The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces h...The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evoluti on of Au nan oparticles (NPs) on few-layer MoS2 by high resol utio n transmissi on electro n microscopy (HRTEM) an d quan titative high-angle annular dark field seanning TEM. It is found that in the transition of Au from nan oparticles to den drites, a dynamically epitaxial align ment betwee n Au and MoS2 lattices is formed, and Moirc patter ns can be directly observed in HRTEM images due to the mismatch between Au and M0S2 lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on M0S2. The structural evoluti on of metal/2D semico nductor in terfaces at atomic scale can provide valuable information for the design and fabricatio n of the metal/2D semicon ductorn ano-devices with desired physical and chemical performa nces.展开更多
Developing non-precious metal catalysts with high activity and stability for electrochemical hydrogen evolution reaction(HER)is of great significance in both scie nee and tech no logy.In this work,N-doped CMK-3,which ...Developing non-precious metal catalysts with high activity and stability for electrochemical hydrogen evolution reaction(HER)is of great significance in both scie nee and tech no logy.In this work,N-doped CMK-3,which was prepared with a casting method using SBA-15 as thehard template and ammonia as the nitrogen source,has been utilized to hold MoS2 and restrict its growth to form MoS2@N-CMK-3 composite.As a result,M0S2 was found to have poorly crystallized and the limited space of porous N-CMK-3 made its size much small.Then there are moreactive sites in MoS2.Accordingly,MoS2@N-CMK-3 has exhibited good electrocatalytic performance toward HER in acids with a quite small Tafelslope of 32 mV·dec^-1.And more importantly,compared to MoS2@CMK-3,its stability has been greatly improved,which can be attributedto the interaction between M0S2 and nitrogen atoms avoiding aggregation and mass loss.This work provides an idea that doping a porouscarbon support with nitrogen is an effective way to enhance the stability of the catalyst.展开更多
Two-dimensional(2D)transition metal dichalcogenides(TMDs)such as molybdenum disulfide(M0S2)have been intensively investigated because of their exclusive physical properties for advaneed electronics and optoelectronics...Two-dimensional(2D)transition metal dichalcogenides(TMDs)such as molybdenum disulfide(M0S2)have been intensively investigated because of their exclusive physical properties for advaneed electronics and optoelectronics.In the present work,we study the M0S2 transistor based on a novel tri-gate device architecture,with dual-gate(Dual-G)in the channel and the buried side-gate(Side-G)for the source/drain regi ons.All gates can be in depe ndently con trolled without in terfere nee.For a MoS2 sheet with a thick ness of 3.6 nm,the Schottky barrier(SB)and non-overlapped channel region can be effectively tuned by electrostatically doping the source/drain regions with Side-G.Thus,the extri nsic resista nee can be effectively lowered,and a boost of the ON-state cur re nt can be achieved.Mean while,the cha nn el c ontrol remai ns efficient under the Dual-G mode,with an ON-OFF current ratio of 3 x 107 and subthreshold swing of 83 mV/decade.The corresponding band diagram is also discussed to illustrate the device operati on mechanism.This no vel device structure ope ns up a new way toward fabricati on of high-performance devices based on 2D-TMDs.展开更多
Exploring high-efficient catalysts for hydrogen evolution reaction(HER)has become very urgeht for resolving the energy related issues.Recently,two-dimensional layered MoS2 and its heterostructures with graphene or oth...Exploring high-efficient catalysts for hydrogen evolution reaction(HER)has become very urgeht for resolving the energy related issues.Recently,two-dimensional layered MoS2 and its heterostructures with graphene or other traditional photocatalysts have presented great potentials for electrocatalytic and photocatalytic HER applications.On-site investigations of the atomic-scale structures and local electronic properties of the catalytically active sites are the key points for understanding the internal mechanisms,which however are hard to be achievec from the practical systems.Hereby,this review focuses on the recent progresses on the on-site scanning tunneling microscopy/spectroscopy investigations of the atomic structures and electronic properties of the ultrahigh-vacuum deposited and chemical vapor deposition(CVD)synthesized monolayer MoS2 and MoSz/graphene vertical stacks on the electrodes of Au(111)and Au foils.The correlations between the respective HER activities,edge types and edge electronic states are comparatively introduced.Secondly,this review also introduces thephotocatalytic HER applications of CVD-grown MoS2/WS2 and WS/MoS2 vertical stacks on Au foils,mainly considering of their type-ll band.alignments and the novel interlayer charge transfer behaviors.Finally,future research directions are also proposed for in-depth understanding of the catalytic mechanism,as well as for exploring more efficient HER catalysts.展开更多
M0 S2 is a promising candidate for hydrogen evolution reaction(HER),while its active sites are mainly distributed on the edge sites rather than the basal plane sites.Herein,a strategy to overcome the inertness of the ...M0 S2 is a promising candidate for hydrogen evolution reaction(HER),while its active sites are mainly distributed on the edge sites rather than the basal plane sites.Herein,a strategy to overcome the inertness of the M0 S2 basal surface and achieve high HER activity by combining single-boron catalyst and compressive strain was reported through density functional theory(DFT)computations.The ab initio molecular dynamics(AIMD)simulation on B@MoS2 suggests high thermodynamic and kinetic stability.We found that the rather strong adsorption of hydrogen by B@MoS2 can be alleviated by stress engineering.The optimal stress of -7%can achieve a nearly zero value of △Gh(〜-0.084 eV),which is close to that of the ideal Pt-SACs for HER.The novel HER activity is attributed to(i)the Bdoping brings the active site to the basal plane of M0 S2 and reduces the band-gap,thereby increasing the conductivity;(ii)the compressive stress regulates the number of charge transfer between(H)-(B)-(MoS2),weakening the adsorption energy of hydrogen on B@MoS2.Moreover,we constructed a SiN/B@MoS2 heterojunction,which introduces an 8.6%compressive stress for B@MoS2 and yields an ideal AGh-This work provides an effective means to achieve high intrinsic HER activity for M0 S2.展开更多
High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode se...High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode severely restrict their further practical application.Here,a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host.A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process,which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres.This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials,high electronic conductivity,and fast lithium-ion diffusive pathways.In addition,additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species,dramatically accelerating their conversion kinetics and re-utilization.The detailed defect-induced interface catalytic reaction mechanism is firstly proposed.As expected,the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g^−1 at 0.2 C and a desirable rate performance(593 mAh·g^−1 at 5.0 C),implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.展开更多
The solid lubricant M0S_(2) demonstrates excellent lubricating properties,but it spontaneously oxidizes and absorbs moisture in air,and thus results in poor wear resistance and short wear-life.In this study,the additi...The solid lubricant M0S_(2) demonstrates excellent lubricating properties,but it spontaneously oxidizes and absorbs moisture in air,and thus results in poor wear resistance and short wear-life.In this study,the additive g-C_(3)N_(4)(CN)was successfully combined with M0S_(2) via hydrothermal synthesis as a solid lubricant for the first time.Meanwhile,a low friction coefficient(COF,y=0.031)and ultra-long wear-life of CN/M0S_(2) compared to pure M0S_(2) in air were demonstrated.The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD).The formed valence states in CN/M0S_(2) were analyzed via X-ray photoelectron spectroscopy(XPS).The characterized results of the scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)show the morphology and interior crystal phase structure of CN/M0S_(2).From the cross-section analysis,the presence of iron oxide nanoparticles lubricating film is synergistic with CN/M0S_(2) film during the friction process,resulting in its ultra-long wear-life.In particular,the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.展开更多
Favourable band alignment and excellent visible light response are vital for photochemical water splitting.In this work,we have theoretically investigated how ferroelectric polarization and its reversibility in direct...Favourable band alignment and excellent visible light response are vital for photochemical water splitting.In this work,we have theoretically investigated how ferroelectric polarization and its reversibility in direction can be utilized to modulate the band alignment and optical absorption properties.For this objective,2D van der Waals heterostructures(HTSs)are constructed by interfacing monolayer M0 S2 with ferroelectric In2 Se3.We find the switch of polarization direction has dramatically changed the band alignment,thus facilitating different type of reactions.In Iri2 Se3/MoS2/In2 Se3 heterostructures,one polarization direction supports hydrogen evolution reaction and another polarization direction can favour oxygen evolution reaction.These can be used to create tuneable photocatalyst materials where water reduction reactions can be selectively controlled by polarization switching.The modulation of band alignment is attributed to the shift of reaction potential caused by spontaneous polarization.Additionally,the formed type-II van der Waals HTSs also significantly improve charge separation and enhance the optical absorption in the visible and infrared regions.Our results pave a way in the design of van der Waals HTSs for water splitting using ferroelectric materials.展开更多
Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality.Monolayer molybdenum disulfide (MoS2) and seed-assistant ar...Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality.Monolayer molybdenum disulfide (MoS2) and seed-assistant are the mostly selected 2D TMDC and growth strategy for such CVD processes,respectively.Though the advantages of seed catalysts in facilitating the nucleation,achieving higher yield and better repeatability,as well as their effects on the morphologies of as-grown MoS2 have been studied,the influence of seeding promoters on both optical and electrical properties of as-grown monolayer MoS2 is not known comprehensively,which is indeed critical for understanding fundamental physics and developing practical application of such emerging 2D semiconductors.In this report,we systematically investigated the effect of different seeding promoters on the properties of CVD-grown monolayer MoS2.It is found that different seed molecules lead to different impacts on the optical and electrical properties of as-grown monolayer MoS2.Among three different seed catalysts (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS),copper phthalocyanine (CuPc),and crystal violet (CV)),PTAS performs better in obtaining large area monolayer MoS2 with good optical quality and high electrical mobility than the other two.Our work gives a guide for modifying the properties of as-grown monolayer MoS2 and other 2D transition metal dichalcogenides in seeding promoters-assisted synthesis process.展开更多
An ordered hollow M0S2 nanocages/RGO nanocomposite is constructed by a simple solvothermal-assisted assembly method combined with freeze-drying and annealing.In this novel nanostructure,hollow M0S2 nanocages are homog...An ordered hollow M0S2 nanocages/RGO nanocomposite is constructed by a simple solvothermal-assisted assembly method combined with freeze-drying and annealing.In this novel nanostructure,hollow M0S2 nanocages are homogeneously distributed on graphene sheets with a tight bond of C-O-Mo.The nanosized and hollow MoS2 nanocages can effectively accommodate the huge volume change during charge/discharge process and increase the number of electrochemical reaction active sites,accelerating the kinetics of lithiation/delithiation.The tight C-O-Mo bond between graphene and MoS2 further reinforces the structural stability,thus improve the electrical conductivity and substantially enhance the lithium storage performance of M0S2 anode material.As a result,this novel nanocomposite shows a long-cycle stability of 717.4 mAh·g^-1 after 800 cycles at a high current density of 3 A·g^-1,exhibiting great potential as an anode nanocomposite for advanced lithium-ion batteries.展开更多
Two-dimensional semiconductors,such as MoS2 are known to be highly susceptible to diverse molecular adsorbates on the surface during fabrication,which could adversely affect device performance.To ensure high device yi...Two-dimensional semiconductors,such as MoS2 are known to be highly susceptible to diverse molecular adsorbates on the surface during fabrication,which could adversely affect device performance.To ensure high device yield,uniformity and performance,the semiconductor industry has long employed wet chemical cleaning strategies to remove undesirable surface contaminations,adsorbates,and native oxides from the surface of Si wafers.A similarly effective surface cleaning technique for two-dimensional materials has not yet been fully developed.In this study,we propose a wet chemical cleaning strategy for MoS2 by using N-methyl-2-pyrrolidone.The cleaning process not only preserves the intrinsic properties of monolayer MoS2,but also significantly improves the performance of monolayer MoS2 field-effect-transistors.Superior device on current of 12 μA·μm-1 for a channel length of 400 nm,contact resistance of 15 kΩ·μm,field-effect mobility of 15.5 cm^2·V^-1·s^-1,and the average on-off current ratio of 10^8 were successfully demonstrated.展开更多
Surface plasmon resonance (SPR) sensor based on the blue phosphorene/MoS2 hetero-structure is presented to enhance the performance parameters, i.e., sensitivity, detection accuracy, and quality fhctor.The blue phospho...Surface plasmon resonance (SPR) sensor based on the blue phosphorene/MoS2 hetero-structure is presented to enhance the performance parameters, i.e., sensitivity, detection accuracy, and quality fhctor.The blue phosphorene/MoS2 hetero-structure works as an interacting layer with the analyte for the enhancement of the sensitivity of the sensor. It is observed that the sensitivity of blue phosphorene/MoS2 based sensor (i.e., structure-Ⅱ) is improved by 5.75%, from the conventional sensor (i.e., structure-Ⅲ). Further, an additional silicon nanolayer is introduced between the metal layer and blue phosphorene/MoS2 hetero-structure. The sensitivity of the proposed blue phosphorene/MoS2 hetero-structure with a silicon layer SPR sensor, i.e., structure-Ⅰ, is enhanced by 44.76% from structure-Ⅱ and 55.75% from structure-Ⅲ due to an enhancement in the evanescent field near the metal-analyte interface. Finally, it is observed that at the optimum thickness of silicon between the gold layer and blue phosphorene/MoS2, performance parameters of the sensor are enhanced.展开更多
Recently,transition metal dichalcogenides(TMDCs)nanoscrolls have exhibited unique electronic and optical properties due to their spiral tubular structures,which are formed by rolling up monolayer TMDCs nanosheets.Insp...Recently,transition metal dichalcogenides(TMDCs)nanoscrolls have exhibited unique electronic and optical properties due to their spiral tubular structures,which are formed by rolling up monolayer TMDCs nanosheets.Inspired by the excellent physical and chemical properties of TMDCs van der Waals heterostructures(vdWHs),it is highly desirable to scroll TMDCs vdWHs for potential optoelectronic applications.In this work,WS2/MoS2 vdWHs nanoscrolls were massively prepared by dropping aqueous alkaline droplet on chemical vapor deposition(CVD)-grown bilayer WS2/MoS2 vdWHs,which were formed by growing monolayer WS2 islands on top of monolayer MoS2 nanosheets simultaneously.The optical microscopy(OM),atomic force microscopy(AFM),ultralow frequency(ULF)Raman spectroscopy and transmission electron microscopy(TEM)were utilized to characterize the WS2/MoS2 vdWHs nanoscrolls.As-obtained WS2/MoS2 vdWHs nanoscrolls exhibited new ULF breathing mode as well as shear mode peaks due to the strong interlayer interaction.Notably,the photosensitivities of WS2/MoS2 vdWHs nanoscrolls-based devices were about ten times higher than those of WS2/MoS2 vdWHs-based devices under blue,green and red lasers,respectively,which could be attributed to the ultrafast charge transfer at alternative WS2/MoS2 and MoS2/WS2 multi-interfaces in scrolled structure.Our work suggested that TMDCs vdWHs scrolls could be promising candidates for optoelectronic applications.展开更多
基金National Natural Science Foundation of China (Nos. 11604010 and 11674023), 111 Project (No. B170003)Fundamental Research Funds for the Central Universities (No. FRF-BD- 18-004A).
文摘The morphology and structural stability of metal/2D semic on ductor interfaces strongly affect the performa nee of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evoluti on of Au nan oparticles (NPs) on few-layer MoS2 by high resol utio n transmissi on electro n microscopy (HRTEM) an d quan titative high-angle annular dark field seanning TEM. It is found that in the transition of Au from nan oparticles to den drites, a dynamically epitaxial align ment betwee n Au and MoS2 lattices is formed, and Moirc patter ns can be directly observed in HRTEM images due to the mismatch between Au and M0S2 lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on M0S2. The structural evoluti on of metal/2D semico nductor in terfaces at atomic scale can provide valuable information for the design and fabricatio n of the metal/2D semicon ductorn ano-devices with desired physical and chemical performa nces.
基金This work was supported by the Nature Science Foundation of Zhejiang Province(No.LY20B010004)and the National Natural Science Foundation of China(Nos.21671152,51672193,51420105002, 21671014).
文摘Developing non-precious metal catalysts with high activity and stability for electrochemical hydrogen evolution reaction(HER)is of great significance in both scie nee and tech no logy.In this work,N-doped CMK-3,which was prepared with a casting method using SBA-15 as thehard template and ammonia as the nitrogen source,has been utilized to hold MoS2 and restrict its growth to form MoS2@N-CMK-3 composite.As a result,M0S2 was found to have poorly crystallized and the limited space of porous N-CMK-3 made its size much small.Then there are moreactive sites in MoS2.Accordingly,MoS2@N-CMK-3 has exhibited good electrocatalytic performance toward HER in acids with a quite small Tafelslope of 32 mV·dec^-1.And more importantly,compared to MoS2@CMK-3,its stability has been greatly improved,which can be attributedto the interaction between M0S2 and nitrogen atoms avoiding aggregation and mass loss.This work provides an idea that doping a porouscarbon support with nitrogen is an effective way to enhance the stability of the catalyst.
基金This work was supported by the National Key Research and Development Program of China(Nos.2016YFA0203900 and 2018YFA0306101)Shanghai Municipal Science and Technology Commission(No.18JC1410300)Natural Science Foundation of China(No.61874154).
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs)such as molybdenum disulfide(M0S2)have been intensively investigated because of their exclusive physical properties for advaneed electronics and optoelectronics.In the present work,we study the M0S2 transistor based on a novel tri-gate device architecture,with dual-gate(Dual-G)in the channel and the buried side-gate(Side-G)for the source/drain regi ons.All gates can be in depe ndently con trolled without in terfere nee.For a MoS2 sheet with a thick ness of 3.6 nm,the Schottky barrier(SB)and non-overlapped channel region can be effectively tuned by electrostatically doping the source/drain regions with Side-G.Thus,the extri nsic resista nee can be effectively lowered,and a boost of the ON-state cur re nt can be achieved.Mean while,the cha nn el c ontrol remai ns efficient under the Dual-G mode,with an ON-OFF current ratio of 3 x 107 and subthreshold swing of 83 mV/decade.The corresponding band diagram is also discussed to illustrate the device operati on mechanism.This no vel device structure ope ns up a new way toward fabricati on of high-performance devices based on 2D-TMDs.
基金This work was supported by the National Natural Science Foundation of China(Nos.51861135201,5147200i,21473001,51290272,and 61774003)the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(No.KF201601).
文摘Exploring high-efficient catalysts for hydrogen evolution reaction(HER)has become very urgeht for resolving the energy related issues.Recently,two-dimensional layered MoS2 and its heterostructures with graphene or other traditional photocatalysts have presented great potentials for electrocatalytic and photocatalytic HER applications.On-site investigations of the atomic-scale structures and local electronic properties of the catalytically active sites are the key points for understanding the internal mechanisms,which however are hard to be achievec from the practical systems.Hereby,this review focuses on the recent progresses on the on-site scanning tunneling microscopy/spectroscopy investigations of the atomic structures and electronic properties of the ultrahigh-vacuum deposited and chemical vapor deposition(CVD)synthesized monolayer MoS2 and MoSz/graphene vertical stacks on the electrodes of Au(111)and Au foils.The correlations between the respective HER activities,edge types and edge electronic states are comparatively introduced.Secondly,this review also introduces thephotocatalytic HER applications of CVD-grown MoS2/WS2 and WS/MoS2 vertical stacks on Au foils,mainly considering of their type-ll band.alignments and the novel interlayer charge transfer behaviors.Finally,future research directions are also proposed for in-depth understanding of the catalytic mechanism,as well as for exploring more efficient HER catalysts.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.21771182 and 21501177)the Open Project Program of Structural Chemistry,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences.The authors also gratefully acknowledge the Supercomputing Center in Yantai university for providing the computing resources.
文摘M0 S2 is a promising candidate for hydrogen evolution reaction(HER),while its active sites are mainly distributed on the edge sites rather than the basal plane sites.Herein,a strategy to overcome the inertness of the M0 S2 basal surface and achieve high HER activity by combining single-boron catalyst and compressive strain was reported through density functional theory(DFT)computations.The ab initio molecular dynamics(AIMD)simulation on B@MoS2 suggests high thermodynamic and kinetic stability.We found that the rather strong adsorption of hydrogen by B@MoS2 can be alleviated by stress engineering.The optimal stress of -7%can achieve a nearly zero value of △Gh(〜-0.084 eV),which is close to that of the ideal Pt-SACs for HER.The novel HER activity is attributed to(i)the Bdoping brings the active site to the basal plane of M0 S2 and reduces the band-gap,thereby increasing the conductivity;(ii)the compressive stress regulates the number of charge transfer between(H)-(B)-(MoS2),weakening the adsorption energy of hydrogen on B@MoS2.Moreover,we constructed a SiN/B@MoS2 heterojunction,which introduces an 8.6%compressive stress for B@MoS2 and yields an ideal AGh-This work provides an effective means to achieve high intrinsic HER activity for M0 S2.
基金The work was financially supported by the National Natural Science Foundation of China(Nos.51672146 and 21805157)the Natural Science Foundation of Shandong Province(No.ZR2018BEM011).
文摘High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode severely restrict their further practical application.Here,a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host.A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process,which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres.This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials,high electronic conductivity,and fast lithium-ion diffusive pathways.In addition,additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species,dramatically accelerating their conversion kinetics and re-utilization.The detailed defect-induced interface catalytic reaction mechanism is firstly proposed.As expected,the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g^−1 at 0.2 C and a desirable rate performance(593 mAh·g^−1 at 5.0 C),implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.
基金the National Natural Science Foundation of China(Grant Nos.U1637204,41663012,51775537,and 51775533)the program of the Light of the Chinese Academy of Science in China's Western Region(2015)the Chinese Academy of Science and its Youth Innovation Promotion Association(2016368)for financial support.
文摘The solid lubricant M0S_(2) demonstrates excellent lubricating properties,but it spontaneously oxidizes and absorbs moisture in air,and thus results in poor wear resistance and short wear-life.In this study,the additive g-C_(3)N_(4)(CN)was successfully combined with M0S_(2) via hydrothermal synthesis as a solid lubricant for the first time.Meanwhile,a low friction coefficient(COF,y=0.031)and ultra-long wear-life of CN/M0S_(2) compared to pure M0S_(2) in air were demonstrated.The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD).The formed valence states in CN/M0S_(2) were analyzed via X-ray photoelectron spectroscopy(XPS).The characterized results of the scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HRTEM)show the morphology and interior crystal phase structure of CN/M0S_(2).From the cross-section analysis,the presence of iron oxide nanoparticles lubricating film is synergistic with CN/M0S_(2) film during the friction process,resulting in its ultra-long wear-life.In particular,the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.
基金We highly acknowledge Queensland Univer-sity of Technology(QUT)and National Computational Infrastruc-ture(NC)Australia for providing high performance computing(HPC)facilities to undertake this project.
文摘Favourable band alignment and excellent visible light response are vital for photochemical water splitting.In this work,we have theoretically investigated how ferroelectric polarization and its reversibility in direction can be utilized to modulate the band alignment and optical absorption properties.For this objective,2D van der Waals heterostructures(HTSs)are constructed by interfacing monolayer M0 S2 with ferroelectric In2 Se3.We find the switch of polarization direction has dramatically changed the band alignment,thus facilitating different type of reactions.In Iri2 Se3/MoS2/In2 Se3 heterostructures,one polarization direction supports hydrogen evolution reaction and another polarization direction can favour oxygen evolution reaction.These can be used to create tuneable photocatalyst materials where water reduction reactions can be selectively controlled by polarization switching.The modulation of band alignment is attributed to the shift of reaction potential caused by spontaneous polarization.Additionally,the formed type-II van der Waals HTSs also significantly improve charge separation and enhance the optical absorption in the visible and infrared regions.Our results pave a way in the design of van der Waals HTSs for water splitting using ferroelectric materials.
基金National Natural Science Foundation of China (Nos. 61774040, 61774042, and 51772317)National Young 1000 Talent Plan of China+1 种基金Shanghai Municipal Natural Science Foundation (Nos. 16ZR1402500, 16ZR1442700, and 17ZR1446500)Opening project of State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences, the National Key R&D program (No. 2017YFF0206106).
文摘Chemical vapor deposition (CVD) is the most efficient method to grow large-area two dimensional (2D) transition metal dichiacogenides (TMDCs) in high quality.Monolayer molybdenum disulfide (MoS2) and seed-assistant are the mostly selected 2D TMDC and growth strategy for such CVD processes,respectively.Though the advantages of seed catalysts in facilitating the nucleation,achieving higher yield and better repeatability,as well as their effects on the morphologies of as-grown MoS2 have been studied,the influence of seeding promoters on both optical and electrical properties of as-grown monolayer MoS2 is not known comprehensively,which is indeed critical for understanding fundamental physics and developing practical application of such emerging 2D semiconductors.In this report,we systematically investigated the effect of different seeding promoters on the properties of CVD-grown monolayer MoS2.It is found that different seed molecules lead to different impacts on the optical and electrical properties of as-grown monolayer MoS2.Among three different seed catalysts (perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS),copper phthalocyanine (CuPc),and crystal violet (CV)),PTAS performs better in obtaining large area monolayer MoS2 with good optical quality and high electrical mobility than the other two.Our work gives a guide for modifying the properties of as-grown monolayer MoS2 and other 2D transition metal dichalcogenides in seeding promoters-assisted synthesis process.
基金This research was supported by the National Natural Science Foundation of China(No.51772150,21808103)Natural Science Foundation of Jiangsu Province(No.BK20171012)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).The authors are grateful to Dr.Lin Gao and the Reviewers for their helpful suggestions and comments.
文摘An ordered hollow M0S2 nanocages/RGO nanocomposite is constructed by a simple solvothermal-assisted assembly method combined with freeze-drying and annealing.In this novel nanostructure,hollow M0S2 nanocages are homogeneously distributed on graphene sheets with a tight bond of C-O-Mo.The nanosized and hollow MoS2 nanocages can effectively accommodate the huge volume change during charge/discharge process and increase the number of electrochemical reaction active sites,accelerating the kinetics of lithiation/delithiation.The tight C-O-Mo bond between graphene and MoS2 further reinforces the structural stability,thus improve the electrical conductivity and substantially enhance the lithium storage performance of M0S2 anode material.As a result,this novel nanocomposite shows a long-cycle stability of 717.4 mAh·g^-1 after 800 cycles at a high current density of 3 A·g^-1,exhibiting great potential as an anode nanocomposite for advanced lithium-ion batteries.
文摘Two-dimensional semiconductors,such as MoS2 are known to be highly susceptible to diverse molecular adsorbates on the surface during fabrication,which could adversely affect device performance.To ensure high device yield,uniformity and performance,the semiconductor industry has long employed wet chemical cleaning strategies to remove undesirable surface contaminations,adsorbates,and native oxides from the surface of Si wafers.A similarly effective surface cleaning technique for two-dimensional materials has not yet been fully developed.In this study,we propose a wet chemical cleaning strategy for MoS2 by using N-methyl-2-pyrrolidone.The cleaning process not only preserves the intrinsic properties of monolayer MoS2,but also significantly improves the performance of monolayer MoS2 field-effect-transistors.Superior device on current of 12 μA·μm-1 for a channel length of 400 nm,contact resistance of 15 kΩ·μm,field-effect mobility of 15.5 cm^2·V^-1·s^-1,and the average on-off current ratio of 10^8 were successfully demonstrated.
文摘Surface plasmon resonance (SPR) sensor based on the blue phosphorene/MoS2 hetero-structure is presented to enhance the performance parameters, i.e., sensitivity, detection accuracy, and quality fhctor.The blue phosphorene/MoS2 hetero-structure works as an interacting layer with the analyte for the enhancement of the sensitivity of the sensor. It is observed that the sensitivity of blue phosphorene/MoS2 based sensor (i.e., structure-Ⅱ) is improved by 5.75%, from the conventional sensor (i.e., structure-Ⅲ). Further, an additional silicon nanolayer is introduced between the metal layer and blue phosphorene/MoS2 hetero-structure. The sensitivity of the proposed blue phosphorene/MoS2 hetero-structure with a silicon layer SPR sensor, i.e., structure-Ⅰ, is enhanced by 44.76% from structure-Ⅱ and 55.75% from structure-Ⅲ due to an enhancement in the evanescent field near the metal-analyte interface. Finally, it is observed that at the optimum thickness of silicon between the gold layer and blue phosphorene/MoS2, performance parameters of the sensor are enhanced.
基金This work was supported by the National Key Research and Development Program of China(No.2017YFB1002900)the National Natural Science Foundation of China(Nos.21571101,51322202,51832001)+1 种基金the Natural Science Foundation of Jiangsu Province in China(No.BK20161543)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.15KJB430016).
文摘Recently,transition metal dichalcogenides(TMDCs)nanoscrolls have exhibited unique electronic and optical properties due to their spiral tubular structures,which are formed by rolling up monolayer TMDCs nanosheets.Inspired by the excellent physical and chemical properties of TMDCs van der Waals heterostructures(vdWHs),it is highly desirable to scroll TMDCs vdWHs for potential optoelectronic applications.In this work,WS2/MoS2 vdWHs nanoscrolls were massively prepared by dropping aqueous alkaline droplet on chemical vapor deposition(CVD)-grown bilayer WS2/MoS2 vdWHs,which were formed by growing monolayer WS2 islands on top of monolayer MoS2 nanosheets simultaneously.The optical microscopy(OM),atomic force microscopy(AFM),ultralow frequency(ULF)Raman spectroscopy and transmission electron microscopy(TEM)were utilized to characterize the WS2/MoS2 vdWHs nanoscrolls.As-obtained WS2/MoS2 vdWHs nanoscrolls exhibited new ULF breathing mode as well as shear mode peaks due to the strong interlayer interaction.Notably,the photosensitivities of WS2/MoS2 vdWHs nanoscrolls-based devices were about ten times higher than those of WS2/MoS2 vdWHs-based devices under blue,green and red lasers,respectively,which could be attributed to the ultrafast charge transfer at alternative WS2/MoS2 and MoS2/WS2 multi-interfaces in scrolled structure.Our work suggested that TMDCs vdWHs scrolls could be promising candidates for optoelectronic applications.
