The photocatalytic oxidation of methane to methanol using molecule oxygen directly is an attractive catalytic reaction,but designing catalysts to avoid over-oxidation remains a significant challenge.Herein,Cu single-a...The photocatalytic oxidation of methane to methanol using molecule oxygen directly is an attractive catalytic reaction,but designing catalysts to avoid over-oxidation remains a significant challenge.Herein,Cu single-atom anchored on the defective carbon nitride structure(Cu SA/Def-CN)is designed for selective photocatalytic oxidation of methane into methanol using O_(2) under mild conditions.The Cu SA/Def-CN catalyst exhibits a high methanol selectivity of 92.8%under optimized conditions.Mechanistic studies reveal a synergistic effect between Def-CN and Cu SA,where Def-CN is responsible for the in-situ generation of hydrogen peroxide,which is subsequently decomposed by the Cu SA sites to produce·OH radicals that play a key role in the rate-determining step of methane activation to form methanol.Additionally,the presence of Cu SA not only enhances the electron-hole separation efficiency and improves the transfer of the photo-generated charges,but also increases the number of active sites for methane adsorption and activation.These insights provide valuable guidance for designing efficient catalysts for the highly selective photocatalytic oxidation of methane to methanol.展开更多
Lithium-sulfur(Li-S)batteries are regarded as the most formidable competitor to lithium-ion batteries due to their superior theoretical capacity.However,the negative impact of soluble lithium polysulfide(LiPSs)and slo...Lithium-sulfur(Li-S)batteries are regarded as the most formidable competitor to lithium-ion batteries due to their superior theoretical capacity.However,the negative impact of soluble lithium polysulfide(LiPSs)and slow redox reaction kinetics seriously hamper the commercialization of Li-S batteries.In this study,a defect-rich single-atom catalyst with an oversaturated asymmetric Fe-N_(5)coordination structure anchored in defective g-C_(3)N_(4)(C_(3)N_(4)-Fe@rGO)is designed via an absorption-pyrolysis strategy.The two-dimensional(2D)conducting C_(3)N_(4)@graphene structure with abundant defect sites accelerates the trans-fer and transportation of lithium ions and electrons.The oversaturated asymmetric Fe-N_(5)coordination structure effectively improves the adsorbility of LiPSs and accelerates the redox kinetics of sulfur species.Hence,the Li-S cell with a C_(3)N_(4)-Fe@rGO modified separator reveals a high initial capacity(1197.1 mAh g^(-1) at 0.2 C)and a low capacity decay rate(0.037%per cycle after 900 cycles at 1 C).Even at high sulfur loading and extreme temperatures of 0℃,it also shows good cycling performance.This work creates ideas for synthesizing oversaturated single-atom coordination environments and an efficient route to the practical realization of the Li-S batteries.展开更多
The rational configuration of built-in electric field(IEF)in heterogeneous materials can significantly optimize the band structure to accelerate the separation of photogenerated charge carriers.However,the strength mo...The rational configuration of built-in electric field(IEF)in heterogeneous materials can significantly optimize the band structure to accelerate the separation of photogenerated charge carriers.However,the strength modulation of IEF formed by various materials has an uncertain enhancing effect on the separation of photogenerated carriers.Herein,a mesoporous MIL-125(Ti)@BiOCl S-scheme heterojunction with controllable IEF is prepared by green photoreduction reaction to investigate the relationship between IEF,microstructure,and photocatalytic activity.Moreover,the corresponding results demonstrate the MIL-125(Ti)@BiOCl effectively regulates the IEF strength through controlling the concentration of ligand defects,thereby optimizing the band structure and improving the efficiency of photogenerated charge separation.The optimized IEF significantly enhances the photocatalytic degradation performance of mesoporous MIL-125(Ti)-3@BiOCl towards tetracycline,with a k value of 0.07 min^(–1),which are approximately 5.5 and 4.7 times greater than that of BiOCl(0.0127 min^(–1))and MIL-125(Ti)-3(0.015 min^(–1)).These findings provide a new pathway for regulating IEF within MOF-based heterojunctions,and offer new insights into the intrinsic correlations between defect structure,IEF,and photocatalytic activity.展开更多
Defective phononic crystals(PnCs)have enabled spatial localization and quantitative amplification of elastic wave energy.Most previous research has focused on applications such as narrow-bandpass filters,ultrasonic se...Defective phononic crystals(PnCs)have enabled spatial localization and quantitative amplification of elastic wave energy.Most previous research has focused on applications such as narrow-bandpass filters,ultrasonic sensors,and piezoelectric energy harvesters,typically operating under the assumption of an external elastic wave incidence.Recently,a novel approach that uses defective PnCs as ultrasonic actuators to generate amplified waves has emerged.However,the existing studies are limited to the generation of either longitudinal or bending waves,with no research addressing the concurrent generation of both.Hence,this paper proposes a straightforward methodology for the concurrent generation and amplification of both wave types utilizing defect modes at independent defect-band frequencies.Bimorph piezoelectric elements are attached to the defect,with each element connected to independent external voltage sources.By precisely adjusting the magnitude and temporal phase differences between the voltage sources,concurrently amplified wave generation is achieved.The paper highlights the advantages of the proposed analytical model.This model is both computationally time-efficient and accurate,in comparison with the COMSOL simulation results.For instance,in case studies,the analytical model reduces the computational time from one hour to mere seconds,while maintaining acceptable error rates of 1%in peak frequencies.This concurrent wave-generation methodology opens new avenues for applications in rotating machinery fault diagnosis,structural health monitoring,and medical imaging.展开更多
Defect engineering improves the catalytic performance of metal-organic frameworks(MOFs)loaded metal nanoparticles(MNPs@MOFs),but there is still a challenge in defining the structure-activity relationships.Herein,the c...Defect engineering improves the catalytic performance of metal-organic frameworks(MOFs)loaded metal nanoparticles(MNPs@MOFs),but there is still a challenge in defining the structure-activity relationships.Herein,the content of linker-missing defects in UiO-66(Ce)was systematically regulated via formic acid as the modulators,and defective UiO-66(Ce)loaded Ni nanoparticles(NPs)were constructed for dicyclopentadiene(DCPD)hydrogenation.The fine regulation of defect engineering and reduction conditions affected the structure properties of UiO-66(Ce)and the electronic metal-support interaction between MOFs and Ni NPs,thereby optimizing the microenvironment and electronic state of Ni NPs.The optimized U(Ce)-40eq with suitable defects,small size and structure stability effectively promoted the production of highly dispersed abundant electron-deficient Ni^(0) active sites,enhancing the adsorption and activation of H_(2) and C=C bonds,especially accelerating the rate-determining step.Therefore,U(Ce)-40eq loaded 5 wt%Ni NPs achieved DCPD saturated hydrogenation to tetrahydrodicyclopentadiene(70℃,2 MPa,90 min),superior to most high-loading Ni-based catalysts.This work reveals the synergistic mechanism of MOFs defect engineering and electronic structure of Ni NPs,providing effective guidance for the precise preparation of highly efficient and stable MNPs@MOFs heterogeneous catalysts.展开更多
A high-activity and stable bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalyst is critical for seawater-based Zn-air batteries(ZABs).Herein,we report a wood-derived chainmail e...A high-activity and stable bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalyst is critical for seawater-based Zn-air batteries(ZABs).Herein,we report a wood-derived chainmail electrocatalyst containing defective nitrogen-doped carbon nanotubes encapsulating cobalt nanoparticles(Co@D-NCNT/CW)to enhance the ORR/OER activity and stability in seawater medium.During the preparation process,the introduction and removal of Zn increased the defect sites and pyridine N content in the carbon material,modulating charge distribution and influencing the adsorption and activation processes.The highly ordered open channels in Co@D-NCNT/CW promoted mass transfer of reactants and accelerated gas diffusion.The resultant chainmail electrocatalyst exhibited impressive bifunctional ORR and OER activities with an ultra-low gap of 0.67 V in sea water-based alkaline electrolyte.The Co@D-NCNT/CW-assembled seawater-based rechargeable liquid ZABs demonstrated a maximum power density of 245.3 mW cm^(-2)and a long-term cycling performance over 500 h.The seawater-based all-solid-state ZABs achieved the maximum power density of 48.2 mW cm^(-2)and stabilized over 30 h.Density functional theory revealed that the presence of defects and pyridine nitrogen in Co@D-NCNT/CW modulated the electronic structure of Co,optimizing the binding affinity of the Co sites with intermediates and weakening Cl^(-)adsorption.This work provides a new approach to preparing high-activity and stable ORR/OER electrocatalyst utilizing wood nanostructures,boosting the development of seawater-based ZABs.展开更多
The photoreduction of CO_(2)into CH_(4)with simultaneous high activity and selectivity is a promising strategy to increase energy supply and alleviate global warming.However,the absence of the active sites that is res...The photoreduction of CO_(2)into CH_(4)with simultaneous high activity and selectivity is a promising strategy to increase energy supply and alleviate global warming.However,the absence of the active sites that is responsible for the adsorption and activation of CO_(2)and the generation of CO and H2via side reactions often lead to poor efficiency and low selectivity of the catalyst.Herein,Cu,Pd,and PdCu metal clusters cocatalyst-anchored defective TiO_(2)nanotubes(Cu/TiO_(2)-SBO,Pd/TiO_(2)-SBO,and Pd1Cu1/TiO_(2)-SBO)were designed via a simple solution impregnation reduction and applied for photocatalytic conversion of CO_(2)to CH_(4).The Pd1Cu1/TiO_(2)-SBO photocatalyst exhibits excellent catalytic performance among the other catalysts for photoreduction of CO_(2)into CH_(4).More interestingly,the product selectivity of CH_(4)reaches up to 100%with a rate of 25μmol g^(-1)h^(-1).In-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)simulations indicate that the main reasons for the high selectivity of CH_(4)are attributed to the PdCu alloy and oxygen vacancies,which jointly enhance the photoinduced carrier separation and lower energy barriers of key intermediates.Moreover,due to the tunable d-band center of the Cu site in the PdCu alloy,the generated intermediates can be well prevented from poisoning and promoted to participate in further reactions.Hopefully,the current study will provide insight into the development of new,highly selective photocatalysts for the visible light-catalytic reduction of CO_(2)into CH_(4).展开更多
The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydro...The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydrogenation properties of MgH_(2)@Ni-CNTs was studied by DFT simulation,and the corresponding models were constructed based on MS.The dehydrogenation process of MgH_(2)can be regarded as the dissociation of Mg-H and desorption of H_(2)from the MgH_(2)surface.In view of the whole dehydrogenation,the dissociation of H^(−)is the rate-determining step,which is the main reason for restricting the dehydrogenation kinetics.Compared with vacancy vacancy-defective MgH_(2)(001)surface,the appearance of vacancy defects on the(110)surface substantially reduces the energy barrier required for H dissociation to 0.070 Ha.The reason is that vacancy defects accelerate the transition of electrons from the H^(−)s orbit to the Mg^(2+)3s orbit,resulting in a decrement of the Mg-H bond strength,which makes H atoms more easily dissociated from the MgH_(2)(110)surface.Therefore,the existence of vacancy defects improves the dehydriding kinetic of MgH_(2).Most importantly,this research offers crucial directions for developing hydrogen storage materials as well as a potential fix for the slow dehydrogenation kinetics of nano-confined MgH_(2).展开更多
Hepatitis B virus(HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understand...Hepatitis B virus(HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.展开更多
One of the fundamental driving forces in the materials science community is the hunt for new materials with specific properties that meet the requirements of rapidly evolving technology.
The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode （WBE）. The electrochemical impedance spectroscopy （EIS） of...The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode （WBE）. The electrochemical impedance spectroscopy （EIS） of the WBE was carded out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.展开更多
Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen redu...Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking.In this study,ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst.These catalysts were prepared via a one-step method at 900℃.Amazingly,the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles.These facilitated the catalyst synthesis,and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium,including a lower onset potential,lower mid-wave potential,four electron transfer process,and better durability compared with 20 wt%Pt/C.More importantly,the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH*from*OO toward oxygen reduction reaction.Therefore,the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells,given the novel catalyst’s resulting performance.展开更多
The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density function...The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory （DFT） method. Twelve possible support models of regular and defective MgC12 （110） and （100） surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate （EB） as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TIC14 from coordinating on the MgC12 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgC12 support, presented stronger adsorption of TiCl4 than that of EB on （110） surface. Since the TIC14 and ethyl benzoate （EB） would compete to adsorb on the support surface, it seems reasonable to assume that TIC14 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.展开更多
Pristine graphene (PG) has been demonstrated to be an excellent substrate for Raman enhancement, which is called graphene-enhanced Raman scattering. However, the chemically inert and hydrophobic surface of PG hinders ...Pristine graphene (PG) has been demonstrated to be an excellent substrate for Raman enhancement, which is called graphene-enhanced Raman scattering. However, the chemically inert and hydrophobic surface of PG hinders the adsorption of molecules especially in aqueous solutions, and consequently limits the Raman enhanced efficiency. Here, we synthesized defective graphene (DG) films by chemical vapor deposition on Au, which has a defect density of ~2.0 ×10^11 cm^-2. The DG shows a much better wettability than PG towards dye solution. Combining with the strong adsorption ability of defects to molecules, DG shows greatly enhanced efficiency than PG with perfect lattice. For example, the detection limit for rhodamine B can reach 2×10^9 M for DG while it is on the order of 10^-7 M for PG. In addition, DG has high enhancement uniformity and the Au substrate can be reused after electrochemical bubbling transfer. These advantages suggest the great potential of the DG grown on Au for practical applications in environmental monitoring.展开更多
NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to me...NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to metal charge transfer(LMCT)of photo-excited electrons,which is caused by inherent energy gap(ΔE_(LMCT)).This study synthesized the defective NU(NUXH,where X is the molar equivalent of the modulator)with reducedΔE_(LMCT)through linkers removal via acid treatment.The electronic structure of NUX-H was systematically investigated,and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms.Furthermore,they substantially lowered the energy of the unoccupied d orbitals(LUMO),which was benefi cial to effi cient LMCT,resulting in an improved photocatalytic activity of NUX-H toward high-concentration(100 mg/L)Cr(VI)reduction.Compared to NU with defect-free structure,the reducing rate of Cr(VI)was increased by 47 times.This work introduced an alternative strategy in terms of designing effi cient photocatalysts for reducing Cr(VI)under ambient conditions.展开更多
Defective layered Mn-based materials were synthesized by Li/Na ion exchange to improve their electrochemical activity and Coulombic efficiency.The annealing temperature of the Na precursors was important to control th...Defective layered Mn-based materials were synthesized by Li/Na ion exchange to improve their electrochemical activity and Coulombic efficiency.The annealing temperature of the Na precursors was important to control the P3-P2 phase transition,which directly affected the structure and electrochemical characteristics of the final products obtained by ion exchange.The O3-Li_(0.78)[Li_(0.25)Fe_(0.075)Mn_(0.675)]O_(δ) cathode made from a P3-type precursor calcined at 700℃ was analyzed using X-ray photoelectron spectrometry and electron paramagnetic resonance.The results showed that the presence of abundant trivalent manganese and defects resulted in a discharge capacity of 230 mAh/g with an initial Coulombic efficiency of about 109%.Afterward,galvanostatic intermittent titration was performed to examine the Li^(+) ion diffusion coefficients,which affected the reversible capacity.First principles calculations suggested that the charge redistribution induced by oxygen vacancies(OV_(s))greatly affected the local Mn coordination environment and enhanced the structural activity.Moreover,the Li-deficient cathode was a perfect match for the pre-lithiation anode,providing a novel approach to improve the initial Coulombic efficiency and activity of Mn-based materials in the commercial application.展开更多
Graphene,as a proof-of-concept two-dimensional material,has proven to have excellent physical and chemical properties.Its derivatives,such as defective or doped graphene,are also applied as catalytic materials for met...Graphene,as a proof-of-concept two-dimensional material,has proven to have excellent physical and chemical properties.Its derivatives,such as defective or doped graphene,are also applied as catalytic materials for metal-air batteries(MABs).MABs have been recognized as possible candidates for new-generation energy storage systems due to their ultra-high theoretical energy density.So far,graphene and its derivatives with optimized structures have been widely explored to improve the electrochemical performance in MABs.Generally speaking,perfect graphene crystalline is inert for many catalytic processes,while defects and heteroatoms can endow graphene with high activity for many electrocatalytic reactions.Under this circumstance,recent progress is summarized for defective/doped graphene as air cathodes in aqueous or organic MABs,which are actually different electrochemical systems with distinct requirements for air cathodes.Also,the relationship is clarified between graphene defects/doping and electrocatalytic mechanisms that can be the guidance for catalyst design.Future directions are also prospected for the development of graphene-based MAB cathodes.展开更多
The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemi...The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.展开更多
Previous studies in our laboratory have demonstrated that the thermosensitivity locus cosegregates with blood pressure and that the elevated expression and restriction fragment length polymorphism of HSP70 gene are as...Previous studies in our laboratory have demonstrated that the thermosensitivity locus cosegregates with blood pressure and that the elevated expression and restriction fragment length polymorphism of HSP70 gene are associ-ated with hypertension. Cell protection against environ-mental stressors such as heat and chemicals is often accom-panied by up-regulated expression of a wide spectrum of heat sliock genes(HSP). To further investigate the interre-lation between HSP expression and blood pressure regulation, we employed an effective method of cloning 2 poten-tial hypertension-related HSPs. Synthetic oligonucleotides corresponding either to a higbly-conserved region of the known HSP family or a repetitive sequence in the protein- encoding gene were used as target primers for polymerase chain reaction (PCR). cDNA prepared from heat-stressed and non-stressed vascular smooth muscle cells (VSMC) of Brown Norway rats (BN.1x) and spontaneously hyperten-sive rats (SHRp) respectively served as template in the reaction. The PCR products were subsequently analyzed in a single-stranded conformational polymorphism (SSCP) electrophoresing system. Differential gene expression in BN.1x and SHRp was seen on autoradiographs of SSCP gel by comparing the migration patterns of PCR-amplified DNA fragments. Using this technique, we also found that HSP27 and a new member of the large HSP gene family were differentially expressed in BN.1x and SHRp VSMC.展开更多
文摘The photocatalytic oxidation of methane to methanol using molecule oxygen directly is an attractive catalytic reaction,but designing catalysts to avoid over-oxidation remains a significant challenge.Herein,Cu single-atom anchored on the defective carbon nitride structure(Cu SA/Def-CN)is designed for selective photocatalytic oxidation of methane into methanol using O_(2) under mild conditions.The Cu SA/Def-CN catalyst exhibits a high methanol selectivity of 92.8%under optimized conditions.Mechanistic studies reveal a synergistic effect between Def-CN and Cu SA,where Def-CN is responsible for the in-situ generation of hydrogen peroxide,which is subsequently decomposed by the Cu SA sites to produce·OH radicals that play a key role in the rate-determining step of methane activation to form methanol.Additionally,the presence of Cu SA not only enhances the electron-hole separation efficiency and improves the transfer of the photo-generated charges,but also increases the number of active sites for methane adsorption and activation.These insights provide valuable guidance for designing efficient catalysts for the highly selective photocatalytic oxidation of methane to methanol.
基金supported by the National Natural Science Foundation of China(Nos.U21A2060 and 22178116)the Natural Science Foundation of Shanghai(No.22ZR1417400)the Fundamental Research Funds for the Central Universities(Nos.222201817001,50321041918013,JKA01221601,JKD01241701).
文摘Lithium-sulfur(Li-S)batteries are regarded as the most formidable competitor to lithium-ion batteries due to their superior theoretical capacity.However,the negative impact of soluble lithium polysulfide(LiPSs)and slow redox reaction kinetics seriously hamper the commercialization of Li-S batteries.In this study,a defect-rich single-atom catalyst with an oversaturated asymmetric Fe-N_(5)coordination structure anchored in defective g-C_(3)N_(4)(C_(3)N_(4)-Fe@rGO)is designed via an absorption-pyrolysis strategy.The two-dimensional(2D)conducting C_(3)N_(4)@graphene structure with abundant defect sites accelerates the trans-fer and transportation of lithium ions and electrons.The oversaturated asymmetric Fe-N_(5)coordination structure effectively improves the adsorbility of LiPSs and accelerates the redox kinetics of sulfur species.Hence,the Li-S cell with a C_(3)N_(4)-Fe@rGO modified separator reveals a high initial capacity(1197.1 mAh g^(-1) at 0.2 C)and a low capacity decay rate(0.037%per cycle after 900 cycles at 1 C).Even at high sulfur loading and extreme temperatures of 0℃,it also shows good cycling performance.This work creates ideas for synthesizing oversaturated single-atom coordination environments and an efficient route to the practical realization of the Li-S batteries.
文摘The rational configuration of built-in electric field(IEF)in heterogeneous materials can significantly optimize the band structure to accelerate the separation of photogenerated charge carriers.However,the strength modulation of IEF formed by various materials has an uncertain enhancing effect on the separation of photogenerated carriers.Herein,a mesoporous MIL-125(Ti)@BiOCl S-scheme heterojunction with controllable IEF is prepared by green photoreduction reaction to investigate the relationship between IEF,microstructure,and photocatalytic activity.Moreover,the corresponding results demonstrate the MIL-125(Ti)@BiOCl effectively regulates the IEF strength through controlling the concentration of ligand defects,thereby optimizing the band structure and improving the efficiency of photogenerated charge separation.The optimized IEF significantly enhances the photocatalytic degradation performance of mesoporous MIL-125(Ti)-3@BiOCl towards tetracycline,with a k value of 0.07 min^(–1),which are approximately 5.5 and 4.7 times greater than that of BiOCl(0.0127 min^(–1))and MIL-125(Ti)-3(0.015 min^(–1)).These findings provide a new pathway for regulating IEF within MOF-based heterojunctions,and offer new insights into the intrinsic correlations between defect structure,IEF,and photocatalytic activity.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea,funded by the Ministry of Education(No.2022R1I1A1A01056406)。
文摘Defective phononic crystals(PnCs)have enabled spatial localization and quantitative amplification of elastic wave energy.Most previous research has focused on applications such as narrow-bandpass filters,ultrasonic sensors,and piezoelectric energy harvesters,typically operating under the assumption of an external elastic wave incidence.Recently,a novel approach that uses defective PnCs as ultrasonic actuators to generate amplified waves has emerged.However,the existing studies are limited to the generation of either longitudinal or bending waves,with no research addressing the concurrent generation of both.Hence,this paper proposes a straightforward methodology for the concurrent generation and amplification of both wave types utilizing defect modes at independent defect-band frequencies.Bimorph piezoelectric elements are attached to the defect,with each element connected to independent external voltage sources.By precisely adjusting the magnitude and temporal phase differences between the voltage sources,concurrently amplified wave generation is achieved.The paper highlights the advantages of the proposed analytical model.This model is both computationally time-efficient and accurate,in comparison with the COMSOL simulation results.For instance,in case studies,the analytical model reduces the computational time from one hour to mere seconds,while maintaining acceptable error rates of 1%in peak frequencies.This concurrent wave-generation methodology opens new avenues for applications in rotating machinery fault diagnosis,structural health monitoring,and medical imaging.
文摘Defect engineering improves the catalytic performance of metal-organic frameworks(MOFs)loaded metal nanoparticles(MNPs@MOFs),but there is still a challenge in defining the structure-activity relationships.Herein,the content of linker-missing defects in UiO-66(Ce)was systematically regulated via formic acid as the modulators,and defective UiO-66(Ce)loaded Ni nanoparticles(NPs)were constructed for dicyclopentadiene(DCPD)hydrogenation.The fine regulation of defect engineering and reduction conditions affected the structure properties of UiO-66(Ce)and the electronic metal-support interaction between MOFs and Ni NPs,thereby optimizing the microenvironment and electronic state of Ni NPs.The optimized U(Ce)-40eq with suitable defects,small size and structure stability effectively promoted the production of highly dispersed abundant electron-deficient Ni^(0) active sites,enhancing the adsorption and activation of H_(2) and C=C bonds,especially accelerating the rate-determining step.Therefore,U(Ce)-40eq loaded 5 wt%Ni NPs achieved DCPD saturated hydrogenation to tetrahydrodicyclopentadiene(70℃,2 MPa,90 min),superior to most high-loading Ni-based catalysts.This work reveals the synergistic mechanism of MOFs defect engineering and electronic structure of Ni NPs,providing effective guidance for the precise preparation of highly efficient and stable MNPs@MOFs heterogeneous catalysts.
基金financial support by the Excellent Youth Foundation of Shandong Province(No.ZR2022YQ22)National Natural Science Foundation of China(No.32101451)Youth Innovation Team Project of Shandong Province(No.2022KJ303)。
文摘A high-activity and stable bifunctional oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)electrocatalyst is critical for seawater-based Zn-air batteries(ZABs).Herein,we report a wood-derived chainmail electrocatalyst containing defective nitrogen-doped carbon nanotubes encapsulating cobalt nanoparticles(Co@D-NCNT/CW)to enhance the ORR/OER activity and stability in seawater medium.During the preparation process,the introduction and removal of Zn increased the defect sites and pyridine N content in the carbon material,modulating charge distribution and influencing the adsorption and activation processes.The highly ordered open channels in Co@D-NCNT/CW promoted mass transfer of reactants and accelerated gas diffusion.The resultant chainmail electrocatalyst exhibited impressive bifunctional ORR and OER activities with an ultra-low gap of 0.67 V in sea water-based alkaline electrolyte.The Co@D-NCNT/CW-assembled seawater-based rechargeable liquid ZABs demonstrated a maximum power density of 245.3 mW cm^(-2)and a long-term cycling performance over 500 h.The seawater-based all-solid-state ZABs achieved the maximum power density of 48.2 mW cm^(-2)and stabilized over 30 h.Density functional theory revealed that the presence of defects and pyridine nitrogen in Co@D-NCNT/CW modulated the electronic structure of Co,optimizing the binding affinity of the Co sites with intermediates and weakening Cl^(-)adsorption.This work provides a new approach to preparing high-activity and stable ORR/OER electrocatalyst utilizing wood nanostructures,boosting the development of seawater-based ZABs.
基金the financial support from the Program for Innovative Research Team in University of Henan Province(21IRTSTHN009)Science and Technology Fund of Henan Province(225200810051)Natural Science Foundation of Henan Province(222300420406)。
文摘The photoreduction of CO_(2)into CH_(4)with simultaneous high activity and selectivity is a promising strategy to increase energy supply and alleviate global warming.However,the absence of the active sites that is responsible for the adsorption and activation of CO_(2)and the generation of CO and H2via side reactions often lead to poor efficiency and low selectivity of the catalyst.Herein,Cu,Pd,and PdCu metal clusters cocatalyst-anchored defective TiO_(2)nanotubes(Cu/TiO_(2)-SBO,Pd/TiO_(2)-SBO,and Pd1Cu1/TiO_(2)-SBO)were designed via a simple solution impregnation reduction and applied for photocatalytic conversion of CO_(2)to CH_(4).The Pd1Cu1/TiO_(2)-SBO photocatalyst exhibits excellent catalytic performance among the other catalysts for photoreduction of CO_(2)into CH_(4).More interestingly,the product selectivity of CH_(4)reaches up to 100%with a rate of 25μmol g^(-1)h^(-1).In-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)simulations indicate that the main reasons for the high selectivity of CH_(4)are attributed to the PdCu alloy and oxygen vacancies,which jointly enhance the photoinduced carrier separation and lower energy barriers of key intermediates.Moreover,due to the tunable d-band center of the Cu site in the PdCu alloy,the generated intermediates can be well prevented from poisoning and promoted to participate in further reactions.Hopefully,the current study will provide insight into the development of new,highly selective photocatalysts for the visible light-catalytic reduction of CO_(2)into CH_(4).
基金financed by the National Key Research and Development Program of China(Grant No.2021YFB3802400)the National Natural Science Foundation of China(Grants Nos.52071141,52271212,52201250,and 51771056)+1 种基金the Natural Science Foundation of Hebei Province(Grant No.E2018502054)the Fundamental Research Funds for the Central Universities(Grant No.2023MS148).
文摘The vacancy defect exhibits a remarkable improvement in the dehydriding property of MgH_(2)@Ni-CNTs.However,the corresponding mechanism is still not fully understood.Herein,the impact of vacancy defects on the dehydrogenation properties of MgH_(2)@Ni-CNTs was studied by DFT simulation,and the corresponding models were constructed based on MS.The dehydrogenation process of MgH_(2)can be regarded as the dissociation of Mg-H and desorption of H_(2)from the MgH_(2)surface.In view of the whole dehydrogenation,the dissociation of H^(−)is the rate-determining step,which is the main reason for restricting the dehydrogenation kinetics.Compared with vacancy vacancy-defective MgH_(2)(001)surface,the appearance of vacancy defects on the(110)surface substantially reduces the energy barrier required for H dissociation to 0.070 Ha.The reason is that vacancy defects accelerate the transition of electrons from the H^(−)s orbit to the Mg^(2+)3s orbit,resulting in a decrement of the Mg-H bond strength,which makes H atoms more easily dissociated from the MgH_(2)(110)surface.Therefore,the existence of vacancy defects improves the dehydriding kinetic of MgH_(2).Most importantly,this research offers crucial directions for developing hydrogen storage materials as well as a potential fix for the slow dehydrogenation kinetics of nano-confined MgH_(2).
基金supported by the National Nature Science Foundation of China,No.31770180the Youth Innovation Promotion Association CAS,No.2016303
文摘Hepatitis B virus(HBV) infection is a global public health concern. HBV causes chronic infection in patients and can lead to liver cirrhosis, hepatocellular carcinoma, and other severe liver diseases. Thus, understanding HBV-related pathogenesis is of particular importance for prevention and clinical intervention. HBV surface antigens are indispensable for HBV virion formation and are useful viral markers for diagnosis and clinical assessment. During chronic HBV infection, HBV genomes may acquire and accumulate mutations and deletions, leading to the expression of defective HBV surface antigens. These defective HBV surface antigens have been found to play important roles in the progression of HBV-associated liver diseases. In this review, we focus our discussion on the nature of defective HBV surface antigen mutations and their contribution to the pathogenesis of fulminant hepatitis B. The relationship between defective surface antigens and occult HBV infection are also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.21701043,21825201 and U19A2017)the Provincial Natural Science Foundation of Hunan(2019GK2031)+1 种基金the Open Project Program of Key Laboratory of Low Dimensional Materials&Application Technology(Xiangtan University),Ministry of Education,China(No.KF20180202)the China Postdoctoral Science Foundation(Grant Nos.2019 M662766,2019 M662759,2020 M682549,and 2020 M672473)。
文摘One of the fundamental driving forces in the materials science community is the hunt for new materials with specific properties that meet the requirements of rapidly evolving technology.
基金supported by the National Natural Science Foundation of China (Grant No. 51131005)
文摘The current distributions over carbon steel under iron red alkyd primer exposed to 3.5% sodium chloride solution were mapped using the wire beam electrode （WBE）. The electrochemical impedance spectroscopy （EIS） of the WBE was carded out to analyze the performance of coating delamination and corrosion behavior of carbon steel beneath defective coating. The EIS data revealed that protective capability of coating decreased with immersion time and the degree of cathodic delamination showed a rapid rise. The current density distribution of WBE indicated that cathodic sites was located at the defect at the beginning of immersion and gradually spread into the intact coating. The cathodic regions were distinguished from the anodic area and distributed over the WBE. The changes of cathodic sites could reflect the deterioration process of defective coating. The cathodic area ratio was a more useful parameter than the cathodic delamination degree to evaluate the coating cathodic delamination. The polarity reversals of electrodes at the defect and beneath coating were observed. A simple discussion of relationship between the blister and the polarity reversal was made from a standpoint of electrochemical distribution. WBE method was able to map and record the changes of local cathodic sites beneath defective coating in real time, which could provide more detailed information about the local degradation of coating.
基金supported by the National Natural Science Foundation of China(21865025)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT_15R46)
文摘Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions.However,the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking.In this study,ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst.These catalysts were prepared via a one-step method at 900℃.Amazingly,the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles.These facilitated the catalyst synthesis,and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium,including a lower onset potential,lower mid-wave potential,four electron transfer process,and better durability compared with 20 wt%Pt/C.More importantly,the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH*from*OO toward oxygen reduction reaction.Therefore,the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells,given the novel catalyst’s resulting performance.
基金supported by the Program of Introducing Talents of Discipline to Universities (B08021)Fundamental Research Funds for the Central Universities
文摘The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory （DFT） method. Twelve possible support models of regular and defective MgC12 （110） and （100） surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate （EB） as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TIC14 from coordinating on the MgC12 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgC12 support, presented stronger adsorption of TiCl4 than that of EB on （110） surface. Since the TIC14 and ethyl benzoate （EB） would compete to adsorb on the support surface, it seems reasonable to assume that TIC14 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.
基金supported by the National Key R&D Program of China (No. 2016YFA0200101)the National Natural Science Foundation of China (Nos. 51325205, 51290273, 51521091, and 51861135201)+1 种基金Chinese Academy of Sciences (No. 174321KYSB20160011)the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB30000000)
文摘Pristine graphene (PG) has been demonstrated to be an excellent substrate for Raman enhancement, which is called graphene-enhanced Raman scattering. However, the chemically inert and hydrophobic surface of PG hinders the adsorption of molecules especially in aqueous solutions, and consequently limits the Raman enhanced efficiency. Here, we synthesized defective graphene (DG) films by chemical vapor deposition on Au, which has a defect density of ~2.0 ×10^11 cm^-2. The DG shows a much better wettability than PG towards dye solution. Combining with the strong adsorption ability of defects to molecules, DG shows greatly enhanced efficiency than PG with perfect lattice. For example, the detection limit for rhodamine B can reach 2×10^9 M for DG while it is on the order of 10^-7 M for PG. In addition, DG has high enhancement uniformity and the Au substrate can be reused after electrochemical bubbling transfer. These advantages suggest the great potential of the DG grown on Au for practical applications in environmental monitoring.
基金This work was supported by the National Key Research and Development Program of China(No.2020YFA0211000)the National Natural Science Foundation of China(Nos.21876114,21761142011,and 51572174)+3 种基金the Shanghai Government(Nos.19DZ1205102 and 19160712900)the International Joint Laboratory on Resource Chemistry(No.IJLRC)the Ministry of Education of China(No.PCSIRT_IRT_16R49)This research was also supported by The Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,the Shuguang Research Program of Shanghai Education Committee,and the Shanghai Engineering Research Center of Green Energy Chemical Engineering(No.18DZ2254200).
文摘NH_(2)-UIO66(NU)is a promising photocatalyst for the reduction of Cr(VI)to low-toxic Cr(III)driven by visible light under ambient conditions.However,the main limitation in this process is the ineffi cient ligand to metal charge transfer(LMCT)of photo-excited electrons,which is caused by inherent energy gap(ΔE_(LMCT)).This study synthesized the defective NU(NUXH,where X is the molar equivalent of the modulator)with reducedΔE_(LMCT)through linkers removal via acid treatment.The electronic structure of NUX-H was systematically investigated,and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms.Furthermore,they substantially lowered the energy of the unoccupied d orbitals(LUMO),which was benefi cial to effi cient LMCT,resulting in an improved photocatalytic activity of NUX-H toward high-concentration(100 mg/L)Cr(VI)reduction.Compared to NU with defect-free structure,the reducing rate of Cr(VI)was increased by 47 times.This work introduced an alternative strategy in terms of designing effi cient photocatalysts for reducing Cr(VI)under ambient conditions.
基金The Beijing Municipal Education Commission(KZ201910005003)supported this work。
文摘Defective layered Mn-based materials were synthesized by Li/Na ion exchange to improve their electrochemical activity and Coulombic efficiency.The annealing temperature of the Na precursors was important to control the P3-P2 phase transition,which directly affected the structure and electrochemical characteristics of the final products obtained by ion exchange.The O3-Li_(0.78)[Li_(0.25)Fe_(0.075)Mn_(0.675)]O_(δ) cathode made from a P3-type precursor calcined at 700℃ was analyzed using X-ray photoelectron spectrometry and electron paramagnetic resonance.The results showed that the presence of abundant trivalent manganese and defects resulted in a discharge capacity of 230 mAh/g with an initial Coulombic efficiency of about 109%.Afterward,galvanostatic intermittent titration was performed to examine the Li^(+) ion diffusion coefficients,which affected the reversible capacity.First principles calculations suggested that the charge redistribution induced by oxygen vacancies(OV_(s))greatly affected the local Mn coordination environment and enhanced the structural activity.Moreover,the Li-deficient cathode was a perfect match for the pre-lithiation anode,providing a novel approach to improve the initial Coulombic efficiency and activity of Mn-based materials in the commercial application.
文摘Graphene,as a proof-of-concept two-dimensional material,has proven to have excellent physical and chemical properties.Its derivatives,such as defective or doped graphene,are also applied as catalytic materials for metal-air batteries(MABs).MABs have been recognized as possible candidates for new-generation energy storage systems due to their ultra-high theoretical energy density.So far,graphene and its derivatives with optimized structures have been widely explored to improve the electrochemical performance in MABs.Generally speaking,perfect graphene crystalline is inert for many catalytic processes,while defects and heteroatoms can endow graphene with high activity for many electrocatalytic reactions.Under this circumstance,recent progress is summarized for defective/doped graphene as air cathodes in aqueous or organic MABs,which are actually different electrochemical systems with distinct requirements for air cathodes.Also,the relationship is clarified between graphene defects/doping and electrocatalytic mechanisms that can be the guidance for catalyst design.Future directions are also prospected for the development of graphene-based MAB cathodes.
基金Project supported by the Ministry of Science and Technology of China (No.2001BA803B03-05).
文摘The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.
文摘Previous studies in our laboratory have demonstrated that the thermosensitivity locus cosegregates with blood pressure and that the elevated expression and restriction fragment length polymorphism of HSP70 gene are associ-ated with hypertension. Cell protection against environ-mental stressors such as heat and chemicals is often accom-panied by up-regulated expression of a wide spectrum of heat sliock genes(HSP). To further investigate the interre-lation between HSP expression and blood pressure regulation, we employed an effective method of cloning 2 poten-tial hypertension-related HSPs. Synthetic oligonucleotides corresponding either to a higbly-conserved region of the known HSP family or a repetitive sequence in the protein- encoding gene were used as target primers for polymerase chain reaction (PCR). cDNA prepared from heat-stressed and non-stressed vascular smooth muscle cells (VSMC) of Brown Norway rats (BN.1x) and spontaneously hyperten-sive rats (SHRp) respectively served as template in the reaction. The PCR products were subsequently analyzed in a single-stranded conformational polymorphism (SSCP) electrophoresing system. Differential gene expression in BN.1x and SHRp was seen on autoradiographs of SSCP gel by comparing the migration patterns of PCR-amplified DNA fragments. Using this technique, we also found that HSP27 and a new member of the large HSP gene family were differentially expressed in BN.1x and SHRp VSMC.
