Coated titanium anode and embedding preparation method thereof

Abstract

The invention discloses a coated titanium anode and an embedding preparation method thereof, and belongs to the technical field of coated titanium anodes, metal salt powder, an organic additive and inert filler are fully mixed to form embedding agent powder, the mass fraction of metal salt is 45-59%, the mass fraction of the organic additive is 1-5%, and the mass fraction of the inert filler is 40-50%; the sintering treatment is as follows: the pretreated titanium substrate is completely immersed in the embedding agent powder, the sintering temperature is 400-600 DEG C, the sintering time is 1-3 hours, and the heating rate is 5-10 DEG C / min. According to the method, low-temperature sintering is realized by precisely regulating and controlling the components and the proportion of the embedding medium and combining process parameters such as low-temperature sintering, and the damage to a titanium substrate is avoided; and meanwhile, the coating binding force of the titanium anode is improved, the service life of the titanium anode is prolonged, and technical innovation and industrial value are achieved.

Description

Technical Field

[0001] This invention relates to the field of coated titanium anode technology, specifically to a coated titanium anode and its embedding preparation method. Background Technology

[0002] In many electrochemical fields, such as the chlor-alkali industry, wastewater treatment, and metal electrodeposition, the performance of the anode material plays a crucial role in the efficiency and cost of the entire electrochemical process. Coated titanium anodes are widely used in these fields due to their excellent conductivity, corrosion resistance, and high oxygen evolution overpotential. Currently, the conventional methods for preparing coated titanium anodes mainly include the thermal decomposition method and the sol-gel method.

[0003] The thermal decomposition method is a relatively mature technology. It involves coating a precursor solution containing active components onto the surface of a titanium substrate, followed by high-temperature heat treatment at >150℃ to decompose the precursor and form an active coating. However, this method has inherent drawbacks: First, the solution precursor undergoes significant volume shrinkage during drying and decomposition, easily leading to stress concentration within the coating and insufficient adhesion between the coating and the substrate. Under long-term, intense electrochemical and mechanical erosion, the coating is prone to cracking and peeling, severely affecting the anode's service life. Second, to obtain a coating of sufficient thickness and activity, multiple "coating-drying-sintering" cycles are required, resulting in a cumbersome process, low production efficiency, and high energy consumption.

[0004] While the sol-gel method can produce coatings with more uniform composition and finer microstructure, the process involves complex hydrolysis and condensation reaction control, has a long preparation cycle, and is extremely demanding on environmental temperature and humidity and precursor stability. This results in poor process reproducibility and high cost for large-scale production, making it difficult to meet the efficiency and cost requirements of industrial production.

[0005] The embedding method involves embedding the substrate material into an embedding agent powder, forming a coating through a single high-temperature heat treatment. Theoretically, this method has the potential to simplify the process. However, for precious metals such as rhodium, ruthenium, and iridium, and rare refractory metals such as tantalum and titanium in titanium anode coatings, the required heat treatment temperature typically needs to be above 800℃. For example, patent application CN 107740039 A discloses an Ir-X coating based on surface alloying modification and its preparation method. This involves depositing a rhenium transition layer and an iridium coating sequentially on a carbon-carbon composite material or graphite substrate. Then, a penetrant is prepared by mixing metal X powder, the corresponding metal oxide XO powder, and a chloride activator. The iridium coating is then surface-alloyed and modified using a powder embedding and solid infiltration method to obtain the Ir-X coating. However, this method requires a heat treatment temperature above 800℃, and for tantalum, the temperature needs to be above 1200℃.

[0006] However, the traditional embedding method faces two major insurmountable technical bottlenecks and widespread technical biases, which have prevented its successful application in the preparation of high-performance titanium anodes for a long time: First, there is a contradiction between the high process temperature and the potential for substrate damage. To achieve effective diffusion of the active component into the substrate and the formation of a dense coating, traditional embedding methods typically require high temperatures. At these high temperatures, the titanium substrate is prone to severe grain growth, oxidation, and embrittlement, resulting in a sharp deterioration in its mechanical strength and corrosion resistance, making it unsuitable as an electrode substrate. This leads to a widespread misconception among those skilled in the art that the embedding method is a high-temperature process fundamentally incompatible with the requirements of titanium anode fabrication that necessitates protecting the properties of the titanium substrate.

[0007] Secondly, there is the uncontrollability of coating composition, structure, and performance. Traditional embedding methods often use elemental metals or alloy powders as embedding agents. Their film-forming mechanism relies on the melting and diffusion of the powder, ultimately forming an alloy coating. However, the core active component of modern DSA anodes is noble metal oxides, such as IrO2 and RuO2. Although alloy coatings can be subsequently oxidized to form oxides, their composition, crystal structure, and porosity are difficult to precisely control, making them incomparable to directly synthesized oxide coatings. Electrocatalytic activity is typically poor, meaning it's difficult to precisely control the formation of noble metal oxide coatings with specific non-stoichiometric ratios and high catalytic activity. Furthermore, defects such as pores are easily formed, and the coating quality and electrochemical performance cannot meet the requirements of DSA electrodes. Therefore, the industry generally believes that embedding methods are only suitable for preparing alloy coatings and are difficult to use for preparing high-performance oxide catalytic coatings that require strict control of crystal structure and surface state.

[0008] In summary, there is an urgent need in this field for a new titanium anode fabrication technology that can balance high performance, high bonding strength, low preparation cost, and good processability. This technology needs to fundamentally solve the high-temperature damage and performance control problems of traditional embedding methods, break through existing technological biases, and thus provide the electrochemical industry with a superior and more economical electrode manufacturing solution. Summary of the Invention

[0009] The present invention addresses the problem of overly simplistic solutions in existing technologies by providing a significantly different solution. It primarily offers a coated titanium anode and its embedding preparation method, thereby solving the high-temperature damage and performance control challenges of traditional embedding methods mentioned in the background section. This invention produces a titanium anode that combines high performance, high bonding strength, low preparation cost, and good processability.

[0010] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: An embedding method for preparing a coated titanium anode includes the following steps: S1. Pretreatment of titanium matrix; This step mainly involves removing the oxide layer, oil, and other impurities from the surface of the titanium substrate through grinding, alkaline cleaning, and acid pickling. S2. Preparation of the embedding agent: The metal salt powder, organic additives, and inert filler are placed in a ball mill and ground thoroughly to ensure complete mixing of the metal salt, organic additives, and inert filler, forming the embedding agent powder; wherein, the mass fraction of the metal salt is 45-59%, the mass fraction of the organic additives is 1-5%, and the mass fraction of the inert filler is 40-50%; Both the oxide intermediate layer and the noble metal oxide catalyst layer consist of 45-59% metal salt, 1-5% organic additives, and 40-50% inert filler, with the total of the three being 100%. If the material ratios of the oxide intermediate layer and the noble metal oxide catalyst layer differ significantly, it will reduce the adhesion between the two coatings.

[0011] S3. Sintering treatment: The pretreated titanium matrix is ​​completely immersed in the embedding agent powder to ensure that the embedding agent is evenly covered on the surface of the titanium matrix; then it is placed in a high-temperature furnace for sintering at a temperature of 400-600℃ for 1-3 hours and a heating rate of 5-10℃ / min. In this step, the metal salt in the embedding agent decomposes and forms a metal oxide coating on the surface of the titanium substrate, and the metal elements penetrate into the substrate, thereby improving the coating adhesion and further improving the service life of the anode.

[0012] S4. Post-treatment: Remove the sintered coated titanium anode and allow it to cool naturally to room temperature; then perform surface cleaning to remove residual impurities and unreacted substances.

[0013] Compared to the thermal decomposition method, each coating in this invention is formed through a single embedding and sintering process, greatly simplifying the process and avoiding multiple coating-sintering cycles. Furthermore, the adhesion between the coating and the substrate is significantly higher than that of the thermal decomposition method, thereby significantly improving the erosion resistance and service life of the anode.

[0014] Compared to the sol-gel method, the encapsulating agents used in this invention are all commercially available common chemicals, eliminating the need to prepare complex sol systems. The process is simple, has low requirements for equipment and environment, does not require precise control of humidity and solution stability, and low-temperature sintering reduces energy consumption. This invention significantly reduces raw material costs and energy consumption while ensuring high performance, and the process flow is more suitable for large-scale continuous production.

[0015] Compared to the high temperatures of over 800℃ required for sintering using the embedding method in existing technologies, the sintering temperature of this invention only requires 400-600℃, resulting in lower energy consumption and less demanding equipment requirements, thus reducing production costs. Furthermore, titanium substrates undergo severe oxidation and grain growth at high temperatures, leading to matrix embrittlement and affecting the mechanical strength of the anode. The low-temperature sintering of this invention fundamentally avoids the oxidation, grain growth, and embrittlement problems of the titanium substrate at high temperatures, breaking the technical prejudice that "embedding methods must be high-temperature processes," and thus contributing to a longer overall anode lifespan.

[0016] Further analysis reveals that existing embedding methods often use elemental metals or alloy powders as embedding agents, and may not necessarily include organic additives, thus failing to promote the formation of oxide coatings. In this invention, the metal salt serves as a precursor for the metal oxide coating; the organic additives not only act as binders but also generate a reducing atmosphere and instantaneous micro-regional high temperatures during low-temperature decomposition and combustion at 200-500℃, promoting the decomposition and activation of the metal salt; the inert filler plays a supporting and dispersing role, promoting coating formation.

[0017] Specifically, organic additives such as polyvinyl alcohol and carboxymethyl cellulose are hydrocarbon polymers. When heated in an inert atmosphere or vacuum, they do not completely burn into CO2 and H2O, but instead undergo incomplete combustion or pyrolysis, producing a large amount of reducing gases, including carbon monoxide, hydrogen, and various small-molecule hydrocarbon gases (CH4, etc.). These reducing gases effectively prevent the titanium substrate surface from being oxidized during heating. Titanium is highly susceptible to oxidation, and the TiO2 layer on the surface hinders the metallurgical bonding between the coating and the substrate. The reducing atmosphere maintains the activity of the substrate surface. Furthermore, for certain metal salts (especially chlorides, such as H2IrCl6 and TaCl5), the reducing atmosphere can promote their decomposition, thereby helping to reduce the sintering temperature requirement; it also prevents the formation of undesirable intermediate products and helps to reduce them to metals or lower valence oxides, which are more easily oxidized to the target oxide during subsequent heat treatment.

[0018] Specifically, the decomposition of organic additives is not gradual, but rather occurs violently near their decomposition temperature points (approximately 200-400℃ for polyvinyl alcohol and approximately 250-300℃ for carboxymethyl cellulose). This violent decomposition reaction is an exothermic process. Because the encapsulating agent in this invention is a powder system with poor thermal conductivity, the heat released by the organic additives cannot dissipate quickly. This creates a brief high-temperature field in a tiny area around each individual organic additive particle, with temperatures potentially far exceeding the furnace's set temperature. For example, in a furnace at 500℃, a local micro-area may momentarily reach 800℃ or even higher. Many metal salts have high decomposition temperatures; when the furnace temperature itself is insufficient, these high-temperature fields provide the energy to initiate and complete the reaction. In other words, this instantaneous localized high temperature provides the necessary activation energy for the decomposition of the surrounding metal salts, thus facilitating low-temperature sintering. Simultaneously, the localized high temperature promotes initial melting and atomic diffusion on the surface of the coating particles, fostering densification of the coating at low temperatures and thereby improving adhesion.

[0019] Furthermore, this invention directly uses high-purity metal salts as precursors. By precisely controlling the salt ratio, a stoichiometric metal oxide mixed coating can be directly and directionally generated, rather than a metal alloy coating. The resulting metal oxide mixed coating possesses a dense columnar crystal structure, which, compared to the needle-like crystal structure obtained by thermal decomposition, exhibits a larger intergranular contact area and stronger mechanical stability.

[0020] In summary, by limiting the raw materials of the embedding agent and the sintering parameters, this invention successfully solves the technical problem that the traditional embedding method is not suitable for the preparation of titanium anodes due to high temperature. It also combines the advantages of the excellent coating performance of the thermal decomposition method and the simple process of the traditional embedding method, providing a new method for preparing coated titanium anodes with high performance, high adhesion, low energy consumption and low cost.

[0021] Further, in step S1, the titanium substrate is first polished to remove the oxide layer and impurities on the surface, so that the surface roughness meets certain requirements; then the polished titanium substrate is placed in an alkaline solution for ultrasonic cleaning to further remove oil and other organic impurities on the surface; next, the titanium substrate after alkaline cleaning is placed in an acid solution for acid washing to remove metal oxides and alkaline residue on the surface; finally, it is rinsed with deionized water and dried for later use.

[0022] Furthermore, during polishing, start with coarse sandpaper, then gradually use progressively finer sandpaper until the surface is smooth and flat. First, coarse sandpaper quickly and effectively removes larger macroscopic defects such as oxide scale, scratches, and dents from the titanium surface. Each coarser grade of sandpaper leaves scratches of specific depth and direction on the surface. The next finer grade of sandpaper removes the deeper scratches created by the previous grade and replaces them with its own finer, shallower scratches. Finally, fine polishing eliminates all directional, deeper scratches, creating an isotropic, uniform surface.

[0023] Preferably, during alkaline cleaning, the alkaline concentration is 5-10 wt%, the cleaning temperature is 50-60℃, and the cleaning time is 20-30 minutes. Preferably, during pickling, the acid solution is a mixture of hydrochloric acid and nitric acid with a volume ratio of 1:1, the pickling temperature is room temperature, and the pickling time is 10-15 minutes.

[0024] Further, in step S2, the metal salt is at least one selected from rhodium, ruthenium, iridium, osmium, titanium, tantalum, niobium, platinum, and palladium. Specifically, if an oxide intermediate layer is to be prepared, the metal salt is at least one selected from rhodium, ruthenium, iridium, osmium, titanium, tantalum, niobium, platinum, and palladium; if a noble metal oxide catalyst layer is to be prepared, the metal salt is at least one selected from rhodium, ruthenium, iridium, osmium, tantalum, platinum, and palladium.

[0025] Preferably, in step S2, the organic additive is at least one of polyvinyl alcohol and carboxymethyl cellulose; Preferably, the inert filler is at least one of platinum powder and graphite powder.

[0026] As one implementation of the above scheme, a noble metal oxide catalyst layer is formed directly on the titanium substrate through steps S2 and S3.

[0027] As another implementation of the above scheme, an oxide intermediate layer is first formed on the titanium substrate through steps S2 and S3, and then a noble metal oxide catalyst layer is formed on the oxide intermediate layer through steps S2 and S3.

[0028] The present invention also discloses a coated titanium anode, which is prepared by the above-described embedding method. The coated titanium anode includes a substrate, and the substrate is provided with an oxide intermediate layer and / or a noble metal oxide catalyst layer. The coating adhesion of the coated titanium anode reaches more than 70N and the service life reaches more than 1400h.

[0029] The thickness of the oxide intermediate layer is 0.1-0.15 μm; the thickness of the noble metal oxide catalyst layer is 0.4-0.6 μm.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: In existing technologies, the embedding method for preparing precious metals such as rhodium, ruthenium, and iridium, or rare refractory metals such as tantalum and titanium, typically requires heat treatment temperatures above 800°C, which is difficult for the titanium matrix to withstand. In this application, the embedding agent comprises precisely controlled proportions of metal salts, organic additives, and inert fillers; and the sintering temperature and time are also specified. The metal salts serve as precursors for the metal oxide coating; the organic additives not only act as binders but also generate a reducing atmosphere and instantaneous micro-region high temperatures during low-temperature decomposition and combustion, promoting the decomposition and activation of the metal salts; the inert fillers provide support and dispersion, promoting coating formation and helping to reduce the furnace temperature required for sintering. This breaks the limitation of the embedding method requiring high-temperature sintering, achieving low-temperature sintering and avoiding high-temperature damage to the titanium matrix.

[0031] In this invention, both the oxide intermediate layer and the noble metal oxide catalyst layer are formed through a single embedding and sintering process, completely eliminating repetitive operations and significantly improving production efficiency, thereby shortening the process cycle. Furthermore, the embedding agents used in this invention are all commercially available common chemicals, eliminating the need for complex sol-gel systems as in the sol-gel method; the low-temperature sintering at 400-600℃ reduces energy consumption compared to the high-temperature processes of traditional embedding methods, and lowers the requirements for equipment heat resistance, significantly reducing equipment investment and operating costs for industrial production.

[0032] This invention uses high-purity metal salts as precursors to directly generate a stoichiometric noble metal oxide catalytic layer by precisely controlling the salt ratio, rather than a lower-performance alloy coating. The coating forms a dense columnar crystal structure, which has a larger intergranular contact area and stronger mechanical stability than the needle-like crystal structure obtained by thermal decomposition. During the decomposition of the metal salt, metal elements penetrate into the titanium matrix to form a metallurgical bond. Combined with the supporting and dispersing effect of inert fillers, the coating adhesion force reaches over 70N. The dense coating structure and strong adhesion enable the electrode to have a service life exceeding 1400 hours.

[0033] In summary, this invention achieves low-temperature sintering by precisely controlling the composition and ratio of the encapsulating agent, combined with process parameters such as low-temperature sintering, thus avoiding damage to the titanium substrate. At the same time, both the oxide intermediate layer and the catalyst layer are formed in one step, and the raw materials are commercially available common chemicals, which greatly simplifies the process and reduces energy consumption and costs. Furthermore, by using metal salts as precursors to generate a stoichiometric noble metal oxide coating, a dense columnar crystal structure is formed, which improves the coating's adhesion and lifespan, thus combining technological innovation with industrial value.

[0034] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0035] Figure 1 This is a SEM image of the morphology of the Ir-Ta oxide electrocatalytic anode coating prepared in Example 1 of the present invention; Figure 2 SEM images of the morphology of the Ir-Ta oxide electrocatalytic anode coating prepared by the thermal decomposition method in Comparative Example 1; Figure 3 This is a schematic diagram illustrating the principle of embedding and sintering in this invention. Detailed Implementation

[0036] 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.

[0037] 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.

[0038] Example 1: An Ir-Ta oxide electrocatalytic anode prepared by an embedding method, comprising an insoluble metal substrate, an oxide intermediate layer, and a noble metal oxide catalyst layer. The specific preparation process is as follows: Titanium substrate pretreatment: Take a titanium plate with dimensions of 10cm×10cm×0.6cm, first polish it with 800-grit sandpaper, then polish it with 1200-grit and 1500-grit sandpaper in sequence until the surface is smooth and flat.

[0039] The purpose of the sanding process described above is as follows: First, coarse sandpaper can quickly and effectively remove larger macroscopic defects such as oxide scale, scratches, and dents from the titanium surface. Then, each coarser grade of sandpaper leaves scratches of a specific depth and direction on the surface. The purpose of using the next finer grade of sandpaper is to remove the deeper scratches created by the previous grade and replace them with finer, shallower scratches. Fine sanding can eliminate all directional, deeper scratches, creating an isotropic, uniform surface.

[0040] The polished titanium plate was then placed in an 8 wt% sodium hydroxide solution and ultrasonically cleaned at 55°C for 25 minutes.

[0041] The role of alkaline ultrasonic cleaning: Most of the titanium substrates coming from the source have oil stains on their surface, which directly affects the cleaning efficiency of the surface metal oxide layer. Alkaline solutions are more efficient at cleaning oil stains.

[0042] The titanium plate is then placed in a 1:1 mixture of hydrochloric acid and nitric acid by volume and pickled at room temperature for 15 minutes to remove metal oxides and alkaline residues from the surface.

[0043] Finally, rinse thoroughly with deionized water and dry for later use.

[0044] Preparation of oxide interlayer powder: Weigh 2.8g of tantalum pentachloride and 3g of titanium tetrachloride, then add 0.2g of polyvinyl alcohol and 4g of platinum powder, and grind them thoroughly in a ball mill to form an interlayer embedding agent powder.

[0045] Intermediate layer embedding and sintering treatment: Please refer to the attached document for details. Figure 3 The pretreated titanium plate was completely immersed in the aforementioned intermediate layer embedding agent powder, with a loading of 4 g / m³. 2 Then it is placed in a muffle furnace and heated to 500°C at a heating rate of 8°C / min, and held for 2 hours to form an intermediate layer of TiO2+Ta2O5 on the titanium plate.

[0046] Preparation of precious metal oxide catalyst layer powder: Weigh 5g of tantalum pentachloride and chloroiridium acid in a ratio of 3:7, then add 0.2g of polyvinyl alcohol and 4.8g of platinum powder, and grind them thoroughly in a ball mill to form catalyst layer embedding agent powder.

[0047] Catalyst layer embedding and sintering treatment: A titanium plate with an intermediate layer is completely immersed in catalyst layer embedding agent powder, with an iridium loading of 16 g / m². 2 The material is placed in a muffle furnace and heated to 560°C at a heating rate of 5°C / min, and held for 3 hours to form a catalyst layer of IrO2+Ta2O5 on the intermediate layer.

[0048] Post-processing: The sintered coated titanium anode was removed and allowed to cool naturally to room temperature. This yielded a coated titanium anode (iridium basis weight 16 g / m²). 2 ).

[0049] In this invention, metal salts serve as precursors for metal oxide coatings. When organic additives decompose at 200-500°C, they generate a reducing atmosphere to prevent oxidation of the titanium substrate surface and simultaneously create instantaneous micro-region high temperatures through intense exothermic reactions, providing activation energy for metal salt decomposition. This allows coating formation to be completed without relying on high furnace temperatures, balancing low temperatures and sufficient reaction. Inert fillers act as supports and dispersers, promoting coating formation. Furthermore, platinum acts as a catalyst, catalyzing the decomposition of metal salts and the formation of oxides at low temperatures, and accelerating the decomposition and oxidation rate of organic additives on their surface. This generates more and stronger micro-region high-temperature points, ultimately resulting in a dense and well-bonded coating formed at temperatures lower than conventional sintering temperatures.

[0050] Example 2: The difference between this example and Example 1 is that: In step (1), the concentration of alkali solution is 10 wt%, the cleaning temperature is 50°C, and the cleaning time is 20 minutes; In step (2), weigh 2.2g of tantalum pentachloride and 2.3g of titanium tetrachloride, then add 0.5g of polyvinyl alcohol and 5g of platinum powder; the pickling time is 10 minutes. In step (3), the sintering temperature is 400℃, the sintering time is 3 hours, and the heating rate is 5℃ / min; In step (4), weigh 4.5g of tantalum pentachloride and chloroiridium acid, then add 0.5g of polyvinyl alcohol and 5g of platinum powder; In step (5), the iridium loading is 32 g / m 2 The sintering temperature was 400℃, the sintering time was 3 hours, and the heating rate was 8℃ / min.

[0051] Everything else is the same as in Example 1.

[0052] Example 3: The difference between this example and Example 1 is that: In step (1), the concentration of alkali solution is 5 wt%, the cleaning temperature is 60°C, and the cleaning time is 30 minutes; In step (2), weigh 2.5g of tantalum pentachloride and 3g of titanium tetrachloride, then add 0.1g of carboxymethyl cellulose and 4.4g of graphite powder; the pickling time is 15 minutes. In step (3), the sintering temperature is 600℃, the sintering time is 1 hour, and the heating rate is 10℃ / min; In step (4), 5.9g of tantalum pentachloride and chloroiridic acid are weighed, then 0.1g of polyvinyl alcohol is added, followed by 4g of platinum powder; In step (5), the sintering temperature is 600℃, the sintering time is 1 hour, and the heating rate is 10℃ / min.

[0053] Everything else is the same as in Example 1.

[0054] Example 4: The difference between this example and Example 1 is that: Steps (2) and (3) are omitted, and the electrode structure has no oxide intermediate layer. Finally, a titanium anode with the structure Ti / IrO2+Ta2O5 is obtained.

[0055] Everything else is the same as in Example 1.

[0056] Comparative Example 1: This comparative example provides a method for preparing an Ir-Ta oxide electrocatalytic anode by thermal decomposition. Compared with the previous example, the difference lies in the use of a thermal decomposition method with coating and sintering to prepare the oxide intermediate layer and the noble metal oxide catalyst layer. The specific steps are as follows: (1) First, take a titanium plate with a size of 10cm×10cm×0.6cm and sandblast it using G18 steel grit at a pressure of 0.55MPa to give the substrate a certain roughness. (2) Place the titanium substrate obtained in step (1) into a 20% hot hydrochloric acid solution and etch for 35 minutes; (3) Preparation of oxide intermediate layer: Take 0.5 mL of mixed intermediate layer solution of TiCl4 and TaCl5, coat it evenly on the surface of the pretreated titanium plate, dry it in an oven at 80 ℃ for 15 min, and sinter it in a sintering furnace at 530 ℃ for 50 min. Repeat the coating-drying-sintering process 4 times before use.

[0057] (4) Preparation of noble metal oxide catalyst layer: Take 0.6 mL of catalyst layer solution of H2IrCl6·6H2O and TaCl5, uniformly coat it on the surface of the pretreated titanium plate, dry it in an oven at 80℃ for 15 min, and sinter it in a sintering furnace at 520℃ for 30 min. Repeat the coating-drying-sintering process 8 times to obtain a coated titanium anode with the structure of Ti / TiO2+Ta2O5 / IrO2+Ta2O5, and the iridium basis weight is 16 g / m 2 .

[0058] Comparative Example 2: The difference from Example 1 is that: The embedding agent was replaced with a slurry formed by mixing metal powder and polyvinyl alcohol adhesive; this slurry was then sprayed onto the surface of the titanium plate using a spray gun; and finally, sintering was performed.

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

[0060] Comparative Example 3: The difference from Example 1 is that: The embedding agent uses only metal salt powder and organic additives, with the metal salt having a mass fraction of 90% and the organic additives having a mass fraction of 10%.

[0061] Everything else is the same as in Example 1.

[0062] Comparative Example 4: The difference from Example 1 is that: The embedding agent uses only metal salt powder and inert filler, with the metal salt having a mass fraction of 60% and the inert filler having a mass fraction of 40%.

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

[0064] Comparative Example 5: The difference from Example 1 is that: The embedding agent contains 65% metal salt by mass, 6% organic additive by mass, and 29% inert filler by mass.

[0065] Everything else is the same as in Example 1.

[0066] Comparative Example 6: The difference from Example 1 is that: The sintering temperature is 350℃ and the sintering time is 4 hours.

[0067] Everything else is the same as in Example 1.

[0068] Comparative Example 7: The difference from Example 1 is that: The sintering temperature is 700℃ and the sintering time is 0.5 hours.

[0069] Everything else is the same as in Example 1.

[0070] Observe the SEM images of the morphology of the Ir-Ta oxide electrocatalytic anode coatings prepared in Example 1 and Comparative Example 1. The former is as follows: Figure 1 As shown, the latter is as Figure 2 As shown.

[0071] from Figure 2 As can be seen, its crystal morphology is needle-like crystals. This structure has weak impact resistance and is easily broken and detached. From Figure 1 The results show that the iridium oxide coating prepared by the embedding method exhibits a columnar crystalline morphology. This structure provides a larger contact area and a tighter bond, enabling it to better withstand the mechanical stress and erosion caused by the continuous precipitation and rupture of bubbles during electrolysis, making it less prone to cracking or peeling. Although needle-like crystals offer a higher specific surface area and expose more active sites, this advantage is temporary and unsustainable. For practical industrial applications, long-term stability is often more important than high initial activity.

[0072] The performance of the products obtained in Example 1 and Comparative Examples 1 to 7 was compared: All test samples (Example 1 and Comparative Examples 1 to 7) were pretreated under the same environmental conditions (temperature 25±2℃, humidity 45±5%): the coated titanium anodes cooled to room temperature after sintering were cut into standard test pieces of 10cm×5cm, ultrasonically cleaned with deionized water for 10min, dried and then subjected to various performance tests to ensure that the test standards were consistent.

[0073] Accelerated life testing Referring to the accelerated life testing specification in JB / T 10222-2021, the testing process is as follows: A three-electrode system was constructed using the test sample as the anode and a platinum sheet as the cathode. The electrolyte was a 0.5 mol / L H2SO4 solution (analytical grade) with a volume of 500 mL. Nitrogen gas was continuously introduced to remove oxygen at a flow rate of 20 mL / min. A constant current density of 500 mA / cm² was applied, and the change in anode potential was recorded using an electrochemical workstation. Set the failure criterion: when the anode potential suddenly rises by 1.0V, stop the test and record the cumulative time from the start of power-on to failure, which is the sample life.

[0074] Coating adhesion Referring to the GB / T 5210-2006 testing standard, the testing procedure is as follows: Clean the sample test area (5cm×5cm) and the surface of the aluminum alloy test block (5cm×5cm×1cm) with anhydrous ethanol to remove oil and impurities; Apply epoxy resin adhesive (shear strength ≥20MPa) to firmly bond the aluminum alloy test block to the sample coating surface, and cure in an oven at 80℃ for 2 hours; Tensile tests were performed using an electronic universal testing machine, with the tensile rate set to 2 mm / min, until the coating peeled off from the titanium substrate surface. Record the maximum load value during the stretching process, and calculate the coating adhesion force based on the bonding area (25cm²). Adhesion force = maximum load / bonding area. Test 3 parallel samples for each sample and take the average value.

[0075] Anode iridium content Referring to the YS / T 372.21-2021 testing standard, the testing process is as follows: Accurately weigh the test sample and record it as m1, with an accuracy of 0.1 mg; use a scribing tool to scribble a 1 cm × 1 cm test area along the edge of the coating and mark the boundary; The marked area was etched with a 1:3 volume ratio hydrochloric acid-nitric acid mixture (analytical grade) until the coating was completely dissolved, i.e., no residue was observed under a microscope. The etching solution was collected and diluted to 100 mL. Blank control: Take an uncoated titanium substrate of the same size, etch and volume-adjust it according to the same steps, and use it as a blank sample; The concentration of iridium in the etching solution was determined using an ICP-OES instrument and denoted as c, in μg / mL. Calculate the iridium content of the anode: Iridium content (g / m²) = (c × 100 × 10) -6 (0.0001m²) / (0.0001m²), each sample is tested in two parallel areas, and the average value is taken.

[0076] The test results are shown in Table 1: Table 1 Test data table of Example 1 and various comparative examples

[0077] From Table 1, we can obtain: Comparing Example 1 with Comparative Example 1, the lifespan of Example 1 was increased by 74.7%, and the coating adhesion was increased by 29.3%. This is because the solution precursor in Comparative Example 1 underwent significant volume shrinkage during drying and decomposition, leading to stress concentration within the coating and weakening the adhesion between the coating and the titanium substrate. Under electrochemical action and mechanical erosion, the coating was prone to cracking and peeling, directly shortening its lifespan. Furthermore, during multiple cycles, micropores and defects easily formed at the coating interface, further reducing its failure resistance. In contrast, this invention, through a single embedding and sintering process, avoids the accumulation of internal stress and interface defects caused by multiple cycles. The dense columnar crystal structure formed after the decomposition of the metal salt in the embedding agent has a larger intergranular contact area and stronger mechanical stability compared to the needle-like crystal structure of the thermal decomposition method. Simultaneously, the metal elements penetrate into the matrix to form a metallurgical bond, improving adhesion and extending lifespan. Moreover, the iridium content control precision is comparable to that of the thermal decomposition method, achieving performance upgrades without increasing costs.

[0078] Compared with Comparative Example 2, Example 1 showed significantly better lifespan and coating adhesion. This is because the film formation mechanism relies on the melting and diffusion of metal powder to ultimately form a titanium-based alloy coating, rather than a high-performance noble metal oxide catalytic layer. This completely lacks the core electrocatalytic active component, resulting in an extremely low lifespan. Furthermore, the slurry coating has poor uniformity, with the coating only physically adhering to the substrate, leading to extremely low adhesion and susceptibility to cracking due to drying shrinkage. This invention overcomes the limitations of traditional metal powder systems by using high-purity metal salts as precursors. Through precise control of the salt ratio, a stoichiometric noble metal oxide catalytic layer is directly and directionally generated, ensuring effective loading of the core active component. Simultaneously, the powder embedding method achieves uniform coating coverage. Combined with the synergistic effect of organic additives and inert fillers, the adhesion is doubled, and the lifespan is increased by more than 1.6 times, completely solving the problems of poor alloy coating performance and lack of active components.

[0079] Compared with Comparative Examples 3, 4, and 5, the data for Example 1 are superior to those for Comparative Examples 3 to 5. This demonstrates that proper control of the proportions of different substances in the inert filler, organic additive, and embedding agent is essential. Without the inert filler, metal salts accumulate locally, resulting in an uneven coating during sintering. Furthermore, unreacted metal salts lead to inflated levels of precious metals, reducing performance and increasing costs. Without the organic additive, the lack of a reducing atmosphere and instantaneous micro-area high temperature results in weak coating adhesion and insufficient deposition of active components. Insufficient inert filler leads to dispersion failure, excessive organic additives leave carbon impurities, and excessive metal salts decompose incompletely. This imbalance causes coating defects and significant waste of precious metals. In this invention, the inert filler ensures uniform coating formation, the organic additive drives a full reaction through a reducing atmosphere and micro-area high temperature, and the metal salt precisely provides the active components. These three elements work synergistically to achieve an optimal balance of high adhesion, long lifespan, and efficient utilization of precious metals, completely resolving the performance shortcomings caused by the imbalance of the embedding agent system.

[0080] Comparing Example 1 with Comparative Examples 6 and 7, the data from Example 1 are superior to those from Comparative Examples 6 and 7, demonstrating the crucial importance of proper control of sintering temperature and time. The sintering temperature range of 400-600℃ in this invention precisely matches the requirements of metal salt decomposition and coating formation: it avoids incomplete reactions at low temperatures while achieving efficient reactions in the mid-temperature range through the micro-regional high-temperature assistance of organic additives. Furthermore, it fundamentally avoids high-temperature damage to the titanium substrate, ensuring the mechanical properties of the substrate and the stability of the coating bond; simultaneously, the sintering time of 1-3 hours provides sufficient time for the complete decomposition of the metal salt and the densification of the coating. This highlights the rationality of the sintering temperature limitation in this invention and the breakthrough of low-temperature sintering technology.

[0081] 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 coated titanium anode by embedding, characterized in that: Includes the following steps: S1. Pretreatment of titanium matrix; S2. Preparation of embedding agent: The metal salt powder, organic additives, and inert filler are thoroughly mixed to form the embedding agent powder; wherein, the mass fraction of the metal salt is 45-59%, the mass fraction of the organic additives is 1-5%, and the mass fraction of the inert filler is 40-50%. S3. Sintering treatment: The pretreated titanium matrix is ​​completely immersed in the embedding agent powder to ensure that the embedding agent is evenly covered on the surface of the titanium matrix; then it is placed in a high-temperature furnace for sintering at a temperature of 400-600℃ for 1-3 hours and a heating rate of 5-10℃ / min. S4. Post-treatment: Remove the sintered coated titanium anode and allow it to cool naturally to room temperature; then perform surface cleaning to remove residual impurities and unreacted substances.

2. The method for preparing a coated titanium anode by embedding according to claim 1, characterized in that: In step S1, the titanium substrate is first polished to remove the oxide layer and impurities on the surface; then the polished titanium substrate is placed in an alkaline solution for ultrasonic cleaning to further remove organic impurities on the surface; next, the titanium substrate after alkaline cleaning is placed in an acid solution for acid washing to remove metal oxides and alkaline residue on the surface; finally, it is rinsed with deionized water and dried for later use.

3. The method for preparing a coated titanium anode by embedding according to claim 2, characterized in that: First, use coarse sandpaper to sand, then use progressively finer sandpaper until the surface is smooth and flat.

4. The method for preparing a coated titanium anode by embedding according to claim 2, characterized in that: When cleaning with alkaline solution, the concentration of alkaline solution is 5-10 wt%, the cleaning temperature is 50-60℃, and the cleaning time is 20-30 minutes. And / or, during pickling, the acid solution is a mixture of hydrochloric acid and nitric acid in a volume ratio of 1:1, the pickling temperature is room temperature, and the pickling time is 10-15 minutes.

5. The method for preparing a coated titanium anode by embedding according to claim 1, characterized in that: In step S2, the metal salt is at least one of rhodium salt, ruthenium salt, iridium salt, osmium salt, titanium salt, tantalum salt, niobium salt, platinum salt, and palladium salt.

6. The method for preparing a coated titanium anode by embedding according to claim 1, characterized in that: In step S2, the organic additive is at least one of polyvinyl alcohol and carboxymethyl cellulose; And / or, the inert filler is at least one of platinum powder and graphite powder.

7. The method for preparing a coated titanium anode by embedding according to claim 1, characterized in that: A noble metal oxide catalyst layer is formed directly on the titanium substrate through steps S2 and S3.

8. The method for preparing a coated titanium anode by embedding according to claim 1, characterized in that: First, an oxide intermediate layer is formed on the titanium substrate through steps S2 and S3, and then a noble metal oxide catalyst layer is formed on the oxide intermediate layer through steps S2 and S3.

9. A coated titanium anode, characterized in that: The coated titanium anode is prepared by the embedding preparation method according to any one of claims 1-8. The coated titanium anode includes a substrate, and the substrate is provided with an oxide intermediate layer and / or a noble metal oxide catalytic layer. The coating adhesion of the coated titanium anode reaches more than 70N and the service life reaches more than 1400h.

10. A coated titanium anode according to claim 9, characterized in that: The thickness of the oxide intermediate layer is 0.1-0.15 μm; And / or, the thickness of the noble metal oxide catalyst layer is 0.4-0.6 μm.

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