Constructing Built-In Electric Fields with Semiconductor Junctions and Schottky Junctions Based on Mo-MXene/Mo-Metal Sulfides for Electromagnetic Response

The exploration of novel multivariate heterostructures has emerged as a pivotal strategy for developing high-performance electromagnetic wave(EMW)absorption materials.However,the loss mechanism in traditional heterostructures is relatively simple,guided by empirical observations,and is not monotonous.In this work,we presented a novel semiconductor-semiconductor-metal heterostructure sys-tem,Mo-MXene/Mo-metal sulfides(metal=Sn,Fe,Mn,Co,Ni,Zn,and Cu),including semiconductor junctions and Mott-Schottky junctions.By skillfully combining these distinct functional components(Mo-MXene,MoS_(2),metal sulfides),we can engineer a multiple heterogeneous interface with superior absorption capabilities,broad effective absorption bandwidths,and ultrathin matching thickness.The successful establishment of semiconductor-semiconductor-metal heterostructures gives rise to a built-in electric field that intensifies electron transfer,as confirmed by density functional theory,which collaborates with multiple dielectric polarization mechanisms to substantially amplify EMW absorption.We detailed a successful synthesis of a series of Mo-MXene/Mo-metal sulfides featuring both semiconductor-semiconductor and semiconductor-metal interfaces.The achievements were most pronounced in Mo-MXene/Mo-Sn sulfide,which achieved remarkable reflection loss values of-70.6 dB at a matching thickness of only 1.885 mm.Radar cross-section calculations indicate that these MXene/Mo-metal sulfides have tremendous potential in practical military stealth technology.This work marks a departure from conventional component design limitations and presents a novel pathway for the creation of advanced MXene-based composites with potent EMW absorption capabilities.

Metal–Organic Gel Leading to Customized Magnetic‑Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances

Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.

Fe-lnduced Electronic Transfer and Structural Evolution of Lotus Pod-Like CoNiFeP_(x)@P,N-C Heterostructure for Sustainable Oxygen Evolution

Transition metal phosphides with metallic properties are a promising candidate for electrocatalytic water oxidation,and developing highly active and stable metal phosphide-based oxygen evolution reaction catalysts is still challenging.Herein,we present a facile ion exchange and phosphating processes to transform intestine-like CoNiP_(x)@P,N-C into lotus pod-like CoNiFeP_(x)@P,N-C heterostructure in which numerous P,N-codoped carboncoated CoNiFeP_(x)nanoparticles tightly anchors on the 2D carbon matrix.Meanwhile,the as-prepared CoNiFeP_(x)@P,N-C enables a core-shell structure,high specific surface area,and hierarchical pore structure,which present abundant heterointerfaces and fully exposed active sites.Notably,the incorporation of Fe can also induce electron transfer in CoNiP_(x)@P,IM-C,thereby promoting the oxygen evolution reaction.Consequently,CoNiFeP_(x)@P,IM-C delivers a low overpotential of 278 mV(vs RHE)at a current density of10 mA cm^(-1)and inherits excellent long-term stability with no observable current density decay after 30 h of chronoamperometry test.This work not only highlights heteroatom induction to tune the electronic structure but also provides a facile approach for developing advanced and stable oxygen evolution reaction electrocatalysts with abundant heterointerfaces.

Coupling of ultrasmall and small CoxP nanoparticles confined in porous SiO2 matrix for a robust oxygen evolution reaction

Rational design of electrocatalysts is important for a sustainable oxygen evolution reaction(OER).It is still a huge challenge to engineer active sites in multi-sizes and multi-components simultaneously.Here,a series of CoxP nanoparticles(NPs)confined in an SiO2matrix(SiO2/CoxP)is designed and synthesized as OER electrocatalysts.The phosphorization of the hydrolyzed Co-phyllosilicate promotes the formation of ultrasmall and small Co2P and CoP.These are firmly confined in the SiO2matrix.The coupling of multi-size and multi-component CoxP catalysts can regulate reaction kinetics and electron transfer ability,enrich the active sites,and eventually promote the intrinsic OER activity.The SiO2matrix provides abundant porous structure and oxygen vacancies,and these facilitate the exposure of active sites and improve conductivity.Because of the synergy and interplay of multisized/component CoxP NPs and the porous SiO2matrix,the unique SiO2/CoxP heterostructure exhibits low overpotential(293 m V@10 mA cm-2),and robust stability(decay 12 mV after 5000 CV cycles,97.4%of initial current after 100 h chronoamperometric)for the OER process,exceeding many advanced metal phosphide electrocatalysts.This work provides a novel tactic to design low-cost,simple,and highly efficient OER electrocatalysts.

A review:(Bi,Na)TiO_(3)(BNT)-based energy storage ceramics

Facing the increasingly serious energy and environmental problems,the research and development of new energy storage technology and environment-friendly energy storage materials are imminent.As a typical lead-free ferroelectric with excellent dielectric properties,(Bi,Na)TiO_(3)(BNT)is supposed to be the most potential and competitive environment-friendly ceramic material and has become a research hotspot for dielectric energy storage in recent years.This paper first briefly introduces the basic physical principles and energy storage performance evaluation parameters of dielectric energy storage materials,then summarizes the critical research systems and related progress of BNT-based lead-free energy storage materials(bulk ceramics,films and multilayer ceramics)from the aspects of ions doping modification and multi-component composite optimization,and finally looks forward to the improvement direction and energy storage application prospect of BNT-based lead-free relaxor ferroelectric materials.

Synthesis of SiOC@C ceramic nanospheres with tunable electromagnetic wave absorption performance

SiOC-based ceramics are considered promising electromagnetic wave-absorbing materials because of their lightweight,high-temperature resistance,and heat insulation properties.Herein,SiOC@C ceramic nanospheres were prepared using a liquid-phase method combined with a polymer-derived ceramic(PDC)method,followed by heat treatment in N_(2) and Ar atmospheres at different temperatures.The morphology,microstructure,phase composition,and electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres were investigated in detail.The SiOC@C ceramic nanospheres obtained in the Ar atmosphere showed a minimum reflection loss(RL_(min))of−67.03 dB,whereas the SiOC@C ceramic nanospheres obtained in the N_(2) atmosphere exhibited an RLmin value of−63.76 dB.The outstanding electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres was attributed to the synergistic effect between conductive loss,interfacial/defect polarization loss,multiple reflections,and scattering.Therefore,this research provides valuable insights into the design and fabrication of SiOC ceramic-based electromagnetic wave absorbers.

Hierarchical assembly of NiFe-PB-derived bimetallic phosphides on 3D Ti_(3)C_(2) MXene ribbon networks for efficient oxygen evolution

The development of MXene-based heterostructures for electrocatalysis has garnered significant attention owing to their potential as high-performance catalysts that play a pivotal role in hydrogen energy.Herein,we present a multistep strategy for the synthesis of a Ti_(3)C_(2) MXene ribbon/NiFePx@graphitic N-doped carbon(NC)heterostructure that enables the formation of three-dimensional(3D)Ti_(3)C_(2) MXene ribbon networks and bimetallic phosphide nanoarrays.With the assistance of HF etching and KOH shearing,the MXene sheets were successfully transformed into 3D MXene networks with interlaced MXene ribbons.Notably,a hydrothermal method,ion exchange route,and phosphorization process were used to anchor NiFeP_(x)@NC nanocubes derived from Ni(OH)_(2)/NiFe-based Prussian blue(NiFe-PB)onto the MXene ribbon network.The resulting MXene ribbon/NiFeP_(x)@NC heterostructure demonstrated enhanced oxygen evolution reaction(OER)activity,characterized by a low overpotential(164 mV at a current density of 10 mA cm^(-2))and a low Tafel slope(45 mV dec^(-1)).At the same time,the MXene ribbons/NiFeP_(x)@NC heterostructure exhibited outstanding long-term stability,with a 12 mV potential decay after 5000 cyclic voltammetry(CV)cycles.This study provides a robust pathway for the design of efficient MXene-based heterostructured electrocatalysts for water splitting.

Construction of dual heterogeneous interface between zigzag-like Mo–MXene nanofibers and small CoNi@NC nanoparticles for electromagnetic wave absorption

Two-dimensional(2D)transition metal carbides(MXene)possess attractive conductivity and abundant surface functional groups,providing immense potential in the field of electromagnetic wave(EMW)absorption.However,high conductivity and spontaneous aggregation of MXene suffer from limited EMW response.Inspired by dielectric–magnetic synergy effect,the strategy of decorating MXene with magnetic elements is expected to solve this challenge.In this work,zigzag-like Mo_(2)TiC_(2)–MXene nanofibers(Mo-based MXene(Mo–MXene)NFs)with cross-linked networks are fabricated by hydrofluoric acid(HF)etching and potassium hydroxide(KOH)shearing processes.Subsequently,Co-metal–organic framework(MOF)and derived CoNi layered double hydroxide(LDH)ultrathin nanosheets are grown inside Mo–MXene NFs,and the N-doped carbon matrix anchored by CoNi alloy nanoparticles formed by pyrolysis is firmly embedded in the Mo–MXene NFs network.Benefiting from synergistic effect of highly dispersed small CoNi alloy nanoparticles,a three-dimensional(3D)conductive network assembled by zigzag-like Mo–MXene NFs,numerous N-doped hollow carbon vesicles,and abundant dual heterogeneous interface,the designed Mo–MXene/CoNi–NC heterostructure provides robust EMW absorption ability with a reflection loss(RL)value of−68.45 dB at the thickness(d)of 4.38 mm.The robust EMW absorption performance can be attributed to excellent dielectric loss,magnetic loss,impedance matching(Z),and multiple scattering and reflection triggered by the unique 3D network structure.This work puts up great potential in developing advanced MXene-based EMW absorption devices.

BS_(0.5)BNT-based relaxor ferroelectric ceramic/glass-ceramic composites for energy storage

Relaxor ferroelectric ceramics have very high dielectric constant(e)but relatively low electrical breakdown strength(Eb),while glass-ceramics exhibit higher E,due to the more uniformly dispersed amorphous phases and submicrocrystals/nanocrystals inside.How to effectively combine the advantages of both relaxor ferroelectric ceramics and glass-ceramics is of great significance for the development of new dielectric materials with high energy storage performance.In this work,we firstly prepared BaO-SrO-Bi_(2)O_(3)-Na_(2)0-TiO_(2)-Al_(2)O_(3)-SiO_(2)(abbreviated as GS)glass powders,and then fabricated(Ba_(0.3)Sr_(0.7))_(0.5)(Bi_(0.5)Na_(0.5))_(0.5)TiO_(3)+x wt%GS ceramic composites(abbreviated as BSo.sBNT-xGS,x=0,2,6,10,14,16,and 18).Submicrocrystals/nanocrystals with a similar composition to BSo.sBNT were crystalized from the glass,ensuring the formation of uniform core-shell structure in BSo.sBNT-xGS relaxor ferroelectric ceramic/glass-ceramic composites.When the addition amount of GS was 14 wt%,the composite possessed both high&r(>3200 at 1 kHz)and high E,(~170 kV/cm)at room temperature,and their recoverable energy storage density and efficiency were Wrec=2.1 J/cm’and n=65.2%,respectively.The BSo.sBNT-14GS composite also had several attractive properties such as good temperature,frequency,cycle stability,and fast charge-discharge speed.This work provides insights into the relaxor ceramic/glass-ceramic composites for pulsed power capacitors and sheds light on the utilization of the hybrid systems.

Honeycomb-like MXene/NiFeP_(x)–NC with“continuous”single-crystal enabling high activity and robust durability in electrocatalytic oxygen evolution reactions

The development of low-cost,stable,and robust non-noble metal catalysts for water oxidation is a pivotal challenge for sustainable hydrogen production through electrocatalytic water splitting.Currently,such catalysts suffer from high overpotential and sluggish kinetics in oxygen evolution reactions(OERs).Herein,we report a“continuous”single-crystal honeycomb-like MXene/NiFeP_(x)–N-doped carbon(NC)heterostructure,in which ultrasmall NiFeP_(x)nanoparticles(NPs)encapsulated in the NC are tightly anchored on a layered MXene.Interestingly,this MXene/NiFeP_(x)–NC delivers outstanding OER catalytic performance,which stems from“continuous”single-crystal characteristics,abundant active sites derived from the ultrasmall NiFeP_(x)NPs,and the stable honeycomb-like heterostructure with an open structure.The experimental results are rationalized theoretically(by density functional theory(DFT)calculations),which suggests that it is the unique MXene/NiFeP_(x)–NC heterostructure that promotes the sluggish OER,thereby enabling superior durability and excellent activity with an ultralow overpotential of 240 mV at a current density of 10 mA×cm^(−2).

Progress and perspectives in dielectric energy storage ceramics

Dielectric ceramic capacitors,with the advantages of high power density,fast chargedischarge capability,excellent fatigue endurance,and good high temperature stability,have been acknowledged to be promising candidates for solid-state pulse power systems.This review investigates the energy storage performances of linear dielectric,relaxor ferroelectric,and antiferroelectric from the viewpoint of chemical modification,macro/microstructural design,and electrical property optimization.Research progress of ceramic bulks and films for Pb-based and/or Pb-free systems is summarized.Finally,we propose the perspectives on the development of energy storage ceramics for pulse power capacitors in the future.

Preliminary 3D printing of large inclined-shaped alumina ceramic parts by direct ink writing

Three dimensional(3D)printing technology by direct ink writing(DIW)is an innovative complex shaping technology,possessing advantages of flexibility in fabrication,high efficiency,low cost,and environmental-friendliness.Herein,3D printing of complex alumina ceramic parts via DIW using thermally induced solidification with carrageenan swelling was investigated.The rheological properties of the slurry under different thermally-induced modes were systematically studied.The solidification properties of thermally-induced pastes with varying contents of carrageenan were optimized.The experimental results showed that the optimized paste consisting of 0.4 wt%carrageenan could be rapidly solidified at about 55℃,which could print inclined-plane more than 60°in vertical without support,resulting in better homogeneity of the green body.A nearly pore-free structure was obtained after sintering at 1600℃ for 2 h.

Remarkably enhanced dielectric stability and energy storage properties in BNT–BST relaxor ceramics by A-site defect engineering for pulsed power applications

Lead-free bulk ceramics for advanced pulsed power capacitors show relatively low recoverable energy storage density(Wrec)especially at low electric field condition.To address this challenge,we propose an A-site defect engineering to optimize the electric polarization behavior by disrupting the orderly arrangement of A-site ions,in which Ba_(0.105)Na_(0.325)Sr_(0.245−1.5x)□_(0.5x)Bi_(0.325)+xTiO_(3)(BNS_(0.245−1.5x)□_(0.5x)B_(0.325+x)T,x=0,0.02,0.04,0.06,and 0.08)lead-free ceramics are selected as the representative.The BNS_(0.245−1.5x)□_(0.5x)B_(0.325+x)T ceramics are prepared by using pressureless solid-state sintering and achieve large W_(rec)(1.8 J/cm^(3))at a low electric field(@110 kV/cm)when x=0.06.The value of 1.8 J/cm3 is super high as compared to all other W_(rec) in lead-free bulk ceramics under a relatively low electric field(<160 kV/cm).Furthermore,a high dielectric constant of 2930 within 15%fluctuation in a wide temperature range of 40–350℃is also obtained in BNS_(0.245−1.5x)□_(0.5x)B_(0.325+x)T(x=0.06)ceramics.The excellent performances can be attributed to the A-site defect engineering,which can reduce remnant polarization(P_(r))and improve the thermal evolution of polar nanoregions(PNRs).This work confirms that the BNS_(0.245−1.5x)□_(0.5x)B_(0.325+x)T(x=0.06)ceramics are desirable for advanced pulsed power capacitors,and will push the development of a series of Bi0.5Na0.5TiO3(BNT)-based ceramics with high W_(rec) and high-temperature stability.

Progress and challenges of ceramics for supercapacitors

Supercapacitors(SCs)are one of the most promising electrical energy storage technologies systems due to their fast storage capability,long cycle stability,high power density,and environmental friendliness.Enormous research has focused on the design of nanomaterials to achieve low cost,highly efficient,and stable electrodes.Ceramic materials provide promising candidates for SCs electrodes.However,the low specific surface area and relatively low surface activity severely hinder the SCs performance of ceramic materials.Therefore,the basic understanding of ceramic materials,the optimization strategy,and the research progress of ceramic electrodes are the key steps to enable good electrical conductivity and excellent electron transport capabilities,and realize economically feasible ceramic electrodes in industry.Herein,we review recent achievements in manufacturing the ceramic electrodes for SCs,including metal oxide ceramics,multi-elemental oxide ceramics,metal hydroxide ceramics,metal sulfide ceramics,carbon-based ceramics,carbide and nitride ceramics,and other special ceramics(MXene).We focus on the unique and key factors in the component and structural design of ceramic electrodes,which correlate them with SCs performance.In addition,the current technical challenges and perspectives of ceramic electrodes for SCs are also discussed.

Synthesis of Acrylonitriles via Mild Base Promoted Tandem Nucleophilic Substitution-Isomerization ofα-Cyanohydrin Methanesulfonates

Main observation and conclusion We have developed an efficient synthesis of acrylonitriles via mild base promoted tandem nucleophilic substitution-isomerization ofα-cyanohydrin methanesulfonates with alkenylboronic acids.This transition metal-free protocol works under simple and mild conditions and offers good chemical yields for a wide range of substrates and demonstrates good functional group tolerance.