Equally-spaced annular carbon nanotube array encapsulated electrode, preparation method therefor and use thereof

Abstract

An equally-spaced annular carbon nanotube array encapsulated electrode, a preparation method therefor and a use of the encapsulated electrode as an electrode in a bioelectrochemical system. The electrode comprises a silicon substrate and circular rings equally spaced on the silicon substrate, wherein the circular rings are composed of carbon nanotubes. The electrode has excellent cycle performance, biocompatibility and large electroactive area. A photoresist is used to pattern a silicon substrate to obtain an equally-spaced annular carbon nanotube array structure. Provided is an aperture-controllable annular carbon nanotube array encapsulated bioelectrode. The pattern design can be obtained according to actual production requirements. By means of the three-dimensional structure and excellent biocompatibility of the equally-spaced annular carbon nanotube array encapsulated electrode, the adhesion growth of electroactive functional bacteria, the formation of biological films, and the conduction of electrons can be enhanced.

Description

An equidistant carbon nanotube annular array packaged electrode and its preparation method and application (1) Technical field

[0001] The present invention relates to a composite material electrode for a bioelectrochemical system, and in particular to an equidistant carbon nanotube annular array packaged electrode, a preparation method thereof, and application of the composite electrode as an electrode in a bioelectrochemical system. (2) Background technology

[0002] The electron transfer efficiency of electroactive biofilms and bioanodes is a key factor in enhancing the performance of microbial fuel cells (MFCs). Carbon nanotubes (CNTs) have excellent electrical conductivity and chemical stability, and their small size significantly promotes electron transfer. They are significantly superior to other carbon electrodes in response rate and reversibility, and are widely used in the study of MFC power generation performance. Three-dimensional (3D) materials provide a larger available surface area for microorganisms, promoting bacterial attachment and biofilm formation. The linear structure of CNTs determines that they can directly enhance the electron transfer rate of cell surfaces. Combining 3D nanostructured materials with CNTs provides a more open structure, which is conducive to microbial attachment and electron transfer. The two have the potential for synergistic electron transfer, so constructing 3D CNT structures can achieve the goal of enhancing power generation.

[0003] Carbon nanotube arrays (CNTAs) possess highly ordered surface structures, excellent electrochemical performance, and high mechanical strength. These arrays also provide additional pathways for substrate diffusion and interfacial reactions. The nanoarrays possess a superior structure, which can reduce the diffusion resistance of 3D nanostructured electrodes. In addition to the 3D nanoarray structure, the pore size of the MFC anode also influences the conductivity, mass transfer, and bacterial growth of the electrode surface. Incorporating micropores into the 3D anode increases the surface area, facilitating microbial enrichment and thus enhancing system performance. However, currently, there are few techniques for preparing 3D CNT array electrodes with controllable pore size. Therefore, developing a high-surface-to-weight ratio 3D CNT array electrode with precisely controllable pore size and good biocompatibility is of great significance for further improving power density, electrogenic bacterial activity, analyzing the relationship between pore size and MFC performance, and promoting the industrial application of microbial fuel cells. (3) Summary of the invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides an equidistant carbon nanotube ring array encapsulated electrode, a preparation method thereof, and its application as an electrode in a bioelectrochemical system. The electrode has excellent cycle performance, biocompatibility, and a large electroactive area.

[0005] The technical solution adopted in the present invention is:

[0006] The present invention provides an equidistant carbon nanotube annular array encapsulated electrode. The electrode is formed by patterning equidistant circular rings on a silicon substrate using photolithography technology, depositing a catalyst by magnetron sputtering, forming a carbon nanotube annular array structure in a vapor deposition device, and finally enhancing the hydrophilicity of the electrode surface using oxygen plasma technology.

[0007] Furthermore, the silicon wafer is a single-side polished N-type 100 crystal plane with a resistivity of 0.002-0.004Ω and a size of 20×30×0.6 mm. It is ultrasonically cleaned in acetone and deionized water for 15 minutes respectively and then dried with nitrogen.

[0008] Furthermore, the equidistant carbon nanotube annular array encapsulated electrode is prepared as follows:

[0009] A silicon wafer (preferably 20×30×0.6 mm) was placed in a spin coater, and 2 ml of AR-P5350 photoresist was added to the surface. The wafer was spin-coated at 500 rpm for 10 seconds and 4000 rpm for 60 seconds, followed by drying at 105°C for 5 minutes. A pattern (equally spaced circular rings) was designed using computer software, imported into a laser direct writing system, and then written onto the silicon wafer. The written silicon wafer was placed in a developer for 1 minute. After the pattern was developed, it was rinsed in deionized water and dried with nitrogen to obtain a silicon wafer with an equal-spaced circular ring pattern. The developed silicon wafer was placed on a magnetron sputtering stage and sputtered at 200 W for 15 seconds under an argon atmosphere to obtain a 5 nm thick aluminum layer (as a barrier layer). Then, it was sputtered at 100 W for 60 seconds to obtain a 20 nm thick iron layer (as a catalyst layer). The sputtered silicon wafer was ultrasonically treated in acetone for 30 seconds to remove the photoresist and the catalyst film attached to it, leaving only the catalyst layer on the ring. The wafer was then rinsed with deionized water and dried with nitrogen. The silicon wafer carrying the catalyst pattern was placed in a quartz tube. The tube was evacuated and then passed through with 120 mL / min of argon at atmospheric pressure. The temperature was raised to 750°C over 30 minutes. Then, 475 mL / min of argon and 25 mL / min of hydrogen were passed through the tube, and the temperature was maintained at 750°C for 60 minutes. Furthermore, 10 mL / min of acetylene was passed through the tube as the feed gas for carbon nanotube synthesis, and the temperature was maintained at 750°C for 20 minutes. Finally, the temperature was cooled to approximately 200°C under a 200 mL / min argon atmosphere, resulting in an equidistant carbon nanotube ring array encapsulated electrode. The resulting equidistant carbon nanotube ring array encapsulated electrode was then subjected to an oxygen plasma hydrophilization treatment. A voltage of 60 W was maintained for 60 seconds in a 30 mL / min oxygen flow, resulting in a hydrophilized equidistant carbon nanotube ring array encapsulated electrode.

[0010] Furthermore, the inner diameter-outer diameter-spacing of the circular rings of different sizes in the equally spaced circular ring pattern are 15 μm-10 μm-5 μm, 25 μm-20 μm-5 μm and 30 μm-25 μm-5 μm (preferably 25 μm-20 μm-5 μm).

[0011] The present invention also provides a method for using the equidistant carbon nanotube annular array-encapsulated electrode as a bioelectrochemical electrode. The method comprises using the equidistant carbon nanotube annular array-encapsulated electrode (10×11 mm) as an anode electrode and a graphite sheet (preferably 10×20 mm) as a cathode electrode. The anode and cathode electrodes are mounted at opposite ends of a microbial fuel cell cavity. Both the anode and cathode electrodes are connected to a 1000Ω external resistor via titanium wires, and the external resistor is connected in parallel to a voltage recorder. Anaerobic sludge from wastewater treatment and an inorganic salt solution serve as the anolyte, while a potassium ferricyanide solution serves as the catholyte. Sodium acetate is added to the anolyte as an electron donor, and inoculation is performed. The output voltage across the external resistor is measured and automatically recorded every four minutes using a recorder.

[0012] The inorganic salt solution consists of phosphate buffer solution, trace elements and vitamin solution.

[0013] The composition of the phosphate buffer solution is: 0.31 g / L NH4Cl, 2.452 g / L NaH2PO4·H2O, 4.576 g / L Na2HPO4, and 0.13 g / L KCl, and the solvent is deionized water;

[0014] The trace element solution is composed of: MgSO4 3g / L, MnSO4·H2O 0.5g / L, NaCl 1g / L, FeSO4·7H2O 0.1g / L, CaCl2·2H2O 0.1g / L, CoCl2·6H2O 0.1g / L, ZnCl2 0.13g / L, CuSO4 5H2O 0.01g / L, AlK(SO4)2·12H2O 0.01g / L, H3BO3 0.01g / L, Na2MoO4 0.025g / L, and Na2WO4·2H2O 0.025g / L, and the solvent is deionized water;

[0015] The vitamin solution is composed of: biotin 0.002 g / L, folic acid 0.002 g / L, pyridoxine 0.01 g / L, riboflavin 0.005 g / L, thiamine 0.005 g / L, niacin 0.005 g / L, pantothenic acid 0.005 g / L, B-12 0.0001 g / L, p-aminobenzoic acid 0.005 g / L, and lipoic acid 0.005 g / L, and the solvent is deionized water.

[0016] The potassium ferricyanide solution is composed of: 16.46 g / L K3[Fe(CN)6], 0.31 g / L NH4Cl, 2.452 g / L NaH2PO4·H2O, 4.576 g / L Na2HPO4, and 0.13 g / L KCl, and the solvent is deionized water.

[0017] The sodium acetate addition concentration is 750 mg / L based on the volume of the anolyte.

[0018] Furthermore, the application is: construction and operation of microbial fuel cells (MFCs). An H-type bioelectrochemical reactor was used, wherein the cathode and anode chambers of the H-type reactor were separated by a proton exchange membrane, the volumes of the anode and cathode chambers were both 100 mL, and the effective working volume was 50 mL. An electrode encapsulated by an equidistant carbon nanotube ring array served as the anode, and a graphite sheet served as the cathode. Under optimal environmental factors (culture temperature 30°C, culture medium pH = 7), anaerobic sludge after wastewater treatment and an inorganic salt solution were added to the anode chamber at a volume ratio of 1:4, and 750 mg / L sodium acetate was added as a carbon source. 50 mL of potassium ferrocyanide solution was added to the cathode chamber. High-purity nitrogen was introduced to remove oxygen from the cathode and anode chambers. Titanium wire was used as a conductor to connect the two electrodes of the battery, and an external 1000Ω resistor was connected. The output voltage was automatically recorded and stored every 4 minutes using a paperless recorder. When the output voltage was less than 20 mV, the anode and cathode liquids were replaced. The anode was replaced with a fresh inorganic salt solution containing 750 mg / L sodium acetate, and the cathode was replaced with a potassium ferrocyanide solution.

[0019] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0020] (1) The present invention provides a method for preparing a patterned equidistant carbon nanotube annular array encapsulated electrode, wherein a silicon substrate is patterned and modified using photoresist to obtain a structure having an equidistant carbon nanotube annular array, thereby providing a novel pore-controllable carbon nanotube annular array encapsulated biological electrode, and the pattern design can be obtained according to actual production requirements.

[0021] (2) Compared with single carbon nanotube electrodes, array electrodes, or silicon-based electrodes, the equidistant carbon nanotube annular array packaged electrode of the present invention has excellent biocompatibility, high electroactive area, and excellent power generation performance.

[0022] (3) The three-dimensional structure of the electrode encapsulated by the equidistant carbon nanotube ring array and its excellent biocompatibility can enhance the attachment and growth of electroactive functional bacteria, the formation of biofilms, and the conduction of electrons. (IV) Description of the accompanying drawings

[0023] FIG1 is a flow chart of the preparation of the equidistant carbon nanotube annular array encapsulated electrode prepared in Example 1.

[0024] FIG2 is a field emission scanning electron microscope photograph of the equidistant carbon nanotube annular array encapsulated electrode-10 prepared in Example 1.

[0025] FIG3 is a field emission scanning electron microscope photograph of the equidistant carbon nanotube annular array encapsulated electrode-20 prepared in Example 2.

[0026] FIG4 is a field emission scanning electron microscope photograph of the equidistant carbon nanotube annular array encapsulated electrode-25 prepared in Example 3.

[0027] FIG5 is a diagram showing the output voltage of the bioelectrochemical system at startup in implementation case 4.

[0028] FIG6 is a field emission scanning electron microscope photograph of the medium-pitch carbon nanotube ring array encapsulated electrode-10 bioelectrode in Example 5.

[0029] FIG7 is a field emission scanning electron microscope photograph of three types of equally spaced carbon nanotube ring arrays encapsulated-20 bioelectrodes in Example 5.

[0030] FIG8 is a field emission scanning electron microscope photograph of three types of equally spaced carbon nanotube ring arrays encapsulated-25 bioelectrodes in Example 5.

[0031] FIG9 is a diagram showing the power density and polarization curves of the three electrodes in Example 6 after the bioelectrochemical system is successfully started. (V) Specific implementation methods

[0032] The present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0033] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources. The room temperature in the present invention refers to 25-30°C.

[0034] Example 1: Preparation of equidistant carbon nanotube ring array encapsulated electrodes

[0035] A silicon wafer (single-side polished N-type 100 crystal surface, resistivity 0.002-0.004Ω, size 20×30×0.6mm) was placed in a spin coater, 2 ml of AR-P5350 photoresist was added to the surface, and spin coating was performed at 500 rpm for 10 seconds and 4000 rpm for 60 seconds, respectively, and then dried at 105°C for 5 minutes; a pattern was designed using computer software (the inner diameter-outer diameter-spacing of the rings in the equidistant circular pattern were 15μm-10μm-5μm, respectively), the pattern was introduced into a laser direct writing system, and then the pattern was written on the silicon wafer. The written silicon wafer was placed in a developer for 1 minute, and after the pattern was developed, it was washed in deionized water and blown dry with nitrogen to obtain a silicon wafer with an equidistant circular pattern. The developed silicon wafer was placed on a magnetron sputtering stage and sputtered at 200W for 15 seconds under an argon atmosphere to form a 5nm thick aluminum layer (as a barrier layer). This was followed by sputtering at 100W for 60 seconds to form a 20nm thick iron layer (as a catalyst layer). The sputtered silicon wafer was then ultrasonicated in an acetone solution for 30 seconds to strip the photoresist and the catalyst film attached to it, leaving only the catalyst layer on the ring. This was then rinsed with deionized water and dried with nitrogen. A silicon wafer bearing a catalyst pattern was placed in a quartz tube. The tube was evacuated and then passed through with 120 mL / min of argon at atmospheric pressure. The temperature was raised to 750°C over 30 minutes. Then, 475 mL / min of argon and 25 mL / min of hydrogen were introduced, and the temperature was maintained at 750°C for 60 minutes. Furthermore, 10 mL / min of acetylene was introduced as the feed gas for synthesizing carbon nanotubes, and the temperature was maintained at 750°C for 20 minutes. Finally, the temperature was lowered to approximately 200°C under a 200 mL / min argon atmosphere, thereby obtaining an equidistant carbon nanotube ring array encapsulated electrode. The obtained equidistant carbon nanotube ring array encapsulated electrode was then subjected to an oxygen plasma hydrophilization treatment. In a 30 mL / min oxygen flow, a voltage of 60 W was maintained for 60 seconds. The hydrophilized equidistant carbon nanotube ring array encapsulated electrode, named equidistant carbon nanotube ring array encapsulated electrode-10, was obtained. A field emission scanning electron micrograph is shown in Figure 2. Scanning electron microscopy showed that by patterning the silicon substrate with photoresist, an electrode with an equidistant carbon nanotube ring array and an inner diameter of 10 μm could be prepared.

[0036] Example 2:

[0037] This embodiment differs from Specific Example 1 in that the inner diameter, outer diameter, and spacing of the equally spaced circular ring pattern are 25 μm, 20 μm, and 5 μm, respectively. This embodiment is designated as the equally spaced carbon nanotube ring array encapsulated electrode-20. All other aspects are the same as Specific Example 1. A field emission scanning electron micrograph is shown in Figure 3. The inner diameter of the ring is 20 μm.

[0038] Example 3:

[0039] This embodiment differs from Specific Example 1 in that the inner diameter, outer diameter, and spacing of the equally spaced circular ring pattern are 30 μm, 25 μm, and 5 μm, respectively. This embodiment is designated as Equally Spaced Carbon Nanotube Ring Array Encapsulated Electrode-25. All other aspects are the same as Specific Example 1. A field emission scanning electron micrograph is shown in Figure 4. The inner diameter of the ring is 25 μm.

[0040] Example 4: Inoculation and startup of the bioelectrochemical system

[0041] An H-type reactor (Tianjin Gaoshi Ruilian Technology Co., Ltd., C007-1) was used. The effective volume of the cathode and anode chambers was 50 mL. The two chambers were separated by a proton exchange membrane (purchased from Tianjin Gaoshi Ruilian Technology Co., Ltd., with a radius of 1.5 cm). The anolyte had a pH of 7.0 and a concentration of 50 mmol·L -1 Phosphate buffer solution, catholyte 50mmol·L -1 Potassium ferricyanide solution. An equidistant carbon nanotube ring array encapsulated electrode (10 × 11 mm) served as the anode, and a graphite sheet (10 × 20 mm) served as the cathode. Under optimal environmental conditions (culture temperature 30°C, culture medium pH = 7), 10 mL of anaerobic sludge from wastewater treatment (Hangzhou Qige Wastewater Treatment Plant, pH 6.8, BOD5 5400, carbohydrate (COD) 1500) and 40 mL of inorganic salt solution (phosphate buffer solution + trace elements + vitamin solution) were added to the anode chamber, and 50 mL of 50 mmol·L -1 Potassium ferrocyanide solution was added to the cathode chamber, and high-purity nitrogen was introduced to remove oxygen from the cathode and anode chambers. 750 mg / L of sodium acetate was added directly to the anode chamber as a carbon source. A 1000Ω external resistor was connected in parallel with a paperless recorder (RX4000A, Hangzhou Meikong Automation Technology Co., Ltd.). The output voltage was recorded and stored every 4 minutes. When the output voltage fell below 20 mV in each batch, the anode and cathode liquids were replaced: 50 mL of fresh inorganic salt solution was used for the anode, and 50 mL of potassium ferrocyanide solution was used for the cathode. As shown in Figure 5, after the third batch, the output voltage of the graphite electrode was essentially consistent, indicating successful startup of the microbial electrode encapsulated with the equally spaced carbon nanotube ring array.

[0042] Each 1L of the inorganic salt solution is prepared by mixing 982.5mL of phosphate buffer solution, 12.5mL of trace element solution, and 5mL of vitamin solution.

[0043] The composition of the phosphate buffer solution is: 0.31 g / L NH4Cl, 2.452 g / L NaH2PO4·H2O, 4.576 g / L Na2HPO4, and 0.13 g / L KCl, and the solvent is deionized water;

[0044] The trace element solution is composed of: MgSO4 3g / L, MnSO4·H2O 0.5g / L, NaCl 1g / L, FeSO4·7H2O 0.1g / L, CaCl2·2H2O 0.1g / L, CoCl2·6H2O 0.1g / L, ZnCl2 0.13g / L, CuSO4 5H2O 0.01g / L, AlK(SO4)2·12H2O 0.01g / L, H3BO3 0.01g / L, Na2MoO4 0.025g / L, and Na2WO4·2H2O 0.025g / L, and the solvent is deionized water;

[0045] The vitamin solution is composed of: biotin 0.002 g / L, folic acid 0.002 g / L, pyridoxine 0.01 g / L, riboflavin 0.005 g / L, thiamine 0.005 g / L, niacin 0.005 g / L, pantothenic acid 0.005 g / L, B-12 0.0001 g / L, p-aminobenzoic acid 0.005 g / L, and lipoic acid 0.005 g / L, and the solvent is deionized water.

[0046] The potassium ferricyanide solution is composed of: 16.46 g / L K3[Fe(CN)6], 0.31 g / L NH4Cl, 2.452 g / L NaH2PO4·H2O, 4.576 g / L Na2HPO4, and 0.13 g / L KCl, and the solvent is deionized water.

[0047] Example 5: Electrode status after successful startup of the bioelectrochemical system

[0048] After successful startup in Example 4, a small piece of electrode at the lower end of the equally spaced carbon nanotube ring array packaged electrode-10, the equally spaced carbon nanotube ring array packaged electrode-20, and the equally spaced carbon nanotube ring array packaged electrode-25 was taken for field emission scanning electron microscopy. Figures 6, 7, and 8 are field emission scanning electron micrographs of the equally spaced carbon nanotube ring array packaged electrode-10, the equally spaced carbon nanotube ring array packaged electrode-20, and the equally spaced carbon nanotube ring array packaged electrode-25, respectively. As can be seen from Figures 6, 7, and 8, the equally spaced carbon nanotube ring array packaged electrode-20 has significantly more microorganisms than the other two biological electrodes. The equally spaced carbon nanotube ring array packaged electrodes all have good biocompatibility.

[0049] Example 6: After the bioelectrochemical system is successfully started, the power generation performance

[0050] Example 4: After the bioelectrochemical system was successfully started, under optimal environmental conditions (culture temperature 30°C, culture medium pH = 7), 50 mL of inorganic salt solution (phosphate buffer solution + trace elements + vitamin solution) was added to the anode chamber, 50 mL of potassium ferricyanide solution was added to the cathode chamber, and high-purity nitrogen was introduced to drive out oxygen in the cathode and anode chambers. In addition, 750 mg / L of sodium acetate was directly added to the anode chamber as a carbon source. After the battery reached a stable stage, the external resistance was changed from 50 to 6000 Ω. The battery was operated for 20 minutes at each external resistance to obtain the corresponding voltage, and the power density and polarization curves were plotted. Figure 9 is a comparison of the power density and polarization curves of bioelectrodes encapsulated with equidistant carbon nanotube ring arrays of different sizes. The equidistant carbon nanotube ring array encapsulated electrode-20 has the best power density of 2672.7 mW m -2 , showing excellent electrode mass transfer and biocompatibility performance at this pore size.

[0051] Although the present invention has been disclosed above with reference to the embodiments, it is not intended to limit the scope of protection of the present invention. Any changes and modifications made by any technician familiar with the technology without departing from the concept and scope of the present invention should fall within the scope of protection of the present invention.

Claims

1. An equidistant carbon nanotube annular array encapsulated electrode, characterized in that: include: Silicon substrate; Circular rings are arranged on the silicon substrate at equal intervals, and the circular rings are composed of carbon nanotubes.

2. The equidistant carbon nanotube annular array packaged electrode according to claim 1, characterized in that: The silicon substrate is a polished N-type 100 crystal surface.

3. The equidistant carbon nanotube annular array packaged electrode according to claim 1, characterized in that: The inner diameter of the ring is 10-20 μm, and the difference between the outer diameter and the inner diameter is 4-6 μm.

4. The method for preparing an equidistant carbon nanotube annular array encapsulated electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Using photolithography technology to draw equally spaced rings on a silicon substrate; 2) depositing catalyst on equally spaced circular rings by magnetron sputtering, and then cleaning to remove excess catalyst to obtain a silicon substrate loaded with catalyst on the circular rings; 3) preparing carbon nanotubes on the catalyst-loaded silicon substrate on the ring obtained in step 2) in a vapor deposition device to form equally spaced rings composed of carbon nanotubes, and finally enhancing the hydrophilicity of the electrode surface by oxygen plasma technology to obtain an equally spaced carbon nanotube ring array encapsulated electrode.

5. The method for preparing an equidistant carbon nanotube annular array encapsulated electrode according to claim 4, characterized in that: In step 1), equidistant circular rings are drawn on a silicon substrate using photolithography technology, specifically including: 1.1) Place the silicon substrate in a spin coater, add photoresist onto the surface, spin coat, and then dry; 1.2) Using computer software, design evenly spaced circular rings. This pattern is imported into a laser direct writing system and then written onto a silicon substrate. The silicon wafer is then placed in a developer for development. After development, the pattern is rinsed in deionized water and dried with nitrogen to obtain a silicon wafer with evenly spaced circular rings.

6. The method for preparing an equidistant carbon nanotube annular array encapsulated electrode according to claim 4, characterized in that: In step 2), the catalyst is deposited on the circular rings at equal intervals by magnetron sputtering, and then the excess catalyst is removed by cleaning to obtain a silicon substrate with the catalyst loaded on the circular rings, which specifically includes: A silicon wafer with an equidistant circular pattern is placed on a magnetron sputtering stage and sputtered under an argon atmosphere to obtain an aluminum layer as a barrier layer. Then, a voltage sputtering is performed to obtain an iron layer as a catalytic layer. The sputtered silicon wafer is placed in an acetone solution and ultrasonically stripped of the photoresist and the catalyst film attached to the photoresist, leaving only the catalyst layer on the circular ring. The silicon wafer is then washed with deionized water and dried with nitrogen to obtain a silicon substrate with a catalyst loaded on the circular ring.

7. Use of the equidistant carbon nanotube annular array encapsulated electrode according to any one of claims 1 to 3 as an anode of a microbial fuel cell.

8. The use according to claim 7, characterized in that Specifically include: An electrode encapsulated with an equidistant carbon nanotube ring array was used as the anode, and a graphite sheet was used as the cathode. The anode and cathode were respectively installed at both ends of the cavity of the microbial fuel cell. The anode and cathode were both led out by titanium wire and connected to the ends of an external resistor of 800 to 1200 Ω, and the external resistor was connected in parallel with a voltage recorder. Anaerobic sludge after wastewater treatment, inorganic salt solution and sodium acetate as electron donor are used as anolyte and reducing solution is used as catholyte for cultivation.

9. The use according to claim 8, characterized in that The inorganic salt solution consists of phosphate buffer solution, trace elements and vitamin solution; The composition of the phosphate buffer solution is: 0.31 g / L NH4Cl, 2.452 g / L NaH2PO4·H2O, 4.576 g / L Na2HPO4, and 0.13 g / L KCl, and the solvent is deionized water; The trace element solution is composed of: MgSO4 3g / L, MnSO4·H2O 0.5g / L, NaCl 1g / L, FeSO4·7H2O 0.1g / L, CaCl2·2H2O 0.1g / L, CoCl2·6H2O 0.1g / L, ZnCl2 0.13g / L, CuSO45H2O 0.01g / L, AlK(SO4)2·12H2O 0.01g / L, H3BO3 0.01g / L, Na2MoO4 0.025g / L, and Na2WO4·2H2O 0.025g / L, and the solvent is deionized water; The vitamin solution is composed of: biotin 0.002 g / L, folic acid 0.002 g / L, pyridoxine 0.01 g / L, riboflavin 0.005 g / L, thiamine 0.005 g / L, niacin 0.005 g / L, pantothenic acid 0.005 g / L, vitamin B-12 0.0001 g / L, p-aminobenzoic acid 0.005 g / L, and lipoic acid 0.005 g / L, and the solvent is deionized water; The potassium ferricyanide solution comprises: 16.46 g / L K3[Fe(CN)6], 0.31 g / L NH4Cl, 2.452 g / L NaH2PO4·H2O, 4.576 g / L Na2HPO4, and 0.13 g / L KCl, and the solvent is deionized water.

10. The use according to claim 8, characterized in that The concentration of sodium acetate in the anolyte is 500-1000 mg / L.

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