Catalyst for water electrolysis and ink composition, electrode for water electrolysis, and water electrolysis cell comprising same

Abstract

The present invention relates to: a catalyst for water electrolysis, having a coating layer including iridium oxide particles and titanium oxide, wherein the coverage rate of the coating layer is 30-120%; and an ink composition, an electrode for water electrolysis, and a water electrolysis cell, each comprising the catalyst for water electrolysis.

Description

Catalyst for water electrolysis, ink composition containing the same, electrode for water electrolysis, and water electrolysis cell

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0193016 filed on December 20, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a catalyst for water electrolysis that includes a coating layer formed on the surface of iridium oxide particles and can exhibit excellent catalytic activity and durability by controlling the coverage rate of the coating layer within a certain range, an ink composition including the same, an electrode for water electrolysis, and a water electrolysis cell.

[0005] Hydrogen has the advantages of being suitable for storage and transportation and being eco-friendly, leading to various recent attempts to utilize it as an energy source. While various methods for producing hydrogen are known, the method of producing hydrogen through water electrolysis has the advantage of being environmentally friendly as it does not generate harmful byproducts.

[0006] Representative methods of water electrolysis include alkaline electrolysis (AEC) and polymer electrolyte membrane (PEM). Among these, alkaline electrolysis is a method that electrolyzes water using an alkaline electrolyte and is the most commercialized technology among various electrolysis methods. Alkaline electrolysis has the advantages of relatively low process operating costs, a simple production structure making it suitable for large-scale hydrogen production, and excellent durability. However, alkaline electrolysis has limitations, such as the need to continuously replenish the electrolyte consumed during the electrolysis process, corrosion problems caused by alkaline components, and low current density efficiency. On the other hand, polymer electrolyte membrane electrolysis utilizes polymer electrolyte membranes as the electrolyte, primarily employing cation exchange membranes. Polymer electrolyte membrane electrolysis offers the advantage of high energy efficiency because it allows operation at high current densities using precious metal catalysts, and the purity of the produced hydrogen is very high as it does not require an electrolyte component. Therefore, various studies on water electrolysis using polymer electrolyte membranes are currently being conducted.

[0007] Meanwhile, water electrolysis using polymer electrolyte membranes involves oxygen evolution at the anode and hydrogen evolution at the cathode, and hydrogen production efficiency is determined by the efficiency of both reactions. Pt / C catalysts are known to exhibit high efficiency for hydrogen evolution, while precious metal catalysts such as iridium are known to exhibit high efficiency for oxygen evolution. However, precious metal catalysts like iridium suffer from a problem where their durability decreases as the electrochemical reaction progresses, and since they are also expensive, various efforts are being made to develop catalysts for oxygen evolution and anodes for water electrolysis that can minimize iridium usage while ensuring durability. For example, there are prior studies that aim to secure the durability of catalyst particles by applying doping or coating films to iridium catalyst particles to reduce the iridium loading per unit area. However, applying doping or coating to particles in this manner increases the difficulty of the manufacturing process and does not result in sufficient improvements in terms of activity and durability. Therefore, it is necessary to develop a new structure of electrode for water electrolysis that can minimize the use of the aforementioned iridium while simultaneously improving performance.

[0008] The present invention aims to solve the above-mentioned problem by introducing a coating layer containing titanium oxide onto iridium oxide particles using an atomic film deposition method, and by controlling the coverage rate of the coating layer within a certain range, thereby providing a catalyst for water electrolysis capable of improving durability and minimizing the reduction of catalytic activity caused by the coating layer.

[0009] To solve the above-mentioned problem, the present invention provides a catalyst for water electrolysis, an ink composition including the same, an electrode for water electrolysis and a water electrolysis cell including the same, and a method for manufacturing the catalyst for water electrolysis.

[0010] More specifically, (1) the present invention provides a catalyst for water electrolysis comprising iridium oxide particles and a coating layer formed on at least a portion of the surface of the particles, wherein the coating layer comprises titanium oxide and the coverage rate of the iridium oxide particles by the coating layer is 30% or more and 120% or less.

[0011] (2) The present invention provides a catalyst for water electrolysis in which, in (1) above, the iridium oxide particles have a secondary particle form formed by aggregating a plurality of primary particles having an average particle size of 0.1 nm or more and 20 nm or less.

[0012] (3) In the present invention according to (1) or (2), the specific surface area of ​​the iridium oxide particles is 30 m² 2 / g or more and 130m 2 A catalyst for water electrolysis with a g or less is provided.

[0013] (4) The present invention provides a catalyst for water electrolysis in which, in any one of (1) to (3), the iridium content based on the total weight of the catalyst is 50% by weight or more and 70% by weight or less.

[0014] (5) The present invention provides a catalyst for water electrolysis in which, in any one of (1) to (4), the titanium content based on the total weight of the catalyst is 0.5 weight% or more and 10 weight% or less.

[0015] (6) The present invention provides a water electrolysis catalyst in which, in any one of (1) to (5), the atomic ratio of O / Ti in the coating layer is 1.2 to 5.0.

[0016] (7) The present invention provides a catalyst for water electrolysis in which, in any one of (1) to (6), the carbon content in the coating layer is 10 at% or more and 30 at% or less.

[0017] (8) The present invention provides a catalyst for water electrolysis in which, in any one of (1) to (7), the thickness of the coating layer is 0.1 nm or more and 2 nm or less.

[0018] (9) In any one of (1) to (8), the present invention comprises iridium oxide particles comprising 40 weight% or more of crystalline iridium oxide, and Ir 4f confirmed by analysis using X-ray photoelectron analysis (XPS). 5 / 2 A catalyst for water electrolysis is provided having a peak binding energy of 64.1 eV or higher and 65 eV or lower.

[0019] (10) In any one of (1) to (9), the present invention relates to Ir 4f confirmed by analysis using X-ray photoelectron analysis (XPS). 7 / 2 A catalyst for water electrolysis is provided having a peak binding energy of 61.4 eV or higher and 62 eV or lower.

[0020] (11) In any one of (1) to (10) above, the iridium oxide particles comprise 60 weight% or more of amorphous iridium oxide, and Ir 4f is confirmed by analysis using X-ray photoelectron analysis (XPS). 5 / 2 A catalyst for water electrolysis is provided having a peak binding energy of 64 eV or more and 65 eV or less.

[0021] (12) In any one of (1) to (11), the present invention relates to Ir 4f confirmed by analysis using X-ray photoelectron analysis (XPS). 7 / 2 A catalyst for water electrolysis is provided having a peak binding energy of 61.8 eV or higher and 62.3 eV or lower.

[0022] (13) The present invention provides a water electrolysis catalyst in any one of (1) to (12), wherein the average value of the width / height of the coffee ring measured as a result of a coffee ring test under the following conditions is 8% or more and 17.5% or less:

[0023] [Coffee Ring Test Conditions]

[0024] 1) Conditions for preparing the dispersion:

[0025] Prepare a dispersion by dispersing 0.01g of a water electrolysis catalyst in 10mL of n-propanol.

[0026] 2) Conditions for entry:

[0027] Slide glass (MarineFiled Microscope slides, Precleaned plain)

[0028] 3) Drying conditions:

[0029] Form a 5 µL droplet on a slide glass heated to 80°C using a 25GA Precision Tip (Nordson), and dry thoroughly until completely dry.

[0030] 4) Measurement conditions: Measured the width and height of the coffee ring at 100x magnification using a Confocal Laser Microscope (KEYENCE, VK-200 series).

[0031] (14) The present invention provides a catalyst for water electrolysis having a contact angle with water of 130° or less in any one of (1) to (13).

[0032] (15) The present invention provides a water electrolysis catalyst having a contact angle with respect to a bubble of 150° or more in any one of (1) to (14).

[0033] (16) The present invention provides an ink composition for a membrane-electrode assembly comprising a catalyst for water electrolysis, an ionomer, and a solvent according to any one of (1) to (15).

[0034] (17) The present invention provides an ink composition in which, in (16) above, the solvent is one or more selected from the group consisting of water, n-propyl alcohol, ethanol and dimethylformamide.

[0035] (18) The present invention provides an electrode for water electrolysis comprising a catalyst for water electrolysis according to any one of (1) to (15).

[0036] (19) The present invention provides a water electrolysis cell comprising an electrode for water electrolysis according to (18).

[0037] (20) The present invention provides a method for manufacturing a catalyst for water electrolysis according to any one of (1) to (15), comprising the step of forming a coating layer containing titanium oxide on the surface of iridium oxide particles.

[0038] The water electrolysis catalyst of the present invention is such that at least a portion of the surface of the iridium oxide particles is coated by a coating layer containing titanium oxide, and as the coating rate of the coating layer is controlled within an appropriate range, the protective effect of the catalyst particles and the effect of preventing the degradation of catalyst activity by the titanium oxide coating layer are maximized, thereby enabling excellent catalyst activity and durability to be achieved simultaneously.

[0039] In addition, the water electrolysis catalyst of the present invention is Ir 4f, which is confirmed by analysis using X-ray photoelectron analysis (XPS) through the coating layer. 5 / 2 By controlling the binding energy of the peak within a certain range, the protective effect on catalyst particles and the prevention of catalyst activity degradation by the titanium oxide coating layer are maximized, thereby enabling the simultaneous realization of excellent catalyst activity and durability.

[0040] In addition, the water electrolysis catalyst of the present invention has excellent hydrophilicity, resulting in excellent contact with water, and thereby can exhibit excellent water electrolysis performance.

[0041] Figure 1 shows a graph of binding energy vs. intensity obtained from XPS analysis results for the water electrolysis catalysts of Comparative Example 1-1, Example 1-1, and Comparative Example 1-3.

[0042] Figure 2 shows a graph of binding energy vs. intensity obtained from XPS analysis results for the water electrolysis catalysts of Comparative Example 2-1 and Examples 2-1 to 2-3.

[0043] The present invention will be described in more detail below.

[0044] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0045]

[0046] catalyst for water electrolysis

[0047] The present invention provides a catalyst for water electrolysis comprising iridium oxide particles and a coating layer formed on at least a portion of the surface of the particles, wherein the coating layer comprises titanium oxide, and the coverage rate of the iridium oxide particles by the coating layer is 30% or more and 120% or less.

[0048]

[0049] The above-mentioned iridium oxide particles are components that exhibit direct catalytic activity for water electrolysis reactions, and iridium oxide is known to exhibit excellent activity for water electrolysis reactions, particularly oxygen evolution reactions. In the present invention, a coating layer containing titanium oxide is applied to the above-mentioned iridium oxide particles, and by controlling the coverage rate of the iridium oxide particles by the coating layer within a certain range, the effect of improving durability and preventing the degradation of catalytic activity by the coating layer can be maximized.

[0050]

[0051] The above iridium oxide may be crystalline iridium oxide or amorphous iridium oxide.

[0052] In the present invention, the fact that the iridium oxide particles have a crystalline structure may mean that the iridium oxide particles contain crystalline iridium oxide in an amount of 40 wt% or more, 45 wt% or more, 50 wt% or more and 100 wt% or less, 99.5 wt% or less, 99 wt% or less, 97 wt% or less, 95 wt% or less, or 90 wt% or less. The iridium oxide particles having a crystalline structure contain such a large amount of crystalline iridium oxide and can be described as crystalline iridium oxide particles themselves. The relative proportion of the crystalline iridium oxide can be measured and calculated through quantitative analysis using XRD.

[0053] In the present invention, the fact that the iridium oxide particles have an amorphous structure may mean that the iridium oxide particles contain amorphous iridium oxide in an amount of 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, 78 wt% or more, or 80 wt% or more, and 100 wt% or less, 99.5 wt% or less, 99 wt% or less, 97 wt% or less, 95 wt% or less, or 90 wt% or less. The iridium oxide particles having an amorphous structure contain such a large amount of amorphous iridium oxide and can be described as amorphous iridium oxide particles themselves. The relative proportion of the amorphous iridium oxide can be measured and calculated through quantitative analysis using XRD.

[0054] The crystalline iridium oxide has the advantage of excellent durability due to its stable surface structure and the ability to maintain performance for a long time even under long-term operating conditions, while the amorphous iridium oxide has the advantage of exhibiting excellent catalytic activity due to the abundance of active sites on its surface.

[0055]

[0056] The iridium oxide may be represented as IrO2, and the iridium oxide particles may have the form of secondary particles formed by the aggregation of a plurality of primary particles having an average particle size of 0.1 nm or more and 20 nm or less, preferably 1 nm or more and 5 nm or less. Additionally, the average particle size of the secondary particles may be 0.1 µm or more and 20 µm or less, and preferably 0.1 µm or more, 0.5 µm or more, or 1 µm or more, while being 20 µm or less, 10 µm or less, 5 µm or less, or 3 µm or less. Furthermore, the specific surface area of ​​the iridium oxide particles is 30 m² 2 / g or more and 130m 2 It may be less than / g. More specifically, if the iridium oxide is crystalline, 30m 2 / g or more and 70m 2 It may be less than / g, preferably 33m 2 / g or more, 35m 2 / g or more, 37m 2 / g or more or 40m 2 / g or more, and 67m 2 / g or less, 65m 2 / g or less, 63m 2 / g or less or 60m 2 It may be less than / g. Meanwhile, if the iridium oxide is amorphous, the specific surface area of ​​the iridium oxide particles is 60 m² 2 / g or more and 130m 2 It may be less than / g, preferably 65m 2 / g or more, 70m 2 / g or more, 75m 2 / g or more or 80m 2 / g or more and 130m 2 / g or less, 125m 2 / g or less, 120m 2 / g or less, 115m 2 / g or less, 110m 2 / g or less or 105m 2It may be less than / g. When the iridium oxide particles satisfy the above-described conditions, the durability of the catalyst particles is superior, and the formation of the coating layer can be facilitated.

[0057]

[0058] The iridium (Ir) content based on the total weight of the catalyst may be 50 wt% or more and 70 wt% or less, and preferably 55 wt% or more or 60 wt% or more and 70 wt% or less. If the proportion of iridium is too low, sufficient catalytic activity may not be exhibited, and if the proportion of iridium is too high, the role of the coating layer may not be sufficiently performed. Meanwhile, the iridium content can be measured through XRF analysis.

[0059]

[0060] The above coating layer can suppress the leaching of iridium during the water electrolysis process by covering at least a portion of the particle surface of the iridium oxide described above, thereby improving the durability of the catalyst itself. The above coating layer may include titanium oxide, and the titanium oxide may be TiO2, Ti2O3, or TiO, preferably TiO2. When titanium oxide is used as a component of the above coating layer, the effect of improving durability can be maximized. In particular, the presence of the above coating layer may reduce the contact area of ​​iridium, which corresponds to the active component, leading to a decrease in catalytic activity; however, in the present invention, by applying titanium oxide as a component of the above coating layer and controlling the coverage rate by the coating layer within a certain range, it is possible to improve durability—which is generally in a trade-off relationship with catalytic activity—while minimizing the decrease in catalytic activity. In particular, in the water electrolysis catalyst of the present invention, when the coverage rate satisfies a certain range, durability and catalytic activity can be improved simultaneously. In addition, the water electrolysis catalyst of the present invention can exhibit excellent hydrophilicity through the coating layer and excellent water electrolysis performance due to excellent contact with water. More specifically, the coating rate may be 30% or more, 33% or more, 35% or more, 36% or more, 37% or more, 38% or more, 40% or more, 43% or more, 45% or more, 47% or more, 50% or more, 52% or more, or 55% or more, and may be 120% or less, 110% or less, 100% or less, 98% or less, 95% or less, 93% or less, 90% or less, 87% or less, 85% or less, 83% or less, 80% or less, 77% or less, 75% or less, 73% or less, 70% or less, 67% or less, 65% or less, 63% or less, or 60% or less.

[0061]

[0062] Meanwhile, the coverage rate in this specification can be defined as shown in Formula 1 below.

[0063] [Equation 1]

[0064] Coverage rate (%) =

[0065] In the above Equation 1,

[0066] m coat represents the total weight of the coating layer, and

[0067] m sub represents the total weight of the substrate particles on which the coating layer is formed before coating, and

[0068] t represents the thickness of the coating layer, and

[0069] SSA refers to the specific surface area of ​​the substrate particles,

[0070] ρ coat represents the theoretical true density value of the coating layer component.

[0071]

[0072] The coverage ratio of the present invention represents the ratio of the actual weight of the formed coating layer to the theoretical weight of the coating layer, assuming that a coating layer of thickness t is completely and uniformly formed on the substrate particle. Therefore, the coverage ratio of the present invention is a concept distinct from the geometric coverage ratio, which refers to the ratio of the area where the coating layer is formed to the surface area of ​​the substrate particle, and may refer to a mass-based ratio of the coating amount relative to the theoretical amount. More specifically, the substrate particle may be an iridium oxide particle, and the coating layer component may include titanium oxide (TiO2). In this case, the theoretical true density value of the titanium oxide (TiO2) is 4.2 g / cm³. 3 The above can be applied. In addition, the thickness t of the coating layer can be measured by observing the catalyst with a TEM image, and the total weight of the coating layer can be measured through ICP analysis.

[0073]

[0074] Meanwhile, the atomic ratio of O / Ti in the coating layer, which can be confirmed through XPS analysis, may be 1.2 or more and 5.0 or less, and preferably 1.2 or more, 1.4 or more, 1.6 or more, 1.8 or more, 2.0 or more, 2.2 or more, 2.4 or more, 2.6 or more, 2.8 or more, or 3.0 or more, and may be 5.0 or less, 4.8 or less, 4.6 or less, 4.4 or less, 4.2 or less, 4.0 or less, 3.8 or less, 3.6 or less, or 3.4 or less.

[0075] In addition, the oxygen content in the coating layer, which can be confirmed through XPS analysis, may be 30 at% or more and 70 at% or less, and preferably 30 at% or more, 33 at% or more, 35 at% or more, 37 at% or more, 40 at% or more, 43 at% or more, 45 at% or more, 47 at% or more, or 50 at% or more, and may be 70 at% or less, 67 at% or less, 65 at% or less, 63 at% or less, 60 at% or less, 57 at% or less, or 55 at% or less.

[0076] In addition, the titanium content in the coating layer, which can be confirmed through XPS analysis, may be 5 at% or more and 40 at% or less, and preferably 5 at% or more, 7 at% or more, 10 at% or more, 11 at% or more, 12 at% or more, 13 at% or more, 14 at% or more, 15 at% or more, or 16 at% or more, and may be 40 at% or less, 37 at% or less, 35 at% or less, 33 at% or less, 30 at% or less, 27 at% or less, 25 at% or less, 23 at% or less, 21 at% or less, or 20.5 at% or less.

[0077] In addition, the carbon content in the coating layer, which can be confirmed through XPS analysis, may be 10 at% or more and 30 at% or less, and preferably 10 at% or more, 12 at% or more, or 14 at% or more, and may be 30 at% or less, 27 at% or less, 25 at% or less, 23 at% or less, 20 at% or less, 18 at% or less, or 15 or less.

[0078] When the content of each component within the coating layer and the ratios between them satisfy the conditions described above, the effect of improving durability by the coating layer can be maximized. Meanwhile, the carbon in the coating layer may originate from residual carbon of the organic precursor used in the process of forming the coating layer.

[0079]

[0080] The thickness of the coating layer may be 0.1 nm or more and 2 nm or less, preferably 0.1 nm or more, 0.2 nm or more, or 0.3 nm or more, and 2 nm or less, 1.5 nm or less, 1.3 nm or less, 1.2 nm or less, 1.1 nm or less, 1.0 nm or less, 0.9 nm or less, 0.8 nm or less, 0.7 nm or less, or 0.6 nm or less. In the present invention, the coating layer may be formed through an atomic film deposition method, and accordingly, the coating layer may be formed thinly and uniformly.

[0081]

[0082] The titanium (Ti) content based on the total weight of the catalyst may be 0.5 wt% or more and 10 wt% or less, preferably 0.5 wt% or more, 1.0 wt% or more, or 1.5 wt% or more, and 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, or 5 wt% or less. Meanwhile, the titanium content may be measured through XRF analysis.

[0083]

[0084] Meanwhile, the water electrolysis catalyst of the present invention is Ir 4f, which is confirmed through analysis using X-ray photoelectron analysis (XPS) by the coating layer described above. 5 / 2 Peak binding energy and Ir 4f 7 / 2 The binding energy characteristics of the peak may have altered characteristics compared to iridium oxide without a coating layer. Meanwhile, regarding the water electrolysis catalyst of the present invention, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) depending on whether the iridium oxide particles are crystalline or amorphous 5 / 2 Peak binding energy and Ir 4f 7 / 2 The specific characteristics of the binding energy of the peaks may differ.

[0085] More specifically, when the iridium oxide particles are crystalline, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 5 / 2 The binding energy of the peak may be 64.1 eV or higher and 65 eV or lower. Ir 4f of crystalline iridium oxide without a coating layer formed. 5 / 2 The binding energy of the peak has a value greater than 65 eV, and the water electrolysis catalyst of the present invention may have a lower binding energy compared to iridium oxide without a coating layer by having a coating layer. More specifically, Ir 4f 5 / 2 The binding energy of the peak may be 64.1 eV or higher, and 65 eV or lower, 64.9 eV or lower, 64.8 eV or lower, 64.7 eV or lower, 64.6 eV or lower, 64.5 eV or lower, or 64.4 eV or lower.

[0086] In the case where iridium oxide particles are crystalline, Ir 4f identified through analysis using X-ray photoelectron analysis (XPS) 7 / 2The binding energy of the peak may be 61.4 eV or higher and 62 eV or lower, and more specifically, 61.4 eV or higher and 62 eV or lower, 61.9 eV or lower, 61.8 eV or lower, 61.7 eV or lower, or 61.6 eV or lower. Ir 4f of crystalline iridium oxide without a coating layer formed 7 / 2 The binding energy of the peak has a value greater than 62 eV, and the water electrolysis catalyst of the present invention may have a coating layer, thereby lowering the binding energy compared to iridium oxide without a coating layer.

[0087] Also, Ir 4f 5 / 2 Peak binding energy and Ir 4f 7 / 2 The difference between the binding energies of the peaks may be 2.5 eV or more and 3.2 eV or less, preferably 2.6 eV or more or 2.7 eV or more, and 3.2 eV or less, 3.1 eV or less, or 3.0 eV or less.

[0088] Also, Ir 4f 7 / 2 Ir 4f for the binding energy of the peak 5 / 2 The ratio of the binding energy of the peak may be 1.02 or higher and 1.1 or lower, preferably 1.02 or higher, 1.025 or higher, 1.03 or higher, 1.035 or higher, or 1.04 or higher, and may be 1.1 or lower, 1.09 or lower, 1.08 or lower, 1.07 or lower, 1.06 or lower, or 1.05 or lower.

[0089] In the case where the above iridium oxide particles are crystalline, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 5 / 2 Peak binding energy and Ir 4f 7 / 2 By satisfying the aforementioned conditions, superior performance and durability can be achieved simultaneously.

[0090] In the water electrolysis catalyst of the present invention, when the iridium oxide particles are crystalline, Ir confirmed through analysis using X-ray photoelectron analysis (XPS)4+ The content of may be 23.5 at% or more and 31 at% or less, preferably 23.5 at% or more, 23.8 at% or more, 24 at% or more, 24.5 at% or more, 25 at% or more, 25.5 at% or more, 26 at% or more, 26.5 at% or more, 27 at% or more, 27.5 at% or more, 28 at% or more, or 28.5 at% or more, while being 31 at% or less, 30.5 at% or less, or 30 at% or less.

[0091] In addition, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 3+ The content of may be 23.3 at% or more and 35 at% or less, preferably 23.3 at% or more or 23.4 at% or more, and may be 35 at% or less, 34.9 at% or less, 34.7 at% or less, 34.5 at% or less, 34.2 at% or less, 34 at% or less, 33.5 at% or less, 33 at% or less, 32.5 at% or less, 32 at% or less, 31.5 at% or less, 31 at% or less, 30.5 at% or less, or 30 at% or less.

[0092] In addition, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 0 The content of may be 1 at% or more and 10 at% or less, preferably 1 at% or more, 1.3 at% or more, 1.5 at% or more, 1.7 at% or more, 2 at% or more, 2.5 at% or more, 3 at% or more, 3.5 at% or more, 4 at% or more, or 4.5 at% or more, and may be 10 at% or less, 9.5 at% or less, 9.3 at% or less, 9 at% or less, or 8.7 at% or less.

[0093] In addition, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 3+ Ir regarding the content of 4+The ratio of the content may be 0.67 or more and 1.3 or less, preferably 0.67 or more, 0.68 or more, 0.69 or more, 0.7 or more, 0.72 or more, 0.74 or more, 0.75 or more, 0.78 or more, or 0.8 or more, and may be 1.3 or less, 1.29 or less, 1.28 or less, or 1.27 or less.

[0094]

[0095] Meanwhile, when the above iridium oxide particles are amorphous, in the water electrolysis catalyst of the present invention, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 5 / 2 The binding energy of the peak may be 64 eV or higher and 65 eV or lower. Ir 4f of amorphous iridium oxide without a coating layer formed 5 / 2 The binding energy of the peak has a value greater than 65 eV, and the water electrolysis catalyst of the present invention may have a coating layer such that the binding energy is lowered compared to iridium oxide without a coating layer. In the water electrolysis catalyst of the present invention, Ir 4f 5 / 2 The binding energy of the peak may be 64 eV or higher, 64.1 eV or higher, 64.2 eV or higher, 64.3 eV or higher, or 64.4 eV or higher, and 65 eV or lower, 64.9 eV or lower, 64.8 eV or lower, or 64.7 eV or lower.

[0096] In addition, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 7 / 2 The binding energy of the peak may be 61.8 eV or higher and 62.3 eV or lower, and more specifically, 61.8 eV or higher or 61.85 eV or higher, and may be 62.3 eV or lower, 62.2 eV or lower, 62.1 eV or lower, 62.0 eV or lower, or 61.9 eV or lower. Ir 4f of amorphous iridium oxide without a coating layer formed 7 / 2The binding energy of the peak has a value greater than 62.3 eV, and the water electrolysis catalyst of the present invention may have a coating layer, thereby lowering the binding energy compared to iridium oxide without a coating layer.

[0097] Also, Ir 4f 5 / 2 Peak binding energy and Ir 4f 7 / 2 The difference between the binding energies of the peaks may be 2.2 eV or more and 2.9 eV or less, and preferably 2.2 eV or more, 2.3 eV or more, or 2.4 eV or more, and 2.9 eV or less, 2.85 eV or less, or 2.8 eV or less.

[0098] Also, Ir 4f 7 / 2 Ir 4f for the binding energy of the peak 5 / 2 The ratio of the binding energy of the peak may be 1.02 or higher and 1.1 or lower, preferably 1.02 or higher, 1.025 or higher, 1.03 or higher, 1.035 or higher, or 1.04 or higher, and may be 1.1 or lower, 1.09 or lower, 1.08 or lower, 1.07 or lower, 1.06 or lower, or 1.05 or lower.

[0099] When the above iridium oxide particles are amorphous, the water electrolysis catalyst of the present invention is Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS). 5 / 2 Peak binding energy and Ir 4f 7 / 2 By satisfying the aforementioned conditions, superior performance and durability can be achieved simultaneously.

[0100]

[0101] In the water electrolysis catalyst of the present invention, when the iridium oxide particles are amorphous, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 4+The content of may be 10 at% or more and 35 at% or less, preferably 10 at% or more, 12 at% or more, 14 at% or more, 16 at% or more, 18 at% or more, 20 at% or more, 22 at% or more, 24 at% or more, 25 at% or more, 27 at% or more, 28 at% or more, or 29 at% or more, and may be 35 at% or less, 34 at% or less, 33 at% or less, or 32 at% or less.

[0102] In addition, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 3+ The content of may be 15 at% or more and 35 at% or less, preferably 15 at% or more, 17 at% or more, 19 at% or more, 20 at% or more, 22 at% or more, 24 at% or more, 25 at% or more, 26 at% or more, 27 at% or more, 28 at% or more, 29 at% or more, or 30 at% or more, and may be 35 at% or less, 34 at% or less, 33.5 at% or less, 33 at% or less, or 32.5 at% or less.

[0103] In addition, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 0 The content of may be 3 at% or more and 50 at% or less, preferably 3 at% or more, 5 at% or more, 6 at% or more, 7 at% or more, 8 at% or more, or 9 at% or more, and may be 50 at% or less, 45 at% or less, 43 at% or less, 40 at% or less, 37 at% or less, 35 at% or less, 33 at% or less, 32 at% or less, 31 at% or less, or 30 at% or less.

[0104] In addition, Ir confirmed through analysis using X-ray photoelectron analysis (XPS) 3+ Ir regarding the content of 4+The ratio of the content may be 0.5 or more and 2 or less, preferably 0.5 or more, 0.53 or more, 0.55 or more, 0.57 or more, 0.6 or more, 0.63 or more, 0.65 or more, 0.67 or more, or 0.7 or more, and may be 2 or less, 1.8 or less, 1.6 or less, 1.5 or less, or 1.3 or less.

[0105]

[0106] Meanwhile, in the present invention, the X-ray photoelectron analysis method may be performed under the following conditions.

[0107] 1) XPS Analysis Equipment: K-alpha+, Thermo Fisher Scientific Inc.

[0108] 2) X-ray source conditions: monochromatic Al Kα (1486.6 eV)

[0109] 3) Calibration Standard: CF2 and IrO2 Reference Standards

[0110] 4) Surface charge compensation: default FG03 mode(150μA, 0.5V)

[0111] 5) Sample Pretreatment: Proceed without pretreatment / sputtering

[0112] 6) Analysis Mode: CAE (Constant Analyzer Energy) Mode

[0113] 7) X-ray spot size: 400㎛

[0114] 8) Sample form: Measured in powder form

[0115] In addition, the previously explained Ir 4f 5 / 2 and Ir 4f 7 / 2 The relative content of the three types of iridium oxide forms described above can be quantified from the binding energy of the peaks. More specifically, the relative content of each oxide form can be quantified by applying the following conditions.

[0116] 1) Software: Avantage Software (version 5.992)

[0117] 2) Peak Background: Smart method applied

[0118] 3) Regarding the titanium peak: Since there is an overlapping region between the Ir 4f and Ti 3s peaks, the Ir 4f content was calculated using peak fitting (estimation of the Ti 3s peak region from the Ti 2p peak region).

[0119] In particular, as the peaks identified from titanium and some regions of the peaks identified from iridium overlap, it is difficult to define the precise binding energy positions represented by each peak of iridium and titanium when the titanium content increases; therefore, by applying the above quantification conditions, the binding energy positions of each peak can be specified more accurately.

[0120] The water electrolysis catalyst of the present invention can satisfy the above-described conditions by changing the oxidation form of iridium through the presence of the aforementioned coating layer, thereby enabling excellent performance and durability of the catalyst.

[0121]

[0122] The water electrolysis catalyst of the present invention may exhibit excellent hydrophilicity due to the aforementioned coating layer, and more specifically, the average value of the width / height of the coffee ring measured as a result of a coffee ring test under the following conditions may be 8% or more and 17.5% or less.

[0123] [Coffee Ring Test Conditions]

[0124] 1) Conditions for preparing the dispersion:

[0125] Prepare a dispersion by dispersing 0.01g of a water electrolysis catalyst in 10mL of n-propanol.

[0126] 2) Conditions for entry:

[0127] Slide glass (MarineFiled Microscope slides, Precleaned plain)

[0128] 3) Drying conditions:

[0129] Form a 5 µL droplet on a slide glass heated to 80°C using a 25GA Precision Tip (Nordson), and dry thoroughly until completely dry.

[0130] 4) Measurement Conditions: Measure the width and height of the coffee ring at 100x magnification using a Confocal Laser Microscope (KEYENCE, VK-200 series).

[0131]

[0132] The water electrolysis catalyst of the present invention has a coating layer formed on iridium oxide particles that satisfies appropriate conditions, so that its hydrophilicity can satisfy a certain range, and accordingly, the average value of the width / height of the coffee ring measured as a result of a coffee ring test under the above conditions can be 8% or more and 17.5% or less.

[0133] More specifically, in the water electrolysis catalyst of the present invention, the average value of the width / height of the coffee ring may be 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 12.5% ​​or more, 13% or more, or 13.5% or more, and 17.5% or less, 17% or less, 16.5% or less, 16% or less, 15.5% or less, or 15% or less.

[0134] Meanwhile, the width of the coffee ring mentioned above refers to the maximum width of the formed coffee ring. More specifically, it refers to the width of the sediment ring formed after the coffee ring test.

[0135] The height of the above coffee ring refers to the thickness of the deposit layer formed after droplet drying, measured from the surface of the above substrate.

[0136] For the width and height values ​​of the coffee rings mentioned above, measurements can be taken at 5 points for one coffee ring and for a total of 3 rings, and the average value of a total of 15 data points can be used.

[0137]

[0138] In addition, the water electrolysis catalyst of the present invention may have a contact angle with water of 130° or less, preferably 80° or more, 85° or more, 90° or more, 95° or more, 100° or more, 105° or more, 108° or more, 110° or more, or 112° or more, and may be 130° or less, 127° or less, 125° or less, 123° or less, 120° or less, 118° or less, or 116° or less.

[0139] The water electrolysis catalyst of the present invention may have a contact angle with respect to bubbles of 150° or more, preferably 150° or more, 152° or more, 154° or more, or 156° or more, and may be 170° or less, 167° or less, 165° or less, 163° or less, 160° or less, or 158° or less.

[0140] The water electrolysis catalyst of the present invention can have appropriate hydrophilicity and aerobicity by satisfying the above-described conditions, and accordingly, the leaching of catalyst components during the water electrolysis process can be minimized while maintaining performance during the water electrolysis process.

[0141] Meanwhile, the contact angle with respect to water and the contact angle with respect to bubbles may be measured through the following method.

[0142] 1) Contact angle with water:

[0143] A 2 µL water droplet was dropped onto the surface of a water electrolysis catalyst, and the contact angle at the interface formed between the droplet and the catalyst surface was measured.

[0144] 2) Contact angle for the bubble:

[0145] After immersing the water electrolysis catalyst in water, 5 μl of air bubbles were injected into the water to form bubbles attached to the surface of the catalyst, and the contact angle of the bubbles was measured.

[0146]

[0147] Ink composition

[0148] The present invention includes an ink composition comprising the water electrolysis catalyst described above. The ink composition may be intended for manufacturing a membrane-electrode assembly by coating the water electrolysis catalyst onto a membrane.

[0149]

[0150] More specifically, the ink composition may include the water electrolysis catalyst, ionomer, and solvent described above.

[0151] The above ionomer refers to a polymer having ion conductivity, and ionomers commonly used in this field may be used. For example, commercial ionomers such as Nafion may be used.

[0152] The above solvent is intended to efficiently disperse the catalyst and ionomer for water electrolysis, and the solvent may be one or more selected from the group consisting of water, n-propyl alcohol, ethanol, and dimethylformamide.

[0153] The content of the water electrolysis catalyst in the ink composition may be 5% by weight or more and 15% by weight or less, preferably 5% by weight or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, or 9% by weight or more, and may be 15% by weight or less, 14% by weight or less, 13% by weight or less, 12% by weight or less, or 11% by weight or less.

[0154] A membrane-electrode assembly can be manufactured by coating the above ink composition onto a membrane.

[0155]

[0156] Electrode for water electrolysis

[0157] The present invention provides an electrode for water electrolysis comprising the above-mentioned catalyst for water electrolysis. The electrode for water electrolysis may have the above-mentioned catalyst coated on a substrate, and the substrate may be a membrane. That is, the electrode for water electrolysis may be a membrane-electrode assembly.

[0158]

[0159] The electrode for water electrolysis provided by the present invention may be an anode. During the water electrolysis process, an oxygen evolution reaction is performed at the anode, and the catalyst for water electrolysis of the present invention may exhibit excellent catalytic activity for the oxygen evolution reaction.

[0160]

[0161] In the electrode for water electrolysis of the present invention, the iridium content per unit area of ​​the electrode for water electrolysis is 0.1 mg / cm² 2 Above and 2 mg / cm² 2 It may be less than or equal to, preferably 0.1 mg / cm² 2 ≥ or 0.2 mg / cm² 2 Above, and 2 mg / cm² 2 Less than 1.5 mg / cm² 2 Less than 1.0 mg / cm² 2 Less than or equal to 0.5 mg / cm² 2 The following may apply. The electrode for water electrolysis according to the present invention has a relatively low iridium content per unit area and can achieve excellent performance even with a small iridium loading amount.

[0162]

[0163] water electrolysis cell

[0164] The present invention provides a water electrolysis cell comprising the aforementioned electrode for water electrolysis.

[0165]

[0166] The above-mentioned electrode for water electrolysis may be an anode, and accordingly, the above-mentioned water electrolysis cell may include an anode for water electrolysis and a cathode for water electrolysis according to the present invention.

[0167]

[0168] More specifically, the anode for water electrolysis may be coated with the water electrolysis catalyst of the present invention on one side of a membrane, and the cathode for water electrolysis may be coated with a hydrogen generation catalyst on the opposite side of the membrane. Accordingly, the anode and cathode for water electrolysis may constitute a membrane-electrode assembly.

[0169] Meanwhile, the above membrane can be any membrane used in a water electrolysis cell without any special restrictions, and more specifically, the above membrane may be a cation exchange membrane.

[0170] In addition, the water electrolysis cell of the present invention may include a gas diffusion layer formed on both sides of the membrane-electrode assembly and a separator formed on the outer side of the gas diffusion layer.

[0171] The above gas diffusion layer may be a porous diffusion layer that allows the formed gas to move smoothly, and the above separator may serve to protect the water electrolysis cell while distinguishing it from other cells.

[0172]

[0173] Method for manufacturing a catalyst for water electrolysis

[0174] The present invention provides a method for manufacturing a catalyst for water electrolysis as described above.

[0175]

[0176] More specifically, the present invention provides a method for manufacturing a catalyst for water electrolysis comprising the step of forming a coating layer containing titanium oxide on the surface of iridium oxide particles.

[0177] In the method for manufacturing a catalyst for water electrolysis according to the present invention, the coating layer can be formed through various methods, and for example, it can be formed through methods such as sonochemical synthesis, sol-gel synthesis, or atomic film deposition. More specifically, when using the sonochemical synthesis method, the catalyst for water electrolysis according to the present invention can be synthesized by introducing a precursor capable of forming titanium oxide and iridium oxide particles, which serve as the substrate, into a solvent, irradiating them with ultrasound for a certain period of time, and then drying and washing. A compound such as TiO(acac)2 can be used as the precursor capable of forming titanium oxide, and DMSO can be used as the solvent. Furthermore, the ultrasonic irradiation can be performed under an inert atmosphere, more specifically under a nitrogen atmosphere, and the washing can be performed using ethanol.

[0178] When using the above sol-gel synthesis method, a titanium precursor such as titanium butoxide is mixed with an acidic solution in a certain ratio, and then iridium oxide is added to the solution and heat treatment is performed to form a coating layer containing titanium oxide on the surface of the iridium oxide.

[0179] The above atomic film deposition method is a suitable method for forming a thin and uniform coating layer, and in particular, when using the above atomic film deposition method, it may be easy to control the water electrolysis catalyst of the present invention to have a coverage rate of 25 to 100%. More specifically, the coverage rate may vary depending on the control of various process variables during the process of forming a coating layer using the atomic film deposition method; for example, by appropriately controlling the number of repetitions of the atomic film deposition cycle, the coverage rate can be controlled to be within the range of 30 to 120%.

[0180]

[0181] Hereinafter, the present invention will be described in more detail through examples and experimental examples to specifically explain the invention, but the present invention is not limited by these examples and experimental examples. The embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0182]

[0183] ingredient

[0184] Crystalline iridium oxide particles with a specific surface area of ​​52 m² 2 It was used that had a particle size of 1 / g, an average particle size of primary particles of 2 nm, and an average particle size of secondary particles of 1 μm. It was confirmed that the crystalline content of the above crystalline iridium oxide particles was 50 wt% or more.

[0185] Amorphous iridium oxide particles with a specific surface area of ​​100 m² 2 A particle with a particle size of 1 / g, an average particle size of 5 nm for the primary particles, and an average particle size of 0.5 μm for the secondary particles was used. It was confirmed that the amorphous content of the above amorphous iridium oxide particles was 80 wt% or more.

[0186]

[0187] Example 1-1

[0188] 2.5 g of prepared crystalline iridium oxide particles were loaded onto a square tray. Then, the tray was placed into a chamber within an ALD apparatus, and the chamber temperature was set to 100°C and the process pressure to 1 Torr. Subsequently, tetrakis(dimethylamino)titanium, a titanium precursor at 50°C, was pulse-injected into the chamber for 360 seconds along with 60 sccm of nitrogen gas as a carrier gas, followed by purging for 800 seconds. Then, water was pulse-injected for 2 seconds and purged again for 540 seconds. This process was defined as one cycle, and the cycle was repeated three times to produce a catalyst for water electrolysis.

[0189]

[0190] Examples 1-2

[0191] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 1-1 above, except that the atomic film deposition cycle was repeated 5 times.

[0192]

[0193] Examples 1-3

[0194] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 1-1 above, except that the atomic film deposition cycle was repeated 7 times.

[0195]

[0196] Examples 1-4

[0197] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 1-1 above, except that the atomic film deposition cycle was repeated 10 times.

[0198]

[0199] Examples 1-5

[0200] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 1-1 above, except that the atomic film deposition cycle was repeated 15 times.

[0201]

[0202] Comparative Example 1-1

[0203] The iridium oxide particles used in Example 1-1 above were used as a catalyst for water electrolysis.

[0204]

[0205] Comparative Example 1-2

[0206] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 1-1 above, except that the atomic film deposition cycle was repeated once.

[0207]

[0208] Comparative Examples 1-3

[0209] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 1-1 above, except that the atomic film deposition cycle was repeated 30 times.

[0210]

[0211] Example 2-1

[0212] 2.5 g of prepared amorphous iridium oxide particles were loaded onto a square tray. Then, the tray was placed into a chamber within an ALD apparatus, and the chamber temperature was set to 100°C and the process pressure to 1 Torr. Subsequently, tetrakis(dimethylamino)titanium, a titanium precursor at 50°C, was pulse-injected into the chamber for 720 seconds along with 60 sccm of nitrogen gas as a carrier gas, followed by purging for 800 seconds. Then, water was pulse-injected for 4 seconds and purged again for 540 seconds. This process was defined as one cycle, and the cycle was repeated three times to produce a catalyst for water electrolysis.

[0213]

[0214] Example 2-2

[0215] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 2-1 above, except that the atomic film deposition cycle was repeated 5 times.

[0216]

[0217] Examples 2-3

[0218] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 2-1 above, except that the atomic film deposition cycle was repeated 7 times.

[0219]

[0220] Comparative Example 2-1

[0221] The iridium oxide particles used in Example 2-1 above were used as a catalyst for water electrolysis.

[0222]

[0223] Comparative Example 2-2

[0224] A catalyst for water electrolysis was prepared by carrying out the same procedure as in Example 2-1 above, except that the atomic film deposition cycle was repeated 30 times.

[0225]

[0226] Experimental Example 1. Measurement of the coating rate of the manufactured water electrolysis catalyst

[0227] The coverage rate of the catalysts prepared in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-3 was measured. The titanium content in each catalyst was measured using ICP. In addition, the total weight of the catalyst was measured, and the weight of titanium oxide in the catalyst was calculated using the titanium content in each catalyst. ICP-OES analysis was performed under the following conditions.

[0228] 1) Sample preparation: 4 mL of aqua regia and 5 drops of hydrogen peroxide were added to 0.01 g of catalyst, and then heated on a hot plate to dissolve it. Afterward, a small amount of hydrogen peroxide was added to promote the dissolution of the catalyst, and once the catalyst was completely dissolved, the sample was diluted with tertiary ultrapure water to a total solution volume of 50 mL to prepare the analytical sample.

[0229] 2) Analysis equipment and conditions: The analysis was performed under the conditions of Agilent 5110, RF power 1300W, Torch Height 15mm, Plasma Gas 15L / min, Sample Gas 0.8L / min, Aux. Gas 0.2L / min, and Pump Speed ​​1.5mL / min.

[0230]

[0231] In addition, the average thickness of the coating layer was measured by observing the prepared catalyst using TEM imaging. A Talos F200X (FETEM, 200kV, ThermoFisher) was used for TEM imaging.

[0232]

[0233] The coverage rate of each catalyst was calculated using Equation 1 and the weight of titanium oxide in the catalyst, the average thickness of the coating layer, the theoretical true density of titanium oxide, and the specific surface area of ​​iridium oxide particles measured by the above method. In calculating the coverage rate using Equation 1, the weight of the iridium oxide particles (m sub ) 2.5g, and the specific surface area (SSA) of the iridium oxide particles is 52m 2 / g was applied. The results are summarized in Table 1 below.

[0234]

[0235] Cycle count Ti (wt%) TiO2 wt (m coat , g) Coating layer thickness (t, nm) Coverage rate (%) Example 1-13 1.8 80.0 80.4 36.6 Example 1-25 2.5 60.1 10.4 50.4 Example 1-37 3.3 20.1 40.4 64.1 Example 1-4 10 4.3 90.1 80.4 82.4 Example 1-5 15 6.5 40.2 70.7 70.6 Comparative Example 1-10 ---- Comparative Example 1-21 1.3 60.0 570.4 26.1 Comparative Example 1-33 13.0 10.5 40.7 141.3

[0236] As indicated in the table above, the coverage rate varied depending on the number of cycles in the atomic film deposition process, and it was confirmed that the coverage rate of the coating layer of the water electrolysis catalyst could be controlled within a certain range by appropriately adjusting the atomic film deposition conditions.

[0237]

[0238] Experimental Example 2. XPS analysis of the prepared water electrolysis catalyst

[0239] The surface of the catalysts prepared in the above examples and comparative examples was analyzed by XPS.

[0240] (1) XPS analysis conditions

[0241] 1) XPS Analysis Equipment: K-alpha+, Thermo Fisher Scientific Inc.

[0242] 2) X-ray source conditions: monochromatic Al Kα (1486.6 eV)

[0243] 3) Calibration Standard: CF2 and IrO2 Reference Standards

[0244] 4) Surface charge compensation: default FG03 mode(150μA, 0.5V)

[0245] 5) Sample Pretreatment: Proceed without pretreatment / sputtering

[0246] 6) Analysis Mode: CAE (Constant Analyzer Energy) Mode

[0247] 7) X-ray spot size: 400㎛

[0248] 8) Sample form: Measured in powder form

[0249]

[0250] (2) Quantification conditions

[0251] 1) Software: Avantage Software (version 5.992)

[0252] 2) Peak Background: Smart method applied

[0253] 3) Regarding the titanium peak: Since there is an overlapping region between the Ir 4f and Ti 3s peaks, the Ir 4f content was calculated using peak fitting (estimation of the Ti 3s peak region from the Ti 2p peak region).

[0254]

[0255] The binding energy graphs obtained for Comparative Example 1-1, Example 1-1, and Comparative Example 1-3 are shown in FIG. 1, and the binding energy graphs obtained for Comparative Example 2-1 and Examples 2-1 to 2-3 are shown in FIG. 2. As can be seen in FIG. 1 and 2, as the number of atomic film deposition cycles increases and the content of titanium oxide in the coating layer formed on the iridium oxide particles increases, the Ir 4f confirmed by analysis using X-ray photoelectron analysis (XPS) 5 / 2 Peak and 4f 7 / 2 It can be seen that the position of the peak shifts to the right (the binding energy decreases). In addition, as the content of titanium oxide in the coating layer increases, the overlapping region of the Ir 4f and Ti 3s peaks (the binding energy region of approximately 60 to 62 eV) increases, and it was confirmed that the precise binding energy value of each peak can be determined by applying the aforementioned quantification conditions related to the titanium peak.

[0256] The results obtained through the above analysis process are summarized in Tables 2 to 6 below.

[0257] O(at%)Ti(at%)O / Ti Atomic RatioC(at%) Example 1-151.713.93.719.1 Example 1-249.811.94.221.5 Example 1-353.316.23.214.9 Example 1-447.620.22.421.5 Example 1-550.620.92.419.6 Comparative Example 1-164.5--4.9 Comparative Example 1-253.96.48.47.4 Comparative Example 1-353.723.72.313.5

[0258] ALD cycle number bond energy (eV) Ir 4f 5 / 2 Ir 4f 7 / 2 Ir 4f5 / 2 - Ir 4f 7 / 2 (Ir 4f 5 / 2 ) / (Ir 4f 7 / 2 Comparative Example 1-10 65.162.13.01.048 Example 1-13 64.761.73.01.049 Example 1-25 64.961.93.01.048 Example 1-37 64.161.42.71.044 Comparative Example 1-33 064.061.32.71.044

[0259] Content (at%) Ir and Ti content (at%) Ir for each oxidation state 4+ Ir 3+ Ir 0 Ir 4+ / Ir 3+ IrTiTi / Ir Comparative Example 1-123.235.12.30.66130.6--Example 1-123.834.91.70.68112.313.91.130 Example 1-225.634.11.30.75113.911.90.862 Example 1-329.623.48.71.26511.416.21.421 Comparative Example 1-332.423.25.21.3974.723.75.043

[0260] ALD cycle number bond energy (eV) Ir 4f 5 / 2 Ir 4f 7 / 2 Ir 4f 5 / 2 - Ir 4f 7 / 2 (Ir 4f 5 / 2 ) / (Ir 4f 7 / 2 Comparative Example 2-10 65.562.531.048 Example 2-13 64.761.92.81.045 Example 2-25 64.261.82.41.039 Example 2-37 64.261.82.41.039 Comparative Example 2-23 063.861.72.11.034

[0261] Content (at%) Ir and Ti content (at%) Ir for each oxidation state 4+ Ir 3+ Ir 0 Ir 4+ / Ir 3+IrTiTi / Ir Comparative Example 2-114.941.41.90.36023.2--Example 2-130.532.49.90.9416.418.62.906Example 2-225.019.532.11.2821.922.812.000Example 2-314.920.620.40.7232.220.29.182Comparative Example 2-29.221.652.00.4350.721.630.857

[0262] As described in the table above, the surface composition of the water electrolysis catalyst of the present invention includes titanium, oxygen, and carbon within a certain range, and by forming a coating layer under appropriate conditions on crystalline or amorphous iridium oxide particles through atomic film deposition, it can be seen that the binding energy and oxidation state content characteristics confirmed by XPS analysis satisfy certain conditions.

[0263]

[0264] Experimental Example 3. Evaluation of Catalytic Activity

[0265] A membrane-electrode assembly was prepared using the catalysts prepared in the above examples and comparative examples. An ink composition containing the catalyst of the example or comparative example, a solvent, and an ionomer was prepared (catalyst content in the ink composition: 13.6 wt%). The ink composition was then applied to a PTFE film and dried to form an electrode layer on the PTFE film. The electrode layer formed on the film was then transferred to an electrolyte membrane (fluorine-based cation exchange membrane) at 140°C to prepare the membrane-electrode assembly. A cell evaluation was performed using the membrane-electrode assembly prepared in this manner. A Pt / C catalyst was used as the negative electrode of the cell, and the negative electrode was formed on the opposite side of the previously prepared membrane-electrode assembly. Titanium felt was used as the gas diffusion layer for the anode, and a carbon gas diffusion layer was used as the gas diffusion layer for the negative electrode. The cell evaluation condition was 3 A / cm² 2 Constant current, temperature of 80℃, water flow rate of 10–40 mL / min, and cell area of ​​4 cm 2 It was conducted for 100 hours.

[0266] 1) LSV (Linear Sweep Voltammetry): Starting from a set initial voltage (1.2V), the current-voltage curve is measured while varying the voltage at a constant scan rate of 10mV / s until a specific voltage (2V) is reached, and the initial performance of the cell is the current density value corresponding to 1.9V (Unit: A / cm²). 2 ) and current density 3A / cm² 2 The voltage value (unit: V) at was read and measured.

[0267] 2) Ohmic resistance (Ω·cm) 2 @ 1.2V): The electrochemical impedance measurement method was used. The x-intercept value of the high-frequency region in the Nyquist plot obtained by applying an AC signal from the high-frequency to low-frequency range at the voltage at which the water electrolysis electrochemical reaction begins was taken as the ohmic resistance value.

[0268] 3) Cell degradation rate: 2 x 2 cm 2 Supplying water to the cell at 80℃, 3A / cm 2 A constant current was applied in 100-hour intervals. Subsequently, using the linear scan potential method under the same conditions as the initial performance measurement above, 0.04 A / cm² 2 From 3A / cm 2 Measure the cell voltage value up to 3A / cm 2 The cell degradation rate (unit: mV / khr) at 1,000 hours was calculated by dividing the change in current cell voltage relative to the initial cell voltage by the evaluation time.

[0269] 4) Iridium Loading Amount: Using the PTFE release film used during the above manufacturing process, the weight of the release film before and after transfer was measured, and the iridium loading amount (unit: mg / cm²) was determined based on this. 2 ) was calculated. The weight ratio of iridium in the electrode layer was confirmed through the ink composition. For the ink solvent used, a mixed solvent of water and n-propanol mixed in a weight ratio of 3:7 was used, Nafion was used as the ionomer, and the ionomer / catalyst weight ratio was set to 10%.

[0270]

[0271] The measurement results were summarized in Tables 7 and 8 below.

[0272] Coverage (%) Iridium Loading Amount Initial Cell Performance Ohmic Resistance @1.2V Cell Degradation Rate (mV / khr) J @1.9V (A / cm²) 2 )V@3A / cm 2 (V) Example 1-1 36.60.42.971.9229.828.5 Example 1-25 0.40.43.031.9226.415.7 Example 1-36 4.10.382.801.9227.46.2 Example 1-482.40.422.451.9830.320 Example 1-5 70.60.382.212.0234.1-30 Comparative Example 1-1-0.42.841.9225.530 Comparative Example 1-226.10.42.681.9429.029 Comparative Example 1-31 41.30.42.331.9731.0136

[0273] Current density (A / cm²) 2 @ 1.9V, 80℃) Degradation rate (mV / khr, 3A / cm²) 2 Comparative Example 2-13.0085 Example 2-12.761.8 Example 2-22.737.3 Example 2-32.6722 Comparative Example 2-22.65630

[0274] From the results in the table above, it can be seen that the water electrolysis catalyst according to the embodiment of the present invention is superior in terms of durability compared to the water electrolysis catalyst according to the comparative example. In addition, some embodiments showed superior initial performance compared to the comparative example and exhibited excellent results in terms of performance due to low ohmic resistance.

[0275]

[0276] Experimental Example 4. Coffee Ring Test for Water Electrolysis Catalyst

[0277] A coffee ring test was performed on the water electrolysis catalysts prepared in Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1-3. The conditions for the coffee ring test are as follows.

[0278] 1) Conditions for preparing the dispersion:

[0279] Prepare a dispersion by dispersing 0.01g of a water electrolysis catalyst in 10mL of n-propanol.

[0280] 2) Conditions for entry:

[0281] Slide glass (MarineFiled Microscope slides, Precleaned plain)

[0282] 3) Drying conditions:

[0283] Form a 5 µL droplet on a slide glass heated to 80°C using a 25GA Precision Tip (Nordson), and dry thoroughly until completely dry.

[0284] 4) Measurement Conditions: Measure the width and height of the coffee ring at 100x magnification using a Confocal Laser Microscope (KEYENCE, VK-200 series).

[0285]

[0286] The width-to-height ratio of the coffee rings formed through the above process was measured. The width and height of the coffee rings were measured at 5 points for one coffee ring and for a total of 3 rings, and the average value of a total of 15 data points was used.

[0287]

[0288] In addition, the contact angle of the water electrolysis catalyst with respect to water and the contact angle with respect to bubbles were measured using the following method.

[0289] 1) Contact angle with water:

[0290] A 2 µL water droplet was dropped onto the surface of a water electrolysis catalyst, and the contact angle at the interface formed between the droplet and the catalyst surface was measured.

[0291] 2) Contact angle for the bubble:

[0292] After immersing the water electrolysis catalyst in water, 5 μl of air bubbles were injected into the water to form bubbles attached to the surface of the catalyst, and the contact angle of the bubbles was measured.

[0293]

[0294] The above measurement results are summarized in Table 9 below.

[0295] Average Width / Height (%) Values ​​of Coffee Ring Contact Angle (°) for Water Contact Angle (°) for Bubble Example 1-1 13.12 122 150 Example 1-2 15.32 116 154 Example 1-3 14.88 110 157 Example 1-4 14.91 12 156 Example 1-5 16.89 111 160 Comparative Example 1-1 4.56 133 148 Comparative Example 1-2 5.12 125 151 Comparative Example 1-3 17.69 111 160

[0296] As indicated in the table above, it can be seen that the water electrolysis catalyst of the present invention possesses appropriate hydrophilicity and aerobicity, and these characteristics of the water electrolysis catalyst can be interpreted as the cause enabling excellent performance and durability when the water electrolysis catalyst is applied to an electrode as described above.

Claims

1. Iridium oxide particles; and A coating layer formed on at least a portion of the surface of the particle; comprising The above coating layer includes titanium oxide, and A catalyst for water electrolysis in which the coverage rate of iridium oxide particles by the above coating layer is 30% or more and 120% or less.

2. In Paragraph 1, The above iridium oxide particles are a catalyst for water electrolysis having a secondary particle form formed by the aggregation of multiple primary particles having an average particle size of 0.1 nm or more and 20 nm or less.

3. In Paragraph 1, The specific surface area of ​​the above iridium oxide particles is 30 m² 2 / g or more and 130m 2 A catalyst for water electrolysis with a g or less.

4. In Paragraph 1, A catalyst for water electrolysis having an iridium content of 50% by weight or more and 70% by weight or less based on the total weight of the catalyst.

5. In Paragraph 1, A catalyst for water electrolysis having a titanium content of 0.5 wt% or more and 10 wt% or less based on the total weight of the catalyst.

6. In Paragraph 1, A catalyst for water electrolysis in which the atomic ratio of O / Ti in the coating layer is 1.2 to 5.

0.

7. In Paragraph 1, A catalyst for water electrolysis having a carbon content of 10 at% or more and 30 at% or less in the coating layer.

8. In Paragraph 1, A catalyst for water electrolysis having a coating layer thickness of 0.1 nm or more and 2 nm or less.

9. In Paragraph 1, The above iridium oxide particles contain 40 weight percent or more of crystalline iridium oxide, and Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 5 / 2 A catalyst for water electrolysis having peak binding energies of 64.1 eV or higher and 65 eV or lower.

10. In Paragraph 9, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 7 / 2 A catalyst for water electrolysis having peak binding energies of 61.4 eV or higher and 62 eV or lower.

11. In Paragraph 1, The above iridium oxide particles contain 60 weight percent or more of amorphous iridium oxide, and Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 5 / 2 A catalyst for water electrolysis having peak binding energies of 64 eV or higher and 65 eV or lower.

12. In Paragraph 11, Ir 4f confirmed through analysis using X-ray photoelectron analysis (XPS) 7 / 2 A catalyst for water electrolysis having peak binding energies of 61.8 eV or higher and 62.3 eV or lower.

13. In Paragraph 1, A water electrolysis catalyst in which the average value of the width / height of the coffee ring measured as a result of a coffee ring test under the following conditions is 8% or more and 17.5% or less: [Coffee Ring Test Conditions] 1) Conditions for preparing the dispersion: Prepare a dispersion by dispersing 0.01g of a water electrolysis catalyst in 10mL of n-propanol. 2) Conditions for entry: Slide glass (MarineFiled Microscope slides, Precleaned plain) 3) Drying conditions: Form a 5 µL droplet on a slide glass heated to 80°C using a 25GA Precision Tip (Nordson), and dry thoroughly until completely dry. 4) Measurement conditions: Measured the width and height of the coffee ring at 100x magnification using a Confocal Laser Microscope (KEYENCE, VK-200 series).

14. In Paragraph 1, A catalyst for water electrolysis having a contact angle with water of 130° or less.

15. In Paragraph 1, A catalyst for water electrolysis having a contact angle with a bubble of 150° or more.

16. A catalyst for water electrolysis according to any one of paragraphs 1 to 15; Ionomer; and Ink composition for a membrane-electrode assembly comprising a solvent.

17. In Paragraph 16, An ink composition in which the solvent is one or more selected from the group consisting of water, n-propyl alcohol, ethanol, and dimethylformamide.

18. An electrode for water electrolysis comprising a catalyst for water electrolysis according to any one of claims 1 to 15.

19. A water electrolysis cell comprising an electrode for water electrolysis according to paragraph 18.

20. A method for manufacturing a catalyst for water electrolysis according to claim 1, comprising the step of forming a coating layer containing titanium oxide on the surface of iridium oxide particles.

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