CN216350483U - Electrochemical gas sensor for detecting target gas - Google Patents

Abstract

The utility model relates to an electrochemical gas sensor for detecting a target gas, having a substrate and a housing which forms a cavity at least together with the substrate. At least one electrode and a conductor circuit connected to the electrode are arranged on the side of the substrate facing the cavity. The conductor circuit is guided through between the substrate and the housing. An electrolyte is disposed in the cavity and in contact with the at least one electrode. The substrate has an entry region that is permeable to a target gas, the entry region being at least partially covered by the at least one electrode. In addition, the substrate has an exhaust region for exhausting gas from the cavity. The electrochemical gas sensor according to the utility model enables a simple solution for venting.

Description

Electrochemical gas sensor for detecting target gas

Technical Field

The present invention relates to an electrochemical gas sensor for detecting a target gas.

Background

In electrochemical gas sensors, a chemical target species reacts with a working electrode. Due to the reduction or oxidation process, the dissolved ions migrate preferentially through the electrolyte to the counter electrode and react again there. This results in that an electrical variable can be measured at the electrodes, which is proportional to the reaction and thus to the concentration of the target substance.

Typically, the electrolyte of such electrochemical gas sensors is disposed in a housing. Such a housing usually requires a passage, i.e. an opening, in order to be able to achieve a pressure compensation between the interior of the housing and the environment of the housing due to temperature fluctuations. Typically, however, such channels in the housing must then be covered, at least to prevent water from spraying, without allowing water to reach the interior of the housing. However, such a construction of the exhaust gas section must be produced in a complex manner.

SUMMERY OF THE UTILITY MODEL

It is therefore an object of the present invention to provide an electrochemical gas sensor which uses a simple solution for venting.

This object is achieved by an electrochemical gas sensor according to the utility model.

The present invention therefore relates to an electrochemical gas sensor for detecting a target gas. Such gas sensors have a substrate and a housing which is arranged next to or on the substrate and/or is connected to the substrate and/or is fastened to the substrate. In particular, the housing and the base plate form a structural component having a cavity therein. In particular, the housing has the shape of a cap placed on a substrate. Since the base plate preferably has a planar extent, i.e. the width of the base plate and the length of the base plate are each dimensioned to be greater than the height of the base plate, the base plate covers the open side of the cap-shaped housing.

An electrolyte is disposed in the interior of the cavity. Preferably, the electrolyte exists in a liquid form or a gel state. In particular, not only the housing but also the substrate cannot be penetrated by liquid. Since all housing components and the base plate prevent the liquid from passing through, the liquid or gel-state electrolyte is enclosed in the cavity and cannot be discharged.

At least one electrode and a conductor circuit electrically connected to the electrode are arranged on the side of the substrate facing the cavity. The electrodes are preferably arranged completely in the interior of the cavity on the substrate, while the conductor circuit is preferably guided in a sealed manner out of the cavity between the housing and the substrate into a region outside the housing. The bottom surface of the base plate is preferably larger than the bottom surface of the housing. The substrate thus protrudes from the housing on at least one side. Preferably, the conductor circuit is guided outwards on this side between the housing and the substrate, so that the substrate also serves as a support for the conductor circuit outside the cavity. The conductor circuit can then be routed to the pad, for example, in order to make electrical contact and thus be connected, for example, to a remote evaluation unit, for example, a microprocessor, which evaluates the signals provided by the gas sensor and/or controls the potential at one or more electrodes.

In order to deliver the target gas to the electrode, an entry region that is permeable at least to the target gas is provided in the substrate. Preferably, the entry region is permeable to the prevailing gas, since, when the gas sensor is used, the air in the environment of the gas sensor should be detected for one or more chemical substances, in particular for a defined target gas. The target gas is therefore the gas to be identified by means of the electrochemical gas sensor, preferably also its concentration. The target gas may be, for example, CO₂、SO₂、NO、NO₂、O₃Or CH₂And O. In particular, the entry region is preferably permeable to ambient air as the gas mixture to be detected. In a further development, a target gas selective filter is arranged upstream or downstream of the entry region in the substrate.

Preferably, the substrate is gas permeable in said entry region, so that gas can penetrate the substrate. It is therefore not provided that the substrate has a macroscopic opening as the entry region. Instead, the substrate also has a material in the entry region, which material is nevertheless gas-permeable at least in the entry region.

The at least one electrode is guided on the substrate in such a way that the electrode is at least partially contactable with the gas passing through the entry region. Then, the target gas present in the mixed gas supplied as necessary can react with the electrode material.

Preferably, not the entire cavity is filled or filled with electrolyte, but only a partial volume. Thus, there is a remaining volume of the cavity that is filled with the mixed gas, preferably air. Preferably, the filling height of the electrolyte on the substrate is less than 500 μm, in particular less than 300 μm. The electrolyte is in contact with the at least one electrode and is thus arranged in the vicinity of the entry region in the substrate, while the remaining volume is adjacent to a further region of the substrate. At least a part of the further region of the substrate is formed as a venting region, which is described in more detail below. The intake region is spatially separated from the exhaust region in the substrate.

The venting region is therefore also a constituent part of the substrate which is designed to be gas-permeable, so that a gas exchange between the cavity and the environment and thus in particular a pressure equalization can take place. Thus, in particular when temperature and/or pressure conditions change, a pressure difference always occurs between the cavity and the environment. Depending on the place of use with different climatic or atmospheric conditions, such pressure differences can arise, which can then be carried out on the exhaust area of the substrate by gas exchange between the cavity and the environment. During the production of the gas sensor, for example during the hardening of the materials used, strong temperature fluctuations can also occur, which lead to a pressure difference, which is compensated for by the venting region.

The substrate is therefore preferably a planar, structural block without macroscopic pores or other fabricated perforations, but preferably has the internal properties, through suitable material selection and/or manipulation, that gases can penetrate the material of the substrate. For this purpose, the substrate is made of a porous and therefore gas-permeable material, at least in the inlet region and in the outlet region. The substrate can also be gas-impermeable outside the inlet region and the outlet region.

In an advantageous alternative, however, the entire substrate is designed to be porous and therefore gas-permeable, i.e. is made of a porous, gas-permeable material in a unified manner.

However, in both alternatives, the substrate is preferably made of a polymeric material. Preferably, the material of the substrate comprises porous polytetrafluoroethylene, or porous polyimide, or porous polyethylene, or porous polypropylene, or porous polyester, or porous polyurethane, or porous fluoropolymer, or porous polyacrylic acid, or porous cellulose polymer, or porous glass fibre, or a mixture thereof. Preferably, the substrate is thinner than 500 μm, preferably between 50 μm and 250 μm thick. Preferably, the pores have a size/diameter of less than 100 μm, preferably between 0.1 μm and 10 μm.

If the entire substrate is porous, precautions are taken, in particular: the regions of the substrate outside the inlet region and the outlet region are designed to be gas-tight. For this purpose, a gas-impermeable coating may be used on selected areas of the substrate. Preferably, the side of the substrate facing away from the cavity, i.e. the side facing the environment of the gas sensor, has such a coating and the gas enters the gas sensor through this side. Preferably, the coating comprises a polymer, such as a fluoroethylene propylene polyimide. Preferably, the coating is applied to the substrate by bonding or lamination (or vice versa). The coating may also have a greater thickness than the substrate. Thus, the coating may also serve simultaneously as a backing plate for the substrate and mechanically stabilize and protect the substrate.

In some cases, however, the side of the substrate facing the cavity may also be provided with such a gas-tight coating, so that the gas can penetrate into the substrate via the entire side facing away from the cavity, but can penetrate into the cavity only in the entry region and theoretically in the venting region.

In a further development of the utility model, in which the entire substrate is porous, the entire side of the substrate facing away from the cavity, and the bottom side of the substrate in spoken language, is preferably provided with such a gas-impermeable coating. The lateral end sides of the substrate then preferably form the entry region and the venting region.

In any case, the inlet region and the outlet region are defined regions in the substrate, in particular, they are also spatially separated from one another.

Since the inlet region and the outlet region are now both arranged in the base plate, the housing need not have perforations, openings or the like, which in turn would extend a film, a cover or other protective means in order to protect the cavity, for example against water sprays or other environmental influences. The exhaust area and the intake area are thus also oriented identically. In particular, if the venting area and the entry area are realized by the porous nature of the substrate, no further measures for water spray protection are provided. This in turn allows for a significantly simplified automated mass production of electrochemical gas sensors, in particular because no additional component parts, such as membranes or other protective elements, are required as described above. The housing and thus the entire gas sensor are simplified in its production and are therefore better suited to automated production.

Preferably, a separating wall is provided in the cavity, which separating wall is arranged between the inlet region and the outlet region when it is projected onto the substrate. The partition wall serves to separate the electrolyte from a remaining volume of the cavity, which volume adjoins the venting area of the substrate. The separating wall serves in particular to separate the electrolyte from the degassing region and thus to prevent the degassing region from becoming blocked by the electrolyte. In particular, the partition wall may be regarded as a member dividing the cavity into two chambers, one being mainly for the electrolyte and the other being free of electrolyte, wherein the chambers are connected to each other. Therefore, preferably, the partition wall does not protrude upward to the top of the housing. Preferably, the partition wall is made of the same material as the housing.

In order to fix the electrolyte on the electrode or electrodes, an element impregnated with electrolyte is preferably provided. The elements are preferably non-woven fabrics, i.e. non-woven materials with irregularly oriented fibres. Preferably, the non-woven fabric is made of silicate, borosilicate, silicon carbide, carbon, graphite, aluminum, glass fiber, plastic or other inert material. Preferably, the non-woven fabric has a height of less than 500 μm, preferably between 100 μm and 300 μm.

Therefore, the electrolyte is in contact with the electrode so as to ensure chemical-electrical conversion of the target gas. The electrode material is selected such that it reacts with the target gas, i.e. when the target gas impinges on the electrode, the target gas is oxidized or reduced. The electrode is in particular a working electrode of a gas sensor. The dissolved ions are transported through the electrolyte due to a reduction or oxidation process initiated by the target gas of the electrode material selected according to the target gas. The electrolyte may be, for example, H₂SO₄Or an ionic liquid. Preferably, a further electrode is provided as counter electrode. The dissolved ions react at the counter electrode, so that an electrical variable proportional to the target gas concentration can be measured at the electrode. Preferably, a third electrode may also be provided as a reference electrode in order to adjust the potential of the working electrode. Preferably, irrespective of the number of electrodes, each electrode is arranged on the substrate, in contact with the electrolyte, with a conductor circuit arranged, which is preferably guided outwards between the housing and the substrate.

The housing is preferably made of plastic, preferably polyimide, fluoroethylene propylene (FEP), perfluoroalkoxy Polymer (PFA), polycarbonate, polyethylene, polypropylene, polyisobutylene, polyester, polyurethane, polyacrylic, fluoropolymer, cellulosic polymer, fiberglass, polytetrafluoroethylene, another non-reactive plastic, or a mixture thereof.

Preferably, the gas sensor is a miniature gas sensor having a base surface with edges of less than 20mm, i.e. a base surface of preferably less than 400mm²And in particular each edge length is less than 15mm and therefore the base surface is less than 225mm². In the case of a gas sensor with a preferred height of less than 2.5mm, a volume of less than 1000mm results³Or preferably even less than 600mm³。

The housing may preferably comprise a plurality of parts. In this case, a component can therefore be placed on the substrate in such a way that it forms, together with the substrate, a partial cavity which is open, for example, upward and thus provides an inlet for filling with electrolyte. Preferably, the electrolyte is applied to the substrate/nonwoven/electrode/in particular when the electrolyte is in the gel state or is bonded by a nonwoven. In the case of a partial housing, finally, a further part of the housing is preferably arranged thereon, so that the two parts together with the substrate form a cavity which encloses the electrolyte. Instead of a housing consisting of several parts, in the case of a complete housing, the electrolyte preferably enters through an inlet into the cavity formed by the housing and the substrate and contacts the electrodes. The inlet is preferably a capillary inlet through which electrolyte enters the cavity. After filling, the inlet or capillary inlet is closed.

The one or more electrodes and/or the one or more conductor circuits may preferably be made by an ink-jet or screen-printing process or a stencil printing process. Preferably, the thickness of the electrode is less than 200 μm, preferably between 100nm and 125 μm. Preference is given here to using or mixing metals (preferably Pt, Au, Ag, Pd, Ru, Rh, Ir, Fe or Ni, or carbon) as electrodes.

Drawings

Further embodiments, advantages and applications of the utility model emerge from the following description with the aid of the figures. In the figure:

FIG. 1 illustrates, in cross-section, an electrochemical gas sensor in accordance with an embodiment of the present invention;

FIG. 2 illustrates, in cross-section, an additional electrochemical gas sensor in accordance with an embodiment of the present invention;

FIG. 3 illustrates, in cross-section, an electrochemical gas sensor in accordance with an embodiment of the present invention; and

fig. 4 shows an electrochemical gas sensor according to an embodiment of the utility model in a cross-sectional view.

Detailed Description

Like elements are represented by like reference numerals across the drawings. The naming of all reference numerals is omitted in fig. 2 and 3 for reasons of clarity. Reference is made instead to the reference in fig. 1.

Fig. 1 shows an electrochemical gas sensor according to an embodiment of the utility model in a cross-sectional view. Here, a porous, planar substrate 2 is provided, which together with a housing 1 arranged thereon forms a cavity 10. At least one electrode 6 and a conductor circuit 7 are applied to a first side 21 of the substrate 2 facing the cavity 10. The electrodes 6 and the conductor circuit 7 are electrically connected to one another here. The conductor circuit 7 is guided outward between the housing 1 and the substrate 2. In the housing bottom surface x, y, the substrate 2 protrudes in at least one direction, here in the-x direction, over the bottom surface x, y of the housing 1. The conductor circuit 7 is guided on this protruding section of the substrate 2 to the outside, i.e. outside the housing 1. Where the conductor circuit 7 can be contacted and thus tap off the electrical signal of the gas sensor, which is proportional to the determined concentration of the target gas. On a second side 22 of the substrate 2 facing away from the cavity 10, a gas-impermeable coating 23 is provided, which has a defined clearance. The void defines an entry region 3 for the mixed gas to be detected. The gas mixture passes through the porous gas-permeable substrate 2 in the inlet region 3 and reacts with the electrodes 6 connected to the electrolyte 5. The electrode 6 at least partially covers the entry region 3. The electrolyte 5 is also adjacent to the entry region 3. The electrolyte 5 is preferably present in a liquid or gel state.

Furthermore, the gas-impermeable coating 23 defines the degassing region 4 of the substrate 2. The degassing region 4 adjoins the remaining volume V of the cavity 10 which is not filled with the electrolyte 5. Instead, a gas mixture, preferably ambient air, is present therein. The overpressure or underpressure relative to the environment in the residual volume V can be compensated for by the exhaust region 4. The venting area therefore generally allows pressure compensation between the cavity 10 and the environment.

The partition wall 11, which is an integral part of the housing 1, separates the electrolyte 5 from the venting region 4, so that the electrolyte cannot cover or block the venting region 4 and therefore cannot achieve venting.

Fig. 2 shows an electrochemical gas sensor according to a further embodiment of the utility model in a sectional view. The gas sensor according to fig. 2 differs from the gas sensor according to fig. 1 in that the nonwoven fabric 8 is introduced into the cavity 10 of the gas sensor. The non-woven fabric 8 serves to contain and thus fix the electrolyte 5. The nonwoven fabric 8 is dimensioned such that the entire electrolyte 5, or, as shown in fig. 2, only a part thereof, is accommodated therein.

Fig. 3 shows an electrochemical gas sensor according to a further embodiment of the utility model in a sectional view. The gas sensor according to fig. 3 differs from the gas sensor according to fig. 2 in that the housing 1 is now of two-part design and comprises a first part 1a which is of hood-shaped design and is placed on the substrate 2. Preferably, only this part 1a is first placed on the substrate 2, without placing the further housing part 1 b. Then, in this state, the electrolyte 5 is introduced into the partial cavity 10a formed by the portion 1a and the substrate 2. After the partial cavity 10a is filled with the electrolyte 5, the housing 10 can be completed by adding a further portion 1b of the housing 10.

Fig. 4 shows an electrochemical gas sensor according to a further embodiment of the utility model in a sectional view. The gas sensor according to fig. 4 differs from the gas sensor according to fig. 3 in that the gas-impermeable coating 23 covers the entire second side 22 of the substrate 2 facing away from the cavity 10 and thus prevents the passage and venting of gas through the second side 22 of the substrate 2. Instead, as indicated by the arrows, the end side 24 of the substrate 2 serves as the inlet region 3 and as the outlet region 4. Because of the lack of structuring, the coating 23 is produced simply and therefore also functions as described.

Claims (9)

1. An electrochemical gas sensor for detecting a target gas, the electrochemical gas sensor comprising:

a substrate (2) having a plurality of grooves,

a housing (1) forming a cavity (10) at least with the substrate (2),

at least one electrode (6) on a first side (21) of the substrate (2) facing the cavity (10) and a conductor circuit (7) connected to the electrode (6), the conductor circuit (7) being guided through between the substrate (2) and the housing (1),

an electrolyte (5) in the cavity (10) in contact with the at least one electrode (6),

the substrate (2) has an entry region (3) that is permeable to a target gas,

the electrode (6) at least partially covers the access area (3) and

the substrate (2) has an exhaust region (4) for exhausting gas from the cavity (10).

2. Electrochemical gas sensor according to claim 1, characterized in that the substrate (2) is porous at least in the inlet region (3) and in the outlet region (4).

3. Electrochemical gas sensor according to claim 2, characterized in that the entire substrate (2) is porous and that a gas-impermeable coating (23) is applied to a second side (22) of the substrate (2) facing away from the cavity (10).

4. Electrochemical gas sensor according to claim 3, characterized in that a gas-impermeable coating (23) is applied to the second side (22) of the substrate (2) facing away from the cavity (10), with the exception of the inlet region (3) and the outlet region (4).

5. An electrochemical gas sensor according to claim 1,

the substrate (2) has a planar extension,

the inlet region (3) is spatially separated from the outlet region (4) in the substrate,

the substrate (2) is impermeable to liquid and

the substrate (2) is made of a polymer.

6. An electrochemical gas sensor according to claim 1,

the electrolyte (5) only partially fills the cavity (10),

the electrochemical gas sensor has a separating wall (11) in the cavity (10) between the inlet region (3) and the outlet region (4), said separating wall serving to separate the electrolyte (5) from a residual volume (V) of the cavity (10), said residual volume (V) adjoining the outlet region (4) of the substrate (2).

7. An electrochemical gas sensor according to claim 1,

the electrolyte (5) is a liquid or gel electrolyte, and

the electrochemical gas sensor has an element for impregnating an electrolyte (5) in a cavity (10).

8. An electrochemical gas sensor according to claim 1,

the bottom surface of the substrate (2) is larger than the bottom surface of the shell (1),

the substrate (2) protrudes from the housing (1) on at least one side and

the conductor circuit (7) is guided outwards on this side between the housing (1) and the substrate (2).

9. An electrochemical gas sensor according to claim 1,

the bottom surface of the substrate (2) is less than 400mm²And is and

the height of the electrochemical gas sensor is less than 2.5 mm.

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