Defect engineered particle electrode, method of making and use thereof

Abstract

This invention belongs to the field of environmental catalysis and electrochemical water treatment technology, and provides a defect-engineered particulate electrode, its preparation method, and its application. The method involves mixing an iron-cobalt precursor solution with activated carbon and carrying out a hydrothermal reaction to obtain a hydrothermal precursor particulate electrode. This electrode is then etched by contacting it with a nitric acid-methanol etching solution to obtain a defect-engineered particulate electrode with abundant oxygen vacancy defects. The particulate electrode prepared by this invention possesses both excellent persulfate (PMS) activation ability and interfacial electron transport ability. The oxygen vacancies and CoFe bimetallic active sites on the surface of the particulate electrode effectively promote PMS adsorption and activation. The oxygen vacancy-induced electronic structure regulation can promote surface charge delocalization, improve interfacial electron migration efficiency, and accelerate Co… 2+ / Co 3+ It exhibits redox cycling and adsorption and degradation of polymer chains such as PS. It also demonstrates high catalytic activity, good structural stability, and recyclability.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis and electrochemical water treatment technology, and in particular to a defect-engineered particle electrode, its preparation method, and its application. Background Technology

[0002] Microplastics (MPs) are plastic particles with a diameter of less than 5 mm. Due to their small size, high stability, and strong environmental durability, they have become a major emerging pollutant in the aquatic environment. Polystyrene (PS) microplastics are widely derived from packaging materials, foam plastics, and industrial products. Their molecular backbone is based on stable C–C bonds and contains benzene ring structures. They are chemically inert and highly hydrophobic, making it difficult for them to undergo effective chain breaking and mineralization in the natural environment.

[0003] Currently, methods for treating microplastics mainly include physical separation, biodegradation, and advanced oxidation technologies. Physical separation only achieves the interception or transfer of pollutants and cannot fundamentally eliminate environmental risks; biodegradation generally suffers from slow degradation rates and a limited range of applicable polymers. In contrast, advanced oxidation technologies, which can disrupt polymer structures by generating highly reactive oxygen species, are considered an important pathway for the deep degradation of microplastics.

[0004] In existing advanced oxidation systems, electro-Fenton technology and persulfate (PMS) activation technology have received widespread attention. Electro-Fenton technology can generate H2O2 in situ at the cathode, and further produce hydroxyl radicals (…). OH); the PMS activation system can generate sulfate free radicals (SO4); - ), hydroxyl radicals ( OH) and singlet oxygen ( 1 Active species such as O2 can promote the oxidative decomposition of organic pollutants.

[0005] However, the aforementioned technologies still have significant limitations in the degradation of microplastics. Due to the solid-phase particle characteristics, hydrophobic interface, and highly stable polymer backbone of PS microplastics, the effective contact and interfacial reaction efficiency between them and reactive oxygen species is low. This often limits the oxidation process to surface functionalization or localized chain segment breakage, making it difficult to achieve sustained pyrolysis and deep mineralization. Simultaneously, traditional two-dimensional electrochemical systems suffer from limited mass transfer, limited reaction interfaces, and low electron transport efficiency, making it difficult to achieve efficient activation of oxidants and continuous generation of reactive species, thus restricting the degradation efficiency and mineralization degree of microplastics.

[0006] Three-dimensional electrochemical systems, by introducing particulate electrodes between the anode and cathode, can significantly expand the reaction interface, shorten the electron transport path, and enhance the mass transfer process, providing a new pathway for the enrichment of microplastic interfaces and the generation of reactive oxygen species. Therefore, three-dimensional electrochemical systems are considered an effective strategy for enhancing the synergistic degradation of microplastics by electro-Fenton / PMS.

[0007] However, the application of existing particulate electrode materials in microplastic treatment is still limited by the following factors: First, the number of active sites is limited, making it difficult to efficiently activate PMS or promote H2O2 conversion; second, the defect structure and conductivity are insufficient, limiting interfacial electron transfer and active species generation; third, the adsorption and enrichment capacity for microplastic particles is weak, making it difficult to achieve the synergistic coupling of "pollutant enrichment - oxidant activation - interfacial degradation".

[0008] Therefore, developing a particulate electrode material that combines microplastic enrichment capacity, efficient oxidant activation capacity, abundant defect sites, and rapid electron transport characteristics, and constructing an efficient three-dimensional electrochemical system based on it, is of great significance for achieving efficient chain scission and deep degradation of PS microplastics. Summary of the Invention

[0009] The purpose of this invention is to overcome the defects in the prior art and provide a defect-engineered particle electrode, its preparation method, and its application.

[0010] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing defect-engineered particle electrodes, comprising the following steps: (1) The iron-cobalt solution and activated carbon were mixed and subjected to a hydrothermal reaction to obtain an intermediate; (2) The intermediate solution and the nitric acid-methanol etching solution are mixed and then etched to obtain the defect-engineered particle electrode.

[0011] Preferably, the iron-cobalt solution in step (1) comprises cobalt nitrate hexahydrate, ferric nitrate nonahydrate, sodium hydroxide, ammonium fluoride and water; The ratio of cobalt nitrate hexahydrate, ferric nitrate nonahydrate, sodium hydroxide, ammonium fluoride, and water is 5~6g: 2.5~3g: 8~10g: 2~2.5g: 200~300mL.

[0012] Preferably, the activated carbon in step (1) is pretreated before mixing; Activated carbon and nitric acid solution are mixed for surface modification; The concentration of the nitric acid solution is 0.05~0.15M; the surface modification time is ≥8h.

[0013] As a preferred option, the ratio of iron-cobalt solution to activated carbon in step (1) is 500 mL: 5~130 g.

[0014] Preferably, the mixing time in step (1) is ≥0.5h; In step (1), the hydrothermal reaction temperature is 100~140℃ and the time is ≥8h.

[0015] Preferably, the intermediate solution in step (2) comprises an intermediate and methanol; The ratio of intermediate to methanol is 5~15g:50~150mL.

[0016] Preferably, the nitric acid-methanol etching solution in step (2) contains nitric acid and methanol; The ratio of nitric acid to methanol is 400~410μL: 5~15mL; The ratio of intermediate to nitric acid is 5~15g:400~410μL.

[0017] Preferably, the etching time in step (2) is ≥6h.

[0018] The present invention also provides a method for preparing the defect-engineered particle electrode to obtain the defect-engineered particle electrode.

[0019] The present invention also provides the application of the defect-engineered particle electrode in the degradation of microplastics.

[0020] This invention provides a method for preparing a defect-engineered particulate electrode, comprising the following steps: (1) mixing an iron-cobalt solution and activated carbon and then performing a hydrothermal reaction to obtain an intermediate; (2) mixing the intermediate solution with a nitric acid-methanol etching solution and then performing an etching treatment to obtain the defect-engineered particulate electrode. The particulate electrode provided by this invention, after defect engineering, forms abundant oxygen vacancy defects on its surface and constructs an active interface structure conducive to electron migration and redox cycles. In an electrochemical system, this particulate electrode can not only effectively activate persulfate (PMS), but also promote direct electron transfer of polymer contaminants at the solid-liquid interface, thereby achieving a synergistic enhancement of the free radical oxidation pathway and the interface electron transfer pathway.

[0021] During the reaction, polymer chains such as PS preferentially adsorb onto the surface of the particulate electrode, and interfacial electron transfer occurs at defect sites. Electrons migrate from the polymer chains to the catalyst surface, inducing polymer chain breakage and subsequent oxidative degradation. Oxygen vacancies play a crucial role in this system: on the one hand, due to their unsaturated coordination structure and high surface energy, oxygen vacancies can serve as preferential adsorption and activation sites, enhancing the enrichment of PMS on the catalyst surface and the activation of peroxy bonds; on the other hand, oxygen vacancies can promote surface charge delocalization, improve interfacial electron migration efficiency, and reduce electron transfer resistance, thereby accelerating the electron exchange process between pollutants and the catalyst. Simultaneously, in the CoFe bimetallic active system, oxygen vacancies can also modulate the electronic structure of the metal center and promote Co… 2+ / Co 3+ The redox cycle maintains the continuous regeneration of active sites and stable catalysis.

[0022] Furthermore, this invention introduces the defect-engineered particle electrode into a synergistic advanced oxidation system of electro-Fenton and PMS, utilizing the sulfate radicals (SO4) generated by PMS activation. - ), hydroxyl radicals continuously generated during the electro-Fenton process ( The synergistic effect of OH groups and interfacial electron transfer pathways jointly drives the breakage, oxidation, and deep transformation of microplastic polymer chains such as PS. Therefore, this invention can achieve efficient degradation of microplastic pollutants at room temperature, while also exhibiting low energy consumption, strong stability, and good engineering application potential.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The degradation efficiency of microplastics is significantly improved.

[0024] This invention achieves a defect-engineered particulate electrode with both high active site density and excellent electron transport performance by constructing a cobalt-iron layered bimetallic hydroxide active layer in situ on the surface of modified activated carbon and further introducing abundant oxygen vacancy defects through etching with a nitric acid-methanol system. In a synergistic advanced oxidation system of electro-Fenton and persulfate (PMS), this particulate electrode effectively promotes chain breaking and oxidative degradation of microplastics such as polystyrene (PS). Its degradation effect is significantly better than that of traditional two-dimensional dual-electrode systems / unetched particulate electrode systems / systems without introduced defects, achieving a degradation rate of up to 62.03%.

[0025] (2) It has abundant defect structures and high utilization efficiency of active sites.

[0026] This invention introduces a large number of oxygen vacancies on the surface of particulate electrodes through defect engineering, which not only increases the number of unsaturated active sites on the surface but also facilitates the adsorption, activation, and transformation of reactants at the interface. Oxygen vacancies can serve as preferential reaction sites to enhance the enrichment and activation capabilities of PMS, while promoting the generation and release of active species, thereby significantly improving the catalytic activity of the material and the degradation efficiency of microplastics.

[0027] (3) Strong interfacial electron transport capability, which is beneficial to polymer chain breakage.

[0028] The defect-engineered particulate electrode constructed in this invention exhibits excellent interfacial electron migration capabilities. Oxygen vacancy defects can promote surface charge delocalization, reduce electron transfer resistance, and enhance the interfacial electron exchange process between contaminants and catalysts. After polymer chains such as PS are enriched on the surface of the particulate electrode, electron extraction and chain segment breakage can occur through direct interfacial electron transfer, thereby realizing a highly efficient chain-splitting degradation pathway other than traditional free radical oxidation.

[0029] (4) It can coordinate the electro-Fenton and PMS double oxidation processes to achieve multi-path coupling enhancement.

[0030] The particulate electrode described in this invention can promote the activation of PMS to generate sulfate radicals (SO4). - Reactive oxygen species such as hydroxyl radicals can enhance the electro-Fenton process in electrochemical systems and continuously generate hydroxyl radicals. This mechanism improves the utilization efficiency of OH radicals, thereby achieving a synergistic effect between the free radical oxidation pathway and the interfacial electron transfer pathway. This synergistic mechanism is beneficial for increasing the degradation depth of microplastics and enhancing the overall oxidation capacity of the system.

[0031] (5) It has good structural stability and excellent recyclability.

[0032] The defect-engineered particulate electrode prepared in this invention uses activated carbon particles as a conductive framework and supports a stable cobalt-iron layered bimetallic hydroxide active phase, exhibiting both good structural integrity and mechanical stability. During recycling, the particulate electrode maintains high catalytic activity; after five cycles, the degradation rate of polystyrene microplastics still reaches 60.15%, demonstrating excellent reusability and engineering application potential.

[0033] (6) It is suitable for microplastic pollution control under normal temperature conditions and has good application prospects.

[0034] This invention can achieve efficient degradation of microplastic pollutants such as PS at room temperature without relying on high-temperature pyrolysis or high-energy-consuming melting treatment conditions. It has the advantages of low energy consumption, high treatment efficiency and recyclable materials, and has good application prospects in the field of microplastic pollution control in aquatic environments. Attached Figure Description

[0035] Figure 1 The images show the actual activated carbon, CoFe-CO3@AC, and CoFe-NO3@AC used in Example 1. Figure 2 Electron microscope images of CoFe-CO3@AC and CoFe-NO3@AC in Example 1; Figure 3 The analytical chromatograms of CoFe-CO3@AC and CoFe-NO3@AC in Example 1 are shown. Figure 4 The oxygen vacancy Gaussian spectrum of CoFe-NO3@AC in Example 1; Figure 5 The full-spectrum XPS spectra of CoFe-CO3@AC and CoFe-NO3@AC in Example 1 are shown below. Figure 6 XPS photoelectron spectroscopy and Raman spectra of CoFe-CO3@AC and CoFe-NO3@AC in Example 1; Figure 7 The electrochemical characterization diagrams of CoFe-CO3@AC and CoFe-NO3@AC in Example 1 are shown. Figure 8 This is a graph showing the mass loss of PS-MPs at different etching times for CoFe-NO3@AC in Example 1. Figure 9 This is a graph showing the relationship between the oxygen vacancy density of CoFe-NO3@AC and the acid etching time in Example 1; Figure 10 Figures showing the mass loss rate of polystyrene microparticles under different conditions; Figure 11 A graph showing the degradation rate of a simulated water sample; Figure 12 The degradation effects of CoFe-CO3@AC and CoFe-NO3@AC after 5 cycles are shown in the figure. Figure 13 This is a pseudo-first-order kinetic fitting diagram of the particle electrode under optimized conditions in Example 1; Figure 14 This is a graph showing the effect of different coexisting substances on degradation in Example 1; Figure 15 Figure 1 shows the reactive oxygen species in different systems in Example 1; Figure 16 This is a diagram of reactive oxygen species in the GF / Ti-Ta-Ir / CoFe-NO3@AC system under different conditions in Example 1. Detailed Implementation

[0036] This invention provides a method for preparing defect-engineered particle electrodes, comprising the following steps: (1) The iron-cobalt solution and activated carbon were mixed and subjected to a hydrothermal reaction to obtain an intermediate; (2) The intermediate solution and the nitric acid-methanol etching solution are mixed and then etched to obtain the defect-engineered particle electrode.

[0037] In this invention, the iron-cobalt solution in step (1) contains cobalt nitrate hexahydrate, ferric nitrate nonahydrate, sodium hydroxide, ammonium fluoride and water.

[0038] In this invention, the preferred ratio of cobalt nitrate hexahydrate, ferric nitrate nonahydrate, sodium hydroxide, ammonium fluoride, and water is 5-6g:2.5-3g:8-10g:2-2.5g:200-300mL, more preferably 5.2-5.8g:2.6-2.9g:8.5-9.5g:2.1-2.4g:220-280mL, and even more preferably 5.4-5.6g:2.7-2.8g:8.8-9.2g:2.2-2.3g:240-260mL.

[0039] In this invention, the activated carbon in step (1) is commercial activated carbon. The purchased commercial activated carbon is sequentially cleaned, ultrasonicated, washed and dried. It is cleaned with water, preferably ≥3 times, more preferably ≥4 times, and more preferably ≥5 times. After cleaning, it is ultrasonicated for a time preferably ≥30 min, more preferably ≥40 min, and more preferably ≥50 min. After ultrasonication, it is washed with ethanol and then dried. The drying temperature is preferably 50~70℃, more preferably 55~65℃, and more preferably 58~62℃. The drying time is preferably ≥12 h, more preferably ≥14 h, and more preferably ≥16 h. After drying, a pretreatment is performed.

[0040] In this invention, the pretreatment process is as follows: activated carbon and nitric acid solution are mixed to perform surface modification.

[0041] In this invention, the concentration of the nitric acid solution is preferably 0.05~0.15M, more preferably 0.06~0.14M, and even more preferably 0.08~0.12M; excess nitric acid solution is used.

[0042] In this invention, the surface modification time is preferably ≥8h, more preferably ≥14h, and even more preferably ≥16h.

[0043] In this invention, after the activated carbon surface modification is completed, it is washed with water until the pH of the filtrate is neutral, and then washed with ethanol. After ethanol washing, it is dried. The drying temperature is preferably 50~70℃, more preferably 55~65℃, and even more preferably 58~62℃. The drying time is preferably ≥12h, more preferably ≥14h, and even more preferably ≥16h.

[0044] In this invention, the preferred ratio of iron-cobalt solution to activated carbon in step (1) is 500mL: 5~130g, more preferably 500mL: 30~100g, and even more preferably 500mL: 60~70g.

[0045] In this invention, the mixing time in step (1) is preferably ≥0.5h, more preferably ≥5h, and even more preferably ≥10h.

[0046] In this invention, the temperature of the hydrothermal reaction in step (1) is preferably 100~140℃, more preferably 110~130℃, and even more preferably 115~125℃; the time is preferably ≥8h, more preferably ≥14h, and even more preferably ≥16h.

[0047] In this invention, after the hydrothermal reaction is completed, the product is collected by natural cooling, then washed with water until neutral, and then washed with ethanol. After washing with ethanol, the product is dried. The drying temperature is preferably 50~70℃, more preferably 55~65℃, and even more preferably 58~62℃. The drying time is preferably ≥12h, more preferably ≥14h, and even more preferably ≥16h.

[0048] In this invention, the intermediate solution in step (2) comprises an intermediate and methanol.

[0049] In this invention, the preferred ratio of intermediate to methanol is 5-15g:50-150mL, more preferably 6-14g:60-140mL, and even more preferably 8-12g:80-120mL.

[0050] In this invention, the intermediate and methanol are mixed, and the mixing time is preferably ≥6h, more preferably ≥8h, and even more preferably ≥10h.

[0051] In this invention, the nitric acid-methanol etching solution in step (2) contains nitric acid and methanol.

[0052] In this invention, the preferred ratio of nitric acid to methanol is 400-410 μL: 5-15 mL, more preferably 402-408 μL: 6-14 mL, and even more preferably 404-406 μL: 8-12 mL.

[0053] In this invention, the preferred ratio of intermediate to nitric acid is 5~15g:400~410μL, more preferably 6~14g:402~408μL, and even more preferably 8~12g:404~406μL.

[0054] In this invention, the mixing in step (2) involves adding the nitric acid-methanol etching solution dropwise into the intermediate solution, and starting the timing etching process after all the solution has been added.

[0055] In this invention, the etching time in step (2) is preferably ≥6h, more preferably ≥10h, and even more preferably ≥14h.

[0056] In this invention, after the etching process is completed, the solid product is collected by filtration and cleaned with anhydrous ethanol to remove residual acid and surface byproducts. The cleaning is preferably performed ≥3 times, more preferably ≥4 times, and even more preferably ≥5 times. After cleaning, the product is dried. The drying temperature is preferably 50~70℃, more preferably 55~65℃, and even more preferably 58~62℃. The drying time is preferably ≥12h, more preferably ≥14h, and even more preferably ≥16h. After drying, a defect-engineered particle electrode is obtained.

[0057] The present invention also provides a method for preparing the defect-engineered particle electrode to obtain the defect-engineered particle electrode.

[0058] The present invention also provides the application of the defect-engineered particle electrode in the degradation of microplastics.

[0059] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] First, commercial activated carbon (AC) was washed three times with deionized water and then sonicated for 30 min. After washing, the AC was rinsed with ethanol and then dried in an oven at 60 °C for 12 h. Subsequently, the dried AC was completely immersed in 0.1 M nitric acid solution and treated under static conditions for 12 h to achieve surface modification. After acid treatment, the AC was repeatedly washed with a large amount of deionized water until the pH of the filtrate reached neutral, and then rinsed with ethanol. Finally, the treated AC was dried at 60 °C for 12 h for later use.

[0062] 5.45 g Co(NO3)2·6H2O and 2.75 g Fe(NO3)3·9H2O were dissolved in 250 mL of deionized water and thoroughly mixed under magnetic stirring to form a homogeneous iron-cobalt solution (denoted as solution A). Then, pretreated AC was added to solution A at a ratio of 500 mL:65 g, and soaked for 12 h to ensure complete impregnation of the precursor into the AC structure. Next, the resulting suspension was transferred to a polytetrafluoroethylene-lined stainless steel reactor and subjected to a hydrothermal reaction at 120 °C for 12 h. After the reaction, the reactor was allowed to cool naturally to room temperature, and the product was collected. The product was then thoroughly washed with deionized water until the pH was neutral, followed by washing with ethanol. Finally, the obtained material was dried at 60 °C for 12 h to obtain the intermediate, denoted as CoFe-CO3@AC.

[0063] 405 μL of concentrated nitric acid was diluted in 10 mL of methanol (MeOH) to obtain solution B. Simultaneously, 10 g of dry CoFe-CO3@AC was dispersed in 100 mL of methanol and stirred thoroughly under mechanical stirring to ensure complete particle submersion. After stirring for 6 h, solution B was slowly added dropwise to the suspension to achieve controlled acid etching. The reaction was then continued for 12 h. After the reaction was complete, the solid product was collected by filtration and washed three times with anhydrous ethanol to remove residual acid and surface byproducts. Finally, the obtained material was dried at 60 °C for 12 h to obtain the defect-engineered particle electrode, denoted as CoFe-NO3@AC.

[0064] Images of activated carbon, CoFe-CO3@AC, and CoFe-NO3@AC are shown below. Figure 1 As shown, Figure 1 In the diagram, a represents activated carbon, b represents CoFe-CO3@AC, and c represents CoFe-NO3@AC.

[0065] Multiple complementary techniques were used to characterize the catalyst samples.

[0066] Diffraction patterns were acquired using a Rigaku MAX-2600 X-ray diffractometer (XRD) in the range of 2θ = 5°–90° at a scan rate of 2° / min. -1 .

[0067] The morphology and microstructure of the material were analyzed using scanning electron microscopy (SEM, ZEISS GeminiSEM 300) and energy-dispersive X-ray spectroscopy (EDS, Oxford X-Max).

[0068] High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns were acquired using a Thermo Fisher Talos F200X G2 transmission electron microscope. Samples were dispersed in ethanol and dropped onto a copper mesh support for testing.

[0069] After the samples were degassed at 120℃ for 6 h, nitrogen adsorption-desorption tests were performed using a Micromeritics ASAP 2020 HD88 analyzer, and the specific surface area, pore volume and pore size distribution were calculated using the Brunauer-Emmett-Teller (BET) method.

[0070] The surface elemental composition and chemical valence state of the samples were analyzed using a Thermo Scientific ESCALAB 250Xi X-ray photoelectron spectroscopy (XPS) instrument.

[0071] Fourier transform infrared spectroscopy (FT-IR) was performed using a Thermo Scientific Nicolet iS20 spectrometer in the range of 400–4000 cm⁻¹. -1 Record within the range.

[0072] Raman spectroscopy was performed using a HORIBA LabRAM HR Evolution spectrometer, with recordings under 785 nm laser excitation and a scanning range of 50–4000 cm⁻¹. -1 .

[0073] To detect paramagnetic species associated with oxygen vacancies, tests were performed at room temperature using a Bruker EMX Plus electron paramagnetic resonance (EPR) spectrometer.

[0074] The static water contact angle of PS-MPs before and after treatment was measured using a contact angle meter (JC2000CD, Shanghai Zhongchen Digital Technology Equipment Co., Ltd.) to evaluate its surface hydrophilicity.

[0075] All samples were washed with deionized water and thoroughly dried before testing to minimize the impact of contamination on the test results.

[0076] Electron micrographs of CoFe-CO3@AC and CoFe-NO3@AC are shown below. Figure 2 As shown, Figure 2 In the diagram, a, b, c, and d represent CoFe-CO3@AC, and e, f, g, and h represent CoFe-NO3@AC. Figure 2It can be seen that under hydrothermal conditions, CoFe-LDH nanosheets grow in situ and are uniformly loaded on the surface of pretreated activated carbon (AC), forming a CoFe-CO3@AC composite material. Subsequently, after further etching with nitric acid, defect-controlled CoFe-NO3@AC material is obtained. This process can induce local lattice distortion and structural reconstruction in the material, leading to an increase in defect sites. CoFe-LDH exhibits a typical layered / sheet-like structure and is uniformly anchored on the activated carbon surface. The CoFe-LDH layered nanosheets grow in situ on the activated carbon substrate, exhibiting obvious interlaced attachment characteristics, which is beneficial to the full exposure of active sites and the efficiency of interfacial contact. After nitric acid etching, the overall layered morphology of the material is still well preserved, and no obvious collapse or peeling of the nanosheet structure is observed, indicating that the treatment process maintains the basic skeletal integrity and structural stability of the composite material while introducing defects.

[0077] The analytical chromatograms of CoFe-CO3@AC and CoFe-NO3@AC are shown below. Figure 3 As shown, Figure 3 In the diagram, a is a schematic diagram of the synthesis of CoFe-CO3@AC and CoFe-NO3@AC; b, c, d, and e are high-resolution transmission electron microscope images of CoFe-NO3@AC; f, g, h, and i are elemental mapping images of CoFe-NO3@AC; j is the X-ray diffraction pattern of CoFe-CO3@AC and CoFe-NO3@AC; and k is the Fourier transform infrared spectrum of CoFe-CO3@AC and CoFe-NO3@AC. Figure 3 It can be seen that under hydrothermal conditions, layered bimetallic hydroxide CoFe-LDH grows in situ on the surface of pretreated activated carbon (AC), forming CoFe-CO3@AC. Subsequently, after further acid etching, defect-engineered CoFe-NO3@AC composite material is obtained. This process induces local lattice distortion, interlayer anion regulation, and the formation of oxygen vacancy defects in the material. Figure 3 a). Based on high-resolution transmission electron microscopy (HRTEM) images ( Figure 3 As can be seen from the image, the layered CoFe-LDH nanosheets are uniformly loaded and firmly anchored on the activated carbon surface, exhibiting a typical layered staggered stacking structure. The layered structure is uniformly distributed on the activated carbon support surface, maintaining a good open interface morphology, which is beneficial for reactant diffusion and interfacial mass transfer. HRTEM further shows that the (009), (104), and (012) crystal planes of CoFe-LDH have clearly distinguishable lattice fringes, with interplanar spacing (d-spacing) of approximately 2.45, 2.55, and 2.63 Å, respectively. Notably, after acid etching, obvious lattice fringes interruption, edge distortion, and lattice discontinuity appeared in local areas, indicating that structural defect sites were successfully introduced into the material.

[0078] Energy dispersive X-ray spectroscopy (EDS) elemental mapping results ( Figure 3 The results (fi) show that Co, Fe, N, O and C elements are uniformly distributed throughout the CoFe-NO3@AC composite material, indicating that the CoFe-NO3 phase after acid etching has achieved good in-situ integration and stable loading on the surface of the activated carbon support, the composite structure remains intact, and no obvious element agglomeration or phase separation phenomenon is observed.

[0079] X-ray diffraction (XRD) pattern Figure 3 (j) further confirmed the successful synthesis of CoFe-LDH and its in-situ growth on a carbon substrate. The diffraction results simultaneously showed characteristic diffraction peaks for both activated carbon (AC, PDF#26-1080) and CoFe-LDH (PDF#50-0235), indicating the successful synthesis of the composite material. Crucially, these characteristic peaks were well preserved after acid etching, demonstrating the stability of the synthesized material and the stability of the CoFe-LDH loading. Fourier transform infrared spectroscopy (FIR) Figure 3 Further verification of the chemical structure characteristics of the material was conducted using the etching method (k). The results showed that the characteristic vibrational peaks of Co–O and Fe–O remained in the etched sample, indicating that the metal-oxygen coordination framework was not disrupted. Meanwhile, at 1386.56 cm⁻¹... -1 A new characteristic absorption peak appears at this location, which can be attributed to NO3. - The characteristic vibrations indicate that partial anion exchange occurred between the material layers, meaning that the original interlayer anions were replaced by NO3. - Partial substitution. This interlayer regulation helps improve the openness and interface accessibility of the layered structure, thereby facilitating the entry of reactants, exposure of active sites, and electron / mass transport during subsequent reactions.

[0080] In summary, the characterization results above collectively demonstrate that acid etching treatment, while maintaining the overall structural integrity of the CoFe-LDH / AC composite material, successfully achieved defect introduction, oxygen vacancy construction, and interlayer anion regulation, thus providing a structural basis for improving the interfacial reactivity and catalytic performance of the material.

[0081] The Gaussian spectrum of oxygen vacancies in CoFe-NO3@AC is as follows: Figure 4 As shown, from Figure 4 This further confirms the above-mentioned defect regulation results. A significantly enhanced oxygen vacancy characteristic signal was detected in CoFe-NO3@AC, indicating that the acid etching process effectively induced oxygen vacancies (O2) in the material. Vs The formation of these defect sites is beneficial for regulating local electronic structure and enhancing interfacial reactivity.

[0082] The full-spectrum XPS spectra of CoFe-CO3@AC and CoFe-NO3@AC are as follows: Figure 5 As shown, from Figure 5 It can be seen that nitric acid etching did not cause a significant valence state change of the metal elements in the material, but rather induced a significant electronic structure reconstruction and defect site evolution within the CoFe-LDH layered structure.

[0083] The BET test results are as follows: the specific surface area of ​​CoFe-CO3@AC is 368.0988 m². 2 / g, the average adsorption pore size of BJH is 3.3336nm, and the average desorption pore size of BJH is 3.2352nm; the specific surface area of ​​CoFe-NO3@AC is 449.5529m². 2 / g, the average adsorption pore size of BJH is 3.4593nm, and the average desorption pore size of BJH is 3.4109nm.

[0084] XPS photoelectron spectroscopy and Raman spectra of CoFe-CO3@AC and CoFe-NO3@AC are as follows: Figure 6 As shown, Figure 6 In the diagram, a represents the Co 2p photoelectron spectrum of CoFe-CO3@AC and CoFe-NO3@AC, b represents the Fe 2p photoelectron spectrum of CoFe-CO3@AC and CoFe-NO3@AC, c represents the N 1s photoelectron spectrum of CoFe-CO3@AC and CoFe-NO3@AC, d represents the O 1s photoelectron spectrum of CoFe-CO3@AC and CoFe-NO3@AC, e represents the Raman spectrum of CoFe-CO3@AC and CoFe-NO3@AC, and f represents the surface area diagram of CoFe-CO3@AC and CoFe-NO3@AC. Figure 6 As can be seen from the X-ray photoelectron spectroscopy (XPS) results, the Co 2p peak shifts by approximately 0.5 eV towards lower binding energies after etching. Figure 6 (a) indicates that the electron cloud density around the Co center increases, suggesting that the acid etching process is accompanied by the removal of local lattice oxygen and the resulting redistribution of electrons.

[0085] Unlike Co, the Fe 2p spectrum shows that the Fe element remains predominantly Fe before and after etching. 3+ state( Figure 6(b) indicates that the process did not induce a significant Fe valence state transition. However, the relative proportions of the Fe 2p3 / 2 and 2p1 / 2 components changed significantly, with the 2p1 / 2 component increasing from 23.60% to 28.90%, while the 2p3 / 2 component decreased from 33.38% to 27.72%. This result suggests a significant modulation of the local coordination environment and electronic coupling state at the Fe center, which is presumably closely related to coordination unsaturation and local structural distortion caused by oxygen vacancies, leading to the formation of an oxygen-vacity-related Fe-O coordination structure.

[0086] The above changes indicate that nitric acid etching does not induce a change in metal valence state in the traditional sense, but rather a non-valence electronic reconstruction process. This means that, while maintaining the basic stability of the host metal valence state, the selective removal of lattice oxygen modulates the electron distribution and interfacial chemical environment of the Co–Fe bimetallic center. This characteristic is beneficial for constructing active structural units that are more conducive to interfacial electron migration and reactant activation.

[0087] The N 1s spectrum further indicates that the chemical environment on the material surface underwent synchronous regulation after etching. Figure 6 c). Among them, with NO2 - The relevant signals were significantly weakened or disappeared, while NO3 - The relevant components were significantly enhanced, with their relative content increasing from 8.5% to 19.8%, indicating that nitric acid etching not only altered the interlayer anion composition but also promoted NO3 production. - Stable existence on defect-rich surfaces. This interlayer anion reconstruction helps to modulate the surface charge distribution and interfacial hydrophilicity, thereby further optimizing the reaction interface environment.

[0088] O 1s spectrum results ( Figure 6 (d) further confirms the successful introduction of oxygen defects. After etching, the O 1s phase shifts towards lower binding energy, and the area ratio of the oxygen vacancy-related peak significantly increases from 18.8% to 58.18%, indicating that nitric acid etching effectively promotes lattice oxygen removal and significantly increases the defect concentration. Electron paramagnetic resonance (EPR) testing also observed a significantly enhanced characteristic signal at g=2.003. Figure 4 This signal is usually attributed to unpaired electrons trapped by oxygen vacancies, thus further independently verifying the enrichment of oxygen vacancies in the material.

[0089] The XPS and EPR results show that nitric acid etching preferentially removes weakly coordinated lattice oxygen while preserving the layered bimetallic hydroxide host framework. This allows for the introduction of high-density oxygen vacancies and electronic structure reconstruction without disrupting the host structure. This defect-driven structural modulation mechanism is further supported by Raman spectroscopy. Figure 6 (e). After etching, it is located at 297.82 cm. -1 The characteristic vibration peaks at the point of origin are significantly weakened or disappear, indicating that the originally well-coordinated metal-oxygen octahedral local structure is disturbed, suggesting that local lattice distortion and short-range ordered structural rearrangement have occurred inside the material, but the overall framework has not collapsed.

[0090] Furthermore, the specific surface area test results show that, as mentioned above, the specific surface area of ​​the material after nitric acid etching increased from 368.10 m² / s². 2 ·g -1 Increased to 449.55 m 2 ·g -1 However, based on the above electronic structure and defect analysis results, it can be seen that the improvement in material performance is not simply due to the increase in specific surface area, but mainly attributed to the non-valence electron reconstruction induced by selective lattice oxygen removal, the construction of high-density oxygen vacancies, and the synergistic electronic coupling effect of Co–Fe bimetallic centers. Figure 6 f).

[0091] In summary, nitric acid etching constructs a defect-rich yet structurally complete electronic control architecture. While maintaining the overall stability of the CoFe-LDH / AC composite material, it achieves synergistic optimization of the local electronic environment, defect structure, and interlayer chemical environment. This provides an important structural and electronic basis for the application of this material as a third electrode in the electrocatalytic degradation of microplastics.

[0092] Electrochemical experiments were conducted in a conventional three-electrode glass electrolytic cell using an LK2010 electrochemical workstation. The experiments were performed at room temperature in an aqueous electrolyte containing 0.4 M Na₂SO₄. The working electrode was either CoFe-CO₃@AC or CoFe-NO₃@AC, the reference electrode was Ag / AgCl, and the counter electrode was a platinum sheet. To assess long-term stability, chronopotentiometry was used under the same experimental conditions without iR compensation.

[0093] All potentials are converted to the reversible hydrogen electrode (RHE) potential according to equation (1): E_RHE=E_(Ag / AgCl)+1.023 V (1) Unless otherwise stated, all three-electrode linear scan voltammetric data are corrected for ohmic drop according to Equation (2), where Rs is the solution resistance measured by electrochemical impedance spectroscopy.

[0094] E_corrected=E_measured-iR_s (2)

[0095] Linear sweep voltammetry (LSV) tests were performed in the potential range of 0–2.5 V (vs RHE) at a scan rate of 10 mVs. -1 .

[0096] Cyclic voltammetry (CV) tests were performed within a potential window of 0–2.0 V (vs RHE) at a scan rate of 1–50 mV s. -1 .

[0097] Electrochemical impedance spectroscopy (EIS) was performed at open-circuit potentials in a frequency range of 10. 5 -0.01 Hz, AC amplitude is 10 mV.

[0098] Tafel polarization curves were measured in the range of 0–0.8 V (vs SCE) at a scan rate of 0.166 mV s. -1 .

[0099] To reduce the influence of solution resistance, iR compensation was performed in LSV, CV, and Tafel tests.

[0100] Electrode stability was assessed at a scan rate of 50 mV / s. -1 The CV loop test was used for evaluation.

[0101] In addition, through 10 mA cm -2 Chronoampere (CP) tests were performed at current density to further evaluate long-term stability.

[0102] By plotting the current density difference (Δj=j) a -j c The relationship curve between the electric double layer capacitance (C) and the scan rate is used to calculate the double layer capacitance (C). dl ), where j a and j c These represent the anode current density and the cathode current density, respectively.

[0103] The slope of the linear fit is C dl Twice as much.

[0104] The electrochemical active surface area (ECSA) of the catalyst is calculated according to equation (3): ECSA=(C dl / C s )×A (3) Where A is the actual surface area of ​​the electrode, and Cs is the specific capacitance of the catalyst, with a value of 0.04 mF / cm². -2 .

[0105] Electrochemical characterization diagrams of CoFe-CO3@AC and CoFe-NO3@AC are shown below. Figure 7 As shown, Figure 7In the figure, a shows a comparison of the linear sweep voltammetric curves of CoFe-CO3@AC and CoFe-NO3@AC. b and c show the sweep voltammetric curves of CoFe-CO3@AC and CoFe-NO3@AC in 1 M KOH solution at sweep rates from 1 to 50 mV / s. -1 The cyclic voltammetry curves are shown. d represents the C at a potential of -0.15 V (relative to RHE). dl Values. e represents the electron transfer rate constant (Ks) of CoFe-CO3@AC and CoFe-NO3@AC. f represents the Nyquist plot of CoFe-CO3@AC and CoFe-NO3@AC in 0.5 M H2SO4 solution and the equivalent circuit diagram used for EIS curve analysis. Figure 7 As can be seen from the linear sweep voltammetry (LSV) results, compared with CoFe-CO3@AC, the anodic onset potential of CoFe-NO3@AC shifted significantly negatively from 1.324 V to 1.245 V. Figure 7 (a) This indicates that the oxidation process begins at significantly lower applied potentials. Notably, the current rise of CoFe-NO3@AC is suppressed at higher potentials, and the oxygen evolution initiation is delayed, indicating better anodic selectivity for microplastic oxidation and effective prevention of parasitic OER. CV also shows that etching leads to improved electrochemical accessibility of active sites and charge transfer kinetics. (a) From 1 to 50 mV·s - Within the scan rate range of ¹, both electrodes exhibited quasi-rectangular CV curves, indicating that the reaction process is surface-controlled ( Figure 7 bc).

[0106] CoFe-NO3@AC consistently exhibits a larger closed-loop cyclic voltammetric area, indicating a higher density of available Co / Fe redox sites. For CoFe-NO3@AC, the double-layer capacitance (C... dl The concentration decreased significantly from 0.128 to 0.036 mF·cm⁻¹. -2 ( Figure 7 The results (de) indicate that the electrochemically active interface is significantly expanded due to acid-induced surface roughening and exposure of low-coordination metal sites. Quantitative analysis based on the Laveron model confirms the accelerated redox kinetics of the regenerated Co-Fe centers, showing that the heterogeneous Ks increased from 0.0685 to 0.0734 s after etching. -1 .

[0107] Meanwhile, electrochemical impedance spectroscopy showed a significant decrease in charge transfer resistance, with Rct decreasing from 766.7 Ω to 539.6 Ω. Figure 7This is consistent with the increase in Ks and the decrease in onset potential, indicating that electron transport at the electrode-electrolyte interface is promoted. In summary, nitric acid etching enhances interfacial charge transfer kinetics, suppresses competitive oxygen evolution, and lowers the energy barrier for anodic oxidation. Crucially, these enhancements stem from the intrinsic electronic and coordination reconstruction of the Co-Fe active centers, rather than merely an increase in specific surface area. This endows CoFe-NO3@AC with unique advantages as a particulate electrode for electro-Fenton reactions and PMS activation—applications where efficient PS-MP degradation and sustained ROS generation depend on rapid redox cycling.

[0108] Degradation experiments were conducted in a single-chamber electrochemical reactor. 150 mL of 0.4 M Na₂SO₄ was added as the supporting electrolyte. An Ir-Ta-Ti electrode was used as the anode, and graphite felt (GF) was used as the cathode, constructing a dual-electrode system. The graphite felt underwent pretreatment before use. First, the purchased graphite felt (GF) was washed with acetone, then three times with deionized water, and once with ethanol. Subsequently, it was dried in a 60°C oven for 6 h. To introduce oxygen-containing functional groups onto its surface, the dried GF was immersed in 1.0 M nitric acid solution with gentle stirring for 6 h. After acid treatment, it was thoroughly washed with deionized water until the pH was neutral, and then dried at 60°C for 12 h. The pretreated GF electrode exhibited better hydrophilicity and stable electrochemical performance and was used as the cathode in all electrochemical experiments.

[0109] To compare the effects of different systems, four systems were set up: (i) a particle-free electrode system, (ii) a system with pure AC as the particle electrode, (iii) a system with CoFe-CO3@AC as the particle electrode, and (iv) a system with CoFe-NO3@AC as the particle electrode; a DC power supply was used to provide a stable current. All PS-MPs degradation experiments were conducted at room temperature. Continuous aeration was maintained during the reaction to ensure thorough mixing of the solutions and to maintain stable reaction conditions.

[0110] All experiments were repeated three times, and the results are expressed as mean and standard deviation. After the reaction, suspended particles were collected by vacuum filtration through a 0.2 μm filter membrane, then washed three times with deionized water to remove residual electrolytes, and dried at 60 °C for 10 h. The residual mass of PS-MPs was calculated by subtracting the mass of the filter membrane, and the degradation efficiency η was calculated according to equation (4): η=(Mi-Mf) / Mi×100% (4) Where Mi and Mf represent the initial mass and final mass of PS-MPs, respectively.

[0111] When the nitric acid dosage was 500 μL, the excessive acidity caused partial damage to the catalyst structure and reduced the loading of CoFe-LDH on the activated carbon surface, resulting in over-etching. When the nitric acid dosage was reduced to 300 μL, insufficient etching intensity made it difficult to form enough defect structures. Considering both structural stability and defect formation effect, this study determined the optimal etching conditions to be: 405 μL of HNO3 added to 10 mL of methanol for etching. This condition can effectively introduce surface defect structures while maintaining the stability of the material structure.

[0112] To further reveal the impact of defect structures on catalytic performance, the oxygen vacancy concentration was quantitatively analyzed using electron paramagnetic resonance (EPR) technology. The mass loss of PS-MPs at different etching times was as follows: Figure 8 As shown, the relationship between oxygen vacancy density and acid etching time is as follows: Figure 9 As shown, from Figure 8 and Figure 9 It can be seen that the oxygen vacancy concentration on the material surface gradually increases with the extension of etching time. When the etching time reaches 12 h, the oxygen vacancy concentration reaches 2.602 × 10⁻⁶. 14 spins g -1 When the etching time was extended to 24 hours, the oxygen vacancy concentration tended to saturate, and correspondingly, the degradation efficiency of PS-MPs showed a significant increasing trend. The degradation efficiency was 40.03% when the etching time was 0 hours, and 62.03% when the etching time was 12 hours. After the etching time was increased to 24 hours, the degradation efficiency showed almost no significant improvement. These results clearly demonstrate a significant structure-performance relationship between oxygen vacancy concentration and catalytic activity. Oxygen vacancies can act as electron enrichment sites, increasing the electron density on the catalyst surface, thereby enhancing the activation ability of oxidant molecules and promoting free radical generation.

[0113] Mass loss rate of polystyrene microparticles, such as Figure 10 As shown.

[0114] Figure 10 In the figure, 'a' represents the loss in different systems. The degradation efficiencies of each system for PS-MPs in the four different electrode systems are as follows: 13.59% for the particle-free electrode system, 18.84% for the pure AC particle electrode system, 40.03% for the CoFe-CO3@AC particle electrode system, and 62.03% for the CoFe-NO3@AC particle electrode system. The results indicate that particle electrodes can construct a three-dimensional reaction interface, effectively increase the reaction area, accelerate interfacial electron transfer, and improve the efficiency of active species generation. Therefore, by controlling the catalyst structure through defect engineering, catalytic activity can be significantly enhanced.

[0115] Figure 10In the figure, b represents the effect of aeration conditions. With the aeration flow rate controlled at 100 mL / min, it can be seen that the degradation efficiency of PS-MPs is 49.95% under no aeration conditions; when the system is aerated, the degradation efficiency increases to 60.08%. This phenomenon indicates that dissolved oxygen can promote the generation of reactive oxygen species (ROS), thereby synergistically enhancing the oxidative degradation process.

[0116] Figure 10 In the figure, c represents the effect of PMS. It can be seen that without PMS, the degradation efficiency is only 23.95%; when PMS is added, the degradation efficiency significantly increases to 60.08%. Electrochemical activation of PMS is a key step in achieving efficient PS-MP degradation. The essence of electrochemical activation of PMS is to break the peroxide bonds (-OO-) in its molecules through electron transfer at the electrode interface, generating sulfate radicals (SO42-) under the synergistic effect of anodic oxidation and cathodic reduction. - ) and hydroxyl radicals ( The electrochemical system utilizes highly reactive oxidizing species such as hydroxyl radicals (OH) to achieve continuous scaling-up through chain reactions. These reactive species possess high oxidation potentials and reaction rates, effectively attacking the aromatic structure and carbon chains of polystyrene molecules to achieve surface oxidation, chain scission, and gradual mineralization, thereby significantly improving the degradation efficiency of PS microplastics. Furthermore, the electrochemical system offers advantages such as controllable reaction conditions, no need for external chemical reducing agents, and avoidance of secondary contamination by metal ions.

[0117] Figure 10 In the figure, d represents the effect of different pH values. The experiment was conducted in the pH range of 4.3–8.0. The results showed that when the pH decreased from 8 to 4.3, the degradation efficiency increased from 36.17% to 63.45%. This phenomenon indicates that acidic conditions are conducive to the generation of reactive oxygen species and polymer chain oxidation reactions. At the same time, the system can still maintain a high degradation efficiency in a wide pH range, indicating that it has good environmental adaptability.

[0118] Figure 10 In this context, e represents the effect of PMS concentration, as the PMS concentration increases from 0.01 mol / L. -1 Increased to 0.04 mol L -1 At that time, the degradation efficiency increased from 33.92% to 60.08%. However, when the concentration was further increased to 0.05 mol L, the degradation efficiency decreased. -1 and 0.06 mol L -1 The degradation efficiency decreased slightly (58.41% and 55.03%). This phenomenon is mainly due to the increased free radical self-quenching reaction and side reactions caused by excessive PMS.

[0119] Figure 10 In this context, f represents the effect of current density; when the current density increases from 10 mA cm⁻¹...-2 Increased to 35 mA cm -2 At that time, the degradation efficiency increased from 41.22% to 62.03%. When the current density was further increased, the degradation efficiency changed little, indicating that there is an optimal balance current density between ROS generation and side reactions in the system.

[0120] Figure 10 In the figure, g represents the effect of the dosage of the particulate electrode. As the dosage of the CoFe-NO3@AC particulate electrode increases from 5 mg / L... -1 Increase to 50 mg L -1 The degradation efficiency of PS-MPs increased from 24.56% to 61.36%, indicating that increasing the catalyst dosage can provide more active sites and expand the three-dimensional reaction interface.

[0121] Figure 10 In the figure, h represents the effect of different initial pollutant concentrations. When the initial concentration is 100 mg / L... -1 At that time, the degradation rate was 99.34%; the initial concentration was 500 mg / L. -1 At that time, the degradation rate was 99.13%; the initial concentration was 1000 mg / L. -1 At that time, the degradation rate was 63.45%; the initial concentration was 2000 mg / L. -1 At that time, the degradation rate was 32.88%; the initial concentration was 3000 mg / L. -1 At that time, the degradation rate was 19.41%; the above results show that the system has a certain tolerance to water bodies with high pollution load.

[0122] Figure 10 In the diagram, i represents the energy consumption in different systems. It can be seen that the energy consumption of the two-dimensional system is 2.65 kWh / g. -1 The energy consumption of the AC particle electrode is 2.07 kWh / g. -1 The energy consumption of the CoFe-CO3@AC particle electrode is 0.93 kWh / g. -1 The energy consumption of the CoFe-NO3@AC particle electrode is 0.43 kWh / g. -1 The results show that defect engineering significantly reduces energy consumption and improves electron utilization efficiency.

[0123] The degradation rate of the simulated water sample is as follows Figure 11 As shown, when the initial concentration of PS-MPs is 10 mg / L... -1 It was almost completely removed within 180 minutes.

[0124] The degradation effects of CoFe-CO3@AC and CoFe-NO3@AC after 5 cycles are as follows: Figure 12 As shown, Figure 12In the figure, a represents CoFe-CO3@AC and b represents CoFe-NO3@AC. After 5 cycles of reaction, the degradation efficiency of the GF / Ir-Ta-Ti / CoFe-NO3@AC system remained above 99%, while the activity of the GF / Ir-Ta-Ti / CoFe-CO3@AC system gradually decreased.

[0125] After the above experiments, it was determined that subsequent tests should be conducted under optimal conditions, namely, an aeration flow rate of 100 mL / min and a PMS concentration of 0.04 mol L. -1 The pH is 4.3 and the current density is 35 mA cm⁻¹. -2 The dosage of CoFe-NO3@AC particle electrode is 50 mg / L. -1 The pseudo-first-order kinetic fit of polystyrene microplastic degradation is as follows: Figure 13 As shown, from Figure 13 It can be seen that the experimental data conforms to the pseudo-first-order kinetic model, and the fitting result R... 2 =0.9799, speed constant: k=0.07723 min -1 .

[0126] The study investigated the effect of coexisting substances on degradation by adding humic acid, sodium chloride, and sodium bicarbonate. The concentrations of humic acid (10 mg / L), sodium chloride (0.01 M), and sodium bicarbonate (0.005 M) were as follows. Figure 14 As shown, the degradation efficiency is 62.03% under undisturbed conditions, 55.90% in the presence of humic acid, 61.11% in the presence of chloride ions, and 54.80% in the presence of bicarbonate ions. Humic acid and bicarbonate ions consume some free radicals, but the system still maintains a degradation efficiency of >54%, indicating that it has good anti-interference ability.

[0127] Reactive oxygen species in the system were detected by electron paramagnetic resonance (EPR) assay. The experimental conditions were: PMS dosage = 0.04 M, CoFe-NO3@AC dosage = 1 g / L, Na2SO4 concentration = 0.4 M, reaction time t = 12 h, and room temperature. The reactive oxygen species in different systems were analyzed as follows: Figure 15 As shown, the reactive oxygen species in the GF / Ti-Ta-Ir / CoFe-NO3@AC system under different conditions are as follows: Figure 16 As shown; Figure 15 In the figure, a represents DMPO- in the GF / Ti-Ta-Ir system. ESR spectra of OH, b is the comparison of DMPO before and after adding CoFe-NO3@AC particle electrode in GF / Ti-Ta-Ir system. OH, DMPO-O2 - DMPO-SO4 - ESR spectra, c represents DMPO in the GF / Ti-Ta-Ir / CoFe-NO3@AC system. OH, DMPO-O2 - DMPO-SO4 - ESR spectrum, d represents TEMP- in the GF / Ti-Ta-Ir system. 1 ESR spectra of O2 at different reaction times, e represents TEMP- in the GF / Ti-Ta-Ir / CoFe-NO3@AC system. 1 ESR spectra of O2 at different reaction times, f represents the free radical quenching experiment results of the GF / Ti-Ta-Ir / CoFe-CO3@AC system at pH 4.3, g represents the free radical quenching experiment results of the GF / Ti-Ta-Ir / CoFe-NO3@AC system at pH 4.3, h represents the free radical quenching experiment results of the GF / Ti-Ta-Ir / CoFe-NO3@AC system at pH=6, and i represents the free radical quenching experiment results of the GF / Ti-Ta-Ir / CoFe-NO3@AC system at pH=8; Figure 16 In the figure, 'a' represents the DMPO content in the GF / Ti-Ta-Ir / CoFe-NO3@AC system before and after energization. OH, DMPO-O2 - DMPO-SO4 - ESR spectrum, b is the DMPO- in the GF / Ti-Ta-Ir / CoFe-NO3@AC system before and after adding PMS under energized conditions. OH, DMPO-O2 - DMPO-SO4 - ESR spectrum.

[0128] from Figure 15 and Figure 16 It can be seen that the system generates OH, SO4 - O2 - , 1 O2, of which SO4 - Mainly derived from PMS activation, OH mainly originates from the electro-Fenton reaction, O2 - Derived from the oxygen reduction reaction, 1O2 is generated through an energy transfer process, and the three-dimensional particulate electrode significantly enhances the generation rate of these ROS.

[0129] The reaction conditions were controlled as follows: pH=4.3, PMS dosage=0.04 M, CoFe-NO3@AC dosage=1 g L-1, Na2SO4 concentration=0.4 M, t=12 h, room temperature. The apparent contributions of reactive oxygen species and electron transfer pathways to PS-MPS degradation were analyzed by adding different scavengers. The results are shown in Table 1.

[0130] Table 1. Degradation effects after treatment with different cleaning agents

[0131] As shown in Table 1, the PS degradation rate is approximately 61% without a scavenger, but increases with the addition of methanol (SO4). - The degradation rate decreased significantly after the addition of scavenger (tert-butanol). The degradation rate decreased significantly after adding OH scavenger (O2), and the degradation rate decreased further after adding p-benzoquinone (O2). - The degradation efficiency decreased after the removal of the scavenger; the results showed that SO4 - and OH is the main active species. At the same time, some degradation still occurs in the presence of the broad-spectrum scavenger ascorbic acid, indicating that there is a non-free radical oxidation pathway in the system.

[0132] The above experiments show that the degradation of microplastics in this system is mainly achieved through the synergistic effect of the free radical oxidation pathway and the non-free radical electron transfer pathway. Specifically, the free radical pathway originates from sulfate radicals and hydroxyl radicals generated during the electrochemical activation of PMS. Highly reactive oxides such as OH radicals possess high oxidation potential and reactivity, enabling non-selective attack on microplastic surfaces, initiating polymer carbon chain breakage, aromatic ring opening, and gradual oxidation to generate small molecule intermediates. Simultaneously, a non-radical electron transfer pathway exists within the system, where pollutant molecules undergo direct electron transfer reactions with activated PMS at the electrode interface or catalytic material surface, selectively oxidizing pollutants without generating free radicals. This pathway features controllable reaction processes, high selectivity, and strong anti-interference capabilities. The two pathways work synergistically: the radical pathway provides strong oxidizing power for efficient chain breaking and mineralization, while the non-radical pathway helps improve electron utilization efficiency and reduce losses from radical quenching, thus enhancing the overall microplastic degradation efficiency and system stability. This synergistic mechanism effectively overcomes the poor selectivity and low energy utilization of single-radical systems, and is key to achieving efficient electrochemical degradation of microplastics. The system of this invention has the following advantages: approximately 62% PS microplastic degradation rate can be achieved at room temperature; energy consumption is low, only 0.43 kWh / g. -1 It exhibits high mineralization efficiency, converting approximately 97% of carbon into inorganic products; the catalyst demonstrates good cycle stability; and it exhibits excellent resistance to interference from common coexisting ions. This system can be widely applied to the remediation of microplastic-contaminated water bodies, the treatment of recalcitrant organic pollutants, the deep oxidation of industrial wastewater, and the development of novel electrocatalytic materials, demonstrating significant engineering application potential.

[0133] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a defect-engineered particle electrode, characterized in that, Includes the following steps: (1) The iron-cobalt solution and activated carbon were mixed and subjected to a hydrothermal reaction to obtain an intermediate; (2) The intermediate solution and the nitric acid-methanol etching solution are mixed and then etched to obtain the defect-engineered particle electrode.

2. The method for preparing the defect-engineered particle electrode as described in claim 1, characterized in that, The iron-cobalt solution in step (1) contains cobalt nitrate hexahydrate, ferric nitrate nonahydrate, sodium hydroxide, ammonium fluoride and water; The ratio of cobalt nitrate hexahydrate, ferric nitrate nonahydrate, sodium hydroxide, ammonium fluoride, and water is 5~6g: 2.5~3g: 8~10g: 2~2.5g: 200~300mL.

3. The method of claim 2, wherein the defect engineered particle electrode is prepared by the steps of: In step (1), the activated carbon is pretreated before mixing; ​ Activated carbon and nitric acid solution are mixed for surface modification; The concentration of the nitric acid solution is 0.05~0.15M; The surface modification time is ≥8h.

4. The method for preparing the defect-engineered particle electrode as described in claim 3, characterized in that, In step (1), the ratio of iron-cobalt solution to activated carbon is 500 mL: 5~130 g.

5. The method for preparing the defect-engineered particle electrode as described in claim 4, characterized in that, The mixing time in step (1) is ≥0.5h; In step (1), the hydrothermal reaction temperature is 100~140℃ and the time is ≥8h.

6. The method for preparing the defect-engineered particle electrode as described in claim 5, characterized in that, Step (2) The intermediate solution contains the intermediate and methanol; The ratio of intermediate to methanol is 5~15g:50~150mL.

7. The method for preparing the defect-engineered particle electrode as described in claim 6, characterized in that, The nitric acid-methanol etching solution in step (2) contains nitric acid and methanol; The ratio of nitric acid to methanol is 400~410μL: 5~15mL; The ratio of intermediate to nitric acid is 5~15g:400~410μL.

8. The method for preparing the defect-engineered particle electrode as described in claim 7, characterized in that, The etching process in step (2) takes ≥6 hours.

9. The defect-engineered particle electrode prepared by the method of any one of claims 1 to 8.

10. The application of the defect-engineered particle electrode of claim 9 in the degradation of microplastics.

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