Anode catalyst layer of membrane electrode for water electrolysis, membrane electrode for water electrolysis and preparation method thereof, and PEM electrolyzer

Abstract

The present application relates to the technical field of water electrolysis, and in particular to an anode catalyst layer of a membrane electrode for water electrolysis, a membrane electrode for water electrolysis, a preparation method thereof, and a PEM electrolyzer. The present invention provides an anode catalyst layer of a membrane electrode for water electrolysis, wherein the anode catalyst on the anode catalyst layer comprises cerium dioxide and an iridium-containing catalyst; the present solution directly adds cerium dioxide to the anode catalyst, and utilizes the cerium dioxide in the anode catalyst to react with hydrogen to generate water, thereby achieving the removal of hydrogen on the anode side of the membrane electrode, and can be used for water electrolysis to effectively eliminate hydrogen on the anode side, thereby improving the purity of oxygen in electrolyzed water, and the preparation process is simple, thereby reducing the cost of hydrogen removal.

Description

Technical Field

[0001] The present application relates to the technical field of water electrolysis, and in particular to an anode catalyst layer of a membrane electrode for water electrolysis, a membrane electrode for water electrolysis and a preparation method thereof, and a PEM electrolyzer. Background Art

[0002] The membrane electrode mainly includes three layers: the cathode / anode catalyst layer and the proton exchange membrane. It can also be expanded to five and seven layers including the cathode / anode gas diffusion layer and the sealing frame. Water electrolysis is the process of decomposing water into oxygen and hydrogen through electrochemical reactions in the electrolyzer. In this process, the anode side and cathode side of the membrane electrode produce oxygen and hydrogen respectively, and then the two gases are blocked by the proton exchange membrane. Since the mixing of hydrogen and oxygen poses a great safety hazard, in order to avoid the risk of mixing the two, the gas barrier effect of the proton exchange membrane is critical to the safety of the water electrolysis system.

[0003] On the one hand, in order to achieve a better gas barrier effect for the proton exchange membrane, in the prior art, researchers usually thicken the proton exchange membrane, for example, setting the thickness of the proton exchange membrane to tens to hundreds of microns to ensure a better gas barrier effect. However, thickening the proton exchange membrane will increase the membrane resistance, resulting in increased power consumption for water electrolysis and increased costs for hydrogen production by electrolysis.

[0004] On the other hand, in actual application, the system may also be negatively affected due to deviations in the sealing effect or defects in the airtightness of the membrane, especially when R&D personnel try to reduce the thickness of the membrane or when there is high-pressure operation in the process, the hydrogen on the cathode side will penetrate into the anode side, resulting in an increase in the hydrogen content on the anode side; in the above application process, when the hydrogen content mixed with the oxygen on the anode side exceeds 4%, there will be an explosion risk, and the risk increases with the increase in content. Reducing the hydrogen content on the anode side is an important guarantee for the safe operation of the electrolyzer; at the same time, oxygen products have certain requirements for purity. Under normal circumstances, the purity of hydrogen produced by the electrolyzer can only reach 99.8%, and the purity of oxygen reaches about 98%, which is a certain distance from the current industrial application needs; for example, the current fuel cell hydrogen purity requirement is 99.97%, and the national standard requires the purity of pure hydrogen to be 99.99%, and the purity of pure oxygen to be 99.99%. To improve the purity of the final product, existing technology adds hydrogen and oxygen purification systems after the electrolysis process; this solution will increase the complexity and footprint of the water electrolysis system, which will not only significantly increase the cost, but also reduce the operational flexibility of the water electrolysis system, which is not conducive to the use of fluctuating renewable energy. Summary of the invention

[0005] In view of this, the present application provides an anode catalyst layer of a membrane electrode for electrolysis of water, a membrane electrode for electrolysis of water and a preparation method thereof, and a PEM electrolyzer, which are used to improve the purity of oxygen in electrolyzed water and reduce costs.

[0006] The first aspect of the present invention provides an anode catalyst layer of a membrane electrode for electrolysis of water, the anode catalyst layer comprising: an anode catalyst; the anode catalyst comprising cerium dioxide (CeO2) and an iridium-containing catalyst;

[0007] The iridium-containing catalyst includes one or more of pure iridium or iridium-containing metal oxides.

[0008] It should be noted that the technical principle of adding cerium dioxide in the present invention is that cerium dioxide can be reduced to cerium trioxide under the action of hydrogen, so that the hydrogen in oxygen becomes water, thereby achieving the effect of eliminating hydrogen; and cerium trioxide can be oxidized to cerium dioxide under the action of oxygen, thereby realizing the recycling of cerium dioxide and continuously removing hydrogen in oxygen. The specific reaction equation is as follows:

[0009] 2CeO2+H2=Ce2O3+H2O

[0010] 2Ce2O3+O2=4CeO2

[0011] More preferably, the iridium-containing metal oxide comprises iridium oxide (IrO2).

[0012] Preferably, the anode catalyst further comprises: platinum (pt).

[0013] It should be noted that in order to eliminate hydrogen on the anode side of the membrane electrode, the present invention adds cerium dioxide to the iridium-containing catalyst to form one of the anode catalysts of the present invention, which will cause the resistance of the anode catalyst layer of the membrane electrode to increase relatively and increase the membrane voltage of a single cell. By adding platinum to the anode catalyst, the effect of cerium dioxide on the cell voltage can be offset.

[0014] Preferably, the mass ratio of iridium, cerium and platinum in the anode catalyst is (15-20): (1-4): (2-8).

[0015] More preferably, the mass ratio of iridium, cerium and platinum in the anode catalyst is 18:5:2.

[0016] A second aspect of the present invention provides a membrane electrode for water electrolysis, wherein the anode catalyst layer of the membrane electrode comprises: the anode catalyst described above.

[0017] Preferably, the cathode catalyst layer of the membrane electrode comprises: a Pt / c catalyst.

[0018] The third aspect of the present invention provides a method for preparing a membrane electrode for water electrolysis, wherein the method for preparing an anode catalyst layer in the membrane electrode comprises:

[0019] The anode catalyst is mixed with Nafion (5%) solution, n-propanol and deionized water, and ultrasonically dispersed and homogenized to obtain an anode slurry;

[0020] Applying the anode slurry on one side of the proton membrane;

[0021] The mass ratio of the anode catalyst, the Nafion (5%) solution, the n-propanol and the deionized water is 1:(3-15):(10-25):(10-20).

[0022] Preferably, the method for preparing the cathode catalyst layer in the membrane electrode comprises:

[0023] The cathode catalyst is mixed with Nafion (5%) solution, n-propanol and water, and ultrasonically dispersed and homogenized to obtain a cathode slurry;

[0024] Applying the cathode slurry to the other side of the proton membrane;

[0025] The cathode catalyst includes: a Pt / c catalyst.

[0026] The mass ratio of the cathode catalyst, the Nafion (5%) solution, the n-propanol and the water is 1:(3-15):(10-25):(10-20).

[0027] Specifically, the water can be double distilled water, ultrapure water, purified water or deionized water.

[0028] More preferably, the mass ratio of the anode catalyst, the Nafion (5%) solution, the n-propanol and the deionized water is 1:8:25:20;

[0029] The mass ratio of the cathode catalyst, the Nafion (5%) solution, the n-propanol and the deionized water is 1:12:25:20.

[0030] Preferably, the coating comprises: drying or hot pressing;

[0031] The drying temperature is 60-140° C., and the drying time is 0.5-2 hours.

[0032] It is understandable that after the anode slurry and the cathode slurry are coated, the membrane electrode for electrolyzed water is dried or hot-pressed.

[0033] A fourth aspect of the present invention provides the use of the membrane electrode for electrolysis of water or the membrane electrode for electrolysis of water obtained by the above preparation method in electrolysis of water.

[0034] A fifth aspect of the present invention provides a PEM electrolyzer, comprising: the membrane electrode for water electrolysis described above or the membrane electrode for water electrolysis obtained by the above preparation method.

[0035] It can be seen from the above technical solutions that the present invention has the following advantages:

[0036] The invention provides an anode catalyst layer of a membrane electrode for electrolyzing water, wherein the anode catalyst on the anode catalyst layer comprises an iridium-containing catalyst and cerium dioxide. In this scheme, cerium dioxide is directly added to the anode catalyst, and cerium dioxide in the anode catalyst is used to react with hydrogen to generate water, thereby achieving the removal of hydrogen on the anode side of the membrane electrode. The membrane electrode can be used for electrolyzing water and can effectively eliminate hydrogen on the anode side, thereby improving the purity of oxygen in the electrolyzed water. The preparation process is simple, and the cost of removing hydrogen is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0038] Figure 1 This is a polarization curve diagram of the membrane electrode performance test provided by the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0040] In order to improve the safety of electrolytic cell operation and improve the purity of the product, a dehydrogenation layer can be separately provided in the membrane electrode, and the catalyst in the dehydrogenation layer can be used to catalyze the hydrogen and oxidation reaction to generate water, so as to achieve the purpose of removing hydrogen. The anode catalyst of the membrane electrode for electrolysis of water and the membrane electrode provided in the embodiments of the present application can further improve the purity of the electrolysis water product and have a lower preparation difficulty or cost.

[0041] The raw materials and reagents used in the following examples are all commercially available or homemade.

[0042] Example 1

[0043] This embodiment provides a first anode catalyst layer and a first membrane electrode for water electrolysis.

[0044] The anode catalyst in the first anode catalyst layer is: iridium oxide and cerium dioxide, wherein the mass ratio of metal elements in IrO2 and CeO2 (ie, the mass ratio of Ir to Ce) is 18:2.

[0045] The first method for preparing a membrane electrode for water electrolysis is as follows:

[0046] According to the ratio, an appropriate amount of the first anode catalyst is weighed, and then deionized water, Nafion solution and n-propanol are added in sequence according to the ratio to obtain a mixture, and then the mixture is ultrasonicated for 10-60 minutes using an ultrasonic disperser, and then the slurry is homogenized for 10-60 minutes using a homogenizer to obtain an anode slurry. The weight ratio of the anode catalyst to the Nafion (5%) solution, n-propanol and deionized water is 1:8:18:15.

[0047] According to the ratio, a proper amount of cathode catalyst is weighed, and then deionized water, Nafion solution and n-propanol are added in sequence according to the ratio to obtain a mixture, and then the mixture is ultrasonicated for 10-60 minutes with an ultrasonic disperser, and then the slurry is homogenized for 10-60 minutes with a homogenizer to obtain an anode slurry. Among them, the cathode catalyst is a Pt / c catalyst, and the Pt loading is 50wt.%; the weight ratio of the cathode catalyst to the Nafion (5%) solution, n-propanol, and deionized water is 1:8:18:15.

[0048] Add the prepared cathode slurry to the spraying equipment and evenly apply the cathode slurry on one side of the previously treated proton membrane. Then turn the proton membrane over and add the prepared anode slurry to the spraying equipment and evenly apply the anode slurry on the other side of the proton membrane. The total metal loading of the anode catalyst is 2.5 mg / cm 2 The total metal loading of the cathode catalyst is 1.0 mg / cm 2 .

[0049] The prepared membrane electrode is placed in a vacuum oven, treated at 60-140° C. for 0.5-2 hours, and then taken out to obtain a membrane electrode for water electrolysis.

[0050] The membrane electrode in this embodiment is used for water electrolysis at a temperature of 60°C and 1A / cm 2 Under the test conditions of current density, the cathode cell gas pressure was measured to be 3.5MPa, the single cell voltage was 1.92V, and the hydrogen content in the oxygen on the anode side of the membrane electrode was 1987ppm.

[0051] In this embodiment, cerium dioxide is directly mixed into the anode catalyst. When preparing the membrane electrode, the anode catalyst layer is formed by a spraying process. There is no need to prepare an additional dehydrogenation layer. The preparation process is simple and has a good dehydrogenation effect, which can effectively improve the purity of oxygen in electrolyzed water.

[0052] Example 2

[0053] This embodiment provides a second anode catalyst layer and a second membrane electrode for water electrolysis. The membrane electrode preparation method is the same as that in Example 1, except that the anode catalyst in the second anode catalyst layer is iridium oxide, cerium dioxide and platinum, wherein the mass ratio of the metal elements in IrO2, CeO2 and Pt is 18:2:5.

[0054] The membrane electrode in this embodiment is used for water electrolysis at a temperature of 60°C and 1A / cm 2 Under the current density test conditions, the cathode cell gas pressure was measured to be 3.5MPa, the single cell voltage was 1.86V, and the hydrogen content in the oxygen on the anode side of the membrane electrode was 2036ppm.

[0055] Example 3

[0056] This embodiment provides a third anode catalyst layer and a third membrane electrode for water electrolysis. The membrane electrode preparation method is the same as that in Example 1, except that the anode catalyst in the third anode catalyst layer is: iridium oxide, cerium dioxide and platinum, wherein the mass ratio of the metal elements in IrO2, CeO2 and Pt is 15:1:2.

[0057] The membrane electrode in this embodiment is used for water electrolysis at a temperature of 60°C and 1A / cm 2 Under the test conditions of current density (the same as the test conditions in Example 1), the cathode cell gas pressure was measured to be 3.5 MPa, the single cell voltage was 1.91 V, and the hydrogen content in the oxygen on the anode side of the membrane electrode was 3504 ppm.

[0058] Example 4

[0059] This embodiment provides a fourth anode catalyst layer and a fourth membrane electrode for water electrolysis. The membrane electrode preparation method is the same as that in Example 1, except that the anode catalyst in the fourth anode catalyst layer is: iridium oxide, cerium dioxide and platinum, wherein the mass ratio of the metal elements in IrO2, CeO2 and Pt is 20:4:8.

[0060] The membrane electrode in this embodiment is used for water electrolysis at a temperature of 60°C and 1A / cm 2 Under the test conditions of current density (the same as the test conditions in Example 1), the cathode cell gas pressure was measured to be 3.5 MPa, the single cell voltage was 1.89 V, and the hydrogen content in the oxygen on the anode side of the membrane electrode was 2017 ppm.

[0061] Comparative Example 1

[0062] This comparative example provides a membrane electrode, the preparation method is the same as that of Example 1, except that the anode catalyst is iridium oxide. The metal element loading is 2.5 mg / cm 2 .

[0063] The membrane electrode in this comparative example was used for electrolysis of water. Under the operating temperature of 60°C and the current density test conditions of 1A / cm2 (the same test conditions as in Example 1), the cathode cell gas pressure was measured to be 3.5MPa, the single cell voltage was 1.82V, and the hydrogen content in the oxygen on the anode side of the membrane electrode was 8519ppm.

[0064] Comparative Example 2

[0065] This comparative example provides another membrane electrode, and the preparation method is different from that of Example 1 in that the preparation of the anode catalyst layer is different.

[0066] The anode catalyst layer in this comparative example is: first prepare CeO2 catalyst, spray a layer of CeO2 catalyst onto the proton membrane, and the metal element loading is 0.25 mg / cm 2 ; Then spray a layer of IrO2 catalyst, the metal element loading is 2.25mg / cm 2 .

[0067] The preparation method of CeO2 catalyst is as follows: nanometer-scale CeO2 is mixed with Nafion (5%) solution, n-propanol and deionized water in a weight ratio of 1: (3-15): (10-25): (10-20), and then the mixture is ultrasonicated for 40 minutes by an ultrasonic disperser, and then the slurry is homogenized for 50 minutes by a homogenizer to obtain CeO2 catalyst. The preparation method of IrO2 catalyst is as follows: nanometer-scale IrO2 is mixed with Nafion (5%) solution, n-propanol and deionized water in a weight ratio of 1: 8: 15: 15, and then the mixture is ultrasonicated for 40 minutes by an ultrasonic disperser, and then the slurry is homogenized for 50 minutes by a homogenizer to obtain IrO2 catalyst.

[0068] The membrane electrode in this comparative example is used for water electrolysis at an operating temperature of 60°C and a current of 1A / cm 2 Under the current density test conditions (the same as the test conditions in Example 1), the cathode cell gas pressure was measured to be 3.5 MPa, the single cell voltage was 1.98 V, and the hydrogen content in the oxygen on the anode side of the membrane electrode was 2997 ppm.

[0069] According to the test results, this comparative example adopts a single hydrogen removal layer, which not only has a complicated preparation process and significantly increases the single cell voltage, but also has a worse effect of removing hydrogen than Example 1 in which cerium dioxide is directly added to the anode catalyst layer.

[0070] Test Case

[0071] This test example tests the use effects and performance of the membrane electrodes prepared in Examples 1-4 and Comparative Example 1 as follows:

[0072] (1) The membrane electrodes of Examples 1-4 and Comparative Example 1 were used for electrolysis of water. The results of the single cell voltage and the hydrogen content in the oxygen on the anode side are shown in Table 1.

[0073] Table 1. Effects of using membrane electrodes in Examples 1-4 and Comparative Example 1 for electrolysis of water

[0074]

[0075] Note: The mass ratio of metal elements in IrO2, CeO2 and Pt in Examples 1-4 in Table 1.

[0076] According to Table 1, the membrane electrode for water electrolysis prepared by adding CeO2 in Examples 1-4 has a significantly improved effect of removing hydrogen from oxygen compared with the membrane electrode for water electrolysis prepared by the comparative example without adding CeO2. When the membrane electrodes of Examples 1-4 are used for water electrolysis, the hydrogen content in oxygen is reduced by 50% compared with the comparative example 1, indicating that the present invention significantly improves the efficiency of removing hydrogen from oxygen at the anode of the membrane electrode by directly adding cerium dioxide to the anode catalyst. When the membrane electrode for water electrolysis prepared by adding Pt in Example 2 is used for water electrolysis, the membrane voltage of a single cell is reduced from 1.92V to 1.86V compared with Example 1 without adding Pt, indicating that the present invention adds platinum to the anode catalyst, offsets the effect of cerium dioxide on the cell voltage, and improves the use effect of the membrane electrode for water electrolysis.

[0077] (2) The performance of the membrane electrode of Example 1-2 and Comparative Example 1-2 was tested. The test method was as follows: the membrane electrode was fixed on a fixture, the water electrolysis temperature was 60 degrees Celsius, and the current density was increased from 0 A / cm 2 Increased to 3.2A / cm 2 To record the polarization curve, keep it at each point for 15 minutes. The polarization curve is as follows Figure 1 shown.

[0078] according to Figure 1 It can be seen that the performance curves of Examples 1-2 of the present invention are between Comparative Example 1 and Comparative Example 2, especially the performance curve of Example 2. Under the same current density, the single cell voltage is not much different from that of Comparative Example 1. For example, at 1 A / cm 2 Under the current density, the single cell voltage of Example 2 is 1.86V, and the single cell voltage of Comparative Example 1 is 1.82V. It can be concluded that with a small loss of membrane electrode performance, the hydrogen content in the oxygen on the anode side is greatly reduced, and the iridium loading is also reduced, thereby reducing the membrane electrode manufacturing cost.

[0079] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An anode catalyst layer of a membrane electrode for water electrolysis, characterized in that: include: an anode catalyst; the anode catalyst comprising cerium dioxide, platinum and an iridium-containing catalyst; The iridium-containing catalyst comprises one or more of pure iridium or iridium-containing metal oxides; The mass ratio of iridium, cerium and platinum in the anode catalyst is (15-20): (1-4): (2-8).

2. A membrane electrode for water electrolysis, characterized in that: The anode catalyst layer of the membrane electrode comprises: the anode catalyst according to claim 1.

3. The membrane electrode for water electrolysis according to claim 2, characterized in that: The cathode catalyst layer of the membrane electrode comprises: a Pt / c catalyst.

4. A method for preparing a membrane electrode for water electrolysis, characterized in that: The method for preparing the anode catalyst layer in the membrane electrode comprises: The anode catalyst according to claim 1 is mixed with 5% Nafion solution, n-propanol and deionized water, and ultrasonically dispersed and homogenized to obtain an anode slurry; Applying the anode slurry on one side of the proton membrane; The mass ratio of the anode catalyst, the 5% Nafion solution, the n-propanol and the water is 1:(3-15):(10-25):(10-20).

5. The method for preparing a membrane electrode for water electrolysis according to claim 4, characterized in that: The method for preparing the cathode catalyst layer in the membrane electrode comprises: The Pt / c catalyst is mixed with 5% Nafion solution, n-propanol and deionized water, and ultrasonically dispersed and homogenized to obtain a cathode slurry; Applying the cathode slurry to the other side of the proton membrane; The mass ratio of the Pt / c catalyst, the 5% Nafion solution, the n-propanol and the deionized water is 1:(3-15):(10-25):(10-20).

6. The method for preparing a membrane electrode for water electrolysis according to claim 5, characterized in that: After the coating, the steps include: drying or hot pressing; The drying temperature is 60-140° C., and the drying time is 0.5-2 hours.

7. Use of a membrane electrode for water electrolysis as claimed in any one of claims 2 to 3 or a membrane electrode for water electrolysis obtained by the preparation method as claimed in any one of claims 5 to 6 in electrolysis of water.

8. A PEM electrolyzer, characterized in that: It comprises the membrane electrode for water electrolysis as described in any one of claims 2 to 3 or the membrane electrode for water electrolysis prepared by the preparation method as described in any one of claims 4 to 6.

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