Electrochemical gas sensor, gas detection device, gas detection system, and manufacturing method of electrochemical gas sensor

Abstract

To provide an electrochemical gas sensor with high reliability.SOLUTION: An electrochemical gas sensor 1 includes: a base plate 10 that has a gas inlet 12; a conductor layer 11 that is formed over a first face 10a of the base plate 10; a catalyst layer 20 that is formed over the first face 10a of the base plate 10 covering part of the conductor layer 11 and the gas inlet 12; an electrolyte layer 30 that is formed over the first face 10a of the base plate 10 in contact with the catalyst layer 20; and a first cover 40 that covers the catalyst layer 20 and the electrolyte layer 30. Part of the conductor layer 11 is exposed out of the first cover 40 in the first face 10a of the base plate 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrochemical gas sensor, a gas detection device using the sensor, a gas detection system using the gas detection device, and a method for manufacturing an electrochemical gas sensor. [Background technology]

[0002] Conventionally, electrochemical gas sensors equipped with a catalytic layer and an electrolyte layer have been known. In electrochemical gas sensors, for example, a working electrode (sensing electrode) made of a catalytic layer and a counter electrode are connected via an external circuit. When a gas to be detected, such as carbon monoxide, flows into the sensor, an oxidation reaction of carbon monoxide occurs at the working electrode, and the concentration of the gas can be detected by measuring the short-circuit current that occurs during this reaction.

[0003] Patent Document 1 discloses an electrochemical gas sensor that includes a polymer solid electrolyte membrane, a sensing electrode, a counter electrode, and a humidifying layer on one side of a substrate. The sensor in Patent Document 1 has a wiring structure that penetrates the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent No. 3234572 Summary of the Invention [Problem to be solved by the invention]

[0005] Improving reliability is an important issue for electrochemical gas sensors. In the sensor disclosed in Patent Document 1, there is a concern that gas may leak from the holes for leading out the wiring, which may result in a decrease in the reliability and sensitivity of the sensor. [Means for solving the problem]

[0006] The electrochemical gas sensor according to the present disclosure comprises a substrate having a gas inlet hole connecting a first surface and a second surface, wiring formed on the first surface of the substrate, a catalyst layer formed on the first surface of the substrate so as to cover a portion of the wiring and the gas inlet hole, an electrolyte layer formed on the first surface of the substrate so as to be in contact with the catalyst layer, and a cover covering the catalyst layer and the electrolyte layer, wherein a portion of the wiring on the first surface of the substrate is exposed to the outside of the cover, or a portion of the wiring on the first surface of the substrate is not exposed to the outside of the cover and extends to the second surface through the hole in the substrate at a portion where the portion of the wiring contacts the cover, or a portion of the wiring on the first surface of the substrate is not exposed to the outside of the cover and extends to the second surface through the hole in the substrate, and when the second surface of the substrate is viewed in plan, the portion where the hole and the wiring overlap is covered with a covering member.

[0007] A gas detection device according to the present disclosure includes the electrochemical gas sensor and a housing that houses the electrochemical gas sensor.

[0008] A gas detection system according to the present disclosure includes the gas detection device and a receiving device that receives the detection result of the gas detection device.

[0009] The manufacturing method of the electrochemical gas sensor according to the present disclosure is characterized by including the steps of: forming wiring on a first surface of a substrate having a gas inlet hole connecting the first surface and a second surface; forming a catalyst layer on the first surface of the substrate so as to cover a portion of the wiring and the gas inlet hole; forming an electrolyte layer on the first surface of the substrate so as to be in contact with the catalyst layer; and arranging a cover so as to cover the catalyst layer and the electrolyte layer and to expose a portion of the wiring on the first surface of the substrate. [Effects of the Invention]

[0010] According to one aspect of the present disclosure, an electrochemical gas sensor with excellent reliability can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of an electrochemical gas sensor according to an embodiment; [Figure 2] 1 is an exploded perspective view of an electrochemical gas sensor according to an embodiment of the present invention; [Figure 3] 5A to 5C are diagrams illustrating a method for manufacturing an electrochemical gas sensor according to an embodiment. [Figure 4] FIG. 1 is a cross-sectional view of an electrochemical gas sensor according to another embodiment. [Figure 5] FIG. 10 is a diagram showing a first modified example of the electrochemical gas sensor. [Figure 6] FIG. 10 is a diagram showing a second modified example of the electrochemical gas sensor. [Figure 7] FIG. 10 is a diagram showing a third modified example of the electrochemical gas sensor. [Figure 8] 1 is a block diagram showing a configuration of a gas detection system according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, with reference to the drawings, embodiments of an electrochemical gas sensor, a gas detection device, and a gas detection system according to the present disclosure will be described in detail. Note that the embodiments described below are merely examples, and the present disclosure is not limited thereto. Furthermore, selective combinations of multiple embodiments and variations described below are also included in the present disclosure.

[0013] FIG. 1 is a cross-sectional view of an electrochemical gas sensor 1 according to an embodiment, and FIG. 2 is an exploded perspective view of the electrochemical gas sensor 1. As shown in FIGS. 1 and 2, the electrochemical gas sensor 1 includes a substrate 10 having a first surface 10a and a second surface 10b, a conductor layer 11 formed as wiring on the first surface 10a of the substrate 10, a catalyst layer 20, and an electrolyte layer 30. The conductor layer 11 is, for example, a metal layer. The substrate 10 includes a gas inlet hole 12 connecting the first surface 10a and the second surface 10b. The catalyst layer 20 is formed on the first surface 10a of the substrate 10 so as to cover a portion of the conductor layer 11 and the gas inlet hole 12. The electrolyte layer 30 is formed on the first surface 10a of the substrate 10 so as to be in contact with the catalyst layer 20. The electrochemical sensor 1 further includes a cover 40 that covers the catalyst layer 20 and the electrolyte layer 30.

[0014] The electrochemical gas sensor 1 includes a catalyst layer 20, which is a catalyst layer 20a serving as a working electrode, a catalyst layer 20b serving as a counter electrode, and a catalyst layer 20c serving as a reference electrode. Note that the catalyst layer 20c can be omitted. The catalyst layers 20a, 20b, and 20c are formed on the first surface 10a of the substrate 10 so as not to contact one another. The conductor layer 11 includes a conductor layer 11a corresponding to the catalyst layer 20a, a conductor layer 11b corresponding to the catalyst layer 20b, and a conductor layer 11c corresponding to the catalyst layer 20c. Similarly, the conductor layers 11a, 11b, and 11c are formed on the first surface 10a of the substrate 10 so as not to contact one another. The electrolyte layer 30 only needs to be in contact with at least portions of the catalyst layers 20a and 20b. If the catalyst layer 20c is formed, the electrolyte layer 30 only needs to be in contact with at least portions of the catalyst layers 20a, 20b, and 20c.

[0015] In the electrochemical gas sensor 1, a laminated structure including a conductor layer 11, a catalyst layer 20, and an electrolyte layer 30 formed directly on the first surface 10a of the substrate 10 functions as a gas detection unit. The catalyst layer 20a, which functions as a working electrode, and the catalyst layer 20b, which functions as a counter electrode, are arranged via the electrolyte layer 30 to enable ion conduction and are electrically connected via an external circuit (not shown). The working electrode is an electrode into which the gas to be detected flows, and is also called a sensing electrode. A portion of the conductor layer 11 is exposed to the outside of the cover 40 on the first surface 10a of the substrate 10. A connection portion to the external circuit is formed in the portion of the conductor layer 11 exposed from the cover 40.

[0016] As will be described in more detail below, by forming the catalyst layer 20 directly on the surface of the substrate 10 on which the conductor layer 11 and the gas inlet hole 12 are formed, and then forming the electrolyte layer 30 directly on the catalyst layer 20, the adhesion between the layers constituting the gas detection unit is strengthened, thereby reducing the contact resistance of the laminated structure. Furthermore, with the electrochemical sensor 1, there is no need to press the gas detection unit to keep the contact resistance low, so no special fastening jig is required, and variations in contact resistance are also suppressed. In other words, the resistance value of the sensor is reduced and stabilized. As a result, the reliability of the sensor is improved, leading to higher sensitivity, smaller size, and lower cost of the sensor.

[0017] The electrochemical gas sensor 1 detects the gas concentration by introducing a gas to be detected into the working electrode, oxidizing or reducing the gas molecules on the working electrode, and measuring the change in current or potential associated with this redox reaction. While the electrochemical gas sensor 1 may be a potential detection type, this embodiment illustrates a current detection type sensor. When gas molecules are oxidized or reduced at the working electrode, electrons are generated or consumed, causing a current to flow between the working electrode and the counter electrode. This current value is proportional to the gas concentration, so the gas concentration can be detected by measuring the current value. Ions generated by the redox reaction at the working electrode and counter electrode migrate between the working electrode and the counter electrode via the electrolyte layer 30.

[0018] As described above, the electrochemical gas sensor 1 includes the catalyst layer 20a functioning as a working electrode, the catalyst layer 20b functioning as a counter electrode, and the catalyst layer 20c functioning as a reference electrode. The reference electrode is an electrode that serves as a reference when controlling and measuring the potential of the working electrode, and is also called a reference electrode. The working electrode is connected to the reference electrode via an external circuit, and is configured to maintain a constant potential relative to the reference electrode via the external circuit. The potential of the working electrode is maintained at a potential that can oxidize the target gas, for example.

[0019] In the following, carbon monoxide (CO) will be used as an example of a gas to be detected. However, sensors to which the configuration of the electrochemical gas sensor according to the present disclosure can be applied are not limited to carbon monoxide sensors. The configuration of the electrochemical gas sensor according to the present disclosure can be widely applied, particularly to electrochemical gas sensors that use solid electrolyte membranes, and can also be applied to sensors that detect gases such as hydrogen sulfide (HS), nitric oxide (NO), nitrogen dioxide (NO), sulfur dioxide (SO), ozone (O), and ammonia (NH).

[0020] When the gas to be detected by the electrochemical gas sensor 1 is CO, an oxidation reaction of CO shown in formula (1) occurs at the working electrode. CO+H2O→CO2+2H + +2e - ···(1) CO that flows into the working electrode reacts with water molecules to generate CO2 and protons (H + ) and electrons are generated. The protons move to the counter electrode via the electrolyte layer 30, and the electrons move via an external circuit. At the counter electrode, the reaction shown in formula (2) occurs. 1 / 2 O2+2H + +2e - →H2O···(2) The protons and electrons generated at the working electrode react with oxygen in the air at the counter electrode to produce water. At this time, the current flowing in the external circuit is proportional to the amount of CO2 flowing into the working electrode, so the CO2 concentration can be detected by measuring this current.

[0021] The electrochemical gas sensor 1 has a structure in which the inside of the sensor, in which the gas detection unit is formed, is sealed by the substrate 10 and the cover 40. The cover 40 is disposed on the first surface 10a of the substrate 10, and covers the entire catalyst layer 20 and electrolyte layer 30. The cover 40 is made of a material with low gas permeability that can block gases such as CO and water vapor, and together with the substrate 10, which is also made of a material with low gas permeability, seals the gas detection unit. A gas inlet 12 is formed in the substrate 10, so that CO, the gas to be detected, is introduced into the sensor only through the gas inlet 12.

[0022] In the electrochemical gas sensor 1, an internal space is formed between the electrolyte layer 30 and the cover 40. That is, there is a gap between the gas detection unit and the cover 40, and the gas detection unit is not pressed by the cover 40. The electrochemical sensor 1 further includes a humidity control member 60 disposed in this internal space. As described above, in the electrochemical sensor 1, the solid electrolyte membrane needs to contain a certain amount of moisture in order to function, and the amount of moisture in the solid electrolyte membrane needs to be controlled. The humidity control member 60 serves to adjust the amount of moisture contained in the solid electrolyte membrane.

[0023] The humidity control member 60 is preferably disposed so as not to come into contact with the catalyst layer 20 and electrolyte layer 30 that constitute the gas detection unit. In the example shown in FIG. 1, the humidity control member 60 is disposed on top of the electrolyte layer, but the humidity control member 60 may also be disposed in a location where it does not overlap with the electrolyte layer 30, such as around the gas detection unit. In addition, a gap exists between the humidity control member 60 and the cover 40. The humidity control member 60 may expand in volume when it absorbs moisture, and if a gap exists between the humidity control member 60 and the cover 40, this gap can absorb the volumetric expansion of the humidity control member 60. As a result, the structure of the sensor is stabilized, leading to improved reliability.

[0024] The electrochemical sensor 1 further includes a breathable partition layer 70 disposed between the electrolyte layer 30 and the humidity control member 60. When the humidity control member 60 is in contact with the electrolyte layer 30, it is difficult to appropriately adjust the amount of moisture contained in the solid electrolyte membrane. By interposing the partition layer 70 between the electrolyte layer 30 and the humidity control member 60, it becomes easier to adjust the amount of moisture contained in the solid electrolyte membrane, leading to improved reliability and sensitivity of the sensor. The partition layer 70 is preferably permeable to water vapor.

[0025] The structures of the substrate 10, catalyst layer 20, electrolyte layer 30, cover 40, humidity control member 60, and partition layer 70 that constitute the electrochemical gas sensor 1 will be described in detail below.

[0026] [substrate] The substrate 10 is an insulating base material having a conductor layer 11 that functions as wiring and a gas inlet hole 12 that connects the first surface 10a and the second surface 10b. The substrate 10 is made of a material similar to that used for conventionally known printed wiring boards, such as epoxy resin or polyphenylene ether. The substrate 10 may be a substrate dedicated to the electrochemical gas sensor 1, or may be a printed wiring board on which other electronic components are mounted. In this embodiment, the substrate 10 functions as a support member for the gas detection unit and, together with the cover 40, as a sealing member that seals the gas detection unit. While FIG. 2 illustrates the substrate having a rectangular shape in a plan view, the shape of the substrate 10 is not particularly limited and can be changed as appropriate depending on the shape of the electrochemical gas sensor 1, etc.

[0027] The gas inlet holes 12 of the substrate 10 are formed at positions overlapping with the catalyst layer 20a, which functions as a working electrode, and function as paths for introducing gas into the catalyst layer 20a. In other words, the catalyst layer 20a is formed in the region of the first surface 10a of the substrate 10 where the gas inlet holes 12 are formed. In this embodiment, the multiple gas inlet holes 12 are formed only at positions overlapping with the catalyst layer 20a. That is, in the region of the first surface 10a covered by the cover 40, there are no through holes for wiring, such as through holes, and no through holes other than the gas inlet holes 12 are formed.

[0028] The electrochemical gas sensor 1 is configured so that CO flows into the sensor interior surrounded by the substrate 10 and cover 40 only through the gas inlet 12, and the amount of CO acting on the catalyst layer 20a is controlled. Therefore, the CO concentration can be accurately determined from the proportional relationship between the amount of CO inflow and the current value. The gas inlet 12 is, for example, a through-hole that is perfectly circular in plan view. In this specification, "plan view" refers to the electrochemical gas sensor 1 and its components viewed from the first surface 10a of the substrate 10.

[0029] The gas introduction holes 12 have a diameter of, for example, 0.05 to 1 mm, or 0.1 to 0.5 mm. The opening area of ​​the gas introduction holes 12 is not particularly limited, but is preferably large enough to prevent the material constituting the catalyst layer 20 from flowing into the gas introduction holes 12 when the material is applied to the first surface 10a of the substrate 10. That is, it is preferable that a large number of gas introduction holes 12 with small opening areas are formed in the substrate 10. However, the number of gas introduction holes 12 is not particularly limited.

[0030] As described above, the conductor layers 11a, 11b, and 11c are formed on the first surface 10a of the substrate 10 so as to be spaced apart and not in contact with each other. The catalyst layer 20a is formed to cover a portion of the conductor layer 11a, the catalyst layer 20b is formed to cover a portion of the conductor layer 11b, and the catalyst layer 20c is formed to cover a portion of the conductor layer 11c. The conductor layers 11a, 11b, and 11c function as extraction electrodes (wiring) that electrically connect each catalyst layer to an external circuit. Portions of the conductor layers 11a, 11b, and 11c are exposed to the outside of the cover 40 in a plan view of the substrate 10, and connections to the external circuit are formed in the exposed portions.

[0031] When the conductor layer 11 is a metal layer, for example, after forming copper foil on the entire surface of the insulating substrate, the copper foil is pattern-etched, and the remaining copper foil is further plated to form the conductor layer on the first surface 10a of the substrate 10. An example of the conductor layer 11 (metal layer) is a layer in which nickel / gold is plated on the surface of copper, and has a thickness of 5 μm to 30 μm. The conductor layer 11 may also be formed by other methods such as vapor deposition or printing. In FIG. 1, for clarity of illustration, the conductor layer 11 is illustrated as being present inside the substrate 10, but in this embodiment, the conductor layer 11 is formed on the first surface 10a of the substrate 10.

[0032] [Catalyst layer] As described above, the catalyst layer 20 is formed directly on the first surface 10a of the substrate 10, which has the conductor layer 11 and the gas inlet hole 12. The catalyst layer 20 is preferably a coating formed by applying a catalyst material to the first surface 10a. The catalyst layer 20 is formed on the conductor layer 11, and a portion of the catalyst layer 20 may be formed in an area of ​​the first surface 10a where the conductor layer 11 is not present. When the catalyst layer 20 is applied to the first surface 10a, the catalyst layer 20 adheres strongly to the first surface 10a. In this embodiment, the electrolyte layer 30 is also applied to the catalyst layer 20, so the laminated structure of the gas detector has strong adhesion. This reduces the resistance of the gas detector without applying strong pressure to the laminated structure, and the resistance value is stabilized. As a result, the reliability of the sensor is improved, and the sensor can be made more sensitive, smaller, and less expensive.

[0033] The thickness of the catalyst layer 20 is, for example, 1 μm to 500 μm, or 10 μm to 200 μm. The catalyst layers 20a, 20b, and 20c are formed apart from each other on the first surface 10a so as not to overlap with each other. The areas of the catalyst layers 20b and 20c may be the same or different. In the example shown in FIG. 2, the catalyst layers 20a, 20b, and 20c have a rectangular shape in a plan view, but the shape of each layer in a plan view is not particularly limited.

[0034] The catalyst constituting the catalyst layer 20 promotes the oxidation reaction of CO. The reaction of the above formula (1) occurs in the catalyst layer 20a, which is the working electrode. In this embodiment, the catalyst layers 20a, 20b, and 20c are made of the same material. Examples of catalysts include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), iridium (Ir), cobalt (Co), iron (Fe), and nickel (Ni). Among these, it is preferable to use a noble metal catalyst such as Pt or a PtRu alloy.

[0035] The catalyst layer 20 further includes a conductive support and an ionomer. The conductive support is a conductive material that holds the catalyst. Suitable examples of the conductive support include carbon black such as acetylene black and ketjen black, graphite carbon, and carbon materials such as carbon nanotubes. The catalyst is, for example, adhered to the particle surface of the carbon material. The ionomer is an ionically conductive material that allows the movement of protons generated by the reaction. Suitable examples of the ionically conductive material include Nafion (registered trademark: manufactured by DuPont), which has the same composition as the electrolyte membrane.

[0036] [Electrolyte layer] The electrolyte layer 30 is an ion-conducting membrane that transfers ions generated in the catalyst layer 20a to the catalyst layer 20b, and is an electrically insulating membrane that does not have electron conductivity. The electrolyte layer 30 may be formed, for example, by absorbing a liquid electrolyte into a support member such as a porous sheet, but is preferably a solid electrolyte membrane made of a polymer material. In this embodiment, a proton-conducting solid electrolyte membrane is used. An example of a proton-conducting solid electrolyte membrane is a polymer membrane in which proton-conducting groups such as sulfonic acid groups are introduced into a hydrocarbon-based polymer or a fluorine-based polymer. A commercially available product such as Nafion (registered trademark: manufactured by DuPont) may be used for the electrolyte layer 30.

[0037] The thickness of the electrolyte layer 30 is not particularly limited, but is, for example, 5 μm to 500 μm. The electrolyte layer 30 is preferably disposed so as to entirely cover the catalyst layers 20 a, 20 b, and 20 c, and a portion of the electrolyte layer 30 is formed directly on the first surface 10 a of the substrate 10. The electrolyte layer 30 is, for example, a coating formed by applying its constituent materials onto the first surface 10 a on which the conductor layer 11 and the catalyst layer 20 are formed. In the example shown in FIG. 2, the electrolyte layer 30 has a rectangular shape in a plan view, but the shape of the electrolyte layer 30 in a plan view is not particularly limited and can be changed as appropriate depending on the shape of the electrochemical gas sensor 1, etc.

[0038] [cover] The cover 40 prevents gases, including CO and water vapor, from entering the sensor interior and protects the gas detection unit from damage. The cover 40 is fixed to the substrate 10 using, for example, adhesives, screws, a locking structure, or by welding or adhesion. The cover 40 is made of a material with low gas permeability that can block gases such as CO and water vapor. While the cover 40 may be made of a metal material, it is preferably made of a resin material from the perspectives of weight reduction, productivity, etc. The cover 40 does not have a gas inlet hole like the cover 50 described below, and is in close contact with the first surface 10a of the substrate 10 around the gas detection unit.

[0039] The cover 40 may be a flexible thin-film sealing sheet, but is preferably made of a hard resin material. The cover 40 is, for example, a hard cover formed in a cylindrical shape with a bottom, and is placed on the first surface 10a of the substrate 10 so as to cover the gas detection unit from above. A gap (internal space) is formed in the thickness direction of the substrate 10 between the cover 40 and the gas detection unit, and the internal space above the gas detection unit serves as a storage space for the humidity control member 60. In this embodiment, the cover 40 is smaller than the first surface 10a of the substrate 10, and the entire opening of the cover 40 is blocked by the substrate 10.

[0040] The cover 40 is formed in the shape of a flattened rectangular tube with a bottom, but the shape of the cover 40 is not particularly limited. However, from the perspective of miniaturizing the sensor, it is preferable to reduce the height of the cover 40 from the first surface 10a of the substrate 10. The cover 40 does not cover the entire first surface 10a, and a conductor layer 11 is formed around the cover 40 in a plan view. The conductor layer 11 passes between the first surface 10a and the cover 40 and extends from the inside of the sensor covered by the cover 40 to the outside of the cover 40. A sealing member may be provided between the first surface 10a and the cover 40 to seal the gap.

[0041] [Humidity control materials] The humidity control member 60 has the function of adjusting the amount of moisture contained in the solid electrolyte membrane, absorbing moisture when the humidity inside the sensor is high and releasing moisture when the humidity is low. The humidity control member 60 prevents, for example, an excessive decrease in humidity inside a sensor covered by the cover 40. The humidity control member 60 is preferably disposed in the internal space between the electrolyte layer 30 and the cover 40 without contacting the cover 40. The humidity control member 60 may expand when it absorbs moisture, but the expansion of the humidity control member 60 can be absorbed by the gap between the cover 40 and the humidity control member 60. The gap between the cover 40 and the humidity control member 60 is preferably large enough so that the cover 40 and the humidity control member 60 do not come into contact with each other even when the humidity control member 60 expands.

[0042] The humidity control member 60 is, for example, in the form of particles, and is disposed opposite the electrolyte layer 30 with the partition layer 70 interposed therebetween. The shape and size of the humidity control member 60 are not particularly limited. For example, the humidity control member 60 has a volume larger than that of the electrolyte layer 30. In this case, the humidity control member 60 has a sufficient amount of moisture relative to the electrolyte layer 30, making it possible to adjust the amount of moisture inside the sensor, leading to improved reliability and higher sensitivity of the sensor.

[0043] The humidity control member 60 is, for example, a sheet-like member containing humidity control particles that reversibly absorb and release water vapor. The humidity control member 60 may have a structure in which a plurality of humidity control particles are sandwiched between two base sheets. In this case, the humidity control particles and the humidity control particles and the two base sheets are bound together by a binder. There are no particular limitations on the type of binder, as long as it can maintain the sheet shape of the humidity control member 60. The base sheet may be a general thermoplastic resin sheet, but a porous sheet with breathability is preferable. Nonwoven fabric, woven fabric, etc. may also be used as the base sheet.

[0044] The humidity-conditioning particles may be particles containing a silicon compound such as silica, sepiolite, or zeolite, or may contain alumina, titania, zirconia, or the like instead of or together with the silicon compound. The humidity-conditioning particles may also be particles containing a highly water-absorbent polymer such as cross-linked sodium polyacrylate. As will be described in detail later, the particle size of the humidity-conditioning particles is preferably larger than the diameter of the vent holes in the partition wall layer 70. The average particle size of the humidity-conditioning particles is, for example, 30 μm to 10 mm or 500 μm to 5 mm. The average particle size of the humidity-conditioning particles is calculated by observing the particles with an optical microscope or a scanning electron microscope and averaging the diameters of the circumscribed circles of the particle images. When the humidity-conditioning particles absorb water and expand, the average particle size in the smallest state is preferably within this range.

[0045] [Partition layer] The partition wall layer 70 is a sheet-like member that is disposed between the electrolyte layer 30 and the humidity control member 60 in order to prevent contact between the electrolyte layer 30 and the humidity control member 60. If the humidity control member 60 is in contact with the electrolyte layer 30, excess moisture is expected to be supplied to the contact area, and therefore, it is preferable to interpose the partition wall layer 70 between the electrolyte layer 30 and the humidity control member 60. The shape and size of the partition wall layer 70 are not particularly limited, but it is preferable that the partition wall layer 70 has the same shape and size as the electrolyte layer 30 and is disposed so as to cover the entire electrolyte layer 30. The thickness of the partition wall layer 70 is not particularly limited, but is, for example, 30 μm to 1000 μm.

[0046] The partition layer 70 is preferably a breathable sheet. By covering the entire electrolyte layer 30 with the water vapor-permeable partition layer 70, the moisture content of the entire electrolyte layer can be adjusted while preventing contact between the electrolyte layer 30 and the humidity control member 60, leading to improved reliability and sensitivity of the sensor. A porous sheet having ventilation holes can be used for the partition layer 70, and nonwoven fabric, woven fabric, etc. may also be used. When the humidity control member 60 includes a porous substrate sheet, the sheet may function as the partition layer 70.

[0047] The diameter of the air vent holes in the partition wall layer 70 is, for example, less than 50 μm, which is smaller than the particle size of the humidity-conditioning particles in the humidity control member 60. The average particle size of the humidity-conditioning particles needs to be larger than the average diameter of the air vent holes, but the particle size of all the humidity-conditioning particles may be larger than the maximum diameter of the air vent holes. In this case, even if the humidity-conditioning particles are present directly on the partition wall layer 70, the humidity-conditioning particles are prevented from penetrating the air vent holes, ensuring the breathability of the partition wall layer 70 and preventing contact between the electrolyte layer 30 and the humidity-conditioning particles. The average diameter of the air vent holes is, for example, 0.1 μm to 30 μm or 0.5 μm to 25 μm. The average diameter of the air vent holes is measured using a mercury porosimeter.

[0048] Alternatively, the partition layer 70 may be made of a sheet-shaped resin material, which has high strength and therefore improves assembly during manufacturing. In this case, the resin material has through-holes for ventilation, which can adjust the moisture content of the entire electrolyte layer while preventing contact between the electrolyte layer 30 and the humidity control member 60, leading to improved reliability and sensitivity of the sensor. The through-holes formed in the sheet-shaped resin material may have, for example, a perfect circular shape in a plan view and a diameter of less than 1000 μm. In this case, by selecting humidity-controlling particles that are larger than the diameter of the through-holes, the humidity-controlling particles are prevented from penetrating the through-holes, ensuring the breathability of the partition layer 70 and preventing contact between the electrolyte layer 30 and the humidity-controlling particles. The average diameter of the through-holes is, for example, 100 μm to 500 μm, and the average diameter of the through-holes is measured using an optical microscope or the like.

[0049] Fig. 3 is a diagram illustrating an example of a manufacturing method for the electrochemical gas sensor 1. Fig. 3 illustrates how the catalyst layer 20 is formed by spray coating a constituent material of the catalyst layer 20 on the first surface 10a of the substrate 10 on which the conductor layer 11 and the gas inlet hole 12 are formed.

[0050] The electrochemical gas sensor 1 is manufactured, for example, through the following steps. (1) A step of forming a conductor layer 11, which is wiring, on the first surface 10a of a substrate 10 having gas introduction holes 12 that connect the first surface 10a and the second surface 10b. (2) A step of forming a catalyst layer 20 on the first surface 10a of the substrate 10 so as to cover a part of the conductor layer 11 and the gas inlet hole 12 (see FIG. 3(a)). (3) A step of forming an electrolyte layer 30 on the first surface 10a of the substrate 10 so as to cover the catalyst layer 20. (4) A step of disposing a cover 40 so as to cover the catalyst layer 20 and the electrolyte layer 30 and to expose a part of the conductor layer 11 on the first surface 10a of the substrate 10 (see FIG. 3(b)).

[0051] In step (1), a conductor layer such as copper foil is formed on the first surface 10a of the substrate 10, and the conductor layer 11 including conductor layers 11a, 11b, and 11c is formed by pattern etching of the copper foil. Alternatively, the conductor layers 11a, 11b, and 11c may be directly formed by vapor deposition, printing, or the like. The conductor layer 11 may also have a plated layer of nickel / gold, etc. In this embodiment, the area of ​​the substrate 10 covered by the cover 40 does not have any through-holes other than the gas inlet hole 12, thereby controlling the amount of CO acting on the gas detector. The substrate 10 may have through-holes or other through-holes for wiring formed outside the cover 40.

[0052] In step (2), for example, an ink containing a catalyst, a conductive carrier, and an ionomer is applied to the first surface 10a of the substrate 10 on which the conductor layer 11 is formed, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the catalyst layer 20. The catalyst layers 20a, 20b, and 20c are formed to the same thickness using the same type of ink. In this embodiment, the catalyst layer 20a is formed by applying ink to the first surface 10a so as to cover all of the gas inlet holes 12. The opening area of ​​the gas inlet holes 12, the viscosity of the ink, and the like are adjusted so that the ink forming the catalyst layer 20a does not penetrate into the gas inlet holes 12.

[0053] Examples of ink application methods include spray coating, screen printing, inkjet printing, electrolytic spray coating, and dispensing.

[0054] In step (3), for example, ink containing a constituent material of the solid electrolyte is applied to the first surface 10a of the substrate 10 so as to cover the entire catalyst layer 20, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the electrolyte layer 30. The method for applying the ink is not particularly limited, and a method similar to that in step (2) can be applied. Forming the electrolyte layer 30 by a coating method strengthens the adhesion of the electrolyte layer 30 to the catalyst layer 20 and the first surface 10a, thereby reducing the contact resistance of the laminated structure of the gas detection unit.

[0055] In step (4), a cover 40 is placed to cover the entire gas detection unit formed on the first surface 10a. Because the conductor layer 11 functions as an extraction electrode, a portion of it is exposed from the cover 40 on the first surface 10a. The cover 40 is fixed to the substrate 10, for example, using an adhesive, screws, or by fusing or welding. The cover 40 does not function as a member that presses the gas detection unit, and an internal space exists between the gas detection unit and the cover 40. A humidity control member 60 and a partition layer 70 are preferably placed in this internal space, and the humidity control member 60 is layered on the gas detection unit via the partition layer 70. It is also possible to form the humidity control layer by applying an ink containing the constituent material of the partition layer 70 onto the electrolyte layer 30 to form the partition layer 70, and then applying an ink containing humidity-controlling particles onto the partition layer 70.

[0056] Fig. 4 is a cross-sectional view of an electrochemical sensor 1x, which is another example of an embodiment. As shown in Fig. 4, the electrochemical sensor 1x has a structure in which a conductor layer 11, a catalyst layer 20, an electrolyte layer 30, a partition layer 70, and a humidity control member 60 are layered in this order on a first surface 10a of a substrate 10, and is similar to the electrochemical sensor 1 in that it includes a first cover 40 that covers the catalyst layer 20 and the like. On the other hand, the electrochemical sensor 1x differs from the electrochemical sensor 1 in that it includes a second cover 50 that is provided so as to cover the gas introduction hole 12 from the second surface 10b side of the substrate 10. The electrochemical sensor 1x has a structure in which the substrate 10 is sandwiched between the two covers 40, 50.

[0057] The cover 50 covers all of the gas inlet holes 12 formed in the substrate 10, and forms an internal space between the cover 50 and the second surface 10b of the substrate 10. The cover 50 has second gas inlet holes 52 for introducing CO to the first gas inlet holes 12 of the substrate 10. CO that flows into the internal space from the gas inlet holes 52 passes through the gas inlet holes 12 and acts on the gas detection unit. The shape of the gas inlet holes 52 in a plan view is not particularly limited, and may be, for example, a circular shape, a polygonal shape, or a slit shape.

[0058] The cover 50 is, for example, a hard cover formed in a cylindrical shape with a bottom, and is disposed on the second surface 10b so as to cover the gas inlet hole 12 of the substrate 10. Like the cover 40, the cover 50 may be a flexible thin-film sealing sheet, but is preferably made of a hard resin material. The cover 50 is fixed to the substrate 10 using, for example, an adhesive, screws, a locking structure, or by welding or adhesion. The cover 50 may be connected to the cover 40 by sandwiching the substrate 10 together with the cover 40.

[0059] The cover 50 is made of a material with low gas permeability that can block gases such as CO and water vapor. It may be made of a metal material, but is preferably made of a resin material from the viewpoint of manufacturing costs. The cover 50 is formed in the shape of a flattened rectangular cylinder with a bottom, but the shape of the cover 50 is not particularly limited. However, from the viewpoint of miniaturizing the sensor, it is preferable that the height of the cover 50 from the second surface 10b of the substrate 10 is low. A sealing member may be provided between the second surface 10b and the cover 50 to seal the gap.

[0060] In the electrochemical sensor 1x, the opening area of ​​each gas inlet hole 12 in the substrate 10 is preferably smaller than the opening area of ​​each gas inlet hole 52 in the cover 50. When the gas inlet holes 12, 52 are perfectly circular, the diameter of the gas inlet hole 12 is preferably smaller than the diameter of the gas inlet hole 52. The gas inlet hole 12 needs to have a small opening area to prevent the infiltration of ink forming the catalyst layer 20, but the gas inlet hole 52 preferably has a larger opening area than the gas inlet hole 12 to ensure good ventilation. However, since the gas inlet hole 52 also serves to control the amount of gas flowing into the sensor, similar to the gas inlet hole 12, when the gas inlet hole 52 is a circular hole, it has a diameter of, for example, 0.2 to 2.0 mm or 0.3 to 1.0 mm. The number of gas inlet holes 52 is not particularly limited.

[0061] The electrochemical sensor 1x further includes activated carbon 80 disposed between the substrate 10 and the cover 50. An internal space exists between the second surface 10b of the substrate 10 and the cover 50, and the activated carbon 80 is disposed in this internal space. The activated carbon 80 has a large specific surface area due to its micropores, so that it adsorbs gases such as organic solvents, SOx, and NOx, while allowing CO, the target gas to pass through. By providing activated carbon 80 in the CO introduction path and trapping non-target gases, it is possible to achieve further improvements in reliability and sensitivity.

[0062] The activated carbon 80 may be granular or powdered activated carbon formed into a block, granular or powdered activated carbon filled in a case with ventilation holes, or activated carbon formed into a cloth shape (activated carbon cloth). From the viewpoint of miniaturizing the sensor, the activated carbon 80 is preferably processed into a sheet shape as a whole, and is arranged so as to cover all of the gas introduction holes 12 formed in the substrate 10. Between the second surface 10b of the substrate 10 and the cover 50, for example, a humidity control member 60 and activated carbon 80 may be layered in this order from the second surface 10b side.

[0063] FIG. 5 shows a modified example of the electrochemical sensor 1x. As shown in FIG. 5, the gas inlet 12 can be formed at a position corresponding to the catalytic layer 20a (working electrode) or at a position overlapping the catalytic layer 20b (counter electrode). In this case, a sealing member 90 such as an O-ring is preferably disposed to surround the gas inlet 12 formed corresponding to the catalytic layer 20a. The gas inlet 52 of the cover 50 is formed in a portion surrounded by the sealing member 90. The sealing member 90 is in close contact with the second surface 10b of the substrate 10 and the inner surface of the cover 50, and the gas inlet 12 formed corresponding to the catalytic layer 20b is positioned outside the annular sealing member 90. In this case, CO outside the cover flows only into the catalytic layer 20a.

[0064] FIG. 6 is a diagram illustrating a modified example of the electrochemical sensor 1. As shown in FIG. 6, a portion of the conductor layer 11, which functions as wiring, does not need to be exposed to the outside of the cover 40 on the first surface 10a of the substrate 10. In the example illustrated in FIG. 6, a portion of the conductor layer 11, which contacts the cover 40, extends toward the second surface 10b of the substrate 10 via a through-hole 10c penetrating the substrate 10 in the thickness direction. The through-hole 10c is formed in the portion that contacts the cover 40, and is filled with, for example, a metal that constitutes the conductor layer 11. The metal filled in the through-hole 10c electrically connects the portion of the conductor layer 11 formed on the first surface 10a with the portion of the conductor layer 11 formed on the second surface 10b. Because the through-hole 10c is blocked by the cover 40, gas leakage is sufficiently suppressed, resulting in a highly reliable sensor.

[0065] FIG. 7 is a diagram showing a modified example of an electrochemical sensor 1x. The configuration shown in FIG. 7 is similar to the configuration shown in FIG. 6 in that a portion of the conductor layer 11 is not exposed to the outside of the cover 40 on the first surface 10a of the substrate 10, but extends toward the second surface 10b of the substrate 10 via the through-hole 10c. In the example shown in FIG. 7, when the second surface 10b of the substrate 10 is viewed from above, a portion of the conductor layer 11 where the through-hole 10c and the conductor layer 11 overlap is covered by a cover 50, which is a covering member. Furthermore, an annular sealing member 90 (e.g., an O-ring) is disposed within the cover 50, and a gas introduction hole 52 of the cover 50 is formed in a portion surrounded by the sealing member 90. The sealing member 90 is in close contact with the second surface 10b of the substrate 10 and the inner surface of the cover 50, and the through-hole 10c of the substrate 10 is located outside the annular sealing member 90. That is, the opening of through-hole 10c on the second surface 10b side is located in a space sealed by cover 50 and sealing member 90, and second surface 10b side of through-hole 10c is sealed. In this case, gas leakage is also sufficiently suppressed, and a highly reliable sensor can be realized.

[0066] FIG. 8 is a block diagram showing the configuration of a gas detection system 100 according to an embodiment. As shown in FIG. 8, the gas detection system 100 includes a gas detection device 110 including an electrochemical gas sensor 1, a receiving device 101 that receives detection information from the gas detection device 110, and a control device 102. The receiving device 101 and the control device 102 may be installed in a location remote from the gas detection device 110, and the receiving device 101 may receive the detection information from the gas detection device 110 via wireless or wired communication, or via a wide area communication network such as the Internet. The control device 102 controls the operation of a predetermined device, for example, based on the detection information from the gas detection device 110.

[0067] Gas detection device 110 includes electrochemical sensor 1 and housing 111 that houses electrochemical gas sensor 1. Gas detection device 110 may also include a holder for holding electrochemical sensor 1, a speaker that outputs an alarm sound, a warning lamp, etc. Electrochemical sensor 1 may be connected to a printed wiring board on which other electronic components are mounted, or substrate 10 that constitutes electrochemical sensor 1 may be a printed wiring board on which other electronic components are mounted. Gas detection device 110 may also include electrochemical sensor 1x instead of electrochemical sensor 1. Gas detection device 110 may further include a detector for detecting at least one of smoke and heat, and in this case may also include a speaker that outputs an alarm sound, a warning lamp, etc.

[0068] As described above, the electrochemical sensors 1 and 1x configured as described above have excellent reliability. Furthermore, the electrochemical sensors 1 and 1x can be manufactured at low cost and have high sensitivity. By providing the humidity control member 60, the partition layer 70, and the activated carbon 80, further improvements in reliability and sensitivity can be achieved.

[0069] The above-described embodiments may be modified as appropriate without departing from the scope of the present disclosure. For example, in the above-described embodiments, the catalyst layer 20c, which serves as the reference electrode, is formed using the same electrode material as the catalyst layer 20a, which serves as the working electrode, and the catalyst layer 20b, which serves as the counter electrode. However, the catalyst layer 20c may be made of a different material from the catalyst layers 20a and 20b, and the catalyst layers 20a and 20b may be made of different materials. The electrochemical gas sensor may also have a two-electrode structure that includes only a working electrode and a counter electrode. Alternatively, a conductor layer may serve as the reference electrode, and the counter electrode may also serve as the reference electrode. The electrochemical gas sensor may also include other components, such as a gas diffusion layer.

[0070] Although the electrochemical sensor 1 has a humidity control member 60 and a partition layer 70, and the electrochemical sensor 1x further has activated carbon 80, the electrochemical sensors according to the present disclosure are not limited to those having a humidity control member 60, a partition layer 70, and activated carbon 80. The electrochemical sensor according to the present disclosure may, for example, only have activated carbon 80 among these, or may have a structure in which activated carbon 80 is disposed between the gas detection unit and the cover 40. Furthermore, the humidity control member 60 may be disposed between the substrate 10 and the cover 50.

[0071] The present disclosure is further illustrated by the following embodiments. Configuration 1: An electrochemical gas sensor comprising: a substrate having a gas inlet hole connecting a first surface and a second surface; wiring formed on the first surface of the substrate; a catalyst layer formed on the first surface of the substrate so as to cover a portion of the wiring and the gas inlet hole; an electrolyte layer formed on the first surface of the substrate so as to cover the catalyst layer; and a cover that covers the catalyst layer and the electrolyte layer, wherein a portion of the wiring on the first surface of the substrate is exposed to the outside of the cover; or a portion of the wiring on the first surface of the substrate is not exposed to the outside of the cover, and a portion of the wiring in contact with the cover extends toward the second surface through the hole in the substrate; or a portion of the wiring on the first surface of the substrate is not exposed to the outside of the cover, and a portion of the wiring in contact with the cover extends toward the second surface through the hole in the substrate; and when the second surface of the substrate is viewed in plan, the portion where the hole and the wiring overlap is covered with a covering member. Configuration 2: An internal space is formed between the electrolyte layer and the cover, 2. The electrochemical gas sensor according to claim 1, further comprising a humidity control member disposed in the internal space. Configuration 3: The electrochemical gas sensor according to configuration 2, wherein the humidity control member is disposed so as not to be in contact with the catalyst layer and the electrolyte layer. Configuration 4: The electrochemical gas sensor according to configuration 3, further comprising an air-permeable partition layer disposed between the electrolyte layer and the humidity control member. Configuration 5: The electrochemical gas sensor according to Configuration 4, wherein the humidity control member includes humidity control particles that reversibly absorb and release water vapor, and the particle diameter of the humidity control particles is larger than the diameter of the ventilation holes in the partition layer. Configuration 6: The electrochemical gas sensor according to any one of configurations 1 to 5, further comprising a second cover provided to cover the gas introduction hole from the second surface side of the substrate, the second cover having a second gas introduction hole. Configuration 7: The electrochemical gas sensor of configuration 6, further comprising activated carbon disposed between the second cover and the substrate. Configuration 8: The electrochemical gas sensor according to configuration 6 or 7, wherein the opening area of ​​the gas introduction hole of the substrate is smaller than the opening area of ​​the second gas introduction hole of the second cover. [Explanation of symbols]

[0072] 1, 1x electrochemical gas sensor, 10 substrate, 10a first surface, 10b second surface, 11, 11a, 11b, 11c conductor layer, 12, 52 gas inlet hole, 20, 20a, 20b, 20c catalyst layer, 30 electrolyte layer, 40, 50 cover, 60 humidity control member, 70 partition layer, 80 activated carbon, 90 sealing member, 100 gas detection system, 101 receiving device, 102 control device, 110 gas detection device, 111 housing

Claims

1. a substrate having a gas introduction hole that connects the first surface and the second surface; Wiring formed on the first surface of the substrate; a catalyst layer formed on the first surface of the substrate so as to cover a portion of the wiring and the gas introduction hole; an electrolyte layer formed on the first surface of the substrate so as to contact the catalyst layer; a cover that covers the catalyst layer and the electrolyte layer; Equipped with A portion of the wiring is exposed to the outside of the cover on the first surface of the substrate. Alternatively, on the first surface of the substrate, a portion of the wiring is not exposed to the outside of the cover, and a portion of the wiring that contacts the cover extends to the second surface side through a hole in the substrate. Alternatively, an electrochemical gas sensor in which, on the first surface of the substrate, a portion of the wiring is not exposed to the outside of the cover, and a portion of the wiring extends toward the second surface through a hole in the substrate, and when the second surface of the substrate is viewed in a plane, the portion where the hole and the wiring overlap is covered with a covering member.

2. an internal space is formed between the electrolyte layer and the cover; 2. The electrochemical gas sensor according to claim 1, further comprising a humidity control member disposed in the internal space.

3. 3. The electrochemical gas sensor according to claim 2, wherein the humidity control member is disposed so as not to contact the catalyst layer and the electrolyte layer.

4. 4. The electrochemical gas sensor according to claim 3, further comprising an air-permeable partition layer disposed between the electrolyte layer and the humidity control member.

5. the humidity control member includes humidity control particles that reversibly absorb and release water vapor; 5. The electrochemical gas sensor according to claim 4, wherein the particle diameter of the humidity-conditioning particles is larger than the diameter of the vent holes of the partition layer.

6. a second cover provided to cover the gas introduction hole from the second surface side of the substrate; 2. The electrochemical gas sensor according to claim 1, wherein the second cover has a second gas inlet hole.

7. 7. The electrochemical gas sensor according to claim 6, further comprising activated carbon disposed between the second cover and the substrate.

8. 7. The electrochemical gas sensor according to claim 6, wherein an opening area of ​​the gas inlet hole of the substrate is smaller than an opening area of ​​the second gas inlet hole of the second cover.

9. 9. A gas detection device comprising: the electrochemical gas sensor according to claim 1; and a housing that houses the electrochemical gas sensor.

10. 10. A gas detection system comprising: the gas detection device according to claim 9; and a receiving device that receives detection information from the gas detection device.

11. forming wiring on a first surface of a substrate having a gas introduction hole that connects the first surface and the second surface; forming a catalyst layer on the first surface of the substrate so as to cover a portion of the wiring and the gas introduction hole; forming an electrolyte layer on the first surface of the substrate in contact with the catalyst layer; disposing a cover to cover the catalyst layer and the electrolyte layer and to expose a portion of the wiring on the first surface of the substrate; A method for manufacturing an electrochemical gas sensor, comprising:

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