Membrane electrode structure

Abstract

The utility model discloses a membrane electrode structure, the middle part of a membrane electrode is provided with a reaction zone, two ends of one side of the membrane electrode are respectively provided with a hydrogen inlet and a hydrogen outlet, and two ends of the other side of the membrane electrode are respectively provided with an air inlet and an air outlet; the membrane electrode is provided with a distribution area, the distribution area comprises a first distribution area and a second distribution area, the first distribution area is arranged on one side of the hydrogen inlet and the air inlet, the second distribution area is arranged on one side of the hydrogen outlet and the air outlet, and by adopting the membrane electrode structure disclosed by the utility model, the distribution uniformity of water in the membrane electrode can be improved, and the reliable performance of the fuel cell is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of membrane electrodes, and specifically relates to a membrane electrode structure. Background Art

[0002] Fuel cells are expected to become a mainstream energy source due to their high energy density and low pollution. PEMFC (proton exchange membrane fuel cell) has the advantages of fast start-up at room temperature, no electrolyte loss, and low noise. It is a potential mobile power source, various portable power sources, and uninterruptible power sources.

[0003] In order to maintain the high battery performance of PEMFC, the electrolyte membrane needs to be fully saturated through an external humidification system. However, an over-humidification system will increase the volume and weight of the entire battery system and increase its complexity. Current research focuses on adding hydrophilic substances to retain water, but no solution is provided for the uniformity of water distribution inside the membrane electrode. Since hydrogen as a fuel has a certain humidity, and under the self-humidification effect of the battery and the permeation of the proton membrane, oxygen also contains a certain amount of water. At present, the gas inlet and outlet structure design on the membrane electrode is single, and water accompanies the gas in and out of the membrane electrode. The water distribution inside the membrane electrode is uneven, and the water accumulation in the membrane electrode causes the alternating dry and wet effects to produce mechanical aging, resulting in a decrease in the performance of the fuel cell.

[0004] The utility model patent with announcement number CN217788457U disclosed on November 11, 2022, a membrane electrode sealing structure, a fuel cell and a CCM structure. The membrane electrode sealing structure includes: CCM, a first sealing frame and a second sealing frame. The membrane electrode structure is divided into a sealing area and an active area. The sealing area is arranged around the active area. The first sealing frame and the second sealing frame are clamped around the CCM to form a sealing area. The CCM includes a proton conductive membrane and a catalytic layer coated on both sides of the proton conductive membrane. The CCM extends from the active area to the sealing area. Filling layers are provided on both sides of the CCM extending to the sealing area. The membrane electrode sealing structure cannot improve the uniformity of water distribution in the membrane electrode, nor can the fuel cell performance be reliable. Utility Model Content

[0005] The utility model aims to provide a membrane electrode structure which can improve the uniformity of water distribution in the membrane electrode and ensure the reliable performance of the fuel cell in view of the shortcomings of the prior art.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] The membrane electrode structure has a reaction zone in the middle of the membrane electrode, a hydrogen inlet and a hydrogen outlet are respectively provided at two ends of one side of the membrane electrode, and an air inlet and an air outlet are respectively provided at two ends of the other side of the membrane electrode; a distribution zone is provided on the membrane electrode, and the distribution zone includes a first distribution zone and a second distribution zone, the first distribution zone is provided on one side of the hydrogen inlet and the air inlet, and the second distribution zone is provided on one side of the hydrogen outlet and the air outlet.

[0008] The edges of the hydrogen inlet and the air inlet are both provided with a first protrusion, and the edges of the hydrogen outlet and the air outlet are both provided with a second protrusion.

[0009] A bipolar plate is disposed outside the membrane electrode, and flow channels are disposed on the bipolar plate. The flow channels are evenly distributed, and the first protrusion and the second protrusion both correspond to the flow channels.

[0010] The reaction zone includes a proton membrane, and a third protrusion is arranged at the boundary of the proton membrane. The third protrusion is an arc-shaped structure and is evenly distributed.

[0011] The first protrusions and the second protrusions are evenly distributed; the first protrusions are semicircular structures, and the second protrusions are arranged in sequence to form a sawtooth structure.

[0012] The distribution areas are all square or polygonal.

[0013] The ends of the distribution area are all provided with rounded corners.

[0014] The technical effect of the utility model is as follows: the membrane electrode structure of the utility model is adopted, and a protruding structure matching the flow channel of the bipolar plate is designed at the gas inlet and outlet of the membrane electrode, so as to improve the water distribution state in the membrane electrode and the fuel cell stack, optimize the water distribution state and uniformity, solve the problem of uneven water distribution inside the membrane electrode and accelerated aging due to dry-wet alternation, avoid the phenomenon of water accumulation and dry-wet alternation in the confluence area of ​​the gas distribution port, thereby improving the performance and durability of the membrane electrode in the self-humidifying fuel cell stack; an arc-shaped protruding structure is also designed at the contact boundary between the distribution area and the proton membrane, so as to avoid failure of the proton membrane due to excessive stress; the membrane electrode has a simple design structure, reliable function and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] This specification includes the following drawings, which show the following contents:

[0016] Figure 1 It is a schematic diagram of hydrogen flow direction of the membrane electrode structure of the utility model;

[0017] Figure 2 It is a schematic diagram of oxygen flow in the membrane electrode structure of the utility model;

[0018] Figure 3 It is a schematic diagram of the matching of the flow channel and the protrusion of the utility model;

[0019] Figure 4 It is a schematic diagram of the position of the third protrusion of the utility model;

[0020] Figure 5 It is a distribution diagram of the first protrusion of the utility model;

[0021] Figure 6 It is a distribution diagram of the second protrusion of the utility model;

[0022] Figure 7 It is a distribution diagram of the third protrusion of the utility model.

[0023] The markings in the figure are: 1. membrane electrode; 2. reaction zone; 3. hydrogen inlet; 4. hydrogen outlet; 5. air inlet; 6. air outlet; 7. first distribution area; 8. second distribution area; 9. first protrusion; 10. second protrusion; 11. third protrusion; 12. fillet; 13. bipolar plate; 14. flow channel; 15. proton membrane. DETAILED DESCRIPTION

[0024] The specific implementation methods of the utility model are further explained in detail below with reference to the accompanying drawings through the description of embodiments, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention and to facilitate their implementation.

[0025] like Figures 1 to 5 As shown, the membrane electrode structure has a reaction zone 2 in the middle of the membrane electrode 1, a hydrogen inlet 3 and a hydrogen outlet 4 are respectively provided at two ends of one side of the membrane electrode 1, and an air inlet 5 and an air outlet 6 are respectively provided at two ends of the other side of the membrane electrode 1; a distribution area is provided on the membrane electrode 1, and the distribution area includes a first distribution area 7 and a second distribution area 8, the first distribution area 7 is provided on one side of the hydrogen inlet 3 and the air inlet 5, and the second distribution area 8 is provided on one side of the hydrogen outlet 4 and the air outlet 6.

[0026] A water distribution zone is established inside the electrode at the outlet of the anode side of the membrane electrode 1, i.e., the hydrogen flow side, with a coverage rate of more than 80% for the hydrogen flow summary area, which accounts for more than 2% of the effective area of ​​the membrane electrode 1. Similarly, a water distribution zone is established inside the electrode at the outlet of the cathode side of the membrane electrode 1, i.e., the air flow side, with a coverage rate of more than 80% for the air flow summary area, which accounts for more than 1% of the effective area of ​​the membrane electrode 1. The first distribution zone 7 and the first distribution zone 7 are used to converge the hydrogen and air entering or exiting the membrane electrode 1.

[0027] The principle of membrane electrode 1 is as follows: hydrogen and air enter the two ends of membrane electrode 1 from the bipolar plate respectively, enter the distribution area and converge, and then the gas passes through the respective gas diffusion layer and catalyst layer in the reaction area 2. Hydrogen undergoes oxidation reaction under the action of the anode catalyst to generate protons and electrons, while oxygen enters the cathode catalyst layer. Protons pass through the proton membrane and enter the cathode catalyst layer and react with oxygen to generate water through catalysis. Electrons move and generate current through the external circuit to power the device. Unreacted gas is discharged from the corresponding gas outlet, and the water generated by the reaction is discharged with the air.

[0028] The edges of the hydrogen inlet 3 and the air inlet 5 are both provided with a first protrusion 9, and the edges of the hydrogen outlet 4 and the air outlet 6 are both provided with a second protrusion 10. Since liquid water passes through both the hydrogen inlet and the air inlet of the membrane electrode 1, the first protrusion 9 is designed for the hydrogen inlet 3 and the air inlet 5 of the frame of the membrane electrode 1 to periodically match the bipolar plate flow channel distribution port, and the size ratio of the bipolar plate flow channel to the first protrusion 9 at the hydrogen inlet 3 is 0.5:5, and the size ratio of the first protrusion 9 at the air inlet 5 is 0.5:10. The first protrusion 9 adopts a zigzag design, and the liquid water in the membrane electrode 1 is secondary refined and homogenized through the frame formed by the zigzag protrusions in the process of following the air flow. , thereby improving the uniformity of water distribution and reducing the phenomenon of alternating dry and wet; the hydrogen outlet 4 and the air outlet 6 of the membrane electrode 1 frame are designed with a second protrusion 10 cycle to match the bipolar plate flow channel distribution port, and the size ratio of the bipolar plate flow channel to the second protrusion 10 cycle at the hydrogen outlet 4 is 0.5:2.5, and the size ratio of the second protrusion 10 cycle at the air outlet 6 is 1:17. The second protrusion 10 adopts a semicircular design. The liquid water in the membrane electrode 1 moves with the airflow through the semicircular frame to achieve the effect of diversion and rapid distribution and discharge.

[0029] A bipolar plate 13 is provided outside the membrane electrode 1, and a flow channel 14 is provided on the bipolar plate 13. The flow channels 14 are evenly distributed, and the first protrusions 9 and the second protrusions 10 correspond to the flow channels. The flow channels 14 on the bipolar plate 13 are distributed periodically, and by matching the hydrogen inlet and outlet and the air inlet and outlet with the period of the flow channels 14, the water discharged from or entering the flow channels 14 corresponds to the frame structure formed by the protrusions, which is conducive to refining or diverting the water.

[0030] The reaction zone 2 includes a proton membrane 15, and a third protrusion 11 is provided at the boundary of the proton membrane 15. The third protrusion 11 is an arc-shaped structure and is evenly distributed. The third protrusion 11 is located on the adjacent boundary between the distribution zone frame and the proton membrane 15. The proton membrane has a water concentration difference diffusion characteristic that can reduce the dry-wet gap and uniformize the water concentration. The distribution zone exists in the form of a blank proton membrane hot-pressed gas diffusion layer. The distribution zone frame and the adjacent boundary of the proton membrane are designed in an arc shape, which can reduce the stress of the proton membrane and the distribution zone boundary during the dry-wet cycle. Since the excessive stress of the proton membrane at the distribution zone boundary is the main factor for its failure, the above structure can extend the service life of the proton membrane.

[0031] The first protrusion 9 and the second protrusion 10 are evenly distributed; the first protrusion 9 is a semicircular structure, and the second protrusion 10 is arranged in sequence to form a sawtooth structure. In the process of water entering with the airflow, it is secondary refined and homogenized through the sawtooth frame. After converging in the distribution area, the water distribution is more even, reducing water accumulation, avoiding the mechanical aging of the membrane electrode 1 caused by the alternation of dry and wet, and ensuring the long-term reliability of the fuel cell performance; the sawtooth protrusion structure is adopted, and the water is relatively more evenly divided and refined. Its monomer structure is unified, which can reduce the processing cost and facilitate the experimental data testing. When the water is discharged with the airflow, the water can be quickly distributed to the corresponding flow channel and discharged therewith under the guiding effect of the semicircular protrusion, which is beneficial to the subsequent water circulation and the self-humidification of the membrane electrode 1. The semicircular structure has a good buffering effect, will not cause disturbance to the passage of gas, can improve the stability of gas and water through the diversion, and the semicircular shape is regular, which is also convenient for design processing and experimental data collection.

[0032] The distribution areas are all square or polygonal. The above structure is conducive to designing the coverage of the air flow collection area according to the battery requirements, and is also convenient for processing and manufacturing, reducing production costs.

[0033] The ends of the distribution area are all provided with rounded corners, which can provide buffer for the converging gas and improve the converging effect.

[0034] Control of the preparation process of CCM, frame and GDL packaging: the relative humidity of the environment is controlled at RH0-10%, CCM is transported under RH0-10%, infrared lamp baking is added at the frame packaging and GDL packaging stations to remove moisture so that the CCM is packaged in a contracted state. Adapt the use conditions to reduce the stress caused by the shrinkage of CCM in dry conditions in dry and wet conditions.

[0035] Embodiment: A water distribution zone is established in the electrode at the gas flow side outlet on both sides of the membrane electrode 1. The distribution zone is a regular rectangle, with a hydrogen flow area coverage rate greater than 80% and an effective area greater than 1%. The distribution zone exists in the form of a blank proton membrane hot-pressed gas diffusion layer.

[0036] The hydrogen and air inlet of the membrane electrode 1 frame adopts a zigzag design cycle to match the cycle of the bipolar plate flow channel distribution port with a size ratio of 1:1. The hydrogen and air outlet of the membrane electrode 1 frame adopts a semicircular design cycle to match the cycle of the bipolar plate flow channel distribution port with a size ratio of 1:2; CCM and frame and GDL packaging preparation process control: CCM is fed under RH10% ambient humidity, and infrared lamps are added to the frame packaging and GDL packaging stations to bake and remove moisture so that the CCM is packaged in a contracted state. The distribution area frame and the adjacent boundary of the proton membrane are designed with a 5mm semicircular arc shape.

[0037] Comparative example: The same membrane electrode 1 was not designed with a water distribution area and a gas inlet and outlet frame shape, and the packaging conditions were not controlled. The rest of the designs were the same.

[0038] The two membrane electrode 1 of the comparative example and the embodiment were assembled in the same short stack for working condition durability test. After 1000 hours, leakage occurred at the hydrogen outlet 4 of the comparative example. After observing the leakage positions of the two membrane electrode 1 by electron microscope, the membrane electrode structure of the embodiment was normal, while the proton membrane ionomer loss and thinning occurred in the comparative example, resulting in leakage.

[0039] The membrane electrode structure is designed with a convex structure matching the flow channel of the bipolar plate at the gas inlet and outlet of the membrane electrode 1, which improves the water distribution state in the membrane electrode 1 and the fuel cell stack, optimizes the water distribution state and uniformity, solves the problem of uneven water distribution inside the membrane electrode 1 and accelerated aging due to dry-wet alternation, avoids the phenomenon of water accumulation and dry-wet alternation in the confluence area of ​​the gas distribution port, thereby improving the performance and durability of the membrane electrode 1 in the self-humidifying fuel cell stack; an arc-shaped convex structure is also designed at the contact boundary between the distribution area and the proton membrane to avoid failure of the proton membrane due to excessive stress; the membrane electrode 1 has a simple design structure, reliable functions and a long service life.

[0040] The above is an exemplary description of the utility model in conjunction with the accompanying drawings. Obviously, the specific implementation of the utility model is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the utility model; or the above concept and technical solution of the utility model are directly applied to other occasions without improvement, they are all within the protection scope of the utility model.

Claims

1. A membrane electrode structure, characterized in that: A reaction zone (2) is provided in the middle of the membrane electrode (1); a hydrogen inlet (3) and a hydrogen outlet (4) are respectively provided at two ends of one side of the membrane electrode (1); and an air inlet (5) and an air outlet (6) are respectively provided at two ends of the other side of the membrane electrode (1); a distribution zone is provided on the membrane electrode (1); the distribution zone comprises a first distribution zone (7) and a second distribution zone (8); the first distribution zone (7) is provided on one side of the hydrogen inlet (3) and the air inlet (5); and the second distribution zone (8) is provided on one side of the hydrogen outlet (4) and the air outlet (6).

2. The membrane electrode structure according to claim 1, characterized in that: The edges of the hydrogen inlet (3) and the air inlet (5) are both provided with a first protrusion (9), and the edges of the hydrogen outlet (4) and the air outlet (6) are both provided with a second protrusion (10).

3. The membrane electrode structure according to claim 2, characterized in that: A bipolar plate is provided outside the membrane electrode (1), and a flow channel (14) is provided on the bipolar plate (13). The flow channels (14) are evenly distributed, and the first protrusion (9) and the second protrusion (10) both correspond to the flow channels (14).

4. The membrane electrode structure according to claim 3, characterized in that: The reaction zone (2) comprises a proton membrane (15), and a third protrusion (11) is provided at the boundary of the proton membrane (15). The third protrusion (11) is an arc-shaped structure, and the third protrusions (11) are evenly distributed.

5. The membrane electrode structure according to claim 4, characterized in that: The first protrusions (9) and the second protrusions (10) are evenly distributed; the first protrusions (9) are semicircular structures, and the second protrusions (10) are arranged in sequence to form a sawtooth structure.

6. The membrane electrode structure according to claim 1, characterized in that: The distribution areas are all square or polygonal.

7. The membrane electrode structure according to claim 6, characterized in that: The ends of the distribution area are all provided with rounded corners.

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