Lithium sulfur(Li-S)batteries demonstrate great promise for efficient energy storage systems once the lithium polysulfide(LPS)shuttling and sluggish redox kinetics can be well addressed.Herein,we developed a sea urchi...Lithium sulfur(Li-S)batteries demonstrate great promise for efficient energy storage systems once the lithium polysulfide(LPS)shuttling and sluggish redox kinetics can be well addressed.Herein,we developed a sea urchin-structured oxygen-deficient titanium dioxide semiconductor anchored with cobalt nano-dots(Co@TiO2-x)as a high-performance multifunctional sulfur host material for Li-S batteries.The sea urchin-structured Co@TiO2-x offers strong structural stability and strengthened chemical interaction towards LPS.Meanwhile,the incorporation of Co nano-dots into TiO2 leads to increased oxygen vacancies,which augments the electrical conduction and benefits LPS conversion acceleration as well.As a result,the oxygen vacancy-rich Co@TiO2-x composite exhibits excellent conductivity,strong LPS confinement and promoted sulfur electrochemical kinetics,rendering enhanced LPS shuttling inhibition and rapid redox reaction.Attributed to these features,the Co@TiO2-x/S cathode exhibits a discharge capacity of 803 mAh g-1at 1 C and a good cyclic stability upon 500 cycles with a low capacity fading rate of 0.07%per cycle.This synergistic design of conductive multifunctional LPS barrier is also promising to enlighten the material engineering in other energy storage applications.展开更多
The fluctuations of the strained layer in a superlattice or quantum well can broaden the width of satellite peaks in double crystal X-ray diffraction （DCXRD） pattern. It is found that the width of the 0^th peak is ...The fluctuations of the strained layer in a superlattice or quantum well can broaden the width of satellite peaks in double crystal X-ray diffraction （DCXRD） pattern. It is found that the width of the 0^th peak is directly proportional to the fluctuation of the strained layer if the other related facts are ignored. By this method, the Ge-Si atomic interdiffusion in Ge nano-dots and wetting layers has been investigated by DCXRD. It is found that thermal annealing can activate Ge-Si atomic interdiffusion and the interdiffusion in the nano-dots area is much stronger than that in the wetting layer area. Therefore the fluctuation of the Ge layer decreases and the distribution of Ge atoms becomes homogeneous in the horizontal Ge （GeSi actually） layer, which make the width of the 0^th peak narrow after annealing.展开更多
Lithium-sulfur(Li-S)batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity.However,the shuttle effect of the solub...Lithium-sulfur(Li-S)batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity.However,the shuttle effect of the soluble lithium polysulfides(LiPS)and intrinsic insulating nature of sulfur lead to low sulfur utilization and coulombic efficiency,leading to poor cycling performance.The impeded charge transportation and retard LiPS catalytic conversion also endows the Li-S batteries with sluggish redox reaction,leading to unsatisfied rate capability.In this study,Co-based MOF material ZIF-67 is used as the precursor to prepare Co nano-dots decorated three-dimensional graphene aerogel as sulfur immobilizer.This porous architecture establishes a highly conductive interconnected framework for fast charge/mass transportation.The exposed Co nano-dots serve as active sites to strongly trap LiPS,which endows CoNDs@G with low decomposition energy barrier for fast LiPS conversion reaction and promote the completely Li2 S catalytic transformation.Li-S cells based on the Co-NDs@G cathode exhibits excellent cyclability and a high capacity retention rate of 91.1%in 100 cycles.This strategy offers a new direction to design sulfur immobilizer for accelerated LiPS conversion kinetics of Li-S batteries.展开更多
A Ge/Si（001） island multilayer structure is investigated by double crystal X-ray diffraction, transmission electron microscopy,and atomic force microscopy. We fit the satellite peaks in the rocking curve by two Lore...A Ge/Si（001） island multilayer structure is investigated by double crystal X-ray diffraction, transmission electron microscopy,and atomic force microscopy. We fit the satellite peaks in the rocking curve by two Lorentz lineshapes, which originate from the wetting layer region and the island region. Then from the ratio of the thick- nesses of the Si and Ge （GeSi） layers as determined by TEM,tbe Ge compositions of the wetting layer and islands are estimated to be about 0. 51 and 0. 67, respectively,according to the positions of the fitted peaks. This proves to be a relatively simple way to investigate the Ge/Si （001） island multilayer structure.展开更多
This perspective paper introduces the concept that nanocarbons and related materials such as carbon dots are an interesting intrinsic photocatalytic semiconducting material, and not only a modifier of the existing (se...This perspective paper introduces the concept that nanocarbons and related materials such as carbon dots are an interesting intrinsic photocatalytic semiconducting material, and not only a modifier of the existing (semiconducting) materials to prepare hybrid materials. The semiconducting properties of the nanocarbons, and the possibility to have the band gap within the visible-light region through defect band engineering, introduction of light heteroatoms and control/manipulation of the curvature or surface functionalization are discussed. These materials are conceptually different from the 'classical' semiconducting photocatalysts, because semiconductor domains with tuneable characteristics are embedded in a conductive carbon matrix, with the presence of various functional groups (as C=0 groups) enhancing charge separation by trapping electrons. These nanocarbons open a range of new possibilities for photocatalysis both for energetic and environmental applications. The use of nanocarbons as quantum dots and photo luminescent materials was also analysed. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
基金support from the National Natural Science Foundation of China(21978063)the“Excellent Going Abroad Experts”Training Program in Hebei ProvinceInnovation Fund for Excellent Youth of Hebei University of Technology(2012002)。
文摘Lithium sulfur(Li-S)batteries demonstrate great promise for efficient energy storage systems once the lithium polysulfide(LPS)shuttling and sluggish redox kinetics can be well addressed.Herein,we developed a sea urchin-structured oxygen-deficient titanium dioxide semiconductor anchored with cobalt nano-dots(Co@TiO2-x)as a high-performance multifunctional sulfur host material for Li-S batteries.The sea urchin-structured Co@TiO2-x offers strong structural stability and strengthened chemical interaction towards LPS.Meanwhile,the incorporation of Co nano-dots into TiO2 leads to increased oxygen vacancies,which augments the electrical conduction and benefits LPS conversion acceleration as well.As a result,the oxygen vacancy-rich Co@TiO2-x composite exhibits excellent conductivity,strong LPS confinement and promoted sulfur electrochemical kinetics,rendering enhanced LPS shuttling inhibition and rapid redox reaction.Attributed to these features,the Co@TiO2-x/S cathode exhibits a discharge capacity of 803 mAh g-1at 1 C and a good cyclic stability upon 500 cycles with a low capacity fading rate of 0.07%per cycle.This synergistic design of conductive multifunctional LPS barrier is also promising to enlighten the material engineering in other energy storage applications.
基金＂863＂ Research Plan Grant No. 2006AA032415 the National Natural Science Foundation of China under Grant Nos. 60336010, 90104003, 90401001,60676005the National High Technology Research and Development Program of China No. 2002AA312010.
文摘The fluctuations of the strained layer in a superlattice or quantum well can broaden the width of satellite peaks in double crystal X-ray diffraction （DCXRD） pattern. It is found that the width of the 0^th peak is directly proportional to the fluctuation of the strained layer if the other related facts are ignored. By this method, the Ge-Si atomic interdiffusion in Ge nano-dots and wetting layers has been investigated by DCXRD. It is found that thermal annealing can activate Ge-Si atomic interdiffusion and the interdiffusion in the nano-dots area is much stronger than that in the wetting layer area. Therefore the fluctuation of the Ge layer decreases and the distribution of Ge atoms becomes homogeneous in the horizontal Ge （GeSi actually） layer, which make the width of the 0^th peak narrow after annealing.
基金the financial support from the Natural Science Foundation of Hebei Province(B2020202069)。
文摘Lithium-sulfur(Li-S)batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity.However,the shuttle effect of the soluble lithium polysulfides(LiPS)and intrinsic insulating nature of sulfur lead to low sulfur utilization and coulombic efficiency,leading to poor cycling performance.The impeded charge transportation and retard LiPS catalytic conversion also endows the Li-S batteries with sluggish redox reaction,leading to unsatisfied rate capability.In this study,Co-based MOF material ZIF-67 is used as the precursor to prepare Co nano-dots decorated three-dimensional graphene aerogel as sulfur immobilizer.This porous architecture establishes a highly conductive interconnected framework for fast charge/mass transportation.The exposed Co nano-dots serve as active sites to strongly trap LiPS,which endows CoNDs@G with low decomposition energy barrier for fast LiPS conversion reaction and promote the completely Li2 S catalytic transformation.Li-S cells based on the Co-NDs@G cathode exhibits excellent cyclability and a high capacity retention rate of 91.1%in 100 cycles.This strategy offers a new direction to design sulfur immobilizer for accelerated LiPS conversion kinetics of Li-S batteries.
文摘A Ge/Si（001） island multilayer structure is investigated by double crystal X-ray diffraction, transmission electron microscopy,and atomic force microscopy. We fit the satellite peaks in the rocking curve by two Lorentz lineshapes, which originate from the wetting layer region and the island region. Then from the ratio of the thick- nesses of the Si and Ge （GeSi） layers as determined by TEM,tbe Ge compositions of the wetting layer and islands are estimated to be about 0. 51 and 0. 67, respectively,according to the positions of the fitted peaks. This proves to be a relatively simple way to investigate the Ge/Si （001） island multilayer structure.
基金Financial support from the Italian MIUR gh the PRIN Project 2015K7FZLH SMARTNESS "Solar driven chemistry:new materials for photo- and electro-catalysis"SINCHEM,a Joint Doctorate programme selected under the Erasmus Mundus Action 1 Programme (FPA 2013-0037)
文摘This perspective paper introduces the concept that nanocarbons and related materials such as carbon dots are an interesting intrinsic photocatalytic semiconducting material, and not only a modifier of the existing (semiconducting) materials to prepare hybrid materials. The semiconducting properties of the nanocarbons, and the possibility to have the band gap within the visible-light region through defect band engineering, introduction of light heteroatoms and control/manipulation of the curvature or surface functionalization are discussed. These materials are conceptually different from the 'classical' semiconducting photocatalysts, because semiconductor domains with tuneable characteristics are embedded in a conductive carbon matrix, with the presence of various functional groups (as C=0 groups) enhancing charge separation by trapping electrons. These nanocarbons open a range of new possibilities for photocatalysis both for energetic and environmental applications. The use of nanocarbons as quantum dots and photo luminescent materials was also analysed. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
