Catalyst for Water Electrolysis Using Fluorine-Doped Tin Oxide Support and Method for Manufacturing the Same

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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 (CHBFO) or ammonium fluoride (NHF).

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.

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.

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.

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.

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

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

In addition, the dopant precursor including the fluorine source may be boron trifluoride etherate (CHBFO), ammonium fluoride (NHF), or other fluorine-including compounds.

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.

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 SnOas a support, without limitation.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 NHF, KF), polymer precursors (PTFE, PVDF) thermal surface treatment may be used.

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.

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.