A composite catalytic layer, a preparation method and application thereof, and a membrane electrode

Abstract

The present invention belongs to the technical field of fuel cells, and particularly relates to a composite catalyst layer, a preparation method and application thereof, and a membrane electrode. The present invention provides a preparation method of a composite catalyst layer, comprising the following steps: performing a melting reaction on 1,3,5-triamino-2,4,6-benzenetriol and 4,4'-biphenyl dialdehyde to obtain a first mixture; mixing the first mixture with a carbon material to obtain a second mixture; coating the second mixture on a diffusion layer and then performing annealing to obtain a catalyst layer substrate; depositing platinum on the surface of the catalyst layer substrate to obtain the composite catalyst layer. The preparation method provided by the present invention utilizes an annealing method to synthesize a COF / carbon composite catalyst layer with a relatively high conductivity, rich nanochannels, and the ability to effectively anchor platinum atoms. Moreover, the composite catalyst layer has a covalent organic framework structure, excellent physical and chemical stability, and can avoid the phenomenon of platinum migration and agglomeration caused by carrier corrosion.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a composite catalyst layer, a preparation method and application thereof, and a membrane electrode. Background Art

[0002] The efficient transport of protons, electrons, hydrogen, oxygen and water in the membrane electrode is crucial for the power generation performance of the catalyst layer. Usually, the catalyst layer consists of a catalyst layer substrate and a catalyst. Generally, the catalyst layer substrate is mainly a carbon layer substrate, and the catalyst is a platinum-based compound. Under conditions such as high potential, start-stop, and variable load, the pure carbon layer substrate is prone to carbon carrier corrosion, which in turn causes platinum migration and agglomeration, and the membrane electrode is deactivated.

[0003] Covalent organic frameworks (COFs) are a promising catalytic framework. They have periodic anchor sites on the pore channel walls, which can serve as well-defined active sites and mass transport channels. However, as a catalyst layer substrate, there is a problem of low conductivity. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite catalyst layer, a preparation method and application thereof, and a membrane electrode. The composite catalyst layer obtained by the preparation method provided by the present invention has high stability and conductivity.

[0005] The present invention provides a preparation method of a composite catalyst layer, comprising the following steps:

[0006] Performing a melting reaction on 1,3,5-triamino-2,4,6-benzenetriol and 4,4'-bisbenzaldehyde acetal to obtain a first mixture;

[0007] Mixing the first mixture with a carbon material to obtain a second mixture;

[0008] After coating the second mixture on a diffusion layer, annealing is performed to obtain a catalyst layer substrate;

[0009] Depositing platinum on the surface of the catalyst layer substrate to obtain the composite catalyst layer.

[0010] Preferably, the mass ratio of 1,3,5-triamino-2,4,6-benzenetriol, 4,4'-bisbenzaldehyde acetal and the carbon material is (1-3):(1-4):(0.5-3).

[0011] Preferably, the carbon material includes one or more of XC-72, carbon nanotubes and Ketjen black.

[0012] Preferably, the temperature of the melting reaction is 300-500 °C, and the time is 0.5-2 h; the melting reaction is carried out under stirring conditions.

[0013] Preferably, the mixing is carried out under stirring; the temperature of the stirring is 300 - 500 °C, and the time is 0.5 - 2 h.

[0014] Preferably, the thickness of the coating is 10 - 50 μm;

[0015] The temperature of the annealing is 600 - 800 °C, and the heat preservation time is 0.5 - 1 h.

[0016] Preferably, the method for depositing platinum is chemical vapor deposition;

[0017] The time of the chemical vapor deposition is 2 - 60 min;

[0018] The platinum source used in the chemical vapor deposition includes platinum acetylacetonate or platinum ammine chloride;

[0019] The carrier gas used in the chemical vapor deposition includes one or more of acetylene, propylene, propyne, and xylene;

[0020] When the diffusion layer is a cathode diffusion layer, the deposition amount of platinum is 0.1 - 0.4 mg / cm 2 ;

[0021] When the diffusion layer is an anode diffusion layer, the deposition amount of platinum is 0.02 - 0.2 mg / cm 2 .

[0022] The present invention also provides a composite catalytic layer obtained by the preparation method of the above technical solution, and the thickness of the composite catalytic layer is 20 - 100 μm.

[0023] The present invention also provides an application of the composite catalytic layer of the above technical solution in a fuel cell.

[0024] The present invention also provides a membrane electrode, which includes a cathode diffusion layer, a cathode catalytic layer, a proton exchange membrane, an anode catalytic layer, and an anode diffusion layer that are sequentially stacked;

[0025] Both the cathode catalytic layer and the anode catalytic layer are the composite catalytic layer of the above technical solution.

[0026] The present invention provides a method for preparing a composite catalytic layer, comprising the following steps: performing a melting reaction on 1,3,5-triamino-2,4,6-benzenetriol and 4,4'-bisbenzodialdehyde to obtain a first mixture; mixing the first mixture with a carbon material to obtain a second mixture; coating the second mixture on a diffusion layer and then performing annealing to obtain a catalytic layer substrate; depositing platinum on the surface of the catalytic layer substrate to obtain the composite catalytic layer. The preparation method provided by the present invention synthesizes a composite catalytic layer substrate in which a COF is tightly combined with a carbon material by an annealing method. It has a relatively high conductivity and abundant nanochannels. When depositing platinum, it can effectively anchor platinum atoms and integrate platinum into the COF channel walls, effectively exposing the active sites of platinum. And this composite catalytic layer has a covalent organic framework structure and has excellent physical and chemical stability under high-temperature and highly acidic conditions, which can avoid the phenomenon of platinum migration and agglomeration caused by carrier corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a transmission electron microscope (TEM) image of the composite catalytic layer obtained in Example 1 after 100 h of reaction;

[0029] Figure 2 It is a polarization curve graph of the membrane electrode prepared from the composite catalytic layers obtained in Examples 1-2 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention provides a method for preparing a composite catalytic layer, comprising the following steps:

[0031] Performing a melting reaction on 1,3,5-triamino-2,4,6-benzenetriol and 4,4'-bisbenzodialdehyde to obtain a first mixture;

[0032] Mixing the first mixture with a carbon material to obtain a second mixture;

[0033] Coating the second mixture on a diffusion layer and then performing annealing to obtain a catalytic layer substrate;

[0034] Depositing platinum on the surface of the catalytic layer substrate to obtain the composite catalytic layer.

[0035] In the present invention, unless otherwise specified, the raw material components are all commercially available products well-known to those skilled in the art.

[0036] The present invention performs a melting reaction on 1,3,5-triamino-2,4,6-benzenetriol and 4,4'-bisbenzodialdehyde to obtain a first mixture.

[0037] In the present invention, the mass ratio of the 1,3,5-triamino-2,4,6-benzenetriol to the 4,4'-bisbenzodialdehyde is preferably (1 to 3):(1 to 4), more preferably (2 to 3):(2 to 4), and most preferably (2 to 3):(2 to 3).

[0038] In the present invention, the temperature of the melting reaction is preferably 300 to 500 °C, more preferably 300 to 450 °C, and most preferably 350 to 400 °C; the time is preferably 0.5 to 2 h, more preferably 0.5 to 1.5 h, and most preferably 1 to 1.5 h; the melting reaction is preferably carried out under stirring conditions; the present invention has no special limitation on the stirring, and a process well-known to those skilled in the art can be adopted.

[0039] In the present invention, the function of the melting reaction is to obtain a covalent organic framework from the melted aromatic benzoxazole and biphenyl structure, which has excellent physical and chemical stability under high temperature and high acidity conditions, and the strong N atoms can effectively integrate Pt into the COF channel wall, thereby effectively exposing the active sites of Pt.

[0040] After obtaining the first mixture, the present invention mixes the first mixture with a carbon material to obtain a second mixture.

[0041] In the present invention, the mass ratio of the 1,3,5-triamino-2,4,6-benzenetriol to the carbon material is preferably (1 to 3):(0.5 to 3), more preferably (2 to 3):(1 to 3), and most preferably (2 to 3):(1 to 2).

[0042] In the present invention, the carbon material preferably includes one or more of XC-72, carbon nanotubes, and Ketjenblack, more preferably includes XC-72 and / or carbon nanotubes; the carbon nanotubes are preferably multi-walled carbon nanotubes; when the carbon material is two or more of the above specific selections, the present invention has no special limitation on the ratio of the above specific substances, and they can be mixed in any ratio.

[0043] In the present invention, the mixing is preferably carried out under stirring conditions; the temperature of the stirring is preferably 300 to 500 °C, more preferably 300 to 450 °C, and most preferably 350 to 400 °C; the time is preferably 0.5 to 2 h, more preferably 0.5 to 1.5 h, and most preferably 1 to 1.5 h; the present invention has no special limitation on the stirring speed, and a process well-known to those skilled in the art can be adopted.

[0044] In the present invention, the role of the mixing is to introduce a carbon-connected skeleton into the COF framework.

[0045] After obtaining the second mixture, in the present invention, the second mixture is coated on the diffusion layer and then annealed to obtain a catalytic layer substrate.

[0046] In the present invention, the diffusion layer is preferably Toray diffusion layer YLS30T.

[0047] In the present invention, the thickness of the coating is preferably 10 - 50 μm, more preferably 20 - 40 μm, and most preferably 30 - 40 μm; the coating is preferably knife coating; the speed of the knife coating is preferably 1 - 10 mm / s, more preferably 1 - 8 mm / s, and most preferably 1 - 4 mm / s; the present invention has no other special limitations on the process of the knife coating, and a process well-known to those skilled in the art can be adopted.

[0048] In the present invention, the temperature of the annealing is preferably 600 - 800 °C, more preferably 650 - 750 °C, and most preferably 650 - 700 °C; the heat preservation time is preferably 0.5 - 2 h, more preferably 0.5 - 1.5 h, and most preferably 1 - 1.5 h.

[0049] In the present invention, the role of the annealing is to make the combination of the organic COF material and the carbon material more dense, forming a COF carbon material with a compact structure.

[0050] After obtaining the catalytic layer substrate, in the present invention, platinum is deposited on the surface of the catalytic layer substrate to obtain the composite catalytic layer.

[0051] In the present invention, the method of depositing platinum is preferably chemical vapor deposition; the time of the chemical vapor deposition is preferably 2 - 60 min, more preferably 10 - 50 min, and most preferably 20 - 40 min; the platinum source used in the chemical vapor deposition preferably includes platinum acetylacetonate or platinum ammine chloride, more preferably includes platinum acetylacetonate; the carrier gas used in the chemical vapor deposition includes one or more of acetylene, propylene, propyne, and xylene, more preferably includes one or more of acetylene, propyne, and xylene, and most preferably includes acetylene and / or propyne; when the carrier gas is more than two of the above specific selections, the present invention has no special limitations on the ratio of the above specific substances, and they can be mixed in any ratio.

[0052] In the present invention, when the diffusion layer is a cathode diffusion layer, the deposition amount of platinum is preferably 0.1 - 0.4 mg / cm 2 , more preferably 0.2 - 0.4 mg / cm 2 , most preferably 0.2 - 0.3 mg / cm 2 ; when the diffusion layer is an anode diffusion layer, the deposition amount of platinum is preferably 0.02 - 0.2 mg / cm2 , more preferably 0.2 - 0.4 mg / cm 2 , most preferably 0.2 - 0.3 mg / cm 2 .

[0053] In the present invention, the function of the vapor deposition of platinum is to uniformly load platinum atoms in the COF / carbon composite structure, so as to expose more active sites.

[0054] The preparation method provided by the present invention uses an annealing method to synthesize a COF / carbon composite catalytic layer with a relatively high conductivity and rich nanochannels. Under the conditions of platinum source vapor deposition, it can effectively anchor platinum atoms and integrate platinum into the COF channel walls, effectively exposing the active sites of platinum. And this composite catalytic layer has a covalent organic framework structure and has excellent physical and chemical stability under high temperature and high acidity conditions, which can avoid the phenomenon of platinum migration and agglomeration caused by carrier corrosion. At the same time, this preparation method is simple to operate and has great practical application value and commercial prospects.

[0055] The present invention also provides a composite catalytic layer obtained by the preparation method described in the above technical solution. The thickness of the composite catalytic layer is 20 - 100 μm, preferably 20 - 80 μm, and more preferably 20 - 40 μm.

[0056] The composite catalytic layer provided by the present invention has relatively high conductivity and proton transport ability, and relatively high physical and chemical stability.

[0057] The present invention also provides the application of the composite catalytic layer described in the above technical solution in a fuel cell.

[0058] The present invention does not have any special limitation on the application method, and the process well-known to those skilled in the art can be adopted.

[0059] The present invention also provides a membrane electrode, which includes a cathode diffusion layer, a cathode catalytic layer, a proton exchange membrane, an anode catalytic layer, and an anode diffusion layer that are sequentially stacked;

[0060] Both the cathode catalytic layer and the anode catalytic layer are the composite catalytic layers described in the above technical solution.

[0061] In the present invention, the preparation method of the membrane electrode preferably includes the following steps:

[0062] The cathode catalytic layer and the anode catalytic layer are respectively prepared according to the preparation method described in the above technical solution;

[0063] The cathode catalytic layer and the anode catalytic layer are placed on both sides of the proton exchange membrane and hot-pressed to obtain the membrane electrode.

[0064] In the present invention, the proton exchange membrane is preferably a Nafion HP membrane.

[0065] In the present invention, the temperature of the hot pressing is preferably 120-135°C, more preferably 125-135°C, and most preferably 125-130°C; the time is preferably 120-135 s, more preferably 125-135 s, and most preferably 125-130 s; the pressure is preferably 90-120 MPa, more preferably 100-115 MPa, and most preferably 105-110 MPa.

[0066] The membrane electrode provided by the present invention has significant advantages in performance, and the current density at the rated power of 0.65 V exceeds 1.55 A / cm 2 , and after the durability test, the current density remains stable, proving that the membrane electrode has high conductivity and proton transport ability.

[0067] In order to further illustrate the present invention, the composite catalytic layer provided by the present invention, its preparation method and application, and the membrane electrode will be described in detail below in conjunction with the drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0068] Example 1

[0069] Weigh 3 g of 1,3,5-triamino-2,4,6-benzenetriol (TABT) and 4 g of 4,4'-bisbenzodialdehyde (BPA) and place them in a high-temperature reaction vessel. Put it into a magnetic stirrer and carry out a melting reaction at 300°C, and stir evenly for 0.5 h. After the stirring is completed, add 3 g of XC-72 as the carbon skeleton into the reaction vessel, and stir again at 300°C for 0.5 h. Cut the Toray diffusion layers YLS30T for the cathode and anode, and evenly scrape the prepared catalytic layer base material on the diffusion layer with a squeegee. The distance between the squeegees is 0.5 mm, and the scraping speed is 1 mm / s. After each scraping and drying, measure the thickness until the thickness increases by 30 μm, and place it in a tube furnace for annealing treatment at 600°C for 0.5 h. Place the prepared cathode and anode catalytic layer bases in a PECVD. Using platinum acetylacetonate as the Pt source and acetylene as the carrier gas, with a gas flow rate of 0.5 L / min, carry out a cathode reaction for 30 min and an anode reaction for 10 min to obtain the final cathode and anode composite catalytic layers.

[0070] Use a Nafion HP membrane as the proton exchange membrane, place the cathode and anode catalytic layers on both sides of the proton exchange membrane, apply a pressure of 90 MPa, and hot press at 135°C for 120 s, and take out to obtain the corresponding membrane electrode.

[0071] Example 2

[0072] Weigh 3 g of TABT and 3 g of BPA and place them in a high-temperature reaction vessel. Put it into a magnetic stirrer and carry out a melting reaction at 350 °C, stirring evenly for 0.5 h. After the stirring is completed, add 3 g of multi-walled carbon nanotubes as the carbon skeleton into the reaction vessel, and stir again at 300 °C for 0.5 h. Cut the anode and cathode Toray diffusion layers YLS30T, and evenly scrape the prepared catalytic layer substrate material onto the diffusion layer with a scraper. The spacing of the scraper is 0.4 mm, and the scraping speed is 2 mm / s. After each scraping and drying, measure the thickness until the thickness increases by 40 μm, and place it in a tube furnace for annealing treatment at 700 °C for 0.5 h. Place the prepared anode and cathode catalytic layer substrates in PECVD. Use platinum acetylacetonate as the Pt source and acetylene as the carrier gas. The gas flow rate is 0.5 L / min. The cathode reaction is 40 min and the anode reaction is 20 min to obtain the anode and cathode composite catalytic layers.

[0073] Use Nafion HP membrane as the proton exchange membrane. Place the anode and cathode catalytic layers on both sides of the proton exchange membrane, apply a pressure of 100 MPa, and hot press at 130 °C for 90 s, then take it out to obtain the corresponding membrane electrode.

[0074] Comparative example

[0075] Use a commercial membrane electrode (YLS25) with the same anode and cathode catalyst loadings as in Example 1. The Pt loading on the cathode is 0.3 mg / cm 2 and the Pt loading on the anode is 0.1 mg / cm 2 .

[0076] Test example

[0077] Carry out polarization tests on the membrane electrodes prepared in Examples 1-2 and the comparative example. The conditions for the polarization test are: 30-570 A / cm 2 as the scanning current density, the anode stoichiometry is 2.2, the cathode stoichiometry is 3.5, the anode humidity is 40% RH, the cathode humidity is 60% RH, the hydrogen back pressure is 135 kPa, and the air back pressure is 120 kPa. The measured current density data are shown in Table 1.

[0078] Table 1 Current density of the membrane electrodes obtained in Examples 1-2 and Comparative Example 1

[0079] Example / Comparative Example Cathode Pt Loading Anode Pt Loading Current Density at 0.65V Example 1 <![CDATA[0.3mg / cm 2 > <![CDATA[0.1mg / cm 2 > <![CDATA[1.603 A / cm 2 > Example 2 <![CDATA[0.4mg / cm 2 > <![CDATA[0.2mg / cm 2 > <![CDATA[1.591 A / cm 2 > Comparative Example 1 <![CDATA[0.3mg / cm 2 > <![CDATA[0.1mg / cm 2 > <![CDATA[1.583 A / cm 2 >

[0080] From Table 1 and Figure 2 it can be seen that the 0.65 V current densities of Example 1 and Example 2 are 1.603 A / cm 2 and 1.591 A / cm 2 , which are higher than 1.583 A / cm of the comparative example 2 , proving that the composite catalytic layer provided by the present invention has high conductivity and proton transport ability.

[0081] It can be seen from Figure 1 that after 100 h of reaction, no agglomeration of platinum atoms occurred, indicating that the physicochemical stability of the substrate structure of the catalytic layer is relatively high.

[0082] It can be seen from the above embodiments that the preparation method provided by the present invention uses an annealing method to synthesize a COF / carbon composite catalytic layer with a relatively high conductivity, rich nanochannels. Under the conditions of platinum source chemical vapor deposition, it can effectively anchor platinum atoms and integrate platinum into the COF channel walls, effectively exposing the active sites of platinum. Moreover, the composite catalytic layer has a covalent organic framework structure and excellent physicochemical stability under high-temperature and high-acidity conditions, which can avoid the phenomenon of platinum migration and agglomeration caused by carrier corrosion. At the same time, the preparation method is simple to operate and has great practical application value and commercial prospects. The composite catalytic layer provided by the present invention has relatively high conductivity and proton transport ability, and relatively high physicochemical stability.

[0083] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite catalytic layer, characterized in that, The steps are as follows: Perform a melting reaction on 1,3,5-triamino-2,4,6-benzenetriol and 4,4'-bisbenzaldehyde acetal to obtain a first mixture; the mass ratio of 1,3,5-triamino-2,4,6-benzenetriol to 4,4'-bisbenzaldehyde acetal is (1 to 3):(1 to 4); the temperature of the melting reaction is 300 to 500 °C, and the time is 0.5 to 2 h; Mix the first mixture and a carbon material to obtain a second mixture; After coating the second mixture on a diffusion layer, perform annealing to obtain a catalytic layer substrate; Deposit platinum on the surface of the catalytic layer substrate to obtain the composite catalytic layer; The mixing is carried out under stirring conditions; the temperature of the stirring is 300 to 500 °C, and the time is 0.5 to 2 h; The temperature of the annealing is 600 to 800 °C, and the heat preservation time is 0.5 to 1 h; The method of depositing platinum is chemical vapor deposition.

2. The preparation method according to claim 1, characterized in that, The mass ratio of 1,3,5-triamino-2,4,6-benzenetriol to the carbon material is (1 to 3):(0.5 to 3).

3. The preparation method according to claim 1 or 2, characterized in that, The carbon material includes one or more of XC-72, carbon nanotubes, and Ketjen black.

4. The preparation method according to claim 1, characterized in that, The melting reaction is carried out under stirring conditions.

5. The preparation method according to claim 1, wherein The thickness of the coating is 10 to 50 μm.

6. The preparation method according to claim 1, characterized in that, The time of the chemical vapor deposition is 2 to 60 min; The platinum source used in the chemical vapor deposition includes platinum acetylacetonate or platinum ammine chloride; The carrier gas used in the chemical vapor deposition includes one or more of acetylene, propylene, propyne, and xylene; When the diffusion layer is a cathode diffusion layer, the deposition amount of platinum is 0.1 to 0.4 mg / cm 2 ; When the diffusion layer is an anode diffusion layer, the deposition amount of platinum is 0.02 to 0.2 mg / cm 2 .

7. The composite catalytic layer obtained by the preparation method according to any one of claims 1 to 6, characterized in that The thickness of the composite catalytic layer is 20 to 100 μm.

8. Application of the composite catalytic layer according to claim 7 in a fuel cell.

9. A membrane electrode, characterized in that, It includes a cathode diffusion layer, a cathode catalytic layer, a proton exchange membrane, an anode catalytic layer, and an anode diffusion layer which are sequentially stacked; Both the cathode catalytic layer and the anode catalytic layer are the composite catalytic layer according to claim 7.

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