Catalyst with net structure for oxygen evolution reaction and preparation method thereof

Abstract

A catalyst, which may have a network structure on its surface, for oxygen evolution reactions based on metal oxides. The catalyst may include a metal catalyst including a central portion and a surface portion surrounding the central portion. The surface portion may include a frame having a mesh structure, and a metal oxide applied on the frame.

Description

Technical Field

[0001] This invention relates to a catalyst having a network structure on its surface and a method for preparing the same. Background Technology

[0002] With increasing global energy demand, climate change caused by fossil fuel use is becoming increasingly severe. Hydrogen is a promising fuel candidate as an alternative energy source due to its sustainable and environmentally friendly production and storage. However, water electrolysis technology, a crucial component of hydrogen production, faces numerous challenges in its verification and commercialization.

[0003] During water electrolysis, the oxygen evolution reaction (OER) at the negative electrode involves a significant amount of electron movement, resulting in a relatively slow reaction rate. To overcome these drawbacks and maximize the performance of water electrolysis devices, it is crucial to develop high-performance, highly durable catalysts.

[0004] Polymer electrolyte membrane water electrolysis (PEMWE) operates in an acidic environment. Therefore, for practical industrial applications, catalysts that maintain high structural stability even under acidic conditions are essential. Currently, catalysts based on noble metals such as iridium (Ir) exhibit excellent activity and stability in the oxygen evolution reaction, but these catalysts face significant challenges in terms of price competitiveness.

[0005] The statements in this background section are only provided as background information in relation to the present invention and may not constitute prior art. Summary of the Invention

[0006] In view of the above, in order to improve the performance of the entire water electrolysis reaction, it is necessary to develop a high-performance, high-durability and low-cost catalyst that can promote the oxygen evolution reaction that occurs at the negative electrode.

[0007] Various aspects of the present invention provide a non-iridium (Ir-free)-based catalyst for the oxygen evolution reaction and a method for preparing the same.

[0008] Various aspects of the present invention provide a highly efficient and highly stable catalyst for the oxygen evolution reaction and a method for preparing the same.

[0009] The various aspects of the present invention are not limited to the objectives described above. These aspects should become more apparent from the following description, and can be realized by means of the claims and combinations thereof.

[0010] According to various aspects of the present invention, the catalyst for the oxygen evolution reaction may include a metal catalyst comprising a central portion and a surface portion surrounding the central portion. The surface portion may include a framework having a mesh structure and a metal oxide applied to the framework by coating.

[0011] Catalysts may also include supports, on which metal catalysts can be loaded.

[0012] The diameter of metal catalysts can range from 30 nm to 100 nm.

[0013] The thickness of the surface portion can range from 2nm to 10nm.

[0014] The framework can include alloys of platinum group elements and transition metals.

[0015] The platinum group elements may include at least one of platinum (Pt), palladium (Pd), or rhodium (Rh).

[0016] The platinum group elements may exclude iridium (Ir).

[0017] Transition metals may include at least one of nickel (Ni), cobalt (Co), copper (Cu), or iron (Fe).

[0018] Metal oxides can be applied to the framework in thicknesses ranging from 2 nm to 5 nm by coating.

[0019] Alternatively, a metal oxide can be applied to the surface of the central portion by coating.

[0020] Metal oxides can include ruthenium oxide (RuO2) which has a rutile structure.

[0021] Metal oxides may not exist in the space extending from the surface of the metal catalyst to a depth of 5 nm (e.g., the region of the metal catalyst).

[0022] Depending on the specifics, methods for preparing catalysts for the oxygen evolution reaction can include: preparing particles of an alloy containing platinum group elements and transition metals; preparing a metal catalyst precursor by coating the particles with a metal oxide precursor; and preparing the catalyst by oxidizing the metal catalyst precursor.

[0023] The preparation of particles may include: preparing a particle precursor containing a platinum group element and a transition metal alloy by reacting a platinum group element precursor and a transition metal precursor; and preparing particles by treating the particle precursor with acid. The particles may include a surface etched by acid.

[0024] The preparation of metal catalyst precursors may include reacting particles with metal oxide precursors in a carbon monoxide atmosphere.

[0025] The preparation of catalysts may include oxidizing metal oxide precursors into metal oxides by heat-treating metal catalyst precursors in an oxygen atmosphere at a temperature ranging from 250°C to 350°C.

[0026] According to various aspects of the present invention, non-iridium (Ir-free) catalysts for oxygen evolution reactions and methods for their preparation can be obtained.

[0027] According to various aspects of the present invention, efficient and highly stable catalysts for the oxygen evolution reaction and methods for their preparation can be obtained.

[0028] The effects of the various aspects of the present invention are not limited to those described above. The effects of each aspect should be understood to include all effects that can be inferred from the following description. Attached Figure Description

[0029] Figure 1 A diagram showing the metal catalyst of the present invention;

[0030] Figure 2 The image shows an analysis of platinum-nickel alloy particles before chemical etching, obtained using transmission electron microscopy (TEM).

[0031] Figure 3 The image shows an analysis of the chemically etched platinum-nickel alloy particles using a transmission electron microscope.

[0032] Figure 4 The diagram shows the analysis of platinum-nickel alloy particles before and after chemical etching by X-ray diffraction (XRD).

[0033] Figure 5 The diagram shows the analysis of the metal catalyst precursor using transmission electron microscopy.

[0034] Figure 6 The diagram shows the analytical results of the metal catalyst precursor obtained by X-ray diffraction.

[0035] Figure 7 The diagram shows the analysis of the metal catalyst precursor by energy dispersive spectroscopy (EDS).

[0036] Figure 8 The diagram shows the linear analysis of the metal catalyst precursor;

[0037] Figure 9 The diagram shows the analysis of the catalyst according to the preparation example using transmission electron microscopy;

[0038] Figure 10 The analysis diagram of the catalyst prepared according to Comparative Example 1 is shown using transmission electron microscopy;

[0039] Figure 11 The analysis diagram of the catalyst prepared according to Comparative Example 2 is shown using transmission electron microscopy;

[0040] Figure 12 The analytical diagrams of the catalysts prepared according to the preparation example, comparative preparation example 1 and comparative preparation example 2 are shown by X-ray diffraction.

[0041] Figure 13 The analysis graphs of nickel in the metal catalyst precursor according to the preparation example, the catalyst according to the preparation example, and the catalyst according to Comparative Preparation Example 1 are shown using X-ray photoelectron spectroscopy (XPS).

[0042] Figure 14 The graphs showing the nickel content in the metal catalyst precursor of the preparation example, the catalyst of the preparation example, and the catalyst of comparative preparation example 1 are shown respectively.

[0043] Figure 15 The analysis chromatograms of ruthenium in the catalyst according to the preparation example and the catalyst according to Comparative Preparation Example 1 are shown using X-ray photoelectron spectroscopy.

[0044] Figure 16 The analysis chromatograms of platinum element in the catalyst according to the preparation example and the catalyst according to Comparative Preparation Example 1 are shown using X-ray photoelectron spectroscopy.

[0045] Figure 17 The diagram shows the oxygen evolution reaction and overpotential of the half-cells according to the examples and Comparative Examples 1 to 3.

[0046] Figure 18 The half-cell shown according to the embodiment is at 10 mA·cm -2 The chronopotentiometric curve at the current density is shown in the figure.

[0047] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Detailed Implementation

[0048] The various aspects should be readily understood from the following aspects related to the accompanying drawings. However, the invention is not limited to the embodiments described herein and may be implemented in other forms. Rather, the aspects described herein are intended to make the disclosure thorough and complete, and to fully convey the spirit of the invention to those skilled in the art.

[0049] In describing each figure, similar reference numerals are used for similar components. In the figures, for clarity of the invention, the dimensions of the structures are enlarged from actual dimensions.

[0050] In this specification, terms such as "comprising," "including," and "having" are used to indicate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be construed as excluding the possibility of the presence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a portion of a layer, film, region, plate, etc., is referred to as "above another component," this includes not only "directly located above another component" but also cases where another component is intermediately located therein. Similarly, when a portion of a layer, film, region, plate, etc., is referred to as "below another component," this includes not only "immediately located below another component" but also cases where another component is intermediately located therein.

[0051] Unless otherwise specified, all numbers, values, and / or expressions used in this specification to represent components, reaction conditions, polymer composition, and dosage should be understood as approximate values, as these values ​​inherently reflect the various uncertainties arising from the measurements used to obtain them. Therefore, in all cases, they should be interpreted as being limited by the term "about". Furthermore, when numerical ranges are disclosed in this specification, unless otherwise stated, these ranges are continuous and include all values ​​from the specified minimum to the maximum value. Additionally, if a range refers to integers, unless otherwise stated, it includes all integers from the specified minimum to the maximum value. In this invention, each phrase such as "A or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", "at least one of A, B, or C", and "at least one of A, B, or C, or a combination thereof" can include any one or all possible combinations of the items listed together in the corresponding phrase.

[0052] Catalysts used for the oxygen evolution reaction can include non-iridium (Ir-free) based metal catalysts.

[0053] Catalysts used in the oxygen evolution reaction may also include a support.

[0054] There are no particular restrictions on the carrier; it can include carbon black.

[0055] There is no particular limitation on the diameter of the carrier, which can be, for example, in the range of 10 nm to 100 nm. The carrier can be in the form of agglomerated particles whose diameter falls within the numerical range.

[0056] There is no particular limitation on the specific surface area of ​​the carrier; for example, it can be 200 m².2 / g to 500m 2 Within a range of / g. When the specific surface area of ​​the support falls within this range, the active sites of the catalyst can expand, and the contact area with the reactants can expand, thereby improving the activity of the catalyst used for the oxygen evolution reaction.

[0057] Figure 1 A diagram illustrating the metal catalyst of the present invention is shown. The metal catalyst may include a central portion 10 and a surface portion 20 surrounding the central portion.

[0058] Metal catalysts can be in the form of spherical particles. However, the shape of metal catalysts is not limited to this; they can also be elliptical or polyhedral.

[0059] The diameter of metal catalysts can range from 30 nm to 100 nm, 40 nm to 80 nm, or 50 nm to 60 nm. When the diameter of the metal catalyst falls within a certain range, the structural stability of the metal catalyst can be ensured while increasing its active surface area.

[0060] The surface portion 20 may include a frame 21 having a mesh structure and a metal oxide applied by coating the frame 21. Figure 1 Metal oxides are not shown in the figure.

[0061] The thickness of the surface portion 20 is not particularly limited and can be, for example, in the range of 2 nm to 10 nm.

[0062] The central portion 10 and the frame 21 can be integrated. The central portion 10 and the frame 21 are obtained by etching the surface of particles of an alloy containing platinum group elements and transition metals through acid treatment. The central portion 10 and the frame 21 can be integrated physically and chemically.

[0063] Frame 21 can have a multi-net structure, in which a series of mesh-like layers are stacked in multiple layers. The mesh structure can refer to a form of mesh. The mesh structure can be a shape formed by a three-dimensional interconnected skeleton. The arrangement of the cells constituting the mesh structure can be regular or irregular.

[0064] The central portion 10 and the frame 21 may comprise an alloy of platinum group elements and transition metals.

[0065] The platinum group elements may include at least one of platinum (Pt), palladium (Pd), or rhodium (Rh). Iridium (Ir) may not be included in the platinum group elements.

[0066] Transition metals may include at least one of nickel (Ni), cobalt (Co), copper (Cu), or iron (Fe).

[0067] Alloys can include alloys of platinum (Pt) and nickel (Ni).

[0068] Metal oxides can be applied to the frame 21 by coating. Alternatively, metal oxides can be applied to the frame 21 without coating in a core-shell configuration. The metal oxides can be integrated with the frame 21, or they can be used to primarily coat regions deeper than the surface of the frame 21, resulting in a relatively large amount of metal oxide available for coating in these regions. This phenomenon may occur as the metal oxides migrate into the interior of the frame 21 during the oxidation of the metal oxide precursor under specific temperature conditions, as described below. Metal oxides may not be present in the space (or region) extending to a depth of approximately 5 nm from the surface of the metal catalyst. This will be described below.

[0069] The metal oxide can be applied not only to the frame 21, but also to the surface of the central portion 10.

[0070] Metal oxides may include ruthenium oxide (RuO2) with a rutile structure.

[0071] Metal oxides can be applied to the surfaces of the frame 21 and the central portion 10 by coating, with a thickness of about 2 nm to 5 nm.

[0072] Methods for preparing catalysts for the oxygen evolution reaction may include preparing particles of an alloy containing platinum group elements and transition metals; preparing metal catalyst precursors by coating particles with metal oxide precursors; and preparing catalysts by oxidizing metal catalyst precursors.

[0073] The preparation of particles can include preparing particle precursors of alloys containing platinum group elements and transition metals by reacting platinum group element precursors and transition metal precursors, and preparing particles by treating particle precursors with acid.

[0074] Platinum group element precursors may include platinum group element halides, platinum group element nanoparticles, platinum group element acetyl acetonate, platinum group element alkoxides, and / or platinum group element hydrates.

[0075] Transition metal precursors may include transition metal halides, transition metal acetylacetonates, transition metal nitrates, transition metal oxides, and / or transition metal hydrates.

[0076] The particulate precursor may not be perfectly spherical, but may have a polyhedral shape. When the particulate precursor is treated with acid, the transition metals present in the face area of ​​the polyhedron come into contact with the acid faster and in greater quantities than those present in the edge area. Most of the transition metals present in the face area can be eluted to form a shape such as... Figure 1 The mesh structure shown.

[0077] There are no particular restrictions on acids, which may include hydrochloric acid, sulfuric acid, and / or nitric acid.

[0078] The preparation of the metal catalyst precursor S20 may include reacting the particles with the metal oxide precursor in a carbon monoxide atmosphere.

[0079] Metal oxide precursors may include ruthenium halide, ruthenium nanoparticles, ruthenium acetylacetonate, ruthenium alkoxide, and / or ruthenium hydrate.

[0080] When the metal oxide precursor reacts with the particles via solvothermal synthesis in a carbon monoxide atmosphere, the ruthenium (Ru) of the metal oxide precursor is uniformly applied to the surface of the particles through coating and can grow in the form of dendrites.

[0081] Metal catalyst precursors may include particles and ruthenium (Ru) grown in a dendritic form by coating uniformly applied to the surface of the particles. Metal oxide precursors may refer to ruthenium halides or ruthenium (Ru), the meaning of which will be clear from the context.

[0082] The preparation of catalyst S30 may include oxidizing the metal oxide precursor into a metal oxide by heat-treating the metal catalyst precursor in an oxygen atmosphere at a temperature in the range of 250°C to 350°C.

[0083] When the heat treatment temperature is below 250°C, the metal oxide precursor may not be oxidized into a metal oxide. When the heat treatment temperature exceeds 350°C, the distribution of elements and electronic structure in the catalyst may differ, which may reduce the efficiency of the catalyst.

[0084] The present invention is characterized by a ruthenium oxide (RuO2)-based catalyst instead of an iridium-based catalyst. Ruthenium oxide exhibits excellent electrochemical performance in acidic electrolytes.

[0085] Ruthenium oxide is applied to particles containing a platinum and nickel alloy by coating. Platinum ensures catalyst stability and prevents the over-oxidation of ruthenium oxide (RuO2) by transferring electrons to ruthenium. During the oxygen evolution reaction in an acidic electrolyte, nickel is eluted, forming vacuum sites in the crystal lattice where no atoms are present. This increases catalyst activity. Furthermore, nickel can promote the migration of ruthenium during thermal oxidation.

[0086] In the catalyst preparation process, the metal catalyst precursor was heat-treated within a specific temperature range of 250°C to 350°C. During the heat treatment, ruthenium can migrate into the interior of the particles, increasing its interaction with platinum. As a result, charge transfer between ruthenium and platinum is promoted, exhibiting high activity and stability for the oxygen evolution reaction.

[0087] The catalyst has a multi-network structure with a large number of voids on its surface, thus exhibiting a large specific surface area and excellent activity for the oxygen evolution reaction.

[0088] Furthermore, since the catalyst is prepared via a solvothermal reaction, this invention is suitable for large-scale production and can make a significant contribution to the commercialization of polymer electrolyte membrane water electrolysis devices.

[0089] Other forms of the invention will now be described in more detail through the following embodiments. These embodiments are merely illustrative of the invention, and the scope of the invention is not limited thereto.

[0090] Preparation Example

[0091] Preparation of platinum-nickel alloy particles

[0092] 0.0590 g (0.15 mmol) of platinum acetylacetonate (II), 0.2826 g (1.1 mmol) of nickel acetylacetonate (II), and 0.2880 g (0.9 mmol) of hexadecyltrimethylammonium chloride were added to a 250 mL reaction vessel, along with 50 mL of oleylamine. The mixture was stirred in a 60 °C oil bath for 15 minutes to melt it. The reaction vessel was then transferred to a preheated 270 °C oil bath, and the reaction product was stirred for 30 minutes and cooled to room temperature. Toluene and ethanol were added to the reaction product in a 1:1 ratio, followed by centrifugation (4000 rpm, 5 min) to precipitate the synthesized nanoparticles. After centrifugation, the supernatant was discarded, and the precipitated particles were dried to obtain powdered platinum-nickel alloy particles.

[0093] Particles with a multi-network structure can be obtained by chemical etching of platinum-nickel alloy particles. Platinum-nickel alloy particles were dispersed in a 1:1 ratio of toluene and ethanol, and 3M hydrochloric acid was added in the same ratio. After stirring in an oil bath at 60°C for 1 hour, ethanol was added to the reaction product, followed by washing three times by centrifugation (4000 rpm, 5 min). To prevent particle agglomeration, 10 mL of oleylamine was added, and the particles were sonicated for 5 minutes to coat the particle surface with oleylamine ligands. Then, toluene and ethanol were added in a 1:1 ratio, and centrifugation was performed (4000 rpm, 5 min). Upon completion of centrifugation, the supernatant was discarded, and the settled particles were dried to obtain platinum-nickel alloy particles with a multi-network structure on the surface.

[0094] Figure 2 The image shows an analysis of platinum-nickel alloy particles before chemical etching, obtained using transmission electron microscopy (TEM). Figure 3 The image shows an analysis of the chemically etched platinum-nickel alloy particles using a transmission electron microscope. Figure 4 The image shows analytical diagrams of platinum-nickel alloy particles before and after chemical etching, obtained by X-ray diffraction (XRD). (Refer to...) Figure 2 It can be confirmed that platinum-nickel alloy particles with a size of approximately 50 nm to 60 nm were synthesized. (Refer to...) Figure 3 It can be confirmed that during chemical etching, all nickel (Ni) present on the particle surface is washed away, revealing the multi-network structure within the remaining framework on the particle surface. At this point, the framework thickness is approximately 2 nm to 3 nm. (Refer to...) Figure 4 It can be confirmed that when nickel is removed by chemical etching, the peak shifts toward the platinum peak.

[0095] Preparation of metal catalyst precursors

[0096] 0.0070 g of platinum-nickel alloy particles and 0.0151 g (0.038 mmol) of ruthenium(III) acetylacetone were added to a 100 mL reaction vessel, along with 5 mL of oleylamine. The mixture was melted under vacuum at 80 °C by stirring. Carbon monoxide gas was injected into the reaction vessel to create a carbon monoxide atmosphere. The mixture in the reaction vessel was stirred and reacted in a preheated oil bath at 260 °C for 30 minutes. Under these conditions, a metal catalyst precursor with a structure in which ruthenium (Ru) is thinly applied to and grown on the platinum-nickel alloy particles was obtained. Toluene and ethanol were added to the reaction product in a 1:1 ratio, followed by centrifugation (4000 rpm, 5 min) to settle the metal catalyst precursor. When the supernatant was discarded and the settled particles were dried, a powdered metal catalyst precursor was obtained.

[0097] Figure 5The diagram shows the analysis of the metal catalyst precursor using transmission electron microscopy. Figure 6 The diagram shows the analysis of the metal catalyst precursor by X-ray diffraction. Figure 7 The diagram shows the analysis of the metal catalyst precursor by energy dispersive spectroscopy (EDS). Figure 8 The diagram shows the line composition of the metal catalyst precursor. (Refer to...) Figure 5 It was confirmed that ruthenium (Ru) was applied via coating and grew in a dendritic form both on the exterior and inside of platinum-nickel alloy particles used as precursors. (See reference...) Figure 6 The presence of ruthenium (Ru) was confirmed to be well preserved in the Pt-Ni phase of the platinum-nickel alloy particles, and the presence of ruthenium (Ru) could be observed near the 45° peak. (Refer to...) Figure 7 and Figure 8 It was confirmed that Pt, Ni, and Ru elements are uniformly distributed throughout the particles. Specifically, it was confirmed that ruthenium exists not only within the framework of the platinum-nickel alloy particles but also in the voids where there is no framework.

[0098] Load on the carrier

[0099] To prevent agglomeration during the oxidation of metal catalyst precursors, the metal catalyst precursors can be loaded onto a support.

[0100] 72 mg of the metal catalyst precursor was added to a 70 mL vial with 40 mL of oleylamine and sonicated for 30 min. Then, 20 mL of hexane was added, and sonication was continued for another 30 min. Centrifugation (4000 rpm, 5 min) was performed to precipitate the metal catalyst precursor. The precipitated metal catalyst precursor was dispersed in 20 mL of chloroform to prepare a metal catalyst precursor dispersion. In a separate vial, 28 mg of the carbon support was dispersed in chloroform to prepare a carbon support dispersion. The metal catalyst precursor dispersion and the carbon support dispersion were mixed and sonicated for 30 min, then stirred at room temperature for 1 hour. After stirring, centrifugation (4000 rpm, 5 min) was performed to precipitate the product, and the supernatant was discarded. The same process was repeated twice using acetone, followed by drying. In this case, a metal catalyst precursor supported on a support was obtained. At this point, the loading ratio was 30% by weight.

[0101] Catalyst preparation

[0102] The metal catalyst precursor supported on the support was thermally oxidized in an oxygen atmosphere at approximately 300°C for 1 hour. Through this process, ruthenium was oxidized to ruthenium oxide (RuO2) with a rutile structure.

[0103] Comparative Preparation Example 1

[0104] Except for changing the heat treatment temperature to 400°C in catalyst preparation, the catalyst was prepared in the same manner as in the preparation example.

[0105] Comparative Preparation Example 2

[0106] Except for changing the heat treatment temperature to 200°C in catalyst preparation, the catalyst was prepared in the same manner as in the preparation example.

[0107] Figure 9 The diagram shows the analysis of the catalyst according to the preparation example using transmission electron microscopy. Figure 10 The diagram shows the analysis of the catalyst prepared according to Comparative Example 1 using transmission electron microscopy. Figure 11 The diagram shows the analysis of the catalyst prepared according to Comparative Example 2 using transmission electron microscopy. Figure 12 The diagrams show X-ray diffraction analysis of the catalysts prepared according to the preparation example, comparative preparation example 1, and comparative preparation example 2, respectively. (Refer to...) Figures 9 to 11 This confirmed that the metal catalyst was dispersed on the carbon support while maintaining the particle structure of all three catalysts before thermal oxidation. (Refer to...) Figure 12 It was confirmed that in the catalysts according to the preparation examples and comparative preparation example 1, the phase for ruthenium metal disappeared, and a new phase for ruthenium oxide (RuO2) with a rutile structure was observed. In comparative preparation example 2, there were almost no peaks corresponding to ruthenium oxide. On the other hand, the preparation examples showed a normalized au of 0.4083 for the 28° peak and 0.3537 for the 35.16° peak. Among these corresponding peak positions, comparative preparation example 1 showed normalized au of 1.3794 and 1.3478. This means that the higher the heat treatment temperature, the more ruthenium metal is oxidized to ruthenium oxide. Furthermore, the preparation examples and comparative preparation example 1 showed a structure in which the surface of the metal catalyst has a multi-network structure within a framework of about 2 nm to 3 nm thickness, and the preparation examples and comparative preparation example 1 showed a structure in which ruthenium oxide has grown within the framework to a thickness of about 2 nm. Even after the phase transformation to ruthenium oxide, it can maintain the network structure of the metal catalyst and the porous structure inside the particles.

[0108] Referring to the analysis of the catalysts according to Preparation Example 1 and Comparative Preparation Example 1 using energy dispersive spectroscopy and line shape analysis for each particle, the incorporation direction of ruthenium oxide and the movement mode of nickel differ depending on the heat treatment temperature. In Preparation Example 1, it was confirmed that ruthenium, uniformly distributed both outside and inside the framework, migrated into the interior of the catalyst. This can be specifically observed through the line shape analysis results. Platinum, nickel, and ruthenium are all uniformly distributed, but ruthenium is essentially present inside the catalyst. Specifically, platinum and nickel are always present in the outermost part of the catalyst, while ruthenium is not present at a depth of about 5 nm in the outermost part. In Comparative Preparation Example 1, where the heat treatment temperature is as high as 400°C, it was shown that ruthenium and nickel were extruded. According to the line shape analysis results of Comparative Preparation Example 1, ruthenium and nickel are more present on the outside than platinum.

[0109] Figure 13 The diagram shows the analysis of nickel in the metal catalyst precursor according to the preparation example, the catalyst according to the preparation example, and the catalyst according to Comparative Preparation Example 1 using X-ray photoelectron spectroscopy (XPS). Figure 14 The graphs showing the nickel content in the metal catalyst precursor of the preparation example, the catalyst of the preparation example, and the catalyst of comparative preparation example 1 are respectively displayed. (Refer to...) Figure 13 The catalysts of the prepared examples and the catalyst of Comparative Prepared Example 1 exhibited zero-valent and divalent core energy level peaks at the Ni 2p peak position. In both catalysts, compared to the metal catalyst precursor of the prepared examples, the number of zero-valent Ni metal species decreased, while the number of divalent Ni oxide species increased. In Comparative Prepared Example 1, Ni was oxidized to NiO using 11.4% zero-valent Ni metal species and 88.62% divalent Ni oxide species. In the prepared examples, Ni was oxidized to NiO using 39.2% zero-valent Ni metal species and 60.8% divalent Ni oxide species.

[0110] Figure 15 The analysis diagrams of ruthenium in the catalysts according to the preparation example and the catalysts according to Comparative Preparation Example 1 are shown using X-ray photoelectron spectroscopy. Figure 16The analysis of platinum in the catalysts according to the preparation example and the catalyst according to Comparative Preparation Example 1 is shown using X-ray photoelectron spectroscopy. XPS results show the Ru 3p and Pt 4f peak positions for both catalysts. At the Ru 3p peak position, zero-valent, trivalent, and tetravalent core level peaks are shown, while at the Pt 4f peak position, zero-valent, divalent, and tetravalent core level peaks are shown. After thermal oxidation, XPS results show that the intensity of the tetravalent Ru core level peak corresponding to ruthenium oxide (RuO2) is very significant for both the preparation example and Comparative Preparation Example 1. The Pt 4f XPS results show a prominent intensity of the zero-valent core level peak corresponding to platinum metal. This indicates that ruthenium-based oxides are effectively formed after thermal oxidation, confirming that the platinum to be oxidized has a relatively weaker tendency than ruthenium. Furthermore, the preparation example shows that compared to Comparative Preparation Example 1, the core level peak at the Ru 3p peak position is shifted to a lower binding energy position by approximately 0.2 eV. Conversely, the Pt 4f peak shifted to a higher binding energy peak by approximately 0.2 eV in the same manner. This indicates a charge transfer effect between Ru and Pt in the preparation example, confirming that some electrons moved from the Pt peak to the Ru peak. In other words, in the preparation example, ruthenium oxide (RuO2) underwent electron transfer through interaction with platinum (Pt) during heat treatment, which is expected to result in better electrochemical performance than Comparative Preparation Example 1. On the other hand, in Comparative Preparation Example 1, XPS data analysis confirmed a reduced interaction between ruthenium and platinum in ruthenium oxide (RuO2) compared to the preparation example. This can be explained by the fact that during high-temperature heat treatment, ruthenium (Ru) also migrated to the outside of the particles along with nickel (Ni), reducing the Pt-Ru interaction and weakening the charge transfer effect.

[0111] Example

[0112] Half-cells were fabricated using the catalysts according to the preparation examples, and their electrochemical performance was evaluated.

[0113] Electrochemical characterization was performed by constructing a three-electrode half-cell system. The three electrodes consisted of a glassy carbon electrode (GCE) as the working electrode, a saturated Ag / AgCl electrode as the reference electrode, and a carbon rod as the counter electrode. Furthermore, a rotating disk electrode using a catalyst-coated GCE was evaluated. A CH Instruments, Inc. potentiostat was used for all electrochemical evaluations. OER measurements were taken at a rotation speed of 1600 rpm in a prepared 0.1 M HClO4 solution. Voltage was converted relative to a reversible hydrogen electrode (RHE). Polarization curves were plotted by correcting for the resistance of the aqueous solution.

[0114] Comparative Example 1

[0115] The half-cell was manufactured in the same manner as in the examples, except that the metal catalyst precursor used in the untreated preparation example was used.

[0116] Comparative Example 2

[0117] The half-cell was prepared in the same manner as in Example 1, except that the catalyst of Comparative Preparation Example 1 was used.

[0118] Comparative Example 3

[0119] The half-cell was manufactured in the same manner as in the examples, except that a commercially available catalyst (IrO2 prepared by the Adams melting method) was used.

[0120] Figure 17 The diagram shows the oxygen evolution reaction and overpotential polarization curves of the half-cells according to the Examples and Comparative Examples 1 to 3. Figure 18 The half-cell shown according to the embodiment is at 10 mA·cm -2 The chronopotential curve at the current density is shown in the figure. (Refer to...) Figure 17 It was confirmed that, compared with Comparative Example 1, the catalysts of Examples 1 and 2 showed a significant increase in OER activity after thermal oxidation. It is believed that the formed rutile oxides played a role in improving the activity. Furthermore, the catalysts of Examples 2 showed a significant increase in OER activity at 10 mA·cm⁻¹. -2 At the given current density, a very low overpotential of 187 mV was observed, while Comparative Example 2 showed an overpotential of 201 mV. Furthermore, a carbon paper electrode (CPE, 1 cm × 1 cm) was used instead of a GCE for chronopotential testing because the stability of the catalyst in the oxygen evolution reaction is a very important factor in water electrolysis. (Refer to...) Figure 18 Even at 10 mA·cm -2 In time-potential tests, the embodiment with the best OER activity also showed high durability. Slight degradation occurred after approximately 50 hours compared to the initial voltage, but oxygen production continued.

[0121] Based on the previously analyzed EDS mapping and XPS analysis results, the interaction between ruthenium (Ru) and platinum (Pt) incorporated into the particles increases during the heat treatment process of the catalyst according to an embodiment of the invention. The heat treatment process is believed to promote the charge transfer effect between ruthenium (Ru) and platinum (Pt), ultimately improving OER performance. Furthermore, when the heat treatment temperature reaches up to 400°C, ruthenium (Ru) and nickel (Ni) migrate together to the exterior of the particles in the form of oxides. The results confirm that not only is the charge transfer effect between Pt / Ru reduced, but the structural instability of the catalyst also increases, leading to a decrease in OER performance.

[0122] Although the experimental examples and embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to the above-described experimental examples and embodiments. Various modifications and improvements made by those skilled in the art using the basic concepts of the present invention as defined in the following patent claims are also included within the scope of the present invention.

Claims

1. A catalyst for the oxygen evolution reaction, said catalyst comprising: A metal catalyst, comprising a central portion and a surface portion surrounding the central portion, The surface portion includes: A frame with a mesh structure, and Metal oxides applied to the frame.

2. The catalyst according to claim 1, further comprising: carrier The metal catalyst is loaded onto the support.

3. The catalyst according to claim 1, wherein the diameter of the metal catalyst is in the range of 30 nm to 100 nm.

4. The catalyst according to claim 1, wherein the thickness of the surface portion is in the range of 2 nm to 10 nm.

5. The catalyst according to claim 1, wherein the framework comprises an alloy of platinum group elements and transition metals.

6. The catalyst according to claim 5, wherein the platinum group element includes at least one of platinum (Pt), palladium (Pd) or rhodium (Rh).

7. The catalyst according to claim 5, wherein the platinum group elements do not include iridium (Ir).

8. The catalyst according to claim 5, wherein the transition metal comprises at least one of nickel (Ni), cobalt (Co), copper (Cu), or iron (Fe).

9. The catalyst according to claim 1, wherein the metal oxide is coated on the frame with a thickness in the range of 2 nm to 5 nm.

10. The catalyst of claim 1, wherein the metal oxide is coated on the surface of the central portion.

11. The catalyst according to claim 1, wherein the metal oxide comprises ruthenium oxide (RuO2) having a rutile structure.

12. The catalyst according to claim 1, wherein the metal oxide is absent in a region extending from the surface of the metal catalyst to a depth of 5 nm.

13. A method for preparing a catalyst for the oxygen evolution reaction, the method comprising: Prepare particles of an alloy comprising platinum group elements and transition metals; Metal catalyst precursors are prepared by coating the particles with metal oxide precursors. as well as The catalyst is prepared by oxidizing the metal catalyst precursor. The catalyst includes a metal catalyst, the metal catalyst comprising a central portion and a surface portion surrounding the central portion, and The surface portion includes A frame with a mesh structure, and Metal oxides applied to the frame.

14. The method of claim 13, wherein preparing the particles comprises: A particulate precursor of an alloy comprising the platinum group elements and the transition metals is prepared by reacting a platinum group element precursor with a transition metal precursor. as well as The particles are prepared by treating the particle precursor with acid. The particles include surfaces etched by the acid.

15. The method according to claim 13, wherein: The platinum group elements include at least one of platinum (Pt), palladium (Pd), or rhodium (Rh). The platinum group elements do not include iridium (Ir), and The transition metal includes at least one of nickel (Ni), cobalt (Co), copper (Cu), or iron (Fe).

16. The method of claim 13, wherein preparing the metal catalyst precursor comprises reacting the particles with the metal oxide precursor in a carbon monoxide atmosphere.

17. The method of claim 13, wherein preparing the catalyst comprises oxidizing the metal oxide precursor to a metal oxide by heat-treating the metal catalyst precursor in an oxygen atmosphere at a temperature ranging from 250°C to 350°C.

18. The method of claim 13, wherein the metal oxide is coated on the frame with a thickness in the range of 2 nm to 5 nm, and The metal oxide is coated onto the surface of the central portion.

19. The method of claim 13, wherein the metal oxide comprises ruthenium oxide (RuO2) having a rutile structure.

20. The method of claim 13, wherein the metal oxide is absent in a region extending from the surface of the metal catalyst to a depth of 5 nm.

Images