CN100461502C - Preparation method of weakly alkaline membrane for direct alcohol fuel cell - Google Patents

Abstract

The preparation method of the weakly alkaline membrane of the direct alcohol fuel cell is to use the porous material as the support body, and the weakly alkaline polymer resin fills the pores of the porous material to form a weakly alkaline membrane surrounded by thin films on both sides. Polymer resins have the following general formula: [RN(R' ₃ )] _y ⁺ H _x CO ₃ ^y- , where: R is a segment with a benzene ring, including polyphenylene ether, polyphenylene sulfide, polyether ketone , polyetheretherketone, polyethersulfone, polybisphenol A ethersulfone, polyetherketone sulfone, polyetherketone ether ketone Ether ketone sulfone, polystyrene or polytrifluorostyrene, R' = C ₁ -C ₆ alkyl, x = 0 or 1, y = 1 or 2, and the average molecular weight of the resin is 10 ⁵ -10 ¹⁰ . The use of weakly alkaline membrane changes the working environment of the fuel cell to a weakly alkaline environment, so that the fuel cell not only has the advantages of an alkaline fuel cell, but also solves the problem of alcohol penetration without removing CO ₂ in the cathode air.

Description

Preparation method of weakly alkaline membrane for direct alcohol fuel cell

technical field

The invention belongs to the preparation method of direct alcohol fuel cell membrane.

Background technique

Direct methanol fuel cell (DMFC) is a kind of low-temperature fuel cell, especially suitable for mobile power supply and micro and small power supply. It has a very wide range of applications and has a very broad market prospect. The direct use of other alcohols as fuel is a direct alcohol fuel cell (DAFC).

Membrane materials are important components of fuel cells, and research on membrane materials with low cost, excellent performance and long service life is one of the key technologies in DMFC research.

Usually, the membrane material used in DMFC is based on the research results of proton exchange membrane fuel cell (PEMFC), and the Nafion membrane of DuPont Company of the United States is used. This type of membrane material is a proton exchange membrane, so the working environment of the battery is an acidic environment. Since some fuel methanol used can permeate the Nafion membrane (up to 40%), resulting in attenuation of battery performance, so research on finding a cheap membrane material with good alcohol-repelling properties has attracted people's attention. Moreover, the battery materials required under acidic conditions are harsh, and fuel cells require noble metals as catalysts, which are expensive and resource-limited, hindering the commercialization of fuel cells.

Common alkaline fuel cells use a strong base, such as KOH solution, as the electrolyte. Under alkaline conditions, the reactivity of methanol and oxygen is much higher than that under acidic conditions, so the electrode reaction can be catalyzed by a slightly less active catalyst. For example, the oxidation of methanol at the anode can be newly prepared foamed nickel, The cathode can be silver. This widens the selection range of catalysts for the anode and cathode. The non-acid environment also widens the choice of electrode plate materials. In the 1960s, the American Apollo (Apollo) moon landing flight successfully developed the PC3A alkaline fuel cell system, which worked for 10,750 hours. Alkaline fuel cells developed by UTC in 1981 are used in space shuttles. The domestic Dalian Institute of Chemical Physics, Tianjin Power Research Institute, Wuhan University and other units have developed alkaline fuel cells.

Since _CO2 in the air and _CO2 produced by the oxidation of methanol can react with KOH or hydroxide in the alkaline polymer film, it will cause the loss of electrolyte solution or the reduction of carriers (hydroxide ions), and the performance of the battery will decrease . In order to prevent the intrusion of carbon dioxide, a carbon dioxide removal device must be equipped. If alcohol is used as fuel, the removal of carbon dioxide becomes difficult because the oxidation product of alcohol is carbon dioxide.

Therefore, the development of a new membrane material for direct alcohol fuel cells can not only enjoy the advantages of alkaline fuel cells, but also overcome the shortcomings of alkaline fuel cells, and will have broad application prospects.

Traditional film preparation techniques generally include hot pressing, scraper method, casting method and so on.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing weakly alkaline membranes for direct alcohol fuel cells. The weakly alkaline membranes have a low alcohol permeation rate and do not need to exclude CO ₂ in the cathode air. The membrane making process is simple and the thickness is easy to control. , small deformation, high mechanical strength.

The preparation method of the weakly alkaline membrane of the direct alcohol fuel cell of the present invention is characterized in that the porous material is used as a support body, the pores of the porous material are filled with weakly alkaline polymer resin, and the weakly alkaline membrane is formed on both sides of the porous material , the weakly basic polymer resin has the following general formula:

[RN(R' ₃ )] _y ⁺ H _x CO ₃ ^y-

Among them: R is polyphenylene ether, polyphenylene sulfide, polyether ketone, polyetherether ketone, polyether sulfone, polybisphenol A ether sulfone, polyether ketone sulfone, polyether ketone ether ketone ketone, polyether ketone Segments of ether ketone, polynaphthyl ether sulfone, polynaphthalene polyether ketone sulfone, polystyrene or polytrifluorostyrene,

R' is a C ₁ -C ₆ alkyl group, preferably R' is a C ₁ -C ₃ alkyl group,

x=0 or 1, y=1 or 2,

The average molecular weight of the resin is between 10 ⁵ and 10 ¹⁰ .

In the resin of the above general formula, the aromatic group with a benzene ring can have two situations:

One is a polymer resin with an aromatic side chain containing a benzene ring.

The second is a polymer resin with an aromatic group containing a benzene ring in the polymer main chain.

The preparation method of the present invention has two methods. One is to dissolve the weakly basic polymer resin in a solvent to obtain a film-forming liquid, soak the porous material in the film-forming liquid, and then dry it.

The second is to dissolve the chloromethylated polymer with the general formula R—CH ₂ Cl (the R group is the same as the above general formula) in a solvent to prepare the intermediate film-making solution, and soak the porous material in the intermediate film-making solution The film is first formed by soaking, and then the film is obtained by quaternization reaction and weak alkalinization reaction in sequence.

The two methods are to prepare weakly basic polymer resin first and then form a film, or to prepare raw materials for weakly basic polymer resin to form a film first and then react sequentially according to the method for preparing resin to form resin.

The porous material of the present invention can be porous ceramics, porous asbestos board, porous polymer material, porous fabric, molecular sieve or porous metal plate, the thickness of the porous material is 10-70 microns, the porosity is 30%-90%, and the aperture is 0.01～0.2mm. The porous material plate is used as a supporting material, which is beneficial to improve the strength of the membrane and reduce the deformation.

The solvent is generally dimethylformamide, dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, etc., weakly alkaline polymer resin or methyl chloride in the film-making solution or intermediate film-making solution The concentration of the base polymer is 2wt%-40wt%.

The weakly basic polymer resin fills the pores of the porous material to form a smooth and dense membrane material surrounded by thin films on both sides. The thickness of the formed film is 30-200 microns.

Advantages of the present invention:

The weakly alkaline membrane has good mechanical properties, thermal stability, and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by a scanning electron microscope (SEM), the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The cross-sectional SEM shows that the membrane material has no through holes, so the membrane material is airtight. X-ray powder diffraction (XRD) analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use. The electrical conductivity of the membrane material is 10S/cm～8.52×10 ^-3 S/cm, and the alcohol permeability is less than 3.56×10 ^-9 cm ² /S.

Weakly alkaline membrane, its conduction ion is weakly alkaline carbonate/bicarbonate ion. Since its conduction direction is from the cathode to the anode, the flow of methanol will not be carried during the ion conduction process, so the problem of alcohol penetration can be solved. It has broad market prospects and important theoretical research value.

The weakly alkaline membrane changes the working environment of the fuel cell to a weakly alkaline environment. This change in the environment can lead to the fuel cell not only having the advantages of an alkaline fuel cell, but also allowing the production of CO ₂ by the reaction product without having to Eliminate CO ₂ in the cathode air, eliminating the trouble caused by the addition of lye.

Other advantages that the use of weakly alkaline membranes can bring to weakly alkaline fuel cells are:

1) The electrode reaction of the battery under alkaline conditions is more favorable than that under acidic conditions, and the selection range of the catalyst is widened. Alkaline fuel cell catalysts can not only use platinum-based noble metal catalysts, but also non-noble metal catalysts. For example, Raney nickel can be used for the anode, and silver, porphyrin and phthalocyanine complexes of transition metals can be used for the cathode.

2) Due to the difference of carriers, methanol will not be carried during the anion conduction process, so that the penetration of methanol is greatly reduced.

3) Alkaline conditions can make the corrosion of the battery worse, making the choice of battery materials wider. Battery materials can also choose some cheap and easy-to-process materials.

In a word, all these can greatly reduce the cost of fuel cells, improve the life of fuel cells, and provide conditions for the commercialization of fuel cells.

The film-making process of the invention is simple; the thickness is easy to control; the deformability is small, and the swelling deformability becomes smaller; the mechanical strength is improved; the performance of the membrane electrode (MEA) is stable, and the service life of the battery is prolonged.

Below weakly basic macromolecule resin film of the present invention and synthetic method are described as follows:

One: Polymer resins with aromatic side chains containing benzene rings:

The above concentration of sodium bicarbonate or sodium carbonate is the mass concentration, the same below.

代表高分子主链，包括碳链上有取代基，如H、F或烷基。最终产品是本发明树脂的结构通式表示一。in:

Represents the main chain of the polymer, including substituents on the carbon chain, such as H, F or alkyl. The final product is the general structural formula of the resin of the present invention.

As can be seen from the synthesis method represented above, the chloromethylated polymer obtained by the chloromethylation reaction of raw materials can be formed into a film first, followed by quaternization reaction and weak alkalinization reaction. It is also possible to carry out quaternization reaction and weak alkalinization reaction in sequence first, and then form a film (weak alkaline film).

2. Synthesis and film-forming method of weakly basic polymer resin with aromatic groups in the polymer main chain:

代表高分子主链，其中的苯基为活性基团，其余部分

为形成高分子长链的基团。最终产品是本发明树脂的结构通式表示二。in:

Represents the main chain of the polymer, in which the phenyl group is an active group, and the rest

It is a group that forms a long chain of a polymer. The final product is the general structural formula of the resin of the present invention.

It can also be seen from the synthesis method shown above that the chloromethylated polymer obtained by the chloromethylation reaction of raw materials can be formed into a film first, followed by quaternization reaction and weak alkalinization reaction. It is also possible to carry out quaternization reaction and weak alkalinization reaction in sequence first, and then form a film (weak alkaline film).

Description of drawings

Fig. 1 is the methanol permeability coefficient measuring device of membrane material;

Fig. 2 is the change relationship diagram of B pool methanol concentration and time;

Fig. 3, Fig. 4 are respectively the performance curve of weak alkaline fuel cell;

In the figure: 1 film to be tested; 2 stirring bar;

Pool A: 1mol/L methanol solution; Pool B: the same amount of pure water as Pool A

Detailed ways

The chloromethylation reaction of embodiment 1 polystyrene (known method)

In a 250ml three-necked flask equipped with a stirrer, a condenser, and a thermometer, add 10-20g polystyrene and 100-190ml dichloroethane (solvent), stir at room temperature to fully dissolve. Then heat up to 60°C to 70°C, add the pre-prepared zinc chloride (catalyst)-chloromethyl ether complex (1.5g zinc chloride completely dissolved in 20g chloromethyl ether) into the bottle, and stir for 3~ After 5 hours, let it slowly cool down to room temperature, add the reactants in the bottle to a large amount of boiling water under vigorous stirring, the chloromethylated polymer precipitates, filter, wash with water several times, and store in an oven at 60°C Dry to obtain the chloromethylated product. The reaction formula is as shown in Example 2. The product after chloromethylation was characterized by ¹ H NMR. The content analysis of chloromethyl group is first decomposed by burning potassium nitrate and sodium hydroxide, then heated and dissolved in water, and the chlorine content is determined by Volhard method. Chlorine content is calculated according to the following formula:

$\mathrm{<span\; class="notranslate">\; Cl</span>}<span\; class="notranslate">\; \%</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{{\mathrm{<span\; class="notranslate">\; AgNO</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{{\mathrm{<span\; class="notranslate">\; AgNO</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; KCNS</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; KCNS</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.03546</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}$

In the formula: N—the molar concentration of the substance (mol/l); V—the volume of the substance (ml);

m—sample mass (g).

Embodiment 2: film-forming and quaternization, weak alkalinization reaction of chloromethylated polystyrene

The chloromethylated polystyrene is dissolved in N,N-dimethylformamide to prepare a film-making solution of 2wt%-40wt%. Immerse the porous support material (such as polytetrafluoroethylene (PTFE) fabric) in the film-making solution, vacuumize the gas in the porous material, soak for 8 hours, take it out and dry it, support it with a frame, put it on a clean glass plate, 60 °C After drying at low temperature for 6-12 hours, heat treatment at 100°C for 4-8 hours, then cool to room temperature naturally, and set aside.

The chloromethylation/quaternization/weak alkalinization reaction of polystyrene is as follows:

Put the above membrane in an aqueous solution of trimethylamine (10wt%-30wt%), aminate it at room temperature for 2-4 days, take it out and rinse it with water to obtain a chlorine-type quaternized polystyrene membrane, and then in 10%-40 Soak in % Na ₂ CO ₃ aqueous solution for 1 to 3 days to make it completely hydrolyzed to obtain carbonate-type quaternized polystyrene weakly basic ion exchange membrane. If it is soaked in 10%-40% NaHCO ₃ aqueous solution for 1-3 days, it is completely hydrolyzed to obtain bicarbonate-type quaternized polystyrene weakly basic ion-exchange membrane.

Other membrane materials The method for preparing bicarbonate type weakly basic quaternary ammonium salt membrane is the same as the above method.

The ion exchange capacity IEC of the weak base type quaternized polystyrene anion exchange membrane is determined by acid-base titration.

Tests show that the weakly basic polystyrene ion exchange membrane has good mechanical properties, thermal stability, and solvent resistance, and meets the standards for use as fuel cell membrane materials. Observed by a scanning electron microscope (SEM), the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The cross-sectional SEM shows that the membrane material has no through holes, so the membrane material is airtight. X-ray powder diffraction (XRD) analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

According to the above operation, if triethylamine solution (or other tertiary amine) is used instead of trimethylamine solution, a membrane material quaternized with triethylamine (or other tertiary amine) can be obtained.

If the weakly alkalized resin is prepared to form a film, solvents such as N-a methylpyrrolidone can be used to dissolve the weakly basic resin, and a film-making solution with a mass concentration of 2% to 40% can be prepared, and the porous (support) material is soaked in the film-forming solution. In the solution, the air bubbles in the porous material are removed by vacuum, taken out after soaking for 8 hours, dried, and dried on a frame support to form a film, which is the same as the method described.

Embodiment 3: the chloromethylation reaction of polyphenylene ether

Adopt the method for embodiment 1, reaction solvent takes chloroform or ethylene dichloride, the reaction equation of the chloromethylation/ammonization/weak alkalinization reaction of polyphenylene ether is as follows:

In the formula: replacing O with S is polyphenylene sulfide, and other structures are the same as above

Example 4: Film-forming/quaternization/weak alkalinization reaction of chloromethylated polyphenylene ether

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. Reaction equation is as shown in embodiment 3

Tests show that the weakly basic polyphenylene ether ion exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for being used as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

The preparation method of weakly basic polyphenylene sulfide is the same as that of Examples 3 and 4.

Example 5: Polyether ketone chloromethylation/film formation/quaternization/weak alkalinization reaction

Adopt the method of embodiment 1, reaction solvent takes ethylene dichloride and reaction equation is as follows

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. The reaction equation is as follows

Tests show that the weakly basic polyetherketone ion-exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for being used as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

Example 6: Bisphenol A polyethersulfone chloromethylation/film formation/quaternization/weak alkalinization reaction

Adopt the method of embodiment 1, reaction solvent takes ethylene dichloride, and reaction equation is as follows:

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. The reaction equation is as follows:

Tests show that the weak base bisphenol A polyethersulfone ion exchange membrane has good mechanical properties, thermal stability, and solvent resistance, and meets the standards for use as fuel cell membrane materials. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

Example 7: Polyether ether ketone chloromethylation/film formation/quaternization/weak alkalinization reaction

Adopt the method of embodiment 1, reaction solvent takes ethylene dichloride and reaction equation is as follows

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. The reaction equation is as follows

Tests show that the weakly basic polyether ether ketone ion exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

Example 8: Chloromethylation/film formation/quaternization/weak alkalinization of polyether ketone ether ketone ketone

Adopt the method for embodiment 1, reaction solvent adopts ethylene dichloride and reaction equation is as follows.

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. The reaction equation is shown below.

Tests show that the weakly basic polyetheretherketone ether ketone ion exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

Embodiment 9: Chloromethylation/film-forming/quaternization/weak alkalinization reaction of phthalazinone polyether ketone (PPEK)

Adopt the method for embodiment 1, reaction solvent adopts chloroform or ethylene dichloride reaction equation is as follows.

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. The reaction equation is shown below.

Tests show that the weakly basic phthalazin polyether ketone ion exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

Embodiment 10: Chloromethylation/film formation/quaternization/weak alkalinization reaction of phthalazinone polyethersulfone (PPES)

Adopt the method for embodiment 1, reaction solvent adopts chloroform or ethylene dichloride reaction equation is as follows.

Adopt the membrane-making method of embodiment 2 and quaternization, weak alkalinization reaction. The reaction equation is shown below.

Tests show that the weakly basic phthalazine polyethersulfone ion exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

Example 11: Chloromethylation/film-forming/quaternization/weak alkalinization of phthalazinone polyether sulfone ketone (PPESK) The method in Example 1 is adopted, and the reaction solvent adopts the reaction equation of chloroform or dichloroethane As follows.

The film-making method and quaternization and weak alkalinization reactions of Example 2 were adopted. The reaction equation is shown below.

Tests show that the weakly basic phthalazine polyether sulfone ketone ion exchange membrane has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use.

The film-forming method of the above-mentioned weakly basic polymer resin is exemplified below.

Example 12: The porous material is a matrix soaked in a polymer resin

Taking a film material of a porous material (eg, porous ceramics, porous asbestos board, porous polymer material, molecular sieve, etc.) The morphology of the membrane was determined by SEM. The parameters such as gas barrier performance and electrical conductivity of the film were measured.

Adopt 0.5～2mm thick porous ceramic plate to immerse in the dimethylacetamide solution of the phthalazinone polyether sulfone ketone (PPESK) of the quaternization of weakly alkalinized carbonate group of 2wt%～40wt%, soak 4～ After 14 hours, take it out and spread it on a clean glass plate, dry it in vacuum at 60°C for 4 hours, and dry it at 130°C for 8 hours for later use.

Tests show that the PPESK ion-exchange membrane quaternized with weakly alkaline carbonates immersed in porous ceramic plates has good mechanical properties, thermal stability, and solvent resistance, and meets the standards for use as fuel cell membrane materials. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use. The electrical conductivity of the membrane material is: 5.23×10 ^-2 S/cm～10.51×10 ^-2 S/cm, and the alcohol permeability is 1.25×10 ^-10 cm ² /S.

Porous asbestos board, porous polymer material board, and molecular sieves are the same as in Example 12.

The solution film-forming method of other carbonate quaternized polymer materials is the same as in Example 12.

Example 13: Preparation of porous PTFE material reinforced polymer membrane material

Polymer membrane material reinforced with porous PTFE fabric

Take a 0.1-0.05mm thick PTFE film with a porosity of 50%-80%, immerse it in dimethylacetamide solution of 2wt%-40wt% carbonate quaternized polystyrene, soak for 1-4 hours, take out Spread it on a clean glass plate and dry it under vacuum at 60°C for 4 hours, and then dry it at 130°C for 8 hours for later use.

Tests show that the polystyrene ion-exchange membrane supported by the porous PTFE fabric soaked in weakly alkalinized carbonate and quaternized has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use. Conductivity of membrane material: 6.35×10 ^-2 S/cm～9.25×10 ^-2 S/cm Alcohol permeability: 6.32×10 ^-9 cm ² /S

The method for preparing porous PTFE membrane reinforced membrane materials from other materials is the same as in Example 13.

The solution film-forming method of other carbonate quaternized polymer materials is the same as that in Example 13.

Embodiment 14: porous metal plate (such as titanium plate)

The porosity of the 0.1-0.5mm porous plate (including the porous metal plate) is 50%-80%, and the pore diameter is less than 0.1mm. Immerse in the dimethylacetamide solution of 2wt%～40wt% carbonate quaternized phthalazinone polyether sulfone ketone (PPESK), soak for 1～4 hours, take out and lay on a clean glass plate Vacuum dry at 60°C for 4 hours, and dry at 130°C for 8 hours for later use. Detect parameters such as air permeability, mechanical properties, surface morphology and structure, thermal stability of the membrane,

Tests show that the polystyrene ion-exchange membrane supported by the porous PTFE fabric soaked in weakly alkalinized carbonate and quaternized has good mechanical properties, thermal stability and solvent resistance, and meets the standards for use as a fuel cell membrane material. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use. Conductivity of membrane material: 3.25×10 ^-2 S/cm～5.24×10 ^-2 S/cm Alcohol permeability: 4.21×10 ^-9 cm ² /S

Example 15: Porous PTFE fabric supported chloromethylated polymer material to prepare weakly alkaline membrane

The porous PTFE fabric is soaked with a chloromethylated polymer material solution to prepare a PTFE-reinforced polymer membrane material, followed by quaternization and weak alkali treatment to prepare a weakly alkaline membrane material. The specific preparation method is as follows:

Take a PTFE film with a thickness of 0.1-0.05mm and a porosity of 50%-80%, and immerse it in a dimethylacetamide solution of 2wt%-40wt% chloromethylated phthalazinone polyethersulfone ketone (PPESK) , soak for 1 to 4 hours, take it out and spread it on a clean glass plate, dry it in vacuum at 60°C for 4 hours, dry it at 130°C for 8 hours, cool to room temperature, and set aside. The prepared membrane material was soaked in pure water to separate it from the glass plate.

The prepared chloromethylated polymer membrane material is soaked in 10% to 60% trimethylamine aqueous solution for 48 hours at 20° C. to 40° C., taken out and rinsed with pure water. Soak in 10% to 40% Na ₂ CO ₃ (or NaHCO ₃ ) for 48 hours at 20°C to 40°C, take it out and rinse it with deionized water, and set it aside.

Tests have shown that the ion-exchange membrane of phthalazinone polyether sulfone ketone (PPESK) ion-exchange membrane supported by porous PTFE fabric soaked in weakly alkaline carbonate quaternization has good mechanical properties, thermal stability and solvent resistance, and meets the requirements as Standard for use in fuel cell membrane materials. Observed by SEM, the membrane material is a smooth and dense membrane, and no micropores are observed at a resolution of 20nm. The SEM of its cross-section shows that the membrane material has no through holes, so the membrane material is airtight. XRD analysis shows that there is no crystalline form in the membrane material, indicating that this type of membrane material is not brittle and will not cause local air leakage during use. The electrical conductivity of the membrane material is: 4.21×10 ^-2 S/cm～8.57×10 ^-2 S/cm and the alcohol permeability is 6.32×10 ^-9 cm ² /S.

The preparation method of other porous support materials and chloromethylated polymer materials to prepare weakly basic quaternized membrane materials is the same as in Example 15.

The method for preparing a weakly basic support membrane from other chloromethylated polymer materials is the same as in Example 15.

Embodiment 16 Methanol permeability coefficient determination of membrane material

The mensuration of membrane material methanol permeability coefficient adopts the prior art device shown in Fig. 1, and the membrane material to be tested is clamped between A and B two ponds during measurement, and concrete test method is as follows: the membrane to be tested is placed in pure water before testing. Soak in the water for at least 24 hours. There are stainless steel meshes on both sides of the membrane that play a supporting role. This three-layer structure is sandwiched between the two pools and fixed with a circular clamp. Add 1mol/L methanol solution to pool A, and add the same amount of pure water as pool A to pool B. Simultaneously turn on the stirrer. Take out a small amount of liquid from pool B at regular intervals and use gas chromatography (using Shimadzu 2010) to detect the content of methanol in the solution. The test temperature range is between room temperature and 80°C. At the same temperature, sampling at different times can obtain a curve of methanol concentration over time (as shown in Figure 2). The alcohol permeability coefficient of the membrane material can be obtained by calculation.

Embodiment 17: Determination of other alcohols through alcohol coefficient

The method for measuring the transmission coefficient of other alcohols (such as ethanol, isopropanol, etc.) is the same as in Example 13, except that the methanol solution in the pool A is replaced with solutions of other alcohols. Since the molecule of methanol is the smallest, it is the most likely to diffuse. Moreover, the polarity of the methanol molecule is the largest, and it is the easiest to combine with ions, so the electric drag is the most serious. Therefore, the alcohol permeability coefficient of other alcohols is smaller than that of methanol.

The following are examples of membrane electrode preparation and battery performance testing.

Embodiment 18: Hydrophobic treatment of carbon paper (known technology)

Cut T-090 (or T-060) carbon paper to the required size, dry it at 110°C for 4 hours, take it out and weigh it after cooling. Soak the carbon paper to be treated in 10wt% polytetrafluoroethylene (PTFE) emulsion (diluted with purchased 30wt% PTFE emulsion and secondary water) for 30min, take it out, bake at 110°C for 2h to remove the solvent, and then Put into the furnace and heat at 350°C for 2h. Weigh after cooling, and calculate the percentage of PTFE in the material.

Embodiment 19: the pretreatment of weak basic polymer film (commonly known technique mode)

Use the weakly basic polymer membrane of the present invention to boil in 5vol% H ₂ O ₂ aqueous solution for 1 hour to remove organic impurities in the membrane, take out the membrane and rinse it repeatedly with deionized water, then put in 1.0mol/L Na ₂ CO ₃ Boil in the solution for 1h to make the membrane completely change to weak alkaline. Rinse with deionized water for several times, then boil the membrane in deionized water for 1 hour, store in deionized water, and set aside.

Example 20: Preparation of Membrane Electrode (1)

The anode catalyst is PtRu/C with 20% platinum loading, and the cathode catalyst is activated at 600°C with bicyclic phthalocyanine cobalt (cobalt loading 20% HNODPcCo(II)/C).

Weigh an appropriate amount of cathode catalyst according to the amount of 1.2 mg/cm ² (or other loading), add an appropriate amount of twice distilled water, 1.0 mol/L NaOH solution, isopropanol, 2w/w% to 10w/w% carbonate Quaternary ammonium type weakly basic polymer (or other weakly basic polymer resin) emulsion and polytetrafluoroethylene emulsion, take out after ultrasonic vibration for about 1 hour, put it in an oven at 40 ° C ~ 60 ° C to bake until it becomes a paste, and apply it evenly on T-090 carbon paper with 20wt% PTFE was used as the cathode. The anode is made in the same way, except that the amount of the anode catalyst is weighed at 1 mg/cm ² (or other loading). Apply an appropriate amount of weakly basic polymer resin emulsion corresponding to the membrane material on the catalyst layer of the two cathode and anode, the cathode adopts a cobalt loading of 1mg/cm ² , and the catalyst adopts hexa(4-nitrobicyclic phthalocyanine cobalt) It is immobilized on XC-72 activated carbon, the cobalt load is 12w/w% at 400°C, activated for 2h under the protection of argon, and the preparation method of the cathode part is the same as that of the anode. Place the cathode and anode catalyst layers on both sides of the treated membrane in the direction of the membrane (similar to a sandwich structure), place it in the middle of the splint, heat press it with a tablet machine at 120°C and 15.5MPa for 2 minutes, and take it out after cooling. Make a mark and reserve. The performance curve of the battery is shown in Figure 3.

Example 21: Preparation of Membrane Electrode (2)

The anode catalyst adopts PtRuSn/C, and the cathode catalyst adopts silver, and other operations are the same as embodiment 20.

Example 22: Preparation of Membrane Electrode (3)

The anode catalyst adopts Raney nickel, and the cathode catalyst adopts porphyrin iron, and other operations are the same as in embodiment 20.

Example 23: Preparation of Membrane Electrode (4)

Membrane material adopts PTFE (polytetrafluoroethylene) net support to soak the membrane that weak basic resin is made, and other operations are with embodiment 20.

Example 24: Battery Assembly and Battery Performance Test

Place the membrane electrode between the graphite flow field plates, use a polytetrafluoroethylene sheet of appropriate thickness as a gasket, and install the battery. Use a lock-in amplifier and a potentiostat to test the impedance, and when the internal resistance is less than 0.4 ohms, you can pass in fuel and oxygen for battery performance testing. The test conditions are: the anode fuel liquid flow rate is 20mL/min, the cathode pressure is 0.2MPa, and the flow rate is 60mL/min. Open circuit work for 1 hour at 50°C, and record the open circuit voltage. Then turn on the load, and carry out activation treatment for 4-5h under the condition of close to the limit current. Then test its discharge performance. Control the current and voltage values by adjusting the resistance of the load, and measure the current and voltage values of multiple groups (about 20 groups) to draw polarization curves. During the measurement, in order to ensure the steady-state operation of the battery, a data is collected every three minutes.

The performance curve of the weak alkaline fuel cell in Fig. 3 is tested according to the following conditions.

A naphthyridine polyether sulfone ketone ion exchange membrane quaternized with weakly basic carbonate groups is used.

The anode uses PtRu/C, and the cathode uses hexa(4-nitro)bicyclic cobalt phthalocyanine, with a Co loading of 12%, a catalyst heat-treated at 400°C, 50°C, and 2mol/L methanol solution.

The performance curve of the weak alkaline fuel cell in Fig. 4 is tested according to the following conditions.

Curve 1 The anode uses PtRuSn/C 1mg Pt/cm ² , the cathode uses Raney nickel, 5mgNi/cm ² , weakly basic carbonate quaternized polyether ether ketone ion exchange membrane.

Curve 2: The anode uses Ag5mg Pt/cm ² , the cathode uses dimethylaminophenylporphyrin iron, 2mgFe/cm ² , and weakly basic carbonate quaternized polytrifluorostyrene ion exchange membrane.

Under the same test conditions, only the fuel methanol is replaced by an ethanol solution, and the direct ethanol fuel cell is obtained, and its performance is slightly worse than that of the direct methanol fuel cell.

If isopropanol solution is used instead of methanol water solution, and other conditions are the same as above, it is a direct isopropanol fuel cell, and its performance is slightly better than that of a direct methanol fuel cell.

Claims (9)

1. A preparation method for a weakly alkaline film for a direct alcohol fuel cell, characterized in that it is a support body using a porous material, filling the pores of the porous material with a weakly alkaline polymer resin, and forming a weak base on both sides of the porous material film, the weakly basic polymer resin has the following general formula: [RN(R' ₃ )] _y ⁺ H _x CO ₃ ^y- Among them: R is polyphenylene ether, polyphenylene sulfide, polyether ketone, polyetherether ketone, polyether sulfone, polybisphenol A ether sulfone, polyether ketone sulfone, polyether ketone ether ketone ketone, polyether ketone Segments of ether ketone, polynaphthalene polyether sulfone, polynaphthalene polyether ketone sulfone or polytrifluorostyrene, R' is a C ₁ -C ₆ alkyl group, x=0 or 1, y=1 or 2, The average molecular weight of the resin is between 10 ⁵ and 10 ¹⁰ . 2. The preparation method according to claim 1, characterized in that R' is a C ₁ -C ₃ alkyl group. 3. The preparation method according to claim 1, characterized in that the weakly basic polymer resin is a polymer resin containing an aromatic side chain of a benzene ring. 4. The preparation method according to claim 1, characterized in that the weakly basic polymer resin is a polymer resin with a benzene ring aromatic group in the polymer main chain. 5. The preparation method according to claim 1, characterized in that the weakly basic polymer resin is dissolved in a solvent to obtain a membrane-forming solution, and the porous material is soaked in the membrane-forming solution, and then dried. 6. The preparation method according to claim 1, characterized in that the film-making liquid of the intermediate is obtained by dissolving the chloromethylated polymer with the general formula as R—CH ₂ Cl in a solvent, and the porous material is soaked into the intermediate Soaked in the film-making solution, the film is first formed, and then the film is obtained by quaternization reaction and weak alkalinization reaction in sequence. 7. The preparation method according to claim 1, 5 or 6, characterized in that the porous material is porous ceramics, porous asbestos board, porous polymer material, molecular sieve or porous metal plate, and the thickness of the porous material is 10 to 70 micron, the porosity is 30% to 90%, and the pore diameter is 0.01 to 0.2mm. 8. according to the described preparation method of claim 1,5 or 6, it is characterized in that described solvent is dimethylformamide, dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, weak in solution The concentration of the basic polymer resin is 2wt%-40wt%. 9. The preparation method according to claim 1, characterized in that the thickness of the weakly basic film is 30-200 microns.

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