Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable ...Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.展开更多
Electrochemical converting NO_(2)^(-)into NH_(3)(NO_(2)RR)holds an enormous prospect to attain efficient NH_(3) electrosynthesis and polluted NO_(2)^(-)mitigation.Herein,we report single-atom Co alloyed Ru(Co_(1)Ru)as...Electrochemical converting NO_(2)^(-)into NH_(3)(NO_(2)RR)holds an enormous prospect to attain efficient NH_(3) electrosynthesis and polluted NO_(2)^(-)mitigation.Herein,we report single-atom Co alloyed Ru(Co_(1)Ru)as an efficient and durable NO_(2)RR catalyst.Extensive experimental and theoretical investigations reveal that single-atom Co alloying of Ru enables the construction of Co_(1)-Ru heteronuclear active sites to synergistically promote NO_(2)^(-)activation/hydrogenation while suppressing the competitive H_(2) evolution,rendering the greatly enhanced activity and selectivity of Co_(1)Ru towards the NO_(2)RR.Consequently,Co_(1)Ru assembled within a flow cell exhibits an impressive NH_(3) yield rate of 2379.2μmol·h^(-1)·cm^(-2) with an NH_(3)-Faradaic efficiency of 92%at a high current density of 415.9 mA·cm^(-2),which is among the highest NO_(2)RR performances reported to date.展开更多
The development of electrocatalysts toward the hydrogen evolution reaction(HER)with high-current-density capability is critical for the practical application of water splitting for hydrogen production.While Pt-based m...The development of electrocatalysts toward the hydrogen evolution reaction(HER)with high-current-density capability is critical for the practical application of water splitting for hydrogen production.While Pt-based materials are regarded as the most efficient HER catalysts,they suffer from scarcity and high price.Thus,it is of vital importance to lower the loading of Pt while maintaining high activity.Here,we report the fabrication of a monolithic aligned porous carbon film electrode co-modified with Pt single atoms and Pt nanoclusters(Pt SA/NC-AF)containing ultralow Pt content(0.038 wt.%)via a facile electrochemical deposition process.Benefiting from the aligned porous structure of the carbon film and the high exposure of the Pt species,the optimized Pt SA/NCAF electrode exhibits outstanding HER performance in 0.5 M H_(2)SO_(4)with exceptional intrinsic activity(turnover frequency(TOF)=904.9 s^(−1)atη=100 mV)and ultrahigh mass activity(888.6 A·mg_(Pt)^(−1)atη=100 mV).Further,it can deliver an industrially relevant current density of 1,000 mA·cm−2 at an overpotential as low as 139 mV.This work provides a feasible avenue for the rational design of metal single-atom and nanocluster catalysts and additionally promotes the application of ultralow-loading noble metal-based catalysts in high-rate hydrogen production.展开更多
The topography and electrical properties are two crucial characteristics that determine the roles and functionalities of materials.Conductive atomic force microscopy(CAFM)is widely recognized for its ability to indepe...The topography and electrical properties are two crucial characteristics that determine the roles and functionalities of materials.Conductive atomic force microscopy(CAFM)is widely recognized for its ability to independently measure the topography and conductivity.The increasing trend towards miniaturization in electrical devices and sensors has encouraged an urgent demand for enhancing the accuracy of CAFM characterization.However,when performing CAFM tests on Bi_(0.5)Na_(0.5)TiO_(3)bulk ceramic,it is interesting to observe significant currents related to the topography.Why do insulators exhibit“conductivity”in CAFM testing?Herein,we thoroughly investigated the topography-dependent current during CAFM testing for the first time.Based on the linear dependence between the current and the first derivative of topography,the calibration method has been proposed to eliminate the topographic crosstalk.This method is evaluated on Bi_(0.5)Na_(0.5)TiO_(3)bulk ceramic,one-dimensional(1D)ZnO nanowire,twodimensional(2D)NbOI_(2)flake,and biological lotus leaf.The corresponding results of negligible topography-interference current affirm the feasibility and universality of this calibration method.This work effectively addresses the challenge of topographic crosstalk in CAFM characterization,thereby preventing the erroneous estimation of the conductivity of any unknown sample.展开更多
We study the spatial structure of a Bose-Einstein condensate(BEC)with a space-dependent s-wave scattering length in a combined trap.There exists a space-dependent nonlinear atomic current in the system.The atomic curr...We study the spatial structure of a Bose-Einstein condensate(BEC)with a space-dependent s-wave scattering length in a combined trap.There exists a space-dependent nonlinear atomic current in the system.The atomic current has an important influence on the spatial structure of the BEC.Research findings reveal that a large chemical potential can effectively suppress the chaotic spatial structure in the BEC system.Due to the large chemical potential,a strong atomic current is necessary to make the system lose its periodic spatial structure and lead the system into a chaotic spatial structure.But when the atomic current intensity exceeds a critical value,the chaotic spatial structure of the BEC will be completely eliminated and the system will always be kept in a series of single-periodic states as the atomic current becomes stronger.For a very weak atomic current,the spatial structure of the BEC is very sensitive to the intensity of the atomic current and a very small change of the intensity can dramatically change the spatial structure of the BEC.The effects of the combined trap parameters on the spatial structure of BECs are also discussed.展开更多
Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion flu...Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion fluxes at 4-min temporal resolution derived from ENA data in the energy ranges 50-81 and 81-158 keV are compared with in situ particle fluxes measured by the LANL-SOPA instruments aboard LANL-01, LANL-02, LANL-97, and LANL-84 （a series of geostationary satellites that encircle the equatorial plane at -6.6 RE）. Also, magnetic fields measured simultaneously by the magetometers aboard GOES-10 and GOES-12 （which are also geostationary satellites） are compared with the particle data. It is demonstrated that ion fluxes in the ring current were enhanced during geomagnetic field tailward stretching in the growth phases of substorms rather than after Earthward directed dipolarization events. This observation, which challenges the existing concept that ring current particles are injected Earthward from the magnetotail following dipolarization events, requires further investigation using a large number of magnetic storm events.展开更多
Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents...Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents the periodic change along with the aggrandizement of the magnetic flux and the number of lattice sites NR in the mesoscopic ring, and for the antiparallel spin alignment the Kondo resonances for spin-up and spin-down configurations appear at the same position. However, for the parallel spin alignment, the Kondo resonance splits for the spin-up and spin-down configurations.展开更多
A new scheme to realize a two-dimensional （2D） array of magnetic micro-lenses for a cold atomic beam. formed by an array of square current-carrying wires, is proposed. We calculate the spatial distributions of the m...A new scheme to realize a two-dimensional （2D） array of magnetic micro-lenses for a cold atomic beam. formed by an array of square current-carrying wires, is proposed. We calculate the spatial distributions of the magnetic fields from the array of current-carrying wires and the magnetic focusing potential for cold rubidium atoms, and study the dynamic focusing processes of cold atoms passing through the mag- netic micro-lens array and its focusing properties by using Monte-Carlo simulations and trajectory tracing method. The result shows that the proposed micro-lens array can be used to focus effectively a cold atomic beam, even to load ultracold atoms or a BEC sample into a 2D optical lattice formed by blue detuned hollow beams.展开更多
基金supported by the National Natural Science Foundation of China(No.21676300)the Shandong Provincial Natural Science Foundation(No.ZR2018MB035)+3 种基金the Fundamental Research Funds for the Central Universities(Nos.19CX02008A and 16CX06007A)PetroChina Innovation Foundation(No.2019D-5007-0401)Taishan Scholars Program of Shandong Province(No.tsqn201909065)Tsinghua University Initiative Scientific Research Program.
文摘Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion.In this regard,meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary.Herein,a coordination environment inheriting strategy is presented for designing low-coordination Ni^(2+)octahedra(L-Ni-8)atomic interface at a high concentration(4.6 at.%).Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode.To improve the efficiency of using the self-modification reaction environment at L-Ni-8,all of the structural features,including high atom economy,mass transfer,and electron transfer,are integrated together from atomic-scale to macro-scale.At high current density of 500 mA/cm2,the samples synthesized at gram-scale can deliver low hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)overpotentials of 262 and 348 mV,respectively.
文摘Electrochemical converting NO_(2)^(-)into NH_(3)(NO_(2)RR)holds an enormous prospect to attain efficient NH_(3) electrosynthesis and polluted NO_(2)^(-)mitigation.Herein,we report single-atom Co alloyed Ru(Co_(1)Ru)as an efficient and durable NO_(2)RR catalyst.Extensive experimental and theoretical investigations reveal that single-atom Co alloying of Ru enables the construction of Co_(1)-Ru heteronuclear active sites to synergistically promote NO_(2)^(-)activation/hydrogenation while suppressing the competitive H_(2) evolution,rendering the greatly enhanced activity and selectivity of Co_(1)Ru towards the NO_(2)RR.Consequently,Co_(1)Ru assembled within a flow cell exhibits an impressive NH_(3) yield rate of 2379.2μmol·h^(-1)·cm^(-2) with an NH_(3)-Faradaic efficiency of 92%at a high current density of 415.9 mA·cm^(-2),which is among the highest NO_(2)RR performances reported to date.
基金H.F.acknowledges financial support from the National Natural Science Foundation of China(Nos.51902099 and 92163116)Fundamental Research Funds for the Central Universities(No.531119200087)+1 种基金the Innovative Research Groups of Hunan Province(No.2020JJ1001)G.Y.acknowledges support from the Hunan Province Natural Science Foundation(No.2020JJ4204).
文摘The development of electrocatalysts toward the hydrogen evolution reaction(HER)with high-current-density capability is critical for the practical application of water splitting for hydrogen production.While Pt-based materials are regarded as the most efficient HER catalysts,they suffer from scarcity and high price.Thus,it is of vital importance to lower the loading of Pt while maintaining high activity.Here,we report the fabrication of a monolithic aligned porous carbon film electrode co-modified with Pt single atoms and Pt nanoclusters(Pt SA/NC-AF)containing ultralow Pt content(0.038 wt.%)via a facile electrochemical deposition process.Benefiting from the aligned porous structure of the carbon film and the high exposure of the Pt species,the optimized Pt SA/NCAF electrode exhibits outstanding HER performance in 0.5 M H_(2)SO_(4)with exceptional intrinsic activity(turnover frequency(TOF)=904.9 s^(−1)atη=100 mV)and ultrahigh mass activity(888.6 A·mg_(Pt)^(−1)atη=100 mV).Further,it can deliver an industrially relevant current density of 1,000 mA·cm−2 at an overpotential as low as 139 mV.This work provides a feasible avenue for the rational design of metal single-atom and nanocluster catalysts and additionally promotes the application of ultralow-loading noble metal-based catalysts in high-rate hydrogen production.
基金supported by the National Natural Science Foundation of China(No.52372107)the Natural Science Foundation of Henan Province in China(Nos.212300410004 and 222300420125).
文摘The topography and electrical properties are two crucial characteristics that determine the roles and functionalities of materials.Conductive atomic force microscopy(CAFM)is widely recognized for its ability to independently measure the topography and conductivity.The increasing trend towards miniaturization in electrical devices and sensors has encouraged an urgent demand for enhancing the accuracy of CAFM characterization.However,when performing CAFM tests on Bi_(0.5)Na_(0.5)TiO_(3)bulk ceramic,it is interesting to observe significant currents related to the topography.Why do insulators exhibit“conductivity”in CAFM testing?Herein,we thoroughly investigated the topography-dependent current during CAFM testing for the first time.Based on the linear dependence between the current and the first derivative of topography,the calibration method has been proposed to eliminate the topographic crosstalk.This method is evaluated on Bi_(0.5)Na_(0.5)TiO_(3)bulk ceramic,one-dimensional(1D)ZnO nanowire,twodimensional(2D)NbOI_(2)flake,and biological lotus leaf.The corresponding results of negligible topography-interference current affirm the feasibility and universality of this calibration method.This work effectively addresses the challenge of topographic crosstalk in CAFM characterization,thereby preventing the erroneous estimation of the conductivity of any unknown sample.
基金Projects supported by the Natural Science Foundation of Hunan Province(2016JJ6020)the Scientific Research Fund of Hunan Provincial Education Department(18A436)the Scientific Research Fund of Hunan First normal University(XYS13N16)。
文摘We study the spatial structure of a Bose-Einstein condensate(BEC)with a space-dependent s-wave scattering length in a combined trap.There exists a space-dependent nonlinear atomic current in the system.The atomic current has an important influence on the spatial structure of the BEC.Research findings reveal that a large chemical potential can effectively suppress the chaotic spatial structure in the BEC system.Due to the large chemical potential,a strong atomic current is necessary to make the system lose its periodic spatial structure and lead the system into a chaotic spatial structure.But when the atomic current intensity exceeds a critical value,the chaotic spatial structure of the BEC will be completely eliminated and the system will always be kept in a series of single-periodic states as the atomic current becomes stronger.For a very weak atomic current,the spatial structure of the BEC is very sensitive to the intensity of the atomic current and a very small change of the intensity can dramatically change the spatial structure of the BEC.The effects of the combined trap parameters on the spatial structure of BECs are also discussed.
基金the National Natural Science Foundation of China(Grant Nos.41431071,41574152)the National Basic Research Program of China(Grant No.2011CB811404)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA04060201)
文摘Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion fluxes at 4-min temporal resolution derived from ENA data in the energy ranges 50-81 and 81-158 keV are compared with in situ particle fluxes measured by the LANL-SOPA instruments aboard LANL-01, LANL-02, LANL-97, and LANL-84 （a series of geostationary satellites that encircle the equatorial plane at -6.6 RE）. Also, magnetic fields measured simultaneously by the magetometers aboard GOES-10 and GOES-12 （which are also geostationary satellites） are compared with the particle data. It is demonstrated that ion fluxes in the ring current were enhanced during geomagnetic field tailward stretching in the growth phases of substorms rather than after Earthward directed dipolarization events. This observation, which challenges the existing concept that ring current particles are injected Earthward from the magnetotail following dipolarization events, requires further investigation using a large number of magnetic storm events.
基金Supported by the Funds for Major Basic Research Project of Sichuan Province under Grant No 02GY029-188, and the Natural Science Foundation of the Committee of Education of Sichuan Province under Grant No 2003A078.
文摘Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents the periodic change along with the aggrandizement of the magnetic flux and the number of lattice sites NR in the mesoscopic ring, and for the antiparallel spin alignment the Kondo resonances for spin-up and spin-down configurations appear at the same position. However, for the parallel spin alignment, the Kondo resonance splits for the spin-up and spin-down configurations.
基金This work was supported by the National Natural Science Foundation of China (No.10174050, 10374029, and 10434060), the Shanghai Priority Academic Discipline,and the 211 Foundation of the Educational Ministry of China.
文摘A new scheme to realize a two-dimensional （2D） array of magnetic micro-lenses for a cold atomic beam. formed by an array of square current-carrying wires, is proposed. We calculate the spatial distributions of the magnetic fields from the array of current-carrying wires and the magnetic focusing potential for cold rubidium atoms, and study the dynamic focusing processes of cold atoms passing through the mag- netic micro-lens array and its focusing properties by using Monte-Carlo simulations and trajectory tracing method. The result shows that the proposed micro-lens array can be used to focus effectively a cold atomic beam, even to load ultracold atoms or a BEC sample into a 2D optical lattice formed by blue detuned hollow beams.
