Iron-doped sludge-based biochar-loaded electrode material and preparation method thereof

Abstract

The invention provides an iron-doped sludge-based biochar-loaded electrode material and a preparation method thereof, and belongs to the technical field of electrode material preparation. The foamed nickel is used as a substrate, a mixture of the modified sludge-based biochar and the modified Fe3O4 powder is mixed with the conductive agent, the binder and the solvent to prepare the electrode slurry, the foamed nickel substrate is coated with the electrode slurry, firm loading of the sludge carbon on the surface of the foamed nickel is achieved through high-temperature heat treatment, and the conductivity and the structural stability of the composite electrode material are remarkably improved. The electrode material prepared by the invention has the characteristics of strong electricity storage capability, high charge transfer efficiency, high energy density, remarkably prolonged electrode life and the like. In addition, the resource utilization rate of sludge solid waste can be increased, and the method is environmentally friendly, low in cost and good in economic benefit.

Description

Technical Field

[0001] This invention relates to the field of electrode material preparation technology, specifically to an iron-doped sludge-based biochar supported electrode material and its preparation method. Background Technology

[0002] With the development of urbanization in my country, the domestic production of sludge has increased dramatically, currently reaching 65 million tons. Sludge contains various pathogens and pollutants, and improper disposal can easily cause secondary pollution such as air, water, and soil pollution. Sludge can be divided into two types according to its source: municipal sludge and industrial sludge. Municipal sludge refers to a byproduct generated during wastewater treatment, mainly consisting of organic and inorganic components, and is also rich in heavy metals, carcinogens, and elements such as phosphorus (P), sulfur (S), and nitrogen (N). The organic matter mainly comes from proteins, fats, and carbohydrates in wastewater, while the inorganic matter mainly comes from chemically synthesized products or soil. Industrial sludge mainly refers to sludge generated during the treatment of industrial wastewater, such as in petrochemical, electroplating, and steelmaking processes. Industrial sludge contains large amounts of organic matter containing nitrogen (N) and phosphorus (P), heavy metals, trace elements, and pathogens.

[0003] Current methods for treating sludge mainly include incineration, landfill, and ocean dumping. However, these methods suffer from problems such as excessive soil occupation and severe pollution. Therefore, there is an urgent need to provide a method for the resource utilization of sludge. Based on this, this invention aims to provide a method for preparing high-efficiency energy storage composite electrode materials using sludge, providing a technical reference for low-cost electrode materials and the resource utilization of sludge. Summary of the Invention

[0004] In view of this, the present invention provides an iron-doped sludge-based biochar-supported electrode material and its preparation method. The present invention uses iron as the main electroactive material, achieving iron doping through the introduction of Fe3O4 to enhance the pseudocapacitive behavior of the electrode. Yttrium is used as an auxiliary modifier to improve the conductivity and interfacial compatibility of the biochar; the two work synergistically to improve the overall electrochemical performance of the electrode material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing an iron-doped sludge-based biochar supported electrode material, comprising the following steps:

[0007] (1) The collected sludge is dehydrated, dried and pyrolyzed in sequence to collect sludge-based biochar. The sludge-based biochar is then crushed and sieved to obtain sludge-based biochar powder.

[0008] (2) The sludge-based biochar powder is placed in yttrium trichloride solution and stirred for a certain time to obtain a dispersion containing sludge-based biochar;

[0009] (3) Add urea to the dispersion of sludge-based biochar to obtain a mixture, wherein the concentration of urea in the mixture is 0.5 mol / L. Transfer the mixture to a high-pressure reactor and carry out a hydrothermal reaction at 120-180℃ for 6-12 hours. Centrifuge to separate the solids and dry the solids to obtain modified sludge-based biochar powder for later use.

[0010] (4) Place Fe3O4 powder in anhydrous ethanol and sonicate until it is evenly dispersed. Then add bis[3-(triethoxysilyl)propyl]amine to the system and heat to react. After the reaction is complete, wash, dry and grind to obtain modified Fe3O4 powder.

[0011] (5) The modified sludge-based biochar powder is mixed with the modified Fe3O4 powder to obtain a mixture. A certain proportion of polyvinyl alcohol and deionized water are added to the mixture. After stirring evenly, the mixture is placed in a mold and pressed into blocks for carbonization to obtain the carbonized product.

[0012] (6) The carbonized product is mixed evenly with a conductive agent, an electrode binder and an organic solvent to obtain a slurry;

[0013] (7) The slurry is coated on the surface of nickel foam and dried to obtain electrode material.

[0014] This invention improves the bonding force between iron and modified sludge-based biochar powder by modifying Fe3O4 powder, thus preventing the active material from falling off.

[0015] This invention prepares a product by mixing and pressing modified sludge-based biochar powder, modified Fe3O4, polyvinyl alcohol, and deionized water, followed by carbonization. The resulting product has a loose and porous structure, numerous functional groups, a large specific surface area, and a high loading of active substances, which helps to optimize electron conduction pathways and interfacial bonding.

[0016] Furthermore, in step (1), the sludge is dehydrated to a moisture content of 60-70%, the drying temperature in step (1) is 80-100℃, the drying time is 20-36h, the pyrolysis temperature in step (1) is 400-800℃, and the pulverized sludge is passed through an 80-150 mesh sieve.

[0017] Furthermore, the concentration of the yttrium trichloride solution in step (2) is 0.002 mol / L-0.01 mol / L.

[0018] Furthermore, in step (2), the solid-liquid ratio of the sludge-based biochar powder and the yttrium trichloride solution is 1-2:10.

[0019] Furthermore, the stirring time in step (2) is 12-20 hours.

[0020] Furthermore, the centrifugal separation speed in step (3) is 5000-10000 r / min.

[0021] Furthermore, the drying temperature in step (3) is 100-120℃.

[0022] Furthermore, in step (4), the mass-to-volume ratio of Fe3O4 powder to anhydrous ethanol is 1-3:100.

[0023] Furthermore, the ultrasonic power in step (4) is 200W-500W.

[0024] Furthermore, the amount of bis[3-(triethoxysilyl)propyl]amine added in step (4) is 0.5%-1.0% of the mass of anhydrous ethanol.

[0025] Furthermore, the reaction temperature in step (4) is 60-85℃, and the reaction time is 10-20h.

[0026] Furthermore, in step (4), the product is repeatedly washed with deionized water and dried at 80-100°C to constant weight.

[0027] Furthermore, in step (5), the mass ratio of the modified sludge-based biochar powder to the modified Fe3O4 powder is 100:0.1-0.5.

[0028] Furthermore, in step (5), the mass ratio of polyvinyl alcohol to the modified sludge-based biochar powder is 1:6-10.

[0029] Furthermore, the mold in step (5) has dimensions of 30 mm × 30 mm × 15 mm.

[0030] Furthermore, in step (5), the carbonization temperature is 1100-1550℃, the carbonization time is 0.5-1.5h, an inert gas is introduced during the carbonization process, the flow rate of the inert gas is 100-200 mL / min, and the heating rate is 4-8℃ / min.

[0031] Furthermore, the mass ratio of the carbonized product, conductive agent, and electrode binder in step (6) is 8-10:1-3:2-5.

[0032] Furthermore, the conductive agent in step (6) is carbon black or acetylene black, the electrode binder is polyvinylidene fluoride, and the organic solvent is N-methylpyrrolidone.

[0033] Furthermore, the area of ​​the nickel foam described in step (7) is 1-3 cm². 2 .

[0034] Furthermore, the drying process in step (7) includes: drying at 70-80℃ for 8-15 hours, followed by heat treatment at 450-600℃ for 3-5 hours.

[0035] The present invention also provides an iron-doped sludge-based biochar supported electrode material prepared by the method, and the application of the iron-doped sludge-based biochar supported electrode material in the degradation of organic pollutants.

[0036] Furthermore, the present invention also includes: placing the electrode material described in step (7) in a cobalt salt solution and immersing it in an argon atmosphere at 40-50°C for 1-5 hours; then placing the immersed electrode material in a high-pressure reactor for reaction at a reaction temperature of 180-220°C for 5-10 hours; after the reaction, centrifuging, washing with water and drying to obtain a dried composite electrode material; subsequently, in a mixed atmosphere of 15% hydrogen / 85% argon, keeping the dried composite electrode material at 550-750°C for 0.5-0.8 hours at a gas flow rate of 80 ml / min to obtain the target electrode material.

[0037] Furthermore, the cobalt salt solution is a cobalt chloride solution; the concentration of the cobalt salt solution is 3-8 mmol / L.

[0038] This invention addresses the problem of increased electrode impedance and impaired electrochemical performance caused by the addition of binders by modifying the dried composite electrode with cobalt, thereby improving the cycle stability and lifespan of the electrode material.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] This invention significantly enhances the electrochemical activity and energy storage performance of electrode materials by using iron doping (in the form of Fe3O4) as the main active component. At the same time, yttrium is used to assist in the modification of sludge-based biochar, promoting electron transfer and improving structural stability. By utilizing the synergistic effect between the two, a high-performance electrode material is constructed.

[0041] This invention involves preparing an electrode slurry by mixing modified sludge-based biochar and modified Fe3O4 powder with a conductive agent, binder, and solvent. This slurry is then coated onto a nickel foam substrate and subjected to high-temperature heat treatment. This process achieves a robust loading of the sludge biochar onto the nickel foam surface, significantly improving the conductivity and structural stability of the composite electrode material. The electrode material prepared by this invention exhibits strong energy storage capacity, high charge transfer efficiency, high energy density, and a significantly extended electrode lifespan.

[0042] This invention can improve the resource utilization rate of sludge solid waste, and is environmentally friendly, low-cost, and economically beneficial.

[0043] The iron-doped sludge-based biochar supported electrode material prepared by this invention can be used as an electrode material for battery-type supercapacitors. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] Unless otherwise specified, the test methods or experimental methods described in the following examples are all conventional methods; unless otherwise specified, the raw materials and additives are obtained from conventional commercial sources or prepared by conventional methods.

[0046] The municipal dewatered sludge described in the following examples comes from sludge produced by a municipal sewage treatment plant in a town in Beijing.

[0047] The bis[3-(triethoxysilyl)propyl]amine was purchased from Aladdin, CAS No.: 13497-18-2, with a purity of ≥95%.

[0048] Example 1

[0049] A method for preparing an iron-doped sludge-based biochar supported electrode material, comprising the following specific steps:

[0050] (1) The municipal dewatered sludge with a moisture content of 80% was dewatered to 60% using a plate and frame filter press, dried at 80℃ for 26h, heated to 800℃ at a heating rate of 5℃ / min, pyrolyzed for 120min, the sludge-based biochar was collected, pulverized and passed through a 150-mesh sieve to obtain sludge-based biochar powder.

[0051] (2) The sludge-based biochar powder and a yttrium trichloride solution with a concentration of 0.007 mol / L were mixed and stirred for 18 h at a solid-liquid ratio of 1:10 to obtain a dispersion containing sludge-based biochar.

[0052] (3) Add urea to the dispersion of sludge-based biochar to obtain a mixture, wherein the concentration of urea in the mixture is 0.5 mol / L. Transfer the mixture to a high-pressure reactor and carry out a hydrothermal reaction at 120-180℃ for 6-12 hours. Centrifuge at 7000 r / min to collect the solid. Then dry the solid at 115℃ to constant weight to obtain modified sludge-based biochar powder.

[0053] (4) Fe3O4 powder and anhydrous ethanol were mixed at a mass-volume ratio of 1:100 and ultrasonicated until uniformly dispersed. The ultrasonic power was 300W. Then, bis[3-(triethoxysilane)propyl]amine was added to the system. The amount of bis[3-(triethoxysilane)propyl]amine added was 0.8% of the mass of anhydrous ethanol. The reaction was carried out at 65°C for 15 hours. After the reaction was completed, the mixture was washed three times with deionized water and dried in an oven at 85°C to constant weight. The mixture was then ground to obtain modified Fe3O4 powder with a particle size of 80 nm.

[0054] (5) The modified sludge-based biochar powder and the modified Fe3O4 powder are mixed at a mass ratio of 100:0.3 and ultrasonically dispersed until uniform. The ultrasonic power is 500W. Polyvinyl alcohol and deionized water are added to the mixture. The mass ratio of polyvinyl alcohol to modified sludge-based biochar powder is 1:6. After stirring evenly, the mixture is placed in a mold with dimensions of 30 mm × 30 mm × 15 mm and pressed into blocks. Then, carbonization is carried out in a nitrogen atmosphere. The flow rate of nitrogen is 180 mL / min. The carbonization temperature is 1250℃, the heating rate is 5℃ / min, and the carbonization time is 1.2h to obtain the carbonized product.

[0055] (6) The carbonized product is mixed with the conductive agent acetylene black and the electrode binder polyvinylidene fluoride in a mass ratio of 8:3:2. Then, the organic solvent N-methylpyrrolidone is added to obtain a slurry with a solid content of 20%.

[0056] (7) The slurry is coated on a foam nickel surface with an area of ​​3 cm2, dried at 75°C for 9.5 h, and then heat-treated at 500°C for 4 h to form a strong electrode material.

[0057] (8) The electrode material described in step (7) is immersed in a cobalt chloride solution with a concentration of 4 mmol / L at a solid-liquid ratio of 1:5. The immersion is carried out at 45°C for 3.5 h under an argon atmosphere. Then, the immersed electrode material is placed in a high-pressure reactor for reaction at a reaction temperature of 185°C for 8 h. After the reaction is completed, the electrode material is centrifuged, washed with water and dried to obtain the dried composite electrode material. Subsequently, the dried composite electrode material is kept at 650°C for 0.7 h under a mixed atmosphere of 15% hydrogen and 85% argon at a gas flow rate of 80 ml / min to obtain the target electrode material.

[0058] Example 2

[0059] A method for preparing an iron-doped sludge-based biochar supported electrode material, comprising the following specific steps:

[0060] (1) The municipal dewatered sludge with a moisture content of 80% was dewatered to 60% using a plate and frame filter press, dried at 100℃ for 20h, heated to 400℃ at a heating rate of 5℃ / min, pyrolyzed for 150min, the sludge-based biochar was collected, pulverized and passed through a 150-mesh sieve to obtain sludge-based biochar powder.

[0061] (2) The sludge-based biochar powder and a yttrium trichloride solution with a concentration of 0.01 mol / L were mixed and stirred for 20 h at a solid-liquid ratio of 2:10 to obtain a dispersion containing sludge-based biochar.

[0062] (3) Add urea to the dispersion of sludge-based biochar to obtain a mixture with a urea concentration of 0.5 mol / L. Transfer the mixture to a high-pressure reactor and carry out a hydrothermal reaction at 120-180℃ for 6-12 hours. Centrifuge at a speed of 10000 r / min to collect the solid. Then dry the solid at 120℃ to constant weight to obtain modified sludge-based biochar powder.

[0063] (4) Fe3O4 powder and anhydrous ethanol were mixed at a mass-volume ratio of 3:100 and ultrasonicated until uniformly dispersed. The ultrasonic power was 500W. Then, bis[3-(triethoxysilane)propyl]amine was added to the system. The amount of bis[3-(triethoxysilane)propyl]amine added was 1.0% of the mass of anhydrous ethanol. The reaction was carried out at 85°C for 20h. After the reaction was completed, the mixture was washed three times with deionized water and dried in an oven at 100°C to constant weight. The mixture was then ground to obtain modified Fe3O4 powder with a particle size of 100 nm.

[0064] (5) The modified sludge-based biochar powder and the modified Fe3O4 powder are mixed at a mass ratio of 100:0.5 and ultrasonically dispersed until uniform. The ultrasonic power is 500W. Polyvinyl alcohol and deionized water are added to the mixture. The mass ratio of polyvinyl alcohol to modified sludge-based biochar powder is 1:10. After stirring evenly, the mixture is placed in a mold with a size of 30 mm × 30 mm × 15 mm and pressed into blocks. Then, carbonization is carried out in a nitrogen atmosphere. The flow rate of nitrogen is 200 mL / min. The carbonization temperature is 1550℃ and the heating rate is 5℃ / min. The carbonization is carried out for 1.5h to obtain the carbonized product.

[0065] (6) The carbonized product is mixed with the conductive agent acetylene black and the electrode binder polyvinylidene fluoride in a mass ratio of 8:3:2. Then, the organic solvent N-methylpyrrolidone is added to obtain a slurry with a solid content of 20%.

[0066] (7) Apply the slurry to an area of ​​3 cm² 2The foamed nickel surface is dried at 80℃ for 15 hours and then heat-treated at 600℃ for 3 hours to form a strong electrode material.

[0067] Comparative Example 1

[0068] The difference from Example 1 is that steps (2) and (3) are not included, while the remaining steps are the same as in Example 1.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that bis[3-(triethoxysilyl)propyl]amine was not added, while the rest of the steps were the same as in Example 1.

[0071] Comparative Example 3

[0072] It is a foamed nickel electrode material.

[0073] Comparative Example 4

[0074] The difference from Example 1 is that the carbonization temperature in step (5) is 1000°C, while the remaining steps are the same as in Example 1.

[0075] Comparative Example 5

[0076] The difference from Example 1 is that the heat treatment temperature in step (7) is 700°C, while the remaining steps are the same as in Example 1.

[0077] The electrochemical performance of the tested examples and comparative examples is shown in Table 1.

[0078] The electrode materials prepared in the examples or comparative examples were used as the working electrode, the counter electrode was a graphite electrode, and the reference electrode was Ag / AgCl. These were assembled into a three-electrode system and placed in an electrolytic cell containing an electrolyte (a 0.1 mol / L tetrabutylammonium hexafluorophosphate solution in dichloromethane). The electrolyte was then subjected to an electrolytic reaction at 5 A·g⁻¹. -1 The charge-discharge performance of the electrode material under tested current density is shown in Table 1. The test environment temperature was 25±1℃ and the ambient humidity was 50±2%.

[0079] Table 1

[0080]

[0081] In Table 1, "-" indicates that the electrode material failed prematurely during the test.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an iron-doped sludge-based biochar supported electrode material, characterized in that, Includes the following steps: (1) The collected sludge is dehydrated, dried and pyrolyzed in sequence to collect sludge-based biochar. The sludge-based biochar is then crushed and sieved to obtain sludge-based biochar powder. (2) The sludge-based biochar powder is placed in yttrium trichloride solution and stirred for a certain time to obtain a dispersion containing sludge-based biochar; (3) Add urea to the dispersion of sludge-based biochar to obtain a mixture, wherein the concentration of urea in the mixture is 0.5 mol / L. Transfer the mixture to a high-pressure reactor and carry out a hydrothermal reaction at 120-180℃ for 6-12 hours. Centrifuge to separate the solids and dry the solids to obtain modified sludge-based biochar powder for later use. (4) Place Fe3O4 powder in anhydrous ethanol and sonicate until it is evenly dispersed. Then add bis[3-(triethoxysilyl)propyl]amine to the system and heat to react. After the reaction is complete, wash, dry and grind to obtain modified Fe3O4 powder. (5) The modified sludge-based biochar powder is mixed with the modified Fe3O4 powder to obtain a mixture. A certain proportion of polyvinyl alcohol and deionized water are added to the mixture. After stirring evenly, the mixture is placed in a mold and pressed into blocks for carbonization to obtain the carbonized product. (6) The carbonized product is mixed evenly with a conductive agent, an electrode binder and an organic solvent to obtain a slurry; (7) The slurry is coated on the surface of nickel foam and dried to obtain electrode material.

2. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The sludge is dehydrated to a moisture content of 60-70% in step (1), the drying temperature is 80-100℃ and the drying time is 20-36h, the pyrolysis temperature is 400-800℃ and the pulverized sludge is passed through an 80-150 mesh sieve in step (1).

3. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The concentration of the yttrium trichloride solution in step (2) is 0.002 mol / L-0.01 mol / L; the solid-liquid ratio of the sludge-based biochar powder and the yttrium trichloride solution in step (2) is 1-2:

10.

4. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The drying temperature in step (3) is 100-120℃.

5. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The mass-to-volume ratio of Fe3O4 powder to anhydrous ethanol in step (4) is 1-3:100; the amount of bis[3-(triethoxysilyl)propyl]amine added in step (4) is 0.5%-1.0% of the mass of anhydrous ethanol; the reaction temperature in step (4) is 60-85℃, and the reaction time is 10-20h.

6. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The mass ratio of the modified sludge-based biochar powder to the modified Fe3O4 powder in step (5) is 100:0.1-0.5; the carbonization temperature in step (5) is 1100-1550℃ and the carbonization time is 0.5-1.5h.

7. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The mass ratio of the carbonized product, conductive agent, and electrode binder in step (6) is 8-10:1-3:2-5.

8. The method for preparing the iron-doped sludge-based biochar supported electrode material according to claim 1, characterized in that, The drying process in step (7) includes: drying at 70-80℃ for 8-15 hours, followed by heat treatment at 450-600℃ for 3-5 hours.

9. The iron-doped sludge-based biochar supported electrode material prepared by the method according to any one of claims 1-8.

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