An electrochemical gas sensor working electrode structure and an electrochemical gas sensor

Abstract

The application discloses an electrochemical gas sensor working electrode structure and an electrochemical gas sensor. The electrochemical gas sensor working electrode structure comprises a waterproof and breathable film, a polymer electrolyte carrier, a catalytic layer and a conductive piece. The polymer electrolyte carrier has a first surface facing a gas inlet side and a second surface facing an electrolyte side. The catalytic layer is loaded on the first surface and electrically connected with the conductive piece. The waterproof and breathable film is located on the gas inlet side of the catalytic layer, and is used for allowing a to-be-detected gas to pass through and preventing liquid electrolyte from passing through. The waterproof and breathable film and the catalytic layer are independent of each other, and the catalytic layer is not loaded on the waterproof and breathable film. The surface energy of the first surface is higher than that of a surface of the waterproof and breathable film facing the catalytic layer. The polymer electrolyte carrier is used for bidirectional migration of ions between the first surface and the second surface. The electrochemical gas sensor working electrode structure can effectively improve the stability and linearity of a sensor output signal.

Description

Technical Field

[0001] This application relates to the field of electrochemical gas detection technology, and in particular to a working electrode structure for an electrochemical gas sensor and an electrochemical gas sensor. Background Technology

[0002] Electrochemical gas sensors utilize the redox reaction of the analyte gas at the working electrode to generate an electrical signal, and achieve gas detection based on the correlation between the electrical signal and the gas concentration. The working electrode typically needs to accommodate the introduction of the analyte gas, electrolyte barrier, catalytic reaction, and charge output.

[0003] However, in existing electrochemical gas sensors, the working electrode often loads the catalytic material onto a waterproof membrane, which is then thermally fused to the sensor cover. The in-plane stretching generated during the thermal fusion process can easily alter the surface morphology of the membrane, leading to uneven thickness, defects, or cracks in the catalytic material. Furthermore, waterproof membranes typically have low surface energy, resulting in insufficient adhesion stability of the catalytic material over long-term use. Their hydrophobic and liquid-blocking properties also limit the transport of water molecules and reactant ions. Summary of the Invention

[0004] This application proposes a working electrode structure for an electrochemical gas sensor and an electrochemical gas sensor in order to reduce the risk of catalyst layer defects, cracking and detachment, and improve the stability of the output signal of the electrochemical gas sensor.

[0005] In a first aspect, embodiments of this application provide a working electrode structure for an electrochemical gas sensor, comprising a waterproof and breathable membrane, a polymer electrolyte carrier, a catalyst layer, and a conductive element; the polymer electrolyte carrier has a first surface facing the gas inlet side and a second surface facing the electrolyte side, the catalyst layer is loaded on the first surface and electrically connected to the conductive element; the waterproof and breathable membrane is located on the gas inlet side of the catalyst layer, allowing the gas to be measured to pass through while blocking the liquid electrolyte; the waterproof and breathable membrane is independent of the catalyst layer, and the catalyst layer is not loaded on the waterproof and breathable membrane; the surface energy of the first surface is higher than the surface energy of the surface of the waterproof and breathable membrane facing the catalyst layer; the polymer electrolyte carrier is used to allow water molecules and ions participating in and generated by the electrode reaction to migrate bidirectionally between the first surface and the second surface.

[0006] As can be seen, in this embodiment, the waterproof and breathable membrane serves as the air intake barrier, while the polymer electrolyte carrier serves as the carrier of the catalyst layer and the transporter of water molecules and ions. Since the catalyst layer is no longer supported by the waterproof and breathable membrane, the deformation of the waterproof and breathable membrane during sealing assembly is not easily transmitted directly to the catalyst layer; since the catalyst layer is supported on the first surface with higher surface energy, its adhesion is more stable; and since the polymer electrolyte carrier allows bidirectional migration of reaction-related substances, it can improve the mass transfer conditions at the reaction interface while maintaining the liquid barrier capability.

[0007] In one possible example, the waterproof and breathable membrane, the catalyst layer, and the polymer electrolyte carrier are arranged sequentially along the transport direction of the gas to be tested; the permeable areas of the waterproof and breathable membrane, the catalyst layer, and the areas of the polymer electrolyte carrier corresponding to the catalyst layer at least partially overlap in their projections perpendicular to the plane, so that the gas to be tested reaches the catalyst layer through the waterproof and breathable membrane, and the water molecules and ions reach the catalyst layer through the polymer electrolyte carrier.

[0008] As can be seen, in this example, the functional regions overlap through projection to form a convergence zone between the gas phase transport path and the liquid phase mass transport path. This convergence zone is located at the catalyst layer, which facilitates the arrival of the target gas, water molecules, and reactant ions in the same reaction region and reduces the ineffective transport area caused by interlayer misalignment.

[0009] In one possible example, the waterproof and breathable membrane is a fluoropolymer film containing fluorine atom groups, the fluoropolymer film forming a hydrophobic surface through the fluorine atom groups; the adhesion of the first surface to the catalyst layer is greater than the adhesion of the hydrophobic surface to the catalyst layer.

[0010] As can be seen, in this example, the fluoropolymer film utilizes its hydrophobic surface to maintain waterproof and breathable capabilities, while the first surface of the polymer electrolyte carrier utilizes its high adhesion to maintain the catalytic layer. These two types of surfaces are matched with different functions, reducing the performance constraints caused by a single membrane material simultaneously undertaking waterproofing, sealing, and catalytic layer support.

[0011] In one possible example, the polymer electrolyte carrier is a proton-conducting polymer electrolyte carrier or a hydroxide ion-conducting polymer electrolyte carrier; the proton-conducting polymer electrolyte carrier is coupled with an acidic electrolyte to allow bidirectional migration of protons and water molecules, and the hydroxide ion-conducting polymer electrolyte carrier is coupled with an alkaline electrolyte to allow bidirectional migration of hydroxide ions and water molecules.

[0012] As can be seen, in this example, the polymer electrolyte carrier can select the ion conduction type according to the acidity or alkalinity of the electrolyte and the target electrode reaction, so that the types of ions transported by the carrier match the ions required or generated by the electrode reaction, which is beneficial to maintaining continuous ion transport between the catalyst layer and the electrolyte.

[0013] In one possible example, the catalyst layer covers the central region of the first surface, and the first surface forms an exposed support region around the catalyst layer; one end of the conductive element is connected to the catalyst layer, and the other end extends along the first surface to the outside of the polymer electrolyte carrier.

[0014] As can be seen, in this example, the central region is used to concentrate the formation of the catalytic reaction zone, while the exposed outer support region provides space for the lead-out of the conductive components and interlayer assembly. The conductive components extend outward along the first surface, which can establish an electron output path without occupying the main gas inlet area and reduce the impact of the lead-out position of the conductive components on the integrity of the catalytic zone.

[0015] In one possible example, the working electrode structure of the electrochemical gas sensor further includes a sensor cover; the sensor cover is provided with a vent hole, the waterproof and breathable membrane covers the vent hole from the inside of the sensor cover and is sealed to the sensor cover through the peripheral area, and the catalyst layer and the polymer electrolyte carrier are disposed on the inside of the waterproof and breathable membrane.

[0016] As can be seen, in this example, the vent and the waterproof and breathable membrane together define the entry point of the gas to be measured, and the outer area of ​​the waterproof and breathable membrane forms a sealed boundary with the sensor cover. The catalyst layer and polymer electrolyte carrier are located inside the sealed boundary, which can obtain a controlled air intake path while preventing the leakage of liquid electrolyte.

[0017] In one possible example, the sensor cover is a plastic part with a melting point lower than that of the waterproof and breathable membrane; the peripheral area of ​​the waterproof and breathable membrane is thermally fused to the sensor cover to form a continuous sealed area surrounding the vent.

[0018] As can be seen, in this example, during hot-melt assembly, the connection points of the sensor cover can be melted or softened first, while the waterproof and breathable membrane maintains its basic membrane shape. The continuous sealing area surrounding the vent hole can seal off the bypass leakage channel from the outside of the vent hole to the inside of the sensor, and ensure that the hot-melt connection acts on the waterproof and breathable membrane rather than directly on the supporting substrate of the catalyst layer.

[0019] In one possible example, the area in the waterproof and breathable membrane corresponding to the vent hole constitutes a breathable area, and the continuous sealing area is located on the periphery of the breathable area; the projection of the catalyst layer on the waterproof and breathable membrane is located within the inner boundary of the continuous sealing area.

[0020] As can be seen, in this example, the projections of the continuous sealing region and the catalyst layer avoid each other in planar position, and the area where thermal melting is concentrated is located outside the catalytic reaction region. This can reduce the impact of temperature changes and in-plane deformation of the sealing region on the catalyst layer, while maintaining an effective correspondence between the permeable region and the catalyst layer.

[0021] In one possible example, the vent, the breathable area, the catalyst layer, and the area of ​​the polymer electrolyte carrier corresponding to the catalyst layer are arranged opposite each other in a direction perpendicular to the waterproof and breathable membrane; the waterproof and breathable membrane and the polymer electrolyte carrier are tightly fitted in the direction, the catalyst layer is located between the two, and the second surface faces the electrolyte inside the sensor.

[0022] As can be seen, in this example, the functional regions establish stable relative positions along the stacking direction, which shortens the transport path of the gas to be tested from the vent to the catalyst layer and ensures that the second surface of the polymer electrolyte carrier faces the electrolyte. This close fit also suppresses disordered interlayer displacement, maintaining the corresponding states of the gas-phase transport region, the catalytic reaction region, and the ion transport region.

[0023] Secondly, embodiments of this application provide an electrochemical gas sensor, including a sensor housing, an electrolyte housed within the sensor housing, a counter electrode in contact with the electrolyte, and an electrochemical gas sensor working electrode structure as described in any example of the first aspect; the electrochemical gas sensor working electrode structure is disposed at the gas inlet position of the sensor housing, the waterproof and breathable membrane is in communication with the outside, and the second surface is in contact with the electrolyte; the catalytic layer forms an ion transport pathway with the counter electrode through the polymer electrolyte carrier and the electrolyte, and the conductive element is connected to the signal output terminal of the electrochemical gas sensor.

[0024] As can be seen, in this embodiment, the gas to be tested can reach the catalyst layer through the gas inlet and the waterproof and breathable membrane, while water molecules and reaction ions in the electrolyte can reach the catalyst layer through the polymer electrolyte carrier, and the electrons generated by the reaction can be output through the conductive components. Therefore, the working electrode structure and the counter electrode form a mutually supportive reaction circuit through the electrolyte, which is beneficial for improving the stability of the sensor's detection signal and the consistency of the concentration response.

[0025] As can be seen, compared to existing working electrode structures that directly load the catalyst layer onto a waterproof and breathable membrane and have the membrane participate in heat-sealing, the electrochemical gas sensor working electrode structure provided in this application establishes mutually cooperating gas inlet and liquid blocking paths, charge output paths, and water molecule and ion transport paths through the layering and surface energy relationship between the waterproof and breathable membrane, the catalyst layer, and the polymer electrolyte carrier. Since the waterproof and breathable membrane and the catalyst layer are independent, the deformation of the waterproof and breathable membrane during sealing does not directly affect the catalyst layer; since the catalyst layer is loaded onto a polymer electrolyte carrier with high surface energy, it maintains high adhesion stability; and since the polymer electrolyte carrier allows bidirectional migration of water molecules and ions participating in and generated by the electrode reaction, reactants and products can be transported between the catalyst layer and the electrolyte, thereby reducing the risk of catalyst layer defects, cracking, and detachment, improving the mass transfer efficiency of the gas-liquid-solid three-phase reaction interface, and contributing to improved stability and linearity of the sensor output signal. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments are briefly described below. It should be understood that the following drawings are used to illustrate structural relationships and working mechanisms, and are not intended to limit the actual proportions, shapes, or dimensions of each component.

[0027] Figure 1 This is an exploded structural diagram of the working electrode structure of the electrochemical gas sensor provided in the embodiments of this application; Figure 2 A cross-sectional schematic diagram showing the waterproof and breathable membrane, catalyst layer, and polymer electrolyte carrier sequentially arranged along the direction of gas transmission for the present application embodiment; Figure 3 A schematic diagram showing the surface energy and adhesion relationship between the hydrophobic surface of the waterproof and breathable membrane provided in this embodiment and the first surface of the polymer electrolyte carrier; Figure 4 A schematic diagram of the mass transfer structure of a proton-conducting polymer electrolyte carrier and a hydroxide ion-conducting polymer electrolyte carrier provided in the embodiments of this application. Figure 5 A schematic diagram of the planar structure of the catalyst layer, exposed bearing area, and conductive component provided in the embodiments of this application; Figure 6 This is a schematic diagram of the assembly of the sensor cover and the working electrode structure provided in an embodiment of this application; Figure 7 A schematic diagram of the structure in which the waterproof and breathable membrane and the sensor cover are thermally fused together to form a continuous sealed area in an embodiment of this application; Figure 8 A planar schematic diagram showing the projected relationship between the permeable area, the continuous sealing area, and the catalyst layer provided in the embodiments of this application; Figure 9 A schematic cross-sectional view of the ventilation holes, permeable areas, catalyst layer and polymer electrolyte carrier arranged opposite each other along the stacking direction in an embodiment of this application; Figure 10 A schematic diagram of the transport paths of the gas to be measured, water molecules, reacting ions, generated ions, and electrons at the working electrode provided in this embodiment of the application; Figure 11 This is a schematic diagram illustrating the stress and catalyst layer damage mechanism of a conventional membrane electrode thermal fusion connection in comparison with the embodiments of this application. Figure 12 This is a schematic diagram of the structure of the electrochemical gas sensor provided in an embodiment of this application.

[0028] Explanation of reference numerals in the attached figures: 100, Working electrode structure of the electrochemical gas sensor; 110, Waterproof and breathable membrane; 111, Breathable area; 112, Peripheral area; 113, Hydrophobic surface; 120, Polymer electrolyte carrier; 121, First surface; 122, Second surface; 123, First area; 124, Exposed bearing area; 130, Catalyst layer; 140, Conductive component; 150, Sensor cover; 151, Vent hole; 152, Continuous sealed area; 170, Detector gas transport path; 171, Bidirectional migration path of water molecules and ions; 172 173. Electron output path; 180. Generated ion migration path; 200. Gas-liquid-solid three-phase reaction interface; 211. Electrochemical gas sensor; 222. Sensor housing; 233. Gas inlet position; 244. Electrolyte; 255. Counter electrode; 36. Signal output terminal; 376. Ion transport pathway; 377. Conventional membrane electrode control structure; 380. Control cover; 391. Control waterproof and breathable membrane; 301. Control catalyst layer; 312. In-plane stretching direction; 313. Control hot-melt area; 314. Thinning area; 315. Crack area. Detailed Implementation

[0029] The embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some, not all, of the embodiments of this application. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the protection scope of this application.

[0030] In this application, "inlet side" and "electrolyte side" are used to characterize the relationship between each layer in the working electrode structure 100 of the electrochemical gas sensor and the source of the analyte gas and the electrolyte 220, and do not imply that the structure must be oriented upwards or downwards in space. "Mutual independence" means that the catalyst layer 130 does not use the waterproof and breathable membrane 110 as a load substrate, but does not exclude the possibility that the waterproof and breathable membrane 110 is in contact with the catalyst layer 130 in the assembled state. "Bidirectional migration" means that water molecules and corresponding ions can be transported in either direction between the first surface 121 and the second surface 122 according to the concentration difference, electrochemical potential difference, and electrode reaction state, without requiring that the transport in both directions occur simultaneously or that the flux is equal. "Projection at least partially overlaps" includes partial overlap and complete overlap. "Close fit" means that adjacent layers maintain a controlled spacing and stable relative position in the assembled state, which can be achieved through direct contact, indirect contact through the catalyst layer 130, or assembly pressing.

[0031] As the basis for the various working electrode embodiments of this application, see [link to relevant documentation]. Figure 1 , Figure 1 This is an exploded structural diagram of the working electrode structure 100 of the electrochemical gas sensor provided in the embodiments of this application, including a waterproof and breathable membrane 110, a catalyst layer 130 and a polymer electrolyte carrier 120 arranged along the gas inlet side to the electrolyte side, and a conductive element 140 led out from the catalyst layer 130. The polymer electrolyte carrier 120 has a first surface 121 facing the air inlet side and a second surface 122 facing the electrolyte side. The catalyst layer 130 is loaded on the first surface 121 and electrically connected to the conductive element 140. The waterproof and breathable membrane 110 is located on the air inlet side of the catalyst layer 130, allowing the gas to be tested to pass through and blocking the liquid electrolyte. The waterproof and breathable membrane 110 is independent of the catalyst layer 130, and the catalyst layer 130 is not loaded on the waterproof and breathable membrane 110. The surface energy of the first surface 121 is higher than the surface energy of the hydrophobic surface 113 of the waterproof and breathable membrane 110 facing the catalyst layer 130. The polymer electrolyte carrier 120 is used to allow water molecules and ions participating in and generated by the electrode reaction to migrate bidirectionally between the first surface 121 and the second surface 122.

[0032] The waterproof and breathable membrane 110 is a membrane component that allows the target gas to pass through from the inlet side while suppressing the leakage of liquid electrolyte inside the sensor. The waterproof and breathable membrane 110 and the catalyst layer 130 are independent of each other; specifically, the catalyst layer 130 is not formed on the waterproof and breathable membrane 110 through coating, deposition, or other loading methods. After assembly, the two can be adjacent or in contact, but the deformation of the waterproof and breathable membrane 110 will not directly pull on the catalyst layer 130 due to its fixed surface.

[0033] The polymer electrolyte carrier 120 serves as both the substrate supporting the catalyst layer 130 and the transport medium for water molecules and reaction-related ions. A first surface 121 is used to support the catalyst layer 130, and a second surface 122 is used to face or contact the liquid electrolyte. The term "surface energy higher than" can be understood as defining the relative relationship between the first surface 121 and the hydrophobic surface 113 under comparable conditions. For example, when using the same noble metal catalyst material, the same layering conditions, and the same effective area, the wetting, spreading, or adhesion states of the catalyst layer 130 on the two surfaces can be compared. The first surface 121 only needs to provide good adhesion for the catalyst layer 130; it is not required to limit the surface energy to a fixed value.

[0034] In one possible embodiment, the polymer electrolyte carrier 120 is adaptively selected according to the sensor electrolyte system and the type of gas to be measured: for CO, H2S, and SO2 gas detection scenarios in acidic electrolyte systems, a proton-conductive Nafion-modified polymer substrate is used; for O2 and NH3 gas detection scenarios in alkaline electrolyte systems, an anion-conductive modified polytetrafluoroethylene-doped substrate is used; and for neutral electrolyte systems, a zwitterionic blended modified polymer substrate is used to achieve simultaneous bidirectional conduction of protons, hydroxide ions, and water molecules.

[0035] In one possible embodiment, the catalyst layer 130 is a noble metal catalyst layer, and the noble metal catalyst layer is a multi-element noble metal composite catalytic system, including a main catalytic phase, an auxiliary catalytic phase, and a conductivity-enhancing phase. Specifically, the main catalytic phase is any one or more combinations of platinum, palladium, and gold, used to provide active sites for gas redox reactions; the auxiliary catalytic phase is one or more of manganese dioxide, cerium oxide, and copper oxide, used to improve gas selectivity and suppress side reactions; the conductivity-enhancing phase is at least one of nano-carbon powder, graphene, and carbon nanotubes, used to reduce the overall resistivity of the electrode and improve the stability of the current signal output.

[0036] The ions participating in the electrode reaction can be protons in an acidic electrolyte system or hydroxide ions in an alkaline electrolyte system. The ions generated by the electrode reaction are determined based on the type of gas to be measured and the specific reaction. Bidirectional migration includes the migration of reactants from the second surface 122 to the first surface 121, and also includes the migration of reaction products from the first surface 121 to the second surface 122. The catalyst layer 130 couples the electrons generated or consumed by the electrode reaction to the conductive element 140, thereby forming the charge output or input path of the working electrode.

[0037] As a concrete example, the working electrode structure 100 of the electrochemical gas sensor can be formed into a circular, layered structure. A waterproof and breathable membrane 110 is located on the side closest to the external gas to be measured; a catalyst layer 130 is formed in the middle of the first surface 121 of the polymer electrolyte carrier 120; the second surface 122 is in contact with the liquid electrolyte after the sensor is assembled; and a conductive element 140 extends outward from the edge of the catalyst layer 130.

[0038] In one possible embodiment, the conductive element 140 adopts a flexible metal tab bonding structure, with the tab bonded to the non-reactive area at the edge of the catalyst layer 130 and fixed by low-temperature pressing, thereby ensuring uniform current acquisition and impedance consistency.

[0039] As can be seen, compared to the working electrode structure where the catalyst layer is directly loaded onto the waterproof membrane and the waterproof membrane participates in the heat-sealing process, the electrochemical gas sensor working electrode structure 100 provided in this application establishes mutually cooperating gas inlet and liquid blocking paths, charge output paths, and water molecule and ion transport paths through the layering and surface energy relationship between the waterproof and breathable membrane 110, the catalyst layer 130, and the polymer electrolyte carrier 120. Since the waterproof and breathable membrane 110 and the catalyst layer 130 are independent of each other, the deformation of the waterproof and breathable membrane 110 during the sealing process does not directly affect the catalyst layer; since the catalyst layer 130 is loaded onto the polymer electrolyte carrier 120 with high surface energy, it maintains high adhesion stability; and since the polymer electrolyte carrier 120 allows bidirectional migration of water molecules and ions participating in and generated by the electrode reaction, reactants and products can be transported between the catalyst layer 130 and the electrolyte, thereby reducing the risk of defects, cracking, and detachment of the catalyst layer 130, improving the mass transfer efficiency of the gas-liquid-solid three-phase reaction interface, and contributing to improving the stability and linearity of the sensor output signal.

[0040] Based on the foregoing embodiments, see Figure 2 This application further defines the stacking order and projection relationship of the functional regions of the waterproof and breathable membrane 110, the catalyst layer 130, and the polymer electrolyte carrier 120, so that the air intake path and the migration path of water molecules and ions converge at the catalyst layer 130. Specifically, along the transmission direction of the gas to be tested, the waterproof and breathable membrane 110, the catalyst layer 130, and the polymer electrolyte carrier 120 are arranged sequentially; the projections of the breathable region 111 of the waterproof and breathable membrane 110, the catalyst layer 130, and the region of the polymer electrolyte carrier 120 corresponding to the catalyst layer 130 in the projection perpendicular to the layer overlap at least partially, so that the gas to be tested reaches the catalyst layer 130 through the waterproof and breathable membrane 110, and the water molecules and ions reach the catalyst layer 130 through the polymer electrolyte carrier 120.

[0041] The breathable region 111 is the area within the waterproof and breathable membrane 110 that actually bears the function of allowing the gas to pass through and enter the sensor. The first region 123 is the region in the polymer electrolyte carrier 120 that corresponds to the breathable region 111 in the stacking direction; that is, the region in the polymer electrolyte carrier 120 located on the side of the catalyst layer 130 away from the air inlet side, corresponding to the catalyst layer 130 in the stacking direction. The breathable region 111, the catalyst layer 130, and the first region 123 are arranged opposite each other along the stacking direction, so that the gas to be tested can reach the surface of the catalyst layer 130 facing the air inlet side after passing through the breathable region 111. At the same time, water molecules and reaction ions in the electrolyte can reach the surface of the catalyst layer 130 facing the electrolyte side through the polymer electrolyte carrier portion corresponding to the first region 123, thereby forming a gas-liquid-solid three-phase reaction interface at the catalyst layer 130.

[0042] It should be noted that the polymer electrolyte carrier 120 as a whole has bidirectional permeability for the supply of water molecules and the bidirectional migration of ions participating in and generated by the electrode reaction between the first surface 121 and the second surface 122, and is not limited to the area defined by the first region 123. The first region 123 is used to indicate the positional correspondence between this region and the permeable region 111 and the catalyst layer 130 in the stacking direction, so as to form a common action area where the gas phase transport path and the liquid phase mass transport path converge at the catalyst layer 130. The supply of water molecules and ions in the non-central region (e.g., the edge region) of the catalyst layer 130 can also reach the surface of the catalyst layer 130 and participate in the reaction through the polymer electrolyte carrier portion outside the first region 123, and it is not required that all mass transfer paths be limited to the first region 123.

[0043] The fact that the projections at least partially overlap does not require the permeable region 111, the catalyst layer 130, and the first region 123 to have exactly the same outline or area, as long as the three form a common projection area that can support the electrode reaction.

[0044] The term "layer" refers to the main plane of any one of the waterproof and breathable membrane 110, the catalyst layer 130, and the polymer electrolyte carrier 120 along its area extension direction, and the main plane is perpendicular to the stacking direction of each layered component. The projection perpendicular to the layer refers to the orthographic projection of the breathable area, the catalyst layer, and the corresponding area along the stacking direction onto the same reference plane parallel to the layer.

[0045] See Figure 2In the cross-sectional direction, the gas to be tested travels along a path 170 from the air inlet side of the waterproof and breathable membrane 110, through the breathable region 111, and reaches the catalyst layer 130; the water molecule and ion bidirectional migration path 171 travels from the second surface 122, through the first region 123, and reaches the catalyst layer 130 on the first surface 121. The two paths converge at the catalyst layer 130, thereby establishing a gas-liquid-solid three-phase reaction interface 180.

[0046] Furthermore, to address the issue of functional area misalignment and reduced effective reaction area caused by assembly tolerances, the projection of the permeable region 111 can cover at least a portion of the catalyst layer 130, and the projection of the first region 123 can cover at least a portion of the catalyst layer 130. The permeable region 111 and the first region 123 can each be slightly larger than the effective reaction area of ​​the catalyst layer 130, so that a common projection area is maintained even with reasonable assembly deviations. This embodiment does not change the functional division of each layer and can improve the consistency of the reaction area in batch assembly.

[0047] Furthermore, different locations within the permeable region 111 can jointly supply the gas to be tested to the catalyst layer 130, and different locations within the first region 123 can jointly supply water molecules and reaction ions to the catalyst layer 130. This forms a planar supply relationship, avoiding reliance on a single narrow channel to deliver reactants to the catalyst layer 130, and helps to reduce the impact of insufficient local supply on the effective utilization area of ​​the catalyst layer 130.

[0048] In this embodiment, the permeable region 111, the catalyst layer 130, and the first region 123 are constrained into mutually synergistic reaction units through the stacking order and projection overlap. The gas to be measured enters from the inlet side, while water molecules and ions enter from the electrolyte side. The two converge at the catalyst layer 130, which can reduce bypass transport that does not participate in the reaction and improve the stability of the effective reaction region in the working electrode structure 100 of the electrochemical gas sensor.

[0049] Based on the layering and projection relationships defined in the foregoing embodiments, see [link to previous document]. Figure 3 This application embodiment further utilizes the property difference between the hydrophobic surface 113 of the waterproof and breathable membrane 110 and the first surface 121 of the polymer electrolyte carrier 120, so that the waterproof and breathable function and the stable bearing function of the catalyst layer 130 are respectively realized by the corresponding surfaces. Specifically, the waterproof and breathable membrane 110 is a fluoropolymer film containing fluorine atom groups, and the fluoropolymer film forms the hydrophobic surface 113 through the fluorine atom groups; the adhesion of the first surface 121 to the catalyst layer 130 is greater than the adhesion of the hydrophobic surface 113 to the catalyst layer 130.

[0050] The fluorine atoms give the hydrophobic surface 113 lower surface energy and hydrophobic properties. The first surface 121 is used to support the catalyst layer 130, and its surface energy is higher than that of the hydrophobic surface 113. The term "adhesion greater than" means that, under the same catalyst layer material, the same layering method, and the same evaluation conditions, the catalyst layer 130 has a higher ability to remain on the first surface 121 than it has to remain on the hydrophobic surface 113. This relative relationship can be compared by examining the integrity of the layer after layering, the retention state after long-term contact, or the tendency to detach under the same external force.

[0051] See Figure 3 The catalyst layer 130 is fixed to the first surface 121, and the hydrophobic surface 113 of the waterproof and breathable membrane 110 faces the catalyst layer 130 but does not support the catalyst layer 130. Thus, even if the hydrophobic surface 113 and the catalyst layer 130 are in contact in a stacked state, the catalyst layer 130 still uses the first surface 121 as the load surface, and its load assignment will not change due to the two surfaces being adjacent.

[0052] Furthermore, to address the issue of the catalyst layer 130 potentially detaching from the supporting surface and migrating to adjacent surfaces during long-term electrochemical reactions, the difference in adhesion between the first surface 121 and the hydrophobic surface 113 can be maintained during material selection and surface condition control. The first surface 121 can remain clean and in continuous contact with the catalyst layer 130, while the hydrophobic surface 113 maintains the hydrophobic state required for the waterproof and breathable membrane 110. This extension relationship makes the catalyst layer 130 more likely to remain on the first surface 121, which is beneficial for maintaining the catalyst layer outline and effective area.

[0053] Furthermore, the higher surface energy of the first surface 121 can also improve the spreading and bonding state of the noble metal catalytic material during the formation of the catalytic layer 130. Compared with forming a catalytic layer on the low surface energy hydrophobic surface 113, the catalytic layer 130 formed on the first surface 121 is less prone to unexpected vacancies due to insufficient local wetting, thereby providing a more continuous reaction interface for subsequent electrochemical reactions.

[0054] In this embodiment, the hydrophobic surface 113 serves as a waterproof, antifouling, and liquid-blocking surface, while the first surface 121 serves as a stable load-bearing surface for the catalyst layer 130. The properties of the two surfaces are each matched to their structural functions, thereby improving the adhesion stability between the catalyst layer 130 and the polymer electrolyte carrier 120 without weakening the liquid-blocking effect of the waterproof and breathable membrane 110.

[0055] Based on the reactant aggregation structure defined in the foregoing embodiments, see [link to previous document]. Figure 4In this embodiment, the ion conduction type of the polymer electrolyte carrier 120 is matched according to the electrolyte system and the target electrode reaction, enabling water molecules and corresponding ions to migrate between the catalyst layer 130 and the electrolyte. Specifically, the polymer electrolyte carrier 120 is a proton-conducting polymer electrolyte carrier or a hydroxide ion-conducting polymer electrolyte carrier; the proton-conducting polymer electrolyte carrier is combined with an acidic electrolyte to allow bidirectional migration of protons and water molecules, and the hydroxide ion-conducting polymer electrolyte carrier is combined with an alkaline electrolyte to allow bidirectional migration of hydroxide ions and water molecules.

[0056] in, Figure 4 The first mass transfer diagram illustrates the combination of a proton-conducting polymer electrolyte carrier 120 and an acidic electrolyte, with a bidirectional migration path 171 for water molecules and ions including the migration of water molecules and protons between the first surface 121 and the second surface 122; the second mass transfer diagram illustrates the combination of a hydroxide ion-conducting polymer electrolyte carrier 120 and an alkaline electrolyte, with a bidirectional migration path 171 for water molecules and ions including the migration of water molecules and hydroxide ions between the first surface 121 and the second surface 122.

[0057] The choice of carrier type is adapted to the electrode reaction of the gas to be measured. For example, when the sensor is used to detect oxygen, carbon monoxide, ammonia, sulfur dioxide, or hydrogen sulfide, the electrolyte system can be determined first based on the acidity or alkalinity of the electrolyte required for the target electrode reaction, and then a polymer electrolyte carrier 120 that can conduct the corresponding ions and allow water molecules to migrate can be selected. Different analytes can correspond to different catalytic reactions and carrier types, but all follow the structural relationship of division of labor between the waterproof and breathable membrane 110, the catalyst layer 130, and the polymer electrolyte carrier 120.

[0058] Furthermore, to address the issue of increased interfacial resistance or limited supply of reaction-related ions when the ion conduction type of the carrier mismatches with the electrolyte system, the type of fixed ion groups on the polymer electrolyte carrier 120 can be matched with the main migrating ions in the electrolyte. In acidic electrolyte systems, the polymer electrolyte carrier 120 primarily forms proton migration channels; in alkaline electrolyte systems, it primarily forms hydroxide ion migration channels. This extended matching relationship enables the formation of continuous mass transfer pathways between the second surface 122 and the electrolyte, and between the first surface 121 and the catalyst layer 130.

[0059] Furthermore, the bidirectional migration is not limited to a unidirectional supply of reactants to the catalyst layer 130. When the electrode reaction generates ions or changes the local water content at the catalyst layer 130, the generated ions and water molecules can migrate from the first surface 121 to the second surface 122; when the electrode reaction requires ions or water molecules, the corresponding substances can migrate from the second surface 122 to the first surface 121. This extension mechanism can alleviate reactant depletion or product accumulation near the catalyst layer 130.

[0060] See Figure 10 The gas to be tested reaches the catalyst layer 130 along the gas transport path 170; water molecules and protons or hydroxide ions pass through the polymer electrolyte carrier 120 along the bidirectional migration path 171; ions generated in the reaction enter the electrolyte side along the generation ion migration path 173; electrons involved in the electrode reaction enter the conductive element 140 along the electron output path 172. The above paths together form a gas-liquid-solid three-phase reaction interface 180 at the catalyst layer 130.

[0061] This embodiment, by matching the ion conduction type with the electrolyte system, enables the polymer electrolyte carrier 120 to not only bear the mechanical support of the catalyst layer 130, but also participate in the transport of water molecules and ions required for the electrochemical reaction. This allows for the establishment of a mass transfer structure adapted to the reaction of different analyte gases, and enables both reactant supply and product extraction to be completed through the same polymer electrolyte carrier 120.

[0062] Based on the stacked structure defined in the foregoing embodiments, see [link to previous document]. Figure 5 This application further defines the coverage position of the catalyst layer 130 on the first surface 121 and the lead-out path of the conductive element 140 to coordinate the catalytic reaction area, conductive connection, and assembly space. Specifically, the catalyst layer 130 covers the central region of the first surface 121, and the first surface 121 forms an exposed bearing area 124 around the catalyst layer 130; one end of the conductive element 140 is connected to the catalyst layer 130, and the other end extends along the first surface 121 to the outside of the polymer electrolyte carrier 120.

[0063] The central region is the internal region relative to the periphery of the polymer electrolyte carrier 120, and it is not required that the geometric center of the catalyst layer 130 coincides perfectly with the geometric center of the polymer electrolyte carrier 120. The exposed bearing region 124 is the area of ​​the first surface 121 that is not covered by the catalyst layer 130 and is located outside the catalyst layer 130. It can continuously surround the catalyst layer 130, or it can be a local exposed region formed according to the lead-out position of the conductive element 140.

[0064] See Figure 5The catalyst layer 130 can be circular or a sheet-like region adapted to the venting region 111. One end of the conductive element 140 is connected to the edge of the catalyst layer 130, and the other end passes through the exposed bearing region 124 and extends beyond the outer edge of the polymer electrolyte carrier 120. The conductive element 140 can be in the form of a wire, and its connection point with the catalyst layer 130 is located inside the continuous sealing region 152, with its external lead used to connect to the signal output terminal 240.

[0065] Furthermore, to address the issue that the conductive element 140 directly passing through the middle of the catalyst layer 130 might obstruct the air intake area and divide the effective catalytic area, the conductive element 140 can be inserted from the edge of the catalyst layer 130 and extend outward along the exposed bearing area 124. This extended layout can reduce the occupation of the common projection area of ​​the permeable area 111 and the catalyst layer 130 by the conductive element 140, while maintaining a stable electrical connection path.

[0066] Furthermore, the exposed bearing area 124 can also provide a location for positioning, holding, or edge support of the polymer electrolyte carrier 120. The catalyst layer 130 is located in the center, and the assembly action is mainly applied to its periphery, thus differentiating the catalytic reaction area from the assembly force-bearing area on the plane. This reduces the possibility of edge assembly forces directly acting on the catalyst layer 130 and makes it easier to maintain the stable position of the conductive element 140.

[0067] In this embodiment, the central catalytic region, the outer exposed bearing region 124, and the conductive element 140 extending along the first surface 121 form a coordinated layout, so that the catalytic layer 130 obtains a relatively complete reaction area, the conductive element 140 obtains a clear lead-out space, and the assembly support position avoids the main catalytic region.

[0068] Based on the layering and projection relationships defined in the foregoing embodiments, see [link to previous document]. Figure 6 In this embodiment, a sensor cover 150 is introduced into the working electrode structure 100 of the electrochemical gas sensor. The gas to be measured enters the region where the catalyst layer 130 is located through the vent 151 of the sensor cover 150 and the waterproof and breathable membrane 110. The leakage of liquid electrolyte is limited by the sealed connection between the waterproof and breathable membrane 110 and the sensor cover 150. The working electrode structure 100 of the electrochemical gas sensor also includes a sensor cover 150; the sensor cover 150 is provided with a vent 151, and the waterproof and breathable membrane 110 covers the vent 151 from the inside of the sensor cover 150 and is sealed to the sensor cover 150 through the peripheral region 112. The catalyst layer 130 and the polymer electrolyte carrier 120 are disposed on the inside of the waterproof and breathable membrane 110.

[0069] The sensor cover 150 defines the air inlet boundary of the sensor and supports the waterproof and breathable membrane 110. The vent 151 may include a single opening or multiple openings arranged in a central arrangement; when multiple openings are provided, they collectively constitute the vent 151 described in this embodiment. The waterproof and breathable membrane 110 covers the vent 151 from the inside of the sensor cover 150, meaning that when viewed from inside the sensor, the entire effective flow range of the vent 151 is covered by the waterproof and breathable membrane 110, thereby preventing liquid electrolyte from directly reaching the outside through the uncovered portion.

[0070] The outer region 112 is the area of ​​the waterproof and breathable membrane 110 located outside the breathable region 111 and used to connect with the sensor cover 150. The outer region 112 and the sensor cover 150 form a closed or substantially closed sealing boundary, allowing the external gas to be measured to enter mainly through the vent 151 and the breathable region 111, while the liquid electrolyte inside the sensor is blocked by the waterproof and breathable membrane 110 and the sealing boundary.

[0071] See Figure 6 The sensor cover 150, waterproof and breathable membrane 110, catalyst layer 130, and polymer electrolyte carrier 120 can be assembled in an order from the outside to the inside. The conductive element 140 extends from the catalyst layer 130 to the side of the electrochemical gas sensor working electrode structure 100. Figure 6 Based on the overall exploded view, the catalyst layer 130 is clearly positioned on the first surface 121 of the polymer electrolyte carrier 120, and the waterproof and breathable membrane 110 is used as a sealing membrane layer that is independent of the catalyst layer 130.

[0072] As a concrete example, the sensor cover 150 can be disc-shaped, with a vent 151 located in the center. The waterproof and breathable membrane 110 can be a sheet-like structure that matches the inner connection area of ​​the sensor cover 150. The catalyst layer 130 is located within the inner projection range of the vent 151, and the polymer electrolyte carrier 120 supports the catalyst layer 130 from the electrolyte side. The specific outer contours of each component can be adapted to the air inlet position 211 of the sensor housing 210.

[0073] In one possible embodiment, the vent 151 is a tapered micropore structure that is wider at the top and narrower at the bottom. The inlet diameter of the micropore is larger than the outlet diameter, thereby achieving uniform gas diffusion and preventing dust and droplets from entering, thus improving the working stability of the electrode under extreme conditions.

[0074] In this embodiment, a controlled air intake and liquid blocking boundary is formed by the sensor cover 150, the vent 151, the waterproof and breathable membrane 110, and the peripheral area 112. The catalyst layer 130 and the polymer electrolyte carrier 120 are located inside this boundary, so the catalyst layer 130 does not need to be formed directly on the waterproof and breathable membrane 110 used for sealing, thereby keeping the sealing bearing path separate from the catalyst layer bearing path.

[0075] Based on the cover assembly structure of the aforementioned embodiment, see... Figure 7 This application further defines the material melting point relationship and heat fusion connection form between the sensor cover 150 and the waterproof and breathable membrane 110 to form a continuous sealing area 152 surrounding the vent 151. Specifically, the sensor cover 150 is a plastic part, and the melting point of the plastic part is lower than that of the waterproof and breathable membrane 110; the peripheral area 112 of the waterproof and breathable membrane 110 is heat-fused to the sensor cover 150 to form a continuous sealing area 152 surrounding the vent 151.

[0076] The sensor cover 150 has a lower melting point than the waterproof and breathable membrane 110. This design allows the connection points of the sensor cover 150 to soften or melt first during the heat-fusion assembly process, while the waterproof and breathable membrane 110 maintains its main structure for covering the vent 151 under the same assembly conditions. This melting point relationship is a material selection relationship relative to the heat-fusion process window used, and does not require the entire area of ​​the sensor cover 150 to melt.

[0077] The continuous sealing region 152 is an annular or closed contour region formed by the thermal fusion connection between the outer region 112 and the sensor cover 150. "Continuous" means that there is no interrupted channel along the periphery of the vent 151 that would allow gas or liquid to bypass the waterproof and breathable membrane 110 and directly connect the inside and outside of the sensor. The continuous sealing region 152 can be concentrically arranged with the vent 151, or it can adopt a non-concentric closed contour adapted to the vent 151 and the outer region 112.

[0078] See Figure 7 The thermal fusion process is applied to the outer region 112 of the waterproof and breathable membrane 110 and the corresponding position in the sensor cover 150. The continuous sealing region 152 is located outside the breathable region 111. The polymer electrolyte carrier 120 carries the catalyst layer 130 from the inside of the waterproof and breathable membrane 110, so the in-plane deformation of the waterproof and breathable membrane 110 near the continuous sealing region 152 will not simultaneously pull the catalyst layer 130 due to the direct adhesion of the catalyst layer 130 to the waterproof and breathable membrane 110.

[0079] See Figure 11The conventional membrane electrode control structure 300 includes a control cover 310, a control waterproof and breathable membrane 311, and a control catalyst layer 312 formed directly on the control waterproof and breathable membrane 311. During hot-melt assembly, the control waterproof and breathable membrane 311 expands along the in-plane stretching direction 313 and connects with the control cover 310 in the control hot-melt region 314. Because the control catalyst layer 312 and the control waterproof and breathable membrane 311 deform together, the control catalyst layer 312 may form a thinned region 315 or a cracked region 316. It is understood that... Figure 11 This is only used to illustrate the thermal melting damage mechanism of conventional membrane electrodes and does not imply that the conventional membrane electrode control structure 300 is a component of the working electrode structure 100 of the electrochemical gas sensor of this application.

[0080] In this embodiment, the hot-melt process may still cause some in-plane stress in the peripheral region 112 of the waterproof and breathable membrane 110, but this stress is mainly transmitted along the sealing connection path between the waterproof and breathable membrane 110 and the sensor cover 150. The load force of the catalyst layer 130 is borne by the polymer electrolyte carrier 120. The two force paths are structurally separated, so even if the waterproof and breathable membrane 110 has some deformation, the direct impact of the deformation on the catalyst layer 130 can be reduced.

[0081] This embodiment utilizes the melting point difference between the sensor cover 150 and the waterproof and breathable membrane 110 to form a continuous sealing area 152. While maintaining the sealing integrity of the vent 151, it avoids direct heat fusion bonding of the catalyst layer 130. Compared to the control structure where the catalyst layer 312 is stretched together with the control waterproof and breathable membrane 311, this embodiment can reduce the risk of uneven thickness, defects, or cracking of the catalyst layer 130 caused by heat fusion assembly.

[0082] Based on the continuous hot-melt sealing structure defined in the foregoing embodiments, see... Figure 8 This application embodiment further defines the planar projection relationship between the breathable region 111, the continuous sealing region 152, and the catalyst layer 130, so that the sealing region and the catalytic reaction region avoid each other. Specifically, the region in the waterproof and breathable membrane 110 corresponding to the vent 151 constitutes the breathable region 111, and the continuous sealing region 152 is located on the periphery of the breathable region 111; the projection of the catalyst layer 130 on the waterproof and breathable membrane 110 is located within the inner boundary of the continuous sealing region 152.

[0083] The breathable area 111 is defined by the corresponding area of ​​the vent 151 on the waterproof and breathable membrane 110. It may have the same outline as the vent 151, or it may cover the vent 151 and extend outwards. The inner boundary of the continuous sealing area 152 is the side boundary of the continuous sealing area 152 facing the breathable area 111. The projection of the catalyst layer 130 lies within this inner boundary, meaning that the effective outline of the catalyst layer 130 does not extend into the continuous sealing area 152.

[0084] See Figure 8 Viewed from the air intake side, the vent 151 and the breathable area 111 are located in the middle of the sensor cover 150 and the waterproof and breathable membrane 110, and the continuous sealing area 152 forms a closed ring around its periphery. The projection of the catalyst layer 130 is located inside the closed ring. The first region 123 of the polymer electrolyte carrier 120 is located on the electrolyte side of the catalyst layer 130, and its projection at least partially overlaps with the catalyst layer 130.

[0085] As a concrete example, when the continuous sealing region 152 is annular, the catalyst layer 130 can be a circular region located inside the annulus; when the continuous sealing region 152 is another closed shape adapted to the contour of the cover, the catalyst layer 130 can be an adapting contour that does not cross the inner boundary of the closed shape. As long as the catalyst layer 130 does not enter the main heat-melting action area and maintains an effective correspondence with the venting region 111, the projection avoidance relationship of this embodiment can be satisfied.

[0086] In this embodiment, the continuous sealing region 152 is disposed around the venting region 111, and the projection of the catalyst layer 130 is constrained within the inner boundary of the continuous sealing region 152. Thus, the sealing region, where heat and in-plane deformation are concentrated, is spaced apart from the catalyst layer 130 on the plane, which helps to further reduce the impact of the hot-melt process on the structural integrity of the catalyst layer 130, while maintaining the gas transport relationship between the vent 151, the venting region 111, and the catalyst layer 130.

[0087] Based on the planar projection avoidance relationship defined in the foregoing embodiments, see Figure 9 This application embodiment further defines the relative positions of the vent 151, the breathable region 111, the catalyst layer 130, and the first region 123 in the stacking direction, and ensures that the waterproof and breathable membrane 110 and the polymer electrolyte carrier 120 are tightly fitted together. Specifically, the vent 151, the breathable region 111, the catalyst layer 130, and the first region 123 of the polymer electrolyte carrier 120 corresponding to the catalyst layer 130 are arranged opposite each other in a direction perpendicular to the waterproof and breathable membrane 110; the waterproof and breathable membrane 110 and the polymer electrolyte carrier 120 are tightly fitted together in the aforementioned direction, the catalyst layer 130 is located between them, and the second surface 122 faces the electrolyte 220 inside the sensor.

[0088] The phrase "arranged relative to each other along a direction perpendicular to the waterproof and breathable membrane 110" is used to define the common range of action of each functional area in the stacking direction, without requiring that the components be strictly coaxial in the manufacturing state. The close fit between the waterproof and breathable membrane 110 and the polymer electrolyte carrier 120 means that after assembly, the two maintain a stable relative distance at the location of the catalyst layer 130 and its surroundings, avoiding the formation of uncontrolled gaps that would allow the gas to be tested to bypass the catalyst layer 130 or allow the layers to move freely.

[0089] See Figure 9 The sensor cover 150 is located on the air inlet side. The waterproof and breathable membrane 110 is close to the inner side of the sensor cover 150. The catalyst layer 130 is located between the waterproof and breathable membrane 110 and the polymer electrolyte carrier 120, and is loaded on the first surface 121. The second surface 122 faces the electrolyte 220. The conductive element 140 extends from the side of the catalyst layer 130 and avoids the main heat-melting locations in the continuous sealing area 152.

[0090] At the location covered by the catalyst layer 130, the waterproof and breathable membrane 110 can be in adjacent contact with the catalyst layer 130, and the polymer electrolyte carrier 120 supports the catalyst layer 130 through the first surface 121; around the catalyst layer 130, the waterproof and breathable membrane 110 can be adjacent to the exposed bearing area 124. This close fit maintains the load assignment of the catalyst layer 130 and also restricts the relative displacement between layers.

[0091] As a concrete assembly method, a catalyst layer 130 can be first formed on the first surface 121 of the polymer electrolyte carrier 120 and connected to the conductive component 140. Then, this assembly is placed inside the waterproof and breathable membrane 110, which is already sealed to the sensor cover 150, aligning the breathable area 111, the catalyst layer 130, and the first area 123. The assembled second surface 122 faces the space containing the liquid electrolyte. This assembly sequence avoids the catalyst layer 130 undergoing a direct thermal fusion process between the waterproof and breathable membrane 110 and the sensor cover 150.

[0092] This embodiment further stabilizes the longitudinal position of each layer based on planar projection avoidance, which can shorten the effective transmission distance of the gas to be tested from the vent 151 to the catalyst layer 130 and maintain reliable contact between the catalyst layer 130 and the polymer electrolyte carrier 120. This reduces interlayer misalignment and bypass diffusion, and also facilitates the continuous acquisition of water molecules and reactive ions from the electrolyte 220 by the second surface 122.

[0093] Based on the electrochemical gas sensor working electrode structure 100 of the aforementioned embodiment, see... Figure 12In this embodiment, the working electrode structure 100 of the electrochemical gas sensor is disposed at the gas inlet position 211 of the electrochemical gas sensor 200, and a complete detection structure is formed by the electrolyte 220, the counter electrode 230, and the signal output terminal 240. The electrochemical gas sensor 200 includes a sensor housing 210, an electrolyte 220 housed within the sensor housing 210, a counter electrode 230 in contact with the electrolyte 220, and the working electrode structure 100 of the electrochemical gas sensor as described in any one of this embodiment; the working electrode structure 100 of the electrochemical gas sensor is disposed at the gas inlet position 211 of the sensor housing 210, the waterproof and breathable membrane 110 is in communication with the outside, and the second surface 122 is in contact with the electrolyte 220; the catalyst layer 130 forms an ion transport path 250 with the counter electrode 230 through the polymer electrolyte carrier 120 and the electrolyte 220, and the conductive element 140 is connected to the signal output terminal 240 of the electrochemical gas sensor 200.

[0094] The sensor housing 210 defines the internal space for accommodating the electrolyte 220, and the electrochemical gas sensor working electrode structure 100 is installed at the air inlet 211. The air inlet 211 can be formed by the sensor cover 150 and its vent 151. A waterproof and breathable membrane 110 faces outwards, allowing the gas to be measured to enter while preventing leakage of the electrolyte 220 from the air inlet 211. The second surface 122 of the polymer electrolyte carrier 120 contacts the electrolyte 220, allowing water molecules and reactive ions in the electrolyte 220 to enter the polymer electrolyte carrier 120.

[0095] The counter electrode 230 is in contact with the electrolyte 220, and forms an ion transport pathway 250 with the catalyst layer 130 through the electrolyte 220 and the polymer electrolyte carrier 120. A conductive element 140 electrically connects the catalyst layer 130 to the signal output terminal 240. The counter electrode 230 can also be connected to a detection circuit interface that cooperates with the signal output terminal 240, so that electron transfer between the working electrode and the counter electrode can be collected by an external detection circuit; the specific form of this detection circuit interface does not change the interlayer relationship of the working electrode structure 100 of the electrochemical gas sensor of this application.

[0096] See Figure 12The gas to be tested from the outside reaches the catalyst layer 130 through the air inlet 211, the vent 151, and the waterproof and breathable membrane 110. Water molecules and protons or hydroxide ions in the electrolyte 220 enter the polymer electrolyte carrier 120 through the second surface 122 and reach the first surface 121 along the bidirectional migration path 171 of water molecules and ions. The gas to be tested, water molecules, reacting ions, and catalyst layer 130 undergo an electrochemical reaction at the gas-liquid-solid three-phase reaction interface 180. Electrons involved in the reaction are transmitted to the signal output terminal 240 through the conductive element 140, and the ions generated in the reaction enter the electrolyte 220 through the polymer electrolyte carrier 120 and participate in the reaction on the electrode 230 side.

[0097] In an example of detecting an oxidizing or reducing analyte gas, the electrochemical gas sensor 200 can select an appropriate catalyst layer 130, electrolyte 220, and polymer electrolyte carrier 120 based on the reaction properties of the target gas. If an acidic electrolyte 220 is used, a proton-conductive polymer electrolyte carrier 120 can be configured; if an alkaline electrolyte 220 is used, a hydroxide ion-conductive polymer electrolyte carrier 120 can be configured. This allows the same structural concept to be applied to different electrochemical gas sensors such as those for oxygen, carbon monoxide, ammonia, sulfur dioxide, and hydrogen sulfide, without requiring different target gases to use the same specific electrode reactions.

[0098] When the electrochemical gas sensor 200 is in operation, the signal output terminal 240 obtains an electrical signal related to the electrode reaction at the catalyst layer 130. This electrical signal can be converted into the concentration of the gas to be measured by the matching detection circuit. The gas inlet and liquid blocking effect of the waterproof and breathable membrane 110, the catalyst layer bearing and mass transfer effect of the polymer electrolyte carrier 120, the electrochemical catalytic effect of the catalyst layer 130, and the charge transport effect of the conductive element 140 together constitute the detection link.

[0099] In this embodiment, the working electrode structure 100 of the electrochemical gas sensor is located at the gas inlet position 211 of the sensor housing 210, allowing the gas to be measured to enter from the outside, water molecules and reaction ions to enter from the electrolyte 220 side, and electrons to be output from the signal output terminal 240. The working electrode structure 100 and the counter electrode 230 form a reaction circuit through the ion transport pathway 250. Because the sealing and supporting functions are separated from the catalyst layer supporting function, and the polymer electrolyte carrier 120 can transport reaction-related substances, it is beneficial to maintain the structural integrity of the catalyst layer 130, improve the mass transfer continuity of the gas-liquid-solid three-phase reaction interface 180, and enhance the stability of the output signal and the consistency of the linear response of the electrochemical gas sensor 200.

[0100] The structural features in the above embodiments can be combined with each other without technical conflict. The circular, annular, and layered contours shown in the accompanying drawings are merely illustrative representations and do not constitute a limitation on the actual product shape and size. For those skilled in the art, any equivalent adjustments to the component contours, relative dimensions, connection positions, or assembly directions made without departing from the concept of this application should fall within the scope of protection claimed in this application.

Claims

1. A working electrode structure for an electrochemical gas sensor, characterized in that, It includes a waterproof and breathable membrane (110), a polymer electrolyte carrier (120), a catalyst layer (130), and a conductive element (140). The waterproof and breathable membrane (110), the catalyst layer (130), and the polymer electrolyte carrier (120) are arranged sequentially along the transmission direction of the gas to be tested. The polymer electrolyte carrier (120) has a first surface (121) facing the air intake side and a second surface (122) facing the electrolyte side, and the catalyst layer (130) is loaded on the first surface (121) and electrically connected to the conductive element (140); The waterproof and breathable membrane (110) is located on the air inlet side of the catalyst layer (130), allowing the gas to be tested to pass through and blocking the liquid electrolyte (220). The waterproof and breathable membrane (110) and the catalyst layer (130) are independent of each other, and the catalyst layer (130) is not loaded on the waterproof and breathable membrane (110). The surface energy of the first surface (121) is higher than the surface energy of the hydrophobic surface (113) of the waterproof and breathable membrane (110) facing the catalyst layer (130), and the polymer electrolyte carrier (120) is used to supply water molecules and ions participating in and generated by the electrode reaction to migrate bidirectionally between the first surface (121) and the second surface (122).

2. The working electrode structure of the electrochemical gas sensor according to claim 1, characterized in that, The permeable area (111) of the waterproof and breathable membrane (110), the catalyst layer (130), and the first area (123) of the polymer electrolyte carrier (120) corresponding to the catalyst layer (130) have at least partial overlap in their projections perpendicular to the surface, so that the gas to be tested reaches the catalyst layer (130) through the waterproof and breathable membrane (110), and the water molecules and ions reach the catalyst layer (130) through the polymer electrolyte carrier (120).

3. The working electrode structure of the electrochemical gas sensor according to claim 2, characterized in that, The waterproof and breathable membrane (110) is a fluoropolymer film containing fluorine atom groups, and the fluoropolymer film forms the hydrophobic surface (113) through the fluorine atom groups; the adhesion of the first surface (121) to the catalyst layer (130) is greater than the adhesion of the hydrophobic surface (113) to the catalyst layer (130).

4. The working electrode structure of the electrochemical gas sensor according to claim 2, characterized in that, The polymer electrolyte carrier (120) is either a proton-conducting polymer electrolyte carrier (120) or a hydroxide ion-conducting polymer electrolyte carrier (120). The proton-conducting polymer electrolyte carrier (120) is combined with an acidic electrolyte (220) to allow bidirectional migration of protons and water molecules, and the hydroxide ion-conducting polymer electrolyte carrier (120) is combined with an alkaline electrolyte (220) to allow bidirectional migration of hydroxide ions and water molecules.

5. The working electrode structure of the electrochemical gas sensor according to claim 2, characterized in that, The catalyst layer (130) covers the central region of the first surface (121), and the first surface (121) forms an exposed bearing area (124) around the catalyst layer (130); one end of the conductive element (140) is connected to the catalyst layer (130), and the other end extends along the first surface (121) to the outside of the polymer electrolyte carrier (120).

6. The working electrode structure of the electrochemical gas sensor according to claim 2, characterized in that, The working electrode structure (100) of the electrochemical gas sensor also includes a sensor cover (150); the sensor cover (150) is provided with a vent (151), the waterproof and breathable membrane (110) covers the vent (151) from the inside of the sensor cover (150) and is sealed to the sensor cover (150) through the peripheral area (112), the catalyst layer (130) and the polymer electrolyte carrier (120) are disposed on the inside of the waterproof and breathable membrane (110).

7. The working electrode structure of the electrochemical gas sensor according to claim 6, characterized in that, The sensor cover (150) is made of plastic and the melting point of the plastic is lower than that of the waterproof and breathable membrane (110). The outer area (112) of the waterproof and breathable membrane (110) is heat-fused to the sensor cover (150) to form a continuous sealing area (152) surrounding the vent (151).

8. The working electrode structure of the electrochemical gas sensor according to claim 7, characterized in that, The area in the waterproof and breathable membrane (110) corresponding to the vent (151) constitutes a breathable area (111), and the continuous sealing area (152) is located on the periphery of the breathable area (111); the projection of the catalyst layer (130) on the waterproof and breathable membrane (110) is located within the inner boundary of the continuous sealing area (152).

9. The working electrode structure of the electrochemical gas sensor according to claim 8, characterized in that, The vent (151), the breathable area (111), the catalyst layer (130), and the first area (123) of the polymer electrolyte carrier (120) corresponding to the catalyst layer (130) are arranged opposite each other in a direction perpendicular to the waterproof and breathable membrane (110); the waterproof and breathable membrane (110) and the polymer electrolyte carrier (120) are tightly fitted in the direction, the catalyst layer (130) is located between the waterproof and breathable membrane (110) and the polymer electrolyte carrier (120), and the second surface (122) faces the electrolyte (220) inside the sensor.

10. An electrochemical gas sensor, characterized in that, The sensor includes a sensor housing (210), an electrolyte (220) housed within the sensor housing (210), a counter electrode (230) in contact with the electrolyte (220), and an electrochemical gas sensor working electrode structure as described in any one of claims 1 to 9; the electrochemical gas sensor working electrode structure is disposed at the gas inlet position (211) of the sensor housing (210), the waterproof and breathable membrane (110) is in communication with the outside, and the second surface (122) is in contact with the electrolyte (220); the catalyst layer (130) forms an ion transport pathway (250) with the counter electrode (230) through the polymer electrolyte carrier (120) and the electrolyte (220), and the conductive element (140) is connected to the signal output terminal (240) of the electrochemical gas sensor (200).

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