Interplay between cold densification and malic acid addition (C4H6O5) for the fabrication of near-isotropic MgB2 conductors for magnet application

The effect of cold high pressure densification(CHPD)on anisotropy of the critical current density(Jc)in《in situ》single core binary and alloyed MgB2 tapes has been determined as a function of temperatures at 4.2 K,20 K and 25 K as well as at applied magnetic fields up to 19 T.The study includes binary and C4H6O5(malic acid)doped MgB2 tapes before and after CHPD.It is remarkable that the CHPD process not only improved the Jc values,in particular at the higher magnetic fields,but also decreased the anisotropy ratio,Г=JC^///JC^⊥In binary MgB2 tapes,the anisotropy factor F increases with higher aspect ratios,even after applying CHPD.In malic acid(C4H6O5)doped tapes,however,the application of CHPD leads only to small enhancements ofГ,even for higher aspect ratios.This is attributed to the higher carbon content in the MgB2 filaments,which in turn is a consequence of the reduced chemical reaction path in the densified filaments.At all applied field values,it was found that CHPD processed C4H6O5 doped tapes exhibit an almost isotropic behavior.This constitutes an advantage in view of industrial magnet applications using wires with square or slightly rectangular configuration.

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.

In-situ formation of MOF derived mesoporous Co3N/amorphous N-doped carbon nanocubes as an efficient electrocatalytic oxygen evolution reaction

The suitable materials,metal nitrides,are a promising class of electrocatalyst materials for a highly efficient oxygen evolution reaction (OER) because they exhibit superior intrinsic conductivity and have higher sustainability than oxide-based materials.To our knowledge,for the first time,we report a designable synthesis of three-dimensional (3D) and mesoporous Co3N@ amorphous N-doped carbon (AN-C) nanocubes (NCs) with well-controlled open-framework structures via monodispersed Co3[Co(CN)6]2 Prussian blue analogue (PBA) NC precursors using in situ nitridation and calcination processes.Co3N@AN-C NCs (2 h) demonstrate better OER activity with a remarkably low Tafel plot (69.6 mV-dec-1),low overpotential of 280 mV at a current density of 10 mA-crrf2.Additionally,excellent cycling stability in alkaline electrolytes was exhibited without morphological changes and voltage elevations,superior to most reported hierarchical structures of transition-metal nitride particles.The presented strategy for synergy effects of metal-organic frameworks (MOFs)-derived transition-metal nitrides-carbon hybrid nanostructures provides prospects for developing high-performance and advanced electrocatalyst materials.

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.

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.

实现照明与显示的新途径:基于单一发光层的白色发光二极管

Light sources,especially white light sources,are indispensable and their development is strongly correlated with the progress of our technology-based society.White light sources have evolved from the primitive flame-based devices of 600,000 years ago to the current LED and electroluminescence devices,and continue to illuminate human activities and technological achievements.The 2014 Nobel Prize in Physics was awarded to Professor Shuji Nakamura et al.for their outstanding contributions in the invention of blue light emitting diodes and white light emitting diodes(WLED),which have become some of the most important sources for lighting,televisual displays,and for other applications[1].

Theoretical insights into nitrogen oxide activation on halogen defect-rich{001}facets of bismuth oxyhalide

Surface vacancies,serving as the activation centers for surface-adsorbed species,have been widely applied in catalysts to improve their activity and selectivity.In the case of ternary compound semiconductors,there is some controversy about exposed atoms and surface defects.Two-dimensional layered BiOCl is an important photocatalyst,which has had numerous studies focused on its oxygen vacancy(O_V)and bismuth vacancy(Bi_V).It has been realized that its(001)surface can consist of exposed halogen atoms rather than oxygen atoms,which thus needs a new explanation for its surface defect engineering mechanism.Using first-principles calculations,the activation behavior of NO_X(NO_(2),NO,N_(2)O)at a chlorine vacancy(Cl_V)on the BiOCl(001)surface is systematically studied.It is found that after introducing Cl_V on BiOCl(001)surfaces,NO_X molecules all show excellent activities with longer chemical bonds by capturing electrons from the catalyst.Our work furnishes fundamental insight into the activation of small molecules on defect-rich surfaces of ternary compound catalysts.