A high-stability modified manganese dioxide catalyst anode and a preparation method thereof

Abstract

The application discloses a high-stability modified manganese dioxide catalyst anode and a preparation method thereof. The anode comprises, from bottom to top, a conductive base, a corrosion-resistant conductive layer, a modified manganese dioxide catalyst layer and a silica gel coating layer; the modified manganese dioxide catalyst layer comprises fluorine and metal co-doped nanometer manganese dioxide and carbon materials, the metal is at least one of niobium, bismuth, tin, cerium, lanthanum, cobalt, silver, nickel, platinum, tantalum, ruthenium, iridium and antimony, and the carbon materials comprise graphene and / or carbon nanotubes; the anode has the characteristics of good stability, high current efficiency and long service life, and the preparation method is simple in operation, mild in reaction condition and low in cost, and is favorable for large-scale production.

Description

Technical Field

[0001] This invention relates to a manganese dioxide catalyst anode, specifically a highly stable modified manganese dioxide catalyst anode, and also to a method for preparing the highly stable modified manganese dioxide catalyst anode, belonging to the field of hydrometallurgy and electrode preparation technology. Background Technology

[0002] In the hydrometallurgical processes of copper, zinc, manganese, nickel, cobalt, chromium, and other metals, electrodeposition is the main energy-consuming step. The anode is one of the key components in the electrodeposition process, and the choice of its material directly affects not only energy consumption and electrode life but also the quality of the cathode product. Generally, electrode materials must meet the following requirements: good electrical conductivity, strong corrosion resistance, good mechanical strength and processing performance, and good electrocatalytic effect on the electrode reaction.

[0003] Currently, anodes used in the electrolysis industry include platinum (platinum-plated titanium, sintered platinum) electrodes, lead dioxide electrodes, titanium-based noble metal oxide coated electrodes, magnetic iron oxide electrodes, graphite electrodes, and lead and lead-based alloy electrodes. However, among these electrodes, platinum and its alloys are expensive and consume significantly at high current densities; lead oxide electrodes are difficult to manufacture and have poor corrosion resistance; titanium-based noble metal coated electrodes have expensive coatings and do not fundamentally solve the passivation problem of the titanium substrate, resulting in a short service life; magnetic iron oxide electrodes have poor mechanical properties and are difficult to scale up; and graphite electrodes have high consumption and high overpotential. Therefore, none of these have been widely used. Lead and lead-based alloy anodes have advantages such as easy molding and stability in sulfuric acid media, and are currently widely used in non-ferrous metal industrial production. However, lead and lead-based alloy anodes have disadvantages such as high oxygen evolution potential and non-dense surface passivation film, which lead to high electrolytic cell voltage (e.g., 3.2-3.8V for zinc electrowinning), low current efficiency (75-90%) in the electrowinning process, high energy consumption (e.g., 3200-3800 kW / ton for zinc electrowinning), short anode life (6-12 months), and corrosion products of lead anodes easily entering cathode products, affecting the quality of cathode products.

[0004] Chinese patent (publication number CN104492426A) discloses a modified manganese dioxide catalyst electrode. Specifically, it is prepared by sequentially fabricating a corrosion-resistant conductive layer composed of a metal oxide having both rutile crystal structure and oxygen-deficient structure, and a modified manganese dioxide catalyst layer composed of nano-manganese dioxide simultaneously doped with fluorine ions and metal ions, on a conductive substrate. The modified manganese dioxide catalyst and electrode feature high current efficiency and long service life, specifically, at 2 A / cm². 2The modified manganese dioxide catalyst electrode exhibits a lifespan exceeding 400 hours at a cutoff voltage of 7V under high current density, demonstrating excellent electrochemical activity and an ultra-long service life. However, some technical problems still exist in actual industrial applications: 1) During electrolysis, the electrode surface is easily adhered to by anode mud, reducing its catalytic activity and current efficiency; 2) The modified manganese dioxide catalyst layer of the electrode is susceptible to electrolyte corrosion, leading to the loss of its active components; 3) The electrode has poor oxidation resistance and is easily corroded by oxygen in the air and electrolyte; 4) The modified manganese dioxide catalyst layer of the electrode suffers from poor conductivity and poor catalyst bonding stability. These technical problems result in low current efficiency and a shorter service life for the modified manganese dioxide catalyst electrode. Summary of the Invention

[0005] In view of the shortcomings of existing modified manganese dioxide catalyst anodes in the electrolysis industry, such as low current efficiency and short service life, the first objective of this invention is to provide a modified manganese dioxide catalyst electrode with good stability, high current efficiency and long service life.

[0006] The second objective of this invention is to provide a method for preparing highly stable modified manganese dioxide catalyst anodes that is simple to operate, has mild reaction conditions, and is low in cost.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a highly stable modified manganese dioxide catalyst anode, comprising, from bottom to top, a conductive substrate, a corrosion-resistant conductive layer, a modified manganese dioxide catalyst layer, and a silica gel coating; the modified manganese dioxide catalyst layer comprises fluorine and metal co-doped nano-manganese dioxide and carbon materials, wherein the metal is at least one selected from niobium, bismuth, tin, cerium, lanthanum, cobalt, silver, nickel, platinum, tantalum, ruthenium, iridium, and antimony; the carbon materials comprise graphene and / or carbon nanotubes.

[0008] This invention addresses the relatively poor stability and low current efficiency of existing modified manganese dioxide catalyst anodes. The key improvement lies in incorporating carbon materials such as graphene and carbon nanotubes into the modified manganese dioxide catalyst layer, while simultaneously coating the surface with a silicone coating. The synergistic effect of these two elements allows the modified manganese dioxide catalyst anode to maintain high current efficiency over a long period and significantly improves its stability. The addition of graphene or carbon nanotubes to the modified manganese dioxide catalyst layer, both possessing excellent electrical conductivity, is crucial. Graphene nanoparticles primarily fill the spaces between fluorine and metal-coated manganese dioxide nanoparticles, while linear carbon nanotubes intersperse within them. Both enhance the conductivity of the catalyst layer, thereby improving catalytic efficiency. In particular, the naturally coiled linear structure of carbon nanotubes, when uniformly mixed within the fluorine and metal-coated manganese dioxide nanoparticles, provides a binding effect, increasing the bonding strength between the fluorine and metal-coated manganese dioxide nanoparticles and thus improving their physical stability. The technical solution of this invention involves coating the surface of a modified manganese dioxide catalyst layer with a silica gel coating. This silica gel coating physically modifies the modified manganese dioxide catalyst layer. The surface of the silica gel coating is relatively smooth, which can effectively prevent the deposition of anode mud on the electrode surface and thus reduce the effective area of ​​the electrode, thereby improving current efficiency. At the same time, the silica gel coating can effectively protect the modified manganese dioxide catalyst layer, effectively reducing the oxidation of the modified manganese dioxide catalyst layer by infiltrated oxygen and the corrosion by infiltrated electrolyte, thereby greatly improving the service life of the modified manganese dioxide catalyst anode.

[0009] As a preferred embodiment, the carbon material in the modified manganese dioxide catalyst layer is 0.01-10% of the mass of fluorine and metal co-doped nano-manganese dioxide; more preferably, it is 1-8%. If the doping ratio of carbon material is too low, the purpose of improving catalytic efficiency and enhancing physical stability will not be achieved, while if the doping ratio is too high, the catalytic efficiency of the catalyst will be affected.

[0010] As a preferred embodiment, the carbon material is composed of graphene and carbon nanotubes. The carbon material may also include highly conductive materials such as carbon black, but is most preferably composed of graphene and carbon nanotubes. Graphene is a nanoscale powder. The technical solution of this invention simultaneously includes graphene and carbon nanotubes in the modified manganese dioxide catalyst layer. Their roles and principles differ. Graphene mainly fills the spaces between fluorine and metal-doped nano-manganese dioxide particles, while linear carbon nanotubes are interspersed among them. Graphene possesses ultra-high conductivity, while carbon nanotubes also exhibit good conductivity. The combination of these two forms a good conductive network to improve the conductivity of the catalytic material, thereby increasing current efficiency. Furthermore, the introduction of an appropriate proportion of carbon nanotubes, utilizing their naturally coiled linear structure and uniformly mixed within the fluorine and metal-doped nano-manganese dioxide particles, can act as an interlocking agent, improving the bonding strength between the fluorine and metal-doped nano-manganese dioxide particles and thus enhancing their physical stability.

[0011] As a preferred embodiment, the carbon material is composed of graphene and carbon nanotubes in a mass percentage ratio of 10-90%:10-90%; more preferably, it is 20-50%:50-80%. Graphene mainly imparts good electrical conductivity to the modified manganese dioxide catalyst layer, while carbon nanotubes mainly impart good physical stability to the modified manganese dioxide catalyst layer. The two are best used in an appropriate ratio to achieve the best modification effect.

[0012] As a preferred embodiment, the surface thickness of the silicone coating is 0.01–2 mm; more preferably 0.5–1.5 mm. The silicone coating can penetrate the entire corrosion-resistant conductive layer and catalytic coating. If the silicone coating is too thin, it is difficult to achieve the purpose of modification, while if the silicone coating is too thick, it will affect the catalytic activity of fluorine and metal co-doped nano-manganese dioxide.

[0013] As a preferred embodiment, the molar ratio of manganese:metal:fluorine in the fluorine-metal co-doped nano-manganese dioxide is 20:0.1–20:1–35; most preferably, it is 20:1–10:5–20. Within this preferred ratio range, the modified manganese dioxide catalyst exhibits optimal catalytic activity.

[0014] As a preferred embodiment, the corrosion-resistant conductive layer is composed of titanium suboxide and / or lead dioxide. Preferably, both the titanium suboxide and lead dioxide possess rutile crystal structures and oxygen-deficient structures. More preferably, the total content of Ti4O7 and Ti5O9 in the titanium suboxide is not less than 60%, and the Ti4O7 content is not less than 40%. Titanium suboxide can be commercially available (e.g., Dongguan Kaiman Optoelectronic Technology Co., Ltd., Shanghai Jinglian New Materials Co., Ltd.), or it can be prepared by conventional methods, such as reacting TiO2 with metallic titanium under an inert atmosphere.

[0015] As a preferred option, the thickness of the corrosion-resistant conductive layer in the highly stable modified manganese dioxide catalyst electrode is 0.01–1 mm.

[0016] As a preferred embodiment, the amount of modified manganese dioxide catalyst layer on the conductive substrate surface in the modified manganese dioxide catalyst electrode is 20 to 1000 g / m².

[0017] As a preferred option, the conductive substrate in the highly stable modified manganese dioxide catalyst electrode is valve-type metallic titanium or titanium alloy.

[0018] This invention also provides a method for preparing a highly stable modified manganese dioxide catalyst anode, the method comprising the following steps:

[0019] 1) Perform surface cleaning pretreatment on the conductive substrate;

[0020] 2) A corrosion-resistant conductive layer is generated on the surface of the conductive substrate after surface cleaning and pretreatment;

[0021] 3) Add carbon material, fluorine source and metal salt solution to manganese salt solution and mix evenly to obtain mixed slurry. Coat the mixed slurry on the surface of the corrosion-resistant conductive layer, dry, calcine, and repeat the coating, drying and calcine process several times to generate a modified manganese dioxide catalyst layer on the surface of the corrosion-resistant conductive layer.

[0022] 4) Coat the surface of the modified manganese dioxide catalyst layer with silica sol, dry, calcine, and repeat the coating, drying and calcining process several times to generate a silica gel coating on the surface of the modified manganese dioxide catalyst layer.

[0023] As a preferred embodiment, in step 4), the calcination conditions are: a temperature of 150–600°C and a time of 5–120 minutes. A further preferred embodiment is: a temperature of 200–400°C and a time of 10–60 minutes.

[0024] As a preferred embodiment, in step 4), the coating, drying, and calcination processes are repeated 2 to 20 times; more preferably, the coating, drying, and calcination processes are repeated 3 to 10 times.

[0025] As a preferred embodiment, the surface cleaning pretreatment process for the conductive substrate in step 1) is as follows: after degreasing, removing the surface oxide layer, and washing, the conductive substrate is immersed in oxalic acid solution and then dried. The preferred oxalic acid solution has a mass percentage concentration of 2-15%. The conductive substrate immersed in the oxalic acid solution is then removed, washed, dried, and subjected to sandblasting to increase the surface area; the sandblasting material is one of corundum, diamond, or tungsten carbide.

[0026] As a preferred embodiment, the process of generating the corrosion-resistant conductive layer in step 2) is as follows: After impurity removal treatment, the metal oxide support possessing both rutile crystal structure and oxygen-deficient structure is coated onto the conductive substrate pretreated in step 1) using industrial thermal spraying or cold spraying. Before use, the metal oxide support with both rutile crystal structure and oxygen-deficient structure undergoes impurity and oil removal treatment: first, it is soaked in nitric acid with a concentration of 2–3.5 mol / L, washed with water until neutral, and the soaking and washing process is repeated several times to thoroughly remove acid-soluble impurities; then, it is soaked in an alkaline solution with a concentration of 4–6 mol / L, washed with water until neutral, and the soaking and washing process is repeated several times to thoroughly remove alkali-soluble impurities; finally, it is washed several times with acetone to remove organic matter; vacuum dried, and passed through a 300-mesh sieve for later use. The metal oxide support with both rutile crystal structure and oxygen-deficient structure is dried at a temperature of 80–150℃ before use.

[0027] As a preferred embodiment, the calcination process in step 3) is as follows: the calcination time is 2 to 120 minutes at a temperature of 300 to 600°C.

[0028] As a preferred embodiment, the metal salt solution in step 3) is a soluble salt solution of at least one of niobium, bismuth, tin, cerium, lanthanum, cobalt, silver, nickel, platinum, tantalum, ruthenium, iridium, and antimony. Specifically, it could be a nitrate, chloride, or similar salt.

[0029] As a preferred option, the manganese salt is a soluble manganese salt, with manganese nitrate being a more preferred option.

[0030] As a preferred option, the fluorine source is a soluble salt containing fluoride ions, such as sodium fluoride or ammonium fluoride.

[0031] As a preferred embodiment, the drying process in step 3) is carried out at 80–120°C for 5–20 minutes.

[0032] As a preferred option, the solvent used for the metal salt solution in step 3) is at least one of ethanol, ethylene glycol, propanol, isopropanol, acetone, and water.

[0033] As a preferred option, the conductive substrate can be cut into various geometric configurations as needed, such as planar milled plates, perforated mesh plates, or expanded mesh plates.

[0034] As a preferred option, industrial thermal spraying or cold spraying is atmospheric plasma spraying, with argon as the main gas and hydrogen as the auxiliary gas.

[0035] As a preferred option, it is optimal to repeat the coating, drying and calcination process 3 to 15 times in step 3).

[0036] The present invention provides a method for preparing a highly stable modified manganese dioxide catalyst electrode, the method comprising the following steps:

[0037] Step 1: Conductive substrate pretreatment

[0038] After degreasing, removing the surface oxide layer, and washing, the conductive substrate is soaked in oxalic acid solution and then dried.

[0039] Step 2: Prepare a corrosion-resistant conductive layer

[0040] After impurity removal, the metal oxide carrier with both rutile crystal structure and oxygen vacancy structure is coated onto the conductive substrate after the pretreatment in step one by industrial thermal spraying or cold spraying.

[0041] Step 3: Preparation of modified manganese dioxide catalytic coating

[0042] First, a fluorine source and carbon material are added to a manganese salt solution and mixed evenly. Then, a metal salt solution is added dropwise and mixed evenly to obtain a mixed solution. The resulting mixed solution is coated onto the surface of the conductive substrate with a corrosion-resistant conductive layer obtained in step two by immersion-lifting, brushing, or spraying. After drying, it is calcined at 300–600°C for 2–120 min. The coating and calcination process is repeated at least 5 times, and finally, the temperature is set at 300–600°C and held for 0.5–2 h. The metal salt solution is a soluble salt solution of at least one of niobium, bismuth, tin, cerium, lanthanum, cobalt, silver, nickel, platinum, tantalum, ruthenium, iridium, and antimony.

[0043] Step 4: Apply silica sol to the surface of the modified manganese dioxide catalyst layer by immersion-lifting, brushing, or spraying, dry, and calcine at a temperature of 150–600℃ for 5–120 minutes. Repeat the coating, drying, and calcination process several times, and finally set the temperature at 150–600℃ and hold for 0.5–2 hours. A silica gel coating is formed on the surface of the modified manganese dioxide catalyst layer, thus obtaining the product.

[0044] The highly stable modified manganese dioxide catalyst anode prepared by the technical solution of this invention needs to be activated before use: the highly stable modified manganese dioxide catalyst anode is placed in an acidic electrolyte at 50-300 A / m 2 Activation is performed at a specific current density. The acidic electrolyte is a mixed solution of sulfuric acid, nitric acid, and hydrofluoric acid. In a further preferred preparation method, each liter of acidic electrolyte contains 0.8–1.2 mol of sulfuric acid, 0.08–0.12 mol of nitric acid, and 15–25 mg of hydrofluoric acid.

[0045] Compared with the prior art, the beneficial effects of the technical solution of this invention are:

[0046] This invention incorporates carbon materials such as graphene and carbon nanotubes into a modified manganese dioxide catalyst layer, while simultaneously coating the surface of the modified manganese dioxide catalyst layer with a silicone coating. The synergistic effect of these two elements enables the modified manganese dioxide catalyst anode to maintain high current efficiency over a long period and significantly improves its electrode stability. The addition of graphene or carbon nanotubes to the modified manganese dioxide catalyst layer provides excellent conductivity. Graphene primarily fills the spaces between fluorine and metal-co-doped manganese dioxide nanoparticles, while the linear carbon nanotubes interspersed among them enhance the conductivity of the catalyst layer, thereby improving catalytic efficiency. In particular, the naturally coiled linear structure of carbon nanotubes, when uniformly mixed within the fluorine and metal-co-doped manganese dioxide nanoparticles, provides a binding effect, increasing the bonding strength between the fluorine and metal-co-doped manganese dioxide nanoparticles and thus improving their physical stability. The technical solution of this invention involves coating the surface of a modified manganese dioxide catalyst layer with a silica gel coating. This silica gel coating physically modifies the modified manganese dioxide catalyst layer. The surface of the silica gel coating is relatively smooth, which can effectively prevent the deposition of anode mud on the electrode surface and thus reduce the effective area of ​​the electrode, thereby improving current efficiency. At the same time, the silica gel coating can effectively protect the modified manganese dioxide catalyst layer, effectively reducing the oxidation of the modified manganese dioxide catalyst layer by infiltrated oxygen and the corrosion by infiltrated electrolyte, thereby greatly improving the service life of the modified manganese dioxide catalyst anode.

[0047] The technical solution of this invention introduces both graphene and carbon nanotubes into a modified manganese dioxide catalyst layer. Their roles and principles differ. Graphene particles primarily fill the spaces between fluorine and metal-doped manganese dioxide nanoparticles, while linear carbon nanotubes are interspersed within them. Graphene particles possess ultra-high conductivity, while carbon nanotubes also exhibit good conductivity. Their combined use forms a robust conductive network to enhance the conductivity of the catalytic material, thereby improving current efficiency. Furthermore, the introduction of an appropriate proportion of carbon nanotubes, with their naturally coiled linear structure, allows for uniform mixing within the fluorine and metal-doped manganese dioxide nanoparticles, acting as an interlocking agent. This enhances the bonding strength between the fluorine and metal-doped manganese dioxide nanoparticles, thus improving their physical stability. Attached Figure Description

[0048]

Figure 1

[0049] 【 Figure 2[Image 1] shows the oxygen evolution reaction potential polarization curves of the highly stable modified manganese dioxide electrodes prepared in Examples 1-3 and the modified manganese dioxide electrode prepared in Comparative Example 1, obtained by scanning at a speed of 10 m / Vs on a Shanghai Chenhua CHI660D electrochemical workstation, using a saturated calomel electrode as the reference electrode. 5 represents Comparative Example 1; 6 represents Example 2; 7 represents Example 3; and 8 represents Example 1.

[0050] 【 Figure 3 The graph shows the cyclic voltammetry curves of the highly stable modified manganese dioxide electrodes prepared in Examples 1-3 and the modified manganese dioxide electrode prepared in Comparative Example 1, obtained by scanning at a speed of 20 m / Vs on a Shanghai Chenhua CHI660D electrochemical workstation with a saturated calomel electrode as the reference electrode in 1 mol sulfuric acid solution. 9 represents Comparative Example 1; 10 represents Example 2; 11 represents Example 3; and 12 represents Example 1.

[0051] 【 Figure 4 The high-stability modified manganese dioxide electrode prepared in Examples 1-3 and the modified manganese dioxide electrode prepared in Comparative Example 1 are compared at 4 A / cm. 2 The high current density enhanced lifetime test graphs are shown in Figure 13, which is Comparative Example 1; Figure 14 is Example 2; Figure 15 is Example 3; and Figure 16 is Example 1. Detailed Implementation

[0052] The following examples are intended to further illustrate the present invention, but not to limit the scope of protection of the claims of the present invention.

[0053] Unless otherwise specified, the chemical reagents and raw materials used in the following examples are all conventional commercially available products.

[0054] Example 1

[0055] (1) Process TA1 into a product with an effective end area of ​​2 cm². 2 It is long and narrow. After degreasing and corundum sandblasting, it is cleaned with water and soaked in a 3% oxalic acid solution until ready for use.

[0056] (2) Titanium suboxide powder with a total crystal content of 80% of Ti4O7 (45%) and Ti5O9 (35%) was pretreated. The treatment process was as follows: first, it was soaked in 3 mol / L nitric acid, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove acid-soluble impurities; then, it was soaked in 5 mol / L sodium hydroxide solution, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove alkali-soluble impurities; finally, it was washed 3 times with acetone to remove organic matter; vacuum dried, passed through a 300-mesh sieve, and set aside for use.

[0057] (3) After cleaning the titanium plate immersed in oxalic acid solution and drying it at 100°C, the surface is subjected to corundum sandblasting. The titanium suboxide powder is dried at 80°C. The titanium plate is sprayed with atmospheric plasma spraying equipment (argon as the main gas and hydrogen as the auxiliary gas) to obtain a corrosion-resistant and conductive intermediate layer with a coating thickness of 0.2 mm.

[0058] (4) Preparation of modified manganese dioxide catalytic coating:

[0059] Preparation process of coating solution: (A) First, add fluoride ions (the fluoride source can be a compound containing F ions) to a 50% manganese nitrate solution and stir the solution evenly; (B) Add cerium nitrate hexahydrate particles to a mixed solvent of ethanol and water (volume ratio 1:2) and stir evenly until completely dissolved; (C) Mix the above two solutions at a molar ratio of Mn, Ce and F of 20:5:15 and stir evenly; (D) Mix graphene and carbon nanotubes at a mass ratio of 1:2 and a mass content of 6% of the total mass of the catalyst layer with the above solution and stir evenly for later use.

[0060] Coating process: Immerse the titanium plate in the coating solution for 5 minutes, then lift it out and let it air dry until the coating solution evenly covers the titanium plate. Dry the titanium plate at 100℃ for 10 minutes, and then thermally decompose it at 400℃ in an oxidizing atmosphere for 12 minutes. Repeat the above process 8 times. For the last time, raise the temperature to 450℃ and keep it at that temperature for 1.5 hours.

[0061] (5) Silica coating: The modified manganese dioxide catalyst layer is immersed in silica sol (solid content is about 20%), lifted out and air-dried, then dried at 100°C for 10 minutes, then calcined at 200°C for 10 minutes, and the coating, drying and calcination process is repeated 5 times. Finally, it is kept at 200°C for 1 hour to form a silica coating on the surface of the modified manganese dioxide catalyst layer.

[0062] (6) The prepared electrode plate is immersed in an active electrolyte solution consisting of 1 mol / L sulfuric acid, 0.1 mol / L nitric acid solution, and 20 mg / L hydrofluoric acid. A small current is passed through the electrode plate to activate its catalytic activity at a current density of 100 A / m. 2 The activation time is 20 minutes. After drying, a highly stable modified manganese dioxide electrode is obtained.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that step (D) in step (4) is missing, and step (5) is also missing.

[0065] Example 2

[0066] The difference from Example 1 is that in step (4) (D), the graphene mass accounts for 6% of the total mass content of the catalyst layer and is mixed with the above solution and stirred evenly for later use.

[0067] Example 3

[0068] The difference from Example 1 is that in step (4) (D), carbon nanotubes are mixed with the above solution at a ratio of 6% of the total mass of the catalyst layer and stirred evenly for later use.

[0069] Figure 1 This is a schematic diagram of the structure of a highly stable modified manganese dioxide electrode.

[0070] Figure 2 The oxygen evolution reaction polarization curves are shown for the highly stable modified manganese dioxide electrodes prepared in Examples 1-3 and the modified manganese dioxide electrode prepared in Comparative Example 1. Figure 2 It can be seen that introducing carbon materials into the manganese dioxide catalyst layer of the modified manganese dioxide electrode and coating the surface of the electrode catalyst layer with a silicone coating does not affect the kinetic process of the oxygen evolution reaction at the anode, and has a certain promoting effect.

[0071] Figure 3 Cyclic voltammetry curves of the highly stable modified manganese dioxide electrodes prepared in Examples 1-3 and the modified manganese dioxide electrode prepared in Comparative Example 1 are shown below. Figure 3 It can be seen that the integral area of ​​the cyclic voltammetry curve of the modified manganese dioxide catalyst electrode is not much different from that of the other three electrodes in Comparative Example 1, and the voltage of the corresponding peak is also similar to that of the other three electrodes; indicating that introducing carbon materials into the manganese dioxide catalyst layer of the modified manganese dioxide electrode and coating the surface of the electrode catalyst layer with a silica gel coating do not affect the catalytic activity of the electrode.

[0072] Figure 4 The images show enhanced lifespan test results for the highly stable modified manganese dioxide electrodes prepared in Examples 1-3 and the modified manganese dioxide electrode prepared in Comparative Example 1. Figure 4 The paper shows that the highly stable modified manganese dioxide electrode at 4 A / cm 2 The electrode exhibits a lifespan of over 900 hours at a cutoff voltage of 7V under high current density, which is a significant improvement over the other three electrodes in Comparative Example 1. The highly stable modified manganese dioxide catalyst electrode demonstrates excellent electrochemical activity and an ultra-long lifespan.

[0073] Example 3

[0074] (1) Process TA1 into a product with an effective end area of ​​2 cm². 2 It is long and narrow. After degreasing and corundum sandblasting, it is cleaned with water and soaked in a 3% oxalic acid solution until ready for use.

[0075] (2) Titanium suboxide powder with a total crystal content of 80% of Ti4O7 (45%) and Ti5O9 (35%) was pretreated. The treatment process was as follows: first, it was soaked in 3 mol / L nitric acid, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove acid-soluble impurities; then, it was soaked in 5 mol / L sodium hydroxide solution, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove alkali-soluble impurities; finally, it was washed 3 times with acetone to remove organic matter; vacuum dried, passed through a 300-mesh sieve, and set aside for use.

[0076] (3) After cleaning the titanium plate immersed in oxalic acid solution and drying it at 100°C, the surface is subjected to corundum sandblasting. The titanium suboxide powder is dried at 80°C. The titanium plate is sprayed with atmospheric plasma spraying equipment (argon as the main gas and hydrogen as the auxiliary gas) to obtain a corrosion-resistant and conductive intermediate layer with a coating thickness of 0.2 mm.

[0077] (4) Preparation of modified manganese dioxide catalytic coating:

[0078] Preparation process of coating solution: (A) First, add fluoride ions (the fluoride source can be a compound containing F ions) to a 50% manganese nitrate solution and stir the solution evenly; (B) Add cerium nitrate hexahydrate particles to a mixed solvent of ethanol and water (volume ratio 1:2) and stir evenly until completely dissolved; (C) Mix the above two solutions at a molar ratio of Mn, Ce and F of 20:5:15 and stir evenly; (D) Mix graphene and carbon nanotubes at a mass ratio of 1:1 and a mass content of 4% of the total mass of the catalyst layer with the above solution and stir evenly for later use.

[0079] Coating process: Immerse the titanium plate in the coating solution for 5 minutes, then lift it out and let it air dry until the coating solution evenly covers the titanium plate. Dry the titanium plate at 100℃ for 10 minutes, and then thermally decompose it at 400℃ in an oxidizing atmosphere for 12 minutes. Repeat the above process 8 times. For the last time, raise the temperature to 450℃ and keep it at that temperature for 1.5 hours.

[0080] (5) Silica coating: The modified manganese dioxide catalyst layer is immersed in silica sol (solid content is about 20%), lifted out and air-dried, then dried at 80°C for 20 minutes, then calcined at 300°C for 6 minutes, and the coating, drying and calcination process is repeated 8 times. Finally, it is kept at 300°C for 1 hour to form a silica coating on the surface of the modified manganese dioxide catalyst layer.

[0081] (6) The prepared electrode plate is immersed in an active electrolyte solution consisting of 1 mol / L sulfuric acid, 0.1 mol / L nitric acid solution, and 20 mg / L hydrofluoric acid. A small current is passed through the electrode plate to activate its catalytic activity at a current density of 100 A / m. 2The activation time is 20 minutes. After drying, a highly stable modified manganese dioxide electrode is obtained.

[0082] The prepared highly stable modified manganese dioxide electrode operates at 4 A / cm 2 It has a lifespan of over 850 hours when the cutoff voltage is 7V under high current density.

[0083] Example 4

[0084] (1) Process TA1 into a product with an effective end area of ​​2 cm². 2 It is long and narrow. After degreasing and corundum sandblasting, it is cleaned with water and soaked in a 3% oxalic acid solution until ready for use.

[0085] (2) Titanium suboxide powder with a total crystal content of 80% of Ti4O7 (45%) and Ti5O9 (35%) was pretreated. The treatment process was as follows: first, it was soaked in 3 mol / L nitric acid, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove acid-soluble impurities; then, it was soaked in 5 mol / L sodium hydroxide solution, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove alkali-soluble impurities; finally, it was washed 3 times with acetone to remove organic matter; vacuum dried, passed through a 300-mesh sieve, and set aside for use.

[0086] (3) After cleaning the titanium plate immersed in oxalic acid solution and drying it at 100°C, the surface is subjected to corundum sandblasting. The titanium suboxide powder is dried at 80°C. The titanium plate is sprayed with atmospheric plasma spraying equipment (argon as the main gas and hydrogen as the auxiliary gas) to obtain a corrosion-resistant and conductive intermediate layer with a coating thickness of 0.2 mm.

[0087] (4) Preparation of modified manganese dioxide catalytic coating:

[0088] Preparation process of coating solution: (A) First, add fluoride ions (the fluoride source can be a compound containing F ions) to a 50% manganese nitrate solution and stir the solution evenly; (B) Add cerium nitrate hexahydrate particles to a mixed solvent of ethanol and water (volume ratio 1:2) and stir evenly until completely dissolved; (C) Mix the above two solutions at a molar ratio of Mn, Ce and F of 20:8:10 and stir evenly; (D) Mix graphene and carbon nanotubes at a mass ratio of 2:1 and a mass content of 8% of the total mass of the catalyst layer with the above solution and stir evenly for later use.

[0089] Coating process: Immerse the titanium plate in the coating solution for 5 minutes, then lift it out and let it air dry until the coating solution evenly covers the titanium plate. Dry the titanium plate at 100℃ for 10 minutes, and then thermally decompose it at 350℃ in an oxidizing atmosphere for 12 minutes. Repeat the above process 10 times. For the last time, raise the temperature to 400℃ and keep it at that temperature for 1.5 hours.

[0090] (5) Silica coating: The modified manganese dioxide catalyst layer is immersed in silica sol (solid content is about 20%), lifted out and air-dried, then dried at 100°C for 10 minutes, then calcined at 350°C for 15 minutes, and the coating, drying and calcination process is repeated 7 times. Finally, it is kept at 350°C for 1 hour to form a silica coating on the surface of the modified manganese dioxide catalyst layer.

[0091] (6) The prepared electrode plate is immersed in an active electrolyte solution consisting of 1 mol / L sulfuric acid, 0.1 mol / L nitric acid solution, and 20 mg / L hydrofluoric acid. A small current is passed through the electrode plate to activate its catalytic activity at a current density of 100 A / m. 2 The activation time is 20 minutes. After drying, a highly stable modified manganese dioxide electrode is obtained.

[0092] The prepared highly stable modified manganese dioxide electrode operates at 4 A / cm 2 It has a lifespan of over 820 hours when the cutoff voltage is 7V under high current density.

[0093] Example 5

[0094] (1) Process TA1 into a product with an effective end area of ​​2 cm². 2 It is long and narrow. After degreasing and corundum sandblasting, it is cleaned with water and soaked in a 3% oxalic acid solution until ready for use.

[0095] (2) Titanium suboxide powder with a total crystal content of 80% of Ti4O7 (45%) and Ti5O9 (35%) was pretreated. The treatment process was as follows: first, it was soaked in 3 mol / L nitric acid, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove acid-soluble impurities; then, it was soaked in 5 mol / L sodium hydroxide solution, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove alkali-soluble impurities; finally, it was washed 3 times with acetone to remove organic matter; vacuum dried, passed through a 300-mesh sieve, and set aside for use.

[0096] (3) After cleaning the titanium plate immersed in oxalic acid solution and drying it at 100°C, the surface is subjected to corundum sandblasting. The titanium suboxide powder is dried at 80°C. The titanium plate is sprayed with atmospheric plasma spraying equipment (argon as the main gas and hydrogen as the auxiliary gas) to obtain a corrosion-resistant and conductive intermediate layer with a coating thickness of 0.2 mm.

[0097] (4) Preparation of modified manganese dioxide catalytic coating:

[0098] Preparation process of coating solution: (A) First, add fluoride ions (the fluoride source can be a compound containing F ions) to a 50% manganese nitrate solution and stir the solution evenly; (B) Add cerium nitrate hexahydrate particles to a mixed solvent of ethanol and water (volume ratio 1:2) and stir evenly until completely dissolved; (C) Mix the above two solutions at a molar ratio of Mn, Ce and F of 20:5:15 and stir evenly; (D) Mix graphene and carbon nanotubes at a mass ratio of 1:2 and a mass content of 6% of the total mass of the catalyst layer with the above solution and stir evenly for later use.

[0099] Coating process: Immerse the titanium plate in the coating solution for 5 minutes, then lift it out and let it air dry until the coating solution evenly covers the titanium plate. Dry the titanium plate at 100℃ for 10 minutes, and then thermally decompose it at 400℃ in an oxidizing atmosphere for 12 minutes. Repeat the above process 8 times. For the last time, raise the temperature to 450℃ and keep it at that temperature for 1.5 hours.

[0100] (5) Silica coating: The modified manganese dioxide catalyst layer is immersed in silica sol (solid content is about 20%), lifted out and air-dried, then dried at 100°C for 10 minutes, then calcined at 200°C for 10 minutes, and the coating, drying and calcination process is repeated 20 times. Finally, it is kept at 200°C for 1 hour to form a silica coating on the surface of the modified manganese dioxide catalyst layer.

[0101] (6) The prepared electrode plate is immersed in an active electrolyte solution consisting of 1 mol / L sulfuric acid, 0.1 mol / L nitric acid solution, and 20 mg / L hydrofluoric acid. A small current is passed through the electrode plate to activate its catalytic activity at a current density of 100 A / m. 2 The activation time is 20 minutes. After drying, a highly stable modified manganese dioxide electrode is obtained.

[0102] The prepared highly stable modified manganese dioxide electrode operates at 4 A / cm 2 At a high current density and a cutoff voltage of 7V, it has a lifespan of over 1000 hours, but the electrocatalytic activity of the electrode is slightly reduced, indicating that further increasing the thickness of the silicone coating will affect the electrocatalytic activity of the electrode.

[0103] Comparative Example 2

[0104] (1) Process TA1 into a product with an effective end area of ​​2 cm². 2 It is long and narrow. After degreasing and corundum sandblasting, it is cleaned with water and soaked in a 3% oxalic acid solution until ready for use.

[0105] (2) Titanium suboxide powder with a total crystal content of 80% of Ti4O7 (45%) and Ti5O9 (35%) was pretreated. The treatment process was as follows: first, it was soaked in 3 mol / L nitric acid, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove acid-soluble impurities; then, it was soaked in 5 mol / L sodium hydroxide solution, washed with water until neutral, and the soaking and washing process was repeated 3 times to fully remove alkali-soluble impurities; finally, it was washed 3 times with acetone to remove organic matter; vacuum dried, passed through a 300-mesh sieve, and set aside for use.

[0106] (3) After cleaning the titanium plate immersed in oxalic acid solution and drying it at 100°C, the surface is subjected to corundum sandblasting. The titanium suboxide powder is dried at 80°C. The titanium plate is sprayed with atmospheric plasma spraying equipment (argon as the main gas and hydrogen as the auxiliary gas) to obtain a corrosion-resistant and conductive intermediate layer with a coating thickness of 0.2 mm.

[0107] (4) Preparation of modified manganese dioxide catalytic coating:

[0108] Preparation process of coating solution: (A) First, add fluoride ions (the fluoride source can be a compound containing F ions) to a 50% manganese nitrate solution and stir the solution evenly; (B) Add cerium nitrate hexahydrate particles to a mixed solvent of ethanol and water (volume ratio 1:2) and stir evenly until completely dissolved; (C) Mix the above two solutions at a molar ratio of Mn, Ce and F of 20:5:15 and stir evenly; (D) Mix graphene and carbon nanotubes at a mass ratio of 1:2 and a mass content of 6% of the total mass of the catalyst layer with the above solution and stir evenly for later use.

[0109] Coating process: Immerse the titanium plate in the coating solution for 5 minutes, then lift it out and let it air dry until the coating solution evenly covers the titanium plate. Dry the titanium plate at 100℃ for 10 minutes, and then thermally decompose it at 400℃ in an oxidizing atmosphere for 12 minutes. Repeat the above process 8 times. For the last time, raise the temperature to 450℃ and keep it at that temperature for 1.5 hours.

[0110] (5) Immerse the prepared electrode plate in an active electrolyte solution composed of 1 mol / L sulfuric acid, 0.1 mol / L nitric acid solution, and 20 mg / L hydrofluoric acid. Activate the catalytic activity of the electrode plate by passing a small current at a current density of 100 A / m. 2 The activation time is 20 minutes. After drying, a highly stable modified manganese dioxide electrode is obtained.

[0111] The prepared highly stable modified manganese dioxide electrode operates at 4 A / cm 2 It has a lifespan of over 600 hours when the cutoff voltage is 7V under high current density.

Claims

1. A highly stable modified manganese dioxide catalyst anode, characterized in that: From bottom to top, the structure consists of a conductive substrate, a corrosion-resistant conductive layer, a modified manganese dioxide catalyst layer, and a silica gel coating. The modified manganese dioxide catalyst layer comprises fluorine and metal co-doped nano-manganese dioxide and carbon materials, wherein the metal is at least one selected from niobium, bismuth, tin, cerium, lanthanum, cobalt, silver, nickel, platinum, tantalum, ruthenium, iridium, and antimony; the carbon materials include graphene and / or carbon nanotubes. The carbon material in the modified manganese dioxide catalyst layer is 0.01~10% of the mass of fluorine and metal co-doped nano-manganese dioxide; The surface thickness of the silicone coating is 0.01~2mm.

2. The highly stable modified manganese dioxide catalyst anode according to claim 1, characterized in that: The carbon material is composed of graphene and carbon nanotubes.

3. The highly stable modified manganese dioxide catalyst anode according to claim 1, characterized in that: The carbon material is composed of graphene and carbon nanotubes in a mass percentage ratio of 10-90%:10-90%.

4. The highly stable modified manganese dioxide catalyst anode according to claim 1, characterized in that: The molar ratio of manganese:metal:fluorine in the fluorine-metal co-doped nano-manganese dioxide is 20:0.1~20:1~35.

5. The highly stable modified manganese dioxide catalyst anode according to claim 1, characterized in that: The corrosion-resistant conductive layer is composed of titanium suboxide and / or lead dioxide.

6. A method for preparing a highly stable modified manganese dioxide catalyst anode according to any one of claims 1 to 5, characterized in that: Includes the following steps: 1) Perform surface cleaning pretreatment on the conductive substrate; 2) A corrosion-resistant conductive layer is generated on the surface of the conductive substrate after surface cleaning and pretreatment; 3) Mix the manganese salt solution with carbon material, fluorine source and metal salt solution evenly to obtain a mixed slurry. Coat the mixed slurry on the surface of the corrosion-resistant conductive layer, dry, calcine, and repeat the coating, drying and calcine process several times to generate a modified manganese dioxide catalyst layer on the surface of the corrosion-resistant conductive layer. 4) Coat the surface of the modified manganese dioxide catalyst layer with silica sol, dry, calcine, and repeat the coating, drying and calcine process several times to generate a silica gel coating on the surface of the modified manganese dioxide catalyst layer.

7. The method for preparing a highly stable modified manganese dioxide catalyst anode according to claim 6, characterized in that: In step 4), the calcination conditions are: temperature of 150~600℃ and time of 5~120 minutes.

8. The method for preparing a highly stable modified manganese dioxide catalyst anode according to claim 6, characterized in that: In step 4), the coating, drying, and calcination processes are repeated 2 to 20 times.

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