Membrane electrode and preparation method and application thereof
By introducing a platinum catalyst layer between the anodic catalyst layer and the proton exchange membrane in the membrane electrode, the problem of high hydrogen permeation rate was solved, the safety and stability of the electrolyzer were improved, the concentration of hydrogen in oxygen was reduced, and the working load range of the electrolyzer was expanded.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI LANZE ENERGY TECH CO LTD
- Filing Date
- 2024-10-12
- Publication Date
- 2026-04-14
AI Technical Summary
The high hydrogen permeation rate of existing membrane electrodes leads to safety risks and unstable operation of the electrolyzer, especially when the hydrogen concentration exceeds the standard under low load conditions, affecting the purity and safety of the product gas.
A platinum catalyst layer is added between the anode catalyst layer and the iridium-containing catalyst layer of the proton exchange membrane. The hydrogen oxidation ability of the platinum catalyst layer is used to reduce the hydrogen content in oxygen. Hydrogen permeation is reduced by oxidizing hydrogen at the anode and reducing it to protons under the action of an electric field.
It effectively reduces the hydrogen permeation rate of the membrane electrode, improves the safety and stability of the electrolyzer, expands the working load range of the electrolyzer, reduces the concentration of hydrogen in oxygen, and avoids the need for an external gas purification system.
Smart Images
Figure CN121852979A_ABST
Abstract
Description
Technical Field
[0001] This invention provides a membrane electrode, its preparation method, and its application. Background Technology
[0002] Gas cross-contamination in electrolyzers occurs when generated gases pass through the diaphragm. Since hydrogen and oxygen are water-soluble, they can be transported across the well-hydrated membrane to another compartment of the electrolyzer, leading to product gas contamination. Therefore, membrane characteristics (porosity, tortuosity, and thickness), pressure and heat differences between the anode and cathode, etc., all affect the purity of the product gas. Hydrogen cross-contamination is more severe than oxygen cross-contamination because: firstly, in water electrolysis, oxygen permeability is lower than hydrogen, with oxygen production only half that of hydrogen. Secondly, at the cathode, permeated oxygen can be reduced to water by the platinum catalyst. However, at the anode, hydrogen is not easily oxidized on the iridium-based catalyst, thus contaminating the product gas. Furthermore, the lower explosive limit of hydrogen is 3.9 vol%, posing a safety hazard. At low current densities, the high hydrogen concentration in the oxygen at the anode of a PEM electrolyzer is the reason why most differential pressure PEM electrolyzers cannot operate under low load conditions.
[0003] The explosive range of hydrogen in pure oxygen is 3.9%-95% (volume fraction). According to the international standard for hydrogen production by water electrolysis, the maximum hydrogen content in oxygen is 2%. If this range is exceeded, the system will be forced to shut down. Summary of the Invention
[0004] To overcome the shortcomings of existing membrane electrode assemblies (MEAs) such as high hydrogen permeation rates and poor durability, which pose safety risks to electrolyzers using these MEAs, this application provides a MEA, its preparation method, and its application. The MEA of this invention has a double-layer anode catalyst layer structure. An iridium-containing catalyst layer with hydrogen-oxidizing capabilities is added between the iridium-containing catalyst layer and the proton exchange membrane, reducing the hydrogen content in the oxygen. Therefore, by reducing the hydrogen permeation rate of the MEA during electrolyzer operation, safety is improved, and the durability of the MEA and the stability of the electrolyzer operation are increased.
[0005] This invention provides a membrane electrode comprising: a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer, wherein the anode catalyst layer and the cathode catalyst layer are respectively disposed on opposite sides of the proton exchange membrane; the anode catalyst layer comprises an iridium-containing catalyst layer and a platinum catalyst layer; the platinum catalyst layer is disposed between the proton exchange membrane and the iridium-containing catalyst layer; in the iridium-containing catalyst layer, the iridium loading is 1-3.5 mg / cm³. 2 In the platinum catalyst layer, the platinum loading is 0.1-0.5 mg / cm³. 2 .
[0006] In this invention, the introduction of a platinum catalyst layer into the anode catalyst layer can solve the problems of hydrogen-oxygen cross-contamination and safety issues caused by H2 generated at the anode dissolving in water and passing through the proton exchange membrane.
[0007] In some embodiments, the iridium-containing catalyst layer is one or more of iridium black, iridium oxide, and iridium-ruthenium alloy.
[0008] In some embodiments, the loading ratio of iridium to platinum is (10-35):(1-5), more preferably (10-20):(1-5).
[0009] In some embodiments, the iridium loading is 1-2 mg / cm³. 2 For example, 2mg / cm 2 This loading capacity can meet the requirements of electrolysis efficiency while avoiding excessive iridium oxide.
[0010] In some embodiments, the platinum loading is 0.1-0.3 mg / cm³. 2 For example, 0.1 mg / cm 2 Or 0.3 mg / cm 2 This loading capacity is beneficial for the oxygen evolution reaction at the anode of the electrolytic cell.
[0011] In some embodiments, the thickness of the iridium-containing catalyst layer is 10-30 μm, preferably 10-15 μm.
[0012] In some embodiments, the thickness of the platinum catalyst layer is 2-6 μm.
[0013] In a specific embodiment, when the iridium-containing catalyst layer is iridium oxide, the particle size of the iridium oxide is 10-100 nm.
[0014] In a specific embodiment, when the iridium-containing catalyst layer is iridium oxide, the loading of the iridium oxide is 1.16-4.0 mg / cm³. 2 The preferred concentration is 1.2-4.0 mg / cm³. 2 For example, 2.33 mg / cm³ 2 .
[0015] In some embodiments, the platinum has a particle size of 3-50 nm.
[0016] In some embodiments, the proton exchange membrane includes a Nafion membrane or a Dongyue membrane.
[0017] In some embodiments, the cathode catalyst layer comprises a platinum-carbon catalyst layer; preferably, the platinum-carbon loading in the cathode catalyst layer is 0.1-2 mg / cm³. 2 For example, 0.5 mg / cm 2.
[0018] In this invention, platinum, which has the ability to recombine hydrogen and oxygen, is introduced as a double-layer anode electrode between the proton exchange membrane and the anode catalyst layer. This can reduce hydrogen cross-linking and lower the probability of hydrogen reaching the explosion limit in oxygen, thereby increasing the working load range of the electrolyzer and improving the durability of the membrane electrode.
[0019] The present invention also provides a method for preparing a membrane electrode, which includes the following steps: placing the coating surface of the transfer material on a proton exchange membrane for transfer; the transfer temperature is 120-150℃, and the transfer pressure is 3-10MPa;
[0020] The transfer material comprises a transfer substrate, an iridium-containing catalyst layer, and a platinum catalyst layer; the iridium-containing catalyst layer and the platinum catalyst layer are sequentially disposed on the transfer substrate; in the iridium-containing catalyst layer, the iridium loading is 1-3.5 mg / cm³. 2 In the platinum catalyst layer, the platinum loading is 0.1-0.5 mg / cm³. 2 .
[0021] In this invention, those skilled in the art should know that "the iridium-containing catalyst layer and the platinum catalyst layer are sequentially disposed on the transfer substrate" means that the iridium-containing catalyst layer is disposed on the transfer substrate, and the platinum catalyst layer is disposed on the iridium-containing catalyst layer.
[0022] In this invention, by setting the above-mentioned transfer temperature and pressure, the iridium-containing catalyst layer and the platinum catalyst layer can be detached from the transfer substrate without damaging their structure, so that they can be tightly and firmly bonded to the proton exchange membrane, thereby achieving the effect of reducing impedance.
[0023] In some embodiments, the transfer temperature is 130-140°C, for example, 140°C.
[0024] In some embodiments, the transfer pressure is 3-5 MPa, for example 5 MPa.
[0025] In some implementations, the transfer time is 3-20 minutes, for example, 3 minutes.
[0026] In some embodiments, the iridium-containing catalyst layer is one or more of iridium black, iridium oxide, and iridium-ruthenium alloy.
[0027] In a specific embodiment, when the iridium-containing catalyst layer is iridium oxide, the particle size of the iridium oxide is 10-100 nm.
[0028] In a specific embodiment, when the iridium-containing catalyst layer is iridium oxide, the loading of the iridium oxide is 1.16-4.0 mg / cm³. 2The preferred concentration is 1.2-4.0 mg / cm³. 2 For example, 2.33 mg / cm³ 2 .
[0029] In some embodiments, the iridium loading is 1-2 mg / cm³. 2 For example, 2mg / cm 2 .
[0030] In some embodiments, the preparation method of the transfer material includes the following steps: S1, spraying an iridium-containing solution onto the transfer substrate, and drying to obtain a first sheet, wherein the first sheet is a transfer substrate with an iridium-containing catalyst layer; S2, spraying a platinum-containing solution onto one side of the first sheet containing the iridium catalyst layer, drying to remove the transfer substrate, and obtaining the transfer material.
[0031] In a specific implementation, in step S1, the spraying temperature is 80-100℃. By controlling the spraying temperature here, the substances in the solution can be prevented from evaporating too quickly, which could cause cracks in the layer.
[0032] In a specific implementation, in step S1, the iridium-containing solution includes iridium oxide, water, an organic solvent, and a binder.
[0033] In a preferred embodiment, the iridium oxide has a particle size of 10-100 nm.
[0034] In a preferred embodiment, the iridium oxide loading is 1.16-4.0 mg / cm³. 2 .
[0035] In a preferred embodiment, the organic solvent includes isopropanol.
[0036] In a preferred embodiment, the adhesive is a perfluorosulfonic acid dispersion.
[0037] The perfluorosulfonic acid dispersion may be Nafion TM A 5% perfluorosulfonic acid dispersion of D520; preferably, the perfluorosulfonic acid dispersion contains 5 wt% perfluorosulfonic acid polymer, 45±3 wt% water, and 50±3 wt% VOC volatile organic solvents, wherein the active ingredient is Nafion. TM .
[0038] In a preferred embodiment, the ratio of the total mass of water to the total mass of organic solvent in the iridium-containing solution is 1:1 to 1:3; wherein, "total mass of water" and "total mass of organic solvent" refer to the sum of the masses of water in the iridium-containing solution and the sum of the masses of organic solvent in the iridium-containing solution, respectively; the water includes water in the perfluorosulfonic acid dispersion and water added in addition to the preparation of the iridium-containing solution, and the organic solvent includes organic solvent in the perfluorosulfonic acid dispersion and organic solvent added in addition to the preparation of the iridium-containing solution.
[0039] In a preferred embodiment, in the iridium-containing solution, the Nafion in the adhesive TM The mass ratio of Nafion to iridium oxide is 1:20 to 2:3; after heating, the solvent in the adhesive evaporates, leaving only the 5 wt% active ingredient Nafion. TM The mass ratio of the binder to iridium oxide here refers to Nafion TM The mass ratio to iridium oxide.
[0040] In one embodiment, in the iridium-containing solution, the mass ratio of iridium oxide, water, organic solvent, and binder is 0.15:1.92:6.22:0.53, where "water" and "organic solvent" refer to water and organic solvent added in addition to the binder; in the binder, Nafion... TM The mass ratio of water to organic solvent is 0.05:0.45:0.5.
[0041] In this case, according to the above mass ratio, when the mass of iridium oxide is 0.15g, the masses of water, organic solvent, and binder are 1.92g, 6.22g, and 0.53g, respectively. The Nafion in the binder... TM The masses of water, organic solvent, and iridium are 0.0265 g, 0.239 g, and 0.265 g, respectively. Therefore, in the iridium-containing solution, the total mass of water is 2.159 g, the total mass of organic solvent is 6.485 g, and the ratio of the total mass of water to the total mass of organic solvent is 1:3. Meanwhile, the Nafion in the adhesive... TM The mass ratio of iridium oxide to iridium oxide is 1:5.66.
[0042] In a specific implementation, in step S1, the iridium-containing solution is obtained by ultrasonic dispersion.
[0043] In a specific implementation, in step S1, the material of the transfer substrate includes polytetrafluoroethylene.
[0044] In a specific implementation, in step S2, the spraying temperature is 80-100℃. By controlling the spraying temperature here, the substances in the solution can be prevented from evaporating too quickly, which could cause cracks in the layer.
[0045] In a specific implementation, in step S2, the platinum-containing solution includes platinum, water, organic solvent, and adhesive.
[0046] In a preferred embodiment, the platinum loading is 0.1-0.3 mg / cm³. 2 .
[0047] In a preferred embodiment, the platinum has a particle size of 3-50 nm.
[0048] In a preferred embodiment, the organic solvent includes isopropanol.
[0049] In a preferred embodiment, the adhesive is a perfluorosulfonic acid dispersion.
[0050] The perfluorosulfonic acid dispersion may be Nafion TM A 5% perfluorosulfonic acid dispersion of D520; the perfluorosulfonic acid dispersion contains 5 wt% perfluorosulfonic acid polymer, 45±3 wt% water, and 50±3 wt% VOC volatile organic solvents, wherein the active ingredient is Nafion. TM .
[0051] In a preferred embodiment, the ratio of the total mass of water to the total mass of organic solvent in the platinum-containing solution is 1:1 to 1:3, where "total mass of water" and "total mass of organic solvent" refer to the sum of the masses of water in the platinum-containing solution and the sum of the masses of organic solvent in the platinum-containing solution, respectively. The water includes water in the perfluorosulfonic acid dispersion and water added in addition to the preparation of the platinum-containing solution, and the organic solvent includes organic solvent in the perfluorosulfonic acid dispersion and organic solvent added in addition to the preparation of the platinum-containing solution.
[0052] In a preferred embodiment, the Nafion in the adhesive is in the platinum-containing solution. TM The mass ratio of Nafion to platinum is 1:20 to 2:3; after heating, the solvent in the adhesive evaporates, leaving only the 5 wt% active ingredient Nafion. TM The mass ratio of adhesive to platinum here refers to Nafion TM The mass ratio to iridium oxide.
[0053] In one embodiment, in the platinum-containing solution, the mass ratio of platinum, water, organic solvent, and binder is 0.1:1.36:4.82:0.86, where "water" and "organic solvent" refer to water and organic solvent added in addition to the binder; in the binder, Nafion... TM The mass ratio of water to organic solvent is 0.05:0.45:0.5.
[0054] In this context, based on the aforementioned mass ratio, when the mass of platinum is 0.1g, the masses of water, organic solvent, and binder are 1.36g, 4.82g, and 0.86g, respectively. The Nafion in the binder... TM The masses of water, organic solvent, and water are 0.043 g, 0.387 g, and 0.43 g, respectively; therefore, in the platinum-containing solution, the total mass of water is 1.75 g, the total mass of organic solvent is 5.25 g, and the ratio of the total mass of water to the total mass of organic solvent is 1:3; while the Nafion in the adhesive... TM The mass ratio of platinum to platinum is 1:2.33.
[0055] In a specific implementation, in step S1, the platinum-containing solution is obtained by ultrasonic dispersion.
[0056] In a specific implementation, in step S1, the ratio of the iridium loading to the platinum loading is (10-35):(1-5), preferably (10-20):(1-5).
[0057] In some embodiments, the method for preparing the membrane electrode further includes: coating a cathode catalyst onto one side of the proton exchange membrane that does not contain an anode catalyst layer, and drying it to form a cathode catalyst layer; the coating step is performed after the transfer step.
[0058] In a specific embodiment, the cathode catalyst layer comprises a platinum-carbon catalyst layer; preferably, the platinum-carbon loading in the cathode catalyst layer is 0.1-2 mg / cm³. 2 For example, 0.5 mg / cm 2 .
[0059] In a specific embodiment, the cathode catalyst comprises platinum carbon, water, organic solvent, and binder.
[0060] In a preferred embodiment, the organic solvent includes isopropanol.
[0061] In a preferred embodiment, the ratio of the total mass of water to the total mass of organic solvent in the cathode catalyst is 1:1 to 1:3.
[0062] In a preferred embodiment, the Nafion in the adhesive TM The mass ratio of platinum to carbon is 1:20 to 2:3.
[0063] In this invention, a platinum catalyst layer is added between the proton exchange membrane and the iridium oxide catalyst layer. Hydrogen gas that permeates from the cathode to the anode will be oxidized into protons on the metal Pt of the platinum catalyst layer. The protons will return to the anode under the action of the electric field and be reduced back into hydrogen gas, thereby reducing hydrogen permeation.
[0064] In one embodiment, the method for preparing the membrane electrode includes the following steps:
[0065] Step 1: Weigh the iridium oxide catalyst, add water, organic solvent and binder in sequence into a container, mix and then ultrasonically disperse in an ultrasonic instrument for 1 hour to obtain slurry A, which is then continuously stirred for later use.
[0066] Step 2: Weigh the Pt catalyst, add water, organic solvent and binder in sequence into a container, mix and then ultrasonically disperse in an ultrasonic instrument for 1 hour to obtain slurry B, which is continuously stirred.
[0067] Step 3: Use a polytetrafluoroethylene (PTFE) sheet as the transfer substrate, clean it with deionized water and ethanol, and dry it for later use;
[0068] Step 4: Spray slurry A onto the PTFE membrane from step 3 at 90°C and let it dry for later use;
[0069] Step 5: Spray slurry B onto one side of the PTFE membrane with dried slurry A from step 4 at 90°C, and dry it for later use to obtain a double-layer anode catalyst layer.
[0070] Step 6: Place the anode catalyst layer on one side of the proton exchange membrane, apply a pressure of 5 MPa at 140°C, maintain for 180 seconds, remove, wait for room temperature cooling, peel off the PTFE membrane, and the double-layer anode catalyst layer is transferred to one side of the proton exchange membrane.
[0071] In step 1 or 2, the organic solvent is isopropanol, the binder is a perfluorosulfonic acid dispersion, and the ratio of the total mass of water to the total mass of isopropanol is 1:1 to 1:3; Nafion in the binder TM The mass ratio of the catalyst to the catalyst is 1:20 to 2:3.
[0072] In step 6, the proton exchange membrane may be a Nafion membrane or a Dongyue membrane.
[0073] The present invention also provides a membrane electrode, which is prepared by the membrane electrode preparation method described above.
[0074] The present invention also provides a membrane electrode as described above, or the application of the membrane electrode as described above in an electrolytic cell.
[0075] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.
[0076] The reagents and raw materials used in this invention are all commercially available.
[0077] The positive and progressive effects of this invention are as follows:
[0078] (1) Through the design of the membrane electrode of the present invention, a platinum catalyst layer is added between the iridium-containing catalyst layer and the proton exchange membrane, which has the ability to oxidize hydrogen and reduce the hydrogen in oxygen; under the working state of the electrolyzer, the hydrogen permeation rate can be reduced; in particular, the hydrogen permeation rate is reduced by 30% or more at low current density, which increases the working load range of the electrolyzer; thereby improving safety, increasing the durability of the membrane electrode and the stability of the electrolyzer operation.
[0079] (2) When the membrane electrode of the present invention is used in an electrolyzer, there is no need to set up an external gas purification system to avoid the hydrogen content in oxygen reaching the explosion limit.
[0080] (3) The preparation method of the present invention is simple to operate; the prepared membrane electrode has high stability and high durability. Attached Figure Description
[0081] Figure 1 This is a scanning electron microscope (SEM) image of the membrane electrode of Embodiment 1 of the present invention.
[0082] Figure 2 This is a comparison diagram of the membrane electrode and the transfer substrate in Embodiment 1 of the present invention.
[0083] Figure 3 This is a comparison diagram of the membrane electrode, the transferred substrate after transfer, and the original transferred substrate in this comparative example.
[0084] Figure 4 This is a comparison diagram of the membrane electrode and the transfer substrate after the transfer was completed, which is a comparative example.
[0085] Figure 5 This is a diagram showing the effect of the completed transfer substrate for this comparative example.
[0086] Figure 6 The diagram shows the voltage change effect of the membrane electrode in the electrolytic cell of Embodiments 1-2 and Comparative Example 1 of the present invention.
[0087] Figure 7 The diagram shows the effect of the membrane electrode of Embodiments 1-2 and Comparative Example 1 on the hydrogen content in oxygen in an electrolyzer. Detailed Implementation
[0088] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.
[0089] In the following embodiments, the adhesive used is Nafion. TMD520 is a 5% perfluorosulfonic acid dispersion containing 5 wt% perfluorosulfonic acid polymer, 45 ± 3 wt% water, and 50 ± 3 wt% VOC volatile organic solvents. The active ingredient is Nafion. TM .
[0090] In the following examples, the organic solvent used is isopropanol, which is common in the art.
[0091] In the following embodiments, the average particle diameter of iridium oxide is 10.0 nm and the average particle diameter of platinum is 5.0 nm.
[0092] Example 1
[0093] This embodiment discloses a method for preparing a membrane electrode, which includes the following steps:
[0094] Step 1: Weigh 0.15g of iridium oxide catalyst, add 1.92g of water, 6.22g of organic solvent, and 0.53g of binder into a container, mix, and then ultrasonically disperse in an ultrasonic instrument for 1 hour to obtain slurry A, which is then stirred continuously for later use.
[0095] Step 2: Weigh 0.1g of platinum catalyst, add 1.36g of water, 4.82g of organic solvent, and 0.86g of binder into a container, mix, and then ultrasonically disperse in an ultrasonic instrument for 1 hour to obtain slurry B.
[0096] Step 3: Use a polytetrafluoroethylene (PTFE) sheet as the transfer substrate, clean it with deionized water and ethanol, and dry it for later use;
[0097] Step 4: Spray slurry A onto the PTFE membrane from step 3 at 90°C, dry and weigh for later use;
[0098] Step 5: Spray slurry B onto one side of the PTFE membrane with dried slurry A from step 4 at 90°C, dry and weigh for later use, thus obtaining the double-layer anode catalyst layer;
[0099] Step 6: Place the anode catalyst layer on one side of the proton exchange membrane Nafion115, apply a pressure of 5MPa at 140°C, maintain for 180s, remove, wait for room temperature cooling, peel off the PTFE membrane, and the double anode catalyst layer is transferred to one side of the proton exchange membrane.
[0100] The iridium oxide loading was controlled at 2.33 mg / cm³. 2 (That is, the iridium loading is 2 mg / cm³) 2 (Iridium loading = iridium oxide loading ÷ iridium oxide formula weight × iridium formula weight), the Pt catalyst loading is 0.1 mg / cm³. 2Using a Pt / C catalyst as the cathode catalyst, 0.2 g of Pt / C was weighed and mixed with 2.67 g of Nafion binder. Water and isopropanol were added in a 1:3 ratio to disperse the mixture. This mixture was then sprayed and transferred onto the other side of the proton exchange membrane, with the loading controlled at 0.5 mg / cm³. 2 , thus obtaining the membrane electrode.
[0101] The membrane electrode was tested using a scanning electron microscope (SEM) (Thermo Fisher Scientific FEI Nova NanoSEM). Figure 1 The image shown is a scanning electron microscope (SEM) image of the membrane electrode in this embodiment, revealing that the iridium oxide layer has a thickness of 21.5 μm and the Pt layer has a thickness of 2.5 μm.
[0102] Figure 2 This is a comparison diagram of the membrane electrode and the transfer substrate after transfer in this embodiment. Figure 2 In the image, the material on the left is a membrane electrode containing a bilayer anode catalyst layer and a proton exchange membrane, while the material on the right is the transfer substrate after complete transfer, such as... Figure 2 As shown, there is no residue on the PTFE film of the transfer substrate on the right.
[0103] Example 2
[0104] This embodiment discloses a method for preparing a membrane electrode, which includes the following steps:
[0105] Repeat the steps of Example 1, controlling the Pt catalyst loading to be 0.3 mg / cm³. 2 All other conditions were the same as in Example 1. Using a Pt / C catalyst as the cathode catalyst, 0.2 g of Pt / C was weighed, and 2.67 g of Nafion binder was added. Water and isopropanol were added and mixed in a 1:3 ratio to disperse the mixture. This mixture was then sprayed and transferred onto the other side of the proton exchange membrane, with the loading controlled at 0.5 mg / cm³. 2 The membrane electrode was obtained, and the thickness of the iridium oxide layer was measured to be 23.5 μm and the thickness of the Pt layer was 3.2 μm using a scanning electron microscope (Thermo Fisher Scientific FEI Nova NanoSEM).
[0106] Comparative Example 1
[0107] This comparative example discloses a method for preparing a membrane electrode, which includes the following steps:
[0108] Step 1: Weigh 0.15g of iridium oxide catalyst, add 1.92g of water, 6.22g of organic solvent and 0.53g of binder to a container, mix and then ultrasonically disperse in an ultrasonic instrument for 1 hour to obtain slurry A, which is then stirred continuously for later use.
[0109] Step 2: Use a polytetrafluoroethylene (PTFE) sheet as the transfer substrate, clean it with deionized water and ethanol, and dry it for later use;
[0110] Step 3: Spray slurry A onto the PTFE membrane from Step 3 at 90°C, dry and weigh for later use;
[0111] Step 4: Place the anode catalyst layer on one side of the proton exchange membrane Nafion115, apply a pressure of 5 MPa at 140°C, maintain for 180 seconds, remove, wait for room temperature cooling, peel off the PTFE membrane, and the monolayer anode catalyst layer is transferred to one side of the proton exchange membrane.
[0112] The iridium oxide loading was controlled at 2.33 mg / cm³. 2 Using a Pt / C catalyst as the cathode catalyst, 0.2 g of Pt / C was weighed and mixed with 2.67 g of Nafion binder. Water and isopropanol were added in a 1:3 ratio to disperse the mixture. This mixture was then sprayed and transferred onto the other side of the proton exchange membrane, with the loading controlled at 0.5 mg / cm³. 2 The membrane electrode was obtained. The membrane electrode was tested by SEM (Thermo Fisher Scientific FEI Nova NanoSEM), and the thickness of the iridium oxide layer was found to be 23.8 μm.
[0113] Comparative Example 2
[0114] This comparative example discloses a method for preparing a membrane electrode; in step 6, the anode catalyst layer is placed on one side of the proton exchange membrane Nafion 115 and transferred at a transfer temperature of 110°C, with other conditions being the same as in Example 1.
[0115] Figure 3 This is a comparison image of the membrane electrode, the transferred substrate after transfer, and the original transferred substrate in this comparative example. Two experiments were conducted using the preparation method of this comparative example, yielding the following results: Figure 3 A comparison diagram of the upper and lower sets of materials. Figure 3 In each group, the leftmost element is the membrane electrode, the middle element is the transfer substrate after the transfer is completed, and the rightmost element is the original transfer substrate. Figure 3 It is known that at the transfer temperature of this comparative example, complete transfer cannot be achieved, and the anode catalyst layer is difficult to peel off from the PTFE transfer substrate. If the anode catalyst layer is to be further peeled off from the transfer substrate, a larger transfer pressure is required. However, applying a larger transfer pressure will damage the pore structure inside the catalyst layer.
[0116] Comparative Example 3
[0117] This comparative example discloses a method for preparing a membrane electrode; in step 6, the anode catalyst layer is placed on one side of the proton exchange membrane Nafion 115 and transferred under a transfer pressure of 2 MPa, with other conditions being the same as in Example 1.
[0118] Figure 4 This is a comparison image of the membrane electrode and the transfer substrate used in this comparative example. Figure 4In the image, the material at the top is the membrane electrode, and the material at the bottom is the transfer substrate for the completed transfer. Figure 4 It can be seen that under the transfer pressure of this comparative example, after transfer, the catalyst layer remains on the transfer substrate, thus affecting the performance of the membrane electrode.
[0119] Comparative Example 4
[0120] This comparative example discloses a method for preparing a membrane electrode; in step 6, the anode catalyst layer is placed on one side of the proton exchange membrane Nafion 115, and transfer is performed under a transfer pressure of 15 MPa, with other conditions being the same as in Example 1. Under these conditions, the membrane electrode coils due to overpressure.
[0121] Figure 5 This is an illustration of the completed transfer substrate for this comparative example. Figure 5 As shown, after the transfer was completed, the PTFE substrate was also significantly deformed and could not be used subsequently.
[0122] Example 1
[0123] The electrical properties of the membrane electrode were tested on a water electrolysis testing system. The electrolyzer was purchased from Shaanxi Qintai Hydrogen Metal Co., Ltd., and it has an active area of 4 cm². 2 The PEM electrolytic cell is equipped with a temperature control device. The test power supply is an NGI programmable DC power supply, model N3618-016-250.
[0124] The membrane electrode assembly was placed into the electrolyzer, and a single-chamber anode circulating water feed method was used. Polarization curves were tested at 80℃. (See the attached polarization curve.) Figure 6 .Depend on Figure 6 It is evident that the platinum catalyst layer does not exhibit the same catalytic performance as the iridium catalyst for the oxygen evolution reaction (OER), but it still plays a role. However, excessive loading may have the opposite effect. Therefore, in the experiment, the platinum catalyst layer was controlled at a relatively low loading of 0.1 mg / cm³. 2 Under the same current, the overall voltage decreased by about 60mV, 0.3mg / cm. 2 The performance change under load is not significant.
[0125] Example 2
[0126] The gas generated at the anode was collected using a gas sampling bag, dried with anhydrous calcium sulfate to remove moisture, and then injected into a gas chromatograph (Agilent 8890GC) for analysis. The obtained area was calibrated using standard gases to determine the content. The hydrogen in the anode mixture was calibrated using 2 vol% and 10 vol% hydrogen (in nitrogen) standard gases, while the oxygen was calibrated using 99.998% oxygen. The variation of hydrogen content in oxygen at different current densities is shown in [reference needed]. Figure 7 .
[0127] Depend on Figure 7 It is known that after using a membrane electrode with a platinum catalytic layer, the oxygen content in hydrogen in this application is less than 2%, so as to achieve the "the maximum content of hydrogen in oxygen is 2%, and the system will be forced to stop operating if this range is exceeded" mentioned in the background technology of this application.
Claims
1. A membrane electrode, comprising: A proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer, wherein the anode catalyst layer and the cathode catalyst layer are respectively disposed on both sides of the proton exchange membrane; characterized in that, The anode catalyst layer includes an iridium-containing catalyst layer and a platinum catalyst layer; the platinum catalyst layer is disposed between the proton exchange membrane and the iridium-containing catalyst layer; In the iridium-containing catalyst layer, the iridium loading is 1-3.5 mg / cm³. 2 ; In the platinum catalyst layer, the platinum loading is 0.1-0.5 mg / cm³. 2 .
2. The membrane electrode as described in claim 1, characterized in that, The anode catalyst layer satisfies one or more of the following conditions: ①The iridium-containing catalyst layer is one or more of iridium black, iridium oxide, and iridium-ruthenium alloy; ②The loading ratio of iridium to platinum is (10-35):(1-5), preferably (10-20):(1-5); ③ The iridium loading is 1-2 mg / cm³. 2 For example, 2mg / cm 2 ; ④ The platinum loading is 0.1-0.3 mg / cm³. 2 For example, 0.1 mg / cm 2 Or 0.3 mg / cm 2 ; ⑤ The thickness of the iridium-containing catalyst layer is 10-30 μm, preferably 10-15 μm; ⑥ The thickness of the platinum catalyst layer is 2-6 μm.
3. The membrane electrode as described in claim 2, characterized in that, The membrane electrode satisfies one or more of the following conditions: ①When the iridium-containing catalyst layer is iridium oxide, the particle size of the iridium oxide is 10-100 nm; ② When the iridium-containing catalyst layer is iridium oxide, the loading of the iridium oxide is 1.16-4.0 mg / cm³. 2 The preferred concentration is 1.2-4.0 mg / cm³. 2 For example, 2.33 mg / cm³ 2 ; ③ The particle size of the platinum is 3-50 nm; ④ The proton exchange membrane includes a Nafion membrane or a Dongyue membrane; ⑤ The cathode catalyst layer includes a platinum-carbon catalyst layer; preferably, the platinum-carbon loading in the cathode catalyst layer is 0.1-2 mg / cm³. 2 For example, 0.5 mg / cm 2 .
4. A method for preparing a membrane electrode, characterized in that, It includes the following steps: The coating surface of the transfer material is placed on a proton exchange membrane for transfer; the transfer temperature is 120-150℃ and the transfer pressure is 3-10MPa. The transfer material comprises a transfer substrate, an iridium-containing catalyst layer, and a platinum catalyst layer; the iridium-containing catalyst layer and the platinum catalyst layer are sequentially disposed on the transfer substrate; in the iridium-containing catalyst layer, the iridium loading is 1-3.5 mg / cm³. 2 In the platinum catalyst layer, the platinum loading is 0.1-0.5 mg / cm³. 2 .
5. The method for preparing a membrane electrode as described in claim 4, characterized in that, The transfer process satisfies one or more of the following conditions: ① The transfer temperature is 130-140℃, for example, 140℃; ② The transfer pressure is 3-5 MPa, for example 5 MPa; ③ The transfer time is 3-20 minutes, for example, 3 minutes.
6. The method for preparing a membrane electrode as described in claim 4, characterized in that, The preparation method of the transfer material includes the following steps: S1. Spray an iridium-containing solution onto the transfer substrate, and after drying, obtain a first sheet. The first sheet is a transfer substrate with an iridium-containing catalytic layer. S2. A platinum-containing solution is sprayed onto one side of the first sheet containing an iridium catalyst layer. After drying, the transfer substrate is removed to obtain the transfer material.
7. The method for preparing a membrane electrode as described in claim 6, characterized in that, Step S1 satisfies one or more of the following conditions: ① The spraying temperature is 80-100℃; ② The iridium-containing solution comprises iridium oxide, water, an organic solvent, and a binder; preferably, the iridium oxide has a particle size of 10-100 nm; preferably, the iridium oxide loading is 1.16-4.0 mg / cm³. 2 Preferably, the organic solvent includes isopropanol; preferably, the adhesive is a perfluorosulfonic acid dispersion; preferably, in the iridium-containing solution, the ratio of the total mass of water to the total mass of the organic solvent is 1:1 to 1:3, and the Nafion in the adhesive... TM The mass ratio of iridium oxide to iridium is 1:20 to 2:3; for example, in the iridium-containing solution, the mass ratio of iridium oxide, water, organic solvent, and binder is 0.15:1.92:6.22:0.
53. ③ The iridium-containing solution was obtained by ultrasonic dispersion; ④ The material of the transfer substrate includes polytetrafluoroethylene; And / or, step S2 satisfies one or more of the following conditions: ① The spraying temperature is 80-100℃; ② The platinum-containing solution comprises platinum, water, an organic solvent, and a binder; preferably, the platinum loading is 0.1-0.3 mg / cm³. 2 Preferably, the platinum particle size is 3-50 nm; preferably, the organic solvent includes isopropanol; preferably, the binder is a perfluorosulfonic acid dispersion; preferably, in the platinum-containing solution, the ratio of the total mass of water to the total mass of the organic solvent is 1:1 to 1:3, and the Nafion in the binder... TM The mass ratio of platinum to water is 1:20 to 2:3; for example, in the platinum-containing solution, the mass ratio of platinum, water, organic solvent, and binder is 0.1:1.36:4.82:0.
86. ③ The platinum-containing solution was obtained by ultrasonic dispersion; ④ The ratio of the iridium loading to the platinum loading is (10-35):(1-5), preferably (10-20):(1-5).
8. The method for preparing a membrane electrode as described in claim 4, characterized in that, The method for preparing the membrane electrode further includes: coating a cathode catalyst onto one side of the proton exchange membrane that does not contain an anode catalyst layer, and drying it to form a cathode catalyst layer; the coating step is performed after the transfer step; Preferably, the cathode catalyst layer comprises a platinum-carbon catalyst layer; preferably, the platinum-carbon loading in the cathode catalyst layer is 0.1-2 mg / cm³. 2 For example, 0.5 mg / cm 2 ; Preferably, the cathode catalyst comprises platinum carbon, water, an organic solvent, and a binder; more preferably, the organic solvent comprises isopropanol; even more preferably, in the cathode catalyst, the ratio of the total mass of water to the total mass of the organic solvent is 1:1 to 1:
3.
9. A membrane electrode, characterized in that, It is prepared by the method of preparing the membrane electrode as described in any one of claims 4-8.
10. The application of a membrane electrode as described in any one of claims 1-3, or the membrane electrode as described in claim 9, in an electrolytic cell.