CN102945968A - Composite polyepoxy chloropropane alkaline polymer membrane electrode and preparation method thereof - Google Patents

Abstract

The invention discloses a composite polyepichlorohydrin alkaline polymer membrane electrode and a preparation method thereof. The membrane electrode includes a basic anion exchange membrane and an electrode layer. The basic anion exchange membrane undergoes a nucleophilic substitution reaction between a halogen atom and a tertiary amine to obtain a quaternary aminated polyepichlorohydrin, and then combines with a porous polytetrafluoroethylene membrane Composite; the electrode layer includes a hydrogen electrode and an oxygen electrode, the hydrogen electrode includes a gas diffusion layer and a hydrogen electrode catalytic layer sprayed thereon, and the oxygen electrode includes a gas diffusion layer and an oxygen electrode catalytic layer sprayed thereon; The membrane electrode is integrally molded according to the combination sequence of hydrogen electrode, alkaline anion exchange membrane and oxygen electrode; the gas diffusion layer is formed by using carbon material as a matrix and adding hydrophobic polymer. The alkaline membrane electrode involved in the present invention has a simple synthesis method of the alkaline anion exchange membrane, high ion conductivity, and a non-platinum-based catalyst with low cost can be selected, and is suitable for the alkaline anion exchange membrane fuel cell.

Description

A kind of composite polyepichlorohydrin alkaline polymer membrane electrode and preparation method thereof

technical field

The invention belongs to the field of fuel cells, and relates to a membrane electrode, in particular to a composite polyepichlorohydrin alkaline polymer membrane electrode for a fuel cell and a preparation method thereof.

Background technique

Alkaline fuel cell (AFC) is the first practical fuel cell, and its biggest advantage lies in the superior redox kinetics of the cathode, which can use low-load Pt catalysts or even non-Pt catalysts. Its working principle is that under the action of the electrocatalyst, the anode hydrogen and hydroxide ions undergo an oxidation reaction to generate water and electrons, and the electrons are conducted to the cathode through an external circuit. Under the action of the cathode catalyst, they react with oxygen and water to form hydrogen and oxygen. The generated hydroxide ions migrate through the electrolyte to the anode to continue to participate in the reaction. However, the traditional alkaline fuel cell uses a liquid electrolyte (potassium hydroxide solution), which is not only highly corrosive, but also only suitable for pure hydrogen and pure oxygen reactants, and is sensitive to acidic impurity gases such as CO ₂ , and its performance drops sharply.

The proposal of Alkaline Anion Exchange Membrane Fuel Cell (AAEMFC) avoids the defects and deficiencies of traditional Alkaline Fuel Cells. AAEMFC has the following obvious advantages: (1) AAEMFC is the same as traditional AFC, the biggest advantage lies in the electrode reaction. The amount of precious metals used can be reduced, and platinum can be replaced by cobalt, silver, and nickel. In alkaline medium, methanol oxidation is more thorough than in acidic medium, and the oxygen reduction kinetics is superior under alkaline conditions; (2) There are no mobile metal cations such as Na ⁺ and K ⁺ in the anion exchange membrane, and no Metal carbonates will be formed to damage the electrolyte and electrode layers; (3) In alkaline media, the damage of oxygen free radicals to polymer membranes is inhibited, so the selection of fluorine-free polymer electrolyte membranes is more likely to reduce environmental pollution; (4) In AAEMFC, water is produced at the anode and consumed at the cathode, which greatly simplifies system water management; (5) Using solid electrolyte, there are no problems such as leakage and strong corrosion, and low-cost metal bipolar plates can be used.

The current technical difficulty of AAEMFC lies in the lack of an efficient and stable alkaline polymer membrane electrode. One of the main reasons is the lack of an anion exchange membrane (AAEM) suitable for fuel cells. Since the mobility of OH ^- is less than 1/4 of that of H ⁺ , the conductivity of AAEM is lower than that of PEM; AAEM has poor high temperature resistance, and most of them Degradation occurs at ≥60°C; poor chemical stability and low mechanical strength. Another main reason is the lack of electrodes suitable for alkaline solid electrolytes. The hydrophobic electrodes in traditional alkaline fuel cells and the acidic system electrodes in proton exchange membrane fuel cells are not suitable for AAEMFC.

Contents of the invention

The purpose of the present invention is to solve the technical problems mentioned above, and to provide a membrane electrode of an alkaline anion exchange membrane fuel cell with high efficiency and stability.

In order to achieve the above object, the invention provides a kind of composite polyepichlorohydrin alkaline polymer membrane electrode, and this membrane electrode comprises alkaline anion exchange membrane, electrode layer, wherein:

The basic anion exchange membrane is formed by nucleophilic substitution reaction between polyepichlorohydrin chlorine atoms and tertiary amines to obtain quaternized polyepichlorohydrin, and then compounded with porous polytetrafluoroethylene membrane;

The electrode layer includes a hydrogen electrode and an oxygen electrode, the hydrogen electrode includes a gas diffusion layer and a hydrogen electrode catalytic layer sprayed on the gas diffusion layer, and the oxygen electrode includes a gas diffusion layer and a hydrogen electrode catalyst layer sprayed on the gas diffusion layer Oxygen electrode catalytic layer on top;

The membrane electrode is integrally formed according to the combination sequence of hydrogen electrode, alkaline anion exchange membrane and oxygen electrode;

Wherein, the gas diffusion layer is formed by using a carbon material as a matrix and adding a hydrophobic polymer.

The above composite polyepichlorohydrin alkaline polymer membrane electrode, wherein the tertiary amine is selected from N,N,N`,N`-tetramethyl-1,6-methanediamine, N,N, N`,N`-tetramethyl-1,6-ethylenediamine, N,N,N`,N`-tetramethyl-1,6-propylenediamine or N,N,N`,N`- Any one of tetramethyl-1,6-hexanediamine.

The above-mentioned composite polyepichlorohydrin alkaline polymer membrane electrode, wherein:

The hydrogen electrode catalytic layer includes a platinum-based catalyst and a polymer emulsion;

The oxygen electrode catalytic layer comprises a platinum-based catalyst and a polymer emulsion; or, a non-platinum-based catalyst and a polymer emulsion;

Wherein, the platinum-based catalyst is Pt black or 40%Pt/C, the non-platinum-based catalyst is Ni, Ag, Co or its carbon-supported Ni, Ag, Co catalyst; the polymer emulsion is polyperfluoro One or more of ethylene propylene, Nafion (Nafion is a perfluorosulfonic acid polymer, a patented product of DuPont, without Chinese translation) or quaternized polymer emulsion. The quaternized polymer refers to an aliphatic or aromatic polymer with a quaternary amine group on the branch chain, such as the quaternized polyepichlorohydrin mentioned herein, and the quaternized Polychlorostyrene (aliphatic backbone), quaternized polysulfone (aromatic backbone), etc.

Preferably, the quaternized polyepichlorohydrin used in the present invention is selected from the same quaternized polyepichlorohydrin as the membrane material, or the AS-x emulsion of Tokuyama Company (with quaternized branched chain, the detailed structure is not disclosed) ).

The above composite polyepichlorohydrin basic polymer membrane electrode, wherein the carbon material used in the base of the gas diffusion layer is carbon paper or carbon cloth, and polytetrafluoroethylene or polyperfluoroethylene propylene is added for hydrophobic deal with.

The present invention also provides a kind of preparation method of above-mentioned composite polyepichlorohydrin alkaline polymer membrane electrode, and this method comprises following concrete steps:

Step 1, preparation of basic anion exchange membrane:

Step 1.1, dissolving polyepichlorohydrin in N,N-dimethylsulfoxide, heating while stirring, to a temperature of 80-100°C;

Step 1.2, under an inert atmosphere, add 30wt%-85wt% tertiary amine based on the weight of polyepichlorohydrin to the polyepichlorohydrin solution, react for 12-48 hours, remove the solution after the reaction is completed, Standby after filtering to obtain quaternized polyepichlorohydrin;

Step 1.3, adding ethanol and acetone to the homogeneous solution of quaternized polyepichlorohydrin obtained in the above step 1.2, and stirring for 0.5-2 hours to form a uniform film-forming solution of 10-20wt%;

Step 1.4, casting the above film-forming solution into the pretreated porous polytetrafluoroethylene film, heating and evaporating the solvent at 60-80°C, and vacuum heat treatment at 60-120°C for 4-20 hours to obtain the desired anion exchange membrane ;

Step 2, preparation of the electrode layer:

Step 2.1, Hydrophobic treatment of the diffusion layer base: treat the carbon paper or carbon cloth as the base material of the diffusion layer with polytetrafluoroethylene or polyperfluoroethylene propylene emulsion and sinter, first sinter at 120-130°C for 15-30min, and then Sinter at 280-350°C for 15-30min; among them, carbon paper or carbon cloth plays a supporting role in the entire gas diffusion electrode, but in order to effectively conduct gas, it is treated with hydrophobic treatment (water will hinder gas conduction);

Step 2.2, preparation of the diffusion layer: blend the carbon powder and the polyperfluoroethylene propylene emulsion to prepare the gas diffusion layer slurry, and then spray the diffusion layer slurry on the base material after the hydrophobic treatment in step 2.1, First sinter at 120-130°C for 15-30min, then sinter at 280-350°C for 15-30min, and roll and flatten to form a gas diffusion layer; among them, carbon paper or carbon cloth is flattened (because microscopically, Carbon paper is porous), if it is not leveled, a large amount of catalyst will be filled into the pores of carbon paper or carbon cloth when the catalytic layer is subsequently coated, away from the electrolyte, and the proper catalytic effect cannot be achieved;

Step 2.3, preparation of the catalytic layer: uniformly mix the components of the catalyst slurry, spray on the prepared diffusion layer, and then dry it in an oven at 50-80°C to form a catalytic layer; the diffusion layer and its sprayed The catalytic layer constitutes the electrode layer to obtain a hydrogen electrode and an oxygen electrode respectively;

Step 3, preparation of basic polymer membrane electrode assembly

Step 3.1, immerse the anion exchange membrane prepared in step 1 in KOH solution, replace Cl- with OH-, rinse with deionized water repeatedly, and then dry it for later use;

Step 3.2, cut the hydrogen electrode and oxygen electrode of appropriate size and place them on the upper and lower sides of the alkaline anion exchange membrane. -100°C for 60-150s, turn on the press, and take out the prepared membrane electrode after natural cooling.

The preparation method of the above-mentioned composite polyepichlorohydrin basic polymer membrane electrode, wherein, in step 1.3, the concentration of the quaternized polyepichlorohydrin in ethanol and acetone is 14wt%.

The technical scheme adopted in the present invention is to prepare quaternary aminated polyepichlorohydrin through nucleophilic substitution reaction, and then compound with porous polytetrafluoroethylene to form an anion exchange membrane. The prepared anion exchange membrane has good film-forming property, The preparation method is simple, the toxicity and pollution are small, and it has good thermal stability and high ion conductivity; then prepare an electrode suitable for alkaline solid electrolyte, according to the principle of hydrogen electrode-alkaline anion exchange membrane-oxygen electrode The combined sequence is integrally formed to form a membrane electrode.

The basic anion exchange membrane involved in the membrane electrode of the present invention is formed by compounding quaternary aminated polyepichlorohydrin and porous polytetrafluoroethylene membrane. Compared with the current technology, the preparation method is simple, the toxicity and pollution are small, and it has relatively high Good thermal stability and high ionic conductivity.

In the hydrogen electrode and the oxygen electrode involved in the membrane electrode of the present invention, the quaternized polymer emulsion (mainly composed of quaternized polyepichlorohydrin) is used, which improves the conductivity ^of OH in the electrode and avoids solid The disadvantage of the limited contact interface between the electrolyte and the electrode improves the performance of the membrane electrode; the non-platinum catalyst is used in the oxygen electrode involved, which reduces the cost of the fuel cell.

Description of drawings

Fig. 1 is the thermogravimetric curve of PECH, QPECH and QPECH/PTFE composite membrane.

Figure 2 shows the ion conductivity of QPECH/PTFE composite membrane at different temperatures (30-80°C).

Fig. 3 is the polarization characteristic curve of the membrane electrode of the present invention (experimental conditions are: hydrogen and oxygen inlet gauge pressure 0.12MPa; hydrogen and oxygen humidification temperature 70 ℃, battery temperature 60-65 ℃; hydrogen, oxygen gas inlet metering ratio 2.0:1).

Detailed ways

Below in conjunction with embodiment, the present invention is further elaborated. It should be understood that these examples are only used to illustrate the present invention in detail and are not intended to limit the scope of the present invention.

Example 1

Dissolve polyepichlorohydrin (PECH) in N,N-dimethylsulfoxide (DMSO), heat while stirring, to a temperature of 100°C; under an inert atmosphere, add 30% N to the reactor, N,N`,N`-tetramethyl-1,6-ethylenediamine was reacted for 48 hours. After the reaction was completed, the solution was removed and filtered for later use to obtain quaternized polyepichlorohydrin (QPECH); Add a certain amount of ethanol and acetone to the mixture, stir for 2 hours to form a 14% uniform film-forming solution; cast the film-forming solution into a pretreated porous polytetrafluoroethylene film, heat and evaporate the solvent at 60°C, and then heat it at 100°C After vacuum heat treatment for 12 hours, the desired anion exchange membrane was obtained.

The carbon paper is treated with polytetrafluoroethylene (PTFE) emulsion and sintered, firstly sintered at 120°C for 15 minutes, then at 350°C for 15 minutes; then a certain amount of carbon powder and polyperfluoroethylene propylene (FEP) emulsion are sintered Reconcile and prepare the gas diffusion layer slurry, spray the carbon powder slurry on the base material after hydrophobic treatment, first sinter at 120°C for 15min, then sinter at 280°C for 30min, and roll and level it to form a gas diffusion layer layer.

The preparation of the oxygen electrode catalytic layer is to prepare 80% Pt black and 20% quaternized polymer emulsion (preferably the same quaternized polyepichlorohydrin as the membrane material) with 1:1 ethanol aqueous solution to form a slurry Mix evenly, spray on the prepared diffusion layer, and then dry in an oven at 80°C. The diffusion layer together with the oxygen electrode catalytic layer sprayed on it constitutes the oxygen electrode.

The preparation of the hydrogen electrode catalytic layer is to prepare a slurry of 70% Pt/C and 30% quaternized polymer emulsion (preferably the same quaternized polyepichlorohydrin as the membrane material) with 1:1 ethanol aqueous solution The materials are mixed evenly, sprayed on the prepared diffusion layer, and then dried in an oven at 80°C. The diffusion layer together with the hydrogen electrode catalytic layer sprayed on it constitutes the hydrogen electrode.

Immerse the anion exchange membrane in the KOH solution, replace the exchange ions with OH ^- , wash it repeatedly with deionized water and dry it; cut the appropriate size hydrogen electrode and oxygen electrode and place them on the upper and lower sides of the alkaline anion exchange membrane, aligning up and down , The fit is in good condition, and it is heat-pressed by a high-precision press. The pressure of the press is 2MPa, the temperature of the press is 100°C, and the duration is 60s. Turn on the press, and take out the membrane electrode after natural cooling.

Example 2

The preparation process of the anion exchange membrane is as described in Example 1, except that the tertiary amine is N,N,N',N'-tetramethyl-1,6-hexanediamine. Polyepichlorohydrin (PECH), synthesized quaternized polyepichlorohydrin (QPECH), and the prepared anion exchange membrane (QPECH/PTFE) were tested by thermogravimetric analysis. As shown in Figure 1, the prepared anion exchange The membrane (QPECH/PTFE) has a decomposition temperature greater than 200°C and has good thermal stability, which can meet the needs of low-temperature fuel cell operation (the operating temperature is generally lower than 120°C); the ion conductivity of the prepared anion exchange membrane Test, test As shown in Figure 2, the prepared anion exchange membrane has high ion conductivity, the highest ion conductivity is greater than 10 ^-2 S·cm ^-1 (the current advanced level of anion exchange membrane is on the order of 10 ^-2 ).

The preparation process of the gas diffusion layer is as described in Example 1.

The preparation of the oxygen electrode catalytic layer is to mix 70% Ag/C and 30% quaternized polymer emulsion (AS-x emulsion of Tokuyama Company) with 1:1 ethanol aqueous solution to form a slurry and mix it evenly, and spray it to the preparation on a good diffusion layer, and then dried in an oven at 80°C.

The preparation process of the hydrogen electrode catalytic layer is as described in Example 1.

Example 3

Apply the membrane electrode in Example 2 to a fuel cell, and conduct a polarization characteristic curve test. The test conditions are: hydrogen and oxygen inlet gauge pressure 0.12MPa; hydrogen and oxygen humidification temperature 70°C, battery temperature 60-65°C; hydrogen, oxygen Air intake metering ratio 2.0. The test results are shown in Figure 3, indicating that the prepared composite polyepichlorohydrin alkaline polymer membrane electrode exhibits good electrical properties for alkaline fuel cells, the open circuit voltage of the battery is greater than 1.0V, and the maximum power density is 16.4 mW· cm ^-2 . This example is the application of the prepared membrane electrode in a fuel cell. The electrochemical performance of the fuel cell is expressed by the polarization curve. The results show that the prepared membrane electrode can operate normally in the fuel cell; Compared with membrane fuel cell performance, the performance is relatively good.

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as limiting the present invention. Various modifications and alterations to the present invention will become apparent to those skilled in the art upon reading the above disclosure. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (6)

1. a compound type polyepichlorohydrin basic polymer membrane electrode, this membrane electrode comprises alkaline anion exchange membrane, electrode layer, is characterized in that: The basic anion exchange membrane is formed by nucleophilic substitution reaction between polyepichlorohydrin chlorine atoms and tertiary amines to obtain quaternized polyepichlorohydrin, and then compounded with porous polytetrafluoroethylene membrane; The electrode layer includes a hydrogen electrode and an oxygen electrode, the hydrogen electrode includes a gas diffusion layer and a hydrogen electrode catalytic layer sprayed on the gas diffusion layer, and the oxygen electrode includes a gas diffusion layer and a hydrogen electrode catalyst layer sprayed on the gas diffusion layer Oxygen electrode catalytic layer on top; The membrane electrode is integrally formed according to the combination sequence of hydrogen electrode, alkaline anion exchange membrane and oxygen electrode; Wherein, the gas diffusion layer is formed by using a carbon material as a matrix and adding a hydrophobic polymer. 2. composite polyepichlorohydrin alkaline polymer membrane electrode as claimed in claim 1, is characterized in that, described tertiary amine selects N, N, N ', N '-tetramethyl-1,6 -Methylenediamine, N,N,N`,N`-tetramethyl-1,6-ethylenediamine, N,N,N`,N`-tetramethyl-1,6-propylenediamine or N , Any one of N,N`,N`-tetramethyl-1,6-hexanediamine. 3. composite polyepichlorohydrin basic polymer membrane electrode as claimed in claim 1, is characterized in that: The hydrogen electrode catalytic layer includes a platinum-based catalyst and a polymer emulsion; The oxygen electrode catalytic layer comprises a platinum-based catalyst and a polymer emulsion; or, a non-platinum-based catalyst and a polymer emulsion; Wherein, the platinum-based catalyst is Pt black or 40%Pt/C, the non-platinum-based catalyst is Ni, Ag, Co or its carbon-supported Ni, Ag, Co catalyst; the polymer emulsion is polyperfluoro One or more of ethylene propylene, Nafion or quaternized polymer emulsion. 4. composite polyepichlorohydrin alkaline polymer membrane electrode as claimed in claim 1, is characterized in that, the carbon material that the matrix of described gas diffusion layer adopts is carbon paper or carbon cloth, adds polytetrafluoroethylene Ethylene or FEP for hydrophobic treatment. 5. a preparation method according to any one of claim 1-4 composite polyepichlorohydrin alkaline polymer membrane electrode, is characterized in that, the method comprises the following specific steps: Step 1, preparation of basic anion exchange membrane: Step 1.1, dissolving polyepichlorohydrin in N,N-dimethylsulfoxide, heating while stirring, to a temperature of 80-100°C; Step 1.2, under an inert atmosphere, add 30wt%-85wt% tertiary amine based on the weight of polyepichlorohydrin to the polyepichlorohydrin solution, react for 12-48 hours, remove the solution after the reaction is completed, Standby after filtering to obtain quaternized polyepichlorohydrin; Step 1.3, adding ethanol and acetone to the homogeneous solution of quaternized polyepichlorohydrin obtained in the above step 1.2, and stirring for 0.5-2 hours to form a uniform film-forming solution of 10-20wt%; Step 1.4, casting the above film-forming solution into the pretreated porous polytetrafluoroethylene film, heating and evaporating the solvent at 60-80°C, and vacuum heat treatment at 60-120°C for 4-20 hours to obtain the desired anion exchange membrane ; Step 2, preparation of the electrode layer: Step 2.1, Hydrophobic treatment of the diffusion layer base: treat the carbon paper or carbon cloth as the base material of the diffusion layer with polytetrafluoroethylene or polyperfluoroethylene propylene emulsion and sinter, first sinter at 120-130°C for 15-30min, and then Sintering at 280-350°C for 15-30min; Step 2.2, preparation of the diffusion layer: blend the carbon powder and the polyperfluoroethylene propylene emulsion to prepare the gas diffusion layer slurry, and then spray the diffusion layer slurry on the base material after the hydrophobic treatment in step 2.1, First sinter at 120-130°C for 15-30min, then sinter at 280-350°C for 15-30min, and carry out rolling and leveling to form a gas diffusion layer; Step 2.3, preparation of the catalytic layer: uniformly mix the components of the catalyst slurry, spray on the prepared diffusion layer, and then dry it in an oven at 50-80°C to form a catalytic layer; the diffusion layer and its sprayed The catalytic layer together constitutes the electrode layer, and the hydrogen electrode and the oxygen electrode are respectively obtained; Step 3, preparation of basic polymer membrane electrode assembly Step 3.1, immersing the anion exchange membrane prepared in step 1 in KOH solution, replacing Cl ^- with OH ^- , washing with deionized water repeatedly, and then drying it for later use; Step 3.2, cut the hydrogen electrode and oxygen electrode of appropriate size and place them on the upper and lower sides of the alkaline anion exchange membrane. -100°C for 60-150s, turn on the press, and take out the prepared membrane electrode after natural cooling. 6. the preparation method of composite type polyepichlorohydrin basic polymer membrane electrode as claimed in claim 5 is characterized in that, in step 1.3, described quaternization polyepichlorohydrin is mixed with ethanol and acetone The concentration is 14wt%.

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