The feature of conduction band （CB） of Tensile-Strained Si（TS-Si） on a relaxed Si1-xGex substrate is systematically investigated, including the number of equivalent CB edge energy extrema, CB energy minima, the po...The feature of conduction band （CB） of Tensile-Strained Si（TS-Si） on a relaxed Si1-xGex substrate is systematically investigated, including the number of equivalent CB edge energy extrema, CB energy minima, the position of the extremal point, and effective mass. Based on an analysis of symmetry under strain, the number of equivalent CB edge energy extrema is presented; Using the K.P method with the help of perturbation theory, dispersion relation near minima of CB bottom energy, derived from the linear deformation potential theory, is determined, from which the parameters, namely, the position of the extremal point, and the longitudinal and transverse masses （m1^＊ and mt^＊）are obtained.展开更多
SnSe crystals have been discovered as one of the most efficient thermoelectric materials due to their remarkable thermal and electrical transports. But the polycrystalline SnSe possesses much lower performance especia...SnSe crystals have been discovered as one of the most efficient thermoelectric materials due to their remarkable thermal and electrical transports. But the polycrystalline SnSe possesses much lower performance especially for the low carrier mobility and electrical conductivity. We firstly attempted to explain and verify the difference in the electrical conductivity as a function of temperature between p-type crystalline and polycrystalline SnSe by considering the grain boundary effects in the polycrystalline samples. On the basis of 2% Na doping to optimize the carrier concentration, the carrier mobility is improved by further introducing In, leading to enhanced carrier mobility from 3 to 9 cm2·V^(-1)·s^(-1) in polycrystalline SnSe. Moreover, In doping introduces extra resonant levels in SnSe, which increases the density of states near Fermi level and leads to an enhanced band effective mass. Large Seebeck coefficient of ~205 l V·K^(-1) at 300 K and maximum power factor of ~7.5 l W·cm^(-1)·K^(-2) at 773 K can be obtained in the Sn_(0.975)Na_(0.02)In_(0.005) Se sample,leading to a competitively high dimensionless figure of merit(ZT) value exceeding 1.1 at 773 K.展开更多
It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without...It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.MoSe_(2),as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/MoSe_(2) nanocomposite was fabricated and phosphoric acid was used to dope phosphorus in BC,in which MoSe_(2) microspheres were dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and MoSe_(2) is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches−53.33 dB with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(−66.84 dB)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.This work is expected to enlighten future exploration of biomass carbon materials on high-performance microwave absorption materials.展开更多
Relationship between the activity for photocatalytic H_(2)O overall splitting(HOS)and the electron occupancy on d orbits of the active component in photocatalysts shows volcanic diagram,and specially the d^(10)electro...Relationship between the activity for photocatalytic H_(2)O overall splitting(HOS)and the electron occupancy on d orbits of the active component in photocatalysts shows volcanic diagram,and specially the d^(10)electronic configuration in valley bottom exhibits inert activity,which seriously fetters the development of catalytic materials with great potentials.Herein,In d^(10)electronic configuration of In_(2)O_(3)was activated by phosphorus atoms replacing its lattice oxygen to regulate the collocation of the ascended In 5p-band(Inɛ5p)and descended O 2p-band(Oɛ2p)centers as efficient active sites for chemisorption to*OH and*H during forward HOS,respectively,along with a declined In 4d-band center(Inɛ4d)to inhibit its backward reaction.A stable STH efficiency of 2.23%under AM 1.5 G irradiation at 65°C has been obtained over the activated d^(10)electronic configuration with a lowered activation energy for H_(2)evolution,verified by femtosecond transient absorption spectroscopy,in situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations of dynamics.These findings devote to activating d^(10)electronic configuration for resolving the reaction energy barrier and dynamical bottleneck of forward HOS,which expands the exploration of high-efficiency catalytic materials.展开更多
超远距离探测雷达主要使用了P波段雷达波,铁氧体、金属微粉等传统吸波材料对P波段雷达波的吸收效果不理想。基于有效媒质理论,制备了镍锌铁氧体与铁粉的复合材料作为吸波材料,提升P波段电磁波的吸波效果,并分析讨论了镍锌铁氧体与铁粉...超远距离探测雷达主要使用了P波段雷达波,铁氧体、金属微粉等传统吸波材料对P波段雷达波的吸收效果不理想。基于有效媒质理论,制备了镍锌铁氧体与铁粉的复合材料作为吸波材料,提升P波段电磁波的吸波效果,并分析讨论了镍锌铁氧体与铁粉不同配比对复合材料在P波段的电磁参数及吸波性能的影响。结果表明:随着铁粉含量增加,复合材料的介电常数逐渐增大,磁导率逐渐降低;当铁粉的质量分数为20%,厚度为10mm,所制得的复合材料的吸波性能最好,其在700~880M Hz反射损耗小于-20 d B。镍锌铁氧体与铁粉的复合材料体现了对P波段电磁波吸收和屏蔽作用的潜力。展开更多
Layered materials with adjustable framework,as the most potential cathode materials for aqueous rechargeable zinc ion batterie,have high capacity,permit of rapid ion diffusion,and charge transfer channels.Previous stu...Layered materials with adjustable framework,as the most potential cathode materials for aqueous rechargeable zinc ion batterie,have high capacity,permit of rapid ion diffusion,and charge transfer channels.Previous studies have widely investigated their preparation and storage mechanism,but the intrinsic relationship between the structural design of layered cathode materials and electrochemical performance has not been well established.In this work,based on the first principles calculations and experiments,a crucial strategy of pre-intercalated metalions in vanadium oxide interlayer with administrable p-band center(ε_(p))of O is explored to enhance Zn^(2+)storage.This regulation of the degree of covalent bond and the average charge of O atoms varies the binding energy between Zn^(2+)and O,thus affecting the intercalation/de-intercalation of Zn2þ.The present study demonstrates thatεp of O can be used as an important indicator to boost Zn2þstorage,which provides a new concept toward the controlled design and application of layered materials.展开更多
The past decade has witnessed a surge of interest in exploring emergent particles in condensed matter systems.Novel particles,emerged as excitations around exotic band degeneracy points,continue to be reported in real...The past decade has witnessed a surge of interest in exploring emergent particles in condensed matter systems.Novel particles,emerged as excitations around exotic band degeneracy points,continue to be reported in real materials and artificially engineered systems,but so far,we do not have a complete picture on all possible types of particles that can be achieved.Here,via systematic symmetry analysis and modeling,we accomplish a complete list of all possible particles in time-reversal-invariant systems.This includes both spinful particles such as electron quasiparticles in solids,and spinless particles such as phonons or even excitations in electric-circuit and mechanical networks.We establish detailed correspondence between the particle,the symmetry condition,the effective model,and the topological character.This obtained encyclopedia concludes the search for novel emergent particles and provides concrete guidance to achieve them in physical systems.展开更多
The oxygen evolution reaction(OER)electrocatalysts,which can keep active for a long time in acidic media,are of great significance to proton exchange membrane water electrolyzers.Here,Ru-Co_(3)O_(4)electrocatalysts wi...The oxygen evolution reaction(OER)electrocatalysts,which can keep active for a long time in acidic media,are of great significance to proton exchange membrane water electrolyzers.Here,Ru-Co_(3)O_(4)electrocatalysts with transition metal oxide Co_(3)O_(4)as matrix and the noble metal Ru as doping element have been prepared through an ion exchange–pyrolysis process mediated by metal-organic framework,in which Ru atoms occupy the octahedral sites of Co_(3)O_(4).Experimental and theoretical studies show that introduced Ru atoms have a passivation effect on lattice oxygen.The strong coupling between Ru and O causes a negative shift in the energy position of the O p-band centers.Therefore,the bonding activity of oxygen in the adsorbed state to the lattice oxygen is greatly passivated during the OER process,thus improving the stability of matrix material.In addition,benefiting from the modulating effect of the introduced Ru atoms on the metal active sites,the thermodynamic and kinetic barriers have been significantly reduced,which greatly enhances both the catalytic stability and reaction efficiency of Co_(3)O_(4).展开更多
Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level....Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level.Herein,CNFs anchored with cobalt nanocluster(CNFs-Co)were prepared using chemical vapor deposition and thermal reduction methods.The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91%and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs.Meanwhile,the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g.These excellent electrochemical properties could be attributed to the involved spin state Co,which endows CNFs with large interplanar spacing(0.39 nm)and abundant vacancy defects.Importantly,the spin state Co downshifts the p-band center of carbon and strengthens the Na+adsorption energy from-2.33 eV to-2.64 eV based on density functional theory calculation.This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.展开更多
文摘The feature of conduction band （CB） of Tensile-Strained Si（TS-Si） on a relaxed Si1-xGex substrate is systematically investigated, including the number of equivalent CB edge energy extrema, CB energy minima, the position of the extremal point, and effective mass. Based on an analysis of symmetry under strain, the number of equivalent CB edge energy extrema is presented; Using the K.P method with the help of perturbation theory, dispersion relation near minima of CB bottom energy, derived from the linear deformation potential theory, is determined, from which the parameters, namely, the position of the extremal point, and the longitudinal and transverse masses （m1^＊ and mt^＊）are obtained.
基金financially supported by the National Key Research and Development Program of China (Nos.2018YFA0702100 and 2018YFB0703600)the National Natural Science Foundation of China (Nos.51772012 and 51671015)+3 种基金Beijing Natural Science Foundation (No.JQ18004)National Postdoctoral Program for Innovative Talents (No.BX20200028)the support from the National Science Fund for Distinguished Young Scholars (No.51925101)the high performance computing (HPC) resources at Beihang University。
文摘SnSe crystals have been discovered as one of the most efficient thermoelectric materials due to their remarkable thermal and electrical transports. But the polycrystalline SnSe possesses much lower performance especially for the low carrier mobility and electrical conductivity. We firstly attempted to explain and verify the difference in the electrical conductivity as a function of temperature between p-type crystalline and polycrystalline SnSe by considering the grain boundary effects in the polycrystalline samples. On the basis of 2% Na doping to optimize the carrier concentration, the carrier mobility is improved by further introducing In, leading to enhanced carrier mobility from 3 to 9 cm2·V^(-1)·s^(-1) in polycrystalline SnSe. Moreover, In doping introduces extra resonant levels in SnSe, which increases the density of states near Fermi level and leads to an enhanced band effective mass. Large Seebeck coefficient of ~205 l V·K^(-1) at 300 K and maximum power factor of ~7.5 l W·cm^(-1)·K^(-2) at 773 K can be obtained in the Sn_(0.975)Na_(0.02)In_(0.005) Se sample,leading to a competitively high dimensionless figure of merit(ZT) value exceeding 1.1 at 773 K.
基金This work was supported by the National Natural Science Foundation of China(Nos.51673040 and 21978048)the Natural Science Foundation of Jiangsu Province(Nos.BK20171357 and BK20180366)+4 种基金Opening Project of Guangxi Key Laboratory of Clean Pulp&Papermaking and Pollution Control(No.GD201802-5)the Fundamental Research Funds for Central Universities(No.2242019k30042)Scientific Innovation Research Foundation of College Graduate in Jiangsu Province(No.KYCX19_0103)Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(No.1107047002)Fund Project for Transformation of Scientific and Technological Achievements of Jiangsu Province of China(No.BA2018045).
文摘It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.MoSe_(2),as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/MoSe_(2) nanocomposite was fabricated and phosphoric acid was used to dope phosphorus in BC,in which MoSe_(2) microspheres were dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and MoSe_(2) is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches−53.33 dB with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(−66.84 dB)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.This work is expected to enlighten future exploration of biomass carbon materials on high-performance microwave absorption materials.
文摘Relationship between the activity for photocatalytic H_(2)O overall splitting(HOS)and the electron occupancy on d orbits of the active component in photocatalysts shows volcanic diagram,and specially the d^(10)electronic configuration in valley bottom exhibits inert activity,which seriously fetters the development of catalytic materials with great potentials.Herein,In d^(10)electronic configuration of In_(2)O_(3)was activated by phosphorus atoms replacing its lattice oxygen to regulate the collocation of the ascended In 5p-band(Inɛ5p)and descended O 2p-band(Oɛ2p)centers as efficient active sites for chemisorption to*OH and*H during forward HOS,respectively,along with a declined In 4d-band center(Inɛ4d)to inhibit its backward reaction.A stable STH efficiency of 2.23%under AM 1.5 G irradiation at 65°C has been obtained over the activated d^(10)electronic configuration with a lowered activation energy for H_(2)evolution,verified by femtosecond transient absorption spectroscopy,in situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations of dynamics.These findings devote to activating d^(10)electronic configuration for resolving the reaction energy barrier and dynamical bottleneck of forward HOS,which expands the exploration of high-efficiency catalytic materials.
文摘超远距离探测雷达主要使用了P波段雷达波,铁氧体、金属微粉等传统吸波材料对P波段雷达波的吸收效果不理想。基于有效媒质理论,制备了镍锌铁氧体与铁粉的复合材料作为吸波材料,提升P波段电磁波的吸波效果,并分析讨论了镍锌铁氧体与铁粉不同配比对复合材料在P波段的电磁参数及吸波性能的影响。结果表明:随着铁粉含量增加,复合材料的介电常数逐渐增大,磁导率逐渐降低;当铁粉的质量分数为20%,厚度为10mm,所制得的复合材料的吸波性能最好,其在700~880M Hz反射损耗小于-20 d B。镍锌铁氧体与铁粉的复合材料体现了对P波段电磁波吸收和屏蔽作用的潜力。
基金Ziyi Feng is now pursuing her Doctor degree in the School of Dalian University of Technology.She current research interest mainly lies in the aqueous Zn-ion batteriesCorresponding author:Yifu Zhang works in School of Chemistry at Dalian University of Technology(DUT).He received his Bachelor's degree(2008)and Ph.D.degree(2013)from Wuhan University.During 2018.12-2019.12,he worked with Prof.John Wang as a visiting scholar at the Department of Materials Science and Engineering,National University of Singapore.His current research focuses on vanadium oxides,silicates and their carbon composites for energy storage and conversation including supercapacitors,aqueous Zn-ion batteries,and oxygen evolution reaction.He has published more than 200 papers in peerreviewed journals.He is selected as Elsevier China Highly Cited Scholarand RSC Highly Cited Top 1%,E-mail addresses:yfzhang@dlut.edu.cnCorresponding author:Tao Hu,E-mail addresses:inorchem@dlut.edu.cn。
文摘Layered materials with adjustable framework,as the most potential cathode materials for aqueous rechargeable zinc ion batterie,have high capacity,permit of rapid ion diffusion,and charge transfer channels.Previous studies have widely investigated their preparation and storage mechanism,but the intrinsic relationship between the structural design of layered cathode materials and electrochemical performance has not been well established.In this work,based on the first principles calculations and experiments,a crucial strategy of pre-intercalated metalions in vanadium oxide interlayer with administrable p-band center(ε_(p))of O is explored to enhance Zn^(2+)storage.This regulation of the degree of covalent bond and the average charge of O atoms varies the binding energy between Zn^(2+)and O,thus affecting the intercalation/de-intercalation of Zn2þ.The present study demonstrates thatεp of O can be used as an important indicator to boost Zn2þstorage,which provides a new concept toward the controlled design and application of layered materials.
基金supported by the National Key R&D Program of China(2020YFA0308800,2016YFA0300600,and 2017YFB0701600)the National Natural Science Foundation of China(11734003,12061131002,12004028,and 12004035)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)the China Postdoctoral Science Foundation(2020M670106)the Singapore Ministry of Education AcRF Tier 2(MOE2019-T2-1-001)Beijing Institute of Technology Research Fund Program for Young Schola。
文摘The past decade has witnessed a surge of interest in exploring emergent particles in condensed matter systems.Novel particles,emerged as excitations around exotic band degeneracy points,continue to be reported in real materials and artificially engineered systems,but so far,we do not have a complete picture on all possible types of particles that can be achieved.Here,via systematic symmetry analysis and modeling,we accomplish a complete list of all possible particles in time-reversal-invariant systems.This includes both spinful particles such as electron quasiparticles in solids,and spinless particles such as phonons or even excitations in electric-circuit and mechanical networks.We establish detailed correspondence between the particle,the symmetry condition,the effective model,and the topological character.This obtained encyclopedia concludes the search for novel emergent particles and provides concrete guidance to achieve them in physical systems.
基金the National Natural Science Foundation of China(Nos.12025503,U23B2072,and 12105208)。
文摘The oxygen evolution reaction(OER)electrocatalysts,which can keep active for a long time in acidic media,are of great significance to proton exchange membrane water electrolyzers.Here,Ru-Co_(3)O_(4)electrocatalysts with transition metal oxide Co_(3)O_(4)as matrix and the noble metal Ru as doping element have been prepared through an ion exchange–pyrolysis process mediated by metal-organic framework,in which Ru atoms occupy the octahedral sites of Co_(3)O_(4).Experimental and theoretical studies show that introduced Ru atoms have a passivation effect on lattice oxygen.The strong coupling between Ru and O causes a negative shift in the energy position of the O p-band centers.Therefore,the bonding activity of oxygen in the adsorbed state to the lattice oxygen is greatly passivated during the OER process,thus improving the stability of matrix material.In addition,benefiting from the modulating effect of the introduced Ru atoms on the metal active sites,the thermodynamic and kinetic barriers have been significantly reduced,which greatly enhances both the catalytic stability and reaction efficiency of Co_(3)O_(4).
基金the National Natural Science Foundation of China(Nos.52271011,52102291).
文摘Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level.Herein,CNFs anchored with cobalt nanocluster(CNFs-Co)were prepared using chemical vapor deposition and thermal reduction methods.The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91%and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs.Meanwhile,the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g.These excellent electrochemical properties could be attributed to the involved spin state Co,which endows CNFs with large interplanar spacing(0.39 nm)and abundant vacancy defects.Importantly,the spin state Co downshifts the p-band center of carbon and strengthens the Na+adsorption energy from-2.33 eV to-2.64 eV based on density functional theory calculation.This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.
