Catalyst for water electrolysis using fluorine-doped tin oxide support and method for manufacturing the same

Abstract

The present invention relates to a method for manufacturing a catalyst for water electrolysis using a fluorine-doped support, comprising: preparing a support; doping fluorine onto the support; and forming a metal particle catalyst on a surface of the fluorine-doped support, and to a catalyst for water electrolysis manufactured thereby. The present invention uses a dry plasma process to omit the cleaning process and can easily form fluorine doping on the surface without causing structural collapse of the support material.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit under 35 USC 119 (a) of Korean Patent Application No. 10-2024-0057076 filed on Apr. 29, 2024, and Korean Patent Application No. 10-2024-0079668 filed on Jun. 19, 2024, in the Korean Intellectual Property Office, the entire disclosures of which are incorporated herein by reference for all purposes.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The present invention relates to a catalyst for water electrolysis using a fluorine-doped tin oxide support and a method for manufacturing the same, specifically, to a method for manufacturing a high-performance and high-durability catalyst for water electrolysis material by treating the support with fluorine doping and by supporting iridium catalyst onto the manufactured fluorine-doped catalyst support.DESCRIPTION OF GOVERNMENT-SPONSORED RESEARCH

[0003] This invention was carried out with the support of Ministry of Science and ICT under a research project of Unique Project identification number: 1711196516 and Project identification number: 2E32520 Titled “Developing core technologies of electro super cellulose composite materials”, as part of the research project of “Support for research operation expenses of the Korea Institute of Science and Technology (main project expenses)” managed by Korea Institute of Science and Technology from Jan. 1 to Dec. 31, 2023.

[0004] This invention was carried out with the support of Ministry of Science and ICT under a research project of Unique Project identification number: 1711181981 and Project identification number: 2022M3H4A7046278 titled “AI-based smart laboratory for the development of water electrolysis catalyst and light-emitting quantum dot”, as part of the research project of “Development of Nanomaterial technology” managed by the National Research Foundation of Korea from Jan. 1 to Dec. 31, 2023.

[0005] This invention was carried out with the support of Ministry of Science and ICT under a research project of Unique Project identification number: 1711195090 and Project identification number: 00209940 titled “Atomic level catalyst design and high current density system application for eco-friendly hydrogen peroxide mass production”, as part of the research project of “Individual Basic Research (Ministry of Science and ICT)” managed by the National Research Foundation of Korea from Mar. 1, 2023 to Feb. 29, 2024.

[0006] This invention was carried out with the support of Ministry of Science and ICT under a research project of Unique Project identification number: 1711195446 and Project identification number: 2020M 3H 4A 3081791 titled “Synthesis of stable perovskite quantum dots for color resist”, as part of the research project of “Development of Nanomaterial technology” managed by the National Research Foundation of Korea from Jan. 1 to Dec. 31, 2023.Description of the Related Art

[0007] Research on electrochemical energy storage and conversion technologies to produce sustainable and renewable energy has been continuously advancing and growing in importance.

[0008] Among others, metal-carried form of catalysts are widely used in various industries due to their high activity, selectivity, and stability, and research is being conducted to highly disperse metals into small sizes to maximize the utilization of expensive metals, and many advanced clean energy technologies such as fuel cells, metal-air batteries, water electrolysis, etc. require highly active catalysts to lower energy barriers and increase reaction rates in an efficient and stable pathway.

[0009] Meanwhile, various metal materials (precious metals, transition metals, etc.) mainly used in high-activity catalysts have limited reserves and high prices. Therefore, there is a demand for economically cost-effective catalyst production with high efficiency using small amounts of catalysts.

[0010] In addition, high-activity catalysts in the form of nanoparticles degrade due to various catalyst degradation mechanisms in harsh environmental electrochemical devices, and thus improvements are required accordingly.

[0011] To address this issue, active research is being conducted on catalyst supports and supported catalysts. The supported catalyst forms metal catalyst particles on the surface of the support, which can reduce the usage of expensive precious metal catalysts and improve durability.SUMMARY OF THE INVENTION

[0012] As described above, when specific phenomena arising from strong catalyst-support interactions between the catalyst particles to be supported, such as precious metals or transition metals, and the fluorine-doped tin oxide support are used, the activity and durability of the water electrolysis catalyst can be improved. Additionally, by introducing the support, the dispersion of the metal catalyst can be increased, thereby enhancing the catalyst utilization efficiency.

[0013] In general, in water electrolysis, metal nanoparticles, including iridium-based catalysts without a support, are used as oxygen evolution electrode catalysts. This is because conventional catalyst supports, which provide a large surface area and excellent electrical conductivity, such as carbon black, cannot be used in the oxidative environment of water electrolysis driving conditions. In addition to carbon-based supports, oxide-based materials are being considered as supports. However, their low electrical conductivity requires the inclusion of dopant elements for use as supports in electrochemical catalysts. In such cases, issues such as the leaching of dopant elements during the water electrolysis driving process arise, which can lead to a decrease in performance. Among doped oxide-based supports, fluorine-doped tin oxide suppresses the leaching of the fluorine dopant element and can enhance the performance and durability of iridium-based catalysts as a support for water electrolysis catalysts.

[0014] Therefore, a method for manufacturing a fluorine-doped tin oxide-based catalyst for water electrolysis is required to enhance the performance and durability of iridium-based catalysts in water electrolysis environments.

[0015] To achieve the aforementioned objects, there is provided a method for manufacturing a catalyst for water electrolysis using a fluorine-doped support, according to the present invention. The method may include: preparing a support; doping fluorine onto the support; and forming a metal particle catalyst on a surface of the fluorine-doped support.

[0016] In addition, the doping of fluorine onto the support, according to the present invention, may be performed by dispersing the support in a solvent and adding a dopant precursor including the fluorine source, and the dopant precursor including the fluorine source may be boron trifluoride etherate (C4H10BF3O) or ammonium fluoride (NH4F).

[0017] In addition, the doping of fluorine onto the support, according to the present invention, may be performed by plasma treating a source gas including the fluorine onto the surface of the support.

[0018] In addition, the support, according to the present invention, may have a form of nanoparticle-formed powder, a nanostructure-formed thin film, or a substrate.

[0019] In addition, the support, according to the present invention, may be a porous carbon material selected from carbon black, carbon nanotubes, carbon fibers, or fullerenes.

[0020] In addition, the preparing of the support, according to the present invention, may further include a preliminary treatment of the surface of the support, and the preliminary treatment may include an oxidation process including one of electrochemical oxidation, oxygen plasma oxidation, or acid treatment.

[0021] In addition, the support, according to the present invention, may use tin oxide.

[0022] In addition, the metal catalyst, according to the present invention, may include precious metals, rare earth metals, and transition metals, and the transition metal may be one or more selected from Ir, Pt, Pd, Os, Ru, Co, Fe, Mo, W, Cr, and Ni, or an alloy including the above metals.

[0023] In addition, the forming of metal particle catalysts on the surface of the fluorine-doped support, according to the present invention, may include: preparing a solution in which the fluorine-doped support is dispersed; adding and mixing a precursor of the metal into the dispersed solution; adding a reducing agent to the mixed solution to carry out a reduction reaction; and filtering the reduced solution to collect powder, and heat treating the collected powder.

[0024] In addition, the present invention may provide a catalyst for water electrolysis manufactured according to one or more of the aforementioned manufacturing methods.

[0025] The present invention uses a dry plasma process to omit the cleaning process and can easily form fluorine doping on the surface without causing structural collapse of the support material.

[0026] In addition, the present invention applies the manufactured fluorine-doped catalyst support as an electrochemical catalyst material for reactions such as oxygen evolution, which can reduce the usage of precious metals and rare earth catalysts used as water electrolysis catalysts. This enables the application of catalyst materials at a lower cost.

[0027] Further, in case of fluorine-doped oxide supports, durability can be secured in electrochemical environments compared to conventional carbon-based supports or existing oxide supports, thereby ensuring excellent price competitiveness and system durability.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a schematic view illustrating a method for doping fluorine onto a support according to an embodiment of the present invention.

[0029] FIGS. 2A and 2B are graphs showing the XRD and Raman spectroscopy results of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0030] FIGS. 3A to 3D are graphs showing the characteristics of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0031] FIGS. 4A and 4B are graphs showing the results of measuring the resistance values and intrinsic conductivity of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0032] FIGS. 5A and 5B are graphs showing the durability of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0033] FIG. 6 is a schematic view illustrating a method for manufacturing a catalyst for water electrolysis in which an iridium metal catalyst is formed on a fluorine-doped support according to an embodiment of the present invention.

[0034] FIGS. 7A and 7B are photographs showing TEM images of the catalyst for water electrolysis manufactured according to an embodiment of the present invention.

[0035] FIGS. 8A and 8B are graphs showing the XRD and Raman spectroscopy results of the catalyst using the fluorine-doped support and the comparison example using the support without fluorine doping, manufactured according to an embodiment of the present invention.

[0036] FIG. 9 is a graph showing the oxygen evolution reaction of the catalyst using the fluorine-doped support and the comparison example using the support without fluorine doping, manufactured according to an embodiment of the present invention.

[0037] FIG. 10 is a graph evaluating the durability of the catalyst using the fluorine-doped support and the comparison example using the support without fluorine doping, manufactured according to an embodiment of the present invention.

[0038] FIG. 11 schematically illustrates a method for applying the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, to an anode electrode for water electrolysis.

[0039] FIG. 12 is a schematic view illustrating the application of the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, in an actual water electrolysis system.

[0040] FIG. 13 is a graph showing the performance evaluation of a unit cell applying the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, in an actual water electrolysis system.

[0041] FIGS. 14A and 14B are graphs showing the performance and durability of a unit cell applying the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, in an actual water electrolysis system.DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, with reference to the attached drawings, a catalyst for water electrolysis using a fluorine-doped tin oxide support and a method for manufacturing the same according to an embodiment of the present invention will be described through the preferred embodiment of the present invention.

[0043] Prior to the description, unless explicitly described to the contrary, the word “comprise” or “include” and variations, such as “comprises”, “comprising”, “includes” or “including”, will be understood to imply the inclusion of stated constituent elements, not the exclusion of any other constituent elements.

[0044] In addition, in the various embodiments, the constituent elements having the same constitution will be described using the same reference numerals, typically in an embodiment, and only different constituent elements will be described in other embodiments.

[0045] Further, while the embodiments of the present invention have been described with reference to the accompanying drawings, they are described for illustrative purposes only and are not intended to limit the technical spirit of the present invention and the constitution and application thereof.

[0046] As described above, the present invention relates to a method for manufacturing a catalyst for water electrolysis using a fluorine-doped support.

[0047] Specifically, in an embodiment of the present invention, the present invention manufactures a fluorine-doped tin oxide catalyst support by doping fluorine onto the support through a dry plasma chemical surface modification treatment. Iridium nanoparticle catalysts may then be supported on this catalyst support and applied as an anode electrochemical catalyst for polymer electrolyte water electrolysis.

[0048] In addition, the step of doping fluorine onto the support in the present invention may be performed by plasma treatment of a source gas including fluorine on the surface of the support.

[0049] Alternatively, in another embodiment of the present invention, the present invention manufactures a fluorine-doped tin oxide catalyst support by doping fluorine onto the support through a solution process in which the support is mixed with a dopant precursor including a fluorine source. Iridium nanoparticle catalysts may then be supported on this catalyst support and applied as an anode electrochemical catalyst for polymer electrolyte water electrolysis.

[0050] In addition, the dopant precursor including the fluorine source may be boron trifluoride etherate (C4H10BF3O), ammonium fluoride (NH4F), or other fluorine-including compounds.

[0051] As described above, an embodiment of the present invention uses a tin oxide support doped with fluorine element to impart high electrical conductivity to the tin oxide support. The fluorine-doped tin oxide support may be in the form of nanotubes, nanofibers, nanoparticles, or microparticles.

[0052] Meanwhile, in an embodiment of the present invention, the tin oxide in an embodiment of the present invention may include any tin oxide-based material including SnO2 as a support, without limitation.

[0053] Additionally, although fluorine is used as an dopant in the tin oxide support, elements such as boron (B), oxygen (O), niobium (Nb), indium (In), antimony (Sb), arsenic (As), phosphorus (P), nitrogen (N), and others may also be applied as dopants.

[0054] Additionally, in an embodiment of the present invention, it is preferable for the fluorine used as the dopant to be doped in an amount of 1 to 15 at (atomic) % relative to the total number of atoms in the support. When fluorine is doped in an amount of less than 1 at % or more than 15 at % relative to the total number of atoms in the support, a problem may arise in which the electrical conductivity of the catalyst support decreases.

[0055] Additionally, in an embodiment of the present invention, iridium nanoparticles are formed on the fluorine-doped tin oxide support. These iridium nanoparticles may be supported on the fluorine-doped tin-based oxide support.

[0056] In this case, for the iridium nanoparticles synthesized on the tin oxide support, strong interactions between the oxide support and the iridium nanoparticles cause compression deformation within the lattice, which weakens the adsorption strength with oxygen species. As a result, the catalytic properties may be ultimately enhanced.

[0057] Additionally, these iridium nanoparticles preferably have an average particle diameter of 1 to 15 nm. When the average particle diameter is less than 1 nm or greater than 15 nm, the mass activity of the nanoparticles may decrease.

[0058] Additionally, the iridium nanoparticles of an embodiment of the present invention, are included in an amount of 1 to 70 wt % relative to the total catalyst weight, and the fluorine-doped tin oxide support is preferably included in an amount of 1 to 70 wt % relative to the total catalyst weight. In this case, when the iridium nanoparticles are included in an amount of less than 1 wt % relative to the total catalyst weight, the catalyst layer may become thicker, leading to a decrease in cell performance. On the other hand, when the iridium nanoparticles are included in an amount greater than 70 wt %, the surface area of the fluorine-doped tin oxide support may be relatively smaller than that of the supported iridium catalyst, leading to a problem where the iridium nanoparticles aggregate due to the lack of support surface area.

[0059] Additionally, the present invention may manufacture a fluorine-doped tin oxide support through dry plasma treatment without using a solvent. In this process, the tin oxide may be in any form, including powder, thin film, or film in particle form. Through surface modification using dry plasma, the residence time of the fluorine source to be doped and the plasma intensity may be adjusted, making it easy to control the high-content fluorine doping and doping concentration.

[0060] Additionally, since the present invention does not use a reducing agent or solvent during the fluorine doping process, it is possible to easily control the doping concentration of fluorine without altering the structure of the support. The manufactured support may be directly applied as a catalyst support without the need for additional chemical or thermal treatments, allowing the catalyst for water electrolysis to be manufactured through a simple process.

[0061] Meanwhile, the catalyst may be manufactured in various forms depending on the element species of the precursor, such as precious metals, rare earth metals, or transition metals on the surface of the support. Specifically, the transition metals may be used in one or more selected from Ir, Pt, Pd, Os, Ru, Co, Fe, Mo, W, Cr, and Ni, or in the form of an alloy.

[0062] Additionally, when supporting metal catalyst particles on the surface of the fluorine-doped support, conventional solution processes may be used. To increase the doping content of fluorine on the support surface and control the concentration, the surface of the support may be pre-treated. Methods such as chemical surface treatment (HF treatment), plasma treatment, solution synthesis (fluorine precursors like NH4F, KF), polymer precursors (PTFE, PVDF) thermal surface treatment may be used.

[0063] Additionally, as a specific embodiment of the present invention, the step of supporting a metal nanoparticle catalyst on the fluorine-doped tin oxide support may include the steps of: preparing a solution in which the fluorine-doped tin oxide support is dispersed; adding a metal precursor to the dispersed solution and mixing; adding a reducing agent to the mixed solution and carrying out a reduction reaction; filtering the reduced solution to collect powder, and heat treating the collected powder to obtain a fluorine-doped tin oxide support with a supported metal nanoparticle catalyst.

[0064] In this case, as an embodiment, when selecting iridium (Ir) as the metal nanoparticle, the iridium precursor may include any iridium precursor including iridium (Ir) without limitation. For example, all iridium precursors such as iridium chloride, iridium (III) chloride, iridium (IV) chloride hydrate, iridium (III) chloride hydrate, iridium (III) bromide hydrate, and iridium (III) acetylacetonate are possible.

[0065] Additionally, as an embodiment, a dispersing solvent may include ethanol or a solvent with similar solubility to ethanol, for example, methanol, 2-propanol, acetone, and the like. As an embodiment, in the step of preparing a solution in which the fluorine-doped tin oxide support is dispersed, a surfactant may be additionally added to the solution to form nano-sized iridium particles. Such surfactants may include one or more selected from the group consisting of cetrimonium bromide (CTAB), sodium acetate (C2H3NaO2), tetraoctylammonium bromide ([CH3(CH2)7]4N(Br)), and oleylamine (CH3(CH2)7CH═CH(CH2)7CH2NH2).

[0066] Alternatively, as an embodiment, the same effect may be achieved by adding a potassium hydroxide solution to the dispersing solution instead of adding a surfactant, thereby adjusting the pH to 10 or higher. As an embodiment, after the addition of the surfactant or the pH adjustment step as described above, an ultrasonic treatment step may further be included.

[0067] Additionally, as an embodiment of the present invention, performing a preliminary treatment such as oxidation on the surface of the support results in the formation of defects on the surface of the support. Fluorine may then be uniformly deposited at these defect positions. More specifically, the present disclosure will be described with reference to specific embodiments below.

[0068] FIG. 1 is a schematic view illustrating a method for doping fluorine onto a support according to an embodiment of the present invention. As illustrated in FIG. 1, a method for doping a dopant onto a support according to an embodiment of the present invention includes the steps of (a) introducing a powder-type material (metal oxide) to be used as the support into a dielectric barrier discharge (DBD) plasma reactor, (b) injecting a precursor source gas of the target material to be doped onto the surface of the material to be used as the support and doping it through DBD plasma treatment, and (c) cleaning by passing nitrogen carrier gas through the DBD plasma reactor to obtain a support with doping completed on the surface of the support.

[0069] Specifically, (a) in the step of introducing the tin oxide support powder into the DBD plasma reactor, the tin oxide nanoparticle powder having an average particle diameter of 100 nm or less is used, and (b) in the step of forming fluorine doping on the surface of the tin oxide support, the support powder was functionalized with fluorine by nitrogen (N2, 3 L / min), nitrogen trifluoride (NF3, 0.3 L / min), and hydrogen (H2, 0.03 L / min), which are plasma gases, through the DBD electrodes in a horizontally oscillating and mixing DBD plasma reactor to uniformly dope the support powder.

[0070] Here, N2 is used as the gas to form the atmosphere, NF3 acts as the gas for generating F radicals, and H2 is used to facilitate the dissociation of NF3.

[0071] Additionally, the applied voltage frequency of the DBD plasma reactor is 30 kHz, the input power is 400 W, and the DBD plasma reactor is maintained at room temperature and atmospheric pressure for 1 to 3 hours. In this case, to uniformly plasma-treat the entire area of the powder, the powder may be placed on a moving stage that moves back and forth horizontally or vertically, rotates, or vibrates for plasma treatment. Alternatively, a fixed stage may also be used.

[0072] The gas including fluorine includes fluorine, nitrogen trifluoride, hydrogen fluoride, carbon tetrafluoride, sulfur hexafluoride, and others. There is no restriction on the use of a single gas. Additionally, inert gases such as nitrogen and argon may be included as the atmosphere gas, and the process is not fixed to power variations or treatment times.

[0073] In step (c), to obtain the fluorine-doped tin oxide support synthesized through process (b), the reactor interior was flushed by passing N2 gas through to remove the residual gas after the DBD plasma treatment was completed and the fluorine-doped support powders were collected.

[0074] FIGS. 2A and 2B are graphs showing the XRD and Raman spectroscopy results of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0075] As shown in FIGS. 2A and 2B, the XRD results confirm that the phases of the fluorine-doped tin oxide support and the tin oxide support without fluorine doping are maintained. This indicates that the structure and phase of the tin oxide are not altered during the plasma surface treatment process.

[0076] Additionally, the Raman spectroscopy analysis results show that both the fluorine-doped tin oxide support and the tin oxide exhibit an amorphous and nanocrystalline structure of the samples at the Eu peak. Through the A1g and B2g peaks, it was observed that there was an overall similar peak with the expansion and contraction of the Sn—O bond. This confirms that the structure of the tin oxide is maintained even after the fluorine doping process.

[0077] Additionally, in case of the fluorine-doped tin oxide, the As peak was formed after fluorine doping, which was different from that of tin oxide, which is attributed to an increase in the oxygen vacancy concentration on the particle surface formed by the fluorine doping on the surface.

[0078] FIGS. 3A to 3D are graphs showing the characteristics of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0079] Specifically, the Sn 3d XPS in (a) of FIG. 3 and the O 1s XPS in (b) of FIG. 3 measurement results show that the peaks of the fluorine-doped tin oxide support and the undoped tin oxide exhibit overall similar peak profiles. Specifically, the Sn3d peak in (a) of FIG. 3 is symmetrical and separated by 8.4 eV, which indicates the chemical state of Sn4+ in SnO2. In addition, the O 1s peak in (b) of FIG. 3 is asymmetric, confirming that the chemical state of oxygen exists in one or more states.

[0080] Further, the fluorine-doped tin oxide showed a shift in binding energy in the Sn 3d and O 1s peaks after the fluorine doping process, which is related to the incorporation of doped fluorine anions into the oxygen positions in the tin oxide lattice. Additionally, the F Is XPS measurement results and survey peaks confirm that, in case of the fluorine-doped tin oxide support, a fluorine peak is formed on the surface, with minimal structural changes of the tin oxide without fluorine doping. This indicates that fluorine doping was successfully synthesized on the surface of the tin oxide without causing structural collapse of the existing tin oxide through the plasma process.

[0081] FIGS. 4A and 4B are graphs showing the results of measuring the resistance and intrinsic conductivity of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0082] Specifically, FIGS. 4A and 4B show the results of resistance values (at 1.6V applied) associated with the actual electrochemical oxygen evolution reaction of the fluorine-doped tin oxide support, the tin oxide without performing fluorine doping, and the commercially available antimony-doped tin oxide support.

[0083] As illustrated in FIGS. 4A and 4B, the fluorine-doped tin oxide and antimony-doped tin oxide exhibited superior charge transfer resistance compared to the tin oxide without fluorine doping. It can be confirmed that the fluorine-doped tin oxide support, according to an embodiment of the present invention, shows improved ohmic resistance similar to that of the antimony-doped tin oxide compared to the fluorine-undoped tin oxide.

[0084] [Table 1] below shows the intrinsic electrical conductivity results of the fluorine-doped tin oxide support, the fluorine-undoped tin oxide, and the commercially available antimony-doped tin oxide support.TABLE 1SampleI (A)E (V)L (cm)σ (S cm−1)Carbon XC-720.2840.0110.1615.498SnO2(TO)2 · 10−50.7020.2759.400 · 10−6FTO1.1290.2340.0490.301ATO0.3540.0420.0800.868

[0085] As shown in [Table 1] above, the fluorine-doped tin oxide support exhibited superior conductivity properties compared to conventional tin oxide. This demonstrates that the fluorine-doped tin oxide support provides excellent conductivity and resistance values (ohmic, charge transfer), which are key factors for electrochemical catalyst-support applications, making it suitable for use in various electrochemical catalysts.

[0086] FIGS. 5A and 5B are graphs showing the durability of the fluorine-doped support and the comparison example without fluorine doping, manufactured according to an embodiment of the present invention.

[0087] Specifically, after evaluating the electrochemical durability of the fluorine-doped tin oxide support, manufactured according to an embodiment of the present invention, and commercially available antimony-doped tin oxide, the ICP-MS analysis results related to element leaching in the electrolyte were obtained. To confirm the electrochemical durability of the dopant (Sb) and tin (Sn) leaching, a high electrochemical oxygen evolution reaction voltage (1.3 to 1.8 V) was applied in the environments of neutral (pH 7) on the left and acidic (pH 1) on the right, and a 10,000 cycle test was performed.

[0088] As shown in FIGS. 5A and 5B, the ICP-MS measurement results of the cations Sn and Sb in both neutral (pH 7) and acidic (pH 1) environments revealed that the Sn leaching from both the commercially available antimony-doped tin oxide and the fluorine-doped tin oxide was similar. However, excessive leaching of the Sb dopant from the commercially available antimony-doped tin oxide was observed.

[0089] Additionally, the ICP-MS measurement results of the cations Sn and Sb leaching under the application of electrochemical voltage in the acidic (pH 1) environment, which represents more harsh conditions, confirmed that the leaching of the Sb dopant from the antimony-doped tin oxide becomes more pronounced in the acidic environment.

[0090] FIG. 6 is a schematic view illustrating a method for manufacturing a catalyst for water electrolysis in which an iridium metal catalyst is formed on a fluorine-doped support according to an embodiment of the present invention.

[0091] Specifically, in an embodiment of the present invention, (a) 50 mg of the aforementioned fluorine-doped tin oxide support (FTO) is added to 60 mL of ethanol to support the iridium metal catalyst, followed by ultrasonic treatment at room temperature for 1 hour, and then stirred to obtain a dispersion.

[0092] Additionally, (b) argon (Ar) gas is purged into the obtained FTO support dispersion at room temperature, and the surfactant cetrimonium bromide (CTAB) is introduced, and then stirred vigorously for 2 hours to manufacture a uniform mixture.

[0093] Meanwhile, in addition to cetrimonium bromide (CTAB), surfactants such as sodium acetate, tetraoctylammonium bromide, and oleylamine may also be applied.

[0094] Next, (c) the iridium precursor, iridium chloride hydrate (IrCl3), is added to the mixture in (b) at 20 wt % of the support powder and stirred for 2 hours to prepare the support and metal precursor in a uniform state.

[0095] Next, (d) a reducing agent, sodium borohydride (NaBH4), is added to the iridium precursor and FTO support mixture in (c) and stirred at room temperature for more than 6 hours to manufacture a catalyst with iridium nanoparticles supported on the surface of the FTO support.

[0096] Additionally, (e) the iridium-supported FTO (Ir / FTO) catalyst formed through the aforementioned process of (c) is washed with ethanol and water, and then vacuum dried for 6 hours to evaporate the washing solvents, resulting in obtaining a black catalyst powder.

[0097] Meanwhile, as a comparative example to the embodiment of the present invention described above, iridium metal was formed on the surface in the same method using fluorine-undoped tin oxide (SnO2; TO) and antimony-doped tin oxide (Sb—SnO2; ATO) depending on the type of support, and the electrochemical catalyst was manufactured and electrochemically evaluated.

[0098] FIGS. 7A and 7B are photographs showing TEM images of the catalyst for water electrolysis manufactured according to an embodiment of the present invention, and is TEM images of a catalyst with iridium formed on the fluorine-doped tin oxide support manufactured according to the embodiment described above and a TEM EDS mapping analysis.

[0099] As illustrated in FIGS. 7A and 7B, the TEM image confirms that the iridium nanoparticles are spherical in shape, with sizes of approximately 2 to 5 nm, and are formed on the surface of the fluorine-doped tin oxide support.

[0100] Additionally, the TEM EDS mapping analysis confirms that the fluorine dopant is evenly dispersed on the fluorine-doped tin oxide support, and that the iridium nanoparticles, which constitute the catalyst on the surface of the support, are uniformly formed on the fluorine-doped tin oxide surface without aggregation.

[0101] FIGS. 8A and 8B are graphs showing the XRD and Raman spectroscopy results of the catalyst using the fluorine-doped support and the comparison example using the support without fluorine doping, manufactured according to an embodiment of the present invention.

[0102] As illustrated in FIGS. 8A and 8B, the XRD results on the left confirm that the structure or phase of the fluorine-doped tin oxide support does not change during the process of supporting iridium nanoparticles onto the surface.

[0103] Additionally, as confirmed through the TEM image of FIGS. 7A and 7B, the size of the iridium nanoparticles is fine, ranging from 2 to 5 nm, and it can be confirmed that the main XRD peaks of amorphous IrOx, (111) and (200), are formed at a smaller intensity.

[0104] In addition, in the Raman spectroscopy results on the right, it was confirmed that for Ir / FTO, the intensity of the main peaks of the fluorine-doped tin oxide is reduced, and the Eg and B2g peaks of iridium oxide are formed. This confirms that IrOx nanoparticles are well formed on the surface of the fluorine-doped tin oxide support.

[0105] FIG. 9 is a graph showing the oxygen evolution reaction of the catalyst using the fluorine-doped support and the comparison example using the support without fluorine doping, manufactured according to an embodiment of the present invention.

[0106] As illustrated in FIG. 9, the Ir / FTO catalyst according to an embodiment of the present invention, evaluated for catalytic activity in 0.5M H2SO4 electrolyte using a rotating disk electrode (RDE), demonstrated a low overpotential of 320 mV at 10 mA cm−2. This shows superior performance and durability compared to the comparative examples (Ir / TO; 350 mV, Ir-black; 330 mV).

[0107] FIG. 10 is a graph evaluating the durability of the catalyst using the fluorine-doped support and the comparison example using the support without fluorine doping, manufactured according to an embodiment of the present invention.

[0108] As illustrated in FIG. 10, the RDE long-term durability performance evaluation (20 mA cm−2, 0.5M H2SO4 electrolyte) confirmed that the Ir / FTO according to an embodiment of the present invention operates stably for a long period, compared to the iridium nanoparticles (Ir black) and the comparative example of the antimony-doped tin oxide supported catalyst (Ir / ATO).

[0109] FIG. 11 schematically illustrates a method for a method for applying the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, to an anode electrode for water electrolysis, and FIG. 12 is a schematic view illustrating the application of the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, in an actual water electrolysis system.

[0110] Specifically, (a) an anode catalyst Ir / FTO particle manufactured according to the embodiment of the present invention, as described above, was mixed with deionized water, Nafion ionomer of 20 wt % and ethanol, and then subjected to ultrasonic treatment at room temperature for 0.5 to 1 hour to prepare a uniform anode slurry ink.

[0111] Additionally, (b) a cathode catalyst platinum-supported carbon (Pt / C, Pt 46.9 wt %) particles were mixed with Nafion ionomer of 20 wt % and isopropyl alcohol, and then subjected to ultrasonic treatment at room temperature for 30 minutes to prepare a cathode slurry ink.

[0112] In addition, as illustrated in FIG. 12, (c) the anode slurry ink and cathode slurry ink, prepared through the processes described in (a) and (b), were evenly spread on each side of a Nafion polymer electrolyte membrane with a thickness of 50 μm using a vacuum plate at 80° C., and then sprayed to form a membrane-electrode assembly consisting of an anode catalyst (Ir / FTO)-polymer electrolyte membrane-cathode catalyst (Pt / C) layers.

[0113] Further, (d) a titanium-based PTL (Ti fiber felt) was applied as the anode gas diffusion layer, and carbon paper was used as the cathode gas diffusion layer in the membrane-electrode assembly prepared in the process described in (c). A unit cell was then assembled, and an actual water electrolysis system evaluation was performed.

[0114] FIG. 13 is a graph showing the performance evaluation of a unit cell applying the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, in an actual water electrolysis system. This is the result of evaluating the performance of water electrolysis unit cell (PEMWE single-cell) by applying oxygen evolution electrodes of the Ir nanoparticle@fluorine-doped tin oxide supported catalyst (Ir / FTO) and other catalysts of the supports (tin oxide (Ir / TO), antimony-doped tin oxide (Ir / ATO)).

[0115] As illustrated in FIG. 13, the initial current density performance of the water electrolysis unit cell at 1.8 V is as Ir / FTO (1.44 A / cm2)>Ir black (1.35 A / cm2)>Ir / ATO (1.28 A / cm2)>Ir / TO (0.80 A / cm2). This confirms that Ir / FTO exhibits the best current density performance under the same conditions.

[0116] FIGS. 14A and 14B are graphs showing the performance and durability of a unit cell applying the catalyst using the fluorine-doped support, manufactured according to an embodiment of the present invention, in an actual water electrolysis system.

[0117] As illustrated in FIGS. 14A and 14B, after performing electrochemical degradation of a water electrolysis unit cell by applying a constant current density of 1 A cm−2, the initial performance and the durability performance after long-term evaluation were compared. The results showed that based on the current density at 1.8 V, Ir / FTO decreased by 6.5%, Ir / ATO decreased by 83.5%, Ir / TO decreased by 85.5%, and Ir black decreased by 70.6%. This confirms that Ir / FTO exhibits the best durability.

[0118] Additionally, under the conditions of 1 A cm−2, 2 A cm−2, as well as under harsh electrochemical current density application at 80° C., it can be confirmed that the Ir / FTO supported catalyst exhibits the best durability.

[0119] A person skilled in the art may understand that the present invention may be carried out in other specific forms with reference to the above-mentioned descriptions without changing the technical spirit or the essential characteristics of the present invention.

[0120] Accordingly, it is to be understood that the embodiments described above are illustrative in all respects and are not intended to limit the present invention to the embodiments, and the scope of the present invention is indicated by the patent claims which are hereinafter recited rather than by the foregoing detailed description, and the meaning and scope of the patent claims and all modifications or variations derived from the equivalent concepts should be interpreted to be included within the scope of the present invention.

Claims

1. A method for manufacturing a catalyst for water electrolysis using a fluorine-doped support, comprising:preparing a support;doping fluorine onto the support; andforming a metal particle catalyst on a surface of the fluorine-doped support.

2. The method of claim 1, wherein the doping of fluorine onto the support is performed by dispersing the support in a solvent and adding a dopant precursor including a fluorine source.

3. The method of claim 2, wherein the dopant precursor including the fluorine source is boron trifluoride etherate (C4H10BF3O) or ammonium fluoride (NH4F).

4. The method of claim 1, wherein the doping of fluorine onto the support is performed by plasma treating a source gas including the fluorine onto the surface of the support.

5. The method of claim 2, wherein the support is a nanoparticle-formed powder, a nanostructure-formed thin film, or a substrate.

6. The method of claim 2, wherein the support is a porous carbon material selected from carbon black, carbon nanotubes, carbon fibers, or fullerenes.

7. The method of claim 6, wherein the preparing of the support further includes a preliminary treatment of the surface of the support.

8. The method of claim 7, wherein the preliminary treatment of the surface of the support is performed by an oxidation process of the support.

9. The method of claim 8, wherein the oxidation process includes one of electrochemical oxidation, oxygen plasma oxidation, or acid treatment.

10. The method of claim 2, wherein the support is tin oxide.

11. The method of claim 10, wherein the preparing of the support further includes one or more preliminary treatments of the surface of the support, the preliminary treatment including chemical surface treatment, plasma treatment, and thermal surface treatment of the support.

12. The method of claim 2, wherein the metal includes precious metals, rare earth metals, and transition metals.

13. The method of claim 12, wherein the transition metal is one or more selected from Ir, Pt, Pd, Os, Ru, Co, Fe, Mo, W, Cr, and Ni, and alloys.

14. The method of claim 2, wherein the forming of metal particle catalysts on the surface of the fluorine-doped support includes:preparing a solution in which the fluorine-doped support is dispersed;adding and mixing a precursor of the metal into the dispersed solution;adding a reducing agent to the mixed solution to carry out a reduction reaction; andfiltering the reduced solution to collect powder, and heat treating the collected powder.

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