Photosynthesis of hydrogen peroxide(H_(2)O_(2))from H_(2)O and O_(2)is considered to be a promising approach.However,limited to the rapid recombination of photo-generated carriers and sluggish kinetics of O_(2)re-duct...Photosynthesis of hydrogen peroxide(H_(2)O_(2))from H_(2)O and O_(2)is considered to be a promising approach.However,limited to the rapid recombination of photo-generated carriers and sluggish kinetics of O_(2)re-duction to H_(2)O_(2),it is a challenge for polymeric photocatalysts to achieve efficient photocatalytic H_(2)O_(2) production.Herein,Ag single atoms and nitrogen defects decorated carbon nitride(Ag@MCT)are con-structed through self-assembly and pyrolysis methods.The optimized photocatalyst displays exceptional performance in pure water,with an H_(2)O_(2) production rate of as high as 528.4μmol g^(-1) h^(-1) and an apparent quantum yield for H_(2)O_(2)production of 4.5%at 420 nm.Experimental and theoretical results reveal that the Ag atomic sites act as electron mediators that promote the capture and transfer of photo-generated charge carriers,while nitrogen defects as electron collectors and reaction sites to enhance the adsorption and activation of O_(2),accelerating reduction kinetics from O_(2) to H_(2)O_(2).This work presents a re-liable strategy to design excellent photocatalysts by rationally modulating electronic structures and active sites for accelerating photo-generated charge carriers transfer and surface reaction kinetics.展开更多
Photocatalytic synthesis of hydrogen peroxide has gradually become a promising method for in-situ pro-duction of hydrogen peroxide,which relies on sustainable solar energy.However,the commonly used photocatalyst,i.e.,...Photocatalytic synthesis of hydrogen peroxide has gradually become a promising method for in-situ pro-duction of hydrogen peroxide,which relies on sustainable solar energy.However,the commonly used photocatalyst,i.e.,carbon nitride(CN),still suffers from the drawbacks of narrow light absorption range and fast charge recombination.Here,we report a facile method to introduce nitrogen defects into carbon nitride together with sodium ion.By adjusting the ratio of sodium dicyandiamide,the band gap of carbon nitride can be controlled,while the carrier separation and transfer ability of carbon nitride is improved.The modified CN with sodium doping and nitrogen defect(SD-CN)demonstrates outstanding H_(2)O_(2)pro-duction performance(H_(2)O_(2)yield rate of 297.2μmol L^(−1)h^(−1))under visible light irradiation,which is approximately 9.8 times higher than that of pristine CN.This work deepens the understanding of the coordinated effect of structural defect and element doping of carbon nitride on the photocatalytic H_(2)O_(2)production performance,and provides new insight into the design of photocatalytic system for efficient production of H_(2)O_(2).展开更多
Defect construction and heteroatom doping are effective strategies for improving photocatalytic activity of carbon nitride(g-C_(3)N_(4)).In this work,N defects were successfully prepared via cold plasma.High-energy el...Defect construction and heteroatom doping are effective strategies for improving photocatalytic activity of carbon nitride(g-C_(3)N_(4)).In this work,N defects were successfully prepared via cold plasma.High-energy electrons generated by plasma can produce N defects and embed sulfur atoms into g-C_(3)N_(4).The N defects obviously promoted photocatalytic degradation performance that was 7.5 times higher than that of pure g-C_(3)N_(4).The concentration of N defects can be tuned by different power and time of plasma.With the increase in N defects,the photocatalytic activity showed a volcanic trend.The g-C_(3)N_(4)with moderate concentration of N defects exhibited the highest photocatalytic activity.S-doped g-C_(3)N_(4)exhibited 11.25 times higher photocatalytic activity than pure g-C_(3)N_(4).It provided extra active sites for photocatalytic reaction and improved stability of N defects.The N vacancy-enriched and S-doped g-C_(3)N_(4)are beneficial for widening absorption edge and improving the separation efficiency of electron and holes.展开更多
Herein,microtubular nanoporous g-C3N4(TPCN)with hierarchical structure and nitrogen defects was prepared via a facile self-templating approach.On one hand,the hexagonal tubular structure can facilitate the light refle...Herein,microtubular nanoporous g-C3N4(TPCN)with hierarchical structure and nitrogen defects was prepared via a facile self-templating approach.On one hand,the hexagonal tubular structure can facilitate the light reflection/scattering,provide internal/external active sites,and endow the electron with oriented transfer channels.The well-developed nanoporosity can result in large specific surface area and abundant accessible channels for charge migration.On the other hand,the existence of nitrogen vacancies can improve the light harvesting(>450 nm)and prompt charge separation by acting as the shallow charge traps.More NHxgroups in g-C3N4 framework can promote the interlayer charge transport by generating hydrogen-bonding interaction between C3N4 layers.Therefore,TPCN possessed highly efficient visible photocatalytic performances to effectively inactivate Escherichia coli(E.coli)cells and thoroughly mineralize organic pollutants.TPCN with the optimum bactericidal efficiency can completely inactivated5×10^6 cfu mL^-1 of E.coli cells after 4 h of irradiation treatment,while about 74.4%of E.coli cells were killed by bulk g-C3N4(BCN).Meanwhile,the photodegradation rate of TPCN towards methylene blue,amaranth,and bisphenol A were almost 3.1,2.5 and 1.6 times as fast as those of BCN.Furthermore,h^+and·O2^- were the reactive species in the photocatalytic process of TPCN system.展开更多
The promising solar irradiated photocatalyst by pairing of bismuth oxide quantum dots(BQDs)doped TiO_(2)with nitrogen doped graphene oxide(NGO)nanocomposite(NGO/BQDs-TiO_(2))was fabricated.It was used for degradation ...The promising solar irradiated photocatalyst by pairing of bismuth oxide quantum dots(BQDs)doped TiO_(2)with nitrogen doped graphene oxide(NGO)nanocomposite(NGO/BQDs-TiO_(2))was fabricated.It was used for degradation of organic pollutants like 2,4-dichlorophenol(2,4-DCP)and stable dyes,i.e.Rhodamine B and Congo Red.X-ray diffraction(XRD)profile of NGO showed reduction in oxygenic functional groups and restoring of graphitic crystal structure.The characteristic diffraction peaks of TiO_(2)and its composites showed crystalline anatase TiO_(2).Morphological images represent spherical shaped TiO_(2)evenly covered with BQDs spread on NGO sheet.The surface linkages of NO-O-Ti,C-O-Ti,Bi-O-Ti and vibrational modes are observed by Fourier transform infrared spectroscopy(FTIR)and Raman studies.BQDs and NGO modified TiO_(2)results into red shifting in visible region as studied in diffused reflectance spectroscopy(DRS).NGO and BQDs in TiO_(2)are linked with defect centers which reduced the recombination of free charge carriers by quenching of photoluminescence(PL)intensities.X-ray photoelectron spectroscopy(XPS)shows that no peak related to C-O in NGO/BQDs-TiO_(2)is observed.This indicated that doping of nitrogen into GO has reduced some oxygen functional groups.Nitrogen functionalities in NGO and photosensitizing effect of BQDs in ternary composite have improved photocatalytic activity against organic pollutants.Intermediate byproducts during photo degradation process of 2,4-DCP were studied through high performance liquid chromatography(HPLC).Study of radical scavengers indicated that O_(2)^(·-) has significant role for degradation of 2,4-DCP.Our investigations propose that fabricated nanohybrid architecture has potential for degradation of environmental pollutions.展开更多
One of the major obstacles to the application of potassium-ion batteries in large-scale energy storage is the lack of safe and effective electrolytes.KNH_(2),a new potassium-ion solid electrolyte has been developed in...One of the major obstacles to the application of potassium-ion batteries in large-scale energy storage is the lack of safe and effective electrolytes.KNH_(2),a new potassium-ion solid electrolyte has been developed in this study.Its ionic conductivity reaches 4.84×10^(-5)S cm^(-1)at 150°C and can reach3.56×10^(-4)S cm^(-1)after mechanochemical treatment.The result from electron paramagnetic resonance(EPR) measurement shows that the increment of ionic conductivity is dependent on the concentration of nitrogen defects in the KNH_(2) electrolyte.To the best of our knowledge,this is the first report that adopts inorganic amide as an electrolyte for potassium-ion battery and initiates the search for a new amidebased solid electrolyte for an all-solid-state potassium-ion battery.展开更多
The commercialization of the lithium-sulfur(Li-S)batteries is severely hampered by the shuttle effect and sluggish kinetics of lithium polysulfides(Li PSs).In this study,porous tubular graphitic carbon nitride(PTCN)wa...The commercialization of the lithium-sulfur(Li-S)batteries is severely hampered by the shuttle effect and sluggish kinetics of lithium polysulfides(Li PSs).In this study,porous tubular graphitic carbon nitride(PTCN)was synthesized as the sulfur host by hydrothermal treatment,thermal shock and etching methods.By etching technology,the hollow nanotube tentacles grow on the tube wall of PTCN,the mesoporous appears on the inner wall,and a large number of nitrogen defects are introduced.The verticallyrooted hollow nanotube tentacles on the PTCN surface facilitate electron conduction for sulfur redox reactions.The hollow and porous architecture exposes plentiful active interfaces for accelerated redox conversion of polysulfide.Furthermore,the nitrogen defects in PTCN enable more excellent intrinsic conductivity,higher adsorbability and conversion catalytic activity to Li PSs.Based on the above synergetic effect,the batteries with PTCN/S cathodes realize a high discharge capacity of 504 m Ah g^(-1) at 4 C and a stable cycling behavior over 500 cycles with a low capacity decay of 0.063%per cycle.The results indicate a promising approach todesigning a high performance electrode material for Li-S batteries.展开更多
Incorporating nitrogen(N)atom in graphene is considered a key technique for tuning its electrical properties.However,this is still a great challenge,and it is unclear how to build N-graphene with desired nitrogen conf...Incorporating nitrogen(N)atom in graphene is considered a key technique for tuning its electrical properties.However,this is still a great challenge,and it is unclear how to build N-graphene with desired nitrogen configurations.There is a lack of experimental evidence to explain the influence and mechanism of structural defects for nitrogen incorporation into graphene compared to the derived DFT theories.Herein,this gap is bridged through a systematic study of different nitrogen-containing gaseous plasma post-treatments on graphene nanowalls(CNWs)to produce N-CNWs with incorporated and substituted nitrogen.The structural and morphological analyses describe a remarkable difference in the plasma–surface interaction,nitrogen concentration and nitrogen incorporation mechanism in CNWs by using different nitrogen-containing plasma.Electrical conductivity measurements revealed that the conductivity of the N-graphene is strongly influenced by the position and concentration of C–N bonding configurations.These findings open up a new pathway for the synthesis of N-graphene using plasma post-treatment to control the concentration and configuration of incorporated nitrogen for application-specific properties.展开更多
Defective electrocatalysts,especially for intrinsic defective carbon,have aroused a wide concern owing to high spin and charge densities.However,the designated nitrogen species favorable for creating defects by the re...Defective electrocatalysts,especially for intrinsic defective carbon,have aroused a wide concern owing to high spin and charge densities.However,the designated nitrogen species favorable for creating defects by the removal of nitrogen,and the influence of defects for the coordination structure of active site and oxygen reduction reaction(ORR)activity have not been elucidated.Herein,we designed and synthesized a pair of electrocatalysts,denoted as Fe-N/C and Fe-ND/C for coordination sites of atomic iron-nitrogen and iron-nitrogen/defect configuration embedded in hollow carbon spheres,respectively,through direct pyrolysis of their corresponding hollow carbon spheres adsorbed with Fe(acac)3.The nitrogen defects were fabricated via the evaporation of pyrrolic-N on nitrogen doped hollow carbon spheres.Results of comparative experiments between Fe-N/C and Fe-ND/C reveal that Fe-ND/C shows superior ORR activity with an onset potential of 30 mV higher than that of Fe-N/C.Fe-ND sites are more favorable for the enhancement of ORR activity.Density functional theory(DFT)calculation demonstrates that Fe-ND/C with proposed coordination structure of FeN_(4-x)(0<x<4)anchored by OH as axial ligand during ORR,weakens the strong binding of OH^(*)intermediate and promotes the desorption of OH^(*)as rate-determining step for ORR in alkaline electrolyte.Thus,Fe-ND/C electrocatalysts present much better ORR activity compared with that of Fe-N/C with proposed coordination structure of FeN_(4).展开更多
以8.0mm厚的高氮钢板为试验材料,采用Nd:YAG激光-熔化极活性气体保护焊(Metal Active Gas,MAG)电弧复合焊接方法,研究了单一成分活性剂(TiO_2,B_2O_3,Cr_2O_3)对复合焊焊缝缺陷的影响。研究表明,在相同的工艺参数下,与无活性剂焊缝相比...以8.0mm厚的高氮钢板为试验材料,采用Nd:YAG激光-熔化极活性气体保护焊(Metal Active Gas,MAG)电弧复合焊接方法,研究了单一成分活性剂(TiO_2,B_2O_3,Cr_2O_3)对复合焊焊缝缺陷的影响。研究表明,在相同的工艺参数下,与无活性剂焊缝相比,活性剂TiO_2,B_2O_3,Cr_2O_3均能使焊缝形貌得到改善;活性剂TiO_2和Cr_2O_3能增加焊缝熔宽、余高,减小咬边深度,但活性剂B_2O_3使焊缝熔宽和余高减小,咬边深度增加。无活性剂和有活性剂的高氮钢激光-电弧复合焊焊缝熔合区的气孔数均比焊缝区的气孔数多;而活性剂的加入,增加了焊缝熔合区和焊缝区的气孔数。展开更多
基金supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.52488201)the National Natural Science Foundation of China(No.52276213)+1 种基金the Key Research and Development Program of Shaanxi Province(No.2024GX-YBXM-459)the Fundamental Research Funds for the Central Universities.
文摘Photosynthesis of hydrogen peroxide(H_(2)O_(2))from H_(2)O and O_(2)is considered to be a promising approach.However,limited to the rapid recombination of photo-generated carriers and sluggish kinetics of O_(2)re-duction to H_(2)O_(2),it is a challenge for polymeric photocatalysts to achieve efficient photocatalytic H_(2)O_(2) production.Herein,Ag single atoms and nitrogen defects decorated carbon nitride(Ag@MCT)are con-structed through self-assembly and pyrolysis methods.The optimized photocatalyst displays exceptional performance in pure water,with an H_(2)O_(2) production rate of as high as 528.4μmol g^(-1) h^(-1) and an apparent quantum yield for H_(2)O_(2)production of 4.5%at 420 nm.Experimental and theoretical results reveal that the Ag atomic sites act as electron mediators that promote the capture and transfer of photo-generated charge carriers,while nitrogen defects as electron collectors and reaction sites to enhance the adsorption and activation of O_(2),accelerating reduction kinetics from O_(2) to H_(2)O_(2).This work presents a re-liable strategy to design excellent photocatalysts by rationally modulating electronic structures and active sites for accelerating photo-generated charge carriers transfer and surface reaction kinetics.
基金supported by the National Natural Science Foundation of China(No.22376159)the Fundamental Research Funds for the Central Universities(No.2022-4-ZD-08).
文摘Photocatalytic synthesis of hydrogen peroxide has gradually become a promising method for in-situ pro-duction of hydrogen peroxide,which relies on sustainable solar energy.However,the commonly used photocatalyst,i.e.,carbon nitride(CN),still suffers from the drawbacks of narrow light absorption range and fast charge recombination.Here,we report a facile method to introduce nitrogen defects into carbon nitride together with sodium ion.By adjusting the ratio of sodium dicyandiamide,the band gap of carbon nitride can be controlled,while the carrier separation and transfer ability of carbon nitride is improved.The modified CN with sodium doping and nitrogen defect(SD-CN)demonstrates outstanding H_(2)O_(2)pro-duction performance(H_(2)O_(2)yield rate of 297.2μmol L^(−1)h^(−1))under visible light irradiation,which is approximately 9.8 times higher than that of pristine CN.This work deepens the understanding of the coordinated effect of structural defect and element doping of carbon nitride on the photocatalytic H_(2)O_(2)production performance,and provides new insight into the design of photocatalytic system for efficient production of H_(2)O_(2).
基金supported by the National Natural Science Foundation of China(Grant Nos.21878214 and 21938009).
文摘Defect construction and heteroatom doping are effective strategies for improving photocatalytic activity of carbon nitride(g-C_(3)N_(4)).In this work,N defects were successfully prepared via cold plasma.High-energy electrons generated by plasma can produce N defects and embed sulfur atoms into g-C_(3)N_(4).The N defects obviously promoted photocatalytic degradation performance that was 7.5 times higher than that of pure g-C_(3)N_(4).The concentration of N defects can be tuned by different power and time of plasma.With the increase in N defects,the photocatalytic activity showed a volcanic trend.The g-C_(3)N_(4)with moderate concentration of N defects exhibited the highest photocatalytic activity.S-doped g-C_(3)N_(4)exhibited 11.25 times higher photocatalytic activity than pure g-C_(3)N_(4).It provided extra active sites for photocatalytic reaction and improved stability of N defects.The N vacancy-enriched and S-doped g-C_(3)N_(4)are beneficial for widening absorption edge and improving the separation efficiency of electron and holes.
基金financially supported by the National Natural Science Foundation of China(No.21707052)the Jiangsu Agriculture Science and Technology Innovation Fund(No.CX(18)2025)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.JUSRP11905 and JUSRP51714B)the Key Research and Development Program of Jiangsu Province(No.BE2017623)。
文摘Herein,microtubular nanoporous g-C3N4(TPCN)with hierarchical structure and nitrogen defects was prepared via a facile self-templating approach.On one hand,the hexagonal tubular structure can facilitate the light reflection/scattering,provide internal/external active sites,and endow the electron with oriented transfer channels.The well-developed nanoporosity can result in large specific surface area and abundant accessible channels for charge migration.On the other hand,the existence of nitrogen vacancies can improve the light harvesting(>450 nm)and prompt charge separation by acting as the shallow charge traps.More NHxgroups in g-C3N4 framework can promote the interlayer charge transport by generating hydrogen-bonding interaction between C3N4 layers.Therefore,TPCN possessed highly efficient visible photocatalytic performances to effectively inactivate Escherichia coli(E.coli)cells and thoroughly mineralize organic pollutants.TPCN with the optimum bactericidal efficiency can completely inactivated5×10^6 cfu mL^-1 of E.coli cells after 4 h of irradiation treatment,while about 74.4%of E.coli cells were killed by bulk g-C3N4(BCN).Meanwhile,the photodegradation rate of TPCN towards methylene blue,amaranth,and bisphenol A were almost 3.1,2.5 and 1.6 times as fast as those of BCN.Furthermore,h^+and·O2^- were the reactive species in the photocatalytic process of TPCN system.
基金International Islamic UniversityPakistan Institute of Engineering and Applied Sciences+1 种基金Higher Education Commission of Pakistan(NRPU grant No.3660)Aalto University Finland。
文摘The promising solar irradiated photocatalyst by pairing of bismuth oxide quantum dots(BQDs)doped TiO_(2)with nitrogen doped graphene oxide(NGO)nanocomposite(NGO/BQDs-TiO_(2))was fabricated.It was used for degradation of organic pollutants like 2,4-dichlorophenol(2,4-DCP)and stable dyes,i.e.Rhodamine B and Congo Red.X-ray diffraction(XRD)profile of NGO showed reduction in oxygenic functional groups and restoring of graphitic crystal structure.The characteristic diffraction peaks of TiO_(2)and its composites showed crystalline anatase TiO_(2).Morphological images represent spherical shaped TiO_(2)evenly covered with BQDs spread on NGO sheet.The surface linkages of NO-O-Ti,C-O-Ti,Bi-O-Ti and vibrational modes are observed by Fourier transform infrared spectroscopy(FTIR)and Raman studies.BQDs and NGO modified TiO_(2)results into red shifting in visible region as studied in diffused reflectance spectroscopy(DRS).NGO and BQDs in TiO_(2)are linked with defect centers which reduced the recombination of free charge carriers by quenching of photoluminescence(PL)intensities.X-ray photoelectron spectroscopy(XPS)shows that no peak related to C-O in NGO/BQDs-TiO_(2)is observed.This indicated that doping of nitrogen into GO has reduced some oxygen functional groups.Nitrogen functionalities in NGO and photosensitizing effect of BQDs in ternary composite have improved photocatalytic activity against organic pollutants.Intermediate byproducts during photo degradation process of 2,4-DCP were studied through high performance liquid chromatography(HPLC).Study of radical scavengers indicated that O_(2)^(·-) has significant role for degradation of 2,4-DCP.Our investigations propose that fabricated nanohybrid architecture has potential for degradation of environmental pollutions.
基金supported by the Key R&D Program of Shandong Province China (2020CXGC010402)the National Natural Science Foundation of China (51801197)+3 种基金the Youth Innovation Promotion Association CAS (2019189)the Liaoning Revitalization Talents Program (XLYC2002076)the Dalian High-level Talents Program (2019RD09)the K.C. Wong Education Foundation (GJTD2018-06)。
文摘One of the major obstacles to the application of potassium-ion batteries in large-scale energy storage is the lack of safe and effective electrolytes.KNH_(2),a new potassium-ion solid electrolyte has been developed in this study.Its ionic conductivity reaches 4.84×10^(-5)S cm^(-1)at 150°C and can reach3.56×10^(-4)S cm^(-1)after mechanochemical treatment.The result from electron paramagnetic resonance(EPR) measurement shows that the increment of ionic conductivity is dependent on the concentration of nitrogen defects in the KNH_(2) electrolyte.To the best of our knowledge,this is the first report that adopts inorganic amide as an electrolyte for potassium-ion battery and initiates the search for a new amidebased solid electrolyte for an all-solid-state potassium-ion battery.
基金Natural Science Foundation of Hebei Province of China(Nos.B2020202052B2021202028)+6 种基金Outstanding Youth Project of Guangdong Natural Science Foundation(No.2021B1515020051)the Program for the Outstanding Young Talents of Hebei Province,China(YG.Z.)Chunhui Project of Ministry of Education of the People’s Republic of China(No.Z2017010)Department of Science and Technology of Guangdong Province(No.2020B0909030004)Guangdong Innovative and Entrepreneurial Team Program(No.2016ZT06C517)Science and Technology Program of Guangzhou(No.2019050001)Science and Technology Program of Zhaoqing(No.2019K038)。
文摘The commercialization of the lithium-sulfur(Li-S)batteries is severely hampered by the shuttle effect and sluggish kinetics of lithium polysulfides(Li PSs).In this study,porous tubular graphitic carbon nitride(PTCN)was synthesized as the sulfur host by hydrothermal treatment,thermal shock and etching methods.By etching technology,the hollow nanotube tentacles grow on the tube wall of PTCN,the mesoporous appears on the inner wall,and a large number of nitrogen defects are introduced.The verticallyrooted hollow nanotube tentacles on the PTCN surface facilitate electron conduction for sulfur redox reactions.The hollow and porous architecture exposes plentiful active interfaces for accelerated redox conversion of polysulfide.Furthermore,the nitrogen defects in PTCN enable more excellent intrinsic conductivity,higher adsorbability and conversion catalytic activity to Li PSs.Based on the above synergetic effect,the batteries with PTCN/S cathodes realize a high discharge capacity of 504 m Ah g^(-1) at 4 C and a stable cycling behavior over 500 cycles with a low capacity decay of 0.063%per cycle.The results indicate a promising approach todesigning a high performance electrode material for Li-S batteries.
基金funded by the European Union’s Horizon Research and Innovation Program under Grant agreement No. 766894partially supported also by JSPS, MESS and ARRS under the Japan-Slovenia Research Cooperative Program grants to U.C., M.H. and H.Kthe allocation of synchrotron radiation beam time at Bessy II via projects 17205612ST/R, 17206156ST, 18106986ST, 19107892-ST/R and 191-08281 ST/R as well as Calypso
文摘Incorporating nitrogen(N)atom in graphene is considered a key technique for tuning its electrical properties.However,this is still a great challenge,and it is unclear how to build N-graphene with desired nitrogen configurations.There is a lack of experimental evidence to explain the influence and mechanism of structural defects for nitrogen incorporation into graphene compared to the derived DFT theories.Herein,this gap is bridged through a systematic study of different nitrogen-containing gaseous plasma post-treatments on graphene nanowalls(CNWs)to produce N-CNWs with incorporated and substituted nitrogen.The structural and morphological analyses describe a remarkable difference in the plasma–surface interaction,nitrogen concentration and nitrogen incorporation mechanism in CNWs by using different nitrogen-containing plasma.Electrical conductivity measurements revealed that the conductivity of the N-graphene is strongly influenced by the position and concentration of C–N bonding configurations.These findings open up a new pathway for the synthesis of N-graphene using plasma post-treatment to control the concentration and configuration of incorporated nitrogen for application-specific properties.
基金the National Natural Science Foundation of China(Nos.21905271,21701168)Liaoning Natural Science Foundation(Nos.20180510029,20180510043,20180510050)+2 种基金the Dalian National Laboratory for Clean Energy(DNL)CAS,DNL Cooperation Fund,CAS(No.DNL180402)Australian Research Council(No.DP180100568).For XAFS measurement,we gratefully acknowledge 1W1B beamline of Beijing Synchrotron Radiation Facility(BSRF)Beijing,China for providing the beam time.
文摘Defective electrocatalysts,especially for intrinsic defective carbon,have aroused a wide concern owing to high spin and charge densities.However,the designated nitrogen species favorable for creating defects by the removal of nitrogen,and the influence of defects for the coordination structure of active site and oxygen reduction reaction(ORR)activity have not been elucidated.Herein,we designed and synthesized a pair of electrocatalysts,denoted as Fe-N/C and Fe-ND/C for coordination sites of atomic iron-nitrogen and iron-nitrogen/defect configuration embedded in hollow carbon spheres,respectively,through direct pyrolysis of their corresponding hollow carbon spheres adsorbed with Fe(acac)3.The nitrogen defects were fabricated via the evaporation of pyrrolic-N on nitrogen doped hollow carbon spheres.Results of comparative experiments between Fe-N/C and Fe-ND/C reveal that Fe-ND/C shows superior ORR activity with an onset potential of 30 mV higher than that of Fe-N/C.Fe-ND sites are more favorable for the enhancement of ORR activity.Density functional theory(DFT)calculation demonstrates that Fe-ND/C with proposed coordination structure of FeN_(4-x)(0<x<4)anchored by OH as axial ligand during ORR,weakens the strong binding of OH^(*)intermediate and promotes the desorption of OH^(*)as rate-determining step for ORR in alkaline electrolyte.Thus,Fe-ND/C electrocatalysts present much better ORR activity compared with that of Fe-N/C with proposed coordination structure of FeN_(4).
文摘以8.0mm厚的高氮钢板为试验材料,采用Nd:YAG激光-熔化极活性气体保护焊(Metal Active Gas,MAG)电弧复合焊接方法,研究了单一成分活性剂(TiO_2,B_2O_3,Cr_2O_3)对复合焊焊缝缺陷的影响。研究表明,在相同的工艺参数下,与无活性剂焊缝相比,活性剂TiO_2,B_2O_3,Cr_2O_3均能使焊缝形貌得到改善;活性剂TiO_2和Cr_2O_3能增加焊缝熔宽、余高,减小咬边深度,但活性剂B_2O_3使焊缝熔宽和余高减小,咬边深度增加。无活性剂和有活性剂的高氮钢激光-电弧复合焊焊缝熔合区的气孔数均比焊缝区的气孔数多;而活性剂的加入,增加了焊缝熔合区和焊缝区的气孔数。
