GB2180653A - Electrochemical cell - Google Patents

Electrochemical cell Download PDF

Info

Publication number
GB2180653A
GB2180653A GB08621325A GB8621325A GB2180653A GB 2180653 A GB2180653 A GB 2180653A GB 08621325 A GB08621325 A GB 08621325A GB 8621325 A GB8621325 A GB 8621325A GB 2180653 A GB2180653 A GB 2180653A
Authority
GB
United Kingdom
Prior art keywords
cell
electrode
electrolyte
ofthe
carrier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08621325A
Other versions
GB8621325D0 (en
GB2180653B (en
Inventor
Robert Fleischmann
Reinhard Schunemann
Harald Bohm
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Licentia Patent Verwaltungs GmbH
Original Assignee
Licentia Patent Verwaltungs GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Licentia Patent Verwaltungs GmbH filed Critical Licentia Patent Verwaltungs GmbH
Publication of GB8621325D0 publication Critical patent/GB8621325D0/en
Publication of GB2180653A publication Critical patent/GB2180653A/en
Application granted granted Critical
Publication of GB2180653B publication Critical patent/GB2180653B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403Cells and electrode assemblies
    • G01N27/404Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
    • G01N27/4045Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors for gases other than oxygen
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004Gaseous mixtures, e.g. polluted air
    • G01N33/0009General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0037NOx
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Landscapes

  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Engineering & Computer Science (AREA)
  • Pathology (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Molecular Biology (AREA)
  • Combustion & Propulsion (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)
  • Inert Electrodes (AREA)
  • Hybrid Cells (AREA)

Abstract

An electrochemical three-electrode cell for measuring of nitrogen oxides comprises a space 1 for a working electrode space 4 separated by a proton-conducting barrier element 3 from a space 2 of a counter-electrode 7 and a reference electrode 8. The working electrode 4 comprises a porous, hydrophobic carrier 5 carrying a catalyser 6 for oxidation to nitrate which has been made water-repellent, e.g. carbon or graphite in PTFE. The barrier prevents reduction of nitrate ions at the counterelectrode. <IMAGE>

Description

SPECIFICATION Electrochemical cell The present invention relates to an electrochemical cell, especiallyforthe measurement of nitric oxides.
Since appreciable environmental pollution emanates from nitric oxides, the exact determination of nitric oxide components in exhaust gases, and also in reaction gases, is necessaryforthe effective control of countermeasures. These countermeasures are, for example, catalytic reduction with exclusion of oxygen to nitrogen or reduction with ammonia to nitrogen and water in case of oxygen components in the exhaust gases.
An electrochemical three-electrode cell for measuring nitric oxide components in a gas is known from DE-OS 25 264. This cell has the disadvantage that disproportionations in the electrolyte occur in the case of high nitric oxide content or over longer periods of operation of the cell. Back reactions occur at the counter- electrode and after a certain time simulate higher nitric oxide concentrations.
It would thus be desirableto prevent back reactions ofthe end products after conversion at the working electrode and also avoid pre-reactions of nitric oxides with water or with still present oxygen components in the combustion or reaction gas.
According to the present invention there is provided an electrochemical cell comprising a cell body, a working electrode disposed in a first space in the body to be in contact with an electrolyte therein, a counter-electrode and a reference electrode disposed in a second space in the body to be in contact with the electrolyte, and a proton-conductive barrier element separating the first and second spaces from each other, the first electrode comprising a porous hydrophobic carrier and a water-repellent catalyser on a side ofthe carrierfacing the electrolyte.
A cell embodying the present invention may have the advantage that the reaction products do not reach the counter-electrode and thus cannot influence the third electrode so that no potential changes falsifying the measurement value are avoided. Through the formation of the working electrode as a two-layer electrode from hydrophobic material, it is ensured that NO2 is not included in the measurement to an intolerably large degree through pre-reaction with condensed water as well as oxygen. Such advantages are due to the mode of operation ofthe cell. The gas to be measured washes the porous carrier of the working electrode and passes through this and the catalyser until it comes into contactwith the electrolyte.Due to the hydrophobic formation of the working electrode, the wetting of this electrode by precipitating watervapour is prevented.
Consequently, the NO2, which readily reacts with water, cannot combine through a pre-reaction with the precipitated water to become NO30, which would lead to the NO2 being only partially detected by the measurement.
Atthe boundary layer between the catalyser of the working electrode and the electrolyte, thefollowing reactions significantforthe measurement take place: NO+2H20 < NO3()+4Hf3+3e(3, NO2+ H2ONO3O+2HO+e.
The hydrated protons diffusethrough the barrier element to the counter-electrode, at which they combine with the oxygen which gets through the carrier material and the material ofthe counter-electrodeto the boundary layer between the counter-electrode and the electrolyte: 4H0++O2+4e2H2O.
The current generated by these reactions is a measure of the concentration of NOx.
The reference electrode serves to keep the potential setting constant at the working electrode.
The barrier element serves to prevent NO30- reaching the counter-electrode and falsifying the measurement result due to the reaction NO36+2H03+e8 < NO2+H20 and further reduction reactions of N030 or NO2.
In this manner, pre-reactions and reduction reactions are prevented by the barrier element and theformation ofthe working electrode. Due to the fact that only the desired reactions take place, the cell is accurate and stable in the long term and is usable for measurement of low concentrations (C < 100 parts per million) aswell as high nitric oxide proportions (C > 1000 parts per million).
The carrier of the working electrode, and a carrier of the counter-electrode and the reference electrode, preferably have capillary passages of such a diameterthatthe capillary openings cannot become clogged by water vapour condensation. This measure enhances the NO2 sensitivity ofthe cell even in the case ofhigh water vapour content of the gas.
The electrolyte can be fixed to a polymer matrix, for example acids held in zeolites, glass powder or other porous materials, and this offers the advantage that there is no dilution, which reaches beyond the edge zones, ofthe electrolyte through precipitating water vapour. Thus, conductivity fluctuations of the electrolyte can be prevented and the sensitivity of the system is stabilised.
Preferably, the working electrode comprises a carbon catalyser layer, which iswater-repellentand comprises a 10 to 100 millimetres thick, oxidation-stable hard carbon, synthetic graphite or graphite with 40 to 80 percentbyweightofpolytetrafluoroethylene binder.
In that case, an optimum measure of hydrophobicity and thereby of diffusion current linearity ofthe electrode may be achieved if the PTFE proportion is so set that the sensitivityfactor NO2/NO rises from 1 to 1/9.
Preferably, the barrier element is a sulfonated polymer foil inserted into the cell body.
Embodiments ofthe present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a first cell embodying the invention; Figure2 is a horizontal sectional view of the cell of Figure 1; and Figure 3 is a horizontal sectional view of a second cell embodying the invention.
Referring now to the drawings, there is shown in Figures 1 and 2 an electrochemical cell having a body which is formed from two synthetic material blocks 11 a and 11 b with a bore for the reception of electrolyte 10. The two blocks 11 a and 11 bare secured together by screws and a barrier element 3 is clamped between them. The bore is closed off outwardly by two carriers 5 and 9. The carrier Son the side facing the electrolyte 10 carries carbon catalyser layer 6 of a working electrode 4. The other carrier 9 on its side facing the electrolyte 10 carries a counter-electrode 7 and a reference electrode 8.
The electrodes 6,7 and 8 can, according to the process described in DE-P 33 24 682, be welded to terminals 12, 13 and 14 in liquid-tight mannerthrough the carriers 5 and 9. A channel 18 servesforfilling-in ofthe electrolyte.
Figure 3 shows a miniature cell in which a foil 15, consisting of sulfonated polymers or of phosphoric acid, held in zeolite, rests directly against the working electrode 4 on one side and against the counter-electrode7 and reference electrode 8 on the other side. Thisfoil 15 takes over the function of the barrier element as weil as that ofthe electrolyte. It can be glued into a groove 17 of a synthetic material body 16 by partially dissolving the walls ofthe groove 17 by a solvent and then pushing in the foil 15, which is matched in size to the groove.

Claims (18)

1. An electrochemical cell comprising a cell body, a working electrode disposed in a first space in the body to be in contact with an electrolyte therein, a counter-electrode and a reference electrode disposed in a second space in the body to be in contact with the electrolyte, and a proton-conductive barrier element separating the first and second spaces from each other, the first electrode comprising a porous hydrophobic carrier and a water-repellent catalyser on a side of the carrier facing the electrolyte.
2. Acell as claimed in claim 1,wherein the porosity of the carrier is provided by capillary bores of such a diameter as to resist clogging by water vapour condensate.
3. A cell as claimed in either claim 1 or claim 2, wherein the electrolyte is captive.
4. A cell as claimed in claim 3, wherein the electrolyte is captive in a polymer matrix.
5. A cell as claimed in claim 4, wherein the electrolyte comprises acids held in a porous material.
6. A cell as claimed in claim 5, wherein the porous material comprises zeolite or glass powder.
7. A cell as claimed in any one of the preceding claims, wherein the catalyser comprises a layer of oxidation-stable material with 40 to 80 percent by weight of polytetrafluoroethylene binder, the layer being 10 to 100 millimetres thick.
8. A cell as claimed in claim 7, wherein the oxidation-stable material is one of carbon, graphite and synthetic graphite.
9. A cell as claimed in either claim 7 or claim 8, wherein the hydrophobicity of the catalyser is so increased by setting ofthe binderthatthe sensitivity factor of nitrogen dioxide/nitric oxide rises from 1/3 to 1/9.
10. A cell as claimed in any one of the preceding claims, wherein the barrier element is a sulfonated polymerfoil.
11. A cell as claimed in any one of the preceding claims, wherein the body comprises two members which are connected togetherwith the barrier element arranged therebetween and which define a bore receiving the electrolyte, the bore being closed at one end thereof by the carrier ofthe first electrode and at the other end thereof by a carrier ofthe counter-electrode and the reference electrode.
12. A cell as claimed in either claim 1 or claim 2, wherein the barrier element comprises a foil in which the electrolyte is integrated and which at one side contacts the working electrode and at the other side contacts the counter-electrode and the reference electrode.
13. A cell as claimed in claim 12, wherein the foil comprises sulfonated polymers.
14. A cell as claimed in claim 12, wherein the foil comprises phosphoric acid held in zeolite.
15. Acell as claimed in any one of claims 12 to 14, wherein thefoil is glued in a groove in the body.
16. A cell as claimed in any one of the preceding claims, wherein the body is made of plastics material.
17. An electrochemical cell substantially as herein before described with reference to Figures 1 and 2 ofthe accompanying drawings.
18. An electrochemical cell substantially as hereinbefore described with reference to Figure 3 ofthe accompanying drawings.
GB8621325A 1985-09-13 1986-09-04 Electrochemical cell Expired - Fee Related GB2180653B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19853532674 DE3532674A1 (en) 1985-09-13 1985-09-13 ELECTROCHEMICAL THREE-ELECTRODE CELL FOR MEASURING NITROGEN OXIDES

Publications (3)

Publication Number Publication Date
GB8621325D0 GB8621325D0 (en) 1986-10-15
GB2180653A true GB2180653A (en) 1987-04-01
GB2180653B GB2180653B (en) 1990-02-07

Family

ID=6280851

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8621325A Expired - Fee Related GB2180653B (en) 1985-09-13 1986-09-04 Electrochemical cell

Country Status (2)

Country Link
DE (1) DE3532674A1 (en)
GB (1) GB2180653B (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2267348A (en) * 1992-05-26 1993-12-01 Walter John King Electrochemical oxygen sensor
EP0637379A1 (en) * 1992-04-21 1995-02-08 MALINSKI, Tadeusz Nitric oxide sensor
US5603820A (en) * 1992-04-21 1997-02-18 The United States Of America As Represented By The Department Of Health And Human Services Nitric oxide sensor
WO2001014864A2 (en) * 1999-08-24 2001-03-01 Central Research Laboratories Ltd. A gas sensor and its method of manufacture

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4132178A1 (en) * 1991-07-26 1993-01-28 Hl Planartechnik Gmbh Electrochemical sensor, esp. for oxygen@ measurement - has reference electrode in separate part of electrolyte chamber, with layer preventing ion transmission
DE4125099C2 (en) * 1991-07-30 1995-02-23 Daimler Benz Ag Method and device for measuring ammonia in air and exhaust gases containing NO¶x¶
DE4316970C1 (en) * 1993-05-21 1994-08-25 Daimler Benz Ag Method for determining ammonia in gases
DE19803805B4 (en) * 1998-01-31 2015-10-29 Volkswagen Ag NOx sensor
DE19859198C2 (en) * 1998-12-21 2003-12-18 Envitec Wismar Gmbh Electrochemical gas sensor with high selectivity for nitrogen monoxide

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025412A (en) * 1975-12-04 1977-05-24 General Electric Company Electrically biased two electrode, electrochemical gas sensor with a H.sub.2
US4265714A (en) * 1980-03-24 1981-05-05 General Electric Company Gas sensing and measuring device and process using catalytic graphite sensing electrode
GB1597413A (en) * 1977-02-28 1981-09-09 Gen Electric Gas sensors
GB2094005A (en) * 1981-02-03 1982-09-08 Coal Industry Patents Ltd Electrochemical gas sensor

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3776832A (en) * 1970-11-10 1973-12-04 Energetics Science Electrochemical detection cell
US4001103A (en) * 1974-05-07 1977-01-04 Energetics Science, Inc. Device for the detection and measurement of NO and NO2 gases
DE2655318C3 (en) * 1976-12-07 1979-11-29 Draegerwerk Ag, 2400 Luebeck Polarographic measuring probe with diffusion film membrane

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4025412A (en) * 1975-12-04 1977-05-24 General Electric Company Electrically biased two electrode, electrochemical gas sensor with a H.sub.2
GB1597413A (en) * 1977-02-28 1981-09-09 Gen Electric Gas sensors
US4265714A (en) * 1980-03-24 1981-05-05 General Electric Company Gas sensing and measuring device and process using catalytic graphite sensing electrode
GB2094005A (en) * 1981-02-03 1982-09-08 Coal Industry Patents Ltd Electrochemical gas sensor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0637379A1 (en) * 1992-04-21 1995-02-08 MALINSKI, Tadeusz Nitric oxide sensor
EP0637379A4 (en) * 1992-04-21 1996-05-08 Tadeusz Malinski Nitric oxide sensor.
US5603820A (en) * 1992-04-21 1997-02-18 The United States Of America As Represented By The Department Of Health And Human Services Nitric oxide sensor
GB2267348A (en) * 1992-05-26 1993-12-01 Walter John King Electrochemical oxygen sensor
WO2001014864A2 (en) * 1999-08-24 2001-03-01 Central Research Laboratories Ltd. A gas sensor and its method of manufacture
WO2001014864A3 (en) * 1999-08-24 2001-05-31 Central Research Lab Ltd A gas sensor and its method of manufacture

Also Published As

Publication number Publication date
DE3532674C2 (en) 1988-01-21
GB8621325D0 (en) 1986-10-15
GB2180653B (en) 1990-02-07
DE3532674A1 (en) 1987-03-26

Similar Documents

Publication Publication Date Title
US4025412A (en) Electrically biased two electrode, electrochemical gas sensor with a H.sub.2
USRE45186E1 (en) Low cost room temperature electrochemical carbon monoxide and toxic gas sensor with humidity compensation based on protonic conductive membranes
Knake et al. Amperometric sensing in the gas-phase
Yao et al. Solid electrolyte CO2 sensor using binary carbonate electrode.
US4394239A (en) Electro-chemical sensor for the detection of reducing gases, in particular carbon monoxide, hydrazine and hydrogen in air
US4820386A (en) Diffusion-type sensor cell containing sensing and counter electrodes in intimate contact with the same side of a proton-conducting membrane and method of use
USRE45100E1 (en) Gas sensor based on protonic conductive membranes
JP2687202B2 (en) Gas sensor
US4171253A (en) Self-humidifying potentiostated, three-electrode hydrated solid polymer electrolyte (SPE) gas sensor
US3296113A (en) Gas-stream monitor
US6746587B2 (en) Electrochemical gas sensor
EP1103807A2 (en) Hydrogen gas sensor
CN1350640A (en) Electrochemical toxic component sensor
Alber et al. Solid‐state amperometric sensors for gas phase analytes: A review of recent advances
WO1996024052A9 (en) Electrochemical gas sensor
GB2225859A (en) Electrochemical measuring cell for determining ammonia and its derivatives.
EP1688736A1 (en) Electrochemical gas sensor
US7189364B2 (en) Hydrogen sensor
US6837987B1 (en) Carbon monoxide sensor
GB2180653A (en) Electrochemical cell
US5041204A (en) Electrochemical measuring cell for detecting hydrogen cyanide or sulfur dioxide
US3258415A (en) Oxygen analyzer and oxygen-depolarized cell therefor
WO2002031485A1 (en) Acid gas measuring sensors and method of making same
US5128018A (en) Electrochemical measuring cell for detecting gas components in a fluid medium
Mayo et al. Electrochemical response to H2, O2, CO2 and NH3 of a solid-state cell based on a cation-or anion-exchange membrane serving as a solid polymer electrolyte

Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19960904