Anode slurry and preparation method thereof

Abstract

The invention belongs to the field of proton exchange membrane water electrolysis, and particularly relates to anode slurry and a preparation method thereof. The anode slurry is used for preparing a membrane electrode, and the membrane electrode is used for electrolysis of proton exchange membrane water; the anode slurry comprises an anode catalyst, an ionic polymer, liquid alcohol, ultrapure water and polyvinyl alcohol, and the solid content of the anode slurry is 0.5%-5%; the anode catalyst is one or more of iridium oxide, iridium black and iridium-based mixed oxide; the mass ratio of the ionic polymer to iridium in the anode catalyst is 0.2-1.2, the ionic polymer is a perfluorinated sulfonic acid resin polymer, and the mass fraction of liquid alcohol in the ionic polymer is 0-50%; the molecular weight of the polyvinyl alcohol is 25,000-300,000, and the mass ratio of the polyvinyl alcohol in the anode slurry is 0.01%-1%. The anode slurry prepared by the method is stable in dispersion and not easy to settle, and the surface of a catalytic base layer of a membrane electrode prepared from the slurry is fluffy and has pore structures with different pore diameters.

Description

Technical Field

[0001] The invention belongs to the field of proton exchange membrane water electrolysis, and in particular relates to an anode slurry and a preparation method thereof. Background Art

[0002] As the core component of the PEM water electrolyzer, the membrane electrode involves steps such as feeding, slurry dispersion, coating and packaging in its preparation process. The slurry is particularly important, mainly including the above-mentioned feeding and slurry dispersion processes. The formula of the anode slurry is usually composed of an iridium-based catalyst, a dispersant and a perfluorosulfonic acid ionomer solution. Among them, in order to disperse the catalyst and quickly dry the slurry during coating, the anode slurry usually needs to add 10-50% of liquid alcohol as a dispersant. The membrane electrode prepared with the above-mentioned commonly used anode slurry usually produces a large mass transfer resistance when working at a high current density, that is, the generated oxygen cannot be discharged in time, thereby reducing the hydrogen production efficiency of the electrolyzer, accompanied by an increase in energy consumption. Therefore, the development of an anode slurry with accelerated degassing characteristics for use in PEM water electrolysis to produce hydrogen is of great significance to the development of this industry. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an anode slurry and a method for preparing the same. The purpose of the present invention is to propose an anode slurry formulation with accelerated degassing characteristics for the existing alcohol-based anode slurry formulation for PEM water electrolysis, which has slow degassing. The catalyst particles dispersed in the slurry formulation are small and evenly distributed. The surface of the membrane electrode catalyst substrate prepared by the above slurry is fluffy and has a pore structure with different pore sizes, which can avoid the problems of difficult degassing and large mass transfer loss in the membrane electrode prepared by the commonly used alcohol-based anode formulation.

[0004] In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is: In a first aspect, an embodiment of the present invention provides an anode slurry, wherein the anode slurry is used to prepare a membrane electrode, and the membrane electrode is used for proton exchange membrane water electrolysis; The anode slurry comprises an anode catalyst, an ion polymer, liquid alcohol, ultrapure water and polyvinyl alcohol, and the solid content of the anode slurry is 0.5%-5%; The anode catalyst is one or more of iridium oxide, iridium black and iridium-based mixed oxides; The mass ratio of the ion polymer to the iridium in the anode catalyst is 0.2-1.2, the ion polymer is a perfluorosulfonic acid resin polymer, and the mass fraction of the liquid alcohol in the ion polymer is 0%-50%; The molecular weight of the polyvinyl alcohol is 25,000-300,000, and the mass proportion of the polyvinyl alcohol in the anode slurry is 0.01%-1%.

[0005] Furthermore, the mass content of iridium in the iridium-based mixed oxide is 20-60%.

[0006] Furthermore, the liquid alcohol is an alcohol having 1-8 carbon atoms, and the mass proportion of the liquid alcohol in the anode slurry is 10%-70%.

[0007] In a second aspect, an embodiment of the present invention provides a method for preparing the anode slurry according to the first aspect, comprising the following steps: Step S1, adding the anode catalyst to predetermined amounts of ultrapure water, liquid alcohol, ion polymer and polyvinyl alcohol, and stirring the solution with a magnetic stirrer to obtain an initial mixed slurry; Step S2, subjecting the initial mixed slurry obtained in step S1 to ultrasonic dispersion to obtain a uniformly dispersed slurry.

[0008] Furthermore, in step S1, the stirring speed of the magnetic stirrer is 300-2000 rpm.

[0009] Furthermore, in step S2, the dispersing device used for ultrasonic dispersion is an ultrasonic cell pulverizer with a power of 50-200w and an ultrasonic duration of 2-24h.

[0010] The technical solution provided by the embodiment of the present invention has the following beneficial effects: The present invention is optimized based on the existing PEM water electrolysis hydrogen production alcohol-based anode slurry formula. By optimizing the amount of polyvinyl alcohol added in slurries with different liquid alcohol contents, the prepared anode slurry is dispersed and stable and not easy to settle. The surface of the membrane electrode catalyst substrate prepared by using the above slurry is fluffy and has a pore structure with different pore sizes. The problems of difficult degassing and large mass transfer loss existing in the membrane electrode prepared by the commonly used alcohol-based anode formula can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The cell performance diagram of the membrane electrode prepared with the catalyst slurry of Example 1 and Comparative Example 1.

[0012] Figure 2 The cell performance diagram of the membrane electrode prepared with the catalyst slurry of Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0014] Example 1 A method for preparing an anode slurry comprises the following steps: Step S1, according to the solid content of 1.5%, the mass ratio of iridium in the ion polymer and iridium oxide catalyst of 0.55, and the mass content of liquid alcohol of 43%, 300 mg of iridium oxide catalyst (iridium mass content 75%), 15.8 mL of ultrapure water, 15.1 mL of isopropanol, 612.6 μL of Nafion resin mixed solution (DuPont D2020) and 15 mg of polyvinyl alcohol (purchased from Aladdin, Lot # L1925029) were weighed into a 50 mL beaker, and the solution was stirred with a magnetic stirrer, the stirrer speed was set to 900 rpm, and the stirring time was 10 min; Step S2: After the stirring is completed, the beaker is placed in cold water and ultrasonically dispersed using a cell crusher with a power of 100 W for 3 h to obtain an anode slurry.

[0015] The obtained anode slurry was sprayed on PTFE by ultrasonic spraying machine, and the platinum loading on PTFE membrane was 0.3 mg / cm 2 The cathode catalyst layer and Nafion 115 proton exchange membrane were prepared into membrane electrodes by double-sided thermal transfer, and the water electrolysis performance was tested.

[0016] Example 2 A method for preparing an anode slurry comprises the following steps: Step S1, according to the solid content of 1.5%, the mass ratio of iridium in the ion polymer and iridium oxide catalyst of 0.55, and the mass content of liquid alcohol of 20%, 300 mg of iridium oxide catalyst (iridium mass content 75%), 26.1 mL of ultrapure water, 8.0 mL of isopropanol, 612.6 μL of Nafion resin mixed solution (DuPont D2020) and 24 mg of polyvinyl alcohol (purchased from Aladdin, Lot # L1925029) were weighed into a 50 mL beaker, and the solution was stirred with a magnetic stirrer, the stirrer speed was set to 900 rpm, and the stirring time was 10 min; Step S2: After the stirring is completed, the beaker is placed in cold water and ultrasonically dispersed using a cell crusher with a power of 100 W for 3 h to obtain an anode slurry.

[0017] The obtained anode slurry was sprayed on PTFE by ultrasonic spraying machine, and the platinum loading on PTFE membrane was 0.3 mg / cm 2 The cathode catalyst layer and Nafion 115 proton exchange membrane were prepared into membrane electrodes by double-sided thermal transfer, and the water electrolysis performance was tested.

[0018] Comparative Example 1 A method for preparing an anode slurry comprises the following steps: Step S1, according to the solid content of 1.5%, the mass ratio of iridium in the ion polymer and iridium oxide catalyst of 0.55, and the mass content of liquid alcohol of 43%, 300 mg of iridium oxide catalyst (iridium mass content 75%), 15.8 mL of ultrapure water, 15.1 mL of isopropanol, and 612.6 μL of Nafion resin mixed solution (DuPont D2020) were weighed into a 50 mL beaker, and the solution was stirred with a magnetic stirrer, the stirrer speed was set to 900 rpm, and the stirring time was 10 min; Step S2: After the stirring is completed, the beaker is placed in cold water and ultrasonically dispersed using a cell crusher with a power of 100 W for 3 h to obtain an anode slurry.

[0019] The obtained anode slurry was sprayed on PTFE by ultrasonic spraying machine, and the platinum loading on PTFE membrane was 0.3 mg / cm 2 The cathode catalyst layer and Nafion 115 proton exchange membrane were prepared into membrane electrodes by double-sided thermal transfer, and the water electrolysis performance was tested.

[0020] Comparative Example 2 A method for preparing an anode slurry comprises the following steps: Step S1, according to the solid content of 1.5%, the mass ratio of iridium in the ion polymer and iridium oxide catalyst of 0.55, and the mass content of liquid alcohol of 20%, 300 mg of iridium oxide catalyst (iridium mass content 75%), 26.1 mL of ultrapure water, 8.0 mL of isopropanol and 612.6 μL of Nafion resin mixed solution (DuPont D2020) were weighed into a 50 mL beaker, and the solution was stirred with a magnetic stirrer, the stirrer speed was set to 900 rpm, and the stirring time was 10 min; Step S2: After the stirring is completed, the beaker is placed in cold water and ultrasonically dispersed using a cell crusher with a power of 100 W for 3 h to obtain an anode slurry.

[0021] The obtained anode slurry was sprayed on PTFE by ultrasonic spraying machine, and the platinum loading on PTFE membrane was 0.3 mg / cm 2 The cathode catalyst layer and Nafion 115 proton exchange membrane were prepared into membrane electrodes by double-sided thermal transfer, and the water electrolysis performance was tested.

[0022] The water electrolysis performance of the membrane electrodes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 was tested. The specific test results are shown in Figure 1 and Figure 2 . Figure 1In Example 1, polyvinyl alcohol (PVA) is introduced into the conventional alcohol-based anode slurry formula (alcohol content 43%). The amount of PVA added is 5% of the mass of iridium oxide. The polarization performance of the membrane electrode is 2.5 A / cm 2 There will be a significant improvement in the future, and the mass transfer loss will be reduced. The reduction in mass transfer loss is due to the fact that under the conditions of temperature and reaction water, PVA dissolves in water and leaves the catalyst layer as the water is discharged. The departure of PVA changes the structure of the catalyst layer, making the surface of the catalyst layer more fluffy and having more porous structures at the microscopic level. Figure 2 The same conclusion can be drawn. In Example 2, PVA is introduced on the basis of the conventional alcohol-based anode slurry formula (alcohol content 20%). The amount of PVA added is 8% of the mass of iridium oxide. The polarization performance of the membrane electrode is 1.0 A / cm 2 There will be a great improvement in the future and the mass transfer loss will be reduced.

[0023] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An anode slurry, characterized in that: The anode slurry is used to prepare a membrane electrode, and the membrane electrode is used for proton exchange membrane water electrolysis; The anode slurry comprises an anode catalyst, an ion polymer, liquid alcohol, ultrapure water and polyvinyl alcohol, and the solid content of the anode slurry is 0.5%-5%; The anode catalyst is one or more of iridium oxide, iridium black and iridium-based mixed oxides; The mass ratio of the ion polymer to the iridium in the anode catalyst is 0.2-1.2, the ion polymer is a perfluorosulfonic acid resin polymer, and the mass fraction of the liquid alcohol in the ion polymer is 0%-50%; The molecular weight of the polyvinyl alcohol is 25,000-300,000, and the mass proportion of the polyvinyl alcohol in the anode slurry is 0.01%-1%.

2. The anode slurry according to claim 1, characterized in that: The mass content of iridium in the iridium-based mixed oxide is 20-60%.

3. The anode slurry according to claim 1, characterized in that: The liquid alcohol is an alcohol having 1-8 carbon atoms, and the mass proportion of the liquid alcohol in the anode slurry is 10%-70%.

4. The method for preparing the anode slurry according to any one of claims 1 to 3, characterized in that: The steps include: Step S1, adding the anode catalyst to predetermined amounts of ultrapure water, liquid alcohol, ion polymer and polyvinyl alcohol, and stirring the solution with a magnetic stirrer to obtain an initial mixed slurry; Step S2, subjecting the initial mixed slurry obtained in step S1 to ultrasonic dispersion to obtain a uniformly dispersed slurry.

5. The method for preparing anode slurry according to claim 4, characterized in that: In step S1, the stirring speed of the magnetic stirrer is 300-2000 rpm.

6. The method for preparing anode slurry according to claim 4, characterized in that: In step S2, the dispersing device used for ultrasonic dispersion is an ultrasonic cell crusher with a power of 50-200w and an ultrasonic duration of 2-24h.

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