MoTe_(2) has emerged as a promising candidate in the field of integrated circuits,memristive devices,and catalysts,owing to its polymorphic nature across different phases.Experimentally,strain engineering has been dem...MoTe_(2) has emerged as a promising candidate in the field of integrated circuits,memristive devices,and catalysts,owing to its polymorphic nature across different phases.Experimentally,strain engineering has been demonstrated as an effective approach for manipulating the phase transition of MoTe_(2),but the mechanism remains unclear.The strain-dependent phase transition and its micro-mechanisms have been investigated based on first principle calculations.As demonstrated,critical strain and phase transition path from H→T'phases are strongly governed by the applied strain's orientation,magnitude,and triaxiality.At the atomic level,nonzero movements of Te atoms within the phase transition domain with mechanical unloading have been clarified,together with an advanced understanding on the impact of strain on Te-vacancies migration.These insights advanced the knowledge of MoTe_(2) phase transition behavior and demonstrated the large space to explore potential applications through strain,defect,and phase engineering.展开更多
The application of conventional manganese dioxide(MnO_(2))materials in sodium-ion supercapacitors(Na-SCs)is considerably limited by their low conductivity and structural instability.Biomimetic morphology engineering c...The application of conventional manganese dioxide(MnO_(2))materials in sodium-ion supercapacitors(Na-SCs)is considerably limited by their low conductivity and structural instability.Biomimetic morphology engineering can optimize the electrochemical performance of MnO_(2).Here,based on the metal-organic frameworks(MOFs)-derived method and electrochemical reconstruction,a coral-like MnO_(2)structure integrated with a functional nitrogen-doped carbon(NC)coating is designed for Na-SC application.The bioinspired coral-like structure captures numerous electrolyte ions and increases the Na+concentration on the electrode surface,which is beneficial for optimizing the Na+transport pathway and accelerating the electrode reaction kinetics.Moreover,the coral-like crosslinked structure effectively enhances the mechanical properties,enabling the maintenance of the structure of MnO_(2)-based electrodes during long-term operation.Furthermore,in/ex-situ characterizations are performed to elucidate the mechanism of lattice transformation during electrochemical phase reconstruction.Additionally,the theoretical calculation and simulation results reveal the ion/electron dynamics in the fabricated electrode.The prepared electrode demonstrates excellent capacitance storage ability(340.7 F g^(−1)at 0.5 A g^(−1))and cycling stability(85.1%capacitance retention after 10,000 cycles).The assembled hybrid device exhibits exceptional life-span(82.0%capacitance retention after 10,000 cycles)and exceptional energy density(36.5 Wh kg^(−1)).This study provides a reliable biomimetic morphology design strategy for MnO_(2)cathodes,paving the way for the fabrication of high-performance Na-SCs.展开更多
This study reported the synthesis of magnetic solid solutions V2(A_(x)B_(y)Sn_(1-x-y))C(where A and B are Mn,Fe,or Co)MAX phases.These materials were prepared by incorporating magnetic elements into the V_(2)SnC MAX p...This study reported the synthesis of magnetic solid solutions V2(A_(x)B_(y)Sn_(1-x-y))C(where A and B are Mn,Fe,or Co)MAX phases.These materials were prepared by incorporating magnetic elements into the V_(2)SnC MAX phase via pressure-less sintering at 1000℃for 3 hours.XRD analysis reveals that the composition with x=y=0.2 exhibits a shift of diffraction peaks to higher angles,indicating lattice parameter changes,and achieves the highest phase purity with the maximum solid solution limit,further increases in the dopant content led to the formation of impurities.While the solid solution of magnetic elements preserves the characteristic layered structure of the MAX phase,it successfully induces magnetic properties.The magnetic transition temperatures for these solid solutions ranges from 61 to 200 K.Specifically,V_(2)(Mn_(x)Co_(y)Sn_(1-x-y))C demonstrated hard magnetic characteristics,with a high saturation magnetization(6.536 emu/g)and large remanence(4.236 emu/g).In contrast,V_(2)(Mn_(x)Fe_(y)Sn_(1-x-y))C and V2(Fe_(x)Co_(y)Sn_(1-x-y))C exhibits soft magnetic behavior,evidenced by their narrow hysteresis loops and low coercivity.Their saturation magnetization values are 3.80 and 1.784 emu/g,respectively.The distinctly"S"-shaped hysteresis loop of V_(2)(Fe_(x)Co_(y)Sn_(1-x-y))C further confirms its soft magnetic nature.展开更多
Light-energy-driven semiconductor catalysis offers attractive ways to address environmental and energy crises.TiO_(2) is the most promising catalyst for photocatalysis,but the lack of charge-carrier separation efficie...Light-energy-driven semiconductor catalysis offers attractive ways to address environmental and energy crises.TiO_(2) is the most promising catalyst for photocatalysis,but the lack of charge-carrier separation efficiency severely limits its catalytic performance.In this study,we carried out crystal phase engineering to prepare in situ Z-scheme hetero-phase homojunction of anatase-rutile and clarified the structure-performance relationship.The efficiency of sulfamerazine removal by hetero-phase homojunction TiO_(2) nanotube arrays in a single-compartment photocatalytic fuel cell system was improved by 1.93 times compared to conventional anatase TiO_(2) nanotube arrays and the degradation pathways were revealed by the Fukui function combined with HP-LCMS.The successful construction of Z-scheme hetero-phase homojunction was confirmed by Raman,X-ray diffraction(XRD),and electron spin resonance(ESR),which combined with density functional theory(DFT)calculations revealed the key role of crystal phase engineering in the construction of hetero-phase homojunction.This work provides a novel strategy for the scientific design of titanium dioxide photocatalysts.展开更多
Achieving high thermal conductivity in polymer composites with micro or nanoparticle fillers are challenging.Typically,over 50 vol%filler loading is necessary to form a thermal conductive network.However,even with suc...Achieving high thermal conductivity in polymer composites with micro or nanoparticle fillers are challenging.Typically,over 50 vol%filler loading is necessary to form a thermal conductive network.However,even with such a network in place,the increase in thermal conductivity may not be significant compared to that in electrically conductive composites.To clarify the ideal filler network structure,we endeavored to selectively disperse nano-sized Al_(2)O_(3)nanoparticles at the interface of co-continuous SEBS/PA6 blends,with and without various filler surface modification methods.A thermal conductive network forms when all interface areas are fully covered by 2.56 vol%of Al_(2)O_(3)nanoparticles(very close to theoretical loading content 2.29 vol%).In this case,the Al_(2)O_(3)nanoparticle has the highest thermal conductive contribution(TCC).However,the absolute TCC values are extremely low because of the interfacial thermal resistance and it will decrease when the filler content exceeds 2.56 vol%,indicating that some nanoparticles are dispersed separately out of the existed thermal conductive network.These findings suggest that the construction of a connected thermal conductive network,relatively lower interfacial thermal resistance and the precise positioning of fillers within this network are essential for achieving high thermal conductivity composites.展开更多
LiNiO_(2)(LNO)is one of the most promising cathode materials for lithium-ion batteries.Tungsten element in enhancing the stability of LNO has been researched extensively.However,the understanding of the specific dopin...LiNiO_(2)(LNO)is one of the most promising cathode materials for lithium-ion batteries.Tungsten element in enhancing the stability of LNO has been researched extensively.However,the understanding of the specific doping process and existing form of W are still not perfect.This study proposes a lithium-induced grain boundary phase W doping mechanism.The results demonstrate that the introduced W atomsfirst react with the lithium source to generate a Li–W–O phase at the grain boundary of primary particles.With the increase of lithium ratio,W atoms gradually diffuse from the grain boundary phase to the interior layered structure to achieve W doping.The feasibility of grain boundary phase doping is verified byfirst principles calculation.Furthermore,it is found that the Li2WO4 grain boundary phase is an excellent lithium ion conductor,which can protect the cathode surface and improve the rate performance.The doped W can alleviate the harmful H2↔H3 phase transition,thereby inhibiting the generation of microcracks,and improving the electrochemical performance.Consequently,the 0.3 wt%W-doped sample provides a significant improved capacity retention of 88.5%compared with the pristine LNO(80.7%)after 100 cycles at 2.8–4.3 V under 1C.展开更多
Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+d...Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.展开更多
基金supported by NSFC Grants(Nos.12032004,11872114,and 11502150)Natural Science Foundation of Hebei Province of China(No.A2016210060)+1 种基金The Higher Education Youth Talents Program of Hebei Province of China(No.BJ2017052)Science and Technology Project of Hebei Education Department(No.QN2020204)。
文摘MoTe_(2) has emerged as a promising candidate in the field of integrated circuits,memristive devices,and catalysts,owing to its polymorphic nature across different phases.Experimentally,strain engineering has been demonstrated as an effective approach for manipulating the phase transition of MoTe_(2),but the mechanism remains unclear.The strain-dependent phase transition and its micro-mechanisms have been investigated based on first principle calculations.As demonstrated,critical strain and phase transition path from H→T'phases are strongly governed by the applied strain's orientation,magnitude,and triaxiality.At the atomic level,nonzero movements of Te atoms within the phase transition domain with mechanical unloading have been clarified,together with an advanced understanding on the impact of strain on Te-vacancies migration.These insights advanced the knowledge of MoTe_(2) phase transition behavior and demonstrated the large space to explore potential applications through strain,defect,and phase engineering.
基金supported by the National Natural Science Foundation of China(22409065)the Guangdong Basic and Applied Basic Research Foundation(2022A1515011906)+2 种基金the China Postdoctoral Science Foundation(2023M731153)the Research Fund Program of Guangdong Provincial Key Laboratory of Fuel Cell Technologythe Postdoctoral Fellowship Program of CPSF(GZC20230868).
文摘The application of conventional manganese dioxide(MnO_(2))materials in sodium-ion supercapacitors(Na-SCs)is considerably limited by their low conductivity and structural instability.Biomimetic morphology engineering can optimize the electrochemical performance of MnO_(2).Here,based on the metal-organic frameworks(MOFs)-derived method and electrochemical reconstruction,a coral-like MnO_(2)structure integrated with a functional nitrogen-doped carbon(NC)coating is designed for Na-SC application.The bioinspired coral-like structure captures numerous electrolyte ions and increases the Na+concentration on the electrode surface,which is beneficial for optimizing the Na+transport pathway and accelerating the electrode reaction kinetics.Moreover,the coral-like crosslinked structure effectively enhances the mechanical properties,enabling the maintenance of the structure of MnO_(2)-based electrodes during long-term operation.Furthermore,in/ex-situ characterizations are performed to elucidate the mechanism of lattice transformation during electrochemical phase reconstruction.Additionally,the theoretical calculation and simulation results reveal the ion/electron dynamics in the fabricated electrode.The prepared electrode demonstrates excellent capacitance storage ability(340.7 F g^(−1)at 0.5 A g^(−1))and cycling stability(85.1%capacitance retention after 10,000 cycles).The assembled hybrid device exhibits exceptional life-span(82.0%capacitance retention after 10,000 cycles)and exceptional energy density(36.5 Wh kg^(−1)).This study provides a reliable biomimetic morphology design strategy for MnO_(2)cathodes,paving the way for the fabrication of high-performance Na-SCs.
基金Funded by the National Natural Science Foundation for Young Scholars of China(No.51302073)the Hubei Provincial Key Laboratory of Green Materials for Light Industry,Hubei University of Technology(No.202509B13)。
文摘This study reported the synthesis of magnetic solid solutions V2(A_(x)B_(y)Sn_(1-x-y))C(where A and B are Mn,Fe,or Co)MAX phases.These materials were prepared by incorporating magnetic elements into the V_(2)SnC MAX phase via pressure-less sintering at 1000℃for 3 hours.XRD analysis reveals that the composition with x=y=0.2 exhibits a shift of diffraction peaks to higher angles,indicating lattice parameter changes,and achieves the highest phase purity with the maximum solid solution limit,further increases in the dopant content led to the formation of impurities.While the solid solution of magnetic elements preserves the characteristic layered structure of the MAX phase,it successfully induces magnetic properties.The magnetic transition temperatures for these solid solutions ranges from 61 to 200 K.Specifically,V_(2)(Mn_(x)Co_(y)Sn_(1-x-y))C demonstrated hard magnetic characteristics,with a high saturation magnetization(6.536 emu/g)and large remanence(4.236 emu/g).In contrast,V_(2)(Mn_(x)Fe_(y)Sn_(1-x-y))C and V2(Fe_(x)Co_(y)Sn_(1-x-y))C exhibits soft magnetic behavior,evidenced by their narrow hysteresis loops and low coercivity.Their saturation magnetization values are 3.80 and 1.784 emu/g,respectively.The distinctly"S"-shaped hysteresis loop of V_(2)(Fe_(x)Co_(y)Sn_(1-x-y))C further confirms its soft magnetic nature.
基金supported by the National Natural Science Foundation of China(Nos.52370025,52372212)BUCEA Postgraduate Education and Teaching Quality Improvement Project(No.J2023016)the BUCEA Post Graduate Innovation Project(Nos.DG2023012 and PG2024073).
文摘Light-energy-driven semiconductor catalysis offers attractive ways to address environmental and energy crises.TiO_(2) is the most promising catalyst for photocatalysis,but the lack of charge-carrier separation efficiency severely limits its catalytic performance.In this study,we carried out crystal phase engineering to prepare in situ Z-scheme hetero-phase homojunction of anatase-rutile and clarified the structure-performance relationship.The efficiency of sulfamerazine removal by hetero-phase homojunction TiO_(2) nanotube arrays in a single-compartment photocatalytic fuel cell system was improved by 1.93 times compared to conventional anatase TiO_(2) nanotube arrays and the degradation pathways were revealed by the Fukui function combined with HP-LCMS.The successful construction of Z-scheme hetero-phase homojunction was confirmed by Raman,X-ray diffraction(XRD),and electron spin resonance(ESR),which combined with density functional theory(DFT)calculations revealed the key role of crystal phase engineering in the construction of hetero-phase homojunction.This work provides a novel strategy for the scientific design of titanium dioxide photocatalysts.
基金supported by the National Natural Science Foundation of China(Nos.51973052 and 51473047)。
文摘Achieving high thermal conductivity in polymer composites with micro or nanoparticle fillers are challenging.Typically,over 50 vol%filler loading is necessary to form a thermal conductive network.However,even with such a network in place,the increase in thermal conductivity may not be significant compared to that in electrically conductive composites.To clarify the ideal filler network structure,we endeavored to selectively disperse nano-sized Al_(2)O_(3)nanoparticles at the interface of co-continuous SEBS/PA6 blends,with and without various filler surface modification methods.A thermal conductive network forms when all interface areas are fully covered by 2.56 vol%of Al_(2)O_(3)nanoparticles(very close to theoretical loading content 2.29 vol%).In this case,the Al_(2)O_(3)nanoparticle has the highest thermal conductive contribution(TCC).However,the absolute TCC values are extremely low because of the interfacial thermal resistance and it will decrease when the filler content exceeds 2.56 vol%,indicating that some nanoparticles are dispersed separately out of the existed thermal conductive network.These findings suggest that the construction of a connected thermal conductive network,relatively lower interfacial thermal resistance and the precise positioning of fillers within this network are essential for achieving high thermal conductivity composites.
基金江西省自然科学基金项目(编号:20202BAB206075)江西省教育厅科技项目(编号:GJJ201202)江西中医药大学中西医结合一级学科平台(Discipline of Chinese and Western Integrative Medicine,Jiangxi University of Chinese Medicine)。
基金supported by the National Natural Science Foundation of China(No.52122407,No.52174285,52404317)the Science and Technology Innovation Program of Hunan Province(No.2022RC3048).
文摘LiNiO_(2)(LNO)is one of the most promising cathode materials for lithium-ion batteries.Tungsten element in enhancing the stability of LNO has been researched extensively.However,the understanding of the specific doping process and existing form of W are still not perfect.This study proposes a lithium-induced grain boundary phase W doping mechanism.The results demonstrate that the introduced W atomsfirst react with the lithium source to generate a Li–W–O phase at the grain boundary of primary particles.With the increase of lithium ratio,W atoms gradually diffuse from the grain boundary phase to the interior layered structure to achieve W doping.The feasibility of grain boundary phase doping is verified byfirst principles calculation.Furthermore,it is found that the Li2WO4 grain boundary phase is an excellent lithium ion conductor,which can protect the cathode surface and improve the rate performance.The doped W can alleviate the harmful H2↔H3 phase transition,thereby inhibiting the generation of microcracks,and improving the electrochemical performance.Consequently,the 0.3 wt%W-doped sample provides a significant improved capacity retention of 88.5%compared with the pristine LNO(80.7%)after 100 cycles at 2.8–4.3 V under 1C.
基金supported by the National Natural Science Foundation of China(No.21805018)by Sichuan Science and Technology Program(Nos.2022ZHCG0018,2023NSFSC0117 and 2023ZHCG0060)Yibin Science and Technology Program(No.2022JB005)and China Postdoctoral Science Foundation(No.2022M722704).
文摘Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.
