Chlor-alkali large-area titanium anode and preparation method thereof

Abstract

The invention discloses a chlor-alkali large-area titanium anode and a preparation method thereof. The chlor-alkali large-area titanium anode comprises a titanium base material used for forming an electrode structure and an electrode coating arranged on the surface of the titanium base material, and the titanium base material is a composite body of a planar net and a three-dimensional net. The electrode coating on the surface of the titanium base material sequentially comprises a compact corrosion-resistant bonding layer serving as a bottom layer, a conductive transition layer serving as a middle layer and an acid-corrosion-resistant high-chlorine-evolution-performance active layer serving as a surface layer. The compact corrosion-resistant binding layer is a tin oxide-cerium oxide coating, the conductive transition layer is a ruthenium oxide-cobalt oxide coating, and the acid corrosion-resistant high-chlorine-evolution-performance active layer is a tin and cerium doped ruthenium oxide-iridium oxide high-chlorine-evolution-performance acid corrosion-resistant coating. In the electrode coating, the transition layer with conductivity can also relieve the difference of thermal expansion coefficients of the bottom layer and the surface layer, and the service life of the electrode is effectively prolonged. By calculating and optimizing the molar ratio of metal in the coating, the cost is remarkably reduced while the chlorine evolution potential is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic material preparation and application, and in particular to a chlor-alkali large-area titanium anode and a preparation method thereof. Background Art

[0002] Chlor-alkali electrolyzers are the heart of the chlor-alkali industry, and the performance of their anodes directly impacts the energy efficiency and sustainability of the entire industry chain. The industry is currently mired in a four-pronged dilemma: resource constraints, interfacial corrosion, operational tolerance barriers, and lifespan degradation. Breakthroughs are urgently needed through material innovation and cross-scale structural design.

[0003] Traditional anodes are dominated by ruthenium-iridium-based oxides, and the precious metal mass ratio must exceed 30% to maintain the catalytic activity threshold of the chlorine evolution reaction (CER). However, with the global proven reserves of ruthenium resources being only about 25,000 tons, the current situation where the raw material cost accounts for more than 60% has seriously threatened the security of the industrial chain. Even more serious is that during the continuous operation of industrial electrolytic cells for tens of thousands of hours, the heterogeneous interface stress (the difference in thermal expansion coefficient between the titanium substrate and the coating is as much as 2.1×10⁻) 6 / K) and electrochemical-mechanical coupling trigger the directional propagation of subsurface microcracks in the coating, leading to the isolation of "catalytically active islands" and localized passivation of the titanium substrate, causing current efficiency to decay at a rate of 0.8% per month. When the current density exceeds 8 kA / m², the heterogeneous charge transport network of conventional coatings triggers localized electric field distortion, causing selective dissolution of the precious metal active phase, further deteriorating anode performance.

[0004] In response to the above problems, it is necessary to develop a low-cost, large-area titanium anode for chlor-alkali with low ruthenium and iridium content, low chlorine evolution potential, corrosion resistance, and high current resistance that can improve heterogeneous interface stress. Summary of the Invention

[0005] The purpose of the present invention is to provide a large-area chlor-alkali titanium anode with low precious metal content, high chlorine evolution performance, corrosion resistance and high current resistance. A dense tin oxide-cerium oxide anti-corrosion coating is first coated on the pre-treated activated titanium substrate as a bottom bonding layer. This layer can effectively prevent the electrolyte from penetrating into the titanium substrate and causing corrosion; then a highly conductive ruthenium oxide-cobalt oxide intermediate layer is coated as a transition, which can alleviate the thermal mismatch between the bottom and surface oxides and reduce the risk of coating peeling during high-temperature cycles; finally, a ruthenium oxide-iridium oxide high chlorine evolution performance and acid corrosion resistance coating doped with tin and cerium is coated on the electrode surface. The specific technical solution is as follows: A chlor-alkali large-area titanium anode comprises a titanium substrate for forming an electrode structure and an electrode coating arranged on the surface of the titanium substrate, wherein the titanium substrate is a composite of a planar mesh and a three-dimensional mesh, and the electrode coating on the surface of the titanium substrate sequentially comprises a dense corrosion-resistant bonding layer as a bottom layer, a conductive transition layer as an intermediate layer, and an acid-corrosion-resistant active layer with high chlorine evolution performance as a surface layer; wherein the dense corrosion-resistant bonding layer as the bottom layer is a tin oxide-cerium oxide coating, the conductive transition layer as the intermediate layer is a ruthenium oxide-cobalt oxide coating, and the acid-corrosion-resistant active layer with high chlorine evolution performance as the surface layer is a ruthenium oxide-iridium oxide acid-corrosion-resistant coating with high chlorine evolution performance doped with tin and cerium.

[0006] The electrode structure is a composite of a planar mesh and a three-dimensional mesh, which can increase the strength and specific surface area of the anode substrate.

[0007] The structure of the above-mentioned acid corrosion-resistant and high chlorine evolution performance active layer serving as the surface layer is mainly composed of ruthenium oxide and iridium oxide to form an active layer, and by doping with tin element, it is beneficial to further reduce the chlorine evolution potential of ruthenium dioxide, while increasing the oxygen evolution potential, inhibiting the formation of oxygen, and making the coating have efficient chlorine evolution selectivity; in addition, on the basis of the strong corrosion resistance of iridium oxide itself in the surface layer, adding a small amount of cerium oxide can significantly inhibit the dissolution of iridium oxide, thereby further enhancing the corrosion resistance of the coating, thereby greatly improving the electrode life.

[0008] Furthermore, the large-area titanium anode for chlor-alkali production of the present invention significantly reduces costs while lowering the chlorine evolution potential by optimizing the metal molar ratio in the coating. The base layer utilizes relatively low-cost tin and cerium; the middle layer is doped with relatively low-cost cobalt, which can appropriately reduce the amount of precious metal ruthenium used in the middle layer coating. Tin doping and cerium addition to the surface layer also appropriately reduce the amount of precious metals ruthenium and iridium used in the surface layer coating, thereby reducing the production cost of the large-area titanium anode for chlor-alkali production.

[0009] Preferably, the structure of the dense corrosion-resistant bonding layer of the bottom layer is mainly composed of tin oxide and cerium oxide, and butyl titanate is used as a binder in the bottom layer. Through the hydrolysis and condensation reaction of butyl titanate during the preparation process, it is converted into titanium oxide with a network structure that can form a chemical bond with the surface of the titanium substrate, so as to enhance the bonding force between the coating and the titanium substrate, and at the same time form a dense tin oxide-cerium oxide coating to avoid the active coating from falling off due to the electrolyte penetrating into the substrate.

[0010] The use of butyl titanate as a binder in the base coating is conducive to forming a tight, crack-free, corrosion-resistant base between the coating and the titanium substrate.

[0011] Preferably, the structure of the conductive transition layer of the intermediate layer is mainly composed of ruthenium oxide and is also doped with a certain proportion of cobalt oxide, and butyl titanate is used as a binder in the intermediate layer; by optimizing the ratio of each compound element in the bottom layer, the intermediate layer and the surface layer, the thermal expansion coefficient of the intermediate layer is between the bottom layer and the surface layer; through the hydrolysis and condensation reaction of butyl titanate during the preparation process, it is converted into titanium oxide with a network structure that can form a strong interface connection with the bottom layer, thereby enhancing the bonding force between the intermediate layer and the bottom layer.

[0012] In the conductive transition layer as the intermediate layer, the addition of a small amount of cobalt element improves the conductivity of the coating, and the ruthenium oxide-cobalt oxide intermediate layer as a transition can alleviate the titanium substrate (CTE≈8.6×10 -6 / K) and outer oxide (RuO2-IrO2 CTE≈6.5×10 -6 The thermal mismatch of 100 nm / K can help alleviate the difference in thermal expansion coefficient between the bottom layer and the surface layer, reduce the risk of coating peeling during high-temperature cycles, and thus effectively extend the life of the electrode.

[0013] In the present invention, the flat mesh is a titanium perforated mesh or a titanium wire mesh, and the three-dimensional mesh is a titanium perforated mesh with a punched arc structure.

[0014] A method for preparing a large-area titanium anode for chlor-alkali includes the following steps: (1) Pretreatment of titanium substrate: Select titanium stamping mesh or titanium wire mesh, sandblast, wash with water, degrease, and then etch with oxalic acid solution to remove the surface oxide layer and activate it; (2) Preparation of electrode structure: The titanium stamping mesh or titanium wire mesh processed as above is processed into a three-dimensional mesh with a circular arc convex structure, and then a piece of titanium stamping mesh or titanium wire mesh as a flat mesh is composited onto the surface of the three-dimensional mesh; (3) Preparation of chlor-alkali large-area titanium anode coating solution: Use tin tetrachloride, cerium trichloride, butyl titanate, ruthenium trichloride, cobalt dichloride and chloroiridic acid as raw materials, and use n-butanol, hydrochloric acid, acetylacetone and pure water as solvents to prepare each layer of coating solution: The bottom bonding layer coating liquid is prepared by using tin tetrachloride, cerium trichloride, butyl titanate, n-butanol and pure water to prepare a tin-cerium-titanium coating liquid, wherein the molar ratio of tin, cerium, titanium, n-butanol and water is (1-5):1:6:50:(200-300); The conductive transition layer coating in the middle is prepared by using ruthenium trichloride, cobalt dichloride, butyl titanate, acetylacetone and n-butanol to prepare a ruthenium cobalt titanium coating solution, wherein the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is (5-12):3:3:2:(100-150); The active layer coating liquid of the surface layer is prepared by using ruthenium trichloride, chloroiridic acid, tin tetrachloride, cerium trichloride, hydrochloric acid, n-butanol and pure water to prepare a ruthenium-iridium-tin-cerium coating liquid, wherein the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is (8-15):5:(1-3):1:30:200:(200-300); (4) The coating and oxidation of the electrode coating are as follows: The pretreated titanium substrate is coated with a base layer, an intermediate layer, and a surface layer in sequence, and each layer is coated several times. After each coating, it needs to be dried at room temperature and then transferred to an oven to be dried at a temperature not higher than 120°C, and finally transferred to a high-temperature oxidation furnace and sintered at 480°C for 10-15 minutes; after the final coating of the surface layer, it is dried and baked, and then sintered at 490°C for 1 hour.

[0015] Preferably, after pretreatment, the titanium substrate is first coated with a base coating solution, air-dried at room temperature, and then placed in an oven for drying at 120°C for 10-15 minutes to prevent cracking of the base coating during high-temperature oxidation. The dried electrode is then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This operation is repeated two or three times. The intermediate coating solution is then applied, air-dried, and then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This operation is repeated two or three times. Finally, the top coating solution is applied, air-dried, and then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This operation is repeated three or four times. The final high-temperature oxidation temperature is 490°C and held for 1 hour.

[0016] Note that in order to prevent the solvent from evaporating too quickly and causing excessive cracking of the coating, in the coating and oxidation of the electrode coating in step (4), each coating liquid needs to be dried at room temperature and then transferred to a 120°C oven for drying for 10 to 15 minutes, and finally transferred to a high-temperature oxidation furnace for calcining at 480°C for 10 to 15 minutes; after the final coating, drying and baking of the surface layer, it is sintered at 490°C for 1 hour.

[0017] The large-area titanium anode for chlor-alkali prepared through the above steps has a dense bottom bonding layer, which is tightly bonded to the titanium substrate without cracks and can effectively protect the substrate from acid corrosion; the surface layer has a tight appearance, and the crack generation is limited and controlled by an optimized coating process, with only a small amount of scattered cracks formed on the surface layer, which is beneficial to increasing the surface roughness and releasing internal stress.

[0018] Preferably, in the preparation of the electrode structure in step (2), the planar mesh and the three-dimensional mesh are composited by ultrasonic welding.

[0019] Preferably, in the coating liquid of the bottom bonding layer, the molar ratio of tin, cerium, titanium, n-butanol and water is 3:1:6:50:(200-300).

[0020] Preferably, in the intermediate conductive transition layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 8:3:3:2:(100-150).

[0021] Preferably, in the active layer coating solution of the surface layer, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:2:1:30:200:(200~300).

[0022] Preferably, in the step (1) pretreatment of the titanium substrate, a titanium stamping mesh or a titanium wire mesh is selected, and medium-coarse sand (40 mesh) is vertically sprayed at a pressure of 0.5 MPa using a pressure-type sandblasting machine. After sandblasting, it is rinsed with pure water and transferred to a 5wt% NaOH solution at 60°C for 30 minutes for degreasing; after degreasing, it is rinsed with pure water and then transferred to a 10wt% oxalic acid solution and etched at 90°C for 60-100 minutes to remove the surface oxide layer and activate it.

[0023] The beneficial effects of the present invention are: First, the present invention provides a large-area titanium anode for chlor-alkali and its preparation method, which divides the coating into three parts, each of which plays an important role. The bottom layer is composed of a bonding layer of tin oxide and cerium oxide. The two oxides are tightly bonded to the titanium substrate through a "pinning effect", providing an anti-corrosion bottom layer and preventing the electrolyte from penetrating into the substrate and causing corrosion. The conductive transition layer in the middle layer is mainly composed of ruthenium oxide and cobalt oxide. The addition of a small amount of cobalt improves the conductivity of the middle layer. In addition, the ruthenium oxide-cobalt oxide as a transition layer can alleviate the thermal mismatch between the titanium substrate and the outer oxide layer, reducing the risk of coating peeling during high-temperature cycles. The surface layer is mainly composed of ruthenium oxide and iridium oxide. By doping with tin, the chlorine evolution potential of ruthenium dioxide is further reduced, while the oxygen evolution potential is increased, inhibiting the formation of oxygen, and making the coating have efficient chlorine evolution selectivity. In addition, the addition of a small amount of cerium oxide can significantly inhibit the dissolution of iridium oxide, further enhancing the corrosion resistance of the coating. Therefore, the rational layering of the coating can achieve the goals of corrosion resistance, reduced chlorine evolution potential, and increased anode life.

[0024] Secondly, the present invention's large-area titanium anode for chlor-alkali production and its preparation method requires that after each application of the coating solution, the electrode is first air-dried at room temperature, then placed in a 120°C oven for 10-15 minutes, and finally placed in a high-temperature oxidation furnace. This procedure effectively avoids excessive cracking in the coating caused by rapid solvent volatilization at high temperatures, ensuring a dense, crack-free basecoat and preventing excessive cracking in the surface coating, which could lead to the formation of "islands of catalytic activity."

[0025] Third, the present invention provides a large-area titanium anode for chlor-alkali and a preparation method thereof. By doping the surface corrosion-resistant active layer with tin, on the one hand, the chlorine evolution potential of surface ruthenium dioxide can be significantly reduced, the adsorption of oxygen free radical intermediates can be weakened, and the CER kinetics can be improved. On the other hand, the presence of tin in a tetravalent form can effectively improve the chlorine evolution selectivity of the surface. In addition, the addition of a trace amount of cerium can form cerium oxide-iridium oxide composite nanoparticles with iridium oxide at high temperature, thereby enhancing the corrosion resistance of iridium oxide.

[0026] Fourth, the large-area titanium anode and preparation method of the present invention have a composite structure of a flat mesh and a three-dimensional mesh that is beneficial to increasing the electrode strength and specific surface area, reducing the actual current density of the anode, and improving its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The surface scanning electron microscope (SEM) image of the titanium electrode coated only with the primer solution; Figure 2 This is a surface scanning electron microscope (SEM) image of Example 1; Figure 3 Schematic diagram of the plane mesh in the titanium anode structure; Figure 4 Schematic diagram of the three-dimensional network in the titanium anode structure; Figure 5 Schematic diagram of the plane network and three-dimensional network complex in the titanium anode structure. DETAILED DESCRIPTION

[0028] The following embodiments of the present invention are further described in conjunction with the accompanying drawings and examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] like Figures 1 to 5 The figure shows the overall implementation scheme of a large-area titanium anode for chlor-alkali and a preparation method of the present invention, wherein the large-area titanium anode for chlor-alkali comprises a titanium substrate for forming an electrode structure and an electrode coating arranged on the surface of the titanium substrate, wherein the titanium substrate is a plane mesh and a three-dimensional mesh complex, and the electrode coating on the surface of the titanium substrate comprises, in sequence, a dense corrosion-resistant bonding layer as a bottom layer, a conductive transition layer as an intermediate layer, and an acid-corrosion-resistant and high-chlorine-evolution performance active layer as a surface layer; wherein the dense corrosion-resistant bonding layer as the bottom layer is a tin oxide-cerium oxide coating, the conductive transition layer as the intermediate layer is a ruthenium oxide-cobalt oxide coating, and the acid-corrosion-resistant and high-chlorine-evolution performance active layer as the surface layer is a ruthenium oxide-iridium oxide high-chlorine-evolution performance acid-corrosion-resistant coating doped with tin and cerium.

[0030] The electrode structure is a composite of a planar mesh and a three-dimensional mesh, which can increase the strength and specific surface area of the anode substrate.

[0031] The structure of the above-mentioned acid corrosion-resistant and high chlorine evolution performance active layer serving as the surface layer is mainly composed of ruthenium oxide and iridium oxide to form an active layer, and by doping with tin element, it is beneficial to further reduce the chlorine evolution potential of ruthenium dioxide, while increasing the oxygen evolution potential, inhibiting the formation of oxygen, and making the coating have efficient chlorine evolution selectivity; in addition, on the basis of the strong corrosion resistance of iridium oxide itself in the surface layer, adding a small amount of cerium oxide can significantly inhibit the dissolution of iridium oxide, thereby further enhancing the corrosion resistance of the coating, thereby greatly improving the electrode life.

[0032] Furthermore, the large-area titanium anode for chlor-alkali production of the present invention significantly reduces costs while lowering the chlorine evolution potential by optimizing the metal molar ratio in the coating. The base layer utilizes relatively low-cost tin and cerium; the middle layer is doped with relatively low-cost cobalt, which can appropriately reduce the amount of precious metal ruthenium used in the middle layer coating. Tin doping and cerium addition to the surface layer also appropriately reduce the amount of precious metals ruthenium and iridium used in the surface layer coating, thereby reducing the production cost of the large-area titanium anode for chlor-alkali production.

[0033] Preferably, the structure of the dense corrosion-resistant bonding layer of the bottom layer is mainly composed of tin oxide and cerium oxide, and butyl titanate is used as a binder in the bottom layer. Through the hydrolysis and condensation reaction of butyl titanate during the preparation process, it is converted into titanium oxide with a network structure that can form a chemical bond with the surface of the titanium substrate, so as to enhance the bonding force between the coating and the titanium substrate, and at the same time form a dense tin oxide-cerium oxide coating to avoid the active coating from falling off due to the electrolyte penetrating into the substrate.

[0034] The use of butyl titanate as a binder in the base coating is conducive to forming a tight, crack-free, corrosion-resistant base between the coating and the titanium substrate.

[0035] Preferably, the structure of the conductive transition layer of the intermediate layer is mainly composed of ruthenium oxide and is also doped with a certain proportion of cobalt oxide, and butyl titanate is used as a binder in the intermediate layer; by optimizing the ratio of each compound element in the bottom layer, the intermediate layer and the surface layer, the thermal expansion coefficient of the intermediate layer is between the bottom layer and the surface layer; through the hydrolysis and condensation reaction of butyl titanate during the preparation process, it is converted into titanium oxide with a network structure that can form a strong interface connection with the bottom layer, thereby enhancing the bonding force between the intermediate layer and the bottom layer.

[0036] In the conductive transition layer as the intermediate layer, the addition of a small amount of cobalt element improves the conductivity of the coating, and the ruthenium oxide-cobalt oxide intermediate layer as a transition can alleviate the titanium substrate (CTE≈8.6×10 -6 / K) and outer oxide (RuO2-IrO2 CTE≈6.5×10 -6The thermal mismatch of 100 nm / K can help alleviate the difference in thermal expansion coefficient between the bottom layer and the surface layer, reduce the risk of coating peeling during high-temperature cycles, and thus effectively extend the life of the electrode.

[0037] In the present invention, the flat mesh is a titanium perforated mesh or a titanium wire mesh, and the three-dimensional mesh is a titanium perforated mesh with a punched arc structure.

[0038] A method for preparing a large-area titanium anode for chlor-alkali includes the following steps: (1) Pretreatment of titanium substrate: Select titanium stamping mesh or titanium wire mesh, sandblast, wash with water, degrease, and then etch with oxalic acid solution to remove the surface oxide layer and activate it; (2) Preparation of electrode structure: The titanium stamping mesh or titanium wire mesh processed as above is processed into a three-dimensional mesh with a circular arc convex structure, and then a piece of titanium stamping mesh or titanium wire mesh as a flat mesh is composited onto the surface of the three-dimensional mesh; (3) Preparation of chlor-alkali large-area titanium anode coating solution: Use tin tetrachloride, cerium trichloride, butyl titanate, ruthenium trichloride, cobalt dichloride and chloroiridic acid as raw materials, and use n-butanol, hydrochloric acid, acetylacetone and pure water as solvents to prepare each layer of coating solution: The bottom bonding layer coating liquid is prepared by using tin tetrachloride, cerium trichloride, butyl titanate, n-butanol and pure water to prepare a tin-cerium-titanium coating liquid, wherein the molar ratio of tin, cerium, titanium, n-butanol and water is (1-5):1:6:50:(200-300); The conductive transition layer coating in the middle is prepared by using ruthenium trichloride, cobalt dichloride, butyl titanate, acetylacetone and n-butanol to prepare a ruthenium cobalt titanium coating solution, wherein the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is (5-12):3:3:2:(100-150); The active layer coating liquid of the surface layer is prepared by using ruthenium trichloride, chloroiridic acid, tin tetrachloride, cerium trichloride, hydrochloric acid, n-butanol and pure water to prepare a ruthenium-iridium-tin-cerium coating liquid, wherein the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is (8-15):5:(1-3):1:30:200:(200-300); (4) The coating and oxidation of the electrode coating are as follows: The pretreated titanium substrate is coated with a base layer, an intermediate layer, and a surface layer in sequence, and each layer is coated several times. After each coating, it needs to be dried at room temperature and then transferred to an oven to be dried at a temperature not higher than 120°C, and finally transferred to a high-temperature oxidation furnace and sintered at 480°C for 10-15 minutes; after the final coating of the surface layer, it is dried and baked, and then sintered at 490°C for 1 hour.

[0039] The large-area titanium anode for chlor-alkali prepared through the above steps has a dense bottom bonding layer, which is tightly bonded to the titanium substrate without cracks and can effectively protect the substrate from acid corrosion; the surface layer has a tight appearance, and the crack generation is limited and controlled by an optimized coating process, with only a small amount of scattered cracks formed on the surface layer, which is beneficial to increasing the surface roughness and releasing internal stress.

[0040] Preferably, after pretreatment, the titanium substrate is first coated with a base coating solution, air-dried at room temperature, and then placed in an oven for drying at 120°C for 10-15 minutes to prevent cracking of the base coating during high-temperature oxidation. The dried electrode is then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This operation is repeated two or three times. The intermediate coating solution is then applied, air-dried, and then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This operation is repeated two or three times. Finally, the top coating solution is applied, air-dried, and then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This operation is repeated three or four times. The final high-temperature oxidation temperature is 490°C and held for 1 hour.

[0041] Preferably, in the preparation of the electrode structure in step (2), the planar mesh and the three-dimensional mesh are composited by ultrasonic welding.

[0042] Preferably, in the coating liquid of the bottom bonding layer, the molar ratio of tin, cerium, titanium, n-butanol and water is 3:1:6:50:(200-300).

[0043] Preferably, in the intermediate conductive transition layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 8:3:3:2:(100-150).

[0044] Preferably, in the active layer coating solution of the surface layer, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:2:1:30:200:(200~300).

[0045] Preferably, in the step (1) pretreatment of the titanium substrate, a titanium stamping mesh or a titanium wire mesh is selected, and medium-coarse sand (40 mesh) is vertically sprayed at a pressure of 0.5 MPa using a pressure-type sandblasting machine. After sandblasting, it is rinsed with pure water and transferred to a 5wt% NaOH solution at 60°C for 30 minutes for degreasing; after degreasing, it is rinsed with pure water and then transferred to a 10wt% oxalic acid solution and etched at 90°C for 60-100 minutes to remove the surface oxide layer and activate it.

[0046] The following are several examples formulated according to the overall implementation scheme of a chlor-alkali large-area titanium anode and a preparation method of the present invention.

[0047] Example 1: Preparation of 300 g / L NaCl solution: Prepare a 300 ml beaker, add 75 g of NaCl and 240 ml of pure water, and continue stirring until the NaCl is completely dissolved. Transfer the mixture to a 250 ml volumetric flask and make up to volume. Set aside.

[0048] Preparation of 40 g / L NaCl solution: Prepare a 150 ml beaker, add 4 g of NaCl and 90 ml of pure water, and continue stirring until the NaCl is completely dissolved. Transfer the solution to a 100 ml volumetric flask and set aside.

[0049] Preparation of 1 M H2SO4 solution: Prepare a 1500 ml beaker, drain 54.4 ml of 98% concentrated H2SO4 using a glass rod, and slowly add it to 945.6 ml of pure water while stirring continuously. Let the solution cool down and set aside.

[0050] Titanium substrate pretreatment: Use a pressure-type sandblaster to vertically spray medium-coarse sand (40 mesh) onto a titanium stamping mesh or nickel wire mesh at a pressure of 0.5 MPa. After sandblasting, rinse with pure water and degrease in a 5 wt% NaOH solution at 60°C for 30 minutes. After degreasing, rinse with pure water and then etch in a 10 wt% oxalic acid solution at 90°C for 60-100 minutes to remove the surface oxide layer and activate the mesh.

[0051] Preparation of chlor-alkali large-area titanium anode coating solution: Use tin tetrachloride, cerium trichloride, butyl titanate, ruthenium trichloride, cobalt dichloride and chloroiridic acid as raw materials, and use n-butanol, hydrochloric acid and pure water as solvents to prepare each layer of coating solution: The bottom bonding layer coating liquid is a tin-cerium-titanium coating liquid prepared with tin tetrachloride, cerium trichloride, butyl titanate, n-butanol and pure water, wherein the molar ratio of tin, cerium, titanium, n-butanol and water is (1-5):1:6:50:(200-300); The conductive transition layer coating in the middle is a ruthenium-cobalt-titanium coating solution prepared with ruthenium trichloride, cobalt dichloride, butyl titanate, acetylacetone and n-butanol, wherein the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is (5-12):3:3:2:(100-150); The active layer coating liquid of the surface layer is a ruthenium-iridium-tin-cerium coating liquid prepared from ruthenium trichloride, chloroiridic acid, tin tetrachloride, cerium trichloride, hydrochloric acid, n-butanol and pure water, wherein the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is (8-15):5:(1-3):1:30:200:(200-300); Preferably, in the primer coating solution, the molar ratio of tin, cerium, titanium, n-butanol, isopropanol and water is 3:1:6:50:(200-300); Preferably, in the intermediate layer coating solution, the molar ratio of ruthenium, cobalt, titanium, isopropyl alcohol and pure water is 8:3:3:2:(100-150); Preferably, in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, n-butanol and pure water is 12:5:2:1:30:200:(200~300).

[0052] Preferably, after each coating, the electrode is first dried at room temperature and then placed in an oven at 120°C for 10-15 minutes, and then placed in a high-temperature oxidation furnace for oxidation at 480°C for 10-15 minutes. The oxidation temperature of the last coating is 490°C and maintained for 1 hour.

[0053] The pretreated titanium substrate is first coated with the base coating solution, air-dried at room temperature, and then placed in an oven for drying at 120°C for 10-15 minutes. This prevents cracking of the base coating during high-temperature oxidation. The dried electrode is then placed in a high-temperature furnace and held at 480°C for 10-15 minutes. This process is repeated two or three times. The intermediate coating solution is then applied, air-dried, and then placed in a high-temperature furnace for holding at 480°C for 10-15 minutes. This process is repeated two or three times. Finally, the top coating solution is applied, air-dried, and then placed in a high-temperature furnace for holding at 480°C for 10-15 minutes. This process is repeated three or four times. The final high-temperature oxidation temperature is 490°C for 1 hour.

[0054] 7. Application (1) Chlorine evolution potential test A three-electrode system was used, with the working electrode being the large-area titanium anode described above, the auxiliary electrode being a platinum sheet electrode, and the reference electrode being a saturated potassium chloride solution calomel electrode (SCE) with a double salt bridge and Luggin capillary. The electrocatalyst exhibited a chlorine evolution potential of 1.045 V (vs SCE) at a current density of 3000 A / m² in a 300 g / L NaCl solution at 25 ± 2°C. The experimental results are shown in Table 1.

[0055] (2) Oxygen evolution potential test A three-electrode system was used, with the working electrode being the large-area titanium anode described above, the auxiliary electrode being a platinum sheet electrode, and the reference electrode being a saturated potassium chloride solution calomel electrode (SCE) with a double salt bridge and Luggin capillary. The electrocatalyst exhibited an oxygen evolution potential of 1.482 V (vs SCE) at a current density of 3000 A / m2 in a 1 mol / L H2SO4 solution at 25±2°C. The experimental results are shown in Table 2. (3) Strengthen life test The anode coating electrode is fed with a constant current DC power supply with a current density of 10000 A / m 2 The solution system is 1 M H2SO4 solution, and the temperature is 40±2℃. The time for the test voltage to rise to 10 V is 655 h. The experimental results are shown in Table 3.

[0056] (4) Chlorine evolution selectivity test In 60 mL of 40 g / L NaCl solution, the - ² Electrolysis was carried out for 20 minutes at a current density of 2. Take 20 mL of electrolyte and mix it with 20 mL of water to dilute it to 500 mL (labeled as solution A). - ¹ Add 10 mL of solution A to a volumetric flask containing KI solution and 10 mL of 3% H2SO4. After standing for 5 minutes, add 2 mL of 0.01 g·mL -1 The starch solution is titrated with 0.01 M Na2S2O3 until the blue color disappears. The chlorine evolution selectivity is calculated according to the following formula: Parameter Description: n: number of transferred electrons F: Faraday constant (96485 C·mol -1 ) C: Active chlorine concentration (mol·L -1 ) V: volume of solution (L) M: Cl2 molecular weight (g·mol -1 ) I: current (A) t: time (s) The chlorine evolution selectivity was tested to be 96%. The experimental results are shown in Table 4.

[0057] Example 2: Compared with Example 1, the difference is that in the primer coating solution, the molar ratio of tin, cerium, titanium, n-butanol and water is 1:1:6:50:(200-300), and the other preparation methods are the same as those in Example 1.

[0058] Example 3: Compared with Example 1, the difference is that in the primer coating solution, the molar ratio of tin, cerium, titanium, n-butanol, isopropanol and water is 5:1:6:50:(200-300), and the other preparation methods are the same as those in Example 1.

[0059] Example 4: Compared with Example 1, the difference is that in the intermediate layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 5:3:3:2:(100-150), and the other preparation methods are the same as those in Example 1.

[0060] Example 5: Compared with Example 1, the difference is that in the intermediate layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 12:3:3:2:(100-150), and the other preparation methods are the same as those in Example 1.

[0061] Example 6: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 8:5:2:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0062] Example 7: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 15:5:2:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0063] Example 8: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:1:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0064] Example 9: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:3:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0065] Comparative Example 1: Compared with Example 1, the difference is that in the primer coating solution, the molar ratio of tin, cerium, titanium, n-butanol and water is 0:1:6:50:(200-300), and the other preparation methods are the same as those in Example 1.

[0066] Comparative Example 2: Compared with Example 1, the difference is that in the primer coating solution, the molar ratio of tin, cerium, titanium, n-butanol and water is 8:1:6:50:(200-300), and the other preparation methods are the same as those in Example 1.

[0067] Comparative Example 3: Compared with Example 1, the difference is that in the intermediate layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 2:3:3:2:(100-150), and the other preparation methods are the same as those in Example 1.

[0068] Comparative Example 4: Compared with Example 1, the difference is that in the intermediate layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 15:3:3:2:(100-150), and the other preparation methods are the same as those in Example 1.

[0069] Comparative Example 5: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 2:5:2:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0070] Comparative Example 6: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 20:5:2:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0071] Comparative Example 7: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:0:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0072] Comparative Example 8: Compared with Example 1, the difference is that in the surface coating solution, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:10:1:30:200:(200-300), and the other preparation methods are the same as those in Example 1.

[0073] Summary of experimental results: Table 1 shows the results of Examples 1-9 and Comparative Examples 1-8 in 300 g / L NaCl solution at 3000 A / m 2 Current density, chlorine evolution potential at 25±2 ℃.

[0074] Table 1 Chlorine evolution potential test sample Chlorine evolution potential / V vs SCE Example 1 1.045 Example 2 1.052 Example 3 1.066 Example 4 1.105 Example 5 1.056 Example 6 1.107 Example 7 1.049 Example 8 1.087 Example 9 1.055 Comparative Example 1 1.153 Comparative Example 2 1.210 Comparative Example 3 1.114 Comparative Example 4 1.065 Comparative Example 5 1.231 Comparative Example 6 1.051 Comparative Example 7 1.122 Comparative Example 8 1.263 The test results in Table 1 show that Examples 1, 2, 3, 5, 7 and 9 have lower hydrogen evolution potentials.

[0075] Table 2 shows the results of Examples 1, 2, 3, 5, 7 and 9 in 1 mol / L H2SO4 solution at 3000 A / m 2 Current density, oxygen evolution potential at 25±2℃.

[0076] Table 2 Oxygen evolution potential test sample Oxygen evolution potential / V vs SCE Example 1 1.482 Example 2 1.465 Example 3 1.477 Example 5 1.472 Example 7 1.481 Example 9 1.355 The test results in Table 2 show that Examples 1, 2, 3, 5 and 7 have higher oxygen evolution potentials, which means that the electrode may inhibit the evolution of oxygen and reduce the oxygen content in chlorine.

[0077] Table 3 shows the chlorine evolution selectivity performance of Example 1, Example 2, Example 3, Example 5 and Example 7 Table 3 Chlorine evolution selectivity sample Chlorine evolution selectivity / % Example 1 96 Example 2 90 Example 3 94 Example 5 92 Example 7 93 The test results in Table 3 show that the chlorine evolution selectivity of Examples 1, 2, 3, 5 and 7 is 90% or above.

[0078] Table 4 shows the results of Examples 1, 2, 3, 5 and 7 in 1 M H2SO4 solution with a current density of 10000 A / m 2 , the time it takes for the test voltage to rise to 10 V at a temperature of 40±2°C.

[0079] Table 4 Strengthening life test sample Simulation test life / h Example 1 655 Example 2 217 Example 3 164 Example 5 439 Example 7 501 The test results in Table 4 show that Examples 1, 5 and 7 have better intensive test life.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A large-area titanium anode for chlor-alkali, characterized in that: The invention comprises a titanium substrate for forming an electrode structure and an electrode coating arranged on the surface of the titanium substrate, wherein the titanium substrate is a complex of a planar mesh and a three-dimensional mesh, and the electrode coating on the surface of the titanium substrate sequentially comprises a dense corrosion-resistant bonding layer as a bottom layer, a conductive transition layer as an intermediate layer, and an acid-corrosion-resistant high-chlorine-evolution performance active layer as a surface layer; wherein the dense corrosion-resistant bonding layer as the bottom layer is a tin oxide-cerium oxide coating, the conductive transition layer as the intermediate layer is a ruthenium oxide-cobalt oxide coating, and the acid-corrosion-resistant high-chlorine-evolution performance active layer as the surface layer is a ruthenium oxide-iridium oxide high-chlorine-evolution performance acid-corrosion-resistant coating doped with tin and cerium.

2. A chlor-alkali large-area titanium anode according to claim 1, characterized in that: In addition to being mainly composed of tin oxide and cerium oxide, the structure of the dense corrosion-resistant bonding layer of the bottom layer also uses butyl titanate as a binder in the bottom layer. During the preparation process, the butyl titanate is converted into titanium oxide with a network structure that can form a chemical bond with the surface of the titanium substrate through hydrolysis and condensation reactions, thereby enhancing the bonding strength between the coating and the titanium substrate. At the same time, a dense tin oxide-cerium oxide coating is formed to prevent the active coating from falling off due to the penetration of the electrolyte into the substrate.

3. The chlor-alkali large-area titanium anode according to claim 1, characterized in that: The conductive transition layer of the intermediate layer is mainly composed of ruthenium oxide and is also doped with a certain proportion of cobalt oxide. Nibutyl titanate is used as a binder in the intermediate layer. By optimizing the ratio of the compound elements in the bottom layer, the intermediate layer, and the surface layer, the thermal expansion coefficient of the intermediate layer is between that of the bottom layer and the surface layer. During the preparation process, the hydrolysis and condensation reaction of butyl titanate is converted into titanium oxide with a network structure that can form a strong interface connection with the bottom layer, thereby enhancing the bonding force between the intermediate layer and the bottom layer.

4. The chlor-alkali large-area titanium anode according to claim 1, characterized in that: The plane mesh is a titanium perforated mesh or a titanium wire mesh, and the three-dimensional mesh is a titanium perforated mesh with a stamped arc structure.

5. The method for preparing a large-area titanium anode for chlor-alkali according to any one of claims 1 to 4, characterized in that: The steps include: (1) Pretreatment of titanium substrate: Select titanium stamping mesh or titanium wire mesh, sandblast, wash with water, degrease, and then etch with oxalic acid solution to remove the surface oxide layer and activate it; (2) Preparation of electrode structure: The titanium stamping mesh or titanium wire mesh processed as above is processed into a three-dimensional mesh with a circular arc convex structure, and then a piece of titanium stamping mesh or titanium wire mesh as a flat mesh is composited onto the surface of the three-dimensional mesh; (3) Preparation of chlor-alkali large-area titanium anode coating solution: Use tin tetrachloride, cerium trichloride, butyl titanate, ruthenium trichloride, cobalt dichloride and chloroiridic acid as raw materials, and use n-butanol, hydrochloric acid, acetylacetone and pure water as solvents to prepare each layer of coating solution: The bottom bonding layer coating liquid is prepared by using tin tetrachloride, cerium trichloride, butyl titanate, n-butanol and pure water to prepare a tin-cerium-titanium coating liquid, wherein the molar ratio of tin, cerium, titanium, n-butanol and water is (1-5):1:6:50:(200-300); The conductive transition layer coating in the middle is prepared with ruthenium trichloride, cobalt dichloride, butyl titanate, acetylacetone and n-butanol to prepare a ruthenium cobalt titanium coating solution, wherein the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is (5-12):3:3:2:(100-150); The active layer coating liquid of the surface layer is prepared by using ruthenium trichloride, chloroiridic acid, tin tetrachloride, cerium trichloride, hydrochloric acid, n-butanol and pure water to prepare a ruthenium-iridium-tin-cerium coating liquid, wherein the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is (8-15):5:(1-3):1:30:200:(200-300); (4) The coating and oxidation of the electrode coating are as follows: The pretreated titanium substrate is coated with a base layer, an intermediate layer, and a surface layer in sequence, and each layer is coated several times. After each coating, it needs to be dried at room temperature and then transferred to an oven to be dried at a temperature not higher than 120°C, and finally transferred to a high-temperature oxidation furnace and sintered at 480°C for 10-15 minutes; after the final coating of the surface layer, it is dried and baked, and then sintered at 490°C for 1 hour.

6. A chlor-alkali large-area titanium anode according to claim 5, characterized in that: In the preparation of the electrode structure in step (2), the planar mesh and the three-dimensional mesh are composited by ultrasonic welding.

7. The method for preparing a large-area titanium anode for chlor-alkali according to claim 5, characterized in that: In the coating and oxidation of the electrode coating in step (4), the bottom bonding layer coating solution is first applied, and after drying at room temperature, the electrode is transferred to an oven and dried at a low temperature of 120°C for 10 to 15 minutes to prevent the bottom coating from cracking during high-temperature oxidation. The dried electrode is then transferred to a high-temperature furnace and kept at a high temperature of 480°C for 10 to 15 minutes. This operation is repeated 2 to 3 times. Then, apply the intermediate coating solution, air-dry, and transfer to a high-temperature furnace, holding it at 480°C for 10-15 minutes. This operation is repeated two to three times. Finally, apply the top coating solution, air-dry, and transfer to a high-temperature furnace, holding it at 480°C for 10-15 minutes. This operation is repeated three to four times. The final high-temperature oxidation temperature is 490°C and held for 1 hour.

8. The method for preparing a large-area titanium anode for chlor-alkali according to claim 5, characterized in that: In the bottom layer bonding layer coating liquid, the molar ratio of tin, cerium, titanium, n-butanol and water is 3:1:6:50:(200-300).

9. The method for preparing a large-area titanium anode for chlor-alkali according to claim 5, characterized in that: In the intermediate conductive transition layer coating solution, the molar ratio of ruthenium, cobalt, titanium, acetylacetone and n-butanol is 8:3:3:2:(100-150).

10. The method for preparing a large-area titanium anode for chlor-alkali according to claim 5, characterized in that: In the active layer coating liquid of the surface layer, the molar ratio of ruthenium, iridium, tin, cerium, hydrochloric acid, n-butanol and pure water is 12:5:2:1:30:200:(200-300).

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