Thermocatalytic nonoxidative ethane dehydrogenation(EDH)is a promising strategy for ethene production but suffers from intense energy consumption and poor catalyst durability;exploring technology that permits efficien...Thermocatalytic nonoxidative ethane dehydrogenation(EDH)is a promising strategy for ethene production but suffers from intense energy consumption and poor catalyst durability;exploring technology that permits efficient EDH by solar energy remains a giant challenge.Herein,we present that an oxygen vacancy(O_v)-rich LaVO_(4)(LaVO_(4)-O_v)catalyst is highly active and stable for photocatalytic EDH,through a dynamic lattice oxygen(O_(latt.))and O_(v)co-mediated mechanism.Irradiated by simulated sunlight at mild conditions,LaVO_(4)-O_(v)effectively dehydrogenates undiluted ethane to produce C_(2)H_(4)and CO with a conversion of 2.3%.By loading a small amount of Pt cocatalyst,the evolution and selectivity of C_(2)H_(4)are enhanced to 275μmol h^(-1)g^(-1)and 96.8%.Of note,LaVO_(4)-O_(v)appears nearly no carbon deposition after the reaction.The isotope tracked reactions reveal that the consumed O_(latt.)recuperates by exposing the used catalyst with O_(2),thus establishing a dynamic cycle of O_(latt.)and achieving a facile catalyst regeneration to preserve its intrinsic activity.The refreshed LaVO_(4)-O_(v)exhibits superior reusability and delivers a turnover number of about 305.The O_(v)promotes photo absorption,boosts ethane adsorption/activation,and accelerates charge separation/transfer,thus improving the photocatalytic efficiency.The possible photocatalytic EDH mechanism is proposed,considering the key intermediates predicted by density functional theory(DFT)and monitored by in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).展开更多
Owing to the large exciton binding energy(>100 meV)of most organic materials,the process of exciton dissociation into free electrons and holes is seriously hindered,which plays a key role in the photocatalytic syst...Owing to the large exciton binding energy(>100 meV)of most organic materials,the process of exciton dissociation into free electrons and holes is seriously hindered,which plays a key role in the photocatalytic system.In this study,a series of chalcogen(S,Se)-substituted mesoporous covalent organic frameworks(COFs)have been synthesized for enhanced photocatalytic organic transformations.Photoelectrochemical measurements indicate that the introduction of semi-metallic Se atom and the enlargement of conjugation degree can not only reduce the exciton binding energy accelerating the charge separation,but also reduce the band gap of COFs.As a result,the COF-NUST-36 with the lowest exciton binding energy(39.5 meV)shows the highest photocatalytic performance for selective oxidation of amines(up to 98%Conv.and 97.5%Sel.).This work provides a feasible method for designing COFs with high photocatalytic activity by adjusting exciton binding energy.展开更多
Searching for high-performance thermoelectric(TE)materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck.Here we report on the discovery of metallic compounds,TiFe_(x)Cu_(2x−1)Sb and TiF...Searching for high-performance thermoelectric(TE)materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck.Here we report on the discovery of metallic compounds,TiFe_(x)Cu_(2x−1)Sb and TiFe1.33Sb,showing the thermopower exceeding many TE semiconductors and the dimensionless figure of merits zTs comparable with the state-of-the-art TE materials.A quasi-linear temperature(T)dependent electrical resistivity in 2–700 K and the logarithmic T-dependent electronic specific heat at low temperature coexist with the high thermopower,highlighting the strong intercoupling of the non-Fermi-liquid(NFL)quantum critical behavior of electrons with TE transports.Electronic structure analysis reveals a competition between the antiferromagnetic(AFM)ordering and Kondo-like spin compensation as well as a parallel two-channel Kondo effect.The T-dependent magnetic susceptibility agrees with the quantum critical scenario of strong local correlation.Our work demonstrates the correlation among high TE performance,NFL quantum criticality,and magnetic fluctuation,which opens up directions for future research.展开更多
Single-atom catalysts(SACs)have attracted extensive attention in the field of heterogeneous catalysis.However,the fabrication of SACs with high loading and hightemperature stability remains a grand challenge,especiall...Single-atom catalysts(SACs)have attracted extensive attention in the field of heterogeneous catalysis.However,the fabrication of SACs with high loading and hightemperature stability remains a grand challenge,especially on oxide supports.In this work,we have demonstrated that through strong covalent metal-support interaction,highloading and thermally stable single-atom Pt catalysts can be readily prepared by using Fe modified spinel as support.Better catalytic performance in N2O decomposition reaction is obtained on such SACs than their nanocatalyst counterpart and low-surface-area Fe2O3 supported Pt SACs.This work provides a strategy for the fabrication of high-loading and thermally stable SACs for applications at high temperatures.展开更多
1.Introduction Cemented carbides are composites of WC ceramic phases and metallic Co binders that endow them with superior hardness and excellent toughness.Hard metals are widely used as metal cutting and rock drillin...1.Introduction Cemented carbides are composites of WC ceramic phases and metallic Co binders that endow them with superior hardness and excellent toughness.Hard metals are widely used as metal cutting and rock drilling tools[1,2].Their hardness is believed to be inversely proportional to the sizes of WC grains^([3]).Grain growth inhibitors are widely employed to achieve smaller grain sizes.展开更多
In this study,we reported that flash sintering(FS)could be efficiently triggered at room temperature(25℃)by manipulating the oxygen concentration within ZnO powders via a versatile defect engineering strategy,fully d...In this study,we reported that flash sintering(FS)could be efficiently triggered at room temperature(25℃)by manipulating the oxygen concentration within ZnO powders via a versatile defect engineering strategy,fully demonstrating a promising method for the repaid prototyping of ceramics.With a low concentration of oxygen defects,FS was only activated at a high onset electric field of~2.7 kV/cm,while arcs appearing on the surfaces of samples.Strikingly,the onset electric field was decreased to<0.51 kV/cm for the activation of FS initiated,which was associated with increased oxygen concentrations coupled with increased electrical conductivity.Thereby,a general room-temperature FS strategy by introducing intrinsic structural defect is suggested for a broad range of ceramics that are prone to form high concentration of point defects.展开更多
The on-demand modulation of defects in materials for the effective modulation of optical nonlinearity is desirable,while it remains a great challenge.In this work,we demonstrate that electrochemical activation is a fa...The on-demand modulation of defects in materials for the effective modulation of optical nonlinearity is desirable,while it remains a great challenge.In this work,we demonstrate that electrochemical activation is a facile and convenient approach to modulating the broadband third-order nonlinear absorption of nanoporous tungsten oxide(WO3-x)thin film.The film does not exhibit optical nonlinearity at the initial state,while shows a distinct saturable absorption under an applied voltage of-2.5 V with the excitation of 515,800,and 1,030 nm laser.The nonlinear absorption coefficient(β_(eff))is-766.38±6.67 cm·GW^(-1) for 1,030 nm laser,-624.24±17.15 cm·GW-1 for 800 nm laser,and-120.70±11.49 cm·GW^(-1) for 515 nm laser,and the performance is competitive among inorganic saturable absorbers.The activation is accomplished in 2 min.The performance enhancement is ascribed to the formation of abundant in-gap defect states because of the reduction of the tungsten atoms,and a Pauli-blocking effect occurs during the excitation of in-gap defect states.The small feature size of WO_(3-x)(-12 nm)enables the effective and fast introduction and removal of the defects in porous film,and accordingly the fast and broadband modulation of optical nonlinearity.Our results suggest a controllable,effective,and convenient approach to tuning the nonlinear absorption of materials.展开更多
Computing the grain boundary(GB)counterparts to bulk phase diagrams represents an emerging research direction.Using a classical embrittlement model system Ga-doped Al alloy,this study demonstrates the feasibility of c...Computing the grain boundary(GB)counterparts to bulk phase diagrams represents an emerging research direction.Using a classical embrittlement model system Ga-doped Al alloy,this study demonstrates the feasibility of computing temperature-and composition-dependent GB diagrams to represent not only equilibrium thermodynamic and structural characters,but also mechanical properties.Specifically,hybrid Monte Carlo and molecular dynamics(MC/MD)simulations are used to obtain the equilibrium GB structure as a function of temperature and composition.Simulated GB structures are validated by aberrationcorrected scanning transmission electron microscopy.Subsequently,MD tensile tests are performed on the simulated equilibrium GB structures.GB diagrams are computed for not only GB adsorption and structural disorder,but also interfacial structural and chemical widths,MD ultimate tensile strength,and MD tensile toughness.This study suggests a research direction to investigate GB composition–structure–property relationships via computing GB diagrams of thermodynamic,structural,and mechanical(or potentially other)properties.展开更多
基金supported by the National Natural Science Foundation of China(82305087,82274612)General Project of China Postdoctoral Science Foundation(2022M711080)Key Research and Development Program of Henan Province(231111312900).
基金financially supported by the National Key R&D Program of China(Nos.2021YFA1502100 and 2022YFE0114800)the National Natural Science Foundation of China(No.21973014)。
文摘Thermocatalytic nonoxidative ethane dehydrogenation(EDH)is a promising strategy for ethene production but suffers from intense energy consumption and poor catalyst durability;exploring technology that permits efficient EDH by solar energy remains a giant challenge.Herein,we present that an oxygen vacancy(O_v)-rich LaVO_(4)(LaVO_(4)-O_v)catalyst is highly active and stable for photocatalytic EDH,through a dynamic lattice oxygen(O_(latt.))and O_(v)co-mediated mechanism.Irradiated by simulated sunlight at mild conditions,LaVO_(4)-O_(v)effectively dehydrogenates undiluted ethane to produce C_(2)H_(4)and CO with a conversion of 2.3%.By loading a small amount of Pt cocatalyst,the evolution and selectivity of C_(2)H_(4)are enhanced to 275μmol h^(-1)g^(-1)and 96.8%.Of note,LaVO_(4)-O_(v)appears nearly no carbon deposition after the reaction.The isotope tracked reactions reveal that the consumed O_(latt.)recuperates by exposing the used catalyst with O_(2),thus establishing a dynamic cycle of O_(latt.)and achieving a facile catalyst regeneration to preserve its intrinsic activity.The refreshed LaVO_(4)-O_(v)exhibits superior reusability and delivers a turnover number of about 305.The O_(v)promotes photo absorption,boosts ethane adsorption/activation,and accelerates charge separation/transfer,thus improving the photocatalytic efficiency.The possible photocatalytic EDH mechanism is proposed,considering the key intermediates predicted by density functional theory(DFT)and monitored by in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS).
基金financially supported by the National Natural Science Foundation of China(No.22171136)the Natural Science Foundation of Jiangsu Province(Nos.BK20220928,BK20220079)+4 种基金the Fundamental Research Funds for the Central Universities(Nos.30921011102,30922010902)the Medical Innovation and Development Project of Lanzhou University(No.lzuyxcx-2022-156)CAMS Innovation Fund for Medical Sciences(CIFMS,Nos.2019-I2M-5-074,2021-I2M-1-026,2021-I2M-3-001)the Startup Funding from Nanjing University of Science and Technology(Nos.AE89990,AE89991/376)G.Zhang acknowledges the support of the Thousand Young Talent Plan.
文摘Owing to the large exciton binding energy(>100 meV)of most organic materials,the process of exciton dissociation into free electrons and holes is seriously hindered,which plays a key role in the photocatalytic system.In this study,a series of chalcogen(S,Se)-substituted mesoporous covalent organic frameworks(COFs)have been synthesized for enhanced photocatalytic organic transformations.Photoelectrochemical measurements indicate that the introduction of semi-metallic Se atom and the enlargement of conjugation degree can not only reduce the exciton binding energy accelerating the charge separation,but also reduce the band gap of COFs.As a result,the COF-NUST-36 with the lowest exciton binding energy(39.5 meV)shows the highest photocatalytic performance for selective oxidation of amines(up to 98%Conv.and 97.5%Sel.).This work provides a feasible method for designing COFs with high photocatalytic activity by adjusting exciton binding energy.
基金This work was supported by the National Key Research and Development Program of China(Nos.2018YFA0702100 and 2019YFA0704901)National Natural Science Foundation of China(Grant Nos.92163212,51632005,U21A2054,52072234,and 51772186)+3 种基金W.Z.also acknowledges the support from the Guangdong Innovation Research Team Project(No.2017ZT07C062)Guangdong Provincial Key-Lab program(No.2019B030301001)Shenzhen Municipal Key-Lab program(ZDSYS20190902092905285)the Centers for Mechanical Engineering Research and Education at MIT and Southern University of Science and Technology,China.Computing resources were supported by the Center for Computational Science and Engineering at the Southern University of Science and Technology.We thank Dr.D.C.Wu at Thermo Fisher Scientific Company for assistance in performing atom-resolved EDS maps.
文摘Searching for high-performance thermoelectric(TE)materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck.Here we report on the discovery of metallic compounds,TiFe_(x)Cu_(2x−1)Sb and TiFe1.33Sb,showing the thermopower exceeding many TE semiconductors and the dimensionless figure of merits zTs comparable with the state-of-the-art TE materials.A quasi-linear temperature(T)dependent electrical resistivity in 2–700 K and the logarithmic T-dependent electronic specific heat at low temperature coexist with the high thermopower,highlighting the strong intercoupling of the non-Fermi-liquid(NFL)quantum critical behavior of electrons with TE transports.Electronic structure analysis reveals a competition between the antiferromagnetic(AFM)ordering and Kondo-like spin compensation as well as a parallel two-channel Kondo effect.The T-dependent magnetic susceptibility agrees with the quantum critical scenario of strong local correlation.Our work demonstrates the correlation among high TE performance,NFL quantum criticality,and magnetic fluctuation,which opens up directions for future research.
基金supported by the National Key Projects for Fundamental Research and Development of China(2016YFA0202801)the National Natural Science Foundation of China(21673226+3 种基金91645203 and 21590792)the “Transformational Technologies for Clean Energy and Demonstration”the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA21040200 and XDB17000000)supported by the Tsinghua Xuetang Talents Program
文摘Single-atom catalysts(SACs)have attracted extensive attention in the field of heterogeneous catalysis.However,the fabrication of SACs with high loading and hightemperature stability remains a grand challenge,especially on oxide supports.In this work,we have demonstrated that through strong covalent metal-support interaction,highloading and thermally stable single-atom Pt catalysts can be readily prepared by using Fe modified spinel as support.Better catalytic performance in N2O decomposition reaction is obtained on such SACs than their nanocatalyst counterpart and low-surface-area Fe2O3 supported Pt SACs.This work provides a strategy for the fabrication of high-loading and thermally stable SACs for applications at high temperatures.
基金the support from the National Natural Science Foundation of China(Nos.51871058 and 51701170)Financial support from the Project of Science and Technology Plan of Fujian Province(No.2018J01520)the Talented Youth Scientist Support Program of the Eyas Program of Fujian Province。
文摘1.Introduction Cemented carbides are composites of WC ceramic phases and metallic Co binders that endow them with superior hardness and excellent toughness.Hard metals are widely used as metal cutting and rock drilling tools[1,2].Their hardness is believed to be inversely proportional to the sizes of WC grains^([3]).Grain growth inhibitors are widely employed to achieve smaller grain sizes.
基金This work was supported by the National Natural Science Foundation of China(No.52077118)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515011778)the State Key Laboratory of New Ceramics and Fine Processing Tsinghua University(No.KFZD201903).
文摘In this study,we reported that flash sintering(FS)could be efficiently triggered at room temperature(25℃)by manipulating the oxygen concentration within ZnO powders via a versatile defect engineering strategy,fully demonstrating a promising method for the repaid prototyping of ceramics.With a low concentration of oxygen defects,FS was only activated at a high onset electric field of~2.7 kV/cm,while arcs appearing on the surfaces of samples.Strikingly,the onset electric field was decreased to<0.51 kV/cm for the activation of FS initiated,which was associated with increased oxygen concentrations coupled with increased electrical conductivity.Thereby,a general room-temperature FS strategy by introducing intrinsic structural defect is suggested for a broad range of ceramics that are prone to form high concentration of point defects.
基金supported by the National Natural Science Foundation of China(Nos.51772214,51432006,and 51701170)the Ministry of Science and Technology of China(No.2011DFG52970)+2 种基金the Ministry of Education of China(IRT14R23),111 Project(No.B13025)the Innovation Program of Shanghai Municipal Education Commission,the national youth talent support program(No.W03070073)the project of science and technology plan of Fujian Province(No.2018J01520).
文摘The on-demand modulation of defects in materials for the effective modulation of optical nonlinearity is desirable,while it remains a great challenge.In this work,we demonstrate that electrochemical activation is a facile and convenient approach to modulating the broadband third-order nonlinear absorption of nanoporous tungsten oxide(WO3-x)thin film.The film does not exhibit optical nonlinearity at the initial state,while shows a distinct saturable absorption under an applied voltage of-2.5 V with the excitation of 515,800,and 1,030 nm laser.The nonlinear absorption coefficient(β_(eff))is-766.38±6.67 cm·GW^(-1) for 1,030 nm laser,-624.24±17.15 cm·GW-1 for 800 nm laser,and-120.70±11.49 cm·GW^(-1) for 515 nm laser,and the performance is competitive among inorganic saturable absorbers.The activation is accomplished in 2 min.The performance enhancement is ascribed to the formation of abundant in-gap defect states because of the reduction of the tungsten atoms,and a Pauli-blocking effect occurs during the excitation of in-gap defect states.The small feature size of WO_(3-x)(-12 nm)enables the effective and fast introduction and removal of the defects in porous film,and accordingly the fast and broadband modulation of optical nonlinearity.Our results suggest a controllable,effective,and convenient approach to tuning the nonlinear absorption of materials.
文摘Computing the grain boundary(GB)counterparts to bulk phase diagrams represents an emerging research direction.Using a classical embrittlement model system Ga-doped Al alloy,this study demonstrates the feasibility of computing temperature-and composition-dependent GB diagrams to represent not only equilibrium thermodynamic and structural characters,but also mechanical properties.Specifically,hybrid Monte Carlo and molecular dynamics(MC/MD)simulations are used to obtain the equilibrium GB structure as a function of temperature and composition.Simulated GB structures are validated by aberrationcorrected scanning transmission electron microscopy.Subsequently,MD tensile tests are performed on the simulated equilibrium GB structures.GB diagrams are computed for not only GB adsorption and structural disorder,but also interfacial structural and chemical widths,MD ultimate tensile strength,and MD tensile toughness.This study suggests a research direction to investigate GB composition–structure–property relationships via computing GB diagrams of thermodynamic,structural,and mechanical(or potentially other)properties.