Key Takeaways & Executive Findings
- •• • Nv-C3N4-CNT/GF electrode achieved a charge transfer resistance of 13.26 Ω and a double-layer capacitance (Cdl) of 3.75 mF·cm−2, 3.30 times higher than pristine GF, indicating enhanced electrocatalytic activity and active site density. • • Under RSM-optimized conditions (current density 41.24 mA·cm−2, pH 7.23, catalyst content 1.02 g, calcination temperature 305.42 °C), H2O2 production reached 1638.73 mg·L−1, with a relative error of 0.92% from the predicted value, confirming model accuracy. • • The electrode demonstrated robust durability: after 6 cycles, H2O2 production decreased by only 13.688%, and in a 1.25 L, 0.1 mol·L−1 Na2SO4 solution, maximum production reached 2014.04 mg·L−1 over 960 min, with a peak Faradaic efficiency of 54.86%. • • The Nv-C3N4-CNT/GF electrode outperformed g-C3N4-CNT/GF and CNT/GF by 1.3 and 1.5 times in H2O2 yield (1622.73 mg·L−1 at 90 min), demonstrating the critical role of nitrogen vacancies in enhancing 2e−ORR selectivity and activity.
Abstract
Electrochemical two-electron oxygen reduction (2e−ORR) for hydrogen peroxide (H2O2) synthesis faces challenges of low cathodic catalytic efficiency and complex catalyst preparation. This study prepared nitrogen-vacancy (Nv) rich carbon nitride via one-step pyrolysis, composited with carbon nanotubes (CNT), and loaded onto graphite felt (GF) to fabricate a non-precious metal gas diffusion electrode Nv-C3N4-CNT/GF. The electrode exhibited a three-dimensional fibrous skeleton with interconnected micro-nano hierarchical pores, facilitating efficient electron transport. Electrochemical impedance spectroscopy revealed a low charge transfer resistance of 13.26 Ω, indicating superior electrocatalytic activity and charge transfer efficiency. Single-factor experiments and response surface methodology (RSM) optimization determined optimal conditions: calcination temperature 300 °C, catalyst mass ratio 3:1, Nv-C3N4-CNT loading 0.1 g, current density 40 mA·cm−2, pH 7, and aeration rate 0.1 L·min−1. Under these conditions, H2O2 accumulation reached 1622.73 mg·L−1 after 90 min, which was 1.3 and 1.5 times higher than g-C3N4-CNT/GF and CNT/GF electrodes, respectively. Stability tests showed that after 6 cycles, H2O2 production remained at 1400.52 mg·L−1, and within 960 min, the maximum production reached 2014.04 mg·L−1 with a highest Faradaic efficiency of 54.86%. These results demonstrate the electrode's potential for cyclic use. This study provides a new approach for developing efficient, low-cost electrodes for electrosynthesis of H2O2, offering a reference for green H2O2 production.
1. Introduction
Industrial H2O2 production predominantly relies on the anthraquinone process, which is energy-intensive, generates significant waste, and involves complex multi-step operations. Electrochemical synthesis via two-electron oxygen reduction (2e−ORR) offers a sustainable alternative, using electricity and clean reactants (O2 and H2O) to produce H2O2 on-site. However, the competing four-electron pathway reduces selectivity and energy efficiency, necessitating highly selective and active catalysts. Carbon-based materials are promising due to their low cost and stability, but pristine carbons exhibit poor 2e−ORR activity due to inert surfaces and limited active sites.
This study addresses these bottlenecks by engineering nitrogen vacancies into graphitic carbon nitride (g-C3N4), which is known for its tunable electronic structure but suffers from poor conductivity and low activity. The nitrogen vacancies modulate charge distribution and intermediate adsorption, enhancing 2e−ORR selectivity. By compositing Nv-C3N4 with carbon nanotubes (CNT) and immobilizing onto graphite felt (GF), the electrode achieves a hierarchical porous structure that facilitates electron transport and mass transfer. The resulting Nv-C3N4-CNT/GF electrode demonstrates significantly improved H2O2 production and stability, offering a scalable, low-cost solution for decentralized H2O2 generation.
Loading authentic research manuscript (Pages 1–5)...
XIE Wanghong, HU Huawei, ZHANG Xinwan, YANG Zhengwu, LU Zilan, ZHU Leilei, JIA Daqing, ZHANG Lehua (2026). Nitrogen-Vacancy Defective Carbon Nitride Modified Graphite Felt Cathode for Efficient Electrochemical Synthesis of Hydrogen Peroxide. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202510081
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the long-term operational stability of the Nv-C3N4-CNT/GF electrode under continuous electrolysis, and what are the primary degradation mechanisms?
The electrode maintained H2O2 production of 1400.52 mg·L−1 after 6 cycles, a decrease of only 13.688%, and sustained production up to 2014.04 mg·L−1 over 960 min. Degradation likely arises from gradual loss of catalyst particles, oxidation of carbon support, or fouling of active sites, but the relatively small decline indicates robust structural integrity and catalytic stability.
How does the Nv-C3N4-CNT/GF electrode's performance compare to state-of-the-art non-precious metal catalysts in terms of H2O2 yield and Faradaic efficiency?
The electrode achieved a maximum Faradaic efficiency of 54.86% and H2O2 yield of 2014.04 mg·L−1 under optimized conditions. This performance is competitive with recent reports, e.g., S-Nv-C3N4 achieved 4.52 mol·g−1·h−1, and g-C3N4@GDE produced 2.59 mg·h−1·cm−2. The Nv-C3N4-CNT/GF electrode offers a balance of high yield and stability, with the advantage of a simple preparation method.
What is the cost-effectiveness of the Nv-C3N4-CNT/GF electrode compared to traditional anthraquinone process or precious metal catalysts?
The electrode uses earth-abundant materials (carbon nitride, carbon nanotubes, graphite felt) and a simple one-step pyrolysis, significantly reducing material and fabrication costs compared to precious metal catalysts. While the anthraquinone process benefits from economies of scale, the electrochemical method offers lower energy consumption and environmental impact, making it cost-competitive for decentralized applications.
What are the critical parameters for scaling up the electrode fabrication process, and what challenges might arise?
Key parameters include the calcination temperature (300 °C), catalyst mass ratio (3:1), and loading (0.1 g). Scaling up requires uniform coating of the catalyst on larger graphite felt substrates, maintaining consistent porosity and electrical conductivity. Challenges include ensuring homogeneous dispersion of Nv-C3N4-CNT in the PTFE binder, controlling thickness to avoid mass transport limitations, and achieving reproducible performance across batches.
How does the electrode perform under different pH conditions, and what is the optimal pH range for practical wastewater treatment applications?
The RSM optimization indicated an optimal pH of 7.23, suggesting near-neutral conditions are favorable. This is advantageous for wastewater treatment, as it avoids the need for pH adjustment. The electrode's performance at pH 7 was validated experimentally, achieving high H2O2 yields, which is practical for treating effluents without additional chemical costs.
Related Chinese Research & Cross-Citations
Analysis of National and Local Policies for Medical Waste Treatment and Disposal in China
The escalating generation of medical waste, driven by healthcare expansion and frequent medical activities, poses significant environmental and public health risks. Under the framework of ecological civilization, China is developing a comprehensive policy system for medical waste treatment and disposal, yet the current framework remains nascent and exhibits inconsistencies between national and local policies. This study systematically analyzes the status of national and local policies from 2003 to 2024, collecting 413 policy documents (166 from national ministries and 247 from provincial governments). The analysis examines temporal evolution, regional distribution, and policy focus, alongside the influence of medical waste output, treatment technologies, facility infrastructure, and major epidemic responses. Findings reveal distinct policy phases: initial self-disposal, exploratory management, foundational system building, and rapid development. Regional disparities are pronounced, with eastern coastal areas showing more advanced policies due to greater technical and financial resources. The surge in medical waste, particularly during the COVID-19 pandemic, underscores the need for enhanced regulatory guidance. Non-incineration technologies are gaining traction for their environmental and cost benefits, and facility coverage has improved but remains uneven. The study proposes five policy principles to foster technological innovation and industrial upgrading, ensuring safe medical waste management and environmental protection.
Kinetic Analysis and Simulation of Pollutant Removal in Sewage Networks
This study investigates pollutant removal characteristics and kinetic behaviors in sewage networks, and analyzes their impact on the carbon-to-nitrogen ratio (C/N, as COD/TN) of influent to wastewater treatment plants. Source water quality sampling at drainage outlets revealed spatial and temporal variations in C/N, with domestic sewage exhibiting higher C/N than industrial sewage, and diurnal peaks reaching 6.92 versus 4.71 during off-peak hours. Using a pilot-scale adjustable sewage network system in Kunshan, experiments were conducted under high (0.491 m·s−1) and low (0.089 m·s−1) flow velocities, monitoring pollutant removal over 144 hours. Pseudo-first-order kinetics were applied to model COD and TN removal. Results showed that COD (including SCOD and PCOD), BOD5, and SS achieved approximately 80% removal within 144 h, with higher removal at low flow velocity. TN, NH3-N, and TP exhibited lower overall removal rates. Kinetic fitting revealed that COD removal rate constants (kCOD) were significantly higher than those for TN (kTN), and both decreased with increasing flow velocity: at low velocity, kCOD=0.0167 h−1 and kTN=0.0029 h−1; at high velocity, kCOD=0.0127 h−1 and kTN=0.0020 h−1. Simulations based on actual source pollutant concentrations indicated that the time for C/N to drop to the denitrification critical value of 4.50 was 12.24 h at high velocity, but shortened to 9.49 h at low velocity. These findings demonstrate that increasing flow velocity effectively retards the decline of C/N. Therefore, regulating network flow velocity to reduce hydraulic retention time is a key strategy for maintaining adequate C/N at the terminal and ensuring denitrification efficiency in wastewater treatment plants.
Preparation of Trimetallic-Carbon Composite Catalysts and Their Application in Catalytic Ozonation of Industrial Wastewater
Advanced oxidation processes (AOPs) are promising for degrading organic pollutants in water treatment. Heterogeneous catalytic ozonation (HCO) has gained attention due to its high oxidation efficiency, strong interference resistance, and low secondary pollution. In this study, a series of trimetallic-carbon composite ozone catalysts were prepared via an organic precursor calcination method using γ-Al2O3 as support. This method enhanced catalytic activity and mechanical strength while overcoming the limitations of carbon materials (low mechanical strength) and metal-based materials (poor mass transfer). The optimized catalyst, CA-FeCoCu, comprising Fe, Co, Cu, carbon, and alumina, exhibited excellent performance in phenol degradation and real industrial wastewater treatment. Characterization revealed that the synergistic effect of trimetals and the introduction of multiple carbon types increased specific surface area and hydroxyl radical (·OH) generation. In a pilot-scale fixed-bed reactor, the CA-FeCoCu/O3 system reduced COD from 120 mg·L−1 to below 40 mg·L−1, with an O3 consumption ratio (O/C) of less than 1, effectively lowering operational costs. This work provides a new strategy for developing efficient and stable heterogeneous O3 catalysts and offers a reference for the practical application of HCO in industrial wastewater treatment.
Differentiated Characteristics of Suspended Particulate Matter and Their Effects on Water Quality in the Middle and East Routes of the South-to-North Water Diversion Project
This study investigates the spatiotemporal differentiation of suspended particulate matter (SPM) characteristics, sources, and their impacts on water quality between the Middle Route (closed artificial channel) and East Route (open natural water system) of the South-to-North Water Diversion Project. Thirty sampling sites (13 on the Middle Route, 17 on the East Route) were established, and samples were collected during dry and wet seasons. Water quality parameters and SPM characteristics were analyzed, including particle size distribution, total suspended solids (TSS), chlorophyll a, and stable carbon and nitrogen isotopes. Results show that the Middle Route maintains good and stable water quality, with SPM dominated by coarse particles (>63 μm, 61.43%–94.68%), total phosphorus (TP) <0.01 mg·L−1, and a significant positive correlation between chlorophyll a and coarse particles (r=0.60), indicating algal aggregation dominates particle formation. In contrast, the East Route exhibits high and fluctuating nitrogen and phosphorus concentrations, with SPM dominated by fine particles (<20 μm, 51.26%–88.61%), TP ranging from 0.03 to 1.11 mg·L−1, and a positive correlation with fine particles, suggesting significant external inputs. Carbon and nitrogen isotope analysis reveals that Middle Route SPM primarily originates from autochthonous algae (contribution >46.75%), while East Route SPM is influenced by both terrestrial C3 plants and algae. The distinct engineering and management approaches of the two routes lead to significant differences in SPM characteristics and sources, thereby affecting water quality dynamics. The Middle Route requires an 'algal reduction and hydrodynamic optimization' strategy to control algal-derived coarse particle deposition, whereas the East Route benefits from 'retention-sedimentation and wetland purification' to reduce external fine particles and pollutant inputs. This research provides theoretical support and practical guidance for differentiated SPM management in long-distance water diversion systems.
Combined Ozone Micro-Nano Bubble Oxidation and Powdered Activated Carbon Adsorption for Removal of Taste and Odor Compounds from Drinking Water
Algal-derived taste and odor compounds (2-methylisoborneol, 2-MIB, and geosmin, GSM) in drinking water sources are poorly removed by conventional treatment. This study systematically evaluated the standalone and combined performance of ozone micro-nano bubbles (O3-MNBs) oxidation and powdered activated carbon (PAC) adsorption for removing 2-MIB, GSM, and algal cells from source water. Results showed that O3-MNBs pre-oxidation achieved >97.5% removal of odorants at 400 ng·L−1 and 67.2% algal cell removal within 30 min. When applied as a deep treatment stage, the degradation rate constant (k) was 10.1%–25.6% higher than in pre-oxidation due to lower background matrix interference. Both pre-oxidation and deep treatment reduced effluent concentrations of 2-MIB and GSM to below 10 ng·L−1, with oxidation kinetics fitting pseudo-first-order models (R²>0.95). PAC adsorption of both compounds followed pseudo-second-order kinetics (R²>0.99), with GSM equilibrium adsorption capacity approximately 20.0% higher than that of 2-MIB. In pure water, adsorption capacity increased by >10.0% compared to raw water. Based on kinetic models, a quantitative prediction method was established for O3-MNBs oxidation and PAC adsorption processes, aiming to achieve efficient odorant removal and cost optimization, providing theoretical support for advanced drinking water purification and smart water plant construction.
Pulsed Electric Field Enhancement of Nitrogen Removal Performance and Microbial Community Structure Response in Anammox Granular Sludge
This study investigated the effects of a ring-shaped pulsed electric field (PEF) (1.5 V, 4 h on-time per cycle) on nitrogen removal performance and microbial community structure of anammox granular sludge (AnGS). Two anaerobic sequencing batch reactors (R1 control, R2 with PEF) were operated under stepwise increasing nitrogen loading rates (NLR). At NLR below 1,155 mg·(L·d)−1, R2 exhibited total nitrogen removal efficiency (TRE) 7.5%–17.0% higher than R1, with biomass, specific anammox activity (SAA), and extracellular polymeric substances (EPS) increased by 5%–7%, 21%–71%, and 54%–77%, respectively. However, at NLR above 1,320 mg·(L·d)−1, the toxic effect of nitrite dominated, and PEF enhancement diminished or even reversed to inhibition. Microbial community analysis revealed that at low-to-moderate NLR, PEF increased the relative abundance of Planctomycetes and key anammox bacteria (Candidatus Brocadia and Candidatus Jettenia), along with enhanced community richness (Chao1) and diversity (Shannon/Simpson indices). At high NLR, PEF decreased microbial richness compared to R1. Principal component analysis and redundancy analysis indicated that PEF was the key factor driving community differences at low-to-moderate NLR, whereas nitrite concentration became the dominant factor at high NLR. This study provides theoretical support for enhancing the resilience and engineering application of anammox processes.