Iridium-tantalum coating titanium anode with high specific surface area and preparation method thereof

Abstract

The invention discloses an iridium-tantalum coating titanium anode with a high specific surface area and a preparation method of the iridium-tantalum coating titanium anode, and belongs to the technical field of coating titanium anodes, and the preparation method comprises the following steps: introducing an alcoholic solution into a middle layer coating solution; during the preparation of the middle layer, drying at low temperature, sintering, cooling, and repeating for at least three times; preparing a precious metal catalysis coating solution; adding a part of the noble metal catalytic coating liquid into an ethylene glycol solution to prepare an alcohol-containing noble metal catalytic coating liquid; when the catalyst layer is prepared, alcohol-containing noble metal catalytic coating liquid is firstly coated, and the process is repeated for at least 15 times; then coating the noble metal catalysis coating liquid, and repeating for at least three times; sintering is performed after drying at low temperature. Compared with a traditional titanium anode, the prepared iridium tantalum coating titanium anode has the advantages of being higher in reaction specific surface area, lower in oxygen evolution potential, longer in catalytic life and the like, and an idea is provided for development of a novel high-catalytic-activity insoluble titanium anode.

Description

Technical Field

[0001] This invention mainly relates to the field of coated titanium anode technology, specifically to an iridium-tantalum coated titanium anode with high specific surface area and its preparation method. Background Technology

[0002] Titanium-based metal oxide coated anodes (also known as size-stabilized anodes, DSAs) have gradually replaced traditional graphite and precious metal anodes due to their excellent electrocatalytic activity, mechanical strength, and stability, becoming the preferred choice for many electrolysis processes. Among them, iridium-tantalum (Ir-Ta) oxide coated anodes are considered one of the ideal candidate materials for applications in acidic or harsh oxidizing environments because they still exhibit excellent oxygen evolution reaction activity and corrosion resistance at high current densities.

[0003] However, there is still room for further optimization of existing Ir-Ta oxide-coated anodes.

[0004] For example, patent application CN116516405A discloses a method for preparing titanium-based anode materials with an iridium-tantalum coating. This method involves uniformly mixing an iridium metal salt solution and an alcohol solution of a tantalum metal chloride salt in a specific ratio, repeatedly brushing the mixture onto the surface of a pre-sandblasted, acid-washed, and surface-treated metal plate, and then sintering it multiple times to form an anode material for electrolysis. The anode material obtained by this method has the characteristics of high electrolysis efficiency and stable and controllable voltage in the electrolytic cell during the electrolysis process; moreover, the electrode material manufacturing process is highly controllable, and anode materials with a precious metal coating amount ranging from 5 to 100 g per unit area can be prepared according to the application requirements of the electrode material. However, this scheme, with "reducing precious metal waste and stabilizing electrolysis voltage" as its core objective, does not address the optimization of specific surface area, resulting in the following shortcomings: ① The coating solution system lacks the ability to actively regulate the microstructure of the coating; ② The single coating logic cannot simultaneously consider specific surface area and density; ③ Insufficient oxygen evolution activity and specific surface area.

[0005] Patent application CN119433451A discloses an iridium-tantalum coating for metal electrolytic anode plates and its preparation method, comprising the following raw materials: iridium acetylacetone, 1,3-propanediol, tantalum pentoxide, and dichlorodimethylplatinum. Grooves are formed on the surface of the metal anode plate, and then a portion of the base liquid is coated onto the surface of the metal anode plate, allowing the base liquid to penetrate into the grooves and form a base film on the surface. A doped film is then formed on the base film using a vacuum evaporation method. Utilizing the adhesive properties of the base film and the high adhesion provided by the grooves, the base film and the doped film are firmly bonded to the surface of the metal anode plate. The remaining base liquid contains 1,3-propanediol, whose carboxyl functional groups crosslink with dichlorodimethylplatinum to improve the coating's corrosion resistance, wear resistance, and adhesion to other materials, resulting in a strongly adhered iridium-tantalum coating that prevents coating peeling and ensures the corrosion resistance of the anode plate. However, this scheme, with "improving coating adhesion" as its core objective, relies on physical trenching and vacuum evaporation, without addressing the optimization of specific surface area and oxygen evolution activity. The technical solution has the following shortcomings: ① The application of high-boiling-point alcohols is limited, with no synergistic regulatory effect; ② It relies on physical deposition and trench structure, resulting in insufficient adaptability and efficiency; ③ The oxygen evolution potential and specific surface area are not optimized.

[0006] Therefore, there is an urgent need in this field for an improved method for preparing iridium-tantalum oxide titanium anodes, which aims to optimize the microstructure of the catalytic coating through innovative process techniques, thereby fundamentally improving its electrochemical active specific surface area, conductivity, and catalytic efficiency, in order to meet the urgent demand of modern electrochemical industry, especially high-end manufacturing, for high-performance anode materials. Summary of the Invention

[0007] This invention addresses the problem of overly simplistic solutions in existing technologies by providing a significantly different approach. It primarily offers a titanium anode with a high specific surface area iridium-tantalum coating and its preparation method, optimizing the microstructure of the catalytic coating to fundamentally enhance its electrochemical activity, specific surface area, conductivity, and catalytic efficiency.

[0008] In existing technologies, the core function of alcohols such as ethanol, isopropanol, and n-butanol is to dissolve metal salts (e.g., TaCl5, H2IrCl6) or adjust the viscosity of the coating solution. They are passive auxiliary solvents and do not involve the active regulation of the coating's microstructure. Those skilled in the art have long been influenced by this understanding, forming a fixed mindset that alcohols' functions are limited to improving coating fluidity and promoting metal salt dissolution, never realizing that high-boiling-point alcohols can actively regulate the coating structure through their complexation-thermal decomposition properties. This functional shift from passive dissolution to active regulation requires overcoming long-standing technological biases within the industry.

[0009] Current technology suggests that high-boiling-point alcohols (such as ethylene glycol, boiling point 197℃) present significant challenges in process adaptation compared to low-boiling-point alcohols (such as ethanol, boiling point 78℃): ① Slow evaporation rates can easily lead to coating accumulation and sagging on the substrate surface, affecting coating uniformity; ② Complexation reactions with metal salts may cause a decrease in coating stability (such as gelation and precipitation). It is widely believed in the industry that high-boiling-point alcohols are unsuitable for multi-coating-sintering processes. Based on past experience, technicians tend to avoid using high-boiling-point alcohols, forming a technological bias of abandoning exploration due to risk.

[0010] In existing technologies, coating modification is only applied to a single coating layer. For example, CN119433451A only adds 1,3-propanediol to the base liquid (to improve adhesion), without alcohol modification to the catalyst layer; CN116516405A only adds low-boiling-point alcohol to the mixed coating liquid (to dissolve metal salts), without distinguishing between the modification synergy of the intermediate layer and the catalyst layer. If alcohol modification is to be introduced into both the intermediate layer and the catalyst layer simultaneously, the alcohol content, volatilization rate, and sintering shrinkage rate of both must be precisely matched; otherwise, the interlayer stress difference will lead to coating cracking and peeling. Based on the industry consensus that interlayer modification easily causes stress imbalance, those skilled in the art would assume that modification is only applied to a single coating layer.

[0011] The traditional approach to increasing the specific surface area of ​​coatings is through physical pore creation (such as surface pore creation in CN116516405A and trenching in CN119433451A). However, this approach has inherent drawbacks: physical pores easily become channels for electrolyte penetration, leading to coating delamination from the substrate and shortened lifespan. Therefore, a misconception has formed within the industry that high specific surface area and long lifespan are mutually exclusive. Technicians generally believe that increasing pore size inevitably reduces stability, and have never attempted to resolve this contradiction through a combination of chemically modified pore creation and layered coating for sealing. This layered logic of first creating pores and then sealing them breaks the industry's binary trade-off of "either high specific surface area or long lifespan." Furthermore, those skilled in the art have long focused on physical pore creation, forming a path dependency and never exploring chemically modified pore creation. This shift from physical to chemical approaches breaks free from the technological framework the industry has long relied on.

[0012] Existing coating technologies all employ a single coating solution applied repeatedly, with the core principle being to increase coating thickness through multiple coatings. However, the catalytic layer of this invention is coated first with an alcohol-containing solution followed by a conventional solution. The core principle is to achieve complementary performance through a layered combination of different functional coating solutions: the alcohol-containing solution is responsible for increasing pore size, while the conventional solution is responsible for stabilizing the structure. This functional layering, rather than thickness stacking, design logic is completely opposite to the industry's conventional method of repeated coating with a single solution. Technicians, due to their preconceived notion that coating equals thickness increase, would find it difficult to conceive of this reverse design where coating equals functional combination.

[0013] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0014] A method for preparing an iridium-tantalum coated titanium anode with high specific surface area includes the following steps:

[0015] S1. Pre-treat the titanium substrate;

[0016] S2. Prepare the intermediate layer coating solution; an alcohol solution is introduced in this process.

[0017] S3. Preparation of intermediate layer: The intermediate layer coating solution prepared in step S2 is coated on the surface of the pretreated titanium substrate and dried at a temperature of 60-100℃ for 5-30 min; then sintering is performed and cooled to room temperature. The coating-drying-sintering-cooling process is repeated at least 3 times to obtain a titanium substrate with an intermediate layer.

[0018] S4. Prepare the precious metal catalytic coating solution: Prepare the coating solution by combining the iridium source, tantalum source, and solvent;

[0019] S5. Prepare an alcohol-containing noble metal catalytic coating solution: Take a portion of the noble metal catalytic coating solution prepared in step S4, add ethylene glycol solution, mix evenly, and obtain an alcohol-containing noble metal catalytic coating solution; wherein, the amount of ethylene glycol solution introduced is 1 / 10 to 3 / 10 of the volume of the noble metal catalytic coating solution.

[0020] The polyhydroxyl groups (-OH) of ethylene glycol and IrCl6 2- TaCl5 forms a polyol complex, stabilizing easily hydrolyzed and volatile metal chlorides at room temperature, preventing coating gelation or metal ion loss. Ethylene glycol, with a boiling point as high as 197℃, maintains liquid film wetting during the subsequent low-temperature drying stage of 60-100℃, slowing down the solvent evaporation gradient and reducing dry cracking. During sintering, the -OH and -CH2- groups of ethylene glycol burn in situ, releasing uniform micro-explosive heat, refining iridium-tantalum oxide grains, and simultaneously constructing a porous structure. The achieved effects include: ① Optimized coating microstructure: significantly increased iridium crystallinity, finer grains, and a substantial increase in electrochemically active specific surface area; ② Improved coating stability: no hydrolysis or agglomeration of metal salts, good coating uniformity, and avoidance of local component segregation; ③ Enhanced interlayer compatibility: simultaneous alcohol modification of the intermediate layer and catalyst layer, matching sintering shrinkage rates, and coating adhesion ≥62N. It breaks through the technical limitations of existing technologies that use only low-boiling-point alcohols as a dissolving medium and cannot actively control the coating structure, and overcomes the industry prejudice that high-boiling-point alcohols easily lead to abnormal viscosity of the coating solution and increased cracks after sintering.

[0021] Furthermore, the proportion of ethylene glycol introduced is precisely controlled at 1 / 10 to 3 / 10 of the volume of the titanium-tantalum mixture or the precious metal catalytic coating solution. The lower limit of the proportion meets the basic complexation requirements, avoids the hydrolysis of metal salts, and ensures the fluidity of the coating solution; the upper limit of the proportion maximizes the micro-bursting and pore-forming effect without causing the coating solution viscosity to exceed the standard, thus avoiding sagging and accumulation during coating. The consistent proportion between the intermediate layer and the catalytic layer ensures that the sintering shrinkage rates of the two are matched and the interlayer stress is balanced. The coating adhesion and electrode potential fluctuations of different batches of anodes are minimal, demonstrating performance stability; the moderate fluidity of the coating solution is conducive to uniform coating; and the precise amount of ethylene glycol avoids waste and reduces the activity loss caused by the agglomeration of precious metals.

[0022] S6. Preparation of the catalyst layer: On the intermediate layer, first coat the alcohol-containing noble metal catalyst coating solution prepared in step S5, and dry it at a temperature of 60-100℃ for 10-30 min; then sinter it and cool it to room temperature, repeating the coating-drying-sintering-cooling process at least 15 times; then coat the noble metal catalyst coating solution prepared in step S4, and repeat the coating-drying-sintering-cooling process at least 3 times, finally obtaining a high specific surface area iridium-tantalum coated titanium anode.

[0023] The catalyst layer employs a layered coating process, first applying an alcohol-containing noble metal catalytic coating solution followed by a conventional noble metal catalytic coating solution. The alcohol-containing catalytic coating solution constructs a highly porous substrate through micro-explosion pore enlargement, providing sufficient active sites for the oxygen evolution reaction (OER). The conventional catalytic coating solution covers the surface of the porous layer, forming a tightly sealed pore layer that blocks electrolyte permeation channels. Multiple coating processes ensure uniform pore structure, and the sealing coating guarantees coating density. The resulting coated titanium anode possesses both high specific surface area and increased number of active sites, while maintaining coating density. It achieves an anode lifespan ≥1550 hours, realizing synergistic performance optimization. Furthermore, the electrode potential is ≤0.90V, improving oxygen evolution efficiency and reducing electrolysis energy consumption. This method is suitable for high-precision electrochemical processes such as copper foil electrolysis, meeting the dual requirements of high activity and long lifespan. It resolves the long-standing industry core contradiction that high specific surface area and long lifespan are mutually exclusive, and also eliminates the traditional process defects of existing technologies that can only achieve single performance optimization and cannot simultaneously consider activity and stability.

[0024] Furthermore, after coating the intermediate layer and the catalyst layer, both are first dried at low temperature and then sintered. Low-temperature drying avoids the rapid evaporation of ethylene glycol that causes the coating solution to dry out quickly, allowing the complexation reaction to proceed fully and ensuring a uniform distribution of metal ions. Sintering and curing transform the metal salt into a stable IrO2 / Ta2O5 oxide structure, while simultaneously enhancing the adhesion between the coating and the substrate, as well as between layers. Separating drying and sintering processes avoids coating warping and cracking caused by direct high-temperature processing. This ensures that coating cracks only widen laterally (increasing the reaction area) without increasing the longitudinal depth (preventing electrolyte penetration), and there are no through cracks, reducing coating defects. The oxide structure is dense, without loosening or detachment, improving structural stability. Moreover, the low-temperature drying process is easy to replicate on a large scale, avoiding batch-to-batch performance differences and enhancing production controllability. This overcomes the technical pain points of traditional integrated drying and sintering processes, which easily lead to insufficient complexation reactions, metal ion agglomeration, and wasted catalytic active sites.

[0025] Further, in step S1, the pretreatment includes sandblasting, alkaline washing, etching, cleaning and drying; wherein, the etching treatment uses a 5% to 25% hydrochloric acid solution or a 10% to 30% sulfuric acid solution, and the etching time is 5 to 60 minutes.

[0026] Further, in step S2, the titanium source and tantalum source are added to the solvent and mixed evenly to obtain a titanium-tantalum mixture, and then ethylene glycol is added and mixed evenly to obtain an intermediate coating solution.

[0027] Further, in step S2, the titanium source is TiCl4, the tantalum source is TaCl5, and the solvent is dilute hydrochloric acid; the molar ratio of the titanium source and the tantalum source is 1:1; and the amount of ethylene glycol introduced is 1 / 10 to 3 / 10 of the volume of the titanium-tantalum mixture.

[0028] Further, in step S3, the sintering operation is as follows: sintering in a sintering furnace at a temperature of 520℃ for 30 minutes; the total metal loading for each coating is 0.4–0.6 g / m³. 2 .

[0029] Further, in step S4, the iridium source is first dissolved in the solvent and stirred until completely dissolved, then the tantalum source is added and mixed evenly to obtain a noble metal catalytic coating solution, wherein the molar ratio of iridium to tantalum is 7:3.

[0030] Furthermore, in step S4, the iridium source is H2IrCl6, the solvent is dilute hydrochloric acid, and the tantalum source is TaCl5.

[0031] Further, in step S5, after adding the ethylene glycol solution, the mixture is ultrasonically stirred for 30 minutes.

[0032] Furthermore, in step S6, the sintering temperature is 450–600℃, and the sintering time for each pass is 10–40 min; the Ir loading for each coating is 0.8–1.0 g / m³. 2 .

[0033] The present invention also provides a titanium anode with a high specific surface area iridium-tantalum coating, which is prepared by the above preparation method. The prepared iridium-tantalum coated titanium anode has a coating adhesion of more than 62N, an electrode potential of less than 0.90V, and a lifespan of more than 1550h.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) This invention introduces a specific proportion of high-boiling-point ethylene glycol into the iridium-tantalum precursor solution and the intermediate coating solution, and combines it with a conventional aqueous solution system to construct a catalytic layer, which effectively controls the microstructure of the coating: on the one hand, it increases the amount of iridium crystals and makes the grains finer, and on the other hand, it improves the crack morphology of the coating (increases the transverse width and keeps the longitudinal depth unchanged), which avoids the risk of electrolyte penetration and provides more active sites for the oxygen evolution reaction, and ultimately significantly improves the electrochemical active specific surface area of ​​the Ir-Ta coating, solving the technical pain point of insufficient active sites in traditional coatings.

[0036] (2) The present invention has a coating structure with a high specific surface area, which can significantly reduce the oxygen evolution potential of the anode. During the electrolysis process, only a lower voltage is required to achieve oxygen evolution, which not only improves the electrolysis efficiency, but also reduces unnecessary energy consumption. At the same time, ethylene glycol improves the dispersion of the catalyst and avoids the aggregation of metal ions. Combined with the uniform crystal structure, it further enhances the conductivity of the coating and the oxygen evolution catalytic activity, so that the electrode potential is stabilized below 0.90V, which meets the stringent requirements of high-precision electrochemical processes for electrode performance.

[0037] (3) The polyhydroxyl groups of ethylene glycol in this invention react with IrCl6 2- TaCl5 forms a polyol complex, stabilizing the easily hydrolyzed and volatile chloride in a true solution state at room temperature, thus preventing coating failure. Its high boiling point (197℃) slows down the solvent evaporation gradient and reduces the formation of dry cracks. Simultaneously, the introduction of an equal amount of alcohol solution into the intermediate layer and the alcohol-containing catalyst layer, combined with a low-temperature drying process, effectively balances the interlayer stress difference, preventing coating peeling and significantly improving coating adhesion. Furthermore, the manufacturing process does not damage the titanium substrate, extending the anode life to over 1550 hours, thus solving the core problems of traditional coatings such as easy cracking, weak adhesion, and short lifespan.

[0038] (4) The process of this invention is simple and controllable, the coating solution is evenly dispersed and the coating process is stable. It can be replicated on a large scale and is especially suitable for high-precision and high-quality electrochemical industrial applications such as electrolytic copper foil, which have high requirements for electrode materials. At the same time, the introduction of ethylene glycol reduces the activity loss caused by the agglomeration of precious metals, reduces energy consumption and production costs. Compared with pure water or pure alcohol solvent systems, the catalytic layer crystallizes more evenly and in greater quantities. It takes into account both high performance and economy, and has a wide range of application prospects.

[0039] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0040] Figure 1 The images show the SEM surface morphology of the iridium-tantalum coated anode in Example 1 of this invention at different magnifications; where a is at a magnification of 300 nm and b is at a magnification of 1 μm.

[0041] Figure 2 The images show the SEM surface morphology of the iridium-tantalum coated anode in Comparative Example 1 of this invention at different magnifications; where a is at a magnification of 300 nm and b is at a magnification of 1 μm.

[0042] Figure 3 The cyclic voltammetry curves are shown for the iridium-tantalum coated anodes in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0043] Figure 4 The polarization curves are shown for the iridium-tantalum coated anodes in Examples 1-3 and Comparative Examples 1-4 of the present invention.

[0044] Figure 5 A process flow diagram of the manufacturing method provided by the present invention. Detailed Implementation

[0045] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described in the text. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] Example 1

[0048] Please pay attention to the attached reference. Figure 5 A method for preparing a high specific surface area iridium-tantalum coated titanium anode includes the following steps:

[0049] (1) Pretreatment of titanium substrate: The titanium substrate is cut and sandblasted, then washed with 10% NaOH solution for 0.5h to remove oil, and finally placed in boiling hydrochloric acid solution with a mass concentration of 5% for 1h for etching. After etching, it is rinsed with pure water to obtain titanium substrate.

[0050] (2) Preparation of intermediate coating solution: Use 10% dilute hydrochloric acid as solvent, add TiCl4 and TaCl5 with a molar ratio of 1:1, stir thoroughly and then add ethylene glycol with a volume of 2 / 10 of the titanium-tantalum mixture, mix thoroughly and obtain intermediate coating solution.

[0051] (3) Preparation of the intermediate layer: The prepared intermediate layer coating solution was fully coated on the surface of the etched titanium substrate. After drying in an oven at 70°C for 15 min, it was sintered in a sintering furnace at 520°C for 30 min. After completion, the sample was taken out and naturally cooled to room temperature. The coating-drying-sintering-cooling process was repeated 4 times to obtain a titanium substrate with an intermediate layer. The total metal loading of each coating was 0.4~0.6g / m 2 ;

[0052] (4) Preparation of precious metal catalytic coating solution: First, dissolve H2IrCl6 in 10% dilute hydrochloric acid and stir until completely dissolved. Then add TaCl5 and stir ultrasonically to obtain precious metal catalytic coating solution, wherein the molar ratio of iridium to tantalum is 7:3.

[0053] (5) Preparation of alcohol-containing noble metal catalytic coating solution: Take a certain volume of noble metal catalytic coating solution, add ethylene glycol solution to the solution, and ultrasonically stir for 30 min to obtain alcohol-containing noble metal catalytic coating solution, wherein the amount of ethylene glycol introduced is 2 / 10 of the volume of noble metal catalytic coating solution;

[0054] (6) Preparation of the catalyst layer: Using an absorbent sponge roller brush, the alcohol-containing noble metal catalyst coating solution was evenly coated onto the titanium substrate with the intermediate layer. The substrate was then placed in an oven and dried at 70°C for 30 min. After drying, the substrate was transferred to a muffle furnace for sintering at 520°C for 30 min each time. After sintering, the sample was removed and allowed to cool naturally to room temperature. The coating-drying-sintering-cooling process was repeated 15 times. The Ir loading for each coating was 0.8–1.0 g / m³. 2 Next, the coating solution was changed to a precious metal catalytic coating solution, and the coating-drying-sintering-cooling process was repeated three times. The Ir loading for each coating was 0.8–1.0 g / m³. 2 This allows for the production of a titanium anode with a high specific surface area iridium-tantalum coating.

[0055] The scanning electron microscope image of the above titanium anode is shown below. Figure 1 As shown.

[0056] Example 2

[0057] This embodiment is basically the same as the method in Embodiment 1, except that:

[0058] In step (5), the amount of ethylene glycol introduced into the alcohol-containing noble metal catalytic coating solution is 1 / 10 of the volume of the noble metal catalytic coating solution.

[0059] Everything else is the same as in Example 1.

[0060] Example 3

[0061] This embodiment is basically the same as the method in Embodiment 1, except that:

[0062] In step (5), the amount of ethylene glycol introduced into the alcohol-containing noble metal catalytic coating solution is 3 / 10 of the volume of the noble metal catalytic coating solution.

[0063] Everything else is the same as in Example 1.

[0064] Example 4

[0065] This embodiment is basically the same as the method in Embodiment 1, except that:

[0066] In step (1), the titanium substrate is etched in a 30% sulfuric acid solution for 5 minutes;

[0067] In step (2), after thorough mixing, 1 / 10 of the volume of ethylene glycol is added to the titanium-tantalum mixture and mixed thoroughly to obtain the intermediate coating solution;

[0068] In step (3), after coating, the sample is dried in an oven at 60°C for 30 minutes and then sintered in a sintering furnace at 520°C for 30 minutes. After completion, the sample is taken out and naturally cooled to room temperature. The coating-drying-sintering-cooling process is repeated 3 times.

[0069] In step (6), after coating with alcohol-containing noble metal catalytic coating solution, the sample is placed in an oven and dried at 60°C for 30 minutes; the sintering temperature is 450°C and the sintering time is 40 minutes each time. After completion, the sample is taken out and naturally cooled to room temperature. The coating-drying-sintering-cooling process is repeated 15 times. Then the coating solution is changed to noble metal catalytic coating solution, and the coating-drying-sintering-cooling process is repeated 3 times.

[0070] Everything else is the same as in Example 1.

[0071] Example 5

[0072] This embodiment is basically the same as the method in Embodiment 1, except that:

[0073] In step (1), the titanium substrate is etched in a 25% hydrochloric acid solution for 30 minutes;

[0074] In step (2), after thorough mixing, 3 / 10 of the volume of ethylene glycol of the titanium-tantalum mixture is added and mixed evenly to obtain the intermediate coating solution;

[0075] In step (3), after coating, the sample is dried in an oven at 100°C for 5 minutes and then sintered in a sintering furnace at 520°C for 30 minutes. After completion, the sample is taken out and naturally cooled to room temperature. The coating-drying-sintering-cooling process is repeated 5 times.

[0076] In step (6), after coating with alcohol-containing noble metal catalytic coating solution, the sample is placed in an oven and dried at 100°C for 10 min; the sintering temperature is 600°C and the sintering time is 10 min each time. After completion, the sample is taken out and naturally cooled to room temperature. The coating-drying-sintering-cooling process is repeated 20 times. Then the coating solution is changed to noble metal catalytic coating solution, and the coating-drying-sintering-cooling process is repeated 4 times.

[0077] Everything else is the same as in Example 1.

[0078] Comparative Example 1

[0079] The method is basically the same as that in Example 1, except that the catalyst layer uses a noble metal catalyst coating solution instead of an alcohol-containing noble metal catalyst coating solution.

[0080] Everything else is the same as in Example 1.

[0081] The final scanning electron microscope image of the titanium anode is shown below. Figure 2 As shown.

[0082] Comparative Example 2

[0083] The method is basically the same as that in Example 1, except that the catalyst layer uses an alcohol-containing noble metal catalyst coating solution instead of a noble metal catalyst coating solution.

[0084] Everything else is the same as in Example 1.

[0085] Comparative Example 3

[0086] The method is basically the same as that in Example 1, except that a noble metal catalytic coating solution is applied first, followed by an alcohol-containing noble metal catalytic coating solution.

[0087] Everything else is the same as in Example 1.

[0088] Comparative Example 4

[0089] The method is basically the same as that in Example 1, except that the alcohol used is a low-boiling-point ethanol solution.

[0090] Everything else is the same as in Example 1.

[0091] Performance testing:

[0092] The titanium anodes prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to electrode potential testing, accelerated life testing, and coating adhesion testing.

[0093] (1) The electrode potential test conditions are as follows:

[0094] Current density: 50A / m 2

[0095] Temperature: 25℃

[0096] Electrolyte: 150 g / L sulfuric acid solution

[0097] Reference electrode: mercurous sulfate

[0098] Cathode: Zr

[0099] Polar distance: 1cm

[0100] (2) The accelerated life test conditions are as follows:

[0101] Current density: 5A / cm 2

[0102] Electrolysis temperature: 60℃

[0103] Electrolyte: 150 g / L sulfuric acid solution

[0104] Cathode: Ti

[0105] Polar distance: 1cm

[0106] (3) The coating adhesion was tested using an automatic scratch tester under the following conditions:

[0107] Detection mode: Acoustic emission

[0108] Load applied: 100N

[0109] Loading method: Unidirectional continuous loading

[0110] Scratch length: 6mm

[0111] Loading rate: 60 N / min

[0112] Accelerated life testing ended with a 1 V increase in electrolysis voltage compared to the initial voltage. Adhesion strength testing yielded the critical load value at which the coating began to fail. Test results are shown in Table 1 and... Figures 3-4 As shown.

[0113] Table 1 Performance data of Examples 1-3 and Comparative Examples 1-4

[0114] Sample number Coating adhesion / N Electrode potential / V Lifespan / h Example 1 65 0.89 1650 Example 2 62 0.90 1550 Example 3 62 0.90 1560 Comparative Example 1 60 0.91 1493 Comparative Example 2 58 0.91 1520 Comparative Example 3 56 0.91 1490 Comparative Example 4 60 0.91 1489

[0115] As shown in Table 1:

[0116] (1) Compared with the comparative example, the iridium-tantalum coated titanium anode prepared in the example has better adhesion, lower electrode potential and longer accelerated life.

[0117] (2) Compared with Example 1, the accelerated life of the coating was reduced due to the introduction of more or less ethylene glycol in Examples 2 and 3. This is because the complexation of -OH with iridium and tantalum was weakened, resulting in a decrease in coating adhesion.

[0118] (3) In Comparative Example 4, the performance of the low-boiling-point ethanol solution after the addition of the coating was not significantly different from that of the conventional aqueous solution system in Comparative Example 1. However, in Examples 1-3, a specific proportion of high-boiling-point ethylene glycol solution was introduced into the iridium-tantalum precursor solution and combined with the conventional aqueous solution system to construct a catalyst layer. Electron microscopy images clearly showed a significant increase in the amount of iridium crystals and finer grains. The transverse width of the cracks increased, but the longitudinal depth did not change significantly, effectively increasing the number of active sites for the reaction and providing a site for the oxygen evolution reaction. Therefore, this combination design strategy of the catalyst layer effectively controlled and optimized the microstructure of the coating. Figure 1 and Figure 2 This can also be verified by comparison. Furthermore, electrochemical tests using a 0.5 mol / L sulfuric acid solution as the electrolyte revealed that the construction of the composite catalyst layer significantly improved the catalyst's electrochemical active surface area and electrochemical impedance, and significantly reduced the oxygen evolution overpotential.

[0119] The present invention has been described by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvement made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, shall be within the protection scope of the present invention.

Claims

1. A method for preparing a titanium anode with a high specific surface area iridium-tantalum coating, characterized in that: Includes the following steps: S1. Pre-treat the titanium substrate; S2. Prepare the intermediate layer coating solution; An alcohol solution was introduced; S3. Preparation of intermediate layer: The intermediate layer coating solution prepared in step S2 is coated on the surface of the pretreated titanium substrate and dried at a temperature of 60-100℃ for 5-30 min; then sintering is performed and cooled to room temperature. The coating-drying-sintering-cooling process is repeated at least 3 times to obtain a titanium substrate with an intermediate layer. S4. Prepare the precious metal catalytic coating solution: Prepare the coating solution by combining the iridium source, tantalum source, and solvent; S5. Prepare an alcohol-containing noble metal catalytic coating solution: Take a portion of the noble metal catalytic coating solution prepared in step S4, add ethylene glycol solution, mix evenly, and obtain an alcohol-containing noble metal catalytic coating solution; wherein, the amount of ethylene glycol solution introduced is 1 / 10 to 3 / 10 of the volume of the noble metal catalytic coating solution. S6. Preparation of the catalyst layer: On the intermediate layer, first coat the alcohol-containing noble metal catalyst coating solution prepared in step S5, and dry it at a temperature of 60-100℃ for 10-30 min; then sinter it and cool it to room temperature, repeating the coating-drying-sintering-cooling process at least 15 times; then coat the noble metal catalyst coating solution prepared in step S4, and repeat the coating-drying-sintering-cooling process at least 3 times, finally obtaining a high specific surface area iridium-tantalum coated titanium anode.

2. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 1, characterized in that: In step S1, the pretreatment includes sandblasting, alkaline washing, etching, cleaning and drying; wherein the etching treatment uses a 5% to 25% hydrochloric acid solution or a 10% to 30% sulfuric acid solution, and the etching time is 5 to 60 minutes.

3. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 1, characterized in that: In step S2, titanium source and tantalum source are added to solvent and mixed evenly to obtain titanium-tantalum mixture. Then ethylene glycol is added and mixed evenly to obtain intermediate coating solution.

4. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 3, characterized in that: In step S2, the titanium source is TiCl4, the tantalum source is TaCl5, and the solvent is dilute hydrochloric acid. And / or, the molar ratio of the titanium source to the tantalum source is 1:1; And / or, the amount of ethylene glycol introduced is 1 / 10 to 3 / 10 of the volume of the titanium-tantalum mixture.

5. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 4, characterized in that: In step S3, the sintering operation is as follows: sintering in a sintering furnace at a temperature of 520℃ for 30 minutes; And / or, in step S3, the total metal loading for each coating is 0.4–0.6 g / m³. 2 .

6. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 1, characterized in that: In step S4, the iridium source is first dissolved in the solvent and stirred until completely dissolved. Then, the tantalum source is added and mixed evenly to obtain a noble metal catalytic coating solution, wherein the molar ratio of iridium to tantalum is 7:

3.

7. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 6, characterized in that: In step S4, the iridium source is H2IrCl6, the solvent is dilute hydrochloric acid, and the tantalum source is TaCl5.

8. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 1, characterized in that: In step S5, after adding the ethylene glycol solution, the mixture is ultrasonically stirred for 30 minutes.

9. The method for preparing a titanium anode with a high specific surface area iridium-tantalum coating according to claim 1, characterized in that: In step S6, the sintering temperature is 450–600℃, and the sintering time for each sintering is 10–40 min. And / or, in step S6, the Ir loading amount for each coating is 0.8–1.0 g / m³. 2 .

10. A titanium anode with an iridium-tantalum coating and high specific surface area, characterized in that: The iridium-tantalum coated titanium anode prepared by the preparation method according to any one of claims 1-9 has a coating adhesion of more than 62N, an electrode potential of less than 0.90V, and a lifespan of more than 1550h.

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