The capability of electrocatalytic reducti on of carbon dioxide(CO2)using nitrogen(N)-doped carb on strongly depe nds on the N-dopi ng level and their types.In this work,we developed a strategy to generate mesoporous ...The capability of electrocatalytic reducti on of carbon dioxide(CO2)using nitrogen(N)-doped carb on strongly depe nds on the N-dopi ng level and their types.In this work,we developed a strategy to generate mesoporous N-doped carb on frameworks with tun able configurati ons and contents of N dopants,by using a secondary doping process via the treatment of N,N-dimethylformamide(DMF)solvent.The obtained mesoporous N-doped carbon(denoted as MNC-D)served as an efficient electrocatalyst for electroreduction of CO2 to CO.A high Faradaic efficiency of^92%and a partial current density for CO of-6.8 mA·cm^-2 were achieved at a potential of-0.58 V vs.RHE.Electrochemical analyses further revealed that the active sites within the N-doped carb on catalysts were the pyridinic N and defects gen erated by the DMF treatme nt,which enhan ced the activati on and adsorpti on CO2 molecules.Our study suggests a new approach to develop efficie nt carb on-based catalysts for potential scalable CO2 reduction reaction(CO2RR)to fuels and chemicals.展开更多
Biomass‐derived carbon is a promising electrode material in energy storage devices.However,how to improve its low capacity and stability,and slow diffusion kinetics during lithium storage remains a challenge.In this ...Biomass‐derived carbon is a promising electrode material in energy storage devices.However,how to improve its low capacity and stability,and slow diffusion kinetics during lithium storage remains a challenge.In this research,we propose a“self‐assembly‐template”method to prepare B,N codoped porous carbon(BN‐C)with a nanosandwich structure and abundant pyridinic N‐B species.The nanosandwich structure can increase powder density and cycle stability by constructing a stable solid electrolyte interphase film,shortening the Li^(+)diffusion pathway,and accommodating volume expansion during repeated charging/discharging.The abundant pyridinic N‐B species can simultaneously promote the adsorption/desorption of Li^(+)/PF_(6)^(−)and reduce the diffusion barrier.The BN‐C electrode showed a high lithium‐ion storage capacity of above 1140 mAh g^(−1)at 0.05 A g^(−1)and superior stability(96.5%retained after 2000 cycles).Moreover,owing to the synergistic effect of the nanosandwich structure and pyridinic N‐B species,the assembled symmetrical BN‐C//BN‐C full cell shows a high energy density of 234.7Wh kg^(−1),high power density of 39.38 kW kg−1,and excellent cycling stability,superior to most of the other cells reported in the literature.As the density functional theory simulation demonstrated,pyridinic N‐B shows enhanced adsorption activity for Li^(+)and PF_(6)^(−),which promotes an increase in the capacity of the anode and cathode,respectively.Meanwhile,the relatively lower diffusion barrier of pyridinic N‐B promotes Li^(+)migration,resulting in good rate performance.Therefore,this study provides a new approach for the synergistic modulation of a nanostructure and an active site simultaneously to fabricate the carbon electrode material in energy storage devices.展开更多
Nitrogen(N)-doped carbon materials as metal catalyst supports have attracted signifi cant attention,but the eff ect of N dopants on catalytic performance remains unclear,especially for complex reaction processes such ...Nitrogen(N)-doped carbon materials as metal catalyst supports have attracted signifi cant attention,but the eff ect of N dopants on catalytic performance remains unclear,especially for complex reaction processes such as Fischer-Tropsch synthesis(FTS).Herein,we engineered ruthenium(Ru)FTS catalysts supported on N-doped carbon overlayers on TiO_(2)nanoparticles.By regulating the carbonization temperatures,we successfully controlled the types and contents of N dopants to identify their impacts on metal-support interactions(MSI).Our fi ndings revealed that N dopants establish a favorable surface environment for electron transfer from the support to the Ru species.Moreover,pyridinic N demonstrates the highest electron-donating ability,followed by pyrrolic N and graphitic N.In addition to realizing excellent catalytic stability,strengthening the interaction between Ru sites and N dopants increases the Ru^(0)/Ru^(δ+)ratios to enlarge the active site numbers and surface electron density of Ru species to enhance the strength of adsorbed CO.Consequently,it improves the catalyst’s overall performance,encompassing intrinsic and apparent activities,as well as its ability for carbon chain growth.Accordingly,the as-synthesized Ru/TiO_(2)@CN-700 catalyst with abundant pyridine N dopants exhibits a superhigh C_(5+)time yield of 219.4 mol CO/(mol Ru·h)and C_(5+)selectivity of 85.5%.展开更多
Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticle...Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.展开更多
Electrochemical reduction of CO_(2)(CO_(2)RR)to value-added chemicals is an attractive strategy for greenhouse gas mitigation and carbon recycle.Carbon material is one of most promising electrocatalysts but its produc...Electrochemical reduction of CO_(2)(CO_(2)RR)to value-added chemicals is an attractive strategy for greenhouse gas mitigation and carbon recycle.Carbon material is one of most promising electrocatalysts but its product selectivity is limited by few modulating approaches for active sites.Herein,the predominant pyridinic N-B sites(accounting for 80%to all N species)are fabricated in hierarchically porous structure of graphene nanoribbons/amorphous carbon.The graphene nanoribbons and porous structure can accelerate electron and ion/gas transport during CO_(2)RR,respectively.This carbon electrocatalyst exhibits excellent selectivity toward CO_(2)reduction to CH_(4)with the faradaic efficiency of 68%at−0.50 V vs.RHE.As demonstrated by density functional theory,a proper adsorbed energy of∗CO and∗CH_(2)O are generated on the pyridinic N-B site resulting into high CH_(4)selectivity.Therefore,this study provides a novel method to modulate active sites of carbon-based electrocatalyst to obtain high CH_(4)selectivity.展开更多
In-depth exploration of the relationship among different adsorption sites is conducive to design of efficient adsorbents for target pollutants removal from water.In this study,the experiments,multivariate non-linear r...In-depth exploration of the relationship among different adsorption sites is conducive to design of efficient adsorbents for target pollutants removal from water.In this study,the experiments,multivariate non-linear regression and density functional theory calculations are applied to explore the possible synergistic effects of three nitrogen(N)-containing sites on cow dung biochar surface for sulfamethoxazole(SMX)adsorption.Notably,a strong synergistic effect between pyridinic N and pyrrolic N sites was found for sulfamethoxazole adsorption.The adsorption energies of SMX on four pyrrolic N-coupled pyridinic N structures were-1.02,-0.41,-0.49 and-0.72 e V,much higher than the sum of adsorption energies(-0.31 e V)on pyrrolic N and pyridinic N.Besides,the alteration of Mulliken charge revealed that the simultaneous presence of pyridinic N and pyrrolic N improved the electron transfer remarkably from-0.459 e and 0.094 e to-0.649 e and 0.186 e,benefiting for SMX adsorption.This work firstly explored the possible synergies of adsorption sites on biochar surface for organic contaminants removal from water,which shed new lights on the adsorption mechanism and provided valuable information to design efficient adsorbents in the field of water treatment.展开更多
Single-atomic transition metal-nitrogen codoped carbon(M-N-C)are efficient substitute catalysts for noble metals to catalyze the electrochemical CO_(2) reduction reaction(CO_(2)RR).However,the uncontrolled aggregation...Single-atomic transition metal-nitrogen codoped carbon(M-N-C)are efficient substitute catalysts for noble metals to catalyze the electrochemical CO_(2) reduction reaction(CO_(2)RR).However,the uncontrolled aggregations of metal and serious loss of nitrogen species constituting the M-N_(x) active sites are frequently observed in the commonly used pyrolysis procedure.Herein,single-atomic nickel(Ni)-based sheet-like electrocatalysts with abundant Ni-N_(4) active sites were created by using a novel ammonium chloride(NH_(4)Cl)-assited pyrolysis method.Spherical aberration correction electron microscopy and X-ray absorption fine structure analysis clearly revealed that Ni species are atomically dispersed and anchored by N in Ni-N_(4) structure.The addition of NH_(4)Cl optimized the mesopore size to 7-10 nm and increased the concentrations of pyridinic N(3.54 wt%)and Ni-N_(4)(3.33 wt%)species.The synergistic catalytic effect derived from Ni-N_(4) active sites and pyridinic N species achieved an outstanding CO_(2) RR performance,presenting a high CO Faradaic efficiency(FE_(CO))up to 98% and a large CO partial current density of 8.5 mA cm^(-2) at a low potential of-0.62 V vs.RHE.Particularly,the FE_(CO) maintains above 80% within a large potential range from -0.43 to -0.73 V vs.RHE.This work provides a practical and feasible approach to building highly active single-atomic catalysts for CO_(2) conversion systems.展开更多
Photocatalytic CO_(2)conversion efficiency is hampered by the rapid recombination of photogenerated charge carriers.It is effective to suppress the recombination by constructing cocatalysts on photocatalysts with high...Photocatalytic CO_(2)conversion efficiency is hampered by the rapid recombination of photogenerated charge carriers.It is effective to suppress the recombination by constructing cocatalysts on photocatalysts with high-quality interfacial contact.Herein,we develop a novel strategy to in-situ grow ultrathin/V-doped graphene(NG)layer on TiO_(2) hollow spheres(HS) with large area and intimate interfacial contact via a chemical vapor deposition(CVD).The optimized TiO^(2)/NG HS nanocomposite achieves total CO_(2)conversion rates(the sum yield of CO,CH_(3)OH and CH_(4))of 18.11μmol·g^(-1)h^(-1),which is about 4.6 times higher than blank T1O_(2)HS.Experimental results demonstrate that intimate interfacial contact and abundant pyridinic N sites can effectively facilitate photogenerated charge carrier separation and transport,realizing enhanced photocatalytic CO_(2)reduction performance.In addition,this work provides an effective strategy for in-situ construction of graphene-based photocatalysts for highly efficient photocatalytic CO_(2)conversion.展开更多
Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carb...Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carbon materials show great potential for potassium-ion storage,poor rate performance,and unsatisfactory cycle lifespan in existing carbon-based PIBs anode,it also cannot match the dynamics and stability of the capacitor cathode.Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials.Hence,we prepare carbon nanofibers and g-C_(3)N_(4)composites with high nitrogen contents(19.78 at%);moreover,the sum of pyrrolic N and pyridinic N is up to 59.51%.It achieves high discharge capacity(391 m Ah g^(-1)at0.05 A g^(-1)),rate capacity(141 m Ah g^(-1)at 2 A g^(-1)),and long cycling performance(201 m Ah g^(-1)at 1 A g^(-1)over 3000 cycles)when as an anode for PIBs.Furthermore,it can deliver promising discharge capacity of132 m Ah g^(-1)at 0℃.Moreover,as battery anode for potassium-ion hybrid capacitors(PIHC)device with an active carbon cathode,it delivers energy/power density(62 and 2102 W kg^(-1))as well as high reversible capacity(106 m Ah g^(-1)at 1 A g^(-1)).展开更多
Electrical double-layer capacitors are widely concerned for their high power density,long cycling life and high cycling efficiency.However,their wide application is limited by their low energy density.In this study,we...Electrical double-layer capacitors are widely concerned for their high power density,long cycling life and high cycling efficiency.However,their wide application is limited by their low energy density.In this study,we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon(CoAT-NC) material.Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix,which is benefit for improving electrical conductivity and density of states of the carbon material.Therefore,an enhanced perfo rmance is expected when CoAT-NC is served as electrode in a supercapacitor device.CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte.Furthermore,a good energy density of 30 Wh/kg can be obtained in the organic electrolyte.展开更多
The use of carbon‐based materials is an appealing strategy to solve the issue of excessive CO_(2) emis‐sions.In particular,metal‐free nitrogen‐doped carbon materials(mf‐NCs)have the advantages of convenient synth...The use of carbon‐based materials is an appealing strategy to solve the issue of excessive CO_(2) emis‐sions.In particular,metal‐free nitrogen‐doped carbon materials(mf‐NCs)have the advantages of convenient synthesis,cost‐effectiveness,and high conductivity and are ideal electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).However,the unclear identification of the active N sites and the low intrinsic activity of mf‐NCs hinder the further development of high‐performance CO_(2)RR electrocat‐alysts.Achieving precise control over the synthesis of mf‐NC catalysts with well‐defined active N‐species sites is still challenging.To this end,we adopted a facile synthesis method to construct a set of mf‐NCs as robust catalysts for CO_(2)RR.The resulting best‐performing catalyst obtained a Far‐adaic efficiency of CO of approximately 90%at−0.55 V(vs.reversible hydrogen electrode)and good stability.The electrocatalytic performance and in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy measurements collectively revealed that graphitic and pyridinic N can synergistically adsorb CO_(2) and H_(2)O and thus promote CO_(2) activation and protonation.展开更多
A new mechanism of catalyst has been demonstrated in this article. With the interaction between carbon nitride(CN) and encapsulated nickel, the CN in the catalyst has been endowed with new active sites for the adsorpt...A new mechanism of catalyst has been demonstrated in this article. With the interaction between carbon nitride(CN) and encapsulated nickel, the CN in the catalyst has been endowed with new active sites for the adsorption and activation of hydrogen while nickel itself is physically isolated from the contact with reactive molecules. For the selective hydrogenation of acetylene in large amount of ethylene, the catalyst shows excellent ethylene selectivity than the nickel catalyst itself, which is almost totally unselective. Meanwhile, the CN itself is inactive for the reaction. The results of characterization demonstrate that pyridinic nitrogen doped in the carbon matrix should be the active sites for hydrogen dissociative adsorption. The theoretical calculations further confirm the results and provide with the detail in the electron transfer between nickel and CN in the catalyst. The current results supply a new concept for design of high performance catalyst.展开更多
提高碳材料中氮的掺杂含量,尤其是吡啶氮的含量,已被证明可以显著提升锂硫(Li-S)电池的性能.尽管在碳材料中氮掺杂具有积极作用,但在实际操作中要实现>5 at.%的高氮掺杂含量仍非易事.此外,无法调节碳材料中特定的氮种类也是研究中的...提高碳材料中氮的掺杂含量,尤其是吡啶氮的含量,已被证明可以显著提升锂硫(Li-S)电池的性能.尽管在碳材料中氮掺杂具有积极作用,但在实际操作中要实现>5 at.%的高氮掺杂含量仍非易事.此外,无法调节碳材料中特定的氮种类也是研究中的一个难题.在本文中,我们通过在氩气气氛下煅烧预先经过磷化处理的泛酸钙,得到了一种三维蜂窝状的氮(N)掺杂介孔碳(PNMC),其N掺杂含量高达8.82 at.%(吡啶N含量为3.49 at.%).磷掺杂不仅有助于提高N掺杂量,还有助于提升对多硫化物的吸附能力.实验证明,在800℃下制备的PNMC组装的硫正极(S/PNMC-800)表现出优异的电化学性能,在1 C下经过300圈循环后仍有556.7 mA h g^(-1)放电比容量.本工作提出了一种调控碳材料中吡啶氮含量的简便方法,为用于锂硫电池的多功能硫载体材料的开发提供启发.展开更多
Even though various nickel-nitrogen-carbon(Ni-N-C)combinations are prospective low-cost catalysts for the CO_(2)electroreduction reaction(CO_(2)RR),which is one avenue for attaining carbon neutrality,the detailed role...Even though various nickel-nitrogen-carbon(Ni-N-C)combinations are prospective low-cost catalysts for the CO_(2)electroreduction reaction(CO_(2)RR),which is one avenue for attaining carbon neutrality,the detailed role of different N species has hardly been investigated.Here,we report a hollow porous N-doped carbon nanofiber with NiNX-pyridinic N active species(denoted as h-Ni-N-C)developed using a facile electrospinning and SiO_(2)space-confined pyrolysis strategy.The NiNX-pyridinic N species are facilely generated during the pyrolysis process,giving rise to enhanced activity and selectivity for the CO_(2)RR.The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3%and a large current density of−15.1 mA cm^(−2)at−0.75 V versus reversible hydrogen electrode in an H-cell.Density functional theory(DFT)results show that NiN4-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN4 and pyridinic N species,without affecting the desorption of CO∗intermediate.展开更多
2D carbon ribbon/Al_(2)O_(3) was synthesized with two-dimensional metal organic frameworks 2D-MOFs as precursors using the solvothermal and calcination methods.Batch experiments of adsorption parameters such as pH,liq...2D carbon ribbon/Al_(2)O_(3) was synthesized with two-dimensional metal organic frameworks 2D-MOFs as precursors using the solvothermal and calcination methods.Batch experiments of adsorption parameters such as pH,liquid/solid ratio,adsorption kinetics,adsorption thermodynamics,and anions competitions were investigated to understand the adsorptive behavior of fluoride on carbon ribbon/Al_(2)O_(3) and nitrogen-doped carbon ribbon/Al_(2)O_(3).The adsorption of fluoride on carbon ribbon/Al_(2)O_(3) could be described as the chemical and multilayer adsorption,while the adsorption of fluoride on nitrogen-doped carbon ribbon/Al_(2)O_(3) followed the chemical and monolayer adsorption phenomenon.The fluoride on nitrogen-doped carbon ribbon/Al_(2)O_(3) had a much faster adsorption rate of 3.1×10^(−7) m/s than carbon ribbon/Al_(2)O_(3),which was 1.2×10^(−7) m/s.The nitrogen-doping on carbon ribbon enhances structural defects and improves the adsorption performance of fluoride.Also,the diacetylene linkages(—C≡C—)and pyridinic-N were studied to understand their influences on removing fluoride.The result indicates that carbon ribbon and nitrogen-doped ribbon could serve as good adsorbents for removing fluoride.展开更多
基金We thank the following funding agencies for supporting this work:the National Key Research and Development Program of China(Nos.2017YFA0206901 and 2018YFA0209401)the National Natural Science Foundation of China(No.21773036)+1 种基金the Science and Technology Commission of Shanghai Municipality(Nos.17JC1402000 and 19XD1420400)the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-07-E00045).
文摘The capability of electrocatalytic reducti on of carbon dioxide(CO2)using nitrogen(N)-doped carb on strongly depe nds on the N-dopi ng level and their types.In this work,we developed a strategy to generate mesoporous N-doped carb on frameworks with tun able configurati ons and contents of N dopants,by using a secondary doping process via the treatment of N,N-dimethylformamide(DMF)solvent.The obtained mesoporous N-doped carbon(denoted as MNC-D)served as an efficient electrocatalyst for electroreduction of CO2 to CO.A high Faradaic efficiency of^92%and a partial current density for CO of-6.8 mA·cm^-2 were achieved at a potential of-0.58 V vs.RHE.Electrochemical analyses further revealed that the active sites within the N-doped carb on catalysts were the pyridinic N and defects gen erated by the DMF treatme nt,which enhan ced the activati on and adsorpti on CO2 molecules.Our study suggests a new approach to develop efficie nt carb on-based catalysts for potential scalable CO2 reduction reaction(CO2RR)to fuels and chemicals.
基金Jiangsu Key Lab of Biomass Energy and Material,Grant/Award Number:JSBEMS‐202101National Natural Science Foundation of China,Grant/Award Numbers:51902162,51902162+4 种基金National Key R&D Program of China,Grant/Award Number:2022YFB4201904Foundation of Jiangsu Key Lab of Biomass Energy and Material,Grant/Award Number:JSBEM‐S‐202101National Key R&D Program,Grant/Award Number:2022YFB4201904Jiangsu Co‐Innovation Center of Efficient Processing and Utilization of Forest Resources,the International Innovation Center for Forest Chemicals and Materialsanjing Forestry University。
文摘Biomass‐derived carbon is a promising electrode material in energy storage devices.However,how to improve its low capacity and stability,and slow diffusion kinetics during lithium storage remains a challenge.In this research,we propose a“self‐assembly‐template”method to prepare B,N codoped porous carbon(BN‐C)with a nanosandwich structure and abundant pyridinic N‐B species.The nanosandwich structure can increase powder density and cycle stability by constructing a stable solid electrolyte interphase film,shortening the Li^(+)diffusion pathway,and accommodating volume expansion during repeated charging/discharging.The abundant pyridinic N‐B species can simultaneously promote the adsorption/desorption of Li^(+)/PF_(6)^(−)and reduce the diffusion barrier.The BN‐C electrode showed a high lithium‐ion storage capacity of above 1140 mAh g^(−1)at 0.05 A g^(−1)and superior stability(96.5%retained after 2000 cycles).Moreover,owing to the synergistic effect of the nanosandwich structure and pyridinic N‐B species,the assembled symmetrical BN‐C//BN‐C full cell shows a high energy density of 234.7Wh kg^(−1),high power density of 39.38 kW kg−1,and excellent cycling stability,superior to most of the other cells reported in the literature.As the density functional theory simulation demonstrated,pyridinic N‐B shows enhanced adsorption activity for Li^(+)and PF_(6)^(−),which promotes an increase in the capacity of the anode and cathode,respectively.Meanwhile,the relatively lower diffusion barrier of pyridinic N‐B promotes Li^(+)migration,resulting in good rate performance.Therefore,this study provides a new approach for the synergistic modulation of a nanostructure and an active site simultaneously to fabricate the carbon electrode material in energy storage devices.
基金the financial support from by the National Key Research and Development Program of China(No.2022YFB4101800)National Natural Science Foundation of China(No.22278298)Program for Introducing Talents of Discipline to Universities of China(No.BP0618007).
文摘Nitrogen(N)-doped carbon materials as metal catalyst supports have attracted signifi cant attention,but the eff ect of N dopants on catalytic performance remains unclear,especially for complex reaction processes such as Fischer-Tropsch synthesis(FTS).Herein,we engineered ruthenium(Ru)FTS catalysts supported on N-doped carbon overlayers on TiO_(2)nanoparticles.By regulating the carbonization temperatures,we successfully controlled the types and contents of N dopants to identify their impacts on metal-support interactions(MSI).Our fi ndings revealed that N dopants establish a favorable surface environment for electron transfer from the support to the Ru species.Moreover,pyridinic N demonstrates the highest electron-donating ability,followed by pyrrolic N and graphitic N.In addition to realizing excellent catalytic stability,strengthening the interaction between Ru sites and N dopants increases the Ru^(0)/Ru^(δ+)ratios to enlarge the active site numbers and surface electron density of Ru species to enhance the strength of adsorbed CO.Consequently,it improves the catalyst’s overall performance,encompassing intrinsic and apparent activities,as well as its ability for carbon chain growth.Accordingly,the as-synthesized Ru/TiO_(2)@CN-700 catalyst with abundant pyridine N dopants exhibits a superhigh C_(5+)time yield of 219.4 mol CO/(mol Ru·h)and C_(5+)selectivity of 85.5%.
基金support by the National Natural Science Foundation of China(U21A20306,U20A20152)Natural Science Foundation of Hebei Province(B2022202077).
文摘Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.
基金supported by the Foundation of Jiangsu Key Lab of Biomass Energy and Material(No.JSBEM-S-202101)National Natural Science Foundation of China(No.51902162)+1 种基金the Foundation Research Project of Jiangsu Province(No.BK20221338)Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources,International Innovation Center for Forest Chemicals and Materials,Nanjing Forestry University,merit-based funding for Nanjing innovation and technology projects.
文摘Electrochemical reduction of CO_(2)(CO_(2)RR)to value-added chemicals is an attractive strategy for greenhouse gas mitigation and carbon recycle.Carbon material is one of most promising electrocatalysts but its product selectivity is limited by few modulating approaches for active sites.Herein,the predominant pyridinic N-B sites(accounting for 80%to all N species)are fabricated in hierarchically porous structure of graphene nanoribbons/amorphous carbon.The graphene nanoribbons and porous structure can accelerate electron and ion/gas transport during CO_(2)RR,respectively.This carbon electrocatalyst exhibits excellent selectivity toward CO_(2)reduction to CH_(4)with the faradaic efficiency of 68%at−0.50 V vs.RHE.As demonstrated by density functional theory,a proper adsorbed energy of∗CO and∗CH_(2)O are generated on the pyridinic N-B site resulting into high CH_(4)selectivity.Therefore,this study provides a novel method to modulate active sites of carbon-based electrocatalyst to obtain high CH_(4)selectivity.
基金the National Natural Science Foundation of China(No.52100156)Natural Science Foundation of Tianjin(No.21JCQNJC00400)Shenzhen Science and Technology Program(Nos.GJHZ20200731095801005 and JCYJ20200109150210400)for offering financial support to this research。
文摘In-depth exploration of the relationship among different adsorption sites is conducive to design of efficient adsorbents for target pollutants removal from water.In this study,the experiments,multivariate non-linear regression and density functional theory calculations are applied to explore the possible synergistic effects of three nitrogen(N)-containing sites on cow dung biochar surface for sulfamethoxazole(SMX)adsorption.Notably,a strong synergistic effect between pyridinic N and pyrrolic N sites was found for sulfamethoxazole adsorption.The adsorption energies of SMX on four pyrrolic N-coupled pyridinic N structures were-1.02,-0.41,-0.49 and-0.72 e V,much higher than the sum of adsorption energies(-0.31 e V)on pyrrolic N and pyridinic N.Besides,the alteration of Mulliken charge revealed that the simultaneous presence of pyridinic N and pyrrolic N improved the electron transfer remarkably from-0.459 e and 0.094 e to-0.649 e and 0.186 e,benefiting for SMX adsorption.This work firstly explored the possible synergies of adsorption sites on biochar surface for organic contaminants removal from water,which shed new lights on the adsorption mechanism and provided valuable information to design efficient adsorbents in the field of water treatment.
基金financially supported by the National Natural Science Foundation of China(Nos.21571159 and U1704256)the Natural Science Foundation of Henan Province,China(No.212300410299)the Doctoral Research Fund of Zhengzhou University of Light Industry(No.2018BSJJ024).
文摘Single-atomic transition metal-nitrogen codoped carbon(M-N-C)are efficient substitute catalysts for noble metals to catalyze the electrochemical CO_(2) reduction reaction(CO_(2)RR).However,the uncontrolled aggregations of metal and serious loss of nitrogen species constituting the M-N_(x) active sites are frequently observed in the commonly used pyrolysis procedure.Herein,single-atomic nickel(Ni)-based sheet-like electrocatalysts with abundant Ni-N_(4) active sites were created by using a novel ammonium chloride(NH_(4)Cl)-assited pyrolysis method.Spherical aberration correction electron microscopy and X-ray absorption fine structure analysis clearly revealed that Ni species are atomically dispersed and anchored by N in Ni-N_(4) structure.The addition of NH_(4)Cl optimized the mesopore size to 7-10 nm and increased the concentrations of pyridinic N(3.54 wt%)and Ni-N_(4)(3.33 wt%)species.The synergistic catalytic effect derived from Ni-N_(4) active sites and pyridinic N species achieved an outstanding CO_(2) RR performance,presenting a high CO Faradaic efficiency(FE_(CO))up to 98% and a large CO partial current density of 8.5 mA cm^(-2) at a low potential of-0.62 V vs.RHE.Particularly,the FE_(CO) maintains above 80% within a large potential range from -0.43 to -0.73 V vs.RHE.This work provides a practical and feasible approach to building highly active single-atomic catalysts for CO_(2) conversion systems.
文摘Photocatalytic CO_(2)conversion efficiency is hampered by the rapid recombination of photogenerated charge carriers.It is effective to suppress the recombination by constructing cocatalysts on photocatalysts with high-quality interfacial contact.Herein,we develop a novel strategy to in-situ grow ultrathin/V-doped graphene(NG)layer on TiO_(2) hollow spheres(HS) with large area and intimate interfacial contact via a chemical vapor deposition(CVD).The optimized TiO^(2)/NG HS nanocomposite achieves total CO_(2)conversion rates(the sum yield of CO,CH_(3)OH and CH_(4))of 18.11μmol·g^(-1)h^(-1),which is about 4.6 times higher than blank T1O_(2)HS.Experimental results demonstrate that intimate interfacial contact and abundant pyridinic N sites can effectively facilitate photogenerated charge carrier separation and transport,realizing enhanced photocatalytic CO_(2)reduction performance.In addition,this work provides an effective strategy for in-situ construction of graphene-based photocatalysts for highly efficient photocatalytic CO_(2)conversion.
基金supported by the National Natural Science Foundation of China(Grants 51772082,51574117,and 51804106)the Research Projects of Degree and Graduate Education Teaching Reformation in Hunan Province(JG2018B031)+2 种基金the Natural Science Foundation of Hunan Province(2019JJ30002,2019JJ50061)the Guangdong Basic and Applied Basic Research Foundation(No.2019B151502045)the National Natural Science Foundation of China(Nos.51802361,51972351)
文摘Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carbon materials show great potential for potassium-ion storage,poor rate performance,and unsatisfactory cycle lifespan in existing carbon-based PIBs anode,it also cannot match the dynamics and stability of the capacitor cathode.Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials.Hence,we prepare carbon nanofibers and g-C_(3)N_(4)composites with high nitrogen contents(19.78 at%);moreover,the sum of pyrrolic N and pyridinic N is up to 59.51%.It achieves high discharge capacity(391 m Ah g^(-1)at0.05 A g^(-1)),rate capacity(141 m Ah g^(-1)at 2 A g^(-1)),and long cycling performance(201 m Ah g^(-1)at 1 A g^(-1)over 3000 cycles)when as an anode for PIBs.Furthermore,it can deliver promising discharge capacity of132 m Ah g^(-1)at 0℃.Moreover,as battery anode for potassium-ion hybrid capacitors(PIHC)device with an active carbon cathode,it delivers energy/power density(62 and 2102 W kg^(-1))as well as high reversible capacity(106 m Ah g^(-1)at 1 A g^(-1)).
基金financial support from the National Natural Science Foundation of China (Nos.51761145046,51672262, 21503064)100 Talents Program of the Chinese Academy of Sciences+1 种基金National Program for Support of Top notch Young ProfessionalFundamental Research Funds for the Central Universities (No.WK2060140003) and iChEM。
文摘Electrical double-layer capacitors are widely concerned for their high power density,long cycling life and high cycling efficiency.However,their wide application is limited by their low energy density.In this study,we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon(CoAT-NC) material.Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix,which is benefit for improving electrical conductivity and density of states of the carbon material.Therefore,an enhanced perfo rmance is expected when CoAT-NC is served as electrode in a supercapacitor device.CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte.Furthermore,a good energy density of 30 Wh/kg can be obtained in the organic electrolyte.
文摘The use of carbon‐based materials is an appealing strategy to solve the issue of excessive CO_(2) emis‐sions.In particular,metal‐free nitrogen‐doped carbon materials(mf‐NCs)have the advantages of convenient synthesis,cost‐effectiveness,and high conductivity and are ideal electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).However,the unclear identification of the active N sites and the low intrinsic activity of mf‐NCs hinder the further development of high‐performance CO_(2)RR electrocat‐alysts.Achieving precise control over the synthesis of mf‐NC catalysts with well‐defined active N‐species sites is still challenging.To this end,we adopted a facile synthesis method to construct a set of mf‐NCs as robust catalysts for CO_(2)RR.The resulting best‐performing catalyst obtained a Far‐adaic efficiency of CO of approximately 90%at−0.55 V(vs.reversible hydrogen electrode)and good stability.The electrocatalytic performance and in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy measurements collectively revealed that graphitic and pyridinic N can synergistically adsorb CO_(2) and H_(2)O and thus promote CO_(2) activation and protonation.
文摘A new mechanism of catalyst has been demonstrated in this article. With the interaction between carbon nitride(CN) and encapsulated nickel, the CN in the catalyst has been endowed with new active sites for the adsorption and activation of hydrogen while nickel itself is physically isolated from the contact with reactive molecules. For the selective hydrogenation of acetylene in large amount of ethylene, the catalyst shows excellent ethylene selectivity than the nickel catalyst itself, which is almost totally unselective. Meanwhile, the CN itself is inactive for the reaction. The results of characterization demonstrate that pyridinic nitrogen doped in the carbon matrix should be the active sites for hydrogen dissociative adsorption. The theoretical calculations further confirm the results and provide with the detail in the electron transfer between nickel and CN in the catalyst. The current results supply a new concept for design of high performance catalyst.
基金supported by the National Key R&D Program of China(2021YFB2401800)the National Natural Science Foundation of China(2217090605 and 21875022)+1 种基金the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0654 and cstc2020jcyj-msxmX0589)support from Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘提高碳材料中氮的掺杂含量,尤其是吡啶氮的含量,已被证明可以显著提升锂硫(Li-S)电池的性能.尽管在碳材料中氮掺杂具有积极作用,但在实际操作中要实现>5 at.%的高氮掺杂含量仍非易事.此外,无法调节碳材料中特定的氮种类也是研究中的一个难题.在本文中,我们通过在氩气气氛下煅烧预先经过磷化处理的泛酸钙,得到了一种三维蜂窝状的氮(N)掺杂介孔碳(PNMC),其N掺杂含量高达8.82 at.%(吡啶N含量为3.49 at.%).磷掺杂不仅有助于提高N掺杂量,还有助于提升对多硫化物的吸附能力.实验证明,在800℃下制备的PNMC组装的硫正极(S/PNMC-800)表现出优异的电化学性能,在1 C下经过300圈循环后仍有556.7 mA h g^(-1)放电比容量.本工作提出了一种调控碳材料中吡啶氮含量的简便方法,为用于锂硫电池的多功能硫载体材料的开发提供启发.
基金This work was financially supported by National Key Research and Development Program of China(2018YFB1502503).
文摘Even though various nickel-nitrogen-carbon(Ni-N-C)combinations are prospective low-cost catalysts for the CO_(2)electroreduction reaction(CO_(2)RR),which is one avenue for attaining carbon neutrality,the detailed role of different N species has hardly been investigated.Here,we report a hollow porous N-doped carbon nanofiber with NiNX-pyridinic N active species(denoted as h-Ni-N-C)developed using a facile electrospinning and SiO_(2)space-confined pyrolysis strategy.The NiNX-pyridinic N species are facilely generated during the pyrolysis process,giving rise to enhanced activity and selectivity for the CO_(2)RR.The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3%and a large current density of−15.1 mA cm^(−2)at−0.75 V versus reversible hydrogen electrode in an H-cell.Density functional theory(DFT)results show that NiN4-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN4 and pyridinic N species,without affecting the desorption of CO∗intermediate.
文摘研制高活性的Fe/N/C氧还原催化剂对于降低燃料电池成本、实现商业化应用有重要意义.为实现Fe/N/C催化剂的理性设计,需要深入研究其活性位结构.本文发展一种研究活性位结构的新策略,以预先合成好的聚间苯二胺基Fe/N/C催化剂(Pm PDA-Fe Nx/C)为起始物,对其在1000~1500 o C高温下再次进行热处理并使其失活,通过关联催化剂热处理前后的结构变化与氧还原催化性能来揭示活性位结构.实验结果表明,随着热处理温度升高,活性中心结构被破坏,铁原子析出团聚并形成纳米颗粒,氮元素挥发损失,导致催化剂失活.XPS分析显示,低结合能含氮物种的含量与催化剂的ORR活性呈良好的正相关性,表明活性中心很可能是由吡啶N和Fe-N物种构成的.
基金the financial supports from the Key R&D Program of Hunan Province,China(No.2018SK2026)the National Key R&D Program of China(No.2018YFC1802204)the National Natural Science Foundation of China(No.51634010).
文摘2D carbon ribbon/Al_(2)O_(3) was synthesized with two-dimensional metal organic frameworks 2D-MOFs as precursors using the solvothermal and calcination methods.Batch experiments of adsorption parameters such as pH,liquid/solid ratio,adsorption kinetics,adsorption thermodynamics,and anions competitions were investigated to understand the adsorptive behavior of fluoride on carbon ribbon/Al_(2)O_(3) and nitrogen-doped carbon ribbon/Al_(2)O_(3).The adsorption of fluoride on carbon ribbon/Al_(2)O_(3) could be described as the chemical and multilayer adsorption,while the adsorption of fluoride on nitrogen-doped carbon ribbon/Al_(2)O_(3) followed the chemical and monolayer adsorption phenomenon.The fluoride on nitrogen-doped carbon ribbon/Al_(2)O_(3) had a much faster adsorption rate of 3.1×10^(−7) m/s than carbon ribbon/Al_(2)O_(3),which was 1.2×10^(−7) m/s.The nitrogen-doping on carbon ribbon enhances structural defects and improves the adsorption performance of fluoride.Also,the diacetylene linkages(—C≡C—)and pyridinic-N were studied to understand their influences on removing fluoride.The result indicates that carbon ribbon and nitrogen-doped ribbon could serve as good adsorbents for removing fluoride.
