Two-dimensional transition metal dichalcogenides heterostructures have stimulated wide in- terest not only for the fundamental research, but also for the application of next generation electronic and optoelectronic de...Two-dimensional transition metal dichalcogenides heterostructures have stimulated wide in- terest not only for the fundamental research, but also for the application of next generation electronic and optoelectronic devices. Herein, we report a successful two-step chemical vapor deposition strategy to construct vertically stacked van der Waals epitaxial In2Se3/MoSe2 heterostructures. Transmission electron microscopy characterization reveals clearly that the In2Se3 has well-aligned lattice orientation with the substrate of monolayer MoSe2. Due to the interaction between the In2Se3 and MoSe2 layers, the heterostructure shows the quench- ing and red-shift of photoluminescence. Moreover, the current rectification behavior and photovoltaic effect can be observed from the heterostructure, which is attributed to the unique band structure alignment of the heterostructure, and is further confirmed by Kevin probe force microscopy measurement. The synthesis approach via van der Waals epitaxy in this work can expand the way to fabricate a variety of two-dimensional heterostructures for potential applications in electronic and optoelectronic devices.展开更多
Lithium-sulfur batteries(LSBs) hold great potential for large-scale electrochemical energy storage applications. Currently, the shuttle of soluble lithium polysulfide(LiPSs) intermediates with sluggish conversion kine...Lithium-sulfur batteries(LSBs) hold great potential for large-scale electrochemical energy storage applications. Currently, the shuttle of soluble lithium polysulfide(LiPSs) intermediates with sluggish conversion kinetics and random deposition of Li2S have severely degraded the capacity, rate and cycling performances of LSBs, preventing their practical applications. In this work, ultrathin MoSe2 nanosheets with active edge sites were successfully grown on both internal and external surfaces of hollow carbon spheres with mesoporous walls(MCHS). The resulting MoSe2@MCHS composite acted as a novel functional reservoir for Li PSs with high chemical affinity and effectively mediated their fast redox conversion during charge/discharge as elucidated by experimental observations and first-principles density functional theory(DFT) calculations. The as-fabricated Li-S cells delivered high capacity, superior rate and excellent cyclability. The current work presents new insights on the delicate design and fabrication of novel functional composite electrode materials for rechargeable batteries with emerging applications.展开更多
Photocatalysis activated by visible light remains highly challenging.Here,we report novel MoSe2/ZnO/ZnSe(ZM)hybrids fabricated via a simple hydrothermal method for photocatalytic reduction of Cr(VI)under visible light...Photocatalysis activated by visible light remains highly challenging.Here,we report novel MoSe2/ZnO/ZnSe(ZM)hybrids fabricated via a simple hydrothermal method for photocatalytic reduction of Cr(VI)under visible light irradiation.ZM hybrids show improved photocatalytic reduction ability under visible light irradiation compared to pure ZnO owing to good visible light absorption and rapid electron transfer and separation.The ZM hybrid shows the highest Cr(VI)reduction rate of 100%.Moreover,the photocatalytic Cr(VI)reduction process is mainly controlled by photoinduced electrons.展开更多
Interface engineering has been widely explored to improve the electrochemical performances of composite electrodes,which governs the interface charge transfer,electron transportation,and structural stability.Herein,Mo...Interface engineering has been widely explored to improve the electrochemical performances of composite electrodes,which governs the interface charge transfer,electron transportation,and structural stability.Herein,MoC is incorporated into MoSe2/C composite as an intermediate phase to alter the bridging between MoSe2-and nitrogen-doped three-dimensional(3D)carbon framework as MoSe2/MoC/N–C connection,which greatly improve the structural stability,electronic conductivity,and interfacial charge transfer.Moreover,the incorporation of MoC into the composites inhibits the overgrowth of MoSe2 nanosheets on the 3D carbon framework,producing much smaller MoSe2 nanodots.The obtained MoSe2 nanodots with fewer layers,rich edge sites,and heteroatom doping ensure the good kinetics to promote pseudo-capacitance contributions.Employing as anode material for lithium-ion batteries,it shows ultralong cycle life(with 90%capacity retention after 5000 cycles at 2 A g−1)and excellent rate capability.Moreover,the constructed LiFePO4//MoSe2/MoC/N–C full cell exhibits over 86%capacity retention at 2 A g−1 after 300 cycles.The results demonstrate the effectiveness of the interface engineering by incorporation of MoC as interface bridging intermediate to boost the lithium storage capability,which can be extended as a potential general strategy for the interface engineering of composite materials.展开更多
Dynamic processes of electron transfer by optical doping in monolayer MoSe2 at 6 K are investigated via measuring time resolved photoluminescence(PL)traces under different excitation powers.Time-dependent electron tra...Dynamic processes of electron transfer by optical doping in monolayer MoSe2 at 6 K are investigated via measuring time resolved photoluminescence(PL)traces under different excitation powers.Time-dependent electron transfer process can be analyzed by a power-law distribution of t^−α withα=0.1-0.24,depending on the laser excitation power.The average electron transfer time of approximately 27.65 s is obtained in the excitation power range of 0.5 to 100μW.As the temperature increases from 20 to 44 K,the energy difference between the neutral and charged excitons is observed to decrease.展开更多
Sb2S3 solar cells with substrate structure usually suffer from pretty low short circuit current(JSC)due to the defects and poor carrier transport.The Sb2S3,as a one-dimensional material,exhibits orientation-dependent ...Sb2S3 solar cells with substrate structure usually suffer from pretty low short circuit current(JSC)due to the defects and poor carrier transport.The Sb2S3,as a one-dimensional material,exhibits orientation-dependent carrier transport property.In this work,a thin MoSe2 layer is directly synthesized on the Mo substrate followed by depositing the Sb2S3 thin film.The x-ray diffraction(XRD)patterns confirm that a thin MoSe2 layer can improve the crystallization of the Sb2S3 film and induce(hk1)orientations,which can provide more carrier transport channels.Kelvin probe force microscopy(KPFM)results suggest that this modified Sb2S3 film has a benign surface with less defects and dangling bonds.The variation of the surface potential of Sb2S3 indicates a much more efficient carrier separation.Consequently,the power conversion efficiency(PCE)of the substrate structured Sb2S3 thin film solar cell is improved from 1.36%to 1.86%,which is the best efficiency of the substrate structured Sb2S3 thin film solar cell,and JSC significantly increases to 13.6 mA/cm^2.According to the external quantum efficiency(EQE)and C-V measurements,the modified crystallization and elevated built-in electric field are the main causes.展开更多
Optoelectronic properties of MoSe2 are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerable increase in electron and hole...Optoelectronic properties of MoSe2 are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerable increase in electron and hole mobilities reveals the highly improved electron and hole transport.Furthermore,the photocurrent is enhanced by nearly four orders of magnitudes under 7 nW laser exposure after annealing.The remarkable enhancement in the photoresponse is attributed to an increase in hole trapping centers and a reduction in resistance.Furthermore,the annealed photodetector shows a fast time response on the order of 10 ms and responsivity of 3×10^(4) A/W.展开更多
文摘Two-dimensional transition metal dichalcogenides heterostructures have stimulated wide in- terest not only for the fundamental research, but also for the application of next generation electronic and optoelectronic devices. Herein, we report a successful two-step chemical vapor deposition strategy to construct vertically stacked van der Waals epitaxial In2Se3/MoSe2 heterostructures. Transmission electron microscopy characterization reveals clearly that the In2Se3 has well-aligned lattice orientation with the substrate of monolayer MoSe2. Due to the interaction between the In2Se3 and MoSe2 layers, the heterostructure shows the quench- ing and red-shift of photoluminescence. Moreover, the current rectification behavior and photovoltaic effect can be observed from the heterostructure, which is attributed to the unique band structure alignment of the heterostructure, and is further confirmed by Kevin probe force microscopy measurement. The synthesis approach via van der Waals epitaxy in this work can expand the way to fabricate a variety of two-dimensional heterostructures for potential applications in electronic and optoelectronic devices.
基金financially supported by the National Natural Science Foundation of China (51302204, 21902122)Postdoctoral Science Foundation of China (2019M652723)+2 种基金Hunan Provincial Science and Technology Plan Project (No.2017TP1001)Program for Changjiang Scholars and Innovative Research Team in University (IRT_15R52)Hubei Provincial Department of Education for the “Chutian Scholar” program。
文摘Lithium-sulfur batteries(LSBs) hold great potential for large-scale electrochemical energy storage applications. Currently, the shuttle of soluble lithium polysulfide(LiPSs) intermediates with sluggish conversion kinetics and random deposition of Li2S have severely degraded the capacity, rate and cycling performances of LSBs, preventing their practical applications. In this work, ultrathin MoSe2 nanosheets with active edge sites were successfully grown on both internal and external surfaces of hollow carbon spheres with mesoporous walls(MCHS). The resulting MoSe2@MCHS composite acted as a novel functional reservoir for Li PSs with high chemical affinity and effectively mediated their fast redox conversion during charge/discharge as elucidated by experimental observations and first-principles density functional theory(DFT) calculations. The as-fabricated Li-S cells delivered high capacity, superior rate and excellent cyclability. The current work presents new insights on the delicate design and fabrication of novel functional composite electrode materials for rechargeable batteries with emerging applications.
基金Financial support from the Natural Science Foundation of Zhejiang Province(LY18E060005,LY19E020006)~~
文摘Photocatalysis activated by visible light remains highly challenging.Here,we report novel MoSe2/ZnO/ZnSe(ZM)hybrids fabricated via a simple hydrothermal method for photocatalytic reduction of Cr(VI)under visible light irradiation.ZM hybrids show improved photocatalytic reduction ability under visible light irradiation compared to pure ZnO owing to good visible light absorption and rapid electron transfer and separation.The ZM hybrid shows the highest Cr(VI)reduction rate of 100%.Moreover,the photocatalytic Cr(VI)reduction process is mainly controlled by photoinduced electrons.
基金This work was supported by the National Natural Science Foundation of China(No 51872334,51932011,51874326,51572299)the Natural Science Foundation of Hunan Province for Distinguished Young Scholars(2018JJ1036)the Independent exploration and innovation Project for graduate students of central south university(2019zzts049).
文摘Interface engineering has been widely explored to improve the electrochemical performances of composite electrodes,which governs the interface charge transfer,electron transportation,and structural stability.Herein,MoC is incorporated into MoSe2/C composite as an intermediate phase to alter the bridging between MoSe2-and nitrogen-doped three-dimensional(3D)carbon framework as MoSe2/MoC/N–C connection,which greatly improve the structural stability,electronic conductivity,and interfacial charge transfer.Moreover,the incorporation of MoC into the composites inhibits the overgrowth of MoSe2 nanosheets on the 3D carbon framework,producing much smaller MoSe2 nanodots.The obtained MoSe2 nanodots with fewer layers,rich edge sites,and heteroatom doping ensure the good kinetics to promote pseudo-capacitance contributions.Employing as anode material for lithium-ion batteries,it shows ultralong cycle life(with 90%capacity retention after 5000 cycles at 2 A g−1)and excellent rate capability.Moreover,the constructed LiFePO4//MoSe2/MoC/N–C full cell exhibits over 86%capacity retention at 2 A g−1 after 300 cycles.The results demonstrate the effectiveness of the interface engineering by incorporation of MoC as interface bridging intermediate to boost the lithium storage capability,which can be extended as a potential general strategy for the interface engineering of composite materials.
基金supported by the National Natural Science Foundation of China under Grant Nos 61674135,11974342 and 61827823.
文摘Dynamic processes of electron transfer by optical doping in monolayer MoSe2 at 6 K are investigated via measuring time resolved photoluminescence(PL)traces under different excitation powers.Time-dependent electron transfer process can be analyzed by a power-law distribution of t^−α withα=0.1-0.24,depending on the laser excitation power.The average electron transfer time of approximately 27.65 s is obtained in the excitation power range of 0.5 to 100μW.As the temperature increases from 20 to 44 K,the energy difference between the neutral and charged excitons is observed to decrease.
基金Project supported by the National Key R&D Program of China(Grant Nos.2019YFB1503500,2018YFE0203400,and 2018YFB1500200)the National Natural Science Foundation of China(Grant No.U1902218)+1 种基金the YangFan Innovative and Entrepreneurial Research Team Project of China(Grant No.2014YT02N037)the 111 Project,China(Grant No.B16027).
文摘Sb2S3 solar cells with substrate structure usually suffer from pretty low short circuit current(JSC)due to the defects and poor carrier transport.The Sb2S3,as a one-dimensional material,exhibits orientation-dependent carrier transport property.In this work,a thin MoSe2 layer is directly synthesized on the Mo substrate followed by depositing the Sb2S3 thin film.The x-ray diffraction(XRD)patterns confirm that a thin MoSe2 layer can improve the crystallization of the Sb2S3 film and induce(hk1)orientations,which can provide more carrier transport channels.Kelvin probe force microscopy(KPFM)results suggest that this modified Sb2S3 film has a benign surface with less defects and dangling bonds.The variation of the surface potential of Sb2S3 indicates a much more efficient carrier separation.Consequently,the power conversion efficiency(PCE)of the substrate structured Sb2S3 thin film solar cell is improved from 1.36%to 1.86%,which is the best efficiency of the substrate structured Sb2S3 thin film solar cell,and JSC significantly increases to 13.6 mA/cm^2.According to the external quantum efficiency(EQE)and C-V measurements,the modified crystallization and elevated built-in electric field are the main causes.
基金Project supported by the National Natural Science Foundation of China(Grant No.61904043)the Natural Science Foundation of Zhejiang Province,China(Grant No.LQ19A040009).
文摘Optoelectronic properties of MoSe2 are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerable increase in electron and hole mobilities reveals the highly improved electron and hole transport.Furthermore,the photocurrent is enhanced by nearly four orders of magnitudes under 7 nW laser exposure after annealing.The remarkable enhancement in the photoresponse is attributed to an increase in hole trapping centers and a reduction in resistance.Furthermore,the annealed photodetector shows a fast time response on the order of 10 ms and responsivity of 3×10^(4) A/W.
