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.

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.

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.

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.

富电子中心完全暴露镍团簇催化剂高性能电催化CO_(2)还原合成CO

单原子催化剂(SAC)因其最大化的金属原子利用率、独特的电子结构和优异的催化性能在电催化领域引起越来越多的关注.然而,对于需要同时活化不同反应物/中间体的反应来说,孤立的位点是不利的.完全暴露的金属簇催化剂(FECC),继承了SACs和金属纳米颗粒的优点,可以在其多原子位点上协同吸附和活化反应物/中间物,在电催化反应中显示了巨大的前景.文本开发了一种简便的方法从团簇到单原子尺度来调节Ni物种的原子分散度,以实现高效的二氧化碳还原.所制备的Ni FECC在CO合成中表现出了高达99%的法拉第效率,347.2 mA cm^(-2)的高CO分电流密度,以及在20 h电解下的优异稳定性.理论计算表明,多原子中心的构建和硫原子掺杂共同加速了反应动力学,从而提高了电化学CO_(2)还原合成CO的活性与选择性.

Reversible hydrogenation restores defected graphene to graphene

Graphene as a two-dimensional material is prone to hydrocarbon contaminations,which can significantly alter its intrinsic electrical properties.Herein,we implement a facile hydrogenation-dehydrogenation strategy to remove hydrocarbon contaminations and preserve the excellent transport properties of monolayer graphene.Using electron microscopy we quantitatively characterized the improved cleanness of hydrogenated graphene compared to untreated samples.In situ spectroscopic investigations revealed that the hydrogenation treatment promoted the adsorption of water at the graphene surface,resulting in a protective layer against the re-deposition of hydrocarbon molecules.Additionally,the further dehydrogenation of hydrogenated graphene rendered a more pristine-like basal plane with improved carrier mobility compared to untreated pristine graphene.Our findings provide a practical post-growth cleaning protocol for graphene with maintained surface cleanness and lattice integrity to systematically carry a range of surface chemistry in the form of a well-performing and reproducible transistor.