CN117954636A - Cathode catalyst layer, preparation method and application thereof - Google Patents
Cathode catalyst layer, preparation method and application thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 258
- 238000002360 preparation method Methods 0.000 title abstract description 12
- 239000012528 membrane Substances 0.000 claims abstract description 86
- 239000002245 particle Substances 0.000 claims abstract description 68
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 40
- 238000001035 drying Methods 0.000 claims description 23
- 238000000034 method Methods 0.000 claims description 23
- 239000002002 slurry Substances 0.000 claims description 22
- 229920000554 ionomer Polymers 0.000 claims description 18
- 229910052697 platinum Inorganic materials 0.000 claims description 17
- 238000000576 coating method Methods 0.000 claims description 16
- 239000000446 fuel Substances 0.000 claims description 16
- 239000002904 solvent Substances 0.000 claims description 15
- 239000011248 coating agent Substances 0.000 claims description 14
- 239000011347 resin Substances 0.000 claims description 10
- 229920005989 resin Polymers 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 8
- UQSQSQZYBQSBJZ-UHFFFAOYSA-N fluorosulfonic acid Chemical compound OS(F)(=O)=O UQSQSQZYBQSBJZ-UHFFFAOYSA-N 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 abstract description 43
- 239000010410 layer Substances 0.000 description 128
- 238000011068 loading method Methods 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- 239000001301 oxygen Substances 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 7
- 238000009792 diffusion process Methods 0.000 description 7
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- 239000006256 anode slurry Substances 0.000 description 6
- 239000006257 cathode slurry Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000004806 packaging method and process Methods 0.000 description 6
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 4
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- 150000003460 sulfonic acids Chemical class 0.000 description 2
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- -1 EW=700 g/mol Substances 0.000 description 1
- 206010024769 Local reaction Diseases 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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Abstract
The invention discloses a cathode catalyst layer and a preparation method and application thereof. One end of the cathode catalyst layer is provided with an air inlet end, the other end of the cathode catalyst layer is provided with an air outlet end, and the particle size of the catalyst in the cathode catalyst layer is sequentially increased from the air outlet end to the length direction of the cathode catalyst layer at the air inlet end. The reaction rate of the cathode catalyst layer is balanced, the humidity and temperature difference of a local area of the cathode catalyst layer are small, the catalyst is not easy to decay and lose efficacy, and the service life of a membrane electrode prepared by adopting the cathode catalyst layer is long.
Description
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a cathode catalyst layer, a preparation method and application thereof.
Background
Membrane Electrodes (MEA) are the core components of proton exchange membrane fuel cells, and are the important components for the fuel cells to produce electrical energy and for electrochemical reactions to occur. The membrane electrode mainly comprises a cathode catalyst layer, a gas diffusion layer, a proton exchange membrane, a frame membrane and other materials. After hydrogen and oxygen are respectively introduced to the two sides of the membrane electrode, under the catalysis of the catalyst layer, potential difference is generated, and electric energy is further generated for people to use. At present, the mass production capacity of domestic fuel cells is gradually established, and membrane electrodes obtained by different production methods have different performances, quality and cost.
The preparation process of the main stream membrane electrode in the market at present mainly adopts a coating method to obtain a uniform catalyst layer, wherein the coating method is as follows: firstly, fully mixing substances such as catalyst powder, ionomer resin, alcohol solvent, water and the like to form slurry, then grinding particles to the required granularity through a dispersing process to form anode or cathode slurry, coating the anode or cathode slurry on two surfaces of a proton exchange membrane by using a slit coater, a comma knife coater and the like, and drying the slurry through a tunnel furnace to form a catalyst/proton exchange membrane module (CCM); or respectively coating the cathode slurry and the anode slurry on another carrier film by adopting a transfer printing method, drying by a tunnel furnace to respectively form a cathode coating and an anode coating, and then respectively transferring the cathode coating and the anode coating to two sides of the proton exchange film by adopting a hot-pressing transfer printing mode to form the required CCM. In the two manufacturing modes, the surface of the cathode catalyst layer and the surface of the anode catalyst layer of the obtained CCM are flat surfaces, the pore size and the material composition of the whole catalyst layer are uniformly distributed, after the catalyst layer is assembled into a galvanic pile, reaction gas permeates into the coating layer by virtue of the porosity of the catalyst layer in the reaction process after hydrogen and air are introduced, and electrochemical reaction occurs on the surface of Pt catalyst particles, so that electric energy is generated; the diffusion depth and diffusion rate of the reaction gas are determined by the pore structure distribution of the coating, and one side shape of the outer surface of the catalyst layer has a certain influence on the diffusion rate, so that the power generation efficiency of the membrane electrode is influenced, and the power exertion of the electric pile is further influenced.
The design concept of the conventional membrane electrode catalyst layer is that the pore structure and the substance components are uniformly distributed in a single cell, and in the actual operation process of the fuel cell, the objective structure of the bipolar plate in the electric pile causes the pressure difference between the air inlet and the air outlet of the fuel gas, so that the concentration difference exists between the reaction gases on the surfaces of the catalyst layer at the air inlet and the air outlet, and the local reaction rate difference is caused to be larger, so that the humidity and the temperature difference between the local catalyst layers are larger, the corrosion attenuation of the catalyst is further accelerated, the local failure of the membrane electrode is caused, and the service life of the membrane electrode is shortened. In particular, the cathode catalyst layer is used as a place of oxygen reduction reaction, and the structure of the catalyst layer and the stability of the catalyst directly affect the use of the fuel cell. With the development of hydrogen fuel cells, the hydrogen fuel cells tend to be applied to more and more fields, such as the fields of airplanes, trains, heavy trucks, ships and the like, the requirements of the application scenes on large-size membrane electrodes are more and more remarkable, and the current common means for solving the problems of the membrane electrodes on the market is to improve the distribution uniformity of reaction gases in the whole area of the membrane electrodes by optimizing the flow channel design of bipolar plates, but the methods have the defects of long design verification period, high cost and the like. Accordingly, the existing cathode catalyst layer is to be improved.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, an object of the present invention is to propose a cathode catalyst layer, a method for its preparation and its use. The reaction rate of the cathode catalyst layer is balanced, the humidity and temperature difference of a local area of the cathode catalyst layer are small, the catalyst is not easy to decay and lose efficacy, and the service life of a membrane electrode prepared by adopting the cathode catalyst layer is long.
In one aspect of the invention, the invention provides a cathode catalyst layer. According to an embodiment of the present invention, an air inlet end is formed at one end of the cathode catalyst layer, an air outlet end is formed at the other end, and the catalyst particle diameter in the cathode catalyst layer increases in order from the air outlet end to the length direction of the cathode catalyst layer at the air inlet end.
According to the cathode catalyst layer of the above-described embodiment of the application, the catalyst particle diameter in the cathode catalyst layer increases in order from the air outlet end to the length direction of the cathode catalyst layer at the air inlet end; the pressure of air from the air inlet end to the air outlet end, namely the oxygen concentration, is sequentially decreased, if a catalyst with uniform particle size is adopted, the reaction rate of the whole cathode catalyst layer is also sequentially decreased, so that the reaction rate of the whole cathode catalyst layer is unbalanced, the catalyst is easy to be locally heated and wet, the service life of a membrane electrode is influenced, the particle size of the catalyst in the cathode catalyst layer is sequentially increased from the air outlet end to the air inlet end, that is, the particle size of the catalyst at the air inlet end is maximum, the specific surface area is minimum, the reaction rate of the cathode catalyst layer at the air inlet end is reduced, the particle size of the catalyst at the air outlet end is minimum, the specific surface area is maximum, the reaction rate of the cathode catalyst layer at the air outlet end is increased, and the gradient structure of the sequentially increased catalyst particle size from the air outlet end to the air inlet end reduces the reaction rate difference of the cathode catalyst layer caused by the existence of air pressure difference; on the other hand, because the reaction rate at the air inlet end is reduced, the required oxygen is reduced, and the air input amount is constant, the air consumed by the air inlet end is reduced and moves towards the air outlet end, so that the oxygen concentration at the air outlet end is increased, the reaction rate of the cathode catalyst layer at the air outlet end is further improved, and the reaction rate of the whole cathode catalyst layer is balanced. Therefore, the reaction rate of the cathode catalyst layer is balanced, the humidity and temperature difference of a local area of the cathode catalyst layer are small, the catalyst is not easy to attenuate and lose efficacy, and the service life of a membrane electrode prepared by the cathode catalyst layer is long.
In addition, the cathode catalyst layer according to the above embodiment of the present invention may further have the following technical features:
In some embodiments of the present invention, the cathode catalyst layer sequentially defines a plurality of regions, designated as S 1、S2…Sn, in sequence from the air outlet end to the air inlet end, and the catalyst particle sizes of the regions S 1 to S n sequentially increase. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In some embodiments of the invention, the catalyst in the S 1 region has a D 50 (1) of 50-110 μm and the catalyst in the S n region has a D 50(n)＝(D50 (1) +20×20 (n-1)) ± 20 μm. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In some embodiments of the invention, 3.ltoreq.n.ltoreq.20, preferably 3.ltoreq.n.ltoreq.10. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In some embodiments of the invention, the catalyst particle size is the same for individual of the zones. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In some embodiments of the invention, each of the S 1 to S n regions has the same area. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In some embodiments of the invention, the catalyst species and content of the S 1 to S n regions are the same. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In yet another aspect of the present invention, there is provided a method of preparing the above cathode catalyst layer. According to an embodiment of the invention, the method comprises:
(1) Respectively mixing n cathode catalysts with different particle sizes, ionomer and solvent so as to obtain n catalyst slurries with different particle sizes;
(2) And sequentially coating the catalyst slurries with n different particle sizes on the S 1、S2、S3......、Sn area of the proton exchange membrane according to the sequence from small particle sizes to large particle sizes, distributing the S 1、S2、S3......、Sn area along the length direction of the exchange membrane, and then drying to obtain the cathode catalyst layer.
Therefore, the cathode catalyst layer which has balanced reaction rate, small local area humidity and temperature difference and is difficult to attenuate and lose efficacy can be prepared by adopting the method.
In addition, the method of preparing a cathode catalyst layer according to the above-described embodiment of the present invention may further have the following technical features:
In some embodiments of the invention, in step (1), the ionomer comprises a perfluorosulfonic acid resin having an EW of 700-1000 g/mol.
In some embodiments of the invention, in step (1), the cathode catalyst comprises at least one of Pt/C, pt/Co/C and Pt/Co/Mn.
In some embodiments of the invention, in step (2), the drying temperature T 1 of the odd numbered regions of the S 1 to S n regions is 60-85 ℃, the drying temperature T 2 of the even numbered regions of the S 1 to S n regions is 75-100 ℃, and 10 ℃ C. Ltoreq.T 2-T1 ℃ C. Ltoreq.20 ℃. Thereby, the reaction rate of the entire cathode catalyst layer can be balanced.
In a third aspect of the invention, a membrane electrode is provided. According to the embodiment of the invention, the membrane electrode comprises a proton exchange membrane, a cathode catalyst layer and an anode catalyst layer, wherein the anode catalyst layer is arranged on one side surface of the proton exchange membrane, and the cathode catalyst layer is arranged on the other side surface of the proton exchange membrane, wherein the cathode catalyst layer is the cathode catalyst layer or the cathode catalyst layer prepared by adopting the method. Thus, the membrane electrode has a longer service life.
In a fourth aspect of the invention, a fuel cell is provided. According to an embodiment of the present invention, the fuel cell includes the above membrane electrode. Thus, the fuel cell has a long service life.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a partial block diagram of a membrane electrode according to an embodiment of the invention;
FIG. 2 is a graph of cathode catalyst distribution for different particle sizes in accordance with an embodiment of the present invention;
Fig. 3 is a partial construction diagram of a membrane electrode according to an embodiment of the present invention.
Detailed Description
The following detailed description of the embodiments of the invention is intended to be illustrative of the invention and is not to be taken as limiting the invention.
In one aspect of the invention, the invention provides a cathode catalyst layer. According to an embodiment of the present invention, referring to fig. 1, the cathode catalyst layer 20 is formed with an air inlet end 12 at one end and an air outlet end 11 at the other end, and catalyst particle diameters in the cathode catalyst layer 20 are sequentially increased in the length direction of the cathode catalyst layer 20 from the air outlet end 11 to the air inlet end 12.
According to the cathode catalyst layer 20 of the above embodiment of the present application, referring to fig. 1, the inventors found that since the pressure of air from the air inlet 12 end to the air outlet 11 end, i.e., the oxygen concentration, decreases in sequence, if a catalyst having a uniform particle diameter is used, the reaction rate of the entire cathode catalyst layer 20 decreases in sequence, so that the reaction rate of the entire cathode catalyst layer 20 is unbalanced, high temperature and high humidity are liable to occur, and thus the catalyst is deactivated, affecting the life of the membrane electrode, whereas the catalyst particle diameter in the cathode catalyst layer 20 of the present application increases in sequence from the air outlet 11 end to the air inlet 12 end, i.e., the catalyst has a maximum particle diameter at the air inlet 12 end, a minimum specific surface area, so that the reaction rate of the cathode catalyst layer 20 at the air inlet 12 end decreases, the catalyst has a minimum particle diameter at the air outlet 11 end, and a maximum specific surface area, so that the reaction rate of the cathode catalyst layer 20 at the air outlet 11 end increases, and the gradient structure of the catalyst particle diameter increases in sequence from the air outlet 11 end to the air inlet 12 end reduces the difference in reaction rate due to the existence of an air pressure difference; on the other hand, since the reaction rate at the air inlet 12 end is decreased, the required oxygen is decreased and the air input amount is constant, the air consumed at the air inlet 12 end is moved toward the air outlet end, thereby increasing the oxygen concentration at the air outlet 11 end, further increasing the reaction rate of the cathode catalyst layer 20 at the air outlet 11 end, and balancing the reaction rate of the entire cathode catalyst layer 20. Thus, the reaction rate of the cathode catalyst layer 20 is balanced, the humidity and temperature difference in the local area of the cathode catalyst layer 20 are small, the catalyst is not easy to decay and lose efficacy, and the service life of the membrane electrode prepared by the cathode catalyst layer 20 is long.
According to an embodiment of the present invention, referring to fig. 1, the cathode catalyst layer 20 sequentially defines a plurality of regions, which are sequentially designated as S 1、S2…Sn, in the length direction of the cathode catalyst layer 20 from the air outlet 11 end to the air inlet 12 end, and the catalyst particle diameters of the above-mentioned regions S 1 to S n sequentially increase. It should be noted that, under the condition that the types and the contents of the catalysts in the respective regions in the cathode catalyst layer 20 are the same, the catalyst particle sizes of the individual regions may be the same or different as long as the catalyst particle sizes of the cathode catalyst layer from the air outlet 11 end to the air inlet 12 end are sequentially increased, and it is preferable that the catalyst particle sizes of the individual regions are the same in order to make the preparation of the cathode catalyst layer more convenient and feasible; further, each of the regions S 1 to S n may have the same or different area, and preferably each of the regions S 1 to S n has the same area.
According to an embodiment of the application, D 50 (1) of the catalyst in the S 1 region is 50-110 μm, D 50(n)＝(D50 (1) +20×20 (n-1) of the catalyst in the S n region is 20 μm. The inventor finds that if the D 50 (1) of the catalyst particle size in the S 1 area is too small, the difficulty of the slurry preparation process is increased, the slurry quality is not easy to control, and a catalyst layer with good quality is difficult to obtain; if the catalyst particle diameter D 50 (1) in the region S 1 is too large, the catalyst particle diameter in the region near S n is too large, the slurry is easy to settle, and the catalyst layer is cracked, which is not beneficial to the quality control of the catalyst layer. Therefore, when the catalyst D 50 (1) in the S 1 area is 50-110 mu m and the catalyst D 50(n)＝(D50 (1) +20 (n-1)) + -20 mu m in the S n area is adopted, engineering of the product can be realized more easily, and the beneficial effect of gradient design is ensured.
According to an embodiment of the present invention, the cathode catalyst layer is divided into n regions, where n is 3.ltoreq.20. The inventor finds that if n is less than 3, the gradient structure is less, and the reaction rates of different areas in the electric pile cannot be effectively balanced; if n is greater than 20, each region becomes narrower, the particle size value of the region near S n in the whole region becomes larger, but the improvement of the electrochemical reaction efficiency in these regions is reduced, and the difficulty of manufacturing the catalyst layer increases, contrary to the gist of the present invention. Thus, when n is 3.ltoreq.20, the reaction rate of the cathode catalyst layer is more uniform. In order to further balance the reaction rate of the whole cathode catalyst layer, it is preferable that 3.ltoreq.n.ltoreq.10.
It will be appreciated by those skilled in the art that the above cathode catalysts are conventional in the art and may be selected by those skilled in the art depending on the actual implementation, for example, the cathode catalysts include at least one of Pt/C, pt/Co/C and Pt/Co/Mn.
In yet another aspect of the present invention, there is provided a method of preparing the above cathode catalyst layer. According to an embodiment of the invention, the method comprises:
S100: respectively mixing cathode catalyst, ionomer and solvent with n different particle sizes
In the step, firstly, designing a gradient distribution structure of a cathode catalyst layer in a membrane electrode reaction zone according to a bipolar plate flow field simulation result; then respectively mixing the cathode catalysts with n different particle sizes, ionomer and solvent to prepare n catalyst slurries with different particle sizes. It will be appreciated by those skilled in the art that the above ionomer and solvent are conventional agents in the art and that the skilled artisan may choose according to practice, for example, the ionomer comprises a perfluorosulfonic acid resin having an EW of 700-1000g/mol, the perfluorosulfonic acid resin comprises a long-chain branched perfluorosulfonic acid resin and a short-chain branched perfluorosulfonic acid resin, and the EW is 700g/mol, 800g/mol or 900g/mol; the solvent includes deionized water, ethanol, isopropanol, n-propanol, etc.
S200: coating n kinds of catalyst slurry with different particle sizes on the S 1、S2、S3......、Sn area of the proton exchange membrane in the order from small particle size to large particle size, and drying
In the step, the S 1、S2、S3......、Sn area is distributed along the length direction of the proton exchange membrane, n kinds of catalyst slurries with different particle sizes are sequentially coated on the S 1、S2、S3......、Sn area of the proton exchange membrane according to the sequence from small particle sizes to large particle sizes, and then the catalyst slurries are dried, so that a cathode catalyst layer with the catalyst particle sizes sequentially increasing from an air outlet end to an air inlet end is formed on the proton exchange membrane. The gradient structure of the catalyst particle size sequentially increasing from the air outlet end to the air inlet end reduces the reaction rate difference of the cathode catalyst layer caused by the existence of air pressure difference; meanwhile, as the reaction rate of the air inlet end is reduced, the required oxygen is reduced, and the air input amount is constant, the air consumed by the air inlet end is reduced and moves towards the air outlet end, so that the oxygen concentration of the air outlet end is increased, the reaction rate of the cathode catalyst layer of the air outlet end is further improved, and the reaction rate of the whole cathode catalyst layer is balanced.
According to an embodiment of the present application, the drying temperature T 1 of the odd numbered regions in the regions S 1 to S n is 60-85 ℃, the drying temperature T 2 of the even numbered regions in the regions S 1 to S n is 75-100 ℃, and 10 ℃ C. Ltoreq.T 2-T1 ℃ C. Ltoreq.20 ℃. The inventors found that if the drying temperature is too high, cracking of the catalyst layer tends to occur; when the drying temperature is too low, the residual quantity of the solvent in the catalyst layer is large, and the exertion of the electric performance of the membrane electrode is affected; particularly, the drying temperature of the even area is higher than that of the odd area, but if the drying temperature of the even area is higher than that of the odd area and is too small, the thickness of the coating at the juncture of the two areas is higher than that of other areas, which is not beneficial to the thickness consistency control of the whole reaction area; if the drying temperature of the even area is higher than that of the odd area, the problem that the thickness of the junction of the two areas is lower than that of other areas is caused, the consistency control of the thickness of the whole reaction area is not facilitated, the local catalyst amount at the junction is reduced, the reaction rate is slower than that of other areas, and the gradual design concept of integral gradient is influenced.
Therefore, the cathode catalyst layer with balanced reaction rate, small local area humidity and temperature difference and difficult catalyst attenuation failure can be prepared by adopting the method. It should be noted that the features and advantages described above for the cathode catalyst layer are equally applicable to the method, and are not described here.
In a third aspect of the invention, a membrane electrode is provided. According to an embodiment of the invention, the membrane electrode comprises a proton exchange membrane, a cathode catalyst layer and an anode catalyst layer, wherein the anode catalyst layer is arranged on one side surface of the proton exchange membrane, and the cathode catalyst layer is arranged on the other side surface of the proton exchange membrane, wherein the cathode catalyst layer is the cathode catalyst layer or the cathode catalyst layer prepared by adopting the method. Thus, the membrane electrode has a longer service life. It should be noted that the features and advantages described above for the cathode catalyst layer and the preparation method thereof are also applicable to the membrane electrode, and are not described herein.
In a fourth aspect of the invention, a fuel cell is provided. According to an embodiment of the present invention, the fuel cell includes the above membrane electrode. Thus, the fuel cell has a long service life. It should be noted that the features and advantages described above for the membrane electrode are equally applicable to the fuel cell, and are not described herein.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
Example 1
(1) And designing a gradient distribution structure of a cathode catalyst layer in the membrane electrode reaction zone according to the simulation result of the bipolar plate flow field.
(2) Mixing 6 cathode catalysts with different particle sizes, ionomer and solvent to prepare 6 catalyst slurries with different particle sizes, wherein the cathode catalysts are Pt/C, the platinum loading of the catalyst is 0.32mg/cm 2, the ionomer is long-chain branched perfluorosulfonic acid resin, EW=950 g/mol, and the solvent is a mixture of water and ethanol; 6g of cathode catalyst, 6g of ionomer and 50g of solvent ethanol and 38g of water with each particle size are mixed.
(3) Referring to fig. 2 and 3, 6 kinds of catalyst slurries having different particle diameters are sequentially coated on the proton exchange membrane in the region S 1、S2、S3、S4、S5、S6, the region S 1 is close to the air outlet 11 end, the region S 6 is close to the air inlet 12 end, and the regions S 1、S2、S3、S4、S5、S6 have the same area, and then dried to form the cathode catalyst layer 20, wherein the drying temperature of the region S 1、S3、S5 is 65 ℃ and the drying temperature of the region S 2、S4、S6 is 75 ℃, and the specific cathode catalyst particle diameters in the region S 1、S2、S3、S4、S5、S6 are shown in table 1.
(4) Referring to fig. 3, an anode catalyst layer 30 was prepared by coating an anode catalyst slurry, which was Pt/C, on the other side of the proton exchange membrane 10, wherein the anode catalyst platinum loading was 0.08mg/cm 2.
(5) And packaging the proton exchange membrane with the cathode and anode catalyst layers and the gas diffusion layer to prepare the membrane electrode.
TABLE 1
| Zone of proton exchange membrane | S1 | S2 | S3 | S4 | S5 | S6 |
| Cathode catalyst D 50/nm | 82 | 115 | 129 | 148 | 170 | 193 |
Example 2
(1) And designing a gradient distribution structure of a cathode catalyst layer in the membrane electrode reaction zone according to the simulation result of the bipolar plate flow field.
(2) Mixing 6 cathode catalysts with different particle sizes, ionomer and solvent to prepare 6 catalyst slurries with different particle sizes, wherein the cathode catalysts are Pt/C, the platinum loading of the catalyst is 0.28mg/cm 2, the ionomer is short-branched-chain perfluorinated sulfonic acid resin, EW=800 g/mol, and the solvent is a mixture of isopropanol and water; 5g of cathode catalyst, 5g of ionomer, and 50g of isopropanol, 40g of ethanol were mixed for each particle size.
(3) Referring to fig. 2 and 3, 6 kinds of catalyst slurries having different particle diameters are sequentially coated on the proton exchange membrane in the region S 1、S2、S3、S4、S5、S6, the region S 1 is close to the air outlet 11 end, the region S 6 is close to the air inlet 12 end, and the regions S 1、S2、S3、S4、S5、S6 have the same area, and then dried to form the cathode catalyst layer 20, wherein the drying temperature of the region S 1、S3、S5 is 70 ℃, the drying temperature of the region S 2、S4、S6 is 85 ℃, and the specific cathode catalyst particle diameters in the region S 1、S2、S3、S4、S5、S6 are shown in table 2.
(4) Referring to fig. 3, an anode catalyst layer 30 was prepared by coating an anode catalyst slurry, which was Pt/C, on the other side of the proton exchange membrane 10, wherein the anode catalyst platinum loading was 0.05mg/cm 2.
(5) And packaging the proton exchange membrane with the cathode and anode catalyst layers and the gas diffusion layer to prepare the membrane electrode.
TABLE 2
| Zone of proton exchange membrane | S1 | S2 | S3 | S4 | S5 | S6 |
| Cathode catalyst D 50/nm | 79 | 108 | 124 | 145 | 166 | 189 |
Example 3
(1) And designing a gradient distribution structure of a cathode catalyst layer in the membrane electrode reaction zone according to the simulation result of the bipolar plate flow field.
(2) Mixing 4 cathode catalysts with different particle sizes, ionomer and solvent to prepare 4 catalyst slurries with different particle sizes, wherein the cathode catalysts are Pt/Co, the platinum loading of the catalyst is 0.28mg/cm 2, the ionomer is short-branched-chain perfluorinated sulfonic acid resin, EW=700 g/mol, and the solvent is n-propanol and water; 6g of cathode catalyst, 5g of ionomer, 49g of n-propanol and 40g of water were mixed with each other.
(3) The catalyst slurries with 4 different particle sizes are coated on the S 1、S2、S3、S4 area, the S 1 area is close to the air outlet end, the S 4 area is close to the air inlet end, the areas of the S 1、S2、S3、S4 are the same in sequence from small particle sizes to large particle sizes, and then the cathode catalyst layer is formed by drying, wherein the drying temperature of the S 1、S3 area is 70 ℃, the drying temperature of the S 2、S4 area is 85 ℃, and the specific cathode catalyst particle sizes in the S 1、S2、S3、S4 area are shown in table 3.
(4) And coating anode catalyst slurry on the other side of the proton exchange membrane to prepare an anode catalyst layer, wherein the platinum loading of the anode catalyst is 0.07mg/cm 2, and the anode catalyst is Pt/C.
(5) And packaging the proton exchange membrane with the cathode and anode catalyst layers and the gas diffusion layer to prepare the membrane electrode.
TABLE 3 Table 3
| Zone of proton exchange membrane | S1 | S2 | S3 | S4 |
| Cathode catalyst D 50/nm | 82 | 109 | 123 | 142 |
Comparative example 1
According to the traditional membrane electrode preparation method, the platinum loading of a cathode catalyst layer is 0.32mg/cm 2, the platinum loading of an anode catalyst layer is 0.08mg/cm 2, cathode slurry and anode slurry with the same catalyst content and type as in example 1 are respectively and directly coated on two surfaces of a proton exchange membrane, and the membrane electrode prepared by the traditional method is obtained through frame packaging and GDL lamination.
Comparative example 2
According to the traditional membrane electrode preparation method, the platinum loading of a cathode catalyst layer is 0.28mg/cm 2, the platinum loading of an anode catalyst layer is 0.05mg/cm 2, cathode slurry and anode slurry with the same catalyst content and type as those of the example 2 are respectively and directly coated on two surfaces of a proton exchange membrane, and the membrane electrode prepared by the traditional method is obtained through frame packaging and GDL lamination.
Comparative example 3
According to the traditional membrane electrode preparation method, the platinum loading of a cathode catalyst layer is 0.28mg/cm 2, the platinum loading of an anode catalyst layer is 0.07mg/cm 2, cathode slurry and anode slurry with the same catalyst content and type as those of the example 2 are respectively and directly coated on two surfaces of a proton exchange membrane, and the membrane electrode prepared by the traditional method is obtained through frame packaging and GDL lamination.
The electrical properties and durability of the membrane electrodes of examples 1 to 3 and comparative examples 1 to 3 were measured as follows:
The power density calculating method comprises the following steps: based on a test polarization curve under hydrogen air conditions at 75 ℃, cathode back pressure of 250/260KPa, voltage was recorded at 1.5A/cm 2, power density = current density.
Accelerated durability test method: DOE test standard, platinum dissolution and carbon corrosion (DOE Durability) voltage drop <30mV loss,ECSA<40%loss.
The measurement results of the electrical properties and durability of the membrane electrodes of examples 1 to 3 and comparative examples 1 to 3 are shown in Table 4.
TABLE 4 Table 4
It can be seen from Table 4 that the power density of the examples is higher than that of the comparative examples, and that the durability of the membrane electrode of the examples is much better than that of the comparative examples, as can also be seen from the results of both the platinum dissolution and carbon corrosion tests. Therefore, the cathode catalyst layer with the catalyst particle sizes sequentially increasing from the air outlet end to the air inlet end has the advantages that the reaction rate of the cathode catalyst layer is balanced, the attenuation failure of the cathode catalyst is effectively reduced, and the power density and the service life of the membrane electrode can be improved.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular 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 invention. In this specification, schematic representations of the above terms are not necessarily directed 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, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (10)
1. A cathode catalyst layer, wherein an air inlet port is formed at one end of the cathode catalyst layer, an air outlet port is formed at the other end of the cathode catalyst layer, and the catalyst particle diameter in the cathode catalyst layer increases in sequence from the air outlet port to the length direction of the cathode catalyst layer at the air inlet port.
2. The cathode catalyst layer according to claim 1, wherein the cathode catalyst layer sequentially defines a plurality of regions, which are sequentially designated as S 1、S2…Sn, from the air outlet end to the air inlet end in a length direction of the cathode catalyst layer, and the catalyst particle diameters of the regions S 1 to S n sequentially increase.
3. The cathode catalyst layer according to claim 2, wherein D 50 (1) of the catalyst in the S 1 region is 50 to 110 μm, and D 50(n)＝(D50 (1) +20 (n-1)) ± 20 μm of the catalyst in the S n region.
4. The cathode catalyst layer according to claim 2, characterized in that 3.ltoreq.n.ltoreq.20, preferably 3.ltoreq.n.ltoreq.10.
5. The cathode catalyst layer according to claim 2, wherein the catalyst particle size of individual of the regions is the same;
Optionally, each of the S 1 to S n regions has the same area;
Optionally, the catalyst types and amounts are the same for the S 1 to S n regions.
6. A method of preparing the cathode catalyst layer of any one of claims 1-5, comprising:
(1) Respectively mixing n cathode catalysts with different particle sizes, ionomer and solvent so as to obtain n catalyst slurries with different particle sizes;
(2) And sequentially coating the catalyst slurries with n different particle sizes on the S 1、S2、S3......、Sn area of the proton exchange membrane according to the sequence from small particle sizes to large particle sizes, distributing the S 1、S2、S3......、Sn area along the length direction of the exchange membrane, and then drying to obtain the cathode catalyst layer.
7. The method of claim 6 wherein in step (1), the ionomer comprises a perfluorosulfonic acid resin having an EW of 700-1000 g/mol;
Optionally, the cathode catalyst comprises at least one of Pt/C, pt/Co/C and Pt/Co/Mn.
8. The method according to claim 6, wherein in the step (2), the drying temperature T 1 of the odd numbered region of the regions S 1 to S n is 60 to 85 ℃, the drying temperature T 2 of the even numbered region of the regions S 1 to S n is 75 to 100 ℃, and T 2-T1 is 10 ℃ to 20 ℃.
9. A membrane electrode comprising a proton exchange membrane, a cathode catalyst layer and an anode catalyst layer, wherein the anode catalyst layer is disposed on one side surface of the proton exchange membrane, and the cathode catalyst layer is disposed on the other side surface of the proton exchange membrane, wherein the cathode catalyst layer is the cathode catalyst layer according to any one of claims 1 to 5 or the cathode catalyst layer prepared by the method according to any one of claims 6 to 8.
10. A fuel cell comprising the membrane electrode of claim 9.
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