A post-modification strategy to precisely construct dual-atom sites for oxygen reduction electrocatalysis

Dual-atom catalysts(DACs) afford promising potential for oxygen reduction electrocatalysis due to their high atomic efficiency and high intrinsic activity.However,precise construction of dual-atom sites remains a challenge.In this work,a post-modification strategy is proposed to precisely fabricate DACs for oxygen reduction electrocatalysis.Concretely,a secondary metal precursor is introduced to the primary single-atom sites to introduce direct metal-metal interaction,which ensures the formation of desired atom pair structure during the subsequent pyrolysis process and allows for successful construction of DACs.The as-prepared FeCo-NC DAC exhibits superior oxygen reduction electrocatalytic activity with a half-wave potential of 0,91 V vs.reversible hydrogen electrode.Zn-air batteries equipped with the FeCo-NC DAC demonstrate higher peak power density than those with the Pt/C benchmark.More importantly,this post-modification strategy is demonstrated universal to achieve a variety of dual-atom sites.This work presents an effective synthesis methodology for precise construction of catalytic materials and propels their applications in energy-related devices.

Identification and Molecular Characterization of the Alkaloid Biosynthesis Gene Family in Dendrobium catenatum

As one of the main active components of Dendrobium catenatum, alkaloids have high medicinal value. The physicochemicalproperties, conserved domains and motifs, phylogenetic analysis, and cis-acting elements of the genefamily members in the alkaloid biosynthesis pathway of D. catenatum were analyzed by bioinformatics, and theexpression of the genes in different years and tissues was analyzed by qRT-PCR. There are 16 gene families,including 25 genes, in the D. catenatum alkaloid biosynthesis pathway. The analysis of conserved domains andmotifs showed that the types, quantities, and orders of domains and motifs were similar among members ofthe same family, but there were significant differences among families. Phylogenetic analysis indicated that thegene family members showed some evolutionary conservation. Cis-acting element analysis revealed that therewere a large number of light-responsive elements and MYB (v-myb avian myeloblastosis viral oncogene homolog)-related elements in these genes. qRT-PCR showed that expressions of gene family members involved in alkaloidsynthesis were different in different years and tissues of D. catenatum. This study provides a theoretical basisfor further exploration of the regulatory mechanisms of these genes in the alkaloid biosynthesis of D. catenatum.

Effect of Peroxiredoxin 1 on the biological function of airway epithelial cells and epithelial-mesenchymal transition

Peroxiredoxin 1(PRDX1)participates in tumor cell proliferation,apoptosis,migration,invasion,and the epithelial-to-mesenchymal transition(EMT).This study aimed to investigate the effect of PRDX1 on the EMT of airway epithelial cells stimulated with lipopolysaccharide(LPS)and transforming growth factor-beta 1(TGF-β1).PRDX1 overexpression significantly increased the proliferation and migration of human bronchial epithelial(BEAS-2B)cells,reduced cell apoptosis(p<0.01),and induced EMT and collagen deposition by upregulating the expression of the matrix metallopeptidase(MMP)2,MMP9,α-smooth muscle actin(α-SMA),N-cadherin,vimentin and twist proteins and inhibiting E-cadherin expression(p<0.05).PRDX1 overexpression promoted TGF-β1-mediated inhibition of cell proliferation and migration and significantly enhanced the TGF-β1-induced EMT and collagen synthesis(p<0.05).Knockdown of PRDX1 inhibited cell proliferation,migration,EMT,and collagen synthesis(p<0.01),reversed LPS-mediated inhibition of cell proliferation and migration,and significantly suppressed LPS-induced EMT and collagen synthesis(p<0.01).The result indicating that PRDX1 may be involved in LPS/TGF-1-induced EMT and collagen synthesis in human bronchial epithelial cells.

Intrinsic Self-Healing Chemistry for Next-Generation Flexible Energy Storage Devices

The booming wearable/portable electronic devices industry has stimulated the progress of supporting flexible energy storage devices.Excellent performance of flexible devices not only requires the component units of each device to maintain the original performance under external forces,but also demands the overall device to be flexible in response to external fields.However,flexible energy storage devices inevitably occur mechanical damages(extrusion,impact,vibration)/electrical damages(overcharge,over-discharge,external short circuit)during longterm complex deformation conditions,causing serious performance degradation and safety risks.Inspired by the healing phenomenon of nature,endowing energy storage devices with self-healing capability has become a promising strategy to effectively improve the durability and functionality of devices.Herein,this review systematically summarizes the latest progress in intrinsic self-healing chemistry for energy storage devices.Firstly,the main intrinsic self-healing mechanism is introduced.Then,the research situation of electrodes,electrolytes,artificial interface layers and integrated devices based on intrinsic self-healing and advanced characterization technology is reviewed.Finally,the current challenges and perspective are provided.We believe this critical review will contribute to the development of intrinsic self-healing chemistry in the flexible energy storage field.

Viscosity reduction of tapioca starch by incorporating with molasses hydrocolloids

As a low cost non-staple food resource,the high-viscosity paste and poor gel-forming ability of tapioca starch limit its industrial application.Herein,molasses hydrocolloids that is a by-product of the sugar refining process was applied as a blending modifier to reduce the viscosity of tapioca starch paste.The test results of paste and rheological properties show that molasses hydrocolloids exhibited a good physical viscosity-reducing effect on tapioca starch paste.The irregular network structure and high K^(+)/Ca^(2+)ion contents of molasses hydrocolloids exerted wrapping,adhesion,barrier,and hydration effects on starch,leading to the reduction of viscosity.The scanning electron microscope images and textural analysis demonstrated that this strategy also improve the structure of tapioca starch gel and enhanced its puncture strength by 75.46%.This work shows the great potential of molasses hydrocolloids as a lowcost and desirable material for the viscosity reduction of tapioca starch.

Topological resonators based on hexagonal-star valley photonic crystals

In valley photonic crystals, topological edge states can be gained by breaking the spatial inversion symmetry without breaking time-reversal symmetry or creating pseudo-spin structures, making highly unidirectional light transmission easy to achieve. This paper presents a novel physical model of a hexagonal-star valley photonic crystal. Simulations based on the finite element method(FEM) are performed to investigate the propagation of TM polarized mode and its application to ring resonators. The results show that such a topologically triangular ring resonator exhibits an optimum quality factor Q of about 1.25×104, and Q has a maximum value for both frequency and the cavity length L. Our findings are expected to have significant implications for developing topological lasers and wavelength division multiplexers.

The potential of domestic production and imports of oil and gas in China:an energy return on investment perspective

Concerns about China's energy security have escalated because of the country's high dependency on oil and gas imports, so it is necessary to calculate the availability of domestic oil and gas resources and China's ability to obtain foreign energy through trade. In this work,the calculation was done by using the energy return on investment(EROI) method. The results showed that the EROI_(stnd)(i.e., standard EROI) of China's oil and gas extraction decreased from approximately 17.3:1 in 1986 to 8.4:1 in 2003, but it increased to 12.2:1 in 2013. From a company-level perspective, the EROI_(stnd)differed for different companies and was in the range of(8–12):1. The EROI_(2,d)(EROI considering energy outputs after processed and direct energy inputs) for different companies was in the range of(3–7):1. The EROI of imported oil(EROI_(IO))declined from 14.8:1 in 1998 to approximately 4.8:1 in 2014, and the EROI of imported natural gas(EROI_(ING))declined from 16.7:1 in 2009 to 8.6:1 in 2014. In 2015, the EROI_(IO) and EROI_(ING) showed a slight increase due to decreasing import prices. In general, this paper suggests that from a net energy perspective, it has become more difficult for China to obtain oil and gas from both domestic production and imports. China is experiencing an EROI decline, which demonstrates the risk in the use of unsustainable fossil resources.

Fe-N-C catalysts for PEMFC: Progress towards the commercial application under DOE reference

Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platinum group metal(PGM)catalysts creates a barrier for the large-scale application of PEMFC.Tremendous efforts have been devoted to the development of low-cost PGM-free catalysts,especially the Fe-N-C catalysts,to replace the expensive PGM catalysts.However,the characterization methods and evaluation standards of the catalysts varies,which is not conducive to the comparison of PGM-free catalysts.U.S.Department of energy(DOE)is the only authority that specifies the testing standards and activity targets for PGM-free catalysts.In this review,the major breakthroughs of Fe-N-C catalysts are outlined with the reference of DOE standards and targets.The preparation and characteristics of these highly active Fe-N-C catalysts are briefly introduced.Moreover,the efforts on improving the mass transfer and the durability issue of Fe-N-C fuel cell are discussed.Finally,the prospective directions concerning the comprehensive evaluation of the Fe-N-C catalysts are proposed.

Gambogic acid induces apoptosis and inhibits colorectal tumor growth via mitochondrial pathways

AIM: To investigate the effect of gambogic acid(GA) on apoptosis in the HT-29 human colon cancer cell line. METHODS: H-29 cells were used for in vitro experiments in this study. Relative cell viability was assessed using MTT assays. Cell apoptosis was detected by terminal deoxynucleotidyl transferase d UTP nick end labeling and Hoechst 33342 staining, and quantified by flow cytometry. Cellular ultrastructure was observed by transmission electron microscopy. Real-time PCR and Western blot analyses were used to evaluate gene and protein expression levels. For in vivo experiments, BALB/c nude mice received subcutaneous injections of HT-29 cells in the right armpit. When well-established xenografts were palpable with a tumor size of 75 mm3, mice were randomly assigned to a vehicle(negative) control, positive control or GA treatment group(n = 6 each). The animals in the treatment group received one of three dosages of GA(in saline; 5, 10 or 20 mg/kg) via the caudal vein twice weekly, whereas animals in the negative and positive control groups were given equal volumes of 0.9% saline or 10 mg/kg docetaxel, respectively, via the caudal vein once weekly. RESULTS: The cell viability assay showed that GA inhibited proliferation of HT-29 cells in a dose- and time-dependent manner after treatment with GA(0.00, 0.31, 0.62, 1.25, 2.50, 5.00 or 10.00 μmol/L) for 24, 48 or 72 h. After 48 h, the percentage of apoptotic cells in cells treated with 0.00, 1.25, 2.50 and 5.00 μmol/L GA was 1.4% ± 0.3%, 9.8% ± 1.2%, 25.7% ± 3.3% and 49.3% ± 5.8%, respectively. Ultrastructural analysis of HT-29 cells treated for 48 h with 2.5μmol/L GA revealed apoptotic bodies and condensed and fragmented nuclei. Levels of caspase-8,-9 and-3 m RNAs were significantly increased after treatment with GA(1.25, 2.50 or 5.00 μmol/L) for 48 h(P < 0.05 for all). Protein levels of apoptosis-related factors Fas, Fas L, FADD, cytochrome c, and Apaf-1 were increased in GA-treated cells, whereas levels of pro-caspase-8,-9 and-3 were significantly decreased(P < 0.05 for all). Furthermore, GA significantly and dose-dependently inhibited the growth of HT-29 tumors in a mouse xenograft model(P < 0.05).CONCLUSION: GA inhibits HT-29 proliferation via induction of apoptosis. The anti-cancer effects are likely mediated by death receptor(extrinsic) and mitochondrial(intrinsic) pathways.

3D atomic-scale growth characteristics of {10-12} twin in magnesium

In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nucleus structures.A detailed atomistic analysis reveals that a stabilized 3D{10-12}twin nucleus is bounded by basal/prismatic(BP)interfaces,prismatic/basal(PB)interfaces,and{10-11}interfaces.Later,a{10-12}twin boundary(TB)occurs at the junction of the BP and PB interface with the growth of the twin nucleus.In this process,two twinning mechanisms are involved:a pure-shuffle mechanism in which{10-11}interface migration along the[11-20]direction is mediated by atomic shuffle,and a glide-shuffle mechanism in which BP/PB and{10-12}TB movements are realized by the migration of disconnections along the relevant interfaces.In addition,we systematically investigate the stress state associated with the activation of twinning,aiming to discover the intrinsic relationship of the elastic stress field to twin growth on an atomic scale.The results suggest that the elastic stress in the matrix is an important driving force for twin growth,much similar to what stress does for a crack.In addition,it is rather remarkable that the{10-11}interface has a greater ability to migrate than other interfaces,and this is thought to be a main factor for the rapid growth of a{10-12}twin.

Energy return on investment, energy payback time, and greenhouse gas emissions of coal seam gas(CSG) production in China: a case of the Fanzhuang CSG project

The studies and development of coal seam gas(CSG) have been conducted for more than 30 years in China, but few of China's CSG projects have achieved large-scale commercial success; faced with the boom of shale gas, some investors are beginning to lose patience and confidence in CSG. China currently faces the following question: Should the government continue to vigorously support the development of the CSG industry? To provide a reference for policy makers and investors, this paper calculates the EROI_(stnd)[a standardized energy return on investment(EROI) method], EROI_(ide)(the maximum theoretical EROI), EROI_(3,i)(EROI considering the energy investment in transport), and EROI_(3,1+e)(EROI with environmental inputs) of a single vertical CSG well in the Fanzhuang CSG project in the Qinshui Basin. The energy payback time(EPT) and the greenhouse gas(GHG) emissions of the CSG systems are also calculated. The results show that over a 15-year lifetime, EROI_(stnd), EROI_(ide), EROI_(3,1), and EROI_(3,1+e)are expected to deliver EROIs of approximately11:1, 20:1, 7:1, and 6:1, respectively. The EPT within different boundaries is no more than 2 years, and the life-cycle GHG emissions are approximately 18.8 million kg CO_2 equivalent. The relatively high EROI and short EPT indicate that the government should take more positive measures to promote the development of the CSG industry.

Preparation of Kenaf Biochar and Its Adsorption Properties for Methylene Blue

The toxic dyestuff's from printing and dyeing wastewater have caused serious damages to the ecological environ-ment,thus exploring effective methods to remove them having become a key topic.Here,a series of biochar sam-ples were synthesized form kenaf to adsorb methylene blue(MB),which was acted as the dye representative for the test of adsorption capacity due to the presence of abundant double bond and aroma tic heterocyclic ring.By tuning the raw materials and pyrolysis temperature,a super adsorption capacity about 164.21 mg·g^(-1) was obtained over the biochar that pyrolyzed at 700℃ with the kenaf fiber as raw material Through the physical adsorption,elemental analysis,FTIR spectra and NH_(3)-TPD,it was found the high surface area and pore volume of biochar played a key role in the adsorption of MB,and the acidic sites would also assist the adsorption process.Besides,the adsorption kinetic model was ftted and calculated,implying the MB physically adsorbed on the bio-char rapidly and then occurred chemical adsorption on the acidic sites.In addition,through KBC700 recycling experiments,it was found that kenaf biochar had a good binding force to MB,which effectively avoided secondary pollution.This work provides important insights for the adsorption mechanism of MB by biochar,also offers some guidance for the further synthesis of biochar from various biomass.

Welding Distortion Control of Thin Al Alloy Plate by Static Thermal Tensioning

The mechanism and effectiveness of welding distortion mitigation by static thermal tensioning were investigated by both finite element analysis and experiments. It shows that preset thermal tensioning can reduce longitudinal plastic compression remained in the weld and its adjacent zone significantly, so decrease the longitudinal residual stress and the susceptibility to welding distortion.

Quasihole Tunneling in Disordered Fractional Quantum Hall Systems

Fractional quantum Hall systems are often described by model wave functions,which are the ground states of pure systems with short-range interaction.A primary example is the Laughlin wave function,which supports Abelian quasiparticles with fractionalized charge.In the presence of disorder,the wave function of the ground state is expected to deviate from the Laughlin form.We study the disorder-driven colla.pse of the quantum Hall state by analyzing the evolution of the ground state and the single-quasihole state.In particular,we demonstrate that the quasihole tunneling amplitude can signal the fractional quantum Hall phase to insulator transition.

A Study on the Lexical Complexity of Narrative Translation by English Major Learners

Vocabulary researches play an important role in language teaching.In recent decades,lexical complexity has drawn great attention by researchers and scholars.A large number of empirical studies have been conducted to find out whether correlations exist between writing quality and lexical complexity in written texts.In the present study,299 English learners participated in the experiment from a comprehensive university.The data were timed CE texts translated by these learners.This study intends to answer the two questions with the assistance of such tools as LCA and SPSS.After analyzing the data with 9 indices from LCA,the results of this study are as follows:1.Chinese students’translated texts gain a high lexical density,which shows that content words can account for a large percentage in narrative translations.In the lexical sophistication measures,LS1 and LS2 do not differ greatly while CVS1 gets the greatest fluctuation.Among lexical variation indices,NDW is generally high.2.All indices in lexical variation and lexical sophistication show a high positive correlation with translation quality,while lexical density bears a negative relationship with translation quality.The findings of the current study indicate students’vocabulary use in translation and provide implications for English teaching,especially translation and vocabulary teaching.

Metal vacancy-enriched layered double hydroxide for biomass molecule electrooxidation coupled with hydrogen production

The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals;however,this strategy is limited by the competing oxygen evolution reactions and high energy consumption.Herein,we report a hierarchical CoNi layered double hydroxides(LDHs)electrocatalyst with abundant Ni vacancies for the efficient anodic oxidation of 5-hydroxymethylfurfural(HMF)and cathodic hydrogen evolution.The unique hierarchical nanosheet structure and Ni vacancies provide outstanding activity and selectivity toward several biomass molecules because of the finely regulated electronic structure and highly-exposed active sites.In particular,a high faradaic efficiency(FE)at a high current density(99%at 100 mA cm^(-2))is achieved for HMF oxidation,and a two-electrode electrolyzer is assembled based on the Ni vacancies-enriched LDH,which realized a continuous synthesis of highly-pure 2,5-furandicarboxylic acid products with high yields(95%)and FE(90%).

超声衰减成像技术评价肝脂肪变性的相关因素分析

目的探讨影响超声衰减系数(AC)变化的相关因素,并评估衰减成像(ATI)技术对非酒精性脂肪性肝病(NAFLD)定量诊断的临床实用性及测量的可重复性。方法选取2019年9月至2020年12月在哈尔滨医科大学附属第一医院使用超声的ATI技术进行肝检测的114例受试者(NAFLD组56例,健康对照组58例),分别获得二维超声和AC,同时收集患者相应的临床资料、血生化检测指标等,通过多因素线性回归分析确定AC的独立影响因素。使用常规二维超声检查对所有研究对象的肝脂肪变性程度进行四分制评分(S0~S3组),采用方差分析检验各组间AC的差异性,使用Spearman相关分析方法评估AC与肝脂肪变性程度的相关性,并计算组内相关系数(ICC),评估2名操作者间(AC-1组和AC-2组)ATI测量的可重复性。结果多因素线性回归分析显示体质量指数(BMI)、肝脂肪变性程度是AC的独立影响因素(β=0.007,95%CI:0.001~0.013,P=0.017;β=0.083,95%CI:0.070~0.095,P<0.001)。NAFLD组AC显著高于健康对照组[AC-1组:(0.716±0.098)dB/(cm·MHz)vs(0.539±0.058)dB/(cm·MHz);AC-2组:(0.699±0.102)dB/(cm·MHz)vs(0.542±0.053)dB/(cm·MHz)],且随着肝脂肪变性程度的加重,AC逐渐升高[S0组(58例)AC为(0.539±0.058)dB/(cm·MHz),S1组(23例)AC为(0.640±0.063)dB/(cm·MHz),S2组(20例)AC为(0.718±0.050)dB/(cm·MHz),S3组(13例)AC为(0.845±0.059)dB/(cm·MHz);F=122.27,P<0.001]。AC与肝脂肪变性程度存在较强的相关性(r=0.840;P<0.001)。不同肝脂肪变性程度AC的组内相关系数(ICC)分别为0.816(95%CI:0.708~0.881)、0.886(95%CI:0.301~0.967)、0.876(95%CI:0.479~0.960)、0.939(95%CI:0.819~0.981),P均<0.001。结论AC与BMI、肝脂肪变性程度显著相关,且ATI技术的操作者间可重复性极好,结果较为稳定,有助于早期发现脂肪肝并对脂肪肝严重程度进行评估。

人腺样体间充质干细胞向嗅感觉神经元诱导分化的体外研究

目的探讨体外分离和培养人腺样体组织来源的间充质干细胞(adenoid-derived mesenchymal stem cells,aMSCs)的可行性,并诱导观察aMSCs向嗅感觉神经元的分化。方法收集2020年9—11月来源于中南大学湘雅二医院腺样体肥大患儿的手术切除腺样体组织,胰蛋白酶消化联合贴壁法培养P0细胞,传代培养,流式细胞技术检测P5代细胞表面抗原CD45、CD73、CD90的表达,观察成骨、成脂诱导分化能力。采用维甲酸(retinoic acid,RA)、音猬因子(sonic hedgehog,SHH)、碱性成纤维生长因子(basic fibroblast growth factor,bFGF),以及RA+SHH、RA+bFGF、SHH+bFGF和RA+SHH+bFGF分别诱导分化P5代aMSCs,倒置显微镜下观察细胞形态,免疫荧光抗体法检测细胞表面感觉神经元标志物β-tubulin 3、嗅感觉神经元标志物生长相关蛋白-43(growth associated protein-43,GAP43)和嗅标记蛋白(olfactory maker protein,OMP)的表达。采用两个样本率的四格表资料的χ2检验比较表达强度的差异。结果P0代aMSCs具有良好的贴壁和增殖性能,P2代细胞已基本纯化。P5代细胞阳性表达CD73和CD90,其纯度分别为99.3%和97.75%,不表达CD45,成骨和成脂诱导分化良好。RA、SHH、bFGF诱导分化细胞均成神经元样外观,β-tubulin 3阳性表达;bFGF+SHH组和RA+SHH+bFGF组诱导细胞均表达GAP43,后组表达阳性更强(χ^(2)=17.48,P<0.005);所有诱导组均未见OMP阳性表达。结论腺样体组织可培养获得能稳定传代、具有良好分化能力的aMSCs。aMSCs是间充质干细胞家族新成员,具有向神经元分化的能力,RA、SHH和bFGF体外联合诱导能促使其分化为未成熟嗅感觉神经元。

Protective Efficacy of Inactivated Vaccine against SARS-CoV-2 Infection in Mice and Non-Human Primates

The ongoing coronavirus disease 2019(COVID-19)pandemic caused more than 96 million infections and over 2 million deaths worldwide so far.However,there is no approved vaccine available for severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),the disease causative agent.Vaccine is the most effective approach to eradicate a pathogen.The tests of safety and efficacy in animals are pivotal for developing a vaccine and before the vaccine is applied to human populations.Here we evaluated the safety,immunogenicity,and efficacy of an inactivated vaccine based on the whole viral particles in human ACE2 transgenic mouse and in non-human primates.Our data showed that the inactivated vaccine successfully induced SARS-CoV-2-specific neutralizing antibodies in mice and non-human primates,and subsequently provided partial(in low dose)or full(in high dose)protection of challenge in the tested animals.In addition,passive serum transferred from vaccine-immunized mice could also provide full protection from SARS-CoV-2 infection in mice.These results warranted positive outcomes in future clinical trials in humans.

Effect of Zn atom in Fe-N-C catalysts for electro-catalytic reactions: theoretical considerations

Due to the high specific surface area,abundant nitrogen and micropores,ZIF-8 is a commonly used precursor for preparing high performance Fe-N-C catalysts.However,the Zn element is inevitably remained in the prepared Fe-N-C catalyst.Whether the residual Zn element affects the catalytic activity and active site center of the Fe-N-C catalyst caused widespread curiosity,but has not been studied yet.Herein,we built several Fe,Zn,and N co-doped graphene models to investigate the effect of Zn atoms on the electrocatalytic performance of Fe-N-C catalysts by using density functional theory method.The calculation results show that all the calculated Fe-Zn-N_(x) structures are thermodynamically stable due to the negative formation energies and relative stabilities.The active sites around Fe and Zn atoms in the structure of Fe-Zn-N_(6)(III)show the lowest oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)overpotentials of 0.38 and 0.43 V,respectively.The bridge site of Fe-Zn in Fe-Zn-N_(5) shows the lowest η^(HER) of−0.26 V.A few structures with a better activity than that of FeN_(4) or ZnN_(4) are attributed to the synergistic effects between Fe and Zn atoms.The calculated ORR reaction pathways on Fe-Zn-N6(III)show that H_(2)O is the final product and the ORR mechanism on the catalyst would be a four-electron process,and the existence of Zn element in the Fe-N-C catalysts plays a key role in reducing the ORR activation energy barrier.The results are helpful for the deep understand of high-performance Fe-N-C catalysts.