Cathode material, preparation method and application thereof, and microbial fuel cell

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to a cathode material, a preparation method and application thereof, and a microbial fuel cell. The cathode material comprises a stainless steel fiber felt, and manganese dioxide, a conductive agent and a binder which are loaded on the stainless steel fiber felt, the conductive agent is carbon black; the binder is polytetrafluoroethylene, has excellent electron transmission capability and oxidation reduction reaction (ORR) performance, can improve the output work density of the microbial fuel cell, and also can enhance the purification effect of the microbial fuel cell on heavy metal-containing wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and in particular relates to a cathode material, a preparation method and application thereof, and a microbial fuel cell. Background Art

[0002] Microbial fuel cell (MFC) is a new bioelectrochemical technology that can oxidize and degrade chemical organic matter while generating electricity through bioelectrocatalytic reactions. This technology uses the metabolism of anode microorganisms to directly degrade organic pollutants, while generating electrons and protons at the anode. Electrons travel through the external circuit to the cathode, and protons migrate through the membrane to the cathode, where they react with anions O2 generated by oxygen reduction at the cathode. - Combined with water, a complete circuit is formed. Although the research on MFC systems in environmental governance and bioenergy has attracted the attention and development of scholars at home and abroad, and has made significant progress, compared with other energy sources, the overall performance of MFC is currently limited by the insufficient electron transport capacity of the cathode material and the poor kinetics of the cathode redox reaction (ORR). This results in relatively low power density and high cost, thus limiting the commercialization and large-scale application of MFC. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a cathode material, a preparation method and application thereof, and a microbial fuel cell. The cathode material provided by the present invention has excellent electron transmission ability and redox reaction (ORR) performance, which can not only improve the output power density of the microbial fuel cell, but also enhance the purification effect of the microbial fuel cell on heavy metals in wastewater.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a cathode material, comprising a stainless steel fiber felt and manganese dioxide, a conductive agent and a binder supported on the stainless steel fiber felt;

[0006] The conductive agent is carbon black;

[0007] The binder is polytetrafluoroethylene.

[0008] Preferably, the mass ratio of the manganese dioxide, the conductive agent and the binder is 8:1:1.

[0009] Preferably, the thickness of the cathode material is 0.4 to 0.8 mm.

[0010] The present invention also provides a method for preparing the cathode material described in the above technical solution, comprising the following steps:

[0011] Manganese dioxide, a conductive agent, a binder and an organic solvent are mixed, the obtained mixed solution is coated on the surface of the stainless steel fiber felt, and the mixture is dried to obtain the cathode material.

[0012] Preferably, the mixing is carried out under ultrasonic conditions; the power of the ultrasound is 150 to 200 W; the frequency of the ultrasound is 40 kHz; and the time of the ultrasound is 0.5 to 1 h.

[0013] Preferably, the coating is as follows: firstly coating the mixed liquid on one side of the stainless steel fiber felt, and then coating the mixed liquid on the other side of the stainless steel fiber felt after drying.

[0014] The present invention also provides the use of the cathode material described in the above technical solution or the cathode material prepared by the preparation method described in the above technical solution in a microbial fuel cell.

[0015] The present invention also provides a microbial fuel cell comprising a cathode chamber, an anode chamber and a diaphragm;

[0016] The diaphragm separates the cathode chamber from the anode chamber;

[0017] The cathode chamber stores cathode liquid and cathode material immersed in the cathode liquid;

[0018] The anode chamber stores an anolyte and an anode material immersed in the anolyte;

[0019] The cathode material is the cathode material described in the above technical solution or the cathode material prepared by the preparation method described in the above technical solution.

[0020] The present invention also provides a method for treating wastewater containing heavy metals and / or organic matter using the microbial fuel cell described in the above technical solution, comprising the following steps:

[0021] The wastewater containing heavy metals and / or organic matter is placed in the cathode chamber of the microbial fuel cell and treated to obtain effluent.

[0022] Preferably, the heavy metal includes Cr(VI); and the organic matter includes p-chlorophenol.

[0023] The present invention provides a cathode material comprising a stainless steel fiber felt and manganese dioxide, a conductive agent, and a binder loaded on the stainless steel fiber felt; the conductive agent is carbon black; and the binder is polytetrafluoroethylene. In the cathode material provided by the present invention, manganese dioxide is used as a transition metal oxide as a catalyst for the cathode redox reaction (ORR) in a microbial fuel cell (MFC), thereby improving the ORR power of the cathode; the stainless steel fiber felt not only has good metallic properties, but also has a high specific surface area and good flexibility similar to chemical fibers. Its open 3D macroporous structure can achieve a large specific surface area, high corrosion resistance, excellent mechanical strength, and uniform pore size distribution. Loading MnO2 on the surface of the stainless steel fiber felt not only solves the disadvantage of weak conductivity of manganese dioxide, but also significantly improves the electrochemical performance of the stainless steel fiber felt by modifying the stainless steel fiber felt with MnO2. It also increases the cathode's ability to transport electrons, thereby enhancing the MFC cathode ORR performance. The results of the present invention show that the exchange current density of the stainless steel fiber felt loaded with MnO2 cathode material (SSFF-MnO2) is 21.38 times that of the stainless steel fiber felt (SSFF-CK), and MnO2 modification increases the power density of the base stainless steel fiber felt by 14.20%. When treating Cr(VI)-containing wastewater, the maximum power density (316.41 mW / m 2 ) increased by 38.01% compared to SSFF-CK, and the SSFF-MnO2 purification capacity of Cr(VI) increased by 24.46% compared to SSFF-CK. When treating mixed wastewater containing Cr(VI) and parachlorophenol (4-CP), the SSFF-MnO2 purification capacity of Cr(VI) increased by 16.83% compared to SSFF-CK.

[0024] The present invention also provides a method for preparing the above-mentioned cathode material. The manganese dioxide (MnO2) used in the present invention has low cost. The method of preparing the cathode material by coating a slurry containing manganese dioxide on the surface of a stainless steel fiber felt is simple, low-cost, environmentally friendly, and easy to mass-produce.

[0025] The present invention also provides a microbial fuel cell prepared using the above-mentioned cathode material, which can not only degrade organic matter in wastewater, but also has an excellent purification effect on heavy metals in wastewater. In addition, the use of the above-mentioned cathode material to prepare a microbial fuel cell can greatly reduce the operating cost of the microbial fuel cell, is simple to prepare, and has good prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 SEM images of the cathode material (SSFF-MnO2) prepared in Example 1 and SSFF-CK of Comparative Example 1;

[0027] Figure 2Power density diagram of the cathode material (SSFF-MnO2) prepared in Example 1 and SSFF-CK of Comparative Example 1;

[0028] Figure 3 Graphs showing power density and Cr(VI) removal rate of the cathode material (SSFF-MnO2) in the microbial fuel cell of Application Example 2 and the cathode material (SSFF-CK) in the microbial fuel cell of Comparative Application Example 2;

[0029] Figure 4 Graph showing the removal rate of Cr(VI) for the cathode material (SSFF-MnO2) in the microbial fuel cell of Application Example 3 and the cathode material (SSFF-CK) in the microbial fuel cell of Comparative Application Example 3;

[0030] Figure 5 Tafel curves of the cathode material (SSFF-MnO2) prepared in Example 1 and SSFF-CK of Comparative Example 1. DETAILED DESCRIPTION

[0031] The present invention provides a cathode material, comprising a stainless steel fiber felt and manganese dioxide, a conductive agent and a binder supported on the stainless steel fiber felt;

[0032] The conductive agent is carbon black;

[0033] The binder is polytetrafluoroethylene.

[0034] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art can be used.

[0035] The cathode material provided by the present invention comprises stainless steel fiber felt. In the present invention, the thickness of the stainless steel fiber felt is preferably 0.4 to 0.8 mm, more preferably 0.6 mm.

[0036] The cathode material provided by the present invention comprises manganese dioxide supported on the stainless steel fiber felt, a conductive agent, and a binder. In the present invention, the conductive agent is carbon black; the binder is polytetrafluoroethylene; and the mass ratio of the manganese dioxide, the conductive agent, and the binder is preferably 8:1:1.

[0037] In the present invention, the thickness of the cathode material is preferably 0.4 to 0.8 mm, more preferably 0.6 mm.

[0038] In the cathode material provided by the present invention, manganese dioxide is used as a transition metal oxide as a catalyst for the cathode redox reaction (ORR) in a microbial fuel cell (MFC) to improve the ORR power of the cathode; the stainless steel fiber felt not only has good metallic properties, but also has a high specific surface area and good flexibility similar to chemical fibers, and its open 3D macroporous structure can achieve a large specific surface area, high corrosion resistance, excellent mechanical strength and uniform pore size distribution. The stainless steel fiber felt is made of extremely fine metal fibers, and the diameter of each metal fiber and the pore size between fibers are at the micron level, which makes it have a high specific surface area and good flexibility similar to chemical fibers in addition to its original metallic properties; MnO2 (macroscopically manifested as powdery black MnO2, and a large number of nanorod-shaped crystals MnO2 can be seen from the microscopic morphology diagram to be formed on the surface of the stainless steel fiber felt) is loaded on the surface of the stainless steel fiber felt, which not only solves the disadvantage of weak conductivity of manganese dioxide, but also MnO2 modification of the stainless steel fiber felt significantly improves the electrochemical properties of the stainless steel fiber felt, and also increases the cathode's ability to transmit electrons, thereby enhancing the MFC cathode ORR performance.

[0039] The present invention also provides a method for preparing the cathode material described in the above technical solution, comprising the following steps:

[0040] Manganese dioxide, a conductive agent, a binder and an organic solvent are mixed, the obtained mixed solution is coated on the surface of the stainless steel fiber felt, and the mixture is dried to obtain the cathode material.

[0041] In the present invention, the method for preparing manganese dioxide preferably includes the following steps: dissolving MnSO2·H2O and (NH4)2S2O3 in deionized water, subjecting the resulting mixed solution to a hydrothermal reaction, and sequentially washing, drying, crushing, and sieving the solid obtained by solid-liquid separation to obtain manganese dioxide. In the present invention, the mass ratio of MnSO2·H2O to (NH4)2S2O3 is preferably 4.225:11.4; the mass ratio of MnSO2·H2O to deionized water is preferably 4.225:100; the temperature of the hydrothermal reaction is preferably 80-200°C, more preferably 120-180°C; the time of the hydrothermal reaction is preferably 2-26 hours, more preferably 14-20 hours; the hydrothermal reaction is preferably carried out in a stainless steel autoclave; the cleaning agent used for the cleaning is preferably deionized water; the cleaning is preferably carried out until the pH value of the cleaning agent after the cleaning is neutral; the crushing is preferably grinding; and the screening is preferably carried out using a 100-mesh sieve.

[0042] In the present invention, the organic solvent is preferably anhydrous ethanol; the mass of the anhydrous ethanol is preferably 400-600% of the mass of the manganese dioxide, more preferably 500%; the mixing is preferably carried out under ultrasonic conditions; the power of the ultrasound is preferably 150-200 W, more preferably 180 W; the frequency of the ultrasound is preferably 40 kHz; the time of the ultrasound is preferably 0.5-1 h, more preferably 0.5 h.

[0043] In the present invention, the coating is preferably: first coating the mixed liquid on one side of the stainless steel fiber felt, and then coating the mixed liquid on the other side of the stainless steel fiber felt after drying; the drying is preferably air-dried under natural conditions. The present invention does not specifically limit the coating method, and a coating method well known in the art can be used. In an embodiment of the present invention, the coating is to use a micro-syringe to absorb the mixed liquid obtained by mixing manganese dioxide, a conductive agent, a binder and an organic solvent, and then inject it into one side of the stainless steel fiber felt. After it is dried under natural conditions, the other side is prepared in the same way.

[0044] Prior to coating, the present invention preferably further comprises: pre-treating the stainless steel fiber felt; the pre-treatment is preferably performed by soaking the stainless steel fiber felt in acetone, ultrasonically cleaning it with deionized water, and finally drying it. In the present invention, the soaking time is preferably 5 hours; the ultrasonic cleaning temperature is preferably room temperature, more preferably 25°C; the ultrasonic cleaning power is preferably 150-200W, more preferably 180W; the ultrasonic frequency is preferably 40kHz; the ultrasonic cleaning time is preferably 0.5 hours; the drying temperature is preferably 60°C; and the drying time is preferably 12 hours.

[0045] In the present invention, the drying temperature is preferably 60° C.; the drying time is preferably 12 hours.

[0046] The production process of manganese dioxide (MnO2) used in the present invention is simple and low-cost. The method of coating a slurry containing manganese dioxide on the surface of a stainless steel fiber felt to prepare a cathode material is simple, low-cost, environmentally friendly, and easy to mass-produce.

[0047] The present invention also provides the use of the cathode material described in the above technical solution or the cathode material prepared by the preparation method described in the above technical solution in a microbial fuel cell.

[0048] The present invention also provides a microbial fuel cell comprising a cathode chamber, an anode chamber and a diaphragm;

[0049] The diaphragm separates the cathode chamber from the anode chamber;

[0050] The cathode chamber stores cathode liquid and cathode material immersed in the cathode liquid;

[0051] The anode chamber stores an anolyte and an anode material immersed in the anolyte;

[0052] The cathode material is the cathode material described in the above technical solution or the cathode material prepared by the preparation method described in the above technical solution.

[0053] In the present invention, the cathode chamber and the anode chamber are preferably a rectangular double-chamber structure, and the material of the cathode chamber and the anode chamber is preferably organic glass; the cathode liquid is preferably a phosphate buffered saline solution (PBS buffer) with a pH value of 6.5, and the components are preferably a mixture of 0.13g / L potassium chloride, 0.31g / L ammonium chloride, 5.618g / L sodium dihydrogen phosphate dihydrate, 2.44g / L anhydrous disodium hydrogen phosphate and water; the anode liquid is preferably a phosphate buffered saline solution (PBS buffer) with a pH value of 7, and the components are preferably a mixture of 0.13g / L potassium chloride, 0.31g / L ammonium chloride, 2.452g / L sodium dihydrogen phosphate dihydrate, 4.576g / L anhydrous disodium hydrogen phosphate, 1.7g / L anhydrous sodium acetate and water; the anode material is preferably graphite felt; the thickness of the graphite felt is preferably 2mm, the length is preferably 2cm, the width is preferably 2cm, and the height is preferably 0.5cm; the diaphragm is preferably DuPont N117 proton exchange membrane. The present invention has no particular limitation on the volume of the cathode chamber and the anode chamber, and can be selected according to actual needs. In the embodiment of the present invention, the volume of the cathode chamber and the anode chamber is 118 mL.

[0054] The stainless steel fiber felt loaded with manganese dioxide as the cathode material in the present invention is low in price and easy to produce in batches, which can greatly reduce the operating cost of the microbial fuel cell. It is also simple to prepare and has good prospects.

[0055] The present invention also provides a method for treating wastewater containing heavy metals and / or organic matter using the microbial fuel cell described in the above technical solution, comprising the following steps: placing the wastewater containing heavy metals and / or organic matter in the cathode chamber of the microbial fuel cell, treating it, and obtaining effluent.

[0056] In the present invention, the heavy metal preferably includes Cr(VI); the organic matter preferably includes p-chlorophenol; in an application example of the present invention, the concentration of Cr(VI) in the wastewater containing heavy metals and / or organic matter is preferably 10 mg / L, and the concentration of p-chlorophenol is preferably 25 mg / L.

[0057] During the treatment process, the open circuit voltage of the microbial fuel cell is preferably 0-0.8V, more preferably 0.1-0.5V; the cathode chamber is preferably operated under aeration conditions; the aeration rate of the aeration is preferably 200mL / min; and the treatment time is preferably 2-12d, more preferably 5-10d.

[0058] The microbial fuel cell prepared using the cathode material provided by the present invention can not only degrade organic matter in wastewater, but also has an excellent purification effect on heavy metals in wastewater. In addition, the use of the cathode material to prepare the microbial fuel cell can greatly reduce the operating cost of the microbial fuel cell, and the preparation is simple, which has good prospects.

[0059] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention, but they should not be understood as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] The purchased stainless steel fiber felt (SSFF) with a thickness of 0.6 mm was soaked in acetone for 5 h, then ultrasonically cleaned with deionized water at 25 °C, 180 W, and 40 kHz for 0.5 h, and then dried at 60 °C for 12 h to obtain SSFF-CK;

[0062] 4.225 g of MnSO2·H2O and 11.4 g of (NH4)2S2O3 were weighed and completely dissolved in 100 mL of deionized water. 70 mL of the mixed liquid was placed in a 100 mL stainless steel autoclave and subjected to hydrothermal reaction at 120°C for 14 h. The solid-liquid separation was performed, and the obtained solid was washed with deionized water until the pH value of the filtrate (the cleaning agent after washing) was neutral. After drying, the solid was ground into a fine powder and sieved through a 100-mesh sieve to obtain MnO2.

[0063] Weigh MnO2, carbon black, and polytetrafluoroethylene (PTFE) in a mass ratio of 8:1:1 and mix them evenly. Add 500% anhydrous ethanol to the mass of MnO2 into a beaker and ultrasonicate in an ultrasonic cleaner at 180W and 40kHz for 0.5h to obtain a uniform mixed solution. Use a microsyringe to draw 1mL of the mixed solution and inject it evenly on one side of SSFF-CK. After it is dried under natural conditions, prepare the other side in the same way. Finally, dry it at 60℃ for 12h to obtain the cathode material (SSFF-MnO2, 0.6mm thick).

[0064] Comparative Example 1

[0065] The SSFF-CK prepared in Example 1 was used as a comparative example.

[0066] Application Example 1

[0067] A graphite felt with a length, width and height of 2 cm × 2 cm × 0.5 cm and a thickness of 2 mm was used as the anode, and the SSFF-MnO2 prepared in Example 1 was used as the cathode. A double-chamber MFC device was used. The cathode chamber and the anode chamber of the device were rectangular double-chamber structures made of organic glass. The volume of the cathode chamber and the anode chamber were both 118 mL (each filled with 100 mL of liquid), and the cathode and anode chambers were separated by a DuPont N117 proton exchange membrane; the cathode liquid was a PBS buffer solution with a pH value of 6.5, and the components were 0.13 g / L potassium chloride, 0.31 g / L ammonium chloride, and 5.618 g / L The microbial fuel cell was prepared by placing the cathode liquid in the cathode chamber, immersing the cathode material in the cathode liquid, placing the anode liquid in the anode chamber, and immersing the anode material in the anode liquid to obtain the microbial fuel cell. The cathode chamber was aerated at an aeration rate of 200 mL / min.

[0068] Application Example 2

[0069] The difference from Application Example 1 is that 10 mg / L of Cr(VI) is added to the cathode liquid of the cathode chamber of the microbial fuel cell.

[0070] Application Example 3

[0071] The difference from Application Example 1 is that a mixture of 10 mg / L Cr(VI) and 25 mg / L p-chlorophenol is added to the cathode liquid of the cathode chamber of the microbial fuel cell.

[0072] Comparative Application Example 1

[0073] The difference from Application Example 1 is that the cathode material is replaced with SSFF-CK of Comparative Example 1.

[0074] Comparative Application Example 2

[0075] The difference from Application Example 2 is that the cathode material is replaced with SSFF-CK of Comparative Example 1.

[0076] Comparative Application Example 3

[0077] The difference from Application Example 3 is that the cathode material is replaced with SSFF-CK of Comparative Example 1.

[0078] Performance Testing

[0079] (1) Figure 1These are SEM images of the cathode material (SSFF-MnO2) prepared in Example 1 and SSFF-CK of Comparative Example 1, where (a) is SSFF-CK and (b) is SSFF-MnO2.

[0080] from Figure 1 As shown in (a), SSFF-CK has a 3D porous structure, which can provide a loading site for the catalyst and also provide sufficient channels for the diffusion and transmission of protons and bubbles within the electrode.

[0081] from Figure 1 As can be seen in (b), a large number of nanorod-shaped MnO2 crystals are loaded on the surface of SSFF. Due to the surface characteristics and more oxygen vacancies, this structure makes the SSFF-MnO2 composite cathode material have a higher redox reaction rate and electron acceptance capacity.

[0082] (2) Figure 2 Power density diagram of the cathode material (SSFF-MnO2) prepared in Example 1 and SSFF-CK of Comparative Example 1.

[0083] Startup, power density, and polarization curve measurement of microbial fuel cells (Application Example 1 and Comparative Application Example 1) assembled using the cathode material (SSFF-MnO2) prepared in Example 1 and the SSFF-CK of Comparative Example 1: Power density and polarization curves are important indicators for evaluating MFC power generation performance. Power density was measured after six cycles (12 days) of operation. The MFC cathode and cathode liquids were replaced, the external resistor was disconnected, and the circuit was left open for at least 12 hours until the voltage stabilized before testing. An SCE electrode was used as a reference electrode and placed in the hole near the anode in the anode chamber. The external resistor was adjusted in the order of 9000Ω, 7000Ω, 5000Ω, 3000Ω, 1000Ω, 900Ω, 700Ω, 500Ω, 300Ω, 200Ω, 100Ω, and 50Ω. Each test was performed with a multimeter after 20 minutes of stabilization. The corresponding current density and power density were calculated using the following Ohm's law formula.

[0084]

[0085] Among them, i A is the current density (mA·m -2 ), A is the anode projected area (4×10 -4 m 2 ), R is the variable external resistance in the test (Ω), U is the output voltage under different R (V), P A is the power density (mW·m -2 ).

[0086] from Figure 2It can be seen that MnO2 modification increases the power density of the base stainless steel fiber felt by 14.20%.

[0087] (3) Figure 3 Figures 2 and 3 show the power density and Cr(VI) removal rate of the cathode material (SSFF-MnO2) in the microbial fuel cell of Application Example 2 and the cathode material (SSFF-CK) in the microbial fuel cell of Comparative Application Example 2, where (a) is the power density graph and (b) is the Cr(VI) removal rate graph. Cr(VI) was determined using the diphenylcarbazide spectrophotometric method (GB 7467-87).

[0088] from Figure 3 It can be seen that the maximum power density of SSFF-MnO2 (316.41mW·m -2 ) is 38.01% higher than that of SSFF-CK, and the Cr(VI) purification ability of SSFF-MnO2 is 24.46% higher than that of SSFF-CK.

[0089] (4) Figure 4 This is a graph showing the removal rate of Cr(VI) for the cathode material (SSFF-MnO2) in the microbial fuel cell of Application Example 3 and the cathode material (SSFF-CK) in the microbial fuel cell of Comparative Application Example 3. The testing method for Cr(VI) is the same as above.

[0090] from Figure 4 It can be seen that the purification ability of SSFF-MnO2 for Cr(VI) is improved by 16.83% compared with SSFF-CK.

[0091] (5) The electrochemical performance of SSFF-CK of Comparative Example 1 and SSFF-MnO2 of Example 1 was tested using an electrochemical workstation (model CHI660E, Shanghai Zhenhua). The exchange current density of SSFF-CK and SSFF-MnO2 was calculated by Tafel curve fitting, as shown in Figure 2. Figure 5 shown.

[0092] from Figure 5 It can be seen that the exchange current density of SSFF-CK is 1.38×10 -5 A.cm -2 , SSFF-MnO2 is 2.95×10 -4 A.cm -2 The exchange current density of the stainless steel fiber felt loaded MnO2 cathode material (SSFF-MnO2) is 21.38 times that of the stainless steel fiber felt (SSFF-CK).

[0093] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A cathode material, characterized in that: It comprises a stainless steel fiber felt and manganese dioxide, a conductive agent and a binder loaded on the stainless steel fiber felt; The conductive agent is carbon black; The binder is polytetrafluoroethylene.

2. The cathode material according to claim 1, characterized in that The mass ratio of the manganese dioxide, the conductive agent and the binder is 8:1:

1.

3. The cathode material according to claim 1 or 2, characterized in that The thickness of the cathode material is 0.4-0.8 mm.

4. The method for preparing the cathode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Manganese dioxide, a conductive agent, a binder and an organic solvent are mixed, the obtained mixed solution is coated on the surface of the stainless steel fiber felt, and dried to obtain the cathode material.

5. The preparation method according to claim 4, characterized in that: The mixing is carried out under ultrasonic conditions; the power of the ultrasound is 150-200W; the frequency of the ultrasound is 40kHz; and the time of the ultrasound is 0.5-1h.

6. The preparation method according to claim 4 or 5, characterized in that: The coating is as follows: firstly coating the mixed liquid on one side of the stainless steel fiber felt, and after drying, coating the mixed liquid on the other side of the stainless steel fiber felt.

7. Use of the cathode material according to any one of claims 1 to 3 or the cathode material prepared by the preparation method according to any one of claims 4 to 6 in a microbial fuel cell.

8. A microbial fuel cell, characterized in that: including a cathode chamber, an anode chamber and a diaphragm; The diaphragm separates the cathode chamber from the anode chamber; The cathode chamber stores cathode liquid and cathode material immersed in the cathode liquid; The anode chamber stores an anolyte and an anode material immersed in the anolyte; The cathode material is the cathode material according to any one of claims 1 to 3 or the cathode material prepared by the preparation method according to any one of claims 4 to 6.

9. A method for treating wastewater containing heavy metals and / or organic matter using the microbial fuel cell according to claim 8, characterized in that: The following steps are involved: The wastewater containing heavy metals and / or organic matter is placed in the cathode chamber of the microbial fuel cell and treated to obtain effluent.

10. The method according to claim 9, characterized in that The heavy metal includes Cr(VI); and the organic matter includes p-chlorophenol.

Images