A surface modification method of bipolar plate for water electrolysis hydrogen production and bipolar plate

Abstract

The present invention provides a surface modification method for a bipolar plate for hydrogen production by water electrolysis and a bipolar plate, which relates to the field of fuel cell technology. A C-N / conductive material composite coating can be prepared on the surface of the bipolar plate, significantly improving the conductivity and corrosion resistance of the bipolar plate. The process is simple and easy to promote. The method comprises the following steps: S1, dispersing a conductive material in a solvent to obtain a first solution; S2, adding a stabilizer to the first solution and stirring to obtain a second solution; S3, placing a pretreated bipolar plate substrate in the second solution for electrophoretic deposition to obtain a substrate prepared with a thin film; S4, sintering the substrate prepared with the thin film to obtain a bipolar plate having a modified coating. The technical solution provided by the present invention is applicable to the process of preparing a bipolar plate.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a surface modification method of a bipolar plate for solid electrolyte water electrolysis to produce hydrogen and a fuel cell, and a bipolar plate. Background Art

[0002] As a key component in SPE (Solid Water Electrolysis) water electrolysis hydrogen production and fuel cell devices, bipolar plates significantly impact the device's operating life, cost, and wide-scale application. Metal materials offer advantages such as excellent electrical and thermal conductivity, high power density, good gas barrier properties, high mechanical strength, ease of processing, and low production costs. However, metal materials such as stainless steel can corrode over time. The presence of metal ions after corrosion can hinder proton migration and have a toxic effect on the membrane electrode. Titanium surfaces are highly susceptible to oxidation, forming a dense oxide film. While this film significantly hinders corrosion and improves corrosion resistance, it also increases the interfacial contact resistance between the titanium and the diffusion layer, contributing to ohmic losses in the entire stack. Therefore, relying solely on the inherent properties of metal materials to simultaneously meet the requirements for high corrosion resistance and low contact resistance is difficult. Currently, the surface modification methods for metal bipolar plates are mainly to prepare a layer of precious metal coating, metal carbon / nitride coating, and conductive polymer coating on the metal bipolar plate substrate through electroplating, magnetron sputtering, embedding co-penetration, etc. to improve the conductivity and corrosion resistance of the base material. However, these methods generally have problems such as complex process technology and high cost.

[0003] Therefore, it is necessary to study a surface modification method and bipolar plate for solid electrolyte water electrolysis hydrogen production and fuel cell to address the shortcomings of the existing technology and solve or alleviate one or more of the above problems. Summary of the Invention

[0004] In view of this, the present invention provides a surface modification method for a bipolar plate for hydrogen production by water electrolysis and a bipolar plate, which can prepare a CN / conductive material composite coating on the surface of the bipolar plate, significantly improving the conductivity and corrosion resistance of the bipolar plate, and the process is simple and easy to promote.

[0005] In one aspect, the present invention provides a method for surface modification of a bipolar plate for hydrogen production by water electrolysis, the method comprising the following steps:

[0006] S1. dispersing a conductive material in a solvent to obtain a first solution;

[0007] S2, adding a stabilizer to the first solution and stirring to obtain a second solution;

[0008] S3, placing the pretreated bipolar plate substrate into the second solution for electrophoretic deposition to obtain a substrate with a thin film prepared thereon;

[0009] S4. Sintering the substrate with the thin film to obtain a bipolar plate with a modified coating.

[0010] According to the above aspects and any possible implementation, a further implementation is provided, in which the pretreatment of the bipolar plate substrate in step S3 includes: placing the original substrate in a prepared acid solution for etching to remove the surface oxide layer.

[0011] According to the above aspects and any possible implementation, an implementation is further provided, wherein the conductive material is any one or more of titanium nitride, chromium nitride, titanium carbide and graphene.

[0012] According to the above aspects and any possible implementation manner, an implementation manner is further provided, wherein the concentration of the conductive material in the first solution is 0.1 g / L to 10 g / L.

[0013] According to the above aspects and any possible implementation, an implementation is further provided, wherein the solvent is any one or more of water, methanol, ethanol, butanol, isopropanol and acetone.

[0014] According to the above aspects and any possible implementation, an implementation is further provided, wherein the stabilizer is any one or more of polyethyleneimine, polyacrylamide, polyaluminum chloride and anionic polyacrylamide.

[0015] According to the above aspects and any possible implementation, an implementation is further provided, wherein the stabilizer accounts for 0 wt.% to 4 wt.% in the second solution.

[0016] According to the above aspects and any possible implementation, an implementation is further provided, in which the electrophoretic deposition voltage in step S3 is 3V to 45V, and the electrophoretic deposition time is 30s to 600s.

[0017] According to the above aspects and any possible implementation, an implementation is further provided, in step S4, the sintering temperature is 300° C. to 600° C., and the holding time is 1 hour to 4 hours.

[0018] According to the above aspects and any possible implementation, an implementation is further provided, wherein the acid solution is a mixed solution of H2NO3 and HF, and the volume ratio of each component in the acid solution is HF:H2NO3:H2O=1:4:5, HF:H2NO3:H2O=1:8:10, and HF:H2NO3:H2O=1:12:15.

[0019] According to the above aspects and any possible implementation, an implementation is further provided, wherein the bipolar plate substrate is a titanium substrate or a stainless steel substrate.

[0020] In another aspect, the present invention provides a bipolar plate for producing hydrogen by water electrolysis, wherein the bipolar plate is modified by any of the above methods;

[0021] The surface of the bipolar plate is provided with a CN / conductive material composite coating.

[0022] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects: the present invention deposits the conductive material onto the substrate surface by electrophoretic deposition, and then decomposes and carbonizes the stabilizer by sintering to produce a CN / conductive material composite coating; the process is simple and efficient, does not require special equipment, is low in cost, and has a wide range of applications;

[0023] Another technical solution among the above technical solutions has the following advantages or beneficial effects: it can improve the conductivity and corrosion resistance of titanium / stainless steel bipolar plates and has broad application prospects; it has high conductivity, and the contact resistance remains stable in a low range after 10 hours of 1.7V high potential polarization;

[0024] Another technical solution among the above technical solutions has the following advantages or beneficial effects: there is a wide room for improvement. The present invention can also introduce different types of conductive materials (carbon nanotubes, nano-titanium nitride, nano-chromium carbide, etc.) and stabilizers (polyethyleneimine, polyacrylamide, polyaluminum chloride and anionic polyacrylamide, etc.), and adjust the different proportions of each component to achieve different degrees of improvement in the performance of the metal bipolar plate.

[0025] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the sample preparation steps provided by an embodiment of the present invention; the sample substrate to be processed is used as the cathode, and an external power supply is used to perform cathode electrophoresis in the electrolytic cell. Titanium nitride particles are adsorbed on the sample surface under the action of the electric field force to form a protective coating. After low-temperature treatment, the organic carbonized titanium nitride molecules in the coating are agglomerated together, providing a channel for the transmission of electrons, thereby improving the conductive performance of the coating.

[0028] Figure 2 This is a real picture of the sample after deposition provided by an embodiment of the present invention; this experiment can adjust the electrolytic cell, deposition voltage and time according to the size of the sample, and has the basis for preparing large-area samples and commercial applications.

[0029] Figure 3 These are scanning electron microscope (SEM) and XPS images of a coating after deposition at 5V for 180s, according to one embodiment of the present invention. From top to bottom, they show the coatings of the unsintered sample, the sample sintered at 300°C, and the sample sintered at 400°C. The unsintered sample exhibits cracks and fractures after deposition, while the sample sintered at low temperature exhibits agglomeration and bonding. In the figure, "Binding Energy" represents binding energy, and "Intensity" represents strength.

[0030] Figure 4 The sintered sample provided by one embodiment of the present invention is heated in 0.5 mol / L H2SO4+2PPM F - Potentiodynamic polarization curve in solution; it can be seen that the corrosion potential of the treated samples is higher than that of the untreated substrate, and the corrosion current density is two orders of magnitude lower than that of the untreated samples, indicating that the preparation of the coating has greatly improved the corrosion resistance of the samples.

[0031] Figure 5 This is a contact resistance change diagram of the samples at different sintering temperatures after 1.7V constant potential polarization provided by an embodiment of the present invention; the contact resistance of all samples tends to gradually decrease with the increase of pressure. Under the same compaction force, the treated samples are lower than the untreated samples and have better conductive properties.

[0032] Figure 6 The sintered sample provided by one embodiment of the present invention is heated in 0.5 mol / L H2SO4+2 mg / L - 1.7V constant potential polarization curve in solution. After high potential polarization, the sample still has a stable corrosion current density. DETAILED DESCRIPTION

[0033] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0034] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0035] To address the issue of bipolar plate corrosion and surface oxide layer thickening during long-term operation in SPE water electrolysis and fuel cells, which reduces electrolytic cell efficiency, the present invention provides a two-step electrophoretic deposition and sintering method for preparing a protective composite coating. This method utilizes the simplicity, efficiency, and speed of the electrophoretic deposition process to produce a highly conductive, corrosion-resistant composite coating.

[0036] The present invention provides a method for surface modification of titanium bipolar plates for SPE (solid electrolyte) water electrolysis hydrogen production, comprising the following steps:

[0037] Step 1: Dispersing the conductive material in a specific solvent;

[0038] Conductive materials include but are not limited to titanium nitride, chromium nitride, titanium carbide, graphene, etc.; the concentration of the conductive material is 0.1g / L to 10g / L; the solvent includes but is not limited to water and organic solvents such as methanol, ethanol, butanol, isopropanol, acetone, etc.;

[0039] Step 2: Add the stabilizer to the solution prepared in step 1 and stir evenly by ultrasonic stirring;

[0040] Stabilizers include but are not limited to polyethyleneimine, polyacrylamide, polyaluminum chloride and anionic polyacrylamide; the addition ratio of the stabilizer is 0wt.% to 5wt.%;

[0041] The stirring time is 10 minutes to 120 minutes;

[0042] Step 3: Place the titanium substrate in a prepared acid solution for etching to remove the surface oxide layer;

[0043] The volume ratio of the acid solution is HF:H2NO3:H2O=1:4:5, HF:H2NO3:H2O=1:8:10, HF:H2NO3:H2O=1:12:15;

[0044] The acid erosion time is 10s to 180s, preferably 10s to 30s;

[0045] Step 4: Place the treated titanium substrate in a solvent containing a conductive material and a stabilizer and perform electrophoretic deposition at a constant voltage to prepare a uniform coating film on the substrate;

[0046] The electrophoretic deposition voltage is 3V to 45V; the electrophoretic deposition time is 30s to 600s;

[0047] Step 5: placing the substrate with the coating film into a vacuum tube furnace, introducing a protective atmosphere, and heating and sintering; finally, a CN / conductive material composite coating is obtained;

[0048] The sintering temperature of the heat treatment is 300°C to 600°C; the holding time of the heat treatment is 1h to 4h.

[0049] The main features of the present invention include:

[0050] In order to solve the problem that the SPE water electrolysis and fuel cell bipolar plates oxidize at high anode potential, resulting in increased internal resistance and reduced power efficiency of the stack, the present invention adopts the method of electrophoretic deposition and temperature-increased sintering to prepare a highly conductive and corrosion-resistant composite coating on the bipolar plates.

[0051] The present invention prepares an electrophoretic suspension by adding a stabilizer and a conductive material to a specific solvent. Under the action of an electric field, the suspension is deposited on an electrode. After a certain period of deposition at a constant voltage, a dense and uniform conductive coating is formed. The coating is then sintered to improve its bonding strength with the substrate and corrosion resistance. The stabilizer is decomposed and carbonized to prepare a composite coating, effectively reducing the contact resistance of the coating.

[0052] The CN / conductive material composite coating bipolar plate prepared by the present invention has greatly improved corrosion resistance. Figure 4 After the curve is fitted by Tafel, it can be seen that the sample after treatment is 0.5mol / LH2SO4+2PPM F - In the solution, the corrosion current density is 1.408·10 -6 A / cm 2 The corrosion potential is 717.518mV (VS·SHE), and the conductivity is greatly improved compared with the substrate. Figure 5 It can be seen that its contact resistance is 140N cm 2 down to 2.4mΩcm 2 . Figure 6 It shows that the treated material is more stable than the untreated one under high potential polarization.

[0053] Example 1:

[0054] Prepare a titanium nitride suspension at a ratio of 10 g / L. Weigh 1.0000 g of titanium nitride powder (20 nm) using a weighing balance. Place the weighed titanium nitride powder into a beaker. Measure 100 mL of ethanol and slowly pour it into the beaker containing the titanium nitride powder while stirring. Label the titanium nitride suspension. Measure a predetermined amount of polyethyleneimine into the beaker. Stir the 10 g / L titanium nitride suspension on an electromagnetic stirrer for 1 hour. Add 50 mL of distilled water to the beaker. Using a graduated cylinder, measure 5 mL of hydrofluoric acid and 40 mL of nitric acid. Add the hydrofluoric acid and nitric acid to the 50 mL distilled water beaker and stir. Using a titanium sheet as the substrate, place the titanium sheet sample in the prepared acid solution (HF:H₂NO₃:H₂O = 1:8:10) and etch for 10 seconds. Ultrasonicate the titanium nitride suspension after stirring for 1 hour to homogenize it. Use a carbon rod as the counter electrode with a 15 mm interelectrode distance and stir at 200 rpm. Connect the two-electrode system to a power source and perform electrophoretic deposition at a constant voltage. Remove the deposited sample and air dry it to form a titanium nitride coating. Place the sample in a vacuum tube furnace, purged with argon. Sinter the sample at a heating rate of 5°C / min to 300°C and hold for 2 hours. After natural cooling, remove the sample to obtain a titanium nitride coating.

[0055] Example 2:

[0056] Prepare a titanium nitride suspension at a ratio of 10 g / L. Weigh 1.0000 g of titanium nitride powder (20 nm) using a weighing balance. Place the weighed titanium nitride powder into a beaker. Measure 100 mL of ethanol and slowly pour it into the beaker containing the titanium nitride powder while stirring. Label the titanium nitride suspension. Measure a predetermined amount of polyethyleneimine into the beaker. Stir the 10 g / L titanium nitride suspension on an electromagnetic stirrer for 1 hour. Add 50 mL of distilled water to the beaker. Using a graduated cylinder, measure 5 mL of hydrofluoric acid and 40 mL of nitric acid. Add the hydrofluoric acid and nitric acid to the 50 mL distilled water beaker and stir. Using a titanium sheet as the substrate, place the titanium sheet sample in the prepared acid solution (HF:H₂NO₃:H₂O = 1:8:10) and etch for 10 seconds. Ultrasonicate the titanium nitride suspension after stirring for 1 hour to homogenize it. Use a carbon rod as the counter electrode with a 15 mm interelectrode distance and stir at 200 rpm. Connect the two-electrode system to a power source and perform electrophoretic deposition at a constant voltage. Remove the deposited sample and air dry it to form a titanium nitride coating. Place the sample in a vacuum tube furnace, purged with argon. Sinter the sample at 400°C at a heating rate of 5°C / min for 2 hours. After cooling naturally, remove the sample to obtain a titanium nitride coating.

[0057] The effects of different sintering temperatures on the contact resistance of bipolar plate samples in Example 1 and Example 2 are shown in FIG. Figure 5As shown in the figure, the contact resistance of all samples tends to decrease gradually with the increase of pressure, and reaches stability in the range of 130-200N / cm2. This is because as the pressure increases, the contact between the bipolar plate and the gold-plated plate becomes more sufficient. The contact resistance of the untreated sample is 4.3mΩ / cm2 at 140N / cm2, while the contact resistance of the treated sample is 2.4mΩ / cm2. It can be seen that the treated sample can significantly improve the conductivity of the bipolar plate.

[0058] The above describes in detail the surface modification method and bipolar plate for water electrolysis hydrogen production provided in the examples of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of this application. In summary, the contents of this specification should not be construed as limiting this application.

[0059] It should also be noted that the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, the phrase "comprising a..." does not preclude the presence of other identical elements in the product or system comprising the element. "Substantially" means that within an acceptable error range, a person skilled in the art would be able to solve the technical problem and substantially achieve the technical effect.

[0060] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. In this application, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "middle", "horizontal", "vertical", etc. are based on the directions or positional relationships shown in the accompanying drawings. In addition to being used to indicate directions or positional relationships, some of the above terms may also be used to indicate other meanings. For example, the term "upper" may also be used to indicate a certain dependency or connection relationship in certain circumstances. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to the specific circumstances. The term "and / or" used herein is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects are in an "or" relationship.

Claims

1. A method for surface modification of bipolar plates for water electrolysis hydrogen production, characterized in that: The steps of the method include: S1. dispersing a conductive material in a solvent to obtain a first solution; S2. Adding a stabilizer to the first solution and stirring to obtain a second solution; S3, placing the pretreated bipolar plate substrate into the second solution for electrophoretic deposition to obtain a substrate with a thin film prepared thereon; S4, sintering the substrate with the thin film to obtain a bipolar plate with a modified coating; The conductive material is any one or more of titanium nitride, chromium nitride, titanium carbide and graphene; The stabilizer is any one or more of polyethyleneimine, polyacrylamide, polyaluminium chloride and anionic polyacrylamide; In step S3, the electrophoretic deposition voltage is 3V to 45V, and the electrophoretic deposition time is 30s to 600s; In step S4, the sintering temperature is 300° C. to 600° C., and the holding time is 1 hour to 4 hours.

2. The surface modification method of a bipolar plate for producing hydrogen by water electrolysis according to claim 1, characterized in that: The pretreatment of the bipolar plate substrate in step S3 includes: placing the original substrate into a prepared acid solution for etching to remove the surface oxide layer.

3. The surface modification method of a bipolar plate for producing hydrogen by water electrolysis according to claim 1, characterized in that: The concentration of the conductive material in the first solution is 0.1 g / L to 10 g / L.

4. The surface modification method of a bipolar plate for producing hydrogen by water electrolysis according to claim 1, characterized in that: The solvent is any one or more of water, methanol, ethanol, butanol, isopropanol and acetone.

5. The surface modification method of a bipolar plate for producing hydrogen by water electrolysis according to claim 1, characterized in that: The stabilizer accounts for 0 wt.% to 4 wt.% in the second solution.

6. A bipolar plate for producing hydrogen by water electrolysis, characterized in that: The bipolar plate is modified by the surface modification method according to any one of claims 1 to 5; The surface of the bipolar plate is provided with a CN / conductive material composite coating.

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