The scarcity and high cost of lithium resources drive the search for sustainable alternatives,positioning potassium-ion batteries(KIBs)as promising energy storage solutions due to the natural abundance and advantageou...The scarcity and high cost of lithium resources drive the search for sustainable alternatives,positioning potassium-ion batteries(KIBs)as promising energy storage solutions due to the natural abundance and advantageous electrochemical properties of the potassium.This study investigates the enhancement of KIB anodes through phase transformation and electronic structure engineering of monolayer 1T-MoS_(2),achieved via doping with highly electronegative non-metal elements:carbon(C),nitrogen(N),oxygen(O),and fluorine(F).Density functional theory(DFT)simulations reveal that electronegative atom doping enhances phase stability,structural robustness,and thermal resilience,which are key properties for highperformance KIB anodes.Among the doped configurations,F and N-doped 1T-MoS_(2)(MoS_(2-)F and MoS_(2)-N)exhibit superior electrochemical performance,showing optimal adsorption energies and significantly improved electronic conductivity,attributable to favorable charge redistribution and increased active potassium adsorption sites.Specifically,MoS_(2)-F and MoS_(2)-N achieve the highest specific capacities of339.65 and 339.17 mAh/g,respectively,while maintaining stability within an ideal open circuit voltage range,outperforming undoped MoS_(2).This work undersco res the potential of electronegative atom doping in 1T-MoS_(2)to enable sustainable,high-capacity energy storage solutions,offering key advancements in the electrochemical and structural properties of KIB anodes.展开更多
The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and t...The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and the sheath almost does not exist there, and that distributions of electrons, negative and positive ions in the sheath form a pure positive ion sheath near the boundary of the electrode. Furthermore, the density distribution of space net charge has a peak near the sheath edge, the spatial potential within the sheath falls faster, and the sheath thickness becomes thinner.展开更多
An electronegative collisional plasma having warm and massive positive ions,non-extensive distributed electrons and Boltzmann distributed negative ions is modelled for the plasma-surface interaction process that is us...An electronegative collisional plasma having warm and massive positive ions,non-extensive distributed electrons and Boltzmann distributed negative ions is modelled for the plasma-surface interaction process that is used for the surface nitriding.Specifically the sheath formation is evaluated through the Bohm’s criterion,which is found to be modified,and the variation of the sheath thickness and profiles of the density of plasma species and the net space charge density in the sheath region in addition to the electric potential.The effect of ion temperature,nonextensivity and collisional parameter is examined in greater detail considering the collisional cross-section to obey power-law dependency on the positive ion velocity.The positive ions are found to enter in the sheath region at lower velocities in the collisional plasma compared to the case of collision-less plasma;this velocity sees minuscule reduction with increasing nonextensivity.The increasing ion temperature and collisional parameter lead to the formation of sheath with smaller thickness.展开更多
A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and...A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.展开更多
A hydrodynamic model is used to investigate the characteristics of positive ions in the sheath region of a low-pressure magnetized electronegative discharge. Positive ions are modeled as a cold fluid, while the electr...A hydrodynamic model is used to investigate the characteristics of positive ions in the sheath region of a low-pressure magnetized electronegative discharge. Positive ions are modeled as a cold fluid, while the electron and negative ion density distributions obey the Boltzmann distribution with two different temperatures. By taking into account the ion-neutral collision effect in the sheath region and assuming that the momentum transfer cross section has a power law dependence on the velocity of positive ions, the sheath formation criterion （modified Bohm＇s criterion） is derived and it is shown that there are specified maximum and minimum limits for the ion Mach number M. Considering these two limits of M, the behaviors of electrostatic potential, charged particle density distributions and positive ion velocities in the sheath region are studied for different values of ion-neutral collision frequency.展开更多
A kinetic simulation model has been employed to study the properties of an electronegative magnetized plasma sheath assuming the cut-off distribution of electrons and negative ions.The fundamental kinetic Bohm conditi...A kinetic simulation model has been employed to study the properties of an electronegative magnetized plasma sheath assuming the cut-off distribution of electrons and negative ions.The fundamental kinetic Bohm condition for the electronegative magnetized plasma has paramount importance for the formation of a stationary plasma sheath near the material wall.The presence of an oblique magnetic field in an electronegative plasma affects the ion distribution at the plasma injection side and at the wall.The temperature profile of negative charged particles has a non-uniform distribution,which determines the energy flow towards the wall.展开更多
In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,firs...In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,first,the intrinsic connection between the electropositive plasma transport equation and spring oscillator dynamic equation is established.Inspired by this similarity,reformed“spring oscillator”equation with dispersing instead of restoring force that gives quasi-delta solution is devised according to the math embodied in the anion equation,which is of potential significance to the disciplines of atomic physics and astronomy as well.For solving the“diffusion confusion”the physics that determines the delta profile within the continuity equation is explored on the basis that recombination loss source term plays the role of drift flux,which is applicable for fluid model of low temperature plasma,but not the ordinary fluid dynamics.Besides,the math and physics revealed in this work predict that the ratio of recombination or attachment(for electrons)frequency versus the species diffusion coefficient is a very important parameter in determining the delta distribution,as it acts as the acceleration of object,according to the reformed oscillator equation.With this theory,the analogous delta profile of electrons density in the famous drift and ambi-polar diffusion heating mechanism of electronegative capacitively coupled plasma is interpreted.展开更多
Kinetic theory has been employed to investigate the magnetized plasma-sheath structure and its characteristics in the presence of more than one species of negatively charged particles:hot electrons,cold electrons,and ...Kinetic theory has been employed to investigate the magnetized plasma-sheath structure and its characteristics in the presence of more than one species of negatively charged particles:hot electrons,cold electrons,and negative ions.The cold electrons and negative ions are considered to obey a Maxwellian distribution,whereas the hot electrons follow a truncated Maxwellian distribution.The Bohm sheath condition has been extended for the case of more than one species of negatively charged particles,in which the concentration of hot electrons has a crucial role in achieving the Bohm velocity.The thermal motion of hot electrons is much higher compared to cold electrons and negative ions,such that the variation of hot electron concentrations and the temperature ratio of hot to cold electrons play a key role in the determination of the plasma-sheath parameters:particle densities,electrostatic potential,the flow of positive ions towards the wall,and sheath thickness.We have estimated the deviation of the resultant drift velocity of positive ions on the plane perpendicular to the wall from the parallel component at the presheath–sheath interface.It is found that the deviation between the two velocity components increases with an increase in the obliqueness of the magnetic field.Furthermore,the results obtained from the kinetic trajectory simulation model are compared with the results obtained using a fluid model;the results are qualitatively similar,although the potential varies by less than 4%in terms of the magnitude at the wall.展开更多
The sheath criterion for an electronegative plasma composed of hot electrons,hot negative ions and cold positive ions in an oblique magnetic field is investigated.We discuss the effects of negative ions and external m...The sheath criterion for an electronegative plasma composed of hot electrons,hot negative ions and cold positive ions in an oblique magnetic field is investigated.We discuss the effects of negative ions and external magnetic field on the sheath criterion.We find that the ion Mach number is of relatively low value because of Coulomb attraction between positive and negative ions.Also the ion Mach number depends on the magnitude and the angle of the magnetic field as well as the initial velocity of ion flow.展开更多
In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Bolt...In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.展开更多
Separation of acetylene(C_(2)H_(2))from carbon dioxide(CO_(2))is important in industry to produce high purity C_(2)H_(2)but challenged by the close physical properties.Herein,a novel microporous TIFSIX anion pillared ...Separation of acetylene(C_(2)H_(2))from carbon dioxide(CO_(2))is important in industry to produce high purity C_(2)H_(2)but challenged by the close physical properties.Herein,a novel microporous TIFSIX anion pillared metal organic framework ZNU-7 with abundant electronegative sites was prepared for efficient C_(2)H_(2)/CO_(2)adsorption separation.The non-coordinating fluorine atoms in the large pores selectively capture C_(2)H_(2)from CO_(2)by hydrogen bonding.The C_(2)H_(2)uptake capacity on ZNU-7 is as high as 92.1 cm^(3)g^(-1),over 2.5 fold of the CO_(2)uptake.The modest C_(2)H_(2)adsorption heat of 35.3 kJ mol^(-1) allows the facile desorption and regeneration of ZNU-7.The much stronger binding of C_(2)H_(2)compared to CO_(2)was further revealed by DFT calculations.The practical separation ability was confirmed by breakthrough experiments using C_(2)H_(2)/CO_(2)gas mixtures with good recyclability.The dynamic separation factor of 3.0 for an equimolar C_(2)H_(2)/CO_(2)mixture is comparable to those of many benchmark materials.展开更多
The development of high-performance metallic cobalt pyrite OER catalysts with suitable electronic structures remains a challenge.In this paper,a low-electronegative Fe-substituted cobalt pyrite(Fe_(x)Co_(1-x))S_(2)OER...The development of high-performance metallic cobalt pyrite OER catalysts with suitable electronic structures remains a challenge.In this paper,a low-electronegative Fe-substituted cobalt pyrite(Fe_(x)Co_(1-x))S_(2)OER catalyst with controllable morphology and electronic structure was designed and prepared,and it exhibited excellent catalytic activity owing to the conversion of(Fe_(x)Co_(1-x))S_(2)to Fe-CoOOH during the OER process.展开更多
The variation of the limiting breakdown strengths of strongly electronegative gases, es-pecially, the gas mixtures, with relative gas concentrations, is discussed. Four basic types ofthe behaviour of the variation hav...The variation of the limiting breakdown strengths of strongly electronegative gases, es-pecially, the gas mixtures, with relative gas concentrations, is discussed. Four basic types ofthe behaviour of the variation have been identified, i.e. the linear relation, the synergisticrelation, the positive synergistic relation and the negative synergistic relation. Here alsodiscussed are the values of the figure of merit of electronegative gases and their mixturesand the relationship of the limiting breakdown strength and the figure of meri?.展开更多
The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron co...The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron concentration−relative electronegativity(VEC−REN)composite descriptor was developed to effectively predict the mechanical properties of HEBs.The results demonstrate that with a fixed VEC,the rise of the REN makes HEBs harder but more brittle when the electronegativity of doped TM atoms is lower than that of boron atoms.However,HEBs become softer and more ductile as REN increases if the doped TM atoms have higher electronegativity than boron atoms.The VEC−REN composite descriptor can accurately classify and predict the mechanical properties of HEBs with different components,which provides important theoretical guidance for the rapid design and development of novel high-entropy ceramic materials.展开更多
High-entropy oxides(HEOs)derive their exceptional properties from the atomic-level homogenization of multiple constituent elements within the crystal lattice,which induces a sophisticated local environment that fundam...High-entropy oxides(HEOs)derive their exceptional properties from the atomic-level homogenization of multiple constituent elements within the crystal lattice,which induces a sophisticated local environment that fundamentally reconfigures electron density distributions and coordination environment at active sites.However,the mechanisms by which multi-component systems in HEOs precisely regulate high-activity catalytic sites remain poorly understood.This work addresses this gap by designing medium-entropy perovskite oxides through the strategic incorporation of transition metals with distinct electronegativities and ionic radii,aiming to unravel how local environmental modifications impact the energy band location,coordination states,and adsorption behavior of the Co site.A family of A_(2)BO_(4)-type medium-entropy oxides PrSr(Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)M_(0.2))O_(4)(M=Sc,Cr,Mn)was successfully synthesized.Divergent atomic properties among Sc,Cr,and Mn(electronegativity,ionic size,and metal-oxygen bond strength)triggered pronounced electron redistribution,effectively tuning the d-band center of Co.Remarkably,Cr substitution significantly enhanced O_(2) adsorption at Co-active sites,as indicated by an elongated O-O bond length(1.234Å→1.279Å).Concurrently,Cr doping destabilized the M'-O-Cr bonds(M'=Fe,Co,Ni,Cu)and lowered the thermodynamic barrier for oxygen vacancy formation.Electrochemical tests revealed that PrSr(Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Cr_(0.2))O_(4)(PSMO-Cr)exhibited the highest electrical conductivity and fastest oxygen surface exchange kinetics.At 700℃,the area-specific resistance(ASR)of the PSMO-Cr cathode was 0.07Ωcm^(2).Corresponding fuel cells achieved a maximum power density of 0.76 W cm^(-2).In electrolysis mode,the maximum current density reached 0.56 A cm^(-2) under 1.3 V at 700℃using PSMO-Cr as the anode.These results demonstrate that PSMO-Cr is a promising bifunctional catalyst for energy conversion applications.展开更多
With the support by the National Natural Science Foundation of China,Dr Liu Yongxin(刘永新)and his coworkers at the Key Laboratory of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),Schoo...With the support by the National Natural Science Foundation of China,Dr Liu Yongxin(刘永新)and his coworkers at the Key Laboratory of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),School of Physics and Optoelectronic Technology,Dalian University of Technology,observed,for the first time,the self-organized striated structures of the plasma emission in展开更多
A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four...A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.展开更多
Metal salts with highly electronegative cations have been used to effectively catalyze the liquid-phase nitration of benzene by NO2 to nitrobenzene under solventfree conditions. Several salts including FeCl3, ZrCl4, A...Metal salts with highly electronegative cations have been used to effectively catalyze the liquid-phase nitration of benzene by NO2 to nitrobenzene under solventfree conditions. Several salts including FeCl3, ZrCl4, AlCl3, CuCl2, NiCl2, ZnCl2, MnCl2, Fe（NO3）3-9H2O, Bi （NO3）3·5H2O, Zr（NO3）4-SH2O, Cu（NO3）2.6H2O, Ni （NO3）2·6H2O, Zn（NO3）2·6H2O, Fe2（SO4）3, and CuSO4 were examined and anhydrous FeCl3 exhibited the best catalytic performance under the optimal reaction conditions. The benzene conversion and selectivity to nitrobenzene were both over 99%. In addition, it was determined that the metal counterion and the presence of water hydrates in the salt affects the catalytic activity. This method is simple and efficient and may have potential industrial application prospects.展开更多
Ferroelectric materials are gaining increasing attention for the development of advanced catalytic technologies due to their field-responsive polarization states.However,achieving dynamic optimization of catalytic act...Ferroelectric materials are gaining increasing attention for the development of advanced catalytic technologies due to their field-responsive polarization states.However,achieving dynamic optimization of catalytic activity using ferroelectrics remains a fundamental challenge.Inspired by the force-adaptive mechanisms of fish scales,we introduce an intracrystalline force regulation strategy to dynamically control cobalt spin states and enhance peroxymonosulfate(PMS)activation in Fenton-like processes.This approach utilizes BaTi_(0.92)Co_(0.08)O_(3-δ)(BTC-8)nano-ferroelectrics,where ultrasound irradiation generates a built-in electric field that drives electrons towards cobalt sites.This electron transfer is further facilitated by electronegativity differences between cobalt and barium/titanium ions.The resulting piezo-driven electron flow promotes continuous regeneration of high-spin Co^(2+),enhancing PMS adsorption and SO_(4)^(-)-OH bond cleavage,leading to increased production of⋅SO_(4)^(-)and singlet oxygen(^(1)O_(2))for organic pollutant degradation.Consequently,BTC-8 achieves a reaction rate(k=1.7960 min^(-1))28.93 times higher than that of pure barium titanate,surpassing previously reported PMS activation and piezocatalytic systems.This work represents a shift from static electronic structure design to dynamic electronic engineering in the development of advanced catalytic strategies for water remediation.展开更多
Heteroatom doping has emerged as a powerful strategy to optimize the catalytic and adsorption abilities of electrocatalysts by regulating the electronic structure,thereby enabling the development of efficient electroc...Heteroatom doping has emerged as a powerful strategy to optimize the catalytic and adsorption abilities of electrocatalysts by regulating the electronic structure,thereby enabling the development of efficient electrocatalysts for lithium-sulfur(Li-S)batteries.However,the correlation between the properties of doped atoms and adsorptio n-catalytic ability,as well as the interconnection between adsorption strength and catalytic activity,remains underexplored.Herein,we employed halogen atoms(F,Cl,and Br)with different electronegativities to dope nickel phosphide(Ni_(2)P),aiming to modulate the adsorption properties toward lithium polysulfides(LiPSs).We systematically explored the relationship between the electronegativity of the doping atoms and the adsorption strength,followed by exploring the connection between adsorption and catalytic capabilities.Combined experimental and theoretical analyses reveal that doping halogen atoms effectively strengthens d-p orbital hybridization between Ni atoms and S atoms,thereby enhancing LiPSs anchoring and conversion.Specifically,the chemical adsorption capability is enhanced as the electronegativity of the doped atoms increases.Moreover,the catalytic activity presents a volcano-like trend with the enhancement of adsorption performance,wherein the activity initially increases and subsequently diminishes.Therefore,Cl-doped Ni_(2)P with moderate chemisorption ability exhibits optimal redox kinetics in bidirectional sulfur conversion.Consequently,the Li-S batteries with Cl-Ni_(2)P-separators deliver a high-rate capacity of 790 mAh g^(-1)at 5 C and achieve a remarkable areal capacity of 7.36 mAh cm^(-2)under practical conditions(sulfur loading:7.10 mg cm^(-2);electrolyte/sulfur(E/S)ratio:5μL mg^(-1)).This work uncovers the significance of achieving a balance between adsorption and catalytic capabilities,offering insights into designing efficient electrocatalysts for lithium-sulfur batteries.展开更多
基金financial support provided by the NORPART-2021/10355 project,funded by the Norwegian Directorate for Higher Education and Skills(HK-Dir)。
文摘The scarcity and high cost of lithium resources drive the search for sustainable alternatives,positioning potassium-ion batteries(KIBs)as promising energy storage solutions due to the natural abundance and advantageous electrochemical properties of the potassium.This study investigates the enhancement of KIB anodes through phase transformation and electronic structure engineering of monolayer 1T-MoS_(2),achieved via doping with highly electronegative non-metal elements:carbon(C),nitrogen(N),oxygen(O),and fluorine(F).Density functional theory(DFT)simulations reveal that electronegative atom doping enhances phase stability,structural robustness,and thermal resilience,which are key properties for highperformance KIB anodes.Among the doped configurations,F and N-doped 1T-MoS_(2)(MoS_(2-)F and MoS_(2)-N)exhibit superior electrochemical performance,showing optimal adsorption energies and significantly improved electronic conductivity,attributable to favorable charge redistribution and increased active potassium adsorption sites.Specifically,MoS_(2)-F and MoS_(2)-N achieve the highest specific capacities of339.65 and 339.17 mAh/g,respectively,while maintaining stability within an ideal open circuit voltage range,outperforming undoped MoS_(2).This work undersco res the potential of electronegative atom doping in 1T-MoS_(2)to enable sustainable,high-capacity energy storage solutions,offering key advancements in the electrochemical and structural properties of KIB anodes.
文摘The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and the sheath almost does not exist there, and that distributions of electrons, negative and positive ions in the sheath form a pure positive ion sheath near the boundary of the electrode. Furthermore, the density distribution of space net charge has a peak near the sheath edge, the spatial potential within the sheath falls faster, and the sheath thickness becomes thinner.
基金Rajat Dhawan acknowledges the Council of Scientific and Industrial Research(CSIR),Government of India for providing financial support(Grant Reference Number:09/086(1289)/2017-EMR-1).
文摘An electronegative collisional plasma having warm and massive positive ions,non-extensive distributed electrons and Boltzmann distributed negative ions is modelled for the plasma-surface interaction process that is used for the surface nitriding.Specifically the sheath formation is evaluated through the Bohm’s criterion,which is found to be modified,and the variation of the sheath thickness and profiles of the density of plasma species and the net space charge density in the sheath region in addition to the electric potential.The effect of ion temperature,nonextensivity and collisional parameter is examined in greater detail considering the collisional cross-section to obey power-law dependency on the positive ion velocity.The positive ions are found to enter in the sheath region at lower velocities in the collisional plasma compared to the case of collision-less plasma;this velocity sees minuscule reduction with increasing nonextensivity.The increasing ion temperature and collisional parameter lead to the formation of sheath with smaller thickness.
文摘A precise theoretical investigation has been made on the cylindrical and spherical （nonplanar） Gardner solitons （GSs） and double layers （DLs） in a dusty electronegative plasma （composed of inertial positive and negative ions, Maxwellian cold electrons, non-thermal hot electrons, and negatively charged static dust）. The reductive perturbation method has been used in derivation of the modified Gardner （MG） equation describing the nonlinear propagation of the dust ion-acoustic （DIA） waves. The MG equation admits solitary waves （SWs） and DLs solutions for σ around its critical value σ c （where σc is the value of σ corresponding to the vanishing of the nonlinear coefficient of the Korteweg de-Vries （K-dV） equation）. The nonplanar SWs and DLs solutions are numerically analyzed and the parametric regimes for the existence of the positive as well as negative SWs and negative DLs are obtained. The basic features of nonplanar DIA SWs and DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations, are discussed.
文摘A hydrodynamic model is used to investigate the characteristics of positive ions in the sheath region of a low-pressure magnetized electronegative discharge. Positive ions are modeled as a cold fluid, while the electron and negative ion density distributions obey the Boltzmann distribution with two different temperatures. By taking into account the ion-neutral collision effect in the sheath region and assuming that the momentum transfer cross section has a power law dependence on the velocity of positive ions, the sheath formation criterion （modified Bohm＇s criterion） is derived and it is shown that there are specified maximum and minimum limits for the ion Mach number M. Considering these two limits of M, the behaviors of electrostatic potential, charged particle density distributions and positive ion velocities in the sheath region are studied for different values of ion-neutral collision frequency.
基金Suresh Basnet would like to acknowledge the University Grants Commission,Nepal for the PhD fellowship.
文摘A kinetic simulation model has been employed to study the properties of an electronegative magnetized plasma sheath assuming the cut-off distribution of electrons and negative ions.The fundamental kinetic Bohm condition for the electronegative magnetized plasma has paramount importance for the formation of a stationary plasma sheath near the material wall.The presence of an oblique magnetic field in an electronegative plasma affects the ion distribution at the plasma injection side and at the wall.The temperature profile of negative charged particles has a non-uniform distribution,which determines the energy flow towards the wall.
文摘In our relevant paper[Zhao S X(2021)Chin.Phys.B 30055201],a delta distribution of negative ions is given by fluid simulation and preliminarily explained by decomposed anions transport equation.In the present work,first,the intrinsic connection between the electropositive plasma transport equation and spring oscillator dynamic equation is established.Inspired by this similarity,reformed“spring oscillator”equation with dispersing instead of restoring force that gives quasi-delta solution is devised according to the math embodied in the anion equation,which is of potential significance to the disciplines of atomic physics and astronomy as well.For solving the“diffusion confusion”the physics that determines the delta profile within the continuity equation is explored on the basis that recombination loss source term plays the role of drift flux,which is applicable for fluid model of low temperature plasma,but not the ordinary fluid dynamics.Besides,the math and physics revealed in this work predict that the ratio of recombination or attachment(for electrons)frequency versus the species diffusion coefficient is a very important parameter in determining the delta distribution,as it acts as the acceleration of object,according to the reformed oscillator equation.With this theory,the analogous delta profile of electrons density in the famous drift and ambi-polar diffusion heating mechanism of electronegative capacitively coupled plasma is interpreted.
基金the University Grants Commission,Nepal for the PhD fellowship Ph D/075-76S&T-16。
文摘Kinetic theory has been employed to investigate the magnetized plasma-sheath structure and its characteristics in the presence of more than one species of negatively charged particles:hot electrons,cold electrons,and negative ions.The cold electrons and negative ions are considered to obey a Maxwellian distribution,whereas the hot electrons follow a truncated Maxwellian distribution.The Bohm sheath condition has been extended for the case of more than one species of negatively charged particles,in which the concentration of hot electrons has a crucial role in achieving the Bohm velocity.The thermal motion of hot electrons is much higher compared to cold electrons and negative ions,such that the variation of hot electron concentrations and the temperature ratio of hot to cold electrons play a key role in the determination of the plasma-sheath parameters:particle densities,electrostatic potential,the flow of positive ions towards the wall,and sheath thickness.We have estimated the deviation of the resultant drift velocity of positive ions on the plane perpendicular to the wall from the parallel component at the presheath–sheath interface.It is found that the deviation between the two velocity components increases with an increase in the obliqueness of the magnetic field.Furthermore,the results obtained from the kinetic trajectory simulation model are compared with the results obtained using a fluid model;the results are qualitatively similar,although the potential varies by less than 4%in terms of the magnitude at the wall.
基金supported by National Natural Science Foundation of China(Nos.11005015,51002017)Program Funded by Liaoning Province Education Administration(No.L2011069)
文摘The sheath criterion for an electronegative plasma composed of hot electrons,hot negative ions and cold positive ions in an oblique magnetic field is investigated.We discuss the effects of negative ions and external magnetic field on the sheath criterion.We find that the ion Mach number is of relatively low value because of Coulomb attraction between positive and negative ions.Also the ion Mach number depends on the magnitude and the angle of the magnetic field as well as the initial velocity of ion flow.
文摘In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.
基金supported by the Natural Science Foundation of China(No.22205207 and 21908193)the Jinhua Industrial Key Project(2021A22648)the Open Research Fund of Key Laboratory of the Ministry of Education for Advanced Catalysis Materials and Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces,Zhejiang Normal University(KLMEACM202111).
文摘Separation of acetylene(C_(2)H_(2))from carbon dioxide(CO_(2))is important in industry to produce high purity C_(2)H_(2)but challenged by the close physical properties.Herein,a novel microporous TIFSIX anion pillared metal organic framework ZNU-7 with abundant electronegative sites was prepared for efficient C_(2)H_(2)/CO_(2)adsorption separation.The non-coordinating fluorine atoms in the large pores selectively capture C_(2)H_(2)from CO_(2)by hydrogen bonding.The C_(2)H_(2)uptake capacity on ZNU-7 is as high as 92.1 cm^(3)g^(-1),over 2.5 fold of the CO_(2)uptake.The modest C_(2)H_(2)adsorption heat of 35.3 kJ mol^(-1) allows the facile desorption and regeneration of ZNU-7.The much stronger binding of C_(2)H_(2)compared to CO_(2)was further revealed by DFT calculations.The practical separation ability was confirmed by breakthrough experiments using C_(2)H_(2)/CO_(2)gas mixtures with good recyclability.The dynamic separation factor of 3.0 for an equimolar C_(2)H_(2)/CO_(2)mixture is comparable to those of many benchmark materials.
基金support from the National Natural Science Foundation of China(Grant no.21875039)the Project on the Integration of Industry-Education-Research of Fujian Province(2021H6020).
文摘The development of high-performance metallic cobalt pyrite OER catalysts with suitable electronic structures remains a challenge.In this paper,a low-electronegative Fe-substituted cobalt pyrite(Fe_(x)Co_(1-x))S_(2)OER catalyst with controllable morphology and electronic structure was designed and prepared,and it exhibited excellent catalytic activity owing to the conversion of(Fe_(x)Co_(1-x))S_(2)to Fe-CoOOH during the OER process.
基金Project supported by the National Natural Science Foundation of China.
文摘The variation of the limiting breakdown strengths of strongly electronegative gases, es-pecially, the gas mixtures, with relative gas concentrations, is discussed. Four basic types ofthe behaviour of the variation have been identified, i.e. the linear relation, the synergisticrelation, the positive synergistic relation and the negative synergistic relation. Here alsodiscussed are the values of the figure of merit of electronegative gases and their mixturesand the relationship of the limiting breakdown strength and the figure of meri?.
基金the National Natural Science Foundation of China (Nos. 52071179, 52271033)the Key Program of National Natural Science Foundation of China (No. 51931003)+2 种基金the Natural Science Foundation of Jiangsu Province, China (No. BK20221493)the Jiangsu Province Leading Edge Technology Basic Research Major Project, China (No. BK20222014)the Foundation of “Qinglan Project” for Colleges and Universities in Jiangsu Province, China。
文摘The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron concentration−relative electronegativity(VEC−REN)composite descriptor was developed to effectively predict the mechanical properties of HEBs.The results demonstrate that with a fixed VEC,the rise of the REN makes HEBs harder but more brittle when the electronegativity of doped TM atoms is lower than that of boron atoms.However,HEBs become softer and more ductile as REN increases if the doped TM atoms have higher electronegativity than boron atoms.The VEC−REN composite descriptor can accurately classify and predict the mechanical properties of HEBs with different components,which provides important theoretical guidance for the rapid design and development of novel high-entropy ceramic materials.
基金supported by the National Natural Science Foundation of China(51872078,52272197,52572219)Heilongjiang Provincial Natural Science Foundation of China(LH2024E106)。
文摘High-entropy oxides(HEOs)derive their exceptional properties from the atomic-level homogenization of multiple constituent elements within the crystal lattice,which induces a sophisticated local environment that fundamentally reconfigures electron density distributions and coordination environment at active sites.However,the mechanisms by which multi-component systems in HEOs precisely regulate high-activity catalytic sites remain poorly understood.This work addresses this gap by designing medium-entropy perovskite oxides through the strategic incorporation of transition metals with distinct electronegativities and ionic radii,aiming to unravel how local environmental modifications impact the energy band location,coordination states,and adsorption behavior of the Co site.A family of A_(2)BO_(4)-type medium-entropy oxides PrSr(Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)M_(0.2))O_(4)(M=Sc,Cr,Mn)was successfully synthesized.Divergent atomic properties among Sc,Cr,and Mn(electronegativity,ionic size,and metal-oxygen bond strength)triggered pronounced electron redistribution,effectively tuning the d-band center of Co.Remarkably,Cr substitution significantly enhanced O_(2) adsorption at Co-active sites,as indicated by an elongated O-O bond length(1.234Å→1.279Å).Concurrently,Cr doping destabilized the M'-O-Cr bonds(M'=Fe,Co,Ni,Cu)and lowered the thermodynamic barrier for oxygen vacancy formation.Electrochemical tests revealed that PrSr(Fe_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Cr_(0.2))O_(4)(PSMO-Cr)exhibited the highest electrical conductivity and fastest oxygen surface exchange kinetics.At 700℃,the area-specific resistance(ASR)of the PSMO-Cr cathode was 0.07Ωcm^(2).Corresponding fuel cells achieved a maximum power density of 0.76 W cm^(-2).In electrolysis mode,the maximum current density reached 0.56 A cm^(-2) under 1.3 V at 700℃using PSMO-Cr as the anode.These results demonstrate that PSMO-Cr is a promising bifunctional catalyst for energy conversion applications.
文摘With the support by the National Natural Science Foundation of China,Dr Liu Yongxin(刘永新)and his coworkers at the Key Laboratory of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),School of Physics and Optoelectronic Technology,Dalian University of Technology,observed,for the first time,the self-organized striated structures of the plasma emission in
基金Project supported by Ministry of Education "Chunhui Program" and Fok Ying Tung Education Foundation.
文摘A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.
基金We gratefully acknowledge the financial support for this work by the National Natural Science Foundation of China （Grant Nos. 21676226 and 21306158）, the Collaborative Innovation Center of New Chemical Technologies for Environmental Benignity and Efficient Resource Utilization, and the Project of Technological Innovation ＆ Entrepreneurship Platform for Hunan Youth （2014）.
文摘Metal salts with highly electronegative cations have been used to effectively catalyze the liquid-phase nitration of benzene by NO2 to nitrobenzene under solventfree conditions. Several salts including FeCl3, ZrCl4, AlCl3, CuCl2, NiCl2, ZnCl2, MnCl2, Fe（NO3）3-9H2O, Bi （NO3）3·5H2O, Zr（NO3）4-SH2O, Cu（NO3）2.6H2O, Ni （NO3）2·6H2O, Zn（NO3）2·6H2O, Fe2（SO4）3, and CuSO4 were examined and anhydrous FeCl3 exhibited the best catalytic performance under the optimal reaction conditions. The benzene conversion and selectivity to nitrobenzene were both over 99%. In addition, it was determined that the metal counterion and the presence of water hydrates in the salt affects the catalytic activity. This method is simple and efficient and may have potential industrial application prospects.
基金the National Natural Science Foundation of China(Grant No.U2002217,52102342,52103024 and 12404116)Key Research Program of the Chinese Academy of Sciences(Grant No.ZDRW-CN2021-3-1-18)+5 种基金Chenguang Program of Shanghai Education Development Foundation,Shanghai Municipal Education Commission(Grant No.21CGA40)9th Young Elite Scientists Sponsorship Program by CAST(Grant No.2023QNRC001)10th Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20240270)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20232832)Donghua University 2024 Cultivation Project of Discipline Innovation(Grant No.xkcx-202413)Student Training Program for Innovation and Entrepreneurship of Hangzhou Institute for Advanced Study,University of Chinese Academy of Sciences(Grant No.CXCY20230305).
文摘Ferroelectric materials are gaining increasing attention for the development of advanced catalytic technologies due to their field-responsive polarization states.However,achieving dynamic optimization of catalytic activity using ferroelectrics remains a fundamental challenge.Inspired by the force-adaptive mechanisms of fish scales,we introduce an intracrystalline force regulation strategy to dynamically control cobalt spin states and enhance peroxymonosulfate(PMS)activation in Fenton-like processes.This approach utilizes BaTi_(0.92)Co_(0.08)O_(3-δ)(BTC-8)nano-ferroelectrics,where ultrasound irradiation generates a built-in electric field that drives electrons towards cobalt sites.This electron transfer is further facilitated by electronegativity differences between cobalt and barium/titanium ions.The resulting piezo-driven electron flow promotes continuous regeneration of high-spin Co^(2+),enhancing PMS adsorption and SO_(4)^(-)-OH bond cleavage,leading to increased production of⋅SO_(4)^(-)and singlet oxygen(^(1)O_(2))for organic pollutant degradation.Consequently,BTC-8 achieves a reaction rate(k=1.7960 min^(-1))28.93 times higher than that of pure barium titanate,surpassing previously reported PMS activation and piezocatalytic systems.This work represents a shift from static electronic structure design to dynamic electronic engineering in the development of advanced catalytic strategies for water remediation.
基金supported by the Beijing Institute of Technology Research Fund Program for Young Scholars and 21C Innovation Laboratory Contemporary Amperex Technology Co.,Limited,Ninde,352100,China(21C-OP-202314)。
文摘Heteroatom doping has emerged as a powerful strategy to optimize the catalytic and adsorption abilities of electrocatalysts by regulating the electronic structure,thereby enabling the development of efficient electrocatalysts for lithium-sulfur(Li-S)batteries.However,the correlation between the properties of doped atoms and adsorptio n-catalytic ability,as well as the interconnection between adsorption strength and catalytic activity,remains underexplored.Herein,we employed halogen atoms(F,Cl,and Br)with different electronegativities to dope nickel phosphide(Ni_(2)P),aiming to modulate the adsorption properties toward lithium polysulfides(LiPSs).We systematically explored the relationship between the electronegativity of the doping atoms and the adsorption strength,followed by exploring the connection between adsorption and catalytic capabilities.Combined experimental and theoretical analyses reveal that doping halogen atoms effectively strengthens d-p orbital hybridization between Ni atoms and S atoms,thereby enhancing LiPSs anchoring and conversion.Specifically,the chemical adsorption capability is enhanced as the electronegativity of the doped atoms increases.Moreover,the catalytic activity presents a volcano-like trend with the enhancement of adsorption performance,wherein the activity initially increases and subsequently diminishes.Therefore,Cl-doped Ni_(2)P with moderate chemisorption ability exhibits optimal redox kinetics in bidirectional sulfur conversion.Consequently,the Li-S batteries with Cl-Ni_(2)P-separators deliver a high-rate capacity of 790 mAh g^(-1)at 5 C and achieve a remarkable areal capacity of 7.36 mAh cm^(-2)under practical conditions(sulfur loading:7.10 mg cm^(-2);electrolyte/sulfur(E/S)ratio:5μL mg^(-1)).This work uncovers the significance of achieving a balance between adsorption and catalytic capabilities,offering insights into designing efficient electrocatalysts for lithium-sulfur batteries.
