CN111463442A - Catalyst layer, fuel cell membrane electrode and preparation method thereof - Google Patents

Catalyst layer, fuel cell membrane electrode and preparation method thereof Download PDF

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CN111463442A
CN111463442A CN202010287060.1A CN202010287060A CN111463442A CN 111463442 A CN111463442 A CN 111463442A CN 202010287060 A CN202010287060 A CN 202010287060A CN 111463442 A CN111463442 A CN 111463442A
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catalyst
catalyst layer
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area
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汪聪敏
杨敏
李晓琳
朱星烨
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Shanghai Electric Group Corp
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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
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H01M4/861—Porous electrodes with a gradient in the porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8803—Supports for the deposition of the catalytic active composition
    • H01M4/881—Electrolytic membranes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
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    • H01M4/8828—Coating with slurry or ink
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
    • H01M4/8882—Heat treatment, e.g. drying, baking
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • 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
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M2004/8678—Inert electrodes with catalytic activity, e.g. for fuel cells characterised by the polarity
    • H01M2004/8689—Positive electrodes
    • 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
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    • 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 catalyst layer, a fuel cell membrane electrode and a preparation method thereof. The catalyst layer has a width and a length, and the catalyst layer includes at least a 1 st region, a 2 nd region, a 3 rd region … …, and an nth region in this order along the width direction; n is not less than 4 and is an integer; from zone 1 to zone n, the catalyst content decreases in order and the pore size increases in order. The invention respectively carries out gradient design on the catalyst content and the pore size of the membrane electrode in different regions, namely the catalyst content in the gas inlet region is high enough, and the number of macropores in the gas outlet region is high enough, so that the reactant concentration of the gas inlet is highly matched with the catalyst content, and the water content of the gas outlet is highly matched with the number of macropores, thereby improving the utilization rate and the drainage capacity of the membrane electrode catalyst and realizing the improvement of the performance of the membrane electrode.

Description

Catalyst layer, fuel cell membrane electrode and preparation method thereof
Technical Field
The invention relates to a catalyst layer, a fuel cell membrane electrode and a preparation method thereof.
Background
A Proton Exchange Membrane Fuel Cell (PEMFC) is a fuel cell using a proton exchange membrane as a conductive medium, and mainly includes a bipolar plate (bipolar plate), a gas diffusion layer (GD L), a catalyst layer (C L), and a proton exchange membrane (proton exchange membrane), wherein a Gas Channel (GC) is formed on the surface of the bipolar plate, as shown in fig. 1.
The basic principle of operation of a proton exchange membrane fuel cell is as follows: on the anode side, hydrogen gas is introduced into the gas channels on the bipolar plate, is transmitted to the catalyst layer through the gas diffusion layer, and generates electrochemical reaction under the action of the catalyst to generate protons and electrons, namely:
H2→2H++2e-
the electrons generated in the anode catalytic layer reach the cathode catalytic layer through an external circuit, and the protons reach the cathode catalytic layer through the proton exchange membrane. Meanwhile, on the cathode side, oxygen is introduced into the gas channel on the bipolar plate, is transmitted to the catalyst layer through the gas diffusion layer, and reacts with protons and electrons transmitted from the anode side under the action of the catalyst to generate water and heat, namely:
O2+4H++4e-→2H2heat of oxygen + concentration
The overall chemical reaction is:
2H2+O2→2H2heat of oxygen + concentration
The PEMFC has the characteristics of high energy density, cleanness, no pollution and the like, and is a popular choice for the next generation of power systems, however, the high cost and limited electrical performance caused by the high catalyst consumption restrict the scale application thereof. The key to promoting the commercialization process of PEMFCs is to reduce the amount of the catalyst used in the membrane electrode and to improve the electrical properties of the membrane electrode.
The existing catalyst gradient distribution technology mainly comprises the following steps: the following schemes are adopted:
1. according to the fuel concentration difference between the air inlet and the air outlet, the membrane electrode with the transversely-increased load is designed, so that the open-circuit voltage of the proton exchange membrane fuel cell is improved. For example, chinese patent document CN 103367757A provides a fuel cell membrane electrode catalyzed by three-level gradient and a preparation method thereof. The cathode catalyst layer and the anode catalyst layer both have catalyst loading capacity distributed in a three-level gradient manner, and the catalyst loading capacity is gradually increased in the width direction from the raw material inlet to the raw material outlet.
2. According to different expansions in the operation process of the membrane electrode, the membrane electrode with the catalyst nanoparticle loading amount gradually increased from the proton exchange membrane to two sides is designed, the connection strength of the membrane and the electrode interface is enhanced, mechanical damage generated in the operation process of the membrane electrode is relieved, and the durability of the membrane electrode is improved. For example, chinese patent document CN110289423A provides a membrane electrode with a catalyst gradient. In the membrane electrode, the load capacity of catalyst nanoparticles in the catalyst layer is increased in three-stage gradient from the position close to the proton exchange membrane to two sides respectively.
3. According to the fuel concentration difference between the air inlet and the air outlet, the membrane electrode with different catalyst loading gradient changes or different catalyst loading surface areas is designed to obtain uniform current distribution of the membrane electrode in the operation process. Chinese patent CN 101263619B, for example, provides a catalyst layer for enhancing current density uniformity in a membrane electrode assembly. The desired variable catalyst activity profile is achieved by varying the catalyst loading in the membrane electrode from inlet to outlet or by varying the surface area of the catalyst loading or by varying the surface area of the catalyst support member.
The different membrane electrode design schemes improve the performance or durability of the membrane electrode, but the design schemes do not consider the problem of flooding of the membrane electrode in the operation process. This problem is urgently needed to be solved.
Disclosure of Invention
The invention aims to solve the technical problem that the membrane electrode only considers the gradient distribution of a catalyst and does not consider the flooding problem of the membrane electrode in the operation process in the prior art, and provides a catalyst layer, a fuel cell membrane electrode and a preparation method thereof.
The invention solves the technical problems through the following technical scheme.
The present invention provides a catalyst layer having a width and a length, the catalyst layer including at least a 1 st region, a 2 nd region, a 3 rd region … …, and an nth region in this order along the width direction; n is not less than 4 and is an integer; from the 1 st zone to the n-th zone, the catalyst content decreases in order, and the pore size increases in order.
In the present invention, preferably, during use of the catalyst layer, the 1 st region is adjacent to an air inlet of the membrane electrode, and the nth region is adjacent to an air outlet of the membrane electrode. The air inlet is generally referred to as an oxygen or air inlet of a cathode in the membrane electrode.
In the present invention, the catalyst layer has at least a four-stage gradient distribution of catalyst content and a four-stage gradient distribution of pore size.
In the present invention, it is preferable that the n regions of the catalyst layer have the same area.
In the present invention, preferably, the catalyst contents are all the same and uniformly distributed in the same region. For example, in zone 1, the catalyst levels are all the same and are uniformly distributed. And so on.
In the present invention, preferably, the pore sizes are all the same and uniformly distributed in the same region. For example, in region 1, the pore sizes are all the same and uniformly distributed. And so on.
In the present invention, the catalyst may be a catalyst species conventionally used on a membrane electrode in the field of proton exchange membrane fuel cells, such as a platinum carbon catalyst.
In the present invention, the catalyst content refers to the weight of Pt in a region as a percentage of the total weight of the catalyst layer in that region, i.e., the Pt loading.
In the present invention, the total Pt content in each square centimeter of the catalyst layer is preferably 0.1-0.5 mg/cm2E.g. 0.4mg/cm2。
In the present invention, the loading amount of Pt in the catalyst layer is preferably 15 to 50 wt%, for example, 22 wt%, 28.5 wt%, 36 wt% or 45 wt%, which is the percentage of the total weight of Pt in the catalyst layer to the total weight of the catalyst layer.
In the present invention, the loading amount of Pt in the 1 st region is preferably 40 to 50 wt%, for example, 45 wt%, and the percentage is the percentage of the total weight of Pt in the 1 st region to the total weight of the catalyst layer in the 1 st region.
In the present invention, the loading amount of Pt in the 2 nd region is preferably 30 to 40 wt%, for example, 36 wt%, and the percentage is the percentage of the total weight of Pt in the 2 nd region to the total weight of the catalyst layer in the 2 nd region.
In the present invention, the loading amount of Pt in the 3 rd zone is preferably 23 to 33 wt%, for example 28.5 wt%, and the percentage is the percentage of the total weight of Pt in the 3 rd zone to the total weight of the catalyst layer in the 3 rd zone.
In the present invention, the loading amount of Pt in the 4 th region is preferably 15 to 27 wt%, for example, 22 wt%, and the percentage is the percentage of the total weight of Pt in the 4 th region to the total weight of the catalyst layer in the 4 th region.
In the preferred embodiment of the present invention, the loading of catalyst employed is gradually reduced from zone 1 to zone 4. Wherein the catalyst loading generally refers to the weight percent of active metal in the feed catalyst based on the total catalyst, e.g., the weight percent of platinum on a platinum carbon catalyst.
The loading of the catalyst is preferably 20 to 90 wt%, more preferably 30 to 80 wt%, most preferably 40 to 70 wt%, for example 40 wt%, 50 wt%, 60 wt% or 70 wt%, wherein the percentage is the weight ratio of the active metal in the catalyst to the total amount of the catalyst.
In a preferred embodiment, the loading of catalyst in zone 1 is preferably 60 to 80 wt%, for example 70 wt%.
In a preferred embodiment, the loading of catalyst in zone 2 is preferably 50 to 70 wt%, for example 60 wt%.
In a preferred embodiment, the loading of catalyst in zone 3 is preferably 40 to 60 wt%, for example 50 wt%.
In a preferred embodiment, the loading of catalyst in zone 4 is preferably 30 to 50 wt%, for example 40 wt%.
In the present invention, the pore size of the catalyst layer is preferably 5 to 100nm, more preferably 5 to 80nm, and most preferably 5 to 60nm, such as 5nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, or 45 nm.
In the present invention, in the region 1, the pore size is preferably 5 to 15nm, for example, 10 nm.
In the present invention, in the 2 nd region, the pore size is preferably 15 to 25nm, for example, 20 nm.
In the present invention, in the 3 rd region, the pore size is preferably 25 to 35nm, for example, 30 nm.
In the present invention, in the 4 th region, the pore size is preferably 35 to 45nm, for example, 40 nm.
In the present invention, it is preferable that the catalyst layer further contains a resin. The resin may be a resin conventionally used in the art, such as Nafion ionomer.
Wherein the solid content of the resin is preferably 15-35 wt%, such as 20 wt%, 25 wt%, 28.5 wt% or 33 wt%, and the solid content of the resin is the weight of the resin in percentage of the total weight of the catalyst layer.
The invention provides a preparation method of the catalyst layer, which comprises the following steps:
(1) the substrate is divided into the 1 st area, the 2 nd area, the 3 rd area … … and the nth area in sequence along the width direction of the substrate; respectively spraying different catalyst slurry in the 1 st area to the nth area, drying, and repeating the spraying and drying operations until the Pt loading capacity of the catalyst in the area reaches a set value;
the catalyst slurry comprises a catalyst, a pore-forming agent, resin and a solvent; the catalyst content is reduced in the 1 st zone, the 2 nd zone, the 3 rd zone … … and the nth zone in sequence; the sizes of the pore-forming agents are sequentially increased;
(2) and (3) removing the pore-forming agent in the product obtained in the step (1) to form the catalyst layer.
In step (1), the substrate is generally a proton exchange membrane.
In step (1), the operation and conditions of the spraying may be conventional in the art. Typically using an ultrasonic spray applicator. In order to avoid contamination of other areas during spraying of area 1, the other areas may be covered with a PI film first to facilitate spraying of area 1.
In the step (1), the substrate is preferably placed on a vacuum microporous aluminum plate during the spraying process.
In step (1), the pressure is preferably maintained between-20 and (-15) Pa, for example-10 Pa or-20 Pa, during said spraying.
In step (1), the drying operation and conditions may be conventional in the art. The drying temperature is generally 70-90 ℃, for example 80 ℃. The drying time is generally 5-15 min, for example 10 min.
In the step (1), the content of the catalyst in the catalyst slurry is not particularly limited, and may be conventional in the art as long as the content of the catalyst set in the region can be satisfied. For example, if the catalyst content in the catalyst slurry is low, the spraying may be performed multiple times to obtain the set catalyst Pt loading, and if the catalyst content in the catalyst slurry is reduced higher, the spraying may be performed multiple times to obtain the set catalyst Pt loading.
In the step (1), the content of the catalyst in the catalyst slurry is preferably 2 to 6 wt%, and more preferably 2 wt% or 4 wt%.
In step (1), the pore-forming agent may be a pore-forming agent with controllable particle size, which is conventional in the art and can be dissolved in a hot strong alkaline solution, such as silica nanosphere. The size of the pore-forming agent is the size of the pore diameter in the catalyst coating.
In the step (1), in the catalyst slurry, the mass ratio of the catalyst to the pore-forming agent is preferably (3-5): 1, e.g. 4: 1.
In step (1), the resin may be a resin conventionally used in the art, such as Nafion ionomer.
In the step (1), in the catalyst slurry, the mass ratio of the catalyst to the resin is preferably 1: (0.2-0.8), for example 1:0.3, 1:0.4, 1:0.5 or 1: 0.6.
In the step (1), in the catalyst slurry, the solid-liquid ratio is preferably 1: (25-45), for example, 1: (30-40).
In step (1), the solvent may be a conventional solvent conventionally used in the art for dispersing the catalyst, such as an alcohol solvent or an aqueous alcohol-containing solution. The alcohol species may be conventional in the art, such as isopropanol. The selected alcohol-containing aqueous solution is preferably a mixture of isopropanol and deionized water, and more preferably the mass ratio of the isopropanol to the deionized water is (10-30): 80, for example 20: 80.
In the step (1), in the catalyst coating layer in each region, the pore-forming agent is preferably contained in an amount of 10 to 20 wt%, for example, 12 wt%, 14.5 wt%, 15 wt%, or 16 wt%, where the weight of the pore-forming agent is a percentage of the total weight of the catalyst layer in the region.
In the step (2), the pore-forming agent can be removed by a method conventional in the art, for example, by soaking in a strong alkaline solution.
The concentration of the strong alkali solution can be conventional in the field, such as 2-6 mol/L, such as 4 mol/L. the soaking operation and conditions can be conventional in the field, the soaking time is preferably 12-24 h. the soaking temperature is preferably 60-100 ℃, such as 80-90 ℃.
Preferably, after removing the pore-forming agent, the solution is soaked in the sulfuric acid aqueous solution again and then washed.
The concentration of the sulfuric acid aqueous solution can be conventional in the art, for example, 0.5-1 mol/L, the temperature of the re-soaking can be conventional, for example, 70-90 ℃, for example, 80 ℃, the time of the re-soaking is preferably 1-3 h, for example, 2 h.
The invention provides a fuel cell membrane electrode, which comprises a first bipolar plate, an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, a cathode gas diffusion layer and a second bipolar plate which are sequentially arranged from left to right, wherein the cathode catalyst layer is the catalyst layer.
In the present invention, the first bipolar plate, the anode gas diffusion layer, the anode catalyst layer, the proton exchange membrane, the cathode gas diffusion layer, and the second bipolar plate are conventional in the art.
In a preferred embodiment, the proton exchange membrane is available from gore
Figure BDA0002448927570000071
A proton exchange membrane.
In a preferred embodiment, the Pt loading may be 0.1mg/cm on the anode catalyst layer2。
The invention also provides a preparation method of the fuel cell membrane electrode, the proton exchange membrane is taken as the base material, and the proton exchange membrane is divided into the 1 st area, the 2 nd area, the 3 rd area … … and the nth area in sequence from the air inlet to the air outlet; preparing the catalyst layer on the proton exchange membrane according to the method as described above;
and laminating the first bipolar plate, the anode gas diffusion layer, the anode catalyst layer, the proton exchange membrane, the cathode catalyst layer, the cathode gas diffusion layer and the second bipolar plate together to form the membrane electrode.
In the present invention, the air inlet is generally referred to as an oxygen or air inlet of a cathode in the membrane electrode.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
the invention respectively carries out gradient design on the catalyst content and the pore size of the membrane electrode in different regions, namely the catalyst content in the gas inlet region is high enough, and the number of macropores in the gas outlet region is high enough, so that the reactant concentration of the gas inlet is highly matched with the catalyst content, and the water content of the gas outlet is highly matched with the number of macropores, thereby improving the utilization rate and the drainage capacity of the membrane electrode catalyst and realizing the improvement of the performance of the membrane electrode.
Drawings
Fig. 1 is a schematic structural diagram of a proton exchange membrane fuel cell in the prior art.
Fig. 2 is a schematic view of the structure of the cathode catalyst layer prepared in example 1.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
The platinum-carbon catalysts used in example 1 are all commercially available, specifically as follows: 70% Pt/C type: HiSPEC13100, available from JM. 60% Pt/C type: HiSPEC 9100, available from JM. 50% Pt/C type: TEC10E50E-HT, available from TKK. 40% Pt/C type: HiSPEC 4100 is available from JM.
The proton exchange membrane is available from Goll
Figure BDA0002448927570000081
A proton exchange membrane.
Example 1
1. A proton exchange membrane is placed on a vacuum microporous aluminum plate, the pressure is kept at-20 Pa, the proton exchange membrane is evenly divided into 4 areas along the plane direction, and the 4 areas are sequentially marked as the 1 st area, the 2 nd area, the 3 rd area and the 4 th area from left to right.
Covering PI films on the 2 nd area, the 3 rd area and the 4 th area, uniformly spraying the 1 st catalyst coating on the surface of the 1 st area by using an ultrasonic spraying instrument, calibrating the catalyst content of the 1 st area after the catalyst is dried (the temperature is 80 ℃ and the time is 10min), and repeating the process until the catalyst content set in the area is reached. And after the spraying is finished, keeping the PI film covering on the surfaces of the 2 nd area, the 3 rd area and the 4 th area.
The formulation of zone 1 sprayed 1 st catalyst slurry was as follows:
the catalyst is 70 wt% of Pt/C, the pore-forming agent is 10nm silicon dioxide, the resin is Nafion ionomer, the solvent is isopropanol and water, and the volume ratio of the isopropanol to the water is 20: 80. In the catalyst slurry of No. 1, the catalyst content is about 2 wt%, the mass ratio of the catalyst to the silica is 4:1, the mass ratio of the catalyst to the Nafion is 1:0.3, and the overall solid-to-liquid ratio is 1:30-1: 40.
After drying, the Pt loading in zone 1 was about 45 wt%, which is the percentage of the total weight of Pt based on the total weight of the catalyst layer in zone 1. The pore former is about 16 wt%, the above percentages being the weight of the pore former as a percentage of the total weight of the catalyst layer in zone 1. The resin solids content is about 20%, the percentages being the weight of the resin as a percentage of the total weight of the catalyst layer in zone 1.
The formulation of zone 2 sprayed 2 nd catalyst slurry was as follows:
the catalyst is 60 wt% of Pt/C, the pore-forming agent is 20nm of silicon dioxide, the resin is Nafion ionomer, the solvent is isopropanol and water, and the volume ratio of the isopropanol to the water is 20: 80. In the 2 nd catalyst slurry, the catalyst content is about 2 wt%, the mass ratio of the catalyst to the silica is 4:1, the mass ratio of the catalyst to the Nafion is 1:0.4, and the overall solid-to-liquid ratio is 1:30-1: 40.
After drying, the Pt loading in zone 2 was about 36 wt%, which is the percentage of the total weight of Pt based on the total weight of the catalyst layer in zone 2. The pore former is about 15 wt%, the percentage being the weight of the pore former as a percentage of the total weight of the catalyst layer in zone 2. The resin solids content is about 25%, the percentages being the weight of the resin as a percentage of the total weight of the catalyst layer in zone 2.
The 3 rd catalyst slurry formulation sprayed in zone 3 was as follows:
the catalyst is 50 wt% of Pt/C, the pore-forming agent is 30nm silicon dioxide, the resin is Nafion ionomer, the solvent is isopropanol and water, and the volume ratio of the isopropanol to the water is 20: 80. In the 3 rd catalyst slurry, the catalyst content is about 2 wt%, the mass ratio of the catalyst to the silica is 4:1, the mass ratio of the catalyst to the Nafion is 1:0.5, and the overall solid-to-liquid ratio is 1:30-1: 40.
After drying, the Pt loading in zone 3 was about 28.5 wt%, which is the total weight of Pt as a percentage of the total weight of the catalyst layer in zone 3. The pore former is about 14.5 wt%, the percentages being the weight of the pore former based on the total weight of the catalyst layer in zone 3. The resin solids content was about 28.5%, the percentage being the weight of the resin as a percentage of the total weight of the catalyst layer in zone 3.
The 4 th catalyst slurry formulation sprayed in zone 4 was as follows:
the catalyst is 40 wt% of Pt/C, the pore-forming agent is 40nm of silicon dioxide, the resin is Nafion ionomer, the solvent is isopropanol and water, and the volume ratio of the isopropanol to the water is 20: 80. In the 4 th catalyst slurry, the catalyst content was about 2 wt%, the mass ratio of the catalyst to silica was 4:1, the mass ratio of the catalyst to Nafion was 1:0.6, and the overall solid-to-liquid ratio was 1:30 to 1: 40.
After drying, the Pt loading in zone 2 was about 22 wt%, which is the percentage of the total weight of Pt based on the total weight of the catalyst layer in zone 2. The pore former is about 12 wt%, the percentage being the weight of the pore former as a percentage of the total weight of the catalyst layer in zone 2. The resin solids content is about 33% by weight of the total weight of the catalyst layer in zone 2.
In the spraying process, when a certain area is sprayed, the area which is not sprayed is always covered by the PI film.
2. After the spraying step is finished, transferring the proton exchange membrane coated with the catalyst into a 4 mol/L sodium hydroxide aqueous solution, treating at 90 ℃ for 24h to remove silicon dioxide in the catalyst layer, then washing with deionized water, then transferring the proton exchange membrane coated with the catalyst into a 0.5 mol/L sulfuric acid aqueous solution, treating at 80 ℃ for 2h, and then washing with deionized water to finally prepare the cathode catalyst layer with the catalyst content and the pore size in gradient distribution.
For the cathode catalyst layer, the total Pt loading of the 1 st area to the 4 th area is controlled to be 0.4mg/cm2。
Fig. 2 is a schematic view of the structure of the cathode catalyst layer prepared in example 1. In fig. 2, from left to right, the 1 st region, the 2 nd region, the 3 rd region, and the 4 th region are arranged in this order. From zone 1 to zone 4, the catalyst content gradient decreases and the pore size gradient increases.
3. Preparing an anode catalyst layer on the other side of the proton exchange membrane, wherein the Pt loading capacity on the anode catalyst layer is 0.1mg/cm2。
4. And laminating the first bipolar plate, the anode gas diffusion layer, the anode catalyst layer, the proton exchange membrane, the cathode catalyst layer, the cathode gas diffusion layer and the second bipolar plate together to form the membrane electrode.

Claims (10)

1. A catalyst layer, characterized in that the catalyst layer has a width and a length, and the catalyst layer includes at least a 1 st region, a 2 nd region, a 3 rd region … …, and an nth region in this order along the width direction; n is not less than 4 and is an integer; from the 1 st zone to the n-th zone, the catalyst content decreases in order, and the pore size increases in order.
2. The catalyst layer of claim 1, wherein, in use, the region 1 is adjacent to an inlet port of a membrane electrode and the region n is adjacent to an outlet port of the membrane electrode;
and/or the n regions of the catalyst layer are equal in area;
and/or the catalyst contents are the same and uniformly distributed in the same region;
and/or, in the same region, the pore sizes are the same and are uniformly distributed;
and/or the catalyst is a platinum carbon catalyst;
and/or, in the catalyst layer, the total content of Pt is 0.1-0.5 mg/cm2The catalyst layer is preferably 0.4mg/cm2The catalyst layer.
3. The catalyst layer of claim 1, wherein the catalyst layer has a Pt loading of 15 to 50 wt%, preferably 22 wt%, 28.5 wt%, 36 wt%, or 45 wt%, as a percentage of the total weight of Pt in the catalyst layer to the total weight of the catalyst layer;
and/or, in the 1 st zone, the Pt loading is 40-50 wt%, preferably 45 wt%, and the percentage is the percentage of the total weight of Pt in the 1 st zone to the total weight of the catalyst layer in the 1 st zone;
and/or, in the 2 nd area, the Pt loading is 30-40 wt%, preferably 36 wt%, and the percentage is the percentage of the total weight of Pt in the 2 nd area to the total weight of the catalyst layer in the 2 nd area;
and/or, in the 3 rd zone, the Pt loading is 23-33 wt%, preferably 28.5 wt%, and the percentage is the percentage of the total weight of Pt in the 3 rd zone to the total weight of the catalyst layer in the 3 rd zone;
and/or, in zone 4, the Pt loading is 15-27 wt%, preferably 22 wt%, the percentage being the total weight of Pt in zone 4 to the total weight of the catalyst layer in zone 4.
4. The catalyst layer of claim 1, wherein the loading of the raw material catalyst used in the 1 st zone to the 4 th zone is 20 to 90 wt%, preferably 30 to 80 wt%, more preferably 40 to 70 wt%, most preferably 40 wt%, 50 wt%, 60 wt% or 70 wt%, the percentage being the weight ratio of the active metal in the catalyst to the total amount of the catalyst;
and/or, in the 1 st area, the loading amount of the catalyst is 60-80 wt%, preferably 70 wt%;
and/or, in the 2 nd area, the loading amount of the catalyst is 50-70 wt%, preferably 60 wt%;
and/or, in the 3 rd zone, the loading amount of the catalyst is 40-60 wt%, preferably 50 wt%;
and/or, in zone 4, the loading of catalyst is 30-50 wt%, preferably 40 wt%.
5. The catalyst layer of claim 1, wherein the pore size on the catalyst layer is 5 to 100nm, preferably 5 to 80nm, more preferably 5 to 60nm, most preferably 5nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm or 45 nm;
and/or, in the area 1, the aperture size is 5-15 nm, preferably 10 nm;
and/or, in the 2 nd area, the aperture size is 15-25 nm, preferably 20 nm;
and/or, in the 3 rd region, the aperture size is 25-35 nm, preferably 30 nm;
and/or, in the 4 th area, the aperture size is 35-45 nm, preferably 40 nm;
preferably, the catalyst layer further contains a resin; the resin is preferably a Nafion ionomer;
the solid content of the resin is preferably 15 to 35 wt%, more preferably 20 wt%, 25 wt%, 28.5 wt%, or 33 wt%, and the solid content of the resin is the percentage of the weight of the resin to the total weight of the catalyst layer.
6. A method for producing a catalyst layer according to any one of claims 1 to 5, comprising the steps of:
(1) the substrate is divided into the 1 st area, the 2 nd area, the 3 rd area … … and the nth area in sequence along the width direction of the substrate; respectively spraying different catalyst slurry in the 1 st area to the nth area, drying, and repeating the spraying and drying operations until the Pt loading capacity of the catalyst in the area reaches a set value;
wherein the catalyst slurry comprises the catalyst, a pore-forming agent, resin and a solvent; the catalyst content is reduced in the 1 st zone, the 2 nd zone, the 3 rd zone … … and the nth zone in sequence; the sizes of the pore-forming agents are sequentially increased;
(2) and (3) removing the pore-forming agent in the product obtained in the step (1) to form the catalyst layer.
7. The method for producing a catalyst layer according to claim 6, wherein in the step (1), the substrate is a proton exchange membrane;
and/or, in the step (1), the base material is placed on a vacuum microporous aluminum plate in the spraying process;
and/or, in the step (1), the pressure is kept between-20 and (-15) Pa, preferably between-10 Pa or-20 Pa during the spraying process;
and/or in the step (1), the drying temperature is 70-90 ℃, preferably 80 ℃;
and/or, in the step (1), the drying time is 5-15 min, preferably 10 min;
and/or, in the step (1), the content of the catalyst in the catalyst slurry is 2-6 wt%, preferably 2 wt% or 4 wt%;
and/or in the step (1), in the catalyst slurry, the mass ratio of the catalyst to the pore-forming agent is (3-5): 1, preferably 4: 1;
and/or, in step (1), the resin is a Nafion ionomer;
and/or in the step (1), in the catalyst slurry, the mass ratio of the catalyst to the resin is 1: (0.2-0.8), preferably 1:0.3, 1:0.4, 1:0.5 or 1: 0.6;
and/or in the step (1), in the catalyst slurry, the solid-to-liquid ratio is 1: (25-45), preferably 1: (30-40);
and/or, in the step (1), the solvent is an alcohol solvent and/or water, preferably a mixture of the alcohol solvent and the water; the alcohol solvent is preferably isopropanol;
the mixture of the alcohol solvent and the water is preferably a mixture of isopropanol and water, wherein the mass ratio of the isopropanol to the water is preferably (10-30): 80, more preferably 20: 80.
8. The method of claim 6, wherein in step (1), the pore-forming agent is contained in the catalyst coating layer in each zone in an amount of 10 to 20 wt%, preferably 12 wt%, 14.5 wt%, 15 wt% or 16 wt%, wherein the weight of the pore-forming agent is the percentage of the total weight of the catalyst coating layer in the zone;
and/or, in the step (2), the method for removing the pore-forming agent comprises the following steps: soaking the product obtained in the step (1) in a strong alkali solution;
the type of the strong base is preferably sodium hydroxide, the concentration of the strong base solution is preferably 2-6 mol/L, the soaking time is preferably 12-24 h, and the soaking temperature is preferably 60-100 ℃, more preferably 80-90 ℃;
and/or, in the step (2), placing the product with the pore-forming agent removed in a sulfuric acid water solution for soaking again, and then washing;
the concentration of the sulfuric acid aqueous solution is preferably 0.5-1 mol/L, the re-soaking temperature is preferably 70-90 ℃, and the re-soaking time is preferably 1-3 hours.
9. A fuel cell membrane electrode, which is characterized by comprising a first bipolar plate, an anode gas diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, a cathode gas diffusion layer and a second bipolar plate which are sequentially arranged from left to right, wherein the cathode catalyst layer is the catalyst layer as claimed in any one of claims 1 to 5.
10. The method for preparing a membrane electrode assembly for a fuel cell according to claim 9, wherein the proton exchange membrane is used as a substrate, and the proton exchange membrane is divided into the 1 st region, the 2 nd region, the 3 rd region … … and the nth region in this order from the gas inlet to the gas outlet; preparing the cathode catalyst layer on the proton exchange membrane according to the preparation method of the catalyst layer as claimed in any one of claims 6 to 8;
and laminating the first bipolar plate, the anode gas diffusion layer, the anode catalyst layer, the proton exchange membrane, the cathode catalyst layer, the cathode gas diffusion layer and the second bipolar plate together to form the membrane electrode.
CN202010287060.1A 2020-04-13 2020-04-13 Catalyst layer, fuel cell membrane electrode and preparation method thereof Pending CN111463442A (en)

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CN116397249A (en) * 2023-06-08 2023-07-07 上海治臻新能源股份有限公司 Diffusion layer, electrolytic cell and processing method
CN116397249B (en) * 2023-06-08 2023-08-15 上海治臻新能源股份有限公司 Diffusion layer, electrolytic cell and processing method

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