DE102008044239A1 - Electrochemical gas sensor used for detecting or measuring chlorine, fluorine, bromine, oxygen or chlorine dioxide, comprises housing with inlet opening, where housing includes two electrodes connected by conductive electrolyte system - Google Patents

Abstract

An electrochemical gas sensor (1) comprises housing with an inlet opening, where the housing includes two electrodes, which are connected by a conductive electrolyte system. The conductive electrolyte system comprises a conductive fluid, which is essentially absorbed in a powdered and/or fibrous unwoven on silicon dioxide-based solid. The conductive fluid is ionic liquid including organic, organometallic and/or inorganic additives.

Description

The invention relates to an electrochemical gas sensor, comprising a housing having at least one inlet opening, wherein in the housing at least two electrodes are connected, which are conductively connected to each other via an electrolyte system comprising a conductive liquid, which is substantially in a powdery and / or fibrous intumescent and SiO ₂ based solid is absorbed.

in the The case of a typical electrochemical gas sensor diffuses the to be determined gas (the analyte) from the environment into the sensor. If the sensor has a housing, this can for example through an opening or by diffusion done for the analyte permeable membrane. Usually the sensor comprises a measuring and a counter electrode, wherein the Analyte undergoes a chemical reaction at the measuring electrode. Corresponding finds a complementary reaction at the counter electrode instead of. The electrochemical redox reaction causes a flow of current between the electrodes that can be measured. In addition to measuring and counter electrode can still other electrodes, such as a reference electrode or a second measuring electrode may be included in the sensor.

The Electrochemical redox reaction must be an electrical signal which result in direct proportion to the concentration of the analyte.

electrolytes which are to be used in electrochemical gas sensors, have to meet different requirements. This implies that they are electrochemically and chemically inert and should be ionically conductive.

Conventional electrolytes are, for example, inorganic acids such as sulfuric or phosphoric acid, which are present as liquid electrolytes. As ionic conductors, the most varied systems are described in the patent literature. The most common is certainly sulfuric acid, which is used in sensors for common gases, such as CO, H ₂ S or O ₂ , and has been described since the 1960s (see Honeywell, 1967: US 3328277 B ).

A Property of common electrolytes is that they are hygroscopic are. At high humidity, the electrolyte can absorb so much water, If necessary, the sensor cell bursts and electrolyte escapes. To prevent this leakage of electrolytes must the sensor cells about 5 to 7 times their Elektrolytfüllvolumens reserve space in the sensor. That, in turn, is the general one Endeavor to miniaturize the cells.

Another decisive factor for an electrochemical gas sensor is the positional independence of the sensor. In order to improve the position independence approaches have been developed to immobilize liquid electrolytes with the help of glass fibers or silicate structures, whereby a quasi-solid electrolyte is achieved. In a quasi-solid-state electrolyte, reaction products and electrolytes are prevented from migrating through the sensor and can not be deposited at sensitive sites (eg, measuring or reference electrodes). Furthermore, there is no depletion by leaching processes between the electrodes. This allows a further miniaturization of the sensor cells. Examples of this can be found in the patents of MSA US 7,145,561 B2 . US 7,147,761 B2 and US 5,565,075 B and especially in the US Pat. No. 5,667,653 B , Above all, the systems described therein offer a better response time and allow a very compact design, but use conventional electrolytes with the disadvantages mentioned above.

One approach to circumvent the water absorption effect of conventional electrolytes is based on the use of organic liquids to which conductive salts have to be added in order to ensure ionic conductivity (eg Catalyst Research Corp., 1978: US 4,169,779 B ). However, the advantage of high relative humidities reverses at low humidities or high ambient temperatures in a disadvantage, since the evaporated solvent can not be taken out of the atmosphere and thus is irretrievably lost for the sensor cell.

A Solution to this problem is in the use of ionic liquids (IL) as electrolytes. Ionian Liquids are defined as liquid salts with a melting point below 100 ° C. The salt-like structure brings with it that ionic liquids no have measurable vapor pressure. The possibility of variation these substances are great. The properties of ionic liquids depend decidedly on the type and number of organic Side chains and cations. So there are representatives who have a melting point below -40 ° C. Lots Ionic liquids are chemical as well as electrochemical very stable and have a high ionic conductivity. The Water absorption capacity of individual representatives is zero. The Properties described above make ionic liquids to good electrolytes in electrochemical gas sensors.

The advantages of using a quasi-solid state electrolyte with ILs as electrolytes are disclosed in International Patent Application of Company Anaxys Technology Ltd. WO 2008/110830 A1 addressed. The application relates to an electrochemical sensor having an ionic liquid immobilized in a carrier material. With regard to the ionic liquid, various anions and cations are described, the cations being mostly imidazolium, pyridinium, tetraalkylammonium and tetraalkylphosphonium cations. The sensor is used for the determination of gases in the breathing air of a patient, for example, to be able to diagnose asthma. The measurement is carried out by cyclovoltametry. A characteristic of this measuring principle is that the potential of the measuring electrode is changed at constant speed between given potential limits.

In Scripture WO 2008/110830 A1 Reducing agents such as quinones and quinolines are added. Since the measurement is carried out cyclovoltametrisch, so the electrochemical reduction of the analyte / analytes is increased at the electrodes. In order to obtain an acceptable solubility, additional co-solvents have to be used when these reducing agents are added. Furthermore, redox catalysts can be added. Due to the cyclovoltamographischen mode of operation, the sensor is not suitable for the continuous monitoring of a gas mixture, but only for temporary measurements of gas mixtures with little varying composition.

adversely or in need of improvement in the case described above Approaches that use as electrolytes pure ionic liquids or mixtures of these, but also quasi-solid electrolytes is the performance of the gas sensors, both in terms of sensitivity, as well as the response time, selectivity and the robustness of the sensors.

task The present invention is an electrochemical gas sensor to provide, which has an improved performance, d. H. a higher selectivity, higher sensitivity as well offers greater robustness.

The Task is solved by an electrochemical gas sensor according to claim 1. Further preferred embodiments emerge from the dependent claims.

In other words, the object is achieved by an electrochemical gas sensor, which comprises a housing with at least one inlet opening, wherein in the housing at least two electrodes are connected, which are conductively connected to each other via an electrolyte system comprising a conductive liquid, which is substantially in a powdery and / or fibrous, unwound SiO ₂ based solid is absorbed. According to the gas sensor is characterized in that the conductive liquid is an ionic liquid having organic and / or organometallic and / or inorganic additives. "Substantially" here means that the ionic liquid is present at least 90%, preferably at least 95%, most preferably 99% absorbed.

It found so far in writings about ionic liquids no notice that the classical (aqueous) sensor systems to increase their sensitivity or selectivity often run over secondary reactions.

One reason for this may be that the chemical processes in ionic liquids differ fundamentally from those in aqueous or organic systems. Pioneer of this new chemistry, like the professors P. Wasserscheid (Angew Chem 2000, 112, 3926-3945) and KR Seddon (Pure Appl. Chem. Vol. 72, No. 7, pp. 1391-1398, 2000) , in this context, speak of a completely new and unexplored part of chemistry.

The insert is tested in 2, 3 and multi-electrode mode. 2 or 3 electrode systems are preferred, ie in the housing are preferably a measuring and a counter electrode (ME, GE) and in the case of a 3-electrode system additionally a reference electrode (RE). By equipping the sensor with a protective electrode or other measuring electrodes, multi-electrode systems are generated. The electrodes are preferably made of a metal from the group consisting of Cu, Ni, Ti, Pt, Ir, Au, Pd, Ag, Ru and Rh or mixtures or oxides of these metals or carbon, the materials of the individual electrodes being the same or different. They can have any suitable shape. The electrodes are preferably applied to a gas-permeable membrane or mixed in powder form directly with the electrolyte, ie with the powdery SiO ₂ -based solid which absorbs the ionic liquid with additives. In the second case, care must be taken that bridges of pure electrolyte powders are always between the electrode powders in order to prevent an electrical short circuit between the electrodes.

The Housing can be made of metal, but also from any other suitable Material exist. As opposed to ionic liquids to conventional electrolytes such as sulfuric acid have no strong corrosive effect, there is also little to no problems with regard to possible corrosion metallic housing. Also suitable are plastics as material for the housing.

The powdery SiO ₂ -based solid is preferably a silicate having an average particle size of at least 5 μm, preferably at least 50 μm, most preferably at least 75 μm; a specific surface area of at least 50 m ² / g, preferably at least 100 m ² / g, most preferably at least 150 m ² / g and an SiO ₂ content of at least 95% by weight. The term "silicate" includes SiO ₂ variants such as silica gels and silicates, for example "Sipernate" and "Sidente". It is preferably pure SiO ₂ and alumino and calcium silicates, with a wide variance in the specific surface area is possible, ie it work 50 m ² / g but also 500 m ² / g. Particularly preferred is a silicate which has an average particle size of 100 microns, a specific surface area of 190 m ² / g and an SiO ₂ content of at least 98 wt .-%.

In another preferred embodiment, the fibrous solid SiO ₂ -based solid is glass fiber.

The powdery and / or fibrous unwound SiO ₂ based solid in which the ionic liquid is substantially absorbed is present in the sensor as a bedding or lamination or in a compressed form. The bedding or stratification allows a very flexible design of the sensors. The pressing can be done in several steps. The pressed form as a pellet is particularly preferred since this also results in considerable advantages in the production. The assembly then takes place such that the pellet is preferably positioned between two electrodes and the whole is finally compressed by the sensor housing.

It is also preferred if the powdery and / or fibrous, SiO ₂ -based solid, in which the ionic liquid is substantially absorbed, is present in the sensor in pressed form with electrodes already pre-compressed therein. This has proved to be advantageous, since on the one hand a further production step is simplified, on the other hand the contact between electrodes and electrolytes is improved, which has a positive influence on the sensor sensitivity and response time.

The ratio of electrolyte to SiO ₂ based solid can be varied within wide limits. A ratio of electrolyte to SiO ₂ based solid of one part by weight to one part by weight to two parts by weight to one part by weight is particularly preferable. Despite the excess of electrolyte, an almost dry powder is still obtained, ie, the electrolyte is substantially absorbed (preferably at least 90%, more preferably at least 95%, most preferably at least 99%). The pellet obtained preferably has a weight of about 200 mg, of which 1/2 to 2/3 account for the electrolyte and 1/2 to 1/3 on the solid.

For the construction of the sensor are in principle all structures conceivable, even in the writings US 7,145,561 B2 . US 5,565,075 B . US 7,147,761 B2 and US 5,667,653 B are described in detail. This applies in particular to the design and the material of the housing, but also the arrangement and design of the quasi-solid electrolyte, ie the powdery and / or fibrous, unwound SiO ₂ based solid, in which the ionic liquid is substantially absorbed, in the sensor.

The ionic liquid contains at least one cation, which is selected from the group of imidazolium, Pyridinium, guanodinium and tetraalkylammonium salts, unsubstituted or substituted with at least one aryl and / or C1 to C4 alkyl group, which itself is unsubstituted or substituted with halogens, C1 to C4 alkyl groups, hydroxyl or amino groups. Preferably contains the ionic liquid at least imidazolium or Pyridinium cations, unsubstituted or with at least one C1- substituted to C4-alkyl group.

Regarding Of the anions it is preferred that the ionic liquid at least one anion from the group of halides, nitrates, nitrites, Tetrafluoroborates, hexafluorophosphates, polyfluoroalkanesulfonates, bis (trifluoromethylsulfonyl) imides, Alkyl sulfates, alkanesulfonates, acetates and the anions of fluoroalkanoic acids contains. Particularly preferred is the at least one anion selected from the group of C1-C6-alkyl sulfates and C1-C6-alkanesulfonates, wherein an anion from the group of methyl, ethyl, butyl sulfate and methane, ethane, butanesulfonate is highly preferred.

In a most preferred embodiment is the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate.

The The present invention also includes mixtures of various ionic Liquids. A mixture of different ionic liquids can used to different polarities in the electrolyte adjust. This can help solve certain additives, but also be helpful to the water absorption of the electrolyte to control.

The ionic liquid has organic and / or organometallic and / or inorganic additives. Surprisingly, these contribute significantly to the performance of the gas senso Both in terms of sensitivity, as well as the response time, selectivity and the robustness of the sensors. Even relatively low percentages result in decisive improvements.

mixtures Various additives are also included. this concerns Mixtures of different additives of the same group, eg. B. mixtures of various organic additives. Includes but also mixtures of different additives, d. H. mixtures from, for example, organic and organic additives. about Mixtures of various additives could cause cross-sensitivity patterns the sensors are adapted to specific needs.

Preferably are the organic and / or organometallic and / or inorganic Additions in 0.05 to 15% by weight in the ionic liquid contain. For the organic additives it has proved to be particularly suitable that these in 0.05 to 1.5% by weight are included. With regard to inorganic additives it is preferred that these are contained in 1 to 12% by weight. With respect to the organometallic additives has a Content of 0.05 to 1% by weight proved to be particularly suitable.

The Organic additives are preferably selected from the group of imidazole, pyridine, pyrrole, pyrazole, pyrimidine, Guanine, unsubstituted or substituted with at least one C1- to C4 alkyl group; Uric acid, benzoic acid and Porphyrins and their derivatives. Particularly preferred is the selection of organic additives from the group of imidazole or Pyrimidine, unsubstituted or substituted with at least one C1 to C4 alkyl group.

in the With regard to the organic additives one can assume that their Effect on a stabilization of the reference potential, as well as the pH value is based. This shows advantages, especially with acidic gases.

The organometallic additives are preferably selected from the group of the organometallic porphyrins and their derivatives, the organometallic porphyrins being particularly preferably selected from the group of porphyrins having at least one meso or β-alkyl or aryl substituent and derivatives thereof. With respect to the organometallic porphyrin derivatives, it is preferable to select them from the group of phthalocyanines having Mn ²⁺ , Cu ²⁺ , Fe ^{2+ / 3+} or 2b ²⁺ as the metal cation.

The inorganic additives are in particular selected from the group of alkali metal halides and ammonium halides, which are unsubstituted or substituted by C1 to C4 alkyl groups and the transition metal salts and lead salts, wherein the transition metal salts or lead salts are particularly preferably selected from the group of salts of Mn ²⁺ , Mn ³⁺ , Ag ⁺ , Cr ³⁺ , Cr ⁶⁺ , Fe ²⁺ , Fe ³⁺ and Pb ²⁺ . Particularly preferred inorganic additives are substances from the group of lithium bromide, lithium iodide, ammonium iodide, tetramethylammonium iodide, tetraethylammonium iodide, tetrapropylammonium iodide, tetrabutylammonium iodide, tetrabutylammonium bromide, manganese (II) chloride, manganese (II) sulfate, manganese (II) nitrate, chromium (III) chloride , Alkali chromates, iron (II) chloride, iron (III) chloride and lead (II) nitrate.

The addition of alkali and ammonium halides, such as. B. LiI or NaBr, NR ₄ I (R = H, methyl, ethyl, butyl or mixtures thereof) in low percentages (0.05 to 15%) leads to a significant increase in the sensitivity of the sensors to halogen Gases and vapors. The same can be observed when adding manganese and copper salts to the sensitivity of ammonia sensors.

One great advantage when using inorganic additives is the selectivity of the sensor, as it is the possibility provides a specific detection reaction for the target gas to generate. So can be different by the combination Additives also generate cross-sensitivity patterns that are classic Sensor systems as well as the use of pure ionic liquids would not be conceivable.

The Effect of supplements seems to rest on two principles. On the one hand, you can see a clear shift in the reference potential watch what the electrolytes without supplements probably leads to the stabilization of the signal. on the other hand the basic system seems to act as a buffer and prevent that the acid gases dissolve in the electrolyte and thus, via a change the pH, in turn, a shift of the reference potential to generate.

Of the Electrochemical gas sensor can be used for various measuring methods can be used, wherein the amperometric measurement is preferred. According to the invention, the electrochemical gas sensor therefore for the amperometric detection / measurement of gases from the group acid, basic, neutral, oxidizing or reducing gases and the halogen gases and vapors as well as the hydride gases. Detection / measurement includes both the qualitative detection, that a corresponding gas is present, as well as the quantitative Determination.

Preferably, the electrochemical Gas sensor Use for the amperometric detection / measurement of gases from the group of F ₂ , Cl ₂ , Br ₂ , I ₂ , O ₂ , O ₃ , ClO ₂ , NH ₃ , SO ₂ , H ₂ S, CO, CO ₂ , NO , NO ₂ , H ₂ , HCl, HBr, HF, HCN, PH ₃ , AsH ₃ , B ₂ H ₆ , GeH ₄ and SiH ₄ .

In a preferred embodiment, in which the ionic liquid contains organic additives, the use for amperometric detection / measurement of gases from the group of NH ₃ , SO ₂ , H ₂ S, H ₂ , HCl, HCN and the hydride gases is preferred.

In another embodiment, wherein the ionic liquid unsubstituted organic substituents selected from the group consisting of imidazole, pyridine, pyrrole, pyrazole, pyrimidine, guanine or substituted with at least one C1 to C4 alkyl group; Uric acid, benzoic acid and porphyrins and their derivatives, the use for the amperometric detection / measurement of gases from the group of NH ₃ , SO ₂ , H ₂ S is preferred. In the amperometric detection / measurement of gases from the group of NH ₃ , SO ₂ , H ₂ S, it is preferred that the ionic liquid organic additives selected from the group of imidazole or pyrimidine, unsubstituted or substituted with at least one C 1 to C 4 -Alkyl group.

For the amperometric detection / measurement of gases from the group of F ₂ , Cl ₂ , Br ₂ , I ₂ , O ₃ , ClO ₂ , NH ₃ , H ₂ , HCl, HCN and the hydride gases, it is preferred that the ionic liquid contains inorganic additives. In the amperometric detection / measurement of gases from the group of Cl ₂ , Br ₂ , O ₃ , ClO ₂ and NH ₃ , it is then particularly preferred that the ionic liquid inorganic additives from the group of alkali halides and ammonium halides, which are unsubstituted or with C1 to C4 alkyl groups are substituted and the transition metal salts and lead salts, preferably selected from the group of salts of Mn ²⁺ , Mn ³⁺ , Ag ⁺ , Cr ³⁺ , Cr ⁶⁺ , Fe ²⁺ , Fe ³⁺ and Pb ²⁺ . With these gases (Cl ₂ , Br ₂ , O ₃ , ClO ₂ and NH ₃ ), it is most preferred if the ionic liquid contains inorganic additives from the group of lithium bromide, lithium iodide, tetrabutylammonium iodide, tetrabutylammonium bromide, manganese (II) chloride, manganese ( II) sulfate, manganese (II) nitrate, chromium (III) chloride, alkali chromates, iron (II) chloride, iron (III) chloride and lead (II) nitrate.

A further preferred embodiment relates to the use of the electrochemical gas sensor for the amperometric detection / measurement of gases from the group of CO, O ₂ , NO, NO ₂ and H ₂ , the ionic liquid containing organometallic additives. In these gases (CO, O ₂ , NO, NO ₂ and H ₂ ), it is particularly preferred if the ionic liquid contains organometallic additives from the group of organometallic porphyrins and their derivatives. Substances from the group of the phthalocyanines with Mn ²⁺ , Cu ²⁺ , Fe ^{2+ / 3+} or Pb ²⁺ as metal cation are particularly preferred as organometallic additions to the ionic liquid.

The Solutions, d. H. the ionic liquids, which organic and / or organometallic and / or inorganic additives contain, act as second-order conductors in gas sensors in the classical sense of a Clark cell with noble metal catalysts or carbon as measuring and counterelectrode (ME, GE) as a two-electrode system or with an additional reference electrode (BE) in three-electrode mode or with additional additional electrodes, if the Sensor equipped with a protective electrode or other measuring electrodes. The additives can be ionic liquids be added in the form of an aqueous solution or also melted together with these or suspended in these become. The type of addition depends on the water solubility of the aggregate, of the hydrophilicity of the ionic liquid and on the expected secondary reaction.

Description of the illustrations / figures

1 Construction diagram of a three-electrode electrochemical gas sensor with quasi-solid electrolyte (variant 1 );

2 Construction diagram of a three-electrode electrochemical gas sensor with quasi-solid electrolyte (variant 2 );

1 Sensor performance of a chlorine sensor with ionic liquid as electrolyte containing imidazole and LiBr as additives to 4 ppm chlorine gas;

2 Performance of a NH3 sensor with 1% MnCl ₂ as an additive to the electrolyte with silica gel;

1 shows a gas sensor 1 that made a sensor housing 2 consists in which the measuring electrode 3a , Reference electrode 5 and counter electrode 6 are installed so that the measuring electrode 3a via a gas-permeable membrane 3 is connected to the outside atmosphere. The measuring electrode 3a consists of a layer of catalyst / electrode material and electrolyte, ie ionic liquid with additive, which is absorbed in a powdery SiO ₂ based solid. The electrodes are connected to each other via a separator 4 based on glass fibers or silicate structures, which are impregnated with said electrolyte, electrically conductively connected. The reference electrode 5 and counter electrode 6 Both are next to each other on the rode of the Messelekt 3a opposite side of the separator 4 , In the sensor backspace provides a compensation volume men 7 that atmospheric moisture can absorb water. The sensor is equipped with measuring electronics 8th connected, on the one hand holds the potential difference between the measuring and the reference electrode stable and on the other hand amplifies the sensor current in the presence of target gas to a measuring signal.

2 shows another variant of a gas sensor 1 that made a sensor housing 2 consists in which the measuring electrode 3a , Reference electrode 5 and counter electrode 6 are installed so that the measuring electrode 3a via a gas-permeable membrane 3 is connected to the outside atmosphere. The measuring electrode 3a consists of a layer of catalyst / electrode material and electrolyte, ie ionic liquid with additive, which is absorbed in a powdery SiO ₂ based solid. The measuring electrode 3a and the reference electrode 5 are with each other via a separate 4a based on glass fibers or silicate structures, which are impregnated with said electrolyte, electrically conductively connected. About another separator 4b there is an electrically conductive connection to the counter electrode 6 which is located on that of the reference electrode 5 opposite side of the separator 4b located. In the sensor backspace provides a compensation volume 7 that atmospheric moisture can absorb water. The sensor is equipped with measuring electronics 8th connected, on the one hand holds the potential difference between the measuring and the reference electrode stable and on the other hand amplifies the sensor current in the presence of target gas to a measuring signal.

1 shows the performance of sensors with aggregate, where the signal stabilization by the addition of lithium bromide and imidazole to the electrolyte takes place. 1-Ethyl-3-Methylimidazoliummethansulfonat (EMIM MeSO3) with 5% lithium bromide or 1% imidazole were mixed together in a ratio of 1 to 2 and then the mixture is also mixed in a ratio of 2 to 1 with a silica gel. The resulting powder was then pressed to about 1 mm thick slices. The fumigation was carried out with 4 ppm Cl ₂ in air at a flow of 200 l / h. The sensors show a short response time and a high sensitivity to chlorine with a small signal spread between different sensors and an excellent signal to noise ratio.

2 shows the performance with an NH ₃ sensor, wherein the electrolyte is EMIM MeSO3 with 1% MnCl ₂ as an additive, absorbed on silica gel. The fumigation was carried out with 50 ppm NH ₃ in air at a flow of 200 l / h.

1

gas sensor

2

sensor housing

3

Gas permeable Membrane between measuring electrode and opening for gas inlet

3a

layer made of catalyst / electrode material and electrolyte as measuring electrode

4, 4a, 4b

Separator (s) impregnated with electrolyte on a fiberglass or silicate basis

5

reference electrode

6

counter electrode

7

compensating volume

8th

measuring electronics for amplifying the sensor signal

following the invention will be further explained by way of examples.

Examples

Example 1: Cl ₂ sensor

The structure is analogous to the sensor sketch in 1 with a measuring electrode (ME) made of a mixture of gold (Au) and carbon (C) counter electrode (GE) = reference electrode (BE) made of platinum (Pt). The electrodes are each applied to a gas-permeable PTFE membrane. Between the electrodes there are electrolyte-impregnated separators made of silica gel in order to ensure electrical conductivity between the electrodes and to prevent short circuits between the electrodes. Deviating from the sketch in 1 The sensor also works if the BEs and GE are not parallel but one above the other (see variant 2 in 2 ). The electrolyte consists of 1-ethyl-3-methylimidazolium methanesulfonate (EMIM MeSO3) with one weight percent imidazole and lithium bromide as additive. The additive is then added in each case in solid form to the heated to 100 ° C EMIM MESO3. It creates a clear solution. This is mixed in a ratio of 1: 2 with silica gel. The resulting powder is pressed in a tablet press to 1 mm thick slices. The fumigation was carried out with 4 ppm Cl ₂ in air at a flow of 200 l / h.

The result is graphically in 1 shown.

Example 2: SO ₂ sensor

The sensor is constructed analogously to Example 1. Deviating the measuring electrode is not applied to a membrane, but pressed the catalyst with the electrolyte powder directly to an electrode, which is covered by a PTFE membrane. Fumigation was carried out with 10 ppm SO ₂ gas in air at a flow of 200 l / h.

Example 3: NH ₃ sensor

The sensor is constructed analogously to Example 1. In contrast to Example 1, the electrolyte EMIM MeSO3 contains 1% MnCl ₂ . This is stirred in crystalline form in the heated to 100 ° C ionic liquid until a clear solution is obtained. This is mixed in a ratio of 1: 2 with silica gel. The resulting powder is pressed in a tablet press to 1 mm thick slices. The sensor also works when a ME of pure carbon is used instead of a ME made from a mixture of gold and carbon. The fumigation was carried out with 50 ppm NH ₃ in air at a flow of 200 l / h.

The result is graphically in 2 shown.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 3328277 B [0005]
• US 7145561 B2 [0007, 0025]
• US 7147761 B2 [0007, 0025]
• US 5565075 B [0007, 0025]
• US 5667653 B [0007, 0025]
• - US 4169779 B [0008]
• WO 2008/110830 A1 [0010, 0011]

Cited non-patent literature

• P. Wasserscheid (Angew Chem 2000, 112, 3926-3945) [0017]
• - KR Seddon (Pure Appl. Chem. Vol. 72, No. 7, pp. 1391-1398, 2000) [0017]

Claims (36)

An electrochemical gas sensor, comprising a housing having at least one inlet opening, wherein in the housing at least two electrodes are connected, which are conductively connected to each other via an electrolyte system comprising a conductive liquid, which is substantially in a powdery and / or fibrous unwound on SiO ₂ is absorbed based solid, characterized in that the conductive liquid is an ionic liquid having organic and / or organometallic and / or inorganic additives. Electrochemical gas sensor according to claim 1, characterized in that the powdery solid based on SiO ₂ is a silicate having an average particle size of at least 5 microns, preferably at least 50 microns, most preferably at least 75 microns; a specific surface area of at least 50 m ² / g, preferably at least 100 m ² / g, most preferably at least 150 m ² / g and an SiO ₂ content of at least 95% by weight. Electrochemical gas sensor according to claim 1 or 2, characterized in that the powdery SiO ₂ based solid is a silicate having a mean particle size of 100 microns, a specific surface area of 190 m ² / g and a SiO ₂ content of at least 98 wt .-% having. Electrochemical gas sensor according to one of Claims 1 to 3, characterized in that the fibrous, unwound SiO ₂ -based solid is glass fiber. Electrochemical gas sensor according to one of claims 1 to 4, characterized in that the powdery and / or fibrous, unwound solid based on SiO ₂ , in which the ionic liquid is substantially absorbed, in the sensor as a bedding or layering or in pressed form. Electrochemical gas sensor according to one of claims 1 to 5, characterized in that the powdery and / or fibrous, unwound SiO ₂ based solid, in which the ionic liquid is substantially absorbed, is present in the sensor in pressed form with already pressed therein electrodes. Electrochemical gas sensor according to one of the claims 1 to 6, characterized in that the electrodes are made of a metal from the group of Cu, Ni, Ti, Pt, Ir, Au, Pd, Ag, Ru and Rh or Mixtures or oxides of these metals or carbon, wherein the materials of the individual electrodes are the same or different are. Electrochemical gas sensor according to one of the claims 1 to 7, characterized in that the ionic liquid contains at least one cation which is selected is from the group of imidazolium, pyridinium, guanodinium and Mono-, di-, tri- and Tetraalkylamonium salts, unsubstituted or with substituted at least one aryl and / or C1 to C4 alkyl group, which itself is unsubstituted or substituted with halogens, C1 to C4 alkyl groups, hydroxyl or amino groups. Electrochemical gas sensor according to one of the claims 1 to 8, characterized in that the ionic liquid at least imidazolium or pyridinium cations, unsubstituted or substituted with at least one C 1 to C 4 alkyl group, contains. Electrochemical gas sensor according to one of the claims 1 to 9, characterized in that the ionic liquid at least one anion from the group of halides, nitrates, nitrites, Tetrafluoroborates, hexafluorophosphates, polyfluoroalkanesulfonates, bis (trifluoromethylsulfonyl) imides, Alkyl sulfates, alkanesulfonates, acetates and the anions of fluoroalkanoic acids contains. Electrochemical gas sensor according to one of the claims 1 to 10, characterized in that the ionic liquid at least one anion from the group of C1-C6-alkyl sulfates and C1-C6-alkanesulfonates contains. Electrochemical gas sensor according to one of the claims 1 to 11, characterized in that the ionic liquid at least one anion from the group of methyl, ethyl, butyl sulfate and methane, ethane, butanesulfonate. Electrochemical gas sensor according to one of the claims 1 to 12, characterized in that the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate. Electrochemical gas sensor according to one of the claims 1 to 13, characterized in that the organic and / or organometallic and / or inorganic additives in 0.05 to 15% by weight are included. Electrochemical gas sensor according to one of the claims 1 to 14, characterized in that the organic additives contained in 0.05 to 1.5% by weight. Electrochemical gas sensor according to one of claims 1 to 15, characterized in that the inorganic additives in 1 to 12 Ge weight% are included. Electrochemical gas sensor according to one of the claims 1 to 16, characterized in that the organometallic additives in 0.05 to 1% by weight. Electrochemical gas sensor according to one of the claims 1 to 17, characterized in that the organic additives are selected from the group of imidazole, pyridine, pyrrole, Pyrazole, pyrimidine, guanine, unsubstituted or substituted with at least a C1 to C4 alkyl group; Uric acid, benzoic acid and porphyrins and their derivatives. Electrochemical gas sensor according to one of the claims 1 to 18, characterized in that the organic additives are selected from the group of imidazole or pyrimidine, unsubstituted or substituted with at least one C1 to C4 alkyl group. Electrochemical gas sensor according to one of the claims 1 to 19, characterized in that the organometallic additives are selected from the group of organometallic porphyrins and their derivatives. Electrochemical gas sensor according to one of the claims 1 to 20, characterized in that the organometallic porphyrins are selected from the group of porphyrins having at least one meso or β-alkyl or aryl substituents and their derivatives. Electrochemical gas sensor according to one of claims 1 to 21, characterized in that the organometallic porphyrin derivatives are selected from the group of phthalocyanines with Mn ²⁺ , Cu ²⁺ , Fe ^{2 + / 3 +} or Pb ²⁺ as metal cation. Electrochemical gas sensor according to one of the claims 1 to 22, characterized in that the inorganic additives are selected from the group of alkali halides and Ammonium halides which are unsubstituted or with C1 to C4 alkyl groups and the transition metal salts and lead salts. Electrochemical gas sensor according to one of claims 1 to 23, characterized in that the transition metal salts or lead salts are selected from the group of salts of Mn ²⁺ , Mn ³⁺ , Ag ⁺ , Cr ³⁺ , Cr ⁶⁺ , Fe ²⁺ , Fe ³⁺ and Pb ²⁺ . Electrochemical gas sensor according to one of the claims 1 to 24, characterized in that the inorganic additives are selected from the group of lithium bromide, lithium iodide, ammonium iodide, Tetramethylammonium iodide, tetraethylammonium iodide, tetrapropylammonium iodide, tetrabutylammonium iodide, Tetrabutylammonium bromide, manganese (II) chloride, manganese (II) sulfate, manganese (II) nitrate, Chromium (III) chloride, alkali chromates, iron (II) chloride, iron (III) chloride and lead (II) nitrate. Use of an electrochemical gas sensor according to one of claims 1 to 25 for amperometric detection / measurement of gases from the group of acidic, basic, neutral, oxidizing or reducing gases and halogen gases and vapors and the hydride gases. Use of an electrochemical gas sensor according to claim 26 for the amperometric detection / measurement of gases from the group of F ₂ , Cl ₂ , Br ₂ , I ₂ , O ₂ , O ₃ , ClO ₂ , NH ₃ , SO ₂ , H ₂ S, CO , CO ₂ , NO, NO ₂ , H ₂ , HCl, HBr, HF, HCN, PH ₃ , AsH ₃ , B ₂ H ₆ , GeH ₄ and SiH ₄ . Use of an electrochemical gas sensor according to one of claims 26 or 27 for the amperometric detection / measurement of gases from the group of NH ₃ , SO ₂ , H ₂ S, H ₂ , HCl, HCN and the hydride gases, wherein the ionic liquid organic additives contains. Use of an electrochemical gas sensor according to any one of claims 26 to 28 for the amperometric detection / measurement of gases from the group of NH ₃ , SO ₂ , H ₂ S, wherein the ionic liquid organic additives from the group of imidazole, pyridine, pyrrole, pyrazole, Pyrimidine, guanine, unsubstituted or substituted with at least one C1 to C4 alkyl group; Uric acid, benzoic acid and porphyrins and derivatives thereof. Use of an electrochemical gas sensor according to any one of claims 26 to 29 for the amperometric detection / measurement of gases from the group of NH ₃ , SO ₂ , H ₂ S, wherein the ionic liquid unsubstituted or substituted organic additives selected from the group of imidazole or pyrimidine with at least one C1 to C4 alkyl group. Use of an electrochemical gas sensor according to one of claims 26 or 27 for the amperometric detection / measurement of gases from the group of F ₂ , Cl ₂ , Br ₂ , I ₂ , O ₃ , ClO ₂ , NH ₃ , H ₂ , HCl, HCN and the hydride gases, the ionic liquid containing inorganic additives. Use of an electrochemical gas sensor according to any one of claims 26 to 27 or 31 for the amperometric detection / measurement of gases from the group of Cl ₂ , Br ₂ , O ₃ , ClO ₂ and NH ₃ , wherein the ionic liquid inorganic additives from the group of alkali halides and ammonia umhalogenide which are unsubstituted or substituted with C1 to C4 alkyl groups and the transition metal salts and lead salts, preferably selected from the group of salts of Mn ^2+, Mn ^3+, Ag ^+, Cr ^3+, Cr ^6+, Fe ²⁺ , Fe ³⁺ and Pb ²⁺ . Use of an electrochemical gas sensor according to any one of claims 26 to 27 or 31 to 32 for the amperometric detection / measurement of gases from the group of Cl ₂ , Br ₂ , O ₃ , ClO ₂ and NH ₃ , wherein the ionic liquid inorganic additives from the group of lithium bromide, lithium iodide, tetrabutylammonium iodide, tetrabutylammonium bromide, manganese (II) chloride, manganese (II) sulfate, manganese (II) nitrate, chromium (III) chloride, alkali chromates, iron (II) chloride, iron (III) chloride and lead (II ) contains nitrate. Use of an electrochemical gas sensor according to claim 26 to 27 for the amperometric detection / measurement of gases from the group of CO, O ₂ , NO, NO ₂ and H ₂ , wherein the ionic liquid contains organometallic additives. Use of an electrochemical gas sensor according to any one of claims 26 to 17 or 34 for amperometric detection / measurement of gases from the group of CO, O ₂ , NO, NO ₂ and H ₂ , wherein the ionic liquid organi cal additions from the group of organometallic porphyrins and their derivatives. Use of an electrochemical gas sensor according to any one of claims 26 to 27 or 34 to 35 for the amperometric detection / measurement of gases from the group of CO, NO, NO ₂ and H ₂ , wherein the ionic liquid organometallic additives from the group of phthalocyanines with Mn ^{2 +} , Cu ²⁺ , Fe ^{2 + / 3 +} or Pb ²⁺ as metal cation.