WO2019056159A1 - Capteur électrochimique amélioré et procédé de détection de formaldéhyde par régulation de tension afin de réduire la sensibilité transversale - Google Patents

Capteur électrochimique amélioré et procédé de détection de formaldéhyde par régulation de tension afin de réduire la sensibilité transversale Download PDF

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Publication number
WO2019056159A1
WO2019056159A1 PCT/CN2017/102201 CN2017102201W WO2019056159A1 WO 2019056159 A1 WO2019056159 A1 WO 2019056159A1 CN 2017102201 W CN2017102201 W CN 2017102201W WO 2019056159 A1 WO2019056159 A1 WO 2019056159A1
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WIPO (PCT)
Prior art keywords
sensor
formaldehyde
sensitivity
working electrode
electrode
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PCT/CN2017/102201
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English (en)
Inventor
Lei Xiao
Keith Francis Edwin Pratt
Yuzhong YU
Feng Liang
Ti ZHENG
Bin Peng
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Honeywell International Inc.
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Application filed by Honeywell International Inc. filed Critical Honeywell International Inc.
Priority to PCT/CN2017/102201 priority Critical patent/WO2019056159A1/fr
Priority to CN201780092322.5A priority patent/CN110741247A/zh
Publication of WO2019056159A1 publication Critical patent/WO2019056159A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/404—Cells 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
    • G01N27/4045—Cells 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0047—Organic compounds

Definitions

  • Electrochemical gas sensors generally comprise electrodes in contact with an electrolyte for detecting a gas concentration.
  • the electrodes are electrically coupled to an external circuit through lead wires that are coupled to connector pins.
  • a reaction can occur that can create a potential difference between the electrodes and/or cause a current to flow between the electrodes.
  • the resulting signal can be correlated with a gas concentration in the environment.
  • the working electrode can comprise a catalyst that can catalyze the reaction of both a target gas and an interferent gas.
  • the presence of the interferent gas may create a cross-sensitivity in the sensor, resulting in the false impression that greater levels of the target gas are present in the ambient gases than are actually present.
  • the threshold level for triggering an alarm can be relatively low, and the cross-sensitivity due to the presence of the interferent may be high enough to create a false alarm (e.g. false positive) for the target gas sensor. This might be especially true in instances where the interferent gas in not hazardous (meaning that the sensor might trigger an alarm even when exposed to a low level (or even no level) or actually hazardous gas) .
  • an electrochemical formaldehyde sensor may comprise a housing; an electrolyte disposed within the housing; and a plurality of electrodes in contact with the electrolyte within the housing, wherein the plurality of electrodes comprise a working electrode and a counter electrode, wherein the working electrode comprises iridium, and wherein the working electrode is biased to a potential equivalent to less than approximately 1.1 volts (V) relative to a reversible hydrogen electrode.
  • V 1.1 volts
  • a method of detecting formaldehyde may comprise receiving an ambient gas into a housing of a formaldehyde sensor, wherein the ambient gas comprises at least formaldehyde, wherein the formaldehyde sensor comprises a plurality of electrodes in contact with an electrolyte within the housing, and wherein the plurality of electrodes comprise a working electrode and a counter electrode; applying a potential to the working electrode equivalent to less than approximately 1.1 V relative to a reversible hydrogen electrode; contacting the ambient gas with the working electrode, wherein the working electrode comprises an iridium material; allowing the ambient gas to diffuse through the working electrode to contact an electrolyte; generating a current between the porous working electrode and the counter electrode in response to a reaction between the ambient gas and the electrolyte at the second surface of the working electrode; and determining a concentration of the formaldehyde in the ambient gas based on the current.
  • an electrochemical formaldehyde sensor may comprise a housing; an electrolyte disposed within the housing; and a plurality of electrodes in contact with the electrolyte within the housing, wherein the plurality of electrodes comprise a working electrode comprising iridium and an applied potential of between approximately 0.9 to 1 V relative to a reversible hydrogen electrode; and a counter electrode, wherein the cross-sensitivity of the sensor to alcohols is less than approximately 25%of the sensitivity to formaldehyde.
  • FIG. 1 illustrates a cross section drawing of an electrochemical sensor according to an embodiment of the disclosure.
  • FIG. 2 illustrates a sensor response to exposure to 1 ppm formaldehyde followed by 3.5 ppm formaldehyde under the conditions described herein.
  • phrases “in one embodiment, ” “according to one embodiment, ” and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present invention, and may be included in more than one embodiment of the present invention (importantly, such phrases do not necessarily refer to the same embodiment) ;
  • ком ⁇ онент or feature may, ” “can, ” “could, ” “should, ” “would, ” “preferably, ” “possibly, ” “typically, ” “optionally, ” “for example, ” “often, ” or “might” (or other such language) be included or have a characteristic, that particular component or feature is not required to be included or to have the characteristic.
  • Such component or feature may be optionally included in some embodiments, or it may be excluded.
  • Embodiments of the disclosure include systems and methods for detecting formaldehyde and increasing the sensitivity of an electrochemical sensor to formaldehyde and/or decreasing the cross-sensitivity of the electrochemical sensor to other (interferent) gases.
  • embodiments may help reduce false positive alarms and/or inaccurate readings by minimizing the impact of such interferent gases during detection of formaldehyde.
  • U.S. Patent No. 4,692,220 describes a method and system for detecting formaldehyde using an electrochemical sensor while reducing the cross-sensitivity to carbon monoxide.
  • the described system maintains the working electrode at a fixed potential between about 1.1 V and 1.5 V with respect to a reversible hydrogen electrode, and the described system has the disadvantage of a significant cross-sensitivity to alcohols, such as isopropanol.
  • disclosed embodiments include an electrochemical sensor comprising at least one iridium electrode with a potential (for example, less than approximately 1.1 Volts) applied to the at least one electrode, where the electrochemical sensor may be configured to detect formaldehyde with a reduced cross-sensitivity to alcohols.
  • a formaldehyde sensor may be highly sensitive to cross-sensitivity from (interferent) gases existing naturally in higher concentration (such as alcohols, CO, etc. ) .
  • a potential typically less than approximately 1.1 V, for example 0.9 to 1 V
  • a sensitive and stable response to formaldehyde may be generated, even at a low concentration (such as 1 ppm) and/or in the when in the presence of interferent gas (es) .
  • the cross-sensitivity to CO may be less than approximately 1%and the cross-sensitivity to alcohols may be less than approximately 25%.
  • a sensor using the iridium electrode system may be significantly less expensive than typical low-level formaldehyde sensors.
  • FIG. 1 is the cross section drawing of the electrochemical sensor 10.
  • the sensor 10 generally comprises a housing 12 defining a cavity or reservoir 14 designed to hold an electrolyte solution.
  • a working electrode 24 can be placed between an opening 28 and the reservoir 14.
  • a counter electrode 16 and a reference electrode 20 can be positioned within the reservoir.
  • a reference electrode 20 may also be positioned within the reservoir 14 to provide a reference for the detected current and potential between the working electrode 24 and the counter electrode 16.
  • the reference electrode 20 may also be configured to provide a reference for the potential of the working electrode 24 relative to a standard reference electrode, such as a reversible hydrogen electrode.
  • FIG. 1 illustrates an example of a “stacked” configuration for an electrochemical sensor 10.
  • the embodiments disclosed herein may also apply to other sensor configurations, such as a planar configuration and/or other stacked configurations.
  • the housing 12 defines the interior reservoir 14, and one or more openings 28 can be disposed in the housing to allow a gas to be detected to enter the housing 12 into a gas space 26.
  • the opening (s) 28 provide connection between the gas space 26 and the external environment (e.g. in which formaldehyde is to be detected) .
  • the housing 12 can generally be formed from any material that is substantially inert to the electrolyte and gas being measured.
  • the housing 12 can be formed from a polymeric material, a metal, or a ceramic.
  • the housing can be formed from a material including, but not limited to, acrylonitrile butadiene styrene (ABS) , polyphenylene oxide (PPO) , polystyrene (PS) , polypropylene (PP) , polyethylene (PE) (e.g., high density polyethylene (HDPE) ) , polyphenylene ether (PPE) , or any combination or blend thereof.
  • ABS acrylonitrile butadiene styrene
  • PPO polyphenylene oxide
  • PS polystyrene
  • PP polypropylene
  • PE polyethylene
  • PE polyethylene
  • HDPE high density polyethylene
  • PPE polyphenylene ether
  • One or more openings 28 can be formed through the housing 12 to allow the ambient gas to enter the gas space 26 and/or allow any gases generated within the housing 12 to escape.
  • the electrochemical sensor 10 may comprise at least one inlet opening 28 to allow the ambient gas to enter the housing 12.
  • the opening 28 can be disposed in a cap when a cap is present and/or in a wall of the housing 12.
  • the opening 28 can comprise a diffusion barrier to restrict the flow of gas (e.g., carbon monoxide, formaldehyde, etc. ) to the working electrode 24.
  • the diffusion barrier can be created by forming the opening 28 as a capillary and/or a film or membrane can be used to control the mass flow rate through the one or more openings 28.
  • the opening 28 may serve as a capillary opening to provide a rate limited exchange of the gases between the interior and exterior of the housing 12.
  • the opening 28 may have a diameter between about 200 ⁇ m and about 1.5 mm, where the opening 28 can be formed using a convention drill for larger openings and a laser drill for smaller openings.
  • the opening 28 may be much larger, where the opening 28 may comprise any diameter up to the total diameter of the housing 12.
  • the opening 28 may have a length between about 0.5 mm and about 5 mm, depending on the thickness of the cap or housing 12.
  • two or more openings may be present for the inlet gases.
  • the opening diameter may be larger than the sizes listed above as the film can contribute to and/or may be responsible for controlling the flow rate of the gases into and out of the housing 12.
  • the reservoir 14 comprises the counter electrode 16, the reference electrode 20, and the working electrode 24.
  • the electrolyte can be contained within the reservoir 14, and the counter electrode 16, the reference electrode 20, and the working electrode 24 can be in electrical contact through the electrolyte.
  • one or more porous separators 18, 22 or other porous structures can be used to retain the electrolyte in contact with the electrodes.
  • the separators 18, 22 can comprise a porous member that acts as a wick for the retention and transport of the electrolyte between the reservoir 14 and the electrodes while being electrically insulating to prevent shorting due to direct contact between any two electrodes.
  • One or more of the porous separators 18, 22 can extend into the reservoir 14 to provide the electrolyte a path to the electrodes.
  • a separator 18 can be disposed between the counter electrode 16 and the reference electrode 20, and a separator 22 can be disposed between the reference electrode 20 and the working electrode 24.
  • One or more of the separators 18, 22 can comprise a nonwoven porous material (e.g., a porous felt member) , a woven porous material, a porous polymer (e.g., an open cell foam, a solid porous plastic, etc. ) , or the like, and is generally chemically inert with respect to the electrolyte and the materials forming the electrodes.
  • the separator 18, 22 can be formed from various materials that are substantially chemically inert to the electrolyte including, but not limited to, glass (e.g., a glass mat) , polymer (plastic discs) , ceramics, or the like.
  • the electrolyte can be any conventional aqueous acidic electrolyte such as sulfuric acid, phosphoric acid, or a neutral ionic solution such as a salt solution (e.g., a lithium salt such as lithium chloride, etc. ) , or any combination thereof.
  • the electrolyte can comprise sulfuric acid having a molar concentration between about 3 M to about 12 M. Since sulfuric acid is hygroscopic, the concentration can vary from about 10 to about 70 wt% (1 to 11.5 molar) over a relative humidity (RH) range of the environment of about 3 to about 95%.
  • the electrolyte can comprise phosphoric acid having a concentration in an aqueous solution between about 30%to about 60%H 3 PO 4 by weight.
  • the electrolyte can include a lithium chloride salt having about 30%to about 60%LiCl by weight, with the balance being an aqueous solution.
  • the electrolyte may be in the form of a solid polymer electrolyte which comprises an ionic exchange membrane.
  • the electrolyte can be in the form of a free liquid, disposed in a matrix or slurry such as glass fibers (e.g., the separator 18, the separator 22, etc. ) , or disposed in the form of a semi-solid or solid gel.
  • the working electrode 24 may be disposed within the housing 12.
  • the gas entering the sensor 10 can contact one side of the working electrode 24 and pass through working electrode 24 to reach the interface between the working electrode 24 and the electrolyte.
  • the gas can then react to generate the current indicative of the gas concentration.
  • the working electrode 24 can comprise a plurality of layers.
  • the base or substrate layer can comprise a hydrophobic material or a hydrophobically treated material.
  • a catalytic material can be formed as an electrode on one side of the working electrode 24 and placed in contact with the electrolyte.
  • the working electrode 24 can comprise a porous substrate or membrane as the base layer.
  • the substrate can be porous to the gas of interest, which can comprise formaldehyde.
  • the substrate can comprise a carbon paper formed of carbon or graphite fibers.
  • the substrate can be made to be electrically conductive through the addition of a conductive material such as carbon. The use of carbon may provide a sufficient degree of electrical conductivity to allow the current generated by the reaction of the gas with the electrolyte at the surface of the working electrode 24 to be detected by a lead coupled to the working electrode 24.
  • electrically conductive substrates may also be used such as carb on felts, porous carbon boards, and/or electrically conductive polymers such as polyacetylene, each of which may be made hydrophobic as described below.
  • an electrically conductive lead can be coupled to the catalytic layer to electrically couple the catalytic material to the external circuitry, as described in more detail herein.
  • the substrate can be between about 5 mils to about 20 mils thick in some embodiments.
  • the porous substrate can be hydrophobic to prevent the electrolyte from passing through the working electrode 24.
  • the substrate can be formed from a hydrophobic material, or the substrate can be treated with a hydrophobic material.
  • the substrate can be made hydrophobic through the impregnation of the substrate with a hydrophobic material such as a fluorinated polymer (e.g., PTFE, etc. ) .
  • the substrate or membrane can comprise GEFC-IES (e.g., the copolymer of perfluorosulfonic acid and PTFE, which is commercially available from Golden Energy Fuel Cell Co., Ltd.
  • the impregnation process can include disposing a hydrophobic material containing solution or slurry on the substrate using a dipping, coating, or rolling process. Alternatively, a dry composition such as a powder can be applied to the substrate.
  • an optional sintering process can be used to in fuse the hydrophobic material into the substrate to create the hydrophobic base layer for the working electrode 24, where both sides of the hydrophobic base layer are hydrophobic.
  • the sintering process can cause the hydrophobic polymer to bond or fuse with the carbon of the substrate to securely bond the hydrophobic material to the substrate.
  • the resulting substrates can contain about 30% to about 50% by weight of the hydrophobic polymer.
  • the amount of hydrophobic material added to the substrate can affect the electrical conductivity of the substrate, wherein the electrical conductivity tends to decrease with an increased amount of the hydrophobic material.
  • the amount of the hydrophobic polymer used with the substrate may depend on the degree of hydrophobicity desired, the porosity of the formaldehyde, and the resulting electrical conductivity ofthe working electrode.
  • the catalytic layer can be formed by mixing the desired catalyst with a binder and depositing the mixture on the substrate material.
  • the binder can comprise a solution of perfluorinated ion electrolyte solution (e.g., GEFC-IES, etc. ) , a hydrophobic material such as PTFE, mixtures thereof, or the like.
  • GEFC-IES and/or PTFE can affect the gas diffusion parameters while supporting the electrocatalyst and maximizing the interfaces between catalyst, gas and electrolyte at which the electrochemical processes occur.
  • Glycol or other similar chemicals can be used as a diluent to form a catalyst slurry, recipe or catalyst system, which can be printed on a substrate by a printer.
  • the catalytic layer might be deposited onto the substrate by for example screen printing, filtering in selected areas from a suspension placed onto the substrate, by spray coating, or any other method suitable for producing a patterned deposition of solid material.
  • Deposition might be of a single material or of more than one material sequentially in layers, so as for example to vary the properties of the electrode material through its thickness or to add a second layer of increased electrical conductivity above or below the layer which is the main site of gas reaction.
  • the printed element can be sintered at an elevated temperature to form the electrode.
  • the catalytic layer can comprise carbon (e.g., graphite) and/or one or more metals or metal oxides such as copper, silver, gold, nickel, palladium, platinum, ruthenium, iridium, and/or oxides of these metals.
  • the working electrode 24 may comprise iridium or an iridium material.
  • the catalyst used can be a pure metal powder, a metal powder combined with carbon, or a metal powder supported on an electrically conductive medium such as carbon, or a combination of two or more metal powders either as a blend or as an alloy.
  • the materials used for the individual electrodes can be the same or different.
  • the counter electrode 16 can be disposed within the housing 12.
  • the counter electrode 16 can comprise a substrate or membrane such as a PTFE membrane, a GEFC-IES membrane, a membrane, or the like having a catalytic material disposed thereon.
  • the catalytic material can be mixed and disposed on the membrane using any suitable process such as rolling, coating, screen printing, or the like to apply the catalytic material on the membrane, as described in more detail herein.
  • the catalyst layer can then be bonded to the membrane through a sintering process as described herein.
  • the catalytic material for the counter electrode can comprise a noble metal such as gold (Au) , platinum (Pt) , ruthenium (Ru) , rhodium (Rh) , iridium (Ir) , oxides thereof, or any combination thereof.
  • the catalyst loading for the counter electrode 16 can be within any of the ranges described herein for the working electrode 24.
  • the catalyst loading for the counter electrode 16 can be the same or substantially the same as the catalyst loading for the working electrode 24, the catalyst loading can also be greater than or less than that of the working electrode 24.
  • a catalytic material can be added to the working electrode 24 that has a higher catalytic activity to wards the target gas such as form aldehyde than an interfering gas or gases such as carbon monoxide.
  • the target gas is form aldehyde and the interfering gas is carbon monoxide
  • the catalytic material that can be added into the working electrode 24 typically might comprise iridium.
  • the reference electrode 20 can be disposed within the housing 12.
  • the reference electrode 20 can comprise a substrate or membrane such as a PTFE membrane, a GEFC-IES membrane, a membrane, or the like having a catalytic material disposed thereon.
  • the catalytic material can be mixed with a hydrophobic material (e.g., PTFE, etc. ) and disposed on the PTFE membrane. Any of the methods used to form the working electrode or the counter electrode can also be used to prepare the reference electrode 20.
  • the catalytic material used with the reference electrode 20 can comprise a noble metal such as gold (Au) , platinum (Pt) , ruthenium (Ru) , rhodium (Rh) , iridium (Ir) , oxides thereof, or any combination thereof.
  • the catalyst loading for the reference electrode 20 can be within any of the ranges described herein for the working electrode 24.
  • the catalyst loading for the reference electrode 20 can be the same or substantially the same as the catalyst loading for the working electrode 24, the catalyst loading can also be greater than or less than that of the working electrode 24. While illustrated in FIG. 1 as having the reference electrode 20, some embodiments of the electrochemical sensor may not include a reference electrode 20.
  • one or more leads or electrical contacts can be electrically coupled to the working electrode 24, the reference electrode 20, and/or the counter electrode 16.
  • the lead contacting the working electrode 24 can contact either side of the working electrode 24 since the substrate comprises an electrically conductive material.
  • the lead contacting the working electrode can contact the side of the working electrode 24 that is not in contact with the electrolyte.
  • Leads may be similarly electrically coupled to the counter electrode 16 and the reference electrode 20.
  • the leads can be electrically coupled to external connection pins to provide an electrical connection to external processing circuitry.
  • the external circuitry can detect the current and/or potential difference between the electrodes and convert the current into a corresponding formaldehyde concentration (by, for example, comparison to a pre-existing table/database which correlates current and/or potential difference to gas level, for example based on prior testing) .
  • the sensor 10 can detect a formaldehyde concentration in the presence of alcohols and/or carbon monoxide.
  • the ambient gas can flow or diffuse into the sensor 10 through the opening 28, which serves as the intake port for the sensor 10.
  • the ambient gas can comprise formaldehyde.
  • the gas can contact the working electrode and pass through the fine pores of the porous substrate layer to reach the surface of the working electrode 24 treated with the catalyst layer.
  • the electrolyte may be in contact with the surface of the working electrode 24, and the formaldehyde may react and result in an electrolytic current forming between the working electrode 24 and the counter electrode 16 that corresponds to the concentration of the formaldehyde in the ambient gas.
  • the concentration of formaldehyde can be determined using, for example, the external detection circuitry.
  • an interfering gas such as the alcohols and/or carbon monoxide can also contact the working electrode 24.
  • the interfering gas can react at the surface of the working electrode 24, though it may not react at the same rate as the target gas.
  • the interfering gas may also experience a diffusional resistance within the sensor 10.
  • a potential may be applied to at least the working electrode 24.
  • the potential may be applied to only the working electrode 24.
  • the potential applied to the working electrode 24 may be less than 1.5 V relative to a reversible hydrogen electrode.
  • a reversible hydrogen electrode (RHE) is a reference electrode, more specifically a subtype of the standard hydrogen electrodes, for electrochemical processes. The measured potential of a reversible hydrogen electrode does not change with the pH, so it can be directly used in the electrolyte. This standard may be referred to when discussing the sensor 10, whether or not a reversible hydrogen electrode is located within the sensor 10.
  • the potential applied to the working electrode 24 may be less than 1.1 V relative to a reversible hydrogen electrode.
  • the working electrode 24 may be biased to between approximately 200 to 300 mV relative to an iridium reference electrode (i.e. the reference electrode 20) .
  • the rest potential of iridium is around 700 mV relative to a reversible hydrogen electrode, so the bias relative to a reversible hydrogen electrode would be between approximately 0.9 to 1 V.
  • the potential applied to the working electrode 24 may be lower (i.e. less anodic) than other typical formaldehyde sensors.
  • Using a lower (less anodic) potential (or bias voltage) may have an additional benefit of a lower baseline current, which will be more stable over time and have less variation with temperature, which is important when measuring low gas concentrations.
  • the less anodic bias voltage may reduce the cross sensitivity of the sensor to oxidizing gases, which is important in domestic use for gases such as ethanol.
  • the benefits of the disclosed embodiments may include low to no generation of unwanted compounds at the working electrode and no build-up of current, which may result in faster reaction times and an extended use-life for the sensor.
  • IPA isopropanol
  • Embodiments disclosed herein may comprise a gas sensor 10 that has a cross sensitivity to alcohols of about 25%or less (e.g. less than 25%, less than 10%, less than 5%or less than 2%) .
  • the gas sensor 10 may have a cross sensitivity to alcohols between approximately 1-5%. In some embodiments, the gas sensor 10 may have a cross sensitivity to alcohols between approximately 2-5%. In some embodiments, the gas sensor 10 may have a cross sensitivity to alcohols between approximately 4-5%.
  • An electrochemical sensor may be prepared with a working electrode comprising iridium.
  • the working electrode may be prepared with iridium powder comprising a surface area of approximately 20 to 25 square meters per gram.
  • the iridium powder may be mixed with approximately 20 wt%PTFE in an aqueous slurry, which may be deposited onto a porous PTFE tape (which may have porosity of about 2200 to 3200 Gurley Seconds) , and dried and cured at approximately 200 to 300°C.
  • the resulting catalyst loading for the working electrode may comprise approximately 14.9 mg per 13 mm diameter electrode.
  • the senor 10 may comprise a working electrode 24 as described above, the sensor may comprise a cross sensitivity to alcohols, such as ethanol and IPA, of about 4 to 5%of the sensitivity to formaldehyde. Additionally, the sensor may comprise a cross sensitivity to carbon monoxide of less than about 1%of the sensitivity to formaldehyde.
  • alcohols such as ethanol and IPA
  • the senor described above was first tested with 1 ppm formaldehyde, and the resulting sensitivity was approximately 1.5 ⁇ A. Then the sensor was exposed to 3.5 ppm formaldehyde and the resulting sensitivity was approximately 4.5 ⁇ A.
  • exemplary embodiments or aspects can include, but are not limited to:
  • an electrochemical formaldehyde sensor may comprise a housing; an electrolyte disposed within the housing; and a plurality of electrodes in contact with the electrolyte within the housing, wherein the plurality of electrodes comprise a working electrode and a counter electrode, wherein the working electrode comprises iridium, and wherein the working electrode is biased to a potential equivalent to less than approximately 1.1 volts (V) relative to a reversible hydrogen electrode.
  • V 1.1 volts
  • a second embodiment can include the sensor of the first embodiment, wherein the sensor comprises a cross-sensitivity to alcohols of less than approximately 25%of the sensitivity to formaldehyde.
  • a third embodiment can include the sensor of the first or second embodiments, wherein the sensor comprises a cross-sensitivity to alcohols of less than approximately 10%of the sensitivity to formaldehyde.
  • a fourth embodiment can include the sensor of any of the first to third embodiments, wherein the sensor comprises a cross-sensitivity to alcohols of less than approximately 5%of the sensitivity to formaldehyde.
  • a fifth embodiment can include the sensor of any of the first to fourth embodiments, wherein the sensor comprises a cross-sensitivity to alcohols approximately 2%of the sensitivity to formaldehyde.
  • a sixth embodiment can include the sensor of any of the first to fifth embodiments, wherein the sensor comprises a cross-sensitivity to carbon monoxide of less than approximately 1%of the sensitivity to formaldehyde.
  • a seventh embodiment can include the sensor of any of the first to sixth embodiments, wherein the potential applied to the working electrode is between approximately 0.9 and 1 V relative to a reversible hydrogen electrode.
  • An eighth embodiment can include the sensor of any of the first to seventh embodiments, wherein the working electrode comprises iridium power mixed with polytetrafluoroethylene (PTFE) .
  • PTFE polytetrafluoroethylene
  • a ninth embodiment can include the sensor of any of the first to eighth embodiments, wherein the electrolyte comprises sulfuric acid.
  • a tenth embodiment can include the sensor of any of the first to ninth embodiments, wherein the housing comprises an opening configured to allow gas flow into the housing, wherein the diameter of the opening is less than or equal to the diameter of the housing.
  • a method of detecting formaldehyde may comprise receiving an ambient gas into a housing of a formaldehyde sensor, wherein the ambient gas comprises at least formaldehyde, wherein the formaldehyde sensor comprises a plurality of electrodes in contact with an electrolyte within the housing, and wherein the plurality of electrodes comprise a working electrode and a counter electrode; applying a potential to the working electrode of between approximately 0.9 V and 1 V relative to a reversible hydrogen electrode; contacting the ambient gas with the working electrode, wherein the working electrode comprises an iridium material; allowing the ambient gas to diffuse through the working electrode to contact an electrolyte; generating a current between the porous working electrode and the counter electrode in response to a reaction between the ambient gas and the electrolyte at the second surface of the working electrode; and determining a concentration of the formaldehyde in the ambient gas based on the current.
  • a twelfth embodiment can include the method of the eleventh embodiment, wherein the ambient gas comprises formaldehyde and one or more alcohols.
  • a thirteenth embodiment can include the method of the twelfth embodiment, wherein a ratio of 1) a sensitivity of the sensor to formaldehyde to 2) a sensitivity of the sensor to alcohols is greater than about 90.
  • a fourteenth embodiment can include the method of any of the eleventh to thirteenth embodiments, wherein the ambient gas comprises formaldehyde and carbon monoxide.
  • a fifteenth embodiment can include the method of the fourteenth embodiment, wherein a ratio of 1) a sensitivity of the sensor to formaldehyde to 2) a sensitivity of the sensor to carbon monoxide is greater than about 90.
  • an electrochemical formaldehyde sensor may comprise a housing; an electrolyte disposed within the housing; and a plurality of electrodes in contact with the electrolyte within the housing, wherein the plurality of electrodes comprise a working electrode comprising iridium and an applied potential of between approximately 0.9 to 1 V relative to a reversible hydrogen electrode; and a counter electrode, wherein the cross-sensitivity of the sensor to alcohols is less than approximately 25%of the sensitivity to formaldehyde.
  • a seventeenth embodiment can include the sensor of the sixteenth embodiment, wherein the sensor comprises a cross-sensitivity to carbon monoxide of less than approximately 1%of the sensitivity to formaldehyde.
  • An eighteenth embodiment can include the sensor of the sixteenth or seventeenth embodiments, wherein the working electrode comprises iridium power mixed with polytetrafluoroethylene (PTFE) .
  • PTFE polytetrafluoroethylene
  • a nineteenth embodiment can include the sensor of any of the sixteenth to eighteenth embodiments, wherein the electrolyte comprises sulfuric acid.
  • a twentieth embodiment can include the sensor of any of the sixteenth to eighteenth embodiments, wherein the housing comprises an opening configured to allow gas flow into the housing, wherein the diameter of the opening is less than or equal to the diameter of the housing.
  • a twenty-first embodiment can include the sensor and/or method of any of the first to twentieth embodiments, wherein the working electrode is be biased to between approximately 200 to 300 mV relative to an iridium reference electrode.

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  • Measuring Oxygen Concentration In Cells (AREA)

Abstract

L'invention concerne un capteur de formaldéhyde électrochimique (10) et un procédé de détection de formaldéhyde. Le capteur électrochimique de formaldéhyde (10) peut comprendre un boîtier (12) ; un électrolyte disposé à l'intérieur du boîtier (12) ; et une pluralité d'électrodes en contact avec l'électrolyte à l'intérieur du boîtier (12), la pluralité d'électrodes comprenant une électrode de travail (24) comprenant de l'iridium et un potentiel appliqué compris entre environ 0,9 et 1 V par rapport à une électrode à hydrogène réversible ; et une contre-électrode (16). La sensibilité transversale du capteur (10) aux alcools est inférieure d'environ 25 % à la sensibilité au formaldéhyde.
PCT/CN2017/102201 2017-09-19 2017-09-19 Capteur électrochimique amélioré et procédé de détection de formaldéhyde par régulation de tension afin de réduire la sensibilité transversale WO2019056159A1 (fr)

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PCT/CN2017/102201 WO2019056159A1 (fr) 2017-09-19 2017-09-19 Capteur électrochimique amélioré et procédé de détection de formaldéhyde par régulation de tension afin de réduire la sensibilité transversale
CN201780092322.5A CN110741247A (zh) 2017-09-19 2017-09-19 改进的电化学传感器和用于通过调节电压来降低交叉敏感性以检测甲醛的方法

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US11760170B2 (en) 2020-08-20 2023-09-19 Denso International America, Inc. Olfaction sensor preservation systems and methods
US11813926B2 (en) 2020-08-20 2023-11-14 Denso International America, Inc. Binding agent and olfaction sensor
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US11932080B2 (en) 2020-08-20 2024-03-19 Denso International America, Inc. Diagnostic and recirculation control systems and methods
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WO2019080025A1 (fr) 2017-10-26 2019-05-02 Honeywell International Inc. Systèmes et procédés d'utilisation d'une pluralité de capteurs à électrolyte solide pour un détecteur de formaldéhyde sélectif à basse résolution
EP3701255A4 (fr) * 2017-10-26 2021-06-23 Honeywell International Inc. Systèmes et procédés d'utilisation d'une pluralité de capteurs à électrolyte solide pour un détecteur de formaldéhyde sélectif à basse résolution
CN111024765A (zh) * 2019-12-31 2020-04-17 深圳市普晟传感技术有限公司 一种甲醛的检测方法及抗干扰性甲醛检测装置
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US11760169B2 (en) 2020-08-20 2023-09-19 Denso International America, Inc. Particulate control systems and methods for olfaction sensors
US11760170B2 (en) 2020-08-20 2023-09-19 Denso International America, Inc. Olfaction sensor preservation systems and methods
US11813926B2 (en) 2020-08-20 2023-11-14 Denso International America, Inc. Binding agent and olfaction sensor
US11828210B2 (en) 2020-08-20 2023-11-28 Denso International America, Inc. Diagnostic systems and methods of vehicles using olfaction
US11881093B2 (en) 2020-08-20 2024-01-23 Denso International America, Inc. Systems and methods for identifying smoking in vehicles
US11932080B2 (en) 2020-08-20 2024-03-19 Denso International America, Inc. Diagnostic and recirculation control systems and methods
US12017506B2 (en) 2020-08-20 2024-06-25 Denso International America, Inc. Passenger cabin air control systems and methods

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