Preparation method of electrolyzed water membrane electrode with precious metal carrying capacity gradient design

Abstract

The preparation method of the electrolytic water film electrode with the precious metal loading capacity gradient design comprises the steps that cathode slurry and anode slurry are prepared, the cathode slurry comprises cathode slurry A-E with the precious metal loading capacity decreasing progressively, and the anode slurry comprises anode slurry F-J with the precious metal loading capacity decreasing progressively; the cathode slurry A-E is placed in five micro-sample injectors S1-S5 respectively, and the micro-sample injectors S1-S5 are connected with a material mixing unit and then connected with spraying equipment through liquid supply pipes; in one spraying period T0, the micro sample injectors S1-S5 are set to inject samples according to the following mode: starting from a spraying starting point of PA (XA, YA), the sample injection flow rate of S1 is C0, the duration time is 0-0.2 * T0, the sample injection flow rates of S1 and S2 are 0.5 * C0, the duration time is 0.2 * T0-0.4 * T0, the sample injection flow rates of S2 and S3 are 0.5 * C0, the duration time is 0.4 * T0-0.6 * T0, the sample injection flow rates of S3 and S4 are 0.5 * C0, the duration time is 0.6 * T0-0.8 * T0, the sample injection flow rates of S4 and S5 are 0.5 * C0, and the duration time is 0.8 * T0-T0, until the spraying ending point of PB (XB, YB).

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical water electrolysis and new energy membrane electrodes, and in particular relates to a method for preparing a water electrolysis membrane electrode with a noble metal loading gradient design and the water electrolysis membrane electrode. Background Art

[0002] The proton exchange membrane electrolyzer (PEM) is currently the most advanced hydrogen production technology, offering advantages such as high efficiency, cleanliness, and high hydrogen purity. In a PEM electrolyzer, the membrane electrode (MEA) consists primarily of a gas diffusion layer (GDL), a frame, a catalyst layer, and a proton exchange membrane. The GDL on the cathode side is typically carbon paper, while the GDL on the anode side is titanium felt. The cathode and anode catalyst layers are ultrasonically sprayed onto both sides of the PEM. The cathode catalyst uses a platinum-on-carbon catalyst with a 40% Pt loading, while the anode catalyst uses an iridium-based catalyst with a mass fraction of the precious metal greater than 70%. The electrolyte in the anode flow channel diffuses through the GDL on the anode side to the reaction sites in the anode catalyst layer, where an electrochemical reaction occurs. Due to the difference in ion concentrations on both sides of the PEM, hydrogen ions (H+) generated electrochemically on the anode side pass through the PEM and are transferred to reaction sites in the anion catalyst layer on the cathode side of the MEA. These hydrogen molecules then pass through the GDL to the cathode channel plate.

[0003] Chinese patent application publication number CN117895035A discloses a method for preparing a fuel cell membrane electrode with a gradient IC ratio. However, this patent has the following shortcomings: 1. A distributed spraying technique using a zoned mask is used to spray cathode slurry with different IC ratios on different proton exchange membrane regions of the membrane electrode. However, this solution involves replacing spray lines and adds a mask spraying step, which is not conducive to large-scale membrane electrode production. 2. The partitioning method is abrupt, resulting in significant boundary effects between different masked regions. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a water electrolysis membrane electrode with a noble metal loading gradient design.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a water electrolysis membrane electrode with a noble metal loading gradient design, comprising the following steps:

[0007] Step S1, preparing cathode slurry and anode slurry, wherein the cathode slurry includes cathode slurries A to E with decreasing precious metal loading, and the anode slurry includes anode slurries F to J with decreasing precious metal loading;

[0008] Step S2, placing the cathode slurries A to E in five micro-injectors S1 to S5 respectively, and connecting the micro-injectors S1 to S5 to the mixing unit and then to the spraying equipment through the liquid supply pipe;

[0009] Step S3, vacuum adsorbing the proton exchange membrane onto the heating plate, setting the spraying area and spraying mode on the spraying equipment and starting spraying, and after completion, a semi-catalyst membrane containing cathode catalyst can be obtained;

[0010] Step S4, cleaning the micro-injectors S1-S5 and pipelines, and placing the anode slurries F-J in the micro-injectors S1-S5 respectively;

[0011] Step S5, the half catalyst film containing the cathode catalyst is reversely vacuum adsorbed on the heating plate, and the spraying equipment sets the spraying area and spraying mode to start spraying, and the catalyst film can be obtained after the spraying is completed; in steps S3 and S5, the starting point of the spraying area is PA(X A ,Y A ), the end point is PB(X B ,Y B ), the spraying pattern is an S-shaped path, starting from the starting point P A To the end point P B The spraying cycle time is T0;

[0012] Step S6: attach the gas diffusion layer to both sides of the catalyst membrane, place it in a mold of a hot press and perform hot pressing to obtain a water electrolysis membrane electrode.

[0013] In step S2, during one spraying cycle T0, the micro-injectors S1-S5 are set to inject samples in the following manner:

[0014] PA(X A ,Y A ) Starting from the spraying starting point, the injection flow rate of S1 is C0, and the duration is 0~0.2*T0,

[0015] The injection flow rate of S1 and S2 is 0.5*C0, and the duration is 0.2*T0~0.4*T0,

[0016] The injection flow rate of S2 and S3 is 0.5*C0, and the duration is 0.4*T0~0.6*T0,

[0017] The injection flow rate of S3 and S4 is 0.5*C0, and the duration is 0.6*T0~0.8*T0,

[0018] The injection flow rate of S4 and S5 is 0.5*C0, and the duration is 0.8*T0~T0, until PB(X B ,Y B )Spraying end point.

[0019] Preferably, the cathode slurries A to E are each prepared by mixing a platinum-carbon catalyst, a perfluorosulfonic acid resin solution, water, and isopropyl alcohol;

[0020] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry A is 0.50;

[0021] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry B is 0.55;

[0022] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry C is 0.60;

[0023] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry D is 0.65;

[0024] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry E is 0.70.

[0025] Preferably, the anode slurries F to J are each prepared by mixing an iridium-based catalyst, a perfluorosulfonic acid resin solution, water, and isopropyl alcohol;

[0026] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry F is 0.090;

[0027] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry G is 0.095;

[0028] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry H is 0.100;

[0029] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry I is 0.105;

[0030] The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry J is 0.110.

[0031] Preferably, in step S2, the mixing unit is a constant volume mixing channel plate.

[0032] Preferably, the liquid supply pipe between the mixing unit and the spraying equipment further has a defoamer.

[0033] Preferably, in step S4, the microinjectors S1-S5 and the pipelines are emptied using a mixture of n-propanol and isopropanol in a volume ratio of 1:1.

[0034] Preferably, when the membrane electrode area is S=a*b, where a is the long side dimension and b is the short side dimension, the spraying area is larger than the membrane electrode area S to be sprayed, that is, the starting point A(X A ,Y A ) and the end point B(X B ,Y B ) satisfies: where: |X A -X B |>a,|Y A -Y B |>b, spraying area (|X A -X B |*|Y A -Y B |) is larger than the membrane electrode area S=a*b with spraying.

[0035] Preferably, the spraying area is divided into five equal areas MEA1-MEA5 in the casting direction;

[0036] The MEA1 area is sprayed with only cathode slurry A or anode slurry F;

[0037] The MEA2 region is sprayed with a mixed slurry of cathode slurries A and B, or anode slurries F and G;

[0038] The MEA3 region is sprayed with a mixed slurry of cathode slurries B and C, or anode slurries G and H;

[0039] The MEA4 region is sprayed with a mixed slurry of cathode slurries C and D, or anode slurries H and I;

[0040] The MEA5 region was sprayed with a mixed slurry of cathode slurries D and E, or anode slurries I and J.

[0041] Preferably, when the spraying pattern is an S-shaped path, the spraying path spacing L0 is 0.1 to 0.6 mm.

[0042] In a second aspect, the present invention provides a water electrolysis membrane electrode prepared by the preparation method described herein.

[0043] Beneficial effects of the invention:

[0044] The preparation of the membrane electrode catalyst layer in the present invention only needs to start spraying according to the established spraying path, spraying mode and injection procedure. There is no need to replace the mask plate, the spray nozzle and the slurry injection pipeline in the middle. After starting the spraying and spraying times reaching the specified times, the membrane electrode catalyst layer is sprayed and formed in one go and formed into an integrated film. Compared with the spraying or scraping scheme of regional film formation, it can more effectively ensure the consistency of the thickness of the catalyst layer film, and realize that a single ultrasonic nozzle can spray a membrane electrode with a precious metal content gradient design in the electrolyte casting direction under the condition of uninterrupted slurry supply.

[0045] Furthermore, the regional spraying method of the present invention uses two slurries with adjacent metal loading gradients mixed in a volume ratio of 1:1, effectively reducing the concentration difference mutation of the catalytic reaction sites (proportional to the metal loading per unit area of ​​the precious metal) between adjacent partitioned membrane electrodes, avoiding the boundary effect. In addition, since the reduction in metal loading is compensated by the resin content (the solid content of all slurries is constant), the increase in resin content can improve the proton transport capacity of the membrane electrode sub-region with reduced metal loading, and this proton transport capacity is gradually improved.

[0046] Furthermore, the preparation method of the present invention reduces the amount of platinum metal used in the cathode by at least 14% and the amount of iridium metal used in the anode by at least 6% without reducing the performance of the membrane electrode, thereby improving the actual utilization efficiency of the precious metal catalyst, greatly simplifying the industrial production process of the membrane electrode of the electrolytic water tank, and realizing a large-scale production plan of the membrane electrode that can be continuously sprayed. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention 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. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 It is a flow chart of a method for preparing a water electrolysis membrane electrode according to a preferred embodiment of the present invention.

[0049] Figure 2 It is a schematic diagram of the connection between the micro-injector and the spraying equipment in a preferred embodiment of the present invention.

[0050] Figure 3 Schematic diagram of the single travel path of the nozzle in a preferred embodiment of the present invention.

[0051] Figure 4 It is a schematic diagram of the membrane electrode partition and the mixed catalyst slurry composition of a preferred embodiment of the present invention.

[0052] Figure 5 This is a performance test data diagram of the water electrolysis membrane electrode of the preferred embodiment of the present invention.

[0053] Figure 6 Performance test data of water electrolysis membrane electrode prepared by existing standard spraying scheme. DETAILED DESCRIPTION

[0054] To make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] refer to Figure 1 As shown, a preferred embodiment of the present invention provides a method for preparing a water electrolysis membrane electrode with a noble metal loading gradient design, which includes the following steps S1-S6. Each step is described in detail below.

[0056] Step S1 , preparing cathode slurry and anode slurry, wherein the cathode slurry includes cathode slurries A to E with decreasing precious metal loading, and the anode slurry includes anode slurries F to J with decreasing precious metal loading.

[0057] In this step, preferably, cathode slurries A to E are each formed by mixing a platinum-carbon catalyst, a perfluorosulfonic acid resin solution, water, and isopropyl alcohol. The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the carbon support of the platinum-carbon catalyst in cathode slurry A is 0.50; the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the carbon support of the platinum-carbon catalyst in cathode slurry B is 0.55; the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the carbon support of the platinum-carbon catalyst in cathode slurry C is 0.60; the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the carbon support of the platinum-carbon catalyst in cathode slurry D is 0.65; and the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the carbon support of the platinum-carbon catalyst in cathode slurry E is 0.70.

[0058] Preferably, anode slurries F to J are each formed by mixing an iridium-based catalyst, a perfluorosulfonic acid resin solution, water, and isopropyl alcohol. The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in anode slurry F is 0.090; the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in anode slurry G is 0.095; the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in anode slurry H is 0.100; the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in anode slurry I is 0.105; and the mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in anode slurry J is 0.110.

[0059] Preferably, the solids content of the cathode slurry (including the dry mass of the perfluorosulfonic acid resin and the mass of the platinum-carbon catalyst) is 1%, and the solids content of the anode slurry (including the dry mass of the perfluorosulfonic acid resin and the mass of the iridium-based catalyst) is 2%. The solids content of each slurry in the catalyst cathode or anode configured in the present invention is completely consistent, ensuring that when the slurries are mixed, the overall solids content is completely consistent and the thickness of the catalytic layer remains consistent. In this way, under the same assembly stress, the overall compression rate of the membrane electrode can remain basically consistent, and the current distribution is more uniform under higher current density conditions.

[0060] Preferably, the preparation of cathode or anode slurry further comprises the following steps:

[0061] S11, put the slurry into a shearing machine according to the proportion, and shear it in an ice water bath for 1 hour at a shearing speed of 10000 rpm;

[0062] S12, the slurry homogenized and emulsified by the shearing machine is placed in a vacuum drying oven, and the slurry is degassed by three vacuuming and nitrogen replenishing operations.

[0063] Step S2, such as Figure 2 As shown, the cathode slurries A-E are placed in five microinjectors S1-S5, each of which is connected to a mixing unit and then to the spraying equipment via a liquid supply pipe. Preferably, the outlets of the microinjectors S1-S5 are connected to a mixing manifold plate M1 with a constant capacity after being connected to a check valve. This mixing manifold plate ensures thorough mixing of the slurries. Preferably, the liquid supply pipe between the mixing unit and the spraying equipment also includes a defoamer. This defoamer removes bubbles from the slurry flowing through it and allows it to exit the liquid supply pipe.

[0064] The spraying equipment is preferably an ultrasonic nozzle. The nozzle houses an ultrasonic generator that converts electrical energy into mechanical vibrations via a piezoelectric transducer. Once the spray material enters the ultrasonic nozzle, the ultrasonic vibrations absorb the vibration energy, causing the material to break into micron-sized droplets on the surface of the ultrasonic transducer. The atomized droplets are then transported by a carrier gas to the object being sprayed or a specific space, forming a uniform coating or film.

[0065] Preferably, in step S2, in one spraying cycle T0, the micro-injectors S1-S5 are configured to inject samples in the following manner:

[0066] PA(X A ,Y A ) Starting from the spraying starting point, the injection flow rate of S1 is C0, and the duration is 0~0.2*T0,

[0067] The injection flow rate of S1 and S2 is 0.5*C0, and the duration is 0.2*T0~0.4*T0,

[0068] The injection flow rate of S2 and S3 is 0.5*C0, and the duration is 0.4*T0~0.6*T0,

[0069] The injection flow rate of S3 and S4 is 0.5*C0, and the duration is 0.6*T0~0.8*T0,

[0070] The injection flow rate of S4 and S5 is 0.5*C0, and the duration is 0.8*T0~T0, until PB(X B ,Y B )Spraying end point.

[0071] Preferably, the above-mentioned specific injection mode can be realized by programming the micro-injection pump connected to the micro-injection device S1-S5. Here, the spraying cycle T0 of completing a single spray from A to B can be completed by recording the time T taken for N times (for example, 10 to 30 times) of spraying. N The calculation formula is T0=T N / N.

[0072] In step S3, the proton exchange membrane is vacuum-adsorbed onto a heating plate. The spraying equipment sets the spray area and spray pattern and begins spraying. Upon completion, a semi-catalyst membrane containing the cathode catalyst is obtained. The proton exchange membrane is preferably 128 microns thick and made of perfluorosulfonic acid resin. The heating plate temperature is 75 degrees Celsius.

[0073] Preferably, the number of cathode slurry spraying is determined according to the cathode platinum loading. Before spraying the catalyst layer on the cathode side of the membrane electrode, a standard membrane electrode needs to be trial-produced to calibrate the cathode platinum metal loading and the number of spraying. The calibration method is: use a single-tube micro-injector to feed the ultrasonic nozzle with cathode slurry, according to the initial position of the nozzle, respectively at points A and B, the injection flow rate C0ml / min, S-shaped path spraying, parallel path interval L0, record the cathode platinum loading as M C mg / cm 2 When the number of spraying is N C That is, N C A spraying cycle from A to B is required to obtain a half catalyst membrane containing cathode catalyst.

[0074] Step S4, clean the micro-injectors S1-S5 and pipelines, and place the anode slurries F~J in the micro-injectors S1-S5 respectively. Preferably, the micro-injectors S1-S5 and pipelines are emptied using a mixture of n-propanol and isopropanol in a volume ratio of 1:1. At this time, preferably, S1-S5 is connected to another constant volume mixing flow channel plate M2. After completing a spraying and changing the slurry, the constant volume mixing flow channel plate can be replaced immediately. This is mainly because different types of spray slurries have different viscosities and rheological properties, so the micro-channel designs of the constant volume flow channel plates used for mixed slurries are different.

[0075] In step S5, the half catalyst membrane containing the cathode catalyst is reversely vacuum-adsorbed on the heating plate. The spraying equipment sets the spraying area and spraying mode and starts spraying. After the spraying is completed, the catalyst membrane is obtained. Here, the temperature of the heating plate is 75 degrees Celsius. The number of anode slurry sprayings is determined by the anode iridium loading. Before spraying the catalyst layer on the anode side of the membrane electrode, a standard membrane electrode needs to be trial-produced to calibrate the anode iridium metal loading and the number of sprayings. The calibration method is the same as that for the cathode slurry.

[0076] In the above steps S3 and S5, Figure 3 As shown, the starting point of the spraying area is PA(X A ,Y A ), the end point is PB(X B ,Y B ), the spraying pattern is an S-shaped path, and the spraying cycle time from the starting point PA to the end point PB is T0. Figure 3 As shown by the middle arrow, after completing one spraying in the spraying direction (transverse direction), the nozzle returns to the spraying origin, does not spray on the return journey, and re-route spraying at the next position in the casting direction (longitudinal direction). Preferably, when the spraying mode is an S-shaped path, the spraying path spacing L0 is 0.1 to 0.6 mm. In a preferred embodiment, L0 = 0.3 mm

[0077] In addition, assuming that the membrane electrode area is S = a * b, where a is the long side size and b is the short side size, the spraying area is larger than the membrane electrode area S to be sprayed, that is, the starting point PA (X A ,Y A ) and the end point PB(X B ,Y B )satisfy:

[0078] Preferably, if Figure 4 As shown, the spraying area is divided into five equal areas MEA1-MEA5 in the casting direction. Specifically, the MEA1 area is sprayed with only cathode slurry A or anode slurry F; the MEA2 area is sprayed with a mixed slurry of cathode slurries A and B, or anode slurries F and G; the MEA3 area is sprayed with a mixed slurry of cathode slurries B and C, or anode slurries G and H; the MEA4 area is sprayed with a mixed slurry of cathode slurries C and D, or anode slurries H and I; and the MEA5 area is sprayed with a mixed slurry of cathode slurries D and E, or anode slurries I and J.

[0079] In addition, preferably, the calculation of the slurry volume required for a single spraying, i.e., a spraying cycle, during the spraying process can be obtained by using a single-tube micro-injector to supply liquid to the ultrasonic nozzle, and the liquid supplied can be replaced by pure water, and the volume of pure water consumed by the micro-injector after N times (e.g., 10 to 30 times) of spraying is recorded. N , calculate the volume of pure water consumed in a single spraying, V0 = V N / N. This volume V0 is also the internal volume of the constant volume mixing plate.

[0080] Preferably, the internal volume V of the connecting pipe between the micro-injector and the ultrasonic nozzle is C , the residual volume in the micro-injector outlet to the spray nozzle and the connected slurry pipeline can be excluded and recorded using air. Vc is used to confirm the starting point of membrane electrode spraying timing. Specifically, the present invention records V C Volume, based on the feed flow rate, is calculated by reversing the starting time t' = Vc / flow rate. The specific operation is as follows: The slurry is initially advanced, with the ultrasonic nozzle positioned at the starting position (using a plain paper or plastic baffle to shield the proton exchange membrane to be sprayed). After the time t' is reached, the ultrasonic spray begins moving along the programmed stepping path, and the microinjector's programmed timer simultaneously jumps to the starting point.

[0081] Finally, in step S6, the gas diffusion layer is attached to both sides of the catalyst membrane, which is then placed in a mold of a hot press and hot pressed to obtain a water electrolysis membrane electrode.

[0082] Preferably, the gas transport material used in conjunction with the cathode catalyst layer is 210 micron thick carbon paper. The gas transport layer material used in conjunction with the anode catalyst layer is 200 micron thick titanium felt. The gaskets used on both sides are made of polytetrafluoroethylene, and the film thickness is 160 micron. The preferred hot pressing temperature is 130 degrees Celsius, the preferred hot pressing pressure applied to the membrane electrode is 5 MPa, and the preferred hot pressing time is 5 minutes.

[0083] In addition, in the present invention, the spraying setting includes the spraying time of a certain slurry, which refers to the time node within a spraying cycle T0.

[0084] The spray mode setting includes the spray flow rate setting, which refers to the propulsion flow rate of the slurry in a specific micro-injector pipeline. The slurry inlet volume in the first spray is V C , ensuring that the slurry occupies the pipeline and mixing flow plate between the micro-injector and the nozzle. The amount of this part of the slurry can meet the liquid volume requirements of the early debugging of the atomization state of the sprayer nozzle.

[0085] The membrane electrode for water electrolysis was prepared by the above preferred embodiment of the present invention, and the membrane electrode was installed in a PEM electrolyzer. The test mode adopted was a long-cycle constant current test with a current density of 2A / cm 2The test temperature is 60 degrees Celsius. The voltage change curve over time is recorded. The test mode is 165 hours of continuous constant current test plus 3 hours of power off for each test cycle. Figure 5 .

[0086] Figure 6 This graph shows performance test data for a water electrolysis membrane electrode produced using an existing unified spray coating method. This conventional membrane electrode, typically a single-piece membrane electrode, features equal precious metal loading at all points on both the cathode and anode catalyst layers. Other parameters are identical to those of the membrane electrode of the present invention. The testing conditions for the conventional membrane electrode are the same as those for the membrane electrode of the present invention.

[0087] from Figure 5 、 6 Comparing the constant current test curves of the two, it can be seen that the voltage data of the membrane electrode prepared by the present invention during the constant current test is lower than that of the conventional membrane electrode, indicating that the electrolysis efficiency of the membrane electrode prepared by the present invention is higher than that of the conventional membrane electrode. Furthermore, within the same constant current test cycle of 165 hours, the water electrolysis membrane electrode prepared by the present invention has a smaller voltage fluctuation range and smaller voltage fluctuations between different test cycles.

[0088] In addition, compared with the existing unified spraying method, the preparation method of the present invention reduces the amount of platinum metal used in the cathode by at least 14% and the amount of iridium metal used in the anode by at least 6% without reducing the performance of the membrane electrode. Overall, it reduces the amount of precious metals by about 10%, improves the actual use efficiency of the precious metal catalyst, and greatly simplifies the industrial production process of the membrane electrode of the electrolytic water tank.

[0089] The technical effect of reducing the use of precious metals by about 10% is achieved by using an actual measurement method to analyze the metal loading of the five-part membrane electrode using X-ray fluorescence spectroscopy (XRF) at different positions. Specifically, the XRF equipment used belongs to the X-MET8000 series, which can perform accurate quantitative analysis of metal platinum and metal iridium. The measurement modes of the two metals are different, and there will be no mutual influence between the metal loading data. For each membrane electrode partition, such as MEA_1, measurements are taken at five points: the upper left corner, the upper right corner, the geometric center, the lower left corner, and the lower right corner of the partition. The readings of the five points are averaged, and the calculation of the average value does not take into account the standard deviation of the experimental readings of the equipment.

[0090] The actual values ​​of the cathode platinum loading and the anode iridium loading in the membrane electrode prepared by the preparation method of the present invention were statistically analyzed, as shown in Tables 1 and 2 below:

[0091]

[0092] Table 1: Actual platinum loading of membrane electrode cathode prepared according to the method of the present invention (unit: mg / cm 2 )

[0093]

[0094] Table 2: Actual platinum loading of membrane electrode cathode prepared according to the method of the present invention (unit: mg / cm 2 )

[0095] In the control example of the standard membrane electrode prepared by the existing uniform spraying preparation method, the platinum loading of the membrane electrode cathode was measured by XRF equipment and was >0.5mg / cm 2 , iridium loading of membrane electrode anode>1.5mg / cm 2 It should be noted that, in the control example, the same slurry was used for ultrasonic spraying throughout the entire process, and the metal loading was very uniform, so there was no need to perform multiple measurements to obtain an average.

[0096] As shown above, by comparing the amount of precious metals used in the membrane electrode prepared by the preparation method of the present invention with the standard membrane electrode prepared by the existing preparation method, the cathode load was reduced by: (0.5-0.427) / 0.5=14.6%; the anode load was reduced by: (1.5-1.408) / 1.5=6%.

[0097] It should be noted that the preferred embodiments of the present invention are given in the specification and drawings of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. In addition, the above-mentioned technical features can be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the description of the present invention. Furthermore, it is obvious to those skilled in the art that improvements or changes can be made based on the above description, and all such improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a water electrolysis membrane electrode with a noble metal loading gradient design, characterized in that: The following steps are involved: Step S1, preparing cathode slurry and anode slurry, wherein the cathode slurry includes cathode slurries A to E with decreasing precious metal loading, and the anode slurry includes anode slurries F to J with decreasing precious metal loading; Step S2, placing the cathode slurries A to E in five micro-injectors S1 to S5 respectively, and connecting the micro-injectors S1 to S5 to the mixing unit and then to the spraying equipment through the liquid supply pipe; Step S3, vacuum adsorbing the proton exchange membrane onto the heating plate, setting the spraying area and spraying mode on the spraying equipment and starting spraying, and after completion, a semi-catalyst membrane containing cathode catalyst can be obtained; Step S4, cleaning the micro-injectors S1-S5 and pipelines, and placing the anode slurries F-J in the micro-injectors S1-S5 respectively; Step S5, the half catalyst film containing the cathode catalyst is reversely vacuum adsorbed on the heating plate, and the spraying equipment sets the spraying area and spraying mode to start spraying, and the catalyst film can be obtained after the spraying is completed; in steps S3 and S5, the starting point of the spraying area is PA(X A ,Y A ), the end point is PB(X B ,Y B ), the spraying pattern is an S-shaped path, starting from the starting point P A To the end point P B The spraying cycle time is T0; Step S6: attach the gas diffusion layer to both sides of the catalyst membrane, place it in a mold of a hot press and perform hot pressing to obtain a water electrolysis membrane electrode. In step S2, during one spraying cycle T0, the micro-injectors S1-S5 are set to inject samples in the following manner: PA(X A ,Y A ) Starting from the spraying starting point, the injection flow rate of S1 is C0, and the duration is 0~0.2*T0, The injection flow rate of S1 and S2 is 0.5*C0, and the duration is 0.2*T0~0.4*T0, The injection flow rate of S2 and S3 is 0.5*C0, and the duration is 0.4*T0~0.6*T0, The injection flow rate of S3 and S4 is 0.5*C0, and the duration is 0.6*T0~0.8*T0, The injection flow rate of S4 and S5 is 0.5*C0, and the duration is 0.8*T0~T0, until PB(X B ,Y B )Spraying end point.

2. The preparation method according to claim 1, characterized in that The cathode slurries A to E are all prepared by mixing platinum-carbon catalyst, perfluorosulfonic acid resin solution, water and isopropyl alcohol; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry A is 0.50; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry B is 0.55; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry C is 0.60; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry D is 0.65; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the platinum-carbon catalyst carbon support in the cathode slurry E is 0.

70.

3. The preparation method according to claim 1, characterized in that The anode slurries F to J are all prepared by mixing an iridium-based catalyst, a perfluorosulfonic acid resin solution, water, and isopropyl alcohol; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry F is 0.090; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry G is 0.095; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry H is 0.100; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry I is 0.105; The mass ratio of the dry weight of the perfluorosulfonic acid resin solution to the iridium-based catalyst in the anode slurry J is 0.

110.

4. The preparation method according to claim 1, characterized in that In step S2, the mixing unit is a constant volume mixing channel plate.

5. The preparation method according to claim 4, characterized in that The liquid supply pipe between the mixing unit and the spraying equipment is also provided with a defoamer.

6. The preparation method according to claim 1, characterized in that In step S4, the microinjectors S1-S5 and the pipelines are emptied using a mixture of n-propanol and isopropanol in a volume ratio of 1:

1.

7. The preparation method according to claim 1, characterized in that When the membrane electrode area is S=a*b, where a is the long side size and b is the short side size, the spraying area is larger than the membrane electrode area S to be sprayed, that is, the starting point A(X A ,Y A ) and the end point B(X B ,Y B ) satisfies: where: |X A -X B |>a,|Y A -Y B |>b, spraying area (|X A -X B |*|Y A -Y B |) is larger than the membrane electrode area S=a*b with spraying.

8. The preparation method according to claim 1, characterized in that The spraying area is divided into five equal areas MEA1-MEA5 in the casting direction; The MEA1 area is sprayed with only cathode slurry A or anode slurry F; The MEA2 region is sprayed with a mixed slurry of cathode slurries A and B, or anode slurries F and G; The MEA3 region is sprayed with a mixed slurry of cathode slurries B and C, or anode slurries G and H; The MEA4 region is sprayed with a mixed slurry of cathode slurries C and D, or anode slurries H and I; The MEA5 region was sprayed with a mixed slurry of cathode slurries D and E, or anode slurries I and J.

9. The preparation method according to claim 1, characterized in that When the spraying pattern is an S-shaped path, the spraying path spacing L0 is 0.1 to 0.6 mm.

10. A water electrolysis membrane electrode prepared by the preparation method according to any one of claims 1 to 9.

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