Cathode nanoarchitectonics with Na_(3)VFe_(0.5)Ti_(0.5)(PO_(4))_(3): Overcoming the energy barriers of multielectron reactions for sodium-ion batteries

High electrochemical stability and safety make Na+superionic conductor(NASICON)-class cathodes highly desirable for Na-ion batteries(SIBs).However,their practical capacity is limited,leading to low specific energy.Furthermore,the low electrical conductivity combined with a decline in capacity upon prolonged cycling(>1000 cycles)related to the loss of active material-carbon conducting contact regions contributes to moderate rate performance and cycling stability.The need for high specific energy cathodes that meet practical electrochemical requirements has prompted a search for new materials.Herein,we introduce a new carbon-coated Na_(3)VFe_(0.5)Ti_(0.5)(PO_(4))_(3)(NVFTP/C)material as a promising candidate in the NASICON family of cathodes for SIBs.With a high specific energy of∼457 Wh kg^(-1) and a high Na+insertion voltage of 3.0 V versus Na^(+)/Na,this cathode can undergo a reversible single-phase solid-solution and two-phase(de)sodiation evolution at 28 C(1 C=174.7 mAh g^(-1))for up to 10,000 cycles.This study highlights the potential of utilizing low-cost and highly efficient cathodes made from Earth-abundant and harmless materials(Fe and Ti)with enriched Na^(+)-storage properties in practical SIBs.

Bi-Atom Electrocatalyst for Electrochemical Nitrogen Reduction Reactions

The electrochemical nitrogen reduction reaction(NRR)to directly produce NH3 from N_(2) and H_(2)O under ambient conditions has attracted significant attention due to its ecofriendliness.Nevertheless,the electrochemical NRR presents several practical challenges,including sluggish reaction and low selectivity.Here,bi-atom catalysts have been proposed to achieve excellent activity and high selectivity toward the electrochemical NRR by Ma and his co-workers.It could accelerate the kinetics of N_(2)-to-NH_(3) electrochemical conversion and possess better electrochemical NRR selectivity.This work sheds light on the introduction of bi-atom catalysts to enhance the performance of the electrochemical NRR.

The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Zn_(1-x) Mn_x O nanocrystals

Zn1-xMnxO （x = 0.0005, 0.001, 0.005, 0.01, 0.02） nanocrystals are synthesized by using a wet chemical process. The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and its X-ray absorption fine structure. It is found that the solubility of substitutional Mn in a ZnO lattice is very low, which is less than 0.4%. Mn ions first dissolve into the substitutional sites in the ZnO lattice, thereby forming Mn2＋O4 tetrahedral coordination when x ≤ 0.001, then entering into the interstitial sites and forming Mn3＋O6 octahedral coordination when x ≥ 0.005. All the samples exhibit paramagnetic behaviors at room temperature, and antiferromagnetic coupling can be observed below 100 K.

Manipulating coupling state and magnetism of Mn-doped ZnO nanocrystals by changing the coordination environment of Mn via hydrogen annealing

Mn-doped ZnO nanocrystals are synthesized by a wet chemical route and treated in H2/Ar atmosphere with different H2/Ar ratios. It is found that hydrogen annealing could change the coordination environment of Mn in ZnO lattice and manipulate the magnetic properties of Mn-doped ZnO. Mn ions initially enter into interstitial sites and a Mn3＋ 06 octahedral coordination is produced in the prepared Mn-doped ZnO sample, in which the nearest neighbor Mn3＋ and 02 ions could form a Mn3＋-O2--Mn3＋ complex. After H2 annealing, interstitial Mn ions can substitute for Zn to generate the Mn2＋O4 tetrahedral coordination in the nanocrystals, in which neighboring Mn2＋ ions and H atoms could form a Mn2＋-O2--Mn2＋ complex and Mn-H-Mn bridge structure. The magnetic measurement of the as-prepared sample shows room temperature paramagnetic behavior due to the Mn3＋-O2--Mn3＋ complex, while the annealed samples exhibit their ferromagnetism, which originates from the Mn-H-Mn bridge structure and the Mn-Mn exchange interaction in the Mn2＋-O2--Mn2＋ complex.

Long-cycling and dendrite-free lithium metal anodes via salt chemistry

With over 30 years of development for lithium ion batteries(LIBs),LIBs have achieved great success in terms of their cathodes,anodes,electrolytes,and other necessary components[1].Their battery chemistry has also been extended to sodium,potassium,and other alkaline ion batteries,which have also made great achievements[2-4].

Beyond electrode materials structure design:Binders play a vital role for battery application of micro-size electroactive materials

Micrometre-sized electroactive particles with high tapping density show significant potential for commercial application since they effectively alleviate low Coulombic efficiency and excessive solid electrolyte interphase(SEI)issues brought by nanostructures.Furthermore,optimizing the electrode architecture using novel design concepts can improve the energy density.Beyond the electrode material structure design strategy,binder plays a vital role in providing the mechanical stability and regulating the charge transport.This highlight presents the latest development to design high-capacity batteries by optimizing the binder structures in electrodes and emphasizes the significance of binder design for further commercial application.

Ti_(3)C_(2)T_(x)/SnO_(2)P–N heterostructure construction boosts room-temperature detecting formaldehyde

Formaldehyde is a common atmospheric pollutant produced in industrial production and daily life.However,the traditional semiconductor formaldehyde gas sensor cannot work at room temperature,which limits its practical application.Therefore,developing high-performance gas sensors for rapidly and accurately detecting formaldehyde at room temperature is an important topic.In this study,Ti_(3)C_(2)Tx/SnO_(2)heterostructures were constructed,which could selectively detect formaldehyde at room temperature with a response value of 29.16%(10×10^(-6)).In addition,the sensor shows a remarkable theoretical detection limit of 5.09×10^(-9)and good longterm stability.Density functional theory(DFT)simulations reveal that SnO_(2)nano spheres provide the majority of adsorption sites that strongly interact with formaldehyde.Meanwhile,Ti_(3)C_(2)T_(x)acting as a conductive layer facilitates the transfer of charge carriers so that they show a sensing response to formaldehyde at room temperature.Moreover,the formation of p-n heterostructures between SnO_(2)and Ti_(3)C_(2)T_(x)boosts the Schottky barrier at the interface,which is the critical factor in enhancing the sensing properties by turning the Schottky barrier upon introducing formaldehyde gas.This perspective is expected to provide instructive guidance for utilizing MXene/metal oxide nanocomposites to improve the gas sensing performance at room temperature.

Recent advances in alloy-based anode materials for potassium ion batteries

Potassium ion batteries(PIBs)are regarded as one of promising low-cost energy storage technologies.Achieving long cycle life and high energy density has been considered as important tasks for developing high-performance PIBs.The alloy-based anodes for PIBs have attracted great attentions because of their high theoretical capacity and relatively low operating voltage.In this review,the latest advance in the related alloy-based anodes was overviewed.Specifically,the correlations among the morphology and potassium storage performance,phase transition mechanisms,the formation of solid electrolyte interphases and ionic transport kinetics are critically discussed.It is expected that this review will provide meaningful guidance and possible pathways for the developments of alloy-based anodes for PIBs.

Epitaxial growth of metal-semiconductor van der Waals heterostructures NbS2/MoS2 with enhanced performance of transistors and photodetectors

Two-dimensional(2D)heterostructures based on layered transition metal dichalcogenides(TMDs)have attracted increasing attention for the applications of the nextgeneration high-performance integrated electronics and optoelectronics.Although various TMD heterostructures have been successfully fabricated,epitaxial growth of such atomically thin metal-semiconductor heterostructures with a clean and sharp interface is still challenging.In addition,photodetectors based on such heterostructures have seldom been studied.Here,we report the synthesis of high-quality vertical NbS2/MoS2metallic-semiconductor heterostructures.By using NbS2as the contact electrodes,the field-effect mobility and current on-off ratio of MoS2can be improved at least 6-fold and two orders of magnitude compared with the conventional Ti/Au contact,respectively.By using NbS2as contact,the photodetector performance of MoS2is much improved with higher responsivity and less response time.Such facile synthesis of atomically thin metal-semiconductor heterostructures by a simple chemical vapor deposition strategy and its effectiveness as ultrathin 2D metal contact open the door for the future application of electronics and optoelectronics.

Promoted CO2 electroreduction over indium-doped SnP3: A computational study

It is generally considered that the hydrogenation of CO2 is the critical bottleneck of the CO2 electroreduction.In this work,with the aid of density functional theory(DFT)calculations,the catalytic hydrogenation of CO2 molecules over Indium-doped SnP3 catalyst were systematically studied.Through doping with indium(In)atom,the energy barrier of CO2 protonation is reduced and OCHO*species could easily be generated.This is mainly due to the p orbital of In exhibits strong hybridization with the p orbital of O,indicating that there is a strong interaction between OCHO*and In-doped SnP3 catalyst.As a result,In-doped SnP3 possesses high-efficiency and high-selectivity for converting CO2 into HCOOH with a low limiting potential of-0.17 V.Our findings will offer theoretical guidance to CO2 electroreduction.

Issues and rational design of aqueous electrolyte for Zn-ion batteries

Aqueous Zn-ion batteries(AZIBs)are regarded as a promising alternative to the widely used lithium-ion batteries in large-scale energy storage systems.The researches on the development of novel aqueous electrolyte to improve battery performance have also attracted great interest since the electrolyte is a key com-ponent for Zn2+migration between cathode and anode.Herein,we briefly sum-marized and illuminated the recent development tendency of aqueous electrolyte for AZIBs,then deeply analyzed its existing issues(water decomposition,cathode dissolution,corrosion and passivation,and dendrite growth)and discussed the corresponding optimization strategies(pH regulation,concentrated salt solution,electrolyte composition design,and functional additives).The internal mecha-nisms of these strategies were further revealed and the relationships between issues and solutions were clarified,which could guide the future development of aqueous electrolytes for AZIBs.

Recent progress on FeS_(2) as anodes for metal-ion batteries

The ever-growing demand for advanced battery technologies with high energy and power density,high security,prolonged cycle life,and sustainably low cost requires the development of novel electrode materials for lithium-ion batteries(LIBs),as well as the alternative electrochemical energy storage technologies of sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs)for their abundant alkali metal elements resources.Among various anode materials,such as graphite,organic compounds,metal oxides,and chalcogenides,iron sulfides have attracted substantial interests for their high theoretical capacity and low price.Specifically,as a common mineral that has been already applied as electrode for primary battery,ferrous disulfide(FeS_(2))has been regarded as one of the promising candidate anode materials and studied widely.Unfortunately,there are some inherent problems handicapping its practical application for alkali-ion batteries,including limited ionic/electrical conductivity,the formation of soluble polysulfides,and large volume change.In the last decade,massive efforts have been devoted to solving those problems.In this review,the various synthesis strategies,the effect of morphologies and particle sizes,the energy storage mechanisms,and the electrochemical performances of FeS_(2) as anode for alkaliion batteries(LIBs,SIBs,and PIBs)are summarized.Furthermore,the existing challenges and prospects of the development of FeS_(2)-based anode materials for alkali-ion batteries are presented at last.

Metal chalcogenides for potassium storage

Potassium-based energy storage technologies,especially potassium ion batteries(PIBs),have received great interest over the past decade.A pivotal challenge facing high-performance PIBs is to identify advanced electrode materials that can store the large-radius K+ions,as well as to tailor the various thermodynamic parameters.Metal chalcogenides are one of the most promising anode materials,having a high theoretical specific capacity,high in-plane electrical conductivity,and relatively small volume change on charge/discharge.However,the development of metal chalcogenides for PIBs is still in its infancy because of the limited choice of high-performance electrode materials.However,numerous efforts have been made to conquer this challenge.In this article,we overview potassium storage mechanisms,the technical hurdles,and the optimization strategies for metal chalcogenides and highlight how the adjustment of the crystalline structure and choice of the electrolyte affect the electrochemical performance of metal-chalcogenide-based electrode materials.Other potential potassium-based energy storage systems to which metal chalcogenides can be applied are also discussed.Finally,future research directions focusing on metal chalcogenides for potassium storage are proposed.

Understanding the Mechanism of the Oxygen Evolution Reaction with Consideration of Spin

The oxygen evolution reaction(OER)with its intractably high overpotentials is the rate-limiting step in many devices,including rechargeable metal-air batteries,water electrolysis systems and solar fuel devices.Correspondingly,spin state transitions from spin singlet OH^(-)/H_(2)O reactants to spin triplet O_(2)product have not yet received enough attention.In view of this,this article will discuss electron behaviours during OER by taking into consideration of spin attribute.The main conclusion is that,regardless of the possible adopted mechanisms(the adsorbate evolution mechanism or the lattice oxygen mechanism),the underlying rationale of OER is that three in four electrons being extracted from adsorbates should be in the same spin direction before O=O formation,superimposing high requirements on the spin structure of electrocatalysts.Therefore,upon fully understanding of the OER mechanism with considerations of spin,the awareness of the coupling between spin,charge,orbital and lattice parameters is necessary in the optimization of geometric and electronic structures in transition metal systems.Based on this,this article will discuss the possible dependency of OER efficiency on the electrocatalyst spin configuration,and the relevance of well-recognized factors with spin,including the crystal field,coordination,oxidation,bonding,the e_(g) electron number,conductivity and magnetism.It is hoped that this article will clarify the underlying physics of OER to provide rational guidance for more effective design of energy conversion electrocatalysts.

S-Doped Carbon-Coated FeS_(2)/C@C Nanorods for Potassium Storage

Potassium-ion batteries(PIBs) are promising scalable energy storage system;however,one of the challenges for its potential application is the huge volume variations during cycling due to the insertion/extraction of large size potassium ions.Here,we fabricated the S-doped carbon-coated rod-like FeS2/C@C,which not only effectively alleviate the volume variations upon cycling but also can improve electrical conductivity and maintain the structural integrity.As an anode material for PIBs,the rod-like FeS2/C@C electrodes delivered excellent rate performance(175 mA h g-1 at 0.5 A g-1) and stable cycle performance(262 mA h g-1 after 100 cycles at 0.1 A g-1).The superior excellent performance is associated with the unique structure of FeS2/C@C.The as-synthesized FeS2/C@C is demonstrated to be a potential anode for PIBs.

二维磁性拓扑材料:基础理论、材料实现及应用前景

在二维材料的研究中,二维磁性和非平庸拓扑能带成为研究焦点.最近,涌现出一类新型材料体系,被称为二维磁性拓扑材料.它们巧妙地将二维磁性与非平庸拓扑特性相结合,引起人们的广泛研究兴趣.特别是在二维尺度上已推出几种新型磁性拓扑态,如反铁磁拓扑绝缘体/半金属、磁性二阶拓扑绝缘体等.本综述全面分析了目前二维磁性拓扑材料领域的研究进展,包括各类二维磁性拓扑绝缘体、二维磁性拓扑半金属以及完全自旋极化二维拓扑半金属等;系统性地剖析了基础拓扑理论、发展历程、材料实现以及潜在应用.最后,讨论了该领域所面临的挑战与前景,强调了未来在这一引人注目的领域取得更大突破的可能途径.

低电负性阴离子掺杂调控钴酸锌的电子结构以提高析氧反应活性

电子结构和电导率是析氧反应活性的重要描述符,它们可以通过掺杂来调节.鉴于金属掺杂通常会减少电催化剂的活性位点数量,本工作探究了阴离子掺杂对尖晶石钴酸锌(ZCO)电子结构及其析氧活性的影响.与三价钴为主的ZCO相比,用电负性较低的硫取代氧会提高低自旋态(t_(2g)-^(6)e_(g)^(1))二价钴的占比,其析氧活性要高于低自旋态的三价钴(t_(2g)-^(6)e_(g)^(0)).掺硫钴酸锌(ZCO-S)中钴离子和阴离子之间的电子密度的再分布导致了二价钴的增多,而且钴和硫离子间的强共价作用也会加速电荷迁移.ZCO-S在1.65伏(相对于可逆氢电极)下的比活性比原始ZCO高11倍.相反,掺入具有较高电负性和价态的氟(F)并不能有效地改善电子结构,最终导致材料析氧活性的降低.本工作建立了所掺阴离子的电负性与钴酸锌本征析氧活性之间的联系,并提供了一种通过掺杂不同电负性的阴离子来调控尖晶石氧化物的电子结构的简单有效的方法,这为合理设计高性能尖晶石电催化剂提供了新途径.

Transition metal carbides in electrocatalytic oxygen evolution reaction

Oxygen evolution reaction(OER) is admitted to an important half reaction in water splitting for sustainable hydrogen production.The sluggish four-electron process is known to be the bottleneck for enhancing the efficiency of OER.In this regard,tremendous efforts have been devoted to developing effective catalysts for OER.In addition to Ir-or Ru-based oxides taken as the benchmark,transition metal carbides have attracted ever-increasing interest due to the high activity and stability as low-cost OER electrocatalysts.In this review,the transition metal carbides for water oxidation electrocatalysis concerning design strategies and synthesis are briefly summarized.Some typical applications for various carbides are also highlighted.Besides,the development trends and outlook are also discussed.

Honeycomb silicon: a review of silicene

Silicene, a new allotrope of silicon in a twodimensional honeycomb structure, has attracted intensive research interest due to its novel physical and chemical properties. Unlike carbon atoms in graphene, silicon atoms prefer to adopt sp2/sp3-hybridized state in silicene,enhancing chemical activity on the surface and allowing tunable electronic states by chemical functionalization. The silicene monolayers epitaxially grown on Ag(111) surfaces demonstrate various reconstructions with different electronic structures. In this article, the structure, phonon modes, electronic properties, and chemical properties of silicene are reviewed based on theoretical and experimental works in recent years.

Enhanced Photocatalytic Activity of Bi_(24)O_(31)Br_(10): Constructing Heterojunction with BiOI

Bismuth-based compounds have been regarded as an important class of visible-light photocatalysts due to their special electronic structures. In this paper, iodide ions are introduced to modify bismuth-based compound, Bi（24）O（31）Br（10）, forming a Bi（24）O（31）Br（10）/BiOI heterojunction structure. A significant enhancement of photocatalytic activity compared to the parent compounds is observed in de-coloration of rhodamine B（Rh.B） solution. The improved photocatalytic property of Bi（24）O（31）Br（10）/BiOI heterojunction is ascribed to the unique electronic structure consisting of complementary band structures of BiOI and Bi（24）O（31）Br（10）.Iodide ions are regarded as an effective reagent to construct bismuth-based photocatalytic heterojunctions with improved photocatalytic activity.