Binary composites(ZIF-67/rGO)were synthesized by one-step precipitation method using cobalt nitrate hexahydrate as metal source,2-methylimidazole as organic ligand,and reduced graphene oxide(rGO)as carbon carrier.Then...Binary composites(ZIF-67/rGO)were synthesized by one-step precipitation method using cobalt nitrate hexahydrate as metal source,2-methylimidazole as organic ligand,and reduced graphene oxide(rGO)as carbon carrier.Then Ru3+was introduced for ion exchange,and the porous Ru-doped Co_(3)O_(4)/rGO(Ru-Co_(3)O_(4)/rGO)composite electrocatalyst was prepared by annealing.The phase structure,morphology,and valence state of the catalyst were analyzed by X-ray powder diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).In 1 mol·L^(-1)KOH,the oxygen evolution reaction(OER)performance of the catalyst was measured by linear sweep voltammetry,cyclic voltammetry,and chronoamperometry.The results show that the combination of Ru doping and rGO provides a fast channel for collaborative electron transfer.At the same time,rGO as a carbon carrier can improve the electrical conductivity of Ru-Co_(3)O_(4)particles,and the uniformly dispersed nanoparticles enable the reactants to diffuse freely on the catalyst.The results showed that the electrochemical performance of Ru-Co_(3)O_(4)/rGO was much better than that of Co_(3)O_(4)/rGO,and the overpotential of Ru-Co_(3)O_(4)/rGO was 363.5 mV at the current density of 50 mA·cm^(-2).展开更多
Inefficient photo-carrier separation and sluggish photoreaction dynamics appreciably undermine the photocatalytic decontamination efficacy of photocatalysts.Herein,an S-scheme Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)heterojunc...Inefficient photo-carrier separation and sluggish photoreaction dynamics appreciably undermine the photocatalytic decontamination efficacy of photocatalysts.Herein,an S-scheme Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)heterojunction with interfacial Mo-S chemical bond is designed as an efficient photocatalyst.In this integrated photosystem,Bi2MoO6 and Mn_(0.5)Cd_(0.5)S function as oxidation and reduction centers of Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)microspheres,respectively.Importantly,the unique charge transfer mechanism in the chemically bonded S-scheme heterojunction with Mo-S bond as atom-scale charge transport highway effectively inhibits the photocorrosion of Mn_(0.5)Cd_(0.5)S and the recombination of photo-generated electron-hole pairs,endowing Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)photocatalyst with excellent photocatalytic decontamination performance and stability.Besides,integration of Mn_(0.5)Cd_(0.5)S nanocrystals into Bi2MoO6 improves hydrophilicity,conducive to the photoreactions.Strikingly,compared with Mn_(0.5)Cd_(0.5)S and Bi2MoO6,the Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)unveils much augmented photoactivity in tetracycline eradication,among which Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)-2 possesses the highest activity with the rate constant up to 0.0323 min-1,prominently outperforming other counterparts.This research offers a chemical bonding engineering combining with S-scheme heterojunction strategy for constructing extraordinary photocatalysts for environmental purification.展开更多
Aim To determine five organic acids in Radix Isatidis . Method The extraction method and the column partition chromatographic conditions were studied. Then a capillary zone electrophoretic method was set up for t...Aim To determine five organic acids in Radix Isatidis . Method The extraction method and the column partition chromatographic conditions were studied. Then a capillary zone electrophoretic method was set up for the determination. Results The linear ranges of quinazolinone acid, n anthranilic acid, benzoic acid, salicylic acid, and syringic acid were 5 52-92 0 μg·mL -1 , 5 12-102 μg·mL -1 , 2 28-84 4 μg·mL-1 , 4 78-159 μg·mL -1 , and 1 74-87 0 μg·mL -1 respectively. Conclusion The established method is accurate and simple.展开更多
A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymale...A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymaleimide(NHMI),serves as a hydrogen atom-transfer mediator.Good-to-excellent site selectivity was observed among different substrates,providing a practical approach for site-selective benzylic C–H oxidation.Additionally,the hydrogen-atom transfer mechanism for C–H electrochemical oxidation allows the oxidation to proceed at much lower anode potentials relative to direct electrolysis and with minimal reliance on the substrate's electronic properties.展开更多
Covalent organic frameworks(COFs)have attracted attention as photocatalysts,however,low electron transfer and reactive oxygen species(ROS)generation still hinder their photocatalytic application.In this work,we constr...Covalent organic frameworks(COFs)have attracted attention as photocatalysts,however,low electron transfer and reactive oxygen species(ROS)generation still hinder their photocatalytic application.In this work,we construct multivariate donor-acceptor(D-A)heterojunctions in the covalent organic frameworks by synchronously introducing electron-withdrawing and donating substituents.Importantly,the optoelectronic characteristics and visible-light photocatalytic performance were improved with the increase of the electron donor carbon chains in multivariate D-A COFs.Combining in‐situ characterization with theoretical calculations,the charge carrier separation and transfer efficiency,•O_(2)–generation and conversion,and the energy barrier of the rate determination steps related to the formation of*OH and*OOH,can be well regulated by the multivariate D-A COFs.More importantly,the ortho-carbon atom of the Br and OCH_(3) group-linked benzene rings and the imine bond(–C=N–)in COF-Br@OCH_(3) were activated to produce the key*OH and*OOH intermediates for effectively reducing the energy barrier of H2O oxidation and O_(2) reduction.This work provides valuable insights into the precise design and synthesis of COFs-based catalysts and the regulation of electron transfer and ROS generation by modulating the electron-withdrawing and donating substituents for highly efficient visible-light photocatalytic degradation of refractory organic pollutants.展开更多
Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen ...Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen evolution reaction(HER).In this study,the intrinsically tunable internal bond electric field(IBEF)at the imine bonds of COFs was manipulated to cooperate with the internal molecular electric field(IMEF)induced by the donor-acceptor(D-A)structure for an efficient HER.The aligned orientation of IBEF and IMEF resulted in a remarkable H_(2) evolution rate of 57.3 mmol·g^(-1)·h^(-1)on TNCA,which was approximately 520 times higher than that of TCNA(0.11 mmol·g^(-1)·h^(-1))with the opposing electric field orientation.The superposition of the dual electric fields enables the IBEF to function as an accelerating field for electron transfer,kinetically facilitat-ing the migration of photogenerated electrons from D to A.Furthermore,theoretical calculations indicate that the inhomogeneous charge distribution at the C and N atoms in TNCA not only pro-vides a strong driving force for carrier transfer but also effectively hinders the return of free elec-trons to the valence band,improving the utilization of photoelectrons.This strategy of fabricating dual electric fields in COFs offers a novel approach to designing photocatalysts for clean energy synthesis.展开更多
Water splitting powered by clean electricity is a sustainable and promising approach to produce green hydrogen.Currently,noble metal(e.g.Iridium,Ruthenium,Platinum)-based catalysts are most widely used for water split...Water splitting powered by clean electricity is a sustainable and promising approach to produce green hydrogen.Currently,noble metal(e.g.Iridium,Ruthenium,Platinum)-based catalysts are most widely used for water splitting electrolysis.However,noble metal-based catalysts often suffer from multiple disadvantages,including high cost,low selectivity and poor durability.The emergence of metal-organic framework nanosheets(MOFNSs)attracts significant attention due to their unique advantages.Here,a concise,yet comprehensive and critical,review of recent advances in the field of MOFNSs is provided.This review explains the fundamental oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)catalytic mechanisms as well as key characterization techniques for the structure-activity relationship study are discussed.Moreover,it discusses efficient design strategies and the brief research advances of MOFNSs in HER,OER,and bifunctional electrocatalysis,along with some challenges and opportunities.展开更多
By virtue of a 3∶1 complementary coordination strategy,a chiral heteroleptic metal-organic cage that con-tains divergent functional units,Pd‑R(Zn),was precisely constructed via self-assembly of monodentate variationa...By virtue of a 3∶1 complementary coordination strategy,a chiral heteroleptic metal-organic cage that con-tains divergent functional units,Pd‑R(Zn),was precisely constructed via self-assembly of monodentate variational Zn-salen ligands RZn and NADH(reduced nicotinamide adenine dinucleotide)mimic modified tridentate ligands with square-planar Pd ions.UV-Vis and luminescence spectra experiments reveal that different anions could selec-tively interact with different sites of Zn-salen modified metal-organic cages to achieve the structural regulation of cage compound,by using the differentiated host-vip electrostatic interactions of counter ions with metal-organic hosts.Compared to other anions,the presence of chloride ions caused the most significant fluorescence emission enhancement of Pd‑R(Zn),meanwhile,the UV-Vis absorption band attributed to the salen aromatic backbone showed an absorption decrease,and the metal-to-ligand induced peak displayed a blue shift effect.Circular dichro-ism and ^(1)H NMR spectra further demonstrate that the introduction of chloride anions is beneficial to keeping a more rigid scaffold.展开更多
Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,w...Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency,achieved through atomic modulation(O,S,and Se)of the COF monomer.Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment,thereby affecting charge separation efficiency and photostability,which in turn affects the rates of photocatalytic H_(2) evolution.As a result,the newly developed TMT-BO-COF,which contains highly electronegative O atoms,exhibits the lowest exciton binding energy,the highest efficiency in charge separation and transportation,and the longest lifetime of the active charges.This leads to an impressive average H_(2) production rate of 23.7 mmol g^(−1) h^(−1),which is 2.5 and 24.5 times higher than that of TMT-BS-COF(containing S atoms)and TMT-BSe-COF(containing Se atoms),respectively.A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations.Our findings provide new insights into the design of highly photoactive organic framework materials for H_(2) evolution and beyond.展开更多
Loess soils are widely distributed worldwide and typical in northwest China,and excessive agricultural irrigation has caused landslides in the area,specifically in the Heifangtai loess region in Lanzhou,Gansu,China.Ge...Loess soils are widely distributed worldwide and typical in northwest China,and excessive agricultural irrigation has caused landslides in the area,specifically in the Heifangtai loess region in Lanzhou,Gansu,China.Geophysical exploration is an essential method in landslide engineering geological surveys,and geological surveying,drilling,geophysical prospecting,monitoring,and other methods are used for performing engineering geological evaluation and obtaining comprehensive basic data for landslide protection design and construction.The theoretical feasibility of using geophysical methods in loess landslide detection is essential.On the basis of the shallow geological structure of the Heifangtai landslide region in Lanzhou,Gansu,China,a typical geoelectric model of the magnetotelluric method was established,and the loess landslide area was modeled through a two-dimensional finite element method,forward numerical simulation,and engineering geological analysis.The distribution characteristics of the magnetotelluric field were determined.This is a typical application of the geological process analysis method in geophysical exploration.This study provides the typical stratigraphic structure and electrical characteristics of different groundwater distributions in Heifangtai,Gansu,China,verifies the accuracy of forward modeling and calculation results,and provides a detailed theoretical basis for landslide detection through magnetotelluric methods.Through the numerical simulation of the forward modeling of the Heifangtai landslide region in Lanzhou,Gansu,China,this study can provide a detailed geophysical basis for landslide investigation,corroborate results of geological investigation and landslide design,and facilitate the sustainable development of agriculture in Heifangtai.展开更多
The coupling effects of electrical pulse,temperature,strain rate,and strain on the flow behavior and plasticity of 5182-O aluminum alloy were investigated and characterized.The isothermal tensile test and electrically...The coupling effects of electrical pulse,temperature,strain rate,and strain on the flow behavior and plasticity of 5182-O aluminum alloy were investigated and characterized.The isothermal tensile test and electrically-assisted isothermal tensile test were performed at the same temperature,and three typical models were further embedded in ABAQUS/Explicit for numerical simulation to illustrate the electroplastic effect.The results show that electric pulse reduces the deformation resistance but enhances the elongation greatly.The calibration accuracy of the proposed modified Lim−Huh model for highly nonlinear and coupled dynamic hardening behavior is not much improved compared to the modified Kocks−Mecking model.Moreover,the artificial neural network model is very suitable to describe the macromechenical response of materials under the coupling effect of different variables.展开更多
The utilization of solar energy for hydrogen production via water splitting has garnered considerable attention in the realm of renewable energy.Si nanowires photocathodes own the advantages of effective photon absorp...The utilization of solar energy for hydrogen production via water splitting has garnered considerable attention in the realm of renewable energy.Si nanowires photocathodes own the advantages of effective photon absorption,non toxicity and industrial applicability.Nevertheless,the photoelectrocatalytic(PEC)performance of Si nanowires photocathodes is still limited by ineffective or deficient active sites on their surfaces.Here,we develop an efficient Si based photocathode modified with Al-porphyrin-based MOF(Al-PMOF),consisted of an earth-abundant metal containing Al(OH)O_(4) cluster bridged by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin.The assembled Al-PMOF significantly enhances the photocurrent density of bare Si nanowires photocathodes,resulting in a twofold increase under equivalent conditions,alongside a positive shift of 200 mV in the onset potential of the Si/Al-PMOF photocathode.The improved PEC hydrogen evolution performance is ascribed to accelerate surface charge transfer of Si photocathode and provision of favorable active site for the hydrogen evolution reaction.This work provides insights into the fabrication of semiconductor/molecule catalyst hybrid photocathodes,thus facilitating the realization of high-efficiency PEC water splitting.展开更多
A wideband monolithic optoelectronic integrated receiver with a high-speed photo-detector,completely compatible with standard CMOS processes,is designed and implemented in 0.6μm standard CMOS technology.The experimen...A wideband monolithic optoelectronic integrated receiver with a high-speed photo-detector,completely compatible with standard CMOS processes,is designed and implemented in 0.6μm standard CMOS technology.The experimental results demonstrate that its performance approaches applicable requirements,where the photo-detector achieves a -3dB frequency of 1.11GHz,and the receiver achieves a 3dB bandwidth of 733MHz and a sensitivity of -9dBm for λ=850nm at BER=10-12.展开更多
Aqueous zinc ion hybrid capacitors(ZIHCs)are considered one of the most promising electrochemical energy storage systems due to their high safety,environmental friendliness,low cost,and high power density.However,the ...Aqueous zinc ion hybrid capacitors(ZIHCs)are considered one of the most promising electrochemical energy storage systems due to their high safety,environmental friendliness,low cost,and high power density.However,the low energy density and the lack of sustainable design strategies for the cathodes hinder the practical application of ZIHCs.Herein,we design the N and O co-doped porous carbon cathode by annealing metal-organic framework(ZIF-8).ZIF-8 retains the original dodecahedral structure with a high specific surface(2814.67 m^(2)/g)and I_(G)/I_(D) ratio of 1.0 during carbonization and achieves self-doping of N and O heteroatoms.Abundant defect sites are introduced into the porous carbon to provide additional active sites for ion adsorption after the activation of carbonized ZIF-8 by KOH treatment.The ZIHCs assembled with modified ZIF-8 as the cathode and commercial zinc foil as the anode show an energy density of 125 W∙h/kg and a power density of 79 W/kg.In addition,this ZIHCs device achieves capacity retention of 77.8%after 9000 electrochemical cycles,which is attributed to the diverse pore structure and plentiful defect sites of ZIF-8-800(KOH).The proposed strategy may be useful in developing high-performance metal-ion hybrid capacitors for large-scale energy storage.展开更多
Three compounds with nitrocarbazole frameworks were synthesized and their electrochemical reversibility as organic electrocatalysts was studied by cyclic voltammetry. The electrochemical reversibility and oxidation‐r...Three compounds with nitrocarbazole frameworks were synthesized and their electrochemical reversibility as organic electrocatalysts was studied by cyclic voltammetry. The electrochemical reversibility and oxidation‐reduction potential of the compounds were greatly affected by their substituents. The oxidation‐reduction potential of the compound with an electron‐donating group was negative, while that of the compound with an electron‐withdrawing group on the carbazole framework was positive. The electrocatalytic oxidation activities of the nitrocarbazole compounds were investigated through cyclic voltammetry and controlled potential electrolysis at room tem‐perature. The electrocatalysts showed excellent selectivity for p‐methoxybenzyl alcohol, converting it to the corresponding aldehyde through electro‐oxidation with just 2.5 mol%of the electrocata‐lysts presented. The electrocatalysts maintained their excellent electroredox activity following re‐cycling.展开更多
A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of th...A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.展开更多
A polymer electro optic modulator has been fabricated with the functional layer acting as a kind of corona poled crosslinkable polyurethane. The three optical layers, namely waveguide, photolithography and oxygen are...A polymer electro optic modulator has been fabricated with the functional layer acting as a kind of corona poled crosslinkable polyurethane. The three optical layers, namely waveguide, photolithography and oxygen are fabricated by spin coating. With the Reactive Ion Etching method, the ridge of the waveguide is constructed. With light at 1 31μm being fiber coupled to waveguide, the mode and the modulation properties of these devices are demonstrated in a micron control system.展开更多
文摘Binary composites(ZIF-67/rGO)were synthesized by one-step precipitation method using cobalt nitrate hexahydrate as metal source,2-methylimidazole as organic ligand,and reduced graphene oxide(rGO)as carbon carrier.Then Ru3+was introduced for ion exchange,and the porous Ru-doped Co_(3)O_(4)/rGO(Ru-Co_(3)O_(4)/rGO)composite electrocatalyst was prepared by annealing.The phase structure,morphology,and valence state of the catalyst were analyzed by X-ray powder diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).In 1 mol·L^(-1)KOH,the oxygen evolution reaction(OER)performance of the catalyst was measured by linear sweep voltammetry,cyclic voltammetry,and chronoamperometry.The results show that the combination of Ru doping and rGO provides a fast channel for collaborative electron transfer.At the same time,rGO as a carbon carrier can improve the electrical conductivity of Ru-Co_(3)O_(4)particles,and the uniformly dispersed nanoparticles enable the reactants to diffuse freely on the catalyst.The results showed that the electrochemical performance of Ru-Co_(3)O_(4)/rGO was much better than that of Co_(3)O_(4)/rGO,and the overpotential of Ru-Co_(3)O_(4)/rGO was 363.5 mV at the current density of 50 mA·cm^(-2).
文摘Inefficient photo-carrier separation and sluggish photoreaction dynamics appreciably undermine the photocatalytic decontamination efficacy of photocatalysts.Herein,an S-scheme Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)heterojunction with interfacial Mo-S chemical bond is designed as an efficient photocatalyst.In this integrated photosystem,Bi2MoO6 and Mn_(0.5)Cd_(0.5)S function as oxidation and reduction centers of Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)microspheres,respectively.Importantly,the unique charge transfer mechanism in the chemically bonded S-scheme heterojunction with Mo-S bond as atom-scale charge transport highway effectively inhibits the photocorrosion of Mn_(0.5)Cd_(0.5)S and the recombination of photo-generated electron-hole pairs,endowing Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)photocatalyst with excellent photocatalytic decontamination performance and stability.Besides,integration of Mn_(0.5)Cd_(0.5)S nanocrystals into Bi2MoO6 improves hydrophilicity,conducive to the photoreactions.Strikingly,compared with Mn_(0.5)Cd_(0.5)S and Bi2MoO6,the Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)unveils much augmented photoactivity in tetracycline eradication,among which Mn_(0.5)Cd_(0.5)S/Bi_(2)MoO_(6)-2 possesses the highest activity with the rate constant up to 0.0323 min-1,prominently outperforming other counterparts.This research offers a chemical bonding engineering combining with S-scheme heterojunction strategy for constructing extraordinary photocatalysts for environmental purification.
文摘Aim To determine five organic acids in Radix Isatidis . Method The extraction method and the column partition chromatographic conditions were studied. Then a capillary zone electrophoretic method was set up for the determination. Results The linear ranges of quinazolinone acid, n anthranilic acid, benzoic acid, salicylic acid, and syringic acid were 5 52-92 0 μg·mL -1 , 5 12-102 μg·mL -1 , 2 28-84 4 μg·mL-1 , 4 78-159 μg·mL -1 , and 1 74-87 0 μg·mL -1 respectively. Conclusion The established method is accurate and simple.
文摘A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymaleimide(NHMI),serves as a hydrogen atom-transfer mediator.Good-to-excellent site selectivity was observed among different substrates,providing a practical approach for site-selective benzylic C–H oxidation.Additionally,the hydrogen-atom transfer mechanism for C–H electrochemical oxidation allows the oxidation to proceed at much lower anode potentials relative to direct electrolysis and with minimal reliance on the substrate's electronic properties.
文摘Covalent organic frameworks(COFs)have attracted attention as photocatalysts,however,low electron transfer and reactive oxygen species(ROS)generation still hinder their photocatalytic application.In this work,we construct multivariate donor-acceptor(D-A)heterojunctions in the covalent organic frameworks by synchronously introducing electron-withdrawing and donating substituents.Importantly,the optoelectronic characteristics and visible-light photocatalytic performance were improved with the increase of the electron donor carbon chains in multivariate D-A COFs.Combining in‐situ characterization with theoretical calculations,the charge carrier separation and transfer efficiency,•O_(2)–generation and conversion,and the energy barrier of the rate determination steps related to the formation of*OH and*OOH,can be well regulated by the multivariate D-A COFs.More importantly,the ortho-carbon atom of the Br and OCH_(3) group-linked benzene rings and the imine bond(–C=N–)in COF-Br@OCH_(3) were activated to produce the key*OH and*OOH intermediates for effectively reducing the energy barrier of H2O oxidation and O_(2) reduction.This work provides valuable insights into the precise design and synthesis of COFs-based catalysts and the regulation of electron transfer and ROS generation by modulating the electron-withdrawing and donating substituents for highly efficient visible-light photocatalytic degradation of refractory organic pollutants.
文摘Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen evolution reaction(HER).In this study,the intrinsically tunable internal bond electric field(IBEF)at the imine bonds of COFs was manipulated to cooperate with the internal molecular electric field(IMEF)induced by the donor-acceptor(D-A)structure for an efficient HER.The aligned orientation of IBEF and IMEF resulted in a remarkable H_(2) evolution rate of 57.3 mmol·g^(-1)·h^(-1)on TNCA,which was approximately 520 times higher than that of TCNA(0.11 mmol·g^(-1)·h^(-1))with the opposing electric field orientation.The superposition of the dual electric fields enables the IBEF to function as an accelerating field for electron transfer,kinetically facilitat-ing the migration of photogenerated electrons from D to A.Furthermore,theoretical calculations indicate that the inhomogeneous charge distribution at the C and N atoms in TNCA not only pro-vides a strong driving force for carrier transfer but also effectively hinders the return of free elec-trons to the valence band,improving the utilization of photoelectrons.This strategy of fabricating dual electric fields in COFs offers a novel approach to designing photocatalysts for clean energy synthesis.
文摘Water splitting powered by clean electricity is a sustainable and promising approach to produce green hydrogen.Currently,noble metal(e.g.Iridium,Ruthenium,Platinum)-based catalysts are most widely used for water splitting electrolysis.However,noble metal-based catalysts often suffer from multiple disadvantages,including high cost,low selectivity and poor durability.The emergence of metal-organic framework nanosheets(MOFNSs)attracts significant attention due to their unique advantages.Here,a concise,yet comprehensive and critical,review of recent advances in the field of MOFNSs is provided.This review explains the fundamental oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)catalytic mechanisms as well as key characterization techniques for the structure-activity relationship study are discussed.Moreover,it discusses efficient design strategies and the brief research advances of MOFNSs in HER,OER,and bifunctional electrocatalysis,along with some challenges and opportunities.
文摘By virtue of a 3∶1 complementary coordination strategy,a chiral heteroleptic metal-organic cage that con-tains divergent functional units,Pd‑R(Zn),was precisely constructed via self-assembly of monodentate variational Zn-salen ligands RZn and NADH(reduced nicotinamide adenine dinucleotide)mimic modified tridentate ligands with square-planar Pd ions.UV-Vis and luminescence spectra experiments reveal that different anions could selec-tively interact with different sites of Zn-salen modified metal-organic cages to achieve the structural regulation of cage compound,by using the differentiated host-vip electrostatic interactions of counter ions with metal-organic hosts.Compared to other anions,the presence of chloride ions caused the most significant fluorescence emission enhancement of Pd‑R(Zn),meanwhile,the UV-Vis absorption band attributed to the salen aromatic backbone showed an absorption decrease,and the metal-to-ligand induced peak displayed a blue shift effect.Circular dichro-ism and ^(1)H NMR spectra further demonstrate that the introduction of chloride anions is beneficial to keeping a more rigid scaffold.
文摘Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency,achieved through atomic modulation(O,S,and Se)of the COF monomer.Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment,thereby affecting charge separation efficiency and photostability,which in turn affects the rates of photocatalytic H_(2) evolution.As a result,the newly developed TMT-BO-COF,which contains highly electronegative O atoms,exhibits the lowest exciton binding energy,the highest efficiency in charge separation and transportation,and the longest lifetime of the active charges.This leads to an impressive average H_(2) production rate of 23.7 mmol g^(−1) h^(−1),which is 2.5 and 24.5 times higher than that of TMT-BS-COF(containing S atoms)and TMT-BSe-COF(containing Se atoms),respectively.A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations.Our findings provide new insights into the design of highly photoactive organic framework materials for H_(2) evolution and beyond.
文摘Loess soils are widely distributed worldwide and typical in northwest China,and excessive agricultural irrigation has caused landslides in the area,specifically in the Heifangtai loess region in Lanzhou,Gansu,China.Geophysical exploration is an essential method in landslide engineering geological surveys,and geological surveying,drilling,geophysical prospecting,monitoring,and other methods are used for performing engineering geological evaluation and obtaining comprehensive basic data for landslide protection design and construction.The theoretical feasibility of using geophysical methods in loess landslide detection is essential.On the basis of the shallow geological structure of the Heifangtai landslide region in Lanzhou,Gansu,China,a typical geoelectric model of the magnetotelluric method was established,and the loess landslide area was modeled through a two-dimensional finite element method,forward numerical simulation,and engineering geological analysis.The distribution characteristics of the magnetotelluric field were determined.This is a typical application of the geological process analysis method in geophysical exploration.This study provides the typical stratigraphic structure and electrical characteristics of different groundwater distributions in Heifangtai,Gansu,China,verifies the accuracy of forward modeling and calculation results,and provides a detailed theoretical basis for landslide detection through magnetotelluric methods.Through the numerical simulation of the forward modeling of the Heifangtai landslide region in Lanzhou,Gansu,China,this study can provide a detailed geophysical basis for landslide investigation,corroborate results of geological investigation and landslide design,and facilitate the sustainable development of agriculture in Heifangtai.
基金the financial supports from the National Natural Science Foundation of China(Nos.52075423,U2141214).
文摘The coupling effects of electrical pulse,temperature,strain rate,and strain on the flow behavior and plasticity of 5182-O aluminum alloy were investigated and characterized.The isothermal tensile test and electrically-assisted isothermal tensile test were performed at the same temperature,and three typical models were further embedded in ABAQUS/Explicit for numerical simulation to illustrate the electroplastic effect.The results show that electric pulse reduces the deformation resistance but enhances the elongation greatly.The calibration accuracy of the proposed modified Lim−Huh model for highly nonlinear and coupled dynamic hardening behavior is not much improved compared to the modified Kocks−Mecking model.Moreover,the artificial neural network model is very suitable to describe the macromechenical response of materials under the coupling effect of different variables.
基金Project(22078368)supported by the National Natural Science Foundation of China。
文摘The utilization of solar energy for hydrogen production via water splitting has garnered considerable attention in the realm of renewable energy.Si nanowires photocathodes own the advantages of effective photon absorption,non toxicity and industrial applicability.Nevertheless,the photoelectrocatalytic(PEC)performance of Si nanowires photocathodes is still limited by ineffective or deficient active sites on their surfaces.Here,we develop an efficient Si based photocathode modified with Al-porphyrin-based MOF(Al-PMOF),consisted of an earth-abundant metal containing Al(OH)O_(4) cluster bridged by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin.The assembled Al-PMOF significantly enhances the photocurrent density of bare Si nanowires photocathodes,resulting in a twofold increase under equivalent conditions,alongside a positive shift of 200 mV in the onset potential of the Si/Al-PMOF photocathode.The improved PEC hydrogen evolution performance is ascribed to accelerate surface charge transfer of Si photocathode and provision of favorable active site for the hydrogen evolution reaction.This work provides insights into the fabrication of semiconductor/molecule catalyst hybrid photocathodes,thus facilitating the realization of high-efficiency PEC water splitting.
文摘A wideband monolithic optoelectronic integrated receiver with a high-speed photo-detector,completely compatible with standard CMOS processes,is designed and implemented in 0.6μm standard CMOS technology.The experimental results demonstrate that its performance approaches applicable requirements,where the photo-detector achieves a -3dB frequency of 1.11GHz,and the receiver achieves a 3dB bandwidth of 733MHz and a sensitivity of -9dBm for λ=850nm at BER=10-12.
基金Project(22109181)supported by the National Natural Science Foundation of ChinaProject(2022JJ40576)supported by the Hunan Provincial Natural Science Foundation of China。
文摘Aqueous zinc ion hybrid capacitors(ZIHCs)are considered one of the most promising electrochemical energy storage systems due to their high safety,environmental friendliness,low cost,and high power density.However,the low energy density and the lack of sustainable design strategies for the cathodes hinder the practical application of ZIHCs.Herein,we design the N and O co-doped porous carbon cathode by annealing metal-organic framework(ZIF-8).ZIF-8 retains the original dodecahedral structure with a high specific surface(2814.67 m^(2)/g)and I_(G)/I_(D) ratio of 1.0 during carbonization and achieves self-doping of N and O heteroatoms.Abundant defect sites are introduced into the porous carbon to provide additional active sites for ion adsorption after the activation of carbonized ZIF-8 by KOH treatment.The ZIHCs assembled with modified ZIF-8 as the cathode and commercial zinc foil as the anode show an energy density of 125 W∙h/kg and a power density of 79 W/kg.In addition,this ZIHCs device achieves capacity retention of 77.8%after 9000 electrochemical cycles,which is attributed to the diverse pore structure and plentiful defect sites of ZIF-8-800(KOH).The proposed strategy may be useful in developing high-performance metal-ion hybrid capacitors for large-scale energy storage.
基金supported by the Special Program for the National Basic Research Program of China(973 Program,2012CB722604)~~
文摘Three compounds with nitrocarbazole frameworks were synthesized and their electrochemical reversibility as organic electrocatalysts was studied by cyclic voltammetry. The electrochemical reversibility and oxidation‐reduction potential of the compounds were greatly affected by their substituents. The oxidation‐reduction potential of the compound with an electron‐donating group was negative, while that of the compound with an electron‐withdrawing group on the carbazole framework was positive. The electrocatalytic oxidation activities of the nitrocarbazole compounds were investigated through cyclic voltammetry and controlled potential electrolysis at room tem‐perature. The electrocatalysts showed excellent selectivity for p‐methoxybenzyl alcohol, converting it to the corresponding aldehyde through electro‐oxidation with just 2.5 mol%of the electrocata‐lysts presented. The electrocatalysts maintained their excellent electroredox activity following re‐cycling.
基金supported by the National Natural Science Foundation of China(No.21501015)the Hunan Provincial Natural Science Foundation,China(No.2022JJ30604)Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation,China(No.2022CL01)。
文摘A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.
文摘A polymer electro optic modulator has been fabricated with the functional layer acting as a kind of corona poled crosslinkable polyurethane. The three optical layers, namely waveguide, photolithography and oxygen are fabricated by spin coating. With the Reactive Ion Etching method, the ridge of the waveguide is constructed. With light at 1 31μm being fiber coupled to waveguide, the mode and the modulation properties of these devices are demonstrated in a micron control system.
