Preparation of dumbbell-shaped fungal carbon material with high iron content and application of dumbbell-shaped fungal carbon material in super capacitor

Abstract

The invention provides preparation of a dumbbell-shaped fungus carbon material with high iron content and application of the dumbbell-shaped fungus carbon material in a super capacitor, a strain comes from a sludge leaching solution of a sewage treatment plant and is cultured by a Martin culture medium, and aspergillus niger with good growth condition is screened; a dumbbell-shaped fungus is obtained by regulating and controlling the morphology of a potato culture solution of a series of inorganic iron elements with a concentration gradient, and then the dumbbell-shaped fungus is carbonized at a high temperature to prepare the biomass carbon material with a stable pore structure, a large specific surface area and abundant active sites. According to the method, sludge-source fungi are used as biological templates, raw materials are easy to obtain and low in cost, and technological operation is simple, convenient and controllable. The prepared biomass carbon material has no accumulation and collapse phenomena, and shows excellent electrochemical performance as a supercapacitor electrode material. The invention provides an economic, environment-friendly and efficient new path for the preparation of the biomass carbon material for the high-performance super capacitor, and has important application value.

Description

Technical Field

[0001] This invention relates to the fields of carbon material preparation and supercapacitor technology, and particularly to the preparation of a dumbbell-shaped fungal carbon material with high iron content and its application in supercapacitors. Background Technology

[0002] The new energy industry is driving up the demand for supercapacitors, and electrode materials are the core determinants of their energy storage efficiency and stability. Carbon materials have become a research focus due to their excellent conductivity, tunable structure, and environmental friendliness. Traditional carbon material preparation processes are complex, costly, and difficult to control in terms of morphology. Metal doping can easily lead to problems such as particle agglomeration and uneven loading. Although biomass fungal-based carbon materials are renewable, low-cost, and porous after carbonization, which is conducive to ion transport, there is a lack of simple and controllable methods to achieve specific functional morphology induction and efficient and uniform metal loading.

[0003] Iron, as a preferred modified metal, is abundant, low-cost, and environmentally friendly, making its unique value particularly prominent. On the one hand, it can introduce Faraday pseudocapacitance, forming a synergistic effect with the double-layer capacitance of carbon materials, significantly improving electrode specific capacitance and energy density. Furthermore, high iron content can further optimize electron conduction efficiency, reduce ion diffusion resistance, and enhance rate performance and cycle stability. On the other hand, iron ions can act as an inducing factor, directionally regulating the formation of dumbbell-shaped morphology in fungi. The dense ends and hollow middle structure prevent pore collapse, constructing multi-layered interconnected channels, significantly increasing specific surface area and active site utilization. Simultaneously, fungi can achieve uniform iron anchoring through bioadsorption and mineralization, achieving atomic-level bonding through a one-step carbonization process, completely solving the aggregation and unevenness problems of traditional doping. It is worth mentioning that if nano-Fe2O3 is directly added to the fungal culture medium, it is prone to aggregation and sedimentation, requiring the addition of additives to increase its suspension and dispersion capabilities. However, ionic Fe3+ does not require additives during cultivation; it can enter the fungus during cultivation, better coating Fe3+, rather than simply being loaded on the surface of the fungus.

[0004] Existing fungal-based carbon materials are mostly tubular / spherical, iron-free or low-iron systems. Iron-free materials suffer from low specific capacitance and limited electronic conductivity, resulting in significant performance degradation at high charge-discharge rates. Low-iron materials exhibit uneven metal dispersion, and both types suffer from pore collapse and limited specific surface area, making their capacitance performance far from meeting requirements. Currently, there is no research on the one-step carbonization of high-iron-content carbon materials by inducing fungi to form dumbbell-shaped morphologies with iron. There is an urgent need to develop this novel preparation technology to fill the technological gap and promote the performance upgrade and industrial application of supercapacitor electrode materials. Summary of the Invention

[0005] To address the problems of existing technologies, such as difficulty in morphological control of fungal-based carbon materials, uneven metal loading, easy collapse of pores, low specific surface area utilization and poor electrochemical performance when used as electrodes in supercapacitors, especially the lack of technical solutions for inducing fungi to form special functional morphologies through metal elements and achieving efficient and uniform metal loading, and the current situation where iron-free or low-iron-content fungal carbon materials rely solely on double-layer capacitance, resulting in limited specific capacitance, energy density and rate performance, the technical problem to be solved by this invention is to provide a method for preparing a dumbbell-shaped fungal carbon material with high iron content and its application in supercapacitors. This scheme induces fungi to form a dumbbell-shaped morphology through iron domestication culture. Utilizing the fungi's feeding and metabolic processes, iron is absorbed into the fungi's body. A one-step carbonization process yields a carbon material with high iron content and stable pore structure. The aim is to achieve the resource utilization of fungal biomass while significantly increasing the specific surface area and number of active sites in the carbon material. By leveraging the synergistic effect of the pseudocapacitance introduced by iron and the double-layer capacitance of the carbon matrix, the electron conduction efficiency and ion diffusion capacity of the material are optimized, significantly improving the electrode's specific capacitance, energy density, rate performance, and cycle stability. This results in a significant performance difference compared to iron-free fungal carbon materials, providing an efficient, low-cost, and environmentally friendly preparation route for supercapacitor electrode materials.

[0006] To achieve the objectives of this invention, the following solution is adopted: Step 1) Screening and culture of dumbbell-shaped fungi: Select sludge leachate from sewage treatment plant, select Martin's selective medium with a certain formula ratio, sterilize by high pressure steam, pour into plates and cool, then take 1 ml of sludge leachate and spread it on solid medium, place it in a constant temperature incubator at 27~29℃ for 6~8 days, and screen out Aspergillus niger mycelia with good growth status. Under aseptic conditions, 10 ml of sterile water was added to Martin's medium containing mycelia. The extract was collected, counted using a hemocytometer, and then serially diluted to obtain a spore solution of 4 × 10⁴ to 4 × 10⁸ cells / ml. A series of potato culture solutions containing Fe³⁺ were prepared using a pre-prepared ferric nitrate (FeN₃O₉·9H₂O) potato culture solution at a certain concentration gradient. 100 µl of the spore solution diluted 10 times was inoculated into the low-concentration culture solution and cultured for 6–9 days at 27–29 °C and 170–190 rpm in a shaker to form spherical fungi. The spherical fungi were then sequentially transferred to culture solutions with slightly higher concentrations and cultured for 3–4 days each for tolerance acclimatization. Finally, the fungi were transferred to a higher-concentration culture solution and cultured for 3–4 days to obtain dumbbell-shaped fungi.

[0007] Step 2) Preparation of high iron content dumbbell-shaped fungal carbon material: The dumbbell-shaped fungi obtained in step 1) are washed with distilled water and freeze-dried in a freeze dryer; the dried dumbbell-shaped fungi are placed in a tube furnace, high-purity nitrogen is introduced for 5-8 minutes, the temperature is then increased to 330-360℃ at 1-5℃ / min and held for 2-2.5h, and then the temperature is increased to 750-820℃ at 1-5℃ / min for carbonization to obtain high iron content dumbbell-shaped fungal carbon material.

[0008] Step 3) Assembly and application of supercapacitor electrodes: The high iron content dumbbell-shaped fungal carbon material prepared in Step 2) is used as the electrode active material. It is mixed with conductive agent and binder at a mass ratio of 8:1:1. 1~2 ml of anhydrous ethanol is added to form a paste, which is then uniformly coated on a nickel foam current collector. The paste is dried under vacuum at 90~110℃ for 10~12 hours and pressed to obtain the working electrode of the supercapacitor. A platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and 6 mol / L NaOH solution is used as the electrolyte. The supercapacitor device is assembled to achieve efficient energy storage applications.

[0009] Further, the Martin selective medium in step 1) is composed of one or more of glucose, peptone, KH2PO4, MgSO4·7H2O and 1% Bengal red aqueous solution, wherein the amount of each component added is: glucose 10~15g, peptone 5~8g, KH2PO4 0.5~1g, MgSO4·7H2O 0.2~0.6g and 1% Bengal red aqueous solution 2~4ml.

[0010] Furthermore, in step 1), the concentration C of the ferric nitrate FeN3O9·9H2O potato culture medium is 0.02~0.03 mol / L.

[0011] Furthermore, in step 1), the concentration gradient of ferric nitrate Fe N3O9·9H2O potato culture medium is one or a combination of more of the following: 1 / 10C, ​​1 / 8C, 1 / 6C, and 1 / 4C.

[0012] Further, the method for preparing the potato culture medium in step 1) is as follows: take 200-300g of peeled potatoes, cut them into pieces, add 1000-1200ml of distilled water and boil for 25-35 minutes, filter through 8 layers of gauze to remove potato residue, add distilled water to 1000-1200ml, add 20-30g of glucose to dissolve, and sterilize by high-pressure steam at 110-125℃ for 20-30 minutes.

[0013] Furthermore, in step 2), the freeze-drying temperature is -50~60℃, the pressure is 8~15Pa, and the drying time is 24~36h.

[0014] Further, in step 3), the conductive agent is one or more of carbon black, graphene, and carbon nanotubes, or a mixture thereof.

[0015] Further, in step 3), the binder is one or a mixture of polyvinylidene fluoride, sodium carboxymethyl cellulose, and polytetrafluoroethylene.

[0016] Furthermore, in step 3), the electrode coating thickness is 50~100μm, and the pressing pressure is 5~10MPa.

[0017] Furthermore, the assembled supercapacitor assembly has a specific capacitance of not less than 250 Fg-1 at a current density of 0.5 Ag-1.

[0018] Compared with existing synthesis methods, the beneficial effects of this invention are: This invention successfully induced fungi to form dumbbell-shaped morphologies through gradient concentration Fe3+ domestication culture. Combined with a gradient temperature carbonization process, a fungal carbon material with high iron content was prepared. This invention has unique advantages over traditional morphology control methods. Fe3+ not only induces fungal growth and affects its morphology through fungal cell metabolism, but also achieves uniform ionic dispersion of iron in the carbon matrix through the bioadsorption and biomineralization of fungi. This solves the problems of metal particle agglomeration and uneven loading caused by traditional secondary addition of additives. Moreover, the high iron content (compared to iron-free or low-iron fungal carbon materials) can significantly improve its electrochemical performance when applied to supercapacitors.

[0019] The preparation method provided by this invention eliminates the need for complex templates, expensive reagents, and cumbersome post-processing steps. The process is simple, controllable, and environmentally friendly, achieving both efficient resource utilization of fungal biomass and precise control of fungal morphology and efficient, uniform iron loading. This significantly reduces the preparation cost and environmental impact of carbon materials. The resulting dumbbell-shaped carbon material possesses a unique structure of "dense at both ends and hollow in the middle" and multi-layered interconnected channels. This effectively avoids the channel collapse defects of traditional tubular and spherical carbon materials and also provides a large specific surface area and abundant active sites. When used as a supercapacitor electrode material, it utilizes a carbon matrix to construct a highly efficient double-layer capacitor while simultaneously forming a synergistic energy storage effect through the Faraday pseudocapacitance introduced by iron. Combined with a stable pore structure, it enables rapid electrolyte penetration and efficient charge transport. Compared to iron-free fungal carbon materials, its specific capacitance, energy density, and rate performance are all improved. Furthermore, it exhibits strong structural stability and minimal performance degradation during cycling, demonstrating excellent overall electrochemical performance. This invention provides a new technical path for the development of supercapacitor electrode materials. It not only fills the gap in the preparation of functionalized fungal-based carbon materials with high iron content, but also provides new ideas for the high-performance and low-cost development of biomass-based energy storage materials, and has broad application prospects and industrialization potential. Attached Figure Description

[0020] Figure 1 It has a dumbbell-shaped fungal morphology; Figure 2 EDS test results for biomass carbon materials; Figure 3 Scanning electron microscope images of biochar with different iron contents; Figure 4 Infrared spectrum of carbon in biomass; Figure 5 Electrochemical performance diagram; Figure 6 (a) is a transmission electron microscope (TEM), and (b) is a diagram of the elemental distribution analysis using a transmission electron microscope. Detailed Implementation

[0021] The present invention will be specifically described below through embodiments, which are only used to further illustrate the invention and should not be construed as limiting the scope of protection of the invention. It should be understood that after reading the contents of this invention, those skilled in the art will be able to make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0022] Example 1 The preparation of a dumbbell-shaped fungal carbon material with high iron content and its application in supercapacitors includes the following steps: (1) Select sludge leachate from sewage treatment plant, select Martin's selective medium with a certain formula ratio, sterilize by high pressure steam, pour into plates and cool, then take 1 ml of sludge leachate and spread it on solid medium, place it in a constant temperature incubator at 27℃ for 6 days, and screen out Aspergillus niger with good growth status. Under aseptic conditions, 10 ml of sterile water was added to Martin's medium containing mycelia, and the extract was collected. After counting with a hemocytometer, the extract was serially diluted to obtain a spore solution of 4 × 10⁴ cells / ml. Then, a series of potato culture solutions containing Fe³⁺ were prepared using a prepared ferric nitrate (FeN₃O₉·9H₂O) potato culture solution at a certain concentration gradient. 100 µl of the spore solution diluted 10 times was inoculated into the low-concentration culture solution and cultured for 6 days at 27℃ and 170 r / min in a shaker to form spherical fungi. The spherical fungi were then transferred to culture solutions with slightly higher concentrations and cultured for 3 days each for tolerance acclimatization. Finally, the fungi were transferred to a high-concentration culture solution and cultured for 3 days to obtain dumbbell-shaped fungi.

[0023] (2) The dumbbell-shaped fungus obtained in step (1) was washed with distilled water and freeze-dried in a freeze dryer. The dried dumbbell-shaped fungus was placed in a tube furnace, high-purity nitrogen was introduced for 5 minutes, and then the temperature was increased to 330°C at 1°C / min and kept for 2 hours. Then the temperature was increased to 750°C at 2°C / min for carbonization to obtain a dumbbell-shaped fungus carbon material with high iron content.

[0024] (3) The high iron content dumbbell-shaped fungal carbon material prepared in step (2) is used as the electrode active material. It is mixed with conductive agent and binder at a mass ratio of 8:1:1. 1 ml of anhydrous ethanol is added to make a paste. The paste is uniformly coated on the foam nickel current collector and dried in vacuum at 90°C for 10 hours. After pressing, the working electrode of the supercapacitor is obtained. A platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and 6 mol / L NaOH solution is used as the electrolyte. The supercapacitor is assembled to realize efficient energy storage application.

[0025] Example 2 (1) Select sludge leachate from sewage treatment plant, select Martin's selective medium with a certain formula ratio, sterilize by high pressure steam, pour into plates and cool, then take 1 ml of sludge leachate and spread it on solid medium, place it in a constant temperature incubator at 28℃ for 7 days, and screen out Aspergillus niger with good growth status. Under aseptic conditions, 10 ml of sterile water was added to Martin's medium containing mycelia, and the extract was collected. After counting with a hemocytometer, the extract was serially diluted to obtain a spore solution of 4 × 10⁶ cells / ml. Then, a series of potato culture solutions containing Fe³⁺ were prepared using a prepared ferric nitrate (FeN₃O₉·9H₂O) potato culture solution at a certain concentration gradient. 100 µl of the spore solution diluted 10 times was inoculated into the low-concentration culture solution and cultured for 7 days at 28℃ and 180 r / min in a shaker to form spherical fungi. The spherical fungi were then transferred to culture solutions with slightly higher concentrations and cultured for 3 days each for tolerance acclimatization. Finally, the fungi were transferred to a higher concentration culture solution and cultured for 4 days to obtain dumbbell-shaped fungi.

[0026] (2) The dumbbell-shaped fungus obtained in step (1) was washed with distilled water and freeze-dried in a freeze dryer. The dried dumbbell-shaped fungus was placed in a tube furnace, high-purity nitrogen was introduced for 7 minutes, and then the temperature was raised to 350°C at 3°C / min and kept at 3°C / min for 2.2 hours. Then the temperature was raised to 780°C at 1°C / min for carbonization to obtain a dumbbell-shaped fungus carbon material with high iron content.

[0027] (3) The high iron content dumbbell-shaped fungal carbon material prepared in step (2) is used as the electrode active material. It is mixed with conductive agent and binder at a mass ratio of 8:1:1. 1.5 ml of anhydrous ethanol is added to make a paste. The paste is uniformly coated on the foam nickel current collector and dried in vacuum at 100°C for 11 hours. After pressing, the working electrode of the supercapacitor is obtained. A platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and 6 mol / L NaOH solution is used as the electrolyte. The supercapacitor is assembled to realize efficient energy storage application.

[0028] Example 3 (1) Select sludge leachate from sewage treatment plant, select Martin's selective medium with a certain formula ratio, sterilize by high pressure steam, pour into plates and cool, then take 1 ml of sludge leachate and spread it on solid medium, place it in a constant temperature incubator at 29℃ for 8 days, and screen out Aspergillus niger with good growth status. Under aseptic conditions, 10 ml of sterile water was added to Martin's medium containing mycelia, and the extract was collected. After counting with a hemocytometer, the extract was serially diluted to obtain a spore solution of 4 × 10⁸ cells / ml. Then, a series of potato culture solutions containing Fe³⁺ were prepared using a prepared ferric nitrate (FeN₃O₉·9H₂O) potato culture solution at a certain concentration gradient. 100 µl of the spore solution diluted 10 times was inoculated into the low-concentration culture solution and cultured for 7 days at 29℃ and 190 r / min in a shaker to form spherical fungi. The spherical fungi were then transferred to culture solutions with slightly higher concentrations and cultured for 4 days each for tolerance acclimatization. Finally, the fungi were transferred to a higher concentration culture solution and cultured for 3 days to obtain dumbbell-shaped fungi.

[0029] (2) The dumbbell-shaped fungus obtained in step (1) was washed with distilled water and freeze-dried in a freeze dryer. The dried dumbbell-shaped fungus was placed in a tube furnace, high-purity nitrogen was introduced for 8 minutes, and then the temperature was increased to 360°C at 5°C / min and kept at 2.5h. Then the temperature was increased to 820°C at 3°C / min for carbonization to obtain a dumbbell-shaped fungus carbon material with high iron content.

[0030] (3) The high iron content dumbbell-shaped fungal carbon material prepared in step (2) is used as the electrode active material. It is mixed with conductive agent and binder at a mass ratio of 8:1:1. An appropriate amount of anhydrous ethanol is added to make a paste. The paste is uniformly coated on the foam nickel current collector and vacuum dried at 110°C for 12 hours. After pressing, the working electrode of the supercapacitor is obtained. A platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and a 6 mol / L NaOH solution is used as the electrolyte. The supercapacitor is assembled to realize efficient energy storage application.

[0031] Comparative Example 1 (1) Sludge leachate from a wastewater treatment plant was selected, and Martin's selective medium with a certain formula ratio was used. After high-pressure steam sterilization, the medium was poured into plates and cooled. Then, 1 ml of the sludge leachate was spread onto a solid medium and placed in a constant temperature incubator at 27℃ for 6 days to screen out Aspergillus niger with good growth. Under aseptic conditions, 10 ml of sterile water was added to Martin's medium with mycelium, the leachate was collected, and after counting with a hemocytometer, it was serially diluted to obtain a spore solution of 4×104 cells / ml. 100 µl of the spore solution diluted 10 times was added to the medium and cultured in a shaker at 27℃ and 170 r / min for 6 days to form spherical fungi.

[0032] (2) The fungi obtained in step (1) are washed with distilled water and freeze-dried in a freeze dryer. The dried fungi are placed in a tube furnace, high-purity nitrogen is introduced for 5 minutes, then the temperature is increased to 330℃ at 1℃ / min and kept at 2h, and then the temperature is increased to 750℃ at 2℃ / min for carbonization to obtain fungal carbon material.

[0033] (3) The fungal carbon material prepared in step (2) is used as the electrode active material, and is mixed with conductive agent and binder at a mass ratio of 8:1:1. 1 ml of anhydrous ethanol is added to make a paste, which is then uniformly coated on the foamed nickel current collector. The paste is dried in vacuum at 90°C for 10 hours and then pressed to obtain the working electrode of the supercapacitor. A platinum sheet is used as the counter electrode, a saturated calomel electrode is used as the reference electrode, and a 6 mol / L NaOH solution is used as the electrolyte. The supercapacitor is assembled to realize efficient energy storage applications.

[0034] Test methods The Aspergillus niger used in this invention was obtained from sludge leachate from a wastewater treatment plant. The morphology of the dumbbell-shaped fungus was obtained by photographing with an optical microscope; the internal structure of the dumbbell-shaped fungus was observed using a scanning electron microscope. Depend on Figure 1 As shown in the scanning morphology sample, the present invention successfully induced Aspergillus niger to form a dumbbell-shaped special morphology. This morphology can not only effectively avoid the problem of pore collapse in traditional tubular or spherical carbon materials, but its unique structure with dense ends and hollow middle can also construct multi-level interconnected pores, greatly improving the specific surface area and the utilization rate of active sites.

[0035] Depend on Figure 2 As shown in the EDS test chart of the biomass carbon material, the iron content of the prepared biomass carbon material is 1.4%, and the iron element is uniformly dispersed. The dumbbell-shaped structure not only prevents the collapse of the pores and increases the specific surface area, but the iron element also gives the biomass carbon material an additional "capacitive boost". This, together with the capacitance of the carbon material itself, forms a supporting effect. Compared with iron-free or low-iron materials, it significantly improves the specific capacitance, energy density, rate performance and cycle stability, verifying the effectiveness of the iron element-induced technology.

[0036] Depend on Figure 3 Scanning electron microscope images of biochar with different iron contents clearly show a filamentous network structure, a typical characteristic of fungal organisms. Furthermore, beneath the interwoven filamentous structure lie complex interconnected channels, which are preserved during gradient-heat carbonization and provide the necessary capillary forces for water transport.

[0037] Depend on Figure 4The infrared spectrum shows that the vibration peak at 3427.87 cm⁻¹ is the stretching vibration peak of NH, the vibration peak at 589.92 cm⁻¹ is the metal peak of Fe-O in Fe₃O₄, and the stretching vibration peaks at 1618.92 cm⁻¹ and 1065.51 cm⁻¹ are the stretching vibration peaks of C=C and COC, respectively. This indicates that iron was successfully induced on dumbbell-shaped fungi.

[0038] Depend on Figure 5 As shown in the electrochemical performance graph, at a current density of 0.5 A g⁻¹, the GCD (galvanostatic charge-discharge curve) yielded a specific capacitance of 285.4 F g⁻¹ for the iron-added material, while the specific capacitance of Comparative Example 1 was only 198.3 F g⁻¹. This indicates that the introduction of iron improved the energy storage capacity of the biomass carbon material by approximately 44%, and also confirms that the modification of iron optimized the capacitance performance of the biomass carbon material.

[0039] Depend on Figure 6 Transmission electron microscopy (TEM) and elemental distribution analysis of planar sections of the biomass carbon material clearly show that iron is uniformly dispersed in the carbon matrix without agglomeration. This not only confirms the good dispersion of iron in the carbon material but also further corroborates that iron has successfully entered the fungal cells and remained in the biomass carbon material during the fungal carbonization process.

[0040] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. Preparation of a high-iron-content dumbbell-shaped fungal carbon material and its application in supercapacitors, characterized in that, Includes the following steps: Step 1) Screening and culture of dumbbell-shaped fungi: Sludge leachate from a wastewater treatment plant was selected, and Martin's selective medium with a specific formulation was used. After autoclaving, the medium was poured onto plates and cooled. 1 ml of the sludge leachate was then spread onto a solid medium and incubated at 27-29°C for 6-8 days. Well-grown Aspergillus niger hyphae were screened. Under aseptic conditions, 10 ml of sterile water was added to the confluent Martin's medium. The leachate was collected, counted using a hemocytometer, and serially diluted to obtain 4×10⁴ to 4×10⁸ cells / days. / ml of spore solution; then, using the prepared ferric nitrate FeN3O9·9H2O potato culture medium, a series of potato culture mediums containing Fe3+ were prepared according to a certain concentration gradient. 100µl of spore solution diluted 10 times was inoculated into the low-concentration culture medium and cultured in a shaker at 27~29℃ and 170~190r / min for 6~9 days to form spherical fungi; the spherical fungi were successively transferred to culture mediums with slightly higher concentrations than the previous ones and cultured for 3~4 days each for tolerance acclimatization. Finally, they were transferred to a culture medium with a higher concentration and cultured for 3~4 days to obtain dumbbell-shaped fungi. Step 2) Preparation of high iron content dumbbell-shaped fungal carbon material: The dumbbell-shaped fungus obtained in step 1) is washed with distilled water and freeze-dried in a freeze dryer; the dried dumbbell-shaped fungus is placed in a tube furnace, high-purity nitrogen is introduced for 5-8 minutes, then the temperature is increased to 330-360℃ at 1-5℃ / min and held for 2-2.5h, and then the temperature is increased to 750-820℃ at 1-5℃ / min for carbonization to obtain high iron content dumbbell-shaped fungal carbon material; Step 3) Assembly and application of supercapacitor electrode: The high iron content dumbbell-shaped fungal carbon material prepared in step 2) is used as the electrode active material. It is mixed with conductive agent and binder at a mass ratio of 8:1:

1. 1~2 ml of anhydrous ethanol is added to make a paste. The paste is uniformly coated on the foamed nickel current collector and vacuum dried at 90~110℃ for 10~12 hours. After pressing, the supercapacitor working electrode is obtained. Using a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and a 6 mol / L NaOH solution as the electrolyte, a supercapacitor is assembled to achieve efficient energy storage applications.

2. The preparation of a high-iron-content dumbbell-shaped fungal carbon material and its application in supercapacitors according to claim 1, characterized in that, The Martin selective medium in step 1) consists of one or more of the following: glucose, peptone, KH2PO4, MgSO4·7H2O and 1% Bengal red aqueous solution. The amount of each component added is as follows: glucose 10-15g, peptone 5-8g, KH2PO4 0.5-1g, MgSO4·7H2O 0.2-0.6g and 1% Bengal red aqueous solution 2-4ml.

3. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, The concentration C of the ferric nitrate FeN3O9·9H2O potato culture medium in step 1) is 0.02~0.03mol / L.

4. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, In step 1), the concentration gradient of the ferric nitrate (Fe N3O9·9H2O) potato culture medium is one or a combination of more than one of the following: 1 / 10C, ​​1 / 8C, 1 / 6C, and 1 / 4C.

5. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, The method for preparing the potato culture medium in step 1) is as follows: Take 200-300g of peeled potatoes, cut them into pieces, add 1000-1200ml of distilled water and boil for 25-35 minutes. Filter through 8 layers of gauze to remove potato residue, add distilled water to 1000-1200ml, add 20-30g of glucose to dissolve, and sterilize by high-pressure steam at 110-125℃ for 20-30 minutes.

6. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, In step 2), the freeze-drying temperature is -50~60℃, the pressure is 8~15Pa, and the drying time is 24~36h.

7. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, In step 3), the conductive agent is one or more of carbon black, graphene, and carbon nanotubes, or a mixture thereof.

8. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, In step 3), the binder is one or a mixture of polyvinylidene fluoride, sodium carboxymethyl cellulose, and polytetrafluoroethylene.

9. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, In step 3), the electrode coating thickness is 50~100μm, and the pressing pressure is 5~10MPa.

10. The preparation of a high-iron-content dumbbell-shaped fungal carbon material according to claim 1 and its application in supercapacitors, characterized in that, The assembled supercapacitor has a specific capacitance of not less than 250 Fg-1 at a current density of 0.5 Ag-1.

Images