Methane gas detection sensor and methane gas detection sensing system

Abstract

This disclosure provides a methane gas detection sensor and a methane gas detection sensing system. The methane gas detection sensor includes a substrate and a sensing structure located on the substrate. The sensing structure includes: a gas detection layer comprising one or more of SnO2, Nb2O5, Y2O3, ZrO2, CeO2, La2O3, HfO2, Ta2O5, In2O3, CuO, Fe2O3, NiO, and Cu2O; and a filter layer located on the gas detection layer, comprising WO3. Using this methane gas detection sensor, the gas first enters the filter layer. The WO3 in the filter layer has a strong adsorption and reactivity with gases such as CO and H2S, reducing the amount of CO and H2S entering the gas detection layer, ensuring high sensitivity, selectivity, and accuracy of methane detection, while also improving the service life of the methane gas detection sensor.

Description

Technical Field

[0001] This disclosure relates to the field of gas detection, and in particular to a methane gas detection sensor and a methane gas detection sensing system. Background Technology

[0002] Gas sensors detect gas concentration by converting information such as gas composition and concentration into electrical signals. Commonly used gas sensors include semiconductor, electrochemical, catalytic combustion, thermal conductivity, and infrared gas sensors.

[0003] Traditional gas sensors employ a cover and sponge filter structure, resulting in a bulky appearance. With the development of microelectromechanical systems (MEMS) technology, gas sensors are gradually becoming smaller. However, existing gas sensors suffer from long-term reliability issues; the materials used to detect gas concentration deteriorate and deteriorate over time, affecting the sensor's lifespan and even reducing concentration detection accuracy.

[0004] Therefore, a new gas detection sensor needs to be developed. Summary of the Invention

[0005] This disclosure provides a methane gas detection sensor, comprising: a substrate and a sensing structure located on the substrate; the sensing structure includes: a gas detection layer for detecting methane, located on the substrate, the gas detection layer comprising one or more of SnO2, Nb2O5, Y2O3, ZrO2, CeO2, La2O3, HfO2, Ta2O5, In2O3, CuO, Fe2O3, NiO, and Cu2O; and a filter layer located on the gas detection layer, the filter layer comprising WO3 and SnO2, wherein the volume fraction of SnO2 in the filter layer is greater than or equal to 0%.

[0006] In some embodiments, the volume fraction of SnO2 in the filter layer is 0% to 50%; when the volume fraction of SnO2 in the filter layer is greater than 0%, the volume ratio of WO3 to SnO2 in the filter layer is 1:1 to 5:1.

[0007] In some embodiments, the filter layer further comprises Pd and / or Ir, and the volume fraction of the filter layer in the sensing structure is 40% to 60%.

[0008] In some embodiments, the filter layer comprises Pd and Ir, the sum of the mass fractions of Pd and Ir in the filter layer being 0.2wt% to 30wt%; or the filter layer comprises Pd or Ir, the mass fraction of Pd or Ir in the filter layer being 0.2wt% to 30wt%.

[0009] In some embodiments, the filter layer further comprises one or more of carbon black, graphite, and zeolite; the mass fraction of one or more of the carbon black, graphite, and zeolite in the filter layer is 40wt%~80wt%, and the specific surface area of ​​one or more of the carbon black, graphite, and zeolite is above 80m² / g.

[0010] In some embodiments, one or more of the carbon black, graphite, and zeolite are present in the filter layer at a mass fraction of 50wt% to 70wt%.

[0011] In some embodiments, the filter layer contains Pd or Ir, and the mass fraction of Pd or Ir in the filter layer is 1wt% to 15wt%; or the filter layer contains Pd and Ir, and the sum of the mass fractions of Pd and Ir in the filter layer is 1wt% to 15wt%.

[0012] In some embodiments, the filter layer contains Pd or Ir, and the mass fraction of Pd or Ir in the filter layer is 4wt% to 8wt%; or the filter layer contains Pd and Ir, and the sum of the mass fractions of Pd and Ir in the filter layer is 4wt% to 8wt%.

[0013] In some embodiments, the sensing structure further includes a moisture-proof layer located on the filter layer; the moisture-proof layer comprises: WO3 and SnO2, wherein the volume fraction of SnO2 in the moisture-proof layer is greater than or equal to 0%, and the volume fraction of the moisture-proof layer in the sensing structure is 30% to 50%; and a water-absorbing material, wherein the water-absorbing material comprises one or more of carbon black, graphite, and zeolite.

[0014] In some embodiments, the volume fraction of SnO2 in the moisture-proof layer is 0% to 50%; when the volume fraction of SnO2 in the moisture-proof layer is greater than 0%, the volume ratio of WO3 to SnO2 in the moisture-proof layer is 1:1 to 5:1.

[0015] In some embodiments, the moisture barrier further comprises Pd, wherein the mass fraction of Pd in ​​the moisture barrier is 0.1wt% to 15wt%.

[0016] In some embodiments, the absorbent material is composed of carbon black and / or graphite, and the mass fraction of the absorbent material in the moisture barrier is 30wt% to 70wt%; or the absorbent material is composed of zeolite, and the mass fraction of the zeolite in the moisture barrier is 20wt% to 60wt%.

[0017] In some embodiments, the gas detection layer further comprises: Pd, Pt, and Au; the volume fraction of the gas detection layer in the sensing structure is 5% to 20%; the mass fraction of Pd in ​​the gas detection layer is 0.1wt% to 10wt%; the mass fraction of Pt in the gas detection layer is 0.1wt% to 10wt%; and the mass fraction of Au in the gas detection layer is 0.01wt% to 10wt%.

[0018] In some embodiments, the mass fraction of Pd in ​​the gas detection layer is 2wt% to 3wt%; the mass fraction of Pt in the gas detection layer is 0.5wt% to 3wt%; and the mass fraction of Au in the gas detection layer is 0.1wt% to 2.5wt%.

[0019] In some embodiments, the gas detection layer further comprises Ir, wherein the mass fraction of Ir in the gas detection layer is 0.1wt% to 20wt%.

[0020] In some embodiments, the mass fraction of Ir in the gas detection layer is 1wt% to 3wt%.

[0021] In some embodiments, the Au particle size in the gas detection layer is 1 nm to 600 nm.

[0022] In some embodiments, the gas detection layer further comprises a porous material having Pd, Pt, and Au within its pores, and the porous material includes one or more of carbon black, graphite, and zeolite.

[0023] In some embodiments, the methane gas detection sensor further includes a support layer located between the substrate and the gas detection layer.

[0024] In some embodiments, the substrate is made of silicon, aluminum oxide, quartz, glass, silicon carbide, or ceramic.

[0025] In some embodiments, the sensing structure further includes a test electrode, at least partially located within the gas detection layer, for testing the resistance of the gas detection layer.

[0026] In some embodiments, the methane gas detection sensor further includes a heating electrode for heating the gas detection layer, the heating electrode being located between the substrate and the gas detection layer.

[0027] This disclosure also provides a methane gas detection sensing system, including: a methane gas detection sensor according to any of the above embodiments; and a control module for controlling the transmission of a first current or a second current to a heating electrode, wherein the first current is used to heat the gas detection layer by the heating electrode, and the second current is used to regenerate the catalyst in the gas detection layer, wherein the second current is greater than the first current.

[0028] In some embodiments, the methane gas detection sensing system further includes: a first power supply electrically connected to the heating electrode; the first power supply is a pulse power supply adapted to provide pulse current to the heating electrode.

[0029] In some embodiments, the methane gas detection sensing system further includes: a second power supply, electrically connected to a test electrode, for providing voltage to the test electrode, the test electrode being used to test the resistance of the gas detection layer.

[0030] In some embodiments, the control module is adapted to control the magnitude of the second current to be less than 1.5 times the magnitude of the first current.

[0031] Compared with the prior art, the technical solutions of the embodiments of this disclosure have the following beneficial effects: The sensing structure of the methane gas detection sensor in this embodiment includes a filter layer located on the gas detection layer. The filter layer contains WO3. When gas enters the sensing structure, it first enters the filter layer. The WO3 in the filter layer has a better adsorption effect on reducing gases such as CO and H2S than on methane, so that reducing gases such as CO and H2S are reacted in the filter layer, reducing their content entering the gas detection layer. This reduces the interference of reducing gases such as CO and H2S in methane gas detection, thereby improving the selectivity and accuracy of methane detection. While ensuring the accuracy of methane detection, it also increases the service life of the methane gas detection sensor.

[0032] Furthermore, the filter layer also contains Pd and / or Ir, which serve as catalytically active components to promote the redox reaction between interfering gases such as CO and H2S and adsorbed oxygen on the WO3 surface. At the same time, the heat released by the redox reaction helps to heat the gas detection layer, keeping it at a constant temperature and thus helping to ensure the sensitivity of gas detection.

[0033] Furthermore, the filter layer also comprises one or more of carbon black, graphite, and zeolite; the mass fraction of one or more of the carbon black, graphite, and zeolite in the filter layer is 40wt%~80wt%, and the specific surface area of ​​one or more of the carbon black, graphite, and zeolite is above 80m² / g. The filter layer has the functions of removing reducing gases such as CO and H2S and removing moisture, without the need to form an additional moisture-proof layer, which is beneficial for the miniaturization of methane gas detection sensors.

[0034] Furthermore, the sensing structure also includes a moisture-proof layer located on the filter layer; the moisture-proof layer comprises WO3, or WO3 and SnO2, and a water-absorbing material; the water-absorbing material comprises one or more of carbon black, graphite, and zeolite. The WO3 in the moisture-proof layer helps remove reducing gases such as CO and H2S, and synergistically with the WO3 in the filter layer to further enhance the removal of reducing gases such as CO and H2S. The moisture-proof layer can also remove water molecules from the gas, enhancing the protection of the gas detection layer and improving the service life of the gas sensor.

[0035] Furthermore, the moisture-proof layer also contains Pd. Pd catalyzes the reaction of oxygen adsorbed on the WO3 surface with reducing gases such as CO and H2S, which releases heat and helps to keep the gas detection layer warm, thus ensuring the sensitivity of gas detection. Attached Figure Description

[0036] Other features and advantages of this disclosure will be better understood through the following detailed description of alternative embodiments in conjunction with the accompanying drawings, in which the same reference numerals denote the same or similar parts, wherein: Figure 1 A schematic diagram of the structure of a methane gas detection sensor according to an embodiment of the present disclosure is shown; Figure 2 A schematic diagram of the structure of a methane gas detection sensor according to an embodiment of the present disclosure is shown. Detailed Implementation

[0037] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0038] Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. In the description of this disclosure, it should be understood that the terms “center,” “longitudinal,” “lateral,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this disclosure and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0039] This disclosure provides a methane gas detection sensor for detecting methane concentration. The methane gas detection sensor includes a substrate and a sensing structure located on the substrate.

[0040] The methane gas detection sensor of this disclosure is described in detail below with reference to the accompanying drawings.

[0041] Figure 1 A schematic diagram of a methane gas detection sensor according to an embodiment of this disclosure is shown. (Reference) Figure 1 This disclosure provides a methane gas detection sensor, which includes a substrate 10 and a sensing structure 20 located on one side of the substrate. The sensing structure 20 includes: a gas detection layer 201 for detecting methane, located on the substrate 10; and a filter layer 202 located on the gas detection layer 201.

[0042] The gas detection layer 201 comprises a metal oxide, which includes one or more of the following: SnO2, Nb2O5, Y2O3, ZrO2, CeO2, La2O3, HfO2, Ta2O5, In2O3, CuO, Fe2O3, NiO, and Cu2O. The filter layer 202 comprises WO3 and SnO2, with the volume fraction of SnO2 in the filter layer 202 being greater than or equal to 0%, meaning that the filter layer 202 contains WO3, and optionally SnO2. The volume of SnO2 (or WO3) in the filter layer 202 can be obtained by dividing the mass of SnO2 (or WO3) added during the preparation of the filter layer 202 by the density of SnO2 (or WO3), and its volume fraction can be calculated by dividing the volume of SnO2 (or WO3) by the total volume of the filter layer 202. The volume fractions of WO3 and SnO2 in other layers can also be calculated using the same method.

[0043] The filter layer 202 contains WO3. When gas enters the sensing structure 20, it first enters the filter layer 202 located on the outside. The WO3 in the filter layer 202 has a good adsorption effect on reducing gases such as CO and H2S. The reducing gases such as CO and H2S react in large quantities in the filter layer 202, thereby reducing their content in the gas detection layer 201. This reduces the interference of interfering gases such as CO and H2S in methane gas detection, ensuring the sensitivity, selectivity and accuracy of methane gas detection, while improving the service life of the methane gas detection sensor.

[0044] In the detection of urban gas, the methane gas sensor of this embodiment can remove a large proportion of reducing gases such as CO and H2S in urban gas in the filter layer 202, thereby improving the accuracy of methane detection and the service life of the methane gas sensor.

[0045] In some embodiments, the volume fraction of SnO2 in the filter layer 202 is 0%, meaning that the filter layer 202 contains only WO3 and no SnO2. In some embodiments, the volume fraction of SnO2 in the filter layer 202 is 0% to 50%.

[0046] In some embodiments, the filter layer 202 contains both WO3 and SnO2; in some embodiments, the volume ratio of WO3 to SnO2 in the filter layer 202 is 1:1 to 5:1, specifically, it can be 2:1, 3:1, 4:1, etc.

[0047] In some embodiments, the volume fraction of the filter layer 202 in the sensing structure 20 is 40% to 60%; specifically, it can be any value or a range of any two values ​​from 40%, 45%, 50%, 55%, to 60%. The volume fraction of the filter layer 202 in the sensing structure 20 can be calculated based on an area ratio estimation method (Dlesser's Principle). Specifically, a cross-sectional view of the sensing structure 20 is obtained, and the area of ​​the filter layer 202 and the total area of ​​the sensing structure 20 are processed and calculated using image analysis software (including but not limited to ImageJ), using the formula: Volume fraction of filter layer 202 = (Area of ​​filter layer 202 / Total area of ​​sensing structure 20) The volume fraction of filter layer 202 is calculated to be 100%. Similarly, the volume fractions of gas detection layer 201 and moisture barrier layer 203 in sensing structure 20 can be calculated using the same method.

[0048] In some embodiments, the filter layer 202 further comprises Pd and / or Ir, which acts as a catalyst supported on WO3 or on WO3 and SnO2, increasing the redox reaction rate of adsorbed oxygen on the WO3 surface with gases such as CO and H2S, thereby achieving rapid removal of gases such as CO and H2S. When the filter layer 202 comprises SnO2 and Pd and / or Ir supported on SnO2, SnO2 readily adsorbs methane molecules, and Pd and / or Ir can pre-activate the methane molecules (reducing the bond energy of the CH bonds in the methane molecules) to lower their oxidation reaction barrier, making it easier for methane molecules to undergo oxidation after diffusing into the gas detection layer 201, thus helping to increase the reaction rate and thereby improve the sensor's response rate. In addition, the exothermic reaction of adsorbed oxygen on the WO3 surface with CO and H2S catalyzed by Pd and / or Ir helps to assist in heating the gas detection layer, maintaining its temperature and thus contributing to the sensitivity of gas detection.

[0049] To better enable SnO2 and the Pd and / or Ir loaded on it to pre-activate methane molecules and reduce the reaction barrier after methane molecules enter the gas detection layer 201, in some embodiments, the volume fraction of SnO2 in the filter layer 202 is controlled to be 10% to 50%, specifically, for example, any value or any combination of two values ​​from 12%, 17%, 20%, 22%, 27%, 30%, 32%, 37%, 40%, 45%, and 50%.

[0050] In some embodiments, filter layer 202 comprises Pd and Ir. Ir has better catalytic performance and corrosion resistance than Pd, while Pd has lower cost than Ir, therefore the two can be used together. In some embodiments, the sum of the mass fractions of Pd and Ir in filter layer 202 is 0.2wt% to 30wt%. In some embodiments, filter layer 202 comprises either Pd or Ir, and the mass fraction of Pd or Ir in filter layer 202 is 0.2wt% to 30wt%.

[0051] In some embodiments, the filter layer 202, in addition to containing Pd and / or Ir, also contains one or more of carbon black, graphite, and zeolite. Carbon black, graphite, and zeolite can absorb water molecules, preventing moisture from entering the gas detection layer and affecting the detection sensitivity. Therefore, the sensing structure 20 has only two layers (gas detection layer 201 and filter layer 202, as shown in the image). Figure 2 As shown, the filter layer 202 has the functions of removing reducing gases such as CO and H2S and removing moisture, without the need to form an additional moisture-proof layer, which is beneficial to the miniaturization of the methane gas detection sensor.

[0052] In some embodiments, the mass fraction of one or more of carbon black, graphite, and zeolite in the filter layer 202 is 40wt% to 80wt%, and the mass fraction of Pd and / or Ir in the filter layer 202 is 1wt% to 15wt%. In some embodiments, the mass fraction of one or more of carbon black, graphite, and zeolite in the filter layer 202 is 50wt% to 70wt%. In some embodiments, the mass fraction of Pd and / or Ir in the filter layer 202 is 4wt% to 8wt%. It should be noted that the mass fraction of Pd and / or Ir in the filter layer 202 refers to: the mass fraction of Pd and Ir when the filter layer 202 contains both Pd and Ir; or the mass fraction of Pd or Ir when the filter layer 202 contains only one of Pd and Ir and not the other.

[0053] In some embodiments, one or more of carbon black, graphite, and zeolite have a specific surface area of ​​80 m² / g or more to ensure sufficient contact area with water molecules.

[0054] Continue to refer to Figure 1 In some embodiments, the sensing structure 20 further includes a moisture barrier 203, which is located on the filter layer 202 and can wrap around the filter layer 202 from one side.

[0055] In some embodiments, the moisture barrier 203 comprises a water-absorbing material, which includes one or more of carbon black, graphite, and zeolite. In some embodiments, the specific surface area of ​​one or more of the carbon black, graphite, and zeolite in the moisture barrier 203 is above 50 m² / g to ensure sufficient contact area with water molecules.

[0056] In some embodiments, the moisture barrier 203 further comprises WO3 and SnO2, wherein the volume fraction of SnO2 in the moisture barrier 203 is greater than or equal to 0%, that is, the moisture barrier 203 contains WO3 and optionally SnO2.

[0057] In some embodiments, the moisture barrier 203 further comprises Pd, which acts as a catalyst loaded on WO3 or on WO3 and SnO2. This increases the redox reaction rate of adsorbed oxygen on the WO3 surface with gases such as CO and H2S. Synergistically, Pd works with WO3 in the filter layer 202 to further enhance the removal of reducing gases such as CO and H2S. The moisture barrier 203 also removes water molecules from the gas, enhancing the protection of the gas detection layer 201 and improving the lifespan of the gas detection sensor. When the moisture barrier 203 comprises SnO2 and Pd loaded on SnO2, SnO2 readily adsorbs methane molecules, and Pd pre-activates the methane molecules (reducing the bond energy of the CH bonds in the methane molecules) to lower their oxidation reaction barrier. This makes it easier for methane molecules to undergo oxidation after diffusing into the gas detection layer 201, helping to increase the reaction rate and thus improving the sensor's response rate. In addition, the adsorbed oxygen on the surface of WO3 in the moisture barrier 203 and the filter layer 202 reacts with CO and H2S to release heat, which helps to maintain the temperature of the gas detection layer 201, thereby helping to save heating power consumption and ensure the sensitivity of gas detection.

[0058] In some embodiments, the volume fraction of SnO2 in the moisture barrier 203 is 0% to 50%.

[0059] To better enable SnO2 and the Pd loaded on it to pre-activate methane molecules and reduce the reaction barrier after methane molecules enter the gas detection layer 201, in some embodiments, the volume fraction of SnO2 in the moisture barrier layer 203 is controlled to be 10% to 50%, specifically, for example, any value or any two values ​​from 12%, 17%, 20%, 22%, 27%, 30%, 32%, 37%, 40%, 45%, and 50%.

[0060] In some embodiments, the mass fraction of Pd in ​​the moisture barrier 203 is 0.1wt% to 15wt%.

[0061] In some embodiments, the volume fraction of the moisture barrier 203 in the sensing structure 20 is 30% to 50%, specifically, it can be any value or a range of any two values ​​among 30%, 35%, 40%, 45%, and 50%.

[0062] In some embodiments, the WO3 in the moisture barrier 203 is beneficial for removing gases with stronger reducing properties than methane, such as CO and H2S. In some embodiments, the moisture barrier 203 contains both WO3 and SnO2; in some embodiments, the volume ratio of WO3 to SnO2 in the moisture barrier 203 is 1:1 to 5:1.

[0063] In some embodiments, the absorbent material in the moisture barrier 203 is composed of carbon black and / or graphite, i.e., composed of carbon material, and the mass fraction of the carbon material in the moisture barrier 203 is 30wt% to 70wt%, specifically, for example, 40wt%, 50wt%, or 60wt%, etc.

[0064] In some embodiments, the water-absorbing material in the moisture barrier 203 is zeolite, and the mass fraction of zeolite in the moisture barrier 203 is 20wt% to 60wt%, specifically, it can be 30wt%, 40wt%, or 50wt%, etc.

[0065] Continue to refer to Figure 1 or Figure 2 In some embodiments, the gas detection layer 201 comprises: metal oxides, Pd, Pt, and Au; the metal oxides comprise one or more of SnO2, Nb2O5, Y2O3, ZrO2, CeO2, La2O3, HfO2, Ta2O5, In2O3, CuO, Fe2O3, NiO, and Cu2O. In some embodiments, Pd, Pt, and Au are adsorbed on the surface of the metal oxides. In some embodiments, oxygen is adsorbed on the surface of the metal oxides and captures electrons in the conduction band of the metal oxides to form O. - and / or O 2- Plasma exists on the surface of the metal oxide. When gas enters the gas detection layer 201, the oxygen adsorbed on the surface of the metal oxide reacts with methane in the gas under the catalysis of Pd, Pt, and Au. The electrons generated in the reaction return to the conduction band of the metal oxide, thereby reducing the resistance value. The higher the methane concentration, the greater the decrease in resistance value. In some embodiments, the metal oxide contained in the gas detection layer 201 is SnO2. Compared with WO3, SnO2 has a stronger adsorption effect on methane. The oxygen adsorbed on the SnO2 surface reacts more easily with methane. Even if there are small amounts of CO and H2S in the gas entering the gas detection layer 201, methane reacts more easily with the oxygen adsorbed on the SnO2 surface, thus ensuring the accuracy of methane concentration detection.

[0066] In some embodiments, the volume fraction of the gas detection layer 201 in the sensing structure 20 is 5% to 20%, specifically, for example, any value or a range of any two values ​​among 7%, 10%, 13%, 16%, and 19%.

[0067] Pd has catalytic and conductive properties in the gas detection layer 201, which helps to reduce the resistance of the gas detection layer 201 and the impedance between the gas detection layer 201 and the external circuit. By controlling the content of Pd in ​​the gas detection layer 201, the catalytic performance and the reduction of resistance and impedance are balanced. In some embodiments, the mass fraction of Pd in ​​the gas detection layer 201 is 0.1wt% to 10wt%; in some embodiments, the mass fraction of Pd in ​​the gas detection layer 201 is 2wt% to 3wt%.

[0068] Pt has better performance than Pd in ​​reducing the resistance of the gas detection layer 201 and the impedance between the gas detection layer 201 and the external circuit. Pd has better catalytic performance than Pt. By controlling the content of Pd and Pt in the gas detection layer 201, the catalytic performance and the reduction of resistance and impedance are balanced. The content of Pd is as described in the above embodiments. In some embodiments, the mass fraction of Pt in the gas detection layer 201 is 0.1wt%~10wt%; in some embodiments, the mass fraction of Pt in the gas detection layer 201 is 0.5wt%~3wt%.

[0069] Au exhibits better performance than Pd and Pt in reducing the resistance of the gas detection layer 201 and the impedance between the gas detection layer 201 and the external circuit. Pd has better catalytic performance than Au. By controlling the content of Au, Pd and Pt in the gas detection layer 201, a balance can be achieved between catalytic performance and the reduction of resistance and impedance. The content of Pd and Pt is as described in the above embodiments. In some embodiments, the mass fraction of Au in the gas detection layer 201 is 0.01wt% to 10wt%; in other embodiments, the mass fraction of Au in the gas detection layer 201 is 0.1wt% to 2.5wt%.

[0070] In some embodiments, the Au particle size loaded with metal oxide in the gas detection layer 201 is 1 nm to 600 nm, specifically, it can be 1 nm to 500 nm, 1 nm to 400 nm, 1 nm to 300 nm, 1 nm to 200 nm, 1 nm to 100 nm, or 1 nm to 50 nm, etc. Nanoscale Au particles can reduce the resistance of the gas detection layer 201 and the impedance between the gas detection layer 201 and external circuits, thereby allowing for the matching of more external circuits.

[0071] In some embodiments, the gas detection layer 201 further comprises Ir, which has better catalytic and corrosion resistance than Pd while maintaining conductivity. Pd has a lower cost than Ir, so the two can be used together. In some embodiments, the mass fraction of Ir in the gas detection layer 201 is 0.1wt% to 20wt%; in some embodiments, the mass fraction of Ir in the gas detection layer 201 is 1wt% to 3wt%.

[0072] In some embodiments, the gas detection layer 201 further comprises a porous material containing Pd, Pt, and Au within its pores. The porous material includes one or more of carbon black, graphite, and zeolite. The porous material has pores, thus possessing a larger specific surface area, allowing it to load more Pd, Pt, and Au, thereby increasing the number of reaction sites and improving the efficiency of the catalytic reaction.

[0073] In some embodiments, the volume fraction of porous material in the gas detection layer 201 is 20% to 60%, which avoids the difficulty of sintering in the manufacturing process due to excessive amount of porous material, while sufficient amount of porous material is beneficial to improving reaction efficiency.

[0074] The methane gas detection sensor of this disclosure uses a gas detection layer 201 made of a metal oxide powder (e.g., SnO2 powder) added to a catalyst colloid (Pd colloid, Pt colloid, Au colloid) solution, heated and mixed, followed by sintering. In some embodiments, the sintering temperature is 400°C to 600°C, and the time is 90 to 300 minutes, and the sintering can be performed in an O2 atmosphere or an atmospheric atmosphere. In some embodiments, sintering is performed in a tube furnace with an inert gas to prevent oxidation of the noble metals (Pd, Pt, Au). In some embodiments, the particle size of the Pd colloid is 10 to 1000 nm, the particle size of the Pt colloid is 10 to 1000 nm, and the particle size of the Au colloid is 10 to 1000 nm.

[0075] In some embodiments, the material of the filter layer 202 is obtained by adding WO3 powder (or WO3 powder and SnO2 powder) to a catalyst colloid (Pd colloid and / or Ir colloid) solution, heating and mixing, and then sintering. In some embodiments, the sintering temperature is 400℃~600℃, the time is 90~300 minutes, and the sintering can be carried out in an O2 atmosphere or an atmospheric atmosphere. In some embodiments, the particle size of the Pd colloid is 10~1000nm, and the particle size of the Ir colloid is 10~1000nm. In some embodiments, the filter layer 202 further comprises one or more of carbon black, graphite, and zeolite. The material of the filter layer 202 is obtained by adding WO3 powder (or WO3 powder and SnO2 powder) to a catalyst colloid (Pd colloid and / or Ir colloid) solution, then adding one or more of carbon black, graphite, and zeolite, heating and mixing, and then sintering.

[0076] In some embodiments, the material of the moisture barrier 203 is obtained by mixing WO3 powder (or WO3 powder and SnO2 powder) with one or more of carbon black, graphite, and zeolite in a suitable solvent (a binder may be further added). In some embodiments, the material of the moisture barrier 203 is obtained by adding WO3 powder (or WO3 powder and SnO2 powder) and one or more of carbon black, graphite, and zeolite to a Pd colloidal solution, heating and mixing, and then sintering. In some embodiments, the sintering temperature is 400°C to 600°C, and the time is 90 to 300 minutes, which can be carried out in an O2 atmosphere or an atmospheric atmosphere.

[0077] Continue to refer to Figure 1 In some embodiments, the methane gas sensor further includes a support layer 30, which is located between the substrate 10 and the sensing structure 20, specifically between the substrate 10 and the gas detection layer 201.

[0078] In some embodiments, the substrate 10 is made of silicon, aluminum oxide, quartz, glass, silicon carbide, or ceramic. In some embodiments, the substrate 10 is made of silicon, and a support layer 30 is formed on the substrate 10, comprising an insulating material, which may be silicon oxide, silicon nitride, etc.

[0079] In some embodiments, the substrate 10 has a cavity 101 on the side near the sensing structure 20. In some embodiments, for ease of manufacturing, the opening of the cavity 101 is located on the surface of the substrate 10 near the sensing structure 20. In some embodiments, the position of the cavity 101 corresponds to the position of the sensing structure 20, and since the thermal conductivity of air is lower than that of the substrate 10, the cavity 101 helps to keep the sensing structure 20 warm.

[0080] Continue to refer to Figure 1 In some embodiments, the methane gas sensor further includes a heating electrode 40 for heating the gas detection layer 201 to ensure that the temperature of the gas detection layer 201 reaches the temperature condition for the reaction of oxygen adsorbed on the metal oxide surface with methane.

[0081] In some embodiments, the heating electrode 40 is located between the substrate 10 and the gas detection layer 201. In some embodiments, the heating electrode 40 is located within the support layer 30.

[0082] In some embodiments, the heating electrode 40 is made of Cr, Au, Ti, Pt, or Cr, Au, Ti, or Cr, Au, Pt, or Cr, Pt, Ti. In some embodiments, the heating electrode 40 has a Cr / Au / Ti / Pt / Ti stacked structure or a Cr / Au / Ti stacked structure.

[0083] In some embodiments, the heating electrode 40 is electrically connected to a pulse power supply, which provides a pulse current to the heating electrode 40. This is more energy-efficient than continuous current, especially when the filter layer 202 and / or the moisture-proof layer 203 undergo an exothermic oxidation-reduction reaction when gas enters. The pulse current can ensure that the gas detection layer 201 reaches the required temperature.

[0084] With the use of methane gas detection sensors, if the Pd catalyst in the gas detection layer 201 comes into contact with gases such as CO and H2S, the Pd's existing form changes from Pd-O to Pd, leading to a significant decrease in detection sensitivity. In some embodiments, a current higher than the normal operating value is applied by the power supply. The larger current helps to raise the temperature, thereby reducing the water vapor content in the gas detection layer 201 and regenerating the catalyst in the gas detection layer 201. To protect the wires and prevent short circuits, in some embodiments, the applied current higher than the normal operating value is less than 1.5 times the normal operating current value; in other embodiments, it is less than 1.3 times.

[0085] The pulse power supply can be part of the methane gas detection sensor or an external power source.

[0086] In some embodiments, the sensing structure 20 further includes a test electrode 204, at least a portion of which is located within the gas detection layer 201, for testing the resistance of the gas detection layer 201.

[0087] In some embodiments, the test electrode 204 is composed of Cr, Au, Ti, and Pt, or Cr, Au, and Ti, or Cr, Au, and Pt, or Cr, Pt, and Ti. In some embodiments, the test electrode 204 has a Cr / Au / Ti / Pt / Ti laminated structure or a Cr / Au / Ti laminated structure. The material of the test electrode 204 may be the same as or different from the material of the heating electrode 40.

[0088] In some embodiments, the substrate 10, heating electrode 40, support layer 30, and test electrode 204 of the methane gas detection sensor are formed using MEMS (Micro-Electro-Mechanical Systems) technology.

[0089] This disclosure also provides a methane gas detection sensing system, including: a methane gas detection sensor according to any of the above embodiments; and a control module for controlling the transmission of a first current or a second current to a heating electrode, wherein the first current is used to heat the gas detection layer by the heating electrode, and the second current is used to regenerate the catalyst in the gas detection layer, and the second current is greater than the first current.

[0090] In some embodiments, the heating electrode is located between the substrate and the gas detection layer.

[0091] In some embodiments, the methane gas detection sensing system further includes a first power source connected to a heating electrode for supplying a first current or a second current to the heating electrode.

[0092] In some embodiments, the first power source is a pulsed power source, suitable for providing pulsed current to the heating electrode. Compared to continuous current, pulsed power supply is more energy-efficient, especially when the filter layer and / or moisture-proof layer undergo exothermic oxidation-reduction reactions upon gas entry; the pulsed current ensures that the gas detection layer reaches the required temperature.

[0093] In some embodiments, the control module is used to control the switching on and off of the first power supply, and the magnitudes of the first current and the second current; in some embodiments, the magnitude of the first current is 0.1mA to 0.5mA. In some embodiments, the control module is used to control the pulse duty cycle of the first power supply, which is a pulse power supply, to be 50% to 83.33%.

[0094] In some embodiments, the methane gas detection sensing system further includes a second power source connected to a test electrode for supplying voltage to the test electrode. The test electrode is used to test the resistance of the gas detection layer. In some embodiments, at least a portion of the test electrode is located within the gas detection layer.

[0095] In some embodiments, the second power supply is a pulsed power supply, suitable for applying a pulsed voltage to the test electrode, and the pulse duty cycle can be 50% to 83.33%. In some embodiments, the second power supply is a continuous power supply, suitable for applying a continuous and uninterrupted voltage to the test electrode to ensure the continuity of the resistance test.

[0096] In some embodiments, the control module is used to control the switching on and off of the second power supply and the magnitude of the voltage applied to the test electrode; in some embodiments, the control module is adapted to control the second power supply to apply a voltage of 100V to 1000V to the test electrode.

[0097] In some embodiments, the control module is adapted to control the second current to be greater than the first current, thereby reducing the water vapor content in the gas detection layer and regenerating the catalyst in the gas detection layer when the second current is applied.

[0098] To protect the conductors and prevent short circuits, in some embodiments, the control module is adapted to control the magnitude of the second current to be less than 1.5 times the magnitude of the first current; in some embodiments, it is less than 1.3 times.

[0099] The above description is merely an exemplary embodiment used to illustrate the principles of this disclosure and is not intended to limit the scope of protection of this disclosure. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and substance of this disclosure, and these modifications and improvements are also within the scope of protection of this disclosure.

Claims

1. A methane gas detection sensor, characterized in that, include: A substrate, and a sensing structure located on the substrate; The sensing structure includes: A gas detection layer for detecting methane is located on the substrate, and the gas detection layer comprises one or more of the following: SnO2, Nb2O5, Y2O3, ZrO2, CeO2, La2O3, HfO2, Ta2O5, In2O3, CuO, Fe2O3, NiO, and Cu2O. A filter layer, located on the gas detection layer, comprises WO3 and SnO2, wherein the volume fraction of SnO2 in the filter layer is greater than or equal to 0%.

2. The methane gas detection sensor according to claim 1, characterized in that, The volume fraction of SnO2 in the filter layer is 0%~50%; When the volume fraction of SnO2 in the filter layer is greater than 0%, the volume ratio of WO3 to SnO2 in the filter layer is 1:1 to 5:

1.

3. The methane gas detection sensor according to claim 1, characterized in that, The filter layer further comprises Pd and / or Ir, and the volume fraction of the filter layer in the sensing structure is 40% to 60%.

4. The methane gas detection sensor according to claim 3, characterized in that, The filter layer comprises Pd and Ir, wherein the sum of the mass fractions of Pd and Ir in the filter layer is 0.2wt% to 30wt%; or The filter layer contains Pd or Ir, and the mass fraction of Pd or Ir in the filter layer is 0.2wt% to 30wt%.

5. The methane gas detection sensor according to claim 3, characterized in that, The filter layer also includes one or more of the following: carbon black, graphite, and zeolite; The mass fraction of one or more of the carbon black, graphite, and zeolite in the filter layer is 40wt%~80wt%, and the specific surface area of ​​one or more of the carbon black, graphite, and zeolite is above 80m² / g.

6. The methane gas detection sensor according to claim 5, characterized in that, The mass fraction of one or more of the carbon black, graphite, and zeolite in the filter layer is 50wt% to 70wt%.

7. The methane gas detection sensor according to claim 5, characterized in that, The filter layer contains Pd or Ir, and the mass fraction of Pd or Ir in the filter layer is 1wt%~15wt%; or The filter layer contains Pd and Ir, and the sum of the mass fractions of Pd and Ir in the filter layer is 1wt% to 15wt%.

8. The methane gas detection sensor according to claim 5, characterized in that, The filter layer contains Pd or Ir, and the mass fraction of Pd or Ir in the filter layer is 4wt%~8wt%; or The filter layer contains Pd and Ir, and the sum of the mass fractions of Pd and Ir in the filter layer is 4wt% to 8wt%.

9. The methane gas detection sensor according to claim 1, characterized in that, The sensing structure also includes a moisture-proof layer located on the filter layer; The moisture-proof layer comprises: WO3 and SnO2, wherein the volume fraction of SnO2 in the moisture-proof layer is greater than or equal to 0%, and the volume fraction of the moisture-proof layer in the sensing structure is 30% to 50%; and The absorbent material comprises one or more of carbon black, graphite, and zeolite.

10. The methane gas detection sensor according to claim 9, characterized in that, The volume fraction of SnO2 in the moisture-proof layer is 0%~50%; When the volume fraction of SnO2 in the moisture-proof layer is greater than 0%, the volume ratio of WO3 to SnO2 in the moisture-proof layer is 1:1 to 5:

1.

11. The methane gas detection sensor according to claim 9, characterized in that, The moisture-proof layer also contains Pd, and the mass fraction of Pd in ​​the moisture-proof layer is 0.1wt% to 15wt%.

12. The methane gas detection sensor according to claim 9, characterized in that, The absorbent material is composed of carbon black and / or graphite, and the mass fraction of the absorbent material in the moisture-proof layer is 30wt%~70wt%; or The absorbent material is composed of zeolite, and the mass fraction of zeolite in the moisture-proof layer is 20wt%~60wt%.

13. The methane gas detection sensor according to claim 1, characterized in that, The gas detection layer also includes: Pd, Pt, and Au; The gas detection layer has a volume fraction of 5% to 20% in the sensing structure; The mass fraction of Pd in ​​the gas detection layer is 0.1 wt% to 10 wt%. The mass fraction of Pt in the gas detection layer is 0.1 wt% to 10 wt%. The mass fraction of Au in the gas detection layer is 0.01wt% to 10wt%.

14. The methane gas detection sensor according to claim 13, characterized in that, The mass fraction of Pd in ​​the gas detection layer is 2wt%~3wt%; The mass fraction of Pt in the gas detection layer is 0.5wt%~3wt%; The mass fraction of Au in the gas detection layer is 0.1wt% to 2.5wt%.

15. The methane gas detection sensor according to claim 13, characterized in that, The gas detection layer also contains Ir, and the mass fraction of Ir in the gas detection layer is 0.1wt% to 20wt%.

16. The methane gas detection sensor according to claim 15, characterized in that, The mass fraction of Ir in the gas detection layer is 1wt% to 3wt%.

17. The methane gas detection sensor according to claim 13, characterized in that, In the gas detection layer, the particle size of Au is 1 nm to 600 nm.

18. The methane gas detection sensor according to any one of claims 1 to 17, characterized in that, The gas detection layer also includes a porous material containing Pd, Pt, and Au within its pores. The porous material includes one or more of carbon black, graphite, and zeolite.

19. The methane gas detection sensor according to any one of claims 1 to 17, characterized in that, Also includes: A support layer is located between the substrate and the gas detection layer.

20. The methane gas detection sensor according to any one of claims 1 to 17, characterized in that, The substrate is made of silicon, aluminum oxide, quartz, glass, silicon carbide, or ceramic.

21. The methane gas detection sensor according to any one of claims 1 to 17, characterized in that, The sensing structure further includes: a test electrode, at least partially located within the gas detection layer, for testing the resistance of the gas detection layer; The methane gas detection sensor further includes a heating electrode for heating the gas detection layer, the heating electrode being located between the substrate and the gas detection layer.

22. A methane gas detection sensing system, characterized in that, include: The methane gas detection sensor as described in any one of claims 1 to 21; The control module is used to control the transmission of a first current or a second current to the heating electrode. The first current is used to heat the gas detection layer by the heating electrode, and the second current is used to regenerate the catalyst in the gas detection layer. The second current is greater than the first current.

23. The methane gas detection sensing system according to claim 22, characterized in that, Also includes: A first power source is electrically connected to the heating electrode; The first power source is a pulse power source, which is suitable for providing pulse current to the heating electrode; A second power source, electrically connected to the test electrode, is used to provide voltage to the test electrode, which is used to test the resistance of the gas detection layer.

24. The methane gas detection sensing system according to claim 22 or 23, characterized in that, The control module is adapted to control the magnitude of the second current to be less than 1.5 times the magnitude of the first current.

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