Crack initiation mechanism of dwell fatigue has always been a key problem in rationalizing the dwell effect,and it is not completely understood yet.This study conducted stress-controlled low-cycle fatigue and dwell fa...Crack initiation mechanism of dwell fatigue has always been a key problem in rationalizing the dwell effect,and it is not completely understood yet.This study conducted stress-controlled low-cycle fatigue and dwell fatigue tests on Ti-6Al-3Nb-2Zr-1Mo alloy with bimodal microstructure to reveal its microstructural characteristics and crack initiation mechanisms.The study demonstrated that the faceted primaryα nodules located near the specimen surface acted as crack initiation sites during both fatigue and dwell fatigue tests.Slip trace analysis revealed that faceted cracking occurred at(0001)basal plane with the maximum Schmid factor value through a special cracking mode referred to as(0001)twist boundary cracking.Innovative criteria of parameters C1 and C2 were proposed based on experimental observation and molecular dynamics simulations,which well identify candidates for(0001)twist boundary crack nucleation.It demonstrated that grain pairs combining a moderately high Schmid factor for basal slip and a well-orientated Burgers vector in the out-of-surface plane was the preferable location for surface(0001)twist-boundary crack initiation,and grain pairs combining a high Schmid factor for basal slip and a high normal stress on basal plane are perfect candidates for subsurface cracking.Based on this,phenomeno-logical models are proposed to explain the surface(0001)twist-boundary cracking mechanism from the perspective of surface extrusion-intrusion-induced micro-notches.展开更多
A numerical simulation based on a regularized phase field model is developed to describe faceted dendrite growth morphology. The effects of mesh grid, anisotropy, supersaturation and fold symmetry on dendrite growth m...A numerical simulation based on a regularized phase field model is developed to describe faceted dendrite growth morphology. The effects of mesh grid, anisotropy, supersaturation and fold symmetry on dendrite growth morphology were investigated, respectively. These results indicate that the nucleus grows into a hexagonal symmetry faceted dendrite. When the mesh grid is above 640×640, the size has no much effect on the shape. With the increase in the anisotropy value, the tip velocities of faceted dendrite increase and reach a balance value, and then decrease gradually. With the increase in the supersaturation value, crystal evolves from circle to the developed faceted dendrite morphology. Based on the Wulff theory and faceted symmetry morphology diagram, the proposed model was proved to be effective, and it can be generalized to arbitrary crystal symmetries.展开更多
Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a cry...Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a crystal nucleus grows into a symmetric dendrite in a free flow and into an asymmetry dendrite in a forced flow. As the forced flow velocity is increased, both of the promoting effect on the upstream arm and the inhibiting effects on the downstream and perpendicular arms are intensified, and the perpendicular arm tilts to the upstream direction. With increasing the anisotropy value to 0.14, all of the dendrite arms tip velocities are gradually stabilized and finally reach their relative saturation values. In addition, the effects of an undercooling parameter and a forced compound flow on the faceted dendrite growth were also investigated.展开更多
Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-ind...Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-index faceted iron oxide(Fe_(2)O_(3))nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts,effectively improving the electrochemical performance of Li-S batteries.The theoretical and experimental results all indicate that high-index Fe_(2)O_(3)crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li_(2)S.The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g^(-1)at 0.1 C and excellent cycling performance with a low capacity fading of 0.025%per cycle during 1600 cycles at 2 C.Even with a high sulfur loading of 9.41 mg cm^(-2),a remarkable areal capacity of 7.61 mAh cm^(-2)was maintained after 85 cycles.This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering,deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry,affording a novel perspective for the design of advanced sulfur electrodes.展开更多
Aiming to increase the efficiency of gem design and manufacturing, a new method in computer-aided-design (CAD) of convex faceted gem cuts (CFGC) based on Half-edge data structure (HDS), including the algorithms for th...Aiming to increase the efficiency of gem design and manufacturing, a new method in computer-aided-design (CAD) of convex faceted gem cuts (CFGC) based on Half-edge data structure (HDS), including the algorithms for the implementation is presented in this work. By using object-oriented methods, geometrical elements of CFGC are classified and responding geometrical feature classes are established. Each class is implemented and embedded based on the gem process. Matrix arithmetic and analytical geometry are used to derive the affine transformation and the cutting algorithm. Based on the demand for a diversity of gem cuts, CAD functions both for free-style faceted cuts and parametric designs of typical cuts and visualization and human-computer interactions of the CAD system including two-dimensional and three-dimensional interactions have been realized which enhances the flexibility and universality of the CAD system. Furthermore, data in this CAD system can also be used directly by the gem CAM module, which will promote the gem CAD/CAM integration.展开更多
A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys...A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.展开更多
Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidatio...Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidation of small organic molecule(such as formic acid,methanol,and ethanol),oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),as well as the oxygen evolution reaction(OER).However,the practical applications of nanocrystals enclosed by HIFs still face many limitations in preparations of advanced electrocatalysts,including preparation strategy,limited life-time and stability.The development of advanced electrocatalysts enclosed with HIFs is crucial for solving these problems if the large-scale application of them is to be realized.Herein,we firstly detailedly demonstrate the identification methods of nanocrystals enclosed by HIFs,and then preparation strategies are elaborated in detail in this review.Current advanced nanocrystals enclosed by HIFs in electrocatalytic application are also summarized and we present representative achievements to further reveal the relationship of excellent electrocatalytic performance and nanocrystals with HIFs.Finally,we predict the remaining challenges and present our perspectives with regards of design strategies of improving electrocatalytic performance of Ptbased catalysts in the future.展开更多
Noble metallic nanocrystals are used in a wide variety of applications,such as catalysis,batteries,and bio-and chemical sensors.Most of the previous studies focus on the preparation of thermodynamically stable nanocry...Noble metallic nanocrystals are used in a wide variety of applications,such as catalysis,batteries,and bio-and chemical sensors.Most of the previous studies focus on the preparation of thermodynamically stable nanocrystals enclosed by low-index facets and discuss their corresponding catalytic properties.Recently,researchers have found that the nanocrystals with high-index facets(HIFs)are of more interest for electrocatalysis.Herein,we review recent key progress in the synthesis of noble metallic nanoparticles enclosed with HIFs and their facetdependent electrocatalytic behaviors.First,we introduce the concept of HIFs,and establish the correlation between their surface structure and catalytic activity.Then,we discuss various synthetic approaches for controlling the shapes and composition of the nanocrystals enclosed by HIFs.Afterwards,we showcase the enhanced electrocatalytic performance realized by HIF-based nanostructures.Finally,we provide guidance on how to improve the electrocatalysis by engineering HIFs on noble metallic nanocrystals.展开更多
Rationally designing the surface structure with desirable facets has been demonstrated as an effective approach to regulating the catalytic activity and anti-CO poisoning capability of Pd-based catalysts for methanol ...Rationally designing the surface structure with desirable facets has been demonstrated as an effective approach to regulating the catalytic activity and anti-CO poisoning capability of Pd-based catalysts for methanol oxidation reaction(MOR).However,the synthesis of Pd-based alloy with high-index facets to further improve Pd utilization remains a fundamental challenge.Herein,a simple solvothermal method was proposed to synthesize the jagged PtPdTe nanotubes(NTs)with abundant zigzag atomic steps on their surfaces.These zigzag facets are more favorable for both the adsorption of OH and the desorption of CO during MOR.Compared with the smooth PtPdTe NTs,the jagged PtPdTe NTs exhibit an enhanced mass activity of 4201.6 mA mg^(-1) and specific activity of 4.12 mA cm^(-2),which are 6.7 and 3.2 times higher than those of commercial Pd/C catalysts,respectively.This work not only advances the understanding of surface engineering in catalysis but also extends the novel design of highly efficient and durable Pd-based catalysts for fuel cells.展开更多
Micro-sized anatase TiO_(2) displays inferior capacity as cathode material for magnesium ion batteries because of the higher diffusion energy barrier of Mg^(2+)in anatase TiO_(2) lattice.Herein,we report that nanosize...Micro-sized anatase TiO_(2) displays inferior capacity as cathode material for magnesium ion batteries because of the higher diffusion energy barrier of Mg^(2+)in anatase TiO_(2) lattice.Herein,we report that nanosized anatase TiO_(2) exposed(001)facet doubles the capacity compared to the micro-sized sample ascribed to the interfacial Mg^(2+)ion storage.First-principles calculations reveal that the diffusion energy barrier of Mg^(2+)on the(001)facet is significantly lower than those in the bulk phase and on(100)facet,and the adsorption energy of Mg^(2+)on the(001)facet is also considerably lower than that on(100)facet,which guarantees superior interfacial Mg^(2+)storage of(001)facet.Moreover,anatase TiO_(2) exposed(001)facet displays a significantly higher capacity of 312.9 mAh g^(−1) in Mg-Li dual-salt electrolyte compared to 234.3 mAh g^(−1) in Li salt electrolyte.The adsorption energies of Mg^(2+)on(001)facet are much lower than the adsorption energies of Li+on(001)facet,implying that the Mg^(2+)ion interfacial storage is more favorable.These results highlight that controlling the crystal facet of the nanocrystals effectively enhances the interfacial storage of multivalent ions.This work offers valuable guidance for the rational design of high-capacity storage systems.展开更多
The facet-dependent photocatalytic performance of TiO_2 nanocrystals has been extensively investigated due to their promising applications in renewable energy and environmental fields. However, the intrinsic distincti...The facet-dependent photocatalytic performance of TiO_2 nanocrystals has been extensively investigated due to their promising applications in renewable energy and environmental fields. However, the intrinsic distinction in the photocatalytic oxidation activities between the {001}and {101} facets of anatase TiO_2 nanocrystals is still unclear and under debate. In this work, a simple photoelectrochemical method was employed to meaningfully quantify the intrinsic photocatalytic activities of {001} and{101} faceted TiO_2 nanocrystal photoanodes. The effective surface areas of photoanodes with different facets were measured based on the monolayer adsorption of phthalic acid on TiO_2 photoanode surface by an ex situ photoelectrochemical method, which were used to normalize the photocurrents obtained from different faceted photoanodes for meaningful comparison of their photocatalytic activities. The results demonstrated that the {001} facets of anatase TiO_2 nanocrystals exhibited much better photocatalytic activity than that of {101} facets of anatase TiO_2 nanocrystals toward photocatalytic oxidation of water and organic compounds with different functional groups(e.g.,–OH, –CHO, –COOH). Furthermore, the instantaneous kinetic constants of photocatalytic oxidation of pre-adsorbates on {001} faceted anatase TiO_2 photoanode are obviously greater than those obtained at {101} faceted anatase TiO_2 photoanode, further verifying the higher photocatalytic activity of {001} facets of anatase TiO_2.This work provided a facile photoelectrochemical method to quantitatively determine the photocatalytic oxidation activity of specific exposed crystal facets of a photocatalyst, which would be helpful to uncover and meaningfully compare the intrinsic photocatalytic activities of different exposed crystal facets of a photocatalyst.展开更多
Metalenses can integrate the functionalities of multiple optical components thanks to the unprecedented capability of optical metasurfaces in light control.With the rapid development of optical metasurfaces,metalenses...Metalenses can integrate the functionalities of multiple optical components thanks to the unprecedented capability of optical metasurfaces in light control.With the rapid development of optical metasurfaces,metalenses continue to evolve.Polarization and color play a very important role in understanding optics and serve as valuable tools for gaining insights into our world.Benefiting from the design flexibility of metasurfaces,we propose and experimentally demonstrate a super metalens that can realize multifaceted control of focal points along any 3D curved trajectory.The wavelengths and polarization states of all focal points are engineered in a desirable manner.The super metalens can simultaneously realize customized 3D positioning,polarization states,and wavelengths of focal points,which are experimentally demonstrated with incident wavelengths ranging from 501 to 700 nm.We further showcase the application of the developed super metalenses in 3D optical distance measurement.The compact nature of metasurfaces and unique properties of the proposed super metalenses hold promise to dramatically miniaturize and simplify the optical architecture for applications in optical metrology,imaging,detection,and security.展开更多
ASEAN’s major power balancing strategy refers to the balancing strategy adopted by ASEAN and its member states to seek national and regional security and development by maintaining multi-faceted friendship and impart...ASEAN’s major power balancing strategy refers to the balancing strategy adopted by ASEAN and its member states to seek national and regional security and development by maintaining multi-faceted friendship and impartiality with surrounding major powers.The evolution of this strategy is a process of dynamic adjustment,with ASEAN and its members being the implementing subjects,major powers the objects.展开更多
Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds.This study provides a comprehensive analysis of the adsorption and photo-oxidation of surface-adsorbed...Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds.This study provides a comprehensive analysis of the adsorption and photo-oxidation of surface-adsorbed acetone on three SrTiO_(3)morphologies:cubes(for which exclusively{100}facets are exposed),{110}-truncated cubes,and{100}-truncated rhombic dodecahedrons,respectively,all prepared by hydrothermal synthesis.In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy shows that cubic crystals contain a high quantity of surface-OH groups,enabling significant quantities of adsorbed acetone in the form ofη^(1)-enolate when exposed to gas phase acetone.Contrary,{110}facets exhibit fewer surface-OH groups,resulting in relatively small quantities of adsorbedη^(1)-acetone,without observable quantities of enolate.Interestingly,acetate and formate signatures appear in the spectra of cubic,surfaceη^(1)-enolate containing,SrTiO_(3)upon illumination,while besides acetate and formate,the formation of(surface)formaldehyde was observed on truncated cubes,and dodecahedrons,by conversion of adsorbedη^(1)-acetone.Time-Resolved Photoluminescence studies demonstrate that the lifetimes of photogenerated charge carriers vary with crystal morphology.The shortest carrier lifetime(τ_(1)=33±0.1 ps)was observed in{110}-truncated cube SrTiO_(3),likely due to a relatively strong built-in electric field promoting electron transport to{100}facets and hole transport to{110}facets.The second lifetime(τ_(2)=259±1 ps)was also the shortest for this morphology,possibly due to a higher amount of surface trap states.Our results demonstrate that SrTiO_(3)crystal morphology can be tuned to optimize performance in photocatalytic oxidation.展开更多
Iron carbodiimide(Fe NCN)anode demonstrates significant potential for rapid sodium-ion storage owing to its high reaction activity and near-metallic conductivity.However,further development of Fe NCN is hindered by in...Iron carbodiimide(Fe NCN)anode demonstrates significant potential for rapid sodium-ion storage owing to its high reaction activity and near-metallic conductivity.However,further development of Fe NCN is hindered by inherent structural instability and ambiguous structure-kinetics correlation.In this study,Fe NCN crystallites with selectively exposed(002)and{010}facets were precisely engineered and synthesized.Notably,the sodium storage kinetics and electrochemical performance of Fe NCN exhibit facet-dependent variations.Polyhedral-Fe NCN(P-Fe NCN)dominated by{010}facets exhibited a pseudocapacitance-driven storage mechanism and delivered exceptional rate capability(372 m Ah/g at5 A/g)and long cyclability(95.8%capacity retention after 300 cycles at 0.5 A/g).In contrast,sheet-like Fe NCN(S-Fe NCN)with predominant(002)facet exposure displayed diffusion-limited kinetics due to sluggish ion diffusion rate.Crucially,time-resolved operando XRD analysis and DFT simulation bridge this performance gap to mechanistic origins:Fe NCN as an intercalation-conversion type anode,the solid-state diffusion is the rate-determining step during charge/discharge process.Active{010}facets possess numerous broad hexagonal tunnels,coupled with a low diffusion barrier of 0.168 e V along{010}directions.This unique architectural configuration enables rapid sodium-ion transport,thereby shifting the diffusioncontrolled kinetics to intercalation-pseudocapacitive behavior.This discovery establishes active facet exposure as a storage kinetic switch,offering a generalized paradigm for optimizing the rate performance and stability of sodium-ion batteries.展开更多
Crystalized CeO_(2)structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’size and ability to absorb light.However,the controllable fabrication of well-def...Crystalized CeO_(2)structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’size and ability to absorb light.However,the controllable fabrication of well-defined hierarchical structures of CeO_(2)with high reactive facets is significant and challenging.Herein,a series of CeO_(2)supports including hierarchical flower-like(F-CeO_(2)),ball-like(B-CeO_(2)),cube-like(C-CeO_(2)),and rod-like CeO_(2)(R-CeO_(2))supports were prepared by hydrothermal method(BCeO_(2),R-CeO_(2)and C-CeO_(2))or ice-bath method(F-CeO_(2))respectively.V atoms were selected as the active atoms and loaded on these supports.Their structure-activity relationship in photo-assisted thermal propane dehydrogenation(PTPDH)was investigated systematically.The samples were characterized by Xray diffraction,scanning electron microscopy,transmission electron microscopy,N2 adsorption-desorption isotherms,and Fourier transform infrared spectrum.Results show that R-CeO_(2)support exhibits the biggest surface area thus achieving the best dispersion of VOx species.UV-vis spectrum and photoluminescence spectrum indicate that V/F-CeO_(2)has the best light adsorption property and V/R-CeO_(2)has the best carrier migration capacity.The activity tests demonstrate that the V/R-CeO_(2)has the largest net growth rate and the V/F-CeO_(2)has the biggest relative growth ratio.Furthermore,the non-thermal effect was confirmed by the kinetic method,which lowers the propane reaction orders,selectively promoting the first C-H bond activation.The light radiation TPSR experiment confirmed this point.DFT calculations show a good linear relationship between the energy barrier and the exchanged electron number.It inspires the design of high-reactive facets for boosting the intrinsic activity of the C-H bond in photoassisted thermal chemical processes.展开更多
Lithium-sulfur(Li-S)batteries are promising for high-energy-density storage,but their performance is limited by sluggish lithium polysulfide(LiPS)conversion kinetics.Here,we tackle this issue by synthesizing ultrafine...Lithium-sulfur(Li-S)batteries are promising for high-energy-density storage,but their performance is limited by sluggish lithium polysulfide(LiPS)conversion kinetics.Here,we tackle this issue by synthesizing ultrafine truncated octahedral TiO_(2) nanocrystals(P-O_(v)-TiO_(2)),featuring specific{101}facets and dual defects—phosphorus doping and oxygen vacancies.Acting as an efficient electrocatalyst in the separator,P-O_(v)-TiO_(2) exhibits superior catalytic properties,where oxygen vacancies modulate the electronic structure,enhancing electron enrichment and charge transfer;phosphorus doping tailors the d-band center of the catalyst,strengthening Ti-S interactions between the{101}facets and LiPSs.As a result,Li-S coin cells modified with P-O_(v)-TiO_(2) achieve a high specific capacity of 895 mAh g^(−1) at 5 C and exhibit a minimal decay rate of 0.14%per cycle over 200 cycles.Furthermore,Li-S pouch cells deliver a high capacity of 1004 mAh g^(−1) at 0.1 C under lean electrolyte conditions.This study elucidates the mechanisms of charge states on specific crystal planes and deepens our understanding of dual-defect engineering in Li-S electrochemistry,offering a promising approach for developing efficient and cost-effective catalysts for Li-S battery applications.展开更多
F-B co-doped TiO_(2)nanosheets with exposed anatase(001)facets were synthesized via a one-pot solvothermal method,and their photocatalytic hydrogen evolution performance was investigated.Characterization results confi...F-B co-doped TiO_(2)nanosheets with exposed anatase(001)facets were synthesized via a one-pot solvothermal method,and their photocatalytic hydrogen evolution performance was investigated.Characterization results confirm that this method effectively promotes the growth of the highly active anatase(001)facets and enhances visible and infrared light absorption while inducing oxygen vacancies.Under optimal conditions,the hydrogen evolution reaches 20.57μmol after 10 h of ultraviolet-visible(UV-Vis)light irradiation,exceeding the commercial TiO_(2)nanoparticles Degussa P25 by more than 10 times.These findings highlight the potential of F-B co-doped TiO_(2)nanosheets for efficient photocatalysis.展开更多
The facets effect on the catalytic properties of inorganic compounds and metal-organic frameworks(MOFs)has been widely demonstrated,but the intrinsic facets effect free of interference of capping agents has not been d...The facets effect on the catalytic properties of inorganic compounds and metal-organic frameworks(MOFs)has been widely demonstrated,but the intrinsic facets effect free of interference of capping agents has not been discussed.Here we give a proof-of-concept illustration on the intrinsic facets effect by employing the popularly investigated NH2-MIL-125(Ti)MOFs with{001},{111}and{100}facets controllably exposed as model photocatalysts,which were synthesized via a simple supersaturation strategy free of any capping agents.Compared to conventional synthetic routes with capping agents employed,the NH2-MIL-125(Ti)MOFs obtained in this work exhibit remarkably different physical and chemical properties such as surface wettability,charge separation as well as trend of facets effect on photocatalytic water splitting performance.The main reason has been unraveled to originate from unavoidable residue/influence of capping agents during the conventional facets-controlled synthetic routes leading to changed local surface structural environment as well as distinct charge separation property.Our results demonstrate the importance and feasibility of facets-controllable synthesis free of capping agents in getting insight into the intrinsic facets effect of MOFs-related materials.展开更多
Nanostructured ceria has attracted much attention in the field of redox catalysts due to the numerous active sites with excellent redox ability.Based on the acidic medium etching strategy,we constructed the strong bin...Nanostructured ceria has attracted much attention in the field of redox catalysts due to the numerous active sites with excellent redox ability.Based on the acidic medium etching strategy,we constructed the strong binding centers(hydroxyl sites and strong acid sites)on the surfaces of nanostructured ceria,which regulate the adsorption process of KA-Oil(the mixture of cyclohexanol and cyclohexanone)and to promote high KA-Oil selectivity in cyclohexane oxidation.The three CeO_(2)(nanocube,nanorod and nanopolyhedron)with different exposed crystal planes were treated by acid etching to change the surface sites and catalytic properties.The transition behavior of surface sites during etching was revealed,abundant strong binding centers were proved to be constructed successfully.And especially for the nanorod treated by acid(Acid@CeO_(2)-NR)with the strongest response for sulfuric acid etching,the strong adsorption of cyclohexanone by strong binding centers was confirmed based on the in-situ DRIFTs.The sulfuric acid etching strategy to enhance the selective oxidation of cyclohexane based on the construction of strong binding centers was proved to be feasible and effective,Acid@CeO_(2)-NR with strongest etching response achieved the dramatic promotion of KA-Oil selectivity from 64.1%to 92.3%.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52074231,52274396 and 52001258)the Chongqing Natural Science Foundation(No.cstc2020jcyj-msxmX1056).
文摘Crack initiation mechanism of dwell fatigue has always been a key problem in rationalizing the dwell effect,and it is not completely understood yet.This study conducted stress-controlled low-cycle fatigue and dwell fatigue tests on Ti-6Al-3Nb-2Zr-1Mo alloy with bimodal microstructure to reveal its microstructural characteristics and crack initiation mechanisms.The study demonstrated that the faceted primaryα nodules located near the specimen surface acted as crack initiation sites during both fatigue and dwell fatigue tests.Slip trace analysis revealed that faceted cracking occurred at(0001)basal plane with the maximum Schmid factor value through a special cracking mode referred to as(0001)twist boundary cracking.Innovative criteria of parameters C1 and C2 were proposed based on experimental observation and molecular dynamics simulations,which well identify candidates for(0001)twist boundary crack nucleation.It demonstrated that grain pairs combining a moderately high Schmid factor for basal slip and a well-orientated Burgers vector in the out-of-surface plane was the preferable location for surface(0001)twist-boundary crack initiation,and grain pairs combining a high Schmid factor for basal slip and a high normal stress on basal plane are perfect candidates for subsurface cracking.Based on this,phenomeno-logical models are proposed to explain the surface(0001)twist-boundary cracking mechanism from the perspective of surface extrusion-intrusion-induced micro-notches.
基金Projects(11102164,11304243)supported by the National Natural Science Foundation of ChinaProject(2014JQ1039)supported by the Natural Science Foundation of Shannxi Province,China+1 种基金Project(3102016ZY027)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(13GH014602)supported by the Program of New Staff and Research Area Project of NWPU,China
文摘A numerical simulation based on a regularized phase field model is developed to describe faceted dendrite growth morphology. The effects of mesh grid, anisotropy, supersaturation and fold symmetry on dendrite growth morphology were investigated, respectively. These results indicate that the nucleus grows into a hexagonal symmetry faceted dendrite. When the mesh grid is above 640×640, the size has no much effect on the shape. With the increase in the anisotropy value, the tip velocities of faceted dendrite increase and reach a balance value, and then decrease gradually. With the increase in the supersaturation value, crystal evolves from circle to the developed faceted dendrite morphology. Based on the Wulff theory and faceted symmetry morphology diagram, the proposed model was proved to be effective, and it can be generalized to arbitrary crystal symmetries.
基金Project(11102164)supported by the National Natural Science Foundation of ChinaProject(G9KY101502)supported by NPU Foundation for Fundamental Research,China
文摘Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a crystal nucleus grows into a symmetric dendrite in a free flow and into an asymmetry dendrite in a forced flow. As the forced flow velocity is increased, both of the promoting effect on the upstream arm and the inhibiting effects on the downstream and perpendicular arms are intensified, and the perpendicular arm tilts to the upstream direction. With increasing the anisotropy value to 0.14, all of the dendrite arms tip velocities are gradually stabilized and finally reach their relative saturation values. In addition, the effects of an undercooling parameter and a forced compound flow on the faceted dendrite growth were also investigated.
基金This work was supported by the National Natural Science Foundation of China(No.22078078)the Natural Science Foundation of Heilongjiang Province(No.LH2020B008)the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.2019DX13).
文摘Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-index faceted iron oxide(Fe_(2)O_(3))nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts,effectively improving the electrochemical performance of Li-S batteries.The theoretical and experimental results all indicate that high-index Fe_(2)O_(3)crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li_(2)S.The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g^(-1)at 0.1 C and excellent cycling performance with a low capacity fading of 0.025%per cycle during 1600 cycles at 2 C.Even with a high sulfur loading of 9.41 mg cm^(-2),a remarkable areal capacity of 7.61 mAh cm^(-2)was maintained after 85 cycles.This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering,deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry,affording a novel perspective for the design of advanced sulfur electrodes.
基金Supported by the National Natural Science Foundation of China(21576240)Experimental Technology Research Program of China University of Geosciences(Key Program)(SJ-201422)
文摘Aiming to increase the efficiency of gem design and manufacturing, a new method in computer-aided-design (CAD) of convex faceted gem cuts (CFGC) based on Half-edge data structure (HDS), including the algorithms for the implementation is presented in this work. By using object-oriented methods, geometrical elements of CFGC are classified and responding geometrical feature classes are established. Each class is implemented and embedded based on the gem process. Matrix arithmetic and analytical geometry are used to derive the affine transformation and the cutting algorithm. Based on the demand for a diversity of gem cuts, CAD functions both for free-style faceted cuts and parametric designs of typical cuts and visualization and human-computer interactions of the CAD system including two-dimensional and three-dimensional interactions have been realized which enhances the flexibility and universality of the CAD system. Furthermore, data in this CAD system can also be used directly by the gem CAM module, which will promote the gem CAD/CAM integration.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2001800)the National Natural Science Foundation of China(Grant No.21978298)+2 种基金the Natural Science Foundation of Shaanxi Province in China(Grant No.2020JM-111)Applied Basic Research Key Project of Yunnan,China(Grant No.202002AB080001-1)Henan Youth Talent Promotion Project.China(Grant No.2020HYTP019)。
文摘A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.
基金financially supported by the National Natural Science Foundation of China(No.22008135)the China Postdoctoral Science Foundation(No.2020M670345)。
文摘Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidation of small organic molecule(such as formic acid,methanol,and ethanol),oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),as well as the oxygen evolution reaction(OER).However,the practical applications of nanocrystals enclosed by HIFs still face many limitations in preparations of advanced electrocatalysts,including preparation strategy,limited life-time and stability.The development of advanced electrocatalysts enclosed with HIFs is crucial for solving these problems if the large-scale application of them is to be realized.Herein,we firstly detailedly demonstrate the identification methods of nanocrystals enclosed by HIFs,and then preparation strategies are elaborated in detail in this review.Current advanced nanocrystals enclosed by HIFs in electrocatalytic application are also summarized and we present representative achievements to further reveal the relationship of excellent electrocatalytic performance and nanocrystals with HIFs.Finally,we predict the remaining challenges and present our perspectives with regards of design strategies of improving electrocatalytic performance of Ptbased catalysts in the future.
基金This work was financially supported by the Beijing Natural Science Foundation(JQ18005)the National Natural Science Foundation of China(NSFC)(No.51671003)+2 种基金National Basic Research Program of China(No.2016YFB0100201)the China Postdoctoral Science Foundation(No.2017M620518)Open Project Foundation of State Key Laboratory of Chemical Resource Engineering,the start-up supports from Peking University and Young Thousand Talented Program.
文摘Noble metallic nanocrystals are used in a wide variety of applications,such as catalysis,batteries,and bio-and chemical sensors.Most of the previous studies focus on the preparation of thermodynamically stable nanocrystals enclosed by low-index facets and discuss their corresponding catalytic properties.Recently,researchers have found that the nanocrystals with high-index facets(HIFs)are of more interest for electrocatalysis.Herein,we review recent key progress in the synthesis of noble metallic nanoparticles enclosed with HIFs and their facetdependent electrocatalytic behaviors.First,we introduce the concept of HIFs,and establish the correlation between their surface structure and catalytic activity.Then,we discuss various synthetic approaches for controlling the shapes and composition of the nanocrystals enclosed by HIFs.Afterwards,we showcase the enhanced electrocatalytic performance realized by HIF-based nanostructures.Finally,we provide guidance on how to improve the electrocatalysis by engineering HIFs on noble metallic nanocrystals.
基金supported by the National Natural Science Foundation of China(22275178)the Fundamental Research Funds for the Central Universities(JUSRP123013,JUSRP123015)。
文摘Rationally designing the surface structure with desirable facets has been demonstrated as an effective approach to regulating the catalytic activity and anti-CO poisoning capability of Pd-based catalysts for methanol oxidation reaction(MOR).However,the synthesis of Pd-based alloy with high-index facets to further improve Pd utilization remains a fundamental challenge.Herein,a simple solvothermal method was proposed to synthesize the jagged PtPdTe nanotubes(NTs)with abundant zigzag atomic steps on their surfaces.These zigzag facets are more favorable for both the adsorption of OH and the desorption of CO during MOR.Compared with the smooth PtPdTe NTs,the jagged PtPdTe NTs exhibit an enhanced mass activity of 4201.6 mA mg^(-1) and specific activity of 4.12 mA cm^(-2),which are 6.7 and 3.2 times higher than those of commercial Pd/C catalysts,respectively.This work not only advances the understanding of surface engineering in catalysis but also extends the novel design of highly efficient and durable Pd-based catalysts for fuel cells.
基金supported by the National Key R&D Program of China(No.2023YFB3809500)the Fundamental Research Funds for the Central Universities(No.2024CDJXY003)+1 种基金the Venture&Innovation Support Program for Chongqing Overseas Returnees(cx2023087)The Chongqing Technology Innovation and Application Development Project(No.2024TIAD-KPX0003).
文摘Micro-sized anatase TiO_(2) displays inferior capacity as cathode material for magnesium ion batteries because of the higher diffusion energy barrier of Mg^(2+)in anatase TiO_(2) lattice.Herein,we report that nanosized anatase TiO_(2) exposed(001)facet doubles the capacity compared to the micro-sized sample ascribed to the interfacial Mg^(2+)ion storage.First-principles calculations reveal that the diffusion energy barrier of Mg^(2+)on the(001)facet is significantly lower than those in the bulk phase and on(100)facet,and the adsorption energy of Mg^(2+)on the(001)facet is also considerably lower than that on(100)facet,which guarantees superior interfacial Mg^(2+)storage of(001)facet.Moreover,anatase TiO_(2) exposed(001)facet displays a significantly higher capacity of 312.9 mAh g^(−1) in Mg-Li dual-salt electrolyte compared to 234.3 mAh g^(−1) in Li salt electrolyte.The adsorption energies of Mg^(2+)on(001)facet are much lower than the adsorption energies of Li+on(001)facet,implying that the Mg^(2+)ion interfacial storage is more favorable.These results highlight that controlling the crystal facet of the nanocrystals effectively enhances the interfacial storage of multivalent ions.This work offers valuable guidance for the rational design of high-capacity storage systems.
基金supported by the National Natural Science Foundation of China (51372248, 51432009 and 51272255)the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences, Chinathe CAS Pioneer Hundred Talents Program
文摘The facet-dependent photocatalytic performance of TiO_2 nanocrystals has been extensively investigated due to their promising applications in renewable energy and environmental fields. However, the intrinsic distinction in the photocatalytic oxidation activities between the {001}and {101} facets of anatase TiO_2 nanocrystals is still unclear and under debate. In this work, a simple photoelectrochemical method was employed to meaningfully quantify the intrinsic photocatalytic activities of {001} and{101} faceted TiO_2 nanocrystal photoanodes. The effective surface areas of photoanodes with different facets were measured based on the monolayer adsorption of phthalic acid on TiO_2 photoanode surface by an ex situ photoelectrochemical method, which were used to normalize the photocurrents obtained from different faceted photoanodes for meaningful comparison of their photocatalytic activities. The results demonstrated that the {001} facets of anatase TiO_2 nanocrystals exhibited much better photocatalytic activity than that of {101} facets of anatase TiO_2 nanocrystals toward photocatalytic oxidation of water and organic compounds with different functional groups(e.g.,–OH, –CHO, –COOH). Furthermore, the instantaneous kinetic constants of photocatalytic oxidation of pre-adsorbates on {001} faceted anatase TiO_2 photoanode are obviously greater than those obtained at {101} faceted anatase TiO_2 photoanode, further verifying the higher photocatalytic activity of {001} facets of anatase TiO_2.This work provided a facile photoelectrochemical method to quantitatively determine the photocatalytic oxidation activity of specific exposed crystal facets of a photocatalyst, which would be helpful to uncover and meaningfully compare the intrinsic photocatalytic activities of different exposed crystal facets of a photocatalyst.
基金funded by the Engineering and Physical Sciences Research Council(EP/P029892/1)the Leverhulme Trust(RPG-2021-145 and RPG-2023-283).
文摘Metalenses can integrate the functionalities of multiple optical components thanks to the unprecedented capability of optical metasurfaces in light control.With the rapid development of optical metasurfaces,metalenses continue to evolve.Polarization and color play a very important role in understanding optics and serve as valuable tools for gaining insights into our world.Benefiting from the design flexibility of metasurfaces,we propose and experimentally demonstrate a super metalens that can realize multifaceted control of focal points along any 3D curved trajectory.The wavelengths and polarization states of all focal points are engineered in a desirable manner.The super metalens can simultaneously realize customized 3D positioning,polarization states,and wavelengths of focal points,which are experimentally demonstrated with incident wavelengths ranging from 501 to 700 nm.We further showcase the application of the developed super metalenses in 3D optical distance measurement.The compact nature of metasurfaces and unique properties of the proposed super metalenses hold promise to dramatically miniaturize and simplify the optical architecture for applications in optical metrology,imaging,detection,and security.
文摘ASEAN’s major power balancing strategy refers to the balancing strategy adopted by ASEAN and its member states to seek national and regional security and development by maintaining multi-faceted friendship and impartiality with surrounding major powers.The evolution of this strategy is a process of dynamic adjustment,with ASEAN and its members being the implementing subjects,major powers the objects.
基金Advanced Research Center for Chemical Building Blocks,ARC CBBC,which is co-foundedco-financed by the Dutch Research Council(NWO)and the Netherlands Ministry of Economic Affairs and Climate Policy.
文摘Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds.This study provides a comprehensive analysis of the adsorption and photo-oxidation of surface-adsorbed acetone on three SrTiO_(3)morphologies:cubes(for which exclusively{100}facets are exposed),{110}-truncated cubes,and{100}-truncated rhombic dodecahedrons,respectively,all prepared by hydrothermal synthesis.In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy shows that cubic crystals contain a high quantity of surface-OH groups,enabling significant quantities of adsorbed acetone in the form ofη^(1)-enolate when exposed to gas phase acetone.Contrary,{110}facets exhibit fewer surface-OH groups,resulting in relatively small quantities of adsorbedη^(1)-acetone,without observable quantities of enolate.Interestingly,acetate and formate signatures appear in the spectra of cubic,surfaceη^(1)-enolate containing,SrTiO_(3)upon illumination,while besides acetate and formate,the formation of(surface)formaldehyde was observed on truncated cubes,and dodecahedrons,by conversion of adsorbedη^(1)-acetone.Time-Resolved Photoluminescence studies demonstrate that the lifetimes of photogenerated charge carriers vary with crystal morphology.The shortest carrier lifetime(τ_(1)=33±0.1 ps)was observed in{110}-truncated cube SrTiO_(3),likely due to a relatively strong built-in electric field promoting electron transport to{100}facets and hole transport to{110}facets.The second lifetime(τ_(2)=259±1 ps)was also the shortest for this morphology,possibly due to a higher amount of surface trap states.Our results demonstrate that SrTiO_(3)crystal morphology can be tuned to optimize performance in photocatalytic oxidation.
基金supported by the National Natural Science Foundation of China(No.52002305)Natural Science Basic Research Program in Shanxi Province of China(Nos.202403021221184,202403021222281)+1 种基金Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2025JC-YBMS-478,23JK0424)College Students’Innovation Program of Taiyuan Normal University(No.CXCY2443)。
文摘Iron carbodiimide(Fe NCN)anode demonstrates significant potential for rapid sodium-ion storage owing to its high reaction activity and near-metallic conductivity.However,further development of Fe NCN is hindered by inherent structural instability and ambiguous structure-kinetics correlation.In this study,Fe NCN crystallites with selectively exposed(002)and{010}facets were precisely engineered and synthesized.Notably,the sodium storage kinetics and electrochemical performance of Fe NCN exhibit facet-dependent variations.Polyhedral-Fe NCN(P-Fe NCN)dominated by{010}facets exhibited a pseudocapacitance-driven storage mechanism and delivered exceptional rate capability(372 m Ah/g at5 A/g)and long cyclability(95.8%capacity retention after 300 cycles at 0.5 A/g).In contrast,sheet-like Fe NCN(S-Fe NCN)with predominant(002)facet exposure displayed diffusion-limited kinetics due to sluggish ion diffusion rate.Crucially,time-resolved operando XRD analysis and DFT simulation bridge this performance gap to mechanistic origins:Fe NCN as an intercalation-conversion type anode,the solid-state diffusion is the rate-determining step during charge/discharge process.Active{010}facets possess numerous broad hexagonal tunnels,coupled with a low diffusion barrier of 0.168 e V along{010}directions.This unique architectural configuration enables rapid sodium-ion transport,thereby shifting the diffusioncontrolled kinetics to intercalation-pseudocapacitive behavior.This discovery establishes active facet exposure as a storage kinetic switch,offering a generalized paradigm for optimizing the rate performance and stability of sodium-ion batteries.
基金the National Key R&D Program of China(Nos.2021YFA1501301,2021YFC2901100)the National Natural Science Foundation of China(Nos.22178381,22035009).
文摘Crystalized CeO_(2)structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’size and ability to absorb light.However,the controllable fabrication of well-defined hierarchical structures of CeO_(2)with high reactive facets is significant and challenging.Herein,a series of CeO_(2)supports including hierarchical flower-like(F-CeO_(2)),ball-like(B-CeO_(2)),cube-like(C-CeO_(2)),and rod-like CeO_(2)(R-CeO_(2))supports were prepared by hydrothermal method(BCeO_(2),R-CeO_(2)and C-CeO_(2))or ice-bath method(F-CeO_(2))respectively.V atoms were selected as the active atoms and loaded on these supports.Their structure-activity relationship in photo-assisted thermal propane dehydrogenation(PTPDH)was investigated systematically.The samples were characterized by Xray diffraction,scanning electron microscopy,transmission electron microscopy,N2 adsorption-desorption isotherms,and Fourier transform infrared spectrum.Results show that R-CeO_(2)support exhibits the biggest surface area thus achieving the best dispersion of VOx species.UV-vis spectrum and photoluminescence spectrum indicate that V/F-CeO_(2)has the best light adsorption property and V/R-CeO_(2)has the best carrier migration capacity.The activity tests demonstrate that the V/R-CeO_(2)has the largest net growth rate and the V/F-CeO_(2)has the biggest relative growth ratio.Furthermore,the non-thermal effect was confirmed by the kinetic method,which lowers the propane reaction orders,selectively promoting the first C-H bond activation.The light radiation TPSR experiment confirmed this point.DFT calculations show a good linear relationship between the energy barrier and the exchanged electron number.It inspires the design of high-reactive facets for boosting the intrinsic activity of the C-H bond in photoassisted thermal chemical processes.
基金supported by the Hebei Province Key R&D Technology Project(23314401D)2023 Hebei Province High-level Talent Team Construction Special Project(235A4401D)+6 种基金Hebei North University Youth Fund Project(XJ2024013)School-level Cultivation Research Project of Hebei North University(XJPY2024025)First Batch of School-level Scientific Research Projects of Hebei North University in 2023(B2023405004)Hebei North University High-level Talent Research Start-up Fund(BSJJ202303,BSJJ202313,BSJJ202421)Science and Technology Research Project of Higher Education Institutions in Hebei Province(QN2023222)Central Guided Local Science and Technology Development Funding Program(236Z4401G)Natural Science Foundation of Hebei Province(B2022405005).
文摘Lithium-sulfur(Li-S)batteries are promising for high-energy-density storage,but their performance is limited by sluggish lithium polysulfide(LiPS)conversion kinetics.Here,we tackle this issue by synthesizing ultrafine truncated octahedral TiO_(2) nanocrystals(P-O_(v)-TiO_(2)),featuring specific{101}facets and dual defects—phosphorus doping and oxygen vacancies.Acting as an efficient electrocatalyst in the separator,P-O_(v)-TiO_(2) exhibits superior catalytic properties,where oxygen vacancies modulate the electronic structure,enhancing electron enrichment and charge transfer;phosphorus doping tailors the d-band center of the catalyst,strengthening Ti-S interactions between the{101}facets and LiPSs.As a result,Li-S coin cells modified with P-O_(v)-TiO_(2) achieve a high specific capacity of 895 mAh g^(−1) at 5 C and exhibit a minimal decay rate of 0.14%per cycle over 200 cycles.Furthermore,Li-S pouch cells deliver a high capacity of 1004 mAh g^(−1) at 0.1 C under lean electrolyte conditions.This study elucidates the mechanisms of charge states on specific crystal planes and deepens our understanding of dual-defect engineering in Li-S electrochemistry,offering a promising approach for developing efficient and cost-effective catalysts for Li-S battery applications.
基金National Natural Science Foundation of China(No.81861138040)。
文摘F-B co-doped TiO_(2)nanosheets with exposed anatase(001)facets were synthesized via a one-pot solvothermal method,and their photocatalytic hydrogen evolution performance was investigated.Characterization results confirm that this method effectively promotes the growth of the highly active anatase(001)facets and enhances visible and infrared light absorption while inducing oxygen vacancies.Under optimal conditions,the hydrogen evolution reaches 20.57μmol after 10 h of ultraviolet-visible(UV-Vis)light irradiation,exceeding the commercial TiO_(2)nanoparticles Degussa P25 by more than 10 times.These findings highlight the potential of F-B co-doped TiO_(2)nanosheets for efficient photocatalysis.
文摘The facets effect on the catalytic properties of inorganic compounds and metal-organic frameworks(MOFs)has been widely demonstrated,but the intrinsic facets effect free of interference of capping agents has not been discussed.Here we give a proof-of-concept illustration on the intrinsic facets effect by employing the popularly investigated NH2-MIL-125(Ti)MOFs with{001},{111}and{100}facets controllably exposed as model photocatalysts,which were synthesized via a simple supersaturation strategy free of any capping agents.Compared to conventional synthetic routes with capping agents employed,the NH2-MIL-125(Ti)MOFs obtained in this work exhibit remarkably different physical and chemical properties such as surface wettability,charge separation as well as trend of facets effect on photocatalytic water splitting performance.The main reason has been unraveled to originate from unavoidable residue/influence of capping agents during the conventional facets-controlled synthetic routes leading to changed local surface structural environment as well as distinct charge separation property.Our results demonstrate the importance and feasibility of facets-controllable synthesis free of capping agents in getting insight into the intrinsic facets effect of MOFs-related materials.
基金supported by National Natural Science Fund for Excellent Young Scholars(22222813)the National Natural Science Foundation of China(22078338)+2 种基金the National Key Research and Development Program of China(2023YFA1506803)the Postdoctoral Fellowship Program of CPSF(GZC20232700)the“Special Research Assistant Project”of the Chinese Academy of Sciences.
文摘Nanostructured ceria has attracted much attention in the field of redox catalysts due to the numerous active sites with excellent redox ability.Based on the acidic medium etching strategy,we constructed the strong binding centers(hydroxyl sites and strong acid sites)on the surfaces of nanostructured ceria,which regulate the adsorption process of KA-Oil(the mixture of cyclohexanol and cyclohexanone)and to promote high KA-Oil selectivity in cyclohexane oxidation.The three CeO_(2)(nanocube,nanorod and nanopolyhedron)with different exposed crystal planes were treated by acid etching to change the surface sites and catalytic properties.The transition behavior of surface sites during etching was revealed,abundant strong binding centers were proved to be constructed successfully.And especially for the nanorod treated by acid(Acid@CeO_(2)-NR)with the strongest response for sulfuric acid etching,the strong adsorption of cyclohexanone by strong binding centers was confirmed based on the in-situ DRIFTs.The sulfuric acid etching strategy to enhance the selective oxidation of cyclohexane based on the construction of strong binding centers was proved to be feasible and effective,Acid@CeO_(2)-NR with strongest etching response achieved the dramatic promotion of KA-Oil selectivity from 64.1%to 92.3%.
