Heterogeneous electro-Fenton Process Research Articles

Metal–Organic Framework Fe-BTC as Heterogeneous Catalyst for Electro-Fenton Treatment of Tetracycline

This study explores the use of the iron-containing metal–organic framework (MOF), Basolite®F300, as a heterogeneous catalyst for electrochemically-driven Fenton processes. Electrochemical advanced oxidation processes (EAOPs) have shown promise on the abatement of recalcitrant organic pollutants such as pharmaceuticals. Tetracyclines (TC) are a frequently used class of antibiotics that are now polluting surface water and groundwater sources worldwide. Acknowledging the fast capability of EAOPs to treat persistent pharmaceutical pollutants, we propose an electrochemical Fenton treatment process that is catalyzed by the use of a commercially available MOF material to degrade TC. The efficiency of H2O2 generation in the IrO2/carbon felt setup is highlighted. However, electrochemical oxidation with H2O2 production (ECO-H2O2) alone is not enough to achieve complete TC removal, attributed to the formation of weak oxidant species. Incorporating Basolite®F300 in the heterogeneous electro-Fenton (HEF) process results in complete TC removal within 40 min, showcasing its efficacy. Additionally, this study explores the effect of varying MOF concentrations, indicating optimal removal rates at 100 mg L−1 due to a balance of kinetics and limitation of active sites of the catalysts. Furthermore, the impact of the applied current on TC removal is investigated, revealing a proportional relationship between current and removal rates. The analysis of energy efficiency emphasizes 50 mA as the optimal current, however, balancing removal efficiency with electrical energy consumption. This work highlights the potential of Basolite®F300 as an effective catalyst in the HEF process for pollutant abatement, providing valuable insights into optimizing electrified water treatment applications with MOF nanomaterials to treat organic pollutants.

Novel MOF-derived Fe/CoNHDC-400@GF cathode with improved in-situ catalytic degradation of chloroquine phosphate during heterogeneous electro-Fenton process

The preparation of stable and high-efficiency heterogeneous electro-Fenton cathodes for the treatment of pollutants is important for environmental remediation. Herein, a novel N-doped MOF-derived Fe/Co bimetallic catalyst was in-situ grown on graphite felt (GF) surface to yield a composite cathode Fe/CoNHDC-400@GF for use in electro-Fenton process. The introduction of cobalt accelerated electron transfer due to existing polyvalent metals. The synergistic effect between Co0, CoⅡ, CoШ, FeⅡ, and FeШ enabled the continuous generation of reactive oxygen species (•OH and •O2−). Under near-neutral conditions (pH=6.5), complete removal of 10 mg L−1 chloroquine phosphate (CQP) was achieved within 60 min. Additionally, efficient removal was also achievable over a wide pH range (pH=3–11). The mechanistic investigations indicated •OH as a major active oxygen species for CQP degradation. A combination of the experimental results with density functional theory calculations (DFT) clarified the degradation pathway and intermediate products of CQP. Moreover, the toxicity of degradation products significantly reduced. Overall, valuable insights on preparing composite cathodes grown in-situ for efficient removal of refractory pollutants from wastewater during the heterogeneous electro-Fenton process were provided, useful for future consideration.

Application of biochar in electro-Fenton process: Advantages and recent advancements

The electro-Fenton (EF) process is a well-known electrochemical advanced oxidation process that produces highly active hydroxyl radicals via the externally added catalytic amount of iron catalyst and in-situ generated hydrogen peroxide. The performance of the EF process depends on the choice of catalyst and the cathode. Biochar, an economically viable carbon-rich material derived from locally available biomass, presents a promising option for both catalyst support and cathode materials. The heterogeneous EF process using biochar-based catalyst has several advantages over the conventional EF process, including enhanced efficiency, declined iron leaching, surface-predominated radical generation, and pollutant degradation even in neutral pH conditions. Moreover, biochar demonstrates the capacity to generate a significant amount of hydrogen peroxide and regenerate ferrous ions rapidly. Additionally, biochar has a high adsorption capacity for many organic pollutants and ensures the contaminants' proximity and generated reactive species when applied as supports, catalysts, or electrodes in EF and related processes. The novelty of this work lies in its comprehensive review of the significant advancements and advantages of the applications of biochar in the EF process, emphasizing its potential to revolutionize wastewater treatment methodologies.

Natural air diffusion electrode modified with metal-organic frameworks derived Fe doped porous carbon for sulfamethazine degradation by heterogeneous electro-Fenton

A novel and efficient heterogeneous electro-Fenton process has been developed, utilizing a modified natural air diffusion electrode (NADE) as a bifunctional cathode. This cathode is based on Fe-doped porous carbon (Fe-PC(800)), which is derived from metal-organic frameworks (MOFs). This cathode has the unique ability to simultaneously generate and activate H2O2 in-situ without the need for aeration. Fe-PC(800) synthesized at a pyrolysis temperature of 800 °C exhibited the optimal catalytic efficiency for sulfamethazine (SMT) degradation over a wide pH between 3 and 11, attributed to the production of Fe0 and Fe3C which improved electron transfer efficiency. The presence of Fe0 facilitated the regeneration of Fe2+ and thus increased the activity of the bifunctional cathode in the Hetero-EF process. The co-action mechanism of •OH and 1O2 was confirmed by the radical quenching and electron paramagnetic resonance (EPR) investigations. NADE modified with Fe-PC(800) demonstrated broad applicability towards diverse contaminants and exceptional stability in ten consecutive cycling experiments. This study shed light on the viability of a straightforward and economically viable cathode utilizing NADE without the need of aeration in a Hetero-EF system, offering novel perspectives on bifunctional electrode design and the activation mechanism involving in-situ production and catalysis of H2O2.

Conversion of CoNiFe-LDH to CoNiFe-MOF/LDH as catalyst for efficient heterogeneous electro-Fenton degradation of sulfonamide antibiotics

The widespread use of antibiotics leads to spread of resistance bacteria and genes in natural water and has a potential threat to human health. Herein, a nanorod CoNiFe-MOF/LDH was synthesized using a self-sacrificial strategy and employed to degrade sulfamethazine (SMT) by heterogeneous electro-Fenton (HEF). The conversion of CoNiFe-LDH to CoNiFe-MOF/LDH resulted in a significant enhancement of specific surface area (from 13.96 to 32.26 m2 g−1) and electroactive surface area (from 2.20 to 4.22 mm2), and the degradation rate of SMT increased from 88.53% to 98.41% within 60 min. The free radical capture experiments indicated that ·OH and 1O2 played a significant role in the HEF process. The CoNiFe-MOF/LDH catalyst could be recycled 5 times with degradation rate of over 90%, it also demonstrated excellent resistance towards inorganic ions and humic acid. In addition, the CoNiFe-MOF/LDH exhibited remarkable degradation efficiency for 8 sulfonamides (over 89%). Mass spectrometry analysis indicated that SMT was oxidatively degraded via three possible pathways. According to the analysis of Toxicity Estimation Software Tool, the acute toxicity of SMT was effectively weakened. The CoNiFe-MOF/LDH catalyst has potential application prospect in wastewater treatment.

Ce/Fe bimetallic MOF derivatives in situ modified bulk carbon aerogel composite cathode for efficient heterogeneous electro-fenton degradation of chloramphenicol

In this study, we utilized a Ce-modified iron-based metal-organic framework derivative to in situ modify bulk CA (Ce/Fe@C-CA) as a bifunctional composite cathode to degrade chloramphenicol (CAP) in the heterogeneous electro-Fenton (EF) process. The composite cathode exhibited satisfactory CAP degradation efficiency, wide pH adaptability (2–9) and low metal leaching. Under the appropriate conditions (pH = 5, current density = 6 mA/cm2), 94.89% of CAP degradation efficiency was obtained within 60 min. The introduction of Ce increased the oxygen vacancy content, enhanced the cathodic electrochemical activity, promoted the production of a variety of reactive oxygen species and participates in the degradation of CAP, of which ·OH and 1O2 were dominant. Meanwhile, the electron transfer and synergistic catalysis between Ce and Fe promoted the regeneration of the metal active site, which was beneficial to improve the reuse stability of the Ce/Fe@C-CA cathode. The degradation pathway of CAP was obtained by DFT calculations and UPLC-MS/MS detection. This study not only proposed a novel bifunctional electro-Fenton cathode, but also provided a effective strategy for the treatment of actual pharmaceutical wastewater.

Novel CoFe-NC bimetallic catalysts for heterogeneous electro-Fenton process to remove BAA in dye wastewater

Electro-Fenton processes are one of the most promising Advanced Oxidation Processes (AOPs). However, the limited stability of electrocatalysts and the amount of in-situ generated H2O2 at the cathode are recognized as bottlenecks in their development and application. This study synthesized a CoFe bimetal-encapsulated carbon nanotube composite, utilizing the easily synthesized ZIF8 template for high-temperature carbonization post-CoFe introduction. When applied to dye chemical wastewater (BAA), the catalyst demonstrated outstanding performance and stability. In contrast to traditional Fenton methods, CoFe-NC enhances the in-situ accumulation of H2O2 and catalyzes the production of additional reactive species (·OH). Electroabsorption, anodic oxidation, and free radical oxidation roles were confirmed through N2/O2 electrocatalysis, biphasic experiments, and quenching studies. Furthermore, a potential pathway for the electro-Fenton degradation of BAA was proposed, and its toxicity was evaluated. Furthermore, a potential pathway for the electro-Fenton degradation of BAA was proposed, and its toxicity was evaluated. This research introduces a novel approach for the electro-Fenton degradation of anthraquinone dyes in wastewater.

CuCo2O4/CF cathode with bifunctional and dual reaction centers exhibits high RhB degradation in electro-Fenton systems

Cobalt-based oxide CuCo2O4-loaded CuCo2O4/carbon felt (CF) composite cathodes were synthesized by hydrothermal deposition of a precursor of Cu/Fe oxides on CF followed by roasting in air. The material serves both catalytic and cathodic dual functions in the heterogeneous electro-Fenton (EF) process. Through XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscope), and catalytic experiments, it was concluded that CuCo2O4 loading was successful and the highest hydrophilic 180-CuCo2O4/CF was obtained by varying the hydrothermal temperature without destroying the original structure. 180-CuCo2O4/CF accomplished 98.03 % degradation in 60 min, and it was found to maintain high degradation capacity in the pH 3 ∼ 9 range in experiments where the experimental parameters were varied. Compared to monometallic oxides, Cu and Co dual active centers are integrated in CuCo2O4, giving it diverse redox properties and oxidation states. As a result, the CuCo2O4/CF material can realize the dual function of catalytic and cathodic, which provides a new development direction in practical wastewater treatment.

Enhanced heterogeneous electro-Fenton process for degradation of rhodamine B: FeOCl/CF@AB composite cathode with superior efficiency and sustainability

With the growing environmental concerns and increasing demand for clean energy, the synthesis of Stable and efficient heterogeneous Electro-Fenton catalysts gains significant attention in the market. We present a novel FeOCl/CF@AB composite cathode designed for efficient heterogeneous electro-Fenton degradation of rhodamine B. The composite cathode exhibits remarkable catalytic performance, outperforming the raw carbon felt electrode, and achieving significantly higher rhodamine B degradation rates. The incorporation of acetylene black encapsulation provides excellent stability, preserving the FeOCl active sites from corrosion and ensuring sustained catalytic activity even after multiple reuse cycles. The electron penetration mechanism on the FeOCl/CF@AB cathode is elucidated through density functional theory calculations, revealing spontaneous O2 activation and H2O2 generation. Electron transfer between Fe(II) species and the acetylene black shell facilitates these processes. The presence of •OH species supports the degradation of rhodamine B to intermediates and mineralization to CO2 and H2O. Furthermore, LC-MS analysis unveils the detoxification effect of the electro-Fenton process with FeOCl/CF@AB, presenting reduced developmental toxicity of degradation intermediates. Economic cost analysis demonstrates the feasibility and cost-effectiveness of the FeOCl/CF@AB cathode for large-scale wastewater treatment applications. In conclusion, the FeOCl/CF@AB composite cathode showcases stability and efficiency, offering a promising and sustainable electro-Fenton technology for dye wastewater treatment.

PFAS-Free Carbon Electrodes for Efficient Micropollutants Removal through Heterogeneous Electro-Fenton: From Material Synthesis to Module Design

Emerging micropollutants (MPs) in water bodies such as pharmaceuticals, pesticides, personal care products, and per-and poly-fluoroalkyl substances (PFAS) have posed environmental, ecological, and anthropological issues since MPs are too persistent to be degraded by conventional biological treatment. On the other hand, electrochemical advanced oxidation processes (EAOPs) have proved themselves as efficient and robust techniques to unselectively degrade MPs by forming OH radicals (•OH). Among EAOPs, electro-Fenton, or more specifically heterogeneous electro-Fenton (HEF), suggests an eco-friendly and energy-efficient treatment technique with a wide pH range for removing persistent MPs. In HEF, hydrogen peroxide (H2O2) is electrochemically produced on the cathode surface, which can react with immobilized, adjacent Fe catalysts for •OH generation. Yet, one challenge for HEF is that most of the studies have primarily focused on synthesizing Fe-containing carbons as a catalyst that suffers from several delicate preparation steps, which are time-, chemical-, and energy-consuming and lack reusability over consecutive runs [1].Additionally, these catalysts are usually powders, entailing adding polymeric binders for the immobilization of the catalyst layer on electrodes. The presence of polymeric binders, e.g., polytetrafluoroethylene (PTFE)—as PFAS-containing compounds on the electrode surface—enhances the risk of PFAS contamination during the HEF process due to mechanical wear-off or degradation under the harsh oxidative condition caused by the formation of unselective •OH. Therefore, developing PFAS-free carbon electrodes for the HEF process offering facile fabrication and good reusability with a scaling-up perspective is imperative to enable decentralized solutions for MPs removal, especially highly recalcitrant PFAS. In this work, freestanding carbons made of bio-based precursors, chitosan and sucrose, serve as electrodes for the HEF process. Chitosan is the backbone for the self-standing feature and a nitrogen-rich biopolymer, while sucrose serves as a carbon-rich compound. The mixture of chitosan and sucrose undergoes silica- and ice-templating to make a hierarchically porous carbon [2]. Bio-based carbons illustrated their capability for oxygen reduction reactions, particularly the electro-generation H2O2 [3]. As-synthesized carbons proved to remove carbamazepine and sulfamethoxazole as two persistent MPs at pH 3 and pH 7 [3]. Moreover, a novel flow-through electrolysis module equipped with as-synthesized carbons has been designed and operated to remove 20 mg/L CBZ solution at a current density of 20 mA/cm2. This module design demonstrates the ease of scaleup for a decentralized water/wastewater treatment unit to remove highly recalcitrant MPs.

Degradation of Dimethyl Phthalate by Heterogeneous Electro-Fenton Process Using Fe3O4-Doped Biomass Porous Carbon

Degradation of Dimethyl Phthalate by Heterogeneous Electro-Fenton Process Using Fe3O4-Doped Biomass Porous Carbon

Fe@Fe2O3/etched carbon felt as a cathode for efficient bisphenol a removal in a flow-through electro-Fenton system: Electron transfer pathway and underlying mechanism

The advanced oxidation processes based on the electro-Fenton reactions show great potentials as a wastewater treatment approach for removing emerging contaminants. In the electro-Fenton system, some factors still exist affecting the treatment efficiency, e.g., the formation of iron sludge, a narrow pH working range, and slow conversion rates between Fe2+ and Fe3+. In this research, a novel heterogeneous flow-through electro-Fenton system was constructed, and carbon felt was used as the template material for the preparation of an etched carbon felt cathode loaded with zero-valent iron and iron oxide (Fe@Fe2O3/ECF) for the degradation of bisphenol A, which addressed the aforementioned issues. The Fe@Fe2O3/ECF electrode showed excellent performance across a pH range between 3 and 11, with exceptional stability and resistance to other substances in water. For the three pollutants, bisphenol A, tetracycline and ciprofloxacin, the highest degradation efficiency can reach 99.3 %. Compared to traditional electro-Fenton systems, the novel process exhibited superior performances due to synergistic effects from feasible flow design, enhanced electrochemical reactivity and greater exposure of active sites. Through electron spin resonance and free-radical quenching experiments, it was determined that the primary species participating in the heterogeneous electro-Fenton process were the hydroxyl radical and superoxide anion. Specifically, the hydroxyl radical was identified as playing a pivotal role in the degradation of bisphenol A. After a continuous operation of 240 min, the electrode showed low metal ion leaching rate and good stability, with the concentrations of leached Fe and Co ions to be only 17 and 7 μg/L, respectively. Meanwhile, the removal efficiency was only decreased by 5.7 % during the process. Through density functional theory calculation and intermediate product analysis, three potential degradation pathways were proposed, with the cleavage of carbon bonds serving as the main degradation approach. The toxicity analysis demonstrated that the intermediates were generally less toxic than BPA during treatments. This research provides a fresh means for promoting a valence state cycling of ferric species in electro-Fenton system, which has potential applications in wastewater treatment containing emerging contaminants.

A magnetically induced self-assembly of Ru@Fe3O4/rGO cathode for diclofenac degradation in electro-Fenton process

In this study, a novel magnetic nanocomposite of Ru@Fe3O4/rGO was successfully synthesized by a simple hydro-thermal method. The Ru@Fe3O4/rGO particles were assembled and immobilized for innovative magnetically assembled electrode (MAE) without any binder, and the electrode was further applied in heterogeneous electro-Fenton (hetero-EF) process for the degradation of diclofenac (DCF). The results showed that rGO could remarkably enhance the conductivity and catalyze the two-electron oxygen reduction, which greatly improved the generation of H2O2. In addition, the mixture valence of Fe and Ru species might provide rich reaction sites and enhance electron transfer by synergy. Thus, the Ru@Fe3O4/rGO MAE exhibited a stable and high electrocatalytic activity in the hetero-EF process for DCF degradation over a wide pH range from 2 to 9 owing to the higher electroactive surface area (EASA) and lower charge/mass-transfer resistance. The DCF degradation efficiency could reach about 100% within 90 min under pH 5 and current 40 mA, and the Ru@Fe3O4/rGO MAE showed high stability and reusability after five cycles. Theoretically, 1O2 and •OH were the main reactive oxygen species (ROS) participating in DCF degradation in the Ru@Fe3O4/rGO MAE hetero-EF process. Furthermore, according to the LC-MS/MS intermediates, the possible DCF degradation pathway was deduced including dechlorination, hydroxylation and ring opening attacked by ROS. Eleven intermediates were detected during DCF degradation in the MAE hetero-EF process, and the ecological risk of DCF degradation in Ru@Fe3O4/rGO MAE hetero-EF process was significantly reduced. This study provides new insights into the magnetically assembled electrode of Ru@Fe3O4/rGO and displays a new practical application prospect of the materials for high-efficient removal and degradation of DCF from wastewater.

Accelerated removal of sulfadiazine by heterogeneous electro-Fenton system with Pt-FeOX/graphene single-atom alloy cathodes

Heterogeneous electro-Fenton (EF) process is emerging as an attractive treatment technology for removal of sulfadiazine (SDZ), in which in situ generation of H2O2 and Fe(II) are crucial steps. In this study, Pt-FeOX/G was synthesized as a heterogeneous EF catalyst by incorporating Pt single atoms into a FeOX nanocrystal. The optimized Pt1-FeOX/G cathode exhibited an SDZ conversion of >90% within 30 min over a broad pH range (3–11). The Pt1-FeOX/G cathode under a strong alkaline medium exhibited very prominent selectivity to H2O2 via 2e− oxygen reduction reaction with a maximum H2O2 concentration of 211.93 mg L−1. The hydroxyl radicals in the cathodic chamber were mainly derived from the in situ conversion of generated H2O2 in the heterogeneous EF system. The structure-activity results of Pt-FeOX/G suggested that the SDZ removal efficiency was closely related to the decentralized morphology and electronic configuration of the Pt-FeOX microcrystalline structure. Three possible SDZ degradation pathways, dominated by S–N bond cleavage, were proposed based on the stage products. The toxicity of the major products was determined using the ecological structure-activity relationship model in conjunction with trophic aquatic organisms. This study demonstrated the feasibility of enhancing heterogeneous EF catalysis for antibiotic-polluted water using multifunctional single-atom alloy cathodes.

Bifunctional metallic composite catalyst cathode in heterogeneous electro-Fenton process: Classification, preparation and reactive species

The application of conventional electro-Fenton (EF) is limited by the narrow pH range and iron-containing sludge production, while the bifunctional cathodes in the heterogeneous electro-Fenton (HEF) can realize the synchronous generation and activation of H2O2, broaden the adaptable pH range and render catalyst easy to recycle, which has gained wide attention in electrochemical advanced oxidation processes (EAOPs). In this review, we summarized the classification of bifunctional metallic composite cathodes in HEF, the preparation and loading methods of catalyst on the cathode, as well as the advantages and the corresponding characterization of the bifunctional cathodes. The approaches to enhance the catalysts performance for H2O2 generation and activation and electrode stability were addressed. The origin, identification and transformation of reactive species in degradation mechanism were explored. Finally, the challenge and trend of bifunctional cathode for HEF was prospected. We hope this review can provide a useful guideline for the design and application of bifunctional cathodes in HEF.

Heterogeneous Electro-Fenton Process Using a Cathode of Carbon Felt Impregnated with Iron for the Degradation and Biodegradability Enhancement of Sulfamethazine

Heterogeneous Electro-Fenton Process Using a Cathode of Carbon Felt Impregnated with Iron for the Degradation and Biodegradability Enhancement of Sulfamethazine

Accelerating Fe(III)/Fe(II) redox cycling in heterogeneous electro-Fenton process via S/Cu-mediated electron donor-shuttle regime

In this study, we developed a Cu0.5Fe2.5S4 nanocatalyst through facile sulfidation of the Cu-MIL-88B(Fe) precursor to expedite surface Fe(III) reduction and enhance H2O2 activation in the heterogeneous electro-Fenton (HEF). The as-prepared catalyst possesses relatively large specific surface area and uniformly dispersed metal active sites. The Cu0.5Fe2.5S4-catalyzed HEF system allowed complete removal of naproxen with minimal metal leaching, surpassing that of Cu-MIL-88B(Fe) or Fe3S4. Quantitative XPS analysis, electrochemical characterization and density functional theory calculations reveal an electron donor-shuttle regime in which S2- and Cu species serve as the electron donor and shuttle, respectively. The Cu species significantly accelerate the internal electron transfer between S and Fe and mitigate the dissolution of the adjacent iron sites, securing the sustainable reducing capacity. Moreover, Cu0.5Fe2.5S4-based HEF exhibits great practicability for treatment of various organics in urban wastewater. This study opens new avenue for addressing the challenge of sluggish Fe(III)/Fe(II) cycling in HEF.

Efficient degradation of 2,4-dichlorophenol by heterogeneous electro-Fenton using bulk carbon aerogels modified in situ with FeCo-LDH as cathodes: Operational parameters and mechanism exploration

In this study, an in situ grown FeCo-Layered double hydroxide anchored to the surface of a bulk carbon aerogel (FeCo-LDH/CA) for contaminant degradation during the heterogeneous electro-Fenton (EF) process. The results exhibited that the FeCo-LDH/CA cathode achieved 100% of 2,4-dichlorophenol (2,4-DCP = 20 mg/L) degradation within 120 min at pH = 3, application current 20 mA, and Na2SO4 concentration 0.05 M. Moreover, the degradation efficiency was impressive in the range of pH = 2–9. The coexistence of the Fe (III)/Fe (II) and Co (III)/Co (II) as active sites on the cathode surface promoted the in-situ decomposition of H2O2 to form reactive oxygen species (ROS). •OH and O2- were confirmed to be the major degradation pollutants of ROS. Furthermore, density functional theory (DFT) was used to predict the reaction sites of 2,4-DCP, and its possible degradation pathways were proposed. The toxicity of intermediate products was evaluated and decreased after degradation. In addition, the eight cycle experiments and the degradation of other typical contaminants demonstrated the satisfactory stability and applicability of the synthetic cathode. This study presents the preparation of an efficient and stable EF cathode, further promoting the application of iron-based composites in wastewater treatment.

Facile synthesis of bimetallic ACF/CC@FeOCl–Cu composite cathode for efficient degradation of sulfamethoxazole at neutral pH by a flow-through heterogeneous electro-Fenton process

Flow-through heterogeneous electro-Fenton (FHEF) process shows a broad prospect for refractory organic pollutants removal. However, maintaining a long-term service life of higher catalytic cathode is crucial for the development of cathode materials, especially for iron-functionalized cathode operated under harsh conditions. In this study, a novel bimetallic CC@FeOCl–Cu composite was synthesized through one-step calcination, coupled with a series of microstructure characterization methodology, including XRD, SEM-EDS, XPS, and FTIR. The superior catalytic activity of CC@FeOCl–Cu could be ascribed to Fe–Cu synergy and better dispersion of FeOCl nanosheets. With the optimal Cu:Fe ratio of 1:60, the bifunctional ACF/CC@FeOCl–Cu cathode was employed in FHEF process, exhibiting an outstanding performance for sulfamethoxazole (SMX) removal over a wide pH range (3.0–9.0). Comparison of experimental results indicated that the ACF/CC@FeOCl–Cu-FHEF process showed higher performance than ACF/CC@FeOCl-FHEF and homogeneous EF processes. The average SMX removal efficiency was 98% and TOC removal efficiency was more than 57% even after 10 cycles. Radical quenching experiments and electron spin resonance test confirmed that •OH was the primary active species. More •OH was generated in the ACF/CC@FeOCl–Cu-FHEF process because the doping of Cu could enhance catalytic activity of cathode. In addition, the satisfactory performance could be observed in the ACF/CC@FeOCl–Cu-FHEF process for the treatment of real landfill leachate, indicating its potential for practical application in wastewater treatment.

FeCo-ZIF derived carbon-encapsulated metal alloy as efficient cathode material for heterogeneous electro-Fenton reaction in 3-electron ORR pathway: Enhanced performance in alkaline condition

Oxygen reduction reaction via 3-electron pathway presents a promising approach for generating reactive oxygen species in heterogeneous electro-Fenton (H-EF) process. This approach overcomes the limitations posed by the slow accumulation of H2O2 via 2- electron ORR and the inefficient activation of H2O2 through Haber-Weiss cycle. In this study, bimetal alloy nanoparticles were encapsulated within carbon layers (FeCo/C) by a general MOF-derived strategy, resulting in an overall electron transfer number of 2.98 during the H-EF process. Under optimal modification conditions, the prepared FeCo/C exhibited exceptional performance in sulfamethoxazole removal. Furthermore, the performance was enhanced under alkaline conditions. The apparent rate constant increased from 0.02 to 0.03 min−1 as the pH value increased from 3 to 11. The mechanism underlying this alkalinity-enhanced activity was attributed to the involvement of a surface-independent outer sphere electron transfer component, which provides valuable insights into the potential application of the H-EF process for treating alkaline wastewater.