Electrochemical devices, electrochemical sensor devices, and electrochemical sensor systems

Abstract

It suppresses the occurrence of ion migration. [Solution] The electrochemical device 1 includes a substrate 10 including a first surface 10a and a second surface, a first metal layer 11a provided on the first surface 10a of the substrate 10, and a second metal layer 11b provided on the first surface 10a of the substrate 10 so as not to contact the first metal layer 11a. The electrochemical device 1 includes a first conductor layer 12a formed to cover at least a portion of the first metal layer 11a and containing a metal or nonmetal with a lower ionization tendency than the first metal layer 11a, a second conductor layer 12b formed to cover at least a portion of the second metal layer 11b and containing a metal or nonmetal with a lower ionization tendency than the second metal layer 11b and provided so as not to contact the first conductor layer 12a, and an electrolyte layer 30 provided so as to contact the first conductor layer 12a and the second conductor layer 12b, respectively.

Description

Technical Field

[0001] The present disclosure relates to an electrochemical device, an electrochemical sensor device, and an electrochemical sensor system.

Background Art

[0002] Conventionally, as an electrochemical device, an electrochemical gas sensor including a working electrode, a counter electrode, and an ion conductor is known. In an electrochemical gas sensor, for example, the working electrode and the counter electrode are connected via an external circuit, and when a detection target gas such as carbon monoxide flows into the sensor, cations and electrons are generated at the working electrode. The electrons flow through the external circuit to the counter electrode, and the concentration of the gas can be detected by measuring the short-circuit current at this time.

[0003] Electrochemical gas sensors are roughly classified into sensors using a liquid electrolyte and sensors using a solid electrolyte as the ion conductor. For example, Patent Document 1 discloses an electrochemical gas sensor including a solid electrolyte film, a working electrode, a counter electrode, and metal wiring disposed on an insulating substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, electrochemical devices using solid electrolytes are expected to be small and highly reliable devices, but our inventors' research has revealed that ion migration occurs, in which the metal constituting the metal wiring in contact with the solid electrolyte membrane is ionized and dissolved. This ion migration can cause short circuits between electrodes, for example, leading to device failure. It should be noted that the device described in Patent Document 1 does not take into consideration the suppression of ion migration. [Means for solving the problem]

[0006] The electrochemical device according to this disclosure is characterized by comprising: a substrate including a first surface and a second surface; a first metal layer provided on the first surface of the substrate; a second metal layer provided on the first surface of the substrate so as not to contact the first metal layer; a first conductor layer formed to cover at least a portion of the first metal layer and containing a metal or nonmetal having a lower ionization tendency than the first metal layer; a second conductor layer formed to cover at least a portion of the second metal layer and containing a metal or nonmetal having a lower ionization tendency than the second metal layer, and provided so as not to contact the first conductor layer; and an electrolyte layer or polymer material layer provided so as to contact the first conductor layer and the second conductor layer, respectively. [Effects of the Invention]

[0007] According to one aspect of this disclosure, it is possible to provide an electrochemical device capable of suppressing the occurrence of ion migration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of an electrochemical device, which is an example of an embodiment. [Figure 2] This is a disassembled perspective view of an electrochemical device, which is an example of an embodiment. [Figure 3] This is a plan view showing a first modified example of an electrochemical device. [Figure 4] This is a cross-sectional view AA in Figure 3. [Figure 5] This is a plan view showing a second modified example of the electrochemical device. [Figure 6] Figure 5 is a cross-sectional view of BB. [Figure 7] This is a schematic cross-sectional view showing a third modified example of an electrochemical device. [Figure 8] This figure shows an electrochemical sensor device in which an electrochemical device, which is an example of an embodiment, is mounted on a circuit board. [Figure 9] Figure 8 is a cross-sectional view of CC. [Figure 10] This figure shows another example of an electrochemical sensor device. [Figure 11] This block diagram shows the configuration of an electrochemical sensor system, which is an example of an embodiment. [Figure 12] This figure shows the output current, etc., related to Example 1. [Figure 13] This figure shows the output current, etc., for Examples 2 and 3.

[0009] Hereinafter, embodiments of the electrochemical devices, electrochemical sensor devices, and electrochemical sensor systems relating to this disclosure will be described in detail with reference to the drawings. The embodiments described below are illustrative and the disclosure is not limited thereto. Furthermore, selective combination of the multiple embodiments and modifications described below is included in this disclosure.

[0010] Figure 1 is a cross-sectional view of an electrochemical device 1, which is an example of an embodiment. Figure 2 is an exploded perspective view of the electrochemical device 1. In Figure 2, the cover 50 and activated carbon 80 are omitted from the description. Note that the drawings are schematic representations, and the dimensional ratios of each component are as described below.

[0011] As shown in Figures 1 and 2, the electrochemical device 1 comprises a substrate 10 including a first surface 10a and a second surface 10b, a metal layer 11a provided on the first surface 10a of the substrate 10, and a metal layer 11b provided on the first surface 10a of the substrate 10 so as not to contact the metal layer 11a. Furthermore, the electrochemical device 1 comprises a conductive layer 12a formed to cover at least a portion of the metal layer 11a and containing a metal or nonmetal with a lower ionization tendency than the metal layer 11a, and a conductive layer 12b formed to cover at least a portion of the metal layer 11b and containing a metal or nonmetal with a lower ionization tendency than the metal layer 11b, and provided so as not to contact the conductive layer 12a. The electrochemical device 1 also comprises an electrolyte layer 30 provided so as to be in contact with the conductive layer 12a and the conductive layer 12b, respectively.

[0012] The metal layer 11 may further have a metal layer 11c, and the metal layers 11a, 11b, and 11c are provided on the first surface 10a of the substrate 10 so as not to contact each other. In this case, the conductive layer 12 includes a conductive layer 12c formed to cover at least a portion of the metal layer 11c. The conductive layer 12c contains a metal or nonmetal with a lower ionization tendency than the metal layer 11c and is provided so as not to contact the conductive layers 12a and 12b.

[0013] The conductor layer 12 is formed so as to cover at least a part of the metal layer 11 as described above. Further, the conductor layer 12 contains a metal or a non-metal having a smaller ionization tendency than the metal layer 11. In the examples shown in FIGS. 1 and 2, the conductor layer 12 is formed so as to cover the surface of the metal layer 11 (a plane parallel to the first surface 10a). Although not shown, when the side surface of the metal layer 11 (for example, a plane perpendicular to the first surface 10a) is exposed, the conductor layer 12 is preferably formed so as to cover the surface and the side surface of the metal layer 11. One conductor layer 12 is arranged for each of the metal layers 11. Further, the conductor layer 12 is preferably formed so as to cover the entire surface of the metal layer 11 exposed within the cover 40. The conductor layer 12 is preferably formed so as to cover all of the regions in the metal layer 11 where the electrolyte layer 30 is formed. Thereby, precipitation of cations can be suppressed more effectively, and generation of ion migration can be suppressed.

[0014] The electrochemical device 1 preferably further includes, as the catalyst layer 20, 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 each other. The catalyst layer 20 is provided so as to contact at least a part of the conductor layer 12. For example, the catalyst layer 20a is provided so as to contact at least a part of the conductor layer 12a, the catalyst layer 20b is provided so as to contact at least a part of the conductor layer 12b, and the catalyst layer 20c is provided so as to contact at least a part of the conductor layer 12c.

[0015] In the electrochemical device 1, a laminated structure including a metal layer 11, a conductor layer 12, 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. A catalyst layer 20a functioning as a working electrode and a catalyst layer 20b functioning as a counter electrode are arranged to be ion-conductive through the electrolyte layer 30 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. Although details will be described later, a part of the metal layer 11 is exposed outside the cover 40 on the first surface 10a of the substrate 10. A connection portion with the external circuit is formed in the portion of the metal layer 11 exposed from the cover 40.

[0016] The electrochemical device 1 detects the gas concentration by flowing the 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 accompanying this oxidation-reduction reaction. The electrochemical device 1 may be a potential detection type, but in this embodiment, a current detection type sensor is exemplified. When gas molecules are oxidized or reduced at the working electrode, electrons are generated or consumed, and a current flows between the working electrode and the counter electrode. Since this current value is in a proportional relationship with the gas concentration, the gas concentration can be detected by measuring the current value. Ions generated by the oxidation-reduction reaction at the working electrode and the counter electrode move between the working electrode and the counter electrode through the electrolyte layer 30.

[0017] As described above, the electrochemical device 1 includes a catalyst layer 20c functioning as a reference electrode in addition to the catalyst layer 20a functioning as a working electrode and the catalyst layer 20b functioning as a counter 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 certain potential with the reference electrode by the external circuit. The potential of the working electrode is maintained, for example, at a potential capable of oxidizing the gas to be detected.

[0018] In the following explanation, carbon monoxide (CO) will be used as an example of the target gas for detection. However, the sensors to which the configuration of the electrochemical device described herein can be applied are not limited to carbon monoxide sensors. The configuration of the electrochemical device described herein can be broadly applied to electrochemical gas sensors, particularly those using a solid electrolyte membrane, and can be applied to sensors that detect gases such as hydrogen sulfide (H2S), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), ammonia (NH3), etc.

[0019] When the target gas for detection by electrochemical device 1 is CO, the oxidation reaction of CO shown in equation (1) occurs at the working electrode. CO + H2O → CO2 + 2H + +2e - ...(1) CO that flows into the working electrode reacts with water molecules to produce 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 the external circuit. At the counter electrode, the reaction shown in equation (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 through the external circuit is proportional to the amount of CO flowing into the working electrode, so the concentration of CO can be detected by measuring this current.

[0020] The electrochemical device 1 has a structure in which the inside of the device, in which the gas detection unit is formed, is sealed by a substrate 10 and a cover 40. The cover 40 is placed on the first surface 10a of the substrate 10 and covers the entire conductive layer 12, 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, it seals the gas detection unit. Since a gas introduction hole 14 is formed in the substrate 10, the gas to be detected, CO, is introduced into the device only through the gas introduction hole 14.

[0021] The electrochemical device 1 further comprises a cover 50, and has a structure in which the substrate 10 is sandwiched between two covers 40 and 50. The cover 50 covers all the gas inlet holes 14 formed in the substrate 10 and forms an internal space between itself and the second surface 10b of the substrate 10. The cover 50 has gas inlet holes 52 for guiding CO into the gas inlet holes 14 formed in the substrate 10. The CO that flows into the internal space from the gas inlet holes 52 acts on the gas detection unit through the gas inlet holes 14. The planar shape of the gas inlet holes 52 is not particularly limited and may be circular, polygonal, or slit-shaped, for example.

[0022] In the electrochemical device 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 device 1 further includes a humidity control member 60 located in this internal space. In the electrochemical device 1, the solid electrolyte membrane needs to contain a certain amount of moisture in order to function, and therefore the amount of moisture in the solid electrolyte membrane needs to be controlled. The humidity control member 60 plays a role in adjusting the amount of moisture contained in the solid electrolyte membrane.

[0023] It is preferable that the humidity control member 60 is positioned so as not to be in contact with the catalyst layer 20 and electrolyte layer 30 that constitute the gas detection unit. In the example shown in Figure 1, the humidity control member 60 is stacked on the electrolyte layer, but the humidity control member 60 may also be positioned in a location that does not overlap with the electrolyte layer 30, such as around the gas detection unit. Furthermore, 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, but if a gap exists between the humidity control member 60 and the cover 40, this gap can absorb the volume expansion of the humidity control member 60. As a result, the structure of the device is stabilized, leading to improved reliability.

[0024] The electrochemical device 1 further comprises a permeable partition layer 70 positioned 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 not easy to properly 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 higher sensitivity of the device. Preferably, the partition layer 70 is permeable to water vapor.

[0025] The electrochemical device 1 further includes activated carbon 80 positioned 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 positioned within this internal space. Due to its large specific surface area created by micropores, the activated carbon 80 adsorbs gases such as organic solvents, SOx, and NOx, while allowing the target gas, CO, to permeate. By placing the activated carbon 80 in the CO introduction path to trap non-target gases, further improvements in reliability and sensitivity can be achieved.

[0026] The activated carbon 80 may be granular or powdered activated carbon molded into a block shape, granular or powdered activated carbon filled in a case with ventilation holes, or activated carbon molded into a cloth shape (activated carbon cloth). From the viewpoint of miniaturizing the device, it is preferable that the activated carbon 80 as a whole is processed into a sheet shape and arranged to cover all the gas introduction holes 14 formed in the substrate 10. Between the second surface 10b of the substrate 10 and the cover 50, for example, the humidity control member 60 and the activated carbon 80 may be stacked in order from the second surface 10b side.

[0027] The following describes in detail the components of the electrochemical device 1, including the substrate 10, metal layer 11, conductive layer 12, catalyst layer 20, electrolyte layer 30, cover 40, 50, humidity control member 60, and partition wall layer 70.

[0028] [substrate] The substrate 10 is an insulating substrate having a metal layer 11 that functions as wiring and gas introduction holes 14 that connect the first surface 10a and the second surface 10b. The substrate 10 is made of a material similar to that of conventionally known printed circuit boards, such as epoxy resin or polyphenylene ether. The substrate 10 may be a dedicated substrate for the electrochemical device 1, or it may be a circuit board such as a printed circuit 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 also functions as a sealing member that seals the gas detection unit together with the cover 40. Figure 2 shows a substrate 10 with a rectangular shape in plan view, but the shape of the substrate 10 is not particularly limited and can be appropriately changed according to the shape of the electrochemical device 1, etc.

[0029] The gas introduction holes 14 of the substrate 10 are formed in a position that overlaps with the catalyst layer 20a, which functions as a working electrode, in the thickness direction of the substrate 10, and function as a path for introducing gas into the catalyst layer 20a. In other words, the catalyst layer 20a is formed in the region on the first surface 10a of the substrate 10 where the gas introduction holes 14 are formed. In this embodiment, multiple gas introduction holes 14 are formed only in positions that overlap 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 introduction holes 14 are formed.

[0030] The electrochemical device 1 is configured such that CO flows into the device interior, surrounded by the substrate 10 and cover 40, only through the gas inlet 14, thereby controlling the amount of CO acting on the catalyst layer 20a. Therefore, the CO concentration can be accurately determined from the proportional relationship between the CO inflow rate and the current value. The gas inlet 14 is, for example, a circular through-hole in plan view. In this specification, "plan view" means viewing the electrochemical device 1 and its components from the first surface 10a side of the substrate 10.

[0031] The gas inlet holes 14 have a diameter of, for example, 0.05 mm to 1 mm, or 0.1 mm to 0.5 mm. The opening area of ​​the gas inlet holes 14 is not particularly limited, but it is preferable that it is large enough so that the constituent material of the catalyst layer 20 does not flow into the gas inlet holes 14 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 inlet holes 14 with small opening areas are formed in the substrate 10. However, the number of gas inlet holes 14 is not particularly limited.

[0032] [Metal layer] As described above, the metal layers 11a, 11b, and 11c are formed on the first surface 10a of the substrate 10, spaced apart so as not to contact each other. The metal layers 11a, 11b, and 11c function as extraction electrodes (wiring) that electrically connect the conductive layer 12 and the catalyst layer 20 to the external circuit. Parts of the metal layers 11a, 11b, and 11c are exposed to the outside of the cover 40 in a plan view of the substrate 10, and connection parts to the external circuit are formed in these exposed portions.

[0033] The metal layer 11 is formed, for example, by first forming a copper foil over the entire surface of the insulating substrate, and then pattern etching the copper foil. As will be described in detail later, a conductive layer 12 is formed on the copper foil remaining after pattern etching. The metal layer 11 has a thickness of, for example, 5 μm to 30 μm. The metal layer 11 may also be formed by other methods such as vapor deposition or printing. In Figure 1, for the sake of clarity, the metal layer 11 is shown as being located within the substrate 10, but in this embodiment, the metal layer 11 is formed on the first surface 10a of the substrate 10.

[0034] [Conductive layer] As described above, the conductive layer 12 is formed to cover at least a portion of the metal layer 11. As shown in Figures 1 and 2, conductive layers 12a, 12b, and 12c are formed on the metal layers 11a, 11b, and 11c, respectively. The conductive layer 12 may also be formed by plating on the metal layer 11 remaining after pattern etching. The conductive layer 12 may also be formed by other methods such as vapor deposition or printing.

[0035] The thickness of the conductive layer 12 may be the same for conductive layers 12a, 12b, and 12c, or they may be different. For example, the thickness of the conductive layer 12 may be 10 nm to 1000 μm, or 20 nm to 500 μm.

[0036] The conductive layers 12a, 12b, and 12c are formed separately on the first surface 10a so as not to contact each other. The areas of the conductive layers 12b and 12c may be the same or different. In the example shown in Figure 2, the conductive layers 12a, 12b, and 12c have a rectangular shape in plan view, but the plan view shape of each layer is not particularly limited.

[0037] The conductive layer 12 is formed to cover the metal layer 11 as described above, but contains a metal or nonmetal with a lower ionization tendency than the metal layer 11. The conductive layer 12 may contain different metals and nonmetals in each of the conductive layers 12a, 12b, and 12c, as long as the ionization tendency is lower than that of the metal layer 11 it is in contact with.

[0038] The conductive layer 12 may contain at least one metal selected from, for example, zinc (Zn), nickel (Ni), tin (Sn), copper (Cu), silver (Ag), platinum (Pt), and gold (Au). Preferably, the conductive layer 12 contains gold, which has a lower ionization tendency than other metals. As a result, ion migration can be suppressed more effectively than with other metals. When the conductive layer 12 is formed solely of metal, it becomes a metallic layer. When the conductive layer 12 is formed by gold plating, it becomes a gold-plated layer.

[0039] The conductive layer 12 may contain metals other than the above-mentioned metals, and may be composed of multiple materials. For example, a gold-nickel alloy may be formed as the conductive layer 12. Alternatively, the conductive layer 12 may be formed by laminating multiple conductive layers 12 composed of different materials.

[0040] The conductive layer 12 may contain at least one selected from nonmetals such as carbon (C), conductive ceramics (alumina-based), and conductive oxides (ITO). From the viewpoint of production costs of the electrochemical device 1, it is more preferable for the conductive layer 12 to contain carbon. In particular, the composition of the conductive layer 12 does not need to be 100% carbon, but it is preferable that carbon be the main component. It is more preferable that the conductive layer 12 contains 50% or more carbon. The conductive layer 12 may contain a binder for binding carbon nanoparticles together. The shape of the carbon can be nanoparticles (spherical), fibrous, wire-like, etc. Furthermore, the conductive layer 12 containing carbon has excellent coating properties.

[0041] The conductive layer 12 preferably contains carbon, as described above. A conductive layer 12 containing carbon is easier to form into any shape compared to a gold plating layer, etc. In the electrochemical device 1, it is preferable that the metal layer 11 and the electrolyte layer 30 do not face each other via the conductive layer 12. This configuration can be easily formed with a conductive layer 12 containing carbon. For example, a conductive layer 12 containing carbon can be easily realized by applying carbon ink to the first surface 10a of the substrate 10.

[0042] The conductive layer 12 may contain, for example, materials other than the nonmetals mentioned above, and may be composed of multiple materials. Furthermore, the conductive layer 12 may be formed by laminating multiple conductive layers 12 composed of different materials.

[0043] [Catalyst layer] As described above, the catalyst layer 20 is directly formed on the first surface 10a of the substrate 10 having the metal layer 11 and the conductive layer 12. Preferably, the catalyst layer 20 is a coating film formed by applying a catalyst material to the first surface 10a. The catalyst layer 20 is formed on the conductive layer 12, and a part of it may be formed in a region of the first surface 10a where the conductive layer 12 does not exist. When the catalyst layer 20 is coated on the first surface 10a, the catalyst layer 20 adheres strongly to the first surface 10a. In this embodiment, since the electrolyte layer 30 is also coated on the catalyst layer 20, the laminated structure of the gas detection unit has strong adhesion, and the resistance value of the gas detection unit decreases and stabilizes even without strong pressure on the laminated structure. As a result, the reliability of the device is improved, and higher sensitivity, miniaturization, and lower cost of the device can be achieved.

[0044] 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 separately so as not to contact each other on the first surface 10a. The areas of the catalyst layers 20b and 20c may be the same or different. In the example shown in Figure 2, the catalyst layers 20a, 20b, and 20c have a rectangular shape in plan view, but the plan view shape of each layer is not particularly limited.

[0045] The catalyst constituting the catalyst layer 20 promotes the oxidation reaction of CO. The reaction of formula (1) above occurs in the catalyst layer 20a, which is the working electrode. In this embodiment, 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), nickel (Ni), etc. Among these, it is preferable to use a precious metal catalyst such as Pt or PtRu alloy.

[0046] The catalyst layer 20 further includes a conductive support and an ionomer. The conductive support is a conductive material that holds the catalyst. Examples of suitable conductive supports include carbon blacks such as acetylene black and Ketjenblack, and carbon materials such as graphite carbon and carbon nanotubes. The catalyst is, for example, fixed to the particle surface of the carbon material. The ionomer is an ionic conductive material that enables the movement of protons generated by the reaction. An example of a suitable ionic conductive material is Nafion (registered trademark: manufactured by DuPont), which has a composition similar to that of the electrolyte membrane.

[0047] [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 electronic conductivity. The electrolyte layer 30 may be constructed by absorbing a liquid electrolyte into a holding member such as a porous sheet, but it is preferably a solid electrolyte membrane made of a polymer material. In this embodiment, a solid electrolyte membrane having proton conductivity is used. An example of a proton-conducting solid electrolyte membrane is a polymer membrane in which a proton-conducting group such as a sulfonic acid group is introduced into a hydrocarbon polymer or a fluorine polymer. A commercially available product such as Nafion (registered trademark: manufactured by DuPont) may be used for the electrolyte layer 30.

[0048] The thickness of the electrolyte layer 30 is not particularly limited, but as an example, it is 5 μm to 500 μm. The electrolyte layer 30 is preferably arranged in contact with the conductive layers 12a, 12b, 12c, or the catalyst layers 20a, 20b, 20c, and a part of it is formed directly on the first surface 10a of the substrate 10. The electrolyte layer 30 is a coating film formed by coating its constituent materials onto the first surface 10a on which the metal layer 11, conductive layer 12, and catalyst layer 20 are formed. In the example shown in Figure 2, the electrolyte layer 30 has a rectangular shape in plan view, but the plan view shape of the electrolyte layer 30 is not particularly limited and can be appropriately changed according to the shape of the electrochemical device 1, etc.

[0049] [cover] The cover 40 prevents gases, including CO and water vapor, from entering the device and protects the gas detection unit from damage. The cover 40 is fixed to the substrate 10, for example, using adhesive, screws, a locking structure, or by welding or other means. The cover 40 is made of a material with low gas permeability that can block gases such as CO and water vapor, and may be made of a metal material, but is preferably made of a resin material from the viewpoint of weight reduction and productivity. Unlike the cover 50 described later, the cover 40 does not have a gas introduction hole 52 and is in close contact with the first surface 10a of the substrate 10 around the gas detection unit.

[0050] The cover 40 may be a flexible thin film sealing sheet, but is preferably made of a rigid resin material. The cover 40 is, for example, a rigid cover formed in the shape of a bottomed cylinder, 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 between the cover 40 and the gas detection unit in the thickness direction of the substrate 10, and the internal space present on the gas detection unit becomes the space for housing 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 closed by the substrate 10.

[0051] The cover 40 is formed in a flat, bottomed rectangular tube shape, but the shape of the cover 40 is not particularly limited. However, from the viewpoint of miniaturizing the device, it is preferable to make the height of the cover 40 from the first surface 10a of the substrate 10 low. The metal layer 11 extends from the inside of the device covered by the cover 40 to the outside of the cover 40, passing between the first surface 10a and the cover 40. A sealing member may be provided between the first surface 10a and the cover 40 to close the gap.

[0052] The cover 50 is, for example, a rigid cover formed in the shape of a bottomed cylinder, and is positioned on the second surface 10b so as to cover the gas introduction hole 14 of the substrate 10. The cover 50 may be a flexible thin film sealing sheet, similar to the cover 40, but is preferably made of a rigid resin material. The cover 50 is fixed to the substrate 10, for example, using adhesive, screws, locking structures, or by welding, etc. The cover 50 may sandwich the substrate 10 together with the cover 40 and be connected to the cover 40.

[0053] The cover 50 is made of a material with low gas permeability that can block gases such as CO and water vapor, and may be made of a metal material, but is preferably made of a resin material from the viewpoint of manufacturing cost. The cover 50 is formed in a flat, bottomed rectangular tube shape, but the shape of the cover 50 is not particularly limited. However, from the viewpoint of miniaturizing the device, it is preferable to make the height of the cover 50 from the second surface 10b of the substrate 10 low. A sealing member may be provided between the second surface 10b and the cover 50 to close the gap.

[0054] In the electrochemical device 1, it is preferable that the opening area of ​​each gas inlet hole 14 in the substrate 10 is smaller than the opening area of ​​each gas inlet hole 52 in the cover 50. If the gas inlet holes 14 and 52 are circular in shape, it is preferable that the diameter of the gas inlet hole 14 is smaller than the diameter of the gas inlet hole 52. The opening area of ​​the gas inlet hole 14 needs to be small from the viewpoint of preventing the ingress of ink forming the catalyst layer 20, but it is preferable that the opening area of ​​the gas inlet hole 52 be larger than that of the gas inlet hole 14 to ensure good air permeability. However, since the gas inlet hole 52 also plays a role in controlling the amount of gas flowing into the device, similar to the gas inlet hole 14, for example, if the gas inlet hole 52 is a circular hole, it should have a diameter of 0.2 to 2.0 mm or 0.3 to 1.0 mm. The number of gas inlet holes 52 is not particularly limited.

[0055] [Humidity control components] 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 device is high and releasing moisture when the humidity is low. The humidity control member 60 prevents, for example, the humidity inside the device covered by the cover 40 from dropping excessively. It is preferable that the humidity control member 60 is positioned 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 gap between the cover 40 and the humidity control member 60 can absorb the expansion of the humidity control member 60. It is preferable that the gap between the cover 40 and the humidity control member 60 is such that the cover 40 and the humidity control member 60 do not come into contact even when the humidity control member 60 expands.

[0056] The humidity control member 60 is, for example, in the form of particles and is positioned opposite the electrolyte layer 30 via a partition layer 70. The shape and size of the humidity control member 60 are not particularly limited. For example, the humidity control member 60 has a larger volume than the electrolyte layer 30. In this case, it will have a sufficient amount of moisture relative to the electrolyte layer 30, allowing for adjustment of the moisture content inside the device, which leads to improved reliability and increased sensitivity of the device.

[0057] 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 are bound to each other, and to the humidity control particles and the two base sheets, by a binder. The type of binder is not particularly limited, 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 good breathability is preferred. Nonwoven fabric, woven fabric, etc. may be used as the base sheet.

[0058] The humidity-regulating particles may be particles containing silicon compounds such as silica, sepiolite, and zeolite, or they may contain alumina, titania, zirconia, etc., instead of or together with silicon compounds. Furthermore, the humidity-regulating particles may contain superabsorbent polymers such as cross-linked sodium polyacrylate. As will be described in detail later, the particle size of the humidity-regulating particles is preferably larger than the diameter of the ventilation holes in the partition layer 70. The average particle size of the humidity-regulating particles is, for example, 30 μm to 10 mm, or 500 μm to 5 mm. The average particle size of the humidity-regulating particles is calculated by observing the particles with an optical microscope or scanning electron microscope and averaging the diameters of the circumscribed circles of each particle image. It is preferable that the average particle size in the minimum state is within this range when the humidity-regulating particles absorb water and expand.

[0059] [Partition layer] The partition layer 70 is a sheet-like member placed between the electrolyte layer 30 and the humidity control member 60 for the purpose of preventing 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, it is expected that an excessive amount of moisture will be supplied to the contact area, so it is preferable to interpose the partition layer 70 between the electrolyte layer 30 and the humidity control member 60. The shape and size of the partition layer 70 are not particularly limited, but it is preferable that it has the same shape and size as the electrolyte layer 30 and that the partition layer 70 is arranged to cover the entire electrolyte layer 30. The thickness of the partition layer 70 is not particularly limited, but as an example, it is 30 μm or more and 1000 μm or less.

[0060] The partition layer 70 is preferably a breathable sheet. By having a water vapor permeable partition layer 70 cover the entire electrolyte layer 30, it is possible to adjust the moisture content of the entire electrolyte layer while preventing contact between the electrolyte layer 30 and the humidity control member 60, which leads to improved device reliability and increased sensitivity. The partition layer 70 can be a porous sheet with ventilation holes, and nonwoven fabrics, woven fabrics, etc., may be used. If the humidity control member 60 includes a porous base sheet, that sheet may function as the partition layer 70.

[0061] The diameter of the ventilation holes in the partition layer 70 is, for example, less than 50 μm, and smaller than the particle size of the humidity-regulating particles of the humidity-regulating member 60. The average particle size of the humidity-regulating particles should be larger than the average diameter of the ventilation holes, but the particle size of all humidity-regulating particles may be larger than the maximum diameter of the ventilation holes. In this case, even if humidity-regulating particles are directly present on the partition layer 70, the penetration of the humidity-regulating particles into the ventilation holes is suppressed, ensuring the permeability of the partition layer 70 and preventing contact between the electrolyte layer 30 and the humidity-regulating particles. The average value of the diameter of the ventilation holes is, for example, 0.1 μm or more and 30 μm or less, or 0.5 μm or more and 25 μm or less. The average value of the diameter of the ventilation holes is measured by a mercury porosimeter.

[0062] Furthermore, the partition layer 70 may be made of a sheet-like resin material, and since resin materials have high strength, assembly during manufacturing is improved. In this case, the resin material is provided with through holes for ventilation, which prevents contact between the electrolyte layer 30 and the humidity control member 60, while also adjusting the moisture content of the entire electrolyte layer, leading to improved device reliability and higher sensitivity. The shape of the through holes provided in the sheet-like resin material is, for example, a perfect circle in plan view, with a diameter of less than 1000 μm. In this case, by selecting humidity control particles that are larger than the diameter of the through holes, the entry of humidity control particles into the through holes is suppressed, ensuring the permeability of the partition layer 70 and preventing contact between the electrolyte layer 30 and the humidity control particles. The average value of the diameter of the through holes is, for example, between 100 μm and 500 μm, and the average value of the diameter of the through holes is measured using an optical microscope or the like.

[0063] The first modified electrochemical device 1x will be described in detail using Figures 3 and 4. Figure 3 is a plan view showing the first modified electrochemical device 1x, and Figure 4 is a cross-sectional view AA of Figure 3. Note that the cover 40, humidity control member 60, and partition layer 70 are omitted from Figure 3. The dotted line shown in Figure 3 indicates the end of the metal layer 11 covered by the conductive layer 12.

[0064] As shown in Figures 3 and 4, the electrochemical device 1x differs from the electrochemical device 1 in that, when the first surface 10a of the substrate 10 is viewed from above, the electrolyte layer 30 is arranged so as not to overlap with the metal layer 11 in the thickness direction of the substrate 10. More specifically, in the electrochemical device 1x, when the first surface 10a of the substrate 10 is viewed from above, the electrolyte layer 30 is arranged so as not to overlap with the metal layers 11a, 11b, and 11c. Furthermore, the electrolyte layer 30 is arranged so as to overlap with the conductive layer 12 and the catalyst layer 20 on the first surface 10a in the thickness direction of the substrate 10.

[0065] The electrochemical device 1x has a structure in which the electrolyte layer 30 and the metal layer 11 are not adjacent to each other via the conductive layer 12. This prevents direct contact between the electrolyte layer 30 and the metal layer 11 even if the conductive layer 12 is missing or otherwise damaged. As a result, the movement of cations deposited from the metal layer 11 through the electrolyte layer 30 can be suppressed. In other words, the movement of cations between the metal layers 11 can be suppressed, thereby suppressing the occurrence of ion migration.

[0066] The second modified electrochemical device 1y will be described in detail using Figures 5 and 6. Figure 5 is a plan view showing the second modified electrochemical device 1y, and Figure 6 shows a cross-sectional view of BB in Figure 6. Note that the cover 40, humidity control member 60, and partition layer 70 are omitted from Figure 5.

[0067] Electrochemical device 1y differs from electrochemical device 1 in that, as shown in Figure 5, at least a portion of the metal layer 11 is covered with an insulating layer 13. In electrochemical device 1y, for example, at least a portion of the metal layer 11 and the conductive layer 12 that are not in contact with the electrolyte layer 30 may be covered with the insulating layer 13. The insulating layer 13 may be formed on the first surface 10a in a portion other than the portion where the electrolyte layer 30 is formed. Also, the portion of the metal layer 11 that is not in contact with the conductive layer 12 may be covered with the insulating layer 13. That is, the insulating layer 13 may be formed on the first surface 10a and on the metal layer 11 that is not in contact with the conductive layer 12. In other words, the conductive layer 12, catalyst layer 20, and electrolyte layer 30 are exposed and not covered with the insulating layer 13.

[0068] The thickness of the insulating layer 13 is, for example, 5 μm to 100 μm. In the example shown in Figure 5, the plan view shape of the insulating layer 13 is a square shape with a hollow portion in the plan view, but the plan view shape of the insulating layer 13 is not particularly limited. In the electrochemical device 1y, even when the insulating layer 13 is formed, the humidity control member 60, partition layer 70, etc., may be formed on the electrolyte layer 30 as shown in Figure 6.

[0069] Using Figure 7, we will describe in detail the electrochemical device 1z, which is a third modified example. Figure 11 is a schematic cross-sectional view illustrating the electrochemical device 1z, which is a third modified example, and the cover 40 and other parts have been omitted for clarity. The electrochemical device 1z differs in that gas introduction holes 14 are not formed in the substrate 10, the catalyst layer 20 is not formed, and a polymer material layer 300 is provided instead of the electrolyte layer 30.

[0070] As shown in Figure 7, the electrochemical device 1z may include a substrate 10 including a first surface 10a and a second surface 10b, a metal layer 311a provided on the first surface 10a of the substrate 10, and a metal layer 311b provided on the first surface 10a of the substrate 10 so as not to contact the metal layer 311a. No gas introduction holes 14 are formed in the substrate 10 of the electrochemical device 1z. Furthermore, the electrochemical device 1z includes a conductive layer 312a formed to cover at least a portion of the metal layer 311a and containing a metal or nonmetal with a lower ionization tendency than the metal layer 311a, and a conductive layer 312b formed to cover at least a portion of the metal layer 311b and containing a metal or nonmetal with a lower ionization tendency than the metal layer 311b, and provided so as not to contact the conductive layer 312a. The electrochemical device 1z also includes a polymer material layer 300 provided so as to be in contact with the conductive layer 312a and the conductive layer 312b, respectively.

[0071] As shown in Figure 7, the polymer material layer 300 may be provided so as to overlap with the metal layer 311 in the thickness direction of the substrate 10 when the first surface 10a of the substrate 10 is viewed from above. Alternatively, the polymer material layer 300 may be provided so as not to overlap with the metal layer 11 in the thickness direction of the substrate 10 when the first surface 10a of the substrate 10 is viewed from above, similar to the electrolyte layer 30 shown in Figure 4.

[0072] The conductive layer 312 is formed to cover at least a portion of the metal layer 311 as described above. The conductive layer 312 also contains a metal or nonmetal with a lower ionization tendency than the metal layer 311. In the example shown in Figure 7, the conductive layer 312 is formed to cover the surface of the metal layer 311 (the surface parallel to the first surface 10a). Although not shown, if the side surface of the metal layer 311 (for example, the surface perpendicular to the first surface 10a) is exposed, it is preferable that the conductive layer 312 be formed to cover both the surface and the side surface of the metal layer 311. One conductive layer 312 is placed for each of the metal layers 311. It is also preferable that the conductive layer 312 be formed to cover the entire surface of the metal layer 311 that is exposed within the cover 40. It is preferable that the conductive layer 312 be formed to cover the entire region in the metal layer 311 where the polymer material layer 300 is formed. This makes it possible to more effectively suppress the deposition of cations and the occurrence of ion migration.

[0073] In the electrochemical device 1z, a laminated structure including a metal layer 311, a conductive layer 312, and a polymer material layer 300, directly formed on the first surface 10a of the substrate 10, functions as a gas detection unit. The polymer material has the property of adsorbing gas molecules and moisture from the environment, which changes the electrical resistance that causes ion conduction. As a result, it can be used as a sensor by measuring the change in resistance value. Furthermore, the metal layer 311a and metal layer 311b, which function as electrodes, are arranged to conduct ions via the polymer material and are electrically connected via an external circuit (not shown).

[0074] The electrochemical device 1z may have a cover 40 that covers the first surface 10a of the substrate 10 and is provided with a gas introduction hole. In this case, a portion of the metal layer 11 is exposed to the outside of the cover. A connection portion to an external circuit is formed in the portion of the metal layer 11 exposed from the cover 40.

[0075] The electrochemical device 1z, also known as a resistance-type sensor, can be used as a sensor capable of detecting changes in the concentration of a gas in the environment by introducing the target gas into a polymer material and measuring the change in the resistance value of the polymer material. In the following explanation, water molecules (H2O) will be used as an example of the target gas. However, the sensors to which the configuration of the electrochemical device described herein can be applied are not limited to H2O sensors (humidity sensors).

[0076] When the amount of H2O, the target gas detected by the electrochemical device 1z, increases, the polymer material absorbs H2O, increasing its ionic conductivity and decreasing its electrical resistance. Since the magnitude of this change in electrical resistance correlates with the H2O concentration (humidity) in the environment, it is possible to detect the H2O concentration (humidity) by measuring the electrical resistance.

[0077] Using Figures 8 and 9, we will describe in detail the case in which an electrochemical device 1, which is an example of an embodiment, is mounted on a circuit board 90. Figure 8 is a diagram showing the electrochemical device 1, which is an example of an embodiment, mounted on a circuit board 90, and Figure 9 is a cross-sectional view of Figure 8. Note that in Figure 9, the circuit board 90 is omitted for clarity.

[0078] As shown in Figures 8 and 9, the substrate 10 has a plurality of protrusions 15 that protrude from the covers 40 and 50. In the example shown in Figure 8, the protrusions 15 extend from both ends of the rectangular covers 40 and 50 to the outside of the cover 40. Two protrusions 15 extend from one end of the cover 40, and one protrusion 15 extends from the other end. The three protrusions 15 are formed parallel to each other, and each has a metal layer 11 and a connecting portion 16. The metal layer 11 extends along the longitudinal direction of each protrusion 15, and the connecting portion 16 is formed at the tip of each protrusion 15. The protrusions 15 and connecting portions 16 exemplified in Figure 8 each have the same size and shape, but their sizes and shapes may differ from each other.

[0079] As shown in Figure 8, the protruding portion 15 is formed such that multiple protruding portions 15 protrude in two directions from opposite ends of the cover 40. The multiple protruding portions 15 may, for example, protrude in three directions from the cover 40, but having them protrude in two directions makes it easier to connect to the circuit board 90.

[0080] The electrochemical sensor device 100 comprises a circuit board 90 and an electrochemical device 1 mounted on the circuit board 90. The electrochemical device 1 is attached to the circuit board 90 using protrusions 15. The circuit board 90 has conductive pins 91 erected on its surface. The pins 91 are, for example, external terminals electrically connected to other electronic devices constituting the circuit board 90, and have a substantially cylindrical shape. The circuit board 90 may also have a recess 92 into which the cover 40 of the electrochemical device 1 fits. The recess 92 is formed, for example, by cutting out a substantially U-shaped notch in the end of the circuit board 90 in plan view, to accommodate the cover 40. The circuit board 90 is, for example, a printed wiring board on which other electronic components are mounted. If the circuit board 90 does not have a recess 92, the electrochemical device 1 may be directly joined to the circuit board 90 by soldering or the like.

[0081] The electrochemical device 1 is mounted on the circuit board 90 by connecting the connection portion 16 formed on the protrusion 15 to the pin 91. In the example shown in Figure 8, the connection portion 16 includes a semicircular through hole in plan view, and the pin 91 is inserted into the through hole of the connection portion 16. Three pins 91 are provided on the periphery of the recess 92 so that they can be inserted into the connection portion 16 of each protrusion 15 when the electrochemical device 1 is housed in the recess 92.

[0082] The connector 16 constitutes a part of the metal layer 11 and has a conductive layer formed on the periphery and inner surface of the through hole. The conductive layer formed on the inner surface of the connector 16 abuts against the outer surface of the pin 91 and is electrically connected to the pin 91. The connector 16 and the pin 91 may be soldered together. The signal generated in the gas detection unit, which includes the metal layer 11, the conductive layer 12, the catalyst layer 20, and the electrolyte layer 30, is transmitted to the connector 16 via the metal layer 11 and to the pin 91 via the connector 16.

[0083] Figure 10 illustrates another example of the electrochemical sensor device 100. Figure 10 is a diagram illustrating another example of the electrochemical sensor device.

[0084] As shown in Figure 10, the electrochemical sensor device 100x may have its connection portion 16 grouped together at one end of the substrate 10. The electrochemical sensor device 100 is joined to the circuit board 90 by inserting the pin 91 into the through hole of the connection portion 16, as described above. In the electrochemical sensor device 100x, the one end of the substrate 10 on which the connection portion 16 is provided becomes a protruding portion 15. That is, the protruding portion 15 protruding from the cover 40 is provided in only one direction, and the connection portion 16 is provided on this protruding portion 15.

[0085] Figure 11 is a block diagram showing the configuration of an electrochemical sensor system 200, which is an example of an embodiment. As shown in Figure 11, the electrochemical sensor system 200 comprises an electrochemical sensor device 100 including an electrochemical device 1, a receiving device 201 that receives detection information from the electrochemical sensor device 100, and a control device 202. The receiving device 201 and the control device 202 may be installed at a location away from the electrochemical sensor device 100, and the receiving device 201 may receive detection information from the electrochemical sensor device 100 via wireless communication, wired communication, or a wide-area communication network such as the Internet. The control device 202 controls the operation of a predetermined device based on the detection information from the electrochemical sensor device 100, for example.

[0086] The electrochemical sensor device 100 comprises an electrochemical device 1 and a housing 110 that houses the electrochemical device 1. The electrochemical sensor device 100 may also include a holder for holding the electrochemical device 1, a speaker for outputting an alarm sound, a warning lamp, etc. The electrochemical device 1 may be connected to a printed circuit board on which other electronic components are mounted, or the board 10 constituting the electrochemical device 1 may be a printed circuit board on which other electronic components are mounted. The electrochemical sensor device 100 may also include an electrochemical device 1x or an electrochemical device 1y instead of the electrochemical device 1. The electrochemical sensor device 100 may further include a detection unit for at least one of smoke and heat, and in this case, it may also include a speaker for outputting an alarm sound, a warning lamp, etc.

[0087] The above embodiments can be modified as appropriate without impairing the purpose of this disclosure. For example, in the above embodiments, the catalyst layer 20c, which is the reference electrode, is formed using the same electrode material as the catalyst layer 20a, which is the working electrode, and the catalyst layer 20b, which is the counter electrode. However, the catalyst layer 20c may be made of a different material than the catalyst layers 20a and 20b, and the catalyst layers 20a and 20b may be made of different materials. Furthermore, the structure of the electrochemical device may be a two-electrode structure comprising only a working electrode and a counter electrode. Alternatively, the conductive layer 12c can be used as the reference electrode, and the counter electrode can also be used as the reference electrode. In addition, the electrochemical device may be provided with other components such as a gas diffusion layer.

[0088] The electrochemical device 1 does not necessarily have a catalyst layer 20. In that case, the electrochemical device 1 does not have a catalyst layer to promote the oxidation reaction of CO, so gas reactivity may decrease, but it is possible to have the conductive layer 12a function as the working electrode, the conductive layer 12b as the counter electrode, and the conductive layer 12c as the reference electrode. When the conductive layer 12 functions as the working electrode, counter electrode, and reference electrode, the conductive layer 12 may be provided so as to overlap with the gas introduction hole 14 in the thickness direction of the substrate 10. In particular, when the first surface 10a is viewed from above, the conductive layer 12 may be provided so as to overlap with the gas introduction hole 14. Specifically, when the conductive layer 12a functions as the working electrode, the conductive layer 12a is provided so as to overlap with the gas introduction hole 14. This allows the conductive layer 12 to detect the gas flowing in from the gas introduction hole 14.

[0089] The electrochemical device 1 has a humidity control member 60, a partition layer 70, and activated carbon 80, but the electrochemical device according to this disclosure is not limited to having a humidity control member 60, a partition layer 70, and activated carbon 80. The electrochemical device according to this disclosure may, for example, have only activated carbon 80, or may have a structure in which activated carbon 80 is arranged between the gas detection unit and the cover 40. Alternatively, the humidity control member 60 may be arranged between the substrate 10 and the cover 50. Furthermore, the electrochemical device according to this disclosure may have a structure in which only the cover 40 is provided without the cover 50. [Examples]

[0090] The present disclosure will be further illustrated by the following examples, but will not be limited thereto.

[0091] <Example 1> [Fabrication of electrochemical devices] A copper foil was formed over the entire first surface of a 1 mm thick substrate with gas inlet holes. A metal layer was then formed by pattern etching of this copper foil. The metal layer consisted of a first, second, and third metal layer, arranged so as not to contact each other. Furthermore, a carbon-containing ink was applied to cover the metal layer, and the coating was dried to remove the dispersion medium, forming a 20 μm thick conductive layer (carbon layer). In this process, the conductive layer also consisted of a first, second, and third conductive layer, arranged so as not to contact each other. The carbon layer was also formed to have an extension portion extending in a direction parallel to the first surface of the substrate. The extension portion is the carbon layer formed on the first surface of the substrate. When the first surface is viewed from above, the extension portion is the region of the carbon layer that does not overlap with the metal layer in the thickness direction of the substrate.

[0092] An ink containing a catalyst, a conductive carrier, and an ionomer was coated onto the first surface of a substrate on which a conductive layer was formed. The coating was dried to remove the dispersion medium, thereby forming a catalyst layer that contacts the conductive layer. In this case, the catalyst layer was formed into a first catalyst layer, a second catalyst layer, and a third catalyst layer, similar to the metal layer and the conductive layer, but without contact with each other. In the electrochemical device, the first catalyst layer functions as the working electrode, the second catalyst layer as the counter electrode, and the third catalyst layer as the reference electrode. When the first surface is viewed from above, the first catalyst layer is positioned to overlap with the gas introduction holes in the thickness direction of the substrate. An ink containing the constituent materials of a solid electrolyte was coated onto the first surface of the substrate so as to contact each of the catalyst layers. The coating was dried to remove the dispersion medium, thereby forming an electrolyte layer. In this case, when the first surface is viewed from above, the electrolyte layer was formed so as not to overlap with the metal layer in the thickness direction of the substrate. When the first surface is viewed from above, the electrolyte layer was formed so as to overlap with the extended portion of the carbon layer in the thickness direction of the substrate.

[0093] A partition layer and a humidity control member are stacked on the catalyst layer in that order, and a first cover is placed to cover the entire conductive layer and other components formed on the first surface. Activated carbon is placed on the second surface, and a second cover is placed to cover the gas inlet hole. A portion of the metal layer is exposed from both the first and second covers as it functions as an extraction electrode.

[0094] <Example 2> An electrochemical device was fabricated in the same manner as in Example 1, except that the conductive layer was a gold-plated layer, the thickness of the conductive layer (gold-plated layer) was set to 2000 nm, and the electrolyte layer was formed to cover the metal layer.

[0095] <Example 3> An electrochemical device was fabricated in the same manner as in Example 1, except that the conductive layer was a gold-plated layer, the thickness of the conductive layer (gold-plated layer) was set to 30 nm, and the electrolyte layer was formed to cover the metal layer.

[0096] Measurements were performed on each electrochemical device in the examples using the following method, and the measurement results are shown in Figures 12 and 13. Figure 12 shows the measured values ​​of the electrochemical device in Example 1. Figure 13 shows the measured values ​​of the electrochemical devices in Examples 2 and 3. In Figures 12 and 13, the vertical axis represents the output current and the horizontal axis represents the temperature. In Figures 12 and 13, the solid line shows the measurement results for Example 1, the dashed line shows the measurement results for Example 2, and the dotted line shows the approximate curve created from the measurement results for Example 3.

[0097] [Output current measurement] An ammeter was placed in the middle of the external circuit electrically connecting the working electrode and the counter electrode, and the output current between the working electrode and the counter electrode was measured. Specifically, the fabricated electrochemical device was placed in a constant temperature and humidity test chamber, and the temperature was changed as shown in Figures 12 and 13, and the output current at each temperature was measured with an ammeter. Specifically, the temperature was changed in steps from 25°C to 60°C. Furthermore, this current measurement measured the baseline output when the target gas was not present. Note that the negative output current shown on the vertical axis in Figures 12 and 13 indicates the magnitude of the current flowing from the working electrode to the counter electrode. That is, it indicates that electrons moved from the counter electrode to the working electrode via the external circuit, and cations (copper ions) moved via the electrolyte layer.

[0098] In electrochemical devices, electrons move from the counter electrode to the working electrode via an external circuit, and cations (copper ions) move through the electrolyte layer. As a result, copper ions that have received electrons at the working electrode return to copper and deposit around the working electrode, causing ion migration. In high-temperature environments where the negative output current is increasing, the movement of electrons from the counter electrode to the working electrode via the external circuit and the movement of cations through the electrolyte layer increase, thus increasing the occurrence of ion migration. In other words, the more the output current increases, the more ion migration occurs.

[0099] In Examples 1-3, the negative output current is maximized under high-temperature conditions around 60°C, as described above. In Example 2, the output current can be suppressed more effectively than in Example 3 by setting the thickness of the gold plating layer to 2000 nm. Specifically, as shown in Figure 13, the maximum value of the negative output current in Example 3 is approximately -1900 nA, while in Example 2 it is approximately -1200 nA. Comparing the gold plating layers of Example 2 and Example 3, Example 2, with its thicker gold plating, can prevent plating defects and other issues more effectively than Example 3, thus effectively suppressing the occurrence of ion migration.

[0100] Furthermore, referring to Figure 12, it can be confirmed that ion migration is suppressed in Example 1 as well. Specifically, in Example 1, the maximum value of the negative output current is approximately -2200 nA, indicating that the output current is suppressed. By forming a carbon layer with an extended portion as in Example 1, the electrolyte layer can be positioned so that it does not face the metal layer via the conductive layer, thereby effectively suppressing the movement of cations and effectively suppressing the occurrence of ion migration. In addition, by suppressing the output current, the baseline noise output when the target gas is not present is suppressed, and the sensor sensitivity is improved.

[0101] This disclosure is further illustrated by the following embodiments. Configuration 1: An electrochemical device comprising a substrate including a first surface and a second surface; a first metal layer provided on the first surface of the substrate; a second metal layer provided on the first surface of the substrate so as not to contact the first metal layer; a first conductor layer formed to cover at least a portion of the first metal layer and containing a metal or nonmetal having a lower ionization tendency than the first metal layer; a second conductor layer formed to cover at least a portion of the second metal layer and containing a metal or nonmetal having a lower ionization tendency than the second metal layer, and provided so as not to contact the first conductor layer; and an electrolyte layer or polymer material layer provided so as to contact the first conductor layer and the second conductor layer, respectively. Configuration 2: The electrochemical device according to Configuration 1, wherein, when the first surface of the substrate is viewed from above, the electrolyte layer or the polymer material layer is provided in contact with the region overlapping with the first metal layer of the first conductor layer and the region overlapping with the second metal layer of the second conductor layer. Configuration 3: The electrochemical device according to Configuration 1, wherein, when the first surface of the substrate is viewed from above, the electrolyte layer or the polymer material layer is provided so as not to overlap with the first metal layer and the second metal layer. Configuration 4: The electrochemical device according to any one of Configurations 1 to 3, wherein at least a portion of the first metal layer, the second metal layer, the first conductive layer, and the portion of the second conductive layer that is not in contact with the electrolyte layer is covered with an insulating layer. Configuration 5: The electrochemical device according to any one of Configurations 1 to 3, wherein the portion of the first metal layer that is not in contact with the first conductive layer and the portion of the second metal layer that is not in contact with the second conductive layer are covered with an insulating layer. Configuration 6: An electrochemical device according to any one of Configurations 1 to 5, wherein the nonmetal includes carbon. Configuration 7: An electrochemical device according to any one of Configurations 1 to 6, comprising a first catalyst layer provided in contact with at least a portion of the first conductive layer and the electrolyte layer, and a second catalyst layer provided in contact with at least a portion of the second conductive layer and the electrolyte layer. Configuration 8: The electrochemical device according to Configuration 7, wherein a portion of the first catalyst layer is exposed from the electrolyte layer so as to be exposed to the outside air. Configuration 9: The electrochemical device according to Configuration 7, wherein the substrate has gas introduction holes connecting the first surface and the second surface, and when the substrate is viewed in plan view, the gas introduction holes are provided in the region where the first catalyst layer is in contact with the substrate. Configuration 10: An electrochemical sensor device comprising a circuit board and an electrochemical device described in any one of Configurations 1 to 9 mounted on the circuit board. Configuration 11: An electrochemical sensor device comprising an electrochemical device described in any one of Configurations 1 to 9 and a housing for housing the electrochemical device. Configuration 12: An electrochemical sensor system comprising an electrochemical sensor device as described in Configuration 10 or 11, and a receiving device for receiving the detection results of the electrochemical sensor device. [Explanation of symbols]

[0102] 1, 1x, 1y, 1z electrochemical device 10 circuit boards 10a 1st page 10b 2nd side 11, 11a, 11b, 11c, 311, 311a, 311b metal layer 12, 12a, 12b, 12c, 312, 312a, 312b conductor layer 13 Insulating layer 14, 52 Gas inlet ports 15 Protrusion 16 Connection part 20, 20a, 20b, 20c catalyst layer 30 Electrolyte layer 40, 50 cover 60 Humidity control components 70 Partition layer 80 activated carbon 90 Circuit boards 91 pins 92 recess 100, 100x electrochemical sensor device 110 cabinets 200 Electrochemical Sensor Systems 201 Receiving device 202 Control device 300 polymer material layer

Claims

1. A substrate including the first and second surfaces, A first metal layer provided on the first surface of the substrate, A second metal layer is provided on the first surface of the substrate so as not to be in contact with the first metal layer, A first conductive layer is formed to cover at least a portion of the first metal layer and contains a metal or nonmetal having a lower ionization tendency than the first metal layer, A second conductive layer is formed to cover at least a portion of the second metal layer, contains a metal or nonmetal with a lower ionization tendency than the second metal layer, and is provided so as not to come into contact with the first conductive layer. An electrolyte layer or polymer material layer provided so as to be in contact with the first conductive layer and the second conductive layer, An electrochemical device having [a certain characteristic].

2. The electrochemical device according to claim 1, wherein, when the first surface of the substrate is viewed from above, the electrolyte layer or the polymer material layer is provided to be in contact with a region overlapping with the first metal layer of the first conductor layer and a region overlapping with the second metal layer of the second conductor layer.

3. The electrochemical device according to claim 1, wherein, when the first surface of the substrate is viewed from above, the electrolyte layer or the polymer material layer is provided so as not to overlap with the first metal layer and the second metal layer.

4. The electrochemical device according to claim 1, wherein at least a portion of the first metal layer, the second metal layer, the first conductive layer, and the portion of the second conductive layer that is not in contact with the electrolyte layer is covered with an insulating layer.

5. The electrochemical device according to claim 1, wherein the portion of the first metal layer that is not in contact with the first conductive layer and the portion of the second metal layer that is not in contact with the second conductive layer are covered with an insulating layer.

6. The electrochemical device according to claim 1, wherein the nonmetal includes carbon.

7. A first catalyst layer is provided so as to be in contact with at least a portion of the first conductive layer and the electrolyte layer, A second catalyst layer is provided so as to be in contact with at least a portion of the second conductive layer and the electrolyte layer, The electrochemical device according to claim 1, having the following characteristics.

8. The electrochemical device according to claim 7, wherein a portion of the first catalyst layer is exposed from the electrolyte layer so as to be exposed to the outside air.

9. The substrate has a gas introduction hole that connects the first surface and the second surface, The electrochemical device according to claim 7, wherein, when the substrate is viewed in plan view, the gas introduction holes are provided in the region where the first catalyst layer is in contact with the substrate.

10. An electrochemical sensor device comprising a circuit board and an electrochemical device according to claim 1 mounted on the circuit board.

11. An electrochemical sensor device comprising an electrochemical device according to any one of claims 1 to 9 and a housing for housing the electrochemical device.

12. An electrochemical sensor system comprising an electrochemical sensor device according to claim 11 and a receiving device for receiving detection results from the electrochemical sensor device.

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