Preparation method of carbon-based graded porous biological electrode material of biomass-resin composite material

Abstract

The invention discloses a preparation method of a carbon-based graded porous biological electrode material of a biomass-resin composite material, belongs to the technical field of microbial electrochemistry, and particularly relates to a preparation method of a porous biological electrode material. Aiming at the problems of low electrode-biological membrane interface electron transfer efficiency, low chemical energy-electric energy conversion efficiency and the like in a microbial electrochemical system, the flexible and controllable preparation of a high-performance, low-cost and graded porous carbon-based electrode material is realized by utilizing renewable biomass resources, and the porous carbon-based electrode material is prepared by compounding with an industrial resin material. And the mechanical property and the modification effect of the carbon-based electrode are enhanced. An industrial-grade resin matrix is introduced as a structural support and a conducting medium, compounding of a resin polymer can effectively improve mechanical defects and enhance durability, the resin material can serve as a structural support and a conducting medium, and target element doping and chemical modification can be achieved by flexibly changing synthetic monomers or adding other components.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial electrochemistry, and in particular relates to a method for preparing a carbon-based hierarchical sub-porous bioelectrode material based on a biomass-resin composite material. Background Art

[0002] At present, sewage treatment processes mostly focus on the removal of pollutants, while ignoring the resource-based properties of sewage. The problems of high material consumption, high energy consumption, and high carbon emissions in traditional sewage treatment have become a bottleneck for the low-carbon development of my country's water treatment industry. 25% to 40% of the operating costs of traditional sewage treatment plants come from energy consumption, of which electricity consumption accounts for 3% of global electricity, and the aeration stage with the highest energy consumption consumes 50% to 60% of the total electricity. In addition, the greenhouse gas emissions generated in the traditional sewage treatment process and the indirect greenhouse gas emissions generated by sewage energy consumption are huge. The chemical energy contained in the organic matter in sewage is a potential energy source. Theoretically, the chemical oxygen demand concentration of 1L is 500mg L -1 Complete oxidation of domestic sewage can generate 1.93kWhm -3 of electricity.

[0003] Bioelectrochemical technology offers a promising solution to my country's low-carbon strategy for wastewater treatment. Electroactive microorganisms are microorganisms capable of bidirectionally exchanging electrons and energy with the external environment through extracellular electron transfer. These include electrogenic microorganisms that release electrons to the environment and electrophilic microorganisms that receive electrons from the environment. Bioelectrochemical systems (MESs) share the common characteristic of utilizing electron and energy exchange between electroactive microorganisms and the external environment. The anode is the primary site for efficient pollutant removal. Electrogenic microorganisms oxidize organic pollutants and release electrons to the anode, achieving efficient pollutant degradation while also serving as a continuous electron source. The cathode is a crucial unit for expanding the functionality of the MES. Electrophilic microorganisms utilize electrons transferred from the anode to bind to various receptors, enabling a variety of functions such as wastewater energy conversion, denitrification, and catalytic CO2 synthesis. Related wastewater energy resource technologies derived from bioelectrochemical technology are expected to play a crucial role in reducing pollution and carbon emissions in water treatment.

[0004] The core bottleneck limiting the performance of bioelectrochemical systems is the inefficient electron transfer between the electrode and microorganisms. The core process of MES is the exchange of electrons and energy between electroactive bacteria and electrodes. Improving the electron transfer rate at the interface between electrode materials and electroactive microorganisms can directly promote functional indicators such as the decomposition efficiency of organic pollutants in MES, the rate of gas extraction for energy conversion, and the rate of CO2 fixation and chemical synthesis. This is essential for achieving the technical and economic viability of MES. Electrodes serve as habitats for electroactive microorganisms and sites for electron and energy exchange. Uncovering the multi-scale electrode-microorganism interaction process, overcoming key material and mechanism bottlenecks, and constructing efficient electrode-microorganism electron transfer systems are of great significance to the application of bioelectrochemical technology and its large-scale expansion.

[0005] Carbon-based electrode materials are widely used in microbial electrochemical systems due to their excellent conductivity and stable physicochemical properties. Commercially available two-dimensional materials, such as carbon cloth and carbon paper, were the earliest and most widely used, but they are expensive and have relatively limited available surface area. To further reduce material preparation costs, increase specific surface area, and enhance electrode performance, three-dimensional carbon-based materials with rich pore structures and more bioaccessible surface area have become a research hotspot. Key properties of efficient three-dimensional MES electrode materials include low cost, high conductivity, large specific surface area, excellent mechanical properties, and biocompatibility. Carbon brushes (CBs) are considered one of the best-performing commercial carbon-based materials. However, their columnar structure results in large inter-electrode spacing, hindering space conservation and the dense stacking of modular MESs. Furthermore, they are costly and difficult to modify. In contrast, flat carbon cloth (CC), carbon felt (CF), and carbon paper (CP) materials are widely used in MESs, but these materials are limited by their relatively low specific surface area, poor conductivity, and lack of capacitive buffering capacity. Capacitive anodes are crucial in MESs because they can rapidly store and release electrons, improving the efficiency of electron transfer in electrochemical reactions while also buffering electrode potential fluctuations to ensure stable system operation. To improve capacitive performance, materials such as activated carbon, carbon nanotubes, and graphene are often incorporated into carbon-based matrices. While these additives can increase specific surface area and optimize pore structure, they still cannot simultaneously provide the high bioavailable surface area required for exoelectric bacterial colonization.

[0006] Biomass-derived materials, with their widespread availability and low cost, offer another alternative. First, biomass is a renewable energy source, derived from carbon dioxide fixed by sunlight. Second, biomass is composed of cellular structures and can be converted into porous carbon materials through pyrolysis and activation as a precursor. Third, biomass contains a variety of elements. Certain biomass precursors with specific enrichments can be used as precursors to introduce heteroatoms at low cost during the carbonization process, providing more active sites for carbon-structured electrodes without incurring additional costs. Currently, carbon derived from natural biomass, such as silkworm cocoons, corn cobs, and coffee grounds, has been explored as electrode materials for MES. Other studies have focused on nitrogen (N) and oxygen (O) doping of biomass, but less research has been conducted on other potentially important elements, such as iron (Fe) and manganese (Mn), from the perspective of biomass precursors. Therefore, research and application in this area urgently need to be advanced. Furthermore, simple biomass carbonization has inherent drawbacks, including insufficient mechanical strength, uncontrollable carbon structure and composition, limited long-term operational stability, and significant performance fluctuations due to differences in raw material sources, all of which seriously hinder its large-scale application. Summary of the Invention

[0007] To address the low efficiency of electron transfer at the electrode-biomembrane interface and the low chemical-to-electrical energy conversion efficiency in microbial electrochemical systems, this paper develops a method for preparing and applying a biomass-resin composite carbon-based hierarchical subporous bioelectrode material. This method utilizes renewable biomass resources to achieve flexible and controllable preparation of high-performance, low-cost, hierarchical subporous carbon-based electrode materials. Furthermore, by combining them with industrial resin materials, the mechanical properties and modification effects of the carbon-based electrodes are enhanced. The high-performance carbon electrodes of this invention enhance electron transfer at the biomembrane-electrode interface, bioelectron storage, and the accumulation of electrogenic microorganisms, while simultaneously removing pollutants and enhancing electricity production in the microbial electrochemical system. The present invention incorporates an industrial-grade resin matrix as both a structural support and a conductive medium. The resin-polymer composite effectively improves mechanical defects and enhances durability. The industrial resin material is low-cost and boasts a carbon residue rate of up to 60% after high-temperature pyrolysis, offering design flexibility and stable performance in the preparation of electrode materials. The resin material serves as both a structural support and a conductive medium, and can be flexibly modified with target elements, chemically modified, and achieves specific electrochemical functions by flexibly varying synthetic monomers or adding other components.

[0008] The preparation method of the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material of the present invention is carried out according to the following steps: 1. Preparation of resin precursor: ①, using formaldehyde and phenol to synthesize phenolic resin, adding melamine to the phenolic resin to perform formaldehyde substitution modification to obtain melamine-modified phenolic resin; The alkaline catalyst is a 20% by mass NaOH solution; the alkaline catalyst is 5% to 15% by mass of phenol, and the melamine is 5% to 30% by mass of phenol; a large amount of melamine will affect the polymerization reaction. If the incompletely reacted melamine forms a white precipitate, the reaction treatment time should be extended.

[0009] ② Preparation of iron-nitrogen co-doped resin: Cool the melamine-modified phenolic resin in step ① to 25-50° C., add the pre-dissolved iron source solution, and react for 10-60 minutes to obtain an iron-nitrogen co-doped resin; The mass of the iron source in the iron source solution is 1% to 12% of the mass of the phenol; if the iron source is too much, the polymerization reaction of the resin and the mechanical properties of the target material will be affected; if the iron source is too little, the modification effect will be affected.

[0010] 2. Biomass Precursor Preparation The biomass is washed, dried, and crushed to obtain 60-100 mesh biomass powder; 3. Activation of biomass precursors The biomass powder obtained in step 2 and the activator are co-dispersed in deionized water to obtain a mixed solution, the mixed solution is stirred at 30-60° C. for 8-12 hours, and then freeze-dried to obtain an activated biomass precursor; The mass ratio of the biomass powder to the activator is 1:0.5-4; 4. Pre-carbonization of biomass precursors Pre-carbonizing the activated biomass precursor obtained in step 3 to obtain a pre-carbonized biomass precursor; The pre-carbonization process is as follows: in an inert gas atmosphere, at 1-5°C min -1 The temperature was heated to 300~400℃ and maintained for 30~60 minutes; the inert gas was N2 and the inert gas flow rate was 80~120mLmin -1 ; 5. Preparation of composite carbonization precursor The iron-nitrogen co-doped resin obtained in step 1, the pre-carbonized biomass precursor obtained in step 4, and the plastic microparticle sacrificial template are uniformly mixed, and the mixture is cured at 90-140° C. for 6-14 hours to obtain a composite carbonized precursor; The plastic microparticle sacrificial template is 1-10% of the mass of the iron-nitrogen co-doped resin; The pre-carbonized biomass precursor is 30-70% of the mass of the iron-nitrogen co-doped resin. If the pre-carbonized biomass precursor is too much, the viscosity of the composite slurry and the mechanical properties of the target material will be reduced; if the pre-carbonized biomass precursor is too little, the electrochemical properties and other properties of the target material will be reduced. The plastic microparticle sacrificial template is a plastic microparticle made of polyethylene (PE), polylactic acid (PLA), polyamide (PA), polystyrene (PS), polyoxymethylene (POM) or polymethyl methacrylate (PMMA); 6. Carrier gas protected carbonization high temperature pyrolysis In an inert gas atmosphere, the composite carbonized precursor obtained in step 5 was heated at 1-8 °C min -1 The temperature is raised to 700-1000°C at a rate of 1000°C and pyrolyzed for 1-3 hours to obtain a high-temperature pyrolysis material. If the heating / cooling rate is too fast, it will affect the structure of the target material during the calcination process; if the heating / cooling rate is too slow, the preparation efficiency will be reduced. 7. Carbonized electrode desalination and decontamination The high-temperature pyrolysis material obtained in step six is ​​desalted and decontaminated with deionized water to obtain a carbon-based hierarchical sub-porous bioelectrode material.

[0011] This invention develops a method for constructing a capacitive carbon electrode material based on a biomass-modified resin. The electrode material's multi-level subporous structure is established using an activator and a sacrificial template, while the heteroatom structure is formed using biomass and a modified resin. These synergistically achieve the electrode material's high capacitance and low energy barrier interface. Application of this electrode material in microbial electrochemical systems can protect against high current shocks through electron storage and electron transfer pathways, promote interfacial electron transport, achieve breakthrough current and power densities, and simultaneously enhance pollutant removal.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) The novel biomass-resin carbon-based hierarchical subporous bioelectrode material prepared by the present invention uses waste biomass and low-cost industrial resin. The raw materials are widely available and the preparation steps are simple, which greatly reduces the construction cost and is more suitable for large-scale application of bioelectrochemical systems.

[0013] (2) The novel biomass-resin carbon-based hierarchical subporous bioelectrode material prepared by this invention has high mechanical properties, a hierarchical subporous structure, high capacitance and low resistance, and good biocompatibility. It can significantly promote the attachment of electroactive bacteria and the storage of biocharge. Compared with traditional carbon electrodes, it has a shorter startup time, faster biofilm acclimatization, and more stable operation.

[0014] (3) The porous carbon electrode material prepared by the present invention has a fast degradation rate for organic wastewater, high chemical energy-electrical energy conversion efficiency, and a coulombic efficiency higher than that of the same type of electrode; the maximum power density is more than 3 times that of the traditional carbon electrode, and the maximum current density is more than 4 times that of the traditional carbon electrode.

[0015] (4) The porous carbon electrode material prepared by the present invention can efficiently and selectively enrich electrogenic bacteria and effectively promote the formation of electroactive biofilms; the elements such as iron, nitrogen, and oxygen introduced based on biomass doping form interfacial active sites, which promote the copy abundance of genes related to direct extracellular electron transfer and have a promoting effect on electron transfer at the bio-electrode interface.

[0016] (5) The porous carbon electrode material prepared by the present invention can be molded and easily shaped. The shape change during the carbonization process is small, and it is easy to prepare porous carbon electrodes of various sizes and shapes, meeting the application of bioelectrochemical systems of different scales.

[0017] (6) The porous carbon electrode material prepared by the present invention has multiple sources of pores, including pores in the resin carbonization process, pores in the biomass porous structure, pores in the sacrificial pore-forming template, and carbonized pores at the interface between biomass particles and resin precursors. The above-mentioned pores form multi-level pores ranging from nanometers to hundreds of micrometers. These porous structures can provide conditions for material transport in bioelectrochemical systems (macroscopic pores ranging from hundreds of micrometers to millimeters), attachment of electroactive microorganisms (1 to 100 micrometers), and catalytic conversion of "chemical energy to electrical energy" (nanometers to 1 micrometers). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a microbial electrochemical system (MES) in the examples; Figure 2 This is a scanning electron micrograph of the carbon-based hierarchical subporous bioelectrode material prepared for control group 2; Figure 3 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in Example 1; Figure 4 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in Example 2; Figure 5 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in Example 3; Figure 6 cyclic voltammetry test curve of the carbon-based hierarchical subporous bioelectrode material prepared in the embodiment; Figure 7 A diagram showing the accumulated charge and coulombic efficiency of a single cycle of the microbial electrochemical system in the embodiment; Figure 8 The power density curve of the biofilm formed on the carbon-based hierarchical sub-porous bioelectrode material in the embodiment; Figure 9 is a graph of capacitance charge on the carbon-based hierarchical subporous bioelectrode material in the embodiment; Figure 10A graph showing the biomass on the carbon-based hierarchical subporous bioelectrode material in the embodiment; Figure 11 Graph showing the community composition and abundance on the carbon-based hierarchical subporous bioelectrode material in the examples. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0020] Specific embodiment 1: The preparation method of the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material of this embodiment is carried out according to the following steps: 1. Preparation of resin precursor: ①, using formaldehyde and phenol to synthesize phenolic resin, adding melamine to the phenolic resin to perform formaldehyde substitution modification to obtain melamine-modified phenolic resin; The alkaline catalyst is a 20% by mass NaOH solution; the alkaline catalyst is 5% to 15% by mass of phenol, and the melamine is 5% to 30% by mass of phenol; ② Preparation of iron-nitrogen co-doped resin: Cool the melamine-modified phenolic resin in step ① to 25-50° C., add the pre-dissolved iron source solution, and react for 10-60 minutes to obtain an iron-nitrogen co-doped resin; The mass of the iron source in the iron source solution is 1% to 12% of the mass of phenol; 2. Biomass Precursor Preparation The biomass is washed, dried, and crushed to obtain 60-100 mesh biomass powder; 3. Activation of biomass precursors The biomass powder obtained in step 2 and the activator are co-dispersed in deionized water to obtain a mixed solution, the mixed solution is stirred at 30-60° C. for 8-12 hours, and then freeze-dried to obtain an activated biomass precursor; The mass ratio of the biomass powder to the activator is 1:0.5-4; 4. Pre-carbonization of biomass precursors Pre-carbonizing the activated biomass precursor obtained in step 3 to obtain a pre-carbonized biomass precursor; The pre-carbonization process is as follows: in an inert gas atmosphere, at 1-5°C min -1 The temperature was heated to 300~400℃ and maintained for 30~60 minutes; the inert gas was N2 and the inert gas flow rate was 80~120mLmin -1 ; 5. Preparation of composite carbonization precursor The iron-nitrogen co-doped resin obtained in step 1, the pre-carbonized biomass precursor obtained in step 4, and the plastic microparticle sacrificial template are uniformly mixed, and the mixture is cured at 90-140° C. for 6-14 hours to obtain a composite carbonized precursor; The plastic microparticle sacrificial template is 1-10% of the mass of the iron-nitrogen co-doped resin; The pre-carbonized biomass precursor is 30-70% of the mass of the iron-nitrogen co-doped resin. The plastic microparticle sacrificial template is plastic microparticles, and the material is polyethylene, polylactic acid, polyamide, polystyrene, polyoxymethylene or polymethyl methacrylate; 6. Carrier gas protected carbonization high temperature pyrolysis In an inert gas atmosphere, the composite carbonized precursor obtained in step 5 was heated at 1-8 °C min -1 The temperature is raised to 700-1000°C at a rate of 1000°C, and the high-temperature pyrolysis is performed for 1-3 hours to obtain a high-temperature pyrolysis material; 7. Carbonized electrode desalination and decontamination The high-temperature pyrolysis material obtained in step six is ​​desalted and decontaminated with deionized water to obtain a carbon-based hierarchical sub-porous bioelectrode material.

[0021] (1) The novel biomass-resin carbon-based hierarchical subporous bioelectrode material prepared in this embodiment uses waste biomass and low-cost industrial resin. The raw materials are widely available and the preparation steps are simple, which greatly reduces the construction cost and is more suitable for large-scale application of bioelectrochemical systems.

[0022] (2) The novel biomass-resin carbon-based hierarchical subporous bioelectrode material prepared in this embodiment has high mechanical properties, a hierarchical subporous structure, high capacitance and low resistance, and good biocompatibility, and can significantly promote the attachment of electroactive bacteria and the storage of biocharge. Compared with traditional carbon electrodes, it has a shorter startup time, faster biofilm acclimatization, and more stable operation.

[0023] (3) The porous carbon electrode material prepared in this embodiment has a fast degradation rate for organic wastewater, a high chemical energy-electrical energy conversion efficiency, and a coulombic efficiency higher than that of the same type of electrode; the maximum power density is more than 3 times that of the traditional carbon electrode, and the maximum current density is more than 4 times that of the traditional carbon electrode.

[0024] (4) The porous carbon electrode material prepared in this embodiment can efficiently and selectively enrich electrogenic bacteria and effectively promote the formation of electroactive biofilms; the elements such as iron, nitrogen, and oxygen introduced based on biomass doping form interfacial active sites, promote the copy abundance of genes related to direct extracellular electron transfer, and have a promoting effect on electron transfer at the bio-electrode interface.

[0025] (5) The porous carbon electrode material prepared in this embodiment can be molded and easily shaped. The shape changes little during the carbonization process, and it is easy to prepare porous carbon electrodes of various sizes and shapes, meeting the application of bioelectrochemical systems of different scales.

[0026] (6) The porous carbon electrode material prepared in this embodiment has multiple sources of pores, including pores in the resin carbonization process, pores in the biomass porous structure, pores in the sacrificial pore-forming template, and carbonized pores at the interface between biomass particles and resin precursors. The above-mentioned pores form multi-level pores ranging from nanometers to hundreds of micrometers. These porous structures can provide conditions for material transport in bioelectrochemical systems (macroscopic pores ranging from hundreds of micrometers to millimeters), attachment of electroactive microorganisms (1 to 100 micrometers), and catalytic conversion of "chemical energy to electrical energy" (nanometers to 1 micrometers).

[0027] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: Step 1① The process for synthesizing phenolic resin is: placing formaldehyde and phenol in a three-necked flask, adding an alkaline catalyst, and condensing and refluxing the mixture under heating conditions at 75-85°C in a water bath for 0.5-1 hour; the molar ratio of formaldehyde to phenol is 1.3-1.8:1.

[0028] Specific embodiment three: This embodiment differs from specific embodiment one or two in that: the process for formaldehyde substitution modification described in step 1① is: continue to add melamine to the phenolic resin, and condense and reflux the reaction under heating conditions at 75~85℃ in a water bath for 1.5~2 hours.

[0029] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the iron source in the iron source solution in step 1② is FeCl3, FeCl2, Fe(NO3), Fe(OAc)2, ferric acetylacetonate or ferric phthalate.

[0030] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that: the solvent in the iron source solution in step 1② is deionized water, N,N-dimethylformamide or dimethyl sulfoxide.

[0031] Specific embodiment six: This embodiment differs from any one of specific embodiments one to five in that: the biomass in step two is spinach, fungus, shiitake mushroom, laver, seaweed, enteromorpha or pumpkin seeds; it is a plant or algae with high iron content.

[0032] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that: the drying in step two is freeze drying at -20 to -80°C for 24 to 48 hours; or drying at 40 to 60°C for 24 to 48 hours.

[0033] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that: the freeze-drying temperature in step three is -20 to -80°C, and the drying time is 24 to 48 hours.

[0034] Specific embodiment 9: This embodiment differs from any one of specific embodiments 1 to 8 in that: the activator in step 3 is ZnCl, KOH, KHCO3, K2FeO4 or NaOH.

[0035] Specific embodiment ten: This embodiment differs from any one of specific embodiments one to nine in that the desalination and decontamination process described in step seven is: first, the electrode material is cleaned in deionized water until it is neutral, and then dried to complete desalination; the desalted electrode material is soaked in an organic solvent for 1 to 6 hours to complete decontamination, and finally ultrasonically cleaned in deionized water for 20 to 60 minutes and dried; the organic solvent is anhydrous ethanol or acetone.

[0036] Example 1: The preparation method of the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material of this embodiment is carried out according to the following steps: 1. Preparation of resin precursor: ①, using formaldehyde and phenol to synthesize phenolic resin, adding melamine to the phenolic resin to perform formaldehyde substitution modification to obtain melamine-modified phenolic resin; The process for synthesizing the phenolic resin is as follows: placing formaldehyde and phenol in a three-necked flask, adding an alkaline catalyst, and heating in a water bath at 80° C. under condensation reflux for 0.5 hours; the molar ratio of formaldehyde to phenol is 1.5:1; The process for formaldehyde substitution modification is as follows: melamine is continuously added to the phenolic resin, and the mixture is heated in a water bath at 80° C. and subjected to condensation reflux for 2 hours; The alkaline catalyst is a 20% by mass NaOH solution; the alkaline catalyst is 15% by mass of phenol, and the melamine is 25% by mass of phenol; ② Preparation of iron-nitrogen co-doped resin: Cool the melamine-modified phenolic resin in step ① to 50° C., add the pre-dissolved iron source solution, and react for 30 minutes to obtain an iron-nitrogen co-doped resin; The iron source in the iron source solution is ferric acetylacetonate; The solvent in the iron source solution is N,N-dimethylformamide; The mass of the iron source in the iron source solution is 3% of the mass of phenol; 2. Biomass Precursor Preparation The biomass was washed, dried, and pulverized to obtain 150 μm biomass powder; The biomass is fungus: The drying is freeze drying at -50°C for 24 hours; 3. Activation of biomass precursors The biomass powder obtained in step 2 and the activator are co-dispersed in deionized water to obtain a mixed solution, the mixed solution is stirred at 60° C. for 10 hours, and then freeze-dried to obtain an activated biomass precursor; The freeze-drying temperature is -50°C, and the drying time is 48 hours.

[0037] The activator is KOH; The mass ratio of the biomass powder to the activator is 1:3; 4. Pre-carbonization of biomass precursors Pre-carbonizing the activated biomass precursor obtained in step 3 to obtain a pre-carbonized biomass precursor; The pre-carbonization process is as follows: in an inert gas atmosphere, -1 The mixture was heated to 400 °C at a rate of 1000 °C and maintained for 60 minutes; the inert gas was N2 and the inert gas flow rate was 100 mL min -1 ; 5. Preparation of composite carbonization precursor 12 g of the iron-nitrogen co-doped resin obtained in step 1, 6 g of the pre-carbonized biomass precursor obtained in step 4, and 1.2 g of the plastic microparticle sacrificial template were mixed evenly, and the mixture was cured at 140 ° C for 6 hours to obtain a composite carbonized precursor; The plastic microparticle sacrificial template is plastic microparticles, and the material is polyamide 6; 6. Carrier gas protected carbonization high temperature pyrolysis In an inert gas atmosphere, the composite carbonized precursor obtained in step 5 was heated at 5 °C min -1 The temperature was raised to 900°C at a rate of 10000 ℃, and the high-temperature pyrolysis was performed for 2 hours to obtain a high-temperature pyrolysis material; 7. Carbonized electrode desalination and decontamination Deionized water is used to desalinate and remove impurities from the high-temperature pyrolysis material obtained in step 6 to obtain a carbon-based hierarchical sub-porous bioelectrode material; The desalination and decontamination process is as follows: first, the electrode material is cleaned in deionized water until it is neutral, and then dried to complete desalination; the desalted electrode material is immersed in an organic solvent for 4 hours to complete decontamination, and finally ultrasonically cleaned in deionized water for 40 minutes and dried; the organic solvent is anhydrous ethanol.

[0038] Example 2: The preparation method of the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material of this embodiment is carried out according to the following steps: 1. Preparation of resin precursor: ①, using formaldehyde and phenol to synthesize phenolic resin, adding melamine to the phenolic resin to perform formaldehyde substitution modification to obtain melamine-modified phenolic resin; The process for synthesizing the phenolic resin is as follows: placing formaldehyde and phenol in a three-necked flask, adding an alkaline catalyst, and heating in a water bath at 80° C. under condensation reflux for 0.5 hours; the molar ratio of formaldehyde to phenol is 1.5:1; The process for formaldehyde substitution modification is as follows: melamine is continuously added to the phenolic resin, and the mixture is heated in a water bath at 80° C. and subjected to condensation reflux for 2 hours; The alkaline catalyst is a 20% by mass NaOH solution; the alkaline catalyst is 15% by mass of phenol, and the melamine is 25% by mass of phenol; ② Preparation of iron-nitrogen co-doped resin: Cool the melamine-modified phenolic resin in step ① to 50° C., add the pre-dissolved iron source solution, and react for 10 to 60 minutes to obtain an iron-nitrogen co-doped resin; The iron source in the iron source solution is ferric acetylacetonate; The solvent in the iron source solution is N,N-dimethylformamide; The mass of the iron source in the iron source solution is 3% of the mass of phenol; 2. Biomass Precursor Preparation The biomass was washed, dried, and pulverized to obtain 150 μm biomass powder; The biomass is spinach: The drying is freeze drying at -50°C for 24 hours; 3. Activation of biomass precursors The biomass powder obtained in step 2 and the activator are co-dispersed in deionized water to obtain a mixed solution, the mixed solution is stirred at 60° C. for 10 hours, and then freeze-dried to obtain an activated biomass precursor; The freeze-drying temperature is -50°C, and the drying time is 48 hours.

[0039] The activator is KOH; The mass ratio of the biomass powder to the activator is 1:3; 4. Pre-carbonization of biomass precursors Pre-carbonizing the activated biomass precursor obtained in step 3 to obtain a pre-carbonized biomass precursor; The pre-carbonization process is as follows: in an inert gas atmosphere, -1 The mixture was heated to 400 °C at a rate of 1000 °C and maintained for 60 minutes; the inert gas was N2 and the inert gas flow rate was 100 mL min -1 ; 5. Preparation of composite carbonization precursor 12 g of the iron-nitrogen co-doped resin obtained in step 1, 5 g of the pre-carbonized biomass precursor obtained in step 4, and 1.2 g of the plastic microparticle sacrificial template were mixed evenly, and the mixture was cured at 140 ° C for 6 hours to obtain a composite carbonized precursor; The plastic microparticle sacrificial template is plastic microparticles, and the material is polyamide 6; 6. Carrier gas protected carbonization high temperature pyrolysis In an inert gas atmosphere, the composite carbonized precursor obtained in step 5 was heated at 5 °C min -1 The temperature was raised to 900°C at a rate of 10000 ℃, and the high-temperature pyrolysis was performed for 2 hours to obtain a high-temperature pyrolysis material; 7. Carbonized electrode desalination and decontamination Deionized water is used to desalinate and remove impurities from the high-temperature pyrolysis material obtained in step 6 to obtain a carbon-based hierarchical sub-porous bioelectrode material; The desalination and decontamination process is as follows: first, the electrode material is cleaned in deionized water until it is neutral, and then dried to complete desalination; the desalted electrode material is immersed in an organic solvent for 4 hours to complete decontamination, and finally ultrasonically cleaned in deionized water for 40 minutes and dried; the organic solvent is anhydrous ethanol.

[0040] Example 3: The preparation method of the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material of this embodiment is carried out according to the following steps: 1. Preparation of resin precursor: ①, using formaldehyde and phenol to synthesize phenolic resin, adding melamine to the phenolic resin to perform formaldehyde substitution modification to obtain melamine-modified phenolic resin; The process for synthesizing the phenolic resin is as follows: placing formaldehyde and phenol in a three-necked flask, adding an alkaline catalyst, and heating in a water bath at 80° C. under condensation reflux for 0.5 hours; the molar ratio of formaldehyde to phenol is 1.5:1; The process for formaldehyde substitution modification is as follows: melamine is continuously added to the phenolic resin, and the mixture is heated in a water bath at 80° C. and subjected to condensation reflux for 2 hours; The alkaline catalyst is a 20% by mass NaOH solution; the alkaline catalyst is 15% by mass of phenol, and the melamine is 25% by mass of phenol; ② Preparation of iron-nitrogen co-doped resin: Cool the melamine-modified phenolic resin in step ① to 50° C., add the pre-dissolved iron source solution, and react for 10 to 60 minutes to obtain an iron-nitrogen co-doped resin; The iron source in the iron source solution is ferric acetylacetonate; The solvent in the iron source solution is N,N-dimethylformamide; The mass of the iron source in the iron source solution is 3% of the mass of phenol; 2. Biomass Precursor Preparation The biomass was washed, dried, and pulverized to obtain 150 μm biomass powder; The biomass is Enteromorpha: The drying is freeze drying at -50°C for 24 hours; 3. Activation of biomass precursors The biomass powder obtained in step 2 and the activator are co-dispersed in deionized water to obtain a mixed solution, the mixed solution is stirred at 60° C. for 10 hours, and then freeze-dried to obtain an activated biomass precursor; The freeze-drying temperature is -50°C, and the drying time is 48 hours.

[0041] The activator is KOH; The mass ratio of the biomass powder to the activator is 1:3; 4. Pre-carbonization of biomass precursors Pre-carbonizing the activated biomass precursor obtained in step 3 to obtain a pre-carbonized biomass precursor; The pre-carbonization process is as follows: in an inert gas atmosphere, -1 The mixture was heated to 400 °C at a rate of 1000 °C and maintained for 60 minutes; the inert gas was N2 and the inert gas flow rate was 100 mL min -1 ; 5. Preparation of composite carbonization precursor 12 g of the iron-nitrogen co-doped resin obtained in step 1, 6 g of the pre-carbonized biomass precursor obtained in step 4, and 1.2 g of the plastic microparticle sacrificial template were mixed evenly, and the mixture was cured at 140 ° C for 6 hours to obtain a composite carbonized precursor; The plastic microparticle sacrificial template is plastic microparticles, and the material is polyamide 6; 6. Carrier gas protected carbonization high temperature pyrolysis In an inert gas atmosphere, the composite carbonized precursor obtained in step 5 was heated at 5 °C min -1 The temperature was raised to 900°C at a rate of 10000 ℃, and the high-temperature pyrolysis was performed for 2 hours to obtain a high-temperature pyrolysis material; 7. Carbonized electrode desalination and decontamination Deionized water is used to desalinate and remove impurities from the high-temperature pyrolysis material obtained in step 6 to obtain a carbon-based hierarchical sub-porous bioelectrode material; The desalination and decontamination process is as follows: first, the electrode material is cleaned in deionized water until it is neutral, and then dried to complete desalination; the desalted electrode material is immersed in an organic solvent for 4 hours to complete decontamination, and finally ultrasonically cleaned in deionized water for 40 minutes and dried; the organic solvent is anhydrous ethanol.

[0042] The microbial electrochemical system in Examples 1 to 3 specifically includes: (1) A dual-chamber microbial electrochemical system, wherein the cathode chamber and the anode chamber can be adjusted in size according to needs, and the cathode chamber and the anode chamber are separated by a cation exchange membrane. The anode material is the carbon-based graded subporous bioelectrode material of Examples 1 to 3, and the cathode material is a carbon brush. The system is a dual-chamber reactor, the anode chamber is 4×4×2 cm, and the cathode chamber is 4×4×4 cm. (2) Anode water inlet is 1 g L -l Sodium acetate, 50mmol / L -1 Phosphate buffer solution, 2mlL -1 Vitamins and 1.25mlL -1 Trace elements, inoculated with domestic sewage (20% of the volume of the anode solution); cathode solution 50mmolL -1 Phosphate buffer solution prepared with 50mmol / L -1 Potassium ferrocyanide solution; (3) Water is introduced into the cathode and anode respectively, and the system is operated in batch mode at 28-31°C. When the output voltage drops to 10-15%, the anolyte and catholyte are replaced. Continuing to operate the system can further enrich microorganisms at the anode; (4) During the operation of the system, the electrons generated by the anode microorganisms are transferred to the cathode for utilization. The microorganisms include Geobacter sp .,Desulfovibrio sp .,Bacteria sp . The reactors were started with an external resistance of 1000Ω and operated at 30 ± 1°C. The anodic biofilm was acclimated by decreasing the resistance in a stepwise manner (1000Ω, 510Ω, 415Ω, 300Ω, and 210Ω). The output voltage of each reactor was recorded every 30 minutes using a data acquisition system. The anolyte and catholyte solutions were replaced when the output voltage dropped below 100mV.

[0043] Figure 1 Schematic diagram of the microbial electrochemical system (MES system) in Examples 1 to 3: 1-external resistance, 2-anode chamber, 3-anode material, 4-cathode chamber, 5-cathode material, 6-ion exchange membrane; The anodes of the microbial electrochemical systems in control groups 1 to 3 were different from those in Examples 1 to 3, and the other components of the microbial electrochemical systems were the same as those in Examples 1 to 3. The anode in control group 1 was carbon felt; the anode in control group 3 was carbon brush; the anode in control group 2 was prepared by curing the iron-nitrogen co-doped resin obtained in step 1 of Example 1 at 140°C for 6 hours and then carbonizing it; the carbonization process was carried out at 5°C min -1 Heat to 900℃ at a heating rate of 1000℃ and keep warm for 3 hours; Figure 2 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in control group 2. Figure 2 A partial enlarged view of the surface pores; Figure 3 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in Example 1; Figure 4 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in Example 2; Figure 5 This is a scanning electron microscope image of the carbon-based hierarchical subporous bioelectrode material prepared in Example 3; Figures 2 to 5 As can be seen, the carbon-based hierarchical subporous bioelectrode materials prepared in the examples possess multi-level pores ranging from nanometers to hundreds of micrometers. The carbonized resin electrode exhibits a macroporous structure (597.7 ± 111.8 μm), with the carbon skeleton between adjacent pores exhibiting a concave surface with a distribution diameter of 63.8 ± 16.5 μm. The biomass-resin composite electrode exhibits a hierarchical subporous structure, including macropores on the surface (surface pores in the figure, 80–150 μm), mesopores on the pore walls of the surface pores (pore wall pores in the figure, 20–30 μm), and small pores (0.5–3 μm) on the carbon skeleton. These porous structures can provide conditions for mass transport in bioelectrochemical systems (macropores ranging from hundreds of micrometers to millimeters), attachment of electroactive microorganisms (1 to 100 micrometers), and catalytic conversion of chemical energy to electrical energy (nanoscale to 1 micrometer).

[0044] Figure 6 Figure 3 is the cyclic voltammetry test curve of the carbon-based hierarchical subporous bioelectrode material prepared in the examples; the electrode materials in Examples 1 to 3 have excellent capacitance properties, with capacitance values ​​10 to 45 times higher than that of carbon cloth (control group 1) and 4 to 17 times higher than that of the electrode without biomass addition (control group 2).

[0045] Figure 7 A diagram showing the accumulated charge and coulombic efficiency of a single cycle of the microbial electrochemical system in the embodiment; Figure 8 The power density curve of the biofilm formed on the carbon-based hierarchical sub-porous bioelectrode material in the embodiment; Figure 9 is a graph of capacitance charge on the carbon-based hierarchical subporous bioelectrode material in the embodiment; Figure 10 A graph showing the biomass on the carbon-based hierarchical subporous bioelectrode material in the embodiment; Figure 11 Graph showing the community composition and abundance on the carbon-based hierarchical subporous bioelectrode material in the examples.

[0046] During the operation of the MES system in Example 1, the average accumulated charge per cycle was 154 ± 9.8 C, and the average coulombic efficiency of the system was 59 ± 8.6%. After the system stabilized, the polarization curve and power density of the system were measured using a variable resistance box, and the maximum power density of the system reached 4100 ± 113 mW m -2 , the maximum current density reaches 12.5± 0.1Am -2The capacitive charge value in the bioanode is 1256 ± 86 C m –2 The biomass of the acclimated biomass on the anode was 1298.6 μg cm -2 , the total abundance of electrogenic bacteria in the electroactive biofilm was 75%.

[0047] During the operation of the MES system in Example 2, the average accumulated charge per cycle was 156 ± 5.1 C, and the average coulombic efficiency of the system was 60 ± 9.3%. The maximum power density of the system reached 5253 ± 7 mW m -2 , the maximum current density reaches 19± 0.9Am -2 The capacitive charge value in the bioanode is 2319 ± 97 C m –2 The biomass of the acclimated biomass on the anode was 1310.8 μg cm -2 , the total abundance of electrogenic bacteria in the electroactive biofilm was 74%.

[0048] During the operation of the MES system in Example 3, the average accumulated charge per cycle was 158 ± 5.3 C, and the average coulombic efficiency of the system was 61 ± 8.1%. The maximum power density of the system reached 6138 ± 118 mW m -2 , the maximum current density reaches 21.8±0.1 Am -2 The capacitive charge value in the bioanode is 3577 ± 160.3 C m -2 The biomass of the acclimated biomass on the anode was 1873.7 μg cm -2 , the total abundance of electrogenic bacteria in the electroactive biofilm was 85%.

[0049] The average accumulated charge per cycle during the operation of the MES system in control group 1 was 138 ± 9.9 C, and the average coulombic efficiency of the system was 55 ± 5.1%. The maximum power density of the system was 1870 ± 91 mW m -2 , the maximum current density is 5.1±0.84Am -2 The capacitive charge value in the bioanode is 13.3 ± 3 C m –2 The biomass of the acclimated biomass on the anode was 324.3 μg cm -2 , the total abundance of electrogenic bacteria in the electroactive biofilm was 69%.

[0050] The average accumulated charge of the MES system in control group 2 during operation was 144 ± 7.7 C per cycle, and the average coulombic efficiency of the system was 57 ± 6.4%. The maximum power density reached 2652 ± 148 mW m -2 , the maximum current density reaches 6± 0.1 Am -2 The capacitive charge value in the bioanode is 414 ± 18 C m –2The biomass of the acclimated biomass on the anode was 324.3 μg cm -2 , the total abundance of electrogenic bacteria in the electroactive biofilm was 71%.

[0051] The maximum power density of control group 3 was 3980 ± 53 mW m -2 , the maximum current density is 8±0.4 A m -2 .

Claims

1. A method for preparing a carbon-based hierarchical sub-porous bioelectrode material of a biomass-resin composite material, characterized by: The preparation method of the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material is carried out according to the following steps:

1. Preparation of resin precursor: ①, using formaldehyde and phenol to synthesize phenolic resin, adding melamine to the phenolic resin to perform formaldehyde substitution modification to obtain melamine-modified phenolic resin; The alkaline catalyst is a NaOH solution with a mass fraction of 20%; The alkaline catalyst is 5% to 15% of the mass of phenol. The melamine is 5% to 30% of the mass of phenol; ② Preparation of iron-nitrogen co-doped resin: Cool the melamine-modified phenolic resin in step ① to 25-50° C., add the pre-dissolved iron source solution, and react for 10-60 minutes to obtain an iron-nitrogen co-doped resin; The mass of the iron source in the iron source solution is 1% to 12% of the mass of phenol; 2. Biomass Precursor Preparation The biomass is washed, dried, and crushed to obtain 60-100 mesh biomass powder; 3. Activation of biomass precursors The biomass powder obtained in step 2 and the activator are co-dispersed in deionized water to obtain a mixed solution, the mixed solution is stirred at 30-60° C. for 8-12 hours, and then freeze-dried to obtain an activated biomass precursor; The mass ratio of the biomass powder to the activator is 1:0.5-4; 4. Pre-carbonization of biomass precursors Pre-carbonizing the activated biomass precursor obtained in step 3 to obtain a pre-carbonized biomass precursor; The pre-carbonization process is as follows: in an inert gas atmosphere, at 1-5°C min -1 Heat to 300~400℃ at a rate of 100~200℃ and maintain for 30~60 minutes; The inert gas is N2; The inert gas flow rate is 80~120mLmin -1 ; 5. Preparation of composite carbonization precursor The iron-nitrogen co-doped resin obtained in step 1, the pre-carbonized biomass precursor obtained in step 4, and the plastic microparticle sacrificial template are uniformly mixed, and the mixture is cured at 90-140° C. for 6-14 hours to obtain a composite carbonized precursor; The plastic microparticle sacrificial template is 1-10% of the mass of the iron-nitrogen co-doped resin; The pre-carbonized biomass precursor is 30-70% of the mass of the iron-nitrogen co-doped resin. The plastic microparticle sacrificial template is plastic microparticles; The material of the plastic particles is polyethylene, polylactic acid, polyamide, polystyrene, polyoxymethylene or polymethyl methacrylate; 6. Carrier gas protected carbonization high temperature pyrolysis In an inert gas atmosphere, the composite carbonized precursor obtained in step 5 was heated at 1-8 °C min -1 The temperature is raised to 700-1000°C at a rate of 1000°C, and the high-temperature pyrolysis is performed for 1-3 hours to obtain a high-temperature pyrolysis material; 7. Carbonized electrode desalination and decontamination The high-temperature pyrolysis material obtained in step six is ​​desalted and decontaminated with deionized water to obtain a carbon-based hierarchical sub-porous bioelectrode material.

2. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: Step 1① The process for synthesizing phenolic resin is as follows: place formaldehyde and phenol in a three-necked flask, add an alkaline catalyst, and heat under condensation reflux in a water bath at 75-85°C for 0.5-1 hour; The molar ratio of formaldehyde to phenol is 1.3-1.8:

1.

3. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The process for formaldehyde substitution modification described in step 1① is: continue to add melamine to the phenolic resin, and condense and reflux under heating conditions at 75~85℃ in a water bath for 1.5~2 hours.

4. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The iron source in the iron source solution of step 1② is FeCl3, FeCl2, Fe(NO3), Fe(OAc)2, ferric acetylacetonate or ferric phthalate.

5. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The solvent in the iron source solution in step 1② is deionized water, N,N-dimethylformamide or dimethyl sulfoxide.

6. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The biomass in step 2 is spinach, wood ear, shiitake mushroom, laver, seaweed, enteromorpha or pumpkin seeds.

7. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The drying in step 2 is freeze drying at -20 to -80°C for 24 to 48 hours; or drying at 40 to 60°C for 24 to 48 hours.

8. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The freeze-drying temperature in step 3 is -20 to -80°C, and the drying time is 24 to 48 hours.

9. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The activator in step 3 is ZnCl, KOH, KHCO3, K2FeO4 or NaOH.

10. The method for preparing the carbon-based hierarchical sub-porous bioelectrode material of the biomass-resin composite material according to claim 1, characterized in that: The desalination and impurity removal process in step 7 is as follows: first, the electrode material is washed in deionized water until it is neutral, and then dried to complete the desalination; the desalted electrode material is soaked in an organic solvent for 1 to 6 hours to complete the impurity removal, and finally, ultrasonically cleaned in deionized water for 20 to 60 minutes and dried; The organic solvent is anhydrous ethanol or acetone.

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