Titanium bipolar plate TiOxNy coating for PEM electrolytic reactor and preparation method of titanium bipolar plate TiOxNy coating
By preparing a TiOxNy coating on a titanium bipolar plate of a PEM electrolytic reactor and combining it with micro-arc oxidation and plasma nitriding techniques, the problems of poor coating bonding strength, high cost, and insufficient corrosion resistance were solved, enabling high-performance and low-cost coating applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-26
- Publication Date
- 2026-04-03
AI Technical Summary
Existing coatings for titanium bipolar plates in PEM electrolytic reactors suffer from poor bonding strength, high cost, significant pollution during the preparation process, and insufficient corrosion resistance. In particular, the coatings are prone to peeling and exhibit poor conductivity in high-potential and high-oxygen environments.
A micro-arc oxidation TiO2 dense layer and TiOxNy coating are stacked. The TiO2 coating is deposited on a titanium bipolar plate by micro-arc oxidation, and nitriding is introduced in plasma vapor deposition to form a Ti-TiO2-TiN gradient structure, which increases the bonding strength and conductivity of the coating, and provides a barrier effect to delay corrosion through the oxide intermediate layer.
It improves the corrosion resistance and conductivity of titanium bipolar plates, reduces manufacturing costs, reduces pollution, enhances the bonding strength between the coating and the substrate, and extends service life.
Smart Images
Figure CN121781243A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metal surface coating preparation technology, specifically a titanium bipolar plate (TiO2) for PEM electrolytic reactors. x N y Coatings and their preparation methods. Background Technology
[0002] Hydrogen energy, with its wide availability, low carbon footprint throughout its lifecycle, and versatility across multiple scenarios, has broken down barriers between renewable energy and end-use energy industries, accelerating the greening of energy across all industries and possessing broad application prospects. Proton exchange membrane (PEM) electrolysis of water for hydrogen production, as a method of producing green hydrogen, is considered an important development direction for hydrogen production due to its green and low-carbon characteristics, fast response speed, and high energy conversion efficiency. Among these components, the bipolar plate, as a core component of the PEM reactor, plays a crucial role in distributing the reaction medium, conducting current, separating and sealing chambers, as well as providing heat dissipation and support, making it one of the key elements affecting the reactor's operating efficiency. However, the service environment of the bipolar plate in the PEM reactor is characterized by strong acidity, high temperature, and strong oxidizing properties, requiring the bipolar plate to have good corrosion resistance and conductivity. Therefore, titanium metal, with its excellent corrosion resistance, has become the preferred substrate for bipolar plates. However, pure titanium metal still undergoes passivation under high potential and high oxygen content environments, forming a high-resistivity oxide film, which affects its conductivity. Therefore, surface treatment is often performed on titanium metal to further improve its conductivity and corrosion resistance. Currently, the most common coating for titanium bipolar plates in PEM electrolytic reactors is a Pt coating. Pt coating can effectively improve the conductivity and corrosion resistance of titanium bipolar plates, but it has the following problems: 1) poor coating bonding strength, which makes it prone to peeling off after long-term service; 2) high cost; 3) significant pollution during the preparation process. Therefore, a new type of non-precious metal coating with high bonding strength and high performance is crucial for the performance and application prospects of titanium bipolar plates.
[0003] To address the aforementioned technical challenges, research has emerged on non-precious coatings such as carbide and nitride coatings. Among these, nitride coatings have attracted widespread attention due to their advantages of low cost, high conductivity, high corrosion resistance, and simple preparation process. The existing technical article, "Performance of Titanium Bipolar Plates Modified by In-situ Nitriding using PECVD," proposes preparing titanium nitride coatings via plasma nitriding. Through in-situ growth, a well-bonded TiN-doped coating is generated on the titanium metal surface, improving both the conductivity and corrosion resistance of the titanium metal. However, while this nitride coating exhibits good bonding, achieving complete nitriding of the titanium bipolar plate surface during nitriding is difficult, thus the corrosion resistance still fails to meet the long-term service requirements of PEMs (Polymer Electrode Manufacturing Systems). Summary of the Invention
[0004] To address the shortcomings of the existing technologies, this invention proposes a titanium bipolar plate (TiO2) for PEM electrolytic reactors. x N y The coating and its preparation method, the present invention relates to a titanium bipolar plate (TiO2) for PEM electrolytic reactors. x N y The coating consists of a dense micro-arc oxidation TiO2 layer and a TiO2 layer stacked together. x N y The coating composition introduces an oxide interlayer between the titanium bipolar plate and the TiN-doped coating, providing a barrier effect against the electrolyte, slowing down the corrosion rate, and improving the TiO2 content of the titanium bipolar plate for PEM electrolytic reactors. x N y The coating enhances corrosion resistance, thereby improving the performance of the titanium bipolar plate. Furthermore, the unique porous structure of the micro-arc oxidation TiO2 dense layer coating provides nitriding channels, increasing the nitrogen doping depth and improving the TiO2 content of the titanium bipolar plate used in PEM reactors. x N y The conductivity of the coating ultimately led to the in-situ synthesis of highly corrosion-resistant and highly conductive TiO2 titanium bipolar plates for PEM electrolytic reactors on the surface of the titanium bipolar plates. x N y coating.
[0005] Based on the above technical objectives, the present invention adopts the following technical solution: This invention protects a titanium bipolar plate (TiO2) for PEM electrolytic reactors. x N y Coating, TiO2 titanium bipolar plate for PEM electrolytic reactor x N y The coating consists of a dense micro-arc oxidation TiO2 layer and a TiO2 layer stacked together. x N y The coating composition consists of a dense micro-arc oxidation TiO2 layer deposited on a titanium bipolar plate. This dense layer is obtained by peeling off the irregularly porous surface layer of the micro-arc oxidation TiO2 coating after depositing a micro-arc oxidation TiO2 layer on the titanium bipolar plate. The dense micro-arc oxidation TiO2 layer is doped with P2O5 and SiO2, with the mass percentage of P and Si not exceeding 1 wt.%. A small amount of P2O5 and SiO2 doping can improve corrosion resistance without affecting the coating's conductivity, while excessive P2O5 and SiO2 doping will reduce the coating's conductivity. x N y The coating consists of TiO2 and TiN, with TiO2 being the most abundant TiO2. x N y In the coating, the mass percentage of N is not less than 3 wt.% and not more than 6 wt.%. Too low a N content will lead to a decrease in the electrical conductivity of the coating, while too high a N content will reduce the corrosion resistance of the coating.
[0006] Preferably, the titanium bipolar plate (TiO2) for PEM electrolytic reactors x N y The coating thickness is 5μm~15μm. If the coating is too thin, the corrosion resistance will be insufficient, and if it is too thick, the risk of coating peeling off will increase.
[0007] This invention also protects the titanium bipolar plate TiO2 for PEM electrolytic reactors. x N y The coating preparation method is as follows: Step 1: In-situ micro-arc oxidation of titanium substrate to prepare micro-arc oxidized TiO2 coating; Step 2: Electrochemical exfoliation of the loose layer of micro-arc oxidized TiO2 coating to expose the dense layer; Step 3: Plasma nitriding to regulate the composition of the dense layer, finally synthesizing in-situ high corrosion resistance and high conductivity titanium bipolar plate TiO2 for PEM electrolytic reactors. x N y The coating, applied to the titanium bipolar plate of the PEM electrolytic reactor, includes the following steps: The main salt, fluoride, complexing agent and hydroxide are dissolved together in water to obtain the micro-arc oxidation electrolyte.
[0008] The main salt is selected from phosphates and silicates.
[0009] Using a titanium bipolar plate as the anode, together with the first cathode, a dual-electrode system is formed. The dual-electrode system is immersed in a micro-arc oxidation electrolyte, and a micro-arc oxidation TiO2 coating is prepared on the titanium bipolar plate in situ by micro-arc oxidation, resulting in a titanium bipolar plate with deposited micro-arc oxidation TiO2 coating. The micro-arc oxidation TiO2 coating is tightly bonded to the substrate titanium bipolar plate and has strong corrosion resistance, making it a high-quality intermediate layer.
[0010] The micro-arc oxidation TiO2 coating consists of a dense layer and a loose layer. The thickness of the dense layer is not less than 5 μm and not more than 15 μm, and the thickness of the loose layer is not more than 15 μm. In the micro-arc oxidation TiO2 coating, the mass percentage of P does not exceed 8 wt.% and the mass percentage of Si does not exceed 15 wt.%.
[0011] A loose layer exfoliation electrolyte is obtained by dissolving a reducing agent and a fluoride together in water. A titanium bipolar plate with a deposited micro-arc oxidation TiO2 coating and a second cathode are used to form a dual-electrode system. The dual-electrode system is immersed in the loose layer exfoliation electrolyte, and electrochemical treatment is performed on the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating. The loose layer with irregular pore structure on the surface of the micro-arc oxidation TiO2 coating is decomposed and exfoliated under the influence of the reducing agent. During the decomposition and exfoliation of the loose layer, the surface pores are closed, forming a dense layer with spherical crown-shaped pits on the surface. A titanium bipolar plate with a deposited dense layer coating of micro-arc oxidation TiO2 is obtained. Due to the closure of the surface pores, the dense layer coating of micro-arc oxidation TiO2 hinders the inflow of corrosive liquid, further improving the corrosion resistance.
[0012] In the micro-arc oxidation TiO2 dense layer coating, the mass percentage of P+Si is no more than 1 wt.%.
[0013] In a nitrogen-containing atmosphere, a titanium bipolar plate with a dense TiO2 micro-arc oxidation coating was subjected to plasma vapor deposition. Plasma-assisted nitriding was used to increase the nitriding depth, thereby controlling the composition of the dense TiO2 micro-arc oxidation coating. This allowed for the in-situ synthesis of TiO2 for PEM reactors on the titanium bipolar plate. x N y coating.
[0014] Preferably, the micro-arc oxidation process is characterized by a constant voltage mode, with the following conditions: micro-arc oxidation for 10-20 minutes at a voltage of 300V~500V, a duty cycle of 10%~20%, and a frequency of 300Hz~500Hz.
[0015] Preferably, in the micro-arc oxidation electrolyte, the amount of the main salt is 20 g / L to 40 g / L, the amount of the complexing agent is 2 g / L to 5 g / L, the amount of hydroxide is 3 g / L to 6 g / L, and the amount of fluoride is 4 g / L to 8 g / L.
[0016] Preferably, the complexing agent is selected from one or more of citric acid, tartaric acid, and ethylenediaminetetraacetic acid; the hydroxide is selected from one or two of potassium hydroxide and sodium hydroxide; and the fluoride is selected from one or two of sodium fluoride and potassium fluoride.
[0017] Preferably, in the loose layer peeling electrolyte, the mass percentage of reducing agent is 0.5 wt.% to 2 wt.%, and the mass percentage of fluoride is 0.2 wt.% to 1 wt.%.
[0018] Preferably, the reducing agent is hydroxylamine hydrochloride, and the fluoride is one or both of sodium fluoride and potassium fluoride.
[0019] Preferably, the electrochemical treatment conditions are: at a temperature of 80°C and a constant voltage of 10V~30V, the electrochemical treatment lasts for 40min~80min.
[0020] Preferably, the conditions for plasma vapor deposition are: in a pure ammonia or a mixed atmosphere of nitrogen and hydrogen, at a temperature of 600℃~800℃, a gas flow rate of 80sccm~150sccm, and a plasma power of 350W~450W, for 1h~3h.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes a combined method of micro-arc oxidation and plasma nitriding to prepare TiO2 titanium bipolar plates for PEM electrolytic reactors on the surface of titanium bipolar plates. x N y The coating has the following advantages compared to traditional bipolar plate coatings: 1) No expensive materials were used in the process, reducing the cost of TiO2 in the titanium bipolar plates of the PEM electrolytic reactor. x N y The cost of coating preparation.
[0022] 2) By introducing a micro-arc oxidation intermediate layer, a Ti-TiO2-TiN gradient structure was established, in which the coefficient of thermal expansion of the titanium bipolar plate substrate is 8.6 × 10⁻⁶. -6 At ℃, the coefficient of thermal expansion of TiO2 is 8.9 × 10⁻⁶. -6 At ℃, the coefficient of thermal expansion of TiN is 9.35 × 10⁻⁶. -6 / ℃, thereby reducing the difference in thermal expansion coefficients between the interfaces of each layer of material and further improving the bonding strength between the coating and the substrate.
[0023] 3) The oxides in the micro-arc oxidation intermediate layer provide a barrier effect to the electrolyte, slowing down the corrosion rate and improving the corrosion resistance of the coating.
[0024] 4) The unique porous structure of the micro-arc oxidation intermediate layer provides nitriding channels, increasing the nitrogen doping depth and improving the performance of TiO2 in titanium bipolar plates for PEM electrolytic reactors. x N y The electrical conductivity of the coating.
[0025] 2. Compared to existing titanium bipolar plate coatings, the titanium bipolar plate TiO2 coating for PEM electrolytic reactors of this invention... x N y The coating has the advantages of low preparation cost, high bonding strength, excellent performance and less pollution in the production process, and has broad application prospects. Attached Figure Description
[0026] Figure 1 This invention relates to a titanium bipolar plate (TiO2) for a PEM electrolytic reactor. x N y Process diagram of coating preparation method.
[0027] Figure 2 This is a plan view of the titanium bipolar plate with a deposited micro-arc oxidation TiO2 coating in Example 1.
[0028] Figure 3 This is a plan view of the titanium bipolar plate with a dense TiO2 micro-arc oxidation coating deposited in Example 1.
[0029] Figure 4 The titanium bipolar plate (TiO2) used in the PEM electrolytic reactor in Example 1 x N y A plan view of the coating.
[0030] Figure 5 The titanium bipolar plate (TiO2) used in the PEM electrolytic reactor in Example 1 xN y Cross-sectional view of the coating.
[0031] Figure 6 The titanium bipolar plate (TiO2) used in the PEM electrolytic reactor in Example 1 x N y Test diagram of coating adhesion strength.
[0032] Figure 7 The titanium bipolar plate (TiO2) used in the PEM electrolytic reactor in Example 2 x N y Cross-sectional view of the coating. Detailed Implementation
[0033] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content.
[0034] Considering that after depositing a titanium nitride coating on a titanium bipolar plate, it is difficult to achieve complete nitriding of the titanium bipolar plate surface through nitriding, thus the corrosion resistance still cannot meet the long-term service requirements of PEM, this invention deposits an intermediate layer between the titanium bipolar plate and the titanium nitride coating. The intermediate layer is a micro-arc oxidation TiO2 dense layer coating. On the one hand, the micro-arc oxidation TiO2 dense layer coating is doped with P2O5 and SiO2. The small amount of P2O5 and SiO2 doping can improve the corrosion resistance without affecting the conductivity of the coating. On the other hand, the micro-arc oxidation TiO2 dense layer coating provides a barrier effect to the electrolyte to improve corrosion resistance, and its unique pore structure provides nitriding channels to improve conductivity, thus overcoming the technical defects of directly depositing a titanium nitride coating on a titanium bipolar plate.
[0035] The technical solution of the present invention will be further studied using the following embodiments. The specific research methods and results are shown below: Example 1 See Figure 1 This embodiment provides a titanium bipolar plate (TiO2) for a PEM electrolytic reactor. x N y The coating preparation method includes the following steps: Step 1: Preparation of Micro-arc Oxidation Electrolyte: Mix the main salt, complexing agent, hydroxide, fluoride, and solvent to obtain the micro-arc oxidation electrolyte. The main salt consists of Na2SiO3 and Na3PO4, with a specific content of 10 g / L Na2SiO3 + 15 g / L Na3PO4. The complexing agent EDTA-2Na is 3 g / L, the hydroxide KOH is 3 g / L, the fluoride sodium fluoride is 6 g / L, and the solvent is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain the micro-arc oxidation electrolyte.
[0036] Step Two: Micro-arc Oxidation Treatment: The titanium bipolar plate is clamped in a micro-arc oxidation tank using a stainless steel clamp, serving as the anode. A stainless steel sheet is placed opposite the titanium bipolar plate as the cathode. Both the titanium bipolar plate and the stainless steel sheet are immersed in the micro-arc oxidation electrolyte. Micro-arc oxidation is performed under constant voltage mode: voltage 450V, duty cycle 15%, frequency 400Hz, and micro-arc oxidation time 10min. A micro-arc oxidized TiO2 coating is prepared on the titanium bipolar plate in situ using micro-arc oxidation, resulting in a titanium bipolar plate with a deposited micro-arc oxidized TiO2 coating. Its morphology is as follows: Figure 2 As shown, a porous micro-arc oxidation island morphology has grown on the surface of the titanium bipolar plate substrate.
[0037] Step 3: Preparation of loose layer exfoliation electrolyte: Add hydroxylamine hydrochloride and sodium fluoride to the solvent and mix to obtain loose layer exfoliation electrolyte; wherein, the mass percentage of hydroxylamine hydrochloride is 1 wt.%, the mass percentage of NaF is 0.4 wt.%, and the balance is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain loose layer exfoliation electrolyte.
[0038] Step 4: Loose Layer Removal Treatment: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating is clamped in an electrochemical tank, serving as the anode. A graphite sheet is clamped in the cathode, placed opposite the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating, with a 20mm gap between them. Both the titanium bipolar plate and the graphite sheet are immersed in the loose layer removal electrolyte. The loose layer is removed at an electrolyte temperature of 80℃, a constant voltage of 20V, and a removal time of 60min, resulting in a titanium bipolar plate with a dense micro-arc oxidation TiO2 coating, the morphology of which is as follows. Figure 3 As shown, after the loose layer falls off, the surface morphology of the micro-arc oxidation TiO2 dense layer coating changes from open pores to closed spherical pits. Compared with the porous structure, it can better isolate the inflow of corrosive liquid and improve corrosion resistance.
[0039] Step 5: Nitriding: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 dense coating is placed in a PECVD apparatus for nitriding. The nitriding temperature is 700℃, the gas is NH3, the gas flow rate is 100 sccm, the plasma power is 400W, and the holding time is 2h, to obtain the titanium bipolar plate TiO2 for PEM electrolytic reactor. x N y The coating, with a thickness of 10 μm, has the following surface morphology: Figure 4 As shown, it can be seen that under the action of plasma, the titanium bipolar plate TiO2 in the PEM electrolytic reactor... x N y The coating surface exhibits increased pit morphology, shallower depth, and more thorough pore sealing; the cross-sectional morphology is as follows: Figure 5 As shown, the titanium bipolar plate TiO2 used in the PEM electrolytic reactor can be seen. x N y The coating thickness is approximately 10 μm.
[0040] The titanium bipolar plate TiO2 prepared for PEM electrolytic reactor x N y The coating underwent a cross-cut adhesion test. A sharp tool was used to create a uniform grid pattern on the surface. Standard 3M tape was then applied to the test area and removed. The morphology of the tested area was compared with the ISO 2409:1992 adhesion standard to determine the bonding strength level. (TiO2 titanium bipolar plate for PEM electrolytic reactor) x N y The results of the coating test are as follows Figure 6 As shown, the PEM electrolytic reactor uses titanium bipolar plates (TiO2). x N y The coating is intact without peeling, has good adhesion, and meets ISO Class 0 standards.
[0041] The titanium bipolar plate (TiO2) for the PEM electrolytic reactor prepared in Example 1 was used. x N y The coating was characterized, and its properties are shown in Table 1: Table 1. Titanium Bipolar Plates (TiO2) for PEM Electrolytic Reactors x N y Coating performance parameters table The titanium bipolar plate (TiO2) for PEM electrolytic reactor prepared in Example 1 x N y The coating was characterized by EDS, and its composition is shown in Table 2. Table 2. Titanium Bipolar Plates (TiO2) for PEM Electrolytic Reactors x N y Coating composition table It is evident that the PEM electrolytic reactor uses titanium bipolar plates (TiO2).x N y The coating mainly contains Ti, O, and N elements, and also contains small amounts of Si and P elements. The Ti comes from the titanium bipolar plate substrate, while the O, P, and Si come from the micro-arc oxidation process and the N comes from the plasma nitriding process.
[0042] In summary, this invention improves interfacial adhesion by introducing a micro-arc oxidation intermediate layer, thereby enhancing the performance of TiO2. x N y The coating strengthens the bond between the coating and the titanium bipolar plate; simultaneously, the oxide interlayer improves the bonding strength of the TiO₂ in the titanium bipolar plate used in PEM electrolytic reactors. x N y The corrosion resistance of the coating further extends the lifespan of the TiO2 bipolar plate used in PEM electrolytic reactors. x N y The service life of the coating. Furthermore, due to the unique porous structure of the micro-arc oxidized TiO2 dense layer coating obtained after micro-arc oxidation, the nitriding depth is more ideal, thereby improving the service life of the TiO2 coating on the titanium bipolar plate of the PEM electrolytic reactor. x N y The electrical conductivity of the coating.
[0043] Example 2 See Figure 1 This embodiment provides a titanium bipolar plate (TiO2) for a PEM electrolytic reactor. x N y The coating preparation method includes the following steps: Step 1: Preparation of Micro-arc Oxidation Electrolyte: Mix the main salt, complexing agent, hydroxide, fluoride, and solvent to obtain the micro-arc oxidation electrolyte. The main salt consists of Na2SiO3 and Na3PO4, with a specific content of 10 g / L Na2SiO3 + 15 g / L Na3PO4. The complexing agent EDTA-2Na is 3 g / L, the hydroxide KOH is 3 g / L, the fluoride sodium fluoride is 6 g / L, and the solvent is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain the micro-arc oxidation electrolyte.
[0044] Step 2: Micro-arc oxidation treatment: The titanium bipolar plate is clamped in the micro-arc oxidation tank using a stainless steel clamp and acts as the anode. A stainless steel sheet is used as the cathode and placed opposite the titanium bipolar plate. Both the titanium bipolar plate and the stainless steel sheet are immersed in the micro-arc oxidation electrolyte. Micro-arc oxidation is carried out in constant voltage mode with a voltage of 450V, a duty cycle of 15%, a frequency of 400Hz, and a micro-arc oxidation time of 10min. A micro-arc oxidized TiO2 coating is prepared on the titanium bipolar plate in situ by micro-arc oxidation, and a titanium bipolar plate with a deposited micro-arc oxidized TiO2 coating is obtained.
[0045] Step 3: Preparation of loose layer exfoliation electrolyte: Add hydroxylamine hydrochloride and sodium fluoride to the solvent and mix to obtain loose layer exfoliation electrolyte; wherein, the mass percentage of hydroxylamine hydrochloride is 1 wt.%, the mass percentage of NaF is 0.4 wt.%, and the balance is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain loose layer exfoliation electrolyte.
[0046] Step 4: Loose Layer Removal Treatment: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating is clamped in an electrochemical tank as the anode, and a graphite sheet is clamped in the cathode, placed opposite the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating. The titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating and the graphite sheet are spaced 20 mm apart. Both the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating and the graphite sheet are immersed in the loose layer removal electrolyte. The loose layer removal treatment is carried out at an electrolyte temperature of 80℃, a constant voltage of 25V, and a removal time of 60 min, to obtain a titanium bipolar plate with a dense layer coating of deposited micro-arc oxidation TiO2.
[0047] Step 5: Nitriding: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 dense coating is placed in a PECVD apparatus for nitriding. The nitriding temperature is 700℃, the gas is NH3, the flow rate is 100 sccm, the plasma power is 400W, and the holding time is 2h, to obtain the titanium bipolar plate TiO2 for PEM electrolytic reactors. x N y The coating has a cross-sectional morphology as follows: Figure 7 As shown, it can be seen that the final TiO2 content increases after the loose layer shedding voltage is increased. x N y The coating thickness was reduced to 8μm.
[0048] Example 3 See Figure 1 This embodiment provides a titanium bipolar plate (TiO2) for a PEM electrolytic reactor. x N y The coating preparation method includes the following steps: Step 1: Preparation of Micro-arc Oxidation Electrolyte: Mix the main salt, complexing agent, hydroxide, fluoride, and solvent to obtain the micro-arc oxidation electrolyte. The main salt consists of Na2SiO3 and Na3PO4, with a specific content of 20 g / L Na2SiO3 + 20 g / L Na3PO4. The complexing agent EDTA-2Na has an amount of 5 g / L, the hydroxide NaOH has an amount of 6 g / L, the fluoride potassium fluoride has an amount of 8 g / L, and the solvent is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain the micro-arc oxidation electrolyte.
[0049] Step 2: Micro-arc oxidation treatment: The titanium bipolar plate is clamped in the micro-arc oxidation tank using a stainless steel clamp and acts as the anode. A stainless steel sheet is used as the cathode and placed opposite the titanium bipolar plate. Both the titanium bipolar plate and the stainless steel sheet are immersed in the micro-arc oxidation electrolyte. Micro-arc oxidation is carried out in constant voltage mode with a voltage of 500V, a duty cycle of 20%, a frequency of 300Hz, and a micro-arc oxidation time of 20min. A micro-arc oxidized TiO2 coating is prepared on the titanium bipolar plate in situ by micro-arc oxidation, and a titanium bipolar plate with a deposited micro-arc oxidized TiO2 coating is obtained.
[0050] Step 3: Preparation of loose layer exfoliation electrolyte: Add hydroxylamine hydrochloride and sodium fluoride to the solvent and mix to obtain loose layer exfoliation electrolyte; wherein, the mass percentage of hydroxylamine hydrochloride is 2 wt.%, the mass percentage of NaF is 1 wt.%, and the balance is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain loose layer exfoliation electrolyte.
[0051] Step 4: Loose Layer Removal Treatment: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating is clamped in an electrochemical tank as the anode. A graphite sheet is clamped in the cathode and placed opposite the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating. The distance between the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating and the graphite sheet is 20 mm. Both the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating and the graphite sheet are immersed in the loose layer removal electrolyte. The loose layer removal treatment is carried out at an electrolyte temperature of 80℃, a constant voltage of 30V, and a removal time of 40 min to obtain a titanium bipolar plate with a dense layer coating of deposited micro-arc oxidation TiO2.
[0052] Step 5: Nitriding: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 dense layer coating is placed in a PECVD apparatus for nitriding. The nitriding temperature is 600℃, the gas is NH3, the flow rate is 150 sccm, the plasma power is 350W, and the holding time is 3h, to obtain the titanium bipolar plate TiO2 for PEM electrolytic reactor. x N y coating.
[0053] Example 4 See Figure 1 This embodiment provides a titanium bipolar plate (TiO2) for a PEM electrolytic reactor. x N y The coating preparation method includes the following steps: Step 1: Preparation of Micro-arc Oxidation Electrolyte: Mix the main salt, complexing agent, hydroxide, fluoride, and solvent to obtain the micro-arc oxidation electrolyte. The main salt consists of Na2SiO3 and Na3PO4, with a specific content of 10 g / L Na2SiO3 + 10 g / L Na3PO4. The complexing agent EDTA-2Na has an amount of 2 g / L, the hydroxide NaOH has an amount of 4 g / L, the fluoride potassium fluoride has an amount of 4 g / L, and the solvent is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain the micro-arc oxidation electrolyte.
[0054] Step 2: Micro-arc oxidation treatment: The titanium bipolar plate is clamped in the micro-arc oxidation tank using a stainless steel clamp and acts as the anode. A stainless steel sheet is used as the cathode and placed opposite the titanium bipolar plate. Both the titanium bipolar plate and the stainless steel sheet are immersed in the micro-arc oxidation electrolyte. Micro-arc oxidation is carried out in constant voltage mode with a voltage of 300V, a duty cycle of 10%, a frequency of 500Hz, and a micro-arc oxidation time of 15min. A micro-arc oxidized TiO2 coating is prepared on the titanium bipolar plate in situ by micro-arc oxidation, and a titanium bipolar plate with a deposited micro-arc oxidized TiO2 coating is obtained.
[0055] Step 3: Preparation of loose layer exfoliation electrolyte: Add hydroxylamine hydrochloride and sodium fluoride to the solvent and mix to obtain loose layer exfoliation electrolyte; wherein, the mass percentage of hydroxylamine hydrochloride is 0.5 wt.%, the mass percentage of NaF is 0.2 wt.%, and the balance is deionized water. Add the above raw materials to the micro-arc oxidation tank and stir with a mechanical stirrer until completely dissolved to obtain loose layer exfoliation electrolyte.
[0056] Step 4: Loose Layer Removal Treatment: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating is clamped in an electrochemical tank as the anode. A graphite sheet is clamped in the cathode and placed opposite the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating. The distance between the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating and the graphite sheet is 20 mm. Both the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating and the graphite sheet are immersed in the loose layer removal electrolyte. The loose layer removal treatment is carried out at an electrolyte temperature of 80℃, a constant voltage of 10V, and a removal time of 80 min to obtain a titanium bipolar plate with a dense layer coating of deposited micro-arc oxidation TiO2.
[0057] Step 5: Nitriding: The titanium bipolar plate with the deposited micro-arc oxidation TiO2 dense coating is placed in a PECVD apparatus for nitriding. The nitriding temperature is 800℃, the gas is NH3, the flow rate is 80 sccm, the plasma power is 450W, and the holding time is 1h, to obtain the titanium bipolar plate TiO2 for PEM electrolytic reactors. x N y coating.
[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A titanium bipolar plate (TiO2) for PEM electrolytic reactors x N y The coating is characterized by, Titanium bipolar plates (TiO2) for PEM electrolytic reactors x N y The coating consists of a dense micro-arc oxidation TiO2 layer and a TiO2 layer stacked together. x N y The coating composition consists of a dense TiO2 micro-arc oxidation layer deposited on a titanium bipolar plate; the dense TiO2 micro-arc oxidation layer is doped with P2O5 and SiO2, with the sum of the mass percentages of P and Si not exceeding 1 wt.%; TiO2... x N y The coating is deposited on a dense TiO2 layer coating formed by micro-arc oxidation. x N y The coating consists of TiO2 and TiN, with TiO2 being the most abundant TiO2. x N y In the coating, the mass percentage of N is not less than 3 wt.% and not more than 6 wt.%. The dense layer coating of micro-arc oxidation TiO2 is obtained by peeling off the loose layer with irregular pore structure on the surface of the micro-arc oxidation TiO2 coating after depositing the micro-arc oxidation TiO2 coating on the titanium bipolar plate by micro-arc oxidation method.
2. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 1 x N y The coating is characterized by, Titanium bipolar plates (TiO2) for PEM electrolytic reactors x N y The coating thickness is 5μm~15μm.
3. A titanium bipolar plate (TiO2) for a PEM electrolytic reactor according to any one of claims 1 to 2. x N y The method for preparing the coating is characterized in that, Includes the following steps: The main salt, fluoride, complexing agent and hydroxide are dissolved together in water to obtain the micro-arc oxidation electrolyte; The main salt is selected from phosphates and silicates; Using a titanium bipolar plate as the anode, a dual-electrode system is formed together with the first cathode. The dual-electrode system is immersed in a micro-arc oxidation electrolyte, and a micro-arc oxidation TiO2 coating is prepared on the titanium bipolar plate by in-situ micro-arc oxidation, thus obtaining a titanium bipolar plate with a deposited micro-arc oxidation TiO2 coating. The micro-arc oxidation TiO2 coating consists of a dense layer and a porous layer. The thickness of the dense layer is not less than 5 μm and not more than 15 μm, and the thickness of the porous layer is not more than 15 μm. In the micro-arc oxidation TiO2 coating, the mass percentage of P does not exceed 8 wt.%, and the mass percentage of Si does not exceed 15 wt.%. A reducing agent and a fluoride are dissolved together in water to obtain a loose layer peeling electrolyte. A titanium bipolar plate with a deposited micro-arc oxidation TiO2 coating and a second cathode are used to form a dual-electrode system. The dual-electrode system is immersed in the loose layer peeling electrolyte, and electrochemical treatment is performed on the titanium bipolar plate with the deposited micro-arc oxidation TiO2 coating to peel off the loose layer with irregular pore structure on the surface of the micro-arc oxidation TiO2 coating, exposing a dense layer containing spherical pits, and obtaining a titanium bipolar plate with a deposited dense layer coating of micro-arc oxidation TiO2. In the micro-arc oxidation TiO2 dense layer coating, the mass percentage of P+Si is no more than 1 wt.%. In a nitrogen-containing atmosphere, a titanium bipolar plate with a dense micro-arc oxidation TiO2 coating was subjected to plasma vapor deposition. The composition of the dense micro-arc oxidation TiO2 coating was controlled by plasma nitriding, and TiO2 for PEM reactors was synthesized in situ on the titanium bipolar plate. x N y coating.
4. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, The micro-arc oxidation process is characterized by constant voltage mode, with the following conditions: voltage 300V~500V, duty cycle 10%~20%, frequency 300Hz~500Hz, and micro-arc oxidation for 10min~20min.
5. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, In the micro-arc oxidation electrolyte, the amount of main salt is 20 g / L to 40 g / L, the amount of complexing agent is 2 g / L to 5 g / L, the amount of hydroxide is 3 g / L to 6 g / L, and the amount of fluoride is 4 g / L to 8 g / L.
6. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, The complexing agent is selected from one or more of citric acid, tartaric acid, and ethylenediaminetetraacetic acid; the hydroxide is selected from one or two of potassium hydroxide and sodium hydroxide; and the fluoride is selected from one or two of sodium fluoride and potassium fluoride.
7. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, In the loose layer peeling electrolyte, the mass percentage of reducing agent is 0.5 wt.%~2 wt.%, and the mass percentage of fluoride is 0.2 wt.%~1 wt.%.
8. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, The reducing agent is hydroxylamine hydrochloride, and the fluoride is one or both of sodium fluoride and potassium fluoride.
9. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, The electrochemical treatment conditions are: 80℃ temperature, constant voltage 10V~30V, electrochemical treatment for 40min~80min.
10. The titanium bipolar plate (TiO2) for PEM electrolytic reactor according to claim 3 x N y The method for preparing the coating is characterized in that, The conditions for plasma vapor deposition are as follows: in a pure ammonia or nitrogen and hydrogen mixed atmosphere, at a temperature of 600℃~800℃, a gas flow rate of 80sccm~150sccm, and a plasma power of 350W~450W, the temperature is maintained for 1h~3h.