查看更多>>摘要：Li metal anode holds great promise to realize high-energy battery systems.However,the safety issue and limited lifetime caused by the uncontrollable growth of Li dendrites hinder its commercial application.Herein,an interlayer-bridged 3D lithiophilic rGO-Ag-S-CNT composite is proposed to guide uniform and stable Li plating/stripping.The 3D lithiophilic rGO-Ag-S-CNT host is fabricated by incorporating Ag-modified reduced graphene oxide(rGO)with S-doped carbon nanotube(CNT),where the rGO and CNT are closely connected via robust Ag-S covalent bond.This strong Ag-S bond could enhance the structural stability and electrical connection between rGO and CNT,significantly improving the electrochemical kinetics and uniformity of current distribution.Moreover,density functional theory calculation indicates that the introduction of Ag-S bond could further boost the binding energy between Ag and Li,which promotes homogeneous Li nucleation and growth.Consequently,the rGO-Ag-S-CNT-based anode achieves a lower overpotential(7.3 mV at 0.5 mA cm-2),higher Coulombic efficiency(98.1％at 0.5 mA cm-2),and superior long cycling performance(over 500 cycles at 2 mA cm-2)as compared with the rGO-Ag-CNT-and rGO-CNT-based anodes.This work provides a universal avenue and guidance to build a robust Li metal host via constructing a strong covalent bond,effectively suppressing the Li dendrites growth to prompt the development of Li metal battery.
查看更多>>摘要：Monolithic carbon electrodes with robust mechanical integrity and porous architecture are highly desired for capacitive deionization but remain challenging.Owing to the excellent mechanical strength and electroconductivity,commercial carbon fibers cloth demonstrates great potential as high-performance electrodes for ions storage.Despite this,its direct application on capacitive deionization is rarely reported in terms of limited pore structure and natural hydrophobicity.Herein,a powerful metal-organic framework-engaged structural regulation strategy is developed to boost the desalination properties of carbon fibers.The obtained porous carbon fibers features hierarchical porous structure and hydrophilic surface providing abundant ions-accessible sites,and continuous graphitized carbon core ensuring rapid electrons transport.The catalytic-etching mechanism involving oxidation of Co and subsequent carbonthermal reduction is proposed and highly relies on annealing temperature and holding time.When directly evaluated as a current collector-free capacitive deionization electrode,the porous carbon fibers demonstrates much superior desalination capability than pristine carbon fibers,and remarkable cyclic stability up to 20 h with negligible degeneration.Particularly,the PCF-1000 showcases the highest areal salt adsorption capacity of 0.037 mg cm-2 among carbon microfibers.Moreover,monolithic porous carbon fibers-carbon nanotubes with increased active sites and good structural integrity by in-situ growth of carbon nanotubes are further fabricated to enhance the desalination performance(0.051 mg cm-2).This work demonstrates the great potential of carbon fibers in constructing high-efficient and robust monolithic electrode for capacitive deionization.
查看更多>>摘要：The electrochemical carbon dioxide reduction reaction(CO2RR),which can produce value-added chemical feedstocks,is a proton-coupled-electron process with sluggish kinetics.Thus,highly efficient,cheap catalysts are urgently required.Transition metal oxides such as CoOx,FeOx,and NiOx are low-cost,low toxicity,and abundant materials for a wide range of electrochemical reactions,but are almost inert for CO2RR.Here,we report for the first time that nitrogen doped carbon nanotubes(N-CNT)have a surprising activation effect on the activity and selectivity of transition metal-oxide(MOx where M=Fe,Ni,and Co)nanoclusters for CO2RR.MOx supported on N-CNT,MOx/N-CNT,achieves a CO yield of 2.6-2.8 mmol cm-2 min-1 at an overpotential of-0.55 V,which is two orders of magnitude higher than MOx supported on acid treated CNTs(MOx/O-CNT)and four times higher than pristine N-CNT.The faraday efficiency for electrochemical CO2-to-CO conversion is as high as 90.3％at overpotential of 0.44 V.Both in-situ XAS measurements and DFT calculations disclose that MOx nanoclusters can be hydrated in CO2 saturated KHCO3,and the N defects of N-CNT effectively stabilize these metal hydroxyl species under carbon dioxide reduction reaction conditions,which can split the water molecules and provide local protons to inhibit the poisoning of active sites under carbon dioxide reduction reaction conditions.
查看更多>>摘要：Developing laminar composite solid electrolyte with ultrathin thickness and continuous conduction channels in vertical direction holds great promise for all-solid-state lithium batteries.Herein,a thin,laminar solid electrolyte is synthesized by filtrating-NH2 functionalized metal-organic framework nanosheets and then being threaded with poly(ethylene oxide)chains induced by the hydrogen-bonding interaction from-NH2 groups.It is demonstrated that the threaded poly(ethylene oxide)chains lock the adjacent metal-organic framework nanosheets,giving highly enhanced structural stability(Young's modulus,1.3 GPa)to 7.5-μm-thick laminar composite solid electrolyte.Importantly,these poly(ethylene oxide)chains with stretching structure serve as continuous conduction pathways along the chains in pores.It makes the non-conduction laminar metal-organic framework electrolyte highly conductive:3.97 × 10-5 S cm-1 at 25 ℃,which is even over 25 times higher than that of pure poly(ethylene oxide)electrolyte.The assembled lithium cell,thus,acquires superior cycling stability,initial discharge capacity(148 mAh g-1 at 0.5 C and 60 ℃),and retention(94％after 150 cycles).Besides,the pore size of nanosheet is tailored(24.5-40.9 Å)to evaluate the mechanisms of chain conformation and ion transport in confined space.It shows that the confined pore only with proper size could facilitate the stretching of poly(ethylene oxide)chains,and meanwhile inhibit their disorder degree.Specifically,the pore size of 33.8 Å shows optimized confinement effect with trans-poly(ethylene oxide)and cis-poly(ethylene oxide)conformation,which offers great significance in ion conduction.Our design of poly(ethylene oxide)-threaded architecture provides a platform and paves a way to the rational design of next-generation high-performance porous electrolytes.
查看更多>>摘要：Thermoelectrics are a promising solution to the recovery of some of the 60％of the worldwide energy wasted as heat.However,their conversion efficiency is low and the best performing materials are brittle,toxic,and made of expensive ceramics.The challenge in developing better performing materials is in disrupting the electrical vs thermal conductivity correlation,to achieve low thermal conductivity simultaneously with a high electrical conductivity.Carbon nanotubes allow for the decoupling of the electronic density of states from the phonon density of states and this paper shows that flexible,thin films of double-walled carbon nanotube(DWCNT)can form effective n-and p-doped semiconductors that can achieve a combined Seebeck coefficient of 157.6 μV K-1,the highest reported for a single DWCNT device to date.This is achieved through selected surfactant doping,whose role is correlated with the length of the hydrocarbon chain of the hydrophobic tail group of the surfactant's molecules.CNTs functionalized with Triton X-405 show the highest output power consisting of a single junction of p-and n-type thermoelectric elements,reaching as high as 67 nW for a 45 K temperature gradient.Thus enabling flexible,cheaper,and more efficient thermoelectric generators through the use of functionalized CNTs.
查看更多>>摘要：Due to the loss of organic amine cations and lead ions in the structure of the iodine-lead methylamine perovskite solar cell,there are a large number of defects within the film and the recombination loss caused by grain boundaries,which seriously hinder the further improvement of power conversion efficiency and stability.Herein,a novel carbon nitride C3N3 incorporated into the perovskite precursor solution is a multifunctional strategy,which not only increases the light absorption strength,grain size,and hydrophobicity of the perovskite film,but also effectively passivates the bulk and interfacial defects of perovskite and verified by the first-principles density functional theory calculations.As a result,the efficiency and stability of perovskite solar cells are improved.The device with 0.075 mg mL-1 C3N3 additive delivers a champion power conversion efficiency of 19.91％with suppressed hysteresis,which is significantly higher than the 18.16％of the control device.In addition,the open-circuit voltage of the modified device with the maximum addition as high as 1.137 V is 90.96％of the Shockley-Queisser limit(1.25 V).Moreover,the power conversion efficiency of the modified device without encapsulation can maintain nearly 90％of its initial value after being stored at 25 ℃ and 60％relative humidity for 500 h.This work provides a new idea for developing additives to improve the power conversion efficiency and stability of perovskite solar cells.
查看更多>>摘要：Metal-organic frameworks(MOFs)can serve as prevailing anodes for lithium-ion batteries,due to their multiple redox-active sites and prominent structural compatibility.However,the poor electronic conductivity and inferior cyclability hinder their further implementation.Herein,a synthetic methodology for trimetallic Fe-Co-Ni MOFs with nanoframe superstructures architecture(Fe-Co-Ni NFSs)via structural evolution is proposed for versatile anode materials for lithium storage.Ascribed to optimal compositional and structural optimization,the Fe-Co-Ni NFSs achieve exceptional electrochemical performance with superior specific capacity(1030 mAh g-1 at 0.1 A g-1),outstanding rate capacity(414 mAh g-1 at 2 A g-1),and prolonged cyclability(489 mAh g-1 upon 1000 cycles at 1 A g-1).Both experimental and theoretical investigations reveal that the multi-component metal centers could boost electronic conductivity,confer multiple active sites,and energetically favor Li adsorption capability.Additionally,the nanoframe superstructures of Fe-Co-Ni NFSs could facilitate stress-buffering effect on volumetric expansion and prevent electrode pulverization,further improving the lithium storage capability.This work envisions a meticulous protocol for high-performance MOF anode materials for lithium-ion batteries.
查看更多>>摘要：Atomically dispersed catalysts are widely adopted in CO2 reduction reaction(CO2RR)due to maximal atomic utilization and high catalytic activity.Dual-atom catalysts(DACs),with more dispersed active sites and distinct electronic structures compared with single-atom catalysts(SACs),may exhibit diverse catalytic performance.Herein,the DAC FeCo-NC and SAC Fe-NC/Co-NC are employed as probes to explore DACs advantage in CO2RR.Results show that the moderate interaction between the dual-atom center and N coordination balances structural stability and catalytic activity.CO is the only product on Fe-NC/Co-NC,and the high limiting potentials from-1.22 to-1.67 V inhibit further reduction.FeCo-NC assisted with CO intermediate exhibits low limiting potentials of-0.64 V for both CH3OH and CH4,comparable to those on Cu-based catalysts.Under circumstance of applied potentials,CO2RR on FeCo-NC has greater advantages in yielding CH3OH and CH4 than that on Fe-NC/Co-NC,and hydrogen evolution reaction is severely inhibited.The intrinsic essence is that dual-atom center can provide large spin-polarization and multi-electron transfer capability,rendering CO intermediates as effective electronic and geometric modifiers in CO2RR.This work highlights FeCo-NC as a high-performance CO2RR catalyst toward deep-reduction C1 products and elucidates CO intermediate assisted promotion mechanism via a dual-atom synergistic effect.
查看更多>>摘要：Solid-state batteries have been considered as a good choice for substituting traditional batteries with liquid electrolytes because of their high energy density and safe property.However,a little amount of flammable non-aqueous liquid electrolyte or polymer electrolyte is usually required to improve the interfacial contact,which is adverse to safety.Here,a nonflammable gel is prepared by hydrogen-bond interaction and applied as an interfacial layer to improve the performance of solid-state batteries.The prepared multilayer hybrid electrolyte(MHE)composed of gel and CPE shows a wide electrochemical window(5.3 V vs Li/Li+),high ionic transference number(0.57),and ionic conductivity(7.18 × 10-4 S cm-1)at room temperature.Thus,the assembled Li symmetric cell with MHE can cycle over 650 h at 0.5 mA cm-2 with a lower overpotential of～61 mV.The LiFePO4|MHE|Li cell exhibits a higher discharge capacity of 107.8 mAh g-1 even cycled at 5 C.It also shows superior capacity retention of 96.4％after 1000 cycles at 0.5 C.This work provides a promising strategy for designing high-performance solid-state batteries.
查看更多>>摘要：It is crucial to efficiently separate and transport photo-induced charge carriers for the effective implementation of photocatalysis toward environmental remediation.A rational design strategy is proposed to validate such proposition through the construction of an interfacial structure in the form of LDH/Zn2SnO4 heterostructures in this research.The interfacial charge transfer on LDH/Zn2SnO4 is greatly promoted via the unique charge transfer pathway,as characterized by transient photocurrent responses,X-ray photoelectron spectroscopy,electron paramagnetic resonance spectrum,and photoluminescence analysis.As such,it contributes to the generation of reactive oxygen species(ROS)and the activation of reactants for the mineralization of toluene.According to the in situ DRIFTS spectra analysis,the accumulation of benzoic acid takes place possibly through the partial oxidation of the methyl group on toluene at the interface of the LDH/Zn2SnO4 heterostructure.This process can greatly promote the photocatalytic oxidation of toluene with the enhanced ring-opening efficiency.The LDH/Zn2SnO4 is thus demonstrated as superior photocatalyst against toluene(removal efficiency of 89.5％;mineralization of 83.1％;and quantum efficiency of 4.55 × 10-6 molecules/photon).As such,the performance of this composite far exceeds that of their individual components(e.g.,P25,pure Mg-Al LDH,or Zn2SnO4).This study is expected to offer a new path to the interfacial charge transfer mechanism based on the design of highly efficient photocatalysts for air purification.
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