A PEMEC electrode with a three-dimensional catalyst layer constructed on an ordered diffusion layer and a preparation method thereof

Abstract

The present invention provides a PEMEC electrode and preparation method for constructing a three-dimensional catalyst layer on an ordered diffusion layer. The diffusion layer of the PEMEC electrode has a three-dimensional microstructure, and the catalyst layer carried thereon is a three-dimensional catalyst layer; the three-dimensional microstructure includes one or a combination of two or more of mechanical embossing, laser engraving, and irregular chemical etching shapes. The technical solution provided by the present invention uses physical and chemical methods to pre-construct a three-dimensional microstructure on a PTL substrate, and then coats the PTL substrate with a catalyst layer to prepare a PTE with a three-dimensional catalyst layer. This eliminates the need for material and process design specific to the catalyst microstructure, increases the contact area between the catalyst layer and the PTL, and thereby improves water electrolysis performance.

Description

Technical Field

[0001] The invention relates to a PEMEC electrode with a three-dimensional catalyst layer constructed on an ordered diffusion layer and a preparation method thereof, belonging to the technical field of water electrolysis. Background Art

[0002] As the upstream of the hydrogen energy industry chain, hydrogen production determines the properties of hydrogen energy and the cost of hydrogen use. Among them, the proton exchange membrane (PEM) electrolyzer (PEMEC) is one of the most promising green hydrogen production technologies due to its advantages such as high current density, high hydrogen purity and fast dynamic response. The core component of the electrolyzer is the electrode, which consists of a PEM, a catalyst layer, and a diffusion layer (PTL). The PEM plays the role of transferring protons. The catalyst layers on both sides of the PEM are where the water electrolysis reaction occurs. The PTL outside the catalyst layer conducts electrons and transports water / gas.

[0003] Since PEMEC uses perfluorinated membrane materials, the electrolyte acidity is high. For the sake of catalytic activity and durability, the anode is usually made of high-content IrO2 (2-4 mg·cm -2 ). The cost of Ir is very high, so it is crucial to improve the efficiency of hydrogen production by water electrolysis while ensuring low Ir usage.

[0004] Currently, the most common membrane electrode preparation method is to coat the catalyst on the PEM to obtain a CCM membrane electrode. Its catalyst layer has a planar structure, while the PTL has a three-dimensional structure. A high catalyst loading is required to increase the thickness of the catalyst layer to achieve contact between the catalyst layer and the PTL, resulting in low catalyst utilization and waste. In addition, the catalyst can be coated on the PTL to obtain a porous transport electrode (PTE). In this case, the catalyst layer adheres to the PTL surface to form a three-dimensional structure. Although this can significantly reduce the amount of Ir used, catalyst islands will form in the irregular grooves of the PTL, causing the electrolysis water performance to deteriorate.

[0005] In order to solve the above problems, a design method to increase the contact area of ​​the catalyst layer in the electrode is urgently needed. Summary of the Invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a PEMEC electrode and a preparation method thereof. By constructing a microstructure on the diffusion layer of the electrode, the contact area and bonding strength between the catalyst layer and the diffusion layer can be increased, thereby improving the water electrolysis performance of the electrode.

[0007] To achieve the above-mentioned object, the present invention first provides a PEMEC electrode having a three-dimensional catalyst layer constructed on an ordered diffusion layer, wherein the diffusion layer of the PEMEC electrode has a three-dimensional microstructure, and the catalyst layer loaded thereon is a three-dimensional catalyst layer;

[0008] The three-dimensional microstructure includes one or a combination of two or more of mechanical embossing, laser engraving and irregular chemical etching shapes.

[0009] In the above-mentioned PEMEC electrode, preferably, the three-dimensional microstructure includes: mold mechanical embossing (blade-shaped, with a width of 10-30 μm, a blade spacing of 20-100 μm, and the embossing arrangement is parallel and / or staggered, and the staggered shape means that the embossings are distributed at a certain angle between each other, for example, 30-90°), various shapes of laser engraving shapes (quadrilaterals, circles, etc., also referred to as lines), and irregular chemical etching shapes. One or a combination of more than two of these. Among them, mechanical embossing with a width of 10 μm and staggered arrangement exhibits the best water electrolysis activity.

[0010] In the above-mentioned PEMEC electrode, preferably, the diffusion layer is a titanium mesh with a mesh size of 40-600 meshes (more preferably 200 meshes) and a thickness of 0.1-1.0 mm (more preferably 0.4 mm).

[0011] In the above-mentioned PEMEC electrode, preferably, the material of the catalyst layer is IrO2, and the loading amount is 0.5-4 mg·cm -2 , more preferably 2 mg·cm -2 .

[0012] The present invention also provides a method for preparing the PEMEC electrode having a three-dimensional catalyst layer constructed on the ordered diffusion layer, which comprises the following steps:

[0013] A three-dimensional microstructure is formed on the diffusion layer, and then a catalyst layer is coated to form a three-dimensional catalyst layer to obtain the PEMEC electrode.

[0014] In the above preparation method, preferably, the three-dimensional microstructure is formed by physical and / or chemical means.

[0015] In the above preparation method, preferably, the physical method includes embossing and / or laser etching.

[0016] In the above preparation method, preferably, when the embossing method is adopted, the mold used is a blade-shaped mold, which includes two opposite flat plates, each of which has a plurality of blade-shaped structures (such as Figure 3 The blade-like structures are arranged in parallel, with a base length of 1 mm, a height of 1 mm, and a spacing of 1 mm between the blades. The pressure applied during embossing is 2-10 MPa. By controlling the specific embossing process parameters, the shape and size of the PTL embossing can be adjusted, resulting in PTL substrates with different embossing patterns. Further coating with a catalyst layer can produce PTE with a three-dimensional catalyst layer.

[0017] In the above preparation method, preferably, the chemical method includes chemical etching, for example, etching using one or a combination of hydrofluoric acid, ammonium fluoride, ammonium bifluoride, hydrofluoric acid, lithium fluoride, sodium fluoride, and potassium fluoride. Preferably, the titanium mesh is soaked in hydrofluoric acid at a concentration of 0.1 mol / L, with 40 mL of hydrofluoric acid used for 100 mg of the titanium mesh.

[0018] The above-mentioned PEMEC electrode provided by the present invention is composed of a proton exchange membrane, two catalyst layers, and two diffusion layers, wherein the two catalyst layers are respectively located on both sides of the proton exchange membrane, and the two diffusion layers are respectively located on the outside of the two catalyst layers. During the preparation process, the method provided by the present invention is first used to obtain a diffusion layer with a three-dimensional catalyst layer, and then it is loaded onto the two layers of the proton exchange membrane respectively, thereby obtaining a PEMEC electrode.

[0019] The technical solution provided by the present invention uses physical, chemical and other methods to pre-construct a three-dimensional microstructure on a PTL substrate, and then coats a catalyst layer based on the PTL substrate to prepare a PTE with a three-dimensional catalyst layer. This eliminates the material process design for the catalyst microstructure, increases the contact area between the catalyst layer and the PTL, and thus improves the water electrolysis performance.

[0020] The technical solution of the present invention can bring the following beneficial effects:

[0021] (1) The PTE prepared by the present invention only requires a one-step pretreatment of PTL on the basis of traditional PTE preparation, and does not require high temperature conditions or electrochemical reaction participation, so the process is simple and the flow is clear.

[0022] (2) The PTE prepared in the present invention has a three-dimensional microstructure, which helps to increase the active area of ​​water electrolysis and thus improve the alkaline OER activity.

[0023] (3) The PTE prepared in the present invention exhibits water electrolysis activity exceeding that of standard porous transport electrodes in PEMEC. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a light microscope photograph of the untreated clean PTL used in Comparative Example 1.

[0025] Figure 2 These are optical microscopy and SEM images of mechanically embossed, laser engraved, and chemically etched embossed PTL substrates of Examples 1, 5-7.

[0026] Figure 3 It is a schematic cross-sectional view of the stamping plate used in Examples 1-5 and 8.

[0027] Figure 4This is a SEM photograph of the three-dimensional catalyst layer PTE in Example 1 after the catalyst layer is sprayed.

[0028] Figure 5 1 is the PEMEC polarization curve of PTE of Examples 1, 5-7 and Comparative Example 1.

[0029] Figure 6 is the double-layer capacitance (C dl ) curves and the calculated electrochemical active area (ECSA). DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0031] Example 1

[0032] This embodiment provides a three-dimensional PTE prepared by physical imprinting, and the preparation method thereof comprises the following steps:

[0033] The cut PTL (titanium mesh, 2×2cm 2 , mesh size 200 mesh, thickness 0.4 mm) were ultrasonically cleaned in acetone, ethanol, 2M HCl solution and deionized water in sequence for 5-30 min to obtain clean PTL;

[0034] Design and process a stainless steel stamping plate with a blade shape (bottom side length 1mm, height 1mm, blade spacing 1mm, parallel distribution);

[0035] A clean PTL and a stainless steel stamping plate were placed in a press, and a pressure (5 MPa) was applied. The stainless steel stamping plate was translated and transposed, and the same pressure was applied to obtain a PTL with staggered embossing with an embossing interval width of 20 μm.

[0036] The embossed PTL was taken out and sprayed with an IrO2 catalyst layer with a loading of 2 mg cm -2 (based on the area of ​​the catalyst layer), a PTE with a three-dimensional catalyst layer was obtained.

[0037] Example 2

[0038] This embodiment provides a three-dimensional PTE prepared by physical imprinting. The difference between the preparation method and the preparation method of Example 1 is that the pressure applied by the press is different, which is 2 MPa in this embodiment; the rest is the same as Example 1.

[0039] Example 3

[0040] This embodiment provides a three-dimensional PTE prepared by physical imprinting. The preparation method thereof differs from the preparation method in Example 1 in that: the pressure applied by the press is different, 10 MPa in this embodiment, and the translational size of the imprinting plate after each imprinting is different, 60 μm in this embodiment; other aspects are the same as in Example 1.

[0041] Example 4

[0042] This embodiment provides a three-dimensional PTE prepared by physical imprinting. The difference between the preparation method and the preparation method of Example 1 is that the translation size of the imprinting plate after each imprinting is different, which is 100 μm in this embodiment; the rest is the same as Example 1.

[0043] Example 5

[0044] This embodiment provides a three-dimensional PTE prepared by physical imprinting. The translation size of the imprinting plate in Example 1 is changed to 100 μm in this comparative example, and no transposition is performed after each imprinting. A PTE with a three-dimensional catalyst layer is obtained. The other steps and process parameters are the same as those in Example 1.

[0045] Example 6

[0046] This embodiment provides a three-dimensional PTE prepared by laser engraving, and the preparation method thereof comprises the following steps:

[0047] The clean PTL obtained in Example 1 was prepared with square grooves (length and width of 100 μm, spacing of 100 μm) using a laser engraving machine, with a laser power of 30 W and an etching time of 10 min; and then sprayed with an IrO2 catalyst layer with a loading of 2 mg·cm -2 (based on the area of ​​the catalyst layer), a PTE with a three-dimensional catalyst layer was obtained.

[0048] Example 7

[0049] This embodiment provides a three-dimensional PTE prepared by chemical etching, and the preparation method thereof comprises the following steps:

[0050] The clean PTL obtained in Example 1 was soaked in 0.1 mol / L hydrofluoric acid for 1 hour (40 mL hydrofluoric acid for 100 mg titanium mesh), then washed; and then sprayed with an IrO2 catalyst layer with a loading of 2 mg cm -2 (based on the area of ​​the catalyst layer), a PTE with a three-dimensional catalyst layer was obtained.

[0051] Comparative Example 1

[0052] This comparative example provides a standard PTE, the preparation method of which comprises the following steps:

[0053] The IrO2 catalyst layer was sprayed directly onto the clean PTL with a loading of 2 mg cm -2 The pretreatment method of PTL was the same as that of Example 1.

[0054] Example 8

[0055] This embodiment provides a three-dimensional PTE prepared by physical imprinting. The difference between the preparation method of this embodiment and the preparation method of embodiment 5 is that the translation size of the imprinting plate after each imprinting is different (20 μm). Other aspects are the same as those of embodiment 5.

[0056] Example 9

[0057] This embodiment provides a three-dimensional PTE prepared by laser engraving. The difference between the preparation method and the preparation method of Example 6 is that the laser engraving shape is circular (diameter 50 μm, interval 80 μm), and the rest is the same as Example 6.

[0058] The properties of the PTE prepared in Examples 1-9 and Comparative Example 1 were tested, and their specific structures are shown in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] In Table 1, the microstructure size refers to the width of the cut, wherein, when the microstructure is blade-shaped, the microstructure size refers to the width of the blade cut; when the microstructure is square (square), the microstructure size refers to the side length of the square; when the microstructure is circular, the microstructure size refers to the diameter of the circle.

[0063] Figure 1 This is a light microscope photograph of the untreated clean PTL used in Comparative Example 1.

[0064] Figure 2 These are optical microscopy and SEM images of mechanically embossed, laser engraved, and chemically etched embossed PTL substrates of Examples 1, 5-7.

[0065] Figure 3 Schematic diagram of the cross section of the stamping plate used in Examples 1-5 and 8. Figure 3 In the figure, the blades correspond to each other up and down, where d1 represents the length of the bottom side of the blade, d2 represents the blade spacing, and h represents the height of the blade.

[0066] Figure 4 This is a SEM photograph of the three-dimensional catalyst layer PTE in Example 1 after the catalyst layer is sprayed.

[0067] Figure 5 1 is the PEMEC polarization curve of PTE of Examples 1, 5-7 and Comparative Example 1.

[0068] PEMEC polarization curve test method: The anode PTE electrodes prepared in this embodiment and the comparative example were assembled in a PEM electrolyzer (active area of ​​4 cm 2 ) was tested, and a single-sided CCM coated with Pt / C catalyst (catalyst loading of 0.5 mg cm -2 The test temperature was 80°C, and the anode water circulation flow rate was 50 ml / min. The voltammetric characteristic curve was collected on an electrochemical workstation with a voltage range of 0-2.4 V and a scan rate of 5 mV / s.

[0069] Figure 6 is the double-layer capacitance (C dl ) curves and the calculated electrochemical active area (ECSA).

[0070] ECSA test method: The Example and Comparative Example PTE were assembled in a PEM electrolyzer (4 cm 2 ) was tested in a single-sided CCM coated with a Pt / C catalyst on the cathode side. The test temperature was 80°C and the anode water circulation flow rate was 50 ml / min. The electrochemical workstation collected the voltammetric characteristic curve with a voltage range of 0-0.2V and scan rates of 20, 40, 60, 80, 100, 120, and 140 mV / s. The current density of each sample at different scan rates was calculated by taking the difference of 0.1V to obtain the C dl The standard electrochemical active area of ​​titanium mesh is 0.04mF·cm -2 According to the formula, the ECSA values ​​of different titanium mesh PTE can be calculated (X ECSA ):

[0071]

[0072] ECSA=C dl (mF·cm -2 ) / 0.04(mF·cm -2 )

[0073] Depend on Figure 2 It can be seen that the PTLs obtained in different embodiments and comparative examples have different morphologies at the micron scale.

[0074] Depend on Figure 4 It can be seen that after the catalyst is coated, the basic appearance of the microstructure can still be retained, with undulations in the three-dimensional spatial direction.

[0075] Depend on Figure 5It can be seen that the microstructures obtained by mechanical embossing, laser engraving and chemical etching are all helpful in improving the electrolytic water activity of PTE, among which the improvement effect of Example 1 is the most significant.

[0076] Depend on Figure 6 It can be seen that the microstructures obtained by mechanical embossing, laser engraving, and chemical etching all help to increase the ECSA of PTE, that is, the contact area between the catalyst and PTL, and thus increase the effective contact area between the electrode and the electrolyte; among them, the improvement effect of Example 1 is the most significant.

Claims

1. A PEMEC electrode having a three-dimensional catalyst layer constructed on an ordered diffusion layer, wherein: The diffusion layer of the PEMEC electrode has a three-dimensional microstructure, and the catalyst layer loaded thereon is a three-dimensional catalyst layer; The three-dimensional microstructure is mechanical embossing; The mechanical embossing includes blade-shaped embossing, wherein the width of the blade-shaped embossing is 10-30 μm, the blade spacing is 20-100 μm, and the embossing arrangement is staggered; The staggered shape means that the embossments are distributed at an angle of 30° to 90° between each other; The diffusion layer is a titanium mesh with a mesh size of 40 to 600 and a thickness of 0.1 mm to 1.0 mm.

2. The PEMEC electrode according to claim 1, wherein The mesh number of the titanium mesh is 200 meshes.

3. The PEMEC electrode according to claim 1, wherein The thickness is 0.4mm.

4. The PEMEC electrode according to claim 1, wherein The material of the catalyst layer is IrO2, and the loading amount is 0.5-4 mg·cm -2 .

5. The PEMEC electrode according to claim 4, wherein The IrO2 loading is 2 mg·cm -2 .

6. The method for preparing a PEMEC electrode having a three-dimensional catalyst layer constructed on an ordered diffusion layer according to any one of claims 1 to 5, comprising the following steps: A three-dimensional microstructure is formed on the diffusion layer, and then a catalyst layer is coated to form a three-dimensional catalyst layer to obtain the PEMEC electrode.

7. The preparation method according to claim 6, wherein The three-dimensional microstructure is formed by a physical method; the physical method is embossing.

8. The preparation method according to claim 7, wherein The mold used for the stamping is a blade-shaped mold, the bottom side length of the blade is 1 mm, the height is 1 mm, and the blade spacing is 1 mm; the blades are distributed in parallel.

9. The preparation method according to claim 7 or 8, wherein The pressure used for the stamping is 2-10 MPa.

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