SiC nanowires with thickness-controlled SiO2 shells have been obtained by a simple and efficient method, namely treatment of SiC/SiO2 core-shell nanowires in NaOH solution. The products were characterized by transmiss...SiC nanowires with thickness-controlled SiO2 shells have been obtained by a simple and efficient method, namely treatment of SiC/SiO2 core-shell nanowires in NaOH solution. The products were characterized by transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Raman spectroscopy, infrared （IR） spectroscopy, and photoluminescence spectroscopy. The thickness of the SiO2 shell can be effectively controlled by selecting the appropriate processing time, and pure SiC nanowires were also obtained by alkaline cleaning in 1 mol-L-1 NaOH solution for 40 min at 70 ~C. A mechanism for the removal of the SiO2 shells has been proposed, and a two-phase reaction kinetic equation was derived to explain the rate of the removal of the SiO2 shells. The validity of this equation was verified by experiment. This work not only describes an effective experimental method for achieving SiC nanowires with thickness-controlled SiO2 coatings but also provides a fundamental theoretical equation with a certain level of generality. In addition, photoluminescence （PL） measurement results showed that the SiC nanowires sheathed with an optimum SiO2 thickness （3.03 nm） have better photoluminescence properties than either the bare SiC nanowires or SiC nanowires with thicker coatings of SiO2.展开更多
Solar-driven photoelectrochemical(PEC) water splitting is a promising technology for sustainable hydrogen production, which relies on the development of efficient and stable photoanodes for water oxidation reaction. T...Solar-driven photoelectrochemical(PEC) water splitting is a promising technology for sustainable hydrogen production, which relies on the development of efficient and stable photoanodes for water oxidation reaction. The thickness and microstructure of semiconductor films are generally crucial to their PEC properties. Herein, three-dimensional(3D) interconnected nanoporous Ta3N5 film photoanodes with controlled thickness were successfully fabricated via galvanostatic anodization and NH3 nitridation. The porous Ta3N5 nanoarchitectures(NAs) of 900 nm in thickness showed the highest PEC performance due to the optimal lightharvesting and charge separation. Compared with the holeinduced photocorrosion, the electrochemical oxidation at high anodic potentials resulted in severer performance degradation of Ta3N5. Although the surface oxide layer on deteriorated Ta3N5 photoanodes could be removed by NH3 re-treatment,the PEC performance was only partially recovered. As an alternative, anchoring a dual-layer Co(OH)x/Co OOH co-catalyst shell on the porous Ta3N5 NAs demonstrated substantially enhanced PEC performance and stability. Overall, this work provides reference to controllably fabricate 3D nanoporous Ta3N5-based photoanodes for efficient and stable PEC water splitting via optimizing the light absorption, hole extraction,charge separation and utilization.展开更多
Two-dimensional(2D)ferroelectrics with high Curie temperature(T_(c))exhibit stable ferroelectricity at the nanoscale and possess significant applications in the miniaturization of ferroelectric devices.However,control...Two-dimensional(2D)ferroelectrics with high Curie temperature(T_(c))exhibit stable ferroelectricity at the nanoscale and possess significant applications in the miniaturization of ferroelectric devices.However,controllable growth of wafer-scale 2D ferroelectric films with desired thickness is still rarely reported.In this study,we develop a two-step vapour deposition method to grow wafer-scale 2D CuCrS_(2)ferroelectric films with a uniform thickness from 2 to 10 nm.These films possess a non-centrosymmetric structure with a 3R stacking sequence,exhibit ferroelectric polarizations,and the Tc of CuCrS_(2)is higher than room temperature.The constructed electronic devices exhibit the characteristics of ferroelectric memristor,which opens up applications for ferroelectric functional devices.展开更多
Control of surface structure at the atomic level can effectively tune catalytic properties of nanomaterials.Tuning surface strain is an effective strategy for enhancing catalytic activity;however,the correlation studi...Control of surface structure at the atomic level can effectively tune catalytic properties of nanomaterials.Tuning surface strain is an effective strategy for enhancing catalytic activity;however,the correlation studies between the surface strain with catalytic performance are scant because such mechanistic studies require the precise control of surface strain on catalysts.In this work,a simple strategy of precisely tuning compressive surface strain of atomic-layer Cu2O on Cu@Ag (AL-Cu2O/Cu@Ag) nanoparticles (NPs) is demonstrated.The AL-Cu2O is synthesized by structure evolution of Cu@Ag core-shell nanoparticles,and the precise thickness-control of AL-Cu2O is achieved by tuning the molar ratio of Cu/Ag of the starting material.Aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) and EELS elemental mapping characterization showed that the compressive surface strain of AL-Cu2O along the [111] and [200] directions can be precisely tuned from 6.5% to 1.6% and 6.6% to 4.7%,respectively,by changing the number of AL-Cu2O layer from 3 to 6.The as-prepared AL-Cu2O/Cu@Ag NPs exhibited excellent catalytic property in the synthesis of azobenzene from aniline,in which the strained 4-layers Cu2O (4.5% along the [111] direction,6.1% along the [200] direction) exhibits the best catalytic performance.This work may be beneficial for the design and surface engineering of catalysts toward specific applications.展开更多
基金The work reported here was supported by the National Natural Science Foundation of China under Grant Nos. 51272117, 51172115, and 50972063, the Natural Science Foundation of Shandong Province under Grant Nos. ZR2011EMZ001, and ZR2011EMQ011, the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20123719110003, the Application Foundation Research Program of Qingdao under Grant No. 13-1-4- 117-jch, and the Tackling Key Program of Science and Technology in Shandong Province under Grant No. 2012GGX10218. We express our grateful thanks to them for their financial support.
文摘SiC nanowires with thickness-controlled SiO2 shells have been obtained by a simple and efficient method, namely treatment of SiC/SiO2 core-shell nanowires in NaOH solution. The products were characterized by transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Raman spectroscopy, infrared （IR） spectroscopy, and photoluminescence spectroscopy. The thickness of the SiO2 shell can be effectively controlled by selecting the appropriate processing time, and pure SiC nanowires were also obtained by alkaline cleaning in 1 mol-L-1 NaOH solution for 40 min at 70 ~C. A mechanism for the removal of the SiO2 shells has been proposed, and a two-phase reaction kinetic equation was derived to explain the rate of the removal of the SiO2 shells. The validity of this equation was verified by experiment. This work not only describes an effective experimental method for achieving SiC nanowires with thickness-controlled SiO2 coatings but also provides a fundamental theoretical equation with a certain level of generality. In addition, photoluminescence （PL） measurement results showed that the SiC nanowires sheathed with an optimum SiO2 thickness （3.03 nm） have better photoluminescence properties than either the bare SiC nanowires or SiC nanowires with thicker coatings of SiO2.
基金financially supported by the National Natural Science Foundation of China (51774145,51872317 and 21835007)China Postdoctoral Science Foundation (2019M661644)China Scholarship Council (CSC) for financial support。
文摘Solar-driven photoelectrochemical(PEC) water splitting is a promising technology for sustainable hydrogen production, which relies on the development of efficient and stable photoanodes for water oxidation reaction. The thickness and microstructure of semiconductor films are generally crucial to their PEC properties. Herein, three-dimensional(3D) interconnected nanoporous Ta3N5 film photoanodes with controlled thickness were successfully fabricated via galvanostatic anodization and NH3 nitridation. The porous Ta3N5 nanoarchitectures(NAs) of 900 nm in thickness showed the highest PEC performance due to the optimal lightharvesting and charge separation. Compared with the holeinduced photocorrosion, the electrochemical oxidation at high anodic potentials resulted in severer performance degradation of Ta3N5. Although the surface oxide layer on deteriorated Ta3N5 photoanodes could be removed by NH3 re-treatment,the PEC performance was only partially recovered. As an alternative, anchoring a dual-layer Co(OH)x/Co OOH co-catalyst shell on the porous Ta3N5 NAs demonstrated substantially enhanced PEC performance and stability. Overall, this work provides reference to controllably fabricate 3D nanoporous Ta3N5-based photoanodes for efficient and stable PEC water splitting via optimizing the light absorption, hole extraction,charge separation and utilization.
基金the National Natural Science Foundation of China(52425203,52221001,62090035,12404216)the Natural Science Foundation of Jiangsu Province(BK20240008,BK20241252,BK20233001)+3 种基金the National Key R&D Program of China(2022YFA1204300)the Key Research and Development Plan of Hunan Province(2023GK2012)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(GZC20231093)the Jiangsu Funding Program for Excellent Postdoctoral Talent(2023ZB553)。
文摘Two-dimensional(2D)ferroelectrics with high Curie temperature(T_(c))exhibit stable ferroelectricity at the nanoscale and possess significant applications in the miniaturization of ferroelectric devices.However,controllable growth of wafer-scale 2D ferroelectric films with desired thickness is still rarely reported.In this study,we develop a two-step vapour deposition method to grow wafer-scale 2D CuCrS_(2)ferroelectric films with a uniform thickness from 2 to 10 nm.These films possess a non-centrosymmetric structure with a 3R stacking sequence,exhibit ferroelectric polarizations,and the Tc of CuCrS_(2)is higher than room temperature.The constructed electronic devices exhibit the characteristics of ferroelectric memristor,which opens up applications for ferroelectric functional devices.
基金the National Natural Science Foundation of China (Nos.51631001,21643003,51872030,51702016,and 51501010)Fundamental Research Funds for the Central Universities, Beijing Institute of Technology Research Fund Program for Young Scholars and ZDKT18-01 from State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology).
文摘Control of surface structure at the atomic level can effectively tune catalytic properties of nanomaterials.Tuning surface strain is an effective strategy for enhancing catalytic activity;however,the correlation studies between the surface strain with catalytic performance are scant because such mechanistic studies require the precise control of surface strain on catalysts.In this work,a simple strategy of precisely tuning compressive surface strain of atomic-layer Cu2O on Cu@Ag (AL-Cu2O/Cu@Ag) nanoparticles (NPs) is demonstrated.The AL-Cu2O is synthesized by structure evolution of Cu@Ag core-shell nanoparticles,and the precise thickness-control of AL-Cu2O is achieved by tuning the molar ratio of Cu/Ag of the starting material.Aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) and EELS elemental mapping characterization showed that the compressive surface strain of AL-Cu2O along the [111] and [200] directions can be precisely tuned from 6.5% to 1.6% and 6.6% to 4.7%,respectively,by changing the number of AL-Cu2O layer from 3 to 6.The as-prepared AL-Cu2O/Cu@Ag NPs exhibited excellent catalytic property in the synthesis of azobenzene from aniline,in which the strained 4-layers Cu2O (4.5% along the [111] direction,6.1% along the [200] direction) exhibits the best catalytic performance.This work may be beneficial for the design and surface engineering of catalysts toward specific applications.
