Anode catalyst layer slurry and preparation method thereof
阅读说明：本技术 一种阳极催化层浆料及其制备方法 (Anode catalyst layer slurry and preparation method thereof ) 是由 张爱京 张宇 柴茂荣 周明正 王顺忠 王志昌 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种阳极催化层浆料,包括：全氟磺酸树脂、聚四氟乙烯、Pt/C催化剂、溶剂和水,其中,所述全氟磺酸树脂为EW值为650-750g/mol的短链树脂。所述阳极催化层浆料中聚四氟乙烯质量含量为1-5％,所述全氟磺酸树脂与Pt/C催化剂中碳载体的质量比I/C为0.7-1.0,所述阳极催化剂层浆料的固含量为2-15％,所述溶剂选自乙醇、正丙醇或异丙醇中的至少一种,所述Pt/C催化剂中Pt质量含量为30-60％。采用本发明实施例的阳极催化层浆料制备膜电极,适用于车用燃料电池工况；在高温、低加湿度、低过量系数和阳极脉冲排水装置下,能够显著提高催化层的扩散,在有效保水的同时,保证了较低的电池内阻。(The invention discloses anode catalyst layer slurry, which comprises the following components in parts by weight: perfluorosulfonic acid resin, polytetrafluoroethylene, a Pt/C catalyst, a solvent and water, wherein the perfluorosulfonic acid resin is short-chain resin with the EW value of 650-750 g/mol. The mass content of polytetrafluoroethylene in the anode catalyst layer slurry is 1-5%, the mass ratio I/C of perfluorosulfonic acid resin to a carbon carrier in a Pt/C catalyst is 0.7-1.0, the solid content of the anode catalyst layer slurry is 2-15%, the solvent is selected from at least one of ethanol, n-propanol or isopropanol, and the mass content of Pt in the Pt/C catalyst is 30-60%. The membrane electrode prepared by the anode catalyst layer slurry is suitable for the working condition of the vehicle fuel cell; under the conditions of high temperature, low humidification, low excess coefficient and anode pulse drainage device, the diffusion of the catalyst layer can be obviously improved, and the lower internal resistance of the battery is ensured while water is effectively retained.)
1. An anode catalyst layer slurry, comprising: perfluorosulfonic acid resin, polytetrafluoroethylene, a Pt/C catalyst, a solvent and water, wherein the perfluorosulfonic acid resin is short-chain resin with the EW value of 650-750 g/mol.
2. The anode catalytic layer slurry according to claim 1, wherein the mass content of polytetrafluoroethylene in the anode catalytic layer slurry is 1-5%.
3. The anode catalytic layer slurry according to claim 1, wherein the mass ratio I/C of the perfluorosulfonic acid resin to the carbon support in the Pt/C catalyst is 0.7 to 1.0.
4. The anode catalytic layer slurry according to claim 1, wherein the solvent is selected from at least one of ethanol, n-propanol or isopropanol.
5. The anode catalytic layer slurry according to claim 1, wherein the anode catalytic layer slurry has a solid content of 2 to 15%.
6. The anode catalytic layer slurry according to claim 1, wherein the Pt/C catalyst has a Pt mass content of 30 to 60%.
7. A method for producing an anode catalytic layer slurry according to any one of claims 1 to 6, comprising:
a. adding a solvent into the perfluorinated sulfonic acid resin solution for dilution, and stirring to obtain a diluted solution, wherein the solid content of the perfluorinated sulfonic acid resin in the diluted solution is 2-20 wt%;
b. and (b) adding water into the Pt/C catalyst, uniformly mixing, then adding the perfluorinated sulfonic acid resin diluent and the polytetrafluoroethylene emulsion obtained in the step (a), and performing ball milling to obtain catalyst slurry.
8. The method for preparing anode catalytic layer slurry according to claim 7, wherein in the step a, the mass concentration of the perfluorinated sulfonic acid resin solution is 20-40%; the stirring speed is 100-400r/min, and the stirring time is 30-60 min; in the step b, the ball milling rotation speed is 100-.
9. A fuel cell membrane electrode CCM comprising an anode catalytic layer made from the anode catalytic layer slurry according to any one of claims 1 to 6.
10. A membrane electrode comprising the CCM of claim 9.
Technical Field
The invention belongs to the technical field of fuel cells, particularly relates to anode catalyst layer slurry, and particularly relates to a preparation method suitable for the anode catalyst layer slurry.
Background
Due to the characteristics of cleanness and high efficiency, the fuel cell is continuously concerned and widely popularized by governments at home and abroad in recent years. The performance of the membrane electrode is mainly limited by three polarizations, and for example, for a vehicle fuel cell, the membrane electrode is expected to have excellent performance under the operating conditions of high temperature, low humidification and low excess coefficient, can effectively retain water, has lower internal resistance, and can effectively transmit water and gas under an anode pulse drainage device; however, in this condition, the mass transfer polarization loss of the membrane electrode is large, which seriously affects the performance of the fuel cell.
CN109103472A discloses a method for improving oxygen transfer of a cathode catalyst layer, in which a cationic salt is introduced, and the compactness of the Pt surface of the catalyst is reduced by the electrostatic interaction of cations and sulfonic acid groups of resin, so as to improve the oxygen transfer of the cathode catalyst layer to improve the battery performance. CN109524676A discloses a method for improving catalyst layer mass transfer, and the method introduces multi-walled carbon nanotubes to optimize catalyst layer gap structure, thereby improving the diffusion problem of cathode catalyst layer; CN112259749A discloses a method for improving mass transfer of a catalyst layer, which is to improve the void structure of the catalyst layer by ammonium salt pore-forming, thereby reducing the concentration polarization of a cathode catalyst layer. CN109524676A and CN112259749A are methods for optimizing the pore structure of the catalyst layer by adding pore-forming agents, which are also commonly used methods, but introducing various pore-forming agents can cause complex process, and may also cause the problems of pollution of the catalyst layer, and the performance is not significantly improved or poor.
The current research mainly focuses on the mass transfer problem of the cathode catalyst layer, and the mass transfer problem of the anode is hardly mentioned. Therefore, it is required to develop an anode catalyst layer slurry which is suitable for the working conditions of high temperature, low humidification and low excess coefficient and an anode pulse drainage device, and the mass transfer capacity of the anode is improved.
Disclosure of Invention
The present invention is based on the discovery and recognition by the inventors of the following facts and problems: at present, the fuel cell for vehicle needs extremely high power density, the membrane electrode uses thinner proton membrane, such as Gore's 12um and 8um membrane, which can strengthen the back diffusion of water, and the fuel cell for vehicle anode adopts hydrogen circulating pump, the anode can cause the difficulty of water drainage and the reduction of outlet hydrogen concentration, therefore the mass transfer problem of the anode needs to be paid attention and solved. The CN112768708A patent discloses a method for improving water retention of an anode, which utilizes a hydrophilic catalyst and short-chain low EW resin to increase the water retention of the anode, so that a membrane electrode can be applied under the working conditions of high temperature and low humidity. However, the method is mainly designed for anode water retention, and the anode diffusion problem caused by anode flooding under the working conditions of vehicle-mounted high temperature, low humidity and low excess coefficient cannot be solved by adopting the hydrophilic catalyst and the short-chain low EW resin.
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the embodiment of the invention provides anode catalyst layer slurry which not only can retain water under the conditions of high temperature, low humidification and low excess coefficient, but also can remarkably improve the diffusion of the anode catalyst layer under an anode pulse drainage device and improve the performance of a battery under the conditions of high temperature, low humidification and low excess coefficient.
The anode catalytic layer slurry according to the embodiment of the invention comprises: perfluorosulfonic acid resin, polytetrafluoroethylene, a Pt/C catalyst, a solvent and water, wherein the perfluorosulfonic acid resin is short-chain resin with the EW value of 650-750 g/mol.
According to the advantages and technical effects brought by the anode catalyst layer slurry in the embodiment of the invention, 1, in the embodiment of the invention, perfluorosulfonic acid resin with EW value of 650-750g/mol is adopted, and the resin can provide more sulfonate groups, so that the membrane electrode prepared by the anode catalyst layer slurry in the embodiment of the invention has lower internal resistance, and the ohmic polarization loss of the cell is reduced; 2. in the embodiment of the invention, the hydrophobic substance polytetrafluoroethylene is added into the catalyst layer slurry, so that the water and gas drainage and guide functions of the catalyst layer are enhanced, water in the anode catalyst layer is effectively prevented from being gathered under the anode pulse water drainage device, an enough exhaust channel is ensured, reaction gas can effectively reach a catalytic active site, the diffusion polarization loss of a cell is reduced, and the mass transfer capacity of the anode catalyst layer of the fuel cell is improved; 3. the anode catalyst layer slurry of the embodiment of the invention is used for preparing the membrane electrode, and is suitable for the working condition of the vehicle fuel cell; under the conditions of high temperature, low humidification, low excess coefficient and anode pulse drainage device, the diffusion of the catalyst layer can be obviously improved, and the lower internal resistance of the battery is ensured while water is effectively retained.
In some embodiments, the mass content of polytetrafluoroethylene in the anode catalytic layer slurry is 1-5%.
In some embodiments, the mass ratio of the perfluorosulfonic acid resin to the carbon support in the Pt/C catalyst, I/C, is from 0.7 to 1.0.
In some embodiments, the solvent is selected from at least one of ethanol, n-propanol, or isopropanol.
In some embodiments, the anode catalytic layer slurry has a solids content of 2-15%.
In some embodiments, the Pt/C catalyst has a Pt mass content of 30-60%.
The invention also provides a preparation method of the anode catalyst layer slurry, which comprises the following steps:
a. adding a solvent into the perfluorinated sulfonic acid resin solution for dilution, and stirring to obtain a diluted solution, wherein the solid content of the perfluorinated sulfonic acid resin in the diluted solution is 2-20 wt%;
b. and (b) adding water into the Pt/C catalyst, uniformly mixing, then adding the perfluorinated sulfonic acid resin diluent and the polytetrafluoroethylene emulsion obtained in the step (a), and performing ball milling to obtain catalyst slurry.
According to the advantages and technical effects brought by the preparation method of the anode catalyst layer slurry in the embodiment of the invention, 1, in the method in the embodiment of the invention, perfluorosulfonic acid resin with EW value of 650-750g/mol is added, and the resin can provide more sulfonate groups, so that the membrane electrode prepared by the anode catalyst layer slurry in the embodiment of the invention has lower internal resistance, and the ohmic polarization loss of the cell is reduced; 2. according to the method provided by the embodiment of the invention, the hydrophobic substance polytetrafluoroethylene emulsion is added, so that the water and gas drainage and guide functions of the catalyst layer are increased, water accumulation in the anode catalyst layer is effectively prevented under the anode pulse water drainage device, an enough exhaust channel is ensured, so that reaction gas can effectively reach a catalytic active site, the diffusion polarization loss of the cell is reduced, and the mass transfer capacity of the anode catalyst layer of the fuel cell is improved; 3. the membrane electrode prepared by adopting the anode catalyst layer slurry prepared by the method of the embodiment of the invention is suitable for the working condition of the vehicle fuel cell; under the conditions of high temperature, low humidification, low excess coefficient and anode pulse drainage device, the diffusion of the catalyst layer can be obviously improved, and the lower internal resistance of the battery is ensured while water is effectively retained.
In some embodiments, in the step a, the mass concentration of the perfluorosulfonic acid resin solution is 20-40%; the stirring speed is 100-400r/min, and the stirring time is 30-60 min; in the step b, the ball milling rotation speed is 100-.
The embodiment of the invention also provides a membrane electrode CCM of a fuel cell, which comprises an anode catalyst layer prepared from the anode catalyst layer slurry. The fuel cell membrane electrode CCM according to the embodiment of the present invention has all the advantages that the anode catalyst layer slurry according to the embodiment of the present invention can provide, and details thereof are not described herein.
The embodiment of the invention also provides a membrane electrode comprising the CCM provided by the embodiment of the invention. The membrane electrode of the embodiment of the invention has all the advantages brought by the CCM of the embodiment of the invention, and is not described in detail herein.
Drawings
FIG. 1 is a polarization diagram of membrane electrodes obtained in examples 1 to 2 of the present invention and comparative examples 1 to 2;
FIG. 2 is a graph showing internal resistances of membrane electrodes obtained in examples 1 to 2 of the present invention and comparative examples 1 to 2;
FIG. 3 is a graph showing the polarization curves of the membrane electrodes obtained in examples 1 to 2 of the present invention and comparative examples 1 to 2 after ir-free.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The anode catalytic layer slurry according to the embodiment of the invention comprises: perfluorosulfonic acid resin, polytetrafluoroethylene, a Pt/C catalyst, a solvent and water, wherein the perfluorosulfonic acid resin is short-chain resin with the EW value of 650-750 g/mol.
According to the anode catalyst layer slurry provided by the embodiment of the invention, perfluorosulfonic acid resin with EW value of 650-750g/mol is adopted, and the resin can provide more sulfonate groups, so that a membrane electrode prepared by the anode catalyst layer slurry provided by the embodiment of the invention has lower internal resistance, and the ohmic polarization loss of a cell is reduced; in the embodiment of the invention, the hydrophobic substance polytetrafluoroethylene is added into the catalyst layer slurry, so that the water and gas drainage and guide functions of the catalyst layer are enhanced, water in the anode catalyst layer is effectively prevented from being gathered under the anode pulse water drainage device, an enough exhaust channel is ensured, reaction gas can effectively reach a catalytic active site, the diffusion polarization loss of a cell is reduced, and the mass transfer capacity of the anode catalyst layer of the fuel cell is improved; the anode catalyst layer slurry of the embodiment of the invention is used for preparing the membrane electrode, and is suitable for the working condition of the vehicle fuel cell; under the conditions of high temperature, low humidification, low excess coefficient and anode pulse drainage device, the diffusion of the catalyst layer can be obviously improved, and the lower internal resistance of the battery is ensured while water is effectively retained.
In some embodiments, the mass content of polytetrafluoroethylene in the anode catalytic layer slurry is 1-5%. In the embodiment of the invention, the addition amount of polytetrafluoroethylene is optimized, the hydrophobic substance polytetrafluoroethylene is added into the catalyst layer slurry in the embodiment of the invention, so that the water drainage and air guide functions of the catalyst layer can be effectively improved, the resistance of the catalyst layer is increased due to excessive addition of polytetrafluoroethylene, and an effective air guide channel cannot be formed due to too little addition of polytetrafluoroethylene.
In some embodiments, the mass ratio of the perfluorosulfonic acid resin to the carbon support in the Pt/C catalyst, I/C, is from 0.7 to 1.0. In the embodiment of the invention, the mass ratio I/C of the perfluorosulfonic acid resin to the carbon carrier in the Pt/C catalyst is optimized, and the coverage rate of the resin on the surface of the catalyst can be reduced by reducing the content of the resin, so that the diffusion of an anode catalyst layer is improved, and the performances of the prepared fuel cell under high temperature, low humidification and low excess coefficient are further improved.
In some embodiments, the solvent is selected from at least one of ethanol, n-propanol, or isopropanol.
In some embodiments, the anode catalytic layer slurry has a solids content of 2-15%. In the embodiment of the invention, the solid content in the catalyst layer slurry is optimized, and the performance of the membrane electrode prepared from the catalyst layer slurry is further improved.
In some embodiments, the Pt/C catalyst has a Pt mass content of 30-60%. In the embodiment of the present invention, the selection of the catalyst is not particularly limited, and the applicability is strong.
The invention also provides a preparation method of the anode catalyst layer slurry, which comprises the following steps:
a. adding a solvent into the perfluorinated sulfonic acid resin solution for dilution, preferably, the mass concentration of the perfluorinated sulfonic acid resin solution is 20-40%, stirring, preferably, the rotating speed is 100-400r/min, the stirring time is 30-60min, and the solid content of the perfluorinated sulfonic acid resin in the obtained diluted solution is 2-20 wt%;
b. and (b) adding water into the Pt/C catalyst, uniformly mixing, then adding the perfluorinated sulfonic acid resin diluent and the polytetrafluoroethylene emulsion obtained in the step (a), and performing ball milling, wherein the preferred rotation speed is 100-500r/min, and the ball milling time is 1-4h, so as to obtain catalyst slurry.
According to the preparation method of the anode catalyst layer slurry provided by the embodiment of the invention, perfluorosulfonic acid resin with EW value of 650-750g/mol is added, and as the resin can provide more sulfonate groups, the membrane electrode prepared by the anode catalyst layer slurry prepared by the embodiment of the invention has lower internal resistance, and the ohmic polarization loss of the cell is reduced; according to the method provided by the embodiment of the invention, the hydrophobic substance polytetrafluoroethylene emulsion is added, so that the water and gas drainage and guide functions of the catalyst layer are increased, water accumulation in the anode catalyst layer is effectively prevented under the anode pulse water drainage device, an enough exhaust channel is ensured, so that reaction gas can effectively reach a catalytic active site, the diffusion polarization loss of the cell is reduced, and the mass transfer capacity of the anode catalyst layer of the fuel cell is improved; the membrane electrode prepared by adopting the anode catalyst layer slurry prepared by the method of the embodiment of the invention is suitable for the working condition of the vehicle fuel cell; under the conditions of high temperature, low humidification, low excess coefficient and anode pulse drainage device, the diffusion of the catalyst layer can be obviously improved, and the lower internal resistance of the battery is ensured while water is effectively retained.
The embodiment of the invention also provides a membrane electrode CCM of a fuel cell, which comprises an anode catalyst layer prepared from the anode catalyst layer slurry. The fuel cell membrane electrode CCM according to the embodiment of the present invention has all the advantages that the anode catalyst layer slurry according to the embodiment of the present invention can provide, and details thereof are not described herein.
The embodiment of the invention also provides a membrane electrode comprising the CCM provided by the embodiment of the invention. The membrane electrode of the embodiment of the invention has all the advantages brought by the CCM of the embodiment of the invention, and is not described in detail herein.
The present invention will be described in detail with reference to examples.
In the following examples and comparative examples, the cathode catalyst layer was fixed to perfluorosulfonic acid resin with EW value of 750-900g/mol, and the same home-made catalyst layer was used for the cathode in each example. The anode/cathode catalytic layer adopts the customized loading capacity of 0.05/0.4mgPt/cm2CCM of size 15cm by 20 cm. Gas diffusion layers are commercially available.
Example 1
Firstly, preparing anode catalyst layer slurry
(1) Preparing a resin diluent: weighing 2g of perfluorosulfonic acid resin solution (the resin content is 25 wt%), wherein the EW of the perfluorosulfonic acid resin is 680g/mol, then adding ethanol for dilution, so that the solid content of the resin diluent is 10 wt%, stirring for 30min by using a magnetic stirrer at the rotating speed of 300rpm, until the resin solution is clear and transparent and has no bubbles;
(2) preparing anode catalyst layer slurry: on the day of analysisWeighing 1g of Pt/C (Pt mass content is 50%) catalyst, putting the Pt/C catalyst into a ball milling tank, dropwise adding 5g of deionized water to fully wet the catalyst, uniformly mixing, sequentially adding the perfluorosulfonic acid resin diluent obtained in the step (1) and 1.25g of polytetrafluoroethylene emulsion (60% PTFE), controlling the mass ratio I/C of the resin to the catalyst carbon carrier to be 1.0, and finally adding ethanol, wherein the solid content of the catalyst layer slurry is controlled to be 8 wt%. Adding ZrO2And (3) 100g of particles are put into a planetary ball mill for ball milling after the ball milling tank is sealed, the rotating speed is 300r/min, and the ball milling time is 1h, so that anode catalyst layer slurry is obtained.
Secondly, preparing an anode catalyst layer
Placing a clean PTFE film on an automatic coating instrument, then selecting a coating rod with proper thickness, dripping the anode catalyst layer slurry prepared in the embodiment into the coating rod side to finish the coating of the catalyst layer coating, placing the coated coating in a drying oven, and drying for 4 hours at 80 ℃.
Third, membrane electrode preparation
Cutting the dried anode coating into the size of 15cm multiplied by 20cm, and the loading capacity is 0.05mgPt/cm2As an anode catalyst layer, the anode and cathode catalyst layers and a proton membrane (Gore 12um) are transferred on a hot press, the hot pressing temperature is 100-.
The membrane electrode prepared in this example was subjected to a performance test: a test bench for accurately measuring 2kW of poplar is adopted, and the anode adopts pulse type drainage (closed for 1min and opened for 30 s); the active area of the battery is 300cm2(ii) a The temperature of the battery is 80 ℃, the humidification of the anode/cathode is 15%/35% RH, and the excess coefficient of the anode/cathode is 1.3/1.8; anode/cathode back pressure 100/90 kPa. The results of the performance tests are shown in FIGS. 1-3.
Example 2
The same procedure as in example 1 was repeated except that in the step (2) of preparing an anode catalytic layer slurry, the mass ratio I/C of the resin to the catalyst carbon support was 0.9.
The results of the performance test of the membrane electrode obtained in example 2 are shown in FIGS. 1 to 3.
Comparative example 1
The same procedure as in example 1, except that the resin in step (1) of preparing an anode catalyst layer slurry was different, the EW of the perfluorosulfonic acid resin used in comparative example 1 was 800g/mol, and no polytetrafluoroethylene emulsion was added in step (2).
The results of the performance test of the membrane electrode obtained in comparative example 1 are shown in FIGS. 1 to 3.
Comparative example 2
The same procedure as in example 1 was repeated, except that no polytetrafluoroethylene emulsion was added in the step (2) of preparing the anode catalytic layer slurry.
The results of the performance test of the membrane electrode obtained in comparative example 2 are shown in FIGS. 1 to 3.
As can be seen from FIG. 1, in the examples 1 and 2 of the present invention, the performance is significantly improved compared to the comparative examples 1 and 2 by using the perfluorosulfonic acid resin with low EW value and adding the PTFE emulsion.
As can be seen from fig. 2, in inventive example 1 and example 2, although the hydrophobic PTFE emulsion was added, the internal resistance increased only slightly in the high current density region and still had a lower internal resistance as compared with comparative example 1 and comparative example 2.
As shown in fig. 3, after ir-Free, that is, after the effect of ohmic polarization loss is removed (the fuel cell voltage loss is divided into 3 sections, specifically, activation polarization loss, ohmic polarization loss, and diffusion polarization loss), it can be found that the difference in output voltages in the low current density region is small in example 1, example 2, comparative example 1, and comparative example 2, which indicates that the EW value of the perfluorosulfonic acid resin, the mass ratio I/C of the resin and the catalyst carbon support, and whether or not adding polytetrafluoroethylene has no effect on the low current density region, which indicates that the activation polarization has not been significantly changed; however, in the high current density region, compared with the comparative example 2, the polytetrafluoroethylene is added in the embodiment 1, so that the output voltage of the battery is obviously improved; compared with the embodiment 1, the mass ratio I/C of the resin and the catalyst carbon carrier is reduced in the embodiment 2, the I/C of the embodiment 2 is 0.9, the I/C of the embodiment 1 is 1.0, and the output voltage of the embodiment 2 is improved to a certain extent after the I/C value is reduced; comparative example 2 in comparison with comparative example 1, in the case where no polytetrafluoroethylene emulsion was added, comparative example 2 using a perfluorosulfonic acid resin having a low EW value, the cell output voltage was improved in the low current density region, but the cell output voltage was slightly different in the high current density region. By comparing the output voltages of the embodiments 1 to 2 and the comparative examples 1 to 2 in the high current density region after ir-Free, it can be seen that the addition of the PTFE emulsion to the anode catalyst layer slurry of the embodiments of the present invention significantly improves the anode diffusion, and the mass ratio I/C of the resin to the catalyst carbon support is reduced, which can further improve the anode diffusion.
In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.