Low-dimensional materials have excellent properties which are closely related to their dimensionality.However,the growth mechanism underlying tunable dimensionality from 2D triangles to 1D ribbons of such materials is...Low-dimensional materials have excellent properties which are closely related to their dimensionality.However,the growth mechanism underlying tunable dimensionality from 2D triangles to 1D ribbons of such materials is still unrevealed.Here,we establish a general kinetic Monte Carlo model for transition metal dichalcogenides(TMDs) growth to address such an issue.Our model is able to reproduce several key findings in experiments,and reveals that the dimensionality is determined by the lattice mismatch and the interaction strength between TMDs and the substrate.We predict that the dimensionality can be well tuned by the interaction strength and the geometry of the substrate.Our work deepens the understanding of tunable dimensionality of low-dimensional materials and may inspire new concepts for the design of such materials with expected dimensionality.展开更多
Developing suitable electrode materials capable of tolerating severe structural deformation and overcoming sluggish reaction kinetics resulting from the large radius of potassium ion(K+)insertion is critical for pract...Developing suitable electrode materials capable of tolerating severe structural deformation and overcoming sluggish reaction kinetics resulting from the large radius of potassium ion(K+)insertion is critical for practical applications of potassium-ion batteries(PIBs).Herein,a superior anode material featuring an intriguing hierarchical structure where assembled MoSSe nanosheets are tightly anchored on a highly porous micron-sized carbon sphere and encapsulated within a thin carbon layer(denoted as Cs@MoSSe@C)is reported,which can significantly boost the performance of PIBs.The assembled MoSSe nanosheets with expanded interlayer spacing and rich anion vacancy can facilitate the intercalation/deintercalation of K+and guarantee abundant active sites together with a low K+diffusion barrier.Meanwhile,the thin carbon protective layer and the highly porous carbon sphere matrix can alleviate the volume expansion and enhance the charge transport within the composite.Under these merits,the as-prepared Cs@MoSSe@C anode exhibits a high reversible capacity(431.8 mAh g^(-1) at 0.05 A g^(-1)),good rate capability(161 mAh g^(-1) at 5 A g^(-1)),and superior cyclic performance(70.5%capacity retention after 600 cycles at 1 A g^(-1)),outperforming most existing Mo-based S/Se anodes.The underlying mechanisms and origins of superior performance are elucidated by a set of correlated in-situ/ex-situ characterizations and theoretical calculations.Further,a PIB full cell based on Cs@MoSSe@C anode also exhibits an impressive electrochemical performance.This work provides some insights into developing high-performance PIBs anodes with transition-metal chalcogenides.展开更多
Two-dimensional(2 D) transition metal dichalcogenides(TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and ...Two-dimensional(2 D) transition metal dichalcogenides(TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and optical properties. Controlling the thickness and doping of 2 D TMDCs are crucial toward their future applications. Here, we report an effective HAu Cl4 treatment method and achieve simultaneous thinning and doping of various TMDCs in one step. We find that the HAu Cl4 treatment not only thins thick Mo S2 flakes into few layers or even monolayers, but also simultaneously tunes Mo S2 into p-type. The effects of various parameters in the process have been studied systematically,and an Au intercalation assisted thinning and doping mechanism is proposed. Importantly, this method also works for other typical TMDCs, including WS2, Mo Se2 and WSe2,showing good universality. Electrical transport measurements of field-effect transistors(FETs) based on Mo S2 flakes show a big increase of On/Off current ratios(from 102 to 107) after the HAu Cl4 treatment. Meanwhile, the subthreshold voltages of the Mo S2 FETs shift from-60 to +27 V after the HAu Cl4 treatment, with a p-type doping behavior. This study provides an effective and simple method to control the thickness and doping properties of 2 D TMDCs, paving a way for their applications in high performance electronics and optoelectronics.展开更多
MoS_(2)is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability.However,the poor conductivity and low activity limit its catalytic performance;furthermore,MoS_(2)is una...MoS_(2)is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability.However,the poor conductivity and low activity limit its catalytic performance;furthermore,MoS_(2)is unable to satisfy the requirements of most industrial applications.In this study,to obtain a P-doped MoS_(2)catalyst with S vacancy defects,P is inserted into the MoS_(2)matrix via a solid phase ion exchange at room temperature.The optimal P-doping amount is 11.4 wt%,and the resultant catalyst delivers excellent electrocatalytic properties for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)with the corresponding overpotentials of 93 and 316 mV at 10 mA cm^(-2) in an alkaline solution;these values surpass the overpotentials of most previously reported MoS_(2)-based materials.Theoretical calculations and results demonstrate that the synergistic effect of the doped P,which forms active centers in the basal plane of MoS_(2),and S vacancy defects caused by P doping intensifies the intrinsic electronic conductivity and electrocatalytic activity of the catalyst.Density functional theory calculations demonstrate that P optimizes the free energy of the MoS_(2)matrix for hydrogen adsorption,thereby considerably increasing the intrinsic activity of the doped catalyst for the HER compared with that observed from pristine MoS_(2).The enhanced catalytic activity of P-doped MoS_(2)for the OER is attributed to the ability of the doped P which facilitates the adsorption of hydroxyl and hydroperoxy intermediates and reduces the reaction energy barrier.This study provides a new environmentally friendly and convenient solid-phase ion exchange method to improve the electrocatalytic capability of two-dimensional transition-metal dichalcogenides in largescale applications.展开更多
Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surfa...Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surface and strong intralayer and interlayer bonding.However,the synthesis of non-layered 2D TMCs is challenging and this has made it difficult to study their structures and properties at thin thickness limit.Here,we develop a universal dual-metal precursors method to grow non-layered TMCs in which a mixture of a metal and its chloride serves as the metal source.Taking hexagonal Fe_(1-x)S as an example,the thickness of the Fe_(1-x)S flakes is down to 3 nm with a lateral size of over 100 μm.Importantly,we find ordered cation Fe vacancies in Fe_(1-x)S,which is distinct from layered TMCs like MoS_(2) where anion vacancies are commonly observed.Low-temperature transport measurements and theoretical calculations show that 2D Fe_(1-x)S is a stable semiconductor with a narrow bandgap of60 meV.In addition to Fe_(1-x)S,the method is universal in growing various non-layered 2D TMCs containing ordered cation vacancies,including Fe_(1-x)Se,Co_(1-x)S,Cr_(1-x)S,and V_(1-x)S.This work paves the way to grow and exploit properties of non-layered materials at 2D thickness limit.展开更多
Topological materials and topological phases have recently become a hot topic in condensed matter physics.In this work,we report an In-intercalated transition-metal dichalcogenide In_(x)TaSe_(2)(named 112 system),a to...Topological materials and topological phases have recently become a hot topic in condensed matter physics.In this work,we report an In-intercalated transition-metal dichalcogenide In_(x)TaSe_(2)(named 112 system),a topological nodal-line semimetal in the prep seffiffinffi ce of both charge density wave(CDW)and superconductivity.In the x=0.58 sample,the 2×√3 commensurate CDW(CCDW)and the 2×2 CCDW are observed below 116 and 77 K,respectively.Consistent with theoretical calculations,the spin–orbital coupling gives rise to two twofold-degenerate nodal rings(Weyl rings)connected by drumhead surface states,confirmed by angle-resolved photoemission spectroscopy.Our results suggest that the 2×2 CCDW ordering gaps out one Weyl ring in accordance with the CDW band folding,while the other Weyl ring remains gapless with intact surface states.In addition,superconductivity emerges at 0.91 K,with the upper critical field deviating from the s-wave behavior at low temperature,implying possibly unconventional superconductivity.Therefore,we think this type of the 112 system may possess abundant physical states and offer a platform to investigate the interplay between CDW,nontrivial band topology and superconductivity.展开更多
Two-dimensional(2D) transition metal dichalcogenides(TMDs) have gained much attention in virtue of their various atomic configurations and band structures.Apart from those thermodynamically stable phases, plenty of me...Two-dimensional(2D) transition metal dichalcogenides(TMDs) have gained much attention in virtue of their various atomic configurations and band structures.Apart from those thermodynamically stable phases, plenty of metastable phases exhibit interesting properties. To obtain 2D TMDs with specific phases, it is important to develop phase engineering strategies including phase transition and phaseselective synthesis. Phase transition is a conventional method to transform one phase to another, while phase-selective synthesis means the direct fabrication of the target phases for2D TMDs. In this review, we introduce the structures and stability of 2D TMDs with different phases. Then, we summarize the detailed processes and mechanism of the traditional phase transition strategies. Moreover, in view of the increasing demand of high-phase purity TMDs, we present the advanced phase-selective synthesis strategies. Finally, we underline the challenges and outlooks of phase engineering of 2D TMDs in two aspects-high phase purity and excellent controllability. This review may promote the development of controllable phase engineering for 2D TMDs and even other2D materials toward both fundamental studies and practical applications.展开更多
Two-dimensional(2D)materials and their heterostructures have been intensively studied in recent years due to their potential applications in electronic,optoelectronic,and spintronic devices.Nonetheless,the realization...Two-dimensional(2D)materials and their heterostructures have been intensively studied in recent years due to their potential applications in electronic,optoelectronic,and spintronic devices.Nonetheless,the realization of 2D heterostructures with atomically flat and clean interfaces remains challenging,especially for air-sensitive materials,which hinders the in-depth investigation of interface-induced phenomena and the fabrication of high-quality devices.Here,we circumvented this challenge by exfoliating 2D materials in an ultrahigh vacuum.Remarkably,ultraflat and clean substrate surfaces can assist the exfoliation of 2D materials,regardless of the substrate and 2D material,thus providing a universal method for the preparation of heterostructures with ideal interfaces.In addition,we studied the properties of two prototypical systems that cannot be achieved previously,including the electronic structure of monolayer phospherene and optical responses of transition metal dichalcogenides on different metal substrates.Our work paves the way to engineer rich interface-induced phenomena,such as proximity effects and moirésuperlattices.展开更多
基金supported by the Ministry of Science and Technology (No.2018YFA0208702)the National Natural Science Foundation of China (No.32090044,No. 21973085,No.21833007,No.21790350)+1 种基金Anhui Initiative in Quantum Information Technologies (AHY 090200)the Fundamental Research Funds for the Central Universities (WK2340000104)。
文摘Low-dimensional materials have excellent properties which are closely related to their dimensionality.However,the growth mechanism underlying tunable dimensionality from 2D triangles to 1D ribbons of such materials is still unrevealed.Here,we establish a general kinetic Monte Carlo model for transition metal dichalcogenides(TMDs) growth to address such an issue.Our model is able to reproduce several key findings in experiments,and reveals that the dimensionality is determined by the lattice mismatch and the interaction strength between TMDs and the substrate.We predict that the dimensionality can be well tuned by the interaction strength and the geometry of the substrate.Our work deepens the understanding of tunable dimensionality of low-dimensional materials and may inspire new concepts for the design of such materials with expected dimensionality.
基金supported by the National Natural Science Foundation of China(52072323,52122211,51872098,21975154,and22179078)the “Double-First Class”Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University+1 种基金the financial support from the Opening Project of National Joint Engineering Research Center for Abrasion Control and Molding of Metal MaterialsHenan Key Laboratory of High-temperature Structural and Functional Materials,Henan University of Science and Technology(HKDNM2019013)。
文摘Developing suitable electrode materials capable of tolerating severe structural deformation and overcoming sluggish reaction kinetics resulting from the large radius of potassium ion(K+)insertion is critical for practical applications of potassium-ion batteries(PIBs).Herein,a superior anode material featuring an intriguing hierarchical structure where assembled MoSSe nanosheets are tightly anchored on a highly porous micron-sized carbon sphere and encapsulated within a thin carbon layer(denoted as Cs@MoSSe@C)is reported,which can significantly boost the performance of PIBs.The assembled MoSSe nanosheets with expanded interlayer spacing and rich anion vacancy can facilitate the intercalation/deintercalation of K+and guarantee abundant active sites together with a low K+diffusion barrier.Meanwhile,the thin carbon protective layer and the highly porous carbon sphere matrix can alleviate the volume expansion and enhance the charge transport within the composite.Under these merits,the as-prepared Cs@MoSSe@C anode exhibits a high reversible capacity(431.8 mAh g^(-1) at 0.05 A g^(-1)),good rate capability(161 mAh g^(-1) at 5 A g^(-1)),and superior cyclic performance(70.5%capacity retention after 600 cycles at 1 A g^(-1)),outperforming most existing Mo-based S/Se anodes.The underlying mechanisms and origins of superior performance are elucidated by a set of correlated in-situ/ex-situ characterizations and theoretical calculations.Further,a PIB full cell based on Cs@MoSSe@C anode also exhibits an impressive electrochemical performance.This work provides some insights into developing high-performance PIBs anodes with transition-metal chalcogenides.
基金support from the National Natural Science Foundation of China (51722206 and 11674150)the Youth 1000-Talent Program of China+3 种基金the Economic, Trade and Information Commission of Shenzhen Municipality for the “2017 Graphene Manufacturing Innovation Center Project” (201901171523)Shenzhen Basic Research Project (JCYJ20170307140956657 and JCYJ20160613160524999)Guangdong Innovative and Entrepreneurial Research Team Program (2017ZT07C341 and 2016ZT06D348)the Development and Reform Commission of Shenzhen Municipality for the development of the “Low-Dimensional Materials and Devices” discipline
文摘Two-dimensional(2 D) transition metal dichalcogenides(TMDCs) have drawn intensive attention due to their ultrathin feature with excellent electrostatic gating capability, and unique thickness-dependent electronic and optical properties. Controlling the thickness and doping of 2 D TMDCs are crucial toward their future applications. Here, we report an effective HAu Cl4 treatment method and achieve simultaneous thinning and doping of various TMDCs in one step. We find that the HAu Cl4 treatment not only thins thick Mo S2 flakes into few layers or even monolayers, but also simultaneously tunes Mo S2 into p-type. The effects of various parameters in the process have been studied systematically,and an Au intercalation assisted thinning and doping mechanism is proposed. Importantly, this method also works for other typical TMDCs, including WS2, Mo Se2 and WSe2,showing good universality. Electrical transport measurements of field-effect transistors(FETs) based on Mo S2 flakes show a big increase of On/Off current ratios(from 102 to 107) after the HAu Cl4 treatment. Meanwhile, the subthreshold voltages of the Mo S2 FETs shift from-60 to +27 V after the HAu Cl4 treatment, with a p-type doping behavior. This study provides an effective and simple method to control the thickness and doping properties of 2 D TMDCs, paving a way for their applications in high performance electronics and optoelectronics.
基金supported by the National Natural Science Foundation of China(52072196)the Major Basic Research Program of the Natural Science Foundation of Shandong Province(ZR2020ZD09)。
文摘MoS_(2)is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability.However,the poor conductivity and low activity limit its catalytic performance;furthermore,MoS_(2)is unable to satisfy the requirements of most industrial applications.In this study,to obtain a P-doped MoS_(2)catalyst with S vacancy defects,P is inserted into the MoS_(2)matrix via a solid phase ion exchange at room temperature.The optimal P-doping amount is 11.4 wt%,and the resultant catalyst delivers excellent electrocatalytic properties for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)with the corresponding overpotentials of 93 and 316 mV at 10 mA cm^(-2) in an alkaline solution;these values surpass the overpotentials of most previously reported MoS_(2)-based materials.Theoretical calculations and results demonstrate that the synergistic effect of the doped P,which forms active centers in the basal plane of MoS_(2),and S vacancy defects caused by P doping intensifies the intrinsic electronic conductivity and electrocatalytic activity of the catalyst.Density functional theory calculations demonstrate that P optimizes the free energy of the MoS_(2)matrix for hydrogen adsorption,thereby considerably increasing the intrinsic activity of the doped catalyst for the HER compared with that observed from pristine MoS_(2).The enhanced catalytic activity of P-doped MoS_(2)for the OER is attributed to the ability of the doped P which facilitates the adsorption of hydroxyl and hydroperoxy intermediates and reduces the reaction energy barrier.This study provides a new environmentally friendly and convenient solid-phase ion exchange method to improve the electrocatalytic capability of two-dimensional transition-metal dichalcogenides in largescale applications.
基金supported by the National Science Fund for Distinguished Young Scholars(52125309)the National Natural Science Foundation of China(51991343,51920105002,51991340,52188101,and 11974156)+3 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2017ZT07C341 and 2019ZT08C044)the Bureau of Industry and Information Technology of Shenzhen for the “2017 Graphene Manufacturing Innovation Center Project”(201901171523)Shenzhen Basic Research Project(JCYJ20200109144616617 and JCYJ20190809180605522)Shenzhen Science and Technology Program(KQTD20190929173815000 and 20200925161102001)。
文摘Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surface and strong intralayer and interlayer bonding.However,the synthesis of non-layered 2D TMCs is challenging and this has made it difficult to study their structures and properties at thin thickness limit.Here,we develop a universal dual-metal precursors method to grow non-layered TMCs in which a mixture of a metal and its chloride serves as the metal source.Taking hexagonal Fe_(1-x)S as an example,the thickness of the Fe_(1-x)S flakes is down to 3 nm with a lateral size of over 100 μm.Importantly,we find ordered cation Fe vacancies in Fe_(1-x)S,which is distinct from layered TMCs like MoS_(2) where anion vacancies are commonly observed.Low-temperature transport measurements and theoretical calculations show that 2D Fe_(1-x)S is a stable semiconductor with a narrow bandgap of60 meV.In addition to Fe_(1-x)S,the method is universal in growing various non-layered 2D TMCs containing ordered cation vacancies,including Fe_(1-x)Se,Co_(1-x)S,Cr_(1-x)S,and V_(1-x)S.This work paves the way to grow and exploit properties of non-layered materials at 2D thickness limit.
基金the National Key R&D Program of the China(2016YFA0300402,2014CB648400,and 2016YFA0300203)the National Natural Science Foundation of China(11774305 and 11274006)the Fundamental Research Funds for the Central Universities of China。
文摘Topological materials and topological phases have recently become a hot topic in condensed matter physics.In this work,we report an In-intercalated transition-metal dichalcogenide In_(x)TaSe_(2)(named 112 system),a topological nodal-line semimetal in the prep seffiffinffi ce of both charge density wave(CDW)and superconductivity.In the x=0.58 sample,the 2×√3 commensurate CDW(CCDW)and the 2×2 CCDW are observed below 116 and 77 K,respectively.Consistent with theoretical calculations,the spin–orbital coupling gives rise to two twofold-degenerate nodal rings(Weyl rings)connected by drumhead surface states,confirmed by angle-resolved photoemission spectroscopy.Our results suggest that the 2×2 CCDW ordering gaps out one Weyl ring in accordance with the CDW band folding,while the other Weyl ring remains gapless with intact surface states.In addition,superconductivity emerges at 0.91 K,with the upper critical field deviating from the s-wave behavior at low temperature,implying possibly unconventional superconductivity.Therefore,we think this type of the 112 system may possess abundant physical states and offer a platform to investigate the interplay between CDW,nontrivial band topology and superconductivity.
基金supported by the National Natural Science Foundation of China (21673161 and 21473124)the Science and Technology Department of Hubei Province (2017AAA114)the Sino-German Center for Research Promotion (1400)
文摘Two-dimensional(2D) transition metal dichalcogenides(TMDs) have gained much attention in virtue of their various atomic configurations and band structures.Apart from those thermodynamically stable phases, plenty of metastable phases exhibit interesting properties. To obtain 2D TMDs with specific phases, it is important to develop phase engineering strategies including phase transition and phaseselective synthesis. Phase transition is a conventional method to transform one phase to another, while phase-selective synthesis means the direct fabrication of the target phases for2D TMDs. In this review, we introduce the structures and stability of 2D TMDs with different phases. Then, we summarize the detailed processes and mechanism of the traditional phase transition strategies. Moreover, in view of the increasing demand of high-phase purity TMDs, we present the advanced phase-selective synthesis strategies. Finally, we underline the challenges and outlooks of phase engineering of 2D TMDs in two aspects-high phase purity and excellent controllability. This review may promote the development of controllable phase engineering for 2D TMDs and even other2D materials toward both fundamental studies and practical applications.
基金supported by the Ministry of Science and Technology of China(2018YFE0202700 and 2019YFA0308000)the National Natural Science Foundation of China(11974391,11825405,1192780039,62022089,11874405,and U2032204)+3 种基金the Beijing Natural Science Foundation(Z180007)the International Partnership Program of Chinese Academy of Sciences(112111KYSB20200012)Chongqing Outstanding Youth Fund(2021ZX0400005)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB33030100 and XDB33000000)。
文摘Two-dimensional(2D)materials and their heterostructures have been intensively studied in recent years due to their potential applications in electronic,optoelectronic,and spintronic devices.Nonetheless,the realization of 2D heterostructures with atomically flat and clean interfaces remains challenging,especially for air-sensitive materials,which hinders the in-depth investigation of interface-induced phenomena and the fabrication of high-quality devices.Here,we circumvented this challenge by exfoliating 2D materials in an ultrahigh vacuum.Remarkably,ultraflat and clean substrate surfaces can assist the exfoliation of 2D materials,regardless of the substrate and 2D material,thus providing a universal method for the preparation of heterostructures with ideal interfaces.In addition,we studied the properties of two prototypical systems that cannot be achieved previously,including the electronic structure of monolayer phospherene and optical responses of transition metal dichalcogenides on different metal substrates.Our work paves the way to engineer rich interface-induced phenomena,such as proximity effects and moirésuperlattices.
