Water electrolysis membrane electrode, and preparation method therefor and water electrolyser applying same

Abstract

A water electrolysis membrane electrode, and a preparation method therefor and a water electrolyser applying same. The water electrolysis membrane electrode comprises a cathode gas diffusion layer, a cathode catalytic layer, an anion exchange membrane, a hydrophobic anode catalytic layer and an anode gas diffusion layer. Raw materials for preparing the hydrophobic anode catalytic layer comprise an anode catalyst, a hydrophobic material and an anode ionomer, wherein calculated by mass, the ratio of the anode catalyst: the hydrophobic material: the anode ionomer is 10:1-3:1-3. The porosity of the hydrophobic anode catalytic layer is 10-40%.

Description

A water electrolysis membrane electrode and its preparation method, and a water electrolysis cell using the same electrode.

[0001] This application claims priority to Chinese Patent Application No. 202410677366.6, filed with the Chinese Patent Office on May 28, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of water electrolysis for hydrogen production technology, specifically relating to a water electrolysis membrane electrode and its preparation method, and a water electrolysis cell using the same. Background Technology

[0003] Anion exchange membrane electrolysis (AEMWE) is a novel water electrolysis technology that uses anion exchange membranes as separators. It combines the low cost of alkaline water electrolysis with the faster response speed and higher current density of proton exchange membrane electrolysis (PEMWE). The membrane electrode assembly (MEA) is the core component of AEMWE technology, consisting of a gas diffusion layer, a catalyst layer, and an anion exchange membrane. It is also the primary site for hydrogen and oxygen production.

[0004] However, the dual-sided electrolyte circulation at both the anode and cathode of the AEMWE electrolyzer in related technologies is not conducive to obtaining relatively dry hydrogen, and it requires a gas-liquid separation module on the cathode side. Subsequent purification units need to add a water removal module, which significantly increases the cost of hydrogen production. To further obtain dry hydrogen and reduce the cost of the hydrogen production system, the AEMWE electrolyzer can be operated in an anode-side electrolyte circulation mode. The principle is that water molecules, the reactants, permeate from the anode side through the anion exchange membrane to the cathode side. These permeated water molecules can participate in the hydrogen reduction reaction, producing hydrogen with less moisture, reducing the need for gas-liquid separation devices, and lowering the cost of hydrogen production. However, since there is no electrolyte circulation on the cathode side, on the one hand, insufficient moisture causes changes in the membrane's wet / dry state and membrane deformation, leading to mechanical damage and poor long-term stability; on the other hand, excessive water permeation prevents the production of relatively dry hydrogen.

[0005] Therefore, it is necessary to seek a water electrolysis membrane electrode that can efficiently produce dry hydrogen by using an anode-supply circulation. Technical issues

[0006] This application provides a water electrolysis membrane electrode and its preparation method, and a water electrolysis cell using the same electrode can efficiently produce dry hydrogen and reduce the cost of hydrogen production. Technical solutions

[0007] In a first aspect, embodiments of this application provide a water electrolysis membrane electrode, which includes a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, a hydrophobic anode catalyst layer, and an anode gas diffusion layer stacked sequentially. The raw materials for preparing the hydrophobic anode catalyst layer include an anode catalyst, a hydrophobic material, and an anode ionomer. The mass ratio of the anode catalyst to the hydrophobic material to the anode ionomer is 10:1-3:1-3. The porosity of the hydrophobic anode catalyst layer is 10-40%.

[0008] In a second aspect, embodiments of this application provide a method for preparing the water electrolysis membrane electrode in the first aspect, comprising the following operations: sequentially stacking a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, a hydrophobic anode catalyst layer, and an anode gas diffusion layer, and hot-pressing them at a pressure of 100-600 psi and a hot-pressing temperature of 50-150°C to obtain the water electrolysis membrane electrode.

[0009] Thirdly, embodiments of this application provide a water electrolyzer, including the water electrolyzer membrane electrode described in the first aspect. Beneficial effects

[0010] This application provides a water electrolysis membrane electrode and its preparation method, a water electrolysis cell using the same, and a water electrolysis device using the anode-side liquid supply circulation of the water electrolysis membrane electrode, which can efficiently produce dry hydrogen, reduce the need for a cathode gas-liquid separation module, reduce the switching frequency of the hydrogen dehydration device, and lower the cost of hydrogen production, which can greatly promote the large-scale development of anion exchange membrane water electrolyzers (AEMWE). Embodiments of the present invention

[0011] This application provides a water electrolysis membrane electrode, which includes a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, a hydrophobic anode catalyst layer, and an anode gas diffusion layer stacked sequentially. The raw materials for preparing the hydrophobic anode catalyst layer include an anode catalyst, a hydrophobic material, and an anode ionomer. The mass ratio of the anode catalyst to the hydrophobic material to the anode ionomer is 10:1-3:1-3. The porosity of the hydrophobic anode catalyst layer is 10-40%.

[0012] Most commercially available AEM water electrolyzers employ a dual-sided liquid supply and circulation system with both anode and cathode. In this circulation mode, water molecules first gain electrons at the cathode side and undergo a reduction reaction to generate hydroxide ions and hydrogen gas. The hydroxide ions then pass through the anion exchange membrane to the anode side, where they participate in the oxygen evolution reaction to generate water and oxygen. Due to the high water molecule content at the cathode side, the produced hydrogen gas carries a large amount of water vapor, which not only affects the purity of the hydrogen gas but also requires an additional water removal module and frequent switching of the hydrogen dehydration and purification device, leading to increased hydrogen production costs. The water electrolysis membrane electrode provided in this application can achieve an anode-supply circulation mode, producing drier hydrogen gas and reducing the frequency of switching the hydrogen dehydration and purification device, thus lowering hydrogen production costs and greatly promoting the large-scale development of anion exchange membrane water electrolyzers (AEMWE). In the anode-supply circulation mode, feed water is first supplied to the anode side of the water electrolysis membrane electrode. The hydrophobicity of the hydrophobic anode catalyst layer is used to control the permeation of water molecules into the catalyst layer. Water molecules permeate from the anode catalyst layer through the anion exchange membrane to the cathode catalyst layer, where they participate in the hydrogen reduction reaction. By adjusting the amount of polytetrafluoroethylene (PTFE) added to the hydrophobic anode catalyst layer, the amount of water molecules permeating can be controlled, resulting in hydrogen gas carrying less moisture.

[0013] The inventors discovered that when using an anode-supply circulation mode, the oxygen generated by a conventional anode catalyst layer is transported slowly in the electrolyte, and mass transfer is hindered. Furthermore, water molecules need to permeate from the anode gas diffusion layer through the anode catalyst layer to the cathode catalyst layer. When using a conventional anode catalyst layer for anode-supply circulation, an excessive amount of water molecules permeates from the anode gas diffusion layer to the anode catalyst layer and then into the anion exchange membrane, resulting in excessive water content on the cathode side and excessive water carried by hydrogen on the cathode side. Therefore, by adjusting the raw material ratio of the hydrophobic anode catalyst layer, the hydrophilic and hydrophobic properties of the hydrophobic anode catalyst layer are balanced, and the porosity of the hydrophobic anode catalyst layer is adjusted to 10-40%. This accelerates the gas mass transfer rate, exposes more active sites, and slows down the rate of water molecule permeation into the hydrophobic anode catalyst layer. The anode ionomer not only acts as a binder in the hydrophobic anode catalyst layer but also plays a role in gas transport and OH- ionization. - The role of ion transfer. If the hydrophobicity of the hydrophobic anode catalyst layer is too low, the oxygen mass transfer efficiency on the anode side will be low, while the water content on the cathode side will be high, and the produced hydrogen will easily contain water molecules, resulting in low hydrogen production cost for the water electrolyzer. If the hydrophobicity of the hydrophobic anode catalyst layer is too high, there will be fewer water molecules remaining on the cathode side, affecting ion conduction and hindering efficient and long-term stable hydrogen production.

[0014] In some embodiments, the contact angle of the hydrophobic anode catalyst layer is >90°.

[0015] In some embodiments, the hydrophobic material includes at least one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and perfluoroethylene propylene copolymer (FEP).

[0016] In some embodiments, the hydrophobic material includes polytetrafluoroethylene.

[0017] In some embodiments, the anodic ionomer includes at least one selected from ALkymer ionomer, Fumasep ionomer, Ionomr ionomer, Versogen ionomer, and Sustainion ionomer. In some examples, the ionomer includes ALkymer ionomer.

[0018] In some embodiments, the porosity of the hydrophobic anode catalyst layer is 20-30%. When the porosity of the hydrophobic anode catalyst layer is 20-30%, the hydrophobic anode catalyst layer has more catalytic active sites, and the generated oxygen bubbles can be discharged in time, improving oxygen transport efficiency. In addition, the structure of the hydrophobic anode catalyst layer is stable, which can slow down the collapse of the catalyst layer structure and extend the stable operation time of the water electrolysis equipment.

[0019] In some embodiments, the preparation method of the hydrophobic anode catalyst layer includes the following steps: mixing raw materials for preparing the hydrophobic anode catalyst layer to obtain an anode catalyst layer slurry; coating the anode catalyst layer slurry onto one side of the anode gas diffusion layer; and calcining the anode catalyst layer slurry at a temperature of 300-500°C to obtain the hydrophobic anode catalyst layer. Since polytetrafluoroethylene (PTFE) needs to be melt-dispersed in the catalyst layer at high temperatures, the CCS (catalyst coated substrate) method is used to prepare the hydrophobic anode catalyst layer. This ensures that the ratio of PTFE to anode catalyst in the actual catalyst layer is close to the preset ratio during material feeding, thereby controlling the hydrophobicity and pore structure of the catalyst layer and accelerating oxygen mass transfer. The CCS method refers to the preparation method of first coating the active components of the catalyst onto the surface of the gas diffusion layer to obtain the catalyst layer, and then attaching the catalyst layer to an anion exchange membrane to obtain a water electrolysis membrane electrode.

[0020] In some embodiments, the anode catalyst slurry is kept at a constant temperature in an inert gas atmosphere. The inert gas includes nitrogen, argon, or helium.

[0021] In some embodiments, the concentration of the anode catalyst in the anode catalyst layer slurry is 10-30 mg / mL.

[0022] In some embodiments, the raw materials for preparing the hydrophobic anode catalyst layer also include a solvent, which includes ethanol and / or water.

[0023] In some embodiments, the loading of the anode catalyst in the hydrophobic anode catalyst layer is 1-10 mg / cm³. 2 The anode catalysts include iridium oxide (IrO2), ruthenium dioxide (RuO2), nickel-iron layered double hydroxide (NiFe LDH), and nickel-iron oxide (NiFe2O3).x At least one of nickel-iron alloy and nickel-iron-cobalt alloy.

[0024] By adjusting the loading of the anode catalyst, the content of hydrophobic materials in the catalyst layer can be adjusted, thereby regulating the hydrophobicity of the hydrophobic anode catalyst layer. When the loading of the anode catalyst falls within 1-10 mg / cm³... 2 The hydrophobic anode catalyst layer prepared in this way exhibits excellent catalytic performance.

[0025] In some embodiments, the raw materials for preparing the cathode catalyst layer include a cathode catalyst, a hydrophilic carbon material, and a cathode ionomer, and the mass ratio of cathode catalyst: hydrophilic carbon material: cathode ionomer is 8:2-6:1-5. Introducing hydrophilic carbon material into the cathode catalyst layer and adjusting the ratio of hydrophilic carbon material to cathode catalyst can improve the hydrophilicity and water retention of the cathode catalyst layer, ensuring sufficient moisture in the reactants on the cathode side, improving the structural stability of the catalyst layer during the operation of the water electrolysis membrane electrode, and reducing the moisture carried by hydrogen. Combining this hydrophilic cathode catalyst layer with a hydrophobic anode catalyst layer can control the amount of water molecules permeating from the anode side to the cathode side, which is beneficial for achieving an anode supply circulation mode in the water electrolyzer and reducing water vapor in the hydrogen.

[0026] In some embodiments, the cathode ionomer includes at least one of ALkymer ionomer, Fumasep ionomer, Ionomr ionomer, Versogen ionomer, and Sustainion ionomer.

[0027] In some embodiments, the hydrophilic carbon material includes at least one of carboxylated carbon material and aminated carbon material. For example, the hydrophilic carbon material employs at least one of carboxylated carbon nanotubes, carboxylated graphene, carboxylated carbon black, carboxylated carbon spheres, carboxylated carbon fibers, hydroxylated carbon nanotubes, hydroxylated graphene, hydroxylated carbon black, hydroxylated carbon spheres, hydroxylated carbon fibers, aminated carbon nanotubes, aminated graphene, aminated carbon black, aminated carbon spheres, and aminated carbon fibers.

[0028] In some embodiments, the hydrophilic carbon material includes carboxylated carbon material. Compared to other hydrophilic groups, carboxylated carbon material not only has strong hydrophilicity, enabling it to retain water molecules that permeate to the cathode side, ensuring that the cathode catalyst layer and anion exchange membrane remain wet, reducing the probability of membrane swelling and shrinkage, and avoiding alternating wet and dry states during circulation, thus affecting the electrochemical performance and stability of the water electrolyzer, but also, by introducing carboxylated carbon material into the cathode catalyst layer, it can improve the adhesion between the cathode catalyst layer and the anion exchange membrane. Furthermore, utilizing the conductivity of carboxylated carbon material, it can also enhance the stability and electrochemical performance of the water electrolysis membrane electrode.

[0029] In some embodiments, the hydrophilic carbon material includes carboxylated carbon nanotubes. Carboxylated carbon nanotubes possess high electrical conductivity, which reduces electron egress impedance. Therefore, when carboxylated carbon nanotubes are used as the hydrophilic carbon material, the ohmic impedance of the cathode catalyst layer can be reduced, thereby improving the performance of the catalyst layer. Furthermore, carboxylated carbon nanotubes are one-dimensional materials. During the preparation of the cathode catalyst layer, they can interconnect with the cathode ionomer and cathode catalyst to form a three-dimensional network structure, thereby adjusting the hydrophilicity and pore structure of the cathode catalyst layer and enhancing its catalytic effect.

[0030] In some embodiments, the preparation method of the cathode catalyst layer includes the following steps: uniformly mixing the raw materials for preparing the cathode catalyst layer to form a cathode catalyst layer slurry; coating the cathode catalyst layer slurry onto one side of an anion exchange membrane to obtain the cathode catalyst layer. The cathode catalyst layer is prepared using the CCM (catalyst coated membrane) method, with the anion exchange membrane as the supporting substrate. This reduces the contact resistance between the cathode catalyst layer and the anion exchange membrane, improving the electrochemical performance of the water electrolysis membrane electrode. The CCM method refers to first coating the active components of the catalyst onto the surface of the anion exchange membrane to obtain a catalyst layer, and then attaching the catalyst layer to a gas diffusion layer to obtain the water electrolysis membrane electrode.

[0031] In some embodiments, during the preparation of the cathode catalyst layer slurry, the slurry is mixed uniformly by high-speed shearing, with a shear rate of 500-20000 rpm and a mixing time of 10-90 min. In some examples, the shear rate is 10000 rpm and the mixing time is 30 min.

[0032] In some embodiments, during the preparation of the cathode catalyst layer slurry, the raw materials for the preparation of the cathode catalyst layer are mixed evenly by ultrasonic dispersion, with an ultrasonic power of 50-150 W and a duration of 10-90 min.

[0033] In some embodiments, the cathode catalyst slurry is coated by means of coating, spraying, or screen printing.

[0034] In some embodiments, the concentration of the cathode catalyst in the cathode catalyst layer slurry is 10-30 mg / mL. In some examples, the concentration of the cathode catalyst in the cathode catalyst layer slurry is 20 mg / mL.

[0035] In some embodiments, the raw materials for preparing the cathode catalyst layer also include a solvent, which includes ethanol and / or water.

[0036] In some embodiments, the loading of the cathode catalyst in the cathode catalyst layer is 1-10 mg / cm³. 2The cathode catalyst includes at least one of platinum-carbon catalyst (Pt / C), nickel-phosphorus catalyst (NiP), nickel-molybdenum alloy (NiMo alloy), nickel-manganese alloy (NiMn alloy), nickel-molybdenum oxide (NiMo oxide), nickel-manganese oxide (NiMn oxide), and molybdenum disulfide (MoS2).

[0037] In some embodiments, the thickness of the anion exchange membrane is 20-100 μm.

[0038] This application provides a method for preparing a water electrolysis membrane electrode in the embodiment of the water electrolysis membrane electrode, including the following operations: stacking a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, a hydrophobic anode catalyst layer, and an anode gas diffusion layer in sequence, and hot-pressing them at a pressure of 100-600 psi and a hot-pressing temperature of 50-150°C to obtain a water electrolysis membrane electrode.

[0039] Thirdly, this application provides a water electrolyzer, including a water electrolyzer electrode in the embodiment of the water electrolyzer electrode, which can efficiently produce dry hydrogen, optimize the post-processing operation of hydrogen production, reduce the cost of hydrogen production, and is expected to bring about a breakthrough change for large-scale renewable energy electrolysis hydrogen production.

[0040] Example 1

[0041] (1) Preparation of hydrophobic anode catalyst layer

[0042] The raw materials for preparing the hydrophobic anode catalyst layer include an anode catalyst, polytetrafluoroethylene (PTFE), an anode ionomer, and a solvent. The anode catalyst is nickel-iron layered double hydroxide (NiFe LDH), the anode ionomer is ALkymer ionomer, and the solvent is a mixed solution of ethanol and water with a volume ratio of 1:1. Based on the mass ratio, the ratio of anode catalyst to PTFE to anode ionomer is 10:1.5:1.5.

[0043] The preparation method of the hydrophobic anode catalyst layer includes the following steps:

[0044] The raw materials used to prepare the hydrophobic anode catalyst layer in step (1) are mixed evenly to form an anode catalyst layer slurry. The concentration of the anode catalyst in the anode catalyst layer slurry is adjusted to 20 mg / mL by adjusting the amount of solvent added.

[0045] The anode catalyst slurry was then coated onto one side of the anode gas diffusion layer. The slurry was heated in a nitrogen atmosphere at a rate of 5°C / min and held at 350°C for 30 minutes, thus obtaining the hydrophobic anode catalyst layer. The anode catalyst loading was 5 mg / cm³. 2 .

[0046] (2) Preparation of cathode catalyst layer

[0047] The raw materials for preparing the cathode catalyst layer include a cathode catalyst, a hydrophilic carbon material, a cathode ionomer, and a solvent. The cathode catalyst is a molybdenum disulfide catalyst, the hydrophilic carbon material is carboxylated carbon nanotubes, the cathode ionomer is Alkymer ionomer, and the solvent is a mixed solution of ethanol and water with a volume ratio of 1:1. Based on the mass ratio, the ratio of cathode catalyst to hydrophilic carbon material to cathode ionomer is 8:4:2 (i.e., 4:2:1).

[0048] The preparation method of the cathode catalyst layer includes the following steps:

[0049] The cathode catalyst, hydrophilic carbon material, and solvent were first mixed uniformly by high-speed shearing, followed by high-speed shearing for 30 minutes at a temperature below 5°C. The ultrasonic power was 100 W for 30 minutes.

[0050] Next, the cathode catalyst slurry was coated onto one side of the anion exchange membrane to prepare the cathode catalyst layer. In the prepared cathode catalyst layer, the cathode catalyst loading was 5 mg / cm³. 2 .

[0051] (3) Preparation of water electrolysis membrane electrode

[0052] The water electrolysis membrane electrode comprises a cathode gas diffusion layer, a cathode catalyst layer obtained in step (2), an anion exchange membrane, a hydrophobic anode catalyst layer obtained in step (1), and an anode gas diffusion layer, which are stacked sequentially. The thickness of the anion exchange membrane is 75 μm.

[0053] The method for preparing a water electrolysis membrane electrode includes the following operations: stacking a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, a hydrophobic anode catalyst layer, and an anode gas diffusion layer in sequence, and hot-pressing them at a pressure of 300 psi, a hot-pressing temperature of 100 ℃, and a hot-pressing time of 15 minutes to obtain a water electrolysis membrane electrode.

[0054] Example 2

[0055] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that in the process of preparing the hydrophobic anode catalyst layer, the amount of polytetrafluoroethylene (PTFE) is adjusted so that the mass ratio of anode catalyst, PTFE and anode ionomer is 10:1:1.5. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0056] Example 3

[0057] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that in the process of preparing the hydrophobic anode catalyst layer, the amount of polytetrafluoroethylene (PTFE) is adjusted so that the mass ratio of anode catalyst, PTFE and anode ionomer is 10:3:1.5. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0058] Example 4

[0059] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that in the process of preparing the hydrophobic anode catalyst layer, the amount of anode ionomer is adjusted so that the mass ratio of anode catalyst, polytetrafluoroethylene and anode ionomer is 10:1.5:1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0060] Example 5

[0061] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that in the process of preparing the hydrophobic anode catalyst layer, the amount of anode ionomer is adjusted so that the mass ratio of anode catalyst, polytetrafluoroethylene and anode ionomer is 10:1.5:3. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0062] Example 6

[0063] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that, in the process of preparing the hydrophobic anode catalyst layer, an equal mass of fluorinated vinyl-tetrafluoroethylene copolymer (FEP) emulsion is used instead of polytetrafluoroethylene in Example 1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0064] Example 7

[0065] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that the addition of hydrophilic carbon material is omitted in the preparation of the cathode catalyst layer. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0066] Example 8

[0067] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that in the process of preparing the cathode catalyst layer, the feeding amounts of hydrophilic carbon material and cathode ionomer are adjusted so that the mass ratio of cathode catalyst, hydrophilic carbon material and cathode ionomer is 8:2:5. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0068] Example 9

[0069] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that in the process of preparing the cathode catalyst layer, the feeding amounts of hydrophilic carbon material and cathode ionomer are adjusted so that the mass ratio of cathode catalyst, hydrophilic carbon material and cathode ionomer is 8:6:1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0070] Example 10

[0071] This embodiment refers to the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this embodiment and Example 1 is that, in the process of preparing the cathode catalyst layer, carboxylated carbon black of equal mass is used instead of carboxylated carbon nanotubes in Example 1. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0072] Comparative Example 1

[0073] This comparative example provides a water electrolysis membrane electrode, which includes a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, an anode catalyst layer, and an anode gas diffusion layer stacked sequentially.

[0074] (1) Preparation of cathode catalyst layer: Refer to the preparation method of cathode catalyst layer provided in Example 1, except that the addition of hydrophilic carbon material is omitted in the preparation raw materials. The other raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0075] (2) Preparation of the anode catalyst layer: Refer to the preparation method of the hydrophobic anode catalyst layer provided in Example 1, except that the addition of hydrophobic polytetrafluoroethylene is omitted in the preparation raw materials. The other raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0076] (3) Preparation of water electrolysis membrane electrode: strictly consistent with Example 1.

[0077] Comparative Example 2

[0078] This comparative example uses the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this comparative example and Example 1 is that the addition of hydrophobic polytetrafluoroethylene (PTFE) is omitted in the preparation of the anode catalyst layer. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0079] Comparative Example 3

[0080] This comparative example follows the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this comparative example and Example 1 is that the amount of hydrophobic polytetrafluoroethylene (PTFE) added is adjusted during the preparation of the hydrophobic anode catalyst layer, so that the mass ratio of anode catalyst, PTFE, and anode ionomer is 10:0.5:4. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0081] Comparative Example 4

[0082] This comparative example follows the preparation method provided in Example 1 to prepare a water electrolysis membrane electrode. The difference between this comparative example and Example 1 is that the amount of polytetrafluoroethylene (PTFE) added is adjusted during the preparation of the hydrophobic anode catalyst layer, so that the mass ratio of anode catalyst, PTFE, and anode ionomer is 10:4:1.5. The remaining raw material ratios and preparation methods are strictly consistent with those in Example 1.

[0083] Test case

[0084] Test objects: The water electrolysis membrane electrodes prepared in Examples 1-10 and Comparative Examples 1-4 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 electrolysis cell, and the assembled water electrolysis cell was used as the test object.

[0085] Test items and test methods:

[0086] (1) Porosity: The anolyte catalyst layer in the water electrolysis membrane electrode was peeled off with adhesive tape, and the porosity of the anolyte catalyst layer was tested according to the test method in GB / T 21650.1-2008 Determination of pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption method, Part 1: Mercury porosimetry. In this test example, a porosity of 10-40% is considered qualified; a porosity of 20-30% is considered good.

[0087] (2) 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 CE are connected to the anode side plate. The constant voltage AC impedance of the test object is measured at the open circuit potential, with the high frequency set to 100,000 Hz, the low frequency to 1 Hz, and the amplitude to 10 mV. After fitting the test results, the ohmic impedance (HFR) value is recorded.

[0088] (3) 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 test method was adopted, at 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.

[0089] (4) Moisture content: Refer to the test method in GB / T 5832.2-2016 Gas analysis - Determination of trace moisture - Part 2: Dew point method. After the test object has been operating stably, collect the produced hydrogen gas, test the moisture content, and record the hydrogen dew point. In this test example, when the hydrogen dew point is below -2.5℃ (0℃, 1 bar, absolute humidity below 4g / m3), it is considered qualified.

[0090] Test results: The raw material composition and test results of the test subjects in this test case are shown in Table 1 and Table 2.

[0091] Table 1. Raw material composition of the test subjects in this test case.

[0092]

[0093] Table 2. Test results of the participants in this test case.

[0094]

[0095] Results analysis:

[0096] Comparing the performance indicators of Examples 1-10 and Comparative Examples 1-4 in Table 2, it can be found that, compared with the water electrolyzers of Comparative Examples 1-4, the membrane electrodes of Examples 1-10, through the adjustment of the hydrophilicity and hydrophobicity of the anode catalyst layer and the regulation of porosity, combined with the water retention effect of the cathode catalyst layer, enable the water electrolyzers prepared using the membrane electrodes of Examples 1-10 to have faster gas diffusion and ion transfer efficiency, lower water electrolyzer pressure, and enable the produced hydrogen to carry less water.

[0097] Comparative Examples 1-2 were set up with Example 1 as a reference. Comparing the performance indicators of Example 1 and Comparative Examples 1-2 in Table 2, it can be found that the water electrolyzer provided by Example 1 has a lower ohmic impedance and the hydrogen produced has less water content. This shows that the water electrolyzer membrane electrode with a hydrophobic anode catalyst layer can not only accelerate gas mass transfer and ion transfer, reduce ohmic impedance and exhibit a lower water electrolyzer pressure, but also improve hydrogen purity and reduce the water content in hydrogen.

[0098] Comparing the performance indicators of Examples 1-5 with Comparative Examples 3-4 in Table 2, it can be found that as the proportion of hydrophobic material in the hydrophobic anode catalyst layer increases and / or the proportion of anode ionomer increases, the porosity and hydrophobicity of the catalyst layer are adjusted, the ohmic impedance increases accordingly, and the cell pressure of the water electrolyzer increases accordingly. By adjusting the raw material ratio in the hydrophobic anode catalyst layer, the porosity of the hydrophobic anode catalyst layer can be adjusted. When the mass ratio of anode catalyst, hydrophobic material, and anode ionomer in the hydrophobic anode catalyst layer is in the range of 10:1-3:1-3, the hydrophobic anode catalyst layer has suitable porosity and hydrophilicity / hydrophobicity, and the water electrolyzer exhibits good water electrolysis performance, with high hydrogen purity and low water content. Specifically, when the porosity of the hydrophobic anode catalyst layer is in the range of 10-40%, the water electrolyzer exhibits better overall performance; when the porosity of the hydrophobic anode catalyst layer is in the range of 20-30%, the water electrolyzer exhibits lower ohmic impedance.

[0099] Comparing the overall performance of Example 1 and Example 7, it can be found that the ohmic impedance measured in Example 1 is lower than that measured in Example 7. This is because Example 1 uses a hydrophilic cathode catalyst layer combined with a hydrophobic anode catalyst layer, which can control the amount of water molecules permeating from the anode side to the cathode side. This is beneficial for the water electrolyzer to achieve an anode supply circulation mode, keep the membrane electrode wet, improve ion transport efficiency, improve electrolysis efficiency, and at the same time produce drier hydrogen.

Claims

1. A water electrolysis membrane electrode, comprising a cathode gas diffusion layer, a cathode catalyst layer, an anion exchange membrane, a hydrophobic anode catalyst layer, and an anode gas diffusion layer, which are sequentially stacked. The raw materials for preparing the hydrophobic anode catalyst layer comprise an anode catalyst, a hydrophobic material, and an anode ionomer, and the mass ratio of the anode catalyst:the hydrophobic material:the anode ionomer is 10:1-3:1-3, and the porosity of the hydrophobic anode catalyst layer is 10-40%.

2. The water electrolysis membrane electrode of claim 1, wherein, The hydrophobic material comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, and perfluoroethylene propylene copolymer.

3. The water electrolysis membrane electrode of any one of claims 1-2, wherein, The porosity of the hydrophobic anode catalyst layer is 20-30%.

4. The water electrolysis membrane electrode of any one of claims 1-3, wherein, The preparation method of the hydrophobic anode catalyst layer comprises the following steps: The raw materials for preparing the hydrophobic anode catalyst layer are mixed to obtain an anode catalyst layer slurry, the anode catalyst layer slurry is coated on one side of the anode gas diffusion layer, and the anode catalyst layer slurry is calcined at a temperature of 300-500℃ to obtain the hydrophobic anode catalyst layer.

5. The water electrolysis membrane electrode of any one of claims 1-4, wherein, In the hydrophobic anode catalytic layer, the loading of the anode catalyst is 1-10 mg / cm 2 ; and the anode catalyst includes at least one of iridium oxide, ruthenium dioxide, nickel-iron layered double hydroxide, nickel-iron oxide, nickel-iron alloy, nickel-iron-cobalt alloy.

6. The water electrolysis membrane electrode of any one of claims 1-5, wherein, The raw materials for preparing the cathode catalyst layer comprise a cathode catalyst, a hydrophilic carbon material, and a cathode ionomer, and the mass ratio of the cathode catalyst:the hydrophilic carbon material:the cathode ionomer is 8:2-6:1-5.

7. The water electrolysis membrane electrode of claim 6, wherein, The hydrophilic carbon material comprises at least one of a carboxylated carbon material and an aminated carbon material.

8. The water electrolysis membrane electrode of any one of claims 6-7, wherein, In the cathode catalytic layer, the loading of the cathode catalyst is 1-10 mg / cm 2 ; and the cathode catalyst includes at least one of platinum carbon catalyst, nickel phosphorus catalyst, nickel molybdenum alloy, nickel manganese alloy, nickel molybdenum oxide, nickel manganese oxide, molybdenum disulfide. 9.A method for preparing the water electrolysis membrane electrode according to any one of claims 1-8, comprising the following steps: The cathode gas diffusion layer, the cathode catalyst layer, the anion exchange membrane, the hydrophobic anode catalyst layer, and the anode gas diffusion layer are sequentially stacked, and hot-pressed at a pressure of 100-600 psi and a temperature of 50-150℃ to obtain the water electrolysis membrane electrode. 10.A water electrolysis cell comprising the water electrolysis membrane electrode according to any one of claims 1-8.

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