Super-hydrophilic titanium oxide nanotube electrode electrodeposited with metal nanoparticles, method for manufacturing same, and anion exchange membrane water electrolyzer using same

Abstract

The present invention relates to a super-hydrophilic titanium oxide nanotube electrode electrodeposited with metal nanoparticles and, more specifically, to a method for manufacturing a super-hydrophilic titanium oxide nanotube-based electrode electrodeposited with metal nanoparticles through simple electrooxidation and electrodeposition.

Description

Superhydrophilic titanium oxide nanotube electrode with metal nanoparticles deposited thereon, method for manufacturing the same, and anion exchange membrane water electrolysis device using the same

[0001] The present invention relates to an electrode for anion exchange membrane electrolysis, and more particularly, to a method for synthesizing superhydrophilic titanium oxide nanotubes on which metal nanoparticles for the purpose of anion exchange membrane electrolysis catalyst are deposited.

[0002]

[0003] Electrolyzers are well-known devices for producing eco-friendly hydrogen using renewable energy sources. Existing devices include alkaline water electrolyzers (AWE) and proton exchange membrane electrolyzers (PEMWE). However, AWE suffers from low current density and requires the use of a potassium hydroxide (KOH) solution with a concentration of approximately 40%. Meanwhile, the high cost of electrocatalysts and corrosion inhibitors in PEMWE hinders the production of hydrogen at megawatt scale. Recently, researchers have developed anion exchange membrane electrolyzers (AEMWE) to balance performance and cost. However, achieving high efficiencies in both the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode remains a challenge, leading to extensive research into the development of cost-effective electrocatalysts.

[0004] Meanwhile, electrocatalyst development alone has limitations in improving electrode performance in water electrolyzers. One of the major obstacles to electrode technology, which degrades electrolytic cell performance, is the accumulation of non-polar gas bubbles, such as H2 and O2, on the electrode surface, which block the active sites of the catalyst. To reduce bubble adhesion on the electrode surface, electrocatalysts with superhydrophilic or ultraporous surfaces have been utilized. However, commonly used electrode materials, such as NF, titanium felt (TF), and carbon paper (CP), are hydrophobic, resulting in bubble accumulation on the electrode during the reaction, leading to particle separation and agglomeration. Therefore, for long-term operation of water electrolyzers, an electrode development strategy that combines the advantages of hydrophilicity with effective gas discharge is essential.

[0005] The present invention proposes a superhydrophilic electrode surface structure through which oxygen bubbles can efficiently escape, and aims to improve oxygen evolution reaction (OER) performance by including an electrode material having a high surface area, strong metal-support interaction (SMSI), and improved stability.

[0006]

[0007] The present invention has been devised to solve the above problems, and the purpose of the present invention is to provide a method for manufacturing a superhydrophilic titanium oxide nanotube-based electrode on which metal nanoparticles are electrodeposited through a simple electrooxidation method and electrodeposition method.

[0008] In addition, the purpose of the present invention is to provide a method for manufacturing an electrode for green hydrogen production that can improve the performance and durability of an anion exchange membrane electrolysis device through rapid removal and discharge of gases (H2 and O2) generated during a water electrolysis reaction using the superhydrophilic titanium oxide nanotube-based electrode.

[0009] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0010]

[0011] In order to achieve the above object, the present invention provides a method for manufacturing a titanium oxide nanotube electrode, characterized by comprising the steps of: washing titanium metal with acetone and deionized water and drying it; anodizing the dried titanium metal to produce titanium oxide nanotubes; heat-treating the titanium oxide nanotubes to produce annealed titanium oxide nanotubes; and immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor to electrodeposit metal nanoparticles.

[0012] In the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, the anodizing can be performed at a voltage of 28 to 32 V for 5 to 7 hours.

[0013] In the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, the anodizing electrolyte contains ethylene glycol, deionized water, and ammonium fluoride, and the ammonium chloride may be contained in an amount of 0.6 to 0.9 parts by weight per 100 parts by weight of the mixture of ethylene glycol and deionized water.

[0014] In the step of manufacturing annealed titanium oxide nanotubes by heat-treating the titanium oxide nanotubes, the heat treatment can be performed at 450 to 550°C for 4 to 6 hours in an air atmosphere.

[0015] In the step of electrodepositing metal nanoparticles by immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor, the aqueous solution containing the metal precursor may be a sulfate-based aqueous solution.

[0016] In the step of immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor to deposit metal nanoparticles, the metal nanoparticles may be at least one selected from the group consisting of Ni, Fe, Ru, Mo, or a combination thereof.

[0017] In addition, the present invention provides a titanium oxide nanotube electrode manufactured according to the above manufacturing method.

[0018] In addition, the present invention provides an anion exchange membrane electrolysis device characterized by including a titanium oxide nanotube electrode manufactured according to the above-described manufacturing method.

[0019]

[0020] By means of solving the above problem, the performance and durability of an anion exchange membrane electrolysis device can be improved through rapid removal and discharge of gases (H2 and O2) generated during electrolysis reaction using a superhydrophilic titanium oxide nanotube-based electrode according to the present invention.

[0021] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0022]

[0023] Figure 1 shows schematic diagrams and FESEM, AFM, and contact angle analysis results of NiFe nanoparticles deposited on various Ti-based substrates: (AD) TF, (EH) NiFe / TF, (IL) TNT, (MP) NiFe / TNT, (QT) ATNT, and (UX) NiFe / ATNT.

[0024] Figure 2 shows SXRD patterns of (A) TF, (B) TNT, and (C) ATNT substrates before and after NiFe deposition.

[0025] Figure 3 shows (A) XANES and (B) FT-EXAFS spectra at the Ti K-edge of a Ti-based substrate.

[0026] Figure 4 shows cross-sectional FESEM images before and after NiFe deposition on (A,D) TF, (B,E) TNT, and (C,F) ATNT substrates.

[0027] Figure 5 shows (A) cross-sectional HRTEM image of NiFe / ATNT, (B) HRTEM image of NiFe nanoparticles of ATNT, (C,D) enlarged views of the red and yellow boxed areas in (B), (E) HAADF-STEM image and EDS elemental mapping of NiFe / ATNT, (F) FIB section and EDS elemental mapping image of NiFe / ATNT single particle, (G) XPS spectra of Ti 2p region for ATNT and NiFe / ATNT, (H) Ni 2p 3 / 2 and (I) XPS spectra for NiFe / ATNT, NiFe / TNT and NiFe / TF in the Fe 2p region.

[0028] Figure 6 shows the Ti 2p region XPS spectra before and after NiFe deposition on (A) TF and (B) TNT substrates.

[0029] Figure 7 shows XANES and FT-EXAFS analyses of NiFe electrodeposited on Ti-based substrates for (A, B) Ni K-edge and (C, D) Fe K-edge.

[0030] Figure 8 shows the OER catalytic performance of the prepared electrodes. (A) Polarization curves, (B) overpotential values, (C) OER Tafel plots, (D) EIS analysis of the prepared electrodes, (E) double-layer charge current versus scan rate plots, and (F) stability test results of NiFe / TF, NiFe / TNT, and NiFe / ATNT, and images captured by a high-definition camera of bubbles emitted from (G) NiFe / TF, (H) NiFe / TNT, and (I) NiFe / ATNT electrodes during half-cell tests at 80 ± 3 °C.

[0031] Figure 9 shows the OER activity of NiFe / ATNT according to various NiFe catalyst loadings. (A) OER polarization curves and (B) comparison of overpotential values ​​at various current densities.

[0032] Figure 10 (A) 1 mg cm -2 , (B) 3 mg cm -2 , (C) 5 mg cm -2 and (D) 10 mg cm -2 FESEM images of NiFe / ATNT with various NiFe loading amounts.

[0033] Figure 11 shows the diameter distribution of O2 bubbles released from (A) NiFe / TF, (B) NiFe / TNT, and (C) NiFe / ATNT during oxygen evolution reaction (OER) at 80 ± 3 ℃.

[0034] Figure 12 shows (A) a schematic image of AEMWE, (B) LSV curves for AEMWE at various settings: 5 mV s -1 Scan speed of 3 mL / min at 80 ± 3 ℃ -1EIS analysis of NiFe / TF ∥ Pt / C / TF and NiFe / ATNT ∥ Pt / C / ATNT, (C) NiFe / TF ∥ Pt / C / TF and NiFe / ATNT ∥ Pt / C / ATNT setups: Comparative study at 1.40 V (without bubble formation) and 1.60 V (with bubbles) at 80 ± 3 °C, schematic diagram of O2 bubbles accumulated in (D) hydrophobic NiFe / TF and (E) hydrophilic NiFe / ATNT during electrolysis.

[0035] Figure 13 shows the results of comparing the performance of anion exchange membrane electrolysis (AEMWE). (A) 3 mL / min -1 LSV curves obtained using different AEMs at flow rates of (A) different flow rates of catholyte on the anode side and (C) 3 mL / min -1 LSV curves obtained at different operating temperatures with a flow rate of .

[0036] Figure 14 shows the results of measuring the AEMWE performance of IrO2 on various Ti-based substrates. (A) 5 mV s -1 Scan speed of 3 mL mim at 80 ± 3 ℃ -1 LSV graphs of AEMWE using various setups of IrO2 / TF ∥ Pt / C / TF and IrO2 / ATNT ∥ Pt / C / ATNT at a flow rate of (A), (B) EIS analysis of AEMWE performance using IrO2 / TF ∥ Pt / C / TF and IrO2 / ATNT ∥ Pt / C / ATNT setups: comparison of 1.40 V (no bubble formation) and 1.60 V (bubble formation) at 80 ± 3 ℃.

[0037] Figure 15 shows the results of long-term stability evaluation of anion exchange membrane electrolysis (AEMWE). (A) 0.50 A cm for 1500 hours at 80 ± 3 ℃. -2 Long-term stability of AEMWE at a constant current density, (B) Comparative evaluation of the current density (j), Ecell, and stability of the fabricated AEMWE with previously reported AEMWE, (C) Ni 2p3 / 2 (D) XPS spectrum of Fe 2p region, (E) FESEM image of NiFe / ATNT after stability test.

[0038] Figure 16 is the XPS spectrum of NiFe / ATNT on Ti 2p.

[0039] Figure 17 shows the EIS measurement results of NiFe / ATNT ∥ Pt / C / ATNT before and after a 1500-hour stability test at 1.60 V.

[0040] Figure 18 is a FESEM image of Ti felt (TF) anodized at 30 V for 6 hours with various ammonium fluoride (NH4F) concentrations of (A) 0.5 wt%, (B) 0.75 wt%, (C) 1 wt%, and (D) 2 wt%.

[0041] Figure 19 is FESEM images of anodized Ti felt (TF) at various voltages of (A) 10 V, (B) 20 V, (C) 30 V, and (D) 40 V.

[0042] Figure 20 shows (A) a damage image observed in an ATNT sample after annealing in an inert gas atmosphere and (B) a transmission electron microscope (TEM) image of a damaged powder sample.

[0043] Figure 21 shows (A) FESEM images of Ni nanoparticles electrodeposited on ATNT samples, (B) HER performance of Ni / ATNT and ATNT in 1.0 M KOH solution, and (C) 10 mA cm -2 This is the result of the stability evaluation of Ni / ATNT for 24 hours at a current density of .

[0044] Figure 22 shows Ru electrodeposited on (A) ATNT sample. SA FESEM images of Ni nanoparticles, (B) Ru in 1.0 M KOH solution SA HER performance of Ni / ATNT and ATNT, and (C) 10 mA cm -2 24 hours in Ru SA This is the stability evaluation result of Ni / ATNT.

[0045] Figure 23 shows (A) HER performance of electrocatalysts manufactured by ATNT, (B) comparative performance analysis results of electrocatalysts at various current densities, and (C) 10 mA cm -2 24 hours a day in Ru SA These are the results of the stability evaluation of Ni / ATNT and the control group.

[0046] Figure 24 shows (A) FESEM images of NiMo nanoparticles (NiMo / ATNT) deposited on ATNT and (B) HER performances of NiMo / ATNT and ATNT in 1.0 M KOH solution.

[0047] Figure 25 is a flow chart of a method for manufacturing a superhydrophilic titanium oxide nanotube electrode on which metal nanoparticles are deposited according to a preferred embodiment of the present invention.

[0048]

[0049] The terms used in this invention have been selected from widely used, current terms, taking into account the functions of the invention. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, in which case their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should not be defined simply as names, but rather based on their inherent meanings and the overall content of the invention.

[0050] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0051] When a part of a specification 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 stated.

[0052] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0053]

[0054] Hereinafter, the present invention will be described in detail.

[0055]

[0056] The present invention provides a method for manufacturing a titanium oxide nanotube electrode, comprising the steps of: washing titanium metal with acetone and deionized water and drying it; anodizing the dried titanium metal to produce titanium oxide nanotubes; heat-treating the titanium oxide nanotubes to produce annealed titanium oxide nanotubes; and immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor to electrodeposit metal nanoparticles.

[0057] The step of washing and drying the titanium metal with acetone and deionized water may include the step of washing the titanium metal with acetone by ultrasonic treatment for 10 to 20 minutes; and the step of washing the ultrasonically washed titanium metal with deionized water and then drying it in an oven at 50 to 60°C for 10 to 30 minutes.

[0058] In the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, the anodizing can be performed at a voltage of 28 to 32 V for 5 to 7 hours, preferably at a voltage of 30 V for 6 hours, but is not limited thereto.

[0059] In the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, the anodizing electrolyte contains ethylene glycol, deionized water, and ammonium fluoride, and the ammonium chloride may be contained in an amount of 0.6 to 0.9 parts by weight per 100 parts by weight of the mixture of the ethylene glycol and the deionized water. Preferably, the electrolyte contains 95 parts by weight of ethylene glycol and 100 parts by volume of deionized water per 100 parts by volume of the mixture of the ethylene glycol and the deionized water, and 0.75 parts by weight of ammonium fluoride per 100 parts by weight of the mixture of the ethylene glycol and the deionized water, but is not limited thereto. According to one embodiment of the present invention, as the concentration of ammonium fluoride exceeds the above range and becomes higher, it can be observed that structures such as flowers or grasses gradually appear instead of tubes.

[0060] In the step of manufacturing titanium oxide nanotubes by anodizing the above-mentioned dried titanium metal, the anodizing process can be performed using titanium metal as the anode and aluminum foil as the cathode.

[0061] The titanium oxide nanotubes manufactured through the above anodization treatment may be in an amorphous form. Since the amorphous titanium oxide nanotubes exhibit low conductivity, the amorphous titanium oxide nanotubes can be converted into the anatase phase through heat treatment in a subsequent step.

[0062] After the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, a step of washing the titanium oxide nanotube electrode with deionized water and air drying it may be further included.

[0063] In the step of manufacturing annealed titanium oxide nanotubes by heat-treating the titanium oxide nanotubes, the heat treatment may be performed at 450 to 550°C for 4 to 6 hours in an air atmosphere. More preferably, the heat treatment may be performed at 500°C for 5 hours in an air atmosphere, but is not limited thereto. If the heat treatment is performed in an inert gas atmosphere instead of an air atmosphere, the titanium oxide nanotubes may become powdery or be damaged.

[0064] In the step of electrodepositing metal nanoparticles by immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor, the aqueous solution containing the metal precursor may be a sulfate-based aqueous solution. According to one embodiment of the present invention, a sulfate-citrate solution may be used for electrodeposition of metal / alloy nanoparticles. In this electrolyte, metal sulfate may act as a source of metal ions, and trisodium citrate may act as a complexing agent for the metal ions. Ammonium chloride may be added to increase cathode current efficiency, and sodium bromide (NaBr) may be introduced to improve solution conductivity and reduce crack formation. The synergistic action of these components allows for precise control of the particle shape and maintenance of a close to its original shape. On the other hand, when a chloride-based solution rather than a sulfate-based solution is used, the shape is not controlled, and some chlorine may remain in the tube, which may result in slight performance degradation during stability testing.

[0065] The above metal nanoparticles may be at least one selected from the group consisting of Ni, Fe, Ru, Mo or a combination thereof.

[0066] The step of immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor to deposit metal nanoparticles may apply magnetic stirring at a speed of 200 to 400 rpm for uniform deposition. The deposition of the metal nanoparticles may be performed at a current of 50 to 150 mA cm -2 It can be performed at a current density and temperature of 30 to 50 ℃, preferably 100 mA cm -2 It can be performed at a current density and a temperature of 40°C, but is not limited thereto. The pH value of the aqueous solution containing the metal precursor is maintained at 7.

[0067] After the step of electrodepositing the metal nanoparticles, the step of washing the electrode on which the metal nanoparticles are electrodeposited with ethanol and deionized water and drying it in an oven at 50 to 70° C. for 20 to 40 minutes may be further included.

[0068]

[0069] In addition, the present invention provides a titanium oxide nanotube electrode manufactured according to the above manufacturing method.

[0070] In addition, the present invention provides an anion exchange membrane electrolysis device characterized by including a titanium oxide nanotube electrode manufactured according to the above manufacturing method. The anion exchange membrane electrolysis device requires a highly stable electrode for long-term operation. The stability of the electrode is related to the effective discharge of hydrogen or oxygen gas generated at the electrode surface during the electrolysis process. The titanium oxide nanotube electrode according to the present invention can promote the rapid removal and discharge of hydrogen or oxygen gas generated during the electrolysis reaction, thereby improving the performance and durability of the anion exchange membrane electrolysis device.

[0071]

[0072] 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.

[0073]

[0074] Example 1. Preparation of titanium oxide nanotubes (TNT) (30 V voltage, 0.75 wt%) of ammonium fluoride

[0075] Titanium felt (TF) was cleaned by ultrasonic treatment in acetone for 15 min. It was then rinsed several times with deionized water (DI water) and dried in an oven at 60°C for 20 min. Subsequently, anodization was performed for 6 h using a direct current (DC) power supply at a constant voltage of 30 V between the anode and cathode in a solution containing 95 vol% ethylene glycol, 5 vol% deionized water (DI water), and 0.75 wt% ammonium fluoride (NH4F), using the titanium felt (TF) as the anode and aluminum foil as the cathode. The distance between the two electrodes was approximately 3 cm. After the anodization process, the resulting amorphous titanium oxide nanotube (TNT) electrode was washed with deionized water and air-dried.

[0076]

[0077] Example 2. Preparation of annealed titanium oxide nanotubes (ATNTs)

[0078] The titanium oxide nanotubes (TNT) synthesized in Example 1 were annealed at 500°C for 5 hours in an air atmosphere to convert the amorphous structure into the anatase phase, thereby producing annealed titanium oxide nanotubes (annealed TiO2 nanotubes, ATNT).

[0079]

[0080] Example 3. Fabrication of NiFe / ATNT electrodes

[0081] NiFe / ATNT electrodes were fabricated using an electrodeposition synthesis process in an electrolyte (100 mL of DI water) containing NiSO4-6H2O (2.64 g), FeSO4-6H2O (0.65 g), Na3C6H5O7-2H2O (14.70 g), NH4Cl (2.67 g), and NaBr (2.04 g). An ATNT substrate and a pure Ni plate (99%) were used as the anode and cathode, respectively. Both electrodes were vertically immersed in the electrolyte solution. Continuous magnetic stirring at 300 rpm was applied to the solution throughout the deposition process to ensure uniform deposition. The deposition was performed at 100 mA cm -2 The synthesis was performed at a constant current density of 10 and a constant bath temperature of 40°C. The pH of the solution was maintained at ~7.0. To optimize the OER performance during the synthesis, different amounts of catalyst were loaded onto the ATNT by varying the deposition time. After the electrodeposition process, the electrode on which the catalyst was deposited was washed several times with ethanol and deionized water to remove the remaining electrolyte solution and dried in an oven at 60°C for 30 min.

[0082]

[0083] Comparative Example 1. Manufacturing of NiFe / TNT electrodes

[0084] It was manufactured in the same manner as Example 3, except that a titanium oxide nanotube (TNT) substrate was used instead of an annealed titanium oxide nanotube (ATNT) substrate.

[0085]

[0086] Comparative Example 2. Manufacturing of NiFe / TF electrodes

[0087] It was manufactured in the same manner as Example 3, except that a titanium felt (TF) substrate was used instead of the annealed titanium oxide nanotube (ATNT) substrate.

[0088]

[0089] Comparative Example 3. Preparation of titanium oxide nanotubes (TNT) (0.5 wt%)

[0090] It was manufactured in the same manner as Example 1, except that 0.5 wt% of ammonium fluoride (NH4F) was used.

[0091]

[0092] Comparative Example 4. Preparation of titanium oxide nanotubes (TNT) (1 wt%) of ammonium fluoride

[0093] It was manufactured in the same manner as Example 1, except that 1 wt% of ammonium fluoride (NH4F) was used.

[0094]

[0095] Comparative Example 5. Preparation of titanium oxide nanotubes (TNT) (2 wt%)

[0096] It was manufactured in the same manner as Example 1, except that 2 wt% of ammonium fluoride (NH4F) was used.

[0097]

[0098] Comparative Example 6. Manufacturing of titanium oxide nanotubes (TNT) (10 V voltage)

[0099] It was manufactured in the same manner as Example 1, except that the anodization process was performed at a voltage of 10 V.

[0100]

[0101] Comparative Example 7. Manufacturing of titanium oxide nanotubes (TNT) (20 V voltage)

[0102] It was manufactured in the same manner as Example 1, except that the anodization process was performed at a voltage of 20 V.

[0103]

[0104] Comparative Example 8. Manufacturing of titanium oxide nanotubes (TNT) (40 V voltage)

[0105] It was manufactured in the same manner as Example 1, except that the anodization process was performed at a voltage of 40 V.

[0106]

[0107] Comparative Example 9. Fabrication of Annealed Titanium Oxide Nanotubes (ATNT) (Inert Gas Atmosphere)

[0108] It was manufactured in the same manner as Example 2, except that annealing was performed in an inert gas atmosphere.

[0109]

[0110] Experimental Example 1. Characteristics of Various Ti-Based Substrates

[0111] Various Ti-based substrates for OER electrodes were prepared by anodizing and annealing titanium felt (TF) (Fig. 1). The clean TF with a smooth surface had a thickness of 3 μm. 2 Field emission scanning electron microscopy (FESEM) (Fig. 1B) and atomic force microscopy (AFM) images (Fig. 1C) showed an average surface roughness (root mean square of image pixel height, Rq) of 18 nm on the surface area. Synchrotron X-ray diffraction (SXRD) revealed hexagonally close-packed Ti (Ti hcp ) showed the metal crystal structure (Fig. 2A).

[0112] After anodization at 30 V for 6 h in an aqueous solution containing ethylene glycol and ammonium fluoride, 14–15 titanium oxide nanotubes were formed on the TF surface (Fig. 1J), increasing the Rq value to 22 nm (Fig. 1K). Since the titanium oxide nanotubes formed on the TF were amorphous, the TNTs exhibited a SXRD pattern similar to that of the pristine TF (Fig. 2B).

[0113] Because amorphous titanium oxide nanotubes exhibit low conductivity, annealing was applied to transform the amorphous phase into the crystalline anatase phase on the TF. A high Rq value of 117 nm was obtained due to the modification of the TNT surface (Figures 1R and 1S). SXRD analysis of the annealed TiO2 nanotubes (ATNT) revealed distinct anatase-TiO2 (101) and (200) peaks at 25.3° and 48.1°, respectively (Figure 2C).

[0114] To investigate the changes in the surface structure of TF due to treatment, X-ray absorption near-edge (XAFS) analysis was performed. X-ray absorption near-edge (XANES) of TF showed a clear pre-edge due to the three-dimensional transition at the dipole 1 s of metallic Ti, similar to that of pure Ti foil (Fig. 3A). The Ti pre-edge was also observed in TNT and ATNT samples due to the non-oxidized Ti in the core. However, TNT and ATNT showed a quadrupole pre-edge as a result of TiO2 formation. In addition, Fourier transform-extended X-ray absorption fine structure (FT-EXAFS) spectra of TNT and ATNT showed two peaks, Ti-O (1.5 Å) and extended Ti-Ti (2.6 Å) bonds indicating TiO2 formation, whereas TF showed a single Ti-Ti (2.5 Å) peak (Fig. 3B). The extended Ti-Ti bonds of TNT were slightly shorter than those of ATNT, indicating the amorphous structure of TNT.

[0115]

[0116] Experimental Example 2. Characterization of various Ti-based electrodes deposited with NiFe nanoparticles.

[0117] NiFe nanoparticles were electrochemically deposited on TF, TNT, and ATAT substrates to obtain NiFe / TF, NiFe / TNT, and NiFe / ATNT. The NiFe / TF electrode exhibited a thick surface coating of aggregated NiFe nanoparticles (Fig. 1F), whereas NiFe / TNT (Fig. 1N) and NiFe / ATNT (Fig. 1V) exhibited less agglomeration of NiFe nanoparticles.

[0118] The Rq values ​​of the deposited electrodes were measured to be 43, 111, and 120 nm for NiFe / TF (Fig. 1G), NiFe / TNT (Fig. 1O), and NiFe / ATNT (Fig. 1W), respectively. The higher Rq value of ATNT suggests that it provides more nucleation sites during the electrodeposition process, resulting in smaller NiFe nanoparticles and improved dispersion compared to the other electrodes.

[0119] SXRD analysis results confirmed the formation of NiFe alloy nanoparticles in the electrode material, as evidenced by the presence of NiFe (111) peaks at 44.0° and 51.5° (Fig. 2). To gain further insight into the distribution of NiFe nanoparticles within TF, TNT, and ATNT, cross-sectional FESEM images were obtained before and after NiFe deposition (Fig. 4). The results showed that NiFe nanoparticles deposited within ATNT exhibited higher SMSI compared to NiFe NPs in TF and TNT.

[0120] Further examination of the cross-sectional transmission electron microscope (TEM) images of NiFe / ATNTs revealed well-dispersed NiFe nanoparticles within the ATNTs (Fig. 5A). High-resolution TEM (HRTEM) images of NiFe / ATNTs revealed that the lattice distances corresponding to anatase TiO2(101) and NiFe(200) were 0.35 and 0.18 nm, respectively (Figs. 5B-D).

[0121] High-angle annular dark-field scanning TEM (HAADF-STEM) images and energy-dispersive X-ray spectroscopy (EDS) elemental mapping of NiFe / ATNTs confirmed that NiFe alloy was formed on the TiO2 substrate without doping of Ni or Fe atoms into TiO2 (Fig. 5E). In addition, HAADF-STEM and EDS mapping images prepared by focused ion beam (FIB) sectioning showed the internal nanoporous structure of the NiFe nanoparticles (Fig. 5F). The well-dispersed nanoporous NiFe nanoparticles of ATNTs with strong metal-support interaction (SMSI) and high Rq value can provide enhanced oxygen evolution reaction (OER) performance by providing a large number of active sites, efficient mass transfer of electrolyte / gas, and catalytic stability.

[0122] The chemical structure of the prepared electrode was investigated using X-ray photoelectron spectroscopy (XPS). The Ti 2p XPS spectrum of the pristine TF showed that Ti arose from the naturally oxidized Ti on the surface. 0 Peak and small Ti Ｘ+ peak, and TNT and ATNT were dominant Ti 4+ and small Ti 2+ The peak was exposed (Fig. 5G and Fig. 6). After NiFe deposition, the Ti 2p peak was not observed because a thick NiFe layer existed on the flat TF surface (Fig. 6A). In the case of TNT and ATNT, the oxidation state of Ti increased after NiFe deposition. Specifically, Ti 4+ / Ti Total The ratio increased from 0.91 for TNT to 0.98 for NiFe / TNT. Also, for NiFe / ATNT, Ti 4+ The peak position of ATNT is blue-shifted. This is a result of charge transfer from Ti to Ni / Fe. In this regard, Ni 2p 3 / 2And Fe 2p XPS spectra were red-shifted for NiFe / TNT and NiFe / ATNT compared to NiFe / TF, with NiFe / ATNT showing a greater shift than NiFe / TNT (Figures 5H and 5I). This greater peak shift could be attributed to the higher Rq value of ATNT than that of TF and TNT, which helped promote SMSI between NiFe NPs and ATNT during electrodeposition.

[0123] XAFS analysis also demonstrated the SMSI effect on the NiFe-deposited Ti-based substrates. The XANES spectra of the Ni K-edge showed that the white line (WL) position of the electrode redshifted in the order NiFe / ATNT < NiFe / TNT < NiFe / TF < Ni foil, indicating that the Ni state was further reduced in NiFe / ATNT due to the enhanced SMSI (Fig. 7A). The Fe K-edge XANES spectra showed a similar trend to that of the Ni K-edge (Fig. 7B). The FT-EXAFS profiles of the Ni K-edge and Fe K-edge for NiFe / TF, NiFe / TNT, and NiFe / ATNT showed metallic structures (Figs. 7C and 7D). The difference in the Fe K-edge peak patterns of the NiFe crystal and the Fe foil is due to the difference in their crystal structures.

[0124] The hydrophilicity of the prepared electrodes was analyzed through wettability tests. As evidenced by the contact angle of 79.6° for water droplets, pristine TF is hydrophobic (Fig. 1D). However, due to the deposition of hydrophilic NiFe, the contact angle of NiFe / TF decreased to 29.8° (Fig. 1H). In contrast, TNT and ATNT exhibited hydrophilicity without measurable contact angles due to the formation of polar TiO2 on the surface (Figs. 1L and 1T). This hydrophilic behavior was maintained even after NiFe deposition on TNT and ATNT (Figs. 1P and 1X). This hydrophilic surface property enhances the electrocatalytic performance by facilitating the unimpeded access of electrolyte to the catalyst during electrochemical reactions and promoting the reaction kinetics.

[0125]

[0126] Experimental Example 3. Electrochemical Characteristics Analysis

[0127] Electrochemical measurements of NiFe nanoparticles formed on various Ti-based substrates in 1.0 M KOH solution were performed using a three-electrode system. The oxygen evolution reaction (OER) polarization curves were obtained at 5 mV s -1 The OER performance of bare ATNT, Ni / ATNT, and commercial IrO2 loaded on glassy carbon (IrO2 / GC) was investigated under the same conditions to provide a basis for comparison. The OER was obtained with appropriate iR compensation via linear sweep voltammetry (LSV) at a scan rate of 10 mA cm -2 To achieve a current density of , NiFe / ATNT showed an overpotential of 235 mV, which was 73, 70, 49, and 104 mV lower than IrO2 / GC, NiFe / TF, NiFe / TNT, and Ni / ATNT, respectively. Also, Fig. 8B shows the overpotential at current densities of 20 and 50 mA cm -2The overpotential values ​​were compared in , indicating that NiFe / ATNT showed the best OER activity among all electrodes. The reaction kinetics of the prepared electrodes were determined by the Tafel slope derived from the steady-state polarization curves, as shown in Fig. 8C. The Tafel slope values ​​of IrO2 / GC, Ni / ATNT, NiFe / TF, NiFe / TNT, and NiFe / ATNT were 95, 130, 85, 65, and 52 mV dec, respectively. -1 , indicating the fastest charge transfer kinetics of NiFe / ATNT.

[0128] To analyze the charge transfer kinetics and interfacial properties of the electrode, electrochemical impedance spectroscopy (EIS) was performed in a 1.0 M KOH solution at 1.52 VRHE over a frequency range of 0.01–100 kHz. The Nyquist plot of the prepared electrode is shown in Figure 8D, which exhibits two major semicircles. The first semicircle region is due to the interfacial resistance between the electrolyte and the electrode, and the second semicircle region corresponds to the charge transfer resistance representing the OER kinetics. Therefore, among the other catalysts, the first and second semicircles of NiFe / ATNT are the smallest, indicating the lowest interfacial and charge transfer resistances.

[0129] The electrochemically active surface area (ECSA) of the electrocatalyst was calculated from the double layer capacitance (C) from the cyclic voltammetry (CV) curves recorded at various scan rates in the non-Faradic region in the potential range of 0.52–0.62 VRHE. dl ) was measured and estimated. C dl Since the ECSA of the silver electrode is proportional to the ECSA, the higher the ECSA, the more active sites there are on the electrode surface, which leads to a faster charge transfer rate and stronger interaction between the electrolyte and the electrode during OER. As shown in Fig. 8E, C dl 4.1 mF cm for NiFe / ATNT -2 was measured as NiFe / TF (1.5 mF cm -2 ) and NiFe / TNT (3.1 mF cm-2 ) showed higher values. Therefore, the increase in ECSA of NiFe / ATNT may be due to the use of porous NiFe nanoparticles and the improvement in surface roughness.

[0130] The OER performance of NiFe / ATNT with various amounts of NiFe loading was measured (Fig. 9A and Fig. 9B). The loading of NiFe nanoparticles was from 1 to 5 mg cm -2 As the concentration increased, OER activity was enhanced until 10 mg cm -2 The FESEM images showed that the loading amount decreased from 1 to 5 mg cm -2 As the NiFe nanoparticle loading increased, the number and size of NiFe nanoparticles increased, and the aggregation on the ATNT surface was limited (Fig. 10A-C). However, when the NiFe nanoparticle loading was 10 mg cm -2 Further increasing the catalyst loading resulted in particle aggregation or clustering in the ATNT (Fig. 10D), which resulted in a decrease in the effective utilization of the active surface area of ​​the electrode, thereby reducing the OER performance. Furthermore, high catalyst loading can cause dense packing of the OER active sites, limiting mass transport and hindering electrolyte penetration, ultimately reducing the reaction rate and overall performance.

[0131] To evaluate the long-term stability of the prepared catalyst, 10 mA cm in 1.0 M KOH solution -2 Chronopotentiometer tests were performed at a constant current density for 100 h (Fig. 8F). As a result, NiFe / TF maintained its performance for up to 72 h, whereas NiFe / TNT and NiFe / ATNT performed for 100 h without a significant increase in overpotential. The stable OER performance of NiFe / TNT and NiFe / ATNT can be attributed to the SMSI effect between the catalyst and the support.

[0132] The influence of hydrophilic behavior on gas (O2) bubble release from the electrode during electrochemical measurements was investigated by capturing and analyzing the bubble release patterns of the electrodes prepared during OER using a high-definition camera. These experiments were conducted in a half-cell configuration at 80 ± 3 °C. Examination of the NiFe / TF electrode revealed that the O2 bubbles formed on the electrode surface were strongly adhered and connected to adjacent bubbles, forming a bubble network (Fig. 8G). Consequently, these bubbles grew in size, forming regions of poor mass transfer, commonly known as "dead zones," on the electrode surface. These dead zones restrict the inflow of reactants to the electrode, resulting in insufficient reactant supply to these regions and, consequently, a reduced reaction rate, as observed in this OER case. The size of the released bubbles was significantly reduced compared to the bubbles observed on the NiFe / TNT surface (Fig. 8H). Although NiFe / TNT is hydrophilic, its flat surface prevents rapid bubble detachment, forming dead zones. For NiFe / ATNT, the generated O2 bubbles were observed to be much smaller than those of the other two electrodes and to escape quickly from the electrode surface, limiting the formation of dead zones on the electrode surface (Fig. 8I). The enhanced surface roughness exposes more active sites, which is effective for gas evolution and enhances the electrochemical performance of the ATNT-supported catalyst at high current densities. The average diameters of the O2 bubbles released from the electrode surface were measured to be 124 ± 13, 75 ± 6, and 23 ± 8 μm for NiFe / TF, NiFe / TNT, and NiFe / ATNT, respectively (Fig. 11).

[0133]

[0134] Experimental Example 4. Performance Evaluation of an Anion Exchange Membrane Electrolysis Device Cell

[0135] To evaluate the potential applicability of NiFe / ATNT, a surface area of ​​5 cm 2Water electrolysis experiments were performed using a customized single-cell electrolyzer (Fig. 12A). NiFe / ATNT was used as the anode, and commercial Pt / C / ATNT was used as the cathode. Since the choice of membrane is important as it directly affects the efficiency, durability, and overall performance of the AEMWE, initial analyses were performed using three commercial membranes: PiperION, Fumasep FAA-3-50, and Sustainion® X37-50 grade T. The assembled electrolyzer (NiFe / ATNT ∥ Pt / C / ATNT) was initially operated at a constant flow rate of 3 mL / min at an operating temperature of 60 ± 3 °C. -1 was cycled with 1.0 M KOH solution. NiFe / ATNT ∥ Pt / C / ATNT using PiperION at 1.80 V was Sustainion® X37-50 grade T (0.86 A cm -2 ) and Fumasep FAA-3-50 (0.88 A cm -2 ) with the best performance (1.28 A cm -2 ) was shown (Fig. 13A).

[0136] The optimal electrolyte flow rate helps to efficiently separate the gas from the electrolyte, thereby increasing gas purity, prevents bubble build-up on the electrodes, thereby exposing more active sites, and maintains a constant temperature in the electrolytic cell when operating at high temperatures. Therefore, the flow rates of 1, 2, 3, and 5 mL min at the anode are recommended. -1 Control the electrolyte flow rate and 3 mL min at the cathode -1 Experiments were performed with NiFe / ATNT ∥ Pt / C / ATNT at a constant flow rate of 1 mL min as shown in Fig. 13B. -1 3 mL min at -1 When increased to , the electrolytic cell performance increased from 0.80 to 1.28 A cm at 1.80 V and 60 ± 3 ℃. -2, which is due to the improved availability of reactants at the electrode. Increasing the electrolyte flow rate to rapidly remove the bubbles formed at the anode (O2) and cathode (H2) is important to prevent the formation of dead zones at the electrode. However, if the flow rate is 5 mL / min -1 When increased to 1.07A cm, the performance is -2 falls. At higher flow rates, OH at the electrode surface - This is because the ions are quickly depleted, limiting the interaction between the catalyst and the ions. Considering this result, the optimal condition for effective electrolyte circulation is 3 mL min. -1 The flow rate was determined.

[0137] In the present invention, the role of the hydrophilicity of the electrode at high temperatures was additionally considered to enhance the efficiency of the electrolytic cell in terms of promoting the separation of gas bubbles and ensuring the immediate availability of catalytic sites for subsequent reactions. The electrolytic cell performance was improved by increasing the operating temperature from 25 °C to 80 ± 3 °C (Fig. 13C). By optimizing all possible parameters, the NiFe / ATNT ∥ Pt / C / ATNT electrolytic cell designed with the PiperION membrane achieved a current of 1.67 A cm at 1.80 V and 80 ± 3 °C. -2 Current density (3 mL min) -1 (Fig. 12B).

[0138] To distinguish the effects of the NiFe nanoporous structure and ATNT on electrolyzer performance under optimal conditions, AEMWE experiments were performed using commercial IrO2 as the anode catalyst on both superhydrophilic ATNT and hydrophobic TF substrates to analyze the substrate effect. Subsequently, NiFe NPs were compared on the same substrate to analyze the NiFe porosity effect.

[0139] In the substrate effect analysis, the LSV curve for the IrO2 / TF configuration was 0.73 A cm at 1.80 V and 80 ± 3 ℃. -2It showed a low current density of about 0.15 A cm than the IrO2 / ATNT configuration. -2 The values ​​were lower (Fig. 14A).

[0140] To understand the influence of hydrophilicity and bubble accumulation on these improvements, comparative EIS analysis was performed on these AEMWE setups at two voltage conditions: 1.40 V (no bubbles) and 1.60 V (with bubbles). As shown in Figure 14B, at 1.40 V, the AEMWE using IrO2 / ATNT showed a higher conductivity than that of IrO2 / TF (0.152 Ω cm 2 ) with a system resistance lower than 0.121 Ω cm 2 ) was shown. Under more demanding conditions of 1.60 V, the system resistance of AEMWE using IrO2 / ATNT was 0.137 Ω cm. 2 , while the IrO2 / TF composition was 0.179 Ω cm 2 It was found that the anode catalyst IrO2 was replaced with a highly active porous NiFe-containing ATNT electrode, and the performance was compared with that of the NiFe TF electrode. As shown in Fig. 12B, the NiFe / TF ∥ Pt / C / TF configuration showed a current density of 0.71 A cm at 1.80 V and 80 ± 3 °C. -2 It showed lower performance than the optimized NiFe / ATNT ∥ Pt / C / ATNT under the same conditions, which was about 0.96 A cm -2 It is a low value. Comparing the EIS analysis at 1.40 V and 1.60 V (Fig. 12C), the optimized NiFe / ATNT ∥ Pt / C / ATNT configuration has a low value of 0.167 Ω cm at 1.40 V, which is higher than the NiFe / TF configuration (NiFe / TF ∥ Pt / C / TF) at 1.60 V. 2 ) with a much lower system resistance (0.089 Ω cm) compared to 2 ) was shown. Also, at 1.60 V, the NiFe / ATNT configuration had a resistance of 0.092 Ω cm. 2, while the NiFe / TF composition showed a slight increase of 0.244 Ω cm 2 was found to have significantly increased. According to Ohm's law, if the internal resistance of the AEMWE using the ATNT electrode is low, a higher current density can be achieved compared to the AEMWE using the TF because there is less dead zone. On the other hand, the AEMWE using the TF was found to have a higher internal resistance due to the accumulation of gas bubbles, which created a dead zone on the electrode surface (Fig. 12D). In addition, the combination of the porous NiFe NPs and the superhydrophilic ATNT substrate was also found to effectively eliminate the formation of dead zones, significantly reduce the electrolytic cell resistance, and improve the overall performance (Fig. 12E).

[0141] The long-term stability of NiFe / ATNT ∥ Pt / C / ATNT is 0.50 A cm at 80 ± 3 ℃. -2 was tested for 1500 h at a constant current density (Fig. 15A). Compared with other AEMWEs using non-precious metals as anodes, the performance and stability of NiFe / ATNT ∥ Pt / C / ATNT surpassed previous results (Fig. 15B, Table 1).

[0142] AnodeCathodeElectrolyteCurrent density (Acm -2 ) @ Cell Voltage (V)Stability(h)ReferencesNiFePt / C1.0 M KOH1.67 @ 1.801500This workNiFe2O4Pt / C1.0 M KOH1.43 @ 1.80721CuCo-oxidePt / C1.0 M KOH1.39 @ 1.80642FeOOH / NiFe LDHsPt / C1.0M KOH1.00@1.801003Ni 0.75 Fe 2.25 O4Pt / C1.0 M KOH1.31 @ 1.80214CuCo2O4Pt / C1.0 M KOH~1.00 @ 1.80125Cu 0.5 Co 2.5O4Pt / C1.0 M KOH1.30 @ 1.801006g-CN-CNF-800Pt / C1.0 M KOH0.48 @ 1.800.57H-Co 0.9 Fe 0.1 -CNFPt / C1.0 M KOH0.79 @ 1.702908CoS b2 O6Pt / C1.0 M KOH1.00 @ 1.975-9NiFe-LDHPt / C1.0 M KOH1.00 @ 1.695010(NiCo)3Se4Pt / C1.0 M KOH1.00 @ 1.759511NiFe-LDHPt / C1.0 M KOH1.00 @ 1.596 M 0.81 Co 2.19 O4Co3S41.0 M KOH1.00 @ 2.201213Ni-Co-TiNi-Co-Ti1.0 M KOH0.32 @ 2.201314CuCoO3Ni / CeO2-La2O3 / C1.0 M KOH1.00 @ 2.2120015Ni 12 P5 / Ni(PO4)2-HSNi 12 P5 / Ni(PO4)2-HS1.0 M KOH1.00 @ 2.3010016Ni filmCu x Co 3-x O41.0 M KOH0.10 @ 2.001817Fe-NiMo-NH3 / H2NiMo-NH3 / H21.0 M KOH1.00 @ 1.572518Fe 0.2 By 0.8 -P 0.5 S 0.5 Fe 0.2 By 0.8 -P 0.5 S 0.5 1.0 M KOH2.50 @ 2.0030019NiFeNiFe1.0 M KOH1.60 @ 2.00100020

[0143]

[0144] XPS and FESEM analyses were performed to investigate the chemical and morphological changes of NiFe / ATNT after the AEMWE stability test. The XPS peaks in the Ti 2p region showed that the ATNT substrate maintained a stable TiO2 phase under the anodic conditions of AEMWE (Fig. 16). However, the Ni 2p 3 / 2 and Fe 2p regions mainly showed 3+ oxidation states, indicating that OER-active NiFeOOH phase was formed during the stability test (Fig. 15C and Fig. 15D). SEM analysis also found morphological changes from NiFe nanoparticles to nanosheets, supporting the formation of NiFeOOH structure (Fig. 15E). EIS analysis performed at 1.60 V showed that the resistance value of the electrolytic cell was 0.092 Ω cm during the stability test. 2 0.126 Ω cm at 2 , which was found to have slightly increased (Fig. 17). Characteristic analysis after these tests confirmed that NiFe / ATNT is very stable even under harsh conditions.

[0145]

[0146] Experimental Example 5. Surface Analysis of Ti Felt (TF) According to Ammonium Fluoride Concentration

[0147] Anodization of TF was performed using various concentrations of ammonium fluoride (NH4F) in a bath containing ethylene glycol and water at 30 V for 6 hours. As a result, it was observed that as the concentration of ammonium fluoride (NH4F) increased, flower- or grass-like structures gradually appeared instead of tubes. Referring to Figure 18, it can be seen that a concentration of 0.75 wt% was the optimal concentration for achieving uniform nanotube formation.

[0148]

[0149] Experimental Example 6. Surface Analysis of Ti Felt (TF) According to Anodizing Voltage

[0150] Anodizing of TF was performed at various voltages while maintaining a constant ammonium fluoride (NH4F) concentration of 0.75 wt% in a bath containing ethylene glycol and water, and maintained for 6 hours. As the voltage increased, the size of the nanotubes also increased, resulting in the formation of larger tubes. Referring to Figure 19, based on these morphological changes, an operating voltage of 30 V is shown to be the optimal condition for synthesizing suitable nanotubes.

[0151]

[0152] Experimental Example 7. Surface Analysis of Titanium Oxide Nanotubes (ATNTs) Annealed in an Inert Gas Atmosphere

[0153] The surface of titanium oxide nanotubes (ATNTs) annealed in an inert gas atmosphere was analyzed using FESEM. Referring to Figure 20, synthesis using an inert gas resulted in the ATNTs being powdered or broken. Therefore, synthesis in an inert gas atmosphere is considered unsuitable.

[0154]

[0155] Experimental Example 8. Analysis of annealed titanium oxide nanotubes (ATNTs) electrodeposited with various metal nanoparticles.

[0156] The surface morphology was analyzed by FESEM, and various metal nanoparticles (Ni, Ru) were added to annealed titanium oxide nanotubes (ATNT). SA Electrodes on which Ni, NiMo) were deposited were fabricated and their hydrogen evolution reaction (HER) performance in 1.0 M KOH was measured. 10 mA cm -2 A 24-hour stability evaluation was performed at a current density of .

[0157] Referring to Figures 21 to 24, Ni and Ru deposited on ATNT SA Ni and NiMo have no voltage drop observed and are less than 10 mA cm -2 It exhibits excellent stability and performance at current densities.

[0158] We have discussed specific embodiments of the present invention. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. Step of washing titanium metal with acetone and deionized water and drying; A step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal; A step of heat-treating the above titanium oxide nanotubes to produce annealed titanium oxide nanotubes; and A method for manufacturing a titanium oxide nanotube electrode, characterized in that it comprises a step of immersing the annealed titanium oxide nanotube in an aqueous solution containing a metal precursor to electrodeposit metal nanoparticles.

2. In paragraph 1, In the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, A method for manufacturing an annealed titanium oxide nanotube electrode, characterized in that the above anodic oxidation is performed at a voltage of 28 to 32 V for 5 to 7 hours.

3. In paragraph 1, In the step of manufacturing titanium oxide nanotubes by anodizing the dried titanium metal, The above anodic oxidation electrolyte contains ethylene glycol, deionized water and ammonium fluoride, A method for manufacturing a titanium oxide nanotube electrode, characterized in that the ammonium chloride is contained in an amount of 0.6 to 0.9 parts by weight per 100 parts by weight of a mixture of ethylene glycol and deionized water.

4. In paragraph 1, In the step of manufacturing annealed titanium oxide nanotubes by heat treating the above titanium oxide nanotubes, A method for manufacturing a titanium oxide nanotube electrode, characterized in that the above heat treatment is performed at 450 to 550°C for 4 to 6 hours in an air atmosphere.

5. In paragraph 1, In the step of electrodepositing metal nanoparticles by immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor, A method for manufacturing a titanium oxide nanotube electrode, characterized in that the aqueous solution containing the metal precursor is a sulfate-based aqueous solution.

6. In paragraph 1, In the step of electrodepositing metal nanoparticles by immersing the annealed titanium oxide nanotubes in an aqueous solution containing a metal precursor, A method for manufacturing a titanium oxide nanotube electrode, characterized in that the metal nanoparticles are at least one selected from the group consisting of Ni, Fe, Ru, Mo or a combination thereof.

7. A titanium oxide nanotube electrode manufactured according to the manufacturing method of paragraph 1.

8. An anion exchange membrane electrolysis device characterized by including a titanium oxide nanotube electrode according to Article 7.

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