Propelling polysulfide redox by Fe_(3)C-FeN heterostructure@nitrogendoped carbon framework towards high-efficiency Li-S batteries

Lithium-sulfur(Li-S) batteries hold great promise in next-generation high-energy-density energy storage systems,but the intractable shuttle effect and the sluggish redox kinetics of polysulfides hinder the practical implementation of Li-S batteries.Here,heterostructured Fe_(3)C-FeN nanoparticles dotted in the threedimensional-ordered nitrogen-doped carbon framework(Fe_(3)C-FeN@NCF) were synthesized by molecular engineering combined with heterointerface engineering,and were applied to regulate the immobilization-diffusion-conversion behavior of polar polysulfides.It is experimentally and theoretically demonstrated that the heterointerface between Fe_(3)C and FeN exhibits high sulfiphilicity and high electronic/ionic conductivity,thus effectively capturing polysulfides and accelerating the bidirectional conversion of sulfur species.Meanwhile,the holey carbon framework functions as the scaffold to highly disperse binary nanoparticles,ensuring the sufficient exposure of active sites and the easy accessibility for lithium ions and electrons.By virtue of these synergistic merits,the Li-S batteries based on Fe_(3)CFeN@NCF-modified separators afford excellent electrochemical performances including a high rate capacity of 858 mA h g^(-1)at 2 C and a low capacity decay rate of 0.07% per cycle after 800 cycles at 1C This work provides inspiration for the design of heterostructured compounds and sheds light on the potential of heterostructure in high-efficiency Li-S batteries.

Influence of the position relationship between gas–liquid interface and laser focus on plasma evolution characteristics in jet LIBS technology

In order to understand the characteristics of breakdown process,plasma evolution and spectral emission in liquid jets laser-induced breakdown spectroscopy methods under the influence of the position variation between laser focus and gas–liquid interface,this work takes the plasma generated by laser-induced liquid jets as the object of study and discusses the changes in the spatial and temporal evolution characteristics and spectral radiation of the plasma when the position parameters between the laser focal point and the gas–liquid interface are different.The initial breakdown position is always between the front interface and the focus when the laser focus moves along the vertical direction of the interface,forming a phenomenon like’interface effect’.The relationship between laser pulse energy and breakdown probability exhibits a law similar to a‘hysteresis curve’in the study of breakdown threshold.In this work,plasma with smaller size,rounder shape,stronger radiation,higher temperature,and higher density can be produced when the focus position is in the liquid column 0.2 mm away from the front interface.Simultaneously,the spectral signal intensity and signal-to-back ratio of the characteristic peaks of target elements in water reach maximum values,and the spectral signal becomes more stable(relative standard deviation value reaches 2%).The Ca element’s ion radiation at 393.366 nm and atomic radiation at 422.673 nm are studied using narrow-band filtering imaging and time-space resolution spectroscopy.The findings demonstrate that the laws of ion and atomic radiation are not perfectly consistent in space and time.

Oxygen vacancy control of electrical,optical,and magnetic properties of Fe_(0.05)Ti_(0.95)O_(2) epitaxial films

High-quality Fe-doped TiO_(2) films are epitaxially grown on MgF_(2) substrates by pulsed laser deposition.The x-ray diffraction and Raman spectra prove that they are of pure rutile phase.High-resolution transmission electron microscopy(TEM)further demonstrates that the epitaxial relationship between rutile-phased TiO_(2) and MgF_(2) substrates is 110 TiO_(2)||110 MgF_(2).The room temperature ferromagnetism is detected by alternative gradient magnetometer.By increasing the ambient oxygen pressure,magnetization shows that it decreases monotonically while absorption edge shows a red shift.The transport property measurement demonstrates a strong correlation between magnetization and carrier concentration.The influence of ambient oxygen pressure on magnetization can be well explained by a modified bound magnetization polarization model.

Application of different fiber structures and arrangements by electrospinning in triboelectric nanogenerators

In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.

Resistive-type sensors based on few-layer MXene and SnO_(2)hollow spheres heterojunctions:Facile synthesis,ethanol sensing performances

High-performance and low-cost gas sensors are highly desirable and involved in industrial production and environmental detection.The combination of highly conductive MXene and metal oxide materials is a promising strategy to further improve the sensing performances.In this study,the hollow SnO_(2)nanospheres and few-layer MXene are assembled rationally via facile electrostatic synthesis processes,then the SnO_(2)/Ti_(3)C_(2)T_(x)nanocomposites were obtained.Compared with that based on either pure SnO_(2)nanoparticles or hollow nanospheres of SnO_(2),the SnO_(2)/Ti_(3)C_(2)T_(x)composite-based sensor exhibits much better sensing performances such as higher response(36.979),faster response time(5 s),and much improved selectivity as well as stability(15 days)to 100ppm C2H5OH at low working temperature(200°C).The improved sensing performances are mainly attributed to the large specific surface area and significantly increased oxygen vacancy concentration,which provides a large number of active sites for gas adsorption and surface catalytic reaction.In addition,the heterostructure interfaces between SnO_(2)hollow spheres and MXene layers are beneficial to gas sensing behaviors due to the synergistic effect.

Laser irradiation constructing all-in-one defective graphenepolyimide separator for effective restraint of lithium dendrites and shuttle effect

The commercialization of lithium-sulfur(Li-S)batteries faces several bottlenecks,and the major two of which are the shuttle effect of polysulfides and the wild growth of Li dendrites,responsible for fast capacity decay and severe safety issues.As an essential component of Li-S batteries,the structure and properties of the separators are closely related to the above problems,and the exploration of multifunctional separators is highly sought-after.Herein,an integrated separator composited of defective graphene and polyimide(DG-PI)was innovatively fabricated by electrospinning combined with the laser-induced carbonization strategy.The all-in-one compact architecture with well-interconnected channels shows superior mechanical and thermal stability and wettability.More importantly,the PI nanofibers containing N–/O–functional groups can induce the uniform deposition of lithium on the anode surface,while the DG framework with abundant pentagonal/heptagonal rings and vacancies can strongly trap polysulfides and accelerate polysulfide transformation on the cathode side.The strong chemical interaction between the insulative PI layer and the conductive DG layer modulates the surface charge distribution of each other,leading to more prominent contributions to restraining lithium dendrites and shuttle effect.Therefore,the Li-S batteries based on the integrated DG-PI separators afford an excellent performance in protecting lithium anode(stable cycles of 200 h at 5 mA·cm^(−2))and good cycling stability with a low capacity decay of 0.05%per cycle after 700 cycles at 1 C.This work offers a new design concept of multifunctional Li-S battery separators and broadens the application scope of laser micro-nano fabrication technology.

近邻Ni位点对双Fe中心电子自旋态调制实现催化剂增强的催化活性和锌空气电池超长稳定性

在锌空气电池(ZABs)领域中,开发具有优异氧还原反应(ORR)活性和超长期稳定性的Fe基单原子催化剂是一项充满挑战的任务.为此,本文在氮掺杂空心碳球上构建了近邻NiN4单原子位点和Fe_(2)N_(5)双原子位点共存的催化剂(Fe/Ni-NHCS),作为ZABs中高效稳定的空气阴极ORR电催化剂.理论计算和磁性测试结果均表明,近邻NiN_(4)位点的引入对优化Fe2Ns位点的电子自旋态和降低含氧中间体吸附和转化能垒起到关键作用,从而使得Fe/Ni-NHCS具有出色的ORR催化活性和极低的副产物HO_(2)产率。更重要的是,由Fe/Ni-NHCS作为空气阴极驱动的ZABs展现出超过1200h的长时间可充放电循环稳定性。该工作通过调制活性位点的自旋态同时实现了对于催化活性和稳定性的双重优化,从而为能量转换技术的发展拓展了一条新路径。

Structural design and characterization of a new chalcone molecular derivative crystal DMNC with high second-order nonlinear coefficient

1.Text In recent years,new organic second-order nonlinear optical materials have been widely used in optical imaging,data storage,information processing and communication,etc.[1].Therefore,designing and growing crystalline materials with strong second-order nonlinear effects is one of the current research hotspots[2].

In situ magnetometry study on the origin of anomalously capacity in transition metal sulfides

Cobalt sulfides are considered as promising candidates for lithium-ion battery(LIB)anode materials with high energy densities.Their energy storage mechanism is widely understood to involve the traditional intercalation and conversion reaction.However,these conventional mechanisms are unable to explain the storage capacities of certain materials which exceed the theoretical limit.Here,utilizing advanced in situ magnetometry to detect the magnetization evolution of Co_(1-x) S LIBs in real time,it is demonstrated that the Co-catalytic lithium storage process and interfacial space charge storage mechanism are strongly related to the additional capacity of cobalt sulfides.During discharge,a Co/Li_(2) S interface is formed,wherein the Co nanoparticles and Li_(2) S could store a large amount of polarized electrons Li^(+),respectively.Subsequently,the electrons stored in Co are transferred to the polymeric film,forming radical anions and contributing extra capacity.These findings reveal the charge storage mechanisms of transition metal sulfides and highlight the critical role of magnetic testing in the investigation of energy storage mechanisms.

Realization of warm white light emitting in single phase Gd(P_(x)V_(1−x))O_(4):y at% Sm^(3+),1 at% Bi^(3+) phosphor

A series of single phase,warm white light emitting phosphors,Gd(P_(x)V_(1−x))O_(4):y at%Sm^(3+),with 1 at%Bi^(3+) doping concentration were synthesized by high temperature solid state method in this work.The experimental results indicate broadband cyan emission of Bi^(3+)and characteristic orange-red emission of Sm^(3+)can be effectively tuned by changing the ratios of PO^(3−)_(4)/VO^(3−)_(4) in Gd(P_(x)V_(1−x))O_(4):1 at%Sm^(3+),1 at%Bi^(3+),and the energy transfer process among VO^(3−)_(4),Sm^(3+),Bi^(3+) also can be adjusted.Based on this,warm white light emitting can be realized by further optimizing the doping concentration of Sm^(3+) in the phosphors.At 423 K,the PL intensity of Gd(P_(0.7)V_(0.3))O_(4):2 at%Sm^(3+),1 at%Bi^(3+) remains~84.3%of the initial value at 293 K,while the measured quantum efficiency is 67.8%.EL spectrum analysis results of the fabricated white light emitting diode(wLED)based on a 310 nm UV-chip and Gd(P_(0.7)V_(0.3))O4:2 at%Sm^(3+),1 at%Bi^(3+)phosphors imply low correlated color temperature(3132 K)and appropriate color-rending index(R_(a)=82.7).These results demonstrate that Gd(P_(0.7)V_(0.3))O4:2 at%Sm^(3+),1 at%Bi^(3+)is a good candidate for manufacturing UV-activated warm white light emitting diodes.

原位磁性测试揭示锂/钠/钾离子的界面空间电荷存储

本文通过先进的实时原位磁性测试成功揭示了碱金属离子电池中的Li^(+)、Na^(+)、K^(+)的界面空间电荷存储机制.磁性测试结果表明,在FeSe_(2)等过渡族金属材料碱金属离子电池体系中,M^(+)(Li^(+)/Na^(+)/K^(+))和自旋极化电子可以分别存储在M2Se和Fe中,即界面空间电荷存储机制.这说明FeSe_(2)碱金属离子电池的储能机制不仅包含嵌入和转化反应,还包括界面空间电荷存储机制.此外,根据Fe/M2Se界面体系中空间电荷存储M^(+)的能力不同,磁学以及动力学测试结果进一步证明了碱金属离子半径是影响空间电荷存储的重要因素.该研究表明磁性测试是研究过渡族金属基材料的储能机制以及电化学过程中复杂界面效应的一种强有力的分析表征手段,为设计具有大存储容量和高功率密度的先进储能装置奠定了坚实的基础.