Molecular dynamics（MD） simulations using the polymer consistent force field（PCFF） were adopted to investigate the pressure and thickness dependent density of squalane film in a nanogap at 373 K, with three differe...Molecular dynamics（MD） simulations using the polymer consistent force field（PCFF） were adopted to investigate the pressure and thickness dependent density of squalane film in a nanogap at 373 K, with three different initial film thicknesses, and for a wide range of pressures. The equivalent densities predicted by MD simulations were compared with the empirical data. Results show that the squalane atoms tend to form layers parallel to the confining substrates but the orientations of squalane molecules are irregular throughout the film. In addition, distinct excluded volumes are not found at the interfaces of the film and substrates. Furthermore, with the same initial film thickness h_0, the film thickness h and compressibility decrease with increasing pressure, but the compressibility is similar for films with different initial film thicknesses. The equivalent densities predicted by MD simulations with the maximum initial film thickness（9.44 nm） are accurate to the values of Tait equation. The MD simulation with adequate initial film thickness can accurately and conveniently predict the bulk densities of lubricants.展开更多
The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a freque...The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled （λ= 532 nm） Nd：YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical （TO） peak can produce higher stress. The highest crystalline fraction （84.5%） is obtained in the optimized laser energy density （1000 mJ/cm2） with a considerable stress release. The absorption edge energy measured by the UV- visible spectra is in fairly good agreement with the bandgap energy in the density functional theory （DFT） simulation.展开更多
A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of dr...A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z- pinch on the Qiangguang-I generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power展开更多
A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from d...A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.展开更多
Developing efficient and stable photocatalysts for hydrogen generation still remains a huge challenge.Herein,we adopted Cynanchum fibers as a carbon source and substrate to construct a ternary hollow core-shell carbon...Developing efficient and stable photocatalysts for hydrogen generation still remains a huge challenge.Herein,we adopted Cynanchum fibers as a carbon source and substrate to construct a ternary hollow core-shell carbon microtubes@TiO_(2)/ZnIn_(2)S_(4)(denoted as CMT@TiO_(2)/ZnIn_(2)S_(4))for photothermal-assisted photocatalytic hydrogen evolution(PHE).For the catalyst system,ZnIn_(2)S_(4)is the main visible light absorber,TiO_(2) is introduced to form a heterojunction with ZnIn_(2)S_(4)to facilitate the separation of photogenerated carriers,and hollow CMT derived from Cynanchum fibers serves as a conductive scaffold and a photothermal core to elevate the surface temperature of the localized reaction system.Benefiting from the rationally designed multicomponents and microstructures,the photocatalyst proposed enhanced PHE activity of 9.71 mmol·g^(−1)·h^(−1),which was 30.3,2.7 and 1.5 times higher than those of binary CMT@TiO_(2),pristine ZnIn_(2)S_(4)and TiO_(2)/ZnIn_(2)S_(4)composite,respectively.The outperformed PHE activity of CMT@TiO_(2)/ZnIn_(2)S_(4)could be ascribed to the synergy of the formation of intimate heterointerface,the CMT-induced photothermal effect and the hierarchical core-shell architecture.This work provides a promising approach for constructing efficient and durable photocatalysts for H_(2) evolution.展开更多
High-performance Ti_(3)C_(2)T_(x)fibers have garnered significant potential for smart fibers enabled fabrics.Nonetheless,a major challenge hindering their widespread use is the lack of strong interlayer interactions b...High-performance Ti_(3)C_(2)T_(x)fibers have garnered significant potential for smart fibers enabled fabrics.Nonetheless,a major challenge hindering their widespread use is the lack of strong interlayer interactions between Ti_(3)C_(2)T_(x)nanosheets within fibers,which restricts their properties.Herein,a versatile strategy is proposed to construct wet-spun Ti_(3)C_(2)T_(x)fibers,in which trace amounts of borate form strong interlayer crosslinking between Ti_(3)C_(2)T_(x)nanosheets to significantly enhance interactions as supported by density functional theory calculations,thereby reducing interlayer spacing,diminishing microscopic voids and promoting orientation of the nanosheets.The resultant Ti_(3)C_(2)T_(x)fibers exhibit exceptional electrical conductivity of 7781 S cm^(-1)and mechanical properties,including tensile strength of 188.72 MPa and Young's modulus of 52.42 GPa.Notably,employing equilibrium molecular dynamics simulations,finite element analysis,and cross-wire geometry method,it is revealed that such crosslinking also effectively lowers interfacial thermal resistance and ultimately elevates thermal conductivity of Ti_(3)C_(2)T_(x)fibers to 13 W m^(-1)K^(-1),marking the first systematic study on thermal conductivity of Ti_(3)C_(2)T_(x)fibers.The simple and efficient interlayer crosslinking enhancement strategy not only enables the construction of thermal conductivity Ti_(3)C_(2)T_(x)fibers with high electrical conductivity for smart textiles,but also offers a scalable approach for assembling other nanomaterials into multifunctional fibers.展开更多
The ferrocene(Fc)-based metal-organic frameworks(MOFs)are regarded as compelling platforms for the construction of efficient and robust oxygen evolution reaction(OER)electrocatalysts due to their superior conductivity...The ferrocene(Fc)-based metal-organic frameworks(MOFs)are regarded as compelling platforms for the construction of efficient and robust oxygen evolution reaction(OER)electrocatalysts due to their superior conductivity and flexible electronic structure.Herein,density functional theory simulations were addressed to predict the electronic structure regulations of CoFc-MOF by nickel doping,which demonstrated that the well-proposed CoNiFc-MOFs delivered a small energy barrier,promoted conductivity,and well-regulated d-band center.Inspired by these,a series of sea-urchin-like CoNiFc-MOFs were successfully synthesized via a facile solvothermal method.Moreover,the synchrotron X-ray and X-ray photoelectron spectroscopy measurements manifested that the introduction of nickel could tailor the electronic structure of the catalyst and induce the directional transfer of electrons,thus optimizing the rate-determining step of^(*)O→^(*)OOH during the OER process and yielding decent overpotentials of 209 and 252 mV at 10 and 200 mA cm^(−2),respectively,with a small Tafel slope of 39 mV dec^(−1).This work presents a new paradigm for developing highly efficient and durable MOF-based electrocatalysts for OER.展开更多
With the advantage of fast charge transfer,heterojunction engineering is identified as a viable method to reinforce the anodes'sodium storage performance.Also,vacancies can effectively strengthen the Na+adsorption...With the advantage of fast charge transfer,heterojunction engineering is identified as a viable method to reinforce the anodes'sodium storage performance.Also,vacancies can effectively strengthen the Na+adsorption ability and provide extra active sites for Na+adsorption.However,their synchronous engineering is rarely reported.Herein,a hybrid of Co_(0.85)Se/WSe_(2) heterostructure with Se vacancies and N-doped carbon polyhedron(CoWSe/NCP)has been fabricated for the first time via a hydrothermal and subsequent selenization strategy.Spherical aberration-corrected transmission electron microscopy confirms the phase interface of the Co_(0.85)Se/WSe_(2) heterostructure and the existence of Se vacancies.Density functional theory simulations reveal the accelerated charge transfer and enhanced Na+adsorption ability,which are contributed by the Co_(0.85)Se/WSe_(2) heterostructure and Se vacancies,respectively.As expected,the CoWSe/NCP anode in sodium-ion battery achieves outstanding rate capability(339.6 mAh g^(−1) at 20 A g^(−1)),outperforming almost all Co/W-based selenides.展开更多
The practical application of Lithium-Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high-sulfur content and low electrolyte/sulfur ratio.Rati...The practical application of Lithium-Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high-sulfur content and low electrolyte/sulfur ratio.Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium-sulfur batteries.Herein,ultrathin nonlayered NiO/Ni_(3)S_(2)heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)_(2)templates to improve the utilization of sulfur and facilitate stable cycling of batteries.As a multifunction catalyst,NiO/Ni_(3)S_(2)not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li_(2)S formation and transformation,which are verified by both in-situ Raman spectroscopy and electrochemical investigations.Thus,the cell with NiO/Ni_(3)S_(2)as electrocatalyst delivers an area capacity of 4.8 mAh cm^(-2)under the high sulfur loading(6 mg cm^(-2))and low electrolyte/sulfur ratio(4.3 pL mg^(-1)).The strategy can be extended to 2D Ni foil,demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities.The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium-sulfur batteries.展开更多
Herein,a unique mesoporous heterostructure(average pore size:15 nm)cobalt disulfide/carbon nanofibers(CoS_(2)/PCNFs)composite with excellent hydrophilicity(contact angle:23.5°)is prepared using polyethylene glyco...Herein,a unique mesoporous heterostructure(average pore size:15 nm)cobalt disulfide/carbon nanofibers(CoS_(2)/PCNFs)composite with excellent hydrophilicity(contact angle:23.5°)is prepared using polyethylene glycol(PEG)as a pore-forming agent.The CoS_(2)/PCNF electrode exhibits excellent cycle stability(95.2%of initial specific capacitance at 10 A·g^(-1)after 8000 cycles),good rate performance(46.5%at 10 A·g^(-1)),and high specific capacity(86.1 mAh·g^(-1)at 1 A·g^(-1),about 688.8 F·g^(-1)at 1 A·g^(-1)).Density functional theory(DFT)simulation elucidates that CoS_(2)tends to transfer substantial charges to CNF.As the center of positive charge,CoS_(2)is more likely to capture negative ions in the electrolyte,thus accelerating the ion diffusion process.The excellent properties of the electrode material can not only accelerate the electrochemical reaction kinetics,but also provide abundant redox-active sites and a high Faradaic capacity for the entire electrode due to the synergistic contributions of CoS_(2)nanoparticles,mesoporous heterostructure of PCNF,and admirable hydrophilicity of the composite material.A CoS_(2)/PCNF-0.25//AC(AC:activated carbon)asymmetric supercapacitor is assembled using CoS_(2)/PCNF-0.25 as the positive electrode and AC as the negative electrode,which possesses a high energy density(35.5 Wh·kg^(-1)at a power density of 824 W·kg^(-1))and superior cycling stability(maintaining over 98%of initial capacitance after 2000 cycles).In addition,the unique CoS_(2)/PCNF electrode is expected to be widely used in other electrochemical energy storage devices,such as lithium-ion batteries,sodium-ion batteries,lithium-sulfur batteries,etc.展开更多
With the progress of electronic communication technology,the intensity of electromagnetic radiation is getting strength,and the traditional absorbing materials can no longer meet the needs of various current environme...With the progress of electronic communication technology,the intensity of electromagnetic radiation is getting strength,and the traditional absorbing materials can no longer meet the needs of various current environments.Dielectric nanomaterials have received much attention in energy conversion,electromagnetic shielding and absorption due to their nanosize effects and structural tunable properties.However,the mismatch impedance and the single loss mechanism severely limit its application in the field of microwave absorption.In this paper,we modified the doped ZnCo_(2)O_(4) with the guidance of density functional theory(DFT)simulation,effectively regulate the dielectric parameters and adjust the microwave absorption characteristics,which stems from the transformation of electron energy between doped ions and some defects.Meanwhile,we further experimentally observe significant magnetic components at the doped ZnCo_(2)O_(4),resulting in improved magnetic properties and producing a large number of dipoles.Due to the best impedance match and enhanced polarization loss,the minimum reflection loss is−37 dB,and the effective absorption bandwidth(EAB)is 7.21 GHz.This provides ideas for the design of cobalt acid-based materials as efficient microwave absorbers.展开更多
Cobalt oxide(Co_(3)O_(4))is currently suitable in energy storage applications because of its high capacity based on the conversion reaction mechanism.However,unmodified Co_(3)O_(4)suffers from distinctly inferior rate...Cobalt oxide(Co_(3)O_(4))is currently suitable in energy storage applications because of its high capacity based on the conversion reaction mechanism.However,unmodified Co_(3)O_(4)suffers from distinctly inferior rate capability and poor cycling stability.On the basis of the aforementioned considerations and density functional theory(DFT)simulations,the three-dimensional hierarchical porous structure(HPS)ultrasmall Co_(3)O_(4)anchored into ionic liquid(IL)modified graphene oxide(GO)has been successfully prepared(ultrasmall/Co_(3)O_(4)-GA-IL).The ultrasmall/Co_(3)O_(4)-GA-IL consists of Co_(3)O_(4)co-assembled with IL modified GO to generate the HPS which can facilitate ion transfer channels through reduction of the electron and ion transportation path and transmission impedance.In addition,N-doping graphene can enhance the inherent electrical conductivity of Co_(3)O_(4),which is proved by the DFT calculations.By virtue of the novel superstructure,the ultrasmall/Co_(3)O_(4)-GA-IL electrode demonstrates a high reversible capacity of 1,304 mAh·g^(−1),an enhanced high-rate capability(715 mAh·g^(−1)at 5 C),and a capacity retention of 98.4%even after 500 cycles at 5 C rate,which corresponds to 0.0003%capacity loss per cycle.Pouch cells based on the cathode are further fabricated and demonstrate excellent mechanical and electrochemical properties under bent and folded state,highlighting the practical application of our deliberately designed electrode in wearable electronics.展开更多
Na-ion batteries(SIBs)have attracted considerable attention as promising alternatives to commercial Li-ion batteries(LIBs)due to comparable redox potential,and natural abundance of Na.However,it remains challenging to...Na-ion batteries(SIBs)have attracted considerable attention as promising alternatives to commercial Li-ion batteries(LIBs)due to comparable redox potential,and natural abundance of Na.However,it remains challenging to explore suitable anodes for SIBs.Herein,a MoO2/N-doped carbon(MoO2/N-C)composite composed of MoO2 nanocrystals embedded within carbon matrix with a Mo–N–C chemical bond is prepared by a simple yet effective carbonization-induced topochemical transformation route.Na-ion half-cells using MoO2/N-C exhibit excellent cycling stability over 5000 cycles at 5 A g^-1 and superior rate capability.Physicochemical characterizations and first-principles density functional theory(DFT)simulations reveal that the formation of chemical bond at the interface between MoO2 and N-doped carbon plays an important role in the excellent charge storage properties of MoO2/N-C.More importantly,the interfacial coupling can efficiently promote interface charge transfer.Benefiting from this,Na-ion capacitors(SICs)constructed with the MoO2/N-C anode and activated carbon cathode can deliver an impressive energy density of 15 W h kg^-1 at a power density of 1760 W kg^-1,together with a capacitance retention of 92.4%over 1000 cycles at 10 A g^-1.The proposed strategy in this paper based on interfacial chemical bond may hold promises for the design of high-performance electrodes for energy storage devices.展开更多
Electronic properties of stanene, the Sn counterpart of graphene are theoretically studied using first-principles simulations. The topological to trivial insulating phase transition induced by an out-of-plane electric...Electronic properties of stanene, the Sn counterpart of graphene are theoretically studied using first-principles simulations. The topological to trivial insulating phase transition induced by an out-of-plane electric field or by quantum confinement effects is predicted. The results highlight the potential to use stanene nanoribbons in gate-voltage controlled dissipationless spin-based devices and are used to set the minimal nanoribbon width for such devices, which is typically approximately 5 nm.展开更多
The common ways to activate a chemical reaction are by heat,electric current,or light.However,mechanochemistry,where the chemical reaction is activated by applied mechanical force,is less common and only poorly unders...The common ways to activate a chemical reaction are by heat,electric current,or light.However,mechanochemistry,where the chemical reaction is activated by applied mechanical force,is less common and only poorly understood at the atomic scale.Here we report a tip-induced activation of chemical reaction of carbon monoxide to dioxide on oxidized rutile TiO_(2)(110)surface.The activation is studied by atomic force microscopy,Kelvin probe force microscopy under ultrahigh-vacuum and liquid nitrogen temperature conditions,and density functional theory(DFT)modeling.The reaction is inferred from hysteretic behavior of frequency shift signal further supported by vector force mapping of vertical and lateral forces needed to trigger the chemical reaction with torque motion of carbon monoxide towards an oxygen adatom.The reaction is found to proceed stochastically at very small tip-sample distances.Furthermore,the local contact potential difference reveals the atomic-scale charge redistribution in the reactants required to unlock the reaction.Our results open up new insights into the mechanochemistry on metal oxide surfaces at the atomic scale.展开更多
基金Funded by the National Natural Science Foundation of China(No.51175085)the Tribology Science Fund of State Key Laboratory of Tribology(No.SKLTKF13A09)the Natural Science Foundation of Fujian Province(No.2016J01226)
文摘Molecular dynamics（MD） simulations using the polymer consistent force field（PCFF） were adopted to investigate the pressure and thickness dependent density of squalane film in a nanogap at 373 K, with three different initial film thicknesses, and for a wide range of pressures. The equivalent densities predicted by MD simulations were compared with the empirical data. Results show that the squalane atoms tend to form layers parallel to the confining substrates but the orientations of squalane molecules are irregular throughout the film. In addition, distinct excluded volumes are not found at the interfaces of the film and substrates. Furthermore, with the same initial film thickness h_0, the film thickness h and compressibility decrease with increasing pressure, but the compressibility is similar for films with different initial film thicknesses. The equivalent densities predicted by MD simulations with the maximum initial film thickness（9.44 nm） are accurate to the values of Tait equation. The MD simulation with adequate initial film thickness can accurately and conveniently predict the bulk densities of lubricants.
基金Project supported by the Shanghai Leading Academic Disciplines,China(Grant No.S30107)
文摘The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled （λ= 532 nm） Nd：YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical （TO） peak can produce higher stress. The highest crystalline fraction （84.5%） is obtained in the optimized laser energy density （1000 mJ/cm2） with a considerable stress release. The absorption edge energy measured by the UV- visible spectra is in fairly good agreement with the bandgap energy in the density functional theory （DFT） simulation.
基金Project supported by the National Natural Science Foundation of China （Grant No 10035020）.
文摘A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z- pinch on the Qiangguang-I generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power
基金Supported by the National Natural Science Foundation of China (50905016)
文摘A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.
基金supported by the National Natural Science Foundation of China(No.21701078)the PhD Initiation Foundation of Liaocheng University(No.318052140).
文摘Developing efficient and stable photocatalysts for hydrogen generation still remains a huge challenge.Herein,we adopted Cynanchum fibers as a carbon source and substrate to construct a ternary hollow core-shell carbon microtubes@TiO_(2)/ZnIn_(2)S_(4)(denoted as CMT@TiO_(2)/ZnIn_(2)S_(4))for photothermal-assisted photocatalytic hydrogen evolution(PHE).For the catalyst system,ZnIn_(2)S_(4)is the main visible light absorber,TiO_(2) is introduced to form a heterojunction with ZnIn_(2)S_(4)to facilitate the separation of photogenerated carriers,and hollow CMT derived from Cynanchum fibers serves as a conductive scaffold and a photothermal core to elevate the surface temperature of the localized reaction system.Benefiting from the rationally designed multicomponents and microstructures,the photocatalyst proposed enhanced PHE activity of 9.71 mmol·g^(−1)·h^(−1),which was 30.3,2.7 and 1.5 times higher than those of binary CMT@TiO_(2),pristine ZnIn_(2)S_(4)and TiO_(2)/ZnIn_(2)S_(4)composite,respectively.The outperformed PHE activity of CMT@TiO_(2)/ZnIn_(2)S_(4)could be ascribed to the synergy of the formation of intimate heterointerface,the CMT-induced photothermal effect and the hierarchical core-shell architecture.This work provides a promising approach for constructing efficient and durable photocatalysts for H_(2) evolution.
基金the support from the National Natural Science Foundation of China(52403112,52473083)Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)+2 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Fundamental Research Funds for the Central Universities(D5000240062,D5000240077)Undergraduate Innovation&Business Program in Northwestern Polytechnical University(202410699041)。
文摘High-performance Ti_(3)C_(2)T_(x)fibers have garnered significant potential for smart fibers enabled fabrics.Nonetheless,a major challenge hindering their widespread use is the lack of strong interlayer interactions between Ti_(3)C_(2)T_(x)nanosheets within fibers,which restricts their properties.Herein,a versatile strategy is proposed to construct wet-spun Ti_(3)C_(2)T_(x)fibers,in which trace amounts of borate form strong interlayer crosslinking between Ti_(3)C_(2)T_(x)nanosheets to significantly enhance interactions as supported by density functional theory calculations,thereby reducing interlayer spacing,diminishing microscopic voids and promoting orientation of the nanosheets.The resultant Ti_(3)C_(2)T_(x)fibers exhibit exceptional electrical conductivity of 7781 S cm^(-1)and mechanical properties,including tensile strength of 188.72 MPa and Young's modulus of 52.42 GPa.Notably,employing equilibrium molecular dynamics simulations,finite element analysis,and cross-wire geometry method,it is revealed that such crosslinking also effectively lowers interfacial thermal resistance and ultimately elevates thermal conductivity of Ti_(3)C_(2)T_(x)fibers to 13 W m^(-1)K^(-1),marking the first systematic study on thermal conductivity of Ti_(3)C_(2)T_(x)fibers.The simple and efficient interlayer crosslinking enhancement strategy not only enables the construction of thermal conductivity Ti_(3)C_(2)T_(x)fibers with high electrical conductivity for smart textiles,but also offers a scalable approach for assembling other nanomaterials into multifunctional fibers.
基金Changjiang Scholars Program of the Ministry of Education,Grant/Award Number:Q2018270Outstanding Youth Funding of Anhui Province,Grant/Award Number:OUFAH 1908085J10+2 种基金Jiangsu Students'Innovation and Entrepreneurship Training Program,Grant/Award Number:202111117079YNatural Science Foundation of Jiangsu Province,Grant/Award Number:BK20200044National Natural Science Foundation of China,Grant/Award Numbers:NSFC 21671004,NSFC 21975001,NSFC U1904215。
文摘The ferrocene(Fc)-based metal-organic frameworks(MOFs)are regarded as compelling platforms for the construction of efficient and robust oxygen evolution reaction(OER)electrocatalysts due to their superior conductivity and flexible electronic structure.Herein,density functional theory simulations were addressed to predict the electronic structure regulations of CoFc-MOF by nickel doping,which demonstrated that the well-proposed CoNiFc-MOFs delivered a small energy barrier,promoted conductivity,and well-regulated d-band center.Inspired by these,a series of sea-urchin-like CoNiFc-MOFs were successfully synthesized via a facile solvothermal method.Moreover,the synchrotron X-ray and X-ray photoelectron spectroscopy measurements manifested that the introduction of nickel could tailor the electronic structure of the catalyst and induce the directional transfer of electrons,thus optimizing the rate-determining step of^(*)O→^(*)OOH during the OER process and yielding decent overpotentials of 209 and 252 mV at 10 and 200 mA cm^(−2),respectively,with a small Tafel slope of 39 mV dec^(−1).This work presents a new paradigm for developing highly efficient and durable MOF-based electrocatalysts for OER.
基金support from the Natural Science Foundation of Jilin Province(Grant No.20200201073JC)the National Natural Science Foundation of China(Grant No.52130101)+1 种基金Interdisciplinary Integration and Innovation Project of JLU(Grant No.JLUXKJC2021ZY01)the Fundamental Research Funds for the Central Universities.
文摘With the advantage of fast charge transfer,heterojunction engineering is identified as a viable method to reinforce the anodes'sodium storage performance.Also,vacancies can effectively strengthen the Na+adsorption ability and provide extra active sites for Na+adsorption.However,their synchronous engineering is rarely reported.Herein,a hybrid of Co_(0.85)Se/WSe_(2) heterostructure with Se vacancies and N-doped carbon polyhedron(CoWSe/NCP)has been fabricated for the first time via a hydrothermal and subsequent selenization strategy.Spherical aberration-corrected transmission electron microscopy confirms the phase interface of the Co_(0.85)Se/WSe_(2) heterostructure and the existence of Se vacancies.Density functional theory simulations reveal the accelerated charge transfer and enhanced Na+adsorption ability,which are contributed by the Co_(0.85)Se/WSe_(2) heterostructure and Se vacancies,respectively.As expected,the CoWSe/NCP anode in sodium-ion battery achieves outstanding rate capability(339.6 mAh g^(−1) at 20 A g^(−1)),outperforming almost all Co/W-based selenides.
基金supported by the National Natural Science Foundation of China(Grant nos.62090013,61974043,and 91833303)the National Key R&D Program of China(Grant no.2019YFB2203403)+1 种基金the Projects of Science and Technology Commission of Shanghai Municipality(Grant nos.21JC1402100 and 19511120100)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning.
文摘The practical application of Lithium-Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high-sulfur content and low electrolyte/sulfur ratio.Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium-sulfur batteries.Herein,ultrathin nonlayered NiO/Ni_(3)S_(2)heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)_(2)templates to improve the utilization of sulfur and facilitate stable cycling of batteries.As a multifunction catalyst,NiO/Ni_(3)S_(2)not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li_(2)S formation and transformation,which are verified by both in-situ Raman spectroscopy and electrochemical investigations.Thus,the cell with NiO/Ni_(3)S_(2)as electrocatalyst delivers an area capacity of 4.8 mAh cm^(-2)under the high sulfur loading(6 mg cm^(-2))and low electrolyte/sulfur ratio(4.3 pL mg^(-1)).The strategy can be extended to 2D Ni foil,demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities.The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium-sulfur batteries.
基金Financial support was received from the National Natural Science Foundation of China(Nos.51976081 and U22A20107)the China Postdoctoral Science Foundation(No.2019T120393)+2 种基金the Jiangsu Province Postdoctoral Foundation(No.2020Z078)the“Grassland Talents”of Inner Mongolia Autonomous Region,the Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NJYT23030)the“Steed Plan High-level Talents”of Inner Mongolia University,and the Carbon Neutralization Research Project(No.STZX202218).
文摘Herein,a unique mesoporous heterostructure(average pore size:15 nm)cobalt disulfide/carbon nanofibers(CoS_(2)/PCNFs)composite with excellent hydrophilicity(contact angle:23.5°)is prepared using polyethylene glycol(PEG)as a pore-forming agent.The CoS_(2)/PCNF electrode exhibits excellent cycle stability(95.2%of initial specific capacitance at 10 A·g^(-1)after 8000 cycles),good rate performance(46.5%at 10 A·g^(-1)),and high specific capacity(86.1 mAh·g^(-1)at 1 A·g^(-1),about 688.8 F·g^(-1)at 1 A·g^(-1)).Density functional theory(DFT)simulation elucidates that CoS_(2)tends to transfer substantial charges to CNF.As the center of positive charge,CoS_(2)is more likely to capture negative ions in the electrolyte,thus accelerating the ion diffusion process.The excellent properties of the electrode material can not only accelerate the electrochemical reaction kinetics,but also provide abundant redox-active sites and a high Faradaic capacity for the entire electrode due to the synergistic contributions of CoS_(2)nanoparticles,mesoporous heterostructure of PCNF,and admirable hydrophilicity of the composite material.A CoS_(2)/PCNF-0.25//AC(AC:activated carbon)asymmetric supercapacitor is assembled using CoS_(2)/PCNF-0.25 as the positive electrode and AC as the negative electrode,which possesses a high energy density(35.5 Wh·kg^(-1)at a power density of 824 W·kg^(-1))and superior cycling stability(maintaining over 98%of initial capacitance after 2000 cycles).In addition,the unique CoS_(2)/PCNF electrode is expected to be widely used in other electrochemical energy storage devices,such as lithium-ion batteries,sodium-ion batteries,lithium-sulfur batteries,etc.
基金supported by the National Natural Science Foundation of China(Nos.52231007,12327804,T2321003,22088101,22405050,12074241,52130204,and 11929401)the National Key Research and Development Program of China(Nos.2024YFA1208902,2024YFA1408001,and 2021YFA1200600)+4 种基金the Science and Technology Commission of Shanghai Municipality(No.24ZR1406400)Aeronautical Science Foundation of China(Nos.202400180P9001 and 2024M0730P9001)Key Laboratory of High Temperature Electromagnetic Materials and Structure of MOE(No.KB202401)Fund of Science and Technology on Surface Physics and Chemistry Laboratory(No.JCKYS2023120201)the Science and Technology Commission of Shanghai Municipality(Nos.19010500500,20501130600,21JC1402600,and 22YF1413300).
文摘With the progress of electronic communication technology,the intensity of electromagnetic radiation is getting strength,and the traditional absorbing materials can no longer meet the needs of various current environments.Dielectric nanomaterials have received much attention in energy conversion,electromagnetic shielding and absorption due to their nanosize effects and structural tunable properties.However,the mismatch impedance and the single loss mechanism severely limit its application in the field of microwave absorption.In this paper,we modified the doped ZnCo_(2)O_(4) with the guidance of density functional theory(DFT)simulation,effectively regulate the dielectric parameters and adjust the microwave absorption characteristics,which stems from the transformation of electron energy between doped ions and some defects.Meanwhile,we further experimentally observe significant magnetic components at the doped ZnCo_(2)O_(4),resulting in improved magnetic properties and producing a large number of dipoles.Due to the best impedance match and enhanced polarization loss,the minimum reflection loss is−37 dB,and the effective absorption bandwidth(EAB)is 7.21 GHz.This provides ideas for the design of cobalt acid-based materials as efficient microwave absorbers.
基金National Key Research and Development Program of China(No.2019YFA0705700)the National Natural Science Foundation of China(Nos.51774017 and 51904016)Key Program of Equipment Pre-Research Foundation of China(No.6140721020103)。
文摘Cobalt oxide(Co_(3)O_(4))is currently suitable in energy storage applications because of its high capacity based on the conversion reaction mechanism.However,unmodified Co_(3)O_(4)suffers from distinctly inferior rate capability and poor cycling stability.On the basis of the aforementioned considerations and density functional theory(DFT)simulations,the three-dimensional hierarchical porous structure(HPS)ultrasmall Co_(3)O_(4)anchored into ionic liquid(IL)modified graphene oxide(GO)has been successfully prepared(ultrasmall/Co_(3)O_(4)-GA-IL).The ultrasmall/Co_(3)O_(4)-GA-IL consists of Co_(3)O_(4)co-assembled with IL modified GO to generate the HPS which can facilitate ion transfer channels through reduction of the electron and ion transportation path and transmission impedance.In addition,N-doping graphene can enhance the inherent electrical conductivity of Co_(3)O_(4),which is proved by the DFT calculations.By virtue of the novel superstructure,the ultrasmall/Co_(3)O_(4)-GA-IL electrode demonstrates a high reversible capacity of 1,304 mAh·g^(−1),an enhanced high-rate capability(715 mAh·g^(−1)at 5 C),and a capacity retention of 98.4%even after 500 cycles at 5 C rate,which corresponds to 0.0003%capacity loss per cycle.Pouch cells based on the cathode are further fabricated and demonstrate excellent mechanical and electrochemical properties under bent and folded state,highlighting the practical application of our deliberately designed electrode in wearable electronics.
基金supported by the National Natural Science Foundation of China(51804089)the Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional Materials(EMFM20181114)the support of the research starting foundation of CAEP(PY20200038)。
文摘Na-ion batteries(SIBs)have attracted considerable attention as promising alternatives to commercial Li-ion batteries(LIBs)due to comparable redox potential,and natural abundance of Na.However,it remains challenging to explore suitable anodes for SIBs.Herein,a MoO2/N-doped carbon(MoO2/N-C)composite composed of MoO2 nanocrystals embedded within carbon matrix with a Mo–N–C chemical bond is prepared by a simple yet effective carbonization-induced topochemical transformation route.Na-ion half-cells using MoO2/N-C exhibit excellent cycling stability over 5000 cycles at 5 A g^-1 and superior rate capability.Physicochemical characterizations and first-principles density functional theory(DFT)simulations reveal that the formation of chemical bond at the interface between MoO2 and N-doped carbon plays an important role in the excellent charge storage properties of MoO2/N-C.More importantly,the interfacial coupling can efficiently promote interface charge transfer.Benefiting from this,Na-ion capacitors(SICs)constructed with the MoO2/N-C anode and activated carbon cathode can deliver an impressive energy density of 15 W h kg^-1 at a power density of 1760 W kg^-1,together with a capacitance retention of 92.4%over 1000 cycles at 10 A g^-1.The proposed strategy in this paper based on interfacial chemical bond may hold promises for the design of high-performance electrodes for energy storage devices.
文摘Electronic properties of stanene, the Sn counterpart of graphene are theoretically studied using first-principles simulations. The topological to trivial insulating phase transition induced by an out-of-plane electric field or by quantum confinement effects is predicted. The results highlight the potential to use stanene nanoribbons in gate-voltage controlled dissipationless spin-based devices and are used to set the minimal nanoribbon width for such devices, which is typically approximately 5 nm.
基金supported by a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science(JSPS)from the Ministry of Education,Culture,Sports,Science,and Technology of Japan(Nos.JP16H06327,JP17H01061,A21J103560,and JP22H00282)supported by the International Joint Research Promotion Program of Osaka University(Nos.J171013014,J171013007,J181013004,J181013006,Ja1999001,Ja19990011,and A21J103560)+1 种基金JSPSthe National Natural Science Foundation of China(No.J191053055)supported by APVV-21-0272,VEGA-2/0070/21,VEGA-2/0125/20,VEGA-2/0131/23,and H2020 TREX GA No.952165 projects。
文摘The common ways to activate a chemical reaction are by heat,electric current,or light.However,mechanochemistry,where the chemical reaction is activated by applied mechanical force,is less common and only poorly understood at the atomic scale.Here we report a tip-induced activation of chemical reaction of carbon monoxide to dioxide on oxidized rutile TiO_(2)(110)surface.The activation is studied by atomic force microscopy,Kelvin probe force microscopy under ultrahigh-vacuum and liquid nitrogen temperature conditions,and density functional theory(DFT)modeling.The reaction is inferred from hysteretic behavior of frequency shift signal further supported by vector force mapping of vertical and lateral forces needed to trigger the chemical reaction with torque motion of carbon monoxide towards an oxygen adatom.The reaction is found to proceed stochastically at very small tip-sample distances.Furthermore,the local contact potential difference reveals the atomic-scale charge redistribution in the reactants required to unlock the reaction.Our results open up new insights into the mechanochemistry on metal oxide surfaces at the atomic scale.
