Oxygen evolution electrode catalyst, method for producing same, and water electrolysis device comprising same

Abstract

The present invention relates to an oxygen evolution electrode catalyst comprising bismuth (Bi), wherein the bismuth exists together with iridium or an iridium compound to provide improved durability in an oxygen evolution reaction.

Description

Oxygen generating electrode catalyst, method for manufacturing the same, and water electrolysis device including the same

[0001] The present invention relates to an oxygen generating electrode catalyst, a method for manufacturing the same, and a water electrolysis device including the same.

[0002] We are currently on the verge of entering a hydrogen society. A hydrogen society refers to a society where hydrogen is utilized as the central energy source and is supplied and available to all regions. To enter a hydrogen society, the establishment of a stable hydrogen industry value chain is required. In particular, for the hydrogen industry value chain to operate smoothly, it is crucial to produce the hydrogen needed in a hydrogen society to meet demand.

[0003] Hydrogen production methods include the byproduct hydrogen method, which utilizes hydrogen as a byproduct of other industries, and the extractive hydrogen method, which actively produces hydrogen by reforming or decomposing fossil fuels or water. As the byproduct hydrogen method alone cannot meet the growing demand for hydrogen, the importance of the extractive hydrogen method is steadily increasing. In particular, from an environmental perspective, the development of water electrolysis methods that decompose water using renewable energy sources such as solar and wind power is crucial, rather than methods that produce hydrogen by reforming fossil fuels.

[0004] A representative water electrolysis device is the proton exchange membrane (PEM) electrolysis device. Iridium oxide has been used as the electrode catalyst for the anode, or the oxygen evolution electrode catalyst, in such PEM devices. When iridium oxide is used as the electrode catalyst for the oxygen evolution electrode in PEM devices, it exhibits the best performance in the oxygen evolution reaction. Although iridium demonstrates excellent performance in OER due to its high chemical stability and electrochemical activity, it presents challenges such as high costs resulting from resource scarcity and economic feasibility issues when used in large quantities. For these reasons, the development of catalyst support materials is becoming increasingly important to achieve performance and stability exceeding that of existing iridium catalysts while reducing the amount of iridium used.

[0005] Previous studies have primarily attempted to improve catalytic performance by loading iridium onto planar electrodes or dispersing iridium nanoparticles on carbon supports. However, these methods faced limitations in maximizing the reaction surface area or difficulties in reducing iridium usage. Therefore, there is a need for innovative catalytic technology capable of achieving performance superior to existing commercial catalysts while effectively reducing iridium consumption through the control of new material compositions and structures, thereby maximizing the reaction surface area.

[0006] One objective of the present invention is to significantly improve durability even under high temperature and high pressure long-term operation conditions by doping iridium oxide with bismuth (Bi) to control the oxidation state and oxygen content of iridium oxide. That is, the purpose is to provide a highly durable electrode catalyst that minimizes performance degradation during long-term use while maintaining electrochemical performance equivalent to or better than that of existing commercial electrode catalysts by using bismuth.

[0007] Another objective of the present invention is to provide a novel oxygen generation electrode catalyst that utilizes a bismuth tantalum oxide (BixTayOz) support to significantly reduce the amount of iridium used compared to existing catalysts, while ensuring activity and stability exceeding that of commercial catalysts in electrochemical reactions such as OER.

[0008] Another objective of the present invention is to provide an electrode catalyst for oxygen generation that can achieve high catalytic performance by maximizing the surface area and electrochemical surface area (ECSA) through a hollow structure with an internally empty interior by providing a catalyst support having a bismuth tellurium (Bi2Te3)-based hollow nanowire structure and supporting iridium (Ir) thereon, while reducing the amount of iridium used compared to existing methods and exhibiting the same or improved reaction activity, and also improving long-term stability and durability.

[0009] Meanwhile, other unspecified objects of the present invention will be further considered to the extent that they can be easily inferred from the following detailed description and effects.

[0010] To solve the problem described above, the present invention proposes an oxygen-generating electrode catalyst containing bismuth (Bi), a method for manufacturing the same, and a water electrolysis device containing the same. In this case, the bismuth is present together with iridium or an iridium compound to provide enhanced durability in the oxygen-generating reaction.

[0011] More specific solutions are as follows.

[0012]

[0013] An oxygen generating electrode catalyst according to one embodiment of the present invention is characterized by comprising bismuth (Bi)-doped iridium oxide.

[0014] In one embodiment, the content of doped bismuth (Bi) may exceed 1.1 at% and be less than 11.1 at% with respect to the total number of atoms of iridium (Ir), bismuth (Bi), and oxygen (O).

[0015] In one embodiment, the content of doped bismuth (Bi) may exceed 1.1 at% and be 3.3 at% or less.

[0016] In one embodiment, the content of doped bismuth (Bi) may be 2.2 at% or more and 3.3 at% or less.

[0017] In one embodiment, the amount of oxygen contained in the iridium oxide may be greater than that of iridium oxide not doped with bismuth.

[0018] In one embodiment, the ratio of oxygen elements (O / (Ir+O)) included in the bismuth-doped iridium oxide may exceed 69.5% and be less than 88.8%.

[0019] In one embodiment, the elemental ratio of Ir4+ to Ir3+ (Ir4+ / Ir3+) of the iridium oxide may be larger than that of iridium oxide not doped with bismuth.

[0020] A water electrolysis device according to one embodiment of the present invention is characterized in that an oxygen generating electrode catalyst and a hydrogen generating electrode are arranged on both sides with a membrane in between, and water is electrolyzed at the oxygen generating electrode catalyst to generate oxygen, and hydrogen is transferred through the membrane to the hydrogen generating electrode catalyst to generate hydrogen. In one embodiment, the oxygen generating electrode catalyst may include iridium oxide doped with bismuth (Bi).

[0021] A method for manufacturing an oxygen generating electrode catalyst according to one embodiment of the present invention comprises: (a) a step of preparing a precursor solution by dissolving an iridium precursor in a solvent and adding a bismuth precursor; (b) a step of homogenizing the precursor solution by ultrasonically treating it; (c) a step of obtaining a dried product by concentrating and drying the homogenized precursor solution; (d) a step of calcining the dried product at 350 to 450°C for 20 to 40 minutes; and (e) a step of washing the calcined product.

[0022] In one embodiment, in step (a), the amount of bismuth precursor added may be such that the atomic ratio (Bi / (Ir+Bi)) of bismuth (Bi) to the total amount of iridium (Ir) and bismuth (Bi) is greater than 5% and less than 50%.

[0023]

[0024] An oxygen-generating electrode catalyst according to another embodiment of the present invention is characterized by comprising a Bi3TaO7 support supported with iridium or iridium oxide.

[0025] In another embodiment, the Bi3TaO7 support may have an amorphous structure.

[0026] In another embodiment, the content of iridium (Ir) supported on the Bi3TaO7 support may be greater than 20 wt% and less than 50 wt%.

[0027] In another embodiment, the iridium or iridium oxide may be doped with bismuth.

[0028] A water electrolysis device according to another embodiment of the present invention is characterized in that an oxygen generating electrode catalyst and a hydrogen generating electrode are arranged on both sides with a membrane in between, and water is electrolyzed at the oxygen generating electrode catalyst to generate oxygen, and hydrogen is transferred through the membrane to the hydrogen generating electrode catalyst to generate hydrogen, and the oxygen generating electrode catalyst comprises a Bi3TaO7 support supported with iridium or iridium oxide.

[0029] A method for manufacturing an electrode catalyst for oxygen generation according to another embodiment of the present invention comprises the steps of: preparing Bi3TaO7 particles; dispersing the Bi3TaO7 particles in a polyol solvent; adding an iridium precursor to the polyol solvent in which the Bi3TaO7 particles are dispersed; performing heat treatment to support iridium metal or iridium oxide on the Bi3TaO7 particles; and recovering the Bi3TaO7 particles supported with iridium metal or iridium oxide.

[0030] In another embodiment, the step of preparing Bi3TaO7 particles may include the step of forming a mixture by grinding and mixing bismuth(III) oxide (Bi2O3) and tantalum(V) oxide (Ta2O5) in ethanol; the step of drying the mixture; the step of forming a calcined product by calcining the dried product; and the step of grinding the calcined product.

[0031] In another embodiment, the step of calcining the dried product may be performed at 800 to 1,200 ℃ for 4 to 6 hours.

[0032] In another embodiment, the polyol solvent may be at least one selected from the group consisting of ethylene glycol, glycerol, and 1,2-propanediol.

[0033] In another embodiment, the Bi3TaO7 particles may have an amorphous structure.

[0034]

[0035] An oxygen-generating electrode catalyst according to another embodiment of the present invention comprises a Bi2Te3 hollow nanowire support; and iridium or iridium oxide supported on the Bi2Te3 hollow nanowire support.

[0036] In another embodiment, the iridium (Ir) content supported on the Bi2Te3 hollow nanowire support may be characterized as being greater than 25 wt%.

[0037] In another embodiment, the Bi2Te3 hollow nanowire support may be characterized by having an average thickness of 60 to 120 nm.

[0038] In another embodiment, the iridium or iridium oxide may be characterized as being doped with bismuth.

[0039] A water electrolysis device according to another embodiment of the invention comprises an oxygen generating electrode catalyst and a hydrogen generating electrode arranged on both sides with a membrane in between, wherein water is electrolyzed at the oxygen generating electrode catalyst to generate oxygen, and hydrogen is transferred through the membrane to the hydrogen generating electrode catalyst to generate hydrogen, wherein the oxygen generating electrode catalyst comprises a Bi2Te3 hollow nanowire support; and iridium or iridium oxide supported on the Bi2Te3 hollow nanowire support.

[0040] An electrode catalyst for hydrogen generation according to another embodiment of the present invention comprises: (a) a step of preparing a Bi2Te3 hollow nanowire support; (b) a step of dispersing the Bi2Te3 hollow nanowire support in a polyol solvent; (c) a step of adding an iridium precursor to a solution in which the support is dispersed, and a step of performing heat treatment to support iridium metal or iridium oxide on the Bi2Te3 hollow nanowire support; and (d) a step of recovering the Bi2Te3 hollow nanowire support supported with iridium metal or iridium oxide.

[0041] In another embodiment, the step (a) may be characterized by comprising: a step of preparing a tellurium precursor solution by mixing TeO2, an additive, and a solvent; a step of performing a first heat treatment on the tellurium precursor solution; a step of adding hydrazine to the first heat-treated tellurium precursor solution; a step of adding a bismuth precursor to the tellurium precursor solution containing hydrazine to form a mixture; and a step of performing a second heat treatment on the mixture.

[0042] In another embodiment, the concentration of the added hydrizine may be greater than 0.187 mM and less than 0.936 mM.

[0043] In another embodiment, the concentration of the added hydrizine may be characterized as being 0.374 to 0.749 mM.

[0044] In another embodiment, the concentration of the added hydrizine may be characterized as being 0.561 to 0.759 mM.

[0045] In another embodiment, the average thickness of the tellurium nanowires formed in the first heat-treated tellurium precursor solution may be 60 to 120 nm.

[0046] In another embodiment, the average thickness of the tellurium nanowires formed in the first heat-treated tellurium precursor solution may be 70 to 90 nm.

[0047] In another embodiment, the polyol solvent may be characterized as being at least one selected from the group consisting of ethylene glycol, glycerol, and 1,2-propanediol.

[0048]

[0049] An oxygen generation electrode catalyst according to one embodiment of the present invention has the effect of maintaining a stable oxygen generation reaction for a long time even under high temperature and high pressure conditions by controlling the oxidation state distribution and oxygen content of the electrode catalyst through doping bismuth (Bi) into an iridium oxide (IrO2)-based electrode catalyst. In addition, by improving the electronic structure and surface reactivity through bismuth doping, low overpotential and excellent electrochemical performance are secured, and performance degradation during long-term operation is minimized, thereby enabling the realization of a long-life electrode catalyst. Consequently, when applied to water electrolysis systems or fuel cells based on oxygen generation reactions, it has the effect of significantly reducing system costs and operational burdens.

[0050] An oxygen-generating electrode catalyst according to another embodiment of the present invention improves the economic efficiency of hydrogen production by drastically reducing the amount of iridium used through the use of a bismuth tantalum oxide support. In particular, by using a bismuth tantalum oxide support, it has the effect of exhibiting catalytic activity equivalent to or greater than that of commercial electrode catalysts while having excellent durability.

[0051] An oxygen-generating electrode catalyst according to another embodiment of the present invention supports iridium or iridium oxide on a hollow nanowire support formed of bismuth tellurium, thereby achieving performance equivalent to or better than that of commercial catalysts by loading only half the amount of iridium compared to commercial catalysts. Therefore, the economic efficiency of water electrolysis can be improved by using the oxygen-generating electrode catalyst according to another embodiment of the present invention. Furthermore, the effective reaction area (ECSA) of the oxygen-generating electrode catalyst according to one embodiment of the present invention increases by approximately twofold as the support is formed in a hollow nanowire structure. Accordingly, this contributes significantly to increasing the reaction rate and total reaction amount by improving accessibility to active sites in electrochemical reactions. Moreover, thanks to the chemical and physical stability of the bismuth tellurium used as the support, the durability of the oxygen-generating electrode catalyst according to another embodiment of the present invention is improved, as structural collapse or degradation of activity is minimized even during long-term operation.

[0052] Meanwhile, it should be added that even if an effect is not explicitly mentioned here, the effects described in the following specification and the provisional effects expected by the technical features of the present invention are treated as described in the specification of the present invention.

[0053]

[0054] Figure 1 is a high-resolution transmission electron microscope (HRTEM) image of the microstructure of an iridium oxide electrode catalyst before and after bismuth doping.

[0055] Figure 2 shows the result of energy dispersive X-ray spectroscopy (EDS) mapping of the elemental distribution within the bismuth-doped iridium oxide electrode catalyst.

[0056] Figures 3a and 3b show the results of evaluating the electrochemical characteristics of the electrode catalysts according to the comparative example and the example using linear sweep voltammetry (LSV), Tafel slope, electrochemical impedance spectroscopy (EIS), and long-term stability.

[0057] Figures 4a and 4b show the results of evaluating the electrochemical characteristics of the electrode catalyst according to changes in bismuth doping amount using Linear Sweep Voltammetry (LSV), Tafel slope, Electrochemical Impedance Spectroscopy (EIS), and long-term stability.

[0058] Figure 5 shows the current-voltage characteristics of a pure iridium oxide electrode catalyst and a bismuth-doped iridium oxide electrode catalyst under single cell conditions, as well as the current-voltage characteristics of an electrode catalyst with internal resistance (IR) corrected.

[0059] Figure 6 is a diagram comparing the changes in characteristics of a bismuth-doped iridium oxide electrode catalyst and a pure iridium oxide electrode catalyst over time under long-term operating conditions.

[0060] Figure 7 shows the change in the oxidation state of iridium through X-ray photoelectron spectroscopy (XPS).

[0061] Figure 8 shows the change in the electronic structure of the iridium oxide electrode catalyst after bismuth doping through X-ray Absorption Near Edge Structure (XANES) analysis.

[0062] Figure 9 is a diagram comparing the oxygen vacancy formation energies before and after bismuth doping through Density Functional Theory (DFT) calculations.

[0063] Figure 10 is a diagram showing the change in the electronic state of iridium atoms on the surface of an iridium oxide electrode catalyst before and after bismuth doping through Bader charge analysis.

[0064] FIG. 11 schematically illustrates each step of the method for manufacturing an oxygen-generating electrode catalyst according to a second embodiment of the present invention.

[0065] Figure 12 shows the particle size and amorphous structure of the Bi3TaO7 support as a result of TEM (Transmission Electron Microscopy) images.

[0066] Figure 13 shows the distribution of Ir, Bi, Ta, and O elements through TEM images and EDS mapping of an oxygen-generating electrode catalyst according to a second embodiment of the present invention.

[0067] Figure 14 is the result of confirming the distribution of Bi and Ir particles through a STEM-HAADF image of an oxygen generation electrode catalyst according to the second embodiment of the present invention.

[0068] FIG. 15 is the result of evaluating the electrochemical properties of an oxygen-generating electrode catalyst according to the second embodiment of the present invention using LSV, Teifel slope, EIS, and mass activity.

[0069] FIG. 16 is the result of evaluating the durability of an oxygen generating electrode catalyst according to the second embodiment of the present invention and a commercial electrode catalyst.

[0070] Figure 17 shows the results of changes in the bismuth oxidation state of Bi2O3, Bi3TaO7, and IrOx / Bi3TaO7 (before and after OER reaction) through X-ray absorption edge near structure (XANES) analysis.

[0071] Figure 18 shows the results of evaluating the bismuth bonding state and oxidation state of the IrOx / Bi3TaO7 electrode catalyst through Bi L3-edge EXAFS analysis.

[0072] Figure 19 shows the results of comparing the change in the Ir oxidation state of a commercial catalyst (Ir black) and an IrOx / Bi3TaO7 electrode catalyst through XANES analysis.

[0073] FIG. 20 schematically illustrates each step of the method for manufacturing an oxygen-generating electrode catalyst according to the third embodiment of the present invention.

[0074] Figure 21 shows the results of measuring the shape and thickness of nanowires manufactured according to the synthesis conditions of TeO2 nanowires.

[0075] Figure 22 shows the EDS measurement results when 0.187 mM of hydrazine was used in the fabrication process of Bi2Te3 nanowires.

[0076] Figure 23 shows the EDS measurement results when 0.374 mM of hydrazine was used in the fabrication process of Bi2Te3 nanowires.

[0077] Figure 24 shows the EDS measurement results when 0.561 mM of hydrazine was used in the fabrication process of Bi2Te3 nanowires.

[0078] Figure 25 shows the EDS measurement results of an oxygen-generating electrode catalyst prepared by supporting iridium on Bi2Te3 nanowires prepared using hydrazine at 0.187 mM, 0.374 mM, and 0.561 mM.

[0079] Figure 26 shows the results of evaluating the electrochemical reaction area of ​​an oxygen-generating electrode catalyst prepared by supporting iridium on Bi2Te3 nanowires prepared using 0.187 mM and 0.561 mM of hydrazine.

[0080] Figure 27 shows the results of measuring the LSV among the electrochemical characteristics of the oxygen generation electrode catalysts of the examples and comparative examples.

[0081] Figure 28 shows the results of measuring the mass activity among the electrochemical characteristics of the oxygen generation electrode catalysts of the examples and comparative examples.

[0082] Figure 29 shows the results of evaluating the long-term durability among the electrochemical characteristics of the oxygen generation electrode catalysts of the examples and comparative examples.

[0083] The drawings above are intended to explain the oxygen generation catalyst electrode of the present invention in more detail. FIGS. 1 to 10 relate to an oxygen generation electrode catalyst according to a first embodiment, FIGS. 11 to 19 relate to an oxygen generation electrode catalyst according to a second embodiment, and FIGS. 20 to 29 relate to an oxygen generation electrode catalyst according to a third embodiment. However, any drawings relating to an oxygen generation electrode catalyst according to any one embodiment may be used to explain other oxygen generation electrode catalysts.

[0084] Meanwhile, it should be noted that the attached drawings are provided as examples for reference to help understand the technical concept of the present invention, and the scope of the rights of the present invention is not limited by them.

[0085]

[0086] Hereinafter, with reference to the drawings, we will examine the configuration of the present invention as guided by various embodiments thereof and the effects derived therefrom. In describing the present invention, detailed descriptions of related known functions are omitted if they are deemed obvious to a person skilled in the art and could unnecessarily obscure the essence of the invention.

[0087] The oxygen-generating electrode catalyst of the present invention can be applied to the field of electrochemical energy storage or generation technology utilizing hydrogen and oxygen evolution reactions as a reaction mechanism. However, for the sake of clarity, the present invention will be described below based on a PEM water electrolysis device.

[0088] In the oxygen-generating electrode catalyst of a PEM water electrolysis device, water is electrolyzed to generate oxygen, and hydrogen is transferred to the hydrogen-generating electrode catalyst through a cation polymer membrane to produce hydrogen. At this time, due to the acidic atmosphere caused by hydrogen cations, both the hydrogen-generating electrode catalyst and the oxygen-generating electrode catalyst are manufactured from precious metals. Platinum (Pt) has been mainly used as the hydrogen-generating electrode catalyst, and iridium (Ir) has been mainly used as the oxygen-generating electrode catalyst.

[0089] In oxygen generation electrode catalysts, iridium oxide is formed as the electrode catalyst layer; however, not only is the price of iridium high, but there is also a problem of low durability when iridium oxide is used as the electrode catalyst layer.

[0090] Moreover, due to the recent global trend toward decarbonization, the production of green hydrogen—that is, hydrogen that does not generate any carbon dioxide—is becoming increasingly important. To produce green hydrogen, renewable energy sources such as solar and wind power are used as the power source for water electrolysis devices; however, renewable energy sources have the problem of significant load fluctuations depending on the time or environment. Such load fluctuations further reduce the durability of oxygen generation electrode catalysts containing iridium oxide electrode catalysts.

[0091] Accordingly, the present invention proposes a novel oxygen generation electrode catalyst capable of improving the durability of the oxygen generation electrode catalyst.

[0092] The oxygen generating electrode catalyst according to the first embodiment of the present invention is characterized by comprising bismuth-doped iridium oxide.

[0093] The content of bismuth doped into iridium oxide may be greater than 1.1 at% and less than 11.1 at% relative to the total amount of iridium, bismuth, and oxygen atoms. Preferably, it may be greater than 1.1 at% and less than or equal to 3.3 at%, and more preferably, between 2.2 at% and 3.3 at%. When the content of doped bismuth is less than or equal to 1.1 at%, the durability of the prepared electrode catalyst is significantly lower compared to an oxygen generation electrode catalyst containing pure iridium oxide, and when the content of doped bismuth is greater than or equal to 11.1 at%, the performance and durability of the prepared electrode catalyst are significantly lower compared to an oxygen generation electrode catalyst containing pure iridium oxide.

[0094] Furthermore, in the case of iridium oxide not doped with bismuth, the ratio of oxygen elements contained in the iridium oxide (O / (Ir+O)) is 63.5%, whereas in the oxygen generation electrode catalyst of the first embodiment, the ratio of oxygen elements contained in the iridium oxide (O / (Ir+O)) increases with bismuth doping. This increase in the ratio of oxygen elements contained in the iridium oxide due to bismuth doping is because the oxidation number of iridium contained within the oxygen generation electrode catalyst increases. That is, the Ir of the iridium oxide 4+ wa Ir 3+ The elemental ratio of (Ir 4+ / Ir 3+ ) is larger compared to iridium oxide not doped with bismuth. Meanwhile, the oxygen generation electrode catalyst of the first embodiment has Ir constituting iridium oxide depending on bismuth doping. 4+The amount of is greater than that of iridium oxide not doped with bismuth. The ratio of oxygen elements (O / (Ir+O)) contained in the iridium oxide of the oxygen generating electrode catalyst of the first embodiment may be greater than 69.5% and less than 88.2%. Preferably, it may be greater than 69.5% and less than or equal to 81.8%, and more preferably, it may be between 75.6% and 81.8%.

[0095] The oxygen generating electrode catalyst of the first embodiment can be applied to a water electrolysis device. The water electrolysis device may be characterized in that an oxygen generating electrode catalyst and a hydrogen generating electrode catalyst are arranged on both sides with a membrane in between, so that water is converted into oxygen by electrolysis at the oxygen generating electrode catalyst, and hydrogen is transferred to the hydrogen generating electrode catalyst through the membrane to produce hydrogen, and the oxygen generating electrode catalyst is the oxygen generating electrode catalyst of the first embodiment.

[0096] A method for manufacturing an oxygen generating electrode catalyst according to the first embodiment of the present invention comprises the steps of preparing a precursor solution, homogenizing the precursor solution, concentrating and drying the precursor solution to obtain a dried product, calcining the dried product, and washing.

[0097] In the step of preparing the precursor solution, an iridium precursor is dissolved in a solvent, and a bismuth precursor is added to the solvent. At this time, sodium nitrate (NaNO3) may be added to the solution in which the iridium precursor is dissolved as an oxidation promoter and particle size regulator.

[0098] The content of the bismuth precursor may be included such that the atomic ratio (Bi / (Ir+Bi)) to the total amount of bismuth (Bi) and iridium (Ir) is greater than 5% and less than 50%. Preferably, the content of the bismuth precursor may be included such that it is greater than 5% and less than or equal to 15%, and more preferably, it may be included between 10% and 15%.

[0099] After preparing the precursor mixture, the precursor mixture is homogenized. During homogenization, ultrasonic treatment may be performed for 10 to 30 minutes.

[0100] After ultrasonic treatment, a step of concentrating and drying the precursor solution to obtain a dried product is performed. Concentration and drying may be performed until the solvent is completely removed. The temperature of the concentration and drying step may be 80 to 180 °C and may be performed for 3 hours or more.

[0101] Next, the dried material undergoes a firing step. Firing can be performed at a temperature of 350 to 450 °C for 20 to 40 minutes.

[0102] Once calcination is complete, washing is performed. For washing, the calcined product is immersed in distilled water and ultrasonically treated to remove residues, then washed with distilled water, and finally washed once more with a mixture of distilled water and ethanol.

[0103] The oxygen generation electrode catalyst of the first embodiment was actually manufactured, and its physical properties and effects were verified.

[0104] 500 mg of H2IrCl6·xH2O (28.1 mM)d was prepared as an iridium precursor and dissolved in 40 mL of distilled water (DI water). 1,000 mg of sodium nitrate (NaNO3) was added to the solution containing the dissolved iridium precursor as an oxidation promoter and particle size regulator. Then, BiCl3 was prepared as a bismuth precursor and mixed into the solution containing the dissolved iridium precursor. At this time, the content of the bismuth precursor was added such that the atomic ratio (Bi / (Ir+Bi)) of the bismuth (Bi) to the total amount of iridium (Ir) and bismuth (Bi) was 0% (Pure IrO2), 5% (5Bi-IrO2), 10% (10Bi-IrO2), and 50% (50Bi-IrO2). Subsequently, the sample was sonicated for 20 minutes, transferred to a 100 mL beaker, and heated on a hot plate at 150 °C. Heating was continued until the solvent completely evaporated, which took more than 5 hours. The resulting dried material was then scraped off and calcined. Calcination was performed in a furnace at 400 °C (ramping rate: 5 °C / min) for 30 minutes. The calcined material was placed in a crucible, immersed in 30–40 mL of distilled water, and sonicated to remove any remaining residue. It was then washed with distilled water and washed two more times with a mixture of ethanol and distilled water.

[0105] First, the microstructure and composition of the manufactured electrode catalyst were analyzed.

[0106] Figure 1 is an image comparing the microstructures of a pure IrO2 electrode catalyst without bismuth doping (Pure IrO2) and a bismuth-doped IrO2 electrode catalyst (10Bi-IrO2) through a high-resolution transmission electron microscope (HRTEM).

[0107] In the case of the pure IrO2 electrode catalyst (Pure IrO2), as can be seen in Fig. 1(a), nanoparticles of a homogeneous size (at the level of a few nm) are clustered, and a relatively uniform particle size distribution can be observed. While this structure provides the IrO2 electrode catalyst with an abundant surface of active sites suitable for electrochemical reactions, performance degradation may occur due to particle growth or structural changes during long-term operation.

[0108] In the case of bismuth-doped IrO2 electrode catalysts (10Bi-IrO2), the basic nanostructure of IrO2 is maintained even after bismuth doping; bismuth atoms enter the crystal lattice, locally altering the electronic structure and adjusting the surface oxygen bonding state, thereby consequently stabilizing the interfacial properties of the particles. These microstructural changes contribute to controlling inter-particle aggregation and stably maintaining the active sites of the electrode catalyst even under long-term reaction conditions.

[0109] Figure 2 visualizes the elemental distribution within the bismuth-doped electrode catalyst through Energy Dispersive X-ray Spectroscopy (EDS) mapping.

[0110] The image on the left shows the overall particle shape, and the EDS mapping results on the right indicate that Bi and Ir atoms are uniformly distributed. It can be confirmed that bismuth atoms are not segregated in specific areas but are evenly doped across the entire region. In other words, bismuth alters the lattice and electronic structure of iridium throughout the crystal structure of iridium oxide, thereby improving the chemical stability of the electrode catalyst surface.

[0111] The composition of each electrode catalyst is listed in Table 1 below.

[0112]

[0113] Ir [at%]Bi [at%]O [at%]O / (Ir+O)Pure IrO236.5063.563.50%5Bi-IrO230.21.168.769.46%10Bi-IrO223.92.27 3.975.56%15Bi-IrO217.63.379.181.80%50Bi-IrO211.311.184.388.18%

[0114]

[0115] Referring to Table 1, it can be seen that the O / (Ir+O) ratio increased due to bismuth doping, which implies that oxygen affinity is enhanced and oxygen vacancy formation is suppressed. As a result, the electrode catalyst allows the oxygen evolution reaction (OER) to proceed more stably under PEM water electrolysis operating conditions.

[0116] Next, the electrochemical performance and stability of the prepared electrode catalyst were evaluated.

[0117] Figures 3a and 3b show the electrochemical characteristics of the electrode catalysts according to the comparative example and the example, including linear sweep voltammetry (LSV), Tafel slope, electrochemical impedance spectroscopy (EIS), and stability evaluation results. In addition, Table 2 shows the results of measuring the overpotential of each sample, and Table 3 shows the results of measuring the Tafel slope of each sample.

[0118]

[0119] 10mA / cm2Overpotential (mV)10Bi-IrO2250AA260Pure-IrO226450Bi-IrO2279

[0120] Tafel slope (mv / dec)10Bi-IrO249AA68Pure-IrO25950Bi-IrO275

[0121]

[0122] In the case of the LSV curve (Fig. 3a), electrochemical activity can be confirmed by comparing the change in current density according to the electrode catalyst potential. The 10Bi-IrO2 electrode catalyst can obtain the same current at a lower overpotential compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA), indicating that the reaction rate at the electrode catalyst active site has been improved.

[0123] The Tafel slope (Fig. 3b) is an indicator reflecting the kinetic characteristics of the electrochemical reaction, allowing for the inference of the activation energy along the reaction pathway. The 10Bi-IrO2 electrode catalyst exhibits a lower Tafel slope compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA), indicating faster reaction rates and lower energy barriers. This implies that changes in the Ir electronic structure and oxygen bond stabilization through bismuth doping have improved the reaction mechanism.

[0124] In the case of EIS analysis (Fig. 3c), the charge transfer resistance (R) at the electrode catalyst-electrolyte interface ct The improvement in the electrical conductivity and reactivity of the catalyst can be evaluated through changes in ). The 10Bi-IrO2 electrode catalyst compared R with pure IrO2 and the commercial IrO2 electrode catalyst (AA). ct Since it is low, it can be seen that electron and ion transfer is smooth and reaction kinetics are improved.

[0125] In the long-term stability evaluation (Fig. 3d), changes in electrode catalyst potential were observed during long-term operation under constant current conditions. As a result, it was confirmed that the 10Bi-IrO2 electrode catalyst exhibited a very small increase in potential, indicating that it operates most stably over the long term. This demonstrates that bismuth doping contributes significantly to improving not only short-term performance but also long-term reliability.

[0126] On the other hand, the 50Bi-IrO2 electrode catalyst doped with an excess amount of bismuth showed reduced performance in all indicators compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA).

[0127] Figures 4a and 4b show the electrochemical characteristics of the electrode catalyst according to changes in bismuth doping amount, including Linear Sweep Voltammetry (LSV), Tafel slope, Electrochemical Impedance Spectroscopy (EIS), and stability evaluation results. Additionally, Table 4 shows the results of measuring the overpotential of each sample, and Table 5 shows the results of measuring the Tafel slope of each sample.

[0128]

[0129] 10mA / cm2Overpotential (mV)10Bi-IrO225015Bi-IrO2266AA260Pure-IrO22645Bi-IrO226950Bi-IrO2279

[0130] Tafel slope (mv / dec)10Bi-IrO24915Bi-IrO245AA68Pure-IrO2595Bi-IrO26250Bi-IrO275

[0131] Referring to the LSV curve (Fig. 4a), the 5Bi-IrO2 electrode catalyst was able to obtain the same current at an overvoltage level equivalent to that of pure IrO2 and the commercial IrO2 electrode catalyst (AA), while the 50Bi-IrO2 electrode catalyst was able to obtain the same current at a higher overvoltage level compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA). The 10Bi-IrO2 electrode catalyst and the 15Bi-IrO2 electrode catalyst were able to obtain the same current at a lower overvoltage compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA), indicating that the reaction rate at the electrode catalyst active site was improved.

[0132] Referring to the Tafel slope (Fig. 4b), the 5Bi-IrO2 electrode catalyst and the 15Bi-IrO2 electrode catalyst showed a Tafel slope equivalent to that of pure IrO2 and the commercial IrO2 electrode catalyst (AA), while the 50Bi-IrO2 electrode catalyst showed a higher Tafel slope compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA), indicating a slower reaction rate and a higher energy barrier. The 10Bi-IrO2 electrode catalyst showed a lower Tafel slope compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA), indicating a faster reaction rate and a lower energy barrier.

[0133] Referring to the EIS analysis (Fig. 4c), the 5Bi-IrO2 electrode catalyst exhibited an Rct level equivalent to that of pure IrO2, while the 50Bi-IrO2 electrode catalyst showed a higher Rct compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA). The 10Bi-IrO2 and 15Bi-IrO2 electrode catalysts showed Rct compared to pure IrO2 and the commercial IrO2 electrode catalyst (AA). ct It can be seen that the low value facilitates electron and ion transfer, and that reaction kinetics are improved through the formation of small semicircles.

[0134] Referring to the long-term stability evaluation (Fig. 4d), the 5Bi-IrO2 electrode catalyst and the 50Bi-IrO2 electrode catalyst exhibited a large increase in potential and had to stop quickly even during significantly shorter operation times compared to pure IrO2. In contrast, the 10Bi-IrO2 electrode catalyst showed a very small increase in potential, confirming that it operated most stably over a long period. The 15Bi-IrO2 electrode catalyst also had a potential increase equivalent to that of pure IrO2, and its operating time was longer than that of pure IrO2.

[0135] Based on the contents of FIG. 4, to improve performance and durability, the content of bismuth doped into iridium oxide may be greater than 1.1 at% and less than 11.1 at%. Preferably, it may be greater than 1.1 at% and less than or equal to 3.3 at%, and more preferably, between 2.2 at% and 3.3 at%. Alternatively, the ratio of oxygen elements (O / (Ir+O)) included in iridium oxide may be greater than 69.5% and less than 88.2%. Preferably, it may be greater than 69.5% and less than or equal to 81.8%, and more preferably between 75.6% and 81.8%.

[0136] Figure 5 shows the current-voltage characteristics of a pure iridium oxide electrode catalyst and a bismuth-doped iridium oxide electrode catalyst under single-cell conditions, as well as the current-voltage characteristics of an electrode catalyst with internal resistance (IR) corrected. Additionally, Table 6 summarizes the current-voltage characteristics of the electrode and the current-voltage characteristics of the electrode catalyst with internal resistance (IR) corrected, and Table 7 summarizes the loading amounts of iridium and platinum, respectively, for the oxygen evolution electrode catalyst and the hydrogen evolution electrode catalyst in a single cell.

[0137]

[0138] CatalystsCell voltage (V)(at 1 A / cm 2 )IR-Corrected Cell voltage (V)(at 1 A / cm 2 Cell voltage (V) (at 1 A / cm²) 2 )IR-Corrected Cell voltage (V)(at 2 A / cm 2 )IrO21.738 V1.582 V1.945 V1.632 V10Bi-IrO21.724 V1.557 V1.936 V1.601 V

[0139] CatalystsLoading amount (mg Ir / cm2 )Loading amount(mg Pt / cm 2 )IrO20.640.11IrBiO20.590.09

[0140] Referring to Figure 5 and Table 6, the 10Bi-IrO2 electrode catalyst exhibits superior performance compared to the pure IrO2 electrode catalyst even after IR correction. This can be interpreted as bismuth doping fundamentally improving the charge transfer pathways and the electronic structure of the active site within the electrode catalyst.

[0141] In addition, as shown in Table 7, the 10Bi-IrO2 electrode catalyst exhibits equivalent or superior performance even with a small amount of electrode catalyst. That is, using the oxygen generation electrode catalyst of the first embodiment can have significant advantages in terms of economic efficiency.

[0142] Figure 6 compares the changes in characteristics of a bismuth-doped iridium oxide electrode catalyst and a pure iridium oxide electrode catalyst over time under long-term operation conditions using a single cell, and Table 8 below shows the results of measuring how much the voltage increased during operation. The amount of precious metal loading on the oxygen evolution electrode catalyst and hydrogen evolution electrode catalyst of the single cell used in Figure 6 is as shown in Table 7.

[0143]

[0144] CatalystsPotential increase (mV)(100 mA / cm 2 )Pure-IrO259.26 mV10Bi-IrO227.75 mV

[0145] Figure 6 and Table 8 show the results of a long-term stability test in which the change in cell voltage was measured after operating a single cell for about 100 hours under conditions of 1 A / cm². Referring to Figure 6 and Table 8, the voltage increase of the 10Bi-IrO2 electrode catalyst is much smaller than that of pure IrO2 even as operating time elapses. This means that the electrode catalyst structure and active site are maintained stably during long-term operation.

[0146] Figure 7 shows the change in the oxidation state of iridium oxide via X-ray Photoelectron Spectroscopy (XPS), and Table 9 shows the Ir of each sample. 4+ and Ir 3+ It is a measurement of the ratio.

[0147]

[0148] Ir 4+ Ir 3+ Pure-IrO278.221.810Bi-IrO282.817.2

[0149] Referring to Figure 7 and Table 9, Ir in the 10Bi-IrO2 electrode catalyst relative to pure IrO2 4+ The ratio is increasing and Ir 3+ The ratio decreases. This means that the Ir atoms in the 10Bi-IrO2 electrode catalyst maintain a higher oxidation state on average compared to pure IrO2. As previously discussed, the 10Bi-IrO2 electrode catalyst exhibited superior water electrolysis performance and durability compared to pure IrO2, indicating that bismuth doping controlled the oxidation state of Ir, thereby minimizing structural degradation that may occur during the reaction and improving reactivity.

[0150] Figure 8 shows the change in the electronic structure of the iridium oxide electrode catalyst after bismuth doping through X-ray Absorption Near Edge Structure (XANES) analysis.

[0151] In Fig. 8, IrO2 [Heat-treated] is the Ir contained through heat treatment 3+ er Ir 4+ It has been converted to. Meanwhile, Ir metal is Ir 0 It consists of. If we compare Ir metal and IrO2 [heat-treated], Ir 0 and Ir 3+ Ir 4+ As it is converted, it can be seen that the white line peak position moves to a high energy region.

[0152] In light of this, it can be seen that the position of the white line peak in bismuth-doped IrO2 has shifted to the right compared to pure IrO2, confirming that the oxidation state of iridium has increased due to doping; this is consistent with the previously obtained XPS result of Ir 4+ It corresponds to an increase in the ratio.

[0153] Figure 9 is a diagram comparing the oxygen vacancy formation energies before and after bismuth doping through Density Functional Theory (DFT) calculations.

[0154] Referring to Fig. 9, compared to pure IrO2, bismuth-doped IrO2 is V O The formation energy increases significantly (approx. 0.184 eV → 0.566 eV), making it difficult to form oxygen vacancies. This implies that oxygen is stably maintained within the electrode catalyst binding structure, suggesting that electrode catalyst degradation or loss of active sites due to oxygen deficiency is significantly reduced. Consequently, both structural stability and oxygen site stability are improved through bismuth doping.

[0155] Figure 10 is a diagram showing the change in the electronic state of iridium atoms on the surface of an iridium oxide electrode catalyst before and after bismuth doping through Bader charge analysis.

[0156] Referring to Fig. 10, it can be seen that the oxidation degree of the Ir atom at a specific site (Site 3) of Ir surrounding Bi remains higher when doped with bismuth compared to pure IrO2. This implies that the doped bismuth changes the local electronic structure, helping to fix the Ir atom in a more oxidized state. This local charge redistribution leads to the stabilization of the electrode catalyst active site and further contributes to the improvement of the overall electrode catalyst performance and durability.

[0157] To summarize the contents of the oxygen generating electrode catalyst according to the first embodiment described above, the bismuth-doped iridium oxide electrode catalyst has the following effects.

[0158] First, bismuth doping induces stable structural changes at nanoparticles and particle interfaces, and also makes the elemental distribution homogeneous, thereby increasing the oxygen content.

[0159] Second, as confirmed by XPS, XANES, and Bader analysis, bismuth doping increases the oxidation level of Ir atoms, thereby maximizing the stability and activity of oxygen reaction sites.

[0160] Third, as confirmed by the results of electrochemical evaluations using LSV, Tafel, and EIS, bismuth doping achieves low overpotential, fast reaction rate, and low charge transfer resistance, thereby exhibiting superior performance compared to conventional electrode catalysts.

[0161] Fourth, bismuth doping minimizes voltage rise even under long-term operating conditions (tens to hundreds of hours) and ensures long-term stability by preventing structural deterioration through the suppression of oxygen vacancy formation.

[0162] Next, we will examine the oxygen generation electrode catalyst according to the second embodiment.

[0163] FIG. 11 schematically illustrates each step of the method for manufacturing an oxygen-generating electrode catalyst according to a second embodiment of the present invention.

[0164] A method for manufacturing an oxygen-generating catalyst electrode according to a second embodiment of the present invention is

[0165] The method includes the steps of preparing Bi3TaO7 particles, dispersing the Bi3TaO7 particles in a polyol solvent, adding an iridium precursor to the polyol solvent in which the Bi3TaO7 particles are dispersed, performing heat treatment to support iridium metal or iridium oxide on the Bi3TaO7 particles, and recovering the Bi3TaO7 particles supported with iridium metal or iridium oxide.

[0166] First, perform the step of preparing Bi3TaO7 particles.

[0167] The step of preparing Bi3TaO7 particles includes the step of forming a mixture by grinding and mixing bismuth(III) oxide (Bi2O3) and tantalum(V) oxide (Ta2O5) in ethanol, the step of drying the mixture, the step of forming a calcined product by calcining the dried product, and the step of grinding the calcined product.

[0168] To prepare Bi3TaO7 particles, bismuth(III) oxide (Bi2O3) and tantalum(V) oxide (Ta2O5) are mixed in a molar ratio of 3:1. The mixture of bismuth(III) oxide (Bi2O3) and tantalum(V) oxide (Ta2O5) is prepared by grinding and mixing by ball milling in ethanol for more than 24 hours. The prepared mixture is dried for several hours and heat-treated at 800 to 1,200 °C for 4 to 6 hours to form Bi3TaO7 particles. During the calcination process, the oxidation number of Bi increases. The Bi3TaO7 particles formed by calcination are ball-milled once again for more than 24 hours and undergo final drying for 2 hours.

[0169] Next, a step of dispersing Bi3TaO7 particles in a polyol solvent is performed. Dispersion may be performed using ultrasound. As the polyol, at least one selected from the group consisting of ethylene glycol, glycerol, and 1,2-propanediol may be used.

[0170] After dispersing Bi3TaO7 particles in a polyol solvent, an iridium precursor is added. H2IrCl6·xH2O can be used as the iridium precursor.

[0171] After adding an iridium precursor to a polyol solvent in which Bi3TaO7 particles are dispersed, heat treatment is performed to support iridium or iridium oxide on the Bi3TaO7 particles. The heat treatment is performed at 160 to 180 °C for 3 to 4 hours.

[0172] Meanwhile, as the synthesis of Ir particles on Bi3TaO7 particles takes place within the polyol, the Bi ions within the Bi3TaO7 particles, whose oxidation state had increased during the calcination process, are reduced to metallic Bi, and the reduced Bi is doped into Ir or IrO2. When Bi is doped, the OER activity and durability of the oxygen generation electrode catalyst according to the second embodiment are improved, as previously discussed.

[0173] In addition, the oxygen generating electrode catalyst according to the second embodiment has iridium or iridium oxide supported on Bi3TaO7 particles, with the supported iridium content being 25 to 35 wt%. This is a significantly smaller amount of iridium used compared to commercial catalysts, which can improve the economic efficiency of the water electrolysis device by reducing the amount of expensive iridium used.

[0174] Bi3TaO7 particles containing iridium or iridium oxide are recovered by washing three times with a hexane / ethanol mixture and then centrifuging.

[0175] An oxygen-generating catalyst electrode according to a second embodiment manufactured by such a method comprises a Bi3TaO7 support; and iridium or iridium oxide supported on the Bi3TaO7 support. The Bi3TaO7 support has higher electrical conductivity than TiO2.

[0176] The oxygen generating electrode catalyst of the second embodiment can be applied to a water electrolysis device. The water electrolysis device may be characterized in that an oxygen generating electrode catalyst and a hydrogen generating electrode catalyst are arranged on both sides with a membrane in between, so that water is converted into oxygen by electrolysis at the oxygen generating electrode catalyst, and hydrogen is transferred to the hydrogen generating electrode catalyst through the membrane to produce hydrogen, and the oxygen generating electrode catalyst is the oxygen generating electrode catalyst of the second embodiment.

[0177] The oxygen generation electrode catalyst of the second embodiment was actually manufactured, and its physical properties and effects were verified.

[0178] First, Bi3TaO7 was prepared by the solid-state method. Bismuth trioxide (Bi2O3: 99.999%, Sigma Aldrich) and tantalum pentoxide (Ta2O5, 99.99%, Sigma Aldrich) were used as precursors. Bi2O3 and Ta2O5 were mixed in a molar ratio of 3:1 (Bi2O3:Ta2O5) and placed in a polypropylene (PP) bottle containing ethanol and zirconia balls. Subsequently, ball milling was performed for 24 hours. After ball milling, the mixture was dried for 2 hours and then calcined at 900°C for 5 hours. The calcined powder was subjected to final ball milling for another 24 hours, followed by a final drying process for 2 hours.

[0179] Next, an electrode catalyst was synthesized by the polyol method by supporting nanoparticles of Ir or IrO2 at 30 wt% Ir on a Bi3TaO7 support. Bi3TaO7 support (40 mg) was placed in a 50 mL vial with ethylene glycol (20 mL) and sonicated for 30 minutes. Then, an Ir precursor (38.0 mg of H2IrCl6·xH2O for 30 wt% support) was added to the mixture and stirred for 30 minutes. The resulting mixture was heat-treated in an oil bath at 170°C for 3.5 hours. The resulting Ir or IrOx-supported Bi3TaO7 support was washed three times with a hexane / ethanol mixture and collected by centrifugation.

[0180] Figure 12 is a TEM (Transmission Electron Microscopy) image of a Bi3TaO7 support.

[0181] Looking at the Fast Fourier Transform (FFT) pattern located in the upper right corner of Fig. 12, thick ring-shaped diffraction patterns appear instead of a distinct lattice, indicating that the Bi3TaO7 particles have an amorphous structure. Additionally, calculations using the XRD Schrer equation show that the Bi3TaO7 particles have a particle size of 30 to 50 nm.

[0182] FIG. 13 is a TEM image and EDS mapping result of an oxygen generation catalyst electrode according to a second embodiment of the present invention.

[0183] The first and second images in the top row of Fig. 13 are TEM images showing the distribution of Ir or IrO2 particles supported on the surface of a Bi3TaO7 support. It can be seen that the Ir or IrO2 particles have a size of approximately 2–3 nm. The Ir particles are relatively uniformly dispersed without forming aggregates, suggesting a homogeneous reduction and growth process of the Ir precursor during the nanoparticle synthesis process.

[0184] The fourth image in the top row and the images in the bottom row of Fig. 13 are EDS mapping overlays, which visually confirm that the iridium (Ir), bismuth (Bi), tantalum (Ta), and oxygen (O) elements are uniformly distributed on the support and nanoparticles. The EDS mapping results show that the Ir, Bi, Ta, and O elements are evenly distributed, and in particular, it can be confirmed that Ir and Bi are homogeneously distributed near the surface of the Bi3TaO7 support.

[0185] FIG. 14 is a STEM-HAADF (Scanning Transmission Electron Microscopy - High Angle Annular Dark Field) image of an oxygen-generating catalyst electrode according to a second embodiment of the present invention.

[0186] STEM-HAADF (High Angle Annular Dark Field) images detect signals of electrons scattered at high angles after passing through a sample. Since the brightness of the image is proportional to the atomic number (Z), elements with larger atomic numbers appear brighter in the image, and this characteristic is called Z-contrast. Referring to Fig. 14, in the high-resolution STEM-HAADF image, Bi is observed as a bright spot because it is an element with a large atomic number. However, the observed Bis cause localized lattice distortion, indicating that Bi is doped into the lattice.

[0187] Figure 15 shows the results of evaluating the electrochemical characteristics of an oxygen generation catalytic electrode and a commercial electrode catalyst according to the second embodiment of the present invention using Linear Sweep Voltammetry (LSV), Tafel slope, Electrochemical Impedance Spectroscopy (EIS), and Mass Activity. As comparative examples, an IrO2 catalyst from Company A and a TiO2-supported catalyst (IrOx / TiO2) from Company U were used.

[0188] Referring to FIG. 15a, in the linear sweeping voltmetry (LSV) results, the example IrO x The / Bi3TaO7 electrode catalyst exhibited an overpotential of 258 mV, whereas the commercial electrode catalysts IrOx / TiO₂ (Company U) and IrO₂ (Company A) exhibited an overpotential of 293 mV and 333 mV, respectively. This result indicates that the oxygen generation electrode catalyst according to the second embodiment consumes less energy for the oxygen generation reaction (OER) than the commercial electrode catalyst. In other words, the oxygen generation electrode catalyst according to the second embodiment has high electrode catalyst activity and performs an efficient reaction.

[0189] Referring to FIG. 15b, in the Tapefel slope analysis, the example IrO x The / Bi3TaO7 electrode catalyst showed a value of 69.2 mV / dec, while the commercial electrode catalysts IrOx / TiO₂ (Company U) showed 81.3 mV / dec and IrO₂ (Company A) showed 89.2 mV / dec. The Tapel slope analysis results indicate the rate of increase in overpotential required for the electrode catalyst to increase current density; the IrO₂ of the example exhibiting a low Tapel slope x It can be seen that the / Bi3TaO7 electrode catalyst has a faster reaction rate and lower activation energy of the electrode reaction compared to commercial electrode catalysts, resulting in higher efficiency.

[0190] Referring to FIG. 15c, in the electrochemical impedance spectroscopy (EIS) analysis, the example IrO x / Bi3TaO7 electrode catalyst exhibits lower charge transfer resistance compared to commercial electrode catalysts IrOx / TiO₂ (Company U) and IrO₂ (Company A).

[0191] Referring to FIG. 15d, the mass activity measurement results show that the example IrO xThe / Bi3TaO7 electrode catalyst exhibited a mass activity of 680 mA / mg-Ir at 1.55 V. In contrast, the commercial electrode catalysts IrOx / TiO₂ (Company U) showed 73.0 mA / mg-Ir under the same conditions, while IrO₂ (Company A) showed 17.9 mV / dec. The example IrO x The / Bi3TaO7 electrode catalyst exhibited mass activity at least approximately 9 to 35 times higher than commercial electrode catalysts. This result implies that economic feasibility can be secured while reducing the use of expensive iridium. Table 10 below shows IrO x 10 mA / cm² depending on iridium loading in / Bi3TaO7 electrode catalyst 2 This is the result of measuring the voltage at. Overpotential ((293mV @ 10 mA / cm²) based on a commercial catalyst. 2 × was marked if the performance was inferior due to a high overpotential, △ was marked if the performance was equivalent due to a similar overpotential compared to a commercial catalyst, and ○ was marked if the performance was superior due to a low overpotential compared to a commercial catalyst.

[0192]

[0193] Iridium Load (wt%) Overvoltage Performance 10×15×20×25△30○35○40○45△50×

[0194] Referring to Table 10, when the iridium loading in the total catalyst electrode was 20 wt% or less, the overpotential was higher than that of the commercial catalyst, resulting in lower performance; however, when the iridium loading was 25 wt%, the overpotential was similar to that of the commercial catalyst, showing equivalent performance. In other words, despite using a smaller amount of iridium compared to the commercial catalyst, it exhibited performance equivalent to that of the commercial catalyst. Therefore, the lower limit of the iridium loading in the total catalyst electrode may be greater than 20 wt%, preferably 25 wt% or more, and more preferably 30 wt% or more. The upper limit of the iridium loading in the total catalyst electrode may be less than 50 wt%, preferably 45 wt% or less, and more preferably 40 wt% or less.

[0195] FIG. 16 is a graph evaluating the durability of an oxygen-generating electrode catalyst according to a second embodiment of the present invention and a commercial electrode catalyst. The durability evaluation was performed at 10 mA / cm² in a 0.5 M aqueous sulfuric acid (H2SO4) solution under conditions of 25°C. 2 It was performed at a current density and a rotational speed of 1600 rpm.

[0196] Referring to FIG. 16, it was confirmed that the oxygen generating electrode catalyst according to the second embodiment of the present invention has significantly higher durability than a commercial catalyst.

[0197] Figure 17 shows the structures of Bi2O3, Bi3TaO7, and IrO through X-ray Absorption Near Edge Structure (XANES) analysis. x This is the result of measuring the change in the oxidation state of bismuth (Bi) in / Bi3TaO7 (before and after OER reaction), and Fig. 18 is

[0198] Comparing Bi2O3 and Bi3TaO7 in Fig. 17, the oxidation state of bismuth (Bi) increases during the preparation of Bi3TaO7. However, bismuth (Bi) is reduced during the process of supporting iridium (Ir) on the Bi3TaO7 support. Then, as the OER reaction proceeds, IrO x The bismuth (Bi) contained in / Bi3TaO7 is partially oxidized again.

[0199] FIG. 18 is an example of IrO x This is the result of evaluating the bonding and oxidation states of bismuth in the Bi3TaO7 electrode catalyst through Bi L3-edge EXAFS (Extended X-ray Absorption Fine Structure) analysis. Figure 18 shows the Bi2O3 reference material, the Bi3TaO7 support, and IrO2 x / Bi3TaO7 (before and after OER reaction) This compares the state of the electrode catalyst before and after synthesis.

[0200] The Bi2O3 reference material and the Bi3TaO7 support exhibit only Bi-O bonds around 1.6 Å between bismuth (Bi) and oxygen (O). However, IrO x In the / Bi3TaO7 electrode catalyst, a Bi-Ir bond at approximately 2.4 Å is identified prior to synthesis, which means that Bi was partially reduced during the polyol synthesis process and then doped into iridium (Ir) or iridium oxide (IrO2). The Bi-Ir bond is maintained even after the OER reaction.

[0201] Figure 19 shows the synthesized Ir electrode catalyst (Ir black) and the IrO of the example through X-ray Absorption Near Edge Structure (XANES) analysis. x This is the result of measuring the change in the Ir electronic structure of the / Bi3TaO7 electrode catalyst.

[0202] As shown in Fig. 19, a commercial electrode catalyst (Ir black) and the IrO of the example were used before and after the OER reaction. x It can be seen that the absorption peak position of both the / Bi3TaO7 electrode catalysts shifts slightly. However, compared to the commercial electrode catalyst (Ir black), where the peak position shifts by 0.88 eV, the IrO of the example x The / Bi3TaO7 electrode catalyst shifted by only 0.26 eV, indicating a very small change. In conclusion, the IrO of the example x The Bi3TaO7 electrode catalyst suppresses excessive oxidation of Ir even during the OER reaction, thereby improving the long-term stability of the catalyst electrode.

[0203] To summarize the details regarding the oxygen generation electrode catalyst according to the second embodiment described above, IrO x The / Bi3TaO7 electrode catalyst has the following effects.

[0204] First, the oxygen generation electrode catalyst according to the second embodiment secures excellent performance with a smaller amount of iridium compared to commercial catalysts, thereby improving the economic efficiency of the water electrolysis device.

[0205] Second, the oxygen generation electrode catalyst according to the second embodiment exhibits lower overpotential and higher mass activity than commercial catalyst electrodes, and thus has superior electrochemical activity in the oxygen generation reaction compared to commercial catalysts.

[0206] Third, the oxygen generating electrode catalyst according to the second embodiment exhibits excellent durability, with a very small increase in potential compared to commercial catalysts even during long-term operation.

[0207] Fourth, in the oxygen generation electrode catalyst according to the second embodiment, when Ir is supported on a Bi3TaO7 support, Bi present in the support is doped into the Ir, thereby controlling the vacancies of Ir and stably controlling the oxidation state of Ir during the electrochemical reaction, which increases the stability of the catalyst during the OER process and prevents long-term performance degradation.

[0208] Fifth, the Bi3TaO7 support of the oxygen generation electrode catalyst according to the second embodiment has superior electrical conductivity compared to the existing TiO2 support, allowing for smooth charge transfer and further improving the catalytic performance of the electrode reaction.

[0209] Next, we will examine the oxygen generation electrode catalyst according to the third embodiment.

[0210] FIG. 20 schematically illustrates each step of the method for manufacturing an oxygen-generating electrode catalyst according to the third embodiment of the present invention.

[0211] A method for manufacturing an oxygen-generating electrode catalyst according to a third embodiment of the present invention comprises the steps of: preparing a Bi2Te3 hollow nanowire support as a support; dispersing the Bi2Te3 hollow nanowire support in a polyol solvent; adding an iridium precursor to a solution in which the support is dispersed; performing heat treatment to support iridium metal or iridium oxide on the Bi2Te3 hollow nanowire support; and recovering the Bi2Te3 hollow nanowire support supported with iridium metal or iridium oxide.

[0212] First, a Bi2Te3 hollow nanowire support is prepared. The preparation of the Bi2Te3 hollow nanowire support includes the steps of: preparing a tellurium precursor solution by mixing TeO2, an additive, and a solvent; performing a first heat treatment on the tellurium precursor solution; adding hydrazine to the first heat-treated tellurium precursor solution; adding a bismuth precursor to the tellurium precursor solution containing hydrazine to form a mixture; and performing a second heat treatment on the mixture.

[0213] In the step of preparing the tellurium precursor solution, sodium hydroxide and polyvinylpyrrolidone may be used as additives, and ethylene glycol may be used as a solvent. Sodium hydroxide may be included in an amount of 62 to 104 parts by weight per 100 parts by weight of TeO2, and polyvinylpyrrolidone may be included in an amount of 94 to 156 parts by weight per 100 parts by weight of TeO2. Sodium hydroxide serves to reduce TeO2, and polyvinylpyrrolidone prevents aggregation between particles and helps nanowires grow in a uniform shape when formed.

[0214] Next, the tellurium precursor solution is subjected to a first heat treatment. Before performing the first heat treatment, the tellurium precursor solution can be sonicated for at least 10 minutes to completely dissolve the TeO2 and additives.

[0215] The first heat treatment of the tellurium precursor solution can be performed in an oil bath at 160 to 180°C for 30 to 90 minutes.

[0216] The thickness and end shape of the tellurium nanowires produced by controlling the sodium hydroxide content and the first heat treatment temperature as previously discussed are determined. In order to produce Bi2Te3 hollow nanowires, the average thickness of the nanowires produced after the first heat treatment must be 60 to 120 nm, preferably 70 to 90 nm, and the end shape must have a wire form with a constant diameter maintained to the end.

[0217] After the first heat treatment is completed, it can be cooled in a water bath for 5 to 10 minutes.

[0218] Hydrazine is added to the first heat-treated tellurium precursor solution. The hydrazine is intended to form a hollow structure, that is, a hollow structure, of the nanowire. The content of the added hydrazine may be greater than 0.187 mM and less than 0.936 mM, preferably 0.374 to 0.749 mM, and more preferably 0.561 to 0.759 mM.

[0219] A bismuth precursor solution is prepared separately. The bismuth precursor is dissolved in a solvent. Bismuth nitrate pentahydrate can be used as the bismuth precursor, and ethylene glycol can be used as the solvent. During dissolution, ultrasonic treatment is performed for at least 10 minutes to ensure that the bismuth precursor is completely dissolved.

[0220] A bismuth precursor solution prepared with hydrazine is added to form a mixture. The elemental ratio of bismuth to tellurium in the mixture is set to 2:3.

[0221] The mixture is subjected to a second heat treatment. The second heat treatment may be performed in an oil bath at 160 to 180°C for 90 to 150 minutes.

[0222] The fabricated Bi2Te3 hollow nanowire support is recovered by washing and drying.

[0223] Next, a step of supporting iridium or iridium oxide on a Bi2Te3 hollow nanowire support is performed. During this process, some of the virismu is doped into the iridium or iridium oxide.

[0224] A Bi2Te3 hollow nanowire support is dispersed in a polyol solvent. The polyol solvent may be at least one selected from the group consisting of ethylene glycol, glycerol, and 1,2-propanediol. After adding the Bi2Te3 hollow nanowire support to the polyol solvent, it is sonicated for 10 to 20 minutes.

[0225] After dispersing the Bi2Te3 hollow nanowire support in a polyol solvent, an iridium precursor is added to the dispersion to prepare a mixture. H2IrCl6·xH2O can be used as the iridium precursor.

[0226] The mixture undergoes a third heat treatment. The third heat treatment may be performed in an oil bath at 160 to 180°C for 150 to 210 minutes.

[0227] The manufactured iridium or iridium oxide-supported Bi2Te3 hollow nanowire support is recovered by drying after washing.

[0228] An oxygen-generating catalyst electrode according to a third embodiment manufactured by such a method comprises a supported Bi2Te3 hollow nanowire support and iridium or iridium oxide supported on the supported Bi2Te3 hollow nanowire support.

[0229] The oxygen generating electrode catalyst of the third embodiment can be applied to a water electrolysis device. The water electrolysis device may be characterized in that an oxygen generating electrode catalyst and a hydrogen generating electrode catalyst are arranged on both sides with a membrane in between, so that water is converted into oxygen by electrolysis at the oxygen generating electrode catalyst, and hydrogen is transferred to the hydrogen generating electrode catalyst through the membrane to produce hydrogen, and the oxygen generating electrode catalyst is the oxygen generating electrode catalyst of the third embodiment.

[0230] The oxygen generation electrode catalyst of the third embodiment was actually manufactured, and its physical properties and effects were verified.

[0231] Bi2Te3 nanowire support materials were prepared via a solution-phase method using hydrazine as a reducing agent. First, 0.04 g, 0.12 g, and 0.20 g of sodium hydroxide, 0.24 g of polyvinylpyrrolidone, and 0.192 g of tellurium dioxide were dissolved in 20 mL of ethylene glycol. The mixture was sonicated for 10 minutes to completely dissolve it. After sonication, the resulting homogeneous solution was heated in an oil bath at 170 °C for 1 hour while stirring. Subsequently, the solution was cooled in a water bath for 5 minutes, and then hydrazine at concentrations of 0.187 mM, 0.374 mM, 0.561 mM, 0.749 mM, 0.936 mM, and 1,123 M was injected, respectively, to control the hollowness of the nanowires. Separately, 0.388 g of bismuth nitrate pentahydrate was dissolved in 5 mL of ethylene glycol and sonicated for 10 minutes. This bismuth solution was added to the tellurium precursor solution after the injection of hydrazine hydrate. Subsequently, the resulting solution was heated again in an oil bath at 170 °C for 2 hours. The prepared support was washed three times by centrifugation using a hexane / ethanol mixture. Finally, the support was dried overnight in an oven at 60 °C.

[0232] Next, a catalyst supported by 50 wt% iridium (Ir) nanoparticles on Bi2Te3 nanowires was prepared via the polyol method. First, 40 mg of the support was dissolved in 20 mL of ethylene glycol and sonicated for 10 minutes. Subsequently, 721 μL of the iridium precursor (H2IrCl6·xH2O, 12.29 g per 100 mL) was added to the solution. The mixture was heated in an oil bath at 170 °C for 3 hours, followed by washing three times with a hexane / ethanol mixture. Finally, the resulting solution was dried overnight in a 60 °C oven.

[0233] Figure 21 shows the results of measuring the shape and thickness of nanowires manufactured according to the synthesis conditions of TeO2 nanowires.

[0234] Referring to Fig. 21, the shape and thickness of the nanowires produced are controlled according to the heat treatment temperature and the content of NaOH.

[0235] The shapes of nanowires can be distinguished into tip shapes where the ends gradually thin, wire shapes where the wire diameter is maintained to the end, and broad shapes where the ends become blunt; however, to manufacture hollow nanowires, it was preferable for the end shape of the nanowire to be wire shape. In addition, to manufacture hollow nanowires, the average thickness of the nanowire must be 60 to 120 nm, preferably 70 to 90 nm.

[0236] Figure 22 shows the EDS measurement results when 0.187 mM of hydrazine is used in the manufacturing process of Bi2Te3 nanowires, Figure 23 shows the EDS measurement results when 0.374 mM of hydrazine is used in the manufacturing process of Bi2Te3 nanowires, and Figure 24 shows the EDS measurement results when 0.561 mM of hydrazine is used in the manufacturing process of Bi2Te3 nanowires.

[0237] As shown in Figure 22, when 0.187 mM of hydrazine was used in the fabrication process of Bi2Te3 nanowires, a hollow structure with an empty interior was not formed in the nanowires.

[0238] In contrast, as shown in Figures 23 and 24, when 0.374 to 0.561 mM of hydrazine was used in the fabrication process of Bi2Te3 nanowires, a translucent appearance was observed inside the nanowires, confirming that a hollow structure was formed in which the inside of the nanowires was empty.

[0239] For reference, when more than 0.936 mM of hydrazine was used during the manufacturing process of Bi2Te3 nanowires, the nanowires broke and became nanoparticles.

[0240] Figure 25 shows the EDS measurement results of an oxygen-generating electrode catalyst prepared by supporting iridium on Bi2Te3 nanowires prepared using hydrazine at 0.187 mM, 0.374 mM, and 0.561 mM.

[0241] When 0.187 mM of hydrazine was used during the nanowire manufacturing process, it was observed that iridium was mainly concentrated at the boundaries of the nanowire. This is because a hollow structure was not formed, so a large amount of bismuth and tellurium was observed in the center, and a relatively small amount of iridium was observed in the center, and iridium was coated separately on the surface of the nanowire to a certain thickness.

[0242] When 0.374 to 0.749 mM of hydrazine was used in the manufacturing process of Bi2Te3 nanowires, it is identifiable even in the central part, and as a hollow structure is formed, iridium is uniformly formed on the inner and outer sides of the hollow nanowire, suggesting that bismuth is doped into the iridium.

[0243] Figure 26 shows the results of evaluating the electrochemical reaction area of ​​an oxygen-generating electrode catalyst prepared by supporting iridium on Bi2Te3 nanowires prepared using 0.187 mM and 0.561 mM of hydrazine.

[0244] Figure 26 shows the double-layer capacitance of the catalytic electrode according to hydrazine concentration. An Ir50@Bi2Te3 sample using 0.561 mM hydrazine and loaded with 50 wt% iridium of the total catalytic electrode exhibits a capacitance approximately twice as high as that of the sample using 0.187 mM. Specifically, the sample using 0.561 mM hydrazine shows a capacitance of approximately 5.5 mF / cm², while the sample using 0.187 mM hydrazine shows a capacitance of approximately 2.2 mF / cm². This result implies that a larger electrochemically active surface area is provided by the hollow structure formed when the hydrazine concentration is high.

[0245] Figure 27 compares the electrochemical performance of a Bi2Te3-based iridium (Ir) catalyst electrode and a commercial Ir catalyst electrode.

[0246] Referring to Fig. 27, the Ir50 Bi2Te3 catalyst electrode exhibited the lowest overpotential of 267 mV at a hydrazine concentration of 0.561 mM, demonstrating the best performance. In contrast, the overpotential of the commercial Ir catalyst electrode was 275 mV, showing lower performance compared to the Ir50 Bi2Te3 catalyst electrode (hydrazine concentration: 0.561 mM). In the case of the Bi2Te3 catalyst electrode (hydrazine concentration: 0.374 mM), performance was slightly inferior to that of the commercial Ir catalyst electrode; however, since the iridium usage in the example is only half that of the commercial catalyst, it can be seen that it possesses high economic efficiency. However, when the hydrazine concentration was insufficient (hydrazine concentration: 0.187 mM), performance was low because a hollow structure was not formed in the support, and when the hydrazine concentration was high (hydrazine concentration: 1.123 mM), performance decreased as the nanowires broke and became nanoparticles.

[0247] Table 10 below shows the results of measuring overpotential according to hydrazine concentration during the fabrication process of Bi2Te3 nanowires. × was marked when the overpotential was high compared to commercial catalysts, indicating inferior performance; △ was marked when the overpotential was similar compared to commercial catalysts, indicating equivalent performance; and ○ was marked when the overpotential was low compared to commercial catalysts, indicating superior performance.

[0248] Hydrazine [mM] 0.187 0.374 0.561 0.749 0.936 1.123 Support Shape: Nanowire, Partially Hollow Nanowire, Hollow Nanowire, Hollow Nanowire, Nanoparticle, Nanoparticle OER Performance ×△○○××

[0249] Referring to the contents of Table 11, the concentration of hydrazine in the manufacturing process of Bi2Te3 nanowires may be greater than 0.187 mM and less than 0.936 mM, preferably 0.374 to 0.749 mM, and more preferably 0.561 to 0.759 mM.

[0250] Table 12 below shows 10 mA / cm² according to the iridium loading amount during the fabrication process of Bi2Te3 nanowires. 2 This is the result of measuring the voltage at. In Table 11, the Bi2Te3 nanowires used as examples had a hydrazine concentration of 0.561 mM during the manufacturing process. Based on a commercial catalyst (overvoltage 275 mA @ 10 mA / cm²) 2 × was marked if the performance was inferior due to a high overvoltage, △ was marked if the performance was equivalent because the overvoltage was similar to that of a commercial catalyst, and ○ was marked if the performance was superior due to a low overvoltage compared to a commercial catalyst.

[0251]

[0252] Iridium Load (wt%) Overvoltage Performance 20×25×30△35○40○50○60○70○

[0253] Referring to Table 12, when the iridium loading in the total catalyst electrode was 30 wt% or less, the overpotential was higher than that of the commercial catalyst, resulting in lower performance; however, when the iridium loading was 40 wt%, the overpotential was similar to that of the commercial catalyst, demonstrating equivalent performance. In other words, despite using a smaller amount of iridium compared to the commercial catalyst, it exhibited performance equivalent to that of the commercial catalyst. Therefore, the lower limit of the iridium loading in the total catalyst electrode may be greater than 25 wt%, preferably 35 wt% or more, and more preferably 40 wt% or more. Although there is no specific limit on the upper limit of the iridium loading in the total catalyst electrode, it may be 70 wt% or less, preferably 60 wt% or less, to ensure economic feasibility. Figure 28 shows the results of measuring the mass activity among the electrochemical characteristics of the oxygen generation electrode catalysts of the examples and comparative examples.

[0254] As a result of measuring mass activity, which indicates catalytic activity relative to iridium loading, at 1.55 V (vs. RHE), the Ir50@Bi2Te3 hollow nanowire catalyst electrode synthesized under 0.561 mM hydrazine conditions showed 215.6 mA / mg Ir It showed the highest value. This is compared to a commercial iridium catalyst electrode (59.6 mA / mg Ir This figure is more than three times improved compared to ). In other words, by using the oxygen generating electrode of the third embodiment, the amount of iridium used can be reduced, thereby increasing the economic efficiency of the water electrolysis device.

[0255] Figure 29 shows the results of evaluating the long-term durability among the electrochemical characteristics of the oxygen generation electrode catalysts of the examples and comparative examples.

[0256] As a result of evaluating the stability of the catalyst at a current density of 10 mA / cm², the Ir50@Bi2Te3 hollow nanowire catalyst electrode synthesized under hydrazine 0.561 mM conditions maintained activity for the longest period of 4.7 hours. This indicates approximately 3 times improved stability compared to a commercial iridium catalyst (1.9 hours).

[0257] To summarize the details regarding the oxygen generation electrode catalyst according to the third embodiment described above, the Ir50@Bi2Te3 hollow nanowire catalyst electrode has the following effects.

[0258] First, the oxygen generating electrode catalyst according to the third embodiment supports iridium or iridium oxide on a hollow nanowire support formed of bismuth tellurium, thereby achieving performance equivalent to or better than that of a commercial catalyst by loading only half the amount of iridium compared to a commercial catalyst. Therefore, the economic efficiency of water electrolysis can be improved by using the oxygen generating electrode catalyst according to one embodiment of the present invention.

[0259] Second, the oxygen-generating electrode catalyst according to the third embodiment has an effective reaction area (ECSA) that is increased by approximately twofold by forming the support as a hollow nanowire structure. Accordingly, this improves the accessibility of active sites in electrochemical reactions, thereby contributing significantly to increasing the reaction rate and total reaction amount.

[0260] Third, the oxygen generating electrode catalyst according to the third embodiment has improved durability because structural collapse or deterioration of activity is minimized even during long-term operation, thanks to the chemical and physical stability of the bismuth tellurium used as a support.

[0261] The oxygen-generating electrode catalyst described above can be applied not only to PEM water electrolysis devices but also to other electrochemical energy storage or generation technologies that utilize hydrogen generation as a reaction mechanism (e.g., chloro-alkali processes, fuel cells, metal-oxygen batteries, etc.).

[0262] The scope of protection of the present invention is not limited to the description and expression of the embodiments explicitly described above. Furthermore, it is added once again that the scope of protection of the present invention cannot be limited by obvious changes or substitutions in the technical field to which the present invention belongs.

Claims

1. As an oxygen-generating electrode catalyst containing bismuth (Bi), An oxygen evolution electrode catalyst characterized by the above-mentioned bismuth being present together with iridium or an iridium compound to provide enhanced durability in the oxygen evolution reaction.

2. In Paragraph 1, An oxygen-generating electrode catalyst characterized by the above-mentioned bismuth existing in a form doped into iridium oxide.

3. In Paragraph 2, An oxygen-generating electrode catalyst characterized by having a doped bismuth content exceeding 1.1 at% and less than 11.1 at% relative to the total number of atoms of iridium (Ir), bismuth (Bi), and oxygen (O).

4. In Paragraph 2, An oxygen-generating electrode catalyst characterized by the ratio of oxygen elements (O / (Ir+O)) contained in the bismuth-doped iridium oxide being greater than 69.5% and less than 88.2%.

5. In Paragraph 2, Ir of the above bismuth-doped iridium oxide 4+ wa Ir 3+ The elemental ratio of (Ir 4+ / Ir 3+ Oxygen evolution electrode catalyst characterized by having a value greater than that of non-bismuth-doped iridium oxide.

6. In Paragraph 1, Bismuth Tantalum Oxide (Bi x Ta y O z An oxygen-generating electrode catalyst characterized by having iridium or iridium oxide supported on a support.

7. In Paragraph 6, The above Bi x Ta y O z The support is Bi3TaO7, and The above Bi3TaO7 support has an amorphous structure, and An oxygen generating electrode catalyst characterized by having an iridium content greater than 20 wt% and less than 50 wt%.

8. In Paragraph 1, Bismuth Tellurium (Bi x Te y Oxygen-generating electrode catalyst characterized by iridium or iridium oxide being supported on a nanostructure.

9. In Paragraph 8, An oxygen-generating electrode catalyst characterized in that the above-mentioned bismuth tellurium nanostructure is a Bi2Te3 hollow nanowire.

10. In Paragraph 8, An oxygen-generating electrode catalyst characterized by the average thickness of the above-mentioned hollow nanowires being 60-120 nm.

11. In Paragraph 8, An oxygen generating electrode catalyst characterized by having a supported iridium content of more than 25 wt%.

12. A water electrolysis device comprising an oxygen generating electrode and a hydrogen generating electrode positioned on both sides with a membrane in between, A water electrolysis device characterized in that the oxygen generating electrode comprises an oxygen generating electrode catalyst containing bismuth (Bi), wherein the bismuth is present together with iridium or an iridium compound to provide enhanced durability in the oxygen generating reaction.

13. In Paragraph 12, The above oxygen generating electrode catalyst is a water electrolysis device characterized by the fact that the bismuth exists in a form doped in iridium oxide.

14. In Paragraph 12, The above oxygen generating electrode catalyst is bismuth tantalum oxide (Bi x Ta y O z A water electrolysis device characterized by having iridium or iridium oxide supported on a support.

15. In Paragraph 12, The above oxygen evolution electrode catalyst is bismuth tellurium (Bi x Te y A water electrolysis device characterized by iridium or iridium oxide being supported on a nanostructure.

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