hydrogen concentration sensor

Abstract

The example hydrogen concentration sensor includes a first end plate. A hydrogen evolution electrode assembly that generates hydrogen is located near the first end plate and is at least partially exposed through an opening in the end plate. A partition is located between the hydrogen evolution electrode assembly and a detection electrode assembly. The partition includes a channel that allows hydrogen generated by the hydrogen evolution electrode assembly to flow to the detection electrode assembly. A second end plate is located near the detection electrode assembly and includes a second opening, wherein a portion of the detection electrode assembly is exposed to the fluid of interest to provide an indication of the concentration of hydrogen in the liquid of interest.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Patent Application No. 17 / 114,746, filed on December 8, 2020. Background Technology

[0003] Various devices and methods rely on hydrogen for their operations. For example, in electrochemical processes, fuel cells typically use hydrogen as a reactant fuel to generate electricity. Insufficient hydrogen concentration in the reactant fuel can lead to unsatisfactory fuel cell performance.

[0004] Hydrogen concentration sensors for fuel cells are known. Some of these sensors rely on a Nernst potential across two electrodes, caused by the difference in hydrogen concentration at each electrode. One drawback of this type of hydrogen sensor is that when current is applied to the reference electrode, hydrogen is generated at the reference electrode. Using the reference electrode in this way to generate hydrogen often introduces a potential shift at the reference electrode, which interferes with the accuracy of hydrogen concentration measurements. Summary of the Invention

[0005] An exemplary embodiment of a hydrogen concentration sensor includes a first endplate and a hydrogen evolution electrode assembly. The first endplate includes a first opening through a portion of the first endplate. The hydrogen evolution electrode assembly is located near the first endplate, wherein at least a portion of the hydrogen evolution electrode assembly is exposed through the first opening. The hydrogen evolution electrode assembly is configured to generate hydrogen by being exposed to a fluid at the first opening. At least one partition is adjacent to the hydrogen evolution electrode assembly on the side opposite to the first endplate. The partition includes a channel configured to allow flow of hydrogen generated by the hydrogen evolution electrode assembly. A detection electrode assembly is located adjacent to the partition on the side opposite to the hydrogen evolution electrode assembly. At least a portion of the detection electrode assembly is exposed to hydrogen in the channel. A second endplate is adjacent to the detection electrode assembly on the side opposite to the partition. The second endplate includes a second opening through a portion of the second endplate. A portion of the detection electrode assembly is exposed to the fluid of interest through the second opening. The detection electrode assembly is configured to provide an indication of the concentration of hydrogen in the fluid of interest.

[0006] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of the foregoing paragraphs, the hydrogen evolution electrode assembly includes a first electrode layer and a second electrode layer and a matrix layer located between the first electrode layer and the second electrode layer, the detection electrode assembly includes a third electrode layer and a fourth electrode layer and a matrix layer located between the third electrode layer and the fourth electrode layer, the first electrode layer is exposed to a first opening, the second electrode layer is at least partially exposed to a channel, the third electrode layer is at least partially exposed to the channel, the fourth electrode layer is exposed to a second opening, and the electrode layers contain a liquid electrolyte.

[0007] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, the liquid electrolyte comprises phosphoric acid.

[0008] An exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs includes a heater positioned to increase the temperature of at least the liquid electrolyte in the electrode layer.

[0009] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, a first end plate is conductive, at least one partition is at least partially conductive, a second end plate is conductive, and the hydrogen concentration sensor includes: at least one isolation layer located between the first end plate and at least one partition, at least one isolation layer located between the second end plate and at least one partition, and at least one isolation layer located within at least one partition, wherein the at least one isolation layer electrically isolates a first side of at least one partition abutting against a hydrogen evolution electrode assembly from a second side of at least one partition abutting against a detection electrode assembly.

[0010] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, each conductive plate comprises graphite.

[0011] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, at least one partition comprises two graphite plates, at least one isolation layer within at least one partition comprises a gasket located between the two graphite plates, and the gasket comprises an opening through the gasket aligned with a channel.

[0012] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, each isolation layer comprises a fluoropolymer.

[0013] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, at least one isolation layer located between a first end plate and at least one partition includes an opening through the at least one isolation layer, a hydrogen evolution electrode assembly is located within the opening through the at least one isolation layer, at least one isolation layer is located between the first end plate and at least one partition, at least one isolation layer located between at least one partition and a second end plate includes an opening through the at least one isolation layer, and a detection electrode assembly is located within the opening through the at least one isolation layer, wherein at least one isolation layer is located between at least one partition and a second end plate.

[0014] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, the hydrogen evolution electrode assembly includes two electrode layers and a matrix layer located between the two electrode layers, and at least one isolation layer located between a first end plate and at least one partition includes three gaskets, one of the two electrode layers having an opening in one of the three gaskets, the other electrode of the two electrode layers having an opening in another of the three gaskets, and the matrix layer having an intermediate gasket among the three gaskets.

[0015] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, the electrode layer contains a liquid electrolyte, the thickness of the electrode layer has a predetermined relationship with the thickness of the gasket, and the thickness of the gasket controls the amount of compression of the electrode layer.

[0016] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, at least one partition includes a discharge port positioned to allow hydrogen to exit the hydrogen concentration sensor from the channel, and the discharge port is positioned such that hydrogen discharged from the discharge port is away from the second opening.

[0017] An exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs includes a housing, the housing including a first side abutting a first end plate and a second side abutting a second end plate, the first side of the housing including a first window aligned with a first opening, and the second side of the housing including a second window aligned with the first opening.

[0018] In an exemplary embodiment of a hydrogen concentration sensor having one or more features of any of the preceding paragraphs, the detection electrode assembly includes two electrode layers and a matrix layer located between the two electrode layers, and provides an indication of the hydrogen concentration of the fluid of interest by means of a voltage across the two electrode layers.

[0019] An example embodiment of a method for assembling a hydrogen concentration sensor includes: positioning a first endplate adjacent to a hydrogen evolution electrode assembly to expose at least a portion of the hydrogen evolution electrode assembly through a first opening through a portion of the first endplate, the hydrogen evolution electrode assembly being configured to generate hydrogen by exposure to a fluid at the first opening; positioning at least one partition adjacent to the hydrogen evolution electrode assembly on a side opposite to the first endplate, wherein the at least one partition includes a channel configured to allow flow of hydrogen generated by the hydrogen evolution electrode assembly; positioning a detection electrode assembly adjacent to at least one partition on a side opposite to the hydrogen evolution electrode assembly such that at least a portion of the detection electrode assembly is positioned to be exposed to hydrogen in the channel; positioning a second endplate adjacent to the detection electrode assembly on a side opposite to the at least one partition such that a portion of the detection electrode assembly is positioned aligned with a second opening through a portion of the second endplate, wherein the portion of the detection electrode assembly is exposed to the fluid of interest through the second opening, the detection electrode assembly being configured to provide an indication of the concentration of hydrogen in the fluid of interest; and securing the plate and electrode assembly in the positioned locations.

[0020] An exemplary embodiment of the method having one or more features of the foregoing paragraphs includes mounting a hydrogen evolution electrode assembly by positioning a first matrix layer between a first electrode layer and a group of second electrode layers, and mounting a detection electrode assembly by positioning a second matrix layer between a third electrode layer and a group of fourth electrode layers. The matrix layer and electrode layers contain a liquid electrolyte.

[0021] An exemplary embodiment of a method having one or more features of any of the preceding paragraphs includes positioning a hydrogen evolution electrode assembly within an opening of at least one gasket, the at least one gasket providing a seal around the edge of the assembly to retain a liquid electrolyte, and positioning a detection electrode assembly within an opening of at least one other gasket, the at least one other gasket providing a seal around the edge of the assembly to retain a liquid electrolyte.

[0022] An exemplary embodiment of a method having one or more features of any of the preceding paragraphs includes sealing at least one gasket to a first end plate on one side of at least one gasket, sealing at least one gasket to at least one partition on the other side of at least one gasket, sealing at least one other gasket to at least one partition on one side of at least one other gasket, and sealing at least one other gasket to a second end plate on the other side of at least one other gasket.

[0023] An exemplary embodiment of the method having one or more features of any of the preceding paragraphs includes positioning a heater near an electrode assembly to increase the temperature of at least a liquid electrolyte in the electrode layer. In an exemplary embodiment of the method having one or more features of any of the preceding paragraphs, a first end plate is conductive, at least one separator is at least partially conductive, and a second end plate is conductive. The method includes positioning at least one insulating layer between a first end plate and at least one separator, positioning at least one insulating layer between a second end plate and at least one separator, and including at least one insulating layer within at least one separator, the at least one insulating layer electrically isolating a first side of at least one separator abutting a hydrogen evolution electrode assembly from a second side of at least one separator abutting a detection electrode assembly.

[0024] From the following detailed description, the various features and advantages of at least one disclosed exemplary embodiment will be apparent to those skilled in the art. The accompanying drawings, which provide a detailed description, are briefly described below. Attached Figure Description

[0025] Figure 1 This is a schematic illustration of an example hydrogen concentration sensor designed according to an embodiment of the present invention.

[0026] Figure 2 It is along Figure 1 The cross-sectional view taken from line 2-2 in the figure.

[0027] Figure 3 It is along Figure 1 The cross-sectional view taken from line 3-3 in the figure.

[0028] Figure 4 yes Figure 1 An exploded view of a portion of the components of the embodiment shown.

[0029] Figure 5 yes Figure 1 An exploded view of another part of the embodiment shown.

[0030] Figure 6 This is a cross-sectional view of selected features of an example electrode assembly and associated gaskets.

[0031] Figure 7 An example washer configuration is shown schematically.

[0032] Figure 8 Selected features of a fuel cell power plant are schematically illustrated, including a hydrogen sensor designed according to an embodiment of the invention. Detailed Implementation

[0033] The hydrogen concentration sensor designed according to embodiments of the present invention can be used for various purposes. Exemplary embodiments for determining hydrogen concentration for fuel cell power plants are discussed below. One feature of embodiments of the invention is that, unlike a hydrogen evolution electrode assembly that detects the electrode assembly, hydrogen is evolved into a channel in the sensor structure, in which the detection electrode assembly is exposed to the evolved hydrogen. The detection electrode assembly is also exposed to the fluid of interest and provides an indication of the hydrogen concentration in the fluid without requiring any current to be supplied to the detection electrode assembly, resulting in improved sensor performance compared to other sensors.

[0034] Figure 1-3 An example of a hydrogen concentration sensor 20 is shown. Multiple components are arranged in a stack, including a first end plate 22, at least one multilayer partition 24, and a second end plate 26. A hydrogen evolution electrode assembly 30 is located between the first end plate 22 and the partition 24. A detection electrode assembly 32 is located between the partition 24 and the second end plate 26.

[0035] The hydrogen evolution electrode assembly 30 is located near the first end plate 22, wherein at least a portion of the hydrogen evolution electrode assembly 30 is exposed through a first opening 34 extending through a portion of the first end plate 22. The hydrogen evolution electrode assembly 30 is configured to generate hydrogen by being exposed to a fluid such as a gas at the first opening 34. The hydrogen evolved by the assembly 30 may be pure hydrogen or may be considered pure for practical purposes, even if it is not completely pure hydrogen.

[0036] The first opening 34 includes a rib 35 providing structural support for the hydrogen evolution electrode assembly 30. A partition 24 is located on the side of the hydrogen evolution electrode assembly 30 opposite to the first end plate 22. The partition 24 includes a channel 36 that allows the flow of evolved hydrogen generated by the hydrogen evolution electrode assembly 30.

[0037] The detection electrode assembly 32 is located near the side of the partition 24 opposite to the hydrogen evolution electrode assembly 30. At least a portion of the detection electrode assembly 32 is exposed to hydrogen evolved or generated in the channel 36. A portion of the detection electrode assembly 32 is exposed to the fluid of interest, such as a gas, through a second opening 38 extending through the second end plate 26. The second opening 38 includes ribs 29 that provide structural support for the detection electrode assembly 32. The detection electrode assembly 32 provides an indication of the hydrogen concentration present in the fluid of interest at the opening 38.

[0038] Plates 22, 24, and 26 are conductive and, in the illustrated example, include graphite. An insulating layer is located between the plates to electrically isolate them from each other. In the illustrated embodiment, the insulating layer also provides a seal at least along the periphery of the interface between the plates. A first insulating layer 40 is located between the first end plate 22 and the spacer 24. In this embodiment, a second insulating layer 42, comprising a dielectric material, is located within the spacer 24 to electrically isolate opposite sides of the spacer 24 from each other. In the illustrated example, the multilayer spacer 24 includes a first layer or plate 24A and a second layer or plate 24B, with the insulating layer 42 between these plates 24A and 24B. A feature of the illustrated exemplary embodiment is that even when layers 24A and 24B are both at a negative potential, they remain electrically isolated from each other by the insulating layer 42.

[0039] Other embodiments include different arrangements of the partition 24, which physically separates the electrode assemblies 30 and 32, provides electrical isolation between the electrode assemblies, and includes electrical isolation between opposite sides of the partition 24.

[0040] Another insulating layer 44 is located between the partition 24 and the second end plate 26. The exemplary embodiment shown includes insulating layers 46 and 48 between the respective end plates 22 and 26 and the housing 50 defining the outer surface of the example sensor 20. The housing 50 includes a first side 52 adjacent to the first end plate 22, wherein the insulating layer 46 is between the first end plate 22 and the first side 52. The first side 52 includes a first window 54 aligned with a first opening 34, leaving at least a portion of the hydrogen evolution electrode assembly 30 exposed through the window 54 and the opening 34.

[0041] The second side 56 of the housing 50 is positioned adjacent to the second end plate 26, with the insulating layer 48 between the second side 56 and the second end plate 26. The second side 56 includes a second window 58 aligned with the second opening 38, leaving a portion of the detection electrode assembly 32 exposed through the second window 58 and the second opening 38.

[0042] In the illustrated example, each of the insulating layers 40-48 comprises a polymer material that electrically isolates adjacent plates or components from each other. In the illustrated exemplary embodiment, the insulating layer comprises a fluoropolymer. The insulating layer providing a gasket is considered a gasket. In some embodiments, the insulating layer used as a gasket comprises tetrafluoroethylene (PTFE).

[0043] The stack of components and example housing 50 are secured in a desired alignment by fasteners 60, which in the illustrated example include threaded rods, such as bolts. The fasteners 60 are electrically isolated from plates 22, 24, and 26 by isolation sleeves 62, which are received in channels 64 extending through the stack of components, as from... Figure 3 As best shown. Sleeve 62 comprises a non-conductive material, such as plastic or polymer.

[0044] Sensor 20 includes conductive leads 70 that facilitate the application of a voltage to the hydrogen evolution electrode assembly 30. In some exemplary embodiments, the applied voltage is approximately 0.3 volts. The electrical energy carried by the leads 70 is applied to a first end plate 22 and a spacer 24A. Each of these plates is in conductive contact with the hydrogen evolution electrode assembly 30, and the voltage across plates 22 and 24A establishes a potential difference across the hydrogen evolution electrode assembly 30.

[0045] An additional lead 72 is associated with the detection electrode assembly 32 to allow measurement of the voltage across the detection electrode assembly 32. The measured voltage provides an indication of the concentration of hydrogen in the fluid of interest. Plates 24B and 26 are in conductive contact with the detection electrode assembly 32, respectively. In this example, lead 72 is connected to plates 24B and 26.

[0046] In some embodiments, the means for measuring the voltage across the detection electrode assembly 32 is a high-impedance means to avoid drawing current from the detection electrode assembly 30.

[0047] like Figure 2 As shown, hydrogen generated by the hydrogen evolution electrode assembly 30 flows through channel 36, as indicated by arrow 74. This hydrogen enters one side of the detection electrode assembly 32. Due to the positive pressure within channel 36, the hydrogen flows along the detection electrode assembly 32 as indicated by arrow 76 and exits the sensor 20 through exhaust port 78, which in the illustrated example is established within partition 24B. Arrow 80 indicates the hydrogen exiting the sensor 20. The exhaust port 78 is located on one side of the sensor 20 such that the hydrogen exiting the exhaust port 78 does not incident on or near the second window 58 and the second opening 38 to avoid affecting the hydrogen concentration measured in the gas or fluid of interest.

[0048] The voltage applied to the hydrogen evolution electrode assembly 32 establishes a pumping rate for hydrogen flowing into the channel 36. A sufficiently high flow rate prevents gas diffusion from the outside of the sensor 20 into the channel 36. A sufficient flow rate modulated by the current applied to the electrode assembly 32 establishes a positive pressure within the channel 36 and the sensor 20, including a positive pressure along the discharge port 78.

[0049] The detection electrode assembly 32 does not require any current or reference potential to be supplied. Instead, the potential formed across the detection electrode assembly 32 results in a voltage that can be measured using the lead 72. The known Nernst potential phenomenon explains how the potential difference or voltage across the detection electrode assembly 32 corresponds to an indication of the hydrogen concentration in the fluid exposed to the detection electrode assembly through the second window 58 in the second opening 38. Given this description and knowledge of the Nernst potential, those skilled in the art will recognize how a measurement of hydrogen concentration can be obtained based on the voltage across the detection electrode assembly 32.

[0050] Figure 4 and Figure 5 This is an exploded view showing selected features of components of an example hydrogen sensor 20. The hydrogen evolution electrode assembly 30 in this example includes a first electrode layer 30A and a second electrode layer 30C. In this example, electrode layers 30A and 30C include carbon paper that allows gas diffusion through each layer. In this embodiment, a matrix layer 30B is formed by a relatively thin coating on the sides of electrode layers 30A and 30C, or relatively thin coatings or layers 30B receiving each other relative to each other when the sensor 20 is assembled. In the figure, coating 30B is applied to the underside of electrode layer 30C and the upper side of electrode layer 30A. Each coating 30B contains a liquid electrolyte, such as phosphoric acid.

[0051] In this example, the first electrode layer 30A is a hydroxide electrode, which receives and is in conductive contact with the first end plate 22. The second electrode layer 30C is a hydrogen evolution electrode that receives the hydrogen evolution electrode relative to the partition 24A and introduces the evolved hydrogen or generated hydrogen into the channel 36.

[0052] As from Figure 4 As shown, the isolation layer 40 comprises three separate layers or gaskets 40A, 40B, and 40C. A first electrode layer 30A is received within a window 90 in gasket 40A. Gasket 40B includes a window 92 that defines the outer edge and operating region of the matrix layer 30B, which is considered to be active during hydrogen generation. A second electrode layer 30C is received within a window 94 in gasket 40C.

[0053] The thickness control of gaskets 40C and 40A determines the amount of compression experienced by electrode layers 30A and 30C during the assembly of the component stacks of sensor 20. Some compression of electrode layers 30A and 30C is desired to establish good electrical contact between electrode layers 30A and 30C and the matrix layer 30B, respectively. Compression also ensures good electrical contact between electrode layers 30A and 30C and plates 22 and 24A, respectively. The amount of compression establishes the desired amount of contact while still allowing gas permeability.

[0054] In some embodiments, the gasket 40B is not compressed, and therefore the matrix layer 30B within the window 92 is not compressed.

[0055] Figure 5 The composition is shown Figure 1-3 Some components of the upper half (according to the accompanying drawings) of the illustrated embodiment. In this embodiment, the detection electrode assembly 32 includes a reference electrode layer 32A and a detection electrode layer 32C. A matrix layer 32B is formed by a coating on the sides of the electrode layers 32A and 32C that receive each other. The matrix 32B includes a liquid electrolyte, such as phosphoric acid.

[0056] In this example, the isolation layer 44 includes three gaskets 44A, 44B, and 44C that receive each other. Electrode layer 32A is received within window 96 in gasket 44A. Gasket 44B includes window 98, which has a smaller area than window 96. Window 98 establishes the area of ​​matrix layer 32B, while the edge of gasket 44B seals the edges of electrode layers 32A and 32C against each other to prevent gas from passing between the electrode layers. Electrode layer 32C is received within window 100 of gasket 44C.

[0057] Gaskets 44C and 44A have thicknesses that, once sensor 10 is assembled, control the amount of compression experienced by electrode layers 32C and 32A, respectively. In this example, gasket 44B and matrix layer 32B, received in window 98, are not compressed.

[0058] In this embodiment, each electrode layer 30A, 30C, 32A, 32C includes a material (such as carbon paper) that has been wetted with a liquid electrolyte (such as phosphoric acid). The matrix layers 30B, 32B of each electrode assembly also contain a liquid electrolyte, such as phosphoric acid.

[0059] The housing 50 and the outermost insulating layers 46 and 48 are not shown in the diagram. Figure 4 and Figure 5 Although they are included in the assembled sensor 20.

[0060] like Figure 2 As shown, the exemplary embodiment includes a heater 84 for controlling the temperature of the liquid electrolyte in electrode assemblies 30 and 32. In this example, the heater 84 is at least partially located within the sensor and accommodated within openings in at least some of the plates 22-26. The heater 84 can heat the partition 24 and plates 22, 26 to achieve a desired temperature or heating effect on the electrode assemblies 30 and 32, thereby ensuring operation at the desired temperature level.

[0061] For example, when sensor 20 is exposed to a gas stream containing acid vapor, it is advantageous to maintain sensor 20 at a temperature higher than the gas stream temperature. This helps to maintain the desired amount of acid in electrode assemblies 30 and 32. If the temperature of sensor 20 is not higher than the temperature of the gas stream, under certain conditions, the gas stream may condense and fill electrode assemblies 30 and 32, thus exposing the electrode assemblies thereto, for example, through openings 34 and 38.

[0062] The heater 84 in the illustrated example configuration comprises a non-conductive material to avoid establishing short circuits between different plates or layers of the sensor 20. In some embodiments, the heater 84 maintains the sensor temperature above 120°C. This is particularly useful when the sensor is exposed to vapors including carbon monoxide, when the liquid electrolyte in the hydrogen sensor 20 is phosphoric acid, and when the sensor 20 is used to determine the hydrogen concentration in the reformate stream of a hydrogen reformer used to produce fuel for a fuel cell.

[0063] Figure 6 A partial cross-sectional view shows the arrangement of gaskets for the detection electrode assembly 32 and the isolation layer 44 when the sensor 20 is assembled. The gaskets for the isolation layer 42 and the hydrogen evolution electrode assembly 30 have the same arrangement. Gaskets 44A and 44C include a sealant that establishes a seal around the detection electrode assembly 32 to prevent unwanted gas migration within the sensor 20. For example, the seal established by the gaskets prevents evolved hydrogen from leaking from channel 36 to other parts of the sensor and prevents other gases from reaching the detection electrode layer 32A. In the example shown, gasket 44B does not have a sealant.

[0064] Figure 7 The thermosetting polymer sealant 110 on the exterior of the insulating gasket is schematically shown. Gasket 44A is as follows. Figure 7 The illustration shows an example of a gasket that includes a sealant. A thermosetting polymer sealant adhesively seals the periphery of the sensor 20 and holds the layers or components of the sensor 20 together. The sealant layer in the illustrated embodiment comprises a fluoropolymer, such as a fluororubber sealant, which is resistant to irritating chemicals (such as phosphoric acid) and can withstand high temperatures.

[0065] Each of the isolation layers 40, 42, 44, 46, and 48 includes a peripheral adhesive for at least sealing the interface of each layer within the assembled sensor 20. Fastener 60 holds all components together, but pressure provided by fastener 60 is not required to maintain the seal between components of sensor 20. Thermosetting polymer seals adhesively seal and hold the layers together, including any defects that may flow into the surfaces of adjacent layers to achieve a reliable seal. The seals prevent unwanted gas from permeating into sensor 20 and unwanted gas flows between components within sensor 20.

[0066] According to one example method of manufacturing sensor 20, all the different layers are adjacent to each other in the arrangement shown, and the assembly is heated to at least partially melt the thermosetting polymer sealant to adhesively seal and fix all the layers together.

[0067] The example arrangement shown allows for the economical manufacture of hydrogen concentration sensors, enables a reliable sensor configuration, and results in a relatively small sensor size. An exemplary embodiment has dimensions of approximately 50 mm (2 inches) long, 25 mm (1 inch) wide, and 25 mm (1 foot) deep.

[0068] One feature of the example shown is that the reference electrode 32A is different from the hydrogen evolution electrode 30C. Using the hydrogen evolution electrode 30C to provide hydrogen to maintain the reference electrode 32A at the desired reference potential eliminates the need to apply current to the reference electrode 32A. This feature eliminates any shift in the reference potential that would otherwise occur if hydrogen evolution were performed using the reference electrode 32A. Exposing the reference electrode 32A only to the hydrogen from channel 36 also ensures the desired potential resulting from the exposure of the reference electrode 32A to the generated hydrogen.

[0069] The hydrogen concentration sensor embodying this invention can be used in various environments and for various purposes. An exemplary embodiment is shown below. Figure 8 As shown, sensor 20 is included in fuel cell power plant 150. Reformer 152 receives hydrocarbon 154, which may be, for example, methane or natural gas. Reformer 152 produces hydrogen fuel at 156, which is supplied to fuel cell stack assembly 158. Hydrogen fuel is one of the reactants used by fuel cell stack assembly 158, and oxygen, which may be supplied as air 160, is another reactant. Hydrogen concentration sensor 20 within reformer 152 provides information about the operation of reformer 152. Reformer control 162 (such as a microprocessor or other computing device) uses the information from sensor 20 to dynamically adjust or tune the operation of reformer 152. In this exemplary embodiment, control 162 does not require any temperature information, which can save costs compared to systems that require temperature sensors and temperature information processing.

[0070] The hydrogen concentration sensor designed according to embodiments of the present invention is more stable and therefore more reliable than previous sensors, which utilize a hydrogen-dependent reference electrode to establish a reference potential. Furthermore, the sensor designed according to embodiments of the present invention can be used in a wider variety of situations where hydrogen level detection is desired.

[0071] The foregoing description is exemplary in nature and not restrictive. Variations and modifications to the disclosed examples will become apparent to those skilled in the art without necessarily departing from the spirit of the invention. The scope of legal protection afforded to this invention can only be determined by examining the appended claims.

Claims

1. A hydrogen concentration sensor, comprising: a first end plate comprising a first opening through a portion of the first end plate; a hydrogen evolution electrode assembly located proximate the first end plate, wherein at least a portion of the hydrogen evolution electrode assembly is exposed through the first opening, the hydrogen evolution electrode assembly configured to generate hydrogen by being exposed to a fluid at the first opening, the hydrogen evolution electrode assembly comprising a first electrode layer and a second electrode layer, each of the first and second electrode layers comprising a coating on one side, the coating comprising a liquid electrolyte; at least one separator plate positioned proximate the hydrogen evolution electrode assembly on an opposite side of the hydrogen evolution electrode assembly from the first end plate, the at least one separator plate comprising a channel configured to allow hydrogen generated by the hydrogen evolution electrode assembly to flow; a detection electrode assembly positioned proximate the at least one separator plate on an opposite side of the at least one separator plate from the hydrogen evolution electrode assembly, at least a portion of the detection electrode assembly being exposed to hydrogen in the channel, the detection electrode assembly comprising a third electrode layer and a fourth electrode layer, each of the third and fourth electrode layers comprising a coating on one side, the coating comprising a liquid electrolyte; a heater positioned to increase a temperature of at least the liquid electrolyte in the coating; and a second end plate positioned proximate the detection electrode assembly on an opposite side of the detection electrode assembly from the at least one separator plate, the second end plate comprising a second opening through a portion of the second end plate, a portion of the detection electrode assembly being exposed to a fluid of interest through the second opening, the detection electrode assembly configured to provide an indication of a concentration of hydrogen in the fluid of interest.

2. The hydrogen concentration sensor of claim 1, wherein: the coating on the first and second electrode layers establishes a matrix layer between the first and second electrode layers; the coating on the third and fourth electrode layers establishes a matrix layer between the third and fourth electrode layers; the first electrode layer is exposed to the first opening; the second electrode layer is at least partially exposed to the channel; and the third electrode layer is at least partially exposed to the channel. the liquid electrolyte comprises phosphoric acid.

3. The hydrogen concentration sensor according to claim 1, wherein 4. The hydrogen concentration sensor of claim 1, wherein: the first end plate is electrically conductive; the at least one separator plate is at least partially electrically conductive; the second end plate is electrically conductive; and the hydrogen concentration sensor comprises: at least one isolation layer between the first end plate and the at least one separator plate, at least one isolation layer between the second end plate and the at least one separator plate, and at least one isolation layer within the at least one separator plate, the at least one isolation layer electrically isolating a first side of the at least one separator plate against the hydrogen evolution electrode assembly from a second side of the at least one separator plate against the detection electrode assembly. each electrically conductive plate contains graphite.

5. The hydrogen concentration sensor according to claim 4, wherein 6. The hydrogen concentration sensor of claim 4, wherein: ​ The at least one spacer includes two graphite plates; The at least one isolation layer within the at least one spacer includes a gasket positioned between the two graphite plates; and The gasket includes an opening through the gasket that is aligned with the channel.

7. The hydrogen concentration sensor according to claim 4, wherein Each of the isolation layers includes a fluoropolymer.

8. The hydrogen concentration sensor of claim 4, wherein, The at least one isolation layer between the first end plate and the at least one spacer includes an opening through the at least one isolation layer; The hydrogen evolution electrode assembly is positioned within the opening through the at least one isolation layer between the first end plate and the at least one spacer; The at least one isolation layer between the at least one spacer and the second end plate includes an opening through the at least one isolation layer; and The detection electrode assembly is positioned within the opening through the at least one isolation layer between the at least one spacer and the second end plate.

9. The hydrogen concentration sensor of claim 8, wherein, The coating on the first electrode layer and the second electrode layer establishes a matrix layer between the first electrode layer and the second electrode layer; The at least one isolation layer between the first end plate and the at least one spacer includes three gaskets; One of the first electrode layer and the second electrode layer is at least partially positioned within an opening in one of the three gaskets; The other of the first electrode layer and the second electrode layer is at least partially positioned within an opening in another of the three gaskets; and The matrix layer is positioned within an intermediate one of the three gaskets.

10. The hydrogen concentration sensor of claim 9, wherein, The thickness of the electrode layers has a predetermined relationship with the thickness of the gaskets; and The thickness of the gaskets controls an amount of compression of the electrode layers.

11. The hydrogen concentration sensor of claim 1, wherein, The at least one spacer includes a vent positioned to allow hydrogen to exit the hydrogen concentration sensor from the channel; and The vent is positioned such that hydrogen exiting the vent is directed away from the second opening.

12. The hydrogen concentration sensor of claim 1, comprising a housing including a first side against the first end plate and a second side against the second end plate, the first side of the housing including a first window aligned with the first opening, the second side of the housing including a second window aligned with the first opening.

13. The hydrogen concentration sensor of claim 1, wherein, The coating on the third electrode layer and the fourth electrode layer establishes a matrix layer between the third electrode layer and the fourth electrode layer; and An indication of a concentration of hydrogen of the fluid of interest is provided by a voltage across the third electrode layer and the fourth electrode layer.

14. A method of assembling a hydrogen concentration sensor, comprising: ​ ​ positioning a first end plate adjacent to a hydrogen evolution electrode assembly to expose at least a portion of the hydrogen evolution electrode assembly through a first opening through a portion of the first end plate, the hydrogen evolution electrode assembly configured to generate hydrogen by being exposed to a fluid at the first opening, the hydrogen evolution electrode assembly comprising a first electrode layer and a second electrode layer, each of the first electrode layer and the second electrode layer comprising a coating on one side, the coating comprising a liquid electrolyte; positioning at least one separator adjacent to the hydrogen evolution electrode assembly on an opposite side of the hydrogen evolution electrode assembly from the first end plate, wherein the at least one separator comprises a channel configured to allow hydrogen generated by the hydrogen evolution electrode assembly to flow; positioning a detection electrode assembly adjacent to the at least one separator on an opposite side of the at least one separator from the hydrogen evolution electrode assembly such that at least a portion of the detection electrode assembly is positioned to be exposed to hydrogen in the channel, the detection electrode assembly comprising a third electrode layer and a fourth electrode layer, each of the third electrode layer and the second electrode layer comprising a coating on one side, the coating comprising a liquid electrolyte; positioning a second end plate adjacent to the detection electrode assembly on an opposite side of the detection electrode assembly from the at least one separator such that a portion of the detection electrode assembly is positioned to be aligned with a second opening through a portion of the second end plate, wherein the portion of the detection electrode assembly is capable of being exposed to a fluid of interest through the second opening, the detection electrode assembly configured to provide an indication of a concentration of hydrogen in the fluid of interest; positioning a heater proximate to the detection electrode assembly to increase a temperature of at least the liquid electrolyte; and securing the plates and the electrode assemblies in the positioned locations.

15. The method of claim 14, comprising: positioning the hydrogen evolution electrode assembly within an opening of at least one gasket, the at least one gasket providing a seal around an edge of the assembly to preserve the liquid electrolyte; and positioning the detection electrode assembly within an opening of at least one other gasket, the at least one other gasket providing a seal around an edge of the assembly to preserve the liquid electrolyte.

16. The method of claim 15, comprising: sealing the at least one gasket to the first end plate on one side of the at least one gasket; sealing the at least one gasket to the at least one separator on another side of the at least one gasket; sealing the at least one other gasket to the at least one separator on one side of the at least one other gasket; and sealing the at least one other gasket to the second end plate on another side of the at least one other gasket.

17. The method of claim 14, wherein: the first end plate is electrically conductive; the at least one separator is at least partially electrically conductive; the second end plate is electrically conductive; and the method comprises: positioning at least one isolation layer between the first end plate and the at least one separator, positioning at least one isolation layer between the second end plate and the at least one separator, and comprising at least one isolation layer that electrically isolates a first side of the at least one separator plate against the hydrogen evolution electrode assembly from a second side of the at least one separator plate against the detection electrode assembly.

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