Electrolytic bath pole plate based on gradient flow channel and composite coating and preparation method of electrolytic bath pole plate

Abstract

The invention discloses an electrolytic bath pole plate based on gradient flow channels and a composite coating, the electrolytic bath pole plate comprises a pole plate base body, a plurality of flow channels are uniformly arranged on the pole plate base body, each flow channel comprises an inlet area, an outlet area and a transition area, the width and depth of the inlet area are relatively large, and the width and depth of the transition area are kept unchanged; the widths and the depths of the inlet area and the outlet area are gradually reduced along the flowing direction, the pole plate substrate is provided with a composite coating on the surface of the flow channel, the composite coating comprises a titanium nitride layer, a carbon-containing layer and a self-repairing polymer layer, and the pole plate substrate is provided with an integrally formed gas diffusion layer on one side of the flow channel; the invention further discloses a preparation method of the electrolytic bath pole plate based on the gradient flow channel and the composite coating. According to the invention, fluid distribution is optimized through flow channel size gradient change, concentration polarization is reduced, the upper limit of current density is improved, the design of the composite coating can reduce resistance, improve corrosion resistance and prolong service life, and at the same time, precious metal is prevented from being used to further reduce cost.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by water electrolysis, and particularly to an electrolytic cell plate based on a gradient flow channel and a composite coating and a preparation method thereof. Background Art

[0002] The technology of hydrogen production by water electrolysis is a key way to achieve green hydrogen production. Especially driven by renewable energy power, it has broad application prospects. The hydrogen produced by it has the characteristics of high purity and is suitable for fields such as fuel cells and chemical industry. In the technology of hydrogen production by water electrolysis, according to the structure of the electrolytic cell and the difference of the electrolyte, the electrolytic cell can be divided into three categories, namely proton exchange membrane electrolytic cell, alkaline electrolytic cell, and solid oxide electrolytic cell. As a key component in the electrolytic cell, the plate plays important roles such as conducting electricity, separating the anode and cathode, supporting, and fluid distribution. The material selection and structural design of the plate directly affect the service performance and life of the electrolytic cell.

[0003] However, the existing anodic plates of electrolytic cells all have the following problems and defects: the current density distribution is uneven. The flow channel design of traditional plates easily leads to uneven distribution of electrolyte or gas, resulting in too high current density in local areas, accelerating material corrosion and reducing efficiency; the contact resistance at the plate interface is high. The contact resistance between the plate and the electrode increases the ohmic loss and affects the energy conversion efficiency; the corrosion resistance is insufficient. In a high-potential and acidic / alkaline environment, the metal plate is prone to corrosion, shortening its service life; the cost is high. Precious metal coatings (such as gold and platinum) are commonly used in existing electrolytic cells. Although they can improve the performance, they greatly increase the manufacturing cost.

[0004] At present, some patented technologies solve the problems of the existing technology by improving the flow channel structure of the anodic plate of the electrolytic cell and by adding coatings, but the obtained effects are single and cannot solve the above defects at the same time. Therefore, there is an urgent need for a new plate structure and electrolytic cell with high efficiency, corrosion resistance, and low cost, which can improve the hydrogen production efficiency and hydrogen quality while reducing the cost. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of an electrolytic cell plate based on a gradient flow channel and a composite coating to solve the problems and defects mentioned in the above background art.

[0006] To achieve the above purpose, the following technical solutions are provided: A preparation method of an electrolytic cell plate based on a gradient flow channel and a composite coating includes the following steps: S1: Select a titanium plate as the plate substrate and perform pretreatment on the plate substrate; S2: Use a fiber laser to uniformly engrave flow channels on the plate substrate, and uniformly engrave micro-grooves on the flow channels. During the engraving process, it is necessary to control the thermal deformation of the flow channels. Insert a 0.5s cooling time every 5mm length of engraving. At the same time, use a copper substrate on the back of the plate substrate and force water cooling with 20°C circulating water; after engraving, detect the flow channels; S3: Deposit a titanium carbide layer on the surface of the flow channels by magnetron sputtering. The sputtering target is a high-purity titanium target. After deposition, detect the crystal orientation; S4: Deposit a carbon-containing layer on the surface of the titanium nitride layer by electrochemistry. The electrolyte contains graphene or / and carbon nanotubes. After deposition, detect the conductivity of the carbon-containing layer; S5: Spray a self-healing polymer layer on the surface of the carbon-containing layer. The spraying uses a two-component spray gun and is sprayed three times crosswise to control the thickness. Use segmented curing, and its curing conditions are set to 80°C×30min + 180°C×1h. After spraying, detect the density of the self-healing polymer layer; S6: Prepare a gas diffusion layer on the plate substrate by laser sintering process; S7: Test the performance of the prepared electrolytic cell plate.

[0007] Furthermore, in step S1, the pretreatment of the plate substrate includes the following steps: First, perform alkaline degreasing on the substrate, that is, ultrasonically clean with a 60°C NaOH solution for 15 - 20 minutes. Then, pickle and activate the substrate, that is, soak it in a mixed acid solution with a ratio of HF:HNO3:H2O = 1:3:10 at room temperature for 3 - 5 minutes. Finally, ultrasonically clean with deionized water and dry with nitrogen.

[0008] Furthermore, in step S6, the method for preparing the gas diffusion layer is: Use the laser sintering process. The material of the gas diffusion layer is titanium powder, and a pore-forming agent is added to the titanium powder. The pore-forming agent is NH4HCO3, and the proportion of the pore-forming agent is 7 - 8wt%. The particle size of the titanium powder is selected to be 15 - 45μm, and the sphericity is greater than 90%; after laser sintering is completed, perform vacuum annealing on the whole of the plate substrate and the gas diffusion layer, and inspect the porosity of the gas diffusion layer to ensure that the porosity is within the range of 45±2%.

[0009] Further, in step S7, the performance test includes a normal test and an accelerated durability test. In the normal test, the electrode plate is assembled in the electrolytic cell and operated at a current density of 2 A / cm² for 1000 hours, ensuring that the voltage decay < 5% and the contact resistance < 5 mΩ·cm². The accelerated durability test means that the electrode plate operates continuously under specific conditions to test its durability. The test conditions are as follows: the electrolyte is H2SO4 solution with a temperature of 80°C and a molar concentration of 1 Mol / L, the pressure difference between the anode and cathode in the electrolytic cell is 0.5 MPa, the current density is 2 A / cm², and a triangular wave scan from 0 to 2 A / cm² is performed every 24 hours with a scan rate of 10 mA / s.

[0010] An electrolytic cell electrode plate based on a gradient flow channel and a composite coating includes an electrode plate substrate. A plurality of flow channels are evenly spaced on the electrode plate substrate. The flow channels include an inlet region, an outlet region, and a transition region located between the inlet region and the outlet region. The width and depth of the inlet region and the outlet region gradually decrease along the flow direction, and the width and depth of the inlet region are respectively greater than those of the outlet region. The width and depth of the transition region remain unchanged. Micro-grooves are evenly arranged at the bottom of the flow channels. The electrode plate substrate is also provided with a composite coating on one side of the flow channels. The composite coating includes a titanium nitride layer, a carbon-containing layer, and a self-healing polymer layer. The carbon-containing layer contains ultra-thin graphene or / and carbon nanotubes, and the self-healing polymer layer contains polyaniline or / and fluorocarbon resin. A gas diffusion layer integrally formed with the electrode plate substrate is provided on one side of the electrode plate substrate through a laser sintering process in the flow channel.

[0011] Preferably, the titanium nitride layer is provided on the electrode plate substrate, the carbon-containing layer is provided on the titanium nitride layer, and the self-healing polymer layer is provided on the carbon-containing layer.

[0012] Preferably, the cross-section of the flow channel of the electrode plate substrate is trapezoidal.

[0013] Preferably, the thickness of the titanium nitride layer is 1 - 2 μm, the thickness of the carbon-containing layer is 0.5 - 1 μm, and the thickness of the self-healing polymer layer is 5 - 12 μm.

[0014] The present invention also discloses an application of an electrolytic cell electrode plate based on a gradient flow channel and a composite coating in a proton exchange membrane electrolytic cell or an alkaline electrolytic cell.

[0015] The present invention has the following beneficial effects compared with the prior art: (1) The present invention optimizes the fluid distribution through the gradient change of the flow channel size, that is, the width and depth of the flow channel gradually decrease from the inlet to the outlet of the flow channel, which can reduce concentration polarization and increase the upper limit of the current density (up to 3 A / cm 2), and by uniformly arranging micro-grooves at the bottom of the flow channel, the local turbulence of the gas in the flow channel can be enhanced, promoting the detachment of bubbles; (2) In the present invention, the gas diffusion layer and the plate substrate are set as an integral structure through the laser sintering technology, which can reduce the interfacial contact resistance and avoid the performance loss caused by the assembly error between the traditional plate and the gas diffusion layer; (3) In the present invention, the design of the composite coating, that is, under the synergistic action of the titanium nitride layer, the carbon-containing layer, and the self-healing polymer layer, can simultaneously take into account low resistance, high corrosion resistance, and long life. Among them, the titanium nitride layer can improve the corrosion resistance of the plate substrate, the graphene and / or carbon nanotubes in the carbon-containing layer can reduce the contact resistance, and the self-healing polymer layer can dynamically repair micro-cracks in the electrolyte environment and extend the life; (4) In the present invention, the use of precious metals is avoided, and the manufacturing cost can be reduced through the laser sintering and coating processes. Description of the Drawings

[0016] Figure 1 It is a flowchart of a preparation method of an electrolytic cell plate based on a gradient flow channel and a composite coating in Embodiment 1 of the present invention; Figure 2 It is a schematic cross-sectional structure diagram of an electrolytic cell plate based on a gradient flow channel and a composite coating in Embodiment 1 of the present invention; Figure 3 It is a schematic diagram of the flow channel distribution of the plate substrate of an electrolytic cell plate based on a gradient flow channel and a composite coating in Embodiment 1 of the present invention; Figure 4 It is a schematic cross-sectional view of the flow channel inlet region of an electrolytic cell plate based on a gradient flow channel and a composite coating in Embodiment 1 of the present invention; Figure 5 is Figure 2 enlarged view of part A; Figure 6 It is a schematic structural diagram of a proton exchange membrane electrolytic cell in Embodiment 2 of the present invention; Reference numerals: 1, plate substrate; 2, flow channel; 21, inlet region; 22, outlet region; 23, transition region; 3, micro-groove; 4, gas diffusion layer; 5, composite coating; 51, titanium nitride layer; 52, carbon-containing layer; 53, self-healing polymer layer; 6, membrane electrode; 7, anode gas diffusion layer; 8, cathode gas diffusion layer; 9, anode plate; 10, cathode plate; 11, sealing ring. Detailed Embodiments

[0017] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0019] Embodiment 1: An electrolytic cell plate based on a gradient flow channel and a composite coating and a preparation method thereof As Figure 1 shown, a preparation method of an electrolytic cell plate based on a gradient flow channel and a composite coating includes the following steps: Step 1: Pretreat the base material of the plate base 1 Among them, the base material for making the plate base 1 is a TA1 grade titanium plate (GB / T 3621 standard), and the thickness of the titanium plate is 2.0 ± 0.05 mm; First, perform alkaline degreasing on the base material, and ultrasonically clean it in a NaOH solution at 60 °C for 15-20 minutes; Then, pickle and activate the base material, and soak the base material in a mixed acid solution with a ratio of HF:HNO3:H2O = 1:3:10 at room temperature for 3-5 minutes; Finally, ultrasonically clean it in deionized water and then dry it with nitrogen.

[0020] Step 2: Laser engrave the flow channel 2 on the plate base 1 Use a fiber laser to laser engrave the flow channel 2 on the pretreated plate base base material, and uniformly engrave micro-grooves 3 on the flow channel 2. When laser engraving, the parameters of the fiber laser are set as wavelength 1064 nm, pulse width 100 ns, and the engraving parameters are adjusted in stages. When engraving the inlet area 21 of the flow channel 2, the power is 300 W, the scanning speed is 800 mm / s, the frequency is 50 kHz, and it is repeatedly engraved 3 times. When engraving the transition area 23 between the inlet area 21 and the outlet area 22 of the flow channel 2, the power is 250 W, the scanning speed is 1000 mm / s, the frequency is 60 kHz, and it is repeatedly engraved 2 times; When engraving the outlet area 22 of the flow channel 2, the power is 200 W, the scanning speed is 1200 mm / s, the frequency is 80 kHz, and it is repeatedly engraved 1 time.

[0021] During the laser engraving process, it is necessary to control the thermal deformation of the flow channel 2. In this embodiment, a segmented cooling strategy is adopted, that is, a 0.5 s cooling time is inserted every 5 mm of engraving length. At the same time, the back surface of the plate substrate 1 uses a copper substrate and is forced water-cooled with 20 °C circulating water. After engraving, quality inspection is carried out. A white light interferometer is used to detect the dimensional tolerance of the flow channel, and the tolerance is ensured to be within the range of ±50 μm. Then, a scanning electron microscope (SEM) is used to observe the heat-affected zone.

[0022] Step 3: Deposit a titanium carbide layer 51 on the surface of the flow channel 2 of the plate substrate 1 by magnetron sputtering A titanium nitride layer 51 is deposited on one side of the flow channel of the plate substrate 1 by magnetron sputtering technology. The sputtering target is a high-purity titanium target with a purity of 99.99%. The working gas is a mixed gas of argon and nitrogen with a volume ratio of 4:1 and a pressure of 0.3 Pa. The bias voltage is set to -100 V, the power density is 5 W / cm², and the deposition rate is 0.1 μm / min. After deposition, the crystal orientation of the titanium carbide layer 51 is detected. Specifically, a X-ray diffractometer is used to perform preferred orientation on the titanium nitride layer 51, and a step profiler is used to measure the crystal thickness of the titanium nitride thin film to ensure that the thickness of the titanium nitride layer 51 is controlled within the range of 1.5 ± 0.2 μm.

[0023] Step 4: Deposit a carbon-containing layer 52 on the surface of the titanium nitride layer 51 by electrochemistry A carbon-containing layer 52, that is, a graphene and carbon nanotube layer, is deposited on the surface of the titanium nitride layer 51 by electrochemistry (electroplating method). Among them, the electrolyte includes a graphene dispersion with a concentration of 2 mg / mL, carboxylated carbon nanotubes with a concentration of 1 mg / mL, and an H2SO4 solution with a molar concentration of 0.1 Mol / L. The following preparation parameters are selected: the potentiostatic mode is -1.2 V vs SCE, the deposition time is 30 min, ultrasonic waves with a frequency of 40 kHz and a power of 100 W are used. After deposition, the conductivity of the carbon-containing layer is detected.

[0024] Step 5: Spray a self-healing polymer layer 53 on the surface of the carbon-containing layer 52 A self-healing polymer layer 53 is sprayed on the surface of the carbon-containing layer 52. In this embodiment, the mass ratio of polyaniline (intrinsic state) to fluorocarbon resin is 1:4, and the solvent uses a solvent system with a volume ratio of NMP to DMF of 3:7 (containing 0.5% BYK-333 dispersant); spraying uses a two-component spray gun, the spray gun pressure is 0.3 MPa, and the nozzle diameter is 0.3 mm; and segmented curing is carried out, and its parameters are set to 80 °C × 30 min + 180 °C × 1 h; and cross-spraying is carried out three times to achieve thickness control.

[0025] Step 6: Prepare a gas diffusion layer 4 on the plate substrate 1 by laser sintering process The gas diffusion layer 4 is prepared by a laser sintering process on one side of the flow channel 2 of the plate substrate 1. The material selected is titanium powder, and a pore-forming agent is added to the titanium powder. The pore-forming agent is NH4HCO3, and the proportion of the pore-forming agent is 7-8 wt%. The particle size of the titanium powder is selected to be 15-45 μm, and the sphericity is greater than 90%. During the preparation of the gas diffusion layer 4, the parameter settings are as follows: laser power 200 W (continuous mode), scanning spacing 80 μm, gas diffusion layer thickness 50 μm, and the protective gas selected is argon with a purity of 99.999%. After the gas diffusion layer 4 is prepared, the plate substrate 1 and the gas diffusion layer 4 are vacuum annealed as a whole, and the porosity of the gas diffusion layer is inspected to ensure that the porosity is within the range of 45±2%.

[0026] Step 7: Plate performance test The performance test is divided into a normal test and an accelerated durability test. First, the normal test means assembling the plate in the electrolytic cell and operating it at a current density of 2 A / cm² for 1000 hours. If the voltage decay < 5% and the contact resistance < 5 mΩ·cm², it is considered qualified; the accelerated durability test means that the plate operates continuously under specific conditions to test its durability. The test conditions are as follows: the electrolyte is H2SO4 solution with a temperature of 80°C and a molar concentration of 1 Mol / L, the pressure difference between the anode and cathode in the electrolytic cell is 0.5 MPa, the current density is 2 A / cm², and a triangular wave scan of 0-2 A / cm² is performed every 24 hours, and the scan rate is 10 mA / s.

[0027] As Figures 2 to 5 shown, an electrolytic cell plate based on a gradient flow channel and a composite coating includes a plate substrate 1. A plurality of flow channels 2 are uniformly and spacedly arranged on the plate substrate 1. The flow channel 2 includes an inlet region 21, an outlet region 22, and a transition region 23 provided between the inlet region 21 and the outlet region 22. Among them, the width and depth of the inlet region 21 and the outlet region 22 gradually decrease along the flow direction, and the width and depth of the inlet region 21 are respectively greater than the width and depth of the outlet region 22. The width and depth of the transition region 23 remain unchanged. Micro-grooves 3 are uniformly arranged at the bottom of the flow channel 2. The plate substrate 1 is coated with a composite coating 5 on one side of the flow channel 2. The composite coating 5 includes a titanium nitride layer 51, a carbon-containing layer 52, and a self-healing polymer layer 53. The carbon-containing layer 51 contains ultra-thin graphene and carbon nanotubes, and the self-healing polymer layer 53 contains polyaniline or fluorocarbon resin. A gas diffusion layer 4 integrally formed with the plate substrate 1 is provided on one side of the flow channel 2 of the plate substrate 1 by a laser sintering process.

[0028] It should be noted that the shape of the electrode plate substrate 1 can be rectangular or other specific shapes. In this embodiment, in order to more intuitively describe the structure of the flow channel 2, the electrode plate substrate 1 is set in a Z shape; at the same time, the shape of the flow channel 2 can be serpentine, wavy, linear, or other shapes. In this embodiment, also for the purpose of more intuitively describing the structural changes of the flow channel 2, the shape of the flow channel 2 is set to be linear.

[0029] Among them, the cross-section of the flow channel 2 on the electrode plate substrate 1 is trapezoidal.

[0030] Among them, the width of the inlet 21 of the flow channel 2 is 3 mm and the depth is 1.5 mm, and the width of the outlet 22 of the flow channel 2 is 1 mm and the depth is 0.5 mm.

[0031] Among them, the length and width of the micro-groove 3 are both set to 150 μm, and the depth of the micro-groove 3 is 80 μm.

[0032] Among them, the carbon-containing layer 52 is a mixed coating of ultra-thin graphene and carbon nanotubes, and the self-healing polymer layer 53 is a mixed coating of polyaniline and fluorocarbon resin.

[0033] Among them, the thickness of the titanium nitride layer 51 is 1 - 2 μm, the thickness of the carbon-containing layer 52 is 0.5 - 1 μm, and the thickness of the self-healing polymer layer 53 is 5 - 12 μm.

[0034] Embodiment 2: A proton exchange membrane electrolyzer As Figure 6 shown, a proton exchange membrane electrolyzer includes a membrane electrode 6, an anode gas diffusion layer 7, a cathode gas diffusion layer 8, an anode plate 9, a cathode plate 10, and a sealing ring 11. Among them, the anode plate 9 and the anode gas diffusion layer 7 belong to an integral structure and are integrally formed by a laser sintering process. It is an application of the electrolyzer electrode plate with a gradient flow channel and a composite coating in Embodiment 1 on a proton exchange membrane electrolyzer. Embodiment 1 simultaneously has the functions of the anode plate 9 and the anode gas diffusion layer 7. The anode gas diffusion layer 7 and the cathode gas diffusion layer 8 are respectively arranged on both sides of the membrane electrode 6. The anode plate 9 and the cathode plate 10 are respectively arranged on both sides of the anode gas diffusion layer 7 and the cathode gas diffusion layer 8, and sealing rings 11 are arranged at the edges of the anode plate 9 and the cathode plate 10.

[0035] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an electrolytic cell plate based on a gradient flow channel and a composite coating, characterized in that: The following steps are involved: S1: Select titanium plate as the plate substrate and pre-treat the plate substrate; S2: Use fiber laser to uniformly engrave the flow channel on the plate substrate, and uniformly engrave micro grooves on the flow channel. During the engraving process, the thermal deformation of the flow channel needs to be controlled. A cooling time of 0.5s is inserted for every 5mm of engraving length. At the same time, a copper substrate is used on the back of the plate substrate, and forced water cooling is performed with 20℃ circulating water. After the engraving is completed, the flow channel is inspected; S3: A titanium carbide layer is deposited on the surface of the flow channel by magnetron sputtering. A high-purity titanium target is selected as the sputtering target. After the deposition, the crystal orientation is tested; S4: depositing a carbon-containing layer on the surface of the titanium nitride layer by an electrochemical method, wherein the electrolyte contains graphene and / or carbon nanotubes, and detecting the conductivity of the carbon-containing layer after the deposition is completed; S5: spraying a self-repairing polymer layer on the surface of the carbon-containing layer, using a two-component spray gun, and cross-spraying three times to control the thickness, using segmented curing, and the curing conditions are set to 80℃×30min+180℃×1h. After the spraying is completed, the compactness of the self-repairing polymer layer is tested; S6: preparing a gas diffusion layer on the plate substrate by laser sintering process; S7: Performing performance tests on the prepared electrolytic cell plates.

2. The method for preparing an electrolytic cell plate based on a gradient flow channel and a composite coating according to claim 1, characterized in that: In step S1, the plate substrate pretreatment includes the following steps: first, alkaline degreasing of the substrate, i.e., ultrasonic cleaning with a 60°C NaOH solution for 15-20 minutes, then acid-washing and activating the substrate, i.e., soaking in a mixed acid solution with a ratio of HF:HNO3:H2O=1:3:10 at room temperature for 3-5 minutes, and finally, ultrasonic cleaning with deionized water and drying with nitrogen.

3. The method for preparing an electrolytic cell plate based on a gradient flow channel and a composite coating according to claim 2, characterized in that: The method for preparing the gas diffusion layer in step S6 is: using a laser sintering process, the gas diffusion layer material is titanium powder, a pore-forming agent is added to the titanium powder, wherein the pore-forming agent is NH4HCO3, the pore-forming agent accounts for 7-8wt%, the particle size of the titanium powder is 15-45μm, and the sphericity is greater than 90%; after the laser sintering is completed, the electrode substrate and the gas diffusion layer are vacuum annealed as a whole, and the porosity of the gas diffusion layer is tested to ensure that the porosity is within the range of 45±2%.

4. The method for preparing an electrolytic cell plate based on a gradient flow channel and a composite coating according to claim 1, characterized in that: In step S7, the performance test includes a normal test and an accelerated durability test, wherein the normal test refers to assembling the electrode plate in the electrolytic cell and running it at a current density of 2A / cm² for 1000 hours to ensure that the voltage decay is less than 5% and the contact resistance is less than 5mΩ·cm²; the accelerated durability test refers to the continuous operation of the electrode plate under specific conditions to test its durability. The test conditions are: the electrolyte uses an H2SO4 solution with a temperature of 80°C and a molar concentration of 1Mol / L, the pressure difference between the anode and cathode in the electrolytic cell is 0.5MPa, the current density is 2A / cm², and a 0-2A / cm² triangle wave scan is performed every 24 hours at a scan rate of 10mA / s.

5. An electrolytic cell plate based on a gradient flow channel and a composite coating prepared by the method for preparing an electrolytic cell plate based on a gradient flow channel and a composite coating as claimed in any one of claims 1 to 4, characterized in that: It includes a plate substrate, on which a plurality of flow channels are evenly spaced, the flow channels include an inlet area, an outlet area and a transition area between the inlet area and the outlet area, the width and depth of the inlet area and the outlet area gradually decrease along the flow direction, and the width and depth of the inlet area are respectively greater than the width and depth of the outlet area, the width and depth of the transition area remain unchanged, micro grooves are evenly arranged at the bottom of the flow channel, the plate substrate is also provided with a composite coating on one side of the flow channel, the composite coating includes a titanium nitride layer, a carbon-containing layer and a self-healing polymer layer, the carbon-containing layer contains ultra-thin graphene and / or carbon nanotubes, the self-healing polymer layer contains polyaniline and / or fluorocarbon resin, and the plate substrate is provided with a gas diffusion layer integrally formed with the plate substrate on one side of the flow channel through a laser sintering process.

6. The electrolytic cell plate based on gradient flow channel and composite coating according to claim 5, characterized in that: The titanium nitride layer is arranged on the polar plate substrate, the carbon-containing layer is arranged on the titanium nitride layer, and the self-repairing polymer layer is arranged on the carbon-containing layer.

7. The electrolytic cell plate based on gradient flow channel and composite coating according to claim 5, characterized in that: The cross section of the electrode plate substrate flow channel is trapezoidal.

8. The electrolytic cell plate based on gradient flow channel and composite coating according to claim 7, characterized in that: The thickness of the titanium nitride layer is 1-2 μm, the thickness of the carbon-containing layer is 0.5-1 μm, and the thickness of the self-healing polymer layer is 5-12 μm.

9. Use of an electrolyzer plate based on a gradient flow channel and a composite coating according to any one of claims 5 to 8 in a proton exchange membrane electrolyzer or an alkaline electrolyzer.

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