CN103367775B - A kind of preparation method of direct liquid fuel battery membrane electrode - Google Patents

Abstract

The invention provides a method for preparing a membrane electrode of a direct liquid fuel cell. Nafion solution, an alcohol solvent, water and a catalyst are mixed, then sprayed onto a transfer film to form a catalytic layer, and then transferred onto a Nafion film to obtain Membrane electrode; the volume V _Nafion of the Nafion solution satisfies V _Nafion =ρ ₁ *m _loading *S/(ρ ₂ *ω*ρ ₃ *a). Compared with the prior art, according to the loading capacity of the catalyst per unit area of the membrane electrode, the present invention analyzes from a microscopic point of view that the volume of the catalyst particle and the Nafion particle is in a certain ratio, so that the volume of the Nafion solution satisfies specific conditions and reduces its impact on the catalyst. The coating improves the utilization rate of the catalyst in the catalytic layer and improves the electrochemical performance of the battery; in addition, using the transfer printing method to transfer the catalytic layer to the Nafion membrane can improve the binding between the two, thereby reducing the the battery resistance.

Description

A kind of preparation method of membrane electrode of direct liquid fuel cell

technical field

The invention belongs to the technical field of fuel cells, in particular to a method for preparing membrane electrodes of direct liquid fuel cells.

Background technique

A fuel cell is a power generation device that converts chemical energy directly into electrical energy through an electrochemical reaction. Compared with traditional energy conversion systems, fuel cells have many advantages, such as: not limited by the Carnot cycle, high energy conversion efficiency; the product is usually water, and has little environmental pollution. Therefore, fuel cells have received increasing attention in recent years.

A direct liquid fuel cell is a device that generates electricity through liquid fuels such as methanol, ethanol, formic acid, etc. through a membrane electrode composed of a proton exchange membrane and a catalyst electrode. Taking a direct methanol battery as an example, its working principle is as follows:

Anode reaction: CH ₃ OH+H ₂ O→CO ₂ +6H ⁺ +6e ^-

Cathodic reaction: 3/2O ₂ +6H ⁺ +6e ^- → 3H ₂ O

The total reaction is: CH ₃ OH+3/2O ₂ →CO ₂ +2H ₂ O

Membrane electrode (MEA) is one of the core components of direct liquid fuel cells, which includes sequentially arranged: anode diffusion layer, anode catalyst layer, proton exchange membrane, cathode catalyst layer and cathode diffusion layer.

Existing membrane electrodes are usually prepared according to the following method: first, the anode catalyst and the cathode catalyst are loaded on the surface of the anode diffusion layer and the cathode diffusion layer by scraping or spraying to obtain the anode catalyst layer and the cathode catalyst layer; then The proton exchange membrane is placed between the anode catalyst layer and the cathode catalyst layer, and they are pressed together by a hot pressing method to obtain a membrane electrode. On this basis, in order to improve the electrochemical performance of the fuel cell, corresponding improvements have been made in the prior art from the aspects of membrane electrode structure, catalyst and proton exchange membrane.

The Chinese patent with publication number CN101222049A discloses a catalyst coated membrane, including its membrane electrode assembly (MEA), its preparation method, and a fuel cell including the membrane electrode assembly. The catalyst coated membrane (CCM) includes an anode catalyst layer, which includes a first catalyst layer composed of a non-supported catalyst and a second catalyst layer composed of a supported catalyst; the cathode catalyst layer is composed of a supported catalyst. This catalyst coating film can degrade the interface resistance between the electrode and the electrolyte membrane, reduce the amount of catalyst used, and reduce the thickness deviation in the electrode layer. The fuel cell using the membrane electrode assembly has high catalyst activity and improves The performance of the battery such as output voltage, output density, efficiency, etc.

The Chinese patent with the application number 200810046956.X discloses a fuel cell catalyst layer based on a porous substrate, a membrane electrode and a preparation method thereof. The porous proton exchange membrane is impregnated with a catalyst slurry and then dried and hot-pressed to form a catalytic layer, which is then coated with a surface coating. Carbon paper with a microporous layer or a water management layer is hot-pressed, and then hot-pressed with a proton exchange membrane to obtain a membrane electrode.

The Chinese patent with the application number 200310102638.8 discloses a membrane electrode structure for proton exchange membrane fuel cells and its preparation method. It uses a catalytic layer, which consists of a hydrophilic catalytic layer and a hydrophobic catalytic layer covering the surface of the membrane. Composite bilayer composition. This electrode structure is conducive to the discharge of CO ₂ from the anode, the diffusion of O ₂ from the cathode and the discharge of water, reduces the mass transfer polarization loss, increases the limiting current density, and improves the electrode performance and the utilization rate of the precious metal catalyst.

The Chinese patent application number 200980106031.2 discloses a method for manufacturing a membrane electrode assembly for solid polymer fuel cells, which uses a mixture of carbon fibers with a fiber diameter of 1 μm to 50 μm and a proton-conducting polymer to form a gas diffusion layer. Good results have been achieved.

Although the above-mentioned different methods can improve the electrochemical performance of the direct liquid fuel cell, the relationship between the catalyst in the catalytic layer and the components of the Nafion solution has not always been a clear value during the preparation of the membrane electrode. The relationship between the catalyst and Nafion solution is different in different research groups, and the amount of Nafion solution has a direct impact on the performance of the catalytic layer. If the Nafion solution is too small, the catalyst will be dispersed unevenly. If the Nafion solution is too much, the catalyst ion The coating of the catalyst is more severe, resulting in a decrease in the active sites and a lower utilization rate of the catalyst.

When Cao et al. prepared MEA, the mass fraction of Nafion solution in the anode and cathode catalyst layer was 15% and 20% respectively (JianyuCao, MeiChen, JiChen, ShenjunWang, ZhiqingZou, ZhilinLi, DanielL.Akins, HuiYang.IntJHydrogenEnerg, 2010,35 , 4622-4629). When Abdelkareem et al. prepared MEA, the mass fractions of Nafion solution in the anode and cathode catalyst layers were 15% and 10% respectively (Mohammad Ali Abdelkareem, Nobuyoshi Nakagawa, JPowerSources, 2006, 162, 114-123). When Zhang et al. prepared MEA, the mass fraction of Nafion solution in the anode and cathode catalytic layers was 20% (Jian Zhang, Geping Yin, Zhenbo Wang, Qinzhi Lai, Kedi Cai, JPower Sources, 2007, 165, 73-81). Liang et al. used 0.8 mg/cm ² of Nafion solution in the anode and cathode catalyst layers when preparing MEA (ZXLiang, TS Zhao, C.Xu, JB Xu, ElectrochimActa, 2007, 53, 894-902). However, when Song et al. prepared MEA, the mass ratio of catalyst and Nafion in the anode and cathode catalytic layers was 1:0.12 (KahyoungSong, HankyuLee, HeetakKim, ElectrochimActa, 2007, 53, 637-643). Among these parameters, the amount of Nafion solution is determined according to respective empirical parameters, resulting in too much amount, serious coating of catalyst ions, and low catalyst utilization.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a direct liquid fuel cell membrane electrode. The membrane electrode prepared by the method has a higher catalyst utilization rate and better electrochemical performance.

The invention provides a method for preparing a direct liquid fuel cell membrane electrode, comprising:

A) Nafion solution, alcohol solvent, water and catalyst are mixed, then sprayed onto the transfer membrane to form a catalytic layer, and then transferred onto the Nafion membrane to obtain a membrane electrode;

The volume V _Nafion of the Nafion solution satisfies V _Nafion =ρ ₁ *m _loading *S/(ρ ₂ *ω*ρ ₃ *a);

Wherein, ρ ₁ is the density of pure Nafion, ρ ₂ is the density of Nafion solution, ρ ₃ is the density of catalyst, m _{loading is the loading capacity} of catalyst per unit area of membrane electrode, S is the total area of membrane electrode, ω is Nafion solution The mass fraction of a is a natural number ranging from 0.5 to 1.

Preferably, the step A) is specifically:

The Nafion solution is divided into the Nafion solution of volume I and the Nafion solution of volume II;

A1) Mix volume I of Nafiion solution, alcohol solvent, water and catalyst, and then spray it on the transfer film to form a catalytic layer;

A2) Spraying the Nafion solution of volume II onto the catalytic layer to form a Nafion layer, and then transferring the Nafion layer and the catalytic layer onto the Nafion membrane to obtain a membrane electrode.

Preferably, the volume of the Nafion solution of volume I is 80% to 90% of the volume of the Nafion solution.

Preferably, the m _{loading is} 2-5 mg/cm ² .

Preferably, the catalyst is a PtRu black catalyst, a PtRu/C catalyst, a Pd-based catalyst, a Pt black catalyst or a Pt/C catalyst.

Preferably, the volume Vwater of the _water satisfies _Vwater = _xmcatalyst /795; wherein x is a natural number from 2 to 3, and mcatalyst is the mass of the _catalyst .

Preferably, the volume of the alcohol solvent is 15-25 times of V _Nafion .

Preferably, the alcoholic solvent is isopropanol.

Preferably, the transfer film is a PTFE film, polyimide film, polydimethylsiloxane or Al sheet.

Preferably, the Nafion solution, alcoholic solvent, water and catalyst are mixed according to the following method: add water, Nafion solution and alcoholic solvent to the catalyst in sequence for mixing.

The invention provides a method for preparing a membrane electrode of a direct liquid fuel cell. Nafion solution, an alcohol solvent, water and a catalyst are mixed, then sprayed onto a transfer film to form a catalytic layer, and then transferred onto a Nafion film to obtain Membrane electrode; the volume V _{Nafion of} the Nafion solution satisfies V _Nafion =ρ ₁ *m _loading *S/(ρ ₂ *ω*ρ ₃ *a); wherein, ρ ₁ is the density of pure Nafion, and ρ ₂ is Nafion The density of the solution, ρ3 is the density _of the catalyst, m _{loading is} the loading of the catalyst per unit area of the membrane electrode, S is the total area of the membrane electrode, ω is the mass fraction of the Nafion solution, and a is a natural number from 0.5 to 1. Compared with the prior art, according to the loading capacity of the catalyst per unit area of the membrane electrode, the present invention analyzes from a microscopic point of view that the volume of the catalyst particle and the Nafion particle is in a certain ratio, so that the volume of the Nafion solution satisfies specific conditions and reduces its impact on the catalyst. The coating of the catalyst layer improves the utilization rate of the catalyst in the catalytic layer, thereby reducing the catalyst loading and improving the electrochemical performance of the battery; using the transfer film to transfer the catalytic layer to the Nafion membrane can improve the catalytic layer and the Nafion membrane. The combination between them reduces the resistance of the battery.

Description of drawings

Fig. 1 is the mixing schematic diagram of membrane electrode when microscopic catalyst particle and microscopic Nafion particle ratio of the present invention are 1:1.5;

Fig. 2 is the discharge voltage and discharge power graph of the direct methanol fuel cell obtained in Example 1 of the present invention and the direct methanol fuel cell obtained in Comparative Example 1;

Fig. 3 is the long-time discharge voltage curve diagram of the direct methanol fuel cell obtained in embodiment 1, embodiment 2, embodiment 3 of the present invention and the direct methanol fuel cell obtained in comparative example 1;

Fig. 4 is the discharge voltage and discharge power curves of the direct methanol fuel cell obtained in Example 1 of the present invention, the direct methanol fuel cell obtained in Example 2, and the direct methanol fuel cell obtained in Comparative Example 1;

Fig. 5 is the discharge voltage and the discharge power graph of the direct methanol fuel cell that embodiment 1 of the present invention, embodiment 2, embodiment 3 and comparative example 1 obtain;

FIG. 6 is a graph showing the discharge voltage and discharge power curves of the direct methanol fuel cells obtained in Example 4 and Comparative Example 1 of the present invention.

Detailed ways

The invention provides a method for preparing a membrane electrode of a direct liquid liquid fuel cell, comprising: mixing Nafion solution, alcohol solvent, water and a catalyst, then spraying it on the transfer film to form a catalytic layer, and then transferring it to the Nafion film above, the membrane electrode is obtained; the volume V _Nafion of the Nafion solution satisfies V _Nafion =ρ ₁ *m _loading *S/(ρ ₂ *ω*ρ ₃ *a); where, ρ ₁ is the density of pure Nafion, ρ ₂ is the density of the Nafion solution, ρ ₃ is the density of the catalyst, m is the _{loading capacity} of the catalyst per unit area of the membrane electrode, S is the total area of the membrane electrode, ω is the mass fraction of the Nafion solution, and a is a natural number from 0.5 to 1 .

The present invention has no special limitation on the sources of all raw materials, which can be commercially available. Wherein, the Nafion solution is a Nafion solution well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferably a commercially available Nafion solution with a mass fraction of 5%; The well-known alcohol solvents used to prepare membrane electrodes can be used without special restrictions. In the present invention, it is preferably isopropanol; the water is preferably deionized water; the catalyst is divided into an anode catalyst and a cathode catalyst, Wherein the anode catalyst is preferably a PtRu black catalyst, a PtRu/C catalyst or a Pd-based catalyst, and the cathode catalyst is preferably a Pt black catalyst or a Pt/C catalyst.

The volume V _Nafion of the Nafion solution satisfies V _Nafion =ρ ₁ *m _loading *S/(ρ ₂ *ω*ρ ₃ *a), where ρ ₁ is the density of pure Nafion, which is 1.4g/cm ³ ; m The _{carrying capacity} is the carrying capacity of the catalyst per unit area of the membrane electrode, preferably ² to 5 mg/cm in the present invention; a is the ratio of catalyst particles to Nafion particles, which is a natural number of 0.5 to 1, that is, the ratio of catalyst particles to Nafion particles is (1:1) to (1:2), more preferably a natural number of 0.6 to 0.7.

According to the loading capacity of the catalyst per unit area of the membrane electrode, the present invention analyzes from a microscopic point of view that the volume of the catalyst particle and the Nafion particle is in a certain ratio (1:1) to (1:2), so that the volume of the Nafion solution satisfies specific conditions, It reduces its coating on the catalyst, improves the utilization rate of the catalyst in the catalytic layer, thereby reducing the catalyst loading and improving the electrochemical performance of the battery; and the Nafion solution in the catalyst can form a proton transfer channel to conduct protons .

The volume of the alcoholic solvent used for mixing is preferably 15 to 25 times the volume of the Nafion solution, more preferably 19 to 22 times.

The volume of water used, V _water , preferably satisfies V _water = xm _catalyst /795; wherein x is a natural number of 2 to 3, preferably a natural number of 2.4 to 2.6, more preferably 2.5; m _catalyst is the mass of the catalyst.

According to the present invention, the above-mentioned raw material Nafion solution, alcoholic solvent, water and catalyst are mixed, and the mixing is preferably carried out according to the following method: add water, Nafion solution and alcoholic solvent to the catalyst in sequence to mix, preferably after mixing, use ultrasonic to disperse.

After mixing, it is sprayed onto the transfer film to form a catalytic layer. Wherein, the transfer film is a transfer film well-known to those skilled in the art, and there is no special limitation. In the present invention, it is preferably PTFE film, polyimide film, polydimethylsiloxane or Al thin film. , more preferably a PTFE membrane.

Then, the catalytic layer was transferred onto the Nafion membrane by a transfer printing method to obtain a membrane electrode.

In the present invention, the mixed Nafion solution, alcohol solvent, water and catalyst are sprayed on the transfer film, and then transferred to the Nafion film, which can improve the bonding between the catalytic layer and the Nafion film, thereby reducing the resistance of the battery , while also avoiding the deformation of the Nafion membrane caused by direct spraying of the mixed slurry onto the Nafion membrane.

In order to further increase the bonding strength between the catalytic layer and the Nafion membrane, the present invention preferably proceeds according to the following steps: the Nafion solution is divided into the Nafion solution of the volume I and the Nafion solution of the volume II; A1) the Nafion solution of the volume I, the alcohol solvent, Water is mixed with the catalyst, and then sprayed onto the transfer film to form a catalytic layer; A2) Nafion solution of volume II is sprayed onto the catalytic layer to form a Nafion layer, and then the Nafion layer and the catalytic layer are transferred to the Nafion film , to obtain a membrane electrode.

Wherein, the volume of the Nafion solution of volume 1 is 80%～90% of the Nafion solution volume, preferably 80%～85%.

Spray 10% to 20% of the Nafion solution volume on the catalytic layer to form a Nafion layer, and then transfer it to the Nafion film. The catalytic layer is combined with the Nafion film through the Nafion layer. The Nafion layer and the Nafion film are the same substance. Strong, so that the membrane electrode is not easy to peel off under long-term application conditions.

In order to further illustrate the present invention, a method for preparing a direct liquid fuel cell membrane electrode provided by the present invention will be described in detail below in conjunction with examples.

The reagents used in the following examples are all commercially available.

Example 1

1.1 The loading capacity of the anode and cathode catalysts is set to 5mg/cm ² , the anode catalyst is a PtRu (1:1) black catalyst, the microscopic particle density is 16.9g/cm ³ , the cathode catalyst is a Pt black catalyst, and the microscopic particle density is 21.45g/cm ³ ; the volume ratio of PtRu (1:1) black catalyst microscopic particles to microscopic Nafion particles is 1:1.5, that is (5*10 ^-3 /16.9): (V ₁ *0.875*5%/1.4S) =1:1.5, where V ₁ is the volume of Nafion solution for the anode, S is the electrode area to be sprayed, the mass fraction of commonly used Nafion solution is 5%, the density is 0.875g/cm ³ , and the density of pure Nafion is 1.4g/cm ^3. According to the electrode area, the volume of Nafion solution required by the anode can be calculated; the volume ratio of Pt black catalyst microscopic particles to microscopic Nafion particles is 1:1.5, that is (5*10 ^-3 /21.45): (V ₂ *0.875*5 %/1.4S)=1:1.5, the volume V ₂ of Nafion solution required by the cathode can be calculated according to the electrode area.

1.2 Calculate the amount m ₁ of the anode catalyst according to the area of the electrode to be sprayed and the loading of the catalyst, and add 2.5 m ₁ /795 of deionized water and 80% V of Nafion solution to the m ₁ anode PtRu (1:1) black catalyst in sequence ₁ and isopropanol 20V ₁ and disperse it uniformly by ultrasonic stirring, then spray it directly onto the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₁ Nafion solution onto the catalytic layer to form Nafion layer, prepared as an anode electrode.

1.3 Calculate the amount of cathode catalyst m ₂ according to the electrode area to be sprayed and the loading of the catalyst, and add deionized water 2.5m ₂ /795, Nafion solution 80% V ₂ and isopropanol to the m ₂ cathode Pt black catalyst in sequence 20V ₂ and disperse it evenly by ultrasonic stirring, and then spray it directly on the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₂ Nafion solution on the catalytic layer to form a Nafion layer and prepare it as a cathode electrode.

1.4 Put the anode electrode obtained in 1.2, the Nafion115 membrane and the cathode electrode obtained in 1.3 in a hot press at 130°C and 3MPa for 90s to transfer the electrode, and after the transfer, remove the PTFE membrane on both sides of the cathode and anode. Get the electrodes.

1.5 Add 100ml of deionized water and 20ml of isopropanol to 18g of VulcanXC-72R carbon powder, and disperse them evenly by stirring, then add 5ml of PTFE solution with a mass concentration of 20%, and disperse evenly to obtain a slurry, which can be scraped by hand Prepare a microporous layer with a loading capacity of 2mg/ ^cm2 on the cathode carbon paper TPG-H-030 (20wt% PTFE), and then put it in a muffle furnace for 300°C for 30min. The cathode carbon paper and the microporous layer constitute the diffusion layer .

1.6 Use TPG-H-060 (10wt% PTFE) carbon paper directly as the diffusion layer on the anode side, the diffusion layer obtained in 1.5 on the cathode side, and install the electrode obtained in 1.4 between the cathode diffusion layer and the anode diffusion layer to form a " Self-breathing" passive direct methanol fuel cell.

When the ratio of microscopic catalyst particles to microscopic Nafion particles is 1:1.5, its mixed schematic diagram as a membrane electrode is shown in Figure 1, where a is catalyst particles, b is Nafion particles, and c is Nafion115 membrane. It can be seen from Figure 1 that the contact between Nafion particles is good, a network structure can be formed in the catalytic layer, and the proton conduction is smooth.

The discharge performance of the direct methanol fuel cell obtained in 1.6 was tested with a 3mol/L methanol solution at room temperature of 15°C, and the discharge voltage and discharge power curves were obtained, as shown in Figure 2, Figure 4, and Figure 5.

At room temperature of 15°C, the direct methanol fuel cell obtained in 1.6 was subjected to a long-term discharge test at a constant current density of 50 mA/cm ^-2 with 3 mol/L and 7.5 ml of methanol solution, and its voltage curve was obtained, as shown in a in Fig. 3 Show.

Example 2

2.1 The loading capacity of both anode and cathode catalysts is set to 5mg/cm ² , the anode catalyst is PtRu (1:1) black catalyst, the microscopic particle density is 16.9g/cm ³ , the cathode catalyst is Pt black catalyst, and the microscopic particle density is 21.45g/cm ³ ; the volume ratio of PtRu (1:1) black catalyst microscopic particles to microscopic Nafion particles is 1:1, that is (5*10 ^-3 /16.9): (V ₁ *0.875*5%/1.4S) =1:1, where V ₁ is the volume of Nafion solution for the anode, S is the electrode area to be sprayed, the mass fraction of commonly used Nafion solution is 5%, the density is 0.875g/cm ³ , and the density of pure Nafion is 1.4g/cm ^3. According to the electrode area, the volume of Nafion solution required by the anode can be calculated; the volume ratio of Pt black catalyst microscopic particles to microscopic Nafion particles is 1:1, that is (5*10 ^-3 /21.45): (V ₂ *0.875*5 %/1.4S)=1:1, the volume V ₂ of Nafion solution required by the cathode can be calculated according to the electrode area.

2.2 Calculate the amount m ₁ of the anode catalyst according to the area of the electrode to be sprayed and the loading of the catalyst, and add 2.5 m ₁ /795 of deionized water and 80% V of Nafion solution to the m ₁ anode PtRu (1:1) black catalyst in sequence ₁ and isopropanol 20V ₁ and disperse it uniformly by ultrasonic stirring, then spray it directly onto the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₁ Nafion solution onto the catalytic layer to form Nafion layer, prepared as an anode electrode.

2.3 Calculate the amount of cathode catalyst m ₂ according to the area of the electrode to be sprayed and the load of the catalyst, and add deionized water 2.5m ₂ /795, Nafion solution 80% V ₂ and isopropanol to the m ₂ cathode Pt black catalyst in sequence 20V ₂ and disperse it evenly by ultrasonic stirring, and then spray it directly on the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₂ Nafion solution on the catalytic layer to form a Nafion layer and prepare it as a cathode electrode.

2.4 Transfer the anode electrode, Nafion115 film obtained in 2.2 and the cathode electrode obtained in 2.3 to the hot press at 130°C and 3MPa for 90s to transfer the electrode. After the transfer, remove the PTFE film on both sides of the cathode and anode. Get the electrodes.

2.5 Add 100ml of deionized water and 20ml of isopropanol to 18g of VulcanXC-72R carbon powder, and disperse it evenly by stirring, then add 5ml of PTFE solution with a mass concentration of 20%, and disperse evenly to obtain a slurry, which is scraped by hand Prepare a microporous layer with a loading capacity of 2mg/ ^cm2 on the cathode carbon paper TPG-H-030 (20wt% PTFE), and then put it in a muffle furnace for 300°C for 30min. The cathode carbon paper and the microporous layer constitute the diffusion layer .

2.6 TPG-H-060 (10wt% PTFE) carbon paper is directly used as the diffusion layer on the anode side, the diffusion layer obtained in 2.5 is used on the cathode side, and the electrode obtained in 2.4 is installed between the cathode diffusion layer and the anode diffusion layer to form a " Self-breathing" passive direct methanol fuel cell.

The direct methanol fuel cell obtained in 2.6 was tested for discharge performance with 3mol/L methanol solution at room temperature of 15°C, and its discharge voltage and discharge power curves were obtained, as shown in Figures 4 to 5.

At room temperature of 15°C, the direct methanol fuel cell obtained in 2.6 was subjected to a long-term discharge test at a constant current density of 50 mA/cm ^-2 with 3 mol/L and 7.5 ml of methanol solution, and its voltage curve was obtained, as shown in b in Fig. 3 Show.

Example 3

3.1 The loading capacity of both anode and cathode catalysts is set to 5mg/cm ² , the anode catalyst is PtRu (1:1) black catalyst, the microscopic particle density is 16.9g/cm ³ , the cathode catalyst is Pt black catalyst, and the microscopic particle density is 21.45g/cm ³ ; the volume ratio of PtRu (1:1) black catalyst microscopic particles to microscopic Nafion particles is 1:2, that is (5*10 ^-3 /16.9): (V ₁ *0.875*5%/1.4S) =1:2, where V ₁ is the volume of Nafion solution for the anode, S is the electrode area to be sprayed, the mass fraction of commonly used Nafion solution is 5%, the density is 0.875g/cm ³ , and the density of pure Nafion is 1.4g/cm ^3. According to the electrode area, the volume of Nafion solution required by the anode can be calculated; the volume ratio of Pt black catalyst microscopic particles to microscopic Nafion particles is 1:2, that is (5*10 ^-3 /21.45): (V ₂ *0.875*5 %/1.4S)=1:2, the volume V ₂ of Nafion solution required by the cathode can be calculated according to the electrode area.

3.2 Calculate the amount m ₁ of the anode catalyst according to the area of the electrode to be sprayed and the loading of the catalyst, and add 2.5 m ₁ /795 of deionized water and 80% V of Nafion solution to the m ₁ anode PtRu (1:1) black catalyst in sequence ₁ and isopropanol 20V ₁ and disperse it uniformly by ultrasonic stirring, then spray it directly onto the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₁ Nafion solution onto the catalytic layer to form Nafion layer, prepared as an anode electrode.

3.3 Calculate the amount of cathode catalyst m ₂ according to the electrode area to be sprayed and the loading of the catalyst, and add deionized water 2.5m ₂ /795, Nafion solution 80% V ₂ and isopropanol to the m ₂ cathode Pt black catalyst in sequence 20V ₂ and disperse it evenly by ultrasonic stirring, and then spray it directly on the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₂ Nafion solution on the catalytic layer to form a Nafion layer and prepare it as a cathode electrode.

3.4 Put the anode electrode obtained in 3.2, Nafion115 film and the cathode electrode obtained in 3.3 in a hot press at 130°C and 3MPa for 90s to transfer the electrodes. After the transfer, remove the PTFE films on both sides of the cathode and anode. Get the electrodes.

3.5 Add 100ml of deionized water and 20ml of isopropanol to 18g of VulcanXC-72R carbon powder, and disperse them evenly by stirring, then add 5ml of PTFE solution with a mass concentration of 20%, and disperse evenly to obtain a slurry, which can be scraped by hand Prepare a microporous layer with a loading capacity of 2mg/ ^cm2 on the cathode carbon paper TPG-H-030 (20wt% PTFE), and then put it in a muffle furnace for 300°C for 30min. The cathode carbon paper and the microporous layer constitute the diffusion layer .

3.6 Use TPG-H-060 (10wt% PTFE) carbon paper directly as the diffusion layer on the anode side, the diffusion layer obtained in 3.5 on the cathode side, and install the electrode obtained in 3.4 between the cathode diffusion layer and the anode diffusion layer to form a " Self-breathing" passive direct methanol fuel cell.

The discharge performance of the direct methanol fuel cell obtained in 3.6 was tested with 3mol/L methanol solution at room temperature of 15°C, and the discharge voltage and discharge power curves were obtained, as shown in Figure 5.

At room temperature of 15°C, the direct methanol fuel cell obtained in 3.6 was subjected to a long-term discharge test with 3mol/L, 7.5ml methanol solution at a constant current density of 50mA/cm ^-2 , and its voltage curve was obtained, as shown in c in Figure 3 Show.

Example 4

4.1 The loading capacity of the anode and cathode catalysts are both set to 2mg/cm ² , the anode catalyst is a PtRu (1:1) black catalyst, the microscopic particle density is 16.9g/cm ³ , the cathode catalyst is a Pt black catalyst, and the microscopic particle density is 21.45g/cm ³ ; the volume ratio of PtRu (1:1) black catalyst microscopic particles to microscopic Nafion particles is 1:1.5, that is (5*10 ^-3 /16.9): (V ₁ *0.875*5%/1.4S) =1:1.5, where V ₁ is the volume of Nafion solution for the anode, S is the electrode area to be sprayed, the mass fraction of commonly used Nafion solution is 5%, the density is 0.875g/cm ³ , and the density of pure Nafion is 1.4g/cm ^3. According to the electrode area, the volume of Nafion solution required by the anode can be calculated; the volume ratio of Pt black catalyst microscopic particles to microscopic Nafion particles is 1:1.5, that is (5*10 ^-3 /21.45): (V ₂ *0.875*5 %/1.4S)=1:1.5, the volume V ₂ of Nafion solution required by the cathode can be calculated according to the electrode area.

4.2 Calculate the amount m ₁ of the anode catalyst according to the area of the electrode to be sprayed and the loading of the catalyst, and add 2.5 m ₁ /795 of deionized water and 80% V of Nafion solution to the m ₁ anode PtRu (1:1) black catalyst in sequence ₁ and isopropanol 20V ₁ and disperse it uniformly by ultrasonic stirring, then spray it directly onto the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₁ Nafion solution onto the catalytic layer to form Nafion layer, prepared as an anode electrode.

4.3 Calculate the amount of cathode catalyst m ₂ according to the electrode area to be sprayed and the loading capacity of the catalyst, and add deionized water 2.5m ₂ /795, Nafion solution 80% V ₂ and isopropanol to the m ₂ cathode Pt black catalyst in sequence 20V ₂ and disperse it evenly by ultrasonic stirring, and then spray it directly on the PTFE membrane with a sprayer to form a catalytic layer, and then spray the remaining 20% V ₂ Nafion solution on the catalytic layer to form a Nafion layer and prepare it as a cathode electrode.

4.4 Put the anode electrode obtained in 4.2, Nafion115 film and the cathode electrode obtained in 4.3 in a hot press at 130°C and 3MPa for 90s to transfer the electrodes. After the transfer, remove the PTFE films on both sides of the cathode and anode. Get the electrodes.

4.5 Add 100ml of deionized water and 20ml of isopropanol to 18g of VulcanXC-72R carbon powder, and disperse it evenly by stirring, then add 5ml of PTFE solution with a mass concentration of 20%, and disperse evenly to obtain a slurry, which is scraped by hand Prepare a microporous layer with a loading capacity of 2mg/ ^cm2 on the cathode carbon paper TPG-H-030 (20wt% PTFE), and then put it in a muffle furnace for 300°C for 30min. The cathode carbon paper and the microporous layer constitute the diffusion layer .

4.6 Use TPG-H-060 (10wt% PTFE) carbon paper directly as the diffusion layer on the anode side, the diffusion layer obtained in 4.5 on the cathode side, and install the electrode obtained in 4.4 between the cathode diffusion layer and the anode diffusion layer to form a " Self-breathing" passive direct methanol fuel cell.

The discharge performance of the direct methanol fuel cell obtained in 4.6 was tested with 3mol/L methanol solution at room temperature of 15°C, and the discharge voltage and discharge power curves were obtained, as shown in Figure 6.

Comparative example 1

The mass fraction of Nafion solution is 5%, and the density is 0.875g/cm ³ .

1.1 Calculate the amount m ₁ of the anode catalyst PtRu (1:1) black catalyst according to the electrode area to be sprayed and the catalyst loading of 5 mg/cm ² , and add deionization to the m ₁ anode PtRu (1:1) black catalyst in sequence Water 2.5m ₁ /795, Nafion solution and isopropanol are dispersed evenly by ultrasonic stirring to obtain a slurry. The mass of Nafion solution is 10% of the mass of the slurry, and then sprayed directly onto the PTFE membrane with a sprayer to prepare into the anode electrode.

_1.2 Calculate the amount m2 of the cathode catalyst Pt black catalyst based _on the area of the electrode to be sprayed and the catalyst loading of 5mg/ ^cm2 , and add deionized water _2.5m2 /795, Nafion solution and Isopropanol was dispersed evenly by ultrasonic stirring to obtain a slurry. The mass of the Nafion solution was 15% of the mass of the slurry, and then sprayed directly onto the PTFE membrane with a sprayer to prepare a cathode electrode.

1.3 Put the anode electrode obtained in 1.1, the Nafion115 membrane and the cathode electrode obtained in 1.2 in a hot press at 130°C and 3MPa for 90 seconds to transfer the electrode. After the transfer, remove the PTFE membrane on both sides of the cathode and anode. Get the electrodes.

1.4 Add 100ml of deionized water and 20ml of isopropanol to 18g of VulcanXC-72R carbon powder, and disperse it evenly by stirring, then add 5ml of PTFE solution with a mass concentration of 20%, and disperse evenly to obtain a slurry, which is scraped by hand Prepare a microporous layer with a loading capacity of 2mg/ ^cm2 on the cathode carbon paper TPG-H-030 (20wt% PTFE), and then put it in a muffle furnace for 300°C for 30min. The cathode carbon paper and the microporous layer constitute the diffusion layer .

1.5 TPG-H-060 (10wt% PTFE) carbon paper is directly used as the diffusion layer on the anode side, the diffusion layer obtained in 1.4 is used on the cathode side, and the electrode obtained in 1.3 is installed between the cathode diffusion layer and the anode diffusion layer to form a " Self-breathing" passive direct methanol fuel cell.

The direct methanol fuel cell obtained in 1.6 was tested for discharge performance with 3mol/L methanol solution at room temperature of 15°C, and its discharge voltage and discharge power curves were obtained, as shown in Fig. 2, Fig. 4-6.

At room temperature of 15°C, the direct methanol fuel cell obtained in 1.6 was subjected to a long-term discharge test at a constant current density of 50 mA/cm ^-2 with 3 mol/L and 7.5 ml of methanol solution, and its voltage curve was obtained, as shown in d in Figure 3 Show.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A preparation method of direct liquid fuel cell membrane electrode, is characterized in that, step comprises: A) Nafion solution, alcohol solvent, water and catalyst are mixed, then sprayed onto the transfer film to form a catalytic layer, and then transferred onto the Nafion film to obtain a membrane electrode; The volume V _Nafion of the Nafion solution satisfies V _Nafion =ρ ₁ *m _load *S/(ρ ₂ *ω*ρ ₃ *a); Wherein, ρ ₁ is the density of pure Nafion, ρ ₂ is the density of Nafion solution, ρ ₃ is the density of catalyst, m _{loading is the loading capacity} of catalyst per unit area of membrane electrode, S is the total area of membrane electrode, ω is Nafion solution The mass fraction of a is a natural number ranging from 0.5 to 1. 2. preparation method according to claim 1, is characterized in that, described step A) is specially: The Nafion solution is divided into the Nafion solution of volume I and the Nafion solution of volume II; A1) Nafion solution of volume 1, alcohol solvent, water and catalyst are mixed, and then sprayed onto the transfer film to form a catalytic layer; A2) Spraying the Nafion solution of volume II onto the catalytic layer to form a Nafion layer, and then transferring the Nafion layer and the catalytic layer to the Nafion membrane to obtain a membrane electrode. 3. preparation method according to claim 2, is characterized in that, the volume of the Nafion solution of described volume 1 is 80%～90% of Nafion solution volume. 4. The preparation method according to claim 1, characterized in that the m _{loading is} 2-5 mg/cm ² . 5. The preparation method according to claim 1, wherein the catalyst is a PtRu black catalyst, a PtRu/C catalyst, a Pd-based catalyst, a Pt black catalyst or a Pt/C catalyst. 6. The preparation method according to claim 1, wherein the volume Vwater of the _water satisfies _Vwater = _xmcatalyst /795; wherein x is a natural number from 2 to 3, and mcatalyst is the mass of the _catalyst . 7. The preparation method according to claim 1, characterized in that the volume of the alcohol solvent is 15-25 times of V _Nafion . 8. The preparation method according to claim 1, characterized in that, the alcoholic solvent is Virahol. 9. The preparation method according to claim 1, wherein the transfer film is a PTFE film, polyimide film, polydimethylsiloxane or Al flake. 10. The preparation method according to claim 1, wherein the Nafion solution, the alcoholic solvent, water and the catalyst are mixed according to the following method: adding water, the Nafion solution and the alcoholic solvent in the catalyst to mix successively.