A PEM electrolyzer membrane electrode and a method of making the same

Abstract

The application discloses a PEM electrolytic cell membrane electrode and a preparation method thereof, relates to the technical field of PEM water electrolysis hydrogen production, and the preparation raw material of the membrane electrode comprises cathode slurry and anode slurry; the structure of the membrane electrode comprises, from inside to outside, a cathode catalytic layer, a proton exchange membrane and an anode catalytic layer; the cathode slurry is composed of an anode catalyst, an ionomer and a solvent; and the anode slurry is composed of a cathode catalyst, an ionomer and a solvent. The preparation method comprises the following steps: the cathode slurry and the anode slurry are mixed uniformly through magnetic stirring for 4-24 hours and ultrasonic stirring for 1-8 hours, and then the cathode slurry and the anode slurry are scraped or sprayed on both sides of the proton exchange membrane to obtain the cathode catalytic layer and the anode catalytic layer; and the cathode catalytic layer and the anode catalytic layer are sequentially subjected to primary drying, rolling, secondary drying and cutting. The preparation method provided by the application increases the contact active area of the catalytic layer of the membrane electrode, improves the catalytic efficiency of the catalytic layer, reduces the use amount of the catalyst, and thus reduces the cost of the PEM electrolytic cell.

Description

Technical Field

[0001] This invention relates to the field of PEM water electrolysis hydrogen production technology, and in particular to a PEM electrolyzer membrane electrode and its preparation method. Background Technology

[0002] A proton exchange membrane (PEM) is a selectively permeable membrane that serves in a PEM electrolyzer to provide channels for proton migration and transport, separate gaseous reactants, and isolate the anode and cathode. Therefore, the structure and fabrication process of the membrane electrode have a significant impact on the performance of the PEM electrolyzer.

[0003] Currently, the most widely used technology is the CCM membrane electrode preparation method, which involves spraying or coating a catalyst slurry onto both sides of a proton exchange membrane. However, the membrane electrode prepared by this method has a planar catalytic layer with a small active area, which cannot maximize the catalytic activity of the catalyst. Moreover, its mass transfer channels are disordered, resulting in severe electrochemical polarization and concentration polarization, which affects the lifespan of the PEM electrolyzer in the long run.

[0004] Therefore, the present invention provides a solution to the problems mentioned in the background art. Summary of the Invention

[0005] The object of the present invention is to provide a solution to at least one of the problems and defects mentioned in the background art.

[0006] The present invention also provides a method for preparing the above-mentioned PEM electrolytic cell membrane electrode.

[0007] Specifically, in a first aspect, the present invention provides a PEM electrolytic cell membrane electrode, wherein the raw materials for preparing the membrane electrode include a cathode slurry and an anode slurry; the structure of the membrane electrode, from the inside out, includes a cathode catalyst layer, a proton exchange membrane, and an anode catalyst layer; the cathode slurry is composed of an anode catalyst, an ionomer, and a solvent; and the anode slurry is composed of a cathode catalyst, an ionomer, and a solvent.

[0008] According to one technical solution of the PEM electrolyzer membrane electrode technology of the present invention, it has at least the following beneficial effects:

[0009] The membrane electrode assembly (MEA) employs a hierarchical structure from the inside out, consisting of a cathode catalytic layer, a proton exchange membrane, and an anode catalytic layer, which helps improve hydrogen generation efficiency. The proton exchange membrane is used for proton transport and separation of hydrogen and oxygen, thereby preventing gas mixing.

[0010] The use of catalysts in the cathode and anode slurries helps to promote the electrochemical reaction of hydrogen and oxygen, reduce polarization losses during electrolysis, and improve electrolysis efficiency. Appropriate catalyst selection and slurry preparation methods can increase electrode activity, reduce electrolysis potential, and thus save energy.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned PEM electrolytic cell membrane electrode, comprising the following steps:

[0012] a. Mix the cathode slurry and anode slurry evenly by magnetic stirring for 4-24 hours and ultrasonication for 1-8 hours, then coat or spray them onto both sides of the proton exchange membrane to obtain the cathode catalyst layer and anode catalyst layer.

[0013] b. The cathode catalyst layer and the anode catalyst layer are sequentially subjected to primary drying, rolling, secondary drying, and cutting.

[0014] The cathode catalyst is a non-precious metal-doped platinum-based catalyst, which includes at least one of platinum-carbon, platinum alloy catalysts, and non-precious metal catalysts.

[0015] The anode catalyst is a non-precious metal-doped iridium-based catalyst, which includes at least one of iridium dioxide, iridium black, and non-precious metal catalysts.

[0016] The platinum loading in the cathode catalyst layer is 0.1-0.3 mg / cm².

[0017] The iridium loading in the anode catalyst layer is 0.2-1 mg / cm2.

[0018] According to one technical solution of the method for preparing PEM electrolytic cell membrane electrode of the present invention, it has at least the following beneficial effects:

[0019] Ultrasonic treatment can help the components in the cathode and anode slurries mix more evenly, improving the uniformity of the slurry and the catalytic efficiency of the electrode. The cathode and anode slurries are coated or sprayed onto both sides of the proton exchange membrane, reducing the proton transport distance during electrolysis. During electrolysis, the cathode and anode catalytic layers can directly participate in the water electrolysis reaction, thereby improving the electrolysis efficiency.

[0020] A two-stage drying method is adopted, which allows for rolling before the slurry is fully cured, to obtain a catalyst layer of a specific shape.

[0021] Platinum-carbon catalysts are platinum particles dispersed on a carbon support. They exhibit good catalytic activity in the oxygen reduction reaction, effectively promoting oxygen reduction and providing high electrochemical activity.

[0022] Platinum alloy catalysts are catalysts obtained by alloying platinum with other metals (such as rhodium, palladium, gold, etc.). They can improve the performance of platinum-carbon catalysts, reduce the cost of catalysts, increase catalytic activity, and reduce the amount of precious metals used.

[0023] Iridium dioxide is an iridium-based catalyst used to promote the oxygen reduction reaction. It is widely used in solid oxide fuel cells (SOFCs) at high temperatures (typically above 800°C) due to its high catalytic activity and stability, making it suitable for the high-temperature conditions of the oxygen reduction reaction.

[0024] Iridium black is a form of iridium, usually used in powder form. It can be used to promote electrochemical reactions such as oxygen reduction reactions, and it has good electrocatalytic properties and good activity for oxygen reduction reactions.

[0025] In this invention, the platinum loading in the cathode catalyst layer and the iridium loading in the anode catalyst layer can significantly optimize the catalytic performance of the electrode. By selecting appropriate loading amounts, catalytic activity can be improved while avoiding excessive catalyst waste.

[0026] In some specific embodiments of the present invention, the temperature of the first-stage drying is 30-60°C and the drying time is 5-20 min.

[0027] In some specific embodiments of the present invention, the temperature of the secondary drying is 30-80°C and the drying time is 10-30 min.

[0028] In this invention, if the temperature is too low or the time is too short during the primary drying stage, the cathode and anode slurries will not be able to heat up sufficiently, making it easy for them to fall off during the subsequent rolling process. If the temperature is too high or the time is too long, the cathode and anode slurries will solidify too quickly, making it difficult to leave marks on them during rolling and thus difficult to form a specific shape.

[0029] In some specific embodiments of the present invention, the temperature of the roller pressing is 25-80°C.

[0030] In some specific embodiments of the present invention, the roller surface used in the rolling step has a convex, uniform shape.

[0031] According to one technical solution of the method for preparing PEM electrolytic cell membrane electrode of the present invention, it has at least the following beneficial effects:

[0032] The convex, uniform shape can increase the contact active area between the cathode and anode catalyst layers, thereby improving their catalytic efficiency and reducing the amount of catalyst used, thus lowering costs. After the membrane electrode is formed, its surface structure also changes accordingly, optimizing the proton and gas transport channels and increasing conductivity, thereby improving the performance and service life of the electrolyzer.

[0033] In some specific embodiments of the present invention, the depth of the protruding shape is <5µm, the width is <50µm, and the spacing is <50µm.

[0034] In some specific embodiments of the present invention, the thickness of the proton exchange membrane is 25-150 μm.

[0035] In some specific embodiments of the present invention, the ionomer is a 2-10% NAFION solution; the solvent is at least one of deionized water, isopropanol, glycerol, and ethanol.

[0036] In some specific embodiments of the present invention, rolling can occur on either side or both sides of the membrane electrode.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] 1. The membrane electrode preparation method provided by the present invention increases the contact active area of ​​the membrane electrode catalytic layer, improves the catalytic efficiency of the catalytic layer, and can reduce the amount of catalyst used, thereby reducing the cost of PEM electrolyzer;

[0039] 2. The membrane electrode prepared by the present invention optimizes the transport channels of protons and gases by changing its surface structure, increases the conductivity, and improves the performance and service life of the PEM electrolyzer.

[0040] 3. The membrane electrode preparation method provided by the present invention is simple and convenient to operate and can achieve mass production. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail below through embodiments. Furthermore, in the following detailed description, many specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments disclosed herein. However, it will be apparent that one or more embodiments may be implemented without these specific details.

[0042] A PEM electrolytic cell membrane electrode is provided. The raw materials for preparing the membrane electrode include a cathode slurry and an anode slurry. The structure of the membrane electrode, from the inside out, includes a cathode catalyst layer, a proton exchange membrane, and an anode catalyst layer. The cathode slurry is composed of an anode catalyst, an ionomer, and a solvent. The anode slurry is composed of a cathode catalyst, an ionomer, and a solvent.

[0043] Example 1

[0044] In this embodiment, the PEM electrolytic cell membrane electrode is prepared according to the following steps:

[0045] (1) Preparation of anode and cathode slurries;

[0046] The anode slurry is prepared as follows: 2wt% IrO2 catalyst (iridium content 85%), 2wt% Nafion solution, 58wt% isopropanol, 26wt% ethanol and 12wt% deionized water are mixed evenly by magnetic stirring for 4h at a magnetic stirring temperature of 40℃, and then ultrasonically dispersed for 1h to obtain the anode catalyst slurry.

[0047] The cathode slurry is prepared as follows: 2 wt% Pt / C catalyst (platinum loading 40%), 2 wt% Nafion solution, 58 wt% glycerol, 26 wt% ethanol and 12 wt% deionized water are mixed evenly by magnetic stirring for 4 h at a magnetic stirring temperature of 40 °C, and then ultrasonically dispersed for 1 h to obtain the cathode catalyst slurry.

[0048] (2) Slurry coating; The anode slurry and cathode slurry obtained in step (1) are respectively loaded into the barrel of the ultrasonic equipment, and then the program is set to spray the anode slurry onto the anode side of the proton exchange membrane and the cathode slurry onto the cathode side of the proton exchange membrane; wherein, the iridium loading of the anode catalyst layer is 0.2 mg / cm2; the platinum loading of the cathode catalyst layer is 0.1 mg / cm2;

[0049] (3) Slurry curing: The proton exchange membrane with coating obtained in step (2) is dried at 30°C for 5 min. When the anode slurry and cathode slurry are not completely cured, the anode slurry is rolled with a roller with uniformly raised horizontal stripes on the surface. The depth of the raised stripes is 2 μm, the spacing is 2 μm, the rolling temperature is 25°C, and then it is dried at 30°C for 10 min to obtain a membrane electrode with a groove on the anode side surface.

[0050] (4) Cutting: Cut the membrane electrode obtained in step (3) into 10cm*12cm sizes.

[0051] Example 2

[0052] In this embodiment, the PEM electrolytic cell membrane electrode is prepared according to the following steps:

[0053] (1) Preparation of anode and cathode slurries;

[0054] The anode slurry is prepared as follows: 2wt% IrO2 catalyst (iridium content 85%), 2wt% Nafion solution, 58wt% isopropanol, 26wt% ethanol and 12wt% deionized water are mixed evenly by magnetic stirring for 24h at a magnetic stirring temperature of 40℃, and then ultrasonically dispersed for 8h to obtain the anode catalyst slurry.

[0055] The cathode slurry is prepared as follows: 2 wt% Pt / C catalyst (platinum loading 40%), 2 wt% Nafion solution, 58 wt% glycerol, 26 wt% ethanol and 12 wt% deionized water are mixed evenly by magnetic stirring for 24 h at a magnetic stirring temperature of 40 °C, and then ultrasonically dispersed for 8 h to obtain the cathode catalyst slurry.

[0056] (2) Slurry coating; The anode slurry and cathode slurry obtained in step (1) are respectively loaded into the barrel of the ultrasonic equipment, and then the program is set to spray the anode slurry onto the anode side of the proton exchange membrane and the cathode slurry onto the cathode side of the proton exchange membrane; wherein, the iridium loading of the anode catalyst layer is 1 mg / cm2; the platinum loading of the cathode catalyst layer is 0.3 mg / cm2;

[0057] (3) Slurry curing: The proton exchange membrane with coating obtained in step (2) is dried at 60°C for 20 min. When the anode slurry and cathode slurry are not completely cured, the anode slurry is rolled with a roller with uniformly raised horizontal stripes on the surface. The depth of the raised stripes is 5 μm, the spacing is 50 μm, the rolling temperature is 80°C, and then it is dried at 80°C for 30 min to obtain a membrane electrode with a groove on the anode side surface.

[0058] (4) Cutting: Cut the membrane electrode obtained in step (3) into 10cm*12cm sizes.

[0059] Example 3

[0060] The method for preparing the PEM electrolytic cell membrane electrode in this embodiment differs from that in Example 1 in that rolling is performed on both sides of the membrane electrode.

[0061] Example 4

[0062] The method for preparing the PEM electrolytic cell membrane electrode in this embodiment differs from that in Embodiment 2 in that rolling is performed on both sides of the membrane electrode.

[0063] Example 5

[0064] The method for preparing the PEM electrolytic cell membrane electrode in this embodiment differs from that in Embodiment 1 in that the rollers used for rolling have a 2um*2um*2um dot matrix protrusions.

[0065] Example 6

[0066] The method for preparing the PEM electrolytic cell membrane electrode in this embodiment differs from that in Embodiment 2 in that the rollers used for rolling have a 2um*2um*2um dot matrix protrusions.

[0067] Comparative Example 1

[0068] The difference between the preparation method of the PEM electrolytic cell membrane electrode in this comparative example and that in Example 1 is that the rollers used for rolling are smooth and without protrusions.

[0069] Comparative Example 2

[0070] The difference between the preparation method of the PEM electrolytic cell membrane electrode in this comparative example and that in Example 2 is that the rollers used for rolling are smooth and without protrusions.

[0071] Electrochemical tests were performed on Examples 1-6 and Comparative Examples 1-2, and the specific test methods are as follows:

[0072] The current density under different operating conditions was obtained by controlling the applied voltages of 1.8V and 2.0V using a DC power supply, and the data are shown in the table below.

[0073] Table 1 Electrolytic Current Density of Membrane Electrode

[0074]

[0075]

[0076] In summary, the membrane electrode prepared by the method provided by this invention exhibits a higher current density than planar membrane electrodes prepared by conventional methods under the same voltage. This is mainly because the membrane electrode provided by this invention is rolled into a grooved shape by rollers with uniformly shaped protrusions on the surface during the catalyst slurry solidification process. This optimizes the proton and gas transport channels, increases conductivity, and improves the performance and lifespan of the PEM electrolyzer. Simultaneously, the grooved membrane electrode structure increases the contact active area of ​​the catalyst layer, improving the catalytic efficiency of the catalyst layer and reducing the amount of catalyst used, thereby reducing the cost of the PEM electrolyzer. The membrane electrode preparation method provided by this invention is simple and convenient to operate and can achieve mass production.

[0077] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A PEM electrolytic cell membrane electrode, characterized in that, The raw materials for preparing the membrane electrode include cathode slurry and anode slurry; The membrane electrode structure, from the inside out, includes a cathode catalytic layer, a proton exchange membrane, and an anode catalytic layer. The cathode slurry is composed of a cathode catalyst, an ionomer, and a solvent; The anode slurry is composed of an anode catalyst, an ionomer, and a solvent; The method for preparing the PEM electrolytic cell membrane electrode includes scraping or spraying cathode slurry and anode slurry onto both sides of a proton exchange membrane, followed by primary drying, rolling, secondary drying, and cutting to obtain the cathode catalyst layer and the anode catalyst layer. The rollers used for the roll forming have a convex, uniform shape on their surface; the convex, uniform shape has a depth of <5µm, a width of <50µm, and a spacing of <50µm; the roll forming occurs on both sides of the membrane electrode. The thickness of the proton exchange membrane is 25-150 μm.

2. A method for preparing a PEM electrolytic cell membrane electrode as described in claim 1, characterized in that, Includes the following steps: a. Mix the cathode slurry and anode slurry evenly by magnetic stirring for 4-24 hours and ultrasonication for 1-8 hours, then coat or spray them onto both sides of the proton exchange membrane to obtain the cathode catalyst layer and anode catalyst layer. b. The cathode catalyst layer and the anode catalyst layer are sequentially subjected to primary drying, rolling, secondary drying, and cutting. The cathode catalyst is a platinum-based catalyst without noble metal doping. The anode catalyst is an iridium-based catalyst that is not doped with precious metals. The platinum loading in the cathode catalyst layer is 0.1-0.3 mg / cm³. 2 ; The iridium loading in the anode catalyst layer is 0.2-1 mg / cm³. 2 ; The rollers used in the roll forming process have a convex, uniform shape on their surface. The protruding uniform shape has a depth of <5µm, a width of <50µm, and a spacing of <50µm; the rolling process occurs on both sides of the membrane electrode. The thickness of the proton exchange membrane is 25-150 μm.

3. The method for preparing the PEM electrolytic cell membrane electrode according to claim 2, characterized in that, The temperature for the first-stage drying is 30-60℃, and the drying time is 5-20 minutes.

4. The method for preparing the PEM electrolytic cell membrane electrode according to claim 2, characterized in that, The temperature for the secondary drying is 30-80℃, and the drying time is 10-30 minutes.

5. The method for preparing the PEM electrolytic cell membrane electrode according to claim 2, characterized in that, The temperature of the roller pressing is 25-80℃.

6. The method for preparing the PEM electrolytic cell membrane electrode according to claim 2, characterized in that, The ionomer is a NAFION solution; the solvent is at least one of deionized water, isopropanol, glycerol, and ethanol.

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