The geometric structure parameters and radial density distribution of 1s2s1S excited state of the two-electron atomic system near the critical nuclear charge Z_(c)were calculated in detail under tripled Hylleraas basi...The geometric structure parameters and radial density distribution of 1s2s1S excited state of the two-electron atomic system near the critical nuclear charge Z_(c)were calculated in detail under tripled Hylleraas basis set.Contrary to the localized behavior observed in the ground and the doubly excited 2p^(23)Pe states,for this state our results identify that while the behavior of the inner electron increasingly resembles that of a hydrogen-like atomic system,the outer electron in the excited state exhibits diffused hydrogen-like character and becomes perpendicular to the inner electron as nuclear charge Z approaches Z_(c).This study provides insights into the electronic structure and stability of the two-electron system in the vicinity of the critical nuclear charge.展开更多
Electrocatalytic oxygen reduction via a two-electron pathway(2e^(-)-ORR)is a promising and eco-friendly route for producing hydrogen peroxide(H_(2)O_(2)).Single-atom catalysts(SACs)typically show excellent selectivity...Electrocatalytic oxygen reduction via a two-electron pathway(2e^(-)-ORR)is a promising and eco-friendly route for producing hydrogen peroxide(H_(2)O_(2)).Single-atom catalysts(SACs)typically show excellent selectivity towards 2e^(-)-ORR due to their unique electronic structures and geometrical configurations.The very low density of single-atom active centers,however,often leads to unsatisfactory H_(2)O_(2)yield rate,significantly inhibiting their practical feasibility.Addressing this,we herein introduce fluorine as a secondary doping element into conventional SACs,which does not directly coordinate with the singleatom metal centers but synergize with them in a remote manner.This strategy effectively activates the surrounding carbon atoms and converts them into highly active sites for 2e^(-)-ORR.Consequently,a record-high H_(2)O_(2)yield rate up to 27 mol g^(-1)h^(-1)has been achieved on the Mo–F–C catalyst,with high Faradaic efficiency of 90%.Density functional theory calculations further confirm the very kinetically facile 2e^(-)-ORR over these additional active sites and the superiority of Mo as the single-atom center to others.This strategy thus not only provides a high-performance electrocatalyst for 2e^(-)-ORR but also should shed light on new strategies to significantly increase the active centers number of SACs.展开更多
The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s^2 configurations of 11 selected He-like ions(10 ≤ Z ≤ 47)...The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s^2 configurations of 11 selected He-like ions(10 ≤ Z ≤ 47) are calculated using the fully relativistic multi-configuration Dirac–Fock method(MCDF). An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of the electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon(TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of the He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.展开更多
In this paper, we theoretically investigate the high-order harmonic generation and attosecond pulse generation when a two-electron He atom is exposed to the intense laser pulse. It shows that due to the two-electron d...In this paper, we theoretically investigate the high-order harmonic generation and attosecond pulse generation when a two-electron He atom is exposed to the intense laser pulse. It shows that due to the two-electron double recombination mechanism, an extended plateau beyond the classical single-electron harmonic has been obtained on the two-electron harmonic spectrum. Further by using this two-electron harmonic extension scheme combined with the two-color field, two supercontinuum bandwidths with 200 e V have been obtained. As a result, a series of sub-60 as extreme ultraviolet（XUV）pulses have been directly generated.展开更多
Br_(2)/Br^(−)is a promising redox couple in fl ow batteries because of its high potential,solubility,and low cost.However,the reaction between Br^(−)and Br_(2)only involves a single-electron transfer process,which lim...Br_(2)/Br^(−)is a promising redox couple in fl ow batteries because of its high potential,solubility,and low cost.However,the reaction between Br^(−)and Br_(2)only involves a single-electron transfer process,which limits its energy density.Herein,a novel two-electron transfer reaction based on Br^(−)/Br^(+) was studied and realized through Br^(+) intercalation into graphite to form a bromine-graphite intercalation compound(Br-GIC).Compared with the pristine Br^(−)/Br_(2)redox pair,the redox potential of Br intercalation/deintercalation in graphite is 0.5 V higher,which has the potential to substantially increase the energy density.Diff erent from Br_(2)/Br^(−)in the electrolyte,the diff usion rate of Br intercalation in graphite decreases with increasing charge state because of the decreasing intercalation sites in graphite,and the integrity of the graphite structure is important for the intercalation reaction.As a result,the battery can continuously run for more than 300 cycles with a Coulombic effi-ciency exceeding 97%and an energy effi ciency of approximately 80%at 30 mA/cm^(2),and the energy density increases by 65%compared with Br^(−)/Br_(2).Combined with double-electron transfer and a highly reversible electrochemical process,the Br intercalation redox couple demonstrates very promising prospects for stationary energy storage.展开更多
We consider two-electron systems for the impurity Hubbard Model and investigate the spectrum of the system in a singlet state for the v-dimensional integer valued lattice Z<sup>v</sup>. We proved the essen...We consider two-electron systems for the impurity Hubbard Model and investigate the spectrum of the system in a singlet state for the v-dimensional integer valued lattice Z<sup>v</sup>. We proved the essential spectrum of the system in the singlet state is consists of union of no more then three intervals, and the discrete spectrum of the system in the singlet state is consists of no more then five eigenvalues. We show that the discrete spectrum of the system in the triplet and singlet states differ from each other. In the singlet state the appear additional two eigenvalues. In the triplet state the discrete spectrum of the system can be empty set, or is consists of one-eigenvalue, or is consists of two eigenvalues, or is consists of three eigenvalues. For investigation the structure of essential spectra and discrete spectrum of the energy operator of two-electron systems in an impurity Hubbard model, for which the momentum representation is convenient. In addition, we used the tensor products of Hilbert spaces and tensor products of operators in Hilbert spaces and described the structure of essential spectrum and discrete spectrum of the energy operator of two-electron systems in an impurity Hubbard model.展开更多
In this work, we propose an efficient method of reducing the computational effort of variational calculation with a Hylleraas-like trial wavefunction. The method consists of introducing integral transforms for the ter...In this work, we propose an efficient method of reducing the computational effort of variational calculation with a Hylleraas-like trial wavefunction. The method consists of introducing integral transforms for the terms as r12^κ exp （-λτ12） which provide the calculation of the expectation value of energy and the relevant matrix elements to be done analytically over single-electron coordinates instead of Hylleraas coordinates. We have used this method to calculate the ground state energy of a two-electron system in a spherical dot and a disk-like quantum dot separately. Under parabolic confinement potential and within effective mass approximation size and shape effects of quantum dots on the ground state energy of two electrons have been investigated. The calculation shows that our results even with a small number of basis states are in good agreement with previous theoretical results.展开更多
This paper calculates the transition wavelengths and probabilities of the two-electron and one-photon （TEOP） transition from the （3s1/2^-14dj）J=1,2 to （3P3/2^-14s1/2）J=1 and the （3P1/2^-14s1/2）J=1 to （3dj^-1...This paper calculates the transition wavelengths and probabilities of the two-electron and one-photon （TEOP） transition from the （3s1/2^-14dj）J=1,2 to （3P3/2^-14s1/2）J=1 and the （3P1/2^-14s1/2）J=1 to （3dj^-14dj＇）J=1,2 for highly charged Ni-like ions with atomic number Z in the range 47 〈 Z 〈 92. In the calculations, the multi-configuration Dirac-Fock method and corresponding program packages GRASP92 and REOS99 were used, and the relativistic effects, correlation effects and relaxation effects were considered systematically. It is found that the TEOP transitions are very sensitive to the correlation of electrons, and the probabilities will be enhanced sharply in some special Z regions along the isoelectronic sequence. The present TEOP transition wavelengths are compared with the available data from some previous publications, good agreement is obtained.展开更多
With the semiclassical ensemble model, we explore the relative phase-dependent nonsequential double ionization (NSDI) of Mg by counter-rotating two-color circularly polarized (TCCP) laser pulses. The yield of Mg2+ sen...With the semiclassical ensemble model, we explore the relative phase-dependent nonsequential double ionization (NSDI) of Mg by counter-rotating two-color circularly polarized (TCCP) laser pulses. The yield of Mg2+ sensitively depends on the relative phase Δφ and the intensity of TCCP laser fields. At Δφ=1.5π, the yield of Mg2+ exhibits a pronounced peak in the 0.05 PW/cm2 laser field. This behavior results from the increase of the initial transverse velocity compensating for the drift velocity with the decreasing angle by analyzing the angular distributions of the electron pairs in four relative phases. By changing the relative phases, we find that the recollision excitation with subsequent ionization and the recollision-impact ionization mechanisms can be controlled with TCCP laser fields.展开更多
The single crystal of two-electron heteropoly blue with Si as the heteroatom and α-Keggin structure K_2H_4SiMo(Ⅴ)_2Mo(Ⅵ)_(10)O_(40)·12H_2O was obtained by electrolytic reduction. It crystallizes in a triclinic...The single crystal of two-electron heteropoly blue with Si as the heteroatom and α-Keggin structure K_2H_4SiMo(Ⅴ)_2Mo(Ⅵ)_(10)O_(40)·12H_2O was obtained by electrolytic reduction. It crystallizes in a triclinic system with space group P , Mr=2117.73, a= 13.702(4), b=14.107(3), c=14.184(2) ; α=119.27(1), β=93.14(2), ;γ=110. 3(2)°, V=2154.29~3, Z=2, F(000)=1999, μ=36.39cm^(-1), Dc=3.26 g/cm^3. Final R factor is 0.0515. Mo(Ⅴ) is situated in two different edge-shared Mo_3O_(13) groups. The heteropoly blue was characterized by IR, UV, polarography, X-ray photoelectron spectra and ESR. All the results show that the structure of the heteropoly anion with Keggin structure remains unchanged basically in the process of reduction.展开更多
Constructing step-scheme(S-scheme)heterojunctions has become a popular strategy for efficient pho-tocatalytic H_(2)O_(2) generation.Herein,we in situ grew BiOBr nanosheets(NSs)on a Schiff-base covalent organic framewo...Constructing step-scheme(S-scheme)heterojunctions has become a popular strategy for efficient pho-tocatalytic H_(2)O_(2) generation.Herein,we in situ grew BiOBr nanosheets(NSs)on a Schiff-base covalent organic framework(COF)with largeπ-conjugated structures to prepare S-scheme BiOBr/COF photocat-alysts for H_(2)O_(2) synthesis.The highest photocatalytic H_(2)O_(2) production performance of the composite sample constituting the S-scheme heterojunction is 3749μmol g−1 h−1,which was 1.85 and 27 times the rates of COF and BiOBr,respectively.The construction of S-scheme heterojunction contributed to ef-ficient carrier transfer and separation in space and enhanced redox power.Moreover,the lying-down O_(2)-adsorption configuration on the COF surface favors the concerted two-electron O_(2) reduction process,which greatly reduced the reduction potential requirement for O_(2)-to-H_(2)O_(2) conversion.The synergy be-tween the S-scheme heterojunction and the unique O_(2)-COF interaction boosted photocatalytic H_(2)O_(2) pro-duction activity.展开更多
Design of electrochemical active boron(B)site at solid materials to understand the relationships between the localized structure,charge state at the B site and electrocatalytic activity plays a crucial role in boostin...Design of electrochemical active boron(B)site at solid materials to understand the relationships between the localized structure,charge state at the B site and electrocatalytic activity plays a crucial role in boosting the green electrochemical synthesis of hydrogen peroxide(H_(2)O_(2))via two-electron oxygen reduction(2eORR)pathway.Herein,we demonstrate a carbon(C)and nitrogen(N)localized bonding microenvironment to modulate the charge state of B site at the boron-carbon nitride solid(BCNs)to realize the efficient selective electrocatalytic H_(2)O_(2)production.The localized chemical structure of N-B-N,N-B-C and C-B-C bonds at B site can be regulated through solid-state reaction between boron nitride(BN)and porous carbon(C)at variable temperatures.The optimized BCN-1100 achieves an outstanding H_(2)O_(2)selectivity of 89%and electron transfer number of 2.2(at 0.55 V vs.RHE),with the production of 10.55mmol/L during 2.5 h and the catalytic stability duration for 15000 cycles.Further first-principles calculations identified the dependency of localized bonding microenvironment on the OOH~*adsorption energies and relevant charge states at the boron site.The localized structure of B site with BNC_(2)-Gr configuration is predicted to be the highest 2eORR activity.展开更多
Two-dimensional diagnosis of laser-induced zirconium(Zr)plasma has been experimentally performed using the time-of-flight method by employing Faraday cups in addition to electric and magnetic probes.The characteristic...Two-dimensional diagnosis of laser-induced zirconium(Zr)plasma has been experimentally performed using the time-of-flight method by employing Faraday cups in addition to electric and magnetic probes.The characteristic parameters of laser-induced Zr plasma have been evaluated as a function of different laser irradiances ranging from 4.5 to 11.7 GW cm-2 at different axial positions of 1–4 cm with a fixed radial distance of 2 cm.A well-supporting correlation between the plume parameters and the laser-plasma-produced spontaneous electric and magnetic(E and B)fields was established.The measurements of the characteristic parameters and spontaneously induced fields were observed to have an increasing trend with the increasing laser irradiance.However,when increasing the spatial distance in both the axial and radial directions,the plasma parameters(electron/ion number density,temperature and kinetic energy)did not show either continuously increasing or decreasing trends due to various kinetic and dynamic processes during the spatial evolution of the plume.However,the E and B fields were observed to be always diffusing away from the target.The radial component of electron number densities remained higher than the axial number density component,whereas the axial ion number density at all laser irradiances and axial distances remained higher than the radial ion number density.The higher axial self-generated electric field(SGEF)values than radial SGEF values are correlated with the effective charge-separation mechanism of electrons and ions.The generation of a self-generated magnetic field is observed dominantly in the radial direction at increasing laser irradiance as compared to the axial one due to the deflection of fast-moving electrons and the persistence of two-electron temperature on the radial axis.展开更多
Amorphous catalysts,thanks to their uniquely coordinated unsaturated properties and abundance of defect sites,tend to possess higher activity and selectivity than their crystalline counterparts.In this work,we report ...Amorphous catalysts,thanks to their uniquely coordinated unsaturated properties and abundance of defect sites,tend to possess higher activity and selectivity than their crystalline counterparts.In this work,we report a facile and general solventcontrolled precipitation method to prepare hybrids of graphene oxide(GO)supporting amorphous metal hydroxide[A-M(OH)_(x)/GO,M=Cu,Co,and Mn],which provides us with tangible materials to study the structure–performance relationship of various amorphous oxides.The systematic investigation of A-Cu(OH)_(2)/GO by coupling ex situ/in situ characteristic techniques with electrochemical studies reveals that electrocatalytic activity and selectivity toward a two-electron oxygen reduction reaction(ORR)is highly dependent on the coordinated Cu catalytic sites and the disordered structure of A-Cu(OH)_(2).In situ X-ray absorption near-edge structure(XANES)and density functional theory(DFT)calculation verify that the degree of OH*poisoning(ΔG0 OH*)tuned by three-OH-coordinated Cu sites in amorphous structures plays a crucial role in selective catalysis of ORR for H_(2)O_(2) production.The optimized A-Cu(OH)_(2)/GO shows superior activity and high selectivity(~95%)toward H_(2)O_(2),as demonstrated by a zinc–air battery capable of on-site H_(2)O_(2) production with a rate as high as 3401.5 mmol h^(−1) g^(−1).展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12074295,12304271,and 12104420).
文摘The geometric structure parameters and radial density distribution of 1s2s1S excited state of the two-electron atomic system near the critical nuclear charge Z_(c)were calculated in detail under tripled Hylleraas basis set.Contrary to the localized behavior observed in the ground and the doubly excited 2p^(23)Pe states,for this state our results identify that while the behavior of the inner electron increasingly resembles that of a hydrogen-like atomic system,the outer electron in the excited state exhibits diffused hydrogen-like character and becomes perpendicular to the inner electron as nuclear charge Z approaches Z_(c).This study provides insights into the electronic structure and stability of the two-electron system in the vicinity of the critical nuclear charge.
基金supported by the National Natural Science Foundation of China(Nos.22179093 and 21905202)。
文摘Electrocatalytic oxygen reduction via a two-electron pathway(2e^(-)-ORR)is a promising and eco-friendly route for producing hydrogen peroxide(H_(2)O_(2)).Single-atom catalysts(SACs)typically show excellent selectivity towards 2e^(-)-ORR due to their unique electronic structures and geometrical configurations.The very low density of single-atom active centers,however,often leads to unsatisfactory H_(2)O_(2)yield rate,significantly inhibiting their practical feasibility.Addressing this,we herein introduce fluorine as a secondary doping element into conventional SACs,which does not directly coordinate with the singleatom metal centers but synergize with them in a remote manner.This strategy effectively activates the surrounding carbon atoms and converts them into highly active sites for 2e^(-)-ORR.Consequently,a record-high H_(2)O_(2)yield rate up to 27 mol g^(-1)h^(-1)has been achieved on the Mo–F–C catalyst,with high Faradaic efficiency of 90%.Density functional theory calculations further confirm the very kinetically facile 2e^(-)-ORR over these additional active sites and the superiority of Mo as the single-atom center to others.This strategy thus not only provides a high-performance electrocatalyst for 2e^(-)-ORR but also should shed light on new strategies to significantly increase the active centers number of SACs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1832126 and 11874051)the National Key Research and Development Program of China(Grant No.2017YFA0402300)。
文摘The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s^2 configurations of 11 selected He-like ions(10 ≤ Z ≤ 47) are calculated using the fully relativistic multi-configuration Dirac–Fock method(MCDF). An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of the electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon(TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of the He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.
基金supported by the Scientific Research Fund of Liaoning Provincial Education Department,China(No.L2014242)the Scientific Research Fund of Liaoning University of Technology,China(Grant Nos.X201319 and X201312)
文摘In this paper, we theoretically investigate the high-order harmonic generation and attosecond pulse generation when a two-electron He atom is exposed to the intense laser pulse. It shows that due to the two-electron double recombination mechanism, an extended plateau beyond the classical single-electron harmonic has been obtained on the two-electron harmonic spectrum. Further by using this two-electron harmonic extension scheme combined with the two-color field, two supercontinuum bandwidths with 200 e V have been obtained. As a result, a series of sub-60 as extreme ultraviolet（XUV）pulses have been directly generated.
基金supported by National Natural Science Foundation of China(Nos.21935003,21925804)the Strategic Priority Research Program of the Chinese Academy of Sci-ences(No.XDA21070100)+1 种基金CAS Engineering Laboratory for Electro-chemical Energy Storage(KFJ-PTXM-027)DICP funding(DICP I202137).
文摘Br_(2)/Br^(−)is a promising redox couple in fl ow batteries because of its high potential,solubility,and low cost.However,the reaction between Br^(−)and Br_(2)only involves a single-electron transfer process,which limits its energy density.Herein,a novel two-electron transfer reaction based on Br^(−)/Br^(+) was studied and realized through Br^(+) intercalation into graphite to form a bromine-graphite intercalation compound(Br-GIC).Compared with the pristine Br^(−)/Br_(2)redox pair,the redox potential of Br intercalation/deintercalation in graphite is 0.5 V higher,which has the potential to substantially increase the energy density.Diff erent from Br_(2)/Br^(−)in the electrolyte,the diff usion rate of Br intercalation in graphite decreases with increasing charge state because of the decreasing intercalation sites in graphite,and the integrity of the graphite structure is important for the intercalation reaction.As a result,the battery can continuously run for more than 300 cycles with a Coulombic effi-ciency exceeding 97%and an energy effi ciency of approximately 80%at 30 mA/cm^(2),and the energy density increases by 65%compared with Br^(−)/Br_(2).Combined with double-electron transfer and a highly reversible electrochemical process,the Br intercalation redox couple demonstrates very promising prospects for stationary energy storage.
文摘We consider two-electron systems for the impurity Hubbard Model and investigate the spectrum of the system in a singlet state for the v-dimensional integer valued lattice Z<sup>v</sup>. We proved the essential spectrum of the system in the singlet state is consists of union of no more then three intervals, and the discrete spectrum of the system in the singlet state is consists of no more then five eigenvalues. We show that the discrete spectrum of the system in the triplet and singlet states differ from each other. In the singlet state the appear additional two eigenvalues. In the triplet state the discrete spectrum of the system can be empty set, or is consists of one-eigenvalue, or is consists of two eigenvalues, or is consists of three eigenvalues. For investigation the structure of essential spectra and discrete spectrum of the energy operator of two-electron systems in an impurity Hubbard model, for which the momentum representation is convenient. In addition, we used the tensor products of Hilbert spaces and tensor products of operators in Hilbert spaces and described the structure of essential spectrum and discrete spectrum of the energy operator of two-electron systems in an impurity Hubbard model.
基金supported by the Cumhuriyet University,National MOVPE Crystal Growth and Characterization Laboratory,Turkey,DPT-K 120,TUBITAK (Grant Nos TBAG 105T492,TBAG 107T012,and TBAG-108T015)
文摘In this work, we propose an efficient method of reducing the computational effort of variational calculation with a Hylleraas-like trial wavefunction. The method consists of introducing integral transforms for the terms as r12^κ exp （-λτ12） which provide the calculation of the expectation value of energy and the relevant matrix elements to be done analytically over single-electron coordinates instead of Hylleraas coordinates. We have used this method to calculate the ground state energy of a two-electron system in a spherical dot and a disk-like quantum dot separately. Under parabolic confinement potential and within effective mass approximation size and shape effects of quantum dots on the ground state energy of two electrons have been investigated. The calculation shows that our results even with a small number of basis states are in good agreement with previous theoretical results.
基金supported by the National Natural Science Foundation of China (Grant Nos 10434100 and 10774122)the Foundation of China/Ireland Science and Technology Collaboration Research (Grant No CI-2004-07)+2 种基金the Foundation of the Center of Theoretical Nuclear Physics,National Laboratory of Heavy Ion Accelerator of Lanzhouthe Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20070736001)the Foundation of Northwest Normal University of China(Grant Nos NWNU-KJCXGC-03-21 and NWNU-QN-2003-28)
文摘This paper calculates the transition wavelengths and probabilities of the two-electron and one-photon （TEOP） transition from the （3s1/2^-14dj）J=1,2 to （3P3/2^-14s1/2）J=1 and the （3P1/2^-14s1/2）J=1 to （3dj^-14dj＇）J=1,2 for highly charged Ni-like ions with atomic number Z in the range 47 〈 Z 〈 92. In the calculations, the multi-configuration Dirac-Fock method and corresponding program packages GRASP92 and REOS99 were used, and the relativistic effects, correlation effects and relaxation effects were considered systematically. It is found that the TEOP transitions are very sensitive to the correlation of electrons, and the probabilities will be enhanced sharply in some special Z regions along the isoelectronic sequence. The present TEOP transition wavelengths are compared with the available data from some previous publications, good agreement is obtained.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2019M661108)the Fundamental Research Funds for the Central Universities,China(Grant No.N2005023).
文摘With the semiclassical ensemble model, we explore the relative phase-dependent nonsequential double ionization (NSDI) of Mg by counter-rotating two-color circularly polarized (TCCP) laser pulses. The yield of Mg2+ sensitively depends on the relative phase Δφ and the intensity of TCCP laser fields. At Δφ=1.5π, the yield of Mg2+ exhibits a pronounced peak in the 0.05 PW/cm2 laser field. This behavior results from the increase of the initial transverse velocity compensating for the drift velocity with the decreasing angle by analyzing the angular distributions of the electron pairs in four relative phases. By changing the relative phases, we find that the recollision excitation with subsequent ionization and the recollision-impact ionization mechanisms can be controlled with TCCP laser fields.
文摘The single crystal of two-electron heteropoly blue with Si as the heteroatom and α-Keggin structure K_2H_4SiMo(Ⅴ)_2Mo(Ⅵ)_(10)O_(40)·12H_2O was obtained by electrolytic reduction. It crystallizes in a triclinic system with space group P , Mr=2117.73, a= 13.702(4), b=14.107(3), c=14.184(2) ; α=119.27(1), β=93.14(2), ;γ=110. 3(2)°, V=2154.29~3, Z=2, F(000)=1999, μ=36.39cm^(-1), Dc=3.26 g/cm^3. Final R factor is 0.0515. Mo(Ⅴ) is situated in two different edge-shared Mo_3O_(13) groups. The heteropoly blue was characterized by IR, UV, polarography, X-ray photoelectron spectra and ESR. All the results show that the structure of the heteropoly anion with Keggin structure remains unchanged basically in the process of reduction.
基金This work was supported by the National Natural Science Foundation of China(Nos.22278324,51932007,22238009,U1905215,52073223,52073034,and 22208332)the Postdoctoral Science Foundation of China(No.2022M712946)the Natural Science Foundation of Hubei Province of China(No.2022CFA001).
文摘Constructing step-scheme(S-scheme)heterojunctions has become a popular strategy for efficient pho-tocatalytic H_(2)O_(2) generation.Herein,we in situ grew BiOBr nanosheets(NSs)on a Schiff-base covalent organic framework(COF)with largeπ-conjugated structures to prepare S-scheme BiOBr/COF photocat-alysts for H_(2)O_(2) synthesis.The highest photocatalytic H_(2)O_(2) production performance of the composite sample constituting the S-scheme heterojunction is 3749μmol g−1 h−1,which was 1.85 and 27 times the rates of COF and BiOBr,respectively.The construction of S-scheme heterojunction contributed to ef-ficient carrier transfer and separation in space and enhanced redox power.Moreover,the lying-down O_(2)-adsorption configuration on the COF surface favors the concerted two-electron O_(2) reduction process,which greatly reduced the reduction potential requirement for O_(2)-to-H_(2)O_(2) conversion.The synergy be-tween the S-scheme heterojunction and the unique O_(2)-COF interaction boosted photocatalytic H_(2)O_(2) pro-duction activity.
基金financially supported by the National Natural Science Foundation of China(Nos.22161036,11904187,21961024 and 21961025)Natural Science Foundation of Inner Mongolia(Nos.2018JQ05 and 2019BS02007)+2 种基金Incentive Funding from Nano Innovation Institute(NII)of Inner Mongolia Minzu Universitythe Inner Mongolia Autonomous Region Funding Project for Science&Technology Achievement Transformation(Nos.CGZH2018156 and 2019GG261)Doctoral Scientific Research Foundation of Inner Mongolia Minzu University(Nos.BS437 and BS480)。
文摘Design of electrochemical active boron(B)site at solid materials to understand the relationships between the localized structure,charge state at the B site and electrocatalytic activity plays a crucial role in boosting the green electrochemical synthesis of hydrogen peroxide(H_(2)O_(2))via two-electron oxygen reduction(2eORR)pathway.Herein,we demonstrate a carbon(C)and nitrogen(N)localized bonding microenvironment to modulate the charge state of B site at the boron-carbon nitride solid(BCNs)to realize the efficient selective electrocatalytic H_(2)O_(2)production.The localized chemical structure of N-B-N,N-B-C and C-B-C bonds at B site can be regulated through solid-state reaction between boron nitride(BN)and porous carbon(C)at variable temperatures.The optimized BCN-1100 achieves an outstanding H_(2)O_(2)selectivity of 89%and electron transfer number of 2.2(at 0.55 V vs.RHE),with the production of 10.55mmol/L during 2.5 h and the catalytic stability duration for 15000 cycles.Further first-principles calculations identified the dependency of localized bonding microenvironment on the OOH~*adsorption energies and relevant charge states at the boron site.The localized structure of B site with BNC_(2)-Gr configuration is predicted to be the highest 2eORR activity.
文摘Two-dimensional diagnosis of laser-induced zirconium(Zr)plasma has been experimentally performed using the time-of-flight method by employing Faraday cups in addition to electric and magnetic probes.The characteristic parameters of laser-induced Zr plasma have been evaluated as a function of different laser irradiances ranging from 4.5 to 11.7 GW cm-2 at different axial positions of 1–4 cm with a fixed radial distance of 2 cm.A well-supporting correlation between the plume parameters and the laser-plasma-produced spontaneous electric and magnetic(E and B)fields was established.The measurements of the characteristic parameters and spontaneously induced fields were observed to have an increasing trend with the increasing laser irradiance.However,when increasing the spatial distance in both the axial and radial directions,the plasma parameters(electron/ion number density,temperature and kinetic energy)did not show either continuously increasing or decreasing trends due to various kinetic and dynamic processes during the spatial evolution of the plume.However,the E and B fields were observed to be always diffusing away from the target.The radial component of electron number densities remained higher than the axial number density component,whereas the axial ion number density at all laser irradiances and axial distances remained higher than the radial ion number density.The higher axial self-generated electric field(SGEF)values than radial SGEF values are correlated with the effective charge-separation mechanism of electrons and ions.The generation of a self-generated magnetic field is observed dominantly in the radial direction at increasing laser irradiance as compared to the axial one due to the deflection of fast-moving electrons and the persistence of two-electron temperature on the radial axis.
基金the Natural Science Foundation of Fujian Province,China(grant no.2020J05079)the National Natural Science Foundation of China(grant nos.21875253,21701175,and 21703248)+1 种基金CAS-Commonwealth Scientific and Industrial Research Organization(CSIRO)Joint Research Projects(no.121835KYSB20200039)the Scientific Research and Equipment Development Project of CAS(no.YJKYYQ20190007).
文摘Amorphous catalysts,thanks to their uniquely coordinated unsaturated properties and abundance of defect sites,tend to possess higher activity and selectivity than their crystalline counterparts.In this work,we report a facile and general solventcontrolled precipitation method to prepare hybrids of graphene oxide(GO)supporting amorphous metal hydroxide[A-M(OH)_(x)/GO,M=Cu,Co,and Mn],which provides us with tangible materials to study the structure–performance relationship of various amorphous oxides.The systematic investigation of A-Cu(OH)_(2)/GO by coupling ex situ/in situ characteristic techniques with electrochemical studies reveals that electrocatalytic activity and selectivity toward a two-electron oxygen reduction reaction(ORR)is highly dependent on the coordinated Cu catalytic sites and the disordered structure of A-Cu(OH)_(2).In situ X-ray absorption near-edge structure(XANES)and density functional theory(DFT)calculation verify that the degree of OH*poisoning(ΔG0 OH*)tuned by three-OH-coordinated Cu sites in amorphous structures plays a crucial role in selective catalysis of ORR for H_(2)O_(2) production.The optimized A-Cu(OH)_(2)/GO shows superior activity and high selectivity(~95%)toward H_(2)O_(2),as demonstrated by a zinc–air battery capable of on-site H_(2)O_(2) production with a rate as high as 3401.5 mmol h^(−1) g^(−1).
