Low Electrical Energy Consumption Research Articles

High performance ozone based advanced oxidation processes catalyzed with novel argon plasma treated iron oxyhydroxide hydrate for phenazopyridine degradation

The present study has focused on the degradation of phenazopyridine (PhP) as an emerging contaminant through catalytic ozonation by novel plasma treated natural limonite (FeOOH·xH2O, NL) under argon atmosphere (PTL/Ar). The physical and chemical characteristics of samples were evaluated with different analyses. The obtained results demonstrated higher surface area for PTL/Ar and negligible change in crystal structure, compared to NL. It was found that the synergistic effect between ozone and PTL/Ar nanocatalyst was led to highest PhP degradation efficiency. The kinetic study confirmed the pseudo-first-order reaction for the PhP degradation processes included adsorption, peroxone and ozonation, catalytic ozonation with NL and PTL/Ar. Long term application (6 cycles) confirmed the high stability of the PTL/Ar. Moreover, different organic and inorganic salts as well as the dissolved ozone concentration demonstrated the predominant role of hydroxyl radicals and superoxide radicals in PhP degradation by catalytic Ozonation using PTL/Ar. The main produced intermediates during PhP oxidation by PTL/Ar catalytic ozonation were identified using LC–(+ESI)–MS technique. Finally, the negligible iron leaching, higher mineralization rate, lower electrical energy consumption and excellent catalytic activity of PTL/Ar samples demonstrate the superior application of non-thermal plasma for treatment of NL.

Reaction mechanism of low-temperature catalysis by surface protonics in an electric field.

The process of combining heterogeneous catalysts and direct current (DC) electric fields can achieve high catalytic activities, even under mild conditions (<500 K) with relatively low electrical energy consumption. Hydrogen production by steam reforming of methane, aromatics and alcohol, dehydrogenation of methylcyclohexane, dry reforming of methane, and ammonia synthesis are known to proceed at low temperatures in an electric field. In situ/operando analyses are conducted using IR, Raman, X-ray absorption fine structure, electrochemical impedance spectroscopy, and isotopic kinetic analyses to elucidate the reaction mechanism for these reactions at low temperatures. The results show that surface proton hopping by a DC electric field, called surface protonics, is important for these reactions at low temperatures because of the higher surface adsorbate concentrations at lower temperatures.

Mechanism and Controller Design of a Transfemoral Prosthesis With Electrohydraulic Knee and Motor-Driven Ankle

This article presents a robotic transfemoral prosthesis that consists of an electrohydraulic knee and a motor-driven ankle. The electrohydraulic knee includes a controllable hydraulic damper to provide stance control and an electrical actuator to provide swing assistance. The motor-driven ankle provides damping adaptation for different terrains. The embedded finite-state-based controller enables the knee–ankle prosthesis to facilitate the amputee's ambulation on five different terrains. The proposed knee is lightweight and compact, with low electrical energy consumption. Experimental results demonstrate the potential advantages of the proposed transfemoral prosthesis compared with the hydraulic prosthesis daily used by the subject.

Modeling and energy analysis of a solar thermal vacuum membrane distillation coupled with a liquid ring vacuum pump

In this paper, a study of the energy performance of a solar powered vacuum membrane distillation coupled with liquid ring vacuum pump was investigated through various energy evaluation criteria. This analysis was investigated for the twelve months of the year. The results showed that the average daily production varied over the months from 598 to 217 kg/day. The average specific energy consumption, the average gained output ratio and the average energy efficiency were between 671 and 699 kWh/m3, 0.93–1.01 and 56.2–59.3% respectively. The maximum productivity and the best energy performance were that of June which is the month corresponding to the most important solar radiation. In addition, it was observed that vacuum liquid ring pump is characterized by a lower electrical energy consumption, which varies during the year between 4.2 and 7.47 kWh/m3. Besides, the effect of the vacuum level applied and liquid ring temperature on the energy performance was examined. Obviously, the results reveal that while increasing the vacuum, the specific energy consumption decreases. Moreover, it has been demonstrated that using an operating liquid at reduced temperatures reduces the flow rate required to ensure total condensation and decreases energy loss and specific energy consumption.

Properties of Micro-Arc Oxidation Coating Fabricated on Magnesium Under Two Steps Current-Decreasing Mode

A concept of two steps current-decreasing mode derived from constant current mode was developed to fabricate micro-arc oxidation (MAO) coatings on ZK60 Magnesium (Mg) alloy in a dual electrolyte system. The growth characteristics of coatings were analyzed by voltage-time curves, and the coating microstructures were characterized by scanning electron microscopy (SEM). Meanwhile, the roughness, corrosion behavior and microhardness of MAO coatings were investigated. The results showed that the MAO coatings exhibit a smooth and compact surface and have improved hardness and thickness, smaller roughness, uneven distribution of holes and even low electrical energy consumption. Such positive characteristics results in an improved corrosion resistance of MAO coatings. The coating produced under the two steps current mode of “1.2-0.6A” showed a smaller corrosion rate of 0.1559 g/m2h as compared to the counterpart produced under the other modes. The nanoscratch tests results showed that the coating fabricated by “1.2-0.6A” mode has strong bond strength with the substrate. Under this optimized mode, the MAO process also had the lowest energy consumption of 49.8 W·(dm2·μm)-1.

A new combined electrocoagulation-electroflotation process for pretreatment of synthetic and real Moquette-manufacturing industry wastewater: Optimization of operating conditions

Abstract Moquette-manufacturing industry produces wastewaters containing high-concentrations of polyvinyl acetate (PVAc), which is highly toxic and can inhibit the activity of microorganisms in biological wastewater treatment plants. In the present study, a new combined electrocoagulation-electroflotation process was used to treat the high organic load wastewater of the moquette manufacturing industry. For this purpose, the efficiency was evaluated on the basis of the removal of chemical oxygen demand (COD), total suspended solid (TSS), PVAc, total dissolved solid (TDS) and electrical conductivity (EC) from the synthetic and real wastewater. The results showed that process efficiency increased with increasing current density (CD) and retention time and with decreasing electrode distant. Under the optimum conditions (electrode distance =1 cm, reaction time = 20 min, pHo = 7, CD = 22 mA/cm2), the removal efficiencies of COD, TSS, PVAc, TDS and EC for the synthetic and actual wastewater were 84.8, 81.9, 91.6, 68.7 and 76.4 and 93.9, 92.9, 95.9, 90.5 and 85 %, respectively. In addition, the iron electrode is preferred to the aluminum electrode because of its higher efficiency, lower cost and lower electrical energy consumption. It was found that this process facilitated the floatation and compaction of the flocs at the surface of the electrochemical reactor and finally eliminated the need for the sedimentation/flotation unit.

Enhanced treatment of landfill leachate wastewater using sono(US)-ozone(O3)–electrocoagulation(EC) process: role of process parameters on color, COD and electrical energy consumption

The combination of advanced oxidation processes (AOPs) and electrochemical process is gaining growing popularity for use in wastewater treatment. The present work explores for the first time, treatment of leachate wastewater from landfill waste using a combination of sonication (US), ozonation (O3) and electrocoagulation (EC) process expressed by % color removal, % Chemical Oxygen Demand (COD) removal and its associated electrical energy consumption. The results revealed that, the combined process (US/O3/EC) is highly successful in the treatment of leachate wastewater from landfill in terms of % color removal (100 %) and % COD removal (97.50 %) with low electrical energy consumption (8kWhr/m3) than the other hybrid and single process such as O3/EC, US/EC, US/O3 and EC, O3, US. The influence of different process parameters such as electrolyte concentration (1.50–7.50 g/L), current density (1.25–7.50 A/dm2), initial effluent pH (2–11), COD concentration (2000–6000 ppm), O3 production (0.75–3.75 g/hr) and sonication power (20–100 Watts) were studied on the efficiency of pollutant removal evaluated by reduction of % color and % COD and electrical energy consumption using hybrid US/O3/EC process. Overall, the analysis clearly showed that the approaches to integrated treatment technologies could synergistically remove the pollutant from the wastewater.

Application of central composite design (CCD) for optimization of cephalexin antibiotic removal using electro-oxidation process

In this work, the removal of cephalexin (CEX) from aqueous solutions using the anodic oxidation process was studied and four significant independent variables including contact time, pH, current density (CD), and initial CEX concentration were optimized using response surface methodology (RSM) involving a five-level central composite design (CCD). The degradation mechanisms and mineralization pathway of CEX were also proposed. To determine the removal and mineralization rate, chemical oxygen demand (COD) and total organic carbon (TOC) were determined. The optimum conditions were experimentally determined as follows: reaction time 52.68 min, pH 5.00, CD 44.69 mA/cm2 and initial CEX concentration 75.88 mg/L. The predicted and experimental removal efficiencies were obtained 100 and 97.38%, respectively. A good agreement between the experimental and predicted values was also observed with coefficient of determination of 0.95. Moreover, under the optimal conditions, 79.64 and 73.25% efficiencies were obtained for COD reduction and TOC removal, respectively, indicating the effectiveness of the developed method. Regarding the relatively low electrical energy consumption (41.28 kWh/kg COD), it can be claimed that the developed method is preferable to other processes in terms of energy consumption.

Treatment of phenolic compound wastewater using CuFe2O4/Al2O3 particle electrodes in a three-dimensional electrochemical oxidation system

ABSTRACT Three-dimensional electrochemical oxidation (3D-ECO) technology is considered as one of the most promising advanced oxidation processes for degrading refractory organic pollutants. However, the preparation of the particle electrodes (PEs) is a key factor for industrial applications. In this study, a new Al2O3-based PE was proposed for 3D-ECO system. The prepared PEs were characterized by scanning electron microscopy, energy-dispersive X-ray microscopy, and X-ray diffraction to examine their morphology, elementary composition, and amount of CuFe2O4 respectively. Experiments comparing different conditions showed that 3D-ECO system equipped with prepared PEs and persulphate (PS) was more efficient in degradingp-nitrophenol (PNP). Based on these results, the critical process parameters of the dosage of the PEs, initial PS concentration, and current density for 3D-ECO using the proposed PEs were examined. Under the optimized operations, the PNP removal rate reached 80.23% with a low electrical energy consumption of 3.97 kW h/mg PNP, which was significantly better than the 69.16% and 9.50 kW·h/mg PNP under conventional ECO process. Moreover, cycling experimental results indicated that the performance of the PEs had no declining trend during the 5 h test period, suggesting acceptable stability of the particles without particle damage or mass loss. These investigations provide a novel route for preparing high-efficiency PEs.

Peroxydisulfate activation by in-situ synthesized Fe3O4 nanoparticles for degradation of atrazine: Performance and mechanism

Herein activation of persoxydisulfate (PDS) was achieved by in-situ synthesized Fe3O4 nanoparticles (NPs) from a sacrificial iron anode in an electrochemical (EC) cell. The as-synthesized Fe3O4 NPs were characterized to be in spherical and in the nano size. The performance of the process, EC-Fe3O4/PDS, was investigated in terms of atrazine (ATZ) degradation. Optimum process conditions were determined as initial pH of 5, electrolyte (Na2SO4) concentration of 1 mM, a current density of 1.67 A m−2, PDS concentration of 0.5 mM and initial ATZ concentration of 10 mg L–1. At optimum conditions, the EC-Fe3O4/PDS process could effectively degrade 80% of ATZ in an aqueous solution within a short reaction time of 20 min. The electrical energy consumption of the process was found to be quite low with 0.0307 kWh/m3. Based on the LC/MS analysis, the degradation pathway of ATZ with seven transformation products was proposed. Finally, a possible mechanism of the EC-Fe3O4/PDS process was put forward, which includes the activation of PDS and the role of radicals in the degradation of ATZ. In conclusion, the combination of Fe3O4 NPs catalyzed PDS oxidation with the EC process was very effective in the degradation of ATZ to dechlorinated final products. The strong synergistic effect makes this process superior to conventional methods due to the high degradation efficiency with low electrical energy and chemical consumption. Application of this method, with very low current density, may not only minimize the electrical energy consumption but also help reduce the sludge production due to the lower iron dissolution.

A novel stacked flow-through electro-Fenton reactor as decentralized system for the simultaneous removal of pollutants (COD, NH3-N and TP) and disinfection from domestic sewage containing chloride ions

Cost-effective treatment of domestic sewage from the scattered and remote residential areas is a big challenge for widely used conventional biotechnical treatment. A novel stacked flow-through electro-Fenton (EF) reactor was firstly constructed using the modified graphite felt cathodes and DSA mesh anodes in this work, and attempted to remove multiple pollutants from domestic sewage. The proportion of dead space was very low and the short circuit phenomenon was not obvious in this designed reactor based on the hydraulic characterization analysis. The influence of important parameters such as initial pH, applied voltage and flow rate were investigated. The COD could be effectively removed from domestic sewage without adding electrolyte and adjusting initial pH by this novel EF reactor, and the effluent COD (in the range of 47–56 mg/L) could meet the prescribed discharge standard in China with a very low electrical energy consumption of 0.97 kWh/m3 under the applied voltage of 2.5 V and flow rate of 30 mL/min. Moreover, the desirable performance in the disinfection and removal of TP (97.6%), NH3-N (90.8%) and suspended solids (nearly 100%) could also be simultaneously obtained by this EF reactor without additional treatment process, and the possible process mechanism of COD, TP and NH3-N removal was further explored. Besides, the effluent met the China's urban miscellaneous water quality standards and could be reused for urban greening, road cleaning or flushing toilets. Therefore, the above analysis demonstrated that this novel stacked flow-through EF reactor could be used as an energy-efficient decentralized system for the treatment and reuse of domestic sewage.

Theoretical Study of Photovoltaic Thermal Integrated Absorption Cooling System under Jordan Climate

This paper presents a theoretical investigation to simulate the utilization of (PV/T) technology to drive an absorption refrigeration system that is used for air conditioning of a classroom under Jordan climate conditions. The absorption refrigeration cycle uses the hot water from the PV/T collector with an assisted electrical heater as a heat source in the generator. In addition to the capability to utilize the PV/T to supply the building by domestic hot water and electricity if no need to run the refrigeration cycle. This analysis was carried using excel program and theoretical equations for the system. It was found that (PV/T) technology is very useful for thermal applications with high efficiency. Also, absorption refrigeration cycle has a good coefficient of performance because it main ly depends on the thermal energy with low electrical energy consumption to run the pump. Moreover, this system has a short payback period, low energy consumption, low running cost, and minimum environmental impact. The results of this study show that the system needs about (84 m 2 PV/T collectors) to cover 16 tons cooling load.

Zeolitic imidazolate framework-8 modified active carbon fiber as an efficient cathode in electro-Fenton for tetracycline degradation

In this work, the active carbon fibers (ACFs) was modified by zeolitic imidazolate framework-8 (ZIF-8) to prepare a novel modified electrode as cathode. The effect of different amount of ZIF-8 modified ACFs (0–0.30 g) on H2O2 production and electric energy consumption (EEC) were investigated and the optimal ZIF-8 amount was 0.15 g. Characterized by linear sweeping voltammetry (LSV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), contact angle, and X-ray photoelectron spectroscopy (XPS) after modification were observed considerably changed. Some nanoparticles and oxygen-contained functional groups appeared on the ZIF-8/ACF cathode surface, which significantly enhanced the hydrophilic property and the electrochemical performance. It was observed that H2O2 production with 0.15 g-ZIF-8/ACF as cathode (1545.1 mg L−1) was much larger than with raw ACF as cathode (64.1 mg L−1). Meanwhile, H2O2 production could also achieve a balance in a high state of H2O2 production (around 1500 mg L−1) with low EEC (<35.0 kWh kg−1) in consecutive 5 runs. Moreover, 50 mg L−1 tetracycline could be completely removed within 20 min in the electro-Fenton (EF) system with 0.15 g-ZIF-8/ACF as cathode and the TOC removal could achieve 82.6% which was also much higher with raw ACF as cathode (15.5%). According to the ESR tests also indicating much more OH radicals could be generated in the EF system with 0.15 g-ZIF-8/ACF. Therefore, EF system with ZIF-8/ACF cathode is a good alternative process for pollutant removal.

Design of High-Efficiency Refrigerator Test System for Industrial Internet of Things

Smart homes are developing rapidly, and refrigerators are an indispensable part of “smart homes”. Therefore, the research efficiency and quality assurance of refrigerators are highly valued by home appliance companies. Refrigerator test is required in both research and production processes. At present, the quality test of refrigerator has a high degree of manual participation, such as the selection of the stable operating range of refrigerator and the conversion of test stage require manual determination, which cause low test efficiency and high electric energy consumption. In order to solve these problems, this paper design a High-Efficiency Refrigerator Test System (HERTS) for Industrial Internet of Things (IIoT). The core test data intelligent analysis module realizes timely determination of test data and automatic transition of test stage. The proposed HERTS increases the efficiency of automate refrigerator test and greatly reduces the power consumption.

Electrochemical/Fe3+/peroxymonosulfate system for the degradation of Acid Orange 7 adsorbed on activated carbon fiber cathode.

Acid Orange 7 (AO7), as a most common and widely used synthetic dyes in the printing and dyeing industry, was hardly degradable by traditional wastewater treatment methods. Here, activated carbon fiber (ACF) as an in-situ regenerated cathodic adsorbent in the electrochemical/Fe3+/peroxymonosulfate process (EC/ACF/Fe3+/PMS) was firstly investigated for AO7 removal and compared with several different processes. The results indicated that the effective adsorption of AO7 on ACF can be enhanced under electrolytic conditions, while the adsorbed AO7 on ACF can be completely degraded and mineralized in EC/ACF/Fe3+/PMS process resulting in the in-situ regeneration of ACF. Besides, the electrical energy per order values were investigated, which showed an apparent reduction of electrical energy consumption from 0.42831 to 0.09779 kWh m-3 when ACF-cathode replaced Pt-cathode. Further study revealed that higher conversion rate of Fe2+ from Fe3+ was observed with ACF-cathode. It deserved to be mentioned that the removal efficiency of AO7 was satisfactory and stable even after reusing ACF cathode for 10 times. Furthermore, structure and elements of ACF surface were investigated, which indicated the structure of ACF was intact in EC/ACF/Fe3+/PMS due to inhibition of ACF corrosion by electron migration at cathode. In addition, the total iron content of the effluent in EC/ACF/Fe3+/PMS was lower than that of EC/Fe3+/PMS due to the deposition of iron on ACF-cathode surface. Therefore, advantages of EC/ACF/Fe3+/PMS for AO7 degradation were not only a much higher oxidation efficiency and in-situ regenerated cathodic adsorbent, but also a lower electrical energy consumption and lesser iron ions contents in the effluent.

Microwave vacuum pyrolysis of waste plastic and used cooking oil for simultaneous waste reduction and sustainable energy conversion: Recovery of cleaner liquid fuel and techno-economic analysis

Microwave vacuum pyrolysis was examined and compared to conventional pyrolysis for its technical and economic feasibility in co-processing of waste plastic and used cooking oil simultaneously to generate fuel product. The pyrolysis demonstrated beneficial process features with respect to high heating rate (29 °C/min) to provide fast heating, high process temperature for extensive cracking (581 °C), short process time (20 min), and low electrical energy consumption (0.38 kWh). The combined use of microwave vacuum pyrolysis and activated carbon reaction bed produced up to 84 wt% yield of liquid oil, containing light hydrocarbons and higher heating value (49 MJ/kg) than diesel and gasoline, hence showing great promise for application as fuel. The use of activated carbon reaction bed showed beneficial effect in creating a reduction environment that prevented the oxidation or formation of oxygenated by-products. A positive synergistic effect between waste plastic and used cooking oil was also observed. The liquid oil obtained from this pyrolysis approach presented a low oxygen and nitrogen content, and free of sulphur, showing ‘cleaner’ properties with respect to reduced char residues, sludge formation, corrosiveness, degradation of oil quality, and emission of undesired SOx and NOx during its utilization in combustion process. The techno-economic analysis indicated that this pyrolysis approach showed low production cost (USD 0.25/L compared to USD 0.523/L of diesel price in Malaysia). Our results demonstrate that microwave vacuum pyrolysis is potentially economically feasible and show promise as a sustainable approach for energy conversion in providing improved process features and production of cleaner liquid fuel.

Long-term durability of La0.75Sr0.25Cr0.5Mn0.5Oδ−3 as a fuel electrode of solid oxide electrolysis cells for co-electrolysis

Electrochemical conversion of carbon dioxide to a hydrocarbon fuel can reduce greenhouse emissions and lead to economic profits. Solid oxide electrolysis cells (SOECs) are potential candidates for decreasing CO2 emission due to their low electrical energy consumption properties for CO2 reduction. However, their fuel electrode, which is nickel-yttria stabilized zirconia (Ni-YSZ), shows critical durability issues. This study aimed to find an SOEC fuel electrode material among perovskite catalysts. The selected catalysts should satisfy the following properties: high catalytic performance in the reverse water gas shift (RWGS) reaction, low carbon deposition rate after the RWGS reaction, high electrical conductivity, and long-term durability in a co-electrolysis environment. Ni-YSZ and perovskite catalysts were fabricated. Their performance was investigated by considering the four properties. In this study, we found La0.75Sr0.25Cr0.5Mn0.5Oδ-3 (LSCM) to be a promising SOEC fuel electrode. The LSCM electrode showed comparably good catalytic performance and electrical conductivity. A 1,200 h co-electrolysis test showed that the electrode had a stable performance.

Enhancement of capacitive accelerometer operation by parameters improvement

AbstractIn the present paper, a mathematical model suitable for capacitive accelerometer is developed by applying the fundamental principle of dynamics and validated by simulation and experiment test. This model aims to visualize the capacitance variation of the accelerometer as a function of relative movement frequency. The main motivation key role of this paper is to propose a capacitive accelerometer with improved parameters. Therefore, in capacitive detection, the damping rate choice is directly influenced by the variation in capacitance; for this purpose, a comparative study of three damping rates is carried out. The first accelerometer is used in practical tests, the second is presented and studied in recent literature, and the third is the accelerometer proposed in this work.A new expression is extracted from the damping ratio as a function of measurement error to determine the damping rate according to a desired measurement error value. Finally, a new capacitive accelerometer with improved parameters having many advantages over the existing accelerometers is obtained. Simulation and experimental results have enabled us to recommend a new capacitive accelerometer design with very low measurement error (limited to 0.25%), high accuracy (equal to 99.75%), high sensitivity and reliability, and low electrical energy consumption.

Simultaneous sulfadiazines degradation and disinfection from municipal secondary effluent by a flow-through electro-Fenton process with graphene-modified cathode.

Conventionally the deep treatment and disinfection are fulfilled by different processes for municipal wastewater treatment, this work verified a breakthrough by one process of novel flow-through electro-Fenton (EF) with graphene-modified cathode, which is usually seemed to be ineffective. This process was firstly confirmed to be cost-effective for simultaneous sulfadiazines (SDZs) degradation and disinfection from municipal secondary effluent with a very low electrical energy consumption (EEC) of 0.21 kW h/m3, attributed to the high H2O2 production of 4.41 mg/h/cm2 on the novel graphite felt cathode modified by electrochemically exfoliated graphene (EEGr) with a low EEC of 3.08 kW h/(kg H2O2). Compared with the ineffective SDZs degradation by the conventional flow EF, this process was more cost-effective and overcame the harsh requirements on electrolyte concentration. It also showed good effectiveness in the degradation of different antibiotics, and the graphene-modified cathode still kept stable performance after eight consecutive runs. Account for the combined action of OH and active chlorine, the formation of hydroxylated and chlorine containing by-products was confirmed, and a possible degradation mechanism for SDZs was proposed. This flow-through EF process provided an alternative method for the disinfection and antibiotics degradation by one process for the treatment and reuse of municipal secondary effluent.

Electrochemical catalytic mechanism of N-doped graphene for enhanced H2O2 yield and in-situ degradation of organic pollutant

Highly efficient electrochemical advanced oxidation processes (EAOPs) based on carbon catalysts are promising and green technologies for environmental remediation. Herein, for the purpose of cost-effectiveness, wide pH suitability and excellent reusability, graphite felt modified with regulatable N-doped graphene was developed as a cathode to electrochemically generate H2O2 with high yield and selectivity, and efficiently catalyze H2O2 to form OH for organic pollutants degradation by in-situ metal-free EAOPs. Particularly, the catalytic mechanism of N-doped graphene for enhanced performance was explored. Optimized N-doped graphene showed a very high H2O2 generation rate of 8.6 mg/h/cm2, low electric energy consumption (9.8 kW h/kg) and high H2O2 selectivity of 78.02% in neutral pH solution. Compared with electro-Fenton (EF), this in-situ metal-free EAOPs on N-doped graphene displayed significant improvement on the degradation performance of organic pollutants in neutral and alkaline solutions, and was certified to be less affected by initial pH. The pyridinic N and CC in N-doped graphene enhanced the onset potential while graphite N determined the disk current of oxygen reduction reaction (ORR) process. Most importantly, it proved that the introduction of graphite N could promote the 2e- ORR process for H2O2 generation, and the presence of pyridinic N could catalyze H2O2 to the production of OH. Taken phenol as target pollutant, OH generated by N-doped graphene accounted for 80.72% while O2− contributed 19.28% to its degradation, based on which a possible mechanism for phenol degradation was proposed. Moreover, in-situ metal-free EAOPs showed excellent stability, reusability and performance for various organic pollutants degradation. This work would shed light on the catalytic mechanism for metal-free EAOPs, and thus promote its application for organic pollutants degradation.