Vapor Deposition of Bilayer 3R MoS2 with Room-Temperature Ferroelectricity.

Two-dimensional ultrathin ferroelectrics have attracted much interest due to their potential application in high-density integration of non-volatile memory devices. Recently, 2D van der Waals ferroelectric based on interlayer translation has been reported in twisted bilayer h-BN and transition metal dichalcogenides (TMDs). However, sliding ferroelectricity is not well studied in non-twisted homo-bilayer TMD grown directly by chemical vapor deposition (CVD). In this paper, for the first time, experimental observation of a room-temperature out-of-plane ferroelectric switch in semiconducting bilayer 3R MoS2 synthesized by reverse-flow CVD is reported. Piezoelectric force microscopy (PFM) hysteretic loops and first principle calculations demonstrate that the ferroelectric nature and polarization switching processes are based on interlayer sliding. The vertical Au/3R MoS2/Pt device exhibits a switchable diode effect. Polarization modulated Schottky barrier height and polarization coupling of interfacial deep states trapping/detrapping may serve in coordination to determine switchable diode effect. The room-temperature ferroelectricity of CVD-grown MoS2 will proceed with the potential wafer-scale integration of 2D TMDs in the logic circuit.

Impacts of climate and land use change on terrestrial carbon storage: A multi-scenario case study in the Yellow River Basin (1992-2050).

Currently, socioeconomic development and climate change pose new challenges to the assessment and management of terrestrial carbon storage (CS). Accurate prediction of future changes in land use and CS under different climate scenarios is of great significance for regional land use decision-making and carbon management. Taking the Yellow River Basin (YRB) in China as the study area, this study proposed a framework integrating the land use harmonization2 (LUH2) dataset, the patch-generating land use simulation (PLUS) model, and the integrated valuation of ecosystem services and trade-offs (InVEST) model. Under this framework, we systematically analyzed the spatiotemporal evolution characteristics of land use and their impact on CS in the YRB from 1992 to 2050. The results showed that (1) CS was highest in forestland and lowest in construction land, with a spatial distribution of high in the south and low in the north. From 1992 to 2020, construction land, forestland, and grassland increased while cropland decreased, reducing the total CS by 74.04 Tg. (2) From 2020 to 2050, under SSP1-2.6 scenario, forestland increased by 158.87 %; under SSP2-4.5 scenario, unused land decreased by 65.55 %; and under SSP5-8.5 scenario, construction land increased by 13.88 %. By 2050, SSP1-2.6 scenario exhibited the highest CS (8105.25 Tg), followed by SSP2-4.5 scenario (7363.61 Tg), and SSP5-8.5 scenario was the lowest (7315.86 Tg). (3) Forestland and construction land were the most critical factors affecting the CS. Shaanxi and Shanxi had the largest CS in all scenarios, and Qinghai had a huge carbon sink potential under SSP1-2.6 scenario. Scenario modeling demonstrated that future climate and land-use changes would have significant impacts on terrestrial CS in the YRB, and green development pathways could strongly contribute to meeting the dual­carbon target. Overall, this study provides a scientific basis for promoting low-carbon development, land-use optimization, and ecological civilization construction in YRB, China.

Stable continuous-wave lasing from discrete cesium lead bromide quantum dots embedded in a microcavity.

All-inorganic cesium lead bromide (CsPbBr3) quantum dots (QDs) with high photoluminescence (PL) quantum efficiency have been reported as ideal gain materials for high-performance lasers. Nevertheless, isolated CsPbBr3 QDs have not achieved lasing emission (LE) due to finite absorption cross-section. Here, we demonstrate continuous-wave lasing of isolated CsPbBr3 QDs embedded in a microcavity. Distributed Bragg reflectors (DBRs), together with isolated CsPbBr3 QDs in a polymer matrix, are introduced to construct a vertical-cavity surface-emitting laser (VCSEL), which exhibits stable single-mode lasing emissions with an ultra-low threshold of 8.8 W cm-2 and a high Q factor of 1787. Such perovskite-based microcavity structures sustain highly stable excitons at room temperature and can provide an excellent experimental platform to further study the single-particle nano-lasers and quantum physics frontiers such as exciton-polariton condensation, single-photon emission, and optical quantum communication.

Ultrastrong Optical Harmonic Generations in Layered Platinum Disulfide in the Mid-Infrared.

Nonlinear optical activities (e.g., harmonic generations) in two-dimensional (2D) layered materials have attracted much attention due to the great promise in diverse optoelectronic applications such as nonlinear optical modulators, nonreciprocal optical device, and nonlinear optical imaging. Exploration of nonlinear optical response (e.g., frequency conversion) in the infrared, especially the mid-infrared (MIR) region, is highly desirable for ultrafast MIR laser applications ranging from tunable MIR coherent sources, MIR supercontinuum generation, and MIR frequency-comb-based spectroscopy to high harmonic generation. However, nonlinear optical effects in 2D layered materials under MIR pump are rarely reported, mainly due to the lack of suitable 2D layered materials. Van der Waals layered platinum disulfide (PtS2) with a sizable bandgap from the visible to the infrared region is a promising candidate for realizing MIR nonlinear optical devices. In this work, we investigate the nonlinear optical properties including third-and fifth-harmonic generation (THG and FHG) in thin layered PtS2 under infrared pump (1550-2510 nm). Strikingly, the ultrastrong third-order nonlinear susceptibility χ(3)(-3ω;ω,ω,ω) of thin layered PtS2 in the MIR region was estimated to be over 10-18 m2/V2, which is about one order of that in traditional transition metal chalcogenides. Such excellent performance makes air-stable PtS2 a potential candidate for developing next-generation MIR nonlinear photonic devices.

Sliding induced multiple polarization states in two-dimensional ferroelectrics.

When the atomic layers in a non-centrosymmetric van der Waals structure slide against each other, the interfacial charge transfer results in a reversal of the structure's spontaneous polarization. This phenomenon is known as sliding ferroelectricity and it is markedly different from conventional ferroelectric switching mechanisms relying on ion displacement. Here, we present layer dependence as a new dimension to control sliding ferroelectricity. By fabricating 3 R MoS2 of various thicknesses into dual-gate field-effect transistors, we obtain anomalous intermediate polarization states in multilayer (more than bilayer) 3 R MoS2. Using results from ab initio density functional theory calculations, we propose a generalized model to describe the ferroelectric switching process in multilayer 3 R MoS2 and to explain the formation of these intermediate polarization states. This work reveals the critical roles layer number and interlayer dipole coupling play in sliding ferroelectricity and presents a new strategy for the design of novel sliding ferroelectric devices.

Strain Quantum Sensing with Spin Defects in Hexagonal Boron Nitride.

Hexagonal boron nitride is not only a promising functional material for the development of two-dimensional optoelectronic devices but also a good candidate for quantum sensing thanks to the presence of quantum emitters in the form of atom-like defects. Their exploitation in quantum technologies necessitates understanding their coherence properties as well as their sensitivity to external stimuli. In this work, we probe the strain configuration of boron vacancy centers (VB-) created by ion implantation in h-BN flakes thanks to wide-field spatially resolved optically detected magnetic resonance and submicro Raman spectroscopy. Our experiments demonstrate the ability of VB- for quantum sensing of strain and, given the omnipresence of h-BN in 2D-based devices, open the door for in situ imaging of strain under working conditions.

Dative Epitaxy of Commensurate Monocrystalline Covalent van der Waals Moiré Supercrystal.

Realizing van der Waals (vdW) epitaxy in the 1980s represents a breakthrough that circumvents the stringent lattice matching and processing compatibility requirements in conventional covalent heteroepitaxy. However, due to the weak vdW interactions, there is little control over film qualities by the substrate. Typically, discrete domains with a spread of misorientation angles are formed, limiting the applicability of vdW epitaxy. Here, the epitaxial growth of monocrystalline, covalent Cr5 Te8 2D crystals on monolayer vdW WSe2 by chemical vapor deposition is reported, driven by interfacial dative bond formation. The lattice of Cr5 Te8 , with a lateral dimension of a few tens of micrometers, is fully commensurate with that of WSe2 via 3 × 3 (Cr5 Te8 )/7 × 7 (WSe2 ) supercell matching, forming a single-crystalline moiré superlattice. This work establishes a conceptually distinct paradigm of thin-film epitaxy, termed "dative epitaxy", which takes full advantage of covalent epitaxy with chemical bonding for fixing the atomic registry and crystal orientation, while circumventing its stringent lattice matching and processing compatibility requirements; conversely, it ensures the full flexibility of vdW epitaxy, while avoiding its poor orientation control. Cr5 Te8 2D crystals grown by dative epitaxy exhibit square magnetic hysteresis, suggesting minimized interfacial defects that can serve as pinning sites.

Localization of Laterally Confined Modes in a 2D Semiconductor Microcavity.

Monolayer semiconductor embedded planar microcavities are becoming a promising light-matter interacting system to uncover a wealth of photonic, excitonic, and polaritonic physics at the two-dimensional (2D) limit. In these 2D semiconductor microcavities employing the longitudinal Fabry-Perot resonance, major attention has been paid to the coupling of excitons with vertically confined cavity photons; by contrast, the lateral confinement effect on exciton-photon interactions is still elusive. Here we observe the localized distribution of laterally confined modes with discrete energies in a 2D semiconductor embedded microcavity. Monolayer tungsten disulfides with equilateral triangular geometries but varied edge lengths are selected as the active media incorporated into a dielectric planar microcavity. With the shortening of the edge length, photoluminescence mappings of active regions present spatially localized emission patterns, which are attributed to the presence of in-plane triangular waveguiding resonance caused by total internal reflection at the one-dimensional closed boundary between the monolayer semiconductor and its surrounding cavity material. Unlike the conventional quantum confinement effect of native excitons appearing at the nanometer scale, the mode emission at the active-medium center exhibits apparent size-dependent features at the micrometer scale due to the optical confinement effect correlated with its photonic nature. By reducing the area of active media, single-mode dominant emission is achieved together with its nondispersive energy and improved directionality. Our work highlights the crucial role of lateral mode control in monolayer semiconductor embedded planar microcavities and encourages the investigation of the quantum billiard problem in 2D semiconductors.

White-Light-Driven Resonant Emission from a Monolayer Semiconductor.

Resonant emission in photonic structures is very useful to construct all-photonic circuits for optical interconnects and quantum computing. Optical generation of most resonant-emitting modes in photonic structures is obtained by coherent pumping rather than incoherent illumination. Particularly, the development of white-light- or even solar-powered on-chip light sources remains challenging but is very attractive in view of the much facile availability of these incoherent excitation sources. Here, net resonant emission from a monolayer semiconductor is demonstrated under simulated solar illumination by a white-light-emitting diode. The device is formed by embedding a 2D gain medium into a planar microcavity on a silicon wafer, which is compatible with the prevailing on-chip photonic technology. Coherent and white-light excitation sources are, respectively, selected for optical pumping, where the output light in two cases exhibits well-consistent resonant wavelength, linewidth, polarization, location, and Gaussian-beam profile. The fundamental TEM00 mode behaves as a doublet emission, resulting from anisotropy-induced non-degenerate states with orthogonal polarizations. The extraordinary spectral flipping is attributed to the competitive interplay of resonant absorption and emission. This work paves a way toward white-light or solar-powered state-of-the-art photonic applications at the chip scale.

Polarization-Dependent Purcell Enhancement on a Two-Dimensional h-BN/WS2 Light Emitter with a Dielectric Plasmonic Nanocavity.

Integrating two-dimensional (2D) transition-metal dichalcogenides (TMDCs) into dielectric plasmonic nanostructures enables the miniaturization of on-chip nanophotonic devices. Here we report on a high-quality light emitter based on the newly designed 2D h-BN/WS2 heterostructure integrated with an array of TiO2 nanostripes. Different from a traditional strongly coupled system such as the TMDCs/metallic plasmonic nanostructure, we first employ dielectric nanocavities and achieve a Purcell enhancement on the nanoscale at room temperature. Furthermore, we demonstrate that the light emission strength can be effectively controlled by tuning the polarization configuration. Such a polarization dependence meanwhile could be proof of the resonant energy transfer theory of dipole-dipole coupling between TMDCs and a dielectric nanostructure. This work gains experimental and simulated insights into modified spontaneous emission with dielectric nanoplasmonic platforms, presenting a promising route toward practical applications of 2D semiconducting photonic emitters on a silica-based chip.

Observation of Strong Valley Magnetic Response in Monolayer Transition Metal Dichalcogenide Alloys of Mo0.5W0.5Se2 and Mo0.5W0.5Se2/WS2 Heterostructures.

Monolayer transition metal dichalcogenide (TMD) alloys have emerged as a unique material system for promising applications in electronics, optoelectronics, and spintronics due to their tunable electronic structures, effective masses of carriers, and valley polarization with various alloy compositions. Although spin-orbit engineering has been extensively studied in monolayer TMD alloys, the valley Zeeman effect in these alloys still remains largely unexplored. Here we demonstrate the enhanced valley magnetic response in Mo0.5W0.5Se2 alloy monolayers and Mo0.5W0.5Se2/WS2 heterostructures probed by magneto-photoluminescence spectroscopy. The large g factors of negatively charged excitons (trions) of Mo0.5W0.5Se2 have been extracted for both pure Mo0.5W0.5Se2 monolayers and Mo0.5W0.5Se2/WS2 heterostructures, which are attributed to the significant impact of doping-induced strong many-body Coulomb interactions on trion emissions under an out-of-plane magnetic field. Moreover, compared with the monolayer Mo0.5W0.5Se2, the slightly reduced valley Zeeman splitting in Mo0.5W0.5Se2/WS2 is a consequence of the weakened exchange interaction arising from p-doping in Mo0.5W0.5Se2 via interlayer charge transfer between Mo0.5W0.5Se2 and WS2. Such interlayer charge transfer further evidences the formation of type-II band alignment, in agreement with the density functional theory calculations. Our findings give insights into the spin-valley and interlayer coupling effects in monolayer TMD alloys and their heterostructures, which are essential to develop valleytronic applications based on the emerging family of TMD alloys.

Visualizing the Anomalous Charge Density Wave States in Graphene/NbSe2 Heterostructures.

Metallic layered transition metal dichalcogenides (TMDs) host collective many-body interactions, including the competing superconducting and charge density wave (CDW) states. Graphene is widely employed as a heteroepitaxial substrate for the growth of TMD layers and as an ohmic contact, where the graphene/TMD heterostructure is naturally formed. The presence of graphene can unpredictably influence the CDW order in 2D CDW conductors. This work reports the CDW transitions of 2H-NbSe2 layers in graphene/NbSe2 heterostructures. The evolution of Raman spectra demonstrates that the CDW phase transition temperatures (TCDW ) of NbSe2 are dramatically decreased when capped by graphene. The induced anomalous short-range CDW state is confirmed by scanning tunneling microscopy measurements. The findings propose a new criterion to determine the TCDW through monitoring the line shape of the A1g mode. Meanwhile, the 2D band is also discovered as an indicator to observe the CDW transitions. First-principles calculations imply that interfacial electron doping suppresses the CDW states by impeding the lattice distortion of 2H-NbSe2 . The extraordinary random CDW lattice suggests deep insight into the formation mechanism of many collective electronic states and possesses great potential in modulating multifunctional devices.

Progressively Exposing Active Facets of 2D Nanosheets toward Enhanced Pseudocapacitive Response and High-Rate Sodium Storage.

Sodium-ion batteries are gradually regarded as a prospective alternative to lithium-ion batteries due to the cost consideration. Here, three kinds of tin (IV) sulfide nanosheets are controllably designed with progressively exposed active facets, leading to beneficial influences on the Na+ storage kinetics, resulting in gradient improvements of pseudocapacitive response and rate performance. Interestingly, different forms of kinetics results are generated accompanying with the morphology and structure evolution of the three nanosheets. Finally, detailed density functional theory simulations are also applied to analyze the above experimental achievements, proving that different exposed facets of crystalline anodes possess dissimilar Na+ storage kinetics. The investigation experiences and conclusions shown in this work are meaningful to explore many other proper structure design routes toward the high-rate and stable metal-ions storage.

Engineering Valley Polarization of Monolayer WS2 : A Physical Doping Approach.

The emerging field of valleytronics has boosted intensive interests in investigating and controlling valley polarized light emission of monolayer transition metal dichalcogenides (1L TMDs). However, so far, the effective control of valley polarization degree in monolayer TMDs semiconductors is mostly achieved at liquid helium cryogenic temperature (4.2 K), with the requirements of high magnetic field and on-resonance laser, which are of high cost and unwelcome for applications. To overcome this obstacle, it is depicted that by electrostatic and optical doping, even at temperatures far above liquid helium cryogenic temperature (80 K) and under off-resonance laser excitation, a competitive valley polarization degree of monolayer WS2 can be achieved (more than threefold enhancement). The enhanced polarization is understood by a general doping dependent valley relaxation mechanism, which agrees well with the unified theory of carrier screening effects on intervalley scattering process. These results demonstrate that the tunability corresponds to an effective magnet field of ≈10 T at 4.2 K. This work not only serves as a reference to future valleytronic studies based on monolayer TMDs with various external or native carrier densities, but also provides an alternative approach toward enhanced polarization degree, which denotes an essential step toward practical valleytronic applications.

Producing more grain yield of rice with less ammonia volatilization and greenhouse gases emission using slow/controlled-release urea.

Ammonia (NH3) volatilization and greenhouse gas (GHG) emission from rice (Oryza sativa L.) fields contaminate the atmospheric environment and lead to global warming. Field trials (2013-2015) were conducted to estimate the influences of different types of fertilization practices on grain yield, NH3 volatilization, and methane (CH4) and nitrous oxide (N2O) emissions in a double rice cropping system in Central China. Results showed that grain yields of rice were improved significantly by using slow/controlled-release urea (S/C-RU). Compared with farmers' fertilizer practice (FFP) treatment, average annual grain yield with application of polymer-coated urea (CRU), nitrapyrin-treated urea (CP), and urea with effective microorganism (EM) treatments was increased by 18.0%, 16.2%, and 15.4%, respectively. However, the effects on NH3 volatilization and CH4 and N2O emissions differed in diverse S/C-RU. Compared with that of the FFP treatment, the annual NH3 volatilization, CH4 emission, and N2O emissions of the CRU treatment were decreased by 64.8%, 19.7%, and 35.2%, respectively; the annual CH4 and N2O emissions of the CP treatment were reduced by 33.7% and 40.3%, respectively, while the NH3 volatilization was increased by 18.5%; the annual NH3 and N2O emissions of the EM treatment were reduced by 6.3% and 28.7%, while the CH4 emission was improved by 4.3%. Overall, CP showed the best emission reduction with a decrement of 34.3% in global warming potential (GWP) and 44.4% in the greenhouse gas intensity (GHGI), followed by CRU treatment with a decrement of 21.1% in GWP and 31.7% in GHGI, compared with that of the FFP treatment. Hence, it is suggested that polymer-coated urea can be a feasible way of mitigating NH3 volatilization and CH4 and N2O emission from rice fields while maintaining or increasing the grain yield in Chinese, the double rice cropping system.

In-Plane Anisotropic Thermal Conductivity of Few-Layered Transition Metal Dichalcogenide Td-WTe2.

2D Td-WTe2 has attracted increasing attention due to its promising applications in spintronic, field-effect chiral, and high-efficiency thermoelectric devices. It is known that thermal conductivity plays a crucial role in condensed matter devices, especially in 2D systems where phonons, electrons, and magnons are highly confined and coupled. This work reports the first experimental evidence of in-plane anisotropic thermal conductivities in suspended Td-WTe2 samples of different thicknesses, and is also the first demonstration of such anisotropy in 2D transition metal dichalcogenides. The results reveal an obvious anisotropy in the thermal conductivities between the zigzag and armchair axes. The theoretical calculation implies that the in-plane anisotropy is attributed to the different mean free paths along the two orientations. As thickness decreases, the phonon-boundary scattering increases faster along the armchair direction, resulting in stronger anisotropy. The findings here are crucial for developing efficient thermal management schemes when engineering thermal-related applications of a 2D system.

Engineering Morphologies of Cobalt Pyrophosphates Nanostructures toward Greatly Enhanced Electrocatalytic Performance of Oxygen Evolution Reaction.

Herein, a surfactant- and additive-free strategy is developed for morphology-controllable synthesis of cobalt pyrophosphate (CoPPi) nanostructures by tuning the concentration and ratio of the precursor solutions of Na4 P2 O7 and Co(CH3 COO)2 . A series of CoPPi nanostructures including nanowires, nanobelts, nanoleaves, and nanorhombuses are prepared and exhibit very promising electrocatalytic properties toward the oxygen evolution reaction (OER). Acting as both reactant and pseudo-surfactant, the existence of excess Na4 P2 O7 is essential to synthesize CoPPi nanostructures for unique morphologies. Among all CoPPi nanostructures, the CoPPi nanowires catalyst renders the best catalytic performance for OER in alkaline media, achieving a low Tafel slope of 54.1 mV dec-1 , a small overpotential of 359 mV at 10 mA cm-2 , and superior stability. The electrocatalytic activities of CoPPi nanowires outperform the most reported non-noble metal based catalysts, even better than the benchmark Ir/C (20%) catalyst. The reported synthesis of CoPPi gives guidance for morphology control of transition metal pyrophosphate based nanostructures for a high-performance inexpensive material to replace the noble metal-based OER catalysts.

Boron Alleviates Aluminum Toxicity by Promoting Root Alkalization in Transition Zone via Polar Auxin Transport.

Boron (B) alleviates aluminum (Al) toxicity in higher plants; however, the underlying mechanisms behind this phenomenon remain unknown. Here, we used bromocresol green pH indicator, noninvasive microtest, and microelectrode ion flux estimation techniques to demonstrate that B promotes root surface pH gradients in pea (Pisum sativum) roots, leading to alkalization in the root transition zone and acidification in the elongation zone, while Al inhibits these pH gradients. B significantly decreased Al accumulation in the transition zone (∼1.0-2.5 mm from the apex) of lateral roots, thereby alleviating Al-induced inhibition of root elongation. Net indole acetic acid (IAA) efflux detected by an IAA-sensitive platinum microelectrode showed that polar auxin transport, which peaked in the root transition zone, was inhibited by Al toxicity, while it was partially recovered by B. Electrophysiological experiments using the Arabidopsis (Arabidopsis thaliana) auxin transporter mutants (auxin resistant1-7; pin-formed2 [pin2]) and the specific polar auxin transporter inhibitor1-naphthylphthalamic acid showed that PIN2-based polar auxin transport is involved in root surface alkalization in the transition zone. Our results suggest that B promotes polar auxin transport driven by the auxin efflux transporter PIN2 and leads to the downstream regulation of the plasma membrane-H+-ATPase, resulting in elevated root surface pH, which is essential to decrease Al accumulation in this Al-targeted apical root zone. These findings provide a mechanistic explanation for the role of exogenous B in alleviation of Al accumulation and toxicity in plants.

Silicon improves growth and alleviates oxidative stress in rice seedlings (Oryza sativa L.) by strengthening antioxidant defense and enhancing protein metabolism under arsanilic acid exposure.

Organoarsenic arsanilic acid (ASA) contamination of paddy soil is a serious but less concerned hazard to agriculture and health of people consuming rice as staple food, for rice is one major pathway of arsenic (As) exposure to human food. To date little research has studied the effect of ASA on biochemical process of rice. Silicon (Si) application is able to reduce the toxicities of heavy metals in numerous plants, but little information about ASA. This work investigated whether and how Si influenced alleviation of ASA toxicity in rice at biochemical level to have a better understanding of defense mechanism by Si against ASA stress. Results showed that ASA reduced rice growth, disturbed protein metabolism, increased lipid peroxidation but decreased the efficiencies of antioxidant activities compared to control plants, more severe in roots than in shoots. The addition of Si in ASA-stressed rice plants noticeably increased growth and development as well as soluble protein contents, but decreased malondialdehyde (MDA) contents in ASA-stressed rice plants, suggesting that Si did have critical roles in ASA detoxification in rice. Furthermore, increased superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities along with elevated glutathione (GSH) and ascorbic acid (AsA) contents implied the active involvement of ROS scavenging and played, at least in part, to Si-mediated alleviation of ASA toxicity in rice, and these changes were related to rice genotypes and tissues. The study provided physio-chemical mechanistic evidence on the beneficial effect of Si on organoarsenic ASA toxicity in rice seedlings.

Controllable Design of MoS2 Nanosheets Anchored on Nitrogen-Doped Graphene: Toward Fast Sodium Storage by Tunable Pseudocapacitance.

Transition-metal disulfide with its layered structure is regarded as a kind of promising host material for sodium insertion, and intensely investigated for sodium-ion batteries. In this work, a simple solvothermal method to synthesize a series of MoS2 nanosheets@nitrogen-doped graphene composites is developed. This newly designed recipe of raw materials and solvents leads the success of tuning size, number of layers, and interplanar spacing of the as-prepared MoS2 nanosheets. Under cut-off voltage and based on an intercalation mechanism, the ultrasmall MoS2 nanosheets@nitrogen-doped graphene composite exhibits more preferable cycling and rate performance compared to few-/dozens-layered MoS2 nanosheets@nitrogen-doped graphene, as well as many other reported insertion-type anode materials. Last, detailed kinetics analysis and density functional theory calculation are also employed to explain the Na+ - storage behavior, thus proving the significance in surface-controlled pseudocapacitance contribution at the high rate. Furthermore, this work offers some meaningful preparation and investigation experiences for designing electrode materials for commercial sodium-ion batteries with favorable performance.