A membrane electrode for preparing ozone and a preparation method thereof

Abstract

The present invention relates to a membrane electrode for preparing ozone and a preparation method thereof. The anode surface of the membrane electrode is loaded with an anode catalyst layer, and the cathode surface is loaded with a cathode catalyst layer. The anode catalyst layer comprises lead dioxide, a binder, a dispersing solvent and a surfactant, and the mass ratio of the lead dioxide, the binder, the dispersing solvent and the surfactant is 1: (6-7): (40-50): (0.13-0.26). The anode catalyst layer is loaded on one side of a proton exchange membrane by a transfer method. The cathode catalyst layer comprises platinum carbon, a binder and a solvent, and the platinum loading amount in the cathode catalyst layer is 0.5-1 mg / cm 2 The mass ratio of carbon content in the platinum carbon to the binder is 1:(0.5-1). The cathode catalyst layer is spray-coated on the other side of the proton exchange membrane. The membrane electrode of this invention has stable performance and can be used in ozone generators. It only needs a voltage of 3.5V to decompose water into ozone, with high efficiency and fast production speed.

Description

Technical Field

[0001] The present invention relates to the technical field of ozone preparation, and in particular to a membrane electrode for preparing ozone and a preparation method thereof. Background Art

[0002] Ozone is also known as superoxide, strong oxygen, rich oxygen, and tri-oxygen. It has a very strong oxidizing ability. It can not only deodorize, decolorize, and disinfect solid, liquid, and gas samples, but can also be used in water treatment, soil remediation and other fields. Compared with some traditional disinfectants, the secondary pollution generated when ozone is used as a disinfectant or oxidant is relatively small, so ozone is widely recognized as a safe disinfectant. There are two traditional methods for preparing ozone: ultraviolet light and corona discharge. The ultraviolet light method is facing elimination due to its extremely low output and short lifespan; the corona discharge method has high energy consumption, is afraid of moisture, has high requirements for the operating environment, produces secondary pollutants such as ammonia oxides, has large equipment, complex operation, and generates low ozone concentration, which are problems that it has not been able to solve.

[0003] Ozone is produced through electrolysis, which involves electrolyzing water with low-voltage direct current, causing a redox reaction at the anode-solution interface to produce ozone. This method offers advantages such as high-purity ozone, no nitrogen oxides, low energy consumption, simple operation, high utilization rate, and environmental friendliness, resulting in a promising future for its application.

[0004] Ozone is produced by electrolysis in an ozone generator. The core component of an ozone generator is the membrane electrode (MEA). The MEA is not only a crucial site for electron generation and separation, but also serves as a transport mechanism for gases and product water, significantly impacting ozone production. However, existing MEA, particularly the anode, is complex to manufacture due to the large anode catalyst particle size and the tendency to agglomerate, making it difficult to directly spray the material onto the anode. Furthermore, due to the working mechanism of existing cathode catalysts, hydrogen is produced as a byproduct at the cathode during ozone production.

[0005] Therefore, there is an urgent need in this field to find a membrane electrode process with better performance, simpler preparation and no hydrogen production. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a membrane electrode with high ozone production efficiency.

[0007] The purpose of this application is also to provide a method for preparing a membrane electrode.

[0008] In order to achieve the purpose of the present invention, this application provides the following technical solutions.

[0009] In a first aspect, the present application provides a membrane electrode for preparing ozone, wherein the membrane electrode comprises a cathode, an anode, and a diaphragm, wherein the surface of the anode is loaded with an anode catalyst layer, and the surface of the cathode is loaded with a cathode catalyst layer, wherein the anode catalyst layer comprises lead dioxide, a binder, a dispersing solvent, and a surfactant, and the mass ratio of the lead dioxide, the binder, the dispersing solvent, and the surfactant is (5-10):1:(40-50):(0.13-0.26); the cathode catalyst layer comprises platinum carbon, a binder, and a solvent, and the platinum loading in the cathode catalyst layer is 0.5-1 mg / cm 2 , the mass ratio of the carbon content in the platinum carbon to the binder is 1: (0.5 ~ 1). In the existing membrane electrode preparation process, the anode catalyst is directly coated on the proton exchange membrane, which can easily cause the proton exchange membrane to deform, resulting in easy desorption of the catalyst layer, shortening the working life of the membrane electrode, and in severe cases, causing a short circuit. The use of the above formula can make the anode and cathode catalyst layers adhere more tightly to the membrane and not easily fall off, making the ozone electrolysis process more stable and more efficient. And this formula has shown the best performance after multiple tests.

[0010] In one embodiment of the first aspect, the binder is a perfluorosulfonic acid resin. The perfluorosulfonic acid resin can effectively bind catalyst particles, preventing the catalyst from falling off. Furthermore, during the low-pressure water electrolysis process, the perfluorosulfonic acid resin can serve as a proton transport channel, enhancing the speed of proton transport and providing a moisturizing effect for the proton exchange membrane.

[0011] In one embodiment of the first aspect, the dispersing solvent comprises n-propanol and water, wherein the mass ratio of lead dioxide, n-propanol, and water is (5-10):(5-10):(30-45). The dispersant effectively disperses the lead dioxide particles in the solvent and prevents them from settling and agglomerating. However, agglomeration of lead dioxide reduces the effective active surface area of ​​the catalyst, affecting the stability and service life of the membrane electrode.

[0012] In one embodiment of the first aspect, the surfactant is a polyether emulsifier, preferably octylphenol polyoxyethylene ether. Surfactants can play an emulsifying and dispersing role. Lead dioxide is insoluble in water and alcohols. In order to better disperse the catalyst slurry, adding a surfactant can reduce the surface tension and interfacial free energy of the system, play a solubilizing effect, and thus form a stable emulsion. Since octylphenol polyoxyethylene ether is a nonionic surfactant, it does not dissociate when dissolved in water, so it has high stability, is not easily affected by the presence of strong electrolytes, is not easily affected by acids and alkalis, and has good solubility in solvents, so it is given priority.

[0013] In one embodiment of the first aspect, the solvent is a liquid alcohol.

[0014] In one embodiment of the first aspect, the membrane is a proton exchange membrane.

[0015] In a second aspect, a method for preparing the membrane electrode as described above is further provided, comprising the following steps:

[0016] (1) mixing lead dioxide, a binder, a dispersing solvent, and a surfactant in proportion, and forming an anode catalyst slurry after ultrasonic cleaning and emulsification; and mixing platinum carbon, a binder, and a solvent in proportion to obtain a cathode catalyst slurry;

[0017] (2) Fix the transfer film, drip the anode catalyst slurry, and evenly apply it on one side of the transfer film. After drying, repeat the dripping and applying steps until a 0.015-0.020 mm thick anode catalyst layer is formed on one side of the transfer film;

[0018] (3) Take a diaphragm and apply the cathode catalyst slurry on one side of the diaphragm by spraying to form a cathode catalyst layer with a thickness of 0.010-0.015 mm;

[0019] (4) Soaking the diaphragm with the cathode catalyst layer and the transfer film with the anode catalyst layer in an ethylene glycol solution, then taking out the anode catalyst layer on the transfer film and coating it on the side of the diaphragm not coated with the cathode catalyst layer, and then removing the transfer film after hot pressing to obtain the membrane electrode.

[0020] In one embodiment of the second aspect, in step (1), the frequency used for the ultrasound is 1000-10000 rpm, and the ultrasound time is 10-30 min; the emulsification is completed in an emulsifying homogenizer, and the emulsification time is 20-60 min.

[0021] In one embodiment of the second aspect, in step (2), the volume of the anode catalyst slurry dripped each time is 1 to 1.5 mL, the drying temperature is 30 to 50° C., and the drying time is 10 to 15 min.

[0022] In one embodiment of the second aspect, in step (4), the mass concentration of the ethylene glycol is 30% to 50%, and the soaking time is 10 to 20 minutes;

[0023] In one embodiment of the second aspect, the temperature used for hot pressing is 140-148°C, the pressure is 2.5-3.0 MPa, and the time is 3-5 minutes. The hot pressing can transform the adhesive into a glassy state, thereby making the catalyst layer smoother and more secure and less likely to fall off. DETAILED DESCRIPTION

[0024] Unless otherwise defined, technical or scientific terms used in this specification and claims shall have the ordinary meaning as understood by persons having ordinary skill in the art to which this invention belongs. All numerical values ​​listed herein, from the lowest value to the highest value, refer to all numerical values ​​obtained by incrementing the lowest value to the highest value by one unit when the difference between the lowest value and the highest value is two units or more.

[0025] The following describes specific embodiments of the present invention. It should be noted that, in the context of describing these embodiments, for the sake of brevity and clarity, this specification does not exhaustively describe all features of the actual embodiments. Those skilled in the art may modify and substitute the embodiments of the present invention without departing from the spirit and scope of the present invention, and the resulting embodiments are also within the scope of protection of the present invention.

[0026] In this application, the materials used are from the following sources:

[0027] Lead dioxide was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0028] Perfluorosulfonic acid resin was purchased from Shanghai Zaiyi New Materials Co., Ltd.

[0029] n-Propanol was purchased from Shanghai Zhanyun Chemical Co., Ltd.;

[0030] Octylphenol polyoxyethylene ether was purchased from Changxing Shixin Chemical Co., Ltd.;

[0031] Platinum carbon is homemade, and its platinum content is 5%;

[0032] The ptfe board was purchased from Taobao platform;

[0033] Proton exchange membranes were purchased from Guizhou Juneng Century Technology Co., Ltd.

[0034] Example

[0035] The embodiments of the present invention will be described in detail below. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] Example

[0037] Prepare the membrane electrode as follows:

[0038] 1. Anode Catalyst Slurry Preparation: The anode catalyst slurry consists of a catalyst, a binder, a dispersing solvent, and a surface reducing agent. The catalyst is lead dioxide, the binder is a perfluorosulfonic acid resin solution, the dispersant is n-propanol and water, and the surface reducing agent is octylphenol polyoxyethylene ether. The mass ratios of these five components are shown in Table 1. After mixing thoroughly, the slurry was cleaned in an ultrasonic cleaner for 10 minutes and dispersed in an emulsifying homogenizer for 30 minutes.

[0039] 2. Preparation of cathode catalyst slurry: The cathode catalyst slurry includes platinum carbon, a binder, and a solvent. The binder is a perfluorosulfonic acid resin solution, and the solvent is n-propanol. The mass ratios of these three components are shown in Table 1. After the three substances are evenly mixed, the cathode catalyst slurry is obtained.

[0040] 3. Apply the anode catalyst slurry. Take a PTFE plate with a size of 63mmx63mm and a thickness of 0.3mm as the transfer film, wipe the surface clean with alcohol, and use a 3mm wide polyimide tape to stick along the edges of the PTFE plate to fix it on the magnetic stirrer. Turn on the magnetic stirrer and set the temperature to about 40℃. Preheat for 2-3 minutes. Stir the dispersed slurry evenly with a glass rod, use a pipette to draw 1-1.5ml of slurry on the PTFE membrane, and immediately use a nylon fiber brush to evenly apply a thin layer. After the slurry surface is dry, repeat the above operation until the catalyst slurry is applied and dried. The application and drying process takes 10-15 minutes. (When applying the catalyst slurry, heat it to a temperature that can quickly dry the catalyst slurry, then turn off the power. Then use the residual heat to dry it. If the subsequent temperature drop is not enough for drying, turn on the power again to heat it.)

[0041] 4. Cathode catalyst slurry spraying: The proton exchange membrane is spread flat on the heating plate in the ultrasonic sprayer through vacuum adsorption, the spraying area is selected, the temperature is set to 100-110℃, the pressure is 1.4psi, the spraying flow rate is 2ml / min, and the sprayer is started. The nozzle automatically sprays evenly in the selected area until the slurry is sprayed. The spraying process takes 30-40 minutes.

[0042] 5. Hot pressing. Immerse the PTFE plate coated with the anode catalyst and the proton exchange membrane sprayed with the cathode catalyst on one side in a 40% ethylene glycol solution. After 15 minutes, remove the plate and place the catalyst layer on the PTFE plate on the other side of the proton exchange membrane. Place the plate in a hot press and press it for 3-5 minutes at a temperature of 140-148°C and a pressure of 2.8 MPa. Immediately remove the PTFE plate after hot pressing to obtain a successfully transferred three-in-one membrane electrode. If the catalyst layer on the PTFE plate is not fully transferred after hot pressing, maintain the above temperature and pressure and hot press for a second time for 10 seconds to complete the transfer.

[0043] The prepared membrane electrode was powered on for ozone production testing. The specific steps are as follows: The ozone membrane electrode test was conducted on a homemade electrolytic cell. The membrane electrode was installed in the cell, the piping was connected, and the power was turned on to start operation. Working principle: Deionized water enters the electrolytic cell's anode, where it decomposes into ozone and protons. Ozone is discharged or collected through the outlet. Protons pass through the proton exchange membrane and enter the cathode. There, they undergo an oxygen reduction reaction with the incoming oxygen to produce water, which is discharged through the lower outlet on the cathode side.

[0044] The performance of the ozone generator was tested, that is, the voltage and current values ​​were tested. The test results are shown in Table 2.

[0045] Comparative Example 1

[0046] The same cathode catalyst layer and proton exchange membrane as in Example 1 are used, and the formula of the anode catalyst layer is also the same. The difference is that the preparation method of the anode catalyst layer is different. The preparation method is as follows: manual brushing is used, that is, the catalyst slurry is dipped with a brush and then directly brushed on the proton exchange membrane, and then repeatedly applied and hot pressed into shape.

[0047] The prepared membrane electrode was applied to an ozone generator and powered on to produce ozone. The test results are shown in Table 2.

[0048] Comparative Example 2

[0049] The same anode catalyst layer and proton exchange membrane as in Example 1 were used, except that a different cathode catalyst layer was used. The preparation method was as follows:

[0050] Formula: platinum carbon: resin = 2.2:1, platinum carbon: n-propanol = 1.1:30, preparation method is the same as above.

[0051] The prepared membrane electrode was applied to an ozone generator and powered on to produce ozone. The test results are shown in Table 2.

[0052] Comparative Example 3

[0053] The same cathode catalyst layer and proton exchange membrane as those in Example 1 were used, except that the anode catalyst formulation disclosed in Example 1 of patent CN102899685A was used, and the anode catalyst layer was prepared by a transfer method.

[0054] The prepared membrane electrode was applied to an ozone generator and powered on to produce ozone. The test results are shown in Table 2.

[0055] Table 1 Composition of cathode and anode catalysts in Examples 1 to 3 and Comparative Examples 1 and 2

[0056]

[0057] Table 2 Performance of ozone generators in Examples 1 to 3 and Comparative Examples 1 and 2

[0058]

[0059] As can be seen from Table 2, the anode performance of the technical solution of this application is stable, and the catalytic layer does not fall off during actual use. However, in Comparative Example 1, the membrane electrode catalytic layer directly falls off, making it difficult to form the membrane electrode. Although the performance of Comparative Example 2 is stable, hydrogen is produced at the cathode. This is because the formulation of the cathode catalyst layer in Comparative Document 2 has been changed, resulting in a change in the cathode reaction mechanism. That is, after protons reach the cathode, they obtain electrons to generate hydrogen.

[0060] The above description of the embodiments is intended to facilitate understanding and application of the present application by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without expending any creative effort. Therefore, the present application is not limited to the embodiments described herein, and improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A membrane electrode for producing ozone, comprising a cathode, an anode and a diaphragm, characterized in that: The anode surface is loaded with an anode catalyst layer, and the cathode surface is loaded with a cathode catalyst layer. The anode catalyst layer includes lead dioxide, a binder, a dispersing solvent, and a surfactant. The mass ratio of the lead dioxide, the binder, the dispersing solvent, and the surfactant is (5-10):1:(40-50):(0.13-0.26). The dispersing solvent includes n-propanol and water. The mass ratio of the lead dioxide, n-propanol, and water is (5-10):(5-10):(30-45). The surfactant is octylphenol polyoxyethylene ether. The cathode catalyst layer includes platinum carbon, a binder, and a solvent. The platinum loading in the cathode catalyst layer is 0.5-1 mg / cm 2 The mass ratio of the carbon content in the platinum carbon to the binder is 1: (0.5-1); the membrane electrode is prepared by the following method: (1) Lead dioxide, a binder, a dispersing solvent, and a surfactant are mixed in proportion, and after ultrasonic cleaning and emulsification, an anode catalyst slurry is formed; platinum carbon, a binder, and a solvent are mixed in proportion, and after ultrasonic cleaning, a cathode catalyst slurry is obtained; (2) Fix the transfer film, drip the anode catalyst slurry, and evenly apply it on one side of the transfer film. After drying, repeat the above dripping and applying steps until a 0.015-0.020 mm thick anode catalyst layer is formed on one side of the transfer film; (3) Take a diaphragm and apply the cathode catalyst slurry on one side of the diaphragm by spraying to form a cathode catalyst layer with a thickness of 0.010-0.015 mm; (4) Soaking the diaphragm with the cathode catalyst layer and the transfer film with the anode catalyst layer in an ethylene glycol solution, then taking out the anode catalyst layer on the transfer film and coating it on the side of the diaphragm not coated with the cathode catalyst layer. After hot pressing, the transfer film is peeled off to obtain the membrane electrode.

2. The membrane electrode for producing ozone according to claim 1, characterized in that The binder is perfluorosulfonic acid resin.

3. The membrane electrode for producing ozone according to claim 1, characterized in that The solvent is liquid alcohol.

4. The membrane electrode for producing ozone according to claim 1, characterized in that The membrane is a proton exchange membrane.

5. A method for preparing a membrane electrode according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) Lead dioxide, a binder, a dispersing solvent, and a surfactant are mixed in proportion, and after ultrasonic cleaning and emulsification, an anode catalyst slurry is formed; platinum carbon, a binder, and a solvent are mixed in proportion, and after ultrasonic cleaning, a cathode catalyst slurry is obtained; (2) Fix the transfer film, drip the anode catalyst slurry, and evenly apply it on one side of the transfer film. After drying, repeat the above dripping and applying steps until a 0.015-0.020 mm thick anode catalyst layer is formed on one side of the transfer film; (3) Take a diaphragm and apply the cathode catalyst slurry on one side of the diaphragm by spraying to form a cathode catalyst layer with a thickness of 0.010-0.015 mm; (4) Soaking the diaphragm with the cathode catalyst layer and the transfer film with the anode catalyst layer in an ethylene glycol solution, then taking out the anode catalyst layer on the transfer film and coating it on the side of the diaphragm not coated with the cathode catalyst layer. After hot pressing, the transfer film is peeled off to obtain the membrane electrode.

6. The method for preparing a membrane electrode according to claim 5, wherein: In step (1), the frequency of the ultrasound is 1000-10000 rpm, and the ultrasound time is 10-30 min; the emulsification is completed in an emulsifying homogenizer, and the emulsification time is 20-60 min.

7. The method for preparing a membrane electrode according to claim 5, wherein: In step (2), the volume of the anode catalyst slurry dripped each time is 1-1.5 mL, the temperature used for drying is 30-50° C., and the time required for drying is 10-15 min.

8. The method for preparing a membrane electrode according to claim 5, wherein: In step (4), the mass concentration of the ethylene glycol is 30% to 50%, and the soaking time is 10 to 20 minutes; The temperature used in hot pressing is 140~148℃, the pressure is 2.5~3.0Mpa, and the time is 3~5min.

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