Electrocatalyst for polymer electrolyte membrane (PEM) water electrolysis, method for preparing same, PEM water electrolysis electrode comprising same, and PEM water electrolysis unit comprising same

Abstract

An electrocatalyst for water electrolysis of a polymer electrolyte membrane (PEM), the electrocatalyst comprising an iridium-based catalyst wherein the iridium-based catalyst is a core-shell particle, the core comprising an iridium metal, the shell comprising an iridium metal, and the shell comprising an iridium metal, a method for preparing the electrocatalyst, a PEM water electrolysis electrode comprising the electrocatalyst, and a PEM water electrolysis unit comprising the same are presented. And the shell contains an iridium tin composite oxide. The electrocatalyst for PEM water electrolysis exhibits improved dispersibility and durability. In addition, electrodes comprising such electrocatalysts exhibit improved oxygen evolution reaction (OER) activity.

Description

Technical Field

[0001] This disclosure relates to electrocatalysts for polymer electrolyte membrane (PEM) water electrolysis, methods for preparing the same, PEM water electrolysis electrodes comprising the same, and PEM water electrolysis units comprising the same.

[0002] The following describes two South Korean national projects supported by the South Korean government that are related to this invention.

[0003] Project unique number 1415186363

[0004] Project serial number 20020437

[0005] government departments Ministry of Trade, Industry and Energy (MOTIE)

[0006] Specialized project management organization Korea Planning & Evaluation of Industrial Technology (KEIT)

[0007] Research Business Name Nano-integrated innovative product technology development

[0008] Project Name Development of fuel cell module technology for hydrogen electric vehicles based on the production of platinum alloy nanocatalysts with a platinum loading of 0.2 g / kW or less in membrane electrode assemblies (MEAs).

[0009] Supervisory bodies THE CARBON STUDIO INC.

[0010] Research period January 1, 2023 to December 31, 2025

[0011] Project unique number 1415185115

[0012] Project serial number 20022451

[0013] government departments MOTIE

[0014] Specialized project management organization KEIT

[0015] Research Business NameMaterials and Component Technology Development - Packaging Types

[0016] Project Name Development of production technologies for electrolyte membranes and catalysts for PEM water electrolysis

[0017] Supervisory bodies CHEMTROS CO.,LTD.

[0018] Research period January 1, 2023 to December 31, 2025 Background Technology

[0019] Active and novel research and development is being conducted in the energy sector, in which electricity generated from renewable energy sources such as solar, wind and tidal power is used to produce hydrogen from water through electrolysis and to store the hydrogen, and when needed, such stored hydrogen is supplied to fuel cells for use as electricity.

[0020] Water electrolysis, one of several methods for producing hydrogen, can be categorized into alkaline water electrolysis, solid oxide water electrolysis, or PEM water electrolysis. Of all these, PEM water electrolysis is characterized by its operation at relatively low temperatures and the use of pure water without any corrosive solutions, resulting in higher hydrogen production efficiency and the production of high-purity hydrogen compared to other water electrolysis methods, offering economic advantages.

[0021] In PEM water electrolysis, it is necessary to develop hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts to initiate reactions in the membrane electrode assembly (MEA), a key component. In particular, oxygen overpotential significantly reduces efficiency in water electrolysis; therefore, developing novel catalysts capable of lowering the overpotential of OER catalysts is crucial for commercialization.

[0022] Currently available iridium oxides (IrO2) (representative OER catalysts) vary in activity and durability depending on their oxygen arrangement. Amorphous iridium oxides with irregular oxygen arrangements exhibit excellent catalytic performance, but operate in acidic atmospheres due to the nature of PEM water electrolysis. For this reason, some iridium dissolves in water, thus reducing the durability of such catalysts. Furthermore, crystalline iridium oxides, prepared at high temperatures, exhibit poor dispersion on the support, resulting in low catalytic activity, but such catalysts exhibit excellent durability. To achieve both high catalytic activity and durability, it is necessary to develop new catalyst structures for IrO2 with high dispersion on the support, reduced particle size, and high crystallinity.

[0023] Furthermore, technologies that satisfy both of these factors—namely, reducing the size of the physical particles and improving the crystallinity of iridium oxides through alloying—have not yet been developed. Therefore, existing known catalysts cannot achieve satisfactory levels of activity and durability, implying a need for improvement. Summary of the Invention

[0024] This disclosure aims to provide novel electrocatalysts for PEM water electrolysis that exhibit improved OER activity and durability.

[0025] Furthermore, this disclosure aims to provide a method for preparing the aforementioned electrocatalyst for PEM water electrolysis.

[0026] Furthermore, this disclosure aims to provide a PEM water electrolysis electrode comprising the aforementioned PEM water electrolysis electrocatalyst and a PEM water electrolysis unit comprising thereto.

[0027] To achieve the above objectives, an electrocatalyst for PEM water electrolysis is provided, the electrocatalyst comprising an iridium-based catalyst, wherein the iridium-based catalyst is a core-shell particle, the core comprising iridium metal and the shell comprising an iridium-tin composite oxide.

[0028] To achieve another objective, a method for preparing the aforementioned electrocatalyst for PEM water electrolysis is provided, the method comprising the steps of: dispersing a support in a polyol to prepare a support dispersion; mixing an iridium precursor and a tin precursor with the polyol to obtain a precursor mixture; mixing the support dispersion with the precursor mixture to prepare a first mixture; subjecting the first mixture to a first heat treatment to prepare a catalyst precursor comprising iridium metal and tin oxide particles; and, after washing and drying the catalyst precursor, performing a second heat treatment in an oxidizing gas atmosphere, wherein the iridium precursor and the tin precursor are mixed in a molar ratio in the range of 1:0.33 to 0.50.

[0029] The first heat treatment is carried out at a temperature ranging from 200°C to 550°C. Furthermore, the oxidizing gas atmosphere is, for example, air, oxygen, or a combination thereof. The second heat treatment is carried out at a higher temperature than the first heat treatment, and may be carried out at a temperature ranging from 350°C to 600°C.

[0030] To achieve another objective, a PEM water electrolysis electrode comprising the aforementioned PEM water electrocatalyst is provided.

[0031] To achieve yet another objective, a PEM water electrolysis unit is provided, comprising PEM and a PEM water electrolysis electrode located on a surface of the PEM, the PEM water electrolysis electrode containing the aforementioned electrocatalyst for PEM water electrolysis.

[0032] Electrodes may include anodes.

[0033] According to this disclosure, the electrocatalyst for PEM water electrolysis exhibits improved dispersibility and durability. PEM water electrolysis electrodes containing such electrocatalysts exhibit improved OER activity. When using such a water electrolysis electrode, PEM water electrolysis units exhibiting improved unit performance can be manufactured.

[0034] However, the effects of this disclosure are not limited to those described above and may include other effects contemplated by the technical features of this disclosure, even if not explicitly described herein. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the core-shell structure of the electrocatalyst for PEM water electrolysis according to this disclosure;

[0036] Figure 2 This is a flowchart describing a method for preparing an electrocatalyst for PEM water electrolysis according to the present disclosure;

[0037] Figure 3 The X-ray diffraction (XRD) spectra of the catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2 are shown.

[0038] Figure 4A , 4B Images 4C, 4D, 5A, 5B, 5C, and 5D show transmission electron microscopy (TEM) images of the catalysts according to Examples 1 and 2 and Comparative Examples 1 and 2, wherein... Figure 4A and 4B The images shown are TEM images of the state before and after the second heat treatment during the preparation process of the electrocatalyst in Example 1. Figure 4C and 4D The images shown are TEM images of the state before and after the second heat treatment during the preparation process of the electrocatalyst in Example 2. Figure 5A and 5B The images shown are TEM images of the state before and after the second heat treatment during the preparation process of the electrocatalyst in Comparative Example 1, respectively. Figure 5C and 5D The images show the state before and after the second heat treatment during the preparation process of the electrocatalyst in Comparative Example 2.

[0039] Figure 6 This is a graph showing the voltage change as a function of current density in a PEM water electrolysis unit equipped with electrodes containing the corresponding electrocatalysts according to Examples 1 and 2 and Comparative Examples 1 and 2; and

[0040] Figure 7The structure of a water electrolysis unit having a MEA for PEM water electrolysis is schematically shown according to this disclosure. Detailed Implementation

[0041] The following describes an electrocatalyst for PEM water electrolysis according to one embodiment, a method for preparing the same, a PEM water electrolysis electrode comprising the same, and a PEM water electrolysis unit comprising the same.

[0042] However, this disclosure may be embodied in many different forms and is therefore not limited to the implementation schemes set forth herein.

[0043] In this disclosure, median particle size refers to "D50," which represents the particle size at which 50% of the total number of particles accumulates in a cumulative distribution curve arranged from smallest to largest, where the total number is defined as 100%. D50 can be measured by methods known to those skilled in the art and can be measured, for example, using a particle size analyzer or by TEM or scanning electron microscopy (SEM) images. As an example of another method for measuring median particle size, it can be readily obtained by calculation using a dynamic light scattering-based measuring device, followed by data analysis to count the number of particles in each size range.

[0044] Furthermore, the median particle size in this disclosure can be measured using a scanning electron microscope or a transmission electron microscope.

[0045] According to this disclosure, the electrocatalyst for PEM water electrolysis may comprise an iridium-based catalyst, wherein the iridium-based catalyst is a core-shell particle, the core comprising iridium metal and the shell comprising an iridium-tin composite oxide.

[0046] PEM water electrolysis uses electrical energy to produce hydrogen and oxygen through oxidation and reduction, as shown in reaction formulas 1 and 2 below.

[0047] <Reaction Formula 1>

[0048] Cathode: 4H + +4e - →2H2

[0049] <Reaction 2>

[0050] Anode: 2H₂O → O₂ + 4H₂O + +4e -

[0051] According to reaction equation 1, H is generated at the anode. + Ions move to the cathode via the PEM.

[0052] In PEM water electrolysis, the electrocatalyst used in PEM water electrolysis according to this disclosure is an OER catalyst, wherein the core contains iridium metal and the shell contains an iridium-tin composite oxide. The iridium-tin composite oxide can be referred to as an iridium oxide-tin oxide (IrSnO2) alloy.

[0053] The electrocatalyst for PEM water electrolysis may also include a support. As a support, any material having a structure on which an iridium-based catalyst can be supported can be used.

[0054] According to one implementation scheme, the carrier may contain a ceramic support.

[0055] Examples of such ceramic supports may include antimony-doped tin oxide (Sb-doped tin oxide, ATO), alumina (Al2O3), titanium dioxide (TiO2), zirconium oxide (ZnO2), or combinations thereof. According to one embodiment, the support is ATO.

[0056] Based on 100 parts by weight of the support, the iridium-based catalyst in the electrocatalyst for PEM water electrolysis can be included in the following amounts: 10 to 90 parts by weight, 20 to 90 parts by weight, 20 to 85 parts by weight, 30 to 85 parts by weight, 30 to 80 parts by weight, or 30 to 70 parts by weight. When the amount of iridium-based catalyst in the electrocatalyst falls within the aforementioned range, the particle size of the iridium-based catalyst is uniform. Furthermore, the iridium-based catalyst is uniformly present on the support without agglomeration, thus exhibiting excellent dispersibility and improved durability. In addition, the OER activity of the electrocatalyst is improved, and based on this, PEM water electrolysis electrodes and PEM water electrolysis units exhibiting improved durability can be manufactured.

[0057] The specific surface area of ​​the carrier is, for example, 5m². 2 / g to 1000m 2 / g, 10m 2 / g to 800m 2 / g, or 20m 2 / g to 600m 2 Within the range of / g.

[0058] The electrocatalyst disclosed herein forms a core containing iridium metal to minimize the aggregation of iridium-based catalyst particles within the support and improve the dispersibility of the support. Furthermore, when iridium is oxidized to iridium oxide (IrO... x When ), tin oxide (SnO) forms on the nucleus. x The oxides are alloyed to increase their crystallinity, thus yielding core-shell particles that exhibit improved performance and durability.

[0059] According to one embodiment, based on 100 parts by weight of the total PEM water electrolysis electrocatalyst, iridium metal can be included in the core of the PEM water electrolysis electrocatalyst in an amount ranging from 60 to 76 parts by weight, 62 to 76 parts by weight, 63 to 75 parts by weight, or 65 to 75 parts by weight. Based on 100 parts by weight of the total PEM water electrolysis electrocatalyst, iridium-tin composite oxide can be included in the shell in an amount ranging from 24 to 40 parts by weight, 25 to 38 parts by weight, 25 to 37 parts by weight, or 25 to 35 parts by weight. When the amount of iridium metal exceeds the above ranges, the particle size of the iridium-based catalyst decreases, but the amount of iridium oxide present in the shell may be relatively small, resulting in reduced OER activity. Furthermore, when the amount of iridium-tin oxide in the shell exceeds the above ranges, the OER activity of the iridium oxide increases, but the particle dispersion may deteriorate, leading to reduced activity and durability.

[0060] The iridium-tin composite oxide, serving as the outermost shell of the electrocatalyst, is a complex comprising iridium oxide and tin oxide. Based on 100 moles of iridium, tin can be included in the iridium-tin composite oxide in amounts ranging from 33 to 50 moles, 34 to 48 moles, 35 to 45 moles, 37 to 45 moles, or 39 to 45 moles. When the amount of tin falls below the aforementioned range, the crystallinity of the iridium oxide may decrease, leading to a reduction in the OER activity of the electrocatalyst. Furthermore, when the amount of tin exceeds the aforementioned range, the amount of iridium oxide exhibiting activity on the surface may be small, resulting in a reduction in the OER activity of the electrocatalyst.

[0061] According to one embodiment, the iridium-tin composite oxide shell is a composite comprising iridium oxide and tin oxide, and based on 100 parts by weight of iridium oxide, the tin oxide is included in the composite in an amount ranging from 33 to 50 parts by weight, 34 to 48 parts by weight, 35 to 45 parts by weight, 37 to 45 parts by weight, or 39 to 45 parts by weight. When the amount of tin oxide falls within the above range, the electrocatalyst for PEM water electrolysis exhibits improved OER activity and durability.

[0062] According to another embodiment, the iridium-tin oxide contained in the shell may also contain a metal dopant. Examples of such dopants include Sb, Nb, Ta, Bi, W, In, or combinations thereof. Based on 100 parts by weight of iridium-tin oxide, the metal dopant may be included in an amount of 10 parts by weight or less, 5 parts by weight or less, or in an amount ranging from 0.01 parts by weight to 5 parts by weight. By including this metal dopant, the electrocatalyst can exhibit improved conductivity.

[0063] The PEM water electrolysis catalyst according to this disclosure can improve the dispersion of core-shell structured catalyst particles within the support by the presence of iridium metal within them, thereby physically enhancing catalytic activity by reducing particle size. Furthermore, the iridium-tin composite oxide catalyst present on the surface can significantly increase the crystallinity of iridium oxide (which has excellent chemical activity). Therefore, when using the electrocatalyst according to this disclosure, both catalytic activity and durability can be achieved simultaneously.

[0064] The median particle size of iridium-based catalysts with core-shell structures can range from 1 nm to 20 nm. In this case, the median particle size of the core particles can range from 0.5 nm to 10 nm or from 1 nm to 10 nm. When the median particle size of the iridium-based catalyst and the median particle size of the core particles fall within the corresponding ranges above, electrocatalysts exhibiting improved OER activity and durability can be prepared.

[0065] Figure 1 The structure of an electrocatalyst for PEM water electrolysis according to one embodiment is illustrated schematically.

[0066] The electrocatalyst 10 has a structure comprising a core 11 and a shell 12 located on the core 11. The core 11 may contain iridium metal, and the shell 12 may contain an iridium-tin composite oxide. The electrocatalyst may have the following characteristics: Figure 1 The structure shown is not limited to the median core size and shell thickness. Figure 1 Those shown in the image.

[0067] The electrocatalysts disclosed herein may comprise, for example, compounds represented by the following chemical formula 1.

[0068] <Chemical Formula 1>

[0069] Ir x Sn 1-x O2

[0070] In chemical formula 1, 0.67 ≤ x ≤ 0.75.

[0071] In the compound of chemical formula 1, iridium exists as a tetravalent cation, as does tin.

[0072] Examples of compounds of formula 1 may include Ir 0.67 Sn 0.33 O2, Ir 0.75 Sn 0.25 O2, or combinations thereof.

[0073] In the XRD pattern of the PEM water electrolysis electrocatalyst according to this disclosure, multiple peaks (first peak) appear at diffraction angles of 2θ in the range of 26.6° to 28°, and single peaks (second peak) appear at diffraction angles of 2θ in the ranges of 40.5° to 40.9°, 40.6° to 40.8°, or 40.7°. In this disclosure, the first peak is associated with the iridium-tin oxide (IrSnO) complex. x The first peak is related to iridium in the nucleus, while the second peak is related to iridium in the nucleus.

[0074] According to another embodiment of this disclosure, a method for preparing an electrocatalyst for PEM water electrolysis is provided, the electrocatalyst comprising an iridium-based catalyst.

[0075] The method includes the following steps: dispersing a support in a polyol to prepare a support dispersion; mixing an iridium precursor and a tin precursor with the polyol to obtain a precursor mixture; mixing the support dispersion and the precursor mixture to prepare a first mixture; subjecting the first mixture to a first heat treatment to prepare a catalyst precursor containing iridium metal and tin oxide particles; and performing a second heat treatment in an oxidizing gas atmosphere after washing and drying the catalyst precursor.

[0076] In the following text, reference will be made to Figure 2 A method for preparing an electrocatalyst for PEM water electrolysis according to this disclosure is described in more detail.

[0077] First, the carrier is dispersed in a polyol to prepare a carrier dispersion.

[0078] In this case, the polyol can be included in an amount ranging from 100 to 1,000 parts by weight or from 200 to 400 parts by weight relative to 1 part by weight of the support. When the amount of polyol falls within the above range, the support can be uniformly dispersed in the polyol, thus obtaining a support dispersion exhibiting excellent dispersibility. Such a dispersion process can be carried out by physical methods using a homogenizer, ultrasonic device, etc. When the amount of ceramic is large but does not fall within the above range, or when the amount of polyol is small, the ceramic particles used as the support may form agglomerates and aggregates. Furthermore, when the amount of ceramic in the support is small, or when the amount of polyol is large, the reactivity processability is greatly deteriorated, making it difficult to demonstrate the intended effects of this disclosure.

[0079] The polyol can be, for example, selected from one or more of the following: ethylene glycol (EG), propylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, and glycerol. For example, EG (which is inexpensive, readily oxidized to glycolaldehyde at high temperatures, and has strong reducing power) can be used as the polyol.

[0080] Separately, the step of mixing the iridium precursor and the tin precursor with a polyol to obtain a precursor mixture is performed.

[0081] Iridium and tin precursors are mixed in molar ratios ranging from 1:0.33 to 1:0.50, 1:0.35 to 1:0.48, or 1:0.37 to 1:0.45. When the iridium and tin precursors are mixed in molar ratios falling within these ranges, electrocatalysts exhibiting a core-shell structure and improved activity can be prepared. When the iridium and tin precursors are mixed in molar ratios not falling within these ranges, Ir-SnO2 or IrSnO2 complexes may be formed, making it impossible to prepare the desired core-shell structured catalyst.

[0082] When preparing the precursor mixture, the polyol used may contain amounts ranging from, for example, 10 to 1000 parts by weight or 200 to 400 parts by weight, based on the total weight of 1 part by weight of the iridium and tin precursors. In the step of obtaining the precursor mixture, physical methods such as homogenizers and ultrasonic devices may be used to obtain a precursor mixture with a homogeneous composition.

[0083] Examples of iridium precursors used may include iridium nitrate, iridium sulfate, iridium chloride, and hexachloroiridium acid (Cl6H). 14 IrO6;H2IrCl6.6H2O), and examples of tin precursors used may include tin chloride and tin sulfate.

[0084] The support dispersion and precursor mixture obtained through the above process are mixed to prepare a first mixture. In this case, the support dispersion and precursor mixture can be stoichiometrically controlled to obtain the desired composition of the electrocatalyst.

[0085] Subsequently, the first mixture obtained through the above process is subjected to a first heat treatment to prepare catalyst precursor A containing iridium metal and tin oxide particles.

[0086] The first heat treatment is carried out at a temperature in the range of 200°C to 550°C, 230°C to 500°C, or 250°C to 400°C. When the first heat treatment is carried out at a temperature below 200°C or above 550°C, the formation of the desired catalyst precursor A is difficult.

[0087] After washing and drying the catalyst precursor A, a second heat treatment can be performed to obtain the electrocatalyst of this disclosure.

[0088] The second heat treatment is carried out at a higher temperature than the first heat treatment.

[0089] The second heat treatment is carried out in an oxidizing gas atmosphere and can be performed at temperatures ranging from 350°C to 600°C, 350°C to 550°C, or 350°C to 450°C. When the temperature of the second heat treatment is below 350°C, Ir-SnO2 complexes may be present, leading to reduced activity. Furthermore, when the temperature exceeds 600°C, an electrocatalyst made of IrSnO2 complexes may be formed instead of the core-shell structure of the electrocatalyst disclosed herein, resulting in performance degradation of the PEM water electrolysis electrode when using this catalyst.

[0090] Examples of oxidizing gas atmospheres may include oxygen or air. When the second heat treatment is performed in an inert gas atmosphere instead of an oxidizing gas atmosphere, an electrocatalyst made of IrSnO2 composite may be formed instead of the core-shell electrocatalyst structure of this disclosure, leading to a degradation in the performance of the electrocatalyst.

[0091] The polyol used in the method for preparing electrocatalysts for PEM water electrolysis serves as both a solvent and a reducing agent, and can reduce metal precursors.

[0092] According to another embodiment, a PEM water electrolysis electrode is provided, comprising an anode containing an electrocatalyst that incorporates the present disclosure. In this case, the water electrolysis electrode can be, for example, an anode.

[0093] According to yet another embodiment, a water electrolysis unit is provided, comprising a PEM and a PEM water electrolysis electrode, wherein the PEM water electrolysis electrode contains the electrocatalyst of this disclosure.

[0094] The water electrolysis unit may include a MEA.

[0095] According to this disclosure, a PEM water electrolysis unit includes one or more MEAs, and the MEAs may have the following characteristics: Figure 7 The structure shown.

[0096] Reference Figure 7 The MEA for PEM water electrolysis has a structure in which the cathode 100 and the anode 200 are located on two opposite surfaces of the PEM 300.

[0097] The anode 200 may contain the electrocatalyst disclosed herein as an electrocatalyst. This electrocatalyst is an OER promoting material.

[0098] The cathode 100 contains a cathode catalyst that serves as a HER promoting material in the PEM water electrolysis unit. As the cathode catalyst, one or a mixture of two or more of platinum, ruthenium, iridium, osmium, palladium, platinum-ruthenium alloys, platinum-osmium alloys, platinum-palladium alloys, and their oxides can be used. For example, platinum-coated carbon powder (Pt / C) can be used as the cathode catalyst.

[0099] Cathode 100 and anode 200 may each independently contain an ionomer. Examples of ionomers of proton-conducting polymers may include polytetrafluoroethylene (PTFE), polymers represented by Formula 2, polymers represented by Formula 3, polymers represented by Formula 4, or combinations thereof.

[0100] <Chemical Formula 2>

[0101]

[0102] In chemical formula 2, m is a natural number.

[0103] <Chemical Formula 3>

[0104]

[0105] In chemical formula 3, p is a natural number.

[0106] <Chemical Formula 4>

[0107]

[0108] In chemical formula 4, n is a natural number.

[0109] The polymer represented by Formula 2 is a polymer consisting of a PTFE backbone as the main chain and perfluoropolyether side chains with sulfonic acid groups at the ends. The equivalent weight (EW) of this polymer (the mass of polymer required to supply 1 mole of protons) is not limited, but is, for example, in the range of 900 g / mol to 1200 g / mol. In Formula 2, m has various ranges that can be calculated from EW.

[0110] Examples of ion-conducting polymers of Formula 2 that may be used include Nafion (EW: 1100 g / mol, average value of m in Formula 2 is 6.6).

[0111] Polymers represented by chemical formula 2 or 3 are polymers consisting of a PTFE backbone in the main chain and perfluoropolyether side chains with sulfonic acid groups at the ends. The EW (mass of polymer required to supply 1 mole of protons) of this polymer is not limited, but is, for example, in the range of 700 g / mol to 9500 g / mol. In chemical formula 3 or 4, p and n have ranges that can be calculated from EW.

[0112] Examples of ionically conductive polymers with chemical formula 3 or 4 may include 3M ionomers available from 3M Corporation.

[0113] PEM 300 refers to a membrane formed from a polymer having cation exchange groups capable of transporting hydrogen ions. PEM 300 (the material located between the anode and cathode in a PEM water electrolysis unit) acts as a channel for the movement of hydrogen ions and may comprise fluorine-based or hydrocarbon-based polymers. Examples of hydrocarbon-based polymers may include sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyether ketone, sulfonated polyether ether ketone, sulfonated polyarylene ether ether ketone, sulfonated polyarylene ether sulfone, sulfonated polyarylene ether benzimidazole, and mixtures thereof. Furthermore, examples of fluorine-based polymers may include polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), PTFE, fluorinated ethylene-propylene (FEP), or mixtures thereof.

[0114] As a PEM, Nafion (DuPont, USA) (a representative fluorine-based polymer) can be used.

[0115] A method for manufacturing MEA for PEM water electrolysis according to this disclosure will be described.

[0116] First, a composition for anode formation is prepared by mixing the PEM water electrolysis electrocatalyst of this disclosure, used as the anode catalyst, an ionomer, and a solvent. Then, the composition is coated onto a substrate and dried to manufacture the anode.

[0117] A composition for cathode formation is prepared separately using a cathode catalyst, an ionomer, and a solvent. This composition is then coated onto a substrate and dried to manufacture the cathode.

[0118] When manufacturing cathodes and anodes, the coating of the various compositions used for cathode and anode formation can be performed by a method selected from spraying, screen printing, ribbon casting, brushing, printing, and slot die casting.

[0119] The cathode and anode are stacked on two opposite surfaces of the PEM to create an MEA. By stacking one or more MEAs, a PEM water electrolysis unit can be manufactured.

[0120] The present disclosure will be described in detail below through embodiments. However, the following embodiments are disclosed merely as examples to illustrate the present disclosure, and the content of the present disclosure is not limited thereto.

[0121] (Preparation of electrocatalysts)

[0122] Example 1

[0123] By using 0.75g of ATO (47.2m)2 The carrier dispersion was prepared by ultrasonically mixing 350g of EG (7g / g, purchased from Sigma-Aldrich) with 350g of EG at high speed for 30 minutes.

[0124] Catalyst particle precursor solution was prepared by mixing 20.60 g of an aqueous solution of iridium precursor (5 wt% H₂IrCl₆·xH₂O, purchased from TMIChem.Co.) and 1.88 g of a tin precursor solution (20 wt% SnCl₂·2H₂O in EG, Sigma-Aldrich). The molar ratio of iridium precursor to tin precursor was 1:0.33.

[0125] The support dispersion and the catalyst particle precursor solution were mixed. The resulting mixture was then placed in an autoclave reactor equipped with a stirrer, and the reactor temperature was raised to approximately 250°C for a first heat treatment to carry out a reduction reaction. After the reduction reaction was complete, the filtration and washing processes were repeated to obtain a slurry, which was then freeze-dried to prepare the catalyst precursor.

[0126] The catalyst precursor was subjected to a second heat treatment in an air atmosphere in a furnace at 450°C for 6 hours to obtain the electrocatalyst (Ir@IrSnO2-1).

[0127] The total composition including both the core and the shell is composed of Ir 0.75 Sn 0.25 O2 represents.

[0128] Example 2

[0129] The electrocatalyst (Ir@IrSnO2-2) was prepared using the same method as in Example 1, except that 18.98 g of an aqueous solution of iridium precursor (5 wt% H2IrCl6·xH2O, purchased from TMIChem.Co.) and 2.60 g of a tin precursor solution (20 wt% SnCl2·2H2O in EG, purchased from Sigma-Aldrich) were mixed. The molar ratio of the iridium precursor to the tin precursor was 1:0.5. The total composition, including both the core and shell, consisted of Ir 0.67 Sn 0.33 O2 represents.

[0130] Example 3

[0131] The electrocatalyst (Ir@IrSnO2-3) was obtained by performing the same method as in Example 1, except that the molar ratio of the iridium precursor and the tin precursor was changed to 1:0.4.

[0132] Example 4

[0133] The electrocatalyst (Ir@IrSnO2-4) was obtained by performing the same method as in Example 1, except that the molar ratio of the iridium precursor and the tin precursor was changed to 1:0.45.

[0134] Comparative Example 1

[0135] The electrocatalyst (IrO2) was prepared using the same method as in Example 1, except that 24.85 g of an aqueous solution of iridium precursor (5 wt% H2IrCl6·xH2O, purchased from TMIChem.Co.) was added, without the tin precursor solution. The molar ratio of the iridium precursor to the tin precursor was 1:0.

[0136] Comparative Example 2

[0137] The electrocatalyst (IrSnO2) was obtained by the same method as in Example 1, except that 15.36 g of an aqueous solution of iridium precursor (5 wt% H2IrCl6·xH2O, purchased from TMIChem.Co.) and 4.21 g of a tin precursor solution (20 wt% SnCl2·2H2O in EG, purchased from Sigma-Aldrich) were mixed. The molar ratio of the iridium precursor to the tin precursor was 1:1.

[0138] Comparative Example 3

[0139] The electrocatalyst (Ir-SnO2 complex) was obtained by performing the same method as in Example 1, except that the catalyst precursor was subjected to a second heat treatment in a nitrogen atmosphere.

[0140] The electrocatalyst prepared in this way was used to obtain an Ir-SnO2 complex by performing the method according to Comparative Example 3. This complex does not have a core-shell structure, but rather exists as a compound with a single composition.

[0141] The molar ratio of the iridium and tin precursors used in the preparation of the electrocatalysts of Examples 1 and 2 and Comparative Examples 1 and 2, and the composition of the final electrocatalysts are shown in Table 1 below.

[0142] [Table 1]

[0143]

[0144]

[0145] (Manufacturing of PEM water electrolysis unit)

[0146] Manufacturing Example 1

[0147] A slurry was prepared comprising 0.5 g of the electrocatalyst (Ir@IrSnO2-1) from Example 1, 2.2 g of water, 2.2 g of dipropylene glycol, and 0.27 g of a 20% Nafion dispersion. This slurry was then coated with a PTFE membrane and dried to fabricate an anode as the electrode layer.

[0148] In addition, a slurry was prepared by using 20% ​​by weight of Pt / C, and then the slurry was coated with a PTFE membrane and dried to manufacture a cathode as an electrode layer in the same manner as the anode used as an electrode layer.

[0149] A cation exchange membrane (Nafion 115) was stacked on top of the cathode, and an anode (OER electrode) was stacked on top of the cation exchange membrane, with the catalyst surface of the anode in contact with it. The MEA was then fabricated by thermal fusion under the following conditions: a temperature of 165 °C, a pressure of 20 bar, and a duration of 10 minutes. The MEA was placed in a unit cell with a flow field, and a titanium porous transport layer (Ti-PTL) was stacked on the anode side to fabricate the final MEA, which was then coupled to fabricate a PEM water electrolysis unit cell.

[0150] Manufacturing Examples 2 to 4

[0151] MEA and PEM water electrolysis unit cells were manufactured using the same method as in Manufacturing Example 1, except that the corresponding electrocatalysts of Examples 2 to 4 were used instead of the electrocatalyst of Example 1.

[0152] Comparative Manufacturing Example 1

[0153] MEA and PEM water electrolysis units were manufactured using the same method as in Manufacturing Example 1, except that the electrocatalyst of Comparative Example 1 was used instead of the electrocatalyst of Example 1.

[0154] Comparative Manufacturing Example 2

[0155] MEA and PEM water electrolysis units were manufactured using the same method as in Manufacturing Example 1, except that the electrocatalyst of Comparative Example 2 was used instead of the electrocatalyst of Example 1.

[0156] Evaluation Example 1: XRD Analysis

[0157] To determine the crystallographic information of the electrocatalysts used in PEM water electrolysis in Examples 1 and 2, and Comparative Examples 1 and 2, XRD analysis (Rigaku DMAX-33) was performed using Cu Kα radiation at diffraction angles of 2θ ranging from 10° to 80°. The analytical results are shown in... Figure 3 middle.

[0158] according to Figure 3 The catalysts in Examples 1 and 2 showed diffraction peaks corresponding to Ir metal, IrSnO2 and ATO support, and in particular, IrSnO2 showed excellent crystallinity.

[0159] In the XRD pattern of the electrocatalyst, multiplets appeared at diffraction angles of 2θ ranging from 26.6° to 28°, and a singlet appeared at diffraction angles of 2θ ranging from 40.5° to 40.9°. The multiplets are related to IrSnO. x The peaks are related to the complex, while the single peaks are related to iridium in the core of the electrocatalyst.

[0160] On the other hand, in the case of the tin-free catalyst (IrSnO2) of Comparative Example 1, iridium oxide (IrO) x The catalyst in Comparative Example 2 (IrSnO2) was non-crystalline, and no Ir metal peak was observed. Furthermore, in the case of the catalyst in Comparative Example 2 (IrSnO2), the amount of Sn was large, and it was observed that the catalyst core had an IrSnO2 (crystalline) composite structure without Ir metal.

[0161] Evaluation Example 2: TEM Analysis

[0162] TEM analysis was performed on the electrocatalysts according to Examples 1 and 2 and Comparative Examples 1 and 2. The TEM analysis results are shown in... Figure 4A , 4B In the cases of 4C, 4D, 5A, 5B, 5C, and 5D, Figure 4A , 4C Images 5A and 5C are TEM images showing the state of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 before the second heat treatment, respectively. Furthermore, Figure 4B , 4D Images 5B and 5D are TEM images showing the state of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 after the second heat treatment, respectively.

[0163] Reference Figure 4A , 4B The electrocatalysts of Examples 1 and 2, namely 4C, 4D, 5A, 5B, 5C and 5D, exhibited improved dispersibility compared to the electrocatalysts of Comparative Examples 1 and 2.

[0164] Evaluation Example 3: Water Electrolysis Performance Evaluation

[0165] PEM water electrolysis electrodes were fabricated using the electrocatalysts of Examples 1 and 2 and Comparative Examples 1 and 2, and then used to fabricate PEM water electrolysis MEAs of Examples 1 and 2 and Comparative Examples 1 and 2, as well as PEM water electrolysis units comprising their respective PEM water electrolysis MEAs. The unit voltage as a function of current density was measured to demonstrate the electrochemical effect of such PEM water electrolysis units to evaluate water electrolysis performance.

[0166] A graph showing the measured voltage (V) and current (A) by evaluation is shown in the figure. Figure 6 The results are shown in Table 2 below.

[0167] [Table 2]

[0168] Classification <![CDATA[Current density (mA / cm 2 ) at 1.7V and 80°C Example 1 1.71 Example 2 2.01 Comparative Example 1 0.78 Comparative Example 2 0.81

[0169] Refer to Table 1 and Figure 6 It was determined that, compared with a water electrolysis unit having an electrode using the electrocatalysts of Examples 1 and 2 at 1.7V, the water electrolysis unit having a PEM water electrolysis electrode using the catalysts of Examples 1 and 2 exhibited a higher current density at the same voltage.

[0170] Furthermore, PEM water electrolysis electrodes were fabricated using the electrocatalysts of Examples 3 and 4, and then used to manufacture the PEM water electrolysis MEAs of Examples 3 and 4, and PEM water electrolysis units comprising the corresponding PEM water electrolysis MEAs. The water electrolysis performance of such PEM water electrolysis units was evaluated using the same method as that used for the water electrolysis unit of Example 1.

[0171] The evaluation results confirmed that the water electrolysis units of Manufacturing Examples 3 and 4 achieved water electrolysis performance comparable to that of the water electrolysis unit of Manufacturing Example 1.

[0172] Although preferred embodiments of this disclosure have been described in detail above, the scope of this disclosure is not limited thereto. That is, various modifications and alternatives made by those skilled in the art using the basic concepts of this disclosure as defined in the appended claims fall within the scope of this disclosure.

Claims

1. An electrocatalyst for water electrolysis using a polymer electrolyte membrane (PEM), said electrocatalyst comprising an iridium-based catalyst, The iridium-based catalyst is a core-shell particle. The core contains iridium metal, and The shell contains an iridium-tin composite oxide.

2. The electrocatalyst according to claim 1, wherein, based on 100 parts by weight of the total electrocatalyst, the iridium metal is contained in the core in an amount ranging from 60 parts by weight to 76 parts by weight, and Based on 100 parts by weight of the total electrocatalyst, the iridium-tin composite oxide is contained in the shell in an amount ranging from 24 to 40 parts by weight.

3. The electrocatalyst according to claim 1, wherein the iridium-tin composite oxide of the shell is a composite comprising iridium oxide and tin oxide, and Based on 100 parts by weight of the iridium oxide, the tin oxide is included in the composite in an amount ranging from 33 parts by weight to 50 parts by weight.

4. The electrocatalyst according to claim 1, wherein tin is contained in the iridium-tin composite oxide of the shell in an amount ranging from 33 to 50 moles based on 100 moles of iridium.

5. The electrocatalyst according to claim 1, further comprising a support, The iridium-based catalyst is supported on the support.

6. The electrocatalyst according to claim 5, wherein the iridium-based catalyst is included in an amount ranging from 10 parts by weight to 90 parts by weight, based on 100 parts by weight of the support.

7. The electrocatalyst according to claim 5, wherein the support further comprises a ceramic support.

8. The electrocatalyst according to claim 7, wherein the ceramic support is antimony-doped tin oxide (Sb-doped tin oxide, ATO), alumina (Al2O3), titanium dioxide (TiO2), zirconium oxide (ZnO2), or a combination thereof.

9. The electrocatalyst according to claim 1, wherein multiple peaks appear at a diffraction angle 2θ in the range of 26.6° to 28° in the X-ray diffraction (XRD) spectrum of the electrocatalyst, and A single peak appears at a diffraction angle of 2θ in the range of 40.5° to 40.9°.

10. The electrocatalyst according to claim 1, wherein the electrocatalyst comprises a compound represented by the following chemical formula 1, <Chemical Formula 1> Ir x Sn 1-x O2 In chemical formula 1, 0.67 ≤ x ≤ 0.

75.

11. The electrocatalyst according to claim 10, wherein the electrocatalyst is Ir 0.67 Sn 0.33 O2, Ir 0.75 Sn 0.25 O2, or combinations thereof.

12. The electrocatalyst according to claim 1, wherein the median particle size of the electrocatalyst is in the range of 1 nm to 20 nm.

13. A method for preparing the electrocatalyst according to claim 1, the method comprising: The carrier is dispersed in a polyol to prepare a carrier dispersion; The iridium precursor and tin precursor are mixed with a polyol to obtain a precursor mixture; The carrier dispersion is mixed with the precursor mixture to prepare a first mixture; The first mixture is subjected to a first heat treatment to prepare a catalyst precursor containing iridium metal and tin oxide particles; as well as After washing and drying the catalyst precursor, a second heat treatment is performed in an oxidizing gas atmosphere. The iridium precursor and the tin precursor are mixed in a molar ratio ranging from 1:0.33 to 0.

50.

14. The method of claim 13, wherein the first heat treatment is performed at a temperature in the range of 200°C to 550°C.

15. The method of claim 13, wherein the second heat treatment is performed at a higher temperature than the first heat treatment. The second heat treatment is carried out at a temperature ranging from 350°C to 600°C, and The oxidizing gas atmosphere includes an air atmosphere or an oxygen atmosphere.

16. The method of claim 13, wherein the iridium precursor and the tin precursor are included in a total amount ranging from 10 parts by weight to 90 parts by weight, based on 100 parts by weight of the carrier.

17. A PEM water electrolysis electrode comprising an electrocatalyst according to any one of claims 1 to 12.

18. A PEM water electrolysis unit, comprising: PEM; and A PEM water electrolysis electrode located on one surface of the PEM, the PEM water electrolysis electrode comprising an electrocatalyst according to any one of claims 1 to 12.

19. The PEM water electrolysis unit according to claim 18, wherein the electrode is an anode.

Images