Multiatom activation of single-atom electrocatalysts via remote coordination for ultrahigh-rate two-electron oxygen reduction

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.

Effects of electron correlation and the Breit interaction on one- and two-electron one-photon transitions in double K hole states of 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.

Bromine-Graphite Intercalation Enabled Two-Electron Transfer for a Bromine-Based Flow Battery

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.

Attosecond pulse generation from two-electron harmonic emission spectrum

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.

Spectra of the Energy Operator of Two-Electron System in the Impurity Hubbard Model

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 Zv. 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.

Fourier transform technique in variational treatment of two-electron parabolic quantum dot

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.

Two-electron and one-photon transitions in highly charged nickel-like ions

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.

Relative phase-dependent two-electron emission dynamics with two-color circularly polarized laser fields

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.

SYNTHESIS AND STRUCTURE OF TWO-ELECTRON HETEROPOLY BLUE K_2H_4SiMo(Ⅴ)_2Mo(Ⅵ)_(10)O_(40)·12H_2O WITH α-KEGGIN STRUCTURE

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.

BiOBr/COF S-scheme photocatalyst for H_(2)O_(2) production via concerted two-electron pathway

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.

Charge state modulation on boron site by carbon and nitrogen localized bonding microenvironment for two-electron electrocatalytic H_(2)O_(2)production

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.

二维材料用于电化学法制备过氧化氢的研究进展

用电化学的方法通过氧还原反应生产过氧化氢更为环保和有效,而实现这一途径的关键在于制备高活性、高选择性和高稳定性的电催化剂。贵金属催化剂是首选,其催化活性好且稳定性高。但是,贵金属成本高,不利于过氧化氢的规模化制备。因此,减少贵金属用量或者寻找低成本的可替代品一直是近年来的研究热点。很多非贵金属材料已被用作氧还原反应的电催化剂,其中部分材料和贵金属的催化性能相当,甚至更加优异。二维材料相比于本体材料更利于电子传递且更加容易进行化学修饰,二维材料的原子利用率高,可以给电化学反应提供较大的反应场所和更多的裸露活性位点。本文根据已报道的大量实验和理论计算研究,讨论了用二电子氧还原反应法制备过氧化氢的反应机理,然后列举了近年来石墨烯类催化材料、二维过渡金属硫族化合物、二维共价有机骨架和二维金属有机骨架、石墨相氮化碳、二维过渡金属碳/氮化物在电催化氧还原反应中的研究进展,重点分析了其电化学反应机理。最后,指出了二维材料在二电子氧还原反应中的研究挑战和趋势。

磁畴壁拓扑结构研究进展

拓扑磁性斯格明子作为信息载体单元具备高可靠性、高集成度、低能耗等优势,有望提高数据读写精度、降低功耗,从而研发新型拓扑自旋电子学材料与原理型器件,为信息技术、5G通信和大数据等的高速发展提供材料与技术支持.但磁性斯格明子同时存在需要磁场稳定以及电流驱动下斯格明子霍尔效应引起偏转等缺点,严重阻碍了其在实际器件中的应用,因此探索新型拓扑磁畴结构和适宜应用的材料体系成为研究的关键.本文将重点介绍自2013年理论预言磁畴壁斯格明子以来,利用高分辨率洛伦兹透射电子显微镜原位实空间发现并研究磁畴壁拓扑麦纫和磁畴壁斯格明子的实验工作.首次在范德瓦耳斯Fe_(5–x)GeTe_(2)二维磁性材料中发现温度诱发的180°磁畴壁转变为拓扑麦韧链,研究了磁畴壁麦纫态在外界电场、磁场作用下的集体运动行为,揭示了基于自旋重取向、磁畴壁限域效应以及弱相互作用下生成磁畴壁拓扑态的机制.在该机制指导下,设计制备了具有自旋重取向的GdFeCo非晶亚铁磁薄膜,不仅获得了磁畴壁麦纫,验证了生成机制的普适性,还成功实现了畴壁麦韧对到畴壁斯格明子的可逆拓扑转变,开辟了基于磁畴壁等内禀限域效应开展拓扑磁性物态探索和研究的新方向.

索末菲展开对二维电子气体费米能级求解的有效性分析

索末菲展开是固体物理学中讨论自由电子气体性质的重要方法,二维电子气体是金属自由电子气体的一个特例,目前受到了科研工作者的广泛关注.利用严格求解和索末菲展开近似求解两种不同方法对二维电子气体的费米能级进行了计算,同时对两种方法进行比对.分析发现,如果气体温度较低,索末菲展开近似引起的误差较小,阐述了索末菲展开方法的有效性和使用条件.该研究将对学生深入理解固体物理学中相关知识内容有所帮助.

气体扩散电极电合成过氧化氢技术研究进展

过氧化氢(H_(2)O_(2))是一种高效的氧化剂,被广泛应用于化学合成、消毒杀菌和废水处理.通过二电子氧还原反应(2e^(-)ORR)原位电合成H_(2)O_(2)的方法具有高性能和环保性,可作为传统蒽醌工艺的替代策略.气体扩散电极(GDEs)可作为阴极,通过电催化生产H_(2)O_(2),具有更低的成本、更低的能耗和更高的氧气利用效率等优点.探讨GDEs作为阴极时通过2e^(-)ORR产H_(2)O_(2)的机制;讨论GDEs的基本构型、原理及优化方法;分析GDEs催化剂的种类及优势;展望了GDEs作为阴极原位制备H_(2)O_(2)时存在的挑战,为推动2e^(-)ORR原位电合成H_(2)O_(2)迈向市场化提供借鉴.

去嵌入法计量双阴或双阳接口矢网电子校准件方法的探讨

本文介绍了去嵌入法,使用矢量网络分析仪检验件计量特殊接口,如双阴或双阳接口电子校准件,避免复杂的数据处理过程。同时,消除夹具对被测校准件的影响,使测量的参考平面从校准网络分析仪转化为测量结果,从而得到特殊接口电子校准件的各S参数值,并验证参数是否符合要求。

Doubly Excited 1,3Fe States of Two-Electron Atoms under Weakly Coupled Plasma Environment

Precise energy eigenvalues of metastable bound doubly excited 1,3Fe states originating from 2 pnf(n=4–6)configuration of helium-like ions(Z=2–4)under weakly coupled plasma(WCP)environment have been estimated within the framework of Ritz variational method.The wavefunction is expanded in explicitly correlated Hylleraas type basis set.The screened Coulomb potential is consideredas mimic the WCP environment.The atomic systems tend towards gradual instability and the number of excited metastable bound states reduces with increasing plasma strength.The wavelengths corresponding to 2 pnf(1,3F^e)→2 pnf(1,3Do)(n=4–6;n′=3–6)transitions occurring between doubly excited states of plasma embedded two-electron ions are also reported.

VARIATION OF THE INNER ELECTRONIC CLOUD IN A TWO-ELECTRON ATOMIC SYSTEM

The variation of the inner electronic cloud of a two-electron system when the outer elec-tron is moving far away or coming close is investigated in this paper mainly by analyzingthe shape-density. The geometric character and features of internal motion of the ~1S^e heliumstates having different K--numbers have been shown, the mechanism for energy transfer andthe details of radial-radial correlation have been inspected. The motion of the inner electroniccloud as a whole is found to be strongly correlated with the motion of the outer electron.

Highly efficient two-electron electroreduction of oxygen into hydrogen peroxide over Cu-doped TiO_(2)

Electrosynthesis of hydrogen peroxide(H2O_(2)),as a sustainable alternative to the anthraquinone oxidation method,provides the feasibility of directly generating H_(2)O_(2).Here,we report Cu-doped TiO_(2) as an efficient electrocatalyst which exhibits the excellent two-electron oxygen reduction reaction(2e-ORR)performance with respect to the pristine TiO_(2).The Cu doping results in the distortion of TiO_(2) lattice and further forms a large number of oxygen vacancies and Ti^(3+).Such Cu-doped TiO_(2) exhibits a positive onset potential about 0.79 V and high H_(2)O_(2) selectivity about 91.2%.Moreover,it also shows a larger H_(2)O_(2) yield and good stability.Density functional theory(DFT)calculations reveal that Cu dopant not only improves the electrical conductivity of pristine TiO_(2) but reduces the*OOH adsorption energy of active sites,which is beneficial to promote subsequently 2e-ORR process.

Calculatons of the Electron Radius

Equating the Rest Mass Energy of a free electron to its Rest Charge Energy we prove that the electron cannot be a dimensionless point particle because if it were dimensionless, it would contain an infinite amount of Rest Charge Energy at the location of its charge since r = 0 gives , which is clearly not possible. Since the electron has no internal structure, equating its Rest Mass Energy to its Rest Charge Energy, we calculate the electron to be a sphere of radius 4.68 × 10-16 meters. We calculate the Electric Field at the surface of the electron due to its charge and the Repulsive Force two electrons in proximity exert on each other.