Fuel cell with cathode flow channel split design and gradient distribution of Pt content in catalyst layer

Abstract

The present invention discloses a fuel cell with a cathode flow channel shunt design and a gradient distribution of Pt content in the catalyst layer, which comprises an anode current collector, an anode diffusion layer, a membrane electrode with a gradient platinum content, a cathode diffusion layer, and a cathode current collector in sequence. A main air inlet and at least one shunt air inlet are provided on the cathode current collector of the cathode module constituting the fuel cell to allow air of different flow rates to pass through, and the catalyst concentration of the cathode catalyst layer of the membrane electrode with a gradient platinum content increases from the air inlet to the air outlet. The catalyst layer of the membrane electrode fuel cell with a gradient platinum content of the present invention adopts a gradient distribution, so that the gas at the battery outlet is completely reacted, achieving the effect of uniform utilization of the active area and reducing production costs; the shunt air intake is adopted to change the distribution of the gas in the battery, and the diffusion and mass transfer of the gas in the cathode side diffusion layer is improved, achieving the effect of improving battery performance.

Description

Technical Field

[0001] The invention relates to the technical field of membrane electrode fuel cells with gradient platinum content, and in particular to a fuel cell with a cathode flow channel split design and a gradient distribution of Pt content in a catalyst layer. Background Art

[0002] The membrane electrode of the gradient platinum content membrane electrode fuel cell is composed of three parts: the gradient platinum content membrane electrode, the catalyst layer, and the diffusion layer. It is also the core component of the fuel cell. How to further reduce the production cost of the gradient platinum content membrane electrode fuel cell and improve its performance are two major problems that must be solved in its gradual commercialization process.

[0003] Platinum (Pt) is a commonly used redox catalyst in the electrochemical reaction of hydrogen-oxygen fuel cells. Nowadays, there are many methods to reduce the platinum loading and improve the platinum utilization rate, such as diffusion, spraying, screen printing, electrodeposition, etc. However, platinum is a rare metal and is very expensive, so it is necessary to further reduce the platinum loading and improve the platinum utilization rate based on the existing methods. Summary of the invention

[0004] The purpose of the present invention is to address the technical defects existing in the prior art and to provide a fuel cell with a cathode flow channel diversion design and a gradient distribution of catalyst Pt content on the catalyst layer in the membrane electrode. The fuel cell is composed of a combination of diverted intake air and a gradient distribution of catalyst, which strengthens the diffusion mass transfer in the gas diffusion layer on the cathode side and reduces the Pt content in the catalyst layer while ensuring the utilization rate of Pt.

[0005] The technical solution adopted to achieve the purpose of the present invention is:

[0006] A fuel cell with a cathode flow channel shunt design and a gradient distribution of Pt content in the catalyst layer, which comprises, in sequence, an anode current collecting plate, an anode diffusion layer, a membrane electrode with a gradient platinum content, a cathode diffusion layer, and a cathode current collecting plate. A main air inlet and at least one shunt air inlet are provided on the cathode current collecting plate of the cathode module constituting the fuel cell to allow air of different flow rates to flow in, and the catalyst concentration of the cathode catalyst layer of the membrane electrode with a gradient platinum content increases gradiently from the air inlet to the air outlet.

[0007] Wherein, the split air inlet is located at one side of the main air inlet, arranged in parallel with the main air inlet, and located between the main air inlet and the air outlet.

[0008] Wherein, when there are more than two diversion air inlets, the multiple diversion air inlets are arranged in parallel and spaced apart, and the air flow rate of each diversion air inlet is the same.

[0009] Wherein, the split air inlet is a circular hole formed on the edge of the cathode current collecting plate.

[0010] The fuel cell of the present invention achieves the effect of uniform distribution of reaction gas in the membrane electrode, improving power density and saving the amount of precious metal catalyst Pt by arranging a branch air inlet on the cathode collecting plate, which is distributed on the right side of the main air inlet, and introducing a gradient distribution of Pt catalyst on the membrane electrode catalyst layer.

[0011] In the fuel cell system of the present invention, air enters the fuel cell through the main air inlet and the branch air inlet at the same time, which changes the distribution of the reaction gas in the cell and effectively improves the diffusion mass transfer in the gas diffusion layer. Subsequently, the air passes through the gradient distribution catalyst layer along the span direction, and the trend is that the catalyst content increases layer by layer from the air inlet to the air outlet side, that is, the gradient trend is that the Pt loading is lower near the air inlet, and the Pt loading is higher near the air outlet. Since more Pt particles are distributed in the low oxygen concentration part of the electrode (the battery outlet), the local reaction speed of the electrode can be significantly improved, and the uniform utilization of the active area is guaranteed, which not only saves the Pt loading, but also achieves the purpose of improving performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of the structure of a fuel cell with a cathode flow channel split design and a gradient distribution of Pt content in the catalyst layer of the present invention;

[0013] Figure 2 It is a schematic diagram of the membrane electrode gradient of the present invention;

[0014] Figure 3 A schematic diagram of a cathode current collecting plate with a split air intake structure according to the present invention;

[0015] In the figure: 1-anode end plate; 2-anode current collecting plate; 3-anode diffusion layer; 4-membrane electrode with gradient platinum content; 5-cathode diffusion layer: 6-cathode current collecting plate; 7-cathode end plate; 8-air inlet; 9-diverter air inlet; 10-air outlet. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The fuel cell with a cathode flow channel shunt design and a catalyst layer Pt content gradient distribution of the present invention has a cathode flow channel shunt structure and a catalyst layer Pt content gradient distribution.

[0018] See also Figure 1-3A fuel cell with a cathode flow channel split design and a gradient distribution of Pt content in the catalyst layer, which comprises an anode current collector 2, an anode diffusion layer 3, a membrane electrode with a gradient platinum content 4, a cathode diffusion layer 5, and a cathode current collector 6 in sequence. A main air inlet and at least one split air inlet are provided on the cathode module constituting the fuel cell to allow air of different flow rates to flow in, and the catalyst concentration of the cathode catalyst layer of the membrane electrode with a gradient platinum content 4 increases gradually from the air inlet to the air outlet, such as Figure 1 shown.

[0019] Among them, it further includes an anode end plate 1 and a cathode end plate 7, which are made of aluminum alloy.

[0020] Among them, in the present invention, the flow channel 11 of the fuel cell with a split flow design is formed by a graphite plate material rib plate 12, and the current collector is a gold-plated copper plate. The split flow inlet 9 is located at the circular hole position formed on the edge surface of the cathode current collector for air intake, and its shape is a circle with a diameter of 1 mm, which is basically the same as the main air inlet 8. Figure 3 As shown, this can achieve the purpose of uniform distribution of the reaction gas.

[0021] As a preferred solution, the cathode catalyst layer is divided into three regions from the air inlet to the air outlet, and the Pt catalyst concentration from the air inlet to the air outlet is 0.2 mg / cm 2 , 0.3mg / cm 2 , 0.4mg / cm 2 .

[0022] Among them, the diverter air volume can be set as follows: the main air inlet flow is 60% of the total air flow, one diverter air inlet takes in 40% of the total air volume, or two diverter air inlets are set, each taking in 20% of the total air volume, or three diverter air inlets are set, each taking in 10% of the total air volume.

[0023] In other words, the air intake of multiple branch air inlets is the same, and the total amount maintains a predetermined distribution ratio with the main air inlet. The specific ratio can be 6:4, or 7:3, etc., which is configured according to needs.

[0024] The working principle of the fuel cell with the cathode flow channel shunt design and the gradient distribution of Pt content in the catalyst layer of the present invention is: first, on the anode side, hydrogen enters the battery from the flow channel on the anode side and flows in the anode flow channel. Due to the concentration difference, hydrogen will diffuse to the diffusion layer, diffuse to the anode catalyst layer and undergo oxidation reaction under the action of the catalyst to generate hydrogen protons and electrons. The electrons reach the cathode catalyst layer through the collector plate and the external circuit, and the generated hydrogen protons reach the cathode catalyst layer through the membrane electrode with gradient platinum content. The reaction on the anode side is basically the same as that of the membrane electrode fuel cell with ordinary gradient platinum content.

[0025] The second is the reaction on the cathode side. Air is introduced into the flow channel from the main air inlet and the branch air inlet at the same time. Under the action of concentration difference, the air reaches the cathode catalyst layer through the diffusion layer. The air gradually reacts in the catalyst layer. When it reaches the outlet side, the air concentration is the lowest. At this time, the Pt catalyst concentration in this area is the highest, so that the air reacts with the hydrogen protons transferred from the membrane electrode with gradient platinum content and the electrons transferred from the external circuit under the action of the catalyst to generate water and release heat. At the same time, the external circuit outputs electrical energy to do work externally.

[0026] Since the gas diffusion mass transfer in the cathode diffusion layer and catalyst layer of the membrane electrode fuel cell with enhanced gradient platinum content is helpful to improve the battery performance, therefore, in the present invention, through the reasonable optimization design of the cathode flow channel, such as the cathode flow channel diversion design, a number of diversion air inlets are added, which can change the distribution of the reaction gas in the battery and discharge excess liquid water, effectively improve the diffusion mass transfer in the gas diffusion layer on the cathode side, and achieve the purpose of improving the battery performance.

[0027] The present invention sets a diversion air inlet on the cathode collecting plate, which is distributed on the right side of the main air inlet. Based on this structure, a gradient distribution of Pt catalyst on the membrane electrode catalyst layer is introduced to achieve the effect of uniform distribution of reaction gas in the membrane electrode, improving power density and saving the amount of precious metal catalyst Pt.

[0028] The novel fuel cell of the present invention combines the split air intake with the gradient catalytic layer, which can improve the power density and save the amount of the precious metal catalyst Pt, thereby reducing the production cost.

[0029] The catalyst layer of the membrane electrode fuel cell with a novel gradient platinum content of the present invention adopts a gradient distribution, so that the gas at the outlet of the battery is completely reacted. Compared with the ordinary catalyst layer without a gradient distribution, it achieves the effect of uniform utilization of the active area and reduced production costs.

[0030] The flow field plate of the novel membrane electrode fuel cell with gradient platinum content of the present invention adopts a split air intake method on the cathode. Compared with the ordinary flow field plate with a single air inlet, it changes the distribution of gas in the battery and improves the diffusion and mass transfer of gas in the diffusion layer on the cathode side, thereby achieving the effect of improving battery performance.

[0031] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fuel cell with a cathode flow channel split design and a gradient distribution of Pt content in the catalyst layer, comprising, in sequence, an anode current collector, an anode diffusion layer, a membrane electrode with a gradient platinum content, a cathode diffusion layer, and a cathode current collector, characterized in that: A main air inlet and at least one branch air inlet are provided on the cathode collecting plate of the cathode module constituting the fuel cell to allow air of different flow rates to pass through, and the catalyst concentration of the cathode catalyst layer of the membrane electrode with a gradient platinum content increases gradiently from the air inlet to the air outlet; the branch air inlet is located on one side of the main air inlet, arranged in parallel with the main air inlet, and located between the main air inlet and the main air outlet; when there are more than two branch air inlets, the multiple branch air inlets are arranged in parallel and spaced apart, and the air flow rate of each branch air inlet is the same; the branch air inlet is a circular hole formed on the edge of the cathode collecting plate.

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