Gas diffusion layer with gradient structure for air cooling

Abstract

The invention discloses an air cooling gas diffusion layer with a gradient structure, and relates to the technical field of fuel cells, the air cooling gas diffusion layer comprises a membrane electrode, the membrane electrode is sequentially composed of an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer which are arranged in a trapezoid shape; through the gradient hydrophilic and hydrophobic structural design of the cathode gas diffusion layer and the overall hydrophilic treatment of the anode gas diffusion layer, the water balance management problem of the air-cooled fuel cell under the variable working condition is effectively solved by matching with the trapezoidal structural layout, the membrane electrode can be kept properly wet under the dry condition, the proton exchange membrane is prevented from being dehydrated, and the service life of the membrane electrode is prolonged. And liquid water can be quickly discharged under a high-humidity condition, the cathode is prevented from being flooded, and meanwhile, the trapezoidal structure enhances the uniformity of reaction gas distribution and the product discharge efficiency, so that the working performance and the operation stability of the fuel cell are remarkably improved, and the service life of the fuel cell is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a gradient structure gas diffusion layer for air cooling. Background Technology

[0002] The gas diffusion layer is one of the core components of a proton exchange membrane fuel cell. It is usually made of porous conductive material and is located between the bipolar plate flow field and the catalyst layer. Its main functions include conducting electrons, supporting the catalyst layer, transporting reactant gases and expelling reaction products. It also needs to have appropriate thermal management capabilities and mechanical strength. In air-cooled fuel cells, the gas diffusion layer also plays an important role in hydrothermal management, and its performance directly affects the overall efficiency and stability of the cell.

[0003] During the operation of a fuel cell, the anode gas diffusion layer uniformly diffuses hydrogen from the flow field to the anode catalyst layer, while simultaneously expelling the generated water vapor or liquid water. The cathode gas diffusion layer transports oxygen from the flow field to the cathode catalyst layer and expelles the water generated by the electrochemical reaction. The gas diffusion layer needs to maintain an appropriate moisture balance. Too much water will cause pore blockage and hinder gas transport, while too little water will cause the proton exchange membrane to dehydrate, resulting in a decrease in ionic conductivity. This balance process is mainly achieved through the pore structure and surface hydrophilic and hydrophobic properties of the gas diffusion layer itself.

[0004] Currently, most traditional fuel cell gas diffusion layers employ uniform hydrophobic treatment. While this method is effective in preventing flooding, it is difficult to adapt to the complex operating requirements of air-cooled fuel cells under varying conditions. In particular, under low humidity operating conditions, the uniformly hydrophobic gas diffusion layer cannot effectively maintain the humidity of the membrane electrode assembly, which can easily lead to dehydration of the proton exchange membrane. Under high humidity conditions, its drainage capacity is insufficient, which can easily cause cathode flooding. In addition, existing gas diffusion layers lack intelligent moisture regulation capabilities and cannot adaptively adjust water management strategies according to changes in operating conditions. This severely limits the performance improvement and commercial application of air-cooled fuel cells. Summary of the Invention

[0005] The purpose of this invention is to provide a gradient structure gas diffusion layer for air cooling to solve the technical problem that the existing technology is difficult to adapt to the complex working requirements of air-cooled fuel cells under varying operating conditions; especially under low humidity operating conditions, the gas diffusion layer with uniform hydrophobic treatment cannot effectively maintain the humidity of the membrane electrode, which easily leads to the dehydration of the proton exchange membrane.

[0006] The technical problem to be solved by this invention can be achieved through the following technical solution: A gradient-structured air-cooled gas diffusion layer includes: a membrane electrode, which is sequentially composed of a trapezoidal anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a trapezoidal cathode catalyst layer, and a cathode gas diffusion layer; the cathode gas diffusion layer itself has a hydrophilicity that decreases gradually from the inner side facing the cathode catalyst layer to the outer side away from the cathode catalyst layer; the anode gas diffusion layer itself has hydrophilic properties; a hydrogen inlet pipe, the outlet of which is connected to the outer trapezoidal surface of the anode gas diffusion layer for supplying hydrogen reactant gas to the anode side; an anode exhaust port, the inlet of which is connected to the outer trapezoidal surface of the anode gas diffusion layer for discharging unreacted excess hydrogen; an air inlet pipe, the outlet of which is connected to the outer trapezoidal surface of the cathode gas diffusion layer for supplying oxygen-containing reactant gas to the cathode side; and a cathode exhaust port, the inlet of which is connected to the outer trapezoidal surface of the cathode gas diffusion layer for discharging reactant tail gas and liquid water from the cathode side.

[0007] As a further aspect of the present invention, the decrease in the hydrophilicity gradient of the cathode gas diffusion layer is achieved by the change in the hydrophilic and hydrophobic properties of its internal material.

[0008] As a further aspect of the present invention: the cathode exhaust port is connected to a water collector or water outlet pipe for collecting and discharging liquid water discharged from the outside of the cathode gas diffusion layer.

[0009] As a further aspect of the present invention: the cathode gas diffusion layer itself has a hydrophilicity that decreases gradually from one side to the other, and its overall shape is trapezoidal.

[0010] As a further aspect of the present invention: the anode gas diffusion layer itself has hydrophilic properties, and its overall shape is trapezoidal.

[0011] As a further aspect of the present invention: the membrane electrode is composed of an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode gas diffusion layer arranged in a trapezoidal shape in sequence; and the cathode gas diffusion layer has hydrophilic-hydrophobic gradient characteristics, and the anode gas diffusion layer has hydrophilic characteristics.

[0012] As a further aspect of the present invention: the trapezoidal layers have the same tilt angle and direction, forming an overall wedge-shaped structure.

[0013] The beneficial effects of this invention are as follows: By designing the gradient hydrophilic and hydrophobic structure of the cathode gas diffusion layer and the overall hydrophilic treatment of the anode gas diffusion layer, combined with the trapezoidal structure layout, the water balance management problem of air-cooled fuel cells under varying operating conditions is effectively solved. It can maintain appropriate moisture of the membrane electrode under dry conditions to prevent dehydration of the proton exchange membrane, and can quickly discharge liquid water under high humidity conditions to avoid cathode flooding. At the same time, the trapezoidal structure enhances the uniformity of the distribution of reactant gases and the efficiency of product discharge, thereby significantly improving the working performance, operational stability and service life of the fuel cell. Attached Figure Description

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; In the diagram: 1. Membrane electrode; 2. Anode gas diffusion layer; 3. Anode catalyst layer; 4. Proton exchange membrane; 5. Cathode catalyst layer; 6. Cathode gas diffusion layer; 7. Hydrogen inlet pipe; 8. Anode exhaust port; 9. Air inlet pipe; 10. Cathode exhaust port. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figure 1 As shown, a gradient structure gas diffusion layer for air cooling includes: a membrane electrode 1, which is composed of a trapezoidal anode gas diffusion layer 2, an anode catalyst layer 3, a proton exchange membrane 4, a trapezoidal cathode catalyst layer 5, and a cathode gas diffusion layer 6; the cathode gas diffusion layer 6 itself has a hydrophilicity that decreases gradually from the inner side facing the cathode catalyst layer 5 to the outer side away from the cathode catalyst layer 5; the anode gas diffusion layer 2 itself has hydrophilic properties; a hydrogen inlet pipe 7, whose outlet is connected to the outer trapezoidal surface of the anode gas diffusion layer 2, for supplying hydrogen reaction gas to the anode side; an anode exhaust port 8, whose inlet is connected to the outer trapezoidal surface of the anode gas diffusion layer 2, for discharging unreacted excess hydrogen; an air inlet pipe 9, whose outlet is connected to the outer trapezoidal surface of the cathode gas diffusion layer 6, for supplying oxygen-containing reaction gas to the cathode side; and a cathode exhaust port 10, whose inlet is connected to the outer trapezoidal surface of the cathode gas diffusion layer 6, for discharging reaction tail gas and liquid water from the cathode side.

[0018] Using carbon fiber paper with a thickness of 0.2-0.4mm as the substrate, it is first processed into a trapezoidal structure with an inclination angle of 30-45 degrees; the cathode gas diffusion layer 6 achieves a decrease in hydrophilicity from the inside to the outside through a gradient coating process, with the inner area coated with a slurry containing 10-15% hydrophilic material and the outer area coated with a slurry containing 20-25% hydrophobic material; the anode gas diffusion layer 2 is impregnated with a solution containing 8-12% hydrophilic material; after the components are assembled in sequence, the hydrogen inlet pipe 7 and the anode exhaust port 8 are connected to the trapezoidal surface of the anode gas diffusion layer 2 by flange connection, and the air inlet pipe 9 and the cathode exhaust port 10 are connected to the cathode gas diffusion layer 6 in the same way; The decrease in hydrophilicity gradient of the cathode gas diffusion layer 6 is achieved through the change in the hydrophilic and hydrophobic properties of its internal material.

[0019] A multi-stage spraying process is adopted, using programmable automatic spraying equipment. By controlling the spraying path and material concentration, the PTFE concentration in the cathode gas diffusion layer 6 increases from 5% to 20% from the inside to the outside, while the concentration of hydrophilic agent SiO2 decreases from 15% to 3%, forming a continuous hydrophilic-hydrophobic gradient distribution.

[0020] The cathode exhaust port 10 is connected to a water collector or water outlet pipe for collecting and discharging liquid water discharged from the outside of the cathode gas diffusion layer 6.

[0021] The lower end of the cathode exhaust port 10 is connected to a water collector made of polytetrafluoroethylene. The water collector has a guide channel with an inclination of 10-15 degrees inside and a drain valve at the bottom, which can automatically collect and periodically discharge liquid water. The water collector has a volume of 50-200ml, which can be selected according to the battery power.

[0022] The cathode gas diffusion layer 6 itself has a hydrophilicity that decreases gradually from one side to the other, and its overall shape is trapezoidal.

[0023] TGP-H-060 carbon fiber paper is used and cut into a trapezoid with a bottom edge of 100mm, a top edge of 80mm, and a height of 50mm. A multi-stage impregnation process is used, with the inner area impregnated with a hydrophilic solution containing 15% nano-silica, the outer area impregnated with a hydrophobic solution containing 20% ​​PTFE, and the middle area using a mixed solution with a transitional concentration. After drying and heat treatment, a gradient hydrophilic and hydrophobic properties are formed.

[0024] The anode gas diffusion layer 2 has hydrophilic properties and is arranged in a trapezoidal shape.

[0025] Carbon fiber paper of the same specification is processed into trapezoids of the same size; the whole is impregnated with a hydrophilic solution containing 10% titanium dioxide for 30 minutes, then dried at 120℃ for 1 hour, and then heat-treated at 350℃ for 30 minutes to ensure that the hydrophilic material is firmly loaded on the substrate.

[0026] The membrane electrode 1 is composed of a trapezoidal anode gas diffusion layer 2, an anode catalyst layer 3, a proton exchange membrane 4, a trapezoidal cathode catalyst layer 5, and a cathode gas diffusion layer 6; and the cathode gas diffusion layer 6 has hydrophilic-hydrophobic gradient characteristics, while the anode gas diffusion layer 2 has hydrophilic characteristics.

[0027] Each component is processed into a trapezoidal shape using the same mold. The catalyst slurry is coated on both sides of the proton exchange membrane 4 using a screen printing process for the anode catalyst layer 3 and the cathode catalyst layer 5. Then, the anode gas diffusion layer 2, the proton exchange membrane 4 with the catalyst layer, and the cathode gas diffusion layer 6 are aligned and assembled in sequence. The membrane electrode 1 is formed by pressing at 130°C and 1MPa pressure for 5 minutes using a hot pressing process.

[0028] The trapezoidal layers have the same tilt angle and direction, forming an overall wedge-shaped structure.

[0029] All functional layers are machined with a uniform 30-degree tilt angle. During assembly, a positioning fixture with a 30-degree tilt angle is used to ensure that each layer is fully aligned to form a complete wedge structure. The inclined surface of the wedge structure is conducive to the uniform distribution of gas and the directional discharge of liquid.

[0030] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A gradient structure gas diffusion layer for air cooling, characterized in that, include: The membrane electrode (1) is composed of a trapezoidal anode gas diffusion layer (2), an anode catalyst layer (3), a proton exchange membrane (4), a trapezoidal cathode catalyst layer (5), and a cathode gas diffusion layer (6). The cathode gas diffusion layer (6) has a hydrophilicity that decreases gradually from the inner side facing the cathode catalyst layer (5) to the outer side away from the cathode catalyst layer (5). The anode gas diffusion layer (2) has hydrophilic properties. The hydrogen inlet pipe (7) has its outlet connected to the outer trapezoidal surface of the anode gas diffusion layer (2) for supplying hydrogen reaction gas to the anode side. The anode exhaust port (8) has its inlet connected to the outer trapezoidal surface of the anode gas diffusion layer (2) for discharging unreacted excess hydrogen gas. The air inlet pipe (9) has its outlet connected to the outer trapezoidal surface of the cathode gas diffusion layer (6) for supplying oxygen-containing reaction gas to the cathode side. The cathode exhaust port (10) has its inlet connected to the outer trapezoidal surface of the cathode gas diffusion layer (6) for discharging reaction tail gas and liquid water from the cathode side.

2. The gradient structure gas diffusion layer for air cooling according to claim 1, characterized in that, The decrease in hydrophilicity gradient of the cathode gas diffusion layer (6) is achieved by the change in the hydrophilic and hydrophobic properties of its internal material.

3. The gradient structure gas diffusion layer for air cooling according to claim 2, characterized in that, The cathode exhaust port (10) is connected to a water collector or water outlet pipe for collecting and discharging liquid water discharged from the outside of the cathode gas diffusion layer (6).

4. The gradient structure gas diffusion layer for air cooling according to claim 3, characterized in that, The cathode gas diffusion layer (6) itself has hydrophilicity that decreases gradually from one side to the other, and its overall shape is trapezoidal.

5. The gradient structure gas diffusion layer for air cooling according to claim 4, characterized in that, The anode gas diffusion layer (2) has hydrophilic properties and is arranged in a trapezoidal shape.

6. The gradient structure gas diffusion layer for air cooling according to claim 5, characterized in that, The membrane electrode (1) is composed of an anode gas diffusion layer (2) arranged in a trapezoidal shape, an anode catalyst layer (3), a proton exchange membrane (4), a cathode catalyst layer (5) arranged in a trapezoidal shape, and a cathode gas diffusion layer (6); and the cathode gas diffusion layer (6) has hydrophilic and hydrophobic gradient characteristics, and the anode gas diffusion layer (2) has hydrophilic characteristics.

7. The gradient structure gas diffusion layer for air cooling according to claim 6, characterized in that, The trapezoidal layers have the same tilt angle and direction, forming an overall wedge-shaped structure.

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