Preparation method and application of iron phthalocyanine / oxygen doped defect-rich biomass charcoal electrocatalyst

Abstract

The invention discloses a preparation method and application of an iron phthalocyanine / oxygen doped defect-rich biomass charcoal electrocatalyst, and relates to an electro-self-Fenton system. The invention provides a preparation strategy of an iron phthalocyanine / oxygen-doped defect-rich biomass charcoal electrocatalyst, which comprises the following steps: by taking waste biomass powder as a carbon precursor, carrying out crushing-calcining coupling pretreatment, high-temperature graphitization and oxygen doping engineering to construct oxygen-doped biomass charcoal (O-BCD) rich in carbon defects; and then, iron phthalocyanine (FePc) is anchored on the biomass charcoal by wet impregnation, so that the FePc / O-BCD electrocatalyst is formed. According to the iron phthalocyanine / oxygen doped defect-rich biomass charcoal electrocatalyst prepared by the preparation method disclosed by the invention, two sites of a defect site and a metal ion center act together, so that in-situ generation and reduction of hydrogen peroxide are realized, the yield of hydroxyl free radicals is increased, and electroauto-Fenton degradation of antibiotics in a water body can be more efficiently carried out; the cost is low, the structural stability is good, and the pollutant degradation efficiency is excellent.

Description

Technical Field

[0001] This invention relates to the electro-Fenton system, specifically to a method for preparing and applying a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst. Background Technology

[0002] Tetracycline antibiotics, due to their widespread use and high dosage, have become one of the most frequently detected active pharmaceutical ingredients in aquatic environments. However, tetracyclines are structurally stable and have poor biochemical permeability, making them difficult to remove effectively using conventional biological treatment processes. Their long-term residues in receiving water bodies at microgram-levels can induce the lateral migration of resistance genes, exacerbating the spread of drug-resistant bacteria and posing a potential threat to aquatic ecosystem safety and public health. Therefore, developing advanced tetracycline purification technologies that are simple to operate, highly efficient, low-cost, and have a low risk of secondary pollution has become a popular research direction in the field of water pollution control.

[0003] Electro-Fenton technology, as a highly efficient electrochemical advanced oxidation process, couples the electrochemical in-situ generation of hydrogen peroxide with a homogeneous Fenton reaction in an acidic medium, thereby achieving deep mineralization of organic pollutants. Its core advantage lies in utilizing the two-electron oxygen reduction reaction at the cathode (2e... - ORR (Organic Regeneration) generates H2O2 in situ, reducing the transportation and storage costs of H2O2 and avoiding the risks of external addition; simultaneously, the cathode can generate Fe 3+ Reduction and regeneration to Fe 2+ (Fe) 3+ + e - →Fe 2+ This process significantly reduces iron sludge production and improves the utilization efficiency of iron catalysts. Furthermore, the process is rapid and can be precisely controlled by adjusting electrochemical parameters such as current and potential, exhibiting good process flexibility.

[0004] However, traditional electro-Fenton systems still face several key limitations. First, to achieve sufficient dissolution of iron species and high reactivity, their operation is heavily dependent on a low pH environment. This necessitates frequent pH adjustments before and after the reaction, increasing operating costs and potentially introducing secondary pollution. Second, the H2O2 generation efficiency is limited by the 2e content of the cathode material. - The selectivity and activity of ORR (Oral Receptor Rating) and the yield and stability of commonly used carbon-based cathodes still need improvement. Furthermore, in water bodies with high chloride or carbonate content, hydroxyl radicals are easily quenched and may generate harmful halogenated byproducts, affecting treatment safety and versatility. Finally, the high energy consumption and insufficient adaptability to complex water qualities limit its large-scale engineering application.

[0005] Electro-Fenton technology is an advanced oxidation process that couples the electro-Fenton reaction, where H2O2 is generated in situ at the cathode, with anodic oxidation to dissolve metal ions or cathodic reduction of high-valence metals to achieve a homogeneous Fenton reaction. Its core advantage lies in the fact that it eliminates the need for external catalysts and oxidants, achieving a continuous in-situ supply of reactants and cyclic regeneration of metal ions through an electrochemical process. This simplifies system construction, reduces chemical reagent consumption and sludge production, and allows for flexible control of the reaction process by adjusting the current and voltage.

[0006] This technology still faces key bottlenecks. Firstly, the anodic stripping method suffers from poor matching between metal dissolution rates and reaction requirements, anode passivation, and metal ion loss. Secondly, the H2O2 generation efficiency is limited by oxygen mass transfer and cathode material performance. Commonly used carbon-based materials (such as carbon felt and graphite) are low-cost but lack sufficient catalytic activity and stability; while high-performance catalytic cathode materials (such as modified carbon materials and metal-organic framework-derived carbon) can improve H2O2 yield and selectivity, they face challenges such as complex preparation, high cost, or poor durability. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing and applying a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst.

[0008] This invention reduces the economic cost of using catalysts in electro-Fenton systems and simultaneously achieves high-value utilization of waste biomass. A strategy for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst is proposed: using waste biomass powders such as rice husks, straw, and coconut shells as carbon precursors, oxygen-doped biomass carbon (O-BCD) rich in carbon defects is constructed through coupled crushing-calcination pretreatment, high-temperature graphitization, and oxygen doping engineering; then, phthalocyanine iron (FePc) is anchored onto the biomass carbon by wet impregnation to form the FePc / O-BCD electrocatalyst; subsequently, the electrocatalyst is uniformly loaded onto a carbon felt support using a coating process to construct a three-dimensional electrode, which is then applied to an electro-Fenton system. During the process, it exhibits excellent pollutant degradation activity and long-term stability, providing a new paradigm for the large-scale application of low-cost, high-efficiency biomass carbon-based electro-Fenton cathode materials.

[0009] A method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst, specifically comprising the following steps:

[0010] 1. The waste biomass powder is crushed and calcined at high temperature to obtain BC biochar;

[0011] 2. Mix BC biochar with KOH, grind, and then calcine at high temperature to obtain biochar BCD rich in carbon defects;

[0012] 3. Immerse the biochar BCD rich in carbon defects into a strong oxidant solution, stir, filter and wash to obtain oxygen-doped O-BCD material.

[0013] IV. Disperse the oxygen-doped O-BCD material in a solvent, add phthalocyanine iron suspension, wet impregnate, separate and dry to obtain FePc / O-BCD electrocatalyst.

[0014] In the electro-Fenton system, phthalocyanine iron / oxygen-doped defect-rich biochar electrocatalysts are used for the electrocatalytic oxidation degradation of antibiotic organic pollutants.

[0015] The phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst composite electrode material prepared by this invention achieves in-situ generation and reduction of hydrogen peroxide through the combined action of defect sites and metal ion centers, thereby increasing the yield of hydroxyl radicals. This enables more efficient electro-Fenton degradation of antibiotics in water, and features economical cost, good structural stability, and excellent pollutant degradation efficiency.

[0016] The principle of this invention:

[0017] Waste biomass powder undergoes a pretreatment process involving crushing and calcination to selectively remove volatile organic compounds such as hemicellulose and lignin, while simultaneously introducing sps into the carbon framework. 2 Hybridized carbon vacancies initially form BC material containing carbon defects. The BC material is then ground and mixed with KOH, and calcined at high temperature in an Ar atmosphere. The residual organic carbon undergoes graphitization, significantly reducing charge transfer resistance and enhancing π-π stacking ability. Simultaneously, KOH is used to oxidize, etch, and intercalate the carbon framework at high temperature. Through a series of gas-solid and solid-solid reactions, porosity is created and expanded on a large scale. The generated gaseous potassium (K) atoms are forcibly inserted between the aromatic layers of carbon, widening the interlayer spacing. When these potassium atoms are removed in the subsequent acid leaching step, abundant slit-shaped micropores are left, providing rich sites for the subsequent anchoring of FePc metal centers.

[0018] During the impregnation stage, O-BCD, with its delocalized conjugated framework, undergoes π-π stacking with the phthalocyanine macrocyclic system, achieving specific, monolayer adsorption of FePc. Simultaneously, oxygen doping modulates the electron density of the carbon material, forming localized negatively charged centers that influence the electron cloud of the central ion of phthalocyanine iron, perturbing the electron distribution. This inhibits metal aggregation on one hand and alters the valence state of the central metal atom on the other, thereby promoting the generation of active species in the electro-Fenton system and improving the degradation rate and mineralization current efficiency of organic pollutants.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The raw material for this invention is waste biomass, which is widely available and has a lower cost compared to materials such as carbon nanotubes and graphene. The preparation method is also simple, making it a high-value recycling method for waste. The biomass carbon material obtained by this invention possesses both short-range ordered graphitization characteristics and high-density defects. In the graphite microcrystals at or near the defect edges, localized delocalized π electrons can serve as active sites, enabling the adsorption of O2 and the absorption of 2e-. - The ORR pathway facilitates the in-situ catalytic generation of H2O2. Furthermore, oxygen doping modulates the local charge density and provides coordinating atoms, increasing the metal valence state and promoting the in-situ reduction of H2O2. Simultaneously, the altered electron cloud density leads to a tighter bond between FePc and biochar, enhancing catalyst stability and resulting in excellent degradation of antibiotics in wastewater. Attached Figure Description

[0021] Figure 1 This is a mechanistic model diagram illustrating the application of the phthalocyanine iron / oxygen-doped defect-rich biochar electrocatalyst prepared in this invention in the degradation of organic pollutants.

[0022] Figure 2 a and 2b are SEM images of the oxygen-doped O-BCD material prepared in Comparative Example 2, and 2c and 2d are SEM images of the FePc / O-BCD electrocatalyst prepared in step four of Example 1.

[0023] Figure 3 EDS image of the FePc / O-BCD electrocatalyst prepared in step four of Example 1;

[0024] Figure 4 The graphs show the electro-Fenton tetracycline degradation performance of the FePc / O-BCD electrocatalysts prepared in Examples 1-3 and Comparative Example 2. In the graphs, 4:1 represents Example 1, 8:1 represents Example 2, 1:1 represents Example 3, and 1:0 represents Comparative Example 2.

[0025] Figure 5 The graph shows the trend of the electro-Fenton tetracycline degradation performance of the FePc / O-BCD electrocatalyst prepared in this invention as a function of oxygen doping time. In the graph, 1h represents Example 1, 2h represents Example 4, 4h represents Example 5, and 0h represents Comparative Example 1. Detailed Implementation

[0026] Specific Implementation Method 1: This implementation method is a preparation method of a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst, which is specifically completed according to the following steps:

[0027] 1. The waste biomass powder is crushed and calcined at high temperature to obtain BC biochar;

[0028] 2. Mix BC biochar with KOH, grind, and then calcine at high temperature to obtain biochar BCD rich in carbon defects;

[0029] 3. Immerse the biochar BCD rich in carbon defects into a strong oxidant solution, stir, filter and wash to obtain oxygen-doped O-BCD material.

[0030] IV. Disperse the oxygen-doped O-BCD material in a solvent, add phthalocyanine iron suspension, wet impregnate, separate and dry to obtain FePc / O-BCD electrocatalyst.

[0031] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that step one includes:

[0032] ① The waste biomass powder is crushed and then ball-milled to form biomass powder;

[0033] ② Place the biomass powder into a tube furnace and calcine it at high temperature in a N2 atmosphere to obtain BC biochar. The other steps are the same as in Specific Implementation Method 1.

[0034] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the waste biomass powder mentioned in step ① is rice husk, straw, or coconut shell; the particle size of the biomass powder is less than 100 mesh; the high-temperature calcination process mentioned in step ② is as follows: in a N2 atmosphere, the temperature is increased from room temperature to 200℃~400℃ at a heating rate of 5℃ / min and maintained for 2 hours. Other steps are the same as in Specific Implementation Method One or Two.

[0035] Specific Implementation Method Four: The difference between this implementation method and Specific Implementation Methods One to Three is that the mass ratio of BC biochar to KOH in step two is 1:(0.5~3). The other steps are the same as in Specific Implementation Methods One to Three.

[0036] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the high-temperature calcination process described in step two is as follows: In an Ar atmosphere, the temperature is increased from room temperature to 600℃~1000℃ at a heating rate of 5℃ / min and maintained for 2 hours. The other steps are the same as in Specific Implementation Methods One to Four.

[0037] In this embodiment, the calcination temperature needs to be above 600 °C to allow KOH to react with C to produce K atoms, which are necessary for etching and intercalation, forming a porous structure. Simultaneously, within a certain range, as the calcination temperature increases, the graphitization degree of the carbon material also increases, resulting in better conductivity and improved electro-Fenton performance.

[0038] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the strong oxidant solution mentioned in step three is an HNO3 solution with a concentration of 5 mol / L to 15 mol / L; in step three, biochar BCD rich in carbon defects is immersed in the strong oxidant solution, stirred at a temperature of 40 ℃ to 80 ℃ for 0.5 h to 4 h, filtered, washed with water until neutral, and dried to obtain oxygen-doped O-BCD material. Other steps are the same as in Specific Implementation Methods One to Five.

[0039] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One through Six is ​​that step four includes:

[0040] ① Disperse 100 mg of oxygen-doped O-BCD material in 30 mL to 100 mL of N,N-dimethylformamide and sonicate for 15 min to 30 min to obtain an O-BCD material suspension;

[0041] ② Disperse 10 mg to 100 mg of phthalocyanine iron in 30 mL to 100 mL of N,N-dimethylformamide and sonicate for 15 min to 30 min to obtain a phthalocyanine iron suspension;

[0042] ③ Add the phthalocyanine iron suspension to the O-BCD material suspension, making the mass ratio of O-BCD material to phthalocyanine iron (1~8):1. Wet impregnate for 6 h~24 h under stirring conditions, then separate the solid and liquid, and dry the obtained solid material to obtain the FePc / O-BCD electrocatalyst. Other steps are the same as in specific embodiments one to six.

[0043] Specific Embodiment Eight: A phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst obtained by any one of Specific Embodiments One to Seven.

[0044] Specific Implementation Method Nine: This implementation method uses phthalocyanine iron / oxygen-doped defect-rich biochar electrocatalysts in an electro-Fenton system for the electrocatalytic oxidation and degradation of antibiotic organic pollutants.

[0045] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that: In the electro-Fenton system, 20 mg of phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst, 800 μL of anhydrous ethanol, and 40 μL of Nafion solution are mixed evenly, and then uniformly loaded onto a carbon felt support using a coating process to form an FePc / O-BCD@CF electrode, which serves as the cathode. A platinum sheet is used as the anode, and Na2SO4 is used as the supporting electrolyte. The distance between the anode and cathode is 2 cm, and the current density is 10 mA / cm². 2The antibiotic organic pollutants are degraded under the following conditions: the concentration of Na2SO4 is 20 mg / L, and the concentration of the antibiotic organic pollutants is 20 mmol / L. Other steps are the same as in embodiments one through nine.

[0046] The beneficial effects of the present invention are verified using the following embodiments:

[0047] Example 1: A method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst, specifically carried out according to the following steps:

[0048] I. Preparation of BC biochar:

[0049] ① The waste biomass powder is crushed and then ball-milled to form biomass powder with a particle size of 100 mesh;

[0050] ② Place the biomass powder into a tube furnace and heat it from room temperature to 300 ℃ at a heating rate of 5 ℃ / min in a N2 atmosphere, and hold for 2 h to obtain BC biochar.

[0051] 2. Mix BC biochar with KOH, grind, and then put it into a tube furnace. In an Ar atmosphere, heat the furnace from room temperature to 900 ℃ at a heating rate of 5 ℃ / min and hold for 2 h to obtain biochar BCD rich in carbon defects.

[0052] The mass ratio of BC biochar to KOH mentioned in step two is 1:1;

[0053] 3. The biochar BCD rich in carbon defects was immersed in a 10 mol / L HNO3 solution, stirred at 60℃ for 1 h, filtered and washed with water until neutral, and dried to obtain oxygen-doped O-BCD material.

[0054] IV. Preparation of FePc / O-BCD electrocatalysts:

[0055] ① Disperse 100 mg of oxygen-doped O-BCD material into 100 mL of DMF and sonicate for 30 min to obtain an O-BCD material suspension;

[0056] ② Disperse 25 mg of ferrophthalocyanine in 100 mL of DMF and sonicate for 30 min to obtain a ferrophthalocyanine suspension;

[0057] ③ Add the iron phthalocyanine suspension to the O-BCD material suspension to make the mass ratio of O-BCD material to iron phthalocyanine 4:1. Wet impregnate for 20 hours under stirring conditions, then separate the solid and liquid, and dry the obtained solid material to obtain the FePc / O-BCD electrocatalyst.

[0058] Example 2: The difference between this example and Example 1 is that in step four ③, the phthalocyanine iron suspension is added to the O-BCD material suspension, making the mass ratio of O-BCD material to phthalocyanine iron 4:1. Wet impregnation is performed for 20 hours under stirring, followed by solid-liquid separation. The resulting solid is then dried to obtain the FePc / O-BCD electrocatalyst. All other steps and parameters are the same as in Example 1.

[0059] Example 3: The difference between this example and Example 1 is that in step four ③, the phthalocyanine iron suspension is added to the O-BCD material suspension, making the mass ratio of O-BCD material to phthalocyanine iron 1:1. Wet impregnation is performed for 20 hours under stirring, followed by solid-liquid separation. The resulting solid is then dried to obtain the FePc / O-BCD electrocatalyst. All other steps and parameters are the same as in Example 1.

[0060] Example 4: The difference between this example and Example 1 is that in step three, the biochar BCD rich in carbon defects is immersed in a 10 mol / L HNO3 solution and stirred at 60°C for 2 h. All other steps and parameters are the same as in Example 1.

[0061] Example 5: The difference between this example and Example 1 is that in step three, the biochar BCD rich in carbon defects is immersed in a 10 mol / L HNO3 solution and stirred at 60°C for 4 h. All other steps and parameters are the same as in Example 1.

[0062] Comparative Example 1: The preparation method of phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst is carried out according to the following steps:

[0063] I. Preparation of BC biochar:

[0064] ① The waste biomass powder is crushed and then ball-milled to form biomass powder with a particle size of 100 mesh;

[0065] ② Place the biomass powder into a tube furnace and heat it from room temperature to 300 ℃ at a heating rate of 5 ℃ / min in a N2 atmosphere, and hold for 2 h to obtain BC biochar.

[0066] 2. Mix BC biochar with KOH, grind, and then put it into a tube furnace. In an Ar atmosphere, heat the furnace from room temperature to 900 ℃ at a heating rate of 5 ℃ / min and hold for 2 h to obtain biochar BCD rich in carbon defects.

[0067] The mass ratio of BC biochar to KOH mentioned in step two is 1:1;

[0068] III. Preparation of FePc / O-BCD electrocatalysts:

[0069] ① Disperse 100 mg of carbon defect-rich biochar BCD in 100 mL of DMF and sonicate for 30 min to obtain a carbon defect-rich biochar BCD flotation.

[0070] ② Disperse 25 mg of ferrophthalocyanine in 100 mL of DMF and sonicate for 30 min to obtain a ferrophthalocyanine suspension;

[0071] ③ Add the iron phthalocyanine suspension to the carbon defect-rich biochar BCD flotation, so that the mass ratio of carbon defect-rich biochar BCD to iron phthalocyanine is 4:1. Wet impregnate for 20 h under stirring conditions, then separate the solid and liquid, and dry the obtained solid material to obtain the FePc / O-BCD electrocatalyst.

[0072] Comparative Example 2: The preparation method of oxygen-doped O-BCD material is specifically carried out according to the following steps:

[0073] I. Preparation of BC biochar:

[0074] ① The waste biomass powder is crushed and then ball-milled to form biomass powder with a particle size of 100 mesh;

[0075] ② Place the biomass powder into a tube furnace and heat it from room temperature to 300 ℃ at a heating rate of 5 ℃ / min in a N2 atmosphere, and hold for 2 h to obtain BC biochar.

[0076] 2. Mix BC biochar with KOH, grind, and then put it into a tube furnace. In an Ar atmosphere, heat the furnace from room temperature to 900 ℃ at a heating rate of 5 ℃ / min and hold for 2 h to obtain biochar BCD rich in carbon defects.

[0077] The mass ratio of BC biochar to KOH mentioned in step two is 1:1;

[0078] 3. The biochar BCD rich in carbon defects is immersed in a 10 mol / L HNO3 solution, stirred at 60 ℃ for 1 h, filtered and washed with water until neutral, and dried to obtain an electrocatalyst, which is the oxygen-doped O-BCD material.

[0079] Performance testing

[0080] The electrocatalytic oxidation degradation rate of antibiotics by the electrocatalysts prepared in Examples 1-5 and Comparative Examples 1-2 in an electro-Fenton system was tested.

[0081] A catalyst dispersion was prepared by mixing 20 mg of the above-mentioned electrocatalyst, 800 μL of anhydrous ethanol, and 40 μL of Nafion solution; the catalyst dispersion was then uniformly coated onto a 4 cm² surface. 2A cathode was fabricated on the surface of a hydrophilic carbon felt; in the Fenton system, at a depth of 1 cm... 2 The platinum plate is used as the anode, and Na2SO4 is used as the supporting electrolyte. The basic parameters are: pollutant concentration of 20 mg / L, electrode spacing of 2 cm, and current density of 10 mA / cm². 2 The electrolyte Na2SO4 concentration was 50 mmol / L. The degradation experiment of tetracycline TC was carried out on a DC power supply. The degradation was carried out for 20 min by adsorption and 60 min by electro-Fenton degradation, for a total of 80 min. A portion of the electrolyte was taken as a sample at fixed time intervals. The content of TC was determined by UV-Vis absorption spectroscopy. The residual rate of the pollutant was obtained by dividing the residual rate by the original concentration of the pollutant, and then the degradation rate could be obtained.

[0082] The performance test data is shown in Table 1 below:

[0083] Table 1. Comparison of electro-self-Fenton degradation performance of pollutants TC by the phthalocyanine iron / oxygen-doped defect-rich biochar electrocatalysts provided in the examples.

[0084]

[0085] Based on the results of Examples 1-3 and Comparative Example 2, in the phthalocyanine iron / oxygen-doped defect-rich biomass carbon electro-Fenton system, the mass ratio of the support (O-BCD) to the active component phthalocyanine iron (FePc) is a key factor in regulating catalytic performance. In Example 1, the total pollutant removal rate reached its highest value of 88.7% when the O-BCD:FePc ratio was 4:1. This was attributed to the optimal distribution of active sites and the effective utilization of the support structure at this ratio. When the support ratio was too high (8:1, Example 2), the density of active sites was insufficient, leading to limited catalytic reaction kinetics; while a high FePc ratio (1:1, Example 3) may cause aggregation of phthalocyanine iron molecules, blocking the mesoporous structure of the carbon support, reducing the specific surface area, and hindering the reaction mass transfer process. This phenomenon indicates that there is a significant synergistic effect threshold between the support and the active component. An appropriate ratio can ensure sufficient catalytic active centers while maintaining good conductivity and structural stability of the support.

[0086] Based on the results of Examples 1, 4, and 5, and Comparative Example 1, oxygen doping treatment, through concentrated nitric acid oxidation, introduces oxygen-containing functional groups such as carboxyl and hydroxyl groups onto the carbon defect surface, effectively improving the catalyst's reactivity. Example 1 (treated for 1 hour) exhibited the best catalytic performance, indicating that moderate oxygen doping can effectively enhance the hydrophilicity of the support, promote pollutant adsorption (adsorption efficiency 8.2%), and indirectly stabilize the metal centers of FePc through charge regulation. However, with prolonged treatment time (Examples 4 and 5), although the adsorption efficiency continued to increase (9.5% to 11.3%), the electrocatalytic degradation efficiency significantly decreased (67.6% to 45.5%). This reveals the negative effects of excessive oxidation: on the one hand, strong oxidizing conditions may destroy the sp(s) of the carbon skeleton. 2 The conjugated structure reduces the specific surface area of ​​the material and decreases the electronic conductivity of the support; on the other hand, excessive oxygen-containing functional groups may cover active sites or change the Fe-N4 coordination environment, hindering Fe... 2+ / Fe 3+ The redox cycle inhibits the generation efficiency of hydroxyl radicals. This divergence between enhanced adsorption and decreased catalytic activity highlights the surface reaction kinetics-driven mechanism in the electro-Fenton process.

[0087] In summary, the successful synthesis of the optimal performance catalyst (Example 1) benefited from the synergistic effect of three aspects: in terms of the support, moderate oxygen doping maintained the conductive network of the carbon material and provided anchoring sites for the active components; in terms of the active components, the optimized FePc loading ensured a high density and well-dispersed catalytic center; and in terms of the interface, the charge regulation effect between the oxygen-containing functional groups of the support and FePc stabilized the active center and optimized its electronic structure.

[0088] Figure 1 This is a mechanistic model diagram illustrating the application of the phthalocyanine iron / oxygen-doped defect-rich biochar electrocatalyst prepared in this invention in the degradation of organic pollutants.

[0089] from Figure 2 As can be seen from the above, the oxidation of organic pollutants by the phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst composite electrode provided by this invention is achieved through O2 and 2e-. - ORR generates H2O2, which is then activated to produce hydroxyl radicals, resulting in indirect oxidation.

[0090] Figure 2 a and 2b are SEM images of the oxygen-doped O-BCD material prepared in Comparative Example 2, and 2c and 2d are SEM images of the FePc / O-BCD electrocatalyst prepared in step four of Example 1.

[0091] from Figure 2As can be seen from a and 2b, the electrocatalyst has a large number of micropores with a pore size of 200 nm to 5 μm, indicating that oxygen-doped defect-rich biochar has been successfully prepared. Figure 2 c and 2d are SEM images of the FePc / O-BCD prepared in Example 1; they also have microporous and mesoporous structures, but due to the loading of FePc, part of the structure collapsed, which also shows that moderate doping of FePc helps to improve catalytic activity.

[0092] Figure 3 The image shows the EDS diagram of the FePc / O-BCD electrocatalyst prepared in step four of Example 1. Figure 3 It can be seen that the present invention has successfully achieved oxygen doping and trace loading of FePc, indicating that the dispersion of FePc plays a key role in the performance of the electrocatalyst.

[0093] Figure 4 The graphs show the electro-Fenton tetracycline degradation performance of the FePc / O-BCD electrocatalysts prepared in Examples 1-3 and Comparative Example 2. In the graphs, 4:1 represents Example 1, 8:1 represents Example 2, 1:1 represents Example 3, and 1:0 represents Comparative Example 2. Figure 5 This is a graph showing the trend of the electro-Fenton tetracycline degradation performance of the FePc / O-BCD electrocatalyst prepared in this invention as a function of oxygen doping time. Samples of 1 mL were taken before the reaction and at 0 min, 10 min, 30 min, and 60 min after energization. After four-fold dilution, the spectrophotometer readings were measured at 356 nm using a UV-Vis spectrophotometer. The absorbance before each reaction is denoted as A0, and the absorbance measured at that moment is denoted as A. The tetracycline removal rate at that moment can be calculated using the following formula:

[0094]

[0095] from Figure 4The results show that in the electro-Fenton system of iron phthalocyanine / oxygen-doped defect-rich biochar, the mass ratio of the support (O-BCD) to the active component iron phthalocyanine (FePc) is the key factor in regulating catalytic performance. The entire process of tetracycline degradation exhibits a rapid-then-slow characteristic, basically conforming to first-order kinetics. In Example 2, when the O-BCD:FePc ratio was 8:1, the degradation rate was significantly improved compared to Comparative Example 2 without FePc doping, but tetracycline was still not completely degraded. In Example 1, when the O-BCD:FePc ratio was 4:1, the pollutant removal rate was the highest after energization, which is attributed to the optimal distribution of active sites and effective utilization of the support structure at this ratio. When the FePc ratio was too high (1:1, Example 3), the degradation rate decreased to some extent compared to Example 1, indicating that FePc molecules may have aggregated, blocking the mesoporous structure of the carbon support, reducing the specific surface area, and hindering the reaction mass transfer process, thereby reducing the rate of the electro-Fenton reaction.

[0096] from Figure 5 The results show that in the phthalocyanine iron / oxygen-doped defect-rich biochar electro-Fenton system, oxygen doping plays a crucial role in regulating the system's performance. Comparative Example 1, without oxygen doping, exhibited the weakest catalyst activity and the lowest degradation rate. After oxygen doping, the performance improved compared to Comparative Example 1. Example 1 demonstrated the best performance in electro-Fenton degradation of tetracycline. With further extension of nitric acid treatment time, the structure of the carbon material may have collapsed, reducing its electron conductivity and resulting in a significant decrease in the degradation rate.

Claims

1. A method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst, characterized in that... The preparation method is specifically carried out according to the following steps:

1. The waste biomass powder is crushed and calcined at high temperature to obtain BC biochar; 2. Mix BC biochar with KOH, grind, and then calcine at high temperature to obtain biochar BCD rich in carbon defects; 3. Immerse the biochar BCD rich in carbon defects into a strong oxidant solution, stir, filter and wash to obtain oxygen-doped O-BCD material. IV. Disperse the oxygen-doped O-BCD material in a solvent, add phthalocyanine iron suspension, wet impregnate, separate and dry to obtain FePc / O-BCD electrocatalyst.

2. The method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 1, characterized in that... Step one includes: ① The waste biomass powder is crushed and then ball-milled to form biomass powder; ② Place the biomass powder into a tube furnace and calcine it at high temperature in a N2 atmosphere to obtain BC biochar.

3. The method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 2, characterized in that... The waste biomass powder mentioned in step ① is rice husk, straw or coconut shell; the particle size of the biomass powder is less than 100 mesh; the high-temperature calcination process mentioned in step ② is as follows: in N2 atmosphere, the temperature is increased from room temperature to 200 ℃~400 ℃ at a heating rate of 5 ℃ / min and held for 2 h.

4. The method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 1, characterized in that... The mass ratio of BC biochar to KOH mentioned in step two is 1:(0.5~3).

5. The method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 1, characterized in that... The high-temperature calcination process described in step two is as follows: In an Ar atmosphere, the temperature is increased from room temperature to 600℃~1000℃ at a heating rate of 5℃ / min and held for 2 hours.

6. The method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 1, characterized in that... The strong oxidant solution mentioned in step three is an HNO3 solution with a concentration of 5 mol / L to 15 mol / L. In step three, the biochar BCD rich in carbon defects is immersed in the strong oxidant solution and stirred at a temperature of 40 ℃ to 80 ℃ for 0.5 h to 4 h. After filtration and washing with water until neutral, it is dried to obtain oxygen-doped O-BCD material.

7. The method for preparing a phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 1, characterized in that... Step four includes: ① Disperse 100 mg of oxygen-doped O-BCD material in 30 mL to 100 mL of N,N-dimethylformamide and sonicate for 15 min to 30 min to obtain an O-BCD material suspension; ② Disperse 10 mg to 100 mg of phthalocyanine iron in 30 mL to 100 mL of N,N-dimethylformamide and sonicate for 15 min to 30 min to obtain a phthalocyanine iron suspension; ③ Add the iron phthalocyanine suspension to the O-BCD material suspension, so that the mass ratio of O-BCD material to iron phthalocyanine is (1~8):

1. Wet impregnate for 6 h~24 h under stirring conditions, then separate the solid and liquid, and dry the obtained solid material to obtain the FePc / O-BCD electrocatalyst.

8. A phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst obtained by the preparation method according to any one of claims 1 to 7.

9. The application of the phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst as described in claim 8, characterized in that... In the electro-Fenton system, phthalocyanine iron / oxygen-doped defect-rich biochar electrocatalysts are used for the electrocatalytic oxidation degradation of antibiotic organic pollutants.

10. The application of the phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst according to claim 9, characterized in that... In the electro-Fenton system, 20 mg of phthalocyanine iron / oxygen-doped defect-rich biomass carbon electrocatalyst, 800 μL of anhydrous ethanol, and 40 μL of Nafion solution were mixed uniformly and then uniformly loaded onto a carbon felt support using a coating process to form an FePc / O-BCD@CF electrode, which served as the cathode. A platinum sheet was used as the anode, and Na2SO4 was used as the supporting electrolyte. The distance between the anode and cathode was 2 cm, and the current density was 10 mA / cm². 2 The organic pollutants from antibiotics are degraded under the following conditions: the concentration of Na2SO4 is 20 mg / L, and the concentration of the organic pollutants from antibiotics is 20 mmol / L.

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