Modulating the exposed facets of metal-organic frameworks(MOFs)is an effective strategy to enhance the synergistic effects between adsorption and photocatalytic reduction of U(Ⅵ).Herein,we successfully synthesized fo...Modulating the exposed facets of metal-organic frameworks(MOFs)is an effective strategy to enhance the synergistic effects between adsorption and photocatalytic reduction of U(Ⅵ).Herein,we successfully synthesized four morphologically distinct types of NH2-MIL-125(Ti),offering insights into the impact of facet engineering on the combined adsorption and photoreduction of U(Ⅵ).An elevated exposure ratio of the{001}facet endows NH2-MIL-125(Ti)with a larger surface area,enhanced light absorption,and efficient separation of photogenerated charge carriers.Among the four photocatalysts(W,D,S and T),T with a high proportion of{001}facets,demonstrated outstanding adsorption-photocatalytic synergy,achieving over 97%of U(Ⅵ)within 20 min of visible light irradiation across a broad concentrations and pH range,without requiring a hole-trapping agent.The uranium extraction mechanism involves U(Ⅵ)coordination and chelation with active sites during adsorption,followed by reduction to U(Ⅳ)via photogenerated electrons during photocatalysis.This study highlights the use of facet engineering to enhance adsorption and photocatalytic efficiency in MOF-based photocatalysts.展开更多
Magnesium hydride serves as a promising solid-state hydrogen storage material owing to its high potential.However,its practical applications are constrained by the high enthalpy of hydrogen absorption and slow kinetic...Magnesium hydride serves as a promising solid-state hydrogen storage material owing to its high potential.However,its practical applications are constrained by the high enthalpy of hydrogen absorption and slow kinetics.In this study,we prepared a Ni/Ti3O5@graphene oxide(GO)dual-heterojunction composite material via solvent heating,electrostatic adsorption,and calcination to improve the hydrogen storage capabilities of MgH2.Adding Ni/Ti3O5@GO to MgH2 lowered the initial dehydrogenation temperature of MgH2 to 183℃;at a dehydrogenation temperature of 275℃,6.4 wt.%of H2 escaped from the MgH2 bulk.In addition,the hydrogen storage material absorbed 1.8 wt.%H2 at 30℃ for 30 min.The calculated activation energy of dehydrogenation was 48.221±0.141 kJ·mol-1,which was significantly lower than that of the ball-milled MgH2(112.63±1.44 kJ·mol-1).Mechanistic analysis results revealed that the heterojunction constructed from the multiphase compound system provided a large number of active sites and hydrogen diffusion routes,resulting in a synergistic catalytic effect that enhanced the hydrogen storage capacity of MgH2.In this work,we clarified the compositions of fuzzy interfaces in heterostructured materials by conducting ultraviolet photoelectron spectroscopy tests and identified key composite materials for the formation of heterojunctions.展开更多
To overcome the strength-ductility trade‐off in fabricated Ti‐2Al‐2.5Zr alloy tubes,we systematically investigated the microstructural evolution and mechanical behavior throughout thermomechanical processing,includ...To overcome the strength-ductility trade‐off in fabricated Ti‐2Al‐2.5Zr alloy tubes,we systematically investigated the microstructural evolution and mechanical behavior throughout thermomechanical processing,including hot working(forging and extrusion)and cold multi‐pass rolling.The results reveal that hot forging promotes limited concurrent discontinuous and continuous dynamic recrystallization(DDRX and CDRX),resulting in a microstructure dominated by high‐dislocation‐density substructures.In contrast,hot extrusion is primarily driven by CDRX through mechanisms of subgrain rotation and grain fragmentation,thereby refining the grain size to 4-8μm and achieving a synergistic improvement in strength and ductility.This refined and homogeneous microstructure provides a requisite plasticity reserve for subsequent cold rolling,thereby mitigating the risk of cracking.In the cold rolling stage,{1012}extension twinning is activated initially,coordinating strain and optimizing texture through an~85°lattice reorientation,which facilitates the transition from basal to prismatic texture.This transition promotes sustained prismatic slip activation.Subsequently,dislocation slip dominates,leading to significant dislocation hardening.The synergistic effect of texture optimization and dislocation hardening ensures both high strength and retained ductility.Consequently,the processed tubes exhibit an excellent combination of ultimate tensile strength(852 MPa)and elongation(11.0%).This study elucidates the intricate interplay among processes,microstructure,and properties,providing a new paradigm for manufacturing high‐performance titanium alloy tubes.展开更多
The mechanism of propylene epoxidation catalyzed by distinct titanium(Ti)species within the TS-1 framework was systematically explored through DFT calculations.To elucidate the reaction pathways,rate-limiting steps,an...The mechanism of propylene epoxidation catalyzed by distinct titanium(Ti)species within the TS-1 framework was systematically explored through DFT calculations.To elucidate the reaction pathways,rate-limiting steps,and the intricate relationship between the catalyst structure and performance,several mononuclear Ti active site models,namely TiO4,Ti-IV,Ti-V,and TiO6,were meticulously constructed.The calculation results revealed that for both TiO4and TiO6,the rate-limiting step is H2O2activation,with barriers of 0.75 and 0.77 eV,respectively.In contrast,for Ti-Ⅳand Ti-Ⅴ,the rate-limiting step is propylene epoxidation,with barriers of 0.74 and 0.47 eV,respectively.Notably,the Ti-V species demonstrated optimal catalytic activity for both H2O2activation and subsequent epoxidation,whereas the other three Ti species exhibited comparable catalytic activities.The electronic property calculations provided a robust theoretical basis for the observed activity trends,aligning well with the activation barrier data.Furthermore,the presence of methanol solvent was found to have a remarkable promotional effect on H2O2activation,significantly altering the kinetic feature of the overall reaction.This effect made the highly coordinated Ti-V and TiO6species particularly promising catalysts for this reaction.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,Nos.U1904215,52371240,22305212)the Program for Young Changjiang Scholars of the Ministry of Education,China(No.Q2018270)。
摘要Modulating the exposed facets of metal-organic frameworks(MOFs)is an effective strategy to enhance the synergistic effects between adsorption and photocatalytic reduction of U(Ⅵ).Herein,we successfully synthesized four morphologically distinct types of NH2-MIL-125(Ti),offering insights into the impact of facet engineering on the combined adsorption and photoreduction of U(Ⅵ).An elevated exposure ratio of the{001}facet endows NH2-MIL-125(Ti)with a larger surface area,enhanced light absorption,and efficient separation of photogenerated charge carriers.Among the four photocatalysts(W,D,S and T),T with a high proportion of{001}facets,demonstrated outstanding adsorption-photocatalytic synergy,achieving over 97%of U(Ⅵ)within 20 min of visible light irradiation across a broad concentrations and pH range,without requiring a hole-trapping agent.The uranium extraction mechanism involves U(Ⅵ)coordination and chelation with active sites during adsorption,followed by reduction to U(Ⅳ)via photogenerated electrons during photocatalysis.This study highlights the use of facet engineering to enhance adsorption and photocatalytic efficiency in MOF-based photocatalysts.
基金supported by the National Natural Science Foundation of China[grant number U24A2044]Science and Technology Major Program of Guangxi Province[grant number GUIKEAA24206007].
摘要Magnesium hydride serves as a promising solid-state hydrogen storage material owing to its high potential.However,its practical applications are constrained by the high enthalpy of hydrogen absorption and slow kinetics.In this study,we prepared a Ni/Ti3O5@graphene oxide(GO)dual-heterojunction composite material via solvent heating,electrostatic adsorption,and calcination to improve the hydrogen storage capabilities of MgH2.Adding Ni/Ti3O5@GO to MgH2 lowered the initial dehydrogenation temperature of MgH2 to 183℃;at a dehydrogenation temperature of 275℃,6.4 wt.%of H2 escaped from the MgH2 bulk.In addition,the hydrogen storage material absorbed 1.8 wt.%H2 at 30℃ for 30 min.The calculated activation energy of dehydrogenation was 48.221±0.141 kJ·mol-1,which was significantly lower than that of the ball-milled MgH2(112.63±1.44 kJ·mol-1).Mechanistic analysis results revealed that the heterojunction constructed from the multiphase compound system provided a large number of active sites and hydrogen diffusion routes,resulting in a synergistic catalytic effect that enhanced the hydrogen storage capacity of MgH2.In this work,we clarified the compositions of fuzzy interfaces in heterostructured materials by conducting ultraviolet photoelectron spectroscopy tests and identified key composite materials for the formation of heterojunctions.
基金financially supported by the National Key Research and Development Program of China(Grant 2023YFB3710701).
摘要To overcome the strength-ductility trade‐off in fabricated Ti‐2Al‐2.5Zr alloy tubes,we systematically investigated the microstructural evolution and mechanical behavior throughout thermomechanical processing,including hot working(forging and extrusion)and cold multi‐pass rolling.The results reveal that hot forging promotes limited concurrent discontinuous and continuous dynamic recrystallization(DDRX and CDRX),resulting in a microstructure dominated by high‐dislocation‐density substructures.In contrast,hot extrusion is primarily driven by CDRX through mechanisms of subgrain rotation and grain fragmentation,thereby refining the grain size to 4-8μm and achieving a synergistic improvement in strength and ductility.This refined and homogeneous microstructure provides a requisite plasticity reserve for subsequent cold rolling,thereby mitigating the risk of cracking.In the cold rolling stage,{1012}extension twinning is activated initially,coordinating strain and optimizing texture through an~85°lattice reorientation,which facilitates the transition from basal to prismatic texture.This transition promotes sustained prismatic slip activation.Subsequently,dislocation slip dominates,leading to significant dislocation hardening.The synergistic effect of texture optimization and dislocation hardening ensures both high strength and retained ductility.Consequently,the processed tubes exhibit an excellent combination of ultimate tensile strength(852 MPa)and elongation(11.0%).This study elucidates the intricate interplay among processes,microstructure,and properties,providing a new paradigm for manufacturing high‐performance titanium alloy tubes.
基金supported by the National Key Research and Development Program of China(Grant 2022YFB3805600)the National Natural Science Foundation of China(Grant 22438004)+2 种基金Fundamental Research Funds for the Central Universities(Grants DUT22LAB602 and DUT25Z2754)Liaoning Provincial Excellent Youth Science Fund Project(Grant 2025JH6/101000006)Liaoning Revitalization Talents Program(Grant XLYC2008032)。
摘要The mechanism of propylene epoxidation catalyzed by distinct titanium(Ti)species within the TS-1 framework was systematically explored through DFT calculations.To elucidate the reaction pathways,rate-limiting steps,and the intricate relationship between the catalyst structure and performance,several mononuclear Ti active site models,namely TiO4,Ti-IV,Ti-V,and TiO6,were meticulously constructed.The calculation results revealed that for both TiO4and TiO6,the rate-limiting step is H2O2activation,with barriers of 0.75 and 0.77 eV,respectively.In contrast,for Ti-Ⅳand Ti-Ⅴ,the rate-limiting step is propylene epoxidation,with barriers of 0.74 and 0.47 eV,respectively.Notably,the Ti-V species demonstrated optimal catalytic activity for both H2O2activation and subsequent epoxidation,whereas the other three Ti species exhibited comparable catalytic activities.The electronic property calculations provided a robust theoretical basis for the observed activity trends,aligning well with the activation barrier data.Furthermore,the presence of methanol solvent was found to have a remarkable promotional effect on H2O2activation,significantly altering the kinetic feature of the overall reaction.This effect made the highly coordinated Ti-V and TiO6species particularly promising catalysts for this reaction.