Multi-level micro-nano structured dense electrode fabric, method of making and electrochemical device

Abstract

The application discloses a multi-layer micro-nano dense electrode fabric, a manufacturing method thereof and an electrochemical device. The application uses electrostatic spinning and liquid phase coating method to manufacture multi-layer micro-nano structure on the surface of carbon nanomaterial conductive fiber, and uses weaving method to prepare the dense arrangement alternating electrode fabric. The fabric has high specific surface area, and the thickness of the fabric is not more than 0.1 mm. The fabric is loaded with nanoparticle electrochemical oxidation catalyst, and is used for electrolytic wastewater treatment. The wastewater treatment device has the characteristics of high water flux, low energy consumption, low cost, bending resistance and rubbing resistance, and is suitable for various liquid phase electrolytic water purification devices, indoor gas pollutant elimination and infectious disease pathogen inactivation. The technology meets the wide market demand.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical redox reaction materials and devices, and specifically relates to a multi-layered micro-nano structured dense electrode fabric, its manufacturing method, and an electrochemical device. Background Technology

[0002] Improving technologies for eliminating pollutants such as industrial wastewater and exhaust gases is crucial for green development, establishing environmentally friendly manufacturing, and promoting energy conservation and carbon reduction for long-term sustainable industrial development. Currently, industrial wastewater treatment often utilizes plate-type electrochemical oxidation reactors, which consist of alternating stainless steel and aluminum plates. Wastewater flows laminarly between the positive and negative metal electrodes, with an electric field applied perpendicular to the flow direction. The pollutants in the water are decomposed and degraded by the electric current, achieving pollutant elimination. However, this method suffers from drawbacks such as low degradation rate and low cost.

[0003] To improve degradation rates, existing technologies have designed various catalysts for different electrochemical reactions. To enhance the reaction efficiency of these catalysts, they are loaded onto the surface of electrodes with high specific surface areas, resulting in a large contact area between the catalyst and the reactants. This increases the efficiency of the catalytic reaction and improves the amount of pollutants treated per unit time, per unit energy consumption, and per unit electrode mass.

[0004] Fabric-based flexible electrodes offer unique advantages for fabricating low-cost, high-throughput, complex-shaped, and large-size environmental treatment reactors. Carbon-based materials possess corrosion resistance, and fabric electrodes made from carbon-based materials exhibit significant advantages over metal electrodes in terms of corrosion resistance and bending resistance. Currently, the only carbon-based fiber material suitable for spinning is carbon fiber filament, but carbon fiber is costly and its weaving performance is far inferior to that of organic polymer fibers. Summary of the Invention

[0005] Purpose of the invention: This invention provides a multi-layered micro / nano three-dimensional structured dense electrode fabric, its preparation method, and an electrochemical device. The fabric of this invention is woven from conductive fibers with multi-layered micro / nano structures on its surface. The catalyst loaded on its high specific surface area has a much higher electrochemical catalytic efficiency than that of a smooth surface.

[0006] To achieve the above objectives, the present invention adopts the following technical approach:

[0007] A multi-layered micro / nano three-dimensional dense electrode fabric includes conductive warp yarns and weft yarns. The conductive warp yarns are organic conductive fibers, and the weft yarns are insulating fibers. Insulating warp yarns are arranged between adjacent conductive warp yarns. Adjacent conductive warp yarns are connected by different current collectors in the transverse direction. Adjacent current collectors are connected to the positive and negative terminals of the power supply, respectively. After the conductive warp yarns and current collectors are cured, they are encapsulated with an insulating coating to obtain the dense electrode fabric.

[0008] Furthermore, the surface of the organic conductive fiber is covered with nanofibers by electrospinning. The nanofibers are organic fibers mixed with nano carbon black, with a diameter of less than 200 nm. The mixing ratio of nano carbon black to organic matter in the organic fibers is no more than 10% wt. The organic matter is any one of polyacrylonitrile, polyvinylidene fluoride, polyamide, and polystyrene.

[0009] Furthermore, the organic conductive fiber is a monofilament prepared by a multilayer coating method on the surface of a polymer matrix, consisting of carbon nanotubes or graphene or a mixture of the two, and alternating layers of carbon black / polyurethane slurry, with a diameter of less than 50 μm and a resistivity of no more than 1 kΩ / cm.

[0010] Furthermore, the warp yarn refers to a yarn composed of multiple monofilaments, which is made by coating a layer of single-walled carbon nanotubes and nanoparticle catalyst mixture with a liquid phase coating method after electrospinning and then spinning it.

[0011] Furthermore, the nanoparticle catalyst is one or a combination of Co, Co3O4, Ni / MnO, TiO2, ZnO, etc., and its mass ratio with single-walled carbon nanotubes is not greater than 50%wt, and the average particle diameter is not greater than 10nm.

[0012] Furthermore, the current collector is a flexible current collector, which is a polymer film with a thickness of no more than 0.1 mm, one surface coated with aluminum foil, the other surface insulated, and a width of 1 to 5 mm.

[0013] Furthermore, the warp yarn is composed of multiple single conductive fibers whose surfaces are covered with nanofibers. The conductive fibers that form the positive or negative electrode can be designed to be covered with nanoparticles loaded with different nanoparticles or not covered with nanofibers.

[0014] This invention also provides a method for manufacturing a multi-layered micro / nano three-dimensional dense electrode fabric, comprising the following steps: organic conductive fiber bundles coated with carbon nanotubes or graphene or a mixture thereof are woven on a loom into a fabric with a certain period, the period being conductive warp, insulating warp, conductive warp, insulating warp, forming a large-area fabric with insulating warp separating two conductive warp yarns at a certain interval; positive and negative electrodes are connected to the two conductive warp yarns to form an electrochemical dense electrode fabric. Since the electrode spacing can be precisely controlled by the weaving process, and the minimum spacing can be less than 1 mm, the fiber electrode has a much higher specific surface area than the planar electrode. Therefore, the dense electrode fabric has a much higher electrochemical reaction efficiency than the planar parallel electrode.

[0015] Furthermore, the organic conductive fiber is made by coating polymer conductive fibers with single-walled carbon nanotubes, graphene, or a mixture of both using a coating method. The number of coating layers can reach up to 20 layers, with a thickness not exceeding 2 micrometers. Interlayer coatings are made of nano-carbon powder mixed with water-based polyurethane slurry to form an adhesive layer. The organic fiber can be prepared using the method provided in Chinese Invention Patent: Highly Conductive Organic Fibers, Conductive Yarn, and Conductive Fiber Structures and Preparation Methods (Publication No. CN113322670 A).

[0016] Furthermore, organic conductive fiber monofilaments are arranged in parallel at a spacing of 2 mm to form a single-layer structure. Through feeding, guiding, and winding, 50 to 100 monofilaments pass under the electrospinning needle at a speed of 0.5 to 5 cm per second. After a certain distance, the electrospinning needle is set under the parallel fibers. 1 to 5 independent electrospinning needles with liquid supply are set on each side. A DC high voltage is applied between the organic conductive fiber and the electrospinning needle, with the positive electrode applied to the electrospinning needle. Electrospinning solution is injected into the electrospinning needle at a certain flow rate. The electrospinning needle scans left and right at a constant speed above the parallel fibers, and the formed nano-electrospun fibers uniformly cover the surface of the organic conductive fiber.

[0017] Furthermore, the spinning solution is a 5-10% wt. polyacrylonitrile DMF solution, with nano carbon black added, the carbon black being 3-10% wt. in the polyacrylonitrile.

[0018] Further, catalyst nanoparticles are added to a 0.1–0.5% wt. aqueous solution of single-walled carbon nanotubes to form a monodisperse solution. The catalyst can be any one of Co, Co3O4, Ni / MnO, ZnO, TiO2, or any nanoparticles with electrochemical oxidation catalytic activity. The nanoparticles are mixed with the carbon nanotube solution at a mass ratio of 2–10:1, and after ultrasonic dispersion, a solution is formed. The solution is then uniformly coated onto the surface of an organic conductive fiber monofilament covered by electrospinning using a coating method.

[0019] Furthermore, the organic conductive fibers are combined into bundles using a yarn-doping process. Each bundle consists of 1 to 5 monofilaments. The conductive bundles and insulating yarns of the same denier are then combined into warp yarns on a loom using a warping process. The width of the warp yarns can be designed. The conductive bundles and insulating yarns are arranged periodically. The distance between the conductive bundles is determined by the number of insulating yarns and can be designed between 0.5 mm and 2 mm.

[0020] Furthermore, the weft yarns are woven from insulating yarns of the same or different denier using a plain weave process. A current collector electrode is set every 10 to 20 cm. This electrode is a flat yarn with a width of 3 to 8 mm, and one side is covered with metal foil. The current collector electrode is a conductive warp yarn that is alternately contacted on the upper and lower surfaces of the weft yarn. The conductive layer on the upper surface of the first weft-inserted current collector flat electrode contacts the odd-numbered conductive warp yarns, the conductive layer on the lower surface of the second weft-inserted current collector flat electrode contacts the even-numbered conductive warp yarns, and so on, forming an alternating woven warp fiber yarn electrode.

[0021] Furthermore, conductive carbon paste is used to fix the conductive warp yarns to the flat electrodes using a printing method, and then an insulating polymer paste is used for encapsulation to form stable contact and insulation.

[0022] Furthermore, DC voltage and grounding are alternately applied to the large-area fabric electrode collector after weaving, forming dense electrochemical planar units. Several planar units are stacked to form an electrochemical device. The stacking spacing needs to be designed according to the specific reactor requirements (water treatment rate, flow rate, pressure, power consumption), and the stacking spacing is 0.5 to 5 cm.

[0023] When used for wastewater treatment via electrochemical oxidation, the aforementioned fabric is fixed to an insulating frame. Multiple fabric planes are stacked at a designable spacing. All positive electrodes are connected to the positive terminal of a power supply, and the grounding electrode is connected to the ground. The stacked fabric is then fixed in a water treatment container. Water flows perpendicularly through the multi-layered, densely packed fabric electrode array at a designable flow rate. Direct current is input, and purified water is obtained at the outlet of the water treatment container. The voltage applied to different layers can be the same or different, and the voltage must be direct current and must not exceed the liquid breakdown voltage.

[0024] When used for indoor air purification, the aforementioned fabric is made into a single-layer wall covering or curtain. The positive and negative electrodes are made of high-conductivity conductive fiber bundles. All positive and negative electrodes are connected to the terminal block. A DC or AC power supply is then applied to the terminal block to remove pollutants from the air or generate negative oxygen ions, thus purifying the indoor air. The voltage applied to different layers can be the same or different, and can be DC or AC, but the voltage must not exceed the gas breakdown voltage.

[0025] Beneficial effects: This invention utilizes a coating method to coat the surface of organic fibers with carbon-based nanomaterials to form a uniform conductive coating. The fibers have good weaving properties and are ideal materials for preparing low-cost flexible fabric electrodes.

[0026] Electrospinning can stably prepare large-area nano-organic fibers. This invention mixes conductive nanoparticles and electrochemical / photoelectrochemical catalytic nanoparticles with organic polymers, and then uses electrospinning to spray submicron conductive organic fibers loaded with nanoparticles onto the surface of micron-scale conductive fibers, forming a three-dimensional, multi-scale, high specific surface area composite fiber structure. This invention creatively fabricates these conductive fibers into yarns, and by designing weaving conditions, produces periodically alternating positive and negative electrode fabrics. The distance between the positive and negative electrodes is adjustable by setting the number of insulating warp yarns, and the minimum distance can be less than 1 mm. This enables the efficient preparation of high-electrode-density, flexible, low-cost, dense electrode materials using high specific surface area fibers, providing a basic unit for the design and manufacture of novel electrochemical devices.

[0027] This invention utilizes electrospinning and liquid-phase coating methods to fabricate multi-layered micro / nano structures on the surface of conductive carbon nanomaterial fibers. These conductive fibers are then used to weave densely packed alternating electrode fabrics. These fabrics possess a high specific surface area, a thickness not exceeding 0.1 mm, and are loaded with nanoparticle electrochemical oxidation catalysts. They feature high water flux, low energy consumption, low cost, and resistance to bending and rubbing, making them suitable for various liquid-phase electrolytic water purification devices. They are also suitable for indoor gaseous pollutant removal and infectious disease pathogen inactivation, meeting a wide range of market demands. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a dense electrode structure.

[0029] Figure 2 This is a schematic diagram illustrating the principle of electrospinning and depositing nanofibers on the surface of conductive fibers.

[0030] Figure 3 Scanning electron microscope image of nanofibers deposited on the surface of conductive fibers.

[0031] Figure 4 A schematic diagram illustrating the principle of using dense electrode fabric for wastewater treatment.

[0032] Figure 5 A schematic diagram illustrating the principle of using dense electrode fabric for indoor air pollutant removal. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the present invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and substance of the invention are within the scope of the present invention. Experimental methods and reagents not specifically described in the embodiments are performed according to conventional conditions in the art.

[0034] Example 1:

[0035] Step 1: Pass the 20D1F continuous nylon filament continuously through three pools of single-walled carbon nanotube slurry (0.2% wt aqueous solution, Chengdu Times Nanomaterials Co., Ltd.) and one pool of nano carbon black / waterborne polyurethane slurry (Cabot nano carbon black, 5% wt in polyurethane, and 40% wt solid content in waterborne polyurethane). After passing through one pool, pass through an electric heating drying tube at a temperature of 100-120℃. After passing through a total of six pools of carbon nanotube slurry and two pools of carbon black slurry, pass through one or two more pools of carbon nanotube slurry, dry and wind up to obtain conductive fiber with a resistivity of no more than 5kΩ / cm.

[0036] Step 2: Arrange the above conductive fibers in parallel at 1mm intervals. Guide 100 fibers into the electrospinning chamber using guide wheels. The fiber array is arranged in a horizontal or vertical direction. The guide wheels are spaced at least 2m apart. The guide wheels are made of metal and the bottom of the wheel rim is covered with conductive rubber. The guide wheels are grounded.

[0037] Step 3: Place six electrospinning needles with an aperture of 0.2 mm in the electrospinning chamber at a spacing of 25 cm. Place three needles above or to the right of the fiber array, and three needles below or to the left of the fiber array. The distance between the three electrospinning needles and the fiber array is 10-15 cm. Place the three needles on the actuation stage and move them back and forth in a direction perpendicular to and parallel to the fiber array. The three needles are evenly staggered to ensure that the electrospinned nanofibers are evenly covered on the surface of the conductive fibers. The three needles are set up in a similar manner in the opposite direction.

[0038] Step 4: The conductive fibers are pulled by the take-up wheel, and all conductive fibers pass through the electrospinning chamber at the same uniform speed of 5-10 cm. A DC voltage of 5-20 kV is applied to the electrospinning needle. The electrospinning solution is injected into the electrospinning needle tube. The electrospinning solution is a polyacrylonitrile / DMF solution with a molecular weight of 150 kDa and a concentration of 9% wt. 5% wt of nano-conductive carbon black is added to the polyacrylonitrile. The electrospinning solution is injected at a rate of 1 ml / h. The electrospinning needle scans and spins on the surface of the conductive fiber array at a scanning speed of 3-5 cm.

[0039] Step 5: Coat the conductive fibers coated with nanofibers with single-walled carbon nanotubes and catalyst nanoparticles under conditions similar to those in Step 1. The catalyst is an aqueous solution of Co nanoparticles with an average diameter of 6 nanometers and a concentration of 0.1 mg / ml, which is mixed with an aqueous solution of 0.2 mg / ml carbon nanotubes. After the conductive fibers pass through 1 to 5 liquid pools, they are dried and wound up.

[0040] Step Six: Combine the above-mentioned conductive fibers into bundles of three monofilaments using a doubling technique. Weave this bundle into a dense electrode fabric on a double-shuttle loom. The conductive bundles are used as warp yarns, alternating between conductive and insulating warp yarns. Three to five insulating warp yarns (20D9F nylon yarn) are placed between the conductive warp yarns. The weft yarns are also 20D9F nylon yarn, with a weft density of 20-40 yarns per centimeter. Each weft pass is 10-20 cm long. Another shuttle passes a flat current-collecting weft electrode through this bundle. This electrode is a nylon flat filament, 3-5 mm wide, with one surface covered by aluminum foil (1-5 μm thick) and the flat filament being 30-100 μm thick. The upper surface of the flat current-collecting weft electrode contacts the odd-numbered conductive warp yarns, while the lower surface of the other flat current-collecting weft electrode contacts the even-numbered conductive warp yarns. This process is repeated to create a dense electrode fabric of any designed width and length.

[0041] Step 7: Coat the surface of the current collector weft electrode with quick-drying conductive carbon adhesive using screen printing. The carbon adhesive bonds the conductive warp yarns to the conductive layer on the surface of the flat current collector weft electrode. The width of the carbon adhesive is lower than that of the flat current collector weft electrode. After drying, cover the surface of the flat current collector weft electrode with a water-based polyurethane layer with a thickness of 20-50 μm using printing. After drying, roll it up to obtain the finished dense electrode fabric.

[0042] Step 8: Adhere the dense electrode fabric to a fixed frame with a design size smaller than the fabric width. Stack and seal several fixed frames to form an electrochemical reactor. Connect the reactor to the inlet and outlet to form an electrochemical reactor. Connect each layer to the odd-numbered conductive warp electrodes with wires to the positive terminal, and connect each layer to the even-numbered conductive warp electrodes with wires to the negative terminal. Connect the positive and negative electrodes of all stacked layers with separate wires and connect them to a DC power supply. Apply a DC voltage of 5-15V. Pass the wastewater to be treated through the inlet. Determine the flow rate and pressure according to the concentration of pollutants in the wastewater, adjust the voltage, and obtain purified water with removed organic pollutants at the outlet.

[0043] Example 2:

[0044] Step 1: Same as Example 1.

[0045] Step 2, same as in Example 1.

[0046] Step 3: Same as Example 1.

[0047] Step 4: Same as Example 1.

[0048] Step 5: Coat the conductive fibers coated with nanofibers with a few layers of small-diameter mechanically exfoliated graphene and catalyst nanoparticles under conditions similar to those in Step 1. The catalyst is an aqueous solution of TiO2 nanoparticles with an average diameter of 3 nanometers and a concentration of 0.1 mg / ml, which is mixed with an aqueous solution of 0.2 mg / ml carbon nanotubes. After the conductive fibers pass through 1 to 5 liquid pools, they are dried and wound up.

[0049] Step 6: Same as Example 1.

[0050] Step 7: Coat the surface of the current collector weft electrode with quick-drying conductive carbon adhesive using screen printing. The carbon adhesive bonds the conductive warp yarns to the conductive layer on the surface of the flat current collector weft electrode. The width of the carbon adhesive is lower than that of the flat current collector weft electrode. After drying, the fabric is rolled up to become the finished dense electrode fabric.

[0051] Step 8: Adhere the dense electrode fabric to a fixed frame with a design size smaller than the fabric width. Stack and seal several fixed frames to form an electrochemical reactor. Connect the reactor to the inlet and outlet to form an electrochemical reactor. Connect each layer to the odd-numbered conductive warp electrodes with wires to the positive terminal, and connect each layer to the even-numbered conductive warp electrodes with wires to the negative terminal. After connecting the positive and negative electrodes of all stacked layers with separate wires, connect them to a DC power supply and apply a DC voltage of 5-15V. Pass the gas to be treated through the inlet. Determine the flow rate and pressure according to the concentration of gas pollutants, adjust the voltage, and obtain the gas with removed organic pollutants at the outlet.

[0052] Example 3:

[0053] Step 1: Same as Example 1.

[0054] Step 2, same as in Example 1.

[0055] Step 3: Same as Example 1.

[0056] Step 4: Same as Example 1.

[0057] Step 5: Coat the conductive fibers coated with nanofibers with single-walled carbon nanotubes and catalyst nanoparticles under conditions similar to those in Step 1. The catalyst is an aqueous solution of ZnO nanoparticles with an average diameter of 3 nanometers and a concentration of 0.1 mg / ml, which is mixed with an aqueous solution of 2 mg / ml carbon nanotubes. After the conductive fibers pass through 1 to 5 liquid pools, they are dried and wound up.

[0058] Step 6: Same as Example 1.

[0059] Step 7: Same as Example 2.

[0060] Step 8: Connect the odd-numbered conductive warp yarns of the single-layer dense electrode fabric to the positive terminal with a wire, and connect the even-numbered conductive warp yarns of the single-layer dense electrode fabric to the negative terminal with a wire. Connect the positive and negative terminals to an AC power source and adjust the frequency. The dense electrode fabric will generate a high concentration of negative oxygen ions, which will purify the air, increase the indoor negative ion content, and have a health-preserving effect.

Claims

1. A multi-layered micro / nano three-dimensional structured dense electrode fabric, comprising conductive warp yarns and weft yarns, characterized in that, The conductive warp yarn is a yarn made of multiple organic conductive fiber monofilaments. The surface of each organic conductive fiber monofilament is successively covered with a nanofiber layer by electrospinning and a mixture layer of single-walled carbon nanotubes and nanoparticle catalysts by liquid phase coating. The weft yarn is an insulating fiber. Insulating warp yarns are set between adjacent conductive warp yarns. Adjacent conductive warp yarns are connected by different current collectors in the transverse direction. Adjacent current collectors are connected to the positive and negative terminals of the power supply, respectively. After curing, the conductive warp yarns and current collectors are encapsulated with an insulating coating to form a dense electrode fabric. The nanofiber layer is an organic fiber mixed with nano carbon black, with a diameter of less than 200 nm. The mixing ratio of nano carbon black to organic matter in the organic fiber is no more than 10% wt. The organic matter is any one of polyacrylonitrile, polyvinylidene fluoride, polyamide, and polystyrene.

2. The multi-layered micro / nano three-dimensional structured dense electrode fabric according to claim 1, characterized in that, The organic conductive fiber is a monofilament with a diameter of less than 50 μm and a specific resistance of no more than 1 kΩ / cm, prepared by multilayer coating of carbon nanotubes, graphene, or a mixture of the two on the surface of a polymer matrix, and alternately covered with carbon black / polyurethane slurry.

3. The multi-layered micro / nano three-dimensional structured dense electrode fabric according to claim 1, characterized in that, The nanoparticle catalyst is one or a combination of Co, Co3O4, Ni / MnO, TiO2, and ZnO, with a mass ratio to single-walled carbon nanotubes not exceeding 50%wt and an average particle diameter not exceeding 10nm.

4. The multi-layered micro / nano three-dimensional structured dense electrode fabric according to claim 1, characterized in that, The current collector is a flexible current collector, which is a polymer film with a thickness of no more than 0.1 mm, one surface coated with aluminum foil, the other surface insulated, and a width of 1~5 mm.

5. A method for manufacturing the multi-layered micro / nano three-dimensional dense electrode fabric according to any one of claims 1-4, characterized in that, The process includes the following steps: warp yarns are woven in a cycle consisting of conductive warp yarns, insulating warp yarns, conductive warp yarns, and insulating warp yarns; after weft insertion, adjacent conductive warp yarns are connected laterally by different collectors, and adjacent collectors are connected to the positive and negative terminals of the power supply, respectively; after curing, the conductive warp yarns and collectors are encapsulated with an insulating coating to obtain a dense electrode fabric.

6. An electrochemical device, characterized in that, The device is prepared by stacking the dense electrode fabrics as described in any one of claims 1-5 to form an electrochemical device.

7. A reactor for liquid or gas electrochemical catalysis, characterized in that, The electrochemical device described in claim 6 is used.

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