Method for producing electrochemical gas sensor and electrochemical gas sensor

Abstract

The invention relates to a method for producing an electrochemical gas sensor and to an electrochemical gas sensor obtainable by the method. The method comprises the following steps that a substrate is provided, and the substrate is provided with a plurality of through holes formed in the normal direction of the substrate; applying an electrode material to the upper side of the substrate and / or to the lower side of the substrate; an electrode material is bonded to the substrate such that the plurality of through-holes are closed by the electrode material in order to obtain a plurality of contact surfaces which can be electrically contacted on a lower side of the substrate opposite the upper side.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrochemical gas sensor and an electrochemical gas sensor obtainable by this method. Background Art

[0002] Electrochemical sensors for measuring gases, also known as electrochemical gas sensors, are known. For these electrochemical gas sensors, usually two or more half-cells containing electrodes and an electrolyte are combined, and these half-cells are accommodated separately from the surrounding environment of these half-cells by a housing. The electrolyte, such as sulfuric acid in an aqueous solution, is usually a permeable liquid that may overflow through the smallest openings in the housing and enter the environment. Thus, the housing must be sealed by a suitable seal to especially ensure that the electrolyte does not leak out.

[0003] The challenge of sealing the housing relative to the environment lies especially in the position where the leads are guided through the housing to the outside. The leads are usually used to provide the measurement signals of the electrodes.

[0004] A gas sensor is known from DE 102014009365 A1, which has a circuit that electrically connects a potentiostat arranged outside the housing to the electrodes of the gas sensor. Summary of the Invention

[0005] The task on which the present invention is based is to provide a method for manufacturing an electrochemical gas sensor and an electrochemical gas sensor obtainable by this method, in which the signal derivation is improved.

[0006] These tasks and other tasks are solved by a method for manufacturing an electrochemical gas sensor according to claim 1 and by a corresponding electrochemical gas sensor according to claim 9.

[0007] In this regard, according to the present invention, a method for manufacturing an electrochemical gas sensor is provided. The method has the following steps: providing a substrate, wherein the substrate has a plurality of through-holes formed along the normal direction of the substrate; coating electrode material on the upper side and / or on the lower side of the substrate; and bonding the electrode material to the substrate such that the plurality of through-holes are closed by the electrode material in order to obtain a plurality of contact surfaces that can be electrically contacted on the lower side of the substrate opposite to the upper side.

[0008] In this way, a plurality of contact surfaces that can be electrically contacted can be obtained, which allow electrical contact of the interior space of the housing without leading leads into the housing.

[0009] By combining the electrode material with the substrate, an integral combination is achieved, such that a substrate is obtained on or beside which the electrode material is formed. In this way, it is also possible to obtain a liquid-tight interface between the electrode material and the substrate by combining the electrode material with the substrate, and thus to obtain a plurality of sealed electrically contactable contact surfaces. Therefore, creep of the electrolyte in the direction of the plurality of electrically contactable contact surfaces can be prevented or at least reduced.

[0010] An electrochemical gas sensor is understood to be an electrochemical cell which is set up to detect at least one gaseous substance (in particular a target gas) in a gas or in a gas mixture (in particular in a sample gas).

[0011] In the following, the terms "electrochemical gas sensor" and "gas sensor" can be used interchangeably.

[0012] The substrate is understood to be a carrier material for the electrode material.

[0013] The substrate can for example be a porous material. For example, the substrate can be designed as a felt made of glass fibers and / or glass particles. In another example, the substrate can be designed as a porous green body made of materials such as ceramics, fibers, fabrics, plastics, glass powder and / or mixtures thereof. Particularly preferably, the porous green body is obtained, i.e. provided, by pressing together silica and / or glass powder with polytetrafluoroethylene powder and / or polypropylene powder.

[0014] The steps "providing a substrate [...]", "coating with an electrode material [...]" and "combining the electrode material [...]" according to the invention can be carried out staggered in time or essentially simultaneously.

[0015] If the substrate is designed as a green body, it is preferred that: before pressing the green body, the electrode material is coated onto a material suitable for forming the substrate by pressing, and during the pressing the electrode material is combined with (i.e. pressed into) the substrate. In this preferred design, the steps "providing a substrate [...]", "coating with an electrode material [...]" and "combining the electrode material [...]" are carried out essentially simultaneously.

[0016] The substrate can be designed as a substantially cylindrical disk.

[0017] The substrate can be treated to improve surface wettability.

[0018] The substrate can for example be designed as a membrane which can be suitable for accommodating an electrolyte, such as an aqueous electrolyte. For this purpose, the substrate is preferably designed to be hydrophilic.

[0019] The normal direction of the substrate is understood as the direction perpendicular to the base plane of the substrate, i.e., the direction corresponding to the normal vector of the base plane of the substrate.

[0020] The cross-sectional shape of the plurality of through-holes can be basically arbitrary. In a simple example, the through-holes can have a circular cross-section and, for example, can extend through the substrate substantially cylindrically. However, the cross-sectional shape of the plurality of through-holes can also be complex. Thus, for example, a plurality of through-holes can be formed by a pore network in a porous substrate.

[0021] The electrode material can be coated in any way. However, it is preferred to coat the electrode material by printing, i.e., by applying the electrode material in a liquid or paste form. For this purpose, the electrode material can be present as a component of a composition suitable for printing, in particular as a component of an ink. Here, substantially any printing process can be applied. In this regard, suitable processes are, for example, screen printing, inkjet printing or embossing printing (Matrizendruck). It is preferred that, if present, the flow behavior of the ink is adapted to the geometry of the plurality of through-holes such that the ink can penetrate into the plurality of through-holes. Particularly preferably, the ink has a thixotropic flow behavior.

[0022] The electrode material is understood as a material that is suitable for directly or through subsequent steps forming one or more conductive elements in or on the substrate.

[0023] In a preferred embodiment of the present invention, by coating the electrode material and binding the electrode material to the substrate, not only is electrode material that can be electrically contacted via a contact surface obtained, but at the same time electrodes of a gas sensor, such as a reference electrode, a measuring electrode or a counter electrode, are formed. However, this is not necessary. Thus, by this method, it is also possible to obtain only electrode material that can be electrically contacted, which can be in direct or indirect contact with electrodes separately provided for the gas sensor.

[0024] Especially in the case of obtaining electrodes of a gas sensor by coating the electrode material, it is preferred that the electrode material includes a catalyst material, a thin film material, an adhesive and / or a plastic.

[0025] The plurality of through-holes can be exactly one through-hole or can be a plurality of through-holes.

[0026] The plurality of through-holes can be introduced into the substrate, for example, by punching. Processes suitable for punching are, for example, stamping or laser.

[0027] The step of coating at least the upper side of the substrate with the electrode material and / or coating the lower side of the substrate can be carried out multiple times. In this way, for example, separate segments of electrode material can be provided on or in the substrate, which can be contacted separately via corresponding electrically contactable contact surfaces.

[0028] Preferably, the bonding of the electrode material to the substrate includes: heat-treating the substrate and the electrode material.

[0029] This heat treatment can be, for example, a sintering process. Here, the temperature of this heat treatment should be adapted to the material properties of the substrate and the electrode material. For example, the temperature of this heat treatment can be in the range between 110 °C and 350 °C.

[0030] Through this heat treatment, the bonding of the electrode material to the substrate can be achieved or improved.

[0031] Preferably, the substrate is designed as a breathable and liquid-tight membrane. This is particularly preferred for electrodes that are to be in contact with the atmosphere (i.e., the sample gas), for example, for measuring electrodes or working electrodes.

[0032] In this way, a composite of the electrode material and the substrate can be used to form the boundary of the gas sensor with the outside. In this way, an electrolyte can be arranged on one side of this composite or a volume for accommodating the electrolyte can be provided, and the liquid-tight substrate can prevent the electrolyte from passing through the substrate. By the substrate being designed to be breathable at the same time, the interface can allow the sample gas to enter. By selecting the gas permeability, the possible gas volume flow into the gas sensor can be adjusted.

[0033] Alternatively, the substrate is preferably designed as a liquid-wettable and preferably gas-tight separator.

[0034] In this alternative, a composite of the electrode material and the substrate can be used within the volume of the gas sensor suitable for accommodating the electrolyte in order to form an electrode that can be separated from another electrode by this substrate. This is particularly advantageous if the gas sensor is to be provided in a stacked structure.

[0035] Preferably, the substrate comprises glass or plastic.

[0036] Glass is understood as a material that comprises or consists of silicon dioxide (SiO2), i.e., an inorganic non-metallic glass.

[0037] In a variant of the present invention, the glass can consist of silicon dioxide and is also referred to as quartz glass in this case.

[0038] In another variant of the present invention, in addition to silica, the glass may further comprise other components, in particular oxides such as alumina, alkali metal oxides, phosphorus pentoxide and / or boron trioxide. Additionally or alternatively, the glass may also have halide ions.

[0039] Silicates are understood to refer to salts and / or esters of orthosilicic acid (Si(OH)4) and its condensates.

[0040] Preferably, the electrode material comprises the glass and / or metal and / or metal oxide and / or the plastic and / or carbon.

[0041] Preferably, the metal and / or the metal oxide is selected from the group consisting of: platinum, platinum oxide, gold, gold oxide, iridium, iridium oxide, silver, silver oxide, ruthenium, ruthenium oxide, rhodium, rhodium oxide, palladium, palladium oxide, copper, copper oxide and nickel.

[0042] Preferably, the plastic is selected from the group consisting of: polytetrafluoroethylene (PTFE), polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polyetheretherketone (PEEK), perfluoroalkoxy polymer (PFA), polyvinylidene fluoride (PVDF), polyamide (PA), polyurethane (PU) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP).

[0043] The above materials have proven to be particularly suitable for forming the substrate and / or contact surface and / or electrode.

[0044] Preferably, the method further comprises the step of providing an electrode on the substrate, wherein the electrode is obtained by coating the electrode material on the upper side and / or the lower side of the substrate, or wherein the electrode is obtained by additionally coating additional electrode material on the electrode material and / or on the upper side and / or the lower side of the substrate.

[0045] In this way, the electrode can be directly obtained by coating the electrode material and integrally bonded to the substrate, or the electrode can be obtained by additional steps.

[0046] The additional electrode material may be different or the same in composition as the electrode material. In particular, when the material properties of the electrode material and the electrode should be different, different compositions are preferred.

[0047] Preferably, the method further comprises the step of hydrophilizing the surface of the electrode.

[0048] In this way, the wettability of the obtained electrode with an aqueous electrolyte can be improved.

[0049] An example of hydrophilization is: coating the electrode material with a layer having a lower hydrophobicity.

[0050] According to the present invention, there is also provided an electrochemical gas sensor which can be obtained by the above method.

[0051] Preferably, in addition to the substrate with the electrode material or the electrode, the gas sensor further has: a sensor housing; optionally, a diffusion barrier layer that prevents gas from flowing from the environment to the substrate; optionally, a sealing element disposed between the substrate and the sensor housing; and a plurality of electrical leads that can maintain electrical connection with a plurality of contact surfaces that can be electrically contacted. Description of the Drawings

[0052] These and other features, advantages and preferred design aspects of the present invention are also derived from the subsequent description of the drawings. Here:

[0053] Figure 1 An embodiment of the gas sensor according to the present invention is shown;

[0054] Figure 2 An embodiment of another gas sensor according to the present invention is shown;

[0055] Figure 3 An embodiment of the substrate according to the present invention is shown;

[0056] Figure 4 An embodiment of the method according to the present invention is shown. Detailed Description of the Invention

[0057] According to the present invention, there is provided a method 100 for manufacturing an electrochemical gas sensor 200. An embodiment of such method 100 with steps S1, S2,... is shown in Figure 4 The step S1 is to provide a substrate 40, wherein the substrate 40 has a plurality of through holes 41a, 41b formed along the normal direction of the substrate 40.

[0058] An example of the substrate 40 is shown in

[0059] in which the substrate has a plurality of through holes 41a, 41b formed along the normal direction N of the substrate 40. The substrate may have a base surface G, and the normal direction N extends perpendicular to the base surface. For the case where the base surface G may not be flat, the normal direction N is formed by a perpendicular line on the tangent plane at the base surface G. Figure 3

[0060]

[0060] In the example shown, the substrate 40 has two through-holes 41a and 41b, which have cross-sections that are not constant when viewed along the normal direction N. Thus, the portions of the respective through-holes 41a, 41b above the viewing plane are designed to be substantially cylindrical, while the portions of the respective through-holes 41a, 41b below the viewing plane have a cross-sectional area that is widened relative to the portions above. However, this is not necessary.

[0061] The substrate 40 of all embodiments can for example be designed as a breathable and liquid-tight membrane, or can be designed as a liquid-wettable separator.

[0062] The substrate 40 can for example include glass or plastic. The plastic can be selected from the group consisting of: PTFE, PE, PET, PP, PVC, PEEK, PFA, PVDF, PA, PU, and FEP.

[0063] According to Figure 4 method 100 further has step S2: coating electrode materials 50a, 50b, 50c onto the upper side O of the substrate 40 and / or onto the lower side U of the substrate 40.

[0064] According to Figure 4 method 100 further has step S3: bonding the electrode materials 50a, 50b, 50c to the substrate 40 such that the plurality of through-holes 41a, 41b are closed by the electrode materials 50a, 50b, 50c in order to obtain a plurality of contact surfaces 51a, 51b that are electrically contactable on the lower side U of the substrate 40 opposite the upper side O.

[0065] Method 100 can further have step S4: providing an electrode 30 on the substrate 40, where the electrode 30 is obtained by coating electrode materials 50a, 50b, 50c onto the upper side O of the substrate 40 and / or onto the lower side U of the substrate 40, or where the electrode 30 is obtained by additionally coating an additional electrode material 52 onto the electrode material 50b and / or onto the upper side O of the substrate 40.

[0066] In Figure 1 is shown a gas sensor 200 that can be obtained by method 100.

[0067] In this regard, the gas sensor 200 has a substrate 40, for example the substrate 40 according to Figure 3 in which the plurality of through-holes 41a, 41b are closed by electrode materials 50a, 50b, 50c coated onto the upper side O and / or the lower side U of the substrate 40 in order to obtain, in this example, a plurality of contact surfaces 51a, 51b that are electrically contactable on the lower side U.

[0068] In accordance withFigure 1 In the exemplary gas sensor 200 shown, the electrode material 50b coated onto the upper side O forms a layer on the substrate 40. However, this is not necessary. All that is required is that the electrode materials 50a, 50c close the plurality of through-holes 41a, 41b and form the electrically contactable contact surfaces 51a, 51b described above.

[0069] Advantageously and as Figure 1 shown in, the electrode material 50b forms the electrode 30 of the gas sensor 200. In this way, electrical contact between the electrode materials 50a, 50c and the electrode 30 can be provided particularly easily.

[0070] These electrically contactable contact surfaces 51a, 51b can be electrically contacted, for example, by electrical leads 60a, 60b. The specific design of the electrical leads 60a, 60b can be substantially arbitrary. For example, the electrical leads 60a, 60b can be metal elements.

[0071] The substrate 40 can be received in the gas sensor 200 by the housing of the gas sensor 200. In the example shown according to Figure 1 , this is achieved in such a way that the housing is designed in a two-part manner with a first housing part 10a and a second housing part 10b. Then, the substrate 40 can be received between the first housing part 10a and the second housing part 10b. It is possible and shown that the gas sensor 200 also has a sealing element 20, such as an O-ring 20, in order to be able to receive the substrate 40 in a sealed manner in or on the housing.

[0072] The gas sensor 200 can have any other elements, such as other electrodes not shown, for example a reference electrode, a counter electrode and a measuring electrode.

[0073] As Figure 1 shown, the gas sensor 200 can have a diffusion barrier layer 70. The diffusion barrier layer can form the gas inlet or gas outlet of the gas sensor 200. In an example not shown, the gas sensor 200 can also have another diffusion barrier layer, which can be arranged below the substrate 40 with respect to the viewing plane.

[0074] Figure 2 Another example of the gas sensor 200 is shown. Since the gas sensor 200 according to Figure 2 is similar to the gas sensor 200 according to Figure 1 , only the differences from the gas sensor 200 according to Figure 1 will be described.

[0075] Different from the one according to Figure 1The gas sensor 200, according to Figure 2 In the gas sensor 200, the electrode 30 is not directly formed by the applied electrode material 50b, but rather by an additional layer applied to the electrode material 50b. This additional layer is formed by an additional electrode material 52. The additional layer can be obtained, for example, by an additional printing step or by any other process. Advantageously, the electrode 30 is in direct contact with the electrode material 50b such that the electrode 30 can be electrically contacted via a plurality of electrically contactable contact surfaces 51a, 51b.

[0076] In accordance with Figure 2 In the embodiment according to

[0077] In accordance with Figure 1 and Figure 2 In each of the embodiments according to

[0078] In all of the described embodiments, it is possible to bond the electrode materials 50a, 50b, 50c to the substrate 40 by heat treatment of the substrate 40 and the electrode materials 50a, 50b, 50c. An example of such heat treatment is sintering.

[0079] In all of the described embodiments, it is possible that the electrode materials 50a, 50b, 50c comprise glass and metal and / or metal oxide and / or plastic and / or carbon. The same applies to the additional electrode material 52, if present.

[0080] Preferably, the metal and / or the metal oxide is selected from the group consisting of: platinum, platinum oxide, gold, gold oxide, iridium, iridium oxide, silver, silver oxide, ruthenium, ruthenium oxide, rhodium, rhodium oxide, palladium, palladium oxide, copper, copper oxide, and nickel.

[0081] Preferably, the plastic is selected from the group consisting of: PTFE, PE, PET, PP, PVC, PEEK, PFA, PVDF, PA, PU, and FEP.

[0082] In all of the described embodiments, it is possible that the method further has step S5: hydrophilizing the surface of the electrode 30.

[0083] All of the features described herein can be combined with one another arbitrarily, unless this affects alternatives or is contradictory.

[0084] List of reference signs

[0085] 10a First housing part

[0086] 10b Second housing part

[0087] 20 Sealing element, O-ring

[0088] 30 Electrode

[0089] 40 Substrate

[0090] 41a Through-hole

[0091] 41b Through-hole

[0092] 50a, 50b, 50c Electrode material

[0093] 51a, 51b Contact surface

[0094] 52 Additional electrode material

[0095] 60, 60a, 60b Electrical lead

[0096] 70 Diffusion barrier layer

[0097] 100 Method

[0098] 200 Gas sensor, electrochemical gas sensor

[0099] G Base plane

[0100] N Normal direction

[0101] O Upper side

[0102] S1, S2,... Method steps

[0103] U Lower side

Claims

1. A method (100) for manufacturing an electrochemical gas sensor (200), the method comprising the following steps (S1, S2, . . . ): (S1) providing a substrate (40), wherein The substrate (40) has a plurality of through holes (41a, 41b) formed along a normal direction (N) of the substrate (40); (S2) applying electrode materials (50a, 50b, 50c) to the upper side (O) of the substrate (40) and / or to the lower side (U) of the substrate (40); and (S3) combining the electrode material (50a, 50b, 50c) with the substrate (40) so that the plurality of through holes (41a, 41b) are closed by the electrode material (50a, 50b, 50c) to obtain a plurality of contact surfaces (51a, 51b) that can be electrically contacted on the lower side (U) of the substrate (40) opposite to the upper side (O).

2. The method (100) according to claim 1, in, The combination of the electrode material (50a, 50b, 50c) and the substrate (40) includes: heat treating the substrate (40) and the electrode material (50a, 50b, 50c).

3. The method (100) according to claim 1 or 2, in, The substrate (40) is designed as a breathable and liquid-tight membrane, or The substrate (40) is designed as a liquid-wettable partition.

4. The method (100) according to any one of the preceding claims, in, The substrate (40) comprises glass or plastic, Therein, the electrode material (50a, 50b, 50c) comprises the glass and / or the metal and / or the metal oxide and / or the plastic and / or carbon.

5. The method (100) according to claim 4, in, The metal and / or the metal oxide is selected from the group consisting of platinum, platinum oxide, gold, gold oxide, iridium, iridium oxide, silver, silver oxide, ruthenium, ruthenium oxide, rhodium, rhodium oxide, palladium, palladium oxide, copper, copper oxide and nickel.

6. The method (100) according to claim 4 or 5, in, The plastic is selected from the group consisting of PTFE, PE, PET, PP, PVC, PEEK, PFA, PVDF, PA, PU and FEP.

7. The method (100) according to any one of the preceding claims, The method also comprises the following steps: (S4) providing an electrode (30) on the substrate (40), in, The electrode (30) is obtained by applying the electrode material (50a, 50b, 50c) to the upper side (O) of the substrate (40) and / or to the lower side (U) of the substrate (40), or The electrode (30) is obtained by additionally applying an additional electrode material (52) to the electrode material (50b) and / or to the upper side (O) of the substrate (40) and / or to the lower side (U) of the substrate (40).

8. The method (100) according to any one of the preceding claims, The method also comprises the following steps: (S5) The surface of the electrode (30) is made hydrophilic.

9. An electrochemical gas sensor (200) obtainable by the method (100) according to any one of claims 1 to 8.

10. The electrochemical gas sensor (200) according to claim 9, further comprising: - sensor housing (10a, 10b); - optionally, a diffusion barrier (70) which prevents the flow of gas from the environment to the substrate (40); - optionally, a sealing element (20) arranged between the substrate (40) and the sensor housing (10b); - A plurality of electrical leads (60a, 60b) which are electrically connected to a plurality of contact surfaces (51a, 51b) which can be electrically contacted.

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