An equidistant carbon nanotube annular array encapsulated electrode and its preparation method and application

Abstract

The present invention discloses an electrode encapsulated by an equidistant carbon nanotube annular array, a preparation method thereof, and an application thereof as an electrode of a bioelectrochemical system. The electrode comprises: a silicon substrate; annular rings arranged on the silicon substrate at equal intervals, the annular rings being composed of carbon nanotubes. The electrode has excellent cycle performance, biocompatibility, and a large electroactive area. The method of the present invention uses photoresist to pattern the silicon substrate to obtain a structure having an equidistant carbon nanotube annular array, providing a novel carbon nanotube annular array encapsulated bioelectrode with controllable aperture, and the pattern design can be designed according to actual production requirements. The three-dimensional structure and excellent biocompatibility of the electrode encapsulated by the equidistant carbon nanotube annular array can enhance the attachment and growth of electroactive functional bacteria, the formation of biofilm, and the conduction of electrons.

Description

(I) 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 and a preparation method thereof, and application of the composite electrode as an electrode in a bioelectrochemical system. (II) Background technology

[0002] The electron transfer efficiency of electroactive biofilm and bioanode is a key factor in enhancing the performance of microbial fuel cells (MFCs). Carbon nanotubes (CNTs) have good electrical conductivity and good chemical stability. Their small size effect promotes electron transfer very well. They are significantly better than other carbon material electrodes in response rate and reversibility, and are widely used in the study of MFCs power generation performance. Three-dimensional (3D) materials provide a larger available surface area for microorganisms, promote bacterial attachment and biofilm formation. The linear structure of CNTs determines that it can directly enhance the electron transfer rate on the cell surface. Combining three-dimensional 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 the construction of a three-dimensional CNTs structure can achieve the purpose of enhancing power generation.

[0003] Carbon nanotube arrays (CNTAs) have highly ordered surface structures, excellent electrochemical properties, and high mechanical strength, and these arrays provide additional channels for substrate diffusion and interfacial reactions. Nanoarrays have excellent structures that can reduce the diffusion resistance of 3D nanostructured electrodes. In addition to the 3D nanoarray structure, the pore size of the MFCs anode also affects the conductivity, mass transfer, and bacterial growth of the electrode surface. Adding micropores to the 3D anode can increase the surface area, which is conducive to the enrichment of microorganisms and thus enhances the system performance. However, there are currently few preparation technologies for 3D carbon nanotube array electrodes with controllable pore size. Therefore, the development of a three-dimensional carbon nanotube array electrode with high specific surface area, precise controllable pore size, good biocompatibility, is of great significance to further improve the power density, the activity of electrogenic bacteria, analyze the relationship between pore size and MFCs performance, and the industrial application of microbial fuel cells. (III) 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 annular array encapsulated electrode and a preparation method thereof and application as an electrode in a bioelectrochemical system, wherein the electrode has excellent cycle performance, biocompatibility and a large electroactive area.

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

[0006] The present invention provides an equidistant carbon nanotube annular array packaged 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 by 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 blown dry 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) is placed in a coating machine, 2 ml of AR-P5350 photoresist is dripped onto the surface, and the wafer is spin-coated at 500 rpm for 10 seconds and 4000 rpm for 60 seconds, respectively, and then dried at 105°C for 5 minutes; a pattern (equidistant circular rings) is designed using computer software, the pattern is imported into a laser direct writing system, and then the pattern is written on the silicon wafer, the silicon wafer after the pattern is written is placed in a developer for 1 minute, and after the pattern is developed, it is placed in deionized water for cleaning and dried with nitrogen to obtain an equidistant circular ring pattern silicon wafer. The developed silicon wafer is placed on a magnetron sputtering stage, and sputtered at 200W voltage for 15 seconds in an argon atmosphere to obtain a 5nm thick aluminum layer (as a barrier layer), and then sputtered at 100W voltage for 60 seconds to obtain a 20nm thick iron layer (as a catalyst layer). The sputtered silicon wafer was placed in an acetone solution for 30 seconds for ultrasonic treatment to remove the photoresist and the catalyst film attached to the photoresist, leaving only the catalyst layer on the ring, which was then washed with deionized water and dried with nitrogen. The silicon wafer carrying the catalyst pattern was placed in a quartz tube, the quartz tube was evacuated and then passed through 120 mL / min of argon at normal pressure, heated for 30 minutes to 750°C; then 475 mL / min of argon and 25 mL / min of hydrogen were passed through, and 750°C was maintained for 60 minutes; then 10 mL / min of acetylene was passed through as the raw material gas for synthesizing carbon nanotubes, and 750°C was maintained for 20 minutes; finally, the temperature was lowered to about 200°C in a 200 mL / min argon atmosphere, thereby obtaining an equidistant carbon nanotube annular array encapsulated electrode. The obtained equidistant carbon nanotube annular array encapsulated electrode was placed in an oxygen plasma hydrophilic treatment, and a voltage of 60W was maintained for 60 seconds in a 30 mL / min oxygen flow, and finally an equidistant carbon nanotube annular array encapsulated electrode after hydrophilic treatment was obtained.

[0010] Furthermore, the inner diameter-outer diameter-spacing of the circular rings of the equally spaced circular ring pattern of different sizes 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 an application of the equidistant carbon nanotube annular array packaged electrode as a bioelectrochemical electrode, wherein the equidistant carbon nanotube annular array packaged electrode (10×11 mm) is used as an anode electrode, and a graphite sheet (preferably 10×20 mm) is used as a cathode electrode, wherein the anode and cathode electrodes are respectively installed at both ends of the cavity of a microbial fuel cell, and the anode and cathode are both led out by titanium wire and connected to both ends of a 1000Ω external resistor, and the external resistor is connected in parallel with a voltage recorder. Anaerobic sludge after wastewater treatment and an inorganic salt solution are used as an anode liquid, and a potassium ferrocyanide solution is used as a cathode liquid. Sodium acetate is added to the anode liquid as an electron donor, and culture and inoculation are performed. The output voltage at both ends of the external resistor is measured and automatically recorded every 4 minutes by 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: NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO4 4.576 g / L, KCl 0.13 g / L, 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, CuSO45H2O0.01g / L, AlK(SO4)2·12H2O 0.01g / L, H3BO3 0.01g / L, Na2MoO4 0.025g / L, Na2WO4·2H2O0.025g / 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 ferrocyanide solution comprises: K3[Fe(CN)6] 16.46 g / L, NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO4 4.576 g / L, KCl 0.13 g / L, 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 is used, wherein the cathode chamber and the anode chamber of the H-type reactor are separated by a proton exchange membrane, the volumes of the anode chamber and the cathode chamber are both 100 mL, and the effective working volume is 50 mL; an electrode encapsulated by an equidistant carbon nanotube ring array is used as an anode, and a graphite sheet is used as a cathode. Under optimal environmental factor conditions (culture temperature 30°C, culture solution pH=7), anaerobic sludge after wastewater treatment and an inorganic salt solution are added to the anode chamber at a volume ratio of 1:4, and 750 mg / L sodium acetate is added as a carbon source, 50 mL of potassium ferrocyanide solution is added to the cathode chamber, high-purity nitrogen is introduced to drive out oxygen in the cathode and anode chambers, and titanium wire is used as a conductor to connect the two poles of the battery, an external 1000Ω resistor is connected, and a paperless recorder is used for output voltage, and data is automatically recorded and stored every 4 minutes; when the output voltage is less than 20 mV, the cathode and anode liquids are replaced, the anode is replaced with a fresh inorganic salt solution containing 750 mg / L sodium acetate, and the cathode is 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 a single carbon nanotube electrode, an array electrode or a silicon substrate electrode, the equidistant carbon nanotube annular array packaged electrode of the present invention has excellent biocompatibility, a high electroactive area and excellent power generation performance.

[0022] (3) The three-dimensional structure of the electrode encapsulated by the equally spaced 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 drawings

[0023] Figure 1 This is a flow chart for preparing the equidistant carbon nanotube annular array encapsulated electrode prepared in Example 1.

[0024] Figure 2 This is a field emission scanning electron microscope photograph of the equally spaced carbon nanotube annular array encapsulated electrode-10 prepared in Example 1.

[0025] Figure 3 This is a field emission scanning electron microscope photograph of the equally spaced carbon nanotube annular array encapsulated electrode-20 prepared in Example 2.

[0026] Figure 4 This is a field emission scanning electron microscope photograph of the equally spaced carbon nanotube ring array encapsulated electrode-25 prepared in Example 3.

[0027] Figure 5 This is a diagram of the startup output voltage of the bioelectrochemical system in implementation case 4.

[0028] Figure 6 This is a field emission scanning electron microscope photo of the medium-pitch carbon nanotube ring array encapsulated electrode-10 biological electrode in implementation case 5.

[0029] Figure 7 Field emission scanning electron microscope photos of three types of equally spaced carbon nanotube ring arrays encapsulated-20 bioelectrodes in implementation case 5.

[0030] Figure 8 Field emission scanning electron microscope photos of three types of equally spaced carbon nanotube ring arrays encapsulated-25 bioelectrodes in implementation case 5.

[0031] Fig. 9 The power density and polarization curves of the three electrodes in implementation case 6 after the bioelectrochemical system is successfully started. (V) Specific implementation methods

[0032] The present invention is further described below in conjunction with 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 annular 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 coater, 2 ml of AR-P5350 photoresist was dripped on 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 of 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 silicon wafer after the pattern was written was placed in a developer for development 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 in an argon atmosphere to obtain a 5nm thick aluminum layer (as a barrier layer), and then sputtered at 100W for 60 seconds to obtain a 20nm thick iron layer (as a catalyst layer). The sputtered silicon wafer was placed in an acetone solution for 30 seconds to ultrasonicate, and the photoresist and the catalyst film attached to the photoresist were stripped, leaving only the catalyst layer on the ring, which was washed with deionized water and dried with nitrogen. The silicon wafer with the catalyst pattern was placed in a quartz tube, and the quartz tube was evacuated and then passed through 120 mL / min of argon at normal pressure, and heated to 750°C for 30 minutes; then 475 mL / min of argon and 25 mL / min of hydrogen were passed through, and the temperature was maintained at 750°C for 60 minutes; then 10 mL / min of acetylene was passed through as the raw gas for synthesizing carbon nanotubes, and the temperature was maintained at 750°C for 20 minutes; finally, the temperature was cooled to about 200°C in a 200 mL / min argon atmosphere, thereby obtaining an equidistant carbon nanotube annular array encapsulated electrode. The obtained equidistant carbon nanotube annular array encapsulated electrode was placed in an oxygen plasma hydrophilic treatment, and a voltage of 60 W was maintained for 60 seconds in a 30 mL / min oxygen flow, and finally an equidistant carbon nanotube annular array encapsulated electrode after hydrophilic treatment was obtained, which was named equidistant carbon nanotube annular array encapsulated electrode-10, and the field emission scanning electron microscope photo is shown in Figure 2 Scanning electron microscopy showed that the photoresist was used to pattern the silicon substrate to prepare an electrode with an equidistant carbon nanotube ring array, with an inner diameter of 10 μm.

[0036] Embodiment 2:

[0037] The difference between this embodiment and the specific embodiment 1 is that the inner diameter, outer diameter and spacing of the equally spaced circular ring pattern are 25 μm-20 μm-5 μm respectively, and it is named as the equally spaced carbon nanotube circular array encapsulated electrode-20. The rest is the same as the specific embodiment 1. The field emission scanning electron microscope photo is shown in Figure 3 , the inner diameter of the ring is 20μm.

[0038] Embodiment 3:

[0039] The difference between this embodiment and the specific embodiment 1 is that the inner diameter, outer diameter and spacing of the equally spaced circular ring pattern are 30 μm-25 μm-5 μm respectively, and it is named as the equally spaced carbon nanotube circular array encapsulated electrode-25. The rest is the same as the specific embodiment 1. The field emission scanning electron microscope photo is shown in Figure 4 , the inner diameter of the ring is 25μm.

[0040] Example 4: Inoculation and start-up of bioelectrochemical system

[0041] An H-type reactor (Tianjin Gaoshi Ruilian Technology Co., Ltd., C007-1) was used. The effective volume of the cathode chamber and the anode chamber 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 was pH 7.0 and 50 mmol·L -1 Phosphate buffer solution, catholyte is 50mmol·L -1 Potassium ferrocyanide solution. The equidistant carbon nanotube ring array encapsulated electrode (10×11 mm) was used as the anode, and the graphite sheet (10×20 mm) was used as the cathode. Under the optimal environmental factor conditions (culture temperature 30°C, culture solution pH = 7), 10 mL of anaerobic sludge after wastewater treatment (Hangzhou Qige Wastewater Treatment Plant, pH 6.8, BOD5 5400, carbohydrate (in terms of 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 drive out the 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. An external 1000Ω resistor was connected, and a paperless recorder (Hangzhou Meikong Automation Technology Co., Ltd., RX4000A) was connected in parallel to the external resistor. The output voltage was recorded and stored every 4 minutes. When the output voltage of each batch was lower than 20mV, the cathode and cathode liquids were replaced, the anode was replaced with a fresh 50mL inorganic salt solution, and the cathode was replaced with a 50mL potassium ferrocyanide solution. Figure 5 As shown, after the third batch, the output voltage of the graphite electrode was basically consistent, and the microbial electrode encapsulated by the equally spaced carbon nanotube ring array was successfully started.

[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: NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO4 4.576 g / L, KCl 0.13 g / L, 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, CuSO45H2O0.01g / L, AlK(SO4)2·12H2O 0.01g / L, H3BO3 0.01g / L, Na2MoO4 0.025g / L, Na2WO4·2H2O0.025g / 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 ferrocyanide solution comprises: K3[Fe(CN)6] 16.46 g / L, NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO4 4.576 g / L, KCl 0.13 g / L, and the solvent is deionized water.

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

[0048] After the successful start-up of 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. Figure 6 , Figure 7 and Figure 8 The following are field emission scanning electron microscope photos of the equally spaced carbon nanotube ring array encapsulated electrode-10, equally spaced carbon nanotube ring array encapsulated electrode-20, and equally spaced carbon nanotube ring array encapsulated electrode-25. Figure 6 , Figure 7 and Figure 8 It can be seen that the equidistant carbon nanotube ring array encapsulated electrode-20 has significantly more microorganisms than the other two biological electrodes. The equidistant carbon nanotube ring array encapsulated electrodes 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 the optimal environmental factor conditions (culture temperature 30°C, culture solution pH = 7), 50mL of inorganic salt solution (phosphate buffer solution + trace elements + vitamin solution) was added to the anode chamber, 50mL of potassium ferrocyanide solution was added to the cathode chamber, high-purity nitrogen was introduced to drive out the oxygen in the cathode and anode chambers, and 750mg / 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 6000Ω, and it was operated for 20min at each external resistance to obtain the corresponding voltage, and the power density and polarization curves were plotted. Fig. 9 The power density and polarization curve comparison of bioelectrodes encapsulated with carbon nanotube ring arrays of different sizes are shown in Figure 2. The electrode encapsulated with carbon nanotube ring arrays of different sizes 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 as above by way of embodiments, it is not intended to limit the protection scope 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 protection scope of the present invention.

Claims

1. Application of an equidistant carbon nanotube annular array encapsulated electrode as an anode of a microbial fuel cell, characterized in that: The method for preparing the equidistant carbon nanotube annular array encapsulated electrode comprises the following steps: 1) Use photolithography technology to draw equally spaced rings on a silicon substrate, including: 1.1) Place the silicon substrate in a coating machine, drip photoresist on the surface, spin coat, and then dry; 1.2) Use computer software to design equally spaced circular rings, import the pattern into a laser direct writing system, and then write the pattern on a silicon substrate. Place the silicon wafer after writing the pattern in a developer for development. After the pattern is developed, place it in deionized water for cleaning and blow dry with nitrogen to obtain a silicon wafer with an equally spaced circular ring pattern; 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 silicon substrate loaded with the catalyst 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; The equidistant carbon nanotube annular array packaged electrode comprises: Silicon substrate; Circular rings are arranged on the silicon substrate at equal intervals, and the circular rings are composed of carbon nanotubes.

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

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

4. The use according to claim 1, characterized in that: In step 2), a 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 loaded with the catalyst on the circular rings, which specifically includes: A silicon wafer with an equidistant circular ring pattern is placed on a magnetron sputtering stage and sputtered in an argon atmosphere to obtain an aluminum layer as a barrier layer. Then, it is voltage sputtered to obtain an iron layer as a catalytic layer. The sputtered silicon wafer is placed in an acetone solution for ultrasonic treatment to peel off the photoresist and the catalyst film attached to the photoresist, leaving only the catalyst layer on the ring. The silicon wafer is washed with deionized water and blown dry with nitrogen to obtain a silicon substrate with a catalyst loaded on the ring.

5. The use according to claim 1, characterized in that: Specifically include: The electrode encapsulated by the carbon nanotube annular array with equal spacing is used as the anode, and the graphite sheet is used as the cathode. The anode and the cathode are respectively installed at the two ends of the cavity of the microbial fuel cell. The anode and the cathode are both led out by titanium wire and connected to the two ends of an external resistor of 800-1200 Ω, and the external resistor is connected in parallel with a voltage recorder. The anaerobic sludge after wastewater treatment is cultured with an inorganic salt solution and sodium acetate as an electron donor as an anode liquid and a reducing solution potassium ferrocyanide solution as a cathode liquid.

6. The use according to claim 5, characterized in that: The inorganic salt solution consists of a phosphate buffer solution, a trace element solution and a vitamin solution; The composition of the phosphate buffer solution is: NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO44.576 g / L, KCl 0.13 g / L, and the solvent is deionized water; The trace element solution is composed of: MgSO4 3 g / L, MnSO4·H2O 0.5 g / L, NaCl 1 g / L, FeSO4·7H2O 0.1 g / L, CaCl2·2H2O 0.1 g / L, CoCl2·6H2O 0.1 g / L, ZnCl2 0.13 g / L, CuSO4·5H2O0.01 g / L, AlK(SO4)2·12H2O 0.01 g / L, H3BO3 0.01 g / L, Na2MoO4 0.025 g / L, Na2WO4·2H2O 0.025 g / 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, lipoic acid 0.005 g / L, and the solvent is deionized water; The potassium ferrocyanide solution is composed of: K3[Fe(CN)6] 16.46 g / L, NH4Cl 0.31 g / L, NaH2PO4·H2O2.452 g / L, Na2HPO4 4.576 g / L, KCl 0.13 g / L, and the solvent is deionized water.

7. The use according to claim 5, characterized in that: The concentration of sodium acetate in the anolyte is 500-1000 mg / L.

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