Method for manufacturing metal oxide electrode and electrode manufactured thereby

Abstract

The present invention relates to a method for manufacturing an electrode and an electrode manufactured by the manufacturing method, the method comprising the steps of: mixing metal hydroxide powder, a binder resin, and water to prepare a catalyst precursor clay; rolling the catalyst precursor clay to obtain a catalyst precursor sheet; and positioning the catalyst precursor sheet on a substrate, followed by hot pressing, to form a catalyst layer including metal oxide nanoparticles. The present invention provides a method for manufacturing a metal oxide electrode, by which an electrode manufacturing process is simplified, thereby reducing electrode manufacturing costs and time.

Description

Method for manufacturing a metal oxide electrode and an electrode manufactured therefrom

[0001] This invention claims the benefit of Korean Patent Application No. 10-2023-0165809 filed with the Korean Intellectual Property Office on November 24, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for manufacturing a metal oxide electrode and an electrode manufactured therefrom, and more particularly, to a method for manufacturing a metal oxide electrode and an electrode manufactured therefrom, which can reduce the cost and time for manufacturing the electrode by a simple process.

[0003] Electrodes containing metal oxides as catalytic materials are being widely studied in various fields such as water electrolysis electrodes, water treatment electrodes, fuel cell electrodes, supercapacitors, displays, and light-emitting devices due to their characteristics of excellent durability and superior electrical conductivity.

[0004] The conventional manufacturing process for obtaining an electrode coated with a catalyst layer containing metal oxide particles on a substrate mainly involves heat-treating metal hydroxide powder, then ball-milling to obtain metal oxide fine particles, and applying catalyst ink or catalyst slurry containing the metal oxide fine particles onto a support such as a substrate to form a catalyst layer.

[0005] However, this conventional electrode manufacturing process has the inconvenience of having to include a process of pulverizing the metal oxide particles before manufacturing the catalyst ink or slurry, as agglomeration of the metal oxide particles inevitably occurs during the process of heat-treating the metal hydroxide powder.

[0006] The technical problem to be achieved by the present invention is to provide a method for manufacturing a metal oxide electrode with reduced manufacturing cost and time, and an electrode manufactured thereby.

[0007] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0008] One embodiment of the present invention provides a method for manufacturing an electrode, comprising the steps of: preparing a catalyst precursor clay by mixing a metal hydroxide powder, a binder resin, and water; rolling the catalyst precursor clay to obtain a catalyst precursor sheet; and positioning the catalyst precursor sheet on a substrate and then hot pressing it to form a catalyst layer including metal oxide nanoparticles.

[0009] Another embodiment of the present invention provides an electrode manufactured by a method according to an embodiment of the present invention, comprising: a substrate; and a catalyst layer positioned on the substrate, the catalyst layer including metal oxide nanoparticles.

[0010] Another embodiment of the present invention provides a water electrolysis device including an electrode according to one embodiment of the present invention as an anode.

[0011] The electrode manufacturing method according to one embodiment of the present invention has a simple manufacturing process, so that the cost and time for manufacturing the electrode can be reduced.

[0012] The electrode manufacturing method according to one embodiment of the present invention uses a metal hydroxide clay capable of free standing as a catalyst precursor, thereby improving the reliability of the manufacturing process and reducing the manufacturing cost.

[0013] An electrode according to one embodiment of the present invention has excellent durability and can have excellent performance as an oxygen generating electrode.

[0014] A water electrolysis device according to one embodiment of the present invention may have excellent water electrolysis performance and improved durability.

[0015] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and the attached drawings.

[0016] FIG. 1 is a schematic diagram showing a conventional method (a) for manufacturing an electrode including a catalyst layer containing metal oxide nanoparticles and a manufacturing method (b) according to the present invention.

[0017] Figure 2 is a drawing showing an XRD pattern (a) and FT-IR spectroscopic analysis results (b) for the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0018] Figure 3 is an SEM image of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 and the Co(OH)2 powder of Manufacturing Example 1.

[0019] FIG. 4 is a drawing showing a TEM image of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 and the size distribution of cobalt oxide nanoparticles formed in the catalyst layer of the electrode.

[0020] Figure 5 is a drawing showing HR-TEM images of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0021] Figure 6 is a drawing showing the XPS analysis results (a, b) and Co3+ / Co2+ ratio (c) for the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0022] Figure 7 is a diagram showing the polarization curve (a), Tafel plot (b), and measured overvoltage and Tafel slope values ​​(c) for the oxygen evolution reaction of the electrodes manufactured in Examples 1-1 to 1-4.

[0023] Figure 8 is a diagram showing polarization curves for the oxygen evolution reaction of the electrodes manufactured in Examples 1-3 and Comparative Example 1.

[0024] Figure 9 is a diagram showing EIS spectra for electrodes manufactured in Examples 1-1 to 1-4.

[0025] Figure 10 is a drawing showing the results of a 50-hour durability test for electrodes manufactured in Examples 1-1 to 1-4.

[0026] Figure 11 is a diagram showing the LSV polarization curve (a) and Tefal diagram (b) of a laboratory-scale anion exchange membrane electrolysis device manufactured in Examples 2-1 to 2-4.

[0027] Figure 12 is a diagram showing the results of EIS analysis (a) for the electrolysis device manufactured in Examples 2-1 to 2-4 and (b) the overvoltage of the electrolysis device divided into ohmic resistance (ηohm), kinetic overvoltage (ηkin), and mass transfer overvoltage (ηmass).

[0028] Figure 13 is a drawing showing the total pore volume measured for the electrodes manufactured in Examples 1-1 to 1-4.

[0029] Figure 14 is a drawing showing the results of a 200-hour durability test for the electrolysis device manufactured in Examples 2-1 to 2-4 (a), the XRD pattern (b), SEM image (c), and XPS analysis results (d, e) of the electrode after the durability test for the device of Example 2-3.

[0030] Figure 15 is a schematic diagram showing the structure of a commercial-scale anion exchange membrane electrolysis device manufactured in Example 3.

[0031] Figure 16 is a diagram showing the results of a long-term durability test for a water electrolysis device manufactured in Example 3 (a), an LSV polarization curve (b) and an EIS spectrum (c) before and after a long-term durability test.

[0032] Figure 17 is a drawing comparing the durability of recently reported commercial-scale anion exchange membrane electrolysis devices and the commercial-scale anion exchange membrane electrolysis device manufactured in Example 3.

[0033] Figure 18 is an SEM image of the catalyst layer of the electrode manufactured in Examples 1-3, 3-1, and 3-2 and the Co(OH)2 powder of Manufacturing Example 1.

[0034] Figure 19 is a drawing showing the XRD spectrum of the catalyst layer of the electrode manufactured in Examples 1-3, 3-1, and 3-2.

[0035] Figure 20 is a diagram showing LSV polarization curves in half-cell experiments for electrodes manufactured in Examples 1-1, 2-1, 2-2, 3-1, and 3-2.

[0036] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0037] Throughout this specification, when it is said that an element is "on" another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0038] Throughout this specification, the unit “parts by weight” may mean the weight ratio between each component.

[0039] Throughout the specification, the formation of a neck between particles may mean a shape in which particles are connected to other particles in the form of a bridge.

[0040] Throughout this specification, “A and / or B” means “A and B, or A or B.”

[0041] Throughout this specification, “clay” may mean a state of matter that has plasticity but does not flow.

[0042] Hereinafter, the present invention will be described in more detail.

[0043] One embodiment of the present invention provides a method for manufacturing an electrode, comprising the steps of: preparing a catalyst precursor clay by mixing a metal hydroxide powder, a binder resin, and water; rolling the catalyst precursor clay to obtain a catalyst precursor sheet; and positioning the catalyst precursor sheet on a substrate and then hot pressing it to form a catalyst layer including metal oxide nanoparticles.

[0044] FIG. 1 is a schematic diagram showing a conventional method (a) for manufacturing an electrode including a catalyst layer containing metal oxide nanoparticles and a manufacturing method (b) according to the present invention.

[0045] Referring to Fig. 1, the conventional method of manufacturing an electrode including a catalyst layer including metal oxide nanoparticles must include a fine grinding process such as ball milling after the heat treatment process because agglomeration of particles occurs in the process of obtaining metal oxide by heat treating metal hydroxide powder. In contrast, the electrode manufacturing method according to one embodiment of the present invention can form a catalyst layer including metal oxide nanoparticles by thermo-compressing clay including metal hydroxide powder, thereby omitting the heat treatment process and ball milling process, and thus can simplify the electrode manufacturing method, thereby ensuring process reliability and being advantageous in terms of electrode manufacturing time and cost.

[0046] In addition, the electrode manufacturing method according to one embodiment of the present invention utilizes clay as a catalyst layer precursor, thereby facilitating storage and transport of materials, and minimizing the amount of catalyst loss occurring during the process of forming a catalyst layer on the electrode, thereby reducing manufacturing costs. In addition, the catalyst precursor clay minimizes changes in viscosity due to drying during the manufacturing process, thereby improving the reliability of the manufacturing process.

[0047] A method for manufacturing an electrode according to one embodiment of the present invention can manufacture an electrode including a catalyst layer in which metal oxide nanoparticles are connected to each other to form a neck, so that the electrochemical performance of the manufactured electrode can be excellent.

[0048] According to one embodiment of the present invention, the metal hydroxide powder may include a hydroxide containing at least one metal among Cu, Co, Ni, Fe, and Mn. Specifically, the metal hydroxide may include at least one among Cu hydroxide, Co hydroxide, Ni hydroxide, Fe hydroxide, and Mn hydroxide, and may include a hydroxide containing two or more metals, such as Cu-Co hydroxide, or may include Ni-Co-Fe layered double hydroxide. The metal hydroxide is a precursor that is applied on a metal substrate and acts as a catalyst through a subsequent process, and its type and content may be selected depending on the composition of the catalyst to be manufactured.

[0049] According to one embodiment of the present invention, the metal hydroxide powder may be purchased and used as a commercially available product or obtained by a coprecipitation method. For example, the metal hydroxide powder may be prepared by mixing a metal hydroxide precursor, a pH adjuster, and a chelating agent with a solvent by a coprecipitation method. Specifically, the metal hydroxide powder may be obtained by mixing Co(OH)2 powder with Co(NO3)2·6H2O, an aqueous NaOH solution, and an ammonia solution (NH4OH, 28-30%), adjusting the pH of the solution to about 9.5, coprecipitating, and drying the obtained precipitate.

[0050] According to one embodiment of the present invention, the binder resin may be a polymer compound, and specifically may include at least one of polytetrafluoroethylene (PTFE), p-phenylenediamine (PDA), polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), natural rubber (SMR), and polyvinyl alcohol (PVA).

[0051] According to one embodiment of the present invention, the binder resin may be included in the catalyst precursor clay in an amount of 10 to 50 parts by weight relative to 100 parts by weight of the metal hydroxide powder. More specifically, the binder resin may be included in the catalyst precursor clay in an amount of 10 to 50 parts by weight, 10 to 40 parts by weight, 10 to 35 parts by weight, 10 to 30 parts by weight, 10 to 25 parts by weight, 20 to 50 parts by weight, 20 to 40 parts by weight, 20 to 35 parts by weight, 20 to 30 parts by weight, or 20 to 25 parts by weight relative to 100 parts by weight of the metal hydroxide powder. When the content of the binder resin is within the above-described range, there may be an effect of preventing deterioration of the catalyst layer when the electrode is introduced into the cell and driven.

[0052] According to one embodiment of the present invention, the water may be deionized water.

[0053] According to one embodiment of the present invention, the water may be included in the catalyst precursor clay in an amount of 2 to 15 parts by weight relative to 100 parts by weight of the metal hydroxide powder. More specifically, the water may be included in the catalyst precursor clay in an amount of 2 to 15 parts by weight, 2 to 13 parts by weight, 2 to 11 parts by weight, 4 to 15 parts by weight, 4 to 13 parts by weight, 4 to 11 parts by weight, 6 to 15 parts by weight, 6 to 13 parts by weight, or 6 to 11 parts by weight relative to 100 parts by weight of the metal hydroxide powder.

[0054] When the water content is within the above-described range, a catalyst precursor material in the form of a clay capable of freestanding can be obtained, and changes in the viscosity of the catalyst precursor clay can be minimized.

[0055] According to one embodiment of the present invention, the step of preparing a catalyst precursor clay by mixing the metal hydroxide powder, binder resin, and water can be performed using a stirrer.

[0056] Then, the precursor clay is rolled to obtain a catalyst precursor sheet.

[0057] According to one embodiment of the present invention, the catalyst precursor sheet may have a thickness of 10 μm or more and 10,000 μm or less. More preferably, the catalyst precursor sheet may have a thickness of 100 μm or more and 1,000 μm or less, but is not particularly limited thereto.

[0058] Then, the catalyst precursor sheet is positioned on a substrate and then thermo-compressed to form a catalyst layer including metal oxide nanoparticles.

[0059] According to one embodiment of the present invention, by the thermocompression step, the metal hydroxide is converted into a metal oxide as shown in the reaction formula below, and at the same time, nano-sized metal oxide particles are formed. Specifically, due to the water vapor (H2O) generated when the metal hydroxide is oxidized and the pressure from the thermocompression, when the metal hydroxide is converted into the metal oxide, a topotactic transformation in which the crystal structure is maintained does not occur, and the shape of the metal hydroxide changes, so that metal oxide nanoparticles can be obtained.

[0060]

[0061] According to one embodiment of the present invention, some of the metal oxide nanoparticles formed by the thermocompression step can form necks connected between the nanoparticles. When necks are formed between the metal oxide nanoparticles, material transfer between the metal oxide nanoparticles is accelerated, so that the performance of an electrode including the same can be further improved.

[0062] According to one embodiment of the present invention, the metal oxide nanoparticles may have an average particle diameter of 5 nm to 50 nm, 5 nm to 40 nm, 5 nm to 30 nm, or 5 nm to 20 nm.

[0063] According to one embodiment of the present invention, the substrate may be a metal substrate, and specifically may include at least one of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam.

[0064] According to one embodiment of the present invention, the thermocompression bonding can be performed at a temperature of 150°C to 300°C, 200°C to 300°C, 150°C to 250°C, or 200°C to 250°C, and the thermocompression temperature range can be controlled depending on the type of metal hydroxide.

[0065] Specifically, when the metal hydroxide powder includes a hydroxide containing at least one metal among Cu, Co, Ni, Fe, and Mn, the thermocompression temperature may preferably be 200°C or more and less than 300°C. By satisfying the above-described range, all of the metal hydroxide included in the catalyst precursor clay can be converted into metal oxide, and deterioration of the formed catalyst layer may not occur.

[0066] According to one embodiment of the present invention, the catalyst precursor clay may include a pore former, a conductive material, etc. in addition to a metal hydroxide powder, a binder resin, and water.

[0067] According to one embodiment of the present invention, the thermocompression may be performed for 5 to 150 minutes, or 10 to 120 minutes. When the time for which the thermocompression is performed is within the above-described range, the formed catalyst layer can be effectively adhered to the metal substrate.

[0068] According to one embodiment of the present invention, the thermocompression may be performed by applying a load of 10 kg / cm2 to 500 kg / cm2, 10 kg / cm2 to 450 kg / cm2, 10 kg / cm2 to 400 kg / cm2, 10 kg / cm2 to 350 kg / cm2, 10 kg / cm2 to 300 kg / cm2, 10 kg / cm2 to 250 kg / cm2, 10 kg / cm2 to 200 kg / cm2, or 10 kg / cm2 to 150 kg / cm2. When the thermocompression is performed with a load within the above range, the phase can be effectively converted from a metal hydroxide to a metal oxide, thereby improving the activity and durability of the catalyst produced, and desorption of the catalyst layer due to an oxygen evolution reaction can be effectively suppressed.

[0069] Another embodiment of the present invention provides an electrode manufactured by a method according to an embodiment of the present invention, comprising: a substrate; and a catalyst layer positioned on the substrate, the catalyst layer including metal oxide nanoparticles.

[0070] An electrode according to one embodiment of the present invention has excellent durability and can have excellent performance as an oxygen generating electrode.

[0071] According to one embodiment of the present invention, the electrode may have a neck formed by the metal oxide nanoparticles being connected to each other. By forming a neck between the metal oxide nanoparticles, material transfer between the metal oxide nanoparticles is accelerated, thereby further improving the performance of the electrode including the same.

[0072] In an electrode according to one embodiment of the present invention, the substrate may be the same as that described in the method for manufacturing the electrode.

[0073] An electrode according to one embodiment of the present invention may be an electrode for water electrolysis, an electrode for fuel cells, an electrode for water treatment, etc., depending on the purpose.

[0074] According to one embodiment of the present invention, the metal oxide nanoparticles may include cobalt oxide.

[0075] According to one embodiment of the present invention, the average particle diameter of the metal oxide nanoparticles may be 5 nm to 50 nm, 5 nm to 40 nm, 5 nm to 30 nm, or 5 nm to 20 nm.

[0076] Another embodiment of the present invention provides a water electrolysis device including an electrode according to an embodiment of the present invention as an anode.

[0077] A water electrolysis device according to one embodiment of the present invention may have excellent water electrolysis performance and improved durability by including an electrode according to one embodiment of the present invention as an anode (oxygen generating electrode).

[0078] The electrolyte, cathode, and anion exchange membrane that can be included in the electrolysis device according to one embodiment of the present invention can be used without any special limitation as long as they are used in the field of electrolysis device technology.

[0079] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0080] Manufacturing Example 1: Manufacturing of Co(OH)2 powder

[0081] Co(OH)2 powder was prepared as a catalytic metal hydroxide powder. First, Co(NO3)2·6H2O (Sigma Aldrich) was prepared as a precursor of Co(OH)2, NaOH aqueous solution as a pH adjuster, and ammonia solution (NH4OH, 28-30%) as a chelating agent.

[0082] 100 mM Co(NO3)2·6H2O was dissolved in 4 L of distilled water for 30 minutes, and then the pH of the solution was adjusted to 9.5, and coprecipitation was performed by injecting ammonia solution at a rate of 5 ml / min. After coprecipitation, the mixed solution was stirred for 3 hours and aged for 1 hour for stabilization. After the stabilization process was completed, the precipitate was separated from the solution using a centrifuge (HERMLE, X36HK), rapidly cooled using liquid nitrogen, and freeze-dried at -95 °C for 24 hours to prepare cobalt hydroxide (Co(OH)2) powder.

[0083] Examples 1-1 to 3-4: Preparation of cobalt oxide coated electrode

[0084] Cobalt hydroxide powder manufactured in Manufacturing Example 1 was used as a metal hydroxide.

[0085] First, 100 parts by weight of the cobalt hydroxide powder manufactured in Manufacturing Example 1, 25 parts by weight of polytetrafluoroethylene (PTFE, Sigma-Aldrich), and 15 parts by weight of deionized water were mixed and stirred for 2 hours using a planetary mixer to prepare a catalyst precursor clay.

[0086] Then, the clay sheet was obtained by roll pressing so that the thickness of the catalyst precursor clay was 500 to 1,000 μm.

[0087] Then, the clay sheet was placed on a Ni foam (Alantum) substrate having a pore size of 450 μm, and the thermocompression temperature, load, and performance time were adjusted as shown in Table 1 below to obtain an electrode coated with a catalyst layer containing cobalt oxide nanoparticles.

[0088] Example 1-1 (CO_150) Example 1-2 (CO_200) Example 1-3 (CO_250) Example 1-4 (CO_300) Example 2-1 Example 2-2 Example 3-1 Example 3-2 Thermocompression temperature (℃) 150 200 250 300 250 250 250 Thermocompression load (kg / cm) 2 )10010010010050300100100Thermocompression time (minutes)3030303030301060

[0089] Comparative Example 1: Fabrication of a cobalt oxide coated electrode

[0090] The cobalt hydroxide powder manufactured in Manufacturing Example 1 was heat-treated at 400°C for 4 hours to obtain cobalt oxide (Co3O4) powder, and then the cobalt oxide powder was pulverized for 2 hours using a ball mill pulverizer (SPEX Corporation) to obtain cobalt oxide powder containing cobalt oxide particles of uniform size.

[0091] 100 parts by weight of the above-mentioned pulverized cobalt oxide powder, 25 parts by weight of polytetrafluoroethylene (PTFE, Sigma-Aldrich), and 30 parts by weight of deionized water were mixed and stirred for 2 hours using a planetary mixer to obtain a cobalt oxide slurry.

[0092] Then, the slurry was transferred onto a Ni foam (Alantum) substrate having a pore size of 450 μm using a decal transfer method, and cobalt oxide was coated by thermal compression at 120°C for 10 minutes, and then additionally heat-treated at 250°C for 30 minutes to fiberize the PTFE, thereby finally manufacturing an electrode coated with a catalyst layer including cobalt oxide.

[0093] <Experimental Example 1. Analysis of Electrode Catalyst Layer Characteristics>

[0094] Experimental Example 1.1. XRD and FT-IR Analysis

[0095] In order to confirm the crystal phase and structure of the particles formed in the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4, an X-ray diffraction analyzer (D / MAX 2500VL / PC) was used in the 2θ range of 10° to 80° for 2 min. -1 X-ray diffraction (XRD) pattern analysis was performed on the catalyst layers of the electrodes manufactured in Examples 1-1 to 1-4 under the scan speed and X-ray source conditions of Cu-Kα.

[0096] Furthermore, in order to confirm the functional groups present in the materials formed in the catalyst layers of the electrodes manufactured in Examples 1-1 to 1-4, a Fourier transform infrared spectroscopy (FT-IR, Frontier, PerkinElmer) was used in the range of 650-4,000 cm -1 In the range of , FT-IR spectroscopy was performed on the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0097] Figure 2 is a drawing showing an XRD pattern (a) and FT-IR spectroscopic analysis results (b) for the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0098] Referring to part (a) of Fig. 2, the peak of the (311) crystal plane was observed as the main peak at a 2θ value of 36.85° for all of Examples 1-1 to 1-4, and peaks of the (111), (200), (222), (400), (422), (511), and (440) crystal planes were also observed. Therefore, it was confirmed that the material included in the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 had a cubic spinel crystal structure of cobalt oxide (Co3O4). In addition, compared to Example 1-1 in which the thermocompression temperature was 150°C, in Examples 1-2 to 1-4 in which the thermocompression temperature was 200°C or higher, no peak corresponding to cobalt hydroxide (Co(OH)2) was observed, indicating that all of the cobalt hydroxide contained in the catalyst precursor clay was converted to cobalt oxide at a thermocompression temperature of 200°C or higher.

[0099] In addition, referring to part (a) of Fig. 2, it was confirmed that the peak (*) corresponding to PTFE was clearly observed in Examples 1-1 to 1-3 where the thermocompression performance temperature was 150°C to 250°C, and therefore it was expected that the performance of the electrode would be excellent because the deterioration of PTFE was prevented in Examples 1-1 to 1-3 where the thermocompression performance temperature was 150°C to 250°C.

[0100] Referring to part (b) of Fig. 2, the absorption band corresponding to the OH bond (3330 cm -1 ) and absorption bands corresponding to water molecules (H2O) (1640 cm -1 ) decreased as the thermocompression temperature increased from 150 ℃ to 300 ℃, which suggests that cobalt hydroxide is converted to cobalt oxide more as the thermocompression temperature increases.

[0101] Experimental Example 1.2. Shape Analysis of Cobalt Oxide Nanoparticles Included in the Catalyst Layer

[0102] In order to observe the structure of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 and the Co(OH)2 powder manufactured in Manufacturing Example 1, SEM images were taken of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 and the Co(OH)2 powder of Manufacturing Example 1 using a field emission scanning electron microscope (FE-SEM; JSM-790F, JEOL, Japan).

[0103] TEM images and high-resolution TEM (HR-TEM) images were taken of the catalyst layers of the electrodes manufactured in Examples 1-1 to 1-4 using a field emission transmission electron microscope (FE-STEM; TALOS F200X, Thermo Fisher Scientific, USA).

[0104] Figure 3 is an SEM image of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 and the Co(OH)2 powder of Manufacturing Example 1.

[0105] Referring to Fig. 3, in the case of the Co(OH)2 powder of Manufacturing Example 1, a plate or sheet-shaped structure was formed and there were no nanoparticles, but it was confirmed that spherical nanoparticles were formed in a uniform size in the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0106] FIG. 4 is a drawing showing a TEM image of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 and the size distribution of cobalt oxide nanoparticles formed in the catalyst layer of the electrode.

[0107] Referring to FIG. 4, it was confirmed that uniform nano-sized cobalt oxide particles were formed in all of Examples 1-1 to 1-4, and the average particle diameters of the cobalt oxide nanoparticles formed in Examples 1-1 to 1-4 were 25.28 ± 0.32, 12.36 ± 0.07, 10.69 ± 0.47 nm, and 11.46 ± 0.12 nm, respectively. It was confirmed that the average particle diameter decreased as the thermocompression temperature increased from 150 °C to 250 °C, and that the average particle diameter increased slightly when the thermocompression temperature increased from 250 °C to 300 °C. In addition, it was confirmed that a connected neck was formed between the formed cobalt oxide nanoparticles.

[0108] Figure 5 is a drawing showing HR-TEM images of the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4.

[0109] Referring to FIG. 5, it was confirmed that the cobalt oxide nanoparticles included in the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4 had a lattice spacing of 0.243 nm corresponding to the (311) crystal plane of the Co3O4 crystal structure.

[0110] Experimental Example 1.3. XPS Analysis of Cobalt Oxide Nanoparticles Included in the Catalyst Layer

[0111] In order to investigate the chemical state of cobalt oxide included in the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4, X-ray photoelectron spectroscopy (XPS) was performed.

[0112] Specifically, an X-ray photoelectron spectrometer (NEXSA, Thermo Fisher Scientific, USA) was used, and XPS analysis was performed using monochrome Al-Kα as a light source and C 1s (binding energy: 284.6 eV) as an internal standard.

[0113] Figure 6 shows the XPS analysis results (a, b) and Co for the catalyst layer of the electrode manufactured in Examples 1-1 to 1-4. 3+ / Co 2+ This is a drawing showing the ratio (c).

[0114] Co present in cobalt oxide 3+ Co corresponds to the active site of the catalyst 3+ / Co 2+ The greater the amount of rain, the better the activity of the catalyst.

[0115] Referring to Fig. 6, Co in Examples 1-2 to 1-4 is higher than in Example 1-1. 3+ / Co 2+ In Example 1-3, where the temperature for performing thermal compression was 250 ℃, the amount of Co increased. 3+ / Co 2+ It was confirmed that the ratio was the highest at 1.32, which would be the best performance as a catalyst for oxygen generation reaction.

[0116] Experimental Example 2. Evaluation of Electrochemical Properties of Electrodes - Half-Cell Test

[0117] In order to analyze the electrochemical characteristics of the electrode manufactured in the example, a half-cell test was conducted on the electrode manufactured in the example.

[0118] Specifically, half-cell tests were performed in a standard three-electrode cell configuration using a potentiostat (VMP-3, Biologic), using 1 M KOH as an electrolyte, the electrodes manufactured in each of the examples and comparative examples as working electrodes, a graphite rod electrode as a counter electrode, and Hg / HgO as a reference electrode.

[0119] Experimental Example 2.1. LSV Polarization Curve Analysis

[0120] The electrocatalytic activity of the electrodes manufactured in Examples 1-1 to 1-4 and Comparative Example 1 for the oxygen evolution reaction (OER) was evaluated using linear scanning voltammetry (LSV).

[0121] Polarization curves were recorded at a scan rate of 1 mV / s, and the measured current densities were obtained with an 85% iR-drop correction. The measured potentials with respect to the reference electrode (Hg / HgO) were converted to the standard hydrogen electrode (RHE) potential using the Nernst equation.

[0122] Figure 7 is a diagram showing the polarization curve (a), Tafel plot (b), and measured overvoltage and Tafel slope values ​​(c) for the oxygen evolution reaction of the electrodes manufactured in Examples 1-1 to 1-4.

[0123] Figure 8 is a diagram showing polarization curves for the oxygen evolution reaction of the electrodes manufactured in Examples 1-3 and Comparative Example 1.

[0124] 50 mAcm for the electrodes manufactured in Examples 1-1 to 1-4 and Comparative Example 1 -2 The overvoltages measured at current densities are shown in Table 2 below.

[0125] Example 1-1 (CO_150) Example 1-2 (CO_200) Example 1-3 (CO_250) Example 1-4 (CO_300) Comparative Example 150 mAcm -2 Overvoltage measured at the current density 360 mV 346 mV 326 mV 342 mV 420 mV

[0126] Referring to Table 2, Figures 7 and 8 above, it was confirmed that the electrodes of Examples 1-1 to 1-4 manufactured by the method according to the present invention had improved performance as oxygen generation reaction electrodes by lowering the overvoltage compared to the electrode of Comparative Example 1 manufactured by transferring and thermocompression of cobalt oxide slurry.

[0127] That is, the electrodes of Examples 1-1 to 1-4 manufactured by the method according to the present invention have a structure in which the size of the cobalt oxide nanoparticles formed in the catalyst layer is small and the nanoparticles are connected to form a neck, so it was confirmed that the performance as an oxygen generating electrode was significantly improved compared to the electrode of Comparative Example 1 manufactured by applying a slurry containing cobalt oxide particles onto a substrate and thermally pressing it.

[0128] This means that the number of active sites is different due to morphological differences between the synthesized catalysts.

[0129] Furthermore, it was confirmed that the overvoltage measured in Example 1-3, where the thermocompression performance temperature was 250 ℃, was the smallest at 326 mV, indicating the best performance as an oxygen evolution reaction electrode.

[0130] For reference, in Examples 1-2 to 1-4 where the thermocompression temperature was 200°C or higher, the Tefal slope value was less than 60 mV / dec, and in particular, the Tefal slope value measured in the electrode of Example 1-3 where the thermocompression temperature was 250°C was confirmed to be the smallest at 43 mV / dec. This indicates that the performance of the electrode manufactured when the thermocompression temperature was 200°C or higher was improved as an oxygen generating electrode, and in particular, it was the best when the temperature was 250°C.

[0131] 2.2. EIS analysis and electrochemically active surface area calculation

[0132] Electrochemical impedance spectroscopy (EIS) of the electrodes manufactured in the examples was performed in the frequency range of 200 kHz to 10 Hz, applying a voltage of 1.7 V (vs. RHE) with an amplitude of 10.0 mV.

[0133] Figure 9 is a diagram showing EIS spectra for electrodes manufactured in Examples 1-1 to 1-4.

[0134] Referring to Figure 9, the smaller the size of the semicircle of the Nyquist plots in the drawing, the greater the charge transfer resistance (R) of the electrode. ct ) is low, and the R of the electrodes of Examples 1-1 to 1-4 ct were 0.22, 0.16, 0.08, and 0.12 Ω, respectively, and it was confirmed that the electrode manufactured in Example 1-3 had the best kinetics for the oxygen evolution reaction.

[0135] The electrochemically active surface area (ECSA) of the electrodes manufactured in the examples is double layer capacitances (C dl ) and was calculated using the following equation.

[0136] ECSA = C dl / C s (C s = 40 μF / cm 2 , the planar capacitance value of the metal surface)

[0137] Double layer capacitances (C dl ) were measured by cyclic voltammetry (CV) at various scan rates from 20 to 100 mV / s.

[0138] The calculated electrochemically active surface areas for the electrodes manufactured in Examples 1-1 to 1-4 are shown in Table 3 below.

[0139] Example 1-1 (CO_150) Example 1-2 (CO_200) Example 1-3 (CO_250) Example 1-4 (CO_300) Electrochemically active surface area 185.25 cm 2 230.75 cm 2 277.5 cm 2 244.5 cm 2

[0140] Referring to Table 3 above, the electrochemically active surface area of ​​the electrode manufactured when the thermocompression temperature was 250°C was the largest, which is explained by the fact that the size of the cobalt oxide nanoparticles formed on the catalyst side of the electrode manufactured in Example 1-3 was the smallest, thereby increasing the active surface area of ​​the catalyst.

[0141] 2.3. Durability Test

[0142] The durability of the electrodes manufactured in Examples 1-1 to 1-4 was tested at a current density of 200 mA / cm² for 50 hours.

[0143] Figure 10 is a drawing showing the results of a 50-hour durability test for electrodes manufactured in Examples 1-1 to 1-4.

[0144] Referring to Fig. 10, all of the electrodes manufactured in Examples 1-1 to 1-4 showed excellent durability test results, and in particular, the electrode manufactured in Example 1-3 showed the least performance degradation in oxygen evolution reaction and thus had the best durability.

[0145] Examples 2-1 to 2-4: Preparation of a laboratory-scale anion exchange membrane electrolysis device

[0146] Using the electrodes manufactured in Examples 1-1 to 1-4, a laboratory-scale anion exchange membrane (AEM) electrolysis device was manufactured as follows.

[0147] First, the electrodes manufactured in Examples 1-1 to 1-4 as shown in Table 4 below were 7.1 cm 2 It was prepared in the size of 4.9 cm and used as an anode. As a cathode, it was 4.9 cm. 2 1 mg in porous carbon fibers having a size of pt An electrode of spray-coated Pt / C (40 wt%, HISPEC 4000, Jonhnson Matthey) was used with a loading amount of .

[0148] A laboratory-scale anion exchange membrane (AEM) electrolysis device was manufactured by assembling the anode, anion exchange membrane (PiperION, Versogen), and cathode.

[0149] The manufactured electrolysis device was immersed in 0.5 M KOH for 24 hours, and then operated at 45°C with a 0.1 M KOH electrolyte supply at a rate of 100 mL / min.

[0150] Example 2-1 Example 2-2 Example 2-3 Example 2-4 Anode type Example 1-1 Example 1-2 Example 1-3 Example 1-4 Anode size 7.1 cm 2 7.1 cm 2 7.1 cm 2 7.1 cm 2

[0151] <Experimental Example 3. Performance Evaluation of a Laboratory-Scale Water Electrolysis Device>

[0152] Electrochemical analysis of the laboratory-scale anion exchange membrane electrolysis device manufactured in Examples 2-1 to 2-4 was performed using a high current booster (20 A, Biologic) and a potentiostat (VMP-3, Biologic).

[0153] 3.1. LSV polarization curve analysis

[0154] The performance of laboratory-scale and commercial-scale anion exchange membrane electrolyzers was 1.35 to 1.9 V at a scan rate of 1 mV / s. cell It was evaluated using LSV polarization curves in the range.

[0155] Figure 11 is a diagram showing the LSV polarization curve (a) and Tefal diagram (b) of a laboratory-scale anion exchange membrane electrolysis device manufactured in Examples 2-1 to 2-4.

[0156] Referring to Fig. 11, the battery voltage (V) of 1.7 cell ) The electrolysis devices manufactured in Examples 2-1 to 2-4 had currents of 0.94, 0.92, 1.1 and 1.01 A / cm, respectively.2 The current density was recorded, and the current density was the highest in the electrolysis device (Example 2-3) using the electrode of Example 1-3, and the Tefal slope was also the lowest in the electrolysis device of Example 2-3, indicating excellent dynamics.

[0157] 3.2. EIS analysis and material transfer analysis

[0158] Electrochemical impedance spectroscopy (EIS) analysis was performed to determine the ohmic resistance and charge transfer resistance of the laboratory-scale anion exchange membrane electrolysis device manufactured in Examples 2-1 to 2-4. Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 100 kHz to 100 mHz, at a current of 0.5 A / cm 2 was performed at a current density of .

[0159] In order to further analyze the effect of intrinsic activity and mass transfer of the electrode according to the present invention in a water electrolysis device, the total overvoltage was measured as ohmic resistance (η ohm ), dynamic overvoltage (η kin ), mass transfer overvoltage (η mass ) was divided into

[0160] Ohmic resistance represents ionic and electronic resistance in the high-frequency range, whereas charge transfer resistance and mass transfer resistance represent electron transfer reactions and the movement of reactants and products.

[0161] Ohmic resistance (η) of the electrolysis device ohm ), dynamic overvoltage (η kin ), mass transfer overvoltage (η mass ) and energy conversion efficiency (ECE) were determined through the following equations (1) to (4).

[0162] (1):

[0163] (2):

[0164] (3):

[0165] (4):

[0166] In the above equations (1) to (4), R b is the bulk resistance of the cell, j is the current density, α is the Tefal slope, b is the voltage of the cell at the exchange current density, V is the voltage of the cell, 1.23 is the thermodynamic voltage demand required to decompose water, W h is the amount of electricity to produce hydrogen, V H2 is the volume of hydrogen gas, and H0 is the lower heating value of hydrogen, which is 10.8*10 6 Jm -3 am.

[0167] Figure 12 shows the EIS analysis results (a) for the electrolysis devices manufactured in Examples 2-1 to 2-4 and the overvoltage of the electrolysis devices in terms of ohmic resistance (η). ohm ), dynamic overvoltage (η kin ), mass transfer overvoltage (η mass ) is a drawing that is divided into (b).

[0168] Figure 13 is a drawing showing the total pore volume measured for the electrodes manufactured in Examples 1-1 to 1-4.

[0169] Referring to part (b) of Fig. 12, the electrolysis device (Example 2-3) using the electrode of Example 1-3 had the smallest dynamic overvoltage, and the proportion of the mass transfer overvoltage contributing to the total overvoltage was approximately 3.1%, which was the lowest compared to other electrolysis devices.

[0170] Referring to part (b) of FIG. 12 and FIG. 13, the total pore volume was the largest in the electrode manufactured in Example 1-3, and this high porosity can promote rapid release of oxygen (O2) gas generated at the electrode, thereby reducing mass transfer overvoltage and improving the performance of the water electrolysis device.

[0171] 3.3. Durability Test

[0172] The durability of the laboratory-scale anion exchange membrane electrolysis devices manufactured in Examples 2-1 to 2-4 was tested at a current density of 0.5 A / cm² for 200 hours. Furthermore, after the 200-hour durability test for the electrolysis device of Example 2-3, SEM images, XRD patterns, and XPS analyses were performed to verify the physical and chemical deterioration of the electrodes used in the device. The specific conditions and methods for each analysis were the same as those described in the experimental examples above.

[0173] Figure 14 is a drawing showing the results of a 200-hour durability test for the electrolysis device manufactured in Examples 2-1 to 2-4 (a), the XRD pattern (b), SEM image (c), and XPS analysis results (d, e) of the electrode after the durability test for the device of Example 2-3.

[0174] Referring to part (a) of Fig. 14, in the case of the water electrolysis device of Example 2-3, 44.4 mV / kh for 200 hours 1 It shows the decomposition rate and confirmed superior stability than the electrolysis devices of Examples 2-1, 2-2 and 2-4.

[0175] Referring to parts (b) and (c) of Fig. 14, the shape and crystallinity of the electrode of Example 1-3 did not show significant changes even after a 200-hour durability test.

[0176] Also, referring to parts (d) and (e) of Fig. 14, the same peak positions were observed in the Co 2p and O s XPS spectra for the electrodes of Examples 1-3 after 200 hours of durability test.

[0177] In summary, it was confirmed that the physical and chemical properties of the electrodes of Examples 1-3 were maintained even after a 200-hour durability test.

[0178] Example 3: Fabrication of a commercial-scale anion exchange membrane electrolysis device

[0179] Using the electrode manufactured in Example 1-3, a commercial-scale anion exchange membrane (AEM) electrolysis device was manufactured as follows.

[0180] First, the electrode manufactured in Example 1-3 was 78.5 cm 2 It was prepared in the size of 63.6 cm and used as an anode. As a cathode, it was used as a cathode. 2 1 mg in porous carbon fibers having a size of pt An electrode of spray-coated Pt / C (40 wt%, HISPEC 4000, Jonhnson Matthey) was used with a loading amount of .

[0181] A commercial-scale anion exchange membrane (AEM) electrolysis device was manufactured by assembling the anode, anion exchange membrane (PiperION, Versogen), and cathode.

[0182] Figure 15 is a schematic diagram showing the structure of a commercial-scale anion exchange membrane electrolysis device manufactured in Example 3.

[0183] Referring to FIG. 15, the anion exchange membrane electrolysis device may have a structure in which a porous transport layer (PTL), an anode, an anion exchange membrane, a cathode, and a porous transport layer (PTL) are stacked in that order, and the nickel foam substrate and porous carbon fiber on the side of the anode and cathode on which the catalyst layer is not coated may function as the porous transport layer (PTL).

[0184] The manufactured electrolysis device was immersed in 0.5 M KOH for 24 hours, and then operated at 45°C with a 0.1 M KOH electrolyte supply at a rate of 100 mL / min.

[0185] <Experimental Example 4. Performance Evaluation of a Commercial-Scale Water Electrolysis Device>

[0186] The electrochemical analysis of the commercial-scale anion exchange membrane electrolysis device manufactured in Example 3 was performed using a high current booster (50 A, Biologic) and a potentiostat (SP-150, Biologic).

[0187] Long-term durability tests on commercial-scale anion exchange membrane electrolysis devices were conducted at 50°C and 0.1 M KOH electrolyte, with a current of 0.5 A / cm. 2 The test was performed for 1,000 hours at a constant current density. LSV polarization curves and EIS analysis were performed on the electrolysis device before and after the long-term durability test to further evaluate the durability of the device.

[0188] Figure 16 is a diagram showing the results of a long-term durability test for a water electrolysis device manufactured in Example 3 (a), an LSV polarization curve (b) and an EIS spectrum (c) before and after a long-term durability test.

[0189] Referring to part (a) of Fig. 16, the commercial-scale anion exchange membrane electrolysis device manufactured in Example 3 exhibited excellent durability, showing a decomposition rate of approximately 2 mV / kh and maintaining 79.46% ECE for 1,000 hours, demonstrating excellent long-term durability.

[0190] Referring to parts (b) and (c) of Fig. 16, the electrolysis device of Example 3 has a current of 0.85 A / cm at a battery voltage of 1.8 V. 2 The current density was achieved, and both the polarization curve and EIS plot confirmed that the initial performance was maintained even after 1,000 hours.

[0191] Figure 17 is a drawing comparing the durability of recently reported commercial-scale anion exchange membrane electrolysis devices and the commercial-scale anion exchange membrane electrolysis device manufactured in Example 3.

[0192] Referring to FIG. 17, the anion exchange membrane electrolysis device according to the present invention exhibited a lower deterioration rate and superior long-term durability compared to other anion exchange membrane electrolysis devices previously reported.

[0193] Overall, these results demonstrate that using electrodes fabricated through a simplified thermocompression process according to the present invention can contribute to the development of commercial anion exchange membrane electrolysis devices.

[0194] <Experimental Example 5: Analysis of the Effects of Changes in Thermocompression Time and Load>

[0195] To determine whether the thermocompression time affects the metal oxide particle size, SEM images and XRD analysis were performed to observe the structure of the catalyst layer formed on the surface of the electrodes manufactured in Examples 1-1, 3-1, and 3-2.

[0196] Figure 18 is an SEM image of the catalyst layer of the electrode manufactured in Examples 1-3, 3-1, and 3-2 and the Co(OH)2 powder of Manufacturing Example 1.

[0197] Referring to Fig. 18, at a temperature of 250 ℃ and 100 kg / cm 2 When performing thermocompression under a load, it was confirmed that nanoparticles of almost uniform size were formed in just 10 minutes, and even if the thermocompression time increased, there was no significant effect on the size of the metal oxide particles.

[0198] Figure 19 is a drawing showing the XRD spectrum of the catalyst layer of the electrode manufactured in Examples 1-3, 3-1, and 3-2.

[0199] Referring to Fig. 19, at a temperature of 250 ℃ and 100 kg / cm 2 When performing thermocompression under a load of , it was confirmed that peaks corresponding to cobalt oxide appeared in just 10 minutes.

[0200] In addition, in order to determine whether the thermocompression time affects the electrochemical performance of the manufactured electrode, a half-cell test was performed on the electrodes manufactured in Examples 1-1, 2-1, 2-2, 3-1, and 3-2 using the same method as in Experimental Example 2.

[0201] Figure 20 is a diagram showing LSV polarization curves in half-cell experiments for electrodes manufactured in Examples 1-1, 2-1, 2-2, 3-1, and 3-2.

[0202] Referring to Figure 20, when the thermocompression time was 10 minutes or more, the electrochemical performance of the manufactured electrode was not significantly affected even when the time was increased, and the thermocompression load was 50 kg / cm. 2 In this case, even if the thermocompression load increased, there was no significant effect on the electrochemical performance of the manufactured electrode.

[0203] Although the present invention has been described above through limited embodiments, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. A step of preparing a catalyst precursor clay by mixing metal hydroxide powder, binder resin and water; A step of rolling the above catalyst precursor clay to obtain a catalyst precursor sheet; and A method for manufacturing an electrode, comprising the step of positioning the above catalyst precursor sheet on a substrate and then hot pressing it to form a catalyst layer including metal oxide nanoparticles.

2. A method for manufacturing an electrode according to claim 1, wherein the metal hydroxide powder comprises a hydroxide containing at least one metal among Cu, Co, Ni, Fe, and Mn.

3. A method for manufacturing an electrode according to claim 1, wherein the binder resin is included in the catalyst precursor clay in an amount of 10 to 50 parts by weight based on 100 parts by weight of the metal hydroxide powder.

4. A method for manufacturing an electrode according to claim 1, wherein the water is included in the catalyst precursor clay in an amount of 2 to 15 parts by weight based on 100 parts by weight of the metal hydroxide powder.

5. A method for manufacturing an electrode according to claim 1, wherein the catalyst precursor sheet has a thickness of 100 ㎛ or more and 1,000 ㎛ or less.

6. A method for manufacturing an electrode according to claim 1, wherein the thermal compression is performed at a temperature of 150° C. to 300° C.

7. In claim 1, the heat pressing is performed at a pressure of 10 to 500 kg / cm 2 A method for manufacturing an electrode, the method being performed under a load.

8. A method for manufacturing an electrode according to claim 2, wherein the thermal compression is performed at a temperature of 200°C or higher and 300°C.

9. A method for manufacturing an electrode according to claim 1, wherein the substrate includes at least one of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam.

10. A method for manufacturing an electrode according to claim 1, wherein the metal oxide nanoparticles have an average particle diameter of 5 nm to 50 nm.

11. A method for manufacturing an electrode according to claim 1, wherein the metal hydroxide powder is manufactured by a co-precipitation method by mixing a metal hydroxide precursor, a pH regulator, and a chelating agent with a solvent.

12. An electrode manufactured by the method according to claim 1, comprising: a substrate; and a catalyst layer positioned on the substrate and including metal oxide nanoparticles.

13. An electrode according to claim 12, wherein the metal oxide nanoparticles are connected to each other to form a neck.

14. An electrode according to claim 12, wherein the metal oxide nanoparticles include cobalt oxide.

15. An electrode according to claim 12, wherein the average particle diameter of the metal oxide nanoparticles is 5 nm to 50 nm.

16. A water electrolysis device comprising an electrode according to any one of claims 12 to 15 as an anode.

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