Electrochemical gas sensor for detecting high phosphine concentration

Abstract

The invention relates to an electrochemical gas sensor for gaseous hydrides, in which the gas sensor comprises at least one housing having a first and a second working electrode, a counter electrode and a reference electrode arranged therein. The first working electrode, the second working electrode, the counter electrode, and the reference electrode are in ion conductive contact with the electrolyte. The reference electrode is disposed between the first working electrode and the second working electrode. The invention further comprises a measuring device for the quantitative or qualitative determination of an analyte gas and a method for the concentration determination of an analyte gas and the use of an electrochemical gas sensor or measuring device for the concentration determination of an analyte gas.

Description

Technical Field

[0001] Electrochemical gas sensor for analyte gas containing hydride compounds, measuring device for quantitatively or qualitatively determining analyte gas containing hydride compounds, and method for concentration determination of analyte gas containing hydride compounds

[0002] The invention relates to an electrochemical gas sensor for gaseous hydrides, wherein the gas sensor comprises at least one housing having a first working electrode and a second working electrode, a counter electrode and a reference electrode arranged therein. The gas sensor further comprises an electrolyte in conductive contact with the first working electrode, the second working electrode, the counter electrode and the reference electrode. The reference electrode is arranged between the first working electrode and the second working electrode. The invention further comprises a measuring device for quantitatively or qualitatively determining an analyte gas and a method for determining the concentration of an analyte gas. Background Art

[0003] Phosphine is used worldwide in agriculture for pest control, especially in cereals. In this process, which is also called disinfestation, cereals or the like are fumigated with phosphine (also called phosphine, monophosphine, phosphine; PH3). This is done in an attempt to reduce or even prevent damage to the cereals that occurs, for example, due to insect damage or also contamination by insect excrement. In this case, it is absolutely necessary to reach a certain minimum concentration of phosphine in the cereals in order to achieve and eliminate all insects or pests in the cereals. It is problematic that the concentration of phosphine must not exceed a certain threshold value, because above a certain gas concentration of phosphine, the pests or insects fall into a so-called chemical protective rigidity, from which the metabolism stops, so that virtually no metabolism occurs and therefore no phosphine is absorbed. Another known problem is that phosphine is a highly toxic, odorless gas in the pure state, which ignites spontaneously from a temperature of approximately 150° C. Therefore, in terms of work protection, it is necessary to know the concentration of the phosphine used.

[0004] For workers in processing rooms such as grain silos, there are portable and fixed gas warning devices which are usually equipped with electrochemical gas sensors and which safeguard the work area or workers against excessive concentrations of analyte gases such as phosphine. Depending on the country, the permitted workplace concentrations are in the single-digit ppm up to the mid-ppb range.

[0005] Electrochemical gas sensors for determining the concentration of hydride gases such as phosphine and / or arsine are already known from the prior art. US 5 997 706 A, EP 0 436 148 B1 and DE 198 32 395 C1 disclose electrochemical gas sensors for detecting hydride gases such as arsine and phosphine, the electrochemical gas sensors comprising a working electrode and a reference electrode in an electrolyte space, the dielectric space being filled with an electrolyte and being closed with a gas-permeable membrane. KR 20200 082 563 A discloses a working electrode for use in a phosphine sensor. DE 19939 011 C1 discloses an electrochemical gas sensor with a gas-permeable membrane, wherein the working electrode is composed of diamond-like carbon and is applied as a thin layer on the gas-permeable membrane. DE 101 59 616 B4 teaches an electrochemical gas sensor for phosphine and arsine with improved cross-sensitivity.

[0006] Electrochemical gas sensors for hydride gases known from the prior art often have the following problem: in the case of high concentrations of analyte gases, such as phosphine and / or arsine, which are required for successful insecticide removal, the analyte gas is not completely converted at the working electrode (also referred to as the measuring electrode) when diffusing into the electrochemical gas sensor, so that in the worst case the analyte gas reaches the reference electrode. This would result in the working potential of the working electrode being shifted, thereby inhibiting the chemical conversion at the working electrode, and thus the sensitivity of the sensor to the analyte gas is reduced to the extent that the analyte gas can no longer be detected or the sensor sensitivity stored in the measuring system is perceived as an erroneous measurement result with a too low measuring current.

[0007] Therefore, there is still a need for electrochemical gas sensors, which can be used in particular at the concentration required by the user for insect control to measure or detect analyte gases including hydride compounds, and can provide high long-term signal stability, i.e. reliable measurement results, over a long period of time without causing the measurement results to "collapse", i.e. be distorted to low measurement values, after a certain period of use.

[0008] The object of the present invention is in particular to provide an electrochemical gas sensor which solves the problems known from the prior art. Therefore, an electrochemical gas sensor should be provided which is suitable for measuring or identifying analyte gases including hydride compounds, such as phosphine (PH3), borane (BH3), diborane (B2H6), arsine (AsH3), SeHH2 and others, which is long-term stable without the measurement signal "collapsing" or becoming inaccurate after a certain point in time and which ideally also has a high resistance to continuous fumigation over a period of at least four hours up to several months, i.e. a high long-term signal stability. In addition, the object of the present invention is to provide an electrochemical gas sensor which can be operated at low cost by the end customer without requiring a high maintenance intensity or a large number of maintenance cycles.

[0009] These and other objects are achieved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent patent claims or are described in more detail below. Summary of the invention

[0010] Surprisingly, it has been found that when at least one first working electrode and a second working electrode and a reference electrode are arranged in the shell, the signal stability of the electrochemical gas sensor according to the present invention can be achieved even in the case of high concentrations of analyte gas of up to 1000 ppm or more, and the measurement signal of the electrochemical gas sensor according to the present invention does not "collapse", that is, the measurement signal remains stable even in the case of high concentrations of analyte gas required for insect removal.

[0011] According to the invention, an electrochemical gas sensor for an analyte gas comprising at least one hydride compound is proposed, wherein the gas sensor comprises at least:

[0012] a) a housing, wherein, among other things, the following is arranged in the housing:

[0013] b) at least one first working electrode and a second working electrode,

[0014] c) corresponding electrode,

[0015] d) a reference electrode, and

[0016] e) an electrolyte in conductive contact with the first working electrode, the second working electrode, the counter electrode, and the reference electrode;

[0017] The reference electrode is arranged between the first working electrode and the second working electrode.

[0018] Furthermore, a measuring device is proposed for the quantitative or qualitative determination of an analyte gas, wherein the measuring device has an electrochemical gas sensor according to the invention.

[0019] Furthermore, the use of the electrochemical gas sensor according to the invention and / or the measuring device according to the invention for determining the concentration of an analyte gas is disclosed.

[0020] Furthermore, the present invention relates to a method for concentration determination of an analyte gas comprising a hydride compound using an electrochemical gas sensor.

[0021] Detailed description of the invention

[0022] The analyte gas is a gas that is loaded to the electrochemical gas sensor or whose concentration is measured. The analyte gas is usually diffused from the ambient atmosphere (ambient air) together with air to the gas sensor according to the present invention, or the electrochemical gas sensor according to the present invention is loaded with the analyte gas. The analyte gas includes one or more hydride gases or one or more gaseous hydride compounds or their vapors, preferably phosphine (PH3), borane (BH3), diborane (B2H6), arsine (AsH3) and / or selenane (SeHH2). The electrochemical gas sensor according to the present invention is preferably used for phosphine and / or arsine as analyte gas, and is particularly preferably used for phosphine. In the sense of the present invention, the hydride gas mentioned or the hydride compound mentioned is also referred to as non-metallic hydride or non-metallic hydride compound or semi-metallic hydride or semi-metallic hydride compound. Typically, the analyte gas is contained in the ambient atmosphere of the gas sensor, but it can also be delivered to the gas sensor separately, for example, in a dose that is undoubtedly determined, in batches, etc.

[0023] The housing of the electrochemical gas sensor defines the electrochemical gas sensor externally. The housing is usually in contact with the ambient atmosphere externally, and in the interior of the housing, electrodes such as a first working electrode, a second working electrode, a counter electrode and a reference electrode and a receiving place for an electrolyte are formed. The housing can be made of different typical materials for use in electrochemical gas sensors. For example, plastics such as polyethylene (PE), polypropylene (PP), perfluoroalkoxy polymers (PFA), fluoroethylene propylene (FEP) or polytetrafluoroethylene (Teflon; PTFE) belong to this. The housing of the electrochemical gas sensor further preferably has an electrolyte reservoir for accommodating an electrolyte, for example, designed as a compensation volume.

[0024] In a preferred embodiment, the first working electrode and / or the second working electrode comprises an electrode material selected from the following group: the group consists of or includes: gold, platinum, rhodium, ruthenium and iridium, preferably gold. The first working electrode and the second working electrode can be made of not only different electrode materials but also the same electrode material or include different electrode materials or the same electrode material. In a preferred embodiment, the first working electrode and the second working electrode are respectively gold electrodes, that is, not only the first working electrode but also the second working electrode preferably comprises or consists of gold.

[0025] The first working electrode and / or the second working electrode can be used in the electrochemical gas sensor according to the present invention with and without a carrier material or an electrode diaphragm, respectively. In another design, the first working electrode and / or the second working electrode can be arranged at or on a polymer fiber mesh or a glass fiber mesh. The polymer fiber mesh can be, for example, a hydrophilic polyolefin fiber mesh or a perfluorinated fiber mesh, such as a hydrophilized PTFE fiber mesh (perfluorinated tetrafluoroethylene fiber mesh). In one design, the first working electrode can be arranged on a barrier layer that is breathable and preferably impermeable to electrolytes. According to the present invention, the first working electrode can be arranged so that the analyte gas directly reaches the first working electrode when it diffuses into the electrochemical gas sensor.

[0026] According to the invention, the reference electrode is arranged between the first working electrode and the second working electrode. Preferably, the reference electrode comprises an electrode material selected from the following group, the group consisting of or including: ruthenium oxide (RuO2), carbon nanotubes, nitrogen-doped carbon nanotubes, graphene, diamond-like carbon and reduced graphene oxide. Further preferably, the reference electrode comprises or consists of an electrode material selected from the following group: ruthenium oxide, carbon nanotubes and nitrogen-doped carbon nanotubes. Very particularly preferably, the reference electrode comprises or consists of ruthenium oxide and / or nitrogen-doped carbon nanotubes. Surprisingly, it has been found that the reference electrode comprising ruthenium oxide and / or nitrogen-doped carbon nanotubes works extremely robustly in the electrochemical gas sensor according to the invention, i.e., even at high concentrations of the analyte gas and at long-term exposure to the analyte gas for several hours, the measurement signal is not distorted. The inventors have surprisingly found that the voltage applied to the reference electrode is particularly stable when using hydride compounds or hydride gases, especially when using phosphine as the analyte gas.

[0027] In one design, the housing of the electrochemical gas sensor according to the present invention is obtained so that the analyte gas can diffuse into the electrochemical gas sensor through the housing. In a preferred design, the housing has an opening or a diffusion membrane for gas exchange with the environment and an electrolyte-filled reaction space, in which electrodes (a first working electrode and a second working electrode, a counter electrode and a reference electrode) are arranged. In this design, the analyte gas diffuses into the reaction space of the gas sensor, for example, through the diffusion membrane and optionally the working electrode membrane, and further diffuses to the first working electrode. A forward reaction occurs at the first working electrode, and a reverse reaction occurs at the counter electrode.

[0028] In the case of a preferred electrochemical gas sensor, in one embodiment, the analyte gas diffuses from the ambient air through a preferably electrolyte-impermeable, preferably hydrophobic (water-repellent) diffusion membrane into the electrochemical gas sensor and reaches a three-phase boundary, which is composed of a first working electrode, an electrolyte and the analyte gas. The analyte gas ultimately reacts at the working electrode (forward reaction), wherein the reaction products formed at the counter electrode (reverse reaction) ultimately reach the electrode again. In this case, water is formed at the counter electrode. Without being bound by theory, the inventors assume that when using phosphine as the analyte gas, the following reaction takes place at the first working electrode and the counter electrode:

[0029] At the first working electrode (cathode), phosphine is oxidized to phosphate according to the following equation:

[0030] PH3+4H2O→H3PO4+8H+

[0031] At the corresponding electrode (anode), oxygen is reduced to 2O2- according to the following equation:

[0032] 2O2→4O2-

[0033] The overall reaction taking place in the electrochemical gas sensor according to the invention results from the two reactions mentioned above, which are also referred to as half-cell reactions:

[0034] PH3+2O2+4H2O→H3PO4+4H2O

[0035] When the electrochemical gas sensor according to the invention is charged with phosphine as the analyte gas, without being bound by theory, according to the above equation, the phosphine is oxidized to phosphoric acid at the first working electrode and oxygen is reduced at the counter electrode.

[0036] In another preferred embodiment, the housing has both a first diffusion membrane and a second diffusion membrane. This has proven to be particularly advantageous, since, for example, the electrolyte may be hygroscopic, which may lead to an increase in the volume of the electrolyte, since the electrolyte may, for example, absorb water present in the ambient air. Therefore, it may be advantageous to arrange at least one second diffusion membrane in the housing, by means of which a pressure balance with the environment can be achieved. In principle, the second diffusion membrane can be arranged everywhere in the housing. When the analyte gas diffuses through the first diffusion membrane, the analyte gas reaches the three-phase boundary between the first working electrode, the analyte gas and the electrolyte. Here, when phosphine is used as the analyte gas, the forward reaction described above takes place at the first working electrode, i.e., the oxidation of phosphine into phosphoric acid.

[0037] It is particularly preferred that the electrochemical gas sensor has a first diffusion membrane and a second diffusion membrane substantially opposite the first diffusion membrane. The second diffusion membrane is therefore particularly advantageous because products formed in the electrochemical gas sensor, such as gas or even water, can diffuse back into the environment through the second diffusion membrane as a gas outlet. The second opening in the form of the second diffusion membrane is also advantageous because overpressure or underpressure may occur in the electrochemical gas sensor, which can also be dissipated through the diffusion membrane. Overpressure or underpressure may occur, for example, due to changes in the ambient temperature.

[0038] In the case of high gas concentrations necessary for insect removal, the analyte gas can also diffuse into the electrochemical gas sensor through the second diffusion membrane similar to the first diffusion membrane. According to the present invention, the reference electrode is arranged between the first working electrode and the second working electrode. In this design, the analyte gas reaches the second working electrode through the second diffusion membrane and the optional working electrode membrane when diffusing into the electrochemical gas sensor, and is oxidized at the second working electrode similar to the first working electrode. By arranging the reference electrode between the first working electrode and the second working electrode according to the present invention, it has been surprisingly found that the signal stability of the electrochemical gas sensor according to the present invention does not "collapse" even at high gas concentrations of high analyte gas required for insect removal, that is, the measurement signal is not distorted even at high concentrations. Here, the second working electrode is used as a type of protective electrode, which is set up to oxidize all analyte gases diffused into the electrochemical gas sensor that have not been oxidized at the first working electrode. By arranging the reference electrode between the first working electrode and the second working electrode according to the present invention, it is ensured that little or ideally no analyte gas reaches the reference electrode. It is known to those skilled in the art that the measurement signal of an electrochemical gas sensor is distorted when the analyte gas passes through the electrolyte to the reference electrode.

[0039] The counter electrode is preferably arranged in the electrochemical gas sensor so that the counter electrode can be easily contacted with the ambient atmosphere, preferably via a diffusion membrane, in which the ambient atmosphere contains oxygen in addition to the analyte gas. The material for the counter electrode is selected so that in the electrochemical gas sensor according to the present invention, oxygen can be reduced at the counter electrode according to the above equation. All electrode materials known to those skilled in the art can be considered for the counter electrode. The inventors have found that the electrode material for the counter electrode is not important. In a preferred design, the housing of the electrochemical gas sensor has a first diffusion membrane and a substantially opposite second diffusion membrane, and the counter electrode is arranged below the second diffusion membrane (i.e., in the longitudinal direction of the gas sensor or the gas inlet direction, it is located outside more than the second diffusion membrane), especially preferably arranged between the second diffusion membrane and the second working electrode. This arrangement can be used to carry out the reverse reaction required for the stability of the electrochemical gas sensor according to the present invention, that is, to reduce oxygen to 2O2-. The counter electrode is arranged below the diffusion membrane, preferably below the second diffusion membrane, causing a continuous gas exchange to occur between the ambient atmosphere and the counter electrode. Thus, the reduction of oxygen contained in the ambient atmosphere at the counter electrode can occur.

[0040] In another preferred design, the reference electrode is at least partially surrounded by a film that is preferably airtight to the analyte gas. This additionally prevents or makes contact between the analyte gas and the reference electrode difficult, which in turn leads to a further improvement in signal stability. In particular, preferably, the reference electrode is at least partially surrounded by a polyvinylidene fluoride film (PVDF film). Very particularly preferably, an electrochemical gas sensor is provided, which has a reference electrode comprising nitrogen-doped carbon nanotubes at least partially surrounded by a PVDF film or a RuO2 reference electrode at least partially surrounded by a PVDF film. Surrounding or winding or wrapping means that the reference electrode is ideally shielded from the analyte gas, but continues to be in contact with the electrolyte for ionic conduction to occur.

[0041] In a preferred electrochemical gas sensor, the housing has two diffusion membranes arranged substantially opposite to each other. In the preferred electrochemical gas sensor, the analyte gas diffuses into the electrolyte of the electrochemical gas sensor through the first diffusion membrane and the reliable working electrode membrane. The analyte gas is at least partially oxidized at the three-phase boundary consisting of the analyte gas, the first working electrode and the electrolyte. Between the first diffusion membrane and the second diffusion membrane, the first working electrode, then the reference electrode, then the second working electrode, and then the corresponding electrode are arranged along the diffusion direction of the analyte gas from the first diffusion membrane to the second diffusion membrane. In another preferred design, one or more separators can be arranged between the first working electrode and the reference electrode and / or between the reference electrode and the second working electrode and / or between the second working electrode and the corresponding electrode. The separator prevents a short circuit from occurring between the electrodes, i.e., the first and second working electrodes, the reference electrode and the corresponding electrode. Particularly preferably, there is at least one separator between all the electrodes mentioned. The separator is, for example, a glass fiber mesh or the like. These separators are constructed to be permeable to the electrolyte and absorb the electrolyte, and thus form a carrier for the electrolyte bridge so that ions can move between the electrodes.

[0042] In another preferred embodiment, it is possible that the second working electrode can include two or more short-circuited single electrodes. In this way, the effective surface of the second working electrode can be increased, which in turn leads to faster oxidation of the analyte gas diffused into the electrochemical gas sensor. This can also reduce the probability that the analyte gas diffused into the electrochemical gas sensor reaches the reference electrode, which is undesirable because it leads to a "collapse" of the measurement signal or thus distorts the measurement signal, as explained at the beginning.

[0043] In the electrochemical gas sensor according to the invention, lithium chloride, ionic liquids, sulfuric acid and / or ethylene carbonate / propylene carbonate solutions (ECPC solutions) with conductive salts are used as possible electrolytes, for example tetrabutylammonium toluenesulfonate or tetrabutylammonium methanesulfonate. Ionic liquids (IL) are in principle understood to be highly concentrated saline solutions or liquid salts (so-called molten salts, MS), which consist primarily of positively and negatively charged ions. Preferably, sulfuric acid (H2SO4) is used.

[0044] According to the present invention, the reference electrode is arranged between the first working electrode and the second working electrode. In a particularly preferred electrochemical gas sensor, wherein the first working electrode, then the reference electrode, then the second working electrode, and then the corresponding electrode are arranged along the diffusion direction from the first diffusion membrane toward the substantially opposite second diffusion membrane, the second working electrode has at least one device, the device can realize the electrolyte to move between the corresponding electrode and the reference electrode. In other words, the device can realize that the electrolyte can flow through. In a particularly preferred design, the second working electrode has an opening and / or a secant, which is designed so that the electrolyte can flow through the opening and / or the secant. The opening and / or the secant are further preferably constructed in the second working electrode so that the diffusion path between the second working electrode and the reference electrode is as large as possible. Therefore, it is preferred that the reference electrode is arranged as far away from the opening and / or the secant as possible. The diffusion path of the analyte gas located in the electrolyte from the second working electrode to the reference electrode is thereby additionally increased, which causes additional signal stability, especially in the case of very high gas concentrations of the analyte gas, which is necessary for deworming.

[0045] The electrochemical gas sensor may have further elements, such as a coupling unit, which may be configured to electrically connect the electrodes, i.e. the first working electrode, the second working electrode, the reference electrode and the counter electrode and other optional electrodes, located in the electrochemical gas sensor to a circuit, such as a potentiostat or a galvanostat. The coupling unit may have one or more contact pins, which may be electrically conductively connected to the electrodes, for example, via platinum wires.

[0046] In a further embodiment, the electrochemical gas sensor according to the invention comprises an analyte gas, wherein the analyte gas is in particular dissolved in an electrolyte.

[0047] Furthermore, the invention includes a measuring device for quantitatively or qualitatively determining an analyte gas comprising hydrides. In a preferred embodiment, the measuring device according to the invention includes an evaluation unit, which measures the current flowing between the first working electrode and the counter electrode when the analyte gas is applied. The concentration of the analyte gas can thus be determined based on the measured current between the first working electrode and the counter electrode.

[0048] The present invention further comprises a method for determining the concentration of an analyte gas comprising a hydride compound. The method according to the present invention comprises at least the following steps:

[0049] i. loading an electrochemical gas sensor with an analyte gas, wherein the electrochemical gas sensor comprises at least a first working electrode, a second working electrode, a counter electrode, a reference electrode disposed between the first working electrode and the second working electrode, and an electrolyte in conductive contact with the first working electrode, the second working electrode, the counter electrode, and the reference electrode,

[0050] ii. applying a voltage between the first working electrode and the reference electrode,

[0051] iii. applying a voltage between the second working electrode and the reference electrode,

[0052] iv. at least partially oxidizing the analyte gas at the first working electrode, wherein at least one reaction product migrates to the counter electrode,

[0053] v. at least partially reducing oxygen at the counter electrode, and

[0054] vi. measuring the current flowing between the first working electrode and the counter electrode.

[0055] In the case of the method according to the invention, the analyte gas is loaded to the electrochemical gas sensor. The electrochemical gas sensor comprises at least one first working electrode, a second working electrode, a counter electrode, a reference electrode arranged between the first working electrode and the second working electrode, and an electrolyte in conductive contact with the first working electrode, the second working electrode, the counter electrode and the reference electrode. The analyte gas comprises at least one hydride compound. A voltage is applied between the first working electrode and the reference electrode and between the second working electrode and the reference electrode, in particular using a potentiostat. Applying a voltage between the first working electrode and the reference electrode (ii.) and applying a voltage between the second working electrode and the reference electrode (iii.) preferably occur simultaneously, i.e. in a consistent manner.

[0056] Preferably, the voltage between the first working electrode and the reference electrode and between the second working electrode and the reference electrode is the same. The analyte gas diffused into the electrochemical gas sensor is at least partially oxidized at the first working electrode. When phosphine is loaded as the analyte gas to the electrochemical gas sensor, the phosphine is oxidized to phosphoric acid. Oxygen is reduced at the counter electrode. The current flowing between the first working electrode and the counter electrode during this reaction is measured. The current between the first working electrode and the counter electrode is proportional to the conversion of the analyte gas at the first working electrode.

[0057] Under the high gas concentration of the analyte gas required for deworming, the analyte gas that is not converted at the first working electrode is oxidized at the second working electrode. This prevents the analyte gas from diffusing to the reference electrode, which will cause the measurement result to be distorted. For this situation, the current flowing between the second working electrode and the corresponding electrode is preferably not measured. In other words, this means that the concentration of the analyte gas is determined only by the current flowing between the first working electrode and the corresponding electrode. The second working electrode is especially used as a type of protective electrode, which is set up for converting the analyte gas that has not been oxidized at the first working electrode so that the analyte gas cannot diffuse to the reference electrode.

[0058] The electrochemical gas sensor according to the invention or the measuring device according to the invention can be used for the concentration determination of an analyte gas comprising hydride compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The advantages of the electrochemical gas sensor according to the present invention and its possible structure are shown below according to the following figure.

[0060] Figure 1 Shown is a cross section through an electrochemical gas sensor according to the invention with electrodes located in a housing. DETAILED DESCRIPTION

[0061] Figure 1 A cross section of an electrochemical gas sensor 100 according to the present invention is shown. The gas sensor 100 comprises a housing 11, a first working electrode 12, a second working electrode 13, a counter electrode 19 and a reference electrode 17. The reference electrode 17 is surrounded by a gas-impermeable film 18. Surrounding or wrapping or wrapping means that the reference electrode is ideally shielded from the analyte gas, but is additionally surrounded by an electrolyte in an ion-conducting manner. The reference electrode 17 is arranged between the first working electrode 12 and the second working electrode 13. Electrolyte-permeable separation layers (spacers) 15 are respectively arranged between the first working electrode 12 and the reference electrode 17. These spacers 15 prevent electrical short circuits between the electrodes 12, 17, 13 and 19. The analyte gas diffused into the electrochemical gas sensor 100 passes from below through the openings. Arrives in the electrochemical gas sensor 100 along the direction R.1. After penetrating the gas-permeable support membrane 14 and the gas-permeable barrier layer 16, the analyte gas dissolved in the electrolyte 22 reaches the first working electrode 12. A chemical reaction occurs at the first working electrode. When phosphine invades as the analyte gas, the phosphine is oxidized to phosphoric acid at the first working electrode 12. A voltage (not shown) is applied between the first working electrode 12 and the reference electrode 17. When phosphine is oxidized to phosphoric acid at the first working electrode 12, a current flows between the first working electrode 12 and the counter electrode 19. With the aid of an evaluation unit (not shown), the concentration of the analyte gas can be determined based on the current flow between the first working electrode 12 and the counter electrode 19. A voltage (not shown) is also applied between the second working electrode 13 and the reference electrode 17. The second working electrode 13 has an opening or cut line 21. The opening or cut line 21 is configured so that the electrolyte 22 in the electrochemical gas sensor 100 connects the electrodes 12, 17, 13 and 19 to each other in an ion-conducting manner. At the upper end of the electrochemical gas sensor 100, there is another supporting membrane 14 and a cover plate 20 above the counter electrode 19. The cover plate 20 is gas-permeable and is used in particular for pressure compensation. The electrolyte 22 located in the electrochemical gas sensor 100 is hygroscopic, i.e., the electrolyte absorbs water from the ambient atmosphere of the electrochemical gas sensor. In order to prevent an overpressure from occurring in the electrochemical gas sensor 100, which would cause the electrolyte 22 to flow out of the electrochemical gas sensor 100, the upper gas-permeable supporting membrane 14 and the cover plate 20 are used for pressure compensation. At high gas concentrations of up to 1000 ppm or more of the analyte gas required for insect removal, the analyte gas also invades the electrochemical gas sensor 100 from above, as indicated by R.2. The analyte gas diffused into the electrochemical gas sensor 100 from the direction R.2 is oxidized at the second working electrode 13. In the case where phosphine is measured as the analyte gas, phosphine is oxidized to phosphoric acid at the second working electrode 13. Arranging second working electrode 13 at the upper end of electrochemical gas sensor 100 according to the present invention prevents analyte gas diffusing into electrochemical gas sensor 100 from above from reaching reference electrode 17. Electrolyte 22 is not located below first working electrode 12 and above counter electrode 19.

[0062] Reference numerals list

[0063] 100 Gas Sensors

[0064] 11 Shell

[0065] 12. First working electrode

[0066] 13. Second working electrode

[0067] 14 Breathable support membrane

[0068] 15Electrolyte can pass through the separation layer (insulator)

[0069] 16 barrier layer

[0070] 17 Reference electrode

[0071] 18. Airtight film

[0072] 19 corresponding electrodes

[0073] 20 Cover

[0074] 21 Secant

[0075] 22 Electrolytes.

Claims

1. An electrochemical gas sensor (100) for an analyte gas comprising a hydride compound, The gas sensor (100) at least comprises: a) a housing (11), wherein the housing (11) further comprises: b) at least one first working electrode (12) and a second working electrode (13), c) a counter electrode (19), d) a reference electrode (17), and e) an electrolyte (22) in conductive contact with the first working electrode (12), the second working electrode (13), the counter electrode (19) and the reference electrode (17); The reference electrode (17) is arranged between the first working electrode (12) and the second working electrode (13).

2. The electrochemical gas sensor (100) according to claim 1, wherein - between the first working electrode (12) and the reference electrode (17), or - between the second working electrode (13) and the reference electrode (17), or - A separator (15) is arranged between the first working electrode (12) and the reference electrode (17) and between the second working electrode (13) and the reference electrode (17), preferably between the first working electrode (12) and the reference electrode (17) and between the second working electrode (13) and the reference electrode (17).

3. The electrochemical gas sensor (100) according to any one of the preceding claims, wherein the counter electrode (19) is arranged between the second working electrode (13) and the housing (11), Preferably, a separator (15) is arranged between the counter electrode (19) and the second working electrode (13).

4. An electrochemical gas sensor (100) according to any of the preceding claims, for use with phosphine (PH3), borane (BH3), diborane (B2H6), arsine (AsH3), SeH2 as analyte gas, in particular for phosphine.

5. An electrochemical gas sensor (100) according to any of the preceding claims, wherein the first working electrode (12) and / or the second working electrode (13) comprises an electrode material selected from the following group: gold, platinum, rhodium, ruthenium and iridium, preferably gold.

6. The electrochemical gas sensor (100) according to any one of the preceding claims, wherein the reference electrode (17) comprises an electrode material selected from the group consisting of ruthenium oxide (RuO2), carbon nanotubes, nitrogen-doped carbon nanotubes, graphene, diamond-like carbon, reduced graphene oxide, Preferably selected from the group consisting of ruthenium oxide, carbon nanotubes and nitrogen-doped carbon nanotubes, In particular, nitrogen-doped carbon nanotubes are preferred.

7. The electrochemical gas sensor (100) according to any one of the preceding claims, wherein the housing (11) has at least one first diffusion diaphragm, preferably at least one first diffusion diaphragm and a second diffusion diaphragm, It is further preferred that the second diffusion membrane is arranged substantially opposite to the first diffusion membrane. It is further preferred that the counter electrode is arranged below the second diffusion membrane.

8. The electrochemical gas sensor (100) according to claim 7, wherein a. in the state according to the application, the analyte gas diffuses at least partially through the first diffusion membrane in the direction of the second diffusion membrane (R.1), wherein the second diffusion membrane is arranged substantially opposite to the first diffusion membrane, wherein in the direction from the first diffusion membrane to the second diffusion membrane first a first working electrode (12) is arranged, then a reference electrode (17), then a second working electrode (13) and then a counter electrode (19), and / or b. in the state according to the application, the analyte gas diffuses at least partially through the second diffusion membrane in the direction of the first diffusion membrane (R.2), wherein the second diffusion membrane is arranged substantially opposite to the first diffusion membrane, The analyte gas at least partially comes into contact first with the counter electrode (19) and subsequently with the second working electrode (13).

9. The electrochemical gas sensor (100) according to any of the preceding claims, wherein the second working electrode (13) comprises a plurality of single electrodes.

10. The electrochemical gas sensor (100) according to any one of the preceding claims, wherein the electrolyte (22) is selected from one or more members of the following group: lithium chloride, ionic liquids, sulfuric acid and ECPC tetrabutylammonium toluenesulfonate or methanesulfonate solution.

11. The electrochemical gas sensor (100) according to any of the preceding claims, wherein the second working electrode (13) has openings and / or cut lines (21) designed to allow an electrolyte (22) to flow through.

12. The electrochemical gas sensor (100) according to any of the preceding claims, wherein the reference electrode (17) is at least partially surrounded by a film (18), preferably a film (18) that is impermeable to the analyte gas, in particular a polyvinylidene fluoride film.

13. The electrochemical gas sensor (100) according to any of the preceding claims, wherein the electrochemical gas sensor (100) comprises an analyte gas, which is preferably dissolved in the electrolyte (22).

14. A measuring device for quantitatively or qualitatively determining an analyte gas comprising a hydride compound, At least comprises the electrochemical gas sensor (100) according to any one of claims 1 to 13.

15. A method for determining the concentration of an analyte gas comprising a hydride compound, The method at least comprises the following steps: i. loading the electrochemical gas sensor (100) with an analyte gas, The electrochemical gas sensor (100) comprises at least one first working electrode (12), a second working electrode (13), a counter electrode (19), a reference electrode (17) arranged between the first working electrode (12) and the second working electrode (13), and an electrolyte (22) in conductive contact with the first working electrode (12), the second working electrode (13), the counter electrode (19) and the reference electrode (17). ii. applying a voltage between the first working electrode (12) and the reference electrode (17), iii. applying a voltage between the second working electrode (13) and the reference electrode (17), iv. at least partially oxidizing the analyte gas at the first working electrode (12), wherein at least one reaction product migrates to a counter electrode (19), v. at least partially reducing oxygen at the counter electrode (19), and vi. Measuring the current flowing between the first working electrode (12) and the counter electrode (19).

16. The method according to claim 15, wherein the electrochemical gas sensor (100) is designed according to any one of claims 2 to 13.

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