Electrodes for electrolytic processes and methods for manufacturing them

Abstract

Electrodes for electrolytic processes, particularly anodes suitable for oxygen evolution in industrial electrolytic processes, and methods for producing them. More specifically, MMO-coated titanium anodes for electrochemical reactions used in oxygen evolution reactions (OER) in various applications such as electrolytic extraction, electroplating, electrogalvanizing, and electrolytic copper foil manufacturing, as well as methods for producing anodes.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefits of U.S. Provisional Patent Application No. 63 / 493,623, filed on 31 March 2023, the contents of which are incorporated herein by reference.

[0002] The present invention relates to electrodes for electrolytic processes, particularly anodes suitable for oxygen generation in industrial electrolytic processes, and a method for manufacturing the same. [Background technology]

[0003] Oxygen-evolving anodes are widely used in various electrolytic applications, some of which are related to the field of electrolytic metallurgy, covering a wide range in terms of applied current density, which can be very low (for example, several hundred A / m² as in the case of electrolytic extraction processes). 2 ), or in some cases very high (for example, in high-speed electroplating, 10 kA / m with respect to the anode surface). 2 (It may work in extreme conditions).

[0004] Electrodes suitable for oxygen anode generation can be obtained starting from a substrate of valve metal, such as titanium or its alloys, coated with a catalyst composition based on a transition metal or its oxide, which is characterized by its ability to reduce the overpotential of the oxygen anode discharge reaction, which is too high to carry out industrial processes in the absence of the catalyst system.

[0005] Mixed metal oxide (MMO) electrodes are characterized by their low consumption rate, long service life (compared to sacrificial anodes), near-constant dimensional stability throughout their entire service life, and lightweight nature. The use of titanium anodes coated with mixed metal oxide (MMO) catalysts has been increasing over the decades.

[0006] MMO-coated titanium anodes for electrochemical reactions are used in oxygen evolution reactions (OER) in a variety of applications, including electrolytic extraction, electroplating, electrogalvanizing, and electrolytic copper foil manufacturing.

[0007] Generally, for MMO-coated titanium anodes used in OER applications, an iridium-based oxide coating (commonly mixed with an oxide of a valve metal such as tantalum) is applied as a catalyst. The MMO coating is applied to the titanium substrate as a liquid metal salt and then thermally decomposed to form a layer of mixed oxides. Multiple layers of MMO coating are applied, and each coating is heat-treated afterward.

[0008] Iridium is a rare metal. Because it is one of the least abundant precious metals in the Earth's crust, it is not only expensive but also difficult to purchase in large quantities for industrial-scale manufacturing processes. Furthermore, the price of iridium has risen significantly in recent years due to increased demand for organic light-emitting diode (LED) applications and "green hydrogen."

[0009] Electrodes with iridium-based catalytic coatings are manufactured by pyrolysis, a well-established and cost-effective technique with lower risks compared to other processes such as PVD (Physical Vapor Deposition) or plasma spraying. However, because iridium-based coatings are typically multi-layer coatings, the manufacturing process is costly.

[0010] Ruthenium-based MMO coatings are commonly used in the production of chlorine or hypochlorite for the chemical industry. Due to the instability of RuO2, ruthenium-based MMO coatings are practically unsuitable for electrolytic processes involving oxygen evolution reactions in acidic environments, such as electro-galvanizing, aluminum anodizing, metal recovery, and metal plating, which ultimately affects their long-term performance.

[0011] The object of the present invention is to provide an oxygen generation electrode that utilizes ruthenium as part of the catalytic coating element, with improved durability while keeping costs low by reducing the amount of iridium used. By utilizing ruthenium as part of the catalytic element, the present invention provides an improved anode for industrial electrolytic processes such as electrolytic extraction and electroplating of base metals such as copper, nickel, and cobalt. [Overview of the project]

[0012] The present invention provides an electrode for an electrolytic process comprising a valve metal substrate including a coating, wherein the coating is composed of a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate, and the coating is characterized by a diffusion region between the barrier layer and the catalyst layer that includes oxides of the metals constituting the barrier layer and the catalyst layer.

[0013] More specifically, the electrode for electrolytic processes according to the present invention is The valve includes a metal substrate with a coating, the coating includes a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate, The catalyst layer contains a metal oxide composition with a percentage ratio of 17-42% Ta, 40-57% Ru, 19.5-26% Ir, and 0-9% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the catalyst layer. The barrier layer comprises a metal oxide composition with a percentage ratio of 25-40% Ta, 0-16% Ru, 0-9% Ir, and 44-55% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the barrier layer. The coating is characterized by a diffusion region throughout the barrier layer and catalyst layer that contains metal oxides of the metals constituting the barrier and catalyst layers, the diffusion region containing metal oxides in the following percentage ratios: 17–41% Ta, 17–39% Ru, 10–26% Ir, and 14–37% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the diffusion region.

[0014] The present invention also relates to a method for manufacturing an electrode for an electrolysis process, comprising: a) optionally, pretreating a valve metal substrate to obtain a pretreated substrate having a suitable surface roughness (e.g., in the range of 2.0 to 10.0 μm with respect to the arithmetic mean value (Ra) of the roughness profile); b) mixing a tin hydroxyacetochloride (SnHAC) complex solution, a tantalum solution, and a 10 wt% aqueous acetic acid solution to obtain a Sn-Ta barrier layer solution; c) preparing a precursor solution of Ru, Ir, and Ta to obtain an Ir-Ru-Ta catalyst coating solution; d) applying the Sn-Ta barrier layer solution from step b) to the pretreated substrate, followed by drying, pyrolysis treatment, and cooling to obtain a Sn-Ta barrier layer-coated substrate; e) optionally, repeating step d) until the total addition amount with respect to Sn and Ta metals in the coated substrate reaches 1.0 to 13.0 g / m 2 ; f) applying the catalyst coating solution from step c) to the Sn-Ta barrier layer-coated substrate, followed by drying, pyrolysis treatment, and cooling; g) optionally, repeating step f) until the total addition amount of the catalyst coating reaches 2.0 to 20.0 g / m 2 with respect to the total of noble metals Ir and Ru. The present invention also provides a method comprising the above steps.

[0015] Furthermore, the present invention also provides an electrode obtained by the method discussed above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] FIG. 1 shows an energy dispersive spectroscopy (EDS) line scan analysis of a Ru-containing coating according to Comparative Example 1: (Sn:Ta = 70:30 mol%, 6 g-(Sn + Ta) / m2, 4 coats) + (Ir:Ru = 25:75 mol%, 9.1 g-NM / m2). [Figure 2]An enlarged view of the Ru-containing coating specified as "line data 11" in FIG. 1 according to the prior art. [Figure 3] A chart showing the % concentration and position of elements on the surface of the Ru-containing coating according to the comparative example. [Figure 4] A diagram showing the EDS line scanning analysis of the Ru-containing coating according to Example 2 of the present invention: Ir-Ru-Ta catalyst coating, Sn:Ta = 70:30 mol%, 6 g-(Sn + Ta) / m2, 4 coats)+(Ir:Ru:Ta = 21:64:15 mol%, 8.3 g-NM / m2). [Figure 5] An enlarged view of the Ru-containing coating specified as "line data 10" in FIG. 4 according to the present invention. [Figure 6] A chart showing the % concentration and position of elements on the surface of the Ru-containing coating according to the present invention. [Figure 7A] A chart showing the respective coating compositions according to the present invention at spot 1 and the different compositions of metal oxides in the diffusion region of the coating composition. [Figure 7B-7C] A corresponding data graph of the coating according to the present invention (designated as F10) at spot 1, respectively. [Figure 7D] A corresponding EDS image of the coating according to the present invention (designated as F10) at spot 1. [Figure 7E] A corresponding EDS image of the coating according to the present invention (designated as F10) at spot 1. [Figure 7F] A chart showing the respective coating compositions according to the present invention at spot 2 and the different compositions of metal oxides in the diffusion region of the coating composition. [Figure 7G-7H] A corresponding data graph of the coating according to the present invention (designated as F10) at spot 2, respectively. [Figure 7I] A corresponding data chart of the coating according to the present invention (designated as F10) at spot 2. [Figure 7J]This is the corresponding EDS image of the coating according to the present invention (indicated as F10) at spot 2. [Figure 7K] This is the corresponding EDS image of the coating according to the present invention (indicated as F10) at spot 2. [Figure 8A] This chart shows the different compositions of the coating compositions (denoted as F7) according to Comparative Example 1, and the different compositions of metal oxides in the diffusion region of the coating compositions. [Figure 8B-8C] These are the corresponding data graphs for the coating (indicated as F7) applied to Spot 1 using Comparative Example 1. [Figure 8D] This is the corresponding EDS image of the coating (labeled F7) at spot 1 using comparative example 1. [Figure 8E] This is the corresponding EDS image of the coating (labeled F7) at spot 1 using comparative example 1. [Figure 8F] This chart shows the different compositions of the coating compositions (indicated as F7) according to Comparative Example 1 in Spot 2, as well as the different compositions of metal oxides in the diffusion region of the coating compositions. [Figure 8G-8H] These are the corresponding data graphs for the coating (indicated as F7) in Spot 2 using Comparative Example 1. [Figure 8I] This is the corresponding data chart for the coating (indicated as F7) in Spot 2 using Comparative Example 1. [Figure 8J] This is the corresponding EDS image of the coating (labeled F7) in Spot 2 according to Comparative Example 1. [Figure 8K] This is the corresponding EDS image of the coating (labeled F7) in Spot 2 according to Comparative Example 1. [Modes for carrying out the invention]

[0017] The present invention An electrode for an electrolytic process comprising a valve metal substrate including a coating, wherein the coating includes a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate, The catalyst layer comprises a metal oxide composition with a percentage ratio of 17-42% Ta, 40-57% Ru, 19.5-26% Ir, and 0-9% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the catalyst layer. The barrier layer comprises a metal oxide composition with a percentage ratio of 25-40% Ta, 0-16% Ru, 0-9% Ir, and 44-55% Sn relative to the total amount of Ta + Ru + Ir + Sn present in the barrier layer. The present invention provides an electrode for electrolytic processes in which the coating is characterized by a diffusion region containing metal oxides of the metals constituting the barrier layer and the catalyst layer throughout the entire space between the barrier layer and the catalyst layer, wherein the diffusion region contains metal oxides in percentage ratios of 17-41% Ta, 17-39% Ru, 10-26% Ir, and 14-37% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the diffusion region.

[0018] In another embodiment, the electrode coating is A catalyst layer containing a total of Ta + Ru + Ir + Sn, with a percentage ratio of 17-21% Ta, 50-57% Ru, 22-26% Ir, and 2-7% Sn. A barrier layer containing a percentage ratio of 34-40% Ta, 7-16% Ru, 4-9% Ir, and 44-46% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the barrier layer, and A diffusion region containing the following percentage ratios of Ta, Ru, Ir, and Sn relative to the total amount of Ta, Ru, Ir, and Sn present in the diffusion region: 21-34% Ta, 22-39% Ru, 12-26% Ir, and approximately 14-31% Sn. It holds.

[0019] In yet another embodiment, the catalyst layer may have a metal oxide composition with respect to the atomic percent of metal present in the catalyst layer, approximately 2.75–5.24% Ta, approximately 8.81–17.63% Ru, approximately 3.73–8.24% Ir, and approximately 0.24–0.53% Sn, and / or a metal oxide composition with respect to the total amount of Ta+Ru+Ir+Sn present in the catalyst layer, where 17–21% Ta, 50–57% Ru, 22–26% Ir, and 0–7% Sn are present. The barrier layer may have a metal oxide composition with respect to the atomic percent of metal present in the barrier layer, approximately 5.98-11.86% Ta, approximately 1.08-5.13% Ru, approximately 1.05-2.30% Ir, and approximately 6.83-14.16% Sn, and / or a metal oxide composition with respect to the total amount of Ta+Ru+Ir+Sn present in the barrier layer, corresponding to a percentage ratio of 34-40% Ta, 7-16% Ru, 0-9% Ir, and 44-46% Sn. The diffusion region may contain metal oxides with atomic percentages of approximately 9.61–14.14% Ta, approximately 9.15–18.11% Ru, approximately 4.91–11.88% Ir, and approximately 6.69–12.86% Sn, and / or metal oxides with percentage ratios of 21–34% Ta, 22–39% Ru, 12–26% Ir, and approximately 14–31% Sn relative to the total Ta+Ru+Ir+Sn present in the diffusion region.

[0020] In one embodiment, the metal oxide in the catalyst layer may have the following composition, measured at different points across the coating thickness: TIFF2026511659000001.tif33170

[0021] This ratio is relative to the total amount of Ta + Ru + Ir + Sn present in the catalyst layer.

[0022] In another embodiment, the metal oxide in the barrier layer may have the following compositions, measured at different points across the coating thickness: TIFF2026511659000002.tif28170

[0023] This ratio is relative to the total amount of Ta + Ru + Ir + Sn present in the barrier layer.

[0024] In a further embodiment, the metal oxide in the diffusion region has the following composition: TIFF2026511659000003.tif28170

[0025] This ratio is relative to the total amount of Ta + Ru + Ir + Sn present in the diffusion region.

[0026] The above are some examples of metal oxide compositions in coatings according to the present invention. Further metal oxide compositions and data such as tables and graphs can be found in Figures 7A to 7K. The metal oxide composition of Comparative Example 1 and data such as charts and graphs can be found in Figures 8A to 8K.

[0027] The cross-sectional line scans in the figure were obtained by energy-dispersive X-ray spectroscopy (EDS) measurements performed on samples (e.g., examples and comparative examples) in conjunction with gallium ion beam milling. The operator selected appropriate spots free of coating defects, as would be recognizable to those skilled in the art, and measured the relative amounts of elements Ru, Ta, Sn, and Ir across the coating thickness. At each data point, the amounts were automatically normalized with respect to the sum of the Ga, C, O, Ta, Ru, Ir, Cl, Sn, and Ti signals. The figure shows the change in the relative amounts of Ru, Ta, Sn, and Ir across the coating thickness. Other elements, including the Ti signal from the substrate, are not shown.

[0028] Here, and throughout this application, it is understood that the relative percentages of Ru, Ta, Sn, and Ir describing the observed electrode composition are obtained via EDS measurements (as shown in the figure) after further normalization with respect to the sum of the Ru, Ta, Sn, and Ir signals individually.

[0029] Depending on the coating thickness, the amount of metal oxide present in each part of the coating, including the diffusion region calculated based on the distance from the substrate, changes slightly. However, the relative amounts of each metal oxide remain within the same range.

[0030] For the purposes of this invention, a diffusion region does not mean the presence or formation of another “layer” between the layers constituting the coating. Rather, a diffusion region refers to a convergence or bonding region where elements of the barrier layer and catalyst layer overlap and diffuse to each other, forming a diffusion region within the coating. In fact, it is known in the art that in single-layer or multi-layer coating compositions, each layer can be obtained by applying multiple precursor solutions, and each coating is heat-treated after drying, and certain elements can ultimately diffuse along the coating thickness. This effect is often due to differences in elemental volatility, interactions between elements, and the temperature and firing time used. However, in most cases, even if the final result is reproducible based on the specific techniques and parameters used in coating preparation, the diffusion pattern cannot be easily and accurately predicted in advance. The way in which elements diffuse throughout the single-layer or multi-layer coating composition can impart unexpected properties to the coating.

[0031] In this invention, the diffusion of elements across the barrier layer and catalyst layer alters their initial composition, i.e., the amount and material used as precursors, and furthermore, regions where the elements of the catalyst layer and barrier layer overlap are formed. The fact that Sn and Ir penetrate a larger portion of the coating than expected is thought to be related to the remarkable robustness and durability of this coating, as well as its activity.

[0032] Furthermore, the inventors surprisingly observed that adding Ta to the Ir-Ru coating stabilizes the active elements Ir and Ru, increasing the compatibility of the catalyst coating with the Sn-Ta barrier layer, thereby improving the adhesion of the catalyst coating to the Sn-Ta barrier layer. This effectively delays the peeling of the catalyst coating from the Sn-Ta barrier layer, resulting in improved durability.

[0033] Furthermore, the Ta in the catalyst coating acts as a binder element for Ir and Ru, stabilizing them. Additionally, the presence of Ta in the catalyst layer improves compatibility with the Sn-Ta barrier layer. The coating of this invention allows for wider diffusion, resulting in a longer electrode lifespan.

[0034] The combination of Ta and Sn in the barrier layer, and their diffusion pattern throughout the coating, protect the substrate from corrosion or passivation in oxidative corrosion environments.

[0035] Therefore, Ta must always be present in the barrier layer. The barrier layer must be conductive and stable in oxidative and corrosive environments. To make the barrier layer conductive, Ta needs to be mixed with another element that has a different valency and is stable in oxidative and corrosive environments. Sn-Ta is an excellent choice as the barrier layer of the present invention because SnO2 is more conductive and stable in oxidative and corrosive environments.

[0036] In one aspect of the present invention, the electrode for an electrolytic process according to the present invention is obtained by applying a catalyst coating solution containing 18-21 mol% iridium, 52-64 mol% ruthenium, and 15-30 mol% tantalum to a valve metal substrate; and a barrier layer solution containing valve metal oxide tin and tantalum.

[0037] More specifically, a method for manufacturing an electrode having the above characteristics is: a) Preferably, a step of pre-treating the valve metal substrate to obtain a pre-treated substrate having a surface roughness in the range of 2.0 to 10.0 μm with respect to the arithmetic mean (Ra) of the roughness profile; b) A step of mixing a tin hydroxyacetochloride (SnHAC) complex solution, a tantalum solution, and a 10 wt% aqueous acetic acid solution to obtain a Sn-Ta barrier layer solution; c) A step of preparing precursor solutions of Ru, Ir, and Ta to obtain an Ir-Ru-Ta catalyst coating solution; d) The Sn-Ta barrier layer solution from step b) is preferably applied to a pre-treated substrate, followed by drying, thermal decomposition, and cooling to room temperature (approximately 25°C) to obtain a substrate coated with a Sn-Ta barrier layer; e) Optionally, 1.0 to 13.0 g / m² of Sn and Ta metals on the coated substrate. 2 The process involves repeating step d) until the total amount of additive is reached; f) The catalyst coating solution from step c) is applied to the substrate coated with a Sn-Ta barrier layer, followed by drying, thermal decomposition treatment, and cooling to room temperature; g) Optionally, 2.0 to 20.0 g / m³ of the total of the precious metals Ir and Ru. 2 The process of repeating step f) until the total amount of catalyst coating is reached, We also provide methods that include this.

[0038] The above method allows for the electrolytic process, particularly the oxygen evolution reaction in electrolytic extraction, or at temperatures of 200 to 2,000 A / m². 2 It is possible to obtain electrodes for similar applications such as electroplating, characterized by operating current densities in the range of [specify range]. The resulting electrodes exhibit comparable or improved durability compared to Ir-rich coatings, while the total amount of Ir is reduced. This is achieved by partially substituting Ir with Ru, and the latter's stability issues in electrolytic extraction applications are overcome by using specific combinations of elements and amounts in the catalyst layer and barrier layer coating solutions described above.

[0039] As a result, SEM analysis reveals a bilayer fingerprint, but the distribution of elements is different from the distinct amounts used in the catalyst layer and barrier layer coating solution, resulting in an electrode with a composite coating structure.

[0040] Indeed, as shown by EDS (energy-dispersive spectroscopy) line scanning performed on multiple samples obtained via the aforementioned method with elements within the claimed scope, the elements of the resulting electrodes are diffused throughout the entire coating thickness, and although not bound by any particular theory, their distribution pattern appears to confer favorable properties of the electrodes in terms of both durability and activity, even if other factors may be at play.

[0041] It would be impossible to capture the observed line scanning pattern without unduly limiting the scope of the patent claims, because electrodes obtained by the above method may exhibit significant structural variability, even while conforming to the desired specifications.

[0042] Advantageously, the above method makes it possible to obtain an electrode for an electrolytic process comprising a valve metal substrate including a coating, wherein the coating is composed of a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate, and the coating layer is characterized by a diffusion region between the barrier layer and the catalyst layer that includes oxides of the metals constituting the barrier layer and the catalyst layer. It has been noted that this electrode exhibits particularly excellent performance in the implementation of the present invention.

[0043] In one embodiment, the method uses a catalyst coating solution containing 18-21 mol% iridium, 52-64 mol% ruthenium, and 15-30 mol% tantalum.

[0044] In another embodiment, the method uses a barrier layer solution containing tin and tantalum oxides in a Sn:Ta ratio of 70-90:30-10 mol%.

[0045] In further embodiments, in steps d) and f) of the above method, the drying temperature may be between 25°C and 60°C. In yet another embodiment, in steps d) and f) of the above method, the pyrolysis treatment is carried out in an electric furnace at a temperature range of 480-530°C for 10 to 20 minutes.

[0046] If the decomposition time is too short, the coated metal precursor cannot be completely converted to oxide. However, if the decomposition time is too long, the coated titanium is given a sufficiently high thermal profile, reducing its durability. Therefore, in this invention, the pyrolysis treatment is carried out in an electric furnace for 10 to 20 minutes.

[0047] Furthermore, the temperature range used during thermal decomposition in this invention is 480 to 530°C. Below this temperature range, the coated metal precursor is not sufficiently converted to oxide and does not function properly as a barrier layer.

[0048] In another aspect of the present invention, in step a) of the method described above, the pretreatment step (which is performed optionally) is carried out by first sandblasting with alumina grit, then blasting with steel grit, and then etching in a 20 wt% hydrochloric acid aqueous solution at boiling temperature for 20 minutes; after etching, rinsing the substrate with deionized water and drying it.

[0049] In a further aspect of the present invention, in step b) of the above method, the Sn-Ta barrier layer solution is obtained by mixing a 1.65 M tin hydroxyacetochloride (SnHAC) complex solution, a 120 g / L tantalum solution, and a 10 wt% aqueous acetic acid solution.

[0050] In yet another aspect of the present invention, in step c) of the above method, the Ru precursor of the catalyst coating solution is RuCl3 or RuHAC. The Ir precursor used in the catalyst coating solution of the present invention is IrCl3, H2IrCl6 or IrHAC, and the Ta precursor fused in the present invention is TaCl5.

[0051] In one embodiment, in step c), the precursor solutions of Ru, Ir, and Ta are obtained by mixing H2IrCl6 solution, 20 wt% RuCl3 solution, 120 g / L tantalum solution, and 10 wt% HCl.

[0052] The valve metal base material can be niobium, zirconium, titanium, or titanium alloy.

[0053] In another embodiment, the present invention relates to an electrode that can be obtained by a method comprising applying a barrier layer solution containing tin and tantalum oxides in a Sn:Ta ratio of 70-90:30-10 mol% to a substrate, followed by drying, thermal decomposition, and cooling; and then applying a catalyst coating solution containing 18-21 mol% iridium, 52-64 mol% ruthenium, and 15-30 mol% tantalum to the barrier layer, followed by drying, thermal decomposition, and cooling.

[0054] In a preferred embodiment, the electrode obtained by the above method includes a substrate having a coating, the coating including a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate. The catalyst layer comprises a metal oxide composition with a proportion of approximately 2.75-5.24% Ta, approximately 8.81-17.63% Ru, approximately 3.73-8.24% Ir, and approximately 0.0-0.53% Sn, with respect to the atomic percentage of metal present in the catalyst layer; and / or a metal oxide composition with proportions of 17-21% Ta, 50-57% Ru, 22-26% Ir, and 0-7% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the catalyst layer. The barrier layer comprises a metal oxide composition with respect to the atomic percentage of metal present in the barrier layer, comprising approximately 5.98-11.86% Ta, approximately 0-5.13% Ru, approximately 0-2.30% Ir, and approximately 6.83-14.16% Sn, and / or a metal oxide composition with respect to the total amount of Ta+Ru+Ir+Sn present in the barrier layer, comprising 34-40% Ta, 0-16% Ru, 0-9% Ir, and 44-46% Sn. The coating is characterized by a diffusion region containing metal oxides that make up the barrier layer and the catalyst layer throughout the entire region between the barrier layer and the catalyst layer. The diffusion region contains, in atomic % of the metal, approximately 9.61 - 14.14% Ta, approximately 9.15 - 18.11% Ru, approximately 4.91 - 11.88% Ir, and approximately 6.69 - 12.86% Sn, and / or metal oxides corresponding to a percentage ratio of 21 - 34% Ta, 22 - 39% Ru, 12 - 26% Ir, and approximately 14 - 31% Sn with respect to the total of Ta + Ru + Ir + Sn present in the diffusion region.

[0055] In one embodiment, the specific addition amount of the catalyst layer according to the present invention is from 2.0 to 20.0 g / m with respect to the noble metals (Ru + Ir) 2 , preferably from 6.0 to 12.0 g / m with respect to the noble metals (Ru + Ir) 2 , more preferably 9.0 g / m with respect to the noble metals (Ru + Ir) 2 and is in the range of.

[0056] In another embodiment, the specific addition amount of the barrier layer is from 1.0 to 13.0 g / m with respect to the Sn and Ta metals 2 , preferably from 3.0 to 9.0 g / m with respect to the Sn and Ta metals 2 , more preferably 6.0 g / m with respect to the Sn and Ta metals 2 and is in the range of.

[0057] Some of the most important results obtained by the inventors are shown in the following examples, which are not intended to limit the scope of the present invention.

Examples

[0058] Example 1 Pretreatment of the substrate The titanium sheet was first sandblasted with alumina grit, then blasted with steel grit, and then subjected to etching in a 20 wt% hydrochloric acid aqueous solution at a boiling temperature of about 106 °C for 20 minutes. After the etching process, the titanium sheet substrate was rinsed with deionized water and then dried. The surface roughness of the substrate is 3.8 μm.

[0059] Preparation of barrier layer solution A 1.65 M tin hydroxyacetochloride (SnHAC) complex solution was prepared according to the procedure described in WO2005014885.

[0060] A 120 g / L tantalum solution was prepared by dissolving Ta(V) chloride salt in concentrated hydrochloric acid.

[0061] A barrier layer solution with a Sn:Ta ratio of 70:30 mol% was prepared by mixing a 1.65 M SnHAC solution, a 120 g / L tantalum solution, and a 10 wt% aqueous acetic acid solution.

[0062] Preparation of catalyst coating solution A catalyst coating solution with an Ir:Ru:Ta ratio of 18:52:30 mol% was prepared by mixing a 20 wt% H2IrCl6 solution, a 20 wt% RuCl3 solution, a 120 g / L tantalum solution, and 10 wt% HCl.

[0063] Application of barrier layer The prepared Sn-Ta barrier layer solution was applied to a pre-treated titanium sheet substrate by brushing it onto the substrate, and then dried at 60°C for 10 minutes. After drying, thermal decomposition was carried out in an air-circulating electric furnace at 520°C for 10 minutes, followed by cooling at room temperature.

[0064] The above cycle of brush application, drying, thermal decomposition, and cooling was performed with a total additive amount of 6.0 g / m² for Sn and Ta metals. 2 This was repeated until it reached the target.

[0065] Application of catalyst layer The prepared Ir-Ru-Ta catalyst coating solution was applied to a barrier-coated titanium sheet substrate by brushing it onto the substrate, and then dried at 60°C for 10 minutes. After drying, thermal decomposition was carried out in an air-circulating electric furnace at 475°C for 10 minutes, followed by cooling at room temperature.

[0066] This cycle of brush application, drying, thermal decomposition, and cooling is performed with a total additive amount of 9.0 g / m² in relation to the combined precious metals Ir and Ru. 2 This was repeated until it reached the target.

[0067] Example 2 Substrate pretreatment The titanium sheet was first sandblasted with alumina grit, then blasted with steel grit, and then etched in a 20 wt% hydrochloric acid aqueous solution at boiling temperature (approximately 106°C) for 20 minutes. After etching, the titanium sheet substrate was rinsed with deionized water and then dried.

[0068] Preparation of barrier layer solution A 1.65 M tin hydroxyacetochloride (SnHAC) complex solution was prepared according to the procedure described in WO2005014885.

[0069] A 120 g / L tantalum solution was prepared by dissolving Ta(V) chloride salt in concentrated hydrochloric acid.

[0070] A barrier layer solution with a Sn:Ta ratio of 70:30 mol% was prepared by mixing a 1.65 M SnHAC solution, a 120 g / L tantalum solution, and a 10 wt% aqueous acetic acid solution.

[0071] Preparation of catalyst coating solution A catalyst coating solution with an Ir:Ru:Ta ratio of 21:64:15 mol% was prepared by mixing a 20 wt% H2IrCl6 solution, a 20 wt% RuCl3 solution, a 120 g / L tantalum solution, and 10 wt% HCl.

[0072] Application of barrier layer The prepared Sn-Ta solution was applied to a pre-treated titanium sheet substrate by brushing it onto the substrate, and then dried at 60°C for 10 minutes. After drying, thermal decomposition was carried out in an air-circulating electric furnace at 520°C for 10 minutes, and then cooled in air at room temperature.

[0073] The above cycle of brush application, drying, thermal decomposition, and cooling was performed with a total additive amount of 6.0 g / m² for Sn and Ta metals. 2 This was repeated until it reached the target.

[0074] Application of catalyst layer The prepared Ir-Ru-Ta solution was applied to a titanium sheet substrate coated with a barrier layer by brushing it onto the substrate, and then dried at 60°C for 10 minutes. After drying, thermal decomposition was carried out in an air-circulating electric furnace at 475°C for 10 minutes, followed by cooling in air at room temperature.

[0075] The cycle of brush application, drying, thermal decomposition, and cooling was performed with a total additive amount of 9.0 g / m² for the combined noble metals Ir and Ru. 2 This was repeated until it reached the target.

[0076] Examples 3-9 Examples 3-9 were prepared in the same manner as in Examples 1-2, except that the molar ratio of the barrier layer solution to the catalyst layer solution was as follows: TIFF2026511659000004.tif54170

[0077] Comparative Example 1 Substrate pretreatment The titanium sheet was first sandblasted with alumina grit, then blasted with steel grit, and then etched in a 20 wt% hydrochloric acid aqueous solution at boiling temperature for 20 minutes. After etching, the titanium sheet substrate was rinsed with deionized water and then dried.

[0078] Preparation of barrier layer solution A 1.65 M tin hydroxyacetochloride (SnHAC) complex solution was prepared according to the procedure described in WO2005014885.

[0079] A 120 g / L tantalum solution was prepared by dissolving Ta(V) chloride salt in concentrated hydrochloric acid.

[0080] A barrier layer solution with a Sn:Ta ratio of 70:30 mol% was prepared by mixing a 1.65 M SnHAC solution, a 120 g / L tantalum solution, and a 10 wt% aqueous acetic acid solution.

[0081] Preparation of catalyst coating solution A catalyst coating solution with an Ir:Ru:Ta ratio of 25:75:0 mol% was prepared by mixing a 20 wt% H2IrCl6 solution, a 20 wt% RuCl3 solution, n-butanol, and acetic acid.

[0082] Application of barrier layer The prepared Sn-Ta barrier layer solution was applied to a pre-treated titanium sheet substrate by brushing it onto the substrate, and then dried at 60°C for 10 minutes. After drying, thermal decomposition was performed in an air-circulating electric furnace at 520°C for 10 minutes, followed by cooling in air.

[0083] The above cycle was performed with a total additive amount of 6.0 g / m² for Sn and Ta metals. 2 This was repeated until it reached the target.

[0084] Application of catalyst layer The prepared Ir-Ru solution was applied to a coated titanium sheet substrate by brushing it onto the substrate, and then dried at 60°C for 10 minutes. After drying, thermal decomposition was performed in an air-circulating electric furnace at 475°C for 10 minutes, followed by cooling in air.

[0085] The above cycle of brush application, drying, thermal decomposition, and cooling was performed with a total additive amount of 9.0 g / m² for the combined noble metals Ir and Ru. 2 This was repeated until it reached the target.

[0086] Comparative Examples 2-3 Comparative Examples 2 and 3 were prepared in the same manner as in Comparative Example 1, except that the molar ratio of the barrier layer solution to the catalyst layer solution was as follows: TIFF2026511659000005.tif28170Table 1 TIFF2026511659000006.tif80170

[0087] The lifespan test of the coating in the example was performed under the following conditions: - Electrolyte: 150 g / L aqueous solution of H2SO4 - Electrolysis temperature: 65℃ - Current density applied to the anode sample: 1 kA / m 2 - Counter electrode: Zr plate

[0088] Lifetime (hours) was defined as the period during which the cell voltage increased by 2 volts from its initial value. Lifetime was normalized by the amount of Ir added. Two tests were performed for each sample. The results are summarized in Table 2. Table 2 TIFF2026511659000007.tif75170

[0089] As can be seen from the results in Table 2, the presence of Ta in the outer catalyst coating layer allows for the dispersion of the noble metal active element. Ta acts as a binder between the catalyst coating and the barrier layer, resulting in higher durability. The results shown in Table 2 are expressed as "lifetime (hours)" and "amount of noble metal added (g / m²)". 2 This was obtained by dividing by "). This is the "normalized" lifetime of the present invention.

[0090] Passivation of the titanium substrate (formation of low-conductivity TiO2), corrosion of the titanium substrate and the resulting peeling of the coating from the titanium substrate, peeling of the catalyst coating from the barrier layer, and consumption of active elements (Ir and Ru) are phenomena that may occur before and after the end of the lifetime test (a voltage increase of 2 volts).

[0091] Examples 1 and 2 contain Ta in the catalyst coating, while Comparative Example 1 does not. Table 2 shows the lifetime test results for each coating formulation. The improvement in lifetime in Examples 1 and 2 is related to the stabilization of Ir and Ru in the catalyst coating by the addition of Ta as a binder, as well as the improvement in adhesion between the catalyst coating and the Sn-Ta barrier layer. These two tests are established procedures and are representative of each sample.

[0092] Similarly, Examples 3-9, which have Ta in the catalyst coating, show improved lifetime test results compared to Comparative Example 1, which does not have Ta in the catalyst coating. The improvement in lifetime in Examples 3-9 is also related to the stabilization of Ir and Ru in the catalyst coating by the addition of Ta as a binder, as well as the improved adhesion between the catalyst coating and the Sn-Ta barrier layer.

[0093] The foregoing description is not intended to limit the present invention, and the present invention can be used in accordance with various embodiments without departing from its scope, which is defined solely by the appended claims.

[0094] Throughout the specification and claims of this application, the term “comprise,” and its variations such as “comprising” and “comprises,” are not intended to exclude the presence of other elements, components, or additional process steps.

[0095] Discussions relating to documents, actions, materials, devices, articles, etc., are included herein solely for the purpose of providing the context of the present invention. It is not implied or represented that any or all of these matters constituted part of the prior art base in the art relating to the present invention or were general knowledge prior to the priority date of each claim of this application.

Claims

1. An electrode for an electrolytic process comprising a valve metal substrate including a coating, wherein the coating includes a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate, The catalyst layer comprises a metal oxide composition in which, relative to the total amount of Ta + Ru + Ir + Sn present in the catalyst layer, the percentage ratios are 17-42% Ta, 40-57% Ru, 19.5-26% Ir, and 0-9% Sn. The barrier layer comprises a metal oxide composition in which, relative to the total amount of Ta + Ru + Ir + Sn present in the barrier layer, the percentage ratios are 25-40% Ta, 0-16% Ru, 0-9% Ir, and 44-55% Sn. An electrode for electrolytic processes, wherein the coating is characterized by a diffusion region throughout the barrier layer and catalyst layer containing metal oxides of the metals constituting the barrier layer and catalyst layer, and the diffusion region contains metal oxides in percentage ratios of 17–41% Ta, 17–39% Ru, 10–26% Ir, and 14–37% Sn relative to the total amount of Ta+Ru+Ir+Sn present in the diffusion region.

2. The catalyst layer contains a percentage ratio of 17-21% Ta, 50-57% Ru, 22-26% Ir, and 2-7% Sn relative to the total amount of Ta + Ru + Ir + Sn present in the catalyst layer. The barrier layer contains a percentage ratio of 34-40% Ta, 7-16% Ru, 4-9% Ir, and 44-46% Sn relative to the total amount of Ta + Ru + Ir + Sn present in the barrier layer. The diffusion region contains a percentage ratio of 21–34% Ta, 22–39% Ru, 12–26% Ir, and approximately 14–31% Sn relative to the total amount of Ta + Ru + Ir + Sn present in the diffusion region. The electrode according to claim 1.

3. The composition of metal oxides in the catalyst layer is in the following percentage ratios relative to the total amount of Ta + Ru + Ir + Sn present in the catalyst layer: The electrode according to claim 1, including the following:

4. The composition of metal oxides in the barrier layer is in the following percentage ratios relative to the total amount of Ta + Ru + Ir + Sn present in the barrier layer: The electrode according to claim 1, including the following:

5. The composition of metal oxides in the diffusion region is in the following percentage ratios relative to the total amount of Ta + Ru + Ir + Sn present in the diffusion region. The electrode according to claim 1, including the following:

6. The electrode according to claim 1, wherein the valve metal substrate is niobium, zirconium, titanium, or titanium alloy.

7. The electrode according to claim 1, wherein the surface roughness of the substrate is 2.0 to 10.0 μm with respect to the arithmetic mean (Ra) of the roughness profile, preferably 2.0 to 5.0 μm, more preferably 3.8 μm.

8. The amount of catalyst coating added ranges from 2.0 to 20.0 g / m² with respect to the total of the precious metals iridium and ruthenium. ２ Preferably, 6.0 to 12.0 g / m³ with respect to the combined total of the precious metals iridium and ruthenium. ２ , more preferably 9.0 g / m³ with respect to the combined total of the precious metals iridium and ruthenium. ２ The electrode according to claim 1.

9. The amount of additives in the barrier layer coating is 1.0 to 13.0 g / m² for tin and tantalum. ２ Preferably, with respect to tin and tantalum, 3.0 to 9. 0 g / m ２ , more preferably 6.0 g / m² with respect to tin and tantalum. ２ The electrode according to claim 1.

10. A method for manufacturing electrodes for an electrolytic process, a. Optionally, pre-treat the valve metal substrate to obtain a pre-treated substrate having a surface roughness in the range of 2.0 to 10.0 μm with respect to the arithmetic mean (Ra) of the roughness profile; b. To obtain a Sn-Ta barrier layer solution by mixing a tin hydroxyacetochloride (SnHAC) complex solution, a tantalum solution, and a 10 wt% aqueous acetic acid solution; c. Preparing precursor solutions of Ru, Ir, and Ta to obtain an Ir-Ru-Ta catalyst coating solution; d. Applying the Sn-Ta barrier layer solution from step b) to an optional pre-treated substrate, followed by drying, thermal decomposition, and cooling, to obtain a substrate coated with a Sn-Ta barrier layer; e. Optionally, 1.0 to 13.0 g / m² of Sn and Ta metals in the coated substrate. ２ Repeat step d) until the total amount of additive is reached; f. The catalyst coating solution from step c) is applied to the substrate coated with a Sn-Ta barrier layer, followed by drying, thermal decomposition treatment, and cooling; g. Optionally, the total amount of precious metals Ir and Ru is between 2.0 and 20.0 g / m³. ２ Repeat step f) until the total amount of catalyst coating is reached. Methods that include...

11. The method according to claim 10, wherein the catalyst coating solution comprises 18 to 21 mol% iridium, 52 to 64 mol% ruthenium, and 15 to 30 mol% tantalum.

12. The method according to claim 10, wherein the barrier layer solution contains tin and tantalum oxides with a Sn:Ta ratio of 70-90:30-10 mol%.

13. The method according to claim 10, wherein in step a), the pretreatment step is carried out by first sandblasting with alumina grit, then blasting with steel grit, and then etching in a 20 wt% hydrochloric acid aqueous solution at boiling temperature for 20 minutes; after etching, rinsing the substrate with deionized water and drying it.

14. The method according to claim 10, wherein in step b), the Sn-Ta barrier layer solution is obtained by mixing a 1.65 M tin hydroxyacetochloride (SnHAC) complex solution, a 120 g / L tantalum solution, and a 10 wt% aqueous acetic acid solution.

15. In step c), the Ru precursor of the catalyst coating solution is RuCl ３ or RuHAC, the Ir precursor is IrCl ３ , H ２ IrCl ６ or IrHAC, and the Ta precursor is TaCl ５ The method according to claim 10, wherein the Ta precursor is TaCl

16. In step c), the precursor solutions of Ru, Ir, and Ta are H ２ IrCl ６ Solution, 20 wt% RuCl ３ The method according to claim 10, obtained by mixing the solution, a 120 g / L tantalum solution, and 10 wt% HCl.

17. The method according to claim 10, wherein in steps d) and f), the drying temperature can be between 25°C and 60°C.

18. The method according to claim 10, wherein in steps d) and f), the pyrolysis treatment is carried out in an electric furnace at a temperature range of 480 to 530°C for 10 to 20 minutes.

19. An electrode that can be obtained by a method comprising applying a barrier layer solution containing tin and tantalum oxides in a Sn:Ta ratio of 70-90:30-10 mol% to a valve metal substrate, followed by drying, thermal decomposition, and cooling; and then applying a catalyst coating solution containing 18-21 mol% iridium, 52-64 mol% ruthenium, and 15-30 mol% tantalum to the barrier layer, followed by drying, thermal decomposition, and cooling, wherein the electrode comprises a coating including a catalyst layer and a barrier layer interposed between the catalyst layer and the substrate.

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