Long-acting low-conductance composite treatment method for inner cavity of hydrogen fuel stack radiator core

Abstract

This invention proposes a long-term low-conductivity composite treatment method for the inner cavity of a hydrogen fuel cell stack heat sink core. The method includes pre-treating the surface of the heat sink core, coating it with a slurry, curing it, and cleaning it. The slurry comprises pH-responsive slow-release microcapsules, which, from the inside out, consist of an ion trapping agent and mesoporous silica grafted with polyacrylic acid. A coating is formed on the surface of the heat sink core by coating and curing the slurry. This slurry integrates the atomic-level physical barrier function of graphene with the intelligent chemical trapping function of the pH-responsive microcapsules, achieving multi-layered protection of "physical barrier as the main component, chemical trapping as a supplement, and intelligent response." This allows the coolant conductivity to be stably controlled below 5 μS / cm under dynamic operating conditions for thousands of hours.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for heat dissipation components of hydrogen fuel cell stacks, and in particular to a long-term low-conductivity composite treatment method for the inner cavity of a heat dissipation core of a hydrogen fuel cell stack. Background Technology

[0002] Hydrogen fuel cell stacks have stringent requirements for coolant conductivity, which must be maintained at a level of <5 μS / cm over a long period. The aluminum heat sink core (Al) 3+ Plasmon ion deposition is the key factor leading to increased coolant conductivity. The coolant used in hydrogen fuel cell stacks is typically ethylene glycol. This coolant enters the power generation unit of the stack to wet the proton exchange membrane. If the coolant conductivity is too high, it can cause the proton exchange membrane to break down, leading to power generation unit failure.

[0003] Current technologies for maintaining low conductivity mainly suffer from the following problems: 1. Existing technical approaches mainly involve passivating the surface of the inner cavity of the aluminum heat sink core. This technology suffers from problems such as passivation layer peeling and degradation, requiring repair after long-term use.

[0004] 2. There is a problem of impurities in the coolant adhering and settling on the inner wall, which reduces the heat dissipation efficiency.

[0005] 3. Relying on "anodic oxidation + organic sealing", the anodic oxidation layer has high porosity. After sealing, ion permeation channels still exist, and there is no active adsorption of conductive ions. Long-term use can easily lead to excessive conductivity. Summary of the Invention

[0006] In view of this, the present invention provides a long-term low-conductivity composite treatment method for the inner cavity of a hydrogen fuel cell stack heat sink core. A coating is applied to the surface of the hydrogen fuel cell stack heat sink core. The coating is formed by coating and curing a slurry. This slurry integrates the atomic-level physical barrier function of graphene with the intelligent chemical capture function of pH-responsive microcapsules, achieving multi-layered protection of "physical barrier as the main component, chemical capture as a supplement, and intelligent response." This allows the coolant conductivity to be stably controlled below 5 μS / cm under dynamic operating conditions for thousands of hours.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a long-term low-conductivity composite treatment method for the inner cavity of a hydrogen fuel cell stack radiator core, comprising: pre-treating the surface of the hydrogen fuel cell stack radiator core, coating it with a slurry, curing it, and cleaning it; The slurry includes graphene and pH-responsive sustained-release microcapsules. The pH-responsive sustained-release microcapsule comprises, from the inside out, an ion trapping agent and mesoporous silica grafted with polyacrylic acid.

[0008] Hydrogen fuel cell stacks have extremely high requirements for coolant conductivity (≤5μS / cm, some require ≤3μS / cm). The inner wall of the aluminum alloy radiator core releases metal ions into the coolant, leading to increased conductivity and damage to the proton exchange membrane. Traditional passivation treatment has the following defects: (1) The membrane is thin (≤2μm), has poor erosion resistance, and fails in about 6 months; (2) The adhesion to the substrate is weak, and it is easy to peel off; (3) It has no ion adsorption function and cannot capture the precipitated ions.

[0009] This invention involves coating the inner surface of a hydrogen fuel cell stack radiator core with a slurry consisting of graphene, silane coupling agent, mesoporous silica, and pH-responsive slow-release microcapsules, which then cures to form a coating. When the coating is intact, graphene plays a primary barrier role; when microcracks or localized failures occur, the pH-responsive microcapsules remove leaked ions, preventing an increase in conductivity. This multi-layered protection system, characterized by "primarily physical barrier, supplemented by chemical capture, and intelligent response," enables the radiator core to maintain a stable coolant conductivity below 5 μS / cm even under dynamic operating conditions lasting thousands of hours, achieving true "long-lasting low conductivity."

[0010] Graphene has the following characteristics: (1) Graphene is a two-dimensional material with a single atomic layer, which is an atomic-level physical barrier. It can form a blocking layer with an extremely dense lattice arrangement and does not contain aluminum ions (Al). 3+ The coating passes through gaps. It does not release any conductive ions and will not contaminate the coolant. Even after long-term immersion (1000~3000 hours), the coating does not swell, decompose, or powder, and the barrier layer remains intact.

[0011] (2) Graphene has extremely high chemical stability and does not react with coolant or aluminum. It can inhibit corrosion of aluminum materials such as acids, alkalis and ethylene glycol from the source.

[0012] (3) High thermal stability, resistant to high and low temperature cycles, does not crack or soften, and can actively adsorb conductive ions in the coolant. Double protection: graphene has a very large specific surface area. Even if a trace amount of ions leaks out, they will be directly adsorbed by graphene, preventing them from entering the coolant and increasing conductivity.

[0013] (4) Graphene has good thermal conductivity and a large specific surface area, which helps to maintain good heat dissipation performance of the heat dissipation core.

[0014] (5) Graphene also has the ability to decompose organic matter and has a self-cleaning function for coolant.

[0015] (6) Graphene is arranged at the atomic level, so large molecules of coolant and their impurities will not adhere to its coating surface, and long-term use will not form a deposit layer that reduces heat dissipation efficiency. The thermal conductivity of graphene is 6 times that of aluminum, which directly improves the heat absorption efficiency of the internal cavity, and the heat dissipation power reduction rate is <1%.

[0016] The pH-responsive slow-release microcapsules consist of, from the inside out, an ion-scavenging agent (such as disodium EDTA or zirconium phosphate) and a mesoporous silica (MSN) shell grafted with polyacrylic acid (PAA). Polyacrylic acid is a pH-responsive polymer. Under normal operating conditions, the PAA molecular chains are in a contracted and folded state through hydrogen bonding, tightly encapsulating the pores of the mesoporous silica and firmly sealing the internal ion-scavenging agent. When the coating undergoes localized micro-corrosion of the aluminum substrate due to long-term erosion, temperature stress, or microscopic defects, the pH in that area changes, and the carboxyl groups (-COOH) on the PAA molecular chains ionize into carboxylate groups (-COO₂). - The molecular chains extend rapidly due to electrostatic repulsion, opening the pores of mesoporous silica and thus slowly releasing the internal ion trapping agent.

[0017] The released disodium EDTA (a strong chelating agent) or zirconium phosphate (an ion exchanger) can rapidly react with Al in the solution. 3+ Fe 3+ Cu 2+ Conductive ions undergo chelation or ion exchange reactions to form stable, non-conductive complexes or precipitates. These products are either adsorbed inside the coating or removed by circulating filtration, thereby maintaining the conductivity of the coolant at an extremely low level (<5 μS / cm).

[0018] This pH-responsive slow-release microcapsule actively releases only when localized micro-corrosion (pH anomaly) occurs, achieving "on-demand release and precise capture." This avoids premature consumption of the ion trap, allowing it to provide continuous protection over several years of service, significantly extending the coating's effective lifespan.

[0019] Mesoporous silica possesses a high specific surface area and ordered nanopores. In slurries, it not only acts as an auxiliary adsorbent to further capture accidentally leaked trace ions, but also serves as a "spacer" for graphene, effectively preventing the agglomeration of graphene sheets during slurry preparation and curing, thus ensuring the uniformity and density of the coating.

[0020] The silane coupling agent has an ethoxy group (-OCH2CH3) at one end and an amino group (-NH2) at the other end. After hydrolysis, the ethoxy group forms a strong Al-O-Si covalent bond with the hydroxyl groups (-OH) on the aluminum substrate surface; the amino group forms hydrogen bonds or chemical bonds with the carboxyl or hydroxyl groups on the surface of graphene and pH-responsive slow-release microcapsules. This "molecular bridge" effect greatly enhances the adhesion between the organic-inorganic hybrid coating and the aluminum substrate, effectively resisting the high-speed erosion of the coolant.

[0021] Based on the above technical solutions, the ion scavenging agent further includes either disodium EDTA or zirconium phosphate.

[0022] Based on the above technical solution, the method for preparing the pH-responsive sustained-release microcapsules further includes: S1, amidizing mesoporous silica to obtain product 1; S2. The product 1 is reacted with acrylic acid monomer and catalyst to obtain the mesoporous silica grafted with polyacrylic acid; S3. Mix the ion trapping agent and mesoporous silica grafted with polyacrylic acid to obtain the pH-responsive sustained-release microcapsules.

[0023] Based on the above technical solution, the mass ratio of the mesoporous silica, acrylic monomer, and ion scavenger is further 1:(2~5):(0.1~0.3).

[0024] Based on the above technical solutions, the catalyst further comprises a transition metal salt and a nitrogen-containing ligand.

[0025] Based on the above technical solutions, the metal salt further includes any one of cuprous bromide, cuprous chloride, and cuprous bromide.

[0026] Based on the above technical solution, the nitrogen-containing ligand further includes any one of pentamethyldiethylenetriamine and 2,2-bipyridine.

[0027] Based on the above technical solutions, the slurry further includes mesoporous silica, silane coupling agent and dispersant.

[0028] Based on the above technical solutions, the mesoporous silicon has a particle size of 20-50 nm, possessing an ultra-large specific surface area and an ordered mesoporous structure, enabling it to form a synergistic adsorption system with graphene and directionally capture Al. 3+ F - Conductive ions such as Na⁺ are trapped within the pores; at the same time, mesoporous silicon can fill the gaps between graphene sheets, improving the density of the coating. Combined with the condensation reaction of its surface silanol groups and silane coupling agents, the internal bonding force of the coating is enhanced. The material is chemically stable, with no conductive ion precipitation, and is resistant to coolant corrosion and high-temperature aging, ensuring that the coating maintains its dual "adsorption-barrier" function for a long time, making it suitable for the low conductivity requirements of hydrogen fuel cell stack coolants.

[0029] Mesoporous silica is the "best assistant" to graphene—it helps graphene absorb more ions, seals the gaps in the coating, and does not affect adhesion and conductivity. It is a key synergistic material for achieving stable conductivity control of <5μS / cm.

[0030] Based on the above technical solutions, the dispersant further includes sodium dodecylbenzenesulfonate, which is an anionic surfactant. It can achieve efficient and stable dispersion of graphene through π-π interactions and electrostatic repulsion effects, prevent graphene sheets from agglomerating and stacking, and ensure that the coating is dense and uniform. The amount of this dispersant added is trace, and the residue is extremely low after post-treatment cleaning. It will not cause an increase in the conductivity of the coolant, which is suitable for the low conductivity requirements of hydrogen fuel cell stacks.

[0031] Based on the above technical solutions, γ-aminopropyltriethoxysilane, as a silane coupling agent, can further construct Al-O-Si covalent bonds between the aluminum heat sink core and graphene through hydrolysis and condensation reaction, significantly improving the interfacial adhesion and structural stability of the graphene coating; at the same time, it can improve the dispersion uniformity of graphene in the aqueous system, ensuring that the coating is dense and defect-free, and that no conductive ions are released after curing, meeting the low conductivity requirements of hydrogen fuel cell stack coolant.

[0032] Based on the above technical solutions, the slurry, with a total mass fraction of 100%, further comprises 1-3% pH-responsive sustained-release microcapsules, 50-60% graphene, 10-15% mesoporous silica, 5-10% silane coupling agent, 0.3-0.5% dispersant, and 20-40% water.

[0033] Based on the above technical solutions, the coating thickness is further 1.5~2.5 μm.

[0034] The slurry coating of this invention has a moderate thickness. A thicker coating provides a longer ion diffusion path and a larger microcapsule containment space, while also acting as a "buffer layer" to resist thermal stress and mechanical shock. Controlling the thickness within this range also avoids excessive thickness that could lead to decreased thermal conductivity or internal stress cracking.

[0035] Based on the above technical solutions, the pretreatment further includes: a1. Immersing the core of the hydrogen fuel cell stack radiator in an alkaline solution, then washing it with water, drying it, and setting it aside for later use.

[0036] Based on the above technical solution, the curing further includes: holding at 120~140℃ for 40~80 minutes.

[0037] The curing temperature range ensures sufficient cross-linking of the silane coupling agent and stability of the PAA grafted chain without damaging the microcapsule structure. It also avoids the softening of the aluminum alloy matrix or residual stress problems that may be caused by high temperature (>200℃). The process is user-friendly and suitable for industrial production.

[0038] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention integrates the physical barrier function of graphene with the intelligent chemical capture function of pH-responsive microcapsules. The atomically dense structure of graphene physically blocks most of the ion precipitation pathways; once trace amounts of ions are released due to microscopic defects in the coating or long-term corrosion, causing local pH changes, the microcapsules will responsively release ion-capturing agents to actively chelate Al. 3+ Equivalently conductive ions. A dual physical and chemical mechanism achieves long-lasting low-conductivity protection far exceeding that of single technologies.

[0039] (3) The silane coupling agent forms chemical bonds, and the vacuum negative pressure coating adheres tightly. The shear strength is ≥4.0 MPa, and there is no peeling after 2000 h of 3 m / s scouring, which is superior to traditional coatings.

[0040] (4) Graphene and mesoporous silicon synergistically adsorb conductive ions, thereby improving the heat absorption efficiency of the coating and reducing the heat dissipation power.

[0041] (5) Excellent chemical and thermal stability; the coating does not dissolve or decompose.

[0042] (6) The process is simplified and suitable for mass production. It only processes the inner cavity. Vacuum negative pressure coating is suitable for complex channels and there is no missed coating. No high-priced equipment is required. The core equipment is a vacuum pump, an ultrasonic cleaner, and an oven. The single batch takes ≤3 hours and the investment is low.

[0043] (7) Dense and defect-free structure: Mesoporous silicon and dispersants prevent graphene agglomeration, the coating is free of pinholes and cracks, and the ion barrier performance lasts throughout the entire life cycle. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] This invention provides a method for long-term low-conductivity composite treatment of the inner cavity of a hydrogen fuel cell stack heat sink core, comprising the following steps: (i) Surface pretreatment of the heat sink core of the hydrogen fuel cell stack 1. Alkaline degreasing: Vertically fix the welded and airtight hydrogen fuel cell stack radiator core, inject 50~55℃ alkaline degreasing solution (sodium hydroxide 30g / L + sodium carbonate 20g / L + OP-10 2g / L) from one end, soak for 5~8 minutes and then drain from the other end to remove the oil stains in the inner cavity.

[0046] 2. Gradient cooling ultrasonic water washing to remove flux residue, completed in 4 steps: (1) First water wash: Inject deionized water at a temperature of 45~50℃, ultrasonically clean for 3 minutes (power 200W), and use thermal expansion to remove flux residue in the inner cavity pores; (2) Secondary water washing: Inject 25~30℃ deionized water, ultrasonically clean for 4 minutes to shrink the pores and capture free ions; (3) Three water washes: Inject 15~20℃ deionized water, ultrasonically clean for 3 minutes, and thoroughly rinse away impurities; (4) Drying the inner cavity: Introduce 80°C hot air into the inner cavity for 15 minutes to remove residual moisture.

[0047] (II) Slurry Preparation After weighing the raw materials according to the proportion, adjust the slurry viscosity to 50~80mPa·s, so that it can be easily flowed and coated on the inner cavity surface.

[0048] (III) Inner cavity vacuum negative pressure adsorption coating 1. Connect the sealing plugs with interfaces to both ends of the core, connect the vacuum pump through one of the interfaces, evacuate the inner cavity to a vacuum degree of -0.08~0.09MPa, maintain for 5 minutes, and then expel the air from the inner cavity. 2. Turn off the vacuum pump and inject the graphene composite slurry through the other side interface. Use negative pressure adsorption to make the slurry evenly wet the inner cavity wall and let it stand for 3 minutes. 3. Open the bottom valve to drain excess slurry, forming a uniform coating (1.5~2.5μm thick) on the inner wall.

[0049] (iv) Low-temperature curing The aluminum core with graphene slurry coating is placed in an oven at 120~140℃ and kept at that temperature for 60 minutes. The silane coupling agent hydrolyzes to generate Si-OH, which forms Al-O-Si covalent bonds with Al-OH on the aluminum surface. At the same time, the graphene and mesoporous silicon are tightly bonded together by van der Waals forces to form a dense coating.

[0050] (v) Post-processing of the cavity Inject room temperature deionized water into the inner cavity, ultrasonically clean for 5 minutes, remove residual slurry, and then dry with 80℃ hot air for 10 minutes to obtain the finished product.

[0051] In the following specific embodiments, the mesoporous silica has a pore size of 4~6nm and a particle size of 100~200nm.

[0052] Example 1 This embodiment provides a method for long-term low-conductivity composite treatment of the inner cavity of a hydrogen fuel cell stack heat sink core, including the following steps: (I) Preparation of pH-responsive sustained-release microcapsules Step (1): Weigh 5g of mesoporous silica and disperse it in 100mL of anhydrous ethanol. Add 2mL of aminopropyltriethoxysilane (APTES) and reflux at 60℃ for 6 hours. After the reaction is complete, centrifuge, wash three times with anhydrous ethanol, and dry under vacuum at 60℃ to obtain aminated mesoporous silica (MSN-NH2).

[0053] Step (2): Disperse the above MSN-NH2 in 50 mL of deionized water, add 15 g of acrylic acid monomer, 0.2 g of copper bromide, and 0.4 g of pentamethyldiethylenetriamine. React at 50 °C for 12 hours under nitrogen protection. After the reaction is complete, centrifuge and wash alternately with deionized water and ethanol to obtain mesoporous silica grafted with polyacrylic acid (MSN-PAA). In this step, the mass ratio of mesoporous silica to acrylic acid monomer is 1:3.

[0054] Step (3): The MSN-PAA was dispersed in 10 mL of disodium EDTA solution (concentration 0.1 g / mL) and stirred at room temperature for 12 hours. After centrifugation, the surface was rapidly washed with deionized water and vacuum dried at 40 °C to obtain pH-responsive sustained-release microcapsules (EDTA@MSN-PAA). The mass ratio of mesoporous silica to ion scavenger (disodium EDTA) was 1:0.2.

[0055] (II) Preparation of composite slurry Weigh the following by weight percentage: 55% graphene, 2% pH-responsive slow-release microcapsules, 15% mesoporous silica, 6.4% KH550, 0.4% SDBS, and 21.2% deionized water.

[0056] SDBS was dissolved in deionized water, and then the remaining components were added. The mixture was ultrasonically dispersed for 60 minutes (300W) to obtain a homogeneous slurry with a solid content of 12% and a viscosity of 65 mPa·s.

[0057] (III) Pretreatment of the inner cavity The welded and airtight hydrogen fuel cell stack radiator core was vertically fixed and injected with 52℃ alkaline degreasing solution (sodium hydroxide 30g / L + sodium carbonate 20g / L + OP-10 2g / L), and drained after soaking for 7 minutes.

[0058] Then, the following steps were performed sequentially: ultrasonic cleaning with deionized water at 48℃ for 3 minutes, ultrasonic cleaning with deionized water at 28℃ for 4 minutes, and ultrasonic cleaning with deionized water at 18℃ for 3 minutes (ultrasonic power 250W). Finally, hot air at 80℃ was introduced for drying for 15 minutes.

[0059] (iv) Vacuum negative pressure coating Seal both ends of the core, connect the vacuum pump, and evacuate to -0.085 MPa, maintaining this pressure for 5 minutes. Turn off the vacuum pump, inject the slurry, and let it stand for 3 minutes. Open the bottom valve to drain excess slurry.

[0060] (v) Curing and post-treatment The coated core was placed in a 130℃ oven for 60 minutes. After removal, room temperature deionized water was injected into the inner cavity, ultrasonically cleaned for 5 minutes, and then dried with 80℃ hot air for 10 minutes to obtain the finished product. The coating thickness was 2μm.

[0061] Example 2 This embodiment is basically the same as Embodiment 1, except that: (I) Preparation of pH-responsive sustained-release microcapsules Step (2): The amount of acrylic monomer used is 25g, and the catalyst is replaced with 0.2g cuprous bromide (CuBr) and 0.5g 2,2-bipyridine. The mass ratio of mesoporous silica to acrylic monomer is 1:5.

[0062] Step (3): Replace the ion scavenger with zirconium phosphate. Disperse MSN-PAA in 10 mL of saturated zirconium phosphate solution and stir. The mass ratio of mesoporous silica to ion scavenger (zirconia phosphate) is 1:0.3.

[0063] The other steps are the same as in Example 1.

[0064] (II) Preparation of composite slurry Weigh the following by weight percentage: 60% graphene, 3% pH-responsive slow-release microcapsules, 10% mesoporous silica, 5% KH550, 0.5% SDBS, and 21.5% deionized water.

[0065] The other steps are the same as in Example 1.

[0066] (III) Pretreatment of the inner cavity The welded and airtight hydrogen fuel cell stack radiator core was vertically fixed and injected with 55℃ alkaline degreasing solution (sodium hydroxide 30g / L + sodium carbonate 20g / L + OP-10 2g / L), and then drained after soaking for 5 minutes.

[0067] The other steps are the same as in Example 1.

[0068] (v) Curing and post-treatment The coated core was placed in a 120℃ oven for 80 minutes. After removal, room temperature deionized water was injected into the inner cavity, and the core was ultrasonically cleaned for 5 minutes. Then, it was dried with 80℃ hot air for 10 minutes to obtain the finished product. The coating thickness was 1.5μm.

[0069] The other steps are the same as in Example 1.

[0070] Example 3 This embodiment is basically the same as Embodiment 1, except that: (i) Preparation of pH-responsive sustained-release microcapsules Step (2): The amount of acrylic monomer used is 10g. The mass ratio of mesoporous silica to acrylic monomer is 1:2.

[0071] Step (3): The mass ratio of mesoporous silica to ion trapping agent is 1:0.1.

[0072] The other steps are the same as in Example 1.

[0073] (II) Preparation of composite slurry Weigh the following by weight percentage: 50% graphene, 1% pH-responsive slow-release microcapsules, 10% mesoporous silica, 10% KH550, 0.53% SDBS, and 28.5% deionized water.

[0074] The other steps are the same as in Example 1.

[0075] (III) Pretreatment of the inner cavity The welded and airtight aluminum radiator core is vertically fixed and injected with 52℃ alkaline degreasing solution (30g / L sodium hydroxide + 20g / L sodium carbonate), soaked for 7 minutes, and then drained.

[0076] The other steps are the same as in Example 1.

[0077] (v) Curing and post-treatment The coated core was placed in a 140℃ oven for 40 minutes. After removal, room temperature deionized water was injected into the inner cavity, and the core was ultrasonically cleaned for 5 minutes. Then, it was dried with 80℃ hot air for 10 minutes to obtain the finished product. The coating thickness was 2.5μm.

[0078] The other steps are the same as in Example 1.

[0079] Comparative Example 1 The difference from Example 1 is that pH-responsive slow-release microcapsules are not added to the composite slurry, the graphene content is adjusted to 57%, and the rest are the same.

[0080] Comparative Example 2 The difference from Example 1 is that the internal cavity of the hydrogen fuel cell stack heat sink core is treated with a traditional anodizing + organic sealing process. The internal cavity of the hydrogen fuel cell stack heat sink core is subjected to sulfuric acid anodizing treatment to generate an oxide film with a thickness of about 10 μm, and then hot water sealing treatment is performed using nickel acetate.

[0081] Performance testing The radiator cores prepared in Examples 1-3 and Comparative Examples 1-2 were respectively connected to a circulating coolant system (ethylene glycol-based coolant, flow rate 3 m / s, temperature 65°C), and the coolant conductivity and Al were periodically tested. 3+ The amount of precipitation. The results are shown below:

[0082] Table 1 Conductivity test results

[0083] Test results show that in the 2000-hour long-term cycling test, the coolant conductivity of Examples 1-3 remained below 3 μS / cm, meeting the stringent requirement of <5 μS / cm for hydrogen fuel cell stacks, and Al 3+ The amount of deposited material is extremely low. Comparative Example 1 showed that its conductivity was close to the critical value after 1000 hours and exceeded the standard after 2000 hours; Comparative Example 2 showed that its conductivity was close to the critical value after 500 hours, and its performance was significantly inferior to that of the present invention.

[0084] In summary, this invention provides a long-term low-conductivity composite treatment method for the inner cavity of a hydrogen fuel cell stack radiator core. A coating is applied to the surface of the radiator core. This coating is formed by coating and curing a slurry. This slurry integrates the atomic-level physical barrier function of graphene with the intelligent chemical capture function of pH-responsive microcapsules, achieving multi-layered protection of "physical barrier as the main component, chemical capture as a supplement, and intelligent response." This method can stably control the coolant conductivity below 5 μS / cm under dynamic operating conditions for thousands of hours.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for long-term low-conductivity composite treatment of the inner cavity of a hydrogen fuel cell stack heat sink core, characterized in that, include: After pretreatment of the surface of the heat sink core of the hydrogen fuel cell stack, a slurry is applied, cured, and then cleaned. The slurry includes pH-responsive sustained-release microcapsules. The pH-responsive sustained-release microcapsule comprises, from the inside out, an ion trapping agent and mesoporous silica grafted with polyacrylic acid.

2. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 1, characterized in that, The ion trapping agent includes either disodium EDTA or zirconium phosphate.

3. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 1, characterized in that, The method for preparing the pH-responsive sustained-release microcapsules includes: S1, amidizing mesoporous silica to obtain product 1; S2. The product 1 is reacted with acrylic acid monomer and catalyst to obtain the mesoporous silica grafted with polyacrylic acid; S3. Mix the ion trapping agent and mesoporous silica grafted with polyacrylic acid to obtain the pH-responsive sustained-release microcapsules.

4. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 3, characterized in that, The mass ratio of the mesoporous silica, acrylic monomer, and ion scavenger is 1:(2~5):(0.1~0.3).

5. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 3, characterized in that, The catalyst comprises a transition metal salt and a nitrogen-containing ligand.

6. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 1, characterized in that, The slurry also includes graphene, mesoporous silica, silane coupling agents, and dispersants.

7. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 6, characterized in that, The slurry, by mass fraction totaling 100%, comprises 1-3% pH-responsive sustained-release microcapsules, 50-60% graphene, 10-15% mesoporous silica, 5-10% silane coupling agent, 0.3-0.5% dispersant, and 20-40% water.

8. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 1, characterized in that, The coating thickness is 1.5~2.5 μm.

9. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 1, characterized in that, The pretreatment includes: a1. Immersing the core of the hydrogen fuel cell stack radiator in an alkaline solution, then washing it with water, drying it, and setting it aside for later use.

10. The method for long-term low-conductivity composite treatment of the core cavity of a hydrogen fuel cell stack heat sink as described in claim 1, characterized in that, The curing process includes holding at 120~140℃ for 40~80 minutes.

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