查看更多>>摘要：To enhance the activity and selectivity of electro-catalytic CO2 reduction to formate is of great im-portance from both environmental and economical viewpoints.Herein,the Bio2-x nanosheets with sur-face electron localizations were constructed and utilized for the efficient CO2-to-formate conversion.The formate Faraday efficiency reaches 99.1％with current density of 12 mA cm-2 at-1.1 V versus the reversible hydrogen electrode(RHE)in an H-type cell while those in the flow cell are 91.3％and 319 mA cm-2 at-1.0 V versus RHE,respectively.Theoretical calculations indicate that the electron localization presenting in the Bio2-x nanosheet favors OCHO*intermediate stabilization and sup-presses H*intermediate adsorption,thus improving the Co2-to-formate efficiency.The Bio2-x electroca-talyst is nondopant,easily prepared,low-cost,high-ly active and selective for CO2RR to formate,which has demonstrated potential for application in the Zn-CO2 battery.The maximum power density can reach 2.33 mW cm-2,and the charge/discharge cy-cling stability is＞100 h(300 cycles)at 4.5 mA cm-2.
查看更多>>摘要：Technological application of the electrochemical reduction of CO2 relies on efficient electrocatalysts.We demonstrate that the introduction of amino groups alongside the porphyrin cobalt centers in a metal-organic framework(MOF)can dramatically accelerate the electrochemical CO2 reduction performance.A classic cobalt porphyrin-based MOF showing moderate C02-to-CO electroreduction performance(turnover frequency[TOF]=0.20 s-1,Faradic efficiency[FE]=47.4％)is modified.By mo-lecular design of the porphyrin-based ligand,amino groups are introduced alongside the cobalt center,giving remarkably enhanced Co2-to-CO electro-reduction performance as high as FE 99.4％,current density 7.2 mA cm-2,and TOF 21.17 s-1,in a near-neutral aqueous solution at a low overpotential of 525 mV.Density functional theory calculations showed that the prepositioned amino groups,al-though located not sufficiently close to the active center,serve as hydrogen-bonding donors to stabilize the intermediate Co-CO2 adduct and impede the for-mation of Co-H2O adduct,which not only promotes the CO2 reduction reaction but also restrains the hydrogen evolution reaction.
查看更多>>摘要：While heterogeneous single-atom catalysts(SACs)have achieved great success in the past decade,their application is potentially limited by their simplistic single-atom active centers,which make single-cluster catalysts(SCCs)a natural extension in the domain of heterogeneous catalysis.SCCs with precise numbers of atoms and structural configurations possess SAC merits,yet have greater potential for catalyzing com-plex reactions and/or bulky reactants.Through sys-tematic quantum-chemical studies and computational screening,we report here the rational design of tran-sition metal three-atom clusters anchored on graph-diyne(GDY)as a novel kind of stable SCC with great promise for efficient and atomically precise heterog-enous catalysis.By investigating their structure and catalytic performance for the oxygen reduction reac-tion,the hydrogen evolution reaction,and the CO2 reduction reaction,we have provided theoretical guidelines for their potential applications as hetero-geneous catalysts.These GDY-supported three-atom SCCs provide an ideal benchmark scaffold for rational design of atomically precise heterogeneous catalysts for industrially important chemical reactions.
查看更多>>摘要：The rapid crystal growth of metal halide perovskite(MHP)nanocrystals inevitably leads to the genera-tion of abundant crystal defects in the lattice.Here,defects-mediated long-lived charges and accompa-nying room-temperature persistent luminescence are demonstrated to be a general phenomenon in MHP nanocrystals.Density functional theory calcula-tions suggest that the collaboration of Schottky and point defects enables upward cascading depletion for electron transfer in MHP nanocrystals,leading to the generation of long-lived photoexcited charges with lifetimes over 30 min.The excellent optical properties including the presence of long-lived charges,high charge separation efficiency,and broad absorption in the visible region make MHPs ideal candidates for both photocatalysis and photo-biocatalysis.The MHPs were further integrated with enzymes to construct a light-driven biosynthetic system for the selective production of fine chemicals from CO2 with solar energy.The biosynthetic system can produce formate with a quantum yield of 3.24％,much higher than that of plants(～0.2-1.6％).These findings will benefit the understanding of the op-toelectronic properties of MHPs and further provide opportunities for the development of biosynthetic systems for solar-to-chemical synthesis.
查看更多>>摘要：Quantifying the microRNAs(miRNAs)levels in living cells,while essential for the study of fundamental biology and medical diagnostics,has barely been achieved due to insufficient probe delivery and unquantifiable signals.We report a cell-anchored and self-calibrated DNA nano-platform,a cholesterol-headed DNA nanowire that is capable of efficiently delivering to various cells and si-multaneously detecting two target miRNAs.One miRNA target can be utilized as an endogenous control against cell-to-cell variations.Moreover,the photocleavable lin-kers inserted in the nanostructures allow us to precisely regulate the probe structure and fluorescence signaling at the desired time and location in vivo.As a second control,the maximum fluorescence can be elicited by UV light,which further facilitates the normalization of the absolute fluorescence signal.With two introduced inter-nal controls,the maximum fluorescence and endogenous control gene,this approach displays excellent stability and self-calibration performance,effectively avoiding the interference from operating conditions and cell-to-cell variations,such as the laser powers and intracel-lular probe concentrations.Importantly,this design is capable of unifying the output signal intensity between in vitro test and cell imaging,making the in vitro linear calibration curve appropriate for the quantification of miRNA expression in living cells.
查看更多>>摘要：To monitor and investigate chemical reactions in real time and in situ is a long-standing,challenging goal in chemistry.Herein,an electric potential-promoted oxidative coupling reaction of organoboron com-pounds without the addition of base is reported,and the transmetallation process involved is moni-tored in real time and in situ with the scanning tunneling microscopy break single-molecule junc-tions(STMBJ)technique.We found that the electric potential applied determined the transmetallation.At low-bias voltage,the first-step transmetallation process occurred and afforded Au—C-bonded aryl gold intermediates.The electronic properties of organoboron compounds have a strong influence on the transmetallation process,and electron-rich com-pounds facilitate this transformation.At high-bias voltage,the second-step transmetallation process took place,and the corresponding intermediate(highly reactive diaryl metal complex)was detected with the assistance of Pd(OAc)2.Our work demonstrates the applications of STMBJ on in situ monitoring and catalyzing of chemical reactions and provides a new methodology to fabricate single-molecule devices.
查看更多>>摘要：Owing to serious poison of downstream olefin poly-merization catalysts from acetylene impurities,selec-tive reduction of acetylene to ethylene is a pivotal process in petrochemical industry.However,during thermocatalytic and electrocatalytic acetylene semi-hydrogenation,acetylene C-C coupling inevitably occurs on current catalysts.The resultant oligomeric species(particularly long-chain hydrocarbons)block active sites and mass transportation,and eventually decrease catalytic activity and stability.In this work,we report Ag nanowires(NWs)as high-performance electrocatalysts for acetylene semihydrogenation,where the C-C coupling is unprecedentedly sup-pressed by weakening acetylene adsorption.In pure acetylene,1,3-butadiene Faradaic efficiency(FE)of Ag NWs is only 2.1％,which is far lower than 41.2％for Cu nanoparticles at-0.2 V versus reversible hydrso-gen electrode.Ethylene partial current density of Ag NWs reaches 217 mA/cm2 at 0.85 V,which is consid-erably higher than those for state-of-the-art Cu-based electrocatalysts.Markedly,no 1,3-butadiene is pro-duced on Ag NWs in a large two-electrode flow cell fed with crude ethylene containing 1 vol％acetylene,presenting thorough termination of acetylene C-C coupling.In situ electrochemical Raman spectroscopy and theoretical investigations reveal that weak acety-lene adsorption on Ag surfaces is intrinsically respon-sible for prohibiting their oligomerization.This work will spark the rapid development of high-performance and stable electrocatalysts for reducing alkynes to olefins.
查看更多>>摘要：The lithium iron phosphate battery(LiFePO4 or LFP)does not satisfactorily deliver the necessary high rates and low temperatures due to its low Li+diffusivity,which greatly limits its applications.The solid-solution reac-tion,compared with the traditional two-phase transi-tion,needs less energy,and the lithium ion diffusivity is also higher,which makes breaking the barrier of LFP possible.However,the solid-solution reaction in LFP can only occur at high rates due to the lattice stress caused by the bulk elastic modulus.Herein,pomegranate-like LFP@C nanoclusters with ultrafine LFP@C subunits(8 nm)(PNCsLFP)were synthesized.Using in situ X-ray diffraction,we confirmed that PNCsLFP can achieve complete solid-solution reaction at the relatively low rate of 0.1C which breaks the limitation of low lithium ion diffusivity of the traditional LFP and frees the lithium ion diffusivity from tempera-ture constraints,leading to almost the same lithium ion diffusivities at room temperature,0,-20,and-40 ℃.The complete solid-solution reaction at all rates breaks the shackles of limited lithium ion diffusivity on LFP and offers a promising solution for next-generation lithium ion batteries with high rate and low temperature applications.
查看更多>>摘要：Dual labeling of an RNA can provide Förster resonance energy transfer(FRET)sensors for studying RNA fold-ing,miRNA maturation,and RNA-protein interactions.Here,we report the development of a highly efficient strategy for direct dual-terminal labeling of any RNA of interest.We explored new Michael cycloaddition for facile labeling of 5'-terminal RNA with improved effi-ciency.Direct chemical tetrazinylation of RNA at the 3'-terminus was achieved with the highly efficient and catalysis-free tetrazine-cycloalkyne ligation.Both single-terminal labeling methods were combined for dual-terminal labeling of an RNA including short hair-pin RNA,pre-miRNA,riboswitch,and noncoding RNA.Notably,these dual-labeled RNA-based FRET sensors were used to monitor RNA-ligand interactions in vitro and in live cells.It is anticipated that these universal RNA labeling strategies will be useful to study RNA structures and functions.
查看更多>>摘要：The prevalent excitonic effects in low-dimensional semiconductors enable energy-transfer-initiated photocatalytic solar-to-chemical energy conversion.However,the generally strong interactions between excitons and lattice vibrations in these low-dimension-al systems lead to robust nonradiative energy loss,which inevitably impedes photocatalytic performance of energy-transfer-initiated reactions.Herein,we high-light the crucial role of engineering exciton-phonon interactions in suppressing nonradiative energy losses in low-dimensional semiconductor-based photocata-lysts.By taking bismuth oxybromide(BiOBr)as an example,we demonstrate that phonon engineering could be effectively implemented by introducing Bi-Br vacancy clusters.Based on nonadiabatic molecular dynamics simulations and spectroscopic investiga-tions,we demonstrate that the defective structure can promote exciton-low-frequency phonon coupling and reduce exciton-high-frequency optical phonon coupling.Benefiting from the tailored couplings,non-radiative decay of excitons in defective BiOBr is sig-nificantly suppressed,thereby facilitating exciton accumulation and hence energy-transfer-initiated photocatalvsis.
NETL
NSTL
万方数据
维普