Method for testing the antioxidation stability of high-temperature-resistant electrolyte membrane and device thereof

Abstract

The application discloses a high-temperature-resistant electrolyte membrane oxidation stability test method and device thereof. The high-temperature-resistant electrolyte membrane oxidation stability test method comprises the following steps: 1) obtaining a phosphoric acid-doped high-temperature-resistant electrolyte membrane; 2) placing the phosphoric acid-doped high-temperature-resistant electrolyte membrane in a mixed solution containing phosphoric acid and Fe 2+ , and heating; 3) introducing a carrier gas carrying H2O2 into the mixed solution, collecting tail gas, and analyzing the stability of the high-temperature-resistant electrolyte membrane through the tail gas. The method is a non-in-situ test method, can truly simulate the acidic environment in which the high-temperature-resistant electrolyte membrane is located, can indirectly reflect the internal changes of the high-temperature-resistant electrolyte membrane, can evaluate the influence of the acid content on the oxidation stability of the high-temperature-resistant electrolyte membrane, and has guiding significance for membrane electrode preparation.

Description

Technical Field

[0001] This application relates to a method and apparatus for testing the antioxidant stability of high-temperature electrolyte membranes, belonging to the field of high-temperature electrolyte membrane technology. Background Technology

[0002] The internal environment of a fuel cell is harsh, encompassing both the electrical, thermal, water, and impurity ion environments that lead to chemical degradation of the electrolyte membrane, and environmental factors affecting mechanical stability such as cold / thermal cycling, wet-dry cycling, and stress changes caused by pressure differentials. These factors collectively contribute to electrolyte membrane failure. Electrolyte membrane failure signifies the end of the fuel cell's lifespan; therefore, predicting electrolyte membrane lifespan is crucial for fuel cell design. Electrolyte membrane lifespan is typically obtained through in-situ testing, where the fuel cell is operated under its own operating conditions to test its performance and lifespan. While this method provides the most accurate reflection of electrolyte membrane lifespan, it is time-consuming, costly, and, most importantly, its lifespan assessment is influenced by multiple failure modes, potentially originating from the membrane or catalyst and interfering with each other, hindering result analysis and offering limited guidance for electrolyte membrane molecular or structural design. To gain a deeper understanding of electrolyte membranes and develop more competitive membrane products, the analysis of their physical and chemical stability is essential.

[0003] The membrane was examined under strong oxidizing reagents (Fenton's reagent: containing Fe). 2+ The antioxidant stability at 4 ppm (3% H2O2) is the most commonly used method for evaluating the chemical stability of membranes. The specific procedure is as follows: immerse the membrane in a container containing Fenton's reagent, heat it in a 60°C water bath, and record the time required for the membrane to rupture from immersion. During this period, the Fenton's reagent needs to be replaced periodically to ensure a consistent oxidant concentration. This method is mainly used to determine the antioxidant stability of perfluorosulfonic acid proton exchange membranes, some fluorosulfonic acid proton exchange membranes, hydrocarbon proton exchange membranes, and other sulfonic acid proton exchange membranes. Fenton's reagent is also frequently used to determine the antioxidant stability of polybenzimidazole membranes, but this method has significant biases in predicting their chemical stability as high-temperature electrolyte membranes. Phosphoric acid, as a proton carrier in high-temperature electrolyte membranes, is present in extremely high concentrations. Its presence mitigates free radical attack on polybenzimidazole membranes; therefore, its content in the electrolyte membrane directly affects the antioxidant stability. Therefore, existing Fenton's reagents are not suitable for evaluating the stability of high-temperature electrolyte membranes. Summary of the Invention

[0004] This invention addresses the lack of effective methods for evaluating the antioxidant stability of high-temperature resistant electrolyte membranes by designing a testing device for the antioxidant stability of high-temperature electrolyte membranes and using this device to conduct research on the antioxidant stability of high-temperature resistant electrolyte membranes. Carrier gas is passed through a gas washing bottle containing an aqueous hydrogen peroxide solution, then carries hydrogen peroxide and water into the lower part of the oxidation tank. It is then passed through a waterproof and breathable membrane into the upper part of the oxidation tank, where it is used to immerse the high-temperature resistant electrolyte membrane in a solution (composed of concentrated phosphoric acid solution and a certain concentration of ferrous sulfate). Finally, it is passed into an aqueous solution containing a certain concentration of potassium hydroxide for tail gas absorption, and then discharged from the entire device.

[0005] According to a first aspect of this application, a method for testing the antioxidant stability of a high-temperature resistant electrolyte membrane is provided. This method is a non-in-situ antioxidant stability testing method for high-temperature fuel cell electrolyte membranes.

[0006] A method for testing the antioxidant stability of a high-temperature resistant electrolyte membrane includes the following steps:

[0007] 1) Obtain a high-temperature resistant electrolyte membrane doped with phosphoric acid;

[0008] 2) Place the phosphoric acid-doped high-temperature resistant electrolyte membrane in a container containing phosphoric acid and Fe. 2+ The mixed solution is heated;

[0009] 3) Pass the carrier gas carrying H2O2 into the above mixed solution, collect the tail gas, and analyze the stability of the high-temperature resistant electrolyte membrane through the tail gas.

[0010] Optionally, step 1) includes: immersing a high-temperature resistant electrolyte membrane in a phosphoric acid solution to obtain the phosphoric acid-doped high-temperature resistant electrolyte membrane.

[0011] Optionally, in step 1), the phosphoric acid doping content of the phosphoric acid-doped high-temperature resistant electrolyte membrane is 300-1000 wt%; wherein, the mass of the undoped phosphoric acid base membrane is used as the calculation basis.

[0012] Optionally, the phosphoric acid doping content of the phosphoric acid-doped high-temperature resistant electrolyte membrane is 415–510 wt%.

[0013] Optionally, the phosphoric acid doping content of the phosphoric acid-doped high-temperature electrolyte membrane is independently selected from any value or a range between 300wt%, 400wt%, 500wt%, 600wt%, 700wt%, 800wt%, 900wt%, and 1000wt%.

[0014] Optionally, the concentration of the phosphoric acid solution is 50–98 wt%.

[0015] Optionally, the concentration of the phosphoric acid solution is independently selected from any value or a range between 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%, and 98wt%.

[0016] Optionally, the impregnation temperature is 20–120°C, and the time is 2–24 hours.

[0017] Optionally, the impregnation temperature is independently selected from any value or a range between 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C.

[0018] Optionally, the immersion time is independently selected from any value of 2h, 5h, 8h, 10h, 15h, 18h, 20h, 22h, 24h or a range between any two.

[0019] In this application, the high-temperature resistant electrolyte membrane is pre-doped and ultimately placed in a phosphoric acid environment, which can maintain dynamic equilibrium during the oxidation process and realistically simulate the acidic environment in which the high-temperature resistant electrolyte membrane is located.

[0020] Optionally, in step 2), in the mixed solution, the Fe 2+ The concentration ranges from 0.1 to 100 ppm;

[0021] The concentration of the phosphoric acid is 50–98 wt%.

[0022] Optionally, the Fe 2+ The concentration is independently selected from any value or a range between any two of 0.1ppm, 0.5ppm, 1ppm, 2ppm, 4ppm, 6ppm, 8ppm, 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm, and 100ppm.

[0023] Specifically, Fe 2+ It comes from ferrous sulfate.

[0024] Optionally, in step 2), the temperature after heating is 70–120°C.

[0025] Optionally, the heated temperature is independently selected from any value of 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or a range between any two.

[0026] Optionally, in step 3), the flow rate of the carrier gas is 100–500 ml / min.

[0027] Optionally, the flow rate of the carrier gas is independently selected from any value or a range between 100 ml / min, 150 ml / min, 200 ml / min, 250 ml / min, 300 ml / min, 350 ml / min, 400 ml / min, 450 ml / min, and 500 ml / min.

[0028] Optionally, the carrier gas is selected from at least one of nitrogen and argon.

[0029] Optionally, the high-temperature resistant electrolyte membrane is selected from at least one of polybenzimidazole high-temperature resistant electrolyte membrane, nitrogen-containing heterocyclic phosphoric acid doped high-temperature resistant electrolyte membrane, quaternary ammonium salt phosphoric acid doped high-temperature resistant electrolyte membrane, and tertiary ammonium phosphoric acid doped high-temperature resistant electrolyte membrane.

[0030] Optionally, the method for collecting the exhaust gas is to use alkaline solution absorption.

[0031] Optionally, the alkaline solution is a NaOH solution and / or a KOH solution.

[0032] In this application, because it is a non-in-situ testing method, the oxidant hydrogen peroxide is stably introduced from the outside, ensuring the stability of the reaction. Furthermore, the carrier gas can carry out the small molecule volatiles obtained during the reaction, making it easy to analyze these substances and thus indirectly reflecting the internal changes of the high-temperature resistant electrolyte membrane.

[0033] According to a second aspect of this application, an apparatus for testing the antioxidant stability of a high-temperature resistant electrolyte membrane is provided.

[0034] An apparatus for testing the antioxidant stability of a high-temperature resistant electrolyte membrane, the apparatus comprising: a gas washing unit, an oxidation tank, and an absorption unit;

[0035] The oxidation tank includes an upper part and a lower part.

[0036] The lower part of the oxidation tank is equipped with a waterproof and breathable membrane;

[0037] The lower part of the oxidation tank is connected to the gas scrubbing unit;

[0038] The upper part of the oxidation tank is connected to the absorption unit.

[0039] Optionally, an inlet valve is provided at the top of the oxidation tank.

[0040] Optionally, a constant temperature unit is provided outside the oxidation tank.

[0041] Optionally, the gas scrubbing unit contains a hydrogen peroxide solution. The carrier gas passes through the gas scrubbing unit, carrying hydrogen peroxide and water vapor into the lower part of the oxidation tank, and then through a waterproof and breathable membrane into the phosphoric acid solution in the upper part of the oxidation tank. The tail gas is absorbed by the alkaline solution in the absorption unit.

[0042] Specifically, the gas washing unit is a gas washing bottle.

[0043] Specifically, the absorption unit is an absorption bottle.

[0044] The beneficial effects that this application can produce include:

[0045] The method for testing the antioxidant stability of high-temperature resistant electrolyte membranes provided in this application can be directly used to evaluate the antioxidant stability of high-temperature resistant electrolyte membranes, rather than indirectly through the analysis of the high-temperature resistant base membrane (a base membrane without phosphoric acid). By pre-doping the high-temperature resistant electrolyte membrane and placing it in a phosphoric acid environment, the acidic environment of the high-temperature resistant electrolyte membrane can be realistically simulated. Because it is a non-in-situ testing method, the oxidant hydrogen peroxide is stably introduced externally, ensuring the stability of the reaction. Furthermore, the carrier gas can carry away the small molecule volatiles obtained during the reaction, making it easy to analyze these substances and indirectly reflecting the internal changes of the high-temperature resistant electrolyte membrane. This method can simulate the free radical generation mechanism of batteries (hydrogen peroxide forming free radicals under the catalysis of metal ions), which is similar to the actual decay principle. It can evaluate the influence of acid content on the antioxidant stability of electrolytically fabricated membranes and has guiding significance for membrane electrode preparation. Attached Figure Description

[0046] Figure 1 This is a device for analyzing the antioxidant stability of high-temperature resistant electrolyte membranes.

[0047] Figure 2 This relates to the mechanism of free radical generation in fuel cells.

[0048] Figure 1 In the middle, 1, the lower part of the gas washing bottle and oxidation tank.

[0049] 4. Upper part of oxidation tank, 5. Inlet valve, 6. Absorption bottle

[0050] Figure 2 In this context, M represents metals such as Fe, Cu, Al, Zn, and Pt. Detailed Implementation

[0051] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0052] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0053] The polybenzimidazole was prepared by self-made cross-linked polybenzimidazole membrane, and the preparation method is as follows:

[0054] 0.06 mol of 3,4-dimethylphenyl-p-benzoquinone, 0.06 mol of 4,4-dihydroxydiphenyl sulfone, 0.12 mol of 4,4'-difluorobenzophenone, and 0.15 mol of potassium carbonate were mixed and reacted under a nitrogen atmosphere with 100 ml of sulfolane as solvent and 30 ml of toluene as dehydrating agent. The mixture was heated to 140 °C and reacted for 3 h. The toluene was then distilled off, and the temperature was raised to 180 °C and reacted for another 4 h. After the reaction, the mixed solution was poured into deionized water to obtain a white, strip-shaped polymer. The polymer strip was crushed into powder using a tissue grinder, washed repeatedly with acetone to remove the solvent, and repeatedly washed with distilled water to remove salts. The powder was then dried in an oven at 60 °C for 24 h to obtain a pure white powdery solid, namely, a dimethylphenyl polyaryl ether (dmPA, structure shown below), 46.3 g, with a yield of 94%.

[0055]

[0056] 8.20 g of the obtained DMPA, 4.45 g (0.025 mol) of N-bromosuccinimide (NBS), 0.05 g of benzoyl peroxide (BPO), and 100 ml of carbon tetrachloride were weighed and added sequentially to a 250 ml three-necked flask equipped with an electric stirrer, a gas delivery tube, and a reflux device. The mixture was reacted at 70 °C for 2 h under a nitrogen atmosphere. After the reaction was completed, the mixed solution was poured into an aqueous solution of 50% ethanol to obtain an orange-yellow precipitate. The precipitate was then pulverized into fine particles using a tissue homogenizer, filtered through a Buchner funnel, and the resulting solid powder was boiled in acetone for one hour, followed by hot filtration. This process was repeated 5 times. The mixture was then boiled in water for half an hour, followed by hot filtration. This process was repeated 5 times. Finally, the mixture was dried in an oven at 120 °C to obtain 9.14 g of benzyl-containing dimethylphenyl polyarylene ether—BrdmPA, with an average of 0.85 moles of bromine per mole of benzyl position.

[0057] Take 0.5g of BrdmPA and add 24.5g of N,N-dimethylacetamide. Stir at room temperature for 0.5h to form a BrdmPA solution with a solid content of 2wt%. Take 20g of poly(2,2'-(m-phenyl)-5,5'-bibenzimidazole)(mPBI) and add 180g of N,N-dimethylacetamide. Stir at room temperature for 24h to form an mPBI solution with a solid content of 10wt%. Weigh 30g of mPBI solution and add 7.5g of BrdmPA solution while stirring. After stirring at room temperature for 0.5h, pour the mixture onto a glass plate for casting and dry it thoroughly in an oven at 80℃. Continue heating at 150℃ for 5h. Finally, remove it from the glass plate to obtain a benzyl-containing bromine-containing side-chain dimethylphenyl polyaryl ether crosslinking agent modified polybenzimidazole film (BrdmPA-c-PBI).

[0058] Example 1.

[0059] like Figure 1 As shown, the lower and upper parts of the oxidation tank are sealed and assembled together using flanges and 20μm thick porous polytetrafluoroethylene. A 30wt% hydrogen peroxide aqueous solution is injected into the gas washing bottle, and a 1M KOH solution is injected into the absorption bottle. Then, all inlet valves are closed, and stainless steel pipes are used to connect the gas washing bottle to the lower part of the oxidation tank, and the upper part of the oxidation tank to the absorption bottle.

[0060] Two self-made polybenzimidazole covalently crosslinked membranes (4×4 cm) were weighed (0.171 g) and immersed in analytical grade concentrated phosphoric acid (85 wt%) for 6 h at 80 °C to obtain a phosphoric acid-doped polybenzimidazole high-temperature resistant electrolyte membrane (PA / PBI) with a phosphoric acid doping content of 415 wt%. The analytical grade phosphoric acid (0.880 g) was then added to the upper part of the oxidation tank along with the PA / PBI membrane. Ferrous sulfate heptahydrate was added to the solution to increase the Fe content. 2+ The concentration reached 4 ppm. After closing the inlet valve of the oxidation tank, nitrogen gas was introduced into the washing bottle as a carrier gas at a flow rate of 100 ml / min. The nitrogen gas carried the hydrogen peroxide and water vapor in the washing bottle into the lower part of the oxidation tank, and further into the phosphoric acid solution through the waterproof and breathable membrane. Throughout the aeration process, the oxidation tank was kept at a specially designed constant temperature chamber at 80°C. The time required from aeration to electrolyte membrane rupture was observed to be 310 h.

[0061] Example 2.

[0062] Everything else is the same as in Example 1, except that Fe 2+ The concentration was increased to 8 ppm. The time required from ventilation to electrolyte membrane rupture was observed to be 126 h.

[0063] Example 3.

[0064] The procedure was the same as in Example 2, except that the phosphoric acid used was high-purity phosphoric acid (98%) with a phosphoric acid doping content of 510 wt%. The time required from aeration to electrolyte membrane rupture was observed to be 26 hours.

[0065] Example 4.

[0066] Everything else is the same as in Example 1, except that the phosphoric acid solution does not contain Fe. 2+ The observation showed that the time required from ventilation to electrolyte membrane rupture was 666 hours.

[0067] Implement item 5.

[0068] The procedure was the same as in Example 1, except that the temperature of the analytical grade phosphoric acid was lowered to room temperature, and the experiment was conducted at room temperature (25°C). The time required from aeration to electrolyte membrane rupture was observed to be 457 hours.

[0069] Comparative Example 1.

[0070] Prepare Fenton's reagent according to the following proportions: containing Fe 2+ 4 ppm, H₂O₂ 3 wt%. Fenton's reagent was poured into a sealed PP container, and a 4×4 cm PBI pure membrane was immersed in the solution and heated in an 80℃ oven. The time required from the start to the rupture of the electrolyte membrane was observed to be 220 h.

[0071] The comparative examples revealed that many factors affect the chemical stability of high-temperature resistant electrolyte membranes, including the phosphoric acid doping content, the ambient temperature of the electrolyte membrane, and the Fe content in the phosphoric acid solution. 2+ Therefore, in order to examine the true durability of the electrolyte membrane in the working environment of a fuel cell, the method and apparatus involved in this patent can realistically simulate the acidic environment in which the high-temperature resistant electrolyte membrane is located, and compared with the comparative example, can more realistically reflect the characteristics of the electrolyte membrane.

[0072] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for testing the antioxidant stability of a high-temperature resistant electrolyte membrane, characterized in that, Includes the following steps: 1) Obtain a phosphoric acid-doped high-temperature resistant electrolyte membrane; wherein the phosphoric acid doping content of the phosphoric acid-doped high-temperature resistant electrolyte membrane is 300~1000wt%; 2) Place the phosphoric acid-doped high-temperature resistant electrolyte membrane in a container containing phosphoric acid and Fe. 2+ A mixed solution, heated; the concentration of the phosphoric acid is 50~98wt%; 3) Pass the carrier gas carrying H2O2 into the above mixed solution, collect the tail gas, and analyze the stability of the high-temperature resistant electrolyte membrane through the tail gas; the flow rate of the carrier gas is 100~500 ml / min.

2. The test method according to claim 1, characterized in that, Step 1) includes: immersing a high-temperature resistant electrolyte membrane in a phosphoric acid solution to obtain the phosphoric acid-doped high-temperature resistant electrolyte membrane.

3. The test method according to claim 1, characterized in that, In step 1), the phosphoric acid doping content of the phosphoric acid-doped high-temperature resistant electrolyte membrane is calculated based on the mass of the undoped phosphoric acid base membrane.

4. The test method according to claim 2, characterized in that, The impregnation temperature is 20~120℃, and the time is 2~24h.

5. The test method according to claim 1, characterized in that, In step 2), in the mixed solution, the Fe 2+ The concentration ranges from 0.1 to 100 ppm.

6. The test method according to claim 1, characterized in that, In step 2), the temperature after heating is 70~120℃.

7. The test method according to claim 1, characterized in that, In step 3), the carrier gas is selected from at least one of nitrogen and argon.

8. The test method according to claim 1, characterized in that, The high-temperature resistant electrolyte membrane is selected from at least one of the following: polybenzimidazole high-temperature resistant electrolyte membrane, nitrogen-containing heterocyclic phosphoric acid doped high-temperature resistant electrolyte membrane, quaternary ammonium salt phosphoric acid doped high-temperature resistant electrolyte membrane, and tertiary ammonium phosphoric acid doped high-temperature resistant electrolyte membrane.

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