Moiré superlattices arising from growth induced by screw dislocations in layered materials

Moiré superlattices(MSLs) are modulated structures produced from homogeneous or heterogeneous two-dimensional layers stacked with a twist angle and/or lattice mismatch. Enriching the methods for fabricating MSL and realizing the unique emergent properties are key challenges in its investigation. Here we recommend that the spiral dislocation driven growth is another optional method for the preparation of high quality MSL samples. The spiral structure stabilizes the constant out-of-plane lattice distance, causing the variations in electronic and optical properties. Taking SnS_(2) MSL as an example, we find prominent properties including large band gap reduction(~ 0.4 e V) and enhanced optical activity. Firstprinciples calculations reveal that these unusual properties can be ascribed to the locally enhanced interlayer interaction associated with the Moiré potential modulation. We believe that the spiral dislocation driven growth would be a powerful method to expand the MSL family and broaden their scope of application.

Recent Progress and Regulation Strategies of Layered Materials as Cathode of Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries(ZIBs)have shown great potential in the fields of wearable devices,consumer electronics,and electric vehicles due to their high level of safety,low cost,and multiple electron transfer.The layered cathode materials of ZIBs hold a stable structure during charge and discharge reactions owing to the ultrafast and straightforward(de)intercalation-type storage mechanism of Zn^(2+)ions in their tunable interlayer spacing and their abilities to accommodate other guest ions or molecules.Nevertheless,the challenges of inadequate energy density,dissolution of active materials,uncontrollable byproducts,increased internal pressure,and a large de-solvation penalty have been deemed an obstacle to the development of ZIBs.In this review,recent strategies on the structure regulation of layered materials for aqueous zinc-ion energy storage devices are systematically summarized.Finally,critical science challenges and future outlooks are proposed to guide and promote the development of advanced cathode materials for ZIBs.

Recent advances in two-dimensional layered and non-layered materials hybrid heterostructures

With the development of Moore's law, the future trend of devices will inevitably be shrinking and integration to further achieve size reduction. The emergence of new two-dimensional non-layered materials(2DNLMs) not only enriches the 2D material family to meet future development, but also stimulates the global enthusiasm for basic research and application technologies in the 2D field. Van der Waals(vd W) heterostructures, in which two-dimensional layered materials(2DLMs)are physically stacked layer by layer, can also occur between 2DLMs and 2DNLMs hybrid heterostructures, providing an alternative platform for nanoelectronics and optoelectronic applications. Here, we outline the recent developments of2DLMs/2DNLMs hybrid heterostructures, with particular emphasis on major advances in synthetic methods and applications. And the categories and crystal structures of 2DLMs and 2DNLMs are also shown. We highlight some promising applications of the heterostructures in electronics, optoelectronics, and catalysis. Finally, we provide conclusions and future prospects in the 2D materials field.

Note:Molecular simulation of the adsorption of linear alkane mixtures in pillared layered materials

The adsorption isotherms of mixtures of linear alkanes, involving n-pentane, n-hexane, and n-heptane in pillared layered materials (PLMs) with three different porosities Ψ=0.98, 0.94 and 0.87, and three pore widths H=1.02, 1.70 and 2.38 nm at temperature T=300 K were simulated by using configurational-bias Monte Carlo (CBMC) techniques in grand canonical ensemble.A grid model was employed to calculate the interaction between a fluid molecule and two layered boards here. For alkane mixtures,the n-heptane, the longest chain component in alkane mixtures, is preferentially adsorbed at low pressures, with its adsorption increasing and then decreasing as the pressure increases continuously while the n-pentane, the shortest chain component in alkane mixtures, is still adsorbed at high pressures; the adsorption of the longest chain component of alkane mixtures increases as the pore width and the porosity of PLMs increase.

Cycling performance of layered oxide cathode materials for sodium-ion batteries

Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the application prospects of batteries.However,facing challenges,including phase transitions,ambient stability,side reactions,and irreversible anionic oxygen activity,the cycling performance of layered oxide cathode materials still cannot meet the application requirements.Therefore,this review proposes several strategies to address these challenges.First,bulk doping is introduced from three aspects:cationic single doping,anionic single doping,and multi-ion doping.Second,homogeneous surface coating and concentration gradient modification are reviewed.In addition,methods such as mixed structure design,particle engineering,high-entropy material construction,and integrated modification are proposed.Finally,a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.

Integrating 2D layered materials with 3D bulk materials as van der Waals heterostructures for photodetections:Current status and perspectives

In the last decade,two-dimensional layered materials(2DLMs)have been drawing extensive attentions due to their unique properties,such as absence of surface dangling bonds,thickness-dependent bandgap,high absorption coeffi-cient,large specific surface area,and so on.But the high-quality growth and transfer of wafer-scale 2DLMs films is still a great challenge for the commerciali-zation of pure 2DLMs-based photodetectors.Conversely,the material growth and device fabrication technologies of three-dimensional(3D)semiconductors photodetectors tend to be gradually matured.However,the further improvement of the photodetection performance is limited by the difficult heterogeneous inte-gration or the inferior crystal quality via heteroepitaxy.Fortunately,2D/3D van der Waals heterostructures(vdWH)combine the advantages of the two types of materials simultaneously,which may provide a new platform for developing high-performance optoelectronic devices.Here,we first discuss the unique advantages of 2D/3D vdWH for the future development of photodetection field and simply introduce the structure categories,working mechanisms,and the typical fabrication methods of 2D/3D vdWH photodetector.Then,we outline the recent progress on 2D/3D vdWH-based photodetection devices integrating 2DLMs with the traditional 3D semiconductor materials,including Si,Ge,GaAs,AlGaN,SiC,and so on.Finally,we highlight the current challenges and pros-pects of heterointegrating 2DLMs with traditional 3D semiconductors toward photodetection applications.

Anisotropic phonon thermal transport in two-dimensional layered materials

Two-dimensional layered materials(2DLMs)have attracted growing attention in optoelectronic devices due to their intriguing anisotropic physical properties.Different members of 2DLMs exhibit unique anisotropic electrical,optical,and thermal properties,fundamentally related to their crystal structure.Among them,directional heat transfer plays a vital role in the thermal management of electronic devices.Here,we use density functional theory calculations to investigate the thermal transport properties of representative layered materials:β-InSe,γ-InSe,MoS2,and h-BN.We found that the lattice thermal conductivities ofβ-InSe,γ-InSe,MoS_(2),and h-BN display diverse anisotropic behaviors with anisotropy ratios of 10.4,9.4,64.9,and 107.7,respectively.The analysis of the phonon modes further indicates that the phonon group velocity is responsible for the anisotropy of thermal transport.Furthermore,the low lattice thermal conductivity of the layered InSe mainly comes from low phonon group velocity and atomic masses.Our findings provide a fundamental physical understanding of the anisotropic thermal transport in layered materials.We hope this study could inspire the advancement of 2DLMs thermal management applications in next-generation integrated electronic and optoelectronic devices.

Bioinspired activation of silent synapses in layered materials for extensible neuromorphic computing

Activation of silent synapses is of great significance for the extension of neural plasticity related to learning and memory.Inspired by the activation of silent synapses via receptor insertion in neural synapses,we propose an efficient method for activating artificial synapses through the intercalation of Sn in layered a-MoO_(3).Sn intercalation is capable of switching on the response of layered a-MoO_(3)to the stimuli of visible and near infrared light by decreasing the bandgap.This mimics the receptor insertion process in silent neural synapses.The Sn-intercalated MoO_(3)(Sn-MoO_(3))exhibits persistent photoconductivity due to the donor impurity induced by Sn intercalation.This enables the two-terminal Sn-MoO_(3)device promising optoelectronic synapse with an ultrahigh paired pulse facilitation(PPF)up to 199.5%.On-demand activation and tunable synaptic plasticity endow the device great potentials for extensible neuromorphic computing.Superior performance of the extensible artificial neural network(ANN)based on the Sn-MoO_(3)synapses are demonstrated in pattern recognition.Impressively,the recognition accuracy increases from 89.7%to 94.8%by activating more nodes into the ANN.This is consistent with the recognition process of physical neural network during brain development.The intercalation engineering of MoO_(3)may provide inspirations for the design of high-performance neuromorphic computing architectures.

Degradation analysis and doping modification optimization for high-voltage P-type layered cathode in sodium-ion batteries

Advancing high-voltage stability of layered sodium-ion oxides represents a pivotal avenue for their progress in energy storage applications.Despite this,a comprehensive understanding of the mechanisms underpinning their structural deterioration at elevated voltages remains insufficiently explored.In this study,we unveil a layer delamination phenomenon of Na_(0.67)Ni_(0.3)Mn_(0.7)O_(2)(NNM)within the 2.0-4.3 V voltage,attributed to considerable volumetric fluctuations along the c-axis and lattice oxygen reactions induced by the simultaneous Ni^(3+)/Ni^(4+)and anion redox reactions.By introducing Mg doping to diminished Ni-O antibonding,the anion oxidation-reduction reactions are effectively mitigated,and the structural integrity of the P2 phase remains firmly intact,safeguarding active sites and precluding the formation of novel interfaces.The Na_(0.67)Mg_(0.05)Ni_(0.25)Mn_(0.7)O_(2)(NMNM-5)exhibits a specific capacity of100.7 mA h g^(-1),signifying an 83%improvement compared to the NNM material within the voltage of2.0-4.3 V.This investigation underscores the intricate interplay between high-voltage stability and structural degradation mechanisms in layered sodium-ion oxides.

High-sensitivity shortwave infrared photodetectors of metal-organic frameworks integrated on 2D layered materials

Photodetectors operating in the shortwave infrared region are of great significance due to their extensive applications in both commercial and military fields.Narrowbandgap two-dimensional layered materials(2DLMs)are considered as the promising candidates for constructing nextgeneration high-performance infrared photodetectors.Nevertheless,the performance of 2DLMs-based photodetectors can hardly satisfy the requirements of practical applications due to their weak optical absorption.In the present study,a strategy was proposed to design high-performance shortwave infrared photodetectors by integrating metalorganic frameworks(MOFs)nanoparticles with excellent optical absorption characteristics and 2DLM with high mobility.Further,this study demonstrated the practicability of this strategy in a MOF/2DLM(Ni-CAT-1/Bi_(2)Se_(3))hybrid heterojunction photodetector.Due to the transfer of photo-generated carriers from the MOF to Bi_(2)Se_(3),the MOF nanoparticles integrated on the Bi_(2)Se_(3) layer can increase the photocurrent by 2-3 orders of magnitude.The resulting photodetector presented a high responsivity of 4725 A W^(−1) and a superior detectivity of 3.5×10^(13) Jones at 1500 nm.The outstanding performance of the hybrid heterojunction arises from the synergistic function of the enhanced optical absorption and photogating effect.In addition,the proposed device construction strategy combining MOF photosensitive materials with 2DLMs shows a high potential for the future high-performance shortwave infrared photodetectors.

Recent progress and prospective on layered anode materials for potassium-ion batteries

Potassium-ion batteries(PIBs),also known as“novel post-lithium-ion batteries,”have promising energy storage and utilization prospects due to their abundant and inexpensive raw materials.Appropriate anode materials are critical for realizing high-performance PIBs because they are an important component determining the energy and power densities.Two-dimensional(2D)layered anode materials with increased interlayer distances,specific surface areas,and more active sites are promising candidates for PIBs,which have a high reversible capacity in the energetic pathway.In this review,we briefly summarize K+storage behaviors in 2D layered carbon,transition metal chalcogenides,and MXene materials and provide some suggestions on how to select and optimize appropriate 2D anode materials to achieve ideal electrochemical performance.

Domain-Decomposition Localized Method of Fundamental Solutions for Large-Scale Heat Conduction in Anisotropic Layered Materials

The localized method of fundamental solutions(LMFS)is a relatively new meshless boundary collocation method.In the LMFS,the global MFS approxima-tion which is expensive to evaluate is replaced by local MFS formulation defined in a set of overlapping subdomains.The LMFS algorithm therefore converts differential equations into sparse rather than dense matrices which are much cheaper to calcu-late.This paper makes thefirst attempt to apply the LMFS,in conjunction with a domain-decomposition technique,for the numerical solution of steady-state heat con-duction problems in two-dimensional(2D)anisotropic layered materials.Here,the layered material is decomposed into several subdomains along the layer-layer inter-faces,and in each of the subdomains,the solution is approximated by using the LMFS expansion.On the subdomain interface,compatibility of temperatures and heatfluxes are imposed.Preliminary numerical experiments illustrate that the proposed domain-decomposition LMFS algorithm is accurate,stable and computationally efficient for the numerical solution of large-scale multi-layered materials.

Research Advances of Typical Two Dimensional Layered Thermoelectric Materials

Thermoelectric technologies have caught our intense attention due to their ability of heat conversion into electricity.The considerable efforts have been taken to develop and enhance thermoelectric properties of materials over the past several decades.Recently,twodimensional layered materials are making the promise for potential applications of thermoelectric devices because of the excellent physical and structural properties.Here,a comprehensive coverage about recent progresses in thermoelectric properties of typical two dimensional(2D)layered materials,including the theoretical and experimental results,is provided.Moreover,the potential applications of 2D thermoelectric materials are also involved.These results indicate that the development of 2D thermoelectric materials take a key role in the flexible electronic devices with thermoelectric technologies.

Size effects in two-dimensional layered materials modeled by couple stress elasticity

In the present study,the effect of material microstructure on the mechanical response of a two-dimensional elastic layer perfectly bonded to a substrate is examined under surface loadings.In the current model,the substrate is treated as an elastic half plane as opposed to a rigid base,and this enables its applications in practical cases when the modulus of the layer(e.g.,the coating material)and substrate(e.g.,the coated surface)are comparable.The material microstructure is modeled using the generalized continuum theory of couple stress elasticity.The boundary value problems are formulated in terms of the displacement field and solved in an analytical manner via the Fourier transform and stiffness matrix method.The results demonstrate the capability of the present continuum theory to efficiently model the size-dependency of the response of the material when the external and internal length scales are comparable.Furthermore,the results indicated that the material mismatch and substrate stiffness play a crucial role in the predicted elastic field.Specifically,the study also addresses significant discrepancy of the response for the case of a layer resting on a rigid substrate.

Recent advances in the electrochemistry of layered post-transition metal chalcogenide nanomaterials for hydrogen evolution reaction

Layered two-dimensional(2 D)materials have received tremendous attention due to their unique physical and chemical properties when downsized to single or few layers.Several types of layered materials,especially transition metal dichalcogenides(TMDs)have been demonstrated to be good electrode materials due to their interesting physical and chemical properties.Apart from TMDs,post-transition metal chalcogenides(PTMCs)recently have emerged as a family of important semiconducting materials for electrochemical studies.PTMCs are layered materials which are composed of post-transition metals raging from main group IIIA to group VA(Ga,In,Ge,Sn,Sb and Bi)and group VI chalcogen atoms(S,selenium(Se)and tellurium(Te)).Although a large number of literatures have reviewed the electrochemical and electrocatalytic applications of TMDs,less attention has been focused on PTMCs.In this review,we focus our attention on PTMCs with the aim to provide a summary to describe their fundamental electrochemical properties and electrocatalytic activity towards hydrogen evolution reaction(HER).The characteristic chemical compositions and crystal structures of PTMCs are firstly discussed,which are different from TMDs.Then,inherent electrochemistry of PTMCs is discussed to unveil the well-defined redox behaviors of PTMCs,which could potentially affect their efficiency when applied as electrode materials.Following,we focus our attention on electrocatalytic activity of PTMCs towards HER including novel synthetic strategies developed for the optimization of their HER activity.This review ends with the perspectives for the future research direction in the field of PTMC based electrocatalysts.

Thermodynamically Revealing the Essence of Order and Disorder Structures in Layered Cathode Materials

Layered transition metal(TM) oxides are one of the most widely used cathode materials in lithium-ion batteries. The atomic configuration in TM layer of these materials is often known to be random when multiple TM elements co-exist in the layer(e.g. Ni, Co and Mn). By contrast, the configuration tends to be ordered if the elements are Li and Mn. Here, by using special quasi-random structures(SQS) algorithm, the essential reasons of the ordering in a promising Li-rich Mn-based cathode material Li2MnO3 are investigated. The difference of internal energy and entropy between ordered and disordered materials is calculated. As a result, based on the Gibbs free energy, it is found that Li2MnO3 should have an ordered structure in TM layer. In comparison, structures with Ni-Mn ratio of 2:1 are predicted to have a disordered TM layer, because the entropy terms have larger impact on the structural ordering than internal energy terms.

Intercalation of Two-dimensional Layered Materials

Two-dimensional(2D)layered materials have attracted great attention due to their unique electrical,optical,thermal and mechanical properties.2D layered materials have miique van der Waals gaps,thus the foreign substance,such as atoms,molecules and ions,can be inserted into the gaps to change the physical and chemical properties of 2D layered materials,which is conducive to realize their multi-fimctional application.Herein,we present a critical review of recent research progress of 2D intercalated materials,including the synthesizing metliods,theoretical calculation,characterization and multifunctional application.Finally,we will summarize llie current challenges and future opportunities in the development of 2D intercalated materials.

Recent Progress and Prospects of Layered Cathode Materials for Potassium-ion Batteries

Layered materials with two-dimensional ion diffusion channels and fast kinetics are attractive as cathode materials for secondary batteries.However,one main challenge in potassium-ion batteries is the large ion size of K^(+),along with the strong K^(+)-K^(+)electrostatic repulsion.This strong interaction results in initial K deficiency,greater voltage slope,and lower specific capacity between set voltage ranges for layered transition metal oxides.In this review,a comprehensive review of the latest advancements in layered cathode materials for potassium-ion batteries is presented.Except for layered transition metal oxides,some polyanionic compounds,chalcogenides,and organic materials with the layered structure are introduced separately.Furthermore,summary and personal perspectives on future optimization and structural design of layered cathode materials are constructively discussed.We strongly appeal to the further exploration of layered polyanionic compounds and have demonstrated a series of novel layered structures including layered K_(3)V_(2)(PO_(4))_(3).

Unlocking high-rate O3 layered oxide cathode for Na-ion batteries via ion migration path modulation

O3-NaNi1/3Fe1/3Mn1/3O2is a promising layered cathode material with high specific capacity,low cost,and simple synthesis.However,sluggish kinetic hindrance is attributed to the size discrepancy between the large Na-ion and narrow tetrahedral interstitial positions,leading to inferior rate capacity and low reversible capacity.Herein,F with light-weight and strong electronegativity is introduced to substitute O atoms in the bulk structure,which intensifies the bond strength of transition metal and oxygen and enlarges the Na+diffusion channel.In addition,density-functional theory(DFT) calculations demonstrate that the electrostatic interaction is weakened between Na+in the tetrahedral site and the transitionmetal cation directly below it,dramatically reducing the migration barriers of Na+diffusion.Consequently,the as-obtained NaNi1/3Fe1/3Mn1/3O1.95F0.05sample displays outstanding rate performance of 86.7 mA h g^(-1)at 10 C and excellent capacity retention of 84.1% after 100 cycles at 2 C.Moreover,a full cell configuration using a hard carbon anode reaches the energy density of 307.7 Wh kg^(-1).This strategy paves the way for novel means of modulating the Na-ion migration path for high-rate O3-type layered cathode materials.

Multilayered PdTe_(2)/thin Si heterostructures as self-powered flexible photodetectors with heart rate monitoring ability

Two-dimensional layered material/semiconductor heterostructures have emerged as a category of fascinating architectures for developing highly efficient and low-cost photodetection devices.Herein,we present the construction of a highly efficient flexible light detector operating in the visible-near infrared wavelength regime by integrating a PdTe2 multilayer on a thin Si film.A representative device achieves a good photoresponse performance at zero bias including a sizeable current on/off ratio exceeding 105,a decent responsivity of~343 mA/W,a respectable specific detectivity of~2.56×10^(12)Jones,and a rapid response time of 4.5/379μs,under 730 nm light irradiation.The detector also displays an outstanding long-term air stability and operational durability.In addition,thanks to the excellent flexibility,the device can retain its prominent photodetection performance at various bending radii of curvature and upon hundreds of bending tests.Furthermore,the large responsivity and rapid response speed endow the photodetector with the ability to accurately probe heart rate,suggesting a possible application in the area of flexible and wearable health monitoring.