A gas diffusion layer for an electrolytic cell and a preparation method thereof

Abstract

The present invention discloses a gas diffusion layer for an electrolytic cell and a preparation method thereof, belonging to the technical field of gas diffusion layer preparation. The preparation method includes: taking large-particle-size titanium powder, adding a first pore-forming agent, and pressing into a blank; taking small-particle-size titanium powder, adding a second pore-forming agent, and preparing a titanium powder slurry; spraying the titanium powder slurry onto the surface of the blank and extruding to obtain a precursor; heating the precursor under vacuum conditions at a rate of 5-10 °C / min to 90-130 °C, and holding the temperature; then heating at a rate of 10-15 °C / min to 230-280 °C, holding the temperature, and finally heating at a rate of 20-30 °C / min to 1100-1300 °C, holding the temperature to obtain. The gas diffusion layer has advantages such as high porosity and large specific surface area, and the gas diffusion layer has a gradient pore structure inside, has excellent water-vapor transmission performance, and can effectively solve the problems of disordered internal pores and poor fluid backflow effect existing in the existing gas diffusion layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas diffusion layer preparation, and specifically relates to a gas diffusion layer for an electrolytic cell and a preparation method thereof. Background Art

[0002] Electrolytic hydrogen production is a new energy storage method and one of the methods that can largely consume renewable resources, which has been unanimously recognized in the world. The electrolytic hydrogen production methods are mainly divided into traditional alkaline electrolytic water hydrogen production and emerging solid polymer electrolyte (SPE) electrolytic water hydrogen production. SPE electrolytic water hydrogen production has the advantages of high efficiency, miniaturization of devices, quick start and stop, no pollution, high hydrogen production purity, etc.

[0003] The main components of an SPE electrolytic cell are bipolar plates, gas diffusion layers (anode and cathode), and membrane electrodes. The main functions of the gas diffusion layer are to form a protective membrane electrode, conduct electricity, and guide the flow of gas and liquid. Due to the strong oxidizing property generated by the anodic oxygen evolution reaction during the process of water electrolysis reaction, the gas diffusion layer and bipolar plates of the SPE electrolytic cell mostly adopt titanium metal materials.

[0004] The existing gas diffusion layer for SPE electrolytic cells mainly uses titanium foam plates. As the gas diffusion layer, the internal pores of the titanium foam plates are disordered, and the guiding effect on fluid flow is poor. Summary of the Invention

[0005] Aiming at the above deficiencies in the prior art, the present invention provides a gas diffusion layer for an electrolytic cell and a preparation method thereof. This gas diffusion layer has the advantages of high porosity, large specific surface area, etc. Moreover, the gas diffusion layer has a gradient pore structure inside, has excellent water and gas transmission performance, and can effectively solve the problems of disordered internal pores and poor fluid backflow guiding effect existing in the existing gas diffusion layer.

[0006] To achieve the above object, the technical solution adopted by the present invention to solve its technical problems is:

[0007] A preparation method of a gas diffusion layer for an electrolytic cell, comprising the following steps:

[0008] (1) Take large-particle-size titanium powder, add a first pore-forming agent and ethanol thereto, stir and mix evenly, and then press into a blank;

[0009] (2) Take small-particle-size titanium powder, add a second pore-forming agent and ethanol thereto, stir and mix evenly to obtain a titanium powder slurry;

[0010] (3) Spray the titanium powder slurry onto the surface of the blank, and then extrude the surface of the titanium powder slurry to obtain a precursor;

[0011] (4) Place the precursor at 1×10 -3 -1×10 -4Under a Pa vacuum, heat it at a rate of 5-10 °C / min to 90-130 °C and keep it warm for 20-40 min; then heat it at a rate of 10-15 °C / min to 230-280 °C and keep it warm for 30-60 min, and finally heat it at a rate of 20-30 °C / min to 1100-1300 °C and keep it warm for 90-180 min to obtain a gas diffusion layer for an electrolytic cell.

[0012] Further, in step (1), the particle size of the large-particle titanium powder is 50-150 μm.

[0013] Further, in step (1), the first pore-forming agent includes ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000 is 1-2:1-2:1-2:1-2.

[0014] Further, in step (1), the dosage of the first pore-forming agent is 5-15% of the mass of the large-particle titanium powder.

[0015] Further, in step (1), the thickness of the blank is 0.25-2.5 mm.

[0016] Further, in step (2), the particle size of the small-particle titanium powder is 5-25 μm.

[0017] Further, in step (2), the second pore-forming agent includes ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000 is 1-2:1-2:2-4:2-4.

[0018] Further, in step (2), the dosage of the second pore-forming agent is 5-15% of the mass of the small-particle titanium powder.

[0019] Further, in step (3), the spraying thickness of the titanium powder slurry is 0.3-1 mm.

[0020] A gas diffusion layer for an electrolytic cell is prepared by the above method.

[0021] The beneficial effects produced by the present invention are as follows:

[0022] During the preparation process of the present invention, pore-forming agents with gradient decomposition temperatures are added to the titanium powder, so that during the sintering process, the pore-forming agents with different decomposition temperatures decompose step by step, forming a uniformly distributed pore structure with appropriate pore diameters inside the titanium powder. The internal porosity is as high as 50.4%, and the pore diameters are between 10 - 100 μm. This gas diffusion layer has a large specific surface area and good water vapor transmission performance and gas diffusion performance.

[0023] The gas diffusion layer in the present invention has a gradient pore structure. The micropores can inhibit the aggregation of bubbles on the surface of the membrane electrode, and the macropore structure is conducive to the transmission of liquid from the bipolar plate to the electrode surface. The combination of these two pore structures can promote gas-liquid transfer and reduce the energy consumption of electrolyzing water.

[0024] The thickness of the gas diffusion layer in the present invention can be prepared to be 0.25 - 2.8 mm according to needs. The surface roughness is less than 30 μm. The porosity of the macropore layer is 50.4%, and the average pore diameter is 18 μm. The porosity of the micropore layer is 38.9%, and the average pore diameter is 12 μm. The overall tensile strength of gas diffusion layers with different thicknesses is 0.6 - 2.0 KN / 50 mm, having good mechanical properties. Description of the Drawings

[0025] Figure 1 It is a low-magnification transmission electron microscope scanning image of the cross-section of the gas diffusion layer in Example 1;

[0026] Figure 2 It is a high-magnification transmission electron microscope scanning image of the cross-section of the gas diffusion layer in Example 1;

[0027] Figure 3 It is a transmission electron microscope scanning image of the macropore gas diffusion layer in Example 1;

[0028] Figure 4 It is a pore size distribution statistical chart of the gas diffusion layer in Example 1. Detailed Embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0030] Therefore, the following detailed description of the provided embodiments of the present invention is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0031] It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0032] The features and performance of the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings.

[0033] Embodiment 1

[0034] A gas diffusion layer for an electrolytic cell, and its preparation method includes the following steps:

[0035] (1) Take large-particle-size titanium powder with a particle size of 100 μm, add a first pore-forming agent and ethanol, where the mass of the first pore-forming agent is 10% of the mass of the large-particle-size titanium powder. The first pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500 is 2:2:2:1, and the amount of ethanol used is 15% of the weight of the large-particle-size titanium powder. Stir and mix evenly, and then press into a blank with a thickness of 1.5 mm;

[0036] (2) Take small-particle-size titanium powder with a particle size of 10 μm, add a second pore-forming agent and ethanol, where the mass of the second pore-forming agent is 10% of the mass of the small-particle-size titanium powder. The second pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500 is 1:1:2:3, and the amount of ethanol used is 30% of the weight of the small-particle-size titanium powder. Stir and mix evenly to obtain a titanium powder slurry;

[0037] (3) Spray the titanium powder slurry onto the surface of the blank, with a spraying thickness of 1 mm, and then extrude the surface of the titanium powder slurry to obtain a precursor;

[0038] (4) Place the precursor in 1×10 -3Under a vacuum degree, heat it up to 110 °C at a rate of 7 °C / min and keep it warm for 30 min; then heat it up to 250 °C at a rate of 12 °C / min and keep it warm for 60 min, and finally heat it up to 1200 °C at a rate of 25 °C / min and keep it warm for 160 min to obtain the gas diffusion layer for the electrolytic cell.

[0039] Example 2

[0040] A gas diffusion layer for an electrolytic cell, and its preparation method includes the following steps:

[0041] (1) Take large-particle-size titanium powder with a particle size of 50 μm, add a first pore-forming agent accounting for 15% of the mass of the large-particle-size titanium powder and ethanol to it. The first pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 200, polyethylene glycol with a molecular weight of 1000, and polyethylene glycol with a molecular weight of 3000. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 200, polyethylene glycol with a molecular weight of 1000, and polyethylene glycol with a molecular weight of 3000 is 1:1:1:1, and the ethanol dosage is 15% of the weight of the large-particle-size titanium powder. Stir and mix evenly, and then press it into a blank with a thickness of 0.25 mm;

[0042] (2) Take small-particle-size titanium powder with a particle size of 5 μm, add a second pore-forming agent accounting for 15% of the mass of the small-particle-size titanium powder and ethanol to it. The second pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 200, polyethylene glycol with a molecular weight of 1000, polyethylene glycol with a molecular weight of 3000 and ethanol. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 200, polyethylene glycol with a molecular weight of 1000, and polyethylene glycol with a molecular weight of 3000 is 1:1:2:2, and the ethanol dosage is 30% of the weight of the small-particle-size titanium powder. Stir and mix evenly to obtain the titanium powder slurry;

[0043] (3) Spray the titanium powder slurry onto the surface of the blank, with a spraying thickness of 0.3 mm, and then extrude the surface of the titanium powder slurry to obtain the precursor;

[0044] (4) Place the precursor under a vacuum degree of 1×10 -4 Pa, heat it up to 90 °C at a rate of 5 °C / min and keep it warm for 40 min; then heat it up to 230 °C at a rate of 10 °C / min and keep it warm for 60 min, and finally heat it up to 1100 °C at a rate of 20 °C / min and keep it warm for 180 min to obtain the gas diffusion layer for the electrolytic cell.

[0045] Example 3

[0046] A gas diffusion layer for an electrolytic cell, and its preparation method includes the following steps:

[0047] (1) Take large-sized titanium powder with a particle size of 150 μm, add a first pore-forming agent accounting for 5% of the mass of the large-sized titanium powder and ethanol thereto. The first pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 600, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 4000. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 600, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 4000 is 2:1:2:1. The amount of ethanol used is 15% of the weight of the large-sized titanium powder. Stir and mix evenly, and then press into a blank with a thickness of 2.5 mm;

[0048] (2) Take small-sized titanium powder with a particle size of 25 μm, add a second pore-forming agent accounting for 5% of the mass of the small-sized titanium powder and ethanol thereto. The second pore-forming agent includes ammonium bicarbonate, polyethylene glycol with a molecular weight of 600, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 4000 mixed and made. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 600, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 4000 is 1:1:4:4. The amount of ethanol used is 30% of the weight of the small-sized titanium powder. Stir and mix evenly to obtain a titanium powder slurry;

[0049] (3) Spray the titanium powder slurry onto the surface of the blank with a spraying thickness of 0.8 mm, and then extrude the surface of the titanium powder slurry to obtain a precursor;

[0050] (4) Place the precursor under a vacuum of 1×10 -4 Pa, heat it to 130 °C at a rate of 10 °C / min, and keep it warm for 20 min; then heat it to 280 °C at a rate of 15 °C / min and keep it warm for 30 min. Finally, heat it to 1300 °C at a rate of 30 °C / min and keep it warm for 90 min to obtain a gas diffusion layer for an electrolytic cell.

[0051] Example 4

[0052] A gas diffusion layer for an electrolytic cell, and its preparation method includes the following steps:

[0053] (1) Take large-sized titanium powder with a particle size of 100 μm, add a first pore-forming agent accounting for 12% of the mass of the large-sized titanium powder and ethanol thereto. The first pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 400, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 4000. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 400, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 4000 is 2:2:1:1. The amount of ethanol used is 15% of the weight of the large-sized titanium powder. Stir and mix evenly, and then press into a blank with a thickness of 1 mm;

[0054] (2) Take small-sized titanium powder with a particle size of 15 μm, add a second pore-forming agent and ethanol accounting for 8% of the mass of the small-sized titanium powder. The second pore-forming agent is prepared by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 600, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 3000. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 600, polyethylene glycol with a molecular weight of 2000, and polyethylene glycol with a molecular weight of 3000 is 2:2:4:2. The ethanol dosage is 30% of the weight of the small-sized titanium powder. Stir and mix evenly to obtain a titanium powder slurry.

[0055] (3) Spray the titanium powder slurry onto the surface of the blank with a spraying thickness of 0.5 mm, and then extrude the surface of the titanium powder slurry to obtain a precursor.

[0056] (4) Place the precursor under a vacuum of 1×10 -4 Pa, heat it at a rate of 8 °C / min to 110 °C, and keep it warm for 40 min; then heat it at a rate of 15 °C / min to 250 °C, keep it warm for 50 min, and finally heat it at a rate of 20 °C / min to 1300 °C, keep it warm for 120 min to obtain a gas diffusion layer for an electrolytic cell.

[0057] Comparative Example 1

[0058] A gas diffusion layer for an electrolytic cell, and its preparation method includes the following steps:

[0059] (1) Take large-sized titanium powder with a particle size of 100 μm, add a first pore-forming agent and ethanol accounting for 10% of the mass of the large-sized titanium powder. The first pore-forming agent is polyethylene glycol with a molecular weight of 1500. The ethanol dosage is 15% of the weight of the large-sized titanium powder. Stir and mix evenly, and then press it into a blank with a thickness of 1.5 mm.

[0060] (2) Take small-sized titanium powder with a particle size of 10 μm, add a second pore-forming agent and ethanol accounting for 10% of the mass of the small-sized titanium powder. The second pore-forming agent is polyethylene glycol with a molecular weight of 3500. The ethanol dosage is 30% of the weight of the small-sized titanium powder. Stir and mix evenly to obtain a titanium powder slurry.

[0061] (3) Spray the titanium powder slurry onto the surface of the blank with a spraying thickness of 1 mm, and then extrude the surface of the titanium powder slurry to obtain a precursor.

[0062] (4) Place the precursor under a vacuum of 1×10 -3 and heat it at a rate of 7 °C / min to 110 °C, keep it warm for 30 min; then heat it at a rate of 12 °C / min to 250 °C, keep it warm for 60 min, and finally heat it at a rate of 25 °C / min to 1200 °C, keep it warm for 160 min to obtain a gas diffusion layer for an electrolytic cell.

[0063] Comparative Example 2

[0064] A gas diffusion layer for an electrolytic cell, and a preparation method thereof comprises the following steps:

[0065] (1) Take large-particle-size titanium powder with a particle size of 100 μm, add a first pore-forming agent accounting for 10% of the mass of the large-particle-size titanium powder and ethanol thereto. The first pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500 is 2:2:2:1. The amount of ethanol used is 15% of the weight of the large-particle-size titanium powder. Stir and mix evenly, and then press into a blank with a thickness of 1.5 mm;

[0066] (2) Take small-particle-size titanium powder with a particle size of 10 μm, add a second pore-forming agent accounting for 10% of the mass of the small-particle-size titanium powder thereto. The second pore-forming agent is made by mixing ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500. The mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 500, polyethylene glycol with a molecular weight of 1500, and polyethylene glycol with a molecular weight of 3500 is 1:1:2:3. The amount of ethanol used is 30% of the weight of the small-particle-size titanium powder. Stir and mix evenly to obtain a titanium powder slurry;

[0067] (3) Spray the titanium powder slurry onto the surface of the blank with a spraying thickness of 1 mm, and then extrude the surface of the titanium powder slurry to obtain a precursor;

[0068] (4) Place the precursor under a vacuum of 1×10 -3 Vacuum degree, heat it to 200 °C at a rate of 13 °C / min, and keep it warm for 60 min; then heat it to 600 °C at a rate of 20 °C / min, and keep it warm for 90 min. Finally, heat it to 1200 °C at a rate of 25 °C / min, and keep it warm for 240 min to obtain the gas diffusion layer for the electrolytic cell.

[0069] Test example

[0070] Taking the gas diffusion layers prepared in Example 1, Comparative Example 1, and Comparative Example 2 as examples, the porosity of the gas diffusion layer was measured by X-ray diffraction method, the average pore diameter of the gas diffusion layer was measured by mercury intrusion method, and the tensile strength of the gas diffusion layer was measured by an electronic universal testing machine. The specific test results are shown in Table 1;

[0071] Table 1: Measurement results of the gas diffusion layer

[0072]

[0073] It can be seen from the data in the above table that, under the same thickness, the porosity and average pore size of the gas diffusion layer prepared by the method in Example 1 are both larger than those of the gas diffusion layers in Comparative Example 1 and Comparative Example 2, and the tensile strength is slightly smaller than that of the gas diffusion layers in Comparative Example 1 and Comparative Example 2;

[0074] Compared with Example 1, Comparative Example 1 only uses one pore-forming agent. Since the decomposition temperature range of a single pore-forming agent is relatively narrow, it will affect the formation of pores inside the gas diffusion layer during the preparation process, thereby reducing the average pore size and porosity of the gas diffusion layer. Moreover, due to fewer pores inside the material, the tensile strength of the gas diffusion layer increases.

[0075] Compared with Example 1, Comparative Example 2 adjusted the heating rate and holding temperature during the calcination process. It is speculated that this may be because pore-forming agents with different decomposition temperatures were used. After adjusting the heating rate and holding temperature, the pore-forming agents could not fully exert their pore-forming ability, thereby affecting the performance of the gas diffusion layer.

[0076] Figure 1 is a transmission electron microscope scanning image of the cross-section of the gas diffusion layer in Example 1, where Figure 1 is a transmission electron microscope scanning image at a low magnification. It can be seen that the gas diffusion layer prepared in Example 1 has a small pore membrane layer structure and a large pore matrix structure inside, and the two structures form an obvious gradient pore structure; Figure 2 is Figure 1 a transmission electron microscope scanning image at a high magnification of the structure within the blue circle in Figure 2 It can be seen from the structure within the red circle in

[0077] Figure 3 is a transmission electron microscope scanning image of the large pore gas diffusion layer in Example 1. It can be seen that there are a large number of pore structures inside, and the pores are interconnected with each other.

[0078] Figure 4It is a statistical graph of the pore size distribution of the gas diffusion layer in Example 1. Among them, the red area is enclosed by the red curve (differential mercury intrusion increment - pore length) and the abscissa, indicating the cumulative situation of the differential mercury intrusion increment within different pore size ranges. Intuitively, it reflects the total volume contribution of mercury entering the pores per unit length and unit mass of the material during the mercury intrusion process. It can be seen from the figure that within the smaller pore size range (about 2 - 10 μm), the area of the red region is larger, indicating that the cumulative differential mercury intrusion increment within this pore size range is relatively large, that is, the pores of the material within this pore size interval contribute more to the mercury intrusion volume. As the pore size increases, the differential mercury intrusion increment first decreases and then fluctuates slightly at about 90 μm, indicating that there are differences in the ease of mercury intrusion for different pore sizes. It can also be seen from the figure that the porosity of the material is 43.58%, the pores are abundant, the average pore size is about 18 μm, most of the pore sizes are concentrated between 7 - 30 μm, and the pore volume ratio of pores with a pore size less than 60 μm is as high as 70.26%, which is the main pore size interval of the material, indicating that the pores in the material are mainly small pore sizes.

Claims

1. A method for preparing a gas diffusion layer for an electrolytic cell, characterized in that: The following steps are involved: (1) taking a large-particle titanium powder with a particle size of 50-150 μm, adding a first pore-forming agent and ethanol thereto, stirring and mixing, and pressing into a blank; the first pore-forming agent comprises ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000, and the mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000 is 1-2:1-2:1-2:1-2; (2) taking a small-particle titanium powder with a particle size of 5-25 μm, adding a second pore-forming agent and ethanol thereto, stirring and mixing, and preparing a titanium powder slurry; the second pore-forming agent comprises ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000, and the mass ratio of ammonium bicarbonate, polyethylene glycol with a molecular weight of 200-600, polyethylene glycol with a molecular weight of 1000-2000, and polyethylene glycol with a molecular weight of 3000-4000 is 1-2:1-2:2-4:2-4; (3) Spraying titanium powder slurry onto the surface of the blank, and then extruding the surface of the titanium powder slurry to obtain a precursor; (4) Place the precursor at 1×10 -3 -1×10 -4 Pa vacuum degree, heating to 90-130°C at a rate of 5-10°C / min, and keeping the temperature for 20-40min; then heating to 230-280°C at a rate of 10-15°C / min, and keeping the temperature for 30-60min; finally heating to 1100-1300°C at a rate of 20-30°C / min, and keeping the temperature for 90-180min, to obtain a gas diffusion layer for an electrolytic cell; In step (1), the amount of the first pore-forming agent is 5-15% of the mass of the large-particle titanium powder; The amount of the second pore-forming agent used in step (2) is 5-15% of the mass of the small-particle titanium powder.

2. The method for preparing a gas diffusion layer for an electrolytic cell according to claim 1, characterized in that: The thickness of the blank in step (1) is 0.25-2.5 mm.

3. The method for preparing a gas diffusion layer for an electrolytic cell according to claim 1, characterized in that: In step (3), the spraying thickness of the titanium powder slurry is 0.3-1 mm.

4. A gas diffusion layer for an electrolytic cell, characterized in that: The method according to any one of claims 1 to 3 is adopted to prepare the present invention.

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