WO2017161335A1 - Amperometric electrochemical sensors, sensor systems and detection methods - Google Patents
Amperometric electrochemical sensors, sensor systems and detection methods Download PDFInfo
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- WO2017161335A1 WO2017161335A1 PCT/US2017/023069 US2017023069W WO2017161335A1 WO 2017161335 A1 WO2017161335 A1 WO 2017161335A1 US 2017023069 W US2017023069 W US 2017023069W WO 2017161335 A1 WO2017161335 A1 WO 2017161335A1
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Classifications
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- 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
- G01N27/406—Cells and probes with solid electrolytes
- G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
- G01N27/4071—Cells and probes with solid electrolytes for investigating or analysing gases using sensor elements of laminated structure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
- F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- 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
- G01N27/406—Cells and probes with solid electrolytes
- G01N27/4067—Means for heating or controlling the temperature of the solid electrolyte
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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
- G01N27/406—Cells and probes with solid electrolytes
- G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
- G01N27/4075—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
- G01N27/4076—Reference electrodes or reference mixtures
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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
- G01N27/416—Systems
- G01N27/4162—Systems investigating the composition of gases, by the influence exerted on ionic conductivity in a liquid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
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- 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
- G01N33/0054—Ammonia
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Definitions
- Amperometric devices disclosed in the literature typically rely upon the catalytic decomposition of NOx to provide the detected current under the imposed voltage, as shown by the following equations: the reduction of N0 2 to NO: N0 2 ⁇ 1 ⁇ 2 0 2 + NO, and/or the reduction of NO to N 2 and 0 2 : NO ⁇ 1 ⁇ 2 N 2 + 1 ⁇ 2 0 2 .
- Other amperometric sensors such as those described in U.S. Pat. No.
- 9,304, 102 are based on an adsorbed gas species (e.g., NOx) increasing the rate of oxygen reduction at the sensing electrode, rather than relying on the decomposition of that gas species (e.g., the catalytic decomposition of NOx) in order to sense target gas (e.g., NOx) concentration.
- An increase in oxygen reduction current, caused by the presence of adsorbed NOx, is used to detect the presence and/or concentration of NOx in oxygen-containing gas streams.
- FIG. 1 is a schematic, cross-sectional view of an electrochemical sensor incorporated into a sensor system, wherein the active and counter electrodes are located on the same side of the electrolyte layer (i.e., surface electrodes), the active electrode has a full coverage current collector layer, and a passive, signal amplifying layer is located on the opposite side of the electrolyte layer, encapsulated (i.e., buried) between the electrolyte layer and the supporting substrate.
- the active and counter electrodes are located on the same side of the electrolyte layer (i.e., surface electrodes)
- the active electrode has a full coverage current collector layer
- a passive, signal amplifying layer is located on the opposite side of the electrolyte layer, encapsulated (i.e., buried) between the electrolyte layer and the supporting substrate.
- FIG. 2 is an exploded view of an electrochemical sensor design similar to that of
- FIG. 1 (without a biasing source or current measuring device), wherein the sensor includes a pair of substrate layers, a heater layer embedded between the substrate layers, a resistance temperature detector (“RTD”) layer on a bottom substrate face, and multiple sequential layers on an upper substrate face: a signal amplifying layer (labeled “Pt-B”), an electrolyte membrane layer (labeled “GDC”), an active electrode layer (labeled “AE”), a counter electrode layer (labeled "CE”), and a current collector layer (labeled "CC”) that covers the active electrode layer.
- a signal amplifying layer labeleled "labeled "Pt-B”
- GDC electrolyte membrane layer
- AE active electrode layer
- CE counter electrode layer
- CC current collector layer
- FIG. 3 is a schematic illustration of circuitry for use in conjunction with the sensors described herein, wherein the current measuring functionality (i.e., an ammeter) is provided by measuring the voltage drop across a shunt resistor with the voltage drop being proportional to the current flowing through the sensor.
- the current measuring functionality i.e., an ammeter
- FIG. 4A and FIG. 4B are top and cross-sectional schematic views, respectively, of yet another alternative embodiment of a sensor system comprising two electrochemical cells having a common electrolyte layer and a common counter-electrode layer located between the two active electrode layers on the same side of the electrolyte layer (also referred to as a surface electrode sensor), along with a signal amplifying layer encapsulated between the electrolyte layer and the supporting substrate.
- a sensor system comprising two electrochemical cells having a common electrolyte layer and a common counter-electrode layer located between the two active electrode layers on the same side of the electrolyte layer (also referred to as a surface electrode sensor), along with a signal amplifying layer encapsulated between the electrolyte layer and the supporting substrate.
- FIG. 4C and FIG. 4D are top and cross-sectional schematic views, respectively, of an alternative embodiment of a surface electrode sensor system comprising two electrochemical cells having separate electrolyte layers and a common counter-electrode layer located between the two active electrode layers, along with a signal amplifying layer encapsulated between the electrolyte layer and the supporting substrate.
- FIG. 4E and FIG. 4F are top and cross-sectional schematic views, respectively, of another alternative embodiment of a surface-electrode sensor system comprising two electrochemical cells having separate electrolyte layers and separate counter-electrode layers, along with a signal amplifying layer encapsulated between the electrolyte layer and the supporting substrate.
- FIG. 4G and FIG. 4H are top and cross-sectional schematic views, respectively, of yet another embodiment of a surface-electrode sensor system having separate electrolyte layers and a common counter-electrode layer, wherein the electrodes have an interdigitated configuration, along with a signal amplifying layer encapsulated between the electrolyte layer and the supporting substrate.
- FIGS. 5-11 are schematic cross-sectional views of various additional sensor electrochemical cell (or sense element) embodiments that include a SAL, as further described herein.
- FIGS. 12 and 13 depict the sense elements used in Examples 1 and 2, as well as the results of the testing of these sensors with simulated combustion exhaust.
- FIG. 14 is a bar chart comparing current signals in simulated combustion exhaust atmospheres (baseline gas, baseline with 100 ppm NO, baseline with 100 ppm N0 2 , and baseline with 100 ppm NH 3 ) for the sensor of Example 3, tested at 525°C with an applied bias voltage of 200 mV.
- FIG. 15 is a bar chart comparing current signals in simulated combustion exhaust atmospheres (baseline gas, baseline with 100 ppm NO, baseline with 100 ppm N0 2 , and baseline with 100 ppm NH 3 ) for the sensor of Example 4, tested at 525°C with an applied bias voltage of 200 mV.
- FIG. 16 is a bar chart comparing current signals in simulated combustion exhaust atmospheres (baseline gas, baseline with 100 ppm NO, baseline with 100 ppm N0 2 , and baseline with 100 ppm NH 3 ) for the sensor of Example 5, tested at 525°C with an applied bias voltage of 200 mV.
- FIG. 17 is a bar chart comparing current signals in simulated combustion exhaust atmospheres (baseline gas, baseline with 100 ppm NO, baseline with 100 ppm N0 2 , and baseline with 100 ppm NH 3 ) for the sensor of Example 6, tested at 525°C with an applied bias voltage of 200 mV.
- FIG. 18 schematically depicts the sense element used in Example 11, operated with a forward bias and depicting the results of the testing of this sensor with simulated combustion exhaust and showing the response to NO, N0 2 and NH 3 at varying oxygen levels in the gas sample.
- FIG. 19 schematically depicts the sense element used in Example 12, operated with a reverse bias and depicting the results of the testing of this sensor with simulated combustion exhaust and showing the response to NO, N0 2 and NH 3 at varying oxygen levels in the gas sample.
- FIG. 20 graphically depicts the results of the testing of the sense element of FIG.
- FIGS. 21-25 depict schematic cross-sectional views of alternative embodiments of sense elements wherein one or both of the electrodes comprise a current collecting layer located on the electrolyte layer and a catalyst layer is located over the current collecting layer, as further described herein.
- the present disclosure provides amperometric electrochemical sensors, as well as sensor systems and gas species detection methods employing such sensors, wherein those sensors comprise two (or more) surface electrodes located on an electrolyte, as well as a passive, conductive, signal amplifying layer.
- the signal amplifying layer is positioned in contact with the electrolyte and below, but not in contact with, the surface electrodes (e.g., encapsulated within or immediately below the electrolyte layer).
- the signal amplifying layer despite being spaced away from the surface electrodes by the electrolyte layer, enhances signal strength and, in some instances, desirably affects sensor selectivity with respect to one or more gas species.
- the addition of a signal amplifying layer between the bottom surface of the electrolyte layer and the sensor substrate increased the signal strength of the sensor more than tenfold while also significantly increasing the sensor's sensitivity to NO, ⁇ and NH 3 .
- the signal amplifying layer provides a lateral current path and effectively increases the areas of the active and counter electrodes. This finding is surprising in that electricity is normally conducted between the electrodes through or along the surface of the electrolyte layer by oxygen ions only.
- the signal amplifying layer when the signal amplifying layer is present, some of the oxygen ions, normally conducted between the electrodes through the electrolyte layer, are converted into electrons at the interface of the electrolyte layer and the signal amplifying layer. These electrons are then transported through the signal amplifying layer and thereafter react with oxygen to form oxygen ions at the interface of the signal amplifying layer and the electrolyte layer. Even though this requires two additional electrochemical reactions, the signal amplifying layer provides a faster pathway for the transport of charge carriers between the electrodes.
- Day et al. amperometric sensors that include an electrically conductive active electrode comprising at least one molybdate or tungstate compound.
- the sensors described in Day et al. are highly responsive to NO x levels at desirable temperatures (e.g., 500- 600°C), and, in some instances, are highly responsive to both ⁇ and NH 3 .
- the sensors of Day et al. also are responsive to ⁇ and H 3 in the presence of steam, carbon dioxide and sulfur oxides (SO x ), which are additional constituents of diesel exhaust streams.
- selection of the molybdate and/or tungstate compound used in the active electrode(s), and/or selection of a current collector(s) layer applied over the active electrode(s) can be used to tailor the sensor such that it can be used to determine, for example, both the NO x and NH 3 concentrations in a gas sample (i.e., the amount of ⁇ and the amount of NH 3 , rather than the total amount of ⁇ and NH 3 ).
- Electrodes are located on the same side of the electrolyte membrane rather than located on opposite sides of the electrolyte.
- the electrodes are located on the same side of the sensor with respect to the electrolyte layer(s).
- An electrode e.g., a counter electrode
- Such surface electrodes are located on the upper surface of the electrolyte layer such that both are exposed to the gaseous analyte sample or stream being analyzed.
- the present disclosure is based, in part, on the surprising discovery that a passive, conductive, signal amplifying layer (hereinafter, a "SAL") located below, but not in contact with, the surface electrodes of an amperometric sensor surprisingly enhances signal strength and, in some instances, sensor selectivity with respect to one or more gas species.
- the sensor electrodes can be located on the upper surface of an electrolyte, with the SAL located within or beneath the electrolyte.
- one or both of the electrodes of an amperometric sensor comprise a current collecting layer located on the electrolyte layer and a catalyst layer is located over the current collecting layer.
- Embodiments of the amperometric electrochemical sensors, sensor systems and detection methods described herein are adapted to detect target gas species in a gaseous analyte sample or stream using a surface electrode arrangement.
- the electrodes instead of locating the electrodes on opposite sides of the sensor with respect to an electrolyte layer(s), the electrodes are located on the same side of the sensor with respect to the electrolyte layer(s).
- a passive, conductive, signal amplifying layer, or SAL is also provided, spaced away from the sensors.
- the SAL is in conductive contact with the electrolyte layer and can be located, for example, on the side of the electrolyte layer opposite that of the electrodes— e.g., between the electrolyte layer and a sensor substrate.
- the SAL can be fully encapsulated between the electrolyte layer and the substrate (see, e.g., FIG. 1), or only partially encapsulated (e.g., such that the outer edges of the SAL are not covered by the electrolyte or substrate).
- the SAL can be fully encapsulated within the electrolyte layer, spaced away from both the upper and lower surfaces of the electrolyte layer such that the SAL is not in contact with a substrate on which the electrolyte layer is located.
- the advantages provided by the SAL are greater when the distance between the SAL and the electrodes is minimized without being so small that shorting between an electrode and the SAL occurs.
- the signal amplifying layer is passive in that it has no direct electrical connection to, or contact with the sensors, a biasing source or a current measuring device.
- the SAL is only in direct, conductive contact with the electrolyte layer and the substrate (which is typically non-conductive). All conductivity between the electrodes and the SAL is through the electrolyte layer of the sensor, and no other current or electrical bias is supplied to the SAL.
- the signal amplifying layer surprisingly and significantly enhances signal strength and, in some instances, sensor sensitivity to certain gas species.
- the SAL can be made from any of a variety of conductive materials suitable for sensor fabrication. Suitable materials include, for example, Pt, Pd, Au, Ag, alloys of the foregoing metals (e.g., an alloy of Pt with Pd, Au and/or Au), and other conductive metals conductive ceramics or cermets. Platinum is particularly useful.
- the amperometric electrochemical sensors, sensor systems and detection methods described herein are adapted to detect one or more target gas species in a gaseous analyte sample or stream.
- the sensor comprises at least one electrochemical cell.
- the sensors generally include at least two electrochemical cells.
- a sensor comprising two electrochemical cells can be configured such that one of the cells exhibits an additive response to the gas species of interest and another cell exhibits a selective response to at least one of the gas species.
- a sensor comprising a single electrochemical cell can be operated under two or more distinct conditions (e.g., forward bias and reverse bias) in order to provide two or more response characteristics, as further described herein.
- the two (or more) electrochemical cells of a sensor are completely separate structures, while in other embodiments the two (or more) electrochemical cells of a sensor share one or more components such as a common electrolyte layer, SAL, substrate, counter electrode or active electrode.
- each electrochemical cell of an amperometric surface electrode sensor includes an electrically conductive active electrode, an electrically conductive counter electrode (in some instances referred to as a second active electrode), an electrolyte layer, and a SAL.
- the active and counter electrodes are located on the same side of the electrolyte layer, in spaced-apart relationship, such that oxygen ions are conducted across the surface of and within the electrolyte layer.
- the active and counter electrodes are in a side-by-side arrangement on the electrolyte layer.
- the active and counter electrodes can be formed in an interdigitated arrangement (e.g., as seen in FIG. 4G).
- a current collector layer in electrical communication with the active electrode is also included, as well as, in some instances, a current collector layer in electrical communication with the counter (or second active) electrode.
- the current collector layer(s) can be applied on top of the electrode.
- the current collector layer(s) can be located between the electrode and the electrolyte layer, as also discussed below.
- the amperometric sensors, systems and methods described herein can be used to detect target gas species such as ⁇ and/or H 3 in the oxygen- containing environment of a combusted hydrocarbon fuel exhaust, using, at least in part, an electro-catalytic effect.
- the amperometric sensors, sensor systems and detection methods can operate in combustion exhaust streams (e.g., exhaust from a diesel engine of a vehicle), with significantly enhanced sensitivity to both ⁇ and NH 3 .
- the sensor can be configured to enable differentiation and quantification of NO x and H 3 concentrations.
- Embodiments of the electrochemical sensors, sensor systems and methods described herein are configured as amperometric devices/methods which respond in a predictable manner when an adsorbed gas species (e.g., ⁇ ) changes the rate of oxygen reduction at an active electrode of the sensor, under the influence of a bias applied between the two electrodes, rather than relying on the decomposition of that gas species (e.g., the catalytic decomposition of ⁇ ) in order to sense target gas (e.g., NO x ) concentration.
- a change in oxygen reduction current, caused by the presence of adsorbed ⁇ is used to detect the presence and/or concentration of ⁇ in oxygen-containing gas sample or stream. This mechanism is extremely fast and produces a current greater than what is possible from the reduction of NO x alone. Further, this catalytic approach has been demonstrated to extend to H 3 .
- each electrochemical cell of the amperometric ceramic electrochemical sensor comprises: an electrolyte layer comprising a continuous network of a material which is ionically conducting at an operating temperature of about 400 to 700°C; a counter electrode layer which is electrically conductive at an operating temperature of about 400 to 700°C; and an active electrode layer which is electrically conductive at an operating temperature of about 400 to 700°C.
- the active electrode layer is operable to exhibit a change in charge transfer in the presence of one or more target gas species and comprises a molybdate or tungstate compound, typically in combination with other materials such as an electrolyte and a metal.
- the electrode layers are located on the same side of the electrolyte layer, but are not in physical contact with one another (i.e., they are spaced apart).
- Embodiments of the electrochemical cells are operable to exhibit conductivity to oxygen ions at an operating temperature of about 400 to 700°C. When bias is applied between the electrodes, the electrochemical cell(s) generates an electrical signal as a function of target gas concentration in an oxygen-containing gas stream, in the absence of oxygen pumping currents.
- the electrochemical cell(s) further includes a current collector layer which is electrically conductive at an operating temperature of about 400 to 700°C, wherein the current collector layer is in electrical communication with (e.g., located on the surface of) the active electrode layer(s).
- the current collector layer is more electrically conductive than the active electrode layer, particularly at an operating temperature of about 400 to 700°C.
- the purpose of the current collector layer is to augment the electrical conductivity of the active electrode.
- the current collector layer can also be chosen such that it also manipulates the catalytic and electrochemical reactions occurring at the active electrode, thereby providing reduced or enhanced sensitivity to one or more gas species of interest (e.g., NO, N0 2 or NH 3 ).
- the combination of the active electrode and the current collector layer can be considered a two-layer active electrode.
- the sensors described herein can be fabricated to have the ability to detect, for example, NO, N0 2 and NH 3 , including at levels as low as 3 ppm and/or to exhibit response times as fast as 50 ms, allowing for better system controls or even engine feedback control.
- NO x and NH 3 responses of some embodiments are greater than the sensitivity to variable background exhaust gases.
- sensors, sensor systems and detection methods described herein have applicability to the detection of ⁇ in diesel exhaust systems, including exhaust systems found in heavy duty trucks and stationary generators, the same are also useful in a wide range of other applications in which rapid response to low levels of NO x and/or H 3 is desired, particularly in oxygen-containing gas streams or samples.
- Examples include diesel generator sets, large-scale stationary power generators, turbine engines, natural gas fired boilers and even certain appliances (e.g., natural gas powered furnaces, water heaters, stoves, ovens, etc.).
- the sensors, sensor systems and detection methods are particularly useful in sensing low levels of NO x in the presence of fixed or variable concentrations of other gases, such as 0 2 , C0 2 , SOx (SO and/or S0 2 ), H 2 0, and H 3 .
- the active electrode and/or current collector layer of a first electrochemical cell is exposed to two or more target gas species (e.g., ⁇ and H 3 ) such that the target gas species change the amount of oxygen reduced within the first electrochemical cell proportional to their concentrations.
- target gas species e.g., ⁇ and H 3
- the total concentration of the target gas species in a gas sample or stream can be correlated with the oxygen ion current through the first electrochemical cell at any given applied voltage bias and sensor temperature.
- the response of the first electrochemical cell of the sensor in this example is "additive" in that the measured current at a given voltage bias and temperature can be correlated with the combined total concentration of the target gas species (e.g., NO x and H 3 ).
- the active electrode and/or current collector layer of the second electrochemical cell also is exposed to the two or more target species.
- the second electrochemical cell is configured and/or operated such that a first one of the target gas species (e.g., ⁇ ) measurably changes the amount of oxygen reduced within the second cell, while a second one of the target gas species (e.g., H 3 ) has a significantly smaller effect (if any) on the amount of oxygen reduced within the second cell.
- the second electrochemical cell is "selective" with respect to a first one of the target gas species in that the measured current through the second electrochemical cell can be correlated with the concentration of the first target gas species (e.g., ⁇ ) while changes in the concentration of the second target gas species do not appreciably affect (if at all) the measured current through the second electrochemical cell. In this manner, the concentrations of the target gas species can be determined.
- concentration of the target gas species can be determined.
- any number of electrochemical cells can be provided as part of a single sensor in order to, for example, detect more than two gas species.
- FIG. 1 illustrates an exemplary amperometric sensor system (10) comprising a single electrochemical cell (20) (i.e., a sensor) as well as circuitry comprising a biasing source (40) and a current measuring device (50).
- a single electrochemical cell (20) i.e., a sensor
- circuitry comprising a biasing source (40) and a current measuring device (50).
- FIG. 4F depicts a sensor generally comprising two electrochemical cells, each of which is similar in construction to the individual cell (20) of the sensor shown in FIG. 1, with the cells deposited onto a common substrate (428).
- Electrochemical cell (20) includes an active electrode (22), a counter electrode
- the electrically conductive active electrode (22) comprises at least one molybdate or tungstate compound.
- a passive, conductive, signal amplifying layer (or SAL)
- Biasing source (40) is configured to apply a bias voltage between the two electrodes (22, 26), and current measuring device (50) is configured to measure the resulting current through sensor (20).
- Biasing source (40) can comprise any of a variety of power supplies or other devices suitable for applying a bias between the active electrode (22) and the counter electrode (26).
- the current measuring device (50) in FIG. 1 can comprise any of a variety of structures and devices known to those skilled in the art (or hereafter developed), such as an ammeter. As is well known to those skilled in the art, an ammeter can be provided by the combination of a shunt resistor and a voltmeter (as shown in FIG. 3).
- FIG. 2 is an exploded view of an electrochemical sensor similar to that of FIG. 1, with the addition several components.
- the sensor of FIG. 2 is fabricated by sequentially depositing the following layers onto an insulating substrate (i.e., the uppermost A1 2 0 3 layer in FIG.
- a signal amplifying layer (“Pt-B”); a single, common electrolyte layer (“GDC") that is deposited on the SAL; an active electrode layer (“AE”) that is deposited on a portion of the upper surface of the electrolyte layer; a counter electrode layer (CE) that is deposited on a different portion of the upper surface of the electrolyte layer, spaced apart from the active electrode; and a first current collector layer (“CC”) that is deposited on the upper surface of the active electrode layer.
- a second current collector layer can be deposited on the upper surface of the counter electrode layer.
- the senor includes a second insulating A1 2 0 3 substrate layer, along with a platinum resistive heater (“Pt-H”) embedded between the substrate layers, and a platinum resistance temperature detector (“Pt- RTD", for monitoring sensor temperature) laminated to the bottom surface of the second substrate layer.
- Pt-H platinum resistive heater
- Pt- RTD platinum resistance temperature detector
- Leads for the electrodes and current collectors (“Pt-L”) are also shown along with leads for the Pt-H and Pt-RTD, are also depicted.
- the SAL (27) enhances the transport of oxygen ions from one electrode to the other.
- the SAL (27) provides an interface with the electrolyte layer whereat oxygen ions from the active electrode (22) are converted into electrons. These electrons are then transported through the SAL (27) to the region beneath the counter electrode (26), and then react with oxygen to form oxygen ions at the SAL/electrolyte interface. These oxygen ions are then transported through the electrolyte layer to the counter electrode (26).
- the SAL (27) provides an additional (and faster) pathway for the transport of oxygen ions from one electrode to the other through the electrolyte.
- the electrolyte layer is porous. In other embodiments the electrolyte layer is dense (no through porosity).
- electrolyte membrane (24) extends over the sides of the SAL (27) such that the SAL (27) is fully encapsulated between the electrolyte membrane (24) and the substrate (28). In other embodiments, e.g. FIGS. 7 and 8, the SAL is not fully encapsulated. It will therefore be understood that the full encapsulated SAL (27) in the embodiment of FIG. 1 can be replaced by the SAL arrangement shown in FIGS.
- the electrolyte does not extend over the entire periphery of the SAL.
- "fully encapsulated” means that the SAL is surrounded by the electrolyte layer and substrate, or by the electrolyte layer alone (i.e., the SAL is not in contract with the substrate, but rather a portion of the electrolyte layer is located between the SAL and the substrate).
- Embodiments of the sensors described herein include a substrate on which the electrochemical cell(s) is fabricated or otherwise supported, thereby providing mechanical support for the sensor.
- the substrate is generally non-conductive (i.e., insulating).
- the substrate may comprise any suitable insulating material such as an insulating ceramic material (e.g., aluminum oxide) or a metal or cermet material coated with an insulating material.
- the sensor includes a zirconia substrate, more specifically, an yttrium-stabilized zirconia (YSZ) substrate.
- the substrate may comprise a semiconducting material such as silicon or silicon carbide, with the components of the electrochemical cell(s) fabricated on the surface of the substrate using semiconductor fabrication techniques.
- the active electrode comprises a molybdate and/or tungstate compound
- any of a variety of molybdate and/or tungstate compounds can be used. Suitable compounds include those having the formula ⁇ ( ⁇ ( 1 - Z )W Z ) Y O( X + 3Y ), wherein X and Y are each independently selected integers from 1 to 5, 0 ⁇ Z ⁇ 1, and A is one or more ions that form binary compounds with Mo and/or W.
- A is one or more of Mg, Zn, Ni, Co, Fe, Mn, Cu, Ca, Sr, Ba, and Pb.
- X and Y are both 1, and Z is 0.
- molybdate compounds include: MgMo0 4 , ZnMo0 4 , NiMo0 4 , CoMo0 4 , FeMo0 4 , MnMo0 4 , CuMo0 4 , CaMo0 4 , SrMo0 4 , BaMo0 4 , and PbMo0 4 .
- X and Y are both 1, and Z is 1.
- Such tungstate compounds include: MgW0 4 , ZnW0 4 , NiW0 4 , CoW0 4 , FeW0 4 , MnW0 4 , CuW0 4 , CaW0 4 , SrW0 4 , BaW0 4 , and PbW0 4 .
- Active electrodes comprising at least one molybdate or tungstate compound may have a variety of specific compositions, including, for example:
- a molybdate compound ( ⁇ ( ⁇ +3 ⁇ ) ) or a tungstate compound including, for example, an active electrode comprising more than 30%, more than 50%, more than 80% or even more than 90% (by volume) of the molybdate or tungstate compound;
- a composite made from a ceramic phase comprising one or more of (a)- (d), and a metallic phase e.g., silver, gold, platinum, palladium, rhodium, ruthenium, iridium or alloys or mixtures thereof; or
- one or more additives or other materials may be added to the active electrode composition during fabrication, while in other embodiments no such additives are included.
- molybdate and tungstate compounds may be doped with one or more metals.
- one or more oxides may be added, such as manganese oxide, iron oxide, cobalt oxide, vanadium oxide, chromium oxide, tin oxide, niobium oxide, tantalum oxide, ruthenium oxide, indium oxide, titanium oxide, and zirconium oxide.
- these oxide additives may be present at an amount of between about 0.1 and 10% by volume in the active electrode layer, or between about 1 and 3% by volume in the active electrode layer.
- the active electrode(s) comprises a multiphase composite of: (a) a molybdate and/or tungstate-containing ceramic phase (e.g., a molybdate, a tungstate, a solid solution or composite mixture of a molybdate and a tungstate, or a composite mixture of one or more of the foregoing and an electrolyte); and (b) a metallic phase (Ag, Au, Pt, Pd, Rh, Ru, Ir, or alloys or mixtures thereof).
- a molybdate and/or tungstate-containing ceramic phase e.g., a molybdate, a tungstate, a solid solution or composite mixture of a molybdate and a tungstate, or a composite mixture of one or more of the foregoing and an electrolyte
- a metallic phase Au, Pt, Pd, Rh, Ru, Ir, or alloys or mixtures thereof.
- the amount of the metallic phase can range from about 0.1% to 10% by weight or about 30 to 70% by volume.
- the multi-phase ceramic/metal composites having low levels of the metallic phase e.g., about 0.1% to 10%, or about 1% to 5% by weight.
- Pt, Pd, Rh, Ru, or Ir are particularly useful.
- Ag, Au, Pt, Pd, Rh, Ru, or Ir may be used in order to improve electrical conductivity (although some sensitivity may be sacrificed).
- the active electrode(s) comprises a composite mixture of: (a) one or more ceramic electrolyte materials (e.g., gadolinium -doped ceria, "GDC,” or samarium-doped ceria, "SDC”); (b) one or more molybdate and/or tungstate compounds; and, optionally, (c) a metallic phase (e.g., silver, gold, platinum, palladium, rhodium, ruthenium, iridium, or alloys or mixtures thereof).
- ceramic electrolyte materials e.g., gadolinium -doped ceria, "GDC,” or samarium-doped ceria, "SDC”
- GDC gadolinium -doped ceria
- SDC samarium-doped ceria
- the ceramic electrolyte material(s) in the active electrode (22) may be any of the electrolytes described below for electrolyte membrane (24), or another ceramic electrolyte material which conducts electricity through the conduction of oxygen ions (i.e., ionic conductivity rather than electronic conductivity).
- suitable ceramic electrolytes for use in the active electrode include:
- the ceramic electrolyte used in the active electrode comprises cerium oxide doped with one or more of Ca, Sr, Sc, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or La.
- GDC or SDC is employed, in some instances in combination with Pt as the metallic phase.
- the relative amounts of ceramic electrolyte and one or more molybdate/tungstate compounds in the composite mixtures described in the previous paragraph may be varied depending on, among other things, the nature of the application (e.g., the analyte gas stream/sample and surrounding environment), the configuration of the sensor and/or sensor system, the desired sensitivity, the identity of the target gas(es), etc.
- the volumetric ratio of ceramic electrolyte(s) to molybdate/tungstate compound(s) in the active electrode is between about 1 :9 and 9: 1. In other embodiments, this ratio is between about 2.5:7.5 and 7.5:2.5, or even between about 4:6 and 6:4. And in still other embodiments this ratio is about 1 : 1.
- volumetric ratios are based upon the ratio of the total volume of ceramic electrolytes to the total volume of molybdate and tungstate compounds in the active electrode layer in question.
- the nature and amount of the metallic phase may be any of the various metals and amounts described previously.
- the active electrode material can be any of the materials described in previous sensor patents and published patent applications of Applicant previously incorporated by reference herein.
- the active electrode material can be electronically conductive or ionically conductive.
- the active electrode material can be highly conductive such that a current collector layer is not required to achieve optimum signal strength, or minimally or moderately conductive such that a current collector layer is required to achieve optimum signal strength. (Signal strength is defined as the electrical current that results when a bias voltage is applied.)
- suitable active electrode materials for use in combination with a SAL for increasing signal strength include: a lanthanide manganite perovskite material, doped with Ca, Sr, Ba, Fe, Co, Ni, Cu, Zn, Mg or a mixture thereof; lanthanide ferrite perovskite material, doped with Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn, Mg or a mixture thereof; lanthanide cobaltite perovskite material, doped with Ca, Sr, Ba, Mn, Fe, Ni, Cu, Zn, Mg or a mixture thereof; lanthanide nickelate perovskite material, doped with Ca, Sr, Ba, Mn, Fe, Co, Cu, Zn, Mg or a mixture thereof; lanthanide cuprate perovskite material, doped with Ca, Sr, Ba, Mn,
- a current collector layer is provided for the active electrode layer(s) of the electrochemical cell(s), and, optionally, for the counter electrode layer(s).
- the current collector layer is more electrically conductive than the active electrode layer, and therefore augments the electrical conductivity of the active electrode so as to increase signal strength.
- the current collector layer also manipulates the catalytic and electrochemical reactions occurring at the underlying electrode such that reduced or enhanced sensitivity to one or more gas species of interest (e.g., NO, N0 2 or NH 3 ) is achieved.
- electrochemical cell (20) in FIG. 1 includes a current collector layer
- Active electrode layer (22) is adjacent electrolyte membrane (24), while current collector layer (36) is located over active electrode layer (22).
- Current collector layer (36) has a higher electrical conductivity than the active electrode layer (22).
- the current collector layer is configured as a full coverage current collector in that it covers at least about 90% of the top surface of the active electrode layer (22).
- the current collector can be configured to cover about 10-25% of the surface of the active electrode, as further described in Patent Pub. No. US 2016/077044.
- the current collector layer when the current collector is used merely to augment the electrical conductivity of the active electrode rather than manipulate the catalytic and/or electrochemical reactions at the underlying electrode, the current collector layer can comprise a noble metal such as platinum, palladium, gold, silver, or any other noble metal, an alloy of two or more noble metals, an alloy of one or more noble metals and one or more base metals, or a cermet of a noble metal and a ceramic electrolyte material.
- a noble metal such as platinum, palladium, gold, silver, or any other noble metal
- an alloy of two or more noble metals an alloy of one or more noble metals and one or more base metals
- cermet of a noble metal and a ceramic electrolyte material a noble metal such as platinum, palladium, gold, silver, or any other noble metal, an alloy of two or more noble metals, an alloy of one or more noble metals and one or more base metals, or a cermet of a noble metal and a ceramic electrolyt
- the current collector layer can comprise a cermet comprising a metal (e.g., platinum or gold) and a ceramic phase such as GDC, SDC, zirconium-doped ceria ("ZDC"), yttrium stabilized zirconia (“YSZ”), scandium stabilized zirconia (“ScSZ”), or one of the other ceramic electrolytes mentioned as being suitable for use in the active electrode.
- the metal content of such cermet current collector layers should be sufficient to make the electrical conductivity of the current collector layer higher than that of the underlying electrode layer.
- such cermet current collectors can be used to manipulate the catalytic and/or electrochemical reactions of the electrochemical cell(s) of the sensor (e.g., to provide reduced or enhanced sensitivity to one or more gas species of interest).
- the cermet current collector(s) comprises platinum and a ceramic electrolyte (e.g., ScSz) in order to provide additive behavior with respect to ⁇ and H 3
- cermet current collector(s) comprising gold and a ceramic electrolyte (e.g., GDC) provide selective behavior with respect to ⁇ in the presence of H 3
- the current collector can comprise about 40 to 80 vol%, or about 50 to 70 vol% of the metal phase (e.g., Pt or Au), with the remainder being the ceramic electrolyte phase (e.g., GDC or ScSz).
- the counter electrode of the electrochemical cells of the sensors described herein can comprise any of a variety of materials, depending in part on the configuration of the electrochemical cell(s).
- the counter electrode can comprise any of the compositions described above with respect to the current collector, such as a metallic material such as platinum or gold, or a conductive cermet comprising a metal (e.g., platinum or gold) and a ceramic phase (GDC, SDC, ZDC, YSZ or ScSZ).
- the counter electrode can also be any of the materials identified above for the active electrode.
- Other suitable materials for the counter electrodes of the sensors described herein include:
- cermet of any of the foregoing e.g., a cermet comprising one or more of these metals, particularly Pt, and YSZ, ScSZ, GDC or SDC
- various other conductive materials suitable for sensor fabrication particularly materials which catalyze the re-oxidation of oxygen ions to molecular oxygen, including, for example, conductive perovskites, such as (La,Sr)Mn0 3 , (La,Sr)Co0 3 , (La,Sr)(Co,Fe)0 3 , La(Ni,Fe)0 3 , La(Ni,Co)0 3 , and related perovskite and brownmillerite structured materials.
- the counter electrode material can be any of the materials described in the previous sensor patents and published patent applications of Applicant previously incorporated by reference herein.
- suitable counter electrode materials for use in combination with a SAL for increasing signal strength include: a lanthanide manganite perovskite material, doped with Ca, Sr, Ba, Fe, Co, Ni, Cu, Zn, Mg or a mixture thereof; lanthanide ferrite perovskite material, doped with Ca, Sr, Ba, Mn, Co, Ni, Cu, Zn, Mg or a mixture thereof; lanthanide cobaltite perovskite material, doped with Ca, Sr, Ba, Mn, Fe, Ni, Cu, Zn, Mg or a mixture thereof; lanthanide nickelate perovskite material, doped with Ca, Sr, Ba, Mn, Fe, Co, Cu, Z
- each "electrode" of an electrochemical cell can be considered to be the combination of an active (or “functional") electrode layer and a current collecting layer (if any).
- a single electrochemical cell of a sensor can comprise first and second two-layer electrodes, each having an active (or "functional") layer and a current collecting layer, wherein at least one of the layers of the first electrode has a composition that is different from the corresponding layer of the second electrode. Accordingly, the first and second electrodes are different with respect to their catalytic and/or electro-catalytic responses to the gas species to be detected.
- the first electrode is a combination of an active electrode layer and an overlying current collecting layer, an active electrode layer only, or a current collecting layer only (i.e., a traditional counter electrode), and the second electrode is a different combination of an active electrode layer and/or current collecting layer.
- suitable materials include doped ceria electrolyte and doped zirconia electrolyte. More specific examples include gadolinium-doped ceria (Cei.xGdx0 2 -x/2, wherein X ranges from approximately 0.05 to 0.40), samarium-doped ceria (Cei-xSmx0 2- x/2, where X ranges from approximately 0.05 to 0.40), yttrium-doped ceria (YDC), cerium oxide doped with other lanthanide elements, and cerium oxide doped with two or more lanthanide or rare earth elements.
- gadolinium-doped ceria Caei.xGdx0 2 -x/2, wherein X ranges from approximately 0.05 to 0.40
- samarium-doped ceria Cei-xSmx0 2- x/2, where X ranges from approximately 0.05 to 0.40
- YDC yttrium-doped c
- Still other suitable electrolyte materials include: fully or partially doped zirconium oxide, including but not limited to yttrium stabilized zirconia (YSZ) and scandium doped zirconia (ScSZ); other ceramic materials that conduct electricity predominantly via transport of oxygen ions; mixed conducting ceramic electrolyte materials; and mixtures of two or more of the foregoing.
- YSZ yttrium stabilized zirconia
- ScSZ scandium doped zirconia
- an interfacial layer of GDC, SDC or another suitable electrolyte material may be provided between the electrolyte membrane and one or both of the active and counter electrodes.
- Particularly suitable electrolyte materials include GDC, SDC, YSZ and ScSZ.
- the ceramic electrolyte material can be beta alumina, sodium zirconium phosphate, lithium silicate, lithium aluminum silicate, or any alkali-ion conducting electrolyte material.
- some embodiments of the sensors and sensor systems described herein generally comprise at least two electrochemical cells, wherein the first cell is configured (or operated) so as to provide an additive response with respect to two or more target gas species of interest (e.g., ⁇ and 3 ⁇ 4) and the second cell is configured (or operated) so as to provide a selective response with respect to a first one of the target gas species but not a second one of the target gas species.
- a sensor can be constructed with two electrochemical cells having different active electrodes: one that is sensitive to both ⁇ and H 3 and one that is sensitive only to ⁇ (with little or no sensitivity to H 3 ).
- Total ⁇ plus H 3 concentration can be quantified by measuring current when applying a bias to the first electrochemical cell, the ⁇ concentration can be quantified by measuring current when applying a bias to the second electrochemical cell, and the H 3 concentration can be calculated by subtraction (total ⁇ plus H 3 concentration minus ⁇ concentration).
- both ⁇ and H 3 can be measured in a single sensor.
- the two electrochemical cells can be physically combined into one structure (e.g., with a common electrolyte layer, common SAL, common substrate and, optionally, common counter electrode), or two physically separate electrochemical cells may be fabricated.
- a sensor can be constructed with two electrochemical cells having different current collector materials and the same or different active electrode materials, such that one cell is sensitive to both ⁇ and H 3 , and the other cell is sensitive only to NO x .
- Total ⁇ plus H 3 concentration can be quantified by measuring current when applying a bias to the first electrochemical cell
- NO x concentration can be quantified by measuring current when applying a bias to the second electrochemical cell
- H 3 concentration can be calculated by subtraction.
- both ⁇ and H 3 can be measured in a single sensor.
- the two electrochemical cells can be physically combined into one structure, or two physically separate electrochemical cells may be employed.
- Yet another alternative is a sensor constructed with two electrochemical cells having active electrodes of the same or similar composition, with or without associated current collectors of the same or similar composition, and the sensor can be operated with forward bias (i.e., from active electrode to counter-electrode) applied to one electrochemical cell to detect and quantify total NO x plus H 3 , and with reverse bias (i.e., from counter electrode to active electrode) applied to the second electrochemical cell to detect and quantify either NO x or H 3 (with the other concentration calculated by subtraction).
- forward bias i.e., from active electrode to counter-electrode
- reverse bias i.e., from counter electrode to active electrode
- both ⁇ and H 3 can be measured in a single sensor.
- the two electrochemical cells can be physically combined into one structure, or two physically separate electrochemical cells may be employed.
- a single electrochemical cell is operated with forward and reverse bias (e.g., alternating between the two), wherein the response characteristics are different in the two biasing modes (e.g., additive in one biasing direction, and selective in the other).
- a sensor in another alternative embodiment, can be constructed with two electrochemical cells, each having an active electrode of the same or different composition, with or without associated current collectors of the same or similar composition, and the sensor can be operated such that one cell is operated with forward bias (i.e., from active electrode to counter- electrode) to detect and quantify total NO x , and the second cell operated with reverse bias (i.e., from counter electrode to active electrode) to detect and quantify NH 3 .
- one cell is selective to ⁇ and the other cell is selective to NH 3 .
- both ⁇ and NH 3 can be measured in a single sensor.
- the two electrochemical cells can be physically combined into one structure, or two physically separate electrochemical cells may be employed.
- certain current collector layers are adapted to manipulate the catalytic and electrochemical reactions occurring in the sensor such that reduced or enhanced sensitivity to one or more gas species of interest (e.g., NO, N0 2 or NH 3 ) is achieved in the electrochemical cells.
- gas species of interest e.g., NO, N0 2 or NH 3
- the cells can be configured so as to share a common substrate and, in some instances, a common electrolyte layer and/or a common counter electrode layer.
- FIGS. 4A-H depict such sensor arrangements. It will be understood, however, that the arrangements shown in FIGS.
- the current collector layers can be omitted (if the active electrode layer is sufficiently conductive) or the current collector layers can be configured as a non-full coverage current collector (e.g., as a grid or mesh). It should be noted that the biasing source and current measuring device are not included in FIGS. 4A-H.
- a sensor comprising two electrochemical cells is fabricated by sequentially depositing the necessary layers onto an appropriate insulating substrate (428): a single, common SAL (427); a single, common electrolyte layer (424) deposited over the SAL; a first active electrode layer (422A) that is deposited on a portion of the electrolyte layer surface; a second active electrode layer (422B) that is deposited on a different portion of the electrolyte layer surface; a single, common counter- electrode layer (426) that is deposited on a different portion of the electrolyte layer in close proximity to the first and second electrode layers (e.g., between the first and second active electrode layers) thus defining two electrochemical cells; a first current collector layer (436A) that is deposited on the first active electrode layer; and a second current collector layer (436B) that is deposited on the second active electrode layer.
- a sensor comprising two electrochemical cells is fabricated by sequentially depositing the necessary layers onto an appropriate insulating substrate (428): a first SAL (427A) that is deposited on one area of the insulating substrate; a second SAL (427B) that is deposited on a second area of the insulating substrate; a first electrolyte layer (424A) that is deposited over the first SAL (427A); a second electrolyte layer (424B) that is deposited over the second SAL (427B); a first active electrode layer (422A) that is deposited on a portion of the first electrolyte layer; a second active electrode layer (422B) that is deposited on a portion of the second electrolyte layer; a single, common counter-electrode layer (426) that is deposited on both the first and second electrolyte layers (and an area of the insulating substrate between the first and second electrolyte layers) in
- a sensor comprising two electrochemical cells is fabricated by sequentially depositing the necessary layers onto an appropriate insulating substrate (428): a first SAL (427A) that is deposited on one area of the insulating substrate; a second SAL (427B) that is deposited on a second area of the insulating substrate; a first electrolyte layer (424A) that is deposited over the first SAL (427A); a second electrolyte layer (424B) that is deposited over the second SAL (427B); a first active electrode layer (422A) that is deposited on a portion of the first electrolyte layer; a second active electrode layer (422B) that is deposited on a portion of the second electrolyte layer; a first counter- electrode layer (426A) that is deposited on the first electrolyte layer in close proximity to the first electrode layer (thus defining a first electrochemical cell); a second counter-electrode
- FIGS. 4G and 4H is similar to that of FIGS. 4C and 4D.
- the active and counter electrodes are interdigitated, thereby increasing the effective area of the surface electrodes while minimizing the gap between the electrodes.
- FIGS. 5-11 depict additional sensor embodiments (not to scale), in these instances of single sense elements (i.e., a single electrochemical cell), each of which includes a SAL (527, 627, 727, 827, 927, 1027, 1127).
- SAL single sense elements
- the SAL is fully encapsulated between the electrolyte membrane (524, 624) and the substrate (528, 628).
- the SAL (727, 827, 927, 1027, 1127) is not fully encapsulated between the electrolyte layer (724, 824, 924, 1024, 1124) and the substrate (728, 828, 928, 1028, 1128).
- the SAL is simply located between the electrolyte layer and the substrate, with portions of the SAL exposed. It will be understood that the SAL in the sensors of FIGS. 5 and 6 can be configured in this same way, and the SAL in the sensors of FIGS. 7-11 can alternatively be fully encapsulated as in FIGS. 5 and 6.
- the sense element comprises an insulating substrate (528), a conductive signal amplifying layer (527), a ceramic electrolyte layer (524) that can be porous or dense, an active electrode layer (522), a counter electrode layer (526), and current collector layers (536, 537) that cover at least about 90% of the top surface of the active and counter electrode layers, respectively.
- the active and counter electrode layers (522, 526) can be the same or different compositions.
- the current collector layers (536, 537) can be the same or different compositions. In general, if the active and counter electrode layers in the embodiments of FIGS.
- the current collector layers are of different compositions (i.e., different from each other, or one of the current collector layers omitted).
- the active and counter electrode layers are of different compositions (i.e., different from each other).
- a biasing voltage is applied between the two current collector layers, and the resulting current between the current collecting layers measures.
- the sense element comprises an insulating substrate (628), a conductive signal amplifying layer (627), a ceramic electrolyte layer (624) that can be porous or dense, a single active electrode layer (622), and two current collector layers (636, 637) located on the single active electrode layer (622) in spaced-apart relationship.
- the two current collector layers (636, 637) are of different compositions.
- the first current collector layer (636) comprises a cermet of Au and a ceramic phase (GDC, SDC, zirconium- doped ceria (ZDC), yttrium stabilized zirconia (YSZ), scandium stabilized zirconia (ScSZ), or one of the other ceramic electrolytes mentioned as being suitable for use in the active electrode), and the second current collector layer (637) comprises a cermet of Pt and a ceramic phase (GDC, SDC, zirconium-doped ceria (ZDC), yttrium stabilized zirconia (YSZ), scandium stabilized zirconia (ScSZ), or one of the other ceramic electrolytes mentioned as being suitable for use in the active electrode).
- one current collector comprises Au/GDC and the other comprises Pt/ScSz.
- one of the current collector layers (636, 637) and the portion of active electrode layer (622) therebeneath together provide an active electrode, while the other current collector layer and the portion of active electrode layer (622) therebeneath together provide a counter electrode (or a second active electrode).
- a biasing voltage is applied between the two current collector layers, and the resulting current between the current collecting layers measures.
- the sense element of FIG. 7 comprises an insulating substrate (728), a conductive signal amplifying layer (727), a ceramic electrolyte layer (724) that can be porous or dense, an active electrode layer (722), a counter electrode layer (726), and current collector layers (736, 737) that cover at least about 90% of the top surface of the active and counter electrode layers, respectively.
- the active and counter electrode layers (722, 726) can be the same or different compositions
- the current collector layers (736, 737) can be the same or different compositions.
- the SAL (727) is not fully encapsulated between the electrolyte membrane (724) and substrate (728). Instead, the SAL layer (727) is simply located between the electrolyte membrane layer and the substrate layer, as shown.
- the sense element is similar to that of FIG. 6, only differing by the use of a SAL that is not fully encapsulated.
- the sense element comprises an insulating substrate (828), a conductive signal amplifying layer (827), a ceramic electrolyte layer (824) that can be porous or dense, a single active electrode layer (822), and two current collector layers (836, 837) located on the single active electrode layer (822) in spaced-apart relationship.
- the two current collector layers (836, 837) are of different compositions, and may be, for example, the compositions described above with respect to FIG. 6.
- the SAL (827) is not fully encapsulated between the electrolyte membrane (824) and substrate (828). Instead, the SAL layer (827) is simply located between the electrolyte membrane layer and the substrate layer.
- the designation of one electrode as the "counter electrode” and the other as the “active electrode” in the sensor embodiments described herein is, in some instances, arbitrary.
- the direction of electronic and ionic current flow between the two electrodes can be changed by switching from one bias direction to the other.
- the counter electrodes in FIGS. 5-8, where present, can also be characterized as a second active electrode layer.
- the substrate can be alumina, the SAL Pt, and the electrolyte layer GDC.
- the active electrode can be a molybdate or tungstate compound (e.g., MgW0 4 or BaW0 4 ) in combination with an electrolyte (e.g., GDC) and a metal (e.g., Pt).
- the counter electrode can be a metal (e.g., Pt or Au), a cermet of an electrolyte (e.g., GDC or ScSZ) and a metal (e.g., Pt or Au), or a molybdate or tungstate compound (e.g., MgW0 4 or BaW0 4 ) in combination with an electrolyte (e.g., GDC) and a metal (e.g., Pt).
- the current collectors can similarly be a metal (e.g., Pt or Au), or a cermet of an electrolyte (e.g., GDC or ScSZ) and a metal (e.g., Pt or Au).
- a current collector is not provided over the counter electrode.
- the current collector over the active electrode comprises a cermet chosen from Au/GDC, Pt/GDC, and Pt/ScSZ; and the counter electrode (without an overlying current collector) comprises a cermet chosen from Au/GDC, Pt/GDC, and Pt/ScSZ, wherein the metal used in the cermet of the counter electrode (Au or Pt) is different than the metal used in the cermet of the current collector of the active electrode (Pt or Au).
- the SAL can allow for the use of single layer electrodes rather than the combination of an active/counter electrode and current collecting layer. Furthermore, the SAL can allow for the use of certain components of the active electrode and electrolyte layers to be combined (which can alternatively be characterized as the elimination of the electrolyte layer beneath one or both of the electrodes) provided that the modified electrolyte layer includes a substantial amount of ceramic electrolyte material (e.g., greater than about 60 volume percent, or enough such that the electrolyte material is above its percolation limit and the non-electrolyte materials is below the percolation limit) so that the modified electrolyte layer active conducts electricity primarily via oxygen ions. In this instance, differentiation between the electrodes can be provided by having two different current collector materials.
- FIG. 9 depicts such an embodiment of a sense element employing a SAL (927).
- the sense element comprises an insulating substrate (928), a conductive signal amplifying layer (927), a ceramic electrolyte layer (924) that can be porous or dense, a first electrode layer (922) located on a portion of the upper surface of the electrolyte layer (924), and a second electrode layer (926) located on another portion of the upper surface of the electrolyte layer (924) adjacent the first electrode layer (922).
- the first and second electrodes (922, 926) e.g., an active electrode and a counter electrode
- the electrolyte layer (924) can be, for example, doped ceria or doped zirconia electrolyte, it can alternatively be a modified electrolyte material comprising at least about 60% by volume of doped ceria or doped zirconia electrolyte (e.g., GDC, SDC, ZDC, YSZ, or ScSZ) in combination with: one or more of the molybdate or tungstate compounds described previously herein (e.g., MgW0 4 or BaW0 4 ); and/or one or more metals such as Pt, Pd, Rh, Ru, or Ir (or alloys or mixtures thereof).
- doped ceria or doped zirconia electrolyte e.g., GDC, SDC, ZDC, YSZ, or ScSZ
- one or more of the molybdate or tungstate compounds described previously herein e.g., MgW0 4 or BaW0 4
- metals such as Pt,
- the modified electrolyte layer comprises: about 60% to about 95% by volume of a doped ceria or doped zirconia electrolyte (e.g., GDC, SDC, ZDC, YSZ, or ScSZ); and about 5% to about 40% of a molybdate or tungstate compound in combination with a metal chosen from the group consisting of Pt, Pd, Rh, Ru, and Ir.
- a doped ceria or doped zirconia electrolyte e.g., GDC, SDC, ZDC, YSZ, or ScSZ
- a molybdate or tungstate compound in combination with a metal chosen from the group consisting of Pt, Pd, Rh, Ru, and Ir.
- the benefits of molybdate/tungstate compounds can be taken advantage of in the electrolyte layer rather than in an additional electrode layer.
- the electrodes (922, 926) should have different compositions.
- one electrode can comprise a cermet containing platinum and an electrolyte (GDC, SDC, YSZ, ScSZ), while the other comprises a cermet containing gold and an electrolyte (GDC, SDC, YSZ, ScSZ).
- the SAL can allow for the bifurcation of the electrolyte into two adjacent layers, each located beneath one of the surface electrodes.
- the lateral conduction between the electrodes under bias is solely through the SAL.
- the oxygen ions that would normally be conducted between the electrodes through the electrolyte layer are converted into electrons at the interface of the first electrolyte layer and the SAL. These electrons are then transported through the SAL and thereafter react with oxygen to form oxygen ions at the interface of the SAL and the second electrolyte layer.
- the sense element comprises an insulating substrate (1028), a conductive signal amplifying layer (1027), a first ceramic electrolyte layer (1024 A) located on a portion of the SAL, a second ceramic electrolyte layer (1024B) located on another portion of the SAL adjacent the first electrolyte layer (1024 A), a first electrode layer (1022) located on first ceramic electrolyte layer (1024A), and a second electrode layer (1026) located on the second ceramic electrolyte layer (1024B).
- the first and second electrodes (1022, 1026) e.g., an active electrode and a counter electrode
- the first and second electrolyte layers can be the same or different compositions, and can comprise, for example, doped ceria or doped zirconia electrolyte, or alternatively a modified electrolyte material as described above with respect to FIG. 9.
- FIG. 11 depicts yet another alternative embodiment of a sense element employing a bifurcated electrolyte layer.
- the sense element comprises an insulating substrate (1128), a conductive signal amplifying layer (1127), a first ceramic electrolyte layer (1124A) located on a portion of the SAL, a second ceramic electrolyte layer (1124B) located on another portion of the SAL adjacent the first electrolyte layer (1124A), a first electrode layer (1122) located on first ceramic electrolyte layer (1024 A), a current collector layer (1136) located on the first electrode layer (1122), and a second electrode layer (1126) located on the second ceramic electrolyte layer (1124B).
- the first and second electrodes (1122, 1126) have the same or different compositions and can comprise any of the various compositions described herein for an active electrode, a counter electrode or even a current collector.
- the first and second electrolyte layers can be the same or different compositions, and can comprise, for example, doped ceria or doped zirconia electrolyte, or alternatively a modified electrolyte material as described above with respect to FIG. 9.
- the first electrolyte layer (1124A) comprises doped ceria or doped zirconia electrolyte
- the second electrolyte layer comprises a modified electrolyte material (e.g., includes a molybdate compound along with GDC or SDC) as described above with respect to FIG. 9.
- Embodiments of the sensors described herein generally include a substrate, in combination with the described electrochemical cells, in order to provide mechanical support.
- the substrate may comprise any suitable insulating material, for example, an insulating ceramic material such as aluminum oxide, magnesium oxide, magnesium aluminate, mullite, steatite, or cordierite.
- Aluminum oxide is particularly useful as a substrate material.
- Devices also can be constructed with a metal or alloy as the substrate material (instead of an insulating material). In these instances, the metallic substrate itself would then serve as the signal amplifying layer.
- electrolyte material or electrolyte containing active electrode material
- electrolyte containing active electrode material directly onto the metallic substrate in such a way that an insulating layer is not created at the interface during deposition of the electrolyte, active electrode and current collector layers.
- sputtering processes or the like can be used to deposit the various layers.
- the sensors and sensor systems herein can be configured to be compatible with various application environments, and can include substrates with modifications to provide structural robustness, the addition of one or more heaters to control sensor temperature, and/or the addition of a resistance temperature detector ("RTD"), a thermistor, a thermocouple or other device to measure temperature and provide feedback to the electronic controller for temperature control.
- RTD resistance temperature detector
- An alternative temperature measurement approach based on the use of impedance of the electrolyte layer at a specific frequency, also can be used (this approach would require the addition of specific features to the sensor device architecture). Modifications can also be made to the overall sensor size and shape, external packaging and shielding to house and protect the sensor, and appropriate leads and wiring to communicate the sensor signal to an external device or application.
- the sensor can optionally include a heater which is electrically isolated from the electrolyte and electrodes.
- the heater comprises a resistive heater formed, for example, from a conductive metal such as, but not limited to, platinum, palladium, silver, or the like.
- the heater can, for example, be applied to or embedded in the substrate, or applied to the cell through another insulating layer such as an additional insulating layer (e.g., aluminum oxide).
- a temperature measurement mechanism is applied to the sensor to measure temperature and feed that back to the electronic controller to enable closed- loop temperature control.
- the temperature measurement mechanism for example, is a resistance temperature device (RTD) made from a conductive metal or metal/ceramic composite with a high temperature coefficient of resistance (e.g., platinum or a platinum based cermet).
- RTD resistance temperature device
- the electrochemical sensor is made using tape casting and screen printing techniques commonly used during the manufacture of multilayer ceramic capacitors and multilayer ceramic substrates.
- the first part of this process involves tape casting of aluminum oxide sheets (or tape).
- via holes are cut into the substrate using a laser cutter or punch, providing electrical pathway connections from an embedded heater or other structures to the contact pads on an outer surface of the ceramic element.
- Platinum or platinum based material
- the SAL is screen printed onto one face of a green aluminum oxide tape.
- the SAL is generally a continuous, conductive layer configured to extend beneath at least about 50% of the surface electrodes, including spanning beneath the gap between the two electrodes.
- the SAL is located beneath the surface electrodes and has a size that is about 50% to about 120% of the combined size of the surface electrodes (including the gap between the electrodes).
- the cross-sectional length (L) of the SAL (727) is about 120% of the edge- to-edge width (W) of the electrodes (722, 726).
- the SAL size is approximately the same as the electrode area (including the gap between the surface electrodes).
- the SAL can be made from a variety of conductive materials suitable for sensor fabrication. Suitable materials include Pt, Pd, Au, Ag, alloys of the foregoing metals (e.g., an alloy of Pt with Pd, Au and/or Au), or other conductive metal or ceramic material. Platinum is particularly useful.
- Platinum is screen printed onto the outer face of the sintered element, in patterns that, after sintering, will provide an RTD to enable a temperature measurement.
- another suitable material for an RTD may be applied in the green state prior to sintering of the aluminum oxide substrates and co-sintered therewith.
- a glass layer can be applied over the RTD and cured to protect the RTD in the application.
- both the heater and RTD layers can be embedded within the substrate in the green state and connections made with platinum vias (as described above), or only the platinum RTD can be embedded within the substrate, and the heater layer can be printed on the exterior surface and protected with a glass layer.
- the RTD can be omitted, and another means used for temperature measurement and control can be used.
- Manufacture of the electrochemical cell or sensor is then completed by screen printing of the active and counter electrode layers (made of any of the compositions described herein) onto the electrolyte layer, followed by sintering of the electrode layers in order to anneal the electrode layers and promote adhesion.
- a current collector layer than can be applied in a similar manner.
- a porous ceramic coating such as a zeolite or gamma alumina, can additionally be applied over the electrodes/current collector to protect these layers in the application and calcined to improve adhesion. It should be noted that multiple electrochemical cells or sensors can be made simultaneously with the above described process by array processing.
- Sensor systems are formed, for example, by coupling one or more of the sensors described herein with one or more electronic controllers configured to controllably apply the bias voltage, control temperature (e.g., through pulse width modulation of the input voltage to the heater based on the sensor temperature measurement supplied to the controller).
- the controller is configured to provide a conditioned sensor output, such as calibrated or linearized output.
- Methods of detecting, sensing and/or monitoring the concentration of one or more target gas species such as NO x and/or H 3 are also provided, employing any of the various sensors and sensor systems described herein.
- a bias voltage is applied to the electrochemical cells of the sensor and the resulting current is measured.
- the measured current is correlated with the target gas species at a sensor temperature, based on previously compiled sensor data.
- the measured current changes as the concentration of target gas species in the gas sample or stream increases.
- target gas species may be determined on the basis of the generated current through the sensor cell.
- the sensors, sensor systems and methods described herein can also be adapted for detecting a variety of other gas species, including carbon monoxide (CO), methane (CH 4 ), ethanol (C 2 H 6 ), hydrogen sulfide (H 2 S), sulfur oxides (SOx), hydrogen (H 2 ), refrigerants, oxygen (0 2 ), volatile organic compounds (VOC's) and other hydrocarbons.
- CO carbon monoxide
- CH 4 methane
- C 2 H 6 ethanol
- SOx sulfur oxides
- H 2 hydrogen
- refrigerants oxygen (0 2 ), volatile organic compounds (VOC's) and other hydrocarbons.
- VOC's volatile organic compounds
- sensors can be constructed with two active electrodes, effectively providing two different electrochemical cells, in order to provide for measurement of both ⁇ concentration and NH 3 concentrations.
- exemplary sensors were fabricated as a single electrochemical cell and tested under conditions that would enable the design of dual NO x /NH 3 sensors having multiple electrochemical cells. Through this testing, applicants have discovered multiple approaches for fabricating sensors for measuring both NO x and H 3 concentrations.
- An additive response means that the magnitude of the signal provided by the electrochemical cell is proportional to the total combined concentration of the analytes (e.g., NO, N0 2 and NH 3 ) in the gas sample or gas stream being analyzed.
- an individual electrochemical cell of a sensor which exhibits an additive response to NO, N0 2 and NH 3 will provide a signal which is proportional to the total, combined concentration of NO, N0 2 and NH 3 .
- the electrochemical cell of the sensor exhibits approximately equal responses to NO, N0 2 and NH 3 such that approximately the same current is generated when that electrochemical cell is exposed to a given concentration of NO, N0 2 and NH 3 (e.g., approximately the same current is generated when the electrochemical cell is exposed to 20 ppm NO, 20 ppm N0 2 or 20 ppm NH 3 ).
- an individual electrochemical cell of a sensor is considered to be additive with respect to two or more analyte species when the sensitivity to each of those species is within a range of ⁇ 20% for a given concentration within the range of 10-200 ppm of the gas analyte species.
- the sensitivity is the percent change in the current signal compared to the current signal in the absence of the analyte species. In some embodiments, the sensitivity to two or more analyte species of an additive electrochemical cell is within a range of ⁇ 10%, or even ⁇ 5%.
- one electrochemical cell of the sensor exhibits an additive response to two or more target gas species (e.g., NO x and NH 3 )
- the other electrochemical cell of the sensor is minimally responsive or non-responsive to one of the target gas species (e.g., either NO x or H 3 )— i.e., a selective response.
- Selectivity is provided by either the configuration of the second electrochemical cell (e.g., the selection of the active electrode material and/or the current collector) and/or the mode of operation of the second electrochemical cell (e.g., direction of biasing).
- An electrochemical cell of a sensor is minimally responsive (i.e., selective) with respect to a particular analyte when the sensitivity for that analyte is less than 20% of the sensitivity to the other analyte(s) of interest at a given concentration within the range of 10-200 ppm.
- the sensitivity to one analyte is less than 10% of the sensitivity to the other analyte(s), or even less than 5%.
- a first electrochemical cell of a sensor when a first electrochemical cell of a sensor is additive with respect to ⁇ and H 3 , and the second electrochemical cell of the sensor is responsive to ⁇ but only minimally responsive or non-responsive to H 3 , it is preferred that the second electrochemical cell exhibits additive properties with respect to NO and N0 2 .
- two electrochemical cells one having an additive response to two or more target gas species, and one having a selective response to at least one of the target gas species, can be provided by tailoring the current collectors of the two cells in order to provide additive and selective sensor responses (e.g., to enable dual ⁇ / ⁇ 3 detection and quantification). Signal strength and, in some instances, selectivity, is also enhanced by the SAL.
- These discoveries were achieved by making devices where the current collector completely covers the surface of the active electrode (> about 90% coverage) and utilizing a device architecture where both the counter and active electrodes are deposited on the same surface of the electrolyte, in spaced-apart relationship.
- electrochemical sensing reactions become controlled by the current collector in this alternative arrangement.
- electrochemical cells having the same active electrodes based on MgW0 4 or BaW0 4
- additive sensor responses are achieved in cells incorporating a platinum based current collector over the active electrode and selective responses are achieved in cells incorporating a gold based current collector over the active electrode. This is made clearer by the Examples described further herein.
- FIGS. 21-24 depict further alternative embodiments of sense elements of the present disclosure wherein one or both of the electrodes comprise a current collecting layer located on the electrolyte layer and a catalyst layer is located over the current collecting layer— either covering at least about 90% of the top surface of the current collecting layer (FIGS. 22 and 24), or fully encapsulating the current collector layer between the catalyst layer and the electrolyte layer (FIGS. 21 and 23).
- a SAL is also provided in the embodiments of FIGS. 21 -25, as shown.
- the current collector layers have higher electrical conductivity than the catalyst layers.
- the catalyst layers can be any of the materials previously identified herein for use as an active electrode layer, particular the compositions comprising a molybdate or tungstate (e.g., a molybdate or tungstate compound in combination with an electrolyte material and a metal, as described above).
- the current collector layer can be any of the materials previously identified herein for use as a current collector layer, particular a metal (e.g., Pt or Au) or a cermet of an electrolyte and a metal (e.g., Au/GDC, Pt/GDC, or Pt/ScSZ).
- the biasing voltage is applied between the current collector layers, and the resulting signal also obtained from between the current collector layers, as shown, it is believed that the catalyst layers will manipulate the concentrations of NO, N0 2 and NH 3 that are present at the catalyst / current collector interface, thereby changing the amount of current when a bias is applied (compared to the amount of current if no catalyst layer was present).
- the sense element comprises an insulating substrate (2028), a conductive signal amplifying layer (2027), a ceramic electrolyte layer (2024) that can be porous or dense, a first current collector layer (2036) located on a portion of the upper surface of the electrolyte layer (2024), and a second current collector layer (2037) located on another portion of the upper surface of the electrolyte layer (2024) adjacent the first current collector layer (2036).
- a first catalyst layer (2022) encapsulates the first current collector layer (2036) (i.e., between the catalyst and the electrolyte), and a second catalyst layer (2026) encapsulates the second current collector layer (2037).
- the two current collector layers (2036, 2037) can be the same or different compositions, and the two catalyst layers (2022, 2026) can be the same or different compositions. However, at least one of either the current collector layers or the catalyst layers should have a different composition than the other current collector layer or catalyst layers (i.e., 2036 has a different composition than 2037, and/or 2022 has a different composition than 2026). It will also be understood that the SAL (2027) can optionally be fully encapsulated rather than partially encapsulated as shown (also the case with the sense elements of FIGS. 22-24).
- the sense element of FIG. 22 is similar to that of FIG. 21, however, in this embodiment the catalyst layers (2122, 2126) do not fully encapsulate the underlying current collector layers (2136, 2137).
- the sense element of FIG. 22 also once again comprises an insulating substrate (2128), a conductive signal amplifying layer (2127), and a ceramic electrolyte layer (2124) that can be porous or dense.
- the two current collector layers (2136, 2137) can be the same or different compositions
- the two catalyst layers (2122, 2126) can be the same or different compositions.
- at least one of either the current collector layers or the catalyst layers should have a different composition than the other current collector layer or catalyst layers (i.e., 2136 has a different composition than 2137, and/or 2122 has a different composition than 2126).
- the sense element comprises an insulating substrate (2228), a conductive signal amplifying layer (2227), a ceramic electrolyte layer (2224) that can be porous or dense, a current collector layer (2236) located on a portion of the upper surface of the electrolyte layer (2224), a counter electrode layer (2226) located on another portion of the upper surface of the electrolyte layer (2224) adjacent the current collector layer (2236).
- a catalyst layer (2222) encapsulates the current collector layer (2236) (i.e., between the catalyst and the electrolyte).
- the counter electrode layer 2226 can comprise any of the compositions described herein for use as a counter electrode or as a current collector.
- the sense element of FIG. 24 is similar to that of FIG. 23, however, in this embodiment the catalyst layer (2322) does not fully encapsulate the underlying current collector layer (2336).
- the sense element of FIG. 24 also once again comprises an insulating substrate (2328), a conductive signal amplifying layer (2327), a ceramic electrolyte layer (2324) that can be porous or dense, and a counter electrode layer (2326).
- the sense element of FIG. 25 includes a catalyst layer (2422) that encapsulates a current collector layer (2436) (i.e., between the catalyst and the electrolyte (2424)).
- the second (counter) electrode (2426) is buried under the electrolyte layer (2424) such that the counter electrode (2426) is located between the electrolyte layer (2424) and the substrate (2422).
- the sense element of FIG. 25 does not include a SAL.
- the sensor of Example 1 was made without a platinum signal amplifying layer, while the sensor of Example 2 included a platinum signal amplifying layer between the GDC electrolyte layer and the substrate with the SAL fully encapsulated (as seen in FIG. 13). It should be noted that the dimensions of the sensor architectures shown in FIGS. 12 and 13 are not to scale.
- the gap between the active and counter electrodes on the electrolyte surface was approximately 500 microns, whereas the thickness of the GDC electrolyte layer (and thus the gap between the active electrode and the buried platinum layer) was approximately 30 microns.
- the sensors of Examples 1 and 2 were exposed to a baseline simulated diesel exhaust gas atmosphere of 77 vol% N 2 , 10 vol% 0 2 , 8 vol% C0 2 , 5 vol% H 2 0 and 1 ppm S0 2 , with the sensor maintained at a temperature of 525 °C.
- a forward (positive) bias of 200 mV applied from the Pt/GDC current collector to the Pt/GDC counter electrode layers the resulting currents were determined by measuring the voltage across a 100-ohm shunt resistor.
- the baseline signal (exposed only to the baseline simulated diesel exhaust gas) was measured, as well as signals (i.e., current) when 100 ppm of NO, N0 2 and NH 3 were added to the simulated exhaust gas.
- the sensitivities to 100 ppm exposures of NO, N0 2 and NH 3 were determined as the percent change in current signal when the analytes were present.
- FIGS. 12 and 13 wherein it is seen that the platinum signal amplifying layer increased the baseline signal from 0.28 to 3.8 ⁇ (a more than tenfold increase).
- the sensitivities to each of the gas species tested was also significantly increased, thereby providing a significantly more useful sensor.
- the SAL provided a lateral current path and effectively increased the areas of the active and counter electrodes.
- the lateral current path provided by the platinum is a faster path for charge carriers, even though two additional electrochemical reactions must occur (conversion of oxygen ions to electrons at the GDC/Pt-SAL interface and conversion of electrons back to oxygen ions at the Pt-SAL/GDC interface).
- the sensors were tested, as described above for Examples 1 and 2, with bias voltage of 200 mV at a temperature of 525°C.
- the baseline gas atmosphere consisted of 8 vol% C0 2 , 5% vol% H 2 0, 1 ppm S0 2 , 10 vol% 0 2 , and 77 vol% N 2 , and sensor responses were measured for exposures to the baseline atmosphere with analytes of 100 ppm NO, 100 ppm N0 2 , or 100 ppm NH 3 added thereto. Results are summarized in Table 2 and described in the paragraphs that follow.
- Test data obtained for the sensor of Example 3, with a Pt-MgW0 4 /GDC active electrode, an Au/GDC current collector and a Pt/ScSZ counter electrode, are presented in Table 2 and FIG. 14.
- this sensor With a 200 mV bias applied at a temperature of 525°C, this sensor exhibited a baseline current signal of 8.9 ⁇ , with selective sensing behavior to NO and N0 2 (33% and 43% sensitivities to 100 ppm NO and 100 ppm N0 2 , respectively, and only 2% sensitivity to 100 ppm NH 3 ).
- the lack of sensitivity to NH 3 is seen in FIG. 14 wherein the signal when 100 ppm NH 3 is added to the baseline simulated diesel exhaust is only slightly higher than the baseline signal (9.1
- Test data obtained for the sensor of Example 4 with a Pt-MgW0 4 /GDC active electrode, a Pt/SCSZ current collector and a Pt/ScSZ counter electrode, are presented in Table 2 and FIG. 15. With a 200 mV bias applied at a temperature of 525°C, this sensor exhibited a baseline current signal of 6.5 ⁇ , with additive sensing behavior to NO, N0 2 and NH 3 (39%, 31% and 33% percent sensitivities to 100 ppm NO, 100 ppm N0 2 and 100 ppm NH 3 , respectively).
- Test data obtained for the sensor of Example 6, with a Pt-BaW0 4 /GDC active electrode, a Pt/SCSZ current collector and a Pt/ScSZ counter electrode are presented in Table 2 and FIG. 17. With a 200 mV bias applied at a temperature of 525°C, this sensor exhibited a baseline current signal of 3.8 ⁇ , with additive sensing behavior to NO, N0 2 and NH 3 (167%), 164%. and 164%. sensitivities to 100 ppm NO, 100 ppm N0 2 and 100 ppm NH 3 , respectively).
- this sensor With a 200 mV bias applied at a temperature of 525°C, this sensor exhibited a very low baseline current signal of 0.85 ⁇ , with relatively low and less than optimal additive sensitivities (21%, 13% and 21% sensitivities to 100 ppm NO, 100 ppm N0 2 and 100 ppm NH 3 , respectively).
- the data demonstrate the advantage of including platinum (or another metal) in the active electrode in order to achieve more desirable ⁇ and NH 3 sensing behavior.
- electrolyte material e.g., ScSZ or GDC
- Example 11 The demonstration of how the sensors described herein can be adapted for ammonia detection is illustrated in Examples 11 and 12.
- a sensor was fabricated as described above for Example 2 (i.e., the architecture of FIG. 1, including a fully encapsulated Pt SAL).
- the sensor employed an A1 2 0 3 substrate, a Pt-MgW0 4 /GDC active electrode layer, a Au/GDC current collector layer and a Pt/GDC counter electrode layer, as shown in FIGS. 18 and 19.
- the Pt-MgW0 4 /GDC, Pt/GDC and Au/GDC layers were made with higher surface area constituents and with higher annealing temperatures, which led to increased density (and durability) of these layers.
- the senor When tested in the forward bias mode (i.e., with oxygen ions being generated at the active electrode and conducting through the electrolyte to the counter electrode), the sensor was highly cross-sensitive to oxygen, the responses to NO and N0 2 were positive and unequal (33% and 108%) percent, respectively), and the response to NH 3 was highly negative (- 86%>), with an oxygen content of 5 vol%>.
- H 3 sensitivities were insensitive to oxygen content.
- the combination of very high sensitivity to H 3 (relative to ⁇ ) and insensitivity to oxygen is advantageous for use as a stand-alone H 3 sensor or as an H 3 selective cell in a dual ⁇ / ⁇ 3 sensor.
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2020020737A (en) * | 2018-08-03 | 2020-02-06 | 株式会社Soken | Gas sensor |
CN113054119A (en) * | 2019-12-28 | 2021-06-29 | Tcl集团股份有限公司 | Composite material, preparation method and application thereof, light-emitting diode and preparation method thereof |
US20210247354A1 (en) * | 2018-10-30 | 2021-08-12 | Denso Corporation | Ammonia detector |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4264425A (en) * | 1979-05-25 | 1981-04-28 | Nissan Motor Company, Limited | Device for detection of air/fuel ratio from oxygen partial pressure in exhaust gas |
DE102007052754A1 (en) * | 2007-11-06 | 2009-05-07 | Robert Bosch Gmbh | Gas sensor for detecting particles i.e. nitrogen oxide particles, in gas flow in exhaust gas after-treatment system in automobile, has oxygen pumping electrodes connected in series with each other via electrical resistors |
US20090218220A1 (en) | 2008-02-28 | 2009-09-03 | Nextech Materials Ltd. | Amperometric Electrochemical Cells and Sensors |
US20100161242A1 (en) * | 2008-12-18 | 2010-06-24 | Delphi Technologies, Inc. | Exhaust gas sensing system and method for determining concentrations of exhaust gas constituents |
EP2375247A1 (en) * | 2010-03-29 | 2011-10-12 | NGK Insulators, Ltd. | Gas sensor |
US20130233728A1 (en) * | 2012-03-08 | 2013-09-12 | Nextech Materials, Ltd. | Amperometric electrochemical sensors, sensor systems and detection methods |
US8974657B2 (en) | 2010-09-03 | 2015-03-10 | Nextech Materials Ltd. | Amperometric electrochemical cells and sensors |
US20160077044A1 (en) | 2014-09-12 | 2016-03-17 | Gene B. Arkenberg | Amperometric electrochemical sensors, sensor systems and detection methods |
-
2017
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Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4264425A (en) * | 1979-05-25 | 1981-04-28 | Nissan Motor Company, Limited | Device for detection of air/fuel ratio from oxygen partial pressure in exhaust gas |
DE102007052754A1 (en) * | 2007-11-06 | 2009-05-07 | Robert Bosch Gmbh | Gas sensor for detecting particles i.e. nitrogen oxide particles, in gas flow in exhaust gas after-treatment system in automobile, has oxygen pumping electrodes connected in series with each other via electrical resistors |
US20090218220A1 (en) | 2008-02-28 | 2009-09-03 | Nextech Materials Ltd. | Amperometric Electrochemical Cells and Sensors |
US20100161242A1 (en) * | 2008-12-18 | 2010-06-24 | Delphi Technologies, Inc. | Exhaust gas sensing system and method for determining concentrations of exhaust gas constituents |
EP2375247A1 (en) * | 2010-03-29 | 2011-10-12 | NGK Insulators, Ltd. | Gas sensor |
US8974657B2 (en) | 2010-09-03 | 2015-03-10 | Nextech Materials Ltd. | Amperometric electrochemical cells and sensors |
US20130233728A1 (en) * | 2012-03-08 | 2013-09-12 | Nextech Materials, Ltd. | Amperometric electrochemical sensors, sensor systems and detection methods |
US9304102B2 (en) | 2012-03-08 | 2016-04-05 | Nextech Materials, Ltd. | Amperometric electrochemical sensors, sensor systems and detection methods |
US20160077044A1 (en) | 2014-09-12 | 2016-03-17 | Gene B. Arkenberg | Amperometric electrochemical sensors, sensor systems and detection methods |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2020020737A (en) * | 2018-08-03 | 2020-02-06 | 株式会社Soken | Gas sensor |
JP7068090B2 (en) | 2018-08-03 | 2022-05-16 | 株式会社Soken | Gas sensor |
US20210247354A1 (en) * | 2018-10-30 | 2021-08-12 | Denso Corporation | Ammonia detector |
CN113054119A (en) * | 2019-12-28 | 2021-06-29 | Tcl集团股份有限公司 | Composite material, preparation method and application thereof, light-emitting diode and preparation method thereof |
CN113054119B (en) * | 2019-12-28 | 2022-05-17 | Tcl科技集团股份有限公司 | Composite material, preparation method and application thereof, light-emitting diode and preparation method thereof |
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