Abstract
An electrochemical gas sensor (10) includes a housing (11) which has a number of electrodes (31, 32), i.e. at least one working electrode (31) and at least one counter electrode (32), in addition to a liquid electrolyte (60). At least one of the electrodes (31, 32) and/or the housing (11) are at least partially formed of an absorption agent composition. A method of detecting acid gases employs the electrochemical gas sensor (10).
Claims
1. An electrochemical gas sensor comprising: a housing; a plurality of electrodes comprising at least one working electrode and at least one counterelectrode; and a liquid electrolyte, wherein at least one of the plurality of electrodes or the housing, or both at least one of the electrodes and the housing is comprised of an absorbent composition, the absorbent composition comprising a carbonate compound.
2. An electrochemical gas sensor in accordance with claim 1, wherein the counterelectrode consists of the absorbent composition.
3. An electrochemical gas sensor in accordance with claim 1, wherein the housing has a recess, which forms a gas outlet, wherein the absorbent composition is arranged fully or partially in the recess.
4. An electrochemical gas sensor in accordance with claim 1, wherein the absorbent composition contains at least one absorbent, a carrier material and an additive.
5. An electrochemical gas sensor in accordance with claim 4, wherein the absorbent composition contains carbon nanotubes as the additive.
6. An electrochemical gas sensor in accordance with claim 1, wherein the absorbent composition contains an absorbent, which is poorly soluble or insoluble in the electrolyte.
7. An electrochemical gas sensor in accordance with claim 1, wherein the carbonate compound comprises an alkali carbonate compound or an alkaline earth compound, comprising BaCO.sub.3 as the absorbent.
8. An electrochemical gas sensor in accordance with claim 1, wherein the absorbent composition contains a microfibrous material as a carrier material.
9. An electrochemical gas sensor in accordance with claim 1, wherein the absorbent composition contains a Teflon material as an additive.
10. An electrochemical gas sensor in accordance with claim 1, wherein the electrolyte is a composition that contains an organic solvent and a conducting salt.
11. An electrochemical gas sensor in accordance with claim 1, wherein the counterelectrode is rod-shaped.
12. An electrochemical gas sensor in accordance with claim 11, wherein the working electrode surrounds the rod-shaped counterelectrode in a tubular manner.
13. An electrochemical gas sensor in accordance with claim 1, further comprising at least one separating layer comprising a hydrophilic separating layer or an electrolyte-impregnated separating layer or both a hydrophilic and electrolyte-impregnated separating layer, is arranged between the counterelectrode and the working electrode.
14. An electrochemical gas sensor in accordance with claim 1, further comprising a protective electrode or a reference electrode or both a protective electrode and a reference electrode.
15. An electrochemical gas sensor in accordance with claim 1, wherein the absorbent composition contains a carrier material comprising glass fibers, microfibers, nanofibers, polymer microfibers or polymer nanofibers or any combination of glass fibers, microfibers, nanofibers, polymer microfibers and polymer nanofibers.
16. An electrochemical gas sensor in accordance with claim 1, wherein the electrolyte is a composition that contains an organic solvent, which contains a quinoid system, and a conducting salt, which contains an organic cation.
17. A method of detecting a gas, the method comprising the steps of: providing a gas sensor comprising: a housing; a plurality of electrodes comprising at least one working electrode and at least one counterelectrode; and a liquid electrolyte; forming at least one of the plurality of electrodes or the housing at least partially of an absorbent composition, the absorbent composition comprising a carbonate compound; detecting a gas with the gas sensor.
18. A method according to claim 17, wherein the step of detecting a gas with the gas sensor comprises detecting sour gases or gas mixtures containing one or more sour gas with the gas sensor.
19. A method according to claim 17, wherein HF, HCl or acetic acid or any combination of HF, HCl and acetic acid is detected with the gas sensor.
20. A method according to claim 17, wherein: the carbonate compound comprises an alkali carbonate compound or an alkaline earth compound comprising BaCO.sub.3 as the absorbent; and the absorbent composition contains a carrier material comprising glass fibers, microfibers, nanofibers, polymer microfibers or polymer nanofibers or any combination of glass fibers, microfibers, nanofibers, polymer microfibers and polymer nanofibers.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) In the drawings:
(2) FIG. 1a is a schematic top view showing a design of a gas sensor according to the present invention, in which the counterelectrode consists of the absorbent composition;
(3) FIG. 1b is a schematic cross sectional view through the reaction chamber of the gas sensor along line A-A in FIG. 1a;
(4) FIG. 1c is a schematic side view of the gas sensor of FIG. 1a;
(5) FIG. 2a is a schematic top view showing a design of a gas sensor according to the present invention with an auxiliary electrode, which consists of the absorbent composition;
(6) FIG. 2b is a schematic cross sectional view through the reaction chamber of the gas sensor along line A-A in FIG. 2a;
(7) FIG. 2c is a schematic side view of the gas sensor of FIG. 2a;
(8) FIG. 3a is a schematic top view showing a design of a gas sensor according to the present invention, in which the absorbent composition forms a plug in the gas outlet of the gas sensor;
(9) FIG. 3b is a schematic cross sectional view through the reaction chamber of the gas sensor along line A-A in FIG. 3a; and
(10) FIG. 3c is a schematic side view of the gas sensor.
(11) FIG. 4a is a schematic top view showing a design of a gas sensor according to the present invention;
(12) FIG. 4b is a cross sectional view through the reaction chamber of the gas sensor along line A-A in FIG. 4a; and
(13) FIG. 4c is a schematic side view of the gas sensor;
(14) FIG. 5 is a schematic perspective view showing a design of an electrode arrangement according to the present invention, in which a separating layer and a working electrode are wound around a rod-shaped counterelectrode consisting of the absorbent composition;
(15) FIG. 6a is a schematic sectional view showing an alternative schematic design of a gas sensor according to the present invention; and
(16) FIG. 6b is a schematic sectional view showing the sensor shown of FIG. 6a rotated by 90.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(17) Referring to the drawings, The gas sensor 10 shown in FIGS. 1a through 1c, 2a through 2c, 3a through 3c, 4a through 4c, 6a and 6b has a housing 11, which encloses a reaction chamber 21. A first recess 23 and a second recess 24 are formed in the housing 11. The first recess 23 is a gas inlet, through which gas to be analyzed can flow into the reaction chamber 21. The second recess 24 is a gas outlet, through which gas formed at the counterelectrode 32 can flow out of the reaction chamber 21. The electrodes 31, 32 of the gas sensor 10, namely, the working electrode 31 and the counterelectrode 32, are arranged in the reaction chamber 21. There is a separating layer 50 between the working electrode 31 and the counterelectrode 32. The separating layer 50 is hydrophilic.
(18) Furthermore, there is a hydrophobic membrane 41 between the working electrode 31 and the first recess 23. Another hydrophobic membrane 43 is located between the counterelectrode 32 and the second recess 24. The two hydrophobic membranes 41, 43 prevent electrolyte 60 from escaping from the reaction chamber 21 and at the same time protect the electrodes 31, 32 located opposite the recesses 23, 24 from dust and contamination, which could otherwise possibly be introduced into the reaction chamber 21 through the recesses 23, 24.
(19) The gas sensor 10 has, furthermore, an electrolyte reservoir 12, in which a liquid electrolyte 60 is contained. It is seen that the separating layer 50 connects the electrolyte reservoir 12 with the reaction chamber 21. The separating layer 50 is impregnated with the liquid electrolyte 60. The reaction chamber 21 is in fluidic connection in this way with the electrolyte reservoir 12. Electrolyte channels 51 are formed on the side of the separating layer 50. These are used to support the fluidic connection between the electrolyte reservoir 12 and the reaction chamber 21.
(20) The gas sensor 10 shown in FIGS. 2a through 2c and 4a through 4c has, furthermore, a reference electrode 33. It is seen that the reference electrode 33 is also connected with the electrolyte reservoir 12 via the separating layer 50. As can also be seen, the reference electrode 33 is covered by the separating layer 50 in the examples shown. It is, however, also conceivable in a variant, not shown, that the reference electrode 33 is embedded in the separating layer 50. In any case, the reference electrode 33 is also in fluidic connection with the electrolyte reservoir 12, so that the electrolyte 60 is sent to the reference electrode 33 from the electrolyte reservoir 12 by means of the separating layer 50. It is seen in the top view shown in FIG. 2a that the reference electrode 33 is arranged at a laterally spaced location from the electrodes 31, 32, 34 arranged in the reaction chamber 21. However, all electrodes of the gas sensor 10 are at the same time in a conductive contact with one another through the electrolyte 60.
(21) The gas sensor 10 shown as an example in FIGS. 2a through 2c and 4a through 4c has, in addition to the electrodes 31, 32, 33 already described, a protective electrode 34 arranged between the working electrode 31 and the counterelectrode 32. It is seen that the electrodes 31, 32, 34 are arranged in a sandwich-like manner. The separating layer 50 is arranged above the working electrode 31. It is seen that the separating layer 50 fully covers the working electrode 31. The protective electrode 34 is arranged above the separating layer 50. The protective electrode 34 is covered by a membrane 42. The membrane 42 is a diffusion-limiting membrane in a special variant. Another layer of the separating layer 50 is formed above the membrane 42. The counterelectrode 32 is arranged on this separating layer 50. The protective electrode 34 is designed in this arrangement of the electrodes 31, 32, 34 such that the surface area of the protective electrode 34 is larger than the surface area of the working electrode 31 and larger than the surface area of the counterelectrode 32.
(22) In the embodiment shown in FIGS. 4a through 4c as well as 6a and 6b, the housing 11 is formed by an electrolyte reservoir 12 and an electrode carrier 20. The part of the housing 11 facing the viewer is shown as being transparent in the view shown in FIG. 4a especially in the area of the electrode carrier 20 to illustrate how the arrangement of the components described below may be in the interior of the electrode carrier 20.
(23) A liquid electrolyte 60 is present in the electrolyte reservoir 12 here as well. The electrode carrier 20 has a reaction chamber 21. Gas can enter the reaction chamber 21 through a first recess 23 (can be seen in FIGS. 4b and 6b) and escape through a second recess 24. The first recess 23 is formed on the underside of the electrode carrier 20 in the example being shown, while the second recess 24 is formed in the opposite top side of the electrode carrier 20. It is obvious that it is also conceivable, as an alternative, that the first recess 23 is formed in the top side and the second recess 24 in the underside of the electrode carrier 20. It is thus seen that the electrode carrier 20 has at least one first recess 23.
(24) The reaction chamber 21 is connected with the electrolyte reservoir 12 via a separating layer 50 here as well, so that the reaction chamber 21 is in a fluidic connection with the electrolyte reservoir 12 via the separating layer 50. To improve the feed of the electrolyte 60 even more, electrolyte channels 51 are formed on the side of the separating layer 50. It is, of course, also conceivable that only one electrolyte channel 51 is formed or that more than two electrolyte channels 51 are present.
(25) It is seen in both FIG. 4b and FIG. 4c as well as in FIG. 6b that the reaction chamber 21 is defined by a first wall section 25 and a second wall section 26 of the electrode carrier 20. Therefore, the electrode carrier 20 forms the reaction chamber 21. The electrodes 31, 32, 34 are arranged here between the first wall section 25 and the second wall section 26. Furthermore, it is seen that the reaction chamber 21 is connected with the ambient air via the first and second recesses 23, 24. It is seen, furthermore, in FIG. 4c that the electrode carrier 20 forms a section of the housing 11 of the gas sensor 10. The housing 11 comprises here the wall of the electrolyte reservoir 12 and the wall of the electrode carrier 20. The separating layer 50 is arranged in the electrode carrier 20 such that it is in direct contact with the electrolyte 60 present in the electrolyte reservoir 12.
(26) The separating layer 50, especially a section 52 of the separating layer 50 protruding from the electrode carrier 20, is in direct contact with the electrolyte 60 present in the electrolyte reservoir 12 in the alternative embodiment of the gas sensor 10 shown in FIGS. 6a and 6b as well. It is seen here as well that the electrode carrier 20 forms a section of the housing 11. The electrode carrier 20 has a fastening section 22. The electrode carrier 20 is fixed with this fastening section 22 in a receptacle 13 of the electrolyte reservoir 12. The electrode carrier 20 is arranged here such that the part of the electrode carrier 20 in which the reaction chamber 21 is formed forms a section of the housing 11. The electrode carrier 20 has an inner surface and an outer surface 28 in this area. The inner surface defines the reaction chamber 21. The outer surface 28 forms a section of the outer housing wall of the gas sensor 10.
(27) In the exemplary embodiments shown in FIGS. 1a through 1c and 2a through 2c, the counterelectrode 32 consists of the absorbent composition 70. In a first variant, the absorbent composition 70 consists of a mixture of BaCO.sub.3 as an absorbent, comminuted glass fibers as the carrier material and carbon nanotubes as the additive.
(28) The absorbent composition 70 is arranged in the form of a plug in the recess 24, which forms the gas outlet, in the gas sensor 10 shown in FIGS. 3a through 3b. Gas flowing out of the gas sensor 10 must now flow through the recess 24, i.e., through the gas outlet, and therefore through the absorbent composition 70. In a first variant, the absorbent composition 70 consists of a composition that contains BaCO.sub.3 as the absorbent, glass fibers as the carrier material and Teflon fibers as an additive. In a second variant, the absorbent composition 70 consists of CaCO.sub.3 as an absorbent, glass fibers as a carrier material and Teflon fibers as an additive. It is also conceivable, as an alternative, that another alkali carbonate or alkaline earth carbonate is contained as the absorbent in the absorbent composition 70.
(29) In one embodiment, not shown, the gas sensor 10 is configured as shown in FIGS. 1a through 1c. In addition to the counterelectrode 32 consisting of a first absorbent composition, absorbent composition 70 may also be arranged in this embodiment in the form of a plug in the recess 24 that forms the gas outlet. In a first variant, the absorbent composition 70 has the same composition as the first absorbent composition, of which the counterelectrode 32 consists. The absorbent composition contains here BaCO.sub.3 as an absorbent, glass fibers as a carrier material and carbon nanotubes as an additive. In a second variant, the absorbent composition 70 has a different composition than the absorbent composition of which the counterelectrode 32 consists. In this variant, the absorbent composition, of which the counterelectrode 32 consists, contains BaCO.sub.3 as an absorbent, glass fibers as a carrier material and carbon nanotubes as an additive. The absorbent composition 70, which is arranged in the recess 24, i.e., in the gas outlet, contains BaCO.sub.3 or, in other variants, another alkali or alkaline earth carbonate as the absorbent, glass fibers as the carrier material and Teflon fibers as the additive.
(30) In another embodiment, not shown, the gas sensor 10 is configured corresponding to FIGS. 2a through 2c, and absorbent composition 70 is additionally arranged in the recess 24, which forms the gas outlet. The absorbent composition 70 has, in a first variant, the same composition as the absorbent composition of which the counterelectrode 32 consists. As in the variants of the embodiment shown in FIGS. 1a through 1c, the absorbent composition contains BaCO.sub.3 as the absorbent, glass fibers as the carrier material and carbon nanotubes as the additive. In a second variant, the absorbent composition 70 has a different composition than the absorbent composition of which the counterelectrode 32 consists. The absorbent composition, of which the counterelectrode 32 consists, contains BaCO.sub.3 as the absorbent, glass fibers as the carrier material and carbon nanotubes as the additive in this variant as well. The absorbent composition 70, which is arranged in the recess 24, i.e., in the gas outlet, contains BaCO.sub.3 or, in other variants, another alkali carbonate or alkaline earth carbonate, glass fibers as the carrier material and Teflon fibers as the additive.
(31) In yet another embodiment, not shown, the gas sensor 10 is configured corresponding to the FIGS. 3a through 3c, and absorbent composition 70 is arranged not only in the recess 24, which forms the gas outlet, but the counterelectrode 32 also consists of absorbent composition. In a first variant, the absorbent composition 70 has the same composition as the absorbent composition of which the counterelectrode 32 consists. In a second variant, the absorbent composition 70 has a different composition than the absorbent composition of which the counterelectrode 32 consists. The respective absorbent compositions may have the compositions as described above in both variants.
(32) The counterelectrode 32 consists of the absorbent composition in the embodiments of the gas sensor 10 shown in FIGS. 4a through 4c and 6a as well as 6b as well. In a first variant, not shown, absorbent composition 70 is additionally arranged in the form of a plug in the recess 24 in this case as well. The absorbent composition 70, which is arranged in the gas outlet, i.e., in the recess 24, as the same as the absorbent composition of which the counterelectrode 32 consists. Absorbent composition 70 is also additionally arranged in the form of a plug in the recess 24, which forms the gas outlet, in a second variant, not shown. However, the composition of the absorbent composition 70 arranged in the gas outlet, i.e., in the recess 24, differs from the composition of the absorbent composition of which the counterelectrode 32 consists.
(33) A special embodiment variant of the arrangement of the working and counterelectrodes 31, 32 is seen in FIG. 5. The counterelectrode 32 is formed here from the absorbent composition and is rod-shaped. The working electrode 31 is configured as a tube (is tubular) and is plugged onto the counterelectrode 32. The separating layer 50 is formed between the working electrode 31 and the counterelectrode 32. In an alternative embodiment, the counterelectrode 32 may also be in the form of a tube (tubular).
(34) An example of a composition of an electrolyte, as it can be used together with the above-described exemplary embodiments, is a mixture of about 60 wt. % of propylene carbonate, about 40 wt. % of ethylene carbonate, about 0.1 mole of HMIM FAP [1-hexyl-3-methyl-imidazolium-tris(pentafluoroethyl)-trifluorophosphate] and about 0.5 mole of tert.-butyl hydroquinone. This composition is, of course, variable, and the ratio of propylene carbonate to ethylene carbonate is not limited to a ratio of 60:40 wt. % by any means. The molar quantity of HMIM FAP and tert.-butyl hydroquinone contained is also variable.
(35) All the features and advantages, including configuration details, arrangements in space and method steps appearing from the claims, the specification and the drawings may be essential both in themselves and in the many different combinations.
(36) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
