阅读说明：本技术 长寿命全氟质子膜及其制备方法 (Long-life perfluorinated proton membrane and preparation method thereof ) 是由 马晓娟 邹业成 张永明 王丽 王振华 张恒 于 2020-11-30 设计创作，主要内容包括：本发明涉及一种长寿命全氟质子膜及其制备方法,属于离子交换膜技术领域。本发明所述的长寿命全氟质子膜,由全氟离子交换树脂和添加剂组成,所述添加剂由添加剂A和添加剂B组成；其中添加剂A为由金属和配体形成的金属络合物,其结构为Mx(L)y；其中全氟磺酸树脂的质量占比为97wt％-99.98wt％,添加剂含量为0.02wt％-3wt％；所制备的质子膜厚度为5-50μm。本发明所述的长寿命全氟质子膜,不仅具有较高的自由基氧化耐受性,而且具有较长的使用寿命；本发明同时提供了简单易行的制备方法。(The invention relates to a long-life perfluorinated proton membrane and a preparation method thereof, belonging to the technical field of ion exchange membranes. The long-life perfluorinated proton membrane consists of perfluorinated ion exchange resin and an additive, wherein the additive consists of an additive A and an additive B; wherein the additive A is a metal complex formed by a metal and a ligand, and has a structure of Mx (L) y; wherein the mass ratio of the perfluorinated sulfonic acid resin is 97-99.98 wt%, and the additive content is 0.02-3 wt%; the thickness of the prepared proton membrane is 5-50 μm. The long-life perfluorinated proton membrane has high free radical oxidation tolerance and long service life; the invention also provides a simple and feasible preparation method.)

1. The long-life perfluoro proton membrane consists of perfluoro ion exchange resin and additive, and is characterized in that: the additive consists of an additive A and an additive B; wherein the additive A is a metal complex formed by a metal and a ligand, and has a structure of Mx (L) y; wherein the metal in the additive a is selected from a metal, a metal oxide, a metal salt, or a combination thereof; the structure of the ligand in the additive A is one or more of the following structural formulas:

wherein R is₁，R₂，R₃，R₄Are respectively H, OH, CH₃(CH₂)_nO，CH₃(CH₂)_n，NH₂，CH₂OH，C₆H₅，CF₃(CF₂)_n，CF₃(CF₂)_nO, COOH, wherein n is an integer of 0-10;

the structure of the additive B is one or more of the following structural formulas:

wherein R is₁，R₂，R₃，R₄Are respectively H, OH, CH₃(CH₂)_nO，CH₃(CH₂)_n，NH₂，CH₂OH，C₆H₅，CF₃(CF₂)_n，CF₃(CF₂)_nO, wherein n is an integer of 0 to 10.

2. The long life perfluorinated proton membrane of claim 1 wherein: the metal in the additive A is metal element Mn, Co, Rh, Cu, Ni, Ir, Ag, Ti, Ce, Ru, Cr, Zr, Fe, V, Zn, La, Pt or Pd, or metal compound Pt (NH)₃)₄(NO₃)₂、PtCl₄、WO₃、CeF₃、SiO₂、CeO₂、CePO₄、Ce(NO₃)₃·6H₂O、Ce(SO₄)₂、Ce(OH)₄、(NH₄)₂Ce(NO₃)₆、Ce₂(CO₃)₃·xH₂O、Ce(CH₃COO)₃·xH₂O、CrPO₄、AlPO₄、MnO、MnO₂、Mn₂O₃、MnSO₄、MnCl₂、Mn(NO₃)₂、Mn(CH₃COO)₂·4H₂O、ZnO、ZnCl₂Or Zn (NO)₃)₂One or more of (a).

3. The long life perfluorinated proton membrane of claim 1 wherein: the molar ratio of the metal M to the ligand L in the additive A is 1:1-1: 5.

4. The long life perfluorinated proton membrane of claim 1 wherein: the content of the perfluorinated sulfonic acid resin is 97-99.98 wt%, and the content of the additive is 0.02-3 wt%.

5. The long life perfluorinated proton membrane of claim 4 wherein: the additive A is added in an amount of 0.01-2 wt%; the addition amount of the additive B is 0.01-1 wt%.

6. The long life perfluorinated proton membrane of claim 1 wherein: the perfluorinated ion exchange resin is one or more of long-chain branched perfluorosulfonic acid resin or short-chain branched perfluorosulfonic acid resin.

7. The long life perfluorinated proton membrane of claim 1 wherein: the number average molecular weight of the perfluorinated ion exchange resin is 15-70 ten thousand, and the exchange capacity is 0.85-1.6 mmol/g.

8. The long life perfluorinated proton membrane of claim 7 wherein: the number average molecular weight of the perfluorinated ion exchange resin is 20-60 ten thousand, and the exchange capacity is 0.9-1.4 mmol/g.

9. A method for producing a long-life perfluoroproton membrane according to any one of claims 1 to 8, characterized by comprising the steps of:

(1) adding perfluorinated ion exchange resin and an additive into a solvent, and performing ultrasonic or mechanical stirring to obtain a dispersion liquid;

(2) and (2) performing solution casting, solution casting and screen printing on the dispersion liquid obtained in the step (1), forming a film by using a blade coating, spraying or dipping mode, and heating to obtain the long-life perfluorinated proton membrane.

10. The method for producing a long-life perfluoroproton membrane according to claim 9, wherein: the thickness of the prepared long-life perfluorinated proton membrane is 5-50 mu m.

Technical Field

The invention relates to a long-life perfluorinated proton membrane and a preparation method thereof, belonging to the technical field of ion exchange membranes.

Background

Proton Exchange Membrane Fuel Cells (PEMFCs), which convert reactants, i.e., a fuel (e.g., hydrogen) and an oxidant (e.g., oxygen or air), to generate electric energy, are considered to be the first clean and efficient power generation technology in the 21 st century. Proton exchange membranes are a key material of PEMFCs.

The polymer electrolyte membrane is used as a separator to prevent mixing of reactive gases and as an electrolyte to transport protons from an anode to a cathode. During operation of the fuel cell, a small amount of oxygen will always permeate through the membrane from the cathode to the anode and react with the hydrogen attached to the platinum-carbon catalyst to form hydrogen peroxide. The hydrogen peroxide diffuses into the membrane and reacts with trace metal ion impurities in the membrane, such as iron ions, which have a Fenton catalytic effect, and copper ions catalyze the decomposition of the hydrogen peroxide to generate hydroxyl radicals (. OH) or peroxy radicals (. OOH) with strong oxidizing property.

In order to improve the durability of the polymer electrolyte membrane, the membranes currently used are mostly perfluorinated ion exchange membranes. But because an unstable carboxyl (-COOH) group is inevitably introduced during the synthesis of the perfluorinated ion exchange resin. The hydroxyl groups (. OH) or peroxy groups (. OOH) thus generated attack weak groups (such as carboxylic acid groups) on the ionomer molecular chain.

The hydroxyl groups attack unstable end groups of the polymer, leading to chain scission, and/or may also attack SO under dry conditions₃ ^-The groups thereby break the polymer chains. Both attacks degrade the membrane and eventually lead to membrane rupture, thinning or pinhole formation. The membrane degradation rate increases significantly with increasing operating time and decreasing inlet Relative Humidity (RH).

To improve the performance and/or durability of the film, several approaches have been proposed to address these issues. For example, in a method (US5547551, US 56565041, US5599614) for filling a Nafion ionic conducting solution in Gore-Select series composite membrane liquid developed by w.l. Gore company, a polytetrafluoroethylene microporous membrane reinforcing layer is added to the membrane, so that the membrane has excellent oxidation stability, can play a role in locally slowing down the degradation of a fuel cell membrane, but cannot fundamentally solve the problem after all.

Another solution to the long term free radical oxidative stability of the membrane is to add a catalyst to the membrane that can promote free radical degradation, including 1) adding an aqueous material to the membrane for preventing the fuel cell from operating at low humidity (e.g., US 200701564); 2) Adding metal element or alloy with free radical trapping effect into the membrane (such as US 2004043283); 3) the free radical scavenger of phenol and hindered amine is added into the film to eliminate hydroxyl free radical.

Although the above-described techniques can partially solve the problem of radical resistance of the film, they cannot fundamentally solve the problem. Their major difficulties mainly include: 1) the added water-retaining substances have a limited water content and cannot fundamentally increase the humidity of the reaction environment and solve the dehydration problem of the membrane, and the added substances also reduce the strength and conductivity of the membrane: 2) the addition of metal or alloy trapping agents requires a very precise control of the content and distribution in the membrane, since these metallic species, besides having the effect of trapping hydroxyl radicals, also catalyze the degradation of hydrogen peroxide, that is to say they have a dual nature. If the amount is too large, the concentration of hydroxyl radicals in the film increases, and the degradation of the film is further promoted. However, because the metal substance has a higher density and a hydrophilic surface, the metal substance is spontaneously precipitated and aggregated with a perfluorinated ion exchange membrane mainly composed of hydrophobic chains in the membrane preparation process, and the phenomenon cannot avoid the phenomenon of accelerating hydrogen peroxide degradation and membrane degradation caused by the increase of the local concentration of metal elements. 3) Some added substances such as phenol, hindered amine and the like are mostly used as polymerization inhibitors in free radical polymerization, namely, the substances have very good reactivity on carbon free radicals, but the activity on oxygen-containing hydroxyl free radicals is greatly reduced; moreover, they are not protected by themselves which are degraded and lost continuously when scavenging free radicals.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects in the prior art and provide a long-life perfluorinated proton membrane which not only has higher free radical oxidation tolerance, but also has longer service life; the invention also provides a simple and feasible preparation method.

The long-life perfluorinated proton membrane consists of perfluorinated ion exchange resin and an additive, wherein the additive consists of an additive A and an additive B; wherein the additive A is a metal complex formed by a metal and a ligand, and has a structure of Mx (L) y; the structure of the additive B is one or more of the following structural formulas:

wherein R is₁，R₂，R₃，R₄Are respectively H, OH, CH₃(CH₂)_nO，CH₃(CH₂)_n，NH₂，CH₂OH，C₆H₅，CF₃(CF₂)_n，CF₃(CF₂)_nO, wherein n is an integer of 0 to 10.

The structure of the ligand in the additive A is one or more of the following structural formulas:

wherein R is₁，R₂，R₃，R₄Are all H, OH, CH₃(CH₂)_nO，CH₃(CH₂)_n，NH₂，CH₂OH，C₆H₅，CF₃(CF₂)_n， CF₃(CF₂)_nO, COOH, wherein n is an integer of 0-10.

The metal in the additive A is selected from metal, metal oxide, metal salt or combination thereof.

Preferably, the metal in the additive A is a metal element Mn, Co, Rh, Cu, Ni, Ir, Ag, Ti, Ce, Ru, Cr, Zr, Fe, V, Zn, La, Pt or Pd, or a metal compound Pt (NH)₃)₄(NO₃)₂、PtCl₄、WO₃、CeF₃、 SiO₂、CeO₂、CePO₄、Ce(NO₃)₃·6H₂O、Ce(SO₄)₂、Ce(OH)₄、(NH₄)₂Ce(NO₃)₆、Ce₂(CO₃)₃·xH₂O、 Ce(CH₃COO)₃·xH₂O、CrPO₄、AlPO₄、MnO、MnO₂、Mn₂O₃、MnSO₄、MnCl₂、Mn(NO₃)₂、 Mn(CH₃COO)₂·4H₂O、ZnO、ZnCl₂Or Zn (NO)₃)₂One or more of (a).

The molar ratio of the metal M to the ligand L in the additive A is 1:1-1: 5.

The content of the perfluorinated sulfonic acid resin is 97-99.98 wt%, and the content of the additive is 0.02-3 wt%.

Preferably, the additive A is added in an amount of 0.01-2 wt%; the addition amount of the additive B is 0.01-1 wt%.

The perfluorinated ion exchange resin is one or more of long-chain branched perfluorosulfonic acid resin or short-chain branched perfluorosulfonic acid resin.

The number average molecular weight of the perfluorinated ion exchange resin is 15-70 ten thousand, preferably 20-60 ten thousand; the exchange capacity is from 0.85 to 1.6mmol/g, preferably from 0.9 to 1.4 mmol/g.

The preparation method of the long-life perfluorinated proton membrane comprises the following steps:

(1) adding perfluorinated ion exchange resin and an additive into a solvent, and obtaining uniform dispersion liquid by means of ultrasonic or mechanical stirring and the like;

(2) and (2) performing solution casting, solution casting and screen printing on the dispersion liquid obtained in the step (1), forming a film by using a blade coating, spraying or dipping mode, and heating to volatilize the solvent to obtain the long-life perfluorinated proton membrane.

The thickness of the prepared long-life perfluorinated proton membrane is 5-50 mu m, and preferably 8-25 mu m.

The additive B adopted by the invention is a remover with stronger scavenging ability to oxygen-containing free radicals, especially hydroxyl free radicals, and is particularly suitable for scavenging the generated hydroxyl free radicals in the fuel cell environment. Whereas in additive a metal complex, the metal and ligand components each can potentially act as good radical scavengers or hydrogen peroxide decomposition catalysts (without forming new groups) or both. The presence of the ligand component or the metal component alone under certain conditions may also improve membrane stability, which may adversely affect fuel cell performance. Therefore, the invention uses the ligand and simultaneously adds the metal element with the free radical degradation catalytic function, so that the durability of the catalyst can be improved without causing performance loss. In addition, two different regions with the functions of catalyzing and degrading or eliminating oxygen-containing free radicals are arranged in the same additive, and the two regions are conjugated and connected together through a large pi bond to play a role in synergistically degrading the oxygen-containing free radicals, so that the tolerance of the film is increased in a geometric progression manner.

Compared with the prior art, the invention has the following beneficial effects:

(1) the long-life perfluorinated proton membrane prepared by the invention not only has higher free radical oxidation tolerance, but also has longer service life;

(2) the preparation method of the long-life perfluorinated proton membrane is simple and feasible, and is beneficial to industrial production.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the practice of the invention.

The perfluorinated proton membrane sample is cast by a perfluorinated sulfonic acid resin solution.

For the perfluorinated proton membrane sample containing the additive, the additive component was added to the perfluorosulfonic acid resin solution while stirring to obtain a transparent and uniformly dispersed resin solution dispersion containing the additive. The resulting clear solution is then degassed and cast on a support, and the solvent is evaporated at a certain temperature and dried to give a film sample.

Example 1

Selecting long-chain branched perfluorosulfonic acid resin with exchange capacity of 0.91mmol/g and number average molecular weight of 40 ten thousand, dissolving the resin to form 20 wt% resin dispersion, and respectively adding 1.3 wt% of additive A, formula (VII) and 0.27 wt% of Ce into the dispersion₂(CO₃)₃·xH₂O (VII and Ce)³⁺In a molar ratio of 4:1), 0.3 wt% of additive B of formula (VIII); wherein R in the formula (VII)₁，R₄Is C₆H₅，R₃Is H, R₂Is OH; r in the formula (VIII)₁，R₂Is OCH₃；R₃，R₄Is H. Stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the 12um perfluorinated proton membrane.

Example 2

Dissolving a long-chain branched perfluorosulfonic acid resin having an exchange capacity of 1.1mmol/g and a number average molecular weight of 55 ten thousand to form a 17 wt% resin dispersion, and adding 1 wt% of the additive A of the formula (VII), 0.84 wt% of Mn (CH)₃COO)₂·4H₂O (VII and Mn)²⁺In a molar ratio of 2:1), 1% by weight of additive B of formula (VIII); wherein R in the formula (VII)₁，R₃，R₄Is H; r₂Is OH; r in the formula (VIII)₁，R₂Is C₄H₉；R₃，R₄Is H. After being dispersed uniformly, the solution is formed into a film by tape casting, and the solvent is volatilized after being heated to obtain the perfluorinated proton membrane of 8 um.

Example 3

Dissolving a long-chain branched perfluorosulfonic acid resin having an exchange capacity of 1.2mmol/g and a number average molecular weight of 45 ten thousand to form a 26 wt% resin dispersion, and adding 0.5 wt% of the additive A of the formula (V) and 0.2 wt% of Ce to the dispersion₂(CO₃)₃·xH₂O (V and Ce)³⁺In a molar ratio of 3:1), and 0.8% of an additive(ix) in the additive B, wherein R in the formula (V)₁Is NH₂；R₂,R₃,R₄Is H, R in formula (IX)₁,R₂Is OH; r₃R₄H, forming a film by tape casting after uniform dispersion, and volatilizing the solvent after heating to obtain the perfluorinated proton membrane of 30 um.

Example 4

A short-chain branched perfluorosulfonic acid resin having an exchange capacity of 1.4mmol/g and a number average molecular weight of 23 ten thousand was dissolved to form a 30 wt% resin dispersion, and 1.5 wt% of the formula (IV) in additive A and 0.28 wt% of Mn (CH) were added to the dispersion₃COO)₂·4H₂O (IV and Mn)²⁺In a molar ratio of 4:1), and 0.5% by weight of additive B of formula (VIII); in the formula (IV), R₁,R₂Is C₆H₅,R₃R₄Is H; r in the formula (VIII)₁,R₃Is C₆H₅；R₂,R₄Is H. Stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the perfluorinated proton membrane of 40 um.

Example 5

Dissolving a short-chain branched perfluorosulfonic acid resin having an exchange capacity of 1.25mmol/g and a number average molecular weight of 40 ten thousand to form a 22 wt% resin dispersion, adding to the dispersion 0.1 wt% of an additive B of formula (VIII) wherein R is₁,R₂Is OCH₃；R₃,R₄Is H; and 0.52% by weight of formula (VII), 0.3% by weight of formula (IV) and 0.23% by weight of Ce in additive A₂(CO₃)₃·xH₂O (VII, IV and Ce)³⁺In a molar ratio of 4:1:1), R in the formula (VII)₁,R₃,R₄Is H; r₂Is OH; in the formula (IV), R₁，R₂Is H; r₃,R₄Is C₆H₅. Stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the perfluorinated proton membrane of 15 um.

Example 6

Dissolving the mixture into 3 percent by using long-chain branched perfluorosulfonic acid resin with the exchange capacity of 0.95mmol/g and the number average molecular weight of 30 ten thousand5% by weight of a resin dispersion, to which dispersion 0.2% by weight of additive B of the formula (VIII) in which R is present₁,R₂Is C₄H₉；R₃,R₄Is H; and 0.2% by weight of formula (I), 0.16% by weight of Ce (NO) in additive A₃)₃·6H₂O (I and Ce)³⁺In a molar ratio of 3:1), R in the formula (I)₁,R₂,R₃,R₄Is H. Stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the perfluorinated proton membrane of 50 um.

Example 7

Dissolving a long-chain branched perfluorosulfonic acid resin having an exchange capacity of 1.01mmol/g and a number average molecular weight of 35 ten thousand to form a 20 wt% resin dispersion, and adding 0.6 wt% of an additive of formula (VIII) in which R in formula (VIII) is₁,R₂Is C₄H₉；R₃,R₄Is H; and 1% by weight of formula (V), 0.7% by weight of formula (IV) and 0.2% by weight of CeO in additive A₂(V and Ce)³⁺In a molar ratio of 5:1), R in the formula (V)₁Is NH₂；R₂,R₃,R₄Is H; in the formula (IV), R₁，R₂Is H; r₃,R₄Is C₆H₅. Stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the perfluorinated proton membrane of 20 um.

Example 8

Dissolving a short-chain branched perfluorosulfonic acid resin having an exchange capacity of 1.3mmol/g and a number average molecular weight of 25 ten thousand to form a 26% by weight resin dispersion, adding 0.05% by weight of an additive of the formula (IX) in which R is R in the formula (IX), to the dispersion₁,R₂Is OH; r₃R₄Is H; and 0.25 wt% of formula (I), 0.03 wt% of MnO in additive A₂(I and Mn)³⁺In a molar ratio of 4:1), R in the formula (I)₁,R₂,R₃,R₄Is H. Stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the perfluorinated proton membrane with the thickness of 35 um.

Comparative example 1

Selecting short-chain branch perfluorinated sulfonic acid resin with exchange capacity of 1.25mmol/g and number average molecular weight of 40 ten thousand, dissolving the resin to form 22 wt% resin dispersion, adding no additive, stirring and dispersing uniformly, forming a film by tape casting, and heating to volatilize the solvent to obtain the perfluorinated proton membrane of 25 um.

Accelerated oxidation test of the films:

the experimental test is carried out by a Fenton reagent method, and the method comprises the following specific steps:

80ppm Fe was added to 100mL of 30 wt% hydrogen peroxide solution²⁺Ion, carefully weighing a certain mass (0.06-0.3g) of the proton exchange membrane of the fuel cell, placing the proton exchange membrane in the proton exchange membrane, keeping the proton exchange membrane at 80 ℃ for 8h, and taking out a sample from the solution. Washed with deionized water, dried at 80 ℃ for 2h, and weighed. Calculating the weight loss and determining F in solution^－The content of (a).

The conductivity was measured using an electrochemical impedance tester at 85 ℃ and 95% RH.

Durability test of the film:

each MEA was prepared by bonding a suitable membrane sample between the cathode and anode electrodes. The cathode and anode had a density of 0.4mg/cm²Pt loading of (a).

To evaluate durability, the above 5 MEA samples were assembled into a single sheet having 50cm²An active area short stack of fuel cells. The durability of the film was evaluated using the OCV Holding test. The test conditions were: 30% RH and 90 ℃. The test method and the failure criterion refer to the method corresponding to the U.S. department of energy.

TABLE 1 conductivity, durability and accelerated Oxidation test data for films

As shown in table 1, the polymer electrolyte membranes of examples 1 to 8 to which the additive was added reduced the degradation rate of the membranes as compared with comparative example 1. The additive disclosed by the invention can effectively reduce the chemical degradation of ionomer in the membrane, thereby effectively improving the durability of the membrane.

The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.