Preparation method of anode catalyst slurry of PEM electrolyzed water, slurry and catalytic layer

Abstract

The invention relates to the technical field of hydrogen production by electrolyzing water, and provides a preparation method of anode catalyst slurry of PEM electrolyzed water, slurry and a catalytic layer.The preparation method comprises the steps that S1, an anode catalyst, a first ionomer and a first solvent are mixed and dispersed, and first catalyst slurry is obtained; s2, mixing and dispersing a dehydrogenation catalyst, a second ionomer and a second solvent to obtain second catalyst slurry; the dehydrogenation catalyst is a carbon-supported noble metal catalyst; and S3, mixing the first catalyst slurry and the second catalyst slurry, and carrying out homogenization treatment to obtain the anode catalyst slurry. The method has the advantages that the effects of improving uniformity, improving mass transfer and reducing hydrogen in oxygen are achieved at the same time through the cooperative arrangement of the adding of the hydrogen elimination additive, the slurry preparation process steps and the like, and the performance and the safety of the membrane electrode are improved.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, and more specifically, to a method for preparing an anode catalyst slurry for PEM water electrolysis, as well as the slurry and catalyst layer. Background Technology

[0002] Proton exchange membrane (PEM) water electrolysis technology is considered a promising green hydrogen production technology due to its high efficiency, fast response, and ability to be coupled with renewable energy sources. However, its anodic oxygen evolution reaction (OER) kinetics are slow and heavily reliant on precious metal iridium (Ir)-based catalysts. The high cost of these catalysts is one of the main bottlenecks restricting the large-scale commercial application of PEM electrolyzers. Therefore, developing a high-performance anode catalyst layer with low iridium loading is crucial.

[0003] Reducing the iridium loading leads to a thinner catalyst layer, posing a series of technical challenges: First, during slurry coating, the thin wet film with low iridium loading is difficult to form a uniform, defect-free thin layer, affecting the consistency of the membrane electrode; Second, during operation, the thin catalyst layer has insufficient pore structure and mass transfer capacity, especially at high current densities, making it difficult to expel bubbles, resulting in increased mass transfer polarization and a sharp decline in performance; Third, the thin catalyst layer with low iridium loading may not be able to effectively suppress the reverse permeation of hydrogen, leading to a high hydrogen content in the anode oxygen, which poses a safety hazard.

[0004] Existing technologies attempt to address the aforementioned problems through various approaches. For example, some patents (such as CN116397265A) propose using layered preparation of catalyst loading and adding substances such as sulfonated silica to construct a gradient catalyst layer, thereby improving proton transport and catalyst utilization. Other patents (such as CN119121287A and CN120330747A) propose adding conductive noble metals such as platinum black and platinum nanowires to the catalyst layer to enhance its electronic conductivity and improve electrical contact with the PTL. Further research has attempted to use pore-forming agents (such as ammonium carbonate) to increase the porosity of the catalyst layer.

[0005] However, these methods all have certain limitations. Adding static pore-forming agents or conductive materials cannot dynamically optimize the pore structure during operation and may cover active sites or increase costs. Gradient design can optimize transport, but the process is complex and fails to solve the fundamental problem of coating uniformity with low iridium loading. More importantly, existing technologies do not address how to actively utilize the high-potential environment during electrolyzer operation to "activate" the catalyst layer, nor do they synergistically integrate the functions of improving mass transfer and eliminating safety hazards (reducing hydrogen in oxygen). Summary of the Invention

[0006] The present invention aims to overcome at least one defect (deficiency) of the prior art and provides a method for preparing an anode catalyst slurry for PEM water electrolysis, as well as the slurry and catalyst layer, to improve the performance of the anode catalyst layer under low iridium loading.

[0007] One object of the present invention is to provide a method for preparing an anode catalyst slurry for PEM water electrolysis, comprising the following steps: S1. Mix and disperse the anode catalyst, the first ionomer, and the first solvent to obtain the first catalyst slurry; S2. Mix and disperse the hydrogen removal catalyst, the second ionomer, and the second solvent to obtain a second catalyst slurry; the hydrogen removal catalyst is a carbon-supported noble metal catalyst. S3. Mix the first catalyst slurry and the second catalyst slurry and homogenize them to obtain the anode catalyst slurry.

[0008] In this technical solution, the anode catalyst is an iridium-based catalyst, including but not limited to at least one of iridium black, iridium oxide, supported iridium oxide, and alloy-type iridium-based catalysts. The carbon-supported noble metal includes but is not limited to Pt / C.

[0009] The carbon support of the hydrogen removal catalyst in this invention is easily corroded under high-potential operating conditions, that is, it will be gradually oxidized and corroded in the early stage of electrolyzer operation. It is equivalent to a "self-sacrificing" pore-forming template, which can form a large number of micro-nano pores in situ within the catalyst layer, significantly enhancing the mass transfer capacity of reactants and products, and is particularly beneficial for performance improvement under high current density.

[0010] After the carbon support in the hydrogen removal catalyst is corroded, the noble metal originally supported on it is exposed and firmly embedded in the catalyst layer, serving as an excellent hydrogen removal catalyst. It can efficiently catalyze the combination of hydrogen and oxygen that penetrates through to form water, thereby significantly reducing the hydrogen content in the anode oxygen, eliminating safety hazards, and improving the reliability of system operation.

[0011] Furthermore, the I / C ratio in the first catalyst slurry is lower than that in the second catalyst slurry. Preferably, the I / C mass ratio in the first catalyst slurry is 0.05 to 0.5, and the I / C mass ratio in the second catalyst slurry is 0.6 to 2.0.

[0012] In this technical solution, the mass ratio of ionomer to anode catalyst in the first catalyst slurry is 0.05~0.5, for example, 0.2, 0.3, or 0.4; the mass ratio of ionomer to carbon support in the second catalyst slurry is 0.6~2.0, for example, 1 or 1.5. If the anode catalyst and the hydrogen removal catalyst are uniformly dispersed in the ionomer with the same I / C ratio, when the I / C ratio is low, although the ratio requirement for the iridium-based catalyst is met, the hydrogen removal catalyst will severely agglomerate due to insufficient ionomer coating, resulting in uneven corrosion of the subsequent carbon support and uneven dispersion of the formed mass transfer pores. When the I / C ratio is high, although the ratio requirement for the hydrogen removal catalyst is met, excessive ionomers will cover the active sites of the iridium-based catalyst, increase the ohmic resistance of the anode catalyst layer, and cause a significant decrease in anode catalytic performance.

[0013] Therefore, this scheme uses a two-step method to prepare the slurry separately and then mix them, so that the anode catalyst and the hydrogen removal catalyst can be matched with their respective optimal I / C ratios, which takes into account the full utilization of the catalytic performance of the anode catalyst and the high dispersion of the hydrogen removal catalyst, laying the foundation for subsequent uniform pore formation.

[0014] Furthermore, in step S2, the carbon support of the hydrogen removal catalyst is graphitized, and the specific surface area of ​​the hydrogen removal catalyst is less than 300 m². 2 / g. In this technical solution, the carbon support is a graphitized carbon material with a low specific surface area. This type of carbon material has high stability and is not easily removed quickly in a short time, thus avoiding the collapse of the low-iridium catalyst layer structure and catalyst loss caused by rapid removal of the carbon material. Preferably, the degree of graphitization of the carbon support is 0.001~0.7, the graphitization temperature is 2000~3000℃, and the specific surface area of ​​the hydrogen removal catalyst is 50 m². 2 / g ~250 m 2 / g.

[0015] Furthermore, the mass fraction of noble metal in the hydrogen elimination catalyst is 5 to 60 wt%, for example, 20 wt%, 40 wt%, or 50 wt%. Furthermore, both the first solvent and the second solvent are selected from at least one of water, isopropanol, n-propanol, ethanol, methanol, tert-butanol, ethylene glycol, glycerol, ethoxyethanol, and methoxyethanol.

[0016] Furthermore, both the first ionomer and the second ionomer are selected from at least one of perfluorosulfonic acid resin, partially fluorinated sulfonic acid resin, non-fluorinated sulfonic acid resin, and hydrocarbon resin.

[0017] Another object of the present invention is to provide an anode catalyst slurry for PEM water electrolysis, wherein the anode catalyst slurry is prepared by any of the above-described preparation methods.

[0018] Another object of the present invention is to provide an anode catalyst layer for PEM water electrolysis, wherein the anode catalyst layer is prepared from any of the above-mentioned anode catalyst slurries, the anode catalyst is an iridium-based catalyst, and the hydrogen removal catalyst is a platinum-based catalyst. In step S3, the first catalyst slurry and the second catalyst slurry are mixed in a preset ratio, wherein the preset ratio satisfies the following condition: the mass ratio of iridium in the first catalyst slurry to platinum in the second catalyst slurry is equal to the ratio of iridium loading to platinum loading in the anode catalyst layer.

[0019] Furthermore, the iridium loading of the anode catalyst layer is 10~2000 µg / cm³. 2 Platinum loading is 5~200 µg / cm³ 2 For example, the iridium loading of the anode catalyst layer is 400 µg / cm³. 2 800µg / cm 2 1200µg / cm 2 Or 1600µg / cm 2 etc.; the platinum loading is 50 µg / cm³. 2 100µg / cm 2 Or 150µg / cm 2 wait.

[0020] In this technical solution, an appropriate platinum loading not only creates sufficient porosity to improve mass transfer and increases the thickness of the anode catalyst layer to optimize coating quality, but also avoids excessive collapse of the catalyst layer due to excessive carbon corrosion, achieving an optimal balance between performance and durability. Furthermore, it prevents excessive Pt content from increasing heat generation during the hydrogen elimination reaction, thus avoiding thermal degradation of the membrane electrode material and unnecessary cost increases.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The carbon support of the hydrogen removal catalyst in this invention is easily corroded in a high potential operating environment. That is, it will be gradually oxidized and corroded in the early stage of operation of the electrolyzer. It is equivalent to a "self-sacrificing" pore-forming template, which can form a large number of micro-nano pores in situ in the catalyst layer, significantly enhancing the mass transfer capacity of reactants and products, and is particularly beneficial to the performance improvement under high current density.

[0022] (2) In this invention, after the carbon support in the hydrogen removal catalyst is corroded, the noble metal originally loaded on it is exposed and firmly embedded in the catalyst layer, serving as an excellent hydrogen removal catalyst. It can efficiently catalyze the combination of hydrogen and oxygen that penetrates through to form water, thereby significantly reducing the hydrogen content in the anode oxygen, eliminating safety hazards, and improving the reliability of system operation.

[0023] (3) In this invention, the method of preparing the slurry in two separate steps and then mixing them allows the anode catalyst and the hydrogen removal catalyst to match their respective optimal I / C ratios, taking into account both the full utilization of the catalytic performance of the anode catalyst and the high dispersion of the hydrogen removal catalyst, thus laying the foundation for subsequent uniform pore formation.

[0024] (4) By adding hydrogen removal additives, adjusting the slurry preparation process, and coordinating I / C settings, this invention simultaneously improves uniformity, mass transfer, and reduces hydrogen in oxygen, thereby enhancing the performance and safety of the membrane electrode. Attached Figure Description

[0025] Figure 1 The images show cross-sectional SEM images of the anode catalyst layers in Examples 1, 1, and 3.

[0026] Figure 2 For Example 1 and Comparative Example 4, at 3A / cm 2 The graph shows the change of voltage over time. Detailed Implementation

[0027] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate the following embodiments, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0028] One object of the present invention is to provide a method for preparing an anode catalyst slurry for PEM water electrolysis, comprising the following steps: S1. Mix and disperse the anode catalyst, the first ionomer, and the first solvent to obtain the first catalyst slurry; S2. Mix and disperse the hydrogen removal catalyst, the second ionomer, and the second solvent to obtain a second catalyst slurry; the hydrogen removal catalyst is a carbon-supported noble metal catalyst. S3. Mix the first catalyst slurry and the second catalyst slurry and homogenize them to obtain the anode catalyst slurry.

[0029] Furthermore, the I / C ratio in the first catalyst slurry is lower than that in the second catalyst slurry. Preferably, the I / C mass ratio in the first catalyst slurry is 0.05~0.5; and the I / C mass ratio in the second catalyst slurry is 0.6~2.0.

[0030] Furthermore, in step S2, the carbon support of the hydrogen removal catalyst is graphitized, and the specific surface area of ​​the hydrogen removal catalyst is less than 300 m². 2 / g. Furthermore, the mass fraction of noble metal in the hydrogen elimination catalyst is 5 to 60 wt%, for example, 20 wt%, 40 wt%, or 50 wt%. Furthermore, both the first solvent and the second solvent are selected from at least one of water, isopropanol, n-propanol, ethanol, methanol, tert-butanol, ethylene glycol, glycerol, ethoxyethanol, and methoxyethanol.

[0031] Furthermore, both the first ionomer and the second ionomer are selected from at least one of perfluorosulfonic acid resin, partially fluorinated sulfonic acid resin, non-fluorinated sulfonic acid resin, and hydrocarbon resin.

[0032] Another object of the present invention is to provide an anode catalyst slurry for PEM water electrolysis, wherein the anode catalyst slurry is prepared by any of the above preparation methods.

[0033] Another object of the present invention is to provide an anode catalyst layer for PEM water electrolysis, wherein the anode catalyst layer is prepared from any of the above-mentioned anode catalyst slurries, the anode catalyst is an iridium-based catalyst, and the hydrogen removal catalyst is a platinum-based catalyst. In step S3, the first catalyst slurry and the second catalyst slurry are mixed in a preset ratio, wherein the preset ratio satisfies the following condition: the mass ratio of iridium in the first catalyst slurry to platinum in the second catalyst slurry is equal to the ratio of iridium loading to platinum loading in the anode catalyst layer.

[0034] Furthermore, the iridium loading of the anode catalyst layer is 10-2000 µg / cm³. 2 Platinum loading is 5-200 µg / cm³ 2 .

[0035] Another object of the present invention is to provide a membrane electrode for PEM water electrolysis, the membrane electrode comprising the above-described anode catalyst layer.

[0036] Another object of the present invention is to provide an application of the above-described membrane electrode in a PEM electrolyzer.

[0037] The following are specific examples.

[0038] Example 1 This embodiment provides a method for preparing a catalyst-coated membrane for PEM water electrolysis, including the following steps: S1. Preparation of OER catalyst slurry: Iridium oxide catalyst, perfluorosulfonic acid resin dispersion, water and isopropanol solvent are mixed, wherein the mass ratio of perfluorosulfonic acid resin to iridium oxide catalyst is set to 0.2. After ball milling dispersion treatment, OER catalyst slurry is obtained.

[0039] S2. Preparation of Platinum-Carbon Catalyst Slurry: A Pt / C catalyst (50 wt% Pt), perfluorosulfonic acid resin dispersion, water, and isopropanol solvent were mixed, with the mass ratio of perfluorosulfonic acid resin to the carbon support in the Pt / C catalyst set at 1.1. After ball milling dispersion, a platinum-carbon catalyst slurry was obtained. The carbon support in the Pt / C catalyst underwent graphitization treatment at a temperature of 2500℃ to a degree of graphitization of 0.5. The BET specific surface area of ​​the Pt / C catalyst was 100 m². 2 / g.

[0040] S3. Mixing the slurry: Mix the two slurries prepared in steps 1 and 2 in a certain proportion, wherein the mass ratio of iridium in the OER catalyst slurry to platinum in the platinum-carbon catalyst slurry is 3. Continue ball milling the mixed slurry for 30 minutes to ensure that the two are fully mixed and uniform, to obtain the final anode catalyst layer slurry.

[0041] S4. Coating and Forming: Using slit coating technology, the final slurry is uniformly coated onto the proton exchange membrane, and after drying, an anode catalyst layer is formed. The target iridium loading is 300 µg / cm², and the Pt loading is 100 µg / cm². Subsequently, a cathode catalyst layer is coated on the other side to obtain a complete catalyst coating membrane (CCM).

[0042] Comparative Example 1 (prepared without pulping, uniformly low I / C ratio) This comparative example provides a method for preparing a catalyst-coated membrane for PEM water electrolysis, comprising the following steps: Weigh out the same amount of iridium-based catalyst and Pt / C catalyst as in Example 1, and physically mix them. Use the same low I / C ratio as in the iridium-based slurry in Example 1, i.e., the mass ratio of resin to catalyst (iridium oxide + Pt / C) is 0.2. Add perfluorosulfonic acid resin, water, and isopropanol, and disperse the mixture in the same manner to obtain the slurry. Use the same preparation method to prepare the anode catalyst layer and further prepare the catalyst coating film.

[0043] Comparative Example 2 (prepared without pulping, uniformly high I / C ratio) This comparative example provides a method for preparing a catalyst-coated membrane for PEM water electrolysis, comprising the following steps: Weigh out the same catalyst as in Example 1 and mix physically. Use the same high I / C ratio as the Pt / C slurry in Example 1, that is, the mass ratio of resin to catalyst (iridium oxide + Pt / C) is 0.55 (convert the resin to carbon support ratio to the resin to Pt / C catalyst mass ratio). Add perfluorosulfonic acid resin, water and isopropanol, and disperse in the same way to obtain a slurry. Use the same preparation method to prepare the anode catalyst layer and further prepare the catalyst coating film.

[0044] Comparative Example 3 (without Pt / C, serving as a blank control) This comparative example provides a method for preparing a catalyst-coated membrane for PEM water electrolysis, which differs from Example 1 in that Pt / C is not added.

[0045] Comparative Example 4 (using Pt / C with ungraphitized carbon support and high BET specific surface area) This comparative example provides a method for preparing a catalyst-coated membrane for PEM water electrolysis, which differs from Example 1 in that: The carbon support in Pt / C was not graphitized, and the BET specific surface area of ​​Pt / C was 330 m². 2 / g.

[0046] Comparative Example 5 (prepared as a slurry, but with a high I / C ratio in the platinum-carbon catalyst slurry). This comparative example provides a method for preparing a catalyst-coated membrane for PEM water electrolysis, which differs from Example 1 in that: The mass ratio of perfluorosulfonic acid resin to carbon support in the Pt / C catalyst was set to 2.1.

[0047] The catalyst coating films obtained in Example 1 and Comparative Examples 1-5 were further assembled into membrane electrodes for performance testing. The performance testing and effect verification are described below.

[0048] (1) Coating quality: Figure 1 The SEM images show that the anode catalyst layer of Example 1 has a uniform thickness and good Pt / C dispersion; obvious Pt / C agglomerates are visible in Comparative Example 1 (as shown by the red circles in the figure); the anode catalyst layer of Comparative Example 3 is thinner overall, with poor uniformity, and the thickness of the catalyst layer is very uneven, with some uncoated areas even visible.

[0049] (2) Electrolysis performance: The results are shown in Table 1. At a high current density of 3 A / cm², the voltage of Example 1 is lower than that of Comparative Example 3, indicating that its mass transfer performance is optimal. The voltage of Comparative Example 2 is higher, indicating that its OER activity is suppressed. The voltage of Comparative Example 4 is significantly higher than that of Example 1, indicating that the rapid corrosion of the carbon support leads to the collapse of the catalyst layer structure and the loss of OER catalyst, making the performance of Comparative Example 4 worse than that of Example 1. The voltage of Comparative Example 5 is significantly higher than that of Example 1. This is because, on the one hand, the specific surface area of ​​the highly graphitized carbon support is low, and too much ionomer will make the ionomer cover the carbon support surface too thickly, resulting in poor electronic conductivity of Pt / C / ionomer agglomerates and increasing the ohmic resistance of the anode catalyst layer; on the other hand, when the carbon support is removed during operation, too much ionomer will continue to remain in the anode catalyst layer, blocking the electronic connection pathway and increasing the ohmic resistance of the catalyst layer.

[0050] Table 1. Voltage Comparison Table between Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5

[0051] (3) Stability: Figure 2 For Example 1 and Comparative Example 4, at 3A / cm 2 The voltage variation over time is shown in the figure. As can be seen from the figure, Example 1, using Pt / C with graphitized carbon support and low BET specific surface area, exhibits a more stable voltage due to the better corrosion resistance of the carbon support, slower carbon support removal, and less impact on the catalyst layer structure. In contrast, Comparative Example 4, using Pt / C with ungraphitized carbon support and high BET specific surface area, suffers from rapid carbon support corrosion during operation, leading to catalyst layer structure collapse and OER catalyst loss, resulting in a voltage of 3 A / cm². 2 The voltage gradually increases.

[0052] (4) Hydrogen content in oxygen: The results are shown in Table 2. At 0.6 A / cm 2 Under a cathode back pressure of 30 bar, the hydrogen concentration in the oxygen at the anode outlet was measured. The hydrogen concentration in the oxygen of Example 1 (<0.1%) was significantly lower than that of Comparative Example 3 (0.25%), which verified its excellent hydrogen removal ability.

[0053] Table 2 Comparison of hydrogen in oxygen in Example 1 and Comparative Example 3

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an anode catalyst slurry for PEM water electrolysis, characterized in that, Includes the following steps: S1. Mix and disperse the anode catalyst, the first ionomer, and the first solvent to obtain the first catalyst slurry; S2. Mix and disperse the hydrogen removal catalyst, the second ionomer, and the second solvent to obtain a second catalyst slurry; the hydrogen removal catalyst is a carbon-supported noble metal catalyst. S3. Mix the first catalyst slurry and the second catalyst slurry and homogenize them to obtain the anode catalyst slurry.

2. The method for preparing the anode catalyst slurry for PEM water electrolysis according to claim 1, characterized in that, The I / C ratio in the first catalyst slurry is lower than that in the second catalyst slurry.

3. The method for preparing the anode catalyst slurry for PEM water electrolysis according to claim 2, characterized in that, The I / C mass ratio in the first catalyst slurry is 0.05~0.5, and the I / C mass ratio in the second catalyst slurry is 0.6~2.

0.

4. The method for preparing the anode catalyst slurry for PEM water electrolysis according to claim 1, characterized in that, In step S2, the carbon support of the hydrogen removal catalyst is graphitized, and the specific surface area of ​​the hydrogen removal catalyst is less than 300 m². 2 / g.

5. The method for preparing the anode catalyst slurry for PEM water electrolysis according to claim 1, characterized in that, The mass fraction of noble metals in the hydrogen removal catalyst is 5-60 wt%.

6. The method for preparing the anode catalyst slurry for PEM water electrolysis according to claim 1, characterized in that, The first solvent and the second solvent are both selected from at least one of water, isopropanol, n-propanol, ethanol, methanol, tert-butanol, ethylene glycol, glycerol, ethoxyethanol, and methoxyethanol.

7. The method for preparing the anode catalyst slurry for PEM water electrolysis according to claim 1, characterized in that, The first ionomer and the second ionomer are both selected from at least one of perfluorosulfonic acid resin, partially fluorinated sulfonic acid resin, non-fluorinated sulfonic acid resin and hydrocarbon resin.

8. An anode catalyst slurry for PEM water electrolysis, characterized in that, The anode catalyst slurry is prepared by any one of the preparation methods described in claims 1 to 7.

9. An anode catalyst layer for PEM water electrolysis, characterized in that, The anode catalyst layer is prepared from the anode catalyst slurry according to claim 8. The anode catalyst is an iridium-based catalyst and the hydrogen removal catalyst is a platinum-based catalyst. In step S3, the first catalyst slurry and the second catalyst slurry are mixed in a preset ratio. The preset ratio satisfies the following condition: the mass ratio of iridium in the first catalyst slurry to platinum in the second catalyst slurry is equal to the ratio of iridium loading to platinum loading in the anode catalyst layer.

10. The anode catalyst layer according to claim 9, characterized in that, The iridium loading of the anode catalyst layer is 10~2000 µg / cm³. 2 Platinum loading is 5-200 µg / cm³ 2 .

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