Electron Oxygen Reduction Reaction Research Articles

Oxygen Reduction Reaction Coupled Electro-Oxidation for Highly-Efficient and Sustainable Water Treatment.

Electro-oxidation (EO) technology demonstrates significant potential in wastewater treatment. However, the high energy consumption has become a pivotal constraint hindering its large-scale implementation. Herein, we design an EO and 4-electron oxygen reduction reaction coupled system (EO-4eORR) to replace the traditional EO and hydrogen evolution reaction (HER) coupled system (EO-HER). The theoretical cathodic potential of the electrolytic reactor is tuned from 0 V (vs. RHE) in HER to 1.23 V (vs. RHE) in 4eORR, which greatly decreases the required operation voltage of the reactor. Moreover, we demonstrate that convection can improve the mass transfer of oxygen and organic pollutants in the reaction system, leading to low cathodic polarization and high pollutant removal rate. Compared with traditional EO-HER system, the energy consumption of the EO-4eORR system under air aeration for 95 % total organic carbon (TOC) removal is greatly decreased to 2.61 kWh/kgTOC (only consider the electrolyzer energy consumption), which is superior to previously reported EO-based water treatment systems. The reported results in this study offer a new technical mode for development of highly efficient and sustainable EO-based treatment systems to remove organic pollutants in waste water.

Metal-Based Oxygen Reduction Electrocatalysts for Efficient Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) is a high-value chemical widely used in electronics, textiles, paper bleaching, medical disinfection, and wastewater treatment. Traditional production methods, such as the anthraquinone oxidation process and direct synthesis, require high energy consumption, and involve risks from toxic substances and explosions. Researchers are now exploring photochemical, electrochemical, and photoelectrochemical synthesis methods to reduce energy use and pollution. This review focuses on the 2-electron oxygen reduction reaction (2e- ORR) for the electrochemical synthesis of H2O2, and discusses how catalyst active sites influence O2 adsorption. Strategies to enhance H2O2 selectivity by regulating these sites are presented. Catalysts require strong O2 adsorption to initiate reactions and weak *OOH adsorption to promote H2O2 formation. The review also covers advances in single-atom catalysts (SACs), multi-metal-based catalysts, and highlights non-noble metal oxides, especially perovskite oxides, for their versatile structures and potential in 2e- ORR. The potential of localized surface plasmon resonance (LSPR) effects to enhance catalyst performance is also discussed. In conclusion, emphasis is placed on optimizing catalyst structures through theoretical and experimental methods to achieve efficient and selective H2O2 production, aiming for sustainable and commercial applications.

Platinum-induced nanolization and electron-deficient gold in platinum@gold cocatalyst for efficient photocatalytic hydrogen peroxide production

Simultaneous optimization of the number and intensity of oxygen (O2) adsorption on gold (Au) cocatalyst is highly required to greatly improve their interfacial hydrogen peroxide (H2O2)-production activity. However, it is a great challenge to realize the above effective modulation of Au by traditional photodeposition route. In this study, a platinum (Pt)-induced selective photodeposition method was designed to simultaneously regulate the particle size and electronic structure of Au cocatalyst for boosting the photocatalytic H2O2-production activity of bismuth vanadate (BiVO4) via the selective deposition of Pt@Au core–shell cocatalyst. The photocatalytic results indicate that the as-prepared BiVO4/Pt0.1@Au photocatalyst achieves a considerable H2O2-production activity with a rate of 2752.13 μmol L−1 (AQE = 13.76 %), which is obviously higher than that of BiVO4/Pt (137.63 μmol L−1) and BiVO4/Au (475.33 μmol L−1). It was found that the introduction of Pt successfully induced the formation of Au nanoparticles for enhancing the number of O2 adsorption. Meanwhile, the spontaneous transfer of free electrons of Au to Pt induces the generation of electron-deficient Auδ+ sites, which spontaneously enhances the O2-adsorption intensity for facilitating the 2-electron oxygen reduction reaction (ORR), resulting in efficient H2O2 production. The present strategy may be useful for more comprehensively regulating the intensity and number of O2 adsorption on cocatalysts to facilitate artificial photosynthesis.

Efficient hydrogen peroxide synthesis with Pluggable Capsule cathode for Electro-Fenton treating actual landfill leachate

Membrane concentrate of landfill leachate is the typical refractory wastewater with high contaminants concentration, high complexity, and high toxicity, posing a huge potential threat to the surface and subsurface water. Electro-Fenton (EF) based on in-situ synthesis of H2O2 is an effective method for the treatment of refractory organic pollutants. However, the low accumulative concentration of H2O2 and the poor scalability of the system remain major bottlenecks, limiting the practical application of EF. This study presented a modular air-breathing cathode, Pluggable Capsule Cathode (PCC), for efficient in-situ H2O2 synthesis through 2-electron oxygen reduction reaction (ORR). Based on PCC, corridor reactors (CR) were fabricated for in-situ H2O2 synthesis and actual landfill leachate treatment. Operated under the optimal conditions (dual-chamber, A/V=240 cm2 L−1, 2 M NaOH electrolytes and J=20 mA cm−2), the H2O2 concentration reached 28.1 g/L. In the EF system based on single-chamber CR equipped with PCCs, 81 % of COD and 89 % of NH3-N in landfill leachate were removed within 3 h. The total cost of landfill leachate treatment by the EF system based on CR-PCC was calculated as $ 5.06 m−3. The PCC based EF system was a promising process for the treatment of actual refractory wastewater, which provides a new insight for the structure design of cathode and reactor in the future.

Remarkable mass-transfer enhancement via constructing ordered framework structure by 3D-priniting strategy for stable pesticides removal

Heterogeneous electro-Fenton (HEF) processes are potential pathways for aquatic contaminants removal. However, synergies from catalysts dense accumulation, the sluggish inner diffusion and the loss of active sites inside the catalyst, have limited the practical application of traditional monolithic cathodes. In this work, it has been proofed that the highly controlled porosity in 3D-printed ordered framework shows obvious diffusion enhancement and offers more active sites. The stable and efficient HEF catalysts guarantee the removal and mineralization of aqueous pesticides. H2O2 is effectively generated in situ via 2-electron oxygen reduction reaction by the carbon lattice in the pH range of 4–10, which is then activated into hydroxyl radicals by the encapsulated Fe2P/Fe in 3D printed cathodes. Estimated by the mass-transfer simulation, the Grid structure has the largest convective transport velocity of 8 × 10-5 m∙s-1, which optimizing mass-transfer effect and maximizing the active sites utilization. Grid-2 % achieves 3.54 ± 0.05 mg∙g-1 napropamide degradation at neutral condition in one hour, which is 82 % and 269 % higher than degradation obtained by Star-2 % and Diamond-2 %, respectively.

Oxygen-doped defects modified C3N5 in enhanced molecule oxygen photoactivation for tetracycline hydrochloride degradation and H2O2 in situ production: Double pathways of 1O2 and O2–· high yield

The study aims to investigate the mechanism by which O-doped defect engineering in C3N5 enhances molecular oxygen photoactivation. A feasible one-step roasting method was adopted to synthesize a novel C3N5 with multiple O-doped defects sites (O-C3N5). The experimental characterizations and DFT analysis reveal that O atoms were doped into the in-plane structure of C3N5 to form O-doped defects located at both linked and terminal positions on triazine units. The O-doped defects transform C3N5 morphologies and diminish the band gap, favoring charge migration and electron accumulation under visible-light irradiation. Furthermore, O-doped defects improve the adsorption performance for molecular oxygen, which provides the prerequisite for photoactivating molecular oxygen. The prominent photoelectric property can high effectively photoactivate the adsorbed O2 to directly generate 1O2 in the energy transfer-mediated pathway and O2–· in the electron oxygen reduction reaction pathway. In addition, the well photoelectric property also facilitates the interconversion between 1O2 and O2–·, which enables diverse reaction applications to be achieved. Hence, the outstanding performance of O-C3N5 can be verified in photoactivating molecular oxygen for TC degradation and H2O2 in situ production. The results not only demonstrate the universality and feasibility of utilizing O-C3N5 photoactivating molecular oxygen for the advanced treatment of the complicated sewage, but also provide a comprehensive understanding on the enhanced molecule oxygen photoactivation of C3N5 through O-doped defects.

Dimensionally Intact Construction of Ultrathin S-Scheme CuFe2O4/ZnIn2S4 Heterojunctional Photocatalysts for CO2 Photoreduction.

The conversion of CO2 into carbon-neutral fuels such as methane (CH4) through selective photoreduction is highly sought after yet remains challenging due to the slow multistep proton-electron transfer processes and the formation of various C1 intermediates. This research highlights the cooperative interaction between Fe3+ and Cu2+ ions transitioning to Fe2+ and Cu+ ions, enhancing the photocatalytic conversion of CO2 to methane. We introduce an S-scheme heterojunction photocatalyst, CuFe2O4/ZnIn2S4, which demonstrates significant efficiency in CO2 methanation under light irradiation. The CuFe2O4/ZnIn2S4 heterojunction forms an internal electric field that aids in the mobility and separation of exciton carriers under a wide solar spectrum for exceptional photocatalytic performance. Remarkably, the optimal CuFe2O4/ZnIn2S4 heterojunction system achieved an approximately 68-time increase in CO2 conversion compared with ZnIn2S4 and CuFe2O4 nanoparticles using only pure water, with nearly complete CO selectivity and yields of CH4 and CO reaching 172.5 and 202.4 μmol g-1 h-1, respectively, via a 2-electron oxygen reduction reaction (ORR) process. The optimally designed CuFe2O4/ZnIn2S4 heterojunctional system achieved approximately 96% conversion of BA and 98.5% selectivity toward benzaldehyde (BAD). Additionally, this photocatalytic system demonstrated excellent cyclic stability and practical applicability. The photogenerated electrons in the CuFe2O4 conduction band enhance the reduction of Fe3+/Cu2+ to Fe2+/Cu+, creating a microenvironment conducive to CO2 reduction to CO and CH4. Simultaneously, the appearance of holes in the ZnIn2S4 valence band facilitates water oxidation to O2. The synergistic function within the CuFe2O4/ZnIn2S4 heterojunction plays a pivotal role in facilitating charge transfer, accelerating water oxidation, and thereby enhancing CO2 reduction kinetics. This study offers valuable insights and a strategic framework for designing efficient S-scheme heterojunctions aimed at achieving carbon neutrality through solar fuel production.

Monosymmetric Fe-N4 sites enabling durable proton exchange membrane fuel cell cathode by chemical vapor modification.

The limited durability of metal-nitrogen-carbon electrocatalysts severely restricts their applicability for the oxygen reduction reaction in proton exchange membrane fuel cells. In this study, we employ the chemical vapor modification method to alter the configuration of active sites from FeN4 to the stable monosymmetric FeN2+N'2, along with enhancing the degree of graphitization in the carbon substrate. This improvement effectively addresses the challenges associated with Fe active center leaching caused by N-group protonation and free radicals attack due to the 2-electron oxygen reduction reaction. The electrocatalyst with neoteric active site exhibited excellent durability. During accelerated aging test, the electrocatalyst exhibited negligible decline in its half-wave potential even after undergoing 200,000 potential cycles. Furthermore, when subjected to operational conditions representative of fuel cell systems, the electrocatalyst displayed remarkable durability, sustaining stable performance for a duration exceeding 248 h. The significant improvement in durability provides highly valuable insights for the practical application of metal-nitrogen-carbon electrocatalysts.

A quaternary ammonium cyclodextrin polymer for efficient photocatalytic production of hydrogen peroxide from pure water

A photocatalytic system can be used to efficiently produce hydrogen peroxide (H2O2) without introducing a sacrificial agent or oxygen (O2). This system has practical application potential but remains challenging to implement. To increase the H2O2 yield of this system, a quaternary ammonium cyclodextrin polymeric photocatalyst QCD36A1-1350 is successfully synthesized using quaternization modification and low-temperature polycondensation. The photocatalyst is used to produce H2O2 from pure water and air by the one-step two electron oxygen reduction reaction. Under irradiation by visible light, QCD36A1-1350 produces a higher H2O2 yield (of up to 2.51 mmol g−1h−1) than unquaternized polymers and reported metal-free catalysts under similar conditions. Experimental and theoretical studies clearly show that the introduction of quaternary ammonium groups can effectively broaden the visible light absorption of polymer catalysts, while increasing the hydrophilicity, charge transfer efficiency and surface stability. The practicability of efficient photocatalytic production of H2O2 is realized by increasing the activity and selectivity of the polymer photocatalyst.

Mechanistic Insights into Surfactant-Modulated Electrode-Electrolyte Interface for Steering H2O2 Electrosynthesis.

Electrocatalytic reactions taking place at the electrified electrode-electrolyte interface involve processes of proton-coupled electron transfer. Interfacial protons are delivered to the electrode surface via a H2O-dominated hydrogen-bond network. Less efforts are made to regulate the interfacial proton transfer from the perspective of interfacial hydrogen-bond network. Here, we present quaternary ammonium salt cationic surfactants as electrolyte additives for enhancing the H2O2 selectivity of the oxygen reduction reaction (ORR). Through in situ vibrational spectroscopy and molecular dynamics calculation, it is revealed that the surfactants are irreversibly adsorbed on the electrode surface in response to a given bias potential range, leading to the weakening of the interfacial hydrogen-bond network. This decreases interfacial proton transfer kinetics, particularly at high bias potentials, thus suppressing the 4-electron ORR pathway and achieving a highly selective 2-electron pathway toward H2O2. These results highlight the opportunity for steering H2O-involved electrochemical reactions via modulating the interfacial hydrogen-bond network.

Effective photo-electrochemical production of H2O2 and green Fenton reaction on hierarchical Fe/C/N @ ZIF-8 @ACF for abatement of antibiotics in water

Heterogeneous photo-electro-Fenton (HPEF) reaction is a highly efficient process using H2O2 produced by in-situ two electron oxygen reduction reaction (2e ORR) after aerating for the elimination of refractory organic pollutants. Herein, an effective MOFs derived Fe/C/N @ ZIF-8 @ACF composite electrode for HPEF was prepared by loading Fe/C/N derived from Fe-based metal-organic frameworks (Fe-MOFs) and zeolitic imidazolate framework-8 (ZIF-8) on activated carbon felt (ACF). By supplying air, solar light, and low external electric current (32 mA·cm−2) to the cathode, ZIF-8 could generate H2O2 by 2e- ORR process, and Fe/C/N could react with H2O2 to form strong oxidative radicals (·OH). Photocatalysis accelerates the Fenton reaction greatly with the abundant photo-generated electrons. The HPEF activity of different systems for the degradation of antibiotics was compared. The results showed that the degradation rate of antibiotics can be greatly increased with the best of ∼100% within 100 min. Moreover, the electrode could still maintain a high activity after reuse for 4 times, which proved to be highly active, stable, and well recyclable for a rapid HPEF oxidation for abatement of antibiotic pollutants in water.

Enriched Ti3+ in TiONC electrocatalyst for efficient H2O2 generation via 2-electron oxygen reduction reaction

The 2-electron electrochemical oxygen reduction reaction (ORR) is considered a viable method for synthesizing H2O2 because of its efficiency and environmental friendliness. However, conventional catalysts for this reaction predominantly rely on high-cost metals and require complex preparation procedures. Herein, we synthesized an electrocatalyst containing TiN and N-doped carbon via the pyrolysis of melamine and MIL125(Ti)–NH2. The effects of melamine and pyrolysis temperature on the chemical composition and defect site formation were investigated. Importantly, the obtained results suggest that the generated Ti3+ sites are more important in enhancing the performance of the 2-electron ORR, surpassing defective carbon and oxygen functional groups. In particular, the resulting TiONC-MA-1000 catalyst prepared through pyrolysis at 1,000 °C contained abundant Ti3+ sites, resulting in high 2-electron ORR activity with a molar selectivity exceeding 91 % and high stability over a 12 h testing period. The electrochemical H2O2 generation experiments conducted in an H-cell configuration employing TiONC-MA-1000 as the electrocatalyst yielded 6.99 mol⋅gcatalyst−1⋅h−1 H2O2. Therefore, the present study proposes a facile approach for fabricating highly active electrocatalysts suitable for large-scale H2O2 production.

Engineering Electrode Polarity for Enhancing In Situ Generation of Hydroxyl Radicals Using Granular Activated Carbon.

Recently, granular activated carbon (GAC) has shown its effectiveness as a cathode material for in situ ROS generation. Here, we present an electrochemically modified GAC cathode using electrode polarity reversal (PR) approach for enhanced H2O2 decomposition via 2-electron oxygen reduction reaction (2e-ORR). The successful GAC modification using PR necessitates tuning of the operational parameters such as frequency, current, and time intervals between the PR cycles. This modification enhances the GAC hydrophilicity by increasing the density of surface oxygen functionalities. After optimization of the electrode polarity, using the 20 (No PR)-2 (PR) interval and 140 mA current intensity, the •OH concentration reaches 38.9 μM compared to the control (No PR) (28.14 μM). Subsequently, we evaluated the enhanced •OH generation for the removal of glyphosate, a persistent pesticide used as a model contaminant. The modified GAC using PR removed 67.6% of glyphosate compared to 40.6% by the unmodified GAC without PR, respectively. The findings from this study will advance the utilization of GAC for in situ ROS synthesis, which will have direct implications on increasing the effectiveness of electrochemical water treatment systems.

Introduction of electron-deficient unit in resorcinol-formaldehyde resin to construct donor–acceptor conjugated polymer for enhancing photocatalytic H2O2 production

Intramolecular donor–acceptor conjugated polymer was constructed in resorcinol-formaldehyde resin by embedding benzothiadiazole, which can reduce the Gibbs free energy for two-electron oxygen reduction and improve photocatalytic H2O2 evolution.

Dipole-Dipole Tuned Electronic Reconfiguration of Defective Carbon Sites for Efficient Oxygen Reduction into H2O2.

Metal-free carbon-based materials are one of the most promising electrocatalysts toward 2-electron oxygen reduction reaction (2e-ORR) for on-site production of hydrogen peroxide (H2O2), which however suffer from uncontrollable carbonizations and inferior 2e-ORR selectivity. To this end, a polydopamine (PDA)-modified carbon catalyst with a dipole-dipole enhancement is developed via a calcination-free method. The H2O2 yield rate outstandingly reaches 1.8mol gcat -1 h-1 with high faradaic efficiency of above 95% under a wide potential range of 0.4-0.7 VRHE, overwhelming most of carbon electrocatalysts. Meanwhile, within a lab-made flow cell, the synthesized ORR electrode features an exceptional stability for over 250h, achieved a pure H2O2 production efficacy of 306g kWh-1. By virtue of its industrial-level capabilities, the established flow cell manages to perform a rapid pulp bleaching within 30min. The superior performance and enhanced selectivity of 2e-ORR is experimentally revealed and attributed to the electronic reconfiguration on defective carbon sites induced by non-covalent dipole-dipole influence between PDA and carbon, thereby prohibiting the cleavage of O-O in OOH intermediates. This proposed strategy of dipole-dipole effects is universally applicable over 1D carbon nanotubes and 2D graphene, providing a practical route to design 2e-ORR catalysts.

Elucidating Oxygen Reduction Mechanisms on Organic Mixed Ionic-Electronic Conducting Polymers

Atmospheric oxygen is an attractive oxidant for the generation of electricity from chemical fuels and for the electrochemical production of hydrogen peroxide. Although not universal, it is generally assumed that an electrocatalyst is needed to reduce oxygen. Recently, a variety of organic mixed ionic-electronic conducting polymers (OMIECs) have been reported to exhibit catalytic behavior for both the 4-electron/4-proton and the 2-electron/2-proton oxygen reduction reaction (ORR).This work sets out to identify the oxygen reduction mechanism of OMIECs through a multi-faceted experimental and theoretical approach. We primarily focus our efforts on p(NDI-T2 P75)—a random copolymer comprised of naphthalene diimide (NDI) and bithiophene (T2) units with 75% polar sidechains—and then expand the understanding built on this system to a range of other OMIECs. Using rotating ring disk electrochemistry, we find that the investigated OMIECs exhibit a high selectivity towards the 2-electron ORR product. Using operando UV-Vis and Raman spectroscopy measurements, we identify changes in OMIEC performance when in the presence of O2. To gain further insights about the catalytic reaction path, we construct and test a microkinetic model. Through this model, we show that the performance of the tested OMIECs can be rationalized through an EC’D reaction mechanism. Our results suggest that these materials do not operate as electrocatalysts for the initial reduction of oxygen to superoxide but do function as catalysts for the disproportionation of superoxide.

Kinetic Insights into the Mechanism of Oxygen Reduction Reaction on Fe2O3 /C Composites

Electrochemical energy storage and conversion systems are the appealing replacement for nonrenewable resources to provide clean and sustainable energy. Of particular interest are fuel cells and metal-air batteries, both of which rely on the oxygen reduction reaction (ORR) for their operation. Fe-N-C catalyst has been widely used as a prominent catalyst towards ORR, but there is still some ambiguity regarding its active sites. This study describes the role of Fe2O3, an inevitable species formed in Fe-N-C catalyst towards the ORR. The Fe2O3 is carefully synthesised on various carbon supports and characterised using XPS spectra, HRTEM images, and surface area analysis. The particle size of the Fe2O3 nanoparticles synthesised on the pores of the carbon support was determined to be ~10 nm from the HRTEM analysis. The current density of ORR and the number of electrons transferred on Fe2O3/C catalysts is increased compared with bare carbon supports. Based on the kinetic analysis, the ORR on Fe2O3/C follows pseudo-4-electron (or) 2+2-electron ORR, where the first 2-electron ORR to H2O2 and second 2-electron H2O2 reduction reaction (HPRR) to H2O are assigned to the graphitic carbon (carbon defects) and Fe2O3 active sites, respectively. The role of Fe2O3 is further studied using the Theoretical method, which reveals the decreased formation of free energy of O2 adsorption. The Fe2O3 reduces the energy barrier for the reduction of *OOH to OH-. The Fe2O3/C shows higher stability by retaining 95% of the initial activity even after 20,000 cycles. Figure 1

Synthesis of Metal-Free Carbon Aerogel with Nitrogen-Doped from Pyrolysis of Cellulose Aerogels Based on Coir Fibers Using Ammonia-Urea System as Electrocatalyst of Oxygen Reduction Reaction for Cathode in Seawater Batteries

Performance of seawater batteries is still limited by the sluggish nature of oxygen reduction reaction (ORR). One way to optimize the performance of the battery is by utilizing an electrocatalyst with the ability to increase the ORR rate of reaction. Nitrogen-doped carbon aerogel based on coir fiber is one of the alternatives because of its excellent electrocatalytic performance and was made from an abundant material. Carbon aerogel was obtained from pyrolyzing coir fiber-based aerogel cellulose. Nitrogen atom structure in carbon aerogel was affected by the temperature of cellulose aerogel pyrolysis. Pyridinic N content in the Nitrogen-doped carbon aerogel has effective for the activity of the ORR. The electrocatalytic performance of the carbon aerogel synthesized from coir fiber with nitrogen doping at the pyrolysis temperature of 600 °C was investigated in this study. The research process began with the synthesis of cellulose aerogel using urea-ammonia crosslinking precursor. Next, cellulose aerogel was pyrolyzed at 600 °C to create carbon aerogel. FTIR, XRD, CV, LSV, and LP were used to characterize the samples. The carbon aerogel was N-doped with pyridinic N, according to an analysis of the FTIR spectra. The carbon aerogel shows 4-electron ORR with kinetic current density (ik) of 0.74 mA/cm2 and current density (io) of 0.583 μA/cm2, according to electrochemical performance analysis in 3.5% NaCl as electrolyte.

H2O2 electrosynthesis activity and selectivity of Pd–Te nanoparticles with different surface compositions in acidic electrolyte

The selective 2-electron oxygen reduction reaction (2e− ORR) has emerged as a promising alternative for H2O2 production to the traditional anthraquinone process, which has energy and environmental issues. H2O2 electrosynthesis in acidic electrolytes is more relevant to practical conditions but requires a much higher overpotential, where precious metal-based electrocatalysts have exhibited high efficiency for the 2e− ORR. The electrocatalytic activity and selectivity are critically affected by the surface composition of the constituent elements. However, such effects in acidic electrolytes have been rarely investigated for precious metal compounds. In this work, palladium–tellurium binary compounds with two different surface compositions were prepared, and their electrocatalytic properties were compared to reveal the structure–activity–selectivity correlations. It was found that the compound with a higher surface Te/Pd ratio exhibited higher H2O2 selectivity but lower activity due to the decreased numbers of Pd ensemble sites as well as surface Pd binding sites, respectively.

Multicomponent Synthesis of Imidazole‐Linked Fully Conjugated 3D Covalent Organic Framework for Efficient Electrochemical Hydrogen Peroxide Production

AbstractThe semiconducting properties and applications of three dimensional (3D) covalent organic frameworks (COFs) are greatly hampered because of their long‐ranged non‐conjugated skeletons and relatively unstable linkages. Here, a robust imidazole‐linked fully conjugated 3D covalent organic framework (BUCT‐COF‐7) is synthesized through the one‐pot multicomponent Debus‐Radziszewski reaction of the saddle‐shaped aldehyde‐substituted cyclooctatetrathiophene, pyrene‐4,5,9,10‐tetraone, and ammonium acetate. The semiconducting BUCT‐COF‐7, as a metal‐free catalyst, shows excellent two electron oxygen reduction reaction (ORR) activity in alkaline medium with high hydrogen peroxide (H2O2) selectivity of 83.4 %. When the BUCT‐COF‐7 as cathode catalyst is assembled into the electrolyzer, the devices showed high electrochemical production rate of H2O2 up to 326.9 mmol g−1 h−1. The accumulative amount of H2O2 could totally degrade the dye methylene blue via Fenton reaction for wastewater treatment. This is the first report about intrinsic 3D COFs for efficient electrochemical synthesis of H2O2, revealing the promising applications of fully conjugated 3D COFs in the environment‐related field.