CN117080480A - Porous substrate membrane, catalyst coated membrane electrode and application thereof - Google Patents
Porous substrate membrane, catalyst coated membrane electrode and application thereof Download PDFInfo
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- CN117080480A CN117080480A CN202210506332.1A CN202210506332A CN117080480A CN 117080480 A CN117080480 A CN 117080480A CN 202210506332 A CN202210506332 A CN 202210506332A CN 117080480 A CN117080480 A CN 117080480A
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- 239000012528 membrane Substances 0.000 title claims abstract description 129
- 239000000758 substrate Substances 0.000 title claims abstract description 123
- 239000003054 catalyst Substances 0.000 title claims abstract description 86
- 238000000034 method Methods 0.000 claims abstract description 35
- 229920000295 expanded polytetrafluoroethylene Polymers 0.000 claims abstract description 31
- 238000010023 transfer printing Methods 0.000 claims abstract description 21
- 239000011148 porous material Substances 0.000 claims abstract description 19
- 239000000446 fuel Substances 0.000 claims abstract description 15
- 238000010030 laminating Methods 0.000 claims abstract description 11
- 239000000853 adhesive Substances 0.000 claims abstract description 7
- 230000001070 adhesive effect Effects 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims description 33
- 238000010438 heat treatment Methods 0.000 claims description 16
- 239000007789 gas Substances 0.000 claims description 13
- 238000002360 preparation method Methods 0.000 claims description 11
- 230000009477 glass transition Effects 0.000 claims description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 229920002799 BoPET Polymers 0.000 claims description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 6
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 6
- -1 polytetrafluoroethylene Polymers 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 229920000554 ionomer Polymers 0.000 abstract description 35
- 239000011248 coating agent Substances 0.000 abstract description 25
- 238000000576 coating method Methods 0.000 abstract description 25
- 230000008569 process Effects 0.000 abstract description 25
- 230000009471 action Effects 0.000 abstract description 12
- 238000009792 diffusion process Methods 0.000 abstract description 8
- 230000005484 gravity Effects 0.000 abstract description 8
- 239000012466 permeate Substances 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 113
- 229920000139 polyethylene terephthalate Polymers 0.000 description 17
- 230000003197 catalytic effect Effects 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 10
- 238000007731 hot pressing Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 229920000642 polymer Polymers 0.000 description 7
- 239000000376 reactant Substances 0.000 description 7
- 230000005540 biological transmission Effects 0.000 description 6
- 239000002985 plastic film Substances 0.000 description 5
- 229920006255 plastic film Polymers 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000011949 solid catalyst Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011534 incubation Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920003207 poly(ethylene-2,6-naphthalate) Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0239—Organic resins; Organic polymers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/023—Porous and characterised by the material
- H01M8/0241—Composites
- H01M8/0245—Composites in the form of layered or coated products
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Composite Materials (AREA)
- Laminated Bodies (AREA)
Abstract
The application provides a porous substrate membrane, a catalyst coating membrane electrode and application thereof, and relates to the technical field of fuel cells. The porous base film is mainly prepared by laminating an expanded polytetrafluoroethylene porous film on a substrate layer; the porous membrane layer of the expanded polytetrafluoroethylene is provided with micropores, and after the catalyst coating is coated, ionomer in the catalyst ink is subjected to the action of gravity and capillary force and can downwards permeate into the pores of the porous substrate membrane, so that the structure that the ionomer content of the catalyst coating membrane electrode prepared by transfer printing is more in the part of the catalyst layer close to the proton exchange membrane side and less in the part of the catalyst layer close to the gas diffusion layer is realized. Meanwhile, the substrate layer has higher strength and heat resistance, and the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous membrane is more than 2N/m, so that the stripping phenomenon in the transfer printing process is effectively avoided, and the deformation problem of the porous substrate membrane in the transfer printing process is also avoided.
Description
Technical Field
The application relates to the technical field of fuel cells, in particular to a porous substrate membrane, a catalyst coating membrane electrode and application thereof.
Background
The catalyst coated membrane (Catalyst Coated Membrane, CCM) is a core component of a proton exchange membrane fuel cell (Proton Exchange Membrane Fuel Cell, PEMFC) and mainly consists of three parts, namely a proton exchange membrane (Proton Exchange Membrane, PEM), a cathode catalytic layer and an anode catalytic layer. The preparation of the catalyst coating film and the optimization of the catalytic layer structure are key technologies of the PEMFC, and the structure and the preparation process of the PEMFC not only directly determine the performance of the fuel cell, but also are very important for reducing the production cost, improving the specific power and accelerating the commercialization process.
In the preparation of the catalyst coated film, the base film is a material for coating ink. The fluid catalyst ink is uniformly coated onto a substrate membrane and then dried in an oven to form a solid catalyst layer, and then the catalyst layer on the substrate membrane is transferred onto a proton exchange membrane by a hot pressing process to form a catalyst coated membrane electrode. Typically, the substrate film is a smooth surfaced plastic film, such as PTFE, PET, PEN or PP, etc. However, the plastic film as the base film needs to maintain flatness at the time of coating, and cannot be bent, curled, deformed, and wrinkled. In addition, in the transfer process, sufficient heat resistance is required so that deformation due to temperature rise is not generated in the hot pressing process at about 160 ℃.
The porous base film consists of a plastic film (substrate layer, such as PET, PI, PEN, POM) and an e-PTFE layer laminated on the substrate layer. Since the e-PTFE layer has pores of controllable size and shape, this structure has the advantage that the ionomer in the ink printed on the substrate film is subjected to gravity and capillary forces, and the ionomer in the catalyst ink penetrates down into the pores of the porous substrate film, forming a gradient of ionomer concentration.
However, as shown in fig. 1, due to the lower bonding force between the e-PTFE layer and the substrate layer, a film detachment phenomenon often occurs during the transfer process, i.e., the e-PTFE is transferred to the proton exchange membrane together with the catalyst layer; meanwhile, the existing plastic film with a substrate layer is poor in thermal stability and easy to shrink and deform in the hot-pressing transfer printing process. Thus, the two conditions lead to the existence of a great technical defect of the existing catalyst coated membrane electrode prepared from the porous substrate membrane.
Therefore, it has become necessary and urgent to develop a porous base film which is not liable to release film during transfer and which has excellent heat resistance and is not liable to deform in the base layer to overcome the above problems.
In view of this, the present application has been made.
Disclosure of Invention
A first object of the present application is to provide a porous base membrane that realizes a structure in which the ionomer content of the catalyst layer portion of the transfer-prepared catalyst coated membrane electrode on the side close to the Proton Exchange Membrane (PEM) is higher, and the ionomer content of the catalyst layer portion close to the Gas Diffusion Layer (GDL) is lower, while the porous base membrane also has higher strength and heat resistance.
A second object of the present application is to provide a method for producing a porous base film.
A third object of the present application is to provide a catalyst coated membrane electrode in which a catalyst layer is mainly transferred from the porous base membrane.
The fourth object of the application is to provide an application of the porous substrate membrane and the catalyst coating membrane electrode, which can be widely applied to the preparation process of proton exchange membrane fuel cells.
In order to achieve the above object of the present application, the following technical solutions are specifically adopted:
the porous base film is mainly prepared by laminating a bulked polytetrafluoroethylene porous film on a substrate layer;
the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous membrane is more than 2N/m;
the properties of the substrate layer satisfy at least one of:
the glass transition temperature is more than 90 ℃, the crystallinity is 35-39%, and the mechanical strength is 320-355 Mpa.
Further, the substrate layer includes any one of a PET film, a PI film, a PEN film, and a POM film, and is preferably a PET film.
Further, the pore diameter of the expanded polytetrafluoroethylene porous membrane is 0.5-50 um;
the surface tension of the expanded polytetrafluoroethylene porous membrane is less than 30mN/m.
The application provides a preparation method of the porous substrate film, which comprises the following steps:
(a) Heating the substrate layer to 250-280 ℃, and preserving heat for 10-60min to obtain an intermediate A;
(b) When the intermediate A is cooled to 200-230 ℃, laminating the intermediate A and the expanded polytetrafluoroethylene porous membrane to obtain an intermediate B;
(c) And cooling the intermediate B to 100-140 ℃, preserving heat for 10-60min, and then cooling to 20-30 ℃ to obtain the porous substrate film.
Further, said step (a) is performed under a protective gas;
preferably, the protective gas includes at least one of nitrogen, argon, and carbon dioxide.
Further, the temperature rising speed of the substrate layer in the step (a) is 1-10 ℃/min;
preferably, the cooling speed of the intermediate A in the step (b) is 1-5 ℃/min;
preferably, the cooling speed of the intermediate B in the step (c) is 1-5 ℃/min.
Further, the pressure of laminating the intermediate A with the expanded polytetrafluoroethylene porous membrane in the step (b) is 1-2.5Mpa.
The catalyst layer of the catalyst coated membrane electrode is mainly obtained by transfer printing of the porous substrate membrane.
The porous substrate membrane and the catalyst coating membrane electrode provided by the application are applied to the preparation of proton exchange membrane fuel cells.
Compared with the prior art, the application has the beneficial effects that:
the porous base film is mainly prepared by laminating a bulked polytetrafluoroethylene porous film on a substrate layer; the expanded polytetrafluoroethylene porous membrane (e-PTFE) layer is provided with micropores with controllable size and shape, after the catalyst coating is coated, ionomer in the catalyst ink is subjected to gravity and capillary force and can downwards permeate into the pores of the porous substrate membrane, so that the ionomer content of the catalyst coating membrane electrode prepared by transfer printing is higher in the catalytic layer part close to the Proton Exchange Membrane (PEM) side, the ionomer content of the catalytic layer part close to the Gas Diffusion Layer (GDL) is lower, and the ionomer concentration gradient distribution state is more favorable for constructing a transmission channel of protons, electrons and reactants in the catalytic layer.
Meanwhile, the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous membrane is more than 2N/m, so that the phenomenon of stripping of the e-PTFE layer in the transfer printing process is effectively avoided; in addition, the properties of the substrate layer of the present application satisfy at least one of the following: the glass transition temperature is more than 90 ℃, the crystallinity is 35-39%, and the mechanical strength is 320-355 Mpa. Therefore, the substrate layer has higher strength and heat resistance, and the problem of shrinkage deformation in the hot-pressing transfer printing process of the porous substrate film is avoided.
The preparation method of the porous base film provided by the application comprises the step of carrying out composite lamination on a base material layer and a bulked polytetrafluoroethylene porous film in the process of heat treatment of the base material layer to obtain the porous base film. The preparation method has the advantages of simple processing technology and easy operation.
The catalyst layer of the catalyst coated membrane electrode is mainly obtained by transfer printing the porous substrate membrane. Because the e-PTFE layer in the porous substrate film is provided with micropores with controllable size and shape, and ionomer in the catalyst ink printed on the substrate film is penetrated downwards into the pores of the porous substrate film under the action of gravity and capillary force, the ionomer content of the catalyst coating film electrode prepared by hot-press transfer printing of the e-PTFE porous substrate film is higher in the ionomer content of the catalyst layer part close to a proton exchange film (PEM), and the ionomer content of the catalyst layer part close to a Gas Diffusion Layer (GDL) is lower, and the ionomer concentration gradient distribution state is more favorable for constructing a transmission channel of protons, electrons and reactants in the catalyst layer. And further, the electrochemical performance of the catalyst coating membrane electrode is improved, the CCM structure is optimized, and the specific power of a Proton Exchange Membrane Fuel Cell (PEMFC) is improved so as to meet the whole fuel cell requirement.
The porous substrate membrane and the catalyst coating membrane electrode provided by the application can be widely applied to the preparation process of proton exchange membrane fuel cells.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram showing the technical drawbacks of a catalyst coated membrane electrode made from a porous substrate membrane according to the prior art;
FIG. 2 is a schematic structural view of a porous base film according to example 1 of the present application;
FIG. 3 is a graph showing the electrochemical performance of a catalyst coated membrane electrode prepared from the porous substrate membrane according to experimental example 2 of the present application compared with that of a catalyst coated membrane electrode prepared from a conventional non-porous substrate membrane.
Detailed Description
The technical solutions of the present application will be clearly and completely described in connection with the embodiments, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
According to one aspect of the present application, a porous base film is produced mainly by laminating an expanded polytetrafluoroethylene porous film on a base material layer;
the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous membrane is more than 2N/m;
the properties of the substrate layer satisfy at least one of:
the glass transition temperature is more than 90 ℃, the crystallinity is 35-39%, and the mechanical strength is 320-355 Mpa.
The porous base film is mainly prepared by laminating a bulked polytetrafluoroethylene porous film on a substrate layer; the expanded polytetrafluoroethylene porous membrane (e-PTFE) layer is provided with micropores with controllable size and shape, after the catalyst coating is coated, ionomer in the catalyst ink is subjected to gravity and capillary force and can downwards permeate into the pores of the porous substrate membrane, so that the ionomer content of the catalyst coating membrane electrode prepared by transfer printing is higher in the catalytic layer part close to the Proton Exchange Membrane (PEM) side, the ionomer content of the catalytic layer part close to the Gas Diffusion Layer (GDL) is lower, and the ionomer concentration gradient distribution state is more favorable for constructing a transmission channel of protons, electrons and reactants in the catalytic layer.
Meanwhile, the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous membrane is more than 2N/m, so that the phenomenon of stripping of the e-PTFE layer in the transfer printing process is effectively avoided; in addition, the properties of the substrate layer of the present application satisfy at least one of the following: the glass transition temperature is more than 90 ℃, the crystallinity is 35-39%, and the mechanical strength is 320-355 Mpa. Therefore, the substrate layer has higher strength and heat resistance, and the problem of shrinkage deformation in the hot-pressing transfer printing process of the porous substrate film is avoided.
In a preferred embodiment of the present application, the substrate layer includes any one of a PET film, a PI film, a PEN film, and a POM film, and is preferably a PET film.
In a preferred embodiment of the present application, the pore size of the expanded polytetrafluoroethylene porous membrane is 0.5 to 50um;
the surface tension of the expanded polytetrafluoroethylene porous membrane is less than 30mN/m.
As a preferred embodiment, the pore diameter, the porosity and the thickness of the e-PTFE porous substrate membrane are controllable, so that the structure of the catalytic layer can be optimized by controlling the porosity and the thickness. The expanded polytetrafluoroethylene porous membrane with the pore diameter and the surface tension range can better penetrate downwards into the pores of the porous substrate membrane under the action of gravity and capillary force after the ionomer in the catalyst ink is coated with the catalyst coating.
According to an aspect of the present application, a method for producing the above porous base film, the method comprising:
(a) Heating the substrate layer to 250-280 ℃, and preserving heat for 10-60min to obtain an intermediate A;
it should be noted that, the step (a) can make the substrate layer in a viscoelastic state at the temperature of 250-280 ℃, and keep the temperature for 10-60min, so that the polymer chain is fully extended, and further, the steric hindrance of the molecular chain can be reduced in the next cooling process, so as to form more crystallization areas;
(b) When the intermediate A is cooled to 200-230 ℃, laminating the intermediate A and the expanded polytetrafluoroethylene porous membrane to obtain an intermediate B;
in the step (b), the intermediate A is cooled to 200-230 ℃ to enable the polymer chains to shrink orderly, so that the winding is reduced, and the formation and the growth of a crystallization area are facilitated; then laminating the intermediate A and the expanded polytetrafluoroethylene porous membrane, so that the polymer chains near the contact surface of the two layers of materials can penetrate and wind each other, and the e-PTFE and the PET can move under the action of a roller press under the temperature, so that the mechanical property of the interface of the two materials can be improved, and the pore structure of the e-PTFE layer is not affected;
(c) And cooling the intermediate B to 100-140 ℃, preserving heat for 10-60min, and then cooling to 20-30 ℃ to obtain the porous substrate film.
In the step (c), the intermediate B is cooled to 100-140 ℃ and kept for 10-60min, so that the polymer chain can be further contracted, the crystallization area is increased, and the mechanical strength and the thermal stability of the polymer chain are further improved;
as a preferred embodiment, the heat treatment process can effectively improve the crystallinity of the porous substrate film, raise the glass transition temperature, and further improve the mechanical stability and the thermal stability of the porous substrate film; the substrate layer of the porous substrate film can keep flatness during coating, and can not generate phenomena of bending, curling, deformation and wrinkling, and the porous substrate film has better heat resistance, and can not generate deformation caused by temperature rise in the hot pressing process at about 160 ℃.
Meanwhile, the porous substrate film prepared by the process can realize the technical effects that the glass transition temperature of the substrate layer is more than 90 ℃, the crystallinity is 35-39% and the mechanical strength is 320-355 Mpa, so that the high-temperature deformation of the substrate layer in the transfer printing process is effectively avoided; meanwhile, the mechanical strength of the e-PTFE layer in the porous substrate film can be greatly improved; the mechanical strength of the e-PTFE layer was tested to satisfy the following conditions:
"(a) = (B) > (C)", or "(a) > (B) > (C)", or "(B) > (C), and (B) > (a)";
wherein, (A) is the interfacial adhesion force (2N/m) between the substrate layer and the e-PTFE;
(B) Mechanical strength of e-PTFE;
(C) Is the interfacial adhesion between e-PTFE and the catalyst layer.
In a preferred embodiment of the application, said step (a) is carried out under a protective gas;
preferably, the protective gas includes at least one of nitrogen, argon, and carbon dioxide.
In a preferred embodiment of the present application, the substrate layer in the step (a) is heated at a heating rate of 1 to 10 ℃/min;
preferably, the cooling speed of the intermediate A in the step (b) is 1-5 ℃/min;
preferably, the cooling speed of the intermediate B in the step (c) is 1-5 ℃/min.
As a preferred embodiment, the temperature is raised.
In a preferred embodiment of the present application, the pressure at which intermediate A is laminated with the expanded polytetrafluoroethylene porous membrane in step (b) is 1 to 2.5MPa.
According to one aspect of the present application, a catalyst coated membrane electrode whose catalyst layer is mainly transferred from the above porous base membrane.
The catalyst layer of the catalyst coated membrane electrode is mainly obtained by transfer printing the porous substrate membrane. Because the e-PTFE layer in the porous substrate film is provided with micropores with controllable size and shape, and ionomer in the catalyst ink printed on the substrate film is penetrated downwards into the pores of the porous substrate film under the action of gravity and capillary force, the ionomer content of the catalyst coating film electrode prepared by hot-press transfer printing of the e-PTFE porous substrate film is higher in the ionomer content of the catalyst layer part close to a proton exchange film (PEM), and the ionomer content of the catalyst layer part close to a Gas Diffusion Layer (GDL) is lower, and the ionomer concentration gradient distribution state is more favorable for constructing a transmission channel of protons, electrons and reactants in the catalyst layer. And further, the electrochemical performance of the catalyst coating membrane electrode is improved, the CCM structure is optimized, and the specific power of a Proton Exchange Membrane Fuel Cell (PEMFC) is improved so as to meet the whole fuel cell requirement.
It should be noted that, in the existing substrate membrane solution only being a plastic film, after the catalyst ink fluid is coated on the substrate membrane, the ionomer concentration on the side close to the substrate membrane is higher due to the action of gravity, so that when the catalyst ink fluid is transferred onto the PEM, the ionomer concentration on the side close to the PEM is lower than that on the side close to the substrate membrane, which is not beneficial to construct the transmission channels of protons, electrons and reactants in the catalytic layer. The catalytic layer structure formed on the premise of using the same material is unfavorable for optimizing the performance of the PEMFC.
By arranging the e-PTFE layer, the ionomer in the catalyst ink is penetrated downwards into the holes of the porous substrate membrane, so that gradient change of the concentration of the ionomer is realized, the problem that the concentration of the ionomer close to the PEM side is lower than that of the ionomer close to a Gas Diffusion Layer (GDL) in the prior art is avoided, the CCM structure is optimized, and the electrochemical performance of the catalyst coating membrane electrode is improved.
According to one aspect of the application, the use of a porous substrate membrane, a catalyst coated membrane electrode in the manufacture of a proton exchange membrane fuel cell.
The porous substrate membrane and the catalyst coating membrane electrode provided by the application can be widely applied to the preparation process of proton exchange membrane fuel cells.
The technical scheme of the application will be further described with reference to examples.
Example 1
As shown in fig. 2, a porous base film is prepared by a method comprising the steps of:
(a) Under the protection of inert gas, heating the PET substrate layer to 250 ℃ at a heating rate of 1 ℃/min to enable the PET substrate layer to be in a viscoelastic state; then preserving heat for 10min to obtain an intermediate A;
(b) Slowly cooling the intermediate A at a cooling speed of 1 ℃/min, and introducing an e-PTFE reel when the temperature is reduced to 200 ℃, wherein the e-PTFE and the PET move under the action of a roller press, and the macromolecular chains near the contact surface penetrate and wind each other to obtain an intermediate B;
the pore diameter of the expanded polytetrafluoroethylene porous membrane (e-PTFE) is 0.5um, and the surface tension is 28mN/m;
(c) And slowly cooling the intermediate B to 100 ℃ at a cooling rate of 1 ℃/min, preserving heat for 20min, and then cooling to 20 ℃ to obtain the porous substrate film.
Example 2
A porous base film, the method of preparing the porous base film comprising the steps of:
(a) Under the protection of inert gas, heating the PET substrate layer to 280 ℃ at a heating rate of 10 ℃/min to enable the PET substrate layer to be in a viscoelastic state; then preserving heat for 60min to obtain an intermediate A;
(b) Slowly cooling the intermediate A at a cooling speed of 5 ℃/min, and introducing an e-PTFE reel when the temperature is reduced to 230 ℃, wherein the e-PTFE and the PET move under the action of a roller press under the action of a high polymer chain near a contact surface and penetrate and wind each other to obtain an intermediate B;
the pore diameter of the expanded polytetrafluoroethylene porous membrane (e-PTFE) is 50um, and the surface tension is 10mN/m;
(c) And slowly cooling the intermediate B to 140 ℃ at a cooling speed of 5 ℃/min, preserving heat for 60min, and then cooling to 30 ℃ to obtain the porous substrate film.
Example 3
A porous base film, the method of preparing the porous base film comprising the steps of:
(a) Under the protection of inert gas, heating the PET substrate layer to 270 ℃ at a heating rate of 8 ℃/min, so that the PET substrate layer is in a viscoelastic state; then preserving heat for 40min to obtain an intermediate A;
(b) Slowly cooling the intermediate A at a cooling speed of 3 ℃/min, and introducing an e-PTFE reel when the temperature is reduced to 220 ℃, wherein the e-PTFE and the PET move under the action of a roller press, and the macromolecular chains near the contact surface penetrate and wind each other to obtain an intermediate B;
the pore diameter of the expanded polytetrafluoroethylene porous membrane (e-PTFE) is 25um, and the surface tension is 18mN/m;
(c) And slowly cooling the intermediate B to 125 ℃ at a cooling rate of 3 ℃/min, preserving heat for 40min, and then cooling to 25 ℃ to obtain the porous substrate film.
Comparative example 1
This example is the same as example 3 except that the holding time in step (a) is 5 min.
Comparative example 2
This example is the same as example 3 except that the cooling rate in steps (b) and (c) is 10 ℃/min.
Comparative example 3
A porous base film, the method of preparing the porous base film comprising the steps of:
(a) Under the protection of inert gas, heating the PET substrate layer to 270 ℃ at a heating rate of 8 ℃/min, so that the PET substrate layer is in a viscoelastic state; then preserving heat for 40min to obtain an intermediate A;
(b) Slowly cooling the intermediate A at a cooling speed of 3 ℃/min, and introducing an e-PTFE reel when the temperature is reduced to 220 ℃, wherein the e-PTFE and the PET move under the action of a roller press, and the macromolecular chains near the contact surface penetrate and wind each other to obtain an intermediate B; and then cooling to 25 ℃ to obtain the porous substrate film.
The pore diameter of the expanded polytetrafluoroethylene porous membrane (e-PTFE) is 25um, and the surface tension is 18mN/m;
this example is the same as example 3 except that step (c) is not included for a 40min incubation at 125 ℃.
Comparative example 4
A porous base film, the method of preparing the porous base film comprising the steps of:
(a) Introducing an e-PTFE reel when the temperature of the PET substrate layer is raised to 220 ℃ at a heating rate of 8 ℃/min, wherein the e-PTFE and the PET move under the action of a roller press under the condition that polymer chains near the contact surface penetrate and wind each other; and then cooling to 25 ℃ to obtain the porous substrate film.
The pore diameter of the expanded polytetrafluoroethylene porous membrane (e-PTFE) is 25um, and the surface tension is 18mN/m.
Experimental example 1
In order to show that the porous substrate film prepared by the method can effectively avoid the phenomenon that the e-PTFE layer and the substrate layer have lower binding force and often have stripping in the transfer printing process; and the existing substrate layer has poor thermal stability and is easy to shrink and deform in the hot-pressing transfer printing process. The porous base films prepared in examples 1 to 3 and comparative examples 1 to 4 were subjected to performance test after being coated with a catalyst ink, and the specific results are shown in the following table:
as shown by the experiment, the porous substrate film prepared by the process can realize the technical effects that the glass transition temperature of the substrate layer is more than 90 ℃, the crystallinity is 35-39% and the mechanical strength is 320-355 Mpa, and effectively avoids the high-temperature deformation of the substrate layer in the transfer printing process; meanwhile, the mechanical strength of the e-PTFE layer in the porous substrate film can be greatly improved, and the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous film is more than 2N/m; through detection, the mechanical strength of the e-PTFE layers in the technical schemes of the embodiments 1 to 3 can meet the following conditions:
"(a) = (B) > (C)", or "(a) > (B) > (C)", or "(B) > (C), and (B) > (a)";
wherein, (A) is the interfacial adhesion (> 2N/m) between the substrate layer and the e-PTFE;
(B) Tear strength for e-PTFE;
(C) Is the interfacial adhesion between e-PTFE and the catalyst layer.
Thereby effectively avoiding the phenomenon of stripping the e-PTFE layer in the transfer printing process.
The interfacial adhesion between the substrate layer and the e-PTFE in comparative examples 1-4 is low, and particularly the interfacial adhesion between the substrate layer and the e-PTFE in comparative examples 1, 3 and 4 is even less than the interfacial adhesion between the e-PTFE and the catalyst layer, so that the e-PTFE layer is easy to be de-molded in the thermal transfer process. Meanwhile, the glass transition temperatures, crystallinity, mechanical strength and other properties of comparative examples 1 to 4 are also poor, and in particular, in the embodiment in which the substrate layer of comparative example 4 is not heat treated, the glass transition temperature is only 77 ℃, the crystallinity is more 5%, and the mechanical strength is only 75Mpa, and as is apparent from the above properties, the porous substrate films produced in comparative examples 1 to 4 are also more prone to high temperature deformation during transfer.
Experimental example 2
To demonstrate the higher ionomer content of the catalyst coated membrane electrode transferred from the porous substrate membrane made by the present application, the ionomer content of the catalyst layer portion near the Proton Exchange Membrane (PEM) was lower, and the ionomer content of the catalyst layer portion near the Gas Diffusion Layer (GDL) was lower, which was more beneficial to the construction of proton, electron and reactant transport channels in the catalyst layer. Thereby improving the technical effect of the electrochemical performance of the catalyst coating membrane electrode.
The applicant now dries the porous base membrane coated catalyst ink of example 3 to form a solid catalyst layer, as well as a solid catalyst coating layer made from the existing conventional non-porous base membrane; transferring the catalyst layer on the substrate membrane to the proton exchange membrane through a hot pressing process to form a catalyst coating membrane electrode, and detecting the catalyst coating membrane electrode, wherein the specific result is shown in fig. 3:
as can be seen from fig. 3, compared with the catalyst coated membrane electrode prepared from the existing non-porous substrate membrane, the catalyst coated membrane electrode prepared from the porous substrate membrane according to the embodiment 3 of the present application has more efficient construction of the proton, electron and reactant transmission channels in the catalyst layer, and as the current density increases, the catalyst coated membrane electrode prepared from the porous substrate membrane according to the present application can still maintain a higher average voltage than the existing catalyst coated membrane electrode.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.
Claims (10)
1. A porous base film, characterized in that the porous base film is mainly prepared by laminating a bulked polytetrafluoroethylene porous film on a substrate layer;
the adhesive force between the substrate layer and the expanded polytetrafluoroethylene porous membrane is more than 2N/m;
the properties of the substrate layer satisfy at least one of:
the glass transition temperature is more than 90 ℃, the crystallinity is 35-39%, and the mechanical strength is 320-355 Mpa.
2. The porous base film according to claim 1, wherein the substrate layer comprises any one of a PET film, PI film, PEN film, POM film, preferably a PET film.
3. The porous base membrane of claim 1, wherein the pore size of the expanded polytetrafluoroethylene porous membrane is 0.5-50 um;
the surface tension of the expanded polytetrafluoroethylene porous membrane is less than 30mN/m.
4. A method of producing the porous base film according to any one of claims 1 to 3, characterized by comprising:
(a) Heating the substrate layer to 250-280 ℃, and preserving heat for 10-60min to obtain an intermediate A;
(b) When the intermediate A is cooled to 200-230 ℃, laminating the intermediate A and the expanded polytetrafluoroethylene porous membrane to obtain an intermediate B;
(c) And cooling the intermediate B to 100-140 ℃, preserving heat for 10-60min, and then cooling to 20-30 ℃ to obtain the porous substrate film.
5. The method of producing a porous base film according to claim 4, wherein the step (a) is performed under a protective gas.
6. The method for producing a porous base film according to claim 5, wherein the protective gas includes at least one of nitrogen, argon, and carbon dioxide.
7. The method for producing a porous base film according to claim 4, wherein the substrate layer in the step (a) is heated at a heating rate of 1 to 10 ℃/min;
preferably, the cooling speed of the intermediate A in the step (b) is 1-5 ℃/min;
preferably, the cooling speed of the intermediate B in the step (c) is 1-5 ℃/min.
8. The method of producing a porous base film according to claim 4, wherein the pressure at which the intermediate a is laminated with the expanded polytetrafluoroethylene porous film in the step (b) is 1 to 2.5Mpa.
9. A catalyst coated membrane electrode, characterized in that the catalyst layer of the catalyst coated membrane electrode is mainly obtained by transfer printing the porous substrate membrane according to any one of claims 1 to 3.
10. Use of a porous substrate membrane according to any one of claims 1 to 3, a catalyst coated membrane electrode according to claim 9, in the preparation of a proton exchange membrane fuel cell.
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