Electrochemical gas sensor and method for manufacturing the same

Abstract

To prevent peeling of an electrode in a portion covered by an electrolyte layer.SOLUTION: An electrochemical gas sensor 1 includes: an insulating substrate 10; a working electrode 20 formed on the insulating substrate 10; and an electrolyte layer 50 formed on the insulating substrate 10 so as to cover at least part of the working electrode 20. In the electrochemical gas sensor 1, there are four or more intersection points P at which an outer edge 25 of the working electrode 20 and a first side 55, which is an outer edge of the electrolyte layer 50, intersect each other in a plan view of the insulating substrate 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrochemical gas sensor and a method for manufacturing the same. [Background technology]

[0002] Conventionally, electrochemical gas sensors having a working electrode, a counter electrode, and an electrolyte are known. In an electrochemical gas sensor, for example, the working electrode and the counter electrode are connected via an external circuit, and when a gas to be detected such as carbon monoxide flows into the sensor, positive ions and electrons are generated at the working electrode. The electrons flow to the counter electrode through the external circuit, and the concentration of the gas can be detected by measuring the short-circuit current at this time. For example, Patent Document 1 discloses an electrochemical gas sensor in which an electrolyte layer made of a conductive polymer is arranged to cover the electrodes on an insulating substrate on which electrodes are formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Publication No. 2021 / 148850 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it has been found that in an electrochemical gas sensor having an electrolyte layer covering an electrode, peeling of the electrode occurs due to a change in volume of the electrolyte layer. In particular, when an electrolyte layer is formed by applying an electrolyte material onto an electrode, the electrolyte layer shrinks when the applied film dries, making the electrode more likely to peel off. An object of the present disclosure is to prevent peeling of the electrode in the portion covered by the electrolyte layer. [Means for solving the problem]

[0005] The electrochemical gas sensor according to the present disclosure comprises an insulating substrate, an electrode formed on the insulating substrate, and an electrolyte layer formed on the insulating substrate so as to cover at least a portion of the electrode, and is characterized in that, in a plan view of the insulating substrate, there are multiple intersections where the outer edge of the electrode intersects with the outer edge of the electrolyte layer, and the number of intersections is four or more.

[0006] The manufacturing method of the electrochemical gas sensor according to the present disclosure is a manufacturing method of an electrochemical gas sensor comprising an insulating substrate, an electrode, and an electrolyte layer, and is characterized in that an electrode material is applied onto the insulating substrate to form electrodes, and an electrolyte material is applied onto the insulating substrate to form an electrolyte layer, so that the number of intersections between the outer edges of the electrodes and the outer edges of the electrolyte layer in a plan view of the insulating substrate is four or more. Effect of the Invention

[0007] According to the electrochemical gas sensor according to the present disclosure, peeling of the electrodes in the portions covered with the electrolyte layer can be effectively prevented. [Brief description of the drawings]

[0008] [Figure 1] 1 is a plan view of an electrochemical gas sensor according to an embodiment; [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 2 is an enlarged view showing an overlapping portion between a working electrode and an electrolyte layer and its vicinity in an electrochemical gas sensor according to an embodiment of the present invention. [Figure 4] 5A to 5C are diagrams for explaining the effects of the electrochemical gas sensor according to the embodiment; [Diagram 5] FIG. 2 is a cross-sectional view showing an electrochemical gas sensor according to another embodiment. [Figure 6] FIG. 2 is a cross-sectional view showing an electrochemical gas sensor according to another embodiment. [Figure 7] FIG. 2 is a cross-sectional view showing an electrochemical gas sensor according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] As described above, in an electrochemical gas sensor having an electrolyte layer covering an electrode, it is an important issue to prevent the electrode from peeling off due to a change in the volume of the electrolyte layer. In the sensor disclosed in the above patent document, the electrolyte material may penetrate into the gas introduction hole formed in the substrate and block the hole, causing the sensor to no longer function. As a method for avoiding this issue, it is possible to form an electrolyte layer by applying an electrolyte material so as not to cover the entire surface of the electrode, without forming a gas introduction hole in the substrate. In this case, an electrochemical reaction occurs in the exposed part of the electrode, and the sensor functions as a gas sensor.

[0010] On the other hand, if an electrolyte layer is provided so as to cover a portion of an electrode, the electrode is more likely to peel off due to a change in volume of the electrolyte layer, and the electrode may peel off particularly from the portion that overlaps with the outer edge of the electrolyte layer (e.g., see FIG. 4(b) described below). However, the electrochemical gas sensor according to the present disclosure can effectively prevent such electrode peeling.

[0011] Hereinafter, an example of an embodiment of an electrochemical gas sensor according to the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure includes configurations that are obtained by selectively combining multiple embodiments described below.

[0012] Fig. 1 is a plan view of an electrochemical gas sensor 1 according to an embodiment, and Fig. 2 is a cross-sectional view (cross-sectional view taken along line AA in Fig. 1) of the electrochemical gas sensor 1. In Fig. 1, a sealing layer 60 is shown by a virtual line. Note that the drawings are schematic, and the dimensional ratios of the respective components are as follows:

[0013] 1 and 2, the electrochemical gas sensor 1 includes an insulating substrate 10, electrodes formed on the insulating substrate 10, and an electrolyte layer 50 formed on the insulating substrate 10 so as to cover at least a part of the electrodes. The electrochemical gas sensor 1 also includes a current collector formed on the insulating substrate 10, and a sealing layer 60 covering the electrodes and the electrolyte layer 50. As will be described in detail later, the electrochemical gas sensor 1 has a plurality of intersections P at which the outer edges of the electrodes and the outer edges of the electrolyte layer 50 intersect when viewed from above the insulating substrate 10. In the embodiment illustrated in FIG. 1, there are ten intersections P.

[0014] The electrochemical gas sensor 1 includes a working electrode 20, a counter electrode 30, and a reference electrode 40 as electrodes. The working electrode 20 is an electrode into which a gas to be detected flows, and is also called a detection electrode. The working electrode 20 and the counter electrode 30 are arranged to be capable of ion conduction via an electrolyte layer 50. The counter electrode 30 is formed on an insulating substrate 10 so as not to come into contact with the working electrode 20. The reference electrode 40 is an electrode that serves as a reference when controlling and measuring the potential of the working electrode 20, and is also called a reference electrode.

[0015] The electrochemical gas sensor 1 includes a first metal layer 11, a second metal layer 12, and a third metal layer 13 as current collectors. The metal layer 11 is electrically connected to the working electrode 20, the metal layer 12 to the counter electrode 30, and the metal layer 13 to the reference electrode 40, and are formed on the insulating substrate 10 so as not to contact each other. Each metal layer functions as an extraction electrode that electrically connects each electrode to an external circuit (not shown). Each metal layer is formed on the insulating substrate 10 from the area covered by the sealing layer 60 to the outside.

[0016] The electrochemical gas sensor 1 detects the gas concentration by flowing a gas to be detected into the working electrode 20, oxidizing or reducing the gas molecules on the working electrode 20, and measuring the change in current or potential associated with this oxidation-reduction reaction. The electrochemical gas sensor 1 may be a potential detection type, but in this embodiment, a current detection type sensor is exemplified. When the gas molecules are oxidized or reduced at the working electrode 20, electrons are generated or consumed, and a current flows between the working electrode 20 and the counter electrode 30. Since the current value is proportional to the gas concentration, the gas concentration can be detected by measuring the current value. When electrons are generated or consumed by the oxidation-reduction reaction at the working electrode 20, positive ions or negative ions are generated, and the generated ions move to the counter electrode 30 through the electrolyte layer 50.

[0017] In the following, carbon monoxide (CO) will be taken 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 to electrochemical gas sensors using a solid electrolyte membrane, and can also be applied to sensors that detect gases such as hydrogen sulfide (H2S), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and ammonia (NH3).

[0018] When the target gas to be detected by the electrochemical gas sensor 1 is CO, an oxidation reaction of CO occurs at the working electrode 20 as shown in formula (1). CO+H2O→CO2+2H + +2e - (1) The CO that flows into the working electrode 20 reacts with water molecules to generate CO2 and protons (H + ) and electrons are generated. The protons move to the counter electrode 30 via the electrolyte layer 50, and the electrons move to the counter electrode 30 via an external circuit. At the counter electrode 30, the reaction shown in formula (2) occurs. 1 / 2 O2+2H + +2e - →H2O···(2) The protons and electrons generated at the working electrode 20 react with oxygen in the air at the counter electrode 30 to produce water. At this time, the current flowing in the external circuit is proportional to the amount of CO flowing into the working electrode 20, so the CO concentration can be detected by measuring this current.

[0019] The electrochemical gas sensor 1 has a laminated structure in which an electrode is disposed on a metal layer formed on the surface 10a of an insulating substrate 10, and an electrolyte layer 50 is disposed so as to cover at least a part of the electrode. The sealing layer 60 is disposed on the surface 10a together with the insulating substrate 10 so as to sandwich the metal layer, the electrode, and the electrolyte layer 50. The working electrode 20 is disposed on the metal layer 11, and a part of it is formed directly on the surface 10a. Similarly, the counter electrode 30 and the reference electrode 40 are disposed on the metal layers 12 and 13, respectively, and a part of them is formed directly on the surface 10a. The working electrode 20, the counter electrode 30, and the reference electrode 40 are formed separately from each other on the surface 10a of the insulating substrate 10 so as not to contact each other.

[0020] In this embodiment, in a plan view of the insulating substrate 10, the counter electrode 30 and the reference electrode 40 are arranged side by side in the X direction, and the working electrode 20, the counter electrode 30, and the reference electrode 40 are arranged side by side in the Y direction. The counter electrode 30 and the reference electrode 40 are formed in a generally rectangular shape in a plan view with an area smaller than that of the working electrode 20. The working electrode 20 has a shape in a plan view in which comb-like irregularities are formed on a part of the outer edge 25. The electrolyte layer 50 covers a part of the working electrode 20, and covers the entire counter electrode 30 and the reference electrode 40. In this embodiment, the gas to be detected acts on the part of the working electrode 20 exposed from the electrolyte layer 50, and the above reaction occurs.

[0021] As will be described in detail later, the electrodes are preferably formed by applying an electrode material onto the surface 10a of the insulating substrate 10 on which the metal layer is formed. In this case, the electrodes are easily formed, and good adhesion of the electrodes to the insulating substrate 10 and the metal layer can be obtained without using a special fastening jig or the like. Similarly, the electrolyte layer 50 is preferably formed by applying an electrolyte material onto the surface 10a of the insulating substrate 10 on which the electrodes are formed.

[0022] The sealing layer 60 is preferably made of a material with low gas (CO) permeability, and includes a gas barrier layer such as a metal layer or a ceramic layer. The sealing layer 60 has a gas introduction hole 61, which is a through hole for introducing CO into the working electrode 20. The gas introduction hole 61 is formed at a position overlapping the working electrode 20 in the thickness direction of the insulating base material 10. The location where the gas introduction hole 61 is formed is not limited to the sealing layer. The gas introduction hole may be formed in the insulating base material, for example. The sealing layer 60 covers the entire electrodes and the electrolyte layer 50 so that CO flows in only from the gas introduction hole 61, and the peripheral portion of the sealing layer 60 is joined to the surface 10a.

[0023] The insulating substrate 10, electrodes, current collectors, and electrolyte layer 50 that constitute the electrochemical gas sensor 1 will be described in detail below.

[0024] [Insulating substrate] The insulating substrate 10 is a substrate that ensures insulation at least in the portion where the electrochemical gas sensor 1 is constructed. The insulating substrate 10 functions as a support member for the electrodes, current collectors, and electrolyte layer 50, and also functions as a sealing member that seals the electrodes and electrolyte layer 50 together with the sealing layer 60. In the example shown in FIG. 1, the insulating substrate 10 is a substrate that has a rectangular shape in a plan view and a flat surface 10a. The shape, dimensions, etc. of the insulating substrate 10 are not particularly limited, and any substrate can be used for the insulating substrate 10.

[0025] The insulating substrate 10 may be a substrate dedicated to the electrochemical gas sensor 1, or may be a circuit board (generally also called a "printed wiring board") on which other electronic components are mounted. The insulating substrate 10 is, for example, a substrate on which wiring is formed on at least one of the surface and the interior, and on which a plurality of electronic components are mounted. The electrochemical gas sensor 1 may be connected to other electronic components mounted on the same circuit board, and processing based on the sensor detection information may be performed within this circuit board. In other words, the electrochemical gas sensor 1 can be constructed on a circuit board on which other electronic components are mounted.

[0026] [electrode] As described above, the electrodes include the working electrode 20, the counter electrode 30, and the reference electrode 40. The working electrode 20 is connected to the reference electrode 40 via an external circuit, and is configured to maintain a constant potential with the reference electrode 40 by the external circuit. The potential of the working electrode 20 is maintained at a potential that can oxidize the detection target gas, for example. The thicknesses of the working electrode 20, the counter electrode 30, and the reference electrode 40 are, for example, greater than the thickness of the metal layer and equal to or less than the thickness of the electrolyte layer 50, and are the same as each other. An example of the thickness of each electrode is 1 μm to 300 μm, or 10 μm to 100 μm.

[0027] The working electrode 20 and the counter electrode 30 include, for example, a catalyst, a conductive carrier, and an ionomer. In this embodiment, the reference electrode 40 is also made of the same material as the working electrode 20 and the counter electrode 30, and for example, each electrode is made of the same material. The catalyst promotes the oxidation reaction of CO, and the reaction of the above formula (1) occurs on the catalyst of the working electrode 20. Examples of the catalyst include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), iridium (Ir), cobalt (Co), iron (Fe), nickel (Ni), and the like. Among them, it is preferable to use a precious metal catalyst such as Pt or a PtRu alloy.

[0028] The conductive support is a conductive material that holds the catalyst. An example of a suitable conductive support is carbon material such as carbon black, such as acetylene black or Ketjen black, graphite carbon, or carbon nanotubes. The catalyst is, for example, fixed to the particle surface of the carbon material. The ionomer is an ionically conductive material that enables the movement of protons generated by the reaction. An example of a suitable ionically conductive material is Nafion (registered trademark: manufactured by DuPont).

[0029] As described above, the outer edge 25 of the working electrode 20 has projections and recesses. In a plan view of the insulating substrate 10, the working electrode 20 has a plurality of projections 21 extending in the Y direction so as to protrude toward the counter electrode 30 and the reference electrode 40. In the example shown in FIG. 1, five projections 21 are formed at a predetermined interval in the X direction. Therefore, between adjacent projections 21, recesses are formed that are recessed inside the working electrode 20 in a plan view of the insulating substrate 10. As will be described in detail later, the surface 10a of the insulating substrate 10 is exposed between the adjacent projections 21, and the first side 55, which is the outer edge of the electrolyte layer 50, is in close contact with the projections 21 and the surface 10a located between the adjacent projections 21.

[0030] The counter electrode 30 and the reference electrode 40 are formed in a generally rectangular shape in plan view, but the shape in plan view of the counter electrode 30 and the reference electrode 40 is not limited to this. The counter electrode 30 and the reference electrode 40 may have a convex portion like the working electrode 20, and a part of the counter electrode 30 and the reference electrode 40 may be exposed without being covered by the electrolyte layer 50.

[0031] [Metal layer] As described above, the metal layers include the first metal layer 11 connected to the working electrode 20, the second metal layer 12 connected to the counter electrode 30, and the third metal layer 13 connected to the reference electrode 40. Each metal layer is interposed between the insulating substrate 10 and each electrode, a part of which is covered by the sealing layer 60, and the remaining part of which extends from the area covered by the sealing layer 60. For example, wiring leading to an external circuit is connected to the metal layer.

[0032] The metal layers 11, 12, and 13 are formed, for example, by forming a metal thin film on the surface 10a of the insulating substrate 10, and then pattern-etching the thin film into the shape of each metal layer. Each metal layer may be formed by further depositing a plating layer on the patterned metal thin film. An example of the metal layer is a layer in which nickel / gold is plated on a copper foil. The thicknesses of the metal layers are substantially the same. An example of the thickness of each metal layer is 1 μm to 100 μm. The metal layers may be formed by a method such as vapor deposition.

[0033] [Electrolyte layer] The electrolyte layer 50 is an ion conductor membrane that transmits ions generated at the working electrode 20 to the counter electrode 30, and is a layer made of an insulating membrane that does not have electronic conductivity. The electrolyte layer 50 may be, for example, a layer made of a solid electrolyte membrane made of a polymer material, although it may be formed by absorbing a liquid electrolyte into a holding member such as a porous sheet. In this embodiment, a solid electrolyte having proton conductivity is used. An example of a proton conductive solid electrolyte is a hydrocarbon-based polymer or a fluorine-based polymer into which a proton conductive group such as a sulfonic acid group is introduced. The electrolyte layer 50 may be a commercially available product such as Nafion (registered trademark: manufactured by DuPont).

[0034] The thickness of the electrolyte layer 50 is not particularly limited, but is, for example, 1 μm to 400 μm. In the example shown in FIG. 1, the electrolyte layer 50 has a rectangular shape in a plan view, but the shape of the electrolyte layer 50 in a plan view is not particularly limited and can be appropriately changed depending on the shape of the insulating base material 10, and may have a convex portion as exemplified in FIG. 5 described later. The electrolyte layer 50 may be formed by attaching a solid electrolyte film onto the surface 10a of the insulating base material 10, but is preferably formed by applying a constituent material of the solid electrolyte (for example, solid electrolyte dispersion solution DE2020 CS manufactured by FUJIFILM Wako Chemical Co., Ltd.).

[0035] Hereinafter, the configuration of the portion where the working electrode 20 and the electrolyte layer 50 overlap and the vicinity thereof will be described in detail with reference to FIGS.

[0036] 1 and 3, the electrolyte layer 50 is disposed so as to cover a portion of the working electrode 20, and therefore, in a plan view of the insulating substrate 10, the electrochemical gas sensor 1 has a plurality of intersections P at which the outer edge 25 of the working electrode 20 intersects with the outer edge of the electrolyte layer 50. From the viewpoint of preventing peeling of the working electrode 20, there are at least four intersections P, and in this embodiment, ten intersections P are formed aligned in the X direction. Fig. 3 shows six of the ten intersections P, namely, intersections P1 to P6.

[0037] As described above, a part of the outer edge 25 of the working electrode 20 has projections and recesses in a plan view of the insulating substrate 10. The outer edge 25 of the working electrode 20 has five projections 21 extending in the Y direction in a portion facing the counter electrode 30 and the reference electrode 40. The projections 21 are arranged at intervals in the X direction, so that the outer edge 25 of the working electrode 20 has a comb-like projection and recess in a plan view. The projections 21 may have different widths, but in the example shown in FIG. 1, they are formed with substantially the same width. The intervals between the projections 21 adjacent to each other in the X direction may be different, but in the example shown in FIG. 1, the projections 21 are formed with substantially the same intervals.

[0038] The planar shape of the protrusions 21 may be a square, semicircular, triangular, or the like, and is not particularly limited. For example, the protrusions 21 extend parallel to each other with a substantially constant width, and have a shape in which the width gradually decreases near the tip. In this embodiment, the tip of each protrusion 21 is formed in a rounded semicircular shape, but the protrusions 21 may be formed with a constant width all the way to the tip.

[0039] Each of the protrusions 21 is covered by the electrolyte layer 50 over a predetermined length range from the tip. The predetermined length may be any length that does not reach the base of the protrusion 21, and is, for example, 30% to 90% of the length of the protrusion 21. The electrolyte layer 50 is disposed on the surface 10a of the insulating base material 10 so as to cover a portion of each of all the protrusions 21. The outer edge of the electrolyte layer 50 that overlaps with the protrusion 21 is a first side 55 formed in a straight line, and the electrolyte layer 50 is disposed so that the first side 55 is aligned along the X direction. Therefore, in a plan view of the insulating base material 10, multiple intersections P where the outer edge 25 of the working electrode 20 and the first side 55 of the electrolyte layer 50 intersect are aligned in a row in the X direction.

[0040] In this embodiment, the multiple intersections P include only intersections P where the uneven portion of the outer edge 25 of the working electrode 20 intersects with the first side 55 of the outer edge of the electrolyte layer 50. That is, the electrolyte layer 50 covers only a portion of each protrusion 21 of the working electrode 20, and does not cover any portion other than the protrusions 21. In this case, the continuous length of the outer edge of the electrolyte layer 50 disposed on the working electrode 20 can be shortened, and peeling of the working electrode 20 is more effectively suppressed.

[0041] In addition, in a plan view of the insulating substrate 10, the electrolyte layer 50 includes a first region 51 covering a part of the working electrode 20 and a second region 52 in direct contact with the surface 10a of the insulating substrate 10. At least a part of the first region 51 of the electrolyte layer 50 is sandwiched between the second regions 52. The first region 51 is a region covering the protrusions 21, and the second region 52 is a region located between the adjacent protrusions 21. For example, the protrusions 21 are pulled by the electrolyte layer 50 when the coating film of the electrolyte layer 50 shrinks, but if there are regions on both sides of the protrusions 21 where the electrolyte layer 50 and the insulating substrate 10 are in direct contact with each other, the force acting on the protrusions 21 is reduced, and peeling of the working electrode 20 is more effectively suppressed.

[0042] The width W1 of the protrusion 21 is preferably 5 mm or less at the portion where the first side 55 of the electrolyte layer 50 overlaps. Since the electrolyte layer 50 is arranged such that the first side 55 crosses each protrusion 21 in the width direction, an intersection P is formed on both sides of each protrusion 21 in the width direction. The width direction of the protrusion 21 is substantially parallel to the first side 55. In this embodiment, the distance between the intersections P1 and P2, the distance between the intersections P3 and P4, and the distance between the intersections P5 and P6 formed on both sides of the width direction of one protrusion 21 are preferably 5 mm or less. In other words, the continuous length of the outer edge of the electrolyte layer 50 arranged on the working electrode 20 is preferably 5 mm or less. In this case, peeling of the working electrode 20 is more effectively suppressed.

[0043] As described above, in this embodiment, the continuous length of the outer edge of the electrolyte layer 50 disposed on the working electrode 20 can be represented by the width W1 of the protrusion 21. From the viewpoint of preventing peeling of the working electrode 20, it is preferable to set the width W1 of the protrusion 21 to 4 mm or less, or 3 mm or less. The lower limit of the width W1 of the protrusion 21 is not particularly limited, but an example is 0.1 mm. In addition, the interval W2 between adjacent protrusions 21 is not particularly limited, and may be any length that allows the electrolyte layer 50 to strongly adhere to the surface 10a of the insulating base material 10 and reduces the force acting from the electrolyte layer 50 to the protrusion 21. A suitable example of the interval W2 is 0.1 mm or more, or 0.5 mm or more.

[0044] An example of a method for manufacturing the electrochemical gas sensor 1 having the above configuration will be described below. The electrochemical gas sensor 1 is manufactured by applying an electrode material onto the insulating substrate 10 to form an electrode, and applying an electrolyte material onto the insulating substrate 10 to form an electrolyte layer 50 so that the number of intersections P between the outer edge of the electrode and the outer edge of the electrolyte layer 50 is four or more in a plan view of the insulating substrate 10. In this embodiment, projections and recesses are formed on the outer edge 25 of the working electrode 20, and the electrolyte layer 50 is formed to cover the portion where the projections and recesses are formed. As a result, four or more intersections P between the first side 55, which is the outer edge of the electrolyte layer 50, and the outer edge 25 of the working electrode 20 are formed.

[0045] The electrochemical gas sensor 1 is manufactured, for example, through the following steps. (1) A step of forming a first metal layer 11, a second metal layer 12, and a third metal layer 13 on a surface 10a of an insulating substrate 10 so that the layers do not contact each other. (2) A step of forming the working electrode 20, the counter electrode 30, and the reference electrode 40 so as not to contact each other on the surface 10a of the insulating substrate 10 on which the metal layer is formed. (3) A step of forming an electrolyte layer 50 on the surface 10a of the insulating substrate 10 on which the metal layer and the electrodes are formed.

[0046] In the above step (1), for example, a copper foil is formed on the surface 10a of the insulating substrate 10, the copper foil is pattern-etched into the shape of each metal layer, and the remaining copper foil is plated to form each metal layer. A plating layer having a two-layer structure of nickel and gold may be formed on the etched copper foil.

[0047] In the above step (2), for example, an ink containing an electrode material such as a catalyst, a conductive carrier, and an ionomer is applied to the surface 10a of the insulating substrate 10 on which the metal layer is formed, and the coating is dried to volatilize and remove the dispersion medium, thereby forming each electrode. The dispersion medium contained in the ink is not particularly limited, but an example thereof is a mixed solvent of water and a lower alcohol such as ethanol. Examples of the ink application method include spray application, screen printing, inkjet printing, electrolytic spray application, dispensing, etc. Among them, spray application or screen printing is preferable.

[0048] In the above step (3), for example, an ink containing a constituent material of a solid electrolyte is applied to the surface 10a of the insulating substrate 10 on which the metal layer and the electrodes are formed, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the electrolyte layer 50. The dispersion medium contained in the ink is not particularly limited, but an example thereof is a mixed solvent of water and a lower alcohol such as ethanol. The ink can be applied in the same manner as in step (2).

[0049] In this embodiment, the working electrode 20 is formed having five protrusions 21, and the electrolyte layer 50 is formed so as to cover a portion of each of the protrusions 21. Between adjacent protrusions 21, the electrolyte layer 50 is formed directly on the surface 10a of the insulating substrate 10. A first side 55, which is the outer edge of the electrolyte layer 50 overlapping each protrusion 21, is formed linearly in a plan view, thereby forming ten intersections P aligned in a row in the X direction.

[0050] 4A shows a plan view of the electrochemical gas sensor 1 in which ten intersections P are formed (same as FIG. 1), and FIG. 4B shows a plan view of an electrochemical gas sensor 1x in which two intersections P are formed as a comparative example. As shown in FIG. 4B, in the electrochemical gas sensor 1x in which an electrolyte layer 50 is provided to cover a part of an electrode (working electrode 20x), it has been found that peeling of the working electrode 20x occurs due to a change in volume of the electrolyte layer 50. In particular, when the electrolyte layer 50 is formed by applying an electrolyte material onto an electrode, the electrolyte layer 50 shrinks when the applied film dries, and the electrode is likely to peel off.

[0051] In contrast, in the electrochemical gas sensor 1 having the above configuration, peeling of the protrusions 21 of the working electrode 20 covered with the electrolyte layer 50 is not observed, as shown in Fig. 4(a). Even when the electrolyte layer 50 is formed by applying an electrolyte material onto the protrusions 21, the protrusions 21 can maintain a state of being strongly adhered to the surface 10a of the insulating substrate 10. In particular, when the width W1 of the protrusions 21 is set to 5 mm or less, peeling of the working electrode 20 can be more reliably prevented.

[0052] As described above, the electrochemical gas sensor 1 having the above-mentioned configuration can effectively prevent the electrodes from peeling off in the portion covered by the electrolyte layer 50. In addition, since the metal layer, the electrodes, and the electrolyte layer 50 are directly formed on the surface 10a of the insulating substrate 10 and have a laminated structure in which they are integrally bonded, good adhesion of the laminated structure is obtained, and the contact resistance of the laminated structure is reduced and stabilized. As a result, for example, noise in the base current can be suppressed, and the sensor can be made highly sensitive. According to the electrochemical gas sensor 1, a good contact state of each component can be ensured even if the pressing force of the laminated structure is small, so that no special fastening members are required, and the sensor can be made smaller and less expensive.

[0053] Another example of the embodiment will be described below with reference to Figures 5 to 7. The following mainly describes the differences from the above embodiment.

[0054] 5 differs from the electrochemical gas sensor 1 in that the working electrode 20 has two protrusions 21 and there are four intersections P between the outer edge 25 of the working electrode 20 and the first side 55, which is the outer edge of the electrolyte layer 50. The electrochemical gas sensor 2 has in common with the electrochemical gas sensor 1 that the four intersections P are aligned in a row in the X direction and that it is preferable that the width W1 of the protrusions 21 is 5 mm or less. As a result of studies by the present inventors, it was found that if the number of intersections P is four or more, peeling of the electrode is effectively suppressed, whereas if the number of intersections P is three or less, peeling of the electrode occurs.

[0055] The electrochemical gas sensor 3 shown in FIG. 6 is different from the electrochemical gas sensor 1 in that the working electrode 20 is formed in a square shape in a plan view, and the outer edge 25 does not have any unevenness, whereas the outer edge 56 of the electrolyte layer 50 has unevenness formed in a part thereof. In a plan view of the insulating substrate 10, the electrolyte layer 50 has two protruding portions 57 extending in the Y direction so as to protrude toward the working electrode 20. In the example shown in FIG. 6, the two protruding portions 57 are spaced apart in the X direction of the electrolyte layer 50 and formed at both ends in the X direction. Therefore, between the adjacent protruding portions 57, a recess is formed that is recessed inward of the electrolyte layer 50 in a plan view of the insulating substrate 10.

[0056] A part of each protrusion 57 of the electrolyte layer 50 is formed so as to cover a part of the working electrode 20, and four intersections P are formed in the electrochemical gas sensor 3. For example, the protrusions 57 are formed parallel to each other with the same width, and the outer edge 25 of the working electrode 20 where the protrusions 57 overlap is formed linearly along the X direction. Therefore, in the electrochemical gas sensor 3, the four intersections P are also arranged in a line in the X direction. In this case, too, it is preferable that the continuous length of the outer edge of the electrolyte layer 50 arranged on the working electrode 20 is short. The width of the protrusions 57 is, for example, 1 mm to 5 mm.

[0057] The electrochemical gas sensor 4 shown in Fig. 7 differs from the above-described embodiments in that both the working electrode 20 and the electrolyte layer 50 are formed in a rectangular shape in a plan view. In the embodiment shown in Fig. 7, a wide area of ​​the working electrode 20 is covered with the electrolyte layer 50. Both ends of the working electrode 20 in the X direction extend beyond the outer edge 58 of the electrolyte layer 50 in the X direction. In this case, two intersections P aligned in the Y direction are formed at both ends of the electrolyte layer 50 in the X direction. That is, there are a total of four intersections P.

[0058] 5 to 7, peeling of the working electrode 20 in the portion covered by the electrolyte layer 50 can be suppressed, but it is preferable that the multiple intersections P include four or more intersections where the outer edge of the electrode on which the unevenness is formed intersects with one side of the outer edge of the electrolyte layer 50. Moreover, it is preferable that the electrolyte layer 50 includes a first region 51 covering the electrode and a second region 52 in direct contact with the insulating substrate 10, and at least a part of the first region 51 is sandwiched between the second regions 52. In other words, the embodiments illustrated in FIGS. 1 and 5 are particularly suitable.

[0059] The above-mentioned embodiments may be appropriately modified in design without impairing the object of the present disclosure. For example, the above-mentioned embodiments include the working electrode 20, the counter electrode 30, and the reference electrode 40, but the electrochemical gas sensor may have a bipolar structure including only the working electrode and the counter electrode. Alternatively, the counter electrode may also be used as the reference electrode to set the potential of the working electrode. The electrochemical gas sensor may also include other members such as a gas diffusion layer and a filter to prevent drying. [Explanation of symbols]

[0060] 1 electrochemical gas sensor, 10 insulating substrate, 10a surface, 11, 12, 13 metal layer, 20 working electrode, 21 protrusion, 25 outer edge, 30 counter electrode, 40 reference electrode, 50 electrolyte layer, 51 first region, 52 second region, 55 first side, 56 second side, 57 third side, 60 sealing layer, 61 gas inlet hole, P intersection

Claims

1. An insulating substrate; An electrode formed on the insulating substrate; an electrolyte layer formed on the insulating substrate so as to cover at least a portion of the electrodes; Equipped with When viewed from above, the insulating substrate has a plurality of intersections where an outer edge of the electrode intersects with an outer edge of the electrolyte layer; The number of intersections is four or more.

2. In a plan view of the insulating substrate, The outer edge of the electrode is formed with projections and recesses, 2. The electrochemical gas sensor according to claim 1, wherein the plurality of intersections include only intersections where the portion of the outer edge of the electrode where the projections and recesses are formed intersect with one side of the outer edge of the electrolyte layer.

3. In a plan view of the insulating substrate, The outer edge of the electrode is formed with projections and recesses, 2. The electrochemical gas sensor according to claim 1, wherein the electrolyte layer includes a first region covering the electrode and a second region in direct contact with the insulating substrate, and at least a portion of the first region is sandwiched between the second region.

4. 4. The electrochemical gas sensor according to claim 1, wherein a continuous length of an outer edge of the electrolyte layer disposed on the electrode is 5 mm or less.

5. 4. The electrochemical gas sensor according to claim 1, wherein the electrode is a working electrode.

6. 4. The electrochemical gas sensor according to claim 1, further comprising an inlet for introducing a gas into the electrode.

7. 4. The electrochemical gas sensor according to claim 1, further comprising a sealing layer disposed on the insulating substrate and covering the electrodes and the electrolyte layer.

8. A method for manufacturing an electrochemical gas sensor including an insulating substrate, an electrode, and an electrolyte layer, comprising the steps of: A method for manufacturing an electrochemical gas sensor, comprising the steps of: applying an electrode material onto the insulating substrate to form the electrodes; and applying an electrolyte material onto the insulating substrate to form the electrolyte layer, so that, in a plan view of the insulating substrate, there are four or more intersections between outer edges of the electrodes and outer edges of the electrolyte layer.

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