A high-stability membrane electrode, a preparation method thereof, and a water electrolyzer using the same

Abstract

The application provides a high-stability membrane electrode and a preparation method and application thereof, and a water electrolysis cell applying the same. The high-stability membrane electrode comprises an anode gas diffusion layer, an anode catalytic layer, an anion exchange membrane, a cathode catalytic layer and a cathode gas diffusion layer which are sequentially stacked. The anode catalytic layer is prepared by the following steps: S1. mixing a nickel ferrite catalyst, polytetrafluoroethylene and an anion exchange membrane ionomer with a solvent, stirring uniformly to obtain a nickel ferrite catalyst slurry; S2. coating the nickel ferrite catalyst slurry on the anode gas diffusion layer, drying to obtain a membrane electrode intermediate, and performing heat preservation of the membrane electrode intermediate in an inert gas at a heat preservation temperature of 300-500 DEG C for 5-60 minutes to obtain the anode catalytic layer. The membrane electrode provided by the application has good structural stability, excellent water electrolysis catalytic performance, can make the water electrolysis cell applying the same operate for a long time, and has high hydrogen production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis for hydrogen production technology, specifically relating to a highly stable membrane electrode and its preparation method, and a water electrolyzer using the same. Background Technology

[0002] Compared to proton exchange membrane (PEM) water electrolysis for hydrogen production, anion exchange membrane (AEM) water electrolysis can use pure water or low-concentration alkaline solutions as electrolytes and can utilize low-cost, highly active non-precious metal catalysts. It boasts advantages in both cost and performance, and thus has a promising future. The core component of AEM water electrolysis for hydrogen production is the membrane electrode assembly (MEA), which mainly consists of a gas diffusion layer, a catalyst layer, and an anion exchange membrane.

[0003] However, during the operation of the AEM water electrolyzer, an oxygen evolution reaction occurs on the anode side, and the metal catalyst in the catalyst layer is prone to dissolution, leading to the collapse of the catalyst layer structure and subsequent mechanical detachment. This reduces the water electrolysis catalytic performance of the AEM water electrolyzer to some extent and increases the risk of clogging the hydrogen production pipeline, seriously affecting the long-term stable operation of the AEM water electrolysis equipment.

[0004] Therefore, it is necessary to prepare membrane electrodes with high stability and excellent water electrolysis performance to achieve efficient and stable long-term operation of AEM water electrolysis hydrogen production equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a highly stable membrane electrode and its preparation method, as well as a water electrolyzer using the same. The membrane electrode provided by this invention has good structural stability and excellent water electrolysis catalytic performance, which can enable the water electrolyzer using it to operate for a long time and has high hydrogen production efficiency.

[0006] According to a first aspect of the present invention, a highly stable membrane electrode is provided, comprising an anode gas diffusion layer, an anode catalyst layer, an anion exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer stacked sequentially; wherein the anode catalyst layer is prepared by the following steps: S1. mixing nickel ferrite catalyst, polytetrafluoroethylene, anion exchange membrane ionomer, and solvent, stirring evenly to obtain a nickel ferrite catalyst slurry; S2. coating the nickel ferrite catalyst slurry onto the anode gas diffusion layer, drying it to obtain a membrane electrode intermediate, and then holding the membrane electrode intermediate in an inert gas at a temperature of 300–500°C for 5–60 minutes to obtain the anode catalyst layer.

[0007] This invention uses polytetrafluoroethylene (PTFE), anion exchange membrane ionomer, and nickel ferrite catalyst to form a slurry, which is then subjected to a pyrolysis reaction at 300–500°C. At this temperature, PTFE is dispersed in a molten state within the anode catalyst layer, and some of the anion exchange membrane ionomer undergoes pyrolysis, resulting in a large number of microporous structures in the anode catalyst layer and improved hydrophobicity. This effectively improves the pore structure of the anode catalyst layer, resulting in a high porosity, which enhances gas conductivity, exposes more catalytic active sites, and thus improves the catalytic efficiency of the membrane electrode using this anode catalyst layer. If the reaction temperature in step S2 is too high, the resulting anode catalyst layer structure is loose and prone to collapse; if the reaction temperature in step S2 is too low, the structural improvement effect of the resulting anode catalyst layer is not significant, and the improvement in catalytic efficiency is minimal.

[0008] Furthermore, the polytetrafluoroethylene (PTFE) used in this invention can act as a binder. The anode catalyst layer is prepared using a nickel ferrite catalyst slurry containing PTFE. By coating this nickel ferrite catalyst slurry onto the anode gas diffusion layer and then reacting them together at a temperature of 300–500°C, not only is a tight bond formed between the anode catalyst layer and the anode gas diffusion layer, significantly reducing the possibility of the anode catalyst layer cracking or detaching from the anode gas diffusion layer, but this also enhances the stability and service life of the anode catalyst layer, further improving the stability of the water electrolyzer using this membrane electrode during operation. Moreover, the tight bond between the nickel ferrite catalyst in the anode catalyst layer and the PTFE reduces the possibility of nickel ferrite catalyst detachment, preventing structural collapse of the anode catalyst layer. Secondly, using non-precious metal nickel ferrite catalyst and PTFE can also effectively reduce the raw material cost of preparing the membrane electrode.

[0009] Preferably, the solvent is selected from at least one of water and isopropanol.

[0010] Preferably, the solvent is a mixed solution of isopropanol and water, wherein the mass ratio of isopropanol to water in the mixed solution is 1:1.

[0011] Preferably, in step S2, the drying temperature is 50–90°C.

[0012] Preferably, in step S2, the drying temperature is 80°C.

[0013] Preferably, in S2, the heat preservation temperature is 350°C and the heat preservation time is 30 minutes.

[0014] By controlling the holding temperature and holding time, the prepared anode catalyst layer can have better structural stability, reduce the possibility of the anode side catalyst layer falling off from the anode gas diffusion layer, and avoid a large amount of dissolution of metal ions of nickel ferrite catalyst in the anode catalyst layer, effectively reducing the possibility of anode catalyst layer cracking and further improving the structural stability of the anode catalyst layer.

[0015] Preferably, in S2, the heating rate is 2–10 °C / min.

[0016] If the temperature rises too quickly in S2, the pyrolysis reaction of the molten polytetrafluoroethylene and some of the anion exchange membrane ionomers will be too rapid, which can easily lead to excessively large pores and uneven pore structure in the anode catalyst layer, affecting the structural stability of the anode catalyst layer. If the temperature rises too slowly in S2, the calcination will take too long, increasing the production time cost and making it unfavorable for large-scale production.

[0017] Preferably, the heating rate is 5°C / min.

[0018] Preferably, in S2, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0019] Preferably, in S1, the ratio of nickel ferrite catalyst: polytetrafluoroethylene: anion exchange membrane ionomer is 100:1-30:1-30 by mass.

[0020] Using the nickel ferrite catalyst in the anode catalyst layer as a benchmark, the addition amounts of polytetrafluoroethylene (PTFE) and anion exchange membrane ionomer were adjusted to achieve a mass ratio of nickel ferrite catalyst to PTFE and anion exchange membrane ionomer of 100:1–30:1–30. This resulted in anode catalyst layer with more catalytic active sites, further enhancing its catalytic performance. Furthermore, the feeding ratio of nickel ferrite catalyst to PTFE and anion exchange membrane ionomer also affected the dispersibility of the nickel ferrite catalyst slurry. When the feeding ratio fell within the aforementioned range, the solid matter in the nickel ferrite catalyst slurry was less likely to aggregate during the drying process of S2, resulting in a more uniform anode catalyst layer with more stable catalytic performance.

[0021] Preferably, in the anode catalyst layer, the mass ratio of nickel ferrite catalyst: polytetrafluoroethylene: anion exchange membrane ionomer is 100:10:15.

[0022] Preferably, in S1, the mass-volume concentration of nickel ferrite catalyst in the nickel ferrite catalyst slurry is 3–15 mg / mL.

[0023] By adjusting the amount of solvent in the nickel ferrite catalyst slurry, the mass-volume concentration of the nickel ferrite catalyst can be maintained at 3–15 mg / mL, thereby regulating the viscosity of the nickel ferrite catalyst slurry. This prevents the nickel ferrite catalyst slurry from flowing to other areas when coated on the anode gas diffusion layer. It also allows for a suitable thickness of the nickel ferrite catalyst slurry, facilitating smooth subsequent drying operations.

[0024] Preferably, in S1, the mass-volume concentration of nickel ferrite catalyst in the nickel ferrite catalyst slurry is 10 mg / mL.

[0025] Preferably, the loading of nickel ferrite catalyst in the anode catalyst layer is 0.5–15 mg / cm³. 2 .

[0026] By adjusting the coating amount of the nickel ferrite catalyst slurry to ensure that the loading of the nickel ferrite catalyst falls within the aforementioned range, the resulting anode catalyst can exhibit excellent catalytic performance. If the loading is too small, there will be too few effective catalytic components in the anode catalyst layer, which is detrimental to the oxygen evolution reaction. If the loading is too large, the structure of the anode catalyst layer will be too dense, which is detrimental to gas conduction, reduces electrical conductivity, increases ohmic impedance, and increases the overpotential of the oxygen evolution reaction.

[0027] Preferably, the loading of nickel ferrite catalyst in the anode catalyst layer is 8 mg / cm³. 2 .

[0028] Preferably, in S2, the nickel ferrite catalyst slurry is coated onto the anode gas diffusion layer by at least one of spraying, dripping, or coating.

[0029] Preferably, the anode gas diffusion layer is selected from at least one of nickel foam, nickel mesh, and nickel felt.

[0030] Using the aforementioned loosely structured nickel-containing material with many voids as the anode gas diffusion layer is beneficial for gas diffusion. Furthermore, the good compatibility between the anode gas diffusion layer and the anode catalyst layer helps the membrane electrode maintain high structural stability during the water electrolysis hydrogen production process.

[0031] Preferably, the thickness of the anolyte gas diffusion layer is 0.2 to 1 mm.

[0032] Preferably, the anode gas diffusion layer is acid-washed with a hydrochloric acid solution and / or sulfuric acid solution with a concentration of 0.1 to 2 mol / L, and then rinsed with deionized water and dried.

[0033] Preferably, the anion exchange membrane ionomer is selected from at least one of ALkymer, Fumasep, Versogen, and Sustainion, and the thickness of the anion exchange membrane is 10–100 μm.

[0034] When the above-mentioned anion exchange membrane ionomer is selected, the resulting anode catalyst layer has more catalytic reaction active sites, which is also conducive to the transport of hydroxide ions between the catalytic active sites on the anode catalyst layer and the anion exchange membrane, and makes the nickel ferrite catalyst more dispersed in the nickel ferrite catalyst slurry.

[0035] Preferably, the thickness of the anion exchange membrane is 50 μm.

[0036] Preferably, the cathode catalyst layer includes a platinum-carbon catalyst and anion exchange membrane ionomer.

[0037] Preferably, in the cathode catalyst layer, the ratio of platinum-carbon catalyst to anion exchange membrane ionomer is 100:1 to 30 by mass.

[0038] Preferably, in the cathode catalyst layer, the ratio of platinum-carbon catalyst to anion exchange membrane ionomer is 100:15 by mass.

[0039] Preferably, the loading of platinum-carbon catalyst in the cathode catalyst layer is 0.1–2 mg / cm³. 2 .

[0040] Preferably, the loading of platinum-carbon catalyst in the cathode catalyst layer is 0.5 mg / cm³. 2 .

[0041] Preferably, the cathode gas diffusion layer is selected from at least one of carbon paper, carbon cloth, and carbon felt.

[0042] Preferably, the thickness of the cathode gas diffusion layer is 0.2 to 1 mm.

[0043] According to a second aspect of the present invention, a method for preparing a highly stable membrane electrode is provided, comprising the following steps: S1. Mixing a nickel ferrite catalyst, polytetrafluoroethylene, anion exchange membrane ionomer, and a solvent, and stirring until homogeneous to obtain a nickel ferrite catalyst slurry; S2. Coating the nickel ferrite catalyst slurry onto an anode gas diffusion layer, drying it to obtain a membrane electrode intermediate, and holding the membrane electrode intermediate in an inert gas at a holding temperature of 300–500°C for 5–60 minutes to obtain an anode gas diffusion layer and an anode catalyst layer stacked sequentially; S3. Stacking the anode gas diffusion layer, the anode catalyst layer, the anion exchange membrane, the cathode catalyst layer, and the cathode gas diffusion layer sequentially, and hot-pressing them to obtain a highly stable membrane electrode, wherein the hot-pressing pressure is 100–600 psi, the hot-pressing temperature is 20–80°C, and the hot-pressing time is 1–60 minutes.

[0044] This preparation method ensures a tight bond between the anolyte gas diffusion layer and the anolyte catalyst layer, and exposes more catalytic active sites in the anolyte catalyst layer, which is more conducive to the electrolysis reaction of the membrane electrode. Furthermore, the hot-pressing method under the aforementioned conditions improves the flatness of the membrane electrode, ensuring uniform thickness and eliminating gaps between layers. This results in a tight, sequential bonding of the anolyte gas diffusion layer, anolyte catalyst layer, anion exchange membrane, cathode catalyst layer, and cathode gas diffusion layer, shortening the ion diffusion distance and reducing the internal resistance of the membrane electrode. Secondly, this preparation method is simple, effectively improving the integration and assembly efficiency of the membrane electrode, and is easy for large-scale industrial production.

[0045] Preferably, in S1, the stirring rate is 500–20000 rpm and the stirring time is 10–60 minutes.

[0046] Adjusting the stirring speed and stirring time used in S1 to prepare the nickel ferrite catalyst slurry ensures good dispersion of the materials in the slurry. When the stirring speed is 500–20000 rpm and the stirring time is 10–60 minutes, the temperature rise caused by stirring can be kept below 5°C. This prevents the nickel ferrite in the slurry from agglomerating due to temperature rise caused by operation, which would affect the structural uniformity and catalytic performance of the prepared anode catalyst layer.

[0047] Preferably, in S1, the stirring speed is 8000 rpm and the stirring time is 30 minutes.

[0048] Preferably, in S3, the hot pressing pressure is 300 psi, the hot pressing temperature is 50°C, and the hot pressing time is 15 minutes.

[0049] The membrane electrode prepared under the above hot-pressing conditions has good structural stability and good adhesion between the layers, making it less prone to detachment during the electrolysis of water to produce hydrogen.

[0050] According to a third aspect of the present invention, a water electrolyzer is provided, comprising the aforementioned highly stable membrane electrode.

[0051] The water electrolyzer provided by the present invention includes the aforementioned highly stable membrane electrode, which can reduce the risk of partial detachment of the membrane electrode and blockage of the hydrogen production pathway, enabling the water electrolyzer to operate for a long time. Furthermore, the highly stable membrane electrode has high catalytic efficiency, thereby giving the water electrolyzer of the present invention high hydrogen production efficiency. Detailed Implementation

[0052] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0053] Example 1

[0054] Experimental group 1-1

[0055] This experimental group provides a highly stable membrane electrode, which includes an anode gas diffusion layer, an anode catalyst layer, an anion exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer stacked sequentially. In this experimental group, the anode catalyst layer is prepared using a nickel ferrite catalyst slurry. The nickel ferrite catalyst slurry is made of polytetrafluoroethylene (PTFE) emulsion, and the anion exchange membrane ionomer solution of type ALkymer is used. A mixed solution of isopropanol and water at a mass ratio of 1:1 is used as the solvent. In the nickel ferrite catalyst slurry, the mass ratio of nickel ferrite catalyst:polytetrafluoroethylene:anion exchange membrane ionomer is 100:10:15.

[0056] A cathode catalyst layer was prepared using a cathode catalyst slurry. The cathode catalyst slurry used a platinum-carbon catalyst as the cathode catalyst and an anion exchange membrane ionomer solution of type ALkymer was selected. The mass ratio of the platinum-carbon catalyst to the anion exchange membrane ionomer solution was 100:15.

[0057] A 0.6 mm thick nickel foam was selected as the anode gas diffusion layer; an ALkymer anion exchange membrane with a thickness of 50 μm was selected as the anion exchange membrane; and a 0.3 mm thick carbon paper was selected as the cathode gas diffusion layer.

[0058] S1. Weigh 500mg of nickel ferrite catalyst, 50mg of polytetrafluoroethylene, 75mg of anion exchange membrane ionomer and solvent, mix them evenly, and then stir at a stirring rate of 8000rpm for 30 minutes using a high-speed shear machine, followed by ultrasonic dispersion to prepare a nickel ferrite catalyst slurry with a concentration of 10mg / mL.

[0059] S2. Heat the anode gas diffusion layer to 80℃, and apply the nickel ferrite catalyst slurry onto the anode gas diffusion layer in small amounts multiple times, so that the loading of the nickel ferrite catalyst is 8 mg / cm³. 2The membrane electrode intermediate was dried to obtain a membrane electrode intermediate. The membrane electrode intermediate was transferred to a nitrogen-filled environment and held at 350°C for 30 minutes with a heating rate of 5°C / min to obtain an anode catalyst layer disposed on the anode gas diffusion layer.

[0060] S3. The cathode catalyst and anion exchange membrane ionomer solution were dispersed in isopropanol, mixed and ultrasonically dispersed using a high-speed shear mixer to prepare a cathode catalyst slurry with a concentration of 10 mg / mL. The cathode catalyst slurry was coated onto the anion exchange membrane. Finally, the anolyte gas diffusion layer, anolyte catalyst layer, anion exchange membrane, cathode catalyst layer, and cathode gas diffusion layer were sequentially stacked and hot-pressed to obtain the highly stable membrane electrode assembly. The hot-pressing pressure was 300 psi, the hot-pressing temperature was 50 °C, and the hot-pressing time was 15 minutes.

[0061] Experimental group 1-2

[0062] This experimental group followed the method provided in Experimental Group 1-1 for preparing a highly stable membrane electrode to prepare a membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that in step S2, the membrane electrode intermediate was kept at 300℃ for 60 minutes. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0063] Experimental groups 1-3

[0064] This experimental group followed the method provided in Experimental Group 1-1 for preparing a highly stable membrane electrode to prepare a membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that in step S2, the membrane electrode intermediate was kept at 500℃ for 5 minutes. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0065] Example 2

[0066] Experimental group 2-1

[0067] This experimental group followed the method provided in Experimental Group 1-1 for preparing highly stable membrane electrodes to prepare a highly stable membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that the heating rate in S2 is 2℃ / min. The remaining raw material ratios and preparation methods are strictly consistent with those of Experimental Group 1-1.

[0068] Experimental group 2-2

[0069] This experimental group followed the method provided in Experimental Group 1-1 for preparing highly stable membrane electrodes to prepare a highly stable membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that the heating rate in S2 is 10℃ / min. The remaining raw material ratios and preparation methods are strictly consistent with those of Experimental Group 1-1.

[0070] Example 3

[0071] Experimental group 3-1

[0072] This experimental group followed the method provided in Experimental Group 1-1 for preparing a highly stable membrane electrode to prepare a high-stability membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that, in the anode catalyst layer, the mass ratio of nickel ferrite catalyst: polytetrafluoroethylene: anion exchange membrane ionomer is 100:1:1. Specifically, the nickel ferrite catalyst slurry in S1 includes 500 mg of nickel ferrite catalyst, 5 mg of polytetrafluoroethylene, and 5 mg of anion exchange membrane ionomer. The remaining raw material ratios and preparation methods are strictly consistent with those of Experimental Group 1-1.

[0073] Experimental group 3-2

[0074] This experimental group followed the method provided in Experimental Group 1-1 for preparing a highly stable membrane electrode to prepare a high-stability membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that, in the anode catalyst layer, the mass ratio of nickel ferrite catalyst: polytetrafluoroethylene: anion exchange membrane ionomer is 100:30:30. Specifically, the nickel ferrite catalyst slurry includes 500 mg of nickel ferrite catalyst, 150 mg of polytetrafluoroethylene, and 150 mg of anion exchange membrane ionomer. The remaining raw material ratios and preparation methods are strictly consistent with those of Experimental Group 1-1.

[0075] Example 4

[0076] Experimental group 4-1

[0077] This experimental group followed the method provided in Experimental Group 1-1 for preparing highly stable membrane electrodes to prepare a highly stable membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that in S3, a hot-pressing pressure of 50 psi, a hot-pressing temperature of 15℃, and a hot-pressing time of 70 minutes were used. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0078] Experimental group 4-2

[0079] This experimental group followed the method provided in Experimental Group 1-1 for preparing highly stable membrane electrodes to prepare a highly stable membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that in S3, a hot-pressing pressure of 100 psi, a hot-pressing temperature of 20℃, and a hot-pressing time of 60 minutes were used. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0080] Experimental group 4-3

[0081] This experimental group followed the method provided in Experimental Group 1-1 for preparing a highly stable membrane electrode to prepare a high-stability membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that in S3, a hot-pressing pressure of 600 psi, a hot-pressing temperature of 80℃, and a hot-pressing time of 1 minute were used. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0082] Experimental group 4-4

[0083] This experimental group followed the method provided in Experimental Group 1-1 for preparing highly stable membrane electrodes to prepare a highly stable membrane electrode. The difference between this experimental group and Experimental Group 1-1 is that in S3, a hot-pressing pressure of 700 psi, a hot-pressing temperature of 90℃, and a hot-pressing time of 45 seconds were used. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0084] Comparative Example 1

[0085] Control group 1

[0086] This control group prepared a highly stable membrane electrode using the method provided in Experimental Group 1-1. The difference between this control group and Experimental Group 1-1 is that in S1, an equal amount of anion exchange membrane ionomer was used instead of polytetrafluoroethylene used in Experimental Group 1-1. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0087] Control group 2

[0088] This control group prepared a highly stable membrane electrode using the method provided in Experimental Group 1-1. The difference between this control group and Experimental Group 1-1 is that in S1, an equal amount of polytetrafluoroethylene was used instead of the anion exchange membrane ionomer used in Experimental Group 1-1. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0089] Control group 3

[0090] This control group prepared a highly stable membrane electrode using the method provided in Experimental Group 1-1. The difference between this control group and Experimental Group 1-1 is that in S1, an equal amount of polyvinylidene fluoride (PVDF) was used instead of polytetrafluoroethylene (PTFE) used in Experimental Group 1-1. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0091] Control group 4

[0092] This control group followed the method provided in Experimental Group 1-1 for preparing a highly stable membrane electrode, and prepared a highly stable membrane electrode. The difference between this control group and Experimental Group 1-1 was that the heat preservation operation in S2 was omitted during the preparation of the membrane electrode. Instead, the dried membrane electrode intermediate was directly stacked sequentially with the anion exchange membrane, the cathode catalyst layer, and the cathode gas diffusion layer, and then hot-pressed. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0093] Control group 5

[0094] This control group prepared a highly stable membrane electrode using the method provided in Experimental Group 1-1. The difference between this control group and Experimental Group 1-1 is that in step S2, the membrane electrode intermediate was kept at 200℃ for 70 minutes. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0095] Control group 6

[0096] This control group prepared a highly stable membrane electrode using the method provided in Experimental Group 1-1. The difference between this control group and Experimental Group 1-1 is that in step S2, the membrane electrode intermediate was kept at 600℃ for 3 minutes. The remaining raw material ratios and preparation methods were strictly consistent with those of Experimental Group 1-1.

[0097] Test case

[0098] Test objects: The highly stable membrane electrodes prepared in Examples 1 to 4 and the membrane electrode prepared in Comparative Example 1 were assembled with a cathode plate (with flow field), an anode plate (with flow field), an end plate and an insulating plate to form a water electrolyzer. The assembled water electrolyzer was used as the test object.

[0099] Test items and test methods:

[0100] (1) Ohmic Impedance: Using an electrochemical workstation, the working electrode line WE and the working sensing electrode line WS are connected to the cathode side plate, and the reference electrode line RE and the auxiliary electrode line are connected to the anode side plate. The constant voltage AC impedance of the test object is measured at open circuit potential, with a high frequency of 10000Hz, a low frequency of 1Hz, and an amplitude of 10mV. After fitting the test results, the ohmic impedance value is recorded.

[0101] (2) Electrolysis performance of the electrolyzer: An electrochemical workstation was used. The working electrode line WE and the working sensing electrode line WS were connected to the cathode side plate, and the reference electrode line RE and the auxiliary electrode line were connected to the anode side plate. A constant current testing method was used, with a current range of 0–1 A / cm. 2 Under the given current, 10 current steps were set, and each step was tested for 10 seconds. A voltage value was recorded every second, and the average voltage value on each current step was recorded.

[0102] (3) Stability Test: An electrochemical workstation was used. The working electrode line WE and the working sensing electrode line WS were connected to the cathode side plate, and the reference electrode line RE and the auxiliary electrode line were connected to the anode side plate. The test was conducted at 0.5 A / cm. 2 The current was subjected to constant current testing for 600 hours, and the voltage was recorded at a frequency of 10 seconds.

[0103] (4) Catalyst layer loss: Using an electrochemical workstation, the working electrode line WE and the working sensing electrode line WS are connected to the cathode side plate, and the reference electrode line RE and the auxiliary electrode line are connected to the anode side plate. The current is 0.5 A / cm. 2 A constant current test was performed on the current for 600 hours. The loss of the catalyst layer was calculated by weighing the mass of the catalyst layer before and after the test. The loss of the catalyst layer (%) was calculated as follows: (mass of the catalyst layer before the test - mass of the catalyst layer after the test) / mass of the catalyst layer before the test.

[0104] (5) Cell voltage fluctuation: Using an electrochemical workstation, the working electrode line WE and the working sensing electrode line WS are connected to the cathode side plate, and the reference electrode line RE and the auxiliary electrode line are connected to the anode side plate. The voltage fluctuation is 0.5 A / cm. 2 A constant current test was performed on the current for 600 hours. The voltage at the end of the test and the voltage at the start of the test were recorded, and the cell voltage fluctuation was calculated. The cell voltage fluctuation (mV / h) is calculated as: (V / h) = (V / h) = (V / h) / (test time)

[0105] Test results: The raw material composition and preparation process of the test subjects in this test case are shown in Table 1, and the test data obtained in this test case are shown in Table 2.

[0106] Table 1. Raw material composition and preparation process of the test subjects in this test case.

[0107]

[0108]

[0109] Table 2. Test data obtained in this test case

[0110]

[0111]

[0112] Results analysis:

[0113] As shown in Tables 1 and 2, the high-stability membrane electrodes prepared in Examples 1-4 exhibit lower ohmic impedance, better stability, higher water electrolysis performance, and longer cycle life compared to the membrane electrode prepared in Comparative Example 1. Comparing the high-stability membrane electrode provided in Experimental Group 1-1 with those in Control Groups 1-4, the test data in Table 2 show that the high-stability membrane electrode provided in Experimental Group 1-1 has lower ohmic impedance, lower transient test cell voltage, and lower average cell voltage. Furthermore, it exhibits smaller cell voltage fluctuations and less mass loss of the catalyst layer before and after electrolysis. This indicates that the membrane electrode prepared by high-temperature pyrolysis of nickel ferrite catalyst, polytetrafluoroethylene (PTFE), and anion exchange membrane ionomer has better structural stability and is more conducive to ion migration and gas diffusion in the water electrolyzer. Therefore, the selection of PTFE, anion exchange membrane ionomer, and nickel ferrite catalyst for slurry preparation and co-pyrolysis at 300-500°C demonstrates the effectiveness of this method. At this temperature, PTFE is dispersed in a molten state within the anode catalyst layer. Some of the anion exchange membrane ionomers undergo pyrolysis, resulting in a large number of microporous structures in the anode catalyst layer and improved hydrophobicity. This effectively improves the pore structure of the anode catalyst layer, giving it high porosity, increasing gas conductivity, exposing more catalytic active sites, and thus improving the catalytic efficiency of the membrane electrode using this anode catalyst layer. Furthermore, it ensures a tight bond between the anode catalyst layer and the anode gas diffusion layer, significantly reducing the possibility of the anode catalyst layer cracking or detaching from the anode gas diffusion layer, thereby enhancing the stability and lifespan of the anode catalyst layer and further improving the stability of the water electrolyzer using this membrane electrode during operation.

[0114] Comparing the high-stability membrane electrode provided in experimental group 1-1 with those in control groups 5-6, it was found that the overall performance of experimental group 1-1 was better than that of control groups 5-6. This indicates that in the high-temperature pyrolysis reaction in S2, membrane electrodes prepared at a holding temperature of 300-500℃ and a holding time of 5-60 minutes are superior. In control group 5, the holding temperature was too low, resulting in minimal improvement in the structure of the anode catalyst layer and a weak effect on improving catalytic efficiency. In control group 6, the holding temperature was too high, resulting in a loose and easily collapsing anode catalyst layer structure. Further investigation into the optimal holding conditions, comparing the data of the high-stability membrane electrode prepared in Example 1 in Table 2, revealed that the high-stability membrane electrode provided in experimental group 1-1 exhibited the best overall performance, demonstrating superior stability and water electrolysis performance. This demonstrates that by controlling the holding temperature to 350℃ and the holding time to 30 minutes, the prepared anode catalyst layer can have better structural stability, reduce the possibility of the anode side catalyst layer detaching from the anode gas diffusion layer, and avoid a large amount of dissolution of nickel ferrite catalyst in the anode catalyst layer, effectively reducing the possibility of the anode catalyst layer cracking and further improving the structural stability of the anode catalyst layer.

[0115] Comparing the data of the highly stable membrane electrodes prepared in Experimental Group 1-1 and Example 2 in Table 2, it can be found that as the heating rate in S2 increases, the structural stability and catalytic performance of the anode catalyst layer in the prepared membrane electrode show a trend of first increasing and then decreasing. If the heating rate in S2 is too fast, the pyrolysis reaction of the molten polytetrafluoroethylene and some of the anion exchange membrane ionomers will be too rapid, resulting in excessively large pores and uneven pore structure in the anode catalyst layer, which cannot improve the structural stability of the anode catalyst layer. If the heating rate in S2 is too slow, the calcination time will be too long, increasing the production time cost and hindering large-scale production. Among them, when the heating rate in S2 is 5℃ / min, the anode catalyst layer prepared in this way contains more microporous structures and more catalytic active sites.

[0116] Comparing the overall performance of the highly stable membrane electrodes prepared in Experimental Group 1-1 and Example 3, it can be found that both experimental group 1-1 and Example 3 exhibit good structural stability. When applied in a water electrolyzer, they also contribute to the excellent water electrolysis performance. This indicates that when the mass ratio of nickel ferrite catalyst to polytetrafluoroethylene and anion exchange membrane ionomer is 100:1 to 30:1 to 30, the anode catalyst layer can have more catalytic active sites, further enhancing its catalytic performance. Furthermore, when the mass ratio is within the above range, the solid matter in the nickel ferrite catalyst slurry is less prone to aggregation during the drying process of S2, resulting in a more uniform anode catalyst layer with more stable catalytic performance. Specifically, in Experimental Group 1-1, the mass ratio of nickel ferrite catalyst, polytetrafluoroethylene, and anion exchange membrane ionomer was 100:10:15, resulting in an anode catalyst layer with even better catalytic performance.

[0117] Comparing the test data of the high-stability membrane electrodes prepared in Experimental Group 1-1 and Example 4 in Table 2, it can be seen that the high-stability membrane electrodes prepared in Experimental Group 1-1 and Experimental Groups 4-2 to 4-3 have lower ohmic impedance and catalyst layer loss rate. When these high-stability membrane electrodes are applied in water electrolyzers, they can provide longer cycle life and better catalytic performance. This indicates that when preparing membrane electrodes using hot-pressing conditions of 100–600 psi, hot-pressing temperature of 20–80 °C, and hot-pressing time of 1–60 minutes, the flatness of the membrane electrode can be further improved, making the thickness of the membrane electrode uniform and eliminating gaps between layers. This ensures that the anode gas diffusion layer, anode catalyst layer, anion exchange membrane, cathode catalyst layer, and cathode gas diffusion layer are tightly bonded in sequence, shortening the ion diffusion distance and further reducing the internal resistance of the membrane electrode. Among the membrane electrodes provided in Experimental Group 1-1 and Example 4, the high-stability membrane electrode prepared in Experimental Group 1-1 has the best cycle stability and electrochemical performance. This indicates that the hot-pressing conditions selected in Experimental Group 1-1, with a hot-pressing pressure of 300 psi, a hot-pressing temperature of 50°C, and a hot-pressing time of 15 minutes, are the optimal hot-pressing conditions. These conditions can produce a high-stability membrane electrode with good structural stability and good adhesion between the layers, making it less prone to detachment during the electrolysis of water to produce hydrogen.

[0118] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A highly stable membrane electrode, characterized in that, The membrane electrode comprises an anode gas diffusion layer, an anode catalyst layer, an anion exchange membrane, a cathode catalyst layer, and a cathode gas diffusion layer, which are stacked sequentially. The anode catalyst layer is prepared by the following steps: S1. Nickel ferrite catalyst, polytetrafluoroethylene, anion exchange membrane ionomer and solvent are mixed and stirred evenly to obtain nickel ferrite catalyst slurry. According to the mass calculation, the ratio of nickel ferrite catalyst: polytetrafluoroethylene: anion exchange membrane ionomer is 100:1~30:1~30, and the anion exchange membrane ionomer includes ALkymer type anion exchange membrane ionomer. S2. The nickel ferrite catalyst slurry is coated onto the anode gas diffusion layer and dried to obtain a membrane electrode intermediate. The membrane electrode intermediate is then placed in an inert gas and kept at a temperature of 300-350°C for 5-60 minutes to obtain the anode catalyst layer disposed on the anode gas diffusion layer.

2. The high-stability membrane electrode as described in claim 1, characterized in that, In S2, the heating rate is 2~10℃ / min.

3. The high-stability membrane electrode as described in claim 1, characterized in that, In S1, the nickel ferrite catalyst in the nickel ferrite catalyst slurry has a mass-volume concentration of 3~15 mg / mL.

4. The high-stability membrane electrode as described in claim 1, characterized in that, In the anode catalyst layer, the loading of the nickel ferrite catalyst is 0.5~15 mg / cm³. 2 .

5. The high-stability membrane electrode as described in claim 1, characterized in that, The anode gas diffusion layer is selected from at least one of nickel foam, nickel mesh, and nickel felt.

6. The high-stability membrane electrode as described in claim 1, characterized in that, The thickness of the anion exchange membrane is 10~100 μm.

7. A method for preparing a highly stable membrane electrode, characterized in that, Includes the following steps: S1. Nickel ferrite catalyst, polytetrafluoroethylene, anion exchange membrane ionomer and solvent are mixed and stirred evenly to obtain nickel ferrite catalyst slurry. According to the mass calculation, the ratio of nickel ferrite catalyst: polytetrafluoroethylene: anion exchange membrane ionomer is 100:1~30:1~30, and the anion exchange membrane ionomer includes ALkymer type anion exchange membrane ionomer. S2. The nickel ferrite catalyst slurry is coated onto the anode gas diffusion layer, dried, and a membrane electrode intermediate is obtained. The membrane electrode intermediate is then placed in an inert gas and kept at a temperature of 300-350°C for 5-60 minutes to obtain an anode catalyst layer disposed on the anode gas diffusion layer. S3. The anode gas diffusion layer, the anode catalyst layer, the anion exchange membrane, the cathode catalyst layer, and the cathode gas diffusion layer are sequentially stacked and hot-pressed to obtain the high-stability membrane electrode. The hot-pressing pressure is 100~600psi, the hot-pressing temperature is 20~80℃, and the hot-pressing time is 1~60 minutes.

8. The method for preparing a highly stable membrane electrode as described in claim 7, characterized in that, In S3, the hot-pressing pressure is 300 psi, the hot-pressing temperature is 50°C, and the hot-pressing time is 15 minutes.

9. A water electrolysis cell, characterized in that, Including the highly stable membrane electrode as described in any one of claims 1 to 6.

Images