A bipolar plate and its application in PEM water electrolysis hydrogen production

Abstract

The present invention discloses a bipolar plate and its application in PEM water electrolysis hydrogen production, belonging to the field of water electrolysis hydrogen production. An alloy steel bipolar plate is perforated in an array to form a group of holes. Titanium slurry is then scraped onto the front and back surfaces of the alloy steel plate and into the holes, then dried and solidified. The scraped titanium layer is compacted and densified using a hot press. The titanium slurry is then printed using a mold to form an integrated flow field and multifunctional area on the surface of the plate. The resulting high-performance water electrolysis bipolar plate is simple to process, has lower contact resistance, better adhesion between the coating and the substrate, and is highly durable.

Description

Technical Field

[0001] The present invention belongs to the field of hydrogen production by water electrolysis, and in particular relates to a bipolar plate and its application in PEM water electrolysis hydrogen production. Background Art

[0002] Hydrogen is becoming increasingly popular as a clean energy source. Proton exchange membrane (PEM) water electrolysis technology can produce hydrogen using excess energy from wind and solar power. Proton exchange membrane (PEM) water electrolysis has many advantages. The only raw material in this process is water, and the products are oxygen and hydrogen. The resulting gas is highly pure, safe, efficient, and environmentally friendly, enabling on-site hydrogen production and addressing hydrogen transportation challenges. Therefore, PEM water electrolysis technology has important applications in energy, transportation, chemical engineering, and other fields.

[0003] Bipolar plates are one of the key technologies in proton exchange membrane water electrolysis technology. The bipolar plates are equipped with a flow field structure, which includes flow channel ridges, flow columns in the flow disturbance area, and hydrogen and oxygen frames. In addition, the bipolar plates also include flow channel grooves and hydrogen and oxygen cavities. The flow channel ridges, flow channel grooves, flow columns, and hydrogen and oxygen frames form the flow field structure of the bipolar plates. In actual operation, there are very high requirements for the mechanical properties, electrical conductivity, thermal conductivity, chemical stability, and cost of the bipolar plate materials. Traditional water electrolysis bipolar plates contain hydrogen frames, oxygen frames, and separators. During production, multiple complex processes such as positioning, gluing, hot pressing, and welding are required. For example, patent CN104716329B first processes each component of the bipolar plate separately; then the separator is subjected to conductive treatment; finally, it is fixed and formed and then welded into a complete bipolar plate. Due to the unique operating environment of water electrolysis, water electrolysis bipolar plates are generally made of titanium or other highly corrosion-resistant and conductive materials, which greatly increases their production cost. High-alloy steel plates are inexpensive, but due to the inherent properties of the material, it is difficult to achieve the operating environment of water electrolysis without further treatment. Therefore, high-alloy steel plates require additional processing to meet corrosion resistance requirements. Traditional high-alloy steel coating methods involve directly applying a layer of precious metal to the surface of the high-alloy steel through physical or chemical plating to reduce the substrate's contact resistance and improve its conductivity and corrosion resistance. However, with traditional preparation methods, the film is prone to detachment or poor adhesion after the plate has been in operation for a period of time, resulting in higher plate resistance. Moreover, after the film detaches, the high-alloy steel itself is more susceptible to corrosion. This results in material waste and increased costs. Therefore, how to simply modify metal bipolar plates to reduce their contact resistance and improve the performance of water electrolysis bipolar plates is currently a top priority. Summary of the Invention

[0004] The purpose of the present invention is to provide a bipolar plate and its application in PEM water electrolysis hydrogen production, to optimize the preparation process and reduce the preparation cost without reducing the water electrolysis performance.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A PEM water electrolysis bipolar plate, comprising an alloy steel plate as a substrate, a plurality of through-holes provided on the substrate, a titanium layer provided on both the upper and lower surfaces of the substrate, the titanium layer filling the through-holes to form a connection between the upper and lower titanium layers, and a functional coating provided on the surface of the titanium layer to form a flow field structure of the bipolar plate;

[0007] The titanium layer contains titanium powder with a particle size of 10-30 μm, and the functional coating contains titanium powder with a particle size of 50-100 μm.

[0008] The present invention is further configured as follows: the titanium layer comprises spherical atomized titanium powder with a particle size of 10-30 μm, a solvent, an adhesive and a plasticizer; the functional coating comprises spherical atomized titanium powder with a particle size of 50-100 μm, a solvent, an adhesive, a pore-forming agent and a plasticizer.

[0009] The present invention is further configured as follows: the mass ratio of spherical atomized titanium powder with a particle size of 10-30 μm, solvent, binder and plasticizer in the titanium layer is 50-70:15-35:3-4:1-2; the mass ratio of spherical atomized titanium powder with a particle size of 50-100 μm, solvent, binder, pore former and plasticizer in the functional coating is 20-40:52-64:2-10:3-4:1-2;

[0010] The solvent in the titanium layer and the functional coating is independently at least one of ethanol, toluene or methanol, the binder in the titanium layer and the functional coating is independently at least one of polyvinyl butyral resin or acrylic resin, the plasticizer in the titanium layer and the functional coating is independently at least one of dioctyl phthalate, dibutyl phthalate or propylene glycol oxalate polyester, and the pore-forming agent includes one or a combination of two or more of urea, ammonium bicarbonate, sodium carbonate and oxalic acid.

[0011] The present invention is further configured as follows: the diameter of the hole group is 0.5-2 cm, and the total area of ​​the hole group is 20%-30% of the total area of ​​the alloy steel plate.

[0012] The present invention is further configured as follows: the thickness of the titanium layer is 1-5 mm, and micropores with a pore size of 10 nm-10 μm are distributed in the titanium layer; and micropores with a pore size of >10 μm and ≤300 μm are distributed in the functional coating.

[0013] The present invention is further configured as follows: the alloy steel plate is an alloy steel containing one or more alloy elements of Ni, Ti, and Mo, with a total alloy element mass content of 10%-30%, and a thickness of 0.5-1 mm.

[0014] The present invention is further configured as follows: the titanium layer slurry forming the titanium layer is combined with the alloy steel plate in sequence by scraping, drying, and hot pressing, and the slurry forming the functional coating is printed onto the surface of the titanium layer formed by the titanium layer slurry by mold printing;.

[0015] A method for preparing a PEM water electrolysis bipolar plate comprises the following steps:

[0016] (1) Preparation of titanium layer slurry: Spherical atomized titanium powder with a particle size of 10-30 μm is stirred and mixed with a solvent, a binder, and a plasticizer to obtain a titanium layer slurry;

[0017] Preparation of functional coating slurry: Spherical atomized titanium powder with a particle size of 50-100 μm is stirred and mixed with a solvent, a binder, a pore-forming agent and a plasticizer to obtain a functional coating slurry;

[0018] (2) Pretreatment of alloy steel plate: punch holes in the alloy steel plate array to form a group of holes, grind, polish and clean the surface, then put it into acetone solution for ultrasonic cleaning, take it out and use ultrapure water for ultrasonic cleaning, take it out and blow dry it for later use;

[0019] (3) Plate scraping: The titanium layer slurry is evenly scraped onto the alloy steel plate to fill the group holes at the same time, and a titanium layer is formed on the front and back sides of the alloy steel plate, followed by drying;

[0020] (4) hot pressing of the plate: placing the plate obtained in step (3) on a hot press platform for hot pressing;

[0021] (5) The functional coating slurry is printed onto the surface of the titanium layer by mold printing to form a flow field structure of the water electrolysis bipolar plate, and the plate is dried and demolded to prepare the water electrolysis bipolar plate. The flow field structure described herein is a broad flow field structure, including but not limited to the flow field reaction area (flow channel ridges and flow to grooves), for example, also including the inlet and outlet frames of the bipolar plate, the sealing frame (hydrogen and oxygen frame), the flow field distribution area, the bridge area, or the turbulence area. Those skilled in the art can form various structures by mold printing according to actual needs.

[0022] The present invention is further configured as follows: the conditions for the hot pressing are: pressure 4 MPa, holding time 120-180 s, room temperature; the temperature for the drying is 100-150° C., time 3-5 min.

[0023] The present invention is further configured as follows: steps (3)-(5) are completed using a continuous production line with an annular guide rail, and the annular guide rail is provided with a plurality of electrically driven sliders, and the stainless steel plates are placed on the sliders; the continuous production line is provided with working electrical appliances for scraping, hot pressing, and mold printing on the stainless steel plates in sequence, and the working electrical appliances are all connected to the PLC system circuit signal.

[0024] The present invention is further configured as follows: the polishing is performed step by step using sandpaper with a mesh size of 500 to 1200.

[0025] The present invention is further configured as follows: the polishing is performed step by step using sandpaper with mesh sizes of 500, 700, 900 and 1200 respectively.

[0026] The present invention has the following beneficial effects:

[0027] 1. Low cost and simple operation: The present invention perforates the alloy steel substrate and physically coats it with a titanium layer. Compared with pure titanium or other highly corrosion-resistant materials used in traditional water electrolysis plates, the preparation cost of the present invention is greatly reduced. Traditional water electrolysis bipolar plates are manufactured by 3D printing or one-piece molding. The present invention uses mold printing to realize the flow field and other functional areas of the water electrolysis plate. The operation is simpler, and the entire preparation process does not require other expensive equipment, which greatly reduces the preparation cost. The present invention only needs to punch holes in the alloy steel plate and then apply titanium slurry to complete the physical modification of the alloy steel plate. In addition, after applying the titanium slurry, the present invention dries it and performs hot pressing treatment to make the titanium layer in the hole and the titanium layer on the surface of the alloy steel substrate compacted by hot pressing to prevent water from flowing between the anode and cathode.

[0028] 2. Strong film-base bonding: Different from traditional alloy steel coating methods, the present invention adopts a physical modification method. First, the alloy steel body is perforated, and then the whole is wrapped with titanium slurry. Finally, the whole is hot-pressed using a hot press. The titanium layers on the front and back sides of the alloy steel plate are connected by the perforations in the middle of the plate to form an integral structure. Therefore, the titanium layer will not fall off easily. In addition, the press is used to apply pressure, so the film-base bonding on the front and back sides of the alloy steel plate is stronger and the durability is better.

[0029] 3. High performance: Although the water electrolysis bipolar plate prepared by the present invention is made of metal alloy steel, its performance is improved after the physical modification of the titanium slurry on its front and back surfaces. The present invention adds a pore-forming agent to the slurry of the printed flow field and functional area, and dries it after printing. The pore-forming agent evaporates when heated, forming micropores inside the flow field, which is beneficial to the transmission of water vapor in the flow field and improves its output performance. In terms of corrosion resistance, since the flow field and other functional areas of the bipolar plate are made of titanium material with strong corrosion resistance, during the stacking process, the water electrolysis membrane electrode directly contacts the titanium layer, so its conductivity and corrosion resistance are effectively improved, and the overall performance of the electrolytic cell is significantly improved. In addition, the titanium layer and the functional layer are filled in the through-hole of the alloy steel to form a connection between the upper and lower titanium layers, which can increase the bonding degree between the titanium layer and the substrate and reduce the contact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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 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 labor.

[0031] Figure 1 Schematic diagram of high alloy steel plate.

[0032] Figure 2 Schematic diagram of the overall structure of the mold in an embodiment of the present invention.

[0033] Figure 3 Schematic diagram of the cross section of the plate.

[0034] In the figure: 1, group of holes; 2, high-alloy steel plate; 3-1, titanium slurry in the hole; 3-2, titanium layer; 4-1, flow channel ridge; 4-2, flow channel groove; 5, closed area; 6, hollow area. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] Preparation of functional coating slurry: Weigh 20g of spherical atomized titanium powder with a particle size of 50μm (spherical atomized titanium powder obtained by atomization treatment can be prepared by a general method in this field), 64g of anhydrous ethanol, 10g of polyvinyl butyral resin, 4g of ammonium bicarbonate, and 2g of dioctyl phthalate in a beaker, and stir evenly with a mechanical stirrer for later use.

[0038] Preparation of titanium layer slurry: weigh 60 g of spherical atomized titanium powder with a particle size of 20 μm, 35 g of anhydrous ethanol, 4 g of polyvinyl butyral resin, and 1 g of dioctyl phthalate into a beaker, and stir them evenly with a mechanical stirrer for later use.

[0039] A 0.5mm thick, 20cm x 10cm high-alloy steel sheet with a 30% Mo alloy content was cut and perforated with a punch to form a cluster of holes 1. The clusters corresponded to the bipolar plate flow channels, and the total area of ​​the clusters accounted for 20%-30% of the plate's total area. The sheet was then polished using 200-500 grit sandpaper in a gradual process. The sheet was then ultrasonically cleaned in acetone for three 10-minute washes, then rinsed with ultrapure water and air-dried.

[0040] The titanium layer slurry is evenly applied to the front and back surfaces of the high-alloy steel plate to form a titanium layer 3-2 and fill the hole cluster 1. The titanium layers 3-2 on both sides are connected through the titanium slurry 3-1 filled in the hole cluster 1. The titanium layer applied to the surface of the high-alloy steel plate is 1mm thick. It is then placed in a 100°C oven for heat treatment for 5 minutes. After the time is up, it is removed and placed on a hot press platform for hot pressing. The hot press platform pressure is 4MPa and the pressure is maintained for 120 seconds. After hot pressing, a titanium layer with pores of 10μm in diameter is formed on the upper and lower surfaces of the high-alloy steel plate and in the hole clusters. The titanium layer has pores of 10μm in diameter. The mold is then placed on the surface of the plate with the titanium layer formed. The functional coating slurry is printed on the plate surface along the mold shape to form the flow field structure of the bipolar plate. After heat treatment in a 100°C oven for 5 minutes, the mold is removed, and a functional coating with a flow field structure is formed on the surface of the titanium layer. The functional coating has pores of 100μm in diameter. Finally, a laser cutting machine is used to cut and form a hydrogen and oxygen cavity to obtain a water electrolysis bipolar plate.

[0041] The structure of the obtained water electrolysis bipolar plate is as follows Figure 1 and Figure 3 As shown, Figure 1 Schematic diagram of high alloy steel plate. Figure 3 The diagram is a schematic cross-sectional view of a bipolar plate. The flow field region of the bipolar plate corresponding to the high-alloy steel plate 2 is provided with a plurality of through-hole clusters 1. These clusters 1 are filled with a titanium layer slurry, forming an in-hole titanium slurry 3-1. Titanium layer slurry is scraped onto both sides of the high-alloy steel plate 1-2, forming a titanium layer 3-2. A flow field structure formed of a functional coating slurry is applied to the surface of the titanium layer slurry. The flow field structure is conventional in shape and is located on one or both sides of the high-alloy steel plate 2.

[0042] The mold used includes a hollow area 6 and a closed area 5. The hollow area is for the functional coating slurry to pass through to form the required bipolar plate flow field structure, which corresponds to the flow channel ridge 4-1 of the bipolar plate, the spoiler column in the spoiler area, and the hydrogen and oxygen frame (the hydrogen and oxygen frame is the peripheral frame of the hydrogen and oxygen cavity and the sealant wire groove part that needs to be sealed around the bipolar plate). The closed area is for blocking the bipolar plate where no structure is required, which corresponds to the plate flow channel groove 4-2 of the bipolar plate, other areas of the spoiler area except the spoiler column, and the hydrogen and oxygen cavity (for hydrogen and oxygen to enter and exit the bipolar plate respectively) reserved area, etc. Figure 2 shown.

[0043] The test results show that the prepared plate has excellent performance. As shown in Table 1, its contact resistance is only 0.51mΩ·cm 2 , the corrosion current density is 2.53μA / cm 2 .

[0044] Example 2

[0045] Preparation of functional coating slurry: weigh 30 g of spherical atomized titanium powder with a particle size of 75 μm, 58 g of anhydrous ethanol, 6 g of polyvinyl butyral resin, 3.5 g of ammonium bicarbonate, and 1.5 g of dioctyl phthalate into a beaker, stir evenly with a mechanical stirrer, and set aside.

[0046] Preparation of titanium layer slurry: weigh 70 g of spherical atomized titanium powder with a particle size of 35 μm, 20 g of anhydrous ethanol, 3.5 g of polyvinyl butyral resin, and 1.5 g of dioctyl phthalate in a beaker, and stir them evenly with a mechanical stirrer for later use.

[0047] A 0.5mm thick, 20cm x 10cm high-alloy steel sheet with a 10% Ti alloy content was cut and perforated with a punch to form a cluster of holes 1. The clusters corresponded to the bipolar plate flow channels, and the total area of ​​the clusters accounted for 20%-30% of the total plate area. The sheet was then polished using 200-500 grit sandpaper in a gradual process. The sheet was then ultrasonically cleaned in acetone for three 10-minute washes, then rinsed with ultrapure water and air-dried.

[0048] The titanium layer slurry is evenly applied by scraping to the front and back surfaces of the high-alloy steel sheet, forming a titanium layer 3-2 and filling the hole cluster 1. The titanium layers 3-2 on both sides are connected by the titanium slurry 3-1 in the hole cluster 1. The titanium layer applied to the high-alloy steel sheet is 1 mm thick. The sheet is then heat-treated in a 130°C oven for 4 minutes. After the heat treatment is complete, the sheet is removed and placed on a hot press platform for hot pressing at a pressure of 4 MPa and a holding time of 150 seconds. After hot pressing, a titanium layer with pores of 100 nm in diameter is formed on both the top and bottom surfaces of the high-alloy steel sheet and in the hole clusters. A mold is then placed over the plate surface, and a functional coating slurry is printed onto the plate surface along the mold shape to form the bipolar plate's flow field structure. The sheet is then heat-treated in a 130°C oven for 4 minutes. The mold is then removed, leaving a functional coating with a flow field structure on the titanium layer surface, with pores of 12 μm in diameter. This completes the water electrolysis bipolar plate. The mold structure is the same as that of Example 1, or a mold in the prior art that can realize a flow field structure by printing is used.

[0049] Thanks to the direct connection of the titanium layers on the front and back of the plate, the effect is equivalent to that of using titanium material as a whole. After testing, the contact resistance is 0.59mΩ·cm 2 , the corrosion current density is 2.57μA / cm 2 .

[0050] Example 3

[0051] Preparation of functional coating slurry: Weigh 40 g of spherical atomized titanium powder with a particle size of 100 μm, 52 g of anhydrous ethanol, 2 g of polyvinyl butyral resin, 3 g of ammonium bicarbonate, and 1 g of dioctyl phthalate into a beaker, stir evenly with a mechanical stirrer, and set aside.

[0052] Preparation of titanium layer slurry: weigh 80 g of spherical atomized titanium powder with a particle size of 50 μm, 15 g of anhydrous ethanol, 3 g of polyvinyl butyral resin, and 1 g of dioctyl phthalate in a beaker, and stir them evenly with a mechanical stirrer for later use.

[0053] A 0.5mm thick, 20cm x 10cm high-alloy steel sheet with a 30% Ni alloy content was cut and perforated with a punch to form a cluster of holes 1. The clusters corresponded to the bipolar plate flow channels, and the total area of ​​the clusters accounted for 20%-30% of the total plate area. The sheet was then polished using 200-500 grit sandpaper in a gradual process. The sheet was then ultrasonically cleaned in acetone for three 10-minute washes, then rinsed with ultrapure water and air-dried.

[0054] The titanium layer slurry is evenly applied by doctor blade to the front and back surfaces of the high-alloy steel sheet, forming a titanium layer 3-2 and filling the hole cluster 1. The titanium layers 3-2 on both sides are connected by the titanium slurry 3-1 in the hole cluster 1. The titanium layer applied to the high-alloy steel sheet is 1 mm thick. The sheet is then heat-treated in a 150°C oven for 3 minutes. After the heat treatment is complete, the sheet is removed and placed on a hot press platform for hot pressing at a pressure of 4 MPa and a holding time of 180 seconds. After hot pressing, a titanium layer with 10 μm pores is formed on both the top and bottom surfaces of the high-alloy steel sheet and in the hole clusters. A mold is then placed over the electrode surface, and a functional coating slurry is printed onto the plate surface along the mold shape to form the bipolar plate's flow field structure. The sheet is then heat-treated in a 150°C oven for 3 minutes. The mold is then removed, leaving a functional coating with a flow field structure on the titanium layer surface, with 50 μm pores. This completes the water electrolysis bipolar plate. The mold structure is the same as that of Example 1, or a mold in the prior art that can realize a flow field structure by printing is used.

[0055] The test results show that the prepared plate has excellent performance. As shown in Table 1, its contact resistance is only 0.52mΩ·cm 2 , the corrosion current density is 2.55μA / cm 2 .

[0056] Example 4

[0057] A continuous production line applicable to embodiments 1-3, the production line consists of a circular guide rail and a driving electrical transmission line, a plurality of electrically driven sliders are provided on the circular guide rail so as to simultaneously place multiple stainless steel plates for batch transmission, and at the same time, along the transmission direction of the circular guide rail, a scraping area, a No. 1 thickness detection area, a mold printing area, a No. 2 thickness detection area, and a hot pressing area are sequentially provided on the production line for acting on the stainless steel plates, and at the same time, the entire continuous production line is intelligently and logically controlled by a CPU control system, the scraping area mainly includes a scraping machine, the mold printing area mainly includes a screen printing machine, the No. 1 thickness detection area and the No. 2 thickness detection area mainly include a thickness detector, the hot pressing area mainly includes a hot press, and the scraping machine, the screen printing machine, the thickness detector, and the hot press are all connected to the C The PU control system circuit is connected to achieve controllability of whether multiple areas are working and the working order; multiple stainless steel plates are placed on the above-mentioned slider in turn for transmission, and are prepared in sequence through scraping, first thickness detection, screen printing, and second thickness detection. In this process, according to the actual size requirements of the metal bipolar plate and the thickness detection results, the relevant data are recorded and controlled in real time by the CPU system. If the size is not met, it can be circulated and transmitted to the corresponding area for re-brushing. At the same time, the entire production line is also equipped with manual and robotic arm positions. The manual position realizes the processing of detailed work such as fine tubes at the mold printing site, and the robotic arm realizes the flipping of the stainless steel plate to realize the printing of the anode and cathode; finally, those that meet the requirements are removed by the robotic arm and transmitted to other production lines.

[0058] Comparative Example 1

[0059] Preparation of functional coating slurry: weigh 20 g of spherical atomized titanium powder with a particle size of 50 μm, 64 g of anhydrous ethanol, 10 g of polyvinyl butyral resin, 4 g of ammonium bicarbonate, and 2 g of dioctyl phthalate into a beaker, stir evenly with a mechanical stirrer, and set aside.

[0060] Preparation of titanium layer slurry: weigh 60 g of spherical atomized titanium powder with a particle size of 20 μm, 35 g of anhydrous ethanol, 4 g of polyvinyl butyral resin, and 1 g of dioctyl phthalate into a beaker, and stir them evenly with a mechanical stirrer for later use.

[0061] A high-alloy steel plate with a Mo alloy content of 30% and a thickness of 0.5 mm and an area of ​​20 cm x 10 cm was cut and polished step by step using 200-500 mesh sandpaper. The high-alloy steel plate was then ultrasonically cleaned in an acetone solution three times for 10 minutes each time. After cleaning, it was rinsed with ultrapure water and then taken out and blown dry.

[0062] The titanium layer slurry is evenly scraped onto the front and back of the high-alloy steel plate to form a titanium layer with a thickness of 1mm. It is then placed in a 100°C oven for heat treatment for 5 minutes. After the time is up, it is taken out and the plate is placed on the hot press platform for hot pressing. The hot press platform pressure is 4Mpa and the holding time is 120s. After hot pressing, the mold is covered on the surface of the plate, and the functional coating slurry is printed on the surface of the plate along the shape of the mold to form the flow field structure of the bipolar plate. It is then placed in a 100°C oven for heat treatment for 5 minutes, and then the mold is removed to obtain a water electrolysis bipolar plate. The mold structure is the same as in Example 1, or a mold that can realize the flow field structure by printing in the prior art is used.

[0063] Since the high alloy steel plate was not perforated, the titanium layers on the front and back of the steel plate lost contact with each other. After a period of stability, the printed titanium layer fell off significantly. As shown in Table 1, the contact resistance was 3.3 mΩ·cm. 2 When the contact between the membrane and the substrate is insufficient, the high alloy steel plate is more exposed and its corrosion resistance is poor, up to 5.05μA / cm 2 .

[0064] Comparative Example 2

[0065] Preparation of functional coating slurry: weigh 20 g of spherical atomized titanium powder with a particle size of 50 μm, 64 g of anhydrous ethanol, 10 g of polyvinyl butyral resin, 4 g of ammonium bicarbonate, and 2 g of dioctyl phthalate into a beaker, stir evenly with a mechanical stirrer, and set aside.

[0066] Preparation of titanium layer slurry: weigh 60 g of spherical atomized titanium powder with a particle size of 20 μm, 35 g of anhydrous ethanol, 4 g of polyvinyl butyral resin, and 1 g of dioctyl phthalate into a beaker, and stir them evenly with a mechanical stirrer for later use.

[0067] A 0.5mm thick, 20cm x 10cm high-alloy steel sheet with a 30% Ti alloy content was cut and perforated with a punch, creating clusters of holes aligned with the bipolar plate flow channels. The total area of ​​the clusters accounted for 20%-30% of the sheet's total area. The sheet was then polished using 200-500 grit sandpaper in a gradual process. The sheet was then ultrasonically cleaned in acetone for three 10-minute washes, then rinsed with ultrapure water and air-dried.

[0068] The titanium layer slurry is evenly scraped onto the front and back of the high-alloy steel plate to form a titanium layer and fill the group holes, so that the titanium layers 3-2 on both sides are connected through the titanium slurry 3-1 in the hole filled in the group control 1. The thickness of the titanium layer scraped onto the surface of the high-alloy steel plate is 1 mm, and then placed in a 100°C oven for heat treatment for 5 minutes. After the time is up, it is taken out and the mold is covered on the surface of the plate. The functional coating slurry is printed on the surface of the plate along the shape of the mold to form the flow field structure of the bipolar plate. Then, it is placed in a 100°C oven for heat treatment for 5 minutes, and then the mold is removed to obtain the water electrolysis bipolar plate. The mold structure is the same as in Example 1, or a mold in the prior art that can realize the flow field structure by printing is used.

[0069] In the preparation of this comparative example, since the titanium slurry layer was not hot-pressed after being perforated and scraped, the titanium slurry was loose, and during the heat treatment, part of the resin volatilized, resulting in poor density of the scraped titanium layer, which would cause water cross-contamination of the anode and cathode of the water electrolysis plate, resulting in poor performance. After testing, its contact resistance was 1.02mΩ·cm 2 , the corrosion current density is 6.07μA / cm 2 , its durability is poor.

[0070] Comparative Example 3

[0071] Preparation of titanium layer slurry: weigh 60 g of spherical atomized titanium powder with a particle size of 20 μm, 35 g of anhydrous ethanol, 4 g of polyvinyl butyral resin, and 1 g of dioctyl phthalate into a beaker, and stir them evenly with a mechanical stirrer for later use.

[0072] Cut a 0.5mm thick, 20cm x 10cm high-alloy steel plate with a 30% Mo alloy content. Place a mold over the plate surface, then print a titanium layer slurry along the mold's shape onto the plate surface to form the bipolar plate's flow field structure. Heat treat the plate in a 100°C oven for 5 minutes before removing the mold to produce the water electrolysis bipolar plate. The mold structure can be the same as in Example 1, or a conventional mold capable of printing a flow field structure can be used.

[0073] Since the high alloy steel plate was not pretreated or coated during the plate preparation process, the flow field structure of the bipolar plate was directly printed on the mold. The printed flow field coating had poor bonding with the high alloy steel plate body and was easily detached, resulting in poor performance. As shown in Table 1, its contact resistance was 5.6 mΩ·cm 2 , the corrosion current density is 7.2μA / cm 2 , whether it is the output performance or durability of water electrolysis, the effect is relatively poor.

[0074] Table 1 Test results

[0075] Serial number <![CDATA[Contact resistance mΩ·cm 2 > <![CDATA[Corrosion current density μA / cm 2 > Example 1 0.51 2.53 Example 2 0.59 2.57 Example 3 0.52 2.55 Comparative Example 1 3.3 5.05 Comparative Example 2 1.02 6.07 Comparative Example 3 5.6 7.2

[0076] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A PEM water electrolysis bipolar plate, characterized by: An alloy steel plate is used as a substrate, a plurality of through-holes (1) are provided on the substrate, a titanium layer (3-2) is provided on both the upper and lower surfaces of the substrate, the titanium layer (3-2) fills the pores (1) to form a connection between the upper and lower titanium layers (3-2), a functional coating is provided on the surface of the titanium layer (3-2), and the functional coating forms a flow field structure of the bipolar plate; The titanium layer slurry forming the titanium layer (3-2) is bonded to the alloy steel plate by means of scraping, drying and hot pressing; The titanium layer (3-2) contains titanium powder with a particle size of 10-30 μm, and the functional coating contains titanium powder with a particle size of 50-100 μm.

2. A PEM water electrolysis bipolar plate according to claim 1, characterized in that: The titanium layer (3-2) comprises spherical atomized titanium powder with a particle size of 10-30 μm, a solvent, an adhesive and a plasticizer; and the functional coating comprises spherical atomized titanium powder with a particle size of 50-100 μm, a solvent, an adhesive, a pore-forming agent and a plasticizer.

3. A PEM water electrolysis bipolar plate according to claim 2, characterized in that: The mass ratio of spherical atomized titanium powder with a particle size of 10-30 μm, solvent, binder and plasticizer in the titanium layer (3-2) is 50-70:15-35:3-4:1-2; the mass ratio of spherical atomized titanium powder with a particle size of 50-100 μm, solvent, binder, pore-forming agent and plasticizer in the functional coating is 20-40:52-64:2-10:3-4:1-2; The solvent in the titanium layer (3-2) and the functional coating is independently at least one of ethanol, toluene or methanol, the binder in the titanium layer (3-2) and the functional coating is independently at least one of polyvinyl butyral resin or acrylic resin, the plasticizer in the titanium layer (3-2) and the functional coating is independently at least one of dioctyl phthalate, dibutyl phthalate or propylene glycol oxalate polyester, and the pore-forming agent includes one or a combination of two or more of urea, ammonium bicarbonate, sodium carbonate and oxalic acid.

4. A PEM water electrolysis bipolar plate according to claim 1, characterized in that: The diameter of the group of holes (1) is 0.5-2 cm, and the total area of ​​the group of holes (1) is 20%-30% of the total area of ​​the alloy steel plate.

5. A PEM water electrolysis bipolar plate according to claim 1, characterized in that: The thickness of the titanium layer (3-2) is 1-5 mm; pores with a pore size of 10 nm-10 μm are distributed on the titanium layer (3-2); and pores with a pore size of >10 μm and ≤300 μm are distributed on the functional coating.

6. A PEM water electrolysis bipolar plate according to claim 1, characterized in that: The alloy steel plate contains one or more alloy elements of Ni, Ti, and Mo, with a total alloy element mass content of 10%-30% and a thickness of 0.5-1 mm.

7. A PEM water electrolysis bipolar plate according to claim 1, characterized in that: The titanium layer slurry forming the titanium layer (3-2) is combined with the alloy steel plate by scraping, drying and hot pressing in sequence, and the slurry forming the functional coating is printed onto the surface of the titanium layer (3-2) formed by the titanium layer slurry by mold printing.

8. A method for preparing a PEM water electrolysis bipolar plate, characterized in that: The following steps are involved: (1) Preparation of titanium layer slurry: Spherical atomized titanium powder with a particle size of 10-30 μm is stirred and mixed with a solvent, a binder and a plasticizer to obtain a titanium layer slurry; Preparation of functional coating slurry: Spherical atomized titanium powder with a particle size of 50-100 μm is stirred and mixed with a solvent, a binder, a pore-forming agent, and a plasticizer to obtain a functional coating slurry; (2) Pretreatment of alloy steel plate: punch holes in the alloy steel plate array to form a group of holes, grind, polish and clean the surface, then put it into acetone solution for ultrasonic cleaning, take it out and use ultrapure water for ultrasonic cleaning, take it out and blow dry it for use; (3) Plate coating: The titanium layer slurry is evenly coated on the alloy steel plate to fill the group holes at the same time, and a titanium layer is formed on the front and back of the alloy steel plate, and then dried; (4) Hot pressing of the plate: placing the plate obtained in step (3) on the hot press platform for hot pressing; (5) The functional coating slurry is printed onto the surface of the titanium layer by mold printing to form the flow field structure of the water electrolysis bipolar plate, and then the mold is removed after drying to prepare the water electrolysis bipolar plate.

9. The method for preparing a PEM water electrolysis bipolar plate according to claim 8, characterized in that: The conditions of the hot pressing are: pressure 4 MPa, holding time 120-180 s, room temperature; the temperature of the drying is 100-150°C.

10. The method for preparing a PEM water electrolysis bipolar plate according to claim 8, characterized in that: Steps (3) to (5) are completed using a continuous production line with an annular guide rail, on which are provided several electrically driven sliders, on which are placed stainless steel and alloy steel plates; the continuous production line is provided with working electrical appliances for performing scraping, hot pressing, and mold printing on the alloy steel and stainless steel plates, and the working electrical appliances are all connected to the PLC system circuit signal.

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