Proton exchange membrane fuel cell with directly added ionomer and preparation method of proton exchange membrane fuel cell
By filling ionomers in the macropores of the catalyst support to form an ionomer concentration gradient, the problem of ionomers covering the catalyst active sites in the prior art is solved, and the catalyst activity and battery performance are improved.
Patent Information
- Application Number
- CN202510235560.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2025-05-23
AI Technical Summary
In the existing method of preparing the catalytic layer of the proton exchange membrane fuel cell (PEMFC) electrode, the ionomer can easily cover the active site of the catalyst, resulting in kinetic loss, and it is difficult to effectively control the distribution of the ionomer, affecting the performance of the battery.
The method of direct addition of ionomers is used to fill the macropores of the catalyst support to form an ionomer concentration gradient to avoid blockage of micropores and mesopores, ensure the opening of the proton transfer channel, and maintain the porous structure of the catalyst layer.
It effectively reduces the direct contact between the ionomer and the Pt surface, reduces the toxicity of the active site, improves the activity and stability of the catalyst, optimizes the catalytic layer structure, and improves the performance of the fuel cell.
Smart Images
Figure CN120033254A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of fuel cells, and in particular relates to a proton exchange membrane fuel cell with direct ionomer addition and a preparation method thereof. Background Art
[0002] As a highly efficient energy conversion device, proton exchange membrane fuel cells (PEMFCs) have broad application prospects in the field of renewable energy due to their advantages such as low operating temperature, high power density, and environmental friendliness. The existing method for preparing the electrode catalyst layer of PEMFC is usually to combine ionomers (for example, Nafion) with supported catalysts to form a catalyst ink dispersion, and deposit it on a membrane or gas diffusion layer to form a catalyst layer. This method causes the sulfonic acid groups in the ionomer to be strongly adsorbed on the Pt surface, thereby poisoning the active sites and causing kinetic losses. On the other hand, in order to form an effective electrocatalytic interface and ensure efficient proton transport, the catalyst and ionomer must be in close contact. Therefore, the distribution of ionomers in the catalyst layer must be optimized to achieve the best balance between avoiding poisoning of the catalyst active sites and ensuring proton transport. Existing research is committed to reducing the poisoning effect of ionomers on catalysts from aspects such as material and structure optimization, but there is still a lack of a simple and efficient method for preparing electrode catalyst layers that can effectively control the distribution of ionomers, improve the catalyst layer structure, and thus optimize battery performance. Summary of the invention
[0003] The present invention aims at the problem of ionomer covering the active sites of the catalyst in the existing preparation method of the PEMFC electrode catalyst layer, and proposes a proton exchange membrane fuel cell with direct addition of ionomer and a preparation method thereof. In the catalyst carrier, there are mainly three kinds of pores: micropores (<2 nm) formed in the primary carbon particles, mesopores (2-20 nm) formed between the primary particles, and macropores (>20 nm) formed by the aggregation of primary carbon particles. This direct addition method of ionomer mainly fills the macropores, thereby avoiding the blockage of micropores and mesopores. While connecting the Pt / C catalyst to provide a channel for proton transfer, it can also ensure that there are enough gaps in the catalyst layer to achieve unimpeded mass transfer of gas. Therefore, this direct addition method of ionomer not only avoids the problem of catalyst poisoning caused by direct contact between ionomer and Pt in the traditional catalyst ink dispersion by forming an ionomer concentration gradient, but also ensures the mass transfer performance, and improves the battery performance by improving the structure of the electrode catalyst layer.
[0004] The technical solution of the present invention is as follows:
[0005] A proton exchange membrane fuel cell with direct addition of ionomer is prepared by the following steps:
[0006] Step 1, catalyst coating: first take Pt / C catalyst, use ultrapure water and isopropanol as solvents to prepare catalyst ink; after the catalyst ink is evenly dispersed by ultrasonic, take carbon paper containing a diffusion layer, and use an ultrasonic sprayer to evenly spray the evenly dispersed catalyst ink on the surface of the carbon paper. After spraying, continue to dry to fully evaporate the solvent and form a uniform catalytic layer.
[0007] Step 2: Directly add the ionomer: After the catalyst layer is dry, use a brush to evenly coat the Nafion solution on the catalyst layer, control the coating speed and pressure so that the Nafion directly forms a uniform thin layer on the catalyst layer surface; or immerse the carbon paper sprayed with the catalyst surface in the Nafion solution, control the solution concentration and immersion time, so that the Nafion directly forms a uniform thin layer on the catalyst layer surface.
[0008] Step 3: Drying: Dry the coated electrode to allow Nafion to evenly penetrate into the catalyst layer and tightly bond with the catalyst.
[0009] Step 4: hot pressing: hot pressing the prepared electrode and Nafion-HP proton exchange membrane, taking them out and cooling them to room temperature to obtain a proton exchange membrane fuel cell with direct addition of ionomer.
[0010] In the above technical solution, when the relative humidity of the proton exchange membrane fuel cell reaches 65%, the peak power density is 1.20 W / cm².
[0011] In the above technical solution, the electrochemical active area of the proton exchange membrane fuel cell is 33.5 m 2 g -1 .
[0012] A method for preparing a proton exchange membrane fuel cell with direct addition of ionomer comprises the following steps:
[0013] Step 1, catalyst coating: first take Pt / C catalyst, use ultrapure water and isopropanol as solvents to prepare catalyst ink; after the catalyst ink is evenly dispersed by ultrasonic, take carbon paper containing a diffusion layer, and use an ultrasonic sprayer to evenly spray the evenly dispersed catalyst ink on the surface of the carbon paper. After spraying, continue to dry to fully evaporate the solvent and form a uniform catalytic layer.
[0014] Step 2: Directly add the ionomer: After the catalyst layer is dry, use a brush to evenly coat the Nafion solution on the catalyst layer, control the coating speed and pressure so that the Nafion directly forms a uniform thin layer on the catalyst layer surface; or immerse the carbon paper sprayed with the catalyst surface in the Nafion solution, control the solution concentration and immersion time, so that the Nafion directly forms a uniform thin layer on the catalyst layer surface.
[0015] Step 3: Drying: Dry the coated electrode to allow Nafion to evenly penetrate into the catalyst layer and tightly bond with the catalyst.
[0016] Step 4: hot-press the prepared electrode and Nafion-HP proton exchange membrane, take them out and cool them to room temperature to obtain a proton exchange membrane fuel cell with direct addition of ionomer.
[0017] In the above technical solution, in step 1, the volume ratio of ultrapure water to isopropanol is 1:9.
[0018] In the above technical solution, in step 1, preferably, the size of the carbon paper is 2.25 cm × 2.25 cm.
[0019] In the above technical solution, in step 1, preferably, the ultrasonic time is 30 min.
[0020] In the above technical solution, in step 1, preferably, the spraying temperature is 60° C., the spraying flow rate is 15 μL / min, and the number of spraying is 6 times.
[0021] In the above technical solution, in step 2, preferably, the concentration of the Nafion solution is 5 wt%, and the volume of the Nafion solution is 25 μL.
[0022] In the above technical solution, in step 4, the hot pressing temperature is preferably 120° C. and the pressure is 4 MP.
[0023] In the above technical solution, the method also includes performance testing: testing the catalytic performance of the electrode and evaluating its application effect in PEMFC, including but not limited to polarization curves, cyclic voltammetry (CV) curves, etc.
[0024] Beneficial effects:
[0025] Compared with the prior art, this technical solution has the following advantages:
[0026] (1) Improving catalyst activity: The optimized ionomer addition method of the present invention effectively reduces the direct contact between the ionomer and the Pt surface, significantly reduces the poisoning phenomenon of the active sites, and improves the activity and stability of the catalyst.
[0027] (2) Optimizing the structure of the catalyst layer: In the present invention, the filling of the ionomer in the macropores provides an effective channel for proton transfer, while maintaining the porous structure of the catalyst layer, ensuring unimpeded mass transfer of the gas and improving the transport efficiency of the reactants.
[0028] (3) The preparation process is simple and efficient: This method has a simple process flow, is easy to operate, is easy to implement large-scale production, and has relatively low equipment requirements, which reduces production costs and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 The linear sweep voltammetry (LSV) curves of PEMFC prepared by the brush coating method at different relative humidity conditions (RH=0%, 30%, 65%) at 75 °C show the cell output performance of PEMFC assembled with electrodes prepared by the optimized method under different humidity conditions.
[0030] Figure 2 The CV curve of PEMFC prepared by brush coating method reflects the electrochemical activity of the catalyst layer under the optimized preparation method. DETAILED DESCRIPTION
[0031] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. However, the following embodiments are limited to explaining the present invention, and the protection scope of the present invention should include the entire contents of the claims, and through the description of the following embodiments, those skilled in the art can fully implement the entire contents of the claims of the present invention.
[0032] Example
[0033] In this embodiment, 7 mg of Pt / C catalyst (60% wt%) was taken, and ultrapure water and isopropanol (volume ratio of 1:9) were used as solvents to prepare 2.0 mL of catalyst ink. After the prepared catalyst ink was evenly dispersed by ultrasonication for 30 min, a 2.25 cm × 2.25 cm carbon paper containing a diffusion layer was taken, and the evenly dispersed catalyst ink was evenly sprayed on the surface of the carbon paper at a flow rate of 15 μL / min at 60 ° C by an ultrasonic sprayer for 6 times. After spraying, it was continued to dry for 30 min to fully evaporate the solvent and form a uniform catalytic layer. After the catalytic layer is dried, 25 μL of 5 wt% Nafion solution is evenly applied to the catalyst layer using a brush to ensure that it is fully covered. The coated electrode was dried at room temperature to obtain a catalyst loading of 0.5 mg cm -2 The prepared electrode and Nafion-HP proton exchange membrane were hot pressed at 120 °C and 4 MP pressure for 90 s. Finally, the membrane electrode was taken out and cooled to room temperature to obtain the performance test of proton exchange membrane fuel cell.
[0034] The electrochemical test of the electrode was performed by linear sweep voltammetry and cyclic voltammetry using an electrochemical workstation Solartron XM. The linear sweep voltammetry method was set to have a potential scan range of 0.9 V-0.4 V and a scan rate of 10 mV / s. The cyclic voltammetry method was set to have 100% RH nitrogen gas flowing into the cathode side of the tested battery and 100% RH hydrogen gas flowing into the anode side, with a gas flow rate of 50 mL min -1 The cathode side was connected to the sensitive electrode and the working electrode, the anode side was connected to the counter electrode and the reference electrode, the scanning potential was between 0.05 V and 1.1 V, and the scanning speed was 50 mV s -1 .
[0035] Depend on Figure 1 It can be seen that under dry conditions with a relative humidity of 0%, the battery shows a faster voltage decay in the low current density region, and the power density peak (1.17 W cm -2 ) is relatively low, indicating that in an anhydrous environment, the electrochemical reaction kinetics and proton conductivity of the battery are greatly inhibited. When the relative humidity is increased to 30%, the battery performance is improved, the iV curve shows a more gentle downward trend, and the power density peak (1.33 W cm -2 ) significantly increased, indicating that moderate humidity is conducive to enhancing battery reaction activity and reducing polarization loss. When the relative humidity reaches 65%, the performance of the fuel cell reaches its best state. Under this humidity condition, the battery exhibits the best voltage retention capability in the full current density range, and the power density peak is the highest, close to 1.20 W / cm². It can be seen that at a relative humidity of 65%, the water management, catalyst activity and proton conductivity inside the battery have reached a good balance, and the battery exhibits good electrochemical performance.
[0036] Figure 2 In the CV curve of , a very obvious hydrogen absorption / desorption peak appeared near 0.1 V. During the positive scan, as the potential increased to around 0.85 V, an oxidation peak of oxides formed on the Pt surface was observed; and during the negative scan, a Pt-O reduction peak appeared near 0.82 V. The electrochemical active area (ECSA) of the catalyst was obtained by integrating the peak area of hydrogen absorption and desorption of the catalyst to be 33.5 m 2 g -1 , indicating that the direct addition of ionomers effectively retains the active sites on the catalyst surface, and the electrode catalyst layer prepared by it has good electrochemical properties.
[0037] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.
Claims
1. A proton exchange membrane fuel cell with direct addition of ionomer, characterized in that: Prepared by the following steps: Step 1, catalyst coating: first, take Pt / C catalyst, use ultrapure water and isopropanol as solvents, and prepare catalyst ink; after the catalyst ink is evenly dispersed by ultrasonic, take carbon paper containing a diffusion layer, and use an ultrasonic sprayer to evenly spray the evenly dispersed catalyst ink on the surface of the carbon paper. After spraying, continue to dry to fully volatilize the solvent and form a uniform catalyst layer; Step 2: Directly add ionomer: After the catalyst layer is dried, use a brush to evenly coat the Nafion solution on the catalyst layer, control the coating speed and pressure, so that the Nafion directly forms a uniform thin layer on the catalyst layer surface; or immerse the carbon paper sprayed with the catalyst surface in the Nafion solution, control the solution concentration and immersion time, so that the Nafion directly forms a uniform thin layer on the catalyst layer surface; Step 3: Drying: Dry the coated electrode to allow Nafion to evenly penetrate into the catalyst layer and tightly bond with the catalyst; Step 4: hot pressing: hot pressing the prepared electrode and Nafion-HP proton exchange membrane, taking them out and cooling them to room temperature to obtain a proton exchange membrane fuel cell with direct addition of ionomer.
2. The proton exchange membrane fuel cell with direct ionomer addition according to claim 1, characterized in that: The proton exchange membrane fuel cell has a power density peak of 1.20 W / cm² when the relative humidity reaches 65%.
3. The ionomer direct addition proton exchange membrane fuel cell according to claim 1, characterized in that: The electrochemical active area of the proton exchange membrane fuel cell is 33.5 m 2 g -1 .
4. A method for preparing a proton exchange membrane fuel cell with direct addition of ionomer, characterized in that: The steps include: Step 1, catalyst coating: first, take Pt / C catalyst, use ultrapure water and isopropanol as solvents, and prepare catalyst ink; after the catalyst ink is evenly dispersed by ultrasonic, take carbon paper containing a diffusion layer, and use an ultrasonic sprayer to evenly spray the evenly dispersed catalyst ink on the surface of the carbon paper. After spraying, continue to dry to fully volatilize the solvent and form a uniform catalyst layer; Step 2: Directly add ionomer: After the catalyst layer is dried, use a brush to evenly coat the Nafion solution on the catalyst layer, control the coating speed and pressure, so that the Nafion directly forms a uniform thin layer on the catalyst layer surface; or immerse the carbon paper sprayed with the catalyst surface in the Nafion solution, control the solution concentration and immersion time, so that the Nafion directly forms a uniform thin layer on the catalyst layer surface; Step 3: Drying: Dry the coated electrode to allow Nafion to evenly penetrate into the catalyst layer and tightly bond with the catalyst; Step 4: hot pressing: hot pressing the prepared electrode and Nafion-HP proton exchange membrane, taking them out and cooling them to room temperature to obtain a proton exchange membrane fuel cell with direct addition of ionomer.
5. The method for preparing a proton exchange membrane fuel cell with direct addition of ionomer according to claim 4, characterized in that: In step 1, the volume ratio of ultrapure water to isopropanol is 1:
9.
6. The method for preparing a proton exchange membrane fuel cell with direct addition of ionomer according to claim 4, characterized in that: In step 1, the size of the carbon paper is 2.25 cm × 2.25 cm.
7. The method for preparing a proton exchange membrane fuel cell with direct addition of ionomer according to claim 4, characterized in that: In step 1, the ultrasonication time was 30 min.
8. The method for preparing a proton exchange membrane fuel cell with direct ionomer addition according to claim 4, characterized in that: In step 1, the spraying temperature is 60°C, the spraying flow rate is 15 μL / min, and the number of spraying is 6 times.
9. The method for preparing a proton exchange membrane fuel cell with direct ionomer addition according to claim 4, characterized in that: In step 2, the concentration of the Nafion solution is 5 wt %, and the volume of the Nafion solution is 25 μL.
10. The method for preparing a proton exchange membrane fuel cell with direct ionomer addition according to claim 4, characterized in that: In step 4, the hot pressing temperature is 120°C and the pressure is 4 MPa.