Anode catalyst layer for PEM water electrolysis and its preparation method, membrane electrode

Abstract

This invention provides a method for preparing an anode catalyst layer for PEM water electrolysis. By doping additives into the catalyst layer, not only are proton transport channels between catalysts constructed, reducing the proton transport impedance between catalysts and improving the electrochemical reaction rate, but the additives also disperse the catalyst, exposing more active sites, increasing catalyst utilization, and improving the performance of PEM water electrolysis. Furthermore, by separating the additive slurry and the anode catalyst slurry and using dual-channel ultrasonic spraying to control the feeding of each slurry, the layered composition of the catalyst layer can be efficiently and quickly adjusted to prepare a catalyst layer with the desired structure and composition distribution, eliminating the need for multiple slurry preparations and sprayings. This process offers high flexibility and a short cycle time. By preparing a catalyst layer with gradients in catalyst loading and sulfonated silica content through layering, not only is catalyst utilization improved, but also efficient electron and proton transport channels are constructed, improving the water electrolysis rate.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis, specifically relating to an anode catalyst layer for PEM water electrolysis, its preparation method, and a membrane electrode. Background Technology

[0002] Studies show that the oxygen evolution reaction (OER) mainly occurs near the porous transport layer, where higher catalyst utilization requires more catalyst to participate in the reaction. As the distance from the porous transport layer increases, the OER rate slows down, and catalyst utilization decreases. Furthermore, from the porous transport layer to the proton exchange membrane, the proton transport capacity increases, requiring more proton transport channels; conversely, from the proton exchange membrane to the porous transport layer, the electron transport capacity increases, requiring higher conductivity for electron transport.

[0003] However, the most common method for preparing the catalyst layer currently involves mixing the catalyst, proton conductor, and binder in a dispersion medium using ultrasonication or stirring to form a slurry, which is then coated onto a proton exchange membrane to form the catalyst layer. In this method, the catalyst loading, conductivity, and proton transport channels are at the same level from the porous transport layer to the proton exchange membrane. This results in insufficient catalyst loading near the porous transport layer to meet reaction requirements, while catalyst further away from the porous transport layer cannot fully participate in the reaction, leading to low catalyst utilization. Furthermore, the homogeneity of the catalyst layer's conductivity and proton transport channels prevents the formation of efficient electron and proton transport channels. The low catalyst utilization and insufficient electron and proton transport channels severely affect the reaction rate of PEM water electrolysis. Summary of the Invention

[0004] To address the above problems, this invention provides an anode catalyst layer for PEM water electrolysis and its preparation method.

[0005] To address the aforementioned technical issues, the following solutions are proposed:

[0006] A method for preparing an anode catalyst layer for PEM water electrolysis, comprising:

[0007] S1. The anode catalyst and proton conductor are dispersed in a mixed solution of water and organic solvent, and ultrasonically dispersed evenly in an ice-water bath to obtain an anode catalyst slurry.

[0008] S2. Disperse the additive and proton conductor in a mixed solution of water and organic solvent, and ultrasonically disperse them evenly in an ice-water bath to obtain an additive slurry.

[0009] S3. The anode catalyst slurry and additive slurry are added to storage tanks A and B for dual-channel ultrasonic spraying, respectively. The catalyst loading and additive mass ratio of each layer in the single or multi-layer catalyst layer are controlled by adjusting the solid content of the anode catalyst slurry and additive slurry and the feed rate of the two spraying channels. Ultrasonic spraying is then performed on the base film. In this step, the catalyst loading refers to the areal density of the anode catalyst, and the additive mass content refers to the ratio of the mass of the additive to the total mass of (additive + proton conductor + anode catalyst).

[0010] S4. After the catalyst layer is sprayed, the catalyst of the base film is transferred to the surface of the proton exchange membrane using a hot pressing process to obtain the anode catalyst layer.

[0011] Preferably, in step S3, the additive content of each catalyst layer is 1-20 wt.%, more preferably 1-15 wt.%.

[0012] Preferably, the anode catalyst layer is a gradient anode catalyst layer; the number of layers in the gradient anode catalyst layer is 2 to 5.

[0013] As a further preferred embodiment, the additive content in the gradient anode catalyst layer decreases in a gradient direction from the surface of the proton exchange membrane to the gradient anode catalyst layer to ensure a high proton transport rate; even more preferably, the difference in additive content between adjacent gradient anode catalyst layers does not exceed 5 wt.%.

[0014] As a further preferred embodiment, the catalyst loading in the gradient anode catalyst layer increases in a gradient direction from the surface side of the proton exchange membrane to the gradient anode catalyst layer, so as to improve the utilization rate of the catalyst.

[0015] Furthermore, the catalyst mass ratio between adjacent gradient anode catalyst layers is preferably 1.2–2, and the catalyst mass difference between adjacent gradient anode catalyst layers does not exceed 0.1 mg / cm³. -2 .

[0016] Preferably, the anode catalyst is at least one selected from Ir, IrO2, RuO2, and IrRuO2;

[0017] The additive is at least one of sulfonated silicon dioxide, sulfonated titanium dioxide, and sulfonated tin dioxide;

[0018] The proton conductor is perfluorosulfonic acid.

[0019] Preferably, in steps S1 and S2, the organic solvent is one or a mixture of two or more of methanol, ethanol, isopropanol, n-propanol, tert-butanol, ethylene glycol, and glycerol.

[0020] Preferably, in steps S1 and S2, the volume ratio of water to organic solvent is 1~5:1~5, and more preferably, this ratio is equal in steps S1 and S2. Water usually refers to ultrapure water, deionized water, etc.

[0021] Preferably, the solid content of the anode catalyst slurry is 0.1~10 wt.%, more preferably 0.5~5 wt.%; in the anode catalyst slurry, the proton conductor accounts for 5~20 wt.% of the total mass of the anode catalyst and the proton conductor.

[0022] The solid content of the additive slurry is 0.1~10 wt.%, more preferably 0.1~2 wt.%; in the additive slurry, the proton conductor accounts for 5~20 wt.% of the total mass of the additive and the proton conductor.

[0023] Preferably, the base membrane is at least one of DuPont N117 membrane, DuPont N115 membrane, DuPont N212 membrane, DuPont N211 membrane, Gore M765.08, Gore M788.12, Gore M820.15, Kronen N-301X PTFE, Kronen N-41PTFE, Kronen N-21, and Kronen N-11.

[0024] Preferably, in step S4, the hot pressing temperature is 100~160℃, the holding pressure is 0.5~10MPa, and the holding time is 1~15min.

[0025] Preferably, in step S3, the base film is first placed on a heating platform at a preset temperature for preheating, and then ultrasonically sprayed. The preset temperature of the heating platform is 30~80℃.

[0026] Preferably, in steps S1 and S2, the dispersion is ultrasonic dispersion; the duration of ultrasonic dispersion is 30~180 min.

[0027] As a general inventive concept, the present invention also provides a gradient anode catalyst layer for PEM water electrolysis prepared by the aforementioned preparation method.

[0028] As a general inventive concept, the present invention also provides a membrane electrode including the aforementioned anode catalyst layer.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. In this invention, by incorporating appropriate amounts of specific additives into the catalyst layer, not only are proton transport channels between catalysts constructed, reducing the transport impedance of protons between catalysts and increasing the proton conductivity in the catalyst layer, thereby increasing the electrochemical reaction rate, but the additives also have a dispersing effect on the catalyst, thus exposing more active sites, increasing the utilization rate of the catalyst, and improving the performance of PEM water electrolysis. Furthermore, by separating the additive slurry and the anode catalyst slurry and using dual-channel ultrasonic spraying to control the feeding of each slurry, the layered composition of the catalyst layer can be efficiently and quickly adjusted to prepare a catalyst layer with the required structure and composition distribution without the need for multiple slurry preparations and sprayings, resulting in high process flexibility and a short cycle time.

[0031] 2. In this invention, a gradient catalyst layer with varying catalyst loading and sulfonated silica content is formed by layering the catalyst layer. From the porous transport layer to the proton exchange membrane, the catalyst loading gradually decreases while the additive content gradually increases. This gradient catalyst layer not only improves the catalyst utilization rate but also constructs efficient electron and proton transport channels, effectively improving the water electrolysis rate. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The following are comparative graphs showing the electrochemical performance of the membrane electrodes prepared with the catalyst layers of Examples 1-5 and Comparative Example 1: (a) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 30°C; (b) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 60°C; (c) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 80°C; and (d) is the membrane electrode impedance diagram at a test temperature of 30°C and a current of 0.5A.

[0034] Figure 2 The following are comparative graphs of the electrochemical performance of membrane electrodes prepared with the catalysts of Examples 2 and 6-9: (a) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 30°C; (b) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 60°C; (c) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 80°C; and (d) is the membrane electrode impedance diagram at a test temperature of 30°C and a current of 0.5A. Detailed Implementation

[0035] This invention, by incorporating appropriate amounts of specific additives into the catalyst layer, not only constructs proton transport channels between catalysts, reduces the transport impedance of protons between catalysts, and improves the proton conductivity in the catalyst layer, thereby increasing the electrochemical reaction rate, but also disperses the catalyst, thus exposing more active sites, increasing catalyst utilization, and improving the performance of PEM water electrolysis. Furthermore, by separating the additive slurry and the anode catalyst slurry and using dual-channel ultrasonic spraying to control the feeding of each slurry, it is possible to efficiently and quickly achieve layered composition adjustment of the catalyst layer, preparing a catalyst layer with the required structure and composition distribution, without the need for multiple slurry preparations and sprayings, resulting in high process flexibility and a short cycle time.

[0036] Specifically, a method for preparing an anode catalyst layer for PEM water electrolysis is provided, including:

[0037] S1. The anode catalyst and proton conductor are dispersed in a mixed solution of water and organic solvent, and ultrasonically dispersed evenly in an ice-water bath to obtain an anode catalyst slurry.

[0038] S2. Disperse the additive and proton conductor in a mixed solution of water and organic solvent, and ultrasonically disperse them evenly in an ice-water bath to obtain an additive slurry.

[0039] S3. The anode catalyst slurry and additive slurry are added to storage tanks A and B for dual-channel ultrasonic spraying, respectively. The catalyst loading and additive mass ratio of each layer in the single or multi-layer catalyst layer are controlled by adjusting the solid content of the anode catalyst slurry and additive slurry and the feed rate of the two spraying channels. Ultrasonic spraying is then performed on the base film. In this step, the catalyst loading refers to the areal density of the anode catalyst, and the additive mass content refers to the additive mass / (additive + proton conductor + anode catalyst) total mass.

[0040] S4. After the catalyst layer is sprayed, the catalyst of the base film is transferred to the surface of the proton exchange membrane using a hot pressing process to obtain the anode catalyst layer.

[0041] In some preferred embodiments, in step S3, the additive content of each catalyst layer is 1-20 wt.%, more preferably 1-15 wt.%.

[0042] In some preferred embodiments, the anode catalyst layer is a gradient anode catalyst layer; the number of layers in the gradient anode catalyst layer is 2 to 5.

[0043] In some preferred embodiments, the additive content in the gradient anode catalyst layer decreases in a gradient direction from the surface of the proton exchange membrane to the gradient anode catalyst layer to ensure a high proton transport rate; more preferably, the difference in additive content between adjacent gradient anode catalyst layers does not exceed 5 wt.%.

[0044] In some preferred embodiments, the catalyst loading in the gradient anode catalyst layer increases in a gradient direction from the surface of the proton exchange membrane to the gradient anode catalyst layer, so as to improve the utilization rate of the catalyst.

[0045] In some preferred embodiments, the catalyst mass ratio between adjacent gradient anode catalyst layers is 1.2 to 2, and the catalyst mass difference between adjacent gradient anode catalyst layers does not exceed 0.1 mg / cm³. -2 .

[0046] In some preferred embodiments, the anode catalyst is at least one of Ir, IrO2, RuO2, and IrRuO2;

[0047] In some preferred embodiments, the additive is at least one of sulfonated silicon dioxide, sulfonated titanium dioxide, and sulfonated tin dioxide;

[0048] In some preferred embodiments, the proton conductor is perfluorosulfonic acid.

[0049] In some preferred embodiments, in steps S1 and S2, the organic solvent is one or a mixture of two or more of methanol, ethanol, isopropanol, n-propanol, tert-butanol, ethylene glycol, and glycerol.

[0050] In some preferred embodiments, in steps S1 and S2, the volume ratio of water to organic solvent is 1~5:1~5, and more preferably, this ratio is equal in steps S1 and S2. Water typically refers to ultrapure water, deionized water, etc.

[0051] In some preferred embodiments, the solid content of the anode catalyst slurry is 0.1~10 wt.%, more preferably 0.5~5 wt.%; in the anode catalyst slurry, the proton conductor accounts for 5~20 wt.% of the total mass of the anode catalyst and the proton conductor.

[0052] The solid content of the additive slurry is 0.1~10 wt.%, more preferably 0.1~2 wt.%; in the additive slurry, the proton conductor accounts for 5~20 wt.% of the total mass of the additive and the proton conductor.

[0053] In some preferred embodiments, the base membrane is at least one of DuPont N117 membrane, DuPont N115 membrane, DuPont N212 membrane, DuPont N211 membrane, Gore M765.08, Gore M788.12, Gore M820.15, Kronen N-301X PTFE, Kronen N-41PTFE, Kronen N-21, and Kronen N-11.

[0054] In some preferred embodiments, in step S4, the hot pressing temperature of the hot pressing process is 100~160℃, the holding pressure is 0.5~10MPa, and the holding time is 1~15min.

[0055] In some specific embodiments, in step S3, the base film is first placed on a heating platform at a preset temperature for preheating, and then ultrasonic spraying is performed. The preset temperature of the heating platform is 30~80℃.

[0056] In some preferred embodiments, in steps S1 and S2, the dispersion is ultrasonic dispersion; the duration of ultrasonic dispersion is 30~180 min.

[0057] As a general inventive concept, the present invention also provides a gradient anode catalyst layer for PEM water electrolysis prepared by the aforementioned preparation method.

[0058] As a general inventive concept, the present invention also provides a membrane electrode including the aforementioned anode catalyst layer.

[0059] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0060] Example 1

[0061] The detailed steps for preparing the anode catalyst layer are as follows:

[0062] (1) Preparation of sulfonated silica: 1g of silica was dispersed in a mixed solution of 15mL methanol and 15mL sulfuric acid with a concentration of 0.5mol / L and stirred for 1h, sonicated for 1h, and then heated at 100~140℃ for 24h to completely evaporate the solution to obtain sulfonated silica.

[0063] (2) Preparation of anode catalyst slurry: 20 mg of iridium dioxide powder and 32 mg of 5% Nafion solution (perfluorosulfonic acid resin solution) were added to a mixed solution of 1 mL of ultrapure water and 1 mL of isopropanol, and ultrasonically dispersed in an ice-water bath for 60 min to obtain anode catalyst slurry.

[0064] (3) Preparation of sulfonated silica slurry: 6 mg of sulfonated silica powder and 16 mg of Nafion solution with a mass fraction of 5% were added to a mixed solution of 3 mL of ultrapure water and 3 mL of isopropanol, and ultrasonically dispersed in an ice-water bath for 60 min to obtain sulfonated silica slurry.

[0065] (4) Preparation of the anode coating: The anode catalyst slurry and sulfonated silica slurry were added to clean storage tanks A and B, respectively. A polytetrafluoroethylene (PTFE) membrane was laid flat on a heating table at 60°C. Ultrasonic spraying was performed at a height of 5 cm, a spraying spacing of 5 mm, and a spraying speed of 5 mm / s. The feed rate of storage tank A was 0.02 ml / s, and the feed rate of storage tank B was 0.01 ml / s. The spraying was performed once, covering an area of ​​5 cm x 5 cm, for 100 s. After spraying, the coating was dried at 60°C for 60 min to obtain an iridium dioxide loading of 0.6 mg / cm³. -2 An anode coating with a sulfonated silica content of 4.4 wt.% (referring to the total mass of sulfonated silica / (sulfonated silica + anode catalyst + Nafion) in the anode coating; the sulfonated silica content in the following examples and comparative examples refers to this ratio).

[0066] Example 2

[0067] The difference from Example 1 is that the feeding rate of storage tank B in step (4) is 0.016 ml / s, resulting in an iridium dioxide loading of 0.6 mg / cm³. -2 An anodic coating with a sulfonated silica content of 6.44 wt.%.

[0068] Example 3

[0069] The difference from Example 1 is that the feeding rate of storage tank B in step (4) is 0.022 ml / s, and the final iridium dioxide loading is 0.6 mg cm⁻¹. -2 An anodic coating with a sulfonated silica content of 8.38 wt.%.

[0070] Example 4

[0071] The difference from Example 1 is that the feeding rate of storage tank B in step (4) is 0.036 ml / s, and the final iridium dioxide loading is 0.6 mg cm⁻¹. -2 An anodic coating with a sulfonated silica content of 12 wt.%.

[0072] Example 5

[0073] The difference from Example 1 is that the feeding rate of storage tank B in step (4) is 0.05 ml / s, resulting in an iridium oxide loading of 0.6 mg / cm³.-2 An anodic coating with a sulfonated silica content of 15.31 wt.%.

[0074] Example 6

[0075] The difference from Example 1 is that the anode coating in step (4) was prepared by three coatings, each with an equal coating time. The feed rate of storage tank A was 0.0075 ml / s for each coating, the feed rate of storage tank B was 0 for the first coating, 0.0018 ml / s for the second coating, and 0.0035 ml / s for the third coating. Other parameters were the same as in Example 1. The final result was a three-layer anode coating with a first layer of sulfonated silica containing 0%, a second layer of sulfonated silica containing 2.26 wt.%, and a third layer of sulfonated silica containing 4.4 wt.%. The iridium dioxide loading in each layer was 0.2 mg cm⁻¹. -2 .

[0076] Example 7

[0077] The difference from Example 1 is that the anode coating in step (4) was prepared by three coatings, each with an equal coating time. The feed rate of storage tank A was 0.0065 ml / s each time; the feed rate of storage tank B was 0.0018 ml / s for the first coating, 0.0035 ml / s for the second coating, and 0.005 ml / s for the third coating. Other parameters were the same as in Example 1. A three-layer anode coating was obtained, with the first layer containing 2.26 wt.% sulfonated silica, the second layer containing 4.4 wt.% sulfonated silica, and the third layer containing 6.44 wt.% sulfonated silica. The iridium dioxide loading in each layer was 0.2 mg / cm³. -2 .

[0078] Example 8

[0079] The difference from Example 1 is that the anode coating in step (4) was prepared by three coatings, each with an equal coating time. For the first coating, the feed rate of storage tank A was 0.01 ml / s, and the feed rate of storage tank B was 0. For the second coating, the feed rate of storage tank A was 0.0065 ml / s, and the feed rate of storage tank B was 0.0017 ml / s. For the third coating, the feed rate of storage tank A was 0.0034 ml / s, and the feed rate of storage tank B was 0.0018 ml / s. Other parameters were the same as in Example 1. The final iridium dioxide loading of the first, second, and third layers was 0.3 mg cm⁻¹. -2 0.2 mg cm -2 and 0.1mg cm -2A three-layer anodic coating with sulfonated silica contents of 0, 2.26 wt.% and 4.4 wt.%.

[0080] Example 9

[0081] The difference from Example 1 is that the anode coating in step (4) was prepared by three coatings, each with an equal coating time. The first coating involved a feed rate of 0.01 ml / s for tank A and 0.0025 ml / s for tank B. The second coating involved a feed rate of 0.0065 ml / s for tank A and 0.0035 ml / s for tank B. The third coating involved a feed rate of 0.0034 ml / s for tank A and 0.0025 ml / s for tank B. Other parameters were the same as in Example 1. The final iridium dioxide loading of the first, second, and third layers was 0.3 mg / cm³. -2 0.2 mg cm -2 and 0.1 mg cm -2 A three-layer anodic coating with sulfonated silica content of 2.26 wt.%, 4.4 wt.%, and 6.44 wt.%.

[0082] Comparative Example 1

[0083] The difference from Example 1 is that the feed rate of storage tank B in step (4) is 0, resulting in an iridium dioxide loading of 0.6 mg / cm³. -2 An anodic coating with 0% sulfonated silica content.

[0084] Fabrication of membrane electrodes:

[0085] (1) Pretreatment of proton exchange membrane: The Nafion 212 membrane (7cm×7cm) was placed in an aqueous solution of 5 wt.% H2O2 at 80℃ for 60min. After washing the membrane with ultrapure water more than 5 times, the membrane was placed in ultrapure water at 80℃ for 60min. Then the membrane was placed in an aqueous solution of 0.7mol / L sulfuric acid at 80℃ for 60min. After washing the membrane with ultrapure water more than 5 times, the membrane was placed in ultrapure water at 80℃ for 60min. Then the membrane was stored in ultrapure water at room temperature for later use.

[0086] (2) Preparation of porous transport layer: Toray carbon paper 060 (5cm×5cm) was immersed in 5wt.% polytetrafluoroethylene dispersion for 2min, then dried at 70℃ for 2h to obtain hydrophobic carbon paper. Then, carbon powder (Vulcan XC-72R) and PTFE were dispersed in isopropanol dispersion, ultrasonicated to homogenize, and uniformly sprayed onto one side of the hydrophobic carbon paper. It was dried at 70℃ for 2h, sintered in a muffle furnace at 370℃ for 30min, cooled, weighed and calculated, and the carbon powder loading was found to be 0.5mg / cm³. 2 A hydrophobic microporous layer with a PTFE content of 5 wt.% was used as the cathode porous transport layer. Titanium fiber felt (5 cm × 5 cm, 0.25 mm thick) was immersed in a 20 wt.% hydrochloric acid solution at 50 °C until a large number of bubbles appeared, and then washed three times with ultrapure water to obtain the anode porous transport layer.

[0087] (3) Preparation of cathode catalyst slurry: 20 mg of 50% platinum Pt / C powder and 130 mg of 5% Nafion solution were added to a mixed solution of 0.4 mL of ultrapure water and 1.6 mL of isopropanol. The mixture was ultrasonically dispersed in an ice-water bath for 60 min to ensure uniform dispersion and obtain cathode catalyst slurry.

[0088] (4) Preparation of cathode coating: The cathode catalyst slurry was added to a clean storage tank A. The polytetrafluoroethylene membrane was laid flat on a heating table at 60°C. The ultrasonic spraying height was 5cm, the spraying spacing was 1cm, the spraying speed was 5mm / s, the feed rate was 0.02ml / s, and the spraying was repeated twice. After the spraying was completed, the membrane was dried at 60°C for 60min to obtain the cathode coating. Then, the proton exchange membrane and the polytetrafluoroethylene membrane with the cathode coating were placed on a hot press plate, with the side with the coating in close contact with the proton exchange membrane. The pressure was maintained at 130°C and 3MPa for 6min, and the cathode coating was transferred onto the proton exchange membrane by hot pressing to obtain the cathode catalyst layer.

[0089] (5) Preparation of membrane electrode: The pretreated proton exchange membrane, the polytetrafluoroethylene membrane with cathode coating and the polytetrafluoroethylene membrane with anode coating are placed on a hot press plate. The proton exchange membrane is placed between the two polytetrafluoroethylene membranes with coating, with the coated side close to the proton exchange membrane. The pressure is maintained at 130℃ and 3MPa for 6 minutes. The coating is transferred to both sides of the proton exchange membrane by hot pressing to obtain the PEM water electrolysis membrane electrode.

[0090] Performance testing:

[0091] PEM water electrolysis test: The cathode porous transport layer, membrane electrode, and anode porous transport layer were assembled in an electrolyzer fixture according to a "sandwich" structure. The torque was set to 6 N·m, and water electrolysis polarization curve and impedance tests were performed. Water electrolysis polarization curve test conditions: The fixture operating temperatures were 30℃, 60℃, and 80℃. Ultrapure water at 32℃, 63℃, and 84℃ was continuously flowed into the anode end at a flow rate of 40 ml / min. A DC power supply was connected, with the anode of the fixture connected to the positive terminal and the cathode connected to the negative terminal. The current values ​​at different voltages were measured.

[0092] Electrolysis impedance test conditions: After the polarization curve test is completed, turn off the voltage, turn on the electrochemical workstation, connect the working electrode to the anode of the fixture, and connect the counter electrode and the reference electrode to the cathode. Test the impedance curve at a current of 0.5A.

[0093] Figure 1 The figures show a comparison of the electrochemical performance parameters of the membrane electrodes prepared with the catalyst layers of Examples 1-5 and Comparative Example 1. (a) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 30°C; (b) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 60°C; (c) is the polarization curve of the membrane electrode after removing the internal resistance at a test temperature of 80°C; and (d) is the impedance diagram of the membrane electrode at a test temperature of 30°C and a current of 0.5A. Figure 1 It can be observed that the performance of the membrane electrode exhibits significant differences with the addition of sulfonated silica. Compared with the undoped sulfonated silica membrane electrode, the electrolysis performance is significantly improved at sulfonated silica doping levels of 8.38 wt.%, 6.44 wt.%, and 4.4 wt.%. The reasons for this phenomenon are speculated to be: 1. The excellent proton conductivity of sulfonated silica improves the proton transport channels between catalysts, allowing protons generated in the anolyte reaction to be transported more quickly to the interface between the catalyst layer and the proton exchange membrane, and then to the cathode to participate in the hydrogen evolution reaction; 2. The addition of sulfonated silica has a certain dispersing effect on iridium dioxide, allowing the catalyst to expose more active sites to participate in the electrochemical reaction, increasing the reactivity of the anolyte catalyst layer and accelerating the anolyte reaction rate. Furthermore, sulfonated silica is cheaper than commonly used Nafion solution, which can further reduce the manufacturing cost of the membrane electrode. The performance shown in Examples 4 and 5 was not significantly improved, and even decreased. This is because the weak conductivity of sulfonated silica means that excessive doping will increase the internal resistance of the catalyst layer, thereby affecting the water electrolysis performance.

[0094] Figure 2Comparison of the electrochemical performance of membrane electrodes prepared with the catalysts of Examples 2 and 6-9: (a) Polarization curve of the membrane electrode after removing internal resistance at a test temperature of 30°C; (b) Polarization curve of the membrane electrode after removing internal resistance at a test temperature of 60°C; (c) Polarization curve of the membrane electrode after removing internal resistance at a test temperature of 80°C; (d) Impedance diagram of the membrane electrode at a test temperature of 30°C and a current of 0.5A. Figure 2 It can be seen that the performance of the membrane electrode can be further improved by gradient doping of sulfonated silica in the anode catalyst layer (Examples 6 and 7). This is mainly because the sulfonated silica content gradually increases from the porous transport layer to the proton exchange membrane, which can improve the proton transport channels inside the catalyst layer, increase the proton transport rate, and thus improve the water electrolysis performance of the membrane electrode. Figure 2 The impedance diagram in (d) also confirms this conclusion; the impedances of Examples 6 and 7 are significantly lower than that of Example 2. Furthermore, based on the gradient doping of sulfonated silica, a gradient design for the catalyst loading (see Examples 8 and 9) can again significantly improve the membrane electrode performance. It is speculated that this effect is because the anolyte oxygen evolution reaction mainly occurs near the porous transport layer; therefore, concentrating more catalyst on the porous transport layer side can increase catalyst utilization, thereby improving the water electrolysis performance of the membrane electrode. Figure 2 (d) further confirms this result. With the gradient design of catalyst loading, the impedance of the membrane electrode is further reduced, especially the charge transport impedance, which is significantly reduced, indicating that the catalyst layer has a faster electrochemical reaction rate.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an anode catalyst layer for PEM water electrolysis, characterized in that, include: S1. The anode catalyst and proton conductor are dispersed in a mixed solution of water and organic solvent, and the dispersion is uniform in an ice-water bath to obtain an anode catalyst slurry. S2. Disperse the additive and proton conductor in a mixed solution of water and organic solvent, and disperse evenly in an ice-water bath to obtain an additive slurry; S3. Add the anode catalyst slurry and additive slurry to storage tanks A and B for dual-channel ultrasonic spraying, respectively. By adjusting the solid content of the anode catalyst slurry and additive slurry and the feed rate of the two spraying channels, the catalyst loading and additive mass content of each layer in the single or multi-layer catalyst layer are controlled, and ultrasonic spraying is performed on the base film. The anode catalyst layer is a gradient anode catalyst layer; the number of layers in the gradient anode catalyst layer is 2 to 5; the additive content in the gradient anode catalyst layer decreases gradually from the surface of the proton exchange membrane to the gradient anode catalyst layer; the difference in additive mass content between adjacent gradient anode catalyst layers does not exceed 5 wt.%. S4. After the catalyst layer is sprayed, the catalyst of the base film is transferred to the surface of the proton exchange membrane using a hot pressing process to obtain the anode catalyst layer.

2. The method for preparing the anode catalyst layer for PEM water electrolysis as described in claim 1, characterized in that, In step S3, the mass content of the additive in each catalyst layer is 1~15 wt.%.

3. The method for preparing the anode catalyst layer for PEM water electrolysis as described in claim 1, characterized in that, From the surface side of the proton exchange membrane to the gradient anode catalytic layer, the catalyst loading in the gradient anode catalytic layer increases in a gradient manner. The catalyst mass ratio between adjacent gradient anode catalyst layers is 1.2–2, and the catalyst mass difference between adjacent gradient anode catalyst layers does not exceed 0.1 mg / cm³. -2 .

4. The method for preparing the anode catalyst layer for PEM water electrolysis as described in claim 1, characterized in that, The anode catalyst is at least one of Ir, IrO2, RuO2, and IrRuO2; The additive is at least one of sulfonated silicon dioxide, sulfonated titanium dioxide, and sulfonated tin dioxide; The proton conductor is perfluorosulfonic acid; The base membrane is at least one of DuPont N117 membrane, DuPont N115 membrane, DuPont N212 membrane, DuPont N211 membrane, Gore M765.08, Gore M788.12, Gore M820.15, Kronen N-301X PTFE, Kronen N-41PTFE, Kronen N-21, and Kronen N-11.

5. The method for preparing the anode catalyst layer for PEM water electrolysis as described in claim 1, characterized in that, In steps S1 and S2, the organic solvent is one or a mixture of two or more of methanol, ethanol, isopropanol, n-propanol, tert-butanol, ethylene glycol, and glycerol. In steps S1 and S2, the volume ratio of water to organic solvent is 1~5:1~5.

6. The method for preparing the anode catalyst layer for PEM water electrolysis as described in claim 1, characterized in that, The solid content of the anode catalyst slurry is 0.1~10 wt.%; in the anode catalyst slurry, the proton conductor accounts for 5~20 wt.% of the total mass of the anode catalyst and the proton conductor. The solid content of the additive slurry is 0.1~10 wt.%; in the additive slurry, the proton conductor accounts for 5~20 wt.% of the total mass of the additive and the proton conductor.

7. The method for preparing the anode catalyst layer for PEM water electrolysis as described in claim 1, characterized in that, In step S4, the hot pressing temperature is 100~160℃, the holding pressure is 0.5~10MPa, and the holding time is 1~15min.

8. The anode catalyst layer for PEM water electrolysis prepared by the preparation method according to any one of claims 1-7.

9. A membrane electrode, characterized in that, Includes the anode catalyst layer as described in claim 8.

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