A membrane electrode, device and method

Abstract

This application relates to the technical field of environmental engineering sewage resource utilization, and specifically relates to a membrane electrode, a device and a method. Among them, the membrane electrode includes: a support layer; a plurality of microporous fiber membrane filaments woven into the support layer, and the surfaces of the microporous fiber membrane filaments and the support layer are covered with a conductive material. Among them, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, the wall thickness of the microporous fiber membrane filaments is 10 - 100 μm, and the plurality of microporous fiber membrane filaments are arranged side by side. The membrane electrode provided by this application has a large surface area, fast air mass transfer, and strong water pressure bearing capacity.

Description

Technical Field

[0001] The present application relates to the technical field of environmental engineering sewage resource utilization, and particularly relates to a membrane electrode, a device and a method. Background Art

[0002] With the continuous improvement of the construction level of China's economic society, the utilization efficiency and recovery of basic resources have been increasingly emphasized by people. Among them, the treatment and reuse of sewage are one of the most prominent construction projects. Converting the organic matter in domestic sewage into resources and energy for recovery and utilization is an important development direction for domestic sewage treatment. However, at present, most domestic sewage treatments adopt the traditional activated sludge treatment method, which not only consumes a large amount of electric energy (the electric energy consumed by aeration in the biochemical process accounts for 50% of the total electric energy consumed in sewage treatment), but also converts the organic matter in the sewage into carbon dioxide and directly discharges it, failing to realize the resource utilization of sewage.

[0003] The microbial electrochemical technology is a new and efficient domestic sewage restoration process, which can accelerate the removal efficiency of toxic organic pollutants in domestic sewage sediments, especially has a very significant effect on the decomposition and removal of organic pollutants with high molecular weight, strong toxicity and difficult degradation, so it has received great attention. Moreover, the microbial electrochemical technology can convert sewage organic matter into energy by using microbial processes, realizing sewage resource utilization, reducing the cost of sewage treatment and reducing the emission of greenhouse effect gases (carbon dioxide) in the sewage treatment process.

[0004] The microbial electrochemical technology (Microbial Electrochemical Technology, MET) can use anode microorganisms to metabolize and degrade organic matter and export electrons to the anode. Subsequently, the electrons collected by the anode participate in the cathode reduction reaction through the external circuit to form a current and achieve energy output. Taking acetic acid degradation as an example, organic matter reacts and releases electrons in the anode chamber, while the cathode undergoes an oxygen reduction reaction to consume electrons to complete the circuit. The electrode reactions are as follows:

[0005] Anode: CH3COO - +4H2O→2HCO3 - +9H + +8e

[0006] Cathode: O2+4H + +4e→2H2O

[0007] However, the air cathode used in the above microbial electrochemical device is generally a common carbon cloth air cathode, which has a small surface area per unit volume, a slow air mass transfer rate and a weak bearing capacity for water pressure, restricting the application of the microbial electrochemical device in actual production. Summary of the Invention

[0008] To solve the above problems, embodiments of the present application provide a membrane electrode, a device, and a method. The electrode provided by the present application has a large surface area, fast air mass transfer, and strong water pressure bearing capacity.

[0009] For this reason, the following technical solutions are adopted in the embodiments of the present application:

[0010] In a first aspect, the present application provides a membrane electrode, which includes:

[0011] A support layer;

[0012] A plurality of microporous fiber membrane filaments woven into the support layer, the surfaces of the microporous fiber membrane filaments and the support layer being covered with a conductive material. Among them, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, the wall thickness of the microporous fiber membrane filaments is 10 - 100 μm, and the plurality of microporous fiber membrane filaments are arranged side by side.

[0013] Preferably, the conductive material is a powdered conductor coated with polyvinylidene fluoride; among them, the conductor includes multi-walled carbon nanotubes and / or activated carbon powder; the outer diameter of the multi-walled carbon nanotubes is 20 - 30 nm.

[0014] Preferably, each cubic meter of the membrane electrode is covered with 11.5 g / m 2 Multi-walled carbon nanotubes and 10.5 g / m 2 Activated carbon powder.

[0015] Preferably, the microporous fiber membrane filaments are hollow fiber microporous membranes; the inner diameter of the pore diameter of the microporous fiber membrane filaments is 350 μm, the outer diameter is 450 μm, the wall thickness of the microporous fiber membrane filaments is 50 μm, and the length is 16 - 20 cm.

[0016] Preferably, the hollow fiber microporous membrane is any one of a polypropylene hollow fiber microporous membrane, a polydimethylsiloxane hollow fiber microporous membrane, and a polyvinylidene fluoride membrane.

[0017] Preferably, the number of microporous fiber membrane filaments in the plurality of microporous fiber membrane filaments is not less than 20.

[0018] In a second aspect, the present application provides a method for preparing the above-mentioned membrane electrode, including the following steps:

[0019] (1), Spraying a conductive material onto the surface of the microporous fiber membrane filaments to obtain a microporous membrane covered with a conductive material; among them, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, and the wall thickness of the microporous fiber membrane filaments is 10 - 100 μm;

[0020] (2) Weave the micro-porous membrane covered with the conductive material into the support layer to obtain the membrane electrode precursor;

[0021] (3) Spray the conductive material on both sides of the membrane electrode precursor respectively to obtain the membrane electrode.

[0022] Preferably, the method further includes: dispersing polyvinylidene fluoride powder in a solution according to a ratio of 1:200 wt% to obtain a mixed solution; then, adding powdery conductor to the mixed solution according to a ratio of 1:100 wt% to obtain a composite material mixed solution; wherein, the conductor includes multi-walled carbon nanotubes and / or activated carbon powder; the outer diameter of the multi-walled carbon nanotubes is 20 - 30 nm; the solution is any one of N,N-dimethylformamide, dimethyl sulfoxide or N,N-dimethylacetamide;

[0023] In the step (1), spray the composite material mixed solution on the surface of the micro-porous fiber membrane filaments to obtain a micro-porous membrane precursor covered with the conductive material; dry the micro-porous membrane precursor covered with the conductive material to obtain the micro-porous membrane covered with the conductive material.

[0024] Preferably, in the step (2), immerse the membrane electrode in a 1% polyvinyl alcohol solution, then take it out and crosslink it in glutaraldehyde and hydrochloric acid;

[0025] The step of dispersing polyvinylidene fluoride powder in a solution to obtain a mixed solution includes: dispersing polyvinylidene fluoride powder in a solution and performing ultrasonic treatment to obtain a mixed solution; wherein, the power of the ultrasonic treatment is 40 kHz and the ultrasonic time is 30 minutes.

[0026] In the third aspect, the present application provides a microbial electrochemical device, including: an anode and a cathode, wherein, the cathode is composed of the above-mentioned membrane electrode.

[0027] Compared with the existing carbon cloth-based air cathode, the beneficial effects of the present application are as follows:

[0028] (1) The hollow fiber micro-porous membrane has good permeability. The present application uses multiple hollow fiber micro-porous membranes to make the membrane electrode, which can effectively increase the surface area per unit volume of the membrane electrode, accelerate the gas mass transfer rate, and provide sufficient electron acceptors for the cathode reduction reaction;

[0029] (2) By spraying the conductive material, which includes carbon nanotubes and activated carbon powder, the insulating hollow fiber micro-porous membrane can be modified into an electrode with good conductivity;

[0030] (3) Construct a microscopic water, gas, and solid three-phase interface on the surface of the membrane electrode to promote the reaction between electrons, protons and electron acceptors, and improve the power generation efficiency and the removal efficiency of organic pollutants;

[0031] (4) This application uses a hollow fiber microporous membrane, which can significantly increase the water pressure bearing capacity of the cathode (≤0.3 Mpa). The fiber microporous membrane is woven on a stainless steel mesh to further increase the conductivity of the hollow fiber microporous membrane and improve the mechanical strength of the entire electrode.

[0032] (5) The product obtained by crosslinking polyvinyl alcohol and glutaraldehyde (pentanedial) under acidic conditions is coated on the surface of the membrane electrode, which can further improve the stability, conductivity, and structural strength of the membrane electrode.

[0033] In summary, applying the hollow fiber microporous membrane electrode of this application to a microbial electrochemical device can effectively overcome problems such as the small surface area per unit volume of a common carbon cloth air cathode, slow air mass transfer rate, and weak water pressure bearing capacity, which helps to improve the removal efficiency of pollutants and power generation efficiency in sewage, and can further promote the application of electrochemical technology in sewage treatment and sewage resource utilization. Description of the Drawings

[0034] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 Shows a method for preparing an electrode based on a hollow fiber microporous membrane provided in Embodiment 1 of this application:

[0036] Among them, (a) untreated polypropylene hollow fiber microporous membrane;

[0037] (b) Polypropylene hollow fiber microporous membrane sprayed with multi-walled carbon nanotubes and activated carbon powder;

[0038] (c) Weaving the treated hollow fiber microporous membrane on a stainless steel mesh and spraying a composite conductive material (multi-walled carbon nanotubes, activated carbon powder) on this structure;

[0039] (d) Using a scanning electron microscope to observe the microscopic structure of the surface of the untreated polypropylene hollow fiber microporous membrane;

[0040] (e) Using a scanning electron microscope to observe the microscopic structure of the surface of the polypropylene hollow fiber microporous membrane sprayed with multi-walled carbon nanotubes and activated carbon powder;

[0041] (f) From left to right are the changes in the resistance of the untreated single polypropylene hollow fiber microporous membrane, the single polypropylene hollow fiber microporous membrane sprayed with composite conductive material, the multiple polypropylene hollow fiber microporous membranes sprayed with composite conductive material, and the membrane electrode woven on the stainless steel mesh.

[0042] Figures 2(a) and 2(b) show the power generation performance of the microbial electrochemical device loaded with the membrane electrode provided in Embodiment 1 of the present application;

[0043] Specifically: Figure 2(a) shows the power generation efficiency (current) during the startup stage (MEC), the membrane electrode loaded with the sprayed composite conductive material, and the membrane electrode woven on the stainless steel mesh;

[0044] Figure 2(b) shows the current generated by the membrane electrode wrapped with polyvinyl alcohol during the startup stage (MEC).

[0045] Figure 3 Shows the Fourier transform infrared spectrum of the surface of the membrane electrode in Embodiment 1 of the present application. It can be seen that after being wrapped with polyvinyl alcohol and subsequent cross-linking treatment, the characteristic peak of the functional group -O-H on the surface of the membrane electrode decreases, and at the same time, -C-O-C appears, indicating that the wrapping with polyvinyl alcohol and subsequent cross-linking treatment are successful. Figure 3 It can be seen that after being wrapped with polyvinyl alcohol and subsequent cross-linking treatment, the characteristic peak of the functional group -O-H on the surface of the membrane electrode decreases, and at the same time, -C-O-C appears, indicating that the wrapping with polyvinyl alcohol and subsequent cross-linking treatment are successful. Detailed implementation mode

[0046] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application.

[0047] It should be understood that the protection scope of the present application is not limited to the specific specific implementation modes described below; it should also be understood that the terms used in the embodiments of the present application are for the purpose of describing specific specific implementation modes, rather than for limiting the protection scope of the present application; in the specification and claims of the present application, unless otherwise clearly indicated in the text, the singular forms "a", "an", and "the" include the plural forms.

[0048] When an embodiment gives a numerical range, it should be understood that unless otherwise specified in the present application, any value at both ends of each numerical range and any value between the two ends can be selected. Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the art of this technology. In addition to the specific methods, equipment, and materials used in the embodiments, according to the knowledge of those skilled in the art of this technology and the description of the present application, any methods, equipment, and materials similar to or equivalent to the methods, equipment, and materials described in the embodiments of the present application can also be used to implement the present application.

[0049] It should be specifically noted that: unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this application belongs. The experimental reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the raw materials, instruments, and equipment used in the following embodiments can all be obtained through market purchases or by existing methods; the dosages of the experimental reagents are the dosages of the reagents in conventional experimental operations unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0050] Unless otherwise stated, the following terms used in the specification and claims have the following meanings.

[0051] As used in this application, "room temperature" has the meaning well-known in the art and generally refers to 24 - 28 °C.

[0052] In order to solve the problems of the existing carbon cloth air cathode, such as small surface area per unit volume, slow air mass transfer rate, and weak water pressure bearing capacity, this application designs a membrane electrode and assembles the membrane electrode into a microbial electrochemical device for sewage resource utilization.

[0053] This application is realized through the following technical solutions: First, a conductive material (carbon nanotubes, activated carbon powder) is sprayed on the surface of a hollow fiber microporous membrane to modify the hollow fiber microporous membrane to increase its conductivity. Then, the hollow fiber microporous membrane is woven and loaded on a stainless steel mesh and the conductive material is sprayed again to form a membrane electrode with good electrical conductivity and high mechanical strength.

[0054] Specifically, in a first aspect, this application provides a membrane electrode, and the membrane electrode includes:

[0055] A support layer;

[0056] Multiple microporous fiber membrane filaments woven into the support layer, and the surfaces of the microporous fiber membrane filaments and the support layer are covered with a conductive material. Among them, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, the wall thickness of the microporous fiber membrane filaments is 10 - 100 μm, and the multiple microporous fiber membrane filaments are arranged side by side.

[0057] In a specific embodiment, the conductive material is a powdered conductor coated with polyvinylidene fluoride; among them, the conductor includes multi-walled carbon nanotubes and / or activated carbon powder; the outer diameter of the multi-walled carbon nanotubes is 20 - 30 nm.

[0058] In this embodiment, polyvinylidene fluoride acts as a binder to adhere the conductive material to the microporous fiber membrane filaments, so that the binding property between the conductive material and the hollow fiber microporous membrane is better, effectively extending the service life of the membrane electrode.

[0059] In some embodiments, the conductor can also be graphene, carbon black, or carbon fiber.

[0060] Compared with graphene, carbon black, and carbon fiber, carbon nanotubes and activated carbon powder can not only modify the insulating hollow fiber microporous membrane into an electrode with good conductivity, but also act as a catalyst to catalyze the oxygen reduction reaction at the air cathode where the electrode is located, reducing energy consumption.

[0061] In a specific embodiment, each cubic meter of the hollow fiber microporous membrane is covered with 2.88 g / m 2 multi-walled carbon nanotubes and 2.88 g / m 2 activated carbon powder.

[0062] In this embodiment, when the spraying amount of the conductive material is controlled within the above range, the composite conductive material can be evenly sprayed on the surface of the hollow fiber microporous membrane, with better bonding between the two, reducing the possibility of the conductive material peeling off the hollow fiber microporous membrane, and prolonging the service life of the membrane electrode.

[0063] In a specific embodiment, each cubic meter of the membrane electrode is covered with 11.5 g / m 2 multi-walled carbon nanotubes and 10.5 g / m 2 activated carbon powder.

[0064] When the spraying amount of the conductive material is less than the above range, the conductivity of the prepared membrane electrode is poor; when the spraying amount of the conductive material is greater than the above range, the service life of the prepared membrane electrode is poor, and it has a certain negative impact on the power generation efficiency of the membrane electrode and the removal efficiency of organic pollutants.

[0065] In a specific embodiment, the microporous fiber membrane filament is a hollow fiber microporous membrane; the inner diameter of the pore of the microporous fiber membrane filament is 350 μm, the outer diameter is 450 μm, the wall thickness of the microporous fiber membrane filament is 50 μm, and the length is 16 - 20 cm.

[0066] In this embodiment, the hollow fiber microporous membrane has good permeability. In this application, multiple hollow fiber microporous membranes are used as electrodes, which can effectively increase the surface area per unit volume of the electrode, accelerate the gas mass transfer rate, provide sufficient electron acceptors for the cathode reduction reaction, and using the hollow fiber microporous membrane with the above size parameters in this application can significantly increase the water pressure bearing capacity of the cathode (≤0.3 Mpa). After weaving the hollow fiber microporous membrane on a stainless steel mesh, the conductivity of the hollow fiber microporous membrane can be further increased, and the mechanical strength of the entire electrode can be improved.

[0067] In a specific embodiment, the hollow fiber microporous membrane is any one of a polypropylene hollow fiber microporous membrane, a polydimethylsiloxane hollow fiber microporous membrane, and a polyvinylidene fluoride membrane.

[0068] The hollow fiber microporous membranes of the above materials have the advantages of better mechanical strength, resistance to strong acids and alkalis, resistance to bacterial corrosion, good heat resistance, non-polar surface, strong anti-pollution ability, uniform micropores, and large unit surface area.

[0069] In a specific embodiment, the number of the microporous fiber membrane filaments among the plurality of microporous fiber membrane filaments is not less than 20.

[0070] In this embodiment, by using the above number of microporous fiber membrane filaments, the resistance of the membrane electrode can be effectively reduced, and thus the conductivity of the membrane electrode can be effectively improved.

[0071] In a second aspect, the present application provides a method for preparing the above-mentioned membrane electrode, including the following steps:

[0072] (1) Spraying a conductive material onto the surface of the microporous fiber membrane filaments to obtain a microporous membrane covered with the conductive material; wherein, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, and the wall thickness of the microporous fiber membrane filaments is 10 - 100 μm;

[0073] (2) Weaving the microporous membrane covered with the conductive material onto a support layer to obtain a membrane electrode precursor;

[0074] (3) Spraying a conductive material on both sides of the membrane electrode precursor to obtain the membrane electrode.

[0075] In a specific embodiment, the method further includes: dispersing polyvinylidene fluoride powder in a solution at a ratio of 1:200 wt% to obtain a mixed solution; then, adding powdery conductor to the mixed solution at a ratio of 1:100 wt% to obtain a composite material mixed solution; wherein, the conductor includes multi-walled carbon nanotubes and / or activated carbon powder; the outer diameter of the multi-walled carbon nanotubes is 20 - 30 nm; the solution is any one of N,N-dimethylformamide, dimethyl sulfoxide, or N,N-dimethylacetamide;

[0076] In the step (1), spraying the composite material mixed solution onto the surface of the microporous fiber membrane filaments to obtain a microporous membrane precursor covered with the conductive material; drying the microporous membrane precursor covered with the conductive material to obtain the microporous membrane covered with the conductive material.

[0077] In a specific embodiment, in the step (2), immersing the membrane electrode in a 1% polyvinyl alcohol solution, then taking it out and crosslinking it in glutaraldehyde and hydrochloric acid;

[0078] Dispersing the polyvinylidene fluoride powder in a solution to obtain a mixed solution includes: dispersing the polyvinylidene fluoride powder in a solution and performing ultrasonic treatment to obtain a mixed solution; wherein, the power of the ultrasonic treatment is 40 kHz and the ultrasonic time is 30 minutes.

[0079] The product obtained by cross-linking polyvinyl alcohol and glutaraldehyde under acidic conditions is coated on the surface of the membrane electrode, which can further improve the stability, conductivity and structural strength of the membrane electrode. At the same time, ultrasonic dispersion can make the dispersion of polyvinylidene fluoride powder in the solution more uniform. At the same time, using polyvinylidene fluoride with the above ratio can make the combination between the conductive material and the microporous fiber membrane filaments more stable.

[0080] In a third aspect, the present application provides a microbial electrochemical device, including: an anode and a cathode, wherein, the cathode is composed of the above-mentioned membrane electrode.

[0081] When the membrane electrode of the present application is used for the cathode of a microbial electrochemical device to purify domestic sewage, a microscopic water, gas, and solid three-phase interface can be constructed on the surface of the membrane electrode, promoting the reaction between electrons, protons and electron acceptors, and improving the power generation efficiency and the removal efficiency of organic pollutants.

[0082] To more fully understand the present application, the following examples are given. These examples are used to specifically illustrate the implementation scheme of the present application and should not be construed as limiting the scope of the present application in any way.

[0083] Example

[0084] Example 1

[0085] <Preparation of a hollow fiber microporous membrane electrode>

[0086] A method for preparing a hollow fiber microporous membrane electrode includes the following steps:

[0087] Select a polypropylene hollow fiber microporous membrane with an inner diameter of 350 μm, an outer diameter of 450 μm, a wall thickness of 50 μm, and a length of 16 - 20 cm, as shown in Figure 1 (a).

[0088] Take polyvinylidene fluoride powder with a molecular weight of 600,000 and add it to N,N-dimethylformamide at a ratio of 1:200 wt%. Under room temperature conditions (24 - 28 °C) and a power of 40 kHz, perform ultrasonic dispersion for 30 minutes to uniformly disperse it in N,N-dimethylformamide to form a mixed solution.

[0089] According to the surface area of the polypropylene hollow fiber microporous membrane, the composite conductive material is added at 5.76 g / m 2, and added to the mixed solution at a ratio of 1:100 wt%, and after all components were uniformly dispersed, a composite material mixed solution was formed. The composite material mixed solution was uniformly sprayed on the surface of the polypropylene hollow fiber microporous membrane using a high-pressure sprayer, as shown in Figure 1 (b), and then dried in an oven at 50 °C for 12 h. Among them, the nozzle diameter of the high-pressure sprayer was 1 mm, and the working pressure was 0.2 - 0.3 Bar. The composite material mixed solution was loaded into the sprayer of the high-pressure spray gun, and the high-pressure spray gun was held so that the spraying direction was perpendicular to the surface of the polypropylene hollow fiber microporous membrane. The high-pressure spray gun was opened, and the high-pressure spray gun was moved uniformly so that the composite material was evenly covered on the surface of the polypropylene hollow fiber microporous membrane.

[0090] Among them, the composite conductive material was multi-walled carbon nanotubes and activated carbon, and each cubic meter of the polypropylene hollow fiber microporous membrane was covered with 2.88 g / m 2 multi-walled carbon nanotubes and 2.88 g / m 2 activated carbon.

[0091] The hollow fiber microporous membrane sprayed with the composite conductive material was woven into 304 stainless steel, as shown in Figure 1 (c). According to the above operation, polyvinylidene fluoride powder with a molecular weight of 600,000 was added to the solvent at a ratio of 1:200 wt%, and under room temperature conditions (24 - 28 °C) and a power of 40 kHz, it was ultrasonically dispersed for 30 minutes to be uniformly dispersed in the solvent to form a mixed solution.

[0092] According to the surface area of the polypropylene hollow fiber microporous membrane, the composite conductive material was added to the mixed solution at 22 g / m 2 , and added to the mixed solution at a ratio of 1:100 wt%. After all components were uniformly dispersed, a composite material mixed solution was formed. Then, the composite material mixed solution was uniformly sprayed on the surface of the hollow fiber microporous membrane and the stainless steel mesh in the same manner using a high-pressure sprayer again, and then dried in an oven at 50 °C for 12 h to form a membrane electrode.

[0093] Among them, the composite conductive material was multi-walled carbon nanotubes and activated carbon, and the addition amounts of carbon nanotubes and activated carbon powder were 11.5 g / m 2 and 10.5 g / m 2 .

[0094] Finally, to prevent the composite material from falling off the membrane electrode, the membrane electrode was immersed in a 1% polyvinyl alcohol solution, and then taken out and placed in 1 g / L glutaraldehyde (glutaraldehyde) and 0.37 g / L hydrochloric acid, and cross-linked at 80 °C for 4 hours to obtain a cross-linked membrane electrode. As shown in Figure 3 , for the cross-linked membrane electrode, the -O-H characteristic peak decreased, and at the same time, -C-O-C- appeared, indicating that the polyvinyl alcohol wrapping and subsequent cross-linking treatment were successful.

[0095] After testing, the water pressure bearing capacity of the hollow fiber microporous membrane electrode prepared in Example 1 is ≤0.3 Mpa.

[0096] Example 2

[0097] <Measurement of the conductivity of the membrane electrode>

[0098] After the polypropylene hollow microporous membrane is spray-coated with a conductive material, its conductivity is significantly enhanced. As Figure 1 (f) shows, the conductivity of the untreated polypropylene hollow fiber microporous membrane is poor, and the resistance is 1x10 16 Ω. After spraying the conductive material, the resistance of a single membrane electrode drops to 3x10 4 Ω. When 20 membrane electrodes are connected in parallel, the resistance is further reduced to 700 Ω. Then, after the hollow fiber microporous membrane is woven on the stainless steel mesh, the resistance drops to 50 Ω. The above results show that after the above treatment, the polypropylene hollow fiber microporous membrane with poor conductivity is successfully modified into a membrane electrode with certain conductivity.

[0099] Example 3

[0100] <Application of the membrane electrode in a microbial electrochemical device>

[0101] Install the membrane electrode in a single-chamber microbial electrochemical device. The cathode part uses the treated hollow fiber microporous membrane electrode. One end of this membrane electrode is connected to an air pump, and the other end is connected to the outside, as Figure 1 (b) shows. The anode part uses 4 carbon brushes with a length of 5 cm and a diameter of 2.5 cm. After the carbon brushes are heat-treated (30 mins @ 400 °C), they are assembled into the single-chamber microbial electrochemical device. The cathode uses the above-treated membrane electrode, and a 2.2 Ω external resistor is used to connect the cathode and the anode. The inoculum for starting the single-chamber microbial electrochemical device is the effluent from the primary sedimentation tank of a municipal sewage treatment plant, and an external voltage of 0.8 v is applied to accelerate the start-up of the microbial electrochemical device.

[0102] As shown in Figure 2(a), during the start-up stage (MEC), a stainless steel mesh is used as the cathode, and the peak current reaches 3 mA. After replacing the stainless steel mesh cathode with a membrane electrode only spray-coated with a conductive material, the current drops to 1 mA; and then, after replacing it with a membrane electrode woven on the stainless steel mesh, the peak current reaches 6 mA. To test the embedding effect of polyvinyl alcohol on the conductive material, the microbial electrochemical device is restarted. During the start-up stage (MEC), as shown in Figure 2(b), the peak voltage of two cycles is stable at 0.5 - 0.7 mA. After replacing the stainless steel mesh cathode with a membrane electrode, the peak current reaches 1.7 mA. The above data show that the membrane electrode prepared in this application can significantly improve the power generation efficiency of the microbial electrochemical device.

[0103] In the above specific embodiments, the purpose, technical solution and beneficial effects of the present application have been further described in detail. It should be understood that the above are only specific embodiments of the present application and are not used to limit the protection scope of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A membrane electrode, characterized in that, The membrane electrode includes: A support layer; A plurality of microporous fiber membrane filaments woven into the support layer, the surfaces of the microporous fiber membrane filaments and the support layer being covered with a conductive material. Among them, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, the wall thickness of the microporous fiber membrane filaments is 10 - 100 μm, and the plurality of microporous fiber membrane filaments are arranged side by side; the conductive material is a powdered conductor coated with polyvinylidene fluoride; among them, the conductor includes multi-walled carbon nanotubes and / or activated carbon powder; the outer diameter of the multi-walled carbon nanotubes is 20 - 30 nm.

2. The membrane electrode according to claim 1, wherein Each cubic meter of the membrane electrode is covered with 11.5 g / m 2 multi-walled carbon nanotubes and 10.5 g / m 2 activated carbon powder.

3. The membrane electrode according to claim 1, wherein The microporous fiber membrane filaments are hollow fiber microporous membranes; the inner diameter of the pore diameter of the microporous fiber membrane filaments is 350 μm, the outer diameter is 450 μm, the wall thickness of the microporous fiber membrane filaments is 50 μm, and the length is 16 - 20 cm.

4. The membrane electrode according to claim 3, wherein The hollow fiber microporous membrane is any one of a polypropylene hollow fiber microporous membrane, a polydimethylsiloxane hollow fiber microporous membrane, and a polyvinylidene fluoride membrane.

5. The membrane electrode according to claim 1, wherein The number of microporous fiber membrane filaments in the plurality of microporous fiber membrane filaments is not less than 20.

6. A method for preparing the membrane electrode according to any one of claims 1-5, characterized in that, It includes the following steps: (1), Dispersing polyvinylidene fluoride powder in a solution according to a ratio of 1:200 wt% to obtain a mixed solution; then, adding the powdered conductor to the mixed solution according to a ratio of 1:100 wt% to obtain a composite material mixed solution; spraying the composite material mixed solution onto the surface of the microporous fiber membrane filaments to obtain a microporous membrane precursor covered with a conductive material; drying the microporous membrane precursor covered with the conductive material to obtain a microporous membrane covered with a conductive material. Among them, the inner diameter of the pore diameter of the microporous fiber membrane filaments is 100 - 1000 μm, the outer diameter is 100 - 1000 μm, the wall thickness of the microporous fiber membrane is 10 - 100 μm; the conductor includes multi-walled carbon nanotubes and / or activated carbon powder; the outer diameter of the multi-walled carbon nanotubes is 20 - 30 nm; the solution is any one of N,N-dimethylformamide, dimethyl sulfoxide, or N,N-dimethylacetamide; (2), Weaving the microporous membrane covered with the conductive material into the support layer to obtain the membrane electrode precursor; (3), Spraying the conductive material on both sides of the membrane electrode precursor respectively to obtain the membrane electrode.

7. According to the method described in claim 6, characterized in that In the step (2), immersing the membrane electrode in a 1% polyvinyl alcohol solution, then taking it out and cross-linking it in glutaraldehyde and hydrochloric acid; The step of dispersing polyvinylidene fluoride powder in a solution to obtain a mixed solution includes: dispersing polyvinylidene fluoride powder in a solution and performing ultrasonic treatment to obtain a mixed solution; among them, the power of the ultrasonic treatment is 40 kHz, and the ultrasonic time is 30 minutes.

8. A microbial electrochemical device, characterized in that, It includes: An anode and a cathode, where the cathode is composed of the membrane electrode according to any one of claims 1 - 5.

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