Fluid-structure interaction(FSI) is a class of mechanics-related problems with mutual dependence between the fluid and structure parts and it is observable nearly everywhere, in natural phenomena to many engineering s...Fluid-structure interaction(FSI) is a class of mechanics-related problems with mutual dependence between the fluid and structure parts and it is observable nearly everywhere, in natural phenomena to many engineering systems. The primary challenges in developing numerical models with conventional grid-based methods are the inherent nonlinearity and timedependent nature of FSI, together with possible large deformations and moving interfaces. Smoothed particle hydrodynamics(SPH) method is a truly Lagrangian and meshfree particle method that conveniently treats large deformations and naturally captures rapidly moving interfaces and free surfaces. Since its invention, the SPH method has been widely applied to study different problems in engineering and sciences, including FSI problems. This article presents a review of the recent developments in SPH based modeling techniques for solving FSI-related problems. The basic concepts of SPH along with conventional and higher order particle approximation schemes are first introduced. Then, the implementation of FSI in a pure SPH framework and the hybrid approaches of SPH with other grid-based or particle-based methods are discussed. The SPH models of FSI problems with rigid, elastic and flexible structures, with granular materials, and with extremely intensive loadings are demonstrated. Some discussions on several key techniques in SPH including the balance of accuracy, stability and efficiency, the treatment of material interface, the coupling of SPH with other methods, and the particle regularization and adaptive particle resolution are provided as concluding marks.展开更多
Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble m...Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble metal as co-catalyst for visible-light-driven hydrogen evolution, while more efficient photocatalytic systems are still a major challenge. Herein, we report a facile strategy for synthesizing faceto-face ultrathin Pd nanosheets-amorphous carbon nitride(Pd NSs-ACN) structure with large contacting interface and short electronic transmission pathway, which can work as an efficient photocatalyst for hydrogen production. The synthesis starts with the growth of ultrathin Pd NSs, followed by assembly with the visible-light-response ACN through a simple stirring and annealing procedure. The resultant two dimensional face-to-face structures deliver an average hydrogen generation rate of 1.45 mmol h-1g-1 at a temperature of 25℃,almost 2.6 times higher than that of Pd Nps-ACN with particle-to-face structural feature. The efficient photocatalytic activity is ascribed to the formation of high-density of active sites between ultrafine face-to-face contacted Pd NSs and the ACN, which cooperate more synergistically towards photocatalytic hydrogen production. The face-to-face engineered Pd NSs-ACN hybrids also offer a good stability revealed by photocatalytic hydrogen production measurements. The extraordinary performance highlights a powerful engineering model for designing other face-to-face contacting co-catalyst/photocatalysts, which will be a great impetus to optimize new catalytic transformations.展开更多
Electrochemical water splitting for hydrogen production has sparked intensive interests because it provides a new approach for sustainable energy resources and the avoidance of environmental problems.The precious meta...Electrochemical water splitting for hydrogen production has sparked intensive interests because it provides a new approach for sustainable energy resources and the avoidance of environmental problems.The precious metal-based sin-gle atomic catalysts(PMSACs)have been widely employed in water splitting catalysis by virtue of their maximum atom utilization and unique electronic structure,which can reduce metal amounts and remain high catalytic perfor-mance simultaneously.In this review,we will summarize recent research efforts toward developing SACs based on precious metals with excellent performance for electrochemical water splitting catalysis.First,the synthesis strategies for PMSACs will be classified and introduced including high-temperature pyrolysis,electrochemical method,photochemical reduction,wet chemistry method,etc.Then,a short description of characterization techniques for SACs will be given,which mainly involves the aberration-corrected scanning-transmission electron microscopy(AC-STEM)and X-ray absorption spectroscopy(XAS).In particular,the relationship between the electronic structure of the precious metal atomic sites and performance for water splitting will be discussed according to the the-oretical and experimental results.Finally,a brief perspective will be provided to highlight the challenges and opportunities for the development of novel PMSACs suitable for electrochemical water splitting applications.展开更多
Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employ...Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgxAl1-hydrotalcite(denoted as re-MgxAl1-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid(GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg6Al1-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations(XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Ptd+species at metal-support interface, which accelerates bond cleavage of a-C–H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.展开更多
Despite various 2H-MoS/carbon hybrid nanostructures have been constructed and committed to improve the performance for sodium-ion batteries(SIBs),they still show the limited cycle stability due to the relatively large...Despite various 2H-MoS/carbon hybrid nanostructures have been constructed and committed to improve the performance for sodium-ion batteries(SIBs),they still show the limited cycle stability due to the relatively large volumetric expansion during the charge-discharge process Herein,we report the construction of cobalt-doped few-layered 1T-MoS2 nanosheets embedded in N,S-doped carbon(CMS/NSC)nanobowls derived from metal-organic framework(MOF)precursor via a simple in situ sulfurization process.This unique hierarchical structure enables the uniformly dispersed Co-doped 1T-MoS2 nanosheets intimately couple with the highly conductive carbon nanobowls,thus efficiently preventing the aggregation.In particular,the Co-doping plays a crucial role in maintaining the integrity of structure for MoS2 during cycling tests,confirmed by first-principles calculations.Compared with pristine MoS2,the volume deformation of Co-doped MoS2 can be shrunk by a prominent value of 52%during cycling.Furthermore,the few-layered MoS2 nanosheets with 1T metalic phase endow higher conductivity,and thus can surpass its counterpart 2H semiconducting phase in battery performance.By virtue of the synergistic effect of stable structure,appropriate doping and high conductivity,the resulting CMS/NSC hybrid shows superior rate capability and cycle stability.The capacity of CMS/NSC can still be 235.9 mAh·g^-1 even at 25 A·g^-1,which is 51.3%of the capacity at 0.2 A·g^-1.Moreover,the capacity can still remain 218.6 mAh·g^-1 even over 8,240 cycles at 5 Ag·g^-1 with a low decay of 0.0044%per cycle,one of the best performances among the reportec MoS2-based anode materials for SIBs.展开更多
Instability-induced wrinkle patterns of thin sheets are ubiquitous in nature,which often result in origami-like patterns that provide inspiration for the engineering of origami designs.Inspired by instability-induced ...Instability-induced wrinkle patterns of thin sheets are ubiquitous in nature,which often result in origami-like patterns that provide inspiration for the engineering of origami designs.Inspired by instability-induced origami patterns,we propose a computational origami design method based on the nonlinear analysis of loaded thin sheets and topology optimization.The bar-and-hinge model is employed for the nonlinear structural analysis,added with a displacement perturbation strategy to initiate out-of-plane buckling.Borrowing ideas from topology optimization,a continuous crease indicator is introduced as the design variable to indicate the state of a crease,which is penalized by power functions to establish the mapping relationships between the crease indicator and hinge properties.Minimizing the structural strain energy with a crease length constraint,we are able to evolve a thin sheet into an origami structure with an optimized crease pattern.Two examples with different initial setups are illustrated,demonstrating the effectiveness and feasibility of the method.展开更多
Data-driven discovery of partial differential equations(PDEs)has recently made tremendous progress,and many canonical PDEs have been discovered successfully for proof of concept.However,determining the most proper PDE...Data-driven discovery of partial differential equations(PDEs)has recently made tremendous progress,and many canonical PDEs have been discovered successfully for proof of concept.However,determining the most proper PDE without prior references remains challenging in terms of practical applications.In this work,a physics-informed information criterion(PIC)is proposed to measure the parsimony and precision of the discovered PDE synthetically.The proposed PIC achieves satisfactory robustness to highly noisy and sparse data on 7 canonical PDEs from different physical scenes,which confirms its ability to handle difficult situations.The PIC is also employed to discover unrevealed macroscale governing equations from microscopic simulation data in an actual physical scene.The results show that the discovered macroscale PDE is precise and parsimonious and satisfies underlying symmetries,which facilitates understanding and simulation of the physical process.The proposition of the PIC enables practical applications of PDE discovery in discovering unrevealed governing equations in broader physical scenes.展开更多
Perovskite solar cell has gained widespread attention as a promising technology for renewable energy.However, their commercial viability has been hampered by their long-term stability and potential Pb leakage. Herein,...Perovskite solar cell has gained widespread attention as a promising technology for renewable energy.However, their commercial viability has been hampered by their long-term stability and potential Pb leakage. Herein, we demonstrate a bifunctional passivator of the potassium tartrate(PT) to address both challenges. PT minimizes the Pb leakage in perovskites and also heals cationic vacancy defects, resulting in improved device performance and stability. Benefiting from PT modification, the power conversion efficiency(PCE) is improved to 23.26% and the Pb leakage in unencapsulated films is significantly reduced to 9.79 ppm. Furthermore, the corresponding device exhibits no significant decay in PCE after tracking at the maximum power point(MPP) for 2000 h under illumination(LED source, 100 mW cm^(-2)).展开更多
The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroel...The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroelastic toughening mechanism.Microstructure and interface tension play a critical role in ferroelastic variant switching at the micro-and nano-scale.This paper presents an original thermodynamically consistent phase field(PF)theory for analyzing ferroelastic variant switching at the micro-and nano-scale of t’-YSZ.The theory incorporates strain gradient elasticity using higher-order elastic energy and interface tension tensor via geometric nonlinearity to represent biaxial tension resulting from interface energy.Subsequently,a mixed-type formulation is employed to implement the higher-order theory through the finite element method.For an interface in equilibrium,the effects of strain gradient elasticity result in a more uniform distribution of stresses,whereas the presence of interface tension tensor significantly amplifies the stress magnitude at the interface.The introduction of an interface tension tensor increases the maximum value of stress at the interface by a factor of 4 to 10.The nucleation and evolution of variants at a pre-existing crack tip in a mono-phase t’-YSZ have also been studied.The strain gradient elasticity is capable of capturing the size effect of ferroelastic variant switching associated with microstructures in experiments.Specifically,when the grain size approaches that of the specimen,the critical load required for variant switching at the crack tip increases,resulting in greater dissipation of elastic energy during ferroelastic variant switching.Moreover,the interface tension accelerates the evolution of variants.The presented framework exhibits significant potential in modeling ferroelastic variant switching at the micro-and nano-scale.展开更多
A novel carbon quantum dots modified potassium titanate nanotubes(CQDs/K2 Ti6 O13)composite photocatalyst was synthesized by hydrothermal treatment combined with calcination.X-ray diffraction(XRD)pattern and transmiss...A novel carbon quantum dots modified potassium titanate nanotubes(CQDs/K2 Ti6 O13)composite photocatalyst was synthesized by hydrothermal treatment combined with calcination.X-ray diffraction(XRD)pattern and transmission electron microscopy(TEM)indicated formation of potassium titanate nanotubes and successful deposition of CQDs onto K2 Ti6 O13.The photocatalytic performance of CQDs/K2 Ti6 O13 composite was evaluated by degradation of amoxicillin(AMX)under the irradiation of visible light and lights with the wavelengths of 365,385,420,450,485,520,595 and 630 nm.The results showed that the photocatalytic activity of CQDs/K2 Ti6 O13 hybrid material was greatly enhanced compared with the neat K2 Ti6 O13 calcined at 300 ℃.The narrowed band gap energy(Eg)and transfer of photo-excited electron by CQDs inhibited the immediate combination of electron-hole pairs,thus promoting photocatalytic activity.Moreover,CQ,Ds/K2 Ti6 O13 exhibited a broad spectrum of photocatalytic ability and it was interesting that the photocatalytic activity decreased with the increase of the irradiation wavelength.Reactive oxygen species(ROS)quenching tests suggested the hole(h^+)and hydroxyl radical(^·OH)played the primary roles in photocatalytic degradation of AMX.Moreover,CQ.Ds/K2 Ti6 O13 showed good reusability for AMX photocatalytic degradation after five successive runs.This study proposed an available method for titanate nanomaterials modification,and the developed novel CQDs/K2 Ti6 O13hyb rid material is p ro mising fo r potential application on antibiotics removal fro m water and wastewater.展开更多
The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relations...The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relationship between two order vibration modes of the system is verified.The resonance response of this class of bistable structures in the dynamic snap-through mode is investigated,and the four-dimensional(4D)nonlinear modulation equations are derived based on the 1:1 internal resonance relationship by means of the multiple scales method.The Hopf bifurcation and instability interval of the amplitude frequency and force amplitude curves are analyzed.The discussion focuses on investigating the effects of key parameters,e.g.,excitation amplitude,damping coefficient,and detuning parameters,on the resonance responses.The numerical simulations show that the foundation excitation and the degree of coupling between the vibration modes exert a substantial effect on the chaotic dynamics of the system.Furthermore,the significant motions under particular excitation conditions are visualized by bifurcation diagrams,time histories,phase portraits,three-dimensional(3D)phase portraits,and Poincare maps.Finally,the vibration experiment is carried out to study the amplitude frequency responses and bifurcation characteristics for the bistable laminated composite shell,yielding results that are qualitatively consistent with the theoretical results.展开更多
The complex air pollution driven by both Ozone(O_(3))and fine particulate matter(PM2.5)sig nificantly influences the air quality in the Sichuan Basin(SCB).Understanding the O_(3)for mation during autumn and winter is ...The complex air pollution driven by both Ozone(O_(3))and fine particulate matter(PM2.5)sig nificantly influences the air quality in the Sichuan Basin(SCB).Understanding the O_(3)for mation during autumn and winter is necessary to understand the atmospheric oxidative capacity.Therefore,continuous in-site field observations were carried out during the late summer,early autumn and winter of 2020 in a rural area of Chongqing.The total volatile organic compounds(VOCs)concentration reported by a Proton-Transfer-Reaction Time-of Flight Mass Spectrometry(PTR-ToF-MS)were 13.66±9.75 ppb,5.50±2.64 ppb,and 9.41±5.11 ppb in late summer,early autumn and winter,respectively.The anthropogenic VOCs(AVOCs)and biogenic VOCs(BVOCs)were 8.48±7.92 ppb and 5.18±2.99 ppb in late sum mer,3.31±1.89 ppb and 2.19±0.93 ppb in autumn,and 6.22±3.99 ppb and 3.20±1.27ppb in winter.A zero-dimensional atmospheric box model was employed to investigate the sensitivity of O_(3)-precursors by relative incremental reactivity(RIR).The RIR values of AV OCs,BVOCs,carbon monoxide(CO),and nitrogen oxides(NOx)were 0.31,0.71,0.09,and-0.36 for late summer,0.24,0.59,0.22,and-0.38 for early autumn,and 0.30,0.64,0.33 and-0.70 for winter,and the results showed that the O_(3)formation of sampling area was in the VOC-limited region,and O_(3)was most sensitive to BVOCs(with highest RIR values,>0.6)This study can be helpful in understanding O_(3)formation and interpreting the secondary formation of aerosols in the winter.展开更多
Highly-branched dendritic Pt-based nanocrystals possess great potential in catalyzing the oxygen reduction reaction(ORR),but encounter performance ceiling due to their poor thermal and electrochemical stability.Here,w...Highly-branched dendritic Pt-based nanocrystals possess great potential in catalyzing the oxygen reduction reaction(ORR),but encounter performance ceiling due to their poor thermal and electrochemical stability.Here,we present a novel Pt Fe nanodendrites(NDs)branched with two-dimensional(2 D)twinned nanoplates rather than conventional 1 D nanowires,which breaks the ORR performance ceiling of dendritic catalysts by inducing the unique Pt-skin configuration via rationally thermal treatment.By further hybridizing the Pt-skin Pt Fe NDs/C with amino-functionalized ionic liquids(ILs),we achieve an unprecedented mass activity of 3.15 A/mgPtat 0.9 V versus reversible hydrogen electrode(RHE)in the Pt Fe-based ORR electrocatalytic system.They also show excellent electrocatalytic durability for ORR with negligible activity decay and no apparent structural change after 20,000 cycles,in sharp contrast to the nanowires branched Pt Fe NDs counterpart.The remarkable catalytic performance is attributed to a combination of several structural features,including 2 D morphology,twin boundary,partially ordered phase and strong coordination with amino group.This work highlights the significance of stabilizing electrocatalytic structures via morphology tuning,which thus enables further surface and interface modification for performance breakthrough in ORR electrocatalysis.展开更多
Failure due to interfacial oxidation is one of the most important factors in the failure of alloy systems at high temperatures.To analyze high-temperature interfacial oxidation in alloys under deformation,we develop a...Failure due to interfacial oxidation is one of the most important factors in the failure of alloy systems at high temperatures.To analyze high-temperature interfacial oxidation in alloys under deformation,we develop a thermodynamically consistent continuum theory of alloy interfacial oxidation process considering diffusion,oxidation,expansion,viscoplasticity,and deformation processes.Balance equations of force,mass,and energy are presented at first,while the coupled constitutive laws and evolution equations are constructed according to energy dissipation inequality.The coupled kinetics reveals a new mechanism whereby deformation affects the oxidation reaction by changing the alloy’s critical oxygen concentration.External tensile loads decrease the critical oxygen concentration and promote oxidation of the alloy.Conversely,external compressive loads increase the critical oxygen concentration and suppress the oxidation of the alloy.Finally,this theory is applied to thermal barrier coatings(TBCs),exhibiting a good consistency with the high-temperature oxidation experiment of TBCs under external loads.The model successfully explains that the experimental phenomenon of external tensile load accelerates the growth of Al_(2)O_(3)-TGO(thermally grown oxides).Besides,external compressive loads slow down the growth of Al_(2)O_(3)-TGO at the interface and lead to internal oxidation of the bond coat.The presented framework has shown great potential for modeling high-temperature interfacial oxidation processes in alloy systems under deformation.展开更多
Developing high-efficiency,stable and non-precious electrocatalysts for oxygen reduction reaction(ORR)is highly important for energy conversion and storage.Single atom catalysts(SACs)show good potential in enhancing O...Developing high-efficiency,stable and non-precious electrocatalysts for oxygen reduction reaction(ORR)is highly important for energy conversion and storage.Single atom catalysts(SACs)show good potential in enhancing ORR,however,the specifical control over the coordination surroundings around single metal center to intrinsically modify the electron structure is still a great challenge.Herein,we demonstrate that a 3 D hybrid MOF composed of cobalt doped ZIF-L and ZIF-8,featuring star morphology with six equal branches,can be used as an advanced precursor for making the Co SACs for greatly boosted ORR.The as-synthesized Co_(SA)-N-C exhibits excellent ORR activity with E_(1/2) of 0.891 V in alkaline medium,outperforming the commercial Pt/C by 39 m V.Moreover,the E_(1/2) of Co_(SA)-N-C(0.790 V)is merely 15 m V,less than that of Pt/C(0.805 V)in acid medium,which is among the best in the reported state-of-the-art SACs.DFT calculations demonstrate that the enhanced ORR performance is assigned to the formation of atomically isolated cobalt atom coordinated three N atoms and one C atom,which is easier to decrease the free energy of rate determining step and accelerate the ORR process than that of traditional cobalt atom coordinated four N atoms.In addition,a primary Zn-air battery with Co_(SA)-N-C cathode reveals a maximum power density of 92.2 m W cm^(-2) at 120.0 m A cm^(-2),far higher than that of commercial catalysts(74.2 m W cm^(-2) at 110.0 m A cm^(-2)).展开更多
H_(2) tends to be a crucial medium in the foreseeable future as it is not only a green and renewable energy source for vehicles but also a fundamental feedstock for the chemical industry.For instance,selective hydroge...H_(2) tends to be a crucial medium in the foreseeable future as it is not only a green and renewable energy source for vehicles but also a fundamental feedstock for the chemical industry.For instance,selective hydrogenation,one of the catalytic processes used to produce fine compounds,is of vital importance because it enables the selective and efficient conversionof a variety of functional groups under mild reaction conditions.Catalytic hydrogenation of liquid organic hydrogen carriers(LOHCs;eg,methylbenzene)is a safe and economic approach for H_(2) storage.展开更多
Air pollution is known to be a major risk factor for cardiopulmonary disease, but this is unclear for cardiometabolic disease (e.g.diabetes). This is of considerable public health importance, given the nationwide epid...Air pollution is known to be a major risk factor for cardiopulmonary disease, but this is unclear for cardiometabolic disease (e.g.diabetes). This is of considerable public health importance, given the nationwide epidemic of diabetes, accompanied by severe air pollution, in China. The evidence so far remained inadequate to answer questions of whether individuals with cardiometabolic dysfunctions are susceptible to air pollution and whether air pollution exacerbates diabetes development via certain biological pathways. In this manuscript, we summarize the results and limitations of studies exploring these two topics and elaborate our design of a prospective panel study (SCOPE) as a solution. We assessed and compared the health effect of air pollution among pre-diabetic individuals and matched healthy controls through four repeated clinical visits over 1 year. Comprehensive evaluation was made to both health endpoints and exposure. The primary biomarkers were assessed to reveal the impact on multiple biological pathways, including glycolipid metabolism and insulin resistance, endothelial function, and inflammation. Detailed chemical and size fractional components of particulate matter were measured in this study, along with the application of personal monitors.The work should increase our understanding of how air pollution affects individuals with cardiometabolic dysfunction and the underlying mechanisms.展开更多
The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we presen...The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.展开更多
Alkene hydroformylation is an extremely important industry process currently accomplished via homogeneous catalysis.Heterogeneous hydroformylation is being avidly pursued as a more economical and sustainable process.H...Alkene hydroformylation is an extremely important industry process currently accomplished via homogeneous catalysis.Heterogeneous hydroformylation is being avidly pursued as a more economical and sustainable process.Herein,we report the construction of zeolite-encaged rhodium catalyst for efficient hydroformylation.Through a facile in situ hydrothermal strategy,isolated Rh^(δ+)(δ=2.5)can be encaged in faujasite and efficiently stabilized via interaction with framework oxygen atoms,producing a Rh@Y model catalyst with well-defined rhodium sites and coordination environment.Rh@Y exhibits high catalytic activity,perfect chemoselectivity,and recyclability in 1-hexene hydroformylation under mild reaction conditions,making it a robust heterogeneous catalyst for potential applications.A state-of-the-art turnover frequency value of 6567 molC=C/molRh/h for Rh@Y can be achieved in 1-hexene hydroformylation at 393 K,outperforming all heterogeneous catalysts and most homogeneous catalysts under comparable conditions.With the well-defined structure of Rh@Y,the detailed mechanism of alkene hydroformylation can be interpreted via theoretical calculations,and the advantages of heterogeneous hydroformylation are well explained.This work provides a promising solution toward efficient heterogeneous noble metal catalysis by encaging stable isolated ions in a zeolite matrix.展开更多
This paper presents an innovative design for a biomimetic whale shark-like underwater glider aiming at the combination of high maneuverability and long duration.As a hybrid of the underwater glider and the robotic fis...This paper presents an innovative design for a biomimetic whale shark-like underwater glider aiming at the combination of high maneuverability and long duration.As a hybrid of the underwater glider and the robotic fish,its pectoral fins and tail can serve as not only the external control surfaces for attitude regulation during gliding but also the propellers for agile fish-like swimming mode.To verify the gliding capability of the whale shark-like glider and prepare for future dynamic analysis,the hydrodynamic coefficients,including drag,lift,sliding force,and corresponding moments are estimated through computational fluid dynamics method.In addition,the hydrodynamic analyses of the proposed glider and an equivalent conventional glider during steady gliding motion are executed for comparison.Extended experiments are performed to verify the downward gliding performance.The results reveal that the whale shark-like glider has less drag as well as higher lift-to-drag ratio and a markable gliding capability in practice.It may offer important inspiration for improving the gliding efficiency and performance of an underwater glider in biomimetic shape design.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51779003)the National Key Research and Development Project of China(Grant No.2018YFB0704000)
文摘Fluid-structure interaction(FSI) is a class of mechanics-related problems with mutual dependence between the fluid and structure parts and it is observable nearly everywhere, in natural phenomena to many engineering systems. The primary challenges in developing numerical models with conventional grid-based methods are the inherent nonlinearity and timedependent nature of FSI, together with possible large deformations and moving interfaces. Smoothed particle hydrodynamics(SPH) method is a truly Lagrangian and meshfree particle method that conveniently treats large deformations and naturally captures rapidly moving interfaces and free surfaces. Since its invention, the SPH method has been widely applied to study different problems in engineering and sciences, including FSI problems. This article presents a review of the recent developments in SPH based modeling techniques for solving FSI-related problems. The basic concepts of SPH along with conventional and higher order particle approximation schemes are first introduced. Then, the implementation of FSI in a pure SPH framework and the hybrid approaches of SPH with other grid-based or particle-based methods are discussed. The SPH models of FSI problems with rigid, elastic and flexible structures, with granular materials, and with extremely intensive loadings are demonstrated. Some discussions on several key techniques in SPH including the balance of accuracy, stability and efficiency, the treatment of material interface, the coupling of SPH with other methods, and the particle regularization and adaptive particle resolution are provided as concluding marks.
基金financially supported by the National Natural Science Foundation of China (51772255)Hunan Natural Science Foundation (2016JJ3123)+2 种基金the National Key Research and Development Program of China (2016YFB0100201)the start-up supports from Peking UniversityYoung Thousand Talented Program
文摘Photocatalytic hydrogen production represents a promising strategy for clean, sustainable, and environmentfriendly energy supply. Up to now, great efforts have been devoted to designing the photocatalysts with noble metal as co-catalyst for visible-light-driven hydrogen evolution, while more efficient photocatalytic systems are still a major challenge. Herein, we report a facile strategy for synthesizing faceto-face ultrathin Pd nanosheets-amorphous carbon nitride(Pd NSs-ACN) structure with large contacting interface and short electronic transmission pathway, which can work as an efficient photocatalyst for hydrogen production. The synthesis starts with the growth of ultrathin Pd NSs, followed by assembly with the visible-light-response ACN through a simple stirring and annealing procedure. The resultant two dimensional face-to-face structures deliver an average hydrogen generation rate of 1.45 mmol h-1g-1 at a temperature of 25℃,almost 2.6 times higher than that of Pd Nps-ACN with particle-to-face structural feature. The efficient photocatalytic activity is ascribed to the formation of high-density of active sites between ultrafine face-to-face contacted Pd NSs and the ACN, which cooperate more synergistically towards photocatalytic hydrogen production. The face-to-face engineered Pd NSs-ACN hybrids also offer a good stability revealed by photocatalytic hydrogen production measurements. The extraordinary performance highlights a powerful engineering model for designing other face-to-face contacting co-catalyst/photocatalysts, which will be a great impetus to optimize new catalytic transformations.
基金National Science Fund for Distinguished Young Scholars,Grant/Award Number:52025133Tencent Foundation through the XPLORER PRIZE,China Postdoc-toral Science Foundation,Grant/Award Numbers:2019M650337,2020M670021+2 种基金Beijing Natural Science Foundation,Grant/Award Number:JQ18005National Key Research and Development Pro-gram of China,Grant/Award Number:2017YFA0206701Fund of the State Key Laboratory of Solidification Process-ing in NWPU,Grant/Award Number:SKLSP202004。
文摘Electrochemical water splitting for hydrogen production has sparked intensive interests because it provides a new approach for sustainable energy resources and the avoidance of environmental problems.The precious metal-based sin-gle atomic catalysts(PMSACs)have been widely employed in water splitting catalysis by virtue of their maximum atom utilization and unique electronic structure,which can reduce metal amounts and remain high catalytic perfor-mance simultaneously.In this review,we will summarize recent research efforts toward developing SACs based on precious metals with excellent performance for electrochemical water splitting catalysis.First,the synthesis strategies for PMSACs will be classified and introduced including high-temperature pyrolysis,electrochemical method,photochemical reduction,wet chemistry method,etc.Then,a short description of characterization techniques for SACs will be given,which mainly involves the aberration-corrected scanning-transmission electron microscopy(AC-STEM)and X-ray absorption spectroscopy(XAS).In particular,the relationship between the electronic structure of the precious metal atomic sites and performance for water splitting will be discussed according to the the-oretical and experimental results.Finally,a brief perspective will be provided to highlight the challenges and opportunities for the development of novel PMSACs suitable for electrochemical water splitting applications.
基金supported by the National Natural Science Foundation of China (21871021 and 21521005)the National Key Research and Development Program (2017YFA0206804)the Fundamental Research Funds for the Central Universities (buctylkxj01 and XK1802-6)
文摘Glycerol(GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals(mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgxAl1-hydrotalcite(denoted as re-MgxAl1-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid(GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-Mg6Al1-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations(XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Ptd+species at metal-support interface, which accelerates bond cleavage of a-C–H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.
基金This work was financially supported by the National Key R&D Program of China(No.2016YFB0100200)Young Thousand Talents Program,the Open Project Foundation of State Key Laboratory of Chemical Resource Engineering,the China Postdoctoral Science Foundation(No.2017M610018)the National Natural Science Foundation of China(No.51671003),Start-up Funding from Peking University.
文摘Despite various 2H-MoS/carbon hybrid nanostructures have been constructed and committed to improve the performance for sodium-ion batteries(SIBs),they still show the limited cycle stability due to the relatively large volumetric expansion during the charge-discharge process Herein,we report the construction of cobalt-doped few-layered 1T-MoS2 nanosheets embedded in N,S-doped carbon(CMS/NSC)nanobowls derived from metal-organic framework(MOF)precursor via a simple in situ sulfurization process.This unique hierarchical structure enables the uniformly dispersed Co-doped 1T-MoS2 nanosheets intimately couple with the highly conductive carbon nanobowls,thus efficiently preventing the aggregation.In particular,the Co-doping plays a crucial role in maintaining the integrity of structure for MoS2 during cycling tests,confirmed by first-principles calculations.Compared with pristine MoS2,the volume deformation of Co-doped MoS2 can be shrunk by a prominent value of 52%during cycling.Furthermore,the few-layered MoS2 nanosheets with 1T metalic phase endow higher conductivity,and thus can surpass its counterpart 2H semiconducting phase in battery performance.By virtue of the synergistic effect of stable structure,appropriate doping and high conductivity,the resulting CMS/NSC hybrid shows superior rate capability and cycle stability.The capacity of CMS/NSC can still be 235.9 mAh·g^-1 even at 25 A·g^-1,which is 51.3%of the capacity at 0.2 A·g^-1.Moreover,the capacity can still remain 218.6 mAh·g^-1 even over 8,240 cycles at 5 Ag·g^-1 with a low decay of 0.0044%per cycle,one of the best performances among the reportec MoS2-based anode materials for SIBs.
基金National Key Research and Development Program of China(2020YFE0204200,2022YFB4701900)National Natural Science Foundation of China(11988102,12202008)Experiments for Space Exploration Program and the Qian Xuesen Laboratory,China Academy of Space Technology(TKTSPY-2020-03-05).
文摘Instability-induced wrinkle patterns of thin sheets are ubiquitous in nature,which often result in origami-like patterns that provide inspiration for the engineering of origami designs.Inspired by instability-induced origami patterns,we propose a computational origami design method based on the nonlinear analysis of loaded thin sheets and topology optimization.The bar-and-hinge model is employed for the nonlinear structural analysis,added with a displacement perturbation strategy to initiate out-of-plane buckling.Borrowing ideas from topology optimization,a continuous crease indicator is introduced as the design variable to indicate the state of a crease,which is penalized by power functions to establish the mapping relationships between the crease indicator and hinge properties.Minimizing the structural strain energy with a crease length constraint,we are able to evolve a thin sheet into an origami structure with an optimized crease pattern.Two examples with different initial setups are illustrated,demonstrating the effectiveness and feasibility of the method.
基金the National Center for Applied Mathematics Shenzhen(NCAMS),the Shenzhen Key Laboratory of Natural Gas Hydrates(Grant No.ZDSYS20200421111201738)the SUSTech-Qingdao New Energy Technology Research Institute.
文摘Data-driven discovery of partial differential equations(PDEs)has recently made tremendous progress,and many canonical PDEs have been discovered successfully for proof of concept.However,determining the most proper PDE without prior references remains challenging in terms of practical applications.In this work,a physics-informed information criterion(PIC)is proposed to measure the parsimony and precision of the discovered PDE synthetically.The proposed PIC achieves satisfactory robustness to highly noisy and sparse data on 7 canonical PDEs from different physical scenes,which confirms its ability to handle difficult situations.The PIC is also employed to discover unrevealed macroscale governing equations from microscopic simulation data in an actual physical scene.The results show that the discovered macroscale PDE is precise and parsimonious and satisfies underlying symmetries,which facilitates understanding and simulation of the physical process.The proposition of the PIC enables practical applications of PDE discovery in discovering unrevealed governing equations in broader physical scenes.
基金funding support from the National Natural Science Foundation of China (52172182, 21975028, 22011540377, 22005035, U21A20172)。
文摘Perovskite solar cell has gained widespread attention as a promising technology for renewable energy.However, their commercial viability has been hampered by their long-term stability and potential Pb leakage. Herein, we demonstrate a bifunctional passivator of the potassium tartrate(PT) to address both challenges. PT minimizes the Pb leakage in perovskites and also heals cationic vacancy defects, resulting in improved device performance and stability. Benefiting from PT modification, the power conversion efficiency(PCE) is improved to 23.26% and the Pb leakage in unencapsulated films is significantly reduced to 9.79 ppm. Furthermore, the corresponding device exhibits no significant decay in PCE after tracking at the maximum power point(MPP) for 2000 h under illumination(LED source, 100 mW cm^(-2)).
基金supported by the National Natural Science Foundation of China(Grant Nos.11890684,12032001&51590891)the Technology Innovation Leading Program of Shaanxi(Grant No.2022TD-28)Hunan Provincial Natural Science Innovation Research Group Fund(Grant No.2020JJ1005)。
文摘The 6–8 wt%yttria-stabilized zirconia with a tetragonal structure(t’-YSZ)is extensively employed in thermal barrier coatings.The exceptional fracture toughness of t’-YSZ can be attributed to its distinctive ferroelastic toughening mechanism.Microstructure and interface tension play a critical role in ferroelastic variant switching at the micro-and nano-scale.This paper presents an original thermodynamically consistent phase field(PF)theory for analyzing ferroelastic variant switching at the micro-and nano-scale of t’-YSZ.The theory incorporates strain gradient elasticity using higher-order elastic energy and interface tension tensor via geometric nonlinearity to represent biaxial tension resulting from interface energy.Subsequently,a mixed-type formulation is employed to implement the higher-order theory through the finite element method.For an interface in equilibrium,the effects of strain gradient elasticity result in a more uniform distribution of stresses,whereas the presence of interface tension tensor significantly amplifies the stress magnitude at the interface.The introduction of an interface tension tensor increases the maximum value of stress at the interface by a factor of 4 to 10.The nucleation and evolution of variants at a pre-existing crack tip in a mono-phase t’-YSZ have also been studied.The strain gradient elasticity is capable of capturing the size effect of ferroelastic variant switching associated with microstructures in experiments.Specifically,when the grain size approaches that of the specimen,the critical load required for variant switching at the crack tip increases,resulting in greater dissipation of elastic energy during ferroelastic variant switching.Moreover,the interface tension accelerates the evolution of variants.The presented framework exhibits significant potential in modeling ferroelastic variant switching at the micro-and nano-scale.
基金Innovative Research Group of the National Natural Science Foundation of China (NFSC) (No. 51721006)China Postdoctoral Science Foundation (No. 2017M620132)
文摘A novel carbon quantum dots modified potassium titanate nanotubes(CQDs/K2 Ti6 O13)composite photocatalyst was synthesized by hydrothermal treatment combined with calcination.X-ray diffraction(XRD)pattern and transmission electron microscopy(TEM)indicated formation of potassium titanate nanotubes and successful deposition of CQDs onto K2 Ti6 O13.The photocatalytic performance of CQDs/K2 Ti6 O13 composite was evaluated by degradation of amoxicillin(AMX)under the irradiation of visible light and lights with the wavelengths of 365,385,420,450,485,520,595 and 630 nm.The results showed that the photocatalytic activity of CQDs/K2 Ti6 O13 hybrid material was greatly enhanced compared with the neat K2 Ti6 O13 calcined at 300 ℃.The narrowed band gap energy(Eg)and transfer of photo-excited electron by CQDs inhibited the immediate combination of electron-hole pairs,thus promoting photocatalytic activity.Moreover,CQ,Ds/K2 Ti6 O13 exhibited a broad spectrum of photocatalytic ability and it was interesting that the photocatalytic activity decreased with the increase of the irradiation wavelength.Reactive oxygen species(ROS)quenching tests suggested the hole(h^+)and hydroxyl radical(^·OH)played the primary roles in photocatalytic degradation of AMX.Moreover,CQ.Ds/K2 Ti6 O13 showed good reusability for AMX photocatalytic degradation after five successive runs.This study proposed an available method for titanate nanomaterials modification,and the developed novel CQDs/K2 Ti6 O13hyb rid material is p ro mising fo r potential application on antibiotics removal fro m water and wastewater.
基金Project supported by the National Natural Science Foundation of China(Nos.12293000,12293001,11988102,12172006,and 12202011)。
文摘The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relationship between two order vibration modes of the system is verified.The resonance response of this class of bistable structures in the dynamic snap-through mode is investigated,and the four-dimensional(4D)nonlinear modulation equations are derived based on the 1:1 internal resonance relationship by means of the multiple scales method.The Hopf bifurcation and instability interval of the amplitude frequency and force amplitude curves are analyzed.The discussion focuses on investigating the effects of key parameters,e.g.,excitation amplitude,damping coefficient,and detuning parameters,on the resonance responses.The numerical simulations show that the foundation excitation and the degree of coupling between the vibration modes exert a substantial effect on the chaotic dynamics of the system.Furthermore,the significant motions under particular excitation conditions are visualized by bifurcation diagrams,time histories,phase portraits,three-dimensional(3D)phase portraits,and Poincare maps.Finally,the vibration experiment is carried out to study the amplitude frequency responses and bifurcation characteristics for the bistable laminated composite shell,yielding results that are qualitatively consistent with the theoretical results.
基金supported by the National Natural Science Foundation of China(No.42075109)the National Key Research and Development Program of China(No.2018YFC0214001)。
文摘The complex air pollution driven by both Ozone(O_(3))and fine particulate matter(PM2.5)sig nificantly influences the air quality in the Sichuan Basin(SCB).Understanding the O_(3)for mation during autumn and winter is necessary to understand the atmospheric oxidative capacity.Therefore,continuous in-site field observations were carried out during the late summer,early autumn and winter of 2020 in a rural area of Chongqing.The total volatile organic compounds(VOCs)concentration reported by a Proton-Transfer-Reaction Time-of Flight Mass Spectrometry(PTR-ToF-MS)were 13.66±9.75 ppb,5.50±2.64 ppb,and 9.41±5.11 ppb in late summer,early autumn and winter,respectively.The anthropogenic VOCs(AVOCs)and biogenic VOCs(BVOCs)were 8.48±7.92 ppb and 5.18±2.99 ppb in late sum mer,3.31±1.89 ppb and 2.19±0.93 ppb in autumn,and 6.22±3.99 ppb and 3.20±1.27ppb in winter.A zero-dimensional atmospheric box model was employed to investigate the sensitivity of O_(3)-precursors by relative incremental reactivity(RIR).The RIR values of AV OCs,BVOCs,carbon monoxide(CO),and nitrogen oxides(NOx)were 0.31,0.71,0.09,and-0.36 for late summer,0.24,0.59,0.22,and-0.38 for early autumn,and 0.30,0.64,0.33 and-0.70 for winter,and the results showed that the O_(3)formation of sampling area was in the VOC-limited region,and O_(3)was most sensitive to BVOCs(with highest RIR values,>0.6)This study can be helpful in understanding O_(3)formation and interpreting the secondary formation of aerosols in the winter.
基金supported by the National Key Research and Development Program of China(2016YFB0100201)the National Natural Science Foundation of China(51671003)+3 种基金Beijing Natural Science Foundation(JQ18005)BIC-ESAT Projectthe China Postdoctoral Science Foundation(2017M610022)Young Thousand Talented Program.
文摘Highly-branched dendritic Pt-based nanocrystals possess great potential in catalyzing the oxygen reduction reaction(ORR),but encounter performance ceiling due to their poor thermal and electrochemical stability.Here,we present a novel Pt Fe nanodendrites(NDs)branched with two-dimensional(2 D)twinned nanoplates rather than conventional 1 D nanowires,which breaks the ORR performance ceiling of dendritic catalysts by inducing the unique Pt-skin configuration via rationally thermal treatment.By further hybridizing the Pt-skin Pt Fe NDs/C with amino-functionalized ionic liquids(ILs),we achieve an unprecedented mass activity of 3.15 A/mgPtat 0.9 V versus reversible hydrogen electrode(RHE)in the Pt Fe-based ORR electrocatalytic system.They also show excellent electrocatalytic durability for ORR with negligible activity decay and no apparent structural change after 20,000 cycles,in sharp contrast to the nanowires branched Pt Fe NDs counterpart.The remarkable catalytic performance is attributed to a combination of several structural features,including 2 D morphology,twin boundary,partially ordered phase and strong coordination with amino group.This work highlights the significance of stabilizing electrocatalytic structures via morphology tuning,which thus enables further surface and interface modification for performance breakthrough in ORR electrocatalysis.
基金supported by the National Natural Science Foundation of China(Grant Nos.11890684,12032001,and 51590891)the Technology Innovation Leading Program of Shaanxi(Grant No.2022TD-28)the Hunan Provincial Natural Science Innovation Research Group Fund(Grant No.2020JJ1005)。
文摘Failure due to interfacial oxidation is one of the most important factors in the failure of alloy systems at high temperatures.To analyze high-temperature interfacial oxidation in alloys under deformation,we develop a thermodynamically consistent continuum theory of alloy interfacial oxidation process considering diffusion,oxidation,expansion,viscoplasticity,and deformation processes.Balance equations of force,mass,and energy are presented at first,while the coupled constitutive laws and evolution equations are constructed according to energy dissipation inequality.The coupled kinetics reveals a new mechanism whereby deformation affects the oxidation reaction by changing the alloy’s critical oxygen concentration.External tensile loads decrease the critical oxygen concentration and promote oxidation of the alloy.Conversely,external compressive loads increase the critical oxygen concentration and suppress the oxidation of the alloy.Finally,this theory is applied to thermal barrier coatings(TBCs),exhibiting a good consistency with the high-temperature oxidation experiment of TBCs under external loads.The model successfully explains that the experimental phenomenon of external tensile load accelerates the growth of Al_(2)O_(3)-TGO(thermally grown oxides).Besides,external compressive loads slow down the growth of Al_(2)O_(3)-TGO at the interface and lead to internal oxidation of the bond coat.The presented framework has shown great potential for modeling high-temperature interfacial oxidation processes in alloy systems under deformation.
基金financially supported by the National Natural Science Foundation of China(NSFC)(21802003,51672007,11974023)the China Postdoctoral Science Foundation(No.2019M650337)the Science Foundation for High-Level Talents of Wuyi University,China(2018RC50)。
文摘Developing high-efficiency,stable and non-precious electrocatalysts for oxygen reduction reaction(ORR)is highly important for energy conversion and storage.Single atom catalysts(SACs)show good potential in enhancing ORR,however,the specifical control over the coordination surroundings around single metal center to intrinsically modify the electron structure is still a great challenge.Herein,we demonstrate that a 3 D hybrid MOF composed of cobalt doped ZIF-L and ZIF-8,featuring star morphology with six equal branches,can be used as an advanced precursor for making the Co SACs for greatly boosted ORR.The as-synthesized Co_(SA)-N-C exhibits excellent ORR activity with E_(1/2) of 0.891 V in alkaline medium,outperforming the commercial Pt/C by 39 m V.Moreover,the E_(1/2) of Co_(SA)-N-C(0.790 V)is merely 15 m V,less than that of Pt/C(0.805 V)in acid medium,which is among the best in the reported state-of-the-art SACs.DFT calculations demonstrate that the enhanced ORR performance is assigned to the formation of atomically isolated cobalt atom coordinated three N atoms and one C atom,which is easier to decrease the free energy of rate determining step and accelerate the ORR process than that of traditional cobalt atom coordinated four N atoms.In addition,a primary Zn-air battery with Co_(SA)-N-C cathode reveals a maximum power density of 92.2 m W cm^(-2) at 120.0 m A cm^(-2),far higher than that of commercial catalysts(74.2 m W cm^(-2) at 110.0 m A cm^(-2)).
基金financially supported by the National Natural Science Foundation of China(21725301,21932002,21821004,22209129,and 22278367)the National Key R&D Programof China(2021YFA1501100)+2 种基金“Young Talent Support Plan”of Xi’an Jiaotong University(HG6J024)the High-Level Innovation and Entrepreneurship Talent Project of Qinchuangyuan(QCYRCXM-2022-123)support from the Tencent Foundation through the EXPLORER PRIZE.
文摘H_(2) tends to be a crucial medium in the foreseeable future as it is not only a green and renewable energy source for vehicles but also a fundamental feedstock for the chemical industry.For instance,selective hydrogenation,one of the catalytic processes used to produce fine compounds,is of vital importance because it enables the selective and efficient conversionof a variety of functional groups under mild reaction conditions.Catalytic hydrogenation of liquid organic hydrogen carriers(LOHCs;eg,methylbenzene)is a safe and economic approach for H_(2) storage.
基金supported by the National Natural Science Foundation of China (41421064,21190051, 41121004)the China Postdoc Science Foundation (154248)
文摘Air pollution is known to be a major risk factor for cardiopulmonary disease, but this is unclear for cardiometabolic disease (e.g.diabetes). This is of considerable public health importance, given the nationwide epidemic of diabetes, accompanied by severe air pollution, in China. The evidence so far remained inadequate to answer questions of whether individuals with cardiometabolic dysfunctions are susceptible to air pollution and whether air pollution exacerbates diabetes development via certain biological pathways. In this manuscript, we summarize the results and limitations of studies exploring these two topics and elaborate our design of a prospective panel study (SCOPE) as a solution. We assessed and compared the health effect of air pollution among pre-diabetic individuals and matched healthy controls through four repeated clinical visits over 1 year. Comprehensive evaluation was made to both health endpoints and exposure. The primary biomarkers were assessed to reveal the impact on multiple biological pathways, including glycolipid metabolism and insulin resistance, endothelial function, and inflammation. Detailed chemical and size fractional components of particulate matter were measured in this study, along with the application of personal monitors.The work should increase our understanding of how air pollution affects individuals with cardiometabolic dysfunction and the underlying mechanisms.
基金supported by the National Natural Science Foundation of China (51125001,51172005)the NSFCRGC Joint Research Scheme (51361165201)the Start-up Foundation of High-level Talents in Chongqing Technology and Business University (1856008)
文摘The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.
基金This work was supported by the National Natural Science Fund of China(grant nos.21872072 and 22025203)the Frontiers Science Center for New Organic Matter,Nankai University(grant no.63181206)Haihe Laboratory of Sustainable Chemical Transformations,Tianjin.
文摘Alkene hydroformylation is an extremely important industry process currently accomplished via homogeneous catalysis.Heterogeneous hydroformylation is being avidly pursued as a more economical and sustainable process.Herein,we report the construction of zeolite-encaged rhodium catalyst for efficient hydroformylation.Through a facile in situ hydrothermal strategy,isolated Rh^(δ+)(δ=2.5)can be encaged in faujasite and efficiently stabilized via interaction with framework oxygen atoms,producing a Rh@Y model catalyst with well-defined rhodium sites and coordination environment.Rh@Y exhibits high catalytic activity,perfect chemoselectivity,and recyclability in 1-hexene hydroformylation under mild reaction conditions,making it a robust heterogeneous catalyst for potential applications.A state-of-the-art turnover frequency value of 6567 molC=C/molRh/h for Rh@Y can be achieved in 1-hexene hydroformylation at 393 K,outperforming all heterogeneous catalysts and most homogeneous catalysts under comparable conditions.With the well-defined structure of Rh@Y,the detailed mechanism of alkene hydroformylation can be interpreted via theoretical calculations,and the advantages of heterogeneous hydroformylation are well explained.This work provides a promising solution toward efficient heterogeneous noble metal catalysis by encaging stable isolated ions in a zeolite matrix.
基金the National Natural Science Foundation of China(Nos.61725305,U1909206,61421004,61633017)the Pre-Research Fund of Equipment of China(No.61402070304)the Beijing Natural Science Foundation(No.4192060)the Youth Innovation Promotion Association CAS(No.2019138)。
文摘This paper presents an innovative design for a biomimetic whale shark-like underwater glider aiming at the combination of high maneuverability and long duration.As a hybrid of the underwater glider and the robotic fish,its pectoral fins and tail can serve as not only the external control surfaces for attitude regulation during gliding but also the propellers for agile fish-like swimming mode.To verify the gliding capability of the whale shark-like glider and prepare for future dynamic analysis,the hydrodynamic coefficients,including drag,lift,sliding force,and corresponding moments are estimated through computational fluid dynamics method.In addition,the hydrodynamic analyses of the proposed glider and an equivalent conventional glider during steady gliding motion are executed for comparison.Extended experiments are performed to verify the downward gliding performance.The results reveal that the whale shark-like glider has less drag as well as higher lift-to-drag ratio and a markable gliding capability in practice.It may offer important inspiration for improving the gliding efficiency and performance of an underwater glider in biomimetic shape design.
