A method for preparing a fuel cell CCM

Abstract

This invention belongs to the field of fuel cell technology, and particularly relates to a catalyst slurry spraying process and a method for preparing a fuel cell CCM. The spraying path includes an interdigitated serpentine path I and a serpentine path II, both of which include straight paths and turning paths. This invention controls the spraying speed and slurry flow rate during the catalyst layer spraying process, employs an interdigitated serpentine path for spraying, and controls the temperature of the drying platform in zones. This makes the spraying speed of the turning path 1.1-2 times faster than that of the straight path, and the flow rate of the turning path is 0.1-0.9 times that of the straight path. A blank area is left between the two sequentially sprayed straight paths to avoid slurry accumulation during the turning path spraying, thus solving the problem of excessively thick catalyst layer at the catalyst layer edge caused by traditional uniform speed / uniform flow rate spraying.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and particularly relates to a catalyst slurry spraying process and a method for preparing fuel cell CCM. Background Technology

[0002] Hydrogen energy, as an important member of the renewable energy family, has gradually gained prominence in recent years, and fuel cells, as the most efficient energy conversion device for hydrogen utilization, have also seen rapid technological development. The pioneering commercialization of Toyota's fuel cell vehicles in Japan has spurred a global surge in fuel cell technology development.

[0003] A proton exchange membrane fuel cell (PEMFC) consists of dozens to hundreds of membrane electrode assemblies (MEAs) and bipolar plates connected in series. The two ends of the cell are sealed and clamped together with insulating end plates. During operation, gas is distributed to each MEA via a shared pipeline for reaction, and the water generated by each cell flows out through the same pipeline. To ensure efficient gas transport, the generated water is often discharged in a pulsed manner. During this pulsed process, the pressure in the cell's gas chamber fluctuates, and the wet / dry environment of the MEAs changes drastically, causing stress on the MEAs. Furthermore, during stack assembly, the MEAs are subjected to greater pressure around their perimeter due to assembly forces, while the central area experiences less stress. This stress variation weakens the perimeter of the MEAs, accelerating mechanical degradation during fluctuating operating conditions and potentially leading to fatal damage such as proton rupture or perforation. The CCM (Chemical Electrode Membrane) is often referred to as the three-in-one membrane electrode assembly in fuel cells, consisting of a proton exchange membrane and two catalytic layers. Its preparation methods include spraying, transfer printing, and coating. Spraying is the easiest method to implement in laboratory testing and small-batch production, and is therefore widely used.

[0004] In the traditional spray coating process for preparing CCM, the catalyst slurry is directly sprayed onto the membrane surface in a cross-hatching pattern according to the required size and shape. Multiple layers are applied to achieve the desired catalyst loading and thickness. During the spraying process, the solvent evaporates rapidly under the influence of a heating stage, ensuring the membrane does not swell or deform. However, this traditional spraying method results in slower catalyst slurry evaporation at the edges of the catalyst layer compared to the center, leading to a thicker catalyst layer and increased susceptibility to membrane swelling and damage. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a spraying process in which catalyst slurry is sprayed onto both sides of a proton exchange membrane using two interdigitated serpentine paths. The spraying speed of the nozzles and the slurry flow rate are controlled separately, ensuring that the spraying speed of the turning paths is higher than that of the straight paths, and the slurry flow rate of the turning paths is lower than that of the straight paths. A gap is left between two adjacent straight paths, which is then covered by the other interdigitated serpentine path. This avoids edge aggregation caused by slurry overlap, thereby preventing high catalyst concentration and membrane swelling at the edges.

[0006] In fuel cell technology, when using the spray coating method to prepare the CCM, the catalyst slurry is directly sprayed onto the proton exchange membrane surface. Heating and vacuum adsorption are necessary to prevent membrane swelling during the spraying process, and the slurry flow rate, spraying speed, and heating temperature must be coordinated. In conventional catalyst layer spraying, the nozzle completes the entire process at a uniform slurry flow rate, and the two slurries sprayed sequentially overlap. This causes slurry to accumulate more on the membrane surface at nozzle bends, resulting in slower evaporation and unavoidable swelling of the membrane at the catalyst layer edges, thus affecting reliability. Furthermore, the thickness of the catalyst layer at the edges is higher than in the center due to the accumulation of the slurry.

[0007] Based on the above ideas, this invention increases the nozzle speed and reduces the slurry flow rate during the spraying process at the turning path, so that two adjacent straight paths maintain a certain distance and leave a blank area, thereby avoiding the accumulation of liquid on the film surface at the turning point, ensuring the rapid evaporation of solvent, improving the consistency of the formed catalyst layer thickness, and avoiding the decrease in reliability caused by swelling.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] The present invention provides a catalyst slurry spraying process, wherein the spraying path includes an interlaced serpentine path I and a serpentine path II, wherein both the serpentine path I and the serpentine path II include a straight path and a turning path;

[0010] The spraying process includes the following steps:

[0011] (1) Spraying of serpentine path I: The catalyst slurry is sprayed onto both sides of the proton exchange membrane in a straight path, and then sprayed in a reverse straight path after a turning path. The above spraying method is repeated in sequence.

[0012] (2) Spraying of serpentine path II: The gaps between two adjacent straight paths in serpentine path I are covered by serpentine path II, and the edges of serpentine path II and the straight and turning paths of serpentine path I are partially overlapped.

[0013] The spraying speed for the straight path is v1, and the spraying speed for the turning path is v2, where v2:v1 = 1.1-2;

[0014] The slurry flow velocity along the straight path is α1, and the slurry flow velocity along the turning path is α2, where α1:α2 = 0.1-0.9;

[0015] In the serpentine path I and serpentine path II, the distance between two adjacent straight paths is 10-40mm, and the radius of the turning path is 5-20mm.

[0016] In the above technical solution, the overlap width of the straight path is 1 / 3 to 1 / 2 of the width of the straight path, and the overlap width of the turning path is 1 / 3 to 1 / 2 of the width of the turning path.

[0017] In the above technical solution, the spraying speed is 10-500mm / s.

[0018] In the above technical solution, the slurry flow rate is 0.1-10 ml / min.

[0019] Another aspect of the present invention provides a method for preparing a fuel cell CCM, the method comprising the following steps:

[0020] (1) Preparation of catalyst slurry;

[0021] (2) The catalyst slurry is sprayed onto both sides of the proton exchange membrane using the above-mentioned spraying process;

[0022] (3) Drying to obtain CCM.

[0023] In the above technical solution, the preparation method of the catalyst slurry in step (1) includes the following steps:

[0024] (a) Wet the catalyst with deionized water at a weight ratio of 5-10:1.

[0025] (b) Add a dispersant, with a mass ratio of dispersant to catalyst of 20-40:1, and mix well;

[0026] (c) Add perfluorosulfonic acid solution, wherein the mass ratio of perfluorosulfonic acid solution to carbon in the catalyst is 0.5-1:1;

[0027] (d) The catalyst slurry was obtained by ultrasonic dispersion for 20-40 min.

[0028] In the above technical solution, the drying process in step (3) includes two stages:

[0029] a) The first stage is drying during the spraying process. The film is placed on a heating plate with a vacuum function and infrared lamps are placed around the spraying area so that the edge temperature of the spraying area is higher than the center temperature.

[0030] b) The second stage is drying after spraying. A vacuum oven is used to dry the CCM at 80-100℃ and 0.01-0.1 bar.

[0031] In the above technical solution, in step (a), the catalyst is any one of Pt / C and its binary or ternary alloy catalysts.

[0032] In the above technical solution, the dispersant in step (b) is one or a mixture of two of ethanol, isopropanol, and n-propanol.

[0033] The beneficial effects of this invention are as follows:

[0034] This invention addresses the problem of excessively thick catalyst layer at the edges caused by traditional uniform speed / uniform flow rate spraying. By controlling the spraying speed and slurry flow rate during the catalyst layer spraying process, employing an interlaced serpentine spraying path, and controlling the temperature of the drying platform in zones, the spraying speed on the turning path is 1.1-2 times faster than that on the straight path. The flow rate of the turning path spraying is 0.1-0.9 times that of the straight path spraying. A blank area is left between the two consecutive straight paths to avoid slurry accumulation during the turning path spraying.

[0035] The present invention uses a zoned temperature-controlled heating platform to prepare CCM, so that the temperature of the periphery of the spraying area is higher than that of the center. This allows the solvent in the catalyst slurry sprayed to the periphery to evaporate quickly, thereby effectively avoiding the film swelling problem caused by slurry accumulation at the edge of conventional spraying. Attached Figure Description

[0036] Figure 1 This invention relates to a catalyst slurry spraying process;

[0037] Where a is serpentine path I and b is serpentine path II;

[0038] Figure 2 Here are the spraying effect diagrams for Example 1: a is the effect diagram of spraying serpentine path I, and b is the effect diagram after spraying serpentine path II.

[0039] Figure 3 This is a diagram showing the spraying effect of Comparative Example 1;

[0040] Figure 4 This is a spraying effect diagram of Example 2;

[0041] Figure 5 This is a diagram showing the spraying effect of Comparative Example 2. Detailed Implementation

[0042] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0043] Example 1

[0044] Preparation of catalyst slurry: 1g Pt / C catalyst (Pt content is 50wt.%), 8g perfluorosulfonic acid resin (concentration is 5wt.%), 1g deionized water, and 40g isopropanol are mixed evenly under ultrasonic vibration to form catalyst slurry.

[0045] A 25 μm thick proton exchange membrane was laid flat on the hot plate of a spraying machine. The spraying speed for the straight path of serpentine path I and serpentine path II nozzles was set to 200 mm / s, and the spraying speed for the turning path was set to 100 mm / s. The slurry flow rate was set to 4 ml / min for the straight path spraying and 3 ml / min for the turning path spraying. The width of the slurry sprayed onto the membrane surface was 20 mm, and the spacing between two adjacent straight paths was 30 mm. The heating plate temperature was set to 70℃, and infrared lamps were placed around it. The completed serpentine path I spraying photograph is shown in Figure 2a. The blank area of ​​serpentine path I was covered by the interlaced serpentine path II, and the spraying photograph is shown in Figure 2a. Figure 2 As shown in b.

[0046] After the entire catalyst layer is sprayed, the thickness of the sprayed CCM is tested. The thickness of the middle and edge of the method of the present invention is 5μm±0.1.

[0047] Comparative Example 1

[0048] The traditional method of spraying with uniform speed, uniform flow, and no interruption is used. Spraying photos are shown below. Figure 3 As shown.

[0049] After the entire catalyst layer was sprayed, the thickness of the sprayed CCM was tested. The thickness in the middle of Comparative Example 1 was 5 μm ± 0.1, and the thickness at the edge was 5.5 μm ± 0.1.

[0050] Example 2

[0051] Preparation of catalyst slurry: 1g Pt / C catalyst (Pt content is 50wt.%), 8g perfluorosulfonic acid resin (concentration is 5wt.%), 10g deionized water, and 10g ethanol are mixed evenly under ultrasonic vibration to form catalyst slurry.

[0052] A 15μm thick proton exchange membrane was laid flat on the hot table of a spraying machine. The spraying speed for the straight path of serpentine path I and serpentine path II nozzles was set to 100mm / s, and the spraying speed for the turning path was set to 200mm / s. The slurry flow rate was set to 2ml / min during straight path spraying and 1ml / min during turning path spraying. The width of the slurry sprayed onto the membrane surface was 10mm, and the spacing between adjacent straight paths was 10mm. The heating table temperature was set to 70℃, and infrared lamps were placed around it. After the spraying of serpentine path I was completed, the blank area of ​​serpentine path I was covered by the interlaced serpentine path II. A spraying photograph of Example 2 is shown in Figure 4.

[0053] Comparative Example 2

[0054] Under the same conditions, uniform speed and uniform flow rate spraying were used for comparison. Spraying photos are shown below. Figure 5 As shown.

[0055] Depend on Figure 4 and Figure 5 As can be seen, the catalyst layer sprayed using the segmented control method does not accumulate at the turning point, while the catalyst layer sprayed using the uniform speed process shows obvious unevenness in thickness at the turning point.

[0056] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A catalyst slurry spray process characterized by, The spraying path includes intersecting serpentine path I and serpentine path II, both of which include straight paths and turning paths; The spraying process includes the following steps: (1) Spraying of serpentine path I: The catalyst slurry is sprayed onto both sides of the proton exchange membrane in a straight path, and then sprayed in a turning path and then sprayed in the opposite straight path. The above spraying method is repeated in sequence. (2) Spraying of serpentine path II: There is a gap between two adjacent straight paths in serpentine path I, which is covered by serpentine path II, and the edges of serpentine path II and the straight and turning paths of serpentine path I are partially overlapped. The spraying speed for the straight path is v1, and the spraying speed for the turning path is v2, where v2:v1 = 1.1-2; The slurry flow velocity along the straight path is α1, and the slurry flow velocity along the turning path is α2, where α2:α1 = 0.1-0.9; In the serpentine path I and serpentine path II, the distance between two adjacent straight paths is 10-40mm, and the radius of the turning path is 5-20mm; The overlap width of the straight path is 1 / 3 to 1 / 2 of the width of the straight path, and the overlap width of the turning path is 1 / 3 to 1 / 2 of the width of the turning path.

2. The spray process of claim 1, wherein, The spraying speed is 10-500mm / s.

3. The spray process of claim 2, wherein, The slurry flow rate is 0.1-10 ml / min.

4. A method of making a fuel cell CCM, characterized by, The method includes the following steps: (1) Preparation of catalyst slurry; (2) The catalyst slurry is sprayed onto both sides of the proton exchange membrane using the spraying process described in any one of claims 1-3; (3) Drying to obtain CCM.

5. The preparation method according to claim 4, characterized in that, The preparation method of the catalyst slurry in step (1) includes the following steps: (a) Wet the catalyst with deionized water at a weight ratio of 5-10:

1. (b) Add a dispersant, with a mass ratio of dispersant to catalyst of 20-40:1, and mix well; (c) Add perfluorosulfonic acid solution, wherein the mass ratio of perfluorosulfonic acid solution to carbon in the catalyst is 0.5-1:1; (d) The catalyst slurry was obtained by ultrasonic dispersion for 20-40 min.

6. The preparation method according to claim 4, characterized in that, The drying process in step (3) includes two stages: a) The first stage is drying during the spraying process. The film is placed on a heating plate with a vacuum function and infrared lamps are placed around the spraying area so that the edge temperature of the spraying area is higher than the center temperature. b) The second stage is drying after spraying. A vacuum oven is used to dry the CCM at 80-100℃ and 0.01-0.1 bar.

7. The preparation method according to claim 5, characterized in that, In step (a), the catalyst is any one of Pt / C and its binary or ternary alloy catalysts.

8. The preparation method according to claim 5, characterized in that, In step (b), the dispersant is one or a mixture of two of ethanol, isopropanol, and n-propanol.

Images