WO2014100912A1

WO2014100912A1 - Gas diffusion electrode and preparation method thereof

Info

Publication number: WO2014100912A1
Application number: PCT/CN2012/001722
Authority: WO
Inventors: 王峰; 曹寅亮; 刘景军; 李志林
Original assignee: 北京化工大学
Priority date: 2012-12-24
Filing date: 2012-12-24
Publication date: 2014-07-03
Also published as: CN104603331B; EP2937449B1; JP2016505716A; JP6128709B2; EP2937449A1; CN104603331A; EP2937449A4

Abstract

Provided are a gas diffusion electrode and a preparation method thereof. The gas diffusion electrode comprises a current collector 1, a gas diffusion layer 2, a gas catalyst layer 3 coated on the gas diffusion layer, and a liquid phase diversion layer 4 located on the gas catalyst layer. The gas diffusion layer comprises carbon black of high degree of graphitization and polytetrafluoroethylene. The gas catalyst layer comprises a catalyst, acidified carbon black of high degree of graphitization, and polytetrafluoroethylene. The carbon black of high degree of graphitization has a Raman spectrum Id/Ic peak intensity ratio of 0.3 to 1.0. The degree of graphitization of the gas diffusion layer may be identical to or different from that of the gas catalyst layer. The gas diffusion electrode has good corrosion resistance and excellent and stable electrochemical performance in alkali solutions, and therefore, is suitable for electrolytic reactions in the chlorine alkali industry.

Description

Gas diffusion electrode and preparation method thereof

This application belongs to the field of chemical industry and, in particular, relates to a gas diffusion electrode suitable for use in the chlor-alkali industry and a preparation method thereof.

Background technique

The chlor-alkali industry is a basic chemical industry and plays an important role in promoting the development of the national economy. At the same time, the chlor-alkali industry is a high-energy industry, and minimizing the energy consumption of the chlor-alkali industry has always been a topic of concern to all countries.

In recent years, the ionic membrane salt electrolysis method using an oxygen cathode instead of a hydrogen evolution cathode has gradually gained attention, and its essence is to replace the hydrogen evolution reaction with an oxygen reduction reaction. The conventional reaction method of the alkali method using an ion-exchange membrane using a hydrogen evolution electrode as a cathode is:

2C1—→Cl ₂ +2e ( 1.36V )

2H ₂ 0+2e→20H"+H ₂ (-0.83V)

2NaCl+2H ₂ 0→Cl ₂ +2Na0H+H ₂ (2.19V) The electrochemical reaction formula of the ionic membrane alkali method using an oxygen cathode is:

0 ₂ +2H ₂ 0+4e-40H" ( 0.4V )

2NaCl+H ₂ 0+l/20 ₂ → Cl ₂ +2NaOH ( 0.96V) It can be seen that the ionic membrane alkali method after replacing the hydrogen evolution cathode with an oxygen cathode can reduce the theoretical decomposition voltage by 1.23V and the theoretical energy saving can reach 40%. Electrolytic strontium can save 700KWh of electricity and has a very impressive application value. Gas diffusion electrodes originated from the development of fuel cells and zinc-air batteries. The research applied in the chlor-alkali industry is relatively rare, mainly due to the following difficulties:

1) The actual electrolysis conditions of the chlor-alkali industry are harsh, usually at 30. /. The above alkali concentration and the operation of 80-9 (TC temperature, the electrode material and the preparation of the electrode are required to be high;

2) During the electrochemical reaction of the oxygen cathode, due to the influence of the electrocatalytic mechanism of the catalyst, there will be a certain degree of secondary reaction of two electrons, which produces a certain amount of H (V, which has a certain etching ability for the carbon material. This has a negative impact on the structure, life and electrochemical performance of the electrode;

3) The electrochemical reaction process of the oxygen cathode is actually a gas-liquid-solid heterogeneous catalytic reaction process, and the gas-liquid-solid three-phase reaction equilibrium is difficult to control, thus affecting the oxygen cathodic electrocatalytic efficiency.

4) The oxygen cathode has low mechanical strength and is difficult to install, which is difficult to meet the needs of large-scale industrial production;

5) The slurry dispersion process of the oxygen cathode and the film formation process are complicated, and the drying is required to be high, and it is difficult to obtain an electrode having a good surface condition and no crack.

At present, around the above difficulties, researchers in various countries have done a lot of work. Among them, Japanese Patent Special Publication 2007-327092 uses AB-6 carbon black as hydrophobic carbon black and AB-12 carbon black as hydrophilic carbon black. The gas diffusion electrode was prepared by using silver powder as a catalyst, and a gas diffusion electrode with high water pressure resistance and slow degradation rate was obtained; 曰 Patent No. 2004-300451 uses AB-6 carbon black as hydrophobic carbon black to be plated. Silver metal mesh as a catalyst layer, through the dispersion of hydrophobic carbon black and binder After the filtration and drying steps, the silver-plated metal mesh is hot-pressed to prepare a gas diffusion electrode with stable performance, but the electrode is difficult to meet the requirements of industrial production of large electrodes;

In CN1 01 736360A, the use of a silver-plated nickel mesh as a support, the mechanical strength of the silver-plated nickel mesh placed on the body is weak, the electrode surface is prone to cracking during the production process, and it is difficult to demold during the hot pressing stage, and it is difficult to solve the problem. Realize the requirements of industrial production.

Summary of the invention

The object of the present invention is to solve the problems of the prior art and to provide a simple and efficient gas diffusion electrode suitable for use in the chlor-alkali industry and a preparation method thereof. In order to achieve the object of the present invention, the following technical solution is adopted: one aspect of the present invention relates to a gas diffusion electrode including a current collecting body, a gas diffusion layer, a gas catalytic layer coated on the gas diffusion layer, and a gas catalytic layer. a liquid phase guiding layer; characterized in that the gas diffusion layer comprises high graphitization carbon black, polytetrafluoroethylene; the gas catalytic layer comprises a catalyst, acidified high graphitization carbon black, polytetrafluoroethylene; The degree of graphitization carbon black is a carbon black between the I _D / I _e peak intensity ratio of the Raman spectrum of 0.3 to 1.0, and the degree of graphitization of the gas diffusion layer and the gas catalytic layer may be the same or different. The thickness of the silver-plated foamed nickel metal silver plating layer is 0.1 - 20 μ ηι; the silver-plated foam metal may be the same or different.

In a preferred embodiment of the present invention, the mass ratio of the high degree of graphitization carbon black and the polytetrafluoroethylene in the gas diffusion layer is (0. 01 ~ 1): (0. 01 ~ 0.1).

In a preferred embodiment of the present invention, the mass ratio of the catalyst, the acidified high graphitization carbon black, and the polytetrafluoroethylene in the gas catalytic layer is (0.1 to 1): (0. 1 ~ 1 ): ( 0. 1 ~ 1 ).

In a preferred embodiment of the invention, the silver-plated metal foam is selected from the group consisting of silver-plated foamed nickel, titanium, tungsten, cobalt or alloys thereof.

In a preferred embodiment of the present invention, the catalyst in the gas catalytic layer is selected from the group consisting of silver powder or silver/carbon composite catalyst, and preferably, the particle size of the catalyst is between

Between 0. 01 ~ 5 μ ιτι.

In a preferred embodiment of the invention, the diffusion electrode is a gas diffusion electrode applied to the chlor-alkali industry.

In a preferred embodiment of the present invention, the gas diffusion layer is made of a material containing a high degree of graphitization carbon black, water, a Triton, a polytetrafluoroethylene emulsion, and an isopropanol during the preparation of the gas diffusion electrode. The mass ratio of the above raw materials is: (0. 01 - 1): (0. 1 - 1): (0. 01 - 0. 1) : 0. 01 ~ 0. 1) : 1.

In a preferred embodiment of the present invention, the gas catalytic layer is prepared from a gas diffusion electrode comprising a catalyst, an acidified high graphitization anthrax, water, a Triton, a polytetrafluoroethylene solution, The raw material of isopropyl alcohol is prepared by using an aqueous solution of Triton as a dispersion medium, and the mass ratio of the above raw materials is: (0.1 to 1): (0.11 to 1): (1 to 10)·· (0. 1 ~ 1 ): ( 0. 1 ~ 1 ): 1.

In a preferred embodiment of the method for producing a gas diffusion electrode according to the present invention, the method for preparing a gas diffusion layer comprises the steps of: (1) dispersing a high degree of graphitization carbon black in a surfactant-containing curve In the aqueous solution of isopropanol, a gas diffusion layer slurry is obtained, and the slurry is ultrasonically sheared and dispersed for 10 to 200 minutes, and then added. Into the polytetrafluoroethylene emulsion with a mass fraction of 40 ~ 80%, continue to shear dispersion for 10 ~ 150min; the temperature of the gas diffusion layer slurry dispersion process is controlled between 10 ~ 100 ° C; in the gas diffusion layer slurry The average particle size after powder dispersion is controlled between 0.2 ~ 10 μηι; the gas diffusion layer slurry is allowed to stand for 5~100h after dispersing; the solid content of the gas diffusion layer is controlled at 5 ~ 40 wt%; (2) the gas The diffusion layer slurry is uniformly applied to the silver-plated metal foam of the current collecting body; after the slurry of the gas diffusion layer is applied, it is dried at 40 to 12 (TC for 5 to 10 hours; after the gas diffusion layer slurry is applied and dried, The preliminary cold press forming treatment is carried out, the cold pressing pressure is G. l ~ 2 MPa, the temperature is controlled at -10 to 50 ° C, and the holding time is 10 to 300 s, and a combination of the current collecting body 1 and the gas diffusion layer 2 is obtained.

In a preferred embodiment of the method for preparing a gas diffusion electrode according to the present invention, the method for preparing the gas catalytic layer comprises the following steps: (1) dispersing the catalyst and the acidified graphitized carbon black on a surface containing In the aqueous solution of the active agent Triton in isopropanol, a catalyst layer slurry is obtained, and the slurry is ultrasonically shear-dispersed for 10 to 200 minutes, and then a polytetrafluoroethylene emulsion having a mass fraction of 40 to 80% is added to continue the shearing. The dispersion is 10 150 min; the temperature of the catalyst layer dispersion process is controlled between 10 and 100 ° C; the average particle size of the powder in the catalyst layer slurry is controlled between 0.2 and ΙΟμηι; (2) the catalyst The layer slurry is smeared on the gas diffusion layer of the current collector and the gas diffusion layer assembly; after the slurry of the catalyst layer is applied, it is dried at 40 ~ 12 (TC for 0.5 ~ lh; the catalyst layer is applied and dried) After the treatment, the assembly is subjected to a secondary cold press forming process, the cold pressing pressure is 0.1 to 2 MPa, the temperature is controlled at -10 to 50 ° C, and the holding time is 10 to 300 s, and a preliminary formed gas diffusion electrode is obtained; gas Powder electrode baking temperature, the baking temperature is controlled at 270 ~ 290 ° C, bake Baking time l ~ 20h; The liquid phase guiding layer silver-plated foam metal is placed on the gas diffusion electrode which is initially formed after baking, and the hot pressing pressure is controlled at 2 ~ 12MPa, and the hot pressing temperature is 330 ~ 450 °C. The pressure holding time is 10 to 300 s to obtain the gas diffusion electrode.

In a preferred embodiment of the above method for producing a gas diffusion electrode, the silver-plated metal foam is prepared by plating silver on a metal foam by electroplating, electroless plating, or displacement plating.

The catalyst used in the present invention comprises a silver powder or a silver/carbon composite catalyst (the preparation of which can be referred to CN 101745390 A), and the silver/carbon composite catalysts mentioned hereinafter are all the catalysts prepared in the publication CN 101745390A.

The invention has the following beneficial effects:

The invention disperses carbon black with high degree of graphitization in an aqueous solution of isopropanol containing a certain surfactant, and obtains a uniformly dispersed gas diffusion layer slurry by ultrasonic shear dispersion and a standing process, and the gas diffusion layer slurry is obtained. They are all smeared on the silver-plated foam metal. After drying, the gas diffusion layer is obtained by cold pressing. The gas diffusion layer not only has good electrical conductivity, gas permeability, but also excellent water pressure resistance; The acidified high graphitization carbon black is dispersed in an aqueous solution of isopropyl alcohol containing a certain surfactant, and is dispersed by ultrasonic shearing to obtain a dispersed catalyst layer slurry, and the catalyst layer slurry is smeared on the gas diffusion layer. After drying, cold pressing is performed to obtain a gas diffusion electrode which is initially formed. The catalyst layer obtained by the method not only has the proper hydrophobic and hydrophobic ability, but also facilitates the gas-liquid-solid three-phase reaction, and has the ability to reduce the hydrogen peroxide side reaction and the resistance to etching, thereby facilitating the long-term electrode. Steady The operation is fixed. By uniformly baking the initially formed gas diffusion electrode to completely remove the surfactant remaining inside the electrode, thereby facilitating the uniformity of the pore structure in the hot press forming stage; by placing the silver plated foam metal in the hot pressing stage Hot pressing on the surface of the catalyst layer to form a gas diffusion electrode with a sandwich structure is not only advantageous for the three-phase reaction in the catalytic process, but also the silver-plated metal foam can improve the electrocatalytic ability of the electrode under an alkaline solution and the electrode itself. Mechanical strength. Therefore, the gas diffusion electrode provided by the invention has good corrosion resistance and electrical conductivity in an alkaline solution, and is stable in operation, and is suitable for an electrolytic reaction in the chlor-alkali industry. DRAWINGS

Figure 1 is a schematic view showing the structure of a gas diffusion electrode provided by the present invention, wherein 1 is a current collector,

2 is a diffusion layer, 3 is a catalytic layer, and 4 is a liquid phase conductivity layer.

Figure 2 is a Raman spectrum of a high graphitization carbon black in a gas diffusion layer provided by the present invention. Figure 3. The catalyst is the result of a rotating ring test of silver powder in an alkaline solution.

Fig. 4 shows the actual electrolysis test data of the gas diffusion electrode electrolyzer prepared in Example 1 and Comparative Example 1.

(Test conditions are current density of 3KA/ra ² in 30% NaOH solution)

detailed description

Example 1

The high graphitization carbon black used is obtained by carbon black (Vu l can XC-72) obtained in a high temperature graphitization furnace at 270 (TC graphitization for 6 ~ 10 h, and the degree of graphitization is measured by Raman spectroscopy). As shown in Fig. 2, the Raman spectrum is 〖./:^ is 0.67, and the silver-plated foamed nickel is used. Prepared by plating method, foamed nickel is purchased from Heze Tianyu Technology Development Co., Ltd., acidified high graphitization carbon black is condensed and refluxed in graphitized carbon black at 12 (TC in a solution of nitric acid (mass fraction 68%) 6 ~ 10 h obtained.

1) Weigh 0.4 ~ 2g of high graphitization carbon black dispersed in an isopropanol aqueous solution containing 0.4 ~ lg Triton, which is 40niL of isopropanol and 10~25mL of water, then ultrasonically shear the slurry solution After 60 minutes of cutting, add a PTFE emulsion with a mass fraction of 60%.

(D-110) 1 - 2g, continue to shear and disperse for 10 min. After the dispersion is completed, the gas diffusion layer slurry is evenly spread on 90mm x 9Gmm silver-plated foamed nickel and dried in an oven at 60 ° C for 30 min. , preliminary cold forming, cold pressing pressure of 0.1 ~ 2MPa, pressing at room temperature for 60s, to obtain a combination of the current collecting body 1 and the gas diffusion layer 2;

2) Dissolve 1 ~ 2g of catalyst silver powder and 2 ~ 3g of acidified graphitized carbon black in an isopropanol aqueous solution containing 2.5 ~ 3g / L of Triton, so that the acidified graphitized carbon black surface oxygen-containing functional group concentration is 0.5 - 2mmol/g; wherein the isopropanol is 3mL and the water is 15~30mL. After the slurry solution is ultrasonically sheared for 60min, the polytetrafluoroethylene emulsion with a mass fraction of 60% is added to 1.5~3g, and the shear dispersion is continued. lOniin, after the dispersion is completed, the catalyst layer slurry is uniformly applied to the gas diffusion layer of the combination of the current collecting body 1 and the gas diffusion layer 2, and after drying, it is subjected to secondary cold pressing forming treatment, and the cold pressing pressure is 0.1. - 2MPa, the temperature is controlled at room temperature, the holding time is 30s, and the gas diffusion electrode is formed. The test results of the rotating ring of the catalyst silver powder in the alkaline solution are shown in Fig. 3. It can be found that the electrocatalytic mechanism is close to Four-electron reaction;

3) The preliminary formed gas diffusion electrode obtained in the above step is baked at a high temperature, the baking temperature is controlled at 290 ° C, and the baking time is 2 h; 4) The silver-plated foamed nickel of the guide layer is placed on the gas diffusion electrode which is initially formed after baking, and the hot pressing pressure is controlled at 5-8 MPa, the hot pressing temperature is 360 ° C, and the holding time is 60 s; Diffusion electrode. The actual electrolysis test data of the obtained gas diffusion electrode electrolyzer is shown in Fig. 4. The electrode exhibits good corrosion resistance, excellent electrochemical performance and stability in an alkaline solution, and is suitable for electrolysis reaction in the chlor-alkali industry.

Example 2

The high graphitization carbon black used is obtained by graphitizing carbon black (Vulcan XC-72) at 2600 ° C for 2 ~ 15 h, the Raman spectrum I _{D e} is 0.7 ~ 1.0, and the silver-plated foamed nickel is electroplated. Preparation, foam nickel is purchased from Heze Tianyu Technology Development Co., Ltd., acidified high graphitization carbon black is obtained by condensing and refluxing graphitized carbon black at 14CTC in a solution of nitric acid (68% by mass) for 6-10 hours. .

1) Weigh 1 ~ 3g of high graphitization carbon black dispersed in an isopropanol aqueous solution containing 0.4 ~ 3g of Triton, which is 40mL of isopropanol and 4~16mL of water, then ultrasonically shear the slurry solution After cutting 6 Oni in, add 0.4% to 1.5g of polytetrafluoroethylene emulsion (D-110) with a mass fraction of 60%, continue to shear and disperse lOmin, and after the dispersion is completed, apply the gas diffusion layer slurry evenly to 90mm. X 90mm silver-plated foamed nickel, after being dried in an oven at 60 ° C for 30 min, preliminary cold forming, cold pressing pressure of 0.1 ~ 2MPa, room temperature pressing for 60s, to obtain current collecting body 1 and gas diffusion layer 1 2) 0.3~1.5g catalyst silver powder or silver/carbon composite catalyst, 0.5~2g acidified high graphitization carbon black dispersed in an isopropanol aqueous solution containing 0.3~1.8g/L tritonine to acidify The high graphitization carbon black surface has an oxygen-containing functional group concentration of 1.5 to 4 sec ol/g, wherein isopropyl alcohol is 3 mL, water is 3-8 mL, and the slurry solution is ultrasonicated. After 60 min of shearing, 0.3~1.5 g of a polytetrafluoroethylene emulsion with a mass fraction of 60% was added, and shearing and dispersing was continued for 10 min. After the dispersion was completed, the catalyst layer slurry was uniformly applied to the current collecting body 1 and the gas diffusion layer. 1 On the gas diffusion layer of the composite, after drying, it is subjected to secondary cold press forming treatment, cold pressing pressure Q.1 ~ 2MPa, temperature control at room temperature, holding time 30s, to obtain a preliminary formed gas diffusion electrode;

3) The preliminary formed gas diffusion electrode obtained in the above step is baked at a high temperature, and the baking temperature is controlled at 280 ° C, and the baking time is 4 h;

4) The silver-plated foamed nickel of the guide layer is placed on the gas diffusion electrode which is initially formed after baking, and the hot pressing pressure is controlled at 2 to 5 MPa, the hot pressing temperature is 370 ° C, and the holding time is 180 s; Diffusion electrode.

Example 3

The high graphitization carbon black used is obtained by graphitizing carbon black (Vulcan XC-72) in a high temperature graphitization furnace at 2900 for 2 ~ 15h, the Raman spectrum is 0.3-0.6, and the silver-plated foam nickel is electroplated. Prepared by the method, foamed nickel is purchased from Heze Tianyu Technology Development Co., Ltd., acidified high graphitization carbon black is condensed and refluxed in graphitized carbon black at 16 (TC in a solution of nitric acid (68% mass fraction) for 6 ~ 10h 1) Weigh 2 ~ 4g of high graphitization carbon black dispersed in an isopropanol aqueous solution containing 2.5 ~ 4g of Triton, which is 40mL of isopropanol and 20~40mL of water. After the solution was ultrasonically sheared for 6Omin, add a mass fraction of 60% polytetrafluoroethylene emulsion (D-110) 1.8 ~ 4g, continue to 4亍 shear dispersion 10m in, after the dispersion is completed, the gas diffusion layer slurry is uniform Apply to 90mmx 90mm silver-plated foamed nickel, after drying for 30min at 60Ό, preliminary cold forming by cold press, cold pressing pressure A mixture of the current collector 1 and the gas diffusion layer 2 is obtained by pressing 1.5 to 2 MPa at room temperature for 60 s;

2) 2 ~ 3g catalyst silver powder or silver / carbon composite catalyst, 0.3 ~ lg acidified high graphitization carbon black is dispersed in an isopropanol aqueous solution containing 1.5-2.8g / L Triton, so that acidified high graphitization The concentration of oxygen-containing functional groups on the surface of the carbon black is 3.5~5mmol/g, wherein the isopropanol is 3mL and the water is 5~15mL. After the slurry solution is ultrasonically sheared for 60min, the polytetrafluoroethylene with a mass fraction of 60% is added. The ethylene emulsion is 1.4 ~ 2.8g, and the shear dispersion ΙΟπΰη is continued. After the dispersion is completed, the catalytic layer slurry is smeared on the gas diffusion layer of the combination of the current collecting body 1 and the gas diffusion layer 2, and after drying, The second cold press forming treatment is performed, the cold pressing pressure is 1.5 - 2 MPa, the temperature is controlled at room temperature, and the holding time is 30 s, and a preliminary formed gas diffusion electrode is obtained;

3) The preliminary shaped gas diffusion electrode obtained in the above step is placed in an oven for baking, and the baking temperature is controlled at 27 (TC, baking time 6 h;

4) The silver-plated foamed nickel of the guide layer is placed on the gas diffusion electrode which is initially formed after baking, and the hot pressing pressure is controlled at 8 - 12 MPa, the hot pressing temperature is 35 G ° C, and the holding time is 30 s; Diffusion electrode.

Comparative Example 1

The high graphitization carbon black used is obtained by graphitizing carbon black (Vulcan XC-72) at 2700 ° C for 6-10 h in a high temperature graphitization furnace; the Raman spectrum for testing the degree of graphitization is shown in Fig. 2. The Raman spectrum is 0.67, the silver-plated foamed nickel is prepared by electroplating, the foamed nickel is purchased from Heze Tianyu Technology Development Co., Ltd., and the acidified high graphitization carbon black is made of graphitized carbon black at 120 °C. Nitric acid (mass fraction is 68%) Condensed in solution in a reflux of 6 ~ 1 Oh.

1) Weigh 0.4 ~ 2g of high graphitization carbon black dispersed in an isopropanol aqueous solution containing 0.4 ~ lg Triton, which contains 40mL of isopropanol and 10~25mL of water, then ultrasonically shear the slurry solution After 60 minutes of cutting, add PTFE emulsion (D-110) with a mass fraction of 60% to 1 ~ 2g, continue to shear and disperse lOmin, and after the dispersion is completed, spread the gas diffusion layer slurry evenly on 90 hidden X 90 After the silver-plated foamed nickel was baked in an oven at 60 ° C for 30 min, preliminary cold forming was carried out, the cold pressing pressure was G.1 ~ 2 MPa, and the room temperature was pressed for 60 s to obtain the current collecting body 1 and the gas diffusion layer 1 Combination of

2) Dissolve 1 ~ 2g of catalyst silver powder and 2 ~ 3g of acidified graphitized carbon black in an aqueous solution of isopropanol containing 2.5 ~ 3g / L of Triton, so that the concentration of oxygen-containing functional groups on the surface of acidified graphitized anthrax is 0.5~ 2 Sa ₀ 1 / ^; where isopropyl alcohol is 3mL, water is 15 ~ 30raL, after the slurry solution is ultrasonically sheared 60niin, adding 60% by weight of PTFE emulsion 2.5 ~ 3g, continue After shearing and dispersing lOmin, after the dispersion is completed, the catalyst layer slurry is uniformly applied to the gas diffusion layer of the combination of the current collecting body 1 and the gas diffusion layer 2, and after drying, it is subjected to secondary cold press forming treatment, and cold Pressing pressure 0. l~2MPa, temperature control at room temperature, holding time 30s, to obtain a preliminary formed gas diffusion electrode;

3) the preliminary formed gas diffusion electrode obtained in the above step is baked at a high temperature, the baking temperature is controlled at 290 ° C, and the baking time is 2 h;

4) The gas diffusion electrode which is initially formed after baking is directly placed on a hot press for hot press forming, the hot pressing pressure is controlled at 5 ~ 8 MPa, the hot pressing temperature is 36 CTC, and the holding time is 60 s; a gas diffusion electrode is obtained. The actual number of electrolytic tests of the obtained gas diffusion electrode electrolyzer As shown in Fig. 4, the deterioration of the electrolytic properties in the alkaline solution with time is prolonged, and the long-term electrolytic reaction in the chlor-alkali industry cannot be satisfied. It is to be understood that those skilled in the art will be able to make modifications and changes in accordance with the above description, and all such modifications and variations are intended to fall within the scope of the appended claims.

Claims

1. A gas diffusion electrode, including a current collector, a gas diffusion layer, a gas catalytic layer coated on the gas diffusion layer, and a liquid phase conductive layer located on the gas catalytic layer; characterized in that the gas diffusion layer includes a high Graphitization degree carbon black, polytetrafluoroethylene; The gas catalytic layer includes a catalyst, acidified high graphitization degree carbon black, and polytetrafluoroethylene; The high graphitization degree carbon black is the _ID /I of the Raman spectrum Carbon black with _{a G} peak intensity ratio between 0. 3 and 1. 0. The preferred oxygen functional group concentration on the surface of acidified graphitized carbon black is 0. 5 to 2 letol/g. The graphite of the gas diffusion layer and the gas catalytic layer The degree of corrosion may be the same or different; the current collector and the liquid phase conductive layer are both silver-plated foam metal, and the thickness of the silver-plated foam metal silver coating is 0.1 ~ 20 μ m; the silver-plated foam metal can be They may or may not be the same.

2. The gas diffusion electrode according to claim 1, characterized in that the mass ratio of highly graphitized carbon black and polytetrafluoroethylene in the gas diffusion layer is (0.01~1): (0.01~1).

3. The gas diffusion electrode according to claim 1, characterized in that the mass ratio of catalyst, acidified high-graphitization carbon black, and polytetrafluoroethylene in the gas catalytic layer is

( 0. 1 ~ 1 ): ( 0. 1 ~ 1 ): ( 0. 1 ~ 1

4. The gas diffusion electrode according to any one of claims 1 to 3, characterized in that the silver-plated foam metal is selected from silver-plated nickel foam, titanium, tungsten, cobalt or alloys thereof.

5. The gas diffusion electrode according to claim 1, characterized in that the catalyst in the gas catalytic layer is selected from silver powder or silver/carbon composite catalyst. Preferably, the particle size of the catalyst is between 0.01 ~ 5 μm. .

6. The gas diffusion electrode according to any one of claims 1 to 5, characterized in that the diffusion electrode is a gas diffusion electrode used in the chlor-alkali industry.

7. The method for preparing a gas diffusion electrode according to claim 6, characterized in that the gas diffusion layer is made of raw materials containing carbon black with a high degree of graphitization, water, triton, polytetrafluoroethylene emulsion, and isopropyl alcohol. , in which the isopropyl alcohol aqueous solution of triton is used as the dispersion medium, and the mass ratio of the above raw materials is: (0.01 - 1): (0.1 ~ 1): (0.01 - 0.1): (0.01- 0.1): 1.

8. The method for preparing a gas diffusion electrode according to claim 6, wherein the gas catalytic layer is composed of a catalyst, acidified high-graphitization carbon black, water, triton, polytetrafluoroethylene solution, It is made from the raw materials of isopropyl alcohol, in which the isopropyl alcohol aqueous solution of triton is used as the dispersion medium. The mass ratio of the above raw materials is: (0.1 ~ 1): (0.1 ~ 1): (1 ~ 10): (0.1 ~ 1 ): ( 0.1 ~ 1 ): 1.

9. The method for preparing a gas diffusion electrode according to claim 7, characterized in that the method for preparing a gas diffusion layer includes the following steps: (1) Dispersing high-grade carbon black in a solution containing surfactant Triton In the isopropyl alcohol aqueous solution, the gas diffusion layer slurry is obtained, and the slurry is sheared and dispersed by ultrasonic for 10 to 200 minutes, and then a polytetrafluoroethylene emulsion with a mass fraction of 40 to 80% is added, and the shearing and dispersing is continued for 10 to 150 minutes. ; The temperature of the gas diffusion layer slurry dispersion process is controlled between 10 - 100°C; the average particle size of the powder in the gas diffusion layer slurry after dispersion is controlled between 0.2 ~ 10 μm; the gas diffusion layer slurry is statically dispersed after dispersion Leave for 5 ~ 100h; the solid content of the gas diffusion layer slurry is controlled at 5 ~ 40wt%; (2) Evenly apply the gas diffusion layer slurry on the silver-plated foam metal of the current collector; after the gas diffusion layer slurry is applied, Dry at 40~12Q°C for 5~10h; after the gas diffusion layer slurry is applied and dried, it is subjected to preliminary cold pressing molding process, the cold pressing pressure is 0. l~2MPa, and the temperature is controlled at - 10~50°C , pressure holding time 10~300s, A combination of a current collector and a gas diffusion layer is obtained.

10. The method for preparing a gas diffusion electrode according to claim 8, characterized in that the method for preparing the gas catalytic layer includes the following steps: (1) Dispersing the catalyst and acidified graphitized carbon black in a solution containing surfactant In the isopropyl alcohol aqueous solution of Triton, the catalytic layer slurry is obtained, and the slurry is sheared and dispersed by ultrasonic for 10 to 200 minutes, and then a polytetrafluoroethylene emulsion with a mass fraction of 40 to 80% is added, and the shearing and dispersing is continued. 10-150 rain; the temperature of the catalytic layer slurry dispersion process is controlled between 10 ~ 100°C; the average particle size of the powder in the catalytic layer slurry after dispersion is controlled between 0.2 ~ 10 μm; (2) The catalytic The first layer of slurry is evenly applied on the gas diffusion layer of the current collector and gas diffusion layer combination; after the slurry of the catalytic layer is applied, it is dried at 40~120°C for 0.5~1h; the catalytic layer slurry is applied and dried After processing, the formed assembly is subjected to a secondary cold pressing forming process. The cold pressing pressure is 0.1 ~ 2MPa, the temperature is controlled at -10 ~ 50°C, and the pressure holding time is 10 ~ 300s to obtain a preliminary formed gas diffusion electrode; the preliminary formed gas diffusion electrode is obtained. The formed gas diffusion electrode is baked at high temperature, the baking temperature is controlled at m~iwc, and the baking time is l ~ 20h; the silver-plated foam metal of the liquid phase conductive layer is placed on the preliminarily formed gas diffusion electrode after baking for heating. Press forming, the hot pressing pressure is controlled at 2~12MPa, the hot pressing temperature is 330~450°C, and the pressure holding time is 10-300s, to obtain the gas diffusion electrode.