Catalyst for resisting proton exchange membrane aging and preparation method thereof

Abstract

This application relates to a catalyst for resisting the aging of a proton exchange membrane. The catalyst for resisting the aging of the proton exchange membrane includes: a Pt / C catalyst; an ionomer; a TEMPO-based reagent, and the TEMPO-based reagent is at least one reagent selected from TEMPO or a TEMPO derivative. The catalyst for resisting the aging of the proton exchange membrane provided by this application, by adding a TEMPO-based reagent to the catalyst, when the catalyst is used as a catalytic layer of a proton exchange membrane fuel cell and is in direct contact with the proton exchange membrane, the TEMPO-based reagent therein can effectively combine with hydroxyl radicals, reducing the damage of hydroxyl radicals to the proton exchange membrane.

Description

Technical Field

[0001] This application relates to the field of fuel cells, and particularly to catalysts for proton exchange membrane fuel cells. Background Art

[0002] As a key link in the future popularization of hydrogen energy applications, proton exchange membrane fuel cells have made great progress and development in recent years due to their advantages such as cleanliness and high efficiency. However, their short lifespan severely limits their large-scale application. Therefore, improving the battery lifespan is a necessary condition for enhancing the market competitiveness of proton exchange membrane fuel cells. During the use of the proton exchange membrane, the -COOH groups in its structure can generate hydroxyl radicals due to reactions. The hydroxyl radicals can attack the proton exchange membrane, causing its degradation and aging, which seriously affects the battery lifespan. Therefore, solving the aging problem of the proton exchange membrane has become an important research direction for scientists.

[0003] To reduce the hydroxyl radicals in the proton exchange membrane during use, currently in this field, mainly by adding some metal ions and their oxides (such as MnO2, CeO2, etc.) as radical scavengers. However, due to their poor solubility, these radical scavengers are difficult to be evenly distributed in water, and the metal ions are prone to combine with the sulfonate groups in the proton exchange membrane, causing proton conduction resistance and resulting in a decrease in battery performance. Summary of the Invention

[0004] The embodiments of this application provide a catalyst for resisting the aging of proton exchange membranes and its preparation method to solve the technical problem of the easy aging of proton exchange membranes.

[0005] In a first aspect, the embodiments of this application provide a catalyst for resisting the aging of proton exchange membranes, and the catalyst for resisting the aging of proton exchange membranes includes:

[0006] Pt / C catalyst;

[0007] Ionic polymer;

[0008] TEMPO-based reagent, and the TEMPO-based reagent is at least one reagent of TEMPO or TEMPO derivatives.

[0009] In some embodiments of this application, in the Pt / C catalyst, the mass fraction of Pt is 40% - 70%.

[0010] In some embodiments of this application, the TEMPO-based reagent includes molecules with the following general chemical formula:

[0011]

[0012] Among them, the R group is one of -H, -OMe, -OH, -OCH2CH3.

[0013] In some embodiments of the present application, the ionomer is a perfluorosulfonic acid resin.

[0014] Second, embodiments of the present application provide a method for preparing a catalyst for resisting proton exchange membrane aging. The method for preparing the catalyst for resisting proton exchange membrane aging is used to prepare the catalyst for resisting proton exchange membrane aging according to any one of the embodiments in the first aspect. The method for preparing the catalyst for resisting proton exchange membrane aging includes the following steps:

[0015] Disperse the Pt / C catalyst in a solvent to form a first mixed solution;

[0016] Add the TEMPO-based reagent to the solution of the ionomer to form a second mixed solution;

[0017] Mix the first mixed solution and the second mixed solution to obtain a slurry;

[0018] Coat the slurry onto the proton exchange membrane to form the catalyst for resisting proton exchange membrane aging.

[0019] In some embodiments of the present application, the weight ratio of the ionomer to the carbon support in the Pt / C is 0.5-1:1.

[0020] In some embodiments of the present application, based on the weight percentage of the ionomer, the addition amount of the TEMPO-based reagent is 0.1 wt%-0.5 wt% of the ionomer.

[0021] In some embodiments of the present application, adding the TEMPO-based reagent to the solution of the ionomer includes the following steps:

[0022] Add the TEMPO-based reagent to the solution of the ionomer at a predetermined temperature to obtain a mixed solution;

[0023] Ultrasonically treat the mixed solution and then shear-disperse it to obtain the second mixed solution.

[0024] In some embodiments of the present application, the ultrasonic treatment is probe ultrasonic treatment, and the power of the ultrasonic treatment is 200-300 W; and / or,

[0025] The coating is carried out by ultrasonic spraying, and the ultrasonic spraying is carried out at 70-90 °C.

[0026] In some embodiments of the present application, the predetermined temperature is not higher than 5 °C.

[0027] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0028] The catalyst for resisting the aging of the proton exchange membrane provided by the embodiment of the present application adds TEMPO-based reagents to the catalyst. When the catalyst is used as the catalytic layer of the proton exchange membrane fuel cell, it is in direct contact with the proton exchange membrane. The TEMPO-based reagents therein can effectively combine with hydroxyl radicals, reducing the damage of hydroxyl radicals to the proton exchange membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0030] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a polarization curve diagram of the catalysts obtained in Examples 1-2 and Comparative Examples of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0033] Unless otherwise specifically stated, the terms used herein should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present application belongs. In case of contradiction, this specification prevails.

[0034] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through the market or can be prepared by existing methods.

[0035] The existing proton exchange membranes have the technical problems of being easily attacked by hydroxyl groups and being easily aged.

[0036] The technical solutions provided by the embodiments of the present application to solve the above technical problems have the following general ideas:

[0037] In a first aspect, the embodiment of the present application provides a catalyst for resisting the aging of the proton exchange membrane. The catalyst for resisting the aging of the proton exchange membrane includes:

[0038] Pt / C catalyst;

[0039] Ionic polymer;

[0040] TEMPO-based reagent, where the TEMPO-based reagent is at least one reagent selected from TEMPO or TEMPO derivatives.

[0041] TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) is an N,N-disubstituted N-oxyl radical with an unpaired electron. This nitroxide radical forms a resonance structure through the movement of the unpaired electron between nitrogen and oxygen, and thus can exist stably in the radical form. TEMPO and its derivatives have the function of capturing free radicals and can effectively combine with hydroxyl radicals to reduce the damage of hydroxyl radicals to the proton exchange membrane.

[0042] In this application, by adding a TEMPO-based reagent to the catalyst, when this catalyst is used as the catalytic layer of a proton exchange membrane fuel cell and is in direct contact with the proton exchange membrane, the TEMPO-based reagent in it can effectively combine with hydroxyl radicals to reduce the damage of hydroxyl radicals to the proton exchange membrane.

[0043] In some embodiments of this application, in the Pt / C catalyst, the mass fraction of Pt is 40% - 70%.

[0044] Controlling the mass ratio of Pt / C to be 40% - 70% can increase the specific surface area of platinum metal in the system, improve the catalytic performance, and reduce the amount of platinum metal used. If this ratio is too large, it is easy to cause the agglomeration of platinum atoms themselves, and if it is too small, the platinum content is too low to achieve the desired catalytic performance.

[0045] In some embodiments of this application, the TEMPO-based reagent includes molecules with the following general chemical formula:

[0046]

[0047] where the R group is one of -H, -OMe, -OH, -OCH2CH3.

[0048] Molecules with the above general chemical formula include TEMPO and its common derivatives, and have good binding ability to hydroxyl radicals. The mechanism is as follows:

[0049]

[0050] In some embodiments of this application, the ionic polymer is a perfluorosulfonic acid resin.

[0051] The perfluorosulfonic acid resin can play a good binding role, which is beneficial to the shaping of the catalyst; the perfluorosulfonic acid resin has a strong proton conduction effect, and at the same time has a good binding force for TEMPO and its derivatives, which helps the uniform distribution of TEMPO and its derivatives and prevents their loss during battery use.

[0052] In a second aspect, the embodiments of the present application provide a preparation method of a catalyst for resisting proton exchange membrane aging. The preparation method of the catalyst for resisting proton exchange membrane aging is used to prepare the catalyst for resisting proton exchange membrane aging according to any one of the embodiments in the first aspect. The preparation method of the catalyst for resisting proton exchange membrane aging includes the following steps:

[0053] S1: Disperse the Pt / C catalyst in a solvent to form a first mixed solution;

[0054] S2: Add the TEMPO-based reagent to the solution of the ionomer to form a second mixed solution;

[0055] S3: Mix the first mixed solution and the second mixed solution to obtain a slurry;

[0056] S4: Coat the slurry on the proton exchange membrane to form the catalyst for resisting proton exchange membrane aging.

[0057] Coating the slurry on the proton exchange membrane to prepare the catalyst is a conventional operation in the art. The catalyst generally exists in the form of the catalytic layer of a proton exchange membrane fuel cell.

[0058] In some embodiments of the present application, the weight ratio of the ionomer to the carbon support in the Pt / C is 0.5-1:1.

[0059] The ionomer, as a binder, is beneficial to the dispersion of the platinum-carbon catalyst in the system, and at the same time has a good binding force for TEMPO or its derivatives, avoiding loss during use. The beneficial effect of controlling the mass ratio of the ionomer to the carbon support to be 0.5-1:1 is that if the mass ratio value is too large, it will increase the mass transfer resistance of the catalytic layer and may wrap the platinum atoms, and if it is too small, it cannot play a good binding role.

[0060] In some embodiments of the present application, based on the weight percentage of the ionomer, the addition amount of the TEMPO-based reagent is 0.1 wt%-0.5 wt% of the ionomer.

[0061] The reaction efficiency of the TEMPO-based reagent with hydroxyl radicals is extremely high. The TEMPO-based reagent in the above-mentioned addition amount is sufficient to achieve a good elimination effect on hydroxyl radicals. At the same time, although hydroxyl radicals are highly destructive to proton exchange membranes, the amount of hydroxyl radicals generated is small. The TEMPO-based reagent in the above-mentioned addition amount is sufficient to provide long-term protection for proton exchange membranes. The addition amount of the TEMPO-based reagent should not be too much, otherwise it may lead to a decline in catalyst performance, high costs, etc.

[0062] In some embodiments of the present application, adding the TEMPO-based reagent to the solution of the ion polymer includes the following steps:

[0063] S21: Add the TEMPO-based reagent to the solution of the ion polymer at a predetermined temperature to obtain a mixed solution;

[0064] S22: Ultrasonically treat the mixed solution and then shear and disperse it to obtain the second mixed solution.

[0065] During shear dispersion, molecular forces are easily formed between TEMPO and its derivatives and the main chain skeleton of the ion polymer, which is conducive to the dispersion of TEMPO in the solution system.

[0066] In some embodiments of the present application, the ultrasonic treatment is probe ultrasonic treatment, and the power of the ultrasonic treatment is 200 - 300 W; and / or,

[0067] The coating is carried out by ultrasonic spraying, and the ultrasonic spraying is carried out at 70 - 90 °C.

[0068] By controlling the probe ultrasonic power, the forces between TEMPO and its derivatives and the ion polymer can be temporarily broken, which is conducive to the uniform dispersion of TEMPO and its derivatives in the solution system, and further conducive to the re-formation of more uniform and stable forces with the ion polymer during the subsequent high-speed shear process.

[0069] Ultrasonic spraying can prepare a catalytic layer with a more regular and porous structure.

[0070] In some embodiments of the present application, the predetermined temperature is not higher than 5 °C.

[0071] Under low-temperature conditions, it is conducive to the formation of molecular forces between TEMPO and its derivatives and the main chain skeleton of the ion polymer during shear dispersion.

[0072] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions indicated in the following embodiments, they are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0073] Example 1

[0074] This example provides a method for preparing a catalyst for resisting proton exchange membrane aging, including the following steps:

[0075] Step (1): Weigh 1.03 g of TKK 47% Pt / C, add water to moisten the catalyst, and add 55 g of isopropanol and mechanically stir and mix.

[0076] Step (2): Add 6.3 mg of TEMPO to 6.3 g of Nafion (5.2%) solution from DuPont Company under an ice-water bath, probe-ultrasound at 250 W for 10 minutes, and then high-speed shear for 20 minutes to obtain a mixed solution.

[0077] Step (3): Add the mixed solution obtained in step (2) to the mixed solution obtained in step (1) and perform high-speed shear dispersion for 10 minutes to obtain a catalyst slurry.

[0078] Step (4): Add the catalyst slurry prepared in step (3) to a spray coating cylinder, take a 72×72 mm proton exchange membrane, and perform spraying on a heating table at 70°C by the spraying method to obtain a catalytic layer, that is, the catalyst for resisting proton exchange membrane aging.

[0079] Example 2

[0080] This example provides a method for preparing a catalyst for resisting proton exchange membrane aging, including the following steps:

[0081] Step (1): Weigh 1.03 g of TKK 47% Pt / C, add water to moisten the catalyst, and add 55 g of isopropanol and mechanically stir and mix.

[0082] Step (2): Add 31.5 mg of TEMPO reagent to 8.4 g of Nafion (5.2%) solution from DuPont Company under an ice-water bath, probe-ultrasound at 250 W for 10 minutes, and then high-speed shear for 20 minutes to obtain a mixed solution.

[0083] Step (3): Add the mixed solution obtained in step (2) to the mixed solution obtained in step (1) and perform high-speed shear dispersion for 10 minutes to obtain a catalyst slurry.

[0084] Step (4): Add the catalyst slurry prepared in step (3) into the spray coating cylinder. Take a 72×72 mm proton exchange membrane and perform spraying on a heating table at 80 °C using the spraying method to obtain the catalytic layer, namely the catalyst for resisting the aging of the proton exchange membrane.

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is only that:

[0087] Step (2) is not carried out. That is, TEMPO is not added.

[0088] Related experiments and effect data:

[0089] The catalytic layers of the proton exchange membrane fuel cells in Examples 1-2 and Comparative Example 1 were respectively made into corresponding membrane electrodes with a size of 25 cm 2 . After the battery was activated, its polarization curve and hydrogen permeation current density were measured. After maintaining 100% humidity, no back pressure and operating at open circuit voltage for 500 hours, the polarization curve and hydrogen permeation current density were measured again for comparison. Among them, the polarization curve is shown in Figure 1 , and the initial open circuit voltage and the open circuit voltage after 500 h are shown in the following table.

[0090]

[0091]

[0092] As can be seen from the above table, in Examples 1 and 2 with TEMPO added, after 500 hours of open circuit operation, the open circuit voltage hardly changed and the hydrogen permeation current density remained unchanged. On the contrary, in Comparative Example 1, the open circuit voltage and hydrogen permeation current density were normal initially, but after operating for 500 hours, the open circuit voltage decreased significantly from 0.950 V to 0.862 V, and the hydrogen permeation current density increased significantly, indicating that the proton exchange membrane was significantly damaged.

[0093] From Figure 1 , it can be seen that the performance of Examples 1 and 2 hardly decayed before and after operating for 500 hours. In Comparative Example 1, due to the aging of the proton exchange membrane, the performance significantly declined and the battery almost failed.

[0094] Various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0095] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing direction in the drawings. Additionally, in the description of the present application specification, the terms "comprising", "including", etc. mean "including but not limited to". Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also other elements not explicitly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the said element. In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, or B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that these three associated objects can exist alone for any one of them, or any at least two of them exist simultaneously. For example, for A, and / or B, and / or C, it can represent that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one item (individual) below" or similar expressions refer to any combination of these items, including any combination of single item (individual) or plural items (individuals). For example, "at least one item (individual) among a, b, or c", or, "at least one item (individual) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0096] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A preparation method of a catalyst for resisting the aging of a proton exchange membrane, characterized in that, The preparation method comprises the following steps: Disperse the Pt / C catalyst in a solvent to form a first mixed solution; Add a TEMPO-based reagent to the solution of the ionic polymer at an ice-water bath temperature to obtain a mixed solution; Subject the mixed solution to ultrasonic treatment and then shear dispersion to obtain a second mixed solution; Mix the first mixed solution with the second mixed solution to obtain a slurry; Coat the slurry onto a proton exchange membrane to form the catalyst for resisting the aging of the proton exchange membrane; Based on the weight percentage of the ionic polymer, the addition amount of the TEMPO-based reagent is 0.1wt%-0.5wt% of the ionic polymer; The coating is carried out by ultrasonic spraying, and the ultrasonic spraying is carried out at 70-90°C; The TEMPO-based reagent comprises molecules having the following general chemical formula: wherein the R group is one of -H, -OMe, -OH, -OCH2CH3; The ultrasonic treatment is probe ultrasonic treatment, and the power of the ultrasonic treatment is 200-300W.

2. The preparation method of the catalyst for resisting the aging of the proton exchange membrane according to claim 1, wherein The weight ratio of the ionic polymer to the carbon support in the Pt / C is 0.5-1:

1.

3. The preparation method of the catalyst for resisting the aging of the proton exchange membrane according to claim 1, wherein In the Pt / C catalyst, the mass fraction of Pt is 40%-70%.

4. The preparation method of the catalyst for resisting the aging of the proton exchange membrane according to claim 1, wherein The ionic polymer is a perfluorosulfonic acid resin.

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