CN105024084A - High-temperature proton exchange membrane fuel cell membrane electrode and preparation method thereof - Google Patents

Abstract

The invention discloses a high-temperature proton exchange membrane fuel cell membrane electrode and a preparation method thereof. The membrane electrode is composed of an anode diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode diffusion layer, wherein the anode and cathode The layers are made from a mixture of graphene airgel, PTFE and catalyst. Graphene airgel is a low-density solid material with high specific surface area, rich nanoporous structure, good electrical conductivity, and hydrophobic properties. The catalytic layer containing graphene airgel can effectively inhibit the adsorption of phosphoric acid molecules on the surface of the catalytic layer in the proton exchange membrane, avoid the loss of phosphoric acid, and improve the life of the proton exchange membrane. At the same time, its good conductivity can reduce the ohmic resistance of the membrane electrode , thereby increasing the output power of the high temperature proton exchange membrane fuel cell.

Description

High temperature proton exchange membrane fuel cell membrane electrode and preparation method thereof

technical field

The invention belongs to the field of proton exchange membrane fuel cells, and relates to a structure and a preparation method of a high-temperature fuel cell membrane electrode.

Background technique

Energy is the driving force of economic development and the material basis for human survival. Due to its advantages of high energy conversion rate and low emission, fuel cells have become one of the most potential technologies in the future clean energy industry, and will be widely used in aerospace, military, communications, transportation and other fields.

High-temperature proton exchange membrane fuel cell is a new type of proton exchange membrane fuel cell technology developed in recent years, and its working temperature is above 100°C. At present, the most common high-temperature proton exchange membrane fuel cells use PBI/H ₃ PO ₄ membranes, and PBI/H ₃ PO ₄ membranes use phosphoric acid as a carrier to conduct protons, so there is no need for hydration reactions and no humidification, which simplifies the intake system of fuel cells . Its working temperature is 120°C-180°C, and it reacts to generate gaseous water, which can be easily discharged with the cathode airflow, which simplifies the fuel cell water management system. An increase in operating temperature can improve the tolerance of high-temperature fuel cells to CO and S. Due to the large difference between the working temperature and the ambient temperature, the heat released by the reaction can be used more effectively, and the thermal management system is simplified; at the same time, as the reaction temperature increases, the speed of the electrochemical reaction also increases. However, the service life of high-temperature proton exchange membrane fuel cells is not long. On the one hand, during the use of the battery, the performance of the proton exchange membrane is attenuated due to the condensation of the catalyst and the loss of phosphoric acid; The phenomenon of local overheating leads to membrane damage.

Contents of the invention

The object of the present invention is to provide a membrane electrode of a high-temperature proton exchange membrane fuel cell and a preparation method thereof, wherein the catalytic layer is made by mixing graphene airgel with PTFE and a Pt-based catalyst. Graphene airgel is a low-density solid material with high specific surface area, rich nanoporous structure, good electrical conductivity, and hydrophobic properties. The catalytic layer containing graphene airgel can effectively inhibit the adsorption of phosphoric acid molecules on the surface of the catalytic layer in the proton exchange membrane, avoid the loss of phosphoric acid, and improve the life of the proton exchange membrane. At the same time, its good conductivity can reduce the ohmic resistance of the membrane electrode , thereby increasing the output power of the high temperature proton exchange membrane fuel cell.

Said purpose is achieved through the following schemes:

A high-temperature proton exchange membrane fuel cell membrane electrode is composed of an anode diffusion layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer and a cathode diffusion layer. The anode and cathode catalyst layers described therein are made by mixing graphene airgel, PTFE and Pt-based catalyst.

A preparation method for the above-mentioned high-temperature proton exchange membrane fuel cell membrane electrode, using carbon paper or carbon cloth as a support layer, then coating a diffusion layer composed of carbon materials and PTFE, and then coating cathode and anode catalyst slurry multiple times, and then Heat treatment is pressed to form a membrane electrode. Specific steps are as follows:

1. Preparation process of cathode and anode diffusion layer:

Mix carbon material, PTFE emulsion and isopropanol aqueous solution, ultrasonically oscillate, and magnetically stir to form a uniform slurry, in which PTFE accounts for 40-60% of the total solid mass. The slurry is coated on carbon paper or carbon cloth by brushing or spraying, and then dried and calcined to obtain the diffusion layer. Wherein, the loading capacity of the diffusion layer is 2-7 mg. cm ^-2 .

2. The preparation process of the anode catalytic layer:

The graphene airgel is directly prepared from the graphite oxide aqueous dispersion by a hydrothermal method, and then the prepared graphene airgel is ground into nanoparticles.

Take a certain amount of PtRu/C catalyst, wherein the atomic ratio of Pt and Ru is 1:1-1:2, PtRu accounts for 60-90% of the total weight of the catalyst, mix it with pure water, vibrate ultrasonically, and then add an appropriate amount of graphene gas Gel nanoparticles and a small amount of PTFE solution, then add an appropriate amount of isopropanol solution, control the mass ratio of the total weight of graphene airgel and PTFE to the PtRu/C catalyst to be 1/4-1/10, graphene gas The mass ratio of gel to PTFE is 2:1-10:1, ultrasonic vibration and magnetic stirring until a uniform anode catalyst slurry is formed;

The anode catalyst slurry is evenly coated on the anode diffusion layer by brushing or spraying, and the anode catalyst layer is obtained after drying. The Pt loading of the anode catalyst layer is 1-4 mg/cm ² .

3. The preparation process of the cathode catalytic layer:

Weigh a certain amount of Pt/C catalyst, wherein Pt accounts for 35%-85% of the total weight of the catalyst, add an appropriate amount of ultrapure water to mix, ultrasonically oscillate, and then add graphene airgel, PTFE solution and an appropriate amount of isopropanol, wherein The mass ratio of the total mass of graphene airgel and PTFE to the Pt/C mixture is 1/4-1/10, the mass ratio of graphene airgel to PTFE is 2:1-10:1, ultrasonic oscillation, magnetic stirring To form a uniform cathode catalyst slurry;

The cathode catalyst slurry is brushed or sprayed on the surface of the cathode diffusion layer, and then dried to obtain the cathode catalyst layer. The Pt loading of the cathode catalyst layer is 3-6 mg/cm ² .

4. The treatment process of proton exchange membrane:

Cut a PBI film of appropriate size, soak it in a phosphoric acid solution with a concentration of 85% at room temperature for three days, and stir the solution several times during this period to make the PBI film fully contact with the phosphoric acid solution. Then it was taken out, and the phosphoric acid solution on the surface of the membrane was quickly blotted dry with filter paper, and then put into a vacuum drying oven to dry at 110° C. for 10 h.

5. Membrane electrode hot pressing process:

Arrange them in the order of the anode diffusion layer, anode catalyst layer, proton exchange membrane, cathode catalyst layer, and cathode diffusion layer, and heat them at a temperature of 135°C under a pressure of 100-200 kg.cm ^-2 with a hot press Pressing for 3-8 minutes, the membrane electrode of the high-temperature proton exchange membrane fuel cell is prepared.

The invention mainly considers the conductivity of the membrane electrode of the high-temperature proton exchange membrane fuel cell and the loss of phosphoric acid in the phosphorylated PBI proton exchange membrane. Because H ⁺ is transported through the movement of phosphate anions in the membrane, the loss of phosphoric acid will cause a decrease in the performance of the membrane, thereby affecting the performance of the battery. In order to avoid the loss of phosphoric acid, graphene airgel is added to the slurry preparation process of the cathode and anode catalysts. Due to its hydrophobicity, it can reduce the loss of phosphoric acid molecules with water and prevent the adsorption of phosphate anions on the surface of the catalyst. In addition, graphene airgel has good electrical conductivity, so that its electrical conductivity is effectively improved compared with the traditional membrane electrode that only adds PTFE as the catalytic layer binder. In addition, the porosity of graphene airgel can be changed by controlling the manufacturing process. By changing the porosity of graphene airgel, the optimal value can be found to increase the effective surface area of the electrode and reduce the loss of phosphoric acid, which is very important for improving the performance of the battery. There are also positive effects.

Description of drawings

    Figure 1 is a schematic structural view of a high-temperature proton exchange membrane fuel cell membrane electrode with a graphene airgel in the catalytic layer.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the technical solution of the present invention. in the scope of protection.

As shown in FIG. 1 , the high-temperature proton exchange membrane fuel cell membrane electrode provided by the present invention consists of an anode diffusion layer 1 , an anode catalyst layer 2 , a proton exchange membrane 3 , a cathode catalyst layer 4 , and a cathode diffusion layer 5 . Wherein the anode catalytic layer 2 and the cathode catalytic layer 4 are made by mixing graphene airgel, PTFE and Pt-based catalyst.

The preparation steps of high-temperature proton exchange membrane fuel cell membrane electrodes include the preparation of cathode and anode diffusion layers, the preparation of cathode and anode catalyst layers, the phosphorylation of PBI membrane, and the formation of membrane electrodes by hot pressing. The specific steps are as follows:

Step 1, preparation of cathode diffusion layer and anode diffusion layer:

Weigh 10mg of carbon powder XC-72R and 60mg of PTFE (polytetrafluoroethylene) emulsion with a mass percent concentration of 15%, and disperse it in 2ml of isopropanol aqueous solution (the volume ratio of isopropanol to water is 1:1), Ultrasonic oscillation for 30 minutes, followed by magnetic stirring for 30 minutes to obtain a uniformly mixed slurry.

The slurry was coated onto 1 cm x 1 cm carbon paper several times by brushing until the weight gain reached 4 mg. Then dry at a temperature of 120°C for 30 minutes to completely volatilize the isopropanol, water and the surfactant in the PTFE emulsion, and then treat it at a high temperature of 350°C for 30 minutes to melt the PTFE into a network structure, that is, the cathode diffusion layer and Anode diffusion layer.

Step 2, preparation of the anode catalyst layer:

Make graphene oxide powder and deionized water into an aqueous solution with a concentration of 1-10mg/ml, and ultrasonically oscillate for 1-5 hours to obtain a well-dispersed graphene oxide aqueous solution; take 10-500ml of the prepared graphene oxide aqueous solution and add water In the hot kettle, add L-ascorbic acid, wherein the mass ratio of L-ascorbic acid to graphene oxide is 2:1, and treat it at 100-200°C for 12 hours to obtain graphene hydrogel, and then put it into freeze-dried Graphene airgel is obtained after freeze-drying in a machine, which is then ground into nanoparticles.

Weigh 16mg of catalyst 40%Pt20%Ru/40%C (mass ratio) and mix with 1.5ml of pure water, oscillate ultrasonically for 10min, then add 2mg of graphene airgel, 10mg of 5% PTFE solution and 2ml of iso propanol, ultrasonically oscillated for 30 minutes, and then magnetically stirred for 30 minutes to obtain the anode catalyst slurry.

The anode catalyst slurry was applied to the anode diffusion layer several times by brushing until the weight gain reached 5 mg, and then treated at 120° C. for 1 hour to obtain the anode gas diffusion electrode.

Step 3, preparation of cathode catalytic layer:

Weigh 16mg of catalyst 60%Pt/40%C (mass ratio) and mix with 1.5ml of pure water, ultrasonically oscillate for 10min, then add 3.5mg of graphene airgel, 10mg of 5% PTFE solution and 2ml of isopropyl Alcohol, ultrasonic vibration 30min, then magnetic stirring 30min, obtain cathode catalyst slurry;

The cathode catalyst slurry was applied to the cathode diffusion layer several times by brushing until the weight gain reached 5 mg, and then treated at 120° C. for 1 hour to obtain the cathode gas diffusion electrode.

Step 4, the treatment process of proton exchange membrane:

Cut a 1.5cm×1.5cm PBI membrane, soak it in a phosphoric acid solution with a concentration of 85% at room temperature for three days, and stir the solution several times during the period to fully contact the PBI membrane with the phosphoric acid solution. Then it was taken out, and the phosphoric acid solution on the surface of the membrane was quickly blotted dry with filter paper, and then put into a vacuum drying oven to dry at 110° C. for 10 h.

Step 5. Hot pressing to form a membrane electrode:

Place the proton exchange membrane between the anode gas diffusion electrode and the cathode gas diffusion electrode, arrange the three neatly, put them together on a hot press, and press them under a pressure of 180kg.cm ^-2 and a temperature of 135°C After 5 minutes, the high-temperature proton exchange membrane fuel cell membrane electrode is prepared.

Claims (7)

1. A high temperature proton exchange membrane fuel cell membrane electrode is made up of anode diffusion layer, anode catalyst layer, proton exchange membrane, cathode catalyst layer, cathode diffusion layer, it is characterized in that described anode and cathode catalyst layer are made of graphene gas condensation Glue, PTFE and Pt-based catalyst are mixed. 2. high temperature proton exchange membrane fuel cell membrane electrode according to claim 1, it is characterized in that the preparation method of described graphene airgel is as follows: directly by the graphene gas condensation of graphite oxide water dispersion liquid system by hydrothermal method glue. 3. high temperature proton exchange membrane fuel cell membrane electrode according to claim 1, it is characterized in that the mass ratio of the gross weight of described graphene airgel and PTFE and Pt base catalyst is 1/4-1/10, graphite The mass ratio of ethylene airgel to PTFE is 2:1-10:1. 4. a preparation method of the high-temperature proton exchange membrane fuel cell membrane electrode according to claim 1, characterized in that the method steps are as follows: 1. Preparation process of cathode and anode diffusion layer; 2. The preparation process of the anode catalytic layer: Take a certain amount of PtRu/C catalyst, wherein the atomic ratio of Pt and Ru is 1:1-1:2, PtRu accounts for 60-90% of the total weight of the catalyst, mix it with pure water, vibrate ultrasonically, and then add an appropriate amount of graphene gas Gel nanoparticles and a small amount of PTFE solution, then add an appropriate amount of isopropanol solution, control the mass ratio of the total weight of graphene airgel and PTFE to the PtRu/C catalyst to be 1/4-1/10, graphene gas The mass ratio of gel to PTFE is 2:1-10:1, ultrasonic vibration and magnetic stirring until a uniform anode catalyst slurry is formed; The anode catalyst slurry is evenly coated on the anode diffusion layer, and the anode catalyst layer is obtained after drying; 3. The preparation process of the cathode catalytic layer: Weigh a certain amount of Pt/C catalyst, wherein Pt accounts for 35%-85% of the total weight of the catalyst, add an appropriate amount of ultrapure water to mix, ultrasonically oscillate, and then add graphene airgel, PTFE solution and an appropriate amount of isopropanol, wherein The mass ratio of the total mass of graphene airgel and PTFE to the Pt/C mixture is 1/4-1/10, the mass ratio of graphene airgel to PTFE is 2:1-10:1, ultrasonic oscillation, magnetic stirring To form a uniform cathode catalyst slurry; Brush or spray the cathode catalyst slurry onto the surface of the cathode diffusion layer, and dry to obtain the cathode catalyst layer; 4. The treatment process of proton exchange membrane; 5. Membrane electrode hot pressing process. 5 . The method for preparing a membrane electrode of a high-temperature proton exchange membrane fuel cell according to claim 4 , characterized in that the Pt loading of the anode catalyst layer is 1-4 mg/cm ² . 6 . The method for preparing a membrane electrode of a high-temperature proton exchange membrane fuel cell according to claim 4 , characterized in that the Pt loading of the cathode catalytic layer is 3-6 mg/cm ² . 7 . The method for preparing a membrane electrode of a high-temperature proton exchange membrane fuel cell according to claim 4 , characterized in that the loading capacity of the anode and cathode diffusion layers is 2-7 mg.cm ⁻² .