KR20240015979A - Macroporous cathode design for anion-exchange membrane water electrolyzer and fabrication method thereof - Google Patents

Abstract

The cathode electrode for water electrolysis according to the present invention includes a carbon nanotube array stacked structure in which two or more carbon nanotube arrays are stacked crossing each other in the vertical direction, and the carbon nanotube array stacked structure generates macropores. It has the advantages of easy gas discharge, low resistance, and excellent catalytic activity.

Description

Macroporous cathode design for anion-exchange membrane water electrolyzer and fabrication method thereof}

The present invention relates to a cathode electrode for water electrolysis containing macropores and a method of manufacturing the same.

Green hydrogen produced through electrolysis of water is one of the promising alternative energies for reducing carbon emissions because it has high energy density and does not emit carbon dioxide.

In order to commercialize green hydrogen, various methods are being studied to lower the hydrogen production cost, and among the developed methods, cation exchange membrane water electrolysis is a highly efficient process that produces high purity hydrogen. Since this cation exchange membrane water electrolysis is performed with an acidic electrolyte, noble metals such as iridium and platinum are used as catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. These precious metals are one of the factors that contribute most to increasing the production cost of cation exchange membrane water electrolysis devices.

To solve these shortcomings of cation exchange membrane water electrolysis, anion exchange membrane water electrolysis using an anion exchange membrane as an electrolyte was developed. In the case of anion exchange membrane water electrolysis, an alkaline electrolyte is used, so non-precious metal catalysts such as nickel, copper, cobalt, etc. can be used instead of noble metal catalysts in the oxygen evolution reaction and hydrogen evolution reaction, and replacement of these catalysts can significantly lower the hydrogen production cost. there is.

However, even in anion exchange membrane water electrolysis, the non-precious metal catalyst used in the oxygen evolution reaction shows a similar level of activity as the noble metal catalyst, but in the hydrogen evolution reaction, there is still a limitation of showing significantly lower catalytic activity compared to the noble metal catalyst.

Specifically, the developed nickel-based hydrogen generation reaction catalyst has an overvoltage of 80 to 120 mV at a current density of 10 mA/cm2, which is significantly higher than the 15 to 50 mV of the platinum catalyst.

In addition, most of the developed non-precious metal hydrogen generation reaction catalysts were used only in half-cell tests, and when applied to actual anion exchange membrane water electrolysis, they have the limitation of showing lower catalytic efficiency compared to conventional noble metal catalysts.

Water electrolysis catalysts manufactured using conventional methods have a structure in which catalyst particles are densely stacked, blocking the active sites of the catalyst, which reduces catalyst utilization and makes it difficult to contact the reactants with the active sites. Due to these problems, a large amount of There is a problem with using a catalyst. In addition, in the case of conventional water electrolysis catalysts, mass transfer is not smooth, so it is difficult to discharge the generated hydrogen or oxygen, and hydrogen or oxygen that cannot be discharged can be another cause of reduced catalytic activity.

Accordingly, there is a need to develop a water electrolysis catalyst that can significantly increase catalytic activity by increasing the contact ratio between the active site of the catalyst and the reactants due to its high porosity and smoothly discharging the generated hydrogen or oxygen.

U.S. Patent Publication No. 2016-0289849 U.S. Patent Publication No. 2021-0189574 Japanese Patent Publication No. 2020-513064

The purpose of the present invention is to provide a cathode electrode for water electrolysis with excellent catalytic activity.

Another object of the present invention is to provide a cathode electrode for water electrolysis that contains macropores and facilitates discharge of the generated gas.

The cathode electrode for water electrolysis according to the present invention includes a carbon nanotube array stacked structure in which two or more carbon nanotube arrays are stacked in a vertical direction.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the cathode electrode for water electrolysis may further include a base substrate formed on one surface of the carbon nanotube array stacked structure.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the cathode electrode for water electrolysis may include catalyst particles introduced into the carbon nanotube array stacked structure.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the cathode electrode for water electrolysis may be characterized as containing 0.5 to 5 mg of catalyst particles per 1 cm 2 of active area.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the catalyst particles may include one or more noble metals or noble metal alloys selected from platinum, ruthenium, rhonium, palladium, osmium, and iridium.

The cathode electrode for water electrolysis according to an embodiment of the present invention may have an electrochemical active area of 0.5 m2/g or more when a catalyst containing the noble metal or noble metal alloy is introduced as the catalyst particle.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the catalyst particles are made of one or more metals selected from nickel, cobalt, molybdenum, copper, iron, selenium, chromium, barium, tantalum, gallium, tin, and zinc. It may be characterized as containing one or two or more selected from alloys, oxides, phosphides, sulfides, and nitrides.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the catalyst particles may have an average particle diameter of 100 nm or less.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotube array may be characterized as a single layer of carbon nanotubes in which carbon nanotubes are uniformly aligned in one direction.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotube array stacked structure may include 5 to 30 layers of the carbon nanotube array.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotube array stacked structure may be characterized in that odd-layer carbon nanotube arrays and even-layer carbon nanotube arrays are stacked vertically crossing each other. there is.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotube array stacked structure may be characterized as having a pore size of 70 to 300 nm.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotubes included in the carbon nanotube array may have a cross-sectional diameter of 5 to 100 nm.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotube array may be derived from a carbon nanotube forest aligned in the vertical direction.

When the cathode electrode for water electrolysis according to an embodiment of the present invention is applied to a water electrolysis device, the overvoltage based on -10 mA/cm2 is 5 compared to the cathode manufactured by mixing the same catalyst with a binder. It can be characterized as being lowered by more than %.

The present invention also provides a method of manufacturing a cathode electrode for water electrolysis. The method of manufacturing a cathode electrode for water electrolysis according to the present invention includes a first step of extracting a first carbon nanotube array from a carbon nanotube forest and stacking it on a base substrate;

A second step of extracting a second carbon nanotube array from the carbon nanotube forest and stacking it in a vertical direction with the first carbon nanotube array;

A third step of manufacturing a carbon nanotube array stacked structure by repeating the second step until 5 to 30 layers of the carbon nanotube array are stacked; and

It includes a fourth step of introducing catalyst particles into the carbon nanotube array stacked structure.

In the method of manufacturing a cathode electrode for water electrolysis according to an embodiment of the present invention, the base substrate may be stainless steel.

In the method of manufacturing a cathode electrode for water electrolysis according to an embodiment of the present invention, the carbon nanotube array stacked structure may be characterized as having a pore size of 70 to 300 nm.

In the method for manufacturing a cathode electrode for water electrolysis according to an embodiment of the present invention, the fourth step may include applying a catalyst ink containing catalyst particles to the carbon nanotube array stacked structure.

In the method of manufacturing a cathode electrode for water electrolysis according to an embodiment of the present invention, the catalyst ink may be characterized in that it contains 5 to 15% by weight of catalyst particles.

The present invention also provides an anion exchange membrane water electrolysis device, and the anion exchange membrane water electrolysis device according to the present invention includes a cathode electrode for water electrolysis according to an embodiment of the present invention.

The cathode electrode for water electrolysis according to the present invention includes a carbon nanotube array stacked structure in which two or more carbon nanotube arrays are stacked crossing each other in the vertical direction, and the gas generated by the macro pores formed in the carbon nanotube array stacked structure is It is easy to discharge, has a large specific surface area, facilitates contact between the active site of the catalyst and reactants, and has the advantage of excellent catalytic activity.

Figure 1 shows the results of observing a cathode including a carbon nanotube array stacked structure according to an example of the present invention and analyzing it through Raman and XRD.
Figure 2 compares the physical properties of a cathode of a water electrolysis catalyst prepared by a conventional manufacturing method and a cathode according to an embodiment of the present invention and shows the results.
Figure 3 shows the results of measuring the electrochemical active area of a cathode manufactured by a conventional manufacturing method and a cathode according to an example of the present invention.
Figure 4 compares and illustrates the electrochemical properties of catalysts of Preparation Examples and Comparative Examples into which NiFeO _x nanoparticles were introduced.
Figure 5 illustrates and compares the electrochemical properties of catalysts of Preparation Examples and Comparative Examples into which Pt nanoparticles were introduced.
Figure 6 shows the results of measuring the durability of the performance of the cathode electrode for water electrolysis according to the present invention compared to that of an electrode under development or commercially available.

Advantages and features of the embodiments of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to be understood by those skilled in the art. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

In describing embodiments of the present invention, if a detailed description of a known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. The terms described below are terms defined in consideration of functions in the embodiments of the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification.

The cathode electrode for water electrolysis according to the present invention is characterized in that it includes a carbon nanotube array stacked structure in which two or more carbon nanotube arrays are stacked crossing each other in the vertical direction, and the electrode resistance is increased by the high electrical conductivity of the carbon nanotubes. It has the advantage of preventing energy loss, exhibiting high catalytic activity, and allowing rapid discharge of gas generated by the macro pores contained in the carbon nanotube array stacked structure.

Specifically, the cathode electrode for water electrolysis may include catalyst particles introduced into a carbon nanotube layer laminated in a lattice shape, and by introducing the catalyst particles into the carbon nanotube layer laminated in a lattice shape, the active site of the catalyst (active site) is easy to contact with reactants and thus high catalytic activity can be secured.

At this time, the catalyst particles may be nanoscale catalyst particles having an average particle diameter of 100 nm or less, specifically 50 nm or less, and more specifically 30 nm or less.

In the cathode electrode for water electrolysis according to an embodiment of the present invention, the catalyst particles may be one or more noble metals or noble metal alloys selected from platinum, ruthenium, rhodium, palladium, osmium, and iridium. When using a noble metal or noble metal alloy as the catalyst particle, the cathode electrode for water electrolysis may have an electrochemical active area of 0.5 m2/g or more, specifically 0.6 to 1 m2/g, and this high electrochemical active area may be the same Compared to the case where the catalyst particles are applied to the electrode using a binder, the value is 2.5 times, or at best, more than 3 times higher. This high electrochemical active area significantly improves the catalytic activity by increasing the contact rate between the active site of the catalyst and the reactants. It could be a factor.

In the cathode electrode for water electrolysis according to another embodiment of the present invention, the catalyst particles are one or more metals selected from nickel, cobalt, molybdenum, copper, iron, selenium, chromium, barium, tantalum, gallium, tin, and zinc. It may be one or two or more selected from oxides, phosphides, sulfides and nitrides, and preferably the alloys, oxides, phosphides, sulfides and nitrides of metals are one or two or more selected from nickel, iron, molybdenum, copper, cobalt and chromium. It may be an alloy, oxide, phosphide, sulfide or nitride.

The cathode electrode for water electrolysis according to an embodiment of the present invention may contain 0.5 to 5 mg, preferably 1 to 4 mg, of catalyst particles per 1 cm2 of active area, and when the content of catalyst particles is low, the catalytic activity is not sufficient. It is difficult to appear, and if the content of catalyst particles is high, the catalytic activity is not improved and the pore size is reduced, which may actually cause a decrease in water electrolysis efficiency.

In the cathode electrode for water electrolysis according to the present invention, the carbon nanotube array may be a single layer of carbon nanotubes in which carbon nanotubes are consistently aligned in one direction, and this carbon nanotube array may be a carbon nanotube forest aligned in the vertical direction. A carbon nanotube single layer may have been extracted from.

The carbon nanotubes included in the carbon nanotube array can have a cross-sectional diameter of 10 to 20 nm. By using carbon nanotubes that satisfy this diameter range, the durability of the electrode structure is secured and the electrode exhibits high electrical conductivity. Deterioration in water electrolysis efficiency due to resistance can be prevented.

The carbon nanotube array stacked structure may be produced by stacking 5 to 30 layers of the carbon nanotube array, preferably 7 to 25 layers. If the stacked layer is 5 or less, it may be difficult to sufficiently introduce catalyst particles. , if the number of laminated layers is 30 or more, the effect of improving the specific surface area may be minimal, but the production cost may increase.

In detail, the carbon nanotube array stacked structure may be a stack of odd-layer carbon nanotube arrays and even-layer carbon nanotube arrays crossing each other perpendicularly, and due to this crossing structure, the carbon nanotube array stacked structure May include pores with a size of 70 to 300 nm, preferably 80 to 250 nm. By including these large pores, the contact area between the active site of the catalyst and the reactant is increased, and the generated gas can be easily discharged.

The cathode electrode for water electrolysis may further include a base substrate formed on one side of the carbon nanotube layer, and this base substrate can support the carbon nanotube layer and increase the stability of the electrode structure. As a specific example, the base substrate may be a stainless steel substrate, but the present invention is not limited thereto.

The cathode electrode for water electrolysis according to an embodiment of the present invention has the advantage of reducing overvoltage by more than 5% based on -10 mA/cm2 compared to a cathode manufactured by mixing the same catalyst with a binder. At this time, the overvoltage may be based on a single anion exchange membrane water electrolysis cell manufactured using an anion exchange membrane as an electrolyte.

The present invention also provides a method for manufacturing a cathode electrode for water electrolysis.

The method for manufacturing a cathode electrode for water electrolysis according to the present invention includes a first step of extracting a first carbon nanotube array from a carbon nanotube forest and stacking it on a base substrate;

A second step of extracting a second carbon nanotube array from the carbon nanotube forest and stacking it in a vertical direction with the first carbon nanotube array;

A third step of manufacturing a carbon nanotube array stacked structure by repeating the second step until 5 to 30 layers of the carbon nanotube array are stacked; and

It includes a fourth step of introducing catalyst particles into the carbon nanotube array stacked structure.

The cathode electrode for water electrolysis manufactured through the cathode electrode manufacturing method for water electrolysis according to the present invention has the advantage of excellent catalytic activity and easy discharge of the generated gas.

The base substrate, carbon nanotube array lamination structure, and catalyst of the method for manufacturing a cathode electrode for water electrolysis according to the present invention are the base substrate, carbon nanotube array lamination included in the cathode electrode for water electrolysis according to an embodiment of the present invention described above. The structure and catalyst may be the same, and detailed descriptions are omitted to avoid redundant description.

In the method of manufacturing a cathode electrode for water electrolysis according to the present invention, the fourth step includes applying a catalyst ink containing catalyst particles to the carbon nanotube array stack structure. Specifically, the catalyst ink may contain 5 to 15% by weight of catalyst particles, preferably 7 to 12% by weight, and if it contains a small amount of catalyst particles, the amount of catalyst introduced into the electrode structure may be excessively small, and the catalyst particles If it contains a large amount, the catalyst may block the pores of the carbon nanotube array stacked structure, lowering the specific surface area.

Hereinafter, the present invention will be described in detail by examples and comparative examples. The examples below are only intended to aid understanding of the present invention, and the scope of the present invention is not limited by the examples below.

[Production Example 1]

1. Manufacturing of carbon nanotube array layered structure

First, the SUS thin plate was washed with ethanol, and then a carbon nanotube array was extracted from a carbon nanotube forest (A-tech) with a height of about 300 ㎛ and laminated on the SUS. The odd-layer carbon nanotube array and the even-layer carbon The nanotube arrays were stacked to intersect each other perpendicularly to produce a 10-layer carbon nanotube array stacked structure.

2. Manufacture of cathode containing carbon nanotube array stacked structure

NiFeO _x or platinum catalyst nanoparticles were introduced into the manufactured carbon nanotube array stacked structure. Specifically, ink was prepared by mixing each catalyst nanoparticle to 10% by weight in 3 ml ethanol, and then the catalyst was introduced into the carbon nanotube array stacked structure using a drop-wise method. At this time, 2.0 mg of catalyst was introduced per 1 cm2 of the carbon nanotube array stacked structure. After introducing the catalyst, ethanol was evaporated to finally prepare a carbon nanotube array stacked structure into which the catalyst was introduced. Hereinafter, in the present invention, the catalyst into which NiFeO _x is introduced is referred to as NiFeO _x _CNTS, and the catalyst into which platinum is introduced is referred to as Pt_CNTS.

3. Manufacturing of water electrolysis unit cell

Fumapem ^TM was used as an anion exchange membrane, and the anode was an electrode in which NiFe catalyst was plated on a SUS substrate using an electrodeposition method. At this time, the electrodeposition was prepared by immersing a SUS thin plate in a plating solution containing 3mM nickel nitrate, 3mM iron nitrate, and boric acid and applying a current of -50 mA for 600 seconds.

A water electrolysis unit cell was manufactured including the previously prepared cathode, an anion exchange membrane as an electrolyte, and a substrate into which NiFe was introduced by electrodeposition as an anode.

[Comparative Example 1]

1. Manufacturing of a conventional cathode and a water electrolysis unit cell incorporating the same

NiFeO _x or platinum catalyst nanoparticles were introduced into a SUS sheet using a spray method. Specifically, catalyst ink was prepared by adding ionomer (FAA-3-Br, Fumatech Co., Germany), water, and _NiFeO did. The prepared catalyst ink was sprayed on a SUS thin plate washed with ethanol to introduce the catalyst, and the amount of catalyst introduced was 2.0 mg per 1 cm 2 in the same manner as in the preparation example. Hereinafter, in the present invention, the catalyst into which NiFeO _x is introduced is referred to as NiFeO _x _NP, and the catalyst into which platinum is introduced is referred to as Pt_NP.

Thereafter, a water electrolysis unit cell was manufactured in the same manner as Preparation Example 1, except that the cathode was replaced with a cathode manufactured in a conventional manner.

Observation of the cathode prepared in the preparation example

Figure 1a shows an image of the shape of the cathode structure into which the catalyst according to the present invention is introduced, and b roughly shows the manufacturing process of the carbon nanotube cathode structure.

Figure 1c shows the results of observing a carbon nanotube array with a SEM (Scanning Electron Microscope). As the carbon nanotube array is stacked in the vertical direction, a carbon nanotube electrode with square-shaped macro pores is formed. formation can be confirmed.

Figures 1d to 1g illustrate introduction of a catalyst into a carbon nanotube array and observation using SEM and TEM (Transmission Electron Microscope). Referring to Figures d to g of Figure 1, it can be seen that the catalyst aggregated to a size of hundreds of nanometers is dispersed in the carbon nanotube array and exhibits porous characteristics.

In Figure 1, h shows the catalyst analyzed by Raman spectroscopy, and i shows the catalyst analyzed by XRD (X-ray Diffraction). Referring to h in Figure 1, it can be seen that two peaks that can be indexed into D (~1350 cm-1) and G (~1590 cm-1) bands are observed, and for both catalysts, the G band is higher than the D band. Based on the high intensity, it can be confirmed that the carbon nanotube array has been well graphitized.

Referring to i in Figure _{1 ,} for _NiFeO It can be seen that a graphite peak is observed, and the remaining peaks can be seen as originating from the SUS thin plate. Based on these XRD analysis results, it can be confirmed that each catalyst nanoparticle was well introduced into the carbon nanotube.

Observation of the cathode prepared in the comparative example and comparison with the manufacturing example

Figures 2a and b show the comparison between the cathode of the manufacturing example and the cathode of the comparative example observed by SEM. Referring to Figures 2 a and b, the cathode of the preparation example has catalytic nanoparticles dispersed in a porous carbon nanotube array, while the cathode of the comparative example has densely packed catalytic nanoparticles without large pores.

The pore distribution of the cathodes prepared in the Preparation Examples and Comparative Examples was observed using a mercury porosity meter (PM33GT, Quantachrome, USA), and the results are shown in Figure 2c. Referring to c in FIG _. 2, it can be seen that _NiFeO You can see that this hardly appears. In addition, the porosity of the cathode manufactured in the preparation example was confirmed to be 77.3%, and the porosity of the cathode manufactured in the comparative example was confirmed to be 67.1%.

Figure 2d shows the observed electrical resistance of each electrode manufactured in Production Examples and Comparative Examples, and Figure 2e shows the water contact angle of each electrode measured. Referring to d in FIG. 2, it can be seen that the electrical resistance of the preparation example is significantly low, which can be seen to be due to the high electrical conductivity of the non-conductive ionomer and carbon nanotubes included in the comparative example. Figure 2e shows the contact angle of each cathode measured, and it can be seen that the contact angle varies depending on the type of catalyst nanoparticle introduced.

Figure 3 shows the results of measuring the electrochemically active surface area (ECSA) of catalysts prepared in Preparation Examples and Comparative Examples. Referring to Figure 3, it can be seen that the electrochemical active area increases when catalyst particles are introduced into the carbon nanotube array. Specifically, the electrochemical active area when platinum nanoparticles were introduced was compared and shown in Table 1 below.

Manufacturing example Comparative example Pt_CNTS Pt_NP ECSA(㎡/g) 0.731 0.194

Referring to Table 1, it can be seen that the production example in which platinum nanoparticles, a noble metal, are introduced into the carbon nanotube array has an electrochemical active area that is more than two times, specifically 3 to 5 times higher, compared to the comparative example.

Confirmation of electrochemical properties of manufactured cathode

The cathodes of Preparation Examples and Comparative Examples were evaluated as a three-electrode system. Specifically, each catalyst electrode had an active area of 1 cm2, and a graphite rod was used as a counter electrode and Ag/AgCl was used as a reference electrode. To confirm the catalytic activity of the hydrogen evolution reaction, evaluation was performed by linear sweep voltammetry (LSV) in 1 M KOH solution, and scans were performed at a scan rate of 5 mV per second in the voltage range of -0.5 to 0 V. In addition, catalyst stability was measured at a current density of -10 mA/cm2 for 50 hours.

Figure 4 includes NiFeO _x The _{electrochemical} activity was measured for _NiFeO

Referring to Figures 4 and 5, a to c, it can be seen that the water electrolysis catalyst activity of _NiFeO

Specifically, the overvoltage and Tafel slope were measured based on a current density of -10 mA/cm2 in Figures 4 and 5, and the results are shown in Table 2 below.

Manufacturing example Comparative example _{NiFeOx_CNTS} Pt_CNTS _{NiFeOx_NP} Pt_NP -10mA/㎠ overvoltage (mV) 208 38.9 246 42.2 Tafel slope (mV/dec) 49.61 6.09 60.41 5.35

Referring to Table 2, it can be seen that the cathode including the carbon nanotube array stacked structure shows a lower overvoltage compared to the comparative example. Specifically, in the case of _NiFeO

In the case of Tafel slope, there is a significant difference in the cathode incorporating _NiFeO Specifically, in the case of a cathode incorporating NiFeO _x , the Tafel slope may be less than 55 mV/dec.

It can be seen that both the overvoltage and Tafel slope of the cathode containing the carbon nanotube array stacked structure are low, and this difference occurs even though the same catalyst particles are used and the catalyst introduction amount is set to the same, as described above. It is believed to be due to differences in chemical activity area.

Figures 4 and 5c show catalyst stability observed for 50 hours. It can be seen that NiFeO _x _CNTS shows significantly higher stability compared to NiFeO _x _NP, and Pt_CNTS and Pt_NP show similar levels of stability.

Anion exchange membrane water electrolysis single cell test of manufactured cathode

The manufactured cathode was applied to an anion exchange membrane water electrolysis single cell and its performance was confirmed through CV (Cyclic voltammogram). The prepared cathode was used as a working electrode, 0.2 mg of platinum catalyst was loaded per 1 cm2, and a 40% by weight Pt/C electrode prepared by spraying a catalyst ink with an ionomer content of 30% by weight was used as a counter electrode. did. CV was scanned in the range 0.05 to 1.2 V at a rate of 5 mV per second, and the cell temperature was maintained at 30 °C.

The performance durability of the anion exchange membrane water electrolysis single cell was based on single cell testing. Specifically, a SUS-based positive electrode plate was used as an anode, and a porous transport layer was combined with the manufactured cathode to use it as a cathode. The anion exchange membrane used was a FAA-3-50 membrane with a thickness of 50 ㎛, and the membrane was pretreated with 1 M KOH solution for 30 minutes and then washed with deionized water. At this time, the catalyst loading amount of the anode was set to 1 mg/cm2, and the membrane-electrode assembly was manufactured without a heat compression process.

The polarization curve of the anion exchange membrane water electrolysis single cell was determined using a voltage sweep method of 1.35 to 2.15 V at a scan rate of 5 mV per second. A 1 M KOH solution preheated to 60°C was supplied as a reactant to the anode and cathode at a flow rate of 1 mL per minute, and the cell temperature was maintained at 70°C. Charge transfer, ohmic and mass transport resistance were measured using electrochemical impedance spectroscopy (EIS), Nyquist plot was measured at 1.9 V with 50 mV amplitude, and cell durability was measured at 250, 500, and 1000 mA/㎠ for 40 hours. Chronopotentiometry, which operates at a constant current density of , was used.

Figures 4 and 5 d to f illustrate the evaluation of the performance of a single cell using an anion exchange membrane. Figures 4 and 5d illustrate the evaluation of the anion exchange membrane water electrolysis single cell performance of the electrodes manufactured in Preparation Examples and Comparative Examples. Referring to Figure 4d, it can be seen that the cathode of the production example and comparative example with the same catalyst loading amount shows a difference in performance. Specifically, the current density of the cell applying NiFeO _x _CNTS at 2.05 V is 1480 mA/cm2. It can be confirmed that the current density _{of the} cell using _NiFeO

Referring to d in Figure 5, it can be seen that the current density of the cell to which Pt_CNTS is applied at 1.9 V is 4000 mA/cm2, which is significantly higher than the current density of 2486 mA/cm2 to that of the cell to which Pt_NP is applied. The current density was about 1.6 times higher than that of the cell using Pt_NP.

Figures 4 and 5 e show Nyquist plots. The charge transfer resistance of the Nyquist plot is related to catalytic activity, and the ohmic resistance of each cathode in Figures 4 and 5 is shown in Table 4 below.

Manufacturing example Comparative example _{NiFeOx_CNTS} Pt_CNTS _{NiFeOx_NP} Pt_NP Ohm resistance (mΩ cm ² ) 65 75 126 99

Referring to Table 3, it can be seen that the ohmic resistance of the production example including the carbon nanotube array stacked structure is significantly low, and specifically, the ohmic resistance of the production example cathode is at least 20% compared to the ohmic resistance of the comparative example cathode. Specifically ^, in ^the case ^of _NiFeO It may be ² or less. This difference in ohmic resistance can be seen as a result of the cathode electrode in the manufacturing example promoting electron transport and reducing material transport resistance.

Figures 4 and 5f show the results of measuring the time potential difference of each cathode at a constant current density. Referring to Figure 4f, the initial and final voltages of the _NiFeO On the other hand, it can be seen that no voltage loss occurs in NiFeO _x _CNTS, and this confirms that the NiFeO _x _CNTS electrode has excellent durability. Referring to Figure 5f, it can be seen that the two electrodes into which Pt was introduced showed no voltage loss for 10800 seconds and were stable.

Comparison with other electrodes and durability evaluation

Figure 6a shows a comparison between the performance measurement results of applying the cathode according to the manufacturing example of the present invention to an anion exchange membrane water electrolysis single cell and the performance measurement results using under-development or commercially available electrodes. It can be seen that NiFeOx_CNTS has a current density of 1480 mA/cm2 at 2.05 V, the highest value among non-precious metal catalysts, and Pt_CNTS has a current density of 4000 mA/cm2 at 1.9 V, the highest value among electrodes under development or commercially available. It can be confirmed that it represents .

Figure 6b shows the results of testing the durability of an anion exchange membrane water electrolysis single cell containing a cathode according to a production example of the present invention for 40 hours. Referring to b in FIG. 6, it can be seen that in the case of _NiFeO

Claims (21)

A cathode electrode for water electrolysis comprising a carbon nanotube array stacked structure in which two or more carbon nanotube arrays are stacked crossing each other in the vertical direction. According to clause 1,
The cathode electrode for water electrolysis further includes a base substrate formed on one surface of the carbon nanotube array stacked structure. According to clause 1,
The cathode electrode for water electrolysis is characterized in that it includes catalyst particles introduced into the carbon nanotube array stacked structure. According to clause 3,
The cathode electrode for water electrolysis is characterized in that it contains 0.5 to 5 mg of catalyst particles per 1 cm 2 of active area. According to clause 3,
A cathode electrode for water electrolysis, wherein the catalyst particles are one or more noble metals or noble metal alloys selected from platinum, ruthenium, rhodium, palladium, osmium, and iridium. According to clause 5,
The cathode electrode for water electrolysis is characterized in that the cathode electrode for water electrolysis has an electrochemical active area of 0.5 m2/g or more. According to clause 3,
The catalyst particle is one or two or more selected from oxides, phosphides, sulfides and nitrides of one or more metals selected from nickel, cobalt, molybdenum, copper, iron, selenium, chromium, barium, tantalum, gallium, tin and zinc. A cathode electrode for water electrolysis, comprising: According to clause 3,
A cathode electrode for water electrolysis, wherein the catalyst particles have an average particle diameter of 100 nm or less. According to clause 1,
The carbon nanotube array is a cathode electrode for water electrolysis, characterized in that it is a single layer of carbon nanotubes in which carbon nanotubes are uniformly aligned in one direction. According to clause 1,
The carbon nanotube array stacked structure is a cathode electrode for water electrolysis, characterized in that it includes 5 to 30 layers of the carbon nanotube array. According to clause 10,
The carbon nanotube array stacked structure is a cathode electrode for water electrolysis, wherein odd-layer carbon nanotube arrays and even-layer carbon nanotube arrays are stacked vertically crossing each other. According to clause 1,
A cathode electrode for water electrolysis, wherein the carbon nanotube array stacked structure has a pore size of 70 to 300 nm. According to clause 1,
A cathode electrode for water electrolysis, characterized in that the single carbon nanotube included in the carbon nanotube array has a cross-sectional diameter of 5 to 100 nm. According to clause 1,
A cathode electrode for water electrolysis, wherein the carbon nanotube array is derived from a vertically aligned carbon nanotube forest. According to clause 1,
A cathode electrode for water electrolysis, characterized in that when it includes the cathode for water electrolysis, the overvoltage based on -10 mA/cm2 is lowered by more than 5% compared to a cathode manufactured by mixing the same catalyst with a binder. A first step of extracting a first carbon nanotube array from the carbon nanotube forest and stacking it on a base substrate;
A second step of extracting a second carbon nanotube array from the carbon nanotube forest and stacking it in a vertical direction with the first carbon nanotube array;
A third step of manufacturing a carbon nanotube array stacked structure by repeating the second step until 5 to 30 layers of the carbon nanotube array are stacked; and
A method of manufacturing a cathode electrode for water electrolysis comprising a fourth step of introducing catalyst particles into the carbon nanotube array stacked structure. According to clause 16,
A method of manufacturing a cathode electrode for water electrolysis, wherein the base substrate is stainless steel. According to clause 16,
A method of manufacturing a cathode electrode for water electrolysis, wherein the carbon nanotube array stacked structure has a pore size of 70 to 300 nm. According to clause 16,
The fourth step is a method of manufacturing a cathode electrode for water electrolysis, characterized in that it includes applying a catalyst ink containing catalyst particles to the carbon nanotube array stacked structure. According to clause 19,
A method of manufacturing a cathode electrode for water electrolysis, wherein the catalyst ink contains 5 to 15% by weight of catalyst particles. An anion exchange membrane water electrolysis device comprising a cathode electrode for water electrolysis selected from claims 1 to 15.