KR102358255B1 - High temperature type anion exchange membrane, water electrolysis apparatus comprising the same, and method for preparing the same - Google Patents

Abstract

Disclosed herein are a high-temperature anion exchange membrane, a water electrolysis device including the same, and a method for manufacturing the same.

Description

High temperature type anion exchange membrane, water electrolysis device including same, and manufacturing method thereof

The present invention relates to a high-temperature type anion exchange membrane, a water electrolysis device including the same, and a method for manufacturing the same. More specifically, the present invention relates to a high-temperature type anion exchange membrane capable of conducting anions at a high temperature (100° C. or higher), a water electrolysis device including the same, and a method for manufacturing the same.

Hydrogen has a high energy density (compressed hydrogen gas: 142 MJ/kg) and is in the spotlight as a future energy carrier with characteristics most suitable for grid-scale applications. Methods such as steam reforming, gas-shift reaction, and biomass gasification are often used in the production of hydrogen, but since they all generate greenhouse gases, hydrogen production using water electrolysis is the most suitable as the most environmentally friendly method. Water electrolysis is a technology that electrochemically decomposes water to produce hydrogen and oxygen.

The existing water electrolysis operation method, which has been commercialized for decades, involves immersing an electrode in a strong base solution such as a 10 M KOH solution and applying a voltage to perform electrolysis. It has problems such as having limitations.

By replacing this, manufacturing a unit cell based on the intermediate anion linking membrane can solve the above problems. The unit cell includes an anion exchange membrane, an anode electrode formed on one side of the anion exchange membrane, and a cathode electrode formed on the other side of the anion exchange membrane. Water is decomposed at the cathode to generate hydrogen and hydroxide ions (OH-). The generated hydroxide ions are transferred through the intermediate anion exchange membrane, and at the anode, a chemical reaction occurs in which oxygen is generated from the hydroxide ions. Each of these electrochemical reactions takes place in a catalyst on a gas diffusion layer (GDL). At this time, as an intermediate electrolyte, the anion exchange membrane exhibits high conductivity of hydroxide ions in a wet state, and serves to separate hydrogen and oxygen generated by water electrolysis due to low gas permeability. If a battery is constructed based on an anion exchange membrane, not only can a higher hydrogen production rate than solution phase hydrogen production be obtained, but also have the advantage that a catalyst of a non-noble metal can be used, unlike operation under acidic conditions using a cation exchange membrane (Non-patent literature). One). However, it has a limitation in that the performance is lower than 1/3 of that of the cation exchange membrane water electrolysis. In order to improve this and increase the performance of the anion exchange membrane-based water electrolysis cell, attempts such as activation in operation have been made (Patent Document 1). have (non-patent document 2).

When water electrolysis is operated at high temperature, there is an advantage in that catalyst activity increases and ion conductivity can be increased. Therefore, it is necessary to develop an anion exchange membrane capable of conducting anions at high temperature.

Korean Patent Publication No. 10-2018-0128562

Yongjun Leng, Guang Chen, Alfonso J. Mendoza, Timothy B. Tighe, Michael A. Hickner, and Chao-Yang WangChen, Guoying, Simon R. Bare, and Thomas E. Mallouk. “Solid-State Water Electrolysis with an Alkaline Membrane” Journal of American Chemical Society 134 (2012): 9054 - 9057. Dongyang Chen and Michael A. Hickner. “Degradation of Imidazolium- and Quaternary Ammonium-Functionalized Poly(fluorenyl ether ketone sulfone) Anion Exchange Membranes” Applied Materials and Interfaces 4 (2012): 5775 - 5781.

An object of the present invention is to solve the problem that the conventional anion exchange membrane has poor performance at a temperature of 100 ° C. or higher, and has improved performance by increasing catalyst activity and ion transfer rate even at high temperatures, a water electrolysis device including the same, and To provide a manufacturing method thereof.

In an exemplary embodiment of the present invention, as a high-temperature type anion exchange membrane, the high-temperature type anion exchange membrane includes a polybenzimidazole-based polymer capable of KOH doping, and the KOH-doped polybenzimidazole-based polymer is phosphoric acid doped. To provide a high-temperature type anion exchange membrane in which phosphoric acid is removed from a polybenzimidazole-based polymer.

Another exemplary embodiment of the present invention provides a water electrolysis device including the above-described high-temperature type anion exchange membrane.

In another exemplary embodiment of the present invention, there is provided a method for manufacturing the above-described high-temperature type anion exchange membrane, comprising the steps of: polymerizing a polybenzimidazole-based polymer in a solution and then adding phosphoric acid to terminate the polymerization; Dissolving the polybenzimidazole-based polymer after the polymerization reaction has been completed in phosphoric acid, and then casting it on a substrate; hydrolyzing the film cast on the substrate; and immersing the hydrolyzed membrane in an ammonia solution to remove phosphoric acid from the hydrolyzed membrane, thereby obtaining a high-temperature type anion exchange membrane capable of anion conduction.

In another exemplary embodiment of the present invention, manufacturing a high-temperature type anion exchange membrane according to the above-described manufacturing method; preparing an anode on which an oxygen-generating catalyst is supported and a cathode on which a hydrogen-generating catalyst is supported by applying a catalyst on the gas diffusion layer by spraying and then performing heat treatment; and assembling the high-temperature type anion exchange membrane between the positive electrode and the negative electrode. It provides a method for manufacturing a high-temperature type water electrolysis battery comprising a.

The high-temperature type anion exchange membrane manufactured according to the manufacturing method of the present invention is stable even at a high temperature (100° C. or higher) and has high ionic conductivity compared to the existing anion exchange membrane. A high-temperature type anion exchange membrane water electrolyzer using this increases catalytic activity and ion conduction speed due to a high operating temperature (100° C. or higher), thereby providing improved water electrolysis efficiency compared to a conventional anion exchange membrane water electrolysis device.

1 is a graph comparing the ionic conductivity of a typical commercial membrane (FAA-PK-75) and a high-temperature type anion exchange membrane according to an embodiment of the present invention.
2 is a conceptual diagram schematically illustrating the principle of a water electrolysis device including a high-temperature type anion exchange membrane according to an embodiment of the present invention.
3 is a current density-voltage curve graph of a water electrolysis device including a high-temperature type anion exchange membrane according to an embodiment of the present invention.
4 is a view showing that the high-temperature type anion exchange membrane according to an embodiment of the present invention is doped with KOH, which is a solution supplied to the anode during operation of the high-temperature type water electrolyzer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention disclosed in the text are illustrated for the purpose of explanation only, and the embodiments of the present invention may be embodied in various forms and should not be construed as being limited to the embodiments described in the text. .

The present invention can make various changes and can have various forms, and the embodiments are not intended to limit the present invention to a specific disclosed form, and all changes, equivalents or substitutes included in the spirit and scope of the present invention should be understood as including

In the present specification, when a part "includes" a certain component, this means that other components may be further included rather than excluding other components unless otherwise stated.

high temperature anion exchange membrane

In exemplary embodiments of the present invention, as a high-temperature type anion exchange membrane, the high-temperature type anion exchange membrane includes a polybenzimidazole-based polymer capable of KOH doping, and the polybenzimidazole-based polymer capable of doping with KOH is phosphoric acid. To provide a high-temperature type anion exchange membrane in which phosphoric acid is removed from a doped polybenzimidazole-based polymer.

A general polybenzimidazole film manufactured by direct casting exists in a state doped with phosphoric acid after completion. When used as it is, phosphoric acid acts as a cation conductor and can be used as a cation exchange membrane. However, the present inventors used the polybenzimidazole membrane as an anion exchange membrane by removing the doped phosphoric acid and doping it with KOH during battery operation instead. In other words, since PBI has excellent thermal stability, it is doped with KOH to have anion exchange performance and applied to high-temperature water electrolysis.

Therefore, the high-temperature type anion exchange membrane according to an embodiment of the present invention includes a polybenzimidazole-based polymer capable of KOH doping, and has excellent ionic conductivity even at a high temperature of 100° C. or higher, and has stable and high water electrolysis performance. In an exemplary embodiment, the high-temperature type anion exchange membrane may be used in a high-temperature type water electrolysis device operated at a temperature of 100° C. or higher. For example, the temperature may be 110 °C or higher or 120 °C or higher.

For example, in the high-temperature type anion exchange membrane of the present invention, when the high-temperature type water electrolysis device is operated, KOH supplied to the positive electrode is doped in the form of ions as shown in FIG. 4, and in particular, anions can be conducted by OH ions.

In another exemplary embodiment of the present invention, there is provided a water electrolysis device including the above-described high-temperature type anion exchange membrane and having an operating temperature of 100° C. or higher. For example, the operating temperature may be 110 °C or higher or 120 °C or higher.

The present invention will be described in more detail through the following practice. However, the examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

high temperature anion exchange membrane Manufacturing method

In exemplary embodiments of the present invention, as a method for manufacturing the above-described high-temperature type anion exchange membrane, the polybenzimidazole-based polymer is polymerized in a solution, and then phosphoric acid is added to terminate the polymerization reaction (S1); Dissolving the polybenzimidazole-based polymer after the polymerization reaction has been completed in phosphoric acid, and then casting it on a substrate (S2); hydrolyzing the film cast on the substrate (S3); and immersing the hydrolyzed membrane in an ammonia solution to remove phosphoric acid from the hydrolyzed membrane, thereby obtaining a high-temperature anion exchange membrane capable of anion conduction (S4).

According to the manufacturing method of the present invention, phosphoric acid-doped polybenzimidazole membrane mainly used in high-temperature cation exchange membrane fuel cells is treated with ammonia solution to remove phosphoric acid, and KOH, a solution supplied to the anode during battery operation later, is K+ , can be doped in the form of ions of OH-. Therefore, it is possible to conduct anion through the doped OH ions, and since it contains the PBI polymer having high thermal stability, it is possible to manufacture a high-temperature type anion exchange membrane stably having high water electrolysis performance even at a high temperature of 100° C. or more.

Polybenzimidazole-based polymer polymerized in the present invention is not particularly limited, and non-limiting examples thereof include, for example, polybenzimidazole-based polymers of the following [Formula 1] to [Formula 8].

[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

(In Formulas 6 to 8, based on the sum of all repeating units of A and B, A is the percentage of repeating units that do not include a sulfonic acid group, B is the percentage of repeating units that include a sulfonic acid group, and A is 0 to 99%, and B is 100 to 1%. In Formula 8, Y is O or S if no atom is present or is present.)

First, in the polymerization step (S1), after the polymerization of the polybenzimidazole polymer is completed, phosphoric acid is added to make a suitable viscosity for casting. In addition, if phosphoric acid is added during the polymerization process, polyphosphoric acid absorbs a large amount of water in phosphoric acid (85% aqueous solution) rather than H ₂ O generated during polybenzimidazole polymer condensation polymerization, thereby slowing down the polymer polymerization reaction. , resulting in the termination of polymer polymerization.

At this time, if the polymer polymerization proceeds excessively, the molecular weight is excessive and does not dissolve in phosphoric acid, making casting impossible, and if the molecular weight is too low, the physical properties may be very weak. Therefore, the end point of polymerization is measured by the torque value of the overhead stirrer used during stirring, and the reaction can be terminated when, for example, about 8 Nm.

In a non-limiting example, in the case of polybenzimidazole, which is a representative polybenzimidazole-based polymer, 3.3'-diaminobenzidine (3,3'-Diaminobenzidine), isophthalic acid, and polyphosphoric acid are added and in an inert atmosphere. can be polymerized.

When performing polymer polymerization using a solvent, if the polymer material is uniformly dissolved in the solvent, the viscosity and solution temperature should be adjusted. By controlling the viscosity and the solution temperature in this way, it is easy to form a film directly on the substrate without precipitation in a poor solvent.

Thereafter, by dissolving the polymerization-completed polymer in phosphoric acid, the polymerized PBI polymer can be homogeneously released in phosphoric acid, and this can be cast on a substrate.

When the cast membrane is hydrolyzed, polyphosphoric acid used as a solvent during polymer polymerization becomes phosphoric acid through a hydrolysis process as shown in Scheme 2 below, and phosphoric acid can naturally be doped into the membrane.

[Scheme 2]

Such hydrolysis may be performed at a temperature of 40 °C or higher and a relative humidity of 60% or higher, for example, the temperature may be 45 °C or higher or 50 °C or higher, and the relative humidity is 65% or higher, 70% or higher, 75% or higher , or 80% or more.

The hydrolyzed membrane may be immersed in distilled water and alcohol (eg, iopropyl alcohol), and then dried.

Thereafter, the hydrolyzed membrane is immersed in ammonia water to completely remove the phosphoric acid doped inside the membrane through an acid-base reaction. By removing doped phosphoric acid, KOH can be doped during battery operation later, so that anion conduction may be possible (S4).

The phosphoric acid may be removed, and the membrane may be additionally washed with distilled water and dried.

The high-temperature type anion exchange membrane prepared as described above can be usefully used in a water electrolysis device operating at a high temperature.

In another exemplary embodiment of the present invention, according to the above-described manufacturing method, manufacturing a high-temperature type anion exchange membrane; preparing an anode on which an oxygen-generating catalyst is supported and a cathode on which a hydrogen-generating catalyst is supported by applying a catalyst on the gas diffusion layer by spraying and then performing heat treatment; and assembling the high-temperature type anion exchange membrane between the positive electrode and the negative electrode. It provides a method for manufacturing a high-temperature type water electrolysis battery comprising a.

In an exemplary embodiment, in the assembling step, a gold (Au)-plated titanium separator may be assembled on one surface that is not assembled with the high-temperature anion exchange membrane of the positive electrode.

In an exemplary embodiment, the assembly may be fastened and assembled with a fastening pressure of 3 to 6 N/m ² , for example, fastened and assembled with a fastening pressure of 4 N/m ² . When the clamping pressure is less than 3 N/m ² , water may leak between the cells, and if it is more than 6 N/m ² , there is a risk of damaging the electrode.

Example

Manufacture of high temperature type anion exchange membrane (HT-AEM)

Dried 3,3'-diaminobenzidine, terephthalic acid, and polyphosphoric acid as shown in Scheme 1 were put into a round-bottom flask, and stirred at 150 °C in an argon atmosphere for 15 hours. After that, the temperature was raised to 220 °C, stirred for 4-7 hours, and when the appropriate viscosity (when the torque value applied to the overhead stirrer used during stirring was about 8 Nm) was reached, phosphoric acid was added and the reaction was terminated.

[Scheme 1]

After stirring for 2-3 hours to completely dissolve the polymer in phosphoric acid, the polymer mixture was poured on a glass plate and cast using a doctor blade.

The cast polymer membrane was hydrolyzed for 24 hours at a temperature of 50 °C and RH 80% (humidity) in a humidification chamber. The hydrolyzed membrane was immersed in distilled water and isopropyl alcohol and dried. The approximate hydrolysis process of polyphosphoric acid is shown in Scheme 2 below.

[Scheme 2]

Thereafter, to obtain a polymer electrolyte membrane from which phosphoric acid has been removed, it was immersed in ammonia solution, washed with distilled water, and dried.

Comparison of Ion Conductivity of Anion Exchange Membrane

1 shows the results of measuring the ionic conductivity of the high-temperature anion exchange membrane prepared in the above example and the commercial membrane, FFA-PK-75, in a state of hydration with water. Specifically, the in-plane conductivity was measured using a four-probe cell at 50°C and 98% relative humidity, and as a result of the measurement, it can be seen that the ion degree of the high-temperature type anion exchange membrane according to the embodiment of the present invention is more than twice as high. there was.

High-temperature type anion exchange membrane-based water electrolyzer (HT-AEMWE) electrode manufacturing

About 1 mg/cm ² of the Pt/C catalyst was supported on the negative electrode. In the catalyst loading process, polytetrafluoroethylene (PTFE), distilled water, and isopropyl alcohol were first added to 46.2% Pt/C, and then dispersed by ultrasonication to prepare a catalyst slurry. The prepared catalyst slurry is applied to carbon paper (TGP-H-120) using a spray gun. The prepared Pt/C electrode was heat-treated in an argon atmosphere at 350° C. for 5 minutes.

About 3 mg/cm ² of the IrO ₂ catalyst was supported on the positive electrode. In the previous cathode manufacturing method, IrO ₂ was added instead of Pt/C, which was added during slurry preparation, and prepared in the same manner. The prepared catalyst slurry was applied to Ti paper (Bekaert) using a spray gun, and then heat-treated at 350° C. in an argon atmosphere for 5 minutes in the same manner as in the previous conditions. The area of the prepared electrode was 2.25 cm2 (1.5 cm x 1.5 cm).

Manufacturing and operation of high-temperature type anion exchange membrane-based water electrolyzer (HT-AEMWE) battery

As shown in FIG. 2, the unit cell is stacked in the order of end plate-carbon separator-manufactured anode-anion exchange membrane-manufactured anode-gold-plated titanium separator-end plate and assembled by fastening with a clamping pressure of 4 N/m ² did The temperature of the prepared unit cell was maintained at 120° C., and 0.5 M KOH solution was supplied to the positive electrode at a flow rate of 5 ml/min.

The basic principle of anion exchange membrane-based water electrolysis operation is as follows. Water is decomposed at the anode, and the performance evaluation of the water electrolysis operation was conducted by measuring the current density for 10 seconds for each voltage from 1.25 V to 2.2 V at 0.05 V intervals. After that, the average value of the current density measured at each voltage was calculated to obtain a current density-voltage graph.

comparative example

Manufacture of commercial membrane-based water electrolyzer battery

The unit cell operation was compared by changing the high-temperature anion exchange membrane and the commercial membrane (FAA-3-PK-75) according to the embodiment of the present invention while maintaining the same conditions for electrode manufacturing and cell assembly during MEA manufacturing.

Conventional commercial membranes have very poor stability at 120° C., and water electrolysis performance does not come out at all with membrane damage, whereas the developed membrane exhibits excellent AEMWE performance with a current density of 780 mA/cm ² at 1.8 V (FIG. 3).

In this experiment, a noble metal catalyst was used as the operating condition for comparison with the commercial membrane, but this technology can be expected to be a base technology that can bring the expected effect of improving the performance by operating at a high temperature while using a non-noble metal catalyst. .

Claims (9)

delete delete delete A method for manufacturing a high-temperature type anion exchange membrane, comprising:
terminating the polymerization reaction by adding phosphoric acid after polymerization of the polybenzimidazole-based polymer in a solution;
Dissolving the polybenzimidazole-based polymer after the polymerization reaction has been completed in phosphoric acid, and then casting it on a substrate;
hydrolyzing the film cast on the substrate; and
immersing the hydrolyzed membrane in ammonia solution to remove phosphoric acid from the hydrolyzed membrane to obtain a high-temperature type anion exchange membrane capable of anion conduction;
The high-temperature type anion exchange membrane includes a polybenzimidazole-based polymer capable of KOH doping,
The polybenzimidazole-based polymer capable of KOH doping is a method of manufacturing a high-temperature anion exchange membrane by removing phosphoric acid from the polybenzimidazole-based polymer doped with phosphoric acid. 5. The method of claim 4,
The hydrolysis is a high temperature type anion exchange membrane manufacturing method, characterized in that it is carried out at a temperature of 40 ℃ or more and a relative humidity of 60% or more. 5. The method of claim 4,
The polybenzimidazole-based polymer is a polybenzimidazole-based polymer of the following [Formula 1] to [Formula 5], [Formula 7] and [Formula 8], characterized in that the high-temperature type anion exchange membrane manufacturing method:
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 7]

[Formula 8]

(In Formulas 7 and 8, based on the sum of all repeating units of A and B, A is the percentage of repeating units that do not contain a sulfonic acid group, B is the percentage of repeating units that contain a sulfonic acid group, and A is 0~ 99%, and B is 100 to 1%. In Formula 8, Y is O or S when no atom is present or is present.) Preparing a high-temperature type anion exchange membrane by the manufacturing method according to claim 4;
preparing an anode on which an oxygen generating catalyst is supported and a cathode on which a hydrogen generating catalyst is supported by applying a catalyst on the gas diffusion layer by spraying and then performing heat treatment; and
assembling the high-temperature type anion exchange membrane between the positive electrode and the negative electrode; A method for manufacturing a high-temperature type water electrolysis battery comprising a. 8. The method of claim 7,
In the assembling step, a high temperature type water electrolysis battery manufacturing method, characterized in that assembling a gold (Au) plated titanium separator on one surface that is not assembled with the high temperature type anion exchange membrane of the positive electrode. 8. The method of claim 7,
The assembling is a method for manufacturing a high-temperature type water electrolytic battery, characterized in that it is fastened and assembled with a clamping pressure of 3 to 6 N/m ² .

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