Research progress on vanadium oxides for potassium-ion batteries

Potassium-ion batteries(PIBs)have been considered as promising candidates in the post-lithium-ion battery era.Till now,a large number of materials have been used as electrode materials for PIBs,among which vanadium oxides exhibit great potentiality.Vanadium oxides can provide multiple electron transfers during electrochemical reactions because vanadium possesses a variety of oxidation states.Meanwhile,their relatively low cost and superior material,structural,and physicochemical properties endow them with strong competitiveness.Although some inspiring research results have been achieved,many issues and challenges remain to be further addressed.Herein,we systematically summarize the research progress of vanadium oxides for PIBs.Then,feasible improvement strategies for the material properties and electrochemical performance are introduced.Finally,the existing challenges and perspectives are discussed with a view to promoting the development of vanadium oxides and accelerating their practical applications.

Hollow Bio-derived Polymer Nanospheres with Ordered Mesopores for Sodium-Ion Battery

Bio-inspired hierarchical self-assembly provides elegant and powerful bottom-up strategies for the creation of complex materials.However,the current self-assembly approaches for natural bio-compounds often result in materials with limited diversity and complexity in architecture as well as microstructure.Here,we develop a novel coordination polymerization-driven hierarchical assembly of micelle strategy,using phytic acid-based natural compounds as an example,for the spatially controlled fabrication of metal coordination bio-derived polymers.The resultant ferric phytate polymer nanospheres feature hollow architecture,ordered meso-channels of^12 nm,high surface area of 401 m2 g−1,and large pore volume of 0.53 cm3 g−1.As an advanced anode material,this bio-derivative polymer delivers a remarkable reversible capacity of 540 mAh g−1 at 50 mA g−1,good rate capability,and cycling stability for sodium-ion batteries.This study holds great potential of the design of new complex bio-materials with supramolecular chemistry.

Two-dimensional organic cathode materials for alkali-metal-ion batteries

With the increasing demand for large-scale battery systems in electric vehicles（EVs） and smart renewable energy grids, organic materials including small molecules and polymers utilized as electrodes in rechargeable batteries have received increasing attraction. In recent years, two-dimensional（2D） organic materials possessing planar layered architecture exhibit optional chemical modification, high specific surface area as well as unique electrical/magnetic properties, which have been emerging as the promising functional materials for wide applications in optoelectronics, catalysis, sensing, etc. Integrating with high-density redox-active sites and hierarchical porous structure, significant achievements in 2D organic materials as cathode materials for alkali-metal-ion batteries have been witnessed. In this review, the recent progress in synthetic approaches, structure analyses, electrochemical characterizations of 2D organic materials as well as their application in alkali-metal-ion batteries containing lithium ion battery（LIB）, lithium sulfur battery（LSB）, lithium air battery（LAB） and sodium ion battery（SIB） are summarized systematically,and their current challenges including cycling stability and electron conductivity for cathode materials in battery fields are also discussed.

The key challenges and future opportunities of electrochemical capacitors

Electrochemical capacitors(ECs)with unique merits of fast charge/discharge rate and long cyclability are one of the representative electrochemical energy storage systems,possessing wide applications in power electronics and automotive transportation,etc.[1,2].Furthermore.

Fully exposed nickel clusters with electron-rich centers for high-performance electrocatalytic CO_(2) reduction to CO

Single-atom catalysts(SACs)have attracted increasing concerns in electrocatalysis because of their maximal metal atom utilization,distinctive electronic properties,and catalytic performance.However,the isolated single sites are disadvantageous for reactions that require simultaneously activating different reactants/intermediates.Fully exposed metal cluster catalyst(FECC),inheriting the merits of SACs and metallic nanoparticles,can synergistically adsorb and activate reactants/intermediates on their multi-atomic sites,demonstrating great promise in electrocatalytic reactions.Here a facile method to regulate the atomic dispersion of Ni species from cluster to single-atom scale for efficient CO_(2) reduction was developed.The obtained Ni FECC exhibits high Faradaic efficiency of CO up to 99%,high CO partial current density of 347.2 mA cm^(−2),and robust durability under 20 h electrolysis.Theoretical calculations illuminate that the ensemble of multiple Ni atoms regulated by sulfur atoms accelerates the reaction kinetics and thus improves CO production.

NBN-doped nanographene embedded with five-and seven-membered rings on Au(111)surface

Nanographenes(NGs)can be embedded with predesigned dopants or nonhexagonal rings to tailor the electronic properties and provide ideal platforms to study the unique physical and chemical properties.Here,we report the on-surface synthesis of NBN-doped NG embedded with five-and seven-membered rings(NBN-575-NG)on Au(111)from a oligophenylene precursor preinstalled with a NBN unit and a heptagonal ring.Scanning tunneling microscopy and non-contact atomic force microscopy images elucidate the intramolecular cyclodehydrogenation and the existence of the five-and seven-membered rings.Scanning tunneling spectroscopy spectra reveal that the NBN-575-NG is a semiconductor,which agrees with the density functional theory calculation results on a freestanding NBN-575-NG with the same structure.This work provides a feasible approach for the on-surface synthesis of novel NGs containing non-hexagonal rings.

Fabrication of sulfur-doped cove-edged graphene nanoribbons on Au(111)

The on-surface synthesis from predesigned organic precursors can yield graphene nanoribbons(GNRs)with atomically precise widths,edge terminations and dopants,which facilitate the tunning of their electronic structures.Here,we report the synthesis of novel sulfur-doped cove-edged GNRs(S-CGNRs)on Au(111)from a specifically designed precursor containing thiophene rings.Scanning tunneling microscopy and non-contact atomic force microscopy measurements elucidate the formation of S-CGNRs through subsequent polymerization and cyclodehydrogenation,which further result in crosslinked branched structures.Scanning tunneling spectroscopy results reveal the conduction band minimum of the S-CGNR locates at 1.2 e V.First-principles calculations show that the S-CGNR possesses an energy bandgap of 1.17 e V,which is evidently smaller than that of an undoped cove-edged GNR(1.7 e V),suggesting effective tuning of the bandgap by introducing sulfur atoms.Further increasing the coverage of precursors close to a monolayer results in the formation of linear-shaped S-CGNRs.The fabrication of S-CGNRs provides one more candidate in the GNR toolbox and promotes the future applications of heteroatom-doped graphene nanostructures.

Three-Dimensional Sulfated Bacterial Cellulose/Gelatin Composite Scaffolds for Culturing Hepatocytes

The liver is the hub of human metabolism and involves many diseases.To better work on the mechanism and treatment of liver diseases,it is of particular interest to design 3-dimensional scaffolds suitable for culturing hepatocytes in vitro to simulate their metabolic and regenerative abilities.In this study,sulfated bacterial cellulose(SBC)was prepared as the building block of cell scaffolds,motivated by the anionic nature and 3-dimensional structure of hepatic extracellular matrix,and its reaction condition for sulfate esterification was optimized by changing the reaction time.The analysis and study of the microscopic morphology,structure,and cytocompatibility of SBCs showed that they possess good biocompatibility and meet the requirements for tissue engineering.Next,SBC was mixed with gelatin for composite scaffolds(SBC/Gel)for culturing hepatocytes by homogenization and freeze-drying methods,whose physical properties such as pore size,porosity,and compression properties were compared with gelatin(Gel)scaffolds as the control group,and the cytological activity and hemocompatibility of the composite scaffolds were investigated.The results showed that the SBC/Gel composite has better porosity and compression properties,as well as good cytocompatibility and hemocompatibility,and could be applied to 3-dimensional culture of hepatocytes for drug screening or liver tissue engineering.

Exfoliation and Engineering of 2D Materials Through Electrochemistry

Two-dimensional(2D)materials offer countless possibilities for next-generation(opto)electronic devices because of their diverse and tailorable physicochemical characteristics.To bridge the gap between fundamental science and practical applications,simple-to-use universal approaches are essential for the mass production of 2D materials with specific target properties.Electrochemical intercalation/exfoliation stands out from many up-scalable synthetic strategies,thanks to its great time efficiency,mild working conditions,and simple instrumentation.Besides the use for direct exfoliation of 2D materials,device-level controllable intercalation of guest species often results in rich phase diagrams with competing orders and ground states in 2D systems,giving rise to new exotic quantum phenomena.Therefore,making use of electrochemistry in ion intercalation and host–guest interaction is crucial to expand the library,as well as the function of 2D materials.Here,we present a focused review of the exciting advances of electrochemical exfoliation and engineering of 2D materials,including intercalation strategies,intercalation chemistry,exfoliation mechanisms,material properties,and potential applications.An outlook on the major challenges and perspectives is also presented at the end of the discussion.

S-enriched porous polymer derived N-doped porous carbons for electrochemical energy storage and conversion

Porous polymers have been recently recog- nized as one of the most important precursors for fabrication of heteroatom-doped porous carbons due to the intrinsic porous structure, easy available heteroatom- containing monomers and versatile polymerization meth- ods. However, the heteroatom elements in as-produced porous carbons are quite relied on monomers. So far, the manipulating of heteroatom in porous polymer derived porous carbons are still very rare and challenge. In this work, a sulfur-enriched porous polymer, which was prepared from a diacetylene-linked porous polymer, was used as precursor to prepare S-doped and/or N-doped porous carbons under nitrogen and/or ammonia atmo- spheres. Remarkably, S content can sharply decrease from 36.3% to 0.05% after ammonia treatment. The N content and specific surface area of as-fabricated porous carbons can reach up to 1.32% and 1508 m^2·g^-1, respectively. As the electrode materials for electrical double-layer capacitors, as-fabricated porous carbons exhibit high specific capacitance of up to 431.6 F·g^-1 at 5 mW·s^-1 and excellent cycling stability of 99.74% capacitance retention after 3000 cycles at 100 mV·s^-1. Furthermore, as the electro- chemical catalysts for oxygen reduction reaction, as- fabricated porous carbons presented ultralow half-wave- potential of 0.78 V versus RHE. This work not only offers a new strategy for manipulating S and N doping features for the porous carbons derived from S-containing porous polymers, but also paves the way for the structure- performance interrelationship study of heteroatoms co- doped porous carbon for energy applications.

Ligand centered electrocatalytic efficient CO_(2) reduction reaction at low overpotential on single-atom Ni regulated molecular catalyst

Electrochemical CO_(2) reduction reaction(CO_(2)RR)into value-added chemicals/fuels is crucial for realizing the sustainable carbon cycle while mitigating the energy crisis.However,it is impeded by the relatively high overpotential and low energy efficiency due to the lack of efficient electrocatalysts.Herein,we develop an isolated single-atom Ni catalyst regulated strategy to activate and stabilize the iron phthalocyanine molecule(Ni SA@FePc)toward a highly efficient CO_(2)RR process at low overpotential.The well-defined and homogenous catalytic centers with unique structures confer Ni SA@FePc with a significantly enhanced CO_(2)RR performance compared to single-atom Ni catalyst and FePc molecule and afford the atomic understanding on active sites and catalytic mechanism.As expected,Ni SA@FePc exhibits a high selectivity of more significant Faraday efficiency(≥95%)over a wide potential range,a high current density of~252 mA·cm^(−2) at low overpotential(390 mV),and excellent long-term stability for CO_(2)RR to CO.X-ray absorption spectroscopy measurement and theoretical calculation indicate the formation of NiN_(4)-O_(2)-FePc heterogeneous structure for Ni SA@FePc.And CO_(2)RR prefers to occur at the raised N centers of NiN4-O_(2)-FePc heterogeneous structure for Ni SA@FePc,which enables facilitated adsorption of*COOH and desorption of CO,and thus accelerated overall reaction kinetics.

Interfacial synthesis of crystalline quasi-two-dimensional polyaniline thin films for high-performance flexible on-chip micro-supercapacitors

Quasi-two-dimensional(q2 D)conducting polymer thin film synergizes the advantageous features of longrange molecular ordering and high intrinsic conductivity,which are promising for flexible thin film-based micro-supercapacitors(MSCs).Herein,we present the high-performance flexible MSCs based on highly ordered quasi-two-dimensional polyaniline(q2 D-PANI)thin film using surfactant monolayer assisted interfacial synthesis(SMAIS).Owing to high electrical conductivity,rich redox chemistry,and thin-film morphology,the q2 D-PANI MSCs show high volumetric specific capacitance(ca.360 F/cm^(3))and energy density(17.9 m Wh/cm^(3)),which outperform the state-of-art PANI thin-film based MSCs and promise for future flexible electronics.

On-surface synthesis and edge states of NBN-doped zigzag graphene nanoribbons

Zigzag graphene nanoribbons(ZGNRs)with spin-polarized edge states have potential applications in carbon-based spintronics.The electronic structure of ZGNRs can be effectively tuned by different widths or dopants,which requires delicately designed monomers.Here,we report the successful synthesis of ZGNR with a width of eight carbon zigzag lines and nitrogen-boronnitrogen(NBN)motifs decorated along the zigzag edges(NBN-8-ZGNR)on Au(111)surface,which starts from a specially designed U-shaped monomer with preinstalled NBN units at the zigzag edge.Chemical-bond-resolved non-contact atomic force microscopy(nc-AFM)imaging confirms the zigzag-terminated edges and the existence of NBN dopants.The electronic states distributed along the zigzag edges have been revealed after a silicon-layer intercalation at the interface of NBN-8-ZGNR and Au(111).Our work enriches the ZGNR family with a new dopant and larger width,which provides more candidates for future carbonbased nanoelectronic and spintronic applications.

An aqueous rechargeable zinc-ion battery on basis of an organic pigment

Neutral aqueous rechargeable zinc-ion batteries are receiving continuous attention because of their advantages of low cost,high safety,environmental friendliness,and high performance,which are difficult to attain with current organic electrolyte-based batteries.

Sulfur-doped graphene nanoribbons with a sequence of distinct band gaps

Unlike graphene sheets, graphene nanoribbons （GNRs） can exhibit semiconducting band gap characteristics that can be tuned by controlling impurity doping and the GNR widths and edge structures. However, achieving such control is a major challenge in the fabrication of GNRs. Chevron-type GNRs were recently synthesized via surface-assisted polymerization of pristine or N-substituted oligophenylene monomers. In principle, GNR heterojunctions can be fabricated by mixing two different monomers. In this paper, we report the fabrication and characterization of chevron-type GNRs using sulfur-substituted oligophenylene monomers to produce GNRs and related heterostructures for the first time. First-principles calculations show that the GNR gaps can be tailored by applying different sulfur configurations from cyclodehydrogenated isomers via debromination and intramolecular cyclodehydrogenation. This feature should enable a new approach for the creation of multiple GNR heterojunctions by engineering their sulfur configurations. These predictions have been confirmed via scanning tunneling microscopy and scanning tunneling spectroscopy. For example, we have found that the S-containing GNRs contain segments with distinct band gaps, i.e., a sequence of multiple heterojunctions that results in a sequence of quantum dots. This unusual intraribbon heterojunction sequence may be useful in nanoscale optoelectronic applications that use quantum dots.

Emerging reconfigurable electronic devices based on two-dimensional materials:A review

As the dimensions of the transistor,the key element of silicon technology,are approaching their physical limits,developing semiconductor technology with novel concepts and materials has been the main focus of scientific research and industry.In recent years,emerging reconfigurable technologies that offer device-level run-time reconfigurability have been explored and shown the potential to enhance device and circuit functions.Two-dimensional(2D)materials possess exquisite electronic properties and provide a suitable platform for reconfigurable technology owing to their atomic-thin thickness and high sensitivity to external electrical fields.In this review,we present an intensive survey of 2D-material-based devices with diverse reconfigurability,including carrier polarity,threshold voltage control,as well as multifunctional configurations enabled by 2D heterostructures.We discuss the working principles for these devices in detail and highlight the important figures of merit for performance improvement.We further provide a forward-looking perspective on the opportunities and challenges of these reconfigurable devices based on 2D materials in the field of computing technologies.

Vinylene-Linked Two-Dimensional Covalent Organic Frameworks:Synthesis and Functions

Two-dimensional covalent organic frameworks(2D COFs)with covalently bonded repeat units and crystalline,porous framework backbones have attracted immense attention since the first 2D COFs were reported by Yaghi’s group in 2005.The extended single-layer structures of 2D COFs are also generally considered to be the 2D polymers.The precise incorporation of molecular building blocks into ordered frameworks enables the synthesis of novel organic materials with designable and predictable properties for specific applications,such as in optoelectronics,energy storage,and conversion.In particular,the 2Dπ-conjugated COFs(2D-c-COFs)represent a unique class of 2D conjugated polymers that have 2D molecular-periodic structures with extended in-planeπ-conjugations.In the 2D-c-COFs,the conjugated skeletons andπ−πstacking interactions can provide the pathways for electron transport,while the porous channel can enable the loading of active sites for catalysis and sensing.Thus far,the synthesis of 2D-c-COFs has been mostly limited to Schiff base chemistry based on the condensation reaction between amine and aldehyde/ketone monomers because the construction of 2D COFs as thermodynamically controlled products generally requires a highly reversible reaction for error-correction processes.However,the high reversibility of imine linkages would conversely endow moderateπ-electron delocalization due to the polarized carbon−nitrogen bonds and poor stability against strong acids/bases.To achieve robust and highly conjugated 2D-c-COFs,a series of synthesis strategies have been developed,including a one-step reversible reaction with a bond-forming−bond braking−bond reforming function,a quasi-reversible reaction combing reversible and irreversible processes,and postmodifications converting labile bonds to a robust linkage.Among all of the reported 2D-c-COFs,vinylene-linked(also sp^(2)-carbon-linked)2D covalent organic frameworks(V-2D-COFs)with high in-planeπ-conjugation have attracted increasing interest after we reported the first V-2D-COFs via a Knoevenagel polycondensation in 2016.Although CC bonds have low reversibility,making the synthesis of V-2D-COFs quite challenging,there have been around 40 V-2D-COFs reported over the past 5 years,which demonstrated the merits of V-2D-COFs combining with unique optoelectronic,redox,and magnetic properties.In this Account,we will summarize the development of V-2D-COFs,covering the important aspects of synthesis methods,design strategies,unique physical properties,and functions.First,the solvothermal synthesis of V-2D-COFs using different reaction methodologies and design principles will be presented,including Knoevenagel polycondensation,other aldol-type polycondensations,and Horner−Wadsworth−Emmons(HWE)polycondensation.Second,we will discuss the optoelectronic and magnetic properties of V-2D-COFs.Finally,the promising applications of V-2D-COF in the fields of sensing,photocatalysis,energy storage,and conversion will be demonstrated,which benefit from their robust vinylene-linked skeleton,full in-planeπ-conjugation,and tailorable structures.We anticipate that this Account will provide an intensive understanding of the synthesis of V-2D-COFs and inspire the further development of this emerging class of conjugated organic crystalline materials with unique physicochemical properties and applications across different areas.

Perspective towards atomic-resolution imaging of two-dimensional polymers

Recent years have witnessed the rise of an emerging class of synthetic twodimensional(2D)materials-2D polymers.The combination of organic chemistry and rational design of polymeric crystals has stimulated tremendous research efforts in the controlled synthesis of 2D polymers.However,despite the advancement in synthetic methodologies,the structural characterization of 2D polymers remains a significant challenge.Although aberration-corrected high-resolution transmission electron microscopy(AC-HRTEM)is capable of direct imaging of atomic structures with sub-Ångström resolution,electron radiation damage poses a substantial limit on the achievable image resolution due to instant decomposition of the molecular framework.In this Perspective,we will briefly discuss radiation damage mitigation strategies,which may eventually result in AC-HRTEM imaging of 2D polymers down to the atomic scale.

Ultrasensitive detection of Ebola matrix protein in a memristor mode

We demonstrate the direct biosensing of the Ebola VP40 matrix protein, using a memristor mode of a liquid-integrated nanodevice, based on a large array of honeycomb-shaped silicon nanowires. To shed more light on the principle of biodetection using memristors, we engineered the opening of the current-minima voltage gap VG by involving the third gap-control electrode （gate voltage, VG） into the system. The primary role of VG is to mimic the presence of the charged species of the desired sign at the active area of the sensor. We further showed the advantages of biodetection with an initially opened controlled gap （Vc~ ~a 0）, which allows the detection of the lowest concentrations of the biomolecules carrying arbitrary positive or negative charges; this feature was not present in previous configurations. We compared the bio-memristor performance, in terms of its detection range and sensitivity, to that of the already-known field-effect transistor （FET） mode by operating the same device. To our knowledge, this is the first demonstration of Ebola matrix protein detection using a nanoscaled electrical sensor.

Selective and self-validating breath-level detection of hydrogen sulfide in humid air by gold nanoparticle-functionalized nanotube arrays

We demonstrate the selective detection of hydrogen sulfide at breath concentration levels under humid airflow,using a self-validating 64-channel sensor array based on semiconducting single-walled carbon nanotubes(sc-SWCNTs).The reproducible sensor fabrication process is based on a multiplexed and controlled dielectrophoretic deposition of sc-SWCNTs.The sensing area is functionalized with gold nanoparticles to address the detection at room temperature by exploiting the affinity between gold and sulfur atoms of the gas.Sensing devices functionalized with an optimized distribution of nanoparticles show a sensitivity of 0.122%/part per billion(ppb)and a calculated limit of detection(LOD)of 3 ppb.Beyond the self-validation,our sensors show increased stability and higher response levels compared to some commercially available electrochemical sensors.The cross-sensitivity to breath gases NH3 and NO is addressed demonstrating the high selectivity to H2S.Finally,mathematical models of sensors’electrical characteristics and sensing responses are developed to enhance the differentiation capabilities of the platform to be used in breath analysis applications.