Natural biomass-derived carbon material is one promising alternative to traditional graphene-based catalyst for oxygen electrocatalysis.However,their electrocatalytic performance were constrained by the limited modula...Natural biomass-derived carbon material is one promising alternative to traditional graphene-based catalyst for oxygen electrocatalysis.However,their electrocatalytic performance were constrained by the limited modulating strategy.Herein,using N-doped commercial coconut shell-derived activated carbon(AC)as catalyst model,the controllably enhanced sp^(2)-C domains,through an flash Joule heating process,effectively improve the edge defect density and overall graphitization degree of AC catalyst,which tunes the electronic structure of N configurations and accelerates electron transfer,leading to excellent oxygen reduction reaction performance(half-wave potential of 0.884 VRHE,equivalent to commercial 20%Pt/C,with a higher kinetic current density of 5.88 mA cm^(−2))and oxygen evolution reaction activity(overpotential of 295 mV at 10 mA cm^(2)).In a Zn-air battery,the catalyst shows outstanding cycle stability(over 1200 h)and a peak power density of 121 mW cm^(−2),surpassing commercial Pt/C and RuO_(2)catalysts.Density functional theory simulation reveals that the enhanced catalytic activity arises from the axial regulation of local sp^(2)-C domains.This work establishes a robust strategy for sp^(2)-C domain modulation,offering broad applicability in natural biomass-based carbon catalysts for electrocatalysis.展开更多
CO_(2) conversion to CO via the reverse water-gas shift(RWGS)reaction is limited by a low CO_(2) conversion rate and CO selectivity.Herein,an efficient RWGS catalyst is constructed through Enteromorpha prolifera–deri...CO_(2) conversion to CO via the reverse water-gas shift(RWGS)reaction is limited by a low CO_(2) conversion rate and CO selectivity.Herein,an efficient RWGS catalyst is constructed through Enteromorpha prolifera–derived N-rich mesoporous biochar(EPBC)supported atomic-level Cu-Mo_(2)C clusters(Cu-Mo_(2)C/EPBC).Unlike traditional acti-vated carbon(AC)supported Cu-Mo_(2)C particles(Cu-Mo_(2)C/AC),the Cu-Mo_(2)C/EPBC not only presents the better graphitization degree and larger specific surface area,but also uniformly andfirmly anchors atomic-level Cu-Mo_(2)C clusters due to the existence of pyridine nitrogen.Furthermore,the pyridine N of Cu-Mo_(2)C/EPBC strengthens an unblocked electron transfer between Mo_(2)C and Cu clusters,as verified by X-ray absorption spectroscopy.As a result,the synergistic effect between pyridinic N anchoring and the clusters interaction in Cu-Mo_(2)C/EPBC facilitates an improved CO selectivity of 99.95%at 500℃ compared with traditional Cu-Mo_(2)C/AC(99.60%),as well as about 3-fold CO_(2) conversion rate.Density functional theory calculations confirm that pyr-idine N-modified carbon activates the local electronic redistribution at Cu-Mo_(2)C clusters,which contributes to the decreased energy barrier of the transition state of CO^(*)+O^(*)+2H^(*),thereby triggering the transformation of rate-limited step during the redox pathway.This biomass-derived strategy opens perspective on producing sustain-able fuels and building blocks through the RWGS reaction.展开更多
Red mud(RM)is a low-activity industrial solid waste,and its utilization as a resource is currently a hot topic.In this study,the micro characteristics of red mud at different calcination temperatures were analyzed usi...Red mud(RM)is a low-activity industrial solid waste,and its utilization as a resource is currently a hot topic.In this study,the micro characteristics of red mud at different calcination temperatures were analyzed using X-ray diffraction and scanning electron microscopy.The performance of calcined red mud was determined through mortar strength tests.Results indicate that high-temperature calcination can change the mineral composition and microstructure of red mud,and increase the surface roughness and specific surface area.At the optimal temperature of 700°C,the addition of calcined red mud still leads to a decrease in mortar strength,but its activity index and flexural coefficient increase by 16.2%and 11.9%with respect to uncalcined red mud,reaching values of 0.826 and 0.974,respectively.Compared with the control group,the synergistic activation of calcined red mud with slag can increase the compressive and flexural strength of the mortar by 12.9%and 1.5%,reaching 8.7 and 62.4 MPa,respectively.Correspondingly,the activity index and flexural coefficient of the calcined RM and GGBS(Ground Granulated Blast furnace Slag)mixtures also increase to 1.015 and 1.130,respectively.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
N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates fro...N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates from the coordinating structure between single metal site(M) and the doped nitrogen(N) in carbon matrix by forming M-N_(x)-C structure(1≤x≤4).The M-N4-C structure is widely considered to be the most stable and effective catalytic site.However,there is no in-depth research for the "x" modulation in Pt-Nx-C structure and the corresponding catalytic properties.Herein,atomically dispersed Pt on N-doped carbon(Pt-NC) with Pt-Nx-C structure(1≤x≤4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction.Different carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C structure.The Pt-NC has the predictable low half-wave potential(E_(1/2)) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81 V due to low Pt content.Remarkably,the Pt-NC shows a high onset potential(1.10 V vs RHE,determined for j=-0.1 mA cm^(2)) and a high current density of 5.2 mA cm^(-2),more positive and higher than that of Pt/C 20%(0.96 V) and 4.9 mA cm^(-2),respectively.As the structural characterization and DFT simulation confirmed,the reducing PtN coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic activity.Furthermore,the Pt-NC shows high mass activity(172 times higher than that of Pt/C 20%),better stability and methanol crossover resistance.展开更多
Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous car...Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous carbon materials composed of abundant graphene/hexagonal boron nitride(G/h-BN)heterostructures.Metal Ni powder and nanoscale h-BN sheets are used as a catalytic substrate/hard template and“nucleation seed”for the formation of the heterostructure,respectively.As-prepared G/h-BN heterostructures exhibit enhanced electrocatalytic activity toward H_(2)O_(2) generation with 86%-95%selectivity at the range of 0.45-0.75 V versus reversible hydrogen electrode(RHE)and a positive onset potential of 0.79 versus RHE(defined at a ring current density of 0.3 mA cm^(-2))in the alkaline solution.In a flow cell,G/h-BN heterostructured electrocatalyst has a H_(2)O_(2) production rate of up to 762 mmol g_(catalyst)^(-1) h^(-1) and Faradaic efficiency of over 75%during 12 h testing,superior to the reported carbon-based electrocatalysts.The density functional theory simulation suggests that the B atoms at the interface of the G/h-BN heterostructure are the key active sites.This research provides a new route to activate carbon catalysts toward highly active and selective O_(2)-to-H_(2)O_(2) conversion.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
Stone coal is a special resource, because it is associated with a variety of rare metal elements. The elemental geochemical characteristics of stone coal can provide useful information for the study of its formation a...Stone coal is a special resource, because it is associated with a variety of rare metal elements. The elemental geochemical characteristics of stone coal can provide useful information for the study of its formation and evolution history. The content of rare earth elements in stone coal has been the focus of attention. Stone coal is widely distributed in southern Shaanxi province of China. In order to study the content and distribution of rare earth elements in stone coal, and provide a plan for the comprehensive development and utilization of stone coal, this study tested the rare earth elements content of stone coal, parting and coal ash samples, respectively, compared the content of rare earth elements in stone coal, parting, coal ash with the mean value of China coal, the mean value of world coal and the abundance value of upper crust, and discussed the features of rare earth elements content in different types of samples in southern Shaanxi province of China. The average contents of rare earth elements in the samples of stone coal, parting and coal ash were calculated, and the enrichment coefficients of the samples with the mean value of China coal, the mean value of world coal and the abundance value of upper crust were listed. The distribution rules and characteristics of the contents of rare earth elements in different types of samples in southern Shaanxi province of China were summarized.展开更多
An efficiently catalytic method toward the synthesis of indolin-2-ones featuring an allylic derived C_(3)-quaternary stereocenter via an intramolecular Heck cyclization/Suzuki coupling of N-substituted-N-(2-bromopheny...An efficiently catalytic method toward the synthesis of indolin-2-ones featuring an allylic derived C_(3)-quaternary stereocenter via an intramolecular Heck cyclization/Suzuki coupling of N-substituted-N-(2-bromophenyl)acrylamides and organoboron reagents was successfully developed by using a 1,3-bis(2,6-diisopropylphenyl)acenaphthoimidazol-2-ylidene(AnIPr)-ligated oxazoline palladacycle.It enabled a very broad substrate scope tolerating different functional groups,electronic properties and steric bulkiness.Notably,it revealed a great potential to build diverse heterocycle-fused indoline alkaloids via the same intermediate 3-allyl-1,3-dimethylindolin-2-one.展开更多
High conversion rate and selectivity are challenges for CO_(2)utilization through catalytic reverse water gas shift(RWGS)reaction.Herein,a novel mesoporous biochar(MB)supported Cu-Mo_(2)C nano-interface was prepared b...High conversion rate and selectivity are challenges for CO_(2)utilization through catalytic reverse water gas shift(RWGS)reaction.Herein,a novel mesoporous biochar(MB)supported Cu-Mo_(2)C nano-interface was prepared by consecutive physical activation of coconut shells followed by carbothermal hydrogen reduction of bimetal.As compared with traditional carbon materials,this MB exhibited ultra-high specific surface area(2693 m^(2)g^(−1))and mesopore volume of mesopore(0.81 cm^(3)g^(−1))with a narrow distribution(2-5 nm),responsible for the high dispersion of binary Cu-Mo_(2)C sites,CO_(2)adsorption and mass transfer in the reaction system.Moderate carbothermal reduction led to the sufficient reduction of Mo ion with carbon matrix of MB and dispersive growth of nano Cu-Mo_(2)C binary sites(~6.1 nm)on the surface of MB.Cu+species were formed from Cu0 via electron transfer and showed high dispersion with simultaneous boosted bimetal loading due to the strong interaction between nano Mo_(2)C and Cu.These were advantageous to the intrinsic activity and stability of the Cu-Mo_(2)C binary sites and their accessibility to the reactant molecules.Under the RWGS reaction conditions of 500℃,atmospheric pressure,and 300,000 ml/g/h gas hour space velocity,the CO_(2)conversion rate over Cu-Mo_(2)C/MB reached 27.74×10^(-5)molCO_(2)/gcat/s at very low H_(2)partial pres-sure,which was more than twice that over traditional carbon supported Cu-Mo_(2)C catalysts.In addition,this catalyst exhibited 99.08%CO selectivity and high stability for more than 50 h without a decrease in activity and selectivity.This study offers a new development strategy and a promising candidate for industrial RWGS.展开更多
The structural reconstruction mechanism of lignin and cellulose-derived biochars during direct graphitization under ultra-high temperatures was intensively investigated.It was demonstrated that cellulose-derived char ...The structural reconstruction mechanism of lignin and cellulose-derived biochars during direct graphitization under ultra-high temperatures was intensively investigated.It was demonstrated that cellulose-derived char was almost composed of carbon microcrystallites,whereas lignin-derived char reserved some of its skeleton structures,and such structural difference played a vital role in the morphology of formed graphitic layers.The results illustrated that the graphitized lignin-derived sample under 2800℃had graphitic degree of 89.53%,interlayer spacing of 0.3363 nm and electronic conductivity of 104.6 S cm^(−1),while cellulose-derived sample had graphitic degree of 76.74%,layer distance of 0.3374 nm,and electronic conductivity of only 48.8 S cm^(−1).Combined with the results of structural analysis of the chars derived from lignin and cellulose,it was inferred that the stable and aromatic ring containing skeleton structure in lignin was beneficial to the ring-enlarging reconstruction and the formation of large areas of continuous graphitic layers during graphitizing process,leading to high electronic conductivity.Meanwhile,the interwoven microcrystallites in cellulose-derived char strongly restricted the expanding of continuous lamellar graphitic areas even at such ultra-high temperature,causing the formation of turbostratic structure with numerous structural defects as well,and finally resulting in relatively lower electronic conductivity.This work is expected to provide theoretical guidance for preparing high-performance functional carbon materials from lignocellulosic biomass.展开更多
基金supported by National Natural Science Foundation of China (No. 32371810)China Postdoctoral Science Foundation (2023M731702)+5 种基金National Key Research and Development Program of China (2023YFB4203702)the Foundation Research Project of Jiangsu Province (BK20221338)Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest ResourcesInternational Innovation Center for Forest Chemicals and Materials,Nanjing Forestry Universitymerit-based funding for Nanjing innovation and technology projectsthe Foundation of Jiangsu Key Lab of Biomass Energy and Material (JSBEM-S-202101)
文摘Natural biomass-derived carbon material is one promising alternative to traditional graphene-based catalyst for oxygen electrocatalysis.However,their electrocatalytic performance were constrained by the limited modulating strategy.Herein,using N-doped commercial coconut shell-derived activated carbon(AC)as catalyst model,the controllably enhanced sp^(2)-C domains,through an flash Joule heating process,effectively improve the edge defect density and overall graphitization degree of AC catalyst,which tunes the electronic structure of N configurations and accelerates electron transfer,leading to excellent oxygen reduction reaction performance(half-wave potential of 0.884 VRHE,equivalent to commercial 20%Pt/C,with a higher kinetic current density of 5.88 mA cm^(−2))and oxygen evolution reaction activity(overpotential of 295 mV at 10 mA cm^(2)).In a Zn-air battery,the catalyst shows outstanding cycle stability(over 1200 h)and a peak power density of 121 mW cm^(−2),surpassing commercial Pt/C and RuO_(2)catalysts.Density functional theory simulation reveals that the enhanced catalytic activity arises from the axial regulation of local sp^(2)-C domains.This work establishes a robust strategy for sp^(2)-C domain modulation,offering broad applicability in natural biomass-based carbon catalysts for electrocatalysis.
基金support from National Natural Science Foundation of China(32101474 and 42377249)National Key Research and Development Program of China(2023YFD2201605).
文摘CO_(2) conversion to CO via the reverse water-gas shift(RWGS)reaction is limited by a low CO_(2) conversion rate and CO selectivity.Herein,an efficient RWGS catalyst is constructed through Enteromorpha prolifera–derived N-rich mesoporous biochar(EPBC)supported atomic-level Cu-Mo_(2)C clusters(Cu-Mo_(2)C/EPBC).Unlike traditional acti-vated carbon(AC)supported Cu-Mo_(2)C particles(Cu-Mo_(2)C/AC),the Cu-Mo_(2)C/EPBC not only presents the better graphitization degree and larger specific surface area,but also uniformly andfirmly anchors atomic-level Cu-Mo_(2)C clusters due to the existence of pyridine nitrogen.Furthermore,the pyridine N of Cu-Mo_(2)C/EPBC strengthens an unblocked electron transfer between Mo_(2)C and Cu clusters,as verified by X-ray absorption spectroscopy.As a result,the synergistic effect between pyridinic N anchoring and the clusters interaction in Cu-Mo_(2)C/EPBC facilitates an improved CO selectivity of 99.95%at 500℃ compared with traditional Cu-Mo_(2)C/AC(99.60%),as well as about 3-fold CO_(2) conversion rate.Density functional theory calculations confirm that pyr-idine N-modified carbon activates the local electronic redistribution at Cu-Mo_(2)C clusters,which contributes to the decreased energy barrier of the transition state of CO^(*)+O^(*)+2H^(*),thereby triggering the transformation of rate-limited step during the redox pathway.This biomass-derived strategy opens perspective on producing sustain-able fuels and building blocks through the RWGS reaction.
基金“Key Science and Technology Project of Guangxi Department of Communications-Technology Development and Application of Cement Red Clay Stabilized Sea Sand Semi-Rigid Subgrade”(Grant:Gui Jiaotong 2020-No.150)“Key Science and Technology Project of Guangxi Department of Transportation-Key Technologies and Application Demonstrations for the Multi-Solid Waste Co-Processing of Bayer Red Mud in Large-Scale Road Construction”(Grant:Gui Jiaotong 2021-No.148).
文摘Red mud(RM)is a low-activity industrial solid waste,and its utilization as a resource is currently a hot topic.In this study,the micro characteristics of red mud at different calcination temperatures were analyzed using X-ray diffraction and scanning electron microscopy.The performance of calcined red mud was determined through mortar strength tests.Results indicate that high-temperature calcination can change the mineral composition and microstructure of red mud,and increase the surface roughness and specific surface area.At the optimal temperature of 700°C,the addition of calcined red mud still leads to a decrease in mortar strength,but its activity index and flexural coefficient increase by 16.2%and 11.9%with respect to uncalcined red mud,reaching values of 0.826 and 0.974,respectively.Compared with the control group,the synergistic activation of calcined red mud with slag can increase the compressive and flexural strength of the mortar by 12.9%and 1.5%,reaching 8.7 and 62.4 MPa,respectively.Correspondingly,the activity index and flexural coefficient of the calcined RM and GGBS(Ground Granulated Blast furnace Slag)mixtures also increase to 1.015 and 1.130,respectively.
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financially supported by the National Natural Science Foundation of China (Nos. 51572124 and 51702162)the Natural Science Foundation of Jiangsu Province (No. BK20180154and BK20180490)+1 种基金the Fundamental Research Funds for the Central Universities (No. 30920130111003)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, China)。
文摘N-doped carbon-based single-atom catalysts(NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates from the coordinating structure between single metal site(M) and the doped nitrogen(N) in carbon matrix by forming M-N_(x)-C structure(1≤x≤4).The M-N4-C structure is widely considered to be the most stable and effective catalytic site.However,there is no in-depth research for the "x" modulation in Pt-Nx-C structure and the corresponding catalytic properties.Herein,atomically dispersed Pt on N-doped carbon(Pt-NC) with Pt-Nx-C structure(1≤x≤4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction.Different carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C structure.The Pt-NC has the predictable low half-wave potential(E_(1/2)) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81 V due to low Pt content.Remarkably,the Pt-NC shows a high onset potential(1.10 V vs RHE,determined for j=-0.1 mA cm^(2)) and a high current density of 5.2 mA cm^(-2),more positive and higher than that of Pt/C 20%(0.96 V) and 4.9 mA cm^(-2),respectively.As the structural characterization and DFT simulation confirmed,the reducing PtN coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic activity.Furthermore,the Pt-NC shows high mass activity(172 times higher than that of Pt/C 20%),better stability and methanol crossover resistance.
基金supported by the“National Natural Science Foundation of China (Nos.51902162,21901154)”the FoundationResearch Project of Jiangsu Province (BK20221338)+1 种基金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,Shanghai Pujiang Program (21PJD022)the Foundation of Jiangsu Key Lab of Biomass Energy and Material (JSBEM-S-202101).
文摘Compared with the traditional heteroatom doping,employing heterostructure is a new modulating approach for carbon-based electrocatalysts.Herein,a facile ball milling-assisted route is proposed to synthesize porous carbon materials composed of abundant graphene/hexagonal boron nitride(G/h-BN)heterostructures.Metal Ni powder and nanoscale h-BN sheets are used as a catalytic substrate/hard template and“nucleation seed”for the formation of the heterostructure,respectively.As-prepared G/h-BN heterostructures exhibit enhanced electrocatalytic activity toward H_(2)O_(2) generation with 86%-95%selectivity at the range of 0.45-0.75 V versus reversible hydrogen electrode(RHE)and a positive onset potential of 0.79 versus RHE(defined at a ring current density of 0.3 mA cm^(-2))in the alkaline solution.In a flow cell,G/h-BN heterostructured electrocatalyst has a H_(2)O_(2) production rate of up to 762 mmol g_(catalyst)^(-1) h^(-1) and Faradaic efficiency of over 75%during 12 h testing,superior to the reported carbon-based electrocatalysts.The density functional theory simulation suggests that the B atoms at the interface of the G/h-BN heterostructure are the key active sites.This research provides a new route to activate carbon catalysts toward highly active and selective O_(2)-to-H_(2)O_(2) conversion.
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.
文摘Stone coal is a special resource, because it is associated with a variety of rare metal elements. The elemental geochemical characteristics of stone coal can provide useful information for the study of its formation and evolution history. The content of rare earth elements in stone coal has been the focus of attention. Stone coal is widely distributed in southern Shaanxi province of China. In order to study the content and distribution of rare earth elements in stone coal, and provide a plan for the comprehensive development and utilization of stone coal, this study tested the rare earth elements content of stone coal, parting and coal ash samples, respectively, compared the content of rare earth elements in stone coal, parting, coal ash with the mean value of China coal, the mean value of world coal and the abundance value of upper crust, and discussed the features of rare earth elements content in different types of samples in southern Shaanxi province of China. The average contents of rare earth elements in the samples of stone coal, parting and coal ash were calculated, and the enrichment coefficients of the samples with the mean value of China coal, the mean value of world coal and the abundance value of upper crust were listed. The distribution rules and characteristics of the contents of rare earth elements in different types of samples in southern Shaanxi province of China were summarized.
基金National Natural Science Foundation of China(No.22101133)Natural Science Foundation of Jiangsu Province(No.BK20200768)and Nanjing Forestry University are greatly acknowledged.
文摘An efficiently catalytic method toward the synthesis of indolin-2-ones featuring an allylic derived C_(3)-quaternary stereocenter via an intramolecular Heck cyclization/Suzuki coupling of N-substituted-N-(2-bromophenyl)acrylamides and organoboron reagents was successfully developed by using a 1,3-bis(2,6-diisopropylphenyl)acenaphthoimidazol-2-ylidene(AnIPr)-ligated oxazoline palladacycle.It enabled a very broad substrate scope tolerating different functional groups,electronic properties and steric bulkiness.Notably,it revealed a great potential to build diverse heterocycle-fused indoline alkaloids via the same intermediate 3-allyl-1,3-dimethylindolin-2-one.
基金National Natural Science Foundation of China(32101474,42377249)National Key Research and Development Program of China(2023YFD2201605).
文摘High conversion rate and selectivity are challenges for CO_(2)utilization through catalytic reverse water gas shift(RWGS)reaction.Herein,a novel mesoporous biochar(MB)supported Cu-Mo_(2)C nano-interface was prepared by consecutive physical activation of coconut shells followed by carbothermal hydrogen reduction of bimetal.As compared with traditional carbon materials,this MB exhibited ultra-high specific surface area(2693 m^(2)g^(−1))and mesopore volume of mesopore(0.81 cm^(3)g^(−1))with a narrow distribution(2-5 nm),responsible for the high dispersion of binary Cu-Mo_(2)C sites,CO_(2)adsorption and mass transfer in the reaction system.Moderate carbothermal reduction led to the sufficient reduction of Mo ion with carbon matrix of MB and dispersive growth of nano Cu-Mo_(2)C binary sites(~6.1 nm)on the surface of MB.Cu+species were formed from Cu0 via electron transfer and showed high dispersion with simultaneous boosted bimetal loading due to the strong interaction between nano Mo_(2)C and Cu.These were advantageous to the intrinsic activity and stability of the Cu-Mo_(2)C binary sites and their accessibility to the reactant molecules.Under the RWGS reaction conditions of 500℃,atmospheric pressure,and 300,000 ml/g/h gas hour space velocity,the CO_(2)conversion rate over Cu-Mo_(2)C/MB reached 27.74×10^(-5)molCO_(2)/gcat/s at very low H_(2)partial pres-sure,which was more than twice that over traditional carbon supported Cu-Mo_(2)C catalysts.In addition,this catalyst exhibited 99.08%CO selectivity and high stability for more than 50 h without a decrease in activity and selectivity.This study offers a new development strategy and a promising candidate for industrial RWGS.
基金Fundamental Research Funds of Research Institute of Chemical Industry of Forest Products,CAF(CAFYBB2019SY031)National Key R&D Program(No.2019YFB1503804).
文摘The structural reconstruction mechanism of lignin and cellulose-derived biochars during direct graphitization under ultra-high temperatures was intensively investigated.It was demonstrated that cellulose-derived char was almost composed of carbon microcrystallites,whereas lignin-derived char reserved some of its skeleton structures,and such structural difference played a vital role in the morphology of formed graphitic layers.The results illustrated that the graphitized lignin-derived sample under 2800℃had graphitic degree of 89.53%,interlayer spacing of 0.3363 nm and electronic conductivity of 104.6 S cm^(−1),while cellulose-derived sample had graphitic degree of 76.74%,layer distance of 0.3374 nm,and electronic conductivity of only 48.8 S cm^(−1).Combined with the results of structural analysis of the chars derived from lignin and cellulose,it was inferred that the stable and aromatic ring containing skeleton structure in lignin was beneficial to the ring-enlarging reconstruction and the formation of large areas of continuous graphitic layers during graphitizing process,leading to high electronic conductivity.Meanwhile,the interwoven microcrystallites in cellulose-derived char strongly restricted the expanding of continuous lamellar graphitic areas even at such ultra-high temperature,causing the formation of turbostratic structure with numerous structural defects as well,and finally resulting in relatively lower electronic conductivity.This work is expected to provide theoretical guidance for preparing high-performance functional carbon materials from lignocellulosic biomass.
