NiFe-layered double hydroxides(NiFe-LDHs)are among the most promising earth-abundant electrocatalysts for the oxygen evolution reaction(OER)in alkaline media.However,their practical application is hindered by intrinsi...NiFe-layered double hydroxides(NiFe-LDHs)are among the most promising earth-abundant electrocatalysts for the oxygen evolution reaction(OER)in alkaline media.However,their practical application is hindered by intrinsic activity limitations and poor stability,primarily due to the asymmetric adsorption of oxygen intermediates.To overcome this,the binding strength must be synergistically tuned to a moderate level to optimize catalytic performance.Here,we engineered NiFeCoCr LDH through Co doping to enhance electrical conductivity and controlled Cr leaching to introduce cationic vacancies for modulating intermediate binding strength in NiFe LDH.X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses reveal that NiFe-LDH with Co doping and Cr vacancies modulates the Ni oxidation state and local coordination environment,leading to a balanced electronic structure and enhanced structural complexity around the Ni sites.Additionally,these vacancies can trap OH^(-)/H_(2)O species,which can serve as a reservoir for OH^(-) transfer,facilitating the rapid formation of OER intermediates and enhancing catalytic performance at high current densities.As a result,V_(Cr)-NiFeCo LDH achieves 1.6 A cm^(-2)current density at 1.7 V vs.RHE while maintaining stable operation for over 1000 h at 500 mA cm^(-2).Density functional theory(DFT)calculations validate the synergistic effects of Co doping and Cr-induced vacancies on intermediate binding energies and improved OER kinetics.Overall,this work presents a rational design strategy to simultaneously enhance the activity and durability of NiFe-based OER catalysts for their application in high-performance alkaline water electrolysis.展开更多
Here we report on simultaneous lidar observations of sporadic Ni(Nis)layers and sporadic Na(Nas)layers in the atmosphere over Yanqing,Beijing(40.42°N,116.02°E)from April 2019 to October 2022.During 343 night...Here we report on simultaneous lidar observations of sporadic Ni(Nis)layers and sporadic Na(Nas)layers in the atmosphere over Yanqing,Beijing(40.42°N,116.02°E)from April 2019 to October 2022.During 343 nights of observation,68 Nis and 56 Nas were observed.The seasonal variation of Nis and Nas was also obtained,with the highest occurrence of Nis being in July(43%)and that of Nas being in June(61%).We found that the seasonal variation of Nis is similar to that of Nas and that both occur more frequently in summer than in winter.In addition,we found 23 events in which Nis and Nas occur simultaneously.The average peak altitude of Nas is approximately 1 km higher than that of Nis,and the peak density ratio of Nas to Nis is approximately 5,which is half the density ratio of the two main layers.Additionally,the strength factor for Nas is smaller than that for Nis.Through data analysis of sporadic E layers(Es),we found that Nis and Nas has a significant correlation with Es.The neutralization rates of Ni^(+)/Na^(+)were calculated according to the dissociative recombination reaction of Ni^(+)/Na^(+)and the WACCM-Ni(Whole Atmosphere Community Climate Model of Ni).The production rates of Ni and Na were estimated to be approximately 1:4.4,which is consistent with the density ratio of Nis to Nas.The results showed that the neutralization reaction of Ni+,Na+,and electrons in Es is the main reason for the formation of the Nis layer and the Nas layer.展开更多
AlGaN-based deep-ultraviolet(DUV)laser diodes(LDs)face performance challenges due to elec-tron leakage and poor hole injection which is often worsened by polarization effects from conventional elec-tron blocking layer...AlGaN-based deep-ultraviolet(DUV)laser diodes(LDs)face performance challenges due to elec-tron leakage and poor hole injection which is often worsened by polarization effects from conventional elec-tron blocking layers(EBLs).To overcome these limitations,we propose an EBL-free DUV LD design incor-porating a 1-nm undoped Al_(0.8)Ga_(0.2)N thin strip layer after the last quantum barrier.Using PICS3D simula-tions,we evaluate the optical and electrical characteristics.Results show a significant increase in effective electron barrier height(from 158.2 meV to 420.7 meV)and a reduction in hole barrier height(from 149.2 meV to 62.8 meV),which enhance hole injection and reduce electron leakage.The optimized structure(LD3)achieves a 14%increase in output power,improved slope efficiency(1.85 W/A),and lower threshold current.This design also reduces the quantum confined Stark effect and forms dual hole accumulation regions,im-proving recombination efficiency.展开更多
Interfacial engineering is crucial for developing high-performance Ni-rich layered cathodes for lithiumion batteries.Here,we introduce an interfacial precipitation(IP)strategy,guided by first-principles calculations,t...Interfacial engineering is crucial for developing high-performance Ni-rich layered cathodes for lithiumion batteries.Here,we introduce an interfacial precipitation(IP)strategy,guided by first-principles calculations,to create a functionally graded cathode during precursor synthesis.Based on thermodynamic principles of bulk insolubility and phase separation kinetics,we achieved the selective precipitation of Co onto the surface of a Ni-rich hydroxide precursor.Upon high-temperature lithiation,this engineered precursor spontaneously forms a unique,bifunctional Co-rich spinel-like layer on the final LiNi_(0.88)Co_(0.06)Mn_(0.06)O_(2)(NCM)cathode.This architecture suppresses detrimental Li/Ni cation mixing and protects the active material.Consequently,the IP-driven NCM cathode demonstrates vastly superior rate capability,delivering 140.8 m A h g^(-1)at 5C,compared to 112.9 mA h g^(-1)for its conventionally prepared counterpart.This enhancement is attributed to significantly lower charge-transfer resistance and faster kinetics.Remarkably,in a full-cell configuration,the IP-driven NCM cathode maintains 81.5%capacity after 1000 cycles at an aggressive 5C rate.This work presents a thermodynamically driven,scalable strategy for designing advanced cathodes with exceptional high-power performance and stability.展开更多
If you're tired of megacities that feel like nothing but glass,steel,and constant rush,Guangzhou moves at its own pace.Here,a 19th-century ancestral hall stands next to a 600-meter tower,and the day begins with te...If you're tired of megacities that feel like nothing but glass,steel,and constant rush,Guangzhou moves at its own pace.Here,a 19th-century ancestral hall stands next to a 600-meter tower,and the day begins with tea and delicate steamed treats instead of coffee.展开更多
Layered transition-metal compounds(LTMCs)feature stacked architectures,strong magnetic anisotropy,and tunable magnetic order,making them promising material platforms for low-power spintronic technologies and for enabl...Layered transition-metal compounds(LTMCs)feature stacked architectures,strong magnetic anisotropy,and tunable magnetic order,making them promising material platforms for low-power spintronic technologies and for enabling topological functionalities in the post-Moore era.Here we review recent progress on two-dimensional(2D)magnetism in LTMCs,emphasizing material taxonomy,intrinsic magnetic properties,and external-field controls.This review first presents a classification of LTMCs by crystal structure and chemistry—binary halides,chalcogenides,and ternary families(e.g.,MPX_(3),M_(m)X_(n)Te_(k),MnBi_(2)Te_(4))—followed by a summary of their coupling mechanisms,ordering temperatures,and dimensional effects.It then analyzes the modulation of exchange interactions,magnetic anisotropy,and topological states by electric-field gating,strain engineering,and ion intercalation,with representative experimental demonstrations.Notable advances include room-temperature ferromagnetic metals and semiconductors,observation of the quantum anomalous Hall effect(QAHE)in MnBi2Te4,and synergistic control of magnetic-topological states under multiple external stimuli.Persistent challenges involve the limited availability of intrinsic 2D magnetic semiconductors with high Curie temperatures(Tc),incomplete understanding of the microscopic couplings at interfaces and under quantum confinement,and device-level stability.We conclude by outlining opportunities that lie in the integration of multiscale characterization,first-principles theory,and cross-scale fabrication to precisely co-engineer magnetism,topology,and electronic structure,thereby advancing LTMCs toward spintronic and topological-quantum applications.展开更多
A novel trace nickel(Ni)doped tungsten(W)matrix with coated Ni on W grains was prepared by powder metallurgy method.The introduction of Ni can inhibit the reaction between W and barium-calcium aluminates(Ba-Ca alumina...A novel trace nickel(Ni)doped tungsten(W)matrix with coated Ni on W grains was prepared by powder metallurgy method.The introduction of Ni can inhibit the reaction between W and barium-calcium aluminates(Ba-Ca aluminates)during the impregnation process of the matrix.After cathode activation,the surface Ba:O molar ratio is 0.88:1.00,much higher than the Ba dispenser cathode without Ni doping.The XPS results of the cathode surface showed that the metallic Ba appeared on the activated cathode surface,forming dipoles with oxygen,and effectively reducing the cathode surface work function.The pulse electron emission current density at 1100℃_(b)(brightness temperature)was 18.26 A/cm^(2),and the calculated work function was 1.97 eV.It has a low evaporation rate and the accelerated lifetime test predict a lifetime of over 160000 h.First-principles calculations showed that the charge transfer and dipole moment in the NiW-BaO system were both increased compared to the Ba dispenser cathode,thus improving the emission performance of the Ni-W mixed matrix cathode.展开更多
基金supported by the Natural Science Foundation of China Grant No.52272289 and 5240223,and JSPS(Japan Society for the Promotion of Science)of Grant No.22K19088,23H00313,24H02202,and 24H02205。
文摘NiFe-layered double hydroxides(NiFe-LDHs)are among the most promising earth-abundant electrocatalysts for the oxygen evolution reaction(OER)in alkaline media.However,their practical application is hindered by intrinsic activity limitations and poor stability,primarily due to the asymmetric adsorption of oxygen intermediates.To overcome this,the binding strength must be synergistically tuned to a moderate level to optimize catalytic performance.Here,we engineered NiFeCoCr LDH through Co doping to enhance electrical conductivity and controlled Cr leaching to introduce cationic vacancies for modulating intermediate binding strength in NiFe LDH.X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses reveal that NiFe-LDH with Co doping and Cr vacancies modulates the Ni oxidation state and local coordination environment,leading to a balanced electronic structure and enhanced structural complexity around the Ni sites.Additionally,these vacancies can trap OH^(-)/H_(2)O species,which can serve as a reservoir for OH^(-) transfer,facilitating the rapid formation of OER intermediates and enhancing catalytic performance at high current densities.As a result,V_(Cr)-NiFeCo LDH achieves 1.6 A cm^(-2)current density at 1.7 V vs.RHE while maintaining stable operation for over 1000 h at 500 mA cm^(-2).Density functional theory(DFT)calculations validate the synergistic effects of Co doping and Cr-induced vacancies on intermediate binding energies and improved OER kinetics.Overall,this work presents a rational design strategy to simultaneously enhance the activity and durability of NiFe-based OER catalysts for their application in high-performance alkaline water electrolysis.
基金supported by the Specialized Research Fund for State Key Laboratories,Chinese Meridian Project,the Specialized Research Fund for the State Key Laboratory of Solar Activity and Space Weather,postgraduate Education Reform and Quality Improvement Project of Henan Province(Grant No.YJS2024JD32)Natural Science Foundation Project of Henan Province(Grant No.242300420253)National Natural Science Foundation of China for Young Scientists(Grant No.42504156)funding.
文摘Here we report on simultaneous lidar observations of sporadic Ni(Nis)layers and sporadic Na(Nas)layers in the atmosphere over Yanqing,Beijing(40.42°N,116.02°E)from April 2019 to October 2022.During 343 nights of observation,68 Nis and 56 Nas were observed.The seasonal variation of Nis and Nas was also obtained,with the highest occurrence of Nis being in July(43%)and that of Nas being in June(61%).We found that the seasonal variation of Nis is similar to that of Nas and that both occur more frequently in summer than in winter.In addition,we found 23 events in which Nis and Nas occur simultaneously.The average peak altitude of Nas is approximately 1 km higher than that of Nis,and the peak density ratio of Nas to Nis is approximately 5,which is half the density ratio of the two main layers.Additionally,the strength factor for Nas is smaller than that for Nis.Through data analysis of sporadic E layers(Es),we found that Nis and Nas has a significant correlation with Es.The neutralization rates of Ni^(+)/Na^(+)were calculated according to the dissociative recombination reaction of Ni^(+)/Na^(+)and the WACCM-Ni(Whole Atmosphere Community Climate Model of Ni).The production rates of Ni and Na were estimated to be approximately 1:4.4,which is consistent with the density ratio of Nis to Nas.The results showed that the neutralization reaction of Ni+,Na+,and electrons in Es is the main reason for the formation of the Nis layer and the Nas layer.
文摘AlGaN-based deep-ultraviolet(DUV)laser diodes(LDs)face performance challenges due to elec-tron leakage and poor hole injection which is often worsened by polarization effects from conventional elec-tron blocking layers(EBLs).To overcome these limitations,we propose an EBL-free DUV LD design incor-porating a 1-nm undoped Al_(0.8)Ga_(0.2)N thin strip layer after the last quantum barrier.Using PICS3D simula-tions,we evaluate the optical and electrical characteristics.Results show a significant increase in effective electron barrier height(from 158.2 meV to 420.7 meV)and a reduction in hole barrier height(from 149.2 meV to 62.8 meV),which enhance hole injection and reduce electron leakage.The optimized structure(LD3)achieves a 14%increase in output power,improved slope efficiency(1.85 W/A),and lower threshold current.This design also reduces the quantum confined Stark effect and forms dual hole accumulation regions,im-proving recombination efficiency.
基金supported by grants from the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(MSIT)(RS-2024-00407116)+1 种基金by the Ministry of Education(NRF-2018R1A6A1A03024231)support from the NRF grant funded by the MSIT(RS-2024-00406724)。
文摘Interfacial engineering is crucial for developing high-performance Ni-rich layered cathodes for lithiumion batteries.Here,we introduce an interfacial precipitation(IP)strategy,guided by first-principles calculations,to create a functionally graded cathode during precursor synthesis.Based on thermodynamic principles of bulk insolubility and phase separation kinetics,we achieved the selective precipitation of Co onto the surface of a Ni-rich hydroxide precursor.Upon high-temperature lithiation,this engineered precursor spontaneously forms a unique,bifunctional Co-rich spinel-like layer on the final LiNi_(0.88)Co_(0.06)Mn_(0.06)O_(2)(NCM)cathode.This architecture suppresses detrimental Li/Ni cation mixing and protects the active material.Consequently,the IP-driven NCM cathode demonstrates vastly superior rate capability,delivering 140.8 m A h g^(-1)at 5C,compared to 112.9 mA h g^(-1)for its conventionally prepared counterpart.This enhancement is attributed to significantly lower charge-transfer resistance and faster kinetics.Remarkably,in a full-cell configuration,the IP-driven NCM cathode maintains 81.5%capacity after 1000 cycles at an aggressive 5C rate.This work presents a thermodynamically driven,scalable strategy for designing advanced cathodes with exceptional high-power performance and stability.
文摘If you're tired of megacities that feel like nothing but glass,steel,and constant rush,Guangzhou moves at its own pace.Here,a 19th-century ancestral hall stands next to a 600-meter tower,and the day begins with tea and delicate steamed treats instead of coffee.
基金supported by the National KeyR&D Program of China(Grant No.2024YFB3817400)the National Natural Science Foundation of China(Grants No.12274276 and No.U24A6002)+1 种基金the Natural Science Foundation of Shanxi Province(China)(Grant No.202403021223008)Supported by Scientific and Technology Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2024Q017 and No.2025L043).
文摘Layered transition-metal compounds(LTMCs)feature stacked architectures,strong magnetic anisotropy,and tunable magnetic order,making them promising material platforms for low-power spintronic technologies and for enabling topological functionalities in the post-Moore era.Here we review recent progress on two-dimensional(2D)magnetism in LTMCs,emphasizing material taxonomy,intrinsic magnetic properties,and external-field controls.This review first presents a classification of LTMCs by crystal structure and chemistry—binary halides,chalcogenides,and ternary families(e.g.,MPX_(3),M_(m)X_(n)Te_(k),MnBi_(2)Te_(4))—followed by a summary of their coupling mechanisms,ordering temperatures,and dimensional effects.It then analyzes the modulation of exchange interactions,magnetic anisotropy,and topological states by electric-field gating,strain engineering,and ion intercalation,with representative experimental demonstrations.Notable advances include room-temperature ferromagnetic metals and semiconductors,observation of the quantum anomalous Hall effect(QAHE)in MnBi2Te4,and synergistic control of magnetic-topological states under multiple external stimuli.Persistent challenges involve the limited availability of intrinsic 2D magnetic semiconductors with high Curie temperatures(Tc),incomplete understanding of the microscopic couplings at interfaces and under quantum confinement,and device-level stability.We conclude by outlining opportunities that lie in the integration of multiscale characterization,first-principles theory,and cross-scale fabrication to precisely co-engineer magnetism,topology,and electronic structure,thereby advancing LTMCs toward spintronic and topological-quantum applications.
基金supported by the National Natural Science Foundation of China(Nos.U2341209 and 52130407).
文摘A novel trace nickel(Ni)doped tungsten(W)matrix with coated Ni on W grains was prepared by powder metallurgy method.The introduction of Ni can inhibit the reaction between W and barium-calcium aluminates(Ba-Ca aluminates)during the impregnation process of the matrix.After cathode activation,the surface Ba:O molar ratio is 0.88:1.00,much higher than the Ba dispenser cathode without Ni doping.The XPS results of the cathode surface showed that the metallic Ba appeared on the activated cathode surface,forming dipoles with oxygen,and effectively reducing the cathode surface work function.The pulse electron emission current density at 1100℃_(b)(brightness temperature)was 18.26 A/cm^(2),and the calculated work function was 1.97 eV.It has a low evaporation rate and the accelerated lifetime test predict a lifetime of over 160000 h.First-principles calculations showed that the charge transfer and dipole moment in the NiW-BaO system were both increased compared to the Ba dispenser cathode,thus improving the emission performance of the Ni-W mixed matrix cathode.
