platinum composite measuring electrode 300, tantalum-platinum composite current sensing electrode 701, tantalum-platinum composite temperature sensing electrode 702, and heater 200 are arranged on silicon nitride support film 600; the sensing electrode is divided into temperature sensing electrode and current sensing electrode, the temperature sensing electrode is connected to the heater to make the heater reach a preset temperature, and at the same time, by measuring the current of the heater, the instantaneous temperature change of the heater is estimated. The current sensing electrode is connected to the measuring electrode to monitor the current change of the gas sensitive material layer of the gas sensor;

[0094] The heater 200 is disposed on the silicon nitride support film 600 and distributed around the tantalum-platinum composite measuring electrode 300;

[0095] The heater 200 and the tantalum-platinum composite measuring electrode 300 are arranged on the same plane;

[0096] The insulating layer 500 is disposed on the silicon nitride support film 600;

[0097] The gas-sensitive material layer 400 is disposed on the silicon nitride insulating layer 500;

[0098] The gas-sensitive material layer 400 is a tin dioxide nanosheet layer.

[0099] In this embodiment, different gases and gas concentrations are set for gas identification; the gases are H2, NH3 and CO gases, and the concentration of each gas is set to different concentrations of 150ppm, 200ppm, 250ppm, 300ppm, 350ppm, 400ppm, 450ppm and 500ppm; the gas concentration is calculated based on the volume ratio or flow ratio of the gas to be identified and the dry synthetic air. For example, the standard gas (1000ppm) flow rate is 20sccm, and the dry air flow rate is 80sccm, then the target gas concentration is 1000*20 / (80+20)=200ppm.

[0100] The effects of the above-mentioned embodiments 1 and 2 are described below with reference to the accompanying drawings:

[0101] The sensor response S is defined as the current I in the gas to be identified g The current I in the air a ratio; C is the gas concentration; R 2 is the correlation coefficient.

[0102] Figure 3 Graph showing the relationship between heater temperature and heating voltage in Example 1 of the present invention. Figure 3 The packaged gas sensor was placed in a high temperature drying oven and the electrothermal characteristics were analyzed at 25-295°C. Figure 3 The results show that the temperature coefficient of resistance (TCR) of the heater in the gas sensor shows good linearity, and the TCR value is 2.53×10 -3 ℃ -1 , can be used to establish the relationship between the heater temperature and the heating voltage (V H ). At the same time, analyze Figure 3 It can be seen that to maintain the heater temperature at an isothermal state of about 370° C., power consumption of about 26.6 mW is required.

[0103] Figure 4The dynamic response-recovery curve of the gas sensor when exposed to 150 to 500 ppm of H2, NH3 and CO gases in Example 1 of the present invention. Figure 4 It can be seen that the gas sensor is set to about 370℃ (V H =3V), when exposed to reducing gas, the response of the sensor increases sharply and returns to the initial state after the air is pumped back in. The specific mechanism of this phenomenon is: when the gas sensor is exposed to air, oxygen molecules will chemically adsorb on the surface of SnO2 particles in the gas-sensitive material layer, capture electrons from the SnO2 conduction band, and convert them into active oxygen species, thereby forming an electron depletion layer (EDL); and the introduction of reducing gas will remove these adsorbed oxygen species, resulting in a decrease in EDL, and ultimately increasing the conductivity of the material. Therefore, by monitoring the current change of the measuring electrode 300 to obtain the current change of SnO2, the partial pressure of the gas to be identified can be inferred.

[0104] For SnO2-based gas sensors, their selectivity is affected by the operating temperature and the ratio of active oxygen to reducing gas. Since the oxidation / reduction reaction is temperature-dependent, different gases to be identified exhibit different sensing responses at different temperatures. In addition, the electrical response of the gas sensor at a specific concentration and temperature is related to the electron donor tendency of the functional groups of the gas molecules. For example, the presence of HH bonds (bond energy of 432 kJ / mol) and NH bonds (bond energy of 386 kJ / mol) makes H2 exhibit a more significant sensing response than NH3 at higher temperatures. And because the molecular molar mass of the CO molecule is large, its Knudsen diffusion rate (D k ) is much slower than H2 and NH3, which also leads to its lower response speed. Therefore, the present invention can identify different gases by monitoring the current change of the heater of the gas sensor and calculating the temperature change using the current change.

[0105] The increase in gas sensor temperature is related to chemical reactions during gas chemical adsorption, which usually release heat. The present invention can indirectly obtain a calorimetric signal by monitoring the current change of the heater, and understand the specific situation of the reaction based on the properties of the analyte and the characteristics of tin dioxide. Figure 5 As shown, Figure 5This is a graph showing the change in current when the gas sensor is exposed to different concentrations of H2, NH3 and CO gases in Example 1 of the present invention. It can be seen that a H2 concentration of 500ppm causes a current drop of 0.35mA, and the corresponding temperature change is 28.3°C (estimated by the TCR relationship). As the gas concentration increases, the change in the temperature of the gas sensor also increases, and this change matches the increase in the conductivity of tin dioxide. It is particularly noteworthy that different reducing gases will cause the sensor temperature to rise to varying degrees. For example, when exposed to 500ppm of CO, the temperature rises by about 26.3°C, which is 9.4 times the temperature rise of NH3 (ΔT=2.8°C). This shows that the temperature change is related to the oxidation activity of the gas to be identified, and compared to CO, the oxidation activity of NH3 is lower (i.e., the reaction enthalpy change is smaller). That is, the increase in temperature during the sensing process is due to the exothermic oxidation / reduction reaction between the reducing analyte and the surface active oxygen species, which simultaneously leads to an increase in the conductivity of the metal oxide semiconductor (tin dioxide in the embodiment of the present invention). Therefore, this law can be used to identify the type of gas and predict the concentration.

[0106] According to the above analysis, reducing gases such as NH3 will cause a moderate increase in sensor current, but only cause a slight increase in sensor temperature, while CO gas will cause a smaller electrical response but cause a significant change in sensor temperature within the measured concentration range. These results can be used to distinguish different types of gases and estimate their concentrations.

[0107] At about 370°C, the gas sensor of the present invention is used to identify 150-500 ppm of H2, NH3 and CO gas species by simultaneously measuring the sensor temperature and the current change of the sensing material. Figure 6 As shown, Figure 6 The temperature of the heater and the current response of the gas sensitive material layer of the gas sensor used in Example 1 of the present invention are shown in FIG. By representing the concentration of each gas m in a two-dimensional parameter space and by the point (S m , ΔT m ), as the concentration of the target gas changes, these points will move along a unique curve representing the gas type. If these curves do not intersect, the gas type m can be easily identified by the measurement points on the pre-calibrated curve, thereby effectively distinguishing H2, NH3 and CO. In addition, based on these curves, the concentration of the gas can also be determined. During the gas sensing test, even if the gas concentration changes, it will not hinder the use of characteristic curves (S, ΔT) in two-dimensional space for gas differentiation. It can be seen that compared with the traditional method that requires multiple sensors and complex signal processing, the gas identification method of the present invention is simpler and more cost-effective.

[0108] In summary, the gas identification method based on the temperature change effect provided by the present invention provides a new solution for quickly distinguishing various reducing gases, and shows a high degree of accuracy in gas classification and concentration prediction. In addition, the method of the present invention has the versatility of being able to simultaneously measure the temperature change (i.e., calorimetric signal) and conductivity of the gas sensor, which also enables the method to more accurately analyze the performance of the sensor in different gas environments, and is more suitable for atmospheric environment monitoring than traditional methods.

[0109] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for gas identification, characterized in that: A gas sensor is used for gas identification, the gas sensor comprising a substrate, a support film, an electrode, a heater, an insulating layer and a gas-sensitive material layer; a groove is provided on the upper surface of the substrate; the support film is arranged on the substrate; an electrode, a heater and an insulating layer are respectively arranged on the support film; the gas-sensitive material layer is arranged on the insulating layer; the gas-sensitive material layer comprises a tin dioxide layer; the heater and the electrode are arranged on the same plane; The method comprises the following steps: The gas sensor is exposed to a detection environment containing a gas to be identified; a heater of the gas sensor is heated by direct current; current changes in the gas-sensitive material layer and the heater of the gas sensor are monitored, and the temperature change of the heater is calculated using the TCR relationship to determine the type and / or concentration of the gas to be identified.

2. The method according to claim 1, characterized in that The heating voltage of the DC heating is 2 to 5V; And / or, the circuit voltage of the DC heating is 2-5V.

3. The method according to claim 1 or 2, characterized in that: The heating temperature is 200-600°C.

4. The method according to claim 1, characterized in that: The concentration of the gas to be identified in the detection environment is 100-500 ppm.

5. The method according to claim 1 or 4, characterized in that: The gas to be identified includes at least one of H2, NH3, and CO.

6. The method according to claim 1, characterized in that The insulating layer is a silicon nitride layer; and / or, a window is opened on the insulating layer, and the window is used to expose the portion of the electrode connected to the power supply or the portion in contact with the gas-sensitive material layer.

7. The method according to claim 1, characterized in that The support film is a silicon nitride film; and / or the support film has a thickness of 1 to 2 μm.

8. The method according to claim 1 or 6, characterized in that: The electrode is a tantalum-platinum composite electrode; and / or, the electrode includes a measuring electrode and a sensing electrode.

9. The method according to claim 1, characterized in that: The method for preparing the gas-sensitive material in the gas sensor comprises the following steps: The pH value of the soluble tin salt solution is adjusted to 12-14, a hydrothermal reaction is carried out, and the solid-liquid separation and drying are performed to obtain the gas-sensitive material.

10. Application of the gas identification method according to any one of claims 1 to 9 in atmospheric environment monitoring.

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