Anode for high-temperature continuous electrodeionization and preparation method thereof

Abstract

The invention discloses an anode for high-temperature continuous electrodeionization and a preparation method thereof.The anode for high-temperature continuous electrodeionization is composed of a titanium substrate, a middle transition layer and a surface iridium-rich active layer, and the preparation method comprises the steps that polypyrrole derived carbon coated iridium oxide nanoparticles, tantalum salt and transition metal salt are dissolved in a solvent, the mixture is evenly mixed and then coated on the surface of the titanium substrate, and the titanium substrate is obtained; drying, carrying out thermal oxidation, then repeatedly coating for multiple times, and carrying out thermal treatment to prepare a titanium anode containing an intermediate transition layer; and dissolving the polypyrrole derived carbon coated iridium oxide nanoparticles, tantalum salt and transition metal salt in a solvent, uniformly mixing, coating on the surface of the titanium anode containing the intermediate transition layer, drying, carrying out thermal oxidation, repeatedly coating for multiple times, and finally carrying out thermal treatment. Through amorphous carbon coating of iridium oxide nanoparticles, introduction of relatively cheap transition metal elements and combination of gradient composition design, the comprehensive cost of the iridium-tantalum coating is reduced, the service time of the iridium-tantalum coating is prolonged, and the obtained anode shows excellent voltage stability at 75 DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and relates to an anode for high-temperature continuous electro-deionization and a preparation method thereof. Background Art

[0002] Continuous electro-deionization is a new water treatment technology that fills mixed-bed resin between ion exchange membranes and realizes continuous desalination under the action of a direct current electric field. It combines the advantages of continuous desalination by electrodialysis and deep desalination by ion exchange, and has broad application prospects in aspects such as pure water preparation and wastewater treatment.

[0003] As one of the main components of continuous electro-deionization equipment, the material selection of the anode has an important impact on ensuring the current efficiency, energy consumption, and service life of the continuous electro-deionization device. During the operation of the continuous electro-deionization device, the anodic reaction generally releases chlorine (2Cl - –2e→Cl 2 ) and oxygen (H 2 O–2e→2H + +1 / 2O 2 ). Along with the progress of the anodic oxygen evolution reaction, the acidity of the anolyte gradually increases. Therefore, the anode for continuous electro-deionization needs to be able to withstand a complex chemical environment (strong oxidizing property, strong acidity).

[0004] The titanium-coated iridium tantalum electrode is currently an anode with relatively good comprehensive performance in conventional continuous electro-deionization equipment. However, with the diversification and complication of water treatment application scenarios, the service life of the titanium-coated iridium tantalum electrode will significantly decrease under high-temperature and high-current environments (the limiting current can be increased under high-temperature conditions, which is beneficial to preventing polarization precipitation and reducing energy consumption, but it will accelerate the failure of the electrode). In addition, with the continuous increase in the price of metal iridium, the cost issue has also become an obstacle to the industrial use of the titanium-coated iridium tantalum electrode.

[0005] In summary, it is of great practical significance to find an anode that reduces the usage of precious metal iridium and can be applied to higher-temperature scenarios for expanding the application scenarios of continuous electro-deionization technology. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide an anode for high-temperature continuous electro-deionization that can reduce the usage of precious metal iridium and a preparation method thereof.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A preparation method of an anode for high-temperature continuous electro-deionization, including a titanium substrate, an intermediate transition layer on the surface of the titanium substrate, and a surface iridium-rich active layer on the surface of the intermediate transition layer.

[0009] Further, the intermediate transition layer comprises polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum oxide, and transition metal oxide with a mass ratio of (100 - 140):(160 - 195):(20 - 40).

[0010] Further, the iridium-rich surface active layer comprises polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum oxide, and transition metal oxide with a mass ratio of (100 - 140):(60 - 90):(10 - 30).

[0011] A preparation method of an anode for high-temperature continuous electrodialysis desalination, comprising the following steps:

[0012] (1) Dissolve polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt, and transition metal salt in a solvent, mix evenly, coat on the surface of a titanium substrate, dry, and thermally oxidize; then repeat the steps of coating, drying, and thermal oxidation multiple times; finally, perform heat treatment to obtain a titanium anode containing an intermediate transition layer.

[0013] (2) Dissolve polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt, and transition metal salt in a solvent, ultrasonically stir and mix evenly at room temperature, coat on the surface of the titanium anode containing the intermediate transition layer, dry, and thermally oxidize; repeat the steps of coating, drying, and thermal oxidation multiple times; finally, perform heat treatment to obtain the anode for high-temperature continuous electrodialysis desalination.

[0014] Further, the polypyrrole-derived carbon-coated iridium oxide nanoparticles in step (1) and step (2) are prepared through the following process:

[0015] Add pyrrole to a solution containing ammonium persulfate and ammonium hexachloroiridate, stir, dry to obtain a polymerization product; pyrolyze the polymerization product to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0016] Further, the molar ratio of ammonium persulfate to pyrrole is 1:0.5 - 1.5, the molar ratio of ammonium hexachloroiridate to pyrrole is 1:10 - 50, the stirring time is 2 - 4 hours, the pyrolysis temperature is 300 - 700 °C, and the pyrolysis time is 0.5 - 1 hour.

[0017] Further, the tantalum salt in step (1) and step (2) is tantalum pentachloride;

[0018] The transition metal salt is at least one of cobalt hexahydrate nitrate, cobalt hexahydrate chloride, phosphomolybdic acid, and ammonium molybdate tetrahydrate;

[0019] The solvent is at least one of ethanol, isopropanol, n-butanol, ethylene glycol, and N,N-dimethylformamide.

[0020] Further, in step (1), the dosages of polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt and transition metal salt are calculated according to the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal oxide = (100 - 140):(160 - 195):(20 - 40).

[0021] Further, in step (2), the dosages of polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt and transition metal salt are calculated according to the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal oxide = (100 - 140):(60 - 90):(10 - 30).

[0022] Further, in step (1), the temperature of thermal oxidation is 400 - 500 °C and the time is 5 - 10 min; the temperature of heat treatment is 450 - 600 °C and the time is 0.5 - 2 h.

[0023] In step (2), the temperature of thermal oxidation is 300 - 600 °C and the time is 5 - 10 min; the temperature of heat treatment is 350 - 600 °C and the time is 0.5 - 2 h.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) Through the gradient composition design between the intermediate transition layer / surface iridium-rich active layer and the introduction of relatively inexpensive transition metal elements, the present invention can reduce the dosage of precious metal iridium and the cost.

[0026] (2) In the present invention, tantalum oxide with the function of protecting active components has a higher content in the intermediate transition layer, which can better protect the titanium substrate; iridium oxide with good electrochemical activity has a higher content in the surface active layer, which can effectively exert its electrochemical performance.

[0027] (3) In the present invention, the introduction of transition metal elements (molybdenum, cobalt) into the intermediate transition layer and the surface iridium-rich active layer is beneficial to the densification of the iridium tantalum oxide coating, thereby inhibiting the penetration of active oxygen and electrolyte, slowing down the passivation of the titanium substrate, and improving the service life of the electrode.

[0028] (4) The amorphous carbon based on polypyrrole carbonization in the present invention has certain conductivity. Its coating of iridium oxide nanoparticles can not only improve the effective charge conduction in the coating, promote the uniform distribution of iridium oxide nanoparticles in the active layer, ensure a large electrochemical active area, but also slow down the thermal stress between different material interfaces, avoid the shedding of active sites during high-temperature electrolysis, and inhibit the dissolution of active components, thereby contributing to the extension of the service time of the electrode under complex working conditions (such as high temperature). Description of the Drawings

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, obtaining other drawings based on these drawings still belongs to the scope of the present invention.

[0030] Figure 1 It is a process flow diagram of a preparation method of an anode for high-temperature continuous electrodeionization of the present invention;

[0031] Figure 2 It is a schematic diagram of the electrode structure of an anode for high-temperature continuous electrodeionization of the present invention;

[0032] In the figure, 1 is a titanium substrate, 2 is an intermediate transition layer, and 3 is a surface iridium-rich active layer. Specific embodiments

[0033] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present invention disclosed. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0034] See Figure 1 , a preparation method of an anode for high-temperature continuous electrodeionization of the present invention, performs surface pretreatment on a titanium substrate; prepares polypyrrole-derived carbon-coated iridium oxide nanoparticles by pyrolysis of a polypyrrole / iridium complex; formulates a precursor solution for the intermediate transition layer containing carbon-coated iridium oxide, tantalum salt, and transition metal salt, and coats it on the surface of the pretreated titanium substrate 2 to 10 times and performs sintering heat treatment to form an intermediate transition layer; formulates a precursor solution for the surface iridium-rich active layer containing carbon-coated iridium oxide, tantalum salt, and transition metal salt, and coats it on the surface containing the intermediate transition layer 3 to 6 times and performs sintering heat treatment to form a surface iridium-rich active layer, which specifically includes the following steps:

[0035] (1) Pretreatment of the titanium substrate:

[0036] Alkaline washing and degreasing, acid etching, water washing, and infrared drying are performed on the titanium substrate to remove the surface titanium oxide film layer and obtain a clean titanium substrate.

[0037] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0038] Ammonium persulfate and ammonium hexachloroiridate are respectively dissolved in deionized water. After mixing the two, pyrrole is added under vigorous stirring to obtain a mixture. The molar ratio of ammonium persulfate to pyrrole is 1:0.5 - 1.5, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:10 - 50. The above mixture is stirred in an ice-water bath for 2 - 4 hours, and the solvent is removed by freeze-drying to obtain a polymerization product. Then, the freeze-dried polymerization product is placed in a muffle furnace and pyrolyzed at 300 - 700 °C for 0.5 - 1 hour. After natural cooling to room temperature, soluble impurities are removed by washing with deionized water and high-speed centrifugation, and the product is vacuum-dried at 40 - 65 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0039] (3) Preparation of the intermediate transition layer:

[0040] The polypyrrole-derived carbon-coated iridium oxide nanoparticles obtained in step (2), tantalum salt, and transition metal salt are dissolved in a solvent, and ultrasonically stirred at room temperature to mix evenly to form a precursor solution of the intermediate transition layer. The precursor solution of the intermediate transition layer is coated on the surface of the titanium substrate pretreated in step (1), dried at 90 - 120 °C for 10 - 15 min, then oxidized in a muffle furnace at 400 - 500 °C for 5 - 10 min, and after natural cooling, coating and thermal oxidation are carried out again, with a total of 2 - 10 coatings; finally, heat treatment is carried out at 450 - 600 °C for 0.5 - 2 h, and after cooling, a titanium anode containing an intermediate transition layer is prepared.

[0041] Among them, the tantalum salt is tantalum pentachloride.

[0042] The transition metal salt is at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, phosphomolybdic acid, and ammonium molybdate tetrahydrate.

[0043] The solvent is at least one of ethanol, isopropanol, n-butanol, ethylene glycol, and N,N-dimethylformamide.

[0044] For the precursor solution of the intermediate transition layer, according to the different types and molecular weights of the metal salts therein, it can be added after calculation according to the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal oxide = (100 - 140):(160 - 195):(20 - 40).

[0045] The coating can be carried out by brushing, dipping, and spraying methods. Considering the utilization rate of precious metals and simplicity of operation, the brushing method is preferred.

[0046] (4) Preparation of the iridium-rich surface active layer:

[0047] Dissolve polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt, and transition metal salt in a solvent, and ultrasonically stir and mix them evenly at room temperature to form a precursor solution of the iridium-rich active layer on the surface. Coat the precursor solution of the iridium-rich active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), that is, dry the surface of the titanium anode containing the intermediate transition layer at 90-120 °C for 10-15 min, thermally oxidize it in a muffle furnace at 300-600 °C for 5-10 min, and after natural cooling, perform coating and thermal oxidation again. Coat a total of 3-6 times; finally, perform heat treatment and annealing at 350-600 °C for 0.5-2 h, and cool to obtain a titanium anode containing an intermediate transition layer and an iridium-rich active layer on the surface.

[0048] Among them, the tantalum salt is tantalum pentachloride.

[0049] The transition metal salt is at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, phosphomolybdic acid, and ammonium molybdate tetrahydrate.

[0050] The solvent is at least one of ethanol, isopropanol, n-butanol, ethylene glycol, and N,N-dimethylformamide.

[0051] For the precursor solution of the iridium-rich active layer on the surface, according to the different types and molecular weights of the metal salts therein, it can be added after calculation according to the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal oxide = (100-140):(60-90):(10-30).

[0052] The coating can be carried out by brushing, dipping, and spraying methods. Considering the utilization rate of precious metals and simple operation, the brushing method is preferred.

[0053] Preferably, in the above step (2), the molar ratio of ammonium persulfate to pyrrole is 1:0.8-1.2, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:20-30. The pyrolysis temperature of the freeze-dried polymerization product in a muffle furnace is 400-500 °C. When the pyrolysis temperature is too low, it is difficult to form a nanoscale IrO x phase with excellent catalytic activity; when the pyrolysis temperature is too high, it will cause the growth and aggregation of IrO x nanoparticles.

[0054] Preferably, in the above step (3), the coating times of the precursor solution of the intermediate transition layer are 4-8 times. If the coating times of the precursor solution of the intermediate transition layer are too few, it is difficult to form an effective gradient coating; if the coating times of the precursor solution of the intermediate transition layer are too many, it will affect the conductivity and catalytic activity of the coating.

[0055] Preferably, in the above step (4), the oxidation temperature in the muffle furnace is 400-500 °C. When the oxidation temperature is too low, the metal salt precursor cannot be completely oxidized and decomposed. When the oxidation temperature is too high, the oxidation of the titanium substrate will be caused.

[0056] Preferably, in the above step (4), the heat treatment annealing temperature is 400-500 °C. When the heat treatment annealing temperature is too low, it is not conducive to completely eliminating the internal stress in the composite coating. When the heat treatment annealing temperature is too high, the oxidation of the titanium substrate will be caused.

[0057] See Figure 2 , the anode for high-temperature continuous electrodeionization prepared by the method of the present invention as described above is composed of a titanium substrate 1, an intermediate transition layer 2 provided on the titanium substrate, and a surface iridium-rich active layer 3.

[0058] The intermediate transition layer described above includes polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum oxide, and transition metal oxide with a mass ratio of (100-140):(160-195):(20-40).

[0059] The surface iridium-rich active layer described above includes polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum oxide, and transition metal oxide with a mass ratio of (100-140):(60-90):(10-30).

[0060] The following are specific examples.

[0061] Example 1

[0062] A preparation method of an anode for high-temperature continuous electrodeionization includes the following steps:

[0063] (1) Pretreatment of the titanium substrate: The titanium substrate is degreased by alkaline washing in a 7% NaOH solution at 80 °C for 1 h; after rinsing with clean water, it is then etched in a 12% oxalic acid solution at a slightly boiling temperature for 2-4 h; after washing with deionized water, it is dried by infrared to obtain a clean titanium substrate.

[0064] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0065] Dissolve 9.120 g of ammonium persulfate and 0.588 g of ammonium hexachloroiridate in 28 mL and 80 mL of deionized water respectively. After mixing the two, add 2.681 g of pyrrole under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:1, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:30). Stir the resulting mixture in an ice-water bath for 4 hours. Subsequently, remove the solvent by freeze-drying to obtain a polypyrrole nanocomposite embedding iridium complex. Then place the obtained polypyrrole nanocomposite embedding iridium complex in a crucible and put it into a muffle furnace, heat it to 450 °C at a heating rate of 5 °C / min, and hold for 1 h. After natural cooling to room temperature, wash with deionized water and remove soluble impurities by high-speed centrifugation. The final product is dried in vacuo at 65 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0066] (3) Preparation of the intermediate transition layer:

[0067] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.180 g) obtained in step (2), tantalum pentachloride (0.478 g), and cobalt(II) nitrate hexahydrate (0.181 g) in a mixed solvent of ethanol-n-butyl alcohol with a volume ratio of 1:1 (10 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly coat the precursor solution of the intermediate transition layer on the surface of the titanium substrate pretreated in step (1), dry it at 110 °C for 10 min, then thermally oxidize and decompose it in a muffle furnace at 450 °C for 8 min, and perform coating again after natural cooling, for a total of 6 times; finally, heat-treat it at 450 °C for 1 h, and cool to obtain a titanium anode containing an intermediate transition layer.

[0068] In the transition layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 108:177:30.

[0069] (4) Preparation of the iridium-rich surface active layer:

[0070] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.180 g) obtained in step (2), tantalum pentachloride (0.205 g), and cobalt(II) nitrate hexahydrate (0.115 g) in a mixed solvent of ethanol-n-butyl alcohol with a volume ratio of 1:1 (6 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the iridium-rich surface active layer. Use a soft brush to evenly coat the precursor solution of the iridium-rich surface active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), dry it at 110 °C for 10 min, then thermally oxidize it in a muffle furnace at 450 °C for 8 min, and perform coating again after natural cooling, for a total of 4 times; finally, heat-treat and anneal it at 500 °C for 1 h, and cool to obtain a titanium anode containing an intermediate transition layer and an iridium-rich surface active layer, that is, the anode for high-temperature continuous electrodialysis desalination.

[0071] In the iridium-rich active layer of this embodiment, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 108:76:19.

[0072] Example 2

[0073] A preparation method of an anode for high-temperature continuous electrodialysis desalination, comprising the following steps:

[0074] (1) Pretreatment of the titanium substrate: The titanium substrate is degreased by alkaline washing in a 7% NaOH solution at 80 °C for 1 h; after rinsing with clean water, it is then etched in a 12% oxalic acid solution at slightly boiling temperature for 2 h; after washing with deionized water, it is dried by infrared to obtain a clean titanium substrate.

[0075] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0076] Dissolve 9.120 g of ammonium persulfate and 0.881 g of hexachloroiridic acid in 28 mL and 80 mL of deionized water respectively. After mixing the two, 1.341 g of pyrrole is added under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:0.5, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:10). The obtained mixture is stirred in an ice-water bath for 2 hours. Subsequently, the solvent is removed by freeze-drying to obtain a polypyrrole nanocomposite embedding iridium complex. Then the obtained polypyrrole nanocomposite embedding iridium complex is placed in a crucible and put into a muffle furnace, heated to 300 °C at a heating rate of 5 °C / min, and maintained for 1 h. After natural cooling to room temperature, soluble impurities are removed by washing with deionized water and high-speed centrifugation, and the final product is dried in vacuum at 40 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0077] (3) Preparation of the intermediate transition layer:

[0078] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.200 g), tantalum pentachloride (0.519 g) and cobalt chloride hexahydrate (0.145 g) obtained in step (2) in ethanol (10 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution of the intermediate transition layer. The precursor solution of the intermediate transition layer is evenly brushed on the surface of the titanium substrate pretreated in step (1) with a soft brush, dried at 90 °C for 10 min, then thermally oxidized in a muffle furnace at 400 °C for 10 min, and after natural cooling, coating is carried out again, for a total of 10 times; finally, heat treatment is carried out at 500 °C for 1 h, and after cooling, a titanium anode containing an intermediate transition layer is prepared.

[0079] In this embodiment of the transition layer, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 100:160:20.

[0080] (4) Preparation of the iridium-rich surface active layer:

[0081] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.200 g) obtained in step (2), tantalum pentachloride (0.195 g), and cobalt nitrate hexahydrate (0.073 g) in ethanol (6 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the iridium-rich surface active layer. Use a soft brush to evenly apply the precursor solution of the iridium-rich surface active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), dry it at 90 °C for 10 min, then thermally oxidize it in a muffle furnace at 300 °C for 10 min, and after natural cooling, coat it again. A total of 6 coatings are applied; finally, heat-treat and anneal it at 350 °C for 2 h, and after cooling, a titanium anode containing an intermediate transition layer and an iridium-rich surface active layer, that is, the anode for high-temperature continuous electrodialysis demineralization, is prepared.

[0082] In this embodiment of the iridium-rich surface active layer, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is approximately 100:60:10.

[0083] Example 3

[0084] A method for preparing an anode for high-temperature continuous electrodialysis demineralization, comprising the following steps:

[0085] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate is carried out by maintaining it in a 7% (mass fraction) NaOH solution at 80 °C for 1 h; after rinsing thoroughly with clean water, it is then etched in a 12% (mass concentration) oxalic acid solution at a gentle boil for 3 h; after washing with deionized water, it is dried by infrared to obtain a clean titanium substrate.

[0086] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0087] Dissolve 9.120 g of ammonium persulfate and 0.881 g of ammonium hexachloroiridate in 28 mL and 80 mL of deionized water respectively. After mixing the two, add 4.022 g of pyrrole under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:1.5, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:30). Stir the resulting mixture in an ice-water bath for 2 hours. Subsequently, remove the solvent by freeze-drying to obtain a polypyrrole nanocomposite embedding iridium complex. Then place the obtained polypyrrole nanocomposite embedding iridium complex in a crucible and put it into a muffle furnace, heat it to 500 °C at a heating rate of 5 °C / min, and hold for 1 h. After natural cooling to room temperature, wash with deionized water and remove soluble impurities by high-speed centrifugation. The final product is dried in vacuo at 65 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0088] (3) Preparation of the intermediate transition layer:

[0089] By mass, dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.280 g), tantalum pentachloride (0.584 g) and phosphomolybdic acid (0.063 g) obtained in step (2) in an ethanol-isopropanol mixed solvent (10 mL) with a volume ratio of 1:1, and ultrasonically stir and mix evenly at room temperature to form a precursor solution of the intermediate transition layer. Use a soft brush to evenly coat the precursor solution of the intermediate transition layer on the surface of the titanium substrate pretreated in step (1), dry at 100 °C for 12 min, then thermally oxidize at 500 °C in a muffle furnace for 5 min, and perform coating again after natural cooling, for a total of 2 coatings; finally, heat-treat at 600 °C for 0.5 h and cool to obtain a titanium anode containing an intermediate transition layer.

[0090] In the transition layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 140:180:30.

[0091] (4) Preparation of the iridium-rich surface active layer:

[0092] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.280 g), tantalum pentachloride (0.259 g) and phosphomolybdic acid (0.042 g) obtained in step (2) in an ethanol-isopropanol mixed solvent (6 mL) with a volume ratio of 1:1, and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the iridium-rich active layer on the surface. Use a soft brush to evenly coat the precursor solution of the iridium-rich active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), dry at 100 °C for 12 min, then thermally oxidize at 600 °C in a muffle furnace for 5 min, and after natural cooling, coat again. A total of 5 coatings are performed; finally, heat treatment and annealing are carried out at 600 °C for 0.5 h, and after cooling, a titanium anode containing an intermediate transition layer and an iridium-rich active layer on the surface is prepared, that is, the anode for high-temperature continuous electrodialysis desalination.

[0093] In the iridium-rich active layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 140:80:20.

[0094] Example 4

[0095] A preparation method of an anode for high-temperature continuous electrodialysis desalination, comprising the following steps:

[0096] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate is carried out by maintaining it in a 7% NaOH solution at 80 °C for 1 h; after rinsing clean with clear water, it is then placed in a 12% oxalic acid solution at a slightly boiling temperature for etching for 4 h; after washing with deionized water, it is dried by infrared to obtain a clean titanium substrate.

[0097] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0098] Dissolve 9.120 g of ammonium persulfate and 0.529 g of hexachloroiridic acid in 28 mL and 80 mL of deionized water respectively. After mixing the two, 4.022 g of pyrrole is added under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:1.5, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:50). The resulting mixture is stirred in an ice-water bath for 2 hours. Subsequently, the solvent is removed by freeze-drying to obtain a polypyrrole nanocomposite embedding an iridium complex. Then, the obtained polypyrrole nanocomposite embedding the iridium complex is placed in a crucible and put into a muffle furnace, heated to 700 °C at a heating rate of 5 °C / min, and maintained for 0.5 h. After natural cooling to room temperature, soluble impurities are removed by washing with deionized water and high-speed centrifugation, and the final product is dried in vacuo at 50 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0099] (3) Preparation of the intermediate transition layer:

[0100] By mass parts, dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.240 g), tantalum pentachloride (0.632 g), and cobalt nitrate hexahydrate (0.290 g) obtained in step (2) in a mixed solvent (10 mL) of ethanol and N,N-dimethylformamide with a volume ratio of 10:1. Stir and mix evenly by ultrasonic wave at room temperature to form the precursor solution of the intermediate transition layer. Use a soft brush to evenly coat the precursor solution of the intermediate transition layer on the surface of the pretreated titanium substrate in step (1), dry it at 120 °C for 15 min, then thermally oxidize it in a muffle furnace at 420 °C for 8 min, and naturally cool it. Then coat it again, for a total of 5 coatings; finally, heat-treat it at 450 °C for 2 h, and after cooling, a titanium anode with an intermediate transition layer is prepared.

[0101] In the transition layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 120:195:40.

[0102] (4) Preparation of the iridium-rich surface active layer:

[0103] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.240 g), tantalum pentachloride (0.292 g), and cobalt nitrate hexahydrate (0.217 g) obtained in step (2) in a mixed solvent (6 mL) of ethanol and ethylene glycol with a volume ratio of 10:1. Stir and mix evenly by ultrasonic wave at room temperature to form the precursor solution of the iridium-rich surface active layer. Use a soft brush to evenly coat the precursor solution of the iridium-rich surface active layer on the surface of the titanium anode with an intermediate transition layer obtained in step (3), dry it at 120 °C for 15 min, then thermally oxidize it in a muffle furnace at 500 °C for 7 min, and naturally cool it. Then coat it again, for a total of 3 coatings; finally, heat-treat and anneal it at 600 °C for 0.5 h, and after cooling, a titanium anode with an intermediate transition layer and an iridium-rich surface active layer is prepared, that is, the anode for high-temperature continuous electrodialysis demineralization.

[0104] In the iridium-rich surface active layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 120:90:30.

[0105] Example 5

[0106] A preparation method of an anode for high-temperature continuous electrodialysis demineralization, comprising the following steps:

[0107] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate in a 7% NaOH solution at 80 °C for 1 h; after rinsing thoroughly with clean water, then put it into a 12% oxalic acid solution at a slightly boiling state for etching for 4 h; after washing with deionized water, obtain a clean titanium substrate through infrared drying.

[0108] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0109] Dissolve 9.120 g of ammonium persulfate and 0.705 g of hexachloroiridic acid in 28 mL and 80 mL of deionized water respectively. After mixing the two, add 2.145 g of pyrrole under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:0.8, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:20). Stir the resulting mixture in an ice-water bath for 2 hours. Subsequently, remove the solvent by freeze-drying to obtain a polypyrrole nanocomposite embedded with an iridium complex. Then, place the obtained polypyrrole nanocomposite embedded with an iridium complex in a crucible and put it into a muffle furnace, heat it to 400 °C at a heating rate of 5 °C / min, and hold for 0.5 h. After natural cooling to room temperature, wash with deionized water and remove soluble impurities by high-speed centrifugation. The final product is dried in vacuo at 50 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0110] (3) Preparation of the intermediate transition layer:

[0111] By mass, dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.240 g), tantalum pentachloride (0.632 g), and cobalt nitrate hexahydrate (0.290 g) obtained in step (2) in a mixed solvent (10 mL) of ethanol and N,N-dimethylformamide with a volume ratio of 10:1, and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly coat the precursor solution of the intermediate transition layer on the surface of the titanium substrate pretreated in step (1), dry it at 120 °C for 15 min, then thermally oxidize it in a muffle furnace at 420 °C for 8 min, and perform coating again after natural cooling, for a total of 4 times; finally, heat-treat it at 450 °C for 2 h, and cool to obtain a titanium anode containing an intermediate transition layer.

[0112] In the transition layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 120:195:40.

[0113] (4) Preparation of the iridium-rich surface active layer:

[0114] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.240 g) obtained in step (2), tantalum pentachloride (0.292 g), and cobalt nitrate hexahydrate (0.217 g) in a mixed solvent (6 mL) of ethanol and ethylene glycol with a volume ratio of 10:1. Stir and mix evenly by ultrasonic wave at room temperature to form a precursor solution of the iridium-rich active layer on the surface. Use a soft brush to evenly coat the precursor solution of the iridium-rich active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), dry it at 120 °C for 15 min, then thermally oxidize it in a muffle furnace at 400 °C for 7 min. After natural cooling, coat it again, and coat it 3 times in total; finally, perform heat treatment and annealing at 400 °C for 0.5 h, and cool it to obtain a titanium anode containing an intermediate transition layer and an iridium-rich active layer on the surface, that is, the anode for high-temperature continuous electrodialysis desalination.

[0115] In the iridium-rich active layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 120:90:30.

[0116] Example 6

[0117] A preparation method of an anode for high-temperature continuous electrodialysis desalination, comprising the following steps:

[0118] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate by maintaining it in a 7% NaOH solution at 80 °C for 1 h; after rinsing clean with clear water, then put it into a 12% oxalic acid solution at a slightly boiling state for etching for 4 h; after washing with deionized water, obtain a clean titanium substrate through infrared drying.

[0119] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0120] Dissolve 9.120 g of ammonium persulfate and 0.846 g of hexachloroiridic acid in 28 mL and 80 mL of deionized water respectively. After mixing the two, add 3.217 g of pyrrole under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:1.2, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:25). Stir the obtained mixture in an ice-water bath for 2 hours. Subsequently, remove the solvent by freeze-drying to obtain a polypyrrole nanocomposite embedding an iridium complex. Then place the obtained polypyrrole nanocomposite embedding an iridium complex in a crucible and put it into a muffle furnace, heat it to 700 °C at a heating rate of 5 °C / min, and hold it for 0.5 h. After natural cooling to room temperature, wash with deionized water and remove soluble impurities by high-speed centrifugation, and finally dry the product in vacuum at 50 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0121] (3) Preparation of the intermediate transition layer:

[0122] By mass fraction, dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.240 g) obtained in step (2), tantalum pentachloride (0.632 g), and cobalt nitrate hexahydrate (0.290 g) in a mixed solvent (10 mL) of ethanol and N,N-dimethylformamide with a volume ratio of 10:1, and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly coat the precursor solution of the intermediate transition layer on the surface of the pretreated titanium substrate in step (1), dry it at 120 °C for 15 min, then thermally oxidize it in a muffle furnace at 420 °C for 8 min, and after natural cooling, coat it again, for a total of 8 times; finally, heat-treat it at 450 °C for 2 h, and after cooling, a titanium anode containing an intermediate transition layer is prepared.

[0123] In the transition layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 120:195:40.

[0124] (4) Preparation of the iridium-rich surface active layer:

[0125] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.240 g) obtained in step (2), tantalum pentachloride (0.292 g), and cobalt nitrate hexahydrate (0.217 g) in a mixed solvent (6 mL) of ethanol and ethylene glycol with a volume ratio of 10:1, and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the iridium-rich surface active layer. Use a soft brush to evenly coat the precursor solution of the iridium-rich surface active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), dry it at 120 °C for 15 min, then thermally oxidize it in a muffle furnace at 550 °C for 7 min, and after natural cooling, coat it again, for a total of 3 times; finally, heat-treat and anneal it at 550 °C for 0.5 h, and after cooling, a titanium anode containing an intermediate transition layer and an iridium-rich surface active layer is prepared, that is, the anode for high-temperature continuous electrodialysis demineralization.

[0126] In the iridium-rich surface active layer of this example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 120:90:30.

[0127] Comparative Example 1 (without doping transition metals)

[0128] A preparation method of an anode for high-temperature continuous electrodialysis demineralization, comprising the following steps:

[0129] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate by maintaining it in a 7% NaOH solution at 80 °C for 1 h; after rinsing thoroughly with clean water, then put it into a slightly boiling 12% oxalic acid solution for etching for 2 - 4 h; after washing with deionized water, infrared drying is carried out to obtain a clean titanium substrate.

[0130] (2) Preparation of polypyrrole-derived carbon-coated iridium oxide nanoparticles:

[0131] Dissolve 9.120 g of ammonium persulfate and 0.600 g of hexachloroiridic acid in 28 mL and 80 mL of deionized water respectively. After mixing the two, add 2.760 g of pyrrole under vigorous stirring (the molar ratio of ammonium persulfate to pyrrole is 1:1, and the molar ratio of ammonium hexachloroiridate to pyrrole is 1:30). The above mixture is stirred in an ice-water bath for 4 hours. Subsequently, the solvent is removed by freeze-drying to obtain a polypyrrole nanocomposite embedded with iridium complex. Then, the obtained polypyrrole nanocomposite embedded with iridium complex is placed in a crucible and put into a muffle furnace, heated to 450 °C at a heating rate of 5 °C / min, and held for 1 hour. After natural cooling to room temperature, soluble impurities are removed by washing with deionized water and high-speed centrifugation, and the final product is dried in vacuum at 65 °C to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

[0132] (3) Preparation of the intermediate transition layer:

[0133] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.180 g) obtained in step (2) and tantalum pentachloride (0.478 g) in a mixed solvent of ethanol-n-butyl alcohol with a volume ratio of 1:1 (10 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly coat the precursor solution of the intermediate transition layer on the surface of the titanium substrate pretreated in step (1), dry it at 110 °C for 10 min, then thermally oxidize it at 450 °C in a muffle furnace for 8 min, and perform coating again after natural cooling, for a total of 6 times; finally, heat-treat it at 450 °C for 1 h, and cool to obtain a titanium anode containing an intermediate transition layer.

[0134] In the transition layer of this comparative example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 108:177:0.

[0135] (4) Preparation of the iridium-rich surface active layer:

[0136] Dissolve the polypyrrole-derived carbon-coated iridium oxide nanoparticles (0.180 g) obtained in step (2) and tantalum pentachloride (0.205 g) in a mixed solvent of ethanol-n-butyl alcohol with a volume ratio of 1:1 (6 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the iridium-rich active layer on the surface. Use a soft brush to evenly apply the precursor solution for the iridium-rich active layer on the surface of the titanium anode containing the intermediate transition layer obtained in step (3), dry at 110 °C for 10 min, then thermally oxidize at 450 °C in a muffle furnace for 8 min, and after natural cooling, apply the coating again, with a total of 4 coatings; finally, perform heat treatment and annealing at 500 °C for 1 h, and after cooling, a titanium anode containing an intermediate transition layer and an iridium-rich active layer on the surface is prepared.

[0137] In the iridium-rich active layer on the surface of this comparative example, the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal cobalt oxide is 108:76:0.

[0138] Comparative Example 2 (using hexachloroiridic acid instead of polypyrrole-derived carbon-coated iridium oxide nanoparticles)

[0139] A preparation method for an anode used in high-temperature continuous electro-deionization, comprising the following steps:

[0140] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate is carried out by maintaining it in a 7% NaOH solution at 80 °C for 1 h; after rinsing thoroughly with clean water, it is then placed in a slightly boiling 12% oxalic acid solution for etching for 2 - 4 h; after washing with deionized water, it is dried by infrared to obtain a clean titanium substrate.

[0141] (2) Preparation of the intermediate transition layer:

[0142] Dissolve chloroiridic acid (0.327 g), tantalum pentachloride (0.48 g), and cobalt nitrate hexahydrate (0.18 g) in a mixed solvent of ethanol-n-butyl alcohol with a volume ratio of 1:1 (10 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly apply the precursor solution for the intermediate transition layer on the surface of the titanium substrate pretreated in step (1), dry at 110 °C for 10 min, then thermally oxidize at 450 °C in a muffle furnace for 8 min, and after natural cooling, apply the coating again, with a total of 6 coatings; finally, perform heat treatment at 450 °C for 1 h, and after cooling, a titanium anode containing an intermediate transition layer is prepared.

[0143] In the transition layer of this comparative example, the mass ratio of iridium oxide: tantalum oxide: transition metal cobalt oxide is 108:177:30.

[0144] (3) Preparation of the iridium-rich active layer on the surface:

[0145] Dissolve iridium(IV) chloride hydrate (0.327 g), tantalum pentachloride (0.205 g), and cobalt(II) nitrate hexahydrate (0.115 g) in a mixed solvent of ethanol - n - butanol with a volume ratio of 1:1 (6 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the iridium - rich active layer on the surface. Use a soft brush to evenly apply the precursor solution for the iridium - rich active layer on the surface of the titanium anode with the intermediate transition layer obtained in step (3), dry it at 110 °C for 10 min, then thermally oxidize it in a muffle furnace at 450 °C for 8 min, naturally cool it, and then apply the coating again. The coating is applied a total of 4 times; finally, heat - treat and anneal it at 500 °C for 1 h, and after cooling, a titanium anode with an intermediate transition layer and an iridium - rich active layer on the surface is prepared.

[0146] In the iridium - rich active layer on the surface of this comparative example, the mass ratio of iridium oxide: tantalum oxide: transition metal cobalt oxide is 108:76:19.

[0147] Comparative Example 3 (without doping transition metals, using hexachloroiridic acid to replace polypyrrole - derived carbon - coated iridium oxide nanoparticles)

[0148] A preparation method for an anode used in high - temperature continuous electrodialysis demineralization includes the following steps:

[0149] (1) Pretreatment of the titanium substrate: Alkaline degreasing of the titanium substrate is carried out by maintaining it in a 7% NaOH solution at 80 °C for 1 h; after rinsing it thoroughly with clean water, then put it into a slightly boiling 12% oxalic acid solution for etching for 2 - 4 h; after washing it with deionized water, obtain a clean titanium substrate through infrared drying.

[0150] (2) Preparation of the intermediate transition layer:

[0151] Dissolve iridium(IV) chloride hydrate (0.327 g) and tantalum pentachloride (0.478 g) in a mixed solvent of ethanol - n - butanol with a volume ratio of 1:1 (10 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly apply the precursor solution for the intermediate transition layer on the surface of the titanium substrate pretreated in step (1), dry it at 110 °C for 10 min, then thermally oxidize it in a muffle furnace at 450 °C for 8 min, naturally cool it, and then apply the coating again. The coating is applied a total of 6 times; finally, heat - treat it at 450 °C for 1 h, and after cooling, a titanium anode with an intermediate transition layer is prepared.

[0152] In the transition layer of this comparative example, the mass ratio of iridium oxide: tantalum oxide: transition metal cobalt oxide is 108:177:0.

[0153] (3) Preparation of the iridium - rich active layer on the surface:

[0154] Dissolve iridium(IV) chloride hydrate (0.327 g) and tantalum pentachloride (0.205 g) in a mixed solvent of ethanol - n - butanol with a volume ratio of 1:1 (6 mL), and ultrasonically stir and mix evenly at room temperature to form a precursor solution for the intermediate transition layer. Use a soft brush to evenly apply the precursor solution of the intermediate transition layer on the surface of the titanium anode with the intermediate transition layer obtained in step (3), dry it at 110 °C for 10 min, then thermally oxidize it in a muffle furnace at 450 °C for 8 min, and after natural cooling, apply the coating again. The coating is applied a total of 4 times; finally, heat - treat and anneal it at 500 °C for 1 h, and after cooling, a titanium anode containing an intermediate transition layer and a surface iridium - rich active layer is prepared.

[0155] In the iridium - rich active layer on the surface of this comparative example, the mass ratio of iridium oxide: tantalum oxide: transition - metal cobalt oxide is 108:76:0.

[0156] Determination of enhanced electrolysis life: Process the anode in the embodiment into a specimen with an electrode area of 5 cm 2 , use a pure titanium sheet as the cathode, with a current density of 1 A / cm 2 , control the temperature at 75 °C, and in a 1.0 mol / L H 2 SO 4 electrolytic solution, the time experienced when the electrolysis voltage increases by 10 V relative to the initial value of electrolysis is the enhanced life of the electrode. The obtained enhanced electrolysis life is shown in Table 1.

[0157] Table 1

[0158] Group Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Enhanced electrolysis life (h) 2503 2176 2214 1926

[0159] Compared with Comparative Example 3, the enhanced electrolysis life of Comparative Example 1 using polypyrrole - derived carbon - coated iridium oxide nanoparticles as the iridium source increased by 12.98%, the enhanced electrolysis life of Comparative Example 2 with the introduction of transition metals increased by 14.95%, and the enhanced electrolysis life of Example 1 using both carbon - coated iridium oxide nanoparticles as the iridium source and the introduction of transition metals increased by 29.96%. This shows that using carbon - coated iridium oxide nanoparticles as the iridium source and transition - metal doping can effectively improve the high - temperature service time of iridium - coated tantalum titanium anodes. Through the synergistic effect between using carbon - coated iridium oxide nanoparticles as the iridium source and transition - metal doping, the most significant effect of enhancing the electrolysis life is shown.

[0160] The present invention uses amorphous carbon coating of iridium oxide nanoparticles, introduces relatively inexpensive transition - metal elements, and combines gradient composition design, effectively reducing the comprehensive cost of the iridium - tantalum coating, significantly improving the service time of the iridium - coated tantalum titanium anode at 75 °C. The anode shows excellent voltage stability characteristics at 75 °C, solving the problems of high cost and significantly shortened service life in high - temperature scenarios of traditional iridium - coated tantalum titanium anodes.

[0161] In the present invention, tantalum oxide that plays a role in protecting the active component has a higher content in the intermediate transition layer, and iridium oxide with good electrochemical activity has a higher content in the surface active layer. A gradient composition design is adopted between the intermediate transition layer and the iridium-rich surface active layer.

[0162] In the present invention, iridium oxide nanoparticles coated with amorphous carbon based on polypyrrole carbonization are used in the preparation of the intermediate transition layer and the iridium-rich surface active layer; meanwhile, relatively inexpensive transition metal elements are added. The transition metal elements include, but are not limited to, cobalt and molybdenum.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A method for preparing an anode for high-temperature continuous electro-desalination, characterized in that: The invention comprises a titanium substrate, an intermediate transition layer on the surface of the titanium substrate and an iridium-rich active layer on the surface of the intermediate transition layer.

2. The method for preparing anode for high temperature continuous electro-desalination according to claim 1, characterized in that: The intermediate transition layer comprises polypyrrole derived carbon coated iridium oxide nanoparticles, tantalum oxide and transition metal oxide in a mass ratio of (100-140): (160-195): (20-40).

3. The method for preparing an anode for high temperature continuous electro-desalination according to claim 1, characterized in that: The surface iridium-rich active layer comprises polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum oxide and transition metal oxide in a mass ratio of (100-140): (60-90): (10-30).

4. A method for preparing an anode for high-temperature continuous electro-desalination, characterized in that: The following steps are involved: (1) dissolving polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt and transition metal salt in a solvent, coating them on the surface of a titanium substrate after mixing them evenly, drying and thermally oxidizing them; then repeating the coating, drying and thermally oxidizing steps for multiple times; and finally heat treating to obtain a titanium anode containing an intermediate transition layer; (2) dissolving polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salts and transition metal salts in a solvent, mixing them evenly under ultrasonic stirring at room temperature, and then coating them on the surface of a titanium anode containing an intermediate transition layer, drying, and thermally oxidizing them; and repeating the coating, drying, and thermally oxidizing steps for multiple times; and finally heat treating to obtain an anode for high-temperature continuous electro-desalination.

5. The method for preparing the anode for high temperature continuous electro-desalination according to claim 4, characterized in that: The polypyrrole-derived carbon-coated iridium oxide nanoparticles in step (1) and step (2) are prepared by the following process: Adding pyrrole to a solution containing ammonium persulfate and ammonium hexachloroiridate, stirring, and drying to obtain a polymerized product; The polymerization product is pyrolyzed to obtain polypyrrole-derived carbon-coated iridium oxide nanoparticles.

6. The method for preparing the anode for high temperature continuous electro-desalination according to claim 5, characterized in that: The molar ratio of ammonium persulfate to pyrrole is 1:0.5-1.5, the molar ratio of ammonium hexachloroiridate to pyrrole is 1:10-50, the stirring time is 2-4 hours, the pyrolysis temperature is 300-700°C, and the pyrolysis time is 0.5-1 hour.

7. The method for preparing anode for high temperature continuous electro-desalination according to claim 4, characterized in that: The tantalum salt in step (1) and step (2) is tantalum pentachloride; The transition metal salt is at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, phosphomolybdic acid and ammonium molybdate tetrahydrate; The solvent is at least one of ethanol, isopropanol, n-butanol, ethylene glycol and N,N-dimethylformamide.

8. The method for preparing anode for high temperature continuous electro-desalination according to claim 4, characterized in that: In step (1), the amounts of polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt and transition metal salt are calculated according to the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal oxide = (100-140): (160-195): (20-40).

9. The method for preparing anode for high temperature continuous electro-desalination according to claim 4, characterized in that: In step (2), the amounts of polypyrrole-derived carbon-coated iridium oxide nanoparticles, tantalum salt and transition metal salt are calculated according to the mass ratio of polypyrrole-derived carbon-coated iridium oxide nanoparticles: tantalum oxide: transition metal oxide = (100-140): (60-90): (10-30).

10. The method for preparing an anode for high temperature continuous electro-desalination according to claim 4, characterized in that: In step (1), the temperature of thermal oxidation is 400-500°C, and the time is 5-10 min; the temperature of heat treatment is 450-600°C, and the time is 0.5-2 h; In step (2), the temperature of thermal oxidation is 300-600° C., and the time is 5-10 min; the temperature of heat treatment is 350-600° C., and the time is 0.5-2 h.

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