KR20240038300A - Binder for water electrolysis electrode containing cellulose series, hydrophilic water electrolysis negative electrode containing same, and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a binder for water electrolysis electrodes containing (hydroxypropyl)methyl cellulose, a water electrolysis cathode containing the same, and a method for manufacturing the same. The binder may include at least one of first (hydroxypropyl)methyl cellulose, second (hydroxypropyl)methyl cellulose, and third (hydroxypropyl)methyl cellulose with different viscosities. The hydrophilicity of the water electrolysis cathode is strengthened by using the binder, catalyst, and solvent to form a specific contact angle range. Additionally, when manufacturing a negative electrode, the strength of the electrode can be increased by polymerizing (hydroxypropyl)methyl cellulose through IPA gelation to improve crosslinking.

Description

Binder for water electrolysis electrode containing cellulose series, hydrophilic water electrolysis negative electrode containing same, and manufacturing method thereof {Binder for water electrolysis electrode containing cellulose series, hydrophilic water electrolysis negative electrode containing same, and manufacturing method thereof}

The present invention relates to a binder used in a water electrolysis cathode, and more specifically, to a binder containing (hydroxypropyl)methyl cellulose, a hydrophilic water electrolysis cathode containing the binder, and a method of manufacturing the same.

As environmental problems caused by the use of existing fossil fuels become more serious, hydrogen energy is attracting attention as an alternative energy source. A representative method of producing hydrogen energy is water electrolysis technology.

Water electrolysis technology is a technology that applies an electric field to water composed of hydrogen and oxygen to separate and generate hydrogen and oxygen. It is eco-friendly as it does not generate carbon dioxide. A representative water electrolysis technology is polymer electrolyte membrane water electrolysis (PEMWE). The PEMWE is a technology that is in the spotlight because it uses pure water as a raw material instead of electrolyte, so the purity of the produced hydrogen is high, it can be enlarged, and it can respond quickly to rapid changes in renewable energy.

Conventional technology focused on increasing the ionic conductivity of the MEA (Membrane Electrode Assembly) used in the PEMWE. In general, perfluorocarbon-based ionomers, such as Nafion, were mainly used as binders. Nafion has excellent chemical stability and high ionic conductivity, but has the disadvantage of being expensive. Therefore, a technology using a hydrocarbon-based electrolyte membrane was developed to replace this, but there was a limit to unit cost reduction because hydrocarbon alone could not be used.

Moreover, in general water electrolysis research, when energy generation stops, a reverse current phenomenon occurs at the cathode and the cathode surface is oxidized. Conversely, when the power generation suddenly increases, the anode surface is oxidized by a sharply increased voltage, and when load changes are repeated rapidly in short cycles, the cathode This damage caused a problem in which the durability of the water electrolysis device deteriorated.

Therefore, a technology that has excellent ionic conductivity and durability and can reduce unit costs is needed.

The first technical object to be achieved by the present invention is to provide a binder for water electrolysis electrodes containing (hydroxypropyl)methyl cellulose.

The second technical problem is to provide a hydrophilic water electrolysis cathode to which a binder containing (hydroxypropyl)methyl cellulose provided by the first technical problem is applied.

The third technical problem is to provide a method of manufacturing a water electrolysis cathode to which a binder containing (hydroxypropyl)methyl cellulose is applied in order to achieve the second technical problem.

In order to achieve the first technical problem described above, the present invention provides a binder for water electrolysis electrodes containing (hydroxypropyl)methyl cellulose. The binder is composed of at least one of first (hydroxypropyl)methyl cellulose, second (hydroxypropyl)methyl cellulose, and third (hydroxypropyl)methyl cellulose with different viscosities.

In order to achieve the above-described second technical problem, the present invention provides a water electrolysis cathode to which a binder containing (hydroxypropyl)methyl cellulose provided by the first technical problem is applied. The water electrolysis cathode is composed of (hydroxypropyl)methyl cellulose as a catalyst and a binder. By using the catalyst and binder, a specific contact angle range is formed, so that the hydrophilicity is enhanced on the surface of the substrate.

In order to achieve the third technical problem, the present invention provides a method for manufacturing a water electrolysis cathode of the second technical problem. The cathode can be obtained by preparing a slurry containing a catalyst, (hydroxypropyl)methyl cellulose, and a solvent, and through ball milling, degassing, bar coating, IPA gelation, and drying processes.

In order to solve the above-mentioned problems, the present invention can obtain a water electrolysis cathode with improved strength by polymerizing cellulose through IPA gelation in more detail.

The present invention forms a water electrolysis electrode by using (hydroxypropyl)methyl cellulose, a pure cellulose type with a low cost, as a binder instead of Nafion, which has a high cost, thereby reducing the cost in electrode manufacturing.

(Hydroxypropyl)methyl cellulose used as the binder is a non-ionically conductive material, but can transmit hydrogen ions through water, so the ionic conductivity of the electrode is maintained even when the electrode is manufactured including the material. Additionally, since cellulose is a hydrophilic material, when used with a specific catalyst, it can form a more hydrophilic electrode than an electrode containing a Nafion binder, making it easier to transfer hydrogen ions through water.

As cellulose is used as the binder, the voltage level and voltage loss degree are low when current is applied, and when two celluloses with different viscosities are included, it becomes flexible to respond to load fluctuations such as overload or power failure, thereby reducing damage to the cathode and thus durability of the cathode. can increase.

Compared to the conventional technology using Nafion, the present invention maintains a low increase in initial voltage value and cell voltage value over time, and when using a specific catalyst, the voltage value remains constant over time, resulting in excellent cell performance. has

1 is a flowchart of a method for manufacturing a water electrolysis cathode containing (hydroxypropyl)methyl cellulose.
Figure 2 is a schematic diagram of a stack containing a water electrolysis cathode.
Figure 3 is a graph measuring cell voltage before applying current to evaluate durability and performance.
Figure 4 is a graph measuring cell voltage after current application for durability evaluation.
Figure 5 is a graph measuring cell performance evaluation results.
Figure 6 is an image showing the contact angle, which is the angle between the electrode surface and the water surface in hydrophilicity evaluation.
Figure 7 is a graph showing Fourier Transform infrared spectrometer (FT-IR) results to confirm the presence of Nafion and (hydroxypropyl)methyl cellulose.

Since the present invention can be subject to various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

Hereinafter, various embodiments of the present invention will be described in more detail with reference to the attached drawings.

Embodiment 1

1 is a flowchart of a method for manufacturing a water electrolysis cathode containing (hydroxypropyl)methyl cellulose. The water electrolysis cathode is a first step (S10) of mixing a catalyst, (hydroxypropyl)methyl cellulose as a binder, and a solvent to prepare a slurry, and a second step of ball milling the slurry to obtain a uniformly pulverized and mixed slurry. Step (S11), a third step (S12) of degassing the ball milled slurry to remove dissolved gases in the slurry, a fourth step (S13) of bar coating the degassed slurry to form a cathode, the cathode It is manufactured including a fifth step (S14) of polymerizing the (hydroxypropyl)methyl cellulose by gelling it on IPA to obtain a negative electrode with improved strength (S14), and a sixth step (S15) of oven drying the negative electrode with improved strength. .

In order to prepare the water electrolysis cathode in the first step (S10), a slurry is prepared by dissolving (hydroxypropyl)methyl cellulose, which is a catalyst and a binder, in a solvent.

The binder is not hydrogen ion conductive and is composed of at least one selected from the group consisting of first (hydroxypropyl)methyl cellulose, second (hydroxypropyl)methyl cellulose, and third (hydroxypropyl)methyl cellulose) having different viscosities. It is composed. The first (hydroxypropyl)methyl cellulose has a viscosity of 500 cP to 1,500 cP, the second (hydroxypropyl)methyl cellulose has a viscosity of 3,500 cP to 4,500 cP, and the third (hydroxypropyl)methyl cellulose has a viscosity of 500 cP to 1,500 cP. The viscosity is 75,000 cP to 140,000 cP.

The binder preferably consists of tertiary (hydroxypropyl)methyl cellulose with a viscosity of 100,000 cP.

The binder preferably consists of second (hydroxypropyl)methyl cellulose and third (hydroxypropyl)methyl cellulose of different viscosities. More preferably, the second (hydroxypropyl)methyl cellulose has a viscosity of 4,000 cP, and the third (hydroxypropyl)methyl cellulose has a viscosity of 100,000 cP.

When the binder includes the second (hydroxypropyl)methyl cellulose and the third (hydroxypropyl)methyl cellulose, the second (hydroxypropyl)methyl cellulose and the third (hydroxypropyl)methyl cellulose are It is preferable to add it at a weight ratio of 1:2. If the second (hydroxypropyl)methyl cellulose is added at a higher rate than the third (hydroxypropyl)methyl cellulose, it may be difficult to secure a sufficient thickness due to low viscosity.

The water electrolysis cathode is characterized in that one selected from the group consisting of IrO ₂ and Ir/IrOx is used as a catalyst. It is more preferable to use Ir/IrOx as the catalyst. The catalyst is a mixed phase of two or more types of iridium selected from the group consisting of metal iridium, iridium(III)-oxide (Ir ₂ O ₃ ), and iridium(IV)-oxide (IrO ₂ ), and uses Ir/IrOx as a catalyst. By doing so, the hydrophilicity on the surface of the substrate is strengthened to form a specific contact angle range when forming an electrode, and ion conduction through water is increased to ensure excellent performance. Additionally, when Ir/IrOx is used as a catalyst, the amount of catalyst elution is reduced, resulting in excellent electrochemical stability.

The solvent is characterized in that it is at least one selected from the group consisting of DI Water, IPA, and NMP, and it is more preferable to use NMP. When NMP is used, the measured voltage is low, so the durability of the cell is superior to when DI Water is used.

In the second step (S11), the slurry produced by dissolving the catalyst and (hydroxypropyl)methyl cellulose in the solvent is ball milled to pulverize the powder contained in the slurry and mix it evenly.

In the third step (S12), the pulverized and uniformly mixed slurry is degassed through ball milling to remove dissolved gas in the slurry. By carrying out the degassing process, it is possible to prevent bubbles from occurring during electrode manufacturing.

In the fourth step (S13), the slurry from which the dissolved gas has been removed through deaeration is bar coated on a PI (polyimide) film to form a cathode. The PI film preferably has a thickness of 90 um to 100 um. If the thickness of the PI film is less than 90 um or more than 100 um, it may be difficult to remove the film after attaching the cathode formed on the PI film to the membrane during MEA manufacturing.

In the fifth step (S14), the negative electrode formed on the PI film is immersed in IPA to proceed with gelation. When the cellulose is polymerized through the gelation process, crosslinking is strengthened and the strength of the electrode is improved.

In the sixth step (S15), the gelated negative electrode is dried in an oven to prepare a negative electrode. The drying temperature is performed at 50° to 70°, and it is more preferable to dry overnight at 60°.

The water electrolysis cathode becomes hydrophilic by manufacturing the cathode including the catalyst and the binder. Since the cathode is hydrophilic, the contact angle is preferably 30° or less, and is preferably 15.99° or less. More preferably, the range of the contact angle is 6.50° to 15.99°. Due to the limitations of the experiment, the lower limit of the measured contact angle is 6.50°, but when the contact angle is less than 30°, it is hydrophilic, so even if the contact angle is less than 6.50°, excellent performance can be achieved in forming and using a hydrophilic electrode.

In the electrode using (hydroxypropyl)methyl cellulose, water performs the function of conducting hydrogen ions. However, when the contact angle exceeds 15.99°, there may be difficulty in transferring a sufficient amount of hydrogen ions by forming an electrode with lower hydrophilicity than when the contact angle is 15.99° or less.

Preparation Example 1: Preparation of electrode containing first (hydroxypropyl)methyl cellulose

IrO ₂ catalyst was manufactured and used in-house. The catalyst used the Adams fusion method. 12.5 g _of 8 wt% IrCl _{3 ·} The dried product was heated to 450°C for 2 hours and then heat-treated at 450°C for 30 minutes. After completion of the heat treatment, the obtained product was filtered with DI Water, and the catalyst was obtained through oven drying at a temperature of 60°C overnight.

0.2 g of the IrO ₂ catalyst prepared through the above method and 0.012 g of first (hydroxypropyl)methyl cellulose with a viscosity of 1,000 cP were dissolved in 1.280 g of NMP to form a slurry. Three zirconia balls with a diameter of 10 mm and five balls with a diameter of 5.3 mm were added to the slurry, and then ball milled at 250 rpm for 30 minutes. At this time, the direction was changed every 15 minutes, and the temperature was not additionally set. After the ball milling process, the slurry was degassed to remove air bubbles. The degassing process was carried out for 5 minutes in a degassing device at 1600 rpm. After the degassing process, a gasket with a hole of 26 mm After the bar coating, the gasket was removed to form a cathode with a size of 26 mm x 26 mm on the PI film. After forming a negative electrode by applying bar coating on the PI film, it was immersed in IPA and gelled to polymerize (hydroxypropyl)methyl cellulose. After the gelation, a water electrolysis cathode was manufactured through oven drying.

Preparation Example 2: Preparation of electrode containing second (hydroxypropyl)methyl cellulose

A negative electrode was manufactured in the same manner as in Preparation Example 1, except that 0.012 g of second (hydroxypropyl)methyl cellulose was added instead of first (hydroxypropyl)methyl cellulose.

Preparation Example 3: Preparation of electrode containing tertiary (hydroxypropyl)methyl cellulose

A negative electrode was manufactured in the same manner as in Preparation Example 1, except that 0.012 g of third (hydroxypropyl)methyl cellulose was added instead of first (hydroxypropyl)methyl cellulose.

Preparation Example 4: Preparation of electrode containing second (hydroxypropyl)methyl cellulose and third (hydroxypropyl)methyl cellulose

A negative electrode was manufactured in the same manner as in Preparation Example 2, except that the second (hydroxypropyl)methyl cellulose was reduced to 0.004 g and the third (hydroxypropyl)methyl cellulose was added in an amount of 0.008 g.

Preparation Example 5: Preparation of electrode comprising second (hydroxypropyl)methyl cellulose and third (hydroxypropyl)methyl cellulose

A negative electrode was manufactured in the same manner as in Preparation Example 4, except that DI Water was added instead of NMP as a solvent.

Preparation Example 6: Preparation of electrode containing second (hydroxypropyl)methyl cellulose and third (hydroxypropyl)methyl cellulose

A cathode was manufactured in the same manner as in Preparation Example 4, except that Ir/IrOx black was added instead of IrO ₂ as the catalyst.

The Ir/IrOx black catalyst was formed by adding 4 g of sodium acetate to 170 g of ethylene glycol to form a mixture, stirring at room temperature for 3 hours, and then adding 207.4 g of formic acid and 12.5 g of 8 wt% IrCl ₃ hydrate to form a mixture at room temperature. and stirred for 5 minutes. Afterwards, the mixture was reacted at 395 K for 5 hours and a catalyst was prepared through washing and drying.

Comparative Example 1: Preparation of electrode containing Nafion

A slurry was created by mixing 0.2 g of the IrO ₂ catalyst of Preparation Example 1, 0.120 g of Nafion 10 wt% ionomer (Sigma Aldrich), 0.760 g of NMP, and 0.320 g of IPA. The slurry was ball milled at 250 rpm for 30 minutes and then degassed at 1600 rpm for 5 minutes. The degassed slurry was bar coated on a 100 um PI film and dried overnight at 60° C. to prepare a water electrolysis cathode containing Nafion as a binder.

Comparative Example 2: Preparation of electrode containing PTFE

A slurry was created by mixing 0.2 g of the IrO ₂ catalyst of Preparation Example 1, 0.068 g of 60 wt% PTFE (Sigma Aldrich), 0.640 g of DI Water, 0.540 g of IPA, and 0.02 g of FC-4430. The slurry was ball milled at 250 rpm for 30 minutes and then degassed at 1600 rpm for 5 minutes. The degassed slurry was bar coated on a 100 um PI film and dried overnight at 60°C. After drying, FC-4430 was removed through heat treatment at 350°C for 15 minutes, and a water electrolysis cathode containing PTFE as a binder was manufactured.

Experimental Example 1: Durability evaluation

Stacks containing the water electrolysis cathodes of Preparation Examples 1 to 6 and Comparative Examples 1 to 2 were prepared and durability was evaluated.

Figure 2 is a schematic diagram of a stack containing a water electrolysis cathode. Current collector (21), bipolar plate (22), and MEA were placed in order on the end plate (20), and a stack was formed in a symmetrical structure based on the MEA. The MEA presses a water electrolysis cathode 24 on one side of the membrane 25 and a Pt-coated Ti porous transport layer (PTL, 23) on the water electrolysis cathode 24, and Pt/C on the opposite side. The anode 26 was formed by pressing.

On the membrane 25, the water electrolysis cathode 24 coated with the catalyst formed on the PI film is hot pressed, maintaining the temperature at 165 ° C. for 1 minute at a pressure of 8 MPa and 3 minutes at a pressure of 12 MPa. It was joined by pressing. After the compression, the PTL (23) was bonded to the water electrolysis cathode (24) bonded to the membrane (25) by hot pressing it for 1 minute at a pressure of 2 MPa and for 3 minutes at a pressure of 4 MPa. After the pressing, the Pt/C anode 26 was pressed by hot pressing on the opposite side of the membrane to which the water electrolysis cathode 24 and the PTL 23 were bonded, thereby manufacturing an MEA. At this time, the Pt/C anode 26 used a commercial GDE (Gas Diffusion Electrode, NARA Cell-Tech) containing 0.5 mg/cm ² of 60 wt% Pt/Vulcan XC-72 catalyst, and the water electrolysis cathode (24) and the PTL (23) were placed on the opposite side of the membrane (25) to which the commercially available GDE was bonded and then pressed for 1 minute at a pressure of 1 MPa and for 3 minutes at a pressure of 1.5 MPa. The cathode active area of the MEA manufactured through the above method was 6.76 cm ² .

Durability evaluation was conducted by continuously supplying water at a temperature of 80°C to each stack. The process of applying a current density of 1 Acm ^-2 for 24 hours was repeated a total of three times, and the voltage was measured at 2.0 Acm ^-2 before and after applying the current.

Figures 3 and 4 are graphs measuring cell voltage for durability evaluation, and the results are shown in Table 1 below.

Figure 3 is a graph measuring cell voltage before current application in Preparation Examples 1 to 6 and Comparative Examples 1 to 2 to evaluate durability.

On the graph, Comparative Example 1 and Comparative Example 2 showed the highest initial voltage of 1.95 V at 2.0 Acm ^-2 , and Preparation Examples 1 to 6 showed voltages of 1.84 V to 1.91 V, It has a relatively lower initial voltage than Comparative Example 1 and Comparative Example 2.

Figure 4 is a graph measuring cell voltage after current application in Preparation Examples 1 to 6 and Comparative Examples 1 to 2 to evaluate durability. After applying a constant current of 1 Acm ^-2 three times for 24 hours each, the cell voltage at 2.0 Acm ^-2 was measured. Comparative Example 1 showed the highest voltage of 2.01 V, and Preparation Examples 1 to 6 showed voltages of 1.85 V to 1.92 V, which were lower than Comparative Example 1. Comparative Example 2 had a voltage of 1.9 V, which was similar to the Preparation Example.

Catalyst loading
(mg/cm ² ) Cell voltage (initial)
At 2.0 A/ ^cm2 Cell voltage
(after 72h)
At 2.0 A/ ^cm2 Voltage loss(mV/h) Comparative Example 1


≒ 1 mg/cm ² 1.95 2.01 0.83 Comparative Example 2 1.95 1.90 -0.69 Manufacturing example 1 1.86 1.86 0.00 Production example 2 1.91 1.92 0.14 Production example 3 1.84 1.85 0.14 Production example 4 1.87 1.86 -0.14 Production example 5 1.88 1.91 0.42 Production example 6 1.90 1.88 -0.28

Table 1 above is a table showing the voltage and voltage loss of FIGS. 3 and 4. Voltage loss was calculated by subtracting the initial voltage from the voltage 72 hours after current application and dividing by time. Comparative Example 1 and Preparation Examples 1 to 6 had the same ratio of nafion and (hydroxypropyl)methyl cellulose at 5.66 wt% in the slurry. When the PTFE of Comparative Example 2 was added at the same ratio as Comparative Example 1 and Preparation Examples 1 to 6, an electrode was not formed, so the amount of PTFE on the slurry was increased to form an electrode at a rate of 16.98 wt%. Manufactured. In Table 1, about 1 mg/cm ² of catalyst was loaded in the Comparative Example and the Preparation Example.

The initial cell voltage of Comparative Example 1 was the highest at 1.95 V, the cell voltage 72 hours after current application was also the highest at 2.01 V, and the voltage loss was 0.83 mV/h. Comparative Example 2 had the same initial cell voltage as Comparative Example 1, but the cell voltage 72 hours after current application was 1.9 V, which was lower than Comparative Example 1. In Comparative Example 2, the voltage loss was -0.69 mV/h, and the performance was improved compared to the initial version.

Preparation Examples 1 to 3 used negative electrodes containing (hydroxypropyl)methyl cellulose with different viscosities. In Preparation Example 1 using first (hydroxypropyl)methyl cellulose, the initial voltage and after 72 hours of current application were the same, and no voltage loss occurred. Preparation Example 2 using the second (hydroxypropyl)methyl cellulose has a voltage 0.07 V higher at the beginning and after 72 hours than Preparation Example 3 using the third (hydroxypropyl)methyl cellulose, but Preparation Example 2 and the above The voltage loss of Preparation Example 3 is the same at 0.14 mV/h, and when compared to Comparative Example 1, it can be seen that the voltage loss when using (hydroxypropyl)methyl cellulose is less than when using Nafion. . In addition, Preparation Example 3 had an initial voltage of 1.84 V, and the cell voltage 72 hours after current application was also 1.85 V, the lowest voltage among Comparative Examples 1 to 2 and Preparation Examples 1 to 6. see. Therefore, using (hydroxypropyl)methyl cellulose is more durable than using Nafion.

Preparation Examples 4 to 6 used negative electrodes containing two (hydroxypropyl)methyl cellulose with different viscosities. Preparation Examples 4 to 6 showed lower voltage loss compared to Comparative Example 1, and Preparation Example 4 and Preparation Example 6 showed voltage loss after 72 hours of current application lower than the initial voltage, resulting in voltage loss. Performance has improved without doing so. In terms of voltage loss measurements, Comparative Example 2 had the best performance at -0.69 mV/h, but the initial voltage and voltage 72 hours after current application were higher than those of the Production Example, and the range of variation was large. Therefore, when the measurement time is long, the measured voltage loss values of the comparative example and the manufacturing example may differ. Therefore, it can be considered that durability is superior when using the above manufacturing example in which the voltage fluctuation range over time, rather than the measured voltage loss value, is relatively constant.

Experimental Example 2: Cell performance evaluation

Performance was evaluated using a stack containing the water electrolysis cathodes of Preparation Examples 1 to 6 and Comparative Examples 1 to 2 prepared in Experimental Example 1, respectively. Measurements were carried out while continuously supplying water at a temperature of 80°C, and performance was evaluated by measuring the voltage a total of three times at 2.0 Acm ^-2 at 24-hour intervals.

Figure 5 is a graph measuring cell voltage over time for performance evaluation, and the results are shown in Table 2 below.

Catalyst loading
(mg/cm ² ) Cell voltage (initial) at 2.0 A/cm ² Cell voltage(after 24h) at 2.0 A/cm ² Cell voltage(after 48h) at 2.0 A/cm ² Cell voltage(after 72h) at 2.0 A/cm ² Comparative Example 1



≒ 1 mg/cm ² 1.95 1.93 1.97 2.01 Comparative Example 2 1.95 1.90 1.90 1.90 Manufacturing Example 1 1.86 1.85 1.85 1.86 Production example 2 1.91 1.89 1.91 1.92 Production example 3 1.84 1.83 1.85 1.85 Production example 4 1.87 1.87 1.86 1.86 Production example 5 1.88 1.87 1.88 1.91 Production example 6 1.90 1.88 1.88 1.88

Looking at Figure 5 and Table 2, the voltage of Comparative Example 1 decreases from 1.95 V to 1.93 V 24 hours after current application, but shows a steep increase from 24 hours to 72 hours after current application. Therefore, Comparative Example 1 using Nafion can be considered to have poor cell performance. In Comparative Example 2, the voltage drops sharply until 24 hours after current application, but remains constant after 24 hours.

On the other hand, in Preparation Examples 1 to 6, the overall measured voltage over time was 1.83 V to 1.92 V on the graph, which is lower than Comparative Example 1. In particular, compared to the graphs of Preparation Example 1 to Preparation Example 3 and Preparation Example 5 where the voltage decreases and then increases, the voltage of Preparation Example 4 and Preparation Example 6 remains low over time. In addition, in Preparation Example 6, the voltage value remains constant 24 hours after current application, so the performance of the anode manufactured using two (hydroxypropyl)methyl cellulose and Ir/IrOx Black catalysts with different viscosities is the best. .

Experimental Example 3: Hydrophilicity evaluation

Figure 6 is an image showing the contact angle in hydrophilicity evaluation. The standard for evaluating hydrophilicity is the size of the contact angle. The contact angle is the angle measured between the surface of the electrode and the surface of the water within 3 seconds after dropping water on the electrode, and a contact angle of 30° or less was evaluated as the standard for hydrophilicity.

Comparative Example 1, which is an electrode manufactured using Nafion as a binder in Figure 6, had a contact angle of 75.52° immediately after being dropped, and a contact angle of 46.55° after 3 seconds. The contact angle of Comparative Example 1 did not exceed 90°, so it is difficult to consider that it is not a hydrophobic electrode, but has high hydrophilicity.

Comparative Example 2, an electrode manufactured using PTFE as a binder, had a contact angle of 78.00° immediately after being dropped, and a contact angle of 60.5° after 3 seconds. The contact angle of Comparative Example 2 was close to 90° even after 3 seconds of application, so it can be viewed as a nearly hydrophobic electrode.

Preparation Example 1, which is an electrode manufactured using first (hydroxypropyl)methyl cellulose as a binder, has a contact angle of 25.07° immediately after water is dropped on Preparation Example 1, and a contact angle after 3 seconds of 7.50°, showing hydrophilicity. It can be viewed as an electrode with .

Preparation Example 2, which is an electrode manufactured using second (hydroxypropyl)methyl cellulose as a binder, has an initial contact angle of 45.69° immediately after dropping water on the electrode and 6.50° after 3 seconds, which is higher than that of Preparation Example 1. Although it was large, the contact angle after 3 seconds was low, showing that water was absorbed into the electrode in a short period of time. Preparation Example 3, an electrode manufactured using third (hydroxypropyl)methyl cellulose as a binder, was 39.25° immediately after dropping the water, and 9.00° 3 seconds later, and the initial contact angle was lower than that of Preparation Example 2. It showed low absorption. However, Preparation Examples 1 to 3 have a smaller contact angle than Comparative Examples 1 and 2, so it can be seen that the hydrophilicity is higher than Comparative Examples 1 and 2.

Preparation Examples 4 to 6 are electrodes manufactured using two types of (hydroxypropyl)methyl cellulose with different viscosities as binders. In Preparation Examples 4 to 6, the contact angle immediately after water was dropped was greater than that in Preparation Example 1. However, Preparation Examples 3 to 6 have a smaller contact angle immediately after dropping water compared to Comparative Example 1 and Comparative Example 2, and the contact angle after 3 seconds is also up to 15.99°, compared to Comparative Example 1 and Comparative Example 2. Since the measured value is small, it can be said that hydrophilicity is high. In particular, in Preparation Example 4, the contact angle immediately after dropping the water was 45.21°, but the contact angle after time was 6.57°, showing very fast absorption. In addition, in Preparation Examples 1 to 6 using (hydroxypropyl)methyl cellulose as a binder, all water was absorbed within about 1 minute to about 2 minutes.

Therefore, it is preferable to use an electrode containing hydrophilic (hydroxypropyl)methyl cellulose.

Experimental Example 4: FT-IR evaluation

Figure 7 is a graph showing the results of FT-IR to confirm the presence of Nafion and (hydroxypropyl)methyl cellulose. The experiment was measured in the infrared light wavelength range of 600 cm ^-1 to 2000 cm ^-1 . Comparative Example 1 showed peaks distinct from Preparation Examples 4 to 6 around 1237 cm ^-1 and 1157 cm ^-1 , so it can be seen that Nafion was included in Comparative Example 1. On the other hand, Preparation Examples 4 to 6 were 1260 cm ^-1 and 1110 Since the peak was observed at cm ^-1 , it can be seen that (hydroxypropyl)methyl cellulose was formed.

The present invention forms a water electrolysis electrode by using (hydroxypropyl)methyl cellulose, a pure cellulose type with a low cost, as a binder instead of Nafion, which has a high cost, thereby reducing the cost in electrode manufacturing.

(Hydroxypropyl)methyl cellulose used as the binder is a material without ionic conductivity, but is capable of transferring hydrogen ions through water, so ionic conductivity is maintained even when an electrode is manufactured including the material. Additionally, since cellulose is a hydrophilic material, it can form a more hydrophilic electrode than a Nafion binder, making it easier to transfer hydrogen ions through water.

As cellulose is used as the binder, the voltage value and voltage loss degree are low when current is applied, and when two binders with different viscosities are included, it is flexible in responding to load changes such as overload or power outage, thereby reducing damage to the cathode and thus durability of the cathode. can increase.

When manufacturing the negative electrode, the cellulose is polymerized through IPA gelation and crosslinking is strengthened, thereby obtaining a negative electrode with improved strength.

In the present invention, the initial cell voltage value is lower than that of the electrode containing Nafion, and the cell voltage value maintains a low increase compared to the electrode containing Nafion, where the cell voltage value increases rapidly starting 24 hours after current application. Additionally, when using a specific catalyst, the voltage level remains constant over time, resulting in excellent cell performance.

Therefore, by using a water electrolysis electrode containing a (hydroxypropyl)methyl cellulose binder, which is cheaper than Nafion, which is currently used, the durability and performance of the cathode can be improved and the cost of electrode manufacturing can be reduced.

20: End plate
21: Current collector
22: Bipolar plate
23: Pt-coated Ti porous transport layer
24: Water electrolysis cathode
25: membrane
26: Pt/C anode

Claims (19)

In the binder used as an electrode assembly for a water electrolysis cathode,
A binder for a water electrolysis cathode, characterized in that the binder contains (hydroxypropyl)methyl cellulose having hydrophilic properties.
According to paragraph 1,
The binder is a first (hydroxypropyl)methyl cellulose with a viscosity of 500 cP to 1,500 cP, a second (hydroxypropyl)methyl cellulose with a viscosity of 3,500 cP to 4,500 cP, and a third (hydroxypropyl)methyl cellulose with a viscosity of 75,000 cP to 140,000 cP. A binder for a water electrolysis cathode comprising at least one of hydroxypropyl)methyl cellulose.
According to paragraph 2,
A binder for a water electrolysis cathode, characterized in that the binder includes the second (hydroxypropyl)methyl cellulose and the third (hydroxypropyl)methyl cellulose.
According to paragraph 2,
The binder includes the third (hydroxypropyl)methyl cellulose, and the third methyl cellulose has a viscosity of 100,000 cP.
According to paragraph 1,
A binder for a water electrolysis cathode, characterized in that the binder has no hydrogen ion conductivity.
write; and
It includes a cathode formed on the substrate,
The substrate is removed during electrode manufacturing after the cathode is formed,
The cathode is composed of a catalyst and a binder to increase the activity of oxygen generation in the water electrolysis reaction,
The binder is composed of (hydroxypropyl)methyl cellulose, and is hydrophilic and has a contact angle of 15.99° or less.
According to clause 6,
A water electrolysis cathode wherein the contact angle ranges from 6.50° to 15.99°.
According to clause 6,
The binder is a first (hydroxypropyl)methyl cellulose with a viscosity of 500 cP to 1,500 cP, a second (hydroxypropyl)methyl cellulose with a viscosity of 3,500 cP to 4,500 cP, and a third (hydroxypropyl)methyl cellulose with a viscosity of 75,000 cP to 140,000 cP. A water electrolysis cathode comprising at least one of hydroxypropyl)methyl cellulose.
According to clause 8,
The water electrolysis cathode, wherein the binder includes the second (hydroxypropyl)methyl cellulose and the third (hydroxypropyl)methyl cellulose.
According to clause 8,
The binder includes the third (hydroxypropyl)methyl cellulose, and the viscosity of the third methyl cellulose is 100,000 cP.
According to clause 6,
A water electrolysis cathode, wherein the binder has no hydrogen ion conductivity.
According to clause 6,
A water electrolysis cathode, wherein the catalyst includes one of IrO ₂ and Ir/IrOx.
According to clause 12,
The Ir/IrOx is a water electrolysis cathode characterized in that it is a mixed phase of two or more types of iridium selected from the group consisting of metal iridium, iridium(III)-oxide (Ir ₂ O ₃ ), and iridium(IV)-oxide (IrO ₂ ). .
Preparing a slurry by mixing a catalyst, a binder that is (hydroxypropyl)methyl cellulose, and a solvent;
ball milling the slurry to obtain a uniformly pulverized and mixed slurry;
Degassing the slurry to remove dissolved gases in the pulverized and mixed slurry;
Forming a cathode by bar coating the degassed slurry on a PI film;
forming a negative electrode with improved strength by polymerizing the (hydroxypropyl)methyl cellulose through IPA gelation of the negative electrode; and
Oven drying the cathode with improved strength;
A method of manufacturing a water electrolysis cathode comprising.
According to clause 14,
The binder is a first (hydroxypropyl)methyl cellulose with a viscosity of 500 cP to 1,500 cP, a second (hydroxypropyl)methyl cellulose with a viscosity of 3,500 cP to 4,500 cP, and a third (hydroxypropyl)cellulose with a viscosity of 75,000 cP to 140,000 cP. A method for producing a water electrolysis cathode, characterized in that at least one of propyl) methyl cellulose is selected.
According to clause 14,
A method of manufacturing a water electrolysis cathode, wherein the cathode has hydrophilicity and has a contact angle of 15.99° or less.
According to clause 16,
A method of manufacturing a water electrolysis cathode, characterized in that the contact angle has a range of 6.50° to 15.99°.
According to clause 14,
A method of manufacturing a water electrolysis cathode, wherein the solvent is at least one selected from the group consisting of DI Water, IPA, and NMP.
According to clause 14,
A method of manufacturing a water electrolysis negative electrode, characterized in that the strength of the negative electrode is improved by polymerizing cellulose through IPA gelation to strengthen crosslinking.