Sensors

Abstract

The present disclosure provides a fuel cell with a first sensor including a membrane electrode assembly (MEA) including a plurality of electrodes 102, 104 and a membrane electrolyte layer disposed between the plurality of electrodes 102, 104. The MEA is disposed between a first substrate 122 and a second substrate 120. The first substrate 122 has at least one opening 112 for providing a gas flow path to one of the electrodes 104. The fuel cell also includes an electrical control unit 402 for determining an electrical characteristic of the MEA. The electrical characteristic is indicative of a gas composition of the gas at one of the electrodes 104. The electrical control unit 402 generates an output based on or in response to a change in the electrical characteristic.

Description

[Technical field]

[0001] The present disclosure relates to sensors and sensor devices, fuel cells including sensor devices, uses of said fuel cells, uses of said sensors, uses of membrane electrode assemblies (MEAs) as sensors, sensor systems, and methods for detecting gases or changes in gas composition.

[0002] The invention has particular application to fuel cells, for example solid polymer electrolyte fuel cells. [Background technology]

[0003] Electrochemical sensors are common and are generally physical sensors that detect gases by detecting a change in the electrical conductivity of air in the presence of that gas.

[0004] Conventional electrochemical sensors rely on the oxidation of some solid species (e.g., lead dioxide or tin dioxide) to determine the presence of gas. Because the presence of the gas being detected consumes the sensor's fuel, this type of prior art sensor can rapidly degrade and become unusable, essentially limiting the number of times the sensor can be used. Conventional electrochemical sensors are typically heated to account for environmental factors such as relative humidity. This is accomplished by constantly heating the sensing element to high temperatures (over 300°C). This means that such sensors, even when part of a system, will continually consume significant parasitic power. Such sensors require 2.25 W of power for about 10 seconds at start-up, and then 0.9 to 1 W of power during normal operation.

[0005] Conventional electrochemical sensors are often heated sensors that can take hours to reach the right temperature when powered on. See for example Micro's Hydrogen click® hydrogen sensor. This sensor relies on a tin dioxide sensor layer that changes conductivity in the presence of hydrogen and requires 24 hours to heat up and reach the right temperature. This is typical of sensors currently available on the market.

[0006] A fuel cell (such as a solid polymer electrolyte fuel cell) is an electrochemical device that produces electrical energy and heat from reactants or oxidants (such as pure oxygen or air) and fuels (such as hydrogen or hydrogen-containing mixtures, hydrocarbons or hydrocarbon derivatives). Fuel cell technology is found in stationary and mobile applications such as power plants, automobiles, and laptop computers.

[0007] According to British Standard 62282-2 for fuel cells, fuel cells that consume gas must be equipped with a sensor to monitor internal gas leakage. Gas leakage sensors are a key element to ensure the safety of fuel cells. Therefore, fuel cells require low-cost, energy-efficient gas sensors.

[0008] Existing sensors are relatively expensive due to the large number of components and the use of expensive components. Existing sensors act as relatively large continuous parasitic elements and consume the power generated by the fuel cell since they need to take a certain amount of power from the fuel cell output in order to operate. In the operation of fuel cells, especially low wattage fuel cells such as those below 200 W, especially around 20 W, a loss of output power, for example 1 W to 2 W, corresponds to 5% to 10% of the total generated power of the system. Currently available gas sensors act as relatively large parasitic elements to fuel cells, especially small scale fuel cells.

[0009] It would be advantageous to have a sensor that works immediately upon power up, and also to have a sensor that can be used after multiple sensing events, i.e., does not degrade rapidly with sensing events as the sensor's fuel is consumed. Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above, it would be desirable to provide an improved sensor device for detecting the presence, level and leaks of gases used, for example, in fuel cells. [Means for solving the problem]

[0011] According to a first aspect of the present invention, a fuel cell is provided. The fuel cell comprises a sensor comprising a membrane electrode assembly (MEA) and an electrical control unit for determining an electrical characteristic of the MEA. The MEA comprises a plurality of electrodes and a membrane electrolyte layer disposed between the plurality of electrodes. The MEA is disposed between a first substrate and a second substrate. The first substrate has at least one opening to provide a gas flow path therethrough to one of the plurality of electrodes. The electrical characteristic is indicative of a gas composition of the gas at one of the plurality of electrodes. The electrical control unit generates an output based on or in response to a change in the electrical characteristic.

[0012] Although in the first aspect of the invention the sensor is in a fuel cell, the following discussion of the sensor applies mutatis mutandis to all aspects of the invention, in particular the second to fifth aspects of the invention described below. Throughout this specification "sensor" and "sensor arrangement" are used interchangeably. All properties, components, configurations and characteristics of the sensor described for the first aspect of the invention are applicable to the other aspects of the invention.

[0013] A pair of electrodes separated by an electrolyte membrane is a membrane electrode assembly (MEA). Each MEA consists of an ion-permeable membrane (e.g., an electrolyte membrane that is a proton exchange membrane). The MEA also consists of two electrodes on either side of the electrolyte membrane. The electrolyte membrane allows ions (e.g., hydrogen ions / protons) to pass through, but not free electrons. The electrodes are electrically insulated from each other by the electrolyte membrane. When "fuel" (i.e., something that reacts with the electrodes) is present adjacent to one of the electrodes, a reaction occurs at this electrode, producing electrons and ions. The ions move across the electrolyte membrane between the electrodes and are consumed (reacted) at the opposing electrode. A circuit is then formed for electrons to flow between the two electrodes, generating an electric current. A catalyst layer or catalyst can be integrated with the electrodes to speed up the reaction at both electrodes. MEAs can be stacked and used in fuel cells to generate electrical energy.

[0014] The inventors have newly discovered that the MEA can be used as part of a relatively simple, low-cost gas sensor. This use and the sensor device described herein have not been reported anywhere else. The sensor can be used as an ambient sensor and as part of an alarm or alarm system to indicate that there has been a change in gas composition in the environment in which such a change is to be detected. The sensors described herein do not utilize a specially captured, enclosed or supplied "reference gas" as in prior art sensors. The ambient air or any gas to which the sensor is normally exposed serves as an equivalent "reference gas" in prior art sensors. Preferably, the reference (gas) for the sensor is ambient air or the gas composition to which the sensor is normally exposed. In a fuel cell, the gas composition to which the sensor is normally exposed would be ambient air. However, when used as a sensor outside of a fuel cell, the gas composition to which the sensor is normally exposed may be different from ambient air or may be completely devoid of gas (i.e., vacuum).

[0015] The first substrate of the sensor has at least one opening for providing gas formation (e.g. from the external surface of the first substrate or from the ambient atmosphere surrounding the substrate) to one of the electrodes of the MEA. This means that the gas composition at the electrode adjacent to the substrate with the opening is the same or very similar to the gas composition at the substrate. The electrode reacts with the gas present at its surface. Any change in the gas composition at the electrode surface will cause a change in the reaction or a new reaction to occur. Thus, a change in the gas composition at one or more electrodes of the MEA will cause a change in the electrical properties of the MEA. A change in the electrical properties of the MEA indicates a change in the gas composition around at least one electrode or in the respective substrate layer.

[0016] Preferably, the MEA is comprised of at least two electrodes, at least one of which on either side of the MEA is exposed to the atmosphere. With both the sensing electrode and the reference electrode exposed to the atmosphere, a standard atmospheric gas can be used as the reference gas.

[0017] The sensor device is an efficient, low power fuel cell. In this case, an electrical property can be detected or measured when a difference in gas exists between the two sides, for example when hydrogen is present in a higher concentration on one side of the sensor (i.e., one of the electrodes) than on the other side. A change in the electrical property can be interpreted as indicating the presence of a gas not previously present, or a change in the gas composition around the sensor.

[0018] The electrical control unit can determine an electrical property of the MEA indicative of the gas composition at one of the electrodes and generate an output based on (or in response to) the change in the electrical property. This can generate a signal indicative of a change in the gas concentration around the sensor (i.e., the presence of a gas such as hydrogen). This signal can cause a further action or event. The output or signal can be sent to some form of control module to affect a change in the wider system to which the sensor device belongs. In the case of a fuel cell, the presence of fuel gas at the sensor can turn off the fuel cell, indicating a potentially dangerous and / or fuel-wasting gas leak. The control module itself (comprised of a device that detects changes in the potential difference between the electrodes) may also monitor changes in the electrical property of the MEA of the sensor device disclosed herein. The fuel cell or an external control device connected to or controlling the fuel cell can constitute the control module. The electrical property measured can be, for example, the potential difference, the open circuit voltage between the anode and cathode sides of the MEA, the generated current, the capacitance or the conductivity. It is also possible to measure multiple electrical properties at once (or with one device).

[0019] The proposed solution does not require a constant current to flow through the sensor device, which reduces the parasitic power of the system utilizing such a sensor compared to prior art fuel sensors. This is particularly useful for small systems such as fuel cells. That is, the sensor itself does not have a large parasitic load, as in conventional sensors that require a large amount of power to heat the sensor. The sensor device disclosed herein requires a power of about 1-10 mW for operation. This is significantly less than the 0.9-1 W power required for normal operation of the prior art sensors described in the background art.

[0020] The sensors disclosed herein are smaller than prior art sensors, thus occupying less space that can be used for other components within the fuel cell. Again, this is particularly useful for small fuel cells. These sensors are also advantageous over prior art sensors because they are ready for use sooner than prior art sensors that require hours of power ramp-up and equilibration to reach the proper temperature. The sensor devices disclosed herein are essentially "always on" and have no warm-up time. Prior art sensors contain metal oxides that degrade at a much greater rate and therefore can only be used a few times. The sensors of the present invention can withstand the sensing and use of many more events than prior art sensors that degrade after a few uses. The sensors disclosed herein can withstand tens of thousands of uses due to the robust nature of the MEA utilized. These sensors are more cost-effective than prior art sensors, in part because they use fewer parts and are easier to manufacture.

[0021] The sensors disclosed herein are more sensitive than prior art sensors. These sensors are more sensitive than prior art sensors and can operate at nanovolt levels as opposed to millivolt levels. Such sensors can detect relatively small changes in gas composition, as very small changes in gas composition necessarily lead to changes in the electrical properties of the MEA. Only a change in the electrical properties (e.g. potential difference) needs to be detected, allowing for more sensitive measurements than prior art sensors.

[0022] Fuel cell safety is improved by having accurate sensors to detect hydrogen leaks. Fuel cells using the sensors disclosed herein are safer than fuel cells that do not. The improvements from using these sensors are particularly beneficial when used with fuel cells.

[0023] The use of these sensors was initially envisioned as being in a fuel cell where leaking gas is present, such as on top of the fuel cell, but they can be used anywhere gas detection or sensing is required. The electrochemical components of the sensor device are modified to allow for use with different gases to be sensed.

[0024] Such sensor devices may be utilized anywhere that gas detection is a priority.

[0025] Preferably, the first and second substrates are printed circuit boards (PCBs). Preferably, the sensor is formed by compression lamination of a PCB.

[0026] The sensors disclosed herein can withstand harsher environmental conditions than many prior art sensors due to the use of robust materials, e.g., PCB materials, and a sealed MEA structure that is highly resistant to high temperatures and pressures, and the sensors disclosed herein can also withstand relatively high mechanical stresses.

[0027] Preferably, the sensor is mounted internally to the fuel cell in an area of ​​the fuel cell where leakage gas would escape, such that the sensor is able to detect leakage of fuel from the fuel cell.

[0028] Preferably, when a change in gas composition is detected by the sensor, the fuel cell is switched off. Preferably, there is a threshold where the fuel cell is powered off when the electrical characteristic is above or below this threshold. The threshold is set as part of the detection means. The threshold may be set such that changes in gas concentration below the threshold are not indicated to the user or the system. This is to prevent very small differences in gas composition being indicated, such as small differences that may naturally occur in normal ambient air (e.g. small fluctuations in oxygen, carbon monoxide or carbon dioxide levels in air). The threshold may be calculated by the electronic control unit to be equal to the threshold gas level.

[0029] Preferably, the fuel cell further comprises means for indicating that an output based on or responsive to the electrical characteristic has been produced.

[0030] Preferably, the second substrate has at least one opening therethrough to provide a gas flow path to one of the electrodes.

[0031] Preferably, at least one of the first and second substrates has a plurality of openings to provide a plurality of gas flow paths through the substrate, and preferably, only one substrate has a plurality of openings and the other substrate has only one opening.

[0032] Preferably, one of the first or second substrates has more openings than the other substrate, forming more gas flow paths through that substrate to one of the electrodes than the other substrate, or the openings or openings of one substrate are larger in size than the openings or openings of the other substrate, providing a wider gas flow path through that substrate to one of the electrodes. Preferably, one of the first or second substrates is configured with dimensions such that the flow to one of the electrodes is increased compared to the other. Preferably, one electrode has more openings, flow paths, or larger openings, flow paths, or flow paths such that the gas flow to that electrode is increased compared to the other electrode. Preferably, the flow of gas to one electrode is more restricted than the flow of gas to the other electrode (i.e., the access to the electrode from the outside atmosphere is reduced), e.g., by one electrode having fewer openings, gas flow paths compared to the other electrode.

[0033] Preferably, the MEA is comprised of at least two electrodes with a gas passage to each electrode, one of the gas passages being smaller or having a restricted gas flow than the other gas passage.

[0034] These arrangements ensure that there is a difference in the gas amount, concentration, and / or reaction at the two electrodes, creating a difference between the two electrodes. This is particularly useful in fuel cell applications, since it is particularly advantageous to have a sensor sized to allow gas sensing when the entire sensor is filled with gas (i.e., when a gas leak occurs).

[0035] Preferably, the electrical property is the potential difference, the open circuit voltage between the anode and cathode sides of the MEA, the current, the capacitance or the conductivity. It is also possible to measure more than one electrical property at a time.

[0036] Preferably, the electrode and / or the sensor device further comprises a catalyst, which can facilitate the reaction between the electrode and the gas to be sensed.

[0037] Preferably, the substrate further comprises a conductive metal layer, preferably the conductive metal is copper, which allows for simplified measurement of electrical properties.

[0038] Preferably, the fuel cell or the sensor is configured with electronics that can short out the sensor in order to recalibrate it.

[0039] Preferably, the electrodes are carbon paper electrodes consisting of a carbon supported platinum catalyst.

[0040] Preferably, the electrolyte layer is a proton exchange membrane, preferably made of a sulfonated tetrafluoroethylene electrolyte.

[0041] Preferably, at least one of the electrodes is an electrode that reacts with the fuel of the fuel source that is consumed in the fuel cell.

[0042] In a second aspect of the invention, a sensor for detecting a change in gas composition is provided. The sensor comprises a membrane electrode assembly (MEA) including a plurality of electrodes and a membrane electrolyte layer disposed between the plurality of electrodes. The sensor also comprises a first substrate and a second substrate, with the MEA disposed between the first substrate and the second substrate. At least one of the first substrate and the second substrate has at least one opening to provide a gas flow path through to one of the electrodes. When there is a change in gas composition of the gas at one of the electrodes, an electrical characteristic indicative of the gas composition of the gas at one of the electrodes can be determined and an output indicative of the change in gas composition detected by the sensor can be generated.

[0043] Preferably, one of the first and second substrates has more openings than the other substrate, forming more gas flow paths through that substrate to one of the electrodes than the other substrate, or the openings or openings in one substrate are larger in size than the openings or openings in the other substrate, providing a wider gas flow path through that substrate to one of the electrodes.

[0044] Preferably, the MEA is comprised of at least two electrodes with a gas passage to each electrode, one of the gas passages being smaller or having a restricted gas flow than the other gas passage.

[0045] The sensor may have any or all of the other structural elements or properties of the sensor described in the fuel cell of the first aspect of the invention.

[0046] The sensor and sensor device disclosed herein can be used as a gas sensor in a fuel cell. Preferably, at least one of the electrodes is selected or designed to react with fuel from a fuel source consumed by the fuel cell. Preferably, the sensor device is located within a housing of the fuel cell. Preferably, if a gas leak is detected, the output stops normal operation of the fuel cell.

[0047] In a third aspect of the present invention, there is provided a sensor system comprising a sensor device as disclosed herein as a gas sensor and an electrical control unit for determining an electrical property of the MEA.

[0048] In a fourth aspect of the present invention, there is provided the use of a membrane electrode assembly (MEA) as a gas sensor. The MEA disclosed herein can be used as a sensor or sensor device for gas.

[0049] In a fifth aspect of the invention, there is provided a method of detecting a gas or a change in gas composition, the method comprising determining a change in an electrical property of an MEA, the change in the electrical property of the MEA being indicative of the presence or absence of a gas or the change in the electrical property of the MEA being indicative of a change in gas composition in the MEA.

[0050] Preferably, the method of detecting a gas or a change in gas composition uses any one of the sensors disclosed in relation to the first aspect of the invention, or any of the other aspects of the invention, and preferably the method is part of a method of operating a fuel cell.

[0051] The sensors, sensor systems, sensor uses and methods for detecting gases using the sensors described in the methods may have any of the other structural elements or characteristics of the sensors described in the fuel cell of the first aspect of the invention, all of which are interchangeable between aspects of the invention. [Brief description of the drawings]

[0052] [Figure 1] FIG. 2 is a schematic exploded view of the present invention. [Diagram 2] 2A is a schematic diagram of an embodiment of the present invention, FIG. 2A is a top view, FIG. 2B is a bottom view or an alternative view thereof, FIG. 2C is an alternative top (plan) view, FIG. 2D is an alternative bottom (plan) view, FIG. 2E is a side view, and FIG. 2F is an alternative side view of an embodiment of the present invention. [Diagram 3] 3A and 3B are schematic diagrams of a further embodiment of the present invention, respectively a top view and a top (plan) view of a further embodiment of the present invention; [Figure 4] FIG. 1 illustrates an exemplary sensor or system of the present invention, where the sensor is connected to other components of a wider system. [Diagram 5] FIG. 1 is a schematic diagram of a sensor of the present invention installed in a hydrogen fuel cell. [Figure 6] 1 is a graph of voltage versus time for an embodiment of the present invention illustrating the use of a sensor of the present invention; [Figure 7] 1 is a graph of voltage versus time for an embodiment of the present invention, demonstrating the use of a sensor of the present invention; [Figure 8] 1 is a graph of two voltage versus time plots for an embodiment of the present invention, illustrating the sensitivity using a sensor of the present invention; [Figure 9] 1 is a graph of voltage versus time for an embodiment of the present invention, illustrating repeated use of a sensor of the present invention. [Figure 10]10A and 10B show graphs of voltage versus time for an embodiment of the present invention, demonstrating the use of the inventive sensor disclosed herein under different environmental conditions, and FIG. 10B shows voltage measurements for three different segments (A, B, and C) of the graph from FIG. 10A. [Figure 11] 1 is a graph of voltage versus time for an embodiment of the present invention, illustrating the stability during use of a sensor of the present invention; [Figure 12] 6 is a graph showing the results of further experiments utilizing the oxygen sensor of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] Throughout this specification, like features and elements will be designated by like reference numerals in the drawings. Descriptions of sensor locations, such as "top", "bottom", and "side", are merely relative terms to describe particular embodiments and are not intended to limit the invention.

[0054] Next, the embodiments will be described in detail with reference to the accompanying drawings. In the following detailed description, numerous specific details are illustrated in order to fully understand the relevant teachings. However, it will be apparent to those skilled in the art that the present teachings can be practiced without these specific details.

[0055] 1 is a schematic exploded view of an implementation of a sensor device 100 according to an embodiment of the present invention. Outermost, substrate layers 120 and 122 are shown. Between the substrate layers 120, 122 is disposed an MEA consisting of an electrolyte layer 106 sandwiched between two electrodes 102, 104.

[0056] The electrodes 102, 104 may also be referred to as "electrode layers." The electrodes 102, 104 are made of a catalyst. The electrodes 102, 104 are located in the center of the sensor device 100, on either side of the electrolyte layer 106. However, the claims are not so limited. These electrodes 102, 104 are considered the "top" and "bottom" electrodes when the sensor device 100 is held horizontally (as shown in Figures 2 and 3). They may be considered the "left" and "right" electrodes when the sensor device 100 is held vertically (as shown in Figure 1). The substrate layers 120, 122 may also be considered the "top" and "bottom," or "left" and "right."

[0057] In the sensor device 100, the two electrodes 102, 104 are in contact with substrate layers 120, 122. The electrodes 102, 104 are in contact with the substrate layers 120, 122, respectively. The substrate layers 120, 122 are in contact with the electrodes 102, 104 so that electrical properties of the sensor device 100 can be measured. The substrate 122 may also be referred to as a reference layer, reference voltage plate or reference substrate. The substrate 120 may also be referred to as a sensing layer, or a sensing voltage plate or a sensing substrate.

[0058] Point 116 is a measurement or connection point for the reference plate and point 114 is a measurement or connection point for the sensing plate. Electrical probes can be electrically communicatively connected to these points 114, 116 to detect or measure electrical properties of the MEA.

[0059] Through holes or openings 110, 112 penetrate the substrate layers 120, 122, respectively. These through holes penetrate the substrates 120, 122 and provide a flow path or channel between each electrode 102, 104 and the local gas composition or atmosphere surrounding each substrate layer 120, 122. Thus, the through holes 110, 112 in the substrates 120, 122 provide a flow path from the exterior of the sensor device 100 to the electrodes 102, 104 inside the sensor device 100. This allows the gas composition surrounding the sensor device 100 to diffuse to the electrodes 102, 104 of the MEA. The through holes 110 through the substrate layer 120 provide a flow path from the gas composition surrounding the substrate layer 120 to the electrodes 102.

[0060] 1 and 2, the substrate layer 122 has only a single through-hole 112 providing a flow path from the gas composition surrounding the substrate layer 122 to the other electrode 104. The single through-hole provides a more restricted flow path access or reduced gas flow compared to the electrode 102 having multiple flow paths to the electrode 104 via multiple through-holes 110 through the substrate 120. As described herein, restricting gas access to one electrode compared to gas access to another electrode creates a difference in the gas diffusion characteristics (and therefore reaction rates) between the two electrodes, resulting in a voltage difference.

[0061] A "through-hole" refers to an opening, hole, channel, passage, flow path, pathway, or other means known in the art for providing diffusion of gas to an electrode. In FIG. 1, multiple through-holes 110 in substrate 120 and a single through-hole 112 in substrate 122 are shown. However, the size, shape, and number of through-holes can be varied in the sensor devices and systems disclosed herein. These can be adjusted to control the reaction of gas at the electrodes. As shown in FIG. 1, a single through-hole 112 can be provided in substrate 122 to provide access to electrode 104, or multiple through-holes 110 can be provided in substrate 110 to provide access to electrode 102. The through-holes can be the size of the entire electrode area, or a completely open electrode can be provided as part of an MEA held by the substrate. The through-holes can be any shape, for example, circular, square, rectangular, hexagonal through-holes. The through-holes can be patterned across the substrate in a manner that best suits the design of the sensor. Through-holes can be present on only one substrate of the sensor device disclosed herein.

[0062] Flow paths formed by through-holes 110, 112 through the substrates 102, 104 between the electrodes 102, 104 of the MEA and the gas composition surrounding each substrate allow diffusion of gas to the electrodes 102, 104 of the MEA. Thus, a change in the gas composition surrounding at least one of the respective substrate layers 120, 122 results in a change in the gas composition of the electrodes 102, 104 themselves.

[0063] The sensor device 100 of FIG. 1 (or embodiments throughout this specification) does not have through-holes that extend through the MEA itself (and thus through the electrodes 102, 104 or electrolyte layer 106).

[0064] In the exemplary embodiment depicted in Figure 1, the substrates 120, 122 are printed circuit boards (PCBs) and the sensor device 100 is a laminated structure, although the claims are not so limited. The lamination provides a strong structure with contact between the individual layers resulting in a monolithic, lightweight and hermetically sealed sensor device 100. A copper layer is on either side of each substrate 120, 122, and a non-copper square 108, 118 is etched in the center of each substrate 120, 122. The unique advantages of PCB technology are discussed below.

[0065] A circuit diagram of a sensor device 100 according to the present invention is shown in Figures 2A-2F, with like reference numerals used to describe like features shown in Figure 1.

[0066] A plan view of sensor device 100 from one side (sensing side) is shown in FIG. 2A, a plan view of sensor device 100 from the other second side (reference side) is shown in FIG. 2B, a plan view of one side (sensing side) of sensor device 100 is shown in FIG. 2C, a second plan view of the other side (reference side) of sensor device 100 is shown in FIG. 2D, a side view of sensor device 100 is shown in FIG. 2E, and an alternative side view of sensor device 100 is shown in FIG. 2F.

[0067] In Figures 2A, 2B, 2C, 2D, 2E and 2F, the laminate sensor device 100 has two printed circuit board (PCB) layers 120 and 122. The particular advantages of PCB technology are described below. The MEA shown and described in Figure 1 is not visible as the device is not shown exploded, but is present in the device 100 in Figure 2. Figures 2A and 2C show a through hole 110 through the substrate 120. Figures 2B and 2D show a through hole 112 through the substrate 122. Both sides of each substrate 120, 122 are provided with a copper layer, and a non-copper rectangle 108, 118 is etched away in the center of each substrate 120, 122.

[0068] The diameter of the through holes 110, 112 is 1 mm. The length and width of the sensor device 100 including the connection points 114, 116 is 23 mm, and the length and width excluding the connection points 114, 116 is 20 mm. The distance from one side to the through hole 112 in the substrate 122 is 10 mm. The distance from the edge to the nearest through hole 110 in the substrate 120 is 5.5 mm. The total thickness of the sensor device 100 is 2 mm. The thickness of each substrate layer 120, 122 is 1 mm. The connection points 114, 116 are on the substrate layers 120, 122 as described with reference to FIG. 1. However, the scope of the claims is not limited thereto.

[0069] The sensor device 100 of FIG. 1 and FIG. 2 is a 1 cm2 sensor made of a sulfonated tetrafluoroethylene electrolyte layer (thickness 10 μm). 2 The sensor has an MEA of 1 mm thickness and two gas diffusion electrodes made of carbon paper (200 μm thick when uncompressed) with a carbon-supported platinum catalyst. The sensor has a 1 mm thick PCB (FR4 material) sheet on either side of the MEA, and an 18 μm copper layer on either side of the PCB layer. All copper layers exposed to the MEA are coated with a 20 μm thick layer of carbon ink.

[0070] The sensor device 100 can be connected to an electrical sensor unit (or means) for detecting or measuring electrical properties of the MEA. For example, the electrical sensor unit can be used to detect or measure the potential difference between the electrodes of the MEA or the open circuit voltage between the anode and cathode sides of the MEA. Electrical connections can be provided, for example, at connection points 114, 116 at the corners of each substrate layer 120, 122. Lamination of the sensor device 100 creates contact between the individual layers. Copper layers are etched into the substrates 120, 122 and the laminated structure of the sensor device 100 provides electrical connections at each corner of each substrate layer, so that electrical properties of the MEA / substrate / electrodes 120, 122 / 102, 104 can be determined, detected and measured. Plated through holes (or vias) can also be introduced into the sensor device 100 to measure electrical properties of the external surface of the device. The plated-through holes provide a low resistance electrical path from one side (i.e., the side of the copper in contact with the electrode) to another side (i.e., the outside surface of the device), making it more convenient to measure voltage.

[0071] The electrical control unit that determines the electrical properties of the MEA can be any suitable type of potentiometric or voltage measuring device or module known in the art. By monitoring the potential difference between the electrodes of the sensor, the presence or change in the gas composition sensed by the sensor device 100 can be detected. The module can be, for example, an ADC (analog-to-digital converter) on a microcontroller. The ADC is used to convert analog signals, such as voltage, into a digital form that can be read and processed by the microcontroller. The microcontroller may have an ADC converter built in, or an external ADC converter can be connected to any type of microcontroller. The ADC has very little or no parasitic effect on the overall system while the system is doing other things.

[0072] During operation, when no change in gas composition or presence of gas is indicated, i.e., when the sensor device 100 is in a normal atmosphere (e.g., ambient air), the sensor device 100 is normally exposed to the normal or standard atmosphere surrounding the sensor device 100. The electrical property can be determined for normal operation. For example, if the electrical property determined is a potential difference, this provides a baseline or "normal" potential difference across the electrodes 102, 104. This potential difference depends on the nature of the electrodes 102, 104 and whether or to what level the electrodes 102, 104 normally react with gases present in the atmosphere. One or both of the electrodes 102, 104 may be constantly reacting with gases present in the normal atmosphere, for example with oxygen. Thus, a resting or normal potential difference exists between the electrodes 102, 104.

[0073] If there is a change in the gas composition surrounding the sensor device 100, i.e., if the concentration of a gas such as hydrogen, carbon monoxide, oxygen increases, or if a new gas is present in the through-holes 110, 112 that was not previously present, the gas composition at one or more of the electrodes 102, 104 will also change. If the MEA electrodes 102, 104 are of a material composition that reacts with the newly present gas, a reaction will occur at one or more of the electrodes 102, 104, causing a change in the electrical properties of the MEA, e.g., a change in the potential difference between the two electrodes 102, 104. The electrical properties change due to the movement of chemical species produced by the reaction.

[0074] In normal operation, only one side of the sensor device 100 is likely to be exposed to a large change in gas composition. Although both sides may be exposed to some gas, one side is more likely to be exposed to more gas due to the location of the sensor device 100 or the layout / size / design of the through-holes through the substrate. This results in a change in the electrical properties of the MEA between the two electrodes 102, 104 or a change in the potential difference already existing between the two electrodes 102, 104. The reference electrode 104 opposite the sensing electrode 102 may react with oxygen in the air and consume ions generated from the sensing electrode 102 passing through the electrolyte membrane. If the sensor device 100 is in the surrounding air, oxygen from the air will be consumed.

[0075] The sensors disclosed herein may have features that are specifically intended to be exposed to the gas to be sensed. Thus, the sensor may be directional, having a gas sensing side and a non-gas sensing side (or reference side). This non-gas sensing side (or reference side) need only be exposed to ambient air, e.g., outside the device in which the sensor is placed. The sensing side is placed inside the device. For example, if the electrochemistry of the sensor is designed to react with hydrogen, the reference side may be placed so that it is not exposed to hydrogen, or the level of hydrogen may be reduced compared to the other side. Then, when hydrogen (or an increased amount of hydrogen) is present on the sensing side of such a sensor, the hydrogen reacts with the electrode, which acts as the anode. The other electrode consumes oxygen from the ambient air, which acts as the cathode. In some embodiments described herein, the sensor may not utilize a specially captured, encapsulated, or supplied "reference gas" as in the prior art. In such cases, the ambient air or any gas to which the sensor is normally exposed serves as the equivalent of the "reference gas" of the prior art sensors.

[0076] 1 and 2, a change in gas concentration in the substrate 120 can cause a change in the potential difference between the two electrodes 102, 104 to be detectable across the respective measurement points 114, 116 on the substrates 120, 122. If both substrates 120, 122 of the sensor device 100 were exposed to gas equally at the same time due to the different flow paths resulting from the different through-holes 110, 112 in the substrates 120, 122, a potential difference would exist between the electrodes 102, 104 despite them being the same electrode type, as the electrodes 102, 104 would be exposed to different concentrations of gas due to the different flow paths to the electrodes 102, 104.

[0077] A change in the gas composition can therefore cause a detectable change in the potential difference between the electrodes. This can be detected using means for detecting the potential difference between the two electrodes, as described above. Such means may be included in the sensor, or may be implemented as part of a wider sensor system or apparatus of which the sensor is a part.

[0078] In addition to, or as an alternative to, detecting the change in potential difference between the electrodes, the sensor can detect the current generated at the electrodes upon reaction with the gas. When a reaction occurs at the electrodes, electrons are generated. A load can be applied to generate a current due to this flow of electrons (e.g., through a wire). The sensing and reference sides are set to a low resistance and the current is measured with an in-line ammeter. A change in current indicates a change in gas concentration. The current can be detected or measured as a separate indicator or can be used to power a means to indicate that there has been a change in the gas composition surrounding the sensor. The means to detect the generation of a current can be included in the sensor or can be implemented as part of a broader sensor system or device that includes the sensor as a part of it.

[0079] By detecting the change in the electrical property, an output is obtained. This output may be a signal generated to indicate a change in the gas concentration around the sensor, i.e. the presence of a gas such as hydrogen or an increase in the concentration of a gas such as hydrogen. This output may lead to further actions or events. The signal may be sent to a means to indicate that there has been a change in the gas composition or that a gas has been detected at the sensor (e.g. an alarm or warning light to indicate to a user that there is a change in the gas concentration such as a gas leak) or it may be sent to some form of control module to affect a change in the wider system to which the sensor device belongs. In the case of a fuel cell, the presence of fuel gas at the sensor device may cause the fuel cell to be turned off (possibly via a control module) due to the detection of a gas leak. A control module (including a means for measuring the change in the potential difference between the electrodes) may monitor, measure or detect the change in the electrical property of the MEA of the sensor device disclosed herein and define a change in the system to which the sensor belongs (e.g. a fuel cell).

[0080] A further electrochemical sensor device according to the invention is shown diagrammatically in Figure 3. Figure 3A shows a perspective view of the sensor device 300 and Figure 3B shows a further plan view of the sensor device 300.

[0081] In Figures 3A and 3B, the sensor device 300 is shown with two printed circuit board (PCB) layers 320 and 322 visible. An MEA, as described with reference to Figures 1 and 2, is provided / disposed between these two substrate layers 320, 322 but is not visible in Figure 3.

[0082] In Figures 3A and 3B, the laminate sensor device 300 has two printed circuit board (PCB) layers 320 and 322 that function as a reference substrate and a sensing substrate, as described with reference to Figures 1 and 2. In the embodiment shown in Figure 3, the through holes 110 through the substrate layers 320, 322 are shown as being equal in number and size through both substrate layers 320, 322. Points 116 and 114 are measurement or connection points. At these points 114, 116, the potential difference between the electrodes can be detected or measured by providing an electrical detection unit that can be in electrical communication with the electrodes to detect the potential difference. A copper layer is provided on the outside of each substrate 320, 322, and a non-copper square 308 is etched away in the center of each substrate 320, 322.

[0083] The total thickness of the sensor device 300 is 2 mm. The length of the sensor device 300 is 40 mm, the width is 33.11 mm, and the diameter of the hole 306 is 5.2 mm. Each PCB substrate layer 320, 322 is made of FR4 material and is 1 mm thick, with an 18 μm copper layer on each side of the PCB substrate layer. All copper layers exposed to the MEA are covered with a 20 μm thick carbon ink layer. The sensor device 300 is a 5 cm2 sintered body consisting of a sulfonated tetrafluoroethylene electrolyte layer (10 μm thick) and two gas diffusion electrodes consisting of carbon paper (200 μm thick when uncompressed) with a platinum catalyst supported on carbon. 2 It has an MEA of:

[0084] Mounting holes 306 are also provided through both the substrates 320, 322 and the electrolyte layer. They do not contact the electrodes and do not penetrate the electrodes, and therefore do not provide a flow path to the electrodes from the gas composition surrounding the respective substrate layers 320, 322. These mounting holes can be used for mounting the sensor device 300.

[0085] Figure 4 shows the exemplary sensor device 300 of Figures 3A and 3B connected as part of a larger system. Connection points 114 and 116 are in electrical communication with electrical conducting means 414 and 416, respectively. Electrical conducting means 414 and 416 may comprise, for example, electrical cables or wires.

[0086] The wires 414 and 416 connect the sensor device 300 to an electrical control unit 402 (here the potential difference detection means 402) via a connecting wire tie / sheath 418. The wires 414 and 416 may be a two-core wire / cable or may be bundled with the wire sheath 418 as shown. The potential difference detection means 402 is connected to a control module 404. The control module 404 is shown connected to the rest of a larger system. In further embodiments, the potential difference detection means 402 and the control module 404 may be part of the same single module or device. The wires may be attached by soldering, but also by using surface mount electrical connectors or clip connectors. The detection means 402 may also be connected to the sensor device 300 by a direct metal / metal interface (e.g. a push fit connector) or they may be joined by nuts and bolts.

[0087] The control module 404 can provide a means to shut down the fuel cell upon sensing a gas leak or change in gas composition within the fuel cell. The control module 404 can control other features of the broader device to which the sensors disclosed herein belong.

[0088] Figure 5 shows a typical example of the sensor device 300 of figure 4. It is implemented in a hydrogen fuel cell 500, which is shown in a simplified schematic diagram. The fuel cell components are not shown to scale. The connection points 114 and 116 are connected to wires 414 and 416, respectively. The wires 414 and 416 connect the sensor device 300 to the potential difference detection means 402 via a connecting wire bond 418. Wires connecting the potential difference detection means 402 to further parts of the fuel cell are shown in figure 5. Also shown are cooling 504 for the fuel cell stack 502, a lower casing 506 and a fuel cell casing lid 508 for holding the sensor device 300.

[0089] One side of the sensor device 300 (the side of the substrate 320) faces downwards towards the inside of the fuel cell. With the sensor device 100 positioned in this way, in the event of a gas leak, the gas rises inside the fuel cell and comes into contact with the sensor. Due to the through holes 110 in the substrate 320, the hydrogen gas diffuses through the through holes to the electrodes on the MEA side. In the fuel cell, this gas is likely to be pressurized, so in the event of a gas leak, the gas comes into contact with the sensor almost immediately (i.e. within 1 second). The gas reacts at the electrodes, causing a change in the potential difference between the electrodes. This change can be detected or measured by the potential difference detection means 402. As a result, a signal can be generated to raise an alarm or to stop the operation of the fuel cell as part of a wider safety system.

[0090] In all of the embodiments described herein, the electrochemistry of the MEA can be varied (i.e., the electrodes, catalyst, and electrolyte can be varied) to produce sensors for different gases or with different levels of sensitivity. Electrodes of different composition can react with different gases. Also, the electrolyte material and properties can be changed to allow different ions to pass through. This allows sensing of different gases that produce different ions. Thus, based on the electrochemistry of the MEA, the sensor can be tuned to detect different gases.

[0091] In all embodiments described herein, the electrolyte layer may be any suitable electrolyte membrane that allows the passage of ions (e.g., hydrogen ions) but not free electrons, such as Nafion® membrane sheets, sulfonated tetrafluoroethylene electrolyte layers, GORE-SELECT® membranes based on EPTFE reinforced electrolytes, Aquivion® ionomers, or copolymers of tetrafluoroethylene (TFE) and sulfonyl fluorinated vinyl ether. Electrolytes that allow proton exchange are suitable for gases such as H2 and H2S.

[0092] In all embodiments of the invention described herein, the electrodes can be any electrodes that react with the gas that the sensor is designed to detect. Such electrodes are well known to those skilled in the art. Both electrodes can be made of the same material. The electrodes can be constructed of the same material or different materials. The electrodes can be configured to react with the gas that is desired to be detected, e.g., a combustible gas. For example, H2, CO, H2S, CO2 can be detected with the appropriate electrode and electrolyte combination.

[0093] A sensor unit may consist of multiple MEAs stacked or arranged according to the individual sensor. They may all be of the same type and detect the same gas, or one MEA may be composed of multiple different MEAs and respond to different gases. A single sensor device may have multiple different electrodes and / or MEA structures of different types designed to react with different gases, producing detectable changes in the presence of different types of gases in the electrode layer or layers of the sensor device. For example, a single sensor device may be sensitive to different gases by placing three different sensing electrodes opposite a reference electrode, and the sensing electrodes or electrolytes adjacent to the electrodes may be composed of different materials, different catalysts designed to react with different gases, or may pass different ions.

[0094] The electrodes may also include a catalyst. A catalyst layer on the electrode or embedded in the composition of the electrode promotes a reaction with the gas to be detected. The catalyst will be a catalytic material suitable for the reaction of interest, as generally understood by researchers familiar with the technology of MEA fabrication. For example, the catalyst layer may consist of platinum nanoparticles deposited on carbon and bound to a proton conducting polymer (e.g. Nafion®), as described in "PEM Fuel Cell Electrocatalysts and Catalyst Layers Fundamentals and Applications", Jiujun Zhang (Ed.), 1st Edition., 2008, XXII, 1 137 p. 489 illus., Springer- Verlag London, ISBN: 978-1- 84800-935. Suitable catalysts are known to those skilled in the art. For example, palladium, iron, vanadium, aluminum, nickel-based catalysts, etc. are suitable. For example, an iron catalyst supported on a carbon electrode is suitable for CO2 detection.

[0095] Because the sensors are potentially very sensitive, in some cases detecting the change in potential difference or current generated by the MEA requires the setting of a threshold as part of the detection means. The threshold may be set such that changes in gas concentration below that threshold are not indicated to the user or system. This is to prevent the indication of small differences in gas composition, such as differences that may occur naturally in normal ambient air (i.e., small fluctuations in oxygen, carbon monoxide, or carbon dioxide levels in the air).

[0096] Separate electronics may be used to periodically short-circuit the sensor so that the sensor can be recalibrated to zero by resetting both sides of the MEA to the same conditions during use. This improves the sensing capability to take into account typical small changes in the atmosphere and gas composition. Shorting the sensor essentially returns the electrode surface to the same concentration. Any potential difference measured after the short-circuit is removed is due to the new gas present at the sensor surface. The short-circuit may be performed periodically at a set time so that the sensor device can be periodically reset to account for atmospheric changes. The short-circuit may also be triggered automatically or manually after a detection event to allow for continued use of the sensor.

[0097] Multiple sensor devices disclosed herein may be linked together as part of a broader sensor system made up of multiple sensors.

[0098] As used herein, "atmosphere surrounding a sensor" or "atmosphere" refers to the standard or normal atmosphere surrounding a sensor. This may vary depending on the environment. For example, it may be the ambient atmosphere, i.e., the standard air composition in which the sensor is used, or it may be the complete absence of gas surrounding the sensor (i.e., a vacuum (e.g., glove box) environment). In such a scenario, the change in gas composition may simply be the presence of gas, which may result in a reaction and subsequent change in potential across a single electrode, causing the gas to be detected or sensed.

[0099] The environment in which the sensor is installed, such as temperature, humidity, ambient atmosphere, or standard atmosphere composition around the sensor configuration, may affect performance. However, the sensor can detect any change in gas composition. Therefore, advantageously, the sensors, methods, and applications disclosed herein can be used in a variety of different environments. They can be used in any environment because the changes are always compared to a baseline or reference. This is advantageous over prior art sensors that only operate under certain environmental conditions, such as ideal operating temperature and humidity levels. The sensors disclosed herein can withstand harsher environmental conditions than many prior art sensors due to the use of robust PCB materials and the use of a sealed MEA structure that is highly resistant to high temperatures and pressures. The sensors disclosed herein can also withstand relatively high mechanical stresses.

[0100] The substrate of the sensor device, and optionally other components of the sensor device, can consist of a printed circuit board (PCB). The individual layers can consist of a PCB that is glued to a solid structure using an epoxy-containing glass fiber composite. The PCB can be made from pre-impregnated composite fibers or a pre-impregnated composite fiber mask can be applied to the PCB to contain the necessary amount of material to glue the individual layers and to glue the MEA to the PCB. The layer structure can be formed by laser bonding the MEA to the PCB. The PCB boards can also be laminated together. Gaps between the electrodes and sealing of the gaps with epoxy resin prevent intermixing between the layers.

[0101] PCB technology has the advantage that elements can be manufactured in large quantities and at low cost. For example, several sensors can be manufactured at the same time by stacking thin laminate substrates and wiring them at the same time. The individually wired substrates are then laminated and bonded together. The PCB structure also has high mechanical strength, and the stacking results in a robust structure with good contact between the individual layers. Thus, a monolithic, light and completely sealed structure is obtained. If necessary, the PCB can also be used as an end plate. Both fuel cells and sensor devices for fuel cells can be built from PCBs. A method for manufacturing fuel cells from PCBs and its advantages are disclosed in WO 2013 / 164639, which is incorporated herein by reference.

[0102] To make the sensor disclosed herein, the substrate and MEA are laminated together. This can be done, for example, at 180°C for 1 hour, which allows enough time for heat to pass through all layers of the substrate. At this temperature, the epoxy or phenolic resin cures, bonding adjacent layers together, ensuring good electrical contact and forming an airtight seal.

[0103] In all of the embodiments described herein, a thin layer of copper can be applied to the outside of each substrate layer and etched away (e.g., using a mask) to retain the desired conductive pattern. The copper layer can be applied by electroplating. The copper can be etched away to form a non-copper rectangle in the center of the sensor device (e.g., rectangles 108, 118, 308 in Figures 1, 2, 3 above). Copper is etched away from the areas above and below the electrodes. This ensures that the active area of ​​the MEA is copper-free, preventing copper reacting with the electrodes in the presence of moisture and causing unnecessary electrode corrosion. The etched copper area corresponds to a housing into which the sensor will reside. This may be, for example, for connecting the sensor to a voltage detection means or to hold the sensor in place in a wider system.

[0104] The copper surface of the sensor may be coated with a corrosion resistant coating. This coating is used to passivate the copper surface of the PCB and prevent corrosion of the copper layer. The fuel cell environment is very acidic and oxidizing, which makes copper susceptible to corrosion. 0 From Cu 2+ "The coating must be stable and not electrochemically or chemically degraded in the fuel cell environment. At the same time, it must be a durable material that will not peel off from the copper surface."

[0105] The sensor coating may also consist of a carbon ink coating. Carbon inks for coating copper on PCBs are known and commercially available. Carbon inks are materials consisting of a carbon-based material and an organic binder. The carbon inks disclosed herein are preferably conductive carbon inks. The carbon inks disclosed herein are in line with common understanding in the art. In general, carbon inks are inks that can be easily screen printed and comprise carbon as a pigment along with a binder. Carbon inks may have a dynamic viscosity of about 2.9 poise to about 7 poise calculated at 20° C. and 1 atm. Thus, carbon inks may be viscous materials. The dynamic viscosity may be measured by a viscometer calibrated to the viscosity of distilled water (0.01 poise) at 20° C. and 1 atm. When the carbon-based material is provided as a component in the carbon ink, the organic binder consists of a resin that can also be used to form the carbon ink. Typical carbon inks include PCB1 Sun Chemical Ink 2sp, PCB3 Sun Chemical Ink 2sp, PCB4 Sun Chemical Ink 2sp, etc. The carbon ink prevents the copper in the sensor device from corroding, which can contaminate the catalyst and reduce the measurement accuracy.

[0106] The sensor devices disclosed herein are particularly suitable for use in fuel cells. A fuel cell (such as a solid polymer electrolyte fuel cell) is an electrochemical device that produces electrical energy and heat from a reactant or oxidant (such as pure oxygen or air) and a fuel (such as hydrogen or a hydrogen-containing mixture, a hydrocarbon or a hydrocarbon derivative). Fuel cell technology is used in stationary and mobile applications such as power plants, automobiles, laptop computers, etc. Fuel cells require sensors to monitor for internal gas leakage. Thus, the sensor devices disclosed herein can be placed within the fuel cell housing and used to detect the presence of gas.

[0107] The fuel cell assembly housing may be mounted with an electrochemical sensor device proximate a leak detection area of ​​the fuel cell such that leakage of fuel from the fuel cell may be detected by the electrochemical sensor. The sensor may be connected to stop normal operation of the fuel cell upon detection of a gas leak. The sensor may be directionally mounted on the fuel cell, specifically with the detection side facing in the direction of a likely gas leak. The fuel cell, fuel cell board, and components may be constructed of any suitable and desired material, such as PCB, graphite, metal, and the like.

[0108] As explained in the Background of the Invention, existing sensors require a constant current for operation, and therefore act as a large parasitic on the power generated by the fuel cell. In contrast, the sensor device disclosed in this specification does not require a constant current. Therefore, the sensor device is not parasitic on the power of the fuel cell, and can reduce parasitic power, making the fuel cell system more efficient while detecting gas.

[0109] Thus, the sensor device disclosed herein is particularly useful for fuel cells that generate only small amounts of power (e.g., 20 W fuel cells) where prior art sensors have a large parasitic drain (relative to power) that is particularly detrimental to power output. A sensor that requires 1 W or 2 W of power to operate is a large drain on a low wattage fuel cell, as it requires a constant current supply. In low wattage fuel cell operation, particularly below 200 W (especially around 20 W), the loss of 2 W of power can amount to 10% of the power generated by the entire system.

[0110] Larger fuel cells, ie, fuel cells that hold larger gas (fuel) volumes, may require more sensors to detect gas leaks in various parts of the fuel cell.

[0111] As mentioned above, the sensor device can be used, for example, in an inert gas type environment (such as a "glove box") to detect the presence of unwanted entities (eg, oxygen in leaking air).

[0112] The sensor device disclosed herein tolerates a pressure difference across the two surfaces. Thus, the sensor device disclosed herein can be used in pressurized environments. The sensor device is suitable for use in high pressure environments, unlike many prior art sensors. The structure of the device can be adjusted to account for the pressure difference across the device. For example, the thickness of the membrane can be increased to make the membrane thicker for higher pressure differences. Such sensors can also be designed to be used as in-line sensors, for example, to detect hydrogen in gas pipes or to detect certain contaminants in pressurized pipelines. One or both sides of the sensor can be pressurized. The sensor can be used in small gas lines as well as large gas lines.

[0113] The sensor devices disclosed herein can be used as part of a fuel cell or as an in-line gas sensor, as well as in other scenarios where detection of the presence of gas is required, for example in manufacturing plants where gas leaks are a hazard (such as fuel coal manufacturing plants) or as part of a gas detection system in the home (such as a carbon monoxide sensor).

[0114] [Example] The hydrogen sensor devices disclosed herein (such as the exemplary embodiments shown in Figures 3, 4 and 5) have been demonstrated to function as sensors for hydrogen gas. One side of the sensor was exposed to hydrogen gas and the other side was used as a reference electrode exposed to ambient air.

[0115] The sensor was mounted so that the reference electrode was exposed to air but not to hydrogen. Hydrogen was briefly flowed over the working electrode in such a way that it would indicate a significant hydrogen leak (slightly restricted flow and slightly pressurized). In this benchtop test, a potentiostat was used to record the voltage every 100 milliseconds.

[0116] Figure 6 shows a graph of the experimental results. The voltage trace of the sensor over a period of 1 minute was recorded. The measurement side was exposed to hydrogen for 1 second every 16 seconds. Each circle on the graph represents the voltage measurement at a certain point in time. As soon as hydrogen is introduced, the voltage spikes to approximately 900mV. After the gas is turned off, the sensor voltage returns to below 0mV within 2 seconds.

[0117] 7 is a graph showing the results of further experiments using the hydrogen sensor disclosed herein. The graph shows voltage versus time for a sensor exposed to hydrogen in one sensing event. There are three segments in the graph showing three different environmental conditions: "A" where the sensor is not exposed to hydrogen, "B" where the sensor is exposed to hydrogen, and "C" where the sensor is not exposed to hydrogen again but after being exposed to hydrogen in segment B.

[0118] Each circle on the graph represents a voltage measurement at a certain point in time. The sensor voltage trace was recorded over a 3 minute period. The measurement side was exposed to hydrogen for just under 2 minutes after the 1 minute mark. The voltage measurement before hydrogen introduction is approximately 0mV. After hydrogen introduction, the voltage immediately rises sharply to approximately 950mV. After the gas is turned off, the sensor voltage returns to approximately 0mV just before the 3 minute mark.

[0119] The results above show an immediate response to hydrogen exposure, instantly returning to the same sensing level as before hydrogen exposure. The graph shows that the sensing is immediate and fully reversible, with a clear voltage response and stable voltage measurements before and after hydrogen exposure.

[0120] 8A and 8B are graphs showing the results of further experiments using the hydrogen sensor described herein. One side of the sensor was exposed to hydrogen and the other side was placed in air. Two graphs of voltage versus time are shown, demonstrating the sensitivity of the sensor. Each circle on the graph represents a voltage measurement at a point in time. The sensitivity of the sensor is shown at 10 ppm, 1 vol%, and 100 vol% hydrogen, showing the varying sensitivity of the reference and sensing electrode sides of the sensor. This shows that both sides of the sensor are operational to sense a gas, such as hydrogen here.

[0121] FIG. 9 is a graph showing the results of further experiments using the hydrogen sensor described herein. One side of the sensor was exposed to hydrogen and the other side was exposed to ambient air. The graph shows voltage versus time, showing the results of repeated consecutive sensing events. Each circle on the graph represents a voltage measurement at a point in time.

[0122] This shows that the same sensor can sense a gas, e.g., hydrogen, many times in succession with clear and unambiguous results: the sensitivity of the sensor does not decrease across all three sensing events, and the sensor signal is thus highly reproducible and fully reversible.

[0123] FIG. 10A is a graph showing the results of further experiments using the hydrogen sensor described herein. Each circle on the graph represents a voltage measurement at a point in time. The graph shows voltage versus time, but for three different environmental conditions. There are three segments on the graph that represent the three different environmental conditions: "A" shows air on either side of the sensor, "B" shows air on the reference side and hydrogen on the sensing / measurement side, and "C" shows hydrogen on either side of the sensor.

[0124] Figure 10B shows voltage measurements for three different segments (A, B, C) of the graph in Figure 10A. Segment B shows the highest reading (0.6V). Segment C shows a reading of about 0.75V, well above the near-zero reading of segment A.

[0125] This shows that the sensor can sense hydrogen gas, i.e. there is an output signal, even when both sides of the sensor are exposed to a gas, for example hydrogen in this case. This is due to the construction of the sensor, one side or substrate of the sensor has more or larger openings than the other side or substrate of the sensor, so that even when both sides are exposed to the same volume of gas at the same time, there is an increased gas volume on one side of the sensor. This experiment was performed with a sensor as seen in Figures 1 and 2. Due to its design, the sensor is sensitive even when exposed to gas on both sides.

[0126] 11 is a graph showing the results of further experiments using the hydrogen sensor disclosed herein. The graph shows voltage versus time for a sensor that was not exposed to hydrogen (above ambient air levels) for one hour. Each circle on the graph represents a voltage measurement at a point in time.

[0127] This indicates that the sensor exhibits minimal signal drift, with the drift over time being orders of magnitude smaller than the typical voltage response to hydrogen.

[0128] 12 is a graph showing the results of a further experiment using an oxygen sensor as disclosed herein. The temperature was the ambient temperature during the experiment and is plotted along with the response to show the need to account for sensor drift at different temperatures or correct the sensor response.

[0129] Here, two oxygen sensors ("Cell A" and "Cell B" on the graph) were tested alongside a commercial calibrated oxygen sensor from Fluke ("Fluke" on the graph). Various concentrations of oxygen were tested and placed in a nitrogen environment. The reference side of each sensor was exposed to air. The sensors showed strong correlation and high sensitivity at oxygen concentrations below 70%. However, due to experimental error settings, they did not perfectly correlate with the commercial sensor mentioned above. The voltage of both sensors increased with increasing oxygen concentration (below 70%) indicating a strong correlation / response of the sensors in different environments.

[0130] The sensor used here is the same as that used in the hydrogen detection experiment shown above.

[0131] The above results demonstrate that the sensor technology disclosed herein can be used to detect gases other than hydrogen (here, oxygen). These sensors can be used in a number of different applications.

[0132] The above results demonstrate that the sensor disclosed herein operates with high sensitivity and accuracy.

[0133] It will be apparent to those skilled in the art that many modifications and variations can be made to the exemplary embodiments described above without departing from the scope of the present disclosure.

Claims

1. a sensor comprising a membrane electrode assembly (MEA); an electrical control unit that determines the electrical characteristics of the MEA; Equipped with The MEA comprises a plurality of electrodes and a membrane electrolyte layer disposed between the plurality of electrodes; the MEA is disposed between a first substrate and a second substrate; the first substrate has at least one opening for providing a gas passage therethrough to one of the plurality of electrodes; the electrical characteristic is indicative of a gas composition of the gas at one of the plurality of electrodes; the electrical control unit generates an output based on or in response to the change in the electrical characteristic; The MEA comprises at least two electrodes; There is a gas flow path to each of the two electrodes; 1. A fuel cell comprising: a first gas passage having a smaller gas flow passage than the second gas passage; a second gas passage having a more restricted gas flow passage than the second gas passage;

2. the sensor is mounted within the fuel cell in an area of ​​the fuel cell from which leakage gas would escape so as to detect leakage of fuel from the fuel cell; 10. The fuel cell of claim 1, wherein optionally the fuel cell is turned off when a change in gas composition is detected by the sensor.

3. 3. The fuel cell according to claim 1, wherein the second substrate has at least one opening for providing a gas flow path therethrough to one of the plurality of electrodes.

4. 4. A fuel cell according to claim 1, further comprising means for indicating that an output has been generated based on or in response to said electrical characteristic.

5. 5. A fuel cell according to any one of claims 1 to 4, characterized in that the first substrate and the second substrate are printed circuit boards (PCBs), preferably the sensor being formed by compression lamination of the PCBs.

6. 6. The fuel cell according to claim 1, wherein at least one of the first substrate and the second substrate has a plurality of openings for providing a plurality of gas flow paths through the substrate.

7. 7. The fuel cell according to claim 1, wherein one of the first substrate and the second substrate has more openings than the other substrate, and more gas flow paths are provided to one of the plurality of electrodes through the substrate having more openings than the other substrate; or, wherein the dimensions of the openings of one of the first substrate and the second substrate are larger than the dimensions of the openings of the other substrate, and a wider gas flow path is provided to one of the plurality of electrodes through the substrate having the larger openings than the other substrate.

8. 8. A fuel cell according to claim 1, wherein the electrical property is a potential difference, an open circuit voltage between the anode and cathode sides of the MEA, a current, a capacitance, or a conductivity.

9. i) The electrode comprises a catalyst, or ii). The first substrate and the second substrate are provided with a conductive metal layer, preferably the conductive metal layer is copper; or iii) the fuel cell or the sensor includes electronics that short-circuit the sensor to recalibrate it; or iv). The electrode is a carbon paper electrode containing a carbon supported platinum catalyst; or v). The membrane electrolyte layer is a proton exchange membrane, preferably made of a sulfonated tetrafluoroethylene electrolyte, or vi). At least one of the electrodes is an electrode that reacts with a fuel of a fuel source consumed by the fuel cell, or vii) A fuel cell according to any one of claims 1 to 8, characterized in that it comprises or comprises any combination of the features i) to vi).

10. A sensor for detecting a change in gas composition, comprising: a membrane electrode assembly (MEA); A first substrate; A second substrate; Equipped with The MEA comprises a plurality of electrodes and a membrane electrolyte layer disposed between the plurality of electrodes; the MEA is disposed between the first substrate and the second substrate; At least one of the first substrate and the second substrate has at least one opening for providing a gas passage therethrough to one of the plurality of electrodes; determining an electrical characteristic indicative of the gas composition when there is a change in the gas composition at one of the plurality of electrodes to generate an output representative of the change in gas composition; The MEA comprises at least two electrodes; There is a gas flow path to each of the two electrodes; A sensor according to claim 1, wherein one of said gas flow paths is smaller than the other of said gas flow paths or has a more restricted gas flow than the other of said gas flow paths.

11. 11. The sensor of claim 10, wherein one of the first and second substrates has more openings than the other substrate, providing more gas flow paths through the substrate having more openings to one of the plurality of electrodes than the other substrate, or wherein the dimensions of the openings of one of the first and second substrates are larger than the dimensions of the openings of the other substrate, providing a wider gas flow path through the substrate having the larger openings to one of the plurality of electrodes than the other substrate.

12. A fuel cell sensor or a gas line sensor, Optionally, one of the electrodes reacts with a fuel from a fuel source that is consumed by the fuel cell; Further alternatively, the use of a sensor, the sensor device being arranged within the housing of the fuel cell.

13. 13. Use of a sensor according to claim 12, characterized in that if a gas leak is detected, the output shuts down normal operation of the fuel cell.

14. A sensor system comprising a sensor according to claim 10 or 11 as a gas sensor and an electrical control unit for determining an electrical characteristic of the MEA.

15. 1. A method for detecting a gas or a change in gas composition, comprising: determining a change in an electrical property of the MEA; a change in the electrical properties of the MEA indicates the presence or absence of gas; or a change in an electrical property of the MEA indicates a change in gas composition in the MEA; the MEA is part of a sensor; The MEA comprises at least two electrodes; There is a gas flow path to each of the two electrodes; 4. The method of claim 3, wherein one of the gas flow passages is smaller or has a more restricted gas flow than the other gas flow passage.

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