Preparation method of microbial fuel cell air cathode catalyst AB-N-P-x
By preparing AB-NPx catalysts, the problems of high cost and poor stability of cathode catalysts in microbial fuel cells were solved, achieving efficient and low-cost oxygen reduction, thus promoting the development of microbial fuel cells.
Patent Information
- Application Number
- CN202410740994.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-11
- Publication Date
- 2025-12-12
AI Technical Summary
Existing microbial fuel cell cathode catalysts are expensive and have poor stability, which limits their large-scale application.
A heteroatom-doped porous carbon-based composite material was prepared by alkaline method. After treating straw with melamine, KOH and KHCO3, and then doping with NaH2PO4, an AB-NPx catalyst was formed for use as the air cathode of a microbial fuel cell.
It improves oxygen reduction rate and long-term stability, reduces material costs, and exhibits superior catalytic performance compared to the precious metal Pt, making it suitable for large-scale production of microbial fuel cells.
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing AB-NPx cathode catalyst for microbial fuel cells. Background Technology
[0002] Water resources have become a bottleneck restricting my country's sustainable development. Wastewater treatment, reuse, and recycling are key to solving this problem. Microbial fuel cells (MFCs), as an emerging technology, can treat organic wastewater and utilize microorganisms in the wastewater for redox reactions to generate electricity. At the anode of MFCs, microorganisms release electrons by oxidizing organic matter. These electrons are transferred to the cathode through an external circuit. Air cathode MFCs utilize oxygen from the air as the final electron acceptor for direct reaction in the catalyst layer. However, the slow redox reaction (ORR) kinetics at the cathode limit its large-scale application. Therefore, the cathode catalyst that can accelerate the ORR process becomes the main factor affecting the performance of air cathode MFCs.
[0003] Platinum (Pt) is widely reported due to its excellent ORR performance; however, its high cost makes finding alternatives to Pt a primary research focus. Developing and designing efficient, low-cost, and stable cathode oxygen reduction reaction catalysts is crucial for promoting the development of MFCs (Multi-Fuel Cells) in order to reduce the cathode reduction potential and improve cathode ORR efficiency. To date, numerous reports have focused on non-precious metals, and while some non-precious metals have outperformed Pt in electrochemical performance, the dissolution of transition metal catalysts can exacerbate environmental pollution. In recent years, research has turned to metal-free catalysts due to their availability, low cost, good conductivity, high specific surface area, and chemical stability. However, the inherent activity of metal-free catalysts often falls short of requirements, especially on some unmodified carbon-based materials. To transform metal-free catalysts into high-performance and inexpensive catalysts, heteroatom doping (S, O, N, F, P, B, etc.) is generally employed.
[0004] This invention aims to solve the problems of high cost and poor stability of catalysts. Porous carbon was prepared using an alkaline method, and then heteroatom doping was performed on the porous carbon. The heteroatom-doped porous carbon-based composite catalyst prepared by this invention not only improves the oxygen reduction rate and long-term stability under biological conditions at the cathode of MFCs, but also minimizes the cost of material preparation, making it an ideal oxygen reduction catalyst for MFCs cathodes. Summary of the Invention
[0005] The purpose of this invention is to solve the problems of high cost and poor stability of existing catalysts, and to provide a method for preparing a catalyst suitable for the air cathode of microbial fuel cells.
[0006] The present invention discloses a method for preparing an air cathode catalyst for a microbial fuel cell, characterized in that the preparation method of the air cathode material for the microbial fuel cell is achieved through the following steps: (1) Preparation of AB-NPx cathode catalyst: ① Dissolve a certain amount of straw in deionized water, disperse it by ultrasonication, and obtain a uniformly dispersed solution; ② Dissolve a certain amount of melamine, KOH, and KHCO3 in deionized water, and disperse by ultrasonication to obtain a uniformly dispersed solution; ③ Add the solution obtained in step ② dropwise to the solution obtained in step ① to obtain a mixed solution; ④ After heating and stirring the solution obtained in step ③ for 3 hours, let it stand, wash it with ethanol, and then dry it to obtain AB; ⑤ Place the product AB obtained in step ④ in a tube furnace, calcine it under a nitrogen atmosphere for a certain time, and then cool it naturally to room temperature to obtain AB-N; ⑥ The product AB-N obtained in step ⑤ is placed in 1M hydrochloric acid solution for acid washing for 1 hour, and then centrifuged and dried. ⑦ Place the product AB-N obtained in step ⑥ into the downstream of a tube furnace, place 0.2g of NaH2PO4 in the upstream of the tube furnace, calcine at a constant temperature, and cool to room temperature to obtain the black product AB-NPx (x is the mass ratio of NaH2PO4 to AB-N).
[0007] (2) Preparation of AB-NPx cathode electrode and assembly of single-chamber MFC reactor: This invention uses carbon brushes as the anode. To remove residual impurities, the carbon brushes are first soaked in acetone for 24 hours, then rinsed with deionized water and dried in an oven at 60°C. They are then calcined in a muffle furnace at 450°C for 30 minutes. The air cathode consists of a catalyst layer, a stainless steel mesh, and a gas diffusion layer, and is manufactured using a rolling method. A mixture of carbon black and polytetrafluoroethylene (PTFE) at a mass ratio of 7:3 is coated onto stainless steel, then rolled, and finally the resulting gas diffusion layer is calcined in a muffle furnace at 340°C for 20 minutes. The prepared AB-NPx sample is mixed with PTFE and then pressed onto the other side of the gas diffusion layer. These components are then dried at 40°C for 12 hours and cut into pieces with an area of 7 cm². -2 A round disc.
[0008] Preferably, in step (1)①, the amount of straw used is 3g and the amount of deionized water used is 25mL.
[0009] Preferably, in step (1) ②, the amount of melamine used is 3g, the amount of KOH used is 1g, the amount of KHCO3 used is 3g, and the amount of deionized water used is 25mL.
[0010] Preferably, in step (1) ④, the heating and stirring temperature is 70°C, the stirring rate is 300 r / min, and the product is placed in a 60°C oven to dry for 12 hours.
[0011] Preferably, the calcination process in step (1) ⑤ is to raise the temperature from room temperature to 900°C at a heating rate of 5°C / min and calcine at a constant temperature for 2 hours.
[0012] Preferably, the calcination process in step (1) ⑦ is to raise the temperature from room temperature to 350°C at a heating rate of 2°C / min and calcine at a constant temperature for 2 hours.
[0013] Compared with the prior art, the advantages of the present invention are: (1) The AB-NPx microbial fuel cell cathode catalyst material prepared by the method of the present invention, after being treated by alkaline method, yields a porous composite material with good conductivity, stability, large specific surface area and mesoporous structure; (2) The AB-NPx microbial fuel cell cathode catalyst material prepared by the method of the present invention uses inexpensive KOH and KHCO3 as pore-forming agents, and the amount used is extremely low, which saves costs.
[0014] (3) The AB-NPx microbial fuel cell cathode catalyst material prepared by the method of the present invention has a better power generation performance than noble metal catalysts such as Pt by heteroatom doping of porous carbon materials, effectively reducing the catalyst manufacturing cost and providing a theoretical basis for the large-scale production and application of microbial fuel cells. Attached Figure Description
[0015] Figure 1 Here is a SEM image of the AB-NPx catalyst; Figure 2 TEM image of AB-NPx catalyst; Figure 3 XPS plot of AB-NPx catalyst; Figure 4 The cyclic voltammetry curves for the AB-NPx catalyst are shown below. Figure 5 Cyclic voltammetry curves of AB-NPx catalysts with different P-doped ratios; Figure 6 The polarization-power density curves of the AB-NPx catalyst are shown. Figure 7 This is a voltage-time graph for the AB-NPx catalyst. Detailed Implementation (1) Preparation of AB-NPx cathode catalyst
[0016] ① Dissolve 3g of straw in 25mL of deionized water and disperse by ultrasonication to obtain a uniformly dispersed solution; ② Dissolve 3g of melamine, 1g of KOH, and 3g of KHCO3 in 25mL of deionized water and disperse by ultrasonication to obtain a uniformly dispersed solution; ③ Add the solution obtained in step ② dropwise to the solution obtained in step ① to obtain a mixed solution; ④ Heat and stir the solution obtained in step ③ for 3 hours, then let it stand. The heating and stirring temperature was 70℃, and the stirring speed was 300 rpm. After washing 6 times with ethanol at a rate of r / min, the product was dried in a 60℃ oven for 12 hours; ⑤ The product obtained in step ④ was calcined in a tube furnace at 900℃ under a nitrogen atmosphere at a heating rate of 5℃ / min for 2 hours, and then cooled for later use; ⑥ The product AB-N obtained in step ⑤ was acid-washed in 1M hydrochloric acid solution for 1 hour, and then centrifuged and dried; ⑦ The product AB-N obtained in step ⑥ was placed downstream of a tube furnace, and 0.2 g of NaH2PO4 was placed upstream of the tube furnace. The temperature was increased from room temperature to 350℃ at a heating rate of 2℃ / min, and calcined at this temperature for 2 hours. After cooling to room temperature, the black product AB-NPx was obtained, which is the modified catalyst material for the air cathode.
[0017] (2) Preparation of AB-NPx cathode electrode and assembly of single-chamber MFC reactor: This invention uses carbon brushes as the anode. To remove residual impurities, the carbon brushes are first soaked in acetone for 24 hours, then rinsed with deionized water and dried in an oven at 60°C. They are then calcined in a muffle furnace at 450°C for 30 minutes. The air cathode consists of a catalyst layer, a stainless steel mesh, and a gas diffusion layer, and is manufactured using a rolling method. A mixture of carbon black and polytetrafluoroethylene (PTFE) at a mass ratio of 7:3 is coated onto stainless steel, then rolled, and finally the resulting gas diffusion layer is calcined in a muffle furnace at 340°C for 20 minutes. The prepared AB-NPx sample is mixed with PTFE and then pressed onto the other side of the gas diffusion layer. These components are then dried at 40°C for 12 hours and cut into pieces with an area of 7 cm². -2 A round disc.
[0018] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass of NaH2PO4 in step (1) ⑦ is 0.1g. Other steps and parameters are the same as in Specific Implementation Method One.
[0019] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 in that the mass of NaH2PO4 in step (1) ⑦ is 0.3g. Other steps and parameters are the same as in Specific Implementation Method 1.
[0020] Characterization and performance analysis of the catalytic materials in specific embodiments one through three: Figure 1This is a SEM image. In the image, we can observe that the material has a porous and rough structure. The rough surface exposes more active sites to the electrolyte and oxygen, thereby enhancing the ORR reaction kinetics.
[0021] Figure 2 This is a TEM image, in which we can observe the porous structure of the material, further proving the successful synthesis of the porous material.
[0022] Figure 3 The XPS plot shows C, N, O, and P peaks, further confirming the success of heteroatomization.
[0023] Figure 4 The figure shows the CV curves of Pt / C and porous carbon with different heteroatoms in 0.1M KOH. As shown in the figure, the series of materials all have reduction peaks symbolizing ORR between 0.80-0.86V, and the peak positions are all higher than those of the Pt / C catalyst. Among them, the reduction peak position of AB-NP-10 is the highest, which proves that the synergistic effect of heteroatoms P and N increases the number of active sites and improves the ORR activity.
[0024] Figure 5 The figure shows the CV curves of porous carbon doped with different proportions of P in 0.1M KOH. The series of materials all have reduction peaks symbolizing ORR between 0.80-0.86V. Among them, the reduction peak of AB-NP-10 is the highest, which proves that the reduction peak is the highest when the doping ratio is 10.
[0025] Figure 6 This is a schematic diagram of the polarization and power density curves at the end of the cycle. MFCs using AB-NP-10 as the cathode catalyst exhibited a maximum power density of 896.4 mW / m³. -2 This is higher than the 538.2 mW / m of Pt / C. -2 The significant improvement indicates that AB-NP-10 still exhibits excellent ORR activity in MFCs at the end of its operation. Furthermore, the voltage changes slowly with increasing current, suggesting a higher charge transfer rate at the electrode surface.
[0026] Figure 7 This diagram illustrates the voltage output of single-chamber MFCs using AB-N, Pt / C, and AB-NP-10 catalysts, showing their performance over a 1000-hour test period under an external resistance of 1000 Ω. The diagram clearly shows that the co-doped AB-NP-10 exhibits the most stable and highest output voltage, likely attributed to the co-doping of P and N atoms and the synergistic effect between the heteroatoms.
[0027] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.
Claims
1. A method for preparing a heteroatom-doped porous carbon microbial fuel cell air cathode catalyst, characterized in that... The preparation of air cathode materials for microbial fuel cells is achieved through the following steps: (1) Preparation of AB-NPx cathode catalyst: ① Dissolve a certain amount of straw in deionized water, disperse it by ultrasonication, and obtain a uniformly dispersed solution; ② Dissolve a certain amount of melamine, KOH, and KHCO3 in deionized water, and disperse by ultrasonication to obtain a uniformly dispersed solution; ③ Add the solution obtained in step ② dropwise to the solution obtained in step ① to obtain a mixed solution; ④ After heating and stirring the solution obtained in step ③ for 3 hours, let it stand, wash it with ethanol, and then dry it to obtain AB; ⑤ Place the product AB obtained in step ④ in a tube furnace, calcine it under a nitrogen atmosphere for a certain time, and then cool it naturally to room temperature to obtain AB-N; ⑥ The product AB-N obtained in step ⑤ is placed in 1M hydrochloric acid solution for acid washing for 1 hour, and then centrifuged and dried. ⑦ Place the product AB-N obtained in step ⑥ into the downstream of a tube furnace, place 0.2g of NaH2PO4 in the upstream of the tube furnace, calcine at a constant temperature, and cool to room temperature to obtain the black product AB-NPx (x is the mass ratio of NaH2PO4 to AB-N).
2. (2) Preparation of AB-NPx cathode electrode and assembly of single-chamber MFC reactor: This invention uses carbon brushes as the anode. To remove residual impurities, the carbon brushes are first soaked in acetone for 24 h, then rinsed with deionized water and dried in an oven at 60 °C. They are then calcined in a muffle furnace at 450 °C for 30 min. The air cathode consists of a catalyst layer, a stainless steel mesh, and a gas diffusion layer, and is manufactured using a rolling method. A mixture of carbon black and polytetrafluoroethylene (PTFE) at a mass ratio of 7:3 is coated onto stainless steel, then rolled, and finally the resulting gas diffusion layer is calcined in a muffle furnace at 340 °C for 20 min. The prepared AB-NPx sample is mixed with PTFE and then pressed onto the other side of the gas diffusion layer. These components are then dried at 40 °C for 12 h and cut into pieces with an area of 7 cm². -2 A round disc.
3. The method for preparing an air cathode catalyst for a microbial fuel cell according to claim 1, characterized in that... In step (1)①, the amount of straw used is 3g and the amount of deionized water used is 25mL.
4. The method for preparing an air cathode catalyst for a microbial fuel cell according to claim 1, characterized in that... In step (1) ②, the amount of melamine used is 3g, the amount of KOH used is 1g, the amount of KHCO3 used is 3g, and the amount of deionized water used is 25mL.
5. The method for preparing an air cathode catalyst for a microbial fuel cell according to claim 1, characterized in that... In step (1) ④, the heating and stirring temperature is 70℃, the stirring speed is 300 r / min, and the product is placed in a 60℃ oven to dry for 12h.
6. The method for preparing an air cathode catalyst for a microbial fuel cell according to claim 1, characterized in that... The calcination process in step (1) ⑤ is to raise the temperature from room temperature to 900℃ at a rate of 5℃ / min and calcine at a constant temperature for 2 hours.
7. The method for preparing an air cathode catalyst for a microbial fuel cell according to claim 1, characterized in that... The calcination process in step (1) ⑦ is to raise the temperature from room temperature to 350℃ at a heating rate of 2℃ / min and calcine at a constant temperature for 2 hours.