CN102255085A - Catalyst sizing agent for preparing catalytic membrane electrode of fuel cell and preparation thereof - Google Patents

Abstract

The invention relates to a catalyst sizing agent for preparing a catalytic membrane electrode of a proton exchange membrane fuel cell. The catalyst sizing agent consists of an electric catalyst, proton conductor polymer distilled water and an organic solvent. The catalyst sizing agent is controlled in a colloid state, so that the pore structure of a prepared catalytic layer of a catalytic membrane electrode is improved, and the cell performance is enhanced. The conventional sizing agent for preparing the catalytic membrane electrode is in a solution state, so that the utilization ratio of a prepared electrode catalyst is not high, the porosity of a catalytic layer is very low, and the gas diffusion process is suppressed. In the invention, the composition and adding sequence of organic solvents in the sizing agent are changed. A preparation method of the catalyst sizing agent comprises the following steps of: conditioning a solution-state catalyst sizing agent with isopropanol, ethanol, ethanediol and the like; and dropwise adding the formed sizing agent into butyl acetate under ultrasonic oscillation condition to form a colloid-state catalyst sizing agent.

Description

Catalyst slurry for preparing fuel cell catalytic membrane electrode and preparation thereof

technical field

The invention relates to a catalyst slurry composition for preparing fuel cell catalytic membrane electrodes and a preparation process thereof.

Background technique

Proton exchange membrane fuel cell is a power generation device that uses hydrogen as fuel and can effectively convert its chemical energy into electrical energy. Its high energy density, fast start-up speed, low operating temperature, and environmental friendliness determine its It is very suitable as a power source for electric vehicles, a portable small power source, and a power source for underwater power systems. Therefore, since the 1990s, it has been widely concerned by governments of various countries and various aspects such as energy, automobiles, home appliances and military industries, and the technology has developed rapidly.

The key component of proton exchange membrane fuel cell - the electrode part, is the place where the chemical reaction takes place inside the battery. The preparation method and structural modification of the electrode are research hotspots in recent years. In the electrode preparation process, if the catalytic layer is directly prepared on the gas diffusion layer, the formed electrode is called a gas diffusion electrode; if the catalytic layer is directly prepared on the proton exchange membrane, the formed electrode is called a catalytic membrane electrode. The preparation method of the catalytic membrane electrode includes a pressure-reversing method and a direct spraying method. The rotary pressure method is to spray the catalyst slurry on an intermediate medium first, and then transfer it to the proton exchange membrane by heating and pressure. Although this process is relatively cumbersome, it effectively avoids swelling and deformation of the membrane when it encounters a solvent. , and after the hot pressing process, the catalytic layer is in good contact with the membrane. Another preparation method is the direct spraying method, that is, the catalyst slurry is directly sprayed onto the proton exchange membrane to prepare a film-forming electrode. This preparation method is simple and convenient, greatly improves the efficiency of electrode preparation and simplifies the process. The catalytic layer of the catalytic membrane electrode is relatively thin, the catalyst is in good contact with the proton conductor polymer, the utilization rate of the catalyst is higher than that of the gas diffusion electrode, and the battery performance is more outstanding. However, the porosity of the catalytic layer in the catalytic membrane electrode is low, which is not conducive to the gas diffusion process, and the utilization rate of the electrode catalyst needs to be improved.

During the electrode preparation process, the state of the catalyst slurry has an important influence on the microstructure of the formed catalytic layer. According to the dielectric constant of the organic solvent and its interaction with the proton conductor polymer, when using different organic solvents to prepare the catalyst slurry, the slurry will show different states (solution state, colloid state, coprecipitate). In the solution state catalyst slurry, the proton conducting polymer is wrapped on the surface of the catalyst. Due to its insulating properties, the performance of the formed catalytic layer is not ideal, and the gas mass transfer process will be affected. If the type of organic solvent is changed to make the catalyst slurry appear in a colloidal state, the proton conductor polymer will be adsorbed on the surface of the catalyst particles, which will improve the utilization rate of the catalyst, and the pores used for gas mass transfer in the catalytic layer will also increase. increase, which is beneficial to improve battery performance.

Related patents are as follows:

CN1477724

The invention relates to a method for preparing the membrane electrode assembly of a proton exchange membrane fuel cell. The catalyst slurry prepared by using low-boiling point and low-viscosity alcohol as a dispersant and high-boiling point and high-viscosity alcohol as a stabilizer can be directly coated on the surface of the conductive film. The proton conductive membrane pre-impregnated with high-boiling point and high-viscosity alcohol can form a membrane-electrode assembly with a uniform, continuous and highly active catalytic layer without deformation of the catalyst slurry placed on it.

CN101098007

A catalyst slurry for making fuel cell membrane electrodes, which comprises 1-40wt.% of solid catalyst particles, 1-40wt.% of polymer proton conductors, 0.1-50wt.% of water and 1-50wt.% of alcohol And organic acid 1-90wt.%. A method for preparing a catalyst slurry, comprising the steps of making a dispersion liquid of a high molecular polymer proton conductor, making a catalyst slurry, and the like. The performance of the electrode prepared by using the catalyst slurry of the present invention is obviously better than that of the electrode prepared by the catalyst slurry of the prior art, and the preparation of the catalyst slurry of the present invention is very convenient, saves time, labor and energy.

Contents of the invention

Different from the above two inventions, the present invention focuses on the selection and addition sequence of organic solvents when preparing the catalyst slurry, so as to ensure that the slurry is in a colloidal state, so as to improve the porosity of the catalytic layer and the performance of the battery.

The object of the present invention is to provide a catalyst slurry for preparing catalytic membrane electrodes of proton exchange membrane fuel cells. Since the proton conductor polymer is an electrical insulator, its state in the slurry will directly affect the utilization rate of the catalyst. In the preparation process of traditional catalytic membrane electrodes, the catalyst slurry is in a solution state, and the catalyst aggregates will be completely wrapped by the proton conductor polymer, thereby reducing the utilization rate of the catalyst; the porosity of the formed catalytic layer is small, which is not conducive to gas mass transfer process. In the invention, the catalyst slurry is presented as a colloidal state by changing the type of the organic solvent in the catalyst slurry and the order of adding the organic solvent. In the colloidal catalyst slurry, since the proton conductor polymer forms a colloid, it does not completely wrap the catalyst aggregate, but adsorbs on the surface of the catalyst aggregate, that is, only covers a part of the surface area of the catalyst aggregate, which can improve the catalyst utilization and improve the porosity of the formed catalytic layer.

To achieve the above object, the technical solution adopted in the present invention is:

水、异丙醇和/或乙醇、乙二醇、醋酸丁酯组成，催化剂、质子导体聚合物

水、异丙醇和/或乙醇、乙二醇、醋酸丁酯的质量比例为2∶1∶8∶80∶10∶80。利用这种胶体态浆料制备的催化膜电极，其催化剂的利用率高，催化层的孔隙率得到改善。The catalyst slurry is in a colloidal state, which is composed of a catalyst, a proton conductor polymer

Composition of water, isopropanol and/or ethanol, ethylene glycol, butyl acetate, catalyst, proton conductor polymer

The mass ratio of water, isopropanol and/or ethanol, ethylene glycol, and butyl acetate is 2:1:8:80:10:80. The catalytic membrane electrode prepared by using the colloidal slurry has high utilization rate of the catalyst, and the porosity of the catalytic layer is improved.

The catalyst is a fuel cell anode or cathode electrocatalyst, such as: carbon-supported platinum, carbon-supported platinum palladium.

The preparation method of the catalyst slurry, which adjusts the composition and addition order of the organic solvent, so that the catalyst slurry presents a colloidal state;

Specifically: first wet the catalyst with water; under ultrasonic vibration conditions, mix the wet catalyst with isopropanol and/or ethanol, use isopropanol and ethanol to disperse the electrocatalyst, and then add proton conductors to polymerize Continue to ultrasonically oscillate, add ethylene glycol during the oscillating process, and finally form a solution state, highly dispersed homogeneous catalyst slurry;

Then, under the condition of ultrasonic vibration, the above slurry was added dropwise into butyl acetate to form a catalyst slurry in a colloidal state. During this process, the proton conductor polymer in the slurry reacts with butyl acetate to form a colloidal state, and after the slurry is completely transferred to the butyl acetate, the catalyst slurry in a colloidal state is prepared.

The present invention has chosen isopropanol and/or ethanol, ethylene glycol, butyl acetate as solvent, and isopropanol, ethanol, ethylene glycol disperse catalyst and proton conductor polymer uniformly, and butyl acetate can be mixed with proton conductor polymer interaction to form a colloidal state slurry; wherein the use of isopropanol and/or ethanol can improve the dispersion of the catalyst in the slurry, the use of ethylene glycol can increase the viscosity of the slurry, and the use of butyl acetate can make The catalyst slurry forms a colloidal state.

In the colloidal slurry, the proton conductor polymer does not completely wrap the catalyst aggregate, but adsorbs on the surface of the catalyst aggregate, that is, only covers a part of the surface area of the catalyst aggregate, which can improve the utilization rate of the catalyst. At the same time, due to the increase in the size of the catalyst aggregates, after spraying the formed catalyst slurry to form a catalytic layer, the porosity of the electrode catalytic layer can be improved, that is, the pore structure of the catalytic layer can be further improved.

The present invention has the following advantages:

1. In the present invention, the catalyst slurry is made to be in a colloidal state by changing the type of organic solvent and the order of addition, which is very simple and feasible.

2. The colloidal catalyst slurry is beneficial to improve the utilization rate of the catalyst, can reduce the cost, and has a certain application prospect.

2. The colloidal catalyst slurry is conducive to improving the pore structure in the formed catalytic layer, thereby improving the gas mass transfer process and improving battery performance.

Description of drawings

The pore distribution integral curve of Fig. 1 electrode catalytic layer: a catalytic membrane electrode prepared by solution state slurry; b catalytic membrane electrode prepared by colloidal state slurry;

Figure 2 Electrode battery performance: a catalytic membrane electrode prepared by solution state slurry; b catalytic membrane electrode prepared by colloidal state slurry.

Detailed ways

Below in conjunction with example the present invention is described in further detail.

Example 1

质子导体聚合物500mg，继续超声振荡半小时，振荡过程中再加入乙二醇250mg；然后称取2g醋酸丁酯，在超声振荡条件下，将配置好的催化剂浆料滴加到其中，这一过程完成后，即可形成胶体态的催化剂浆料。Weigh 50mg of 50wt.% Pt/C electrocatalyst, wet it with 2ml of distilled water, add 2g of isopropanol, and oscillate evenly with ultrasonic to form a uniform feed liquid, then add 5wt.% of

Proton conductor polymer 500mg, continue to ultrasonically oscillate for half an hour, add ethylene glycol 250mg during the oscillating process; then weigh 2g of butyl acetate, and add the prepared catalyst slurry to it under ultrasonic oscillating conditions, this After the process is completed, a colloidal catalyst slurry can be formed.

115)平铺在抽真空加热台上，热台温度设定为80℃，开启真空泵使膜牢固的吸附于台面上。The proton exchange membrane (

115) Lay flat on the vacuum heating platform, set the temperature of the heating platform at 80°C, turn on the vacuum pump to make the film firmly adsorb on the platform.

Spray the above-mentioned catalyst slurry directly on the surface of the membrane. When spraying at the beginning, control the spraying with a relatively small flow rate (0.1-0.2ml/min). When a thin layer of catalyst is formed on the membrane, the flow rate can be increased appropriately ( 0.4～0.5ml/min), gradually forming a catalytic layer.

When one side is sprayed, turn off the vacuum pump, turn the membrane over, and continue to spray the other side, and finally form a catalytic membrane electrode.

Calculation of the Pt load of the formed electrode: Prepare a batch of electrodes (including spraying area, spraying speed, total amount of slurry, etc.) according to the same method, and then extract 2 to 3 electrodes, and use inductively coupled plasma atomic emission spectrometry to measure Pt content, that is, after the electrode is ashed at high temperature, it is dissolved in aqua regia, a standard solution is prepared, and the concentration of Pt in the solution is measured by an atomic emission spectrometer. To determine the Pt loading of the prepared electrodes.

The porosity of the formed catalytic layer was tested by mercury porosimetry. The type of mercury porosimeter was PoremasterGT60 (Quantachrome), and the pressure range was 1.38×10 ³ ~4.13×10 ⁷ Pa (0.2~0.6×10 ⁴ psi). The contact angle was 140°. The obtained void ratio distribution integral curve is shown in Fig. 1 . It can be seen from the figure that the porosity of the catalytic layer prepared by the colloidal slurry is significantly higher than that of the catalytic layer prepared by the traditional solution slurry.

Assemble the prepared catalytic membrane electrode into a single cell, and then evaluate its polarization curve under the condition of hydrogen and oxygen. The flow rate of hydrogen and oxygen gas is 40/100ml min ^-1 ; completely normal pressure; The temperature is 60°, and the catalytic membrane electrode prepared by the traditional solution state slurry is compared with the catalytic membrane electrode prepared by the colloidal state slurry, as shown in Figure 2. It can be seen from the figure that the performance of the catalytic membrane electrode prepared by the colloidal slurry is improved in the high current density range.

Example 2

The difference from Example 1 is that the electrocatalyst used is a Pt-Pd alloy catalyst.

Example 3

The difference with example 1 is: the proton exchange membrane adopted is 212 film.

Example 4

The difference from Example 1 is that the spraying temperature is set to 80°C.

Claims (3)

1. one kind prepares the catalyst pulp that fuel cell catalytic membrane electrode is used, and it is characterized in that:

Described catalyst pulp is a colloidal state, and it is by catalyst, proton conductor polymer

Water, isopropyl alcohol and/or ethanol, ethylene glycol, butyl acetate are formed catalyst, proton conductor polymer The mass ratio of water, isopropyl alcohol and/or ethanol, ethylene glycol, butyl acetate is 2: 1: 8: 80: 10: 80.

2. according to the described catalyst pulp of claim 1, it is characterized in that: described catalyst is anode of fuel cell or electrocatalyst for cathode.

3. the preparation method of the described catalyst pulp of claim 1 is characterized in that: it is by the composition and the interpolation order of modulation organic solvent, so that catalyst pulp presents colloidal state;

Be specially: at first that catalyzer with water is wetting; Under the supersonic oscillations condition, catalyst after wetting is mixed with isopropyl alcohol and/or ethanol, utilize isopropyl alcohol and/or ethanol that catalyst is scatter, add the proton conductor polymer then, continue sonic oscillation, add ethylene glycol in the oscillatory process again, finally form homogeneous catalyst pulp solution state, high degree of dispersion;

Under the condition of supersonic oscillations, above-mentioned slurry dropwise is added drop-wise in the butyl acetate then, forms the catalyst pulp of colloidal state.

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